CN109639170B - Auxiliary resonant pole active clamping three-level soft switching inverter circuit and modulation method - Google Patents

Abstract

The invention provides an auxiliary resonant pole active clamping three-level soft switching inverter circuit and a modulation method thereof. The circuit comprises an active clamping main inverter circuit, an auxiliary resonance converter circuit, a filter circuit and a load. The active clamping main inverter circuit comprises six switching tubes with anti-parallel diodes and two same supporting capacitors, and the auxiliary resonance converter circuit comprises two auxiliary switching tubes with anti-parallel diodes, two resonance capacitors and a resonance inductor. The filter circuit is an LC filter circuit. The modulation method provided by the invention can realize zero-voltage switching of the main switching tube and zero-current switching of the auxiliary switching tube. The invention can reduce the loss of the active clamp three-level hard switch, improve the system efficiency and reduce the electromagnetic interference.

Description

Auxiliary resonant pole active clamping three-level soft switching inverter circuit and modulation method

Technical Field

The invention relates to the technical field of power electronics, in particular to an auxiliary resonant pole active clamping three-level soft switching inverter circuit and a modulation method thereof.

Background

With the continuous development of power electronic technology, the power density of inverters is higher and higher, and people have higher and higher demands for high-frequency, small-sized and light-weight high-power inverters. As the switching frequency increases, the conventional pwm technology faces many problems, such as increased switching loss of the switching tube and external electromagnetic interference (EMI) generated by the system.

In order to overcome the above problems, since the 80 s in the 20 th century, the soft switching technology has been intensively studied, and various topologies and modulation strategies have been continuously developed. The soft switching technology is to utilize the resonance principle to execute the switching action when the voltage or current resonance reaches zero, so as to reduce the voltage and current overlapping area when the switching tube is switched on and off. The soft switching inverter topology is mainly divided into a direct current side type and an alternating current side type, an auxiliary resonance circuit of the direct current side soft switching inverter is connected in series on a direct current bus, and an alternating current side soft switching inverter is divided into a zero voltage conversion type and a zero current conversion type. The zero-voltage conversion type auxiliary resonant transformation extremely-soft switching inverter is applied to high-power occasions with independent control and reliable performance.

Compared with a two-level converter, the multi-level converter has many advantages, the active clamping three-level converter is widely applied at present, and how to further reduce the switching loss, reduce the electromagnetic interference and improve the power density is a hot point of research. In the active neutral point voltage clamped three-level zero-current switching soft switching converter disclosed in the chinese invention patent (CN200910023828.8) on 21/9/2011, the zero-current switching soft switching circuit is added to turn off the switching tube at zero current, so as to reduce the loss of the switching tube, but the circuit has the following disadvantages:

1. in order to further improve the switching frequency, silicon carbide and other wide bandgap semiconductor devices are mostly power field effect transistors (MOSFET), and the MOSFET is more suitable for zero-voltage conversion due to large turn-on loss caused by the output capacitance of the MOSFET;

2. the switching-on current of the circuit switching tube rises at the rate of the resonant current, and the switching-on loss is large;

3. the resonant circuit is changed four times in the commutation process, so that the loss of the resonant circuit is increased, and the operation reliability of the circuit is reduced.

In the novel double-auxiliary resonant pole type three-phase soft switching inverter circuit and the modulation method thereof disclosed in 2018, 9, 21, the invention patent (CN201810448352.1) realizes zero-voltage switching of a switching tube by adding a double-auxiliary resonant inverter circuit, reduces the loss of the switching tube, can reduce system oscillation caused by coupling resonance of the inverter circuit, and has a controllable output voltage change rate, but the circuit has the following defects:

1. the added double-auxiliary resonant converter circuit has more used devices, and the hardware cost is increased;

2. the number of auxiliary switching tubes is large, so that the difficulty of a modulation method of the auxiliary switching tubes is increased;

3. the inverter circuit is a two-level circuit, and is difficult to be applied to a three-level circuit.

Disclosure of Invention

In view of the above-mentioned shortcomings of the prior art, the present invention aims to provide an auxiliary resonant conversion pole active clamping three-level soft switching inverter circuit and a modulation method thereof with high efficiency and simple structure.

In order to achieve the purpose, the invention is realized by adopting the following technical scheme.

