JP2013258863A - Multilevel power converter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a multilevel power converter that supports a higher voltage with fewer elements and dispenses with a separate voltage regulation circuit.SOLUTION: The multilevel power converter includes: a DC power supply V; capacitors C3, C4 connected in series between positive and negative ends of V; switching elements S5, S6, S1-S4, S7, S8 connected in series between the positive and negative ends of V; diodes D1, D2 connected in series between a common junction of S1, S2 and a common junction of S3, S4; C1, C2 connected in series between a common junction of S1, S6 and a common junction of S4, S7; a series circuit of S9, S10; C5 connected in parallel with the series circuit; a series circuit of S11, S12 connected in parallel with C5; and control means for controlling on/off S1-S12 to switch a multilevel voltage. A common junction of S2, S3 and a common junction of C3, C4, S9, S10 are AC output terminals A, B.

Description

  The present invention relates to a power conversion circuit capable of outputting a multi-level phase voltage and operating with a single DC voltage source, and outputs the AC voltage converted from a DC voltage source into a plurality of voltage levels. Related to the vessel.

  Conventionally, as a multilevel power converter, for example, a power conversion device that outputs nine voltage levels described in Patent Document 1 has been proposed. FIG. 4 shows a configuration diagram of one phase (U phase) of the main circuit of the 9-level inverter described in Patent Document 1.

In the circuit of FIG. 4, a positive DC power source E, is connected a series circuit of a capacitor C _1, C ₂ between the negative electrode, and a series circuit of semiconductor switches S _1, S ₂ in parallel, the semiconductor switches S _5, S ₆ series circuit, capacitor C ₃ , series circuit of semiconductor switches S ₇ and S ₈ , and bidirectional switch S _3D , S _4D series circuit having bidirectional breakdown voltage are connected in parallel to form a semiconductor switch The common connection point of S ₁ and S ₂ is connected to the common connection point of the semiconductor switches S ₅ and S ₆ , and the common connection point (middle point M) of the capacitors C ₁ and C ₂ is connected to the bidirectional switches S _3D and S _4D . Connected to the common connection point, the common connection point of the semiconductor switches S ₇ and S _{8 and} the common connection point of the bidirectional switches S _3D and S _4D are connected in common to form a U-phase output terminal.

In the power converter configured as described above, when the voltage of the DC power source E is E _d , the voltage of the capacitor C ₁ is V _C1 , the voltage of the capacitor C ₂ is V _C2 , and the voltage of the capacitor C ₃ is V _C3 , The relationship between the output voltage V _UM observed from the middle point M and the on / off states of the switches S ₁ , S ₂ , S _3D , S _4D , S _{5 to} S ₈ is shown in FIG.

In FIG. 5, the operation modes corresponding to the on / off states of the switches S ₁ , S ₂ , S _3D , S _4D , and S _{5 to} S ₈ are Modes 1 to 12, respectively.

In FIG. 5, “current polarity” is the polarity of the load current i _U , the direction of the arrow in FIG. 4 is +, and the voltage value at the charge (c) and discharge (d) of the capacitor C ₃ is the output voltage V _Shown on the right side of the _UM column.

When an appropriate switch in FIG. 4 is selected and turned on / off based on FIG. 5, the output voltage V _UM is divided into nine voltage levels (V _C1 + V _C3 , V _C1 , V _C1 −V _C3 , V _C3 , 0, −V _C3 , −V _C2 + V _C3 , −V _C2 , −V _C2 −V _C3 ), and the average voltage is a sinusoidal waveform.

According to the configuration of FIG. 4, a multi-level voltage is generated by a small number of elements (10 semiconductor elements and one capacitor (C ₃ ) when each of the bidirectional switches S _3D and S _4D is constituted by two series IGBTs). A power conversion circuit capable of outputting (equivalent to 9 levels) is realized.

  When this is expanded to three phases, a three-phase multilevel converter (corresponding to nine levels) can be realized with 30 semiconductor switches and three capacitors.

JP 2010-246189 A

In the circuit shown in FIG. 4, a multi-level converter can be realized with a small number of elements. However, since the voltage Ed of the DC power supply E is applied to the switching elements S ₁ and S ₂ , the voltage Ed is changed to the switching element. When the withstand voltage of the series body in which S ₁ and S ₂ are connected in series is higher, the number of elements needs to be increased.

