Control method of bidirectional two-stage boost circuit of high-power energy storage power supply

Abstract

The application discloses a bidirectional two-stage voltage-boosting circuit control method of a high-power energy storage power supply, relates to the technical field of power electronic conversion, and comprises the following steps: input voltage, output voltage, LLC resonant current, Buck-Boos inductance current and battery terminal voltage of the bidirectional two-stage voltage-boosting circuit are collected in real time, circuit real-time parameters are obtained, and working state judgment is carried out; if in the charging and discharging state, voltage regulation and energy transmission are carried out based on the LLC resonant converter and the bidirectional Buck-Boost converter; if in the soft start state, the segmented soft start control is adopted under energy forward transmission and energy reverse transmission; the application is used for solving the problem that the existing power electronic conversion technology cannot realize the collaborative control of two converters when converting the voltage of the energy storage power supply needing bidirectional energy transmission, retaining the high-efficiency advantage of LLC soft switching, widening the voltage regulation range with the aid of Buck-Boost, reducing the voltage impact problem of power flow switching, and improving the stability of control.

Description

Technical Field

[0001] This invention relates to the field of power electronic conversion technology, specifically to a bidirectional two-stage boost circuit control method for high-power energy storage power supplies. Background Technology

[0002] Power electronic conversion technology is a technology that uses power electronic devices as its core to transform and control the voltage, current, frequency, phase, number of phases, and power flow direction of electrical energy, thereby achieving efficient, accurate, and flexible transmission and utilization of electrical energy.

[0003] Existing power electronic conversion technologies typically use bidirectional LLC resonant converters or Buck-Boost converters when converting the voltage of energy storage power supplies requiring bidirectional energy transfer. Bidirectional LLC resonant converters, with their soft-switching characteristics, offer advantages such as low switching losses and high efficiency; however, they suffer from problems such as a narrow output voltage regulation range, susceptibility to runaway under light loads, and large starting current spikes. Voltage regulation in bidirectional LLC resonant converters relies entirely on frequency modulation control, and their voltage gain can only be effectively adjusted within a limited range near the resonant frequency. When the switching frequency is below the resonant frequency, the circuit enters the capacitive operating region, and the switching transistor loses its zero-voltage turn-on condition, becoming a hard switch. This not only drastically increases losses but also generates extremely large voltage and current spikes, potentially damaging the device. When the load current is too low, the LLC resonant converter enters an intermittent conduction mode, where even a small change in the switching frequency can cause significant voltage drops. This leads to drastic fluctuations in output voltage, which traditional PI regulation cannot effectively track, easily resulting in output voltage overshoot or undershoot, and even system oscillation. While Buck-Boost converters can achieve a wide range of voltage rise and fall, their high losses in hard-switching mode make it difficult to balance efficiency and regulation range when used alone. Bidirectional Buck-Boost converters employ hard-switching, with the switching transistor turning on when the voltage is not zero and turning off when the current is not zero, thus enduring extremely high voltage and current stress and generating significant switching losses. Therefore, existing power electronic conversion technologies cannot effectively control energy storage power supplies requiring bidirectional energy transfer by combining two types of converters to retain the high efficiency of LL soft-switching while leveraging Buck-Boost to widen the voltage regulation range, reduce voltage surges during power flow switching, and improve control stability. Summary of the Invention

[0004] This invention aims to at least partially solve one of the technical problems in the prior art. By real-time acquisition of the input voltage, output voltage, LLC resonant current, Buck-Boost inductor current, and battery terminal voltage of the bidirectional two-stage boost circuit, real-time circuit parameters are obtained, and the operating status is determined. If it is in the charging / discharging state, voltage regulation and energy transfer are performed based on the LLC resonant converter and the bidirectional Buck-Boost converter. If it is in the soft-start state, segmented soft-start control is adopted for both forward and reverse energy transfer. This solves the problem that existing power electronic conversion technology cannot coordinate the control of two converters when converting the voltage of energy storage power sources that require bidirectional energy transfer. It retains the high efficiency advantage of LLC soft switching while expanding the voltage regulation range with the help of Buck-Boost, reducing the voltage surge problem during power flow switching, and improving control stability.

[0005] To achieve the above objectives, this application provides a bidirectional two-stage boost circuit control method for a high-power energy storage power supply, comprising the following steps: The input voltage, output voltage, LLC resonant current, Buck-Boos inductor current, and battery terminal voltage of the bidirectional two-stage boost circuit are collected in real time to obtain the circuit's real-time parameters and determine its operating status. If in a charging / discharging state, voltage regulation and energy transfer are performed based on LLC resonant converter and bidirectional Buck-Boost converter; If in soft-start mode, segmented soft-start control is used for both forward and reverse energy transmission.

