Battery equalization and backflow optimization control method for modular half-bridge full-bridge converter

Abstract

This invention discloses a battery balancing and return current optimization control method for a modular half-bridge to full-bridge converter, applied to an input-series-output-parallel architecture. The method includes: acquiring parameters such as the voltage of each individual battery cell and the inductor current on the half-bridge side; in the intra-group balancing control stage, generating a DC bias current reference value based on the voltage difference between individual cells within the module, and performing closed-loop regulation and limiting based on the actual DC component of the inductor current to generate a DC regulation duty cycle for asymmetric modulation; in the inter-group balancing and power transfer stage, synthesizing the outward phase shift angle on the full-bridge side based on the global average voltage deviation; simultaneously, calculating the real-time voltage conversion ratio, and applying limiting constraints based on zero-voltage turn-on boundary conditions, calculating the optimal inward phase shift angle on the full-bridge side piecewise; finally, generating the drive signal. This invention can achieve rapid battery balancing under small voltage difference conditions and significantly reduce the return current power under non-unity voltage gain, ensuring wide-range soft-switching operation.

Description

Technical Field

[0001] This invention relates to the field of power electronic converters and their control technology, specifically to a battery balancing and return current optimization control method and system for a modular half-bridge to full-bridge converter for electric vehicle auxiliary power modules (APM). Background Technology

[0002] Due to manufacturing processes and operating conditions, battery packs for new energy vehicles are prone to inconsistencies in individual cell voltages, necessitating active battery balancing control. Simultaneously, the onboard auxiliary power module (APM) needs to step down the high-voltage side power and convert it to low-voltage DC.

[0003] Because the main circuit and active balancing circuit of the APM (Automated Power Management) system highly overlap in topology, existing technologies often integrate auxiliary step-down and battery balancing functions in hardware. A typical solution is a modular half-bridge to full-bridge (HFB) converter with an input-series-output-parallel (ISOP) architecture. This architecture utilizes the primary-side half-bridge for local energy transfer between battery cells, while simultaneously using the secondary-side full-bridge in parallel to supply power externally. However, existing control methods still have the following technical shortcomings in actual operation: Firstly, regarding battery equalization and bias suppression: traditional symmetrical duty cycle modulation results in slow equalization speed under small voltage differences. While some solutions introduce asymmetrical duty cycles to actively inject DC bias current, they mostly employ open-loop feedforward calculations, lacking closed-loop monitoring and limiting control of the actual DC component of the inductor. Affected by non-ideal factors such as power device parameter drift and drive delay, open-loop regulation is prone to triggering uncontrollable DC bias current, leading to unidirectional magnetic saturation of the high-frequency transformer. Furthermore, existing equalization control is mostly limited to independent adjustment of a single module, lacking an inter-module coordination mechanism based on a global voltage perspective.

[0004] Secondly, regarding power transmission and efficiency optimization: existing full-bridge converters typically employ a traditional single-phase-shift (SPS) control strategy. In actual operation, due to battery voltage fluctuations and load changes, the converter is often in a non-unity voltage gain state (i.e., the transformer primary and secondary voltages are mismatched). At this time, the lack of multi-degree-of-freedom adjustment in single-phase-shift control leads to a prolonged time interval between the primary voltage and secondary current polarities, resulting in significant backflow power and reactive circulating current on the full-bridge side. This not only increases the effective value of the system current and conduction losses but also disrupts the zero-voltage switching (ZVS) soft-switching boundary condition of the switching transistors, increasing high-frequency hard-switching losses and reducing the overall system conversion efficiency.

[0005] In summary, existing integrated converter control methods struggle to simultaneously achieve rapid anti-magnetic equalization under small voltage differentials, global inter-group coordinated scheduling, and return current power suppression and soft-switching operation under non-unity voltage gain conditions in a single system. Summary of the Invention

[0006] Objective: To address the problems of slow equalization speed and easy induction of transformer DC bias under small voltage difference conditions, and large return current power and difficulty in soft-switching operation under non-unity voltage gain conditions in the multi-objective cooperative control of existing modular half-bridge-full-bridge converters, this invention proposes a battery equalization and return current optimization control method and system for modular half-bridge-full-bridge converters. It utilizes asymmetric modulation and closed-loop limiting control on the half-bridge side to actively inject DC bias to achieve anti-bias equalization, and combines multi-degree-of-freedom internal phase-shift control on the full-bridge side based on zero-voltage turn-on boundary constraints to suppress return current power. This invention aims to achieve efficient, safe, and stable operation of the converter system through hierarchical decoupling control of intra-group equalization, inter-group coordination, and power transfer.

