CN108964490B

CN108964490B - T-shaped conversion circuit and corresponding three-phase conversion circuit and conversion device

Info

Publication number: CN108964490B
Application number: CN201710358454.XA
Authority: CN
Inventors: 黄文俊; 苏先进; 易龙强
Original assignee: Xiamen Kehua Hengsheng Co Ltd
Current assignee: Kehua Data Co Ltd
Priority date: 2017-05-19
Filing date: 2017-05-19
Publication date: 2020-08-28
Anticipated expiration: 2037-05-19
Also published as: CN108964490A

Abstract

The invention discloses a T-shaped conversion circuit, a corresponding three-phase conversion circuit and a corresponding conversion device. In the T-type conversion circuit, an inductor, four diodes and two capacitors are added in the T-type conversion circuit in the prior art, so that soft switching can be realized by a controllable switching device and a diode device, and the power consumption of a power device and the power consumption of the diode device are reduced. By adopting the conversion device of the T-shaped conversion circuit, components in the prior art and newly added components in the technical scheme are combined into a circuit module, so that the improvement cost can be greatly reduced under the condition of basically not changing the internal circuit layout of the existing inversion/rectification device, the topological structure is compact, the busbar design is simple, and the electrical layout and the structural design are greatly facilitated.

Description

T-shaped conversion circuit and corresponding three-phase conversion circuit and conversion device

Technical Field

The invention relates to the field of electric energy conversion, in particular to a T-shaped conversion circuit.

Background

In the prior art, a conversion circuit with a T-type layout has been widely used. A T-topology conversion circuit generally includes two vertically arranged controllable switching devices and two horizontally arranged controllable switching devices; two controllable switching devices which are vertically arranged are connected in series, one end of each controllable switching device is connected with a positive bus, and the other end of each controllable switching device is connected with a negative bus; a connection point between the two vertically arranged controllable switching devices is used as an input end and an output end of the conversion circuit; two controllable switching devices arranged transversely are generally arranged on a middle bridge arm, one end of the middle bridge arm is connected to an input end and an output end, and the other end of the middle bridge arm is connected to a neutral line. The two laterally arranged controllable switching devices are generally connected in series and in parallel on the middle bridge arm, wherein the parallel connection is shown in fig. 1. The controllable switching devices comprise IGBT tubes and freewheeling diodes connected with the IGBT tubes in an anti-parallel mode. Compared with a double-level conversion circuit, the T-type three-level conversion circuit in the prior art has the advantages of halving blocking voltage of a single IGBT tube, small harmonic wave, 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 be divided into on-stage power consumption and off-stage power consumption. When the operating frequency is low, the on-state power consumption is dominant; however, when the operating frequency is high, the on-off power consumption is increased to be the main power consumption, wherein the power consumption in the on-state is larger than that in the off-state. Therefore, in case of high operating frequencies, it is necessary to implement "soft switching", which means that the controllable switching device can implement Zero Voltage Switching (ZVS), Zero Current Switching (ZCS) or zero voltage zero current switching (ZVZXCS), or that the current or voltage rises with a limited slope during switching. If soft switching cannot be achieved, the following problems arise:

1. the power device (controllable switch device) has large loss; the temperature of the power device is increased, so that the working frequency cannot be improved, the current and voltage capacity of the power device cannot reach the rated index, and the power device cannot operate under the rated condition, thereby restricting the application of the three-level topology;

2. the power device is easy to be broken down for the second time; under the condition of inductive load, peak voltage exists when the power device is switched off; under the condition of capacitive load, peak current exists when the power device is switched on; therefore, secondary breakdown is easily caused, the safe operation of the power device is greatly damaged, and a larger Safe Operating Area (SOA) needs to be designed;

3. generating larger EMI electromagnetic interference; in the operation of the high-frequency operation state, the inter-electrode parasitic capacitance of the power device is an extremely important parameter. Such an interelectrode capacitance causes two disadvantages during switching of the power device: (1) when the device is switched on under high voltage, the inter-electrode parasitic capacitance energy storage is absorbed and dissipated by the device, so that temperature rise is generated, and the temperature rise is more serious when the frequency is higher; (2) dv/dt is coupled to the output terminal during the voltage conversion of the interelectrode capacitor, which causes electromagnetic interference and makes the system unstable. In addition, the inter-electrode capacitance and stray inductance in the circuit can generate oscillation, and the normal work of the system is interfered;

4. the circuit topology is very sensitive to the parasitic parameters of the power device; when the soft switch cannot be realized, the problem of direct connection of an upper bridge arm and a lower bridge arm may exist, and because the soft switch cannot be realized, the power device also has turn-on delay time (dead time), and under the condition of high frequency, in order to eliminate the influence of the dead time on the performance of the inverter, the adopted correction measures further complicate the design of the whole system;

5. an absorption circuit is required to be designed, the absorption circuit is used for limiting di/dt when the power device is switched on and dv/dt when the power device is switched off, so that a dynamic switch track is reduced to a SOA (service oriented architecture) in a direct current safety area, the power device can be ensured to run safely, but the absorption circuit cannot eliminate switching loss, the design difficulty of the whole conversion device is increased, and meanwhile, larger device stress caused by reverse recovery of a freewheeling diode and mutual interference of the absorption circuit in the energy regeneration process can be caused;

6. the power device generates noise pollution when switching at high frequency, so that the requirement of the conversion circuit on an input filter and an output filter is high.

