A current control and voltage limiting protection method for an isolated bidirectional DC-DC converter in boost charging mode

Abstract

This invention discloses a current control and voltage limiting protection method for an isolated bidirectional DC-DC converter in Boost charging mode. In Boost charging mode, 1) a maximum current-limiting charging PI regulator is constructed by sampling the battery-side current. Using the actual charging current as feedback, a closed-loop compensation is used to compensate for the control error introduced by the duty cycle proportional coefficient between the average inductor current and the charging current, achieving precise control of the charging current; 2) a full-bridge high-voltage side voltage regulator is constructed. When the high-voltage side voltage exceeds the protection threshold, the regulator output directly clamps the upper limit of the duty cycle of the Boost switch, suppressing voltage spikes under abnormal operating conditions; 3) for dual independent PV inputs, current sharing control is implemented under a unified current setpoint during the constant-voltage charging stage. Single-path faults are identified based on the voltage drop threshold, and the faulty path is automatically disconnected to ensure continuous system operation. This invention requires no additional hardware, has clear control logic, and significantly improves the current control accuracy and system safety under Boost charging mode.

Description

Technical Field

[0001] This invention relates to the fields of power electronics and new energy storage technology, and in particular to a current control and voltage limiting protection method for an isolated bidirectional DC-DC converter in Boost charging mode. Background Technology

[0002] With the increasing popularity of residential photovoltaic (PV) energy storage, isolated bidirectional DC-DC converters, as the core unit of energy storage inverters, undertake the bidirectional conversion function of PV energy charging the battery and battery energy discharging to the DC bus. To support multiple independent PV inputs and achieve independent MPPT control, the mainstream topology in the industry adopts a two-stage structure of "Buck / Boost + Full Bridge," with two technical approaches for its operation in charging mode:

[0003] Option A (Buck mode charging): During charging, the Buck / Boost circuit operates in Buck step-down mode, and the inductor current is directly equal to the charging current, resulting in high control accuracy. However, in this option, the two PV inputs need to be connected in parallel before being connected to the Buck circuit, making it impossible to achieve independent MPPT control and resulting in poor adaptability.

[0004] Option B (Boost Mode Charging): During charging, the Buck / Boost circuit operates in Boost mode, and the two PV channels can be connected and controlled independently by MPPT, offering better flexibility and voltage adaptation range. However, it has the following inherent drawbacks:

[0005] (1) Insufficient charging current control accuracy: In Boost mode, the average inductor current I _L With battery charging current I batf The relationship between I and batf =N s × I _L × (1-D), where N s Where is the transformer turns ratio and D is the duty cycle. When operating in critical continuous mode, D fluctuates with the input voltage, and controlling only the inductor current cannot accurately control the charging current; the measured error can reach more than ±10%.

[0006] (2) High-voltage side overvoltage risk: The Boost output side is the high-voltage side bus of the full bridge. Under normal operation, the battery voltage is clamped to the bus voltage through the transformer reflection. When abnormalities such as full bridge drive blockage or sudden battery disconnection occur, the reflection clamping disappears, and the high-voltage side bus voltage spikes sharply due to the boost characteristics of the Boost circuit, which can easily damage power devices. The existing solution lacks an effective voltage limiting protection loop.

[0007] (3) Lack of current sharing and fault handling for independent input of dual PV: The existing solution cannot achieve current sharing control of the two inputs during the constant voltage charging stage. When the input voltage of a single PV drops due to fault or shadowing, the system cannot automatically disconnect the faulty path, which may cause system oscillation or charging interruption. Summary of the Invention

[0008] To address the shortcomings of existing technologies, this invention provides a current control and voltage limiting protection method for an isolated bidirectional DC-DC converter in Boost charging mode. This method solves the problem of low charging current control accuracy caused by the proportional coefficient (1-D) between inductor current and charging current in Boost charging mode; it also solves the overvoltage protection problem caused by the high-voltage bus voltage surge due to full-bridge drive blockage or battery disconnection in Boost charging mode; and it solves the problems of current sharing control and single-path fault identification and isolation for dual independent PV inputs during the constant voltage charging stage.