[0006] Furthermore, the input voltage, output voltage, LLC resonant current Ir, Buck-Boos inductor current, and battery terminal voltage of the bidirectional two-stage boost circuit are collected in real time to obtain the circuit's real-time parameters. The operating status is then determined through the following sub-steps: The bidirectional two-stage boost circuit is referred to as the working circuit, which includes a bidirectional LLC resonant converter and a bidirectional Buck-Boost converter; the bidirectional LLC resonant converter includes a primary-side full bridge, an LLC resonant cavity, a high-frequency transformer, and a secondary-side full bridge; The primary-side full bridge consists of four switches, Q11, Q12, Q21, and Q22, in series, Q11 and Q21 are connected in series, Q12 and Q22 are connected in parallel, and Q21 and Q22 are connected in parallel. The secondary-side full bridge consists of four switches, Q1, Q2, Q3, and Q4, in series, Q1 and Q3 are connected in series, Q2 and Q4 are connected in parallel, and Q3 and Q4 are connected in parallel. The bidirectional LLC resonant converter is connected in series between the high-voltage DC bus and the bidirectional Buck-Boost converter, and the bidirectional Buck-Boost converter is connected in series between the secondary full-bridge and the battery pack; the battery pack connected to the working circuit is denoted as the energy storage battery.

[0007] Further, the input voltage, output voltage in real time, LLC resonant current Ir, Buck-Boos inductor current, and battery terminal voltage of the bidirectional two-stage boost circuit are collected in real time to obtain the real-time parameters of the circuit, and the judgment of the working state further includes the following sub-steps: The input voltage Vin, output voltage Vout, LLC resonant current, Buck-Boost inductor current, and battery terminal voltage of the working circuit are collected synchronously in real time, which are denoted as the real-time parameters of the working circuit; the LLC resonant current, Buck-Boos inductor current, and battery terminal voltage are denoted as the resonant current Ir, inductor current Ib, and battery voltage Vbat in sequence. Judge whether the system where the normally operating working circuit is located is in soft start. If it is in soft start, it is judged that the working circuit is in the soft start state; otherwise, it is judged that the working circuit is in the charge and discharge state.

[0008] Further, if it is in the charge and discharge state, the voltage regulation and energy transfer based on the LLC resonant converter and the bidirectional Buck-Boost converter include the following sub-steps: For the working circuit in the charge and discharge state, if the energy flows from the high-voltage DC bus to the energy storage battery, it is judged that the working circuit is in the charging state; if the energy flows from the energy storage battery to the high-voltage DC bus, it is judged that the working circuit is in the discharging state; obtain the transformer turns ratio of the high-frequency transformer, denoted as n1. If the working circuit is in the charging state, judge whether the working circuit is in the buck mode or the boost mode according to the current Vin, Vout, and Vbat, and calculate the target duty cycle D1 of the bidirectional Buck-Boost converter. If Vin / n1 ≥ Vbat, it is judged to be in the buck mode, then D1 = Vbat × n1 / Vin; if Vin / n1 < Vbat, it is judged to be in the boost mode, then D1 = (Vbat - Vin / n1) / Vbat.

[0009] Further, if it is in the charge and discharge state, the voltage regulation and energy transfer based on the LLC resonant converter and the bidirectional Buck-Boost converter include the following sub-steps: Obtain the charging power of the energy storage battery, denoted as the load power FP, and adjust the switching frequency LF of the bidirectional LLC resonant converter according to the load power FP to make the bidirectional LLC resonant converter operate in the soft-switching state. Obtain the target voltage Vref1 corresponding to the energy storage battery. Based on closed-loop PI regulation, dynamically correct the target duty cycle D1 according to the difference between the real-time collected Vout and the target voltage Vref1, and limit the change rate of the inductor current Ib to no more than 5 A / μs; Set Q1 and Q4 of the secondary full-bridge to conduct synchronously, and Q2 and Q3 to conduct synchronously, and set the corresponding conduction time to lag the zero-crossing time of Ir by 50 ns to 200 ns, and the corresponding turn-off time to lead the zero-crossing time of Ir by 50 ns to 200 ns.

[0010] Further, if in the charge-discharge state, the voltage regulation and energy transfer based on the LLC resonant converter and the bidirectional Buck-Boost converter further include the following sub-steps: If the working circuit is in the discharge state; obtain the normal input voltage of the high-voltage DC bus, denoted as V0out, and judge whether the working circuit is in the step-down inversion mode or the boost inversion mode according to Vbat at this time, and calculate the target duty cycle D2 of the bidirectional Buck-Boost converter; If Vbat < V0out / n1, it is judged to be in the boost inversion mode, then D2 = 1 - Vbat×n1 / V0out; if Vbat ≥ V0out / n1, it is judged to be in the step-down inversion mode, then D2 = V0out / Vbat×n1.

[0011] Further, if in the charge-discharge state, the voltage regulation and energy transfer based on the LLC resonant converter and the bidirectional Buck-Boost converter further include the following sub-steps: Obtain the target voltage Vref2 corresponding to the energy storage battery. Based on closed-loop PI regulation, dynamically adjust the target duty cycle D2 according to the difference between the real-time collected Vbat and the target voltage Vref2; Set Q11 and Q22 of the full-side full-bridge to conduct synchronously, and Q12 and Q21 to conduct synchronously, and the duty cycle of each synchronous conduction is 45%, and the conduction time is synchronized with the inverter current of the secondary full-bridge.

