Control device for reactive power compensation device, control method for reactive power compensation device, and program

Abstract

To provide a controller of a reactive power compensator, a control method of the reactive power compensator and a program, which can suppress overshoot of reactive power, which may occur when recovering from a system accident which occurs in a power transmission system, and which the reactive power compensator outputs.SOLUTION: A controller of a reactive power compensator includes: a proportional-integral controller; a command value conversion part; and a limit value switching part. The controller of the reactive power compensator controls output of reactive power from the reactive power compensator connected to an AC system on the basis of a voltage detection value detected by a voltage detection device arranged at least at a connection point with the AC system. The proportional-integral controller outputs a proportional-integral value based on the voltage detection value and based on a proportional value of a proportional device and an integral value of an integrator. The command value conversion part converts the proportional-integral value into a reactive power output command value. The limit value switching part switches a limit value for limiting integration of a value based on at least the voltage detection value by the integrator.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] An embodiment of the present invention relates to a control device for a reactive power compensation device, a control method for a reactive power compensation device, and a program. [Background technology]

[0002] In a power transmission system, a reactive power compensator for compensating for reactive power is connected to a busbar to which an AC system is connected. The reactive power compensator is a device that suppresses voltage fluctuations in the busbar by outputting reactive power according to the difference between a voltage command value and a voltage detection value of the busbar. For example, when the system voltage drops due to an accident (system accident) that occurs in any of the power transmission paths connected to the busbar, the reactive power compensator increases the system voltage by outputting capacitive reactive power, thereby suppressing voltage fluctuations in the busbar. In general, the operation of the reactive power compensator is controlled by a control device that performs proportional-integral control (PI control) so that the voltage detection value of the busbar follows the voltage command value. The reactive power compensator outputs reactive power to the busbar according to a gate signal based on an output command value output by the control device.

[0003] The power transmission system also includes components for preventing the accident from spreading to other power transmission paths, such as a circuit breaker for interrupting the power transmission path where the accident has occurred, and for recovering from the accident. For this reason, when the accident is recovered from, that is, when the voltage of the bus is restored, the reactive power compensator operates to stop or reduce the capacitive reactive power output that was being output during the accident. In this case, the operation of the reactive power compensator is also controlled by the control device. For this reason, for example, when the accident is recovered from (power is restored) instantly, it is possible that the control device is not able to stop or reduce the capacitive reactive power output in time, and the reactive power compensator continues to output capacitive reactive power according to the amount of drop in the system voltage caused by the accident for a while. In this case, the reactive power continuously output by the reactive power compensator may cause an overvoltage on the bus.

[0004] In this regard, for example, Patent Document 1 discloses a technique relating to a reactive power compensation device and a control circuit that prevent the occurrence of overvoltage. Patent Document 1 describes switching of a command value so that a predetermined small command value is output when a drop in the grid voltage is detected, and a minute command value is output when the grid voltage is restored. Patent Document 1 further describes holding the output of a control circuit (PI control) at zero when a drop in the grid voltage is detected. Patent Document 1 also describes resetting integral control in the control circuit when the grid voltage is restored. In this way, the technique described in Patent Document 1 prevents overvoltage from occurring when the grid voltage is restored.

[0005] However, in the technology described in Patent Document 1, the control circuit continues to integrate the difference between the voltage command value and the grid voltage even while the grid voltage is dropping. Therefore, in the technology described in Patent Document 1, the integral value becomes large at the moment the grid voltage is restored, and more integral control than necessary is performed in response to this large integral value, which may cause the reactive power output by the reactive power compensation device to overshoot. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] JP 2019-122144 A Summary of the Invention [Problem to be solved by the invention]

[0007] The problem that the present invention aims to solve is to provide a control device for a reactive power compensation device, a control method for a reactive power compensation device, and a program that can suppress an overshoot in reactive power output by the reactive power compensation device, which may occur when recovering from a grid fault that has occurred in a power transmission system. [Means for solving the problem]

[0008] A control device for a reactive power compensation device according to an embodiment includes a proportional-integral controller, a command value conversion unit, and a limit value switching unit. The control device for a reactive power compensation device controls an output of reactive power from a reactive power compensation device connected to an AC system based on at least a voltage detection value detected by a voltage detection device arranged at a connection point with the AC system. The proportional-integral controller includes a proportional unit and an integrator. The proportional unit outputs a proportional value according to a value based on the voltage detection value. The integrator outputs an integral value obtained by integrating a value based on the voltage detection value according to an input limit value. The proportional-integral controller outputs a proportional-integral value based on the proportional value and the integral value. The command value conversion unit converts the proportional-integral value into a reactive power output command value for causing the reactive power compensation device to output the reactive power. The limit value switching unit switches the limit value for limiting at least the integration of a value based on the voltage detection value by the integrator. The limit value switching unit switches the limit value to a first limit value that limits the integral value to a low value when the voltage detection value drops, and switches the limit value to a second limit value that does not limit the integral value when the voltage detection value recovers. [Brief description of the drawings]

[0009] [Figure 1] 1 is a diagram showing an example of the configuration of an AC grid system included in a power transmission system according to an embodiment. [Diagram 2] 1 is a diagram showing an example of the configuration of a control device for a reactive power compensation device included in an AC system according to an embodiment; [Diagram 3] FIG. 4 is a diagram showing an example of integral action in an integrator in a PI controller included in the control device of the embodiment. [Figure 4] 5 is a diagram showing an example of the operation of a rate limiter in a limiter selector included in the control device of the embodiment. [Diagram 5] 5 is a flowchart showing an example of a process in a limiter selector included in the control device of the embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a control device for a reactive power compensation device, a control method for a reactive power compensation device, and a program according to embodiments will be described with reference to the drawings.

[0011] [AC system configuration] Fig. 1 is a diagram showing an example of the configuration of an AC system included in a power transmission system according to an embodiment. The power transmission system is a system that transmits power from an AC system on a power transmission side to an AC system on a power receiving side. Power transmission in the power transmission system may directly transmit AC power from the AC system on the power transmission side to the AC system on the power receiving side, or may convert AC power from the AC system on the power transmission side to DC power before transmitting the power, and convert it back to AC power on the power receiving side before transmitting the power to the AC system on the power receiving side. The AC system 1 shown in Fig. 1 may be the AC system on the power transmission side or the AC system on the power receiving side.

