Self-adaptive photovoltaic panel power generation control device and method

Abstract

The invention relates to the technical field of photovoltaic power generation systems, solves the problems that in a high-power mode, devices cannot be selected, and heating loss of the devices is large, and particularly relates to a self-adaptive photovoltaic panel power generation control device and method.The self-adaptive photovoltaic panel power generation control device comprises a front-end solar panel side, a rear-end battery pack side and an LLC circuit which is arranged corresponding to the front-end solar panel side and has constant output voltage; the output side of the LLC circuit is provided with an adaptive circuit which controls the at least two groups of LLC circuits to be in a series connection mode or a parallel connection mode according to the current voltage of the front-end solar panel side. According to the invention, the voltage accessed to the solar panel by a client can be automatically identified, the rear-end series-parallel connection of the LLC circuit can be realized through the controllable tube Q1, the BOOST circuit is accessed to the vehicle battery pack, the maximum power point of the photovoltaic module can be effectively tracked through the controller MPPT, and the optimal electric energy can be obtained under different illumination conditions.

Description

Technical Field

[0001] The present invention relates to the technical field of photovoltaic power generation systems, and in particular to an adaptive photovoltaic panel power generation control device and method. Background Art

[0002] Photovoltaic power generation system is a power generation system that uses the photovoltaic effect of semiconductor materials to convert solar radiation energy into electrical energy. The energy of photovoltaic power generation system comes from inexhaustible solar energy, which is a clean, safe and renewable energy. The photovoltaic power generation process does not pollute the environment or damage the ecology. Therefore, in recent years, photovoltaic power generation systems have been widely used in large-scale photovoltaic power stations, commercial rooftop power stations, household rooftop power stations, buildings, automobiles and other fields. Photovoltaic power generation system consists of photovoltaic arrays, high-frequency DC / DC boost circuits, power electronic converters (inverters) and system monitoring parts.

[0003] Photovoltaic power generation systems are usually used in the automotive field to charge vehicle batteries. In recent years, with the continuous development of new energy vehicles, pure electric vehicles have also achieved unprecedented development and the continuous improvement of photovoltaic power generation technology. The demand for photovoltaic power generation systems is not limited to charging vehicle batteries, and the demand for power batteries has become the mainstream. However, charging new energy vehicles through solar panels cannot be directly charged due to different electrical level systems. It is necessary to convert the electrical topology and then directly connect to the battery end to achieve maximum efficiency charging.

[0004] like Figure 1 The electrical topology shown is a conventional solar direct charging circuit, which often uses parallel connection to provide greater charging power. Since the voltage on the solar panel side is usually low (30V or 60V), the power will increase after parallel connection, and the current will become very large, resulting in the inability to select components on the LLC side (L1 / C1 / L2). At the same time, due to the different voltage levels of solar panels used in the market, different inductors need to be replaced to meet the LLC resonance point in order to achieve soft switching control and achieve maximum efficiency. Therefore, when using low-voltage solar panels, without changing the software and hardware, the voltage on the right side of the LLC will also decrease accordingly, and the BOOST side will not be able to achieve maximum efficiency control, affecting the overall photovoltaic charging efficiency. Summary of the invention

[0005] In view of the deficiencies in the prior art, the present invention provides an adaptive photovoltaic panel power generation control device and method, which solves the technical problems that conventional electrical topology causes LLC side components to be incompatible with each other, and when low-voltage solar panels are used, the BOOST side will not be able to achieve maximum efficiency control, affecting the overall photovoltaic charging efficiency.

[0006] To solve the above technical problems, the present invention provides the following technical solutions: an adaptive photovoltaic panel power generation control device, comprising at least two groups of front-end solar panel sides, a rear-end battery group side serving as a power battery for a new energy vehicle, and an LLC circuit with a constant output voltage arranged corresponding to the front-end solar panel side. An adaptive circuit is arranged on the output side of the LLC circuit for controlling at least two groups of LLC circuits to be in series mode or parallel mode according to the current voltage of the front-end solar panel side. The output side of the adaptive circuit is provided with a BOOST circuit for pumping up the voltage on the LLC circuit side again and then connecting it to the rear-end battery group side.

[0007] Further, the adaptive circuit includes fast recovery diodes D5, D6 and a field effect transistor MOSFET Q1 respectively connected to the output sides of the two groups of LLC circuits;

[0008] When the current voltage when the front-end solar panel is connected is high voltage, the field effect tube MOSFET Q1 is in the off state, and the outputs of the two sets of LLC circuits are connected in parallel through the fast recovery diodes D5 and D6;

[0009] When the current voltage when the front-end solar panel is connected is low voltage, the field effect transistor MOSFET Q1 is in a closed state, and the outputs of the two groups of LLC circuits are connected in series through the field effect transistor MOSFET Q1.

