CN112636567B

CN112636567B - IGBT voltage-sharing circuit and converter

Info

Publication number: CN112636567B
Application number: CN202011461301.6A
Authority: CN
Inventors: 周志达; 吴轩钦; 王国建; 耿程飞; 张旭
Original assignee: Shenzhen Invt Electric Co Ltd
Current assignee: Shenzhen Invt Electric Co Ltd
Priority date: 2020-12-11
Filing date: 2020-12-11
Publication date: 2022-04-22
Anticipated expiration: 2040-12-11
Also published as: CN112636567A

Abstract

The embodiment of the invention discloses an IGBT voltage-sharing circuit and a frequency converter, and relates to the technical field of voltage sharing of frequency converters. The IGBT voltage-sharing circuit comprises an IGBT, a grid clamping unit, a resistor series assembly, a first current pouring unit and a second current pouring unit, wherein the resistor series assembly comprises a first resistor and a second resistor; the grid clamping unit is respectively connected with the grid of the IGBT, the first resistor and the second resistor; the first resistor and the second resistor are connected in series between the collector of the IGBT and the emitter of the IGBT; the first current injection unit is connected with the first resistor in parallel, and the second current injection unit is connected with the second resistor in parallel; the first current injection unit and the second current injection unit are both provided with clamping voltages; the first current pouring unit and the second current pouring unit are used for pouring current into the grid of the IGBT when the voltage is higher than the self clamping voltage. The active control effect of the grid electrode on the IGBT can be enhanced by pouring current into the grid electrode of the IGBT, so that the voltage-sharing effect is improved.

Description

IGBT voltage-sharing circuit and converter

Technical Field

The invention relates to the technical field of voltage sharing of frequency converters, in particular to an IGBT voltage sharing circuit and a frequency converter.

Background

An Insulated Gate Bipolar Transistor (IGBT) is a commonly used power semiconductor device in the field of medium-high voltage transmission and an execution unit of a modulation and control algorithm, and the voltage resistance level of the IGBT greatly affects key indexes such as frequency converter power topology type selection, control algorithm complexity, overall cost and volume, and operation efficiency. In recent years, medium and high voltage frequency converters are rapidly developed towards the trends of energy conservation, environmental protection, home-made replacement and high reliability. By applying the IGBT series technology, the voltage grade of the frequency converter can be effectively expanded, high-voltage IGBT devices with lower domestic rate can be replaced, the switching loss of the devices can be reduced, the carrier frequency of the frequency converter can be improved, the cost ratio of semiconductor devices can be reduced, the supply period can be shortened, and the like. In addition, the topological structure of the medium-high voltage frequency converter can be simplified by adopting the IGBT series connection technology, the modulation and control algorithm is simplified, and the reliability of the frequency converter is improved.

The medium-high voltage frequency converter applying the IGBT series technology comprises 1 direct current bus capacitor, three-phase (u, v, w) inverter bridge arms and three-phase output reactors (Lu, Lv, Lw). Each phase of bridge arm is composed of an upper switch unit and a lower switch unit, and each switch unit is formed by connecting the collector and the emitter of N IGBTs (N is an integer more than or equal to 2) in series end to end. Each IGBT is ensured to be divided into 1/N of the bus voltage when being cut off and the voltage is evenly distributed when the switch is in transient state through one or more voltage equalizing circuits. According to different connection relations between the voltage equalizing circuit and the IGBT, the voltage equalizing circuit comprises a passive voltage equalizing scheme connected between a collector electrode and an emitter electrode and an active voltage equalizing scheme connected between the collector electrode and a grid electrode. However, the existing voltage equalizing circuit has the problem of poor active control effect in the voltage equalizing process.

Disclosure of Invention

The embodiment of the invention provides an IGBT voltage-sharing circuit and a frequency converter, and aims to solve the problem that the active control effect is poor in the voltage-sharing process of the existing voltage-sharing circuit.