[0012] The AC system 1 shown in FIG. 1 includes, for example, an AC system 10, a bus 20, a static var compensator 30, a voltage detector 40, a current detector 50, and a control device 60.

[0013] The AC system 10 is a facility that supplies AC power to the interconnected bus bar 20 or receives AC power from the bus bar 20. The AC system 10 may be, for example, a power generation facility that generates AC power, or may be a facility that transmits AC power transmitted from an AC system included in another AC system on the power transmission side to an AC system included in an AC system on the power receiving side, or may be a facility that supplies AC power to each of the consumers present at the connected destinations.

[0014] The reactive power compensator 30 is connected to the AC system 10 via a bus 20. The reactive power compensator 30 outputs capacitive or inductive reactive power (hereinafter simply referred to as "reactive power") to the bus 20 under control of a control device 60. The reactive power compensator 30 outputs reactive power to the bus 20 according to a gate pulse signal indicating a reactive power output command value output by the control device 60, thereby suppressing voltage fluctuations on the bus 20.

[0015] The voltage detector 40 detects the voltage at the interconnection point between the bus 20 and the static var compensator 30. The voltage detector 40 outputs information on the detected voltage value (hereinafter referred to as the "detected voltage value") to the control device 60. The voltage detector 40 is an example of a "voltage detection device" in the claims.

[0016] The current detector 50 detects a current flowing between the bus 20 and the static var compensator 30. The current detector 50 outputs information on the detected current value (hereinafter referred to as a "current detection value") to the control device 60. The current detector 50 is an example of a "current detection device" in the claims.

[0017] The control device 60 controls the output of reactive power from the reactive power compensator 30. The control device 60 generates a command value (hereinafter referred to as a "reactive power output command value") for causing the reactive power compensator 30 to output reactive power, based on information on the voltage detection value output by the voltage detector 40 and information on the current detection value output by the current detector 50. The control device 60 outputs a gate pulse signal based on the generated reactive power output command value to the reactive power compensator 30. As a result, the reactive power compensator 30 outputs reactive power corresponding to the gate pulse signal to the bus 20.

[0018] The control device 60 and components included in the control device 60 described below realize the following functions by, for example, a hardware processor such as a CPU (Central Processing Unit) executing a program (software). Some or all of the functions of the control device 60 and the components included in the control device 60 may be realized by hardware (including circuitry) such as an LSI (Large Scale Integration), an ASIC (Application Specific Integrated Circuit), an FPGA (Field-Programmable Gate Array), or a GPU (Graphics Processing Unit), or may be realized by a combination of software and hardware. Some or all of the functions of the control device 60 and the components included in the control device 60 may be realized by a dedicated LSI. The program may be stored in advance in a storage device (storage device with a non-transient storage medium) such as an HDD (Hard Disk Drive) or flash memory provided in the control device 60 or the AC system 1, or may be stored in a removable storage medium (non-transient storage medium) such as a DVD or CD-ROM, and installed in the storage device provided in the control device 60 by attaching the storage medium to a drive device provided in the control device 60 or the AC system 1.

[0019] [Control device configuration] Fig. 2 is a diagram showing an example of the configuration of the control device 60 of the reactive power compensation device 30 included in the AC system 1 of the embodiment. The control device 60 includes, for example, an adder 610, an adder 620, a multiplier 630, an adder 640, a PI controller 650, a limiter 660, a Q / θ converter 670, a pulse generator 680, and a limiter selector 690. The configuration of the control device 60 shown in Fig. 2 is merely an example, and some of the components may be omitted, some of the components may be replaced with different configurations, or other components may be added.

[0020] The adder 610 calculates the difference between the voltage detection value detected by the voltage detector 40 and the voltage command value. The voltage command value is a command value for controlling the voltage of power output to the bus 20 and a power transmission path (power transmission line) connected to the bus 20 in the AC system 1. In FIG. 2, the adder 610 subtracts the voltage detection value from the voltage command value. In other words, the adder 610 calculates the deviation between the voltage detection value and the voltage command value. The adder 610 may be configured as a subtractor, for example. The adder 610 outputs the calculated result (hereinafter referred to as the "voltage difference value") to the adder 640.

[0021] The adder 620 calculates the difference between the current detection value detected by the current detector 50 and the current command value. The current command value is a command value for controlling the current of power output to the bus bar 20 or the power transmission path connected to the bus bar 20 in the AC system 1. In FIG. 2, the adder 620 subtracts the current command value from the current detection value. In other words, the adder 620 calculates the deviation between the current detection value and the current command value. The adder 620 may be configured as a subtractor, for example. The adder 620 outputs the calculated result (hereinafter referred to as the "current difference value") to the multiplier 630.

[0022] The multiplier 630 multiplies the current difference value calculated by the adder 620 with a predetermined gain. Although FIG. 2 shows a configuration in which the current difference value calculated by the adder 620 is input to the multiplier 630, the input to the multiplier 630 is not limited to this. For example, the current detection value detected by the current detector 50 may be directly input to the multiplier 630, that is, a predetermined gain may be multiplied to the current detection value detected by the current detector 50. In this configuration, the adder 620 may be omitted. For example, the predetermined gain is set so that the bus voltage changes at a predetermined rate from the voltage command value according to the current difference value. The multiplier 630 outputs the result of multiplying the gain (hereinafter referred to as the "current multiplication value") to the adder 640.

[0023] The adder 640 subtracts the current multiplication value multiplied by the gain by the multiplier 630 from the voltage difference value calculated by the adder 610. As a result, the adder 640 corrects the voltage difference value by the current multiplication value. The adder 640 outputs the result of correcting the voltage difference value (hereinafter, referred to as a "voltage correction value") to the PI controller 650. Although a configuration including the adder 640 is shown in FIG. 2, the adder 640 may be omitted. In other words, a configuration may be such that the voltage difference value calculated by the adder 610 is directly output to the PI controller 650. In this case, the adder 620 and the multiplier 630 may be omitted. The adder 620 (which may include the multiplier 630 and the adder 640) is an example of a "correction unit" in the claims.

