WO2014044007A1 - Wind farm automatic dynamic voltage control system - Google Patents

Abstract

A wind farm automatic dynamic voltage control (AVC) system comprises: a AVC controller, multiple wind turbine control systems arranged on multiple wind turbines of the wind farm, a static reactive power compensation device (SVC), and multiple voltage transformers and current transformers arranged on wind power transmission lines, wind power assemble lines, SVC lines, high voltage buses and low voltage buses. Each wind power assemble line connects to the multiple wind turbines so as to receive the power output of the multiple wind turbines, and also connects to the low voltage buses. The AVC controller communicates with each wind turbine control system through an optical fiber network and electrically connects to the multiple voltage transformers and current transformers. The AVC controller determines the total reactive power that needs to be generated or absorbed by the wind farm, the total reactive power that can be generated or absorbed by each wind power assemble line and the total reactive power that can be generated or absorbed by each wind turbine, and sends the control signal corresponding to the reactive power that can be generated or absorbed by each wind turbine to the corresponding wind turbine control system.

Description

 Wind farm dynamic voltage automatic control system

 The present invention relates to a wind farm dynamic voltage automatic control (AVC) system, and more particularly to a wind farm AVC system capable of dynamically compensating reactive power. Background technique

 With the development of technology, the focus and utilization of renewable energy is increasing. Among them, wind power is a relatively mature energy technology. However, China's wind power industry's development plan of “building a large base and integrating into the large power grid” is different from that of “distributing the Internet and in-situ consumption” in Europe. It has the characteristics of “large scale” and “high concentration”. Intermittent wind power causes grid voltage fluctuations, system short-circuit capacity increase, and transient stability changes, especially in the case of large-scale wind power centralized access to the grid. At the same time, the power quality at the end of the grid will also affect the wind farm. For example, the grid disturbance causes the wind turbine to be disconnected from the wind farm, and the unbalanced voltage will cause the unit to vibrate and overheat.

 The key to studying the integration of wind farms is to analyze the wind farm as an integral unit to the grid, and improve the grid-connected performance of the entire wind farm by improving the stability of the wind farm grid point (PCC).

 The most important indicator of the stability of the PCC point is voltage stability. The voltage fluctuation directly affects the safe and stable operation of the fan, and the damage even affects the connected power network. According to the trend analysis technology,

The voltage at the PCC point is mainly affected by the reactive power at this point: When the inductive reactive power is consumed (ie, the reactive power is absorbed), the voltage will drop; on the contrary, when the inductive reactive power is emitted (ie, the reactive power is emitted) The voltage will rise for a long time. By controlling the reactive power dynamic balance of the PCC point by some techniques, the voltage stability of the PCC point can be controlled.

 However, in the prior art, controlling the reactive power balance of the PCC point of the wind farm will be restricted by two technical points: First, it must meet the control principle of "stratified partitioning" of reactive power in China's power system, and secondly, the wind farm must be fully considered. The control mechanism of the reactive power source.

There are two main types of reactive power sources for wind farms: fans and centralized reactive power compensation equipment. Centralized reactive power compensation equipment, such as static reactive power compensation device (SVC), plays an active and effective role in the reactive power balance of wind farms, but also has the disadvantages of high cost, large loss and poor stability, and SVC and The fan operation is poor. On the other hand, the fan has the ability to generate additional reactive power, but the free control of a single fan can cause the reactive power of the wind farm to fail to reach the specified control target. The wind farm voltage automatic control (AVC) system can mine the ability of the wind turbine to generate reactive power in the wind farm, and cooperate with the SVC to achieve a better dynamic balance of the reactive power of the wind farm.

 BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a topological view showing a wind farm AVC system for realizing voltage control of a PCC point by means of a concentrated reactive power compensation apparatus according to the prior art.

 As shown in FIG. 1, in a wind farm AVC system according to the prior art, a plurality of wind power collecting lines 1-N (each wind power collecting line includes a plurality of fans) and an SVC line provided with an SVC are connected to the low voltage bus. The voltage on the low voltage bus is boosted by the transformer, connected to the high voltage bus, and then connected to the large power grid through the PCC point through the wind power transmission line, thereby implementing wind farm integration, wherein the SVC changes according to the voltage of the low voltage bus and/or the high voltage bus. The reactive power is automatically generated or the reactive power is absorbed to adjust the voltage at the PCC point.

 However, the wind farm AVC system according to the prior art has the following disadvantages: (1) To achieve voltage stability of the entire wind farm, it is necessary to install a centralized reactive power compensation device (for example, SVC or more than 30% to 50% of the total installed capacity). SVG), while SVC is expensive, has inherent losses, but is not stable;

(2) When the bus voltage decreases, the SVC's ability to discharge reactive power decreases, and its compensation capacity decreases by a factor of square; (3) The centralized use of centralized reactive power compensation equipment is not conducive to releasing the fan's ability to generate reactive power. It causes waste of important reactive power source; (4) The coordination of concentrated reactive power compensation equipment and fan operation is poor, which is characterized by frequent lag behind real-time reactive power regulation.

 To this end, it is necessary to provide such a wind farm dynamic voltage automatic control (AVC) system, which can excavate the ability of the wind turbine to generate reactive power in the wind farm, and cooperate with the SVC-channel to make the reactive power of the wind farm better. The dynamic balance improves the grid-connected performance of the wind farm. Summary of the invention

 Aspects of the present invention are to address at least the above problems and/or disadvantages and to provide at least the advantages described. Accordingly, an aspect of the present invention is to provide a wind farm dynamic voltage automatic control (AVC) system.

According to an aspect of the present invention, a wind farm dynamic voltage automatic control (AVC) system is provided, comprising: an AVC controller, a plurality of fan master systems disposed on a plurality of wind turbines in a wind farm, and a static reactive power compensation a device (SVC), a plurality of voltage transformers and current transformers disposed on a wind power supply line, a wind power collection line, an SVC line, a high voltage bus, and a low voltage bus, wherein each wind power The collection line is connected with a plurality of fans, receives the output of the plurality of fans, and is connected to the low voltage bus. The AVC controller communicates with each fan main control system through the optical fiber network, and is electrically connected to the plurality of voltage transformers and current transformers. Wherein, the AVC controller compares the voltage provided by the voltage transformer provided on the high-voltage bus wind power supply line with the target voltage of the wind farm, and determines the total amount of reactive power or reactive power required by the wind farm according to the voltage difference. Value; determine the total value of reactive power that can be emitted or absorbed by each wind power collection line according to the voltage data and current data provided by the voltage transformer and current transformer set on each wind power collection line; according to the fan main control system The voltage data and current data determine the reactive power that the corresponding fan can emit or absorb, and send a control signal corresponding to the reactive power that each fan needs to emit or absorb to the corresponding fan master system.

 In addition, when the reactive power generated or absorbed by each fan is insufficient to increase or decrease the actual voltage of the grid-connected point to the target value, the AVC controller can control the SVC to automatically put into operation to emit or absorb reactive power, thereby further increasing or decreasing. The voltage at the grid point.

 Furthermore, the wind farm dynamic voltage automatic control system may further include: an AVC primary station for performing remote control, the AVC primary station being disposed at any position away from the wind farm, and being connected to the AVC controller by wired or wireless communication. Communication and remote control of the AVC controller.

 In addition, the AVC controller can calculate the measured reactive power on the wind power transmission line according to the voltage and current provided by the voltage transformer and the current transformer set on the wind power transmission line, and measure the reactive power of the reactive power and the target reactive power of the wind farm. For comparison, the total value of the reactive power or the reactive power required by the wind farm is determined according to the difference between the measured reactive power and the target reactive power of the wind farm.

 In addition, the AVC controller can calculate the measured power factor according to the voltage and current provided by the voltage transformer and the current transformer provided on the wind power transmission line, and compare the measured power factor with the target power factor, according to the measured power factor and the target power factor. The difference determines the total value of the reactive power required to generate reactive power or absorb reactive power.

