WO2015145971A1

WO2015145971A1 - Power conversion device and power conversion method

Info

Publication number: WO2015145971A1
Application number: PCT/JP2015/000973
Authority: WO
Inventors: 後藤　周作
Original assignee: パナソニックＩｐマネジメント株式会社
Priority date: 2014-03-28
Filing date: 2015-02-26
Publication date: 2015-10-01
Also published as: JP2015192549A

Abstract

A power control system (U1) is provided with a DC bus (L1) for connecting at least one converter (21-26) to an inverter (30), and a control unit (31) for controlling the bus voltage of the DC bus (L1). The control unit (31) is connected to sensors (M1, M2) for detecting power inputted/outputted with respect to the at least one converter (21-26) and the inverter (30). The control unit (31) calculates the power loss of the entire system on the basis of the input/output power detected by the sensors (M1, M2), and controls the bus voltage of the DC bus (L1) on the basis of the calculated power loss.

Description

Power conversion device and power conversion method

The present invention relates to a power conversion device and a power conversion method using an inverter.

In recent years, distributed power supply devices using distributed power sources such as solar power generation and fuel cells are becoming popular. The distributed power supply device converts DC power generated by the distributed power supply into AC power by a power converter such as a power conditioner and outputs the AC power to a commercial power system.

The power conditioner includes a converter and an inverter connected to the converter by a DC bus. The inverter converts the DC voltage generated by the converter into an AC voltage having the same frequency as the system voltage.

In order to reduce the loss of the inverter, a technique for changing the amplitude of the voltage of the bus between the inverter and the converter has been studied (for example, see Patent Document 1).

JP 2004-104963 A

In the technique of Patent Document 1, when a solar cell is used in a distributed power source, it is difficult to use in combination with maximum power tracking (MPPT) that controls the maximum output power of the solar cell due to the influence of bus voltage fluctuations. The power generation efficiency of the entire system does not increase.

Generally, the bus voltage is set to a value obtained by adding a margin of 20 to 40 V to the maximum amplitude value of the system voltage as an inverter output. Since the maximum amplitude when the system voltage is AC200V is 283V, the bus voltage is set to around 320V. If the bus voltage is too high, the loss in the inverter increases, so the bus voltage is set as low as possible. When the bus voltage is lowered, the distortion rate of the output current increases. For this reason, it is necessary to lower the bus voltage in a range where the distortion rate satisfies a specified value.

However, even when the bus voltage is lowered, the loss of the entire device is not necessarily reduced.
As shown in FIG. 9A, the inverter loss is minimized at a low bus voltage. On the other hand, in the converter, the bus voltage that minimizes the loss differs. Further, the bus voltage at which the loss is minimized varies depending on the type of converter. For example, when the first converter having the characteristics shown in FIG. 9B and the second converter having the characteristics shown in FIG. 9C are connected to the inverter having the characteristics shown in FIG. As shown in FIG. 9D, the bus voltage for minimizing the loss in the entire system is calculated.

Also, since the output voltage of the distributed power supply also changes, when the bus voltage is fixed, the power loss is deviated from the low bus voltage. For this reason, it is difficult to reduce power loss and efficiently convert input power to output power.

The objective of this invention is providing the power converter device which converts input power into output power efficiently.
A power converter according to an aspect of the present invention is connected to a DC bus that connects a converter and an inverter, and a sensor that detects input / output power of each of the converter and the inverter, and controls the bus voltage of the DC bus. A part. The control unit calculates a power loss in the converter and the inverter based on the input / output power acquired from the sensor, and executes a loss reduction process for controlling the bus voltage of the DC bus based on the power loss. .

According to one aspect of the present invention, input power can be efficiently converted to output power. Other aspects and advantages will become apparent from the following description taken in conjunction with the drawings, which illustrate examples of the technical spirit of the present invention.