[0012] Further, if in the soft start state, the segmented soft start control is adopted both in the forward energy transfer and the reverse energy transfer, including the following sub-steps: If the working circuit is in the soft start state and the energy flows from the high-voltage DC bus to the energy storage battery, it is judged that the working circuit is in the charge soft start; if the working circuit is in the soft start state and the energy flows from the energy storage battery to the high-voltage DC bus, it is judged that the working circuit is in the discharge soft start; If the working circuit is in charge soft-start mode, the bidirectional Buck-Boost converter is initially set to run in Boost mode, and the corresponding duty cycle is gradually and linearly increased from 0.1 to the target duty cycle D2, with the increase rate set to 0.01 / ms.

[0013] Furthermore, if in a soft-start state, the segmented soft-start control, which applies to both forward and reverse energy transfer, also includes the following sub-steps: Obtain the resonant frequency F0 of the LLC resonant converter, and gradually and linearly reduce the switching frequency of the LLC resonant converter from 1.5×F0 to F0, while limiting the resonant current Ir to no more than 1.2 times the corresponding rated current; When the real-time battery voltage Vbat rises to 80% of the corresponding rated voltage, the operating circuit switches to constant current charging mode, stabilizing the inductor current Ib to the corresponding rated charging current.

[0014] Furthermore, if in a soft-start state, the segmented soft-start control, which applies to both forward and reverse energy transfer, also includes the following sub-steps: If the working circuit is in the discharge soft-start state, the bidirectional Buck-Boost converter is initially set to run in Boost mode, and the corresponding duty cycle is gradually and linearly increased from 0.1 to the target duty cycle D1, with the increase rate set to 0.01 / ms. Obtain the resonant frequency F0 of the LLC resonant converter, obtain the actual voltage of the primary-side full-bridge output to the high-voltage DC bus, and denote it as the reverse output voltage VLout; gradually and linearly reduce the switching frequency of the LLC resonant converter from 1.5×F0 to F0; at the same time, limit the rise rate of the reverse output voltage VLout to no more than 10V / ms; When the real-time reverse output voltage VLout rises to 90% of the corresponding target voltage, the operating circuit switches to voltage regulation mode to maintain the stability of the real-time reverse output voltage VLout.

[0015] The beneficial effects of this invention are as follows: This invention obtains real-time circuit parameters and determines the operating status by real-time acquisition of the input voltage, output voltage, LLC resonant current, Buck-Boost inductor current, and battery terminal voltage of the bidirectional two-stage boost circuit. If it is in a charging / discharging state, voltage regulation and energy transfer are performed based on the LLC resonant converter and the bidirectional Buck-Boost converter. If it is in a soft-start state, segmented soft-start control is used for both forward and reverse energy transfer. When changing the voltage of an energy storage power supply that requires bidirectional energy transfer, the two converters can be controlled in tandem, which retains the high efficiency advantage of LLC soft switching and widens the voltage regulation range with the help of Buck-Boost, reduces the voltage surge problem during power flow switching, and improves the stability of control. This invention enables a wider range of voltage adaptation and bidirectional energy transfer during charging and discharging by coordinating the control of an LLC resonant converter and a bidirectional Buck-Boost converter in a closed-loop regulation manner. Specifically, the LLC resonant converter adjusts its switching frequency according to the load power to maintain soft-switching operation, effectively reducing switching losses and improving conversion efficiency. The bidirectional Buck-Boost converter, through dynamic correction of the target duty cycle and limitation of the inductor current change rate, reduces current surges and improves output voltage regulation accuracy and operational stability. During soft-start charging, the Buck-Boost converter's duty cycle is linearly increased from small to large, while the LLC switching frequency is gradually reduced from above the resonant frequency to the resonant frequency, allowing for smooth energy build-up and suppressing starting current spikes. During soft-start discharging, the same segmented progressive control is used to reduce bus voltage surges and improve the smoothness of reverse energy transfer. Attached Figure Description

[0016] Figure 1 This is a flowchart illustrating the steps of the method of the present invention; Figure 2 This is a schematic diagram of the working circuit connection of the present invention; Figure 3 This is a flowchart of the segmented soft-start control of the present invention; Figure 4 This is a schematic diagram of the electronic device 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. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0018] Example 1, please refer to Figure 1 As shown, this application provides a bidirectional two-stage boost circuit control method for a high-power energy storage power supply, including the following steps: Step S1 involves real-time acquisition of the input voltage, output voltage, LLC resonant current, Buck-Boos inductor current, and battery terminal voltage of the bidirectional two-stage boost circuit to obtain real-time circuit parameters and determine its operating status. Step S1 includes the following sub-steps: Step S101: The bidirectional two-stage boost circuit is referred to as the working circuit. The working circuit includes a bidirectional LLC resonant converter and a bidirectional Buck-Boost converter. The bidirectional LLC resonant converter includes a primary-side full bridge, an LLC resonant cavity, a high-frequency transformer, and a secondary-side full bridge. Step S102: The primary-side full bridge includes four switches, namely Q11, Q12, Q21 and Q22, wherein Q11 and Q21 are connected in series, Q12 and Q22 are connected in series, Q11 and Q12 are connected in parallel, and Q21 and Q22 are connected in parallel; the secondary-side full bridge includes four switches, namely Q1, Q2, Q3 and Q4, wherein Q1 and Q3 are connected in series, Q2 and Q4 are connected in series, Q1 and Q2 are connected in parallel, and Q3 and Q4 are connected in parallel. For step S103, please refer to... Figure 2 As shown, the bidirectional LLC resonant converter is connected in series between the high-voltage DC bus and the bidirectional Buck-Boost converter, and the bidirectional Buck-Boost converter is connected in series between the secondary full-bridge and the battery pack; the battery pack connected to the working circuit is referred to as the energy storage battery.

