CN106356874A - Synchronous oscillation inhibiting method of wind turbine generator and inhibiting system - Google Patents

Abstract

The invention discloses a synchronous oscillation inhibiting method of a wind turbine generator and an inhibiting system. The synchronous oscillation inhibiting method is realized on the basis of a wind power converter; a secondary synchronous oscillation inhibitor based on a secondary synchronous locking phase is added in an original power generation control; a damping component is generated by means of a synchronous coordinate system, and acted on a DQ axis current closed loop; current is dynamically adjusted, electric damping of the unit is enhanced, and thereby happening of secondary synchronous oscillation is inhibited. According to the method, the secondary synchronous oscillation signal is extracted from the electrical quantities, and the method can be adapted to the oscillation frequency and is strong in project practicability.

Description

A wind turbine subsynchronous oscillation suppression method and suppression system

technical field

The invention belongs to the field of new energy power generation, and in particular relates to a subsynchronous oscillation suppression method and suppression system of a wind turbine.

Background technique

With the gradual expansion of wind power grid-connected capacity, its impact on the grid is also gradually emerging. In recent years, subsynchronous oscillations of regional power grids involving wind turbines have occurred in many regions, causing large-scale wind turbines to go off-grid, and even triggering the action of subsynchronous protection devices for adjacent thermal power units, causing thermal power units to shut down. In order to avoid subsynchronous oscillation from threatening the security of power grid, necessary measures should be taken to suppress the occurrence of subsynchronous oscillation.

The research on wind power's participation in subsynchronous oscillation is still in its infancy. At present, the suppression measures proposed by relevant scholars are mostly from the perspective of the power grid, such as installing FACTS devices near wind farms, which will increase additional costs and make engineering parameter debugging difficult. Some scholars have also begun to pay attention to the suppression method on the fan side. Referring to the experience of thermal power units, they proposed to increase the damping control with the feedback of the speed deviation signal. However, there are still two difficulties in the engineering application of this method: 1. The speed deviation of the current fan The detection accuracy is too low to meet the control requirements; 2. The control method is based on the known subsynchronous oscillation frequency. However, the current subsynchronous oscillation involving wind power shows that the oscillation frequency changes with the operating conditions, and it is difficult to predict the oscillation frequency.

Therefore, a new technical solution is needed to solve the above problems.

Contents of the invention

The object of the present invention is to provide a subsynchronous oscillation suppression method and suppression system suitable for wind turbines. The subsynchronous oscillation of the wind turbine can be effectively suppressed without adding hardware equipment, and it is easy to implement in engineering.

In order to achieve the purpose of the above invention, the subsynchronous oscillation suppression method for wind turbines in the present invention can adopt the following technical solutions:

A method for suppressing subsynchronous oscillation of a wind turbine, comprising the following steps:

(1), input the current DQ axis component into the subsynchronous oscillation suppressor;

(2), the DQ axis component is filtered in the subsynchronous oscillation suppressor;

(3) In the subsynchronous oscillation suppressor, the DQ axis components I_SSD and I_SSQ under the subsynchronous coordinates are obtained through Park transformation, wherein, I_SSD is the component of the D axis subsynchronous oscillation frequency, and I_SSQ is the component of the Q axis subsynchronous oscillation frequency ; Pass I_SSQ through the PI regulator to obtain the sub-synchronous angular velocity ω_SSO, and integrate the sub-synchronous angular velocity ω_SSO to obtain the sub-synchronous angle θ_SSO;

(4), in the subsynchronous oscillation suppressor, the input subsynchronous angle θ_SSO and the compensation angle Adding to get the angle for inverse Park transformation is where the compensation angle It is used to compensate the phase deviation generated by sampling filtering and other processes;

(5) According to the inverse Park transformation angle θ'_SSO, the DQ axis components I_SSD and I_SSQ in the subsynchronous coordinates are transformed into the synchronous coordinate system, and the subsynchronous current DQ axis damping quantities I_SD and I_SQ are obtained after limiting, where I_SD is D-axis damping amount, I_SQ is Q-axis damping amount;

(6), DQ axis damping I_SD and I_SQ and the original DQ axis current set value are superimposed as the current loop setting; I_SD forms a closed-loop feedback control for I_SSD, and produces a damping effect to suppress the D-axis sub-synchronous oscillation; I_SQ controls I_SSQ It forms a closed-loop feedback control and produces a damping effect to suppress the Q-axis subsynchronous oscillation.

