Voltage control method for power distribution substation equipment, voltage control system, and power distribution substation equipment

Abstract

To provide a voltage control method and the like for distribution transformation facility capable of detecting signs and occurrence of flicker and performing appropriate voltage control.SOLUTION: A voltage control method for a distribution transformation facility (1) that transforms extra-high voltage power of an extra-high voltage power system into high-voltage power of a high-voltage power system linked to a photovoltaic power generation facility by a transformer (21, 31, 41) includes the steps of: controlling a secondary voltage V2 of the transformer on the basis of a reference value determined according to an active power P on the secondary side of the transformer; determining occurrence or a sign of voltage flicker on the basis of a primary side voltage V1 or the secondary side voltage V2 of the transformer; and increasing the reference value when the occurrence or the sign of voltage flicker exists.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a voltage control method, a voltage control system, and a substation facility, and more particularly to a voltage control method, a voltage control system, and a substation facility for power distribution. [Background technology]

[0002] Distribution substation equipment is installed between transmission lines in a power system, and transforms transmitted extra-high voltage power into high voltage power for high voltage consumers using a transformer, and transmits the power to the distribution lines of the high voltage power system. In order to maintain the voltage of the high voltage power system within a predetermined range, distribution substation equipment is equipped with a voltage control device such as that shown in Patent Document 1. Voltage control is performed by stepping up and down operation (LR control) by changing the tap of an on-load tap changing transformer (LRT), and by phase modification control by opening and closing a power capacitor (SC) and a shunt reactor (Shr). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 11-206018 Summary of the Invention [Problem to be solved by the invention]

[0004] 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 to prevent electrical accidents and ensure safety. When a large number of photovoltaic power generation systems are connected, sudden voltage fluctuations occur in the distribution system, and when a large amount of reactive power is injected into the distribution line, this is one of the causes of voltage flicker, which causes repeated fluctuations in the system voltage.

[0005] One type of voltage control device for power systems is a voltage-reactive-power controller (VQC) installed in transmission substations. VQCs are capable of highly accurate voltage control, but they do not have the functionality to deal with voltage flicker. Therefore, even if VQCs, which have traditionally been used in transmission substations, are introduced directly into distribution substations, they are unable to detect the signs or occurrence of voltage flicker, and are therefore 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 system, causing reverse power flow, appropriate voltage control is not possible.

[0006] The present invention has been 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, and distribution substation equipment using the same. [Means for solving the problem]

[0007] The above problem can be solved by a voltage control method 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 solar power generation facility is connected, the voltage control method including 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.

[0008] When voltage flicker occurs, the voltage on the secondary side of the transformer fluctuates wildly. Therefore, by detecting the occurrence of voltage flicker or its signs, and if voltage flicker occurs or its signs are detected, the reference value that serves as the basis for secondary voltage control can be increased, allowing for appropriate voltage control.

[0009] Furthermore, it is desirable that 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 is below a predetermined voltage for a predetermined period of time, or when the flicker value of the primary side voltage or secondary side voltage is above a predetermined value for a predetermined period of time.

[0010] Voltage flicker can be detected by an increase in the flicker value of the primary or secondary voltage of a transformer, and a sign of voltage flicker can be determined by a decrease in the primary voltage of a transformer. 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.

[0011] Furthermore, it is 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 side voltage remains above a predetermined voltage for a predetermined period of time and the flicker value of the primary side voltage or secondary side voltage remains below a predetermined value for a predetermined period of time.

[0012] 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 flicker has been eliminated, the reference value that serves as the basis for secondary voltage control can be restored to its original value, enabling 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 predetermined period of time.

[0013] Furthermore, the step of controlling the transformer secondary voltage is performed by at least one of phase modification control and LR control, and it is desirable to prioritize control that takes reactive power into account.Since the main cause of voltage flicker is the injection of excessive reactive power by photovoltaic power generation equipment, prioritizing control of reactive power by phase modification control enables appropriate voltage control.

