JP6521325B2 - Voltage stabilization device and control method thereof - Google Patents

Description

  Embodiments of the present invention relate to a voltage stabilization device and a control method thereof. More specifically, SVC (Static Var Compensator) that supplies reactive power using switching elements, and a phase-advancing capacitor or a shunt reactor that supplies fixed reactive power are used appropriately switched. The present invention relates to a switching function of a reactive power supply source of a voltage stabilization device aiming to reduce operating loss.

  Connect reactive power sources such as SVC, phase advancing capacitor (hereinafter referred to as SC (Static Capacitor)), shunt reactor (hereinafter referred to as S-Re (Shunt Reactor), etc. to the system bus of AC power system Therefore, a voltage stabilization device that stabilizes the voltage of the power system is known. Capacitive reactive power supplied by SC raises the voltage, and inductive reactive power supplied by S-Re lowers the voltage. However, since SC and S-Re can only supply fixed reactive power, the stabilizing effect on fluctuating voltage is low. On the other hand, SVC is a power electronics device using a switching element, and can supply reactive power which fluctuates continuously or stepwise. For this reason, it is common to perform voltage stabilization with SVC for fluctuating voltages.

  While SVC has the advantage of being able to change the reactive power following the voltage fluctuation or the reactive power fluctuation of the load that is the cause, SVC supplies the reactive power of the same capacity because it uses switching elements in the main circuit. The operating loss is large compared to the SC or S-Re. For this reason, it is considered to achieve both stabilization of the voltage and reduction of the operating loss by switching SVC and SC or S-Re appropriately.

  For example, when the voltage fluctuation source is a wind power generator or a solar power generator, the simplest idea is to stop the voltage stabilizer when the power generator stops. Furthermore, even when the generator is in operation, if the reactive power output of the SVC is stuck at the device rating of the SVC (if the maximum output continues), the reactive power is fluctuated and supplied There is no need. Therefore, in this case, the reactive power supply source is switched to stop the SVC, connect the SC if fixed on the capacitive side, and connect the S-Re if fixed on the inductive side, It is possible to reduce the operating loss without losing the function (voltage stabilization) as a voltage stabilization device.

  Although the switching judgment of the reactive power supply source as described above is simple, there is a concern that the following problems may occur. For example, if the SVC output is stuck (fixed maximum output) if the output of the generator happens to be stable only for a short time, SVC is required for voltage stabilization if the output suddenly changes. Could be In this case, it is necessary to immediately open the SC and S-Re with a mechanical switch (VCB: Vacuum Circuit Breaker, etc.) and restart the SVC. Voltage stabilization becomes difficult.

  Also, even if the above switching time delay is allowed, it is expected that SVC and SC or S-Re perform frequent switching. The switches of SC and S-Re have a high switching frequency and a short life. The SC is repeatedly charged and discharged of the charge of the capacitor to reduce the life. In the case of the SVC, in the case of the self-excitation system, deterioration is promoted by repeated charging and discharging of the DC capacitor.

  Furthermore, SC and S-Re having large capacities cause voltage fluctuation due to inrush current when the power system is turned on. Frequent switching on and off may adversely affect the power system.

  As described above, in the method of switching to SC or S-Re when the SVC continues the maximum output, the device life may be shortened and the power system may be adversely affected. For this reason, in the voltage stabilization device and the control method thereof, it is desirable to improve the reliability by suppressing the reduction of the life of the device and the adverse effect on the power system while achieving both the stabilization of the voltage and the reduction of the operation loss Be

JP, 2012-039818, A

  An embodiment of the present invention provides a voltage stabilization device that achieves both stabilization of voltage and reduction of operating loss and improved reliability and a control method thereof.

  According to an embodiment of the present invention, there is provided a voltage stabilization device comprising a reactive power supply unit and a control unit. The reactive power supply unit includes at least one of a phase advancing capacitor and a shunt reactor, and a static reactive power compensating device, and is connected to a system bus in parallel with a power generating device that supplies AC power, and the phase advancing The reactive power fixed by the at least one of the capacitor and the shunt reactor and the variable reactive power variable by the static reactive power compensation device are selectively supplied to the system bus. The control unit controls supply of reactive power to the system bus by the reactive power supply unit. The control unit is configured to calculate a difference between an AC voltage of the system bus and a voltage target value of the system bus, reactive power supplied from the static reactive power compensator to the system bus, active power of the power generation system, The reactive power output from the static reactive power compensation device in a state where reactive power is obtained and the reactive power is not supplied from the at least one of the phase advance capacitor and the shunt reactor to the grid bus The command value of is calculated from the difference, and the reactive power according to the command value is supplied from the static reactive power compensator to the system bus from the static reactive power compensator, and the reactive power of the static reactive power compensator is the static Attached to the device rating of the reactive power compensator, the absolute value of the difference is larger than the first set value, and the active power and the reactive power of the power generation device are stable. Case, from said static var compensator reduces the reactive power supplied to the system bus, the supply reactive power to the system bus from said at least one of the phase advancing capacitor and the shunt reactor.

  There is provided a voltage stabilization device and a control method thereof, in which the stabilization of voltage and the reduction of operation loss are compatible and the reliability is improved.

FIG. 1 is a block diagram schematically showing a power system and a voltage stabilization device according to a first embodiment. It is a block diagram showing the SVC typically. It is a flow chart which expresses operation of a voltage stabilization device concerning a 1st embodiment typically. FIG. 4A to FIG. 4G are graphs schematically showing an example of the operation of the voltage stabilization device according to the first embodiment. FIG. 5A and FIG. 5B are block diagrams schematically showing modifications of the SVC. It is a block diagram which represents typically the electric power system and voltage stabilizer which concern on 2nd Embodiment. It is a flow chart which expresses operation of a voltage stabilization device concerning a 2nd embodiment typically.

Hereinafter, each embodiment will be described with reference to the drawings.
The drawings are schematic or conceptual, and the relationship between the thickness and width of each part, the ratio of sizes between parts, and the like are not necessarily the same as the actual ones. In addition, even in the case of representing the same portion, the dimensions and ratios may be different from one another depending on the drawings.
In the specification of the present application and the drawings, the same elements as those described above with reference to the drawings are denoted by the same reference numerals, and the detailed description will be appropriately omitted.