In addition, the AVC controller may perform the following operations: detecting a current value of the grid-connected point voltage; comparing the current value of the grid-connected point voltage with an expected value of the grid-connected point voltage, determining whether the current value of the grid-connected point voltage deviates from the expected value of the grid-connected point point exceeding a first predetermined threshold; When the current value of the grid-connected point voltage deviates from the expected value of the grid-connected point point exceeds the first predetermined threshold value, the current value of the grid-connected system impedance is calculated according to the voltage and current measured at the grid-connected point; the current value of the grid-connected system impedance is compared with the previous value of the grid-connected system impedance Determining whether the current value of the system impedance of the grid point deviates from the previous value of the grid point system impedance exceeds a second predetermined threshold; if the current value of the grid point system impedance deviates from the grid point system impedance previous value exceeds a second predetermined threshold, the current value of the grid point system impedance is used Update the previous value of the grid point system impedance to connect to the grid Point system impedance is corrected.

 In addition, the AVC controller can perform the following operations: Real-time monitoring of the status of each of the monitoring sources that affect electrical topological integrity; if it is determined that any of the monitored monitoring sources is generating an abnormality that would result in electrical topological integrity disruption, then the execution of the grid scheduling command is stopped.

 In addition, the AVC controller can perform the following operations: determining the active power and the terminal voltage of the fan; determining the reactive power capability according to the determined active power and the terminal voltage.

 In addition, the AVC controller can perform the following operations: (a) confirm whether the i-th fan of the N fans in the wind power collection line is in operation, where N is a natural number greater than 0, and the initial value of i is 1; If it is confirmed that the i-th fan is not in operation, it is determined that the reactive power capability of the i-th fan is zero; (c) if it is confirmed that the i-th fan is in operation, the model and active power of the i-th fan are determined. And the terminal voltage; (d) determine the reactive power capability of the i-th fan according to the determined model, active power and terminal voltage of the i-th fan; (e) make i=i+l and determine whether i More than N; (f) If i is not greater than N, return to step (a); (g) If i is greater than N, the determined reactive power capabilities of the N fans are added.

 In addition, the AVC controller can perform the following operations: determining the total reactive power demand of the grid-connected point; assigning reactive power to each wind power collecting line according to the total reactive power demand of the grid-connected point and the reactive power capability of each wind power collecting line Power task; according to the reactive power task of each wind power collection line and the reactive power capability of each fan in the running state of each wind power collection line, each fan in the running state of each wind power collection line Assign reactive power tasks.

 In addition, the AVC controller may perform the following operations: determining whether the wind farm grid-connected PCC point voltage suddenly decreases; when it is determined that the PCC point voltage suddenly decreases, the control of the wind farm AVC system is blocked after waiting for the first predetermined time; Determining that the SVC is absorbing reactive power, issuing a control command to stop the SVC from absorbing reactive power; determining whether the PCC point voltage rises above a certain threshold within a second predetermined time after a sudden decrease occurs; when determining that the PCC point voltage is When the second predetermined time rises above the certain threshold, the control of the wind farm by the wind farm AVC system is resumed.

 In addition, the AVC controller may perform the following operations: determining whether the wind farm grid-connected PCC point voltage suddenly rises; when determining that the PCC point voltage suddenly rises, after waiting for the first predetermined time, issuing a command to each fan master control system, so that Each fan stops emitting reactive power; when it is determined that the SVC is emitting reactive power, a control command is issued to stop the SVC from issuing reactive power; after waiting for the second predetermined time, the reactive power of the wind farm AVC system to the wind farm is restored. control.

The wind farm dynamic voltage automatic control system provided by the invention can fully release the fan to issue additional The ability to generate reactive power, reduce the construction investment and operating loss of the SVC, achieve the synergistic effect of the reactive power of the fan and the reactive power of the SVC, and realize the voltage stability control of the PCC point of the wind farm more dynamically and accurately. The reactive power of the wind farm achieves a better dynamic balance and improves the grid-connected performance of the wind farm. DRAWINGS

 These and/or other aspects and advantages of the present invention will become apparent and more readily understood from

 1 is a topological view showing a wind farm AVC system that implements voltage control of a PCC point by means of a concentrated reactive power compensation device according to the prior art;

 2 is a diagram showing a wind farm AVC system according to an embodiment of the present invention;

 3 is a schematic diagram showing a remote control mode and a local control mode of a wind farm AVC system according to an embodiment of the present invention;

 4 is a flow chart showing a method for automatically identifying and correcting impedance of a wind farm grid point system according to an embodiment of the present invention;

 Figure 5 is a view schematically showing a monitoring source (a component marked with an ellipse in the figure) monitored by the monitoring method of the electrical main topology integrity of the present invention;

 6 is a flow chart showing a method of monitoring electrical main topology integrity according to an exemplary embodiment of the present invention;

 7 shows a flow diagram of a method of estimating reactive power capability of a wind turbine, in accordance with an embodiment of the present invention;

 8 shows a flowchart of a method of acquiring a mapping relationship between active power of a wind turbine and a terminal voltage and reactive power capability, according to an exemplary embodiment of the present invention;

 9A and 9B show examples of mapping curves (i.e., PQ curves) between the active power and the reactive power capability of the fan at different terminal voltages;

 Figure 9C shows an example of determining reactive power capability based on a PQ curve;

 Figure 10 illustrates a flow chart of a method of estimating reactive power capability of a wind power collection line, in accordance with an exemplary embodiment of the present invention;

 Figure 1 1 shows a flow chart of a reactive power task assignment method for a wind turbine group in accordance with an embodiment of the present invention;

Figure 12 illustrates the distribution of reactive power for a wind power collection line, in accordance with an embodiment of the present invention. Flow chart

 Figure 13 illustrates a flow diagram of a method of estimating reactive power capability of a wind turbine, in accordance with an embodiment of the present invention;

 FIG. 14 illustrates a flow of a method of acquiring a mapping relationship between active power of a wind turbine and a terminal voltage and reactive power capability according to an exemplary embodiment of the present invention; FIG.

 15A and 15B show an example of a mapping relationship between the active power and the reactive power capability of the fan at the terminal voltage (i.e., the PQ curve);

 Figure 15C shows an example of determining reactive power capability based on a PQ curve;

 16 shows a flow chart of a method for estimating reactive power capability of a wind power gathering line based on the method of FIG. 13 in accordance with an exemplary embodiment of the present invention;

 17 is a flow chart showing a method of improving grid-connected transient stability in a wind farm AVC system in accordance with an embodiment of the present invention;

 18 is a flow chart showing a method of improving grid-connected transient stability in a wind farm AVC system in accordance with another embodiment of the present invention. detailed description

 The embodiments of the present invention are now described in detail with reference to the accompanying drawings The embodiments are described below to explain the present invention by referring to the figures.

 2 is a diagram showing a wind farm AVC system according to an embodiment of the present invention.

As shown in FIG. 2, a wind farm AVC system according to an embodiment of the present invention may include an AVC controller, a plurality of fan master systems disposed on a plurality of fans, a centralized reactive power compensation device (eg, SVC), and a wind power generator. A plurality of voltage transformers and current transformers for the outgoing line, the wind power collecting line, the SVC line, the high voltage bus, and the low voltage bus, the AVC controller communicates with each of the fan main control systems through the optical fiber network, and is electrically connected to the plurality of voltages Transformers and current transformers. Specifically, the AVC controller receives voltage data and current data detected by the voltage transformer and the current transformer, and receives various data of the fan itself provided by the wind turbine main control system (for example, voltage data, current data, and active power of the fan port). Power, fan temperature and fault information, etc.). In addition, the AVC controller sends control signals to each fan main control system, and each fan main control system controls the converters in the corresponding fans according to the control signals, so that there is an angle between the current and the voltage of the corresponding fan ports, so that the corresponding fans Capable of emitting reactive power or absorbing reactive power, where, when the current is ahead of the voltage, the fan The reactive power is emitted, and when the current lags behind the voltage, the fan absorbs the reactive power.

 Alternatively, the AVC controller can be implemented by a variety of power panels. Further, the wind farm AVC system according to an embodiment of the present invention may further include an AVC main station for performing remote control, the number of which is not limited, and may be set at any position away from the wind farm (for example, city level) A power control center, a provincial power control center, etc., and communicate with the AVC controller via wired or wireless communication and remotely control the AVC controller. The AVC master can be implemented by a computer. Further, the wind farm AVC system according to an embodiment of the present invention may further include an AVC monitoring device for monitoring the operating state of the AVC. The AVC monitoring device can be implemented by a computer.