[0009] The objective of this invention is achieved as follows: a current control and voltage limiting protection method for an isolated bidirectional DC-DC converter in Boost charging mode, wherein the converter includes two independent PV input units, a Buck / Boost bidirectional DC-DC converter unit, a high-frequency isolated full-bridge converter unit, and a control unit, comprising the following steps:

[0010] 1) Closed-loop control of charging current: A battery-side current sampling is used to construct a maximum current-limiting charging PI regulator. The difference between the preset maximum charging current limit and the actual charging current is used as the regulator input. When the actual charging current reaches the limit, the regulator exits saturation and outputs the limit values ​​of the two Buck / Boost inductor currents. The inner loop current setpoint is clamped to a safe range. At the same time, it compensates for the control error introduced by the proportional coefficient (1-D) between the average inductor current and the actual charging current in Boost mode, so as to achieve precise closed-loop control of charging current.

[0011] 2) Full-bridge high-voltage side voltage limiting protection: Construct a full-bridge high-voltage side voltage PI regulator, and use the difference between the preset high-voltage side voltage protection threshold and the actual sampled voltage as the regulator input; when the high-voltage side voltage rises to the protection threshold, the output value of the full-bridge high-voltage side voltage PI regulator is directly used as the upper limit of the duty cycle of the Boost switch, thereby achieving duty cycle clamping and suppressing voltage spikes;

[0012] 3) Dual-channel PV input unit current sharing and fault handling: In constant voltage charging mode, the output of the battery voltage regulator is used as the current setpoint of the battery current regulator, and the output of the battery current regulator is used as the unified current setpoint of the inner loop current regulators of the two Buck / Boost circuits to achieve current sharing control; the two PV input voltages are monitored in real time. When the voltage of a single PV input drops below the preset threshold, all switching transistor drive signals of that channel are blocked, the channel stops working, and the other channel operates independently.

[0013] Furthermore, step 1) compensates for the control error introduced by the proportional coefficient between the average inductor current and the actual charging current in Boost mode. Specifically, this includes: using the output of the battery maximum current limiting charging PI regulator as the upper limit amplitude of the inductor current setpoint, instead of directly using it as the setpoint; the inductor current setpoint is jointly determined by the MPPT regulator output and the upper limit amplitude, so that while the inductor current tracks the target value, the actual charging current is precisely limited within the set range, thereby eliminating the influence of proportional coefficient fluctuations caused by real-time changes in duty cycle D.

[0014] Furthermore, in step 2), the clamping function of the full-bridge high-voltage side voltage PI regulator is independent of the inner current loop. When the high-voltage side voltage does not reach the protection threshold, the regulator outputs a value higher than the normal duty cycle upper limit and does not participate in the control. When the high-voltage side voltage reaches or exceeds the protection threshold, the regulator output value is lower than the current duty cycle and is directly used as the forced upper limit of the duty cycle of the Boost switch, thereby realizing hardware-level overvoltage protection.

[0015] Furthermore, the preset threshold mentioned in step 3) is 22.6%~24.8% of the rated input voltage; the two PV input voltages are detected in real time, and when the single PV input voltage is lower than the preset threshold for N consecutive sampling cycles, all switching transistor drive signals of that channel are blocked, and the other channel operates independently; N≥3.

[0016] Furthermore, it also includes initiating a multi-loop collaborative control process for discharge in the discharge working mode, using the PV terminal voltage as the outer loop control target and the inductor current as the inner loop control target, and configuring battery discharge current limiting switching logic.

[0017] Furthermore, the battery discharge current limiting switching logic is as follows: a battery discharge current PI regulator is constructed, and the difference between the preset maximum discharge current limit and the actual discharge current is used as the regulator input; when the actual discharge current does not reach the limit, the outer loop control is dominated by the PV terminal voltage regulator; when the actual discharge current reaches the limit, the outer loop control smoothly switches to the battery discharge current regulator, and the system enters the constant current discharge mode.

