JP6080210B2 - Power converter - Google Patents

Description

  The present invention relates to a power conversion device.

  FIG. 15 shows a circuit diagram of a power system including a conventional power converter (see, for example, Patent Document 1). Under the control of the control unit 920, the inverter circuit 910 that converts direct current to alternating current performs a single-phase two-wire output during a linked operation, and performs a single-phase three-wire output during a self-sustained operation (when a power failure occurs). That is, during the interconnection operation, the interconnection switch 931 is closed, and a single-phase AC voltage (for example, an AC voltage of 200 V) is output to the power system 960 via the U-phase and W-phase wirings. On the other hand, in the independent operation, the interconnection switch 931 is opened to disconnect the inverter circuit 910 from the power system 960, while the independent switch 932 is closed, and the independent load unit is connected via the U-phase, W-phase, and N-phase wirings. Two AC voltages having opposite phases to each other (for example, an AC voltage of 100 V) are output to 980.

  Reactors L1, L2, and L3 are inserted between the inverter circuit 910 and the U-phase, W-phase, and N-phase wirings, respectively. A capacitor C1 is connected between the U-phase and N-phase wirings and a capacitor C2 is connected between the W-phase and N-phase wirings for the purpose of voltage smoothing during the self-sustaining operation. In addition, a capacitor C3 is connected between the U-phase and W-phase wirings for the purpose of voltage smoothing during interconnected operation.

JP 2003-18859 A

  Connection of the capacitors C1 and C2 during the independent operation and connection of the capacitor C3 during the interconnection operation are necessary. However, when the capacitor C3 is connected during the autonomous operation, the following behavior may occur. is there.

In self-sustained operation, the voltage V _{C1 to} V _C3 of the capacitors C1 to _C3 is almost stable, and the load connected between the W phase and the N phase is turned on. Consider the case where the current F1 flows (see FIG. 16). In this case, the voltage V _C2 sharply decreases due to the inrush current F1, and in response to this decrease, the current F2 is supplied from the capacitor C3 to the series circuit of the capacitors C1 and C2 (see FIG. 16). The supply of the current F2 has no problem for the voltage V _{C2 of the} capacitor C2 in which the voltage drop has occurred. However, the supply of the current F2 transiently increases the voltage V _{C1 of the} capacitor C1 in which the voltage drop based on the inrush current F1 does not occur. In some cases, the instantaneous value of the voltage V _C1 is a general value for an AC of 100 V. The upper limit value “107 × √2” of the normal voltage range may be exceeded or a predetermined overvoltage protection level (for example, 170 V) may be reached. When the instantaneous value of the voltage V _C1 reaches the overvoltage protection level, the output of the inverter circuit 910 may stop to protect the load and the circuit. An abnormal increase (overvoltage) of the voltage V _C1 during the self-sustained operation due to the presence of the capacitor C3 should be avoided.

  Then, an object of this invention is to provide the power converter device which can suppress the influence of a capacitor | condenser required at the time of a grid operation at the time of a self-sustained operation.

  The power conversion device according to the present invention includes an inverter circuit that converts direct current to alternating current, a first line, a second line, and a neutral line that are provided on the output side of the inverter circuit, and the first line and the second line. An interconnection operation for connecting the power system to output alternating current from the inverter circuit to the power system via the first line and the second line, and disconnecting the first line and the second line from the power system and An operation switching unit that switches between independent operation for outputting different alternating currents from the inverter circuit between the first line and the neutral line and between the second line and the neutral line, and the first line in the interconnection operation. And connecting a capacitor between the first line and the second line, while disconnecting the connection between the first line and the second line by the capacitor in the self-sustained operation, and connecting the second line and the first line and the neutral line. Connect a separate capacitor between the neutral wires. And capacitors connection switching unit, characterized by comprising a.

  ADVANTAGE OF THE INVENTION According to this invention, it is possible to provide the power converter device which can suppress the influence of a capacitor | condenser required at the time of a grid operation at the time of a self-sustained operation.

1 is a circuit diagram of a power system including a power conversion device according to a first embodiment of the present invention. FIG. 2 is a partial circuit diagram of FIG. It is a figure which concerns on 1st Embodiment of this invention and shows the connection relation of the capacitor | condenser at the time of interconnection operation. It is a figure which concerns on 1st Embodiment of this invention and shows the connection relation of the capacitor | condenser at the time of a self-supporting operation. It is a circuit diagram of the electric power system containing the power converter device which concerns on 2nd Embodiment of this invention. It is a figure which shows the modification of the circuit of FIG. It is a circuit diagram of the electric power system containing the power converter device which concerns on 3rd Embodiment of this invention. It is a figure which shows the modification of the circuit of FIG. It is a figure which shows the modification of the circuit of FIG. It is a circuit diagram of the electric power system containing the power converter device which concerns on 4th Embodiment of this invention. It is a figure which shows the modification of the circuit of FIG. It is a circuit diagram of the electric power system containing the power converter device which concerns on 5th Embodiment of this invention. It is a circuit diagram of the electric power system containing the power converter device which concerns on 6th Embodiment of this invention. It is a partial circuit diagram of the electric power system concerning a 7th embodiment of the present invention. It is a circuit diagram of the electric power system containing the conventional power converter device. It is a figure for demonstrating the behavior of the circuit of FIG.

  Hereinafter, an example of an embodiment of the present invention will be specifically described with reference to the drawings. In each of the drawings to be referred to, the same part is denoted by the same reference numeral, and redundant description regarding the same part is omitted in principle. In this specification, for simplification of description, a symbol or reference that refers to information, signal, physical quantity, state quantity, member, or the like is written to indicate information, signal, physical quantity, state quantity or Names of members and the like may be omitted or abbreviated.

<First Embodiment>
A first embodiment of the present invention will be described. FIG. 1 is a circuit diagram of a power system including a power conversion device (inverter device) 1 according to the first embodiment. The power conversion device 1 includes an inverter circuit 10, a control unit 20, an interconnection switch 31, a self-supporting switch 32, a power failure detection unit 33, reactors L1 and L2, a capacitor connection switching unit 50, and the like. Wiring connected in a predetermined relationship is provided. The circuit configuration of the capacitor connection switching unit 50 will be described later. A DC power source 2 is connected to the input side of the inverter circuit 10 and the power system 60 and the system load unit 70 are connected to the power converter 1 via the interconnection switch 31 on the output side of the inverter circuit 10 and are independent. A self-supporting load unit 80 is connected via the switch 32.

