Multi-mode electric energy conversion system and method thereof

Abstract

The invention discloses a multi-mode electric energy conversion system and a method thereof, and relates to the technical field of power electronic conversion, the system comprises a signal acquisition module, a mode discrimination module, a soft switching control module and a switching execution module, the signal acquisition module acquires an input voltage, an output voltage, a load current and a switching tube temperature signal; the mode judgment module determines a target working mode according to an input voltage interval and a load rate interval, dynamic switching among a full-bridge phase shift mode, a half-bridge mode and an interleaving parallel mode is achieved, the soft switching control module generates a soft switching time sequence signal, a main power switch tube is enabled to achieve zero-voltage switching, and the main power switch tube is enabled to achieve zero-voltage switching. The switching execution module adopts a current ramp control strategy to execute mode switching, the switching time is less than 5ms, the voltage fluctuation is less than 3%, and the global efficiency is greater than 95% and the peak efficiency is greater than 98% under the conditions of wide voltage and wide load.

Description

Technical Field

[0001] This invention relates to the field of power electronic conversion technology, and in particular to a multi-mode power conversion system and method based on topology reconstruction and soft switching coordinated control. Background Technology

[0002] With the rapid development of new energy vehicles and energy storage systems, power converters face the severe challenge of optimizing efficiency under a wide voltage range input conditions. Traditional fixed topology converters, due to their single efficiency curve, struggle to achieve optimal efficiency under different operating conditions. Especially under light and heavy load conditions, fixed topology converters can often only be optimized for a specific operating condition, leading to a significant decrease in efficiency under other conditions.

[0003] Chinese invention CN118713417A discloses a power conversion control method and device. This technical solution obtains the target voltage and target current values ​​of the load through a system controller. The power conversion unit determines the optimal voltage and current output parameters of the power conversion unit based on the power supply voltage and the target voltage and target current values ​​of the load, according to the principle of minimizing power loss, and then determines the target operating mode of the switching unit. This technical solution mainly addresses the wide voltage output range requirement of charging systems, achieving a wider output voltage range through switching between series and parallel modes.

[0004] However, the aforementioned existing technology has the following technical problems: First, this technical solution only considers two operating modes: series and parallel. The mode selection strategy is relatively simple and cannot perform fine-grained efficiency optimization for intermediate load ranges. Second, this technical solution does not involve the application of soft-switching technology. The hard turn-on of the switching transistor during mode switching will generate significant switching losses, affecting conversion efficiency. Third, the mode switching strategy of this technical solution is mainly based on output voltage and current requirements, and does not fully consider the combined impact of input voltage changes and load rate changes on efficiency. In addition, this technical solution does not provide a continuous current control strategy during mode switching, which may cause output voltage fluctuations during the switching process, affecting the power supply quality to the load.

[0005] The aforementioned technical issues make it difficult for existing power conversion systems to achieve high efficiency across a wide input voltage and load range. Taking a typical application scenario with an input voltage range of 250V to 450V and a load range of 10% to 100% as an example, the light-load efficiency of traditional fixed topology converters is typically only 85% to 90%, while the peak efficiency, although reaching over 95%, can only be maintained within a relatively narrow load range. This uneven efficiency distribution severely restricts the overall energy efficiency level of new energy vehicles and energy storage systems.

[0006] Therefore, there is an urgent need for a multi-mode power conversion technology that can achieve high-efficiency operation across a wide input voltage range and a wide load range. This technology should have a refined mode discrimination strategy, soft-switching control capability, and a smooth mode switching mechanism. Summary of the Invention

[0007] To address the technical problems of existing fixed topology converters having a single efficiency curve and difficulty in achieving efficiency under both light and heavy load conditions, this invention provides a multi-mode power conversion system and method.

[0008] The multi-mode power conversion system provided by this invention includes a signal acquisition module, a mode discrimination module, a soft-switching control module, and a switching execution module. The signal acquisition module acquires input voltage signals, output voltage signals, load current signals, and switching transistor temperature signals, and performs analog-to-digital conversion on the acquired signals to generate digital acquisition data. The mode discrimination module receives the digital acquisition data and determines the target operating mode based on the voltage range of the input voltage signal and the load range of the load rate calculated based on the load current signal. The soft-switching control module generates soft-switching timing signals based on the target operating mode and the digital acquisition data to enable the main power switching transistor to achieve zero-voltage turn-on. The switching execution module, in response to the difference between the target operating mode and the current operating mode, generates a current ramp command and a main switch drive signal, controls the output current to decrease to a preset safety threshold according to a preset ramp before restoring to the target value, and controls the reconfigurable bridge arm unit to switch to the topology corresponding to the target operating mode when the output current decreases to the preset safety threshold.

[0009] Preferably, when the input voltage signal is in the high voltage range and the load rate is in the heavy load range, the target operating mode is the full-bridge phase-shift mode; when the input voltage signal is in the low voltage range or the load rate is in the light load range, the target operating mode is the half-bridge mode; and when the load rate is in the medium load range, the target operating mode is the interleaved parallel mode.

