JP2001157364A - System power stabilization device and controlling method thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To always ensure electric energy required for power compensation without damaging a DC energy storage device like a lead battery and shortening service life, in a system power stabilization device 10 restraining effective power fluctuations by taking electric power from/into a DC energy storage device 1 into/from an AC power system 3 through an AC-DC power converter 2. SOLUTION: This device is provided with a means 7 for measuring the SOC of a DC energy storage device 1, and a controlling means 12 for controlling the AC-DC power converter based on the measurements so that a fluctuation in the SOC of the optimized DC energy storage device may be minimum.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power system stabilizing device for suppressing power fluctuations in a power system by transferring power from a DC energy storage device such as a lead battery to an AC power system via an AC / DC converter. In particular, the SOC (S
It is an object of the present invention to provide a method and an apparatus for optimizing (state of charge).

[0002]

2. Description of the Related Art In the case of wind power generation or solar cell power generation, the output fluctuates greatly depending on weather conditions. Therefore, in an AC power system to which the power is connected, the power fluctuation seen from the power plant is very large. This is the same when a large-capacity variable load is connected to the AC power system. These fluctuations cause fluctuations in the power generation frequency of the power plant and cause voltage fluctuations in the system.

[0003] Therefore, a power system stabilizing device is used which detects fluctuations in the active power of the AC power system and compensates such fluctuations to make the fluctuations constant.

As shown in FIG. 5, this power system stabilization device is one in which a lead battery 1 as a DC energy storage device is connected to an AC power system 3 via an AC / DC power converter 2. In this device, the active power Pa of the load connected to the power system 3 and the wind power generator 4 is detected by the active power detector 5, and the fluctuation component Pb is extracted by the fluctuation component detector 6.
The AC / DC power converter 2 outputs the active power Pc from the lead battery 1 so as to cancel this Pb, as shown in FIG. As a result, the active power Pd flowing toward the AC power system 3
Becomes constant, and the frequency fluctuation of the AC power system 3 can be kept constant.

In the above-mentioned power system stabilizing device, frequent large current charging / discharging is required for the lead battery 1. The lead battery 1 is shown in FIG.
The battery has charge / discharge characteristics as shown in FIG. 7A. Generally, as shown in FIG. 7B, when a large current is charged in a high SOC range, the battery voltage rises sharply and the battery is damaged. There is a restriction on the use of the battery that if the high current charge / discharge is continued in a low SOC range, the battery life is significantly reduced.

In the configuration shown in FIG. 5, when the power system stabilizing device is continuously operated by focusing only on the power fluctuation Pb of the load, the loss of the lead battery 1 due to charging and discharging and the power loss of the AC / DC power converter 2 cause As shown in FIG. 8, the SOC of the lead battery 1 decreases with the operation time. As a result, a situation where the power system stabilizing device cannot be operated continuously for a long time cannot be obtained, and the life of the lead battery is significantly reduced.

For this reason, conventionally, the voltage of a lead battery during fluctuation countermeasures is monitored, and the offset amount of the threshold value for determining whether to charge or discharge is switched to the discharge side when the set voltage reaches the upper limit value. When the lower limit of the set voltage is reached, the battery is switched to the charging side and the state of charge of the battery is controlled within a certain range.

[0008]

However, in the method of monitoring and controlling the terminal voltage, the terminal voltage is controlled toward a set voltage regardless of the magnitude of the output capacity. When the lower limit voltage is reached when is small, the SOC of the battery is low,
At this time, when the maximum countermeasure capacity command is received and the battery is discharged, the voltage drop of the battery becomes large, and there is a possibility that the fluctuation cannot be compensated. At that time, the battery is over-discharged and the battery deteriorates.

Further, as the output capacity of the AC / DC power converter increases, the loss also increases accordingly.
The amount of offset for recovery must be set large. In this case, if the compensation output shifts to the charging side of the battery during control toward the upper limit set voltage, the average voltage of the battery increases, and an overvoltage occurs at the peak charging current, which causes battery deterioration.