  The power converter 1 includes a U-phase wiring U1, an N-phase wiring (neutral line) N1, and a W-phase wiring W1 provided between the inverter circuit 10 and the switches 31 and 32. It may be considered that part or all of the wirings U2 and W2 between the interconnection switch 31 and the power system 60 are also included in the power converter 1. It may be considered that part or all of the wirings U3, N3, and W3 between the self-standing switch 32 and the self-supporting load unit 80 are also included in the power conversion device 1.

The DC power source 2 outputs a DC voltage V _DC between the wirings 3 and 4 with reference to the potential of the wiring 3. For example, the DC power source 2 is composed of a storage battery such as a lithium ion battery or a nickel metal hydride battery, and outputs the output voltage of the storage battery as a DC voltage V _DC . Alternatively, for example, the DC power source 2 performs power generation based on natural energy (solar light, hydropower, wind power, geothermal heat, etc.) and outputs a DC voltage obtained by the power generation as a DC voltage V _DC . The DC power source 2 may output the DC voltage V _DC using any other energy source.

  The inverter circuit 10 includes legs LG0, LG1, and LG2, and outputs AC power obtained by converting DC power from the DC power source 2 into AC power.

Each of the legs LG0 to LG2 is a series circuit (series connection circuit) of an upper arm and a lower arm, and a DC voltage V _DC is applied to each of the legs LG0 to LG2. In each leg, a higher potential is applied to the upper arm than to the lower arm. In each leg, the upper arm and the lower arm are formed of any kind of switching element. Specifically, the leg LG0 is formed by the IGBTs 41 and 42, the leg LG1 is formed by the IGBTs 43 and 44, and the leg LG2 is formed by the IGBTs 45 and 46. Each of the IGBTs 41 to 46 is an N-channel insulated gate bipolar transistor (IGBT). The IGBTs 41, 43 and 45 correspond to the upper arms in the legs LG0, LG1 and LG2, and the IGBTs 42, 44 and 46 correspond to the lower arms in the legs LG0, LG1 and LG2. Below, IGBT41-46 is also only called an arm. In each of the IGBTs 41 to 46, a diode whose forward direction is from the emitter to the collector is connected in parallel to the IGBT.

  The collectors of the IGBTs 41, 43 and 45 are commonly connected to the wiring 4 connected to the positive output terminal of the DC power supply 2, and the emitters of the IGBTs 42, 44 and 46 are the wirings connected to the negative output terminal of the DC power supply 2. 3 is commonly connected. The emitter of the IGBT 43 and the collector of the IGBT 44 are connected at a connection point 48, and the connection point 48 is connected to the wiring U1 via the reactor L1. The emitter of the IGBT 45 and the collector of the IGBT 46 are connected at a connection point 49, and the connection point 49 is connected to the wiring W1 via the reactor L2. The emitter of the IGBT 41 and the collector of the IGBT 42 are connected at a connection point 47, and the connection point 47 is connected in series to the wiring N1. However, as shown in FIG. 2, the connection point 47 may be connected to the wiring N1 via the reactor L0.

  The interconnection switch 31 includes a switch 31U interposed in series between the wirings U1 and U2 and a switch 31W interposed in series between the wirings W1 and W2. The interconnection switch 31 takes a closed state in which the interconnection switch 31 is closed or an open state in which the interconnection switch 31 is open. When the interconnection switch 31 is closed, the switches 31U and 31W are closed, the wirings U1 and U2 are connected to each other, and the wirings W1 and W2 are connected to each other. When the interconnection switch 31 is open, the switches 31U and 31W are opened, and the wirings U1 and U2 are cut off and the wirings W1 and W2 are cut off. The wirings U2 and W2 are connected to the power system 60.

  The power system 60 includes power sources 61 and 62 that generate and output a commercial AC voltage with reference to the potential of the wiring N2. The wiring N2 has a potential (ground potential) that is exactly between the potential of the wiring U2 and the potential of the wiring W2. The commercial AC voltages output from the power sources 61 and 62 are the same in amplitude, but are 180 ° out of phase with each other. When a power failure has not occurred, commercial AC voltage from the power source 61 is applied between the wirings U2 and N2, and commercial AC voltage from the power source 62 is applied between the wirings W2 and N2, and the wirings U2 and W2 are applied. In the meantime, a composite voltage of these commercial AC voltages is applied. The system load unit 70 is connected between the wirings U2 and N2 and driven based on the AC voltage between the wirings U2 and N2. The system load unit 70 is connected between the wirings W2 and N2 and driven based on the AC voltage between the wirings W2 and N2. And a load 70UW connected between the wirings U2 and W2 and driven based on an AC voltage between the wirings U2 and W2. However, any number of loads 70U, 70W, and 70UW may be connected, or none may be connected. Each load is an industrial machine, a home appliance, or the like.

  The self-standing switch 32 includes a switch 32U interposed in series between the wires U1 and U3, a switch 32W interposed in series between the wires W1 and W3, and a switch 32N interposed in series between the wires N1 and N3. Consists of. The wirings U1, W1, and N1 are connected to the switches 32U, 32W, and 32N, respectively. The self-supporting switch 32 takes a closed state in which the self-supporting switch 32 is closed or an open state in which the self-supporting switch 32 is open. When the self-standing switch 32 is closed, the switches 32U, 32W, and 32N are closed, the wirings U1 and U3 are connected to each other, the wirings W1 and W3 are connected to each other, and the wirings N1 and N3 are connected to each other. When the self-standing switch 32 is open, the switches 32U, 32W and 32N are opened, the wirings U1 and U3 are cut off, the wirings W1 and W3 are cut off, and the wirings N1 and N3 are cut off. The self-supporting load unit 80 is connected between the wirings U3 and N3 and driven based on the AC voltage between the wirings U3 and N3, and is connected between the wirings W3 and N3 and driven based on the AC voltage between the wirings W3 and N3. And a load 80UW connected between the wirings U3 and W3 and driven based on an AC voltage between the wirings U3 and W3. However, any number of loads 80U, 80W, and 80UW may be connected, or none may be connected. Each load is an industrial machine, a home appliance, or the like.

