WO2021143658A1

WO2021143658A1 - Three-phase pulse width modulation rectifier circuit and pre-charging method therefor

Info

Publication number: WO2021143658A1
Application number: PCT/CN2021/071162
Authority: WO
Inventors: 郭晓露; 张登科; 张冬宇
Original assignee: 山特电子（深圳）有限公司
Priority date: 2020-01-17
Filing date: 2021-01-12
Publication date: 2021-07-22
Also published as: CN111130376B; CN111130376A

Abstract

Provided in the present invention are a three-phase pulse width modulation rectifier circuit and a pre-charging method therefor, the three-phase pulse width modulation rectifier circuit comprising: a three-phase pulse width modulation rectifier, comprising an input terminal, a positive electrode output terminal, and a negative electrode output terminal; first, second, and third switches connected between the input terminal of the three-phase pulse width modulation rectifier and a three-phase alternating current; a first capacitor and a second capacitor connected in series between the positive electrode output terminal and the negative electrode output terminal, a node formed by the connection of the first capacitor and the second capacitor being connected to a neutral point; a first one-way charging branch connected between a first phase alternating current in the three-phase alternating current and the positive electrode output terminal, and being used for pre-charging the first capacitor; and a second one-way charging branch connected between the first phase alternating current and the negative electrode output terminal, and being used for pre-charging the second capacitor. The pre-charging method of the present invention can avoid the production of input spike currents.

Description

Three-phase pulse width modulation rectifier circuit and its precharging method

Technical field

The invention relates to a pulse width modulation rectification circuit, in particular to a three-phase pulse width modulation rectification circuit and a precharging method thereof.

Background technique

The three-phase pulse width modulation rectifier circuit has the advantages of low grid-side current harmonics, high power factor, and two-way energy flow. It has been widely used and researched.

Figure 1 is a three-phase pulse width modulation rectifier circuit in the prior art. As shown in FIG. 1, the three-phase pulse width modulation rectifier circuit 1 includes a three-phase pulse width modulation rectifier 11; a first switch S11, a second switch S12, and a third switch S13 connected to the input end of the three-phase pulse width modulation rectifier 11 ; Capacitor C11 connected to the output end of the three-phase pulse width modulation rectifier 11; and a pre-charging circuit 12, wherein the output end of the pre-charging circuit 12 is connected to both ends of the capacitor C11 for starting the three-phase pulse width modulation rectifier circuit ( That is, the capacitor C11 is charged before the first switch S11, the second switch S12, and the third switch S13 are closed). After the precharging of the capacitor C11 is completed, the first switch S11, the second switch S12, and the third switch S13 are controlled to be closed to avoid or reduce the input peak current or the input peak current in the first switch S11, the second switch S12, and the third switch S13. Inrush current.

However, the three-phase pulse width modulation rectifier circuit 1 has one or more of the following defects: the circuit structure of the precharge circuit 12 is complicated, the number of electronic components is large, and the cost is relatively high. The control method of the precharge circuit 12 is complicated. The pre-charging circuit 12 cannot make the voltage across the capacitor C11 higher than the peak voltage of the three-phase alternating current. At this time, the two ends of the first switch S11 and the inductor L11 in series, the two ends of the second switch S12 and the inductor L12 in series are connected in series. The third switch S13 and the inductor L13 have a relatively large voltage at both ends. If the first switch S11, the second switch S12, and the third switch S13 are controlled to be closed, the first switch S11, the second switch S12, and the third switch S13 will Generate input spike current or surge current. Especially when the voltage of a certain phase of alternating current is too large, a very large input peak current or surge current will be generated in the switch and inductance connected in series with the phase of alternating current, thereby causing damage to the switch.

Summary of the invention

In view of the above technical problems in the prior art, the present invention provides a three-phase pulse width modulation rectifier circuit, including:

A three-phase pulse width modulation rectifier, which includes an input terminal, a positive output terminal and a negative output terminal;

A first switch, a second switch and a third switch connected between the input terminal of the three-phase pulse width modulation rectifier and the three-phase alternating current;

A first capacitor and a second capacitor connected in series between the positive output terminal and the negative output terminal, and a node formed by connecting the first capacitor and the second capacitor is connected to a neutral point;

A first unidirectional charging branch connected between the first phase of the three-phase alternating current and the positive output terminal, which is used to precharge the first capacitor; and

A second unidirectional charging branch connected between the first-phase alternating current and the negative output terminal is used to precharge the second capacitor.

