JP2018046622A - Distribution type power supply system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide self-supported output of a single-phase three-wire type while reducing the number of circuits being used for the self-supported output only and having a low use frequency and suppressing cross current, in a distribution type power supply system including a plurality of distribution type power supplies.SOLUTION: A distribution type power supply system connected to a single-phase three-wire type AC electric path 3 (U, O, W) comprises: a single-phase first distribution type power supply ES-1 that includes a first DC power supply and a power conversion device provided between the first DC power supply and the AC electric path and includes two wires for self-support; a single-phase second distribution type power supply ES-2 that includes a second DC power supply and a power conversion device provided between the second DC power supply and the AC electric path and includes two wires for self-support; a self-support output electric path that connects the two wires of the first distribution type power supply to a U line and O line of the AC electric path and connects the two wires of the second distribution type power supply to a W line and O line of the AC electric path; and a control unit that makes an AC phase of self-support output by the first distribution type power supply and an AC phase of self-support output by the second distribution type power supply be reverse to each other.SELECTED DRAWING: Figure 6

Description

  The present invention relates to a distributed power supply system.

A distributed power source linked to a single-phase three-wire commercial power system generally has a voltage synchronized with an AC voltage (200 V) between the voltage lines U and W among the voltage lines U and W and the neutral line O. Output power.
When a commercial power system fails due to an accident, the distributed power supply itself provides AC power with a constant voltage and a constant frequency to the load as an independent output. However, in that case, 100V must be provided for 100V and 200V for 200V. Therefore, a circuit configuration different from that at the time of system interconnection is required.

  As such a circuit configuration, for example, if an insulating transformer is placed between the inverter and the distribution board of the customer, the single-phase two-wire output of the inverter is converted into a single-phase three-wire output with a neutral wire. can do. The inverter itself may be a three-leg full bridge circuit capable of single-phase three-wire output (see, for example, Patent Documents 1 to 5).

JP-A-6-319266 JP 7-163153 A JP 2003-18859 A Japanese Patent Laying-Open No. 2015-27197 JP 2015-2111537 A

  However, when an insulation transformer is used, the insulation transformer is used only in the case of a self-sustained output, and is not used at the time of grid connection that is a lot of time. In the case of a three-leg inverter, the neutral wire leg and reactor are actually used only in the case of a self-sustained output, and not used during grid connection.

  In particular, in a distributed power supply system in which a plurality of distributed power supplies are combined, each distributed power supply must be provided with a circuit element that is used only for independent output. In addition, during independent output, inverters controlled at a constant voltage and a constant frequency are operated in parallel, so it is difficult to make the voltage and phase exactly match. Decreases the efficiency.

  In view of such a conventional problem, the present invention provides a single-phase power supply system that includes a plurality of distributed power supplies and reduces circuit elements that are not used frequently only for a stand-alone output and suppresses cross current. The purpose is to provide a three-wire self-supporting output.

  The present invention according to one expression is a distributed power supply system connected to a single-phase three-wire AC circuit, wherein the single-phase three-wire voltage line is a U line and a W line, and the neutral line is an O line. A first DC power source, and a power converter provided between the first DC power source and the AC circuit, and a single-phase first distributed power source having two wires for self-sustained output, and a second DC Including a power source and a power converter provided between the second DC power source and the AC circuit, a single-phase second distributed power source having two wires for self-sustained output, and the first distributed power source A self-sustained output circuit that connects the two lines to the U and O lines of the AC circuit, and connects the two lines of the second distributed power source to the W and O lines of the AC circuit, and the first distribution The AC phase of the self-sustained output by the power source and the AC phase of the self-sustained output by the second distributed power source are reversed. And it includes a control unit, a.

  The present invention according to another expression is a distributed power supply system that can be connected to a single-phase three-wire AC circuit connected to a commercial power system, wherein the single-phase three-wire voltage line is a U-line, a W-line, and a neutral line. Includes a first DC power source and a power converter provided between the first DC power source and the AC circuit, and has two lines of independent output in addition to the normal output line. It includes a single-phase first distributed power source, a second DC power source, and a power converter provided between the second DC power source and the AC circuit. A single-phase second distributed power source having a line, and the output line of the first distributed power source and the output line of the second distributed power source are connected in parallel to each other and connected to the AC circuit An electric circuit and the two lines of the first distributed power supply are connected to a U line and an O line of the AC electric circuit; A self-sustained output circuit that connects the two lines of the distributed power source to the W line and the O line of the AC power circuit, an AC phase of the self-sustained output by the first distributed power source, and a self-sustained output by the second distributed power source And a controller that inverts the AC phase with each other.

  According to the distributed power supply system of the present invention including a plurality of distributed power supplies, a single-phase three-wire self-sustained output can be achieved while reducing infrequently used circuit elements used only for self-sustained outputs and suppressing cross current. Can be provided.