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

Disclosure of Invention

The present invention is directed to solve the problems of the prior art, and provides a T-type converter circuit, a three-phase converter circuit and a converter apparatus thereof, so that a power device can perform soft switching operation, thereby reducing power consumption of the power device and a diode device, and solving the problems of the prior art.

In order to achieve the purpose, the invention adopts the following technical scheme:

a T-type conversion circuit comprises a first controllable switch device, a second controllable switch device, a third controllable switch device, a fourth controllable switch device, an inductor, a first diode, a second diode, a third diode, a fourth diode, a fifth diode, a sixth diode, a first capacitor and a second capacitor; the first controllable switching device and the fourth controllable switching device are connected in series, the drain electrode or the collector electrode of the first controllable switching device is connected with the positive bus, and the source electrode or the emitter electrode of the fourth controllable switching device is connected with the negative bus; the connection point between the first controllable switching device and the fourth controllable switching device is used as an input end and an output end; the second controllable switch device and the third controllable switch device are respectively connected with the fifth diode and the sixth diode in series and then connected in parallel to form a middle bridge arm, one end of the middle bridge arm is connected to the input and output end, the other end of the middle bridge arm is connected to one end of the inductor, and the other end of the inductor is connected to the neutral line; wherein the drain or collector of said second controllable switching device is connected to the input or output terminal or the source or emitter of said second controllable switching device is connected to the inductor; the drain or collector of the third controllable switching device is connected to the inductor or the source or emitter of the third controllable switching device is connected to the input/output end; the first diode and the second diode are connected in series, the cathode of the first diode is connected to the positive bus, the anode of the second diode is connected to the connection point of the inductor and the middle bridge arm, one end of the first capacitor is connected to the connection point of the first diode and the second diode, and the other end of the first capacitor is connected to the input and output end; 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 anode of the sixth diode; one end of the second capacitor is connected to the connection point of the third diode and the fourth diode, and the other end of the second capacitor is connected to the cathode of the sixth diode.

In the first embodiment, in the middle bridge arm, the source or the emitter of the second controllable switching device is connected to the inductor, the drain or the collector of the second controllable switching device is connected to the cathode of the fifth diode, and the anode of the fifth diode is connected to the input and output end; the drain or collector of the third controllable switching device is connected to the inductor, the source or emitter of the third controllable switching device is connected to the anode of the sixth diode, and the cathode of the sixth diode is connected to the input/output terminal.

In a second embodiment, in the middle bridge arm, the cathode of the fifth diode is connected to the inductor, the anode of the fifth diode is connected to the source or the emitter of the second controllable switching device, and the drain or the collector of the second controllable switching device is connected to the input/output end; the anode of the sixth diode is connected to the inductor, the cathode of the sixth diode is connected to the drain or collector of the third controllable switching device, and the source or emitter of the third controllable switching device is connected to the input/output terminal.

Further, any one of the two vertically arranged controllable switching devices adopts an IGBT unit or an MOS unit, and when the IGBT unit is adopted, the IGBT unit comprises an IGBT tube and a diode connected with the IGBT tube in an anti-parallel manner; when the MOS unit is adopted, the MOS unit can be an MOS tube with a body diode or comprise an MOS tube without a body diode and an anti-parallel diode.

Further, any one of the two laterally arranged controllable switching devices adopts an IGBT unit or an MOS unit, and when the IGBT unit is adopted, the IGBT unit comprises an IGBT tube and a diode connected with the IGBT tube in anti-parallel; when the MOS unit is adopted, the MOS unit can be an MOS tube with a body diode or comprise an MOS tube without a body diode and an anti-parallel diode.

A three-phase conversion circuit comprises 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 any one of the T-shaped conversion circuits; the neutral line of the first conversion circuit, the neutral line of the second conversion circuit and the neutral line of the third conversion circuit are connected with each other.

A conversion apparatus using the T-type conversion circuit of the first embodiment, wherein a first diode, a second controllable switching device, a fifth diode, and a first capacitor are integrally provided as a first circuit block; the first end of the first circuit module is connected with the cathode of the first diode and is used for being connected to the positive bus; the second end of the first circuit module is connected with the anode of the second diode and is used for being connected to the inductor; and the third end of the first circuit module is connected with the anode of the fifth diode and is used for being connected to the input end and the output end.

A conversion apparatus using the T-type conversion circuit of the first embodiment, wherein a third diode, a fourth diode, a third controllable switching device, a sixth diode, and a second capacitor are integrally provided as a second circuit block; the fourth end of the second circuit module is connected with the anode of a fourth diode and is used for being connected to a negative bus; the fifth end of the second circuit module is connected with the drain electrode or the collector electrode of the third controllable switching device and is used for being connected to the inductor; and the sixth end of the second circuit module is connected with the cathode of the sixth diode and is used for being connected to the input end and the output end.

A conversion apparatus using the T-type conversion circuit of the second embodiment, wherein a first diode, a second controllable switching device, a fifth diode, and a first capacitor are integrally provided as a third circuit block; the seventh end of the third circuit module is connected with the cathode of the first diode and is used for being connected to the positive bus, and the eighth end of the third circuit module is connected with the anode of the second diode and is used for being connected to the inductor; and the ninth end of the third circuit module is connected with the drain electrode or the collector electrode of the second controllable switching device and is used for being connected to the input end and the output end.

