JP7234596B2 - power converter - Google Patents

Description

TECHNICAL FIELD The present invention relates to a power conversion device, and more particularly to a power conversion device including a power supply device for a gate drive circuit in a modular multi-level converter circuit in which inverter cells are connected in multiple stages.

In recent years, power converters have been used in many technical fields. A modular multilevel converter (MMC) is one of the circuit configurations that are used especially in the field of handling high voltage.
FIG. 1 shows an example of the circuit configuration of the MMC. Power converter 101 includes U-phase arm portion 102 , V-phase arm portion 103 , W-phase arm portion 104 and reactor 105 .
Each of U-phase arm portion 102, V-phase arm portion 103 and W-phase arm portion 104 includes a plurality of inverter cells 102a, 102b, 102c, 103a, 103b, 103c, 104a, 104b and 104c.

Each phase arm portion is delta-connected via reactors 105a, 105b, and 105c, and is connected to the system. The interconnection to the system may be via a transformer (not shown). Although delta connection is shown as an example in FIG. 1, U-phase arm portion 102, V-phase arm portion 103, and W-phase arm portion 104 may be star-connected.

The inverter cells 102a, 102b, 102c, 103a, 103b, 103c, 104a, 104b, and 104c are unit converters, and a plurality of inverter cells are connected in series to form each phase arm. Each inverter cell includes a power conversion circuit including switching elements such as IGBTs (Insulated Gate Bipolar Transistors) and MOSFETs (Metal Oxide Semiconductor Field Effect Transistors), and a gate drive circuit for turning the switching elements on and off.

The power converter 101 can output a voltage higher than the withstand voltage of the switching element and a multi-level voltage waveform with less harmonics by having the inverter cells output voltage waveforms in different phases. Therefore, the power converter 101 is applied to a reactive power compensator or a high-voltage inverter that is directly connected to an extra-high voltage system.
Generally, a gate drive circuit section that drives switching elements is fed with power from a dedicated power supply through an isolation transformer. However, in the case of the switching elements in the inverter cells that make up the power conversion device 101, the maximum potential difference in the phase arm is about several kV to several hundreds of kV, and the isolation transformer needs to ensure a dielectric strength equal to or higher than this. There is As a result, the capacity of the insulating transformer increases, resulting in an increase in the size of the device.

On the other hand, Japanese Patent Application Laid-Open No. 2002-200001 proposes a circuit system in which power is supplied from a collector terminal of a switching element that constitutes a main circuit to a gate drive circuit section through a power supply resistor in a non-insulated manner.
In such a circuit system, by connecting the collector terminal of the switching element to the gate drive circuit unit via the power supply resistor, power can be supplied without using an isolation transformer.

Japanese Patent No. 5638194

However, in the circuit system of Patent Document 1, power is supplied from the collector terminal side on the high voltage side to the gate drive circuit unit through the power supply resistor, so there is a concern that the loss generated by the power supply resistor increases.
The present invention is a power conversion device equipped with a power supply device that supplies power to a gate drive circuit, in which a circuit method that does not use a power supply resistor without increasing the capacity of the isolation transformer and reduces the loss that occurs in the isolation transformer during power supply. Provided is a power conversion device with a possible feeder.

In order to solve the above problems, the present invention has the following technical features.

an inverter section including a plurality of switching elements, a first AC output terminal, and a second AC output terminal; a gate drive circuit section for driving the plurality of switching elements;
and a power supply circuit unit for supplying power to the gate drive circuit unit, wherein the power supply circuit unit includes any one of the first AC output terminals of the plurality of inverter cells and the plurality of and converting the AC power supplied from the second AC output terminal of any one of the inverter cells into DC power to supply the gate drive circuit unit with the AC power.

With the configuration as described above, it is possible to reduce the loss generated in the isolation transformer without increasing the capacity of the isolation transformer, without using a feed resistor.