[0019] Step S104: Real-time synchronous acquisition of the input voltage Vin, output voltage Vout, LLC resonant current, Buck-Boost inductor current, and battery terminal voltage of the working circuit, and recording them as real-time circuit parameters of the working circuit; the LLC resonant current, Buck-Boost inductor current, and battery terminal voltage are recorded as resonant current Ir, inductor current Ib, and battery voltage Vbat, respectively. The input voltage Vin is the voltage of the primary full-bridge input to the high-voltage DC bus, the output voltage Vout is the voltage of the secondary full-bridge output, the battery voltage Vbat is the voltage across the energy storage battery, the resonant current Ir is the current of the LLC resonant cavity, and the inductor current Ib is the current of the energy storage inductor of the bidirectional Buck-Boost converter. Step S105: Determine whether the system containing the normally operating circuit is in a soft-start state. If it is, determine that the operating circuit is in a soft-start state; otherwise, determine that the operating circuit is in a charging / discharging state. Soft-start refers to the process of slowly and linearly increasing the output voltage or current when the circuit starts up or switches operating modes. It allows the circuit to smoothly transition from the initial state to the normal operating state by gradually increasing the duty cycle, decreasing the switching frequency, or adjusting the phase shift angle. The entire process usually lasts from several hundred milliseconds to several seconds. In practical implementation, soft start is the core protection mechanism of high-power power electronic circuits. It avoids current spikes, voltage overshoots and device stresses when the circuit is powered on or the mode is switched by gradually adjusting the control parameters instead of directly applying a full drive signal. It is a key technology to ensure system reliability and extend battery life.

[0020] Step S2: If the circuit is in a charging / discharging state, voltage regulation and energy transfer are performed based on the LLC resonant converter and the bidirectional Buck-Boost converter. Step S2 includes the following sub-steps: Step S201, for the working circuit in the charge-discharge state, if the energy flows from the high-voltage DC bus to the energy storage battery, it is determined that the working circuit is in the charging state; if the energy flows from the energy storage battery to the high-voltage DC bus, it is determined that the working circuit is in the discharging state; obtain the transformer turns ratio of the high-frequency transformer, denoted as n1. In this embodiment, the transformer turns ratio n1 is 6; Step S202, if the working circuit is in the charging state, determine whether the working circuit is in the buck mode or the boost mode according to the current Vin, Vout, and Vbat at this time, and calculate the target duty cycle D1 of the bidirectional Buck-Boost converter; that is, the buck mode is the working mode in which the bidirectional Buck-Boost converter converts a higher input voltage into a lower output voltage, and the boost mode is the working mode in which the bidirectional Buck-Boost converter converts a lower input voltage into a higher output voltage; Step S203, if Vin / n1 ≥ Vbat, it is determined that it is in the buck mode, then D1 = Vbat × n1 / Vin; if Vin / n1 < Vbat, it is determined that it is in the boost mode, then D1 = (Vbat - Vin / n1) / Vbat; For example, Vin = 360v, n1 = 6, Vbat = 50v, then Vin / n1 ≥ Vbat, it is in the buck mode, and D1 = Vbat × n1 / Vin = 6 × 50 / 360 = 0.83; if Vin = 31V0, n1 = 6, Vbat = 55v, then Vin / n1 < Vbat, it is in the boost mode, and D1 = (Vbat - Vin / n1) / Vbat = (55 - 310 / 6) / 55 = 0.06.

[0021] Step S204, obtain the charging power of the energy storage battery, denoted as the load power FP, and adjust the switching frequency LF of the bidirectional LLC resonant converter according to the load power FP to make the bidirectional LLC resonant converter operate in the soft-switching state; that is, when the load is heavy, make LF close to the resonant frequency F0, and when the load is light, LF deviates from F0 but avoid out-of-control through phase-shift compensation; the division criteria for heavy load and light load can be set according to the actual application scenario; The soft-switching state is a working state in power electronics conversion technology where, through resonance or an auxiliary circuit, the power switch tube is turned on when the voltage is zero and turned off when the current is zero. Its core is to eliminate the overlapping area of voltage and current during the switching process, thereby significantly reducing switching losses and electromagnetic interference. The LLC resonant converter is mainly responsible for efficient energy transfer in the intermediate stage; by obtaining the charging power FP of the energy storage battery and adjusting the switching frequency LF accordingly, the LLC resonant converter can be made to operate as much as possible in the soft-switching interval, thereby using its resonant characteristics to achieve low-loss energy transmission.

