JP2023088599A - Ac power feed system - Google Patents

Abstract

To provide an AC power feed system capable of allowing distributed power supplies to operate in isolation when AC power supply fails while using existing distributed power supplies.SOLUTION: An AC power feed system comprises: a feeder line 3 for supplying AC power to loads 6; a circuit breaker 1 connected between a commercial AC power supply 5 and the feeder line 3 to be turned on when the commercial AC power supply 5 is healthy and turned off when the commercial AC power supply 5 fails; distributed power supplies 4 for supplying AC power to the feeder line 3 in synchronization with an AC voltage Va of the feeder line 3; and a reactive power compensator 30 for supplying reactive power to the feeder line 3 so that a frequency Fa of the AC voltage Va of the feeder line 3 becomes a commercial frequency Fc when the commercial AC power supply 5 fails.SELECTED DRAWING: Figure 4

Description

The present invention relates to an AC power supply system, and more particularly to an AC power supply system with distributed power sources.

For example, Japanese Patent Application Laid-Open No. 2013-207853 (Patent Document 1) discloses a power supply line for supplying AC power to a load, a breaker connected between the AC power supply and the power supply line, and AC power to the power supply line. An AC power feeding system is disclosed that includes a distributed power supply that supplies power and a setting unit that sets whether to permit individual operation of the distributed power supply.

A signal indicating the setting result of the setting unit is transmitted to the distributed power supply via the communication network. If isolated operation of the distributed power sources is not permitted, the circuit breaker is turned off and the operation of the distributed power sources is stopped at the time of power failure of the AC power supply, thereby stopping power supply to the load. When isolated operation of the distributed power sources is permitted, when the AC power supply fails, the circuit breaker is turned off and the distributed power sources are islanded, and AC power is supplied from the distributed power sources to the load.

JP 2013-207853 A

However, in Patent Document 1, it is necessary to use a new distributed power source that operates by receiving a signal from the setting unit, and there is a problem that the existing distributed power source cannot be used.

SUMMARY OF THE INVENTION Therefore, it is a primary object of the present invention to provide an AC power supply system capable of using an existing distributed power supply and allowing the distributed power supply to operate independently during a power failure of the AC power supply.

An AC power supply system according to the present invention includes a power supply line for supplying AC power to a load, one terminal receiving an AC voltage supplied from an AC power supply, and the other terminal being connected to the power supply line. A breaker that is turned on and turned off when the AC power supply fails, a distributed power supply that supplies AC power to the power supply line in synchronization with the AC voltage of the power supply line, and a frequency of the AC voltage of the power supply line when the AC power supply fails. and a reactive power compensator for supplying reactive power to the feeder so that is the reference frequency.

In the AC power supply system according to the present invention, when a power failure occurs in the AC power supply, reactive power is supplied from the reactive power compensator to the power supply line so that the AC voltage of the power supply line becomes the reference frequency. Operation is not detected and operation of the distributed generation continues. Therefore, while using an existing distributed power supply, the distributed power supply can be operated independently when the AC power supply fails.

1 is a circuit block diagram showing the configuration of an AC power supply system that forms the basis of the present invention; FIG. 2 is a block diagram showing the configuration of a control device shown in FIG. 1; FIG. 2 is a circuit block diagram showing the configuration of the distributed power supply shown in FIG. 1; FIG. 1 is a circuit block diagram showing the configuration of an AC power feeding system according to Embodiment 1 of the present invention; FIG. 5 is a block diagram showing the configuration of the reactive power compensator shown in FIG. 4; FIG. 6 is a block diagram showing the configuration of a control unit shown in FIG. 5; FIG. FIG. 4 is a block diagram showing a main part of an AC power supply system according to Embodiment 2 of the present invention;

In order to facilitate understanding of the present invention, first, an AC power feeding system that forms the basis of the present invention will be described. FIG. 1 is a circuit block diagram showing the configuration of an AC power supply system that forms the basis of the present invention. In FIG. 1, this AC power supply system includes a circuit breaker 1, a control device 2, a power supply line 3, and a plurality of distributed power sources 4, and supplies AC power to a plurality of loads 6 in cooperation with a commercial AC power source 5. .

