JP2015050818A - Power conditioner and distributed power-supply system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve the problem that noise occurring due to, for example, a switch operation of a step-up circuit can be transmitted via an electrical wire when a middle point of a capacitor of the step-up circuit and a neutral point of an AC power supply are connected via the electrical wire.SOLUTION: A power conditioner, which converts a DC voltage from a DC power supply into an AC voltage and is interconnected to a system power supply, includes: a noise reduction circuit reducing noise included in a DC voltage inputted from the DC power supply; a DC-AC conversion circuit converting the DC voltage with reduced noise by the noise reduction circuit into an AC voltage; a first cut-off circuit switching whether to electrically connect or disconnect between the DC-AC conversion circuit and the system power supply; a first resistor circuit having one end connected between a positive electrode of the noise reduction circuit and a positive electrode of the DC power supply, and having the other end connected to a neutral phase of the system power supply; and a second resistor circuit connected between the neutral phase and a ground point.

Description

  The present invention relates to a power conditioner and a distributed power supply system.

In Patent Document 1 and Patent Document 2, two resistors are provided at both ends of a capacitor for smoothing the voltage boosted by the booster circuit, and the midpoint between the two resistors is connected to the neutral point of the AC power supply. Thus, it is described that erroneous detection of the leakage detection circuit is prevented when the interconnection switch is turned on.
Patent Document 1 Japanese Patent Laid-Open No. 10-271688 Patent Document 2 Japanese Patent Laid-Open No. 11-252803

  As described above, when the midpoint between the two resistors and the neutral point of the AC power supply are connected via a wire, noise generated due to the switch operation of the booster circuit can be transmitted via the wire There is sex.

  A power conditioner according to an aspect of the present invention is a power conditioner that converts a DC voltage from a DC power supply into an AC voltage and is linked to a system power supply, and includes noise included in the DC voltage input from the DC power supply. A noise reduction circuit that reduces noise, a DC / AC conversion circuit that converts a DC voltage whose noise has been reduced by the noise reduction circuit, to an AC voltage, and an electrical connection between the DC / AC conversion circuit and the system power supply. A first cutoff circuit for switching between the first resistance circuit, one end connected between the positive electrode of the noise reduction circuit and the positive electrode of the DC power supply, and the other end connected to the neutral phase of the system power supply, and the neutral phase And a second resistance circuit connected between the ground and the ground point.

  In the power conditioner, the positive electrode and the neutral phase of the noise reduction circuit are electrically connected via the first resistance circuit, or the positive electrode and the neutral phase of the noise reduction circuit are electrically disconnected. You may further provide the 2nd cutoff circuit which switches whether to do.

  The power conditioner controls the first cutoff circuit to reduce the noise by controlling the second cutoff circuit before switching from the state where the DC / AC converter circuit and the system power supply are electrically disconnected to the connected state. After switching from a state where the positive electrode and neutral phase of the circuit were electrically disconnected to a connected state, the first circuit was controlled to electrically disconnect between the DC / AC converter circuit and the system power supply. You may further provide the control part which switches from a state to the connected state.

  In the power conditioner, the control unit controls the second cutoff circuit after controlling the first cutoff circuit to switch from the state in which the DC / AC converter circuit and the system power supply are electrically disconnected to the connected state. Then, the state in which the positive electrode and the neutral phase of the noise reduction circuit are electrically connected may be switched to a state in which the noise reduction circuit is disconnected.

  The power conditioner may further include a backflow prevention circuit that prevents current from flowing from the neutral phase side to the positive electrode side of the noise reduction circuit.

  The power conditioner includes a differential amplifier circuit that detects a potential difference between the first phase and the neutral phase of the system power supply and a potential difference between the second phase and the neutral phase of the system power supply. The resistor circuit may be a resistor circuit included in the differential amplifier circuit.

  The power conditioner may further include a non-insulated booster circuit that boosts a DC voltage whose noise is reduced by the noise reduction circuit and outputs the boosted voltage to the DC-AC converter circuit.