A conversion apparatus using the T-type conversion circuit of the second embodiment, wherein a third diode, a fourth diode, a third controllable switching device, a sixth diode, and a second capacitor are integrally provided as a fourth circuit block; the tenth end of the fourth circuit module is connected with the anode of a fourth diode and is used for being connected to the negative bus, and the eleventh end of the fourth circuit module is connected with the anode of a sixth diode and is used for being connected to the inductor; and the twelfth end of the fourth circuit module is connected with the source electrode or the emitter electrode of the third controllable switching device and is used for being connected to the input end and the output end.

Compared with the prior art, the technical scheme of the invention has the following beneficial effects:

1. in the T-type conversion circuit, all controllable switching devices and diode devices can realize soft switching, namely Zero Voltage Switching (ZVS), Zero Current Switching (ZCS) or Zero Voltage Zero Current Switching (ZVZCS), or on-off switching with limited dv/dt and di/dt. Therefore, the on-off loss of the controllable switch device is greatly reduced, and the working efficiency of the conversion circuit is improved; the power device is not easy to be subjected to secondary breakdown, and the dead time is eliminated;

2. the controllable switching device is switched on and off with limited dv/dt and di/dt, so the EMI electromagnetic interference of the system is much more optimized than that of the system without realizing soft switching;

3. because the on-off loss of the controllable switch device is reduced, the conversion device can work above the working frequency of the traditional conversion device in multiples, so that the parameter requirement of an output filter required by the conversion device is low, and the size can be reduced in multiples, thereby being beneficial to further reducing the material cost, reducing the product size and improving the product power density;

4. compared with the prior art, the invention only adds one inductor, four diodes and two capacitors, has less added devices, simple and compact structure and does not need to additionally add a controllable switch device and a control circuit;

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

6. The circuit module is formed by combining the components in the prior art and the newly added components in the technical scheme, the technical scheme can be realized under the condition that the internal circuit layout of the existing inversion/rectification device is basically not changed, the transformation cost is greatly reduced, the topological structure is compact, the busbar design is simple, and the circuit module is very favorable for electrical layout and structural design.

Drawings

The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description serve to explain the invention and not to limit the invention. In the drawings:

FIG. 1 is a schematic circuit diagram of a prior art circuit;

FIG. 2 is a circuit diagram of a first embodiment of a T-type conversion circuit according to the present invention;

FIG. 3 is a circuit diagram of a second embodiment of a T-type conversion circuit according to the present invention;

FIG. 4 is a schematic diagram of the T-type converter circuit according to the first embodiment of the present invention, before the vertical tube commutates to the horizontal tube when the inverted output voltage is a positive half-cycle;

FIG. 5 is a schematic diagram illustrating a first stage operation of a vertical tube to horizontal tube converter when the inverter output voltage is a positive half cycle after DC/AC conversion according to an embodiment of the T-type converter circuit of the present invention;

FIG. 6 is a schematic diagram of a second stage operation of the T-type inverter circuit according to the present invention, in which the vertical tube performs DC/AC conversion and the inversion output voltage is a positive half-cycle, and the vertical tube performs current conversion to the horizontal tube;

FIG. 7 is a schematic diagram of the T-type converter circuit according to the first embodiment of the present invention, before the horizontal tube is commutated to the vertical tube when the inverted output voltage is a positive half-cycle;

FIG. 8 is a schematic diagram illustrating a third stage of the horizontal to vertical pipe commutation when the T-type inverter circuit performs DC/AC conversion and the inverted output voltage is a positive half cycle according to the first embodiment of the present invention;

FIG. 9 is a schematic diagram illustrating a fourth stage of the horizontal to vertical pipe commutation when the inverted output voltage is a positive half cycle after DC/AC conversion according to the first embodiment of the T-type inverter circuit of the present invention;

FIG. 10 is a schematic diagram of the T-converter circuit according to the first embodiment of the present invention, before the vertical tube commutates to the horizontal tube when the AC input voltage is a positive half-cycle;

fig. 11 is a schematic diagram illustrating a first stage operation of a vertical tube to horizontal tube converter when an AC/DC conversion is performed and an AC input voltage is a positive half cycle according to an embodiment of the T-type converter circuit of the present invention;

FIG. 12 is a schematic diagram illustrating a second stage operation of the T-type inverter circuit according to the present invention, in which the vertical tube commutates to the horizontal tube when the AC input voltage is a positive half-cycle after AC/DC conversion;

FIG. 13 is a schematic diagram of the T-converter circuit according to the first embodiment of the present invention, before the horizontal tube commutates to the vertical tube when the AC input voltage is a positive half-cycle;

FIG. 14 is a schematic diagram of the operation of the T-converter circuit according to the present invention for AC/DC conversion with a positive half-cycle of the AC input voltage;

FIG. 15 is a schematic circuit diagram of an embodiment of a three-phase inverter circuit according to the present invention;

FIG. 16 is a diagram of a first embodiment of a transformation device according to the present invention;

FIG. 17 is a diagram of a second embodiment of the transforming device of the present invention.

Detailed Description

In order to make the technical problems, technical solutions and advantageous effects to be solved by the present invention clearer and clearer, the present invention is further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

Fig. 2 is a circuit diagram of a first embodiment of the T-type conversion circuit according to the present invention. As shown in fig. 2, the second embodiment of the T-type hydrocarbon converter circuit includes a first controllable switching device, a second controllable switching device, a third controllable switching device, a fourth controllable switching device, an inductor L, a first diode D1, a second diode D2, a third diode D3, a fourth diode D4, a fifth diode D5, a sixth diode D6, a first capacitor C1, a second capacitor C2, a third polar capacitor C3, and a fourth polar capacitor C4.