[0022] Step S205: Obtain the target voltage Vref1 corresponding to the energy storage battery. Based on closed-loop PI regulation, dynamically correct the target duty cycle D1 according to the difference between the real-time collected Vout and the target voltage Vref1, so that the output gradually approaches the target value, and limit the change rate of the inductor current Ib to no more than 5 A / μs; this is to suppress current mutation and avoid excessive transient impact; Step S206: Set Q1 and Q4 of the secondary full-bridge to conduct synchronously, and Q2 and Q3 to conduct synchronously. Set the corresponding conduction time to lag the zero-crossing time of Ir by 50 ns to 200 ns, and the corresponding turn-off time to lead the zero-crossing time of Ir by 50 ns to 200 ns, to ensure soft switching of the synchronous rectifier tube. The relevant lag and lead durations can be flexibly adjusted according to the actual application scenario; Through the synchronous conduction mode of the secondary full-bridge, and making a small offset of the conduction and turn-off times relative to the zero-crossing point of the resonant current Ir, the switching action is closer to the current zero-crossing time, so as to achieve a soft-switching or near-soft-switching operating state as much as possible; it can reduce switching losses, reduce the energy loss at the instant of turn-on and turn-off, relieve device stress, reduce the impact caused by voltage and current superposition, suppress switching noise and electromagnetic interference, improve the electromagnetic compatibility of the system, improve the high-frequency operation stability, and make the circuit more suitable for high-power high-frequency working scenarios.

[0023] Step S207: If the working circuit is in the discharge state; obtain the normal input voltage of the high-voltage DC bus, denoted as V0out, and judge whether the working circuit is in the step-down inverter mode or the boost inverter mode according to Vbat at this time, and calculate the target duty cycle D2 of the bidirectional Buck-Boost converter; Step S208: If Vbat < V0out / n1, it is judged to be in the boost inverter mode, then D2 = 1 - Vbat×n1 / V0out; if Vbat ≥ Vout / n1, it is judged to be in the step-down inverter mode, then D2 = V0out / Vbat×n1; when the energy storage battery supplies energy to the high-voltage DC bus, the Buck-Boos converter needs to judge whether it is boost inversion or step-down inversion according to the relationship between the battery voltage and the normal input voltage of the bus, and then calculate the target duty cycle D2 to achieve adaptive reverse energy transmission; For example, V0out = 330V, Vbat = 40V, n1 = 6, then Vbat < V0out / n1. It is in the boost inverter mode, then D2 = 1 - Vbat×n1 / V0out = 1 - 40×6 / 330 = 0.33; if V0out = 330V, Vbat = 60V, n1 = 6, then Vbat ≥ V0out / n1, it is in the step-down inverter mode, then D2 = V0out / Vbat×n1 = 330 / 60×6 = 0.861.

[0024] Step S209: Obtain the target voltage Vref2 corresponding to the energy storage battery. Based on closed-loop PI regulation, dynamically adjust the target duty cycle D2 according to the difference between the real-time collected Vbat and the target voltage Vref2. Correct D2 in real time through closed-loop PI regulation so that the battery-side output voltage remains near the target during the discharge process, thereby ensuring the continuity and controllability of discharge control. Step S210: Set Q11 and Q22 of the full-bridge to conduct synchronously, and Q12 and Q21 to conduct synchronously, with a duty cycle of 45% for each synchronous conduction. The conduction time is synchronized with the inverter current of the secondary full-bridge; this ensures soft switching of the primary full-bridge; by synchronously conducting the primary full-bridge in pairs and limiting the duty cycle to 45%, the inverter currents of the primary and secondary sides are kept coordinated, thereby enabling the bidirectional LLC resonant converter to achieve smoother energy conversion under discharge conditions, ensuring coordinated power transmission between the primary and secondary sides, reducing circulating current and ineffective power, suppressing current surges and device stress, and enhancing system reliability; by fixing an appropriate duty cycle, control consistency is improved, facilitating stable system operation, reducing commutation losses, and improving efficiency; In the specific implementation process, the energy flow signal can be monitored in real time. When the current direction is reversed, the seamless switching of the two-stage converter control logic is triggered. The switching time should not exceed 10μs to avoid voltage drop or spike.

[0025] Step S3: If in soft-start mode, segmented soft-start control is used for both forward and reverse energy transfer. Step S3 includes the following sub-steps: For step S301, please refer to... Figure 3 As shown, if the working circuit is in a soft-start state and energy flows from the high-voltage DC bus to the energy storage battery, then the working circuit is judged to be in a charging soft-start state; if the working circuit is in a soft-start state and energy flows from the energy storage battery to the high-voltage DC bus, then the working circuit is judged to be in a discharging soft-start state. In step S302, if the working circuit is in charging soft-start mode, the bidirectional Buck-Boost converter is initially set to run in Boost mode, and the corresponding duty cycle is gradually and linearly increased from 0.1 to the target duty cycle D2, with the increase rate set to 0.01 / ms. The increase rate can be adjusted according to the actual application scenario. The duty cycle slowly increases from 0.1, which allows the inductor current and output voltage to be gradually established, avoiding the current surge caused by an excessively large duty cycle at startup.

