JP6895643B2 - Power converter - Google Patents

Description

The present invention relates to a power conversion device that converts DC power into AC power.

Power conditioners connected to solar cells, storage batteries, fuel cells, etc. are required to have high-efficiency power conversion and compact design. In particular, in the grid-connected single-phase inverter of a household power conditioner, in order to suppress the leakage current, it is necessary to perform power conversion by a switching pattern in which the change in the common mode voltage is small.

In order to reduce the size of the power conditioner, it is effective to reduce the size of the reactor of the output stage, and one of the methods for reducing the size of the reactor of the output stage is a multi-level power converter. In the multi-level power converter, a pseudo sine wave can be output to the reactor of the output stage, so that the reactor of the output stage can be miniaturized.

A general power converter converts two levels of power supply voltage and ground voltage into sinusoidal AC power with an H-bridge circuit and a filter including a reactor. On the other hand, in a multi-level power converter, for example, a flying capacitor circuit is used to generate a voltage of 3 levels or more, and a filter including a reactor converts it into sinusoidal AC power (see, for example, Patent Document 1).

If a flying capacitor circuit is used, more switching elements will be used accordingly. Usually, a switching element having a relatively low withstand voltage is used for the switching element included in the flying capacitor circuit, and a switching element having a relatively high withstand voltage is used for the switching element at other parts of the inverter section. Since the switching elements included in the flying capacitor circuit are used by being connected in series and the voltage is defined by the capacitor, it is possible to use a switching element having a relatively low withstand voltage.

A low withstand voltage switching element is cheaper than a high withstand voltage switching element, has a small size, and has a small conduction loss and switching loss during power conversion. Further, a high withstand voltage switching element has a slow switching speed and is basically unsuitable for high frequency control. Further, in a high withstand voltage switching element, the increase in switching loss due to high frequency is larger than that of the low withstand voltage switching loss.

Japanese Unexamined Patent Publication No. 2014-50135

The switching element of the inverter unit is usually driven by PWM (Pulse Width Modulation) control. When PWM control is performed, the higher the switching frequency, the smaller the reactor of the output stage can be. However, in a high withstand voltage switching element, the switching loss greatly increases.

The present invention has been made in view of these circumstances, and an object of the present invention is to provide a highly efficient and compact power conversion device.

In order to solve the above problems, the power conversion device of one embodiment of the present invention is a first arm circuit in which a first switching element, a first flying capacitor circuit, and a second switching element are connected in series in parallel with a DC power supply. A second arm circuit in which a third switching element, a second flying capacitor circuit, and a fourth switching element are connected in series in parallel with the DC power supply and the first arm circuit, and the first switching element and the first arm circuit. The connection point with the 1-flying capacitor circuit, the 5th switching element connected between the connection point between the 2nd flying capacitor circuit and the 4th switching element, the 3rd switching element and the 2nd flying capacitor. It includes a connection point with the circuit and a sixth switching element connected between the connection point between the first flying capacitor circuit and the second switching element. AC power is output from the midpoint of the first flying capacitor circuit and the midpoint of the second flying capacitor circuit.

According to the present invention, a highly efficient and compact power conversion device can be realized.

It is a figure for demonstrating the structure of the power conversion apparatus which concerns on embodiment of this invention. 2 (a)-(c) are diagrams showing a configuration example of a flying capacitor circuit. It is a figure which shows the structure when the 1-stage flying capacitor circuit is used for the 1st flying capacitor circuit and the 2nd flying capacitor circuit of FIG. 4 (a) and 4 (b) are diagrams showing the current paths of the states 1 and 2A of the orthogonal transform section of FIG. 5 (a) and 5 (b) are diagrams showing the current paths of the states 2B and 3A of the orthogonal transform section of FIG. 6 (a) and 6 (b) are diagrams showing the current paths of the states 5 and 4A of the orthogonal transform section of FIG. 7 (a) and 7 (b) are diagrams showing the current paths of the states 4B and 3B of the orthogonal transform section of FIG. First switching element to sixth switching element, 7-1 switching element to seventh-4 switching element, first in state 1, state 2A, state 2B, state 3A, state 3B, state 4A, state 4B, state 5. It is the figure which summarized the on / off state of 8-1 switching element to 8-4th switching element. It is a figure which shows the pseudo sine wave generated by the voltage of 5 levels (+ Vdc, + Vdc / 2, 0, -Vdc / 2, -Vdc). 10 (a)-(d) show the first switching element to the sixth switching element, the 7-1 switching element to the seventh-4 switching element, and the 8-1 switching element to the eighth in the switching patterns AD. 8-4 It is a figure which summarized the on / off state of a switching element. 11 (a)-(d) show the first switching element to the sixth switching element, the 7-1 switching element to the seventh-4 switching element, and the 8-1 switching element to the eighth in the switching pattern EH. 8-4 It is a figure which summarized the on / off state of a switching element. It is a figure which shows an example of the switching state transition and the output voltage in the period 2 of FIG. It is a figure which shows the circuit structure which replaced the 1st switching element to the 4th switching element of the circuit structure of FIG. 3 with the switching element of the lower withstand voltage of 2 series, respectively. It is a figure which shows the circuit structure which replaced the 5th switching element and the 6th switching element of the circuit structure of FIG. 3 with the switching element of 4 series lower withstand voltage, respectively. It is a figure which shows the circuit structure which added the short-circuit circuit to the circuit structure of FIG. It is a figure which shows the zero cross of the pseudo sine wave shown in FIG. 17 (a) and 17 (b) show the first switching element to the sixth switching element, the 7-1 switching element to the seventh-4 switching element, and the 8-1 switching element to the eighth-in the switching pattern I. It is a figure which summarized the on / off state of 4 switching element, 9-1th switching element, 9-2th switching element. It is a figure which shows the circuit structure which added the 1st DC / DC converter and the 2nd DC / DC converter to the circuit structure of FIG. It is a figure which shows the circuit structure which added the insulation type DC / DC converter to the circuit structure of FIG. It is a figure which shows the circuit structure which added the active buffer circuit to the circuit structure of FIG. FIG. 3 is a diagram showing a circuit configuration in which the first flying capacitor circuit and the second flying capacitor circuit of the circuit configuration of FIG. 13 are replaced with a three-stage flying capacitor circuit.

FIG. 1 is a diagram for explaining the configuration of the power conversion device 1 according to the embodiment of the present invention. The power conversion device 1 converts the DC power supplied from the DC power supply unit 2 into AC power and outputs it to the commercial power system 3 (hereinafter, simply referred to as system 3). The DC power supply unit 2 includes a DC power supply such as a solar cell, a storage battery, and a fuel cell, and a DC / DC converter capable of adjusting the output voltage of the DC power supply.

The power conversion device 1 includes an orthogonal conversion unit 10, a filter unit 20, and a control unit 30. The orthogonal transform unit 10 includes a first arm circuit (U phase) and a second arm circuit (W phase) connected in parallel with the DC power supply unit 2. The first arm circuit is configured by connecting the first switching element Q1, the first flying capacitor circuit F1, and the second switching element Q2 in series between the positive side wiring and the negative side wiring of the DC power supply unit 2. .. The second arm circuit is configured by connecting the third switching element Q3, the second flying capacitor circuit F2, and the fourth switching element Q4 in series between the positive side wiring and the negative side wiring of the DC power supply unit 2. ..

The fifth switching element Q5 is connected between the connection point between the first switching element Q1 and the first flying capacitor circuit F1 and the connection point between the second flying capacitor circuit F2 and the fourth switching element Q4. The sixth switching element Q6 is connected between the connection point between the third switching element Q3 and the second flying capacitor circuit F2 and the connection point between the first flying capacitor circuit F1 and the second switching element Q2.