  The power failure detection unit 33 detects whether or not a power failure has occurred in the power system 60, and outputs a power failure detection signal when a power failure occurs (that is, when power supply from the power system 60 is stopped). The power failure detection signal is not output at the time of occurrence). For example, the power failure detection unit 33 is based on the voltage of the wirings U2 and W2 (that is, the U-phase and W-phase voltages of the power system 60) or the voltage between the wirings U2 and W2 viewed from a predetermined reference potential, or their Based on the frequency of the voltage or the rate of frequency change, the presence or absence of a power failure in the power system 60 is detected by a known method.

  The control unit 20 includes a microcomputer or the like, and performs state control of the switches 31 and 32 and on / off control of each arm in the inverter circuit 10 based on the output of the power failure detection unit 33 and the like. The on / off control of each arm is realized by controlling the gate potential of each arm.

  When the power failure has not occurred, that is, when the power failure detection signal is not output from the power failure detection unit 33, the control unit 20 performs the interconnection operation, and when the power failure has occurred, that is, the power failure detection unit 33. When a power failure detection signal is output from, autonomous operation is performed. However, even when the power failure detection signal is not output from the power failure detection unit 33, the control unit 20 may perform the autonomous operation when a predetermined instruction is input from the outside.

In the interconnection operation, the control unit 20 closes the interconnection switch 31 and opens the self-standing switch 32 to drive the legs LG1 and LG2 as inverters. That is, the control unit 20 controls each arm of the legs LG1 and LG2 so that two AC voltages having a phase difference of 180 ° with respect to the intermediate potential between the wirings 3 and 4 are generated in the wirings U1 and W1. Perform on / off control. At this time, the AC voltage V _UW between the wirings U1 and W1 based on the output of the inverter circuit 10 and the AC voltage between the wirings U2 and W2 based on the power supplied from the power system 60 match each other in terms of effective value and phase. Thus, the control unit 20 performs on / off control of each arm of the legs LG1 and LG2. As a result, the output power of the DC power source 2 can be supplied to the power system 60. The supply of power to the power system 60 includes the supply of power to the system load unit 70. When the power system is configured as shown in FIG. 14 described later, the power supplied to the power system 60 based on the output power of the DC power supply 2 may be supplied to the self-supporting load unit 80. In the interconnection operation, the effective value of the AC voltage between the wirings U1 and W1 is, for example, 200V. There is no need to drive the leg LG0 in the interconnected operation.

  In the independent operation, the control unit 20 opens the interconnection switch 31 and closes the independent switch 32 to drive the legs LG0, LG1, and LG2 as inverters. That is, the control unit 20 turns on / off each arm of the legs LG0, LG1, and LG2 so that two AC voltages having a phase difference of 180 ° with respect to the potential of the wiring N1 are generated in the wirings U1 and W1. Take control.

Specifically, for example, in the independent operation, the arms 41 and 42 are turned on alternately and uniformly, and as a result, the DC potential between the wiring 3 and N1 becomes V _DC / 2. A voltage sensor (not shown) for detecting the voltage V _{UN of the} wiring U1 and the voltage V _{WN of the} wiring W1 with the potential of the wiring N1 as a reference can be provided in the power converter 1. Then, the control unit 20, so that the voltage V _UN and V _WN with and desired amplitude has a phase difference of 180 ° from one another, may be performed feedback control based on the detection value of the voltage sensor leg LG1 and LG2 . In the independent operation, the effective value of each of the AC voltages _VUN and _VWN is, for example, 100V. In the autonomous operation, the autonomous load unit 80 receives the output AC voltage of the inverter circuit 10 via the autonomous switch 32. In the independent operation, the alternating voltage V _UN can be supplied to the load 80U in the independent load unit 80, the alternating voltage V _WN can be supplied to the load 80W in the independent load unit 80, and the independent load unit 80 to the load 80UW in can be supplied to synthesis AC voltage of the AC voltage V _UN and V _WN (e.g. 200V). The load 80UW is, for example, an air conditioner.

  As described above, the power conversion device 1 connects the wirings U1 and W1 to the power system 60 during the interconnection operation, and exchanges power (power, voltage, current) from the inverter circuit 10 to the power system 60 via the wirings U1 and W1. Is output (ie, single-phase two-wire output is performed). During the self-sustaining operation, the power conversion device 1 disconnects the wirings U1 and W1 from the power system 60 by opening the interconnection switch 31, and separate alternating currents from the inverter circuit 10 between the wirings U1 and N1 and between the wirings W1 and N1. (Power, voltage, current) is output (that is, single-phase three-wire output is performed).

The capacitor connection switching unit 50 will be described with reference to FIGS. 3 and 4. FIG. 3 is a diagram illustrating a connection state of the capacitors during the interconnection operation. FIG. 4 is a diagram illustrating a connection state of the capacitors during the self-sustaining operation. The capacitor connection switching unit 50 includes two or more capacitors and one or more switches. By controlling the switches, the capacitor C _UW is connected between the wirings U1 and W1 in the interconnection operation (see FIG. 3). . On the other hand, in the self-sustaining operation, the capacitor connection switching unit 50 cuts off the connection between the wirings U1 and W1 by the capacitor _CUW through the control of the switch, and separate capacitors C _UN between the wirings U1 and N1 and between the wirings W1 and N1. And C _WN are connected (see FIG. 4). Some circuit configurations for realizing this will be exemplified in the following embodiments. However, as long as the function of the capacitor connection switching unit 50 described herein is realized, the number of capacitors and switches in the capacitor connection switching unit 50 and those The connection relationship of is arbitrary. The connection of the capacitor C _UN between the wirings U1 and N1 and the connection of the capacitor C _WN between the wirings W1 and N1 may be maintained during the interconnection operation.

In the interconnection operation, the reactors L1 and L2 and the capacitor C _UW smooth the potential difference between the connection points 48 and 49 to obtain the AC voltage V _UW or the AC current I _UW having the quality required for the interconnection. An interconnection filter circuit is formed. The alternating current I _UW is a current that flows through the wirings U1 and W1 based on the alternating voltage V _UW . This interconnection filter circuit also helps to suppress the influence of noise. In the self-sustained operation, the reactor L1 and the capacitor _CUN form a filter circuit for smoothing the voltage at the connection point 48 based on the potential of the wiring N1 to obtain the U-phase AC voltage _VUN , and the reactor L2 and the capacitor C _WN forms a filter circuit for smoothing the voltage at the connection point 49 with the potential of the wiring N1 as a reference to obtain a W-phase AC voltage V _WN . These filter circuits also contribute to suppressing the influence of noise. The capacitors _CUN and _CWN can be provided between the self-supporting switch 32 and the self-supporting load unit 80 (see FIG. 10 described later). In addition, a common capacitor can also function as the capacitor C _UW and the capacitor C _UN or C _WN (see FIG. 12 described later).