[0026] Step S303: Obtain the resonant frequency F0 of the LLC resonant converter, and gradually and linearly reduce the switching frequency of the LLC resonant converter from 1.5×F0 to F0, while limiting the resonant current Ir to no more than 1.2 times the corresponding rated current. During the soft start process, the switching frequency is first set to a position higher than the resonant frequency, and then gradually reduced to the resonant frequency F0. This avoids voltage and current surges caused by a one-step frequency change, and is more suitable for the stable energy transmission operating range. Setting a limit on the resonant current Ir is to prevent overcurrent during the start-up phase, suppress the start-up current spike, effectively prevent excessive start-up transient current, and protect the switching transistor and transformer. In step S304, when the real-time battery voltage Vbat rises to 80% of the corresponding rated voltage, the working circuit switches to constant current charging mode to stabilize the inductor current Ib at the corresponding rated charging current. That is, when the battery voltage has risen to a certain level, the soft-start control switches to the constant current charging mode, which is more suitable for subsequent charging, to stabilize the inductor current Ib at the rated charging current, which helps to improve charging consistency.

[0027] Step S305: If the working circuit is in the discharge soft start state, at the beginning, the bidirectional Buck-Boost converter is run in Boost mode, and the corresponding duty cycle is gradually increased linearly from 0.1 to the target duty cycle D1, with the increase rate set to 0.01 / ms. Step S306: Obtain the resonant frequency F0 of the LLC resonant converter, obtain the actual voltage of the primary-side full-bridge output to the high-voltage DC bus, and denot it as the reverse output voltage VLout; gradually and linearly reduce the switching frequency of the LLC resonant converter from 1.5×F0 to F0; at the same time, limit the rise rate of the reverse output voltage VLout to no more than 10V / ms; by limiting the rise rate of VLout to within 10V / ms, it is possible to prevent the voltage from rising too quickly during the discharge process, which could cause an impact or false protection, and reduce the control oscillation caused by excessive reverse power supply. Step S307: When the real-time reverse output voltage VLout rises to 90% of the corresponding target voltage, the working circuit switches to voltage regulation mode to maintain the real-time reverse output voltage VLout stable; thus achieving a smooth transition from the soft-start stage to the normal regulation stage. In practical implementation, segmented soft-start control is adopted in soft-start mode to avoid large voltage and current surges during startup and power direction switching. During charging soft-start, the duty cycle of the Buck-Boost converter is linearly increased from small to large, and the LLC switching frequency is gradually reduced from above the resonant frequency to the resonant frequency to suppress startup current spikes and avoid excessive transient stress on the devices. During discharging soft-start, the same segmented progressive control is adopted, and the rise rate of the reverse output voltage is constrained to reduce bus voltage surges and improve the stability of reverse energy transfer. When the battery voltage or reverse output voltage reaches a preset threshold, the system switches to constant current charging mode or voltage regulation mode to further ensure the continuity of the startup process and the reliability of system control.

[0028] Example 2, please refer to Figure 4 As shown, Figure 4 A schematic diagram of an electronic device is provided, which may include a processor, a communication interface, a memory, and a communication bus. The processor, communication interface, and memory communicate with each other via the communication bus. The memory stores computer-readable instructions, which the processor can call. When the processor executes a computer-readable instruction, it performs steps similar to those in a bidirectional two-stage boost converter control method for high-power energy storage power supplies to achieve the following functions: real-time acquisition of the input voltage, output voltage, LLC resonant current, Buck-Boost inductor current, and battery terminal voltage of the bidirectional two-stage boost converter to obtain real-time circuit parameters and determine the operating status; if in a charging / discharging state, voltage regulation and energy transfer are performed based on the LLC resonant converter and the bidirectional Buck-Boost converter; if in a soft-start state, segmented soft-start control is used for both forward and reverse energy transfer.

[0029] Furthermore, when the logical instructions in the aforementioned memory can be implemented as software functional units and sold or used as independent products, they can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of this application, in essence, or the part that contributes to the prior art, or a portion of the technical solution, can be embodied in the form of a software product. This computer software product is stored in a storage medium and includes several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute all or part of the steps of the methods described in the various embodiments of this application. The aforementioned storage medium includes various media capable of storing program code, such as USB flash drives, portable hard drives, read-only memory (ROM), random access memory (RAM), magnetic disks, or optical disks.

[0030] Example 3: This application also provides a computer-readable storage medium storing a computer program. When the computer program is executed by a processor, it performs steps such as those in the bidirectional two-stage boost circuit control method for a high-power energy storage power supply to achieve the following functions: real-time acquisition of the input voltage, output voltage, LLC resonant current, Buck-Boost inductor current, and battery terminal voltage of the bidirectional two-stage boost circuit to obtain real-time circuit parameters and determine the operating state; if in a charging / discharging state, voltage regulation and energy transfer are performed based on the LLC resonant converter and the bidirectional Buck-Boost converter; if in a soft-start state, segmented soft-start control is used for both forward and reverse energy transfer.

