Sensorless Starting Control of the Brushless Synchronous Starter/Generator Based on Rotor Current Characteristics of the Main Exciter

The unique characteristics of the main exciter (ME) in the brushless synchronous starter/generator (BSSG) have been extensively studied to achieve sensorless starting control. However, the existing methods face drawbacks such as insufficient dynamic performance, complex demodulation processes, and estimation phase delays. In this article, the dynamic characteristics of ME rotor currents are analyzed and summarized quantitatively. Based on these characteristics, a novel sensorless starting control method is proposed. First, a position detection method of signal reconstruction is established. The rotor position can be derived from the complex dynamic features of estimated ME rotor currents. Meanwhile, a parameter estimation method for ME at a standstill is proposed by utilizing the current characteristic in the commutation interval. With this method, the stator parameters of ME can be estimated with a single $\alpha $-axis voltage and current, removing the restriction of the commutation mode of rotating rectifier in ME parameter estimation. Finally, the sensorless starting control of BSSG is realized with the proposed methods.

I. Introduction

In more-electrical aircraft (MEA) system, since nonpropulsion systems are mainly based on electricity, significant reductions in weight, volume, and fuel consumption are achieved [1]. Integrated starter/generator (ISG) plays an important part in MEA. Mounted near the aviation engine case, ISG not only provides sufficient electrical power during flight, but also can serve to start the aviation engine, eliminating the need for a separate starter unit [2]. Many machines can serve ISG systems, such as induction machines, doubly salient electromagnetic machines, and permanent magnet synchronous machines (PMSM) [3], [4], [5], [6], [7]. In fields such as the military and commercial aviation, the brushless synchronous starter/generator (BSSG) stands out, due to its merits of mature generation technology and high reliability [8]. Fig. 1 illustrates the structure of BSSG. A main generator (MG), a main exciter (ME), and a pre-exciter (PE) are coupled on the same shaft. A rotating rectifier (RR) is used to connect the rotor windings of MG and ME. Fig. 1.

Structure of BSSG.