US-12627213-B2 - Switching-loss balancing circuit for power conversion device

US12627213B2US 12627213 B2US12627213 B2US 12627213B2US-12627213-B2

Abstract

A balancing circuit according to an embodiment of the present invention comprises: a second resistor connected to the same node as that of a first resistor of a voltage sensing unit connected to a first terminal of an output end of a power conversion device; and a fourth resistor connected to the same node as that of a third resistor of the voltage sensing unit connected to a second terminal of the output end of the power conversion device, wherein the second resistor and the fourth resistor are connected to an upper switch of the power conversion device.

Inventors

Dong Keun YOON
Sung Jae KONG
Sang Gyu Choi

Assignees

LG INNOTEK CO., LTD.

Dates

Publication Date: 20260512
Application Date: 20220704
Priority Date: 20210702

Claims (14)

1 . A balancing circuit, comprising: a second resistor, one end of which is connected to a same node as that of a first resistor of a voltage sensing unit; and a fourth resistor, one end of which is connected to a same node as that of a third resistor of the voltage sensing unit, wherein the first resistor is connected to a first terminal of an output end of a power conversion device, wherein the third resistor is connected to a second terminal of the output end of the power conversion device, wherein the power conversion device comprises: a first upper switch and a first lower switch connected in series with one end of the first upper switch; a second upper switch and a second lower switch connected in series with one end of the second upper switch; a first switch and a second switch connected in series between a first node between the first upper switch and the second lower switch, and a second node between said second upper switch and the second lower switch; and a diode connected between a third node connecting the other end of the first upper switch and the other end of the second upper switch, and a fourth node between the first switch and the second switch, wherein the first terminal of the output end of the power conversion device is a terminal connected to the second node, wherein the second terminal of the output end of the power conversion device is a terminal connected to the first node, wherein the other end of the second resistor and the other end of the fourth resistor are connected to the third node of the power conversion device, and wherein the voltage sensing unit is connected to a same ground as the power conversion device.
2 . The balancing circuit of claim 1 , wherein a difference between a sum of switching losses of the first upper switch and the second upper switch and a sum of switching losses of the first lower switch and the second lower switch is within a preset range.
3 . The balancing circuit of claim 1 , wherein the power conversion device is an inverter configured to operate at a multi-level according to operation of the first upper switch, the second upper switch, the first lower switch and the second lower switch.
4 . The balancing circuit of claim 3 , wherein the power conversion device operates at one of a first level, a second level, and a third level.
5 . The balancing circuit of claim 3 , wherein the first level, the second level, and the third level are +Vdc, 0V, and −Vdc respectively.
6 . The balancing circuit of claim 1 , wherein a difference between a value of the first resistor and a value of the second resistor is set within a preset range, and wherein a difference between a value of the third resistor and a value of the fourth resistor is set within a preset range.
7 . The balancing circuit of claim 1 , wherein a value of the first resistor is same as a value of the second resistor, and wherein a value of the third resistor is same as a value of the fourth resistor.
8 . The balancing circuit of claim 1 , wherein the power conversion device is bidirectional inverter which supplies power to grid through a filter or receives power from grid.
9 . A power conversion device, comprising: a switching unit comprising an upper switch and a lower switch; an output unit configured to output a multi-level voltage according to operation of the switching unit; a voltage sensing unit configured to sense output voltage by connecting a first terminal and a second terminal of the output unit through a first resistor and a third resistor respectively; a second resistor, one end of which is connected to one end of the first resistor; and a fourth resistor, one end of which is connected to one end of the third resistor, wherein the switching unit comprises: a first upper switch and a first lower switch connected in series with the first upper switch; a second upper switch and a second lower switch connected in series with the second upper switch; a first switch and a second switch connected in series between a first node between the first upper switch and the second lower switch, and a second node between the second upper switch and the second lower switch; and a diode connected between a third node connecting the other end of the first upper switch and the other end of the second upper switch, and a fourth node between the first switch and the second switch, wherein the first terminal of the output end of the power conversion device is a terminal connected to the second node, wherein the second terminal of the output end of the power conversion device is a terminal connected to the first node, wherein the other end of the second resistor and the other end of the fourth resistor are connected to the third node of the power conversion device, and wherein the voltage sensing unit is connected to a same ground as the lower switch.
10 . The power conversion device of claim 9 , wherein the power conversion device operates at one of a first level, a second level, and a third level.
11 . The power conversion device of claim 10 , wherein the first level, the second level, and the third level are +Vdc, 0V, and −Vdc respectively.
12 . The power conversion device of claim 9 , wherein a difference between a value of the first resistor and a value of the second resistor is set within a preset range, and wherein a difference between a value of the third resistor and a value of the fourth resistor is set within a preset range.
13 . The power conversion device of claim 9 , wherein a value of the first resistor is same as a value of the second resistor, and wherein a value of the third resistor is same as a value of the fourth resistor.
14 . The power conversion device of claim 9 , wherein the power conversion device is bidirectional inverter which supplies power to grid through a filter or receives power from grid.