In order to achieve the purpose of the above invention, the wind turbine subsynchronous oscillation suppression system of the present invention can adopt the following technical solutions:

A wind turbine subsynchronous oscillation suppression system, comprising:

Subsynchronous oscillation suppressor; the current DQ axis component is input into the subsynchronous oscillation suppressor, and the DQ axis component is filtered in the subsynchronous oscillation suppressor; and the DQ axis under the subsynchronous coordinates is obtained through Park transformation in the subsynchronous oscillation suppressor Components I_SSD and I_SSQ, where I_SSD is the component of the D-axis subsynchronous oscillation frequency, and I_SSQ is the component of the Q-axis subsynchronous oscillation frequency;

PI regulator, I_SSQ obtains the sub-synchronous angular velocity ω_SSO through the PI regulator, and obtains the sub-synchronous angle θ_SSO after integrating the sub-synchronous angular velocity ω_SSO;

A compensating device for combining the input subsynchronous angle θ_SSO with the compensating angle in the subsynchronous oscillation suppressor Adding to get the angle for inverse Park transformation is where the compensation angle It is used to compensate the phase deviation generated by sampling filtering and other processes;

The damping amount generating device is used to transform the DQ axis components I_SSD and I_SSQ in the sub-synchronous coordinates to the synchronous coordinate system according to the inverse Park transformation angle θ'_SSO, and obtain the sub-synchronous current DQ axis damping amounts I_SD and I_SQ after clipping, Among them, I_SD is the D-axis damping amount, and I_SQ is the Q-axis damping amount;

The suppression device is used to superimpose the DQ-axis damping amount I_SD and I_SQ and the original DQ-axis current given value as the current loop setting; I_SD forms a closed-loop feedback control for I_SSD and produces a damping effect to suppress the D-axis sub-synchronous oscillation; I_SQ A closed-loop feedback control is formed for I_SSQ, and a damping effect is produced to suppress the subsynchronous oscillation of the Q axis.

The beneficial effects of the present invention are:

1. The suppression of subsynchronous oscillation is achieved by changing the control strategy of the fan, without adding additional costs;

2. To adapt to the characteristic that the measurement accuracy of the electrical signal of the existing fan is greater than that of the rotational speed signal, the sub-synchronous oscillation information is extracted from the electrical signal, with higher accuracy and better suppression effect;

3. Self-adaptive to the subsynchronous oscillation frequency, there is no need to predict the subsynchronous oscillation frequency, and it is not necessary to apply complex algorithms such as Fourier analysis to extract the subsynchronous oscillation frequency in real time, reducing the difficulty of engineering implementation.

Description of drawings

Fig. 1 is a control block diagram of the doubly-fed unit rotor side after subsynchronous oscillation suppression is added in Embodiment 1 of the present invention.

FIG. 2 is a schematic diagram of a subsynchronous oscillation suppressor used in the present invention.

FIG. 3 is a schematic diagram of the secondary genlock phase-locked loop used in the present invention.

Fig. 4 is a simulation waveform diagram of the application effect of the subsynchronous oscillation suppressor in the doubly-fed wind turbine in the first embodiment of the present invention.

detailed description

Below in conjunction with accompanying drawing and specific embodiment, further illustrate the present invention, should be understood that these embodiments are only for illustrating the present invention and are not intended to limit the scope of the present invention, after having read the present invention, those skilled in the art will understand various aspects of the present invention Modifications in equivalent forms all fall within the scope defined by the appended claims of this application.

The invention discloses a subsynchronous oscillation suppression method and suppression system for wind turbines based on subsynchronous phase-locking. The suppressor SSOI acts on the D-axis current closed-loop and Q-axis current closed-loop respectively, and at the same time dynamically adjusts the DQ-axis current to enhance the electrical damping of the unit, thereby suppressing the occurrence of subsynchronous oscillation.

Specifically, the suppression method includes the following steps:

(1) A subsynchronous oscillation suppressor is provided, and the DQ axis component of the current is input into the subsynchronous oscillation suppressor.

