JP-7855380-B2 - Power converter

JP7855380B2JP 7855380 B2JP7855380 B2JP 7855380B2JP-7855380-B2

Inventors

真木康次
餅川宏

Assignees

株式会社東芝

Dates

Publication Date: 20260508
Application Date: 20220324

Claims (7)

The energy storage unit, An upper arm comprising a first upper arm circuit and a second upper arm circuit connected in series between the AC terminal and the positive DC terminal, A lower arm comprising a first lower arm circuit and a second lower arm circuit connected in series between the AC terminal and the negative DC terminal, A flying capacitor electrically connected to the upper arm between the first upper arm circuit and the second upper arm circuit, and electrically connected to the lower arm between the first lower arm circuit and the second lower arm circuit, Equipped with, Each of the first upper arm circuit and the second upper arm circuit is configured by connecting one or more first switch circuits having a first switching element in series, Each of the first lower arm circuit and the second lower arm circuit is configured by connecting one or more second switch circuits having a second switching element in series. At least one of the first switch circuits has a first capacitor connected in parallel with the first switching element, or at least one of the second switch circuits has a second capacitor connected in parallel with the second switching element. When at least one of the first switch circuits has a first capacitor connected in parallel with the first switching element, there is a first regenerative rectifier circuit that can connect a plurality of the first capacitors in parallel via one or more of the first switching elements, and can connect the first capacitor and the energy storage unit in parallel. When at least one of the second switch circuits has a second capacitor connected in parallel with the second switching element, the second regenerative rectifier circuit has the ability to connect a plurality of the second capacitors in parallel via one or more of the second switching elements, and to connect the second capacitor and the energy storage unit in parallel. Power converter.
The first regenerative rectifier circuit is a circuit that connects the low-potential side of the energy storage unit and the low-potential side of the first capacitor when at least one of the first switch circuits has a first diode whose cathode is connected to the low-potential side of the first switching element, and a first capacitor connected between the anode of the first diode and the high-potential side of the first switching element, The power conversion device according to claim 1, wherein the second regenerative rectifier circuit is a circuit that connects the high-potential side of the energy storage unit and the high-potential side of the second capacitor when at least one of the second switch circuits has a second diode whose anode is connected to the high-potential side of the second switching element and a second capacitor connected between the cathode of the second diode and the low-potential side of the second switching element.
The aforementioned energy storage unit is a floating capacitor, The power conversion device according to claim 1, wherein an upper switching element connected between the AC terminal and the high-potential side terminal and a lower switching element connected between the AC terminal and the low-potential side terminal are connected in parallel .
The first regenerative rectifier circuit is a circuit having one or more first regenerative rectifier diodes connected in series and a first resistor connected between the cathode of one of the first regenerative rectifier diodes and the low-potential side terminal of the first capacitor, or a circuit having multiple first regenerative rectifier diodes and multiple first resistors connected between the cathodes of each of the first regenerative rectifier diodes and the corresponding low-potential side terminal of the first capacitor, The power conversion device according to claim 1, wherein the second regenerative rectifier circuit is a circuit having one or more second regenerative rectifier diodes connected in series and a second resistor connected between the anode of one of the second regenerative rectifier diodes and the high-potential side of the second capacitor, or a circuit having a plurality of the second regenerative rectifier diodes and a plurality of second resistors connected between the anodes of each of the second regenerative rectifier diodes and the corresponding high-potential side of the second capacitor.
The capacitance of the first capacitor included in the first switch circuit connected to the lowest potential side of the first upper arm circuit and the second upper arm circuit is greater than the capacitance of the other first capacitors. The power conversion device according to claim 1, wherein the capacitance of the second capacitor included in the second switch circuit connected to the highest potential side of the first lower arm circuit and the second lower arm circuit is greater than the capacitance of the other second capacitors.
The energy storage unit comprises a first energy storage unit with one end electrically connected to the positive DC terminal, and a second energy storage unit with one end electrically connected to the negative DC terminal. The first regenerative rectifier circuit is electrically connected to the other end of the first energy storage unit, and when at least one of the first switch circuits has the first capacitor connected in parallel with the first switching element, it is possible to connect a plurality of the first capacitors in parallel via one or more of the first switching elements, and it is also possible to connect the first capacitor and the first energy storage unit in parallel. The power conversion device according to claim 1, wherein the second regenerative rectifier circuit is electrically connected to the other end of the second energy storage unit, and when at least one of the second switch circuits has the second capacitor connected in parallel with the second switching element , a plurality of the second capacitors can be connected in parallel via one or more of the second switching elements, and the second capacitor and the second energy storage unit can be connected in parallel.
The first switch circuit comprises the first switching element, a first diode whose anode is connected to the high-potential side of the first switching element, and the first capacitor connected between the cathode of the first diode and the low-potential side of the first switching element. The second switch circuit comprises the second switching element, a second diode whose cathode is connected to the low-potential side of the second switching element, and the second capacitor connected between the anode of the second diode and the high-potential side of the second switching element. The first regenerative rectifier circuit connects the high-potential end of the first capacitor to the other end of the first energy storage unit, with the direction from the low-potential side to the high-potential side being the forward direction. The power conversion device according to claim 6, wherein the second regenerative rectifier circuit connects the low-potential end of the second capacitor of the lower arm to the other end of the second energy storage unit, with the direction from the low-potential side to the high-potential side being the forward direction.