Description

CROSS-REFERENCE TO RELATED PATENT APPLICATIONS This application is a U.S. National Stage Application under 35 U.S.C. § 371 of PCT Application No. PCT/KR2022/009626, filed Jul. 4, 2022, which claims priority to Korean Patent Application No. 10-2021-0087296, filed Jul. 2, 2021, whose entire disclosures are hereby incorporated by reference. TECHNICAL FIELD The teachings in accordance with exemplary and non-limiting embodiments of this invention relate generally to a balancing circuit and a power conversion device, and more particularly to a balancing circuit that balances a switching loss of a multilevel inverter and a power conversion device. BACKGROUND ART Photovoltaic power generation is an eco-friendly energy generation method that has been widely used to replace conventional chemical and nuclear power generation. Photovoltaic power generation includes a stand-alone power generation connected to a converter by a battery and a connected type connected to a grid system, and in general, the stand-alone generation consists of solar cells, storage batteries, and power conversion devices, while grid-connected systems are connected to commercial power sources so that power can be exchanged with the load grid. The power generated by solar photovoltaics (PV) is transmitted to the power system, the grid, through an inverter. As shown in FIG. 1, the inverter converts the power to match the voltage of the power outputted from the solar panel with the voltage of the grid, and it is transmitted to the grid through a filter. At this time, when the inverter is in free-wheeling switching mode, the (−) node of the DC-LINK is floating relative to the grid power, so the difference in impedance between the upper and lower sides determines the VDS voltage of each switch (S1, S2, S3, S4). As the lower impedance is reduced by the differential amplifier added for sensing the AC voltage at the output end, the VDS voltage of the switches (S1, S3) becomes DC-LINK voltage, and because the VDS voltage of the switches (S2, S4) is reduced to 0V level, the switching loss is concentrated on S1 and S3 due to the large VDS voltage of S1 and S3, and the upper switches generate more heat, so there is a problem that the use temperature condition is limited under the same switching loss condition. DETAILED DESCRIPTION OF INVENTION Technical Subject The technical problem that the present invention seeks to solve is to provide a balancing circuit that balances the switching losses of a multilevel inverter and a power conversion device. Technical Solution In one general aspect of the present invention, there may be provided a balancing circuit, comprising: a second resistor connected to the same node as that of a first resistor of a voltage sensing unit connected to a first terminal of an output end of a power conversion device; anda fourth resistor connected to the same node as that of a third resistor of the voltage sensing unit connected to a second terminal of the output end of the power conversion device, whereinthe second resistor and the fourth resistor are connected to an upper switch of the power conversion device. Preferably, but not necessarily, the power conversion device may include a plurality of upper switches and a plurality of lower switches. Preferably, but not necessarily, the power conversion device may be an inverter that operates at a multilevel based on the operation of the plurality of upper switches and the plurality of lower switches. Preferably, but not necessarily, said power conversion device may include: a first upper switch and a first lower switch connected in series with said first upper switch; a second upper switch and a second lower switch connected in series with said second upper switch; a first switch and a second switch connected in series between a first node between said first upper switch and said second lower switch and a second node between said second upper switch and said second lower switch; and a diode connected between a first node connecting said first upper switch and said second upper switch and a third node between said first switch and said second switch. Preferably, but not necessarily, the node to which said second resistor is connected may be a (+) terminal of said power conversion device, and the node to which said fourth resistor is connected may be a (−) terminal of said power conversion device. Preferably, but not necessarily, said voltage sensing unit may be connected to the same ground as said power conversion device. In another general aspect of the present invention, there may be provided a power conversion device, comprising: a switching unit including an upper switch and a lower switch; an output unit that outputs a multi-level voltage according to the operation of the switching unit; a voltage sensing unit that senses the output voltage by connecting both ends of the output part through a first resistor and a third resistor, respectively; and a balancing unit including a second re