利用单端口阻抗测量值和灵敏度分析的耦合线圈参数辨识

Parameter Identification of the Coupling Coil by Using the Measurement of the Single-Port Impedance and Sensitivity Analysis

在无线电能传输技术中,电磁耦合线圈的电路模型参数是设计阻抗补偿电路、计算功率损耗、研究频率特性的关键参数。该文利用单端口阻抗和灵敏度分析,提出了一种电磁耦合线圈模型参数的离线辨识方法。将电磁耦合线圈连接成单端口网络,利用阻抗分析仪的测量值和基于模型参数的理论计算结果,构造了以阻抗误差模的平方和为最小的目标函数;利用单端口等效阻抗对模型参数的灵敏度,计算目标函数的寻优方向;借助双端口网络的T形等效电路,提出了计算灵敏度的单位电流源激励法。该方法根据单位电流源相量作用下,元件上的电流相量或电压相量的平方,或它们的乘积,便可计算出阻抗对不同参数的灵敏度,避免了难以求解的阻抗解析表达式及其偏导数。在实验研究中,将耦合线圈置于海水槽中,在参数辨识中考虑了海水的电磁作用和导线的集肤效应与内电抗。

In the wireless power transfer（WPT） technique, the parameters of the magnetic coupling coil circuit model are the key parameters for the design of impedance compensation circuits, the calculation of power losses, and the research on the frequency characteristics. The off-line identification method for the parameters of magnetic coupling coil model was proposed by using the measurement of the single-port impedance and the sensitivity analysis. The coils were connected into a single port network, and then the objective function was constructed to get the minimum sum of squares of the modulus of complex impedance error, according to the measurement results by the impedance analyzer and the theoretical results calculated by the model parameters. The sensitivities of the impedance to the parameters were used to calculate the searching direction of the objective function. The unit current source excitation method was also proposed to find the sensitivities by means of the two-port T-type equivalent network. According to this method, the sensitivities of the impedance to different parameters can be determined only by the square of the current phasor or the voltage phasor of the elements, or by their multiplication, when the unit current source was applied to the circuit. That is much easier than deducing the analytical expression of impedance and its partial derivative. In the experimental research, the coupling coils are set under the seawater tank, the electromagnetism effects of the seawater, the skin effects, as well as the internal inductance of the coils are considered in the parameter identification.