[0024] The PI controller 650 performs proportional-integral control (PI control) based on the voltage correction value output by the adder 640. Alternatively, in a configuration in which the adder 640 is omitted in the control device 60, the PI controller 650 performs proportional-integral control based on the voltage difference value output by the adder 610. In the following description, it is assumed that the voltage correction value is input to the PI controller 650, and the PI controller 650 performs proportional-integral control based on the voltage correction value. The PI controller 650 includes, for example, a proportional controller 652, an integrator 654, and an adder 656. The PI controller 650 is an example of a "proportional-integral controller" in the claims. The voltage correction value or the voltage difference value is an example of a "value based on a voltage detection value" in the claims.

[0025] The proportional unit 652 performs proportional control on the input voltage correction value. The proportional unit 652 outputs the result of the proportional control (hereinafter, referred to as a “proportional value”) to the adder 656.

[0026] The integrator 654 integrates the input voltage correction value. At this time, the integrator 654 integrates the voltage correction value according to a limit value (hereinafter referred to as a "limit value"), which is output by the limiter selector 690 and will be described later. In other words, the integrator 654 is an integrator with a limiter. The integrator 654 prevents the result of integrating the voltage correction value (hereinafter referred to as an "integral value") from exceeding the upper limit value Lim-max and the lower limit value Lim-min output by the limiter selector 690. The integrator 654 outputs the integral value to the adder 656.

[0027] Here, an example of the operation of the integrator 654 integrating the input value according to the limit value will be described. FIG. 3 is a diagram showing an example of the integral operation in the integrator 654 in the PI controller 650 included in the control device 60 of the embodiment. FIG. 3(a) shows an example of a model of the integrator 654 described below. Here, a case will be described in which the integrator 654 integrates the input input value IN and outputs the integral value OUT when the upper limit value Lim-max is "1" and the lower limit value Lim-min is "-1". FIG. 3(b) shows an example of a change over time of the input value IN input to the integrator 654, and FIG. 3(c) shows an example of a change over time of the integral value OUT integrated and output by the integrator 654. FIG. 3(d) shows, for reference, an example of the change over time in the integral value OUT in the case where the integrator 654 simply integrates the input value IN without following a limit value, that is, the integrator 654 is an ordinary integrator without a limiter, similar to the integrator in a PI controller provided in a control device of a conventional reactive power compensation device.

[0028] 3B, when the input value IN of a positive value="1" starts to be input from time t1, the integrator 654 starts integrating a value corresponding to the input value IN. The integrator 654 integrates a value corresponding to the input value IN based on, for example, the following formula (1).

[0029]

number

[0030] In the above formula (1), T is the integration time T. If the integration time T is, for example, 0.03 [sec], the integrator 654 periodically integrates a value corresponding to the input value IN at a timing of every 0.03 [sec].

[0031] As a result, as shown in (c) and (d) of FIG. 3, the integral value OUT output by the integrator 654 increases. When the integral value OUT reaches the upper limit value Lim-max="1", the integral value OUT output by the integrator 654 is held at the magnitude of the upper limit value Lim-max. On the other hand, when the integrator 654 integrates the input value IN without following the limit value, the integral value OUT output by the integrator 654 increases beyond the upper limit value Lim-max. (c) of FIG. 3 shows a state in which the integral value OUT becomes the same value as the upper limit value Lim-max at time t2, and the value is held after time t2. When the integral value OUT reaches the upper limit value Lim-max, the integrator 654 may stop integrating the value according to the input value IN, or may continue the integration operation with the value according to the input value IN set to "0". On the other hand, FIG. 3(d) similarly shows a state in which the integral value OUT becomes equal to the upper limit value Lim-max at time t2, but the integral value OUT continues to increase after time t2.

[0032] By such an integral operation, the integrator 654 integrates a value according to the input value IN until the integral value OUT becomes the limit value output by the limiter selector 690, and after the integral value OUT becomes the limit value, the integrator 654 holds the value so as not to exceed the limit value. In the above explanation, the case where the input value IN is a positive value has been explained, but the same applies when the input value IN is a negative value. Therefore, the explanation of the integral operation of the integrator 654 when the input value IN is a negative value will be omitted.

[0033] 2, the adder 656 calculates the sum of the proportional value output by the proportional unit 652 and the integral value output by the integrator 654. The adder 656 outputs the calculated result (hereinafter referred to as the “proportional integral value”) to the limiter 660.

[0034] The limiter 660 calculates a reactive power output command value for making the reactive power compensator 30 output reactive power based on the proportional integral value output by the PI controller 650 (more specifically, the adder 656). The limiter 660 may have a configuration similar to that of a conventional control device for a reactive power compensator, or may be configured to limit the magnitude of reactive power represented by the calculated reactive power output command value according to a limit value output by the limiter selector 690, which will be described later. FIG. 2 shows a configuration in which the limiter 660 applies a limit according to an upper limit value Lim-max and a lower limit value Lim-min output by the limiter selector 690. The limiter 660 calculates a reactive power output command value with the upper limit value Lim-max as the upper limit value and the lower limit value Lim-min as the lower limit value. The limiter 660 outputs the calculated reactive power output command value (hereinafter referred to as "reactive power output command value Qc") to the Q / θ converter 670. The limiter 660 is an example of the “command value conversion section” in the claims.

[0035] The Q / θ converter 670 converts the reactive power (Q) to be output by the reactive power compensation device 30 into a phase angle (θ) based on the reactive power output command value Qc output by the limiter 660. The Q / θ converter 670 outputs the converted phase angle to the pulse generator 680.

[0036] The pulse generator 680 generates a pulse signal representing the phase angle output by the Q / θ converter 670. That is, the pulse generator 680 generates a pulse signal representing the reactive power output command value Qc calculated by the limiter 660. The pulse generator 680 outputs the generated pulse signal as a gate pulse signal to the reactive power compensation device 30. As a result, the reactive power compensation device 30 outputs to the bus 20 reactive power according to the gate pulse signal output by the pulse generator 680, that is, the control device 60.

[0037] The configuration of the control device 60 up to this point is similar to that of a conventional control device for a reactive power compensation device, except that the integrator 654 and limiter 660 in the PI controller 650 operate according to the limit value output by a limiter selector 690. In the control device 60, a limiter selector 690 is added to the conventional control device for a reactive power compensation device.

