CN105005669B - IPT systematic parameter optimization methods based on frequency Bifurcation Characteristics - Google Patents

Abstract

The present invention proposes an IPT system parameter optimization method based on frequency bifurcation characteristics, the method obtains the initial value of the primary side compensation capacitor through the AC impedance analysis method , and then according to iterative calculation and computer simulation, the optimal value C _p of the primary side compensation capacitor is obtained, so that the soft switching frequency bifurcation diagram of the IPT system is a standard fork bifurcation diagram, that is, there is a frequency-invariant region. In this way, as long as the IPT The load _RL of the system does not exceed the load range in the frequency constant region, which can ensure that the soft switching frequency of the IPT system remains constant. The optimization method is simple, direct and effective, and can quickly obtain the optimal value C _p of the primary side compensation capacitor.

Description

Parameter Optimization Method of IPT System Based on Frequency Bifurcation Characteristics

technical field

The invention relates to the field of inductive power transmission (IPT), in particular to an IPT system parameter optimization method based on frequency bifurcation characteristics.

Background technique

Inductive power transfer technology, referred to as IPT technology, is based on the principle of electromagnetic field near-field loose coupling induction, and comprehensively utilizes power electronic conversion technology, magnetic field coupling technology and control theory to realize electrical equipment to obtain energy from the grid in a non-wire contact manner. It is widely used in urban electrified rail transit, pure electric vehicles, mobile electrical equipment in special environments such as flammable and explosive, new energy power generation, oil drilling, tailless household appliances, and electrical equipment implanted in organisms.

As shown in Figure 1, from the perspective of system structure, the IPT system includes two parts, the primary side and the secondary side. The electric energy is output to the load after reactive power compensation and energy conversion. The particularity and complexity of the structure lead to the typical high-order nonlinear characteristics of the system, which leads to complex dynamic behavior and increases the difficulty of system modeling, analysis and control.

In the basic reactive power compensation network of the IPT system, according to the position of the compensation capacitor, it can be divided into primary-side series-secondary-side series compensation (hereinafter referred to as SS topology), primary-side series-secondary parallel compensation and parallel connection (hereinafter referred to as SP-type topology), primary There are four basic reactive power compensation topologies: side-parallel-secondary-side series compensation (hereinafter referred to as PS topology), and primary-side parallel-secondary parallel compensation (hereinafter referred to as PP-type topology).

IPT systems usually have two common control strategies, namely fixed frequency control and floating frequency control:

① Fixed frequency control

In the fixed frequency mode, the controller actively sends out a pulse signal of a certain frequency to control the switching of the inverter, and the system performs forced oscillation at this frequency. The switching frequency of the system is fixed and does not change with the change of parameters. Therefore, when the load is switched or the parameters drift, the system is easy to enter the hard switching working state, causing large switching loss and electromagnetic interference (EMI), which is not conducive to the long-term stable operation of the system.

② Floating frequency control

Under floating frequency control, the controller controls the switching of the inverter in real time according to the zero-crossing signal of the feedback voltage or current. The switching frequency of the system tracks the resonance frequency. Switching the switching tube every time the switching resonance voltage or current crosses zero can ensure the total operation of the system. In the soft switching state, the floating frequency mode has better parameter adaptive ability than the fixed frequency mode. However, floating frequency control also has some limitations: the structure is relatively complex, and detection, transmission and control links are required, which reduces the reliability of the system; it cannot work at an unstable soft switching point, and frequency jumps may occur in the frequency bifurcation area change; the response speed of the control circuit is relatively high, and if there is a delay, the system will work in a hard switching state; if it is detuned, it may cause great damage to the system, so it is generally used in systems with low power.

Literature research shows that in the IPT system, when system parameters such as mutual inductance, primary and secondary side resonance network parameters, and load impedance change, the bifurcation of the system resonance frequency may be caused. The most common bifurcation is the static bifurcation. The static bifurcation refers to the sudden change of the number and stability of the equilibrium point with the change of the parameters. The most common one is the fork bifurcation, the standard graph of the fork bifurcation As shown in Figure 2, the frequency is continuous at the bifurcation, and there is a frequency-invariant region.

If the soft switching frequency of the IPT system can always work in this frequency constant region, the working stability of the IPT system will be greatly improved.