In order to solve the above problem, in a first aspect, an embodiment of the present invention provides an IGBT voltage equalizing circuit, where the IGBT voltage equalizing circuit includes an IGBT, a gate clamping unit, a resistor series assembly, a first current sinking unit, and a second current sinking unit, where the resistor series assembly includes a first resistor and a second resistor; the grid clamping unit is respectively connected with the grid of the IGBT, the first resistor and the second resistor; the first resistor and the second resistor are connected in series between the collector of the IGBT and the emitter of the IGBT; the first current filling unit is connected with the first resistor in parallel, and the second current filling unit is connected with the second resistor in parallel; the first current injection unit and the second current injection unit are both provided with clamping voltages; the first current pouring unit and the second current pouring unit are used for pouring current into the grid of the IGBT when the voltage is higher than the self clamping voltage.

The further technical scheme is that the first current injection unit comprises a first clamping diode and a first capacitor, the negative electrode of the first clamping diode is connected with the collector electrode of the IGBT, the positive electrode of the first clamping diode is connected with the first capacitor, and the first capacitor is connected with the first resistor.

The second current injection unit comprises a second clamping diode and a second capacitor, wherein the cathode of the second clamping diode is connected with the second capacitor, the anode of the second clamping diode is connected with the second resistor, and the second capacitor is connected with the first capacitor.

The second current sinking unit comprises a second clamping diode and a second capacitor, wherein the second clamping diode is connected in parallel with the second resistor, and the second capacitor is connected in parallel with the second clamping diode.

According to a further technical scheme, the IGBT voltage-sharing circuit further comprises a third current injection unit, and the third current injection unit is connected with the first clamping diode in parallel.

The third current injection unit comprises a third resistor and a third capacitor, the third resistor is connected with the collector of the IGBT and the third capacitor, and the third capacitor is connected with the anode of the first clamping diode.

According to a further technical scheme, the IGBT voltage equalizing circuit further comprises a trailing voltage equalizing unit, the trailing voltage equalizing unit comprises a trailing clamping diode and a trailing resistor, the negative electrode of the trailing clamping diode is connected with a first capacitor, the positive electrode of the trailing clamping diode is connected with the trailing resistor, and the trailing resistor is connected with a second capacitor.

According to a further technical scheme, the IGBT voltage equalizing circuit further comprises a trailing voltage equalizing unit, the trailing voltage equalizing unit comprises a trailing clamping diode and a trailing resistor, the negative electrode of the trailing clamping diode is connected with a first capacitor, the positive electrode of the trailing clamping diode is connected with the trailing resistor, and the trailing resistor is connected with the first capacitor.

The further technical scheme is that the grid clamping unit comprises a current-limiting resistor, a diode and a grid clamping diode; the current limiting resistor is respectively connected with the first resistor, the second resistor and the anode of the diode; the cathode of the diode is connected with the cathode of the grid clamping diode; the anode of the gate clamping diode is connected with the gate of the IGBT.

In a second aspect, an embodiment of the present invention provides a frequency converter, where the frequency converter includes the IGBT grading circuit according to the first aspect.

The IGBT voltage-sharing circuit provided by the embodiment of the invention comprises a first current injection unit and a second current injection unit, wherein after the voltage between the collector electrode and the emitter electrode of the IGBT rises to the clamping voltage of the first current injection unit, the first current injection unit injects current to the grid electrode of the IGBT, and after the voltage further rises to the clamping voltage of the second current injection unit, the second current injection unit injects current to the grid electrode of the IGBT, so that the current injected into the grid electrode of the IGBT is further increased, and the active control effect of the grid electrode on the IGBT can be enhanced by injecting the current into the grid electrode of the IGBT, thereby improving the voltage-sharing effect.

Drawings

In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings needed to be used in the description of the embodiments are briefly introduced below, and it is obvious that the drawings in the following description are some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings based on these drawings without creative efforts.

Fig. 1 is a circuit diagram of an IGBT equalizer circuit according to an embodiment of the present invention;

fig. 2 is a circuit diagram of an IGBT equalizer circuit according to another embodiment of the present invention;

fig. 3 is a circuit diagram of a single-phase inverter of a frequency converter according to an embodiment of the present invention.

