JP2015046974A - Power conversion device and power conversion method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a power conversion device and a power conversion method capable of supplying power preferentially to a grid having a specific apparatus connected thereto by controlling output in accordance with the amount of power inputted to the power conversion device.SOLUTION: A power conversion device 100 according to the present invention is a power conversion device capable of grid-connected operation, comprising a single-phase three-wire inverter 102 for outputting a two-phase voltage in two voltage lines and outputting an intermediate potential in a neutral line; and a control unit 103 for controlling the voltage or frequency of the voltage lines in accordance with the amount of power at input. The control unit 103 switches, in accordance with the amount of power at input, between a first operation mode for outputting AC output in opposite phases each other in the two voltage lines and a second operation mode for exerting first control for outputting AC output in one of the two voltage lines and outputting the same potential as the output potential of the neutral line in the other of the two voltage lines and second control for outputting AC output in phase with each other in the two voltage lines.

Description

  The present invention relates to a power conversion device and a power conversion method for controlling output according to the amount of input power.

  The power conditioner for photovoltaic power generation, the power conditioner for storage battery, and the like have an AC output of 100V. Some of these power conditioners are capable of supplying power to devices by independent operation that can be independently supplied from a power system as an independent power source in the event of a power failure. In recent years, power conditioners having a single-phase three-wire AC output of 100 V / 200 V have been commercialized. For example, Patent Document 1 proposes a control method for a single-phase three-wire inverter device that is interconnected with a single-phase three-wire distribution network. A power conditioner having such a single-phase three-wire AC output outputs a 100-V / 200-V single-phase three-wire AC output in the event of a power failure, and is connected to a single-phase three-wire wiring in the home. 100V and 200V devices can be operated.

JP 7-163153 A

  However, in solar power generation, for example, when solar radiation is weakened during self-sustained operation and the power required by the connected equipment cannot be supplied, the power generation must be stopped. Supply will be stopped. For this reason, when the user wants to continue supplying power to a specific device when the power generation amount decreases, it is necessary to stop some devices according to the power generation amount in order to prevent the power generation from stopping.

  Further, in the storage battery, the supply of power is stopped when the remaining battery level is exhausted. Since the power consumption depends on the connected device, when the remaining battery level is low and the user wants to maintain the power supply to a specific device, some devices can be used to reduce the power consumption. Need to stop.

  An object of the present invention, which has been made in view of the above problems, is to preferentially supply power to a system to which a specific device is connected by controlling the output according to the amount of power input to the power converter. An object of the present invention is to provide a power conversion device and a power conversion method that can be supplied.

In order to solve the above-described problems, the invention of the power converter according to the present invention is as follows.
A power conversion device capable of grid connection operation,
A single-phase three-wire inverter that outputs a two-phase voltage on two voltage lines and outputs an intermediate potential on a neutral line when converting the input direct current into an alternating current;
A control unit for controlling the voltage or frequency of the voltage line according to the amount of power of the input;
It is characterized by providing.

In the power converter according to the present invention,
According to the amount of power of the input, the control unit
A first operation mode in which AC output is performed in opposite phases to each other in the two voltage lines;
A first control in which one of the two voltage lines is AC output and the other is output the same potential as the output potential of the neutral line, or a second AC output is in phase with each other on the two voltage lines The second operation mode for performing the control is switched.

  In the power conversion device according to the present invention, the control unit may switch at least one of the two voltage lines in switching between the first operation mode and the second operation mode for performing the second control. One frequency is changed until the phase of the frequency of the two voltage lines coincides.

  Further, in the power conversion device according to the present invention, the control unit changes at least one frequency of the two voltage lines within a frequency deviation target value of a jurisdiction electric power company.

In the power converter according to the present invention,
The input is supplied from a power generator,
The control unit controls a voltage or a frequency of the voltage line according to a power generation amount of the power generation device.

In the power converter according to the present invention,
The input is supplied from a storage battery,
The said control part controls the voltage or frequency of the said voltage line according to the battery remaining charge of the said storage battery, It is characterized by the above-mentioned.

  The power conversion device according to the present invention further includes a storage unit that stores which of the first control and the second control is performed in the second operation mode. .

  Moreover, in the power converter according to the present invention, the control unit monitors the output currents of the two voltage lines during the first operation mode, and steadily exceeds a predetermined value of the two voltage lines. A voltage line for outputting the current of the second operation mode, the AC output of the determined voltage line in the first control of the second operation mode, and the other voltage line having the same potential as the output potential of the neutral line. Is output.