[0014] Furthermore, 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. By selectively connecting a power capacitor and a shunt reactor with different phase control directions to the high-voltage power grid, reactive power can be adjusted, and by changing the transformation ratio of the transformer, both active power and reactive power can be adjusted.

[0015] 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 sign of voltage flicker can cause power transmission trouble, issuing an alarm to a power system manager or a power system management system makes it possible to take the necessary measures to prevent trouble before it occurs.

[0016] Furthermore, the above-mentioned problems can also be solved by a distribution substation facility and its voltage control system that implements the above-mentioned voltage control method. [Effects of the Invention]

[0017] According to the voltage control method, voltage control system, and distribution substation equipment of the present invention, it is possible to detect signs of flicker or the occurrence of flicker in the distribution substation equipment and perform appropriate voltage control. [Brief explanation of the drawings]

[0018] [Figure 1] 1 is a schematic configuration diagram of a distribution substation facility according to an embodiment of the present invention. [Figure 2] 1 is a schematic configuration diagram of a voltage control system according to an embodiment of the present invention; [Figure 3] 3 is a flowchart of a voltage control method according to an embodiment of the present invention. [Figure 4] FIG. 1 is an explanatory diagram of a PV curve. [Figure 5a] 3 is a flowchart of a voltage control method according to an embodiment of the present invention. [Figure 5b] 3 is a flowchart of a voltage control method according to an embodiment of the present invention. [Figure 6] FIG. 10 is an explanatory diagram of a reference value change. [Figure 7] FIG. 2 is an explanatory diagram of an operation mode transition. DETAILED DESCRIPTION OF THE INVENTION

[0019] 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.

[0020] Furthermore, distribution substation equipment 1 includes distribution voltage control system (distribution VQC) 10, which is voltage control means for controlling the secondary voltages of transformers 21, 31, and 41, and receives as input primary voltage V1 of transformers 21, 31, and 41 measured by transformer 52. Distribution VQC 10 controls secondary voltage V2 of transformers 21, 31, and 41 by controlling phase modifying means 25, 26, 35, 36, 45, and 46 (described later) and / or the transformation ratios of transformers 21, 31, and 41 based on a reference value determined in accordance with active power P on the secondary sides of transformers 21, 31, and 41. 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 transformers 21, 31, and 41, and increasing the reference value described above if voltage flicker has occurred or is a sign of it.

[0021] 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.

[0022] 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 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.

[0023] 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 and changing the transformation ratio 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. When the transformation ratio of the transformers 21, 31, and 41 is controlled by the distribution VQC 10, the control by the 90 relays 24, 34, and 44 is disabled.

[0024] The shunt reactors (Shr) 25, 35, 45 are inductive phase modifying means connected to the secondary buses 53, 54, 55 via the switches 27, 37, 47, and control the reactive power of the high-voltage power system. The shunt reactors (Shr) 25, 35, 45 can be connected to or disconnected from the high-voltage power system by closing or opening the switches 27, 37, 47.

[0025] The power capacitors (SC) 26, 36, 46 are capacitive phase modifying means connected to the secondary buses 53, 54, 55 via the switches 28, 38, 48, and control the reactive power of the high-voltage power system. The power capacitors (SC) 26, 36, 46 can be connected to or disconnected from the high-voltage power system by closing or opening the switches 28, 38, 48.

[0026] Since the shunt reactors (Shr) 25, 35, 45 and the power capacitors (SC) 26, 36, 46 have opposite phase correction directions, when performing phase correction control, either switches 27, 37, 47 or switches 28, 38, 48 are turned on. Furthermore, any required number of phase correcting means (shunt reactors (Shr) and power capacitors (SC)) can be installed, and by connecting each phase correcting means individually or multiple units together to a switch, it is possible to control connection / disconnection to the high-voltage power system.