For example, an IGBT (Insulated Gate Bipolar Transistor) can be used for the first switching element Q1 to the sixth switching element Q6. The first diode D1 to the sixth diode D6 are connected to the first switching element Q1 to the sixth switching element Q6 in parallel and in opposite directions, respectively. A MOSFET (Metal-Oxide-Semiconductor Field-Effect Transistor) may be used for the first switching element Q1 to the sixth switching element Q6. In this case, the first diode D1 to the sixth diode D6 can utilize a parasitic diode formed in the drain direction from the source. The first diode D1 to the sixth diode D6 act as a freewheeling diode.

The orthogonal conversion unit 10 converts the DC power of the DC power supply unit 2 connected in parallel to the first arm circuit and the second arm circuit into AC power, and converts the AC power into the first flying capacitor circuit F1 and the second flying capacitor circuit. It operates as an inverter circuit that outputs from the midpoint of F2.

The filter unit 20 includes a first reactor L1, a second reactor L2, and a third capacitor C3, attenuates harmonic components of the output voltage and output current of the orthogonal transform unit 10, and outputs the output voltage and output of the orthogonal transform unit 10. Bring the current closer to a sine wave.

The control unit 30 PWM-controls the first switching element Q1 to the sixth switching element Q6, and a plurality of switching elements included in the first flying capacitor circuit F1 and the second flying capacitor circuit F2. The control unit 30 can be realized by the collaboration of hardware resources and software resources, or only by hardware resources. Analog devices, microcomputers, DSPs, ROMs, RAMs, FPGAs, and other LSIs can be used as hardware resources. Programs such as firmware can be used as software resources.

2 (a)-(c) are diagrams showing a configuration example of a flying capacitor circuit. FIG. 2A shows a one-stage flying capacitor circuit. The flying capacitor circuit shown in FIG. 2A includes a 7-1 switching element Q71, a 7-2 switching element Q72, a 7-3 switching element Q73, and a 7-4 switching element Q74 connected in series. 1 Capacitor C1 is provided. The first capacitor C1 is located between the connection point between the 7-1 switching element Q71 and the 7-2 switching element Q72 and the connection point between the 7-3 switching element Q73 and the 7-4 switching element Q74. Be connected.

An IGBT or MOSFET can be used for the 7-1st switching element Q71 to the 7-4th switching element Q74. The 7-1 diode D71 to the 7-4 diode D74 are connected or formed in parallel and in opposite directions to the 7-1 switching element Q71 to the 7-4 switching element Q74, respectively.

FIG. 2B shows a two-stage flying capacitor circuit. In the two-stage flying capacitor circuit, the 7-5 switching element Q75 is further connected to the high potential side of the 7-1 switching element Q71, and the 7-6 switching element is further connected to the low potential side of the 7-4 switching element Q74. Q76 is further connected. A 1-2 capacitor between the connection point between the 7th-5th switching element Q75 and the 7-1 switching element Q71 and the connection point between the 7th-4th switching element Q74 and the 7-6th switching element Q76. C1b is further connected.

FIG. 2C shows a three-stage flying capacitor circuit. In the three-stage flying capacitor circuit, the 7-7 switching element Q77 is further connected to the high potential side of the 7-5 switching element Q75, and the 7-8 switching element is further connected to the low potential side of the 7-6 switching element Q76. Q78 is further connected. A 1-3 capacitor between the connection point between the 7th-7th switching element Q77 and the 7-5 switching element Q75 and the connection point between the 7-6th switching element Q76 and the 7-8 switching element Q78. C1c is further connected.

When two arms of the flying capacitor circuit shown in FIGS. 2A to 2C are connected in parallel to the DC power supply unit 2 and switching control is performed for the two arms so as to keep the common mode voltage constant. It is possible to output a voltage of (2N + 1) level from the N-stage flying capacitor.

FIG. 3 is a diagram showing a configuration when a one-stage flying capacitor circuit is used for the first flying capacitor circuit F1 and the second flying capacitor circuit F2 of FIG. The first flying capacitor circuit F1 includes a 7-1 switching element Q71 to a 7-4 switching element Q74 and a first capacitor C1. The second flying capacitor circuit F2 includes the 8-1st switching element Q81 to the 8-4th switching element Q84 and the second capacitor C2. Each connection relationship is the same as the connection relationship of the one-stage flying capacitor circuit shown in FIG. 2 (a). The connection point between the 7-2 switching element Q72 and the 7-3 switching element Q73 and the connection point between the 8-2 switching element Q82 and the 8-3 switching element Q83 are the output points of the orthogonal transform unit 10. Become.

In the circuit configuration shown in FIG. 3, since the first arm circuit and the second arm circuit are cross-connected, there are five levels (+ Vdc, + Vdc / 2, 0, -Vdc / 2) from the orthogonal transform unit 10 to the filter unit 20. , -Vdc) can be output.

As described above, the first switching element Q1, the sixth switching element Q6, and the fourth switching element Q4 are fixed in the on state for a period of generating a positive half wave of AC power and a period of generating a negative half wave. , Fixed to off state. The second switching element Q2, the fifth switching element Q5, and the third switching element Q3 are fixed in the off state during the period of generating a positive half wave of AC power, and fixed in the on state during the period of generating a negative half wave. Will be done. Since the frequency of the system 3 is 50/60 Hz in Japan, the first switching element Q1 to the sixth switching element Q6 are switched and controlled at a frequency half of 50/60 Hz.

On the other hand, the 7-1 switching elements Q71 to 7-4 switching elements Q74 included in the first flying capacitor circuit F1 and the 8-1 switching elements Q81 to 8-2 switching included in the second flying capacitor circuit F2. The element Q82 is switched and controlled at a high frequency (for example, 20 kHz). Hereinafter, the operation of the power conversion device 1 shown in FIG. 3 will be described in detail with reference to the drawings.

In the following description, the on state of the first switching element Q1 to the sixth switching element Q6 means a steady on state, and the off state of the first switching element Q1 to the sixth switching element Q6 is a steady off state. Means the state. On the other hand, the ON state of the 7-1st switching element Q71 to 7-4 switching element Q74 and the 8-1 switching element Q81 to 8-2 switching element Q82 means a PWM switched state, and the 7th- 1 The off state of the switching elements Q71 to 7-4 switching elements Q74 and the 8-1 switching elements Q81 to 8-2 switching elements Q82 means a steady off state.

4 (a) and 4 (b) are diagrams showing the current paths of the states 1 and 2A of the orthogonal transform unit 10 of FIG. 5 (a) and 5 (b) are diagrams showing the current paths of the states 2B and 3A of the orthogonal transform unit 10 of FIG. 6 (a) and 6 (b) are diagrams showing the current paths of the states 5 and 4A of the orthogonal transform unit 10 of FIG. 7 (a) and 7 (b) are diagrams showing the current paths of the state 4B and the state 3B of the orthogonal transform unit 10 of FIG. FIG. 8 shows the first switching element Q1 to the sixth switching element Q6 and the 7-1 switching element Q71 to the first in the states 1, the state 2A, the state 2B, the state 3A, the state 3B, the state 4A, the state 4B, and the state 5. It is the figure which summarized the on / off state of 7-4 switching element Q74, 8-1 switching element Q81-8-4 switching element Q84.

State 1 shown in FIG. 4A is a state in which the voltage Vdc of the DC power supply unit 2 is output as it is without changing the polarity. The control unit 30 includes a first switching element Q1, a fourth switching element Q4, a sixth switching element Q6, a 7-1 switching element Q71, a 7-2 switching element Q72, an 8-3 switching element Q83, and an 8-4th. The switching element Q84 is controlled to be in the ON state, and the second switching element Q2, the third switching element Q3, the fifth switching element Q5, the seventh-3 switching element Q73, the seventh-4 switching element Q74, and the eighth-1 switching element are controlled. The Q81 and the 8-2 switching elements Q82 are controlled to be in the off state. In the state 1, the current flows through the DC power supply unit 2 and without interposing the first capacitor C1 and the second capacitor C2.

