Method for realizing load constant voltage-constant current control on primary side of WPT system

Abstract

The invention relates to a method for realizing load constant voltage-constant current control on a primary side of a WPT system. The method comprises the following steps: S1, acquiring a simplified model; s2, constructing a WPT system model in a two-dimensional rotating dq coordinate system; s3, coordinate decomposition is carried out to obtain a secondary side current expression; s4, constructing a primary side impedance value equation; s5, substituting the formula into a secondary side current expression to obtain a secondary side current value, and substituting the secondary side current value into a WPT system model loop equation under a two-dimensional rotating dq coordinate system to obtain a secondary side voltage value; and S6, the fuzzy controller tracks voltage or current according to the secondary side current value and the secondary side voltage value, outputs a control signal and sends the signal to an H-bridge inverter of the WPT system to realize constant voltage-constant current control. Compared with the prior art, the problems that a control method needs a secondary side to transmit data, an additional device is needed for achieving communication, the device is large in size, or an identification algorithm is complex, and calculation time is long are solved.

Description

Technical Field

[0001] The present invention relates to the technical field of wireless charging systems, and in particular to a method for implementing load constant voltage and constant current control on the primary side of a WPT system. Background Art

[0002] Electricity has many advantages, such as being clean and environmentally friendly, widely available, easily transmitted, and easy to control and regulate. Devices directly driven by electricity are constantly developing. Traditional direct contact charging methods have disadvantages such as redundant wiring, rapid wear and aging, and range limitations. In some special charging environments, there are risks such as leakage and sparks, which pose safety risks during the charging process. Wireless power transmission (WPT) technology is a technology that transmits electric energy through electromagnetic fields in space. It has the advantages of long transmission distances, high transmission efficiency, and good flexibility. In recent years, with the development of science and technology, WPT technology has been widely researched and applied, especially in the fields of wireless charging of electric vehicles, smart homes, and medical equipment.

[0003] Electronic products are widely used in daily life, including common appliances such as LED lights, motors, chargers, and batteries. These devices require a constant current during normal operation to ensure performance and longevity. For these devices, wireless power transmission systems must provide a constant current function to ensure stable performance. Currently, there are four main methods for achieving this. The first is to use a compensation network for regulation, but due to the presence of passive components such as capacitors and inductors, parasitic resistance is not negligible, making current regulation difficult. The second method uses closed-loop control to control the transmitter based on information fed back from the secondary side. However, this method has drawbacks such as latency and signal interference in certain environments. The third method uses signals fed back from the secondary side to identify the primary side for transmitter control. While communication between the primary and secondary sides is unnecessary, the identification algorithm is generally complex and requires a long computation time. The fourth method is to achieve closed-loop control by controlling the receiver. However, this requires additional circuitry at the receiver, increasing its size and requiring an additional power supply.

[0004] In summary, existing WPT system control methods have the problem of requiring data transmission from the secondary side, requiring additional devices to achieve communication, and having large device sizes, or having complex identification algorithms and long calculation times. Summary of the Invention

[0005] The purpose of the present invention is to provide a method for realizing constant voltage and constant current control of the load on the primary side of a WPT system in order to overcome the problems of the existing WPT system control method in that the calculation is complex and the additional equipment is required, resulting in a larger device volume.

[0006] The purpose of the present invention can be achieved by the following technical solutions:

[0007] A method for implementing constant voltage and constant current control of a load on the primary side of a WPT system, the method comprising the following steps:

[0008] S1: Obtain the current and voltage at the transmitting end of the main circuit of the WPT system, build a WPT system model, and simplify it to obtain a simplified model;

[0009] S2: Based on the simplified model, a WPT system model is constructed in a two-dimensional stationary αβ coordinate system and converted into a WPT system model in a two-dimensional rotating dq coordinate system;

[0010] S3: Decompose the coordinates in the two-dimensionally rotated dq coordinate system to obtain the secondary current expression;

[0011] S4: Select another system operating angular frequency ω1 near the operating angular frequency ω0 when the system is resonant, and construct the primary side impedance value equation;

[0012] S5: Substitute the secondary current expression into the primary impedance value equation to obtain the secondary current value. Substitute the secondary current value into the WPT system model in the two-dimensional rotated dq coordinate system to obtain the secondary voltage value.

