AC power supply system

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

Technical Field

[0001] The present invention relates to an AC power supply system, and more particularly to an AC power supply system provided with a distributed power source.

Background Art

[0002] For example, Japanese Patent Application Laid-Open No. 2013-207853 (Patent Document 1) discloses an AC power supply system including a power supply line for supplying AC power to a load, a circuit breaker connected between an AC power source and the power supply line, a distributed power source for supplying AC power to the power supply line, and a setting unit for setting whether or not to permit independent operation of the distributed power source.

[0003] A signal indicating the setting result of the setting unit is transmitted to the distributed power source via a communication network. When the independent operation of the distributed power source is not permitted, in the event of a power failure of the AC power source, the circuit breaker is turned off and the operation of the distributed power source is stopped, and the power supply to the load is stopped. When the independent operation of the distributed power source is permitted, in the event of a power failure of the AC power source, the circuit breaker is turned off and the distributed power source is independently operated, and AC power is supplied from the distributed power source to the load.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, in Patent Document 1, there is a problem that it is necessary to use a new distributed power source that operates by receiving a signal from the setting unit, and an existing distributed power source cannot be used.

[0006] Therefore, the main object of the present invention is to provide an AC power supply system capable of operating a distributed power source independently during a power outage of an AC power supply while using an existing distributed power source.

Means for Solving the Problems

[0007] The AC power supply system according to the present invention includes 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 source and the other terminal connected to the power supply line, which is turned on when the AC power source is normal and turned off when the AC power source has a power outage, a distributed power source for supplying AC power to the power supply line in synchronization with the AC voltage of the power supply line, and a reactive power compensation device for supplying 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 source has a power outage.

Effects of the Invention

[0008] In the AC power supply system according to the present invention, when a power outage of the AC power source occurs, reactive power is supplied from the reactive power compensation device to the power supply line so that the AC voltage of the power supply line becomes the reference frequency. Therefore, the independent operation of the distributed power source is not detected, and the operation of the distributed power source is continued. Accordingly, it is possible to operate the distributed power source independently during a power outage of the AC power supply while using an existing distributed power source.

Brief Description of the Drawings

[0009]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Embodiments for Carrying Out the Invention

[0010] To facilitate the understanding of the present invention, first, the AC power supply system that is the basis of the present invention will be described. FIG. 1 is a circuit block diagram showing the configuration of the AC power supply system that is 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 association with a commercial AC power supply 5.

[0011] One terminal of the circuit breaker 1 receives an AC voltage VA of commercial frequency supplied from the commercial AC power supply 5, and the other terminal is connected to the power supply line 3. The on and off of the circuit breaker 1 are controlled by the control device 2.

[0012] When the AC voltage VA is normally supplied from the commercial AC power supply 5 (when the commercial AC power supply 5 is healthy), the control device 2 turns on the circuit breaker 1, and when the AC voltage VA is not normally supplied from the commercial AC power supply 5 (during a power outage of the commercial AC power supply 5), the control device 2 turns off the circuit breaker 1.

[0013] FIG. 2 is a block diagram showing the configuration of the control device 2. In FIG. 2, the control device 2 includes a voltage detector 10, a power outage detector 11, and a control unit 12. The voltage detector 10 detects the instantaneous value of the AC voltage VA supplied from the commercial AC power supply 5 and outputs a signal VAf indicating the detected value.

[0014] The power outage detector 11 detects whether the voltage value of the AC voltage VA indicated by the output signal VAf of the voltage detector 10 is within the normal range, and outputs a power outage detection signal DB indicating the detection result. When the voltage value of the AC voltage VA is within the normal range, the power outage detection signal DB is set to the "H" level of the non-activated level. When the value of the AC voltage VA is lower than the normal range, the power outage detection signal DB is set to the "L" level of the activated level. The control unit 12 turns on the circuit breaker 1 when the power outage detection signal DB is at the "H" level, and turns off the circuit breaker 1 when the power outage detection signal DB is at the "L" level.