The state 2A shown in FIG. 4B is a state in which the voltage Vdc of the DC power supply unit 2 is halved and output without changing the polarity. The control unit 30 includes the first switching element Q1, the fourth switching element Q4, the sixth switching element Q6, the 7-1 switching element Q71, the seventh-3 switching element Q73, the 8-2 switching element Q82, and the eighth-4. The switching element Q84 is controlled to be on, and the second switching element Q2, the third switching element Q3, the fifth switching element Q5, the 7-2 switching element Q72, the 7-4 switching element Q74, and the 8-1 switching element Q81, the 8th-3rd switching element Q83 is controlled to the off state. In the state 2A, the first capacitor C1 and the second capacitor C2 are each charged with a charge corresponding to a voltage width of 1/4 of the voltage Vdc of the DC power supply unit 2. In the state 2A, a current flows through the DC power supply unit 2, the first capacitor C1 and the second capacitor C2. The potential on the positive electrode side of the DC power supply unit 2 is pulled down by the first capacitor C1 by 1/4 of the voltage width, and the potential on the negative electrode side of the DC power supply unit 2 is pulled by the second capacitor C2 by 1/4 of the voltage width. By being up, + Vdc / 2 is output.

The state 2B shown in FIG. 5A is also a state in which the voltage Vdc of the DC power supply unit 2 is halved and output without changing the polarity. The control unit 30 includes a first switching element Q1, a fourth switching element Q4, a sixth switching element Q6, a seventh-2 switching element Q72, a seventh-4 switching element Q74, an 8-1 switching element Q81, and an 8-3. The switching element Q83 is controlled to be in the ON state, and the second switching element Q2, the third switching element Q3, the fifth switching element Q5, the 7-1 switching element Q71, the 7th-3 switching element Q73, and the 8-2 switching element are controlled. Q82, the 8th-4th switching element Q84 is controlled to the off state. In the state 2B, the electric charges charged in the first capacitor C1 and the second capacitor C2 are discharged, respectively. In the state 2B, the reflux current flows through the first capacitor C1 and the second capacitor C2 without interposing the DC power supply unit 2. Since the first capacitor C1 and the second capacitor C2 are each charged with a charge corresponding to 1/4 of the voltage Vdc of the DC power supply unit 2, + Vdc / 2 is output.

The state 3A shown in FIG. 5B is a state in which 0V is output. The control unit 30 includes a first switching element Q1, a fourth switching element Q4, a sixth switching element Q6, a seventh-3 switching element Q73, a seventh-4 switching element Q74, an 8-1 switching element Q81, and an 8-2. The switching element Q82 is controlled to be in the ON state, and the second switching element Q2, the third switching element Q3, the fifth switching element Q5, the 7-1 switching element Q71, the 7-2 switching element Q72, and the 8-3 switching element are controlled. The Q83 and the 8th-4th switching elements Q84 are controlled to be in the off state. In the state 3A, a short-circuit path is formed without interposing the DC power supply unit 2, the first capacitor C1 and the second capacitor C2.

The state 5 shown in FIG. 6A is a state in which the voltage Vdc of the DC power supply unit 2 is output with its polarity reversed. The control unit 30 includes a second switching element Q2, a third switching element Q3, a fifth switching element Q5, a seventh-third switching element Q73, a seventh-fourth switching element Q74, an eighth-1 switching element Q81, and an eighth-2. The switching element Q82 is controlled to be in the ON state, and the first switching element Q1, the fourth switching element Q4, the sixth switching element Q6, the 7-1 switching element Q71, the 7-2 switching element Q72, and the 8-3 switching element are controlled. The Q83 and the 8th-4th switching elements Q84 are controlled to be in the off state. In the state 5, the current flows without interposing the first capacitor C1 and the second capacitor C2 with the DC power supply unit 2 interposed therebetween. Compared with FIG. 4A, the relationship between the currents flowing in the first arm circuit and the second arm circuit is opposite.

The state 4A shown in FIG. 6B is a state in which the voltage Vdc of the DC power supply unit 2 is output with its polarity reversed and halved. The control unit 30 includes a second switching element Q2, a third switching element Q3, a fifth switching element Q5, a 7-2 switching element Q72, a 7-4 switching element Q74, an 8-1 switching element Q81, and an 8-3. The switching element Q83 is controlled to be in the ON state, and the first switching element Q1, the fourth switching element Q4, the sixth switching element Q6, the 7-1 switching element Q71, the seventh-3 switching element Q73, and the 8-2 switching element are controlled. Q82, the 8th-4th switching element Q84 is controlled to the off state. In the state 4A, the first capacitor C1 and the second capacitor C2 are each charged with a charge corresponding to a voltage width of 1/4 of the voltage Vdc of the DC power supply unit 2. In the state 4A, a current flows through the DC power supply unit 2, the first capacitor C1 and the second capacitor C2. The potential on the positive electrode side of the DC power supply unit 2 is pulled down by the second capacitor C2 by 1/4 of the voltage width, and the potential on the negative electrode side of the DC power supply unit 2 is pulled by the first capacitor C1 by 1/4 of the voltage width. By being increased, -Vdc / 2 is output. Compared with FIG. 4B, the relationship between the currents flowing in the first arm circuit and the second arm circuit is opposite.

The state 4B shown in FIG. 7A is also a state in which the voltage Vdc of the DC power supply unit 2 is output with the polarity reversed and halved. The control unit 30 includes a second switching element Q2, a third switching element Q3, a fifth switching element Q5, a 7-1 switching element Q71, a seventh-3 switching element Q73, an 8-2 switching element Q82, and an 8-4th. The switching element Q84 is controlled to be in the ON state, and the first switching element Q1, the fourth switching element Q4, the sixth switching element Q6, the 7-2 switching element Q72, the 7-4 switching element Q74, and the 8-1 switching element are controlled. The Q81 and the 8th-3rd switching elements Q83 are controlled to be in the off state. In the state 4B, the electric charges charged in the first capacitor C1 and the second capacitor C2 are discharged, respectively. In the state 4B, the reflux current flows through the first capacitor C1 and the second capacitor C2 without interposing the DC power supply unit 2. Since the first capacitor C1 and the second capacitor C2 are each charged with a charge corresponding to 1/4 of the voltage Vdc of the DC power supply unit 2, −Vdc / 2 is output. Compared with FIG. 5A, the relationship between the currents flowing in the first arm circuit and the second arm circuit is opposite.

The state 3B shown in FIG. 7B is a state in which 0V is output. The control unit 30 includes a second switching element Q2, a third switching element Q3, a fifth switching element Q5, a 7-1 switching element Q71, a 7-2 switching element Q72, an 8-3 switching element Q83, and an 8-4th. The switching element Q84 is controlled to be in the ON state, and the first switching element Q1, the fourth switching element Q4, the sixth switching element Q6, the seventh-3 switching element Q73, the seventh-4 switching element Q74, and the eighth-1 switching element are controlled. The Q81 and the 8-2 switching elements Q82 are controlled to be in the off state. In the state 3B, a short-circuit path is formed without interposing the DC power supply unit 2, the first capacitor C1 and the second capacitor C2. Compared with FIG. 5B, the relationship between the currents flowing in the first arm circuit and the second arm circuit is opposite.

FIG. 9 is a diagram showing a pseudo sine wave generated at a voltage of 5 levels (+ Vdc, + Vdc / 2, 0, −Vdc / 2, −Vdc). In period 1, + Vdc / 2 and 0 are output alternately, in period 2, + Vdc and + Vdc / 2 are output alternately, in period 3, 0 and -Vdc / 2 are output alternately, and in period 4, -Vdc / 2 is output. And -Vdc are output alternately. When the voltage command value is positive, state 1, state 2A, state 2B, and state 3A are used. In these states, the first switching element Q1, the sixth switching element Q6, and the fourth switching element Q4 are fixed in the on state, and the second switching element Q2, the fifth switching element Q5, and the third switching element Q3 are turned off. Fixed, the power converter 1 produces a positive half-wave of AC power.

