A modulation method of bidirectional three-level resonant converter and power supply system

Abstract

The application relates to a bidirectional three-level resonant converter modulation method, which realizes a forward transmission power mode from a left side of a resonant tank to a right side of the resonant tank and a reverse transmission power mode from the right side of the resonant tank to the left side of the resonant tank by adjusting the duty cycle of each voltage level. The forward transmission power mode comprises a forward high-gain mode, a forward medium-gain mode and a forward low-gain mode, and the reverse transmission power mode comprises a reverse high-gain mode, a reverse medium-gain mode and a reverse low-gain mode. By adjusting the duty cycle of the corresponding MOSFET, the gain modes and the smooth switching between the gain modes are realized. The application can realize better output performance and efficiency by adjusting the duty cycle of the MOSFET, better control the output voltage or current, thereby reducing the harmonic distortion and noise, and has no power backflow problem, is simple to implement, has small overall loss and improves the system reliability.

Description

Technical Field

[0001] This invention relates to the field of power electronics technology, and in particular to a modulation method and power supply system for a bidirectional three-level resonant converter. Background Technology

[0002] Existing three-level resonant converters typically employ frequency modulation (FM) or phase modulation (PM) to control the output voltage or current by adjusting the converter's operating frequency or phase. However, the converter's operating frequency changes with the load, potentially leading to system instability or noise. Furthermore, for precise control, phase modulation requires adjusting the phase relationship between the two switching transistors, resulting in complex control circuit design and potential dead-time issues, leading to poor output performance. Additionally, conventional modulation methods have limitations for certain applications. For example, under light load conditions, the efficiency of conventional modulation methods may decrease, and this efficiency further decreases as the load lightens. Moreover, conventional modulation methods generate significant ripple voltage, which can affect system stability and reliability.

[0003] In summary, the application of existing conventional modulation methods in three-level resonant converters has some drawbacks, including low power conversion efficiency and the occurrence of harmonic distortion and noise. Summary of the Invention

[0004] Therefore, the technical problem to be solved by the present invention is to overcome the problem of harmonic distortion and noise in the output caused by controlling the output voltage or current by adjusting the operating frequency or phase of the converter in the prior art.

