JPH1023766A - Power inverter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain high power inverter efficiency at a low cost. SOLUTION: A power inverter has a switching bridge unit 2 in which one (21) of the nodes 21 and 23 on one side of a diagonal is connected to one end of a solar cell 1 through a reactor L1 and the other node 23 facing the node 21 is connected to the other end of the solar cell 1 and two nodes 22 and 24 on the other side of the diagonal are connected to one end of a reactor L2 and one end of a reactor L3 respectively and a capacitor C1 whose both ends are connected to the other end of the reactor L2 and the other end of the reactor L3. A DC power is inverted into a commercial AC power by a pulse width modulation wherein switching devices Q1 and Q3 whose one side ends are connected to the one node 21 on the one side of the diagonal are turned on and off synchronously with a commercial power supply and reversely to each other and switching devices Q2 and Q4 whose one side ends are connected to the other node 23 are alternately turned on and off and the commercial AC power is outputted from both terminals of a capacitor C2.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power converter, and more particularly to a power converter for converting a DC power supply such as a solar cell into an AC power supply.

[0002]

2. Description of the Related Art Conventionally, as a power converter for converting a DC output of a self-generated power supply such as a solar cell into an AC and outputting an AC voltage, for example, Japanese Patent Application Laid-Open No. 6-332554 shown in FIG.
Has the configuration disclosed in US Pat. The booster circuit unit 8 boosts a direct current of which voltage value changes from the solar cell 1 to a predetermined magnitude by an output of a booster control circuit 9 and outputs the boosted voltage. And an inverter main circuit section 2 for converting the output to a line and outputting the converted signal to a line.

More specifically, reference numeral 1 denotes a solar cell as a DC power supply, and D5 denotes a backflow prevention diode, whose anode is connected to the positive electrode side of the solar cell 1. C2 is a smoothing capacitor formed by an electrolytic capacitor, one end of which is connected to the cathode of the backflow prevention diode D5 and the other end of which is connected to the negative electrode side of the solar cell 1 to smooth and stabilize the output voltage from the solar cell 1. I have.

[0006] The booster circuit section 8 includes a switch element Q0 such as a transistor, a reactor L1, and diodes D0 and D6. And the smoothing capacitor C2
, And the DC power from the solar cell 1 is input after the voltage is stabilized by the smoothing capacitor 3.
The booster circuit unit 8 detects the output voltage V2 at the output terminal by the booster control circuit 9 and performs switching control to boost the input voltage whose magnitude changes to a predetermined voltage value.

[0005] C0 is a smoothing capacitor formed by an electrolytic capacitor, both ends of which are connected to the output of the booster circuit section 8 to absorb and smooth the high-frequency components generated by the boosting switching.

The inverter main circuit section 2 includes a switch element Q
1, Q2, Q3, Q4 and each of the switch elements, diodes D1, D
2, D3 and D4, reactors L2 and L3 for a low-pass filter, and a capacitor C1. Then, a DC having a predetermined voltage value, which is an output from the booster circuit section 8, is input, and the DC is converted into a commercial AC power and output.

SW is a switch, one end of which is connected to one output terminal of the inverter main circuit section 2 and the other end is connected to one end of a load 5. The other end of the load 5 is connected to the other output terminal of the inverter main circuit section 2. A commercial power supply 4 is connected to both ends of the load 5.
Therefore, the AC power output from the inverter main circuit unit 2 is connected to the commercial power system 4 via the switch SW, and is connected to the load 5.
Supplied to Reference numeral 6 denotes an inverter control circuit, which switches the switching elements Q1, Q2, and Q2 of the inverter main circuit unit 2 so that the output power of the solar cell 1 is substantially maximized and AC output is performed.
This is a control circuit for generating and controlling a gate signal that performs pulse width modulation on Q3 and Q4.

