JP2013085358A - Power conversion device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a power conversion device that has an easily manufacturable configuration.SOLUTION: The present invention relates to a power conversion device 10 including: a series three-level inverter group of 2three-level inverters 10a, 10b connected in series; and at least one switch circuit 11 for selecting outputs of two three-level inverters of the series three-level inverter group. The switch circuit 11 is connected in 2so as to select either of the outputs of two adjacent three-level inverters 10a, 10b of the series three-level inverter group, and in the case of two switch circuits or more, a switch circuit connected in order in a later stage so as to select either of outputs of two switch circuits connected in the preceding stage produces a single output.

Description

  The present invention relates to a power converter, and more particularly, to a power converter capable of outputting a plurality of different voltage levels.

  There has been proposed a power conversion device that changes the stack of DC voltages from a plurality of DC power sources in one cycle and converts DC power into AC power. This power conversion device does not generate a constant pulse voltage like an inverter having one DC power supply, but stacks a plurality of DC voltages having different potentials to convert DC power into AC power. For this reason, this power conversion device converts DC power into AC power with less harmonics than a power conversion device having one DC power supply by finely stacking a plurality of DC voltages with different potentials without waste. Can do.

  Specifically, Patent Document 1 discloses a multilevel inverter which is the above-described power conversion device.

  The multilevel inverter disclosed in Patent Document 1 is a redox flow type secondary battery that is connected in series and forms a multilevel terminal voltage, and an inverter unit that forms AC power by controlling the stacking of the potentials of the multilevel terminals. And. The inverter unit includes a total of eight switching elements and six diodes, and controls opening and closing of the switching elements according to instructions from the control unit.

JP 2000-341964 A

  FIG. 5 is a circuit diagram showing a circuit configuration of a conventional power conversion device disclosed in Patent Document 1. As shown in FIG. The power conversion device 100 shown in FIG. 5 is a 5-level inverter that can output five different voltage levels. The power conversion apparatus 100 includes four DC power supplies V, eight switch elements S101 to S108, and six diodes D101 to D106.

The power conversion apparatus 100 sets the midpoint of the four DC power sources V as the midpoint V ₀ and sets the voltage level at the midpoint V ₀ to “0 V”. Therefore, the power conversion device 100, the voltage level of plus only one of the DC power supply V component than the midpoint V ₀ potential "+ 1V", and the only two of the DC power supply V component than the midpoint V ₀ voltage level of positive potential Becomes “+ 2V”. Conversely, the power conversion device 100, the voltage level of one of the DC power supply V component only negative potential than the midpoint V ₀ is "-1 V", and the only two of the DC power supply V component than the midpoint V ₀ which negative potential The voltage level becomes “−2V”.

  The power conversion device 100 outputs the potential of the voltage level of “+ 2V” to the output terminal by turning on the switch elements S101, S102, S103, and S104, and turns on the switch elements S102, S103, S104, and S105. As a result, a potential of a voltage level of “+1 V” can be output to the output terminal. Further, the power conversion device 100 can output a potential of a voltage level of “0 V” to the output terminal by turning on the switch elements S103, S104, S105, and S106. Further, the power conversion device 100 outputs the potential of the voltage level of “−1V” to the output terminal by turning on the switch elements S104, S105, S106, and S107, and switches the switch elements S105, S106, S107, and S108. By setting the ON state, a potential of a voltage level of “−2V” can be output to the output terminal. Therefore, the power conversion apparatus 100 can output five different voltage levels (“−2V”, “−1V”, “0V”, “+ 1V”, “+ 2V”) from the output terminal.

  However, in the power conversion device 100, when the switch elements S105, S106, S107, and S108 are turned on in order to output the potential of the voltage level of “−2V” from the output terminal, the anode terminals of the diodes D102, D104, and D106 The voltage level of the diode D102 is “−2V”, and the cathode terminal of the diode D102 is connected to the voltage level of “+ 1V”, so that a voltage corresponding to three DC power sources V is applied. Similarly, the voltage for two DC power sources V is applied to the diode D104, and the voltage for one DC power source V is applied to the diode D106.

  Further, in the power conversion device 100, when the switch elements S101, S102, S103, and S104 are turned on in order to output the potential of the voltage level of “+ 2V” from the output terminal, the anode terminals of the diodes D101, D103, and D105 are turned on. Since the voltage level becomes “+2 V” and the cathode terminal of the diode D105 is connected to the voltage level of “−1 V”, a voltage corresponding to three DC power sources V is applied. Similarly, a voltage for two DC power sources V is applied to the diode D103, and a voltage for one DC power source V is applied to the diode D101.