[0018] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0019] (1) The accuracy of charging current control is greatly improved: By directly closing the loop through the battery side current, the proportional deviation caused by the change of duty cycle in Boost mode is compensated. The measured charging current error is reduced from ±10% of the traditional solution to within ±2%, which is especially suitable for scenarios with a wide input voltage range.

[0020] (2) Completely solve the overvoltage risk of Boost mode: The added full-bridge high-voltage side voltage limiting protection ring can limit the bus voltage within a safe threshold within 1ms under abnormal conditions such as full-bridge drive blockage and battery disconnection, preventing device damage and filling the safety loophole of the existing Boost charging scheme.

[0021] (3) Dual-path PV intelligent management: Automatic current sharing during constant voltage charging with an error of ≤ ±3%; automatic disconnection when a single path fails, allowing the system to continue operating, thus improving system redundancy and reliability in multi-photovoltaic input scenarios.

[0022] (4) Pure software implementation with zero hardware cost: All control logic is integrated in the digital controller, without the need to add any external protection circuits, making it easy to promote in engineering. Attached Figure Description

[0023] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0024] Figure 1 This is the main circuit topology diagram of the present invention.

[0025] Figure 2 This is a schematic diagram of the control principle of the present invention in charging mode.

[0026] Figure 3 This is a schematic diagram of the control principle of the present invention in discharge mode.

[0027] Figure 4 The waveform diagram is shown in the current sharing control experiment of the present invention under constant voltage charging mode.

[0028] Figure 5 For the present invention Figure 4 A magnified waveform of a portion of the waveform.

[0029] Figure 1 Symbol names in:

[0030]

[0031] Figure 2 Symbol names in:

[0032]

[0033] Figure 3 Symbol names in:

[0034]

[0035] Figure 4 and Figure 5 The symbol names in Figure 2 Detailed Implementation

[0036] 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.

[0037] A current control and voltage limiting protection method for an isolated bidirectional DC-DC converter in Boost charging mode, such as Figure 1 The diagram shown is the main circuit topology of this invention. The converter includes two independent PV input units, a Buck / Boost bidirectional DC-DC converter unit, a high-frequency isolated full-bridge converter unit, an energy storage battery unit, and a control unit with a digital signal processor as its core; it includes the following steps:

[0038] The charging or discharging mode is switched according to the energy flow direction; in the charging mode, the Buck / Boost circuit operates in the Boost conversion state, and in the discharging mode, the Buck / Boost circuit operates in the Buck conversion state.

[0039] like Figure 2 The diagram shown is a control principle diagram of the present invention in charging mode. In this mode, the charging multi-loop collaborative control process is started, including: generating the initial current setpoint value of the inner loop of the Boost inductor current through the MPPT current perturbation method.

[0040] 1) Precise closed-loop control of charging current: A maximum current-limiting charging PI regulator is constructed using battery-side current sampling. The difference between the preset maximum charging current limit and the actual charging current is used as the regulator input. When the actual charging current reaches the limit, the regulator exits saturation and outputs the limit values ​​of the two Buck / Boost inductor currents, clamping the inner loop current setpoint to a safe range. At the same time, it compensates for the control error introduced by the proportional coefficient (1-D) between the average inductor current and the actual charging current in Boost mode, thus achieving precise closed-loop control of the charging current. The difference between the limited current setpoint and the actual Buck / Boost inductor current is input to the inductor current PI regulator, and the regulator output forms the PWM duty cycle signal of the Boost switch.

[0041] In the charging operation mode, the specific method for compensating the ratio between the average inductor current and the actual charging current in the Boost circuit is as follows: the output of the battery maximum current limiting charging PI regulator is used as the upper limit amplitude of the inductor current setpoint, rather than directly as the setpoint; the inductor current setpoint is jointly determined by the output of the MPPT regulator and the upper limit amplitude, so that while the inductor current tracks the target value, the actual charging current is precisely limited within the set range, thereby eliminating the influence of proportional coefficient fluctuation caused by real-time changes in duty cycle D.

