Series resonant hybrid three-level converter, modulation and closed-loop control method and system

Abstract

The invention discloses a series resonant hybrid three-level converter and a modulation and closed-loop control method and system, the series resonant hybrid three-level converter comprises a series resonant hybrid three-level inverter bridge circuit and a full-bridge rectifier circuit, and the series resonant hybrid three-level inverter bridge circuit and the full-bridge rectifier circuit are connected through a high-frequency isolation transformer with the transformation ratio of 0. Based on the series resonant hybrid three-level converter, a discontinuous pulse width modulation method is provided, only two control angles are needed, the implementation simplicity is ensured, under the modulation, the converter shows excellent zero-voltage switching performance under different voltage gains, the soft switching range is remarkably expanded, and the switching loss is reduced. Besides, an efficient current running track control strategy is constructed based on the modulation method, so that the secondary side voltage and the resonance current are in the same phase, the backflow power of the secondary side is eliminated, the minimum root-mean-square current running is realized, the conduction loss is effectively reduced, and the overall transmission efficiency of the system is further improved.

Description

Technical Field

[0001] This invention belongs to the field of photovoltaic power generation technology, specifically relating to a series resonant hybrid three-level converter, modulation and closed-loop control method and system. Background Technology

[0002] Photovoltaic power converters are key components in photovoltaic power generation systems, and their performance directly affects the efficiency and stability of the entire system. Series resonant converters, as one of the classic types of photovoltaic power converters, are widely used in grid-connected, off-grid, and distributed photovoltaic systems due to their advantages such as electrical isolation, soft switching, and high power density. However, with the continuous development of photovoltaic power generation technology, the performance requirements for converters are becoming increasingly stringent.

[0003] When the input voltage or load changes, or when the output voltage fluctuates due to other factors, the negative feedback loop can adjust the on-time of the power devices in the switching converter within one switching cycle to achieve stable output voltage.

[0004] Furthermore, series resonant converters typically employ single-phase-shift (SPS) modulation, which has only one degree of control freedom and is relatively simple to control. However, under light load conditions or input-output voltage mismatch, single-phase-shift modulation can easily cause the converter to lose zero-voltage switching (ZVS), and the large return current power on the primary and secondary sides increases current stress, leading to higher converter losses. To address these issues, many researchers have proposed modulation strategies such as dual-phase-shift (DPS), extended-phase-shift (EPS), and triple-phase-shift (TPS) to optimize the efficiency of dual active bridge converters. However, as the control angle increases, the complexity also gradually increases, and it is impossible to achieve zero-voltage switching over a wide voltage gain range, affecting the converter's conversion efficiency. Therefore, a modulation strategy that expands the zero-voltage switching range, reduces switching losses, and offers more flexible control is needed to improve the converter's performance. Summary of the Invention

[0005] The purpose of this invention is to provide a series resonant hybrid three-level converter, a modulation and closed-loop control method and system. A series resonant hybrid three-level converter is proposed, and a closed-loop control method based on output voltage feedback and an intermittent pulse width modulation method are given for the converter to improve the output performance and dynamic response capability of the series resonant hybrid three-level converter, expand the zero-voltage switching range of the converter, reduce conduction loss and improve transmission efficiency.