  In the power converter according to the present invention, the control unit controls the voltage or the frequency of the voltage line during a self-sustained operation in which power can be independently supplied after being disconnected from the power system. .

  As described above, the solution of the present invention has been described as an apparatus, but the present invention can be realized as a method substantially corresponding to these, and the scope of the present invention also includes these. I want you to understand.

For example, the power conversion method according to the present invention is:
Single-phase three-wire that outputs two-phase voltage on two voltage lines and outputs an intermediate potential on a neutral line when converting input direct current to alternating current in a power conversion device capable of system interconnection operation A power conversion method for controlling an output voltage of an inverter of a formula,
The method includes a step of controlling a voltage or a frequency of the voltage line in accordance with the input electric energy.

  According to the power conversion device and the power conversion method according to the present invention configured as described above, by controlling the output according to the amount of power input to the power conversion device, to the system to which a specific device is connected Power can be supplied preferentially.

It is a block diagram which shows the schematic structural example of the power converter device which concerns on one Embodiment of this invention. It is a circuit block diagram of the single phase three-wire inverter in the power converter device which concerns on one Embodiment of this invention. It is a schematic diagram of the change of the voltage of the U-phase line and the W-phase line in switching from the first operation mode to the first control in the second operation mode according to an embodiment of the present invention. It is a schematic diagram of the change of the voltage of the U-phase line and the W-phase line in switching from the first operation mode to the second control of the second operation mode according to one embodiment of the present invention. It is a flowchart which shows the process of the power converter device which concerns on one Embodiment of this invention.

  Hereinafter, an embodiment according to the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a block diagram illustrating a schematic configuration example of a power conversion device according to an embodiment of the present invention. As shown in FIG. 1, the power converter (power conditioner) 100 includes a DC / DC converter 101, a single-phase three-wire inverter 102, a control unit 103, and a storage unit 104. The DC / DC converter 101, the inverter 102, and the storage unit 104 are connected to the control unit 103. The DC / DC converter 101 and the inverter 102 are connected to each other.

  The power conversion device 100 converts DC power input from an arbitrary power input device 105 such as a power generation device such as a solar battery or a wind power generator or a storage battery. The power conversion device 100 is normally connected to the power system and performs a connected operation. When a power failure occurs in the power system, the power conversion apparatus 100 releases the connection and performs a self-sustained operation. Supply to the load (loading device 106) in the consumer. Hereinafter, in the description of the present embodiment, the power input device 105 will be described as being a solar cell 105.

  The DC / DC converter 101 converts the input DC voltage from the solar cell 105 to the power conversion device 100 into a required voltage, and outputs the converted voltage to the inverter 102.

  Inverter 102 converts the DC voltage from DC / DC converter 101 into an AC voltage. The inverter 102 is normally connected to the power system, but performs an independent operation in the event of a power failure or the like, and disconnects from the power system via the distribution board 107 and supplies AC power to the load device 106. FIG. 1 shows the connection between the power conversion apparatus 100 and the load device 106 during a self-sustained operation. Hereinafter, in the description of this embodiment, the inverter 102 will be described as performing a self-sustained operation.

  The control unit 103 controls the output of the DC / DC converter 101 and the inverter 102 by controlling the duty ratio of the switching elements of the DC / DC converter 101 and the inverter 102. In addition, the control unit 103 monitors the power amount of the solar cell 105 via the DC / DC converter 101 during the independent operation disconnected from the power system, and outputs the output of the inverter 102 according to the monitored input power amount. Control. A specific output control method will be described in detail with reference to FIGS.

  The storage unit 104 stores control settings performed by the control unit 103 in accordance with the amount of power of the solar battery 105. In FIG. 1, the storage unit 104 is shown as a functional unit independent of the control unit 103, but the storage unit 104 can be omitted by incorporating the function of the storage unit 104 into the control unit 103.

  The distribution board 107 supplies power from the power conversion apparatus 100 to each load device 106. The distribution board 107 uses an internal current sensor 108 to monitor the current of each system supplied from the inverter 102. The monitoring result is sent to the storage unit 104 of the power conversion device 100 as necessary, and information regarding the monitoring result is stored in the storage unit 104. The current sensor 108 can be, for example, a CT (Current Transformer), and hereinafter, the current sensor 108 will be described as being a CT.

