JP7651399B2 - Control device for reactive power compensation device, control method for reactive power compensation device, and program - Google Patents

Description

Embodiments of the present invention relate to a control device for a reactive power compensation device, a control method for a reactive power compensation device, and a program.

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 corresponding 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) occurring in one 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 the output command value output by the control device.

The power transmission system also includes components for preventing the accident from spreading to other power transmission paths, such as a circuit breaker that cuts off the power transmission path where the accident occurred, and for recovering from the accident. For this reason, when the accident is recovered from, that is, when the voltage of the busbar 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 will not be able to stop or reduce the capacitive reactive power output in time, and the reactive power compensator will continue to output capacitive reactive power in accordance with the amount of drop in the system voltage due to the accident for a while. In this case, the reactive power that is continuously output by the reactive power compensator may cause an overvoltage on the busbar.

In this regard, for example, Patent Document 1 discloses technology relating to a reactive power compensation device and a control circuit that prevent the occurrence of overvoltage. Patent Document 1 describes switching the 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 the 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 technology described in Patent Document 1 prevents overvoltage from occurring when the grid voltage is restored.

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. For this reason, 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.

JP 2019-122144 A

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 the reactive power output by the reactive power compensation device, which can occur when recovering from a grid fault that occurs in a power transmission system.

The control device of the reactive power compensation device of the embodiment has a proportional integral controller, a command value conversion unit, and a limit value switching unit. The control device of the reactive power compensation device controls the output of reactive power from the reactive power compensation device connected to the 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 that limits at least the integration of the 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.

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. 1 is a diagram showing an example of a configuration of a control device for a reactive power compensation device included in an AC system according to an embodiment; 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. 6 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. 5 is a flowchart showing an example of a process in a limiter selector included in the control device of the embodiment.

The control device for a reactive power compensation device, the control method for a reactive power compensation device, and the program of the embodiment will be described below with reference to the drawings.

[Configuration of AC system]
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 transmit AC power from the AC system on the power transmission side directly 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.

The AC system 1 shown in FIG. 1 includes, for example, an AC system 10, a busbar 20, a reactive power compensation device 30, a voltage detector 40, a current detector 50, and a control device 60.

The AC system 10 is a facility that supplies AC power to the interconnected bus 20, or receives AC power from the bus 20. The AC system 10 may be, for example, a power generation facility that generates AC power, or a facility that transmits AC power transmitted from an AC system in another AC system on the power transmission side to an AC system in an AC system on the power receiving side, or a facility that supplies AC power to each consumer at the connected end.

The reactive power compensation device 30 is connected to the AC system 10 via the bus 20. The reactive power compensation device 30 outputs capacitive or inductive reactive power (hereinafter simply referred to as "reactive power") to the bus 20 in accordance with control from the control device 60. The reactive power compensation device 30 suppresses voltage fluctuations on the bus 20 by outputting reactive power to the bus 20 according to a gate pulse signal representing a reactive power output command value output by the control device 60.

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

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

The control device 60 controls the output of reactive power from the reactive power compensation device 30. 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 generates a command value (hereinafter referred to as the "reactive power output command value") for causing the reactive power compensation device 30 to output reactive power. The control device 60 outputs a gate pulse signal based on the generated reactive power output command value to the reactive power compensation device 30. As a result, the reactive power compensation device 30 outputs reactive power corresponding to the gate pulse signal to the bus 20.

The control device 60 and the components of 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 of the control device 60 may be realized by hardware (including circuitry) such as an LSI (Large Scale Integration), ASIC (Application Specific Integrated Circuit), FPGA (Field-Programmable Gate Array), or 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 of 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 a hard disk drive (HDD) 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 mounting the storage medium in a drive device provided in the control device 60 or the AC system 1.

[Configuration of the control device]
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 a different configuration, or other components may be added.

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 the power output to the bus 20 and the 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, for example, as a subtractor. The adder 610 outputs the calculated result (hereinafter referred to as the "voltage difference value") to the adder 640.