First Embodiment
FIG. 1 is a block diagram schematically showing a power system and a voltage stabilizer according to a first embodiment.
As shown in FIG. 1, the power system 2 includes a system bus 4 of the power system, a power generation device 5, and a voltage stabilization device 10. The power generation device 5 is connected to the system bus 4 via the interconnection transformer 6 and the secondary bus 8. The power generation device 5 generates AC power, and supplies the generated AC power to the system bus 4. The power system 2 supplies the AC power generated by the power generation device 5 to a customer etc. via the system bus 4.

  The AC power supplied from the grid bus 4 to the consumer and the AC power generated by the power generation device 5 are, for example, three-phase AC power. The AC power of the system bus 4 and the power generation device 5 is not limited to three-phase AC power, and may be, for example, single-phase AC power.

  For the power generation device 5, for example, a power generation device using natural energy such as a wind power generation device or a solar power generation device is used. The power generation device 5 is not limited to these, and may be, for example, a thermal power generation device or a nuclear power generation device. The power generation device 5 may be any power generation device capable of generating AC power.

  The voltage stabilization device 10 is connected to the system bus 4 via the interconnection transformer 6 and the secondary bus 8. The voltage stabilization device 10 stabilizes the AC voltage of the system bus 4 by supplying at least one of the lead reactive power and the delayed reactive power to the system bus 4.

  In this example, the power generation device 5 and the voltage stabilization device 10 are connected to the system bus 4 via the interconnection transformer 6 and the secondary bus 8. The power generation device 5 and the voltage stabilization device 10 may be directly connected to the system bus 4 without via the interconnection transformer 6 and the secondary bus 8. The interconnection transformer 6 and the secondary bus 8 are provided as necessary and can be omitted.

The power system 2 further includes, for example, voltage detectors 12 and 14 and a current detector 16. The voltage detector 12 is connected to the system bus 4 and the voltage stabilizer 10. The voltage detector 12 detects the AC voltage V _EPS of the system bus 4, and inputs the detected AC voltage V _EPS to the voltage stabilization device 10. In this example, the voltage detector 12 detects the voltage (phase voltage) of each phase of the three-phase AC voltage, and inputs the detection result to the voltage stabilization device 10.

  The voltage detector 14 is connected to the output of the power generation device 5 and the voltage stabilization device 10. The voltage detector 14 detects the output voltage Vg of the power generation device 5 and inputs the detected output voltage Vg to the voltage stabilization device 10. In this example, the voltage detector 14 detects the voltage (phase voltage) of each phase of the three-phase AC voltage, and inputs the detection result to the voltage stabilization device 10.

  The current detector 16 is connected to the output of the generator 5 and the voltage stabilizer 10. The current detector 16 detects the output current Ig of the power generation device 5 and inputs the detected output current Ig to the voltage stabilization device 10. In this example, the current detector 16 detects the current (phase current) of each phase of the three-phase AC voltage, and inputs the detection result to the voltage stabilization device 10.

  As shown in FIG. 1, the voltage stabilization device 10 includes a reactive power supply unit 30 and a control unit 34. The reactive power supply unit 30 is connected to the system bus 4 via the interconnection transformer 6 and the secondary bus 8. That is, reactive power supply unit 30 is connected to system bus 4 in parallel with power generation device 5. The reactive power supply unit 30 supplies at least one of lead reactive power and delayed reactive power to the system bus 4. Control unit 34 controls the supply of reactive power to system bus 4 by reactive power supply unit 30.

  The reactive power supply unit 30 includes an SVC 31, an SC 32, an S-Re 33, and switches 41 to 43. The SVC 31 is connected to the secondary bus 8 via the switch 41. The SVC 31 has a switching element, and supplies lead reactive power or delayed reactive power, which fluctuates continuously or stepwise, to the system bus 4 by turning on / off the switching element. For the SVC 31, for example, a self-excitation reactive power compensation device called STATCOM (Static Synchronous Compensator) or SVG (Static Var Generator) is used. In this case, lead reactive power and delayed reactive power which fluctuate continuously can be supplied to the system bus 4.

  The switch 41 is provided between the SVC 31 and the secondary bus 8, and has a closed state in which the SVC 31 is connected to the secondary bus 8 and an open state in which the SVC 31 is disconnected from the secondary bus 8. In other words, the input state of the switch 41 is a state in which the SVC 31 is connected to the system bus 4, and the open state of the switch 41 is a state in which the SVC 31 is disconnected from the system bus 4. In the SVC 31, the supply and the stop of the supply of reactive power can be controlled by turning on and off the switching element. Therefore, the switch 41 is not necessarily required and can be omitted. The SVC 31 may be directly connected to the secondary bus 8.

  The SC 32 is connected to the secondary bus 8 via the switch 42. The SC 32 supplies predetermined lead reactive power to the system bus 4 when connected to the secondary bus 8. The lead reactive power supplied by the SC 32 is, for example, substantially the same as the maximum value (rated output) of the lead reactive power supplied by the SVC 31.

  The switch 42 is provided between the SC 32 and the secondary bus 8 and has a closed state in which the SC 32 is connected to the secondary bus 8 and an open state in which the SC 32 is disconnected from the secondary bus 8. In other words, the closed state of the switch 42 is a state in which the SC 32 is connected to the system bus 4, and the open state of the switch 42 is a state in which the SC 32 is disconnected from the system bus 4. The lead reactive power of the SC 32 is supplied to the system bus 4 by turning on the switch 42, and the supply to the system bus 4 is stopped by opening the switch 42.

  The S-Re 33 is connected to the secondary bus 8 via the switch 43. The S-Re 33 supplies predetermined delay reactive power to the system bus 4 when connected to the secondary bus 8. The delayed reactive power supplied by the S-Re 33 is, for example, substantially the same as the maximum value (rated output) of the delayed reactive power supplied by the SVC 31.

  The switch 43 is provided between the S-Re 33 and the secondary bus 8 and is in a closed state in which the S-Re 33 is connected to the secondary bus 8 and in an open state in which the S-Re 33 is disconnected from the secondary bus 8; Have. In other words, the closed state of the switch 43 is a state in which the S-Re 33 is connected to the system bus 4, and the open state of the switch 42 is a state in which the S-Re 33 is disconnected from the system bus 4. The delayed reactive power of S-Re 33 is supplied to the system bus 4 by putting the switch 43 into the on state, and the supply to the system bus 4 is stopped by making the switch 43 into the open state.