Further, the output voltage V _UM against DC voltage E _d is _{3E d / 4~-3E d /} 4 , and the AC of the AC input voltage and the multi-level converter when the rectified in by entering the AC voltage rectifier There is a problem that the output voltage is not 1: 1 and voltage adjustment is required. SUMMARY OF THE INVENTION The present invention solves the above-mentioned problems, and an object of the present invention is to adjust the voltage between input and output to 1: 1 in a system that can cope with a high voltage with a small number of elements and that inputs and outputs an alternating voltage. An object of the present invention is to provide a multi-level power converter that does not require a separate circuit.

  The multilevel power converter according to claim 1 for solving the above-mentioned problem is a multilevel power converter that outputs an AC voltage obtained by converting a DC voltage into a plurality of voltage levels, and includes first to fourth switching. A first switching element series circuit in which elements are sequentially connected in series, and a first switching element in series connected between a first switching element side end and a fourth switching element side end of the first switching element series circuit. And a second capacitor, a first common connection point between the first switching element and the second switching element, and a second common connection point between the third switching element and the fourth switching element. And a fifth switching element having one end connected to a common connection point of the first capacitor and the first switching element. A sixth switching element having one end connected to a common connection point of the second capacitor and the fourth switching element; a positive end connected to the other end of the fifth switching element; and a negative end connected to the sixth switching element. The DC voltage source connected to the other end of the switching element, the third and fourth capacitors connected in series between the positive and negative terminals of the DC voltage source, and the seventh and eighth switching elements are connected in series. And a second switching element series circuit whose common connection point is connected to the common connection point of the first and second capacitors and the common connection point of the first and second diodes, and the ninth and tenth circuits A third switching element series circuit in which the common connection point is connected to the common connection point of the third and fourth capacitors; A fifth capacitor connected between a common connection point where the first and ninth switching elements are commonly connected and a common connection point where the eighth and tenth switching elements are commonly connected; and the first to tenth switching points Control means for outputting a plurality of voltage levels by controlling on and off of the element, a common connection point of the second and third switching elements, and a common connection point of the third and fourth capacitors Is an AC output terminal having a plurality of voltage levels.

  A multilevel power converter according to claim 2 is the multilevel power converter according to claim 1, wherein the first to third switching element series circuits, the first and second diodes, the first, second, and fifth A multi-level voltage conversion unit is configured with a capacitor, the multi-level voltage conversion unit is provided in each phase of the three-phase AC, and the ninth and tenth switching elements of the multi-phase voltage conversion unit of the three-phase each phase A common connection point is defined as a neutral point, and the common connection point of the second and third switching elements is used as an output terminal of each of the U phase, V phase, and W phase.

  According to the above configuration, the fifth switching element, the first to fourth switching elements, and the sixth switching element exist in series between the positive and negative terminals of the DC voltage source. It becomes easy to increase the voltage to the total withstand voltage. As a result, a multi-level power converter that can cope with a high voltage with a small number of elements and can make the AC input / output voltage 1: 1 without providing a separate voltage adjusting circuit is realized.

(1) According to the invention described in claim 1, multilevel power conversion that can cope with a high voltage with a small number of elements and that can provide an AC input / output voltage of 1: 1 without providing a separate voltage adjustment circuit. Can be provided.
(2) According to the invention described in claim 2, a three-phase multi-function which can cope with a high voltage with a small number of elements and can make the AC input / output voltage 1: 1 without separately providing a voltage adjusting circuit. A level power converter can be provided.

1 is a circuit diagram of a 9-level power converter according to a first embodiment of the present invention. The voltage characteristic view showing the relationship between the mode of the switching pattern in the 9 level power converter of Example 1 of this invention, and the voltage between output terminals. The circuit diagram of the 9 level power converter of Example 2 of this invention. The circuit diagram which shows an example of the conventional multilevel power converter. OFF states of the switches in FIG. 4, the output voltage, the load current polarity, diagram showing the relationship between charging and discharging of the capacitor C _3. FIG. 5 is a waveform diagram of the output voltage V _UM in FIG. 4.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings, but the present invention is not limited to the following embodiments. Examples 1 and 2 shown below are examples in which the present invention is applied to a 9-level power converter (9-level inverter).