[0027] Power capacitor control devices 29, 39, 49 are devices that adjust the reactive power of the high-voltage power system and control the secondary-side voltage V2 by switching switches 28, 38, 48 during set time periods to connect power capacitors (SC) 26, 36, 46 to the high-voltage power system. When phase-modifying control is performed by distribution VQC 10, the control by power capacitor control devices 29, 39, 49 is disabled.

[0028] 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 a 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 secondary-side transformers 22, 32, and 42 of each bank 20, 30, and 40, acquires a 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 of the magnitude of voltage flicker. The power distribution VQC 10 of this embodiment uses an IEC flicker meter that takes into account the visual sensitivity curve of flicker as the flicker value, but other measures may also be used.

[0029] Wireless router 17 is a router that relays wireless communications between devices inside and outside power distribution VQC 10. For example, flicker value f determined by flicker meters 15 and 16 can be transmitted via wireless router 17 to system control device 11 or to control PC 18 installed outside power distribution VQC 10. In addition, an alarm issued by system control device 11 can be transmitted to control PC 18.

[0030] 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 transformers 21, 31, 41 and the switches 27, 28, 37, 38, 47, 48 of the phase correcting means 25, 26, 35, 36, 45, 46, and can change the taps of the transformers 21, 31, 41 to change the transformation ratios of the transformers 21, 31, 41, and can connect or disconnect the phase correcting means (shunt reactors 25, 35, 45 and power capacitors 26, 36, 46) to or 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.

[0031] System control device 11 has the function of determining whether voltage flicker has occurred or is a sign of it based on primary voltage V1 of transformers 21, 31, and 41 or flicker value f determined by flicker meters 15 and 16, controlling secondary voltage V2 of transformers 21, 31, and 41 based on a reference value determined according to secondary active power P of transformers 21, 31, and 41, and increasing the reference value if voltage flicker f has occurred or is a sign of it. These functions are written in a program stored in recording medium 13 and are realized by processor 12 executing the program.

[0032] The recording medium 13 is a computer-readable recording medium that is configured from semiconductor memory such as RAM, SSD, or flash memory, or magnetic memory such as HDD, etc. The timer 14 generates a clock signal at a predetermined cycle and provides it to the processor 12, and is used to manage the operation of the processor 12 and to measure time when flicker occurs or when signs of flicker are detected.

[0033] 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 FIGS. 3 to 7. FIG. 3 is a flowchart of the basic voltage control operation of the power distribution VQC 10. FIG. 4 is an explanatory diagram of a PV curve used in the basic voltage control operation. FIGS. 5a and 5b are flowcharts of the voltage control operation that determines the occurrence of voltage flicker or a sign thereof, switches the operation mode (normal mode or flicker mode), and changes the reference value used in the basic voltage control operation according to the operation mode to optimize voltage control. FIG. 6 is an explanatory diagram of the change in the reference value. FIG. 7 is an explanatory diagram of the transition of operation modes due to flicker detection / sign determination.

[0034] 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 on 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 and reverse power flow occurs 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 PV 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).

[0035] FIG. 4 shows an example of a PV curve. The PV 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 convenience of explanation, the PV curves are shown in graph form in FIG. 4, but the PV curves are stored in the recording medium 13 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.

[0036] 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 constant 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.

[0037] When the measured value of the secondary voltage V2 with respect 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 PV curve (exceeding the PV 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 that an abnormality has occurred (step 105).

[0038] If the measured value of the secondary-side voltage V2 is outside the alarm output range of the PV 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 PV 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 that reverse power flow has occurred (step 105).

[0039] 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 necessary, 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 curve 72 and curve 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).

[0040] Next, 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 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 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, processor 12 first selects an appropriate phase modification means from shunt reactors (Shr) 25, 35, and 45 and 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 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).

[0041] If control is possible using only the selected phase compensating means, the processor 12 connects or disconnects the selected phase compensating means to the high-voltage power grid by closing or opening the 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 cannot be achieved using only the selected phase compensating means, the processor 12 performs LR control by switching the taps of the transformers 21, 31, and 41 to change the transformation ratio in addition to closing or opening the switches 27, 28, 37, 38, 47, and 48 corresponding to the phase compensating means (step 111). Thereafter, the processor 12 resets the integrated value and ends the basic voltage control operation (step 112).