  Thus, reactive power supply unit 30 selectively selects the system of reactive power fixed by SC 32 or S-Re 33 and reactive power variable by SVC 31 selectively by switching on / off of switches 41 to 43. Supply to the bus 4

  In this example, the reactive power supply unit 30 includes the SC 32 and the S-Re 33, and supplies the lead reactive power and the delayed reactive power to the system bus 4. The reactive power supply unit 30 may be capable of supplying at least one of the lead reactive power and the delayed reactive power to the system bus 4. The reactive power supply part 30 should just have at least one of SC32 and S-Re33.

The voltage stabilizer 10 further includes, for example, a voltage detector 36 and a current detector 38. The voltage detector 36 is connected to the output of the SVC 31 and the control unit 34. The voltage detector 36 detects the output voltage V _SVC of the _SVC 31, and inputs the detected output voltage V _SVC to the control unit 34. In this example, the voltage detector 36 detects the voltage (phase voltage) of each phase of the three-phase AC voltage, and inputs the detection result to the control unit 34.

The current detector 38 is connected to the output of the SVC 31 and the control unit 34. The current detector 38 detects the output current I _SVC of the _SVC 31, and inputs the detected output current I _SVC to the control unit 34. In this example, the current detector 38 detects the current (phase current) of each phase of the three-phase AC voltage, and inputs the detection result to the control unit 34.

The control unit 34 includes a subtractor 50, a Q calculator 51, PQ calculators 52 and 53, and a switching function unit 54. The subtractor 50 receives an AC voltage V _EPS (effective value) of the system bus 4 detected by the voltage detector 12 and a voltage target value Vref (effective value) of the system bus 4. Subtractor 50 subtracts the voltage target value Vref from the AC voltage _{V EPS,} calculates a difference ΔV between the AC voltage _{V EPS} and the voltage target value Vref is detected values. Then, the subtractor 50 inputs the calculated difference ΔV to the Q calculator 51 and the switching function unit 54. Further, for example, the subtractor 50 calculates the difference ΔV for each phase of the system bus 4, and inputs the difference ΔV of each phase to the Q calculator 51 and the switching function unit 54. The voltage target value Vref may be a predetermined fixed value, or may be a fluctuation value input from a host controller or the like.

  The Q computing unit 51 calculates a command value (Q command value) of reactive power to be output from the SVC 31 based on the input difference ΔV, and inputs the calculated Q command value to the SVC 31. The Q computing unit 51 calculates a Q command value from the difference ΔV by, for example, a control method such as PI control, PID control, or IP control, modern control theory, or the like. Also, the Q computing unit 51 calculates, for example, the Q command value for each phase of the system bus 4 from the difference ΔV of each phase, and inputs the Q command value for each phase to the SVC 31.

  The SVC 31 supplies reactive power according to the Q command value to the system bus 4 by controlling on / off of the switching element based on the input Q command value. The SVC 31 supplies reactive power to each phase of the system bus 4 according to, for example, the Q command value of each phase.

For example, when the AC voltage V _EPS is lower than the voltage target value Vref, the Q computing unit 51 and the SVC 31 raise the AC voltage of the system bus 4 by supplying the reactive power according to the difference ΔV to the system bus 4 Let On the other hand, when, for example, the AC voltage V _EPS is higher than the voltage target value Vref, the Q computing unit 51 and the SVC 31 supply delayed reactive power corresponding to the difference ΔV to the system bus 4 to thereby operate the AC voltage of the system bus 4 Reduce Thereby, the alternating voltage of system bus 4 can be stabilized.

  The output voltage Vg of the power generation device 5 detected by the voltage detector 14 and the output current Ig of the power generation device 5 detected by the current detector 16 are input to the PQ calculator 52. The PQ calculator 52 calculates active power Pg and reactive power Qg output from the power generation device 5 based on the input output voltage Vg and output current Ig. Then, the PQ calculator 52 inputs the calculated active power Pg and reactive power Qg to the switching function unit 54.

  The PQ calculator 52 calculates, for example, the effective value of the output voltage Vg, the effective value of the output current Ig, and the phase difference θg of the output voltage Vg and the output current Ig. Then, the PQ calculator 52 calculates the active power Pg by Pg = Vg · Ig · cos θg, and calculates the reactive power Qg by Qg = Vg · Ig · sin θg.

The PQ calculator 53 receives the output voltage V _SVC of the _SVC 31 detected by the voltage detector 36 and the output current I _SVC of the _SVC 31 detected by the current detector 38. The PQ calculator 53 calculates the reactive power Q _SVC output from the _SVC 31 based on the input output voltage V _SVC and the output current I _SVC . Then, the PQ calculator 53 inputs the calculated reactive power Q _SVC to the switching function unit 54. For the calculation of the reactive power Q _SVC by the PQ calculator 53, for example, a method similar to that of the PQ calculator 52 is used.

Switching function unit 54 operates _SVC 31 on / off command and SC 32 on / off based on the input difference ΔV, active power Pg and reactive power Qg of power generation device 5, and reactive power Q _{SVC of SVC} 31. An open command and an S-Re 33 on / off command are generated.

  The switching function unit 54 inputs the generated operation / stop command of the SVC 31 to the SVC 31 and the switch 41. When the operation / stop command indicates the operation, the switch 41 is turned on, and the SVC 31 supplies reactive power. Thereby, as described above, reactive power according to the Q command value is supplied from the SVC 31 to the system bus 4. On the other hand, when the operation / stop command indicates a stop, the switch 41 is in the open state, and the SVC 31 stops the supply of reactive power.

  Further, the switching function unit 54 inputs the generated ON / OFF command of the SC 32 to the switch 42. When the on / off command indicates the on state, the switch 42 is in the on state, the SC 32 is connected to the system bus 4, and the reactive power by the SC 32 is supplied to the system bus 4. On the other hand, when the on / off command indicates the open state, the switch 42 is in the open state, the SC 32 is disconnected from the system bus 4 and the supply of reactive power to the system bus 4 by the SC 32 is stopped.