Accordingly, the present invention provides a system power stabilizing device which can always secure the amount of power required for power compensation without damaging a DC energy storage device such as a lead battery and shortening its life. It is an object to provide a controlling method and apparatus.

[0011]

According to the first aspect of the present invention, power is transferred from a DC energy storage device to an AC power system via an AC / DC power converter in accordance with an active power fluctuation of the AC power system. In the power system stabilizing device that suppresses the active power fluctuation of the AC power system, the SOC of the DC energy storage device is not damaged by overcharging and within a certain range in which the life is not shortened by overdischarging. A method for controlling a power system stabilizing device, characterized by controlling an AC / DC power conversion device so as to be included in a power system.

According to a second aspect of the present invention, there is provided a control method of a power system stabilizing apparatus according to the first aspect, wherein
It is characterized in that the SOC of the DC energy storage device is set so that the amount of electricity required for fluctuation compensation can always be secured, and the AC / DC power conversion device is controlled so that the fluctuation of the SOC is minimized.

According to a third aspect of the present invention, an AC power supply is carried out from a DC energy storage device to an AC power system via an AC / DC converter in accordance with a change in active power of the AC power system. In a power system stabilizing device configured to suppress a change in active power of a system, a means for measuring an SOC of a DC energy storage device, and an SOC of the DC energy storage device based on the measured value.
Control means for controlling the AC / DC power conversion device so as to be within a certain range not to be damaged by overcharging and not to shorten the life due to overdischarging. .

[0014] According to a fourth aspect of the present invention, an AC power supply is carried out from an AC power system to an AC power system via an AC / DC converter in accordance with an active power fluctuation of the AC power system. In a power system stabilizing device configured to suppress a change in active power of a power system, a means for measuring an SOC of a DC energy storage device, and based on the measured value, the DC energy storage device is not damaged by overcharging and is not damaged. S of the DC energy storage device is set within a certain range in which the life is not shortened by the discharge, and is set so that the amount of electricity necessary for fluctuation compensation is always secured.
A power system stabilizing device comprising: a control unit that controls an AC / DC power conversion device so that a variation of the OC is minimized.

According to a fifth aspect of the present invention, there is provided an electric power system stabilizing apparatus according to the third or fourth aspect, wherein
As means for measuring C, there is provided means for measuring the amount of charge and the amount of discharge of the DC energy storage device, and the control means comprises:
The AC / DC power converter is controlled based on the measured value so that the difference between the charged electricity amount and the discharged electricity amount is minimized.

According to a sixth aspect of the present invention, in the power system stabilizer according to the fifth aspect, the SOC measuring means includes means for calculating a power loss of the AC / DC power converter, and the control means includes: The amount of electricity charged to the DC energy storage device is increased by the calculated power loss to control the AC / DC power conversion device.

According to a seventh aspect of the present invention, there is provided an electric power system stabilizing apparatus according to the fifth or sixth aspect,
The measuring means of C includes a means for calculating a loss of electricity caused by the current efficiency in the DC energy storage device, and the control means causes the control unit to charge the DC energy storage device with a larger amount of electricity to charge the DC energy storage device. In addition, the AC / DC power converter is controlled.

According to an eighth aspect of the present invention, in the power system stabilizing apparatus according to the seventh aspect, the means for measuring the SOC includes means for measuring the temperature of the DC energy storage device and means for measuring the average voltage. And a means for correcting the current efficiency in the DC energy storage device based on these measured values.

According to a ninth aspect of the present invention, in the electric power system stabilizing apparatus according to any one of the fifth to eighth aspects, there is provided means for detecting a maximum charging current during power control, Is the direct current energy storage device SO
C is provided with means for setting the maximum charging current to be equal to or less than an allowable value that does not damage the DC energy storage device.

