JP2018183035A - Power conversion device and control method thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a power conversion device in which conversion efficiency of power conversion is improved and in which a stable and excellent total current distortion factor of an alternating current is achieved.SOLUTION: A power conversion device 1 is provided between a commercial power system 3 and a DC power supply 2 having a lower voltage than a peak value of an absolute value of an AC voltage of the commercial power system, and performs conversion of DC power into AC power or vice versa. The power conversion device is provided with a control unit 12 which generates a period in which, in a half cycle of an AC, according to the phase of the AC, one among a DC/DC converter 10 and a full-bridge circuit performs a switching operation, and the other is paused. The control unit sets, on the basis of a voltage of the AC power, a voltage change by an AC reactor, respective reactive currents flowing through an intermediate capacitor and an AC-side capacitor, and a voltage of the DC power, a current target value of the DC/DC converter to be synchronized with a current of the AC power, and uses, as a voltage of the AC power, a voltage in which a phase is compensated, in consideration of detection or a delay in a control system, to a fundamental wave that is extracted on the basis of an AC voltage detection value of the commercial power system.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a power converter and a control method thereof.

A power conversion device that converts a DC voltage output from a storage battery into an AC voltage and provides it to a load is often used as a backup power supply device such as a UPS (Uninterruptible Power Supply) (for example, See Figure 1). Such a power conversion device includes a DC / DC converter that boosts the voltage of a storage battery, and an inverter that converts direct current into alternating current. In addition, the power conversion device is bi-directional, and usually converts the AC voltage output from an AC power supply such as a commercial power supply into a DC voltage suitable for charging to charge the storage battery. In this case, the inverter is an AC / DC converter, and the DC / DC converter exhibits a step-down function.
On the other hand, a power conditioner (power conditioner) is also used to convert direct current power obtained from a direct current power source such as solar power generation into alternating current power and perform grid interconnection with an alternating current power system (for example, patent document 2)).

JP 2003-348768 A Unexamined-Japanese-Patent No. 2000-152651 JP, 2014-241714, A

  In the conventional power converter as described above, both the AC / DC converter and the DC / DC converter are constituted by switching elements, and always perform high-speed switching. Such switching elements are associated with minute switching losses. Although the switching loss per one time is small, when a plurality of switching elements perform switching at a high frequency, a switching loss that can not be ignored as a whole occurs. This switching loss is naturally a power loss. On the other hand, although the control system which reduces a loss is proposed by patent document 2, a sufficient loss reduction effect can not be acquired by that alone, and there also exists a problem that distortion generate | occur | produces in alternating current waveform.

  Therefore, a conversion scheme (hereinafter referred to as the minimum switching conversion) in which switching pause periods are alternately provided in the AC / DC converter and the DC / DC converter by a part of the inventor of the present invention to minimize the number of switching times as a whole The power conversion device which reduces switching loss etc. and obtains high conversion efficiency is proposed by the method. However, regarding the total current distortion factor during grid connection, the quality is further improved, and even if the AC voltage of the commercial power system is not very good, oscillation and the like of the power conversion device are prevented and stable excellent I want to make it possible to obtain an overall current distortion rate.

  In view of the above problems, the present invention aims to stably improve the overall current distortion rate of alternating current, as well as to improve conversion efficiency in a power conversion device.

  The present disclosure includes the following inventions. However, the present invention is defined by the scope of claims.

  The power conversion device according to one aspect of the present invention is provided between a commercial power grid and a DC power supply having a voltage lower than the peak value of the absolute value of the AC voltage, and converts DC power into AC power or vice versa. A DC / DC converter connected between the DC power supply and the DC bus, an intermediate capacitor connected between two lines of the DC bus, the DC bus, and the DC bus A full bridge circuit provided between a commercial power system, a filter circuit provided between the commercial power system and the full bridge circuit and including an alternating current reactor and an alternating current side capacitor; A control unit for causing one of the DC / DC converter and the full bridge circuit to perform a switching operation and the other for causing a pause according to the phase of The unit is based on a voltage of the AC power, a current flowing through the AC reactor, a voltage change due to an impedance of the AC reactor, a reactive current flowing through each of the intermediate capacitor and the AC side capacitor, and a voltage of the DC power. The current target value of the DC / DC converter is set to be synchronized with the current of the AC power, and a fundamental wave extracted based on the AC voltage detection value of the commercial power system as a voltage of the AC power, This power converter uses a voltage whose phase is captured in consideration of delay of detection and control system.

  A control method of a power conversion device according to one aspect of the present invention includes a DC / DC converter connected between a DC power supply and a DC bus, and an intermediate capacitor connected between two lines of the DC bus. A full bridge circuit provided between the DC bus and a commercial power system, and a filter circuit provided between the commercial power system and the full bridge circuit and including an AC reactor and an AC-side capacitor; In a power conversion device that performs conversion of DC power of the DC power supply having a voltage lower than the peak value of the absolute value of the commercial power system into AC power or vice versa, the control method of the power conversion device executed by the control unit The voltage of the AC power, the current flowing through the AC reactor, and the voltage change due to the impedance of the AC reactor, the intermediate capacitor, and the AC side co The current target value of the DC / DC converter is set to be synchronized with the current of the AC power based on the reactive current flowing through each of the capacitors and the voltage of the DC power, thereby generating an AC current within the AC half cycle. According to the phase of one of the DC / DC converter and the full bridge circuit to perform a switching operation, the other causes a pause period, wherein the voltage of the AC power is an AC voltage of the commercial power system. It is a control method of a power converter using a voltage in which a phase is supplemented in consideration of a delay of a detection or control system as a fundamental wave extracted based on a voltage detection value.

  The power converter according to another expression of the present invention is provided between the commercial power grid and the DC power supply having a voltage lower than the peak value of the absolute value of the AC voltage, and converts DC power into AC power or A power conversion device that performs the reverse conversion, comprising: a DC / DC converter connected between the DC power supply and a DC bus; an intermediate capacitor connected between two lines of the DC bus; and the DC bus A full bridge circuit provided between the first and the commercial power system, a filter circuit provided between the commercial power system and the full bridge circuit, the circuit including an alternating current reactor and an alternating current side capacitor; And a control unit that causes one of the DC / DC converter and the full bridge circuit to perform a switching operation and the other causes a pause depending on the phase of the alternating current. The control unit is based on a voltage of the AC power, a current flowing through the AC reactor, a voltage change due to an impedance of the AC reactor, a reactive current flowing through each of the intermediate capacitor and the AC side capacitor, and a voltage of the DC power. Setting the current target value of the DC / DC converter to be synchronized with the current of the AC power, and as the voltage of the AC power, a fundamental wave extracted based on the AC voltage detection value of the commercial power system Power converter using a voltage in consideration of harmonics.

  Further, according to another aspect of the present invention, there is provided a control method of a power converter, comprising: a DC / DC converter connected between a DC power supply and a DC bus; and an intermediate capacitor connected between two lines of the DC bus. A full bridge circuit provided between the DC bus and a commercial power system, and a filter circuit provided between the commercial power system and the full bridge circuit and including an AC reactor and an AC-side capacitor; In a power conversion device that performs conversion of DC power of the DC power supply having a voltage lower than the peak value of the absolute value of the commercial power system into AC power or vice versa, the control method of the power conversion device executed by the control unit A voltage change due to a voltage of the AC power, a current flowing through the AC reactor, and an impedance of the AC reactor, the intermediate capacitor, and the AC side The current target value of the DC / DC converter is set to be synchronized with the current of the AC power on the basis of the reactive current flowing through each of the capacitor and the voltage of the DC power, so that According to the phase of one of the DC / DC converter and the full bridge circuit to perform a switching operation, the other causes a pause period, wherein the voltage of the AC power is an AC voltage of the commercial power system. It is a control method of a power converter using a voltage in which a harmonic is considered to a fundamental wave extracted based on a voltage detection value.

  According to the present invention, in addition to enhancing the conversion efficiency of power conversion, the total current distortion rate of alternating current can be stably made excellent.

It is a block diagram showing an example of a system provided with an inverter device. It is an example of the circuit diagram of an inverter apparatus. It is a block diagram of a control part. It is a graph which shows an example of a result of having asked for a time-dependent change of a direct current input voltage detection value and a booster circuit current detection value by simulation. It is a figure which the averaging process part performs and which shows the aspect at the time of averaging DC input voltage detection value Vg. It is a control block diagram for explaining the control processing by a control processing part. It is a flow chart which shows control processing of a booster circuit and an inverter circuit. (A) is a graph which shows an example of a result of calculating | requiring the booster circuit electric current target value which the control processing part calculated | required in feedback control, and the booster circuit electric current detected value according to this by simulation, (b) It is a graph which shows an example of the result of having calculated | required the booster circuit voltage target value which the control processing part calculated | required in feedback control, and the booster circuit voltage detection value at the time of controlling according to this by simulation. It is a figure which shows an example of an inverter output voltage target value. (A) is the graph which compared the carrier wave for booster circuits, and the reference wave for booster circuits, (b) is a drive waveform for driving the switching element Qb which the booster circuit control part produced | generated. (A) is a graph comparing the carrier wave for the inverter circuit and the reference wave for the inverter circuit, (b) is a drive waveform for driving the switching element Q1 generated by the inverter circuit control unit, (c) is It is a drive waveform for driving the switching element Q3 which the inverter circuit control part produced | generated. It is the figure which showed an example of the current waveform of the alternating current power which an inverter apparatus outputs with an example of a reference wave and a drive waveform of each switching element. (A) is the graph which showed each voltage waveform of the alternating voltage output from the inverter circuit, the commercial power grid, and the both-ends voltage of an alternating current reactor, (b) showed the current waveform which flows into an alternating current reactor It is a graph. It is a block diagram which shows an example of the electrical storage system provided with the power converter device from alternating current to direct current. It is an example of the circuit diagram of a power converter. It is a figure of the voltage waveform which showed operation | movement of a power converter device notionally. (A) shows the good alternating current voltage of the grid simulated power supply, and (b) shows the AC grid current when control is performed using the measured grid voltage V _ad as the control grid voltage FIG. (A) shows the alternating current voltage of a system | strain simulated power supply, (b) is a wave form diagram showing the alternating current system current at the time of performing control using system voltage Va for control. (A) is a waveform diagram showing an actual AC system voltage, and (b) shows an AC system current when control is performed using a measured value V _ad of the system voltage for control FIG. (A) is a wave form diagram which shows the system voltage of actual alternating current, (b) is a wave form diagram showing the system current of alternating current at the time of performing control using system voltage Va for control. It is a wave form diagram (upper) of a system voltage and a wave form diagram (lower) of output current in the case of defining and controlling an inverter output voltage target value, without considering harmonics of a system voltage with a particularly large distortion. It is a wave form diagram (upper) of a system voltage and a wave form diagram (lower) of output current in the case of defining and controlling an inverter output voltage target value in consideration of harmonics of a system voltage with particularly high distortion.

[Summary of the embodiment]
The subject matter of the embodiments of the present invention includes at least the following.

  (1) This is provided between a commercial power system and a DC power supply having a voltage lower than the peak value of the absolute value of the AC voltage, and is a power conversion that converts DC power into AC power or vice versa. A DC / DC converter connected between the DC power supply and the DC bus, an intermediate capacitor connected between two lines of the DC bus, and the DC bus and the commercial power system A filter circuit including an AC reactor and an AC-side capacitor provided between the full bridge circuit provided in the commercial power system and the full bridge circuit, according to the AC phase in an AC half cycle, A control unit that causes one of the DC / DC converter and the full bridge circuit to perform a switching operation, and the other causes a pause period, and the control unit is configured to Voltage, current flowing through the AC reactor, voltage change due to impedance of the AC reactor, reactive current flowing through the intermediate capacitor and the AC-side capacitor, and current of the DC / DC converter based on the voltage of the DC power The target value is set to be synchronized with the current of the AC power, and a delay of the detection and control system is applied to the fundamental wave extracted based on the AC voltage detection value of the commercial power system as the voltage of the AC power. It is a power converter which uses the voltage which considered the phase supplementation.