One terminal of circuit breaker 1 receives commercial frequency AC voltage VA supplied from commercial AC power supply 5 , and the other terminal is connected to feeder line 3 . The on and off of circuit breaker 1 is controlled by control device 2 .

The controller 2 turns on the breaker 1 when the AC voltage VA is normally supplied from the commercial AC power supply 5 (when the commercial AC power supply 5 is healthy), and the AC voltage VA is normally supplied from the commercial AC power supply 5. If it is not supplied (during a power failure of the commercial AC power supply 5), the circuit breaker 1 is turned off.

FIG. 2 is a block diagram showing the configuration of the control device 2. As shown in FIG. In FIG. 2 , control device 2 includes voltage detector 10 , power failure detector 11 , and control section 12 . Voltage detector 10 detects an instantaneous value of AC voltage VA supplied from commercial AC power supply 5 and outputs a signal VAf indicating the detected value.

Power failure detector 11 detects whether the voltage value of AC voltage VA indicated by output signal VAf of voltage detector 10 is within a normal range, and outputs power failure detection signal DB indicating the detection result. When the voltage value of AC voltage VA is within the normal range, power failure detection signal DB is set to the "H" level of the inactivation level. When the value of AC voltage VA is lower than the normal range, power failure detection signal DB is set to the activation level of "L" level. The control unit 12 turns on the circuit breaker 1 when the power failure detection signal DB is at the "H" level, and turns off the circuit breaker 1 when the power failure detection signal DB is at the "L" level.

Again referring to FIG. 1 , each of the plurality of distributed power sources 4 and the plurality of loads 6 is connected to the power supply line 3 . Each distributed power source 4 determines whether or not the distributed power source 4 is independently operated without linking with the commercial AC power source 5 based on the time change Fchg of the frequency Fa of the AC voltage Va of the power supply line 3. .

When it is determined that the power supply line 3 is not operated alone, the distributed power supply 4 supplies AC power to the power supply line 3 in synchronization with the AC voltage Va of the power supply line 3 . When it is determined that the distributed power source 4 is operating independently, the operation of the distributed power source 4 is stopped.

When the commercial AC power supply 5 is healthy, the power supply line 3 is connected to the commercial AC power supply 5 via the circuit breaker 1, and the frequency change Fchg of the AC voltage Va of the power supply line 3 is small. not.

When the commercial AC power supply 5 fails, the circuit breaker 1 is turned off to electrically disconnect the feeder line 3 from the commercial AC power supply 5. Since the frequency Fa of the AC voltage Va of the power supply line 3 changes toward the determined predetermined frequency, islanding operation of the distributed power supply 4 is detected. When the frequency Fa of the AC voltage Va exceeds the allowable range, the load 6 and the like are adversely affected, so the operation of the distributed power supply 4 is stopped when islanding is detected.

FIG. 3 is a block diagram showing the configuration of the distributed power source 4. As shown in FIG. In FIG. 3 , distributed power source 4 includes DC power source 20 and power conditioner 21 . DC power supply 20 converts natural energy into DC power. Natural energy includes, for example, sunlight, wind power, tidal power, and geothermal power, and is also called renewable energy. The power conditioner 21 operates in synchronization with the AC voltage Va of the power supply line 3 , converts the DC power generated by the DC power supply 20 into AC power, and supplies the AC power to the power supply line 3 .

Power conditioner 21 includes current detectors 22 and 26 , voltage detectors 23 and 27 , power converter 24 , circuit breaker 25 , islanding detector 28 , and controller 29 . An output terminal 20 a of the DC power supply 20 is connected to a DC terminal 24 a of the power converter 24 . AC terminal 24 b of power converter 24 is connected to one terminal of circuit breaker 25 , and the other terminal of circuit breaker 25 is connected to power supply line 3 .