[0007] Technical Solution: A battery balancing and return current optimization control method for a modular half-bridge to full-bridge converter, applied to a power conversion system with series input and parallel output. The system includes multiple converter modules connected in series on the high-voltage side and in parallel on the low-voltage side. For each converter module, the control method includes the following steps: Step S1, Parameter Acquisition: Collect the voltage of each series-connected battery cell in the current converter module, the actual DC component of the inductor current on the half-bridge side, the output voltage of the full-bridge on the low-voltage side, the actual output current on the low-voltage side, and the output power requirement, and calculate the global average voltage of the high-voltage side battery pack corresponding to all converter modules. Step S2, Intra-group equalization control: Generate a DC bias current reference value based on the voltage difference between two series-connected battery cells in the current converter module; compare the DC bias current reference value with the actual DC component of the inductor current on the half-bridge side, and generate a DC regulation duty cycle for controlling the half-bridge side switching transistors through closed-loop regulation and limiting processing. Step S3, Inter-group balancing and external phase shift control: Compare the voltage of the high-voltage side battery pack of the current converter module with the global average voltage to generate an inter-group balancing current correction; superimpose the inter-group balancing current correction with the system base current setpoint obtained based on the output power requirement to synthesize the low-voltage side output current setpoint; compare the low-voltage side output current setpoint with the actual output current of the low-voltage side to generate a closed-loop external phase shift angle on the full-bridge side, wherein the external phase shift angle on the full-bridge side is the phase difference between the primary half-bridge and the secondary full-bridge leading arm; Step S4, Return Optimization and Internal Phase Shift Control: Calculate the real-time voltage conversion ratio of the current converter module, combine it with the preset zero-voltage turn-on boundary constraint, and calculate the optimal internal phase shift angle of the full bridge side according to the different numerical ranges of the real-time voltage conversion ratio. The optimal internal phase shift angle of the full bridge side is the phase difference between the leading and lagging arms of the secondary full bridge. Step S5, drive signal generation: Based on the DC regulation duty cycle, the outward phase shift angle of the full-bridge side, and the optimal inward phase shift angle of the full-bridge side, generate corresponding control signals to drive the switching transistors on the half-bridge side and the full-bridge side of the corresponding converter module.

[0008] Further, the half-bridge side switching transistors include a first switching transistor and a second switching transistor; in step S5, when generating the control signal for the half-bridge side switching transistors based on the DC-regulated duty cycle, an asymmetric modulation strategy is adopted: the on-state duty cycle of the first switching transistor is configured as follows: The duty cycle of the second switch is configured as follows: ,in The DC-regulated duty cycle is referred to here.

[0009] Further, in step S4, the real-time voltage conversion ratio k The calculation formula is: in, n This refers to the turns ratio of a high-frequency transformer. This represents the average voltage of each series-connected battery cell within the current converter module. This is the output voltage of the low-voltage side full bridge.

[0010] Further, in step S4, the control logic for calculating the optimal inner phase shift angle on the full-bridge side in segments, based on the preset zero-voltage turn-on boundary constraints, is as follows: First, calculate the ideal inner phase shift angle that makes the return current power zero; then, determine whether the ideal inner phase shift angle satisfies the preset zero-voltage turn-on boundary constraints; when the real-time voltage conversion ratio When the ideal inner phase shift angle satisfies the zero-voltage turn-on boundary constraint condition, the ideal inner phase shift angle is directly taken as the optimal inner phase shift angle on the full-bridge side; when the real-time voltage conversion ratio When the ideal internal phase shift angle exceeds the range of the zero-voltage turn-on boundary constraint, the optimal internal phase shift angle on the full-bridge side is forcibly limited to the upper limit critical value of the zero-voltage turn-on boundary constraint to maintain the soft-switching operation of the switching transistor.

