Photovoltaic controller and soft-switching modulation technology and multi-mode cooperative control method thereof

Abstract

The present application relates to the technical field of DC / DC power converter and control, and discloses a kind of photovoltaic controller, including input side switch, two-fold Boost converter and multi-mode control module;Input side switch is connected with photovoltaic array, two-fold Boost converter includes two parallel Boost branch, multi-mode control module realizes MPPT mode, constant voltage output mode and LPPT mode, and executes the smooth switching control between MPPT mode, constant voltage output mode and LPPT mode.The present application also discloses a kind of soft switching modulation technology and multi-mode collaborative control method of photovoltaic controller.The photovoltaic controller and its soft switching modulation technology and multi-mode collaborative control method of the present application are based on two-fold Boost topology, according to different scene requirements, the power conversion power is accurately regulated through multiple working modes, and the photovoltaic controller is smoothly switched between multiple working modes through multi-mode system control method.

Description

Technical Field

[0001] This invention relates to the field of DC / DC power converter and control technology, specifically to a photovoltaic controller and its soft-switching modulation technology and multi-mode cooperative control method. Background Technology

[0002] Solar energy, as a typical clean energy source, has advantages such as easy accessibility, renewability, and low cost. Under the dual pressures of resource scarcity and environmental pollution, photovoltaic (PV) power generation systems have shown tremendous development potential. Solar-powered power generation platforms and DC microgrid systems are the main operating forms of PV power generation systems. A typical DC microgrid power generation system structure is as follows: Figure 10 As shown, it mainly includes a photovoltaic array, a photovoltaic controller, an energy storage battery, a DC bus, and load units. Among them, the photovoltaic controller, as the core energy conversion device, realizes the task of converting and controlling the power from the photovoltaic array to the DC bus through a DC-DC converter.

[0003] The performance of a photovoltaic (PV) controller is determined by both hardware design and control strategy. At the hardware design level, to meet the miniaturization requirements of power conversion devices, high-frequency design has become the main technical path for reducing the size of energy storage components. However, the resulting surge in switching losses severely restricts system efficiency improvement. Soft-switching technology, as a key breakthrough in resolving this contradiction, currently relies on auxiliary resonant circuits or composite topologies to achieve zero-voltage / zero-current switching. However, in practical applications, it has revealed significant shortcomings such as high topological complexity and limited power density, severely restricting its engineering application.

[0004] At the control strategy level, the quality of the control algorithm directly affects the optimization of the system's output power. While Maximum Power Point Tracking (MPPT) control is a fundamental function of photovoltaic controllers, in actual operation, constraints such as bus voltage stability and dynamic power generation / consumption balance must be considered. Therefore, a multi-modal control system is needed, incorporating MPPT, constant voltage output, and finite power point tracking (LPPT) modes. The definitions and characteristics of each mode are as follows:

[0005] (1) Maximum Power Point Tracking (MPPT) mode: The maximum power point of the photovoltaic array is tracked in real time through algorithms such as perturbation observation method, incremental conductance method or constant voltage method to maximize energy capture efficiency;

[0006] (2) Constant voltage output mode: When the DC bus voltage approaches the safety threshold, the photovoltaic controller needs to control the power transmission to maintain a stable output voltage;

[0007] (3) Finite Power Point Tracking (LPPT) mode: In response to upper-level scheduling instructions, the output power is actively limited to a preset threshold P. limit The following describes how to achieve flexible control of power generation.

[0008] The operation of a photovoltaic (PV) controller involves multiple adjustment targets, making the design of its control and switching strategies quite complex. Existing methods have certain shortcomings in terms of control accuracy, robustness, and switching smoothness. Specifically, the accuracy in tracking the steady-state power point needs improvement, the dynamic switching between multiple modes is not smooth, and there is a risk of output power oscillation, which can negatively impact the system's stability and operating efficiency, hindering the efficient and stable operation of the PV controller. Summary of the Invention

[0009] The purpose of this invention is to address the shortcomings of the aforementioned technologies by providing a photovoltaic controller, its soft-switching modulation technology, and a multi-mode collaborative control method. Based on a dual-boost topology, the power conversion is precisely regulated through multiple operating modes according to different scenario requirements, and the photovoltaic controller smoothly switches between multiple operating modes through a multi-mode system control method.