In the above configuration, the booster circuit section 8 is provided to secure a potential difference between the output voltage from the solar cell 1 and the commercial power supply voltage of the inverter main circuit section 2, and is a one-piece chopper circuit. Is formed by Therefore, the output of the DC voltage is supplied to the current sensor CT1 and the voltage sensor PT1 for detecting the output of the solar cell 1 and the current sensor CT2 and the voltage for detecting the output to the commercial power system by the inverter main circuit unit 2 at the subsequent stage. Sensor PT2
Are input to the inverter control circuit 6 for calculation, and the switching elements Q1, Q2, Q3, and Q4 are stably switched. Then, it is converted into a sine wave including a high frequency component and output, and the reactors L2 and L3
The high-frequency component is removed by a low-pass filter including a capacitor C1 and the power is converted and output to the load 5.

[0009]

By the way, in the above-mentioned circuit configuration, the switch loss or the on-resistance loss of each switch element and diode greatly affects the conversion efficiency of power conversion. Then, a control method of a booster circuit for reducing a loss for the purpose of improving power conversion efficiency has been devised. As a result, the cost was increased due to the complicated circuit configuration.

[0010] The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a power conversion device capable of obtaining high power conversion efficiency at low cost.

[0011]

In order to achieve the above object, a power converter according to claim 1 converts a direct current, which varies in voltage value input from a direct current power supply, into an alternating current having a predetermined voltage value. An output power converter, wherein one vertex of one diagonal is connected to one end of a DC power supply via a first reactor,
A switch bridge section in which the other apex opposite the apex is connected to the other end of the DC power source, and the other two diagonal apexes are respectively connected to one end of a second reactor and a third reactor; A capacitor having both ends connected to the other ends of the second reactor and the third reactor, and synchronizing a switch element having one end connected to one vertex of the one diagonal of the switch bridge section with a commercial power supply DC power is converted to commercial AC by pulse width modulation control for turning on and off each other and alternately turning on and off each of the switch elements having one end connected to the other vertex, and outputting the same from both ends of the capacitor. I have to do that. Thus, the direct current is connected such that one vertex of one diagonal is connected to one end of the DC power supply via the first reactor, and the other vertex opposed to the vertex is connected to the other end of the DC power supply. In a switch bridge section in which two vertexes of a corner are respectively connected to one end of a second reactor and a third reactor, a switch element having one end connected to one vertex of one diagonal is synchronized with a commercial power supply and mutually connected. Both ends are connected to the other end of the second reactor and the third reactor by pulse width modulation control in which each of the switch elements that are inverted and turned on and off and one end of which is connected to the other vertex are alternately turned on and off. Both ends of the capacitor are converted to commercial AC and output.

According to a second aspect of the present invention, in the power converter, the switch element having one end connected to one vertex of the one diagonal is formed by a bipolar element. Thus, a switch element having one end connected to one vertex of one diagonal is formed by the bipolar element.

According to a third aspect of the present invention, there is provided the power conversion device, wherein the pulse width modulation control according to the first or second aspect is configured such that an absolute value of a voltage value of an AC output in a half cycle of a commercial power supply is equal to an input voltage from the DC power supply. When smaller, only one of the switch elements having one end connected to the other vertex is on,
When the absolute value of the voltage value of the AC output is substantially equal to or greater than the input voltage from the DC power supply, each of these switch elements is alternately turned on and off. Accordingly, when the pulse width modulation control is performed, when the absolute value of the voltage value of the AC output in a half cycle of the commercial power supply is smaller than the input voltage from the DC power supply, any one of the switch elements having one end connected to the other vertex. Pulse width modulation control for turning on or off only one of them, and when the absolute value of the voltage value of the AC output is substantially equal to or larger than the input voltage from the DC power supply, these switch elements are turned on and off alternately. This is based on pulse width modulation control.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a first embodiment of the power converter of the present invention will be described with reference to FIGS. 1 to 4, and a second embodiment will be described with reference to FIGS. .

[First Embodiment] FIG. 1 is a circuit configuration diagram of a power converter according to a first embodiment. FIG. 2 is a configuration diagram of a switch bridge control unit which is a main part of the power conversion device shown in FIG. FIG. 3 is a control flowchart of a switch bridge controller, which is a main part of the power converter shown in FIG. FIG. 4 is a waveform diagram for explaining the operation of the switch bridge control unit of the power converter shown in FIG.

