A dynamic regulation control system and control method for a DAB converter

Abstract

The invention discloses a dynamic regulation control system and control method of a DAB converter. The control system comprises a DAB converter, a PWM signal generator, and a modulation unit. The output current I o , output voltage V o After multiplication, the output power P is obtained o , output power P o With reference output power P O_ref The deviation signal is input into the PI controller; the output voltage V o With reference output voltage V O_ref The voltage deviation signal proportional coefficient k is obtained by operation. The voltage deviation signal proportional coefficient k is correlated with the output signal of the PI controller to obtain the shift factor x. At the same time, nVo is related to the input voltage V dc Divide the phase to get the voltage transfer ratio d; calculate the full power section transfer ratio D 0 , D 1 and D 2 , shift ratio D 0 , D 1 and D 2 The invention can ensure that the stabilization time of the controlled quantity in the control system is reduced in the DAB converter, the overshoot is reduced, the response speed of the control system is improved, and the loss in the starting process is reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of DAB converters, and in particular to a dynamic regulation control system and a control method of a DAB converter. Background Art

[0002] In recent years, in order to achieve the "dual carbon" goal, the installed capacity of new energy power generation systems represented by solar energy and wind energy has increased year by year. Promoting DC microgrids is an effective way to deal with the volatility and randomness of new energy power generation systems, and is of great significance to achieving sustainable development of energy. With the rapid development of DC microgrid technology and the popularization of renewable energy, bidirectional DC-DC converters have also become a hot topic of research in recent years. Bidirectional DC-DC converters have the ability to flow energy in both directions and are important devices for achieving DC microgrid bus voltage balance and efficient power distribution. DAB (dual active bridge) has the advantages of high power density, electrical isolation, bidirectional energy flow, and easy soft switching, and has been widely used in DC microgrid systems.

[0003] Common modulation modes of DAB converters include single phase shift modulation (SPS), extended phase shift modulation (EPS), double phase shift modulation (DPS) and triple phase shift modulation (TPS). Since TPS modulation has three phase shift control ratios, it has high control flexibility. By calculating the relationship between the three phase shift control ratios, the constraints of the global optimal modulation can be obtained. However, when the DAB converter adopts the traditional PI control loop, the settling time and overshoot of the controlled quantity are large, resulting in large losses during the startup process. Summary of the invention

[0004] The object of the present invention is to provide a dynamic regulation control system and control method of a DAB converter, which can ensure that the stabilization time of the controlled quantity in the control system is reduced in the DAB converter, the overshoot is reduced, the response speed of the control system is improved, and the loss during the startup process is reduced.

[0005] To achieve the above object, the present invention provides a dynamic regulation control system for a DAB converter, comprising a DAB converter, a PWM signal generator, and a modulation unit. The output current I o , output voltage V o After multiplication, the output power P is obtained o , output power P o With reference output power P O_ref The deviation signal is input into the PI controller; the output voltage V o With reference output voltage V O_refThe voltage deviation signal proportional coefficient k is obtained by operation. The voltage deviation signal proportional coefficient k is correlated with the output signal of the PI controller to obtain the shift factor x. At the same time, the n-fold output voltage nVo is correlated with the input voltage V dc The voltage transfer ratio d is obtained by performing a division operation, where n is the transformation ratio of the high-frequency transformer in the DAB converter; the phase shift ratio factor x and the voltage transfer ratio d are input into the modulation unit, and the phase shift ratios D0, D1 and D2 of the full power section are calculated. The phase shift ratios D0, D1 and D2 are transmitted to the PWM signal generator to drive the corresponding switch tube of the DAB converter to turn on and off.