Reference numerals

IGBT10, gate clamp 20, resistor series assembly 30, first current sinking unit 40, second current sinking unit 50, third current sinking unit 60, trailing voltage grading unit 70, IGBT voltage grading circuit 100.

Detailed Description

The technical solutions in the embodiments will be described clearly and completely with reference to the accompanying drawings in the embodiments of the present invention, wherein like reference numerals represent like elements in the drawings. It is apparent that the embodiments to be described below are only a part of the embodiments of the present invention, and not all of them. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

It will be understood that the terms "comprises" and/or "comprising," when used in this specification and the appended claims, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof.

It is also to be understood that the terminology used in the description of the embodiments of the invention herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the embodiments of the invention. As used in the description of embodiments of the present invention and the appended claims, the singular forms "a," "an," and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise.

Referring to fig. 1, an embodiment of the present invention provides an IGBT voltage equalizing circuit, and as can be seen from the figure, the IGBT voltage equalizing circuit includes an IGBT, a gate clamping unit 20, a resistor series assembly 30, a first current sinking unit 40, and a second current sinking unit 50, where the resistor series assembly 30 includes a first resistor R1 and a second resistor R2. The specific connection mode of the IGBT voltage-sharing circuit is as follows:

the gate clamping unit 20 is connected to the gate G of the IGBT, the first resistor R1, and the second resistor R2, respectively. The first resistor R1 and the second resistor R2 are connected in series between the collector C of the IGBT and the emitter E of the IGBT. The resistor series arrangement 30 on the one hand acts as a static equalizing resistor and on the other hand ensures that when the device is turned off, the voltage division across the second resistor R2 is not sufficient to break down the gate clamp 20, thereby ensuring a reliable turn-off of the device.

The first current sinking unit 40 is connected in parallel with the first resistor R1, and the second current sinking unit 50 is connected in parallel with the second resistor R2. The first current sinking unit 40 and the second current sinking unit 50 are both provided with clamping voltages; the first current sinking unit 40 and the second current sinking unit 50 are both used for sinking current into the gate G of the IGBT when the voltage is higher than the clamping voltage of the IGBT.

Specifically, after the voltage between the collector C and the emitter E of the IGBT rises to the clamping voltage of the first current pouring unit 40, the first current pouring unit 40 pours current into the gate G of the IGBT, and after the voltage further rises to the clamping voltage of the second current pouring unit 50, the second current pouring unit 50 pours current into the gate G of the IGBT, so that the current poured into the gate G of the IGBT is further increased, thereby enhancing the active control effect of the gate G on the IGBT, and promoting the voltage equalizing effect.

With reference to fig. 1, in the present embodiment, the first current sinking unit 40 includes a first clamping diode T1 and a first capacitor C1, a cathode of the first clamping diode T1 is connected to the collector C of the IGBT, an anode of the first clamping diode T1 is connected to the first capacitor C1, and the first capacitor C1 is connected to the first resistor R1. It will be appreciated that the clamping voltage of the first current sinking unit 40 is determined by a first clamping diode T1.

In this embodiment, the first clamping diode T1 and the first capacitor C1 are connected in series, so that the capacitance value, the voltage stress, and the charging and discharging range of the buffer capacitor (i.e., the first capacitor C1) can be effectively reduced, and the loss of the voltage equalizing circuit is reduced.

Further, the second current sinking unit 50 includes a second clamping diode T2 and a second capacitor C2, a cathode of the second clamping diode T2 is connected to the second capacitor C2, an anode of the second clamping diode T2 is connected to the second resistor R2, and the second capacitor C2 is connected to the first capacitor C1. It will be appreciated that the clamping voltage of the second current sinking cell 50 is determined by a second clamping diode T2.

In this embodiment, the second clamping diode T2 and the second capacitor C2 are connected in series, so that the capacitance value, the voltage stress, and the charging and discharging range of the buffer capacitor (i.e., the second capacitor C2) can be effectively reduced, and the loss of the voltage equalizing circuit is reduced.

