Research On Load And Mutual Inductance Identification For Magnetic Coupling Wireless Power Transfer Systems

Magnetic Coupling Wireless Power Transfer?MC-WPT?technology is a technology synthesized multiple techniques such as the power electronic,resonance compensation and control technology and transfer power wirelessly based on the alternating electromagnetic field.With the development and research of MC-WPT,it has attracted a wide attention recently and the applicational process of MC-WPT has been promoted.In some applications,the relative position between the energy receiving side and the energy receiving side is fixed.Therefore,the mutual inductance can be regarded as constant,while the variation of the load can not be ignored.In some other applications,the energy receiving side can be moved freely from the energy transmitting side,which leads to variations of the mutual inductance.In addition,different types of energy receiving equipment present different load characteristics.An important feature of a MC-WPT system is its power transfer efficiency and capability can be significantly affected by the load and the magnetic coupling variations.Therefore,identifying the load and mutual inductance is essential for improving the power transfer capability and power transfer efficiency of MC-WPT systems.In this thesis,the research is focused on the load and mutual inductance identification of different types of MC-WPT systems including four basic compensation topologies.Also,the feasibility of each proposed method has been verified by both simulation and experimental results.Further,all the identification methods proposed in this thesis can be achieved without any extra circuits.As a result,the cost and complexity of system is decreased.The main works of this thesis are as follows.1.Based on least squares algorithm,a load identification method for P/S-type MC-WPT systems when the mutual inductance is invariable is proposed.The differential equations are derived based on the system model.In order to build the system process parameters vector and the data matrix,the mathematical description of the relationship between two state variable has been derived based on Laplace transform and Tustin transform.By using least squares algorithm,the identification result can be obtained finally.The proposed method has been verified under stead state and transient condition respectively based on the simulation model,while the experimental results have also verified the feasibility of the proposed method.Further,the general relationship between the identification error and running time is discussed through the simulation model.2.A load and mutual inductance identification method for S/S-type MC-WPT systems based on Genetic Algorithm is proposed.The detailed description of Genetic Algorithm which is adopted in this paper has been given.The steady-state circuit model is established by taking into account the higher harmonics.Based on the circuit model,the relationship between the circuit parameters and the state variables is obtained.Further,the load and the mutual inductance identification are achieved by using Genetic Algorithm.Based on the simulation model,the general relationship between the measured value and the calculated value of the primary resonant current is discussed.And,the value of the harmonic order can be determined.In the simulation verification,the minimum and mean fitness before the 20^th generation are listed and all the results have proved the property of fast convergence of Genetic Algorithm.Finally,the feasibility and the validity of the proposed method has been verified by both simulation and experimental results.3.A steady-state load and mutual inductance identification method focusing on series-parallel compensated MC-WPT systems is proposed.According to the steady-state characteristics of the system,the identification model is established based on the approximation theory of fundamental wave.Based on this model,the expressions of the parameters to be identified are derived.Further,two sets of identification results are obtained and then they are analyzed in detail to eliminate the untrue one.The simulation model is built and the range of the normalized angular frequency under normal operation is analyzed.Under the different set values of the load resistance and the mutual inductance,more simulations are performed to verify the validity of the proposed method.Finally,a prototype of the series-parallel compensated MC-WPT system is built to verify the feasibility and the validity of the proposed method.4.Focusing on the MC-WPT systems with parallel-tuned secondary power pickup,this paper proposes a load and mutual inductance identification method based only on the information detected from the primary side.And the proposed method can be implemented for primary resonant circuits regardless they are series or parallel tuned,or with a hybrid compensation such as an LCL configuration.An identification model is established according to the steady-state characteristics of the system and two sets of identification results are obtained.The ranges of the two results is discussed under general operating condition.If both the two results are positive,the RMS values of high order harmonic of a certain variable are need to be calculated based on the two results.Then,the mean-squared error?MSE?between the measured values and the two calculated values are computed respectively to eliminate the unreasonable solution.Finally,both simulation and experimental results verify the feasibility of the proposal.