This power conversion device is a system interconnection inverter corresponding to a power conversion device that converts a direct current having a variable voltage value input from a solar cell 1 serving as a direct current power supply into an alternating current having a predetermined voltage value and outputs the alternating current. In the device, a first reactor L1;
The switch bridge unit 2, the low-pass filter 3 including the second reactor L2, the third reactor L3, and the capacitor C1, and the switch bridge control unit 6 are main components.

The switch bridge unit 2 is used together with the first reactor L1 and a capacitor C1 of a low-pass filter, which will be described later, to systematically connect a DC whose voltage value changes to a commercial AC and output an AC through a pulse width modulation control. , And is formed by switch elements Q1, Q2, Q3, and Q4 connected in a bridge. The switch bridge unit 2 is configured such that one vertex 21 of one diagonal is connected to one end (positive electrode) of the solar cell 1 via the first reactor L1 and the other vertex 23 facing the vertex is the other end of the solar cell 1 (Negative electrode), and each of the other two vertexes 22 and 24 of the other diagonal is connected to a second reactor L2 and a third reactor L3 of the low-pass filter 3 described later.
Is connected to one end. Switch elements Q1, Q2, Q
3. A diode D1, between the emitter and collector of Q4,
D2, D3, and D4 are connected such that the emitter side is an anode and the collector side is a cathode.
The diodes D1, D2, D3, and D4 are connected to the collectors of the switch elements Q1, Q2, Q3, and Q4 at the moment when the switching operation of the switch elements is turned off, by the voltage of the reverse electromotive force generated between the emitter and the collector. This prevents the insulation between the emitters from being destroyed.

In the switch bridge section 2, the switch elements Q1 and Q3 are constituted by bipolar switch transistor elements, and the switch elements Q2 and Q4 are constituted by IGBT elements. This IGBT element is a MOS
High-speed response and voltage-driven characteristics of the FET element,
This is a power control element having characteristics of low saturation voltage characteristics of a bipolar transistor, capable of high-frequency switching control, and having a low on-resistance. Further, the bipolar switch transistor has a characteristic of a lower saturation voltage characteristic than the IGBT element, and is most suitable for the switching control at about the commercial frequency in the present invention.

The first reactor L1 accumulates electric charges at the moment when all of the switch elements of the switch bridge unit 2 are turned off by the switching operation, and then directs the electric charge toward the low-pass filter 3 when a predetermined switch element is turned on. It has a function of outputting electric charge.

The low-pass filter 3 is for preventing high-frequency current noise generated by the switching operation of each switch element of the switch bridge section 2 from being emitted to the wiring line, and includes a second reactor L2 and a third reactor L2. L3 and a capacitor C1. One end of the second reactor L2 and one end of the third reactor L3 are connected to two vertices 22 and 2 of the other diagonal of the switch bridge unit 2.
4 has the other end connected to both ends of the capacitor C1. The low-pass filter 3 receives an alternating current including a high-frequency component from the switch bridge unit 2, removes the high-frequency current component, smoothes the output, and outputs the result. Note that the capacitor C1 also has a function of receiving and accumulating the electric charge accumulated by the first reactor L1 and outputting it as AC power in power conversion by pulse width modulation control of the switch element of the switch bridge unit 2.

The switch bridge control unit 6 is for generating a gate signal for performing pulse width modulation control of each switch element of the switch bridge unit 2, and as shown in FIG.
It is formed by a one-chip microcomputer having a storage unit 62, an AD conversion unit 63, and an output unit 64 with the central processing unit 61 at the center. The switch bridge controller 6 includes a current sensor C for detecting the output of the solar cell 1.
A DC current signal Ii from T1, a DC voltage signal Vi from the voltage sensor PT1, an AC current signal Io from the current sensor CT2 for detecting an output to the commercial power system 4, and an AC voltage signal Vo from the voltage sensor PT2. Each detection signal is
The signals are input to the AD converter 63, respectively. Then, according to a predetermined program stored in the storage unit 62, the central processing unit 61 converts each signal of Vi, Ii, Vo, and Io into an AD signal.
After the conversion, the operation is performed, and control pulse signals sQ1, sQ2, sQ3, s are output from the output unit 64 to the gates of the switch elements Q1, Q2, Q3, Q4 of the switch bridge unit 2.
Output Q4.

