Application of digital phase locked loop for control of SRM drive

High performance SRM drive requires precise information concerning instantaneous rotor position. Sensors mounted internally by manufacturers of SRM, are often inaccurate and of low resolution. The substantial improvement of both: resolution and accuracy has been achieved by application of unconventional all digital phase locked loop (ADPLL), which has been implemented in complex programmable logic device (CPLD). The ADPLL is fully synchronized with supervising DSP-based control system for high-performance SRM drive. Such solution is very flexible; the PLL can be easily tuned with DSP or re-programmed in purpose to perform various control strategies. Some proposals for sensorless control with ADPLL are also presented in the paper. Usually, equations describing position estimator or observer are calculated in software. Our approach enables time-critical equations resolved in hardware and there are no limits for high-speed operation.