[0010] To achieve the above objectives, the photovoltaic controller involved in this invention includes an input-side switch, a dual-boost converter, and a multi-mode control module for controlling the input-side switch and the dual-boost converter.

[0011] The input-side switch is connected to the photovoltaic array and adopts a half-bridge circuit topology, including a lower bridge arm power switch device with a freewheeling resistor connected in parallel and an upper bridge arm power switch device for controlling the on / off of the input voltage on the photovoltaic array side.

[0012] The dual-boost converter includes two parallel boost branches, each of which consists of a filter inductor and a half-bridge power switch. The input filter inductor is connected to the midpoint of the bridge arm of the input-side switch, and the half-bridge power switch includes an upper bridge arm power switch device and a lower bridge arm power switch device.

[0013] The multi-mode control module implements MPPT mode, constant voltage output mode and LPPT mode, and performs smooth switching control between MPPT mode, constant voltage output mode and LPPT mode.

[0014] A soft-switching modulation technique for a photovoltaic controller is disclosed, wherein the lower bridge arm power switch device in the input-side switch remains normally off, and the upper bridge arm power switch device in the input-side switch remains on during normal system operation, with the input voltage of the input-side switch equal to the photovoltaic array voltage; during shutdown, the upper bridge arm power switch device is turned off, the equivalent resistance tends to infinity, the input voltage of the input-side switch is approximately zero, blocking the transmission path of the photovoltaic array voltage to the load unit.

[0015] Preferably, in the dual-boost converter, the two parallel boost branches are implemented with alternating conduction control with a 180° phase difference. The upper and lower bridge arm power switching devices inside each boost branch use complementary PWM drive signals. Dead time is set for the upper and lower bridge arm power switching devices inside each boost branch to ensure circuit reliability. Within one switching cycle, the waveforms of the filter inductor currents of the two boost branches are the same but the phase difference is 180°.

[0016] Preferably, based on the ripple cancellation principle, while keeping the total input current ripple constant, the filter inductor parameters of each Boost branch are reduced, thereby minimizing the filter inductor current of the Boost branch. Controlled below zero, satisfying: , In the formula, I L For the filter inductor current, Δi L I is the peak-to-peak value of the inductor current ripple. o The output current is given by D, the duty cycle of the lower transistor is given by V. o Where L is the output voltage, f is the inductance value, and f is the output voltage. s t is the switching frequency. d For dead time, C oss The parasitic capacitance of the switching transistor allows the energy stored in the filter inductor to form a reverse freewheeling path through the body diodes of the upper and lower bridge arm power switching devices in the Boost branch during the dead time interval. This pre-discharges the junction capacitance of the lower bridge arm power switching device, creating a zero-voltage turn-on condition for the lower bridge arm power switching device.

[0017] A multi-mode collaborative control method for a photovoltaic controller is proposed. MPPT mode is the default operating mode of the photovoltaic controller. In MPPT mode, the output voltage is given by the variable step size perturbation observation method. Then, the driving signals of each upper and lower bridge arm power switching device are obtained by voltage and current dual closed-loop control, so that the photovoltaic array works in the optimal power output state.

[0018] In constant voltage output mode, the output voltage is maintained within a predetermined voltage range by adjusting the filter inductor current through current increment control.

[0019] In LPPT mode, different control algorithms are selected according to the operating mode at the previous moment. If it is in MPPT mode, the photovoltaic array voltage is adjusted. If it is in constant voltage output mode, the filter inductor current is adjusted to achieve finite power point tracking.

[0020] When switching operating modes, the system considers the comparison between external commands, the output power of the photovoltaic array, the actual value of the DC bus voltage and the preset threshold. By setting hysteresis, it avoids frequent switching between different operating modes due to small fluctuations in parameters, thus ensuring the stability of the system operation.

[0021] Preferably, in MPPT mode and constant voltage output mode, if a power limiting command is received and Enter LPPT mode, P k For the current power, P limit To limit power, k u The hysteresis width;

[0022] In LPPT mode, if k d If the hysteresis width is specified, exit LPPT mode and enter MPPT mode. If a power limit shutdown command is received, or V o V is the output voltage. limit If the output voltage limit is reached, exit LPPT mode and enter constant voltage output mode;

[0023] In MPPT mode, if Enter constant voltage output mode. In constant voltage output mode, if... ΔV is the voltage hysteresis width, and the system enters MPPT mode.