  The distributed power supply system which concerns on 1 aspect of this invention is equipped with the said power conditioner and the distributed power supply as DC power supply.

  It should be noted that the above summary of the invention does not enumerate all the necessary features of the present invention. In addition, a sub-combination of these feature groups can also be an invention.

It is a figure which shows an example of the system configuration | structure of the whole solar cell system which concerns on this embodiment. It is a figure for demonstrating the ON / OFF timing of a bypass relay and a connection relay.

  Hereinafter, the present invention will be described through embodiments of the invention, but the following embodiments do not limit the invention according to the claims. In addition, not all the combinations of features described in the embodiments are essential for the solving means of the invention.

  FIG. 1 is a diagram illustrating an example of a system configuration of the entire solar cell system according to the present embodiment. The solar cell system includes a solar cell array 200 and a power conditioner 10. The solar cell array 200 has a plurality of solar cell modules connected in series or in parallel. The solar cell array 200 is an example of a distributed power source. The distributed power source may be a gas engine, a gas turbine, a micro gas turbine, a fuel cell, a wind power generator, an electric vehicle, or a power storage system.

  The power conditioner 10 converts the DC voltage from the solar cell array 200 into an AC voltage and connects to the system power supply 400. The system power supply 400 may be a single-phase three-wire power supply, for example. The power conditioner 10 includes a positive input terminal 11, a negative input terminal 12, a first output terminal 14, a second output terminal 15, and a ground terminal 16.

  The positive electrode input terminal 11 is connected to the positive electrode side of the solar cell array 200. The negative electrode input terminal 12 is connected to the negative electrode side of the solar cell array 200. The first output terminal 14 is connected to the U phase that is the first phase of the system power supply 400. The second output terminal 15 is connected to the W phase that is the second phase of the system power supply 400. The ground terminal 16 is connected to the O phase that is the neutral phase of the system power supply 400.

  The power conditioner 10 further includes a capacitor C1, a booster circuit 20, a capacitor C2, an inverter 30, a filter circuit 40, an interconnection relay 50, a capacitor C4, a capacitor C5, and a control unit 100.

  One end of the capacitor C1 is electrically connected to the positive electrode of the solar cell array 200. The other end of the capacitor C1 is electrically connected to the negative electrode of the solar cell array 200. Capacitor C <b> 1 is an example of a noise reduction circuit that reduces noise included in the DC voltage output from solar cell array 200. In other words, the capacitor C1 is an example of a smoothing filter that smoothes the DC voltage output from the solar cell array 200.

  The booster circuit 20 boosts and outputs a DC voltage with reduced noise by the capacitor C1. The booster circuit 20 is an example of a non-insulated booster circuit. The booster circuit 20 may be a so-called chopper type switching regulator. The booster circuit 20 includes a coil L1, a switch Tr, and a diode D1.

  One end of the coil L1 is connected to one end of the capacitor C1, and the other end of the coil L1 is connected to the collector of the switch Tr. The switch Tr may be, for example, an insulated gate bipolar transistor (IGBT). The collector of the switch Tr is connected to the anode of the diode D1, and the emitter of the switch Tr is connected to the other end of the capacitor C1.

  The coil L1 accumulates energy based on the electric power from the solar cell array 200 while the switch Tr is on, and releases the accumulated energy while the switch Tr is off. As a result, the booster circuit 20 boosts the DC voltage from the solar cell array 200. The diode D1 rectifies the output from the coil L1. The diode D1 prevents the boosted DC voltage from flowing from the output side of the booster circuit 20 to the input side.

  Capacitor C2 smoothes the DC voltage output from booster circuit 20. In other words, the capacitor C <b> 2 reduces noise included in the DC voltage output from the booster circuit 20.

  The inverter 30 includes a switch. When the switch is turned on / off, the inverter 30 converts the DC voltage output from the booster circuit 20 into an AC voltage and outputs the AC voltage to the system power supply 400 side. The inverter 30 is an example of a DC / AC conversion circuit that converts a DC voltage whose noise has been reduced by the noise reduction circuit into an AC voltage. Inverter 30 links the power from solar cell array 200 with the power from system power supply 400.

