Sensorless control of switched reluctance drive with small DC-link capacitor for high-speed blowers

This paper presents a design concept of a sensorless control for high-speed SRM drives with small DC-link capacitor. In a cost-sensitive application, the expensive large DC-link capacitor should be replaced with a smaller DC-link capacitor for cost reduction. Using a small DC-link capacitor, the DC-link voltage extremely fluctuates during operation. The fluctuating DC-link voltage deteriorates the control stability and performance of the sensorless control. In the literature, the previous work has shown that the workable speed range of the existing sensorless control concept for high speed has been degraded to a smaller range when operating with fluctuating DC-link voltage. The proposed design concept deals with the challenge of improving the control stability of the sensorless control to operate in a wider operating speed range up to 75% (8000–35,000 rpm) under the fluctuating DC-link voltage. The control scheme is developed based on two basis sensorless control techniques, inactive phase method and current gradient method for covering the entire speed range. The proposed solutions work based on the appropriate selection of the detected signals according to the state of DC-link voltage. At the end, the functionality of the proposed technique is validated by experimental results.