 According to an embodiment of the invention, the AVC controller first acquires voltage data of the wind power delivery line. The voltage data of the wind power supply line reflects the actual voltage at the PCC point. Subsequently, the AVC controller compares the voltage of the wind power supply line with the target voltage of the wind farm, and determines the total value of the reactive power or reactive power required by the wind farm based on the voltage difference. Alternatively, the AVC controller can calculate the measured reactive power on the wind power transmission line according to the voltage and current provided by the voltage transformer and the current transformer provided on the wind power transmission line, and the target of the measured reactive power and the wind farm is not The power is compared, and the total value of the reactive power or the reactive power required by the wind farm is determined according to the difference between the measured reactive power and the target reactive power of the wind farm. Optionally, the AVC controller can calculate the measured power factor according to the voltage and current provided by the voltage transformer and the current transformer disposed on the wind power transmission line, and compare the measured power factor with the target power factor, according to the measured power factor and the target. The difference in power factor determines the total value required for the wind farm to emit reactive power or absorb reactive power. Thereafter, the AVC controller can determine the total value of reactive power that can be emitted or absorbed by each wind power collection line according to the voltage data and current data of the wind power collection line, and determine corresponding according to the voltage data and current data provided by the wind turbine main control system. The reactive power that the fan can emit or absorb. Finally, the AVC controller sends a control signal corresponding to the reactive power that each fan needs to emit or absorb to the corresponding fan master system. In this way, the fan master control system can control the converters in the corresponding fans according to the control signals, so that there is an angle between the current and the voltage of the corresponding fan ports, so that the corresponding fans can emit reactive power or absorb reactive power. Finally, by making the fan reactive power or absorbing reactive power, the actual voltage at the PCC point can be increased or decreased to ensure grid stability.

 Alternatively, when the reactive power generated or absorbed by each fan is insufficient to increase or decrease the actual voltage of the PCC point to a target value, the AVC controller can control the SVC to be put into operation to emit or absorb reactive power, thereby further improving or Reduce the voltage at the PCC point.

Hereinafter, the operation of the wind farm AVC system according to an embodiment of the present invention will be further described. 1. Remote control mode and local control mode

 Fig. 3 is a diagram showing a remote control mode and a local control mode of a wind farm AVC system according to an embodiment of the present invention.

 As shown in Figure 3, in the remote control mode, the control commands can be sent to the prefecture-level AVC master station by the provincial AVC master station for grid dispatching, and then the control commands are forwarded to the power plant by the prefecture-level AVC master station. The AVC substation (i.e., the AVC controller described above) then the power plant AVC substation adjusts the fan in the wind farm to emit or absorb reactive power based on the received command. On the other hand, in the local control mode, the AVC substation of the plant generates its own control commands to regulate the fan's output or absorption of reactive power. A wind farm AVC system according to an embodiment of the invention can only operate in one mode at a time. The two modes can be switched between the "Remote Control Mode Platen" and "Local Control Mode Platen" set on the AVC controller.

 2. Automatic identification of system impedance

 The PCC system impedance reflects the strength of the electrical connection between the wind farm and the grid, and can be stable for a long time. However, as the fan operates in a different way, the PCC system impedance will mutate. Obtaining accurate system impedance determines control accuracy and efficiency. Therefore, the system impedance needs to be calculated and updated in real time to make the reactive power control more accurate.

 4 is a flow chart showing a method for automatically identifying and correcting impedance of a wind farm grid point system according to an embodiment of the present invention. This method is performed by the AVC controller.

 At step 401, the current value of the PCC voltage is detected. At step 402, comparing the PCC voltage current value with the PCC voltage expected value (gp, PCC rated voltage), determining whether the PCC voltage current value deviates from the PCC voltage expected value by more than a first predetermined threshold (eg, the first predetermined threshold may be 1% to 3%).

 If the PCC voltage current value deviates from the PCC voltage expected value by more than the first predetermined threshold, it indicates that the PCC reactive power expectation value needs to be adjusted such that the PCC voltage current value is close to the PCC voltage expected value. Therefore, at step 403, the current value of the PCC system impedance is calculated based on the voltage and current (e.g., three-phase voltage and three-phase current) measured at the PCC.

 Preferably, the PCC system impedance value may be calculated a plurality of times (e.g., 10 times) during a predetermined period of time (e.g., 10 seconds), and the average value of the PCC system impedance values may be calculated a plurality of times as the PCC system impedance current value.

 At step 404, comparing the PCC system impedance current value with the PCC system impedance previous value, determining whether the PCC system impedance current value deviates from the PCC system impedance previous value by a second predetermined threshold (eg, the second predetermined threshold may be 30% to 50) %).

The impedance of the PCC system changes little when the wind farm operates in the same way. When the wind farm is short-circuited, When the load is faulty, the impedance of the PCC system will suddenly change greatly, which may also be called the change of the operation mode of the wind farm. Therefore, the impedance of the PCC system has a sudden change.

 If the PCC system impedance current value deviates from the PCC system impedance previous value by a second predetermined threshold, it indicates that the PCC system impedance has abruptly changed. Therefore, in step 305, the PCC system impedance current value is used to update the PCC system impedance previous value to the PCC system. The impedance is corrected.

 If the PCC system impedance current value deviates from the PCC system impedance previous value does not exceed the second predetermined threshold, it means that the PCC system impedance has not changed greatly, so the PCC system impedance is not corrected, that is, the PCC system impedance previous value is taken as the PCC system impedance current. value.

 After correcting the impedance of the PCC system, the PCC reactive power expectation value can be calculated. Specifically, the PCC reactive power expectation value can be calculated using the PCC voltage expected value, the PCC voltage current value, the PCC reactive power current value, and the PCC system impedance current value according to the formula (1) described above. Then, the AVC controller disposed in the wind farm controls the phase difference between the current and the voltage of the fan port in the wind farm according to the calculated PCC reactive power expectation value, so that the fan emits reactive power or absorbs reactive power, thereby The current value of the PCC reactive power is made close to the expected value of the PCC reactive power, which in turn causes the PCC voltage current value to be close to the PCC voltage expected value. Thereby, the PCC voltage can be stabilized, thereby improving the grid-connected performance of the wind farm.

 When the current value of PCC reactive power is less than the expected value of PCC reactive power, the AVC controller controls the wind turbine to generate reactive power. When the phase of the current of the fan port is ahead of the phase of the voltage, the fan emits reactive power.

 When the current value of the PCC reactive power is greater than the expected value of the PCC reactive power, the AVC controller controls the wind turbine to absorb the reactive power. When the phase of the current of the fan port lags behind the phase of the voltage, the fan absorbs the reactive power.

 In addition, when the reactive power generated or absorbed by each fan is insufficient to change the current value of the PCC reactive power to stabilize the PCC voltage, the AVC controller controls the concentrated reactive power compensation device (such as SVC) set in the wind farm to emit or absorb no The power of the PC makes the current value of the PCC reactive power close to the expected value of the PCC reactive power, so that the current value of the PCC voltage is close to the expected value of the PCC voltage, so that the voltage of the PCC is stabilized, thereby ensuring the stability of the grid connection.

Similarly, when the current value of the PCC reactive power is less than the expected value of the PCC reactive power, the AVC controller controls the fan to emit reactive power. When the current value of the PCC reactive power is greater than the expected value of the PCC reactive power, the AVC controller controls the fan to absorb the reactive power. In the present invention, the electrical main topology integrity of the wind farm is defined as that no operation failure occurs in each component of the wind farm, the entire wind turbine group is in a power generation state or a standby state, the main switch is in a closed state, the wind farm is maintained in a grid-connected state, and the collection is performed. The loop is normal.

 Generally speaking, the main causes of electrical main topology integrity damage of wind farms are: 1) grid-connected transformer failure, low-voltage busbar fault; 2) wind farm loses grid-connected operation state, such as PCC point breaker disconnection; 3) wind power The field loses all wind power collection lines; or 4) The electrical collection circuit of the wind power delivery line or any bus bar is abnormally disconnected. The trigger for any of the above causes of destruction is considered to be a topological integrity breach, at which point the response to the remote command must be stopped.