The block diagram of the power converter device in 1st Embodiment. The flowchart of the bus voltage control in 1st Embodiment. Explanatory drawing of the fluctuation | variation process of the bus voltage in 1st Embodiment. The flowchart of the bus voltage control in 2nd Embodiment. It is a bus voltage characteristic of the power converter device in 2nd Embodiment, Comprising: (a) is a total loss, (b) is explanatory drawing of the distortion rate of the output current of an inverter. The flowchart of the bus voltage control in 3rd Embodiment. Explanatory drawing of two bus voltage control modes in 3rd Embodiment. It is explanatory drawing of the time change of the bus voltage in 3rd Embodiment, (a) is the waveform matched with the inverter output, (b) is the waveform which provided the lower limit, (c) is a stepped waveform, (D) is explanatory drawing of a square-wave-like waveform. It is explanatory drawing of the relationship between the power loss and bus voltage in a prior art, (a) is the loss in an inverter, (b) is the loss in a 1st converter, (c) is the loss in a 2nd converter, (d) Is an explanatory diagram of the total loss.

<First Embodiment>
The first embodiment will be described with reference to FIGS. As shown in FIG. 1, the power control system U <b> 1 of the first embodiment is configured to effectively use energy creation and energy storage. The power control system U1 includes a converter unit 20 including at least one converter and an inverter 30. Converter unit 20 and inverter 30 are connected via a DC wiring (DC bus L1). The DC bus L1 is preferably provided with monitors M1 and M2, which will be described later. The converter unit 20 is connected to the distributed power source 10, and the inverter 30 is connected to a system power source 50 that is a commercial power source. This power control system U1 functions as a power converter that adjusts the DC voltage (bus voltage) of the DC bus L1 in order to reduce the overall power loss (for example, the total power loss of the converter unit 20 and the inverter 30).

The distributed power supply 10 can include one or a plurality of power supply devices such as the

solar cell panels

11, 12, 13, the fuel cell 14, the storage battery 15, and the electric vehicle 16.

Solar cell panels

11, 12, and 13 are power generation devices that convert solar energy into DC power, and function as energy creation devices. Each

solar panel

11, 12, 13 includes a plurality of solar cells.

The fuel cell 14 is a power generation device that obtains DC power by chemically reacting hydrogen and oxygen using a hydrogen-containing fuel gas such as natural gas and an oxygen-containing oxidant gas such as air. Function.

The storage battery 15 is a battery that charges electric power or supplies charged electric power, and is an energy storage device that can be used repeatedly.
The electric vehicle 16 includes an in-vehicle charging device and is driven by an electric motor, and functions as an energy storage device that supplies electric power stored in the in-vehicle charging device to a house. The electric vehicle 16 includes a plug-in hybrid car that is provided with a gasoline engine and that can be supplied and charged directly from a household power source using a plug (plug-in device).

The converter unit 20 can include converters 21 to 26 connected to the

solar cell panels

11, 12, 13, the fuel cell 14, the storage battery 15, and the electric vehicle 16 of the distributed power source 10. Each of the converters 21 to 26 generates a pulse voltage from the input DC voltage by turning on / off the switching element (switching control), and generates a necessary DC voltage (for example, DC 350 V) based on the duty ratio of the pulse current. Perform chopper control.

Converters 21 to 23 are connected to the solar cell panels 11 to 13, respectively, and perform maximum power point tracking control (MPPT control) according to the generated power affected by the solar radiation condition. Each converter 21 to 23 converts the output (DC voltage) of the corresponding solar cell panel 11 to 13 into a bus voltage value and outputs it to the DC bus L1. A monitor M1, which will be described later, is provided on the power line connecting the converters 21 to 23 and the corresponding solar cell panels 11 to 13.

The converter 24 is connected to the fuel cell 14, converts the output (direct current) of the fuel cell 14 into a bus voltage value, and outputs it to the DC bus L1. A power supply line connecting the converter 24 and the fuel cell 14 is provided with a monitor M1 described later.

The converter 25 is connected to the storage battery 15, converts the output (direct current) of the storage battery 15 into a bus voltage value and outputs it to the DC bus L 1, or supplies power supplied from the DC bus L 1 to the storage battery 15. . A power line connecting the converter 25 and the storage battery 15 is provided with a monitor M1 described later.

When the converter 26 is connected to the electric vehicle 16, the converter 26 converts the output (direct current) of the electric vehicle 16 into a bus voltage value and outputs it to the DC bus L 1, or supplies the electric power supplied from the DC bus L 1 to the electric vehicle 16. Or supply. A power supply line connecting the converter 26 and the electric vehicle 16 is provided with a monitor M1 described later.