  In the power converter configured as described above, the control unit causes one of the DC / DC converter and the full bridge circuit to perform a switching operation according to the phase of the alternating current in an alternating current half cycle, and the other is Implement a "minimum switching conversion scheme" that produces a pause period. In order to realize this method with high conversion efficiency, DC based on the voltage of the AC power, the voltage change by the current and impedance flowing through the AC reactor, the reactive current flowing in each of the intermediate capacitor and the AC side capacitor, and the DC power voltage The current target value of the / DC converter is set to synchronize with the current of the AC power. Then, using a voltage obtained by supplementing the phase in consideration of the delay of the detection or control system to the fundamental wave extracted based on the AC voltage detection value of the commercial power system as the voltage of the AC power, It is possible to obtain a stable, less distorted AC current by suppressing the delay and eliminating the influence of the disturbance of the system voltage of the commercial power system.

(2) For example, in the power converter of (1), the control unit sets the target value of the output current to the load to Ia *, the capacitance of the AC side capacitor to Ca, the AC system voltage to Va, the DC Assuming that the voltage on the power supply side is V _DC and the Laplace operator is s, the AC output current target value Iinv * of the full bridge circuit at the circuit connection point between the filter circuit and the full bridge circuit,
Iinv * = Ia * + s CaVa
Further, when the impedance of the AC reactor is Za, the AC output voltage target value Vinv * of the full bridge circuit at the circuit connection point is
Vinv * = Va + ZaIinv *
Setting the voltage V _DC and the absolute value of the AC output voltage target value Vinv * of the full bridge circuit, whichever is larger, to the output voltage target value Vo * of the DC / DC converter; Assuming that the capacitance of the intermediate capacitor is C, the current target value Iin * of the DC / DC converter is
Iin * = {(Iinv * × Vinv *) + (s C Vo *) × Vo *} / V _DC
The system voltage Va of the alternating current is set such that the effective value is _{Va_rms} and the phase of the timing for instructing the switching operation is ωt.
Va = √2 V _{a_rms} x sin (ωt)
It can be done.

  In this case, the current target value Iin * of the DC / DC converter reflects all of the voltage of the AC power, the voltage change due to the current and impedance flowing through the AC reactor, the reactive current flowing through the intermediate capacitor and the AC side capacitor, and the DC power voltage Therefore, even when the voltage of the DC power supply or the AC output current changes, it is possible to always output power synchronized with the AC output current. Therefore, the DC / DC converter and the full bridge circuit can perform DC / AC power conversion with the minimum number of times of high frequency switching. As a result, the switching loss of the semiconductor switching element and the iron loss of the alternating current and direct current reactors are significantly reduced, and high conversion efficiency can be obtained. Further, by setting the system voltage Va in this manner, it is possible to obtain a low distortion alternating current.

(3) Further, in the power conversion device of (1), the phase of the timing for instructing the switching operation is obtained based on the phase stored immediately at this point and the unit phase for advancing the phase. You may
In this case, the current phase can be determined by calculation based on the previous phase and the unit phase.

(4) Further, in the power conversion device of (3), a phase obtained by multiplying a unit phase for advancing the phase by a predetermined value is added to the phase stored immediately at this time to obtain the phase of the timing. You may do so.
In this case, while changing the predetermined value, it is possible to obtain a preferable value of the predetermined value at which the total current distortion factor of the alternating current and the power factor become the best.

  (5) On the other hand, this includes a DC / DC converter connected between a DC power supply and a DC bus, an intermediate capacitor connected between two lines of the DC bus, the DC bus and a commercial power system And a filter circuit provided between the commercial power system and the full bridge circuit and including an AC reactor and an AC-side capacitor, the peak of the absolute value of the commercial power system What is claimed is: 1. A method of controlling a power conversion device, the control unit executing in the power conversion device performing conversion from direct current power to direct current power to alternating current power of a direct current power supply having a voltage lower than a value. Voltage change due to the current flowing through the alternating current reactor and the impedance of the alternating current reactor, reactive current flowing through the intermediate capacitor and the alternating current side capacitor And setting a current target value of the DC / DC converter to be synchronized with the current of the AC power on the basis of the voltage of the DC power, in accordance with the AC phase within the AC half cycle. One of the DC / DC converter and the full bridge circuit is caused to perform switching operation, and the other causes a pause period, wherein the voltage of the AC power is extracted based on the AC voltage detection value of the commercial power system. It is a control method of a power converter using the voltage which supplemented the phase in consideration of the delay of detection and a control system to the fundamental wave which was carried out.

  In the control method of the power converter as described above, one of the DC / DC converter and the full bridge circuit is caused to perform switching operation and the other causes a pause period according to the phase of the alternating current in the alternating current half cycle. To execute the "minimum switching conversion method". In order to realize this method with high conversion efficiency, DC based on the voltage of the AC power, the voltage change by the current and impedance flowing through the AC reactor, the reactive current flowing in each of the intermediate capacitor and the AC side capacitor, and the DC power voltage The current target value of the / DC converter is set to synchronize with the current of the AC power. Then, using a voltage obtained by supplementing the phase in consideration of the delay of the detection or control system to the fundamental wave extracted based on the AC voltage detection value of the commercial power system as the voltage of the AC power, It is possible to obtain a stable, less distorted AC current by suppressing the delay and eliminating the influence of the disturbance of the system voltage of the commercial power system.

  (6) Moreover, this is provided between the commercial power grid and the DC power supply of a voltage lower than the peak value of the absolute value of the AC voltage, and performs conversion from DC power to AC power or vice versa A power converter, comprising: a DC / DC converter connected between the DC power supply and a DC bus; an intermediate capacitor connected between two lines of the DC bus; the DC bus; and the commercial power system And a filter circuit including an AC reactor and an AC-side capacitor provided between the commercial power system and the full bridge circuit, and in accordance with the AC phase within an AC half cycle. A control unit for causing one of the DC / DC converter and the full bridge circuit to perform a switching operation, and the other for causing a pause period, and the control unit is configured to The DC / DC converter based on the voltage of the power, the current flowing through the AC reactor, the voltage change due to the impedance of the AC reactor, the reactive current flowing through each of the intermediate capacitor and the AC side capacitor, and the voltage of the DC power Voltage target value of the AC power is set to be synchronized with the current of the AC power, and a voltage considering harmonics in the fundamental wave extracted based on the AC voltage detection value of the commercial power system as the voltage of the AC power Is a power converter using

  In this case, even if the AC voltage of the commercial power system is distorted, it is possible to obtain a more stable, less distorted AC current than the power conversion device of (1).

  (7) Also, this includes a DC / DC converter connected between a DC power supply and a DC bus, an intermediate capacitor connected between two lines of the DC bus, and the DC bus and a commercial power system. And a filter circuit provided between the commercial power system and the full bridge circuit and including an AC reactor and an AC-side capacitor, the peak of the absolute value of the commercial power system What is claimed is: 1. A method of controlling a power conversion device, the control unit executing in the power conversion device performing conversion from direct current power to direct current power to alternating current power of a direct current power supply having a voltage lower than a value. Voltage change due to the current flowing through the alternating current reactor and the impedance of the alternating current reactor, reactive current flowing through the intermediate capacitor and the alternating current side capacitor And setting a current target value of the DC / DC converter to be synchronized with the current of the AC power on the basis of the voltage of the DC power, in accordance with the AC phase within the AC half cycle. One of the DC / DC converter and the full bridge circuit is caused to perform switching operation, and the other causes a pause period, wherein the voltage of the AC power is extracted based on the AC voltage detection value of the commercial power system. It is a control method of a power converter using a voltage in which harmonics are taken into consideration for the fundamental wave.

  In this case, even if the AC voltage of the commercial power system is distorted, it is possible to obtain a stable, less distorted AC current more than the control method of (5).

Details of Embodiment
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

First Embodiment
[DC to AC power converter]
First, a direct current to alternating current power conversion device (hereinafter, simply referred to as an inverter device) having a grid connection function will be described in detail.

<< About the whole composition >>
FIG. 1 is a block diagram showing an example of a system provided with an inverter device according to an embodiment. In the figure, the photovoltaic power generation panel 2 as a DC power supply is connected to the input end of the inverter device 1, and the AC commercial power grid 3 (AC grid) is connected to the output end. This system converts the DC power generated by the photovoltaic panel 2 into AC power and performs an interconnected operation to output to the commercial power system 3.

  The inverter device 1 converts the power supplied from the booster circuit 10 into AC power and outputs the AC power to the commercial power grid 3, to which the DC power output from the solar panel 2 is supplied. An inverter circuit (full bridge circuit) 11 and a control unit 12 for controlling the operation of both circuits 10 and 11 are provided.

FIG. 2 is an example of a circuit diagram of the inverter device 1.
The booster circuit 10 includes a DC reactor 15, a diode 16, and a switching element Qb made of, for example, an IGBT (Insulated Gate Bipolar Transistor), and constitutes a boost chopper circuit.
On the input side of the booster circuit 10, a first voltage sensor 17, a first current sensor 18, and a capacitor 26 for smoothing are provided.

The first voltage sensor 17 detects the DC input voltage detection value Vg (DC input voltage value) of the DC power output from the solar power generation panel 2 and input to the booster circuit 10, and outputs the detected value to the control unit 12. The first current sensor 18 detects a booster circuit current detection value Iin (DC input current value) which is a current flowing through the DC reactor 15, and outputs the detected value to the control unit 12. A current sensor may be further provided in front of the capacitor 26 in order to detect the DC input current detection value Ig.
Control unit 12 calculates input power Pin from DC input voltage detection value Vg and boost circuit current detection value Iin, and has a function to perform MPPT (Maximum Power Point Tracking) control for photovoltaic power generation panel 2 doing.

  Further, switching element Qb of booster circuit 10 is controlled such that the total number of switching operations combined with inverter circuit 11 is minimized, as will be described later, and a stop period occurs. Therefore, the boosting circuit 10 outputs boosted power to the inverter circuit 11 during the switching operation, and the photovoltaic panel 2 outputs the boosted power during the switching operation is stopped. Is outputted to the inverter circuit 11 without boosting the DC input voltage value of the DC power inputted to the.

A smoothing capacitor 19 (intermediate capacitor) is connected between the booster circuit 10 and the inverter circuit 11.
The inverter circuit 11 includes switching elements Q1 to Q4 formed of, for example, FETs (Field Effect Transistors). These switching elements Q1 to Q4 constitute a full bridge circuit. Each of the switching elements Q1 to Q4 is connected to the control unit 12 and can be controlled by the control unit 12. The control unit 12 performs PWM (Pulse Width Modulation) control on the operation of each of the switching elements Q1 to Q4. Thus, the inverter circuit 11 converts the power supplied from the booster circuit 10 into alternating current power.

The inverter device 1 includes a filter circuit 21 between the inverter circuit 11 and the commercial power grid 3.
The filter circuit 21 is configured to include an AC reactor 22 and a capacitor 23 (AC side capacitor) provided at a subsequent stage of the AC reactor 22. The filter circuit 21 has a function of removing high frequency components included in the AC power output from the inverter circuit 11. The AC power from which the high frequency component has been removed by the filter circuit 21 is given to the commercial power system 3.

