Dynamic Performance Improvement of Doubly Salient Brushless DC Generator System With Controlled Rectifier

Abstract

The doubly salient electromagnetic generator (DSEG) is gaining increasing attention in aircraft high voltage dc generator application due to its simplicity and de-excitation ability. However, the field winding inductance and the dc-link capacitor result in a larger electrical time constant. The dynamic response is decelerated, leading to difficulties in meeting aircraft electrical power standards. Minimum transient point tracking (MTPT) strategy based on the trajectory with minimum field current variation is proposed for the DSEG system with an angular position control (APC) controlled rectifier. Since the dc load current depends on both field current and the turn- off angle, the change in the field current is minimized and the dc load current is varied by controlling the turn- off angle. The trajectory of the optimized turn- off angle is studied to partly or fully fill the gap between the field currents at different loads. By tracking the MTPT trajectory, the change of the field current is decreased during the sudden load changes. The transient process is accelerated and the voltage variation is suppressed. In most operations, the voltage variation can be even neglected under both loaded and unloaded conditions. A 9-kW DSEG system based on controlled rectifier is implemented. The MTPT strategy is verified by experiments. The performances of the diode rectifier, controlled rectifier with fixed turn- off angle, and controlled rectifier with MTPT are compared. The dynamic performance is improved by the proposed method, making the DSEG more competitive in aircraft applications.