In the power converter having the above-described configuration, both ends of the capacitor C1 of the low-pass filter 3 are appropriately connected to the switch S
Connected to both ends of the load 5 via the W
In addition, the system is interconnected to supply AC power. Note that a backflow prevention diode and a smoothing capacitor may be appropriately provided in a stage preceding the switch bridge unit 2 as in the conventional example.

Next, the operation of converting the DC power of the solar cell 1 into the AC power by the power converter described above will be described.

When DC power is output from the solar cell 1,
The DC voltage signal Vi is input from the voltage sensor PT1 to the switch bridge control unit 6. Then, when it is detected that the DC voltage signal Vi has become equal to or higher than a predetermined voltage value, a program for a gate signal creation process of the switch elements Q1, Q2, Q3, Q4 starts.

First, it is determined whether the voltage of the AC voltage signal Vo of the commercial power supply from the commercial power system 4 is positive or negative, and one end of the switch bridge unit 2 is connected to one vertex 21 of one diagonal of the switch bridge unit 2 according to the positive or negative condition. Is connected to the switching element Q
1. Synchronize Q3 with the commercial power supply and invert each other to turn on and off.

Next, the AC current signal Io is AD-converted, the difference between the AD-converted data and the waveform data of the sine-wave reference wave f2 'stored in advance is calculated, and the sine-wave reference wave to be output is calculated. Generate the waveform data of f2. Next, the waveform data of the sine wave reference wave f2 is compared with the previously stored waveform data of the triangular wave reference wave f1, and the switch elements Q2, Q4, one ends of which are connected to the other vertex 23 of the switch bridge unit 2, are connected. Are alternately turned on and off, respectively, based on a predetermined program.

Next, for example, the on / off state of the signal of the switch element Q1 is detected, and if the signal of the switch element Q1 is on, the switching elements Q2 and Q4 are respectively t1 / 2.
, And if the signal of the switching element Q1 is off, the switching elements Q4 and Q2 are in the order of t1 / 2, respectively.
And outputs a pulse width modulation control signal that is turned on by time.

For example, when the switching element Q1 is turned on and the switching element Q2 is turned on for a time t1 / 2,
Solar cell 1, first reactor L1, switch element Q1,
A current flows through the loop of the switching element Q2, and the electric charge is accumulated in the first reactor L1. Next, the switching element Q2 is turned off and the switching element Q4 is turned on only for a time period of t1 / 2, so that the current corresponding to the added charge of the solar cell 1 and the first reactor L1 is increased by the switching element Q1, the low-pass filter 3, It flows into the loop of the switch element Q4. As a result, both ends of the capacitor C1 of the low-pass filter 3 are charged and simultaneously discharged as power. In the power output level adjustment, the charge stored in the first reactor L1 is increased by increasing the time t1, and the output power can be increased. By decreasing the time t1, the power is accumulated in the first reactor L1. The charge is reduced, and the output power can be reduced. That is, this t1
, The energy stored in the reactor L1 can be adjusted, the power itself supplied to the capacitor C1 reflected on the output power can be adjusted, and as a result, the output power can be adjusted.

As described above, the switch bridge controller 6
Is an AC voltage signal Vo of a commercial power supply from the commercial power system 4.
Is input, and the respective detection signals of the DC current signal Ii and the DC voltage signal Vi and the AC current signal Io and the AC voltage signal Vo are used to synchronize with the commercial power supply based on a predetermined program and to alternately turn on and off the total. The solar cell 1 which calculates the time t1 and changes the voltage value from 0 to approximately 300 V
DC power is converted to AC power with high efficiency,
Switch elements Q1, Q2, Q of switch bridge unit 2
3. Pulse width modulation control of Q4.

The AC output obtained by the above-described pulse width modulation control is applied to the capacitor C1 of the low-pass filter 3 including the high-frequency current component caused by the switching operation. The high-frequency current component is applied to the second reactor L2 and the third reactor L2. The passage thereof is substantially blocked by the reactor L3, and the charge accumulated by the first reactor L1 and the charge of the high-frequency current component not blocked by the capacitor C1 are accumulated, smoothed, and output as the output current Io. You. This output Io is combined with the supply current Iu from the commercial power system 4 and input to the load 5 as the load current IL.