[0010] Furthermore, the BOOST circuit includes an inductor L5 connected in sequence to the positive electrode of the output side of the adaptive circuit, and a fast recovery diode D7 for current single-phase output, a silicon carbide MOSFET Q2 is connected in parallel between the positive and negative electrodes of the output side of the adaptive circuit, and the drain of the silicon carbide MOSFET Q2 is connected between the inductor L5 and the fast recovery diode D7.

[0011] Furthermore, the BOOST circuit also includes a filter capacitor C3 connected in parallel between the positive electrode and the negative electrode of the output side of the adaptive circuit, which is used for DC smoothing.

[0012] Furthermore, a discharge circuit connected in parallel to the positive and negative electrodes is provided on the output side of the BOOST circuit, and the discharge circuit includes a field effect transistor MOSFET Q3, a discharge resistor and a thin film capacitor.

[0013] The technical solution also provides a maximum power point tracking method applied to the above-mentioned adaptive photovoltaic panel power generation control device, which includes the following process:

[0014] S1. Set the initial voltage U o and current I o , set the step size and sampling time to complete parameter initialization;

[0015] S2, detecting the input voltage on the front-end solar panel side, and switching the series-parallel mode between at least two groups of LLC circuits through an adaptive circuit according to the input voltage;

[0016] S3, measure the voltage V(k) and current I(k) of the front solar panel side in real time through the voltage and current sensors, and calculate the current power P(k);

[0017] S4, compare the current power P(k) with the power P(k-1) of the previous sampling point, and adjust the step size according to the increase or decrease of the current power P(k);

[0018] If P(k)>P(k-1), the current power P(k) increases, and the step size continues to be adjusted in the direction of the current voltage U; if the voltage U(k)>U(k-1), the current voltage U=U+ΔU is increased, and if U(k)<U(k-1), the current voltage U=U-ΔU is reduced;

[0019] If P(k)=P(k-1), return to measuring output power;

[0020] If P(k)<P(k-1), the current power P(k) is reduced, and the step size is adjusted in the opposite direction of the current voltage U; if U(k)<U(k-1), the current voltage U=U-ΔU is reduced, and if U(k)>U(k-1), the current voltage U=U+ΔU is increased;

[0021] S5, updating the output of the controller MPPT according to the step adjustment result, changing the input of the load or inverter to achieve dynamic adjustment step of the voltage;

[0022] S6. Repeat the above steps S3-S5 to form a closed-loop control system to continuously optimize power output.

[0023] Furthermore, in step S2, the specific process includes:

[0024] The input voltage on the front-end solar panel side is detected in real time. If the input voltage is a low voltage, the field effect tube Q1 is closed, and the LLC circuits are in a series mode; if the input voltage is a high voltage, the field effect tube Q1 is disconnected, and the LLC circuits are in a series mode.

[0025] Furthermore, the bottom voltage is 15V-30V, and the high voltage is 30-60V.

[0026] By means of the above technical solution, the present invention provides an adaptive photovoltaic panel power generation control device and method, which has at least the following beneficial effects:

[0027] 1. The present invention adopts the front-end parallel design of LLC circuit, which solves the problems of inability to select devices and large heat loss of devices in high-power mode. The LLC back-end adaptive series-parallel design can automatically identify the voltage of the customer's solar panel, and realize the back-end series-parallel connection of LLC circuit through the controllable tube Q1. The BOOST circuit is connected to the vehicle battery pack, and the maximum power point of the photovoltaic module can be effectively tracked through the controller MPPT to ensure that the optimal electric energy can be obtained under different lighting conditions.

[0028] 2. The present invention can achieve access to solar panels with different voltage specifications by setting an adaptive circuit and controlling the disconnection of components D5, D6, and Q1, thereby solving the problem that components L1, C1, and L2 are not compatible with high and low voltage photovoltaic panels.

[0029] 3. The present invention adopts an MPPT controller to monitor the output voltage and current of the photovoltaic module in real time, and achieves maximum power output by adjusting the working point. It is directly connected to the high-voltage battery pack through the BOOT circuit to realize charging of the battery pack in a wide voltage range to meet the voltage charging requirements of different vehicle models.

[0030] 4. The present invention adopts a method combining particle swarm algorithm and perturbation observation method, which can improve tracking speed and accuracy, solve local optimal situations, and dynamically adjust the step size according to environmental changes to avoid over-adjustment caused by frequent adjustments under rapidly changing conditions.

[0031] 5. The present invention can significantly improve the energy output of the photovoltaic system by accurately tracking the maximum power point, reduce output fluctuations caused by environmental changes, improve the working stability of the system, and reduce the load fluctuation of the system by optimizing operations, thereby extending the service life. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] The drawings described herein are used to provide a further understanding of the present application and constitute a part of the present application. The illustrative embodiments of the present application and their descriptions are used to explain the present application and do not constitute an improper limitation on the present application. In the drawings:

[0033] Figure 1 It is a circuit diagram of the conventional solar direct charging topology in the present invention;

[0034] Figure 2 A circuit diagram of the photovoltaic panel adaptive electrical topology in the present invention;

[0035] Figure 3 The circuit diagram of the high voltage LLC parallel working mode of the photovoltaic panel in the present invention;

[0036] Figure 4 A circuit diagram of the low voltage LLC series working mode of the photovoltaic panel in the present invention;

[0037] Figure 5 A circuit diagram of the MPPT discharge mode of the controller in the present invention;

[0038] Figure 6 It is a corresponding relationship diagram between particle position and output power in the present invention;

[0039] Figure 7 Schematic diagram of updating the particle position in the present invention;

[0040] Figure 8 It is a schematic diagram of the PV curve in the present invention;

[0041] Fig. 9 It is a schematic diagram of the relative position of the working point at the maximum power point MPP in the present invention;

[0042] Fig.10 is a flow chart of the perturbation and observation method in the present invention;

[0043] Fig.11 This is a result diagram of the photovoltaic simulator in the present invention. DETAILED DESCRIPTION

[0044] In order to make the above-mentioned purposes, features and advantages of the present invention more obvious and easy to understand, the present invention is further described in detail below with reference to the accompanying drawings and specific implementation methods, so that the implementation process of how the present application uses technical means to solve technical problems and achieve technical effects can be fully understood and implemented accordingly.

[0045] Currently, the on-board photovoltaic controller has a single function, which is mainly to charge the vehicle battery and convert DC low voltage to low voltage. The battery mainly provides power for the vehicle's low-voltage electrical system. It does not generate obvious economic benefits, and they are all independent systems that do not communicate with the on-board system, so the economic benefits generated cannot be calculated.

[0046] like Figure 1 The electrical topology shown is a conventional solar direct charging circuit. On the front solar panel side, a multi-stage parallel connection is often used to provide greater power. The voltage standards of solar panels from different manufacturers are also different. Here, this embodiment assumes 30V and 60V. The right side is the LLC circuit, which is a resonant circuit that controls the switching frequency to achieve a constant output voltage, including an inductor, a capacitor, and a transformer. The LLC circuit reduces the switching loss of the power supply through soft switching technology, improves efficiency and power density. The right side is the BOOST circuit, which pumps up the LLC side voltage again through switch control and inductors and other components to reach the voltage of the new energy vehicle battery pack, and achieves maximum power charging through MPPT.

[0047] But there are the following problems in actual testing:

[0048] 1. On the front-stage solar panel side, parallel connection is often used to provide greater charging power. Since the voltage on the solar panel side is usually low (30V or 60V), the power will increase after parallel connection, and the current will become very large, resulting in the inability to select components on the LLC side (L1 / C1 / L2). For example, if the voltage on the solar panel side is 30V, to achieve an input power of 2kW, the current needs to reach 67A, so the selection, carrying capacity, and efficiency of the components are greatly challenged.

[0049] 2. When the LLC circuit operates at the resonance point and the gain is 1, the voltage is boosted by setting the turns ratio of transformer L2. The calculation formula of LLC resonant frequency is:

[0050]

[0051] Where, f is the LLC resonant frequency; L is the inductance; C is the capacitance; and π is 3.14.

[0052] The gain is calculated as:

[0053] V o =n*V in

[0054] Where n is the primary-to-secondary turns ratio, ensuring maximum efficiency; V o is the output voltage; V in is the input voltage. Due to the different voltage levels of solar panels used in the market, different inductors L1 need to be replaced to meet the LLC resonance point in order to achieve soft switching control and achieve maximum efficiency. (For detailed principles, please refer to: In-depth analysis of LLC resonant converter circuit design and its working principle (https: / / baijiahao.baidu.com / s?id=1799899002136276956&wfr=spider&for=pc)).

[0055] 3. When using low-voltage solar panels, without changing the software and hardware, the voltage on the right side of LLC will also decrease accordingly, and the BOOST side will not be able to achieve maximum efficiency control, affecting the overall photovoltaic charging efficiency.

[0056] 4. When disassembling and repairing the mainboard, due to the presence of large capacitors in the circuit board, the mainboard will be charged for a long time, and there is a risk of electric shock.

[0057] In summary, conventional solar direct charging circuits have the following disadvantages:

[0058] 1) In the case of 2KW low voltage 30V solar panel, the front-end LLC circuit current is large and the device cannot be selected;

[0059] 2) Components L1 / C1 / L2 are not compatible with the two power supply systems of 2KW solar panels (30V or 60V);

[0060] 3) The maximum efficiency control cannot be achieved under the two power supply modes of 2KW solar panels (30V or 60V);

[0061] 4) After the mainboard is powered off, large capacitors remain charged for a long time.

[0062] In the face of the drawbacks of conventional solar direct charging circuits, this embodiment uses LLC+PFC topology to achieve maximum solar power charging through MPPT control, without changing the software and hardware, to achieve the functions and optimal control of the photovoltaic controller. Please refer to Figure 2-Figure 5 This embodiment proposes an adaptive photovoltaic panel power generation control device. This embodiment takes two front-end solar panel sides as examples, including solar panel 1N side and solar panel 2N side, and of course, solar panel 3N side, solar panel 4N side, etc. The LLC circuit with a constant output voltage set on the front-end solar panel side, that is, the solar panel 1N side and the solar panel 2N side both correspond to an identical LLC circuit. Figure 2 As shown, M1, M2, M3, and M4 are all controllable power tubes, and L1, C1, L3, D1, and D2 are implemented in LLC1 circuit; M5, M6, M7, and M8 are all controllable power tubes, and L2, C2, L4, D3, and D4 are implemented in LLC2 circuit. Figure 2 The photovoltaic panel adaptive electrical topology circuit diagram shown includes the front-end solar panel side, LLC circuit, adaptive circuit, BOOST circuit, and the back-end battery pack side. D5, D6, and Q1 are the adaptive circuit implementation methods; L5, Q2, and D7 are the BOOST circuit implementation methods. The above devices are all necessary devices, which are the smallest components of the LLC circuit, adaptive circuit, and BOOST circuit and cannot be deleted. C3 is a filter circuit with a DC smoothing function, and Q3 is a discharge circuit to achieve a rapid discharge function. The lack of C3 and Q3 does not affect the operation of the overall circuit. The selection of components is shown in Table 1:

[0063] Table 1 Component parameter selection

[0064]

[0065]

[0066] An adaptive circuit is provided on the output side of the LLC circuit for controlling at least two groups of LLC circuits to be in series mode or parallel mode according to the current voltage on the front-end solar panel side. A BOOST circuit is provided on the output side of the adaptive circuit for pumping up the voltage on the LLC circuit side again and then connecting it to the rear-end battery pack side, wherein the rear-end battery pack side is the power battery of the new energy vehicle in this embodiment.

[0067] In this embodiment, the front-stage LLC circuit is connected in parallel to reduce the current on L1, C1, and L3, which can solve the problem of the inability to select devices in the market; the voltage of the front-end photovoltaic panel is detected by software, and the D5, D6, and Q1 components are controlled to be disconnected to realize the series-parallel mode of the LLC circuit, which can meet the requirements of the LLC circuit working at the resonance point under the high and low voltage photovoltaic panels; the back end is connected to the battery pack through the BOOT circuit, and the maximum power charging is realized through the MPPT controller to meet the charging requirements of the wide voltage battery pack. Among them, the software uses the MPPT controller to monitor the output voltage and current of the photovoltaic module in real time, and achieves the maximum power output by adjusting the working point. The MPPT controller and the vehicle communication use CAN communication and interact according to the prescribed communication protocol. The high-voltage battery pack is directly connected through the BOOT circuit to realize the wide voltage range charging of the battery pack to meet the voltage charging requirements of different models. In this embodiment, the circuit modal analysis takes 30V and 60V as examples, but is not limited to this voltage.

[0068] The MPPT tracking algorithm used in this embodiment is not limited to: perturbation observation method, incremental conduction method, etc. Application scenarios of the MPPT tracking algorithm include:

[0069] Photovoltaic power generation system: mainly used for solar panels to improve the efficiency of photovoltaic power generation.

[0070] Wind energy system: It can also be used in wind power generation to optimize power generation performance.

[0071] Battery Charging: Used to optimize the battery charging process, especially in charging systems for renewable energy sources.

[0072] The adaptive circuit includes fast recovery diodes D5 and D6 and MOSFET Q1 connected to the output sides of the two LLC circuits respectively. When the current voltage when the front solar panel is connected is high, the MOSFET Q1 is in the off state, and the outputs of the two LLC circuits are connected in parallel through the fast recovery diodes D5 and D6. Please refer to Figure 3The circuit diagram of the high voltage LLC parallel working mode of the photovoltaic panel is shown. When multiple 60V photovoltaic panels are connected, they can be connected in parallel and evenly to the solar panel 1N and solar panel 2N ports. The 60V voltage passes through the LLC circuit. When working at the resonance point, the voltage on the right side of L3 and L4 is 300V (not limited to this value). When the system detects that the voltage at the solar panel terminal is 60V, Q1 is in the disconnected state, and the LLC output is connected in parallel through D5 and D6. The fast recovery diodes D5 and D6 play a parallel role ( Figure 3 The red line is positive and the green line is negative), the voltage of C3 is 300V at this time (not limited to this value), and it is connected to the vehicle battery through the BOOST circuit and charged at maximum power through MPPT.

[0073] When the current voltage when the front solar panel is connected is low, the MOSFET Q1 is in a closed state, and the outputs of the two LLC circuits are connected in series through the MOSFET Q1. Figure 4 The circuit diagram of the low-voltage LLC series working mode of the photovoltaic panel is shown. When multiple 30V photovoltaic panels are connected, they can be connected in parallel and evenly to the solar panel 1N and solar panel 2N ports. The 30V voltage passes through the LLC circuit. When working at the resonance point, the voltage on the right side of L3 and L4 is 150V (not limited to this value). When the system detects that the voltage at the solar panel terminal is 30V, Q1 is in a closed state, and the LLC output is connected in series through Q1. The Q1 controllable tube plays a series role ( Figure 4 The red line is positive, the orange is in series, and the green line is negative). The voltage of C3 is 300V at this time (not limited to this value). It is connected to the vehicle battery through the BOOST circuit and charged at maximum power through MPPT.

[0074] The BOOST circuit includes an inductor L5 connected to the positive electrode of the output side of the adaptive circuit in sequence, and a fast recovery diode D7 for current single-phase output. A silicon carbide MOSFET Q2 is connected in parallel between the positive and negative electrodes of the output side of the adaptive circuit, and the drain of the silicon carbide MOSFET Q2 is connected between the inductor L5 and the fast recovery diode D7. The BOOST circuit also includes a filter capacitor C3 connected in parallel between the positive and negative electrodes of the output side of the adaptive circuit for DC smoothing. The output side of the BOOST circuit is provided with a discharge circuit connected in parallel to the positive and negative electrodes, and the discharge circuit includes a field effect transistor MOSFET Q3, a discharge resistor and a film capacitor.

[0075] Please refer to Figure 5, shows the circuit diagram of the photovoltaic controller discharge mode. When the battery pack voltage is detected to be 0V, the capacitor voltage in the circuit is sufficient to support the chip circuit, and the maintenance signal switch signal is enabled. At this time, the software controls Q3 to close, and the discharge resistor is connected to the bus circuit to discharge the voltage in the circuit, quickly discharging C3 and all the voltages on the bus until the voltage is lower than 3.3V. By adding a diode D7 at the output end, it plays the role of single-phase current output, output backflow prevention, and prevent the high voltage of the whole vehicle from backflowing into the photovoltaic controller, saving battery costs as much as possible.

[0076] The present invention can maximize power and convert solar energy into electrical energy, which is applied to the roof of a truck and charges the vehicle battery through a photovoltaic controller. The front-end parallel design of the LLC circuit solves the problems of the inability to select devices and large heat loss of devices in high-power mode. The back-end adaptive series-parallel design of the LLC circuit can automatically identify the voltage of the customer's solar panel, and realize the series-parallel connection of the LLC back-end through the controllable tube Q1. The BOOST circuit is connected to the vehicle battery pack, and the maximum power point of the photovoltaic module can be effectively tracked through the controller MPPT to ensure that the optimal electrical energy can be obtained under different lighting conditions. Since the intermediate links are in the optimal working mode, the overall charging efficiency is optimally designed.

[0077] Please refer to Figure 6-Figure 11 This embodiment proposes a maximum power point tracking method applied to an adaptive photovoltaic panel power generation control device, and the method includes the following process:

[0078] Initialization parameters: Set the initial voltage U o and current I o (In this embodiment, it is set to 0.9 times the open circuit voltage), determine the output characteristics of the solar panel, set the step size (variation value, that is, the voltage change ΔU) and sampling time (in this embodiment, it is set to 500ms) for subsequent adjustments.

[0079] Series-parallel mode switching: After the normal device is powered on, the input voltage on the front-end solar panel side is detected. The default value between 15-30V is 30V (not limited to this value), at this time Q1 is closed, and the LLC circuits are in series mode; the default value between 30-60V is 60V (not limited to this value), at this time Q1 is disconnected, and the LLC circuits are in parallel mode.

[0080] Special case 1: When the initial state of the photovoltaic panel is between 15-30V when the panel is blocked, and then recovers to between 30-60V, the voltage across C3 will double. When the voltage across C3 is detected to be greater than 300V (not limited to this value), Q1 is disconnected and the circuit switches to parallel mode.

[0081] Special case 2: When the initial state of the photovoltaic panel is between 30-60V, and then the shielding voltage is between 15-30V, when the voltage across C3 is detected to be lower than 150V (not limited to this value), Q1 is closed and the circuit switches to series mode.

[0082] In parallel mode, MPPT control indirectly adjusts the input voltage on the front-end solar panel side by adjusting the duty cycle of the back-end BOOST circuit. Since the front-end adopts the parallel mode, it cannot be determined whether the A / B photovoltaic panel monomer is at maximum power. The duty cycle of the LLC circuit is adjusted again through local MPPT, sacrificing the LLC circuit efficiency, and further looking for the maximum power point until the power change is less than the threshold. If the power does not meet the preset target, the LLC resonance point frequency is restored to continue working.

[0083] In the series mode, MPPT control indirectly adjusts the input voltage on the front-end solar panel side by adjusting the duty cycle of the back-end BOOST circuit. Since the front-end adopts the series mode, the front-end voltage adjustment ratio is 50% each. At this time, it cannot be determined whether the A / B photovoltaic panel monomer is at maximum power. The duty cycle of the LLC circuit is adjusted again through local MPPT, sacrificing the LLC circuit efficiency, and further looking for the maximum power point until the power change is less than the threshold. If the power does not meet the preset target, the LLC resonance point frequency is restored to continue working.

[0084] Measuring output power: The voltage V(k) and current I(k) on the front-end solar panel side are measured in real time through voltage and current sensors, and the current power P(k) is calculated.

[0085] Determine power changes: compare the current power P(k) with the power P(k-1) of the previous sampling point to determine whether the current power P(k) increases or decreases to adjust the step size;

[0086] Adjustment operation: If P(k)>P(k-1), the current power P(k) increases, and the step size continues to be adjusted in the direction of the current voltage U. If the voltage U(k)>U(k-1), the current voltage U=U+ΔU is increased; if U(k)<U(k-1), the current voltage U=U-ΔU is reduced;

[0087] If P(k)=P(k-1), return to measuring output power;

[0088] If P(k)<P(k-1), the current power P(k) is reduced, and the step size is adjusted in the opposite direction of the current voltage U. If U(k)<U(k-1), the current voltage U=U-ΔU is reduced. If U(k)>U(k-1), the current voltage U=U+ΔU is increased.

[0089] Update control signal: Update the output of the controller MPPT according to the step adjustment result, change the input of the load or inverter to achieve dynamic adjustment step of voltage;

[0090] Loop execution: Repeat the above process to form a closed-loop control system to continuously optimize power output.

[0091] In the process of judging power changes and adjusting operations, this embodiment adopts a method combining particle swarm algorithm and perturbation observation method to improve tracking speed and accuracy, solve local optimal situations, and dynamically adjust the step size according to environmental changes to avoid over-adjustment caused by frequent adjustments under rapidly changing conditions. By accurately tracking the maximum power point, the energy output of the photovoltaic system can be significantly improved, the output fluctuations caused by environmental changes can be reduced, the working stability of the system can be improved, and by optimizing operations, the load fluctuations of the system can be reduced, thereby extending the service life. The specific algorithm working process is as follows:

[0092] This embodiment first uses a particle swarm algorithm to effectively search over a large range to avoid falling into a local optimum. The particle swarm algorithm usually has a faster convergence speed when finding the maximum power point. Figure 6 and Figure 7 As shown in the figure, the specific process of using the particle swarm algorithm at the maximum power point is:

[0093] 1. Initialize the particle swarm and randomly generate a group of particles, each of which represents a specific operating voltage or current value.

[0094] 2. Evaluate the fitness, calculate the output power of the working point represented by each particle, and determine its fitness value.

[0095] 3. Update personal best and group best. For each particle, if its current power is greater than the personal best power, update the personal best position. If the current power is greater than the group best power, update the group best position.