[0006] As a further solution of the present invention: the DAB converter comprises a DC voltage source V dc , voltage stabilizing filter capacitor C in , C O , high-frequency isolation transformer with a transformation ratio of n:1, energy storage inductor L t , a primary full bridge H1, a secondary full bridge H2; the primary full bridge H1 is composed of fully controlled switching devices S1, S2, S3, S4, and the secondary full bridge H2 is composed of fully controlled switching devices Q1, Q2, Q3, Q4; the gate input terminals of the fully controlled switching devices S1, S2, S3, S4 and the fully controlled switching devices Q1, Q2, Q3, Q4 are connected to the PWM signal output terminals corresponding to the PWM signal generator;

[0007] DC voltage source V dc The positive electrode and the voltage stabilizing filter capacitor C in and the positive pole of the DC bus of the primary full bridge H1, the DC voltage source V dc The negative electrode and the voltage stabilizing filter capacitor C in The midpoint of the two switching devices S1 and S2 of the front bridge arm of the primary full bridge H1 is connected to the negative pole of the DC bus of the primary full bridge H1; t One end of the energy storage inductor L t The other end is connected to the positive pole of the primary side of the high-frequency isolation transformer, and the midpoint of the two switch devices S3 and S4 of the rear bridge arm of the primary full bridge H1 is connected to the negative pole of the primary side of the high-frequency isolation transformer; the midpoint of the two switch devices Q1 and Q2 of the front bridge arm of the secondary full bridge H2 is connected to the positive pole of the secondary side of the high-frequency isolation transformer, and the midpoint of the two switch devices Q3 and Q4 of the rear bridge arm of the secondary full bridge H2 is connected to the negative pole of the secondary side of the high-frequency isolation transformer; the voltage stabilizing filter capacitor C O The positive electrode of the secondary full bridge H2 DC bus is connected to the positive electrode of the output load, and the voltage stabilizing filter capacitor C O The negative electrode is connected to the negative electrode of the secondary full bridge H2 DC bus and the negative electrode of the output load.

[0008] A control method for a dynamic regulation control system of a DAB converter comprises the following steps:

[0009] Step 1: At the beginning of each switching cycle, the output voltage V O , input voltage V dc , and the output current I O Take samples;

[0010] Step 2: Calculate the voltage transfer ratio d according to the following formula;

[0011]

[0012] Where n is the transformation ratio of the high-frequency isolation transformer, V O is the DAB converter output voltage, V dc is the input voltage of the DAB converter;

[0013] Step 3: Use the output voltage V sampled in step 1 O and output current I O Calculate the output power P O ;

[0014] P o =V o I o

[0015] Step 4: The actual output power P O With reference output power P O_ref The deviation signal is input into the PI controller, and then added to the voltage deviation signal to obtain the shift-phase correlation factor x. The calculation formula is as follows

[0016]

[0017] Where K p and K i is the PI controller parameter, k is the voltage deviation proportional coefficient, which is preset to 0.001;

[0018] Step 5: Send the phase shift factor x obtained in step 4 to the modulation unit to calculate the phase shifts D0, D1 and D2 of the full power range. According to the range of x, the power range of the DAB converter is determined as

[0019]

[0020] Where P n,t is the per-unit value of the output power, f s is the switching frequency, L t is the energy storage inductance value, n is the transformation ratio of the high-frequency isolation transformer;

[0021] Step 6: Generate a corresponding PWM modulation signal according to the calculated shift ratio to drive the corresponding switch tube to turn on and off, so that the output power of the DAB converter is stable.

[0022] As a further solution of the present invention: in step 5, the range of the shift ratio factor x is divided into: 0≤x≤d; d≤x≤1; x≥1; wherein

[0023] i) When 0≤x≤d, the DAB converter works under triple phase shift modulation (TPS), and the phase shift ratio calculation formula is:

[0024]

[0025] In this working mode, the converter transfer power is

[0026]

[0027] Substituting D0 and D2 in the above formula with D1 yields

[0028]

[0029] In the above formula, P o 、V dc 、V o And D1 adds the disturbance component

[0030]

[0031] in, V dc 、V o ,D0,P o , the disturbance component of D1;

[0032] After removing the high-order small signal components from the above equation, the small signal equivalent model of the converter in this working mode is obtained as follows:

[0033]

[0034] A1, B1 and C1 are

[0035]

[0036] ii) When d≤x≤1, D2 is 0, and the shift ratio calculation formula is:

[0037]

[0038] In this working mode, the converter transfer power is

[0039]

[0040] Substituting D0 in the above formula with the expression about D1 yields

[0041]

[0042] In the above formula, P o 、V dc 、V o And D1 adds the disturbance component

[0043]

[0044] After removing the high-order small signal components from the above equation, the small signal equivalent model of the converter in this working mode is obtained as follows:

[0045]

[0046] A2, B2 and C2 are

[0047]

[0048] iii) When x≥1, D1 and D2 are both 0. At this time, the DAB converter is equivalent to working under single phase shift modulation (SPS). The phase shift ratio calculation formula is:

[0049]

[0050] The transmission power of the converter in this working mode is

[0051]

[0052] In the above formula, P o 、V dc 、V o After adding disturbance components to D0 and removing high-order small signal components, the small signal equivalent model of the converter in this working mode is obtained as follows:

[0053]

[0054] A3, B3 and C3 are

[0055]

[0056] The open-loop transfer function of the DAB converter control system is:

[0057]

[0058] Where k1 is a proportional coefficient before the PI controller.

[0059] Before adding the voltage deviation signal, the closed-loop transfer function of the control system is:

[0060]

[0061] After adding the voltage deviation signal, the closed-loop transfer function of the control system is:

[0062]

[0063] Among them G c for

[0064]

[0065] Where K p is the proportional coefficient of the PI controller, K i is the integral coefficient of the PI controller.

[0066] Compared with the prior art, the present invention introduces a voltage deviation feedback signal in the output power control loop. When the DAB converter performs power transmission, it can ensure that the output voltage of the DAB converter remains unchanged while reducing its overshoot, ensuring that the stabilization time of the controlled quantity in the control system is reduced in the DAB converter, and can achieve zero-voltage switching of all switching tubes within the full power range, thereby improving the response speed of the control system and reducing the loss during the startup process. BRIEF DESCRIPTION OF THE DRAWINGS

[0067] Figure 1 It is a structural diagram of the dynamic regulation control system of the DAB converter of the present invention.

[0068] Figure 2 This is the circuit connection diagram of the DAB converter.

[0069] Figure 3 It is a small signal control structure block diagram of the DAB converter of the present invention.

[0070] Figure 4 It is the output voltage waveform when the DAB converter of the present invention works in the low power section, the control loop does not add the voltage deviation signal and the output voltage waveform after adding the voltage deviation signal.

[0071] Figure 5 It is the output voltage waveform when the DAB converter of the present invention works in the middle power range, the control loop does not add the voltage deviation signal and the output voltage waveform after adding the voltage deviation signal.

[0072] Figure 6 It is the output voltage waveform when the DAB converter of the present invention works in the high power section, the control loop does not add the voltage deviation signal and the output voltage waveform after adding the voltage deviation signal.

[0073] Figure 7 It is the Bode diagram when the DAB converter of the present invention works in the low power range.

[0074] Figure 8 This is the Bode diagram when the DAB converter of the present invention works in the middle power range.

[0075] Fig. 9 This is the Bode diagram when the DAB converter of the present invention works in the high power range. DETAILED DESCRIPTION

[0076] The present invention will be further described below in conjunction with the accompanying drawings.

[0077] like Figure 1 As shown, the dynamic regulation control system of the DAB converter includes a DAB converter, a PWM signal generator, a modulation unit, and an output current I o , output voltage V o After multiplication, the output power P is obtained o , output power P o With reference output power P O_ref The deviation signal is input into the PI controller, and the output voltage V o With reference voltage V O_ref The voltage deviation signal proportional coefficient k is obtained by operation. The voltage deviation signal proportional coefficient k is correlated with the output signal of the PI controller to obtain the shift factor x. At the same time, the n-fold output voltage nVo is correlated with the input voltage V dc A phase division operation is performed to obtain a voltage transfer ratio d, where n is the transformation ratio of the high-frequency transformer in the DAB converter; the phase shift ratio factor x and the voltage transfer ratio d are input into the modulation unit, and the phase shift ratios D0, D1 and D2 of the full power section are calculated. The phase shift ratios D0, D1 and D2 are transmitted to the PWM signal generator to drive the corresponding switch tube of the DAB converter to turn on and off, so that the output power of the DAB converter is stable.