The first controllable switching device adopts an IGBT unit and comprises a first IGBT tube Q1 and a first freewheeling diode Dq1 connected in anti-parallel with the first IGBT tube Q1; the second controllable switching device adopts an IGBT unit and comprises a second IGBT tube Q2 and a second freewheeling diode Dq2 connected in anti-parallel with the second IGBT tube Q2; the third controllable switching device adopts an IGBT unit and comprises a first IGBT tube Q3 and a third freewheeling diode Dq3 connected in anti-parallel with the first IGBT tube Q3; the fourth controllable switching device adopts an IGBT unit and comprises a fourth IGBT tube Q4 and a fourth freewheeling diode Dq4 connected in anti-parallel with the fourth IGBT tube Q4.

First IGBT tube Q1 and fourth IGBT tube Q4 are connected in series, the collector of first IGBT tube Q1 is connected to the positive bus bar, and the emitter of fourth IGBT tube Q4 is connected to the negative bus bar. The emitter of the first IGBT Q1 is connected to the collector of the fourth IGBT Q4, and the connection point serves as an input/output terminal.

The second IGBT tube Q2 and the third IGBT tube Q3 are connected in series with the fifth diode D5 and the sixth diode D6 respectively and then connected in parallel to form a middle bridge arm, one end of the middle bridge arm is connected to the input end and the output end, and the other end of the middle bridge arm is connected to one end of the inductor L. The other end of the inductor L is connected to the neutral line. On the middle bridge arm, an emitter of a second IGBT tube Q2 is connected to the inductor L, a collector of a second IGBT tube Q2 is connected with a cathode of a fifth diode D5, and an anode of a fifth diode D5 is connected to the input end and the output end; the collector of the third IGBT Q3 is connected to the inductor, the emitter of the third IGBT Q3 is connected to the anode of the sixth diode D6, and the cathode of the sixth diode D6 is connected to the input/output terminal.

A first diode D1 and a 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 connection point of the inductor L and the middle bridge arm; one end of the first 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 input/output terminal.

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 emitter of the second IGBT tube Q2; one end of the second capacitor 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 collector of the second IGBT.

The anode of the third polar capacitor C3 is connected with the positive bus, and the cathode is connected with the neutral line; the positive electrode of the fourth polarity capacitor C4 is connected with the neutral line, and the negative electrode is connected with the negative bus.

In this embodiment, the controllable switch device may also adopt an MOS unit, and when the MOS unit is adopted, the MOS unit may be an MOS transistor with a body diode or include an MOS transistor without a body diode and an anti-parallel diode.

When the first embodiment of the T-type inverter circuit works in inversion, the first embodiment of the T-type inverter circuit includes two half cycles, namely a positive half cycle and a negative half cycle, of the inversion output voltage, and each half cycle is divided into two processes, namely vertical pipe-to-horizontal pipe commutation and horizontal pipe-to-vertical pipe commutation:

when the inversion output voltage is a positive half period, the vertical tube current conversion process to the horizontal tube is as follows:

figure 4 shows the vertical tubes before flow to the horizontal tubes. Before the vertical horizontal tube is commutated, the first IGBT tube Q1 and the third IGBT tube Q3 are in a conducting state, and the second IGBT tube Q2 and the fourth IGBT tube Q4 are in a blocking state. At this time, the current flows to the load Z through the first IGBT Q1, and due to the topology of the circuit, no current flows through the third IGBT Q3 although it is in the normally open state. At this time, the voltage of the first capacitor C1 is clamped to zero, and the first capacitor C1 is in a zero-voltage discharge state. Since the first IGBT Q1 is turned on, the second capacitor C2 is charged to Vdc. At this time, the current through the inductor L is zero.

Fig. 5 shows the operation of the first stage of the vertical tube to horizontal tube commutation process. In the first phase, the third IGBT Q3 is kept in the on state, the fourth IGBT Q4 is kept in the off state, the first IGBT Q1 is turned from the on state to the off state, and the second IGBT Q2 is turned from the off state to the on state. As shown in fig. 5, during the process of turning off the first IGBT Q1 and turning on the second IGBT Q2, the second capacitor C2 discharges to the load Z through the fourth diode D4. Meanwhile, the second capacitor C2 charges the inductor L through the fourth diode D4, the fifth diode D5 and the second IGBT Q2. Since the voltage across the second capacitor C2 is discharged gradually to zero, the voltage of the first IGBT tube Q1 during turn-off is built up at a finite rate dV/dt, and the current of the load Z is supplied by the second capacitor C2. Therefore, the first IGBT Q1 is turned off in a zero-voltage manner, and the turn-off loss is very small, which is a typical soft switching process. Meanwhile, due to the existence of the inductor L, the current passing through the second IGBT Q2 is also increased at a finite rate di/dt, so that the second IGBT is turned on in a zero-current manner, and the conduction loss is very small, which also belongs to a typical soft switching process.