It is a figure which shows an example of the circuit structure of the distributed power supply which uses a storage battery as DC power supply. It is a figure which shows an example of the circuit structure of the distributed power supply which uses photovoltaic power generation as DC power supply. It is a figure which shows an example of the circuit structure of a distributed power supply system including the distributed power source which uses a storage battery as a DC power supply, and the distributed power source which uses a photovoltaic power generation panel as a DC power supply. It is a figure which shows an example of the circuit structure of a distributed power supply system including two distributed power supplies which use a storage battery as a DC power supply, and one distributed power supply which uses a photovoltaic power generation panel as a DC power supply. It is a figure which shows an example of the circuit structure which uses two distributed power supplies which use a storage battery as a DC power supply, and uses the distributed power supply which uses a photovoltaic power generation panel as a DC power supply as an auxiliary input. It is a figure which shows an example of the circuit structure which uses two distributed power supplies which use a storage battery as a DC power supply, and uses the distributed power supply which uses a photovoltaic power generation panel as a DC power supply as an auxiliary input. FIG. 7 is a diagram showing a circuit configuration in which FIG. 4 (system interconnection) and FIG. 6 (independent output by a series connection method) are superimposed.

[Summary of Embodiment]
The gist of the embodiment of the present invention includes at least the following.

  (1) This is a distributed power supply system connected to a single-phase three-wire AC circuit, where the single-phase three-wire voltage line is the U line and W line, and the neutral line is the O line. A first DC power supply, a power converter provided between the first DC power supply and the AC circuit, a single-phase first distributed power supply having two wires for self-sustained output, and a second DC power supply And a single phase second distributed power source having two wires for self-sustained output, including a power converter provided between the second DC power source and the AC circuit, and the first distributed power source. A self-sustained output circuit that connects two lines to the U line and the O line of the AC circuit, and connects the two lines of the second distributed power source to the W line and the O line of the AC circuit; and the first distributed type A controller that inverts the AC phase of the self-sustained output from the power supply and the AC phase of the self-sustained output from the second distributed power supply; It is equipped with a.

  In the distributed power supply system configured as described above, the self-sustained outputs of the first and second distributed power supplies are connected in series with each other at both ends of the series to the U line and W line, and the interconnection point to the O line. Each is connected. Thereby, the U-O line power is provided by the first distributed power source, the W-O line power is provided by the second distributed power source, and the U-W line power is the first and second distributed power sources. Provided by mold power supply. Therefore, it is possible to provide a single-phase, three-wire self-sustained output for both 100V load and 200V load. In addition, cross current does not flow. Furthermore, since the power conversion device has a single-phase output and does not use a neutral wire leg or an AC reactor, it is possible to reduce circuit elements that are used infrequently and used only for self-sustained output.

  (2) In addition, this is a distributed power supply system that can be connected to a single-phase three-wire AC circuit connected to a commercial power system, and a single-phase three-wire voltage line is connected to a U line, a W line, and a neutral line. Includes a first DC power source and a power converter provided between the first DC power source and the AC circuit, and has two lines of independent output in addition to the normal output line. It includes a single-phase first distributed power source, a second DC power source, and a power converter provided between the second DC power source and the AC circuit. A single-phase second distributed power source having a line, and the output line of the first distributed power source and the output line of the second distributed power source are connected in parallel to each other and connected to the AC circuit An electric circuit and the two lines of the first distributed power source are connected to a U line and an O line of the AC circuit, and the second distribution A self-sustained output power circuit that connects the two wires of the power source to the W line and the O wire of the AC power circuit, an AC phase of the self-sustained output by the first distributed power source, and an AC phase of the self-sustained output by the second distributed power source And a control unit for inverting each other.

  In the distributed power supply system configured as described above, the output lines of the first and second distributed power supplies are connected in parallel to each other during grid connection. On the other hand, during the self-sustained operation, the self-sustained outputs of the first and second distributed power sources are connected in series, and both ends of the series are connected to the U line and the W line, and the interconnection point is connected to the O line. Thereby, the U-O line power is provided by the first distributed power source, the W-O line power is provided by the second distributed power source, and the U-W line power is the first and second distributed power sources. Provided by mold power supply. Therefore, it is possible to provide a single-phase, three-wire self-sustained output for both 100V load and 200V load. In addition, cross current does not flow. Furthermore, since the power conversion device has a single-phase output and does not use a neutral wire leg or an AC reactor, it is possible to reduce circuit elements that are used infrequently and used only for self-sustained output.

(3) In the distributed power supply system according to (1) or (2), each of the first distributed power supply and the second distributed power supply has an auxiliary input port that receives an input from an independent external AC power supply. One of the first distributed power supply and the second distributed power supply outputs a voltage of the external AC power supply via the auxiliary input port, and a signal for performing synchronized control based on the voltage The other of the first distributed power source and the second distributed power source is disconnected from the auxiliary input port and synchronized with the voltage of the external AC power source and inverted based on the signal A voltage may be output.
In this case, one distributed power source outputs the voltage of the external AC power source, and the other distributed power source matches the absolute value of the voltage of one distributed power source with a signal for performing synchronized control, and , The phase can be reversed.

(4) In the distributed power supply system of (3), it is preferable that the one distributed power supply and the other distributed power supply are alternately switched.
In this case, when the DC power supply is a storage battery, the remaining power of each storage battery is prevented from becoming unbalanced between one distributed power supply and the other distributed power supply, and as a result, the discharge capacity of the storage battery is sufficiently Can be demonstrated.

(5) Also, in the distributed power supply system of (3) or (4), the DC power supply is a storage battery, and the one distributed power supply is charged by outputting the voltage of the external AC power supply to the storage battery. You may do it.
In this case, the output of the external AC power supply can be used without waste.

