Keywords: stand–alone WECS, wind energy conversion systems, wind power, voltage source converter, VSC, voltage control, frequency control, zig–zag transformers, neutral current compensation, consumer loads, wind speed, modelling, simulation, harmonic elimination, load balancing
Zig–zag transformer for neutral current compensation in an isolated wind energy system
This paper presents a voltage and frequency controller with neutral current compensation in a stand alone wind energy conversion system (WECS) employing an asynchronous generator. The proposed controller consists of a three leg insulated gate bipolar junction transistor (IGBT)–based voltage source converter and a battery energy storage system (BESS) at its DC bus. The neutral terminal for the consumer loads is created using a zigzag transformer with an additional secondary winding. This additional secondary winding of zigzag transformer facilitates to select the optimum voltage rating of the battery system at DC bus. The control algorithm of the controller is developed for bidirectional flow capability of the active power and reactive power control by which it controls the system voltage and frequency under different dynamic conditions such as varying consumer loads and varying wind speeds. The complete system is modelled and simulated in MATLAB using Simulink and PSB toolboxes. Extensive simulation results are presented to demonstrate the capability of the controller as a harmonic eliminator, a load balancer, a neutral current compensator along with voltage and frequency controller.