Sensorless Starting Of A Brushless Synchronous Starter/Generator In Variable Frequency Power System

The potential benefits in terms of improved efficiency and reliability, decreased operating costs areincreasing the interest for Variable Frequency (VF) AC power system in the aerospace industry. Thecore technology of VF system is starting and generating system. Brushless synchronous machine hasmature technologies and has been applied as a generator in modern aircrafts widely. It is a suitablestarter/generator(S/G) for VF power system. For this purpose, this work focuses on the startingcontrol strategies of the brushless synchronous starter/generator (BSSG).The structure of the brushless synchronous machine and its mathematical models are discussedfirstly. Then the starting principles of the exciter generator and main S/G of the machine are given: themain S/G works in a three-phase-six-step starting mode; the exciter generator adopts the single-phaseAC excitation and the DC excitation in different speed range. At last, the simulation model of theBSSG starting systems is constructed in MATLAB/SIMULINK. The starting process and field currentof the BSSG are analyzed in detail.To satisfy the request of high reliability in aircraft, the work presents a control strategy forsensorless starting from zero up to a sufficiently high speed when aircraft engine ignition can beinitiated. Firstly, a novel method of the initial rotor position estimation is designed, which is based onthe saliency tracking technique. Then the other-control starting strategy is used to solve thestarting-difficulty of brushless synchronous motors. When at a certain speed，the whole system adoptsthe Back electromotive force estimation method to ensure good position estimation. The validity ofthe proposed technique is verified on a BSSG.Moreover, a digital experimental test-bed on DSP and CPLD for the BSSG is built to verify thetheory and simulation analysis. The hardware composing of the sensorless BSSG starting system andsoftware flowchart are introduced in detail.