  FIG. 2 is a circuit configuration diagram of a single-phase three-wire inverter in the power conversion device according to the embodiment of the present invention, that is, a specific circuit configuration diagram of the inverter 102 in FIG. 1. As shown in FIG. 2, the inverter 102 includes a U-phase leg 201, an O-phase leg 202, and a W-phase leg 203. These U-phase leg 201, O-phase leg 202, and W-phase leg 203 are each provided with one switching element 204 at the top and bottom, and by performing complementary PWM (Pulse Width Modulation) control in each phase. The output voltage of each phase with respect to the input voltage from the DC / DC converter 101 is determined. In this embodiment, the O-phase leg 202 outputs an intermediate potential of the input voltage from the DC / DC converter to a neutral line (O-phase line) 206. That is, the duty ratio (on / off time ratio) of the switching element 204 related to the O-phase leg 202 is 0.5.

  In the circuit configuration shown in FIG. 2, for example, in order to output an AC voltage of 100 V to be supplied to a general household, the O-phase line 206 is fixed at an intermediate potential, so that the U-phase leg 201 and the W-phase leg 203 are output. , Sine waves of the same frequency are output to the voltage line (U-phase line) 205 and the voltage line (W-phase line) 207, respectively. Thereby, an AC voltage of 100 V can be realized between the O-phase line and the U-phase line and between the O-phase line and the W-phase line. Furthermore, if the 100 V sine wave of the same frequency of the U-phase line 205 and the W-phase line 207 is set in opposite phases, the potential difference between the U-phase line and the W-phase line becomes 200 V. A voltage output of 200V AC is realized. As described above, the case where the U-phase wire 205 and the W-phase wire 207 output alternating current in opposite phases is hereinafter referred to as “first operation mode”. In the first operation mode in the above example, the AC 100V output is between the O-phase line and the U-phase line and between the O-phase line and the W-phase line, and the AC 200V output is 1 between the U-phase line and the W-phase line. A system is provided.

  When it is necessary to suppress the power supply of the load device 106, the control unit 103 switches from the first operation mode to the second operation mode. In the second operation mode, the control unit 103 maintains the output of one system among the two systems of the AC 100 V output, and stops the output of the other one system, or the above The second control for stopping the AC 200V output is performed.

  First, the first control will be described. In order to perform the first control, the control unit 103 causes one of the two voltage lines (the U-phase line 205 and the W-phase line 207) to output 100 V AC similarly to the first operation mode, and the other to The voltage of the voltage line is controlled so that the same potential as the potential of the O-phase line 206 is output. For example, while the U-phase line 205 outputs 100 V alternating current, the W-phase line 207 outputs the same potential as the potential of the O-phase line 202, that is, an intermediate potential. While the voltage is output, the output is stopped because there is no potential difference between the O-phase line and the W-phase line.

  In order to switch from the first operation mode to the first control in the second operation mode, the control unit 103 sets the duty ratio of the switching element 204 related to the W-phase leg 203 to the switching element 204 in the O-phase leg 202. The voltage is controlled by making it equal to the duty ratio. That is, the first control is realized by the control unit 103 controlling the duty ratio of the switching element 204 in the W-phase leg 203 to be 0.5.

  FIG. 3 is a schematic diagram of changes in voltages of the U-phase line 205 and the W-phase line 207 in switching from the first operation mode to the first control in the second operation mode. The W-phase line 207 outputs 100V AC before time 301 and outputs it at the same potential (0V) as that of the O-phase line 206 after time 301. That is, two 100V AC outputs were provided before time 301, but after 301, 100V AC output was provided only in one system between the O-phase line and the U-phase line.

  Next, the second control will be described. In order to perform the second control, the control unit 103 controls the duty ratio of the switching element 204 so that the two voltage lines (the U-phase line 205 and the W-phase line 207) output 100 V AC in phase with each other. Thus, the frequency of the voltage line is controlled. When the U-phase line 205 and the W-phase line 207 output 100V AC in phase with each other, two AC 100V voltages are provided between the O-phase line and the U-phase line and between the O-phase line and the W-phase line. On the other hand, since the U-phase line 205 and the W-phase line 207 are in phase, there is no potential difference between the U-phase line and the W-phase line, and the AC 200V output is stopped.

