Research On Circulating Suppression In MC-WPT System With Multiple Inverter Modules Operated In Parallel

With the magnetic coupling wireless power transfer(MC-WPT)technology gradually becoming a major research hotspot,MC-WPT technology is applied to large power applications such as electric vehicle charging and downhole drilling rod field commonly.Sometimes,the single high frequency inverter module is difficult to meet the power demand of a large-power MC-WPT system because of its own power capacity,heat dissipation,the price of the switches and other factors.It is an acknowledged method to improve the power capacity of the power supply system by using multiple sets of high-frequency inverter modules.The technology with multiple high-frequency inverter modules operated in parallel has many advantages.However,the circulating current among multiple inverters in parallel-connected system is the key and difficult point to realize MC-WPT system.In a MC-WPT system with multiple inverters operated in parallel,due to the difference of parameters such as device tolerance,control delay,gate drive delay,randomness of pulse width modulator and input voltage of inverters,it is possible to cause circulating current between various inverter modules.The circulating current makes the output current of each inverter module deviate from its rated value,resulting in distortion of the output current of the inverter and electromagnetic interference.In addition,the circulating current also causes the output power of each module to be unbalanced,and the heating of some modules is serious,so that the overall performance and life of the MC-WPT system are reduced.The suppression of the circulating current among the inverter modules becomes the key and difficult point in realizing parallel inverter MC-WPT system.In this paper,the MC-WPT system with multiple inverters operated in parallel is applied to be the research object.The circulating current between the high frequency inverter modules is studied.The purpose of this paper is to achieve large-power MC-WPT system with low power switches and to solve the circulating current between inverters.First of all,the research background and the current research situation and development trend of parallel inverter MC-WPT system are analyzed in detail.Secondly,the mathematical model of a high-frequency inverter module is analyzed,and the related problems of parallel inverter technology are expounded in detail.On this basis,the research work of this paper is based on a high-flexibility and low-loss SP-T type parallel inverter MC-WPT system.The topological structure of the system is given,and the characteristics of circulating current among inverters and the output power of each module are analyzed.In order to ensure the transmission performance of the system,the design method of partial system parameters and design process are given.At the same time,in order to suppress the circulating current between the high-frequency inverter modules,a current decomposition method and the circulating current suppression strategy based on the current decomposition method are proposed.Finally,in order to verify the rationality of the proposed parameter design method and the effectiveness of the circulating suppression strategy,both the simulation and experiment are carried out to verify the results.The experimental results show that the circulating current suppression strategy proposed in this paper can effectively restrain the circulation between inverter modules.