  Thus, the booster circuit 10 and the inverter circuit 11 convert the DC power output from the photovoltaic panel 2 into AC power, and output the converted AC power to the commercial power system 3 through the filter circuit 21. The converter is configured.

Further, the filter circuit 21 is connected to a second current sensor 24 for detecting an inverter current detection value Iinv (a current flowing through the AC reactor 22) which is a current value of an output of the inverter circuit 11. Furthermore, between the filter circuit 21 and the commercial power system 3, a second voltage sensor 25 for detecting a voltage value on the commercial power system 3 side (system voltage detection value V _ad ) is connected.

The second current sensor 24 and the second voltage sensor 25 output the detected system voltage detection value V _ad (voltage value of the commercial power system) and the inverter current detection value I inv to the control unit 12. Although the second current sensor 24 is provided at the front stage of the capacitor 23 as shown in the drawing, a third current sensor for detecting the output current of the inverter device 1 may be added at the rear stage of the capacitor 23.

<< About control part >>
First, based on the system voltage detection value V _ad sampled a large number during one cycle from the zero crossing of the system voltage detection value V _ad to the next zero cross, the control unit 12 _executes the system voltage effective by the following equation (01) _{Determine the} value V _{a_rms} . Here, the system voltage detection value V _ad can be expressed as a function of the phase ωt.

In addition, although the calculation which calculates | requires an effective value does not necessarily need to be performed continuously, it is preferable to perform regularly.

Hereinafter, not the detected value but the fundamental wave component calculated from the effective value is used as the system voltage Va. That is, assuming that the system voltage Va has a phase from zero crossing as ωt,
Va = 2 2 · V a _rms × sin (ωt) · · · (02)
It is. The effect of using the value of Formula (02) instead of an actual measurement value as the grid voltage Va will be described later.

The below-mentioned operation of the minimum switching conversion method is performed in the interrupt process, and the phase of the system voltage is determined for each interrupt process. Here, _assuming that the phase to be advanced in one interrupt process is ωt — unit, the frequency of the interrupt process is f _int , and the voltage frequency of the commercial power system is f _com , the following equation (03) is established.
ωt _{_unit} = 2π / (f _int / f _com ) (03)

Also, _assuming that the phase before the interrupt processing is _{ωt_normal_before} and the phase of the current grid voltage is _{ωt_normal} ,
ωt _{_normal} = ωt _{_normal_before} + ωt _{_unit}
... (04)
It becomes.

Further, the phase of the present system voltage is corrected by the following equation (05). _Assuming that the system voltage phase after correction is ωt _{_correct} , the predetermined value as the multiplication factor is N (> 1).
_{ωt _correct = ωt _normal + ωt _unit} × N
... (05)
_{= Ωt _normal_before + ωt _unit × (} N + 1)
... (06)
It becomes. For example, 3 is suitable as the value of N.

  In the control of the minimum switching conversion system, the system voltage is actually measured and then the operation is performed, and the switching element is controlled according to the result, but there is a slight delay time from the measurement to the control. The inventors of the present invention have found that this delay time adversely affects power quality such as the overall current distortion rate of alternating current. Also, the system voltage may include noise and the like. Therefore, by setting the system voltage Va shown in the equation (02) to a fundamental wave whose amplitude is determined based on a known effective value, the influence of noise etc. which may be contained in an actual system voltage can be eliminated. it can. With regard to the phase, as shown in equations (05) and (06), delaying detection and control can be suppressed by advancing the phase when controlling the switching element based on the cycle of the interrupt processing. be able to.

  The control unit 12 controls the booster circuit 10 and the inverter circuit 11 based on the system voltage Va and the inverter current detection value Iinv, the above-described DC input voltage detection value Vg, and the booster circuit current detection value Iin.

FIG. 3 is a block diagram of the control unit 12. As shown in FIG. 3, the control unit 12 functionally includes a control processing unit 30, a booster circuit control unit 32, an inverter circuit control unit 33, and an averaging processing unit 34.
A part or all of each function of control unit 12 may be configured by a hardware circuit, or a part or all thereof may be realized by executing software (computer program) by a computer . Software (computer program) for realizing the function of the control unit 12 is stored in a storage device (not shown) of the computer.

The booster circuit control unit 32 controls the switching element Qb of the booster circuit 10 based on the target value and the detection value given from the control processing unit 30, and causes the booster circuit 10 to output the power of the current according to the target value. .
Further, the inverter circuit control unit 33 controls the switching elements Q1 to Q4 of the inverter circuit 11 based on the target value and the detection value given from the control processing unit 30, and the inverter circuit performs the power of the current corresponding to the target value. Make it output to 11.

Control processing unit 30 receives DC input voltage detection value Vg, booster circuit current detection value Iin, grid voltage Va, and inverter current detection value Iinv.
The control processing unit 30 calculates the input power Pin and its average value <Pin> from the DC input voltage detection value Vg and the booster circuit current detection value Iin. The symbol <> indicates the average value of the values in parentheses. The same is true below.
The control processing unit 30 sets the DC input current target value Ig * (described later) based on the input power average value <Pin> to perform MPPT control on the photovoltaic panel 2, and the booster circuit 10 and the inverter Each circuit 11 has a function of feedback control.

  The DC input voltage detection value Vg and the booster circuit current detection value Iin are provided to the averaging processing unit 34 and the control processing unit 30.

  The averaging processing unit 34 samples the DC input voltage detection value Vg and the booster circuit current detection value Iin provided from the first voltage sensor 17 and the first current sensor 18 at predetermined time intervals set in advance, respectively. , And provides the control processing unit 30 with an averaged DC input voltage detection value Vg and a boost circuit current detection value Iin.

FIG. 4 is a graph showing an example of a result obtained by simulation of temporal changes in the DC input voltage detection value Vg and the booster circuit current detection value Iin.
Further, the DC input current detection value Ig is a current value detected on the input side of the capacitor 26.

  As shown in FIG. 4, it can be seen that the DC input voltage detection value Vg, the booster circuit current detection value Iin, and the DC input current detection value Ig fluctuate in a cycle of 1/2 of the system voltage.

The reason that the DC input voltage detection value Vg and the DC input current detection value Ig periodically fluctuate as shown in FIG. 4 is as follows. That is, in accordance with the operation of the booster circuit 10 and the inverter circuit 11, the boost circuit current detection value Iin largely fluctuates from approximately 0 A to a peak value in a half cycle of the AC cycle. Therefore, the fluctuation component can not be completely removed by the capacitor 26, and the DC input current detection value Ig becomes a pulsating flow including a component that fluctuates in a half cycle of the alternating current cycle. On the other hand, in the photovoltaic panel, the output voltage is changed by the output current.
For this reason, the periodic fluctuation which arises in direct-current input voltage detection value Vg has become 1/2 cycle of the exchange electric power which inverter device 1 outputs.

  The averaging processing unit 34 averages the DC input voltage detection value Vg and the booster circuit current detection value Iin in order to suppress the influence of the above-described periodic fluctuation.

  FIG. 5 is a diagram showing an aspect when the averaging processing unit 34 averages the DC input voltage detection value Vg.

  The averaging processing unit 34 samples the DC input voltage detection value Vg given a plurality of times at predetermined time intervals Δt set in advance in a period L between a certain timing t1 and a timing t2 (in FIG. The timing of the black spot) is performed, and the average value of the plurality of DC input voltage detection values Vg obtained is obtained.

Here, the averaging processing unit 34 sets the period L to a half length of the period length of the commercial power grid 3. In addition, the averaging processing unit 34 sets the time interval Δt to a period sufficiently shorter than the length of a half cycle of the commercial power system 3.
Thereby, the averaging processing unit 34 accurately determines the average value of the DC input voltage detection value Vg periodically fluctuating in synchronization with the period of the commercial power grid 3 while shortening the sampling period as much as possible. Can.
The sampling time interval Δt can be set to, for example, 1/100 to 1/1000 of the period of the commercial power grid 3, or 20 microseconds to 200 microseconds or the like.

The averaging processing unit 34 can also store the period L in advance, or can acquire the system voltage Va and set the period L based on the period of the commercial power system 3.
Here, although the period L is set to a half length of the cycle length of the commercial power grid 3, if the period L is set to at least a half cycle of the commercial power grid 3, the DC input is The average value of the voltage detection values Vg can be determined with high accuracy. This is because, as described above, the DC input voltage detection value Vg periodically fluctuates by a half of the cycle length of the commercial power system 3 by the operation of the booster circuit 10 and the inverter circuit 11.
Therefore, when the period L needs to be set longer, the period L is set to an integral multiple of the half period of the commercial power system 3 such as three times or four times the half period of the commercial power system 3 do it. This makes it possible to grasp the voltage fluctuation on a cycle basis.

As described above, the boost circuit current detection value Iin also periodically fluctuates in a half cycle of the commercial power grid 3 as in the case of the DC input voltage detection value Vg.
Therefore, the averaging processing unit 34 also obtains the average value of the boost circuit current detection values Iin by the same method as the DC input voltage detection value Vg shown in FIG. 5.
The control processing unit 30 sequentially obtains, for each period L, the average value of the DC input voltage detection value Vg and the average value of the booster circuit current detection value Iin.

  The averaging processing unit 34 provides the control processing unit 30 with the average value of the DC input voltage detection values Vg and the average value of the booster circuit current detection values Iin.

  In the present embodiment, as described above, the averaging processing unit 34 calculates the average value of the DC input voltage detection value Vg (DC input voltage average value <Vg>) and the average value of the boost circuit current detection value Iin (boost circuit current Since the control processing unit 30 controls the booster circuit 10 and the inverter circuit 11 while performing the MPPT control on the photovoltaic power generation panel 2 using these values, the photovoltaic power generation panel 2 is determined. Even when the DC current fluctuates and becomes unstable, the control unit 12 controls the output from the photovoltaic power generation panel 2 from the DC input voltage average value <Vg> from which the fluctuation component due to the operation of the inverter device 1 is removed. The current average value <Iin> can be accurately obtained. As a result, MPPT control can be suitably performed, and the reduction in the power generation efficiency of the solar panel 2 can be effectively suppressed.

Further, as described above, when the voltage (DC input voltage detection value Vg) or the current (boost circuit current detection value Iin) of the DC power output from the solar power generation panel 2 changes due to the operation of the inverter device 1; The fluctuation period coincides with a half cycle of the AC power output from the inverter circuit 11 (1/2 cycle of the commercial power grid 3).
In this respect, in the present embodiment, the DC input voltage detection value Vg and the booster circuit current detection value Iin are each obtained during the period L set to a half length of the cycle length of the commercial power system 3 Since the DC input voltage average value <Vg> and the booster circuit current average value <Iin> were determined multiple times at a time interval Δt shorter than a half cycle of the AC system, the voltage and current of the DC current Even if the value of V.sub.i varies periodically, the DC input voltage average value <Vg> and the booster circuit current average value <Iin> can be accurately obtained while shortening the sampling period as much as possible.

The control processing unit 30 sets the DC input current target value Ig * based on the above-described input power average value <Pin>, and based on the set DC input current target value Ig * and the above value, the booster circuit A target value for each of 10 and the inverter circuit 11 is obtained.
The control processing unit 30 has a function of providing the determined target value to the booster circuit control unit 32 and the inverter circuit control unit 33 and performing feedback control of each of the booster circuit 10 and the inverter circuit 11.