On the other hand, when the voltage command value is negative, the state 5, the state 4A, the state 4B, and the state 3B are used. In these states, the second switching element Q2, the fifth switching element Q5, and the third switching element Q3 are fixed in the on state, and the first switching element Q1, the sixth switching element Q6, and the fourth switching element Q4 are turned off. Fixed, the power converter 1 produces a negative half-wave of AC power.

As described above, in the present embodiment, a voltage of 5 levels can be output by a one-stage flying capacitor circuit. This is because the first arm circuit and the second arm circuit are connected by a cross via the fifth switching element Q5 and the sixth switching element Q6, so that two positive and negative voltages can be output. .. On the other hand, when the first arm circuit and the second arm circuit are not connected by crossing, only three levels of voltage can be output.

The above findings are the same for two or more stages of flying capacitor circuits. When the first arm circuit and the second arm circuit which are not connected by crossing are used, which uses the N-stage flying capacitor circuit, the voltage of (2N + 1) level can be output. On the other hand, as in the present embodiment, when the first arm circuit and the second arm circuit which are cross-connected using the N-stage flying capacitor circuit are used, a voltage of (2N + 3) level can be output. is there. That is, in this embodiment, the number of capacitors can be reduced by one step. Since the flying capacitor circuit controls the charging and discharging of the capacitor, the switching pattern becomes more complicated as the number of stages increases. On the other hand, in the present embodiment, the number of capacitors when achieving the same multi-level output can be reduced.

Each period of FIG. 9 has two switching patterns. Period 1 has switching pattern C and switching pattern D, period 2 has switching pattern A and switching pattern B, period 3 has switching pattern E and switching pattern F, and period 4 has switching pattern G and switching. It has a pattern H.

10 (a)-(d) show the first switching element Q1 to the sixth switching element Q6 and the 7-1 switching element Q71 to the 7-4 switching elements Q74 and 8-1 in the switching patterns AD. It is a figure which summarized the on / off state of the switching element Q81 to the 8-4th switching element Q84. 11 (a)-(d) show the first switching element Q1 to the sixth switching element Q6 and the 7-1 switching element Q71 to the 7-4 switching elements Q74 and 8-1 in the switching pattern EH. It is a figure which summarized the on / off state of the switching element Q81 to the 8-4th switching element Q84.

As shown in FIG. 10A, the switching pattern A is a switching pattern in which state 1 (+ Vdc) and state 2A (+ Vdc / 2) are alternately repeated, and a dead time period is inserted between them. The dead time period is inserted to prevent through current. During the dead time period, the control unit 30 controls the first switching element Q1, the fourth switching element Q4, the sixth switching element Q6, the 7-1 switching element Q71, and the 8-4 switching element Q84 in the ON state. 2nd switching element Q2, 3rd switching element Q3, 5th switching element Q5, 7-2 switching element Q72, 7-3 switching element Q73, 7-4 switching element Q74, 8-1 switching element Q81, The 8th-2nd switching element Q82 and the 8th-3rd switching element Q83 are controlled to be in the off state.

As shown in FIG. 10B, the switching pattern B is a switching pattern in which state 1 (+ Vdc) and state 2B (+ Vdc / 2) are alternately repeated, and a dead time period is inserted between them. During the dead time period, the control unit 30 controls the first switching element Q1, the fourth switching element Q4, the sixth switching element Q6, the 7-2 switching element Q72, and the 8-3 switching element Q83 in the ON state. 2nd switching element Q2, 3rd switching element Q3, 5th switching element Q5, 7-1 switching element Q71, 7-3 switching element Q73, 7-4 switching element Q74, 8-1 switching element Q81, The 8th-2nd switching element Q82 and the 8th-4th switching element Q84 are controlled to be in the off state.

As shown in FIG. 10C, the switching pattern C is a switching pattern in which the state 3A (0V) and the state 2A (+ Vdc / 2) are alternately repeated, and a dead time period is inserted between them. During the dead time period, the control unit 30 controls the first switching element Q1, the fourth switching element Q4, the sixth switching element Q6, the seventh-3 switching element Q73, and the 8-2 switching element Q82 in the ON state. 2nd switching element Q2, 3rd switching element Q3, 5th switching element Q5, 7-1 switching element Q71, 7-2 switching element Q72, 7-4 switching element Q74, 8-1 switching element Q81, The 8th-3rd switching element Q83 and the 8th-4th switching element Q84 are controlled to be in the off state.

As shown in FIG. 10D, the switching pattern D is a switching pattern in which the state 3A (0V) and the state 2B (+ Vdc / 2) are alternately repeated, and a dead time period is inserted between them. During the dead time period, the control unit 30 controls the first switching element Q1, the fourth switching element Q4, the sixth switching element Q6, the seventh-4 switching element Q74, and the 8-1 switching element Q81 in the ON state. 2nd switching element Q2, 3rd switching element Q3, 5th switching element Q5, 7-1 switching element Q71, 7-2 switching element Q72, 7-3 switching element Q73, 8-2 switching element Q82, The 8th-3rd switching element Q83 and the 8th-4th switching element Q84 are controlled to be in the off state.

As shown in FIG. 11A, the switching pattern E is a switching pattern in which the state 3B (0V) and the state 4A (−Vdc / 2) are alternately repeated, and a dead time period is inserted between them. During the dead time period, the control unit 30 controls the second switching element Q2, the third switching element Q3, the fifth switching element Q5, the 7-2 switching element Q72, and the 8-3 switching element Q83 in the ON state. 1st switching element Q1, 4th switching element Q4, 6th switching element Q6, 7-1 switching element Q71, 7th-3 switching element Q73, 7-4 switching element Q74, 8-1 switching element Q81, The 8th-2nd switching element Q82 and the 8th-4th switching element Q84 are controlled to be in the off state.

As shown in FIG. 11B, the switching pattern F is a switching pattern in which the state 3B (0V) and the state 4B (−Vdc / 2) are alternately repeated, and a dead time period is inserted between them. During the dead time period, the control unit 30 controls the second switching element Q2, the third switching element Q3, the fifth switching element Q5, the 7-1 switching element Q71, and the 8-4 switching element Q84 in the ON state. 1st switching element Q1, 4th switching element Q4, 6th switching element Q6, 7-2 switching element Q72, 7-3 switching element Q73, 7-4 switching element Q74, 8-1 switching element Q81, The 8th-2nd switching element Q82 and the 8th-3rd switching element Q83 are controlled to be in the off state.

As shown in FIG. 11 (c), the switching pattern G is a switching pattern in which the state 5B (-Vdc) and the state 4A (-Vdc / 2) are alternately repeated, and a dead time period is inserted between them. During the dead time period, the control unit 30 controls the second switching element Q2, the third switching element Q3, the fifth switching element Q5, the seventh-4 switching element Q74, and the 8-1 switching element Q81 in the ON state. 1st switching element Q1, 4th switching element Q4, 6th switching element Q6, 7-1 switching element Q71, 7-2 switching element Q72, 7-3 switching element Q73, 8-2 switching element Q82, The 8th-3rd switching element Q83 and the 8th-4th switching element Q84 are controlled to be in the off state.

As shown in FIG. 11D, the switching pattern H is a switching pattern in which the state 5B (−Vdc) and the state 4B (−Vdc / 2) are alternately repeated, and a dead time period is inserted between them. During the dead time period, the control unit 30 controls the second switching element Q2, the third switching element Q3, the fifth switching element Q5, the seventh-3 switching element Q73, and the 8-2 switching element Q82 in the ON state. 1st switching element Q1, 4th switching element Q4, 6th switching element Q6, 7-1 switching element Q71, 7-2 switching element Q72, 7-4 switching element Q74, 8-1 switching element Q81, The 8th-3rd switching element Q83 and the 8th-4th switching element Q84 are controlled to be in the off state.