(2) The DQ axis component is filtered in the subsynchronous oscillation suppressor; the filter is a high-pass filter with a cut-off frequency set at 2-5 Hz to filter out the DC component. For the cutoff frequency of 2Hz, the transfer function of the filter is G(s)=s/(s+12.57); for the cutoff frequency of 5Hz, the transfer function of the filter is G(s)=s/(s+31.42).

(3), in the subsynchronous oscillation suppressor, the DQ axis components I_SSD and I_SSQ under the subsynchronous coordinates are obtained through Park transformation, wherein, I_SSD is the D axis component, and I_SSQ is the Q axis component; the I_SSQ is obtained through the PI regulator to obtain the subsynchronization Angular velocity ω_SSO, that is, ω_SSO=(Kp+Ki/s)*I_SSQ, where Kp is a proportional coefficient whose size affects the tracking speed, Ki is an integral coefficient whose size affects overshoot and adjustment time, and these two coefficients are based on engineering applications To determine the specific requirements, 1/s is the frequency domain expression of the integral. After integrating the sub-synchronous angular velocity ω_SSO, the sub-synchronous angle θ_SSO is obtained, that is, θ_SSO=(1/s)*ω_SSO, where 1/s is the frequency domain expression of the integration.

(4), in the subsynchronous oscillation suppressor, the input subsynchronous angle θ_SSO and the compensation angle Add to get the angle for inverse Park transformation where the compensation angle It is used to compensate the phase deviation generated by the process of sampling and filtering. For example, the phase deviation generated by the hardware sampling and filtering circuit can be measured by a signal generator and an oscilloscope.

(5) According to the inverse Park transformation angle θ'_SSO, the DQ axis components I_SSD and I_SSQ in the subsynchronous coordinates are transformed into the synchronous coordinate system, and the subsynchronous current DQ axis damping quantities I_SD and I_SQ are obtained after limiting, where I_SD is D-axis damping amount, I_SQ is Q-axis damping amount. In this embodiment, the calculation method of the limit is: if I_SD>Max, then set I_SD=Max; if I_SD<Min, then set I_SD=Min; otherwise, I_SD remains unchanged, and Max and Min are the upper limit of the limit Limit value and lower limit value are the same for I_SQ.

(6) The DQ axis damping value I_SD and I_SQ and the original DQ axis current setting value are superimposed as the current loop setting.

Corresponding to the above suppression method, the wind turbine subsynchronous oscillation suppression system provided by the present invention includes:

Subsynchronous oscillation suppressor; the current DQ axis component is input into the subsynchronous oscillation suppressor, and the DQ axis component is filtered in the subsynchronous oscillation suppressor; and the DQ axis under the subsynchronous coordinates is obtained through Park transformation in the subsynchronous oscillation suppressor Components I_SSD and I_SSQ, where I_SSD is the component of the D-axis subsynchronous oscillation frequency, and I_SSQ is the component of the Q-axis subsynchronous oscillation frequency; among them, the filtering in the subsynchronous oscillation suppressor is a high-pass filter, and the cut-off frequency of the high-pass filter is set to 2 ~5Hz, used to filter out the DC component;

PI regulator, I_SSQ obtains the sub-synchronous angular velocity ω_SSO through the PI regulator, and the sub-synchronous angular velocity ω_SSO is integrated to obtain the sub-synchronous angle θ_SSO; that is, ω_SSO=(Kp+Ki/s)*I_SSQ, where Kp is the proportional coefficient and Ki is the integral Coefficient, 1/s is the frequency domain expression of the integral. θ_SSO=(1/s)*ω_SSO, where 1/s is the frequency domain expression of the integral;

A compensating device for combining the input subsynchronous angle θ_SSO with the compensating angle in the subsynchronous oscillation suppressor Adding to get the angle for inverse Park transformation is where the compensation angle It is used to compensate the phase deviation generated by sampling filtering and other processes;