Preferably, the first unidirectional charging branch includes a first diode, a first charging switch, and a first resistor connected in series.

Preferably, the second unidirectional charging branch includes a second diode, a second charging switch and a second resistor connected in series.

Preferably, the three-phase pulse width modulation rectifier includes a first bridge arm, a second bridge arm, and a third bridge arm connected in parallel between the positive output terminal and the negative output terminal, connected to the first switch And the first inductance between the intermediate node of the first bridge arm, and the second inductance connected between the second switch and the intermediate node of the second bridge arm, connected between the third switch and the intermediate node of the second bridge arm. The third inductance between the intermediate nodes of the third bridge arm.

Preferably, the three-phase pulse width modulation rectifier circuit includes a control device for controlling the conduction of the first unidirectional charging branch and the second unidirectional charging branch; when the voltage across the first capacitor is equal to /Or when the voltage across the second capacitor reaches the first threshold voltage, the first unidirectional charging branch and the second unidirectional charging branch are controlled to stop charging, wherein the first threshold voltage is less than the first threshold voltage. The peak voltage of the phase alternating current; controlling the first switch to close; controlling the operation of the three-phase pulse width modulation rectifier to convert the first phase alternating current into direct current to charge the first capacitor and the second capacitor; when When the voltage across the first capacitor and/or the voltage across the second capacitor reaches a second threshold voltage, stop charging the first capacitor and the second capacitor, wherein the second threshold voltage is greater than the The peak voltage of any phase of the three-phase alternating current; and controlling the second switch and the third switch to close.

Preferably, the first unidirectional charging branch includes a first diode, a first charging switch, and a first resistor connected in series, and the second unidirectional charging branch includes a second diode, a second diode, and a second diode connected in series. A charging switch and a second resistor, the control device is used to control the first charging switch and the second charging switch to close to charge the first capacitor and the second capacitor respectively; and when the voltage across the first capacitor And/or when the voltage across the second capacitor reaches the first threshold voltage, the first charging switch and the second charging switch are controlled to be turned off.

Preferably, the three-phase pulse width modulation rectifier includes a first bridge arm, a second bridge arm, and a third bridge arm connected in parallel between the positive output terminal and the negative output terminal, connected to the first switch And the first inductance between the intermediate node of the first bridge arm, and the second inductance connected between the second switch and the intermediate node of the second bridge arm, connected between the third switch and the intermediate node of the second bridge arm. The third inductance between the intermediate nodes of the third bridge arm; the control device is used to provide a pulse width modulation signal to the first bridge arm to make it work in a pulse width modulation mode, and to transfer the first phase alternating current Convert to direct current.

The present invention provides a precharging method for the above-mentioned three-phase pulse width modulation rectifier circuit, which sequentially includes the following steps:

Step 1), controlling the conduction of the first unidirectional charging branch and the second unidirectional charging branch;

Step 2), when the voltage across the first capacitor and/or the voltage across the second capacitor reaches the first threshold voltage, control the first unidirectional charging branch and the second unidirectional charging branch to stop Charging, wherein the first threshold voltage is less than the peak voltage of the first phase alternating current;

Step 3), controlling the first switch to close;

Step 4), controlling the operation of the three-phase pulse width modulation rectifier to convert the first-phase alternating current into direct current to charge the first capacitor and the second capacitor;

Step 5), when the voltage across the first capacitor and/or the voltage across the second capacitor reaches a second threshold voltage, stop charging the first capacitor and the second capacitor, wherein the second capacitor The threshold voltage is greater than the peak voltage of any phase of the three-phase alternating current;

Step 6), controlling the second switch and the third switch to close.