FIG. 6 is a control block diagram for explaining feedback control of the booster circuit 10 and the inverter circuit 11 by the control processing unit 30.
The control processing unit 30 has a first operation unit 41, a first adder 42, a compensator 43, and a second adder 44 as functional units for controlling the inverter circuit 11.
The control processing unit 30 further includes a second operation unit 51, a third adder 52, a compensator 53, and a fourth adder 54 as functional units for controlling the booster circuit 10.

FIG. 7 is a flowchart showing control processing of the booster circuit 10 and the inverter circuit 11. Each functional unit shown in FIG. 6 controls the booster circuit 10 and the inverter circuit 11 by executing the process shown in the flowchart shown in FIG. 7.
Hereinafter, control processing of the booster circuit 10 and the inverter circuit 11 will be described with reference to FIG.

First, the control processing unit 30 obtains the current input power average value <Pin> (step S9), and sets the DC input current target value Ig * in comparison with the input power average value <Pin> at the previous calculation time. (Step S1). The input power average value <Pin> is obtained based on the following equation (1).
Input power average value <Pin> = <Iin × Vg> (1)

In equation (1), Iin is a boost circuit current detection value, and Vg is a DC input voltage detection value (DC input voltage value), and is a DC input voltage average value averaged by the averaging processing unit 34 <Vg> and boost circuit current average value <Iin> are used.
Further, in each of the equations regarding control shown below other than the equation (1), instantaneous values which are not averaged are used as the boost circuit current detected value Iin and the DC input voltage detected value Vg.

The control processing unit 30 supplies the set DC input current target value Ig * to the first calculation unit 41.
In addition to the DC input current target value Ig *, the first calculation unit 41 is also supplied with a DC input voltage detection value Vg and a grid voltage Va.

The first calculation unit 41 calculates an average value <Ia *> of the output current target value as the inverter device 1 based on the following equation (2). η is a constant representing the conversion efficiency of the inverter device 1.
Average value of output current target value <Ia *> = η <Ig * × Vg> / <Va> (2)

Further, the first calculator 41 obtains the output current target value Ia * based on the following equation (3) (step S2).
Here, the first calculation unit 41 obtains the output current target value Ia * as a sine wave having the same phase as the system voltage Va.
Output current target value Ia * = (√2) × <Ia *> × sin (ωt) (3)

As described above, the first calculation unit 41 obtains the output current target value Ia * based on the input power average value <Pin> (the input power value of the DC power) and the grid voltage Va.
Next, the first calculation unit 41 calculates an inverter current target value Iinv * (current target value for the inverter circuit), which is a current target value for controlling the inverter circuit 11, as shown in the following equation (4) Step S3).
Inverter current target value Iinv * = Ia * + s CaVa (4)

However, in Formula (4), Ca is an electrostatic capacitance of the capacitor | condenser 23 (output smoothing capacitor), s is a Laplace operator.
If expression (4) above is expressed using differentiation at time t,
Iinv * = Ia * + Ca × (d Va / dt) (4a)
It becomes. Also, if the current flowing to the capacitor 23 is detected and this is Ica,
Iinv * = Ia * + Ica (4b)
It becomes.
In the equations (4), (4a) and (4b), the second term on the right side is a value obtained by taking into consideration the current flowing in the capacitor 23 of the filter circuit 21.
The output current target value Ia * is obtained as a sine wave having the same phase as the system voltage Va, as shown in the above equation (3). That is, the control processing unit 30 controls the inverter circuit 11 so that the current Ia (output current) of the AC power output from the inverter device 1 has the same phase as the system voltage Va.

When first inverter 41 obtains inverter current target value Iinv *, first operation unit 41 applies this inverter current target value Iinv * to first adder 42.
The inverter circuit 11 is feedback-controlled by the inverter current target value Iinv *.

In addition to the inverter current target value Iinv *, the first adder 42 receives the current inverter current detection value Iinv.
The first adder 42 calculates the difference between the inverter current target value Iinv * and the current inverter current detection value Iinv, and gives the calculation result to the compensator 43.

When the difference is given, the compensator 43 performs an operation based on a proportional coefficient or the like, and the second adder 44 adds it to the system voltage Va, thereby converging this difference and setting the inverter current detection value Iinv to an inverter. An inverter voltage reference value Vinv # that can be used as the current target value Iinv * is obtained. A control signal obtained by comparing the inverter voltage reference value Vinv # with the output voltage target value Vo * of the DC / DC converter supplied from the first calculation unit 41 is supplied to the inverter circuit control unit 33, whereby the inverter circuit 11 is obtained. Outputs a voltage according to the inverter voltage reference value Vinv #.
The voltage output from the inverter circuit 11 is given to the AC reactor 22 and is fed back as a new inverter current detection value Iinv. Then, the difference between the inverter current target value Iinv * and the inverter current detection value Iinv is calculated again by the first adder 42, and the inverter circuit 11 is controlled based on this difference as described above.

  As described above, the inverter circuit 11 is feedback-controlled by the inverter current target value Iinv * and the inverter current detection value Iinv (step S4).

On the other hand, the inverter current target value Iinv * calculated by the first calculation unit 41 is given to the second calculation unit 51 in addition to the DC input voltage detection value Vg and the system voltage Va.
The second calculation unit 51 calculates an inverter output voltage target value Vinv * (voltage target value of the inverter circuit) based on the following formula (5) (step S5).
Inverter output voltage target value Vinv * = Va + ZaIinv * (5)

However, in Formula (5), Za is the impedance of an alternating current reactor, s is a Laplace operator.
If expression (5) above is expressed using differentiation at time t,
Vinv * = Va + RaIinv * + La × (d Iinv * / dt)
... (5a)
It becomes. However, Ra is a resistance of an alternating current reactor, La is an inductance of an alternating current reactor, and is (Za = Ra + sLa).
The second term of the right side of the equation (5) and the second term and the third term of the right side of (5a) are values added in consideration of the voltage generated at both ends of the AC reactor 22.
As described above, in the present embodiment, the inverter current target value Iinv *, which is a current target value for controlling the inverter circuit 11 such that the current phase of the AC power output from the inverter device 1 is in phase with the system voltage Va. The inverter output voltage target value Vinv * is set based on.

  As described above, the output target values (Iinv *, Vinv *) of the inverter circuit 11, which are target values on the AC side, are the bridge output terminal of the inverter circuit 11, that is, the circuit connection point P between the inverter circuit 11 and the filter circuit 21. It is set by. Thus, the grid connection is such that the set point of the target value is moved ahead of the original grid connection point (the circuit connection point between the commercial power grid 3 and the filter circuit 21), and finally settles in the appropriate grid connection. The system is done.

When the inverter output voltage target value Vinv * is obtained, as shown in the following equation (6), the second calculation unit 51 determines the voltage Vg as the voltage V _DC on the DC power supply side or preferably the following DC voltage Vgf The absolute value of the output voltage target value Vinv * is compared, and the larger one is determined as the boost circuit voltage target value Vo * (step S6). The DC voltage Vgf is a voltage taking into account the voltage drop due to the impedance Z of the DC reactor 15 to Vg, and the booster circuit current is Iin, and Vgf = Vg−ZIin. Therefore,
Vo * = Max (Vg-ZIin, absolute value of Vinv *) (6)
It can be done.
If expression (6) above is expressed using differentiation at time t,
Vo * = Max (Vg- (RIin + L (dIin / dt), absolute value of Vinv *))
... (6a)
It is. However, R is resistance of a direct current reactor, L is inductance of a direct current reactor, and is (Z = R + sL).

Furthermore, the second calculation unit 51 calculates the boost circuit current target value Iin * based on the following equation (7) (step S7).
Boost circuit current target value Iin * =
{(Iinv * × Vinv *) + (s C Vo *) × Vo *} / (Vg−ZIin)
... (7)

Where C is the capacitance of the capacitor 19 (smoothing capacitor) and s is the Laplace operator.
If expression (7) above is expressed using differentiation at time t,
Iin * =
{(Iinv * × Vinv *) + C × (d Vo * / dt) × Vo *} /
{Vg- (R + sL) Iin} (7a)
It becomes. Also, if the current flowing to the capacitor 19 is detected and this is Ic,
Iin * =
{(Iinv * × Vinv *) + Ic × Vo *} / {Vg-ZIin}
... (7b)
It becomes.

  The terms added to the product of the inverter current target value Iinv * and the inverter output voltage target value Vinv * in the equations (7), (7a) and (7b) take account of the reactive power passing through the capacitor 19 It is a value. That is, in addition to the power target value of inverter circuit 11, the value of Iin * can be determined more accurately by considering the reactive power.

Furthermore, if the power loss _PLOSS of the inverter device 1 is measured in advance, the above equation (7a) can also be expressed as follows.
Iin * =
{(Iinv * × Vinv *) + C × (d Vo * / dt) × Vo * + P _LOSS } / {Vg−ZIin} (7c)
Similarly, the above formula (7b) can also be expressed as follows.
Iin * =
{(Iinv * × Vinv *) + Ic × Vo * + P _LOSS } / {Vg-ZIin}
... (7d)
In this case, by considering reactive power and power loss _PLOSS in addition to the power target value of inverter circuit 11, the value of Iin * can be determined more precisely.

Incidentally, the capacitance C and the power loss _{P LOSS} of the capacitor 19, is sufficiently small, the following equation (8) is established as compared with the (Iinv * × Vinv *). The Iin * determined by the equation (8) can be used as Iin included in the right side of the equations (6), (6a), (7), (7a), (7b), (7c) and (7d).
Boost circuit current target value Iin * = (Iinv * × Vinv *) / Vg (8)

When the second calculation unit 51 obtains the boost circuit current target value Iin *, the second calculation unit 51 applies the boost circuit current target value Iin * to the third adder 52.
The booster circuit 10 is feedback-controlled by the booster circuit current target value Iin *.

To the third adder 52, the current boost circuit current detection value Iin other than the boost circuit current target value Iin * is given.
The third adder 52 calculates the difference between the boost circuit current target value Iin * and the current boost circuit current detection value Iin, and supplies the calculation result to the compensator 53.

When the above difference is given, the compensator 53 performs an operation based on a proportional coefficient or the like, and further subtracts this from the DC input voltage detection value Vg by the fourth adder 54 to converge this difference and to boost the circuit. A booster circuit voltage reference value Vbc # that can set the current detection value Iin as the booster circuit current target value Iin * is obtained. The booster circuit control unit 32 is provided with a control signal obtained by comparing the booster circuit voltage reference value Vbc # with the output voltage target value Vo * of the DC / DC converter supplied from the first calculation unit 41. At 10, a voltage according to the booster circuit voltage reference value Vbc # is output.
The power output from the booster circuit 10 is supplied to the DC reactor 15, and is fed back as a new booster circuit current detection value Iin. Then, the difference between the boosting circuit current target value Iin * and the boosting circuit current detection value Iin is calculated again by the third adder 52, and the boosting circuit 10 is controlled based on this difference as described above.

  As described above, the booster circuit 10 is feedback-controlled by the booster circuit current target value Iin * and the booster circuit current detection value Iin (step S8).

  After the step S8, the control processing unit 30 obtains the present average input power value <Pin> based on the equation (1) (step S9).

  The control processing unit 30 compares the input power average value <Pin> with the input power average value <Pin> in the previous calculation so that the input power average value <Pin> becomes the maximum value (so as to follow the maximum power point). Set the target value Ig *.

  As described above, the control processing unit 30 controls the booster circuit 10 and the inverter circuit 11 while performing the MPPT control on the photovoltaic power generation panel 2.