  In order to switch from the first operation mode to the second control in the second operation mode, the control unit 103 sets the frequency of at least one of the U-phase line 205 and the W-phase line 207 to the frequency of both phases. The frequency is controlled so as to change until the phases match. For example, the control unit 103 generates a phase shift between both phases by increasing the frequency of the W-phase line 207 out of the U-phase line 205 and the W-phase line 207 that output alternating current in opposite phases in the first operation mode. When the phases of both phases are synchronized, control is performed so that the frequency of the W-phase line 207 is the same as that of the original U-phase line 205 in the first operation mode. By such control, the U-phase line 205 and the W-phase line 207 that are in opposite phases in the first operation mode can be output in the same phase in the second control. In order to synchronize the phases of both phases, the control unit can also synchronize the phases by making the frequency of the W-phase line 207 lower than the original frequency in the first operation mode. Similarly, the phase can be synchronized by changing the phase of the U-phase line 205 instead of the W-phase line 207.

  Furthermore, the frequency control performed by the control unit 103 to switch from the first operation mode to the second control in the second operation mode is performed simultaneously for the frequencies of both the U-phase line 205 and the W-phase line 207. be able to. For example, the control unit 103 increases the frequency of the W-phase line 207 and decreases the frequency of the U-phase line 205 so that when the phases of both phases are synchronized, the frequencies of both phases are restored to the original in the first operation mode. Control to make the frequency. By such control, it is possible to shorten the time until both phases are synchronized as compared with the case where the frequency of only one of the U-phase line 205 and the W-phase line 207 is changed.

  FIG. 4 is a schematic diagram of changes in voltages of the U-phase line 205 and the W-phase line 207 in switching from the first operation mode to the second control in the second operation mode. In FIG. 4, the U-phase line 205 and the W-phase line 207 initially output alternating current in opposite phases. However, when the frequency of the alternating-current output of the W-phase line 207 is increased, a shift occurs in both phases. When both phases are synchronized, the frequency of the W phase line 207 becomes the original frequency. In this way, the AC 200V output between the U-phase line and the W-phase line is stopped.

  When the control unit changes the frequency in order to switch from the first operation mode to the second control in the second operation mode as described above, the control unit 103 includes the U-phase line 205 and the W-phase line 207. At least one frequency can be changed within a frequency deviation target value of the jurisdiction electric power company. Since it is a standard for quality assurance that electrical appliances normally operate within the frequency deviation target value of the jurisdiction electric power company, each load device 106 is normal if the frequency fluctuates within the frequency deviation target value. This is because it is considered that the operation can be continued. For example, Tokyo Electric Power Co., Inc. defines a frequency deviation target value within ± 0.2 Hz with respect to a standard frequency of 50 Hz. Regarding this point, Tokyo Electric Power Co., Inc. “Frequency adjustment and inter-company interconnection in electric power companies” (URL: www.re-policy.jp/keito/2/030912_09.pdf), General Electric Power System Utilization Council “Summary of the proceedings of the 6th Wind Power Linkage Possible Working Group” (URL: http://www.escj.or.jp/energy/wg/pdf/wind_wg_6th_summary.pdf) and Tokyo Electric Power Company “Frequency Please refer to documents such as “Adjustment and Supply and Demand Operation Rules” (URL: www.tepco.co.jp/corporateinfo/provide/engineering/wsc/freq-j.pdf). Therefore, in the TEPCO jurisdiction, even if the control unit 103 changes the frequency of the U phase or the W phase within a range of ± 0.2 Hz, there is a possibility that the control unit 103 falls within the fluctuation of the frequency deviation target value range. High and can minimize the impact on appliance operation.

  The control unit 103 switches between the first operation mode and the second operation mode in which the first control or the second control is performed according to the amount of power of the solar cell 105 to the power conversion device 100. A specific switching method will be described in detail in the description of FIG. 5 below.

  Then, the process which the power converter device 100 in this embodiment performs is demonstrated using FIG. FIG. 5 is a flowchart illustrating processing of the power conversion device according to the present embodiment. It is assumed that the power conversion device 100 is operating in the first operation mode at the start of this flowchart.

  First, the control part 103 of the power converter device 100 acquires the electric power generation amount of the solar cell which is the power input device 105 via the DC / DC converter 101 (step S101). And the control part 103 judges whether switching of an operation mode is performed according to the acquired electric power generation amount of the solar cell 105. FIG. That is, the control unit 103 determines whether or not the acquired power generation amount is equal to or less than a set reference value (step S102). For example, the reference value may be unchanged, or may be set every time the load device 106 to be connected is changed or increased or decreased.