[0042] The control unit samples the total charging current I in real time through the shunt resistor on the battery side. batf Construct a PI regulator for maximum current charging of the battery. The input of this regulator is the preset maximum charging current limit I. batf_ref_max "and actual charging current I" batf The difference between the two values ​​is output as the upper limit amplitude of the two Buck / Boost inductor current setpoints. At the same time, the MPPT current regulator outputs the initial inductor current setpoint, which, after being clamped by the upper limit amplitude, is sent to the inner loop of the inductor current.

[0043] Key principle: When the actual charging current I batf Not yet reached I batf_ref_max When the battery current limiting regulator is saturated, it outputs a relatively large upper limit value, without limiting the output of the MPPT regulator; when I batf Approaching or reaching I batf_ref_max When the current limiting regulator exits saturation, its output value decreases, becoming the actual limiting value for the inductor current setpoint. Since the response speed of the inner loop of the inductor current is much faster than that of the outer loop of the battery current, this cascaded structure of "outer loop limiting + inner loop tracking" achieves control over I... batf It provides precise closed-loop control and automatically compensates for the fluctuations in the proportional coefficient (1-D) caused by changes in the duty cycle D.

[0044] 2) Full-bridge high-voltage side voltage limiting protection: According to Figure 2The bus voltage loop shown constructs a full-bridge high-voltage side voltage PI regulator. The difference between the preset high-voltage side voltage protection threshold and the actual sampled voltage is used as the regulator input. When the high-voltage side voltage rises to the protection threshold, the regulator output directly clamps the upper limit of the duty cycle of the Boost switch, suppressing voltage spikes. The clamping action of the full-bridge high-voltage side voltage PI regulator is independent of the inner current loop: when the high-voltage side voltage does not reach the protection threshold, the regulator outputs a value higher than the normal upper limit of the duty cycle and does not participate in control; when the high-voltage side voltage reaches or exceeds the protection threshold, the regulator output value is lower than the current duty cycle and is directly used as the forced upper limit of the duty cycle of the Boost switch, realizing hardware-level overvoltage protection.

[0045] When constructing a full-bridge high-voltage side voltage PI regulator, a preset protection threshold V is used. busf_th (e.g., 100V) is the given value, and the actual sampled high-voltage side voltage V is used. busf This is the feedback value. Under normal operating conditions, V busf The battery's reflected voltage clamps the voltage at a level far below V. busf_th The value of the voltage regulator, with a saturation output higher than the maximum normal duty cycle (e.g., 0.95), does not affect PWM generation. When abnormal operating conditions cause V... busf Rise to near V busf_th When the voltage limit regulator exits saturation, its output value becomes the effective upper limit of the duty cycle of the Boost switch, directly clamping the duty cycle and preventing the voltage from rising further. This voltage limit loop is independent of the inner current loop, and its output directly acts on the limit value of the PWM duty cycle, rather than being indirectly adjusted through the current setting. It has a fast response speed and can still work independently in the event of failure of any current loop.

[0046] 3) Dual-channel PV current sharing and fault handling: For the two independent PV input units, in constant voltage charging mode, the output of the battery voltage regulator simultaneously serves as the unified current setpoint for the inner loop current regulators of both Buck / Boost circuits, achieving current sharing control; the input voltage V of the two PV circuits is monitored in real time. pv1 V pv2 When the input voltage of a single PV channel drops below a preset threshold (e.g., 11V, corresponding to 23.7% of the rated voltage of 46.4V), all switching transistor drive signals (including Buck / Boost switching transistors and full-bridge switching transistors) of that channel are blocked, and that channel stops working, while another channel operates independently.

[0047] The preset threshold for single-channel PV fault identification is 22.6%~24.8% of the rated input voltage. A fault is identified when the voltage is detected to be below the threshold for three or more consecutive sampling cycles, thus avoiding false disconnection caused by transient disturbances. The Buck / Boost circuit of the bidirectional DC-DC energy storage converter operates in critical continuous mode, with charging current control accuracy better than ±2%. The method is implemented entirely through software logic of a digital signal processor, requiring no additional hardware circuitry and adaptable to DSP or MCU embedded control platforms.