[0015] Referring again 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 the distributed power source 4 is operating independently without being associated with the commercial AC power supply 5 based on the time change Fchg of the frequency Fa of the AC voltage Va of the power supply line 3.

[0016] When it is determined that the distributed power source 4 is not operating independently, the distributed power source 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.

[0017] 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, so the independent operation of the distributed power source 4 is not detected.

[0018] During a power outage of the commercial AC power supply 5, the circuit breaker 1 is turned off and the power supply line 3 is electrically disconnected from the commercial AC power supply 5. Since the frequency Fa of the AC voltage Va of the power supply line 3 changes toward a predetermined frequency determined by the relationship between the output current of the plurality of distributed power sources 4 and the impedance of the plurality of loads 6, the independent operation of the distributed power source 4 is detected. When the frequency Fa of the AC voltage Va exceeds the allowable range, it has an adverse effect on the load 6 and the like. Therefore, when the independent operation is detected, the operation of the distributed power source 4 is stopped.

[0019] FIG. 3 is a block diagram showing the configuration of the distributed power source 4. In FIG. 3, the distributed power source 4 includes a DC power source 20 and a power conditioner 21. The DC power source 20 converts natural energy into DC power. The natural energy is, for example, sunlight, wind power, tidal power, geothermal energy, etc., 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 source 20 into AC power, and supplies it to the power supply line 3.

[0020] The power conditioner 21 includes current detectors 22, 26, voltage detectors 23, 27, a power converter 24, a circuit breaker 25, a stand-alone operation detector 28, and a control unit 29. The output terminal 20a of the DC power source 20 is connected to the DC terminal 24a of the power converter 24. The AC terminal 24b of the power converter 24 is connected to one terminal of the circuit breaker 25, and the other terminal of the circuit breaker 25 is connected to the power supply line 3.

[0021] The current detector 22 detects the DC output current ID of the DC power source 20 and outputs a signal IDf indicating the detected value to the control unit 29. The voltage detector 23 detects the DC output voltage VD of the DC power source 20 and outputs a signal VDf indicating the detected value to the control unit 29.

[0022] The power converter 24 is controlled by the control unit 29. When the stand-alone operation of the distributed power source 4 is not detected, the power converter 24 converts the DC power supplied from the DC power source 20 into AC power. When the stand-alone operation of the distributed power source 4 is detected, the operation of the power converter 24 is stopped.

[0023] The on and off of the circuit breaker 25 are controlled by the control unit 29. When the stand-alone operation of the distributed power source 4 is not detected, the circuit breaker 25 is turned on. When the stand-alone operation of the distributed power source 4 is detected, the circuit breaker 25 is turned off.

[0024] The current detector 26 detects the instantaneous value of the alternating current Ia flowing between the other terminal of the circuit breaker 25 and the power supply line 3, and outputs a signal Iaf indicating the detected value to the control unit 29. The voltage detector 27 detects the alternating voltage Va of the power supply line 3, and outputs a signal Vaf indicating the detected value to the single-operation detector 28 and the control unit 29.

[0025] The single-operation detector 28 obtains the time change Fchg of the frequency Fa of the alternating voltage Va of the power supply line 3 indicated by the output signal Vaf of the voltage detector 27, compares the magnitude of the obtained frequency change Fchg with the threshold value Fth, and outputs a signal indicating the comparison result to the control unit 29 as the single-operation detection signal DI.

[0026] When the frequency change Fchg is smaller than the threshold value Fth (Fchg < Fth), it is determined that the single operation is not being performed, and the single-operation detection signal DI is set to the "L" level of the deactivated level. When the frequency change Fchg is larger than the threshold value Fth (Fchg > Fth), it is determined that the single operation is being performed, and the single-operation detection signal DI is set to the "H" level of the activated level.

[0027] Also, when the frequency change Fchg exceeds a predetermined value Fb that is smaller than the threshold value Fth, the single-operation detector 28 outputs a command signal CMD to the control unit 29 to command the output of reactive power in the direction (leading or lagging) in which the frequency change Fchg increases. Thereby, it is possible to quickly detect the single operation.

