WO2018210301A1

WO2018210301A1 - T-type converter circuit and corresponding three-phase converter circuit

Info

Publication number: WO2018210301A1
Application number: PCT/CN2018/087270
Authority: WO
Inventors: 陈成辉; 易龙强; 黄文俊
Original assignee: 厦门科华恒盛股份有限公司
Priority date: 2017-05-19
Filing date: 2018-05-17
Publication date: 2018-11-22

Abstract

Provided are a T-type converter circuit and corresponding three-phase converter circuit. In the T-type converter circuit, one inductor, four diodes and two capacitors are added to a T-type converter circuit of the prior art, thereby enabling both a controllable switch device and a diode device to perform soft switching, reducing the power consumption of a power device and the diode device. The corresponding three-phase converter circuit also is capable of enabling the controllable switch device and diode device to perform soft switching, reducing the power consumption of the power device and the diode device.

Description

A T-type conversion circuit and a corresponding three-phase conversion circuit

This application is required to be submitted to the Chinese Patent Office on May 19, 2017, the application number is 201710361250.1, the invention name is “a T-type conversion circuit and the corresponding three-phase conversion circuit”, and the same day is submitted to the Chinese Patent Office, the application number is 201720561647.0 The present invention is entitled to the benefit of the Chinese Patent Application, the disclosure of which is incorporated herein by reference.

Technical field

The present invention relates to the field of electrical energy conversion, and in particular to a T-type conversion circuit and a corresponding three-phase conversion circuit.

Background technique

In the prior art, a conversion circuit of a T-type layout has been widely used. The conversion circuit of the T-shaped layout generally comprises two vertically arranged controllable switching devices and two laterally arranged controllable switching devices; two vertically arranged controllable switching devices are connected in series, one end is connected to the positive bus bar and the other end is connected Negative busbar; the connection point between two vertically arranged controllable switching devices is used as the input and output end of the conversion circuit; two laterally set controllable switching devices are generally disposed on the intermediate bridge arm, and one end of the intermediate bridge arm is connected to Input and output, the other end of the intermediate bridge is connected to the neutral line. The two laterally disposed controllable switching devices are generally connected in three ways on the intermediate bridge arms, as shown in Figures 1, 2 and 3. Fig. 1 shows a case where two laterally disposed controllable switching devices are connected in reverse series with each other and connected to each other with a drain or a collector. Figure 2 shows the case where two laterally disposed controllable switching devices are connected in series in anti-phase with each other connected to the source or emitter. Fig. 3 shows the case where two laterally arranged controllable switching devices are connected in series with one diode and then connected in parallel to the intermediate bridge arm. In the above three figures, the controllable switching devices each include an IGBT tube and a freewheeling diode connected in anti-parallel with the IGBT tube. Compared with the bi-level conversion circuit, the T-type three-level conversion circuit in the prior art has the advantages of a single IGBT tube blocking voltage halving, small harmonics, low loss, high efficiency and the like.

In the T-type three-level conversion circuit, the power consumption of each IGBT tube can be divided into on-state power consumption and on-off power consumption, wherein the on-off power consumption can separately separate the phase power consumption and the power consumption in the shutdown phase. When the operating frequency is low, the on-state power consumption is dominant; but when the operating frequency is high, the on-off power consumption is increased to the main power consumption, where the power consumption in the turn-on phase is greater than the power consumption in the turn-off phase. Therefore, in the case of a high operating frequency, a "soft switching" is required. The so-called "soft switching" means that the controllable switching device can realize zero voltage switching (ZVS), zero current switching (ZCS) or zero voltage zero current. The switch (ZVZXCS), or the current or voltage rises with a finite slope during the on/off process. If the soft switch is not possible, the following problems occur:

1) Power device (controllable switching device) has large loss; and the temperature of the power device rises, not only the operating frequency cannot be improved, but also the current and voltage capacity of the power device cannot reach the rated index, so that the power device cannot operate under the rated condition. , thereby restricting the application of the three-level topology;

2) The power device is easily broken down twice; under the inductive load condition, there is a spike voltage when the power device is turned off; and under the capacitive load condition, there is a spike current when the power device is turned on; thus, it is easy to cause secondary breakdown. Greatly jeopardize the safe operation of power devices, making it necessary to design a large safe working area (SOA);

3) Large EMI electromagnetic interference is generated; the inter-electrode parasitic capacitance of the power device itself is an extremely important parameter when operating in a high frequency operating state. This kind of inter-electrode capacitance has two disadvantages in the switching process of the power device: (1) When the high-voltage is turned on, the inter-pole parasitic capacitance energy is absorbed and dissipated by the device itself, which is bound to generate temperature rise and frequency. The higher the temperature rises, the more serious it is; (2) the dv/dt is coupled to the output when the inter-electrode voltage is switched, causing electromagnetic interference and making the system unstable. In addition, the inter-electrode capacitance and the stray inductance in the circuit will oscillate, interfering with the normal operation of the system;