[0078] like Figure 2 As shown, the DAB converter includes a DC voltage source V dc , voltage stabilizing filter capacitor C in , C O , high-frequency isolation transformer with a transformation ratio of n:1, energy storage inductor L t , primary full bridge H1, secondary full bridge H2; primary full bridge H1 is composed of fully controlled switching devices S1, S2, S3, S4, secondary full bridge H2 is composed of fully controlled switching devices Q1, Q2, Q3, Q4; the gate input terminals of the fully controlled switching devices S1, S2, S3, S4 and the fully controlled switching devices Q1, Q2, Q3, Q4 are connected to Figure 1 is connected to the PWM signal output end corresponding to the PWM signal generator in;

[0079] DC voltage source V dc The positive electrode and the voltage stabilizing filter capacitor C in and the positive pole of the DC bus of the primary full bridge H1, the DC voltage source V dc The negative electrode and the voltage stabilizing filter capacitor Cin The midpoint of the two switching devices S1 and S2 of the front bridge arm of the primary full bridge H1 is connected to the negative pole of the DC bus of the primary full bridge H1; t One end of the energy storage inductor L t The other end is connected to the positive pole of the primary side of the high-frequency isolation transformer, and the midpoint of the two switch devices S3 and S4 of the rear bridge arm of the primary full bridge H1 is connected to the negative pole of the primary side of the high-frequency isolation transformer; the midpoint of the two switch devices Q1 and Q2 of the front bridge arm of the secondary full bridge H2 is connected to the positive pole of the secondary side of the high-frequency isolation transformer, and the midpoint of the two switch devices Q3 and Q4 of the rear bridge arm of the secondary full bridge H2 is connected to the negative pole of the secondary side of the high-frequency isolation transformer; the voltage stabilizing filter capacitor C O The positive electrode of the secondary full bridge H2 DC bus is connected to the positive electrode of the output load, and the voltage stabilizing filter capacitor C O The negative electrode is connected to the negative electrode of the secondary full bridge H2 DC bus and the negative electrode of the output load.

[0080] The present invention provides a dynamic regulation control method for a DAB converter, comprising the following steps:

[0081] Step 1: At the beginning of each switching cycle, the DAB converter output voltage V O , input voltage V dc , and the output current I O Take samples;

[0082] Step 2: Calculate the voltage transfer ratio d according to the following formula;

[0083]

[0084] Where n is the transformation ratio of the high-frequency isolation transformer, V O is the DAB converter output voltage, V dc is the input voltage of the DAB converter;

[0085] Step 3: Use the output voltage V sampled in step 1 O and output current I O Calculate the output power P O ;

[0086] P o =V o I o

[0087] Step 4: The actual output power P O With reference output power P O_ref The deviation signal is input into the PI controller, and then added to the voltage deviation signal to obtain the shift-phase correlation factor x. The calculation formula is as follows:

[0088]

[0089] Where K p and K i is the PI controller parameter, k is the voltage deviation proportional coefficient, which is preset to 0.001;

[0090] Step 5: Send the phase shift factor x obtained in step 4 to the modulation unit to calculate the phase shifts D0, D1 and D2 of the full power range. According to the range of x, the power range of the DAB converter is determined as

[0091]

[0092] Where P n,t is the per-unit value of the output power, P o is the output power, f s is the switching frequency, L t is the energy storage inductance value, n is the transformation ratio of the high-frequency isolation transformer;

[0093] Step 6: Generate a corresponding PWM modulation signal according to the calculated shift ratio to drive the corresponding switch tube to turn on and off, so that the output power of the DAB converter is stable.