[0031] Based on the above description of the embodiments, the embodiments of the present invention can be provided as methods, systems, or computer program products. Based on this understanding, the above technical solutions, in essence or in terms of their contribution to the prior art, can be embodied in the form of a software product. This computer software product can be stored in a computer-readable storage medium, such as ROM / RAM, magnetic disk, optical disk, etc., and includes several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute the methods described in the various embodiments or certain parts of the embodiments.

[0032] In the embodiments provided in this application, it should be understood that the disclosed system or method can be implemented in other ways. The embodiments described above are merely illustrative. For example, the division of modules or units is only a logical functional division, and there may be other division methods in actual implementation. Furthermore, multiple modules or units may be combined or integrated into another system, or some features may be ignored or not executed. Additionally, the coupling or direct coupling or communication connection shown or discussed may be through some communication interfaces. The indirect coupling or communication connection between systems, modules, and units may be electrical, mechanical, or other forms.

[0033] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of this application.

Claims

1. A bidirectional two-stage boost circuit control method for high-power energy storage power supplies, characterized in that, It includes the following steps: Collect the input voltage, output voltage, LLC resonant current, Buck-Boos inductor current, and battery terminal voltage of the bidirectional two-stage boost circuit in real time, obtain the real-time parameters of the circuit, and judge the working state; If it is in the charge-discharge state, voltage regulation and energy transfer are performed based on the LLC resonant converter and the bidirectional Buck-Boost converter; for the working circuit in the charge-discharge state, if the energy flows from the high-voltage DC bus to the energy storage battery, it is judged that the working circuit is in the charging state; if the energy flows from the energy storage battery to the high-voltage DC bus, it is judged that the working circuit is in the discharging state; obtain the transformer turns ratio of the high-frequency transformer, denoted as n1; if the working circuit is in the charging state, judge whether the working circuit is in the step-down mode or the step-up mode according to the input voltage Vin, output voltage Vout, and battery voltage Vbat at this time, and calculate the target duty cycle D1 of the bidirectional Buck-Boost converter; if Vin / n1≥Vbat, it is judged to be in the step-down mode, then D1 = Vbat×n1 / Vin; if Vin / n1<Vbat, it is judged to be in the step-up mode, then D1=(Vbat - Vin / n1) / Vbat; If it is in the soft start state, segmented soft start control is adopted both in the forward energy transfer and the reverse energy transfer.

2. The bidirectional two-stage boost circuit control method for a high-power energy storage power supply according to claim 1, characterized in that, Collect the input voltage, output in real time, LLC resonant current Ir, Buck-Boos inductor current, and battery terminal voltage of the bidirectional two-stage boost circuit in real time, obtain the real-time parameters of the circuit, and the judgment of the working state includes the following sub-steps: Denote the bidirectional two-stage boost circuit as the working circuit, and the working circuit includes a bidirectional LLC resonant converter and a bidirectional Buck-Boost converter; the bidirectional LLC resonant converter includes a primary full-bridge, an LLC resonant cavity, a high-frequency transformer, and a secondary full-bridge; The primary full-bridge includes four switching tubes, namely Q11, Q12, Q21, and Q22 in sequence, where Q11 and Q21 are in series, Q12 and Q22 are in series, Q11 and Q12 are in parallel, and Q21 and Q22 are in parallel; the secondary full-bridge includes four switching tubes, namely Q1, Q2, Q3, and Q4 in sequence, where Q1 and Q3 are in series, Q2 and Q4 are in series, Q1 and Q2 are in parallel, and Q3 and Q4 are in parallel; The bidirectional LLC resonant converter is connected in series between the high-voltage DC bus and the bidirectional Buck-Boost converter, and the bidirectional Buck-Boost converter is connected in series between the secondary full-bridge and the battery pack; denote the battery pack connected to the working circuit as the energy storage battery.

3. The bidirectional two-stage boost circuit control method for a high-power energy storage power supply according to claim 2, characterized in that, Collect the input voltage, output in real time, LLC resonant current Ir, Buck-Boos inductor current, and battery terminal voltage of the bidirectional two-stage boost circuit in real time, obtain the real-time parameters of the circuit, and the judgment of the working state further includes the following sub-steps: Real-time synchronously collect the input voltage Vin, output voltage Vout, LLC resonant current, Buck-Boost inductor current, and battery terminal voltage of the working circuit, and record them as the circuit real-time parameters of the working circuit; sequentially record the LLC resonant current, Buck-Boos inductor current, and battery terminal voltage as the resonant current Ir, inductor current Ib, and battery voltage Vbat. Judge whether the system where the normally operating working circuit is located is in soft start. If it is in soft start, judge that the working circuit is in the soft start state, otherwise judge that the working circuit is in the charge-discharge state.

