JP7754700B2 - Voltage control method for power distribution substation equipment, voltage control system, and power distribution substation equipment - Google Patents

Description

The present invention relates to a voltage control method, a voltage control system, and substation equipment, and to a voltage control method, a voltage control system, and substation equipment for distribution substation equipment.

Distribution substations are power facilities installed between transmission lines within a power system. They transform transmitted extra-high voltage power using transformers to high voltage power for high-voltage consumers, and then transmit the power to the distribution lines of the high-voltage power system. Distribution substations are equipped with voltage control devices such as those shown in Patent Document 1 to maintain the voltage of the high-voltage power system within a specified range. Voltage control is performed by stepping up and down the voltage (LR control) through tap switching of an on-load tap changing transformer (LRT), and by phase modification control through the opening and closing of power capacitors (SC) and shunt reactors (Shr).

Japanese Patent Application Publication No. 11-206018

In recent years, with the introduction of the photovoltaic power generation feed-in system, a large number of photovoltaic power generation facilities have been installed and are now connected to the distribution system (high-voltage power system) via photovoltaic power generation power conditioners. Photovoltaic power conditioners inject reactive power into the distribution line according to the status of the connected distribution line. They also inject reactive power into the distribution line as a method of detecting power outages in the distribution system. When a power outage is detected, they have the function of disconnecting the distribution line from the photovoltaic power generation system, preventing electrical accidents and ensuring safety. When a large number of photovoltaic power generation systems are connected, sudden voltage fluctuations occur in the distribution system, and a large amount of reactive power is injected into the distribution line, this is one of the causes of voltage flicker, in which the system voltage repeatedly fluctuates.

Voltage and reactive power controllers (VQCs) installed in transmission substations are one type of voltage control device for power grids. While VQCs are capable of highly accurate voltage control, they do not have the functionality to deal with voltage flicker. Therefore, even if VQCs, which have traditionally been used in transmission substations, are simply introduced into distribution substations, they are unable to detect the signs or occurrence of voltage flicker, and are unable to control voltage in response to voltage flicker. Another issue is that when the amount of power generated by a solar power generation system exceeds the amount of power demand in the distribution grid, causing reverse power flow, proper voltage control is not possible.

The present invention was made in consideration of the above-mentioned problems, and aims to provide a voltage control method and voltage control system that can detect signs of voltage flicker or its occurrence in distribution substation equipment and perform appropriate voltage control, as well as distribution substation equipment using the same.

The above problem can be solved by a voltage control method for distribution substation equipment that uses a transformer to transform extra-high voltage power from an extra-high voltage power system into high voltage power from a high voltage power system connected to a solar power generation facility. The voltage control method includes the steps of controlling the secondary voltage of the transformer based on a reference value determined according to the active power on the secondary side of the transformer, determining whether voltage flicker has occurred or is a sign of it based on the primary or secondary voltage of the transformer, and increasing the reference value if voltage flicker has occurred or is a sign of it.

When voltage flicker occurs, the voltage on the secondary side of the transformer fluctuates wildly. Therefore, by determining whether voltage flicker has occurred or if there are signs of it, and if it has occurred or if there are signs of it, the reference value that serves as the basis for secondary side voltage control can be increased, allowing for appropriate voltage control.

Furthermore, the step of determining whether voltage flicker has occurred or is a sign of it preferably includes a step of determining whether voltage flicker has occurred or is a sign of it when the primary side voltage remains below a predetermined voltage for a predetermined period of time, or when the flicker value of the primary side voltage or secondary side voltage remains above a predetermined value for a predetermined period of time.

Voltage flicker can be detected by an increase in the flicker value of the transformer's primary or secondary voltage, and signs of voltage flicker can be detected by a decrease in the transformer's primary voltage. Because voltage and flicker values are constantly fluctuating, highly accurate determinations can be made by comparing the voltage and flicker values with threshold values over a specified period of time.

It is also desirable to further include a step of restoring the reference value to the value before it was increased if, after it is determined that voltage flicker has occurred or is a sign of it, the primary voltage remains above a predetermined voltage for a predetermined period of time and the flicker value of the primary voltage or secondary voltage remains below a predetermined value for a predetermined period of time.

The elimination of voltage flicker can be determined by a decrease in the flicker value of the transformer's primary or secondary voltage, and the elimination of signs of voltage flicker can be determined by an increase in the transformer's primary voltage. When the problem is eliminated, the reference value that serves as the basis for secondary voltage control is returned to its original value, making it possible to perform appropriate voltage control in normal conditions without voltage flicker. Furthermore, because voltage and flicker values are constantly fluctuating, highly accurate determinations can be made by comparing the voltage and flicker values with threshold values over a specified period of time.