[0010] Preferably, the lower limit of the high-voltage range is a preset input voltage threshold, and the preset input voltage threshold ranges from 320V to 380V; the lower limit of the heavy-load range is a first preset load rate threshold, and the first preset load rate threshold ranges from 45% to 55%; the upper limit of the light-load range is a second preset load rate threshold, and the second preset load rate threshold ranges from 25% to 35%.

[0011] Preferably, the sum of the time for the output current to decrease and the time for it to recover under the current ramp command control does not exceed 5ms, and the output voltage fluctuation does not exceed 3%.

[0012] The present invention also provides a multi-mode power conversion method, including the steps of acquiring input voltage signal, output voltage signal, load current signal and switching transistor temperature signal and generating digital acquisition data, determining a target operating mode based on the voltage range of the input voltage signal and the load range of the load rate, generating a soft-switching timing signal based on the target operating mode and the digital acquisition data, and performing continuous current control and topology switching in response to the difference between the target operating mode and the current operating mode.

[0013] Compared with the prior art, the present invention has the following beneficial effects:

[0014] This invention achieves refined mode discrimination based on the input voltage range and load rate range by setting up a signal acquisition module, a mode discrimination module, a soft-switching control module, and a switching execution module working in synergy. It can dynamically switch between full-bridge phase-shifting mode, half-bridge mode, and interleaved parallel mode, enabling the converter to operate within its optimal efficiency range under different operating conditions. The soft-switching control module generates soft-switching timing signals and utilizes auxiliary switching transistors and a resonant network to achieve zero-voltage turn-on of the main power switching transistors, effectively reducing switching losses. The switching execution module employs a current ramp control strategy to maintain continuous output current variation during mode switching, controlling the switching transition time to within 5ms and output voltage fluctuation to within 3%. Under input voltage ranges of 250V to 450V and load ranges of 10% to 100%, this invention achieves a global efficiency greater than 95% and a peak efficiency greater than 98%, representing a 5 to 8 percentage point improvement in light-load efficiency compared to traditional single-topology converters. Attached Figure Description

[0015] Figure 1 This is a schematic diagram of the structure of the multi-mode power conversion system of the present invention.

[0016] Figure 2 This is a flowchart illustrating the multi-mode power conversion method of the present invention. Detailed Implementation

[0017] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0018] like Figure 1As shown, the multi-mode power conversion system provided by the present invention includes a signal acquisition module 1, a mode discrimination module 2, a soft-switching control module 3, a switching execution module 4, a reconfigurable bridge arm unit 5, a resonant network unit 6, an input filtering unit 7, an isolation transformer 8, a rectification unit 9, and an output filtering unit 10.

[0019] The signal acquisition module 1 is used to acquire key electrical parameters during system operation, providing a data foundation for subsequent mode discrimination and control decisions. In a preferred embodiment of the present invention, the signal acquisition module 1 includes an input voltage acquisition unit, an output voltage acquisition unit, a load current acquisition unit, and a temperature acquisition unit.

[0020] The input voltage acquisition unit is used to acquire the voltage signal at the output of the input filtering unit 7. In the application scenario of this invention, the input voltage range is 250V to 450V, which covers the typical operating voltage range of new energy vehicle power batteries and energy storage systems. The input voltage acquisition unit uses a resistor divider network to convert the high-voltage signal into a low-voltage signal suitable for processing by the analog-to-digital converter. The voltage division ratio should be selected to ensure that the voltage after voltage division does not exceed the upper limit of the input voltage of the analog-to-digital converter when the highest input voltage is 450V. Preferably, the voltage division ratio is set to 100:1, that is, a 450V input voltage corresponds to a 4.5V sampling voltage, leaving an appropriate margin to cope with transient overshoot of the input voltage.

[0021] The output voltage acquisition unit is used to acquire the voltage signal at the output terminal of the output filter unit 10. The acquisition method for the output voltage is similar to that of the input voltage, also employing a resistor divider network for voltage level conversion. The output voltage signal is used for closed-loop control and efficiency calculation, requiring high acquisition accuracy. Preferably, the acquisition accuracy of the output voltage acquisition unit is not less than 0.5% to ensure the accuracy of mode discrimination and efficiency prediction.

[0022] The load current acquisition unit is used to acquire the current signal flowing through the load. In a preferred embodiment of the invention, the load current acquisition unit employs a Hall current sensor, which has advantages such as fast response speed, good isolation performance, and high linearity. The output voltage of the Hall current sensor is proportional to the measured current, and the load current value can be accurately calculated after calibration. Preferably, the bandwidth of the Hall current sensor is not less than 100kHz to ensure accurate capture of dynamic changes in the current. The load current signal is a key input for calculating the load factor, which is defined as the ratio of the actual load current to the rated output current. This parameter is one of the important bases for mode discrimination.