[0094] Further: In step 5, the range of the shift ratio factor x is divided into: 0≤x≤d; d≤x≤1; x≥1; where

[0095] i) When 0≤x≤d, the DAB converter works under triple phase shift modulation (TPS), and the phase shift ratio calculation formula is:

[0096]

[0097] In this working mode, the converter transfer power is

[0098]

[0099] Substituting D0 and D2 in the above formula with D1 yields

[0100]

[0101] In the above formula, P o 、V dc 、V o And D1 adds the disturbance component

[0102]

[0103] in, V dc 、V o ,D0,P o , the disturbance component of D1;

[0104] After removing the high-order small signal components from the above equation, the small signal equivalent model of the converter in this working mode is obtained as follows:

[0105]

[0106] A1, B1 and C1 are

[0107]

[0108] ii) When d≤x≤1, D2 is 0, and the shift ratio calculation formula is:

[0109]

[0110] In this working mode, the converter transfer power is

[0111]

[0112] Substituting D0 in the above formula with the expression about D1 yields

[0113]

[0114] In the above formula, P o 、V dc 、V o And D1 adds the disturbance component

[0115]

[0116] After removing the high-order small signal components from the above equation, the small signal equivalent model of the converter in this working mode is obtained as follows:

[0117]

[0118] A2, B2 and C2 are

[0119]

[0120] iii) When x≥1, D1 and D2 are both 0. At this time, the DAB converter is equivalent to working under single phase shift modulation (SPS). The phase shift ratio calculation formula is:

[0121]

[0122] The transmission power of the converter in this working mode is

[0123]

[0124] In the above formula, P o 、V dc 、V oAfter adding disturbance components to D0 and removing high-order small signal components, the small signal equivalent model of the converter in this working mode is obtained as follows:

[0125]

[0126] A3, B3 and C3 are

[0127]

[0128] according to Figure 3 The control block diagram calculates the open-loop transfer function of the control system as follows:

[0129]

[0130] Where k1 is a proportional coefficient before the PI controller.

[0131] Before adding the voltage deviation signal, the closed-loop transfer function of the control system is:

[0132]

[0133] After adding the voltage deviation signal, the closed-loop transfer function of the control system is:

[0134]

[0135] Among them G c for

[0136]

[0137] Where K p is the proportional coefficient of the PI controller, K i is the integral coefficient of the PI controller.

[0138] Figure 4 The output voltage waveforms of the DAB converter when it is working in the low power range are shown in Figure 2, when the control loop does not add the voltage deviation signal and when the control loop adds the voltage deviation signal. In the low power range, the output voltage of the DAB converter is 250V. Figure 4 As shown in a, when the voltage deviation signal is not added to the control loop, the voltage overshoot σ% is 29.6% and the rise time t r is 3.233ms, peak time t m is 4.994ms, and the adjustment time is t s =6.864ms. Figure 4 As shown in b, after adding the voltage deviation signal, the voltage overshoot σ% is reduced to 8.92%, and the rise time t r Reduced to 3.207ms, adjusted time t s Reduced to 3.635ms.

[0139] Figure 5 The output voltage waveforms of the DAB converter when it is working in the medium power range are shown in Figure 2 when the control loop does not add a voltage deviation signal and when the control loop adds a voltage deviation signal. In the medium power range, the output voltage of the DAB converter is 375V. Figure 5 As shown in a, when the voltage deviation signal is not added to the control loop, the voltage overshoot σ% is 17.95%, and the rise time t r is 1.865ms, peak time t m is 2.587ms, and the adjustment time is t s =3.6ms. Figure 5 After adding the voltage deviation signal as shown in b, the voltage overshoot σ% is reduced to 5.73%, and the rise time t r Reduced to 1.614ms, adjusted time t s Reduced to 2.539ms.