  FIG. 1 shows a nine-level power converter 100 according to the first embodiment of the present invention. In FIG. 1, S1 to S4 are first to fourth switching elements sequentially connected in series, and constitute a first switching element series circuit of the present invention.

  Capacitors C1 and C2 are connected in series between both ends of the first switching element series circuit. Diodes D1, D2 are connected in series between the common connection point of the switching elements S1, S2 and the common connection point of S3, S4.

V _DC is a DC power source, and C3 and C4 are capacitors to which the voltage of the DC power source V _DC is charged or discharged.

Switching elements S5 and S6 are connected in series between the positive terminal P of the DC power source V _DC and the common connection point of the capacitor C1 and the switching element S1, and the common connection point of the capacitor C2 and the switching element S4 and the DC power source V are connected. Switching elements S7 and S8 are connected in series with the negative electrode terminal N of _DC .

  The switching elements S5 and S6 constitute a fifth switching element of the present invention, and the switching elements S7 and S8 constitute a sixth switching element of the present invention. In consideration of the withstand voltage, each of the fifth switching element and the sixth switching element may be composed of one switching element.

  S11 and S12 are the seventh and eighth switching elements of the present invention, and these switching elements S11 and S12 are connected in series to form the second switching element series circuit of the present invention.

  S9 and S10 are the ninth and tenth switching elements of the present invention, and these switching elements S9 and S10 are connected in series to form a third switching element series circuit of the present invention.

  A capacitor C5 is connected between the common connection point of the switching elements S9 and S11 and the common connection point of the switching elements S10 and S12.

  The common connection point of the switching elements S9 and S10 is connected to the common connection point (middle point NP) of the capacitors C3 and C4, the common connection point of the switching elements S11 and S12, the common connection point of the capacitors C1 and C2, Common connection points of the diodes D1 and D2 are connected in common.

  The common connection point of the switching elements S2 and S3 is an output terminal A, and the common connection point of the capacitors C3 and C4 is an output terminal B.

  A multilevel voltage conversion unit 200 is configured by the switching elements S1 to S12, the capacitors C1, C2, and C5 and the diodes D1 and D2 that are surrounded by a broken line in FIG.

  The switching elements S1 to S12 are constituted by semiconductor switches such as IGBTs, for example. The switching elements S1 to S12 are on / off controlled by a control unit (control means) (not shown) in accordance with a switching pattern for outputting a 9 level voltage. As a result, a 9 level voltage is applied between the output terminals A and B Is output.

The power source voltage of the DC power source V _DC may be fixed or variable.

  In the above configuration, on / off of the switching elements S1 to S12 is controlled, for example, according to a switching pattern having modes 1 to 13 shown in Table 1.

Table 1 shows the voltage V _AB output between the output terminals A and B and the capacitors C1 and C2 according to the ON / OFF modes 1 to 13 of the switching elements S1 to S12 (shown as Modes 1 to 13 in Table 1). , C5 indicates the presence or absence of charge / discharge.

If the voltage of the DC power supply V _DC is 4E, the voltages of the capacitors C3 and C4 are 2E, the voltages of the capacitors C1 and C2 are E, and the voltage of the capacitor C5 is E / 2, the voltage between the output terminals A and B is 2E. , 3E / 2, E, E / 2, 0, -E / 2, -E, -3E / 2, and -2E can be output.

  Next, the path of the current I between each mode 1 to mode 13 of the switching pattern in Table 1 and the output terminals A and B will be described below. Table 1 shows the case where the current I> 0.

<Mode 1>
There are two modes 1 when the switching element S10 or S11 is turned on and when it is turned off. In both cases, the path of the current I is the same.

  That is, switching elements S3, S4, S7 to S9, S12 are each off, switching elements S1, S2, S5, S6 are each on, switching element S10 is off or on, switching element S11 is on or off, and current I is , The output terminal B, NP, C3, P, S5, S6, S1, S2, and the output terminal A. In mode 1, the capacitors C1, C2 and C5 are not charged / discharged, and the voltage between the output terminals A and B is + 2E.