The invention provides an auxiliary resonant electrode active clamping three-level soft switching inverter circuit, which comprises an active clamping main inverter circuit, an auxiliary resonant converter circuit, a filter circuit and a load R;

the active clamping main inverter circuit comprises a direct current positive bus P, a direct current negative bus N, a direct current bus midpoint O, six switching tubes with anti-parallel diodes and two same supporting capacitors; six switch tubes with anti-parallel diodes are respectively marked as switch tubes S₁Switch tube S₂Switch tube S₃Switch tube S₄Switch tube S₅And a switching tube S₆Six anti-parallel diodes are respectively marked as diode D₁Diode D₂Diode D₃Diode D₄Diode D₅Diode D₆The two support capacitors are respectively marked as the support capacitor C₁And a support capacitor C₂Wherein, the DC bus voltage is denoted as V_dcSupporting capacitor C₁Connected between the positive DC bus P and the midpoint O of the DC bus, and supporting a capacitor C₂The direct current bus neutral point O is connected with the direct current negative bus N; switch tube S₁Switch tube S₂Switch tube S₃Switch tube S₄Are sequentially connected in series, and switch tube S₁The input end of the switch tube is connected with a direct current positive bus P and a switch tube S₁The output end of the switch tube S₂Of the input terminal, switching tube S₂The output end of the switch tube S₃Of the input terminal, switching tube S₃The output end of the switch tube S₄Of the input terminal, switching tube S₄The output end of the direct current negative bus is connected with a direct current negative bus N; switch tube S₅Is connected with the switch tube S₁Of the output terminal, switching tube S₅The output end of the direct current bus is connected with a midpoint O of the direct current bus; switch tube S₆The input end of the switch tube S is connected with a DC bus midpoint O and a switching tube S₆The output end of the switch tube S₃An output terminal of (a);

the auxiliary resonance commutation circuit comprises two auxiliary switching tubes with anti-parallel diodes, two resonance capacitors and a resonance inductor L_rTwo auxiliary switch tubes with anti-parallel diodes are respectively marked as an auxiliary switch tube S_a1And an auxiliary switching tube S_a2Two antiparallel diodes are respectively denoted as auxiliary diode D_a1And assistanceDiode D_a2The two resonant capacitors are respectively denoted as resonant capacitor C_r1And a resonance capacitor C_r2Wherein an auxiliary switch tube S_a1The output end of the switch is connected with an auxiliary switch tube S_a2Output terminal of (2), auxiliary switch tube S_a2Is connected with the resonant inductor L_r(ii) a Resonant capacitor C_r1Switch tube S of active clamping main inverter circuit₂Parallel resonant capacitor C_r2Switch tube S of active clamping main inverter circuit₃Parallel connection;

the filter circuit is an LC filter circuit and is formed by connecting a filter inductor L and a filter capacitor C in series, and a resonance inductor L_rAuxiliary switch tube S_a1And an auxiliary switching tube S_a2After being sequentially connected in series, the filter capacitor C is connected with a load R in parallel.

The invention also provides a modulation method of the auxiliary resonant pole active clamping three-level soft switching inverter circuit, and a switching tube in the auxiliary resonant pole active clamping three-level soft switching inverter circuit works in the following mode:

(1) six switching tubes in the active clamping main inverter circuit work in the following mode:

switch tube S₁Switch tube S₄Switch tube S₅Switch tube S₆Power frequency action, switch tube S₂And a switching tube S₃Conducting in a high-frequency complementary manner;

when switching tube S₁Switch tube S₂Switch tube S₆In a conducting state, the switch tube S₃Switch tube S₄Switch tube S₅When the bridge arm is in a turn-off state, the bridge arm side outputs a positive level;

when switching tube S₁Switch tube S₃Switch tube S₆In a conducting state, the switch tube S₂Switch tube S₄Switch tube S₅When the bridge arm is in a turn-off state, the bridge arm side outputs zero level;

when switching tube S₃Switch tube S₄Switch tube S₅In a conducting state, the switch tube S₁Switch tube S₂Switch tube S₆When the bridge arm is in a turn-off state, the bridge arm side outputs a negative level;

when switching tube S₂Switch tube S₄Switch tube S₅In a conducting state, the switch tube S₁Switch tube S₃Switch tube S₆When the bridge arm is in a turn-off state, the bridge arm side outputs zero level;

the switch tube S₂And a switching tube S₃High frequency complementary conduction, meaning switch tube S₂Switch tube S₃Complementary conduction according to sine pulse width modulation, switching tube S₂On-time ratio of switching tube S₃Delay the turn-off time by a dead time_tdSwitch S₃On-time ratio of switching tube S₂The turn-off time of (c) is delayed by a dead time td;

(2) the two auxiliary switching tubes in the auxiliary resonant converter circuit work in the following way:

recording the voltage on the filter capacitor C as the voltage V of the filter capacitor_oThe current on the filter inductor L is recorded as the filter inductor current I_L；

At the filter capacitor voltage V_oIs positive, filtering the inductive current I_LWhen the output of the positive and bridge arm sides is converted between zero level and positive level, the auxiliary switch tube S_a1On-time ratio of switching tube S₃The turn-off time of is advanced by_td1Auxiliary switch tube S_a1Turn-off time ratio of the switching tube S₂Is delayed by the time of opening_td2Auxiliary switch tube S_a2Constant turn-off;

at the filter capacitor voltage V_oIs a negative, filtering inductor current I_LWhen the output of the negative bridge arm side and the output of the bridge arm side are switched between zero level and negative level, the auxiliary switch tube S_a2On-time ratio of switching tube S₂The turn-off time of is advanced by_td1Auxiliary switch tube S_a2Turn-off time ratio of the switching tube S₃Is delayed by the time of opening_td2Auxiliary switch tube S_a1Constant turn-off;

the advance time_td1And time delay_td2Respectively satisfy the followingConditions are as follows:

wherein L is_rIs the value of the resonant inductance, V_dcIs the DC bus voltage i_chIs a resonant inductor L_rAt the maximum charging current value, which is recorded as charging current i_ch。