  As described above, the multilevel inverter disclosed in Patent Document 1 has a withstand voltage that is three times higher than that of the diodes D101 and D106 in the diodes D102 and D105 that connect the DC power supply and the switching element, and the diodes D103 and D104. A double withstand voltage is required for each of the diodes D101 and D106. Therefore, in the multilevel inverter disclosed in Patent Document 1, it is necessary to use diodes with different withstand voltages, or to connect two or three diodes in series to increase the withstand voltage, and the device becomes complicated, which is manufactured. It was difficult.

  In addition, the multilevel inverter disclosed in Patent Document 1 requires a higher withstand voltage to the diode as the number of output voltage levels increases, and the configuration of the diode connected between the DC power supply and the switch element is increased. Complicated and difficult to manufacture.

  Therefore, the present invention has been made to solve the above-described problems, and an object thereof is to provide a power conversion device having a configuration that can be easily manufactured.

In order to solve the above-described problems, the present invention provides first to fourth switch elements connected in series, a first connection point between the first switch element and the second switch element, and a third switch element. And a second connection point between the first switch element and the fourth switch element, two diodes connected in series, a third connection point connecting the diodes, and a first switch element connected between the first switch element and the second switch point. A first charge storage element, a third connection point, and a second charge storage element connected between the fourth switch element and a combination of the ON state and the OFF state of the first to fourth switch elements Three n-level inverters capable of outputting three voltage levels, where n is an integer equal to or greater than 1, 2 ⁿ series three-level inverter groups connected in series and three series three-level inverter groups Select the output of two 3-level inverters A power converter including at least one switch circuit to be selected, wherein the series three-level inverter group includes a fourth connection point between the fourth switch element of the adjacent one of the three-level inverters and the second charge storage element. And repeating the connection between the first switch element of the other adjacent three-level inverter and the fifth connection point of the first charge storage element to connect 2 ⁿ three-level inverters in series, Connect 2 ^n-1 units so that either one of the outputs of two adjacent three-level inverters in the series 3-level inverter group can be selected, and if there are two or more switch circuits, The next-stage switch circuit is connected in order so that one of the outputs of the two connected switch circuits can be selected to obtain one output.

  According to the power conversion device of the present invention, a configuration is provided that includes a series three-level inverter group in which a plurality of three-level inverters are connected in series, and at least one switch circuit that selects the outputs of the plurality of three-level inverters. As a result, regardless of the number of output voltage levels, elements that require a withstand voltage can be concentrated on the switch circuit, so that the structure can be easily manufactured.

It is a circuit diagram which shows the circuit structure of the power converter device which concerns on Embodiment 1 of this invention. It is a wave form diagram which shows the waveform of the voltage level which the power converter device shown in FIG. 1 outputs. It is a circuit diagram which shows another circuit structure of the power converter device which concerns on Embodiment 1 of this invention. It is a wave form diagram which shows the waveform of the voltage level which the power converter device shown in FIG. 3 outputs. It is a circuit diagram which shows the circuit structure of the conventional power converter device currently disclosed by patent document 1. FIG.

Hereinafter, embodiments according to the present invention will be described with reference to the drawings.
(Embodiment 1)
FIG. 1 is a circuit diagram showing a circuit configuration of a power conversion device according to Embodiment 1 of the present invention. The power conversion device 10 shown in FIG. 1 is a 5-level inverter that can output five different voltage levels. The power conversion device 10 includes four DC power supplies V, ten switch elements S1 to S10, four diodes D1 to D4, and an output terminal.

  The power conversion apparatus 10 includes two three-level inverters 10a and 10b that can output three different voltage levels, and one switch circuit 11 that selects the outputs of the two three-level inverters 10a and 10b. With. The three-level inverter 10a includes four switch elements S1 to S4 connected in series, diodes D1 and D2 connected in series, and capacitors C1 and C2 that are DC power supplies V connected in series. The three-level inverter 10a connects diodes D1 and D2 in series between a connection point P1 between the switch elements S1 and S2 and a connection point P2 between the switch elements S3 and S4. Further, the three-level inverter 10a connects the capacitor C1 between the connection point P3 connecting the diodes D1 and D2 and the switch element S1, and connects the capacitor C2 between the connection point P3 and the switch element S4. Since 3-level inverter 10b has the same circuit configuration as 3-level inverter 10a, detailed description will not be repeated.