[0140] Figure 6 The output voltage waveforms of the DAB converter when it is working in the high power range are shown in Figure 2 when the control loop does not add the voltage deviation signal and when the control loop adds the voltage deviation signal. In the high power range, the output voltage of the DAB converter is 440V. Figure 6 As shown in a, when the voltage deviation signal is not added to the control loop, the voltage overshoot σ% is 22.25%, and the rise time t r is 1.76ms, peak time t m is 2.813ms, and the adjustment time is t s =3.403ms. Figure 6 As shown in b, after adding the voltage deviation signal, the voltage overshoot σ% is reduced to 5.73%, and the rise time t r Reduced to 1.51ms, adjust the time t s Reduced to 2.559ms.

[0141] Figure 7 The Bode diagram of the control system before and after adding the deviation signal when the DAB converter works in the low power range. The bandwidth frequency of the closed-loop system is 131Hz before adding the voltage deviation signal, and the bandwidth frequency of the closed-loop system is 185Hz after adding the voltage deviation signal.

[0142] Figure 8 The Bode diagram of the control system before and after adding the deviation signal when the DAB converter works in the medium power range. The bandwidth frequency of the closed-loop system is 2980Hz before adding the voltage deviation signal, and the bandwidth frequency of the closed-loop system is 3330Hz after adding the voltage deviation signal.

[0143] Fig. 9The Bode diagram of the control system before and after adding the deviation signal when the DAB converter works in the high power range. The bandwidth frequency of the closed-loop system is 636Hz before adding the voltage deviation signal, and the bandwidth frequency of the closed-loop system is 1170Hz after adding the voltage deviation signal. The increase in the bandwidth frequency when the DAB converter works in three different power ranges improves the dynamic response speed of the control system.

Claims

1. A control method for a dynamic regulation control system of a DAB converter, wherein the control system comprises a DAB converter, a PWM signal generator, and a modulation unit, characterized in that: The output current I of the DAB converter o , output voltage V o After multiplication, the output power P is obtained o , output power P o With reference output power P O_ref The deviation signal is input into the PI controller; the output voltage V o With reference output voltage V O_ref The voltage deviation signal proportional coefficient k is obtained by operation. The voltage deviation signal proportional coefficient k is correlated with the output signal of the PI controller to obtain the shift factor x. At the same time, the n-fold output voltage nVo is correlated with the input voltage V dc The voltage transfer ratio d is obtained by performing a phase division operation, where n is the transformation ratio of the high-frequency transformer in the DAB converter; the phase shift ratio factor x and the voltage transfer ratio d are input into the modulation unit, and the phase shift ratios D0, D1 and D2 of the full power section are calculated. The phase shift ratios D0, D1 and D2 are transmitted to the PWM signal generator to drive the corresponding switch tube of the DAB converter to turn on and off; The control method comprises the following steps: Step 1: At the beginning of each switching cycle, the output voltage V O , input voltage V dc , and the output current I O Take samples; Step 2: Calculate the voltage transfer ratio d according to the following formula; Where n is the transformation ratio of the high-frequency isolation transformer, V O is the DAB converter output voltage, V dc is the input voltage of the DAB converter; Step 3: Use the output voltage V sampled in step 1 O and output current I O Calculate the output power P O ; P o =V o I o Step 4: The actual output power P O With reference output power P O_ref The deviation signal is input into the PI controller, and then added to the voltage deviation signal to obtain the shift-phase correlation factor x. The calculation formula is as follows Where K p and K i is the PI controller parameter, k is the voltage deviation proportional coefficient, which is preset to 0.001; Step 5: Send the phase shift factor x obtained in step 4 to the modulation unit to calculate the phase shifts D0, D1 and D2 of the full power range. According to the range of x, the power range of the DAB converter is determined as Where P n,t is the per-unit value of the output power, f s is the switching frequency, L t is the energy storage inductance value, n is the transformation ratio of the high-frequency isolation transformer; Step 6: Generate a corresponding PWM modulation signal according to the calculated shift phase, drive the corresponding switch tube to turn on and off, so that the output power of the DAB converter reaches stability; In step 5, the range of the shift ratio factor x is divided into: 0≤x≤d; d≤x≤1; x≥1; wherein i) When 0≤x≤d, the DAB converter works under triple phase shift modulation (TPS), and the phase shift ratio calculation formula is: In this working mode, the converter transfer power is Substituting D0 and D2 in the above formula with D1 yields In the above formula, P o 、V dc 、V o And D1 adds the disturbance component in, V dc 、V o ,D0,P o , the disturbance component of D1; After removing the high-order small signal components from the above equation, the small signal equivalent model of the converter in this working mode is obtained as follows: A1, B1 and C1 are ii) When d≤x≤1, D2 is 0, and the shift ratio calculation formula is: In this working mode, the converter transfer power is Substituting D0 in the above formula with the expression about D1 yields In the above formula, P o 、V dc 、V o And D1 adds the disturbance component After removing the high-order small signal components from the above equation, the small signal equivalent model of the converter in this working mode is obtained as follows: A2, B2 and C2 are iii) When x≥1, D1 and D2 are both 0. At this time, the DAB converter is equivalent to working under single phase shift modulation (SPS). The phase shift ratio calculation formula is: The transmission power of the converter in this working mode is In the above formula, P o 、V dc 、V o After adding disturbance components to D0 and removing high-order small signal components, the small signal equivalent model of the converter in this working mode is obtained as follows: A3, B3 and C3 are The open-loop transfer function of the DAB converter control system is: Where k1 is a proportional coefficient before the PI controller, G c (s) is the transfer function of the PI controller; Before adding the voltage deviation signal, the closed-loop transfer function of the control system is: After adding the voltage deviation signal, the closed-loop transfer function of the control system is: Among them G c for Where K p is the proportional coefficient of the PI controller, K i is the integral coefficient of the PI controller.

