Stability analysis of a slip power recovery system under open loop and field orientation control

The slip power recovery configuration provides an attractive alternative for variable speed drives and generating systems, due to its high-efficiency and low converter rating. The core component is the doubly-excited machine. The authors present a stability analysis of the doubly-excited machine with open-loop voltage and open-loop current control in the rotor circuit. The possibilities of open loop control are analyzed. The authors then present a unified model of a high-performance slip power recovery system comprising a field-orientation controlled doubly-excited machine, power converters, and a DC bus in the rotor circuit. The stability of this composite system is also studied. Of special interest is when the system functions as a variable-speed motor or as a variable-speed constant-frequency generating system. It is concluded that, under certain conditions, rotor open-loop voltage and current control are both stable for both motor and generator operations. The field orientation process is stable if the computation is fast enough or if there is additional compensation