A wireless power transmitter, a wireless power receiver, and a photovoltaic power generation system

Abstract

A wireless power transmitter, a wireless power receiver, and a photovoltaic power generation system, which relate to the technical field of photovoltaic power generation. The wireless power transmitter includes an inverter circuit, a transmitting coil, and a first controller. The first controller performs maximum power point tracking control on the inverter circuit. The wireless power receiver includes a rectifier circuit, a receiving coil, and a second controller. The second controller performs maximum transmission efficiency point tracking control on the rectifier circuit. With this solution, maximum power point tracking control is used to control the inverter to ensure the maximum utilization rate of power generation. Maximum efficiency point tracking control is used to control the rectifier, which can quickly match the optimal impedance of the resonant power transfer converter when the light intensity changes. The two controllers are independent of each other and do not require communication feedback, avoiding problems such as water seepage and heat transfer in traditional rooftop photovoltaic power generation systems, reducing maintenance costs, being easy to install and disassemble, and also supporting avoiding damage to devices caused by extreme weather through disassembly, improving practicability.

Description

Technical Field

[0001] The present application relates to the field of photovoltaic power generation technology, and in particular to a wireless power transmitter, a wireless power receiver, and a photovoltaic power generation system. Background Art

[0002] Currently, due to the rapid growth of energy demand, the distribution system is increasingly dependent on renewable energy sources (RESs). The rational use of renewable energy can help alleviate environmental pollution. Therefore, renewable energy with high energy density and environmental friendliness has attracted increasing attention.

[0003] Renewable energy sources primarily include solar energy, wind energy, and biogas. Due to the abundance of solar radiation, technologies for generating electricity from solar energy have been widely applied and improved. Furthermore, since most electronic devices rely on DC power supplies, and many distributed renewable energy generation systems output DC power, low-voltage direct current (LVDC) grids have also gained widespread application.

[0004] In LVDC power grids, rooftop photovoltaic power generation systems are an important solution for building-integrated centralized power generation. Traditional rooftop photovoltaic power generation systems are usually part of a building, with wires connecting the photovoltaic array and the power converter, such as Figure 1 As shown, holes are drilled in the wall for passing the wires.

[0005] However, the complex wiring involved in these approaches leads to high installation costs and cable losses. Furthermore, the wires of rooftop PV systems are exposed to rain and heat on an irregular basis, which can cause long-term water seepage and heat transfer issues, accelerate wire aging, and result in high ongoing maintenance costs. Summary of the Invention

[0006] In order to solve the above-mentioned problems existing in the prior art, the present application provides a wireless power transmitter, a wireless power receiver and a photovoltaic power generation system, which reduce installation costs, cable losses and maintenance costs, and are easy to install and disassemble.

[0007] In a first aspect, the present application provides a wireless power transmitter for use in photovoltaic power generation systems, with a typical application scenario being rooftop photovoltaic power generation systems. The wireless power transmitter includes an inverter circuit, a transmitting coil, and a first controller. The input of the inverter circuit serves as the input of the wireless power transmitter, and the output of the inverter circuit is connected to the transmitting coil. The inverter circuit is used to convert direct current (DC) into alternating current (AC). The transmitting coil is used to transmit the AC power in the form of an alternating magnetic field. The first controller is used to perform maximum power point tracking control on the inverter circuit.

[0008] Using the wireless power transmitter provided by this application, the first controller uses maximum power point tracking to control the inverter. Thus, under different lighting conditions, it can still ensure the tracking of the maximum input power, thereby ensuring the maximum utilization rate of clean energy. In addition, due to wireless power transmission, drilling operations on the building structure are avoided, reducing installation costs, cable losses, and maintenance costs, and it is easy to install and disassemble.

[0009] In a possible implementation, the inverter circuit is a full-bridge inverter circuit. The inverter circuit includes two bridge arms, and each upper half-bridge arm and lower half-bridge arm of the two bridge arms includes a controllable switch tube. The first controller is specifically configured to perform maximum power point tracking control on the inverter circuit by controlling each controllable switch tube in the inverter circuit.

[0010] In a possible implementation, the first controller is specifically configured to determine the input power of the inverter circuit according to the input voltage and input current of the inverter circuit, and determine the conduction angle of the inverter circuit according to the input voltage of the inverter circuit, the input power of the inverter circuit, and the maximum power point tracking algorithm. The pulse width modulation signal for controlling each controllable switch tube in the inverter circuit is determined according to the conduction angle.

[0011] In a possible implementation, the wireless power transmitter further includes a first resonant circuit; the two bridge arms included in the inverter circuit are a first bridge arm and a second bridge arm. The midpoint of the first bridge arm is the first output end of the inverter circuit, and the midpoint of the second bridge arm is the second output end of the inverter circuit. The first end of the first resonant circuit is connected to the first output end of the inverter circuit, and the second end of the first resonant circuit is connected to the second output end of the inverter circuit through a transmitting coil.

[0012] In a possible implementation, the first resonant circuit includes a first capacitor. The first end of the first capacitor is the first end of the first resonant circuit, and the second end of the first capacitor is the second end of the first resonant circuit.

[0013] In a possible implementation, the first resonant circuit includes a first capacitor and a first inductor. The first end of the first capacitor is the first end of the first resonant circuit, the second end of the first capacitor is connected to the first end of the first inductor, and the second end of the first inductor is the second end of the first resonant circuit.

[0014] In a possible implementation, the first controller is specifically configured to control the inverter circuit to convert direct current into alternating current with a fixed frequency. Specifically, the first controller controls the frequency of the control signal of the inverter circuit to be a first frequency, and the second controller controls the frequency of the control signal of the rectifier circuit to be a second frequency. The first frequency can be equal to the second frequency, so that the controllers on both sides do not need to feedback wireless communication, enhancing the working stability of the system.

[0015] In a second aspect, the present application also provides a wireless power receiving end, which is applied to a photovoltaic power generation system, and a typical application scenario is a rooftop photovoltaic power generation system. The wireless power receiving end includes a rectifying circuit, a receiving coil, and a second controller. The input end of the rectifying circuit is connected to the receiving coil, and the output end of the rectifying circuit is connected to the output end of the wireless power receiving end. The receiving coil is used to convert the received alternating magnetic field into alternating current. The rectifying circuit is used to rectify the alternating current obtained from the receiving coil into direct current. The second controller is used to perform maximum efficiency point tracking control on the rectifying circuit.

[0016] When the photovoltaic power generation system adopts the wireless power receiving end provided by the present application, the second controller uses maximum transfer efficiency point tracking control for the rectifier, and can maintain the maximum transfer efficiency when the light intensity changes. When applied to a rooftop photovoltaic system, the solution provided by the present application avoids using the cables required by the traditional solution, facilitates installation and disassembly, and reduces the installation cost, cable loss, and maintenance cost.