4) The circuit topology is very sensitive to the parasitic parameters of the power device; when the soft switch cannot be realized, there may be a problem of the pass-through of the upper and lower arms, and since the soft switch cannot be realized, the power device also has a turn-on delay time (dead time). In the case of high frequency, in order to eliminate the influence of dead time on the performance of the inverter, the corrective measures taken make the design of the whole system complicated;

5) It is necessary to design an absorbing circuit for limiting the di/dt when the power device is turned on and the dv/dt when the power device is turned on, so that the dynamic switching trajectory is reduced to the DC safe area SOA, ensuring that the power device can operate safely, but absorbs The circuit can not eliminate the switching loss, and increases the design difficulty of the entire converter. At the same time, it may cause the reverse recovery of the freewheeling diode during the energy regeneration process and the mutual interference of the absorbing circuit to cause large device stress;

6) The power device will generate noise pollution during high-frequency switching, which will result in higher requirements for the input and output filters of the conversion circuit.

Based on the above six points, it is urgent to implement the soft switching of the T-type three-level conversion circuit.

Summary of the invention

The object of the present invention is to solve the problems in the prior art, and provide a T-type conversion circuit and a corresponding three-phase conversion circuit, so that the power device can realize soft switching operation, thereby reducing power consumption of the power device and the diode device, and Solve the problems in the prior art.

In order to achieve the above object, the present invention adopts the following technical solutions:

A T-type conversion circuit comprising two vertically arranged controllable switching devices, two laterally disposed controllable switching devices, an inductor, a first diode, a second diode, a third diode, and a a four diode, a first capacitor and a second capacitor; the two vertically arranged controllable switching devices are connected in series, one end is connected to the positive bus bar, and the other end is connected to the negative bus bar; the two vertically arranged The connection point between the control switching devices is used as an input and output terminal; the two laterally disposed controllable switching devices are located on the intermediate bridge arm; one end of the intermediate bridge arm is connected to the input and output ends, and the other end of the intermediate bridge arm is connected to One end of the inductor; the other end of the inductor is connected to the neutral line; among the two laterally set controllable switching devices, the controllable switching device that meets the first condition or the second condition is defined as the second controllable switching device, which conforms to the The third condition or the fourth condition of the controllable switching device is defined as a third controllable switching device; the first condition is that the source or emitter of the controllable switching device is connected to the inductor; the second condition is The drain of the controllable switching device or The collector is connected to the input and output terminals; the third condition is that the source or the emitter of the controllable switching device is connected to the input and output terminals; the fourth condition is the drain or collector of the controllable switching device Connected to the inductor; the first diode and the second diode are connected in series, the cathode of the first diode is connected to the positive bus, and the anode of the second diode is connected to the drain of the third controllable switching device a pole or a collector, the first capacitor is connected to a connection point of the first diode and the second diode, and the other end is connected to a source or an emitter of the third controllable switching device; The third diode and the fourth diode are connected in series, the anode of the fourth diode is connected to the negative bus, the cathode of the third diode is connected to the connection point of the intermediate bridge arm and the inductor; Connect to the connection point of the third diode and the fourth diode, and connect the other end to the input and output terminals.

In one embodiment, the second controllable switching device is connected in reverse series with the third controllable switching device, the drain or collector of the second controllable switching device and the third controllable switching device The drain or collector is connected.

In a second embodiment, the second controllable switching device is connected in reverse series with the third controllable switching device, and the source or emitter of the second controllable switching device and the third controllable switch The source or emitter of the device is connected.

In a third embodiment, the intermediate bridge arm further includes a fifth diode and a sixth diode; a source or an emitter of the third controllable switching device and the second controllable switch a drain or a collector of the device is connected to the input and output terminals; a source or an emitter of the second controllable switching device is connected to an anode of the fifth diode; and a drain of the third controllable switching device Or the collector is connected to the cathode of the sixth diode; the cathode of the fifth diode and the anode of the sixth diode are connected to the inductor.

Further, any one of the two vertically disposed controllable switching devices adopts an IGBT unit or a MOS unit, and when the IGBT unit is used, the IGBT unit includes an IGBT tube and a diode connected in anti-parallel with the IGBT tube. When the MOS unit is used, the MOS unit may be a MOS transistor with a body diode or a MOS transistor without an body diode and an anti-parallel diode.

Further, any one of the two laterally disposed controllable switching devices adopts an IGBT unit or a MOS unit, and when the IGBT unit is used, the IGBT unit includes an IGBT tube and a diode connected in anti-parallel with the IGBT tube; When a MOS unit is employed, the MOS unit may be a MOS transistor with a body diode or a MOS transistor without an body diode and an anti-parallel diode.