In order to smooth the voltage and prevent noise, it is necessary to connect the capacitors C _UW during the interconnection operation and also to connect the capacitors C _UN and C _WN during the independent operation. On the other hand, when the capacitor C _UW is connected during the self-sustained operation, as described above with reference to FIG. 16, the capacitor C _UN or C _WN is generated when a surge current (inrush current) to the self-supporting load unit 80 occurs. May rise abnormally and become overvoltage.

In order to avoid this, in the power converter 1, the connection of the capacitor C _UW between the wirings U1 and W1 during the interconnection operation is canceled during the autonomous operation (the capacitor C between the wirings U1 and W1 during the autonomous operation). _UW is not connected). As a result, the voltage fluctuation of the second phase (for example, U phase) induced by the surge current of the first phase (for example, W phase) during the independent operation is suppressed. The voltage fluctuation can include an overvoltage. For this reason, it is possible to prevent the operation stop of the power conversion device 1 itself due to the activation of the second-phase overvoltage protection, the breakage of parts, the operation stop or the damage of the home appliances as the second-phase load, and the like. There is expected.

  The above-described feedback control during the self-sustained operation acts to suppress voltage fluctuation of the second phase (for example, U phase) induced by the surge current of the first phase (for example, W phase). Since control is performed after recognizing the voltage fluctuation of the second phase, the control inevitably delays. According to the power converter 1, the undesirable second-phase voltage fluctuation (overvoltage, etc.) is fundamentally solved.

Second Embodiment
A second embodiment of the present invention will be described. A second embodiment of the present invention will be described. The second embodiment and the third to seventh embodiments described later are embodiments based on the first embodiment, and the matters not particularly described in the second to seventh embodiments are not particularly described and contradictory. As long as there is no, description of 1st Embodiment is applied also to 2nd-7th embodiment.

  FIG. 5 is a circuit diagram of a power system including the power conversion device 1a according to the second embodiment. The power conversion device 1a and the capacitor connection switching unit 50a are examples of the power conversion device 1 and the capacitor connection switching unit 50 of FIG. The capacitor connection switching unit 50a includes capacitors C1 to C3 and a switch 101.

  In the power converter 1a, the connection point 48 is connected to one end of the reactor L1, and the other end of the reactor L1 is commonly connected to one end of the capacitor C1 and one end of the switch 101. A wire that commonly connects the other end of the reactor L1, one end of the capacitor C1, and one end of the switch 101 is a wire U1. The other end of the capacitor C1 is connected to the wiring N1, and the other end of the switch 101 is connected to one end of the capacitor C3 and to the switch 31U. That is, in the power conversion device 1a, the wiring U1 is connected to the switch 31U via the switch 101. The other end of the capacitor C3 is connected to the wiring W1. The connection point 49 is connected to one end of the reactor L2, and the other end of the reactor L2 is connected to the wiring W1. One end and the other end of the capacitor C2 are connected to the wirings W1 and N1, respectively. The wirings U1, N1, and W1 are connected to the switches 32U, 32N, and 32W, respectively. In FIG. 5, only the wiring between the reactor L1 and the switch 101 is shown as the wiring U1 in order to prevent the drawing from being complicated, but the wiring coupled thereto (for example, the reactor L1 and the switch 101). Wiring connecting the connection point between them and the switch 32U) is also included in the wiring U1 (the same applies to FIG. 8 described later).

  Thus, in the power conversion device 1a, the capacitor C1 is always connected between the wirings U1 and N1, and the capacitor C2 is always connected between the wirings W1 and N1, while the capacitor C3 is connected via the switch 101. Connected to U1. In other words, a series circuit of the switch 101 and the capacitor C3 is interposed in series between the wirings U1 and W1.

The capacitor connection switching unit 50a connects the capacitor C3 between the wirings U1 and W1 by turning on the switch 101 during the interconnection operation, while turning off the switch 101 during the independent operation. The connection between the wirings U1 and W1 by the capacitor C3 is cut off. Thereby, the operation and effect described in the first embodiment are realized. Capacitors C1, C2, and C3 function as capacitors C _UN , C _WN , and C _UW shown in FIG. 3 or FIG. 4, respectively (the same applies to second to fourth embodiments described later). However, during the interconnection operation, the combined capacity “((C1 × C2) / (C1 + C2)) + C3” of the capacitors C1, C2 and C3 connected in the relationship shown in FIG. 5 functions as the capacity of the capacitor C _UW. Become.

  As a matter of course, turning on the switch 101 means connecting between one end and the other end of the switch 101, and turning off the switch 101 means closing between the one end and the other end of the switch 101. This also applies to the other switches described later. The on / off of the switch 101 may be controlled by the control unit 20 (the same applies to other switches described later). The switch 101 is a bidirectional switch composed of a semiconductor switching element such as a triac, a relay, or a breaker (the same applies to other switches described later). The capacitances of the capacitors C1, C2, and C3 are arbitrary (the same applies to other embodiments described later). For example, the capacitance of each of the capacitors C1 and C2 is about 10 μF (microfarad), and the capacitance of the capacitor C3 is about 5 μF.

  Further, the power conversion device 1a and the capacitor connection switching unit 50a in FIG. 5 may be modified into the power conversion device 1a 'and the capacitor connection switching unit 50a' in FIG. In the power conversion device 1a ′, the wiring U1 is directly connected to the switch 31U without going through the switch 101, and one end of the switch 101 is commonly connected to the reactor L1, the capacitor C1, and the switch 31U through the wiring U1. The other end of the switch 101 is connected to one end of the capacitor C3, and the other end of the capacitor C3 is connected to the wiring W1. In other respects, the power converters 1a and 1a 'are the same. Also in the power conversion device 1a ', as in the power conversion device 1a, a series circuit of the switch 101 and the capacitor C3 is interposed in series between the wirings U1 and W1.

