Research On Energy Efficiency Optimization Of Wireless Power Transfer System Based On PT Symmetry

Magnetic resonance wireless power transfer(MCRWPT)systems are widely used in electric vehicles,medical equipment,and underwater operations due to their high transmission efficiency,moderate transmission distance,and high output power.However,the inherent drawback of MCRWPT systems is that their transmission efficiency and output power will not remain constant when the transmission distance changes.On the other hand,wireless power transfer systems based on parity-time symmetry(PT-WPT)theory can overcome this drawback.When the system is above the critical coupling coefficient and within the effective transmission distance,the transmission efficiency and output power will remain constant even if the transmission distance changes,thus maintaining the system’s energy efficiency characteristics.However,the existence of the critical coupling coefficient and effective transmission distance is a major flaw of PT-WPT systems.To address this issue,this paper focuses on the series-series(S-S)type PT-WPT system and conducts a series of studies to expand the effective transmission distance and achieve system energy efficiency optimization.Specifically,the paper first introduces the overall structure of the magnetic coupling wireless power transfer system and analyzes the impedance and output characteristics of four traditional topologies.Then,the background and physical significance of parity-time theory are introduced,and the principle of applying parity-time theory to WPT systems is explained.The PT-WPT system is theoretically modeled using circuit analysis,and the expressions for the transmission efficiency,output power,critical coupling coefficient,and system parameters are obtained.Next,this paper proposes the use of a bilateral capacitance array to change the natural resonance frequency of the original and secondary sides,thereby further reducing the critical coupling coefficient and expanding the effective transmission distance of the singletransmitter-single-receiver PT-WPT system.To verify the feasibility of the proposed solution,the general expression for the input impedance of the WPT system in PT symmetric state is derived.A self-adaptive critical coupling coefficient adjustment strategy that does not require bilateral communication is proposed to implement this solution.Finally,through simulation and experimentation,it is demonstrated that the proposed solution achieves a reduction in the critical coupling coefficient while maintaining constant transmission efficiency and output power.Lastly,this paper proposes a multi-transmitter-multi-receiver PT-WPT system and conducts energy efficiency optimization research on the system.The general expressions for the output power,transmission efficiency,and critical coupling coefficient of the system are derived.The energy efficiency problem of the system is actually a nonlinear programming problem.To solve this problem,a particle swarm algorithm based on penalty function constraints is proposed to optimize the parameters,with the energy efficiency index required by the project as the objective function.The optimization result is a dual-transmitter-singlereceiver PT-WPT system.To satisfy the mutual inductance assumption between the coils of the multi-transmitter-multi-receiver PT-WPT system,a BP coil is used for the original side,and a DD coil is used for the secondary side,and the decoupling of the BP coil is verified in Maxwell.Finally,the PT-WPT system constructed by the optimization result is experimentally verified,and its energy efficiency characteristics meet the expected values of the project.While having a low critical coupling coefficient,the system also has a high transmission efficiency and stable output power.