A three-phase conversion circuit comprising a first conversion circuit, a second conversion circuit, and a third conversion circuit; wherein the first conversion circuit, the second conversion circuit, and the third conversion circuit are both as claimed in claims 1 to 6 A T-type conversion circuit according to the invention; a center line of the first conversion circuit, a center line of the second conversion circuit, and a center line of the third conversion circuit are connected to each other.

Compared with the prior art, the technical solution described in the present invention has the following beneficial effects:

1) In the T-type conversion circuit of the present invention, all controllable switching devices and diode devices can implement soft switching, that is, zero voltage switching (ZVS), zero current switching (ZCS) or zero voltage zero current switching (ZVZCS). Or switch between on and off with limited dv/dt and di/dt. Thereby, the on-off loss of the controllable switching device is greatly reduced, the working efficiency of the conversion circuit is improved, the power device is not easily broken down twice, and the dead time is eliminated at the same time;

2) The controllable switching device switches on and off with limited dv/dt and di/dt, so the system EMI electromagnetic interference is much more optimized than the unimplemented soft switch;

3) Since the on-off loss of the controllable switching device becomes smaller, the conversion device can work twice as much as the operating frequency of the conventional conversion device, so the output filter parameter requirements of the conversion device are reduced, and the size can be doubled. Small, which is beneficial to further reduce material costs, reduce product size, and increase product power density;

4) Compared with the prior art, only one inductor, four diodes and two capacitors are added in the invention, the number of components is increased, the structure is simple and compact, and no additional controllable switching device and control circuit are needed;

5) The three-phase conversion circuit using the above-described T-type conversion circuit also has the above effects.

DRAWINGS

The drawings described herein are intended to provide a further understanding of the invention, and are intended to be a part of the invention. In the drawing:

1 is a circuit diagram of a first case in the prior art;

2 is a schematic circuit diagram of a second case in the prior art;

3 is a schematic circuit diagram of a third case in the prior art;

4 is a schematic circuit diagram of Embodiment 1 of a T-type conversion circuit according to the present invention;

5 is a schematic circuit diagram of a second embodiment of a T-type conversion circuit according to the present invention;

6 is a schematic circuit diagram of a third embodiment of a T-type conversion circuit according to the present invention;

7 is a schematic diagram of the operation of the first embodiment of the T-type conversion circuit of the present invention before DC/AC conversion, when the inverter output voltage is a positive half cycle, before the vertical pipe is commutated to the horizontal pipe;

FIG. 8 is a schematic diagram of the first stage of the T-type conversion circuit of the present invention performing DC/AC conversion, and the inverter output voltage is a positive half cycle, and the vertical pipe is commutated to the horizontal pipe;

FIG. 9 is a schematic diagram showing the second stage operation of the first embodiment of the T-type conversion circuit of the present invention for DC/AC conversion, when the inverter output voltage is a positive half cycle;

FIG. 10 is a schematic diagram showing the operation of the first embodiment of the T-type conversion circuit of the present invention after performing DC/AC conversion, and the inverter output voltage is a positive half cycle before the horizontal pipe is commutated to the vertical pipe;

11 is a schematic diagram showing the operation of the first stage of the T-type conversion circuit of the present invention in which the DC/AC conversion is performed, and the inverter output voltage is a positive half cycle, and the horizontal pipe is commutated to the vertical pipe;

12 is a schematic diagram showing the operation of the fourth stage of the T-type conversion circuit of the present invention for DC/AC conversion, when the inverter output voltage is a positive half cycle, and the horizontal pipe is commutated to the vertical pipe;

FIG. 13 is a schematic diagram showing the operation of the first embodiment of the T-type conversion circuit of the present invention before AC/DC conversion, when the AC input voltage is positive half cycle, before the vertical pipe is commutated to the horizontal pipe;

14 is a schematic diagram showing the first stage of operation of the AC-DC conversion of the T-type conversion circuit of the present invention, in which the AC input voltage is a positive half cycle, and the vertical pipe is commutated to the horizontal pipe;

15 is a schematic diagram showing the second stage of the AC-DC conversion of the T-type conversion circuit of the present invention, in which the AC input voltage is a positive half cycle, and the vertical pipe is commutated to the horizontal pipe;

16 is a schematic diagram showing the operation of the first embodiment of the T-type conversion circuit of the present invention before AC/DC conversion, when the AC input voltage is positive half cycle, before the horizontal pipe is commutated to the vertical pipe;

17 is a schematic diagram of the operation of the first embodiment of the T-type conversion circuit of the present invention for AC/DC conversion, when the AC input voltage is a positive half cycle;

Figure 18 is a circuit diagram showing an embodiment of a three-phase conversion circuit in the present invention.

detailed description

The present invention will be further described in detail below with reference to the accompanying drawings and embodiments, in order to make the present invention. It is understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

Fig. 4 is a circuit diagram showing the first embodiment of the T-type conversion circuit of the present invention. As shown in FIG. 4, the first embodiment of the T-type conversion circuit includes two vertically arranged controllable switching devices, two laterally disposed controllable switching devices, an inductor L, a first diode D1, and a second two. The transistor D2, the third diode D3, the fourth diode D4, the first capacitor C1, the second capacitor C2, the third polarity capacitor C3, and the fourth polarity capacitor C4.