[0013] S6: The fuzzy controller tracks the voltage or current according to the secondary current value and the secondary voltage value, outputs a control signal and sends the signal to the H-bridge inverter of the WPT system to achieve constant voltage-constant current control.

[0014] Furthermore, the WPT system includes an H-bridge inverter, a transmitter series resonant circuit, a receiver series resonant circuit and a full-bridge rectifier circuit. dc is the DC power supply, C S is the power filter capacitor, field effect transistors Q1 to Q4 form an H-bridge inverter, L p is the transmitting coil inductance, L s is the receiving coil inductance, C p 、C s is the resonant compensation capacitor corresponding to the transmitting end and the receiving end, M is the mutual inductance between the transmitting coil and the receiving coil, i s 、i p are the high-frequency resonant currents at the transmitting and receiving ends, R p 、R s is the parasitic resistance of the transmitting circuit and the receiving circuit, and the rectifier diodes D1 to D4 form an uncontrolled rectifier. f is the rectifier bridge filter capacitor, and RL is the equivalent resistance on the load side.

[0015] Furthermore, the WPT system model in the two-dimensional rotating dq coordinate system is:

[0016]

[0017] Among them, U dqp represents the inverter output voltage in the dq coordinate system, I dqp Represents the primary current in the dq coordinate system, I dqs represents the secondary current in the dq coordinate system, R e represents the resistive equivalent load, and ω represents the angular frequency.

[0018] Furthermore, the specific steps of S3 are:

[0019] Definition I dqp =I dp +jI qp ,I dqs =I ds +jI qs , where I dp Represents the primary d-axis current, I qp Represents the primary q-axis current, I ds Represents the secondary d-axis current, I qs Represents the secondary q-axis current.

[0020] Perform coordinate decomposition on the original and secondary circuits in the two-dimensional rotated dq coordinate system, and decompose the original and secondary circuits into a set of real and imaginary part equations;

[0021] The secondary current expression is obtained based on the imaginary part equation group.

[0022] Furthermore, the real and imaginary part equations are:

[0023]

[0024] Among them, U s Represents the real voltage of the inverter.

[0025] Furthermore, the secondary current expression is:

[0026] ω 2 M 2 I s 2 =A 2 +B 2

[0027] Among them, I s represents the secondary current, A and B are intermediate parameters;

[0028]

[0029] Among them, U p Indicates the fundamental component of the inverter output voltage.

[0030] Furthermore, the primary impedance equation is:

[0031]

[0032]

[0033] Among them, Z p Represents the reflected impedance.

[0034] Furthermore, one side of the H-bridge inverter is connected to a DC power supply, and the other side is connected to the transmitting coil, and the full-bridge rectifier circuit is connected to the receiving coil.

[0035] Furthermore, the specific steps of S1 are:

[0036] Get the current i at the transmitting end of the main circuit of the WPT system p and voltage u p , converting the transmitting end current into a square wave signal with the same frequency and phase, the square wave signal and the transmitting end voltage u p Perform phase comparison to generate phase difference pulse signal and obtain primary current impedance angle Based on the primary current impedance angle and the main circuit transmitter current i p A WPT system model is constructed and simplified to obtain a simplified model.

[0037] Furthermore, the step of converting the transmitting end current into a square wave signal with the same frequency and phase is achieved by a digital phase detector.

[0038] Compared with the prior art, the present invention has the following beneficial effects:

[0039] 1. This invention uses a coordinate transformation algorithm to perform parameter identification, requiring only primary-side voltage and current information, eliminating the need for secondary-side data transmission. This enables communication-free control of the primary and secondary sides. This eliminates the need for additional circuitry on the secondary side, reducing the size of the device.

[0040] 2. The present invention uses a coordinate transformation algorithm to perform parameter identification without iterative calculation. Compared with other identification algorithms, the operation steps are simple, the calculation is convenient, the time required is short, and the accuracy is high, which is suitable for engineering practice.

