Research On Starter/Generator For Variable Frequency Power System Based On Brushless Excitation Synchronous Machine

Conventional aircraft power system is a constant-frequency (CF) supply based on mechanical-regulated constant-speed mechanism that has relatively low efficiency. Replacing the CF system with variable-frequency (VF) power will improve overall efficiency, and reduce the system's weight and volume. Novel VF-power architecture will likely combine the main engine starting functions with the electric power generation. For this purpose, this thesis focuses on the study and implementation of the digital control for the aircraft Starter/Generator basd on the Brushless Excitation Synchronous Machines (BESM).Firstly, the working principles of BESM in starting and generating mode are presented, and then the model of BESM in stator reference frame is given briefly. The simulation model of the Starter/Generator system based on BESM is constructed in MATLAB. The operational characteristics of starting, switching, generating process are analyzed.Furthermore, the control strategies for BESM are proposed. Three-phase-six-state control strategy is adopted for the BESM in starting mode. To solve the mutation problems of the excitation current, two chopping ways to inhibit the mutation are proposed. Besides, a multi-loop voltage control scheme is used in generating mode. The selection methods of PI parameters for the control loops are also discussed.Finally, the design of hardware and software controller based on DSP + CPLD is introduced in details. Numerous experiments results are given in order to illustrate the efficiency of the control strategy and the structure of the system.