The two vertically arranged controllable switching devices are respectively a first controllable switching device and a fourth controllable switching device, wherein the first controllable switching device adopts an IGBT unit, including the first IGBT tube Q1 and the first anti-parallel connection thereof A freewheeling diode Dq1; the fourth controllable switching device adopts an IGBT unit, and includes a fourth IGBT tube Q4 and a fourth freewheeling diode Dq4 connected in anti-parallel thereto. The first IGBT tube Q1 and the fourth IGBT tube Q4 are connected in series, the collector of the first IGBT tube Q1 is connected to the positive bus, the emitter of the fourth IGBT tube Q4 is connected to the negative bus, the emitter of the first IGBT tube Q1 and the fourth IGBT The collector of the tube Q4 is connected, and the connection point serves as an input and output terminal.

Two laterally controllable switching devices on the intermediate bridge arm are respectively a second controllable switching device and a third controllable switching device, wherein the second controllable switching device adopts an IGBT unit, including a second IGBT tube Q2 and The second freewheeling diode Dq2 connected in anti-parallel; the third controllable switching device adopts an IGBT unit, and includes a third IGBT tube Q3 and a third freewheeling diode Dq3 connected in anti-parallel thereto. The second IGBT transistor Q2 and the third IGBT transistor Q3 are connected in reverse series to the intermediate bridge arm. The emitter of the third IGBT transistor Q3 is connected to the input and output terminals; the collector of the third IGBT transistor Q3 is connected to the collector of the second IGBT transistor Q2; the emitter of the second IGBT transistor Q2 is connected to the inductor L; One end is connected to the center line.

The first diode D1 and the second diode D2 are connected in series, the cathode of the first diode D1 is connected to the positive bus, and the anode of the second diode D2 is connected to the collector of the third IGBT tube Q3; One end of the capacitor C1 is connected to the connection point of the first diode D1 and the second diode D2, and the other end of the first capacitor C1 is connected to the emitter of the third IGBT tube Q3.

The third diode D3 and the fourth diode D4 are connected in series, the anode of the fourth diode D4 is connected to the negative bus, and the cathode of the third diode D3 is connected to the connection point of the inductor L and the intermediate bridge; One end of the two capacitors C2 is connected to the connection point of the third diode D3 and the fourth diode D4, and the other end of the second capacitor C2 is connected to the input and output ends.

The positive pole of the third polarity capacitor C3 is connected to the positive bus, the negative pole is connected to the neutral line; the positive pole of the fourth polarity capacitor C4 is connected to the neutral line, and the negative pole is connected to the negative bus.

In this embodiment, the controllable switching device can also adopt a MOS unit. When the MOS unit is used, the MOS unit can be a MOS tube with a body diode or a MOS tube and an anti-parallel diode without a body diode.

The T-type conversion circuit of this embodiment can realize that in the inverter and rectification process, all controllable switching devices and diode devices can realize soft switching, that is, zero voltage switching (ZVS), zero current switching (ZCS) or zero voltage. Zero current switch (ZVZCS), or on/off switching with limited dv/dt and di/dt. in particular:

When the first embodiment of the T-type conversion circuit operates in the inverter, the inverter output voltage is a positive half cycle and the inverter output voltage is a negative half cycle two half cycles, and each half cycle is further divided into a vertical pipe to a horizontal pipe. Two processes of commutation and cross tube commutation to the standpipe:

When the inverter output voltage is positive half cycle, the process of commutating the vertical pipe to the horizontal pipe is as follows:

Figure 7 shows the state before the standpipe is commutated to the cross tube. Before the vertical pipe is commutated to the horizontal pipe, before the vertical pipe is commutated to the horizontal pipe, the first IGBT pipe Q1 and the third IGBT pipe Q3 are in an on state, and the second IGBT pipe Q2 and the fourth IGBT pipe Q4 are in an off state. At this time, the current flows to the load Z through the first IGBT tube Q1, and although the third IGBT tube Q3 is turned on, no current flows. Since the first IGBT transistor Q1 is turned on, the second capacitor C2 is charged to the Vdc state. At this time, no current flows through the inductor L, and the voltage of the first capacitor C1 is zero.