<Third Embodiment>
A third embodiment of the present invention will be described. FIG. 7 is a circuit diagram of a power system including the power conversion device 1b according to the third embodiment. The power conversion device 1b and the capacitor connection switching unit 50b are examples of the power conversion device 1 and the capacitor connection switching unit 50 of FIG. The capacitor connection switching unit 50b includes capacitors C1 to C3 and switches 111 to 113.

  In the power converter 1b, the connection point 48 is connected to one end of the reactor L1, the other end of the reactor L1 is connected to the wiring U1, and the wiring U1 is connected to the switches 31U and 32U and the switch 113 and 111 is commonly connected to one end of each. The other ends of the switches 113 and 111 are connected to one end of the capacitor C3 and one end of the capacitor C1, respectively. The other end of the capacitor C3 and the other end of the capacitor C1 are connected to the wirings W1 and N1, respectively. In the power converter 1b, the connection point 49 is connected to one end of the reactor L2, the other end of the reactor L2 is connected to the wiring W1, and the wiring W1 is connected to the switches 31W and 32W and the switch 112 Connected to one end. The other end of the switch 112 is connected to one end of the capacitor C2, and the other end of the capacitor C2 is connected to the wiring N1. The wiring N1 is connected to the switch 32N.

  Thus, in the power conversion device 1b, the capacitor C1 is connected between the wirings U1 and N1 via the switch 111, the capacitor C2 is connected between the wirings W1 and N1 via the switch 112, and the capacitor C3. Is connected between the wirings U1 and W1 via the switch 113. In other words, a series circuit of the switch 111 and the capacitor C1 is interposed in series between the wirings U1 and N1, a series circuit of the switch 112 and the capacitor C2 is interposed in series between the wirings W1 and N1, and the switch 113 and the capacitor C3 A series circuit is interposed in series between the wirings U1 and W1.

  The capacitor connection switching unit 50b connects the capacitor C3 between the wirings U1 and W1 by turning off the switches 111 and 112 and turning on the switch 113 during the interconnection operation. On the other hand, during the independent operation, the capacitor connection switching unit 50b turns off the switch 113 to cut off the connection between the wires U1 and W1 by the capacitor C3 and turns on the switches 111 and 112 to turn on the wires U1 and W1. A capacitor C1 is connected between N1 and a capacitor C2 is connected between the wirings W1 and N1. Thereby, the operation and effect described in the first embodiment are realized. In addition, the capacity of the capacitor required during the interconnection operation and the capacity of the capacitor required during the independent operation can be set independently and freely.

  Further, the power conversion device 1b and the capacitor connection switching unit 50b of FIG. 7 may be modified into the power conversion device 1b 'and the capacitor connection switching unit 50b' of FIG. In the power conversion device 1b ′, unlike the power conversion device 1b, the wiring U1 connected to the reactor L1 is connected to the switch 31U via the switch 113, and the connection point and wiring between the switch 113 and the switch 31U are connected. A capacitor C3 is connected to W1. The power converters 1b and 1b 'are the same in other points. Also in the power conversion device 1b ', as in the power conversion device 1b, a series circuit of the switch 113 and the capacitor C3 is interposed in series between the wirings U1 and W1.

  Further, in the power converter 1b ′, as shown in FIG. 9, the switch 111 may be interposed in series between the reactor L1 and the switch 32U and between the reactor L1 and the capacitor C1. 112 may be interposed in series between the reactor L2 and the switch 32W and between the reactor L2 and the capacitor C2. Similar modifications can be made to the power conversion device 1b.

  Further, any one of the switches 111 and 112 may be deleted in the power conversion device 1b of FIG. 7 or the power conversion device 1b ′ of FIG. 8 or FIG. This is because it is not necessary to drive the leg LG0 during the interconnected operation, and it is considered that no problem occurs even if one of the switches 111 and 112 is omitted. When the switch 111 is deleted, the capacitor C1 is directly connected between the wirings U1 and N1 (that is, always connected), and when the switch 112 is deleted, the capacitor C2 is directly connected between the wirings W1 and N1 (that is, always connected). )

<Fourth embodiment>
A fourth embodiment of the present invention will be described. FIG. 10 is a circuit diagram of a power system including the power conversion device 1c according to the fourth embodiment. The power conversion device 1c and the capacitor connection switching unit 50c are examples of the power conversion device 1 and the capacitor connection switching unit 50 in FIG. The capacitor connection switching unit 50c includes capacitors C1 to C3 and a switch 121.

  In the power conversion device 1c, the connection point 48 is connected to one end of the reactor L1, and the other end of the reactor L1 is connected to one end of the switch 121. A wiring that commonly connects the other end of the reactor L1 and one end of the switch 101 is a wiring U1. The other end of the switch 101 is connected to one end of the capacitor C3 and to the switch 31U. That is, in the power conversion device 1c, the wiring U1 is connected to the switch 31U via the switch 121. The other end of the capacitor C3 is connected to the wiring W1. Therefore, a series circuit of the switch 121 and the capacitor C3 is interposed in series between the wirings U1 and W1. The wirings U1, N1, and W1 are connected to the switches 32U, 32N, and 32W, respectively.

  Capacitors C <b> 1 and C <b> 2 are always connected to the self-supporting load unit 80. That is, the capacitors C1 and C2 in the power conversion device 1c are always connected to the three wires U3, N3, and W3 that connect the self-standing switch 32 and the self-supporting load unit 80. More specifically, one end of the capacitor C1 and one end of the capacitor C2 are connected to the wirings U3 and W3, respectively, and the other ends of the capacitors C1 and C2 are commonly connected to the wiring N3. Therefore, when the self-standing switch 32 is closed, the capacitor C1 is connected between the wirings U1 and N1 via the switches 32U and 32N, and the capacitor C2 is wired via the switches 32W and 32N. It will be connected between W1 and N1.

  The capacitor connection switching unit 50c connects the capacitor C3 between the wirings U1 and W1 by turning on the switch 121 during the interconnection operation, while turning off the switch 121 during the independent operation. The connection between the wirings U1 and W1 by the capacitor C3 is cut off. As described above, since the self-supporting switch 32 is closed during the self-supporting operation, the capacitor C1 is connected between the wirings U1 and N1 through the switches 32U and 32N, and the capacitor C2 is connected to the wiring W1 through the switches 32W and 32N. And N1. Thereby, the operation and effect described in the first embodiment are realized. Further, in the configuration of FIG. 10, the provision of the switches (111, 112) to the capacitors C1 and C2 can be omitted in comparison with the configuration of FIG.