 Fig. 5 is a view schematically showing a monitoring source (a member marked with an ellipse in the figure) monitored by the monitoring method of the electrical main topology integrity of the present invention. Referring to FIG. 5, the monitoring sources affecting electrical topological integrity include, but are not limited to, a high voltage bus of a wind farm power generation system, a wind power transmission line of a grid connection point, all low voltage bus lines in the wind farm, all grid-connected transformers, and all Collecting line. Among them, all the collector lines are used as a monitoring line source for monitoring, and all the grid-connected transformers are used as a grid-connected transformer monitoring source. That is to say, only when all the collector lines stop working, it is considered that the occurrence of the collector line monitoring source will cause the abnormality of the electrical topological integrity damage, resulting in the destruction of the electrical main topology integrity; similarly, only in all When the grid-connected transformer fails, it is considered that the grid-connected transformer source will cause an abnormality in the electrical topological integrity damage, resulting in the destruction of the electrical main topology integrity.

 FIG. 6 is a flow chart showing a method of monitoring electrical main topology integrity according to an exemplary embodiment of the present invention.

 Referring to Figure 6, in step S610, the AVC controller monitors the status of each of the monitoring sources that affect electrical topology integrity in real time. The AVC controller collects status information of each monitoring source through voltage transformers and current transformers disposed at the respective monitoring sources in the power grid to monitor the status of the respective monitoring sources.

 At step S620, the AVC controller determines whether each of the monitored monitoring sources has an abnormality that would result in electrical topology integrity breach.

According to an exemplary embodiment of the present invention, when the state information collected by the voltage transformer and the current transformer monitors that the current of the wind power transmission line of the grid point is less than a predetermined operating current threshold, and the high voltage bus voltage is lower than a predetermined operation At the voltage threshold, it is determined that an abnormality occurs in the wind power transmission line that will cause electrical topological integrity damage. The predetermined operating current threshold value may be set to 5% to 8% of the rated operating current of the wind power sending line of the grid point, the predetermined operating voltage threshold value. It can be set to 20% of the rated working voltage of the wind power transmission line at the grid point.

 According to another exemplary embodiment of the present invention, when one or more phases of the electrical data collection loop of the wind power transmission line are detected to be disconnected, resulting in the electrical data of the grid connection point being unable to be collected normally, determining that the wind power transmission line occurs will result in electrical Topological integrity is broken.

 In accordance with an exemplary embodiment of the present invention, when a short circuit fault occurs on a high voltage bus or any low voltage bus, it is determined that an abnormality in the high voltage bus or low voltage bus will result in electrical topological integrity damage. Wherein, when one or more phases of the high voltage bus or any low voltage bus electrical data acquisition loop are detected, it is determined that the occurrence of the high voltage bus or the low voltage bus will cause an abnormality in electrical topological integrity damage.

 In accordance with an exemplary embodiment of the present invention, when it is detected that all of the grid-connected transformers have failed, it is determined that the grid-connected transformer has an abnormality that would result in electrical topological integrity damage. Among them, when one or more phases of the electrical data acquisition loop of any grid-connected transformer are detected to be disconnected, the correct power calculation value and the like cannot be obtained, so that the grid-connected transformer is determined to be faulty.

 According to an exemplary embodiment of the present invention, when it is monitored that the current of each collector line is less than a predetermined operating current threshold, and none of the connected fans generate power, all the collector lines are determined as one collector line. Monitoring the occurrence of an anomaly that would result in the destruction of electrical topological integrity. The predetermined operating current threshold may be set to 5% to 8% of the rated operating current of the collector line. If the AVC controller determines in step S620 that any of the monitored monitoring sources has an abnormality that would cause electrical topological integrity to be corrupted, then in step S630, the AVC controller stops executing the electric field scheduling command. The electric field scheduling command may be at least one of a reactive power control command, a grid point voltage control command, and a grid point power factor control command.

 4. Real-time evaluation of total reactive power capability of wind turbines

 Figure 7 shows a flow diagram of a method of estimating reactive power capability of a wind turbine, in accordance with an embodiment of the present invention. This method is performed by the AVC controller.

 At step 701, the AVC controller receives the temperature of the converter of the fan and determines if the temperature of the converter of the fan is normal (e.g., the temperature is too high or too low). It should be understood that the normal operating temperature of the converter is one of its own performance parameters, which may vary depending on the model. The temperature of the converter's converter can be detected by a temperature sensor set in each fan.

 If it is determined in step 701 that the converter's converter temperature is not normal, then in step 702, the AVC controller determines that the fan's reactive power capability is zero.

If it is determined in step 701 that the converter temperature of the fan is normal, then in step 703, the AVC controller Determine the active power and terminal voltage of the fan.

 At step 704, the AVC controller determines the reactive power capability based on the determined active power of the wind turbine and the terminal voltage.

 Specifically, the reactive power capability is determined based on a pre-stored active power and a mapping relationship between the terminal voltage and the reactive power capability.

 8 shows a flow chart of a method of obtaining a mapping relationship between active power and terminal voltage and reactive power capability of a wind turbine, in accordance with an exemplary embodiment of the present invention.

 In step 801, the terminal voltage of the fan is stabilized at a predetermined voltage value;

 At step 802, the active power of the fan is stabilized at a predetermined power value;

 At step 803, the reactive power capability in the event that the converter of the fan is not overcurrent is detected. Specifically, the reactive power output capability and the absorption capability are detected while ensuring the limit current of the converter of the fan, thereby obtaining the reactive power output capability and/or the reactive power absorbing capability indicating the reactive power capability. It should be understood that the reactive power output capability represents the maximum reactive power that the fan can output. The reactive power absorption capacity represents the maximum reactive power that the fan can absorb.

 Step 801 is performed for at least one predetermined voltage value, and step 802 is performed using different active powers for each predetermined voltage, thereby obtaining a mapping relationship between different active powers and reactive power capabilities at at least one predetermined voltage in step 803. .

 Preferably, in the case of the same predetermined voltage value, a mapping relationship between the plurality of active power and the reactive power capability is first obtained, and then the obtained mapping relationship is fitted to obtain the active power and the reactive power capability of the wind turbine. Mapping relationship. The mapping relationship obtained by the above fitting may be an active power-reactive power capability relationship (PQ) curve. At this time, in step 704, the reactive power can be obtained from the PQ curve corresponding to the detected terminal voltage by using the detected active power.

 In another embodiment, the predetermined voltage value described above is a predetermined voltage range. In other words, the terminal voltage of the fan is stabilized in the predetermined voltage range in step 801. This is because it is difficult to stabilize the terminal voltage of the fan at a fixed value, and for the terminal voltage within a certain range, the reactive power capability corresponding to the predetermined active power does not change much, and the influence on the detection result is small. Therefore, the mapping relationship between active power and reactive power capability may be determined not for each terminal voltage but for different terminal voltage ranges (ie, predetermined voltage ranges).

The width of the predetermined range may vary depending on the type of fan or the accuracy required. In one example, the predetermined range of widths may be 1% to 10% of the rated terminal voltage of the fan. Preferably, the predetermined range of width is 5% of the rated terminal voltage of the fan. For example, the predetermined voltage range may be 90%-95%, 95%-105%, 105%-110% of the rated terminal voltage.

 In addition, the above mapping relationship is different for different models of fans. For the different types of fans, the above method based on Figure 3 can be performed to obtain the mapping between the active power and the terminal voltage and reactive power capability of different types of fans. That is, the PQ curves of different types of fans corresponding to different predetermined voltage values or predetermined voltage ranges.

 Figures 9A and 9B show examples of mapping curves (i.e., PQ curves) between the active power and the reactive power capability of the fan at different terminal voltages.

 In Figs. 9A and 9B, the horizontal axis of the graph represents reactive power, and the vertical axis of the graph represents active power. The positive coordinate portion of the horizontal axis represents the reactive power that can be output (i.e., the reactive power output capability), and the negative coordinate portion of the horizontal axis represents the reactive power that can be absorbed (i.e., the reactive power absorption capability).

 As shown in FIG. 9A, the PQ curve 901 indicates a PQ curve when the predetermined voltage range is a percentage range [95%, 105%) of the rated terminal voltage, and the PQ curve 902 indicates that the predetermined voltage range is the rated terminal voltage. The PQ curve for the percentage range [105%, 110%).

 As shown in Fig. 9B, the PQ curve 903 indicates the PQ curve when the above predetermined voltage range is a percentage range [90%, 95%) of the rated terminal voltage.