1 is a schematic configuration of a power conversion device 101 for describing an embodiment of the present invention; It is a circuit configuration of an inverter cell and a power supply circuit section for describing the first embodiment of the present invention. It is a circuit configuration of an arm portion for one phase according to the first embodiment of the present invention. It is a circuit configuration of an inverter cell and a power supply circuit unit for describing a second embodiment of the present invention. It is a circuit configuration of an arm portion for one phase according to a second embodiment of the present invention. It is a voltage waveform in the feeder circuit section of the first embodiment of the present invention.

Hereinafter, the present invention will be described through embodiments of the invention, but the following embodiments do not limit the invention according to the claims. Also, not all combinations of features described in the embodiments are essential for the solution of the invention.

A configuration of a gate driving device according to an embodiment of the present invention will be described with reference to FIGS. 1 to 6. FIG. Also, in FIGS. 1 to 6, the same numbers are assigned to the same functions and substantially corresponding portions, and the description thereof is omitted.
<First embodiment>
FIG. 2 shows a diagram for explaining the inverter cell 102a of the U-phase arm section 102 and the feeder circuit section 9 of the power converter 101 according to the first embodiment of the present invention. Since the V-phase arm portion 103 and the W-phase arm portion 104 have the same configuration as the U-phase arm portion 102, description thereof will be omitted.

The inverter cell 102a includes an inverter section 10a, a capacitor section 3a, and a gate drive circuit section 8a (GDU (Gate Drive Unit)). Inverter section 10a includes switching elements 4a to 7a each having a diode connected in antiparallel.
A power supply circuit section 9 includes an isolation transformer 1 and a converter section 2 .
The switching elements 4a to 7a included in the inverter cell 102a are IGBTs, and diodes are connected in anti-parallel to the switching elements 4a to 7a. The switching elements are connected in series to form upper and lower arms of the single-phase inverter section. A connection point between the upper and lower arms is provided with a first AC output terminal a and a second AC output terminal b.
Although IGBTs are used as switching elements in this embodiment, switching elements having a switching function such as MOSFETs and thyristors may be used.
At least one switching element of the switching elements included in the inverter section 10a may be a switching element including a wide bandgap semiconductor. Examples include switching elements based on silicon carbide, gallium nitride, diamond, and the like.

The gate drive circuit section 8a is connected to the gate terminal G and the emitter terminal E of the switching elements 4a to 7a, and applies a voltage between the gate terminal G and the emitter terminal E so as to control ON/OFF of the switching elements 4a to 7a. do.
A positive terminal P and a negative terminal N of the capacitor section 3a are connected to the DC side of the inverter section 10a.

A primary side terminal of the insulating transformer 1 is connected to a first AC output terminal and a second AC output terminal of the inverter section, and a secondary side terminal is connected to an AC input side of the converter section 2 . The DC side of the converter section 2 is connected to the gate drive circuit section 8a.
The operation of the power converter 101 will be described below.
<When the system is normal>
When the system 200 is normal, the plurality of inverter cells (102a, 102b, 102c, 103a, 103b, 103c, 104a, 104b, 104c) included in the power converter 101 are stopped without inverter operation. Since the first AC output terminal a and the second AC output terminal b of each inverter cell are connected to the system 200 via the reactor 105, the AC voltage from the system 200 is applied.
Therefore, the voltage supplied from the system 200 is applied to the input side of the power supply circuit section 9 . FIG. 6(a) shows voltage waveforms applied to the first AC output terminal a and the second AC output terminal b when the inverter cells are stopped.

In the voltage waveform of FIG. 6A, the voltage is constant during period t. This is because the capacitor section 3a is charged. Since the capacitor section 3a is ideally charged with a voltage equal to the peak value of the AC voltage supplied from the system, the voltage is not constant. However, since the capacitor unit 3a actually discharges slightly, the capacitor unit 3a is charged during the period t in which the voltage of the system 200 exceeds the voltage Eds of the capacitor unit 3a.
At this time, the switching elements 4a, 5a, 6a, and 7a of the inverter section 10a are turned off, and the diodes connected in anti-parallel to the switching elements operate as a rectifier circuit.