[0041] 3. The present invention uses fuzzy control to perform phase-shift output control, which has the characteristics of nonlinear tolerance, rule-driven, and strong robustness, and is suitable for nonlinear, high-order, and strongly coupled WPT systems. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Figure 1 It is an overall block diagram of the present invention;

[0043] Figure 2 This is the WPT system topology diagram used in the present invention;

[0044] Figure 3 This is the WPT system modeling diagram of the present invention;

[0045] Figure 4 is a flow chart of the present invention;

[0046] Figure 5 It is the fuzzy control flow chart of the present invention;

[0047] Figure 6 This is an identification comparison diagram of an example of the present invention;

[0048] Figure 7 This is a constant pressure control curve diagram of an example of the present invention;

[0049] Figure 8 This is a constant current control curve diagram of an example of the present invention. DETAILED DESCRIPTION

[0050] The present invention is described in detail below with reference to the accompanying drawings and specific embodiments. This embodiment is implemented based on the technical solution of the present invention, and provides a detailed implementation method and specific operation process, but the protection scope of the present invention is not limited to the following embodiments.

[0051] The present invention proposes a method for realizing constant voltage and constant current control of the load on the primary side of a WPT system. Compared with general identification algorithms, the use of a coordinate transformation algorithm for identification has a simpler operation process, faster calculation speed, higher accuracy, and more identifiable parameters. Compared with other identification algorithms, it is more suitable for engineering practice. Considering that the WPT system is a loosely coupled system with the characteristics of nonlinearity, high order and strong coupling, the commonly used linear control algorithm is not applicable to this. Fuzzy control, which is suitable for systems that are difficult to model, is used for control. The identified data is imported into the fuzzy controller, and feedback control is performed on the high-frequency inverter to achieve constant current and constant voltage control.

[0052] The present invention proposes a method for realizing constant voltage and constant current control of load on the primary side of a WPT system. Figure 1 The invention comprises a sampling circuit, a zero-crossing detection circuit, a digital phase detector, an algorithm module, a fuzzy controller and a microprocessor.

[0053] The sampling circuit completes the WPT system main circuit transmitting end current i p (θ) and voltage u p (θ) is detected. The zero-crossing detection circuit detects the current i p (θ) is converted into a square wave signal u with the same frequency and phase i (θ), the digital phase detector converts the voltage signal u p (θ) and current signal u i (θ) is used for phase comparison to generate a phase difference pulse signal and obtain the primary current impedance angle. The algorithm module processes the primary side current impedance angle through frequency conversion and ip (θ) The secondary side voltage u is obtained through the coordinate transformation algorithm s With current i s ; The fuzzy controller is based on the voltage u s With current i s , the fuzzy controller is based on the voltage u s With current i s , combined with fuzzy algorithm to implement voltage or current tracking, reduce the voltage difference or current difference to 0, and realize constant voltage and constant current control.

[0054] The microprocessor generates the H-bridge drive logic signal to control the switching of the MOSFETs in the H-bridge high-frequency inverter. Based on the feedback from the fuzzy controller, the original logic signal is phase-shifted to adjust the on-time of the inverter bridge arm to control the output voltage and current, achieving a constant voltage and constant current function. The drive signal is also frequency-converted at regular intervals to help the algorithm module complete its calculations.

[0055] Combine Figure 1 and Figure 2 The main circuit of the WPT system adopts a typical dual-coil series topology main circuit structure, which is mainly composed of an H-bridge inverter, a transmitter series resonant circuit, a receiver series resonant circuit and a full-bridge rectifier circuit; among them, U dc is the DC power supply, C S is the power filter capacitor, field effect transistors Q1 to Q4 form an H-bridge inverter, L p is the transmitting coil inductance, L s is the receiving coil inductance, C p 、C s is the resonant compensation capacitor corresponding to the transmitting end and the receiving end, M is the mutual inductance between the transmitting coil and the receiving coil, and the tightness of the magnetic coupling between the two coils is represented by the coupling coefficient, i s 、i p are the high-frequency resonant currents at the transmitting and receiving ends, R p 、R s is the parasitic resistance of the transmitting circuit and the receiving circuit. The rectifier diodes D1 to D4 form a full-bridge rectifier. C f It is the filter capacitor of the rectifier bridge, and its charging and discharging function is used to make the output voltage U o tends to be smooth; RL is the equivalent resistance on the load side;

[0056] Combine Figure 2 The constant voltage-constant current control circuit includes an acquisition circuit, a zero-crossing detection circuit, a digital phase detector, an algorithm module, a fuzzy controller, a microprocessor and an H-bridge inverter drive circuit;