[0017] In a possible implementation manner, the rectifying circuit specifically includes a third bridge arm and a fourth bridge arm. The third bridge arm includes a first diode and a first controllable switch tube connected in series; the fourth bridge arm includes a second diode and a second controllable switch tube connected in series, and the second controller is specifically used to perform maximum efficiency point tracking control on the rectifying circuit by controlling the first controllable switch tube and the second controllable switch tube.

[0018] In a possible implementation manner, the second controller is specifically used to determine the equivalent impedance of the current wireless power receiving end according to the output voltage and output current of the rectifying circuit, and the conduction angle of the current rectifying circuit, and determine the pulse width modulation signal for controlling the first controllable switch tube and the second controllable switch tube according to the equivalent impedance of the current wireless power receiving end and the reference value of the equivalent impedance.

[0019] In a possible implementation manner, the wireless power receiving end further includes a second resonant circuit. The midpoint of the third bridge arm is the first input end of the rectifying circuit, and the midpoint of the fourth bridge arm is the second input end of the rectifying circuit. The first end of the second resonant circuit is connected to the first input end of the rectifying circuit, and the second end of the second resonant circuit is connected to the second input end of the rectifying circuit through the receiving coil.

[0020] In a possible implementation manner, the second resonant circuit includes a second capacitor. The first end of the second capacitor is the first end of the second resonant circuit, and the second end of the second capacitor is the second end of the second resonant circuit.

[0021] In a possible implementation, the first resonant circuit includes a second capacitor and a second inductor. The first end of the second capacitor is the first end of the second resonant circuit, the second end of the second capacitor is connected to the first end of the second inductor, and the second end of the second inductor is the second end of the second resonant circuit.

[0022] In a possible implementation, the second controller is specifically configured to control the rectifier circuit with a control signal of a fixed frequency. Specifically, the frequency of the control signal for which the first controller controls the inverter circuit is a first frequency, and the frequency of the control signal for which the second controller controls the rectifier circuit is a second frequency. The first frequency may be equal to the second frequency, so that the controllers on both sides do not need to perform feedback wireless communication, enhancing the operating stability of the system.

[0023] In a third aspect, the present application further provides a photovoltaic power generation system. The photovoltaic power generation system includes the wireless power transmitting end and the wireless power receiving end provided in the above embodiments, and further includes one or more photovoltaic arrays. The output ends of the one or more photovoltaic arrays are used to connect to the input end of the wireless power transmitting end. The one or more photovoltaic arrays are used to convert light energy into direct current and then transmit it to the input end of the wireless power transmitting end.

[0024] When the photovoltaic power generation system adopts the wireless power transmitting end and the wireless power receiving end provided in the embodiments of the present application, the module size of the photovoltaic power generation system is reduced, and there is no need to cascade other converters additionally, thereby reducing the hardware cost of the photovoltaic power generation system. The first controller uses maximum power point tracking (MPPT) to control the inverter, and thus, under different lighting conditions, it can still ensure tracking of the maximum input power, thereby ensuring maximum utilization of clean energy; the second controller uses maximum efficiency point tracking (MEPT) to control the rectifier, and can maintain the maximum transmission efficiency when the light intensity changes. In addition, when the wireless power transmitting end and the wireless power receiving end are operating, they adopt a fixed operating frequency, so there is no need to establish feedback wireless communication between the first controller and the second controller, improving the stability of the system.

[0025] Furthermore, when applied to a rooftop photovoltaic system, the solution provided by the present application avoids using the cables required by the traditional solution, so there is no need to drill holes in the building structure, facilitating installation and disassembly, and reducing the installation cost, cable loss, and maintenance cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 It is a schematic diagram of a traditional rooftop photovoltaic power generation system;

[0027] Figure 2Schematic diagram of a wireless power transmitter and a wireless power receiver provided by an embodiment of the present application;

[0028] Figure 3 Schematic diagram of an application scenario of a wireless power transmitter and a wireless power receiver provided by an embodiment of the present application;

[0029] Figure 4 Schematic diagram of a photovoltaic power generation system provided by an embodiment of the present application;

[0030] Figure 5 Schematic diagram of the working waveforms of an inverter and a rectifier provided by an embodiment of the present application;

[0031] Figure 6 Schematic diagram of an equivalent circuit model of an inductive wireless power transfer converter provided by an embodiment of the present application;

[0032] Figure 7 Test photovoltaic array provided by an embodiment of the present application;

[0033] Figure 8A P-V characteristic curves of Case 1 to Case 4 provided by an embodiment of the present application;

[0034] Figure 8B I-V characteristic curves of Case 1 and Case 4 provided by an embodiment of the present application;

[0035] Figure 9A P-V characteristic curves of Case 1, Case 5 and Case 6 provided by an embodiment of the present application;

[0036] Figure 9B I-V characteristic curves of Case 1, Case 5 and Case 6 provided by an embodiment of the present application;

[0037] Figure 10 Schematic diagram of the corresponding relationship between the conduction angle β of the rectifier and the output power, and the corresponding relationship between the equivalent resistance value and the output power provided by the present application;

[0038] Figure 11 Schematic diagram of the relationship between the conduction angle α of the inverter and the DC resistance corresponding to the maximum input power provided by an embodiment of the present application;

[0039] Figure 12 Schematic diagram of the optimal load matching control on the secondary side provided by an embodiment of the present application;

[0040] Figure 13 Schematic diagram of the simulation results of the loss resistance ratio and the transmission efficiency corresponding to 6 light-receiving test cases provided by an embodiment of the present application;

[0041] Figure 14Schematic diagram of maximum input power control on the primary side provided by the embodiments of the present application;

[0042] Figure 15 Schematic diagram of the conduction angle α of the inverter and the conduction angle β of the rectifier corresponding to 6 light-receiving test cases provided by the embodiments of the present application;

[0043] Figure 16A Waveform diagram of the working waveforms and output power of the inverter and the rectifier corresponding to Case1 provided by the embodiments of the present application;

[0044] Figure 16B Waveform diagram of the working waveforms and output power of the inverter and the rectifier corresponding to Case2 provided by the embodiments of the present application;

[0045] Figure 16C Waveform diagram of the working waveforms and output power of the inverter and the rectifier corresponding to Case3 provided by the embodiments of the present application;

[0046] Figure 16D Waveform diagram of the working waveforms and output power of the inverter and the rectifier corresponding to Case4 provided by the embodiments of the present application;

[0047] Figure 16E Waveform diagram of the working waveforms and output power of the inverter and the rectifier corresponding to Case6 provided by the embodiments of the present application;

[0048] Figure 16F Waveform diagram of the working waveforms and output power of the inverter and the rectifier corresponding to Case5 provided by the embodiments of the present application;

[0049] Figure 17 Provided by the embodiments of the present application Figures 16A to 16F Corresponding specific parameter information;

[0050] Figure 18 Transient waveform diagram of uniform irradiance changing to partial shading provided by the embodiments of the present application;

[0051] Figure 19 Transient waveform diagram when uniform irradiance changes provided by the embodiments of the present application;

[0052] Figure 20 Schematic diagram of a photovoltaic power generation system provided by the embodiments of the present application. Detailed implementation manners

[0053] To enable those skilled in the art to understand the solution of the present application more clearly, the application scenario of the technical solution of the present application will be described first below.

