Three-phase single-stage isolated half-bridge bidirectional ACDC matrix converter and control method

Abstract

The invention discloses a three-phase single-stage isolated half-bridge bidirectional ACDC matrix converter and a control method. The matrix conversion switch group is connected between a three-phase power supply and a first bus Y, the isolation converter is connected between the first bus Y and a second bus O, the second bus O is coupled to the three-phase power supply, and the secondary full-bridge unit is connected to the secondary side of the isolation converter. A controller controls the switches of the matrix conversion switch group to be turned on in turn, so that the three phases of the three-phase power supply ABC are connected to the first bus Y end in sequence, and an alternating voltage is generated at both ends of the isolation converter, so that the isolation converter generates an alternating electromagnetic field. The invention can realize soft switching control by controlling the timing of the switch tubes in each bridge arm. The level of the input end of the isolation converter can realize three levels of positive, zero and negative. The control method can simultaneously adopt frequency modulation and duty cycle adjustment. Compared with single frequency modulation or duty cycle adjustment, a wider output voltage range can be realized, the reactive power of power conversion can be reduced, and the overall efficiency and the power density of the converter can be improved.

Description

Technical Field

[0001] The invention relates to a power converter, and in particular to a three-phase single-stage isolated half-bridge bidirectional ACDC matrix converter and a control method. Background Art

[0002] Modern electrical equipment cannot do without power supply. In the field of communication power supply application, the converter must meet the requirements of total harmonic distortion, harmonic current limitation, isolation and high conversion efficiency. The converter with higher power adopts a three-phase two-stage design. The first stage adopts PFC controlled boost to meet the purpose of power factor correction. The second stage realizes the purpose of voltage transformation / isolation and output voltage / current control. This stage of converter usually uses resonant switching technology to maximize the conversion efficiency and minimize the size and heat dissipation requirements of the power supply design (thus minimizing the cost). The problem with this two-stage converter is that the total conversion loss is the sum of the conversion losses of each stage. When each stage achieves a typical conversion efficiency of about 96%, the total conversion efficiency is only 92% at most.

[0003] Advantages such as high efficiency and low cost have attracted many power designers to try to develop effective single-stage AC / DC converters. Existing single-stage AC / DC converters cause losses when the current flows through the bidirectional switch, and the conversion efficiency of the converter is low. In addition, the bidirectional switch can only use the frequency modulation control method, which has a single control method and a narrow adjustment range of the entire converter. Summary of the invention

[0004] In order to solve the above defects in the prior art, the present invention proposes a three-phase single-stage isolated half-bridge bidirectional ACDC matrix converter and a control method.

[0005] The technical solution adopted by the present invention is to design a three-phase single-stage isolated half-bridge bidirectional ACDC matrix converter, including a matrix conversion switch group, a first bus Y, a second bus O, an isolation converter, a secondary full-bridge unit and a controller, wherein the matrix conversion switch group is connected between the three-phase power supply and the first bus Y, the isolation converter is connected between the first bus Y and the second bus O, the second bus O is coupled to the three-phase power supply, and the secondary full-bridge unit is connected to the DC port; the controller controls the switches of the matrix conversion switch group to be turned on in turn, providing a branch for the isolation converter to transmit energy in time.

[0006] Preferably, the matrix conversion switch group includes an A-phase bridge arm, a B-phase bridge arm, a C-phase bridge arm and a zero-level bridge arm, the A-phase bridge arm is connected between the first bus Y and the A-phase input terminal of the three-phase power supply, the B-phase bridge arm is connected between the first bus Y and the B-phase input terminal of the three-phase power supply, the C-phase bridge arm is connected between the first bus Y and the C-phase input terminal of the three-phase power supply, and the zero-level bridge arm is connected between the first bus Y and the second bus O.

[0007] Preferably, the A-phase bridge arm, the B-phase bridge arm, the C-phase bridge arm and the zero-level bridge arm all include upper switches and lower switches connected in series, and the upper switches and lower switches all use switch tubes with parallel diodes, and the upper switches and lower switches in one bridge arm adopt a reverse series connection structure; the A-phase bridge arm includes an A-phase upper switch Q1 and an A-phase lower switch Q2, the B-phase bridge arm includes a B-phase upper switch Q3 and a B-phase lower switch Q4, the C-phase bridge arm includes a C-phase upper switch Q5 and a C-phase lower switch Q6, and the zero-level bridge arm includes a zero-level upper switch Q7 and a zero-level lower switch Q8.

[0008] Optionally, the isolation converter includes a resonant inductor Lr, a resonant capacitor Cr and an isolation transformer Tr, the isolation transformer Tr includes a primary winding Lm and a secondary winding Ln, the resonant inductor Lr, the resonant capacitor Cr and the primary winding Lm are connected in series and then connected between the first bus Y and the second bus O, and the secondary winding Ln is connected to the secondary full-bridge unit.

[0009] Optionally, the second bus O is connected to the power frequency zero potential point in the three-phase power supply.