According to the technical scheme, compared with the prior art, the invention has the following advantages:

1) the auxiliary resonant electrode active clamping three-level soft switching inverter circuit provided by the invention has the advantages of small quantity of the added auxiliary switching tubes and auxiliary resonant inductor capacitors and simple structure.

2) The modulation strategy of the added auxiliary switching tube is simple, and the zero-voltage switching of the main switching tube and the zero-current switching of the auxiliary switching tube are realized.

3) The auxiliary resonant electrode active clamping three-level soft switching inverter circuit and the modulation method provided by the invention are suitable for a high-power high-frequency high-voltage inverter circuit, effectively reduce the switching loss and reduce the electromagnetic interference.

Drawings

Fig. 1 is a circuit diagram of an auxiliary resonant pole active clamping three-level soft switching inverter circuit of the invention.

FIG. 2 shows the voltage V of the filter capacitor of the active clamp main inverter circuit and the auxiliary resonant inverter circuit according to the embodiment of the present invention_oIs positive, filtering the inductive current I_LAnd when the output voltage is positive, the bridge arm side outputs the driving state of each switching tube, the auxiliary resonant inductor current and the resonant capacitor voltage working waveform when the zero level and the positive level are switched.

FIG. 3 shows the voltage V at the filter capacitor_oIs positive, filtering the inductive current I_LAnd the output of the bridge arm side is positive, and the commutation stage 1 is schematic when the zero level and the positive level are switched.

FIG. 4 shows the voltage V at the filter capacitor_oIs positive, filtering the inductive current I_LAnd the output of the bridge arm side is positive, and the commutation stage 2 is schematically shown when the zero level and the positive level are switched.

FIG. 5 shows the voltage V at the filter capacitor_oIs positive, filtering the inductive current I_LAnd the output of the bridge arm side is positive, and the commutation stage 3 is schematically shown when the zero level and the positive level are switched.

FIG. 6 shows the voltage V at the filter capacitor_oIs positive, filtering the inductive current I_LAnd the output of the bridge arm side is positive, and the commutation stage 4 is schematically shown when the zero level and the positive level are switched.

FIG. 7 shows the voltage V at the filter capacitor_oIs positive, filtering the inductive current I_LAnd the output of the bridge arm side is positive, and the commutation stage 5 is schematically shown when the zero level and the positive level are switched.

FIG. 8 shows the voltage V at the filter capacitor_oIs positive, filtering the inductive current I_LAnd the output of the bridge arm side is positive, and the commutation stage 6 is schematically shown when the zero level and the positive level are switched.

FIG. 9 shows the voltage V at the filter capacitor_oIs positive, filtering the inductive current I_LAnd the output of the bridge arm side is positive, and the commutation stage 7 is schematically shown when the zero level and the positive level are switched.

FIG. 10 shows the voltage V at the filter capacitor_oIs positive, filtering the inductive current I_LAnd when the output of the bridge arm side is positive, the commutation stage 8 is schematically shown when the zero level and the positive level are switched.

FIG. 11 shows the voltage V at the filter capacitor_oIs positive, filtering the inductive current I_LAnd the output of the bridge arm side is positive, and the commutation stage 9 is schematically shown when the zero level and the positive level are switched.

FIG. 12 shows the voltage V of the filter capacitor of the active clamp main inverter circuit and the auxiliary resonant inverter circuit according to the embodiment of the present invention_oIs a negative, filtering inductor current I_LAnd when the output voltage is negative, the bridge arm side outputs the driving state of each switching tube, the auxiliary resonant inductor current and the resonant capacitor voltage working waveform when the zero level and the negative level are switched.

FIG. 13 shows the voltage V at the filter capacitor_oIs a negative, filtering inductor current I_LIs negative, the output of the bridge arm side commutates when the zero level and the negative level are switchedStage 1 is a schematic.

FIG. 14 shows the voltage V at the filter capacitor_oIs a negative, filtering inductor current I_LAnd the output of the bridge arm side is negative, and the commutation stage 2 is schematically shown when the zero level and the negative level are switched.

FIG. 15 shows the voltage V at the filter capacitor_oIs a negative, filtering inductor current I_LAnd the output of the bridge arm side is negative, and the commutation stage 3 is schematically shown when the zero level and the negative level are switched.

FIG. 16 shows the voltage V at the filter capacitor_oIs a negative, filtering inductor current I_LAnd the output of the bridge arm side is negative, and the commutation stage 4 is schematically shown when the zero level and the negative level are switched.