Fig. 6 shows the second stage of operation during the vertical tube to horizontal tube commutation. After the first stage is completed, the fourth diode D4 and the fifth diode D5 are turned off, the current through the inductor L becomes zero again, and the fourth freewheeling diode Dq4 starts freewheeling. The load Z output level is clamped at-Vdc/2 level. The inductor L starts to store energy through the sixth diode D6 and the third IGBT Q3. While the current of the inductor L increases linearly from zero, at the same time the current through the fourth freewheeling diode Dq4 decreases proportionally. The commutation process is completed when the current through the fourth freewheeling diode Dq4 decreases to zero. The fourth freewheeling diode Dq4 is turned off after the second phase is completed.

In the above process, all the current changes in the second IGBT Q2, the third IGBT Q3, the sixth diode D6 and the fourth freewheeling diode Dq4 are performed at the finite current change rate di/dt, so in this process, the second IGBT Q2, the third IGBT Q3 and other devices above are all operated in the soft-switching state. At the same time, the freewheeling process of the fourth diode D4 is also switched on or off at a limited current rate di/dt, and therefore, also belonging to soft switching, the conduction loss of D4 can be significantly reduced.

When the inversion output voltage is a positive half period, the current conversion process of the horizontal axial vertical pipe is as follows:

fig. 7 shows the state after the vertical tube is commutated to the horizontal tube, or before the horizontal tube is commutated to the vertical tube, when the inverter output voltage is in the positive half period. Before the horizontal axial vertical pipe is commutated, the first IGBT pipe Q1 and the fourth IGBT pipe Q4 are in a cut-off state, and the second IGBT pipe Q2 and the third IGBT pipe Q3 are in a conducting state. At this time, current flows from inductor L, sixth diode D6, and third IGBT Q3 to load Z. The second IGBT tube is in a conductive state, but no current flows. The current through the inductor L is equal to the current through the load Z.

Figure 8 illustrates the operation of the third stage of the process for horizontal to vertical tube flow reversal. In the third phase, the third IGBT Q3 is kept in the on state, the fourth IGBT Q4 is kept in the off state, the first IGBT Q1 is turned from the off state to the on state, and the second IGBT Q2 is turned from the on state to the off state. As shown in fig. 8, when first IGBT Q1 is turned on and second IGBT Q2 is turned off, the upper half bus voltage reversely pressurizes inductor L via first IGBT Q1, sixth diode D6, and third IGBT Q3, and the current in inductor L is forced to linearly decrease. Meanwhile, the upper half bus establishes a power supply loop for the load Z through the first IGBT tube Q1. The two circuits coexist and operate simultaneously. As the current through the inductor L gradually decreases, the load current transitions to the loop through the first IGBT Q1. When the current flowing through the inductor L is reduced to zero, the sixth diode D6 is turned off in the reverse direction, and the middle bridge arm is not turned on any more because the second IGBT is turned off.

During the conduction process of the first IGBT Q1, since the inductor L carries the load current and the current cannot change abruptly during the conduction process of the first IGBT Q1, the current passing through the first IGBT Q1 is established at a finite current change rate di/dt, and thus the conduction process of the first IGBT Q1 is a soft switching operation process. The second IGBT Q2 also belongs to the soft switching mode, in which no current flows during the transition from the on state to the off state.

Fig. 9 shows the fourth stage of operation during the horizontal to vertical tube flow reversal. After the third stage is completed, the second freewheeling diode Dq2 is turned off in the reverse direction, and the third polar capacitor C3, the first IGBT Q1, the second capacitor C2, the third diode D3, the third freewheeling diode Dq3 and the inductor L form a resonant circuit to charge the second capacitor C2. Due to the inductor L, when the second capacitor C2 is charged to Vdc, the third freewheeling diode Dq3 and the third diode D3 are turned off in reverse direction, the charging and commutation process is completed, and the state where the current flows to the load Z through the first IGBT Q1, that is, the state shown in fig. 4, is returned.

During the charging of the second capacitor C2, the third diode D3 and the third freewheeling diode Dq3 are turned on and off at a finite current change rate di/dt, and therefore, the switching loss during the turning on and off of the third diode D3 and the third freewheeling diode Dq3 is very low, and the soft-switching operation mode is adopted.

The commutation process when the inversion output voltage is a negative half cycle is similar to the commutation process when the inversion output voltage is a positive half cycle, and the vertical tube commutation or the horizontal tube commutation also needs to go through two stages, which is not described in detail herein.

When the conversion circuit works in rectification, the conversion circuit comprises two half cycles of a positive half cycle of alternating input voltage and a negative half cycle of the alternating input voltage, and each half cycle is divided into two processes of vertical pipe commutation and horizontal pipe commutation:

when the alternating current input voltage is in a positive half period, the vertical pipe current conversion process to the horizontal pipe is as follows:

fig. 10 shows the vertical tube before flow to the horizontal tube. Before the vertical horizontal tube is commutated, the first IGBT tube Q1 and the third IGBT tube Q3 are in a conducting state, and the second IGBT tube Q2 and the fourth IGBT tube Q4 are in a blocking state. The rectified current flows from the first freewheeling diode Dq1 to the bus. The third IGBT Q3 is conducting but no current flows through it. The first capacitor C1 is in a zero voltage discharge state. The second capacitor C2 is charged to Vdc, at which time the current in the inductor L is zero.