  It is also conceivable that the capacitor C3 is disposed on the power system 60 side when viewed from the interconnection switch 31. However, when such an arrangement is made, it is difficult to protect the power system 60 because the capacitor C3 cannot be disconnected from the power system 60 even if a short circuit failure occurs in the capacitor C3. However, safety can be ensured even if the capacitors C1 and C2 are arranged at positions as shown in FIG. This is because, even if a short circuit failure occurs in the capacitor C1 or C2 in FIG. 10, by stopping the output of the inverter circuit 10, adverse effects (abnormal heat generation or the like) due to the short circuit can be avoided.

  Further, the power conversion device 1c and the capacitor connection switching unit 50c in FIG. 10 may be modified into the power conversion device 1c ′ and the capacitor connection switching unit 50c ′ in FIG. In the power conversion device 1c ′, the wiring U1 is directly connected to the switch 31U without the switch 121, and one end of the switch 121 is commonly connected to the reactor L1 and the switch 31U via the wiring U1, and The other end of the switch 101 is connected to one end of the capacitor C3, and the other end of the capacitor C3 is connected to the wiring W1. The power converters 1c and 1c 'are the same in other points. Also in the power conversion device 1c ', as in the power conversion device 1c, a series circuit of a switch 121 and a capacitor C3 is interposed in series between the wirings U1 and W1.

<Fifth Embodiment>
A fifth embodiment of the present invention will be described. FIG. 12 is a circuit diagram of a power system including the power conversion device 1d according to the fifth embodiment. The power conversion device 1d and the capacitor connection switching unit 50d are examples of the power conversion device 1 and the capacitor connection switching unit 50 in FIG. The capacitor connection switching unit 50d includes capacitors C2 and C3 and a changeover switch 131.

  In the power converter 1d, the connection point 48 is connected to one end of the reactor L1, the other end of the reactor L1 is connected to the wiring U1, and the wiring U1 is connected to the switches 31U and 32U and the capacitor C3 ( Is connected to one end of a switching capacitor. The other end of the capacitor C3 is selectively connected to the wiring N1 or W1 via the changeover switch 131. That is, the changeover switch 131 is a switch that selectively connects the other end of the capacitor C3 whose one end is always connected to the wiring U1 to the wiring N1 or W1. On the other hand, one end and the other end of the capacitor C2 (non-switching capacitor) are always connected to the wirings N1 and W1, respectively. The wiring N1 is connected to the switch 32N, and the wiring W1 is commonly connected to the switches 31W and 32W.

The capacitor connection switching unit 50d connects the capacitor C3 between the wirings U1 and W1 through the control of the changeover switch 131 during the interconnection operation. On the other hand, during the self-sustained operation, the capacitor connection switching unit 50d disconnects the connection between the wirings U1 and W1 by the capacitor C3 and controls the switching switch 131 to connect the capacitor C3 between the wirings U1 and N1. Thereby, the operation and effect described in the first embodiment are realized. Further, according to the configuration of FIG. 12, the installation of the capacitor C1 can be omitted in comparison with the configurations of the second to fourth embodiments. In the power converter 1d, the capacitor C2 corresponds to the capacitor C _WN in FIG. 4, and the capacitor C3 selectively realizes the function as the capacitor C _{UW in} FIG. 3 and the function as the capacitor C _{UN in} FIG. Concurrent with time division).

<Sixth Embodiment>
A sixth embodiment of the present invention will be described. FIG. 13 is a circuit diagram of a power system including the power conversion device 1J according to the sixth embodiment. In the power system of FIG. 13, based on the power system of FIG. 1, a series circuit of DC power supplies 201 and 202 and a series circuit of capacitors 203 and 204 are provided instead of the DC power supply 2. Leg LG0 has been deleted. Except for these points, the circuit configuration is the same between the power system of FIG. 1 and the power system of FIG. 13. However, in the power conversion device 1J, the wiring N1 is commonly connected to the connection point between the capacitors 203 and 204 and the connection point between the DC power supplies 201 and 202.

The DC power supplies 201 and 202 are the same DC power supplies as the DC power supply 2, and each of the DC power supplies 201 and 202 outputs a DC voltage of V _DC / 2. The DC power source 202 is located on the higher voltage side than the DC power source 201. Accordingly, the negative output terminal of the DC power supply 201 is connected to the wiring 3, the positive output terminal of the DC power supply 202 is connected to the wiring 4, and the positive output terminal of the DC power supply 201 and the negative output terminal of the DC power supply 202 are connected to each other. The Capacitor 203 is connected in parallel to DC power supply 201, and capacitor 204 is connected in parallel to DC power supply 202. Since the power converter 1J does not have the leg LG0, the power converter 1J naturally does not need to control the arms in the leg LG0. Except that there is no control of the arm in the legg LG0, the operation of each part in the power converter 1J is the same as that of the power converter 1 in FIG. The configuration of the capacitor connection switching unit described in the second to fifth embodiments may be applied to the sixth embodiment.

<Seventh embodiment>
A seventh embodiment of the present invention will be described. In the seventh embodiment, a technique that can be commonly applied to the first to sixth embodiments will be described. The power conversion device 1 described in the seventh embodiment refers to any of the power conversion devices (1, 1a to 1d, 1a ′ to 1c ′, 1J) described in any of the above-described embodiments. A distribution board 90 shown in FIG. 14 may be connected to the power converter 1. The distribution board 90 may be considered to be a component of the power conversion device 1 or a component of a power system that includes the power conversion device 1.

  The distribution board 90 includes a first input terminal group and a second input terminal group, and an output terminal group to which the first or second input terminal group is selectively connected. When the distribution board 90 is connected to the power converter 1, the wirings U2, N2, and W2 connected to the power system 60 are connected to the first input terminal group of the distribution board 90. In the present embodiment, the wires U3, N3, and W3 connected to the self-standing switch 32 are not directly connected to the self-supporting load unit 80 but are connected to the second input terminal group of the distribution board 90. Then, the output terminal group of the distribution board 90 is connected to the self-supporting load unit 80. Therefore, the wiring group composed of the wirings U2, N2, and W2 or the wiring group composed of the wirings U3, N3, and W3 is alternatively connected to the self-supporting load unit 80 via the distribution board 90.