FIG. 17 shows the voltage V at the filter capacitor_oIs a negative, filtering inductor current I_LAnd the output of the bridge arm side is negative, and the commutation stage 5 is schematically shown when the zero level and the negative level are switched.

FIG. 18 shows the voltage V at the filter capacitor_oIs a negative, filtering inductor current I_LAnd the output of the bridge arm side is negative, and the commutation stage 6 is schematically shown when the zero level and the negative level are switched.

FIG. 19 shows the voltage V at the filter capacitor_oIs a negative, filtering inductor current I_LAnd the output of the bridge arm side is negative, and the commutation stage 7 is schematically shown when the zero level and the negative level are switched.

FIG. 20 shows the voltage V at the filter capacitor_oIs a negative, filtering inductor current I_LAnd when the output of the bridge arm side is negative, the commutation stage 8 is schematically shown when the zero level and the negative level are switched.

FIG. 21 shows the voltage V at the filter capacitor_oIs a negative, filtering inductor current I_LAnd the output of the bridge arm side is negative, and the commutation stage 9 is schematically shown when the zero level and the negative level are switched.

Detailed Description

In order to make the purpose and technical solution of the present invention more clearly understood, the following detailed description of the embodiments of the present invention is made with reference to the accompanying drawings and examples.

Fig. 1 is a circuit diagram of an auxiliary resonant pole active clamping three-level soft switching inverter circuit of the invention. The figure shows that the auxiliary resonant pole active clamping three-level soft switching inverter circuit comprises an active clamping main inverter circuit, an auxiliary resonant converter circuit, a filter circuit and a load R.

The active clamping main inverter circuit comprises a direct current positive bus P, a direct current negative bus N, a direct current bus midpoint O, six switching tubes with anti-parallel diodes and two same supporting capacitors; six switch tubes with anti-parallel diodes are respectively marked as switch tubes S₁Switch tube S₂Switch tube S₃Switch tube S₄Switch tube S₅And a switching tube S₆Six anti-parallel diodes are respectively marked as diode D₁Diode D₂Diode D₃Diode D₄Diode D₅Diode D₆The two support capacitors are respectively marked as the support capacitor C₁And a support capacitor C₂Wherein, the DC bus voltage is denoted as V_dcSupporting capacitor C₁Connected between the positive DC bus P and the midpoint O of the DC bus, and supporting a capacitor C₂The direct current bus neutral point O is connected with the direct current negative bus N; switch tube S₁Switch tube S₂Switch tube S₃Switch tube S₄Are sequentially connected in series, and switch tube S₁The input end of the switch tube is connected with a direct current positive bus P and a switch tube S₁The output end of the switch tube S₂Of the input terminal, switching tube S₂The output end of the switch tube S₃Of the input terminal, switching tube S₃The output end of the switch tube S₄Of the input terminal, switching tube S₄The output end of the direct current negative bus is connected with a direct current negative bus N; switch tube S₅Is connected with the switch tube S₁Of the output terminal, switching tube S₅The output end of the direct current bus is connected with a midpoint O of the direct current bus; switch tube S₆The input end of the switch tube S is connected with a DC bus midpoint O and a switching tube S₆The output end of the switch tube S₃To the output terminal of (a).

The auxiliary resonance commutation circuit comprises two auxiliary switching tubes with anti-parallel diodes, two resonance capacitors and a resonance inductor L_rTwo auxiliary switch tubes with anti-parallel diodes are respectively marked as an auxiliary switch tube S_a1And an auxiliary switching tube S_a2Two antiparallel diodes are respectively denoted as auxiliary diodesD_a1And an auxiliary diode D_a2The two resonant capacitors are respectively denoted as resonant capacitor C_r1And a resonance capacitor C_r2Wherein an auxiliary switch tube S_a1The output end of the switch is connected with an auxiliary switch tube S_a2Output terminal of (2), auxiliary switch tube S_a2Is connected with the resonant inductor L_r(ii) a Resonant capacitor C_r1Switch tube S of active clamping main inverter circuit₂Parallel resonant capacitor C_r2Switch tube S of active clamping main inverter circuit₃And (4) connecting in parallel.

The filter circuit is an LC filter circuit and is formed by connecting a filter inductor L and a filter capacitor C in series, and a resonance inductor L_rAuxiliary switch tube S_a1And an auxiliary switching tube S_a2After being sequentially connected in series, the filter capacitor C is connected with a load R in parallel.