[0011] Furthermore, in step S4, the optimal inward phase shift angle for the entire bridge side is calculated piecewise. The specific mathematical relationship is as follows: When the real-time voltage conversion ratio hour, When the real-time voltage conversion ratio hour, in, The phase shift angle on the full-bridge side is defined as follows, and the preset zero-voltage turn-on boundary constraint is: .

[0012] This invention also provides a battery balancing and return current optimization control system for a modular half-bridge to full-bridge converter, applied to a power conversion system with series input and parallel output. The system comprises multiple converter modules connected in series on the high-voltage side and in parallel on the low-voltage side. For each converter module, the control system includes: The sampling module is used to collect the voltage of each series-connected battery cell in the current converter module, the actual DC component of the inductor current on the half-bridge side, the output voltage of the full-bridge on the low-voltage side, the actual output current on the low-voltage side, and the output power demand, and to calculate the global average voltage of the high-voltage side battery pack corresponding to all converter modules. The group equalization control unit is used to generate a DC bias current reference value based on the voltage difference between two series-connected battery cells in the current converter module; compare the DC bias current reference value with the actual DC component of the inductor current on the half-bridge side, and generate a DC regulation duty cycle for controlling the switching transistors on the half-bridge side after closed-loop regulation and limiting processing. The power transfer and inter-group equalization control unit is used to compare the voltage of the high-voltage side battery pack of the current converter module with the global average voltage to generate an inter-group equalization current correction; to superimpose the inter-group equalization current correction with the system base current setpoint obtained based on the output power demand to synthesize a low-voltage side output current setpoint; and to compare the low-voltage side output current setpoint with the actual output current of the low-voltage side to generate a closed-loop outward phase shift angle on the full-bridge side, wherein the outward phase shift angle on the full-bridge side is the phase difference between the leading arm of the primary half-bridge and the leading arm of the secondary full-bridge; and to calculate the real-time voltage conversion ratio of the current converter module, and, in conjunction with a preset zero-voltage turn-on boundary constraint, to calculate the optimal inward phase shift angle on the full-bridge side in segments according to the different numerical ranges of the real-time voltage conversion ratio, wherein the optimal inward phase shift angle on the full-bridge side is the phase difference between the leading arm and the lagging arm of the secondary full-bridge. The driving unit is used to generate corresponding control signals to drive the switching transistors on the half-bridge side and the full-bridge side of the corresponding converter module based on the DC regulation duty cycle, the outward phase shift angle of the full-bridge side and the optimal inward phase shift angle of the full-bridge side.

[0013] The implementation process and methods of the system are the same and will not be described again.

[0014] A computer device includes a memory, a processor, and a computer program stored in the memory and executable on the processor. When the processor executes the computer program, it implements the steps of the battery balancing and backflow optimization control method for a modular half-bridge to full-bridge converter as described above.

[0015] A computer-readable storage medium having a computer program / instructions stored thereon, which, when executed by a processor, implements the steps of the battery balancing and backflow optimization control method for a modular half-bridge to full-bridge converter as described above.

[0016] Beneficial effects: Compared with the prior art, the present invention has the following advantages: (1) Improving the balancing speed under small voltage difference conditions and effectively suppressing transformer DC bias. This invention employs asymmetrical modulation on the half-bridge side with a first switch duty cycle of 0.5-Di and a second switch duty cycle of 0.5+Di in the intra-group balancing stage, and constructs a closed-loop regulation mechanism based on the actual DC component of the inductor current. Compared to traditional open-loop feedforward or natural balancing schemes, this method can actively inject and maintain a stable balancing current under small voltage difference conditions, improving the balancing speed; simultaneously, by using closed-loop limiting control, the DC bias current is constrained within a safe range, effectively reducing the risk of unidirectional magnetic saturation in the high-frequency transformer and improving the safety of hardware operation.

[0017] (2) Reduce return current power under non-unity voltage gain conditions and ensure wide-range soft-switching operation. This invention employs a multi-degree-of-freedom phase-shift control strategy in the power transmission stage, combining real-time voltage conversion ratio and zero-voltage turn-on (ZVS) boundary constraints to calculate the optimal inner phase shift angle in segments. This control logic shortens the time interval between the primary and secondary voltages and currents with opposite polarities, reducing system return current power, reactive circulating current, and conduction losses; at the same time, boundary constraints enable the switching transistors to maintain ZVS operation, reducing high-frequency hard-switching losses and improving the overall conversion efficiency of the converter.