[0024] Preferably, the LPPT mode is nested within the control strategies of the MPPT mode and the constant voltage output mode, and the working process is as follows:

[0025] Before entering LPPT mode, the system is in MPPT mode: if the currently observed output power of the photovoltaic controller is greater than the set value P. ref Then it forces a forward search, V k+1 =V k +ΔV k V k V is the current search voltage. k+1 For the next search voltage, ΔV k V is the voltage search step size; otherwise, a reverse search is performed. k+1 =V k -ΔV kMeanwhile, by adaptively adjusting the search step size, rapid tracking of output power and high-precision steady-state control are achieved.

[0026] Before entering LPPT mode, the output is in constant voltage output mode: if an LPPT command is present and the output voltage V o Less than its limit V limit If the current is exceeded, the system enters LPPT mode. In LPPT mode, if the real-time power is greater than the power limit, a forward search is performed, with the current setpoint changing in step size ΔI. L If the current is less than 0, reduce the current input; if the real-time power is less than the power limit, perform a reverse search, ΔI. L >0, increase the current setting.

[0027] Preferably, in MPPT mode, a variable step-size perturbation observation method is adopted. The search direction is determined based on the difference between the input voltage and power values ​​of the current cycle and the previous cycle, and the search step size is determined based on the power value difference. The output voltage of the photovoltaic array is periodically increased or decreased. If the output power increases, the same perturbation amount as in the current cycle is applied in the next control cycle; if the output power decreases, the opposite perturbation amount is applied in the next control cycle. After several perturbation cycles, the output power of the photovoltaic array gradually approaches the maximum power point.

[0028] During maximum power point tracking, the search step size ΔV k The adjustment principles for the disturbance amount are as follows: Where ΔV0 is the initial step size, P k With P k-1 These represent the power values ​​of the current cycle and the previous cycle, respectively, with l being the scaling factor. The search step size ΔV is adjusted according to certain principles. k Dynamically adjust ΔV based on the distance between the current operating point and the maximum power point. k Scale to [ΔV] min , ΔV max Between ], where ΔV min For the minimum perturbation step size, ΔV max This represents the maximum perturbation step size.

[0029] Preferably, in constant voltage output mode, when the photovoltaic array output voltage is close to its upper limit, the photovoltaic controller controls the output power to maintain a constant output voltage, V limit The output voltage limit for the photovoltaic controller; when the output voltage approaches V... limit At this time, the photovoltaic controller reduces the output power by decreasing the photovoltaic array current, thereby stabilizing the output voltage at V. limit Hysteresis is set when switching between constant voltage output mode and other modes. In constant voltage output mode, when the output voltage is lower than V... limit When a certain threshold is reached, the constant voltage output mode is exited.

[0030] Record the filter inductor current value I when entering constant voltage output mode. Lref0 This causes the filter inductor current in this mode to be I Lref0 Based on the current given variation step size ΔI, L To increase or decrease the step size, detect the current output voltage of the photovoltaic controller and V. limit The deviation is calculated in real time by adjusting the current setpoint change step size ΔI. L The inductor current is given by the following formula: , .

[0031] Preferably, when switching from constant voltage output mode to MPPT mode, the reference value I of the filter inductor current in constant voltage output mode is... Lref The value is assigned to the integrator of the photovoltaic voltage control loop, so that the integrator has sufficient initial state reserve at the switching time to suppress the sudden change of control quantity caused by mode switching, avoid fluctuations in output voltage and current, and ensure a smooth transition of output performance.

[0032] Compared with the prior art, the present invention has the following advantages:

[0033] 1. Based on the dual-mode Boost topology, the power conversion is precisely controlled through multiple working modes according to different scenario requirements, and the photovoltaic controller can smoothly switch between multiple working modes through a multi-mode system control method.