[0005] To solve the above-mentioned technical problems, the present invention provides a modulation method for a bidirectional three-level resonant converter, comprising: The forward power transfer mode from the left side of the resonant slot to the right side of the resonant slot includes: In the forward high-gain mode, during the first half of the cycle, the duty cycle of the primary-side first MOSFET drive signal is at most 50%, and the duty cycles of the primary-side second MOSFET drive signals, the primary-side sixth MOSFET drive signals, and the secondary-side fourth MOSFET drive signals are all 50%. During the second half of the cycle, when the primary-side first MOSFET drive signals, the primary-side second MOSFET drive signals, the primary-side sixth MOSFET drive signals, and the secondary-side fourth MOSFET drive signals are turned off, the duty cycles of the primary-side third MOSFET drive signals, the primary-side fifth MOSFET drive signals, and the secondary-side third MOSFET drive signals are all turned on, with a total duty cycle of 50%. The control timings of the primary-side fifth MOSFET and the secondary-side third MOSFET are consistent, as are the control timings of the primary-side sixth MOSFET and the secondary-side fourth MOSFET. By adjusting the duty cycles of the primary-side first MOSFET drive signals and the primary-side fourth MOSFET drive signals, forward high gain is achieved. In the forward medium gain mode, during the first half of the cycle, the duty cycle of the primary-side first MOSFET drive signal is at most 50%, and the duty cycles of the primary-side second MOSFET drive signals, the primary-side sixth MOSFET drive signals, and the secondary-side fourth MOSFET drive signals are all 50%. During the second half of the cycle, when the primary-side first MOSFET drive signals, the primary-side second MOSFET drive signals, the primary-side sixth MOSFET drive signals, and the secondary-side fourth MOSFET drive signals are off, the duty cycle of the primary-side third MOSFET drive signal is at most 50%, and the duty cycle of the primary-side fifth MOSFET drive signal is also 50%. The control timings of the primary-side fifth MOSFET and the secondary-side third MOSFET are consistent, as are the control timings of the primary-side sixth MOSFET and the secondary-side fourth MOSFET. The forward medium gain is achieved by adjusting the duty cycles of the primary-side first MOSFET drive signals and the primary-side third MOSFET drive signals. In the forward low-gain mode, during the first half of the cycle, the duty cycle of the primary-side second MOSFET drive signal is at most 50%, and the duty cycles of the primary-side sixth MOSFET drive signal and the secondary-side fourth MOSFET drive signal are both 50%. During the second half of the cycle, when the primary-side second MOSFET drive signal, the primary-side sixth MOSFET drive signal, and the secondary-side fourth MOSFET drive signal are turned off, the duty cycles of the primary-side fifth MOSFET drive signal and the secondary-side third MOSFET drive signal are both 50%, and the maximum duty cycle of the primary-side third MOSFET drive signal is 50%. The control timing of the primary-side fifth MOSFET and the secondary-side third MOSFET is consistent, as is the control timing of the primary-side sixth MOSFET and the secondary-side fourth MOSFET. By adjusting the duty cycles of the primary-side second MOSFET drive signal and the primary-side third MOSFET drive signal, forward low gain is achieved. The power transmission mode from the right side of the resonant tank to the left side of the resonant tank ensures that the duty cycle of all MOSFET drive signals on the secondary side is 50%. The drive signals of the first and second MOSFETs on the secondary side are complementary, as are the drive signals of the third and fourth MOSFETs on the secondary side. The drive signals of the seventh and eighth MOSFETs on the primary side are complementary, as are the drive signals of the first and fourth MOSFETs on the primary side, and the drive signals of the second and third MOSFETs on the primary side. This includes: In reverse high-gain mode, the maximum duty cycle of the primary-side first MOSFET and primary-side third MOSFET drive signals is 50%. First, the primary-side first MOSFET drive signal, the primary-side eighth MOSFET drive signal, and the primary-side second MOSFET and the secondary-side first MOSFET and fourth MOSFET drive signals are turned on. After a quarter cycle, the primary-side fourth MOSFET drive signal, the primary-side seventh MOSFET drive signal, and the secondary-side second MOSFET and third MOSFET drive signals are turned on. By adjusting the duty cycle of the primary-side first MOSFET drive signal and the primary-side third MOSFET drive signal, reverse high gain is achieved. In the reverse mid-gain mode, the primary side second MOSFET is kept on while the primary side third MOSFET is off. First, the secondary side first MOSFET drive signal and the secondary side fourth MOSFET drive signal are turned on. The duty cycle of the primary side first MOSFET drive signal and the primary side eighth MOSFET drive signal is 50% at most. By decreasing the duty cycle of the primary side first MOSFET drive signal and the primary side eighth MOSFET drive signal and increasing the duty cycle of the primary side third MOSFET drive signal, the reverse mid-gain mode is achieved. In reverse low gain mode, the drive signals of the first MOSFET on the secondary side, the fourth MOSFET on the secondary side, the second MOSFET on the primary side, and the seventh MOSFET on the primary side are turned on. When the drive signals of the fourth MOSFET on the primary side, the first MOSFET on the secondary side, and the fourth MOSFET on the secondary side are turned off, the drive signals of the first MOSFET on the primary side, the second MOSFET on the secondary side, and the third MOSFET on the secondary side are turned on. By adjusting the phase of the drive signals of the first MOSFET on the primary side and the third MOSFET on the primary side, reverse low gain is achieved.

[0006] In one embodiment of the present invention, after achieving the positive high gain in the positive high gain mode, the method further includes: By reducing the duty cycle between the primary-side third MOSFET drive signal and the primary-side fourth MOSFET drive signal, the switching from the positive high-gain mode to the positive medium-gain mode is achieved.

[0007] In one embodiment of the present invention, after achieving the positive mid-gain mode, the method further includes: By reducing the duty cycle between the primary-side first MOSFET drive signal and the primary-side second MOSFET drive signal, the switching from the positive medium gain mode to the positive low gain mode is achieved.

[0008] In one embodiment of the present invention, after achieving the positive low gain mode, the method further includes: By increasing the duty cycle between the primary-side first MOSFET drive signal and the primary-side second MOSFET drive signal, the switching from the positive low-gain mode to the positive medium-gain mode is achieved.

