Rotor Position Estimation Method of Brushless Electrically Excited Synchronous Starter/Generator Based on Multistage Structure

This article proposes a rotor position estimation method for brushless electrically excited synchronous starter/generator (BEESSG) at low speed region. Based on the multistage characteristics of BEESSG, two high frequency pulsating voltages with different frequencies are injected into phase $\alpha$ and phase $\beta$ of stator of the main machine simultaneously. The rotor position is estimated by the high frequency induced signals extracted from the stator windings of the main exciter through a position estimator. Low-pass filters are replaced by an auxiliary square wave sampling method to demodulate the rotor position from high frequency induced signals. Due to the amplitude unbalance of demodulated position related signals. A novel first quadrant definite integral method is proposed in this article for position compensation. Furthermore, the effectiveness and feasibility of the proposed method are verified by experimental results.

I. Introduction

With the rapid development of more-electric/all-electric aircraft in recent years [1]–[3], the integrated start and generate system has been used in aircrafts like F-35 and Boeing 787. As the key part of the integrated start/generate system, starter/generator has become the focus of research [4]–[9]. Because of its high reliability and adjustable magnetic field, the brushless electrically excited synchronous starter/generator (BEESSG) is widely used in aircraft power system. The BEESSG performs two functions: starting the main aero-engine in the starting mode and generating electrical power for aircraft power system in the generating mode. Fig. 1 shows the structure diagram of a BEESSG, which consists of four parts: the main machine (MM), the main exciter (ME), the preexciter (PE), and the rotating rectifier. The MM is an electrically excited synchronous machine. The ME is a rotating-armature synchronous generator. The rotating rectifier is used to connect the rotor windings of ME and MM, and the PE is a permanent magnet synchronous machine. In the starting mode, the ME controller supplies two-phase ac excitation for the ME. Then the rotor armature winding of ME provides dc excitation current for the MM through the rotating rectifier. Since the PE can not provide dc excitation voltage for ME in the starting mode and does not participate in the start control of BEESSG, the PE is not discussed in this article.