As described above, the control processing unit 30 performs feedback control of the inverter circuit 11 and the booster circuit 10 with the current target value.
(A) of FIG. 8 shows an example of the result of simulation for determining the boost circuit current target value Iin * obtained by the control processing unit 30 in the above feedback control and the boost circuit current detection value Iin when controlled according thereto. It is a graph, and (b) shows an example of the result of having calculated the booster circuit voltage target value Vo * which control processing part 30 asked in the above-mentioned feedback control, and booster circuit voltage detection value Vo at the time of controlling according to this by simulation. FIG.

As shown in (a) of FIG. 8, it is understood that the control circuit 30 controls the boost circuit current detection value Iin in accordance with the boost circuit current target value Iin *.
Further, as shown in FIG. 8B, since the boost circuit voltage target value Vo * is obtained by the above equation (6), the absolute value of the inverter output voltage target value Vinv * is substantially equal to the DC input voltage detection value Vg. In the above period, the absolute value of the inverter output voltage target value Vinv * is followed, and in the other period, the DC input voltage detection value Vg is followed.
It can be seen that the control circuit 30 controls the step-up circuit voltage detection value Vo in accordance with the step-up circuit voltage target value Vo *.

FIG. 9 is a diagram showing an example of the inverter output voltage target value Vinv *. In the figure, the vertical axis represents voltage, and the horizontal axis represents time. The broken line shows the voltage waveform of the commercial power system 3, and the solid line shows the waveform of the inverter output voltage target value Vinv *.
The inverter circuit 11 outputs power using the inverter output voltage target value Vinv * shown in FIG. 9 as a voltage target value by control according to the flowchart in FIG. 7.
Therefore, inverter circuit 11 outputs power of a voltage according to the waveform of inverter output voltage target value Vinv * shown in FIG.

  As shown in the figure, both waves have substantially the same voltage value and frequency, but the phase of the inverter output voltage target value Vinv * is several degrees ahead of the voltage phase of the commercial power system 3 ing.

As described above, the control processing unit 30 according to the present embodiment performs the feedback control of the booster circuit 10 and the inverter circuit 11 by setting the phase of the inverter output voltage target value Vinv * to the voltage phase of the commercial power system 3. I am advancing about three times against.
The angle for advancing the phase of the inverter output voltage target value Vinv * with respect to the voltage phase of the commercial power system 3 may be several degrees, and as will be described later, the difference between the voltage waveform of the commercial power system 3 and the voltage waveform The voltage waveform obtained when the above is determined is set in a range where the phase is 90 degrees ahead of the voltage waveform of the commercial power grid 3. For example, it is set in a range of values greater than 0 degrees and less than 10 degrees.

The angle to be advanced is determined by the system voltage Va, the inductance La of the AC reactor 22, and the inverter current target value Iinv *, as shown in the above equation (5). Among these, since the system voltage Va and the inductance La of the AC reactor 22 are fixed values not to be controlled, the angle to be advanced is determined by the inverter current target value Iinv *.
The inverter current target value Iinv * is determined by the output current target value Ia * as shown in the above equation (4). As the output current target value Ia * becomes larger, the advanced component in the inverter current target value Iinv * increases, and the lead angle (advance angle) of the inverter output voltage target value Vinv * becomes larger.

  Since the output current target value Ia * is obtained from the above equation (2), the phase advancing angle is adjusted by the DC input current target value Ig *.

<< About control of boost circuit and inverter circuit >>
The booster circuit control unit 32 controls the switching element Qb of the booster circuit 10. Further, the inverter circuit control unit 33 controls the switching elements Q1 to Q4 of the inverter circuit 11.

  The booster circuit control unit 32 and the inverter circuit control unit 33 respectively generate a carrier wave for the booster circuit and a carrier wave for the inverter circuit, and the carrier wave is used as a target value given by the control processing unit 30 for the booster circuit voltage reference value Vbc #, Modulating with the inverter voltage reference value Vinv # generates a drive waveform for driving each switching element.

  The boost circuit control unit 32 and the inverter circuit control unit 33 control the respective switching elements based on the drive waveform to generate an alternating current of a current waveform approximate to the boost circuit current target value Iin * and the inverter current target value Iinv *. The power is output to the booster circuit 10 and the inverter circuit 11.

FIG. 10A is a graph comparing the carrier wave for the booster circuit with the waveform of the booster circuit voltage reference value Vbc #. In the figure, the vertical axis represents voltage, and the horizontal axis represents time. In FIG. 10A, the wavelength of the carrier wave for the booster circuit is shown to be longer than the actual one for easy understanding.
The booster circuit carrier generated by the booster circuit control unit 32 is a triangular wave whose minimum value is “0”, and the amplitude A 1 is set as a booster circuit voltage target value Vo * given from the control processing unit 30.
Further, the frequency of the carrier wave for the booster circuit is set by the booster circuit control unit 32 so as to have a predetermined duty ratio according to a control instruction from the control processing unit 30.

  As described above, boost circuit voltage target value Vo * is inverter output voltage target value Vinv * in period W1 in which the absolute value of inverter output voltage target value Vinv * is substantially equal to or greater than DC input voltage detection value Vg. The absolute value is followed, and in the other period, it changes so as to follow the DC input voltage detection value Vg. Therefore, the amplitude A1 of the carrier wave for the booster circuit also changes according to the booster circuit voltage target value Vo *.

  In the present embodiment, it is assumed that the DC input voltage detection value Vg is 250 volts and the voltage amplitude of the commercial power grid 3 is 288 volts.

  The waveform of the booster circuit voltage reference value Vbc # (hereinafter, also referred to as a booster circuit reference wave Vbc #) is a value obtained by the control processing unit 30 based on the booster circuit current target value Iin *, and the inverter output voltage target value Vinv The absolute value of * is a positive value in a period W1 in which the DC input voltage detection value Vg is larger. The boosting circuit reference wave Vbc # has a waveform that approximates the wave shape of the boosting circuit voltage target value Vo * in the period W1, and intersects the boosting circuit carrier.

  The booster circuit control unit 32 compares the carrier wave for the booster circuit with the reference wave Vbc # for the booster circuit, and the reference wave Vbc # for the booster circuit, which is the target value of the voltage across the DC reactor 15, becomes higher than the carrier wave for the booster circuit. A drive waveform for driving the switching element Qb is generated so as to be on in part and off in parts below the carrier wave.

FIG. 10B is a drive waveform for driving the switching element Qb generated by the booster circuit control unit 32. In the figure, the vertical axis is voltage, and the horizontal axis is time. The horizontal axis is shown to coincide with the horizontal axis of FIG.
This drive waveform shows the switching operation of the switching element Qb, and by applying to the switching element Qb, it is possible to execute the switching operation according to the drive waveform. The drive waveform constitutes a control command for turning off the switch of the switching element at a voltage of 0 volt and turning on the switch of the switching element at a positive voltage.

The booster circuit control unit 32 generates a drive waveform so that the switching operation is performed in a period W1 in which the absolute value of the inverter output voltage target value Vinv * is equal to or more than the DC input voltage detection value Vg. Therefore, switching element Qb is controlled to stop the switching operation in the range of DC input voltage detection value Vg or less.
Also, each pulse width is determined by the intercept of the booster circuit carrier, which is a triangular wave. Therefore, the pulse width is larger as the voltage is higher.

  As described above, the booster circuit control unit 32 modulates the carrier wave for the booster circuit with the reference wave Vbc # for the booster circuit, and generates a drive waveform representing a pulse width for switching. The booster circuit control unit 32 performs PWM control of the switching element Qb of the booster circuit 10 based on the generated drive waveform.

  When a switching element Qbu conducting in the forward direction of the diode is disposed in parallel with the diode 16, the switching element Qbu uses a drive waveform inverted from the drive waveform of the switching element Qb. However, in order to prevent the switching element Qb and the switching element Qbu from conducting simultaneously, a dead time of about 1 microsecond is provided when the drive pulse of the switching element Qbu shifts from off to on.

  FIG. 11A is a graph comparing the carrier wave for the inverter circuit with the waveform of the inverter voltage reference value Vinv #. In the figure, the vertical axis represents voltage, and the horizontal axis represents time. Also in (a) of FIG. 11, the wavelength of the carrier wave for the inverter circuit is shown to be longer than the actual one for easy understanding.

The carrier wave for the inverter circuit generated by the inverter circuit control unit 33 is a triangular wave having a center of amplitude of 0 volt, and one side amplitude thereof is set to a target voltage for boost circuit voltage Vo * (target voltage for the capacitor 23). Therefore, the amplitude A2 of the carrier wave for the inverter circuit has a period twice (500 volts) of the DC input voltage detection value Vg and a period twice (maximum 576 volts) of the voltage of the commercial power grid 3 .
The frequency is set by the inverter circuit control unit 33 so as to have a predetermined duty ratio according to a control instruction from the control processing unit 30 or the like.

  As described above, boost circuit voltage target value Vo * is inverter output voltage target value Vinv * in period W1 in which the absolute value of inverter output voltage target value Vinv * is substantially equal to or greater than DC input voltage detection value Vg. Following the absolute value, in the period W2 which is the other period, it changes so as to follow the DC input voltage detection value Vg. Therefore, the amplitude A2 of the carrier wave for the inverter circuit also changes in accordance with the boost circuit voltage target value Vo *.

  The waveform of the inverter voltage reference value Vinv # (hereinafter also referred to as a reference wave Vinv # for the inverter circuit) is a value that the control processing unit 30 obtains based on the inverter current target value Iinv *. It is set to the same as (288 volts). Therefore, the inverter circuit reference wave Vinv # crosses the inverter circuit carrier in a portion where the voltage value is in the range of -Vg to + Vg.

  The inverter circuit control unit 33 compares the carrier wave for the inverter circuit with the reference wave Vinv # for the inverter circuit, and turns on the portion where the reference wave Vinv # for the inverter circuit, which is the voltage target value, is equal to or higher than the carrier wave for the inverter circuit. The drive waveform for driving the switching elements Q1 to Q4 is generated so as to be turned off at the portion where

FIG. 11B is a drive waveform for driving the switching element Q1 generated by the inverter circuit control unit 33. In the figure, the vertical axis is voltage, and the horizontal axis is time. The horizontal axis is shown to coincide with the horizontal axis of FIG.
The inverter circuit control unit 33 generates a drive waveform so that the switching operation is performed in the range W2 in which the voltage of the inverter circuit reference wave Vinv # is in the range of −Vg to + Vg. Therefore, in the other range, the switching element Q1 is controlled to stop the switching operation.

FIG. 11C is a drive waveform for driving the switching element Q3 generated by the inverter circuit control unit 33. In the figure, the vertical axis is voltage, and the horizontal axis is time.
For the switching element Q3, the inverter circuit control unit 33 compares the inverted wave of the inverter circuit reference wave Vinv # indicated by a broken line in the drawing with the carrier wave to generate a drive waveform.
Also in this case, the inverter circuit control unit 33 generates a drive waveform so that the switching operation is performed in the range W2 of −Vg to + Vg of the voltage of (the inverted wave of) the inverter circuit reference wave Vinv #. Therefore, in the other range, the switching element Q3 is controlled to stop the switching operation.

  The inverter circuit control unit 33 generates an inverted drive waveform of the switching element Q1 for the drive waveform of the switching element Q2, and reverses the drive waveform of the switching element Q3 for the drive waveform of the switching element Q4. Generate what you

  As described above, the inverter circuit control unit 33 modulates the carrier wave for the inverter circuit with the reference wave Vinv # for the inverter circuit, and generates a drive waveform representing a pulse width for switching. The inverter circuit control unit 33 performs PWM control of the switching elements Q1 to Q4 of the inverter circuit 11 based on the generated drive waveform.