Preferably, the first unidirectional charging branch of the three-phase pulse width modulation rectifier circuit includes a first diode, a first charging switch, and a first resistor connected in series, and the second unidirectional charging branch includes a first diode connected in series. Two diodes, a second charging switch and a second resistor, wherein the step 1) includes controlling the first charging switch and the second charging switch to be closed to charge the first capacitor and the second capacitor respectively; The step 2) includes controlling the first charging switch and the second charging switch to be turned off.

Preferably, the three-phase pulse width modulation rectifier includes a first bridge arm, a second bridge arm, and a third bridge arm connected in parallel between the positive output terminal and the negative output terminal, connected to the first switch And the first inductance between the intermediate node of the first bridge arm, and the second inductance connected between the second switch and the intermediate node of the second bridge arm, connected between the third switch and the intermediate node of the second bridge arm. The third inductance between the intermediate nodes of the third bridge arm; wherein, the step 4) includes providing a pulse width modulation signal to the first bridge arm to make it work in a pulse width modulation mode, and connecting the first bridge arm Phase alternating current is converted to direct current.

The precharging circuit in the three-phase pulse width modulation rectifier circuit of the present invention has a simple circuit structure, a small number of electronic components and a low cost. The control method of pre-charging is simple and avoids the input spike current during the start-up process.

Description of the drawings

The following further describes the embodiments of the present invention with reference to the accompanying drawings, in which:

Figure 1 is a three-phase pulse width modulation rectifier circuit in the prior art.

Fig. 2 is a circuit diagram of a three-phase pulse width modulation rectifier circuit according to a preferred embodiment of the present invention.

FIG. 3 is an equivalent circuit diagram when the first switch in the three-phase pulse width modulation rectifier circuit shown in FIG. 2 is closed.

Detailed ways

In order to make the objectives, technical solutions, and advantages of the present invention clearer, the following further describes the present invention in detail through specific embodiments with reference to the accompanying drawings.

Fig. 2 is a circuit diagram of a three-phase pulse width modulation rectifier circuit according to a preferred embodiment of the present invention. As shown in FIG. 2, the three-phase pulse width modulation rectifier circuit 2 includes: a three-phase pulse width modulation rectifier 21, which includes three AC input terminals, a positive output terminal 211 and a negative output terminal 212; a first switch S21, a second switch S22 and the third switch S33, one ends of which are respectively connected to the three AC input terminals of the three-phase pulse width modulation rectifier 21, and the other ends are respectively connected to the first phase AC power V1, the second phase AC power V2, and the third phase AC power V3; The capacitor C21 and the capacitor C22 are connected in series between the positive output terminal 211 and the negative output terminal 212. The node formed by the connection of the capacitor C21 and the capacitor C22 is connected to the neutral point N; The first one-way charging branch 221 between the other end of the) and the positive output terminal 211; and the second one connected between the first-phase alternating current V1 (that is, the other end of the first switch S21) and the negative output terminal 212 To the charging branch 222.

Those skilled in the art can know that, in order to clearly show the circuit connection relationship of the present invention, FIG. 2 does not show the circuit modules such as the control device and the detection device for detecting voltage.

The three-phase pulse width modulation rectifier 21 includes a first bridge arm, a second bridge arm, and a third bridge arm connected in parallel between the positive output terminal 211 and the negative output terminal 212, and is connected between the first switch S21 and the first bridge arm The inductance L21 between the nodes, the inductance L22 connected between the second switch S22 and the intermediate node of the second bridge arm, and the inductance L23 connected between the third switch S23 and the intermediate node of the third bridge arm. The three-phase pulse width modulation rectifier 21 is controlled under the pulse width modulation signal provided by the control device to convert three-phase alternating current into direct current while keeping the input current and the input voltage in the same phase.

The first unidirectional charging branch 221 includes a first diode D221, a first charging switch K221, and a first resistor R221 connected in series, which are used to make the current flow from the first-phase alternating current V1 to the positive output terminal 211 to prevent the capacitor C21. Charge it.

The second unidirectional charging branch 222 includes a second diode D222, a second charging switch K222, and a second resistor R222 connected in series, which are used to make the current flow from the negative output terminal 212 to the first phase alternating current V1, so as to protect the capacitor C22. Charge it.