FIG. 12 is a diagram showing an example of the switching state transition and the output voltage in the period 2 of FIG. In FIG. 12, the “transition” corresponds to the dead time period. The control unit 30 switches between two switching patterns in each period according to the voltage of the first capacitor C1, the voltage of the second capacitor C2, and the polarity of the output current. As the voltage value of the first capacitor C1 and the voltage value of the second capacitor C2, the values measured by the voltage sensor (not shown) may be used. A value estimated based on the charge / discharge characteristics that defines the relationship between the charge / discharge time and the voltage of the capacitor to be used may be used. Whether the first capacitor C1 and the second capacitor C2 are being charged or discharged is determined by the polarity of the output current. The output voltage during the transition in the period 2 is also determined to be Vdc or Vdc / 2 depending on the polarity of the output current.

The control unit 30 determines the on-time T1 of the state 1 and the on-time T2 of the state 2 in the unit control cycle based on the set target duty ratio. The target duty ratio is determined based on the difference between the target value of the output current and the measured value of the output current actually measured by the current sensor (not shown). The control unit 30 sets the ON time T2 of the state 2 determined based on the target duty ratio to ON of the state 2A according to the voltage of the first capacitor C1, the voltage of the second capacitor C2, and the polarity of the output current. The time is divided into the on-time T2B of the time T2A and the state 2B. The control unit 30 controls so that the sum of the on-time T2A in the state 2A and the on-time T2B in the state 2B becomes equal to the on-time T2 in the state 2 determined based on the target duty ratio.

In the circuit configuration shown in FIG. 3, a switching element having a withstand voltage higher than the voltage of the DC power supply unit 2 is used for the fifth switching element Q5 and the sixth switching element Q6. On the other hand, DC is applied to the first switching element Q1 to the fourth switching element Q4, the 7-1 switching element Q71 to the 7-4 switching element Q74, and the 8-1 switching element Q81 to the 8-4 switching element Q84. A switching element having a withstand voltage lower than the voltage of the power supply unit 2 is used.

For example, when the voltage of the system 3 is AC200V and a solar cell or a storage battery is connected in parallel to one DC bus as the DC power supply unit 2, the voltage of the DC bus may rise up to about 450V. Since the fifth switching element Q5 and the sixth switching element Q6 may form a path for receiving the voltage of the DC bus by one switching element, the fifth switching element Q5 and the sixth switching element Q6 are 450V. The above withstand voltage is required. For example, when a path of the first switching element Q1 → the fifth switching element Q5 → the fourth switching element Q4 is formed and the first switching element Q1 and the fourth switching element Q4 are in the ON state, the fifth switching element Q5 may have a path. 450V may be applied. Therefore, for the 5th switching element Q5 and the 6th switching element Q6, a switching element having a withstand voltage of about 600V, which is 450V plus a margin, is used.

Since the first switching element Q1 to the fourth switching element Q4 may form a path for receiving the voltage of the DC bus by the two switching elements, the first switching element Q1 to the fourth switching element Q4 are respectively. A withstand voltage of (450/2) V or higher is required. For example, when a path of the first switching element Q1 → the fifth switching element Q5 → the fourth switching element Q4 is formed and the fifth switching element Q5 is in the ON state, the first switching element Q1 and the fourth switching element Q4 are respectively. (450/2) V may be applied. Therefore, for the first switching element Q1 to the fourth switching element Q4, a switching element having a withstand voltage of about 300 V, which is obtained by adding a margin to (450/2) V, is used.

The 7-1st switching element Q71 to 7-4 switching element Q74 and the 8-1st switching element Q81 to 8-4 switching element Q84 are formed with a path for receiving the voltage of the DC bus by the four switching elements. The 7-1st switching element Q71 to 7-4 switching element Q74 and the 8-1st switching element Q81 to 8-4 switching element Q84 are each (450/4) V or more. Withstand voltage is required. For example, a path of the first switching element Q1 → 7-1 switching element Q71 → 7-2 switching element Q72 → 7-3 switching element Q73 → 7-4 switching element Q74 → second switching element Q2 is formed. When the first switching element Q1 and the second switching element Q2 are in the ON state, (450/4) V may be applied to the 7-1 switching elements Q71 to 7-4 switching elements Q74, respectively. Therefore, the 7-1st switching element Q71 to 7-4 switching element Q74 and the 8-1st switching element Q81 to 8-4 switching element Q84 have a withstand voltage of about 150 V, which is obtained by adding a margin to (450/4) V. Use a switching element.

A first capacitor is located between the connection point between the 7-1 switching element Q71 and the 7-2 switching element Q72 and the connection point between the 7-3 switching element Q73 and the 7-4 switching element Q74. Since C1 is connected and the first capacitor C1 can charge a charge corresponding to 1/4 of the voltage of the DC power supply unit 2, between the 7-1 switching elements Q71 to the 7-4 switching elements Q74. , It is possible to divide the voltage by about 1/4.

As described above, the high withstand voltage switching element has a low switching speed limit, but in the circuit configuration of FIG. 3, the high withstand voltage fifth switching element Q5 and sixth switching element Q6 are used in places where high frequency switching is not performed. Therefore, basically no follow-up delay with respect to switching control occurs. On the other hand, in the first flying capacitor circuit F1 and the second flying capacitor circuit F2, the low withstand voltage 7-1 switching element Q71 to 7-4 switching element Q74 and the 8-1 switching element Q81 to 8-4 switching By using the element Q84, conduction loss and switching loss can be reduced, and high efficiency can be achieved.

FIG. 13 is a diagram showing a circuit configuration in which the first switching element Q1 to the fourth switching element Q4 having the circuit configuration of FIG. 3 are replaced with two series of switching elements having a lower withstand voltage. The first switching element Q1 in FIG. 3 is replaced with a series circuit of the 1-1 switching element Q1a and the 1-2 switching element Q1b. The same applies to the second switching element Q2-fourth switching element Q4.

For each of the 1-1 switching element Q1a and the 1-2 switching element Q1b, a switching element having a withstand voltage about half the withstand voltage of the first switching element Q1 is used. For example, the same switching elements as the 7-1 switching elements Q71 to 7-4 switching elements Q74 included in the first flying capacitor circuit F1 are used. The same applies to the 2-1 switching element Q2a and the 2-2 switching element Q2b, the 3-1 switching element Q3a and the 3-2 switching element Q3b, and the 4-1 switching element Q4a and the 4-2 switching element Q4b. Is.

If a switching element with a withstand voltage of 300 V is replaced with a switching element with a withstand voltage of 150 V, the conduction loss can be made smaller than 1/2. Therefore, it is possible to reduce the conduction loss by using two switching elements with a withstand voltage of 150 V in series.

When the switching element with a withstand voltage of 300 V is replaced with two switching elements with a withstand voltage of 150 V in series (two), the current capacity may be insufficient. In that case, the switching elements with a withstand voltage of 300 V are replaced with switching elements (4) with a withstand voltage of 150 V in two series and two parallels.

The first switching element Q1 to the fourth switching element Q4 are switching elements at locations where high frequency switching is not performed. Therefore, a slight deviation in on / off timing due to element variation or the like is allowed between a plurality of switching elements in which two series / two series / two parallels are arranged.

FIG. 14 is a diagram showing a circuit configuration in which the fifth switching element Q5 and the sixth switching element Q6 of the circuit configuration of FIG. 3 are replaced with four series of lower withstand voltage switching elements, respectively. The fifth switching element Q5 in FIG. 3 is replaced with a series circuit of the 5-1st switching element Q5a to the 5-4th switching element Q5d. The same applies to the sixth switching element Q6.

For each of the 5-1st switching element Q5a to the 5th-4th switching element Q5d, a switching element having a withstand voltage of about 1/4 of the withstand voltage of the fifth switching element Q5 is used. For example, the same switching elements as the 7-1 switching elements Q71 to 7-4 switching elements Q74 included in the first flying capacitor circuit F1 are used. The same applies to the 6-1st switching element Q6a to the 6th-4th switching element Q6d.