[0009] In one embodiment of the present invention, the reverse high-gain mode further includes, after achieving the reverse high gain: By increasing the duty cycle of the primary-side first MOSFET drive signal and the primary-side eighth MOSFET drive signal, and decreasing the duty cycle of the primary-side third MOSFET drive signal, the switching from the reverse high-gain mode to the reverse medium-gain mode is achieved.

[0010] In one embodiment of the present invention, the inverted mid-gain mode further includes, after implementing the inverted mid-gain, the following: By shifting the phases of the primary-side first MOSFET drive signal, the primary-side third MOSFET drive signal, and the primary-side seventh MOSFET drive signal to the right by a quarter phase, the switching from reverse medium gain to reverse low gain is achieved.

[0011] In one embodiment of the present invention, in the forward power transmission mode from the left side of the resonant slot to the right side of the resonant slot, the switching between different gain modes is achieved by controlling the duty cycle of the driving signal of the corresponding MOSFET in the forward high gain mode, forward medium gain mode and forward low gain mode.

[0012] This invention also provides a power supply system, comprising: A bidirectional three-level resonant converter controlled by the modulation method of the bidirectional three-level resonant converter as described above.

[0013] In one embodiment of the present invention, the bidirectional three-level resonant converter is one of the following: a bidirectional three-level resonant DC-DC converter with a CLLLC resonant structure, a bidirectional three-level resonant converter without an external inductor, a bidirectional three-level resonant converter with an added LLC structure, or a bidirectional three-level resonant converter with an added LC structure.

[0014] The technical solution of the present invention has the following advantages over the prior art: The bidirectional three-level resonant converter modulation method described in this invention allows for direct control of the duty cycle of each voltage level by adjusting the main duty cycle parameter, without needing to adjust the phase relationship between the two switching transistors. This achieves better output performance and efficiency, better control of the output voltage or current, and thus reduces harmonic distortion and noise. Furthermore, this invention can achieve a wide voltage gain bandwidth by adjusting the duty cycle of each MOSFET, enabling smooth switching between forward high-gain, forward medium-gain, and forward low-gain modes, as well as smooth switching between reverse high-gain, reverse medium-gain, and reverse low-gain modes. It also eliminates power backflow issues, is simple to implement, has low overall losses, and improves system reliability. Attached Figure Description

[0015] To make the content of this invention easier to understand, the invention will be further described in detail below with reference to specific embodiments and accompanying drawings, wherein... Figure 1 This is a schematic diagram of the bidirectional three-level resonant DC-DC converter with CLLLC resonant structure of the present invention; Figure 2 This is a timing diagram of the driving state waveform of the positive step-down power transmission mode from the left side of the resonant slot to the right side of the resonant slot in this invention. Figure 3 This is the high-gain mode of the forward buck transmission power mode of the present invention. A schematic diagram of the current flow at a given moment; Figure 4 This is the high-gain mode of the forward buck transmission power mode of the present invention. A schematic diagram of the current flow at a given moment; Figure 5 This is the high-gain mode of the forward buck transmission power mode of the present invention. A schematic diagram of the current flow at a given moment; Figure 6 This is the high-gain mode of the forward buck transmission power mode of the present invention. A schematic diagram of the current flow at a given moment; Figure 7 This is a timing diagram of the driving state waveform of the reverse boost power transmission mode from the right side of the resonant slot to the left side of the resonant slot in this invention. Figure 8 This is the high-gain mode of the reverse boost transmission power mode of the present invention. A schematic diagram of the current flow at a given moment; Figure 9 This is the high-gain mode of the reverse boost transmission power mode of the present invention. A schematic diagram of the current flow at a given moment; Figure 10 This is the high-gain mode of the reverse boost transmission power mode of the present invention. A schematic diagram of the current flow at a given moment; Figure 11 This is the high-gain mode of the reverse boost transmission power mode of the present invention. A schematic diagram of the current flow at a given moment; Figure 12 This invention provides a bidirectional three-level resonant converter that does not use an external inductor. Figure 13 This invention provides a bidirectional three-level resonant converter with an added LLC structure; Figure 14 This invention provides a bidirectional three-level resonant converter with an added LC structure. Detailed Implementation

[0016] The present invention will be further described below with reference to the accompanying drawings and specific embodiments, so that those skilled in the art can better understand and implement the present invention. However, the embodiments described are not intended to limit the present invention.