 It can be determined from the PQ curve shown in FIGS. 9A and 9B that as the predetermined voltage value or the median or endpoint voltage of the predetermined voltage range increases, the PQ curve shifts to the right; with a predetermined voltage value or a median value of the predetermined voltage range or The endpoint voltage is reduced and the PQ curve is shifted to the left. In other words, at the same active power, the larger the median value or the terminal voltage of the predetermined voltage value or the predetermined voltage range, the larger the reactive power output capability and the smaller the reactive power absorption capability.

 Fig. 9C shows an example of determining the reactive power capability based on the PQ curve.

 As shown in Fig. 9C, when the detected active power is P1, the reactive power output capability Q1 and the absorption capacity Q2 can be determined by the PQ curve.

 In another embodiment, step 701 further includes determining if the fan issues an operational alert. If the temperature of the converter of the fan is not normal and/or the fan issues an operational alarm, then at step 702 it is determined that the reactive power capability of the fan is zero.

 In another embodiment, steps 701 and 702 are not included in the method illustrated in FIG.

 In another embodiment, the relationship between at least one of the reactive power output capability and the absorbing capability of the fan and the active power may be obtained.

FIG. 10 illustrates reactive work on a wind power collection line in accordance with an exemplary embodiment of the present invention. A flow chart of the method of estimating the ability. This method is performed by the AVC controller.

 In a wind farm, the fans are divided into groups, and each group of fans forms a wind power collection line. In step 1001, it is confirmed whether the n (i is an initial value of 1) in the fan connected to the wind power collection line N (N is a natural number greater than 0) is in a running state.

 If it is confirmed that the i-th fan is not in operation, then in step 1002, it is determined that the reactive power capability of the i-th fan is zero.

 If it is confirmed that the i-th fan is in operation, in step 1003, it is determined whether the temperature of the converter of the i-th fan is normal.

 If it is determined in step 1003 that the converter temperature of the i-th fan is abnormal, then in step 1004 it is determined that the reactive power capability of the i-th fan is zero.

 If it is determined in step 1003 that the converter temperature of the i-th fan is normal, then in step 1005, the model, active power, and terminal voltage of the i-th fan are determined.

 In step 1006, the reactive power capability of the i-th fan is determined according to the determined model, active power, and terminal voltage of the i-th fan.

 Specifically, the reactive power capability of the i-th fan is determined based on a predetermined model, active power, and a mapping relationship between the terminal voltage and the reactive power capability. For each type of fan in N fans, the mapping between active power and terminal voltage and reactive power capability can be determined according to the method described above based on Figure 3.

 Then, in step 1007, let i=i+l, and determine if i is greater than ^

 If i is not greater than N, then return to step 1001.

 If i is greater than N, then step 1008 is performed.

 At step 908, the reactive power capabilities of the N fans are added to obtain the reactive power capability of the entire wind power collection line.

 It should be understood that when the reactive power capability only indicates the reactive output capability, the reactive output capabilities of the N fans are added; when the reactive power capability only indicates the reactive absorption capability, the N fans are The reactive power absorption capacity is added; when the reactive power capability indicates the reactive power output capability and the reactive power absorption capability, the reactive power output capacities of the N fans are added, and the reactive power absorption capability of the N fans is added. Add together.

 In another embodiment, steps 1003 and 1004 are not included in the method illustrated in Figure 10, but step 1005 is performed when it is determined that the i-th fan is in operation.

In another embodiment, step 1001 further includes determining if the fan issues an operational alert. in case 11 shows a flow chart of a reactive power task assignment method for a wind turbine group in accordance with an embodiment of the present invention. This method is performed by the AVC controller.

 At step 1101, a total reactive power demand for the grid point is determined. The reactive power demand represents the need to absorb reactive power or to output reactive power. The absorption of reactive power or the output of reactive power is usually determined by the sign of the total reactive power demand. A positive total reactive power demand indicates that reactive power needs to be output, and a negative total reactive power demand indicates that reactive power needs to be absorbed. The need to obtain the reactive power of the grid-connected point belongs to the existing technology and will not be described again.

 In step 1102, a reactive power task is assigned to each wind power collection line according to the total reactive power demand of the grid connection point.

 At step 1103, a reactive power task is assigned to each of the wind turbines operating in each of the wind power collection lines based on the reactive power tasks assigned to each of the wind power collection lines.

 Specifically, the reactive power task of a single wind power collection line will be assigned to each of the operating fans (i.e., the wind turbine operating in the wind power collection line) corresponding to the wind power collection line.

Suppose that the reactive power task assigned to a wind power collection line is Q _braMh , and the number of fans operating in the wind power collection line is M, then the reactive power task assigned to the nth fan of the M fans (n) Expressed as equation (1):

 M

Qref ( ⁿ ) = Qb _r£m ch X Qcapacity ( ⁿ )/∑Qcapacity & CD Here, Q. _Apaaty (n) indicates the reactive power capability of the nth fan, Q. _Aparaty (i) indicates the reactive power capability of the i-th fan.

 It should be understood that when the total reactive power demand mode is reactive power output, the reactive power capability of the wind power collecting line is the reactive power output capability of the wind power collecting line, and the reactive power capability of the fan is the reactive power output of the fan. Capacity; When the total reactive power demand is reactive power absorption, the reactive power capability of the wind power collection line is the reactive power absorption capability of the wind power collection line, and the reactive power capability of the fan is the reactive power absorption capability of the fan. .

For example, when the reactive power task is output reactive power (for example, a positive value), the reactive power of the fan in equation (1) is the reactive power output capability of the fan; when the reactive power task is absorbed, When the power is (for example, a negative value), the reactive power of the fan in equation (1) is the reactive power of the fan. Rate absorption capacity. In other words, when the reactive power task is positive, Q. _Aparaty (i) indicates the reactive power output capability of the i-th fan, which is positive; when the reactive power task is negative, Q. _Aparaty (i) indicates the reactive power absorption capacity of the i-th fan, which is negative.

 The absolute value of the reactive power output capability represents the maximum reactive power that can be output. The absolute value of the reactive power absorption capacity represents the maximum reactive power that can be absorbed.

 The reactive power capability of the fan can be determined according to the prior art. The reactive power capability of the fan is its own performance indicator, so the corresponding performance indicators of the fan can be used to determine its reactive power capability.

 Further, in another embodiment of the present invention, a scheme for determining the reactive power capability of a fan in consideration of its operating state is proposed, which overcomes the drawback of the prior art that the reactive power of the fan cannot be accurately estimated. Description will be made later with reference to Fig. 13.

 Figure 1 2 shows a flow chart for assigning reactive power tasks to a wind power collection line in accordance with an embodiment of the present invention.

 In step 1 20 1, the active power of the grid-connected point is detected, and the expected power factor of the grid-connected point is determined according to the detected active power and the total reactive power demand of the grid-connected point.

 It should be understood that, assuming that the active power is P and the total reactive power demand is Q, according to the relationship between active power and reactive power, P/Q=cot Θ, the expected power factor can be expressed as cos Θ .

At step ₁₂₀₂ , the active power P _braMh of the wind power collection line and the reactive power force Qbranch-capacity of the wind power collection line are detected.

The reactive power capability of the operating fan in the wind power collection line obtained by the prior art can be added to obtain the reactive power capability Q _{braMh of the} wind power collecting line. _Apa . _Ity . It should be understood that the addition here refers to adding the reactive power output capability and the reactive power absorption capability respectively, thereby obtaining the reactive power capability Q _braMh —. _aPa . _The reactive power output capability and reactive power absorption capability of the wind power collection line of _ity .

 Further, it is also possible to obtain the reactive power Qbranch-capacity of the wind power collecting line by the method which will be described later with reference to Fig. 16.

In step 1 203, the desired power factor of the grid-connected point determined in step 1200 is used as the desired power factor of the wind power collection line, according to the active power P _{bran of the} wind power collection line. _h and the desired power factor, calculating the desired reactive power of the wind power collection line.

The expected reactive power of the wind power collection line Q _bra∞h . Can be expressed as:

 QbranchO II Pbranch X tg Θ ( 2 )

At step ₁₂₀₄ , the desired reactive power Q _{branEh is determined} . Whether it exceeds the reactive power of the wind power collection line ^ ¹匕J Qbranch— capacity. That is, Q _braMh . Whether it exceeds the reactive power output capability of the wind power collection line

(ie, the maximum reactive power that can be output) or the reactive power absorption capability (ie, the maximum reactive power that can be absorbed).