[0006] The technical solution to achieve the purpose of this invention is as follows: A series resonant hybrid three-level converter includes a series resonant hybrid three-level inverter bridge circuit and a full-bridge rectifier circuit. The series resonant hybrid three-level inverter bridge circuit and the full-bridge rectifier circuit are connected by a transformation ratio of... Connected to a high-frequency isolation transformer; The series resonant hybrid three-level inverter bridge circuit includes a DC input voltage source and a... A Bridge arm and one B The bridge arm, with the first and second voltage-equalizing capacitors connected in series, is connected across the DC input voltage source. A The bridge arm includes clamping diodes. , Flying capacitor Switching transistor ; B Bridge arm includes switching transistors , Flying capacitor Connected to the switching transistor Drain and switching transistor The source of the clamping diode , Connected in series with the flying capacitor Clamping diodes at both ends , The connection point is connected to the connection point of the voltage equalizing capacitor, and the switching transistor... Drain and switching transistor The drains of the transistors are connected together and are also connected to the positive terminal of the DC input power supply. Source and switch The sources of the transistors are connected together and are also connected to the negative terminal of the DC input power supply. Source and switch The drains are connected, and the switching transistor is switched. Source and switch The drains are connected; the switching transistor Source and switch The drain electrode is A Midpoint of the bridge arm, B The midpoint of the bridge arm is located at the switching transistor. Source and switch At the drain connection, A Midpoint of bridge arm and B A series resonant slot is connected between the midpoints of the bridge arms; The full-bridge rectifier circuit includes a switching transistor. and filter capacitors The switching transistor The filter capacitor forms a full-bridge circuit. Connected to the switching transistor Drain and switching transistor The source pole.

[0007] This invention also discloses a modulation method for a series resonant hybrid three-level converter, applied to the aforementioned series resonant hybrid three-level converter, comprising the following steps: S01: Control switch transistor The phase shift angle is , For switching transistors Conduction angle, switching transistor The phase shift angle is arrive Switching transistor The phase shift angle is arrive Switching transistor The phase shift angle is arrive Switching transistor The phase shift angle is arrive Switching transistor The phase shift angle is arrive Thus producing , , Three voltage levels waveform, Input voltage, For switching transistors source and switch The connection point formed by the drain and the switching transistor source and switch The voltage between the connection points formed by the drain electrodes; S02: Switching transistor controlling the full-bridge rectifier circuit and The phase shift angle is arrive , For switching transistors and Start-up lag switching transistor The angle of the opening point, the switching transistor and The phase shift angle is arrive Thus producing , voltage level Waveform, For output voltage, For switching transistors source and switch The connection point formed by the drain and the switching transistor source and switch The voltage between the connection points formed by the drain of the electrode.

[0008] In the preferred technical solution, the voltage level The pulse width is determined by the switching transistor. conduction angle Decision, control exist to Within the range of adjustment, to achieve Pulse width adjustment; voltage level and The pulse widths are complementary in phase, when The pulse width is At that time, voltage level The pulse width is to Voltage level The pulse width is determined by the switching transistor. , The coordinated conduction time determines the control switching transistor. Turn-off and switching transistors Interruption time is set between conductions. to Voltage level The corresponding pulse width is determined by the switching transistor. , , The coordinated conduction time determines the switching transistor. , , The drive signal in arrive The internal conduction time remains constant, thus maintaining the voltage level. The pulse width remains constant.

[0009] In the preferred technical solution, after step S02, the normalized power is calculated, including: Steady-state analysis was performed using the fundamental frequency component approximation method, and the following results were obtained. and Normalized phasor:

[0010] In the formula, yes The normalized phasor, yes Normalized phasor; Based on the normalized switching frequency quality factor The normalized impedance of the capacitor is obtained as follows: ; The normalized resonant current expression is obtained as follows:

[0011] in, The switching angular frequency, t For time, This is the peak current. Resonant current and AC voltage The phase shift angle; The normalized power is calculated based on the normalized resonant current. .

[0012] In the preferred embodiment, the formula for calculating the peak current is:

[0013] Resonant current and AC voltage The formula for calculating the phase shift angle is:

[0014] Normalized power : .

[0015] In the preferred technical solution, after step S02, a high-efficiency current-driven trajectory control strategy is calculated, including: Through peak current Obtain the minimum resonant current :

[0016] make Establish a framework for Lagrange's equation:

[0017] in, For the Lagrange optimization function, It is a scalar value; Will right Taking the partial derivative, we get: Will right Taking the partial derivative, we get: Will right Taking the partial derivative, we get:

[0018] The relationship for the efficient current-driven trajectory control strategy is as follows: .

[0019] The preferred technical solution also includes: Substituting the obtained high-efficiency current trajectory control strategy formula into the normalized power... To obtain the optimal conduction power :

[0020] Control Angle right The size is controlled.