The

converters

25 and 26 connected to the energy storage devices (15, 16) charge the energy storage device when the bus voltage value increases, and discharge the energy storage device when the bus voltage value decreases, thereby causing the bus voltage to discharge. Configured or programmed to maintain a constant value.

Converters 21 to 26 are connected to a single inverter 30 via DC bus L1. The inverter 30 includes a switching control unit that may be the control unit 31.
The switching control unit of the inverter 30 adjusts the output voltage using the duty ratio of the pulse by performing switching control of the switching element of the inverter 30. Here, it converts into the alternating current power (for example, AC202V, 50Hz) of the voltage and frequency which can be connected with the system power supply 50 with the duty ratio of pulse current.

The inverter 30 supplies AC power to the system power supply 50 via a distribution board (not shown). The amount of AC power is measured by a power meter provided between the distribution board and the commercial system. A home load for supplying AC power is connected to the distribution board.

The inverter 30 includes a control unit 31. The control unit 31 performs switching control in the inverter 30 and controls the bus voltage of the DC bus L1. In order to control the bus voltage, the control unit 31 includes a monitor management unit 311 and a voltage adjustment unit 312.

The monitor management unit 311 acquires information on the input values (voltage, current) and output values (voltage, current) of the converters 21 to 26 and the inverter 30 from the monitors M1 and M2.
The voltage adjustment unit 312 optimizes the bus voltage based on the total loss.

The converters 21 to 26 and the inverter 30 are provided with monitors M1 and M2, respectively. Each monitor M1, M2 measures the voltage and current of the connected power supply line. The monitors M1 and M2 are connected to the control unit 31 of the inverter 30 through the communication line L2.

In each of the converters 21 to 26, the monitor M1 is provided between the converter and the distributed power source 10, and the monitor M2 is provided on the DC bus between the converter and the inverter 30.

In the inverter 30, the monitor M1 is provided on the DC bus L1 side (converters 21 to 26 side), and the monitor M2 is provided on the system power supply 50 side.
Next, a bus voltage control process for reducing the total loss will be described with reference to FIG.

First, the control unit 31 of the inverter 30 executes a forced change process of the bus voltage (step S01). For example, the voltage adjustment unit 312 of the control unit 31 slightly changes the bus voltage from the high voltage side to the low voltage side. In the example shown in FIG. 3, the bus voltage is oscillated by a minute voltage ΔVB from the median to the high voltage side and the low voltage side. A voltage that is forcibly changed to the high voltage side by a minute voltage ΔVB from the median value may be referred to as a high voltage fluctuation voltage. Similarly, a voltage that is forcibly changed from the median to the low voltage side by a minute voltage ΔVB may be referred to as a low voltage fluctuation voltage. The median may be referred to as the candidate bus voltage.

Next, the control unit 31 of the inverter 30 executes a monitoring process (step S02). For example, the monitor management unit 311 of the control unit 31 obtains a voltage value and a current value corresponding to each of the median value of the bus voltage, the high voltage side fluctuation voltage, and the low voltage side fluctuation voltage from each of the plurality of monitors M1 and M2. Acquire and store in memory.

Next, the control unit 31 of the inverter 30 executes a comparison process of the total loss before and after the forced fluctuation of the bus voltage (step S03). Here, the voltage adjustment unit 312 of the control unit 31 is based on the voltage value and the current value stored in the memory, and the power loss at the median value of the bus voltage, the power loss at the high voltage side fluctuation voltage, and the low voltage side fluctuation voltage. Calculate power loss. For example, the voltage adjustment unit 312 performs the following processing for each of the median value of the bus voltage, the high voltage side fluctuation voltage, and the low voltage side fluctuation voltage. First, the voltage adjustment unit 312 calculates input power and output power of each of the converters 21 to 26 and the inverter 30. Then, voltage adjustment unit 312 calculates the power loss in each of converters 21-26 and inverter 30 from the difference between the input power and output power of each of converters 21-26 and inverter 30. Furthermore, voltage adjustment unit 312 calculates the power loss in DC bus L1 using the difference between the total output power of converters 21 to 26 and the input power in inverter 30. Then, the voltage adjustment unit 312 adds up the power loss in each of the converters 21 to 26, the inverter 30, and the DC bus L1, and calculates the total loss.