The circuit structure of the first unidirectional charging branch 221 and the second unidirectional charging branch 222 in the three-phase pulse width modulation rectifier circuit 2 of this embodiment is simple, the number of electronic components is small, and the cost is low. In addition, the first unidirectional charging branch 221 and the second unidirectional charging branch 222 make full use of the AC power provided by the first-phase AC power V1, and no additional power supply is introduced.

The precharging method of the three-phase pulse width modulation rectifier circuit 2 will be described in detail below, which includes the following steps in sequence.

Step 1), control the first charging switch K221 and the second charging switch K222 to close. At this time, the first-phase alternating current V1 charges the capacitor C21 through the unidirectional first unidirectional charging branch 221 within a positive half cycle, and The capacitor C22 is charged through the second unidirectional charging branch 222 which conducts unidirectionally in the negative half cycle.

Step 2), detecting the voltage across the capacitors C21 and C22, and when the voltage across the capacitor C21 and/or the voltage across the capacitor C22 reaches the first threshold voltage, the first charging switch K221 and the second charging switch K222 are controlled to be turned off. The first threshold voltage is smaller or slightly smaller than the peak voltage of the first phase alternating current V1.

Step 3), control the first switch S21 to close.

FIG. 3 is an equivalent circuit diagram when the first switch S21 in the three-phase pulse width modulation rectifier circuit 2 shown in FIG. 2 is closed. As shown in Figure 3, the intermediate node of the first bridge arm (ie, the node formed by the connection of insulated gate bipolar transistors T211 and T212) is connected to one end of the first phase alternating current V1 through the inductor L21, and the capacitors C21 and C22 are connected to form The intermediate node (ie, the neutral point N) is connected to the other end of the first phase alternating current V1, whereby the inductor L21, insulated gate bipolar transistors T211, T212 and capacitors C21, C22 form a single-phase half-bridge pulse width modulation rectification Circuit 21'.

Step 4) Provide corresponding pulse width modulation signals to the insulated gate bipolar transistors T211 and T212 to operate in a pulse width modulation mode, thereby converting the AC power of the first phase AC power V1 into DC power. In this step, the existing control method is used to control the operation of the single-phase half-bridge PWM rectifier circuit 21' to further charge the capacitor C21 and the capacitor C22.

Step 5), detecting the voltage across the capacitors C21 and C22, and when the voltage across the capacitor C21 and/or the voltage across the capacitor C22 rise to the second threshold voltage, the single-phase half-bridge pulse width modulation rectifier circuit 21' is controlled to stop working. The second threshold voltage is greater than the peak voltage of each phase of the three-phase alternating current.

Step 6), controlling the second switch S22 and the third switch S23 to close. Thus, the startup of the three-phase pulse width modulation rectifier circuit 2 is realized.

The advantages of the above-mentioned pre-charging method are described below in conjunction with specific voltage values.

Suppose the effective value of the voltage of the first-phase alternating current V1, the second-phase alternating current V2, and the third-phase alternating current V3 is 220 volts (the corresponding peak voltage is 311 volts). In step 2), the voltage across the capacitor C21 and the capacitor C22 are both 290 volts. In step 3), when the first switch S21 is controlled to be closed, the maximum voltage shared by the first switch S21, the inductor L21 and the diode D211 in anti-parallel with the insulated gate bipolar transistor T211 at this time is 21 (that is, 311-290) Therefore, when the first switch S21 is controlled to be closed, there is only a small conduction current, and no input spike current or surge current is generated. In step 5), the voltage across the capacitor C21 and the capacitor C22 are both 360 volts. When the second switch S22 and the third switch S23 are controlled to be closed in step 6), no current flows in the second switch S22 and the inductor L22 in series, and the third switch S23 and the inductor L23 in series. Therefore, there is no input spike current or surge current at all, and damage to the second switch S22 and the third switch S23 is avoided.