FIG. 15 is a diagram showing a circuit configuration in which a short circuit is added to the circuit configuration of FIG. The short circuit is connected between the midpoint of the first flying capacitor circuit F1 and the midpoint of the second flying capacitor circuit F2. That is, they are connected between the output terminals of the orthogonal transform unit 10. FIG. 15 shows an example in which the short-circuit circuit is composed of a bidirectional switch in which the 9-1 switching element Q91 and the 9-2 switching element Q92 are connected in series in opposite directions. A wide bandgap semiconductor switch such as GaN (gallium nitride) may be used for the short-circuit circuit instead of the IGBT or MOSFET.

FIG. 16 is a diagram showing a zero cross of the pseudo sine wave shown in FIG. As shown in FIG. 16, when transitioning from period 1 to period 3, the output voltage crosses zero. Similarly, when transitioning from period 3 to period 1, the output voltage crosses zero. The control unit 30 turns on the 9-1 switching element Q91 and the 9-2 switching element Q92 in the vicinity of the zero cross of the AC power output by the power conversion device 1 to short-circuit the short-circuit circuit.

17 (a) and 17 (b) show the first switching element Q1 to the sixth switching element Q6, the 7-1 switching element Q71 to the 7-4th switching element Q74, and the eighth switching element Q74 in the switching pattern I. It is the figure which summarized the on / off state of Q81-th8-4th switching element Q84, 9-1th switching element Q91, 9-2th switching element Q92. FIG. 17A shows a switching pattern I when a short-circuit circuit is not provided, and FIG. 17B shows a switching pattern I when a short-circuit circuit is provided. In the state 3A and the state 3B, the 9-1st switching element Q91 and the 9-2 switching element Q92 are controlled to the off state.

The switching pattern I is a switching pattern at the time of switching between the state 3A (0V) and the state 3B (0V), and a dead time period is inserted between them. In the example shown in FIG. 17A, during the dead time period, the control unit 30 uses the first switching element Q1 to the sixth switching element Q6, the 7-1 switching element Q71 to the 7-4 switching elements Q74, and the eighth. -1 Switching elements Q81 to 8-4 All of the switching elements Q84 are controlled to the off state (hereinafter referred to as the all off state).

In the fully off state, the midpoint of the first flying capacitor circuit F1 and the midpoint of the second flying capacitor circuit F2 are electrically separated. Therefore, when a current flows through the freewheeling diode of either arm, the first flying The midpoint of the capacitor circuit F1 or the potential of the second flying capacitor circuit F2 may fluctuate and move away from 0V.

In the example shown in FIG. 17B, between the state 3A and the fully off state, the first switching element Q1 to the sixth switching element Q6, the 7-1 switching element Q71 to the 7-4 switching element Q74, and the first switching element Q74. The on / off state of the 8-1 switching element Q81 to 8-4 switching element Q84 is the same as the on / off state of the state 3A, and the 9-1 switching element Q91 and the 9-2 switching element Q92 are in the off state. A short-circuit state A is provided.

Similarly, between the state 3B and the all-off state, the first switching element Q1 to the sixth switching element Q6, the 7-1 switching element Q71 to the 7-4 switching element Q74, and the 8-1 switching element Q81 to the first. 8-4 The on / off state of the switching element Q84 is the same as the on / off state of the state 3B, and the short-circuit state B in which the 9-1 switching element Q91 and the 9-2 switching element Q92 are off is provided.

By controlling the 9-1st switching element Q91 and the 9-2 switching element Q92 to the off state and short-circuiting the output terminals before shifting to the all off state in this way, the state becomes the state 3A (0V). It is possible to prevent the output voltage from deviating from 0V when switching between 3B (0V). That is, it is possible to prevent the output voltage from deviating from 0V by short-circuiting the short-circuit circuit during the period when the output voltage should be maintained at 0V.

FIG. 18 is a diagram showing a circuit configuration in which a first DC / DC converter 11 and a second DC / DC converter 12 are added to the circuit configuration of FIG. When the first capacitor C1 and the second capacitor C2 are charged, they should be stable at a voltage width of 1/4 of the voltage of the DC power supply unit 2, respectively. However, when a transient response or phase jump of the system 3 occurs, the balance between the voltage of the first capacitor C1 and the voltage of the second capacitor C2 may be lost.

In the circuit configuration shown in FIG. 18, the first DC / DC converter 11 is connected in parallel with the first capacitor C1 to stabilize the voltage of the first capacitor C1. Similarly, the voltage of the second capacitor C2 is stabilized by connecting the second DC / DC converter 12 in parallel with the second capacitor C2. In the state where the first capacitor C1 is charged, the first DC / DC converter 11 sets the positive electrode potential of the first capacitor C1 to the positive electrode potential of the DC power supply unit 2 and the negative electrode potential of the first capacitor C1 to the DC power supply unit 2. It is controlled to a potential of 3/4 of the voltage. In the state where the first capacitor C1 is charged, the second DC / DC converter 12 sets the positive potential of the second capacitor C2 to 1/4 of the voltage of the DC power supply unit 2 and the negative potential of the second capacitor C2. It is controlled to the negative potential of the DC power supply unit 2.

FIG. 19 is a diagram showing a circuit configuration in which an isolated DC / DC converter 13 is added to the circuit configuration of FIG. In the circuit configuration shown in FIG. 19, the isolated DC / DC converter 13 is connected in parallel with the first capacitor C1 and the second capacitor C2. As described above, the positive electrode potential of the first capacitor C1 and the positive electrode potential of the second capacitor C2, and the negative electrode potential of the first capacitor C1 and the negative electrode potential of the second capacitor C2 are different from each other. On the other hand, in the isolated DC / DC converter 13, since the primary side and the secondary side are insulated by the transformer, it is not necessary that the reference potentials of the primary side and the secondary side are aligned. In the circuit configuration shown in FIG. 19, the electric power of the first capacitor C1 and the electric power of the second capacitor C2 can be interchanged via the isolated DC / DC converter 13.

FIG. 20 is a diagram showing a circuit configuration in which the active buffer circuit 14 is added to the circuit configuration of FIG. In the circuit configuration shown in FIG. 20, the active buffer circuit 14 is connected in parallel with the DC power supply unit 2. A large-capacity electrolytic capacitor is often connected between the positive and negative wirings of the DC bus that connects the DC power supply unit 2 and the orthogonal transform unit 10. In recent years, a design method for replacing the electrolytic capacitor with a film capacitor having a longer life than the electrolytic capacitor has begun to be adopted.

Film capacitors are more expensive and have a larger volume than electrolytic capacitors. In the case of the same capacity, the volume of the film capacitor may be 10 times or more the volume of the electrolytic capacitor. Therefore, it is conceivable to reduce the capacity of the film capacitor. As a result, when the capacity of the DC bus becomes smaller, the influence of ripple noise becomes larger. On the other hand, by adding the active buffer circuit 14, the influence of ripple noise can be reduced. Therefore, the large-capacity electrolytic capacitor can be replaced with a film capacitor having a smaller capacity than the electrolytic capacitor, and the life of the capacitor can be extended.

As described above, according to the present embodiment, it is possible to realize a highly efficient and compact power conversion device 1. Since it is a multi-level power conversion device using the first flying capacitor circuit F1 and the second flying capacitor circuit F2, the sizes of the first reactor L1 and the second reactor L2 of the filter unit 20 can be reduced.

Further, it is included in the 7-1 switching element Q71 to 7-4 switching element Q74 and the second flying capacitor circuit F2 included in the first flying capacitor circuit F1 that actually generates a half wave of a pseudo sine wave. By switching the 8-1st switching element Q81 to the 8-4th switching element Q84 at a high speed (for example, 20 kHz), the size of the first reactor L1 and the second reactor L2 of the filter unit 20 can be further reduced. it can.

Further, by using low withstand voltage switching elements for the 7-1 switching elements Q71 to 7-4 switching elements Q74 and the 8-1 switching elements Q81 to 8-4 switching elements Q84 that are switched at high speed. , Conduction loss and switching loss can be reduced.