[0020]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of the present invention will be described with reference to FIG. In FIG. 1, 1 is a lead battery as a DC energy storage device, 2 is an AC / DC power converter, 3 is an AC power system equipped with a generator, 4 is a load or wind generator connected to the system, and 5 is active power Pa Active power detector to detect the
Reference numeral 6 denotes a fluctuation component detector for extracting a fluctuation component Pb of the active power Pa. Reference numeral 7 denotes an SOC detector, which detects the SOC of the lead battery from the amount of charge electricity and the amount of discharge electricity of the lead battery 1. Reference numeral 8 denotes an offset determination circuit which is a control means, and adds an offset to a threshold value for determining battery discharge and charge in accordance with the detected SOC value, as shown in FIG. While keeping Pd constant, the SOC of the DC energy storage device is kept constant within a certain range in which the lead battery 1 is not damaged by overcharging and the life is not shortened by overdischarging.

The embodiment of FIG. 1 achieves prevention of damage to the lead battery 1 and shortening of the service life thereof by keeping the SOC within a certain range. However, the SOC is controlled by setting the set value to an appropriate value. In addition, by devising a suitable control method, the capacity of the lead battery can be maximized, and the amount of electricity required for fluctuation compensation can always be secured.

An embodiment in this case will be described with reference to FIGS. In this embodiment, the SOC measuring means is:
It is incorporated as a means for indirectly detecting SOC by measuring battery current, voltage, temperature, and power loss of the AC / DC power converter. In FIG. 3, a power system stabilizing device 10 of the present invention is connected to an AC power system 3 to which a wind power generator 4 is connected, via an interconnection transformer 9.

The power system stabilizing device 10 includes an AC / DC power converter 2 having a lead-acid battery 1 as a DC energy storage device on the DC side and a control signal generator (control means) 12 thereof. It is composed of an interconnection transformer 11 connected to the system 3.

The AC / DC power converter 2 includes an inverter unit 2a
And a control circuit unit 2b.
2 includes a DC current transformer DCCT and a DC voltage transformer D as means for measuring the amount of charge and discharge of the storage battery.
Means 13 are provided for detecting the output of AC / DC power converter 2 from CPT and linkage transformer 11. Further, the control signal generator 12 receives the fluctuation component Pb of the active power Pa extracted from the active power detector 5 and the fluctuation component detector 6.

The control signal generator 12 is configured as shown in FIG. The control signal generator 12 measures the amount of charge and the amount of discharge of the storage battery 1 which is a DC energy storage device, and controls the difference between the amount of charge and the amount of discharge based on the measured value to minimize the difference. At the same time, the power loss of the AC / DC power converter 2 is determined, and the amount of electricity charged in the storage battery 1 is increased by the loss.

In the above-described control for minimizing the difference between the amount of charged electricity and the amount of discharged electricity, an error occurs due to the loss of electricity caused by the current efficiency of the storage battery as the DC energy storage device. It has. Since this charging efficiency changes depending on the battery voltage and the temperature, the battery voltage and the temperature are measured to determine the charging efficiency.

In FIG. 4, reference numeral 14 denotes a battery current measuring device.
For example, it comprises the DCCT. Reference numeral 15 denotes a charged electricity meter, and reference numeral 16 denotes a discharged electricity meter, which is composed of, for example, a general watt-hour meter that V / F converts an analog output of the battery current meter 14 and counts its pulse. An adder 17 subtracts the amount of discharged electricity from the amount of charged electricity and extracts the difference. Reference numeral 18 denotes a comparison circuit, which is an SOC for discharging.
It has a shift determination value (-a) and a shift determination value (+ b) to the charging side. When the shift value is exceeded, an offset command is generated, and the offset command is held until the output of the adder 17 becomes zero. . Reference numeral 19 denotes a first offset circuit which, when receiving an offset command, outputs a voltage corresponding to an offset current that can be superimposed without imposing a load on a storage battery to be controlled, with a polarity corresponding to the offset direction.
20 is a second offset circuit which receives the output capacity of the AC / DC power converter 2 measured by the measuring means 13;
The power loss of the AC / DC power converter 2 is calculated, and an offset voltage corresponding to the loss of electricity of the battery is generated.

Reference numeral 21 denotes a current efficiency correction circuit which corrects the integrated value of the charging current amount measuring device 15 based on the charging efficiency of the storage battery.
Are the same, the charge current amount measuring device 15 and the discharge current amount measuring device 16 are reset.