If the three-phase alternating current is unbalanced, the effective value of the voltage of the first phase of alternating current V1 is 200 volts (corresponding to the peak voltage of 283 volts), and the effective value of the voltage of the second phase of alternating current V2 and the third phase of alternating current V3 is 230 volts (corresponding to The peak voltage is 325 volts). In step 2), the voltage across the capacitor C21 and the capacitor C22 are both 260 volts. In step 3), when the first switch S21 is controlled to be closed, the maximum voltage that the first switch S21, the inductor L21 and the diode D211 can bear is 23 (ie 283-260) volts. Therefore, the first switch S21 is not controlled when it is closed. Will produce input spike current or surge current. In step 5), the voltage across the capacitor C21 and the capacitor C22 are both 360 volts. When the second switch S22 and the third switch S23 are controlled to be closed in step 6), no current flows in the second switch S22 and the inductor L22 in series, and the third switch S23 and the inductor L23 in series. Therefore, there is no input spike current or surge current at all, and damage to the second switch S22 and the third switch S23 is avoided.

The pre-charging method of the foregoing embodiment adopts a two-stage charging method. In the first stage, two unidirectional charging branches with a simple circuit structure are used to respectively charge the capacitor C21 and the capacitor C22 to reach the first threshold voltage. When the first switch S21 is then controlled to close, the conduction current in the first switch S21 is very small, and high input spike current or input surge current is not generated, thus avoiding damage to electronic components such as the first switch S21. In the second stage, the single-phase half-bridge pulse width modulation rectifier circuit 21' is used to further charge the capacitor C21 and the capacitor C22 to make their voltage higher than the peak voltage of any phase of the three-phase alternating current. On the one hand, the existing The control method is used to control the single-phase half-bridge pulse width modulation rectifier circuit 21'. On the other hand, it solves the problem that the voltage across the capacitor C21 and the capacitor C22 cannot reach or exceed the peak voltage of any phase of the three-phase alternating current in the first stage. On the other hand, when the second switch S22 and the third switch S23 are closed, there is no input surge current at all.

Even if the voltage of the three-phase AC power is unbalanced, the two-stage precharging method of the present invention avoids the generation of input spike currents or input surge currents in the three AC input terminals of the three-phase pulse width modulation rectifier circuit 2.

In other embodiments of the present invention, the diodes and switches connected in series in the first unidirectional charging branch 221 and the second unidirectional charging branch 222 can be replaced with controllable unidirectional conducting devices such as thyristors.

Those skilled in the art can know that the voltage values for charging the capacitor C21 and the capacitor C22 in the above-mentioned embodiments are merely illustrative, and are not intended to specifically limit the present invention. In other embodiments of the present invention, it may be determined according to the peak voltage of the three-phase alternating current and the voltage and current values that the first switch S21, the inductor L21, and the diode D211 can withstand.

Although the present invention has been described through preferred embodiments, the present invention is not limited to the embodiments described here, and also includes various changes and changes made without departing from the scope of the present invention.

Claims

A three-phase pulse width modulation rectifier circuit, characterized in that it comprises:

A three-phase pulse width modulation rectifier, which includes an input terminal, a positive output terminal and a negative output terminal;

A first switch, a second switch and a third switch connected between the input terminal of the three-phase pulse width modulation rectifier and the three-phase alternating current;

A first capacitor and a second capacitor connected in series between the positive output terminal and the negative output terminal, and a node formed by connecting the first capacitor and the second capacitor is connected to a neutral point;

A first unidirectional charging branch connected between the first phase of the three-phase alternating current and the positive output terminal, which is used to precharge the first capacitor; and

A second unidirectional charging branch connected between the first-phase alternating current and the negative output terminal is used to precharge the second capacitor.
The three-phase pulse width modulation rectifier circuit according to claim 1, wherein the first unidirectional charging branch includes a first diode, a first charging switch, and a first resistor connected in series.
The three-phase pulse width modulation rectifier circuit according to claim 2, wherein the second unidirectional charging branch includes a second diode, a second charging switch, and a second resistor connected in series.
The three-phase pulse width modulation rectifier circuit according to claim 1, wherein the three-phase pulse width modulation rectifier comprises a first bridge arm and a second bridge connected in parallel between the positive output terminal and the negative output terminal. The second bridge arm and the third bridge arm, the first inductor connected between the first switch and the intermediate node of the first bridge arm, are connected to the intermediate node of the second switch and the second bridge arm The second inductance between is connected to the third inductance between the third switch and the intermediate node of the third bridge arm.
The three-phase pulse width modulation rectifier circuit according to claim 1, wherein the three-phase pulse width modulation rectifier circuit includes a control device for

