Operation of new variable speed constant voltage and frequency generator connected to the grid

Wind is an uncontrolled and stochastic source of power because its speed is continuously changing in magnitude and direction. In order to maximise the obtainable power, wind driven power systems must be able to generate power at all wind speeds whether this speed is low or high. This is not possible when conventional generators are used unless complicated control systems or electronic circuits are used. In this paper, the feasibility of using an AC commutator machine as a generator for wind power plants is experimentally investigated. The machine is connected as a shunt generator in parallel with the grid. It can be operated in a wide range of speeds without any stability problems. Hence, the speed can be controlled such that the maximum output power is obtained at all wind speeds. This type of machine generates a constant frequency voltage irrespective of the shaft speed when excited from a separate constant frequency source. The experimental set has been prepared in the lab such that all variables which affect the generated power can be controlled. These variables include shaft speed, grid coupling voltage and brush angle. The effects of these variables on the amount and quality of power generated are carefully tested. The results obtained show that this machine is a suitable power converter for wind power applications. (C) 2000 Elsevier Science Ltd. All rights reserved.