Next, the operation of controlling the pulse width modulation of the switching elements Q1, Q2, Q3, Q4 of the switch bridge unit 2 by the switch control unit 6 of the power converter described above will be described with reference to the flowchart of FIG. .

When the program for the gate signal generation processing of the switch elements Q1, Q2, Q3, Q4 starts, first, the polarity of the commercial power supply voltage from the commercial power system 4 connected to the system is determined by the AC voltage signal Vo ( Step 1). If positive, the gate signal of the switch element Q1 is set to High to turn on the switch element Q1 (step 2), and the gate signal of the switch element Q3 is set to Lo.
The switch element Q3 is turned off as w (step 3).
If it is negative, the switch element Q1 is turned off (step 4) and the switch element Q3 is turned on (step 5).

Next, the AC current signal Io is AD-converted (step 6). Then, a difference between the data after the AD conversion and the waveform data of the sine wave reference wave f2 ′ stored in advance is calculated to generate the waveform data of the sine wave reference wave f2. (Step 7). Next, the data of the sine wave reference wave f2 is compared with the previously stored triangular wave reference value data f1, and a total time t1 for turning on and off the switching elements Q2 and Q4 alternately is calculated (step 8).
Then, the result of the determination in step S1 is referred to by turning on / off the switching element Q1 (step 9). If the switch element Q1 is on, the switch element Q2 is turned on for t1 / 2 (step 10), and then the switch element Q4 is turned on for t1 / 2 (step 11). If the switch element Q1 is off, the switch element Q4 is turned on for t1 / 2 (step 12).
Next, the switching element Q2 is turned on for t1 / 2 (step 13).

The output level of the power conversion can be adjusted by changing the data of the sine wave reference wave f2 'by adjusting the time of t1 by a program (not shown) other than the above program.

According to the power converter described above, the direct current is applied to the first reactor L1
Is connected to one end of the solar cell 1, and the other apex 22 facing the apex 21 is connected to the other end of the solar cell 1,
One apex 21 of one diagonal of switch bridge portion 2 in which each of two vertices 23 and 24 of the other diagonal are connected to one end of second reactor L2 and one end of third reactor L3, respectively.
The switch elements Q1 and Q3, one ends of which are connected to the commercial power supply, are turned on and off in synchronization with each other and inverted, and the switch elements Q2 and Q4 whose one ends are connected to the other vertex 23 are connected.
Are alternately turned on and off by pulse width modulation control, and are converted to commercial AC from both ends of a capacitor C1 whose both ends are connected to the other ends of the second reactor L2 and the third reactor L3, and output. Therefore, the switching element Q0 for boosting the DC voltage, which is required in the conventional example, becomes unnecessary, and the switch loss or the on-resistance loss is eliminated, so that the power conversion efficiency can be obtained at a low cost for the device. In addition, since the switching elements Q1 and Q3 each having one end connected to one vertex 21 of one diagonal are formed by bipolar switch transistor elements, on-resistance loss is further reduced and power conversion is performed. The efficiency is further improved.

[Second Embodiment] FIG. 5 is a circuit configuration diagram of a power converter according to a second embodiment. FIG. 6 is a configuration diagram of a signal passage limiting circuit of a switch bridge control unit, which is a main part of the power conversion device shown in FIG. FIG. 7 is a waveform diagram for explaining the operation of the signal passage limiting circuit.

This power conversion apparatus differs from the first embodiment only in the configuration of the switch bridge control unit 6, and the other components are the same as those in the first embodiment.

[0038] The switch bridge control unit 6 has
Between the output terminal of the output section 64 of the first embodiment and the gates of the switching elements Q1, Q2, Q3, Q4, a control pulse signal sQ1 directed to the gates of the switching elements Q1, Q2, Q3, Q4. , SQ2, sQ3, and sQ4. The signal passage limiting circuit 7 is provided at the output end of the output unit 64, and performs the pulse width modulation control of the first embodiment to control the AC output voltage value in a half cycle of the commercial power supply of the commercial power system 4. When the absolute value of Vo is smaller than the input voltage Vi from the solar cell 1, only one of the switch elements Q2 and Q4, one end of which is connected to the other vertex 23, is turned on and off to perform pulse width modulation control. When the absolute value of the voltage value Vo is substantially equal to or larger than the input voltage Vi from the solar cell 1, pulse width modulation control is performed to alternately turn on and off each of these switch elements Q2 and Q4.