Figure 8 shows the operational state of the first stage in the process of commutating the riser to the cross tube. In the first stage, the third IGBT tube remains in the on state, the fourth IGBT tube Q4 remains in the off state, and the first IGBT tube Q1 is switched from the on state to the off state, and the second IGBT tube Q2 is switched from the off state to the off state. On state. As shown in FIG. 8, during the process in which the first IGBT transistor Q1 is turned off and the second IGBT transistor Q2 is turned on, the second capacitor C2 is discharged to the load Z through the fourth diode D4. At the same time, the second capacitor C2 also charges the inductor L through the third freewheeling diode Dq3, the second IGBT transistor Q2, and the fourth diode D4. Since the voltage on the second capacitor C2 is gradually discharged to zero, the current of the load Z at the moment when the first IGBT transistor Q1 is turned off is supplied from the second capacitor C2. Therefore, the first IGBT tube Q1 is turned off in a zero voltage manner, and the turn-off loss is very small, which is a typical soft switching process. Due to the presence of the inductance L, the second IGBT tube Q2 is switched from the off state to the on state, and the current is also established in the form of di/dt, which is also a soft switching process.

Figure 9 shows the operating state of the second stage during the commutation of the riser to the cross tube. After the first phase is completed, the fourth diode D4 is turned off, and the current of the inductor L is again zero. At the same time, the fourth freewheeling diode Dq4 starts to be continuously turned on. The load Z output level is clamped at the -Vdc/2 level. The inductor L starts to store energy through the second freewheeling diode Dq2 and the third IGBT transistor Q3, and the current of the inductor L increases linearly from zero, while the current through the fourth freewheeling diode Dq4 decreases in proportion. When the current through the fourth freewheeling diode Dq4 is reduced to zero, the commutation process is completed. At this time, the fourth freewheeling diode Dq4 is turned off, and the load current is carried by the second freewheeling diode Dq2 and the third IGBT transistor Q3. In the above process, due to the presence of the inductance L, the current changes occurring through the second freewheeling diode Dq2, the second IGBT tube Q2, the fourth freewheeling diode Dq4, and the third IGBT tube Q3 are all finite current change rates. Di/dt. So in the process, they all implement soft switching. The freewheeling process of the fourth diode D4 is also turned on and off with a limited current change rate di/dt, so that the conduction loss of the fourth diode D4 can be significantly reduced.

When the inverter output voltage is in the positive half cycle, the commutation process of the horizontal pipe to the vertical pipe is as follows:

Fig. 10 shows the state after the inverter tube is commutated to the horizontal tube when the inverter output voltage is in the positive half cycle, or the state before the cross tube is commutated to the vertical tube. Before the horizontal pipe is commutated to the vertical pipe, the first IGBT pipe Q1 and the fourth IGBT pipe Q4 are in an off state, and the second IGBT pipe Q2 and the third IGBT pipe Q3 are in an on state. At this time, current flows from the inductor L through the second freewheeling diode Dq2 and the third IGBT transistor Q3 to the load Z, and the second IGBT transistor Q2 is turned on but no current flows. The first capacitor C1 and the second capacitor C2 are in a zero voltage discharge state, and the current passing through the inductor L is equal to the current passing through the load Z.

Figure 11 shows the operational state of the third stage during the commutation of the cross tube to the riser. In the third stage, the third IGBT tube Q3 is kept in an on state, the fourth IGBT tube Q4 is kept in an off state, and the first IGBT tube Q1 is turned from the off state to the on state, and the second IGBT tube Q2 is turned on. The status goes to the cutoff state. As shown in FIG. 11, after the first IGBT transistor Q1 is turned on and the second IGBT transistor Q2 is turned off, the upper half bus voltage passes through the first IGBT transistor Q1, the second freewheeling diode Dq2, and the third IGBT transistor Q3 is opposite to the inductor L. Pressurization forces the current through inductor L to decrease linearly. At the same time, the upper half bus supplies power to the load Z through the first IGBT tube Q1. The above two circuits coexist and work at the same time. As the current flowing through the inductor L is gradually reduced, the load current transitions to the current flowing through the first IGBT transistor Q1. When the current flowing through the inductor L is zero, the second freewheeling diode Dq2 is reversely turned off, and since the second IGBT transistor Q2 is turned off, the current does not flow through the intermediate bridge arm.

When the first IGBT transistor Q1 is turned on, since the load current is taken up by the inductor L, the first IGBT transistor Q1 is turned on to be a zero current conduction, and the current of the first IGBT transistor Q1 during the conduction is limited di/ The dt mode is established, so the first IGBT tube Q1 is in a soft switching mode of operation. The second IGBT transistor Q2 has no current flowing during the transition from the on state to the off state, and also belongs to the soft switching mode of operation.

Figure 12 shows the operational state of the fourth stage in the process of commutating the cross tube to the standpipe. After the third phase is completed, the load Z output level is clamped at the Vdc/2 level due to the zero voltage of the second capacitor C2. Therefore, as shown in FIG. 16, the upper half bus voltage charges the second capacitor C2 through the first IGBT transistor Q1, the third diode D3, and the inductor L. Due to the presence of the inductance L, when the second capacitor C2 is charged to a voltage of Vdc, the third diode D3 is reversely turned off, the charging and commutation processes are completed, and the current flows back to the load Z through the first IGBT tube Q1, that is, The state of Figure 7.

