Rotor Position Estimation Method of Brushless Synchronous Starter/Generators by Using Stator Currents of the Main Exciter in Both Excitation Modes

The brushless synchronous starter-generator (BSSG) consists of a coaxially connected main exciter (ME) and main machine (MM), of which ME has two excitation modes (ac excitation mode and dc excitation mode). However, most of the existing rotor position estimation methods are suitable for only one of the excitation methods, and there are often situations where signal injection is required or dependent on the saliency of the MM. In this article, a method for estimating the rotor position using the sum of squared stator currents of ME is proposed. The proposed method uses the correspondence between the extreme value of the sum of squared stator currents of ME and the speed of the BSSG to extract the real-time speed of the BSSG. Combined with the existing initial rotor position estimation method, the continuous rotor position of MM can be obtained. Since the change law of the sum of squared stator currents of ME is not affected by the change of the excitation mode of ME, the proposed method is suitable for two different excitation methods. Otherwise, the proposed method requires no high-frequency signal injection and avoids dependence on the saliency of MM. The experimental results verified the feasibility and effectiveness of the proposed rotor position estimation method.