Furthermore, the step of controlling the transformer's secondary voltage is carried out using at least one of phase-modulating control and LR control, and it is desirable that control that takes reactive power into consideration be applied with priority. Since the main cause of voltage flicker is the injection of excessive reactive power by solar power generation equipment, prioritizing reactive power control using phase-modulating control enables appropriate voltage control.

In addition, it is desirable that phase modifying control is performed by connecting either a power capacitor or a shunt reactor to the high-voltage power grid, and LR control is performed by changing the transformation ratio of the transformer. Reactive power can be adjusted by selectively connecting power capacitors and shunt reactors with different phase control directions to the high-voltage power grid, and both active power and reactive power can be adjusted by changing the transformation ratio of the transformer.

It is also desirable to further include a step of issuing an alarm when it is determined that voltage flicker has occurred or is a sign of it. Since the occurrence or signs of voltage flicker can cause power transmission problems, issuing an alarm to the power system manager or power system management system makes it possible to take the necessary measures to prevent problems from occurring.

Furthermore, the above problems can also be solved by distribution substation equipment and its voltage control system that implement the above-mentioned voltage control method.

The voltage control method, voltage control system, and distribution substation equipment of the present invention make it possible to detect signs of flicker and its occurrence in distribution substation equipment, and to perform appropriate voltage control.

1 is a schematic configuration diagram of a distribution substation facility according to an embodiment of the present invention. 1 is a schematic configuration diagram of a voltage control system according to an embodiment of the present invention; 3 is a flowchart of a voltage control method according to an embodiment of the present invention. FIG. 1 is an explanatory diagram of a PV curve. 3 is a flowchart of a voltage control method according to an embodiment of the present invention. 3 is a flowchart of a voltage control method according to an embodiment of the present invention. FIG. 10 is an explanatory diagram of a reference value change. FIG. 2 is an explanatory diagram of an operation mode transition.

Specific examples of embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows an example of the configuration of a distribution substation according to an embodiment of the present invention. The distribution substation 1 transforms 66 kV extra-high voltage power into 6 kV high voltage power. The distribution substation 1 has three banks 20, 30, and 40, each of which is provided with on-load tap-changing transformers (LRTs) 21, 31, and 41 that transform extra-high voltage power into high voltage power. A primary bus 51 of the extra-high voltage power system is connected to the primary side of each transformer 21, 31, and 41. A transformer 52 is connected to the primary bus 51, measuring the voltage of the extra-high voltage power system, i.e., the primary-side voltage _V1 of the transformers 21, 31, and 41. Furthermore, secondary buses 53, 54, and 55 of the high voltage power system are connected to the secondary side of each transformer 21, 31, and 41. Photovoltaic power generation facilities 61, 62, and 63 are connected to the secondary buses 53, 54, and 55.

Furthermore, the distribution substation equipment 1 includes a distribution voltage control system (distribution VQC) 10, which is a voltage control means for controlling the secondary voltages of the transformers 21, 31, and 41, and to which the primary voltage _V1 of the transformers 21, 31, and 41 measured by a transformer 52 is input. The distribution VQC 10 controls the secondary voltage V2 of the transformers 21, 31, and 41 by controlling at least one of the phase modifying means 25, 26, 35, 36, 45, and 46 (described later) and the transformation ratios of the transformers 21, 31, and 41 based on a reference value determined in accordance with the active power _P of the secondary sides of the transformers 21, 31, and 41. The distribution VQC 10 also has the function of determining whether voltage flicker has occurred or is a sign of it based on the primary voltage _V1 or secondary voltage V2 of the transformers 21, 31, and ₄₁ , and increasing the reference value described above if voltage flicker has occurred or is a sign of it.

Each bank 20, 30, 40 includes a primary transformer 21, 31, 41, a secondary transformer 22, 32, 42, a current measuring means 23, 33, 43, a 90 relay 24, 34, 44, a shunt reactor (Shr) 25, 35, 45, a power capacitor (SC) 26, 36, 46, a switch 27, 28, 37, 38, 47, 48, and a power capacitor control device 29, 39, 49.

Transformers 22, 32, 42 are connected to secondary buses 53, 54, 55 and measure the voltage of the high-voltage power system, i.e., the secondary voltage _V2 of transformers 21, 31, 41. The measured secondary voltage _V2 is input to distribution VQC 10 and 90 relays 24, 34, 44. Current measuring means 23, 33, 43 measure the secondary current _I2 of transformers 21, 31, 41 based on the magnitude of the magnetic field generated around secondary buses 53, 54, 55. The measured secondary current _I2 is input to distribution VQC 10 and 90 relays 24, 34, 44.