[0010] Optionally, a three-phase resonant capacitor group is connected between the second bus O and the three-phase power supply, and the three-phase resonant capacitor group includes a seventh capacitor C7, an eighth capacitor C8 and a ninth capacitor C9, wherein the seventh capacitor C7 is connected between the A-phase input terminal and the second bus O, the eighth capacitor C8 is connected between the B-phase input terminal and the second bus O, and the ninth capacitor C9 is connected between the C-phase input terminal and the second bus O.

[0011] Optionally, the isolation converter includes a resonant inductor Lr and an isolation transformer Tr, the isolation transformer Tr includes a primary winding Lm and a secondary winding Ln, the resonant inductor Lr is connected in series with the primary winding Lm and is connected between the first bus Y and the second bus O, and the secondary winding Ln is connected to the secondary full-bridge unit.

[0012] Optionally, a three-phase resonant capacitor group is connected between the second bus O and the three-phase power supply, and the three-phase resonant capacitor group includes a seventh capacitor C7, an eighth capacitor C8 and a ninth capacitor C9, wherein the seventh capacitor C7 is connected between the A-phase input terminal and the second bus O, the eighth capacitor C8 is connected between the B-phase input terminal and the second bus O, and the ninth capacitor C9 is connected between the C-phase input terminal and the second bus O; the three-phase resonant capacitor group also includes a tenth capacitor C10, an eleventh capacitor C11 and a twelfth capacitor C12, wherein the tenth capacitor C10 is connected between the A-phase input terminal and the B-phase input terminal, the eleventh capacitor C11 is connected between the B-phase input terminal and the C-phase input terminal, and the twelfth capacitor C12 is connected between the C-phase input terminal and the A-phase input terminal.

[0013] The present invention also designs a control method for a three-phase single-stage isolated half-bridge bidirectional ACDC matrix converter, wherein the converter adopts the above-mentioned three-phase single-stage isolated half-bridge bidirectional ACDC matrix converter, and the control method comprises: collecting the voltage parameters of the three-phase power supply, dividing one power frequency cycle of the three-phase power supply into twelve sectors starting from the zero-crossing point where the A-phase voltage changes from negative to positive, each sector occupies 30°, and in each sector, the phase with the largest absolute voltage value in the three-phase power supply is recorded as the L phase, the phase with the larger absolute voltage value is recorded as the M phase, and the phase with the smallest absolute voltage value is recorded as the S phase; controlling the switches in the bridge arms connecting the L phase, the M phase, the S phase and the zero-level bridge arm to perform frequency modulation and duty cycle modulation, so that the bus voltage Uyo between the first bus Y and the second bus O generates positive level, negative level, and zero level changes within one control cycle.

[0014] Preferably, within the control cycle, the positive level is the L-phase voltage, the negative level is the M-phase voltage and the S-phase voltage, and the positive level, zero level and negative level change alternately; or within the control cycle, the negative level is the L-phase voltage, the positive level is the M-phase voltage and the S-phase voltage, and the negative level, zero level and positive level change alternately.

[0015] Preferably, the control method also includes: detecting the positive and negative values ​​of the L phase and the M phase in each sector; when the L phase is a positive value and the M phase is a negative value, controlling the upper tube switch in the bridge arm connected to the L phase to be normally open or to perform frequency modulation and duty cycle modulation, and the lower tube switch to perform frequency modulation and duty cycle modulation, and controlling the lower tube switch in the bridge arm connected to the M phase to be normally open or to perform frequency modulation and duty cycle modulation, and the upper tube switch to perform frequency modulation and duty cycle modulation; when the L phase is a negative value and the M phase is a positive value, controlling the lower tube switch in the bridge arm connected to the L phase to be normally open or to perform frequency modulation and duty cycle modulation, and the upper tube switch to perform frequency modulation and duty cycle modulation, controlling the upper tube switch in the bridge arm connected to the M phase to be normally open or to perform frequency modulation and duty cycle modulation, and the lower tube switch to perform frequency modulation and duty cycle modulation.

[0016] Preferably, the control method also includes: when the L phase is a positive value and the M phase is a negative value, the on-time period of the lower tube switch in the bridge arm connected to the L phase is within the on-time period of the lower tube switch in the zero-level bridge arm, and the on-time period of the upper tube switch in the bridge arm connected to the M phase and the on-time period of the upper tube switch and the lower tube switch in the bridge arm connected to the S phase are both within the on-time period of the upper tube switch in the zero-level bridge arm; when the L phase is a negative value and the M phase is a positive value, the on-time period of the upper tube switch in the bridge arm connected to the L phase is within the on-time period of the upper tube switch in the zero-level bridge arm, and the on-time period of the lower tube switch in the bridge arm connected to the M phase and the on-time period of the upper tube switch and the lower tube switch in the bridge arm connected to the S phase are both within the on-time period of the lower tube switch in the zero-level bridge arm.