[0028] Note that such a detection method is called a new active method. However, the single-operation detector 28 may detect the single operation by a conventional active method or a passive method.

[0029] The control unit 29 controls the power converter 24 based on the output signals IDf, Iaf of the current detectors 22, 26, the output signals VDf, Vaf of the voltage detectors 23, 27, and the output signals DI, CMD of the single-operation detector 28.

[0030] When the single - operation detection signal DI is at the "L" level of the inactivation level, the control unit 29 turns on the circuit breaker 25 and controls the power converter 24 based on the output signals of the current detectors 22, 26 and the voltage detectors 23, 27, and converts the DC power generated by the DC power supply 20 into AC power.

[0031] Also, the control unit 29 controls the power converter 24 according to the command signal CMD, and outputs leading - reactive power or lagging - reactive power from the power converter 24 to the feeder line 3. When the single - operation detection signal DI is at the "H" level of the activation level, the control unit 29 turns off the circuit breaker 25 and stops the operation of the power converter 24.

[0032] Next, the operation of this AC power supply system will be described. When the commercial AC power supply 5 is normal, 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). Thereby, 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.

[0033] In each distributed power source 4, natural energy is converted into DC power by the DC power supply 20 (Fig. 3), the DC power is converted into AC power by the power converter 24, and the AC power is supplied to the plurality of loads 6 via the circuit breaker 25 and the feeder line 3.

[0034] 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 supply 5. When the AC power generated by the plurality of distributed power sources 4 is larger than the power consumption of the plurality of loads 6, the surplus power is regenerated to the commercial AC power supply 5.

[0035] When a power failure occurs in the commercial AC power supply 5, the power failure detection signal DB is set to the "L" level of the activation level by the power failure detector 11 (Fig. 2), the circuit breaker 1 (Fig. 1) is turned off by the control unit 12, and the commercial AC power supply 5 (Fig. 1) and the power supply line 3 are electrically disconnected. When the commercial AC power supply 5 and the power supply line 3 are electrically disconnected, the frequency Fa of the AC voltage Va of the power supply line 3 changes 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.

[0036] When the time change Fchg of the frequency Fa exceeds a predetermined value Fb, a command signal CMD is output from the single - operation detection unit 28 to the control unit 29. The control unit 29 controls the power converter 29 in response to the command signal CMD and outputs reactive power in a direction to increase the frequency change Fchg to the power supply line 3.

[0037] When the frequency change Fchg further increases and exceeds a threshold value Fth, the single - operation detection signal DI is set to the "H" level of the activation level by the single - operation detection unit 28, the operation of the power converter 24 is stopped, and 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 power supply line 3 is stopped, and the operation of the plurality of loads 6 is stopped.

[0038] Thus, in the AC power supply system shown in Figs. 1 to 3, when a power failure occurs in the commercial AC power supply 5, in order to prevent the load 6 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 the distributed power sources 4 is stopped. However, when a power failure of the commercial AC power supply 5 occurs due to a natural disaster or the like, it is desirable to effectively utilize the AC power generated by the plurality of distributed power sources 4. In the present invention, this problem is solved.

[0039] [Embodiment 1] Fig. 4 is a circuit block diagram showing the configuration of an AC power supply system according to Embodiment 1 of the present invention, and is a diagram for comparison with Fig. 1. Referring to Fig. 4, the difference between this AC power supply system and the AC power supply system of Fig. 1 is that a reactive power compensation device 30 is added.

[0040] When the power failure detection signal DB is at the active level "L" level, the reactive power compensation device 30 outputs reactive power to the power supply line 3 so that the frequency Fa of the AC voltage Va of the power supply line 3 becomes the commercial frequency Fc (reference frequency). The reactive power compensation device 30 includes, for example, a STATCOM (Static synchronous compensator).

[0041] FIG. 5 is a block diagram showing the configuration of the reactive power compensation device 30. In FIG. 5, the reactive power compensation device 30 includes a reactive power generation unit 31, a current detector 32, a voltage detector 33, a frequency detector 34, and a control unit 35.