  Further, the switching function unit 54 inputs the generated S-Re 33 closing / opening command to the switch 43. When the on / off command indicates the on state, the switch 43 is in the on state, the S-Re 33 is connected to the system bus 4, and the reactive power delayed by the S-Re 33 is supplied to the system bus 4. On the other hand, when the on / off command indicates the open state, the switch 43 is in the open state, the S-Re 33 is disconnected from the system bus 4, and the delayed reactive power supply to the system bus 4 by the S-Re 33 is stopped. Be done.

FIG. 2 is a block diagram schematically showing the SVC.
As shown in FIG. 2, the SVC 31 includes, for example, a reactor 71, an inverter circuit 72, a capacitor 73, and a driver 74.

  The reactor 71 is connected to the switch 41. The reactor 71 may be connected to the switch 71 via a transformer. Also, instead of the reactor 71, a transformer may be used. The inverter circuit 72 has an AC output point and a DC output point. An AC output point of the inverter circuit 72 is connected to the reactor 71. The DC output point of the inverter circuit 72 is connected to the capacitor 73.

  The inverter circuit 72 has a plurality of switching elements 75 and a plurality of rectifying elements 76. Each switching element 75 is, for example, full bridge connected. For each switching element 75, for example, a self-arc-extinguishing switching element such as an IGBT (Insulated Gate Bipolar Transistor) or a GTO (Gate Turn-Off thyristor) is used. Each rectifying element 76 is connected in anti-parallel to each switching element 75. For example, a diode is used for each rectifying element 76. Each rectifying element 76 is a so-called reflux diode. The control terminal of each switching element 75 is connected to the driver 74.

  The Q command value output from the Q computing unit 51 of the control unit 34 is input to the driver 74. The driver 74 controls on / off of each switching element 75 in accordance with the Q command value. Thus, the driver 74 supplies the reactive power and the delayed reactive power of any magnitude according to the Q command value to the system bus 4.

For example, the driver 74 is provided with the functions of the subtractor 50 and the Q computing unit 51 in the driver 74, and the alternating voltage V _EPS of the system bus 4 detected by the voltage detector 12 or the difference ΔV is input to the driver 74. The command value may be calculated.

FIG. 3 is a flow chart schematically showing the operation of the voltage stabilization device according to the first embodiment.
As shown in FIG. 3, when the control unit 34 of the voltage stabilization device 10 starts operation, alternating current is generated based on the detection values of the voltage detectors 12, 14 and 36 and the current detectors 16 and 38. The difference ΔV between the voltage V _EPS and the voltage target value Vref, the reactive power Q _SVC of the _SVC 31, and the active power Pg and reactive power Qg of the power generation device 5 are acquired (step S101 in FIG. 3). The acquired difference ΔV, reactive power Q _SVC , active power Pg, and reactive power Qg are input to the switching function unit 54.

  Immediately after the start of operation, the switching function unit 54 sets the operation / stop command of the SVC 31 to the operation state, and sets each of the closing / opening commands of the SC 32 and the S-Re 33 to the open state. Also, in the control unit 34, the difference ΔV is input to the Q computing unit 51. The Q calculator 51 calculates a Q command value from the difference ΔV, and inputs the calculated Q command value to the SVC 31. The SVC 31 controls on / off of each switching element 75 based on the input Q command value. Thereby, reactive power according to the Q command value is supplied from the SVC 31 to the system bus 4, and stabilization of the AC voltage of the system bus 4 is achieved.

After the operation of the _SVC 31 is started, the switching function unit 54 determines whether the reactive power Q _SVC of the _SVC 31 is stuck to the device rating of the _SVC 31 or not. In other words, the switching function unit 54 determines whether the state in which the SVC 31 is outputting the maximum reactive power continues for a predetermined time. Further, the switching function unit 54 determines whether the absolute value of the difference ΔV is larger than the set value ΔV _S1 (first set value). Furthermore, the switching function unit 54 determines whether the active power Pg and the reactive power Qg are stable (step S102 in FIG. 3).

For example, when the state in which the _SVC 31 is outputting the maximum lead reactive power or the delayed reactive power is continued for 0.5 seconds or longer, the switching function unit 54 causes the reactive power Q _SVC of the _SVC 31 to be rated for the device of the _SVC 31. It is judged that it is stuck to

The set value ΔV _S1 is set to, for example, about 1% to 2% of the voltage target value Vref. For example, when the voltage target value Vref is 66 kV, the set value ΔV _S1 is set to about 1 kV. For determining whether the active power Pg and the reactive power Qg are stable, for example, the difference between the average value of the active power Pg and the reactive power Qg within a predetermined time and the maximum value and the minimum value within that period is taken. A known method such as a method or a method of differentiating the average value (time variation) can be used. For example, when the difference between the average value, the maximum value, and the minimum value is equal to or less than a predetermined value, the switching function unit 54 determines that the switching function unit 54 is stable. Alternatively, when the time variation is equal to or less than a predetermined value, it is determined to be stable.

When the switching function unit 54 determines that at least one of the above three conditions is not satisfied, the switching function unit 54 operates the SVC 31 and keeps the state in which the SC 32 and the S-Re 33 are open. On the other hand, if the switching function unit 54 determines that all the above three conditions are satisfied, then it determines whether the AC voltage V _EPS of the system bus 4 is lower than the voltage target value Vref (FIG. 3). Step S103).

When the switching function unit 54 determines that the AC voltage V _EPS is lower than the voltage target value Vref, the switching function unit 54 causes the operation / stop command of the SVC 31 to be in the stop state and the on / off command of the SC 32 is in the on state. The operation is stopped and the advanced reactive power of SC32 is supplied to the system bus 4 (step S104 in FIG. 3).

On the other hand, when the switching function unit 54 determines that the AC voltage V _EPS is higher than the voltage target value Vref, the operation / stop command of the SVC 31 is in the stop state, and the closing / opening command of the S-Re 33 is in the closing state. Thus, the operation of the SVC 31 is stopped, and the delayed reactive power of S-Re 33 is supplied to the system bus 4 (step S105 in FIG. 3).

After switching SC32 or S-Re 33, switching function unit 54 determines whether or not the absolute value of difference ΔV is less than or equal to the set value ΔV _S2 (second set value) (step S106 in FIG. 3). . The set value ΔV _S2 is smaller than the set value ΔV _S1 . The set value ΔV _S2 is set to, for example, 1% or less of the voltage target value Vref. That is, after switching SC 32 or S-Re 33 is performed, switching function unit 54 determines whether or not AC voltage V _EPS has substantially become equal to voltage target value Vref.