Next, the control unit 31 of the inverter 30 executes a determination process as to whether or not the loss is reduced (step S04). For example, the voltage adjustment unit 312 of the control unit 31 compares the total loss at the median, the total loss at the high voltage side fluctuation voltage, and the total loss at the low voltage side fluctuation voltage. If either the overall loss at the high voltage side fluctuation voltage or the overall loss at the low voltage side fluctuation voltage is reduced with respect to the overall loss at the median value, it is determined that the loss is reduced.

When it is determined that the overall median loss is the smallest and the loss is not reduced (in the case of “NO” in step S04), the control unit 31 of the inverter 30 returns to the forced fluctuation processing of the bus voltage (step S01).

On the other hand, when it is determined that either the total loss at the high voltage side fluctuation voltage or the total loss at the low voltage side fluctuation voltage is a loss reduction (in the case of “YES” in step S04), the control unit 31 of the inverter 30 The median value of forced change is changed (step S05). For example, the voltage adjustment unit 312 of the control unit 31 updates the bus voltage (high voltage side or low voltage side) with the smallest overall loss as the median value of the bus voltage.

Then, using the updated median value, control unit 31 of inverter 30 repeats the forced change processing (step S01) of the bus voltage.
According to the first embodiment, the following effects can be obtained.

(1) In the first embodiment, the control unit 31 of the inverter 30 performs a forced change process of the bus voltage (step S01), a monitoring process (step S02), and a comparison process of the total loss before and after the forced change of the bus voltage (step S03). ). When any of the total loss at the high voltage side fluctuation voltage and the total loss at the low voltage side fluctuation voltage is determined to be a loss reduction with respect to the median total loss (in the case of “YES” in step S04), The control unit 31 of the inverter 30 changes the median value of forced fluctuation (step S05). Thus, the overall loss of the power control system U1 is reduced by changing the bus voltage to the minimum loss. Therefore, the power control system U1 can sell more electric power, and can extend the life of devices and the like by reducing loss.

(2) In the first embodiment, the control unit 31 of the inverter 30 repeats the forced fluctuation processing (step S01) of the bus voltage. The bus voltage value at which the loss is minimized varies depending on the operating status of the distributed power supply 10. Therefore, the overall loss of the power control system U1 can be reduced in accordance with the operating status of the distributed power source 10.

<Second Embodiment>
Next, a second embodiment will be described with reference to FIGS. In the first embodiment, the control unit 31 determines the bus voltage based on the decrease in overall loss. In the second embodiment, the control unit 31 of the inverter 30 calculates the distortion rate of the output current of the inverter 30 in order to optimize the bus voltage. The control unit 31 holds data relating to the upper limit value of the distortion rate of the output current.

The bus voltage control of the second embodiment will be described with reference to the flowchart of FIG.
As in steps S01 to S04 in FIG. 2, the control unit 31 of the inverter 30 performs a forced fluctuation process of the bus voltage (step S11), a monitoring process (step S12), and a comparison process of the total loss before and after the forced fluctuation (step S13). The determination process (step S14) is executed. When it is determined that the total loss of the median is the smallest and the loss is not reduced (in the case of “NO” in step S14), the control unit 31 of the inverter 30 returns to the forced fluctuation processing of the bus voltage (step S11).

When it is determined that either the total loss at the high voltage side fluctuation voltage or the total loss at the low voltage side fluctuation voltage is a loss reduction (in the case of “YES” in step S14), the control unit 31 of the inverter 30 Is executed to determine whether or not is within the specified range (step S15). For example, the voltage adjustment unit 312 of the control unit 31 calculates the distortion rate of the output current, and compares the calculated distortion rate with the upper limit value. When the calculated distortion rate is less than or equal to the upper limit value, it is determined that the calculated distortion rate is within the specified range.

When it is determined that the distortion rate is not within the specified range (in the case of “NO” in step S15), the control unit 31 of the inverter 30 returns to the forced variation processing of the bus voltage (step S11).
On the other hand, when it is determined that the distortion rate is within the specified range (in the case of “YES” in Step S15), the control unit 31 of the inverter 30 changes the median value of the forced variation (Step S16), similarly to Step S05.