[0048] Figure 3 This is the control principle diagram of the present invention in discharge mode. In this mode, the discharge multi-loop collaborative control process is started, with the PV terminal voltage as the outer loop control target and the inductor current as the inner loop control target, and the battery discharge current limiting switching logic is configured.

[0049] The specific logic for switching the battery discharge current limit in the discharge working mode is as follows: a battery discharge current PI regulator is constructed, and the difference between the preset maximum discharge current limit and the actual discharge current is used as the regulator input; when the actual discharge current does not reach the limit, the outer loop control is dominated by the PV terminal voltage regulator; when the actual discharge current reaches the limit, the outer loop control smoothly switches to the battery discharge current regulator, and the system enters the constant current discharge mode.

[0050] The following describes the specific implementation of this invention in detail using a 1kW / 6.4V battery / dual PV input isolated bidirectional DC-DC energy storage converter as an example. System parameters:

[0051] Single-channel PV input voltage range: 16V~60V, rated 46.4V;

[0052] Energy storage battery: 6.4V (5V~7.3V), maximum charge / discharge current 157A;

[0053] The high-voltage side busbar of the full bridge is rated at 80V, and the overvoltage protection threshold is 100V.

[0054] Switching frequency: 100kHz, control sampling frequency: 20kHz;

[0055] Digital controller: TI TMS320F28035.

[0056] Implementation steps:

[0057] Step 1: System Initialization and Mode Determination

[0058] After the system powers on, the DSP initializes the PWM, ADC, timer, and all PI regulator parameters. One inductor current flows through resistor R. s1 Sampling is performed, and the two inductor currents pass through resistor R. s2 Sampling is performed, and the battery-side current flows through resistor R.s3 Sampling is performed. V is acquired at a sampling rate of 20kHz. pv1 V pv2 I Lb1 I Lb2 V bus1f V bus2f V batf I batf If there is no fault, set Mode_Sel according to the energy flow direction: if V pv1 or V pv2 If the voltage is >16V and the battery is charging, Mode_Sel = 1 (charging mode); if the PV side needs power and the battery SOC is >10%, Mode_Sel = 0 (discharging mode).

[0059] Step 2: Charging mode control (Mode_Sel = 1)

[0060] The Buck / Boost circuit operates in Boost mode, with the lower transistors Q11 and Q21 serving as the main control switches.

[0061] MPPT current loop: Each channel independently executes the disturbance observation method, and the MPPT regulator output I... Lb_ref0 (0~40A).

[0062] Battery maximum current limiting loop: given I batf_ref_max = 157A, Feedback I batf The upper limit of the current-limiting PI regulator output value I Lb_max (40A). When I batf When < 157A, I Lb_max Saturated at 40A; when I batf When it reaches 157A, I Lb_max Automatically reduce to maintain I batf = 157A required value.

[0063] Inductor current given: I Lb_ref = min(I Lb_ref0 , I Lb_max ).

[0064] Inductor current inner loop: PI regulator based on I Lb_ref with I Lb The error generation duty cycle D (0~0.95).

[0065] Full-bridge high-voltage side pressure limiting ring: given V busf_th = 100V, feedback V bus1f V bus2f Normally V busf ≈ 80V, the voltage regulator's saturated output D_max = 0.95; when Vbusf When the voltage rises to 100V (e.g., when the full-bridge drive is blocked), the voltage regulator output D_max decreases to the actual value, forcing the duty cycle D ≤ D_max, thus suppressing voltage spikes.

[0066] Constant voltage charging switching: when V batf When the voltage rises to 7.3V, the battery voltage regulator engages, and its output serves as the setpoint for the battery current regulator, switching to constant voltage charging.

[0067] Step 3: Discharge mode control (Mode_Sel = 0)

[0068] The Buck / Boost circuit operates in Buck mode, with the upper transistors Q12 and Q22 serving as the main control switches.