The invention also provides a modulation method of the auxiliary resonant pole active clamping three-level soft switching inverter circuit. In the method, a switching tube in the auxiliary resonant pole active clamping three-level soft switching inverter circuit works in the following mode:

(1) six switching tubes in the active clamping main inverter circuit work in the following mode:

switch tube S₁Switch tube S₄Switch tube S₅Switch tube S₆Power frequency action, switch tube S₂And a switching tube S₃Conducting in a high-frequency complementary manner;

when switching tube S₁Switch tube S₂Switch tube S₆In a conducting state, the switch tube S₃Switch tube S₄Switch tube S₅When the bridge arm is in a turn-off state, the bridge arm side outputs a positive level;

when switching tube S₁Switch tube S₃Switch tube S₆In a conducting state, the switch tube S₂Switch tube S₄Switch tube S₅When the bridge arm is in a turn-off state, the bridge arm side outputs zero level;

when switching tube S₃Switch tube S₄Switch tube S₅In a conducting state, the switch tube S₁Switch, and electronic device using the samePipe S₂Switch tube S₆When the bridge arm is in a turn-off state, the bridge arm side outputs a negative level;

when switching tube S₂Switch tube S₄Switch tube S₅In a conducting state, the switch tube S₁Switch tube S₃Switch tube S₆When the bridge arm is in a turn-off state, the bridge arm side outputs zero level;

the switch tube S₂And a switching tube S₃High frequency complementary conduction, meaning switch tube S₂Switch tube S₃Complementary conduction according to sine pulse width modulation, switching tube S₂On-time ratio of switching tube S₃Is delayed by a dead time td, switch S₃On-time ratio of switching tube S₂Is delayed by a dead time td.

(2) The two auxiliary switching tubes in the auxiliary resonant converter circuit work in the following way:

recording the voltage on the filter capacitor C as the voltage V of the filter capacitor_oThe current on the filter inductor L is recorded as the filter inductor current I_L；

At the filter capacitor voltage V_oIs positive, filtering the inductive current I_LWhen the output of the positive and bridge arm sides is converted between zero level and positive level, the auxiliary switch tube S_a1On-time ratio of switching tube S₃The turn-off time of the auxiliary switch tube S is advanced, the advance time is td1_a1Turn-off time ratio of the switching tube S₂The switching-on time of (1) is delayed, the delay time is td2, and an auxiliary switch tube S_a2Constant turn-off;

at the filter capacitor voltage V_oIs a negative, filtering inductor current I_LWhen the output of the negative bridge arm side and the output of the bridge arm side are switched between zero level and negative level, the auxiliary switch tube S_a2On-time ratio of switching tube S₂The turn-off time of the auxiliary switch tube S is advanced, the advance time is td1_a2Turn-off time ratio of the switching tube S₃The switching-on time of (1) is delayed, the delay time is td2, and an auxiliary switch tube S_a1Constant turn-off;

the advance time td1 and the delay time td2 respectively satisfy the following conditions:

wherein L is_rIs the value of the resonant inductance, V_dcIs the DC bus voltage i_chIs a resonant inductor L_rAt the maximum charging current value, which is recorded as charging current i_ch。

Because a pulse width modulation period is very small compared with the output phase voltage period of the inverter, the output of the inverter can be considered as a current source characteristic when an inductive load and a power grid are connected, and the filter inductance current I is considered to be a filter inductance current I in a switching period for convenient analysis_LConstant, filter capacitor voltage V_oConstant and unchanged. By filtering the capacitor voltage V_oThe upper positive and the lower negative are defined as positive to filter the inductive current I_LThe in-filter inductance is defined as positive. Under different load conditions, the following three conditions occur for a short time: voltage V of filter capacitor_oAnd the filter inductor current I_LWhen having different polarities; voltage V of filter capacitor_oIs positive, filtering the inductive current I_LWhen the output of the bridge arm side is positive, the output of the bridge arm side is converted between zero level and negative level; voltage V of filter capacitor_oIs a negative, filtering inductor current I_LThe output of the bridge arm side is converted between zero level and positive level for negative, and in the three cases, the auxiliary switch tube S needs to be changed_a1Auxiliary switch tube S_a2To avoid this complexity and because of the short time that exists in these three cases, the auxiliary resonant commutation circuit is inactive for this short time.

The working principle and modulation method of the circuit topology of the present invention will be described below for two cases.

(1) Voltage V of filter capacitor_oIs positive, filtering the inductive current I_LThe bridge side output is positive, switching between zero and positive levels.

The driving state of the switching tube, the auxiliary resonant inductor current and the working waveform of the resonant capacitor voltage in the active clamping main inverter circuit and the auxiliary resonant inverter circuit thereof are shown in fig. 2. The high-frequency switching cycle comprises nine commutation stages, wherein the nine commutation stages are respectively as follows:

stage 1[ t 0-t 1]: as shown in fig. 3, the switch tube S at this stage₁Switch tube S₃Switch tube S₆In a conducting state, the switch tube S₂Switch tube S₄Switch tube S₅Auxiliary switch tube S_a1Auxiliary switch tube S_a2In the off state, filtering the inductor current I_LFlows through the switch tube S₆And a diode D₃Providing energy to a load R;

stage 2[ t 1-t 2]: as shown in fig. 4, the auxiliary switch tube S is turned on at time t1_a1Voltage of filter capacitor V_oAdded to the resonant inductor L_rTwo ends, charged by an inductor, are allowed to flow through L_rAuxiliary inductor current i_LrLinearly increasing, auxiliary inductor current i_LrSwitch tube S flowing through auxiliary tube_a1And an auxiliary diode D_a2；

