Abstract：Electrically excited synchronous machines (EESM) has the advantages of low dependence on rare earth permanent magnet materials, controllable excitation field and wide speed regulation range, and has a good application prospect in electric vehicles. However, the traditional EESM's brush-slip ring structure caused friction loss, increased maintenance costs, and reduced reliability. Therefore, brushless excitation has become an urgent requirement and a critical issue to be solved for EESM applications. Inductively coupled brushless excitation technology can effectively reduce friction losses and maintenance costs. Currently, mainstream brushless excitation methods include exciter type, harmonic excitation type, and wireless power transfer type. Wireless power transfer excitation can be divided into inductive coupling and capacitive coupling types. Inductive coupling excitation has a simple structure and high transmission efficiency, making it promising for applications. However, the usage of brushless excitation technology will bring a new challenges. The excitation winding of brushless excitation system rotates with the rotor, and there is no direct electrical connection between the transmitting circuit and the receiving circuit, resulting in the acquisition of excitation current value facing technical challenges. To estimate the field current in similar scenarios has been the scope of some previous studies. The existing current estimation methods can achieve good results in their respective application fields, but there are some limitations and shortcomings, which need to be further developed. In view of this, an indirect excitation current estimation method based on reduced order dynamic phasor model is proposed for series-series compensation inductively coupled brushless excitation system, which has the characteristics of simple calculation, strong load adaptability and low hardware cost. The topology structure of excitation energy transmission circuit is designed. The equivalent circuit model of excitation system is established. In order to avoid the influence of load parameter disturbance, an indirect current estimation method is proposed by using the inductive coupling relation and the secondary side reflection voltage as the intermediate variable. A reduced order dynamic phasor estimation model is established to further improve the estimation accuracy of the indirect estimation method. Considering the harmonic effect of subside current, an improved method of variable waveform coefficient is proposed. Finally, the validity of the current estimation method is verified by simulation and experiment. The experimental results show that indirect estimation method has high robustness, the maximum relative estimation error is 4.7% under load variation. Compared with the steady-state estimation model, the reduced order dynamic phasor estimation model can maintain higher estimation accuracy when the load condition changes. Using approximately fitted variable waveform coefficientkαto modify the estimation model can effectively reduce the estimation error caused by secondary current harmonics. The proposed excitation current estimation method has a good effect in series-series inductively coupled excitation system. And only one current sensor is required, resulting in low hardware cost. However, the detailed analysis and accurate acquisition of waveform coefficients in the rectification model need further research. In addition, the indirect estimation idea and the dynamic phasor model can be used to estimate the current of more inductively coupled excitation systems with non-series-series topology with high accuracy and high robustness, and broaden the application range of the proposed current estimation method.
付兴贺, 夏宏伟, 熊嘉鑫. 基于降阶动态相量模型的电感耦合式励磁系统间接励磁电流估计[J]. 电工技术学报, 2023, 38(19): 5152-5163.
Fu Xinghe, Xia Hongwei, Xiong Jiaxin. Indirect Field Current Estimation Algorithm for Inductively Coupled Excitation Systems Based on Reduced-Order Dynamic Phasor Model. Transactions of China Electrotechnical Society, 2023, 38(19): 5152-5163.
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2023, Vol. 38 