[0021] This invention further discloses a closed-loop control method for a series resonant hybrid three-level converter, applied to the aforementioned series resonant hybrid three-level converter, comprising the following steps: S01: Calculate the voltage gain based on the input voltage and the output voltage collected by the sensor. M , , This refers to the number of transformer turns. Input voltage, This refers to the output voltage. S02: The PI controller adjusts the output voltage and output power based on the voltage error between the reference voltage and the output voltage; S03: Based on the high-efficiency current-driven trajectory control strategy: Calculate the control angle and , For switching transistors Conduction angle, For switching transistors and Start-up lag switching transistor The angle of the opening point; S04: Generate trigger pulses for each switch transistor of the converter through the PWM unit.

[0022] This invention further discloses a modulation system for a series resonant hybrid three-level converter, applied to the aforementioned series resonant hybrid three-level converter, comprising: Waveform modulation module, control switching transistor The phase shift angle is , For switching transistors Conduction angle, switching transistor The phase shift angle is arrive Switching transistor The phase shift angle is arrive Switching transistor The phase shift angle is arrive Switching transistor The phase shift angle is arrive Switching transistor The phase shift angle is arrive Thus producing , , Three voltage levels waveform, Input voltage, For switching transistors source and switch The connection point formed by the drain and the switching transistor source and switch The voltage between the connection points formed by the drain electrodes; The waveform modulation module controls the switching transistors of the rectifier full-bridge circuit. and The phase shift angle is arrive , For switching transistors and Start-up lag switching transistor The angle of the opening point, the switching transistor and The phase shift angle is arrive Thus producing , voltage level Waveform, For output voltage, For switching transistors source and switch The connection point formed by the drain and the switching transistor source and switch The voltage between the connection points formed by the drain of the electrode.

[0023] This invention further discloses a closed-loop control system for a series resonant hybrid three-level converter, applied to the aforementioned series resonant hybrid three-level converter, comprising: The voltage gain calculation module calculates the voltage gain based on the input voltage and the output voltage collected by the sensor. M , , This refers to the number of transformer turns. Input voltage, This refers to the output voltage. A PI controller adjusts the output voltage and output power based on the voltage error between the reference voltage and the output voltage. The high-efficiency current operating trajectory control module, based on the high-efficiency current operating trajectory control strategy: Calculate the control angle and , For switching transistors Conduction angle, For switching transistors and Start-up lag switching transistor The angle of the opening point; The PWM unit generates trigger pulses for each switch transistor in the converter.

[0024] Compared with the prior art, the significant advantages of this invention are: (1) This invention provides a closed-loop control system based on a series resonant hybrid three-level converter and its output voltage feedback. This system combines the steady-state accuracy of PI control with the optimal dynamic performance of efficient current trajectory control, achieving a unity of fast response and precise control. It effectively overcomes the limitations of single control. Its efficient current trajectory control strategy can directly obtain the analytical solution of the control angle, which not only simplifies the control loop structure and eliminates complex calculations, but also fundamentally ensures the simplicity of the system design and the reliability of long-term operation.

[0025] (2) This invention proposes a method that includes three voltage levels , , Intermittent pulse width modulation method, wherein voltage level , The pulse width can be flexibly adjusted within a specific range, while the voltage level The pulse width remains constant. Under this modulation method, the converter achieves excellent ZVS performance at different voltage gains: when M=0.75 and M=1, all switches achieve ZVS operation in the full power range; when M=0.875, all switches at more than 21.82% of the rated power can achieve ZVS operation, expanding the range of zero voltage turn-on and reducing switching losses.