[0017] The bidirectional three-level resonant converter modulation method of the present invention, wherein the bidirectional three-level resonant DC-DC converter with a CLLLC resonant structure specifically includes: The forward power transfer mode from the left side of the resonant slot to the right side of the resonant slot includes: In the forward high-gain mode, during the first half of the cycle, the duty cycle of the primary-side first MOSFET drive signal is at most 50%, and the duty cycles of the primary-side second MOSFET drive signals, the primary-side sixth MOSFET drive signals, and the secondary-side fourth MOSFET drive signals are all 50%. During the second half of the cycle, when the primary-side first MOSFET drive signals, the primary-side second MOSFET drive signals, the primary-side sixth MOSFET drive signals, and the secondary-side fourth MOSFET drive signals are turned off, the duty cycles of the primary-side third MOSFET drive signals, the primary-side fifth MOSFET drive signals, and the secondary-side third MOSFET drive signals are all turned on, with a total duty cycle of 50%. The control timing of the primary-side fifth MOSFET and the secondary-side third MOSFET is consistent, as is the control timing of the primary-side sixth MOSFET and the secondary-side fourth MOSFET. By adjusting the duty cycle of the primary-side first MOSFET drive signals and the primary-side fourth MOSFET drive signals, forward high gain is achieved. In the forward medium gain mode, during the first half of the cycle, the duty cycle of the primary-side first MOSFET drive signal is at most 50%, and the duty cycles of the primary-side second MOSFET drive signals, the primary-side sixth MOSFET drive signals, and the secondary-side fourth MOSFET drive signals are all 50%. During the second half of the cycle, when the primary-side first MOSFET drive signals, the primary-side second MOSFET drive signals, the primary-side sixth MOSFET drive signals, and the secondary-side fourth MOSFET drive signals are off, the duty cycle of the primary-side third MOSFET drive signal is at most 50%, and the duty cycle of the primary-side fifth MOSFET drive signal is also 50%. The control timings of the primary-side fifth MOSFET and the secondary-side third MOSFET are consistent, as are the control timings of the primary-side sixth MOSFET and the secondary-side fourth MOSFET. The forward medium gain is achieved by adjusting the duty cycles of the primary-side first MOSFET drive signals and the primary-side third MOSFET drive signals. In the forward low-gain mode, during the first half of the cycle, the duty cycle of the primary-side second MOSFET drive signal is at most 50%, and the duty cycles of the primary-side sixth MOSFET drive signal and the secondary-side fourth MOSFET drive signal are both 50%. During the second half of the cycle, when the primary-side second MOSFET drive signal, the primary-side sixth MOSFET drive signal, and the secondary-side fourth MOSFET drive signal are turned off, the duty cycles of the primary-side fifth MOSFET drive signal and the secondary-side third MOSFET drive signal are both 50%, and the maximum duty cycle of the primary-side third MOSFET drive signal is 50%. The control timing of the primary-side fifth MOSFET and the secondary-side third MOSFET is consistent, as is the control timing of the primary-side sixth MOSFET and the secondary-side fourth MOSFET. By adjusting the duty cycles of the primary-side second MOSFET drive signal and the primary-side third MOSFET drive signal, forward low gain is achieved. The power transmission mode from the right side of the resonant tank to the left side of the resonant tank ensures that the duty cycle of all MOSFET drive signals on the secondary side is 50%. The drive signals of the first and second MOSFETs on the secondary side are complementary, as are the drive signals of the third and fourth MOSFETs on the secondary side. The drive signals of the seventh and eighth MOSFETs on the primary side are complementary, as are the drive signals of the first and fourth MOSFETs on the primary side, and the drive signals of the second and third MOSFETs on the primary side. This includes: In reverse high-gain mode, the maximum duty cycle of the primary-side first MOSFET and primary-side third MOSFET drive signals is 50%. First, the primary-side first MOSFET drive signal, the primary-side eighth MOSFET drive signal, and the primary-side second MOSFET and the secondary-side first MOSFET and fourth MOSFET drive signals are turned on. After a quarter cycle, the primary-side fourth MOSFET drive signal, the primary-side seventh MOSFET drive signal, and the secondary-side second MOSFET and third MOSFET drive signals are turned on. By adjusting the duty cycle of the primary-side first MOSFET drive signal and the primary-side third MOSFET drive signal, reverse high gain is achieved. In the reverse mid-gain mode, the primary side second MOSFET is kept on while the primary side third MOSFET is off. First, the secondary side first MOSFET drive signal and the secondary side fourth MOSFET drive signal are turned on. The duty cycle of the primary side first MOSFET drive signal and the primary side eighth MOSFET drive signal is 50% at most. By decreasing the duty cycle of the primary side first MOSFET drive signal and the primary side eighth MOSFET drive signal and increasing the duty cycle of the primary side third MOSFET drive signal, the reverse mid-gain mode is achieved. In reverse low gain mode, the drive signals of the first MOSFET on the secondary side, the fourth MOSFET on the secondary side, the second MOSFET on the primary side, and the seventh MOSFET on the primary side are turned on. When the drive signals of the fourth MOSFET on the primary side, the first MOSFET on the secondary side, and the fourth MOSFET on the secondary side are turned off, the drive signals of the first MOSFET on the primary side, the second MOSFET on the secondary side, and the third MOSFET on the secondary side are turned on. By adjusting the phase of the drive signals of the first MOSFET on the primary side and the third MOSFET on the primary side, reverse low gain is achieved.

