Control of SCIG Based Constant Voltage Generation Scheme for Distributed Power Supply

Abstract

This paper addresses the supply of power to the stand-alone load at constant voltage and constant frequency (CVCF), from a variable source distributed generation system. The inherent problem of having a fixed output from a variable input is prominent in all of the distributed generation systems, run by uncertain renewable sources like wind. This paper proposes a topology to maintain output load voltages and frequency during changes in both input torque and load perturbation. The control is designed for both the generator side and load side converters, connected as a back-to-back converter with one dc link capacitor. The voltage across dc link capacitor is maintained at a desired level by power flow control through the generator side voltage source converter (VSC). The proposed three-stage controller technique for the generator side converter is analysed and tested in all operating conditions. The outer most dc link voltage error is passing through the controller is generating the speed reference of the speed controller. Then the inner loop current controller follows the speed controller. The load side VSC is controlled to produce a constant voltage at the output of the load side filter. The stand-alone system has successfully been tested in the simulation environment. It is found to be capable of maintaining input power level to the demand, even with 50% increment in load and 50% increment in input torque. These dynamic responses of the variables are found to be satisfactory throughout the operation.