A sensor-less sliding mode control scheme for a stand-alone wound rotor synchronous generator under unbalanced load conditions

•The paper presents a sliding mode controller for a wound rotor synchronous machine.•The wound rotor synchronous machine is acting as an isolated generator connected to an unbalanced load.•A frequency locked loop algorithm in order to extract the positive sequence and control it.

This paper presents a sliding mode control for a wound rotor synchronous machine acting as an isolated generator connected to an unbalanced load. In order to simplify the control methodology, the standard dq-model of the machine is connected to a balanced resistive load. A switching function is defined in order to fulfill the control objective. From the desired surface, the standard sliding methodology is applied to obtain a robust and very simple controller. Then, the actual measured voltage of the machines is acquired and treated trough a frequency locked loop algorithm in order to extract the positive sequence and control it to guarantee a good definition of the park transformation. A phase locked loop algorithm is also used to avoid speed sensors. Numerical simulations and experimental results validate the control law and show good performance and a fast response to load and reference changes.