  The inverter 30 may be constituted by, for example, a single-phase full-bridge PWM inverter that includes four semiconductor switches that are bridge-connected. Of the four semiconductor switches, one pair of semiconductor switches is connected in series. Of the four semiconductor switches, the other pair of semiconductor switches are connected in series and connected in parallel with the one pair of semiconductor switches.

  The filter circuit 40 reduces noise included in the AC voltage output from the inverter 30. The filter circuit 40 includes a pair of coils L2 and a capacitor C3. One end of each of the pair of coils L <b> 2 is connected to the output end of the inverter 30. The other ends of the pair of coils L2 are connected to one end and the other end of the capacitor C3.

  An interconnection relay 50 is connected between one end of the capacitor C3 and the first output terminal 14 and between the other end of the capacitor C3 and the second output terminal 15. The interconnection relay 50 is an example of a first cutoff circuit that switches between electrically connecting or disconnecting the inverter 30 and the system power supply 400. When the interconnection relay 50 is turned on, the power conditioner 10 and the system power supply 400 are electrically connected. When the interconnection relay 50 is turned off, the power conditioner 10 and the system power supply 400 are electrically disconnected.

  Both ends of one capacitor C4 are connected to the first output terminal 14 and the ground terminal 16, and both ends of the other capacitor C4 are connected to the second output terminal 15 and the ground terminal 16. The ground terminal 16 is grounded via a capacitor C5.

  The power conditioner 10 further includes voltage sensors 61, 63 and 72 and current sensors 62 and 64. The voltage sensor 61 detects a voltage V1 corresponding to a potential difference between both ends of the solar cell array 200. The voltage sensor 63 detects a voltage V2 corresponding to a potential difference between both ends on the output side of the booster circuit 20. The voltage sensor 72 detects a voltage V3 corresponding to the potential difference between the first output terminal 14 and the ground terminal 16, and a voltage V4 corresponding to the potential difference between the second output terminal 15 and the ground terminal 16. The current sensor 62 detects a current I1 output from the solar cell array 200 and flowing to the input side of the booster circuit 20. The current sensor 64 detects the current I2 output from the booster circuit 20.

  The voltage sensor 72 has two differential amplifier circuits that detect the voltage V3 and the voltage V4. One differential amplifier circuit includes a resistor R11, a resistor R12, a resistor R13, a resistor R14, a resistor R15, and an operational amplifier OP1. Another differential amplifier circuit includes a resistor R21, a resistor R22, a resistor R23, a resistor R24, a resistor R25, and an operational amplifier OP2.

  One end of the resistor R11 is electrically connected to the first output terminal 14. That is, one end of the resistor R11 is electrically connected to the U phase that is the first phase of the system power supply 400. The other end of the resistor R11 is connected to the non-inverting input terminal of the operational amplifier OP1. One end of the resistor R13 is connected between the resistor R11 and the non-inverting input terminal of the operational amplifier OP1. The other end of the resistor R13 is grounded. One end of the resistor R12 is electrically connected to the ground terminal 16. That is, one end of the resistor R12 is electrically connected to the neutral phase of the system power supply 400. The other end of the resistor R12 is connected to the inverting input terminal of the operational amplifier OP1. One end of the resistor R14 is connected to the inverting input terminal of the operational amplifier OP1, and the other end of the resistor R14 is connected to the output terminal of the operational amplifier OP1. One end of the resistor R15 is connected to the output terminal of the operational amplifier OP1, and the other end of the resistor R15 is electrically connected to the control unit 100. One differential amplifier circuit configured in this way outputs a voltage V3 corresponding to the potential difference between the potential of the first output terminal 14 and the potential of the ground terminal 16.