[0017] The beneficial effects of the technical solution provided by the present invention are:

[0018] The present invention can realize soft switching control by controlling the timing of the switch tubes in each bridge arm; the level of the input end of the isolation converter can realize three levels: positive, zero and negative; the control method can simultaneously adopt frequency modulation and duty cycle adjustment, and compared with single frequency modulation or duty cycle adjustment, a wider output voltage range can be achieved; in addition, compared with the traditional two-stage AC / DC converter, the present invention can reduce the energy conversion level, reduce the reactive power of power conversion, improve the overall efficiency and the power density of the converter, and better meet the current design requirements for AC / DC power supply equipment. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] The present invention is described in detail below with reference to the embodiments and accompanying drawings, wherein:

[0020] Figure 1 It is a matrix converter with capacitor star connection;

[0021] Figure 2 It is a matrix converter with capacitor triangle connection;

[0022] Figure 3 It is a matrix converter with three-phase input and power frequency zero potential point;

[0023] Figure 4-1 It is the corresponding relationship diagram of input voltage waveform, sector and L phase, M phase and S phase;

[0024] Figure 4-2 It is a comparison diagram of input voltage waveform, sector and switch timing;

[0025] Figure 5 It is the timing diagram of the open tube in the 30° to 60° sector matrix converter;

[0026] Figure 6 is the timing diagram of the open tube in the 60° to 90° sector matrix converter;

[0027] Figure 7 It is an isolation converter with resonant inductor and resonant capacitor on the primary side and capacitor on the secondary side;

[0028] Figure 8 It is an isolation converter with resonant inductor and resonant capacitor on the primary side and inductor and capacitor on the secondary side;

[0029] Fig. 9 The invention discloses a circuit diagram in which a secondary full-bridge unit can implement phase shift control. DETAILED DESCRIPTION

[0030] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0031] The present invention discloses a three-phase single-stage isolated half-bridge bidirectional ACDC matrix converter. Figures 1 to 3 As shown in the circuit diagram, the matrix converter at least includes: a matrix conversion switch group, a first bus Y, a second bus O, an isolation converter, a secondary full-bridge unit and a controller. The matrix conversion switch group is connected between the three-phase power supply and the first bus Y, the isolation converter is connected between the first bus Y and the second bus O, the second bus O is coupled to the three-phase power supply, and the secondary full-bridge unit is connected to the DC port; the controller controls the switches of the matrix conversion switch group to be turned on in turn, providing a branch for the isolation converter to transmit energy in time.

[0032] It should be noted that the present invention is a bidirectional AC / DC converter that can convert alternating current ( Figure 1 middle left) into direct current ( Figure 1 The DC power can also be converted into AC power.

[0033] In a preferred embodiment, the matrix conversion switch group includes an A-phase bridge arm (Q1 and Q2), a B-phase bridge arm (Q3 and Q4), a C-phase bridge arm (Q5 and Q6) and a zero-level bridge arm (Q7 and Q8), the A-phase bridge arm is connected between the first bus Y and the A-phase input terminal of the three-phase power supply, the B-phase bridge arm is connected between the first bus Y and the B-phase input terminal of the three-phase power supply, the C-phase bridge arm is connected between the first bus Y and the C-phase input terminal of the three-phase power supply, and the zero-level bridge arm is connected between the first bus Y and the second bus O.

[0034] The A-phase bridge arm, the B-phase bridge arm, and the C-phase bridge arm provide forward current for the isolation converter, and the zero-level bridge arm, together with the A, B, and C-phase bridge arms, provide reverse current for the isolation converter. In the isolation converter, the primary winding Lm of the isolation transformer Tr generates an alternating current, and the secondary winding Ln of the alternating electromagnetic field isolation transformer Tr outputs alternating current, and after rectification by the secondary full-bridge unit, direct current is provided to the load. Since the present invention is provided with a zero-level bridge arm that can provide freewheeling current and zero level, three levels are generated at the input end of the isolation converter, that is, between the first bus Y and the second bus O, that is, Uyo has three levels of positive voltage, zero voltage, and negative voltage.

[0035] See also Figures 1 to 3In the circuit diagram shown, the A-phase bridge arm, the B-phase bridge arm, the C-phase bridge arm and the zero-level bridge arm all include upper switches and lower switches connected in series, the upper switches and lower switches all use switch tubes with parallel diodes, and the upper switches and lower switches in one bridge arm use a reverse series connection structure; the A-phase bridge arm includes an A-phase upper switch Q1 and an A-phase lower switch Q2, the B-phase bridge arm includes a B-phase upper switch Q3 and a B-phase lower switch Q4, the C-phase bridge arm includes a C-phase upper switch Q5 and a C-phase lower switch Q6, and the zero-level bridge arm includes a zero-level upper switch Q7 and a zero-level lower switch Q8. Each switch can use a switching device such as MOS and IGBT.

[0036] See also Figure 1 or Figure 3 In the illustrated embodiment, the isolation converter includes a resonant inductor Lr, a resonant capacitor Cr and an isolation transformer Tr, the isolation transformer Tr includes a primary winding Lm and a secondary winding Ln, the resonant inductor Lr, the resonant capacitor Cr and the primary winding Lm are connected in series and then connected between the first bus Y and the second bus O, and the secondary winding Ln is connected to the secondary full-bridge unit.