But not all fork-shaped bifurcations are as standard as shown in Figure 2. In many cases, the soft switching frequency is discontinuous at the bifurcation, and there is no frequency constant region, as shown in Figure 3. Therefore, it is particularly important to study a method to optimize the control parameters of the IPT system so that the system soft switching frequency of the IPT system presents a standard fork-shaped bifurcation.

Contents of the invention

In order to overcome the defects in the above-mentioned prior art, the object of the present invention is to provide a method for optimizing IPT system parameters based on frequency bifurcation characteristics, which can make the soft-switching frequency bifurcation diagram of the IPT system appear as a standard fork-shaped bifurcation diagram, so that When the load _RL of the IPT system changes, its soft-switching frequency has better frequency stability, thereby making the IPT system work at a stable soft-switching frequency.

In order to achieve the above-mentioned purpose of the present invention, the present invention provides a kind of IPT system parameter optimization method based on frequency bifurcation characteristic, comprises the following steps:

S1, establish an IPT system model according to actual requirements, and set the soft switching frequency f, primary inductance L _p and secondary inductance L _s of the system;

S2, according to the set soft switching frequency f, the primary inductance L _p and the secondary inductance L _s , select the value of the secondary resonant compensation capacitor C _s ;

S3, the initial value of the primary side compensation capacitor is calculated based on the AC impedance analysis method

S4, according to the primary side inductance L _p , the secondary side inductance L _s , the secondary side resonant compensation capacitor C _s and the initial value of the primary side compensation capacitor in the established IPT system Perform simulation to obtain the preliminary soft-switching frequency bifurcation diagram of the IPT system;

S5, keep the primary side inductance value L _p , the secondary side inductance value L _s and the secondary side resonant compensation capacitor C _s unchanged, and the initial value of the primary side compensation capacitor Take the trial value of the primary side compensation capacitance nearby, and obtain the simple soft switching frequency bifurcation diagram under the trial value of the primary side compensation capacitance through stroboscopic mapping modeling and computer simulation, until the simple soft switching frequency bifurcation diagram is in the standard fork shape When drawing the bifurcation diagram, the tentative value of the primary side compensation capacitance at this time is taken as the optimal value C _p of the primary side compensation capacitance.

Obtaining the initial value of the primary side compensation capacitor by AC impedance analysis Among them, SS-type topology IPT system, PS-type topology IPT system, SP-type topology IPT system and PP-type topology correspond to different initial values of primary side compensation capacitors The initial value of the primary side compensation capacitance of the IPT system with these four topologies It can be calculated by the known AC impedance analysis method, and then the optimal value C _p of the primary side compensation capacitor is obtained according to iterative calculation and computer simulation, so that the simple soft switching frequency bifurcation diagram of the IPT system is a standard fork bifurcation diagram , that is, there is a frequency-invariant region, so as long as the load _RL of the IPT system does not exceed the load range in the frequency-invariant region, the soft switching frequency of the IPT system can be guaranteed to remain unchanged. The optimization method is simple, direct and effective, and can quickly obtain the optimal value C _p of the primary side compensation capacitor.

Further, the method also includes step S6, performing stroboscopic mapping modeling on the parameter-optimized IPT system, drawing a complete and fine soft-switching frequency bifurcation diagram, and verifying whether the optimized value C _p of the primary side compensation capacitor makes the IPT The soft switching frequency bifurcation diagram of the system meets the requirements of the standard fork bifurcation diagram. If so, the design is completed. If not, step S5 is repeated until the optimal value C _p of the primary side compensation capacitor meets the requirements.

The accuracy of the optimal value C _p of the compensation capacitor on the primary side is guaranteed, thereby further improving the stability of the IPT system.

Further, when the IPT system is an SS topology IPT system, the step S3 includes the following steps:

S3-1, analyze the IPT system by impedance analysis method,

The total impedance of the secondary side is obtained as: _RL is the load of the IPT system, ω is the angular frequency of the IPT system work;

The secondary reflection impedance equivalent to the primary side is: Among them, M is the mutual inductance coefficient;

The total system impedance is: R _p is the impedance of the primary side inductance and the line;

S3-2, when the maximum power transmission is achieved, the secondary side of the IPT system is in a complete resonance mode, and the natural resonance frequency of the system is

S3-3, let the imaginary part of the total system impedance be 0, and get the rough value of the primary side compensation capacitor

S3-4, obtain the rough value of the primary side compensation capacitor by the two formulas in step S3-2 and step S3-3

For the SS topology IPT system, the rough value of the primary side compensation capacitor The calculation method is simple, effective and highly accurate.