[0023] The temperature acquisition unit is used to acquire the junction temperatures of the main power switch and auxiliary switch in the reconfigurable bridge arm unit 5. In a preferred embodiment of the invention, the temperature acquisition unit uses an NTC thermistor or an integrated temperature sensor chip. The temperature information is used for the correction calculation of switching losses and conduction losses in the efficiency prediction algorithm, and also serves as the basis for system protection. When the switch temperature exceeds a preset temperature protection threshold, the system automatically reduces the output power or switches to an operating mode with lower heat loss. Preferably, the temperature protection threshold is set to 120°C, corresponding to approximately 80% of the typical maximum operating junction temperature of the MOSFET or IGBT.

[0024] The signal acquisition module 1 also includes an analog-to-digital converter (ADC) unit for converting the analog signals into digital signals. In a preferred embodiment of the invention, the ADC unit uses a 12-bit high-speed ADC chip with a sampling rate of not less than 1 MSPS. The converted data is organized in vector form to form digitized acquisition data, which is then sent to the mode discrimination module 2. The digitized acquisition data includes four components: digital input voltage, digital output voltage, digital load current, and digital switching transistor temperature. Each component is a 12-bit unsigned integer.

[0025] The mode discrimination module 2 receives the digital acquisition data output by the signal acquisition module 1 and determines the target operating mode based on the voltage range of the input voltage signal and the load range of the load rate. The mode discrimination module 2 is the core module for achieving high-efficiency multi-mode operation in this invention, and its discrimination strategy directly determines the system's efficiency performance under different operating conditions.

[0026] In a preferred embodiment of the present invention, the discrimination logic of the mode discrimination module 2 is as follows: First, the mode discrimination module 2 calculates the load rate based on the digital value of the load current in the digitally acquired data. The load rate is equal to the actual load current divided by the rated output current. Second, the mode discrimination module 2 compares the input voltage signal with a preset input voltage threshold, dividing the input voltage into a high-voltage range and a low-voltage range. When the input voltage is greater than or equal to the preset input voltage threshold, the input voltage is in the high-voltage range; when the input voltage is less than the preset input voltage threshold, the input voltage is in the low-voltage range. Preferably, the preset input voltage threshold is set to 350V, which is near the midpoint of the input voltage range of 250V to 450V, and can effectively distinguish between high-voltage and low-voltage operating conditions. In other embodiments of the present invention, the preset input voltage threshold can also be set to other values ​​within the range of 320V to 380V, and the specific value can be optimized according to the distribution characteristics of the input voltage in the actual application scenario.

[0027] The mode discrimination module 2 divides the load rate into three ranges: light load, medium load, and heavy load. The upper limit of the light load range is a second preset load rate threshold, preferably set to 30%. The lower limit of the heavy load range is a first preset load rate threshold, preferably set to 50%. The medium load range lies between the light and heavy load ranges, i.e., the load rate is between 30% and 50%. The selection of the above load rate thresholds is based on the efficiency characteristic curves of different operating modes under different load rates. The full-bridge phase-shifting mode has the highest efficiency under heavy load conditions because it can fully utilize the transformer leakage inductance to achieve zero-voltage turn-on, and the circulating current loss is relatively low. The half-bridge mode has the highest efficiency under light load conditions because switching losses and circulating current losses are the main sources of loss under light load conditions, and the half-bridge mode effectively reduces these two types of losses by halving the number of switching transistors. The interleaved parallel mode has the highest efficiency under medium load conditions because the interleaving of the two phases can reduce input and output ripple and balance the thermal stress between the two phases.

[0028] Based on the above interval division, the pattern discrimination decision algorithm of pattern discrimination module 2 can be expressed as:

[0029] ,

[0030] in, For the target working mode; It is a full-bridge phase-shifting mode; It is a half-bridge mode; It is an interleaved parallel mode; The input voltage signal; The preset input voltage threshold ranges from 320V to 380V. Load rate; The first preset load rate threshold ranges from 45% to 55%. The second preset load rate threshold ranges from 25% to 35%.

[0031] In a preferred embodiment of the present invention, the mode discrimination module 2 further includes an efficiency prediction unit. The efficiency prediction unit calculates predicted efficiency values ​​for the full-bridge phase-shift mode, half-bridge mode, and interleaved parallel mode based on the input voltage signal, load rate, and switching transistor temperature signal, respectively, before determining the target operating mode. The efficiency prediction unit calculates the total loss of each mode under the current operating condition based on the loss model of each mode, thereby obtaining the predicted efficiency value. The efficiency prediction unit determines the mode with the highest predicted efficiency value as a candidate operating mode and compares it with the target operating mode determined based on interval division. When the candidate operating mode matches the target operating mode, the mode discrimination module 2 directly outputs the target operating mode. When the candidate operating mode does not match the target operating mode, the mode discrimination module 2 compares the difference between their predicted efficiency values. If the difference in predicted efficiency values ​​is greater than a preset efficiency threshold, the candidate operating mode is used as the final output target operating mode; otherwise, the target operating mode determined based on interval division is still output. Preferably, the preset efficiency threshold is set to 2%, meaning that the result of interval division is only overridden when the mode selected based on efficiency prediction is more than 2 percentage points more efficient than the mode selected based on interval division.