[Details of the embodiment]
Hereinafter, a distributed power supply system according to an embodiment of the present invention will be described step by step with an explanation of the examination process.

《Distributed power supply with storage battery and power conversion device》
FIG. 1 is a diagram illustrating an example of a circuit configuration of a distributed power source that uses a storage battery as a DC power source. In the figure, the distributed power source ES is composed of a power conversion device 1B and a storage battery 2B. The power conversion device 1B is provided between the storage battery 2B and the single-phase three-wire AC circuit 3. Note that single-phase three-wire voltage lines are U lines and W lines, and neutral lines are O lines.

  A load (not shown) of a consumer is connected to the AC power line 3 and is connected to a commercial power system at a power receiving point. When the commercial power system fails, the power converter 1B can output AC 101V to the self-sustained output port 4. Further, the power conversion device 1 </ b> B includes an auxiliary input port 5. The auxiliary input port 5 can accept input from an independent external AC power source other than the commercial power system.

  The power conversion device 1B includes, as main circuit components, a DC side capacitor 6, a DC / DC converter 8, an intermediate capacitor 9, an inverter 11, an AC reactor 12, an AC side capacitor 13, capacitors 14 and 15, a grid interconnection switch 16, A self-supporting output switch 17 and an auxiliary input switch 18 are provided. The DC / DC converter 8 includes a DC reactor 7, a high-side switching element Q1, and a low-side switching element Q2. For example, MOSFET (Metal-Oxide-Semiconductor Field Effect Transistor) can be used as the switching elements Q1, Q2. The MOSFET switching elements Q1, Q2 have diodes (body diodes) d1, d2, respectively.

  Each switching element Q1, Q2 is controlled by the control unit 30. The DC / DC converter 8 can operate in both directions. When discharging the storage battery 2B, the DC / DC converter 8 becomes a booster circuit that boosts the discharge voltage and supplies it to the DC bus 10. Conversely, when charging the storage battery 2B, This is a step-down circuit that steps down the voltage of the bus 10 and applies it to the storage battery 2B.

The high voltage side of the DC / DC converter 8 is connected to the DC bus 10. The intermediate capacitor 9 is connected between the two lines of the DC bus 10 and smoothes the DC voltage between the two lines.
The inverter 11 includes switching elements Q3 to Q6 that constitute a full bridge circuit. These switching elements Q3 to Q6 are, for example, MOSFETs. In the case of a MOSFET, the switching elements Q3 to Q6 have diodes (body diodes) d3 to d6, respectively.

  Each of the switching elements Q3 to Q6 is controlled by the control unit 30. The inverter 11 can operate in both directions, and converts the voltage of the DC bus 10 into an AC voltage when discharging the storage battery 2B. Conversely, when charging the storage battery 2 </ b> B, a DC voltage obtained by rectifying the AC voltage is supplied to the DC bus 10.

  On the alternating current side of the inverter 11, the alternating current reactor 12 and the alternating current side capacitor 13 constitute a filter circuit, and the high frequency noise generated in the inverter 11 is prevented from passing to the alternating current circuit 3 side.

  As a circuit element for measurement, a voltage sensor 21 and a current sensor 22 are provided on the low voltage side (left side in the figure) of the DC / DC converter 8. The voltage sensor 21 is connected in parallel with the storage battery 2B and detects the terminal voltage of the storage battery 2B. Information on the detected voltage is provided to the control unit 30. The current sensor 22 detects a current flowing through the DC / DC converter 8. The current flowing through the DC / DC converter 8 is also the current flowing through the storage battery 2B if the current flowing through the DC capacitor 6 is ignored. Information on the detected current is provided to the control unit 30.

  A voltage sensor 23 is connected in parallel to the intermediate capacitor 9. The voltage sensor 23 detects the voltage across the intermediate capacitor 9, that is, the voltage of the DC bus 10. Information on the detected voltage is provided to the control unit 30.

  On the other hand, a current sensor 24 that detects a current flowing through the AC reactor 12 is provided on the AC side. Information on the current detected by the current sensor 24 is provided to the control unit 30. In addition, voltage sensors 25 and 26 are provided in parallel with the capacitors 14 and 15, respectively. Information on the voltages detected by the voltage sensors 25 and 26 is provided to the control unit 30. The sum of the voltages detected by the two voltage sensors 25, 26 is the voltage across the AC capacitor 13.

The grid interconnection switch 16, the independent output switch 17, and the auxiliary input switch 18 are opened and closed by the control unit 30.
The control unit 30 includes, for example, a CPU (Central Processing Unit), and a necessary control function is realized by the CPU executing software (computer program). The software is stored in a storage device (not shown) of the control unit 30.

  In the distributed power source ES at the time of grid connection, the grid connection switch 16 is closed, and the self-supporting output switch 17 and the auxiliary input switch 18 are opened. The voltage / current generated by the discharge of the storage battery 2 </ b> B is converted into an AC voltage / current via the DC / DC converter 8 and the inverter 11 and supplied to the AC circuit 3. The output voltage is AC202V and is supplied between the U line and the W line. The capacitors 14 and 15 are provided for detecting each voltage of the single-phase three-wire on the AC electric circuit 3 side, but the O-line is not involved in the output of the distributed power source ES or the input to the distributed power source ES. .