Further, said step S5 includes the following steps:

S5-1, keeping the primary side inductance L _p , the secondary side inductance L _s and the secondary side resonant compensation capacitor C _s unchanged;

S5-2. According to the bifurcation type adjustment of the preliminary soft switching frequency bifurcation diagram, the value range of the optimal value C _p of the primary side compensation capacitor is obtained, and the stroboscopic mapping is used to model, and any value within the value range is used as the original Substituting the tentative value of side compensation capacitance into the model, and performing simulation to obtain a simple soft switching frequency bifurcation diagram, if the obtained simple soft switching frequency bifurcation diagram is a standard fork bifurcation diagram, then the trial value of the original side compensation capacitance at this time That is, the optimal value C _p of the primary side compensation capacitor. If the obtained simple soft-switching frequency bifurcation diagram is a non-standard fork-shaped bifurcation diagram, perform step S5-3;

S5-3, calculate the soft switching frequency bifurcation diagram by repeating step S5-2, and perform multiple iterative operations until the simple soft switching frequency bifurcation diagram is a standard fork-shaped bifurcation diagram, stop the iterative operation, and obtain the primary side compensation capacitance Optimal value C _p .

Under the condition of keeping the primary side inductance value L _p , the secondary side inductance value L _s and the secondary side resonant compensation capacitor C _s unchanged, iteratively calculate the primary side compensation capacitance test value to obtain the primary side compensation capacitor optimal value C _p , the method is simple, and the calculation accuracy is high and the speed is fast.

Further, when the IPT system is an SS topology IPT system, in step S5-3, if the obtained simple soft-switching frequency bifurcation diagram is an upper-end continuous type, increase the trial value of the primary compensation capacitance; if the obtained simple If the bifurcation diagram of the soft switching frequency is continuous at the lower end, the value of the primary side compensation capacitor should be reduced.

The beneficial effects of the present invention are:

1. Solved the contradiction between the fixed frequency control not adapting to the load change system and the floating frequency control not working at the non-autonomous stable frequency point;

2. Better realize the frequency stability of the system under variable load conditions;

3. Simple implementation, wide adaptability and high reliability;

Additional aspects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention.

Description of drawings

The above and/or additional aspects and advantages of the present invention will become apparent and comprehensible from the description of the embodiments in conjunction with the following drawings, wherein:

Figure 1 is a topological circuit diagram of the SS type IPT system;

Fig. 2 is a standard fork bifurcation diagram;

Figure 3 is a schematic diagram of a non-standard fork bifurcation

Fig. 4 is the schematic flow sheet of this method;

Fig. 5 is a soft switching frequency bifurcation diagram of different primary side compensation capacitance test values;

Figure 6 is a comparison diagram of soft switching frequency bifurcation of the system before and after parameter optimization;

Fig. 7 is a schematic diagram of stroboscopic mapping.

detailed description

Embodiments of the present invention are described in detail below, examples of which are shown in the drawings, wherein the same or similar reference numerals designate the same or similar elements or elements having the same or similar functions throughout. The embodiments described below by referring to the figures are exemplary only for explaining the present invention and should not be construed as limiting the present invention.

In the description of the present invention, unless otherwise specified and limited, it should be noted that the terms "installation", "connection" and "connection" should be understood in a broad sense, for example, it can be mechanical connection or electrical connection, or two The internal communication of each element may be directly connected or indirectly connected through an intermediary. Those skilled in the art can understand the specific meanings of the above terms according to specific situations.

The present invention provides a kind of IPT system parameter optimization method based on frequency bifurcation characteristic, as shown in Figure 4, comprises the following steps:

S1. Establish an IPT system model according to actual requirements, and set the soft switching frequency f, primary inductance L _p and secondary inductance L _s of the system.

S2, according to the set soft switching frequency f, the primary inductance L _p and the secondary inductance L _s , select the value of the secondary resonant compensation capacitor C _s .

S3, the initial value of the primary side compensation capacitor is calculated based on the AC impedance analysis method

When the IPT system is an SS topology as shown in Figure 1, the initial value of the primary side compensation capacitor The calculation method includes the following steps:

S3-1, analyze the IPT system by impedance analysis method,

The total impedance of the secondary side is obtained as: _RL is the load of the IPT system, and ω is the angular frequency of the IPT system.

The secondary reflection impedance equivalent to the primary side is: Among them, M is the mutual inductance coefficient.