Switching function section 54, an absolute value to continue the on state of the SC32 or S-Re33 until the set value or less [Delta] V _S2 of the difference [Delta] V. When switching function unit 54 determines that the absolute value of difference ΔV has become equal to or smaller than set value ΔV _S2 , it sets the operation / stop command of SVC 31 to the operating state, and releases each opening / closing command of SC32 and S-Re33. By doing this, the operation of the SVC 31 is resumed (step S107 in FIG. 3). When the control unit 34 resumes the operation of the SVC 31, the control unit 34 returns to the process of step S101, and repeats the same process.

FIG. 4A to FIG. 4G are graphs schematically showing an example of the operation of the voltage stabilization device according to the first embodiment.
FIG. 4A shows an example of the determination result as to whether the reactive power Q _SVC of the _SVC 31 is stuck to the device rating of the _SVC 31. In FIG. 4A, the stuck state is represented as “1”, and the not stuck state is represented as “0”.
FIG. 4B illustrates an example of the determination result as to whether or not the absolute value of the difference ΔV is larger than the set value ΔV _S1 . FIG. 4 (b), represents the higher state than the set value [Delta] V _S1 "1", the state of being smaller than the set value [Delta] V _S1 as "0".
FIG. 4C shows an example of the determination result as to whether or not the active power Pg and the reactive power Qg are stable. In FIG. 4C, the stable state is represented as “1”, and the unstable state is represented as “0”.
FIG. 4D shows an example of the determination result as to whether or not the absolute value of the difference ΔV is less than or equal to the set value ΔV _S2 . In FIG. 4 (d), the represents the following state setting value [Delta] V _S2 "1", the larger state than the set value [Delta] V _S2 as "0".
FIG. 4E illustrates an example of the state of the SVC 31. In FIG. 4E, the operating state of the SVC 31 is represented as "0" and the stopped state of the SVC 31 is represented as "1". The state of “1” in FIG. 4E is, in other words, the state of injection of SC 32 or S-Re 33. In this case, when the determination results of the reactive power Q _SVC , the difference ΔV, the active power Pg, and the reactive power Qg are “1”, the state of the SVC 31 also becomes “1”.
FIG. _4F shows an example of the AC voltage V _EPS .
FIG. 4 (g) shows an example of the reactive power Q _SVC .

In FIG. 4 (a) ~ FIG 4 (g), at time t0~ time t1, the determination of the sticking of the reactive power _{Q SVC,} the comparison determination between the difference [Delta] V and the set value [Delta] V _S1, the determination of the active power Pg and reactive power Qg The judgment result of each is “0”. That is, reactive power _{Q SVC} is not stuck to the apparatus rating SVC31, the absolute value of the difference [Delta] V is smaller than the set value [Delta] V _S1, is also stable active power Pg and reactive power Qg. Therefore, from time t0 to time t1, the state of the SVC 31 becomes “0”, and reactive power corresponding to the difference ΔV is supplied from the SVC 31 to the system bus 4.

From time t1 to time t2, the determination result of the sticking of the reactive power Q _SVC and the determination result of the comparison determination of the difference ΔV and the set value ΔV _S1 are changed to “1”. However, the determination results of the active power Pg and the reactive power Qg remain “0”. Accordingly, at time t1 to time t2, the state of the SVC 31 is also maintained at "0", and the supply of reactive power from the SVC 31 is continued.

From time t3 to time t4, only the determination result of the comparison determination between the difference ΔV and the set value ΔV _S1 is “1”. From time t5 to time t6, only the determination results of the active power Pg and the reactive power Qg are "1". At time t7 to time t8, only the determination result of the comparison determination between the difference ΔV and the set value ΔV _S1 is “1”. At time t8 to time t9, the determination result of the sticking of the reactive power Q _SVC and the comparison determination of the difference ΔV and the set value ΔV _S1 are “1”. Therefore, also between time t2 and time t9, the state of the SVC 31 is maintained at “0”, and the supply of reactive power from the SVC 31 is continued.

On the other hand, at time t9, the determination results of the sticking determination of reactive power Q _SVC , the comparison determination of difference ΔV and set value ΔV _S1, and determination of active power Pg and reactive power Qg are “1”. . Therefore, the state of the SVC 31 changes to "1", and the operation of the SVC 31 is stopped. At time t9, AC voltage V _EPS is lower than voltage target value Vref. Therefore, at time t9, the SC 32 is turned on, and from the SC 32 to the system bus 4, reactive power is supplied.

At time t10, the determination results of the active power Pg and the reactive power Qg change from "1" to "0". However, at time t10, the determination result of the comparison determination between the difference ΔV and the set value ΔV _S2 remains “0”. Therefore, at time t10, the input state of SC32 is continued.

Similarly, at time t11, the determination result of the comparison and determination between the difference ΔV and the set value ΔV _S1 changes from “1” to “0”, but the determination of the comparison and determination between the difference ΔV and the set value ΔV _S2 The result remains "0". For this reason, the input state of SC32 is continued also at time t11.

At time t12, the with the determination of the sticking of the reactive power Q _SVC changes from "1" to "0", "1" judgment result of the comparison determination of the set value [Delta] V _S2 and the difference [Delta] V is changed from "0" It is changing. That is, at time t12, AC voltage V _EPS is substantially equal to voltage target value Vref. Therefore, at time t12, the connection of the SC 32 is released, and the operation of the SVC 31 is resumed.

As described above, in the voltage stabilization apparatus 10 according to the present embodiment, when the above three conditions are satisfied, the operation of the SVC 31 is switched to SC32 or S-Re33. Whether the absolute value of the difference [Delta] V is greater than the set value [Delta] V _S1, is a judgment, the absolute value is greater state than the set value [Delta] V _S1 of the difference [Delta] V, despite SVC31 is operating, system This means that the AC voltage V _EPS of the bus 4 has not reached the voltage target value Vref. In other words, the required reactive power is still lacking.

Next, it is monitoring that the active power Pg and the reactive power Qg of the power generation device 5 are stable. If the active power Pg and the reactive power Qg are unstable (variations are large), the AC voltage V _EPS is also expected to be unstable, so it can be determined that it is desirable to keep the SVC 31 operating.