[0054] Continue to refer to Figure 1 The shown traditional rooftop photovoltaic power generation system.

[0055] Traditional rooftop photovoltaic power generation systems are usually part of a building. The photovoltaic array is installed outdoors, and the power converter is installed indoors. They are connected by wires passing between the photovoltaic array and the power converter, and holes are drilled in the wall for the wires to pass through.

[0056] Among them, the photovoltaic array includes one or more photovoltaic modules. A photovoltaic module is a DC power source formed by series and parallel packaging of solar cells. When the photovoltaic array includes multiple photovoltaic modules, the multiple photovoltaic modules can form a photovoltaic string by connecting the positive and negative poles in series end to end to form a photovoltaic array; the multiple photovoltaic modules can also be first connected in series to form multiple photovoltaic strings, and then the multiple photovoltaic strings are connected in parallel to form a photovoltaic array.

[0057] However, when using the above methods, complex wiring will lead to high installation costs and cable losses. And the wires of the rooftop photovoltaic power generation system will be exposed to rain and heat irregularly, which will cause dangerous electric shocks and accelerate the aging of the wires, resulting in high daily maintenance costs.

[0058] To solve the above problems, the embodiments of the present application provide a wireless power transmitter, a wireless power receiver, and a photovoltaic power generation system. The wireless power transmitter includes an inverter circuit, a transmitting coil, and a first controller. The first controller is used to perform maximum power point tracking control on the inverter circuit. The wireless power receiver includes a rectifier circuit, a receiving coil, and a second controller. The second controller is used to perform maximum efficiency point tracking control on the rectifier circuit. Using the solution provided by the present application, power point tracking control is adopted when controlling the inverter to ensure the maximum utilization rate of the power generation of the photovoltaic array. When controlling the rectifier, maximum efficiency point tracking control is adopted, which can match the optimal impedance of the resonant power transfer converter when the light intensity changes. The two controllers are independent of each other and do not require communication feedback, thereby reducing installation costs, cable losses, and maintenance costs, and being easy to install and disassemble.

[0059] To enable those skilled in the art to understand the solution of the present application more clearly, the technical solutions in the embodiments of the present application will be described below in conjunction with the accompanying drawings in the embodiments of the present application.

[0060] The terms "first", "second", etc. used in the description of the present application are only for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features.

[0061] In the present application, unless otherwise clearly specified and limited, the term "connection" should be understood in a broad sense. For example, "connection" can be a fixed connection, a detachable connection, or an integral one; it can be a direct connection or an indirect connection through an intermediate medium.

[0062] Embodiments of the present application provide a wireless power transmitter and a wireless power receiver, which will be specifically described below with reference to the accompanying drawings.

[0063] See Figure 2 , which is a schematic diagram of a wireless power transmitter and a wireless power receiver provided by an embodiment of the present application.

[0064] Among them, the wireless power transmitter includes: an inverter circuit 10, a transmitting coil Lp, and a first controller 11.

[0065] The wireless power receiver includes: a rectifier circuit 20, a receiving coil Ls, and a second controller 21.

[0066] The input end of the inverter circuit 10 is the input end of the wireless power transmitter, and the output end of the inverter circuit 10 is used to connect to the transmitting coil Lp.

[0067] The inverter circuit 10 is used to convert direct current into alternating current and then transmit it to the transmitting coil Lp.

[0068] The transmitting coil Lp is used to transmit the alternating current in the form of an alternating magnetic field.

[0069] The first controller 11 is used to perform maximum power point tracking (MPPT) control on the inverter circuit.

[0070] The input end of the rectifier circuit 20 is connected to the receiving coil Ls, and the output end of the rectifier circuit is connected to the output end of the wireless power receiver.

[0071] The receiving coil Ls is used to convert the received alternating magnetic field into alternating current.

[0072] The rectifier circuit 20 is used to rectify the alternating current obtained from the receiving coil into direct current and then output it to the load.

[0073] The second controller 21 is used to perform maximum efficiency point tracking (MEPT) control on the rectifier circuit.

[0074] See Figure 3 , which is a schematic diagram of the application scenario of the wireless power transmitter and the wireless power receiver provided by an embodiment of the present application.

[0075] When the wireless power transmitter and the wireless power receiver provided by the embodiments of the present application are adopted, the wireless power transmitter is placed outdoors, and the wireless power receiver is placed indoors or in the roof interlayer. The inverter circuit, the transmitting coil Lp, and the receiving coil Ls form a single-stage inductive wireless power transfer (IWPT) converter, which reduces the module size of the photovoltaic power generation system and does not require additional cascading of other converters, thereby reducing the hardware cost of the photovoltaic power generation system. The first controller uses MPPT to control the inverter, and thus, under different light conditions, it can still ensure the tracking of the maximum input power, thereby ensuring the maximum utilization rate of clean energy; the second controller uses MEPT to control the rectifier, and can maintain the maximum transmission efficiency when the light intensity changes. In addition, when the wireless power transmitter and the wireless power receiver are working, a fixed operating frequency is adopted, so there is no need to establish feedback wireless communication between the first controller and the second controller, improving the stability of the system.

[0076] Furthermore, when applied to a rooftop photovoltaic system, the solution provided by the present application avoids the use of cables required by traditional solutions. Therefore, there is no need to drill holes in the building structure, reducing the installation cost, cable loss, and maintenance cost. It not only avoids problems such as water seepage and heat transfer of traditional rooftop photovoltaic power generation systems but also supports avoiding damage to devices in extreme weather by disassembly, improving the practicality.

[0077] The first controller 11 and the second controller 21 in the embodiments of the present application can be an application specific integrated circuit (ASIC), a programmable logic device (PLD), a digital signal processor (DSP), or a combination thereof. The above PLD can be a complex programmable logic device (CPLD), a field-programmable gate array (FPGA), a generic array logic (GAL), or any combination thereof, and the embodiments of the present application do not make specific limitations.

[0078] The following is an illustration in combination with specific implementation manners.

[0079] The inverter circuit in the following description is a full-bridge inverter circuit. The inverter circuit includes two bridge arms, and each of the upper half-bridge arm and the lower half-bridge arm of each of the two bridge arms includes a controllable switch tube.

[0080] The wireless power transmitter described below also includes a first resonant circuit. The inverter circuit includes two bridge arms: a first bridge arm and a second bridge arm. The midpoint of the first bridge arm is the first output terminal of the inverter circuit, and the midpoint of the second bridge arm is the second output terminal of the inverter circuit. The first end of the first resonant circuit is connected to the first output terminal of the inverter circuit, and the second end of the first resonant circuit is connected to the second output terminal of the inverter circuit via the transmitting coil.