The 90 relays 24, 34, and 44 are devices that control the secondary voltage V2 by switching the taps of the transformers ₂₁ , 31, and 41 based on the input secondary voltage V2 and secondary current _I2 of the transformers 21, 31, and 41 to change the transformation ratio of the transformers 21, 31, and _41. When the distribution VQC 10 controls the transformation ratio of the transformers 21, 31, and 41, the control by the 90 relays 24, 34, and 44 is disabled.

Shunt reactors (Shr) 25, 35, 45 are connected to secondary buses 53, 54, 55 via switches 27, 37, 47 and are inductive phase modifying means for controlling the reactive power of the high-voltage power system. Shunt reactors (Shr) 25, 35, 45 can be connected to or disconnected from the high-voltage power system by closing or opening switches 27, 37, 47.

Power capacitors (SC) 26, 36, 46 are connected to secondary buses 53, 54, 55 via switches 28, 38, 48 and are capacitive phase correcting means that control the reactive power of the high-voltage power system. Power capacitors (SC) 26, 36, 46 can be connected to or disconnected from the high-voltage power system by closing or opening switches 28, 38, 48.

Shunt reactors (Shr) 25, 35, 45 and power capacitors (SC) 26, 36, 46 modify phase in opposite directions, so when performing phase modification control, either switches 27, 37, 47 or switches 28, 38, 48 are closed. Furthermore, any number of phase modifying means (shunt reactors (Shr) and power capacitors (SC)) can be installed, and by connecting each phase modifying means individually or multiple units together to a switch, it is possible to control connection/disconnection to the high-voltage power grid.

The power capacitor control devices 29, 39, 49 are devices that adjust the reactive power of the high-voltage power system and control the secondary voltage _V2 by switching the switches 28, 38, 48 during a set time period to connect the power capacitors (SC) 26, 36, 46 to the high-voltage power system. When phase-modifying control is performed by the distribution VQC 10, the control by the power capacitor control devices 29, 39, 49 is disabled.

Next, the configuration of a power distribution voltage control system (power distribution VQC) 10, an example of an embodiment of the present invention, will be described with reference to FIG. 2 . The power distribution VQC 10 includes flicker meters 15 and 16, a wireless router 17, and a system control device 11. The flicker meter 15 is connected to a primary-side transformer 52, acquires the primary-side voltage _V1 of the transformers 21, 31, and 41, and calculates a flicker value f of the primary-side voltage _V1 . The flicker meter 16 is connected to the secondary-side transformers 22, 32, and 42 of each bank 20, 30, and 40, acquires the secondary-side voltage _V2 of the transformers 21, 31, and 41, and calculates a flicker value f of the secondary-side voltage. Here, the "flicker value" is a measure representing the magnitude of voltage flicker. The power distribution VQC 10 of this embodiment uses an IEC flicker meter, which takes into account the visual sensitivity curve of flicker, as the flicker value, but other measures may also be used.

The wireless router 17 is a router that relays wireless communications between devices inside and outside the power distribution VQC 10. For example, the flicker value f calculated by the flicker meters 15 and 16 can be transmitted via the wireless router 17 to the system control device 11 or to a control PC 18 installed outside the power distribution VQC 10. Additionally, alarms issued by the system control device 11 can be transmitted to the control PC 18.

System control device 11 has a computer configuration including processor 12, recording medium 13 connected to processor 12, and timer 14. System control device 11 receives flicker value f from flicker meters 15 and 16. System control device 11 is also connected to transformers 22, 32, 42, and 52 and current measuring means 23, 33, and 43, and receives primary voltage _V1 , secondary voltage _V2 , and secondary current _I2 of transformers 21, 31, and 41. Furthermore, the system control device 11 is connected to the switches 27, 28, 37, 38, 47, and 48 of the transformers 21, 31, and 41 and the phase correcting means 25, 26, 35, 36, 45, and 46, and can change the transformation ratios of the transformers 21, 31, and 41 by switching the taps of the transformers 21, 31, and 41, and can connect and disconnect the phase correcting means (shunt reactors 25, 35, and 45 and power capacitors 26, 36, and 46) to and from the high-voltage power system. The system control device 11 is also connected to a remote monitoring and control device 19 that remotely manages the distribution VQC 10 from a location away from the distribution substation equipment 1, and can transmit information processed by the distribution VQC 10 and any generated alarms.