The electric power supplied from the distributed power source ES to the AC electric circuit 3 is consumed by the load of the consumer (the power is not sold by the reverse power).
Moreover, if power conversion from AC to DC is performed in the reverse direction, the storage battery 2B can be charged by the power of the commercial power system.

  On the other hand, when the commercial power system is out of power or not dependent on the commercial power system, the distributed power source ES can perform a self-sustained operation and provide an AC 101V output to the self-sustained output port 4. That is, the DC / DC converter 8 and the inverter 11 during the self-sustained operation perform a switching operation so that the output voltage is AC 101V. At this time, the self-supporting output switch 17 is closed, and the grid connection switch 16 and the auxiliary input switch 18 are opened. The current of the self-supporting output is detected by the current sensor 27. Information on the detected current is provided to the control unit 30.

  Further, the voltage applied from the outside to the auxiliary input port 5 is detected by the voltage sensor 28. Information on the detected voltage is provided to the control unit 30. When the input (AC101V) is applied to the auxiliary input port 5 from the external AC power source, the power of the external AC power source is taken into the distributed power source ES by opening the grid connection switch 16 and closing the auxiliary input switch 18. be able to. When the self-supporting output switch 17 is closed with the auxiliary input switch 18 closed, power can be supplied to the load connected to the self-supporting output port 4 by the auxiliary input. Further, if necessary, the storage battery 2B can be charged by auxiliary input.

《Distributed power supply by photovoltaic power generation and power conversion device》
FIG. 2 is a diagram illustrating an example of a circuit configuration of a distributed power source that uses solar power generation as a DC power source. In the figure, the distributed power source PV is composed of a power conversion device 1P and a photovoltaic power generation panel 2P. The power conversion device 1P is provided between the photovoltaic power generation panel 2P and the single-phase three-wire AC circuit 3. Note that single-phase three-wire voltage lines are U lines and W lines, and neutral lines are O lines.

A load (not shown) of a consumer is connected to the AC power line 3 and is connected to a commercial power system at a power receiving point. At the time of failure of the commercial power system, the power conversion device 1P can output AC 101V to the independent output port 4.
The internal configuration of the power conversion device 1P is different from that of the power conversion device 1B shown in FIG. 1 in that there is no auxiliary input port 5 and that reverse conversion from AC to DC is not performed. The configuration is the same.

  In the distributed power source PV at the time of grid connection, the grid connection switch 16 is closed and the self-sustained output switch 17 is opened. The voltage / current generated by the photovoltaic power generation panel 2 </ b> P is converted into an AC voltage / current via the DC / DC converter 8 and the inverter 11 and supplied to the AC circuit 3. The output voltage is AC202V and is supplied between the U line and the W line.

The electric power supplied from the distributed power source PV to the AC power line 3 is consumed by the load of the consumer and can be sold by reverse tide.
On the other hand, when the commercial power system is out of power or not dependent on the commercial power system, the distributed power source PV can perform a self-sustained operation and provide an AC 101V output to the self-sustained output port 4. That is, the DC / DC converter 8 and the inverter 11 during the self-sustained operation perform a switching operation so that the output voltage is AC 101V. At this time, the self-supporting output switch 17 is closed and the grid connection switch 16 is open.

The distributed power sources ES and PV configured as described above can be combined to be used as a distributed power system.
Hereinafter, such a distributed power supply system will be described.

<< Example of ES + PV >>
FIG. 3 is a diagram illustrating an example of a circuit configuration of a distributed power supply system including the distributed power supply ES and the distributed power supply PV. In the figure, the internal configuration of the distributed power source ES is the same as that of FIG. 1, and the internal configuration of the distributed power source PV is the same as that of FIG. 2 (the same applies hereinafter).

  In the figure, a load Ruo between the U line and the O line, a load Rwo between the W line and the O line, and a load Ruw between the U line and the W line are connected to the AC circuit 3 as the load of the consumer. Yes. A single-phase three-wire commercial power system can be represented as phase power supplies Pu and Pw. The distributed power source ES and the distributed power source PV are connected in parallel to each other on the AC side, and are connected to the AC circuit 3 by three wires (U, O, W). However, two wires (U, W) contribute to the exchange of AC power, and the voltage is AC202V.

A specific load Rs is connected to the independent output port 4 of the distributed power source ES. A self-sustained output of the distributed power source PV can be input to the auxiliary input port 5 of the distributed power source ES.
Currents flowing through the U line and the W line of the AC circuit 3 are detected by current sensors 31 and 32, respectively. Further, a current sensor 33 is provided on the electric circuit connected from the distributed power source PV to the W line of the AC electric circuit 3. The detection outputs of the current sensors 31 to 33 are provided to the control unit 30 in the distributed power source ES.

The distributed power source ES at the time of grid connection is connected between the single-phase three-wire voltage lines U and W (AC202V), and performs an input (charge) or output (discharge) operation. The distributed power source PV at the time of grid connection is connected between the single-phase three-wire voltage lines U and W (AC202V) and supplies generated power to the AC circuit 3.
The distributed power source ES at the time of self-sustained output outputs AC 101 V from the self-sustained output port 4.
The auxiliary input from the self-sustained output port 4 of the distributed power source PV that can be supplied to the auxiliary input port 5 of the distributed power source ES is 1.5 kW at maximum with AC 101V.