The total system impedance is: R _p is the impedance of the primary inductance and the line.

S3-2, when the maximum power transmission is achieved, the secondary side of the IPT system is in a complete resonance mode, and the natural resonance frequency of the system is

S3-3, let the imaginary part of the total system impedance be 0, and get the rough value of the primary side compensation capacitor

S3-4, obtain the rough value of the primary side compensation capacitor by the two formulas in step S3-2 and step S3-3 The rough value of the primary side compensation capacitor The calculation method is simple, effective and highly accurate.

S4, according to the primary side inductance L _p , the secondary side inductance L _s , the secondary side resonant compensation capacitor C _s and the initial value of the primary side compensation capacitor in the established IPT system The simulation is carried out, and the preliminary soft-switching frequency bifurcation diagram of the IPT system is obtained.

S5, keep the primary side inductance value L _p , the secondary side inductance value L _s and the secondary side resonant compensation capacitor C _s unchanged, and the initial value of the primary side compensation capacitor Take the trial value of the primary side compensation capacitance nearby, and obtain the simple soft switching frequency bifurcation diagram under the trial value of the primary side compensation capacitance through stroboscopic mapping modeling and computer simulation, until the simple soft switching frequency bifurcation diagram is in the standard fork shape When drawing the bifurcation diagram, the tentative value of the primary side compensation capacitance at this time is taken as the optimal value C _p of the primary side compensation capacitance.

The value range of the trial value of the primary side compensation capacitor is the initial value of the primary side compensation capacitor

In order to improve the efficiency in the simulation, it is only necessary to take several load values in the frequency transition region, and obtain the soft switching frequencies corresponding to these load values through stroboscopic mapping modeling, so as to obtain the simple soft switching frequency analysis mentioned in this step Fork map.

Specifically, step S5 includes the following three steps:

In the first step, keep the primary inductance L _p , the secondary inductance L _s and the secondary resonant compensation capacitance C _s unchanged.

In the second step, according to the bifurcation type adjustment of the preliminary soft switching frequency bifurcation diagram, the value range of the optimal value C _p of the primary side compensation capacitor is obtained, and the stroboscopic mapping is used to model, and any value in the value range is used as the original Substituting the tentative value of side compensation capacitance into the model, and performing simulation to obtain a simple soft switching frequency bifurcation diagram, if the obtained simple soft switching frequency bifurcation diagram is a standard fork bifurcation diagram, then the trial value of the original side compensation capacitance at this time That is, the optimal value C _p of the primary side compensation capacitor. If the obtained simple soft-switching frequency bifurcation diagram is a non-standard fork-shaped bifurcation diagram, perform step S5-3;

The third step is to calculate the soft-switching frequency bifurcation diagram by repeating step S5-2, and perform multiple iterative operations until the simple soft-switching frequency bifurcation diagram is a standard fork-shaped bifurcation diagram, stop the iterative operation, and obtain the primary side compensation capacitance Optimal value C _p .

When the IPT system is an SS topology as shown in Figure 1, if the obtained simple soft switching frequency bifurcation diagram is the upper-end continuous type, increase the trial value of the primary side compensation capacitor, as shown in Figure 5, if the lower-end For the continuous type, reduce the trial value of the primary side compensation capacitor and perform multiple iterative operations until the simple soft switching frequency bifurcation diagram shows a standard fork-shaped bifurcation diagram, then stop the iterative operation and obtain the optimal value C _p of the primary side compensation capacitor .

The stroboscopic mapping mentioned in this application samples the target system at a fixed sampling frequency, which is consistent with the operating frequency of the system. At the same time, for a system that changes periodically, its stroboscopic mapping model must correspond to a fixed point. Taking the common sinusoidal function curve as an example, the schematic diagram of its stroboscopic mapping modeling is shown in Figure 7. It can be seen that the stroboscopic sampling is performed at a time interval consistent with the operating cycle T, and the result of the stroboscopic mapping is a different Moving point y ^* = Y _s .

The stroboscopic mapping modeling method and the periodic fixed point theory can accurately calculate the soft switching operating point of the resonant converter. For the IPT system with changing load, using this method can establish an accurate mathematical model for the IPT system.