[0032] The prediction efficiency of each mode in the efficiency prediction unit is calculated as follows:

[0033] ,

[0034] in, For the first The predictive efficiency of this model; Output power is equal to the product of output voltage and load current; For the first Switching losses in this mode; For the first Conduction loss in this mode; For the first Core loss in various modes; For the first Copper loss in windings of various modes; subscript Take respectively (Full-bridge phase-shifting mode) (Half-bridge mode) and (Interleaved parallel mode).

[0035] The soft-switching control module 3 generates a soft-switching timing signal based on the target operating mode output by the mode discrimination module 2 and the digital acquisition data output by the signal acquisition module 1. This soft-switching timing signal controls the on / off state of the auxiliary switching transistors in the reconfigurable bridge arm unit 5, enabling the main power switching transistors to achieve zero-voltage turn-on. The soft-switching control module 3 is a key module in this invention for reducing switching losses and improving conversion efficiency.

[0036] In a preferred embodiment of the present invention, the soft-switching control module 3 includes a phase shift angle calculation unit, a dead time calculation unit, and a timing generation unit.

[0037] The phase shift angle calculation unit is used to calculate the phase shift angle of the primary arm in full-bridge phase-shift mode. Full-bridge phase-shift mode utilizes the transformer leakage inductance as a resonant element, adjusting the output power by controlling the phase shift angle between the two primary arms. A larger phase shift angle results in a longer zero-crossing time for the primary current, which is more conducive to achieving zero-voltage turn-on; however, an excessively large phase shift angle leads to a decrease in transmission power and an increase in circulating current loss. Therefore, the phase shift angle needs to be adaptively adjusted according to the load rate. In a preferred embodiment of the invention, the phase shift angle is calculated as follows:

[0038] ,

[0039] in, It is the phase shift angle; The preset maximum phase shift angle ranges from 30° to 45°, and is preferably set to 40°. This is the phase shift angle adjustment coefficient, with a value ranging from 0.2 to 0.5, preferably set to 0.35; Let be the load factor. According to the formula above, when the load factor is 50%, the phase shift angle is approximately 22.5°; when the load factor is 100%, the phase shift angle is approximately 5°. A larger phase shift angle corresponds to a lower load factor, in which case the primary-side current is smaller, requiring a longer zero-crossing time to achieve zero-voltage turn-on; a smaller phase shift angle corresponds to a higher load factor, in which case the primary-side current is larger, and a shorter zero-crossing time is sufficient to achieve zero-voltage turn-on. Simultaneously, a smaller phase shift angle helps reduce circulating current losses.

[0040] The dead time calculation unit is used to calculate the dead time of the main power switch. Dead time refers to the time during which two switches on the same bridge arm are simultaneously off during switching, and its function is to prevent shoot-through short circuits in the bridge arm. In soft-switching converters, the dead time setting also needs to ensure that the parasitic capacitance has been discharged through the auxiliary resonant circuit before the main switch is turned on, thereby achieving zero-voltage turn-on. In a preferred embodiment of the present invention, the dead time is calculated as follows:

[0041] ,

[0042] in, Dead time; This is the resonant inductance value. In full-bridge phase-shift mode, it is the leakage inductance of the isolation transformer. In half-bridge mode and interleaved parallel mode, it is the sum of the external resonant inductance and the transformer leakage inductance. The output capacitor of the main power switching transistor; For a safety margin, it is preferably set to 50ns to 100ns. The physical meaning of the above formula is that the dead time should be greater than or equal to half of the resonant half-cycle plus the safety margin to ensure that the parasitic capacitance of the switching transistor completes resonant discharge within the dead time.

[0043] The timing generation unit generates the turn-on timing of the auxiliary switches and the drive timing of the main switches based on the phase shift angle and dead time. In a preferred embodiment of the invention, the timing generation unit is implemented using a digital signal processor or a field-programmable gate array (FPGA) to generate precise PWM waveforms through a high-resolution timer. The soft-switching timing signals output by the timing generation unit include four main switch drive signals and four auxiliary switch drive signals. In full-bridge phase-shift mode, there is a time difference corresponding to the phase shift angle between the drive signals of the two primary arms; the dead times of the leading and lagging arms can be set separately to adapt to different soft-switching conditions.