For example, as shown in FIG. 5A, it is assumed that the overall loss can be reduced by lowering the bus voltage. As shown in FIG. 5B, when the bus voltage is decreased and the distortion rate exceeds the upper limit value, the control unit 31 does not change the bus voltage.

According to the second embodiment, the following effects can be obtained.
(3) The distortion rate of the output current of a typical inverter may deteriorate at a low bus voltage. Therefore, in the second embodiment, the control unit 31 of the inverter 30 determines whether the distortion rate is within a specified range (step S15). When it is determined that the distortion rate is within the specified range (in the case of “YES” in step S15), the control unit 31 of the inverter 30 changes the median value of forced fluctuation (step S16). Therefore, the overall loss of the power control system U1 can be reduced while avoiding the deterioration of the distortion rate, that is, while maintaining the power quality.

<Third Embodiment>
Next, a third embodiment will be described with reference to FIGS. In 3rd Embodiment, the control part 31 is comprised so that the bus voltage control mode of a bus voltage may be changed according to the condition (for example, the electric power input condition to a converter) of the electric power control system U1.

For example, the voltage adjustment unit 312 includes a storage device that holds data (mode switching reference value) for determining a bus voltage control mode (bus voltage control mode) according to the operating status of the distributed power supply 10. it can. In the example of FIG. 7, a predetermined photovoltaic power generation amount is set as the mode switching reference value. The control unit 31 determines the bus voltage control mode based on the comparison between the power generation amount of the solar battery panels 11 to 13 and the mode switching reference value. The bus voltage control mode can include first and second bus voltage control modes. In the first bus voltage control mode, the control unit 31 executes the bus voltage control process for reducing the overall loss described in the first and second embodiments. In the second bus voltage control mode, the control unit 31 executes a bus voltage control process giving priority to reducing the loss of the inverter 30, as will be described later.

The control unit 31 is connected to each of the converters 21 to 26 via the communication line L2. The control unit 31 transmits a control signal to each of the converters 21 to 26. In this case, each of the converters 21 to 26 adjusts the output based on the control signal.

Next, the bus voltage control process will be described with reference to FIG.
The control unit 31 of the inverter 30 acquires the operating status information of the distributed power supply (step S21). For example, the monitor management unit 311 of the control unit 31 acquires the operating status of the corresponding distributed power supply 10 from the monitor M1 connected to the converters 21 to 26. For example, the operation status of the solar cell panels 11 to 13 is indicated by the input power (the amount of power generated by the solar cell panels 11 to 13) acquired from the monitor M1 connected to the converters 21 to 23. The control unit 31 changes the bus voltage control method according to the operation status of the solar cell panels 11 to 13.

Next, the control unit 31 of the inverter 30 determines whether to give priority to the reduction of the inverter loss (step S22). For example, the voltage adjustment unit 312 of the control unit 31 determines whether to give priority to reducing the power loss of the inverter 30 based on the operating status of the distributed power source 10. The control unit 31 compares the power generation amount of the solar battery panels 11 to 13 with the mode switching reference value, and determines that the inverter loss is not prioritized when the power generation amount is larger than the mode switching reference value.

When it is determined that the inverter loss is not prioritized (in the case of “NO” in step S22), the control unit 31 of the inverter 30 enters the first bus voltage control mode and, as in the first and second embodiments, the total loss A bus voltage control process for reducing the above is executed (step S23).

When it is determined that the inverter loss priority is given (in the case of “YES” in step S22), the control unit 31 of the inverter 30 enters the second bus voltage control mode and acquires the system voltage waveform (step S24). For example, the voltage adjustment unit 312 of the control unit 31 acquires the system voltage waveform and / or the voltage, cycle, and phase of the system voltage waveform from the monitor M2 of the inverter 30, and calculates the rectified waveform.

Next, the control unit 31 of the inverter 30 determines a bus voltage waveform corresponding to the system voltage waveform (step S25). For example, the voltage adjustment unit 312 of the control unit 31 specifies a bus voltage waveform corresponding to the cycle and phase of the system voltage waveform. Further, the voltage adjustment unit 312 determines the voltage value of the bus voltage based on the rectified waveform of the system voltage waveform in the bus voltage waveform.