Fig. 11 shows the operation of the first stage of the vertical tube to horizontal tube commutation process. In the first stage, the third IGBT Q3 is kept in the on state, and the fourth IGBT Q4 is kept in the off state. The first IGBT Q1 is turned from on to off, and the second IGBT Q2 is turned from off to on. In the process, as shown in fig. 11, the voltage across the third capacitor C3 is applied across the inductor L through the first freewheeling diode Dq1, the fifth diode D5, and the second IGBT Q2. Due to the existence of the inductor L, the current passing through the middle bridge arm is linearly increased 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 which time the first freewheeling diode Dq1 turns off.

Due to the existence of the first freewheeling diode Dq1, the process of turning the first IGBT tube Q1 from on to off belongs to zero-voltage, zero-current turn-off. Due to the inductor L, the current linearly increases during the transition from off to on of the second IGBT Q2, so the on process of the second IGBT Q2 belongs to zero current conduction. Both are typical soft switching processes.

Fig. 12 shows the second stage of the standpipe to cross tube shortage flow process. After the first stage is completed, the first freewheeling diode Dq1 is turned off, and the second capacitor C2 starts to discharge through the second IGBT Q2, the fourth diode D4, the fifth diode D5 and the inductor L. After discharging to zero. The second stage is completed.

When the alternating current input voltage is in a positive half period, the current conversion process of the transverse axial vertical pipe is as follows:

fig. 13 shows the state after the end of the vertical tube to horizontal tube commutation, i.e. before the horizontal tube to vertical tube commutation. At this time, the second capacitor C2 finishes discharging, and the fifth diode D5, the second IGBT Q2 and the inductor L carry the rectified current. The first IGBT transistor Q1 and the fourth IGBT transistor Q4 are in an off state, and the second IGBT transistor Q2 and the third IGBT transistor Q3 are in an on state. Although the third IGBT tube Q3 is in the on state, no current flows. And 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 14 shows the operation of the horizontal to vertical tube commutation process. When the horizontal pipe is commutating to the vertical pipe, the third IGBT Q3 is kept in the on state, the fourth IGBT Q4 is kept in the off state, the first IGBT Q1 is turned from the off state to the on state, and the second IGBT Q2 is turned from the on state to the off state. During the turn-off of the second IGBT Q2, the rectified current passes from passing through the second IGBT Q2 to passing through the second capacitor C2 due to the presence of the second capacitor C2. The voltage of the second IGBT Q2 increases linearly from zero, and is turned off at zero voltage and zero current. The input source Z charges the second capacitor C2 through the third freewheeling diode Dq3, the third diode D3, and the inductor L. When the current of the inductor L gradually changes from the rectified current to zero, and the second capacitor C2 finishes the charging process, the current flowing from the rectified current to the bus through the first freewheeling diode Dq1 gradually increases, and no current flows through the first IGBT Q1 due to the existence of the first freewheeling diode Dq1, so the conduction process of the first IGBT Q1 is zero-current and zero-voltage conduction. From the above analysis, in the process of horizontal to vertical pipe commutation, the on and off processes of the first IGBT Q1 and the second IGBT Q2 are soft switching processes.

When the current through the inductor L becomes zero and the second capacitor C2 finishes charging, the third diode D3 and the third freewheeling diode Dq3 are cut off, the first freewheeling diode Dq1 is turned on, and the whole commutation process is finished. Returning to the state of fig. 10.

The commutation process when the ac input voltage is in the negative half cycle is similar to the commutation process when the ac input voltage is in the positive half cycle, and the commutation process of the vertical tube to the horizontal tube or the commutation process of the horizontal tube to the vertical tube is similar, and the details are not described herein.

Fig. 3 shows a circuit diagram of a second embodiment of the T-type conversion circuit of the present invention. As shown in fig. 2, the second embodiment of the T-type hydrocarbon converter circuit includes a first controllable switching device, a second controllable switching device, a third controllable switching device, a fourth controllable switching device, an inductor L, a first diode D1, a second diode D2, a third diode D3, a fourth diode D4, a fifth diode D5, a sixth diode D6, a first capacitor C1, a second capacitor C2, a third polar capacitor C3, and a fourth polar capacitor C4.

The second IGBT tube Q2 and the third IGBT tube Q3 are connected in series with the fifth diode D5 and the sixth diode D6 respectively and then connected in parallel to form a middle bridge arm, one end of the middle bridge arm is connected to the input end and the output end, and the other end of the middle bridge arm is connected to one end of the inductor L. The other end of the inductor L is connected to the neutral line. In the middle bridge arm, the cathode of the fifth diode D5 is connected to the inductor L, the anode of the fifth diode D5 is connected to the emitter of the second IGBT Q2, and the collector of the second IGBT Q2 is connected to the input and output terminals. The anode of the sixth diode D6 is connected to the inductor, the cathode of the sixth diode D6 is connected to the collector of the third IGBT Q3, and the emitter of the third IGBT Q3 is connected to the input/output terminal.

Second embodiment the principle of implementing soft switching by the controllable switching device and the diode in the commutation process is similar to the first embodiment, and will not be described in detail here.

As can be seen from the above two embodiments, in the T-type conversion circuit of the present invention, all the controllable switching devices and diode devices can implement soft switching, i.e., Zero Voltage Switching (ZVS), Zero Current Switching (ZCS) or Zero Voltage Zero Current Switching (ZVZCS), or on-off switching with limited dv/dt and di/dt. Therefore, the on-off loss of the controllable switch device is greatly reduced, and the working efficiency of the conversion circuit is improved; the power device is not easy to be broken down secondarily, and meanwhile dead time is eliminated.