[0044] The soft-switching control module 3 employs different control strategies in different operating modes. In full-bridge phase-shift mode, resonance is achieved using the transformer leakage inductance and the output capacitance of the switching transistors, allowing all four primary-side main switches to achieve zero-voltage turn-on. The auxiliary switches are primarily used to extend the soft-switching range. In half-bridge mode, only two main switches operate. The soft-switching control module 3 controls the turn-on timing of the auxiliary switches to establish a resonant current before the main switches turn on, creating conditions for the parasitic capacitance of the main switches to discharge. In interleaved parallel mode, the two phases are controlled independently. The soft-switching strategy for each phase is similar to that in half-bridge mode, but there is a 180° phase difference between the two phases to achieve mutual cancellation of input and output ripple.

[0045] The switching execution module 4 is used to perform a mode switching operation when the target operating mode output by the mode discrimination module 2 is different from the current operating mode. The switching execution module 4 adopts a continuous current control strategy to ensure that the output voltage fluctuation is minimized during the mode switching process, and is the key module for achieving smooth mode switching in this invention.

[0046] In a preferred embodiment of the present invention, the switching execution module 4 includes a switching judgment unit, a current ramp generation unit, and a topology control unit.

[0047] The switching judgment unit compares the target operating mode with the current operating mode. When the target operating mode matches the current operating mode, the switching judgment unit does not generate a switching trigger signal, and the system maintains operation in the current operating mode. When the target operating mode does not match the current operating mode, the switching judgment unit generates a switching trigger signal and initiates the mode switching process. To avoid frequent mode switching due to small fluctuations in load or input voltage, the switching judgment unit is also equipped with a hysteresis range and a minimum hold time. Preferably, the hysteresis bandwidth of the load rate threshold is set to 5% of the threshold, and the minimum hold time is set to 1 second, meaning that if the operating time in a certain mode is less than 1 second, the system will not switch immediately even if the switching conditions are met.

[0048] The current ramp generation unit generates a current ramp command when the switching trigger signal is valid. The current ramp command controls the output current to decrease to a preset safety threshold before recovering to the target value. In a preferred embodiment of the invention, the current ramp control algorithm is as follows:

[0049] ,

[0050] in, for Reference current value at any given time; To switch the output current value at the start time; The preset slope ranges from 5 A / ms to 20 A / ms, and is preferably set to 10 A / ms; To preset the safety threshold, it is set to 5% to 15% of the rated output current, preferably 10% of the rated output current; The moment when the current drops to a safe threshold; The time when the topology switch is completed; This is the moment when the current recovers to the target value; The target output current value.

[0051] The physical meaning of the aforementioned current ramp control is as follows: During mode switching, the output current is first reduced from its current value to a safe threshold at a preset ramp rate. This process minimizes stored energy while avoiding voltage overshoot caused by sudden current changes. Once the current reaches the safe threshold, the topology control unit performs a topology switching operation, switching the reconfigurable bridge arm unit 5 from the topology corresponding to the current mode to the topology corresponding to the target mode. After the topology switching is complete, the output current is restored from the safe threshold to the target value at the same ramp rate. Using a symmetrical ramp rate for reduction and restoration helps simplify the control logic and ensures the smoothness of the switching process.

[0052] The topology control unit is used to control the on / off state of the switching transistors in the reconfigurable bridge arm unit 5 to achieve switching between different topologies. In a preferred embodiment of the present invention, the switching logic of the topology control unit is as follows: When switching from full-bridge phase-shift mode to half-bridge mode, the third and fourth main power switches are first turned off, and then the third auxiliary switch is turned on, so that the third and fourth main power switches are short-circuited, and the circuit is equivalent to a half-bridge structure. When switching from half-bridge mode to full-bridge phase-shift mode, the opposite operation is performed. When switching from full-bridge phase-shift mode or half-bridge mode to interleaved parallel mode, the reconfigurable bridge arm unit 5 is configured as a two-phase parallel structure, and the phase difference of the drive signals between the two phases is 180°.

[0053] The switching execution module 4 also includes a switching completion judgment function. When the current recovers to the target value and the output voltage stabilizes within the preset range of the target value, the mode switching is judged to be complete, and the current working mode flag is updated. Preferably, the stable output voltage range is set to ±1% of the target value.

[0054] In a preferred embodiment of the present invention, the sum of the time for the output current to decrease and the recovery time is controlled by the current ramp command to not exceed 5 ms, and the output voltage fluctuation is not more than 3%. Achieving this target depends on a reasonable ramp setting and precise timing control. Taking a rated output current of 100A, a preset ramp of 10A / ms, and a preset safety threshold of 10A as an example, it takes 9 ms for the current to decrease from 100A to 10A, and the recovery process also takes approximately 9 ms, for a total switching time of approximately 18 ms. To control the switching time within 5 ms, the preset ramp needs to be increased to approximately 36A / ms, or the preset safety threshold needs to be increased to approximately 25A. In practical applications, a trade-off optimization can be made between switching time and voltage fluctuation based on the load's tolerance to voltage fluctuations and the system's current change rate limit.

[0055] The reconfigurable bridge arm unit 5 is the core hardware structure for realizing multi-mode operation in this invention. By combining the on and off states of the auxiliary switching transistors, it can dynamically switch between full-bridge mode, half-bridge mode and interleaved parallel mode.