When it is determined that the reactive power Q _{braMh is desired} . Exceeding the reactive power capability of the wind power collection line Q _braMh — _∞Pa . _{i ty} , in step 1 205, the reactive power capability Q _{bran of the} wind power collection line. _{h MPa} . _{The ity is the} reactive power task Q _braMh allocated by the wind power collection line.

It should be understood when Q _braMh . When the reactive power output task exceeds the reactive power output capability of the wind power collection line, the reactive power output capability of the wind power collecting line is determined as the reactive power task Q _braMh of the wind power collecting line. At this time, the reactive power task Q _bran . The sign of _h is positive, indicating the output of reactive power.

When Q _bran . _h . When the reactive power absorption task exceeds the reactive power absorption capability of the wind power collection line, the reactive power absorption capability of the wind power collection line is determined as the reactive power task Q _bran of the wind power collection line. _h . At this time, the sign of the reactive power task Q _braMh is negative, indicating that the reactive power is absorbed.

When it is determined that the reactive power Q _{braMh is desired} . There is no reactive power capability Q _bran beyond the wind power collection line. _h . _Apa . _{At ity} , at step ₁₂₀₆ , the reactive power Q _braMh will be expected. Reactive power task as wind power collection line Q branch o

 According to the above scheme for allocating reactive power tasks to the wind power collection line, there may be cases where the total reactive power demand of the grid connection point cannot be fully satisfied. In this case, the remaining reactive power task AVC system will be assigned to the wind farm centralized reactive power compensation device (eg SVC).

 Figure 13 shows a flow diagram of a method of estimating the reactive power capability of a wind turbine, in accordance with an embodiment of the present invention.

 In step 1 30 1, the temperature of the converter of the fan is detected and it is determined whether the temperature of the converter of the fan is normal (for example, the temperature is too high or too low). It should be understood that the normal operating temperature of the converter is one of its own performance parameters and may vary depending on the model.

 If it is determined in step 1 30 1 that the converter temperature of the fan is not normal, then in step 1 302 it is determined that the reactive power capability of the fan is zero.

 If it is determined in step 1 30 1 that the converter temperature of the fan is normal, then in step 1 303, the active power and the terminal voltage of the wind turbine are detected.

 At step 1304, reactive power capability is determined based on the detected active power of the fan and the terminal voltage.

Specifically, based on pre-stored active power and between the terminal voltage and the reactive power capability Mapping relationships to determine reactive power capabilities.

 In another embodiment, steps 1301 and 1302 may be omitted.

 Figure 14 is a flow chart showing a method of obtaining a mapping relationship between active power of a wind turbine and a terminal voltage and reactive power capability, in accordance with an exemplary embodiment of the present invention.

 In step 1401, the terminal voltage of the fan is stabilized at a predetermined voltage value;

 At step 1402, the active power of the fan is stabilized at a predetermined power value;

 At step 1403, the reactive power capability in the event that the converter of the fan is not overcurrent is detected. Specifically, the reactive power output capability and the absorption capability are detected while ensuring the limit current of the converter of the fan, thereby obtaining the reactive power output capability and/or the reactive power absorbing capability indicating the reactive power capability.

 Step 1401 is performed for at least one predetermined voltage value, and step 1402 is performed using different active powers for each predetermined voltage, thereby obtaining at step 1403 between at least one at each predetermined voltage, different active power and reactive power capabilities. Mapping relationship.

 Preferably, in the case of the same predetermined voltage value, a mapping relationship between the plurality of active power and the reactive power capability is first obtained, and then the obtained mapping relationship is fitted to obtain the active power and the reactive power capability of the wind turbine. Mapping relationship. The mapping relationship obtained by the above fitting may be an active power-reactive power capability relationship (PQ) curve. At this time, in step 504, the reactive power capability can be obtained from the PQ curve corresponding to the detected terminal voltage by using the detected active power.

 In another embodiment, the predetermined voltage value described above is a predetermined voltage range. In other words, the terminal voltage of the fan is stabilized in a predetermined voltage range in step 1401. This is because it is difficult to stabilize the terminal voltage of the fan at a fixed value, and for the terminal voltage within a certain range, the reactive power capability corresponding to the predetermined active power does not change much, and the influence on the detection result is small. Therefore, the mapping relationship between active power and reactive power capability may be determined not for each terminal voltage but for different terminal voltage ranges (ie, predetermined voltage ranges).

 The width of the predetermined range may vary depending on the type of fan or the accuracy required. In one example, the predetermined range of widths may be 1% to 10% of the rated terminal voltage of the fan. Preferably, the predetermined range of width is 5% of the rated terminal voltage of the fan.

 For example, the predetermined voltage range may be 90%-95%, 95%-105%, 105%-110% of the rated terminal voltage.

In addition, the above mapping relationship is different for different models of fans. The above described method based on Figure 14 can be performed for different types of fans to obtain the active power of different types of fans. And the mapping relationship between the terminal voltage and the reactive power capability. That is, PQ curves of different types of fans corresponding to different predetermined voltage values or predetermined voltage ranges.

 15A and 15B show an example of a mapping relationship between the active power and the reactive power capability of the fan at the terminal voltage (i.e., the PQ curve).

 As shown in Fig. 15, the horizontal axis of the graph represents reactive power, and the vertical axis of the graph represents active power. The positive coordinate portion of the horizontal axis represents the reactive power that can be output (i.e., the reactive power output capability), and the negative coordinate portion of the horizontal axis represents the reactive power that can be absorbed (i.e., the reactive power absorption capability).

 As shown in FIG. 15A, the PQ curve 1501 represents a PQ curve when the predetermined voltage range is a percentage range [95%, 105%) of the rated terminal voltage, and the PQ curve 402 indicates that the predetermined voltage range is the rated terminal voltage. PQ curve for percentage range [105%, 110%).

 As shown in Fig. 15B, the PQ curve 1503 represents the PQ curve when the above predetermined voltage range is a percentage range [90%, 95%) of the rated terminal voltage.

 It can be determined from the PQ curve shown in FIGS. 15A and 15B that as the predetermined voltage value or the median or endpoint voltage of the predetermined voltage range increases, the PQ curve shifts to the right; with a predetermined voltage value or a median value of the predetermined voltage range or The endpoint voltage is reduced and the PQ curve is shifted to the left. In other words, at the same active power, the larger the median value or the terminal voltage of the predetermined voltage value or the predetermined voltage range, the larger the reactive power output capability and the smaller the reactive power absorption capability.

 Fig. 15C shows an example of determining the reactive power capability based on the PQ curve.

 As shown in Fig. 15C, when the detected active power is P1, the reactive power output capability Q1 and the absorption capacity Q2 can be determined by the PQ curve.

 Optionally, in step 1401, it is further included determining whether the fan issues an operational alarm. If the temperature of the converter of the fan is not normal and/or the fan issues an operational alarm, then at step 1402 it is determined that the reactive power capability of the fan is zero.

 Alternatively, at least one of the reactive power output capability and the absorption capability of the fan may be obtained in relation to the active power.

 Figure 16 shows a flow chart of a method for estimating the reactive power capability of a wind power gathering line based on the method of Figure 13 in accordance with an exemplary embodiment of the present invention.

 In step 1601, it is detected whether the n (i is an initial value of 1) of the N (N is a natural number greater than 0) connected to the wind power collection line is in a running state.

If it is determined that the i-th fan is in a non-operating state, then in step 1602, it is determined that the reactive power capability of the i-th fan is zero. If it is determined that the i-th fan is in an operating state, then in step 1603, it is determined whether the temperature of the converter of the i-th fan is normal.

 If it is determined in step 1603 that the converter temperature of the i-th fan is abnormal, then in step 1604 it is determined that the reactive power capability of the i-th fan is zero.

 If it is determined in step 1603 that the converter temperature of the i-th fan is normal, then in step 1605, the model, active power, and terminal voltage of the i-th fan are detected.

 In step 1606, the reactive power capability of the i-th fan is determined according to the detected type, the active power, and the terminal voltage of the i-th fan.

 Specifically, the reactive power capability of the i-th fan is determined based on a predetermined model, active power, and a mapping relationship between the terminal voltage and the reactive power capability. For each of the N fans, the mapping between active power and terminal voltage and reactive power capability can be determined according to the method described above based on Figure 14.

 Then, in step 1607, let i=i+l, and determine if i is greater than ^

 If i is not greater than N, then return to step 1601.

 If i is greater than N, then step 1608 is performed.

