An enhanced phase locked loop technique for voltage and frequency control of stand-alone wind energy conversion system

This paper deals with the application of enhanced phase locked loop (EPLL) technique for the voltage and frequency controller (VFC) in a stand-alone wind energy conversion system (WECS) using an isolated asynchronous generator (IAG) feeding three-phase four-wire loads. The fundamental component of three-phase load currents is extracted using EPLL. The EPLL is also used for estimation of the frequency of IAG. Three-leg voltage source converter (VSC) with a battery energy storage system (BESS) is used as a VFC for the stand-alone WECS. The star-hexagon transformer is used at point of common coupling (PCC) to realize the three-phase four-wire system. The EPLL based control algorithm is implemented using a digital signal processor. Test results are presented to demonstrate the capabilities of VFC as a load balancer, load leveler, harmonic eliminator and neutral current compensator.