[0069] PV voltage outer loop: given V pv_ref = 46.4V, feedback V pv PV voltage regulator output I Lb_ref .

[0070] Battery discharge current limiting loop: Given I batf_ref_max = 157A (discharge direction), feedback I batf (Positive value). When I batf When I <157A, the outer loop is a PV voltage loop; when I batf When the current reaches 157A, the outer loop switches to the battery discharge current regulator to limit the discharge current.

[0071] Inductor current inner loop: Same as charging mode, generating Buck duty cycle.

[0072] Step 4: Dual-channel PV current sharing and fault handling

[0073] During the constant voltage charging phase, the output of the battery voltage regulator serves as the current setpoint for the battery current regulator, and the output of the battery current regulator simultaneously serves as the setpoint for the inner loop of the two inductor currents, such as... Figure 4 The figure shown is an experimental waveform diagram of current sharing control under constant voltage charging mode according to the present invention. Figure 5 For the present invention Figure 4 The magnified waveform diagram shows that the error between the two inductor currents is less than ±3% based on the data measured in the simulation. Simultaneously, V is judged once per sampling cycle. pv1 and V pv2 If a certain road V pv If the voltage drops below 11.5V three times consecutively (150μs), immediately block all drive signals on that path (Q11 / Q12 or Q21 / Q22, and the corresponding 8 switches of the full bridge), and allow the other path to operate independently. After clearing the fault, a manual reset or waiting for the system to restart is required.

[0074] Actual measurements were taken under the above parameters:

[0075] Charging current control accuracy: within the PV input voltage range of 40V~60V, I batf Steady-state error ≤ ±2.8A (1.8% error relative to 157A).

[0076] Full-bridge high-voltage side overvoltage protection: Manually disable full-bridge drive, V busf When the voltage rises from 80V to 100V, the voltage limiting ring activates within 0.8ms, limiting the duty cycle. busf It stabilized at 101V and did not continue to rise.

[0077] Single-channel PV fault isolation: Disconnect one PV input, and the system will block the drive of that channel within 150μs. The other channel will continue charging, and the charging current will be adjusted to the original single-channel limit. The system will not oscillate.

[0078] This invention provides a current control and voltage limiting protection method for an isolated bidirectional DC-DC energy storage converter suitable for Boost charging mode. For a Buck / Boost+ full-bridge bidirectional energy storage circuit with two independent PV inputs, the Buck / Boost circuit operates in Boost conversion mode during charging and in Buck conversion mode during discharging. In Boost charging mode, a maximum current-limiting charging PI regulator is constructed by sampling the battery-side current. Using the actual charging current as feedback, a closed-loop compensation is used to compensate for the control error introduced by the duty cycle proportional coefficient (1-D) between the average inductor current and the charging current, achieving precise control of the charging current. Simultaneously, a full-bridge high-voltage side voltage regulator is constructed. When the high-voltage side voltage exceeds the protection threshold, the regulator output directly clamps the upper limit of the Boost switch duty cycle, suppressing voltage spikes under abnormal operating conditions. For the two independent PV inputs, current sharing control under a unified current setpoint is implemented during the constant-voltage charging stage. Single-path faults are identified based on voltage drop thresholds, and the faulty path is automatically disconnected to ensure continuous system operation.

[0079] The above description of the embodiments is only for the purpose of helping to understand the method and core ideas of the present invention. It should be noted that those skilled in the art can make several improvements and modifications to the present invention without departing from the principles of the present invention, and these improvements and modifications also fall within the protection scope of the claims of the present invention.