2. The control method of a dynamic regulation control system of a DAB converter according to claim 1, characterized in that: The DAB converter includes a DC voltage source V dc , voltage stabilizing filter capacitor C in , C O , high-frequency isolation transformer with a transformation ratio of n:1, energy storage inductor L t , a primary full bridge H1, a secondary full bridge H2; the primary full bridge H1 is composed of fully controlled switching devices S1, S2, S3, S4, and the secondary full bridge H2 is composed of fully controlled switching devices Q1, Q2, Q3, Q4; the gate input terminals of the fully controlled switching devices S1, S2, S3, S4 and the fully controlled switching devices Q1, Q2, Q3, Q4 are connected to the PWM signal output terminals corresponding to the PWM signal generator; DC voltage source V dc The positive electrode and the voltage stabilizing filter capacitor C in and the positive pole of the DC bus of the primary full bridge H1, the DC voltage source V dc The negative electrode and the voltage stabilizing filter capacitor C in The midpoint of the two switching devices S1 and S2 of the front bridge arm of the primary full bridge H1 is connected to the negative pole of the DC bus of the primary full bridge H1; t One end of the energy storage inductor L t The other end is connected to the positive pole of the primary side of the high-frequency isolation transformer, and the midpoint of the two switch devices S3 and S4 of the rear bridge arm of the primary full bridge H1 is connected to the negative pole of the primary side of the high-frequency isolation transformer; the midpoint of the two switch devices Q1 and Q2 of the front bridge arm of the secondary full bridge H2 is connected to the positive pole of the secondary side of the high-frequency isolation transformer, and the midpoint of the two switch devices Q3 and Q4 of the rear bridge arm of the secondary full bridge H2 is connected to the negative pole of the secondary side of the high-frequency isolation transformer; the voltage stabilizing filter capacitor C O The positive electrode of the secondary full bridge H2 DC bus is connected to the positive electrode of the output load, and the voltage stabilizing filter capacitor C O The negative electrode is connected to the negative electrode of the secondary full bridge H2 DC bus and the negative electrode of the output load.

Images