[0018] (3) Achieving hierarchical decoupling control for intra-group balancing, inter-group coordination, and power transmission. This invention constructs a hierarchical control architecture, utilizing the DC duty cycle on the half-bridge side to adjust intra-group balancing and the internal and external phase shift angles on the full-bridge side to adjust power transmission, thereby achieving mutual decoupling between DC bias and AC phase shift control. While performing auxiliary step-down power supply tasks, it also takes into account the rapid balancing of local individual cells, and achieves balanced scheduling between system-level modules through global average voltage commands, improving the operational stability of the integrated system. Attached Figure Description

[0019] Figure 1 This is a diagram illustrating the overall structure of the battery balancing and recirculation power collaborative optimization control system provided in an embodiment of the present invention. Figure 2 This is a block diagram illustrating the collaborative optimization control principle provided in an embodiment of the present invention. Figure 3 This is a flowchart of the overall process for the battery balancing and recirculation power co-optimization control method provided in an embodiment of the present invention. Figure 4This is a structural diagram of a modular half-bridge to full-bridge converter system provided in an embodiment of the present invention; Figure 5 This is a topology diagram of a single half-bridge to full-bridge converter module provided in an embodiment of the present invention; Figure 6 The waveform diagram of half-bridge side asymmetric modulation provided in the embodiment of the present invention; Figure 7 The waveform diagram under extended phase-shift control provided in the embodiment of the present invention; Figure 8 A flowchart for determining the optimal inner phase shift angle segmentation on the full-bridge side provided in this embodiment of the invention; Figure 9 The optimal inner phase shift angle trajectory diagram under different voltage conversion ratio conditions provided in the embodiments of the present invention; Figure 10 The following is a comparison diagram of return current power under different control strategies provided in the embodiments of the present invention: (a) return current power under traditional single phase shift (SPS) control, and (b) return current power under optimized extended phase shift (EPS) control. Figure 11 The following is a diagram showing the zero-voltage turn-on waveform of the key switch under the optimized control strategy provided in this embodiment of the invention: (a) Key switch (S) on the half-bridge side. i1 (a) Zero-voltage turn-on waveform; (b) Key switching transistor on the full-bridge side ( The zero-voltage turn-on waveform; Symbol names in the diagram: , —Series-connected battery cells; , — Half-bridge side switching transistor; —Auxiliary inductor; —High-frequency transformer; —The turns ratio of a high-frequency transformer; , , , —Full-bridge side switch tube; —Low-voltage side filter capacitor; —Low-voltage battery or load; , —Positive and negative terminals of the low-voltage busbar; —DC-controlled duty cycle; —The phase angle shifted outwards from the entire bridge side; —Optimal inward phase angle for the entire bridge side; —Real-time voltage conversion ratio; —The average voltage of each battery cell connected in series; — Output voltage of the low-voltage side full bridge. Detailed Implementation

[0020] The present invention will be further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. After reading the present invention, any modifications of the present invention in various equivalent forms by those skilled in the art will fall within the scope defined by the appended claims.

[0021] like Figure 2 As shown, a battery balancing and return current optimization control method for a modular half-bridge to full-bridge converter includes the following steps: Step S1: Parameter Acquisition and Preprocessing S1.1 Construct the topology of the modular half-bridge to full-bridge converter; The specific modular half-bridge to full-bridge converter topology is as follows: Figure 1 , Figure 4 and Figure 5 As shown; the modular half-bridge to full-bridge power conversion system with series input and parallel output adopts an overall series input and parallel output architecture. The high-voltage side consists of multiple series-connected lithium battery cells, with the input side of each converter module connected to the corresponding battery cell group; the output side of each converter module is connected in parallel to the same low-voltage DC bus. (The last sentence appears to be incomplete and possibly refers to a different system.) Taking a converter module as an example, it mainly includes a half-bridge side, a high-frequency isolation link, and a full-bridge side. The half-bridge side consists of switching transistors. and Composition; the high-frequency isolation link includes an auxiliary inductor. and high frequency transformer The entire bridge side is equipped with switch tubes. , , and The full-bridge output is connected to a filter capacitor. and low-voltage batteries Specifically, the midpoint of the series connection of two battery cells Bi1 and Bi2 is connected to one end of the primary side of the high-frequency transformer Ti; the first switch Si1 and the second switch Si2 are connected in series across the two battery cells, and the midpoint of the connection between Si1 and Si2 is connected to the other end of the primary side of the high-frequency transformer Ti via an auxiliary inductor Li; the two ends of the secondary side of the high-frequency transformer Ti are respectively connected to the midpoints of the two bridge arms of the full bridge, where Qi1 and Qi2 form the first bridge arm, and Qi3 and Qi4 form the second bridge arm; the DC output terminal of the full bridge is connected in parallel with the filter capacitor C and the low-voltage battery BLV.