The stroboscopic mapping modeling method is:

Let M-dimensional autonomous nonlinear system:

It can be linearized piecewise into k linear modes, and the state space of each mode is described as:

Assuming that under each linear working mode, the system input quantity u _i (t) = c is constant and the system parameter matrix A _i is reversible, then the analytical solution of the system is: In the formula, x is the state variable and x∈R ^M , the dimension is m, u _i ∈ R ^l , (i=1,2,3...k) is the system input variable, the dimension is l. A _i and B _i are system state coefficient matrix and system input coefficient matrix respectively.

x ₀ =x(0) is the initial state of the modal. The state transition matrix can be expressed as:

In the steady state, the operating period of the system is T, and the working duration of each linear mode is ζ _i , then The state mapping function in each mode can be obtained

Assuming that x _n is the initial state of the cycle in the steady state of the system, and x _n+1 is the end state of the cycle in the steady state of the system, the stroboscopic mapping model of the system in the nth cycle can be expressed as: In the formula is the conversion factor, its meaning is

In steady state, the state vector of the system repeats periodically, that is, x _n+1 = x _n ,

Substitute to get the fixed point x ^* of the system,

The boundary conditions of each mode switching can be expressed as:

Among them, Y _j ∈ R ^p×m , (i=1,2,3...k) is the state transition matrix, which is used to extract the p state variables involved in the boundary conditions from the m-dimensional state vector x.

For the IPT system, for the convenience of analysis, it is assumed that all switching devices are ideal devices. The system can be linearized piecewise, taking the voltage of all capacitive devices and the current of inductive devices in the system as state variables to obtain the state space description equation of each mode; according to the state mapping function in each mode, the periodic fixed point can be obtained Function, and then obtain the steady-state value of each state variable in the soft switching period and the system steady-state period.

In the present invention, under the condition of keeping the primary side inductance value L _p , the secondary side inductance value L _s and the secondary side resonant compensation capacitor C _s unchanged, iteratively calculates the trial value of the primary side compensation capacitor, thereby obtaining the optimal value of the primary side compensation capacitor _Cp . Obtaining the initial value of the primary side compensation capacitor by AC impedance analysis Then, according to the dispersion mapping model and computer simulation, the optimal value C _p of the primary side compensation capacitor is obtained, so that the soft switching frequency bifurcation diagram of the IPT system is a standard fork-shaped bifurcation diagram, that is, there is a frequency-invariant region. In this way, as long as the The load _RL of the IPT system does not exceed the load range in the frequency constant region, which can ensure that the soft switching frequency of the IPT system remains constant. The optimization method is simple, direct and effective, and can quickly obtain the optimal value C _p of the primary side compensation capacitor.

The soft-switching frequency bifurcation diagram of the IPT system after parameter optimization is shown in Figure 6. Before optimization, the soft-switching frequency diagram is a non-standard fork-shaped bifurcation diagram, showing discontinuity and no frequency-invariant region, while After optimizing the parameters, the soft switching frequency diagram of the system is a standard fork bifurcation diagram, which presents frequency continuity and has frequency invariant regions.

In order to speed up the calculation and reduce unnecessary calculations in the optimization process, the calculations on the simulation of the soft switching frequency bifurcation diagram in step S5 are all based on a small number of points. In order to improve that the IPT system can work at a constant soft switching frequency throughout the working process, it is necessary to verify the optimized parameters, that is, to draw a complete and detailed bifurcation diagram for verification, see the soft switching frequency bifurcation Whether the graph meets the requirements of standard fork bifurcation.

Therefore, the method also includes step S6, performing stroboscopic mapping modeling on the parameter-optimized IPT system, drawing a complete and fine soft switching frequency bifurcation diagram, and verifying whether the optimized value C _p of the primary side compensation capacitor makes the IPT system soft The switching frequency bifurcation diagram meets the requirements of the standard fork-shaped bifurcation diagram. If so, the design is completed. If not, step S5 is repeated until the optimal value C _p of the primary side compensation capacitor meets the requirements.

This ensures the accuracy of the optimal value C _p of the compensation capacitor on the primary side, thereby further improving the stability of the IPT system.

In the description of this specification, descriptions referring to the terms "one embodiment", "some embodiments", "example", "specific examples", or "some examples" mean that specific features described in connection with the embodiment or example , structure, material or characteristic is included in at least one embodiment or example of the present invention. In this specification, schematic representations of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.

Although the embodiments of the present invention have been shown and described, those skilled in the art can understand that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principle and spirit of the present invention. The scope of the invention is defined by the claims and their equivalents.