[0034] 2. The photovoltaic controller topology can achieve input-output isolation and power on / off control through input-side switches, and can achieve boost DC-DC conversion through dual-stage Boost converters;

[0035] 3. The soft-switching modulation technology of the dual-stage Boost converter can achieve zero-voltage turn-on of all power switches, significantly improving system efficiency;

[0036] 4. Multi-mode control enables the photovoltaic controller to operate in maximum power point tracking, power limiting output, and constant voltage output modes, adjusting the conversion power according to upper-level instructions;

[0037] 5. The integrator reserve scheme for the operation mode switching conditions enables the photovoltaic controller to smoothly switch between three operating modes;

[0038] 6. The finite power point tracking mode is nested within the other two operating modes to achieve unified control quantities across multiple operating modes, facilitating the design and implementation of control parameters. Attached Figure Description

[0039] Figure 1 This is a block diagram illustrating the topology and control principle of the photovoltaic controller of the present invention;

[0040] Figure 2 Schematic diagram of soft-switching modulation technology for a dual-boost converter;

[0041] Figure 3 This is a schematic diagram of the MPPT mode working process;

[0042] Figure 4 This is the control flowchart for MPPT mode;

[0043] Figure 5 Flowchart of the constant voltage output mode control strategy;

[0044] Figure 6 This is a schematic diagram of the LPPT mode working process;

[0045] Figure 7 LPPT mode control flowchart;

[0046] Figure 8 This is a diagram illustrating the conditions for switching working modes.

[0047] Figure 9 A schematic diagram of the integrator's storage;

[0048] Figure 10 This is a schematic diagram of a DC microgrid power generation system. Detailed Implementation

[0049] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments.

[0050] like Figure 1 As shown, a photovoltaic controller includes an input-side switch, a dual-mode Boost converter, and a multi-mode control module that controls the input-side switch and the dual-mode Boost converter.

[0051] The input-side switch is connected to the photovoltaic array and adopts a half-bridge circuit topology, including a lower bridge arm power switch device with a freewheeling resistor in parallel and an upper bridge arm power switch device for controlling the on / off of the input voltage on the photovoltaic array side.

[0052] The dual-boost converter includes two parallel boost branches, each consisting of a filter inductor and a half-bridge power switch. The input filter inductor is connected to the midpoint of the bridge arm of the input-side switch, and the half-bridge power switch includes an upper bridge arm power switch device and a lower bridge arm power switch device.

[0053] The multi-mode control module implements MPPT mode, constant voltage output mode and LPPT mode, and performs smooth switching control between MPPT mode, constant voltage output mode and LPPT mode.

[0054] In this system, the lower bridge arm power switch within the input-side switch remains normally off. During normal system operation, the upper bridge arm power switch within the input-side switch remains on, and its on-resistance is negligible compared to the freewheeling resistance. According to Kirchhoff's voltage divider law, the input voltage of the input-side switch is equal to the photovoltaic array voltage. In the shutdown state, the upper bridge arm power switch is off, and the equivalent resistance tends to infinity. According to the voltage divider law, the input voltage of the input-side switch is approximately zero, blocking the transmission path of the photovoltaic array voltage to the load unit.

[0055] like Figure 2 As shown, in the dual-boost converter, the two parallel boost branches implement alternating conduction control with a 180° phase difference. The upper and lower bridge power switching devices inside each boost branch use complementary PWM drive signals. Dead time is set for the upper and lower bridge power switching devices inside each boost branch to ensure circuit reliability. Within one switching cycle, the waveforms of the filter inductor currents of the two boost branches are the same but the phase difference is 180°. Their superposition effect significantly reduces the total ripple coefficient of the input current and achieves a frequency doubling effect on the equivalent ripple frequency.

[0056] Based on the ripple cancellation principle, while keeping the total input current ripple constant, the filter inductor parameters of each Boost branch are reduced, thereby minimizing the filter inductor current of the Boost branch. Controlled below zero, satisfying: , In the formula, I L For the filter inductor current, Δi L I is the peak-to-peak value of the inductor current ripple. o The output current is given by D, the duty cycle of the lower transistor is given by V. o Where L is the output voltage, f is the inductance value, and f is the output voltage. s t is the switching frequency. d For dead time, C oss The parasitic capacitance of the switching transistors allows the energy stored in the filter inductor to form a reverse freewheeling path through the body diodes of the upper and lower bridge arm power switching devices in the Boost branch during the dead time interval. This pre-discharges the junction capacitance of the lower bridge arm power switching device, creating a zero-voltage turn-on condition for it. The synchronous rectifier naturally meets the zero-voltage turn-on condition during the freewheeling phase. Through this mechanism, all power switching devices achieve soft-switching characteristics, effectively reducing switching losses and significantly improving the overall efficiency of the converter.