  When a self-sustained output is supplied from the distributed power source PV as an external AC power source to the auxiliary input port 5 during the self-sustained output of the distributed power source ES, the distributed power source ES detected by the voltage sensor 28 is a self-sustained output switch. 17 and the auxiliary input switch 18 are closed (the grid connection switch 16 is opened). Thereby, the electric power output from the distributed power source PV can be supplied to the specific load Rs via the self-supporting output port 4. When the power consumption of the specific load Rs is smaller than the maximum input to the auxiliary input port 5, that is, the maximum value of the independent output of the distributed power source PV is 1.5 kW, the storage battery 2B can be charged with the surplus power. Therefore, the output of the distributed power source PV can be used without waste.

<Example of 2 ES + PV>
Next, consider the parallel operation of two distributed power sources ES.

<< grid connection >>
FIG. 4 is a diagram illustrating an example of a circuit configuration of a distributed power supply system including two distributed power supplies and one distributed power supply PV. One of the two distributed power sources is ES-1, and the other is ES-2. In the figure, for the sake of clarity, the circuits of the independent output and auxiliary input that are not used during grid connection are omitted.

  The three lines (U, O, W) of the AC circuit 3 include a grid connection circuit 41 that connects the outputs of the two distributed power sources ES-1 and ES-2 and the distributed power source PV in parallel with each other. It is out. These three distributed power sources ES-1, ES-2, and PV operate to input or output two lines (U line, W line, AC 202V) of the AC circuit 3. Currents flowing through the U line and the W line of the AC circuit 3 are detected by current sensors 31 and 32, respectively. Further, a current sensor 33 is provided on the electric circuit connected from the distributed power source PV to the W line of the AC electric circuit 3. The detection outputs of the current sensors 31 to 33 are provided to the control unit 30 in the distributed power supply ES-1, for example. The control unit 30 can measure the power at the power receiving point based on the current values detected by the current sensors 31 and 32.

  Further, the output current of the distributed power source PV is measured by the current sensor 33. Since the distributed power source PV has a two-wire output, the current sensor 33 may be provided on any one of the U line and the W line branched from the main line.

  First, considering only one distributed power source ES-1, at this time, the current detection signals of the current sensors 31, 32 are input to the control unit 30 of the distributed power source ES-1, and the distributed power source ES- 1 The power at the power receiving point can be obtained by calculation multiplied by the system voltage that can be detected inside. Therefore, if the output current of the distributed power source ES-1 is controlled so that the power at the receiving point becomes zero (that is, so as not to reverse power flow), the power equal to the consumer's load consumption can be obtained. Can be output.

Next, consider power control when two distributed power sources ES-1 and ES-2 and one distributed power source PV are combined with each other.
First, in the distributed power sources ES-1 and ES-2, one of the two is a master and the other is a slave. The detection output signal lines of the current sensors 31 to 33 are input to the master control unit 30. The master calculates the power at the receiving point in the same manner as in the case of one unit, sets the charge / discharge power command value based on the result, and distributes the command value to the master and the slave. Various distribution methods can be considered, but if the power is distributed according to the remaining amount of the storage battery according to the following equation (1) at the time of discharging and according to the equation (2) at the time of charging, the remaining battery amounts of the master and the slave will deviate from each other. It is possible to maintain a consistent state without any problems.

It is defined as follows.
P: Charge / discharge power command value for both master and slave (sign is positive for discharge and negative for charge)
P ₁ : Master charging / discharging power command value P ₂ : Slave charging / discharging power command value X ₁ : Master battery remaining power (full charge state is 1, full discharge state is 0)
X ₂ : Battery level of the slave (full charge state is 1, full discharge state is 0)

Discharge equation (1)
P ₁ = P × {X ₁ / (X ₁ + X ₂ )}
P ₂ = P−P ₁

Charging formula (2)
P ₁ = P × [(1-X ₁ ) / {(1-X ₁ ) + (1-X ₂ )}]
P ₂ = P−P ₁

  All of the above calculations are performed by the master control unit. Therefore, the slave power command value needs to be transmitted from the master control unit to the slave control unit. Therefore, it is necessary to install a communication line for this purpose between the slave and the master. Since the calculation of power is performed in the AC cycle of the voltage of the commercial power system, transmission of the command value from the master to the slave is performed in the AC cycle or a cycle that is a multiple of the AC cycle. The command value is transmitted by RS-485 communication, for example. There is no problem in RS-485 communication because it is only necessary to follow the input / output of the slave with a delay of 100 ms or less with respect to the load of the customer or the fluctuation of the photovoltaic power generation. When the power command value is given, the subsequent control controls the current so that both the master and the slave synchronize with the system voltage detected internally. This control is the same as the operation of one unit.

<Independent output>
Next, the case of independent output will be described.
In the self-sustained output, the connection form (a) in which the self-sustained outputs of the two distributed power sources ES-1 and ES-2 are connected in parallel so that the maximum output is 3 kVA with AC 101 V, and the self-sustained output is connected in series. It is conceivable that the connection form (b) is to provide a phase three-wire output. As the connection form (a), a master / slave system and a CVCF (Constant Voltage Constant Frequency) system are further considered.