[0042] 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 measurements of the secondary voltage V2 and secondary current I2 of transformer 21 of bank 20. The secondary voltage of transformer 31 of bank 30 is also controlled based on a reference value determined in accordance with the secondary active power P of transformer 31 obtained from measurements of the 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 measurements of the secondary voltage V2 and secondary current I2 of transformer 41 of bank 40.

[0043] Next, the voltage control operation that determines whether voltage flicker has occurred or is a sign of it and changes to a PV curve (reference value) according to the operation mode will be described with reference to Figures 5a and 5b. Figures 5a and 5b are repeatedly performed periodically or at a timing according to a predetermined setting, either in synchronization with or independent of the basic voltage control operation shown in Figure 3. Figure 5a is a flowchart when the operation mode is a normal mode in which there is no voltage flicker, and Figure 5b is a flowchart when the operation mode is a flicker mode in which flicker has occurred or is a sign of it.

[0044] When operating in normal mode, first, flicker meter 15 acquires primary voltage V1 of transformers 21, 31, and 41 from transformer 52, and flicker meter 16 acquires secondary voltage V2 of transformers 21, 31, and 41 from transformers 22, 32, and 42 (step 201). Next, flicker meters 15 and 16 determine their respective flicker values ​​f (IEC flicker meter values) from the acquired primary voltage V1 and secondary voltage V2 (step 202).

[0045] Next, the processor 12 receives the flicker value f from the flicker meters 15 and 16 via the wireless router 17, and calculates whether the flicker value f is greater than or equal to the flicker threshold f th The state where this is the case or more continues for a predetermined time t th For example, as described above, the flowchart of FIG. 5a is repeatedly executed, but the flicker value f is not greater than the flicker threshold value f (step 203). th The time at which it is determined that the flicker value f is equal to or greater than the flicker threshold value f is obtained from the timer 14 and stored in the recording medium 13. th If it is determined that the difference between the execution time and the time is equal to or greater than the predetermined time t th It is determined whether the flicker value f is equal to or greater than the flicker threshold value f th If the flicker threshold value f is less than the threshold value f, the recording medium 13 is erased and reset. th or a given time t th 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 set to the same value.

[0046] The flicker value f is the flicker threshold f th The state where this is the case or more continues for a predetermined time t thIf it is determined that the voltage flicker has continued for a certain period of time, i.e., if a voltage flicker has occurred, the processor 12 increases the reference value of the PV curve (step 206). For example, as shown in FIG. 6, each of the multiple target points S1, S2, S3, S4, and S5 that serve as the reference for the curve 73 is increased by a predetermined amount or a predetermined factor to set new target points S1', S2', S3', S4', and S5', and a new curve 73' of the reference value is generated by interpolating the new target points S1', S2', S3', S4', and S5'. 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 the voltage flicker (step 207), and transitions the operating mode to the flicker mode (step 208). After the transition, the flicker mode flow shown in FIG. 5b is repeatedly executed instead of the normal mode flow of FIG. 5a until the mode transitions back to the normal mode.

[0047] Meanwhile, in step 203, the flicker value f is equal to or exceeds the flicker threshold f th The state where this is the case or more continues for a predetermined time t th If it is determined that the voltage flicker has not occurred for a period of time, i.e., if no voltage flicker has occurred, the processor 12 determines whether the primary side voltage V1 is greater than or equal to the voltage threshold V th The following state occurs for a given time t th For example, it is determined whether the primary voltage V1 is greater than or equal to the voltage threshold V th The time at which it is first determined that the primary side voltage V1 is equal to or less than the voltage threshold V is obtained from the timer 14 and stored in the recording medium 13. th If it is determined that the difference between the execution time and the time is equal to or less than the predetermined time t th It is determined whether the primary side voltage V1 is equal to or greater than the voltage threshold V th If the predetermined time t is exceeded, the storage medium 13 is erased and reset. th may be set to a value different from that for voltage flicker detection (step 203), or may be the same value.