Current detector 22 detects a DC output current ID of DC power supply 20 and outputs a signal IDf indicating the detected value to control unit 29 . Voltage detector 23 detects a DC output voltage VD of DC power supply 20 and outputs a signal VDf indicating the detected value to control section 29 .

Power converter 24 is controlled by control unit 29 . When the isolated operation of the distributed power supply 4 is not detected, the power converter 24 converts the DC power supplied from the DC power supply 20 into AC power. When the isolated operation of the distributed power supply 4 is detected, the operation of the power converter 24 is stopped.

The on and off of the circuit breaker 25 are controlled by the controller 29 . If islanding of the distributed power supply 4 is not detected, the circuit breaker 25 is turned on. When isolated operation of the distributed power supply 4 is detected, the circuit breaker 25 is turned off.

Current detector 26 detects an instantaneous value of alternating current Ia flowing between the other terminal of circuit breaker 25 and power supply line 3 and outputs a signal Iaf indicating the detected value to control unit 29 . The voltage detector 27 detects the AC voltage Va of the power supply line 3 and outputs a signal Vaf indicating the detected value to the islanding detection section 28 and the control section 29 .

The islanding detection unit 28 obtains the time change Fchg of the frequency Fa of the AC voltage Va of the power supply line 3 indicated by the output signal Vaf of the voltage detector 27, and compares the obtained frequency change Fchg with the threshold value Fth. , outputs a signal indicating the comparison result to the control unit 29 as an islanding detection signal DI.

When frequency change Fchg is smaller than threshold value Fth (Fchg<Fth), it is determined that islanding operation is not being performed, and islanding operation detection signal DI is set to the deactivation level of "L" level. When frequency change Fchg is larger than threshold value Fth (Fchg>Fth), it is determined that islanding is being performed, and islanding detection signal DI is set to the activation level of "H".

Further, when the frequency change Fchg exceeds a predetermined value Fb smaller than the threshold value Fth, the islanding operation detection unit 28 outputs reactive power in a direction (leading or lagging) to increase the frequency change Fchg. A command signal CMD for commanding is output to the control unit 29 . This makes it possible to quickly detect islanding.

Such a detection method is called a new active method. However, the islanding detection unit 28 may detect islanding by a conventional active method or a passive method.

Control unit 29 controls power converter 24 based on output signals IDf and Iaf from current detectors 22 and 26, output signals VDf and Vaf from voltage detectors 23 and 27, and output signals DI and CMD from islanding detection unit . to control.

When the islanding detection signal DI is at the deactivation level “L” level, the control unit 29 turns on the circuit breaker 25 and outputs the output signals of the current detectors 22 and 26 and the voltage detectors 23 and 27. to convert the DC power generated by the DC power supply 20 into AC power.

Further, the control unit 29 controls the power converter 24 in accordance with the command signal CMD to output leading reactive power or lagging reactive power from the power converter 24 to the feeder line 3 . When islanding detection signal DI is at the “H” activation level, control unit 29 turns off circuit breaker 25 and stops operation of power converter 24 .

Next, the operation of this AC power feeding system will be described. When the commercial AC power supply 5 is sound, the power failure detector 11 (FIG. 2) sets the power failure detection signal DB to the "H" level of the inactivation level, and the control unit 12 turns on the circuit breaker 1 (FIG. 1). As a result, the AC output voltage VA of the commercial AC power supply 5 is supplied to the feeder line 3 via the circuit breaker 1, and the commercial AC power supply 5 and the plurality of distributed power sources 4 are linked.

In each distributed power supply 4, natural energy is converted into DC power by a DC power supply 20 (FIG. 3), and the DC power is converted into AC power by a power converter 24. is supplied to a plurality of loads 6 via.