During the charging of the second capacitor C2, the third freewheeling diode Dq3 and the third diode D3 are turned on and off with a finite current change rate di/dt, therefore, the third freewheeling diode Dq3 and the third two The switching loss during the turn-on and turn-off of the transistor D3 is very low, and belongs to the soft switching mode of operation.

The commutation process when the inverter output voltage is negative half cycle is similar to the commutation process when the inverter output voltage is positive half cycle. The commutation of the vertical pipe to the horizontal pipe or the commutation of the horizontal pipe to the vertical pipe also requires two experiences. Stage, no longer detailed here.

When the conversion circuit operates on rectification, the AC input voltage is a positive half cycle and the AC input voltage is a negative half cycle for two half cycles, and each half cycle is further divided into a vertical tube to a horizontal tube commutation and a horizontal tube to a vertical tube. Flow two processes:

When the AC input voltage is positive half cycle, the process of commutating the vertical pipe to the horizontal pipe is as follows:

Figure 13 shows the state before the riser is commutated to the cross tube. Before the vertical pipe is commutated to the horizontal pipe, the first IGBT pipe Q1 and the third IGBT pipe Q3 are in an on state, and the second IGBT pipe Q2 and the fourth IGBT pipe Q4 are in an off state. The rectified current flows from the first freewheeling diode Dq1 to the bus. The third IGBT transistor Q3 is turned on but no current passes. Since the third IGBT transistor is turned on, the first capacitor C1 is in a zero voltage discharge state. Since the first IGBT transistor Q1 is turned on, the second capacitor C2 is charged to the Vdc state, at which time the current through the inductor L is zero.

Figure 14 shows the operational state of the first stage of the commutation process of the riser to the cross tube. In the first stage, the third IGBT tube Q3 is kept in an on state, and the fourth IGBT tube Q4 is kept in an off state. The first IGBT transistor Q1 is switched from the on state to the off state, and the second IGBT transistor Q2 is turned from the off state to the on state. As shown in FIG. 14, in this process, since the first freewheeling diode Dq1 is in an on state, the first freewheeling diode Dq1, the third freewheeling diode Dq3, the second IGBT transistor Q2, and the inductor L are established with the input source Z. Loop. Due to the presence of the inductance L, the current through the intermediate bridge arm increases linearly from zero; at the same time, the current through the first freewheeling diode Dq1 decreases linearly until the current through the inductor L increases to the rectified current, at this time the first continuation The flow diode Dq1 is turned off.

Due to the presence of the first freewheeling diode Dq1, the process of turning the first IGBT transistor Q1 from on to off belongs to zero voltage and zero current shutdown. Due to the presence of the inductance L, the current of the second IGBT transistor Q2 increases linearly from off to on, so the conduction process of the second IGBT transistor Q2 is zero current conduction. Both are typical soft switching processes.

Figure 15 shows the working state of the second stage of the process of the lack of money from the riser to the cross tube. After the first phase is completed, the first freewheeling diode Dq1 is turned off, and the second capacitor C2 is discharged through the third freewheeling diode Dq3, the second IGBT transistor Q2, the fourth diode D4, and the inductor L. Discharge to zero. The second phase is completed.

When the AC input voltage is in the positive half cycle, the commutation process of the horizontal pipe to the vertical pipe is as follows:

Fig. 16 shows the state after the end of the commutation process of the riser to the cross tube, that is, the state before the cross tube is commutated to the riser. At this time, the second capacitor C2 is discharged, and the rectified current is carried by the third freewheeling diode Dq3, the second IGBT tube Q2, and the inductor L. The first IGBT tube Q1 and the fourth IGBT tube Q4 are in an off state, and the second IGBT tube Q2 and the third IGBT tube Q3 are in an on state. Among them, although the third IGBT transistor Q3 is in an on state, no current flows. The first capacitor C1 and the second capacitor C2 are both in a zero voltage discharge state. The current through the inductor L is the rectified current.

Figure 17 shows the operational state of the flow of the cross tube to the riser. When the horizontal pipe is commutated to the vertical pipe, the third IGBT tube Q3 is kept in an on state, the fourth IGBT tube Q4 is kept in an off state, and the first IGBT tube Q1 is turned from the off state to the on state, and the second IGBT tube Q2 is Go from the on state to the off state. During the turn-off of the second IGBT transistor Q2, the rectified current is transferred from passing through the second IGBT transistor Q2 to passing through the second capacitor C2 due to the presence of the second capacitor C2. The voltage of the second IGBT transistor Q2 increases linearly from zero, and is zero voltage and zero current shutdown. During the charging process of the second capacitor C2 by the input source Z through the third diode D3 and the inductor L, the current flowing through the first freewheeling diode Dq1 to the bus line gradually increases, due to the presence of the first freewheeling diode Dq1, The first IGBT transistor Q1 has no current passing, so the conduction process of the first IGBT transistor Q1 belongs to zero current and zero voltage conduction. It can be seen from the above analysis that in the process of commutating the cross tube to the vertical tube, the on and off processes of the first IGBT tube Q1 and the second IGBT tube Q2 are both soft switching processes.