Reference numeral 22 denotes a battery voltage measuring device which measures the release voltage when the output of the AC / DC power converter 2 is stopped (when charging and discharging are not performed). Reference numeral 23 denotes a voltage correction circuit which sets and stores a battery release voltage in an initial stage (a state where the SOC is set to, for example, an appropriate value of 60 to 80%) as a reference value, and outputs the reference value from the battery voltage measuring device 22. From the difference from the measured voltage, a correction coefficient corresponding to the charging efficiency is commanded to the current efficiency correction circuit 21. Further, during the compensation operation, the state of the SOC can be grasped and the correction can be performed by measuring the average voltage. Such a command of the correction coefficient according to the charging efficiency is also performed for the measured value of the battery temperature.

An adder 24 adds the outputs of the first offset circuit 19 and the second offset circuit 20. This added value is output as a battery control signal 25 and added to the compensation signal Pb of the power converter, and is used as a control signal of the AC / DC power converter 2 as shown in FIG.
Is output to Note that the output of the second offset circuit 20 is such that the output of the comparison circuit 18 is an excessive value on the charging side, for example, +
When it becomes several times b, it is possible to prevent the battery from being damaged by preventing it from being output to the adder 24.

With the above structure, the storage battery is recommended SOC
It can be used at the upper limit of the operating point (for example, 60 to 80% for a lead battery), and it is possible to maximize the performance of the storage battery while extending the battery life.

Although the above embodiment has been described by taking a lead battery as an example of a DC energy storage device, the present invention can be similarly applied to an electric double layer capacitor, an electrolytic capacitor and the like.

[0033]

According to the control method of the power system stabilizing device according to the first aspect of the present invention, the SOI of the DC energy storage device is controlled.
Since the AC / DC power converter is controlled to keep C within a certain range, a DC energy storage device such as a lead battery can be used without being damaged by overcharging and without shortening the life due to overdischarging.

According to a second aspect of the present invention, there is provided a method for controlling a power system stabilizing apparatus, wherein the SOC of a DC energy storage device is set to an optimum value and the SOC fluctuation is minimized. Control so that the battery capacity is maximized. The amount of electricity required for fluctuation compensation can always be secured.

The power system stabilizing apparatus according to the third aspect of the present invention can provide an apparatus for actually implementing the method according to the first aspect.

The power system stabilizing apparatus according to the fourth aspect of the present invention can provide an apparatus for actually implementing the method according to the second aspect.

According to a fifth aspect of the present invention, there is provided a power system stabilizing apparatus according to the third or fourth aspect, wherein
As the OC measuring means, the amount of charge and the amount of discharge of the DC energy storage device are measured, and control is performed so that the difference is minimized, so that the SOC control can be accurately performed.

In the power system stabilizing device according to claim 6 of the present invention, since the power loss of the AC / DC power conversion device is added as a control element of the SOC in the device described in claim 5, the control accuracy of the SOC is improved. Can be improved.

According to a seventh aspect of the present invention, in the power system stabilizing device, the electric energy loss caused by the charging efficiency in the DC energy storage device is converted into a measured value of the battery voltage. Since the correction is performed based on the control, the control accuracy can be further improved.

The power system stabilizing device according to claim 8 of the present invention is the device according to claim 5 or 6, wherein the loss of electricity caused by the charging efficiency in the DC energy storage device is compared with the measured temperature of the battery. Since the correction is performed based on the average voltage value, the control accuracy can be further improved.

A power system stabilizing device according to a ninth aspect of the present invention detects a maximum charging current during power control,
Since the SOC of the DC energy storage device is set to a value that does not damage the maximum charging current, the battery can be used with high reliability.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing one embodiment of the present invention.

FIG. 2 is a waveform chart illustrating the operation of the device of FIG.

FIG. 3 is a circuit diagram showing a second embodiment of the present invention.