  The booster circuit control unit 32 according to the present embodiment causes the electric power to be output so that the current flowing through the DC reactor 15 matches the booster circuit current target value Iin *. As a result, the booster circuit 10 performs the switching operation in a period W1 (FIG. 10) in which the absolute value of the inverter output voltage target value Vinv * is substantially equal to or higher than the DC input voltage detection value Vg. The booster circuit 10 outputs power so as to approximate a voltage equal to or higher than the DC input voltage detection value Vg in the period W1 to the absolute value of the inverter output voltage target value Vinv *. On the other hand, the booster circuit control unit 32 stops the switching operation of the booster circuit 10 in a period in which the absolute value of the inverter output voltage target value Vinv * is approximately equal to or less than the DC input voltage detection value Vg. Therefore, in a period equal to or less than the DC input voltage detection value Vg, the booster circuit 10 outputs the DC input voltage value of the DC power output from the solar panel 2 to the inverter circuit 11 without boosting.

Moreover, the inverter circuit control part 33 of this embodiment outputs electric power so that the current which flows into AC reactor 22 may correspond to inverter current target value Iinv *. As a result, the inverter circuit 11 is caused to perform switching operation in a period W2 (FIG. 11) where the inverter output voltage target value Vinv * is approximately −Vg to + Vg. That is, the inverter circuit 11 is caused to perform switching operation in a period in which the absolute value of the inverter output voltage target value Vinv * is equal to or less than the DC input voltage detection value Vg.
Therefore, while the booster circuit 10 stops the switching operation, the inverter circuit 11 performs the switching operation and outputs AC power approximate to the inverter output voltage target value Vinv *.
Since the inverter circuit reference wave Vinv # and the inverter output voltage target value Vinv * approximate each other, they overlap with each other in (a) of FIG.

  On the other hand, the inverter circuit control unit 33 stops the switching operation of the inverter circuit 11 in a period other than the period W2 in which the voltage of the inverter output voltage target value Vinv * is approximately −Vg to + Vg. During this time, the power boosted by the booster circuit 10 is supplied to the inverter circuit 11. Therefore, the inverter circuit 11 which has stopped the switching operation outputs the power supplied from the booster circuit 10 without stepping down.

  That is, the inverter device 1 according to the present embodiment performs switching operation so as to alternately switch the booster circuit 10 and the inverter circuit 11, and superimposes the powers output from each other to approximate the inverter output voltage target value Vinv *. Output AC power of voltage waveform.

As described above, in the present embodiment, when outputting the voltage of a portion where the absolute value of the inverter output voltage target value Vinv * is higher than the DC input voltage detection value Vg, the booster circuit 10 is operated to set the inverter output voltage target When outputting the voltage of the part where the absolute value of value Vinv * is lower than DC input voltage detection value Vg, control is performed to operate inverter circuit 11. Therefore, since the inverter circuit 11 does not step down the power boosted by the booster circuit 10, the potential difference at the time of stepping down the voltage can be suppressed to a low level, thereby reducing the loss due to the switching of the booster circuit. AC power can be output with efficiency.
Furthermore, since both the booster circuit 10 and the inverter circuit 11 operate based on the inverter output voltage target value Vinv * set by the control unit 12, the power of the booster circuit output so as to be switched alternately and the power of the inverter circuit Between the above and the other, it is possible to suppress the occurrence of deviation or distortion.

FIG. 12 is a diagram showing an example of a current waveform of AC power output from the inverter device 1 together with an example of a reference wave and a drive waveform of a switching element.
12, the reference wave Vinv # and the carrier wave of the inverter circuit, the drive waveform of the switching element Q1, the reference wave Vbc # and the carrier wave of the booster circuit, the drive waveform of the switching element Qb, and the inverter device 1 are output sequentially from the top. The graph which shows the target value and measurement value of the current waveform of alternating current power is represented. The horizontal axes of these graphs indicate time, which are shown to coincide with each other.

As shown in the figure, it can be seen that the actual measurement value Ia of the output current is controlled to match the target value Ia *.
Further, it can be seen that the period of the switching operation of the switching element Qb of the booster circuit 10 and the period of the switching operation of the switching elements Q1 to Q4 of the inverter circuit 11 are controlled to alternate substantially each other.

  Further, in the present embodiment, as shown in (a) of FIG. 8, the booster circuit is controlled such that the current flowing through the DC reactor 15 matches the current target value Iin * obtained based on the above equation (7). Ru. As a result, the voltages of the booster circuit and the inverter circuit have the waveforms shown in FIG. 8B, and the high frequency switching operation of the booster circuit 10 and the inverter circuit 11 has stop periods, respectively. It will be possible.

  Ideally, it is preferable that high-frequency switching be performed "alternately" by the booster circuit 10 and the inverter circuit 11 so that the timings of the high-frequency switching do not overlap, but even if some overlap actually occurs, each stop If there is a period, losses are reduced, which contributes to higher efficiency.

<< About the current phase of the output AC power >>
The booster circuit 10 and the inverter circuit 11 of the present embodiment output the AC power of the voltage waveform approximate to the inverter output voltage target value Vinv * to the filter circuit 21 connected to the subsequent stage under the control of the control unit 12. The inverter device 1 outputs AC power to the commercial power grid 3 via the filter circuit 21.

Here, the inverter output voltage target value Vinv * is generated by the control processing unit 30 as a voltage phase that is several degrees ahead of the voltage phase of the commercial power grid 3 as described above.
Therefore, the AC voltage output from the booster circuit 10 and the inverter circuit 11 is also set to a voltage phase advanced several times with respect to the voltage phase of the commercial power system 3.

  Then, at both ends of the AC reactor 22 (FIG. 2) of the filter circuit 21, a voltage with a voltage phase shifted by several degrees with respect to the commercial power system 3 is applied to one side. It will be different.

(A) of FIG. 13 is a graph showing the voltage waveforms of the AC voltage output from the inverter circuit 11, the commercial power grid 3 and the both-end voltage of the AC reactor 22. In the figure, the vertical axis represents voltage, and the horizontal axis represents time.
As shown in the figure, when the voltage across the alternating current reactor 22 is different in voltage phase by several degrees from each other, the voltage across the alternating current reactor 22 is the voltage across the alternating current reactor 22 whose voltage phase is different by several degrees The difference is

  Therefore, as shown in the figure, the phase of the voltage across the AC reactor 22 is a phase advanced by 90 degrees with respect to the voltage phase of the commercial power grid 3.

FIG. 13 (b) is a graph showing a current waveform flowing in the AC reactor 22. In the figure, the vertical axis represents current, and the horizontal axis represents time. The horizontal axis is shown to coincide with the horizontal axis of FIG.
The current phase of AC reactor 22 is delayed by 90 degrees with respect to the voltage phase. Therefore, as shown in the figure, the current phase of the AC power output through the AC reactor 22 is synchronized with the current phase of the commercial power system 3.

Accordingly, although the voltage phase output from the inverter circuit 11 is advanced several degrees with respect to the commercial power system 3, the current phase matches the current phase of the commercial power system 3.
Therefore, as in the graph shown at the bottom of FIG. 12, the current waveform output from the inverter device 1 matches the voltage phase of the commercial power grid 3.
As a result, since it is possible to output an alternating current having the same phase as the voltage of the commercial power grid 3, it is possible to suppress a decrease in the power factor of the AC power.

<< Utility of system voltage Va >>
(A) of FIG. 17 represents a good alternating current voltage of the grid simulated power supply, and (b) is a control using the measured value V _ad of the grid voltage instead of the aforementioned “Va” for the grid voltage for control. It is a wave form diagram showing the system current of alternating current at the time of having. As a specific use condition, it is a waveform diagram of a state in which power is supplied to a 1 kW load at a system voltage of 217 V from a direct current side voltage 103 V through a power conversion device. In the figure, a large distortion is clearly seen in the grid current of (b).

  On the other hand, under the same conditions of use, (a) in FIG. 18 represents the AC voltage of the grid simulated power supply, and (b) represents the AC grid current when control is performed using the grid voltage Va for control. FIG. In the figure, in (b), large distortion is reduced as compared with (b) in FIG. 17, and small distortion is scattered.

FIG. 19 (a) is a waveform diagram showing an actual alternating current grid voltage, and FIG. 19 (b) is an alternating current grid when control is performed using the measured value V _ad of the grid voltage for control. It is a wave form diagram showing current. When the waveform of the grid voltage in (a) is stable, the AC current in (b) is also generally stable although distortion is present. However, when the vibration component is superimposed on the waveform of the system voltage in (a) and distortion starts, the alternating current in (b) quickly responds to it and starts oscillating, and finally a sharp peak-like overcurrent flows. , The power converter was in the state of protection stop.

  FIG. 20 (a) is a waveform diagram showing an actual AC system voltage, and FIG. 20 (b) is a waveform diagram showing an AC system current when control is performed using a system voltage Va for control. It is. The waveform of the system voltage of (a) is stable, the alternating current of (b) is also stable, and distortion is small. After that, although not shown, the alternating current did not oscillate even if the vibration component was superimposed on the system voltage of (a).

Summary
Alternatively, as a control method, the control unit of the power conversion device causes one of the DC / DC converter and the full bridge circuit to perform a switching operation according to the phase of alternating current in an alternating current half cycle, and the other is In order to perform the operation of the minimum switching system which causes a pause period, the voltage of AC power, the voltage change due to the current flowing through the AC reactor and the impedance of the AC reactor, the reactive current flowing through the intermediate capacitor and the AC side capacitor, and DC power The current target value of the DC / DC converter is set to synchronize with the current of the AC power based on the voltage of. Further, the control unit uses, as the voltage of the AC power, a voltage obtained by supplementing the phase of the fundamental wave extracted based on the AC voltage detection value of the commercial power system, in consideration of the delay of the detection and control system.

  In such a power conversion device, while performing the operation of the minimum switching method, in consideration of the delay of the detection or control system, the fundamental wave extracted based on the AC voltage detection value of the commercial power system as the voltage of the AC power. By using the voltage complemented with the phase, the control delay with respect to the voltage phase is suppressed, and when the grid voltage is connected to the commercial power grid, the influence of the disturbance of the grid voltage is eliminated and stabilized. An alternating current with little distortion can be obtained.

The AC system voltage is, for example, V a — _{rms as} the effective value and ωt as the phase.
Va = √2 V _{a_rms} x sin (ωt)
It can be done.

The phase ωt of the Va can be a phase of timing for instructing a switching operation based on the immediately previous phase stored at the present time and a unit phase for advancing the phase.
In this case, the current phase can be determined by calculation based on the previous phase and the unit phase.
Specifically, the phase ωt may be a phase for instructing switching operation by adding a phase obtained by multiplying a unit phase for advancing the phase by a predetermined value to the phase stored immediately before the current time it can. In this case, while changing the predetermined value, it is possible to obtain a preferable value of the predetermined value at which the total current distortion factor of the alternating current and the power factor become the best.

[AC to DC power converter]
<< About the whole composition >>
Next, an embodiment of a power conversion device 1R that performs power conversion from alternating current to direct current will be described.
FIG. 14 is a block diagram showing an example of a power storage system provided with such a power conversion device 1R. In the figure, the storage battery 2 is connected to the output end of the power conversion device 1R, and the commercial power grid 3 (AC system) is connected to the input end. The storage system can convert power supplied from the commercial power grid 3 from alternating current to direct current and store the power in the storage battery 2.