When the current of the inductor L gradually changes from the rectified current to zero, the second capacitor C2 is completed, the third diode D3 and the third freewheeling diode Dq3 are turned off, and the first freewheeling diode Dq1 is turned on to complete the entire commutation process. Returning to the state of FIG.

The commutation process when the AC input voltage is negative half cycle is similar to the commutation process when the AC input voltage is positive half cycle, and the process of commutating the vertical pipe to the horizontal pipe or the horizontal pipe to the vertical pipe is similar. Detailed.

Fig. 5 is a circuit diagram showing the second embodiment of the T-type conversion circuit of the present invention. As shown in FIG. 5, the second embodiment of the T-type conversion circuit includes two vertically arranged controllable switching devices, two laterally disposed controllable switching devices, an inductor L, a first diode D1, and a second two. The transistor D2, the third diode D3, the fourth diode D4, the first capacitor C1, the second capacitor C2, the third polarity capacitor C3, and the fourth polarity capacitor C4.

Two laterally controllable switching devices on the intermediate bridge arm are respectively a second controllable switching device and a third controllable switching device, wherein the second controllable switching device adopts an IGBT unit, including a second IGBT tube Q2 and The second freewheeling diode Dq2 connected in anti-parallel; the third controllable switching device adopts an IGBT unit, and includes a third IGBT tube Q3 and a third freewheeling diode Dq3 connected in anti-parallel thereto. The second IGBT transistor Q2 and the third IGBT transistor Q3 are connected in reverse series to the intermediate bridge arm. The collector of the second IGBT transistor Q2 is connected to the input and output terminals; the emitter of the second IGBT transistor Q2 is connected to the emitter of the third IGBT transistor Q3; the collector of the third IGBT transistor is connected to the inductor L; the other end of the inductor L Connect to the center line.

The second embodiment is similar to the first embodiment in that the controllable switching device and the diode realize the soft switching in the commutation process, and will not be described in detail herein.

Fig. 6 is a circuit diagram showing the third embodiment of the T-type conversion circuit of the present invention. As shown in FIG. 6, the second embodiment of the T-type conversion circuit includes two vertically arranged controllable switching devices, two laterally disposed controllable switching devices, an inductor L, a first diode D1, and a second two. The transistor D2, the third diode D3, the fourth diode D4, the fifth diode D5, the sixth diode D6, the first capacitor C1, the second capacitor C2, the third polarity capacitor C3, and the Quad polarity capacitor C4.

The intermediate bridge arm includes two laterally disposed controllable switching devices, a fifth diode and a sixth diode. The two laterally controllable switching devices are respectively a second controllable switching device and a third controllable switching device, wherein the second controllable switching device adopts an IGBT unit, including a second IGBT tube Q2 and a second connected in anti-parallel thereto The freewheeling diode Dq2; the third controllable switching device adopts an IGBT unit, and includes a third IGBT tube Q3 and a third freewheeling diode Dq3 connected in anti-parallel thereto. The collector of the second IGBT transistor Q2 and the emitter of the third IGBT transistor Q3 are connected to the input and output terminals; the emitter of the second IGBT transistor Q2 is connected to the anode of the fifth diode D5, and the collector of the third IGBT transistor Q3 Connected to the cathode of the sixth diode D6, the cathode of the fifth diode D5 and the anode of the sixth diode D6 are connected to one end of the inductor L; the other end of the inductor L is connected to the center line.

The third embodiment is similar to the first embodiment in that the controllable switching device and the diode realize the soft switching in the commutation process, and will not be described in detail herein.

As can be seen from the above three embodiments, in the T-type conversion circuit of the present invention, all controllable switching devices and diode devices can implement soft switching, that is, zero voltage switching (ZVS), zero current switching (ZCS) or zero. Voltage zero current switch (ZVZCS), or on/off switching with limited dv/dt and di/dt. Thereby, the on-off loss of the controllable switching device is greatly reduced, the working efficiency of the conversion circuit is improved, the power device is not easily broken by the second breakdown, and the dead time is eliminated.

The controllable switching device switches on and off with limited dv/dt and di/dt, so the system EMI electromagnetic interference is much more optimized than the unimplemented soft switch.

Since the on-off loss of the controllable switching device becomes smaller, the conversion device can be multiplied by the operating frequency of the conventional conversion device, so that the output filter parameter requirements of the conversion device are reduced, and the size can be reduced by a factor of two. This will help to further reduce material costs, reduce product size, and increase product power density.

Compared with the prior art, only one inductor, four diodes and two capacitors are added in the invention, the number of components is increased, the structure is simple and compact, and no additional controllable switching device and control circuit are needed.