[0038] The limiter selector 690 switches the limit value in the control device 60 based on the voltage detection value detected by the voltage detector 40. That is, the limiter selector 690 switches between the limit value used when the integrator 654 of the PI controller 650 integrates the voltage correction value and the limit value used when the limiter 660 calculates the reactive power output command value Qc based on the voltage detection value detected by the voltage detector 40. More specifically, when the voltage detection value detected by the voltage detector 40 is a value that can be used to determine that the AC system 1 is operating in a steady state, the limiter selector 690 does not limit the integral value integrated by the integrator 654, and switches the upper limit value Lim-max to a large (high) value and the lower limit value Lim-min to a small (low) value so that the reactive power represented by the reactive power output command value Qc calculated by the limiter 660 is the magnitude in a steady state. On the other hand, when the voltage detection value detected by the voltage detector 40 drops to a value that allows for determining that a system accident (hereinafter simply referred to as an "accident") has occurred in the bus bar 20 or any of the power transmission paths connected to the bus bar 20, the limiter selector 690 switches the upper limit value Lim-max to a small (low) value and the lower limit value Lim-min to a large (high) value in order to limit the integral value integrated by the integrator 654 to a small value when it is positive and to limit the integral value to a large value when it is negative, and to limit the reactive power represented by the reactive power output command value Qc calculated by the limiter 660 to a small value. After that, when the voltage detection value detected by the voltage detector 40 becomes a value that allows for determining that the AC system 1 is operating normally, the limiter selector 690 switches the upper limit value Lim-max to a large value and the lower limit value Lim-min to a small value. That is, when recovery from the accident occurs, the limiter selector 690 returns the upper limit value Lim-max to a large value and the lower limit value Lim-min to a small value in order to release the limitations on the integrator 654 and the limiter 660. The limiter selector 690 includes, for example, a comparator 692, two switches 694 (switches 694-1 and 694-2), and two rate limiters 696 (rate limiters 696-1 and 696-2).The limiter selector 690 is an example of the "limit value switching section" in the claims.

[0039] The comparator 692 compares the voltage detection value detected by the voltage detector 40 with a preset threshold value Vuv. In other words, the comparator 692 judges whether or not an accident has occurred in the AC system 1 based on the comparison result. The threshold value Vuv is set to a value lower than the rated value (=1 pu) of the voltage in the AC system 1 by, for example, a higher-level control device (not shown) that controls the transmission of power in the power transmission system and the operation of the AC system 1 in order to judge whether or not an accident has occurred in the AC system 1. The voltage detection value output by the voltage detector 40 may be an effective value, an absolute value, an average value of the absolute value, or an amplitude value (maximum value). The threshold value Vuv is set according to the expression format of the voltage detection value output by the voltage detector 40. The comparator 692 outputs a signal representing the comparison result, that is, a signal representing the result of judging whether or not an accident has occurred in the AC system 1, as a switching signal Ss to each of the switches 694-1 and 694-2.

[0040] Each of the switches 694 switches the corresponding limit value according to the switching signal Ss output by the comparator 692. Each of the switches 694 outputs the switched limit value to the corresponding rate limiter 696. More specifically, when the switching signal Ss output by the comparator 692 indicates that no accident has occurred in the AC system 1 (when the system is in a steady state), the switch 694-1 switches to a positive limit value Lim-PH having a large value (i.e., a looser limit). On the other hand, when the switching signal Ss indicates that an accident has occurred (when the system is in an accident state), the switch 694-1 switches to a positive limit value Lim-PL having a small value (i.e., a stricter limit). The switch 694-1 outputs either the switched positive limit value Lim-PH or the positive limit value Lim-PL to the corresponding rate limiter 696-1 as the positive limit value Lim-P. Similarly, the switch 694-2 switches to a small negative limit value Lim-NH when the switching signal Ss indicates a steady state, and switches to a large negative limit value Lim-NL when the switching signal Ss indicates an accident. The switch 694-2 outputs either the switched negative limit value Lim-NH or the negative limit value Lim-NL as the negative limit value Lim-N to the corresponding rate limiter 696-2. The positive limit value Lim-PL and the negative limit value Lim-NL are examples of the "first limit value" in the claims, and the positive limit value Lim-PH and the negative limit value Lim-NH are examples of the "second limit value" in the claims.

[0041] The positive limit value Lim-PH, the positive limit value Lim-PL, the negative limit value Lim-NH, and the negative limit value Lim-NL are each set by, for example, a higher-level control device (not shown). Here, the higher-level control device sets the positive limit value Lim-PH to a value greater (higher) than the positive rated value (=1 pu) of the reactive power output in the reactive power compensator 30, and sets the negative limit value Lim-NH to a value smaller (lower) than the negative rated value (=-1 pu) of the reactive power output. As a result, the limitations imposed by the positive limit value Lim-PH and the negative limit value Lim-NH are wider (less restrictive) than the rated value of the reactive power output in the reactive power compensator 30. On the other hand, the upper control device sets a positive predetermined value smaller (lower) than the positive rated value (=1 pu) of the reactive power output as the positive limit value Lim-PL, and sets a value larger (higher) than the negative rated value (=-1 pu) of the reactive power output as the negative limit value Lim-NL. As a result, the restrictions imposed by the positive limit value Lim-PL and the negative limit value Lim-NL become narrower (stricter) than the rated value of the reactive power output in the reactive power compensator 30. The upper control device may set the positive limit value Lim-PL and the negative limit value Lim-NL to the same value. For example, the upper control device may set each of the positive limit value Lim-PL and the negative limit value Lim-NL to "0".