[0026] (3) The present invention constructs an efficient current operation trajectory control strategy under the modulation method, which makes the secondary side voltage and the resonant current in phase, eliminates the return power of the secondary side, thereby achieving minimum root mean square current operation, reducing conduction loss, and further improving transmission efficiency. Attached Figure Description

[0027] Figure 1 This is a schematic diagram of the topology of a series resonant hybrid three-level converter based on output voltage feedback closed-loop control; Figure 2 Through modulation switch and The voltage waveform and resonant current waveform generated by the duty cycle; Figure 3 This is the equivalent circuit diagram of a series resonant hybrid three-level converter under the fundamental frequency component approximation method; Figure 4 This is a block diagram of a high-efficiency current-driven trajectory control strategy; Figure 5a , Figure 5b , Figure 5c , Figure 5d The series resonant hybrid three-level converter is shown in the following figures. At 100%, 75%, 50%, and 25% load , , And the current waveforms of each switching transistor. Detailed Implementation

[0028] The principle of this invention is as follows: a series resonant hybrid three-level converter employing intermittent pulse width modulation (IPM) and its closed-loop control system. This closed-loop control system effectively improves the system's output performance and dynamic response capability. The IPM method requires only two control angles, ensuring simplicity of implementation. Under this modulation, the converter exhibits excellent zero-voltage switching (ZVS) performance at different voltage gains: when M=0.75 and M=1, all switches achieve ZVS operation across the full power range; when M=0.875, the ZVS operating range covers more than 21.82% of the rated power, significantly expanding the soft-switching range and reducing switching losses. Furthermore, based on this modulation method, a high-efficiency current trajectory control strategy is constructed, making the secondary voltage in phase with the resonant current. This not only eliminates the return power on the secondary side but also achieves minimum RMS current operation, effectively reducing conduction losses and further improving the overall transmission efficiency of the system.

[0029] Example 1: like Figure 1 As shown, a series resonant hybrid three-level converter includes a series resonant hybrid three-level inverter bridge circuit and a full-bridge rectifier circuit. The series resonant hybrid three-level inverter bridge circuit and the full-bridge rectifier circuit are connected by a transformation ratio of... It is connected to a high-frequency isolation transformer.

[0030] The series resonant hybrid three-level inverter bridge circuit includes a DC input voltage source. ,one A Bridge arm and one B Bridge arm, first equalizing capacitor Second equalizing capacitor Connected in series to a DC input voltage source Both ends, A The bridge arm includes clamping diodes. , Flying capacitor Switching transistor ; B Bridge arm includes switching transistors , Flying capacitor Connected to the switching transistor Drain and switching transistor The source of the clamping diode , Connected in series with the flying capacitor Clamping diodes at both ends , Connection point and equalizing capacitor , Connection point connection, switching transistor Drain and switching transistor The drains of the two terminals are connected together and are connected to the DC input power supply. The positive terminal is connected, and the switching transistor is switched on. Source and switch The source terminals are connected together and share a common DC input power supply. The negative terminal is connected, and the switching transistor is switched. Source and switch The drains are connected, and the switching transistor is switched. Source and switch The drains are connected; the switching transistor Source and switch The drain electrode is A Midpoint of the bridge arm, B The midpoint of the bridge arm is located at the switching transistor. Source and switch At the drain connection, A Midpoint of bridge arm and B A series resonant slot is connected between the midpoints of the bridge arms.

[0031] A full-bridge rectifier circuit includes switching transistors. and filter capacitors The switching transistor The filter capacitor forms a full-bridge circuit. Connected to the switching transistor Drain and switching transistor The source pole.

[0032] Specifically, the series resonant tank consists of resonant capacitors connected in series. and resonant inductor composition.

[0033] Switching transistor Includes anti-parallel diodes and parasitic capacitance Switching transistor , Includes anti-parallel diodes and parasitic capacitance Switching transistor Includes anti-parallel diodes Parasitic capacitance .