[0018] In the forward power transmission mode from the left side of the resonant slot to the right side of the resonant slot, the switching between different gain modes is achieved by controlling the duty cycle of the corresponding MOSFET drive signal to a maximum of 50% in the forward high gain mode, forward medium gain mode, and forward low gain mode.

[0019] Specifically, in this embodiment of the invention, after achieving the corresponding voltage gain, smooth switching between different gain modes can be achieved by adjusting the duty cycle, specifically including: In the positive high gain mode, after achieving positive high gain, the switching from positive high gain mode to positive medium gain mode is achieved by reducing the duty cycle of the primary side third MOSFET drive signal and the primary side fourth MOSFET drive signal. In the positive medium gain mode, after achieving positive medium gain, the switching from positive medium gain mode to positive low gain mode is achieved by reducing the duty cycle of the primary side first MOSFET drive signal and the primary side second MOSFET drive signal. In the positive low gain mode, after achieving positive low gain, the switching from positive low gain mode to positive medium gain mode is achieved by increasing the duty cycle of the primary side first MOSFET drive signal and the primary side second MOSFET drive signal. In the reverse high-gain mode, after achieving reverse high gain, the switching from reverse high-gain mode to reverse medium-gain mode is achieved by increasing the duty cycle of the primary-side first MOSFET drive signal and the primary-side eighth MOSFET drive signal, and decreasing the duty cycle of the primary-side third MOSFET drive signal. In the reverse medium gain mode, after achieving reverse medium gain, the switching from reverse medium gain to reverse low gain is achieved by shifting the phases of the primary side first MOSFET drive signal, the primary side third MOSFET drive signal, and the primary side seventh MOSFET drive signal to the right by a quarter phase.

[0020] In this embodiment, the rectifier bridge exhibits zero-current turn-off (ZCS) capability across a wide output voltage range in forward power transmission mode. In reverse mode, for high-gain and medium-gain modes, the converter can be switched when the voltage gain is between 0.5 and 0.75. For medium-gain and low-gain modes, switching can be achieved when the voltage gain is between 0.25 and 0.5. It is known that under the same voltage gain and load conditions, the RMS current in medium-gain mode is smaller than that in high-gain mode; therefore, the conduction loss in high-gain mode is higher than that in medium-gain mode. Furthermore, the control variable should not be too small to achieve zero-voltage turn-on (ZVS). To optimize efficiency, medium-gain mode is preferred when both high-gain and medium-gain modes can achieve the same voltage gain; and high-gain mode is preferred when both medium-gain and high-gain modes can achieve the same voltage gain. A higher voltage gain at the switching point is better, as this results in a smaller RMS current and easier ZVS implementation. The goal is to obtain maximum benefit in different modes.