[0042] Each of the rate limiters 696 adjusts the change in the limit value output by the corresponding switch 694 based on a preset coefficient of the change rate. The coefficient of the change rate determines the change rate of the limit value so that the limit value changes instantly when an accident occurs in the AC system 1 and changes over a predetermined time when the system is restored from the accident. The change rate of the limit value is set by, for example, an upper control device (not shown) based on the requirements for operation of the AC system 1 or the power transmission system to which the AC system 1 is connected, at a change rate that can suppress the voltage fluctuation in the bus 20. The change rate is, for example, a rate at which a predetermined time required for a change of 1.0 pu is 1.0 [sec]. Each of the rate limiters 696 outputs the limit value with the adjusted change to the integrator 654 and the limiter 660 included in the PI controller 650. More specifically, the rate limiter 696-1 adjusts the positive limit value Lim-P output by the switch 694-1 to change instantaneously when the positive limit value Lim-PH is switched to the positive limit value Lim-PL due to the occurrence of an accident, and adjusts the positive limit value Lim-P to change over a predetermined time when the positive limit value Lim-PL is switched to the positive limit value Lim-PH due to recovery from the accident. The rate limiter 696-1 outputs the positive limit value Lim-P after the change adjustment as the upper limit value Lim-max to the integrator 654 and the limiter 660, respectively. Similarly, the rate limiter 696-2 adjusts the negative limit value Lim-N output by the switch 694-2 so that it changes instantaneously when it is switched from the negative limit value Lim-NH to the negative limit value Lim-NL due to the occurrence of an accident, and adjusts it so that it changes over a predetermined time when it is switched from the negative limit value Lim-NL to the negative limit value Lim-NH due to recovery from the accident that has occurred. The rate limiter 696-2 outputs the negative limit value Lim-N after the change adjustment as the lower limit value Lim-min to each of the integrator 654 and the limiter 660.

[0043] Here, an example of the operation of the rate limiter 696 to change the limit value will be described. Fig. 4 is a diagram showing an example of the operation of the rate limiter 696 in the limiter selector 690 included in the control device 60 of the embodiment. Fig. 4 shows an example of the operation of the rate limiter 696-1 to change the upper limit value Lim-max when an accident occurs in the bus bar 20 or any of the power transmission paths connected to the bus bar 20, for example. Fig. 4 shows the change over time of the upper limit value Lim-max.

[0044] When the AC system 1 is operating steadily, the switch 694-1 outputs the positive limit value Lim-PH as the positive limit value Lim-P. Therefore, the rate limiter 696-1 outputs the positive limit value Lim-PH at this time as the upper limit value Lim-max. In other words, the rate limiter 696-1 outputs a large (high) upper limit value Lim-max.

[0045] Here, when an accident occurs at time ta, the switch 694-1 switches the positive limit value Lim-P from the positive limit value Lim-PH to the positive limit value Lim-PL in response to the switching signal Ss output by the comparator 692. As a result, the rate limiter 696-1 instantaneously outputs the positive limit value Lim-PL as the upper limit value Lim-max. In other words, the rate limiter 696-1 instantaneously changes the upper limit value Lim-max from a large (high) value to a small (low) value.

[0046] After that, at time to, for example, when the power transmission path where the accident occurred is cut off and the power transmission path is restored from the accident, the switch 694-1 switches the positive limit value Lim-P from the positive limit value Lim-PL to the positive limit value Lim-PH in response to the switching signal Ss output by the comparator 692. As a result, the rate limiter 696-1 changes the upper limit value Lim-max from the positive limit value Lim-PL to the positive limit value Lim-PH over a predetermined time. FIG. 4 shows a case in which the coefficient of the rate of change set in the rate limiter 696-1 is set to a rate of change at which the upper limit value Lim-max changes over a predetermined time P. As a result, the rate limiter 696-1 sequentially increases the upper limit value Lim-max from time to, and changes the upper limit value Lim-max so that it becomes the positive limit value Lim-PH at time tp when the predetermined time P has elapsed. That is, the rate limiter 696-1 changes the upper limit value Lim-max from a small (low) value to a large (high) value over a predetermined time P.

[0047] Through such an operation, the rate limiter 696-1 changes the positive limit value Lim-P output by the switch 694-1 at different speeds depending on whether an accident has occurred or has been restored from the accident, based on a preset coefficient of change rate. In the above explanation, the operation of the rate limiter 696-1 has been explained, but the operation of the rate limiter 696-2 is similar. Therefore, an explanation of the operation of the rate limiter 696-2 will be omitted.

[0048] Returning to Fig. 2, in the limiter selector 690, each rate limiter 696 may be omitted. In this case, the limiter selector 690 outputs either the positive limit value Lim-PH or the positive limit value Lim-PL switched by the switcher 694-1 as the upper limit value Lim-max to each of the integrator 654 and the limiter 660. Furthermore, the limiter selector 690 outputs either the negative limit value Lim-NH or the negative limit value Lim-NL switched by the switcher 694-2 as the lower limit value Lim-min to each of the integrator 654 and the limiter 660.

[0049] [Limiter selector processing] Next, an example of the processing in the limiter selector 690 will be described. Fig. 5 is a flowchart showing an example of the processing in the limiter selector 690 included in the control device 60 of the embodiment. The processing of this flowchart is repeatedly executed while the reactive power compensation device 30 is in operation. In the following description, it is assumed that the voltage detection value output by the voltage detector 40 is an effective value.

[0050] When the reactive power compensator 30 operates, the limiter selector 690 acquires the voltage detection value detected and output by the voltage detector 40 (step S100).

[0051] The comparator 692 compares the voltage detection value (effective value) with the threshold value Vuv and determines whether the voltage detection value is smaller than the threshold value Vuv (step S102). In step S102, if the voltage detection value is equal to or greater than the threshold value Vuv, the comparator 692 outputs a switching signal Ss representing the comparison result to each of the switches 694-1 and 694-2. Here, the fact that the voltage detection value is equal to or greater than the threshold value Vuv means that it is determined that the AC system 1 is operating normally (no accident has occurred). Therefore, the comparator 692 outputs a switching signal Ss representing that the AC system 1 is operating normally to each of the switches 694-1 and 694-2.