[0057] Among them, the sampling circuit completes the WPT system main circuit transmitting end current i p(θ) detection; the zero-crossing detection circuit will i p (θ) is converted into a square wave signal u with the same frequency and phase i (θ); the digital phase detector converts the voltage signal u p (θ) and current signal u i (θ) is used for phase comparison to generate a phase difference pulse signal to obtain the primary current impedance angle The algorithm module processes the primary side current impedance angle through frequency conversion and i p (θ) The secondary side voltage u is obtained through the coordinate transformation algorithm s With current i s ; The fuzzy controller is based on the voltage u s With current i s , combined with a fuzzy algorithm to track voltage or current, reducing the voltage or current difference to zero, achieving constant voltage and constant current control. The microprocessor generates the H-bridge drive logic signal to control the switching of the MOSFETs in the H-bridge high-frequency inverter. Based on feedback from the fuzzy controller, the original control signal is phase-shifted, adjusting the on-time of the MOSFETs in the inverter to control the output voltage and current, achieving constant voltage and constant current. The drive signal is also frequency-converted at regular intervals to assist the algorithm module in completing calculations.

[0058] The control method of the high-frequency inverter is as follows: the gate input frequency of the switching tubes Q1 and Q4 is equal to the operating frequency f and the driving signal with a duty cycle of D, and the gate input of the switching tubes Q2 and Q3 is delayed by half a cycle compared with the driving signal of Q1 and Q4.

[0059] like Figure 4 The algorithm module receives the primary current impedance angle and i p (θ) starts calculation;

[0060] S1: Build a system model and simplify it;

[0061] At present, the traditional analysis method is to first convert the secondary side rectification, filtering and load into a resistive load R e form, The inverter output voltage can be expressed as the fundamental component U p Alternative, The model is simplified as Figure 3 As shown;

[0062] According to Kirchhoff's voltage law, the loop equation of the equivalent model can be obtained:

[0063]

[0064] Equation 1 is the simplified model.

[0065] At this time, the original secondary voltage and current phase information is introduced, and the default input voltage is the cosine value, i p 、i s is the original secondary current, is the primary-secondary current impedance angle.

[0066]

[0067] S2: Construct a virtual circuit to transform the two-dimensional stationary coordinate system into a two-dimensional rotating coordinate system;

[0068] The primary voltage is lagged by 90° as an analog circuit to construct a two-dimensional stationary αβ coordinate system. After Euler transformation, I dqp with I dqs Respectively represent and The primary and secondary currents of the system can be expressed as:

[0069]

[0070] Through the above current, the primary coil self-inductance voltage It can be expressed as:

[0071]

[0072] Similarly, the self-inductance voltage of the secondary coil and the voltage of the primary-secondary resonant compensation capacitor can be expressed as:

[0073]

[0074] Establishing the primary and secondary side models in the αβ coordinate system, the above loop equation (Formula 1) can be rewritten as:

[0075]

[0076] By multiplying the equations by the rotation factor e jωt , perform coordinate transformation from the two-dimensional stationary αβ coordinate system to the two-dimensional rotating coordinate system dq coordinate system, and extract the rotation factor to obtain:

[0077]

[0078] S3: Decompose the coordinates in a two-dimensional rotating coordinate system to obtain the secondary current expression;

[0079] Definition I dqp =I dp +jI qp ,I dqs =I ds +jI qs , perform coordinate decomposition of the original secondary circuit in the dq coordinate system, and decompose the original circuit into a set of real and imaginary part equations:

[0080]

[0081] The instantaneous value of the primary current and its instantaneous rate of change can be collected in real time through the current detector. At this time, the following can be defined respectively:

[0082]

[0083] From the above formula, we can know that the amplitude of the secondary current can be calculated by multiplying the two formulas:

[0084] ω 2 M 2 I s 2 =A 2 +B 2 (10)

[0085] At this time, there are still no constraints, so there are unknown quantities and the secondary voltage I cannot be calculated. s ;

[0086] S4: Solve the unknowns by frequency modulation;

[0087] According to the definition of reflected impedance, the real part of the primary impedance value can be expressed as:

[0088]

[0089] At resonance, the impedance reflected from the secondary side to the primary side is purely resistive. When it is not purely resistive, this will affect the resonant state of the system, causing the system to no longer be completely resonant, which will have an adverse effect on the system's transmission power and transmission efficiency. The unknown quantity can be measured by changing the frequency.

