PERFORMANCE IMPROVEMENT IN MICRO WIND ENERGY SYSTEMS WITH CASCADED INVERTERS USING A NOVEL SWITCHING NETWORK

Abstract

Electricity generation using technologies involving renewable energy sources have gained momentum in the wake of increased concern on environmental impacts and dwindling fossil reserves. Extraction of wind energy through small and micro wind turbines is an attractive option for distributed generation in isolated regions and standalone green buildings. One of the issues faced in a micro wind energy system (MWES) with multilevel inverters is the unequal voltage source condition which at times decreases the output power delivered to the load and also increases the harmonic contents. A novel switching signal generation logic has been suggested to control the cascaded inverters with unequal dc sources and to improve the output power delivered. This switching network also enables the use of any two level inverter modulation schemes to control any levels of cascaded inverters. To demonstrate the effectiveness of this logic, a micro wind energy system with vertical axis wind turbines and cascaded inverters has been modeled, simulated and the results were analyzed. The incorporation of the proposed switching logic to control the cascaded inverter with unequal voltage sources improves the rms value of output current and voltage, and increases the power delivering capability by around 20%. In addition to increased power delivery, the switching network is capable of maintaining the harmonic contents to satisfactory levels.