Claims

1. A current control and voltage limiting protection method for an isolated bidirectional DC-DC converter in Boost charging mode, the converter comprising two independent PV input units, a Buck / Boost bidirectional DC-DC converter unit, a high-frequency isolated full-bridge converter unit, and a control unit, characterized in that, Includes the following steps: 1) Closed-loop control of charging current: A battery-side current sampling is used to construct a maximum current-limiting charging PI regulator. The difference between the preset maximum charging current limit and the actual charging current is used as the regulator input. When the actual charging current reaches the limit, the regulator exits saturation and outputs the limit values ​​of the two Buck / Boost inductor currents. The inner loop current setpoint is clamped to a safe range. At the same time, it compensates for the control error introduced by the proportional coefficient (1-D) between the average inductor current and the actual charging current in Boost mode, so as to achieve precise closed-loop control of charging current. 2) Full-bridge high-voltage side voltage limiting protection: Construct a full-bridge high-voltage side voltage PI regulator, and use the difference between the preset high-voltage side voltage protection threshold and the actual sampled voltage as the regulator input; when the high-voltage side voltage rises to the protection threshold, the output value of the full-bridge high-voltage side voltage PI regulator is directly used as the upper limit of the duty cycle of the Boost switch, thereby achieving duty cycle clamping and suppressing voltage spikes; 3) Dual-channel PV input unit current sharing and fault handling: In constant voltage charging mode, the output of the battery voltage regulator is used as the current setpoint of the battery current regulator, and the output of the battery current regulator is used as the unified current setpoint of the inner loop current regulators of the two Buck / Boost circuits to achieve current sharing control; the two PV input voltages are monitored in real time. When the voltage of a single PV input drops below the preset threshold, all switching transistor drive signals of that channel are blocked, the channel stops working, and the other channel operates independently.

2. The current control and voltage limiting protection method for an isolated bidirectional DC-DC converter in Boost charging mode according to claim 1, characterized in that, Step 1) The compensation for the control error introduced by the proportional coefficient between the average inductor current and the actual charging current in Boost mode specifically includes: the output of the battery maximum current limiting charging PI regulator is used as the upper limit amplitude of the inductor current setpoint, instead of directly as the setpoint; the inductor current setpoint is jointly determined by the output of the MPPT regulator and the upper limit amplitude, so that while the inductor current tracks the target value, the actual charging current is precisely limited within the set range, thereby eliminating the influence of proportional coefficient fluctuation caused by real-time changes in duty cycle D.

3. The current control and voltage limiting protection method for an isolated bidirectional DC-DC converter in Boost charging mode according to claim 1, characterized in that, The clamping function of the full-bridge high-voltage side voltage PI regulator described in step 2) is independent of the current inner loop. When the high-voltage side voltage does not reach the protection threshold, the regulator outputs a value higher than the normal duty cycle upper limit and does not participate in the control. When the high-voltage side voltage reaches or exceeds the protection threshold, the regulator output value is lower than the current duty cycle and is directly used as the forced upper limit of the duty cycle of the Boost switch, thereby realizing hardware-level overvoltage protection.

4. The current control and voltage limiting protection method for an isolated bidirectional DC-DC converter in Boost charging mode according to claim 1, characterized in that, The preset threshold mentioned in step 3) is 22.6%~24.8% of the rated input voltage; The two PV input voltages are monitored in real time. When the PV input voltage of a single channel is lower than a preset threshold for N consecutive sampling cycles, all switching transistor drive signals of that channel are blocked, and the other channel operates independently; where N≥3.

5. The current control and voltage limiting protection method for an isolated bidirectional DC-DC converter in Boost charging mode according to claim 1, characterized in that, It also includes starting a multi-loop collaborative control process for discharging in the discharge mode, with the PV terminal voltage as the outer loop control target and the inductor current as the inner loop control target, and configuring battery discharge current limiting switching logic.

6. The current control and voltage limiting protection method for an isolated bidirectional DC-DC converter in Boost charging mode according to claim 5, characterized in that, The specific battery discharge current limiting switching logic is as follows: a battery discharge current PI regulator is constructed, and the difference between the preset maximum discharge current limit and the actual discharge current is used as the regulator input; when the actual discharge current does not reach the limit, the outer loop control is dominated by the PV terminal voltage regulator; when the actual discharge current reaches the limit, the outer loop control smoothly switches to the battery discharge current regulator, and the system enters the constant current discharge mode.

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