[0042] The reactive power generation unit 31 includes a plurality of reactors, a plurality of capacitors, and a plurality of 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.

[0043] The current detector 32 detects the AC current IR output from the reactive power generation unit 31 to the power supply line 3 and outputs a signal IRf indicating the detected value to the control unit 35. The voltage detector 33 detects the instantaneous value of the AC voltage Va of the power supply line 3 and outputs a signal Vaf indicating the detected value to the control unit 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 control unit 35.

[0044] The control unit 35 controls the reactive power generation unit 31 based on the power failure detection signal DB, the output signal IRf of the current detector 32, the output signal Vaf of the voltage detector 33, and the output signal Faf of the frequency detector 34.

[0045] The control unit 35 is activated when the power failure detection signal DB is at the activated level of "L", and controls the reactive power output from the reactive power generation unit 31 so that the frequency Fa indicated by the output signal Faf of the frequency detector 34 becomes the commercial frequency Fc.

[0046] FIG. 6 is a block diagram showing the configuration of the control unit 35. In FIG. 6, the control unit 35 includes a subtractor 40, a frequency control unit 41, and a reactive power control unit 42. The subtractor 40 obtains the 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).

[0047] The frequency control unit 41 is activated when the power failure detection signal DB is at the activated level of "L", and generates a reactive power control value ΔQ so that the deviation ΔFa disappears. The frequency control unit 41 generates the reactive power control value ΔQ, for example, by adding a value proportional to the deviation ΔFa and a value proportional to the integral value of the deviation ΔFa.

[0048] The reactive power control unit 42 detects the reactive power output from the reactive power generation unit 31 to the power supply line 3 based on the output signal IRf of the current detector 32 and the output signal Vaf of the voltage detector 33, and controls the reactive power generation unit 31 so that the detected value becomes the reactive power of a value corresponding to the reactive power control value ΔQ.

[0049] Next, the operation of the AC power supply system shown in FIGS. 4 to 6 will be described. The operation during the normal operation of the commercial AC power supply 5 is the same as that of the AC power supply system shown in FIGS. 1 to 3. That is, when the commercial AC power supply 5 (FIG. 4) is normal, the power failure detection signal DB is at the non-activated level of "H", the circuit breaker 1 is turned on, and the reactive power compensation device 30 is deactivated.

[0050] As a result, the AC output voltage VA of the commercial AC power supply 5 is supplied to the power feed line 3 via the circuit breaker 1, and the commercial AC power supply 5 and the plurality of distributed power sources 4 are associated with each other. In each distributed power source 4, natural energy is converted into DC power, the DC power is converted into AC power, and the AC power is supplied to the plurality of loads 6 via the power feed line 3. At this time, no reactive power is output from the reactive power compensation device 30.

[0051] When a power failure occurs in the commercial AC power supply 5, the power failure detection signal DB is set to the "L" level of the activation level, the circuit breaker 1 is turned off, the commercial AC power supply 5 and the power feed line 3 are electrically disconnected, and the reactive power compensation device 30 is activated.

[0052] The frequency Fa of the AC voltage Va of the power feed line 3 is detected by the voltage detector 33 and the frequency detector 34 (Fig. 5), and the deviation ΔFa between the commercial frequency Fc and the frequency Fa of the AC voltage Va is obtained by the subtractor 40 (Fig. 6). The reactive power control value ΔQ is generated by the frequency control unit 41 so that the deviation ΔFa disappears, and the reactive power control unit 42 controls the reactive power generation unit 31 according to the reactive power control value ΔQ, and reactive power is output from the reactive power generation unit 31 to the power feed line 3.

[0053] As a result, the frequency Fa of the AC voltage Va of the power feed line 3 is maintained at the commercial frequency Fc. Since the frequency Fa is maintained at the commercial frequency Fc, single operation is not detected by the single operation detection unit 28, the operation of the distributed power source 4 is continued, and the operation of the load 6 is continued.