The system control device 11 has the function of determining whether voltage flicker has occurred or is a sign of it based on the primary voltage _V1 of the transformers 21, 31, 41 or the flicker value f determined by the flicker meters 15, 16, controlling the secondary voltage _V2 of the transformers 21, 31, 41 based on a reference value determined according to the active power P on the secondary side of the transformers 21, 31, 41, and increasing the reference value if voltage flicker f has occurred or is a sign of it. These functions are described in a program stored in the recording medium 13 and are realized by executing the program by the processor 12.

Recording medium 13 is a computer-readable recording medium composed of semiconductor memory such as RAM, SSD, or flash memory, or magnetic memory such as HDD. Timer 14 generates a clock signal at a predetermined cycle and provides it to processor 12. This is used to manage the operation of processor 12 and to measure time when flicker occurs or when signs of flicker are detected.

Next, the operation of the power distribution voltage control system (power distribution VQC) 10, i.e., an example of an embodiment of a voltage control method according to the present invention, will be described with reference to Figures 3 to 7. Figure 3 is a flowchart of the basic voltage control operation of the power distribution VQC 10. Figure 4 is an explanatory diagram of the P-V curve used in the basic voltage control operation. Figures 5a and 5b are flowcharts of the voltage control operation that determines the occurrence of voltage flicker or its precursor, switches the operating mode (normal mode or flicker mode), and changes the reference value used in the basic voltage control operation depending on the operating mode, thereby optimizing voltage control. Figure 6 is an explanatory diagram of the reference value change. Figure 7 is an explanatory diagram of the transition of operating modes due to flicker detection/precursor determination.

First, the basic voltage control operation of the power distribution VQC 10 will be described with reference to FIG. 3 . The basic voltage control operation is repeatedly performed periodically or at a timing according to a predetermined setting. First, the processor 12 acquires the secondary voltage _V2 of the transformers 21, 31, and 41 from the transformers 22, 32, and 42, and the secondary current _I2 of the transformers 21, 31, and 41 from the current measuring means 23, 33, and 43 (step 101). Next, the processor 12 calculates the active power P and reactive power Q of the secondary sides of the transformers 21, 31, and 41 from the secondary voltage _V2 and the secondary current _I2 (step 102). If the power supplied from the photovoltaic power generation facilities 61, 62, and 63 exceeds the total power demand of the high-voltage power system, causing a reverse power flow from the high-voltage power system to the extra-high-voltage power system, the active power P will be a negative value. Next, the processor 12 refers to the P-V curve stored in the recording medium 13, obtains the upper and lower limit values of the secondary voltage _V2 corresponding to the calculated active power P, and compares them with the secondary voltage V2 obtained from the transformers 22, 32, and ₄₂ (step 103).

FIG. 4 shows an example of a P-V curve. The P-V curve is composed of five curves 71 to 75, with the horizontal axis representing active power P and the vertical axis representing secondary voltage _V2 . For ease of explanation, the P-V curves are shown in graph form in FIG. 4, but the recording medium 13 stores the P-V curves in the form of a function or table showing the relationship between active power P and secondary voltage _V2 . Curve 73 is the optimal value of secondary voltage _V2 corresponding to active power P and is the reference value for voltage control. Curve 73 is created by interpolating multiple target points _S1 , _S2 , _S3 , _S4 , and _S5 . In FIG. 4, linear interpolation is performed between target points _S1 , _S2 , _S3 , _S4 , and _S5 .

Curves 72 and 74 are the upper and lower limits of the dead band, where the difference between the reference value and the measured value is determined to be insignificant. The dead band is provided to prevent continuous operation. Curves 72 and 74 are set based on the reference value of curve 73 (for example, ±1% of the reference value). When the distribution substation equipment 1 is operating normally, the secondary voltage _V2 is located within the range between the upper and lower limit values. Curves 71 and 75 are the upper and lower limit warning values of the secondary voltage _V2 corresponding to the active power P.

When the measured value of the secondary voltage _V2 relative to the active power P is located at _M2 in Fig. 4, it is determined in step 103 in Fig. 3 that the measured value _M2 is within the warning output range of the P-V curve (exceeding the P-V curve 71 of the upper limit of the secondary voltage _V2 ). Then, the processor 12 issues a warning to the control PC 18 and the remote monitoring and control device 19 to notify them that an abnormality has occurred (step 105).

If the measured value of the secondary-side voltage _V2 is outside the alarm output range of the P-V curve, the processor 12 determines whether reverse power flow from the high-voltage power system to the extra-high-voltage power system is occurring (step 104). Specifically, it determines whether the sign of the active power P is negative. For example, if the measured value of the secondary-side voltage _V2 relative to the active power P is located at _M1 in FIG. 4, the measured value _M1 is outside the alarm output range of the P-V curve, but since the active power P is a negative value, it is determined that reverse power flow is occurring. Then, the processor 12 issues an alarm to the control PC 18 and the remote monitoring and control device 19 to notify them of the occurrence of reverse power flow (step 105).