[0090] ω0 is the operating angular frequency of the system when it resonates. Assuming that another system operating angular frequency ω1 is selected near the operating angular frequency ω0 when the system resonates, the equation is as follows:

[0091]

[0092] S5: Get the secondary side parameter value;

[0093] Finally, the secondary current is calculated according to formula (10), and the dynamic detection of the secondary circuit current can be completed. The current value is known, and the secondary voltage value can be derived according to the loop equation. The obtained data is brought into the fuzzy controller for calculation.

[0094] like Figure 5 The fuzzy controller calculates the output Δu based on the voltage / current difference and continuously adjusts the conduction angle to make the error zero.

[0095] The output of the controller is adjusted according to the input error e and the error change rate ec. The input variables are fuzzified. The fuzzy subsets of e are {NB, NM, NS, ZE, PS, PM, PB}, the fuzzy subsets of ec are {NB, NM, NS, ZE, PS, PM, PB}, and the fuzzy subsets of output Δu are {NB, NM, NS, ZE, PS, PM, PB}. The fuzzy subsets are quantitatively described using membership functions. Gaussian membership functions are selected for "NB" and "PB", and triangular membership functions are selected for the other linguistic variables. The fuzzy rules are as follows: Table 1

[0096] Table 1 Fuzzy control rules table

[0097]

[0098] The Mamdani method is used for reasoning, and the rules of fuzzy reasoning are:

[0099] If e=E i and ec=EC i

[0100] Then Δu=U i (i=1,2,3···7)

[0101] According to the fuzzy control rule table, after fuzzy reasoning, the fuzzy value of the output Δu can be obtained; because the precise value needs to be output to the accumulator, the result must be defuzzified; the present invention uses the area centroid method to perform defuzzification and calculate the precise value of the output u;

[0102]

[0103] The microprocessor obtains the output of the fuzzy controller, controls the MOSFET duty cycle of the high-frequency inverter, and adjusts the duty cycle to adjust the output voltage and current to achieve constant voltage and constant current control.

[0104] Therefore, the specific control method of constant voltage-constant current control is: the amplitude and phase difference of the current and voltage at the transmitting end are detected through the sampling detection circuit, the voltage / current of the secondary side is calculated through the algorithm module, the set value is used as a reference, and compared with the calculated voltage / current, the difference and the rate of change of the difference are input into the fuzzy controller, the processor outputs the PWM drive signal to the gate of the switch tube, controls the on and off time of the bridge arm, and adjusts the duty cycle of the drive signal, so that the voltage / current of the secondary side can reach the required value to achieve constant voltage-constant current control.

[0105] In order to verify the above theoretical analysis, the control strategy proposed above was verified based on the data in Table 2.

[0106] Table 2 WPT system parameters

[0107]

[0108] The identification algorithm does not need to use matrix iteration like the traditional algorithm, and the identification speed is fast. Figure 6 As shown in the figure, it is a comparison diagram between the calculated value and the actual value. The secondary current amplitude calculated by identification is basically consistent with the actual value, and the difference error with the actual value is within 0.1%, which does not affect the subsequent stable control of the actual voltage / current. For this system, this error accuracy is within the allowable range.

[0109] Then, a WPT system simulation model was built in MATLAB / Simulink, the system offset was simulated by dynamically adjusting the load and mutual inductance, and a closed-loop control based on fuzzy control was designed. Figure 7 and Figure 8 The constant voltage-constant current curve for the fuzzy control system under offset conditions shows that the output current / voltage values remain stable near the set values. When a disturbance is introduced at 0.05 seconds, the voltage / current values quickly return to the set values, demonstrating stable system operation and achieving constant voltage-constant current control.

[0110] The above describes in detail the preferred embodiments of the present invention. It should be understood that those skilled in the art can make numerous modifications and variations based on the concepts of the present invention without inventive effort. Therefore, any technical solutions that can be derived by those skilled in the art through logical analysis, reasoning, or limited experimentation based on the concepts of the present invention and the prior art should be within the scope of protection defined by the claims.