  One end of the resistor R21 is electrically connected to the second output terminal 15. That is, one end of the resistor R21 is electrically connected to the W phase that is the second phase of the system power supply 400. The other end of the resistor R21 is connected to the non-inverting input terminal of the operational amplifier OP2. One end of the resistor R23 is connected between the resistor R21 and the non-inverting input terminal of the operational amplifier OP2. The other end of the resistor R23 is grounded. One end of the resistor R22 is electrically connected to the ground terminal 16. That is, one end of the resistor R22 is electrically connected to the neutral phase of the system power supply 400. The other end of the resistor R22 is connected to the inverting input terminal of the operational amplifier OP2. One end of the resistor R24 is connected to the inverting input terminal of the operational amplifier OP2, and the other end of the resistor R24 is connected to the output terminal of the operational amplifier OP2. One end of the resistor R25 is connected to the output terminal of the operational amplifier OP2, and the other end of the resistor R25 is electrically connected to the control unit 100. The other differential amplifier circuit configured as described above outputs a voltage V4 corresponding to the potential difference between the potential of the second output terminal 15 and the potential of the ground terminal 16.

  The control unit 100 includes a microcomputer. Based on the voltage detected by voltage sensors 61, 63, and 72 and the current detected by current sensors 62 and 64 so that maximum power can be obtained from solar cell array 200, controller 100 includes boost circuit 20 and The switching operation of the inverter 30 is controlled.

  Further, the power conditioner 10 is connected to the system power supply 400 via the breaker 300. When the breaker 300 detects a leakage current or a ground fault current, the breaker 300 electrically disconnects the power conditioner 10 and the system power supply 400.

  For example, when the voltage output from the solar cell array 200 reaches a predetermined operating voltage, the power conditioner 10 boosts the DC voltage from the solar cell array 200 by the booster circuit 20. Furthermore, after the DC voltage boosted by the booster circuit 20 is converted into an AC voltage by the inverter 30, the interconnection relay 50 is turned on to connect to the system power supply 400.

  Here, stray capacitance exists between the positive electrode of the solar cell array 200 and the ground point, and between the negative electrode of the solar cell array 200 and the ground point. Therefore, in a state where the interconnection relay 50 is turned off, if there is a potential difference between the negative electrode potential of the solar cell array 200 and the neutral phase potential of the system power supply 400, the interconnection relay 50 is turned on. In response to this, a current loop is formed by the stray capacitance of the solar cell array 200, the ground, the inverter 30, and the booster circuit 20, and a ground fault current flows. When the potential difference generated between the negative electrode potential of the solar cell array 200 and the neutral phase potential of the system power supply 400 is large, the breaker 300 is connected to the solar cell in response to the interconnection relay 50 being turned on. There is a possibility that the ground fault current generated by the stray capacitance of the array 200 is detected and the power conditioner 10 and the system power supply 400 are electrically cut off.

  Therefore, in this embodiment, the potential difference between the potential of the negative electrode of the solar cell array 200 and the potential of the neutral phase of the system power supply 400 is reduced. As a result, the ground fault current decreases, and the breaker 300 detects the ground fault current, thereby preventing the power conditioner 10 and the system power source 400 from being electrically disconnected. That is, the breaker 300 detects a ground fault current to prevent tripping.

  The power conditioner 10 further includes a resistor R0, a bypass relay 70, and a diode D2. The resistor R0 is connected between one end connected to the positive electrode side of the solar cell array 200 among both ends of the capacitor C1 and the ground terminal 16. The resistor R0 is an example of a first resistor circuit connected between the positive electrode of the capacitor C1 and the neutral phase of the system power supply 400.

  The bypass relay 70 is connected between the resistor R0 and the diode D2. The bypass relay 70 electrically connects the positive electrode of the capacitor C1 and the neutral phase of the system power supply 400 via a resistor R0, or electrically connects the positive electrode of the capacitor C1 and the neutral phase of the system power supply 400. It is an example of the 2nd interruption | blocking circuit which switches whether it interrupts | blocks automatically. In the present embodiment, the bypass relay 70 is described as an example of an electromagnetic relay that is a contact relay, but the bypass relay 70 may be a semiconductor relay that is a contactless relay. Alternatively, the bypass relay 70 may be a hybrid relay that combines a contact relay and a contactless relay.