The damping amount generating device is used to transform the DQ axis components I_SSD and I_SSQ in the sub-synchronous coordinates to the synchronous coordinate system according to the inverse Park transformation angle θ'_SSO, and obtain the sub-synchronous current DQ axis damping amounts I_SD and I_SQ after clipping, Among them, I_SD is the D-axis damping amount, and I_SQ is the Q-axis damping amount; the calculation method of the limit is: if I_SD>Max, then set I_SD=Max; if I_SD<Min, then set I_SD=Min; otherwise, I_SD remains unchanged, Max and Min are respectively the upper limit and the lower limit of the clipping; if I_SQ>Max, then make I_SQ=Max; if I_SQ<Min, then make I_SQ=Min; otherwise I_SQ remains unchanged;

The suppression device is used to superimpose the DQ-axis damping amount I_SD and I_SQ and the original DQ-axis current given value as the current loop setting; I_SD forms a closed-loop feedback control for I_SSD and produces a damping effect to suppress the D-axis sub-synchronous oscillation; I_SQ A closed-loop feedback control is formed for I_SSQ, and a damping effect is produced to suppress the subsynchronous oscillation of the Q axis.

The application description of the technical solution provided by the present invention will be described below with specific examples.

Example: application in doubly-fed wind turbines

As shown in Figure 1, the power generated by the double-fed unit is mainly injected into the grid through the generator stator, and its control usually adopts the DQ axis decoupling control method. The stator current DQ axis is given by the main control system of the wind turbine and output to the converter. The shaft feedback is obtained by the converter stator current sampling through Park transformation. The difference between the stator DQ axis setting and the feedback is input to the stator current outer loop PI regulator, and the output is used as the DQ axis setting of the rotor current inner loop. The rotor current DQ axis feedback is given by The rotor current sampling of the converter is obtained through Park transformation, and the difference between the rotor DQ axis reference and feedback is input to the rotor current inner loop PI regulator, and the output is the converter side control voltage, which realizes normal control of the doubly-fed generator. Among them, i _sdref and i _sqref are stator current DQ axis reference respectively, i _sd and i _sq are stator current DQ axis feedback, i _rdref and i _rqref are rotor current DQ axis reference, i _rd and i _rq are rotor current DQ Axis feedback, u _rd and u _rq are the output DQ axis control voltages of the rotor converter, ignoring the decoupling term between DQ axes. The present invention adds a sub-synchronous oscillation suppressor SSOI on the basis of the normal control of the doubly-fed unit, and the added position is at the stator current given place in the control loop of the rotor converter. The subsynchronous oscillation suppressor (SSOI) based on subsynchronous phase locking takes the DQ axis stator current as input, automatically extracts the subsynchronous oscillation component and corrects and compensates the phase, thereby generating subsynchronous current DQ axis damping quantities I_SD and I_SQ, The damping amount is superimposed with the stator current setting to adjust the active and reactive current, and damping is generated to suppress the subsynchronous oscillation. The above principle is the same as that of the thermal power unit to suppress the subsynchronous oscillation. The difference is that the subsynchronous oscillation frequency of the thermal power unit is fixed and known in advance, and the subsynchronous component is extracted by a fixed frequency notch filter, while the subsynchronous oscillation generated by the wind turbine on the grid Oscillation is unpredictable, and different grid operation modes may face subsynchronous oscillations of different frequencies. Therefore, the difficulty of suppression lies in the dynamic extraction of subsynchronous oscillation frequency components, and the present invention solves this problem through subsynchronous phase locking, and realizes the suppression of subsynchronous oscillation of wind turbines.

The composition of the subsynchronous oscillation suppressor SSOI is shown in Figure 2. The stator DQ axis currents i _sd and i _sq first pass through a 2Hz high-pass filter to filter out the DC component, and the remaining sub-synchronous components are sent to the phase-locked loop PLL, and the PLL phase-locks the sub-synchronous components to obtain the sub-synchronous angle θ_SSO. Under the system, the DQ axis components I_SSD and I_SSQ are obtained. The deviation generated by the sampling and filtering link is compensated by the angle Compensation is performed, and the inverse Park transformation angle θ'_SSO is obtained after compensation. Then perform inverse Park transformation, transform the sub-synchronous coordinates to synchronous coordinates, and output the sub-synchronous damping quantities I_SD and I_SQ after clipping.