[0054] As described above, in the first embodiment, when a power failure occurs in the commercial AC power supply 5, the frequency Fa of the AC voltage Va of the power feed line 3 is maintained at the commercial frequency Fc by the reactive power compensation device 30, so single operation is not detected by the single operation detection unit 28, and the single operation of the distributed power source 4 is continued. Therefore, even when a power failure occurs in the commercial AC power supply 5 while using the existing distributed power source 4, the single operation of the distributed power source 4 can be continued. For this reason, when a power failure occurs in the commercial AC power supply 5 due to a natural disaster or the like, the AC power generated by the distributed power source 4 can be effectively utilized.

[0055] [Embodiment 2] When the power generation amount of the distributed power source 4 increases during the normal operation of the commercial AC power source 5, 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. When the effective value Ve of the AC voltage Va becomes excessively high, it has an adverse effect on the load 6. In the second embodiment, this problem is solved.

[0056] FIG. 7 is a block diagram showing the main part of the AC power supply system according to the second embodiment of the present invention, and is a diagram for comparison with FIG. 6. Referring to FIG. 7, the difference between this AC power supply system and the first embodiment is that the control unit 35 of the reactive power compensation device 30 is replaced by a control unit 45.

[0057] 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 calculation unit 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). The voltage detector 33 and the effective value calculation unit 50 constitute an example of a voltage value detector. The subtractor 51 obtains the 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 calculation unit 50.

[0058] The voltage control unit 52 is activated when the power failure detection signal DB is set to the "H" level of the inactive level, and generates a reactive power control value ΔQ so that the deviation ΔVe disappears. The voltage control unit 52 generates the reactive power control value ΔQ, for example, by adding a value proportional to the deviation ΔVe and a value proportional to the integral value of the deviation ΔVe.

[0059] The switch 53 supplies 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 to the reactive power control unit 42 according to the power failure detection signal DB. Specifically, when the power failure detection signal DB is at the non-activated level of "H", the switch 53 supplies the reactive power control value ΔQ generated by the voltage control unit 52 to the reactive power control unit 42. When the power failure detection signal DB is at the activated level of "L", the switch 53 supplies the reactive power control value ΔQ generated by the frequency control unit 41 to the reactive power control unit 42.

[0060] Next, the operation of this AC power supply system will be described. When the commercial AC power supply 5 (Fig. 4) is normal, the power failure detection signal DB is at the non-activated level of "H", 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 power supply 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 source 4, natural energy is converted into DC power, the DC power is converted into AC power, and the AC power is supplied to the plurality of loads 6 via the power supply line 3.

[0061] Also, in the reactive power compensation device 30, the voltage control unit 52 (Fig. 7) is activated. The AC voltage Va of the power supply line 3 is detected by the voltage detector 33 (Fig. 5), the effective value Ve of the AC voltage Va is obtained by the effective value calculation unit 50 (Fig. 7), and the deviation ΔVe between the effective value Ve of the AC voltage Va and the reference value Vc is obtained by the subtractor 51.

[0062] The reactive power control value ΔQ is generated by the voltage control unit 52 so that the deviation ΔVe disappears, and is supplied to the reactive power control unit 42 via the switch 53. The reactive power control unit 42 controls the reactive power generation unit 31 according to the reactive power control value ΔQ, and reactive power is output from the reactive power generation unit 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 it is prevented that the effective value Ve of the AC voltage Va becomes excessively high.

[0063] When a power failure occurs in the commercial AC power supply 5, the power failure detection signal DB is set to the "L" level of the activation level, the circuit breaker 1 is turned off, and the commercial AC power supply 5 and the power supply line 3 are electrically disconnected. In the reactive power compensation device 30, the voltage control unit 52 is deactivated and the frequency control unit 41 is activated.

[0064] The frequency Fa of the AC voltage Va of the power supply line 3 is detected by the voltage detector 33 and the frequency detector 34, and the deviation ΔFa between the commercial frequency Fc and the frequency Fa of the AC voltage Va is obtained by the subtractor 40. The reactive power control unit 41 generates a reactive power control value ΔQ so that the deviation ΔFa disappears, and supplies it to the reactive power control unit 42 via the switch 53. The reactive power control unit 42 controls the reactive power generation unit 31 according to the reactive power control value ΔQ, and reactive power is output from the reactive power generation unit 31 to the power supply line 3.