[0021] The bidirectional three-level resonant converter modulation method provided by this invention is applied to, for example... Figure 1 In the bidirectional three-level resonant DC-DC converter with the CLLLC resonant structure shown, the specific MOSFET drive signals include: Reference Figure 2 The figure shows the timing diagram of the drive state waveform during the forward buck power transfer mode from the left side of the resonant slot to the right side; specifically, one switching cycle is divided into four stages, as shown in the figure. Figure 3 , Figure 4 , Figure 5 ,and Figure 6As shown, these are the high-gain modes in the forward buck power transmission mode. , , , A schematic diagram of current flow at a given moment; the medium gain mode in the forward buck power transfer mode. , , A schematic diagram of current flow at a given time, compared to high-gain mode. , , The current flow diagram at any given moment is the same; the low-gain mode in the forward buck power transfer mode is... , A schematic diagram of the current flow at a given time, compared to the high-gain mode. , The current flow diagram at any given time is the same.

[0022] Reference Figure 7 The diagram shown is a timing diagram of the driving state waveform during the reverse boost power transmission mode from the right side of the resonant slot to the left side of the resonant slot according to the present invention; similarly, one switching cycle is divided into four stages, referring to... Figure 8 , Figure 9 , Figure 10 and Figure 11 As shown, these are the high-gain modes in the reverse boost transmission power mode. , , , A schematic diagram of current flow at a given moment; the medium gain mode in reverse boost power transfer mode. , , A schematic diagram of current flow at a given moment, compared to the high-gain mode in reverse boost power transfer mode. , , The current flow diagram at any given moment is the same; the low-gain mode in the reverse boost power transfer mode is... , A schematic diagram of current flow at a given moment, compared to the high-gain mode in reverse boost power transfer mode. , The current flow diagram at any given time is the same.

[0023] Throughout the entire operating state of the bidirectional three-level resonant converter modulation method provided by this invention, the switching frequency of all MOSFETs in the resonant converter is always equal to the resonant frequency of the resonant converter. This invention utilizes a fixed switching frequency, simplifies implementation, and ensures the stability and fault tolerance of the device operation.

[0024] This embodiment regulates the converter's output power by controlling the input voltage. A higher input voltage generates more energy through the resonant tank, while a lower input voltage generates less energy. The absolute value of the input voltage can be varied from 0, 50%V, and V; the output power can be modulated between 0 and V. 1 / 2 The duty cycle of each voltage level is adjusted by adjusting the duty cycle of V. By adjusting the duty cycle of each voltage level, the main duty cycle parameter can directly control the duty cycle of each voltage level without needing to adjust the phase relationship between the two switching transistors, achieving better output performance and efficiency, and better control of the output voltage or current, thereby reducing harmonic distortion and noise. Furthermore, this invention can achieve a wide voltage gain width by adjusting the duty cycle of each MOSFET, enabling smooth switching between forward high-gain mode, forward medium-gain mode, and forward low-gain mode, as well as smooth switching between reverse high-gain mode, reverse medium-gain mode, and reverse low-gain mode. It also eliminates power backflow issues, is simple to implement, has low overall losses, and improves system reliability.

[0025] Based on the above embodiments, this invention also provides a power supply system, including: A bidirectional three-level resonant converter controlled by the modulation method of the bidirectional three-level resonant converter as described above.

[0026] In this embodiment, the bidirectional three-level resonant converter is one of the following: a bidirectional three-level resonant DC-DC converter with a CLLLC resonant structure, a bidirectional three-level resonant converter without an external inductor, a bidirectional three-level resonant converter with an added LLC structure, or a bidirectional three-level resonant converter with an added LC structure. (Refer to...) Figure 1 The image shows a bidirectional three-level resonant DC-DC converter with a CLLLC resonant structure provided by this invention; see reference. Figure 12 As shown, this is a bidirectional three-level resonant converter that does not use an external inductor, provided by the present invention; see reference. Figure 13 The diagram shows a bidirectional three-level resonant converter with an added LLC structure provided by this invention; see reference. Figure 14 As shown, this is a bidirectional three-level resonant converter with an added LC structure provided by the present invention.

[0027] The three-level resonant converter modulation method described in this invention allows for direct control of the duty cycle of each voltage level by adjusting the main duty cycle parameter, without needing to adjust the phase relationship between the two switching transistors. This achieves better output performance and efficiency, better control of the output voltage or current, and thus reduces harmonic distortion and noise. Furthermore, this invention can achieve a wide voltage gain width by adjusting the duty cycle of each MOSFET, enabling smooth switching between forward high-gain, forward medium-gain, and forward low-gain modes, as well as smooth switching between reverse high-gain, reverse medium-gain, and reverse low-gain modes. It also eliminates power backflow issues, is simple to implement, and has low overall losses.