[0022] S1.2 System State Sampling and Calculation: At the beginning of each control cycle, the sampling circuit acquires the real-time data of each series-connected battery cell (e.g., ...) within the converter module. and The calculation includes the voltage of the inductor on the half-bridge side, the actual DC component of the inductor current, the output voltage of the full-bridge on the low-voltage side, the actual output current on the low-voltage side, and the output power requirement. Then, the high-voltage side battery pack voltage of the current module is calculated, and the global average voltage of the high-voltage side battery pack voltages for all converter modules is calculated.

[0023] Step S2: Intra-group balance control Intra-group balancing control, as the first level of regulation, specifically includes the following steps: S2.1 Error Calculation: A DC bias current reference value is generated based on the voltage difference between two series-connected battery cells within the current converter module to achieve active adjustment of battery cell balance within the module. Specifically, assuming the voltage difference between the two battery cells within the current module is ΔUi=UBi1-UBi2, after processing by the group-wide equalization proportional controller KP1, a DC bias current reference value Idc,ref,i=KP1·ΔUi is generated; the sign of this reference value is used to determine the equalization direction, and its absolute value is used to determine the magnitude of the equalization current command.

[0024] S2.2 Closed-Loop Regulation and Limiting: The actual DC component of the auxiliary inductor current on the half-bridge side is extracted and subtracted from the DC bias current reference value to obtain the current error signal eI,i = Idc,ref,i - ILi,dc,i. This current error signal is input to a proportional-integral (PI) controller for closed-loop regulation calculations and, after limiting, generates the DC regulation duty cycle for controlling the half-bridge side switching transistors. .

[0025] S2.3 Asymmetric modulation execution: such as Figure 6 As shown, an asymmetric modulation strategy is adopted, with the first switching transistor... The duty cycle is configured as follows: Second switching transistor The duty cycle is configured as follows: This method actively introduces a controllable DC bias component to improve the balancing speed under small voltage difference conditions, while simultaneously limiting the bias current to a safe range through amplitude limiting constraints. In the simulation of this embodiment, the DC regulation duty cycle Di is limited to -0.02≤Di≤0.02 to prevent the DC bias current from exceeding the set safe range.

[0026] Step S3: Intergroup Equilibrium and External Phase Shift Control S3.1 Inter-module equalization calculation: The high-voltage side battery pack voltage of the current converter module is compared with the global average voltage to generate the inter-module equalization current correction. Specifically, the high-voltage side battery pack voltage of the current module is UMi = UBi1 + UBi2; assuming the system contains N converter modules, the global average voltage is UAV = (1 / N)ΣUMj, j = 1, 2, ..., N; the inter-module equalization current correction is ΔIi = KPi1(UMi - UAV).

[0027] S3.2 Outer Phase Shift Angle Synthesis: The inter-group equalization current correction is superimposed with the system base current setpoint obtained based on the output power demand to synthesize the low-voltage side output current setpoint. The low-voltage side output current setpoint is compared with the actual low-voltage side output current, and the full-bridge side outer phase shift angle is generated through closed-loop regulation. Among them, the phase angle of the outward displacement of the entire bridge side. This represents the phase difference between the leading arms of the primary half-bridge and the secondary full-bridge. When the output power demand is the total output power Pref of the low-voltage bus, the system base current setpoint for each converter module is Iref = Pref / (N·Uo), and the low-voltage side output current setpoint is Io,ref,i = Iref + ΔIi. The output current error is obtained by subtracting Io,ref,i from the actual low-voltage side output current Io,i of the module. This output current error is then processed by the proportional-integral regulator's closed-loop operation to generate the full-bridge side outward phase shift angle Φi2.