[0065] As a result, 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 single operation is not detected by the single operation detection unit 28, the operation of the distributed power source 4 is continued, and the operation of the load 6 is continued. Since other configurations and operations are the same as those in the first embodiment, the description thereof will not be repeated.

[0066] As described above, in the second embodiment, when the commercial AC power supply 5 is healthy, reactive power is supplied from the reactive power compensation device 30 to the power supply line 3 so that the effective value Ve of the AC voltage Va of the power supply line 3 becomes the reference value Vc. Therefore, even when the power generation amount of the distributed power source 4 increases, it is possible to prevent the effective value Ve of the AC voltage Va of the power supply line 3 from increasing and having an adverse effect on the load 6.

[0067] It should be considered that all the embodiments disclosed this time are illustrative in all respects and not restrictive. The present invention is shown not by the above description but by the claims, and it is intended that all modifications within the meaning and scope equivalent to the claims are included.

Explanation of symbols

[0068] 1,25 circuit breaker, 2 control device, 3 power supply line, 4 distributed power source, 5 commercial AC power supply, 6 load, 10,23,27,33 voltage detector, 11 power outage detector, 12,29,35,45 control unit, 20 DC power supply, 21 power conditioner, 22,26,32 current detector, 24 power converter, 28 single operation detector, 30 reactive power compensation device, 31 reactive power generation unit, 34 frequency detector, 40,51 subtracter, 41 frequency control unit, 42 reactive power control unit, 50 RMS value calculation unit, 52 voltage control unit, 53 switch.

Claims

1. 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 source, the other terminal connected to the power supply line, being turned on when the voltage value of the AC power source is within a normal range, and being turned off when the voltage value of the AC power source is lower than within the normal range, A distributed power source for supplying AC power to the power supply line in synchronization with the AC voltage of the power supply line, A reactive power compensation device including a frequency detector for detecting the frequency of the AC voltage of the power supply line, When the voltage value of the AC power source is lower than the normal range, the reactive power compensation device, Generates a first reactive power control value so that there is no deviation between a reference frequency which is the frequency of the AC voltage supplied from the AC power source when the voltage value of the AC power source is within the normal range and the frequency detected by the frequency detector, An AC power supply system that outputs reactive power to the power supply line according to the first reactive power control value.

2. 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 source, the other terminal connected to the power supply line, being turned on when the voltage value of the AC power source is within a normal range, and being turned off when the voltage value of the AC power source is lower than within the normal range, A distributed power source for supplying AC power to the power supply line in synchronization with the AC voltage of the power supply line, A reactive power compensation device including a frequency detector for detecting the frequency of the AC voltage of the power supply line and a voltage value detector for detecting the voltage value of the AC voltage of the power supply line, The reactive power compensation device, When the voltage value of the AC power source is lower than the normal range, Generates a first reactive power control value so that there is no deviation between a reference frequency which is the frequency of the AC voltage supplied from the AC power source when the voltage value of the AC power source is within the normal range and the frequency detected by the frequency detector, Outputs reactive power to the power supply line according to the first reactive power control value, When the voltage value of the AC power source is within the normal range, Generates a second reactive power control value so that the voltage value detected by the voltage value detector becomes a reference voltage value, An AC power supply system that outputs reactive power to the power supply line according to the second reactive power control value.

3. The distributed power source, A DC power source for generating DC power, A power converter that converts the DC power supplied from the DC power source into AC power and supplies it to the power supply line. An AC power supply system according to claim 1 or claim 2, comprising a single operation detector that detects a change in the frequency of the AC voltage of the power supply line and stops the operation of the power converter when the frequency change exceeds a threshold value.

4. The AC power supply is a commercial AC power supply, The reference frequency is a commercial frequency. The AC power supply system according to any one of claims 1 to 3.

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