基于频率调节的电动汽车无线充电互操作性提升方法研究

In recent years, electric vehicle wireless power transfer technology has been popularized and promoted due to its advantages of high safety, high reliability, high energy efficiency and high adaptability. However, with the development of the technology, it will inevitably lead to the coexistence of multiple manufacturers, models and technical routes. There are obvious differences in power level, transmission distance, coil type, compensation structure, control mode, packaging process, communication and other aspects. Therefore how to realize the interoperability between ground terminal equipments and vehicle terminal equipment which comes from different manufacturers and models has become the key to the development of electric vehicle wireless wireless power transfer technology. This paper proposes a method to improve system interoperability based on frequency regulation. And according to this method the output characteristics of systems without interoperability or with poor interoperability can be improved in a wide range. Firstly, the fundamental wave analysis method is used to construct the KVL equation for the wireless power transfer system of LCC-LCC type electric vehicle. By defining the normalized angular frequency, the circuit similar quality factor Q and Q_f to characterize the system frequency and the inherent parameter characteristics and simplify the equation of the system. Then simplify the expressions of the system output power and system efficiency by using the relationship of the order of magnitude under. According to the above study, the change curves of the output power and system efficiency under different system parameters are determined. The above analysis proves theoretically the influence of system frequency on interoperability. A method to improve the interoperability of the wireless power transfer system based on frequency regulation is proposed. U_S, I_S, U_L, I_L is the power supply voltage, power supply current, load voltage and load current respectively. First, determine the optimal resonance point of the system through simulation and record the system frequency at this point as f₀. The experiment starts from f₀, at the same time, determine the maximum values P_outmax and η_max of P_out and η, and the maximum allowable error ranges ε_P and ε_η of P_out and η according to the simulation. Then the system frequency was adjusted. During the experiment, the U_S, I_S, U_L, I_L in the circuit was measured and calculate P_out and η. Select the frequency change step as Δf (Δf ＞0) . Set the system frequency to f₀+nΔf (n=0, 1, 2,…) and it is called forward frequency modulation. Record |P_outmax-P_out|=ε_Pn and |η_max-η|=ε_ηn, and judge the relationship between ε_Pn and ε_P, ε_ηn and ε_η. If the value satisfied ε_Pn≤ε_P and ε_ηn≤ε_η, then the system has met the interoperability requirements. If not, continue to stack the steps. When the frequency changes to the critical point of the specified frequency range, if interoperability has not been achieved, reverse frequency modulation will be carried out like forward adjustment. The experimental results show that the output power and transmission efficiency of the system will change with the change of system frequency and the interoperability of the system will change according to the frequency too. This provides the feasibility of improving system interoperability through frequency regulation. However, compared with the simulation results, the experimental results are relatively low and the resonance points are shifted to the right by 0.25~0.5 kHz. The main reasons are environmental interference, device loss, statistical error, etc.