Fig. 18 is a circuit diagram showing an embodiment of a three-phase conversion circuit in the present invention. As shown in FIG. 18, the three-phase conversion circuit in the embodiment includes a first conversion circuit, a second conversion circuit, and a third conversion circuit; the first conversion circuit, the second conversion circuit, and the third conversion circuit all adopt the T-type conversion described above. The T-type conversion circuit described in Embodiment 1 of the circuit; the center line of the first conversion circuit, the center line of the second conversion circuit, and the center line of the third conversion circuit are connected to each other. Of course, the first conversion circuit, the second conversion circuit, and the third conversion circuit may also adopt the T-type conversion circuit described in the second embodiment or the third embodiment of the above-described T-type conversion circuit, and the effect is the same.

The above description describes the preferred embodiments of the present invention, but it should be understood that the present invention is not limited to the embodiments described above, and should not be construed as limiting the other embodiments. Modifications made by those skilled in the art in light of the teachings of the present invention.

Claims

A T-type conversion circuit, comprising: two vertically arranged controllable switching devices, two laterally set controllable switching devices, an inductor, a first diode, a second diode, and a third a pole tube, a fourth diode, a first capacitor and a second capacitor;

The two vertically arranged controllable switching devices are connected in series, one end is connected to the positive bus bar, and the other end is connected to the negative bus bar;

The connection point between the two vertically disposed controllable switching devices serves as an input and output terminal;

The two laterally disposed controllable switching devices are located on the intermediate bridge arm; one end of the intermediate bridge arm is connected to the input and output ends, and the other end of the intermediate bridge arm is connected to one end of the inductor; the other end of the inductor is connected to the neutral line;

In the two laterally disposed controllable switching devices, the controllable switching device that meets the first condition or the second condition is defined as a second controllable switching device, and the controllable switching device definition conforms to the third condition or the fourth condition. a third controllable switching device; the first condition is that the source or emitter of the controllable switching device is connected to the inductor; and the second condition is that the drain or collector of the controllable switching device is connected to The third condition is that the source or the emitter of the controllable switching device is connected to the input and output terminals; the fourth condition is that the drain or collector of the controllable switching device is connected to the inductor;

The first diode and the second diode are connected in series, the cathode of the first diode is connected to the positive bus, and the anode of the second diode is connected to the drain or collector of the third controllable switching device The first capacitor is connected to the connection point of the first diode and the second diode, and the other end is connected to the source or the emitter of the third controllable switching device;

The third diode and the fourth diode are connected in series, the anode of the fourth diode is connected to the negative bus, and the cathode of the third diode is connected to the connection point of the inductor and the intermediate bridge arm; The second capacitor is connected to the connection point of the third diode and the fourth diode, and the other end is connected to the input and output terminals.
A T-type conversion circuit according to claim 1, wherein said second controllable switching device is connected in reverse series with said third controllable switching device, and leakage of said second controllable switching device The pole or collector is coupled to the drain or collector of the third controllable switching device.
A T-type conversion circuit according to claim 1, wherein said second controllable switching device is connected in reverse series with said third controllable switching device, and the source of said second controllable switching device The pole or emitter is coupled to the source or emitter of the third controllable switching device.
A T-type conversion circuit according to claim 1, wherein the intermediate bridge arm further comprises a fifth diode and a sixth diode;

The source or emitter of the third controllable switching device and the drain or collector of the second controllable switching device are connected to the input and output terminals;

The source or emitter of the second controllable switching device is connected to the anode of the fifth diode;

The drain or collector of the third controllable switching device is connected to the cathode of the sixth diode;

The cathode of the fifth diode and the anode of the sixth diode are connected to the inductor.
A T-type conversion circuit according to any one of claims 1 to 4, wherein any one of said two vertically disposed controllable switching devices employs an IGBT unit or a MOS unit. In the IGBT unit, the IGBT unit includes an IGBT tube and a diode connected in anti-parallel with the IGBT tube; when the MOS unit is used, the MOS unit may be a MOS tube with a body diode or a MOS tube including a body diode And anti-parallel diodes.
A T-type conversion circuit according to any one of claims 1 to 4, wherein any one of said two laterally disposed controllable switching devices employs an IGBT unit or a MOS unit when an IGBT is employed In the unit, the IGBT unit includes an IGBT tube and a diode connected in anti-parallel with the IGBT tube; when the MOS unit is used, the MOS unit may be a MOS tube with a body diode or a MOS tube including a body diode and Anti-parallel diode.
A three-phase conversion circuit, comprising: a first conversion circuit, a second conversion circuit, and a third conversion circuit; wherein the first conversion circuit, the second conversion circuit, and the third conversion circuit are both as claimed in claim 1. A T-type conversion circuit according to any one of the preceding claims; wherein a center line of the first conversion circuit, a center line of the second conversion circuit, and a center line of the third conversion circuit are connected to each other.