[0028] The bidirectional three-level converter modulated by the three-level resonant converter modulation method provided in this invention is widely used in new energy power generation systems, DC microgrids, electric vehicles, spacecraft power systems and energy storage, etc., reducing system losses and improving system reliability.

[0029] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A modulation method for a bidirectional three-level resonant converter, characterized in that, include: The forward power transfer mode from the left side of the resonant slot to the right side of the resonant slot includes: In the forward high-gain mode, during the first half of the cycle, the duty cycle of the primary-side first MOSFET drive signal is at most 50%, and the duty cycles of the primary-side second MOSFET drive signals, the primary-side sixth MOSFET drive signals, and the secondary-side fourth MOSFET drive signals are all 50%. During the second half of the cycle, when the primary-side first MOSFET drive signals, the primary-side second MOSFET drive signals, the primary-side sixth MOSFET drive signals, and the secondary-side fourth MOSFET drive signals are turned off, the duty cycles of the primary-side third MOSFET drive signals, the primary-side fifth MOSFET drive signals, and the secondary-side third MOSFET drive signals are all turned on, with a total duty cycle of 50%. The control timings of the primary-side fifth MOSFET and the secondary-side third MOSFET are consistent, as are the control timings of the primary-side sixth MOSFET and the secondary-side fourth MOSFET. By adjusting the duty cycles of the primary-side first MOSFET drive signals and the primary-side fourth MOSFET drive signals, forward high gain is achieved. In the forward medium gain mode, during the first half of the cycle, the duty cycle of the primary-side first MOSFET drive signal is at most 50%, and the duty cycles of the primary-side second MOSFET drive signals, the primary-side sixth MOSFET drive signals, and the secondary-side fourth MOSFET drive signals are all 50%. During the second half of the cycle, when the primary-side first MOSFET drive signals, the primary-side second MOSFET drive signals, the primary-side sixth MOSFET drive signals, and the secondary-side fourth MOSFET drive signals are off, the duty cycle of the primary-side third MOSFET drive signal is at most 50%, and the duty cycle of the primary-side fifth MOSFET drive signal is also 50%. The control timings of the primary-side fifth MOSFET and the secondary-side third MOSFET are consistent, as are the control timings of the primary-side sixth MOSFET and the secondary-side fourth MOSFET. The forward medium gain is achieved by adjusting the duty cycles of the primary-side first MOSFET drive signals and the primary-side third MOSFET drive signals. In the forward low-gain mode, during the first half of the cycle, the duty cycle of the primary-side second MOSFET drive signal is at most 50%, and the duty cycles of the primary-side sixth MOSFET drive signal and the secondary-side fourth MOSFET drive signal are both 50%. During the second half of the cycle, when the primary-side second MOSFET drive signal, the primary-side sixth MOSFET drive signal, and the secondary-side fourth MOSFET drive signal are turned off, the duty cycles of the primary-side fifth MOSFET drive signal and the secondary-side third MOSFET drive signal are both 50%, and the maximum duty cycle of the primary-side third MOSFET drive signal is 50%. The control timing of the primary-side fifth MOSFET and the secondary-side third MOSFET is consistent, as is the control timing of the primary-side sixth MOSFET and the secondary-side fourth MOSFET. By adjusting the duty cycles of the primary-side second MOSFET drive signal and the primary-side third MOSFET drive signal, forward low gain is achieved. The power transmission mode from the right side of the resonant tank to the left side of the resonant tank ensures that the duty cycle of all MOSFET drive signals on the secondary side is 50%. The drive signals of the first and second MOSFETs on the secondary side are complementary, as are the drive signals of the third and fourth MOSFETs on the secondary side. The drive signals of the seventh and eighth MOSFETs on the primary side are complementary, as are the drive signals of the first and fourth MOSFETs on the primary side, and the drive signals of the second and third MOSFETs on the primary side. This includes: In reverse high-gain mode, the maximum duty cycle of the primary-side first MOSFET and primary-side third MOSFET drive signals is 50%. First, the primary-side first MOSFET drive signal, the primary-side eighth MOSFET drive signal, and the primary-side second MOSFET and the secondary-side first MOSFET and fourth MOSFET drive signals are turned on. After a quarter cycle, the primary-side fourth MOSFET drive signal, the primary-side seventh MOSFET drive signal, and the secondary-side second MOSFET and third MOSFET drive signals are turned on. By adjusting the duty cycle of the primary-side first MOSFET drive signal and the primary-side third MOSFET drive signal, reverse high gain is achieved. In reverse mid-gain mode, the second MOSFET on the primary side is kept on while the third MOSFET on the primary side is turned off. First, the drive signals of the first MOSFET and the fourth MOSFET on the secondary side are turned on. The duty cycle of the drive signals of the first MOSFET and the eighth MOSFET on the primary side is turned on at a maximum of 50%. By reducing the duty cycle of the drive signals of the first MOSFET and the eighth MOSFET on the primary side, reverse mid-gain is achieved. In reverse low gain mode, the drive signals of the first MOSFET on the secondary side, the fourth MOSFET on the secondary side, the second MOSFET on the primary side, and the seventh MOSFET on the primary side are turned on. When the drive signals of the fourth MOSFET on the primary side, the first MOSFET on the secondary side, and the fourth MOSFET on the secondary side are turned off, the drive signals of the first MOSFET on the primary side, the second MOSFET on the secondary side, and the third MOSFET on the secondary side are turned on. By adjusting the phase of the drive signals of the first MOSFET on the primary side and the third MOSFET on the primary side, reverse low gain is achieved.