  The power conversion device 1R includes an AC / DC converter 11u that converts alternating current received from the commercial power grid 3 into direct current, a step-down circuit (DC / DC converter) 10d that steps down the output voltage of the AC / DC converter 11u, and both of them. The control unit 12 controls the operation of the circuits 10d and 11u. As is apparent from the comparison with FIG. 1, the energy flow is in the reverse direction. When the inverter circuit 11 in FIG. 1 and the AC / DC converter 11 u in FIG. 14 are collectively referred to, they are simply referred to as a full bridge circuit structurally.

  FIG. 15 is an example of a circuit diagram of the power conversion device 1R. The difference from FIG. 2 is that, first, the photovoltaic panel 2 in FIG. 2 is replaced with the storage battery 2B. Further, as power conversion device 1R, step-up circuit 10 in FIG. 2 is replaced with step-down circuit 10d, and the circuit which is inverter circuit 11 in FIG. 2 has the same components but cooperates with AC reactor 22. It becomes an AC / DC converter 11 u that can be boosted.

  The step-down circuit 10d uses a switching element Qb2 in parallel with the diode 16 as in FIG. As the switching element Qb2, for example, the illustrated IGBT or FET can be used.

The other configuration of the power conversion device 1R is basically the same as that of the inverter device 1 of FIG. Therefore, the power conversion device 1R is bi-directional and can perform the same operation as the inverter device 1 of FIG. 2 if the solar power generation panel is connected. In addition, the DC power of the storage battery 2B can be converted to AC power to perform a self-sustaining operation.
When the power conversion device 1R operates as an inverter device, the switching element Qb2 is always in the off state (in the case of IGBT) or alternately turned on with the switching element Qb (in the case of FET) , And controlled by the control unit 12. The step-down circuit 10d is a step-up circuit, and the AC / DC converter 11u is an inverter circuit.

  When the storage battery 2B is charged based on the AC power of the commercial AC system 3, the control unit 12 can control the operation of each of the switching elements Q1 to Q4 to perform synchronous rectification. Further, by performing PWM control in the presence of the AC reactor 22, it is possible to perform rectification while boosting. Thus, the AC / DC converter 11 u converts AC power supplied from the commercial AC system 3 into DC power.

The step-down circuit 10d constitutes a step-down chopper circuit. The switching elements Qb and Qb 2 are controlled by the control unit 12.
Further, the switching operation of the step-down circuit 10d is controlled so that the periods in which the switching operation is performed between the AC / DC converter 11u are alternately switched. Therefore, step-down circuit 10d outputs the stepped-down voltage to storage battery 2B during the switching operation, and stops the switching operation (switching element Qb is off, Qb2 is on) during the AC / AC operation. The DC voltage output from the DC converter 11 u and input to the step-down circuit 10 d is applied to the storage battery 2 via the DC reactor 15.

Outline of voltage waveform
FIG. 16 is a voltage waveform diagram conceptually showing the operation of power conversion device 1R.
(A) shows an example of the absolute value of the AC input voltage target value Vinv * to the AC / DC converter 11 u. This is generally a full-wave rectified waveform of commercial alternating current. The two-dot chain line indicates a DC voltage Vg for charging. As shown in (b), in a section (t0 to t1, t2 to t3, t4) in which the DC voltage Vg is higher than the absolute value of the AC input voltage target value Vinv *, the AC / DC converter 11u performs switching operation. , Boost operation in cooperation with the AC reactor 22.

  On the other hand, in these steps (t0 to t1, t2 to t3, and t4), in the step-down circuit 10d, the switching element Qb is off and Qb2 is on, and the step-down operation is stopped. The thin stripe shown in (b) is actually a PWM pulse train, and the duty differs depending on the absolute value of the AC input voltage target value Vinv *. Therefore, assuming that the voltage in this state is applied to the DC / DC converter, the input voltage of the DC / DC converter, that is, the voltage of the capacitor 19 has a waveform as shown in (c).

  On the other hand, in a section (t1 to t2, t3 to t4) in which the DC voltage Vg is lower than the absolute value of the AC input voltage target value Vinv *, the AC / DC converter 11u stops switching, and instead, the step-down circuit 10d Operate. The term "switching" as used herein means high frequency switching of, for example, about 20 kHz, and does not mean low frequency switching of the level (two times the commercial frequency) at which synchronous rectification is performed. Even if all the switching elements Q1 to Q4 are turned off by stopping the switching of the AC / DC converter 11u, the voltage rectified through the built-in diodes of the switching elements Q1 to Q4 is input to the step-down circuit 10d. However, in order to reduce conduction loss, synchronous rectification is preferably performed.

  AC / DC converter 11u in the case of performing synchronous rectification turns on switching elements Q1 and Q4 and turns off switching elements Q2 and Q3 in a period in which the sign of the current of AC / DC converter 11u is positive under the control of control unit 12. Also, in the period in which the sign of the current of the AC / DC converter 11 u is negative, these on / off are reversed. The frequency of this inversion is twice that of the commercial frequency, so the frequency is very small compared to high frequency switching. Therefore, the loss due to on / off is extremely small.

  On the other hand, the step-down circuit 10d performs a step-down operation in the above section (t1 to t2, t3 to t4). The thin stripe shown in (d) is actually a PWM pulse train, and the duty differs depending on the absolute value of the AC input voltage target value Vinv *. As a result of the step-down, the desired DC voltage Vg shown in (e) is obtained.

As described above, the AC / DC converter 11 u operates only while the absolute value of the AC input voltage target value Vinv * based on the AC voltage is lower than the DC voltage Vg, and AC / DC is stopped by stopping switching in other periods. The switching loss of converter 11 u can be reduced.
Similarly, the step-down circuit 10d operates only during a period when the absolute value of the AC input voltage target value Vinv * is higher than the DC voltage Vg, and switching is stopped during other periods to reduce the switching loss of the step-down circuit 10d. it can.

  Thus, the AC / DC converter 11 u and the step-down circuit 10 d perform switching operations alternately, and when one operates, the other stops the switching. That is, a stop period of switching occurs in each of the AC / DC converter 11 u and the step-down circuit 10 d. Further, since the AC / DC converter 11 u operates to avoid the peak of the absolute value of the AC input voltage target value Vinv * and the vicinity thereof, the voltage at the time of switching becomes relatively low. This also contributes to the reduction of the switching loss. Thus, the switching loss of the power converter 1R as a whole can be significantly reduced.

<< Specification of control >>
Control of the power conversion device 1R can be considered as similar control in which control of grid interconnection by the inverter device 1 of FIG. 2 is viewed in the reverse direction. This is control suitable for enhancing the efficiency of the power conversion device 1R also in the reverse direction operation using the power conversion device 1R that can cause the same grid connection as the inverter device 1.

The quantities in the inverter device 1 and the quantities in the corresponding power converter 1 R are as follows.
Ia *: Input current target value from the commercial power grid 3 Iin: Step-down circuit current detection value Iin *: Step-down circuit current target value Iinv *: AC input current target value to the AC / DC converter 11 u Ig *: To the storage battery 2B DC input current target value Ic: current flowing to capacitor 19 Ica: current flowing to capacitor 23

Va: System voltage Vg: Battery voltage value Vinv *: AC input voltage target value to AC / DC converter 11u Vo *: Input voltage target value to step-down circuit 10d Pin: Input power to storage battery 2B P _LOSS : Power converter Power loss of 1R η: Power conversion efficiency of the power converter 1R

Therefore, the following relationship corresponding to the above-mentioned Formula (1)-(8) in the inverter apparatus 1 of FIG. 2 is applicable.
Average value <Pin> of input electric power Pin to storage battery 2B corresponding to Formula (1) is
<Pin> = <Iin × Vg> (R1)
It is.
The average value <Ia *> of the input current target value from the commercial power grid 3 corresponding to the equation (2) is
<Ia *> = <Ig * × Vg> / (η × <Va>) (R2)
It is.
The input current target value Ia * corresponding to the equation (3) is
Ia * = (√2) × <Ia *> × sin (ωt) (R3)
It is.

The AC input current target value Iinv * corresponding to the equation (4) is
Iinv * = Ia *-s CaVa ... (R4)
It is.
If expression (R4) above is expressed using differentiation at time t,
Iinv * = Ia * -Ca × (d Va / dt) (R4a)
It becomes. Also, if the current flowing to the capacitor 23 is detected and this is Ica,
Iinv * = Ia * -Ica (R4b)
It becomes.

Further, the AC input voltage target value Vinv * corresponding to the equation (5) is
Vinv * = Va-Za Iinv * (R5)
It is.
If expression (R5) above is expressed using differentiation at time t,
Vinv * = Va− {RaIinv * + La × (d Iinv * / dt)
... (R5a)
It becomes.

  As described above, input target values (Iinv *, Vinv *) to the AC / DC converter 11u, which are target values on the AC side, are set at a circuit connection point P between the AC / DC converter 11u and the filter circuit 21. . Therefore, as in the case of grid connection, the set point of the target value is moved forward (AC / DC converter 11 u side) from the circuit connection point of the commercial power grid 3 and the power conversion device 1R. By so-called "reverse" grid interconnection, appropriate interconnection between AC and DC is performed.

Further, for the input voltage target value Vo * to the step-down circuit 10d corresponding to the equation (6), Vgf in the equation (6), that is, (Vg−Z Iin) is replaced by Vgr, that is, (Vg + Z Iin)
Vo * = Max (Vg + Z Iin, absolute value of Vinv *) (R6)
It can be done.
If expression (R6) above is expressed using differentiation at time t,
Vo * =
Max (Vg + R Iin + L (d Iin / dt), absolute value of Vinv *)
... (R6a)
It becomes.

Also, the step-down circuit current target value Iin * is
Iin * =
{(Iinv * × Vinv *)-(s C Vo *) × Vo *} /
(Vg + ZIin) · · (R7)
It is.
If expression (R7) above is expressed using differentiation at time t,
Iin * =
{(Iinv * × Vinv *) − C × (d Vo * / dt) × Vo *} /
{Vg + RIin + L (dIin / dt)) (R7a)
It becomes. Also, if the current flowing to the capacitor 19 is detected and this is Ic,
Iin * =
{(Iinv * × Vinv *) − Ic × Vo *} / (Vg + ZIin)
... (R 7 b)
It becomes.

  The terms added to the product of AC input current target value Iinv * and AC input voltage target value Vinv * in the equations (R7), (R7a) and (R7b) take account of reactive power passing through capacitor 19 Value. That is, the value of Iin * can be determined more accurately by considering the reactive power in addition to the power target value of the AC / DC converter 11 u.

Further, if measuring the power loss P _LOSS pre power converter 1R, the formula (R7a) can also be expressed as follows.
Iin * =
{(Iinv * × Vinv *) − C × (d Vo * / dt) × Vo * −P _LOSS } / (Vg + ZIin) (R7c)
Similarly, the above formula (R7b) can also be expressed as follows.
Iin * =
{(Iinv * × Vinv *) − Ic × Vo * −P _LOSS } / (Vg + ZIin)
... (R7d)
In this case, the value of Iin * can be determined more strictly by considering the reactive power and the power loss P _LOSS in addition to the power target value of the AC / DC converter 11 u.

Incidentally, the capacitance C and the power loss _{P LOSS} of the capacitor 19, is sufficiently small, the following formula (R8) is established as compared with the (Iinv * × Vinv *). The Iin * determined by the formula (R8) can be used as Iin included in the right side of the formulas (R6), (R6a), (R7), (R7a), (R7b), (R7c) and (R7d).
Iin * = (Iinv * × Vinv *) / Vg (R8)

  As described above, when the control unit 12 outputs a voltage of a portion where the absolute value of the AC input voltage target value Vinv * to the AC / DC converter 11 u is higher than the DC voltage (Vg + Z Iin), When the circuit 10d is operated to output a voltage of a portion where the absolute value of the AC input voltage target value Vinv * is lower than the DC voltage (Vg + ZIin) to the AC / DC converter 11u, the AC / DC converter 11u operates. Is controlled to Therefore, the potential difference at the time of boosting by the AC / DC converter 11 u can be suppressed low, and the switching loss of the AC / DC converter 11 u and the step-down circuit 10 d can be reduced to output DC power with higher efficiency.