[0052] The switch 694-1 switches the positive limit value Lim-P to be output to the positive limit value Lim-PH and outputs it to the rate limiter 696-1, and the switch 694-2 switches the negative limit value Lim-N to be output to the negative limit value Lim-NH and outputs it to the rate limiter 696-2 (step S104).The rate limiter 696-1 then outputs the positive limit value Lim-P (positive limit value Lim-PH) output by the switch 694-1 as it is as the upper limit value Lim-max to each of the integrator 654 and the limiter 660 included in the PI controller 650 (see FIG. 4). The rate limiter 696-2 outputs the negative limit value Lim-N (negative limit value Lim-NH) output by the switch 694-2 as the lower limit value Lim-min as it is to the integrator 654 and the limiter 660 included in the PI controller 650 (see FIG. 4). As a result, the integrator 654 and the limiter 660 operate under the restriction (that is, in a state where no restriction is applied) according to the upper limit value Lim-max, which is the positive limit value Lim-PH, and the lower limit value Lim-min, which is the negative limit value Lim-NH. Then, the pulse generator 680 outputs a gate pulse signal based on the reactive power output command value calculated by the limiter 660 to the reactive power compensation device 30. As a result, the reactive power compensation device 30 outputs the reactive power in the steady state in the AC system 1 according to the gate pulse signal to the bus 20. Thereafter, the limiter selector 690 returns the process to step S100, and repeats the process for the next voltage detection value detected by the voltage detector 40.

[0053] On the other hand, in step S102, if the voltage detection value is smaller than the threshold value Vuv, the comparator 692 outputs a switching signal Ss representing this comparison result to each of the switches 694-1 and 694-2. Here, the fact that the voltage detection value is smaller than the threshold value Vuv means that it is determined that the AC system 1 is not operating normally (that an accident has occurred). Therefore, the comparator 692 outputs a switching signal Ss representing that the AC system 1 is operating during an accident to each of the switches 694-1 and 694-2.

[0054] The switch 694-1 switches the positive limit value Lim-P to be output to the positive limit value Lim-PL and outputs it to the rate limiter 696-1, and the switch 694-2 switches the negative limit value Lim-N to be output to the negative limit value Lim-NL and outputs it to the rate limiter 696-2 (step S106).Then, the rate limiter 696-1 outputs the positive limit value Lim-P (positive limit value Lim-PL) output by the switch 694-1 as it is (instantaneously) as the upper limit value Lim-max to each of the integrator 654 and the limiter 660 provided in the PI controller 650 (see FIG. 4). The rate limiter 696-2 outputs the negative limit value Lim-N (negative limit value Lim-NL) output by the switch 694-2 as it is (instantaneously) as the lower limit value Lim-min to the integrator 654 and the limiter 660 included in the PI controller 650 (see FIG. 4). As a result, the integrator 654 and the limiter 660 operate under the restriction (that is, in a restricted state) according to the upper limit value Lim-max, which is the positive limit value Lim-PL, and the lower limit value Lim-min, which is the negative limit value Lim-NL. Then, the pulse generator 680 outputs a gate pulse signal based on the reactive power output command value calculated by the limiter 660 to the reactive power compensator 30. As a result, the reactive power compensator 30 outputs reactive power at the time of a fault in the AC system 1 according to the gate pulse signal to the bus 20. As a result, in the AC system 1, voltage fluctuations on the bus bar 20 caused by the occurrence of a fault are suppressed.

[0055] Thereafter, the limiter selector 690 acquires the voltage detection value that is next detected and output by the voltage detector 40 (step S108).

[0056] The comparator 692 compares the voltage detection value with the threshold value Vuv and determines whether the voltage detection value is greater than the threshold value Vuv (step S110). If the voltage detection value is equal to or less than the threshold value Vuv in step S110, the comparator 692 returns the process to step S108 and repeats the determination on the voltage detection value detected next by the voltage detector 40. This means that the voltage detection value being equal to or less than the threshold value Vuv means that it is determined that the AC system 1 has not recovered from the accident that occurred in the AC system 1 (the accident continues). Therefore, the comparator 692 continues to output the switching signal Ss, which indicates that the AC system 1 is operating during an accident, to each of the switches 694-1 and 694-2. As a result, the pulse generator 680 continues to output a gate pulse signal to the reactive power compensation device 30 based on the reactive power output command value in the event of an accident calculated by the limiter 660, and the reactive power compensation device 30 continues to output reactive power to the bus 20 in the event of an accident, thereby continuing to suppress voltage fluctuations on the bus 20 due to the accident.

[0057] On the other hand, in step S110, if the voltage detection value is greater than the threshold value Vuv, the comparator 692 outputs a switching signal Ss representing this comparison result to each of the switches 694-1 and 694-2. Here, the fact that the voltage detection value is greater than the threshold value Vuv means that it is determined that the AC system 1 has recovered from the accident that occurred in the AC system 1 and is operating normally (no accident has occurred). Therefore, the comparator 692 outputs a switching signal Ss representing that the AC system 1 is operating normally to each of the switches 694-1 and 694-2.

[0058] The switch 694-1 switches the positive limit value Lim-P to be output to the positive limit value Lim-PH and outputs it to the rate limiter 696-1, and the switch 694-2 switches the negative limit value Lim-N to be output to the negative limit value Lim-NH and outputs it to the rate limiter 696-2 (step S112). As a result, the rate limiter 696-1 changes the upper limit value Lim-max output to each of the integrator 654 and the limiter 660 included in the PI controller 650 from the positive limit value Lim-PL to the positive limit value Lim-PH over a predetermined time (for example, 1.0 [sec] for a change of 1.0 pu) (see FIG. 4). The rate limiter 696-2 changes the lower limit value Lim-min outputted to the integrator 654 and the limiter 660 of the PI controller 650 from the negative limit value Lim-NL to the negative limit value Lim-NH over a predetermined time (see FIG. 4). As a result, the integrator 654 and the limiter 660 operate under the limit (that is, the limit is gradually relaxed) according to the upper limit value Lim-max and the lower limit value Lim-min inputted when they operate. More specifically, the integrator 654 gradually increases the integral value obtained by integrating the inputted voltage correction value. The limiter 660 gradually releases the limit on the magnitude of the reactive power represented by the calculated reactive power output command value. Then, the pulse generator 680 outputs a gate pulse signal based on the reactive power output command value calculated by the limiter 660 to the reactive power compensation device 30. As a result, the reactive power compensator 30 gradually changes the reactive power output to the bus 20 in response to the gate pulse signal from the fault in the AC system 1 to the steady-state reactive power. As a result, the suppression of the voltage fluctuation in the bus 20 due to the fault is gradually released in the AC system 1. Thereafter, the limiter selector 690 returns the process to step S100 and repeats the process for the voltage detection value detected by the voltage detector 40 next.