(Master / Slave method)
FIG. 5 is a diagram showing an example of a circuit configuration in which two distributed power sources ES-1 and ES-2 are connected in parallel and the distributed power source PV is used as an auxiliary input. This figure focuses only on the interconnection of the self-sustained output, and the illustration of the circuit configuration at the time of system interconnection is omitted.

  In the figure, the independent output ports 4 of the distributed power sources ES-1 and ES-2 are connected in parallel to each other. Further, the auxiliary input ports 5 of the distributed power sources ES-1 and ES-2 and the independent output ports 4 of the distributed power source PV are connected in parallel to each other.

  One of the two distributed power sources ES-1 and ES-2 is a master and the other is a slave. The master performs CVCF control, and the slave performs current control based on the AC power output by the master. Since the slave performs current control, no cross current flows between the master and the slave. To determine the slave current command value, it is necessary to measure the load current.

  Therefore, as shown in FIG. 5, a current sensor 34 is provided in the electric path between the connection point of the outputs of the two distributed power sources ES-1 and ES-2 and the specific load Rs, and the signal of the detected output is slaved. To the control unit 30. At the time of grid connection, the signal lines of the current sensors 31, 32, 33 are connected to the master, but since no current sensor is connected to the slave, the port is vacant. That is, if the master and slave at the time of system interconnection (FIG. 4) are used as the master and slave at the time of independent output, the current sensor port can be assigned.

  The slave sets its own current command value so as to share a part of the load current. Even in the circuit configuration of FIG. 5, the power sharing ratio between the master and the slave can be arbitrarily selected by adjusting the current command value of the slave as in the case of the two-unit parallel operation at the time of grid connection. For example, if the current command value is set according to the equation (1), more power is supplied from the one with the more remaining battery power, so the deviation of the remaining battery power between the two distributed power sources ES-1 and ES-2. Is corrected, and a consistent state can always be maintained. If the power factor of the load is poor and reactive power must be supplied, supply more reactive power from the one with the least remaining battery power, and output more active power from the one with sufficient remaining capacity. Since the output currents of the two distributed power sources ES-1 and ES-2 can be equalized while equalizing the remaining battery power, a load corresponding to a maximum output of 3 kVA can be connected.

  Next, consider the case where the independent output of the distributed power source PV is connected to the auxiliary input ports 5 of the distributed power sources ES-1 and ES-2. As shown in the drawing, the self-sustained output circuit of the distributed power source PV is branched and connected to the auxiliary input ports 5 of the two distributed power sources ES-1 and ES-2. When a voltage by a self-sustained output of the distributed power source PV is input to each auxiliary input port 5 (detected by the voltage sensor 28), the distributed power sources ES-1 and ES-2 close the auxiliary input switch 18, The power of the self-sustained output is supplied to the specific load Rs via the self-sustained output port 4.

  When the auxiliary input switches 18 of the two distributed power sources ES-1 and ES-2 are closed simultaneously, the maximum power that can be supplied to the specific load Rs is determined by the independent output of the distributed power source PV. In general, the independent power output of the distributed power source PV is 1.5 kVA at the maximum, similar to the distributed power sources ES-1 and ES-2, so only one of the power sources of the distributed power sources ES-1 and ES-2 has a specific load. It is impossible to supply to Rs. Therefore, the two auxiliary input switches 18 are not closed at the same time, and only the auxiliary input switch 18 of the distributed power source ES-1 is closed. The auxiliary input switch 18 of the distributed power source ES-2 is opened, and only the self-supporting output switch 17 is closed.

  At this time, the distributed power source ES-2 performs current control based on the output voltage of the distributed power source PV detected by the voltage sensor 28. Therefore, the distributed power source ES-2 needs a measured value of the load current to determine the current command value, and it is necessary to connect the signal line of the current sensor 34 to the control unit 30. If the operation is continued in this state, the remaining battery level is 100% for the distributed power source ES-1 and 0% for the distributed power source ES-2, and the deviation between the two increases. Therefore, when the difference becomes large to some extent, the master and the slave must be changed.

  As a result of the change, the distributed power source ES-2 becomes the master and the distributed power source ES-1 becomes the slave, but the signal line of the current sensor 34 is connected to the distributed power source ES-2. -1 does not have load current information necessary to determine the current command value. Since the signal lines of the current sensors 31 to 33 (FIG. 4) are already connected to the control unit 30 of the distributed power source ES-1, if the signal line of the current sensor 34 is further connected, The number of ports must be increased. Although a method of sending load current information from the distributed power source ES-2 to the distributed power source ES-1 by communication is also conceivable, it is difficult to control because of a delay. If the master-slave change is not performed quickly, there is a risk that the specific load Rs stops.

  As described above, the master / slave system in parallel connection has the advantage that the cross current does not flow and the power sharing between the master and the slave can be arbitrarily adjusted, but there is a problem in quickly switching the auxiliary input.