[0037] See also Figure 3 The three-phase input matrix converter shown has an industrial frequency zero potential point, and the second bus O is connected to the industrial frequency zero potential point in the three-phase power supply. The industrial frequency zero potential point can be the industrial frequency zero potential point directly connected to the three-phase power supply, or it can be an equivalent industrial frequency zero potential point.

[0038] See also Figure 1 In the matrix converter with star-connected capacitors shown in the figure, a three-phase resonant capacitor group is connected between the second bus O and the three-phase power supply, and the three-phase resonant capacitor group includes a seventh capacitor C7, an eighth capacitor C8 and a ninth capacitor C9, wherein the seventh capacitor C7 is connected between the A-phase input terminal and the second bus O, the eighth capacitor C8 is connected between the B-phase input terminal and the second bus O, and the ninth capacitor C9 is connected between the C-phase input terminal and the second bus O.

[0039] In other embodiments, the isolation converter includes a resonant inductor Lr and an isolation transformer Tr, the isolation transformer Tr includes a primary winding Lm and a secondary winding Ln, the resonant inductor Lr is connected in series with the primary winding Lm and is connected between the first bus Y and the second bus O, and the secondary winding Ln is connected to the secondary full-bridge unit.

[0040] See also Figure 2In the matrix converter of the capacitor triangle connection method shown in the figure, a three-phase resonant capacitor group is connected between the second bus O and the three-phase power supply, and the three-phase resonant capacitor group includes a seventh capacitor C7, an eighth capacitor C8 and a ninth capacitor C9, wherein the seventh capacitor C7 is connected between the A-phase input terminal and the second bus O, the eighth capacitor C8 is connected between the B-phase input terminal and the second bus O, and the ninth capacitor C9 is connected between the C-phase input terminal and the second bus O; the three-phase resonant capacitor group also includes a tenth capacitor C10, an eleventh capacitor C11 and a twelfth capacitor C12, wherein the tenth capacitor C10 is connected between the A-phase input terminal and the B-phase input terminal, the eleventh capacitor C11 is connected between the B-phase input terminal and the C-phase input terminal, and the twelfth capacitor C12 is connected between the C-phase input terminal and the A-phase input terminal.

[0041] It should be noted that the above lists some structures of isolation converters, but these structures are not used to limit the protection scope of the present invention. In other embodiments, there are other embodiments, such as Figure 7 An isolation converter with a resonant inductor and a resonant capacitor on the primary side and a capacitor on the secondary side is shown, and Figure 8 An isolation converter with a resonant inductor and a resonant capacitor on the primary side and an inductor and a capacitor on the secondary side is shown. The structures of these isolation converters can be applied to the present invention.

[0042] Fig. 9 In the converter shown, the secondary full-bridge unit adopts a full-bridge topology structure, and the controller can implement phase shift control on the secondary full-bridge unit when controlling the switching action of the isolation converter.

[0043] The present invention also discloses a control method for a three-phase single-stage isolated half-bridge bidirectional ACDC matrix converter, wherein the converter adopts the above-mentioned three-phase single-stage isolated half-bridge bidirectional ACDC matrix converter, and the control method comprises: collecting voltage parameters of the three-phase power supply, dividing a power frequency cycle of the three-phase power supply into twelve sectors starting from the zero-crossing point where the A-phase voltage changes from negative to positive, each sector occupies 30°, and in each sector, the phase with the largest absolute voltage value in the three-phase power supply is recorded as the L phase, the phase with the largest absolute voltage value is recorded as the M phase, and the phase with the smallest absolute voltage value is recorded as the S phase; controlling the switches in the bridge arms connecting the L phase, the M phase, the S phase and the zero-level bridge arm to perform frequency modulation and duty cycle modulation, so that the bus voltage Uyo between the first bus Y and the second bus O generates positive level, negative level, and zero level changes in one sector.

[0044] In a preferred embodiment, during the control period, the positive level is the L phase voltage (such as Figure 6 The negative level is the M-phase voltage and the S-phase voltage (such as Figure 6-Vb and -Vc in the control cycle), the positive level, zero level, and negative level change alternately; or within the control cycle, the negative level is the L phase voltage (such as Figure 5 -Vb), the positive level is the M phase voltage and the S phase voltage (such as Figure 5 +Va and +Vc in the figure), the negative level, zero level and positive level change alternately.

[0045] Figure 4-1 It is a corresponding relationship diagram of input voltage waveform, sector and L phase, M phase and S phase, which includes input voltage waveform, the division position of twelve sectors, and the timing of each switch in the isolation converter. In the figure, the high level of the switch tube means that the switch tube is always on, UL is Max (|UA|, |UB|, |UC|), Us is Min (|UA|, |UB|, |UC|), UM is the third phase voltage except UL and Us; (UL is the maximum absolute value of the three-phase voltage of UA, UB and UC, and Us is the minimum absolute value of the three-phase voltage of UA, UB and UC). Figure 4-2 The input voltage waveform, sectors and switch timing comparison diagram are shown as follows: the input phase voltage is divided into 12 sectors from 0 degrees to 360 degrees, and the control of the isolation converter is as follows:

[0046] When the three-phase AC works at 330°~30°, the switch tubes Q4 and Q5 are normally open, and Q1, Q2, Q3, Q6, Q7 and Q8 are frequency modulated and duty cycle modulated;

[0047] When the three-phase AC works at 30° to 90°, the switches Q1 and Q4 are normally open, and Q2, Q3, Q5, Q6, Q7 and Q8 are frequency modulated and duty cycle modulated;

[0048] When the three-phase AC works at 90° to 150°, the switch tubes Q1 and Q6 are normally open, and Q2, Q3, Q4, Q5, Q7 and Q8 are frequency modulated and duty cycle modulated;

[0049] When the three-phase AC works at 150°~210°, the switch tubes Q3 and Q6 are normally open, and Q1, Q2, Q4, Q5, Q7 and Q8 are frequency modulated and duty cycle modulated;

[0050] When the three-phase AC works at 210°~270°, the switches Q2 and Q3 are normally open, and Q1, Q4, Q5, Q6, Q7 and Q8 are frequency modulated and duty cycle modulated;

[0051] When the three-phase AC works at 270°~330°, the switch tubes Q2 and Q5 are normally open, and Q1, Q3, Q4, Q6, Q7 and Q8 are frequency modulated and duty cycle modulated;

[0052] It should be pointed out that the phase with the largest absolute voltage value is recorded as L phase, the phase with a larger absolute voltage value is recorded as M phase, and the phase with the smallest absolute voltage value is recorded as S phase in order to simplify the subsequent description, and is not intended to limit the present invention.

[0053] In a preferred embodiment, the control method also includes: detecting the positive and negative values ​​of the L phase and the M phase in each sector; when the L phase is a positive value and the M phase is a negative value, controlling the upper tube switch in the bridge arm connected to the L phase to be normally open or to perform frequency modulation and duty cycle modulation, and the lower tube switch to perform frequency modulation and duty cycle modulation, and controlling the lower tube switch in the bridge arm connected to the M phase to be normally open or to perform frequency modulation and duty cycle modulation, and the upper tube switch to perform frequency modulation and duty cycle modulation; when the L phase is a negative value and the M phase is a positive value, controlling the lower tube switch in the bridge arm connected to the L phase to be normally open or to perform frequency modulation and duty cycle modulation, and the upper tube switch to perform frequency modulation and duty cycle modulation, controlling the upper tube switch in the bridge arm connected to the M phase to be normally open or to perform frequency modulation and duty cycle modulation, and the lower tube switch to perform frequency modulation and duty cycle modulation.

[0054] It should be noted that in the above “the switch can be normally open or can be frequency modulated and duty cycle modulated”, when the duty cycle is 1, the switch is normally open, and when the switch is duty cycle modulated, its duty cycle can be larger than the duty cycle of another switch in the bridge arm. In the prior art, since there is no three-level control technology, the switch can only be controlled by frequency modulation, and it is impossible to simultaneously modulate the frequency and the duty cycle. Therefore, the control method of the present invention is more flexible and diverse, and can achieve a wider output voltage range.

[0055] In a preferred embodiment, the control method further includes:

[0056] When the L phase is a positive value and the M phase is a negative value, the conduction period of the lower tube switch in the bridge arm connected to the L phase is within the conduction period of the lower tube switch in the zero-level bridge arm, the conduction period of the upper tube switch in the bridge arm connected to the M phase and the conduction period of the upper tube switch and the lower tube switch in the bridge arm connected to the S phase are all within the conduction period of the upper tube switch in the zero-level bridge arm.

[0057] See also Figure 6The open-tube timing diagram in the 60° to 90° sector matrix converter is shown. In this sector, the A phase voltage has the largest absolute value, the voltage value is positive, and is counted as the L phase. The B phase voltage has a larger absolute value, the voltage value is negative, and is counted as the M phase. The C phase voltage has the smallest absolute value, and is counted as the S phase. The zero-level lower switch Q8 in the zero-level bridge arm follows the A-phase lower switch Q2 in the A-phase bridge arm to act, and from the vertical coordinate in the figure, the conduction period of the A-phase lower switch Q2 is within the conduction period of the zero-level lower switch Q8. The zero-level upper switch Q7 in the zero-level bridge arm follows the B-phase upper switch Q3 in the B-phase bridge arm to act, and from the vertical coordinate in the figure, the conduction period of the B-phase upper switch Q3 and the conduction periods of the C-phase upper switch Q5 and the C-phase lower switch Q6 in the C-phase bridge arm are all within the conduction period of the zero-level upper switch Q7. See. Figure 6 At the bottom, through such resonance control, three levels are generated between the input ends of the isolation converter (the first bus Y and the second bus O), that is, Uyo has three levels of positive voltage (t0 to t1 period), zero voltage (t1 to t2 period) and negative voltage (t2 to t6 period), and the primary side current ir of the isolation transformer Tr appears a sinusoidal waveform.