Stage 3[ t 2-t 3]: as shown in fig. 5, the auxiliary inductor current i_LrIs continuously charged to a charging current i_ch，i_chGreater than the filter inductance current I_LPart of the current of the switch tube S₃Flowing through;

stage 4[ t 3-t 4]: as shown in fig. 6, the switching tube S is turned off at time t3₃Resonant capacitor C_r2Upper voltage u_Cr2From zero to DC bus voltage V_dcOne half of (1), resonant capacitor C_r1Voltage u of_Cr1From the DC bus voltage V_dcIs reduced to zero and the current flows through the diode D₁Diode D₆Follow current due to switching tube S₃Resonance capacitor C after switch-off_r2Charging, switching tube S₃The voltage of the switch cannot rise immediately, and zero voltage turn-off is realized;

stage 5[ t 4-t 5]: as shown in fig. 7, the resonant capacitor C_r1Upper voltage u_Cr1Resonant to zero, diode D₂Naturally conducting, switching tube S₂The upper voltage is zero, and the switching tube S is turned on at the stage₂Tube, realizing switching tube S₂Zero voltage conduction, resonant inductance L_rUpper auxiliary inductor current i_LrLinearly down to the filter inductor current I_L；

Stage 6[ t 5-t 6]: as shown in fig. 8, the auxiliary inductor current i_LrLinear discharge to zero, switching tube S₁Switch tube S₂Current at is linearly increased to the filter inductor current I_LResonant inductor current i_LrAfter the voltage drops to zero, the auxiliary switch tube S_a1The upper current is zero, and the auxiliary switch tube S is turned off after the time t6_a1Zero current turn-off is realized;

stage 7[ t 6-t 7]: as shown in fig. 9, the switching tube S₁Switch tube S₂Switch tube S₆On state, switching tube S₃Switch tube S₄Switch tube S₅Auxiliary switch tube S_a1Auxiliary switch tube S_a2In the off state, filtering the inductor current I_LFlows through the switch tube S₁And a switching tube S₂Providing energy for the load to reach a steady state stage;

stage 8[ t 7-t 8]: as shown in fig. 10, the switching tube S is turned off at time t7₂Resonant capacitor C_r1Voltage u_Cr1From zero to DC bus voltage V_dcOne half of (1), resonant capacitor C_r2Voltage u of_Cr2From the DC bus voltage V_dcOne half of (S) drops to zero due to the switching tube S₂Resonance capacitor C after switch-off_r1Charging, switching tube S₂Zero voltage turn-off is realized;

stage 9[ t 8-t 0]: as shown in FIG. 11, the resonant capacitor C_r2Upper voltage u_Cr2After dropping to zero, the diode D₃Naturally conducting, switching tube S₃The upper voltage is zero, and the switching tube S is turned on at the stage₃Realize the switch tube S₃Zero voltage conduction, filtering of the inductor current I_LFlows through the switch tube S₆And a diode D₃Energy is provided for the load R, the commutation process is finished, and the loop returns to the initial stage 1 before commutation.

(2) Filter capacitor electricityPressure V_oIs a negative, filtering inductor current I_LAnd when the output voltage is negative, the output voltage of the bridge arm side is converted between a zero level and a negative level.

Voltage V of filter capacitor_oAnd the filter inductor current I_LThe filter capacitor voltage in this case will be indicated below as-V, contrary to the positive direction of definition_oThe filter inductor current is represented as-I_L。

The driving state of the switching tube, the auxiliary resonant inductor current and the resonant capacitor voltage operating waveforms in the active clamping main inverter circuit and the auxiliary resonant inverter circuit thereof are shown in fig. 12. Nine commutation stages are still included in one high-frequency switching cycle, and the nine commutation stages are respectively:

stage 1[ t 0-t 1]: as shown in fig. 13, the switch tube S at this stage₂Switch tube S₄Switch tube S₅In a conducting state, the switch tube S₁Switch tube S₃Switch tube S₆Auxiliary switch tube S_a1Auxiliary switch tube S_a2In the off state, filtering the inductor current-I_LFlow-through diode D₂And a switching tube S₅Providing energy to a load R;

stage 2[ t 1-t 2]: as shown in fig. 14, the auxiliary switch tube S is turned on at time t1_a2Filter capacitor voltage-V_oAdded to the resonant inductor L_rTwo ends, which are charged by the inductor, so as to flow through the resonant inductor L_rAuxiliary inductor current i_LrLinearly increasing, auxiliary inductor current i_LrSwitch tube S flowing through auxiliary tube_a2And an auxiliary diode D_a1；