(CVCF parallel operation method)
Next, consider the CVCF parallel operation system. In this case, the two distributed power sources ES-1 and ES-2 are both output by CVCF control. At this time, a cross current flows unless the amplitude and phase of the output voltage are matched. The main circuit configuration is the same as that of FIG. 5 except that the current sensor 34 for measuring the load current is unnecessary. However, it is necessary to provide a communication line for transmitting and receiving a synchronization signal for matching outputs. As the synchronization signal, for example, a pulse that switches from the L level to the H level at a zero cross where the AC voltage changes from negative to positive can be used.

  Even in this method, only one of the two auxiliary input switches 18 is closed. Since the distributed power source with the auxiliary input switch 18 closed is the voltage of the self-sustained output of the distributed power source PV, the other must match the amplitude and phase of the voltage. Therefore, the distributed power source with the auxiliary input switch 18 turned on transmits a synchronization signal generated based on the voltage detection value of the self-sustained output of the distributed power source PV to the other. It is the same as the master / slave method that the auxiliary input is used in the middle so that the deviation of the remaining battery level does not increase. In the master / slave system, the CVCF control and the current control are switched. In the CVCF parallel operation system, the transmission side and the reception side of the synchronization signal are switched.

  The CVCF parallel operation method has an advantage that the current sensor 34 is unnecessary, but has a problem that a cross current easily flows. In particular, when one side supplies the self-sustained output of the distributed power source PV to the specific load Rs via the auxiliary input, it is difficult to match the amplitude even if the phase is adjusted by the synchronization signal, so that a cross current of effective current flows. Cheap.

(Series connection method)
As an embodiment of the present invention, this series connection system is reached.
FIG. 6 is a diagram showing an example of a circuit configuration in which two distributed power sources ES-1 and ES-2 are connected in series and the distributed power source PV is used as an auxiliary input. This figure focuses only on the interconnection of the self-sustained output, and the circuit configuration at the time of system interconnection is not shown.

  In the figure, the self-sustained output port 4 of the distributed power source ES-1 is connected to the U line and the O line by a self-sustained output circuit 42. The self-sustained output port 4 of the distributed power source ES-2 is connected to the W line and the O line by a self-sustained output circuit 42. The AC phase of the self-sustained output from the distributed power source ES-1 and the AC phase of the self-sustained output from the distributed power source ES-2 are controlled by the respective control units 30 that perform synchronized control so as to be inverted. In the serial connection method, a single-phase three-wire output is provided, and power can be supplied to both the 200 V specific load Rsuw and the 100 V specific loads Rsuo and Rswo. Further, the auxiliary input ports 5 of the distributed power sources ES-1 and ES-2 and the independent output ports 4 of the distributed power source PV are connected in parallel to each other.

  In the series connection method, the two distributed power sources ES-1 and ES-2 both perform CVCF control. Cross current does not flow, but for 200V output, the absolute value of the voltage is the same as each other and must be matched so that the phases of the two units are inverted. Therefore, the synchronization signal is necessary as in the CVCF parallel operation method, but the current sensor 34 (FIG. 5) used in the master / slave method is not necessary.

  If all of the two auxiliary input switches 18 and the independent output switch 17 are closed simultaneously, the independent output of the distributed power source PV is short-circuited and breaks down. Therefore, the auxiliary input switch 18 must always be closed out of the two units. Must be one side only. Even in this method, since the auxiliary input switch 18 is closed, the voltage of the self-sustained output of the distributed power source PV becomes the voltage, and the other must match the amplitude and phase of the voltage.

  Therefore, the distributed power source that closed the auxiliary input switch 18 transmits a synchronization signal generated based on the voltage detection value of the self-sustained output of the distributed power source PV to the other side. It is the same as the CVCF parallel operation method that the connection with the self-sustained output of the distributed power source PV and the transmission / reception of the synchronization signal are switched in the middle so that the deviation of the remaining battery level does not increase. In order to shorten the instantaneous interruption at the time of the change as much as possible and maintain the synchronization state immediately after the switching, for example, the change may be made at the timing of the zero crossing of the voltage.

  In the serial connection method, the battery remaining amount differs between the two distributed power sources unless the specific load Rsuo between the U line and the O line and the specific load Rswo between the W line and the O line are balanced. When the stand-alone output of the mold power source PV can be used, it is possible to adjust the auxiliary input appropriately so that the deviation of the remaining battery level does not increase. When the remaining battery level of the battery reaches 0 first, only the remaining battery outputs AC 100V.

《Summary about independent output》
The features regarding the connection mode of the independent output by the two distributed power sources ES-1 and ES-2 are summarized as follows.

The parallel connection master / slave system has the following advantages.
(I) Cross current does not flow.
(Ii) The output power of two units can be set individually.
(Iii) It is not necessary to output a signal such as a synchronization signal for performing synchronized control.
Disadvantages include the following points.
(I) A current sensor for measuring the load current is required.
(Ii) Cannot be used for 200V load.
Further, regarding the auxiliary input, it is necessary to switch between the master (CVCF control) and the slave (current control), and it is also necessary to measure the load current.

The CVCF parallel operation system connected in parallel has the following advantages.
(I) A current sensor for measuring the load current is not required.
(Ii) Load inrush current. Large tolerance for starting current.
Disadvantages include the following points.
(I) A signal output for performing synchronized control is required.
(Ii) A cross current flows unless the amplitude and phase of the two output voltages match each other.
(Iii) The output voltages of the two units cannot be set individually.
(Iv) Cannot be used for 200V load.
Further, regarding the auxiliary input, it is necessary to change between transmission and reception of signal output for performing synchronized control.