  Specifically, the distribution board 90 alternatively takes the interconnection state or the independent state. When the distribution board 90 is in the interconnection state, the wirings U2, N2 and W2 are connected to the self-supporting load unit 80 via the distribution board 90, and as a result, the voltage between the wirings U2 and N2 and the wiring W2 and N2 are connected. And the voltage between the wirings U2 and W2 are supplied to the loads 80U, 80W and 80UW, respectively. On the other hand, when the distribution board 90 is in a self-supporting state, the wirings U3, N3, and W3 are connected to the self-supporting load unit 80 via the distribution board 90. As a result, the voltage between the wirings U3 and N3, the wirings W3 and N3 Voltage between the wirings U3 and W3 is supplied to the loads 80U, 80W, and 80UW, respectively.

  The configuration of FIG. 14 is a kind of general configuration that drives the self-supporting load unit 80 (home appliances or the like) by a self-sustained operation during a power failure. That is, when performing the interconnection operation, the state of the distribution board 90 is set to the interconnection state, and when performing the independent operation during a power failure, the distribution panel 90 may be set to the independent state. . Switching of the state of the distribution board 90 between the interconnection state and the self-sustaining state may be realized by manual switching by the user, or may be performed based on a distribution board control signal from the power converter 1. . Based on the detection result of the power failure detection unit 33 described above, the state of the distribution panel 90 becomes a self-sustaining state when a power failure occurs, and the state of the distribution panel 90 becomes a state for interconnection when no power failure occurs. In addition, a distribution board control signal is generated. The power failure detection unit 33 may be included in the distribution board 90 and the distribution board control signal may be generated in the distribution board 90.

<Deformation, etc.>
The embodiment of the present invention can be appropriately modified in various ways within the scope of the technical idea shown in the claims. The above embodiment is merely an example of the embodiment of the present invention, and the meaning of the term of the present invention or each constituent element is not limited to that described in the above embodiment. The specific numerical values shown in the above description are merely examples, and as a matter of course, they can be changed to various numerical values.

In each of the power converters described above, only DC / AC conversion is performed, but AC / AC conversion may be performed. That is, in each of the power conversion devices (1, 1a to 1d, 1a ′ to 1c ′, 1J) described above, the DC power sources 2, 201 and 202 are obtained by rectifying the AC voltage supplied to the power conversion device. May be. In this case, a converter that obtains a DC voltage V _DC or V _DC / 2 from the supplied AC voltage is added to the power converter (1, 1a to 1d, 1a ′ to 1c ′, 1J).

  In the above-described embodiments, it is assumed that the switching elements that form the legs (LG0 to LG2) are IGBTs. However, the switching elements that form the legs (LG0 to LG2) are any type of semiconductor switching other than IGBTs. It may be an element (such as a field effect transistor) or a mechanical switching element such as a relay.

<Consideration of Invention Content>
Hereinafter, the contents of the present invention will be considered. In the text of the following considerations, the reference numerals shown in parentheses are those when the first line is assumed to be the U-phase wiring U1, but the first line is the W-phase wiring W1. It is possible.

For example, referring to FIGS. 1, 3, and 4, the power converters (1, 1 a to 1 d, 1 a ′ to 1 c ′, 1 J) according to one aspect of the present invention include an inverter circuit (10 ), The first line (U1), the second line (W1) and the neutral line (N1) provided on the output side of the inverter circuit, and the first line and the second line are connected to the power system (60). The interconnection operation for outputting alternating current (V _UW ) from the inverter circuit to the power system via the first line and the second line, and disconnecting the first line and the second line from the power system and An operation switching unit (20) for switching and executing independent operation for outputting different alternating _currents (V _UN , V _WN ) from the inverter circuit between the first line and the neutral line and between the second line and the neutral line; while a capacitor (C _UW) between the first line and the second line in the interconnected operation , Wherein the capacitor (C _UW) by the first line and the shut off the connection between the second line the first line and neutral line between said separate capacitor between the second line and neutral lines in isolated operation And a capacitor connection switching unit (50) for connecting (C _UN , C _WN ).

  By connecting a capacitor between the first line and the second line during the interconnection operation, the voltage quality during the interconnection operation can be improved. During the self-sustaining operation, the connection between the first line and the second line by the capacitor is cut off, and separate capacitors are connected between the first line and the neutral line and between the second line and the neutral line. Thereby, unnecessary voltage fluctuations (such as an abnormal increase in voltage between the first line or the second line and the neutral line) due to the presence of the capacitor between the first line and the second line can be suppressed. That is, it is possible to suppress the influence of the capacitor required during the interconnected operation during the independent operation.

  Specifically, for example (see FIG. 5, FIG. 6, etc.), the capacitor connection switching unit (50a, 50a ′) includes the first capacitor (C1) connected between the first line and the neutral line, A second capacitor (C2) connected between the second line and the neutral line; and a series circuit of a switch (101) and a third capacitor (C3) interposed between the first line and the second line. And in the interconnection operation, the switch is turned on to connect the third capacitor between the first line and the second line, while in the independent operation, the switch is turned off and the third capacitor is connected. The connection between the first line and the second line may be cut off.

  With this configuration, since the connection between the first line and the second line by the third capacitor is cut off during the self-sustaining operation, unnecessary voltage fluctuations associated with the connection of the third capacitor can be suppressed during the self-sustaining operation.

  Or, for example (see FIG. 7, FIG. 8, FIG. 9, etc.), the capacitor connection switching unit (50b, 50b ′) includes the first capacitor (C1) interposed between the first line and the neutral line, and the first capacitor A second capacitor (C2) interposed between the two wires and the neutral wire; and a series circuit of the interconnection switch (113) and the third capacitor (C3) interposed between the first wire and the second wire; And a self-supporting switch (111, 112) of the switch (111) connected in series to the first capacitor and the switch (112) connected in series to the second capacitor. In the interconnection operation, the self-standing switch is turned off and the interconnection switch is turned on to connect the third capacitor between the first line and the second line, Independence In turn, the self-standing switch is turned on and the interconnection switch is turned off to cut off the connection between the first line and the second line by the third capacitor, and between the first line and the neutral line, and The first and second capacitors may be connected between the second line and the neutral line.