Finally, it is a continuation judgment of the state where the reactive power Q _{SVC of SVC} 31 is stuck to the device rating (maximum capacity) of _SVC 31. The fact that the reactive power Q _{SVC of SVC} 31 does not fluctuate, that is, the fixed maximum, is the main premise for switching to SC32 or S-Re 33 that supplies fixed reactive power (= cannot supply variable reactive power). is there.

The above three factors and the determination of switching will be described in detail.
“The difference ΔV is larger than the set value ΔV _S1 = The supply reactive power is not sufficient” and “The SVC 31 is stuck to the device rating” means that the difference is in spite of the device rating of the SVC 31. Since the reactive power to compensate for ΔV is still insufficient for supply, it is expected that the larger the difference ΔV, the longer the output of the SVC 31 will stick to the device rating. . Conversely, if the difference ΔV is small, even if the output of the SVC 31 happens to stick to the device rating, the condition is not known when it is released and a fluctuation output is required.

Therefore, “the state in which the difference ΔV is larger than the set value ΔV _S1 and the state in which the output of the SVC 31 is stuck to the device rating continues” refers to the reactive power supply unit 30 from the SVC 31, SC 32 or S It can be determined that the condition is sufficient for switching to Re 33.

The above is the switching determination while looking at the AC voltage V _EPS , but this is not sufficient. The reason is that the voltage is a "result" and the sudden change in the output of the power generation device 5 can not be sufficiently coped with without considering the movement of the active power Pg and the reactive power Qg of the power generation device 5 which is the "cause". Therefore, "the active power Pg and the reactive power Qg are stable under the condition that the SVC 31 is switched to the SC 32 or S-Re 33 by monitoring the amount of change (not the absolute value) of the active power Pg and the reactive power Qg. Add "as an AND condition.

  Thereby, in the voltage stabilization device 10 according to the present embodiment, it is possible to perform the operation switching between the SVC 31 and the SC 32 or the S-Re 33 at an appropriate timing with an appropriate frequency. As a result, shortening of the device life due to frequent switching and adverse effects on the power system can be suppressed. In the voltage stabilization device 10 according to the present embodiment, the stabilization of the voltage and the reduction of the operating loss can both be achieved, and the reliability can be improved.

In the above embodiment, when the SC 32 or the S-Re 33 is turned on, the operation of the SVC 31 is stopped. For example, the reactive power Q _SVC supplied from the _SVC 31 may be reduced to a predetermined value or less when the SC 32 or the S-Re 33 is supplied. Thereby, for example, compared with the case where the operation of the SVC 31 is stopped, the response speed at the time of returning the SVC 31 to the normal operation state can be improved by releasing the SC 32 or the S-Re 33. On the other hand, when the operation of the _SVC 31 is stopped, the operating loss can be further reduced compared to the case where the reactive power Q _SVC is reduced.

FIG. 5A and FIG. 5B are block diagrams schematically showing modifications of the SVC.
As shown in FIG. 5A, in this example, the SVC 31 includes a reactor 81 and a pair of thyristors 82 and 83 (switching elements).

  The reactor 81 is connected to the secondary bus 8 via the switch 41. The reactor 81 may be connected to the secondary bus 8 via a transformer, for example. For example, instead of the reactor 81, a transformer may be used. The thyristors 82 and 83 are connected in series to the reactor 81. The thyristors 82 and 83 are connected in antiparallel to each other. The respective gates (control terminals) of the thyristors 82 and 83 are connected to a driver 74 (not shown).

  The driver 74 controls the firing of each of the thyristors 82, 83 in accordance with the input Q command value. Thus, the SVC 31 supplies delayed reactive power from the reactor 81 to the system bus 4 in response to the firing of each of the thyristors 82, 83.

  The SVC 31 supplies lead reactive power and delayed reactive power to the system bus 4 arbitrarily, for example, by combining the delayed reactive power by the reactor 81 and the lead reactive power by the SC 32. That is, FIG. 5A schematically shows a so-called SVC 31 of a so-called TCR (Thyristor Controlled Reactor) system.

  As shown in FIG. 5B, in this example, the SVC 31 includes a plurality of capacitors 85a to 85c and a plurality of thyristors 86a to 86c and 87a to 87c (switching elements).

  Each of the capacitors 85 a to 85 c is connected to the secondary bus 8 via the switch 41. Each of the capacitors 85a to 85c may be connected to the secondary bus 8 via a transformer, a reactor, or the like. Each of the thyristors 86a and 87a is connected in series to the capacitor 85a. Each of the thyristors 86b and 87b is connected in series to the capacitor 85b. Each of the thyristors 86 c and 87 c is connected in series to the capacitor 85 c. The respective thyristors 86a and 87a, the respective thyristors 86b and 87b, and the respective thyristors 86c and 87c are connected in antiparallel to one another. The gates (control terminals) of the thyristors 86a to 86c and 87a to 87c are connected to a driver 74 (not shown).

  The driver 74 controls the firing of each of the thyristors 86a to 86c and 87a to 87c in accordance with the input Q command value. Thus, the driver 74 switches the number of capacitors 85 a to 85 c connected to the system bus 4. The driver 74 controls the magnitude of the leading reactive power to be output to the system bus 4 according to the number of capacitors 85 a to 85 c connected to the system bus 4. That is, FIG. 5B schematically shows a so-called SVC 31 of the so-called TSC (Thyristor Switched Capacitor) system. In FIG. 5 (b), three capacitors 85a to 85c are shown. The number of capacitors selectively connected to the system bus 4 is not limited to three, and may be any number of two or more.

  Thus, the circuit system of the SVC 31 may be a TCR system, a TSC system, a STATCOM system, or the like. The circuit scheme of the SVC 31 is not limited to these, and may be any circuit scheme capable of supplying the system bus 4 with reactive power that varies continuously or stepwise.

Second Embodiment
FIG. 6 is a block diagram schematically showing a power system and a voltage stabilizer according to a second embodiment.
As shown in FIG. 6, the control unit 34 of the voltage stabilization device 100 further includes a power generation amount prediction unit 102. The same reference numerals are given to components substantially the same in function and configuration as the first embodiment, and the detailed description will be omitted.