Next, the control unit 31 of the inverter 30 controls the converter so that the determined bus voltage waveform is obtained (step S26). For example, the voltage adjustment unit 312 of the control unit 31 transmits a control signal to each of the converters 21 to 26 so that the same output as the determined bus voltage waveform is obtained.

FIG. 8 shows some specific examples of the bus voltage waveform corresponding to the waveform of the system voltage (the waveform of the output of the inverter 30). The output waveform of the inverter 30 may be a full-wave rectified waveform.

In the example shown in FIG. 8A, the bus voltage waveform has an output voltage slightly higher than the output of the inverter 30 and a waveform that matches the waveform of the inverter 30. When instructing the output of the bus voltage waveform, the control unit 31 causes the

converters

25 and 26 connected to the energy storage device (the storage battery 15 and the electric vehicle 16) to discharge the energy storage device when the bus voltage increases. The target bus voltage waveform is generated by instructing charging of the energy storage device when the bus voltage drops.

In the example shown in FIG. 8B, the lower limit value of the bus voltage is set. The control unit 31 keeps the voltage value constant when the bus voltage drops to a predetermined lower limit value while performing the same control as in FIG. As the lower limit value, the control power supply voltage of various devices such as the inverter 30 can be used, whereby the bus voltage can be used as the control power supply of various devices.

In the example shown in FIG. 8C, the control unit 31 raises and lowers the bus voltage stepwise according to the system voltage waveform. It is preferable that the control unit 31 sets the bus voltage higher than the system voltage by matching the cycle and phase of the bus voltage waveform with the period and phase of the system voltage waveform. Such stepped voltage control can reduce the loss in the inverter 30 while reducing the load required to control the bus voltage.

In the example shown in FIG. 8D, the control unit 31 instructs to output a square wave bus voltage corresponding to the system voltage waveform. The bus voltage value is preferably set so that the cycle and phase of the bus voltage waveform coincide with the cycle and phase of the system voltage waveform and the bus voltage does not become lower than the system voltage. Such square-wave voltage control can reduce the loss in the inverter 30 while reducing the load required to control the bus voltage.

According to the third embodiment, the following effects can be obtained.
(4) In 3rd Embodiment, the control part 31 of the inverter 30 acquires the operating condition information of a distributed power supply (step S21), and determines whether it is inverter loss priority (step S22). As a result, the bus voltage can be controlled in consideration of power loss in accordance with the operating status of the distributed power supply 10. For example, when using photovoltaic power generation as the distributed power source 10, it is desirable to set the bus voltage to a constant value in order to extract the maximum output power of the solar cell. On the other hand, when the output of the solar cell is small, the power loss of the inverter 30 can be reduced by controlling the bus voltage according to the system voltage waveform.

(5) In the third embodiment, when it is determined that the inverter loss is prioritized (in the case of “YES” in step S22), the control unit 31 of the inverter 30 enters the second bus voltage control mode and acquires the system voltage waveform. (Step S24), the bus voltage waveform is determined (Step S25), and the converter is controlled (Step S26). For example, the inverter 30 is caused to function as a switch that switches the polarity of the bus voltage. In this case, since the switching loss can be reduced, the loss of the inverter 30 can be reduced.

(6) In the third embodiment, the control unit 31 has a voltage slightly higher than the output of the inverter 30 and instructs the output of a waveform that matches the output waveform of the inverter 30. The control unit 31 discharges the storage battery 15 when the bus voltage is increased, and charges the storage battery 15 when the bus voltage is decreased, thereby reducing a loss generated when the bus voltage is shaped into a sine wave. it can.

The control unit 31 of the inverter 30 can instruct the output of the bus voltage waveform based on a predetermined lower limit value. In many cases, the bus voltage is a control power supply for the entire inverter 30. Therefore, the bus voltage can be used as the control power supply without preparing a separate control power supply.

The control unit 31 of the inverter 30 can also instruct the output of a waveform that changes the bus voltage in stages. Thereby, the power loss of the inverter 30 can be reduced by changing the bus voltage discretely.