[0034] Another embodiment, such as Figure 2 As shown, a modulation method for a series resonant hybrid three-level converter, applied to the aforementioned series resonant hybrid three-level converter, includes the following steps: S01: Control switch transistor The phase shift angle is , For switching transistors Conduction angle, switching transistor The phase shift angle is arrive Switching transistor The phase shift angle is arrive Switching transistor The phase shift angle is arrive Switching transistor The phase shift angle is arrive Switching transistor The phase shift angle is arrive Thus producing , , Three voltage levels waveform, Input voltage, For switching transistors source and switch The connection point formed by the drain and the switching transistor source and switch The voltage between the connection points formed by the drain electrodes; S02: Switching transistor controlling the full-bridge rectifier circuit and The phase shift angle is arrive , For switching transistors and Start-up lag switching transistor The angle of the opening point, the switching transistor and The phase shift angle is arrive Thus producing , voltage level Waveform, For output voltage, For switching transistors source and switch The connection point formed by the drain and the switching transistor source and switch The voltage between the connection points formed by the drain of the electrode.

[0035] In a preferred embodiment, to extend the zero-voltage switching (ZVS) range of the series resonant hybrid three-level converter, an intermittent pulse width modulation method is proposed, which enables the generation of a high-frequency voltage at the midpoint of the inverter bridge. , , Three voltage levels, among which voltage level The pulse width is determined by the switching transistor. On-time Direct decision, Available to Flexible adjustment within the range, thereby achieving Dynamic adjustment of pulse width in intermittent pulse width modulation, voltage level and The pulse widths are complementary in phase, therefore when The pulse width is At that time, voltage level The pulse width is to This ensures that the sum of the widths of the two within half a cycle is voltage level The pulse width is determined by the switching transistor. , The coordinated conduction time is directly determined, therefore, in the control of the switching transistor, the switching transistor... Turn-off and switching transistors Interruption time is set between conductions. to This avoids clamping diodes. , Switching transistor , and flying capacitor A loop is formed between them, and the voltage level The pulse width is determined by the switching transistor. , , The coordinated conduction time directly determines the switching transistor. , , The drive signal in arrive The internal conduction time remains constant, therefore the voltage level The pulse width remains constant. Based on this characteristic, the output power can be adjusted only through the positive pulse width, avoiding the complexity of coordinated control of positive and negative pulses in traditional symmetrical modulation.

[0036] An equivalent model of the proposed series resonant hybrid three-level converter is established using the discontinuous pulse width modulation method, and power analysis is performed. After step S02, the normalized power is calculated based on the control angle. and Calculate normalized power include: like Figure 3As shown, steady-state analysis is performed using the fundamental frequency component approximation method, yielding... and Normalized phasor:

[0037] In the formula, yes The normalized phasor, yes Normalized phasor; Based on the normalized switching frequency quality factor The normalized impedance of the capacitor is obtained as follows: ; The normalized resonant current expression is obtained as follows:

[0038] in, The switching angular frequency, t For time, This is the peak current. Resonant current and AC voltage The phase shift angle; The normalized power is calculated based on the normalized resonant current. .

[0039] In a preferred embodiment, the formula for calculating the peak current is:

[0040] Resonant current and AC voltage The formula for calculating the phase shift angle is:

[0041] Normalized power : .

[0042] Under this modulation method, the converter achieves excellent ZVS performance at different voltage gains: when M=0.75 and M=1, all switches achieve ZVS operation in the full power range; when M=0.875, all switches with more than 21.82% of the rated power can achieve ZVS operation, which expands the range of zero voltage turn-on and reduces switching losses.

[0043] In a preferred embodiment, after step S02, the method further includes calculating an efficient current-driven trajectory control strategy, including: Through peak current Obtain the minimum resonant current :

[0044] make Establish a framework for Lagrange's equation:

[0045] in, For the Lagrange optimization function, It is a scalar value; Will right Taking the partial derivative, we get: Will right Taking the partial derivative, we get: Will right Taking the partial derivative, we get:

[0046] The relationship for the efficient current-driven trajectory control strategy is as follows: .

[0047] High-efficiency current trajectory control strategy can control resonant current. The zero-crossing point is precisely set in the switching transistor. and The conduction time of the switch transistor causes the phase of the resonant current to be different from that of the switching transistor. , The conduction phase remains consistent, thus effectively eliminating the return power on the secondary side.