[0028] Step S4: Optimization of reflux and internal phase shift control S4.1 Voltage Transformation Ratio Calculation: Obtaining the Turns Ratio of the High-Frequency Transformer The average voltage of each series-connected battery cell in the current converter module and the full-bridge output voltage Calculate the real-time voltage conversion ratio The calculation formula is as follows: S4.2 Boundary Determination and Segmented Solution: Combining the preset zero-voltage turn-on (ZVS) boundary constraints, the optimal inner phase shift angle on the full-bridge side is determined. The process involves segmentation. First, the ideal inward phase shift angle that theoretically results in zero return power is calculated. Then, it is determined whether this ideal inward phase shift angle satisfies the preset zero-voltage turn-on boundary constraint condition. .

[0029] like Figure 8 and Figure 9 As shown, the specific piecewise analytical mathematical relation is: (1) When the real-time voltage conversion ratio satisfies When the ideal inner phase shift angle satisfies the zero-voltage turn-on boundary constraint, it can be directly used as the optimal inner phase shift angle output for the full-bridge side: (2) When the real-time voltage conversion ratio satisfies At this point, the ideal internal phase shift angle exceeds the range of the zero-voltage turn-on boundary constraint. The optimal internal phase shift angle on the full-bridge side is forcibly limited to the upper critical value of the zero-voltage turn-on boundary constraint to maintain soft-switching operation of the switching transistors. Step S5: Drive signal generation and state update The final determined DC regulation duty cycle , phase angle of the entire bridge side outward shift And the optimal inward phase angle of the entire bridge side after boundary limiting constraints. The signal is decoded into a corresponding PWM pulse signal, which drives the power switches on the half-bridge and full-bridge sides of the corresponding converter module. For example... Figure 7 As shown, under the joint control of internal and external phase shifting, the time interval between the primary and secondary voltages and currents with opposite polarities is effectively shortened, thus completing the closed-loop control of the system.

[0030] To verify the effectiveness of the battery balancing and return current optimization control method for the modular half-bridge to full-bridge converter proposed in this invention, under the set simulation parameters, the following strategies were compared and analyzed in terms of the degree of return current power optimization and the soft-switching operation characteristics of the power switches: Strategy 1: Traditional single-phase shift (SPS) control strategy.

[0031] Strategy 2: The Extended Phase Shift Control (EPS-ZVS) strategy based on collaborative optimization proposed in this invention.

[0032] like Figure 10 As shown, when under the same transmission power and non-unity voltage gain ( Under the condition of ), the comparison of return power under the two control strategies shows that: if the traditional single-phase-shift control strategy (strategy one) is used, the return power steady-state average value is high because there is only a single external phase shift angle and the return interval with opposite polarity is relatively long; while under the control strategy (strategy two) proposed in this invention, the controller calculates in real time and applies the optimal internal phase shift angle in segments. This significantly compresses the recirculation range, resulting in a substantial reduction in the steady-state average value of the recirculation power. Therefore, the strategy proposed in this invention is superior to traditional control strategies.

[0033] To further verify that the strategy proposed in this invention can guarantee wide-range soft-switching operation, simulation analysis was performed on the turn-on status of key switching transistors under the two strategies. The simulation results are as follows: Figure 11As shown, when using the optimized control strategy proposed in this invention, the drain-source voltages of the key switches on both the primary and secondary sides can drop to zero before the rising edge of the drive signal arrives. This proves that the ZVS boundary limiting constraint introduced in this invention effectively plays its role in solving the optimal inner phase shift angle, successfully maintaining the soft-switching operation of the converter under all operating conditions while minimizing the return current power.