[0081] In a possible implementation, the first resonant circuit includes a first capacitor, a first end of the first capacitor is the first end of the first resonant circuit, and a second end of the first capacitor is the second end of the first resonant circuit.

[0082] In another possible implementation, the first resonant circuit includes a first capacitor and a first inductor. The first end of the first capacitor serves as the first end of the first resonant circuit, the second end of the first capacitor is connected to the first end of the first inductor, and the second end of the first inductor serves as the second end of the first resonant circuit.

[0083] The following description takes the example where the first resonant circuit includes the first capacitor.

[0084] Furthermore, the rectifier circuit described below specifically includes a third bridge arm and a fourth bridge arm. The third bridge arm includes a first diode and a first controllable switch connected in series, and the fourth bridge arm includes a second diode and a second controllable switch connected in series. The wireless power receiving end also includes a second resonant circuit. The midpoint of the third bridge arm is the first input of the rectifier circuit, and the midpoint of the fourth bridge arm is the second input of the rectifier circuit. The first end of the second resonant circuit is connected to the first input of the rectifier circuit, and the second end of the second resonant circuit is connected to the second input of the rectifier circuit via the receiving coil.

[0085] In a possible implementation, the second resonant circuit includes a second capacitor, a first end of the second capacitor is the first end of the second resonant circuit, and a second end of the second capacitor is the second end of the second resonant circuit.

[0086] In another possible implementation, the first resonant circuit includes a second capacitor and a second inductor. The first end of the second capacitor is the first end of the second resonant circuit, the second end of the second capacitor is connected to the first end of the second inductor, and the second end of the second inductor is the second end of the second resonant circuit.

[0087] The following description takes the second resonant circuit including the second capacitor as an example.

[0088] See also Figure 4 , which is a schematic diagram of a photovoltaic power generation system provided in an embodiment of the present application.

[0089] The illustrated photovoltaic discovery system includes a photovoltaic array 30, an inductive wireless power transfer (IWPT) converter, a rectifier 20, and an LVDC bus 40

[0090] Among them, the IWPT converter includes an inverter 10 and a resonant power transfer circuit. The primary side of the resonant power transfer circuit includes a capacitor Cp (i.e., the first capacitor) and a transmitting coil Lp, and the secondary side includes a capacitor Cs (i.e., the second capacitor) and a receiving coil Ls.

[0091] The IWPT converter is driven by the photovoltaic array 30, and the rectifier 20 is a semi-active rectifier.

[0092] At this time, the inverter 10 adopts maximum input power control and realizes MPPT through phase-shifted pulse width modulation (PWM) modulation.

[0093] In order to verify the feasibility of the photovoltaic power generation system under various shadow conditions, a particle swarm optimization (PSO) algorithm supplemented by a perturb and observe (P&O) algorithm is adopted in the maximum input power control to calculate the corresponding conduction angle and realize global maximum power tracking.

[0094] In addition, due to the change of light intensity and the possible partial occlusion of the photovoltaic array, the equivalent load on the secondary side will change. According to the characteristics of the resonant power transfer circuit, its transmission efficiency will be affected. Therefore, the solution of this application adopts MEPT control in the rectifier 20 on the secondary side, and also uses phase-shifted PWM to track the optimal impedance matching, thereby maintaining the best transmission efficiency, and there is no need for wireless feedback communication with the primary side, thereby enhancing the stability of the photovoltaic power generation system.

[0095] The working principle of the photovoltaic power generation system will be specifically described below.

[0096] L P and L S The mutual inductance M between 1, and its coupling coefficient can be defined as

[0097] Continue to refer to Figure 4 At this time, the resonant angular frequency ω P on the primary side is:

[0098]

[0099] The resonant angular frequency ω s on the secondary side is:

[0100]

[0101] V IN and I IN are respectively the DC input voltage and DC current extracted from the photovoltaic array 30. The photovoltaic array 30 serves as a voltage source.

[0102] The inverter circuit 10 is a full-bridge inverter circuit, including controllable switch tubes S1 to S4. The type of the controllable switch tubes can be Insulated Gate Bipolar Transistor (IGBT), Metal Oxide Semiconductor Filed Effect Transistor (MOSFET), Silicon Carbide Metal Oxide Semiconductor (SiC MOSFET), etc. The embodiments of the present application do not limit this.

[0103] The inverter circuit 10 modulates the voltage output by the photovoltaic array 30 into an AC voltage vp at a constant angular frequency to drive the resonant circuit on the primary side.

[0104] On the secondary side, the AC voltage v S and the AC current i S are the inputs of the rectifier 20. The rectifier 20 is composed of two diodes D5 and D6 and two controllable switch tubes S7 and S8. The output terminal of the rectifier 20 is connected in parallel with a large output capacitor C f,s (not shown in the figure).

[0105] V O and I O are respectively the DC output voltage and DC output current of the rectifier 20, that is, the IWPT converter.

[0106] Since the output of the photovoltaic power generation system is connected to the LVDC 40, V O is the same as the voltage of the LVDC bus 40 and is in a constant state. At this time, the IWPT converter can act as a current source.

[0107] Assume that the photovoltaic power generation system can be well decoupled from the LVDC bus 40 through a large decoupling capacitor C f,s connected in parallel with a semi-active rectifier (SAR). Then the LVDC bus 40 can be modeled as a load resistor R LVDC . Therefore, the change of R LVDC depends on the input power of the photovoltaic array 30.

[0108] See Figure 5 , which is a schematic diagram of the working waveforms of the inverter and rectifier provided by the embodiment of the present application.

[0109] Figure 5 The upper part of Figure 5 corresponds to the working waveform of the inverter 10, aiming to change the input impedance of the IWPT converter by adjusting the conduction angle α of vp, while v P,1 is the fundamental frequency component of v P and always remains consistent with i P .

[0110] Similarly, the working waveform of the rectifier 20 is shown in the lower part, adjusting the conduction angle β of v S to match the optimal load, while v S,1 is the fundamental frequency component of v S and the component aligned with i S . Since the fundamental frequency components of v P and v S are in phase with i P and i S respectively, the zero phase angle characteristic can minimize the voltage - ampere rating.

[0111] According to the First Harmonic Approximation (FHA) analysis, the equivalent circuit model of the IWPT converter is as Figure 6 shown.

[0112] Since the IWPT converter operates at the resonant frequency and is a high - quality factor circuit, this model is accurate enough for subsequent analysis. Here, the equivalent circuit model is divided into a primary circuit and a secondary circuit. V P , I P , V S and I[[ID=4,6]] S are the phasors of the fundamental frequency components of v[[ID=4,8]] P , i P , v S and i S respectively.