 At step 1608, the reactive power capabilities of the N fans are added to obtain the reactive power capability of the entire wind power collection line.

 It should be understood that adding the reactive power capabilities of the N fans includes: adding reactive power absorption capabilities of the N fans; and adding reactive power absorption capabilities of the N fans.

 In another embodiment, steps 1603 and 1604 are not included in the method illustrated in Figure 16, but step 1605 is performed when it is determined that the i-th fan is in an operational state.

 In another embodiment, step 1601 further includes determining if the fan issues an operational alert. If the temperature of the converter of the fan is not normal and/or the fan issues an operational alarm, then at step 1602 it is determined that the reactive power capability of the fan is zero.

 6, AVC system security lock and security protection

 The AVC system safety lockout refers to the wind farm. The AVC system no longer controls the fan in the wind farm to emit or absorb reactive power. The gP, AVC controller gives up control of the reactive power or the reactive power of the fan. Safety lockouts include general lockouts and disturbance lockouts.

General latching is mainly caused by incomplete wind farm topology and AVC system hardware and software anomalies. Incomplete wind farm topology means that the main topology loses all the collection lines, loses electrical connection with the grid, transformer faults, high voltage bus or low voltage bus faults or data acquisition loop anomalies. AVC system hardware and software Exceptions include communication failures, hardware impairments, software initialization failures, and more.

 Disturbance blocking means that when the power grid is affected by large disturbances, there will be severe electrical fluctuations. At this time, the wind farm should cooperate with the grid relay protection and the fan low voltage crossing function. Therefore, the AVC system needs to perform safety blocking. On the other hand, after the promulgation of the high voltage ride through standard, the wind farm also needs to cooperate with the high voltage ride-through function of the wind turbine, so the AVC system also needs to perform safety lockout. The above disturbances are mainly caused by the following transient processes: (1) various short-circuit faults; (2) fault-free tripping of the line; (3) near-electrical distance 甩 load, output force, etc.

 AVC system security protection refers to the limit of the response process of the AVC system. The purpose is to ensure the stable operation of the grid and fans. According to an embodiment of the present invention, the following constraints can be imposed on the AVC system: (1) the grid point voltage limit constraint; (2) the grid point power factor limit constraint; (3) the aggregate line voltage limit constraint; (4) collection The line power factor exceeds the limit and so on.

 7. Grid-connected transient stability control

 The grid-connected transient stability control includes control when the voltage suddenly drops under fault and control when the voltage suddenly rises under fault.

 When the voltage suddenly drops under the fault, the fan will quickly perform the low voltage ride through process. At this point, the wind turbine will emit a large amount of reactive power and a small amount of active power. Therefore, when the wind farm AVC system detects the occurrence of a fault, the wind farm AVC system will temporarily block the control command to the wind turbine and transfer control to the wind turbine. At this time, the fan performs the transient control of the preset logic by itself. When the wind farm AVC system detects the end of the low pressure ride through process, the wind farm AVC system regains control of the wind turbine. According to an embodiment of the present invention, the AVC system can take the same discriminating method as the fan discriminates the low-voltage traverse to detect the occurrence of the fault. Since the discriminating method for discriminating low-voltage traverse by the wind turbine is well known to those skilled in the art, detailed description will not be given here. However, the present invention is not limited thereto, and the AVC system can use various existing methods to detect the occurrence of a failure.

 When the voltage suddenly rises under fault, it is often the result of a sudden reactive power load, which will lead to excess reactive power. At this point, the wind farm AVC system will control the fan to absorb a large amount of reactive power.

 17 is a flow chart showing a method of improving grid-connected transient stability in a wind farm AVC system in accordance with an embodiment of the present invention.

Referring to FIG. 17, at operation 1701, the AVC controller determines whether the PCC point voltage suddenly drops. The AVC controller can determine whether the PCC point voltage suddenly drops based on the voltage data provided by the voltage transformer set on the wind power supply line. However, alternatively, the AVC controller can also be set to high according to The voltage data provided by the voltage transformer on the voltage bus or low voltage bus determines whether the PCC point voltage suddenly drops. In particular, when the PCC point voltage drop rate of change is high and the PCC point voltage drops below a first threshold, the AVC controller can determine that the PCC point voltage suddenly drops. For example, when the PCC point voltage drop rate of change is higher than 0.7 times the rated voltage/second, and the PCC point voltage is lower than 0.8 times the rated voltage, the AVC controller can determine that the PCC point voltage suddenly drops. However, the present invention is not limited thereto, and the rate of change in voltage drop and the first threshold may be arbitrarily set by those skilled in the art according to actual needs.

 When the AVC controller determines that the PCC point voltage has suddenly decreased, at operation 1702, the AVC controller locks the control of the wind farm by the wind farm AVC system after waiting for a predetermined time (e.g., but not limited to, 20 milliseconds). That is to say, the AVC controller gives up control of the reactive power or the reactive power of the fan in the wind farm. In this way, the AVC system can be used with low-voltage traversal that occurs in fans in wind farms.

 Subsequently, at operation 1703, if the AVC controller determines that the SVC is absorbing reactive power based on the voltage data and circuit data provided by the voltage transformer and the current transformer disposed on the SVC line, the AVC controller issues a control command to cause the SVC Stop absorbing reactive power. On the other hand, if the AVC controller determines that the SVC is making a reactive power, the AVC controller does not have any control over the SVC.

 At operation 1704, the AVC controller determines if the PCC point voltage rises above a second threshold (e.g., greater than 0.9 times the rated voltage) for a predetermined time (e.g., but not limited to, 5 seconds) after a sudden drop in occurrence. When the AVC controller determines that the PCC point voltage rises above the second threshold for a predetermined time, at operation 1705, the AVC controller resumes control of the wind farm by the wind farm AVC system. That is to say, the AVC controller is open to control whether the fan in the wind farm emits reactive power or absorbs reactive power, thereby controlling the corresponding fan to emit reactive power or absorb reactive power according to the operation of the wind farm.

 On the other hand, when the AVC controller determines that the PCC point voltage has not risen above the second threshold for a predetermined time, at operation 1706, the AVC controller waits for a predetermined time (eg, but not limited to, 8-10 seconds) The AVC controller restores control of the wind farm. Here, the predetermined time is calculated from the time when the PCC point voltage suddenly decreases.

 18 is a flow chart showing a method of improving grid-connected transient stability in a wind farm AVC system in accordance with another embodiment of the present invention.

Referring to FIG. 18, at operation 1801, the AVC controller determines whether the PCC point voltage suddenly rises. The AVC controller can determine whether the PCC point voltage suddenly rises based on the voltage data provided by the voltage transformer set on the wind power supply line. Alternatively, however, the AVC controller can also determine whether the PCC point voltage is sudden or not based on the voltage data provided by the voltage transformer set on the high voltage bus or the low voltage bus. Rise. Specifically, when the PCC point voltage rise rate of change is high and the PCC point voltage rises above the third threshold, the AVC controller can determine that the PCC point voltage suddenly rises. For example, when the PCC point voltage rise rate of change is higher than 0.5 times the rated voltage/second, and the PCC point voltage is higher than 1.1 times the rated voltage, the AVC controller can determine that the PCC point voltage suddenly rises. However, the present invention is not limited thereto, and the rate of change in voltage rise and the third threshold may be arbitrarily set by those skilled in the art according to actual needs.

 When the AVC controller determines that the PCC point voltage suddenly rises, after the AVC controller waits for the first predetermined time (eg, but not limited to, 20 milliseconds) at operation 1802, the AVC controller issues a command to each of the fan master systems, reducing Reactive power from each fan. Specifically, the AVC controller can issue commands so that all fans no longer emit reactive power. Thereafter, at operation 1803, if the AVC controller determines that the SVC is emitting reactive power based on the voltage data and circuit data provided by the voltage transformer and the current transformer disposed on the SVC line, the AVC controller issues a control command to cause the SVC Stop sending reactive power. Next, at operation 1804, after the AVC controller waits for a second predetermined time (e.g., but not limited to 5 seconds), the AVC controller restores control of the reactive power of the wind farm by the wind farm AVC system. That is to say, the AVC controller restores the control of the reactive power or the reactive power of the fan in the wind farm, thereby controlling the corresponding fan to emit reactive power or absorb reactive power according to the operation of the wind farm. Here, the second predetermined time is calculated from the moment when the PCC point voltage suddenly rises.