  The anode of the diode D2 is connected to the bypass relay 70. The cathode of the diode D <b> 2 is connected to the ground terminal 16. The diode D2 is an example of a backflow prevention circuit that prevents a current from flowing from the neutral phase side of the system power supply 400 to the positive electrode side of the capacitor C1.

  When the bypass relay 70 is turned on, a current loop is formed by the resistor R0, the bypass relay 70, the diode D2, the voltage sensor 72, the ground, and the stray capacitance of the solar cell array 200. The current that flows through the resistor R0, the bypass relay 70, and the diode D2 flows to the ground through the resistor R12, the operational amplifier OP1, and the resistor R13 included in the voltage sensor 72. In addition, the current flowing through the resistor R0, the bypass relay 70, and the diode D2 flows to the ground through the resistor R22, the operational amplifier OP2, and the resistor R23 included in the voltage sensor 72. That is, the second resistor R12, the resistor R13, the resistor R22, and the resistor R23 included in each differential amplifier circuit constituting the voltage sensor 72 are connected between the neutral phase of the system power supply 400 and the ground point. It is an example of a resistance circuit.

  Here, when the resistance value of the resistor R0 is equal to the combined resistance value of the resistor R12, the resistor R13, the resistor R22, and the resistor R23, when the bypass relay 70 is turned on with the interconnection relay 50 turned off, The potential of 16 is half the potential of the positive electrode on the output side of the booster circuit 20. Thereby, the potential difference between the negative electrode potential of the solar cell array 200 and the neutral phase potential of the system power supply 400 is reduced. Therefore, when the interconnection relay 50 is turned on after the bypass relay 70 is turned on, the ground fault current is reduced. Therefore, the breaker 300 can be prevented from tripping by detecting the ground fault current.

  Further, by turning off the bypass relay 70 after the interconnection relay 50 is turned on, a current flows through the resistor R0 while the power conditioner 10 is connected to the system power supply 400, and power is wasted. Can be prevented. In the state where the bypass relay 70 is turned on, even when the interconnection relay 50 is turned off, a current flows to the neutral phase side of the system power supply 400 via the resistor R0. In this case, the operator who maintains the power conditioner 10 cannot perform work safely. Therefore, by providing the bypass relay 70 that can electrically disconnect between the positive electrode of the capacitor C1 and the neutral phase of the system power supply 400, it is possible to ensure the safety of the operator who maintains the power conditioner 10.

  Furthermore, by providing the diode D2, it is possible to prevent a current from flowing from the neutral phase side of the system power supply 400 to the positive electrode side of the capacitor C1. When the diode D <b> 2 is not provided, if the neutral phase potential is higher than the positive electrode potential of the solar cell array 200, the voltage detected by the voltage sensor 61 is the voltage output from the solar cell array 200 to be originally detected. It will be higher. Therefore, by providing the diode D2, it is possible to prevent a current from flowing from the neutral phase side of the power supply 400 to the positive side of the capacitor C1, and therefore it is possible to prevent the voltage sensor 61 from detecting a voltage that should be detected originally. . Therefore, it is possible to prevent the control unit 100 from erroneously controlling the booster circuit 20 based on the voltage detected by the voltage sensor 61.

  When the diode D2 or the bypass relay 70 is not provided, the voltage sensor 61 detects a voltage that is ½ of the output voltage of the booster circuit 20 when the potential of the neutral phase is higher than the potential of the positive electrode of the solar cell array 200. It will be. In this case, even if the voltage output from the solar cell array 200 decreases, the control unit 100 continues the boosting operation of the boosting circuit 20. Therefore, the control unit 100 cannot stop the operation of the power conditioner 10. When the diode D2 or the bypass relay 70 is not provided, even if the voltage output from the solar cell array 200 decreases, the operation of the power conditioner 10 cannot be stopped normally, and power from the system power supply 400 is wasted. There is a possibility that. Therefore, by providing the diode D2 or the bypass relay 70, when the voltage output from the solar cell array 200 decreases, the operation of the power conditioner 10 can be stopped normally. As a result, it is possible to prevent the power from the system power supply 400 from being wasted.