[0113] The series resistance R P includes the coil loss R P,w and the loss from the primary - side inverter, while the series resistance R S includes the coil loss R S,w and the loss from the secondary - side rectifier. According to Kirchhoff's Voltage Laws (KVL), the basic formula for deriving the circuit model is:

[0114] (R P +jX P )I P -jXM I S = V p (3)

[0115] -(R S + R eq + jX S )I S + jX M I P = 0 (4)

[0116] X M = ωM (5)

[0117]

[0118]

[0119] In the above equations, X M is the mutual inductance, X P is the reactance on the primary side, and X S is the reactance on the secondary side.

[0120] The rectifier 20 and the LVDC bus load R LVDC can be represented by an equivalent resistance R eq , as shown in the following equation:

[0121]

[0122] At the same time, the magnitudes of V P and I P are determined by the following equation:

[0123]

[0124]

[0125] The continuously changing solar radiation causes the maximum power output of the photovoltaic array to be inconsistent. Without loss of generality, assume that the maximum power extracted from the photovoltaic array is P MAX , and the losses of the IWPT converter can be ignored. At this time, the input power P IN and the output power P OUT of the IWPT converter are the same and are determined by the following equation:

[0126] P OUT ≈ P IN = P MAX (11)

[0127] The equivalent load of the LVDC bus can be calculated as:

[0128]

[0129] Maximum input power P MAX It is directly affected by the changing solar irradiance, resulting in a wide load range variation of the IWPT converter. Therefore, when the photovoltaic array undergoes uniform or non-uniform irradiance changes, the situation of the photovoltaic power generation system becomes more complex.

[0130] To determine the feasibility of this photovoltaic power generation system under various lighting conditions, experiments are conducted using Figure 7 the test photovoltaic array.

[0131] Figure 7 The test photovoltaic array shown includes six photovoltaic arrays, namely Case1 to Case6. Each photovoltaic array includes four strings of photovoltaic strings connected in parallel, and each photovoltaic string includes two photovoltaic modules connected in series.

[0132] The specifications of Case1 to Case6 are summarized in Table I. In addition, these 6 cases can be divided into two conditions, namely the uniform illumination condition of Case1 to Case4 and the non-uniform illumination conditions of Case5 and Case6. Since the solution of this application only considers the influence of irradiance, the temperature remains constant at 25 °C in all cases.

[0133] Table 1: Data table of test parameters

[0134]

[0135] See Figure 8A and Figure 8B , where Figure 8A shows the P-V characteristic curves of Case1 to Case4; Figure 9A shows the P-V characteristic curves of Case1, Case5, and Case6.

[0136] See also Figure 8B and Figure 9B , where Figure 8B shows the I-V characteristic curves of Case1 to Case4; Figure 9B shows the I-V characteristic curves of Case1, Case5, and Case6.

[0137] Using Figure 6 the circuit equivalent model shown, the transmission efficiency of the photovoltaic power generation system is calculated as follows:

[0138] [[ID=…]]

[0139] To obtain the maximum power efficiency, the optimal operating frequency ω opt and the optimal equivalent resistance R eq,opt are given by the following formula:

[0140] ω opt = ω S (14)

[0141]

[0142] The equivalent load R of the LVDC bus LVDC varies with the input power of the IWPT converter.

[0143] See Figure 10 , which shows the corresponding relationship between the conduction angle β of the rectifier provided in this application and the output power, and the corresponding relationship between the equivalent resistance value and the output power.

[0144] Among them, the circular mark corresponds to the conduction angle β, and the diamond mark corresponds to the equivalent load R LVDC .

[0145] When R LVDC increases, P OUT decreases with the decrease of solar irradiance, and vice versa, which leads to a large change in the load range of the IWPT converter and greatly reduces the transmission efficiency. In order to convert the equivalent load R eq to the optimal value of the IWPT converter, the conduction angle of the rectifier should be satisfied at this time. Therefore, we can obtain the optimal R eq，opt satisfying:[[]]

[0146]

[0147] In addition, based on the condition of (16), the operation of the conduction angle β can be deduced as

[0148]

[0149] Obviously, the conduction angle β is determined by the output power of the IWPT converter, the output voltage, and the optimal equivalent load of the IWPT converter.

[0150] The corresponding relationship between the conduction angle β of the rectifier and the output power is simulated based on the simulation parameters in Table 2.

[0151] Table 2: Simulation parameter table 1

[0152]

[0153]

[0154] Combined with Figure 10 it can be determined that when the output power decreases, the conduction angle β decreases accordingly.

[0155] To determine the AC input resistance Rin of the inverter, the primary side loop can be decoupled from the secondary side loop when the dependent source jωMIs on the primary side is replaced by the equivalent impedance reflected from the secondary side to the primary side. The primary side reflected impedance is Z ref Satisfy:

[0156]

[0157] Analyze the input impedance Z in , and its formula is:

[0158]

[0159] Assume ω P = ω S , and the operating frequency is selected at ω opt , the AC input resistance R in can be obtained,

[0160]

[0161] If the rectifier circuit on the secondary side strictly implements the MEPT control, then the equivalent resistance R eq is converted to the optimal equivalent resistance R eq，opt , and then:

[0162]

[0163] Generally, the output power of the photovoltaic array 30 depends on the DC input resistance of the IWPT converter. Assume that the maximum power can be extracted at the maximum power DC input resistance R IN,MAX , then the DC input resistance and the AC input resistance of the converter should satisfy:

[0164]

[0165] The conduction angle α can also be derived as

[0166]

[0167] See also Figure 11 , which is a schematic diagram of the relationship between the conduction angle α of the inverter provided in the embodiment of the present application and the DC resistance corresponding to the maximum input power.

[0168] Therefore, it can be determined that the optimal operation of the conduction angle α of the inverter is determined by R IN,MAX , depends on the lighting conditions, and the optimal load matching has been achieved in the rectifier.

[0169] See Figure 12 , which is a schematic diagram of the optimal load matching control on the secondary side provided in the embodiment of the present application.

[0170] This process is controlled by a second controller, which determines the equivalent impedance of the current wireless power receiving end according to the output voltage and output current of the rectifier circuit, as well as the conduction angle of the current rectifier circuit, and determines the pulse width modulation signals for controlling the first controllable switch tube and the second controllable switch tube according to the equivalent impedance of the current wireless power receiving end and the reference value of the equivalent impedance.

[0171] That is to say, this control method is mainly realized by controlling the conduction angle β, and the optimal equivalent resistance R can be modulated. eq，opt 。

[0172] The specific process is as follows:

[0173] First of all, based on the above analysis, R LVDC varies with the change of solar irradiation conditions. The output voltage V O and the output current I O can be measured by a Signal Conditioning Board.

[0174] Then, R can be calculated by a Divider LVDC 。

[0175] After that, the value of the equivalent resistance Req is obtained, specifically through the above formula (8).