[0058] When the L phase is a negative value and the M phase is a positive value, the conduction period of the upper tube switch in the bridge arm connected to the L phase is within the conduction period of the upper tube switch in the zero-level bridge arm, the conduction period of the lower tube switch in the bridge arm connected to the M phase and the conduction period of the upper tube switch and the lower tube switch in the bridge arm connected to the S phase are all within the conduction period of the lower tube switch in the zero-level bridge arm.

[0059] See also Figure 5 The open-tube timing diagram in the 30° to 60° sector matrix converter is shown. In this sector, the absolute value of the voltage of phase B is the largest, the voltage value is negative, and it is counted as the L phase. The absolute value of the voltage of phase A is larger, the voltage value is positive, and it is counted as the M phase. The absolute value of the voltage of phase C is the smallest, and it is counted as the S phase. The zero-level upper switch Q7 in the zero-level bridge arm follows the action of the B-phase upper switch Q3 in the B-phase bridge arm, and from the vertical coordinate in the figure, the conduction period of the B-phase upper switch Q3 is within the conduction period of the zero-level upper switch Q7. The zero-level lower switch Q8 in the zero-level bridge arm follows the action of the A-phase lower switch Q2 in the A-phase bridge arm, and from the vertical coordinate in the figure, the conduction period of the A-phase lower switch Q2 and the conduction period of the C-phase upper switch Q5 and the C-phase lower switch Q6 in the C-phase bridge arm are all within the conduction period of the zero-level lower switch Q8. See. Figure 5 At the bottom, through such resonance control, three levels are generated between the input ends of the isolation converter (the first bus Y and the second bus O), that is, Uyo has three levels of positive voltage (period from t2 to t6), zero voltage (period from t6 to t7) and negative voltage (period from t7 to t9), and the primary side current ir of the isolation transformer Tr presents a sinusoidal waveform.

[0060] In each switching cycle, it can be divided into 8 working states. Taking the 30° to 90° sector of the working area as an example, there are: |V A |>|V B |>|V C (Q1 and Q4 are normally open). The following is a detailed analysis of the working states:

[0061] Working state 1: t0~t1. Before t0, ir < 0, Q1 conducts, and the body diodes of Q1 and Q2 provide a loop for the current of the isolated converter. The voltage between the Y and O lines of the isolated converter is Va. At t0, Q2 and Q8 conduct, Va > 0, and the voltage between the Y and O lines of the isolated converter remains Va. Lr, Cr, and Tr form a resonant cavity, and ir changes from negative to positive;

[0062] Working state 2: t1~t2. At t1, ir > 0, Q2 turns off, and the body diodes of Q8 and Q7 conduct to provide a loop for the current of the isolated converter. The voltage between the Y and O lines of the isolated converter changes from Va to 0. Lr, Cr, and Lm form a resonant cavity, and ir > 0;

[0063] Working state 3: t2~t3. At t2, ir > 0, Q8 turns off, and the body diodes of Q4 and Q3 provide a loop for the current of the isolated converter. The voltage between the Y and O lines of the isolated converter changes from 0 to Vb;

[0064] Working state 4: t3~t4

[0065] At t3, Q3, Q5, and Q7 conduct, ir > 0, Q3 achieves ZVS turn-on, and the voltage between the Y and O lines of the isolated converter is Vb. Lr, Cr, and Tr form a resonant cavity, and ir changes from positive to negative. Since Vb < Vc < 0, the voltage between the Y and O lines of the isolated converter remains Vb;

[0066] Working state 5: t4~t5. At t4, Q3 turns off, Q5 and Q7 conduct, ir < 0. At this time, Vc < 0, and the body diodes of Q5 and Q6 provide a loop for the current of the isolated converter. The voltage between the Y and O lines of the isolated converter changes from Vb to Vc. Lr, Cr, and Tr form a resonant cavity, and ir < 0;

[0067] Working state 6: t5~t6. At t5, Q5, Q6, and Q7 turn on, ir < 0, Q6 achieves ZVS turn-on, Vc < 0, and the voltage between the Y and O lines of the isolated converter is Vc. Lr, Cr, and Tr form a resonant cavity, and ir < 0;

[0068] Working state 7: t6~t7, at t6, Q5 and Q6 are turned off, Q7 is turned on, ir<0, Q7 and Q8 body diodes provide a loop for the current of the isolation converter, and the voltage between the Y and O lines of the isolation converter changes from Vc to 0; Lr, Cr, and Lm form a resonant cavity, ir<0;

[0069] Working state 8: t7~t8, at t7, Q7 is turned off, ir<0, Q1 and Q2 diodes provide a loop for the current of the isolation converter, and the voltage between the Y and O lines of the isolation converter changes from 0 to Va; Lr, Cr, and Tr form a resonant cavity, ir<0.

[0070] The other working ranges are similar to the 30° to 90° working state and are not listed here one by one.

[0071] In a preferred embodiment, the secondary side full-bridge unit adopts a full-bridge structure, including a first bridge arm and a second bridge arm; the first bridge arm includes a ninth switch Q9 and a tenth switch Q10 connected in series, and the second bridge arm includes an eleventh switch Q11 and a twelfth switch Q12 connected in series, and the midpoints of the first bridge arm and the second bridge arm are respectively connected to the isolation converter; the first and second bridge arms control the switching action according to the positive, negative, and zero levels required by the secondary side of the isolation converter.