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 the power output to the bus 20 or the power transmission path connected to the bus 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, for example, as a subtractor. The adder 620 outputs the calculated result (hereinafter referred to as the "current difference value") to the multiplier 630.

The multiplier 630 applies a predetermined gain to the current difference value calculated by the adder 620. 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 applied to the current detection value detected by the current detector 50. In this configuration, the adder 620 may be omitted. The predetermined gain is set, for example, 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.

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 with the current multiplication value. The adder 640 outputs the result of correcting the voltage difference value (hereinafter referred to as the "voltage correction value") to the PI controller 650. Although FIG. 2 shows a configuration including the adder 640, the adder 640 may be omitted. In other words, the voltage difference value calculated by the adder 610 may be 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.

The PI controller 650 performs proportional-integral control (PI control) based on the voltage correction value output by the adder 640. Alternatively, if the adder 640 is omitted from 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 that 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 the voltage detection value" in the claims.

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 the "proportional value") to the adder 656.

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 the "limit value"), described later, output by the limiter selector 690. 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 the "integrated 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 integrated value to the adder 656.

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 of the integrator 654 in the PI controller 650 provided 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 value IN inputted 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 the change over time of the input value IN inputted to the integrator 654, and FIG. 3(c) shows an example of the change over time of the integral value OUT integrated and outputted by the integrator 654. For reference, FIG. 3(d) shows an example of the change over time in the integrated value OUT when the integrator 654 simply integrates the input value IN without following a limit value, that is, when the integrator 654 is a normal integrator without a limiter, similar to the integrator in the PI controller provided in the control device of a conventional reactive power compensation device.

As shown in FIG. 3B, when the input of the input value IN of a positive value = "1" starts 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, for example, based on the following formula (1).

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].

As a result, as shown in FIG. 3(c) and FIG. 3(d), the integral value OUT output by the integrator 654 increases. Then, when the integral value OUT becomes 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. FIG. 3(c) 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 becomes the upper limit value Lim-max, the integrator 654 may stop integrating the value corresponding to the input value IN, or may continue the integration operation with the value corresponding 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.

By this integration operation, the integrator 654 integrates a value according to the input value IN until the integrated value OUT becomes the limit value output by the limiter selector 690, and after the integrated value OUT becomes the limit value, it holds that value so that it does not exceed the limit value. In the above explanation, the case where the input value IN is a positive value is described, but the same applies when the input value IN is a negative value. Therefore, a description of the integration operation of the integrator 654 when the input value IN is a negative value is omitted.

Returning to FIG. 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.

The limiter 660 calculates a reactive power output command value for causing the reactive power compensation device 30 to 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 compensation device, or may be configured to limit the magnitude of the 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 the upper limit value Lim-max and the 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 the "reactive power output command value Qc") to the Q/θ converter 670. The limiter 660 is an example of the "command value conversion unit" in the claims.

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.

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 to the reactive power compensation device 30 as a gate pulse signal. As a result, the reactive power compensation device 30 outputs reactive power corresponding to the gate pulse signal output by the pulse generator 680, i.e., the control device 60, to the bus 20.

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

The limiter selector 690 switches the limit value (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 when integrating the voltage correction value in the integrator 654 provided in the PI controller 650 and the limit value 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 steady operation is being performed in the AC system 1, 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 the steady state. On the other hand, when the voltage detection value detected by the voltage detector 40 falls to a value that can be determined to have occurred in the bus 20 or any of the power transmission paths connected to the bus 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 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 can be determined to be operating steadily in the AC system 1, 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. In other words, 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 restrictions on the integrator 654 and the limiter 660. The limiter selector 690 includes, for example, a comparator 692, two switches 694 (switcher 694-1 and switcher 694-2), and two rate limiters 696 (rate limiter 696-1 and rate limiter 696-2). The limiter selector 690 is an example of a "limit value switching unit" in the claims.