[0176] Subtract the signal Req from the reference value of the optimal load R eq,opt . Then correct the difference between Req and the reference value R eq,opt through a PI controller, so as to form a control signal for generating PWM. The control signal is used to indicate the conduction angle β. The controllable switch tubes S7 and S8 are driven by a PWM Generator to achieve MEPT control.

[0177] The control reference R eq,opt is very important for this control process. It can be seen from formula (15) that theoretically R eq,opt varies with the change of the loss resistance ratio , and X M in formula (15) is a constant.

[0178] According to the equivalent circuit analysis, R P and R S respectively include the power losses from the inverter and the rectifier (except for the losses of each coil). Since the losses of the inverter and the rectifier vary with the modulation depth, the R of the IWPT converter eq,opt will be indirectly affected. Therefore, for the design consideration of R eq,opt , theoretical loss analysis can be applied to solve this problem, which will be specifically described below.

[0179] For an inverter, the power loss P loss,inv mainly consists of the switching loss P sw,inv and the conduction loss P con,inv , which is given by:

[0180] P loss,inv = P sw,inv + P con,inv (24)

[0181] Assuming a linear approximation for the switching loss P sw,inv based on the drain-source voltage and current:

[0182]

[0183] ]>where t on and t off are the turn-on time and turn-off time of the MOSFET, respectively, and C oss,1 is the output capacitance of each MOSFET switch in the inverter. and are the average values of v P and i P passing through the inverter. f SW represents the operating frequency of the IWPT converter. In addition, the conduction loss P cov,inv can be estimated as:

[0184]

[0185] where R on，1 is the on-resistance of the MOSFET switches S1 - S4, and V f,1 is the forward voltage of its anti-parallel diode. is the root mean square value of i p . Therefore, considering the losses on the primary side of the inverter, the equivalent series resistance R P can be calculated as

[0186]

[0187] Similarly, considering the switching loss R sw,SAR and the conduction loss R con,SAR of the rectifier, the power loss P loss,SAR of the rectifier is given by:

[0188] P loss,SAR = P sw,SAR + P con,SAR (28)

[0189] Based on the linear approximation, P sw,SAR can be eliminated because Psw,SAR Satisfy:

[0190]

[0191] Wherein And Are the average values of v S And i S Respectively injected into the rectifier. Then, the conduction loss in the rectifier can be estimated as

[0192]

[0193] Assuming that the MOSFET switches S7 and S8 of the rectifier are the same as S1 - S4, then R on,2 Is the on - resistance of the MOSFET switches S7 - S8. Similarly, the forward voltage V f,2 Of the anti - parallel diode of the rectifier is equal to V f,1 S . Is the root - mean - square value of i S . C oss,2 Is the output capacitance of each MOSFET switch in the rectifier. Therefore, the equivalent series resistance R S Can be calculated as

[0194]

[0195] See Figure 13 , which is a schematic diagram of the simulation results of the loss resistance ratio and transmission efficiency corresponding to 6 light - receiving test cases provided by the embodiment of the present application.

[0196] The relationship between the illustrated loss resistance ratio And the irradiation condition is marked with a square frame. The relationship between the transmission efficiency and the irradiation condition is marked with a diamond frame.

[0197] Due to the change of the conduction angle on both sides, the loss resistance ratio varies between 1.3 - 1.4. Theoretically, R eq,opt Should change with the change of this ratio, but the deviation of the optimal load resistance of the IWPT converter is very small, only about 7.5%, and even if the irradiance changes, the transmission efficiency is not significantly affected but remains at the optimal value. Therefore, in order to improve the simplicity of MEPT control, the control reference value R eq,opt Can be fixed and no longer changes.

[0198] In this photovoltaic power generation system, the MPPT function is no longer achieved through an additional cascaded converter, but directly through controlling the inverter, that is, controlling the conduction angle α in the inverter can change the DC input resistance of the IWPT converter, which determines the output power of the photovoltaic array.

[0199] SeeFigure 14 , which is a schematic diagram of the maximum input power control on the primary side provided by the embodiment of the present application.

[0200] This control process is implemented by a first controller. The first controller determines the input power of the inverter circuit according to the input voltage and input current of the inverter circuit, and determines the conduction angle of the inverter circuit according to the input voltage of the inverter circuit, the input power of the inverter circuit and the maximum power point tracking algorithm. The pulse width modulation signal of each controllable switch tube in the inverter circuit is determined according to the conduction angle.

[0201] The following will be specifically described with reference to the drawings.

[0202] Input voltage V IN and input current I IN are measured by a Signal Conditioning Board.

[0203] Then, the input power P is calculated by a Multiplier. IN .

[0204] Through the measured V IN and the calculated average value of P IN , the MPPT algorithm (MPPT Algorithm) correspondingly calculates the conduction angle α, and the controllable switch tubes S1 to S4 are driven by a PWM Generator (PWM Generator) to achieve the maximum input power.

[0205] To verify the feasibility of the system under various shadow conditions, the system applies a combined MPPT algorithm, that is, a Particle Swarm Optimization (PSO) algorithm assisted by the Perturb and Observe (P&O) algorithm. This combined method takes advantage of the fast global maximum power point tracking (Global Maximum Power Point Tracking, GMPPT) ability of PSO during the transition from uniform shadow conditions to partial shadow conditions. The verification method will be briefly described below.

[0206] The PSO algorithm is population-based and moves the individuals in the population to good regions according to their fitness to the environment. However, it does not use evolutionary operators on individuals, but regards each individual as a particle (point) without volume in a multi-dimensional search space, flying at a certain speed in the search space, and this speed is dynamically adjusted according to its own flight experience and the flight experience of its companions.

[0207] When using the PSO algorithm to track the global maximum power point, p Bestis the best position of an individual particle; the index number of the best position experienced by all the particles in the swarm is denoted by the symbol g, also known as G Best . i is the number of iterations. The position of each particle corresponds to power.

[0208] First, initialize the overall particles.

[0209] Then, evaluate and record the best position of each particle.

[0210] By comparing the current position of the particle and the individual best position p Best , G can be temporarily updated Best . Specifically:

[0211] For each particle, compare its current position with the best position p Best it has experienced. If it is better, then use it as the current best position p Best ;

[0212] For each particle, compare its current position with the best position G Best experienced globally. If it is better, then reset the index number of G Best ;

[0213] Calculate the velocity of the particle and update and record its position.

[0214] Continue the above search strategy until the search stop criterion for the convergence condition is reached, that is, approximately reach the Global Maximum Power Point (GMPP). After that, while approximately reaching the GMPP, convert the PSO algorithm to the P&O algorithm and use the P&O algorithm to maintain tracking. This auxiliary algorithm is designed to help the PSO algorithm handle small oscillations under solar irradiance or handle small changes under uniform shading conditions. At this time, if there are any small change situations, the power oscillation caused by the PSO can be reduced.