4. The bidirectional two-stage boost circuit control method for a high-power energy storage power supply according to claim 3, characterized in that, If it is in the charge-discharge state, voltage regulation and energy transfer based on the LLC resonant converter and the bidirectional Buck-Boost converter include the following sub-steps: Obtain the charging power of the energy storage battery, record it as the load power FP, and adjust the switching frequency LF of the bidirectional LLC resonant converter according to the load power FP to make the bidirectional LLC resonant converter operate in the soft-switching state. Obtain the target voltage Vref1 corresponding to the energy storage battery. Based on closed-loop PI regulation, dynamically correct the target duty cycle D1 according to the difference between the real-time collected Vout and the target voltage Vref1, and limit the change rate of the inductor current Ib not to be greater than 5A / μs. Set Q1 and Q4 of the secondary full-bridge to conduct synchronously, Q2 and Q3 to conduct synchronously, and set the corresponding conduction moment to lag the zero-crossing moment of Ir by 50ns to 200ns, and the corresponding turn-off moment to lead the zero-crossing moment of Ir by 50ns to 200ns.

5. The bidirectional two-stage boost circuit control method for a high-power energy storage power supply according to claim 4, characterized in that, If it is in the charge-discharge state, voltage regulation and energy transfer based on the LLC resonant converter and the bidirectional Buck-Boost converter also include the following sub-steps: If the working circuit is in the discharge state; obtain the normal input voltage of the high-voltage DC bus, record it as V0out, and judge whether the working circuit is in the step-down inverter mode or the boost inverter mode according to the Vbat at this time, and calculate the target duty cycle D2 of the bidirectional Buck-Boost converter. If Vbat < V0out / n1, judge that it is in the boost inverter mode, then D2 = 1 - Vbat×n1 / V0out; if Vbat ≥ V0out / n1, judge that it is in the step-down inverter mode, then D2 = V0out / Vbat×n1.

6. The bidirectional two-stage boost circuit control method for a high-power energy storage power supply according to claim 5, characterized in that, If it is in the charge-discharge state, voltage regulation and energy transfer based on the LLC resonant converter and the bidirectional Buck-Boost converter also include the following sub-steps: Obtain the target voltage Vref2 corresponding to the energy storage battery. Based on closed-loop PI regulation, dynamically adjust the target duty cycle D2 according to the difference between the real-time collected Vbat and the target voltage Vref2. Set Q11 and Q22 of the full-side full-bridge to conduct synchronously, Q12 and Q21 to conduct synchronously, and the duty cycle of each synchronous conduction is 45%, and the conduction moment is synchronized with the inverter current of the secondary full-bridge.

7. The bidirectional two-stage boost circuit control method for a high-power energy storage power supply according to claim 6, characterized in that, If it is in the soft start state, segmented soft start control is adopted both in the case of forward energy transfer and reverse energy transfer, including the following sub-steps: If the working circuit is in a soft-start state and energy flows from the high-voltage DC bus to the energy storage battery, then the working circuit is in a charging soft-start state; if the working circuit is in a soft-start state and energy flows from the energy storage battery to the high-voltage DC bus, then the working circuit is in a discharging soft-start state. If the working circuit is in charge soft-start mode, the bidirectional Buck-Boost converter is initially set to run in Boost mode, and the corresponding duty cycle is gradually and linearly increased from 0.1 to the target duty cycle D2, with the increase rate set to 0.01 / ms.

8. The bidirectional two-stage boost circuit control method for a high-power energy storage power supply according to claim 7, characterized in that, If in soft-start mode, segmented soft-start control is used for both forward and reverse energy transfer, and includes the following sub-steps: Obtain the resonant frequency F0 of the LLC resonant converter, and gradually and linearly reduce the switching frequency of the LLC resonant converter from 1.5×F0 to F0, while limiting the resonant current Ir to no more than 1.2 times the corresponding rated current; When the real-time battery voltage Vbat rises to 80% of the corresponding rated voltage, the operating circuit switches to constant current charging mode, stabilizing the inductor current Ib to the corresponding rated charging current.

9. The bidirectional two-stage boost circuit control method for a high-power energy storage power supply according to claim 8, characterized in that, If in soft-start mode, segmented soft-start control is used for both forward and reverse energy transfer, and includes the following sub-steps: If the working circuit is in the discharge soft-start state, the bidirectional Buck-Boost converter is initially set to run in Boost mode, and the corresponding duty cycle is gradually and linearly increased from 0.1 to the target duty cycle D1, with the increase rate set to 0.01 / ms. Obtain the resonant frequency F0 of the LLC resonant converter, obtain the actual voltage of the primary-side full-bridge output to the high-voltage DC bus, and denote it as the reverse output voltage VLout; gradually and linearly reduce the switching frequency of the LLC resonant converter from 1.5×F0 to F0; at the same time, limit the rise rate of the reverse output voltage VLout to no more than 10V / ms; When the real-time reverse output voltage VLout rises to 90% of the corresponding target voltage, the operating circuit switches to voltage regulation mode to maintain the stability of the real-time reverse output voltage VLout.

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