[0048] like Figure 4 As shown, the control angle is calculated based on the high-efficiency current-driven trajectory control strategy. and The PWM unit generates trigger pulses for each switch in the converter. This strategy can directly obtain the control angle. and The analytical solution makes the entire control loop structure simple and eliminates the need for complex calculations.

[0049] Substituting the obtained high-efficiency current trajectory control strategy formula into the normalized power... To obtain the optimal conduction power :

[0050] Control Angle right The size is controlled.

[0051] Another embodiment provides a closed-loop control method for a series resonant hybrid three-level converter, applied to the aforementioned series resonant hybrid three-level converter, comprising the following steps: S01: Calculate the voltage gain based on the input voltage and the output voltage collected by the sensor. M , , This refers to the number of transformer turns. Input voltage, This refers to the output voltage. S02: The PI controller adjusts the output voltage and output power based on the voltage error between the reference voltage and the output voltage; S03: Based on the high-efficiency current-driven trajectory control strategy: Calculate the control angle and , For switching transistors Conduction angle, For switching transistors and Start-up lag switching transistor The angle of the opening point; S04: Generate trigger pulses for each switch transistor of the converter through the PWM unit.

[0052] The calculation method for the high-efficiency current-driven trajectory control strategy can be the same as described above, and will not be repeated here.

[0053] Another embodiment provides a modulation system for a series resonant hybrid three-level converter, applied to the aforementioned series resonant hybrid three-level converter, comprising: Waveform modulation module, control switching transistor The phase shift angle is , For switching transistors Conduction angle, switching transistor The phase shift angle is arrive Switching transistor The phase shift angle is arrive Switching transistor The phase shift angle is arrive Switching transistor The phase shift angle is arrive Switching transistor The phase shift angle is arrive Thus producing , , Three voltage levels waveform, Input voltage, For switching transistors source and switch The connection point formed by the drain and the switching transistor source and switch The voltage between the connection points formed by the drain electrodes; The waveform modulation module controls the switching transistors of the rectifier full-bridge circuit. and The phase shift angle is arrive , For switching transistors and Start-up lag switching transistor The angle of the opening point, the switching transistor and The phase shift angle is arrive Thus producing , voltage level Waveform, For output voltage, For switching transistors source and switch The connection point formed by the drain and the switching transistor source and switch The voltage between the connection points formed by the drain of the electrode.

[0054] Another embodiment provides a closed-loop control system for a series resonant hybrid three-level converter, applied to the aforementioned series resonant hybrid three-level converter, comprising: The voltage gain calculation module calculates the voltage gain based on the input voltage and the output voltage collected by the sensor. M , , This refers to the number of transformer turns. Input voltage, This refers to the output voltage. A PI controller adjusts the output voltage and output power based on the voltage error between the reference voltage and the output voltage. The high-efficiency current operating trajectory control module, based on the high-efficiency current operating trajectory control strategy: Calculate the control angle and , For switching transistors Conduction angle, For switching transistors and Start-up lag switching transistor The angle of the opening point; The PWM unit generates trigger pulses for each switch transistor in the converter.

[0055] The calculation method for the high-efficiency current-driven trajectory control strategy can be the same as described above, and will not be repeated here.

[0056] To ensure the converter operates efficiently, appropriate parameter design is required: choose .

[0057] Design input voltage 220V, output voltage It operates at 110V and has a rated power of 400W.

[0058] Simulations were performed based on the designed input and output voltages and power, and all switches were found to be capable of soft switching.

[0059] To verify the correctness of the theory, simulation tests were conducted in PSIM.

[0060] Figure 5a , Figure 5b , Figure 5c , Figure 5d The series resonant hybrid three-level converter is shown in the following figures. At 100%, 75%, 50%, and 25% load , , And the current waveforms of each switching transistor.