[0057] A multi-mode cooperative control method for the aforementioned photovoltaic controller, wherein MPPT mode is the default operating mode of the photovoltaic controller, and its operating process is as follows: Figure 3As shown, the specific control flow is as follows: Figure 4 As shown, in MPPT mode, the output voltage is given by a variable step size perturbation observation method. Then, the driving signals of each upper and lower bridge arm power switching device are obtained through voltage and current dual closed-loop control, so that the photovoltaic array works in the optimal power output state. Specifically, the variable step size perturbation observation method is used to determine the search direction based on the difference between the input voltage and power values ​​of the current cycle and the previous cycle, and to determine the search step size based on the power value difference. The output voltage of the photovoltaic array is periodically increased or decreased. If the output power increases, the same perturbation amount as in the current cycle is applied in the next control cycle; if the output power decreases, the opposite perturbation amount is applied in the next control cycle. After several perturbation cycles, the output power of the photovoltaic array gradually approaches the maximum power point.

[0058] During maximum power point tracking, the search step size ΔV k The adjustment principles for the disturbance amount are as follows: Where ΔV0 is the initial step size, P k With P k-1 These represent the power values ​​of the current cycle and the previous cycle, respectively, with l being the scaling factor. The search step size ΔV is adjusted according to certain principles. k Dynamically adjust ΔV based on the distance between the current operating point and the maximum power point. k Scale to [ΔV] min , ΔV max Between ], to ensure the speed and stability of the MPPT strategy, where ΔV min For the minimum perturbation step size, ΔV max The maximum perturbation step size is used. In practical applications, the search step size can be adjusted to a specific limit as needed.

[0059] In constant voltage output mode, the output voltage is maintained within a predetermined voltage range by adjusting the filter inductor current through current increment control. Specifically, in constant voltage output mode, when the photovoltaic array output voltage approaches its upper limit, the photovoltaic controller controls the output power to maintain a constant output voltage. limit The output voltage limit for the photovoltaic controller; when the output voltage approaches V... limit At this time, the photovoltaic controller reduces the output power by decreasing the photovoltaic array current, thereby stabilizing the output voltage at V. limit Hysteresis is set when switching between constant voltage output mode and other modes. In constant voltage output mode, when the output voltage is lower than V... limit When a certain threshold is reached, the constant voltage output mode is exited. The implementation process of the constant voltage output mode control strategy is as follows: Figure 5 As shown.

[0060] To unify the control quantities in constant voltage output mode with other control modes, a "current increment control" approach is adopted to replace the traditional voltage loop PI regulator, recording the filter inductor current value I when entering constant voltage output mode. Lref0 This causes the filter inductor current in this mode to be I Lref0 Based on the current given variation step size ΔI, L To increase or decrease the step size, detect the current output voltage of the photovoltaic controller and V. limit The deviation is calculated in real time by adjusting the current setpoint change step size ΔI. L The inductor current is given by the following formula: , .

[0061] In LPPT mode, different control algorithms are selected based on the operating mode at the previous moment. If in MPPT mode, the photovoltaic array voltage is adjusted; if in constant voltage output mode, the filter inductor current is adjusted to achieve finite power point tracking. LPPT mode is nested within the control strategies of MPPT mode and constant voltage output mode, which reduces the introduction of control variables and facilitates multi-mode switching control. Figure 6 As shown, the working process is as follows:

[0062] Before entering LPPT mode, the system is in MPPT mode: if the currently observed output power of the photovoltaic controller is greater than the set value P. ref Then it forces a forward search, V k+1 =V k +ΔV k V k V is the current search voltage. k+1 For the next search voltage, ΔV k V is the voltage search step size; otherwise, a reverse search is performed. k+1 =V k -ΔV k Simultaneously, by adaptively adjusting the search step size, rapid tracking of output power and high-precision steady-state control are achieved. The specific control process is as follows: Figure 7 As shown in the red dashed box;

[0063] Before entering LPPT mode, the output is in constant voltage output mode: if an LPPT command is present and the output voltage V o Less than its limit V limit If the current is exceeded, the system enters LPPT mode. In LPPT mode, if the real-time power is greater than the power limit, a forward search is performed, with the current setpoint changing in step size ΔI. L If the current is less than 0, reduce the current input; if the real-time power is less than the power limit, perform a reverse search, ΔI. L If the current is greater than 0, increase the current setpoint. The specific control process is as follows: Figure 7As shown in the blue dashed box.