  FIG. 2 is a diagram for explaining on and off timings of the bypass relay 70 and the interconnection relay 50.

  When the voltage output from solar cell array 200 reaches a predetermined first voltage, control unit 100 controls boost circuit 20 to start a boost operation. When the voltage V2 that is the output voltage of the booster circuit 20 reaches a predetermined second voltage by the boosting operation by the booster circuit 20, the interconnection relay 50 is controlled to electrically connect the inverter 30 and the system power supply 400. Before switching from the disconnected state to the connected state, the bypass relay 70 is controlled to switch from the electrically disconnected state between the positive electrode of the capacitor C1 and the neutral phase of the system power supply 400 to the connected state.

  Further, the control unit 100 controls the bypass relay 70 to switch from the state where the positive electrode of the capacitor C1 and the neutral phase of the system power supply 400 are electrically disconnected to the connected state, and then for a predetermined period. After t1 (for example, 0.2 seconds) elapses, the interconnection relay 50 is controlled to switch from the state where the inverter 30 and the system power supply 400 are electrically disconnected to the connected state.

  Next, the control unit 100 controls the interconnection relay 50 to switch from the state in which the inverter 30 and the system power supply 400 are electrically disconnected to the connected state, and then the predetermined period t2 (for example, 2 After the elapse of seconds or 3 seconds), the bypass relay 70 is controlled to switch from the state in which the positive electrode of the capacitor C1 and the neutral phase of the system power source 400 are electrically connected to the state in which the capacitor C1 is disconnected. The control unit 100 controls the bypass relay 70 to switch from the state in which the positive electrode of the capacitor C1 and the neutral phase of the system power supply 400 are electrically disconnected to the connected state, and then is determined in advance longer than the period t1. After the time period t3 has elapsed, the bypass relay 70 may be controlled to switch from the state in which the positive electrode of the capacitor C1 and the neutral phase of the system power supply 400 are electrically connected to the state in which they are disconnected.

  Here, if the bypass relay 70 is turned off immediately after the interconnection relay 50 is turned on, the bypass relay 70 may be turned off in a state where the operation by the inverter 30 is not stable. In this case, the potential difference between the negative electrode potential of the solar cell array 200 and the neutral phase potential of the system power supply 400 is still large, and the breaker 300 may trip due to the ground fault current. Therefore, the control unit 100 suspends turning off the bypass relay 70 after turning on the interconnection relay 50 until the operation of the inverter 30 is stabilized. Thereby, it can prevent more reliably that the breaker 300 trips by a ground fault electric current.

  In order to prevent a ground fault current from flowing in response to the switching relay 50 switching from off to on and tripping the breaker 300 due to the ground fault current, two resistors are provided at both ends of the capacitor C2, It is conceivable to connect the midpoint between the two resistors to the neutral point of the AC power supply. However, according to such a configuration, noise generated by the switching operation of the switch Tr of the booster circuit 20 or the like may flow through the electric wire connecting the neutral point and the neutral point. The noise may adversely affect external devices. Further, in order to suppress the generation of noise, it is necessary to provide a noise filter on the electric wire connecting the middle point and the neutral point.

  On the other hand, according to the power conditioner 10 according to the present embodiment, the resistor R0 is connected between the positive electrode of the capacitor C1 and the neutral phase of the system power supply 400. The bypass circuit configured by the resistor R0, the bypass relay 70, and the diode D2 bypasses the booster circuit 20 and the inverter 30, and electrically connects the positive input terminal 11 and the ground terminal 16. Thereby, it is possible to prevent the noise generated by the switching operation by the booster circuit 20 from flowing through the bypass circuit. Therefore, it is not necessary to provide a noise filter in the bypass circuit.