Stage 3[ t 2-t 3]: as shown in fig. 15, the auxiliary inductor current i_LrIs continuously charged to a charging current i_ch，i_chGreater than the filter inductance current I_LPart of the current of the switch tube S₂Flowing through;

stage 4[ t 3-t 4]: as shown in fig. 16, the switching tube S is turned off at time t3₂Resonant capacitor C_r1Upper voltage u_Cr1From zero to DC bus voltage V_dcOne half of (1), resonant capacitor C_r2Voltage u of_Cr2From the DC bus voltage V _dc2 ofOne-half down to zero and current flows through diode D₄Diode D₅Follow current due to switching tube S₂Resonance capacitor C after switch-off_r1Charging, switching tube S₂The voltage of the switch cannot rise immediately, and zero voltage turn-off is realized;

stage 5[ t 4-t 5]: as shown in FIG. 17, the resonant capacitor C_r2Upper voltage u_Cr2Resonant to zero, diode D₃Naturally conducting, switching tube S₃The upper voltage is zero, and the switching tube S is turned on at the stage₃Tube, realizing switching tube S₃Zero voltage conduction, resonant inductance L_rUpper auxiliary inductor current i_LrLinearly down to the filter inductor current I_L；

Stage 6[ t 5-t 6]: as shown in fig. 18, the auxiliary inductor current i_LrLinear discharge to zero, switching tube S₃Switch tube S₄Current at is linearly increased to the filter inductor current I_LAfter the current on the resonant inductor is reduced to zero, the auxiliary switch tube S_a2The upper current is zero, and the auxiliary switch tube S is turned off after the time t6_a2Zero current turn-off is realized;

stage 7[ t 6-t 7]: as shown in fig. 19, the switching tube S₃Switch tube S₄Switch tube S₅On state, switching tube S₁Switch tube S₂Switch tube S₆Auxiliary switch tube S_a1Auxiliary switch tube S_a2In the off state, filtering the inductor current-I_LFlows through the switch tube S₃Switch tube S₄Providing energy for the load to reach a steady state stage;

stage 8[ t 7-t 8]: as shown in FIG. 20, the switch tube S is turned off at time t7₃Resonant capacitor C_r2Voltage u_Cr2From zero to DC bus voltage V_dcOne half of (1), resonant capacitor C_r1Voltage u of_Cr1From the DC bus voltage V_dcOne half of (S) drops to zero due to the switching tube S₃Resonance capacitor C after switch-off_r2Charging, switching tube S₃Zero voltage turn-off is realized;

stage 9[ t 8-t 0]: as shown in FIG. 21, resonant capacitor C_r1At upper voltageAfter falling to zero, the diode D₂Naturally conducting, switching tube S₂The upper voltage is zero, and the switching tube S is turned on at the stage₂Realize the switch tube S₂Zero voltage conduction, filtering of the inductor current-I_LFlow-through diode D₂And a switching tube S₅Energy is provided for the load R, the commutation process is finished, and the loop returns to the initial stage 1 before commutation.

Claims (2)

1. The utility model provides an auxiliary resonance utmost point active clamping three-level soft switch inverter circuit which characterized in that: the active clamping type resonant inverter comprises an active clamping main inverter circuit, an auxiliary resonant converter circuit, a filter circuit and a load R;

the active clamping main inverter circuit comprises a direct current positive bus P, a direct current negative bus N, a direct current bus midpoint O, six switching tubes with anti-parallel diodes and two same supporting capacitors; six switch tubes with anti-parallel diodes are respectively marked as switch tubes S₁Switch tube S₂Switch tube S₃Switch tube S₄Switch tube S₅And a switching tube S₆Six anti-parallel diodes are respectively marked as diode D₁Diode D₂Diode D₃Diode D₄Diode D₅Diode D₆The two support capacitors are respectively marked as the support capacitor C₁And a support capacitor C₂Wherein, the DC bus voltage is denoted as V_dcSupporting capacitor C₁Connected between the positive DC bus P and the midpoint O of the DC bus, and supporting a capacitor C₂The direct current bus neutral point O is connected with the direct current negative bus N; switch tube S₁Switch tube S₂Switch tube S₃Switch tube S₄Are sequentially connected in series, and switch tube S₁The input end of the switch tube is connected with a direct current positive bus P and a switch tube S₁The output end of the switch tube S₂Of the input terminal, switching tube S₂The output end of the switch tube S₃Of the input terminal, switching tube S₃The output end of the switch tube S₄Of the input terminal, switching tube S₄The output end of the direct current negative bus is connected with a direct current negative bus N; switch tube S₅Is connected with the switch tube S₁Of the output terminal, switching tube S₅The output end of the direct current bus is connected with a midpoint O of the direct current bus; switch tube S₆The input end of the switch tube S is connected with a DC bus midpoint O and a switching tube S₆The output end of the switch tube S₃An output terminal of (a);