<Mode 2>
Switching elements S3 to S9 and S12 are turned off, switching elements S1, S2, S10 and S11 are turned on, and current I is output terminal B → NP → S10 → C5 → S11 → C1 → S1 → S2 → output terminal A. It flows in the route. In this mode 2, the capacitors C5 and C1 are discharged, and the voltage between the output terminals A and B becomes + 3E / 2.

<Mode 3>
In this mode 3, there are two ways of switching on the switching elements S9 and S11 and turning off S10 and S12, and turning off the switching elements S9 and S11 and turning on S10 and S12, and the current paths are different. To do.

  That is, when switching elements S3 to S8, S10, and S12 are turned off and switching elements S1, S2, S9, and S11 are turned on, current I is output terminal B → NP → S9 → S11 → C1 → S1 → S2. → Flows along the path of output terminal A.

  When switching elements S3 to S9 and S11 are turned off and switching elements S1, S2, S10 and S12 are turned on, current I is output from output terminal B → NP → S10 → S12 → C1 → S1 → S2 → output. It flows through the route of terminal A.

  In mode 3, the capacitor C1 is discharged, and the voltage between the output terminals A and B becomes + E.

<Mode 4>
There are two modes 4 when the switching element S10 or S11 is turned on and when the switching element S10 is turned off. In either case, the path of the current I is the same.

  That is, switching elements S1, S4, S7 to S9, and S12 are each off, switching elements S2, S3, S5, and S6 are each on, switching element S10 is off or on, switching element S11 is on or off, and current I is The output terminal B, NP, C3, P, S5, S6, C1, D1, S2, and the output terminal A flow. In this mode 4, the capacitor C1 is charged, and the voltage between the output terminals A and B becomes + E.

<Mode 5>
Switching elements S1, S4 to S9, S12 are turned off, switching elements S2, S3, S10, S11 are turned on, and current I is output terminal B → NP → S10 → C5 → S11 → D1 → S2 → output terminal A. It flows in the route. In this mode 5, the capacitor C5 is discharged, and the voltage between the output terminals A and B becomes + E / 2.

<Mode 6>
Switching elements S3 to S8, S10, and S11 are turned off, switching elements S1, S2, S9, and S12 are turned on, and current I is output from output terminal B → NP → S9 → C5 → S12 → C1 → S1 → S2 → output. It flows through the route of terminal A. In this mode 6, the capacitor C5 is charged, C1 is discharged, and the voltage between the output terminals A and B becomes + E / 2.

<Mode 7>
In this mode 7, there are two cases, when switching elements S9 and S11 are turned on and S10 and S12 are turned off, and when switching elements S9 and S11 are turned off and S10 and S12 are turned on, and current paths are different. To do.

  That is, when switching elements S1, S4 to S8, S10, and S12 are turned off and switching elements S2, S3, S9, and S11 are turned on, current I is output terminal B → NP → S9 → S11 → D1 → S2. → Flows along the path of output terminal A.

  When switching elements S1, S4 to S9, S11 are turned off and switching elements S2, S3, S10, S12 are turned on, current I is output from output terminal B → NP → S10 → S12 → D1 → S2 → output. It flows through the route of terminal A.

  In this mode 7, the capacitors C1, C2, and C5 are not charged / discharged, and the voltage between the output terminals A and B becomes zero.

<Mode 8>
Switching elements S1, S2, S5 to S9, and S12 are turned off, switching elements S3, S4, S10, and S11 are turned on, and current I is output terminal B → NP → S10 → C5 → S11 → C2 → S4 → S3. → Flows along the path of output terminal A. In this mode 8, the capacitor C5 is discharged, the C2 is charged, and the voltage between the output terminals A and B becomes -E / 2.

<Mode 9>
Switching elements S1, S4 to S8, S10, and S11 are turned off, switching elements S2, S3, S9, and S12 are turned on, and current I is output from output terminal B → NP → S9 → C5 → S12 → D1 → S2 → output. It flows through the route of terminal A. In this mode 9, the capacitor C5 is charged, and the voltage between the output terminals A and B becomes -E / 2.