When the AC power generated by the plurality of distributed power sources 4 is smaller than the power consumption of the plurality of loads 6 , the insufficient power is supplied from the commercial AC power source 5 . When the AC power generated by the distributed power sources 4 is greater than the power consumption of the loads 6 , the surplus power is regenerated to the commercial AC power source 5 .

When the commercial AC power supply 5 fails, the power failure detector 11 (FIG. 2) sets the power failure detection signal DB to the activation level of "L" level, the control unit 12 turns off the circuit breaker 1 (FIG. 1), and the commercial AC power supply is switched off. The power source 5 (FIG. 1) and the feeder line 3 are electrically disconnected. When the commercial AC power supply 5 and the feeder line 3 are electrically disconnected, the alternating current of the feeder line 3 is applied toward a predetermined frequency determined by the AC output current Ia of the plurality of distributed power sources 4 and the impedance of the plurality of loads 6. The frequency Fa of the voltage Va changes.

When the time change Fchg of the frequency Fa exceeds a predetermined value Fb, a command signal CMD is output from the islanding detection unit 28 to the control unit 29 . Control unit 29 controls power converter 29 in response to command signal CMD to output reactive power to feeder 3 in a direction that increases frequency change Fchg.

When frequency change Fchg further increases and exceeds threshold value Fth, islanding detection unit 28 sets islanding detection signal DI to the "H" activation level, and power converter 24 stops operating. , the circuit breaker 25 is turned off. As a result, the output of AC power from the plurality of distributed power sources 4 to the feeder line 3 is stopped, and the operation of the plurality of loads 6 is stopped.

As described above, in the AC power supply system shown in FIGS. 1 to 3, when the commercial AC power supply 5 fails, the load 6 is prevented from being adversely affected by the change in the frequency Fa of the AC voltage Va of the power supply line 3. , the operation of all distributed power sources 4 is stopped. However, it is desired to effectively use the AC power generated by the plurality of distributed power sources 4 when the commercial AC power supply 5 is cut off due to a natural disaster or the like. The present invention attempts to solve this problem.

[Embodiment 1]
FIG. 4 is a circuit block diagram showing the configuration of the AC power feeding system according to Embodiment 1 of the present invention, which is compared with FIG. Referring to FIG. 4, this AC power feeding system differs from the AC power feeding system of FIG. 1 in that a reactive power compensator 30 is added.

The reactive power compensator 30 is disabled so that the frequency Fa of the AC voltage Va of the power supply line 3 becomes the commercial frequency Fc (reference frequency) when the power failure detection signal DB is at the activation level of "L" level. Power is output to the feed line 3 . Reactive power compensator 30 includes, for example, a STATCOM (Static synchronous compensator).

FIG. 5 is a block diagram showing the configuration of the reactive power compensator 30. As shown in FIG. In FIG. 5 , reactive power compensator 30 includes reactive power generator 31 , current detector 32 , voltage detector 33 , frequency detector 34 and controller 35 .

The reactive power generation unit 31 includes multiple reactors, multiple capacitors, and multiple thyristors, is controlled by the control unit 35 , and outputs reactive power to the power supply line 3 . By turning on and off each of the plurality of thyristors, it is possible to selectively output leading reactive power or lagging reactive power and control the magnitude of the reactive power to a desired value.

Current detector 32 detects AC current IR output from reactive power generator 31 to power supply line 3 and outputs signal IRf indicating the detected value to controller 35 . The voltage detector 33 detects an instantaneous value of the AC voltage Va of the power supply line 3 and outputs a signal Vaf indicating the detected value to the controller 35 . The frequency detector 34 detects the frequency Fa of the AC voltage Va based on the output signal Vaf of the voltage detector 33 and outputs a signal Faf indicating the detected value to the controller 35 .

Control unit 35 controls reactive power generation unit 31 based on power failure detection signal DB, output signal IRf of current detector 32 , output signal Vaf of voltage detector 33 , and output signal Faf of frequency detector 34 .