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 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 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 an accident has occurred in the AC system 1, as a switching signal Ss to each of the switches 694-1 and 694-2.

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 an accident has occurred), 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, when the switching signal Ss indicates that the switching signal is in a steady state, the switch 694-2 switches to a small negative limit value Lim-NH, and when the switching signal Ss indicates that an accident is occurring, the switch 694-2 switches to a large negative limit value Lim-NL. 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.

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, for example, by 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 compensation device 30, and sets the negative limit value Lim-NH to a value less (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 compensation device 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 are narrower (stricter) than the rated value of the reactive power output in the reactive power compensation device 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 both the positive limit value Lim-PL and the negative limit value Lim-NL to "0".

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 when an accident occurs in the AC system 1, the limit value changes instantly, and when the accident is restored, the limit value changes over a predetermined time. 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 voltage fluctuations in the bus 20. The change rate is, for example, a rate at which a predetermined time required for a 1.0 pu change 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 provided 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 so that it changes instantly 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 so that it changes 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 each of the integrator 654 and the limiter 660. Similarly, the rate limiter 696-2 adjusts the negative limit value Lim-N output by the switch 694-2 so that it changes instantly 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. 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.

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 provided 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, for example, an accident occurs on the bus bar 20 or on any of the power transmission paths connected to the bus bar 20. FIG. 4 shows the change over time in the upper limit value Lim-max.

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.

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. This causes the rate limiter 696-1 to instantly output the positive limit value Lim-PL as the upper limit value Lim-max. In other words, the rate limiter 696-1 instantly changes the upper limit value Lim-max from a large (high) value to a small (low) value.

After that, at time t0, when the power transmission path on which the accident occurred is restored by, for example, being cut off, 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. Figure 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 gradually 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. In other words, the rate limiter 696-1 changes the upper limit value Lim-max from a small (low) value to a large (high) value over the predetermined time P.

By operating in this manner, 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 recovered from, 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, a description of the operation of the rate limiter 696-2 will be omitted.

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

[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 provided 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.

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

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 this 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.

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). Then, the rate limiter 696-1 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 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-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. The limiter selector 690 then returns the process to step S100 and repeats the process for the next voltage detection value detected by the voltage detector 40.

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.

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, the 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 compensation device 30. As a result, the reactive power compensation device 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 busbar 20 caused by an accident are suppressed.

Then, the limiter selector 690 next obtains the voltage detection value detected and output by the voltage detector 40 (step S108).

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 of the voltage detection value detected by the voltage detector 40 next. This means that the voltage detection value being equal to or less than the threshold value Vuv means that the system 1 has not recovered from the accident that occurred (the accident continues). Therefore, the comparator 692 continues to output the switching signal Ss, which indicates that the 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 during the accident calculated by the limiter 660, and the reactive power compensation device 30 continues to output reactive power to the bus 20 during the accident, thereby continuing to suppress voltage fluctuations on the bus 20 due to the accident.

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 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.

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 limiter 660 of 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 compensation device 30 gradually changes the reactive power output to the bus 20 in response to the gate pulse signal during an accident in the AC system 1 to the steady-state reactive power. As a result, in the AC system 1, the suppression of the voltage fluctuation of the bus 20 due to the accident that occurred is gradually released. After that, 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.

In the control device 60, when the voltage detection value detected by the voltage detector 40 is a value that can be used to determine that steady operation is being performed in the AC system 1, 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 the steady state. On the other hand, in the control device 60, when the voltage detection value detected by the voltage detector 40 falls to a value that can be used to determine that an accident has occurred in the AC system 1, the limiter selector 690 switches the upper limit value Lim-max and the lower limit value Lim-min to small (low) values so that the integral value integrated by the integrator 654 is limited to a small value and the reactive power represented by the reactive power output command value calculated by the limiter 660 is limited 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, which 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 the large difference between the voltage command value and the voltage detection value at the time of the accident, the limiter 660 limits the calculated reactive power output command value according to the upper limit value Lim-max and the lower limit value Lim-min. As a result, even if a large proportional integral value is output to the limiter 660 in the control device 60, 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 compensation device 30 from becoming larger than necessary at the time of an accident, and to prevent an overvoltage from being generated on the bus 20.