<Mode 10>
There are two modes 10 when the switching element S9 or S12 is turned on and when it is turned off. In either case, the path of the current I is the same.

  That is, switching elements S1, S4 to S6, S10, S11 are each off, switching elements S2, S3, S7, S8 are each on, switching element S9 is on or off, switching element S12 is off or on, and current I is The output terminal B, NP, C4, S8, S7, C2, D1, S2, and the output terminal A flow. In this mode 10, the capacitor C2 is discharged, and the voltage between the output terminals A and B becomes -E.

<Mode 11>
In this mode 11, there are two ways of switching on the switching elements S10 and S12 and turning off the S9 and S11, and turning off the switching elements S10 and S12 and turning on the S9 and S11, and the current paths are different. To do.

  That is, when the switching elements S1, S2, S4 to S9, and S11 are turned off and the switching elements S3, S4, S10, and S12 are turned on, the current I is output from the output terminals B → NP → S10 → S12 → C2 → S4. → S3 → Output terminal A

  When the switching elements S1, S2, S5 to S8, S10, and S12 are turned off and the switching elements S2, S3, S9, and S11 are turned on, the current I is output from the output terminals B → NP → S9 → S11 → C2. → S4 → S3 → Output terminal A

  In this mode 11, the capacitor C2 is charged and the voltage between the output terminals A and B becomes -E.

<Mode 12>
Switching elements S1, S2, S5 to S8, S10, and S11 are turned off, switching elements S3, S4, S9, and S12 are turned on, and current I is output terminal B → NP → S9 → C5 → S12 → C2 → S4. → S3 → Output terminal A In this mode 12, the capacitors C5 and C2 are charged, and the voltage between the output terminals A and B becomes -3E / 2.

<Mode 13>
There are two modes 13 when the switching element S9 or S12 is turned on and when it is turned off. In either case, the path of the current I is the same.

  That is, switching elements S1, S2, S5, S6, S10, and S11 are each off, switching elements S3, S4, S7, and S8 are each on, switching element S9 is on or off, and switching element S12 is off or on. I flows through the path of the output terminal B → NP → C4 → S8 → S7 → S4 → S3 → output terminal A. In this mode 13, the capacitors C1, C2 and C5 are not charged / discharged, and the voltage between the output terminals A and B is -2E.

By the on / off control by the switching patterns in the modes 1 to 13, the voltage of the DC power source V _DC is 4E, the voltages of the capacitors C3 and C4 are 2E, the voltages of the capacitors C1 and C2 are E, and the voltage of the capacitor C5 is E / 2. In this case, 9-level voltages of 2E, 3E / 2, E, E / 2, 0, -E / 2, -E, -3E / 2, and -2E are output between the output terminals A and B. Is possible.

FIG. 2 shows the relationship between the modes 1 to 13 and the voltage V _AB between the output terminals A and B, and shows 9 levels of voltages that can be output by the on / off control by the switching pattern.

As described above, according to the first embodiment, twelve switching elements (or one switching element S5 and S6 and one S7 and S8) provided between the positive and negative ends P and N of the DC power source V _DC are provided. The voltage conversion unit 200 of 9 levels can be realized with only two diodes and three capacitors.

Further, since eight switching elements (S5, S6, S1 to S4, S7, S8) exist in series between the positive and negative ends P, N of the DC power source V _DC , switching for these eight units is performed. It is easy to increase the voltage to the withstand voltage of the element. As a result, a nine-level inverter that can cope with a high voltage with a small number of elements is realized.

Furthermore, (peak value of the AC voltage output to the DC power source V _DC is 4E is ± 2E) DC power supply V _DC the same voltage range as it is possible to output the AC voltage to obtain a DC voltage obtained by rectifying an AC voltage In this system, the DC voltage is inversely converted into AC voltage, and the AC input / output voltage is 1: 1, so that no separate voltage adjusting circuit is required.

FIG. 3 shows a circuit configuration of the second embodiment. In the second embodiment, the multilevel voltage conversion unit 200 including the switching elements S1 to S12, the diodes D1 and D2, and the capacitors C1, C2, and C5 of the first embodiment (FIG. 1) is divided into three phases (200U, 200V, 200 W) and connected to the Y power connection to the DC power source V _DC .

  3, the same parts as those in FIG. 1 are denoted by the same reference numerals.

  The output terminals B of the multi-level voltage converters 200U, 200V, and 200W for each of the three phases are connected in common as a neutral point NP, and the output terminal A is used as the output terminals U, V, and W of the three-phase each phase.

In the configuration of FIG. 3, no separate DC power source is required for each of the three phases, and only one DC power source V _DC is sufficient.

  Each operation of the multilevel voltage converters 200U, 200V, and 200W in FIG. 3 is the same as that of the circuit in FIG.

  In the circuit of FIG. 3, with reference to the neutral point NP of the Y connection, any nine levels of voltages (2E, 3E / 2, E, E / 2, 0, −E / 2) are applied to the three phases U, V, and W. , -E, -3E / 2, -2E).

As described above, according to the second embodiment, three-phase nine-level voltage conversion is achieved by 36 switching elements, six diodes, and nine capacitors provided between the positive and negative terminals P and N of the DC power supply V _DC. Can be realized.

Further, since eight switching elements (S5, S6, S1 to S4, S7, S8) exist in series between the positive and negative ends P, N of the DC power source V _DC , switching for these eight units is performed. It is easy to increase the voltage to the withstand voltage of the element. Thus, a three-phase 9-level inverter that can cope with a high voltage with a small number of elements is realized.

Furthermore, (peak value of the AC voltage output to the DC power source V _DC is 4E is ± 2E) DC power supply V _DC the same voltage range as it is possible to output the AC voltage to obtain a DC voltage obtained by rectifying an AC voltage In this system, the DC voltage is inversely converted into AC voltage, and the AC input / output voltage is 1: 1, so that no separate voltage adjusting circuit is required.

100 ... 9 level power converter 200, 200U, 200V, 200W ... multi-level voltage converter S1-S12 ... switching element V _DC ... DC power source C1-C5 ... capacitor D1, D2 ... diode A, B ... output terminal

Claims (2)

A multi-level power converter that outputs an AC voltage obtained by converting a DC voltage into a plurality of voltage levels,
A first switching element series circuit in which the first to fourth switching elements are sequentially connected in series;
First and second capacitors sequentially connected in series between a first switching element side end and a fourth switching element side end of the first switching element series circuit;
First and second diodes sequentially connected in series between a common connection point of the first switching element and the second switching element and a common connection point of the third switching element and the fourth switching element ,
A fifth switching element having one end connected to a common connection point of the first capacitor and the first switching element;
A sixth switching element having one end connected to a common connection point of the second capacitor and the fourth switching element;
A DC voltage source having a positive end connected to the other end of the fifth switching element and a negative end connected to the other end of the sixth switching element;
A third and a fourth capacitor connected in series between the positive and negative terminals of the DC voltage source;
The seventh and eighth switching elements are connected in series, and the common connection point is connected to the common connection point of the first and second capacitors and the second connection point connected to the common connection point of the first and second diodes. A switching element series circuit;
A third switching element series circuit in which the ninth and tenth switching elements are connected in series and a common connection point thereof is connected to a common connection point of the third and fourth capacitors;
A fifth capacitor connected between a common connection point commonly connecting the seventh and ninth switching elements and a common connection point commonly connecting the eighth and tenth switching elements;
Control means for outputting a plurality of voltage levels by controlling on and off of the first to tenth switching elements;
A multi-level power converter characterized in that a common connection point of the second and third switching elements and a common connection point of the third and fourth capacitors are AC output terminals of a plurality of voltage levels. The first to third switching element series circuits, the first and second diodes, and the first, second, and fifth capacitors constitute a multilevel voltage conversion unit,
The multi-level voltage converter is provided for each phase of the three-phase alternating current,
The common connection point of the ninth and tenth switching elements of the multi-phase voltage converter for each of the three phases is connected as a neutral point, and the common connection point of the second and third switching elements is the U phase. The multi-level power converter according to claim 1, wherein each of the output terminals is a V-phase and a W-phase.

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