Controlling the conduction of the first unidirectional charging branch and the second unidirectional charging branch;

When the voltage across the first capacitor and/or the voltage across the second capacitor reaches the first threshold voltage, the first unidirectional charging branch and the second unidirectional charging branch are controlled to stop charging, wherein The first threshold voltage is less than the peak voltage of the first phase alternating current;

Controlling the first switch to close;

Controlling the operation of the three-phase pulse width modulation rectifier to convert the first-phase alternating current into direct current to charge the first capacitor and the second capacitor;

When the voltage across the first capacitor and/or the voltage across the second capacitor reaches the second threshold voltage, stop charging the first capacitor and the second capacitor, wherein the second threshold voltage is greater than the second threshold voltage. The peak voltage of any phase of the three-phase alternating current; and

The second switch and the third switch are controlled to be closed.
The three-phase pulse width modulation rectifier circuit according to claim 5, wherein the first unidirectional charging branch includes a first diode, a first charging switch, and a first resistor connected in series, and the second The unidirectional charging branch includes a second diode, a second charging switch and a second resistor connected in series, and the control device is used for

Controlling the first charging switch and the second charging switch to be closed to charge the first capacitor and the second capacitor respectively; and

When the voltage across the first capacitor and/or the voltage across the second capacitor reaches the first threshold voltage, the first charging switch and the second charging switch are controlled to be turned off.
The three-phase pulse width modulation rectifier circuit according to claim 5, wherein the three-phase pulse width modulation rectifier comprises a first bridge arm and a second bridge connected in parallel between the positive output terminal and the negative output terminal. The second bridge arm and the third bridge arm, the first inductor connected between the first switch and the intermediate node of the first bridge arm, are connected to the intermediate node of the second switch and the second bridge arm The second inductance between the second inductance is connected to the third inductance between the third switch and the intermediate node of the third bridge arm; the control device is used to provide a pulse width modulation signal to the first bridge arm to enable It works in a pulse width modulation mode, and converts the first-phase alternating current into direct current.
A precharging method for the three-phase pulse width modulation rectifier circuit as claimed in claim 1, comprising the following steps in sequence:

Step 1), controlling the conduction of the first unidirectional charging branch and the second unidirectional charging branch;

Step 2), when the voltage across the first capacitor and/or the voltage across the second capacitor reaches the first threshold voltage, control the first unidirectional charging branch and the second unidirectional charging branch to stop Charging, wherein the first threshold voltage is less than the peak voltage of the first phase alternating current;

Step 3), controlling the first switch to close;

Step 4), controlling the operation of the three-phase pulse width modulation rectifier to convert the first-phase alternating current to direct current to charge the first capacitor and the second capacitor;

Step 5), when the voltage across the first capacitor and/or the voltage across the second capacitor reaches a second threshold voltage, stop charging the first capacitor and the second capacitor, wherein the second capacitor The threshold voltage is greater than the peak voltage of any phase of the three-phase alternating current;

Step 6), controlling the second switch and the third switch to close.
The pre-charging method according to claim 8, wherein the first unidirectional charging branch of the three-phase pulse width modulation rectifier circuit includes a first diode, a first charging switch, and a first resistor connected in series, and the second single The charging branch includes a second diode, a second charging switch and a second resistor connected in series, wherein,

The step 1) includes controlling the first charging switch and the second charging switch to be closed to charge the first capacitor and the second capacitor respectively;

The step 2) includes controlling the first charging switch and the second charging switch to be turned off.
The precharging method according to claim 8, wherein the three-phase pulse width modulation rectifier includes a first bridge arm, a second bridge arm, and a third bridge arm connected in parallel between the positive output terminal and the negative output terminal , The first inductor connected between the first switch and the intermediate node of the first bridge arm, and the second inductor connected between the second switch and the intermediate node of the second bridge arm, connected The third inductance between the third switch and the intermediate node of the third bridge arm; wherein, the step 4) includes providing a pulse width modulation signal to the first bridge arm to make it in a pulse width modulation manner Work, and convert the first-phase alternating current into direct current.