  The switch circuit 11 includes a switch element S9 and a switch element S10, and selects the output of the three-level inverter 10a or the three-level inverter 10b when the switch element S9 or the switch element S10 is turned on.

  The three-level inverter 10a can output the positive potential “+ 2V” of the capacitor C1 in the capacitors C1 and C2 connected in series by turning on the switch elements S1 and S2, and the switch elements S2 and S3 By turning it on, the potential “+1 V” at the connection point P4 between the capacitors C1 and C2 connected in series can be output. Further, the three-level inverter 10a can output the negative potential “0V” of the capacitor C2 in the capacitors C1 and C2 connected in series by turning on the switch elements S3 and S4. Therefore, the three-level inverter 10a can output three voltage levels of “0V”, “+ 1V”, and “+ 2V”.

  Since the 3-level inverter 10b can operate in the same manner as the 3-level inverter 10a, it can output three voltage levels of “0V”, “−1V”, and “−2V”.

  Therefore, the power conversion device 10 selects one output of the three-level inverters 10a and 10b connected in series by switching the ON state of the switch element S9 and the switch element S10 of the switch circuit 11. Five different voltage levels ("-2V", "-1V", "0V", "+ 1V", "+ 2V") can be output from the output terminal. The negative potential of the capacitor C2 and the positive potential of the capacitor C3 are the same potential “0V”.

  Next, operation | movement of the power converter device 10 is demonstrated. FIG. 2 is a waveform diagram showing a waveform of a voltage level output from the power conversion device 10 shown in FIG.

First, the power converter 10 turns on the switch elements S3 and S4, turns on the switch element S9 of the switch circuit 11 (the switch element S10 is turned off), and outputs the voltage level “0 V” from the output terminal. Thereafter, the power conversion apparatus 10, the time _{t 1,} turns on the switch element S2, S3 state, and the switching element (S9) of the switching circuit 11 to the ON state, and outputs a voltage level "+ 1V" from the output terminal.

The power conversion apparatus 10, the time _{t 2,} turns on the switch element S1, S2 state, and the switching element (S9) of the switching circuit 11 to the ON state, and outputs a voltage level "+ 2V" from the output terminal. Thereafter, the power conversion device 10 decreases the voltage level from the output terminal in order of “+1” and “0”.

  The power conversion device 10 may output the voltage level “0 V” from the output terminal by turning on the switch elements S5 and S6 and turning on the switch element S10 of the switch circuit 11.

At time t ₃ , the power conversion device 10 turns on the switch elements S6 and S7 and turns on the switch element S10 of the switch circuit 11, and outputs a voltage level “−1V” from the output terminal.

The power conversion apparatus 10, the time _{t 4,} switch elements S7, S8 and turned on, and the switching element S10 in the switching circuit 11 to the ON state, and outputs a voltage level "-2 V" from the output terminal. Thereafter, the power conversion device 10 increases the voltage level from the output terminal in the order of “−1” and “0”.

  The power conversion apparatus 10 performs an operation of switching and outputting five different voltage levels (“−2 V”, “−1 V”, “0 V”, “+1 V”, “+2 V”) as described above. 2 can be output, and direct current power can be converted into alternating current power.

  In the three-level inverters 10a and 10b, in the switch elements S1 to S8 and the diodes D1 to D4 that constitute the three-level inverters 10a and 10b, only one capacitor voltage is applied to both ends of each element when the switch elements are in the OFF state. . In the switch elements S9 and S10 that constitute the switch circuit 11, when “+2 V” is output from the output terminal, the switch element S9 is turned on and the switch element S10 is turned off. Minute capacitor voltage is applied. In addition, when the switch circuit 11 is configured to output “−2V” from the output terminal in the switch elements S9 and S10 that constitute the switch circuit 11, the switch element S10 is turned on and the switch element S9 is turned off. Two capacitor voltages are applied to the capacitor.

  As described above, the power conversion device 10 according to the first embodiment of the present invention includes a series of three level inverters in which two high level inverters 10a and 10b are connected in series and an element with a particularly high withstand voltage is unnecessary. With the configuration including the switch circuit 11, an element to which a high voltage is applied can be limited to an element configuring the switch circuit 11. That is, the power conversion device 10 can be manufactured simply by connecting two three-level inverters using existing withstand voltage elements in series and providing a switch circuit for selecting the output of the three-level inverter. It can be.