In this case, as shown in FIG. 6, a comparator 71 in which an AC voltage signal Vo is inputted to a non-inverting input and a reference power supply 72 for outputting a predetermined reference voltage E1 is inputted to an inverting input, An OR gate 73 to which the output of the comparator 71 and the control pulse signal sQ3 are input, and an A to which the output of the OR gate 73 and the control pulse signal sQ2 are input.
An ND gate 74, a comparator 75 to which an AC voltage signal Vo is input to an inverting input and a reference power supply 76 for outputting the reference voltage E1 and a reverse polarity voltage E2 are input to a non-inverting input, and the output and control of the comparator 75 O to which the pulse signal sQ1 is input
It comprises an R gate 77, and an AND gate 78 to which the output of the OR gate 77 and the control pulse signal sQ4 are input. Then, the control pulse signal sQ2 ′ of the switch element Q2 is output from the AND gate 74, and the AND gate 7
8 outputs a control pulse signal sQ4 ′ for the switch element Q4. The switch elements Q1 and Q3 are controlled by control pulse signals sQ1 and sQ3 that pass through the signal passage limiting circuit 7 as they are. Note that the signal passage limiting circuit 7 is not limited to the above-described one, and may be configured using, for example, a microcomputer.

Next, the switching elements Q1, Q2, Q3, and Q of the switch bridge section 2 are controlled by the switch control section 6 using the signal passing restriction circuit 7 of the power converter described above.
4 will be described with reference to the waveform diagram of FIG. The reference voltage E of the reference power supply 72
1 and the reference voltage E2 of the reference power source 76 are set as follows: {E1} = {E2} = Vi (DC voltage signal).

First, when E1> Vo during the period when the switching element Q1 is on and the switching element Q3 is off, the control pulse signal sQ4 for the switching element Q4 is output from the AND gate 78 as it is. Since the output of the comparator 71 and the output of the control pulse signal sQ3 of the switch element Q3 are low, the control pulse signal sQ2 of the switch element Q2 is A
No signal is output from the ND gate 74. Also, E1 <Vo
In this case, the output of the comparator 71 becomes High, and the control pulse signal sQ2 of the switch element Q2 is output from the AND gate 74 as it is. Also, on the other hand,
During the period when the switch element Q3 is on and Q1 is off,
When E2 <Vo, the control pulse signal sQ2 of the switch element Q2 is output from the AND gate 74 as it is. Then, the control pulse signal sQ4 of the switch element Q4
Is not output from the AND gate 78 because the output of the comparator 75 and the output of the control pulse signal sQ1 of the switch element Q1 are Low. When E2> Vo, the output of the comparator 75 becomes High, and the control pulse signal sQ4 of the switch element Q4 is output from the AND gate 78.
Is output as is.

As a result, as shown in FIG. 7, the switching element Q for storing energy in the first reactor L1
2. The switching operation period of Q4 is 2 ×
The time t2 is reduced, and the switching elements Q2, Q2
4 further reduces switch loss or on-resistance loss.

According to the power converter described above, the pulse width modulation control is performed when the absolute value of the voltage value Vo of the AC output in a half cycle of the commercial power supply is smaller than the input voltage Vi from the solar cell 1. Pulse width modulation control for turning on or off only one of the switch elements Q2 and Q3 having one end connected to the vertex 23, and whether the absolute value of the AC output voltage value Vo is substantially equal to the input voltage Vi from the solar cell 1 When it is large, the switching elements Q2 and Q4 are turned on and off alternately by pulse width modulation control, so that the switching loss or on-resistance loss generated in the switching elements Q2 and Q4 is reduced. As a result, the power conversion efficiency is further improved.

