In this paper, the steady-state and transient models of the LCC-S compensated wireless power transfer system (LCC-S WPT) are built. From the steady-state model, the secondary charging voltage and current are respectively proportional to the primary inverter current and coil current. Then the indirect control strategy of the secondary charging voltage and current based on the dual primary current closed-loop control is proposed. From the transient model, the controller parameters design criteria are given. The transient characteristics of the both side variables of the indirect control strategy are originally analyzed. It is proven that a good secondary transient performance is ensured under the indirectly way. Furthermore, the feedforward control of the input voltage is proposed to eliminate its transient effect. The feasibility and practicability of the proposed control strategy are verified by the experiments.

In this letter, an integrated wired/wireless charging topology is proposed to expand the adaptability of the electric vehicle charging stations and further improve the utilization of the charging facilities and venues. By reusing the common structures in the independent wired and wireless charging topologies, on the basis of achieving the wired and the wireless charging function, the integration of charging facilities is improved and its cost is reduced. Based on the isolated converter in the wired mode, a frequency tuning strategy in the wireless mode is proposed to overcome the frequency detuning problem caused by the parameter fluctuations. The feasibility and practicability of the proposed topology and the frequency tuning strategy are verified by the experiments.

In the LCC-LCC wireless power transfer system (WPT) with the secondary buck converter, the overvoltage and overcurrent faults occur when the secondary buck converter is shut down suddenly. In order to ensure the safety, this issue is analyzed at the transient level and the dual-side indirect closed-loop control strategy is proposed to achieve the closed-loop control of the terminal voltage and the secondary dc bus voltage. The secondary dc bus voltage is under the indirect control by the closed-loop control of the primary inverter current and this conclusion is proven in the transient level. Under the dual-side closed-loop control strategy, the two-stage WPT system forms a cascade system and there is the instability problem. The integrated design criteria of the dual-side controller parameters based on the cascade system stability theory is given. The feasibility and practicability of the proposed control strategy and parameter design method are verified by the experiments.

In this paper, an improved modulation strategy for the three-phase matrix converter based wireless power transfer (WPT) system is proposed to enhance the system security and reduce the total harmonic distortion (THD) of the grid current. By analyzing the effect of the switching delay on the standard current space vector PWM (CSVPWM), it is revealed there is the risk of the over-voltage and over-current faults in the process of the vector switching. It also causes the synthesis current vector length error and causes the grid current distortion. To enhance the security and reliability, a switching logic of the current vectors suitable for both the resonant and non-resonant states of the compensation network is proposed. Furthermore, an optimal calculation method of the effective current vectors switching moments is proposed to reduce the grid current THD. The feasibility and practicability of the proposed modulation strategy are verified by the experiments.

In order to improve the integration and life time of ac voltage input wireless power transfer (WPT) system, a topology based on electrolytic-capacitor-less matrix converter with inductor-capacitor-capacitor-series (LCC-S) resonant network is proposed. The relationship between the conversion ratio of the output and input voltages and resonant parameters are analyzed. It reveals although the boost operation is achieved by the parameter design of LCC-S network, it makes the system sensitive to the parameter variations. In order to extend the voltage conversion range, the improved two-stage WPT system based on the single-stage one is proposed. The dual-side closed-loop control of the two-stage system without the wireless communication is further proposed. The corresponding small-signal model is built and the parameters of the closed-loop controllers are designed. The feasibility and practicability of the proposed system are verified by the experiments.