  When the acquired power generation amount is larger than the reference value (No in step S102), the control unit 103 continues the first operation mode and acquires the power generation amount of the solar cell 105 again. The control part 103 can acquire these electric power generation amounts of the solar cell 105, and can perform these steps which judge whether it is below a reference value regularly or irregularly. Further, the control unit 103 can always repeat these steps.

  When the power generation amount acquired due to bad weather and a decrease in the amount of solar radiation or the like is below the reference value (Yes in step S102), the control unit 103 changes the operation mode of the power conversion device 100 from the first operation mode. Switch to the second operation mode. As a switching step, first, the control unit 103 determines which of the first control and the second control is performed (step S103). For example, which of the first control and the second control is performed is stored in advance in the storage unit 104, and which control is performed by the control unit 103 based on the storage in the storage unit 104. Can be determined. The storage in the storage unit 104 can be performed by an installer or a user when the power conversion apparatus 100 is installed, for example. Further, for example, when the power generation amount of the solar battery 105 is reduced, the control unit 103 can make a determination based on the user input by causing the user to input which control is to be performed.

  When it is determined that the first control is to be performed (first control in step S103), the control unit 103 determines whether to continue outputting the voltage line of the U-phase line 205 or the W-phase line 207 next. (Step S104). The determination in step S104 is determined based on the relationship with the load device 106 connected to the U-phase line 205 or the W-phase line 207. For example, it is desirable to continue output to the voltage line to which the load device 106 that needs to be continuously operated is connected among the U-phase line 205 and the W-phase line 207. In this case, for example, a voltage line that is desired to continue output from the U-phase line 205 and the W-phase line 207 is stored in the storage unit 104 in advance, and the control unit 103 is based on the storage in the storage unit 104. Thus, it can be determined to continue the output to the voltage line where it is desirable to continue the output. The storage in the storage unit 104 can be performed by an installer or a user when the power conversion apparatus 100 is installed, for example. Further, for example, the user can input which voltage line to continue to output, and the control unit 103 can determine the voltage line to continue output based on the user's input.

  Further, in step S104 for determining a voltage line that continues to be output, the control unit 103 can monitor the output in each of the U-phase line 205 and the W-phase line 207 and make a determination based on the monitoring result. That is, first, the control unit 103 monitors the output voltages of the two voltage lines (U-phase line 205 and W-phase line 207) in the first operation mode. Specifically, the output current in each system of the U-phase line 205 and the W-phase line 207 is measured by the CT that is the current sensor 108 in the distribution board 107. Thereby, the output current in each system can be acquired in the first operation mode in which all systems of the single-wire three-phase inverter 102 can be used. The measured output current is sent to the storage unit 104 of the power conversion device 100. It is estimated that the load device 106 that needs to continue the output is connected to the voltage line that constantly outputs a current of a predetermined value or more among the two output currents obtained. . Therefore, the control unit 103 can determine a voltage line that constantly outputs a current of a predetermined value or more out of the two voltage lines as a voltage line that continues output. Note that the information on the measured output current can be accumulated from the start of measurement, or can be updated every certain unit time. For example, the information on the output current can be initialized at a time interval such as every day or every week and newly measured again.

  When control unit 103 determines to continue outputting to U-phase line 205 (U-phase in step S104), control unit 103 causes the determined U-phase line 205 to be AC output and the voltage line of the other W-phase line 207. Is output with the same potential as that of the O-phase line 206 (step S105). This control stops the output because there is no potential difference between the O-phase line and the W-phase line, and the AC 100V output is continued between the O-phase line and the U-phase line. In this way, the first control in the second operation mode is realized.

  In addition, when the control unit 103 determines to continue the output to the W-phase line 207 (the W-phase in step S104), the control unit 103 causes the determined W-phase line 207 to be AC output and the other U-phase line 203 to be output. The voltage line is made to output the same potential as that of the O-phase line 206 (step S106). This control stops the output because there is no potential difference between the O phase line and the U phase line, and the AC 100 V output is continued between the O phase line and the W phase line. In this way, the first control in the second operation mode is realized.

