A General PLL-Type Algorithm for Speed Sensorless Control of Electrical Drives

Speed control of electrical drives without additional speed sensors is preferable in terms of cost and maintenance effort. Common approaches are either simple but inaccurate with deteriorated drive performance in the low-speed range, or they offer full torque even at zero speed at the cost of high implementation effort and parameter sensitivity. Moreover, most of the suggested solutions are tailor made for specific machine types. The proposed method constitutes a simple phase-locked-loop-type sensorless algorithm that can be related to the former category. The outstanding feature of the presented method is its effectiveness and simplicity at the same time. This paper presents corresponding design guidelines for an easy to implement and robust speed sensorless control algorithm for all kinds of electrical machines that includes induction machines as well as synchronous reluctance machines with and without extra/permanent excitation.