Thereafter, the processor 12 determines whether the measured value of the secondary-side voltage _V2 with respect to the active power P is within the dead band. If it is within the dead band, voltage control is not required, and the process ends (step 106). On the other hand, if it is not within the dead band, the processor 12 calculates the error ΔV between the measured value of the secondary-side voltage _V2 and the reference value. For example, if the measured value of the secondary-side voltage _V2 with respect to the active power P is located at _M3 in FIG. 4, the measured value _M3 is within the dead band (between curves 72 and 74), and the process ends. On the other hand, if the measured value of the secondary-side voltage _V2 with respect to the active power P is located at _M1 or _M4 in FIG. 4, the error ΔV between the measured values _M1 and _M4 and the reference value is calculated. The calculated error ΔV is integrated with the error ΔV obtained in the previous basic voltage control operation (step 107).

Next, the processor 12 determines whether the integrated value is within a predetermined range. If it is within the predetermined range, voltage control is unnecessary, and the process ends (step 108). On the other hand, if it exceeds the predetermined range, the secondary voltage _V2 of the transformers 21, 31, and 41 is controlled. In this case, control that takes reactive power into consideration is applied preferentially. For example, voltage control includes phase modification control, which adjusts reactive power, and LR control, which changes the transformation ratio of the transformers 21, 31, and 41. Since the main cause of voltage flicker is excessive reactive power injection from the solar power generation facility, reactive power control using phase modification control is applied preferentially over LR control. More specifically, the processor 12 first selects an appropriate phase modification means from the shunt reactors (Shr) 25, 35, and 45 and the power capacitors (SC) 26, 36, and 46 depending on the sign of the calculated reactive power Q (or the phase of the secondary voltage _V2 and the secondary current _I2 ). If there are multiple shunt reactors or power capacitors, any number of phase correcting means are selected from them according to the control amount. Next, the processor 12 estimates the secondary voltage _V2 when the selected phase correcting means is connected to the high-voltage power system, and determines whether control is possible using only the selected phase correcting means (step 109).

If control is possible using only the selected phase compensating means, processor 12 connects or disconnects the selected phase compensating means to the high-voltage power grid by closing or opening switches 27, 28, 37, 38, 47, and 48 corresponding to the selected phase compensating means (step 110). On the other hand, if it is expected that sufficient control will not be possible using only the selected phase compensating means, processor 12 performs LR control, which changes the transformation ratio by switching the taps of transformers 21, 31, and 41 in addition to closing or opening switches 27, 28, 37, 38, 47, and 48 corresponding to the phase compensating means (step 111). Processor 12 then resets the integrated value and terminates the basic voltage control operation (step 112).

The basic voltage control operation described above is performed independently for each of banks 20, 30, and 40. That is, the secondary voltage of transformer 21 of bank 20 is controlled based on a reference value determined in accordance with the secondary active power P of transformer 21 obtained from the measured values of secondary voltage _V2 and secondary current _I2 of transformer 21 of bank 20. The secondary voltage of transformer 31 of bank 30 is controlled based on a reference value determined in accordance with the secondary active power P of transformer 31 obtained from the measured values of secondary voltage _V2 and secondary current _I2 of transformer 31 of bank 30. Similarly, the secondary voltage of transformer 41 of bank 40 is controlled based on a reference value determined in accordance with the secondary active power P of transformer ₄₁ obtained from the measured values of secondary voltage _V2 and secondary current I2 of transformer 41 of bank 40.

Next, we will explain the voltage control operation that determines the occurrence or signs of voltage flicker and changes the P-V curve (reference value) according to the operating mode, with reference to Figures 5a and 5b. Figures 5a and 5b are repeatedly performed periodically or at timing according to predetermined settings, either synchronized with or independent of the basic voltage control operation shown in Figure 3. Figure 5a is a flowchart when the operating mode is normal mode, in which there is no voltage flicker, and Figure 5b is a flowchart when the operating mode is flicker mode, in which flicker has occurred or is signs of flicker.

When operating in the normal mode, first, flicker meter 15 acquires the primary voltage _V1 of transformers 21, 31, and 41 from transformer 52, and flicker meter 16 acquires the secondary voltage V2 of transformers 21, 31, and 41 from transformers ₂₂ , 32, and 42 (step 201). Next, flicker meters 15 and 16 calculate the respective flicker values f (IEC flicker meter values) from the acquired primary voltage _V1 and secondary voltage _V2 (step 202).