[0044]

According to a first aspect of the present invention, in the power converter, one of the vertexes of one diagonal is connected to one end of a DC power supply via the first reactor, and the other is connected to the vertexes of the DC power supply. One end is connected to one vertex of one diagonal of the switch bridge section, which is connected to the other end of the power supply and the two vertexes of the other diagonal are respectively connected to one end of the second reactor and the third reactor. The second reactor and the second reactor are controlled by pulse width modulation control in which the switch elements are turned on and off in synchronization with the commercial power supply and inverted with each other, and each of the switch elements having one end connected to the other vertex is alternately turned on and off. Since the three ends are connected to the other end of the reactor and converted to commercial AC from both ends of a capacitor connected to both ends thereof, the output is converted to a commercial AC. Therefore, the switch element for boosting the DC voltage in the conventional example is unnecessary. Together eliminates switching losses or the on-resistance loss, and those obtained with high power conversion efficiency by the apparatus cost is low.

According to a second aspect of the present invention, in addition to the effects of the first aspect, a switch element having one end connected to one vertex of one diagonal is formed by a bipolar element. Therefore, the on-resistance loss is further reduced, and the power conversion efficiency is further improved.

According to a third aspect of the present invention, in addition to the effects of the first or second aspect, the pulse width modulation control is performed such that the absolute value of the voltage value of the AC output of the half cycle of the commercial power supply is the DC value. When smaller than the input voltage from the power supply, only one of the switch elements having one end connected to the other vertex is turned on and off, and pulse width modulation control is performed, and the absolute value of the voltage value of the AC output is changed from the DC power supply. When the input voltage is substantially equal to or larger than the input voltage, the switch elements are turned on and off alternately by pulse width modulation control, so that switch loss or on-resistance loss generated in the switch elements is smaller. As a result, the power conversion efficiency is further improved.

[Brief description of the drawings]

FIG. 1 is a circuit configuration diagram of a power conversion device according to a first embodiment of the present invention.

FIG. 2 is a configuration diagram of a switch bridge control unit which is a main part of the power conversion device shown in FIG.

FIG. 3 is a control flowchart of a switch bridge control unit which is a main part of the power conversion device shown in FIG.

FIG. 4 is a waveform diagram for explaining the operation of the switch bridge control unit of the power converter shown in FIG.

FIG. 5 is a circuit configuration diagram of a power converter according to a second embodiment.

6 is a configuration diagram of a signal passage limiting circuit of a switch bridge control unit, which is a main part of the power conversion device shown in FIG.

7 is a waveform diagram for explaining the operation of a signal passage limiting circuit of a switch bridge control unit which is a main part of the power conversion device shown in FIG.

FIG. 8 is a circuit configuration diagram of a conventional example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Solar cell (DC power supply) 2 Switch bridge part Q1, Q2, Q3, Q4 Switch element L1 1st reactor L2 2nd reactor L3 3rd reactor C1 Capacitor

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Hirotada Higashihama 1048 Kadoma Kadoma, Osaka Prefecture Matsushita Electric Works Co., Ltd. Inside

Claims (3)

[Claims] 1. A power conversion device for converting a direct current of which a voltage value input from a direct current power source is changed into an alternating current of a predetermined voltage value and outputting the alternating current, wherein one vertex of one diagonal corresponds to the first reactor. One end of the DC power supply is connected to one end of the DC power supply, and the other apex opposite to the apex is connected to the other end of the DC power supply, and the other two diagonal vertices are connected to one end of the second reactor and one end of the third reactor. And a capacitor having both ends connected to the other ends of the second reactor and the third reactor, one end connected to one vertex of the one diagonal of the switch bridge unit. Pulse width modulation control that synchronizes the switching elements with a commercial power supply, inverts each other, turns on and off, and alternately turns on and off switching elements each having one end connected to the other vertex. Power converter, characterized in that for converting the commercial AC from both ends of the capacitor DC Te. 2. The power converter according to claim 1, wherein the switch element having one end connected to one vertex of the one diagonal is formed by a bipolar element. 3. The pulse width modulation control according to claim 1, wherein when the absolute value of the voltage value of the AC output is smaller than the input voltage from the DC power supply in a half cycle of the commercial power supply, a switch element having one end connected to the other apex is provided. Only one of them is on,
Pulse width modulation control for turning off, and pulse width modulation control for turning on and off each of these switch elements alternately when the absolute value of the voltage value of the AC output is substantially equal to or greater than the input voltage from the DC power supply. The power converter according to claim 1 or 2, wherein: