JP6337659B2 - 5-level power converter - Google Patents

Description

  The present invention relates to a five-level power converter that performs five-level conversion from DC voltage to AC voltage or five-level conversion from AC voltage to DC voltage.

  Patent Document 1 is disclosed as a five-level power conversion device that selects and arbitrarily converts five voltage levels. The five-level power conversion device of Patent Document 1 includes two DC power supplies, eight semiconductor switching elements, and two capacitors C1, C2 as a conversion circuit for one phase. The maximum number of semiconductor switching elements to be conducted is four among the switching patterns for converting the voltage into five levels. Further, the 5-level power converter of Patent Document 1 maintains the capacitor voltage VC1 = VC2 = + 1E of the capacitors C1 and C2 due to the symmetry of operation.

JP 2012-253981 A

  However, the 5-level power conversion device of Patent Document 1 does not have a switching pattern for arbitrarily charging and discharging the capacitors C1 and C2. Therefore, the capacitor voltage VC1 is caused by variations in circuit characteristics due to variations in semiconductor switching element characteristics, aging, etc. = VC2 = + 1E is not established, and there is a possibility that the five-level phase voltage at a uniform voltage level cannot be output.

  As described above, in the five-level power converter, it is a problem to make the average value of the capacitor voltage of each phase equal without using a voltage uniform circuit.

  The present invention has been devised in view of the above-described conventional problems, and one aspect thereof is a five-level conversion that performs a five-level conversion from a DC voltage to an AC voltage or a five-level conversion from an AC voltage to a DC voltage. A power converter, which is connected in series between the positive and negative terminals of a DC power source, divides a DC voltage between both terminals by half, and a plurality of DC capacitors having the voltage dividing point as a first neutral point; A first semiconductor switching element having one end connected to the positive electrode end of the DC power supply, a second semiconductor switching element having one end connected to the negative electrode end of the DC power supply, the other end of the first semiconductor switching element, and the second semiconductor switching element Are connected in series between the other ends of the two capacitors, the voltage between the other ends is divided by half, a plurality of capacitors having the voltage dividing point as the second neutral point, and the first neutral point and the second neutral point. A bidirectional switch interposed between the point and the first semiconductor Third and fourth semiconductor switching elements sequentially connected in series between the other end of the switching element and the second neutral point, a common connection point of the third and fourth semiconductor switching elements, and a second semiconductor switching element And fifth and sixth semiconductor switching elements having the common connection point as an output terminal.

  According to the present invention, in the five-level power converter, it is possible to equalize the average value of the capacitor voltage of each phase without using a voltage uniform circuit.

FIG. 3 is a circuit configuration diagram of the five-level power conversion device according to the first embodiment. The circuit block diagram of the 5 level power converter device in Embodiment 2. FIG. The block diagram which shows the control method of the 5 level power converter device in Embodiment 2. FIG.

  Hereinafter, Embodiments 1 and 2 of a five-level power converter according to the present invention will be described with reference to FIGS.

[Embodiment 1]
FIG. 1 is a circuit configuration diagram of a five-level power converter according to the first embodiment. As shown in FIG. 1, DC capacitors Ca and Cb are connected in series between the positive and negative terminals PN of the DC power supply. The DC capacitors Ca and Cb divide the DC voltage between the positive and negative terminals PN by half.

  This partial pressure point is defined as a first neutral point NP. Here, in the first embodiment, the DC voltage between the positive and negative electrode terminals PN is divided into two by the two DC capacitors Ca and Cb. However, the voltage is divided into two by two or more DC capacitors. Also good.

  One end of the first semiconductor switching element S1 is connected to the positive terminal P of the DC power source, and one end of the second semiconductor switching element S2 is connected to the negative terminal N of the DC voltage source. Capacitors Cc and Cd are provided between the other end of the first semiconductor switching element S1 and the other end of the second semiconductor switching element S2 to divide the voltage between the other ends by half. This partial pressure point is defined as a second neutral point NP ′.

  The third and fourth semiconductor switching elements S3 and S4 are sequentially connected in series between the other end of the first semiconductor switching element S1 and the second neutral point NP ′. The fifth and sixth semiconductor switching elements S5 and S6 are sequentially connected in series between the common connection point of the third and fourth semiconductor switching elements S3 and S4 and the other end of the second switching element. Here, the common connection point of the fifth and sixth semiconductor switching elements S5 and S6 is defined as an output terminal OUT.

  Further, a bidirectional switch is provided between the first neutral point NP and the second neutral point NP ′. In Embodiment 1, a bidirectional switch is configured by connecting the semiconductor switching elements S7 and S8 in the reverse direction.

  The DC capacitors Ca and Cb are charged with a voltage of 2E, and the capacitors Cc and Cd are charged with a voltage of E.

  The broken line part shown in FIG. 1 shows the conversion circuit 1 for one phase, and inputs the positive terminal P, the negative terminal N, and the divided first neutral point NP of one DC power source, and the semiconductor switching elements S1 to S8. Eight capacitors and two capacitors Cc and Cd are used.

  Table 1 shows the switching pattern of the semiconductor switching elements S1 to S8 in each mode, the phase voltage between the first neutral point NP and the output terminal OUT, and the capacitor Cc when the current I output to the output terminal OUT is positive. The charge / discharge state of Cd is shown.

  The path of the current I between the first neutral point NP and the output terminal OUT in each Mode is as follows.

<Mode 1>
First neutral point NP → Ca → P → S1 → S3 → S5 → output terminal OUT
At this time, the phase voltage between the first neutral point NP and the output terminal OUT is + 2E. The current I conducts the three semiconductor switching elements S1, S3 and S5.

<Mode2>
First neutral point NP → Ca → P → S1 → Cc → S4 → S5 → output terminal OUT
At this time, the phase voltage between the neutral point NP and the output terminal OUT is + E. When the current I is positive, the capacitor Cc is charged. The current I conducts the three semiconductor switching elements S1, S4 and S5.

<Mode3>
First neutral point NP → S8 → S7 → Cc → S3 → S5 → output terminal OUT
At this time, the phase voltage between the first neutral point NP and the output terminal OUT is + E. When the current I is positive, the capacitor Cc is discharged. The current I conducts the four semiconductor switching elements S8, S7, S3 and S5.

<Mode 4>
First neutral point NP → S8 → S7 → S4 → S5 → output terminal OUT
At this time, the phase voltage between the first neutral point NP and the output terminal OUT becomes zero. Further, the current I conducts the four semiconductor switching elements S8, S7, S4, and S5.

<Mode5>
First neutral point NP → S8 → S7 → Cd → S6 → output terminal OUT
At this time, the phase voltage between the first neutral point NP and the output terminal OUT is −E. When the current I is positive, the capacitor Cd is charged. Further, the current I conducts the three semiconductor switching elements S8, S7, and S6.

<Mode 6>
First neutral point NP → Cb → N → S2 → Cd → S4 → S5 → output terminal OUT
At this time, the phase voltage between the first neutral point NP and the output terminal OUT is −E. When the current I is positive, the capacitor Cd is discharged. The current I conducts the three semiconductor switching elements S2, S4, S5.

<Mode 7>
First neutral point NP → Cb → N → S2 → S6 → output terminal OUT
At this time, the phase voltage between the first neutral point NP and the output terminal OUT is −2E. Further, the current I conducts the two semiconductor switching elements S2 and S6.

  As described above, five levels of phase voltages 2E, E, 0, −E, and −2E can be output by the seven modes in the switching pattern of Table 1. In particular, the Mode that outputs the phase voltage as 0 is only one of Mode 4, and the control can be simplified.

  Further, although the output voltage between the first neutral point NP and the output terminal OUT in Mode 2 and Mode 3 is both + E, the voltage of the capacitor Cc can be adjusted because the capacitor Cc can be charged or discharged. It is.

  Similarly, the output voltage between the first neutral point NP and the output terminal OUT in Mode 5 and Mode 6 is both -E, but the capacitor Cd can be charged or discharged, so the voltage of the capacitor Cd is adjusted. Is possible.

  As described above, since the switching patterns Mode2, Mode3, Mode5, and Mode6 that can charge and discharge the capacitors Cc and Cd are provided, even if the characteristics of the elements constituting the circuit vary or changes over time, the capacitors Cc and Cd The voltage can be arbitrarily controlled, and it is possible to output a five-level phase voltage at a uniform voltage level.

  In addition, since the voltage uniform circuit is not used, it is possible to reduce the size and cost of the apparatus.

  Furthermore, the current I does not always conduct to the four semiconductor switching elements, but the number of semiconductor switching elements through which the current I conducts is two, three, or four due to Mode. It becomes possible to reduce.

  In Patent Document 1, a five-level power conversion device is configured by two DC power supplies, eight semiconductor switching elements, and two capacitors. However, in the first embodiment, one DC power supply and semiconductor switching element 8 are used. In addition, a five-level power conversion device can be realized with a small number of two capacitors. Furthermore, by realizing a five-level power conversion device with a small number of elements, it is possible to reduce the size and cost of the device.

[Embodiment 2]
FIG. 2 is a circuit configuration diagram of the multilevel power conversion device according to the second embodiment. As shown in FIG. 2, the multilevel power conversion device according to the second embodiment is provided with the conversion circuit 1 for one phase of the first embodiment over three phases (U phase, V phase, and W phase). Thereby, in the second embodiment, five-level phase voltages 2E, E, 0, -E, and -2E can be output to the three phases of the U phase, the V phase, and the W phase.

  An example of a control method will be described based on a block diagram illustrating a control method of the five-level power conversion device according to the second embodiment in FIG.

As shown in FIG. 3, the control unit 2 includes three-phase voltage command values V _U ^* , V _V ^* , and V _W ^*, and capacitor voltages V _CcU1 , V _CcV1 , and V _CcW1 of capacitors Cc of each phase, Capacitor voltages V _CdU2 , V _CdV2 and V _CdW2 of the capacitor Cd of each phase are input.

Further, the table 3, the deviation between the command value V _DC / 2 and the capacitor voltage V _CcU1, V _CcV1, V _CcW1 the capacitor voltage instruction value V _DC / 2 and the capacitor voltage V of the capacitor voltage _CdU2, V _CdV2, V The deviation of _CdW2 and the three-phase voltage command values V _U ^* , V _V ^* , and V _W ^* are input. In this table 3, the three-phase voltage command values V _U ^* , V _V ^* , V _W ^* , the deviation between the capacitor voltage command value V _DC / 2 and the capacitor voltages V _CcU1 , V _CcV1 , V _CcW1 , capacitor A switching pattern corresponding to the deviation between the voltage command value V _DC / 2 and the capacitor voltages V _CdU2 , V _CdV2 , and V _CdW2 is set. Based on these input values, the switching pattern shown in Table 1 is determined, and the semiconductor The gate command of switching element S1-S8 is output.

  According to the five-level power conversion device of the second embodiment, a three-phase five-level power conversion device can be realized with a small number of elements including one DC power source, 24 semiconductor switching elements, and 6 capacitors.

  In addition, the same effects as those of the first embodiment are obtained.

  Although the present invention has been described in detail only for the specific examples described above, it is obvious to those skilled in the art that various changes and modifications are possible within the scope of the technical idea of the present invention. Such variations and modifications are naturally within the scope of the claims.

P ... Positive terminal of DC power supply N ... Negative terminal of DC power supply Ca, Cb ... DC capacitor Cc, Cd ... Capacitor S1-S8 ... Semiconductor switching element

Claims (1)

A five-level power conversion device that performs five-level conversion from DC voltage to AC voltage, or five-level conversion from AC voltage to DC voltage,
A plurality of DC capacitors connected in series between the positive and negative terminals of the DC power source, dividing the DC voltage between the two terminals in half, and using this voltage dividing point as a first neutral point;
A first semiconductor switching element having one end connected to a positive electrode end of a DC power supply;
A second semiconductor switching element having one end connected to the negative electrode end of the DC power supply;
A plurality of terminals are connected in series between the other end of the first semiconductor switching element and the other end of the second semiconductor switching element, the voltage between the other ends is divided in half, and the divided point is set as a second neutral point. With a capacitor of
A bidirectional switch interposed between the first neutral point and the second neutral point;
Third and fourth semiconductor switching elements sequentially connected in series between the other end of the first semiconductor switching element and the second neutral point;
A common connection point of the third and fourth semiconductor switching elements, and fifth and sixth semiconductor switching elements connected in series between the other ends of the second semiconductor switching element and having the common connection point as an output terminal. A five-level power converter characterized by the above.

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