[0056] In a preferred embodiment of the present invention, the reconfigurable bridge arm unit 5 includes a first main power switch Q1, a second main power switch Q2, a third main power switch Q3, a fourth main power switch Q4, a first auxiliary switch S1, a second auxiliary switch S2, a third auxiliary switch S3, and a fourth auxiliary switch S4. The first main power switch Q1 and the second main power switch Q2 are connected in series to form the first bridge arm, and the third main power switch Q3 and the fourth main power switch Q4 are connected in series to form the second bridge arm. The first auxiliary switch S1 is connected in series with the first resonant inductor Lr1 and then in parallel with the first main power switch Q1. The second auxiliary switch S2 is connected in series with the second resonant inductor Lr2 and then in parallel with the second main power switch Q2. The third auxiliary switch S3 is connected in parallel with the third main power switch Q3, and the fourth auxiliary switch S4 is connected in parallel with the fourth main power switch Q4.

[0057] In a preferred embodiment of the present invention, the main power switch is a silicon carbide (SiC) MOSFET device, which has fast switching speed, low on-resistance, and good high-temperature resistance, making it particularly suitable for high-frequency, high-efficiency power conversion applications. Preferably, the rated voltage of the main power switch is 650V, the rated current is 60A, and the on-resistance does not exceed 40mΩ. The auxiliary switch can be a silicon (Si) MOSFET device, because it only conducts briefly during soft-switching transitions, and its switching characteristics requirements are relatively low. Preferably, the rated voltage of the auxiliary switch is the same as that of the main power switch, and the rated current is one-third to one-half of that of the main power switch.

[0058] The resonant network unit 6, composed of a resonant inductor and a resonant capacitor, works in conjunction with the reconfigurable bridge arm unit 5 to achieve soft-switching functionality. In a preferred embodiment of the invention, the inductance values ​​of the first resonant inductor Lr1 and the second resonant inductor Lr2 are equal, ranging from 5μH to 20μH, preferably set to 10μH. The resonant capacitor Cr is connected in series with the resonant inductor to form a resonant circuit, and its capacitance value is determined according to the required resonant frequency. The resonant frequency setting should ensure that the parasitic capacitance of the switching transistor is discharged within the dead time, while avoiding electromagnetic interference problems caused by excessively high resonant frequencies. Preferably, the capacitance value of the resonant capacitor ranges from 10nF to 100nF.

[0059] The input terminal of the input filter unit 7 is connected to a DC input power supply, and its output terminal is connected to the input terminal of the reconfigurable bridge arm unit 5. The input filter unit 7 is used to filter out high-frequency ripple and electromagnetic interference at the input terminal, while providing a stable DC bus voltage for the reconfigurable bridge arm unit 5. In a preferred embodiment of the invention, the input filter unit 7 includes an input filter inductor and an input filter capacitor. The inductance value of the input filter inductor ranges from 100μH to 500μH, and the capacitance value of the input filter capacitor ranges from 200μF to 1000μF.

[0060] The output of the reconfigurable bridge arm unit 5 is connected to the primary winding of the isolation transformer 8 via the resonant network unit 6. The isolation transformer 8 is used to achieve electrical isolation between the input and output and voltage transformation. In a preferred embodiment of the invention, the isolation transformer 8 uses a high-frequency ferrite core with an operating frequency range of 50kHz to 200kHz, preferably set to 100kHz. The turns ratio of the isolation transformer 8 is determined based on the input voltage range and the output voltage range. Furthermore, the leakage inductance of the isolation transformer 8 participates in the soft-switching process as a resonant element in the full-bridge phase-shifting mode, and its leakage inductance value needs to be designed to balance the soft-switching range and power transmission capability. Preferably, the leakage inductance value ranges from 10μH to 30μH.

[0061] The secondary winding of the isolation transformer 8 is connected to the input terminal of the rectifier unit 9. In a preferred embodiment of the present invention, the rectifier unit 9 is a synchronous rectifier unit, using MOSFET devices instead of traditional diodes for rectification. Synchronous rectification can significantly reduce rectification losses and improve conversion efficiency, especially in applications with low output voltage and high output current. The synchronous rectifier switch in the synchronous rectifier unit achieves zero-voltage turn-on synchronously with the main power switch, further reducing switching losses.

[0062] The output terminal of rectifier unit 9 is connected to the input terminal of output filter unit 10, and the output terminal of output filter unit 10 is connected to the load. Output filter unit 10 is used to filter out high-frequency ripple after rectification, providing a stable DC voltage to the load. In a preferred embodiment of the present invention, output filter unit 10 includes an output filter inductor and an output filter capacitor. The inductance value of the output filter inductor ranges from 50μH to 200μH, and the capacitance value of the output filter capacitor ranges from 100μF to 500μF. The inductance value of the output filter inductor should be selected to ensure that the converter operates in continuous conduction mode across the entire load range, while the current ripple rate is controlled within an acceptable range. Preferably, the current ripple rate does not exceed 20% of the output current.