  Furthermore, since both step-down circuit 10d and AC / DC converter 11u operate based on the target value set by control unit 12, even if the high frequency switching periods of both circuits are alternately switched, AC / DC does not occur. It is possible to suppress the occurrence of phase shift and distortion in the alternating current input to converter 11 u.

  In addition, as described above, the power conversion device IR can perform the same grid connection operation as the inverter device 1 of FIG. 2. Therefore, it is possible to realize an efficient power converter that can be used in both directions of direct current / AC conversion and grid-connected AC / DC conversion.

Second Embodiment
In the first embodiment, not the actual system voltage measurement value but the system voltage Va generated based on the equations (01) and (02) is used as the system voltage Va. Thus, equation (5)
Vinv * = √2 · V _{a_rms} × sin (ωt) + Za · Iinv *
... (5 ')
become. When the inverter output voltage target value Vinv * is determined, when the fundamental wave component of the grid voltage is used, the DC / DC converter or the full bridge circuit generates an output current whose counterpart is only the fundamental wave component. Therefore, if there is voltage distortion in the grid voltage, the distortion acts on the control in a feedforward manner, and the output current distortion is increased because the output current corresponding to the voltage distortion is not output.

Therefore, the output current distortion factor is reduced and the power factor is improved by considering the respective harmonics of the grid voltage when calculating the inverter voltage target value of the minimum switching conversion method, even if the grid voltage is distorted. That is, the following equation (9) is used.
Vinv * = {√2V _{a_rms} × sin (ωt) + V ₂ × sin (2ωt + θ ₂ ) + V ₃ × sin (3ωt + θ ₃ ) +... + V _n × sin (nωt + θ _n )} + Za · Iinv * (9) )
V _n is the peak value of the n th harmonic in the grid voltage, n is an integer, and θ _n is the initial phase of the n th harmonic in the grid voltage.

Therefore, the concept of discrete Fourier transform is used to calculate V _n and θ _n .
A sampling value at, for example, 20 kHz for each phase of the grid voltage is taken as Va_sampling. The n-th order Fourier coefficients a _n and b _n are as follows.

... (10)

... (11)

The peak value V _n of the _n-th harmonic is

... (12)
It is.

Also, the initial phase θ _n of the _n-th harmonic is

... (13)
It is.

FIG. 21 is a waveform diagram (top) of the system voltage and a waveform diagram (bottom) of the output current in the case where the inverter output voltage target value Vinv * is determined and controlled without considering harmonics of the system voltage with particularly high distortion. .
As the conditions, the AC voltage 202 V (frequency 50 Hz) contains 3% of 3rd harmonic of initial phase 0, 3% of 5th harmonic of initial phase 0, and 3% of 7th harmonic of initial phase 0 Consider the case where 1kW discharge is performed with a DC voltage of 100V as the target of the system voltage. The period for sampling voltage and the like and performing PWM control is 20 kHz. In this case, the total current distortion factor is 24.8%, the power factor is 0.955, and the output current is considerably distorted.

FIG. 22 is a waveform diagram (top) of the system voltage and a waveform diagram (bottom) of the output current in the case of determining and controlling the inverter output voltage target value Vinv * in consideration of harmonics of the particularly strained system voltage. .
As conditions, similarly, AC voltage 202 V (frequency 50 Hz), 3rd harmonic of 3rd phase of initial phase 0, 3rd harmonic of 5th harmonic of initial phase 0, 3rd harmonic of 7th harmonic of initial phase 0 Consider the case where 1kW discharge is performed by setting the included voltage as the target of the system voltage and setting the DC side voltage to 100V.

For Figure 22, a _{n =} 0 in view of the operation load of the harmonic considered in the inverter output voltage target value calculation control section 12, i.e. the initial phase 0, cubic as order harmonics, fifth, seventh It is as follows. If the inverter output voltage target value is written by the formula,
Vinv * = √2V _{a_rms} × sin (ωt) + V ₃ × sin (3ωt) + V ₅ × sin (5ωt) + V ₇ × sin (7ωt) (14)
It is. At this time, the total current distortion factor is 2.6%, the power factor is 0.998, and the output current has a sinusoidal shape. Thus, it is understood that the power factor is improved by reducing the output current distortion by considering the harmonics in the inverter output voltage target value.

<Supplementary Note>
It should be understood that the embodiments disclosed herein are illustrative and non-restrictive in every respect. The scope of the present invention is shown by the claim, and it is intended that the meaning of a claim and equality and all the changes within the range are included.

DESCRIPTION OF SYMBOLS 1 inverter apparatus 1R power converter 2 photovoltaic generation panel 2B storage battery 3 commercial power grid 10 step-up circuit (DC / DC converter)
10d Step-down circuit (DC / DC converter)
11 Inverter circuit (full bridge circuit)
11u AC / DC converter (full bridge circuit)
12 control part 15 direct current reactor 16 diode 17 first voltage sensor 18 first current sensor 19 capacitor (intermediate capacitor))
21 filter circuit 22 AC reactor 23 capacitor (AC side capacitor)
24 second current sensor 25 second voltage sensor 26 capacitor 27 third voltage sensor 30 control processing unit 32 step-up circuit control unit 33 inverter circuit control unit 34 averaging processing unit 41 first calculation unit 42 first adder 43 compensator 44 Second adder 51 Second arithmetic unit 52 Third adder 53 Compensator 54 Fourth adder P Circuit connection point Q1 to Q4, Qb Switching element

Claims (7)

A power conversion device provided between a commercial power system and a DC power supply having a voltage lower than a peak value of an absolute value of the AC voltage, which converts DC power into AC power or vice versa.
A DC / DC converter connected between the DC power supply and the DC bus;
An intermediate capacitor connected between the two wires of the DC bus;
A full bridge circuit provided between the DC bus and the commercial power system;
A filter circuit provided between the commercial power system and the full bridge circuit and including an AC reactor and an AC side capacitor;
A control unit for causing one of the DC / DC converter and the full bridge circuit to perform a switching operation and causing the other to perform a rest period according to an alternating current phase in an alternating current half cycle; Is
The voltage of the AC power, the current flowing through the AC reactor, the voltage change due to the impedance of the AC reactor, the reactive current flowing through each of the intermediate capacitor and the AC side capacitor, and the voltage of the DC power, The current target value of the DC converter is set to be synchronized with the current of the AC power, and
A power conversion device using, as a voltage of the AC power, a voltage obtained by supplementing a phase in consideration of a delay of a detection or control system to a fundamental wave extracted based on an AC voltage detection value of the commercial power system. The control unit
Assuming that the output current target value to the load is Ia *, the capacitance of the AC capacitor is Ca, the AC system voltage is Va, the DC power supply voltage is V _DC , and the Laplace operator is s AC output current target value Iinv * of the full bridge circuit at the circuit connection point between the filter circuit and the full bridge circuit,
Iinv * = Ia * + s CaVa
Further, when the impedance of the AC reactor is Za, the AC output voltage target value Vinv * of the full bridge circuit at the circuit connection point is
Vinv * = Va + ZaIinv *
Setting the voltage V _DC and the absolute value of the AC output voltage target value Vinv * of the full bridge circuit, whichever is larger, to the output voltage target value Vo * of the DC / DC converter; Assuming that the capacitance of the intermediate capacitor is C, the current target value Iin * of the DC / DC converter is
Iin * = {(Iinv * × Vinv *) + (s C Vo *) × Vo *} / V _DC
Set to
The ac grid voltage Va has the effective value as _{Va_rms} , and the phase of the timing for instructing the switching operation as ωt.
Va = √2 V _{a_rms} x sin (ωt)
The power conversion device according to claim 1.   The power conversion device according to claim 1, wherein the phase of the timing at which the switching operation is instructed is obtained based on the immediately previous phase stored at this point and a unit phase for advancing the phase.   The power conversion device according to claim 3, wherein a phase obtained by multiplying a unit phase for advancing the phase by a predetermined value is added to the phase stored immediately at the present time to obtain the phase of the timing. A DC / DC converter connected between a DC power supply and a DC bus, an intermediate capacitor connected between two lines of the DC bus, and a full bridge circuit provided between the DC bus and a commercial power system And a filter circuit provided between the commercial power system and the full bridge circuit and including an AC reactor and an AC-side capacitor, wherein the DC power supply has a voltage lower than the peak value of the absolute value of the commercial power system. What is claimed is: 1. A method of controlling a power conversion device, the control unit executing, in a power conversion device that converts direct current power into alternating current power or vice versa.
The voltage of the AC power, the current flowing through the AC reactor, the voltage change due to the impedance of the AC reactor, the reactive current flowing through each of the intermediate capacitor and the AC side capacitor, and the voltage of the DC power, The current target value of the DC converter is set to be synchronized with the current of the AC power, and switching operation is performed to one of the DC / DC converter and the full bridge circuit according to the phase of the AC within an AC half cycle. Create a period of rest, with the other
A control method of a power conversion device, using, as a voltage of the AC power, a voltage obtained by supplementing a phase in consideration of a delay of a detection or control system to a fundamental wave extracted based on an AC voltage detection value of the commercial power system. A power conversion device provided between a commercial power system and a DC power supply having a voltage lower than a peak value of an absolute value of the AC voltage, which converts DC power into AC power or vice versa.
A DC / DC converter connected between the DC power supply and the DC bus;
An intermediate capacitor connected between the two wires of the DC bus;
A full bridge circuit provided between the DC bus and the commercial power system;
A filter circuit provided between the commercial power system and the full bridge circuit and including an AC reactor and an AC side capacitor;
A control unit for causing one of the DC / DC converter and the full bridge circuit to perform a switching operation and causing the other to perform a rest period according to an alternating current phase in an alternating current half cycle; Is
The voltage of the AC power, the current flowing through the AC reactor, the voltage change due to the impedance of the AC reactor, the reactive current flowing through each of the intermediate capacitor and the AC side capacitor, and the voltage of the DC power, The current target value of the DC converter is set to be synchronized with the current of the AC power, and
The power converter which uses the voltage which considered the harmonic to the fundamental wave extracted based on the alternating current voltage detection value of the said commercial power grid as a voltage of the said alternating current power. A DC / DC converter connected between a DC power supply and a DC bus, an intermediate capacitor connected between two lines of the DC bus, and a full bridge circuit provided between the DC bus and a commercial power system And a filter circuit provided between the commercial power system and the full bridge circuit and including an AC reactor and an AC-side capacitor, wherein the DC power supply has a voltage lower than the peak value of the absolute value of the commercial power system. What is claimed is: 1. A method of controlling a power conversion device, the control unit executing, in a power conversion device that converts direct current power into alternating current power or vice versa.
The voltage of the AC power, the current flowing through the AC reactor, the voltage change due to the impedance of the AC reactor, the reactive current flowing through each of the intermediate capacitor and the AC side capacitor, and the voltage of the DC power, The current target value of the DC converter is set to be synchronized with the current of the AC power, and switching operation is performed to one of the DC / DC converter and the full bridge circuit according to the phase of the AC within an AC half cycle. Create a period of rest, with the other
The control method of the power converter device using the voltage which considered the harmonic to the fundamental wave extracted based on the alternating voltage detection value of the said commercial power grid as a voltage of the said alternating current power.