The control unit 35 is activated when the power failure detection signal DB is at the activation level of "L" level, and controls reactive power so that the frequency Fa indicated by the output signal Faf of the frequency detector 34 becomes the commercial frequency Fc. It controls the reactive power output from the generator 31 .

FIG. 6 is a block diagram showing the configuration of the control section 35. As shown in FIG. In FIG. 6, the control section 35 includes a subtractor 40, a frequency control section 41, and a reactive power control section . A subtractor 40 finds a deviation ΔFa=Fc−Fa between the commercial frequency Fc and the frequency Fa indicated by the output signal Faf of the frequency detector 34 (FIG. 5).

Frequency control unit 41 is activated when power failure detection signal DB is set to the activation level of “L” level, and generates reactive power control value ΔQ so as to eliminate deviation ΔFa. Frequency control unit 41 generates reactive power control value ΔQ by, for example, adding a value proportional to deviation ΔFa and a value proportional to the integral value of deviation ΔFa.

Reactive power control unit 42 detects reactive power output from reactive power generation unit 31 to power supply line 3 based on output signal IRf of current detector 32 and output signal Vaf of voltage detector 33, The reactive power generator 31 is controlled so that the detected value becomes reactive power of a value corresponding to the reactive power control value ΔQ.

Next, the operation of the AC power supply system shown in FIGS. 4 to 6 will be described. The operation when the commercial AC power supply 5 is healthy is the same as that of the AC power supply system shown in FIGS. That is, when the commercial AC power supply 5 (FIG. 4) is healthy, the power failure detection signal DB is set to the deactivation level "H" level, the circuit breaker 1 is turned on, and the reactive power compensator 30 is deactivated. be.

As a result, the AC output voltage VA of the commercial AC power supply 5 is supplied to the feeder line 3 via the circuit breaker 1, and the commercial AC power supply 5 and the plurality of distributed power sources 4 are linked. Each distributed power source 4 converts the natural energy into DC power, converts the DC power into AC power, and supplies the AC power to a plurality of loads 6 via the power supply line 3 . At this time, no reactive power is output from the reactive power compensator 30 .

When the commercial AC power supply 5 fails, the power failure detection signal DB is set to the activation level of "L" level, the circuit breaker 1 is turned off, the commercial AC power supply 5 and the feeder line 3 are electrically disconnected, and reactive power compensation is performed. Device 30 is activated.

The voltage detector 33 and the frequency detector 34 (FIG. 5) detect the frequency Fa of the AC voltage Va of the power supply line 3, and the subtractor 40 (FIG. 6) detects the deviation ΔFa between the commercial frequency Fc and the frequency Fa of the AC voltage Va. is required. A reactive power control value ΔQ is generated by the frequency control unit 41 so as to eliminate the deviation ΔFa. 3 outputs reactive power.

Thereby, the frequency Fa of the AC voltage Va of the power supply line 3 is maintained at the commercial frequency Fc. Since the frequency Fa is maintained at the commercial frequency Fc, the islanding operation is not detected by the islanding detection unit 28, the operation of the distributed power supply 4 is continued, and the operation of the load 6 is continued.

As described above, in the first embodiment, when the commercial AC power source 5 fails, the reactive power compensator 30 maintains the frequency Fa of the AC voltage Va of the power supply line 3 at the commercial frequency Fc. The islanding operation is not detected by 28, and the islanding operation of the distributed power source 4 is continued. Therefore, even if a power failure occurs in the commercial AC power supply 5 while using the existing distributed power supply 4, the independent operation of the distributed power supply 4 can be continued. Therefore, in the event of a power failure of the commercial AC power supply 5 due to a natural disaster or the like, the AC power generated by the distributed power supply 4 can be effectively used.

[Embodiment 2]
When the power generation amount of the distributed power supply 4 increases when the commercial AC power supply 5 is sound, there is a problem that the effective value Ve of the AC voltage Va of the power supply line 3 increases due to reverse power flow. If the effective value Ve of the AC voltage Va becomes excessively high, the load 6 will be adversely affected. The second embodiment attempts to solve this problem.