[0063] In the multi-mode power conversion system of this invention, during operation, the signal acquisition module 1 continuously acquires input voltage, output voltage, load current, and switching transistor temperature signals, and sends the acquired data to the mode discrimination module 2. The mode discrimination module 2, based on the range of the input voltage and the range of the load rate, and combined with an efficiency prediction algorithm, determines the optimal operating mode under the current conditions and outputs it as the target operating mode. The soft-switching control module 3, based on the target operating mode and current operating parameters, calculates control parameters such as phase shift angle and dead time, and generates soft-switching timing signals to control the turn-on and turn-off timing of the auxiliary and main switching transistors. When the target operating mode differs from the current operating mode, the switching execution module 4 initiates the mode switching process, first reducing the output current to a safe threshold according to the current ramp control strategy, then controlling the reconfigurable bridge arm unit 5 to switch to the target topology, and finally restoring the output current to the target value.

[0064] Through the coordinated operation of the aforementioned modules, the multi-mode power conversion system of this invention can dynamically select the optimal operating mode based on real-time operating conditions under a wide input voltage range of 250V to 450V and a wide load range of 10% to 100%, achieving high-efficiency operation with an overall efficiency greater than 95% and a peak efficiency greater than 98%. Compared to traditional single-topology converters, the efficiency improvement of this invention under light load conditions is particularly significant, reaching 5 to 8 percentage points.

[0065] like Figure 2 As shown, the present invention also provides a multi-mode power conversion method, which is applied to the above-mentioned multi-mode power conversion system and includes the following steps.

[0066] Step S1: Signal acquisition and analog-to-digital conversion.

[0067] The system acquires input voltage signals, output voltage signals, load current signals, and switching transistor temperature signals, and performs analog-to-digital conversion on the acquired signals to generate digital acquisition data. This step is performed by signal acquisition module 1, and its specific implementation has been described in detail in the system embodiment.

[0068] Step S2: Pattern discrimination and target pattern determination.

[0069] The target operating mode is determined based on the voltage range of the input voltage signal and the load range of the load rate calculated from the load current signal. This step is performed by the mode discrimination module 2. Specifically, when the input voltage signal is in the high-voltage range and the load rate is in the heavy-load range, the target operating mode is determined to be the full-bridge phase-shift mode; when the input voltage signal is in the low-voltage range or the load rate is in the light-load range, the target operating mode is determined to be the half-bridge mode; and when the load rate is in the medium-load range, the target operating mode is determined to be the interleaved parallel mode. The specific algorithm and parameter settings for mode discrimination have been described in detail in the system embodiment.

[0070] Step S3: Generating soft-switching timing signals.

[0071] Based on the target operating mode and digitally acquired data, a soft-switching timing signal is generated to enable the main power switches in the reconfigurable bridge arm unit to achieve zero-voltage turn-on. This step is executed by the soft-switching control module 3. In full-bridge phase-shift mode, the phase shift angle is calculated based on the load rate, and the dead time is calculated based on the phase shift angle and the leakage inductance value of the isolation transformer. The turn-on timing of the auxiliary switches is generated based on the dead time. In half-bridge mode and interleaved parallel mode, corresponding soft-switching control strategies are adopted. The specific generation method of the soft-switching timing signal has been described in detail in the system embodiment.

[0072] Step S4: Mode switching execution.

[0073] In response to a difference between the target operating mode and the current operating mode, the control output current is first reduced to a preset safety threshold according to a preset slope. When the output current drops to the preset safety threshold, the reconfigurable bridge arm unit is controlled to switch to the topology corresponding to the target operating mode. Then, the control output current is restored to the target value according to a preset slope. This step is executed by the switching execution module 4. The specific algorithm and parameter settings for current ramp control have been described in detail in the system embodiment.

[0074] The above steps S1 to S4 are executed cyclically to achieve continuous operation and dynamic mode switching of the multi-mode power conversion system.

[0075] To verify the effectiveness of the technical solution of this invention, a prototype multi-mode power conversion system with a rated power of 10kW was built for experimental testing. The main parameters of the prototype are as follows: input voltage range 250V to 450V, output voltage 48V, rated output current 200A, and switching frequency 100kHz. The prototype uses SiC MOSFETs as the main power switching transistors, Si MOSFETs as auxiliary switching transistors, and a high-frequency ferrite core for the isolation transformer.

[0076] Experimental results show that, under an input voltage of 350V and a load rate of 100%, the system operates in full-bridge phase-shift mode with a peak efficiency of 98.2%. Under an input voltage of 300V and a load rate of 20%, the system operates in half-bridge mode with an efficiency of 95.5%, representing a 6.2 percentage point improvement over the traditional full-bridge topology under the same conditions. Under an input voltage of 350V and a load rate of 40%, the system operates in interleaved parallel mode with an efficiency of 96.8%. Within a wide input voltage range of 250V to 450V and a wide load range of 10% to 100%, the system's overall efficiency is greater than 95%. Mode switching tests show a switching transition time of 4.5ms and an output voltage fluctuation of 2.1%, both better than the design specifications.