Further, the IGBT equalizer circuit further includes a third current sinking unit 60, and the third current sinking unit 60 is connected in parallel to the first clamping diode T1.

Specifically, the third current sinking unit 60 includes a third resistor R0 and a third capacitor C0, the third resistor R0 is connected to the collector C of the IGBT and the third capacitor C0, and the third capacitor C0 is connected to the anode of the first clamping diode T1.

In this embodiment, an additional gate G sink current path is provided by connecting the third current sink unit 60 in parallel across the first clamp diode T1. When the collector C voltage exceeds the clamping voltage of the gate clamping unit 20 but does not reach the clamping voltage of the first current sinking unit 40, the third current sinking unit 60 may sink a weak adjustment current into the gate G of the IGBT, thereby enhancing the control force of the sinking current on the switching trajectory of the IGBT and enhancing the active control effect.

Further, the IGBT voltage equalizing circuit further includes a tail voltage equalizing unit 70, and the tail voltage equalizing unit 70 is connected in parallel with the first capacitor C1 and the second capacitor C2.

Specifically, the trailing voltage equalizing unit 70 includes a trailing clamping diode Ttail and a trailing resistor Rtail, a negative electrode of the trailing clamping diode Ttail is connected to the first capacitor C1, a positive electrode of the trailing clamping diode Ttail is connected to the trailing resistor Rtail, and the trailing resistor Rtail is connected to the second capacitor C2.

When the IGBT enters a current tailing stage, because of the difference of the IGBT and the delay of a trigger signal, tailing current is different, the partial pressure of the IGBT is slowly unbalanced, and the IGBT with the minimum tailing current can finally obtain the voltage of all buses. The invention thus nests a tail stage equalizer circuit to limit the maximum voltage division across the first capacitor C1 and the second capacitor C2. When the tail clamping diode Ttail of the tail voltage equalizing unit 70 is broken down, the equivalent impedance across the collector and emitter of the IGBT rapidly drops, the voltage across the IGBT rapidly drops, and the voltage between the series devices recovers to be balanced.

Further, the gate clamping unit 20 includes a current limiting resistor Rg, a diode Gg, and a gate G clamping diode Tg; the current limiting resistor Rg is respectively connected with the first resistor R1, the second resistor R2 and the anode of the diode Gg; the cathode of the diode Gg is connected with the cathode of the grid G clamping diode Tg; the anode of the gate G clamp diode Tg is connected to the gate G of the IGBT.

It will be appreciated that the clamping voltage of the gate clamp 20 is determined by the gate G clamp diode Tg. The diode Dg ensures that the current flows in one direction.

In the embodiment of the invention, the working process of the IGBT equalizer circuit shown in fig. 1 is as follows:

at the IGBT turn-on instant, the second capacitor C2 is charged reversely due to a sharp drop in the collector-emitter voltage Vce, and therefore, at the IGBT turn-off instant, when the collector-emitter voltage Vce rises, the second clamp diode T2 is broken down in advance. The compensation current generated between the collector and the emitter flows through the third resistor R0, the third capacitor C0, the first capacitor C1, the second clamping diode T2 and the second capacitor C2 in sequence to slow down the voltage change rate.

When the voltages of the third resistor R0 and the third capacitor C0 rise to the breakdown voltage of the first clamping diode T1, the third resistor R0 and the third capacitor C0 are short-circuited, the compensation current further increases, the second capacitor C2 continues to be charged in the forward direction, and the potential across the second resistor R2 continues to rise.

When the voltage at two ends of the second resistor R2 reaches the breakdown voltage of the grid clamping diode Tg, the voltage equalizing circuit starts to inject current into the grid of the IGBT through the first clamping diode T1, the first capacitor C1, the current limiting resistor Rg, the diode Dg and the grid clamping diode Tg, the turn-off track of the IGBT in the active area is adjusted, the deterioration of series connection partial voltage unbalance is limited, and dynamic voltage equalization is achieved.