  The power conversion device according to Embodiment 1 of the present invention is not limited to a power conversion device that can output five different voltage levels, but a three-level inverter and a switch connected in series. By increasing the number of circuits, the number of output voltage levels can be easily increased.

  Specifically, FIG. 3 is a circuit diagram showing another circuit configuration of the power conversion device according to Embodiment 1 of the present invention. The power conversion device 20 shown in FIG. 3 is a 9-level inverter that can output nine different voltage levels. The power conversion device 20 includes eight DC power supplies V, 22 switch elements S1 to S22, and 8 diodes D1 to D8. Note that free wheel diodes are connected to the switch elements S1 to S22, respectively.

  The power conversion device 20 includes a series three-level inverter group in which four three-level inverters 20a, 20b, 20c, and 20d are connected in series, and one switch circuit that selects the outputs of the two three-level inverters 20a and 20b. 21, one switch circuit 22 for selecting the outputs of the two three-level inverters 20 c and 20 d, and the output of the two switch circuits 21 and 22 connected in the previous stage The switch circuit 23 of the next stage is provided.

An intermediate point of the eight DC power sources V is set as a middle point V _0, and a voltage level at the middle point V ₀ is set as “0 V”. Therefore, the voltage level of the connection points of the four DC power supply V of the above the midpoint _{V 0} is, "+ 1V" in order from the side of the midpoint _{V 0, "+ 2V",} "+ 3V" , and the below the midpoint _{V 0} The voltage levels at the connection points of the four DC power sources V on the side are “−1V”, “−2V”, and “−3V” in order from the middle point V ₀ side. The voltage level at the connection point between the DC power supply V and the switch element S1 is “+4 V”, and the voltage level at the connection point between the DC power supply V and the switch element S18 is “−4 V”.

  Next, operation | movement of the power converter device 20 is demonstrated. FIG. 4 is a waveform diagram showing a waveform of a voltage level output from the power conversion device 20 shown in FIG.

First, the power converter 20 turns on the switch elements S7 and S8, turns on the switch element S10 of the switch circuit 21, turns on the switch element S21 of the switch circuit 23, and sets the voltage level “0V” from the output terminal. Output. Thereafter, the power converter 20, the time _{t 1,} the switch element S6, S7 the ON state, the ON state switching element S10 in the switching circuit 21, and the switching element S21 in the switching circuit 23 in ON state, the voltage from the output terminal Outputs level “+ 1V”.

The power converter 20, the time _{t 2,} the switch elements S5, S6 on state, turns on the switch element S10 in the switching circuit 21 state, and the switching element S21 in the switching circuit 23 in ON state, the voltage from the output terminal Outputs level “+ 2V”.

  The power converter 20 turns on the switch elements S3 and S4, turns on the switch element S9 of the switch circuit 21, turns on the switch element S21 of the switch circuit 23, and sets the voltage level “+2 V” from the output terminal. It may be output.

Thereafter, at time t ₃ , the power conversion device 20 turns on the switch elements S2 and S3, turns on the switch element S9 of the switch circuit 21, and turns on the switch element S21 of the switch circuit 23. Outputs level “+ 3V”.

The power converter 20, the time _{t 4,} turns on the switch element S1, S2 state, turns on the switching element (S9) of the switching circuit 21 state, and the switching element S21 in the switching circuit 23 in ON state, the voltage from the output terminal Outputs level “+ 4V”. Thereafter, the power conversion device 20 decreases the voltage level from the output terminal in the order of “+3 V”, “+2 V”, “+1 V”, and “0 V”.

  The power converter 20 turns on the switch elements S11 and S12, turns on the switch element S19 of the switch circuit 22, turns on the switch element S22 of the switch circuit 23, and sets the voltage level “0V” from the output terminal. It may be output.

The power converter 20, the time _{t 5,} the switch elements S12, S13 the ON state, the switch element S19 of the ON state of the switch circuit 22, and the switching element S22 of the switch circuit 23 to the ON state, the voltage level from the output terminal " -1V "is output.

Then, the power converter 20, the time _{t 6,} the switch elements S13, S14 the ON state, turns on the switch element S19 in the switching circuit 22 state, and the switching element S22 of the switch circuit 23 to the ON state, the voltage from the output terminal Outputs level “−2V”.