  The power generation amount prediction unit 102 predicts the power generation amount of the power generation device 5 after the elapse of a predetermined time, and inputs a predicted value to the switching function unit 54. For example, when the power generation device 5 is a wind power generator, the power generation amount prediction unit 102 obtains weather forecast information from the outside, and predicts the power generation amount of the power generation device 5 from the fluctuation prediction of the air volume. For example, when the power generation device 5 is a solar power generation device, the power generation amount prediction unit 102 obtains weather forecast information from the outside, and predicts the power generation amount of the power generation device 5 from the fluctuation prediction of sunshine (light amount). In addition, about prediction of the electric power generation amount of wind power generation, it demonstrates in detail by Unexamined-Japanese-Patent No. 2013-108462 etc., for example. About prediction of the electric power generation amount of solar power generation, it is explained in detail by JP, 2014-63372, A etc., for example.

The switching function unit 54, for example, the reactive power Q _SVC of the _SVC 31 input from the PQ calculator 53, the difference ΔV input from the subtractor 50, and the power generation amount of the power generation device 5 input from the power generation amount prediction unit 102 The switching of the SVC 31, SC 32, and S-Re 33 is controlled based on the predicted value of

FIG. 7 is a flowchart schematically illustrating the operation of the voltage stabilization device according to the second embodiment.
As shown in FIG. 7, when the control unit 34 of the voltage stabilization device 100 starts operation, alternating current is generated based on the detection values of the voltage detectors 12, 14 and 36 and the current detectors 16 and 38. While acquiring the difference ΔV between the voltage V _EPS and the voltage target value Vref and the reactive power Q _SVC of the _SVC 31, the predicted value of the power generation amount of the power generation device 5 is acquired from the power generation amount prediction unit 102 (step of FIG. 7) S201). The acquired difference ΔV, reactive power Q _SVC , and predicted value are input to the switching function unit 54.

  As in the first embodiment, immediately after the start of operation, the operation / stop command of the SVC 31 is in the operation state, and the on / off commands of the SC 32 and S-Re 33 are in the open state. The reactive power corresponding to the Q command value is supplied from the SVC 31 to the system bus 4.

After the operation of the _SVC 31 is started, the switching function unit 54 determines whether the reactive power Q _SVC of the _SVC 31 is stuck to the device rating of the _SVC 31 or not. Further, the switching function unit 54 determines whether the absolute value of the difference ΔV is larger than the set value ΔV _S1 . Further, the switching function unit 54 determines whether or not the predicted value of the power generation amount of the power generation device 5 is stable (step S202 in FIG. 7).

  The switching function unit 54 determines that, for example, the fluctuation of the predicted value is within 2% of the rated power generation amount of the power generation device 5, the switching function unit 54 determines that the power generation amount of the power generation device 5 is stable. If it fluctuates by 2% or more of the rating, it is determined that it is not stable. In other words, the switching function unit 54 determines that the predicted value is stable if the difference between the rated power generation amount and the predicted power value is less than 2% of the generated power power rating, and the power generating power rating It is determined that the predicted value is not stable when the difference between and the predicted value is 2% or more of the rated power generation amount.

When the switching function unit 54 determines that at least one of the above three conditions is not satisfied, the switching function unit 54 operates the SVC 31 and keeps the state in which the SC 32 and the S-Re 33 are open. On the other hand, if the switching function unit 54 determines that all the above three conditions are satisfied, then it determines whether the AC voltage V _EPS of the system bus 4 is lower than the voltage target value Vref (FIG. 7). Step S203). The operations of step S204 to step S207 are substantially the same as step S104 to step S107 described in the first embodiment, and thus detailed description will be omitted.

  As described above, in the voltage stabilization device 100 according to the present embodiment, instead of the determination as to whether or not the active power Pg and the reactive power Qg in the first embodiment are stable, The determination of whether or not the predicted value is stable is used. When the amount of power generation of the power generation device 5 fluctuates, as a result, it is considered that the active power Pg and the reactive power Qg also fluctuate. Therefore, in the voltage stabilization apparatus 100 according to the present embodiment as well as the voltage stabilization apparatus 10 according to the first embodiment, the operation switching between the SVC 31 and the SC 32 or S-Re 33 is performed at appropriate timings. It becomes possible to carry out at an appropriate frequency, and it is possible to suppress the shortening of the device life due to frequent switching and the adverse effect on the power system. Also in the voltage stabilization device 100 according to the present embodiment, it is possible to achieve both the stabilization of the voltage and the reduction of the operating loss, and to improve the reliability.

  For example, in the power generation device 5 using natural energy such as wind power and sunlight, the amount of power generation is likely to fluctuate due to weather conditions and the like. At this time, as described above, switching of the reactive power supply unit 30 is controlled based on the determination as to whether or not the predicted value of the power generation amount of the power generation device 5 is stable. Thereby, for example, changes in weather conditions can be dealt with more quickly. For example, the reactive power supply unit 30 can be switched more quickly and more appropriately, and the AC voltage of the system bus 4 can be stabilized more.

Note that both determination of whether the active power Pg and the reactive power Qg are stable and determination of whether or not the predicted value of the power generation amount of the power generation device 5 is stable may be performed. That is, reactive power Q _{SVC of SVC} 31 sticks to the device rating of _SVC 31, and the absolute value of difference ΔV is larger than set value ΔV _S1 and each of active power Pg, reactive power Qg and predicted value is stable. If it does, the SVC 31 may be switched to the SC 32 or the S-Re 33.

  In the second embodiment, the determination is performed based on the predicted value of the power generation amount of the power generation device 5. The predicted value is not necessarily limited to the power generation amount of the power generation device 5, and may be, for example, a predicted value of the air volume or the amount of sunshine. The predicted value is not limited to the predicted value of the power generation amount of the power generation device 5 itself, and may be any predicted value related to the power generation amount of the power generation device 5. That is, the predicted value may be any predicted value that can predict fluctuations in the amount of power generation of the power generation device 5.

  While certain embodiments of the present invention have been described, these embodiments have been presented by way of example only, and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, substitutions, and modifications can be made without departing from the scope of the invention. These embodiments and modifications thereof are included in the scope and the gist of the invention, and are included in the invention described in the claims and the equivalents thereof.