[0064] Specifically, when switching operating modes, the system considers the comparison between external commands, the output power of the photovoltaic array, the actual value of the DC bus voltage and the preset threshold. By setting hysteresis, it avoids frequent switching between different operating modes due to small fluctuations in parameters, thus ensuring the stability of the system operation.

[0065] Combination Figure 8 As shown, in MPPT mode and constant voltage output mode, if a power limiting command is received and Enter LPPT mode, P k For the current power, P limit To limit power, k u This is the hysteresis width, which can be adjusted according to the actual situation.

[0066] In LPPT mode, if k d The hysteresis width can be adjusted according to the actual situation. Then, exit LPPT mode and enter MPPT mode. If a power limit shutdown command is received, or V o V is the output voltage. limit If the output voltage limit is reached, exit LPPT mode and enter constant voltage output mode;

[0067] In MPPT mode, if Enter constant voltage output mode. In constant voltage output mode, if... ΔV is the voltage hysteresis width, and the system enters MPPT mode.

[0068] like Figure 9 As shown, an integrator reserve scheme is proposed during the multi-mode switching process. When switching from constant voltage output mode to MPPT mode, the reference value I of the filter inductor current during constant voltage output mode is used. Lref The value is assigned to the integrator of the photovoltaic voltage control loop, so that the integrator has sufficient initial state reserve at the switching time to suppress the sudden change of control quantity caused by mode switching, avoid fluctuations in output voltage and current, and ensure a smooth transition of output performance.

[0069] In this embodiment, during use, by Figure 1 The control principle block diagram of the photovoltaic controller shown realizes multi-operating mode control and smooth switching. The input of the photovoltaic controller is the photovoltaic array voltage V. pv DC output voltage V o With the filter inductor current I LThe output is the duty cycle d of the power switch. The LPPT mode is nested within the MPPT mode and the constant voltage output mode. When in MPPT mode or transitioning from MPPT mode to LPPT mode, the photovoltaic voltage setpoint V is first obtained according to the control algorithm. pvref Then, the inductor current command I in MPPT mode is obtained through PI control. Lref1 When in constant voltage output mode or transitioning from constant voltage output mode to LPPT mode, the inductor current command I in constant voltage output mode is directly obtained from the control algorithm. Lref2 I is determined via hysteresis. Lref1 Or I Lref2 The output is given by the final inductor current I. Lref This is thus unified into two control variables V. pvref with I Lref I Lref The duty cycle d is obtained through PI control, and then driven by PWM modulation to drive the power switch, thereby achieving the effect of adjusting the output power of the photovoltaic system.

[0070] This invention relates to a photovoltaic controller, its soft-switching modulation technology, and a multi-mode collaborative control method. Based on a dual-boost topology, it precisely regulates the power conversion power through multiple operating modes according to different scenario requirements, and enables smooth switching between various operating modes through a multi-mode system control method. The photovoltaic controller topology can achieve input-output isolation and power on / off control through input-side switches, and can achieve boost DC-DC conversion through dual-boost. The soft-switching modulation technology of the dual-boost converter can achieve zero-voltage turn-on of all power switches, significantly improving system efficiency. The multi-mode control allows the photovoltaic controller to operate in maximum power point tracking, limited power output, and constant voltage output modes, adjusting the conversion power according to upper-level instructions. The operating mode switching conditions are supplemented by an integrator reserve scheme, enabling the photovoltaic controller to smoothly switch between the three operating modes. The limited power point tracking mode is nested within the other two operating modes, achieving unified control quantities under multiple operating modes, facilitating the design and implementation of control parameters.

[0071] In the above implementation examples, the descriptions of each embodiment have different focuses. For parts that are not described or recorded in detail in a certain embodiment, please refer to the relevant descriptions of other embodiments.

[0072] The embodiments described above 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 embodiments described above, 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, and should all be included within the protection scope of this application.