Claims

1. A method for realizing constant voltage and constant current control of loads on the primary side of a WPT system, characterized in that: The method comprises the following steps: S1: Obtain the current and voltage at the transmitting end of the main circuit of the WPT system, build a WPT system model, and simplify it to obtain a simplified model; S2: Based on the simplified model, a WPT system model is constructed in a two-dimensional stationary αβ coordinate system and converted into a WPT system model in a two-dimensional rotating dq coordinate system; S3: Decompose the coordinates in the two-dimensionally rotated dq coordinate system to obtain the secondary current expression; S4: Select another system operating angular frequency ω1 near the operating angular frequency ω0 when the system is resonant, and construct the primary side impedance value equation; S5: Substitute the secondary current expression into the primary impedance value equation to obtain the secondary current value. Substitute the secondary current value into the WPT system model in the two-dimensional rotated dq coordinate system to obtain the secondary voltage value. S6: The fuzzy controller tracks the voltage or current according to the secondary current value and the secondary voltage value, outputs a control signal and sends the signal to the H-bridge inverter of the WPT system to achieve constant voltage-constant current control.

2. A method for realizing constant voltage and constant current control of a load on the primary side of a WPT system according to claim 1, characterized in that: The WPT system includes an H-bridge inverter, a transmitting end series resonant circuit, a receiving end series resonant circuit and a full-bridge rectifier circuit. dc is the DC power supply, C S is the power filter capacitor, field effect transistors Q1 to Q4 form an H-bridge inverter, L p is the transmitting coil inductance, L s is the receiving coil inductance, C p 、C s is the resonant compensation capacitor corresponding to the transmitting end and the receiving end, M is the mutual inductance between the transmitting coil and the receiving coil, i s 、i p are the high-frequency resonant currents at the transmitting and receiving ends, R p 、R s is the parasitic resistance of the transmitting circuit and the receiving circuit, and the rectifier diodes D1 to D4 form an uncontrolled rectifier. f is the rectifier bridge filter capacitor, and RL is the equivalent resistance on the load side.

3. The method for realizing constant voltage and constant current control of a load on the primary side of a WPT system according to claim 2, characterized in that: The WPT system model in the two-dimensional rotating dq coordinate system is: Among them, U dqp represents the inverter output voltage in the dq coordinate system, I dqp Represents the primary current in the dq coordinate system, I dqs represents the secondary current in the dq coordinate system, R e represents the resistive equivalent load, and ω represents the angular frequency.

4. A method for realizing constant voltage and constant current control of a load on the primary side of a WPT system according to claim 3, characterized in that: The specific steps of S3 are: Definition I dqp =I dp +jI qp ,I dqs =I ds +jI qs , where I dp Represents the primary d-axis current, I qp Represents the primary q-axis current, I ds Represents the secondary d-axis current, I qs represents the secondary q-axis current; Perform coordinate decomposition on the original and secondary circuits in the two-dimensional rotated dq coordinate system, and decompose the original and secondary circuits into a set of real and imaginary part equations; The secondary current expression is obtained based on the imaginary part equation group.

5. A method for realizing constant voltage and constant current control of a load on the primary side of a WPT system according to claim 4, characterized in that: The real and imaginary part equations are: Among them, U s Represents the real voltage of the inverter.

6. A method for realizing constant voltage and constant current control of a load on the primary side of a WPT system according to claim 5, characterized in that: The secondary current expression is: ω 2 M 2 I s 2 =A 2 +B 2 Among them, I s represents the secondary current, A and B are intermediate parameters; Among them, U p Indicates the fundamental component of the inverter output voltage.

7. The method for realizing constant voltage and constant current control of a load on the primary side of a WPT system according to claim 1, characterized in that: The primary impedance equation is: Among them, Z p Represents the reflected impedance.

8. The method for realizing constant voltage and constant current control of a load on the primary side of a WPT system according to claim 2, characterized in that: One side of the H-bridge inverter is connected to a DC power supply, the other side is connected to the transmitting coil, and the full-bridge rectifier circuit is connected to the receiving coil.

9. The method for realizing constant voltage and constant current control of a load on the primary side of a WPT system according to claim 1, characterized in that: The specific steps of S1 are: Get the current i at the transmitting end of the main circuit of the WPT system p and voltage u p , converting the transmitting end current into a square wave signal with the same frequency and phase, the square wave signal and the transmitting end voltage u p Perform phase comparison to generate phase difference pulse signal and obtain primary current impedance angle Based on the primary current impedance angle and the main circuit transmitter current i p A WPT system model is constructed and simplified to obtain a simplified model.

10. A method for realizing constant voltage and constant current control of a load on the primary side of a WPT system according to claim 9, characterized in that: The step of converting the transmitting end current into a square wave signal with the same frequency and phase is achieved by a digital phase detector.

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