[0096] 4. Update particle speed and position according to the personal best position P best and the group's optimal position G best , update the particle's velocity and position, the velocity update formula is:

[0097] V new =w*V old +c 1 *rand()*(P best -X old )+c 2 *rand()*(G best -X old )

[0098] The position update formula is:

[0099] X new =X old +V new

[0100] Where V new 、V old They represent the new speed and current speed of the particle respectively; w is the inertia weight, which controls the influence of the current speed of the particle on the next step speed; c 1 、c 2 is the acceleration coefficient, which controls the particle's personal optimal position P best and the group's optimal position G best The speed of movement; rand() is a random number between 0 and 1; X new , X old They represent the new position of the particle and the current position of the particle respectively.

[0101] 5. Repeat steps 2 to 4 until the stopping condition is met, that is, the maximum number of iterations or the power change is less than the threshold.

[0102] In this embodiment, when the power change is less than the threshold, the disturbance observation method is used to perform local optimal control, as follows:

[0103] like Figure 8 As shown in the PV curve, the photovoltaic cell can reach the maximum power point by controlling the voltage. The perturbation and observation method is based on the following formula:

[0104]

[0105] like Fig. 9 As shown in the figure, from the PV curve, we can see that the slope is small on the left side of the maximum power point, and the power change is small when the voltage is changed. The slope is large on the right side of the maximum power point, so we can choose a larger voltage step on the left side of the maximum power point, and choose a smaller voltage step on the right side of the maximum power point to speed up the tracking effect, that is:

[0106] When ΔP>ΔV, the operating point is to the left of the maximum power point, and the operating voltage needs to be increased;

[0107] When ΔP<ΔV, the operating point is to the right of the maximum power point, and the operating voltage needs to be reduced;

[0108] When ΔP=ΔV, the maximum power point is reached.

[0109] Among them, ΔP and ΔV are power disturbance and voltage disturbance respectively; U mpp is the maximum power point voltage; ΔU represents the voltage change.

[0110] The implementation process of the perturbation and observation method is as follows: Fig.10 As shown. This embodiment uses the MPPT accuracy measurement function provided by the photovoltaic simulator itself to directly calculate the MPPT efficiency. MPPT efficiency = output voltage × output current / Pmp of IV curve × 100%> 99.5%. The test results are shown as Fig.11 As shown, the MPPT efficiency calculated by the photovoltaic simulator is 99.812%.

[0111] In this embodiment, a ZLG power analyzer is used to test the working efficiency of the controller MPPT. The measured working efficiency is shown in Table 2.

[0112] Table 2 Controller MPPT working efficiency

[0113]

[0114]

[0115] It can be seen from Table 2 that the minimum working efficiency of the controller MPPT is 92.8% and the maximum working efficiency is 95.1%. Therefore, the maximum power point tracking method proposed in the present invention can improve the tracking speed and accuracy, solve the local optimal situation, and dynamically adjust the step size according to environmental changes to avoid over-adjustment caused by frequent adjustments under rapidly changing conditions, so as to ensure that the solar panel always works at the maximum power point under different environmental conditions.

[0116] The present invention adopts the method of parallel connection of the front-stage LLC circuit to shunt the current of the components to adapt to the low-voltage solar panel power supply, solve the problem of the inability to select LLC components under the low-voltage solar panel power supply, and realize multi-stage parallel charging of low-voltage solar panels for higher power.

[0117] By setting the adaptive circuit and controlling the disconnection of components D5, D6, and Q1, it is possible to connect solar panels with different voltage specifications, thus solving the problem that components L1, C1, and L2 are not compatible with high and low voltage photovoltaic panels.

[0118] The present invention adopts an MPPT controller to monitor the output voltage and current of the photovoltaic module in real time, and achieves maximum power output by adjusting the working point. It is directly connected to the high-voltage battery pack through the BOOT circuit to realize charging of the battery pack in a wide voltage range to meet the voltage charging requirements of different vehicle models.

[0119] In the present invention, when the device is disconnected from the battery pack and switched to maintenance mode, the software controls Q3 to close, and discharges the photovoltaic controller voltage in the shortest time to ensure personnel safety. By adding diode D7, the current single-phase output can be achieved to prevent the vehicle high voltage from flowing back into the photovoltaic controller.

[0120] Those skilled in the art can understand that all or part of the steps in the above-mentioned embodiment method can be completed by instructing the relevant hardware through a program, so the present application can take the form of a complete hardware embodiment, a complete software embodiment, or an embodiment combining software and hardware. Moreover, the present application can take the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program codes.