The isolation transformer 1 transforms the AC voltage supplied from the first AC output terminal a and the second AC output terminal b to a predetermined voltage, and outputs the voltage to the converter section 2 from the secondary side terminal.
The converter section 2 converts the AC voltage supplied from the secondary terminal of the insulating transformer 1 into a DC voltage, and supplies the DC voltage to the gate drive circuit section 8a.
The power conversion device 101 includes a control unit (not shown), and the control unit detects a voltage between the first AC output terminal a and the second AC output terminal b by a voltage detector (not shown). to control the converter section 2 .

By configuring the power supply circuit section 9 as described above, it is possible to reduce the loss generated in the isolation transformer without providing a dedicated power supply and without increasing the capacity of the isolation transformer.
<When the system is abnormal>
When system 200 is abnormal, for example, when the voltage of system 200 drops, the inverter cells are operated. Specifically, a control unit (not shown) outputs a PWM control signal to the gate drive circuit unit 8a. The gate drive circuit unit 8a turns on and off the switching elements included in the inverter cells. The inverter cell outputs a predetermined voltage to a first AC output terminal a and a second AC output terminal b. The voltage output at this time is applied to the primary side of the insulating transformer 1 .

FIG. 6(b) shows the voltage waveform between the first AC output terminal a and the second AC output terminal b during inverter cell operation.
The isolation transformer 1 transforms an AC voltage supplied from a first AC output terminal a and a second AC output terminal b to a predetermined voltage, and outputs the voltage from a secondary side terminal.
The converter section 2 converts the AC voltage supplied from the secondary terminal of the insulating transformer 1 into a DC voltage, and supplies the DC voltage to the gate drive circuit section 8a.
The power conversion device 101 includes a control unit (not shown), and the control unit detects a voltage between the first AC output terminal a and the second AC output terminal b by a voltage detector (not shown). to control the converter section 2 .

By configuring the power supply circuit section 9 as described above, it is possible to reduce the loss generated in the isolation transformer without providing a dedicated power supply and without increasing the capacity of the isolation transformer.
Further, the power supply circuit 9 can supply power to the gate driving circuit section 8a regardless of whether the inverter cells are operating or not.

FIG. 3 shows an embodiment in which the feeding circuit section 9 shown in FIG. 2 is applied to the U-phase arm section 102. As shown in FIG. In this embodiment, the power supply circuit unit 9 supplies power to the gate drive circuit unit 8a in the inverter cell of the connected first AC output terminal a and the second AC output terminal b. Power may be supplied to some or all of the gate drive circuit units 8 of the inverter cells included in the unit 102 . It should be noted that the U-phase arm portion 102, the V-phase arm portion 103, and the W-phase arm portion 104 may not have the same connection relationship between the power supply circuit portion 9 and the first and second AC output terminals. Further, the power supply circuit unit 9 may supply power to the gate drive circuit unit 8a in the inverter cells other than the inverter cells of the connected first AC output terminal a and the second AC output terminal b. Further, the power supply circuit section 9 may be connected to the second AC output terminal b of an inverter cell different from the connected inverter cell having the first AC output terminal a.
<Second embodiment>
FIG. 4 shows a diagram for explaining the inverter cells 102a and 102b of the U-phase arm section 102 and the feeder circuit section 9 of the power converter 101 according to the second embodiment of the present invention.

Although the configuration is the same as that of the first embodiment shown in FIG. 2, the power supply circuit 9 is connected not only to the inverter cell 102a but also to the gate drive circuit 8b in 102b to supply power. Also, the power supply circuit 9 is connected to the first AC output terminal of the inverter cell 102a, and is connected to the second AC output terminal of the inverter cell 102b. A second AC output terminal of the inverter cell 102a is connected to a first AC output terminal of the inverter cell 102b.

Since the operation of this embodiment is the same as that of the first embodiment, the explanation is omitted.
By configuring the power supply circuit section 9 as described above, it is possible to reduce the loss generated in the isolation transformer without providing a dedicated power supply and without increasing the capacity of the isolation transformer.
Moreover, the power supply circuit 9 can supply power to the gate drive circuit unit 8 regardless of whether the inverter cell is in operation or not.
Furthermore, by supplying power to two inverter cells, the number of power supply circuit units 9 can be reduced.