When the IGBT voltage reaches near the peak, the second clamp diode T2 returns to the off state as the voltage across the second capacitor C2 rises.

At the end of the turn-off process of the IGBT, the current amplitude and the change rate of the device are reduced simultaneously. Due to the difference of device parameters and the delay of trigger signals, the current of the series devices is different, so that the junction capacitance of the anti-parallel diodes is forced to charge and discharge, and the partial voltage of the devices is unbalanced again. Unlike the voltage unbalance in which the turn-off initial voltage rapidly rises, the turn-off tail sound voltage unbalance is slow but deep. When the voltage unbalance degree reaches a preset trailing voltage value, the trailing voltage-sharing unit is put into operation to clamp the voltage at the two ends of the first capacitor C1, and the voltage division of the series device is gradually balanced.

Referring to fig. 2, the present invention provides another embodiment which differs from the above embodiment as follows:

the second current sinking unit 50 includes a second clamping diode T2 and a second capacitor C2, the second clamping diode T2 is connected in parallel with the second resistor R2, and the second capacitor C2 is connected in parallel with the second clamping diode T2. Different from the above embodiments, in the present embodiment, the second capacitor C2 bears the voltage earlier, and after the second clamping diode T2 is broken down, the collector C-emitter E impedance of the IGBT drops sharply, so that the current injected into the gate G can be effectively limited, the effect of protecting the gate G can be achieved, the difference of the collector C current of the IGBT can be compensated quickly, and the imbalance degree of the collector C-emitter E voltage of the device can be limited.

In this embodiment, the second clamping diode T2 and the second capacitor C2 are connected in parallel, so that the capacitance value, the voltage stress and the charging and discharging range of the buffer capacitor (i.e., the second capacitor C2) can be effectively reduced, and the loss of the voltage-sharing circuit is reduced.

Further, the IGBT voltage equalizing circuit further includes a tail voltage equalizing unit 70, and the tail voltage equalizing unit 70 is connected in parallel with the first capacitor C1.

Specifically, the trailing voltage equalizing unit 70 includes a trailing clamping diode Ttail and a trailing resistor Rtail, a negative electrode of the trailing clamping diode Ttail is connected to the first capacitor C1, a positive electrode of the trailing clamping diode Ttail is connected to the trailing resistor Rtail, and the trailing resistor Rtail is connected to the first capacitor C1.

In the embodiment of the invention, the working process of the IGBT equalizer circuit shown in fig. 2 is as follows:

in the turn-off transient state of the IGBT, the third capacitor C0, the first capacitor C1 and the second capacitor C2 are connected in series to serve as a power side buffer absorption capacitor, when a collector-emitter voltage Vce of the IGBT starts to rise, the gate clamping diode Tg is broken down first, and current flows through the third resistor R0, the third capacitor C0, the first capacitor C1, the current limiting resistor Rg, the diode Dg and the gate clamping diode Tg in sequence to flow into the gate, wherein the current limiting resistor R0 and the gate clamping diode Rg limit the amplitude of the flowing current together, the dynamic voltage balancing effect is limited, and the control of the gate on a switching track of a device is mainly enhanced.

As the collector-emitter voltage Vce further rises, the first clamping diode T1 is broken down, the current flowing into the gate is further increased after the third resistor R0 and the third capacitor C0 are short-circuited, and the turn-off trajectory of the IGBT in the active region is adjusted, so that dynamic voltage equalization is realized. Meanwhile, only the first capacitor C1 and the second capacitor C2 are left to be connected in series to serve as buffer capacitors, and the buffer absorption effect is enhanced.

The collector-emitter voltage Vce continues to rise and the voltage across the second capacitor C2 increases until the second clamp diode T2 breaks down. After the second clamping diode T2 is broken down, the current injected into the gate reaches saturation, which plays a role of protecting the gate on one hand, and provides a collector-emitter current branch with lower impedance on the other hand, so as to compensate the current difference inside the IGBT and clamp the collector-emitter voltage Vce at the same time. In the IGBT current tailing stage, when voltage unbalance reaches a preset tailing voltage value, the tailing voltage-sharing unit is put into work, equivalent impedance at two ends of a collector electrode and a grid electrode is greatly reduced, and voltage division balance in the tailing stage is achieved.