[0048] The primary voltage V1 is the voltage threshold V th The following state occurs for a given time t th If it is determined that the voltage flicker has continued for a period of time, i.e., if there is a sign of voltage flicker, the processor 12 increases the reference value of the PV curve (step 206), issues an alarm to the control PC 18 and the remote monitoring and control device 19 to notify them of the presence of a sign of voltage flicker (step 207), and transitions the operation mode to the flicker mode (step 208).

[0049] On the other hand, in step 204, the primary voltage V1 is equal to or exceeds the voltage threshold V th The following state occurs for a given time t th If it is determined that the time has not continued for the entire period, the operation mode is maintained in the normal mode (step 205).

[0050] The above is the voltage control operation for determining the occurrence and sign of voltage flicker and changing the reference value when the operating mode is normal.

[0051] Next, referring to Figure 5b, we will explain the voltage control operation related to the occurrence and sign determination 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.

[0052] That is, first, flicker meter 15 acquires primary voltage V1 of transformers 21, 31, and 41 from transformer 52, and flicker meter 16 acquires secondary voltage V2 of transformers 21, 31, and 41 from transformers 22, 32, and 42 (step 211). Next, flicker meters 15 and 16 determine their respective flicker values ​​f (IEC flicker meter values) from the acquired primary voltage V1 and secondary voltage V2 (step 212).

[0053] Next, the processor 12 receives the flicker value f from the flicker meters 15 and 16 via the wireless router 17, and calculates whether the flicker value f is greater than or equal to the flicker threshold f th The following state occurs for a given time t thIt is determined whether the flicker threshold value f th or a given time t th may be set to different values ​​for the primary voltage V1 and the secondary voltage V2, and for each bank 20, 30, and 40, or may be the same value, and may be the same value as or different from the flicker determination in normal mode (step 203 in Figure 5a).

[0054] The flicker value f is the flicker threshold f th The following state occurs for a given time t th If it is determined that the voltage flicker has continued for a period of time, i.e., if the voltage flicker has been eliminated, the processor 12 determines whether the primary-side voltage V1 has exceeded the voltage threshold V th The state where this is the case or more continues for a predetermined time t th It is determined whether the predetermined time t th may be set to a value different from that in the step of determining whether voltage flicker has been eliminated (step 213), or may be the same value.

[0055] The primary voltage V1 is the voltage threshold V th The following state occurs for a given time t th If it is determined that the voltage flicker has continued for a period of time, i.e., if it is determined that the signs of voltage flicker have disappeared, the processor 12 returns the reference value of the PV curve to the value before it was 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 value 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 resolved (step 217), and transitions the operating mode to the normal mode (step 218). After the transition, the normal mode flow shown in FIG. 5a is repeatedly executed until the operation mode transitions back to the flicker mode.

[0056] Meanwhile, in step 213, the flicker value f is set to a value equal to or greater than the flicker threshold fth The following state occurs for a given time t th If it is determined that the primary voltage V1 has not continued for a period of time, or if the primary voltage V1 has not exceeded the voltage threshold V th The state where this is the case or more continues for a predetermined time t th If it is determined that the flickering has not continued for a certain period of time, the operation mode is maintained as the flicker mode (step 215).

[0057] The above is the voltage control operation for determining the occurrence and sign of voltage flicker and changing the reference value when the operating mode is flicker mode.