Next, the processor 12 receives the flicker value f from the flicker meters 15 and 16 via the wireless router 17 and determines whether the flicker value _f remains equal to or greater than the flicker threshold f for a predetermined time _t (step 203). For example, the flowchart of FIG. 5A is repeatedly executed as described above. The time of the first execution at which it is determined that the flicker value f is equal to _or greater than the flicker threshold f is obtained from the timer 14 and stored in the recording medium 13. If it is determined that the flicker value f is equal to _or greater than the flicker threshold f during subsequent executions, the processor 12 determines whether the difference between the time of the first execution and the time of the previous execution is equal to or greater than the predetermined time _t . If the flicker value f falls below the flicker threshold _f , the memory in the recording medium 13 is erased and reset. The flicker threshold _f and the predetermined time _t may be set to different values or the same values for the primary-side voltage _V1 and the secondary-side voltage _V2 and for each of the banks 20, 30, and 40.

If it is determined that the flicker value f remains equal to or greater than the flicker threshold value _fth for a predetermined time _tth , i.e., if voltage flicker is occurring, the processor 12 increases the reference value of the P-V curve (step 206). For example, as shown in FIG. 6, the processor 12 increases each of the target points _S1 , _S2 , _S3 , _S4 , and _S5 that form the reference of the curve 73 by a predetermined amount or a predetermined factor to set new target points _S1 ', _S2 ', _S3 ', _S4 ', and _S5 ', and interpolates the new target points _S1 ', _S2 ', _S3 ', _S4 ', and _S5 ' to generate a new curve 73' of the reference value. The other four curves 71, 72, 74, and 75 are also generated based on the new curve 73'. The processor 12 also issues an alarm to the control PC 18 and the remote monitoring and control device 19 to notify them of the occurrence of voltage flicker (step 207), and transitions the operation mode to flicker mode (step 208). After the transition, the flicker mode flow shown in Fig. 5b is repeatedly executed instead of the normal mode flow shown in Fig. 5a until the operation mode transitions back to normal mode.

On the other hand, if it is determined in step 203 that the state in which the flicker value f is equal to or greater than the flicker threshold value _fth has not continued for the predetermined time _tth , i.e., if voltage flicker has not occurred, the processor 12 determines whether the state in which the primary-side voltage _V1 is equal to _or less than the voltage threshold value _Vth has continued for the predetermined time _tth (step 204). For example, the execution time at which it was first determined that the primary-side voltage _V1 was equal to or less than the voltage threshold value _Vth is obtained from the timer 14 and stored in the recording medium 13. If it is determined that the primary-side voltage _V1 is still equal to or less than the voltage threshold value Vth during subsequent executions, the processor 12 determines whether the difference between the execution time and the time is equal to or greater than the predetermined time _tth . Note that if the primary-side voltage _V1 exceeds the voltage threshold value _Vth , the storage in the recording medium 13 is erased and reset. The predetermined time _tth may be set to a value different from or the same as that used in voltage flicker detection (step 203).

If it is determined that the state in which the primary side voltage _V1 is equal to or lower than the voltage threshold value _Vth continues for a predetermined time _tth , that is, if there is a sign of voltage flicker, the processor 12 increases the reference value of the P-V curve (step 206), issues an alarm to the control PC 18 or the remote monitoring and control device 19 to notify that there is a sign of voltage flicker (step 207), and transitions the operation mode to the flicker mode (step 208).

On the other hand, if it is determined in step 204 that the state in which the primary side voltage _V1 is equal to or lower than the voltage threshold _Vth has not continued for the predetermined time _tth , the operation mode is maintained in the normal mode (step 205).

The above is the voltage control operation for determining whether voltage flicker has occurred or is a sign of it, and for changing the reference value when the operating mode is normal.

Next, referring to Figure 5b, we will explain the voltage control operation related to the occurrence and prediction of voltage flicker and the change of the reference value when the operating mode is flicker mode. The operation in flicker mode is almost the opposite of the operation in normal mode.

That is, first, flicker meter 15 acquires the primary voltage _V1 of transformers 21, 31, and 41 from transformer 52, and flicker meter 16 acquires the secondary voltage _V2 of transformers 21, 31, and 41 from transformers 22, 32, and 42 (step 211). Next, flicker meters 15 and 16 calculate the respective flicker values f (IEC flicker meter values) from the acquired primary voltage _V1 and secondary voltage _V2 (step 212).

Next, the processor 12 receives the flicker value f from the flicker meters 15 and 16 via the wireless router 17 and determines whether the state in which the flicker value _f is equal to or less than the flicker threshold fth continues for a predetermined time _tth (step 213). The flicker threshold _fth and the predetermined time _tth may be set to different values for the primary voltage _V1 and the secondary voltage _V2 and for each of the banks 20, 30, and 40, or may be the same values. They may also be the same values as those used in the flicker determination in the normal mode (step 203 in FIG. 5a) or different values.