FIG. 5 shows an embodiment in which the feeder circuit section 9 shown in FIG. 4 is applied to the U-phase arm section 102. As shown in FIG. In this embodiment, a feeder circuit 9 connected to the inverter cells 102a, 102b and a feeder circuit 9 connected to the inverter cells 102b, 102c are provided.
By configuring the power supply circuit section 9 as described above, it is possible to reduce the loss generated in the isolation transformer without providing a dedicated power supply and without increasing the capacity of the isolation transformer.
Moreover, the power supply circuit 9 can supply power to the gate drive circuit unit 8 regardless of whether the inverter cell is in operation or not.
Furthermore, by supplying power to two inverter cells, the number of power supply circuit units 9 themselves can be reduced.

Although the present invention has been described along with the embodiments, the technical scope of the present invention is not limited to the scope described in the above embodiments. It is obvious to those skilled in the art that the above embodiments can be modified or improved.

1 Insulation transformer 2 Converter section 3 Capacitor section 4, 5, 6, 7 Switching element 8 Gate drive circuit section 9 Feeder circuit section 10 Inverter section 101 Power converter 102 U-phase arm section 103 V-phase arm section 104 W-phase arm section 105 Reactors 102a, 102b, 102c Inverter cells 103a, 103b, 103c
104a, 104b, 104c
200 lines

Claims (8)

a plurality of inverter cells including an inverter section configured by a plurality of switching elements and having a first AC output terminal and a second AC output terminal; and a gate drive circuit section for driving the plurality of switching elements;
a power supply circuit unit that supplies power to the gate drive circuit unit;
with
The power supply circuit unit
AC power supplied from the first AC output terminal of any of the plurality of inverter cells and the second AC output terminal of any of the plurality of inverter cells is converted into DC power and supplied to the gate drive circuit unit A power conversion device characterized by supplying power. the plurality of inverter cells are connected in series to form a single-phase arm,
The power supply circuit unit
AC power supplied from the first AC output terminal of any of the plurality of inverter cells and the second AC output terminal of any of the plurality of inverter cells included in the single-phase arm section is converted into DC power. 2. The power conversion device according to claim 1, wherein power is supplied to said gate drive circuit unit. The power supply circuit unit
Among the plurality of inverter cells included in the single-phase arm portion, in two of the inverter cells that are adjacent and connected in series, the first AC output terminal of one of the inverter cells and the output terminal of the other inverter cell 3. The power converter according to claim 2, wherein AC power supplied from said second AC output terminal is converted into DC power and supplied to said gate drive circuit unit. The power supply circuit unit
AC power supplied from the first AC output terminal and the second AC output terminal of one of the plurality of inverter cells included in the single-phase arm portion is converted into DC power to drive the gate. 3. The power converter according to claim 2, wherein power is supplied to the circuit unit. The power supply circuit unit
an isolation transformer having a primary side terminal connected to the first AC output terminal and the second AC output terminal;
a converter section having a secondary side terminal and an input side of the isolation transformer connected to each other, and having an output side connected to the gate driving circuit section;
The power converter according to any one of claims 1 to 4, comprising: The plurality of single-phase arm portions are
Star-connected or delta-connected via reactors,
5. The power converter according to any one of claims 2 to 4, wherein said connected connection points are interconnected to a system respectively. The power supply circuit unit
The power converter according to any one of claims 1 to 6, wherein power can be supplied to said gate drive circuit unit regardless of whether said inverter cell is in operation or not. The inverter cell is
The power supply circuit section further includes a capacitor section that supplies DC power to the inverter section,
an isolation transformer having a primary side terminal connected to the first AC output terminal and the second AC output terminal;
a converter section having a secondary side terminal and an input side of the isolation transformer connected to each other, and having an output side connected to the gate driving circuit section;
with
when the inverter cell is in operation, controlling the converter unit according to the output voltage of the inverter cell;
7. The power converter according to claim 6, wherein when the inverter cell is stopped, the converter section is controlled according to the voltage value of the system and the voltage value of the capacitor section.

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