The controllable switching device is switched on and off with a limited dv/dt and di/dt, so the system EMI electromagnetic interference is much more optimized than if soft switching is not implemented.

Because the on-off loss of the controllable switch device is reduced, the conversion device can work on the working frequency of the traditional conversion device in multiples, the parameter requirement of an output filter required by the conversion device is lowered, and the size can be reduced in multiples, so that the material cost is further reduced, the product size is reduced, and the product power density is improved.

Compared with the prior art, the invention only adds one inductor, four diodes and two capacitors, has less added devices, simple and compact structure and does not need to additionally add a controllable switch device and a control circuit.

Fig. 15 shows a circuit schematic of an embodiment of a three-phase inverter circuit of the present invention. As shown in fig. 15, the three-phase inverter circuit in the embodiment includes a first inverter circuit, a second inverter circuit, and a third inverter circuit; the first conversion circuit, the second conversion circuit and the third conversion circuit all adopt the T-shaped conversion circuit described in the first embodiment of the T-shaped conversion circuit; the neutral line of the first conversion circuit, the neutral line of the second conversion circuit and the neutral line of the third conversion circuit are connected with each other. Of course, the first conversion circuit, the second conversion circuit, and the third conversion circuit may be the T-type conversion circuit described in the second embodiment of the T-type conversion circuit, and the same effect is obtained.

The three-phase conversion circuit adopts the T-shaped conversion circuit, and the effect of soft switching of the controllable switching device can be realized.

Fig. 16 is a schematic diagram of a first embodiment of a changer. The first embodiment of the conversion device adopts the T-type conversion circuit described in the first embodiment of the T-type conversion circuit. The first diode D1, the second diode D2, the second controllable switch device, the fifth diode D5 and the first capacitor C1 are integrally configured as a first circuit module U1. The third diode D3, the fourth diode D4, the third controllable switching device, the sixth diode D6 and the second capacitor C2 are integrally configured as a second circuit module U2.

A first terminal S1 of the first circuit module U1 is connected to the cathode of a first diode D1 for connection to the positive bus; the second end S2 of the first circuit module U1 is connected to the anode of the second diode D2 for connection to an inductor; the third terminal S3 of the first circuit module U1 is connected to the anode of the fifth diode D5 for connecting to the input and output terminals.

The fourth end S4 of the second circuit module U2 is connected to the anode of the fourth diode D4 for connection to the negative bus; a fifth end S5 of the second circuit module U2 is connected to a collector of a third IGBT Q3 of the third controllable switching device, and is connected to the inductor L; the sixth terminal S6 of the second circuit block U2 is connected to the cathode of the sixth diode D6 for connection to the input and output terminals.

It should be noted that the first circuit module U1 or the second circuit module U2 may exist separately.

Fig. 17 is a schematic diagram of a second embodiment of a changer. The second embodiment of the conversion apparatus employs the T-type conversion circuit described in the second embodiment of the T-type conversion circuit. The first diode D1, the second diode D2, the second controllable switching device, the fifth diode D5 and the first capacitor C1 are integrally configured as a third circuit module U3. The third diode D3, the fourth diode D4, the third controllable switching device, the sixth diode D6 and the second capacitor C2 are integrally configured as a fourth circuit module U4.

The seventh end S7 of the third circuit module U3 is connected to the cathode of the first diode D1 for connection to the positive bus, and the eighth end S8 of the third circuit module U3 is connected to the anode of the second diode D2 for connection to the inductor L; a ninth terminal S9 of the third circuit module U3 is connected to the collector of the second IGBT Q2 of the second controllable switching device for connecting to the input and output terminals.

The tenth end S10 of the fourth circuit module U4 is connected to the anode of the fourth diode D4 for connecting to the negative bus, and the tenth end S11 of the fourth circuit module U4 is connected to the anode of the sixth diode D6 for connecting to the inductor L; a twelfth terminal S12 of the fourth circuit module U4 is connected to an emitter of a third IGBT Q3 of the third controllable switching device, and is configured to be connected to the input and output terminals.

It is noted that the third circuit module U3 or the fourth circuit module U4 may exist alone.

It can be seen from the above two embodiments of the conversion device that since the components in the prior art and the newly added components in the technical scheme are combined into a circuit module, the technical scheme can be implemented without basically changing the internal circuit layout of the existing inverter/rectifier device, the improvement cost is greatly reduced, the topological structure is compact, the bus bar design is simple, and the electrical layout and the structural design are greatly facilitated.

The above description describes preferred embodiments of the invention, but it should be understood that the invention is not limited to the above embodiments, and should not be viewed as excluding other embodiments. Modifications made by those skilled in the art in light of the teachings of this disclosure, which are well known or are within the skill and knowledge of the art, are also to be considered as within the scope of this invention.