Further, as the high withstand voltage switching element having a relatively large conduction loss and switching loss, only two, the fifth switching element Q5 and the sixth switching element Q6, are used. Further, the fifth switching element Q5 and the sixth switching element Q6, which have relatively slow switching speeds, are used at locations where switching is performed only at the time of polarity switching. Since the high-voltage switching element does not perform high-frequency switching in this way, an increase in switching loss can be suppressed. Further, the power conversion device 1 as a whole can easily have a high frequency, and by increasing the high frequency, the sizes of the first reactor L1 and the second reactor L2 can be reduced.

Further, since the fifth switching element Q5 and the sixth switching element Q6 operate in a complementary manner, a switching pattern in which the current supplied from the DC power supply unit 2 passes through two high withstand voltage switching elements does not occur. On the other hand, in the H-bridge circuit, a switching pattern that passes through two high-voltage switching elements is generated.

The present invention has been described above based on the embodiments. Embodiments are examples, and it will be understood by those skilled in the art that various modifications are possible for each of these components and combinations of each processing process, and that such modifications are also within the scope of the present invention. ..

In the above-described embodiment, an example in which a one-stage flying capacitor circuit is used for the first flying capacitor circuit F1 and the second flying capacitor circuit F2 is shown. In this regard, a flying capacitor circuit having two or more stages may be used.

FIG. 21 is a diagram showing a circuit configuration in which the first flying capacitor circuit F1 and the second flying capacitor circuit F2 having the circuit configuration of FIG. 13 are replaced with a three-stage flying capacitor circuit. In the circuit configuration shown in FIG. 21, there are 9 levels (+ Vdc, + Vdc * 3/4, + Vdc / 2, + Vdc / 4, 0, -Vdc * 3/4, -Vdc / 2, -Vdc / 4, -Vdc). The voltage can be output.

In the circuit configuration of FIG. 21, the 7-1 switching elements Q71 to 7-8 switching elements Q78 included in the first flying capacitor circuit F1 and the 8-1 switching elements Q81 to included in the second flying capacitor circuit F2. A switching element having a withstand voltage of about 75 V is used for the 8th-8th switching element Q88.

For the 5th switching element Q5 and the 6th switching element Q6, a switching element having a withstand voltage of about 600 V is used, and the 1-1 switching element Q1a, the 1-2 switching element Q1b, the 2-1 switching element Q2a, and the second A switching element having a withstand voltage of about 150 V is used for the -2 switching element Q2b, the 3-1 switching element Q3a, the 3-2 switching element Q3b, the 4-1 switching element Q4a, and the 4-2 switching element Q4b. As shown in FIG. 21, if the power conversion device 1 having a 9-level output is used, a smoother pseudo sine wave can be generated.

The embodiment may be specified by the following items.

[Item 1]
A first arm circuit in which the first switching element (Q1), the first flying capacitor circuit (F1), and the second switching element (Q2) are connected in series in parallel with the DC power supply (2).
A second arm circuit in which a third switching element (Q3), a second flying capacitor circuit (F2), and a fourth switching element (Q4) are connected in series in parallel with the DC power supply (2) and the first arm circuit. When,
Between the connection point between the first switching element (Q1) and the first flying capacitor circuit (F1) and the connection point between the second flying capacitor circuit (F2) and the fourth switching element (Q4). With the connected fifth switching element (Q5),
Between the connection point between the third switching element (Q3) and the second flying capacitor circuit (F2) and the connection point between the first flying capacitor circuit (F1) and the second switching element (Q2). It is equipped with a connected sixth switching element (Q6).
A power conversion device (1) characterized in that AC power is output from the midpoint of the first flying capacitor circuit (F1) and the midpoint of the second flying capacitor circuit (F2).
According to this, it is possible to realize a high-efficiency and compact power conversion device (1).
[Item 2]
The first switching element (Q1), the sixth switching element (Q6), and the fourth switching element (Q4) are in the ON state, and the second switching element (Q2), the fifth switching element (Q5), and the like. And when the third switching element (Q3) is off, a half wave of the AC power is generated.
The first switching element (Q1), the sixth switching element (Q6), and the fourth switching element (Q4) are in the off state, and the second switching element (Q2), the fifth switching element (Q5), and the like. The power conversion device (1) according to item 1, wherein the third switching element (Q3) generates a half wave of the opposite polarity of the AC power in the ON state.
By controlling the first switching element (Q1) to the sixth switching element (Q6) in this way, the polarity of the AC power can be switched.
[Item 3]
The first switching element (Q1), the sixth switching element (Q6), and the fourth switching element (Q4) are in the ON state, and the second switching element (Q2), the fifth switching element (Q5), and the like. And when the third switching element (Q3) is in the off state,
The first switching element (Q1), the sixth switching element (Q6), and the fourth switching element (Q4) are in the off state, and the second switching element (Q2), the fifth switching element (Q5), and the like. And switching in the ON state of the third switching element (Q3)
The power conversion device according to item 1, which operates when switching the polarity of the output voltage output from the midpoint of the first flying capacitor circuit (F1) and the midpoint of the second flying capacitor circuit (F2).
By controlling the first switching element (Q1) to the sixth switching element (Q6) in this way, the polarity of the AC power can be switched.
[Item 4]
The first flying capacitor circuit (F1)
7-1 switching element (Q71), 7-2 switching element (Q72), 7-3 switching element (Q73), and 7-4 switching element (Q74) connected in series,
The connection point between the 7-1 switching element (Q71) and the 7-2 switching element (Q72), and the connection point between the 7-3 switching element (Q73) and the 7-4 switching element (Q74). Includes a first capacitor (C1) connected between
The second flying capacitor circuit (F2) is
8-1 switching element (Q81), 8-2 switching element (Q82), 8-3 switching element (Q83), and 8-4 switching element (Q84) connected in series,
The connection point between the 8-1 switching element (Q81) and the 8-2 switching element (Q82), and the connection point between the 8-3 switching element (Q83) and the 8-4 switching element (Q84). The power conversion device (1) according to any one of items 1 to 3, further comprising a second capacitor (C2) connected between the two.
According to this, a voltage of 5 levels can be generated.
[Item 5]
For the fifth switching element (Q5) and the sixth switching element (Q6), an element having a withstand voltage higher than the voltage of the DC power supply (2) is used.
The first switching element (Q1), the second switching element (Q2), the third switching element (Q3), the fourth switching element (Q4), the 7-1 switching element (Q71), the seventh. -2 switching element (Q72), the 7-3 switching element (Q73), the 7-4 switching element (Q74), the 8-1 switching element (Q81), the 8-2 switching element (Q82). ), The 8th-3 switching element (Q83), and the 8-4 switching element (Q84) are characterized in that an element having a withstand voltage lower than the voltage of the DC power supply (2) is used. The power conversion device (1) according to 4.
By using a high withstand voltage switching element in places where high speed switching is not required and a low withstand voltage switching element in places where high speed switching is required, overall conduction loss and switching loss can be reduced while ensuring safety. It can be reduced.
[Item 6]
The first flying capacitor circuit (F1) includes N (N is a natural number) capacitors.
The second flying capacitor circuit (F2) includes N (N is a natural number) capacitors.
Any of items 1 to 3 characterized in that a voltage of (2N + 3) level is output from the midpoint of the first flying capacitor circuit (F1) and the midpoint of the second flying capacitor circuit (F2). The power conversion device (1) according to item 1.
According to this, more voltage levels can be generated with a smaller number of capacitors.
[Item 7]
At least one of the first switching element (Q1), the second switching element (Q2), the third switching element (Q3), and the fourth switching element (Q4) is the first flying capacitor circuit (F1). , And any of items 1 to 6 characterized in that the second flying capacitor circuit (F2) is replaced with a series circuit or a series-parallel circuit composed of a plurality of switching elements corresponding to the withstand voltage of the switching element. The power conversion device (1) according to item 1.
According to this, the conduction loss and the switching loss can be reduced.
[Item 8]
Item 1 is further provided with short-circuit circuits (Q91, Q92) connected between the midpoint of the first flying capacitor circuit (F1) and the midpoint of the second flying capacitor circuit (F2). The power conversion device (1) according to any one of 7 to 7.
According to this, 0V included in one of the multi-levels can be generated with high accuracy.
[Item 9]
The power conversion device (1) according to item 8, wherein the short-circuit circuits (Q91, Q92) are short-circuited in the vicinity of the zero cross of the AC power.
According to this, it is possible to prevent the output of a voltage other than 0V when the AC power is zero-crossed.
[Item 10]
The power conversion device (1) according to item 8 or 9, wherein the short-circuit circuits (Q91, Q92) are short-circuited during a period in which the output voltage of the power conversion device (1) should be maintained at 0V.
According to this, it is possible to prevent the output of a voltage other than 0V when the AC power is zero-crossed.
[Item 11]
A DC / DC converter (11, 12, 13) connected in parallel with at least one capacitor included in the first flying capacitor circuit (F1) and the second flying capacitor circuit (F2) is further provided. The power conversion device (1) according to any one of items 1 to 10.
According to this, the voltage of the first capacitor (C1) and / or the second capacitor (C2) can be stabilized.
[Item 12]
The power conversion device (1) according to any one of items 1 to 11, further comprising an active buffer circuit (14) connected in parallel with the DC power supply (2).
According to this, the ripple noise superimposed on the DC bus can be reduced.