Furthermore, in the control device 60, when the voltage detection value detected by the voltage detector 40 thereafter becomes a value that can be used to determine that the AC system 1 is operating steadily, that is, when the voltage detection value becomes a value that can be used to determine that the AC system 1 has recovered from the accident, 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 sudden changes in the reactive power output by the reactive power compensation device 30 when recovering from a fault, and to prevent overvoltage from occurring on the busbar 20.

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 of the PI controller 650 and the reactive power output command value calculated by the limiter 660 in the event of an accident 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 an accident and cause the reactive power compensation device 30 to output reactive power. As a result, in the AC system 1 to which the reactive power compensation device 30 equipped with the control device 60 of the embodiment is connected, it is possible to suppress overshooting of the reactive power output by the reactive power compensation device 30, which may occur when recovering from an accident that has occurred. As a result, in the AC system 1 to which the reactive power compensation device 30 equipped with 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.

In the embodiment described above, a configuration has been described in which the control device 60 and the reactive power compensation device 30 are provided as different components in the AC system 1. However, the control device 60 and the reactive power compensation device 30 are not limited to being configured separately. For example, the control device 60 may be a component provided in the reactive power compensation device 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, a detailed description of the configuration, operation, and processing in the case where the control device 60 is a component provided in the reactive power compensation device 30 will be omitted.

As described above, for example, the control method executed by the control device 60 of the reactive power compensation device 30 provided in the AC system 1 is a control method for controlling the output of reactive power from the reactive power compensation device 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., bus bar 20) with the AC system 10, in which a computer (processor, etc.) of the control device 60 controls the voltage according to 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 the detected value and an integral value obtained by integrating a value based on the detected value are calculated, the proportional integral value is converted 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, 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.

As explained above, for example, the program executed by the control device 60 of the reactive power compensation device 30 provided 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 compensation device 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., bus bar 20) with the AC system 10, and the program is configured to cause the computer (processor, etc.) of the control device 60 to input a proportional value according to a value based on the voltage detection value and a limit value (upper limit value Lim-max and lower limit value Lim-min). Therefore, the program determines a proportional integral value based on an integral value obtained by integrating a value based on the 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 that integrates 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.

According to the embodiment described above, the control device (60) for a reactive power compensation device controls the output of reactive power from a reactive power compensation device (30) connected to an AC system based on a voltage detection value detected by a voltage detection device (40) arranged at at least a connection point (e.g., 20) with the AC system (10), and includes a proportional device (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 (upper limit value Lim-max and lower limit value Lim-min), a proportional integral controller (650) that outputs a proportional integral value based on the proportional value and the integral value, and a proportional integral controller (652) that outputs the proportional integral value according to the integral value for causing the reactive power compensation device to output reactive power. The power transmission system includes a command value conversion unit (660) that converts the voltage detected by the power supply into a reactive power output command value for the power supply, and a limit value switching unit (690) that switches the limit value that limits the integral of a value based on at least the voltage detection value by an integrator. When the voltage detection value drops, 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, and when the voltage detection value is restored, the limit value switches to a second limit value (positive limit value Lim-PH and negative limit value Lim-NH) that does not limit the integral value. This makes it possible to suppress overshooting 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.

Although several 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 gist of the invention. These embodiments and their modifications are within the scope of the invention and its equivalents as set forth in the claims, as well as the scope and gist of the invention.

1: AC system, 10: AC system, 20: busbar, 30: reactive power compensation device, 40: voltage detector, 50: current detector, 60: control device, 610: adder, 620: adder, 630: multiplier, 640: adder, 650: PI controller, 652: proportional, 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 (7)

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 compensator. 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 compensation device according to claim 1 . 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. 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. 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. 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. 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, the program 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.
program.

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