  The power converter 20 turns on the switch elements S15 and S16, turns on the switch element S20 of the switch circuit 22, turns on the switch element S22 of the switch circuit 23, and sets the voltage level “−2V” from the output terminal. May be output.

Thereafter, the power converter 20, the time _{t 7,} the switch elements S16, S17 the ON state, turns on the switch element S20 in the switching circuit 22 state, and the switching element S22 of the switch circuit 23 to the ON state, the voltage from the output terminal Outputs level "-3V".

Then, the power converter 20, the time _{t 8,} the switch elements S17, S18 the ON state, turns on the switch element S20 in the switching circuit 22 state, and the switching element S22 of the switch circuit 23 to the ON state, the voltage from the output terminal Outputs level “-4V”. Thereafter, the power conversion device 20 increases the voltage level from the output terminal in order of “−3 V”, “−2 V”, “−1 V”, and “0 V”.

  As described above, the power converter 20 has nine different voltage levels (“−4V”, “−3V”, “−2V”, “−1V”, “0V”, “+ 1V”, “+ 2V”, “ By performing the operation of switching and outputting (+ 3V "," + 4V "), it is possible to output an alternating voltage as shown by a broken line in FIG. 4, and to convert direct current power into alternating current power.

  As described above, the power conversion device according to Embodiment 1 of the present invention generally increases the number of output voltage levels by increasing the number of level inverters and switch circuits connected in series as follows. Can be expressed.

That is, the power conversion device according to the first embodiment of the present invention selects the outputs of 2 ⁿ series 3-level inverters connected in series, and two 3-level inverters out of the series 3 level inverters. At least one switch circuit. Then, 2 ^n-1 switch circuits are connected so that any one of the outputs of two adjacent three level inverters of the series three level inverter group can be selected, and two switch circuits are provided. In the above case, the switch circuit in the next stage is connected in order so that either one of the outputs of the two switch circuits connected in the previous stage can be selected, and the power conversion device outputs one output. obtain.

  In the power conversion device according to the embodiment of the present invention, in order to simplify the description of the switch operation, the number of times of selecting the voltage level in one cycle of AC is limited. However, switching is performed a plurality of times in one cycle of AC. By selecting the voltage level a plurality of times, a finer alternating voltage can be output, and a power conversion device with fewer high frequencies can be obtained.

  In the power conversion device according to the embodiment of the present invention, the capacitor is used as the charge storage element. However, the present invention is not limited to this, and for example, a DC power source may be connected.

  Furthermore, in the power conversion device according to the embodiment of the present invention, the charge storage element and the switch element or the diode are directly connected. However, the present invention is not limited to this. For example, the switch element is turned on and off. A configuration in which a snubber circuit or the like that suppresses a sudden change in current in a transient state may be provided.

  The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

  10, 20 Power converter, 10a, 10b, 20a-20d Level inverter, 11, 21-23 Switch circuit, C1, C2, C3, C4 capacitor, D1-D8 diode.

Claims (2)

First to fourth switch elements connected in series;
2 connected in series between the first connection point of the first switch element and the second switch element and the second connection point of the third switch element and the fourth switch element. Diodes,
A first charge storage element connected between a third connection point connecting the diodes and the first switch element;
A second charge storage element connected between the third connection point and the fourth switch element; and a combination of the ON state and the OFF state of the first to fourth switch elements; the three-level inverter which is capable of outputting a voltage level, when integer of 1 or more n, a series three-level inverter groups are connected to ^the 2 ⁿ series,
A power converter comprising: at least one switch circuit that selects the outputs of two of the three-level inverters in the series of three-level inverter groups;
The series three-level inverter group includes a fourth connection point between the fourth switch element of the adjacent one of the three-level inverters and the second charge storage element, and a first connection point of the other adjacent three-level inverter. Repeating the connection of the switch element and the fifth connection point of the first charge storage element to connect 2 ⁿ of the three-level inverters in series;
The switch circuit is connected to 2 ^n-1 pieces so that any one of the outputs of two adjacent three-level inverters of the series three-level inverter group can be selected,
When there are two or more switch circuits, the switch circuits in the next stage are connected in order so that one of the outputs of the two switch circuits connected in the previous stage can be selected. Power converter that obtains one output.   A snubber circuit for suppressing a sudden change in current between the switch element and the first charge storage element or the second charge storage element and between the diode and the first charge storage element or the second charge storage element; The power converter according to claim 1 provided.

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