The embodiment of the invention provides a frequency converter, which comprises the IGBT voltage-sharing circuit in any one of the embodiments.

Specifically, referring to fig. 3, in an embodiment, the single-phase inverter of the frequency converter includes a bus capacitor Ct single-phase arm and an output reactor Lu. The single-phase bridge arm is composed of an upper switch unit and a lower switch unit, each switch unit comprises two forward series-connected IGBTs 10 (the emitter of the first IGBT10 is connected with the collector of the second IGBT 10). The IGBT grading circuit 100 shown in fig. 1 or fig. 2 is connected between the collector, gate, and emitter of each IGBT 10.

In the above embodiments, the descriptions of the respective embodiments have respective emphasis, and for parts that are not described in detail in a certain embodiment, reference may be made to related descriptions of other embodiments.

It will be apparent to those skilled in the art that various changes and modifications may be made in the present invention without departing from the spirit and scope of the invention. Thus, while the invention has been described with respect to the above-described embodiments, it will be understood that the invention is not limited thereto but may be embodied with various modifications and changes.

While the invention has been described with reference to specific embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims. Therefore, the protection scope of the present invention shall be subject to the protection scope of the claims.

Claims

1. The IGBT voltage-sharing circuit is characterized by comprising an IGBT, a grid clamping unit, a resistor series assembly, a first current pouring unit and a second current pouring unit, wherein the resistor series assembly comprises a first resistor and a second resistor; the grid clamping unit is respectively connected with the grid of the IGBT, the first resistor and the second resistor; the first resistor and the second resistor are connected in series between the collector of the IGBT and the emitter of the IGBT; the first current filling unit is connected with the first resistor in parallel, and the second current filling unit is connected with the second resistor in parallel; the first current injection unit and the second current injection unit are both provided with clamping voltages; the first current pouring unit and the second current pouring unit are used for pouring current into the grid electrode of the IGBT when the voltage is higher than the self clamping voltage;

the first current filling unit comprises a first clamping diode and a first capacitor, wherein the cathode of the first clamping diode is connected with the collector of the IGBT, the anode of the first clamping diode is connected with the first capacitor, and the first capacitor is connected with the first resistor;

the second current injection unit comprises a second clamping diode and a second capacitor; the cathode of the second clamping diode is connected with the second capacitor, the anode of the second clamping diode is connected with the second resistor and the emitter of the IGBT, and the second capacitor is connected with the first capacitor; or the second clamping diode is connected with the second resistor in parallel, and the second capacitor is connected with the second clamping diode in parallel;

the grid clamping unit comprises a current-limiting resistor, a diode and a grid clamping diode; the current limiting resistor is respectively connected with the first resistor, the second resistor and the anode of the diode; the cathode of the diode is connected with the cathode of the grid clamping diode; the anode of the gate clamping diode is connected with the gate of the IGBT.

2. The IGBT voltage equalizing circuit of claim 1, further comprising a third current sinking unit connected in parallel with the first clamping diode;

3. The IGBT voltage equalizing circuit according to claim 2, further comprising a trailing voltage equalizing unit, wherein the trailing voltage equalizing unit comprises a trailing clamping diode and a trailing resistor, a cathode of the trailing clamping diode is connected with the first capacitor, an anode of the trailing clamping diode is connected with the trailing resistor, and the trailing resistor is connected with the second capacitor.

4. The IGBT voltage equalizing circuit according to claim 2, further comprising a trailing voltage equalizing unit, wherein the trailing voltage equalizing unit comprises a trailing clamping diode and a trailing resistor, a cathode of the trailing clamping diode is connected with the first capacitor, an anode of the trailing clamping diode is connected with the trailing resistor, and the trailing resistor is connected with the first capacitor.

5. A frequency converter, characterized in that it comprises an IGBT voltage equalizing circuit according to any one of claims 1-4.