FIG. 7 is a block diagram showing essential parts of an AC power supply system according to Embodiment 2 of the present invention, and is a diagram to be compared with FIG. Referring to FIG. 7 , this AC power supply system differs from the first embodiment in that control unit 35 of reactive power compensator 30 is replaced with control unit 45 .

The control unit 45 is obtained by adding an effective value calculation unit 50 , a subtractor 51 , a voltage control unit 52 and a switch 53 to the control unit 35 . The effective value calculator 50 obtains the effective value Ve (voltage value) of the AC voltage Va of the power supply line 3 based on the output signal Vaf of the voltage detector 33 (FIG. 5). Voltage detector 33 and effective value calculator 50 constitute an embodiment of a voltage value detector. The subtractor 51 obtains a deviation ΔVe=Vc−Ve between the reference value Vc (reference voltage value) of the effective value of the AC voltage Va and the effective value Ve obtained by the effective value calculator 50 .

Voltage control unit 52 is activated when power failure detection signal DB is set to the "H" level of the inactivation level, and generates reactive power control value ΔQ so as to eliminate deviation ΔVe. Voltage control unit 52 generates reactive power control value ΔQ by, for example, adding a value proportional to deviation ΔVe and a value proportional to the integrated value of deviation ΔVe.

The switch 53 selects either the reactive power control value ΔQ generated by the frequency control unit 41 or the reactive power control value ΔQ generated by the voltage control unit 52 according to the power failure detection signal DB. Give to 42. Specifically, when the power failure detection signal DB is set to the inactivation level “H” level, the switch 53 provides the reactive power control value ΔQ generated by the voltage control unit 52 to the reactive power control unit 42 . . Switch 53 provides reactive power control value ΔQ generated by frequency control unit 41 to reactive power control unit 42 when power failure detection signal DB is set to the activation level “L” level.

Next, the operation of this AC power feeding system will be described. When the commercial AC power supply 5 (FIG. 4) is healthy, the power failure detection signal DB is set to the "H" level of the inactivation level, and the circuit breaker 1 is turned on. As a result, the AC output voltage VA of the commercial AC power supply 5 is supplied to the feeder line 3 via the circuit breaker 1, and the commercial AC power supply 5 and the plurality of distributed power sources 4 are linked. Each distributed power source 4 converts the natural energy into DC power, converts the DC power into AC power, and supplies the AC power to a plurality of loads 6 via the power supply line 3 .

Also, in the reactive power compensator 30, the voltage control unit 52 (FIG. 7) is activated. The voltage detector 33 (FIG. 5) detects the AC voltage Va of the power supply line 3, the effective value calculator 50 (FIG. 7) obtains the effective value Ve of the AC voltage Va, and the subtractor 51 calculates the effective value Ve of the AC voltage Va. A deviation ΔVe between the value Ve and the reference value Vc is obtained.

The reactive power control value ΔQ is generated by the voltage control section 52 so as to eliminate the deviation ΔVe, and is given to the reactive power control section 42 via the switch 53 . The reactive power controller 42 controls the reactive power generator 31 according to the reactive power control value ΔQ, and the reactive power is output from the reactive power generator 31 to the power supply line 3 . As a result, the effective value Ve of the AC voltage Va of the power supply line 3 is maintained at the reference value Vc, and the effective value Ve of the AC voltage Va is prevented from becoming excessively high.

When the commercial AC power supply 5 fails, the power failure detection signal DB is set to the activation level of "L" level, the circuit breaker 1 is turned off, and the commercial AC power supply 5 and the feeder line 3 are electrically disconnected. In reactive power compensator 30, voltage control section 52 is deactivated and frequency control section 41 is activated.

