Fuzzy system control for combined wind and solar power distributed generation unit

Abstract

For renewable energy generation in the distributed and co-generation (DCG) scheme, photovoltaics and wind power are already in service at many installations. Basically, these types of energy generation are very favourable for the environment but do not produce power on customers load demands, have long intervals of lacking power generation due to absence of power input (no sunshine, no wind), and especially exhibit high costs per installed power respectively per generated energy. So every cost saving and output increasing measure should be taken. Combining a photovoltaic power unit with a wind energy unit will reduce the zero-power intervals and can be composed to high extent of standard commercial variable speed drive elements. These are PWM voltage source inverters with active front end, and also standard induction machines can be taken. Only a few extensions are necessary, thus the total hardware system is rather cost effective. It is essential that a system control unit defines setpoint values for the sub-units and handles abnormal operating conditions. Here a fuzzy control system is proposed to accomplish these tasks. It means performing the standard power insertion into the line on the principle of maximum power tracking, preferable at a rather constant power input without flicker power, ensuring or improving line voltage quality with regard to reactive power and distortion power, or voltage waveform improvement, respectively. In addition, in case of a line interruption, the unit should be able to run independently from the line, establishing an insular power supply for the nearby customers and loads until the reconnection to the mains is done.