[0058] Figure 7 shows an example of transitions in operating modes. In the figure, the horizontal axis is time and the vertical axis is primary voltage V1 and flicker value f, showing the temporal changes in primary voltage V1 and flicker value f, with the operating modes shown at the top. At time t0 during operation in normal mode, the flicker value f reaches the flicker threshold f th The above is true, but the predetermined time t th At time t1 before the elapse of time, the flicker threshold f th After that, at time t2, the primary side voltage V1 drops below the voltage threshold V th The following is true: th The voltage threshold V th The following state is maintained: At time t3, the flicker value f is equal to or less than the flicker threshold value f th After the specified time t th The primary voltage V1 has not yet reached the voltage threshold V th After a predetermined time t th Since time has passed, at time t3, the mode changes from normal mode to flicker mode, and the reference value (PV curve) is increased.

[0059] After that, at time t4, the primary side voltage V1 drops below the voltage threshold V th This is the predetermined time t th Until time t6 has elapsed, the voltage threshold V th The above state is maintained. Meanwhile, the flicker value f reaches the flicker threshold value f at time t5. th At time t6, the flicker threshold fth Although it is less than the flicker threshold f th After a predetermined time t th Therefore, at time t6, the flicker mode is maintained. After that, the primary side voltage V1 drops below the voltage threshold V th The above state is expressed as the flicker value f and the flicker threshold f th The following state is continuously maintained, and at time t7, the flicker value f reaches the flicker threshold f th After a predetermined time t th Then, at time t7, the mode changes from flicker mode to normal mode, and the reference value (PV curve) is returned to the value before it was increased.

[0060] The invention made by the present inventors has been specifically described above based on the embodiments. However, the present invention is not limited to the above-described embodiments and can be modified in various ways without departing from the spirit and scope of the invention. For example, communication between flicker meters 15, 16, system control device 11, control PC 18, and remote monitoring and control device 19 may be wireless, wired, or via an information network such as the Internet. Furthermore, connection between distribution VQC 10 and other components (transformers 22, 32, 42, 52, current measuring means 23, 33, 43, remote monitoring and control device 19, transformers 21, 31, 41, phase modifying means 25, 26, 35, 36, 45, 46, etc.) may also be wireless, wired, or via an information network such as the Internet.

[0061] Furthermore, in the above-described embodiment, the functions of the power distribution VQC 10 are realized by the flicker meters 15 and 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 by the flicker meters 15 and 16, the voltage control method according to the present invention may be implemented by determining the flicker value by the processor 12 of the system control device 11. [Explanation of symbols]

[0062] 1. Distribution substation equipment 10 Distribution voltage control system (distribution VQC) 11 System control device 12 processors 13 Recording media 14 Timer 15, 16 Flicker meter 17 Wireless Router 18 Control PC 19 Remote monitoring and control device 20 1B 21, 31, 41 Transformers 22, 32, 42, 52 transformers 23, 33, 43 Current measurement means 24, 34, 44 90 relay 25, 35, 45 Shunt reactor (phase adjusting means) 26, 36, 46 Power capacitor (phase compensator) 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 Solar power generation facilities 71 PV curve (V2 upper limit alarm value) 72 PV curve (dead band upper limit) 73, 73' PV curve (reference value) 74 PV curve (lower limit of dead zone) 75 PV curve (V2 lower limit alarm value)

Claims

1. 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:

2. 2. 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 is below a predetermined voltage for a predetermined period of time, or when a flicker value of the primary side voltage or the secondary side voltage is above a predetermined value for a predetermined period of time.

3. 3. The method of claim 2, further comprising the step of restoring the reference value to a value before it was increased if, after it is determined that the voltage flicker has occurred or is a sign of occurring, the primary-side voltage remains equal to or higher than a predetermined voltage for a predetermined period of time and the flicker value of the primary-side voltage or the secondary-side voltage remains equal to or lower than a predetermined value for a predetermined period of time.

4. 4. The method according to claim 1, wherein the step of controlling the secondary voltage of the transformer is performed by at least one of phase modifying control and LR control, and control that takes reactive power into consideration is applied preferentially.

5. 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.

6. The method according to claim 1 , further comprising issuing an alarm when it is determined that the voltage flicker has occurred or is a sign of occurring.

7. 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:

8. 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.

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