If it is determined that the state in which the flicker value f is equal to or less than the flicker threshold value _fth continues for a predetermined time _tth , i.e., if the voltage flicker has been eliminated, the processor 12 determines whether the state in which the primary-side voltage _V1 is equal to or greater than the voltage threshold value _Vth continues for a predetermined time _tth (step 214). The predetermined time _tth may be set to a value different from or the same as that set in the step of determining whether the voltage flicker has been eliminated (step 213).

If it is determined that the primary-side voltage _V1 has remained below the voltage threshold _Vth for a predetermined time _tth , i.e., if it is determined that the signs of voltage flicker have disappeared, the processor 12 returns the reference values of the P-V curves to the values before they were increased (step 216). For example, in FIG. 6, the new target points _S1 ', _S2 ', S3', S4', and _{S5 '} set in step 206 are returned to the original target points _S1 , S2, _S3 , _S4 , and _S5 , and interpolated to return curve 73 to the reference values before the increase. The other four curves 71, ₇₂ , ₇₄ , and 75 are also returned to the curves before the increase. In addition, the processor 12 stops the alarm issued to the control PC 18 and the remote monitoring and control device 19 to notify them that the voltage flicker has been eliminated (step 217), and transitions the operating mode to the normal mode (step 218). After the transition, the flow of the normal mode shown in FIG. 5a is repeatedly executed until the mode transitions to the flicker mode again.

On the other hand, if it is determined in step 213 that the state in which the flicker value _f is equal to or less than the flicker threshold value fth has not continued for the predetermined time _tth , or if it is determined in step 214 that the state in which the primary side voltage _V1 is equal to or greater than the voltage threshold value _Vth has not continued for the predetermined time _tth , the operating mode is maintained in the flicker mode (step 215).

The above is the voltage control operation for determining the occurrence and signs of voltage flicker and changing the reference value when the operating mode is flicker mode.

FIG. 7 shows an example of transitions in operating modes. In the figure, the horizontal axis represents time and the vertical axis represents primary-side voltage _V1 and flicker value f. The graph shows the temporal changes in primary-side voltage _V1 and flicker value f, with the operating modes shown at the top. At time _t0 during normal mode operation, flicker value f exceeds flicker threshold _fth . However, at time _t1 , before the predetermined time _tth has elapsed, it falls below flicker threshold _fth , so normal mode is maintained. Thereafter, at time _t2 , primary-side voltage _V1 falls below voltage threshold _Vth , and remains below voltage threshold _{Vth until time t3, when the predetermined time tth has elapsed from time t2 . At time t3} , the predetermined time _tth has not yet elapsed since flicker value f exceeded flicker threshold _fth. However, the predetermined time _tth has elapsed since primary-side voltage _V1 fell below voltage threshold _Vth. Therefore, at time _t3 , the normal mode transitions to flicker mode, and the reference value (P-V curve) is increased.

After that, at time _t4 , the primary-side voltage _V1 becomes equal to or greater than the voltage threshold _Vth , and remains equal to or greater than the voltage threshold _Vth until time _t6 , when a predetermined time _tth has elapsed. Meanwhile, the flicker value f becomes equal to _or less than the flicker threshold fth at time _t5 , and although it is still equal to _or less than the flicker threshold fth at time _t6 , the predetermined time _tth has not yet elapsed since it became equal to or less than the flicker threshold _fth . Therefore, at time _t6 , the flicker mode is maintained. Thereafter, the primary-side voltage _V1 continues to remain equal to or greater than the voltage threshold _Vth , and the flicker value f continues to remain equal to _or less than the flicker threshold fth, until at time _t7 , the predetermined time tth has elapsed since the flicker value f became equal to or less than the flicker threshold _fth . Then, at time _t7 , the mode transitions from the flicker mode to the normal mode, and the reference value (PV curve) returns to _the value before it was increased.

The invention developed by the present inventors has been specifically described above based on an embodiment, but the present invention is not limited to the above-described embodiment and can be modified in various ways without departing from the spirit of the invention. For example, communication between the flicker meters 15, 16, the system control device 11, the control PC 18, and the remote monitoring control device 19 may be wireless, wired, or via an information network such as the Internet. Furthermore, connections between the power distribution VQC 10 and other components (transformers 22, 32, 42, 52, current measuring means 23, 33, 43, remote monitoring control device 19, transformers 21, 31, 41, phase compensating means 25, 26, 35, 36, 45, 46, etc.) may also be wireless, wired, or via an information network such as the Internet.