[0215] Both the primary coil and the secondary coil are constructed as circular spiral windings and are separated by the roof wood. The LVDC bus is simulated by an electronic load in a constant voltage mode. Fix the operating frequency at 50 kHz and adjust the conduction angle α of the inverter to track the maximum power point. At the same time, adjust the conduction angle β in the SAR to track the maximum efficiency point. In Figure 15 the measured operating points under uniform irradiance conditions and partial shading conditions are shown.

[0216] To verify the proposed photovoltaic power generation system and the maximum efficiency point tracking control and maximum power point tracking control, this application constructs a 500W experimental prototype, the parameters of which are in Table 3. The photovoltaic array consists of a programmable DC power supply, denoted as V IN For simulation, this DC power supply V INTwo scenarios can be simulated: uniform illumination conditions (corresponding to Case 1 to Case 4) and partial shading conditions (corresponding to Case 5 and Case 6).

[0217] Table 3: Simulation Parameter Table 2

[0218]

[0219]

[0220] The power transmitting coil on the primary side and the power transmitting coil on the secondary side are separated by the wood of the roof, and the LVDC bus is simulated by an electronic load in constant voltage mode. The operating frequency is fixed at 50 kHz, and the conduction angle α of the inverter is adjusted to track the maximum power point. At the same time, the conduction angle β in the rectifier is adjusted to track the maximum efficiency point.

[0221] See Figure 15 , which is a schematic diagram of the conduction angle α of the inverter and the conduction angle β of the rectifier corresponding to the 6 light-receiving test cases provided by the embodiment of the present application.

[0222] Among them, Case 1 to Case 4 shown in the figure correspond to uniform illumination conditions, identified by cross symbols; Case 5 and Case 6 correspond to partial shading conditions, identified by squares.

[0223] When under uniform illumination conditions, the conduction angle α decreases from 0.475π to 0.287π, and the conduction angle β decreases from 0.834π to 0.180π, because the corresponding maximum DC input resistance R of the photovoltaic array and the maximum input power P decrease respectively due to the change of uniform illumination. IN,MAX and maximum input power P MAX decrease.

[0224] When the shaded part gradually increases from none, specifically referring to Case 1, Case 5, and Case 6 at this time, the conduction angle α increases from 0.475π to 0.834π, because the R corresponding to Case 1, Case 5, and Case 6 continuously increases with the increase of the shaded part. IN,MAX increases continuously with the increase of the shaded part.

[0225] The operating waveforms and output powers of the inverter and rectifier corresponding to Case 1 to Case 6 above can be respectively referred to those shown in Figures 16(A) to 16(F). The corresponding specific parameter information can be seen as shown in Figure 17 , which will not be elaborated one by one in the embodiment of the present application.

[0226] See Figure 18 , which is the transient waveform diagram of the change from uniform irradiation to partial shading provided by the embodiment of the present application.

[0227] Among them, the AC input current ip corresponds to CH6, the AC input voltage corresponds to CH7, the input power corresponds to CH8, the phase shift angle π-α of the inverter corresponds to CH9, and the phase shift angle of the phase shift angle π-β of the SAR corresponds to CH10.

[0228] See Figure 19 , which is the transient waveform diagram when the uniform irradiance changes provided by the embodiment of the present application.

[0229] Among them, when changing from Case1 to Case3, there is a large change in irradiance.

[0230] The tracking time (Atime) of the above test is about 2.5 seconds, and then the stability of the control can be achieved. Therefore, the photovoltaic power generation system provided by the embodiment of the present application has high stability and strong practicability.

[0231] In summary, when the photovoltaic power generation system adopts the wireless power transmitting end and the wireless power receiving end provided by the embodiment of the present application, the module size of the photovoltaic power generation system is reduced, and there is no need to cascade other converters additionally, thereby reducing the hardware cost of the photovoltaic power generation system. The first controller uses MPPT to control the inverter, and thus can still ensure the tracking of the maximum input power under different illumination conditions, thereby ensuring the maximum utilization rate of clean energy; the second controller uses MEPT to control the rectifier, and can maintain the maximum transmission efficiency when the illumination intensity changes. In addition, when the wireless power transmitting end and the wireless power receiving end are working, a fixed working frequency is adopted, so there is no need to establish a feedback wireless communication between the first controller and the second controller, improving the stability of the system.

[0232] Furthermore, when applied to a rooftop photovoltaic system, the solution provided by the present application avoids using the cables required by the traditional solution. Therefore, there is no need to drill holes in the building structure, which is convenient for installation and disassembly, reducing the installation cost, cable loss and maintenance cost.

[0233] Based on the wireless power transmitting end and the wireless power receiving end provided by the above embodiments, the embodiment of the present application also provides a photovoltaic power generation system, which will be specifically described below with reference to the drawings.

[0234] See Figure 20 , which is a schematic diagram of a photovoltaic power generation system provided by the embodiment of the present application.

[0235] The photovoltaic power generation system includes the wireless power transmitting end and the wireless power receiving end provided by the above embodiments, and also includes one or more photovoltaic arrays 30.

[0236] Figure 20 Only the schematic diagram when including one photovoltaic array is shown in

[0237] The output terminals of one or more photovoltaic arrays 30 are used to connect to the input terminals of the wireless power transmitting end.

[0238] One or more photovoltaic arrays 30 are used to convert light energy into direct current and then transmit it to the input terminals of the wireless power transmitting end.

[0239] Regarding the working principles of the wireless power transmitting end and the wireless power receiving end, reference can be made to the relevant descriptions in the above embodiments, and the embodiments of the present application will not be elaborated herein.

[0240] In summary, when the photovoltaic power generation system adopts the wireless power transmitting end and the wireless power receiving end provided by the embodiments of the present application, the module size of the photovoltaic power generation system is reduced, and there is no need to cascade other converters additionally, thereby reducing the hardware cost of the photovoltaic power generation system. The first controller of the wireless power transmitting end uses MPPT to control the inverter, and thus, under different lighting conditions, it can still ensure the tracking of the maximum input power, thereby ensuring the maximum utilization rate of clean energy. The second controller of the wireless power receiving end uses MEPT to control the rectifier, and it can maintain the maximum transmission efficiency when the light intensity changes. In addition, when the wireless power transmitting end and the wireless power receiving end are working, they adopt a fixed working frequency, so there is no need to establish a feedback wireless communication between the first controller and the second controller, improving the stability of the system.

[0241] Furthermore, when applied to a rooftop photovoltaic system, the solution provided by the present application avoids using the cables required by the traditional solution. Therefore, there is no need to drill holes in the building structure, which is convenient for installation and disassembly, reducing the installation cost, cable loss, and maintenance cost.