FIG. 4 is a circuit diagram showing a configuration example of a control signal generator of FIG. 3;

FIG. 5 is a circuit diagram showing a conventional power system stabilizing device.

FIG. 6 is a waveform chart for explaining the device of FIG. 5;

FIG. 7 (a) is a charge / discharge characteristic diagram of a lead battery and its SO
The figure (b) which shows the relationship between C and restrictions on use.

FIG. 8 is a diagram showing a change in SOC when SOC control is not performed.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 DC energy storage device 2 AC / DC power converter 3 AC power system 4 Load or wind power generator 10 Power system stabilization device 12 Control signal generator

Continuing on the front page (72) Inventor Takaya Hasebe, 47 Nishijin Electric Co., Ltd., Umezu Takane-cho, Kyoto, Kyoto-shi F term (reference) 5G003 AA01 BA01 CA06 CC07 DA07 DA13 GB06 GC05 5G066 JA05 JB03

Claims (9)

[Claims] According to the active power fluctuation of the AC power system,
In a power system stabilizing device that suppresses active power fluctuations of an AC power system by transferring power from a DC energy storage device to an AC power system via an AC / DC power conversion device, the SOC of the DC energy storage device is reduced. A method for controlling a power system stabilizing device, comprising: controlling an AC / DC power conversion device so that the AC / DC power conversion device falls within a predetermined range that does not damage the battery due to overcharging and does not shorten the life due to overdischarging. 2. The method according to claim 1, wherein the SOC of the DC energy storage device is set so that the amount of electricity required for fluctuation compensation can be always secured, and the AC / DC power converter is controlled so that the fluctuation of the SOC is minimized. The method for controlling a power system stabilizing device according to claim 1. 3. According to the active power fluctuation of the AC power system,
In a power system stabilizing device that suppresses active power fluctuations of an AC power system by transferring power from a DC energy storage device to an AC power system via an AC / DC power conversion device, the SOC of the DC energy storage device is reduced. Means for measuring and the SOC of the DC energy storage device
And a control means for controlling the AC / DC power conversion device so that the AC power is kept within a certain range not to be damaged by overcharging and not to shorten its life due to overdischarging. 4. According to the active power fluctuation of the AC power system,
In a power system stabilizing device that suppresses active power fluctuations of an AC power system by transferring power from a DC energy storage device to an AC power system via an AC / DC power conversion device, the SOC of the DC energy storage device is reduced. Based on the measuring means and the measured value, the DC energy storage device is not damaged by overcharging, and the life is not reduced by overdischarging within a certain range, and the amount of electricity necessary for fluctuation compensation can always be secured. And a control means for controlling the AC / DC power conversion device so that a fluctuation of the SOC of the DC energy storage device set in (1) is minimized. 5. An apparatus for measuring the SOC, comprising: means for measuring the amount of charge and the amount of discharge of the DC energy storage device, wherein the control means determines the difference between the amount of charge and the amount of discharge based on the measured value. The power system stabilizing device according to claim 3 or 4, wherein the AC / DC power converter is controlled so as to be as follows. 6. The SOC measuring means includes a means for calculating a power loss of the AC / DC power converter, and the control means increases an amount of electricity charged in the DC energy storage device by the calculated power loss, The power system stabilizing device according to claim 5, which controls an AC / DC power converter. 7. The SOC measuring means includes a means for calculating an electric energy loss due to a current efficiency in the DC energy storage device, and the control means controls the electric energy for charging the DC energy storage device by the electric energy loss. The power system stabilizing device according to claim 5 or 6, wherein the AC / DC power conversion device is controlled so that the amount increases. 8. The means for measuring the SOC includes means for measuring the temperature of the DC energy storage device and means for measuring the average voltage, and means for correcting the current efficiency in the DC energy storage device based on these measured values. The power system stabilizing device according to claim 7, comprising: 9. A control device for detecting a maximum charging current during power control, wherein the control device sets the SOC of the DC energy storage device to an allowable value which does not damage the DC energy storage device with respect to the maximum charging current. The power system stabilizing device according to any one of claims 5 to 8, further comprising means for setting as described above.