[0072] The above embodiments are for illustration only and are not intended to be limiting. Any equivalent modifications or changes made thereto without departing from the spirit and scope of the present application shall be included in the scope of the claims of the present application.

Claims

1. A three-phase single-stage isolated half-bridge bidirectional ACDC matrix converter, characterized in that: The invention comprises a matrix conversion switch group, a first bus Y, a second bus O, an isolation converter, a secondary full-bridge unit and a controller, wherein The matrix conversion switch group is connected between the three-phase power supply and the first bus Y, the isolation converter is connected between the first bus Y and the second bus O, the second bus O is coupled to the three-phase power supply, and the secondary full-bridge unit is connected to the DC port; The controller controls the switches of the matrix conversion switch group to be turned on in turn, providing a branch for the isolation converter to transmit energy in time; The matrix conversion switch group includes an A-phase bridge arm, a B-phase bridge arm, a C-phase bridge arm and a zero-level bridge arm, wherein the A-phase bridge arm is connected between the first bus Y and the A-phase input terminal of the three-phase power supply, the B-phase bridge arm is connected between the first bus Y and the B-phase input terminal of the three-phase power supply, the C-phase bridge arm is connected between the first bus Y and the C-phase input terminal of the three-phase power supply, and the zero-level bridge arm is connected between the first bus Y and the second bus O; The voltage parameters of the three-phase power supply are collected, and one power frequency cycle of the three-phase power supply is divided into twelve sectors starting from the zero-crossing point where the voltage of phase A changes from negative to positive, each sector occupies 30°, and the phase with the largest absolute value of voltage in the three-phase power supply in each sector is recorded as L phase, the phase with the largest absolute value of voltage is recorded as M phase, and the phase with the smallest absolute value of voltage is recorded as S phase; Control the switches in the bridge arms connecting the L phase, M phase, S phase and the zero level bridge arm to perform frequency modulation and duty cycle modulation, so that the bus voltage Uyo between the first bus Y and the second bus O generates positive level, negative level and zero level changes within one control cycle; In the control cycle, the positive level is the L phase voltage, the negative level is the M phase voltage and the S phase voltage, and the positive level, zero level and negative level change alternately; Or in the control cycle, the negative level is the L phase voltage, the positive level is the M phase voltage and the S phase voltage, and the negative level, zero level and positive level change alternately; Detect the positive and negative values ​​of L phase and M phase in each sector; When the L phase is positive and the M phase is negative, the upper switch in the bridge arm connected to the L phase can be normally open or frequency modulated and duty cycle modulated, and the lower switch can be frequency modulated and duty cycle modulated; the lower switch in the bridge arm connected to the M phase can be normally open or frequency modulated and duty cycle modulated, and the upper switch can be frequency modulated and duty cycle modulated; When the L phase is a negative value and the M phase is a positive value, the lower tube switch in the bridge arm connected to the L phase can be normally open or can perform frequency modulation and duty cycle modulation, and the upper tube switch can perform frequency modulation and duty cycle modulation. The upper tube switch in the bridge arm connected to the M phase can be normally open or can perform frequency modulation and duty cycle modulation, and the lower tube switch can perform frequency modulation and duty cycle modulation.

2. The three-phase single-stage isolated half-bridge bidirectional ACDC matrix converter according to claim 1, characterized in that: The A-phase bridge arm, the B-phase bridge arm, the C-phase bridge arm and the zero-level bridge arm all include upper switches and lower switches connected in series, the upper switches and lower switches are both connected in parallel with diodes, and the upper switches and lower switches in one bridge arm adopt a reverse series connection structure; the A-phase bridge arm includes an A-phase upper switch Q1 and an A-phase lower switch Q2, the B-phase bridge arm includes a B-phase upper switch Q3 and a B-phase lower switch Q4, the C-phase bridge arm includes a C-phase upper switch Q5 and a C-phase lower switch Q6, and the zero-level bridge arm includes a zero-level upper switch Q7 and a zero-level lower switch Q8.

3. The three-phase single-stage isolated half-bridge bidirectional ACDC matrix converter according to claim 2, characterized in that: The isolation converter includes a resonant inductor Lr, a resonant capacitor Cr and an isolation transformer Tr. The isolation transformer Tr includes a primary winding Lm and a secondary winding Ln. The resonant inductor Lr, the resonant capacitor Cr and the primary winding Lm are connected in series and then connected between the first bus Y and the second bus O. The secondary winding Ln is connected to the secondary full-bridge unit.

4. The three-phase single-stage isolated half-bridge bidirectional ACDC matrix converter according to claim 3, characterized in that: The second busbar O is connected to the power frequency zero potential point in the three-phase power supply.