[0059] With such a configuration and processing, in the control device 60, when the voltage detection value detected by the voltage detector 40 is a value that allows for determining that the AC system 1 is operating steadily, the limiter selector 690 does not limit the integral value integrated by the integrator 654, and switches the upper limit value Lim-max and the lower limit value Lim-min to large (high) values ​​so that the reactive power represented by the reactive power output command value calculated by the limiter 660 is the magnitude in steady state. On the other hand, in the control device 60, when the voltage detection value detected by the voltage detector 40 drops to a value that allows for determining that an accident has occurred in the AC system 1, the limiter selector 690 limits the integral value integrated by the integrator 654 to a small value, and switches the upper limit value Lim-max and the lower limit value Lim-min to small (low) values ​​so as to limit the reactive power represented by the reactive power output command value calculated by the limiter 660 to a small value. As a result, in the AC system 1, the integral value obtained by integrating the voltage correction value by the integrator 654 while a fault occurs in the AC system 1 does not exceed the upper limit value Lim-max and the lower limit value Lim-min output by the limiter selector 690, and even if the AC system 1 subsequently recovers from the fault (including instantaneous recovery), the integral value output by the integrator 654 can be prevented from suddenly becoming a large value. As a result, in the control device 60, the PI controller 650 does not perform proportional-integral control more than necessary due to a large integral value. As a result, in the AC system 1, it is possible to suppress an overshoot of the reactive power output by the reactive power compensator 30 that may occur when recovering from a fault that has occurred, and to prevent an overvoltage from being generated in the bus 20. Furthermore, in the AC system 1, even if the proportional value output by the proportional unit 652 becomes large due to a large difference between the voltage command value and the voltage detection value at the time of an accident, the limiter 660 limits the calculated reactive power output command value in accordance with the upper limit value Lim-max and the lower limit value Lim-min.As a result, in the control device 60, even if a large proportional integral value is output to the limiter 660, for example, when the positive limit value Lim-PL and the negative limit value Lim-NL are set to the same value, the limiter 660 can limit the calculated reactive power output command value regardless of the proportional integral value output by the PI controller 650. As a result, in the AC system 1, it is possible to prevent the reactive power output by the reactive power compensator 30 from becoming larger than necessary in the event of a fault, and to prevent an overvoltage from being generated in the bus 20.

[0060] Furthermore, in the control device 60, when the voltage detection value detected by the voltage detector 40 thereafter becomes a value that allows the AC system 1 to determine that it is operating normally, that is, when it becomes a value that allows the AC system 1 to determine that it has recovered from the fault, the limiter selector 690 switches (returns) the upper limit value Lim-max and the lower limit value Lim-min to larger values ​​in order to release the restrictions on the integrator 654 and the limiter 660. At this time, if the limiter selector 690 is configured to include a rate limiter 696, the rate limiter 696 returns the upper limit value Lim-max and the lower limit value Lim-min to larger values ​​over a predetermined period of time. In other words, the rate limiter 696 slows down the rate of change of the upper limit value Lim-max and the lower limit value Lim-min. As a result, in the AC system 1, it is possible to suppress a sudden change in the reactive power output by the reactive power compensator 30 when recovering from the fault that has occurred, and to prevent an overvoltage from occurring on the bus 20.

[0061] As described above, according to the control device 60 of the embodiment, the limiter selector 690 switches the upper limit value Lim-max to a small (low) value and the lower limit value Lim-min to a large (high) value in order to limit the integral operation of the voltage correction value in the integrator 654 included in the PI controller 650 and the reactive power output command value calculated by the limiter 660 in the event of a fault in the AC system 1 based on the voltage detection value detected by the voltage detector 40. As a result, the control device 60 of the embodiment can limit the reactive power output command value in the event of a fault and cause the reactive power compensator 30 to output reactive power. As a result, in the AC system 1 to which the reactive power compensator 30 including the control device 60 of the embodiment is connected, it is possible to suppress an overshoot of the reactive power output by the reactive power compensator 30, which may occur when recovering from a fault that has occurred. As a result, in the AC system 1 to which the reactive power compensator 30 including the control device 60 of the embodiment is connected, it is possible to realize a system with improved reliability of power transmission in the power transmission system.

[0062] In the above-described embodiment, the AC system 1 has been described as being provided with the control device 60 and the reactive power compensator 30 as different components. However, the configuration is not limited to the control device 60 and the reactive power compensator 30 being separate. For example, the control device 60 may be a component included in the reactive power compensator 30. In this case, the configuration, operation, and processing of the control device 60 may be equivalent to the configuration, operation, and processing of the control device 60 described above. Therefore, detailed description of the configuration, operation, and processing in the case where the control device 60 is a component included in the reactive power compensator 30 will be omitted.

[0063] As described above, for example, the control method executed by the control device 60 of the reactive power compensator 30 included in the AC system 1 is a control method for controlling the output of reactive power from the reactive power compensator 30 connected to the AC system 10 based on a voltage detection value detected by a voltage detector 40 arranged at least at a connection point (e.g., the bus 20) with the AC system 10, and a computer (such as a processor) of the control device 60 controls the output of reactive power based on a proportional value according to a value based on the voltage detection value and limit values ​​(upper limit value Lim-max and lower limit value Lim-min). This is a control method in which a proportional integral value based on an integral value obtained by integrating a value based on a detection value is calculated, the proportional integral value is converted into a reactive power output command value for causing reactive power compensation device 30 to output reactive power, and when the voltage detection value drops, the limit value is switched to a first limit value (positive limit value Lim-PL and negative limit value Lim-NL) that limits at least the integral value obtained by integrating a value based on the voltage detection value to a low value, and when the voltage detection value is restored, the limit value is switched to a second limit value (positive limit value Lim-PH and negative limit value Lim-NH) that does not limit the integral value.