  As mentioned above, although this invention was demonstrated using embodiment, the technical scope of this invention is not limited to the range as described in the said embodiment. It will be apparent to those skilled in the art that various modifications or improvements can be added to the above-described embodiment. It is apparent from the scope of the claims that the embodiments added with such changes or improvements can be included in the technical scope of the present invention.

  The order of execution of each process such as operations, procedures, steps, and stages in the apparatus, system, program, and method shown in the claims, the description, and the drawings is particularly “before” or “prior to”. It should be noted that the output can be realized in any order unless the output of the previous process is used in the subsequent process. Regarding the operation flow in the claims, the description, and the drawings, even if it is described using “first”, “next”, etc. for convenience, it means that it is essential to carry out in this order. It is not a thing.

DESCRIPTION OF SYMBOLS 10 Power conditioner 11 Positive input terminal 12 Negative input terminal 14 1st output terminal 15 2nd output terminal 16 Grounding terminal 20 Booster circuit 30 Inverter 40 Filter circuit 50 Interconnection relay 61,63,72 Voltage sensor 62,64 Current sensor 70 Bypass relay 100 Control unit 200 Solar cell array 300 Breaker 400 System power supply C1, C2, C3, C4, C5 Capacitor D1, D2 Diode L1, L2 Coil OP1, OP2 Operational amplifier R0 Resistor R11, R12, R13, R14, R15 Resistor R21, R22, R23, R24, R25 resistance

Claims (8)

A power conditioner that converts a DC voltage from a DC power source into an AC voltage and links to a system power source,
A noise reduction circuit for reducing noise included in a DC voltage input from the DC power supply;
A DC / AC conversion circuit that converts a DC voltage, in which noise is reduced by the noise reduction circuit, into an AC voltage;
A first cutoff circuit that switches between electrical connection or cutoff between the DC-AC conversion circuit and the system power supply;
A first resistance circuit having one end connected between the positive electrode of the DC power supply and the positive electrode of the noise reduction circuit, and the other end connected to a neutral phase of the system power supply;
A power conditioner comprising: a second resistance circuit connected between the neutral phase and a ground point.   The positive electrode of the noise reduction circuit and the neutral phase are electrically connected via the first resistance circuit, or the positive electrode of the noise reduction circuit and the neutral phase are electrically disconnected. The power conditioner according to claim 1, further comprising a second cutoff circuit that switches between the two.   The noise reduction circuit is controlled by controlling the second cutoff circuit before switching from the state in which the DC / AC converter circuit and the system power supply are electrically disconnected to the connected state by controlling the first cutoff circuit. After switching from a state in which the positive electrode and the neutral phase are electrically cut off to a connected state, the first cut-off circuit is controlled to electrically connect the DC / AC converter circuit and the system power supply. The power conditioner according to claim 2, further comprising a control unit that switches from a disconnected state to a connected state.   The control unit controls the second cutoff circuit after controlling the first cutoff circuit to switch from the state where the DC / AC converter circuit and the system power supply are electrically disconnected to the connected state. The power conditioner according to claim 3, wherein the power conditioner is switched from a state in which the positive electrode of the noise reduction circuit and the neutral phase are electrically connected to a state in which the noise is reduced.   The power conditioner according to any one of claims 1 to 4, further comprising a backflow prevention circuit that prevents a current from flowing from the neutral phase side to the positive electrode side of the noise reduction circuit. A differential amplifier circuit for detecting a potential difference between the first phase of the system power supply and the neutral phase and a potential difference between the second phase of the system power supply and the neutral phase;
The power conditioner according to any one of claims 1 to 5, wherein the second resistance circuit is a resistance circuit included in the differential amplifier circuit.   The power according to any one of claims 1 to 6, further comprising a non-insulating booster circuit that boosts a DC voltage whose noise is reduced by the noise reduction circuit and outputs the boosted voltage to the DC-AC converter circuit. Conditioner. A power conditioner according to any one of claims 1 to 7,
A distributed power supply system comprising a distributed power supply as the DC power supply.

Images