Rectifier Load Analysis for Electric Vehicle Wireless Charging System

ABSTRACT:

This paper presents the analysis of rectifier load used for electric vehicle (EV) wireless charging system, as well as its applications on compensation network design and system load estimation. Firstly, a rectifier load model is established to get its equivalent input impedance, which contains both resistance and inductance components, and can be independently calculated through the parameters of the rectifier circuit. Then, a compensation network design method is proposed, based on the rectifier load analysis. Furthermore, a secondary side load estimation method and a primary side load estimation method are put forward, which adopt only measured voltages and consider the influence of the rectifier load. Finally, an EV wireless charging prototype is developed, and experimental results have proved that the rectifier equivalent load can be correctly calculated on conditions of different system load resistances, rectifier input inductances, DC voltages, and mutual-inductances.  The experiments also show that rectifier load equivalent inductance will impact system performances, and the proposed methods have good accuracy and robustness in the cases of system parameter variations.

KEYWORDS:

  1. Wireless charging system
  2. Rectifier load
  3. Compensation network design
  4. Load estimation

 

SOFTWARE: MATLAB/SIMULINK

 

BLOCK DIAGRAM:

Fig. 1. EV wireless charging system with full-bridge diode rectifier and dual-side LCC compensation networks.

 

EXPECTED SIMULATION RESULTS

Fig.2. Simulation results of Le effects on output power and efficiency.

Fig. 3. Simulated load estimation results of the proposed primary side method, when L1 has the inductance with ±1.5uH errors.

Fig. 4. Simulated load estimation results of the proposed primary side method, when M varies about 23%.

Fig.5. Simulated load estimation errors of the proposed primary side method, when the compensation capacitances vary 25%.

 

CONCLUSION:

This paper presents a systematic analysis of the rectifier load used for EV wireless charging system. The rectifier load model has been established to calculate its equivalent input impedance,  which contains both resistance and inductance components,  and can be independently calculated through the parameters of  the rectifier circuit. Based on the rectifier load analysis, a compensation network design method is proposed to achieve the decoupling design of the primary and secondary side compensation capacitors. Furthermore, a secondary side load estimation method and a primary side load estimation method are put forward, considering the influence of the rectifier load. They adopt only measured voltages to avoid the deviations introduced by different phase delays between measured voltage and current. Finally, the established model, the proposed rectifier load calculation method, compensation network design method, secondary and primary side load estimation methods have been verified, based on the developed EV wireless charging prototype. The experimental results have shown the  following conclusions: the equivalent input impedance of rectifier load is mainly affected by system load resistance and rectifier input inductance; rectifier load equivalent inductance will impact system performances, and should be considered for compensation network design; the proposed load estimation methods have good accuracy, but still need to be improved in further research; the proposed rectifier load calculation method and system load estimation methods all have good robustness on conditions of WCS parameter variations. Although the works in this paper are conducted based on the specific system, they can be extended to more applications, such as wireless charging systems with other rectifier or compensation network topologies, etc. They will be helpful for system design and control to make EV wireless charging systems achieve stable operation and high performance.

 

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