The embodiment may be modified as follows.
In each embodiment, wireless communication or power line communication may be used instead of or in addition to the communication line L2.

In the first embodiment, the control unit 31 of the inverter 30 executes a forced fluctuation process of the bus voltage (step S01). The forced variation includes oscillating at a minute voltage ΔVB with respect to the median value. If the power loss can be evaluated in the forced fluctuation processing of the bus voltage, the fluctuation range is not limited to the minute voltage ΔVB. For example, forced fluctuation may be performed with various fluctuation ranges. In some examples, a wide voltage range is used to search a wide range of bus voltages for reducing the overall loss, and a narrow voltage range is used to optimize the bus voltage.

In the first embodiment, the control unit 31 of the inverter 30 changes the median value of forced fluctuation (step S05). Here, the control unit 31 of the inverter 30 may perform control so that the bus voltage is equal to or higher than the lower limit value. In this case, the control power supply voltage of various devices such as the inverter 30 is used as the lower limit value. Thus, the bus voltage can be used as a control power source for various devices.

The distributed power source 10 is not limited to including all of the

solar cell panels

11, 12, 13, the fuel cell 14, the storage battery 15, and the electric vehicle 16. The distributed power supply 10 may include other distributed power supplies, or may be configured by a combination of some of these.

Some of the converters 21 to 26 of the converter unit 20 may be omitted.
For example, the control unit 31 may be provided in a distributed power system (multi-power conditioner) in which a plurality of converters are connected to a single inverter.

In each embodiment, the control unit 31 of the inverter 30 performs a bus voltage control process. The control unit 31 may not be provided in the inverter 30. Control unit 31 may be a bus voltage control device that is provided separately from inverter 30 and performs a bus voltage control process.

In the third embodiment, the control unit 31 of the inverter 30 acquires the operating status information of the distributed power supply (step S21), and changes the bus voltage control mode according to the operating status. Here, the determination method of the bus voltage control mode is not limited to the operating status of the distributed power supply 10. For example, the bus voltage control mode may be changed according to the time determined according to the season. In this case, the control unit 31 of the inverter 30 changes the bus voltage control mode according to a time zone during which power can be generated by sunlight and a time zone during which power generation is difficult.

In the third embodiment, the control unit 31 may change the bus voltage control mode based on environmental conditions acquired from a natural environment sensor that acquires environmental conditions such as solar radiation and temperature.
In the third embodiment, in the second bus voltage control mode, the bus voltage control process giving priority to the loss reduction of the inverter 30 is executed. Here, converters 21 to 23 connected to

solar cell panels

11, 12, and 13, which are energy creation devices, may perform control (MPPT control: maximum power point tracking control) that maximizes the power to be extracted. . Thereby, it is possible to reduce the overall loss while effectively utilizing the energy creation device.

The control unit 31 includes one or a plurality of computer processors that realize a bus voltage control method by executing program codes or software stored in a computer-readable storage medium or storage device, which may be a RAM, a ROM, an EEPROM, or the like. Can be included.

The present disclosure includes the following examples.
[1] In one example, the power converter is connected to a DC bus that connects a converter and an inverter, and a sensor that detects input / output power of each of the converter and the inverter, and controls a bus voltage of the DC bus. A control unit is provided. The controller calculates a power loss in the converter and the inverter based on the input / output power acquired from the sensor, and executes a loss reduction process for controlling the bus voltage based on the power loss.

[2] In some examples, the control unit forcibly varies the bus voltage and calculates power loss before and after the variation.
[3] In some examples, the control unit calculates a distortion rate of the output current of the inverter, and controls the bus voltage so that the distortion rate is included in a specified range.

[4] In some examples, the control unit controls the bus voltage so as to be included in a range equal to or higher than a predetermined lower limit value.
[5] In some examples, the control unit specifies an input state of electric power to the converter, and performs a first bus voltage control mode and a second bus voltage control mode according to the input state. In the first bus voltage control mode, the loss reduction process is executed, and in the second bus voltage control mode, the bus voltage is controlled with priority on the reduction of power loss in the inverter. Execute.

[6] In some examples, the inverter is connected to a system power supply, and the control unit has a waveform bus voltage corresponding to the system power waveform of the system power supply in the second bus voltage control mode. It is preferable to control.