[0034] In summary, this invention addresses a control method for a modular half-bridge to full-bridge converter. By introducing asymmetric modulation on the half-bridge side and combining it with closed-loop limiting, it achieves rapid equalization under small voltage drop conditions, effectively reducing the risk of unidirectional magnetic saturation of the transformer from a physical perspective. Subsequently, a segmented multi-degree-of-freedom internal phase-shifting mechanism combined with ZVS boundary constraints is introduced on the full-bridge side, significantly reducing return current power and conduction losses under non-unit voltage gain. Simultaneously, system-level inter-module equalization scheduling is achieved through global average voltage. Compared with traditional single-phase-shifting control, the strategy proposed in this invention exhibits superior performance in terms of equalization steady-state performance, bias suppression capability, return current power minimization, and soft-switching maintenance of power switches.

[0035] Obviously, those skilled in the art should understand that the steps of the battery balancing and return current optimization control method for the modular half-bridge to full-bridge converter in the above-described embodiments of the present invention, or the modules of the battery balancing and return current optimization control system for the modular half-bridge to full-bridge converter, can be implemented using general-purpose computing devices. They can be centralized on a single computing device or distributed across a network of multiple computing devices. Optionally, they can be implemented using computer-executable program code, thereby storing them in a storage device for execution by the computing device. In some cases, the steps shown or described can be performed in a different order than those described herein, or they can be fabricated as separate integrated circuit modules, or multiple modules or steps can be fabricated as a single integrated circuit module. Thus, the embodiments of the present invention are not limited to any particular hardware and software combination.

Claims

1. A battery balancing and return current optimization control method for a modular half-bridge to full-bridge converter, applied to a power conversion system with series input and parallel output, wherein the system comprises multiple converter modules connected in series on the high-voltage side and in parallel on the low-voltage side, characterized in that... For each converter module, the control method includes the following steps: Step S1, Parameter Acquisition: Collect the voltage of each series-connected battery cell in the current converter module, the actual DC component of the inductor current on the half-bridge side, the output voltage of the full-bridge on the low-voltage side, the actual output current on the low-voltage side, and the output power requirement, and calculate the global average voltage of the high-voltage side battery pack corresponding to all converter modules. Step S2, Intra-group equalization control: Generate a DC bias current reference value based on the voltage difference between two series-connected battery cells in the current converter module; compare the DC bias current reference value with the actual DC component of the inductor current on the half-bridge side, and generate a DC regulation duty cycle for controlling the half-bridge side switching transistors through closed-loop regulation and limiting processing. Step S3, Inter-group balancing and external phase shift control: Compare the voltage of the high-voltage side battery pack of the current converter module with the global average voltage to generate an inter-group balancing current correction; superimpose the inter-group balancing current correction with the system base current setpoint obtained based on the output power requirement to synthesize the low-voltage side output current setpoint; compare the low-voltage side output current setpoint with the actual output current of the low-voltage side to generate a closed-loop external phase shift angle on the full-bridge side, wherein the external phase shift angle on the full-bridge side is the phase difference between the primary half-bridge and the secondary full-bridge leading arm; Step S4, Return Optimization and Internal Phase Shift Control: Calculate the real-time voltage conversion ratio of the current converter module, combine it with the preset zero-voltage turn-on boundary constraint, and calculate the optimal internal phase shift angle of the full bridge side according to the different numerical ranges of the real-time voltage conversion ratio. The optimal internal phase shift angle of the full bridge side is the phase difference between the leading and lagging arms of the secondary full bridge. Step S5, drive signal generation: Based on the DC regulation duty cycle, the outward phase shift angle of the full-bridge side, and the optimal inward phase shift angle of the full-bridge side, generate corresponding control signals to drive the switching transistors on the half-bridge side and the full-bridge side of the corresponding converter module.

2. The battery balancing and return current optimization control method for the modular half-bridge to full-bridge converter according to claim 1, characterized in that, The half-bridge side switching transistors include a first switching transistor and a second switching transistor; in step S5, when generating the control signal for the half-bridge side switching transistors based on the DC-regulated duty cycle, an asymmetric modulation strategy is adopted: the on-state duty cycle of the first switching transistor is configured as follows: The duty cycle of the second switch is configured as follows: ,in The DC-regulated duty cycle is referred to here.

3. The battery balancing and return current optimization control method for the modular half-bridge to full-bridge converter according to claim 1, characterized in that, In step S4, the real-time voltage conversion ratio k The calculation formula is: in, n This refers to the turns ratio of a high-frequency transformer. This represents the average voltage of each series-connected battery cell within the current converter module. This is the output voltage of the low-voltage side full bridge.