  On the other hand, when it is determined in step S103 that the second control is to be performed (second control in step S103), the control unit 103 includes at least two voltage lines of the U-phase line 205 and the W-phase line 207. One frequency is changed until the phase of the frequency of both voltage lines coincides (step S107). By this control, the AC 100V voltage is maintained between the O-phase line and the U-phase line and between the O-phase line and the W-phase line, and the AC 200V output between the U-phase line and the W-phase line is stopped. In this way, the second control in the second operation mode is realized.

  As described above, in the present embodiment, the control unit 103 of the power conversion device 100 performs the first AC operation in which the two voltage lines 205 and 207 output alternating current in opposite phases according to the power generation amount of the solar cell 105. Mode and the first control in which one of the two voltage lines 205 and 207 outputs an alternating current and the other outputs the same potential as the output potential of the neutral line 206, or the two voltage lines 205 and 207 are identical to each other. The operation mode is switched to the second operation mode in which the second control for AC output in phase is performed. That is, when the power generation amount of the solar battery 105 decreases, the control unit 103 stops the power supply to some systems by switching the inverter 102 from the first operation mode to the second operation mode. Thereby, the electric power which should be supplied to the load apparatus 106 from the power converter device 100 can be suppressed below to the electric power generation amount of the solar cell 105. FIG. Therefore, without stopping the individual devices by the user, stoppage of power supply to all systems is avoided, and preferential power supply to systems to which specific devices that are desired to continue operation is connected is provided. Will continue.

  Moreover, in this embodiment, the control part 103 of the power converter device 100 is the switching of the 1st operation mode and the 2nd operation mode which performs 2nd control, among two voltage lines 205 and 207. At least one frequency is changed within a target frequency deviation value of the jurisdiction electric power company until the frequency phases of the two voltage lines 205 and 207 coincide with each other. That is, in the switching of the operation mode, the control unit 103 changes the frequency within the target frequency deviation value of the jurisdiction electric power company, which is a standard for quality assurance of electrical appliances. Thereby, without interrupting the operation of the load device 106 operating at 100 V AC, the AC 200 V output is stopped, and the preferential power supply to the system to which the load device 106 operating at 100 V AC is connected is continued.

  Further, in the present embodiment, the control unit 103 of the power conversion device 100 monitors the output currents of the two voltage lines 205 and 207 during the first operation mode, and the steady state of the two voltage lines 205 and 207. In the first control of the second operation mode, a voltage line that outputs a current of a predetermined value or more is determined, the determined voltage line is AC output, and the other voltage line is set as the output potential of the neutral line 206. The same potential is output. That is, the control part 103 determines the system | strain which connects the load apparatus 106 with which it is desirable to provide an alternating current output continuously among each system | strain. As a result, even when the load device 106 connected to each system changes, the control unit 103 can determine the system to continue output each time, so the load device 106 that needs to continue output is connected. The power supply can be preferentially continued for the existing system.

  Although the above embodiments have been described as representative examples, it will be apparent to those skilled in the art that many changes and substitutions can be made within the spirit and scope of the invention. Therefore, the present invention should not be construed as being limited by the above-described embodiments, and various modifications and changes can be made without departing from the scope of the claims.

  For example, the functions included in each component, each step, etc. can be rearranged so that there is no logical contradiction, and multiple components, steps, etc. can be combined or divided into one It is.

  In the description of the above-described embodiment, the case where the control unit 103 switches from the first operation mode to the second operation mode has been described. However, the present invention is not limited to this aspect, and the control unit 103 is not limited thereto. Can be switched from the second operation mode to the first operation mode according to the power generation amount of the solar battery 105. That is, the control unit 103 switches from the first operation mode to the second operation mode when the power generation amount of the solar cell 105 decreases due to a decrease in the amount of solar radiation, etc. When the amount increases, the second operation mode can be switched to the first operation mode.

  Switching from the second operation mode to the first operation mode can be performed by the same method as the switching from the first operation mode to the second operation mode in the description of the above-described embodiment. For example, when switching from the first control in the second operation mode to the first operation mode, the control unit 103 uses the neutral line (O) of the two voltage lines (the U-phase line 205 and the W-phase line 207). By controlling the duty ratio of the switching element on the voltage line outputting the same potential as the output potential of the phase line 206), a 100V sine wave is output. Further, when switching from the second control of the second operation mode to the first operation mode, the control unit 103 controls at least the duty ratio of the switching element 204 to at least one of the two voltage lines 205 and 207. One frequency is changed until the phase of the frequency of the two voltage lines 205 and 207 is reversed.