Description

Embodiments of the present invention relate to a power conversion device. In recent years, multilevel power converters capable of outputting multiple voltage levels have been proposed. These multilevel power converters offer the potential for miniaturization and higher efficiency compared to conventional two-level power converters. For example, a multilevel power converter equipped with a flying capacitor can, in principle, uniformly charge and discharge the flying capacitor, eliminating the need for additional circuits to balance the capacitor voltage. Furthermore, since the flying capacitor is charged and discharged at the PWM carrier frequency, increasing the PWM carrier frequency reduces the voltage pulsation of the flying capacitor, making it possible to reduce the capacitance of the flying capacitor and miniaturize the device. Japanese Patent Publication No. 2020-108326 Figure 1 is a schematic diagram showing one example configuration of a power conversion device according to the first embodiment.Figure 2 is a diagram illustrating an example of the operation of the power converter according to the first embodiment.Figure 3 is a schematic diagram showing one example configuration of the power conversion device according to the second embodiment.Figure 4 is a schematic diagram showing one example configuration of the power conversion device according to the third embodiment.Figure 5 is a schematic diagram showing one example configuration of the power conversion device according to the fourth embodiment.Figure 6 is a diagram illustrating an example of the operation of the power converter according to the fourth embodiment. Several embodiments of power conversion devices will be described in detail below with reference to the drawings. Figure 1 is a schematic diagram showing one example configuration of a power conversion device according to the first embodiment. The power converter of this embodiment is, for example, a three-level flying capacitor type power converter capable of mutually converting DC power and single-phase AC power, and comprises a control circuit CTR, an inverter cell 100, an upper arm, a lower arm, n+a (where n and a are positive integers) first regenerative rectifier circuits (regenerative rectifier diodes 6UN, 6UA and first resistors 5UN, 5UA), m+b (where m and b are positive integers) second regenerative rectifier circuits (regenerative rectifier diodes 6XM, 6XB and second resistors 5XM, 5XB), a flying capacitor CF, a positive DC terminal 209, a negative DC terminal 210, and an AC terminal 211. In the embodiments described below, N, A, M, and B are N=1 to n, A=1 to a, M=1 to m, and B=1 to b (where n, a, m, and b are 2 or greater), and the same applies hereafter unless otherwise specified. Furthermore, the first resistors 5UN and 5UA and the second resistors 5XM and 5XB may also be inductance elements. The control circuit CTR controls the operation of the inverter cell 100, the upper arm, and the lower arm based on a control signal from, for example, a higher-level control device of the power converter. The upper arm of the power converter in this embodiment comprises a first upper arm circuit SA and a second upper arm circuit SN. The first upper arm circuit SA includes a number of switch circuits (voltage-type clamp-type switch circuits) 101A. The second upper arm circuit SN includes n number of switch circuits (voltage-type clamp-type switch circuits) 101N. The lower arm of the power converter in this embodiment comprises a first lower arm circuit SB and a second lower arm circuit SM. The first lower arm circuit SB includes b switch circuits (voltage-type clamp switch circuits) 102B. The second lower arm circuit SM includes m switch circuits (voltage-type clamp switch circuits) 102M. In this embodiment, a DC capacitor (not shown) is electrically connected between the positive DC terminal 209 and the negative DC terminal 210 of the power converter. The DC capacitor may be included within the power converter or mounted externally. The inverter cell 100 comprises a switching element (upper switching element) 1U, a switching element (lower switching element) 1X, a power storage unit 2, a positive cell terminal (high potential side end) 200, a negative cell terminal (low potential side end) 201, and a cell AC terminal (AC end) 202. Note that the positive cell terminal 200, the negative cell terminal 201, and the cell AC terminal 202 only need to be configured to allow electrical connection of the circuit at their respective positions; the terminals may be omitted. Switching elements 1U and 1X are, for example, MOSFETs (metal-oxide semiconductor field-effect transistors). The drain (high-potential side) of switching element 1U is electrically connected to the positive cell terminal 200, and its source (low-potential side) is electrically connected to the drain (high-potential side) of switching element 1X. The source (low-potential side) of switching element 1X is electrically connecte