2. The modulation method for a bidirectional three-level resonant converter according to claim 1, characterized in that, In the aforementioned positive high-gain mode, after achieving positive high gain, the following is also included: By reducing the duty cycle between the primary-side third MOSFET drive signal and the primary-side fourth MOSFET drive signal, the switching from the positive high-gain mode to the positive medium-gain mode is achieved.

3. The modulation method for a bidirectional three-level resonant converter according to claim 1, characterized in that, In the positive mid-gain mode, after achieving the positive mid-gain, the following is also included: By reducing the duty cycle between the primary-side first MOSFET drive signal and the primary-side second MOSFET drive signal, the switching from the positive medium gain mode to the positive low gain mode is achieved.

4. The modulation method for a bidirectional three-level resonant converter according to claim 1, characterized in that, In the aforementioned positive low-gain mode, after achieving positive low gain, the following is also included: By increasing the duty cycle between the primary-side first MOSFET drive signal and the primary-side second MOSFET drive signal, the switching from the positive low-gain mode to the positive medium-gain mode is achieved.

5. The modulation method for a bidirectional three-level resonant converter according to claim 1, characterized in that, In the reverse high-gain mode, after achieving the reverse high gain, the following is also included: By increasing the duty cycle of the primary-side first MOSFET drive signal and the primary-side eighth MOSFET drive signal, and decreasing the duty cycle of the primary-side third MOSFET drive signal, the switching from the reverse high-gain mode to the reverse medium-gain mode is achieved.

6. The modulation method for a bidirectional three-level resonant converter according to claim 1, characterized in that, In the inverted mid-gain mode, after implementing the inverted mid-gain, the following is also included: By shifting the phases of both the primary-side first MOSFET drive signal and the primary-side third MOSFET drive signal to the right by a quarter phase, the switching from medium gain to low gain in the reverse direction is achieved.

7. The modulation method for a bidirectional three-level resonant converter according to claim 1, characterized in that, In the forward power transmission mode from the left side of the resonant slot to the right side of the resonant slot, the switching between different gain modes is achieved by controlling the duty cycle of the corresponding MOSFET drive signal in the forward high gain mode, forward medium gain mode, and forward low gain mode.

8. A power supply system, characterized in that, include: A bidirectional three-level resonant converter controlled by the modulation method of the bidirectional three-level resonant converter as described in any one of claims 1 to 7.

9. The power supply system according to claim 8, characterized in that, The bidirectional three-level resonant converter is one of the following: a bidirectional three-level resonant DC-DC converter with a CLLLC resonant structure, a bidirectional three-level resonant converter without an external inductor, a bidirectional three-level resonant converter with an added LLC structure, or a bidirectional three-level resonant converter with an added LC structure.

Images