Claims

1. A T-type conversion circuit is characterized in that: the circuit comprises a first controllable switching device, a second controllable switching device, a third controllable switching device, a fourth controllable switching device, an inductor, a first diode, a second diode, a third diode, a fourth diode, a fifth diode, a sixth diode, a first capacitor and a second capacitor;

the first controllable switch device and the fourth controllable switch device are connected in series, the drain electrode or the collector electrode of the first controllable switch device is connected with the positive bus, the source electrode or the emitter electrode of the fourth controllable switch device is connected with the negative bus, and the first controllable switch device and the fourth controllable switch device are vertically arranged;

the connection point between the first controllable switching device and the fourth controllable switching device is used as an input end and an output end;

the second controllable switch device and the third controllable switch device are respectively connected with the fifth diode and the sixth diode in series and then connected in parallel to form a middle bridge arm, one end of the middle bridge arm is connected to the input and output end, the other end of the middle bridge arm is connected to one end of the inductor, and the other end of the inductor is connected to the neutral line; wherein the drain or collector of said second controllable switching device is connected to the input output terminal and the source or emitter of said third controllable switching device is connected to the input output terminal, or the source or emitter of said second controllable switching device is connected to the inductor and the drain or collector of said third controllable switching device is connected to the inductor, said second and third controllable switching devices being laterally arranged;

the first diode and the second diode are connected in series, the cathode of the first diode is connected to the positive bus, the anode of the second diode is connected to the connection point of the inductor and the middle bridge arm, one end of the first capacitor is connected to the connection point of the first diode and the second diode, and the other end of the first capacitor is connected to the input and output end;

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 anode of the sixth diode; one end of the second capacitor is connected to the connection point of the third diode and the fourth diode, and the other end of the second capacitor is connected to the cathode of the sixth diode.

2. A T-type inverter circuit as claimed in claim 1, wherein in the intermediate leg, the source or emitter of the second controllable switching device is connected to the inductor, the drain or collector of the second controllable switching device is connected to the cathode of a fifth diode, and the anode of the fifth diode is connected to the input/output terminal; the drain or collector of the third controllable switching device is connected to the inductor, the source or emitter of the third controllable switching device is connected to the anode of the sixth diode, and the cathode of the sixth diode is connected to the input/output terminal.

3. A T-type inverter circuit as claimed in claim 1, wherein in the intermediate leg, the cathode of the fifth diode is connected to the inductor, the anode of the fifth diode is connected to the source or emitter of the second controllable switching device, and the drain or collector of the second controllable switching device is connected to the input/output terminal; the anode of the sixth diode is connected to the inductor, the cathode of the sixth diode is connected to the drain or collector of the third controllable switching device, and the source or emitter of the third controllable switching device is connected to the input/output terminal.

4. A T-type conversion circuit as claimed in any one of claims 1 to 3, wherein any one of said two vertically arranged controllable switching devices is an IGBT cell or an MOS cell, and when an IGBT cell is used, said IGBT cell comprises an IGBT tube and a diode connected in anti-parallel with the IGBT tube; when the MOS unit is adopted, the MOS unit can be an MOS tube with a diode or an MOS tube without a diode and an anti-parallel diode.

5. A T-type inverter circuit as claimed in any one of claims 1 to 3 wherein either of said two laterally disposed controllable switching devices employs an IGBT cell or a MOS cell, and when an IGBT cell is employed, said IGBT cell comprises an IGBT tube and a diode connected in anti-parallel with the IGBT tube; when the MOS unit is adopted, the MOS unit can be an MOS tube with a diode or an MOS tube without a diode and an anti-parallel diode.

6. A three-phase conversion circuit is characterized by comprising 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 adopt a T-shaped conversion circuit as claimed in any one of claims 1 to 5; the neutral line of the first conversion circuit, the neutral line of the second conversion circuit and the neutral line of the third conversion circuit are connected with each other.

7. A converter arrangement comprising a T-converter circuit as claimed in claim 2, wherein the first diode, the second controllable switching device, the fifth diode and the first capacitor are integrated to form a first circuit block;

the first end of the first circuit module is connected with the cathode of the first diode and is used for being connected to the positive bus; the second end of the first circuit module is connected with the anode of the second diode and is used for being connected to the inductor; and the third end of the first circuit module is connected with the anode of the fifth diode and is used for being connected to the input end and the output end.

8. A converter arrangement comprising a T-converter circuit as claimed in claim 2, wherein the third diode, the fourth diode, the third controllable switching device, the sixth diode and the second capacitor are integrated to form a second circuit block;

the fourth end of the second circuit module is connected with the anode of a fourth diode and is used for being connected to a negative bus; the fifth end of the second circuit module is connected with the drain electrode or the collector electrode of the third controllable switching device and is used for being connected to the inductor; and the sixth end of the second circuit module is connected with the cathode of the sixth diode and is used for being connected to the input end and the output end.

9. A converter arrangement comprising a T-converter circuit as claimed in claim 3, wherein the first diode, the second controllable switching device, the fifth diode and the first capacitor are integrated to form a third circuit block;

the seventh end of the third circuit module is connected with the cathode of the first diode and is used for being connected to the positive bus, and the eighth end of the third circuit module is connected with the anode of the second diode and is used for being connected to the inductor; and the ninth end of the third circuit module is connected with the drain electrode or the collector electrode of the second controllable switching device and is used for being connected to the input end and the output end.

10. A converter arrangement comprising a T-converter circuit as claimed in claim 3, wherein a third diode, a fourth diode, a third controllable switching device, a sixth diode and a second capacitor are integrated to form a fourth circuit block;

the tenth end of the fourth circuit module is connected with the anode of a fourth diode and is used for being connected to the negative bus, and the eleventh end of the fourth circuit module is connected with the anode of a sixth diode and is used for being connected to the inductor; and the twelfth end of the fourth circuit module is connected with the source electrode or the emitter electrode of the third controllable switching device and is used for being connected to the input end and the output end.