The voltage detector 33 and the frequency detector 34 detect the frequency Fa of the AC voltage Va of the power supply line 3, and the subtractor 40 obtains the deviation ΔFa between the commercial frequency Fc and the frequency Fa of the AC voltage Va. A reactive power control value ΔQ is generated by the frequency control unit 41 so as to eliminate the deviation ΔFa, and is given to the reactive power control unit 42 via the switch 53 . The reactive power controller 42 controls the reactive power generator 31 according to the reactive power control value ΔQ, and the reactive power is output from the reactive power generator 31 to the power supply line 3 .

Thereby, the frequency Fa of the AC voltage Va of the power supply line 3 is maintained at the commercial frequency Fc. Since the frequency Fa is maintained at the commercial frequency Fc, the islanding operation is not detected by the islanding detection unit 28, the operation of the distributed power supply 4 is continued, and the operation of the load 6 is continued. Since other configurations and operations are the same as those of the first embodiment, description thereof will not be repeated.

As described above, in the second embodiment, when the commercial AC power supply 5 is healthy, the power supply line 3 is supplied from the reactive power compensator 30 so that the effective value Ve of the AC voltage Va of the power supply line 3 becomes the reference value Vc. Reactive power is supplied. Therefore, even when the power generation amount of the distributed power supply 4 increases, it is possible to prevent the load 6 from being adversely affected by the increase in the effective value Ve of the AC voltage Va of the power supply line 3 .

It should be considered that the embodiments disclosed this time are illustrative in all respects and not restrictive. The present invention is indicated by the scope of the claims rather than the above description, and is intended to include all modifications within the meaning and scope of equivalents of the scope of the claims.

Reference Signs List 1, 25 breaker, 2 control device, 3 feeder line, 4 distributed power supply, 5 commercial AC power supply, 6 load, 10, 23, 27, 33 voltage detector, 11 power failure detector, 12, 29, 35, 45 Control Unit 20 DC Power Supply 21 Power Conditioner 22, 26, 32 Current Detector 24 Power Converter 28 Islanding Detector 30 Reactive Power Compensator 31 Reactive Power Generating Unit 34 Frequency Detector 40 , 51 subtractor, 41 frequency control section, 42 reactive power control section, 50 effective value calculation section, 52 voltage control section, 53 switch.

Claims (5)

a power supply line for supplying AC power to a load;
a circuit breaker having one terminal receiving an AC voltage supplied from an AC power supply, the other terminal being connected to the feeder line, turned on when the AC power supply is healthy, and turned off when the AC power supply fails;
a distributed power supply that supplies AC power to the power supply line in synchronization with the AC voltage of the power supply line;
and a reactive power compensator that supplies reactive power to the power supply line so that the frequency of the AC voltage of the power supply line becomes a reference frequency when the AC power supply fails. The reactive power compensator,
a frequency detector that detects the frequency of the AC voltage of the power supply line;
a frequency control unit that generates a first reactive power control value so as to eliminate the deviation between the reference frequency and the frequency detected by the frequency detector when the AC power supply fails;
2. The AC power feeding system according to claim 1, further comprising a reactive power generator that outputs reactive power to said power supply line according to said first reactive power control value. The reactive power compensator,
a voltage value detector that detects the voltage value of the AC voltage of the power supply line;
a voltage control unit that generates a second reactive power control value so that the voltage value detected by the voltage value detector becomes a reference voltage value when the AC power supply is healthy;
3. The AC power supply system according to claim 2, wherein said reactive power generator outputs reactive power to said power supply line according to said first and second reactive power control values. The distributed power source is
a DC power supply that generates DC power;
a power converter that converts the DC power supplied from the DC power supply into AC power and supplies the AC power to the power supply line;
and an islanding detection unit that detects a frequency change in the AC voltage of the feeder line and stops the operation of the power converter when the frequency change exceeds a threshold value. The AC power supply system according to any one of items 1 and 2. The AC power supply is a commercial AC power supply,
5. The AC power supply system according to any one of claims 1 to 4, wherein said reference frequency is a commercial frequency.

Images