Claims

1. A soft-switching modulation method for a photovoltaic controller, characterized in that: The photovoltaic controller includes an input-side switch, a dual-mode Boost converter, and a multi-mode control module that controls the input-side switch and the dual-mode Boost converter. The input-side switch is connected to the photovoltaic array and adopts a half-bridge circuit topology, including a lower bridge arm power switch device with a freewheeling resistor connected in parallel and an upper bridge arm power switch device for controlling the on / off of the input voltage on the photovoltaic array side. The dual-boost converter includes two parallel boost branches, each of which consists of a filter inductor and a half-bridge power switch. The input filter inductor is connected to the midpoint of the bridge arm of the input-side switch, and the half-bridge power switch includes an upper bridge arm power switch device and a lower bridge arm power switch device. The multi-mode control module implements MPPT mode, constant voltage output mode and LPPT mode, and performs smooth switching control between MPPT mode, constant voltage output mode and LPPT mode; The lower bridge arm power switch in the input-side switch remains normally off. When the system is running normally, the upper bridge arm power switch in the input-side switch remains on, and the input voltage of the input-side switch is equal to the photovoltaic array voltage. When the system is off, the upper bridge arm power switch is off, the equivalent resistance tends to infinity, and the input voltage of the input-side switch is approximately zero, blocking the transmission path of the photovoltaic array voltage to the load unit. In the dual-boost converter, the two parallel boost branches are implemented with alternating conduction control with a 180° phase difference. The upper and lower bridge arm power switching devices inside each boost branch use complementary PWM drive signals. Dead time is set for the upper and lower bridge arm power switching devices inside each boost branch to ensure circuit reliability. Within one switching cycle, the waveforms of the filter inductor currents of the two boost branches are the same but the phase difference is 180°. Based on the ripple cancellation principle, while keeping the total input current ripple constant, the filter inductor parameters of each Boost branch are reduced, thereby minimizing the filter inductor current of the Boost branch. Controlled below zero, satisfying: In the formula, I L For the filter inductor current, Δ i L This represents the peak-to-peak value of the inductor current ripple. I o For output current, D The duty cycle of the lower tube. V o For output voltage, L Inductance value ，f s For switching frequency, t d Dead time, C oss The parasitic capacitance of the switching transistor allows the energy stored in the filter inductor to form a reverse freewheeling path through the body diodes of the upper and lower bridge arm power switching devices in the Boost branch during the dead time interval. This pre-discharges the junction capacitance of the lower bridge arm power switching device, creating a zero-voltage turn-on condition for the lower bridge arm power switching device.

2. A multi-mode cooperative control method for a photovoltaic controller, characterized in that: The photovoltaic controller includes an input-side switch, a dual-mode Boost converter, and a multi-mode control module that controls the input-side switch and the dual-mode Boost converter. The input-side switch is connected to the photovoltaic array and adopts a half-bridge circuit topology, including a lower bridge arm power switch device with a freewheeling resistor connected in parallel and an upper bridge arm power switch device for controlling the on / off of the input voltage on the photovoltaic array side. The dual-boost converter includes two parallel boost branches, each of which consists of a filter inductor and a half-bridge power switch. The input filter inductor is connected to the midpoint of the bridge arm of the input-side switch, and the half-bridge power switch includes an upper bridge arm power switch device and a lower bridge arm power switch device. The multi-mode control module implements MPPT mode, constant voltage output mode and LPPT mode, and performs smooth switching control between MPPT mode, constant voltage output mode and LPPT mode; MPPT mode is the default operating mode of photovoltaic controller. In MPPT mode, the output voltage is given by the variable step size perturbation observation method. Then, the driving signals of each upper and lower bridge arm power switching device are obtained through voltage and current dual closed-loop control, so that the photovoltaic array works in the optimal power output state. In constant voltage output mode, the output voltage is maintained within a predetermined voltage range by adjusting the filter inductor current through current increment control. In LPPT mode, different control algorithms are selected according to the operating mode at the previous moment. If it is in MPPT mode, the photovoltaic array voltage is adjusted. If it is in constant voltage output mode, the filter inductor current is adjusted to achieve finite power point tracking. When switching operating modes, the comparison between external commands, the output power of the photovoltaic array, the actual value of the DC bus voltage and the preset threshold is considered. By setting hysteresis, frequent switching due to small fluctuations in parameters between different operating modes is avoided, thus ensuring the stability of the system operation. In MPPT mode and constant voltage output mode, if a power limiting command is received and Enter LPPT mode. P k For the current power, P limit To limit power, k u The hysteresis width; In LPPT mode, if , k d If the hysteresis width is specified, exit LPPT mode and enter MPPT mode. If a power limit shutdown command is received, or , V o For output voltage, V limit If the output voltage limit is reached, exit LPPT mode and enter constant voltage output mode; In MPPT mode, if Enter constant voltage output mode. In constant voltage output mode, if... Δ V The voltage hysteresis width is set, and the system enters MPPT mode.