[0061] After verification using simulation waveforms, the theory and practice were found to be consistent, proving the feasibility of the invention. The series resonant hybrid three-level converter based on output voltage feedback closed-loop control and its intermittent pulse width modulation method enable the converter to exhibit excellent zero-voltage switching (ZVS) performance under different voltage gains, reducing switching losses, eliminating the return power of the high-frequency rectified full-bridge, operating with the optimal conduction path, and improving the converter's efficiency. Finally, based on the calculation results of the efficient current trajectory control strategy, trigger pulses for each switch of the converter are generated through the PWM unit, comprehensively realizing the above functions.

[0062] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention shall be considered equivalent substitutions and shall be included within the protection scope of the present invention.

Claims

1. A series resonant hybrid three-level converter, characterized in that, It includes a series resonant hybrid three-level inverter bridge circuit and a full-bridge rectifier circuit, wherein the series resonant hybrid three-level inverter bridge circuit and the full-bridge rectifier circuit are connected through a turns ratio of... Connected to a high-frequency isolation transformer; The series resonant hybrid three-level inverter bridge circuit includes a DC input voltage source and a... A Bridge arm and one B The bridge arm, with the first and second voltage-equalizing capacitors connected in series, is connected across the DC input voltage source. A The bridge arm includes clamping diodes. , Flying capacitor Switching transistor ; B Bridge arm includes switching transistors , Flying capacitor Connected to the switching transistor Drain and switching transistor The source of the clamping diode , Connected in series with the flying capacitor Clamping diodes at both ends , The connection point is connected to the connection point of the voltage equalizing capacitor, and the switching transistor... Drain and switching transistor The drains of the transistors are connected together and are also connected to the positive terminal of the DC input power supply. Source and switch The sources of the transistors are connected together and are also connected to the negative terminal of the DC input power supply. Source and switch The drains are connected, and the switching transistor is switched. Source and switch The drains are connected; the switching transistor Source and switch The drain electrode is A Midpoint of the bridge arm, B The midpoint of the bridge arm is located at the switching transistor. Source and switch At the drain connection, A Midpoint of bridge arm and B A series resonant slot is connected between the midpoints of the bridge arms; The full-bridge rectifier circuit includes a switching transistor. and filter capacitors The switching transistor The filter capacitor forms a full-bridge circuit. Connected to the switching transistor Drain and switching transistor The source pole.

2. A modulation method for a series resonant hybrid three-level converter, applied to the series resonant hybrid three-level converter of claim 1, characterized in that, Includes the following steps: S01: Control switch transistor The phase shift angle is , For switching transistors Conduction angle, switching transistor The phase shift angle is arrive Switching transistor The phase shift angle is arrive Switching transistor The phase shift angle is arrive Switching transistor The phase shift angle is arrive Switching transistor The phase shift angle is arrive Thus producing , , Three voltage levels waveform, Input voltage, For switching transistors source and switch The connection point formed by the drain and the switching transistor source and switch The voltage between the connection points formed by the drain electrodes; S02: Switching transistor controlling the full-bridge rectifier circuit and The phase shift angle is arrive , For switching transistors and Start-up lag switching transistor The angle of the opening point, the switching transistor and The phase shift angle is arrive Thus producing , voltage level Waveform, For output voltage, For switching transistors source and switch The connection point formed by the drain and the switching transistor source and switch The voltage between the connection points formed by the drain of the electrode.

3. The modulation method for the series resonant hybrid three-level converter according to claim 2, characterized in that, The voltage level The pulse width is determined by the switching transistor. conduction angle Decision, control exist to Within the range of adjustment, to achieve Pulse width adjustment; voltage level and The pulse widths are complementary in phase, when The pulse width is At that time, voltage level The pulse width is to Voltage level The pulse width is determined by the switching transistor. , The coordinated conduction time determines the control switching transistor. Turn-off and switching transistors Interruption time is set between conductions. to Voltage level The corresponding pulse width is determined by the switching transistor. , , The coordinated conduction time determines the switching transistor. , , The drive signal in arrive The internal conduction time remains constant, thus maintaining the voltage level. The pulse width remains constant.