1 Power converter, 2 DC power supply, 3 systems, 10 diode converter, 20 filter, 30 control, F1 1st flying capacitor circuit, F2 2nd flying capacitor circuit, Q1 1st switching element, Q2 2nd switching Elements, Q3 3rd switching element, Q4 4th switching element, Q5 5th switching element, Q6 6th switching element, Q71 7-1 switching element, Q72 7-2 switching element, Q73 7-3 switching element, Q74 7-4 switching element, Q81 8-1 switching element, Q82 8-2 switching element, Q83 8-3 switching element, Q84 8-4 switching element, Q91 9-1 switching element, Q92 9-2 Switching element, D1 1st diode, D2 2nd diode, D3 3rd diode, D4 4th diode, D5 5th diode, D6 6th diode, D71 7-1 diode, D72 7-2 diode, D73 7-3 diode, D74 7-4 diode, D81 8-1 diode, D82 8-2 diode, D83 8-3 diode, D84 8-4 diode, D91 9-1 diode, D92 9-2 diode, C1 1st capacitor, C2 2nd capacitor, L1 1st reactor, L2 2nd reactor, L3 3rd capacitor, 11 1st DC / DC converter, 12 2nd DC / DC converter, 13 Insulated DC / DC converter, 14 active buffer circuits.

Claims (11)

A first arm circuit in which the first switching element, the first flying capacitor circuit, and the second switching element are connected in series in parallel with the DC power supply,
A second arm circuit in which a third switching element, a second flying capacitor circuit, and a fourth switching element are connected in series in parallel with the DC power supply and the first arm circuit.
A fifth switching element connected between the connection point between the first switching element and the first flying capacitor circuit and the connection point between the second flying capacitor circuit and the fourth switching element.
A sixth switching element connected between the connection point between the third switching element and the second flying capacitor circuit and the connection point between the first flying capacitor circuit and the second switching element is provided.
AC power is output from the midpoint of the first flying capacitor circuit and the midpoint of the second flying capacitor circuit.
Half of the AC power when the first switching element, the sixth switching element, and the fourth switching element are on, and the second switching element, the fifth switching element, and the third switching element are off. Generate waves,
The reverse of the AC power when the first switching element, the sixth switching element, and the fourth switching element are in the off state, and the second switching element, the fifth switching element, and the third switching element are in the on state. A power converter characterized by generating a half-wave of polarity. A first arm circuit in which the first switching element, the first flying capacitor circuit, and the second switching element are connected in series in parallel with the DC power supply,
A second arm circuit in which a third switching element, a second flying capacitor circuit, and a fourth switching element are connected in series in parallel with the DC power supply and the first arm circuit.
A fifth switching element connected between the connection point between the first switching element and the first flying capacitor circuit and the connection point between the second flying capacitor circuit and the fourth switching element.
A sixth switching element connected between the connection point between the third switching element and the second flying capacitor circuit and the connection point between the first flying capacitor circuit and the second switching element is provided.
AC power is output from the midpoint of the first flying capacitor circuit and the midpoint of the second flying capacitor circuit.
The first switching element, the sixth switching element, and the fourth switching element are in the on state, and the second switching element, the fifth switching element, and the third switching element are in the off state.
Switching that the first switching element, the sixth switching element, and the fourth switching element are in the off state, and the second switching element, the fifth switching element, and the third switching element are in the on state can be performed.
The first flying capacitor circuit at the midpoint between the second flying capacitor circuit operation to power conversion apparatus according to claim Rukoto when switching the polarity of the output voltage outputted from the midpoint of. The first flying capacitor circuit is
The 7-1 switching element, the 7-2 switching element, the 7-3 switching element, and the 7-4 switching element connected in series,
The connection point between the 7-1 switching element and the 7-2 switching element, and the first capacitor connected between the connection point between the 7-3 switching element and the 7-4 switching element. Including
The second flying capacitor circuit is
8-1 switching element, 8-2 switching element, 8-3 switching element, and 8-4 switching element connected in series,
The connection point between the 8-1 switching element and the 8-2 switching element and the second capacitor connected between the connection point between the 8-3 switching element and the 8-4 switching element are formed. The power conversion device according to claim 1 or 2 , wherein the power conversion device includes. For the fifth switching element and the sixth switching element, an element having a withstand voltage higher than the voltage of the DC power supply is used.
The first switching element, the second switching element, the third switching element, the fourth switching element, the 7-1 switching element, the 7-2 switching element, the 7-3 switching element, the first. The 7-4 switching element, the 8-1 switching element, the 8-2 switching element, the 8-3 switching element, and the 8-4 switching element have a withstand voltage lower than the voltage of the DC power supply. The power conversion device according to claim 3 , wherein the element is used. The first flying capacitor circuit includes N (N is a natural number) capacitors.
The second flying capacitor circuit includes N (N is a natural number) capacitors.
The power conversion device according to claim 1 or 2 , wherein a voltage of a (2N + 3) level is output from the midpoint of the first flying capacitor circuit and the midpoint of the second flying capacitor circuit. At least one of the first switching element, the second switching element, the third switching element, and the fourth switching element has a withstand voltage of the switching element included in the first flying capacitor circuit and the second flying capacitor circuit. The power conversion device according to any one of claims 1 to 5 , wherein the power conversion device is replaced with a series circuit or a series-parallel circuit composed of a plurality of switching elements corresponding to the above. The invention according to any one of claims 1 to 6 , further comprising a short circuit circuit connected between the midpoint of the first flying capacitor circuit and the midpoint of the second flying capacitor circuit. Power converter. The power conversion device according to claim 7 , wherein the short-circuit circuit is short-circuited in the vicinity of the zero cross of the AC power. The power conversion device according to claim 7 or 8 , wherein the short-circuit circuit is short-circuited during a period in which the output voltage of the power conversion device should be maintained at 0V. A first arm circuit in which the first switching element, the first flying capacitor circuit, and the second switching element are connected in series in parallel with the DC power supply,
A second arm circuit in which a third switching element, a second flying capacitor circuit, and a fourth switching element are connected in series in parallel with the DC power supply and the first arm circuit.
A fifth switching element connected between the connection point between the first switching element and the first flying capacitor circuit and the connection point between the second flying capacitor circuit and the fourth switching element.
A sixth switching element connected between the connection point between the third switching element and the second flying capacitor circuit and the connection point between the first flying capacitor circuit and the second switching element is provided.
AC power is output from the midpoint of the first flying capacitor circuit and the midpoint of the second flying capacitor circuit.
The first flying capacitor circuit, and the second flying capacitor circuit at least one capacitor further power converter, comprising the connected DC / DC converters in parallel included in. The power conversion device according to any one of claims 1 to 10 , further comprising an active buffer circuit connected in parallel with the DC power supply.

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