Claims (5)

1. The IPT system parameter optimization method based on frequency bifurcation characteristics, is characterized in that, comprises the following steps: S1, establish an IPT system model according to actual requirements, and set the soft switching frequency f, primary inductance L _p and secondary inductance L _s of the system; S2, according to the set soft switching frequency f, the primary inductance L _p and the secondary inductance L _s , select the value of the secondary resonant compensation capacitor C _s ; S3, the initial value of the primary side compensation capacitor is calculated based on the AC impedance analysis method S4, according to the primary side inductance L _p , the secondary side inductance L _s , the secondary side resonant compensation capacitor C _s and the initial value of the primary side compensation capacitor in the established IPT system Perform simulation to obtain the preliminary soft-switching frequency bifurcation diagram of the IPT system; S5, keep the primary side inductance value L _p , the secondary side inductance value L _s and the secondary side resonant compensation capacitor C _s unchanged, and the initial value of the primary side compensation capacitor Take the trial value of the primary side compensation capacitance nearby, and obtain the simple soft switching frequency bifurcation diagram under the trial value of the primary side compensation capacitance through stroboscopic mapping modeling and computer simulation, until the simple soft switching frequency bifurcation diagram is in the standard fork shape When drawing the bifurcation diagram, the tentative value of the primary side compensation capacitance at this time is taken as the optimal value C _p of the primary side compensation capacitance. 2. the IPT system parameter optimization method based on frequency bifurcation characteristic according to claim 1, is characterized in that, also comprises the steps: S6, perform stroboscopic mapping modeling on the parameter-optimized IPT system, draw a complete and detailed soft-switching frequency bifurcation diagram, and verify whether the optimized value C _p of the primary side compensation capacitor makes the soft-switching frequency bifurcation diagram of the IPT system conform to If the requirements of the standard fork-shaped bifurcation diagram are met, the design is completed; if not, step S5 is repeated until the optimal value C _p of the primary side compensation capacitor meets the requirements. 3. the IPT system parameter optimization method based on frequency bifurcation characteristic according to claim 1, is characterized in that, when this IPT system is SS type topology IPT system, described step S3 comprises the following steps: S3-1, analyze the IPT system by impedance analysis method, The total impedance of the secondary side is obtained as: _RL is the load of the IPT system, ω is the angular frequency of the IPT system work; The secondary reflection impedance equivalent to the primary side is: Among them, M is the mutual inductance coefficient; The total system impedance is: R _p is the impedance of the primary side inductance and the line; S3-2, when the maximum power transmission is achieved, the secondary side of the IPT system is in a complete resonance mode, and the natural resonance frequency of the system is S3-3, let the imaginary part of the total system impedance be 0, and get the rough value of the primary side compensation capacitor S3-4, obtain the rough value of the primary side compensation capacitor by the two formulas in step S3-2 and step S3-3 . 4. the IPT system parameter optimization method based on frequency bifurcation characteristic according to claim 1, is characterized in that, described step S5 comprises the following steps: S5-1, keeping the primary side inductance L _p , the secondary side inductance L _s and the secondary side resonant compensation capacitor C _s unchanged; S5-2. According to the bifurcation type adjustment of the preliminary soft switching frequency bifurcation diagram, the value range of the optimal value C _p of the primary side compensation capacitor is obtained, and the stroboscopic mapping is used to model, and any value within the value range is used as the original Substituting the tentative value of side compensation capacitance into the model, and performing simulation to obtain a simple soft switching frequency bifurcation diagram, if the obtained simple soft switching frequency bifurcation diagram is a standard fork bifurcation diagram, then the trial value of the original side compensation capacitance at this time That is, the optimal value C _p of the primary side compensation capacitor. If the obtained simple soft-switching frequency bifurcation diagram is a non-standard fork-shaped bifurcation diagram, perform step S5-3; S5-3, by repeating step S5-2 to calculate the soft-switching frequency bifurcation diagram, and perform multiple iterative operations until the simple soft-switching frequency bifurcation diagram of the system is a standard fork-shaped bifurcation diagram, stop the iterative operation, and obtain the primary side compensation Capacitance optimization value C _p . 5. The IPT system parameter optimization method based on frequency bifurcation characteristics according to claim 4, wherein, when the IPT system is an SS type topology IPT system, in step S5-3, if the obtained simple soft switching frequency If the bifurcation diagram is continuous at the upper end, increase the trial value of the primary compensation capacitor; if the obtained simple soft switching frequency bifurcation diagram is continuous at the lower end, decrease the trial value of the primary compensation capacitor.