4. The modulation method of the series resonant hybrid three-level converter according to claim 2, characterized in that, Step S02 is followed by calculating the normalized power, including: Steady-state analysis was performed using the fundamental frequency component approximation method, and the following results were obtained. and Normalized phasor: In the formula, yes The normalized phasor, yes Normalized phasor; Based on the normalized switching frequency quality factor The normalized impedance of the capacitor is obtained as follows: ; The normalized resonant current expression is obtained as follows: in, The switching angular frequency, t For time, This is the peak current. Resonant current and AC voltage The phase shift angle; The normalized power is calculated based on the normalized resonant current. .

5. The modulation method for the series resonant hybrid three-level converter according to claim 4, characterized in that, The formula for calculating the peak current is: Resonant current and AC voltage The formula for calculating the phase shift angle is: Normalized power : 。 6. The modulation method for the series resonant hybrid three-level converter according to claim 5, characterized in that, Step S02 is followed by calculating an efficient current-driven trajectory control strategy, including: Through peak current Obtain the minimum resonant current : make Establish a framework for Lagrange's equation: in, For the Lagrange optimization function, It is a scalar value; Will right Taking the partial derivative, we get: Will right Taking the partial derivative, we get: Will right Taking the partial derivative, we get: The relationship for the efficient current-driven trajectory control strategy is as follows: 。 7. The modulation method for the series resonant hybrid three-level converter according to claim 6, characterized in that, Also includes: Substituting the obtained high-efficiency current trajectory control strategy formula into the normalized power... To obtain the optimal conduction power : Control Angle right The size is controlled.

8. A closed-loop control method for a series resonant hybrid three-level converter, applied to the series resonant hybrid three-level converter as described in claim 1, characterized in that, Includes the following steps: S01: Calculate the voltage gain based on the input voltage and the output voltage collected by the sensor. M , , This refers to the number of transformer turns. Input voltage, This refers to the output voltage. S02: The PI controller adjusts the output voltage and output power based on the voltage error between the reference voltage and the output voltage; S03: Based on the high-efficiency current-driven trajectory control strategy: Calculate the control angle and , For switching transistors Conduction angle, For switching transistors and Start-up lag switching transistor The angle of the opening point; S04: Generate trigger pulses for each switch transistor of the converter through the PWM unit.

9. A modulation system for a series resonant hybrid three-level converter, applied to the series resonant hybrid three-level converter of claim 1, characterized in that, include: Waveform modulation module, control switching transistor The phase shift angle is , For switching transistors Conduction angle, switching transistor The phase shift angle is arrive Switching transistor The phase shift angle is arrive Switching transistor The phase shift angle is arrive Switching transistor The phase shift angle is arrive Switching transistor The phase shift angle is arrive Thus producing , , Three voltage levels waveform, Input voltage, For switching transistors source and switch The connection point formed by the drain and the switching transistor source and switch The voltage between the connection points formed by the drain electrodes; The waveform modulation module controls the switching transistors of the rectifier full-bridge circuit. and The phase shift angle is arrive , For switching transistors and Start-up lag switching transistor The angle of the opening point, the switching transistor and The phase shift angle is arrive Thus producing , voltage level Waveform, For output voltage, For switching transistors source and switch The connection point formed by the drain and the switching transistor source and switch The voltage between the connection points formed by the drain of the electrode.

10. A closed-loop control system for a series resonant hybrid three-level converter, applied to the series resonant hybrid three-level converter of claim 1, characterized in that, include: The voltage gain calculation module calculates the voltage gain based on the input voltage and the output voltage collected by the sensor. M , , This refers to the number of transformer turns. Input voltage, This refers to the output voltage. A PI controller adjusts the output voltage and output power based on the voltage error between the reference voltage and the output voltage. The high-efficiency current operating trajectory control module, based on the high-efficiency current operating trajectory control strategy: Calculate the control angle and , For switching transistors Conduction angle, For switching transistors and Start-up lag switching transistor The angle of the opening point; The PWM unit generates trigger pulses for each switch transistor in the converter.

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