  DESCRIPTION OF SYMBOLS 2 ... Power system, 4 ... System bus bar, 5 ... Power generator, 6 ... Connection transformer, 8 ... Secondary bus, 10, 100 ... Voltage stabilizer, 12, 14 ... Voltage detector, 16 ... Current detector 30, 30: reactive power supply unit, 31: SVC, 32: SC, 33: S-Re, 34: control unit, 36: voltage detector, 38: current detector, 41 to 43: switch, 50: subtractor , 51: Q arithmetic unit, 52, 53: PQ arithmetic unit, 54: switching function part, 71: reactor, 72: inverter circuit, 73: capacitor, 74: driver, 75: switching element, 76: multiple rectifying elements, 81 ... reactor, 82, 83 ... thyristor, 85 a to 85 c ... capacitor, 86 a to 86 c, 87 a to 87 c ... thyristor, 102 ... power generation amount prediction unit

Claims (7)

At least one of a phase advance capacitor and a shunt reactor, and a static reactive power compensator, connected to a system bus in parallel with a generator for supplying AC power, wherein the phase advance capacitor and the shunt reactor A reactive power supply unit for selectively supplying the fixed reactive power by the at least one and variable reactive power which is variable by the static reactive power compensator to the grid bus;
A control unit configured to control supply of reactive power to the system bus by the reactive power supply unit;
Equipped with
The control unit
The difference between the AC voltage of the system bus and the voltage target value of the system bus, the reactive power supplied from the static reactive power compensator to the system bus, and the active power and the reactive power of the generator Acquired,
In a state where the reactive power is not supplied from the at least one of the phase advancing capacitor and the shunt reactor to the system bus, the command value of the reactive power output from the static reactive power compensator is calculated from the difference Supplying the reactive power according to the command value from the static reactive power compensator to the system bus,
The reactive power of the static reactive power compensator is attached to the device rating of the static reactive power compensator, the absolute value of the difference is larger than a first set value, and the active power of the generator is When the reactive power is stable, the reactive power supplied from the static reactive power compensation device to the grid bus is reduced, and the grid bus from at least one of the phase advancing capacitor and the shunt reactor Voltage regulator for supplying the reactive power to the   After the control unit starts supplying the reactive power from the at least one of the phase advance capacitor and the shunt reactor to the grid bus, a second absolute value of the difference is smaller than the first set value. The supply of the reactive power from the at least one of the phase advance capacitor and the shunt reactor to the grid bus is stopped when the value falls below a set value, and the static reactive power compensator to the grid bus is used. The voltage stabilization apparatus according to claim 1, wherein the supply of the reactive power according to the command value is resumed. The static reactive power compensation device can supply fluctuating lead reactive power and delayed reactive power to the grid bus,
The reactive power supply unit includes both the phase advancing capacitor and the shunt reactor,
The control unit causes the reactive power of the static var compensator to stick to the device rating of the static var compensator, the absolute value of the difference is larger than a first set value, and the generator is The lead reactive power of the phase-advancing capacitor is supplied to the system bus when the AC voltage of the system bus is lower than the voltage target value when the active power and the reactive power of The voltage stabilization device according to claim 1 or 2, wherein when the AC voltage of the system bus is higher than the voltage target value, delayed reactive power of the shunt reactor is supplied to the system bus.   The control unit causes the reactive power of the static var compensator to stick to the device rating of the static var compensator, the absolute value of the difference is larger than a first set value, and the generator is The power supply system according to any one of claims 1 to 3, wherein the supply of the reactive power from the static reactive power compensator to the system bus is stopped when the active power and the reactive power of are stable. Voltage stabilization device.   The control unit further obtains a predicted value related to the power generation amount of the power generation device, and the reactive power of the static type reactive power compensation device is attached to the device rating of the static type reactive power compensation device, and the difference When the absolute value is larger than the first set value, and each of the active power, the reactive power, and the predicted value of the generator is stable, the system power bus from the static reactive power compensator The voltage stabilization according to any one of claims 1 to 4, wherein the reactive power supplied to the power source is reduced, and the reactive power is supplied from the at least one of the phase advancing capacitor and the shunt reactor to the system bus. apparatus. At least one of a phase advance capacitor and a shunt reactor, and a static reactive power compensator, connected to a system bus in parallel with a generator for supplying AC power, wherein the phase advance capacitor and the shunt reactor A reactive power supply unit for selectively supplying the fixed reactive power by the at least one and variable reactive power which is variable by the static reactive power compensator to the grid bus;
A control unit configured to control supply of reactive power to the system bus by the reactive power supply unit;
Equipped with
The control unit
The difference between the AC voltage of the system bus and the voltage target value of the system bus, reactive power supplied from the stationary reactive power compensator to the system bus, and a predicted value related to the amount of power generation of the power generating apparatus To get
In a state where the reactive power is not supplied from the at least one of the phase advancing capacitor and the shunt reactor to the system bus, the command value of the reactive power output from the static reactive power compensator is calculated from the difference Supplying the reactive power according to the command value from the static reactive power compensator to the system bus,
The reactive power of the static var compensator is attached to the device rating of the static var compensator, the absolute value of the difference is larger than a first set value, and the predicted value is stable. In this case, the reactive power supplied from the stationary reactive power compensation device to the grid bus is reduced, and the reactive power is supplied from the at least one of the phase advancing capacitor and the shunt reactor to the grid bus. Stabilizer. At least one of a phase advance capacitor and a shunt reactor, and a static reactive power compensator, connected to a system bus in parallel with a generator for supplying AC power, wherein the phase advance capacitor and the shunt reactor A reactive power supply unit for selectively supplying the fixed reactive power by the at least one and variable reactive power which is variable by the static reactive power compensator to the grid bus;
A control unit configured to control supply of reactive power to the system bus by the reactive power supply unit;
A control method of a voltage stabilization device comprising:
The difference between the AC voltage of the system bus and the voltage target value of the system bus, the reactive power supplied from the static reactive power compensator to the system bus, and the active power and the reactive power of the generator The process to acquire,
In a state where the reactive power is not supplied from the at least one of the phase advancing capacitor and the shunt reactor to the system bus, the command value of the reactive power output from the static reactive power compensator is calculated from the difference Supplying the reactive power according to the command value from the static reactive power compensator to the system bus;
The reactive power of the static reactive power compensator is attached to the device rating of the static reactive power compensator, the absolute value of the difference is larger than a first set value, and the active power of the generator is When the reactive power is stable, the reactive power supplied from the static reactive power compensation device to the grid bus is reduced, and the grid bus from at least one of the phase advancing capacitor and the shunt reactor Supplying the reactive power to the
Method of controlling a voltage stabilization device comprising:

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