  Even in this configuration, since the connection between the first line and the second line by the third capacitor is interrupted during the self-sustaining operation, unnecessary voltage fluctuations associated with the connection of the third capacitor can be suppressed during the self-sustaining operation. .

  Or, for example (see FIG. 10, FIG. 11, etc.), the self-supporting load unit (80) that receives the output AC voltage of the inverter circuit in the self-supporting operation, and the first wire, the second wire, and the neutral wire (U1, W1, N1) and a self-contained switch (32) interposed between the power converter and the capacitor connection switching unit (50c, 50c ′) may include the self-supporting switch and the self-supporting load unit. The first and second capacitors (C1, C2) connected to the three wirings (U3, W3, N3) for connecting to the switch, the switch (121) interposed between the first line and the second line, and A series circuit of third capacitors (C3), and when the self-supporting switch is closed, the first capacitor is connected between the first line and the neutral line via the self-supporting switch; and The second line and neutral through the self-standing switch The first and second capacitors are arranged so that the second capacitor is connected between them, and the capacitor connection switching unit turns on the switch (121) in the interconnection operation and turns on the first line. And the third capacitor is connected between the second line and the switch (121) is turned off in the self-sustained operation to cut off the connection between the first line and the second line by the third capacitor. The first and second capacitors may be connected between the first line and the neutral line and between the second line and the neutral line by closing the self-standing switch.

  Even in this configuration, since the connection between the first line and the second line by the third capacitor is interrupted during the self-sustaining operation, unnecessary voltage fluctuations associated with the connection of the third capacitor can be suppressed during the self-sustaining operation. . In addition, the number of switches can be reduced in comparison with the above configuration that requires the first to third switches.

  Or, for example (see FIG. 12 and the like), the capacitor connection switching unit (50d) includes a non-switching capacitor (C2) connected between the second line and the neutral line, and one end of the first line (U1). And a switch (131) for selectively connecting the other end of the switch capacitor to the neutral line (N1) or the second line (W1). In the interconnected operation, the switching capacitor is connected between the first line and the second line through the control of the changeover switch, while in the independent operation, the switching switch is connected through the control of the changeover switch. The switching capacitor may be connected between the first line and the neutral line by disconnecting the connection between the first line and the second line by a capacitor.

  Even in this configuration, the connection between the first line and the second line by the capacitor is cut off during the self-sustained operation. Can be suppressed. Further, the number of capacitors can be reduced in comparison with a configuration that requires first to third capacitors.

DESCRIPTION OF SYMBOLS 1, 1a-1d, 1a'-1c ', 1J Power converter 10 Inverter circuit 20 Control part 31 Linkage switch 32 Self-supporting switch 33 Power failure detection part 50, 50a-50d, 50a'-50c'
60 Power system 70 System load section 80 Self-supporting load section 90 Distribution board

Claims (5)

An inverter circuit for converting direct current to alternating current;
A first line, a second line and a neutral line provided on the output side of the inverter circuit;
An interconnection operation for connecting the first line and the second line to an electric power system and outputting an alternating current from the inverter circuit to the electric power system via the first line and the second line, and the first line and the second line An operation switching unit that switches between the first line and the neutral line and the independent operation that outputs separate alternating current from the inverter circuit between the first line and the neutral line, and the second line and the neutral line;
In the interconnected operation, a capacitor is connected between the first line and the second line, while in the self-sustained operation, the connection between the first line and the second line by the capacitor is interrupted to disconnect the first line and the middle line. And a capacitor connection switching unit that connects separate capacitors between the second wires and the neutral wires. The capacitor connection switching unit is
A first capacitor connected between the first line and the neutral line;
A second capacitor connected between the second line and the neutral line;
A series circuit of a switch and a third capacitor interposed between the first line and the second line,
In the interconnection operation, while turning on the switch and connecting the third capacitor between the first line and the second line,
2. The power conversion device according to claim 1, wherein in the independent operation, the switch is turned off to cut off the connection between the first line and the second line by the third capacitor. The capacitor connection switching unit is
A first capacitor interposed between the first line and the neutral line;
A second capacitor interposed between the second line and the neutral line;
And a series circuit of an interconnection switch and a third capacitor interposed between the first line and the second line, and having a self-supporting switch, and the self-supporting switch is connected in series to the first capacitor And at least one of a switch connected in series to the second capacitor,
In the interconnection operation, the self-support switch is turned off and the interconnection switch is turned on to connect the third capacitor between the first line and the second line,
In the self-sustained operation, the self-supporting switch is turned on and the interconnection switch is turned off to cut off the connection between the first line and the second line by the third capacitor and between the first line and the neutral line. 2. The power converter according to claim 1, wherein the first and second capacitors are connected between the second line and the neutral line. A self-supporting switch interposed between the self-supporting load section that receives the output AC voltage of the inverter circuit in the self-supporting operation, and the first wire, the second wire, and the neutral wire;
The capacitor connection switching unit is
First and second capacitors connected to three wires connecting the self-supporting switch and the self-supporting load unit;
A series circuit of a switch and a third capacitor interposed between the first line and the second line,
When the self-standing switch is closed, the first capacitor is connected between the first line and the neutral line via the self-standing switch, and the second line and the neutral line are connected via the self-standing switch. The first and second capacitors are arranged such that the second capacitor is connected therebetween,
The capacitor connection switching unit is
In the interconnection operation, while turning on the switch and connecting the third capacitor between the first line and the second line,
In the self-sustained operation, the switch is turned off to disconnect the connection between the first line and the second line by the third capacitor, and between the first line and the neutral line by closing the self-standing switch. The power converter according to claim 1, wherein the first and second capacitors are connected between the second line and the neutral line. The capacitor connection switching unit is
A non-switching capacitor connected between the second line and the neutral line;
A switching capacitor having one end connected to the first wire;
A selector switch that selectively connects the other end of the switching capacitor to the neutral line or the second line;
In the interconnected operation, through the control of the selector switch, while connecting the switching capacitor between the first line and the second line,
In the self-sustained operation, through the control of the changeover switch, the connection between the first line and the second line by the switching capacitor is cut off and the switching capacitor is connected between the first line and the neutral line. The power conversion device according to claim 1.

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