[0242] It should be understood that in the present application, "at least one (item)" means one or more, and "a plurality" means two or more. "And / or" is used to describe the association relationship of associated objects, indicating that there can be three relationships. For example, "A and / or B" can represent: only A exists, only B exists, and both A and B exist simultaneously. Here, A and B can be singular or plural. The character " / " generally represents an "or" relationship between the associated objects before and after. "At least one (one) of the following" or its similar expression means any combination of these items, including any combination of single item (one) or plural items (ones). For example, at least one (one) of a, b, or c can represent: a, b, c, "a and b", "a and c", "b and c", or "a and b and c", where a, b, and c can be single or multiple.

[0243] Each embodiment in this specification is described in a progressive manner. For the same or similar parts among the embodiments, reference can be made to each other. Each embodiment focuses on the differences from other embodiments. The device embodiments described above are merely illustrative. The units and modules described as separate components may or may not be physically separated. Additionally, some or all of the units and modules can be selected according to actual needs to achieve the purpose of the solution of this embodiment. A person of ordinary skill in the art can understand and implement it without creative efforts.

[0244] The above is only the specific implementation manner of this application. It should be noted that for those of ordinary skill in the art in this technical field, without departing from the principle of this application, several improvements and refinements can be made, and these improvements and refinements should also be regarded as the protection scope of this application.

Claims

1. A wireless power transmitter, characterized in that, Applied to a photovoltaic power generation system, the wireless power transmitting end is arranged outdoors and includes: an inverter circuit, a transmitting coil, and a first controller; The input end of the inverter circuit is the input end of the wireless power transmitting end. The output end of the inverter circuit is used to connect to the transmitting coil. The input end of the wireless power transmitting end is used to connect to the output ends of one or more photovoltaic arrays; The inverter circuit is used to convert direct current into alternating current; The transmitting coil is used to transmit the alternating current in the form of an alternating magnetic field; The first controller is used to keep the operating frequency of the inverter circuit unchanged, determine the input power of the inverter circuit according to the input voltage and input current of the inverter circuit, and determine the conduction angle of the inverter circuit according to the input voltage of the inverter circuit, the input power of the inverter circuit, and the maximum power point tracking algorithm. According to the conduction angle, determine the pulse width modulation signals for controlling each controllable switch tube in the inverter circuit, and further perform maximum power point tracking control on the inverter circuit.

2. The wireless power transmitting end according to claim 1, wherein The inverter circuit is a full-bridge inverter circuit. The inverter circuit includes two bridge arms. Each of the upper half-bridge arm and the lower half-bridge arm of each of the two bridge arms includes a controllable switch tube; The first controller is specifically used to perform the maximum power point tracking control on the inverter circuit by controlling each controllable switch tube in the inverter circuit.

3. The wireless power transmitting end according to claim 2, wherein The wireless power transmitting end further includes a first resonant circuit; the two bridge arms included in the inverter circuit are a first bridge arm and a second bridge arm. The midpoint of the first bridge arm is the first output end of the inverter circuit, and the midpoint of the second bridge arm is the second output end of the inverter circuit; The first end of the first resonant circuit is connected to the first output end of the inverter circuit, and the second end of the first resonant circuit is connected to the second output end of the inverter circuit through the transmitting coil.

4. The wireless power transmitting end according to claim 3, characterized in that, The first resonant circuit includes a first capacitor; The first end of the first capacitor is the first end of the first resonant circuit, and the second end of the first capacitor is the second end of the first resonant circuit.

5. The wireless power transmitting end according to claim 3, wherein, The first resonant circuit includes a first capacitor and a first inductor; The first end of the first capacitor is the first end of the first resonant circuit. The second end of the first capacitor is connected to the first end of the first inductor, and the second end of the first inductor is the second end of the first resonant circuit.

6. The wireless power transmitting end according to claim 1, wherein The first controller is specifically used to control the inverter circuit to convert the direct current into alternating current with a fixed frequency.

7. A wireless power receiving end, characterized in that, Applied to a photovoltaic power generation system, the wireless power receiving end is placed indoors or in a roof sandwich layer and includes: a rectifier circuit, a receiving coil, and a second controller; the rectifier circuit includes a third bridge arm and a fourth bridge arm. The third bridge arm includes a first controllable switch tube, and the fourth bridge arm includes a second controllable switch tube; The input end of the rectifier circuit is connected to the receiving coil, and the output end of the rectifier circuit is connected to the output end of the wireless power receiving end; The receiving coil is used to convert the received alternating magnetic field into alternating current; The rectifier circuit is used to rectify the alternating current obtained from the receiving coil into direct current, and the output terminal of the rectifier circuit is connected to the low-voltage DC power grid; The second controller is used to keep the operating frequency of the rectifier circuit unchanged, determine the equivalent impedance of the current wireless power receiving end according to the output voltage and output current of the rectifier circuit and the current conduction angle of the rectifier circuit, and determine the pulse width modulation signals for controlling the first controllable switch tube and the second controllable switch tube according to the current equivalent impedance of the wireless power receiving end and the reference value of the equivalent impedance, so as to perform maximum efficiency point tracking control on the rectifier circuit.

8. The wireless power receiving end according to claim 7, characterized in that, The third bridge arm includes a first diode and a first controllable switch tube connected in series; The fourth bridge arm includes a second diode and a second controllable switch tube connected in series; The second controller is specifically used to perform maximum efficiency point tracking control on the rectifier circuit by controlling the first controllable switch tube and the second controllable switch tube.

9. The wireless power receiving end according to claim 8, characterized in that, The wireless power receiving end further includes a second resonant circuit. The midpoint of the third bridge arm is the first input terminal of the rectifier circuit, and the midpoint of the fourth bridge arm is the second input terminal of the rectifier circuit; The first end of the second resonant circuit is connected to the first input terminal of the rectifier circuit, and the second end of the second resonant circuit is connected to the second input terminal of the rectifier circuit through the receiving coil.

10. The wireless power receiving end according to claim 9, wherein The second resonant circuit includes a second capacitor; The first end of the second capacitor is the first end of the second resonant circuit, and the second end of the second capacitor is the second end of the second resonant circuit.

11. The wireless power receiving end according to claim 9, characterized in that, The first resonant circuit includes a second capacitor and a second inductor; The first end of the second capacitor is the first end of the second resonant circuit, the second end of the second capacitor is connected to the first end of the second inductor, and the second end of the second inductor is the second end of the second resonant circuit.

12. The wireless power receiving end according to claim 7, wherein The second controller is specifically used to control the rectifier circuit with a control signal of a fixed frequency.

13. A photovoltaic power generation system, characterized in that, The photovoltaic power generation system includes the wireless power transmitting end according to any one of claims 1 to 6, and the wireless power receiving end according to any one of claims 7 to 12, and further includes one or more photovoltaic arrays; The output terminals of the one or more photovoltaic arrays are used to connect to the input terminal of the wireless power transmitting end; The one or more photovoltaic arrays are used to convert light energy into direct current and then transmit it to the input terminal of the wireless power transmitting end.

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