In the serial connection method, the following points are mentioned as advantages.
(I) Can be used for both 200V load and 100V load.
(Ii) No cross current flows.
(Iii) A current sensor for measuring the load current is not required.
Disadvantages include the following points.
(I) A signal output for performing synchronized control is required.
(Ii) When one battery level becomes 0, it cannot be used for a 200V load.
Further, regarding the auxiliary input, it is necessary to change between transmission and reception of signal output for performing synchronized control.

  According to the above summary, it can be used for both 200V and 100V loads, and there are fewer control problems than the parallel connection master / slave method and CVCF parallel operation method. It is considered preferable to select In addition, since the power conversion device has a single-phase output and does not use a neutral wire leg or an AC reactor, it is possible to reduce circuit elements that are used infrequently and used only for self-sustained output.

FIG. 7 is a diagram showing a circuit configuration in which FIG. 4 (system interconnection) and FIG. 6 (independent output by a serial connection method) are overlapped.
In the grid connection, the master and slave are determined to distribute the outputs of the two units, current sensors that measure the current at the power receiving point and the output current of the distributed power source PV are connected to the master side, and output to the slave by communication Send power command value. In the self-supporting output, both 200V load and 100V load can be used, and there is no problem of cross current.

<Others>
7 shows an example in which the distributed power sources ES-1 and ES-2 exchange necessary information between the control units 30, but another control is provided above the two control units 30. A section may be provided as a management section, and the management section may instruct necessary information. As such a management unit, for example, a remote control device having display and operation functions related to power can be used.

《Supplementary Note》
The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

1B, 1P Power converter 2B Storage battery 2P Photovoltaic power generation panel 3 AC circuit 4 Autonomous output port 5 Auxiliary input port 6 DC side capacitor 7 DC reactor 8 DC / DC converter 9 Intermediate capacitor 10 DC bus 11 Inverter 12 AC reactor 13 AC side Capacitor 14, 15 Capacitor 16 System interconnection switch 17 Self-sustained output switch 18 Auxiliary input switch 21 Voltage sensor 22 Current sensor 23 Voltage sensor 24 Current sensor 25, 26 Voltage sensor 27 Current sensor 28 Voltage sensor 30 Control unit 31, 32, 33, 34 Current sensor 41 Grid connection circuit 42 Self-sustained output circuit ES, ES-1, ES-2 Distributed power source PV Distributed power source Pu, Pw Phase power source Ruo, Rwo, Ruw load Rsuo, Rswo, Rsuw Specific load

Claims (5)

In a distributed power supply system connected to a single-phase three-wire AC circuit, when the single-phase three-wire voltage lines are U lines and W lines, and the neutral lines are O lines,
A first DC power source, and a power converter provided between the first DC power source and the AC circuit, and a single-phase first distributed power source having two wires for independent output;
A single-phase second distributed power source including a second DC power source and a power conversion device provided between the second DC power source and the AC circuit, and having two wires for self-sustained output;
For the self-sustained output, the two lines of the first distributed power supply are connected to the U line and the O line of the AC circuit, and the two lines of the second distributed power supply are connected to the W line and the O line of the AC circuit. Electric circuit,
A controller that inverts the AC phase of the self-sustained output from the first distributed power source and the AC phase of the self-sustained output from the second distributed power source;
Distributed power supply system. A distributed power supply system that can be connected to a single-phase three-wire AC circuit connected to a commercial power system, where the single-phase three-wire voltage lines are U and W lines, and the neutral line is an O line.
A single-phase first distributed type including a first DC power source and a power converter provided between the first DC power source and the AC circuit, and having two lines of independent outputs in addition to a normal output line Power supply,
A single-phase second distributed type including a second DC power source and a power conversion device provided between the second DC power source and the AC circuit, and having two lines of independent output in addition to a normal output line Power supply,
A grid interconnection circuit that connects the output line of the first distributed power source and the output line of the second distributed power source in parallel to each other and connects to the AC circuit;
For the self-sustained output, the two lines of the first distributed power supply are connected to the U line and the O line of the AC circuit, and the two lines of the second distributed power supply are connected to the W line and the O line of the AC circuit. Electric circuit,
A controller that inverts the AC phase of the self-sustained output from the first distributed power source and the AC phase of the self-sustained output from the second distributed power source;
Distributed power supply system. Each of the first distributed power source and the second distributed power source includes an auxiliary input port that receives an input from an independent external AC power source,
One of the first distributed power supply and the second distributed power supply outputs the voltage of the external AC power supply via the auxiliary input port, and outputs a signal for performing synchronized control based on the voltage And
The other of the first distributed power source and the second distributed power source outputs a voltage that is synchronized with and inverted from the voltage of the external AC power source based on the signal by disconnecting the auxiliary input port. ,
The distributed power supply system according to claim 1 or 2.   The distributed power supply system according to claim 3, wherein the one distributed power source and the other distributed power source are alternately switched.   5. The distributed power supply system according to claim 3, wherein the DC power supply is a storage battery, and the one distributed power supply outputs and charges the voltage of the external AC power supply to the storage battery.