Combined control of stand-alone energy conversion scheme for distributed sources: Development and performance analysis

Abstract

This paper has addressed the variable speed and constant frequency (VSCF) generation from the uncontrolled prime mover-based scheme for a stand-alone system. The small and medium scale wind energy conversion systems, usually dealing with this uncontrolled nature of prime movers, has been handled by the scheme, in this paper. The distributed generation unit (DGU) has considered a squirrel cage induction generator (SCIG) and a back to back converter in its structure. The DGU is developed with a load voltage control, including the filter elements, for the load side voltage source converter (LVSC) and a three-stage control for the generator side voltage source converter (GVSC). This combined controller for the DGU enables it to operate under both input and output side variations. Further, the controller is able to supply constant voltage at a constant frequency throughout the operation. The developed control is successfully implemented in the simulation environment, and the performance of the system is analyzed thoroughly. The variations, considered here are the d-axis component of load voltage, load impedance, dc- link voltage, and the prime mover speed. The performance of the control is verified experimentally with a prototype in reduced power scale in real-time. The results in both environments are found to be satisfactory.