 The method of maintaining the transient stability of the grid-connected wind farm when the PCC point voltage suddenly drops or suddenly rises is described above with reference to Figs. 17 and 18. However, the method of Fig. 18 may be performed after operation 1701 of Fig. 17, in accordance with an embodiment of the present invention. For example, when the AVC controller determines that the PCC point voltage has not suddenly decreased, operation 1801 and subsequent operations may be performed. Alternatively, the method of Figure 17 can be performed after operation 1801 of Figure 18. For example, when the AVC controller determines that the PCC point voltage has not risen abruptly, operation 1701 and subsequent operations may be performed. On the other hand, the AVC controller may repeatedly perform operations 1701 and 1801 (the order of performing operations 1701 and 1801 is not limited) until it is detected that the PCC point voltage suddenly drops or suddenly rises, and then operations 1702 to 1706 or operation 1802 are performed. To 1804.

 Several example operations of the wind farm AVC system according to an embodiment of the present invention have been described above, but the present invention is not limited thereto. The wind farm AVC system according to an embodiment of the present invention can perform various other control operations on the wind farm, for example, wind farm data synchronization and the like.

As described above, by constructing the wind farm AVC system according to the embodiment of the present invention, the ability of the fan to additionally generate reactive power can be fully released, and the construction investment and operation loss of the SVC can be reduced to reach the fan. The combination of reactive power and SVC to generate reactive power, and more stable and accurate voltage stability control of the wind farm PCC point.

 Although a few embodiments have been shown and described, it will be understood by those skilled in the art limited.

Claims

1. A wind farm dynamic voltage automatic control (AVC) system, including: AVC controller, multiple wind turbine main control systems set on multiple wind turbines in the wind farm, static reactive power compensation device (SVC), multiple voltage transformers and current transformers installed on wind power transmission lines, wind power collection lines, SVC lines, high-voltage busbars and low-voltage busbars, Among them, each wind power collection line is connected to multiple wind turbines, receives the output of multiple wind turbines, and is connected to the low-voltage bus. The AVC controller communicates with each wind turbine main control system through the optical fiber network, and is electrically connected to the multiple voltage mutual inductors. transformers and current transformers, Among them, the AVC controller compares the voltage provided by the voltage transformer set on the wind power transmission line with the target voltage of the wind farm, and determines the total value of reactive power that the wind farm needs to emit or absorb based on the voltage difference; The voltage data and current data provided by the voltage transformer and current transformer installed on each wind power collection line determine the total value of reactive power that each wind power collection line can emit or absorb; according to the voltage data and current data provided by the wind turbine main control system The current data determines the reactive power that the corresponding wind turbine can emit or absorb, and the control signal corresponding to the reactive power that each wind turbine needs to emit or absorb is sent to the corresponding wind turbine main control system. 2. The wind farm dynamic voltage automatic control system according to claim 1, wherein when the reactive power emitted or absorbed by each wind turbine is insufficient to increase or decrease the actual voltage of the grid connection point to the target value, the AVC controller controls the SVC Put into operation to generate or absorb reactive power, thereby further increasing or reducing the voltage at the grid connection point. 3. The wind farm dynamic voltage automatic control system according to claim 1, further comprising: an AVC master station for performing remote control, the AVC master station is set at any location away from the wind farm, and communicates through wired or wireless way to communicate with the AVC controller and remotely control the AVC controller. 4. The wind farm dynamic voltage automatic control system according to claim 1, wherein the AVC controller calculates the actual measured voltage on the wind power transmission line based on the voltage and current provided by the voltage transformer and current transformer provided on the wind power transmission line. For reactive power, compare the measured reactive power with the target reactive power of the wind farm, and determine the total amount of reactive power that the wind farm needs to emit or absorb based on the difference between the measured reactive power and the target reactive power of the wind farm. value. 5. The wind farm dynamic voltage automatic control system according to claim 1, wherein the AVC controller calculates the measured power factor based on the voltage and current provided by the voltage transformer and current transformer provided on the wind power transmission line, and converts the measured power The factor is compared with the target power factor, based on the actual measurement The difference between the power factor and the target power factor determines the total amount of reactive power that the wind farm is required to emit or absorb. 6. The wind farm dynamic voltage automatic control system according to claim 1, wherein the AVC controller performs the following operations: Detect the current value of the voltage at the grid connection point; Compare the current value of the grid-connection point voltage with the expected value of the grid-connection point voltage, and determine whether the current value of the grid-connection point voltage deviates from the expected value of the grid-connection point voltage by more than a first predetermined threshold; If the current value of the grid connection point voltage deviates from the expected value of the grid connection point voltage by more than the first predetermined threshold, the current value of the system impedance of the grid connection point is calculated based on the voltage and current measured at the grid connection point; Compare the current value of the grid-connection point system impedance with the previous value of the grid-connection point system impedance, and determine whether the current value of the grid-connection point system impedance deviates from the previous value of the grid-connection point system impedance by more than a second predetermined threshold; If the current value of the grid-connection point system impedance deviates from the previous value of the grid-connection point system impedance by more than the second predetermined threshold, the current value of the grid-connection point system impedance is used to update the previous value of the grid-connection point system impedance to correct the grid-connection point system impedance. 7. The wind farm dynamic voltage automatic control system according to claim 1, wherein the AVC controller performs the following operations: Real-time monitoring of the status of various monitoring sources that affect the integrity of the electrical topology; If it is determined that any of the monitored monitoring sources has an abnormality that will cause the integrity of the electrical topology to be destroyed, the execution of the power grid dispatching instructions will be stopped. 8. The wind farm dynamic voltage automatic control system according to claim 1, wherein the AVC controller performs the following operations: Determine the active power and terminal voltage of the wind turbine; The reactive power capability is determined based on the determined active power and machine terminal voltage. 9. The wind farm dynamic voltage automatic control system according to claim 1, wherein the AVC controller performs the following operations: (a) Confirm whether the i-th wind turbine among the N wind turbines in the wind power collection line is in operation, where N is a natural number greater than 0, and the initial value of i is 1; (b) If it is confirmed that the i-th wind turbine is in a non-operational state, then it is determined that the reactive power capacity of the i-th wind turbine is zero; (c) If it is confirmed that the i-th wind turbine is in operation, determine the model, active power and terminal voltage of the i-th wind turbine; (d) Determine the reactive power capacity of the i-th wind turbine based on the determined model, active power and terminal voltage of the i-th wind turbine; (e) Make i=i+l, and determine whether i is greater than N; (f) If i is not greater than N, return to step (a); (g) If i is greater than N, add the determined reactive power capabilities of the N turbines. 10. The wind farm dynamic voltage automatic control system according to claim 1, wherein the AVC controller performs the following operations: Determine the total reactive power requirement at the grid connection point; According to the total reactive power demand of the grid connection point and the reactive power capacity of each wind power collection line, allocate reactive power tasks to each wind power collection line; According to the reactive power task of each wind power collection line and the reactive power capacity of each operating wind turbine in each wind power collection line, reactive power is allocated to each operating wind turbine in each wind power collection line. power tasks. 11. The wind farm dynamic voltage automatic control system according to claim 1, wherein the AVC controller performs the following operations: Determine whether the voltage at the PCC point of the wind farm connected to the grid suddenly drops; When it is determined that the PCC point voltage suddenly drops, after waiting for the first predetermined time, the control of the wind farm AVC system on the wind farm is blocked; When it is determined that the SVC is absorbing reactive power, issue a control command to stop the SVC from absorbing reactive power; Determining whether the PCC point voltage rises above a specified threshold within a second predetermined time after the sudden decrease occurs; When it is determined that the PCC point voltage rises above the specific threshold within the second predetermined time, the control of the wind farm by the wind farm AVC system is restored. 12. The wind farm dynamic voltage automatic control system according to claim 1, wherein the AVC controller performs the following operations: Determine whether the voltage at the PCC point of the wind farm connected to the grid suddenly rises; When it is determined that the PCC point voltage suddenly rises, after waiting for the first predetermined time, a command is issued to each wind turbine main control system to stop each wind turbine from emitting reactive power; When it is determined that the SVC is emitting reactive power, issue a control command to cause the SVC to stop emitting reactive power; After waiting for the second predetermined time, the reactive power control of the wind farm by the wind farm AVC system is restored.