Furthermore, in the above-described embodiment, the functions of the power distribution VQC 10 are realized by the flicker meters 15, 16 and the system control device 11, but each function may be configured by individual hardware or software, or a combination thereof. For example, instead of determining the flicker value using the flicker meters 15, 16, the voltage control method according to the present invention may be implemented by determining the flicker value using the processor 12 of the system control device 11.

1 Distribution substation equipment 10 Distribution voltage control system (distribution VQC)
11 System control device 12 Processor 13 Recording medium 14 Timer 15, 16 Flicker meter 17 Wireless router 18 Control PC
19 Remote monitoring control device 20 1B
21, 31, 41 Transformers 22, 32, 42, 52 Transformers 23, 33, 43 Current measuring means 24, 34, 44 90 Relay 25, 35, 45 Shunt reactor (phase correcting means)
26, 36, 46 Power capacitor (phase compensating means)
27, 28, 37, 38, 47, 48 Switches 29, 39, 49 Power capacitor control device 30 2B
40 3B
51 Primary bus (extra-high voltage power system)
53, 54, 55 Secondary bus (high voltage power system)
61, 62, 63 Photovoltaic power generation equipment 71 P-V curve ( _V2 upper limit alarm value)
72 P-V curve (upper limit of dead zone)
73, 73' P-V curve (reference value)
74 P-V curve (lower limit of dead zone)
75 P-V curve ( _V2 lower limit alarm value)

Claims (8)

A voltage control method for a distribution substation facility that transforms extra-high voltage power of an extra-high voltage power system into high voltage power of a high voltage power system to which a photovoltaic power generation facility is connected, using a transformer, comprising:
controlling a secondary voltage of the transformer based on a reference value determined according to an active power on the secondary side of the transformer;
determining whether a voltage flicker has occurred or is a sign of one based on a primary-side voltage or a secondary-side voltage of the transformer;
increasing the reference value when the voltage flicker occurs or is predicted to occur;
A voltage control method comprising: The method of claim 1, wherein the step of determining whether voltage flicker has occurred or is a sign of it includes a step of determining whether voltage flicker has occurred or is a sign of it when the primary side voltage remains below a predetermined voltage for a predetermined period of time, or when the flicker value of the primary side voltage or the secondary side voltage remains above a predetermined value for a predetermined period of time. The method of claim 2 further includes a step of restoring the reference value to the value before it was increased if, after determining that the voltage flicker has occurred or is a sign of it, the primary side voltage remains at or above a predetermined voltage for a predetermined period of time and the flicker value of the primary side voltage or the secondary side voltage remains at or below a predetermined value for a predetermined period of time. A method according to any one of claims 1 to 3, wherein the step of controlling the secondary voltage of the transformer is performed using at least one of phase modifying control and LR control, with priority given to control that takes reactive power into account. the phase modifying control is performed by connecting either a power capacitor or a shunt reactor to the high-voltage power system;
The LR control is performed by changing the transformation ratio of the transformer.
The method of claim 4. The method of any one of claims 1 to 5, further comprising issuing an alarm when it is determined that the voltage flicker has occurred or is a sign of it. A voltage control system for a distribution substation facility that uses a transformer to transform extra-high voltage power from an extra-high voltage power system into high voltage power from a high voltage power system to which a photovoltaic power generation facility is connected,
a flicker meter for determining a flicker value of a primary voltage or a secondary voltage of the transformer;
A system control device,
A computer,
The computer,
a function of determining occurrence or sign of voltage flicker based on the primary voltage of the transformer or the flicker value;
a function of controlling a secondary voltage of the transformer based on a reference value determined according to an active power on the secondary side of the transformer;
a function of increasing the reference value when the voltage flicker occurs or is predicted to occur;
A computer-readable recording medium on which a program for realizing the above is recorded;
a system control device comprising:
A power distribution voltage control system comprising: a transformer with a changeable transformation ratio that converts the extra-high voltage of the extra-high voltage power system into the high voltage of the high voltage power system to which the solar power generation facility is connected;
a transformer for measuring a primary voltage and a secondary voltage of the transformer;
a current measuring means for measuring a secondary current of the transformer;
a phase modifying means capable of switching on and off the high-voltage power system;
a voltage control means for controlling at least one of the phase modifying means and the transformation ratio based on a reference value determined in accordance with the active power on the secondary side of the transformer, thereby controlling the secondary side voltage of the transformer;
Equipped with
the voltage control means determines whether a voltage flicker has occurred or is a sign of it based on the primary-side voltage or the secondary-side voltage, and increases the reference value when the voltage flicker has occurred or is a sign of it.
Power distribution substation equipment.