  With such control, it is possible to effectively use the load device 106 in all systems according to the amount of power generated by the solar cell 105 while continuing to supply power preferentially to the system to which the specific load device 106 is connected. .

  In the description of the above-described embodiment, the control unit 103 has been described as controlling the voltage or frequency of the voltage line according to the power generation amount of the solar cell that is the power generation device as the power input device 105. The invention is not limited to this aspect, and the control unit 103 can control the voltage or frequency of the voltage line according to the remaining battery level of the storage battery as the power input device 105, for example. In this case, whether or not the control unit 103 switches from the first operation mode to the second operation mode (corresponding to step S102 in FIG. 3) is whether or not the remaining battery level of the storage battery is equal to or less than a reference value. Is determined based on The control unit 103 does not switch the operation mode when the remaining battery level is greater than the reference value, and switches the operation mode when the remaining battery level is equal to or less than the reference value. In this way, by switching the operation mode according to the remaining battery level of the storage battery, when the remaining battery level is low, the user stops the system to which some load devices 106 are connected without stopping individual devices. As a result, power consumption in the entire load device 106 can be reduced, and preferential power supply to the system to which the specific load device 106 is connected can be continued.

DESCRIPTION OF SYMBOLS 100 Power converter 101 DC / DC converter 102 Inverter 103 Control part 104 Memory | storage part 105 Power input device (solar cell)
106 Load device 107 Distribution board 108 Current sensor 201 U-phase leg 202 O-phase leg 203 W-phase leg 204 Switching element 205 Voltage line (U-phase line)
206 Neutral wire (O-phase wire)
207 Voltage line (W-phase line)
301 time

Claims (10)

A power conversion device capable of grid connection operation,
A single-phase three-wire inverter that outputs a two-phase voltage on two voltage lines and outputs an intermediate potential on a neutral line when converting the input direct current into an alternating current;
A control unit for controlling the voltage or frequency of the voltage line according to the amount of power of the input;
A power conversion device comprising: According to the amount of power of the input, the control unit
A first operation mode in which AC output is performed in opposite phases to each other in the two voltage lines;
A first control in which one of the two voltage lines is AC output and the other is output the same potential as the output potential of the neutral line, or a second AC output is in phase with each other on the two voltage lines The power conversion device according to claim 1, wherein the power conversion device is switched to a second operation mode in which the control is performed. In the switching between the first operation mode and the second operation mode for performing the second control, the control unit sets the frequency of at least one of the two voltage lines to the two voltage lines. The power conversion device according to claim 2, wherein the frequency conversion is performed until the phases of the frequencies coincide with each other. The power converter according to claim 3, wherein the control unit changes at least one frequency of the two voltage lines within a frequency deviation target value of a jurisdiction electric power company. The input is supplied from a power generator,
The said control part controls the voltage or frequency of the said voltage line according to the electric power generation amount of the said electric power generating apparatus, The power converter device as described in any one of Claim 1 to 4 characterized by the above-mentioned. The input is supplied from a storage battery,
The said control part controls the voltage or frequency of the said voltage line according to the battery residual amount of the said storage battery, The power converter device as described in any one of Claim 1 to 4 characterized by the above-mentioned. 7. The storage device according to claim 2, further comprising a storage unit that stores which of the first control and the second control is performed in the second operation mode. 8. The power converter device described in 1. The control unit monitors the output current of the two voltage lines during the first operation mode, and determines a voltage line that constantly outputs a current of a predetermined value or more out of the two voltage lines, The first control in the second operation mode is characterized in that the determined voltage line is AC output, and the other voltage line is output with the same potential as the output potential of the neutral line. The power conversion device according to any one of 2 to 7. 9. The control unit according to claim 1, wherein the control unit controls the voltage or the frequency of the voltage line during a self-sustaining operation in which power can be supplied independently after being disconnected from the power system. 10. The power converter device described in 1. Single-phase three-wire that outputs two-phase voltage on two voltage lines and outputs an intermediate potential on a neutral line when converting input direct current to alternating current in a power conversion device capable of system interconnection operation A power conversion method for controlling an output voltage of an inverter of a formula,
A power conversion method comprising the step of controlling the voltage or frequency of the voltage line in accordance with the amount of input power.

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