[0077] The embodiments of the present invention are not limited to the specific embodiments described above. Those skilled in the art can make various equivalent changes or substitutions based on the technical solutions of the present invention, and all such changes or substitutions should be included within the protection scope of the present invention.

Claims

1. A multi-mode power conversion system, characterized by, The application relates to a reconfigurable bridge arm control method and device. The application relates to a reconfigurable bridge arm control method and device. The application relates to a reconfigurable bridge arm control method and device. The application relates to a reconfigurable bridge arm control method and device. The application relates to a reconfigurable bridge arm control method and device.

2. The multi-mode electric energy conversion system of claim 1, wherein, The application relates to a reconfigurable bridge arm control method and device.

3. The multi-mode electric energy conversion system of claim 1, wherein, The application relates to a reconfigurable bridge arm control method and device.

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The multi-mode electric energy conversion system of claim 1, wherein, The soft-switching control module generates soft-switching timing signals according to the target operating mode, including: when the target operating mode is a full-bridge phase-shifting mode, calculating the phase-shifting angle based on the load rate, calculating the dead time based on the phase-shifting angle and the leakage inductance value of the isolation transformer, and generating the turn-on timing of the auxiliary switching transistor based on the dead time; wherein, the phase-shifting angle decreases as the load rate increases.

6. The multi-mode electric energy conversion system of claim 5, wherein, The phase shift angle is calculated as follows: based on the preset maximum phase shift angle, subtract the product of the load rate and the phase shift angle adjustment coefficient; the preset maximum phase shift angle ranges from 30° to 45°; the phase shift angle adjustment coefficient ranges from 0.2 to 0.

5.

7. The multi-mode electric energy transformation system of claim 1, wherein, Before determining the target operating mode, the mode discrimination module calculates the predicted efficiency values ​​for the full-bridge phase-shift mode, half-bridge mode, and interleaved parallel mode based on the input voltage signal, the load rate, and the switching transistor temperature signal, respectively, and determines the mode with the highest predicted efficiency value as the candidate operating mode. When the candidate operating mode is consistent with the target operating mode determined based on the voltage range and load range, the target operating mode is directly output. When the candidate operating mode is inconsistent with the target operating mode and the difference between the predicted efficiency value of the candidate operating mode and the predicted efficiency value of the target operating mode is greater than a preset efficiency threshold, the candidate operating mode is taken as the final output target operating mode.

8. The multi-mode electric energy transformation system of claim 3, wherein, It also includes an input filter unit, an isolation transformer, a rectifier unit, and an output filter unit; the input terminal of the input filter unit is connected to a DC input power supply, and the output terminal of the input filter unit is connected to the input terminal of the reconfigurable bridge arm unit; the output terminal of the reconfigurable bridge arm unit is connected to the primary winding of the isolation transformer through the resonant network unit; the secondary winding of the isolation transformer is connected to the input terminal of the rectifier unit; the output terminal of the rectifier unit is connected to the input terminal of the output filter unit; and the output terminal of the output filter unit is connected to the load.

9. The multi-mode electric energy transformation system of claim 8, wherein, The rectifier unit is a synchronous rectifier unit, in which the synchronous rectifier switch and the main power switch are turned on at zero voltage simultaneously; the output filter unit includes an output filter inductor and an output filter capacitor, the inductance value of the output filter inductor is in the range of 50μH to 200μH, and the capacitance value of the output filter capacitor is in the range of 100μF to 500μF.

10. A multi-mode power conversion method, using the multi-mode power conversion system of any one of claims 1-9, characterized in that, include: It acquires input voltage signals, output voltage signals, load current signals, and switching transistor temperature signals, and performs analog-to-digital conversion on the acquired signals to generate digital acquisition data; Based on the voltage range of the input voltage signal and the load range of the load rate calculated based on the load current signal, a target operating mode is determined; wherein, when the input voltage signal is in the high voltage range and the load rate is in the heavy load range, the target operating mode is determined to be a full-bridge phase-shift mode; when the input voltage signal is in the low voltage range or the load rate is in the light load range, the target operating mode is determined to be a half-bridge mode; when the load rate is in the medium load range, the target operating mode is determined to be an interleaved parallel mode. Based on the target operating mode and the digitally acquired data, a soft-switching timing signal is generated to enable the main power switch in the reconfigurable bridge arm unit to achieve zero-voltage turn-on. In response to the difference between the target operating mode and the current operating mode, the output current is controlled to decrease to a preset safety threshold according to a preset slope. When the output current decreases to the preset safety threshold, the reconfigurable bridge arm unit is controlled to switch to the topology corresponding to the target operating mode. Then, the output current is controlled to recover to the target value according to the preset slope.

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