The composition of the phase-locked loop PLL is shown in Figure 3. The input quantity is transformed by Park to obtain the DQ axis component, and then the Q axis component is passed through the PI regulator to obtain the sub-synchronous angular velocity ω_SSO, and the sub-synchronous angle θ_SSO is obtained after integration. θ_SSO is also used in the above Park transformation process. The DQ axis components pass through a low-pass filter to filter out other frequency interference signals to obtain sub-synchronous components I_SSD and I_SSQ.

As shown in Figure 4, it is the three-phase waveform of the double-fed unit voltage, stator current, and rotor current. During normal operation, the grid voltage and stator current are standard 50Hz sine waves, and the rotor current is a sine wave of slip frequency (generally 0-10Hz). When subsynchronous oscillation occurs, the subsynchronous frequency component will appear in the grid voltage and stator current, and the subsynchronous slip frequency (rotor mechanical frequency minus subsynchronous frequency) component will appear in the rotor current. Therefore, it is possible to judge whether the system has subsynchronous oscillation or oscillation elimination by observing the subsynchronous component. Build a simulation model of doubly-fed wind power generation system, put into line series compensation 0.6s after normal grid-connected power generation, the subsynchronous oscillation gradually diverges, and observe the oscillation frequency from the AC current waveform to about 6Hz; 1.4s into the above subsynchronous oscillation suppression method, subsynchronous Gradually converge, and basically eliminate the oscillation by 1.7s. Therefore, it can be seen from Figure 4 that the input of analog line series compensation in the simulation causes the subsynchronous oscillation of the doubly-fed unit. After the above suppression method is applied, after the above subsynchronous oscillation suppression method is used in 1.4s, while the grid voltage remains stable, the stator current And the subsynchronous oscillation of the rotor current converges gradually. Furthermore, after 1.7s, while the grid voltage remains stable, the subsynchronous oscillation of the stator current and rotor current gradually disappears, thus verifying the effectiveness of the suppression method.

The above embodiment is only a description of the technical solution of the present invention, and the scope of protection of the present invention is not limited thereto. Any modification or equivalent replacement of the specific embodiments of the present invention by those familiar with the profession shall be included in the rights of the present invention. within the scope of requirements.

Claims (10)