[0121] The above implementation methods have been described in detail. Specific examples are used herein to illustrate the principles and implementation methods of the present invention. The description of the above embodiments is only used to help understand the method of the present invention and its core idea. At the same time, for those skilled in the art, according to the idea of ​​the present invention, there will be changes in the specific implementation methods and application scope. In summary, the content of this specification should not be understood as a limitation on the present invention.

Claims

1. An adaptive photovoltaic panel power generation control device, comprising at least two front-end solar panel sides, a rear-end battery group side as a power battery for a new energy vehicle, and an LLC circuit with a constant output voltage set corresponding to the front-end solar panel side, characterized in that: An adaptive circuit is provided on the output side of the LLC circuit for controlling at least two groups of LLC circuits to be in series mode or parallel mode according to the current voltage on the front-end solar panel side. A BOOST circuit is provided on the output side of the adaptive circuit for pumping up the voltage on the LLC circuit side again and then connecting it to the rear-end battery pack side.

2. The adaptive photovoltaic panel power generation control device according to claim 1, characterized in that: The adaptive circuit comprises fast recovery diodes (D5, D6) and a field effect transistor MOSFET (Q1) respectively connected to the output sides of the two groups of LLC circuits; When the current voltage when the front-end solar panel side is connected is a high voltage, the field effect tube MOSFET (Q1) is in a disconnected state, and the outputs of the two groups of LLC circuits are connected in parallel through the fast recovery diodes (D5, D6); When the current voltage when the front-end solar panel side is connected is a low voltage, the field effect transistor MOSFET (Q1) is in a closed state, and the outputs of the two groups of LLC circuits are connected in series through the field effect transistor MOSFET (Q1).

3. The adaptive photovoltaic panel power generation control device according to claim 1, characterized in that: The BOOST circuit comprises an inductor (L5) connected in sequence to the positive electrode of the output side of the adaptive circuit, and a fast recovery diode (D7) for current single-phase output, a silicon carbide MOSFET (Q2) is connected in parallel between the positive electrode and the negative electrode of the output side of the adaptive circuit, and the drain of the silicon carbide MOSFET (Q2) is connected between the inductor (L5) and the fast recovery diode (D7).

4. The adaptive photovoltaic panel power generation control device according to claim 1, characterized in that: The BOOST circuit also includes a filter capacitor (C3) connected in parallel between the positive electrode and the negative electrode of the output side of the adaptive circuit, which is used for direct current smoothing.

5. The adaptive photovoltaic panel power generation control device according to claim 1, characterized in that: The output side of the BOOST circuit is provided with a discharge circuit connected in parallel to the positive and negative electrodes, and the discharge circuit includes a field effect transistor MOSFET (Q3), a discharge resistor and a film capacitor.

6. A maximum power point tracking method applied to the adaptive photovoltaic panel power generation control device according to any one of claims 1 to 5, the method comprising the following process: S1. Set the initial voltage U o and current I o , set the step size and sampling time to complete parameter initialization; S2, detecting the input voltage on the front-end solar panel side, and switching the series-parallel mode between at least two groups of LLC circuits through an adaptive circuit according to the input voltage; S3, measure the voltage V(k) and current I(k) of the front solar panel side in real time through the voltage and current sensors, and calculate the current power P(k); S4, compare the current power P(k) with the power P(k-1) of the previous sampling point, and adjust the step size according to the increase or decrease of the current power P(k); If P(k)>P(k-1), the current power P(k) increases, and the step size continues to be adjusted in the direction of the current voltage U; if the voltage U(k)>U(k-1), the current voltage U=U+ΔU is increased, and if U(k)<U(k-1), the current voltage U=U-ΔU is reduced; If P(k)=P(k-1), return to measuring output power; If P(k)<P(k-1), the current power P(k) is reduced, and the step size is adjusted in the opposite direction of the current voltage U; If U(k)<U(k-1), then reduce the current voltage U=U-ΔU, if U(k)>U(k-1), then increase the current voltage U=U+ΔU; S5, updating the output of the controller MPPT according to the step adjustment result, changing the input of the load or inverter to achieve dynamic adjustment step of the voltage; S6. Repeat the above steps S3-S5 to form a closed-loop control system to continuously optimize power output.

7. The maximum power point tracking method according to claim 6, characterized in that: In step S2, the specific process includes: The input voltage on the front-end solar panel side is detected in real time. If the input voltage is a low voltage, the field effect tube Q1 is closed, and the LLC circuits are in a series mode; if the input voltage is a high voltage, the field effect tube Q1 is disconnected, and the LLC circuits are in a series mode.

8. The maximum power point tracking method according to claim 7, characterized in that: The bottom voltage is 15V-30V, and the high voltage is 30-60V.

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