[7] In some examples, a chargeable / dischargeable power storage device is connected to the converter, and the control unit instructs the converter to discharge from the power storage device when the bus voltage increases. When the bus voltage drops, the converter is instructed to charge the power storage device.

[8] A power converter comprising: a DC bus that connects the converter and the inverter; and a control unit that is connected to a sensor that detects input / output power of each of the converter and the inverter and controls the bus voltage of the DC bus. Is used to provide a method of converting power. The method calculates power loss in the converter and inverter based on input / output power acquired from the sensor, and controls loss reduction processing for controlling the bus voltage based on the power loss. The department comprises performing.

[9] At least one distributed power source, at least one converter connected to the at least one distributed power source, an inverter connected to the at least one converter via a DC bus, and the at least one converter And a sensor that detects input / output power of each of the inverters, and a controller that is connected to the sensors and controls the bus voltage of the DC bus. The control unit calculates a power loss in the at least one converter and the inverter based on the input / output power acquired from the sensor, and calculates a total of the power loss in the at least one converter and the power loss in the inverter. In order to reduce, the bus voltage of the DC bus is controlled based on the calculated power loss.

[10] In some examples, the distributed power source includes a solar panel.
You may combine embodiment, a modification, and an Example suitably.
This invention is not limited to what was illustrated. For example, the illustrated features should not be construed as essential to the invention, but rather the subject matter of the invention may be present in fewer features than all the features of the particular embodiment disclosed. The present invention is defined by the terms of the claims, and is intended to include any modifications within the scope equivalent to the terms of the claims.

Claims

A DC bus connecting the converter and the inverter;
A power converter connected to a sensor that detects input / output power of each of the converter and the inverter, and a controller that controls a bus voltage of the DC bus,
The controller is
Based on the input / output power acquired from the sensor, the power loss in the converter and the inverter is calculated,
A power conversion apparatus that performs loss reduction processing for controlling a bus voltage of the DC bus based on the power loss.
The power conversion device according to claim 1, wherein the control unit forcibly varies the bus voltage and calculates power loss before and after the variation.
3. The power according to claim 1, wherein the control unit calculates a distortion rate of the output current of the inverter and controls the bus voltage so that the distortion rate is included in a specified range. Conversion device.
The power converter according to any one of claims 1 to 3, wherein the control unit controls the bus voltage so as to be included in a range equal to or greater than a predetermined lower limit value.
The control unit specifies an input state of power to the converter,
According to the input situation, the first bus voltage control mode and the second bus voltage control mode are selected,
In the first bus voltage control mode, the loss reduction processing is executed,
The power according to any one of claims 1 to 4, wherein in the second bus voltage control mode, a process of controlling the bus voltage is executed with priority given to a reduction in power loss in the inverter. Conversion device.
The inverter is connected to a system power supply,
The power converter according to claim 5, wherein the control unit controls the bus voltage to have a waveform corresponding to a system power waveform of the system power supply in the second bus voltage control mode.
The converter is connected to a chargeable / dischargeable power storage device,
The controller instructs the converter to discharge from the power storage device when the bus voltage increases, and instructs the converter to charge the power storage device when the bus voltage decreases. The power converter according to claim 6, wherein
Using a power converter that includes a DC bus that connects the converter and the inverter, and a sensor that detects the input and output power of each of the converter and the inverter, and includes a control unit that controls the bus voltage of the DC bus, A method for converting power,
Based on the input / output power acquired from the sensor, the control unit calculates the power loss in the converter and the inverter,
The power conversion method, wherein the control unit executes a loss reduction process for controlling the bus voltage based on the power loss.
At least one distributed power source;
At least one converter connected to the at least one distributed power source;
An inverter connected to the at least one converter via a DC bus;
A sensor for detecting input / output power of each of the at least one converter and the inverter;
A system connected to the sensor and controlling a bus voltage of the DC bus,
The controller is
Based on the input / output power acquired from the sensor, the power loss in the at least one converter and the inverter is calculated,
The system configured to control the bus voltage of the DC bus based on the calculated power loss to reduce the sum of the power loss of the at least one converter and the power loss in the inverter.
The system of claim 9, wherein the at least one distributed power source includes a solar panel.