Mismatched photovoltaic panel differential power processing control circuit system based on series LC resonance

Abstract

The invention discloses a mismatched photovoltaic panel differential power processing control circuit system based on series LC resonance, and the system does not depend on the model consistency of connected photovoltaic panels, and can be suitable for the high-efficiency output under the mismatching condition after the series connection of any number and model of photovoltaic panels. The circuit system absorbs the current of the current excess photovoltaic panel through the LC resonant cavity and the bidirectional switch and compensates the current to the vacant photovoltaic panel, and the current configuration between the photovoltaic panels is dynamically adjusted through the charging, resonance and discharging processes; the main controller is combined with the voltage monitoring module and the current monitoring module, executes a current balance control algorithm and a maximum power tracking algorithm, and controls charging and discharging of the LC resonant cavity to enable each photovoltaic panel to independently work at a maximum power point; the DC-DC circuit adjusts the back-end equivalent impedance to track the maximum power point. According to the invention, through an LC resonance differential power processing circuit architecture, precise current balance control and global energy optimization of any series photovoltaic panels in many extreme scenes such as space and the field can be realized, and the power generation efficiency and stability are improved.

Description

Technical field:

[0001] The present invention belongs to the technical field of photovoltaic power generation, and more specifically relates to a differential power processing control circuit system that realizes automatic current compensation control based on series LC resonance to achieve accurate maximum power point tracking of photovoltaic panels under photovoltaic power mismatch conditions. Background technology:

[0002] In the field of photovoltaic power generation, to meet the power and voltage requirements of the load, multiple photovoltaic panels are connected in series or parallel to increase output power. However, in actual operation, due to factors such as light intensity, temperature, dust coverage, and aging, photovoltaic panels can exhibit inconsistent output characteristics within the same array. The panels within a string are subject to current limitations imposed by the panel with the lowest output current, severely limiting the string's overall output power. This is known as the "short-board effect," and can even cause some modules to experience hot spots, severely impacting module lifespan and system safety. In extreme scenarios such as space and outdoor environments, limited conditions make it difficult to promptly replace panels of the same model when they experience damage, such as circuit interruptions, degradation of photovoltaic materials, or damage to the packaging structure. PV panels of different models with inconsistent output characteristics must be interconnected to meet the power requirements of back-end equipment. However, when different models of PV panels are operated in series, the short-board effect significantly limits output power, exacerbating mismatch issues and significantly reducing string efficiency and output power.

[0003] At present, the most common maximum power point tracking technology is full power processing. The DC-DC converter processes the total output power of all photovoltaic panels, such as the perturbation observation method and the conductance increment method. Although it can achieve maximum power point tracking of all series-connected photovoltaic panels to a certain extent, under the condition of photovoltaic panel output power mismatch, the maximum power point obtained by tracking is the residual maximum power point after the mismatch (local maximum power point), and the output power of the photovoltaic panel is not improved. In addition, some solutions using bypass diodes can alleviate the hot spot effect, but the improvement effect on power loss is limited, and it cannot fundamentally solve the power loss problem caused by mismatch. The second is differential power processing. At this time, the converter only needs to process the unmatched power between photovoltaic panels, that is, the power difference between the two. By compensating for voltage and current, it can effectively alleviate the mismatch between different photovoltaic panels and improve the output efficiency of each photovoltaic panel. However, the conventional differential power processing structure is relatively complex, and there are problems such as large device and circuit losses and inaccurate tracking of the maximum power point tracking algorithm.

[0004] Therefore, the present invention designs a differential power processing circuit system that realizes accurate maximum power point tracking of a single photovoltaic panel based on series LC resonance automatic current compensation control under the condition of series photovoltaic panel mismatch. The circuit system realizes global energy optimization while dynamically compensating and allocating current, and ensures that each submodule operates independently at its own maximum power point. Under the premise of reducing the number and complexity of the overall system components, efficient power improvement of series mismatched photovoltaic panels is achieved. This is of great significance for improving the power generation efficiency, stability and economy of photovoltaic power generation systems, and can effectively solve the shortcomings of existing technologies in dealing with mismatch problems. Summary of the invention:

[0005] In response to the shortcomings of the existing technology or the need for improvement, the present invention provides a differential power processing control circuit system based on series LC resonance to implement automatic current compensation control to achieve precise maximum power point tracking of photovoltaic panels. It has the characteristics of being able to independently process the power of series mismatched photovoltaic panels and enable each photovoltaic panel to operate at the maximum power point.

[0006] The circuit system for accurate maximum power point tracking of mismatched photovoltaic panels with automatic current compensation provided by the present invention mainly includes:

[0007] The series LC resonant differential power processing circuit is mainly composed of an LC resonant cavity composed of capacitors, inductors, and diodes. It is used to absorb the excess current of the mismatched photovoltaic panels and compensate for the current of the remaining photovoltaic panels that are short of the required amount, thus achieving current balancing to alleviate the photovoltaic panel mismatch problem and provide output power.

[0008] The bidirectional switch circuit is composed of a group of back-to-back connected NMOS transistors, which realizes the bidirectional conduction of current between the photovoltaic panel and the LC resonant cavity, realizes the charging and discharging of the LC resonant cavity, and realizes the current balance between different photovoltaic panels;

[0009] The MOS transistor gate isolation drive circuit mainly consists of a gate isolation driver chip and capacitors. The control signal of the main controller circuit is used as the low-voltage side, and the external 12V power supply voltage is used as the driving voltage to drive the bidirectional switch on the high-voltage side. This achieves signal isolation between the high-voltage and low-voltage sides.

[0010] The voltage and current monitoring circuit uses a high-precision voltage monitor to monitor the real-time voltage and current values ​​of the photovoltaic panel and send the data to the main controller;

[0011] The main controller circuit is used to collect real-time voltage information of the photovoltaic panel and perform logic processing to output the control signal and send it to the MOS tube gate isolation drive circuit;

[0012] The DC-DC conversion circuit, mainly composed of MOS tubes, inductors, capacitors, and diodes, can adjust the equivalent load of all photovoltaic panels connected in series, achieve maximum power point tracking, and adapt to the voltage and power requirements of the back-end equipment;

[0013] Furthermore, the LC resonant differential power processing circuit is mainly composed of a resonant cavity composed of an energy storage inductor, an energy storage capacitor and a diode. The photovoltaic panel charges the capacitor and inductor in the LC resonant cavity through a bidirectional switch. After charging is completed, the current forms a loop through the diode and resonance occurs. When the resonant current is maximum, the LC resonant cavity discharges the current-deficient photovoltaic panel through the bidirectional switch to achieve current balance between the mismatched photovoltaic panels, alleviate the mismatch problem of the photovoltaic panels, and improve the output power of all photovoltaic panels.

[0014] Furthermore, the bidirectional switch circuit is used to realize bidirectional flow of current between the photovoltaic panel and the LC resonant cavity to achieve current balance among all photovoltaic panels, and the signal of the main controller controls the conduction and shutdown after passing through the gate drive circuit.

[0015] Furthermore, the MOS transistor gate isolation drive circuit can establish electrical isolation between the low-voltage control circuit and the high-voltage power circuit, while achieving efficient and rapid driving of the MOS transistor gate in the bidirectional switch.

[0016] Furthermore, the voltage and current monitoring circuit is used to monitor the voltage and current of each photovoltaic panel in real time, and send the data to the main controller to provide real-time data support for achieving current balance, power regulation, efficiency improvement and stable operation of the photovoltaic panel.

[0017] Furthermore, the main controller circuit, primarily composed of a single-chip microcontroller and its peripheral circuits, serves as the core control unit of the entire circuit system. It processes the collected voltage and current signals from all photovoltaic panels and, by implementing a power balancing strategy and maximum power point tracking algorithm, outputs control signals to control bidirectional switches, achieving current balancing control and maximum power point tracking. This ensures that each photovoltaic module operates independently at its maximum power point, achieving global energy optimization through dynamic current balancing.

[0018] Furthermore, the DC-DC conversion circuit matches the output voltage to the input requirements of the subsequent equipment (such as an inverter, battery or load) through step-up or step-down conversion, and adjusts its own equivalent load impedance (i.e., changes the input side equivalent impedance) to match the current maximum power point impedance of all photovoltaic panels, thereby achieving stable operation at the maximum power point.

[0019] Furthermore, according to the working principle of the circuit system, it can be applied to the series connection of any number of photovoltaic panels, and the circuit system does not require the output characteristics of the photovoltaic panels to be uniform. Any photovoltaic panels can be interconnected, and each photovoltaic panel can still operate independently at its own maximum power point, achieving continuous, stable and efficient power output.

[0020] The present invention has at least the following beneficial effects:

[0021] This invention provides a synergistic approach, leveraging an LC resonant differential power processing circuit and a bidirectional switching circuit, to effectively address the "short-panel effect" and hot-spot effects caused by mismatches in series photovoltaic panels. This approach avoids the drawback of limiting the overall power of a series photovoltaic panel to the minimum current panel. Each sub-panel operates independently at its maximum power point under the precise control of a master controller, while achieving global energy optimization through dynamic current compensation. Compared to traditional full-power processing technologies, this significantly improves the power generation efficiency of all photovoltaic panels under mismatch conditions, fundamentally reducing power losses caused by mismatches.

[0022] The circuit system adopts a differential power processing architecture based on series LC resonance. Compared with conventional differential power processing solutions, it significantly reduces the number of energy storage elements and switching elements in the system, effectively reducing device and circuit losses. Combined with high-precision voltage and current monitoring and the main controller's current balancing strategy and maximum power point tracking algorithm, it achieves precise current balancing control and maximum power point tracking of mismatched components, improving system operation stability while reducing hardware costs and maintenance difficulty.

[0023] Furthermore, the present invention is independent of the model and output characteristics of the photovoltaic panels and can accommodate any number of photovoltaic panels with any characteristics connected in series. This is particularly true in extreme environments, such as space and the wild, where replacing identical panels is difficult. Existing photovoltaic panels can be directly connected to the circuit system of the present invention, and the system automatically compensates and controls to ensure continuous, stable, and efficient output power for all photovoltaic panels connected in series. This solution combines the dual advantages of independent tracking control of sub-panels with global current regulation, technically overcoming the limitations of existing solutions for handling mismatches in series photovoltaic panels and providing a new approach for the efficient use of solar energy resources. Description of the drawings:

[0024] Figure 1 This is a structural block diagram of a differential power processing control circuit system for mismatched photovoltaic panels based on series LC resonance according to the present invention;

[0025] Figure 2 A diagram showing the process of charging the LC resonant cavity by the circuit system of the present invention;

[0026] Figure 3 A diagram showing the process of self-resonance of the LC resonant cavity in the circuit system of the present invention;

[0027] Figure 4 A diagram showing the process of LC resonant cavity discharge in the circuit system of the present invention;

[0028] Figure 5 A structural block diagram of a bidirectional switch in the circuit system of the present invention;

[0029] Figure 6 This is a main circuit diagram of the main control part of the mismatched photovoltaic panel differential power processing control circuit system based on series LC resonance of the present invention;

[0030] Figure 7 This is a peripheral circuit diagram of the main control part of the mismatched photovoltaic panel differential power processing control circuit system based on series LC resonance of the present invention;

[0031] Figure 8 A circuit diagram of an optocoupler gate isolation drive of a mismatched photovoltaic panel differential power processing control circuit system based on series LC resonance according to the present invention;

[0032] Figure 9 A circuit diagram of a voltage and current monitoring circuit of a differential power processing control circuit system of a mismatched photovoltaic panel based on series LC resonance according to the present invention;

[0033] Figure 10 This is an experimental voltage curve diagram of the differential power processing control circuit system of the mismatched photovoltaic panel based on series LC resonance of the present invention;

[0034] Figure 11 This is an experimental output power curve of the mismatched photovoltaic panel differential power processing control circuit system based on series LC resonance of the present invention; Specific implementation method:

[0035] The present invention is further described in detail below with reference to specific embodiments.

[0036] Example:

[0037] like Figure 1As shown, the photovoltaic differential power processing circuit system based on series LC resonance of this embodiment includes: a photovoltaic panel series system, which is composed of multiple photovoltaic panels with inconsistent output characteristics connected in series, and their maximum power point current, maximum power point voltage and other parameters vary. In a traditional series system, the overall output current is limited by the photovoltaic panels with lower current, resulting in a total power lower than the sum of the power of each photovoltaic panel when operating independently; an LC resonant differential power processing circuit, which is composed of a resonant cavity composed of an energy storage inductor, an energy storage capacitor and a diode, and a bidirectional switching circuit composed of two sets of back-to-back NMOS transistors to achieve bidirectional current flow between the photovoltaic panel and the resonant cavity. The LC energy storage element works in conjunction with the bidirectional switch to absorb excess current from the excess photovoltaic panels and compensate for it to the photovoltaic panels with insufficient current, alleviating the mismatch problem. The main controller circuit uses a single-chip microcomputer as the core control unit, integrating an I2C communication module and a pulse width modulation output interface. It communicates with the voltage and current monitoring circuit in real time, detects the voltage and current signals, and outputs the control signal to the gate drive circuit through logical processing. The voltage and current monitoring circuit uses a voltage divider resistor network and a high-precision operational amplifier to achieve real-time acquisition of the photovoltaic panel voltage. The signal is input into the main controller after conditioning. The MOS tube gate optocoupler isolation drive circuit uses an optocoupler isolation chip and an external drive power supply to achieve electrical isolation between the low-voltage control signal and the high-voltage power circuit, ensuring the reliable conduction and shutdown of the bidirectional switch. The DC-DC conversion circuit, composed of a power MOS tube, inductor, and capacitor to form a step-up or step-down converter, adjusts the equivalent load of all series-connected photovoltaic panels to match the voltage requirements of the back-end equipment and track the maximum power point.

[0038] like Figure 2 、 3 As shown in Figures 4 and 5, in this embodiment, three photovoltaic panels are used as an example to illustrate the working principle of the photovoltaic differential power processing circuit with series LC resonance, where PV1 and PV2 are photovoltaic panels with the same parameters, i.e., photovoltaic panels with current limitation, and PV3 is a photovoltaic panel with a smaller peak current, i.e., a photovoltaic panel with excess current. After the system is started, the main controller obtains the initial voltage and current of the photovoltaic panel through the monitoring circuit, calculates the initial power and determines whether there is a mismatch. Figure 2 As shown in the figure, in this embodiment, the charging phase of the photovoltaic differential power processing circuit based on series LC resonance is shown. During the charging phase, two sets of bidirectional switches are connected in parallel to each photovoltaic panel. During normal operation, all switches are open. When the main controller detects through the current monitoring circuit that PV3 is an overcurrent photovoltaic panel and PV1 and PV2 are undercurrent photovoltaic panels, the compensation process is triggered. The main controller first controls the MOS transistors Q31, Q32, Q33, and Q34 corresponding to PV3 to conduct, forming a charging circuit: PV3 positive electrode, bidirectional switch, energy storage inductor, energy storage capacitor, and PV3 negative electrode.

[0039] like Figure 3As shown, in this embodiment, the resonance stage in the photovoltaic differential power processing circuit based on series LC resonance. After the energy storage of the energy storage capacitor is completed in the charging stage, the system enters the resonance stage. At this time, all bidirectional switches cut off the connection between the photovoltaic panel and the resonant cavity, and the energy storage capacitor, energy storage inductor and diode form an independent series LC resonant circuit. In this stage, within the first quarter of the resonant cycle, the current direction is consistent with the charging stage; after entering the second quarter of the cycle, the current direction is reversed, and at this time the current direction is consistent with the compensation requirement. The main controller can accurately capture the moment of current direction reversal by calculating the resonant phase in real time, that is, the interval from zero crossing to reverse increase to the peak, in preparation for the discharge stage.

[0040] like Figure 4 As shown in the figure, in this embodiment, the resonant stage of the photovoltaic differential power processing circuit based on series LC resonance is shown. When the direction of the LC circuit current in the resonant stage switches to align with the current direction of the photovoltaic panels (i.e., PV1 and PV2) with insufficient current, the main controller turns on the corresponding bidirectional MOS switches Q11, Q12, Q23, and Q24, forming a charging circuit: energy storage inductor → switch path → photovoltaic panel positive terminal → photovoltaic panel interior → photovoltaic panel negative terminal → switch reverse path → energy storage capacitor. The electromagnetic energy stored in the resonant cavity is compensated for PV1 and PV2 in the form of forward current. During this period, the main controller monitors the current of each photovoltaic panel in real time and dynamically adjusts the switch on time to ensure that the compensation current accurately replenishes the shortfall of PV1 and PV2, ensuring that PV1 and PV2 operate near their maximum power point current, allowing PV1 and PV2 to operate at their own maximum power point. This stage uses soft switching technology to achieve efficient energy transmission, eliminating traditional hard switching losses. Combined with the multi-PV panel coordinated control strategy, it overcomes the "short board effect" of series-connected photovoltaic panels, allowing each photovoltaic panel to independently track its maximum power point while achieving global current balance.

[0041] like Figure 5 As shown, in this embodiment, the bidirectional switch circuit is composed of a pair of NMOS transistors (such as Q11 and Q12) connected back to back to form a bidirectional conduction path, and the gate is connected to the drive signal of the gate optical coupler isolation chip.

[0042] like Figure 6 As shown in Figure 7, in this embodiment, the main controller circuit is based on the STM32F407ZGT6 microcontroller. The peripheral circuits include an ADC sampling interface, a PWM output module, a clock circuit (with an external crystal oscillator), and a reset circuit (NRST). Its core functions are to process voltage and current signals in real time, execute the maximum power point tracking algorithm and current balancing strategy, and output switch control signals.

[0043] like Figure 8As shown, in this embodiment, the optocoupler isolation drive circuit uses a high-speed optocoupler chip to achieve electrical isolation between the low-voltage control signal (3.3V microcontroller output) and the high-voltage power circuit (12V drive voltage). The input side receives the PWM signal from the main controller, and the output side drives the NMOS transistor gate after capacitor filtering, ensuring the reliability and safety of the switching operation.

[0044] like Figure 9 As shown, in this embodiment, the voltage and current monitoring circuit uses the INA226 high-precision bidirectional power supply monitoring chip to achieve high-precision real-time acquisition of the photovoltaic panel voltage and current.

[0045] like Figure 10 As shown, in this embodiment, the following photovoltaic panels are used to carry out the experiment: two 150W photovoltaic panels: standard test conditions (STC, photovoltaic panel temperature 25°C, light intensity 1000W / m 2 , AM1.5G spectrum), the maximum power voltage is 17.28V, the maximum power current is 8.68A; 1 100W photovoltaic panel: standard test conditions (STC, photovoltaic panel temperature 25℃, light intensity 1000W / m 2 , AM1.5G spectrum), the maximum power voltage is 19.44V, and the maximum power current is 5.14A. The experimental illumination conditions are sunlight, and the light intensity is 360W / m 2 The surface temperature of the photovoltaic panels is 50°C. The curve shows the load voltage change after the photovoltaic panels are connected and differential power processing is enabled. At approximately 0.2 seconds, three photovoltaic panels are connected in series to the system. After differential power processing is enabled at approximately 0.4 seconds, the load voltage significantly increases and stabilizes.

[0046] like Figure 11 As shown, in this embodiment, the following photovoltaic panels are used to carry out the experiment: two 150W photovoltaic panels: standard test conditions (STC, photovoltaic panel temperature 25°C, light intensity 1000W / m 2 , AM1.5G spectrum), the maximum power voltage is 17.28V, the maximum power current is 8.68A; 1 100W photovoltaic panel: standard test conditions (STC, photovoltaic panel temperature 25℃, light intensity 1000W / m 2 , AM1.5G spectrum), the maximum power voltage is 19.44V, and the maximum power current is 5.14A. The experimental illumination conditions are sunlight, and the light intensity is 360W / m 2 , the PV panel surface temperature was 50°C. The curve shows the output power change after connecting the PV panels and enabling differential power processing. At approximately 0.2 seconds, three PV panels were connected in series to the system. After enabling differential power processing at approximately 0.4 seconds, the output power increased significantly and stabilized.

Claims

1. A differential power processing control circuit system for mismatched photovoltaic panels based on series LC resonance, characterized in that: Mainly include: A photovoltaic panel system may be composed of multiple interconnected photovoltaic panels with inconsistent output characteristics, and their characteristic parameters such as maximum power point current and maximum power point voltage may vary; The series LC resonant differential power processing circuit consists of a resonant cavity formed by an energy storage inductor, an energy storage capacitor, and a diode. It is used to absorb the excess current of the mismatched photovoltaic panels and compensate for the current of the remaining photovoltaic panels that are short of the required amount. This achieves current balancing to alleviate the mismatch problem of the series-connected photovoltaic panels and improve the output power. A bidirectional switch circuit, comprising a set of back-to-back connected NMOS transistors, enables bidirectional conduction of current between the photovoltaic panel and the LC resonant cavity, is used for charging and discharging the LC resonant cavity, and achieves current balancing between the photovoltaic panels; The MOS tube gate isolation drive circuit is composed of a gate isolation drive chip and a capacitor. It uses the control signal of the main controller circuit as the low-voltage side and the external power supply 12V voltage as the driving voltage to drive the bidirectional switch on the high-voltage side to achieve signal isolation between the high-voltage side and the low-voltage side. The voltage and current monitoring circuit uses a high-precision voltage monitor to monitor the real-time voltage and current values ​​of all photovoltaic panels and send the data to the main controller circuit; A main controller circuit is used to collect real-time voltage and current data of the photovoltaic panel and execute a maximum power point tracking algorithm and a current balancing strategy, thereby outputting a control signal and sending it to the MOS tube gate isolation drive circuit; The DC-DC conversion circuit, consisting of MOS tubes, inductors, capacitors, and diodes, is used to adjust the equivalent load of all photovoltaic panels connected in series, achieve maximum power point tracking, and adapt to the voltage and power requirements of the back-end equipment.

2. The mismatched photovoltaic panel differential power processing circuit control system based on series LC resonance according to claim 1, characterized in that: In the LC resonant differential power processing circuit, the photovoltaic panel charges the capacitor and inductor in the LC resonant cavity through the bidirectional switch. After charging is completed, the current forms a loop through the diode and resonance occurs. When the resonant current is maximum, the LC resonant cavity discharges the photovoltaic panel through the bidirectional switch to achieve current balancing between the mismatched photovoltaic components.

3. The mismatched photovoltaic panel differential power processing control circuit system based on series LC resonance according to claim 1, characterized in that: The bidirectional switch circuit is controlled to be turned on and off by a signal from a main controller circuit after passing through the gate drive circuit, so as to realize bidirectional flow of current between the photovoltaic panel and the LC resonant cavity.

4. The mismatched photovoltaic panel differential power processing control circuit system based on series LC resonance according to claim 1, wherein: The MOS transistor gate isolation drive circuit establishes electrical isolation between the low-voltage control circuit and the high-voltage power circuit, and simultaneously realizes efficient and rapid driving of the MOS transistor gate in the bidirectional switch.

5. The mismatched photovoltaic panel differential power processing control circuit system based on series LC resonance according to claim 1, wherein: The voltage and current monitoring circuit monitors the voltage and current of each photovoltaic panel in real time and sends the data to the main controller circuit, providing real-time data support for achieving current balance, power regulation, efficiency improvement and stable operation of the system among photovoltaic panels.

6. The mismatched photovoltaic panel differential power processing control circuit system based on series LC resonance according to claim 1, characterized in that: The main controller circuit is composed of a single-chip microcomputer chip and its peripheral circuits. As the core control unit, it processes the collected voltage and current signals of all photovoltaic panels, executes the current balancing strategy and the maximum power point tracking algorithm, outputs a control signal to control the bidirectional switch, realizes current balancing control and maximum power tracking, ensures that each submodule operates independently at its own maximum power point, and achieves global energy optimization through dynamic current balancing.

7. The mismatched photovoltaic panel differential power processing control circuit system based on series LC resonance according to claim 1, characterized in that: The DC-DC conversion circuit makes the output voltage of all series-connected photovoltaic panels match the input requirements of the back-end equipment through step-up or step-down conversion, and adjusts its own equivalent load resistance to match the current maximum power point impedance of the series-connected photovoltaic panels, so that the photovoltaic panels can operate stably at the maximum power point.

8. The mismatched photovoltaic panel differential power processing control circuit system based on series LC resonance according to any one of claims 1 to 7, characterized in that: It is applicable to photovoltaic systems consisting of any number of photovoltaic panels connected in series, and does not require the output characteristics of the photovoltaic panels to be uniform. Any photovoltaic panels can be connected in series so that each photovoltaic panel can work independently at its maximum power point, achieving continuous, stable and efficient energy supply to back-end equipment.

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