4. The battery balancing and return current optimization control method for the modular half-bridge to full-bridge converter according to claim 1, characterized in that, In step S4, the control logic for calculating the optimal inner phase shift angle of the full bridge side in segments, based on the preset zero-voltage turn-on boundary constraint condition, is as follows: First, calculate the ideal inner phase shift angle that makes the return power zero. Then, it is determined whether the ideal inner phase shift angle meets the preset zero-voltage turn-on boundary constraint condition; when the real-time voltage conversion ratio When the ideal inner phase shift angle satisfies the zero-voltage turn-on boundary constraint condition, the ideal inner phase shift angle is directly taken as the optimal inner phase shift angle on the full-bridge side; when the real-time voltage conversion ratio When the ideal internal phase shift angle exceeds the range of the zero-voltage turn-on boundary constraint, the optimal internal phase shift angle on the full-bridge side is forcibly limited to the upper limit critical value of the zero-voltage turn-on boundary constraint to maintain the soft-switching operation of the switching transistor.

5. The battery balancing and return current optimization control method for the modular half-bridge to full-bridge converter according to claim 4, characterized in that, In step S4, the optimal inward phase angle of the entire bridge side is calculated piecewise. The specific mathematical relationship is as follows: When the real-time voltage conversion ratio hour, When the real-time voltage conversion ratio hour, in, The phase shift angle on the full-bridge side is defined as follows, and the preset zero-voltage turn-on boundary constraint is: 。 6. A battery balancing and return current optimization control system for a modular half-bridge to full-bridge converter, applied to a power conversion system with series input and parallel output, the system comprising multiple converter modules connected in series on the high-voltage side and in parallel on the low-voltage side, characterized in that... For each converter module, the control system includes: The sampling module is used to collect the voltage of each series-connected battery cell in the current converter module, the actual DC component of the inductor current on the half-bridge side, the output voltage of the full-bridge on the low-voltage side, the actual output current on the low-voltage side, and the output power demand, and to calculate the global average voltage of the high-voltage side battery pack corresponding to all converter modules. The group equalization control unit is used to generate a DC bias current reference value based on the voltage difference between two series-connected battery cells in the current converter module; compare the DC bias current reference value with the actual DC component of the inductor current on the half-bridge side, and generate a DC regulation duty cycle for controlling the switching transistors on the half-bridge side after closed-loop regulation and limiting processing. The power transfer and inter-group equalization control unit is used to compare the voltage of the high-voltage side battery pack of the current converter module with the global average voltage to generate an inter-group equalization current correction; to superimpose the inter-group equalization current correction with the system base current setpoint obtained based on the output power demand to synthesize a low-voltage side output current setpoint; and to compare the low-voltage side output current setpoint with the actual output current of the low-voltage side to generate a closed-loop outward phase shift angle on the full-bridge side, wherein the outward phase shift angle on the full-bridge side is the phase difference between the leading arm of the primary half-bridge and the leading arm of the secondary full-bridge; and to calculate the real-time voltage conversion ratio of the current converter module, and, in conjunction with a preset zero-voltage turn-on boundary constraint, to calculate the optimal inward phase shift angle on the full-bridge side in segments according to the different numerical ranges of the real-time voltage conversion ratio, wherein the optimal inward phase shift angle on the full-bridge side is the phase difference between the leading arm and the lagging arm of the secondary full-bridge. The driving unit is used to generate corresponding control signals to drive the switching transistors on the half-bridge side and the full-bridge side of the corresponding converter module based on the DC regulation duty cycle, the outward phase shift angle of the full-bridge side and the optimal inward phase shift angle of the full-bridge side.

7. A computer device, characterized in that: The computer device includes a memory, a processor, and a computer program stored in the memory and executable on the processor. When the processor executes the computer program, it implements the steps of the battery balancing and backflow optimization control method for the modular half-bridge to full-bridge converter as described in any one of claims 1-5.

8. A computer-readable storage medium having a computer program / instructions stored thereon, characterized in that: When the computer program / instructions are executed by the processor, they implement the steps of the battery balancing and backflow optimization control method for the modular half-bridge to full-bridge converter as described in any one of claims 1-5.

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