3. The multi-mode cooperative control method for a photovoltaic controller as described in claim 2, characterized in that: The LPPT mode is nested within the control strategies of the MPPT mode and the constant voltage output mode, and its working process is as follows: Before entering LPPT mode, the system is in MPPT mode: if the currently observed output power of the photovoltaic controller is greater than the set value. P ref Then it forces a forward search. V k+1 = V k +Δ V k , V k The current search voltage, V k+1 For the next search voltage, Δ V k This is the voltage search step size; otherwise, a reverse search is performed. V k+1 = V k -Δ V k Meanwhile, by adaptively adjusting the search step size, rapid tracking of output power and high-precision steady-state control are achieved. Before entering LPPT mode, the output is in constant voltage output mode: if an LPPT command is present and the output voltage is... V o Less than its limit V limit If the current is exceeded, the system enters LPPT mode. In LPPT mode, if the real-time power is greater than the power limit, a forward search is performed, with the current setpoint changing in step Δ. I L If the current is less than 0, reduce the current setpoint; if the real-time power is less than the limit power value, perform a reverse search, Δ I L >0, increase the current setting.

4. The multi-mode cooperative control method for a photovoltaic controller as described in claim 2, characterized in that: In MPPT mode, a variable step-size perturbation observation method is adopted. The search direction is determined based on the difference between the input voltage and power values ​​of the current cycle and the previous cycle, and the search step size is determined based on the power value difference. The output voltage of the photovoltaic array is periodically increased or decreased. If the output power increases, the same perturbation amount as in the current cycle is applied in the next control cycle; if the output power decreases, the opposite perturbation amount is applied in the next control cycle. After several perturbation cycles, the output power of the photovoltaic array gradually approaches the maximum power point. During maximum power point tracking, the search step size Δ V k The adjustment principles for the disturbance amount are as follows: Where, Δ V 0 is the initial step size. P k and P k-1 These are the power values ​​for the current cycle and the previous cycle, respectively. l The scaling factor is used to adjust the search step size Δ. V k Dynamically adjust Δ based on the distance between the current operating point and the maximum power point. V k Scale to [Δ V min , Δ V max Between ], where Δ V min For the minimum perturbation step size, Δ V max This represents the maximum perturbation step size.

5. The multi-mode cooperative control method for a photovoltaic controller as described in claim 2, characterized in that: In constant voltage output mode, the photovoltaic array output voltage approaches its upper limit, and the photovoltaic controller controls the output power to maintain a constant output voltage. V limit The output voltage limit for the photovoltaic controller; when the output voltage approaches... V limit At this time, the photovoltaic controller reduces the output power by decreasing the photovoltaic array current, thereby stabilizing the output voltage at a certain level. V limit Hysteresis is set when switching between constant voltage output mode and other modes. In constant voltage output mode, when the output voltage is lower than... V limit When a certain threshold is reached, the constant voltage output mode is exited. Record the filter inductor current value when entering constant voltage output mode. I Lref0 This causes the filter inductor current in this mode to be... I Lref0 Based on the reference, the current is given a variation step size Δ I L To increase or decrease the step size, detect the current output voltage of the photovoltaic controller and... V limit The deviation is calculated in real time by adjusting the step size Δ of the current setpoint change. I L The filter inductor current is given by the following formula: 。 6. The multi-mode cooperative control method for a photovoltaic controller as described in claim 2, characterized in that: When switching from constant voltage output mode to MPPT mode, the reference value of the filter inductor current in constant voltage output mode is used. I Lref The value is assigned to the integrator of the photovoltaic voltage control loop, so that the integrator has sufficient initial state reserve at the switching time to suppress the sudden change of control quantity caused by mode switching, avoid fluctuations in output voltage and current, and ensure a smooth transition of output performance.

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