5. The three-phase single-stage isolated half-bridge bidirectional ACDC matrix converter according to claim 3, characterized in that: A three-phase resonant capacitor group is connected between the second bus O and the three-phase power supply, and the three-phase resonant capacitor group includes a seventh capacitor C7, an eighth capacitor C8 and a ninth capacitor C9, wherein the seventh capacitor C7 is connected between the A-phase input terminal and the second bus O, the eighth capacitor C8 is connected between the B-phase input terminal and the second bus O, and the ninth capacitor C9 is connected between the C-phase input terminal and the second bus O.

6. The three-phase single-stage isolated half-bridge bidirectional ACDC matrix converter according to claim 2, characterized in that: The isolation converter includes a resonant inductor Lr and an isolation transformer Tr, the isolation transformer Tr includes a primary winding Lm and a secondary winding Ln, the resonant inductor Lr is connected in series with the primary winding Lm and is connected between the first bus Y and the second bus O, and the secondary winding Ln is connected to the secondary full-bridge unit.

7. The three-phase single-stage isolated half-bridge bidirectional ACDC matrix converter according to claim 6, characterized in that: A three-phase resonant capacitor group is connected between the second bus O and the three-phase power supply, and the three-phase resonant capacitor group includes a seventh capacitor C7, an eighth capacitor C8 and a ninth capacitor C9, wherein the seventh capacitor C7 is connected between the A-phase input terminal and the second bus O, the eighth capacitor C8 is connected between the B-phase input terminal and the second bus O, and the ninth capacitor C9 is connected between the C-phase input terminal and the second bus O; the three-phase resonant capacitor group also includes a tenth capacitor C10, an eleventh capacitor C11 and a twelfth capacitor C12, wherein the tenth capacitor C10 is connected between the A-phase input terminal and the B-phase input terminal, the eleventh capacitor C11 is connected between the B-phase input terminal and the C-phase input terminal, and the twelfth capacitor C12 is connected between the C-phase input terminal and the A-phase input terminal.

8. A control method for a three-phase single-stage isolated half-bridge bidirectional ACDC matrix converter, characterized in that: The converter adopts the three-phase single-stage isolated half-bridge bidirectional ACDC matrix converter according to any one of claims 1 to 7, and the control method comprises: collecting the voltage parameters of the three-phase power supply, dividing a power frequency cycle of the three-phase power supply into twelve sectors starting from the zero-crossing point where the A-phase voltage changes from negative to positive, each sector occupies 30°, and in each sector, the phase with the largest absolute voltage value in the three-phase power supply is recorded as L phase, the phase with the larger absolute voltage value is recorded as M phase, and the phase with the smallest absolute voltage value is recorded as S phase; The switches in the bridge arms connecting the L phase, M phase, S phase and the zero level bridge arm are controlled to perform frequency modulation and duty cycle modulation, so that the bus voltage Uyo between the first bus Y and the second bus O generates positive level, negative level and zero level changes within one control cycle.

9. The control method of the three-phase single-stage isolated half-bridge bidirectional ACDC matrix converter according to claim 8, characterized in that: In the control cycle, the positive level is the L phase voltage, the negative level is the M phase voltage and the S phase voltage, and the positive level, zero level and negative level change alternately; Alternatively, within the control cycle, the negative level is the L-phase voltage, the positive level is the M-phase voltage and the S-phase voltage, and the negative level, zero level, and positive level change alternately.

10. The control method of the three-phase single-stage isolated half-bridge bidirectional ACDC matrix converter according to claim 9, characterized in that: The control method further comprises: detecting positive and negative values ​​of the L phase and the M phase in each sector; When the L phase is positive and the M phase is negative, the upper switch in the bridge arm connected to the L phase can be normally open or frequency modulated and duty cycle modulated, and the lower switch can be frequency modulated and duty cycle modulated; the lower switch in the bridge arm connected to the M phase can be normally open or frequency modulated and duty cycle modulated, and the upper switch can be frequency modulated and duty cycle modulated; When the L phase is a negative value and the M phase is a positive value, the lower tube switch in the bridge arm connected to the L phase can be normally open or can perform frequency modulation and duty cycle modulation, and the upper tube switch can perform frequency modulation and duty cycle modulation. The upper tube switch in the bridge arm connected to the M phase can be normally open or can perform frequency modulation and duty cycle modulation, and the lower tube switch can perform frequency modulation and duty cycle modulation.

11. The control method of the three-phase single-stage isolated half-bridge bidirectional ACDC matrix converter according to claim 10, characterized in that: The control method further comprises: When the L phase is a positive value and the M phase is a negative value, the conduction period of the lower switch in the bridge arm connected to the L phase is within the conduction period of the lower switch in the zero-level bridge arm, and the conduction period of the upper switch in the bridge arm connected to the M phase and the conduction period of the upper switch and the lower switch in the bridge arm connected to the S phase are both within the conduction period of the upper switch in the zero-level bridge arm; When the L phase is a negative value and the M phase is a positive value, the conduction period of the upper tube switch in the bridge arm connected to the L phase is within the conduction period of the upper tube switch in the zero-level bridge arm, the conduction period of the lower tube switch in the bridge arm connected to the M phase and the conduction period of the upper tube switch and the lower tube switch in the bridge arm connected to the S phase are all within the conduction period of the lower tube switch in the zero-level bridge arm.

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