1. A wind turbine subsynchronous oscillation suppression method, is characterized in that, comprises the steps: (1), input the current DQ axis component into the subsynchronous oscillation suppressor; (2), the DQ axis component is filtered in the subsynchronous oscillation suppressor; (3) In the subsynchronous oscillation suppressor, the DQ axis components I_SSD and I_SSQ under the subsynchronous coordinates are obtained through Park transformation, wherein, I_SSD is the component of the D axis subsynchronous oscillation frequency, and I_SSQ is the component of the Q axis subsynchronous oscillation frequency ; Pass I_SSQ through the PI regulator to obtain the sub-synchronous angular velocity ω_SSO, and integrate the sub-synchronous angular velocity ω_SSO to obtain the sub-synchronous angle θ_SSO; (4), in the subsynchronous oscillation suppressor, the input subsynchronous angle θ_SSO and the compensation angle Adding to get the angle for inverse Park transformation is where the compensation angle It is used to compensate the phase deviation generated by sampling filtering and other processes; (5) According to the inverse Park transformation angle θ'_SSO, the DQ axis components I_SSD and I_SSQ in the subsynchronous coordinates are transformed into the synchronous coordinate system, and the subsynchronous current DQ axis damping quantities I_SD and I_SQ are obtained after limiting, where I_SD is D-axis damping amount, I_SQ is Q-axis damping amount; (6), DQ axis damping I_SD and I_SQ and the original DQ axis current set value are superimposed as the current loop setting; I_SD forms a closed-loop feedback control for I_SSD, and produces a damping effect to suppress the D-axis sub-synchronous oscillation; I_SQ controls I_SSQ It forms a closed-loop feedback control and produces a damping effect to suppress the Q-axis subsynchronous oscillation. 2. The method for suppressing subsynchronous oscillations of wind turbines according to claim 1, characterized in that: the filtering in the step (2) is a high-pass filter, and the cut-off frequency of the high-pass filter is set at 2 to 5 Hz to filter out the DC component . 3. The wind turbine subsynchronous oscillation suppression method according to claim 1, characterized in that: in the step (3), obtain the subsynchronous angular velocity ω_SSO, i.e. ω_SSO=(Kp+Ki/s)*I_SSQ, where Kp is the proportional coefficient, Ki is the integral coefficient, and 1/s is the frequency domain expression of the integral. 4. The wind turbine subsynchronous oscillation suppression method according to claim 1, characterized in that: in the step (3), the subsynchronous angle θ_SSO is obtained after integrating the subsynchronous angular velocity, i.e. θ_SSO=(1/s)* ω_SSO, where 1/s is the frequency domain expression of the integral. 5. The wind turbine subsynchronous oscillation suppression method according to claim 1, characterized in that: in the step (5), the calculation method of the limit is: if I_SD>Max, then make I_SD=Max; if I_SD< Min, then make I_SD=Min; otherwise I_SD remains unchanged, Max and Min are the upper limit and lower limit of the limiter, if I_SQ>Max, then make I_SQ=Max; if I_SQ<Min, then make I_SQ= Min; otherwise I_SQ remains unchanged. 6. A wind turbine subsynchronous oscillation suppression system, characterized in that it comprises: Subsynchronous oscillation suppressor; the current DQ axis component is input into the subsynchronous oscillation suppressor, and the DQ axis component is filtered in the subsynchronous oscillation suppressor; and the DQ axis under the subsynchronous coordinates is obtained through Park transformation in the subsynchronous oscillation suppressor Components I_SSD and I_SSQ, where I_SSD is the component of the D-axis subsynchronous oscillation frequency, and I_SSQ is the component of the Q-axis subsynchronous oscillation frequency; PI regulator, I_SSQ obtains the sub-synchronous angular velocity ω_SSO through the PI regulator, and obtains the sub-synchronous angle θ_SSO after integrating the sub-synchronous angular velocity ω_SSO; A compensating device for combining the input subsynchronous angle θ_SSO with the compensating angle in the subsynchronous oscillation suppressor Adding to get the angle for inverse Park transformation is where the compensation angle It is used to compensate the phase deviation generated by sampling filtering and other processes; The damping amount generating device is used to transform the DQ axis components I_SSD and I_SSQ in the sub-synchronous coordinates to the synchronous coordinate system according to the inverse Park transformation angle θ'_SSO, and obtain the sub-synchronous current DQ axis damping amounts I_SD and I_SQ after clipping, Among them, I_SD is the D-axis damping amount, and I_SQ is the Q-axis damping amount; The suppression device is used to superimpose the DQ-axis damping amount I_SD and I_SQ and the original DQ-axis current given value as the current loop setting; I_SD forms a closed-loop feedback control for I_SSD and produces a damping effect to suppress the D-axis sub-synchronous oscillation; I_SQ A closed-loop feedback control is formed for I_SSQ, and a damping effect is produced to suppress the subsynchronous oscillation of the Q axis. 7. The subsynchronous oscillation suppression system for wind turbines according to claim 1, characterized in that: the filter in the subsynchronous oscillation suppressor is a high-pass filter, and the cut-off frequency of the high-pass filter is set at 2-5 Hz to filter out the DC component. 8. The wind turbine subsynchronous oscillation suppression system according to claim 1, characterized in that: subsynchronous angular velocity ω_SSO, i.e. ω_SSO=(Kp+Ki/s)*I_SSQ, wherein Kp is a proportional coefficient, and Ki is an integral coefficient, 1/s is the frequency domain expression of integral. 9. The wind turbine subsynchronous oscillation suppression system according to claim 1, characterized in that: the subsynchronous angle θ_SSO is obtained after the integration of the subsynchronous angular velocity, i.e. θ_SSO=(1/s)*ω_SSO, where 1/s is the integral Frequency Domain Expressions. 10. The wind turbine subsynchronous oscillation suppression system according to claim 1, characterized in that: the calculation method of the limit is: if I_SD>Max, then let I_SD=Max; if I_SD<Min, then make I_SD=Min; Otherwise, I_SD remains unchanged, and Max and Min are the upper limit and lower limit of the limiter respectively; if I_SQ>Max, then set I_SQ=Max; if I_SQ<Min, then set I_SQ=Min; otherwise, I_SQ remains unchanged.