[0064] As described above, for example, the program executed by the control device 60 of the reactive power compensator 30 included in the AC system 1 is a program executed in the control device 60 that controls the output of reactive power from the reactive power compensator 30 connected to the AC system 10 based on at least a voltage detection value detected by a voltage detector 40 arranged at a connection point (e.g., the bus 20) with the AC system 10, and controls a computer (processor, etc.) of the control device 60 to control a proportional value according to a value based on the voltage detection value and a limit value (an upper limit value Lim-max and a lower limit value Lim-min). Therefore, this is a program that calculates a proportional integral value based on an integral value obtained by integrating a value based on a voltage detection value, converts the proportional integral value into a reactive power output command value for causing the reactive power compensation device 30 to output reactive power, and, when the voltage detection value drops, switches the limit value to a first limit value (positive limit value Lim-PL and negative limit value Lim-NL) that limits at least the integral value obtained by integrating a value based on the voltage detection value to a low value, and, when the voltage detection value is restored, switches the limit value to a second limit value (positive limit value Lim-PH and negative limit value Lim-NH) that does not limit the integral value.

[0065] According to the embodiment described above, the control device (60) for a reactive power compensator controls an output of reactive power from a reactive power compensator (30) connected to an AC system, based on a voltage detection value detected by a voltage detection device (40) arranged at least at a connection point (e.g., 20) with the AC system (10). The control device (60) for a reactive power compensator includes a proportional unit (652) that outputs a proportional value according to a value based on the voltage detection value, and an integrator (654) that outputs an integral value obtained by integrating a value based on the voltage detection value according to input limit values ​​(an upper limit value Lim-max and a lower limit value Lim-min), and outputs a proportional integral value based on the proportional value and the integral value, and a proportional / integral controller (650) that outputs the proportional / integral value based on the proportional value and the integral value, and and a limit value switching unit (690) that switches a limit value that limits the integration of a value based on at least a voltage detection value by an integrator, wherein the limit value switching unit switches the limit value to a first limit value (positive limit value Lim-PL and negative limit value Lim-NL) that limits the integral value to a low value when the voltage detection value drops, and switches the limit value to a second limit value (positive limit value Lim-PH and negative limit value Lim-NH) that does not limit the integral value when the voltage detection value is restored, thereby making it possible to suppress overshoot of reactive power output by the reactive power compensation device that may occur when recovering from a grid accident that occurred in the power transmission system.

[0066] Although some embodiments of the present invention have been described, these embodiments are presented as examples and are not intended to limit the scope of the invention. These embodiments can be implemented in various other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their modifications are included in the scope of the invention and its equivalents described in the claims, as well as in the scope and spirit of the invention. [Explanation of symbols]

[0067] 1···AC power system, 10···AC power system, 20···bus, 30···var compensator, 40···voltage detector, 50···current detector, 60···controller, 610···adder, 620···adder, 630···multiplier, 640···adder, 650···PI controller, 652···proportional regulator, 654···integrator, 656···adder, 660···limiter, 670···Q / θ converter, 680···pulse generator, 690···limiter selector, 692···comparator, 694, 694-1, 694-2···switch, 696, 696-1, 696-2···rate limiter

Claims

1. A control device for a reactive power compensation device that controls an output of reactive power from a reactive power compensation device connected to an AC system based on a voltage detection value detected by a voltage detection device disposed at least at a connection point with the AC system, a proportional integral controller including a proportional controller that outputs a proportional value according to a value based on the voltage detection value, and an integrator that outputs an integral value obtained by integrating a value based on the voltage detection value according to an input limit value, and that outputs a proportional integral value based on the proportional value and the integral value; a command value conversion unit that converts the proportional integral value into a reactive power output command value for causing the reactive power compensation device to output the reactive power; a limit value switching unit that switches the limit value that limits the integration of a value based on the voltage detection value by at least the integrator; Equipped with The limit value switching unit is When the voltage detection value decreases, the limit value is switched to a first limit value that limits the integral value to a low value; When the voltage detection value is restored, the limit value is switched to a second limit value that does not limit the integral value. Control device for reactive power compensation device.

2. The limit value switching unit outputs the limit value to the command value conversion unit, the command value conversion unit limits the magnitude of the reactive power output command value to be converted in accordance with the input limit value. The control device for a reactive power compensator according to claim 1.

3. a correction unit that corrects a value based on the voltage detection value based on a current detection value detected by a current detection device that detects a current flowing between the AC system and the static var compensator, The control device for a reactive power compensator according to claim 2.

4. The correction unit corrects the value based on the voltage detection value based on a difference between a current command value of the reactive power compensation device and the current detection value. The control device for a reactive power compensator according to claim 3.

5. the limit value switching unit switches the limit value from the first limit value to the second limit value over a predetermined period of time when the voltage detection value is restored. The control device for a reactive power compensation device according to any one of claims 1 to 4.

6. 1. A method for controlling a reactive power compensation device, the method comprising: controlling an output of reactive power from a reactive power compensation device connected to an AC system, based on a voltage detection value detected by a voltage detection device disposed at least at a connection point with the AC system, the method comprising: A computer of the control device of the static var compensator, determining a proportional integral value based on a proportional value corresponding to a value based on the voltage detection value and an integral value obtained by integrating the value based on the voltage detection value in accordance with a limit value; converting the proportional integral value into a reactive power output command value for causing the reactive power compensation device to output the reactive power; When the voltage detection value decreases, the limit value is switched to a first limit value that limits the integral value, which is an integral of at least a value based on the voltage detection value, to a low value; When the voltage detection value is restored, the limit value is switched to a second limit value that does not limit the integral value. A method for controlling a reactive power compensator.

7. A program executed in a control device of a reactive power compensation device that controls an output of reactive power from a reactive power compensation device connected to an AC system based on a voltage detection value detected by a voltage detection device disposed at least at a connection point with the AC system, A computer of the control device of the static var compensator determining a proportional integral value based on a proportional value corresponding to a value based on the voltage detection value and an integral value obtained by integrating the value based on the voltage detection value in accordance with a limit value; converting the proportional integral value into a reactive power output command value for causing the reactive power compensation device to output the reactive power; When the voltage detection value decreases, the limit value is switched to a first limit value that limits the integral value, which is an integral of at least a value based on the voltage detection value, to a low value; When the voltage detection value is restored, the limit value is switched to a second limit value that does not limit the integral value. program.

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