the auxiliary resonance commutation circuit comprises two auxiliary switching tubes with anti-parallel diodes, two resonance capacitors and a resonance inductor L_rTwo auxiliary switch tubes with anti-parallel diodes are respectively marked as an auxiliary switch tube S_a1And an auxiliary switching tube S_a2Two antiparallel diodes are respectively denoted as auxiliary diode D_a1And an auxiliary diode D_a2The two resonant capacitors are respectively denoted as resonant capacitor C_r1And a resonance capacitor C_r2Wherein an auxiliary switch tube S_a1The output end of the switch is connected with an auxiliary switch tube S_a2Output terminal of (2), auxiliary switch tube S_a2Is connected with the resonant inductor L_rOf the output terminal of the resonant inductor L_rThe input end of the switching tube S is connected with the active clamping main inverter circuit₂An output terminal of (a); resonant capacitor C_r1Switch tube S of active clamping main inverter circuit₂Parallel resonant capacitor C_r2Switch tube S of active clamping main inverter circuit₃Parallel connection;

the filter circuit is an LC filter circuit and is formed by connecting a filter inductor L and a filter capacitor C in series, wherein the input end of the filter inductor L is connected with a switching tube S of the active clamping main inverter circuit₂The output end of the filter inductor L is connected with the input end of the filter capacitor C, and the output end of the filter capacitor C is connected with the midpoint O of the direct current bus;

resonance inductance L of auxiliary resonance commutation circuit_rAuxiliary switch tube S_a2And an auxiliary switching tube S_a1Sequentially connected in series and then connected in parallel with a filter inductor L in an LC filter circuit, wherein the resonance inductor L_rIs connected with the input end of the filter inductor L and the auxiliary switch tube S_a1The input end of the filter capacitor C is connected with the output end of the filter inductor L, and the filter capacitor C is connected with the load R in parallel.

2. The modulation method of the auxiliary resonant pole active clamping three-level soft switching inverter circuit as claimed in claim 1, wherein the switching tube of the auxiliary resonant pole active clamping three-level soft switching inverter circuit operates as follows:

(1) six switching tubes in the active clamping main inverter circuit work in the following mode:

switch tube S₁Switch tube S₄Switch tube S₅Switch tube S₆Power frequency action, switch tube S₂And a switching tube S₃Conducting in a high-frequency complementary manner;

when switching tube S₁Switch tube S₂Switch tube S₆In a conducting state, the switch tube S₃Switch tube S₄Switch tube S₅When the bridge arm is in a turn-off state, the bridge arm side outputs a positive level;

when switching tube S₁Switch tube S₃Switch tube S₆In a conducting state, the switch tube S₂Switch tube S₄Switch tube S₅When the bridge arm is in a turn-off state, the bridge arm side outputs zero level;

when switching tube S₃Switch tube S₄Switch tube S₅In a conducting state, the switch tube S₁Switch tube S₂Switch tube S₆When the bridge arm is in a turn-off state, the bridge arm side outputs a negative level;

when switching tube S₂Switch tube S₄Switch tube S₅In a conducting state, the switch tube S₁Switch tube S₃Switch tube S₆When the bridge arm is in a turn-off state, the bridge arm side outputs zero level;

the switch tube S₂And a switching tube S₃High frequency complementary conduction, meaning switch tube S₂Switch tube S₃Complementary conduction according to sine pulse width modulation, switching tube S₂On-time ratio of switching tube S₃Is delayed by a dead time td, switch S₃On-time ratio of switching tube S₂The turn-off time of (c) is delayed by a dead time td;

(2) the two auxiliary switching tubes in the auxiliary resonant converter circuit work in the following way:

recording the voltage on the filter capacitor C as the filter capacitorVoltage V_oThe current on the filter inductor L is recorded as the filter inductor current I_L；

At the filter capacitor voltage V_oIs positive, filtering the inductive current I_LWhen the output of the positive and bridge arm sides is converted between zero level and positive level, the auxiliary switch tube S_a1On-time ratio of switching tube S₃The turn-off time of the auxiliary switch tube S is advanced, the advance time is td1_a1Turn-off time ratio of the switching tube S₂The switching-on time of (1) is delayed, the delay time is td2, and an auxiliary switch tube S_a2Constant turn-off;

at the filter capacitor voltage V_oIs a negative, filtering inductor current I_LWhen the output of the negative bridge arm side and the output of the bridge arm side are switched between zero level and negative level, the auxiliary switch tube S_a2On-time ratio of switching tube S₂The turn-off time of the auxiliary switch tube S is advanced, the advance time is td1_a2Turn-off time ratio of the switching tube S₃The switching-on time of (1) is delayed, the delay time is td2, and an auxiliary switch tube S_a1Constant turn-off;

the advance time td1 and the delay time td2 respectively satisfy the following conditions:

wherein L is_rIs the value of the resonant inductance, V_dcIs the DC bus voltage i_chIs a resonant inductor L_rAt the maximum charging current value, which is recorded as charging current i_ch。

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