Digital Control of a Wind Turbine Supplying an Isolated Load in Cooperation with a Hydro Power Unit

Abstract

This paper presents different discrete control strategies for a variable speed pitch-controlled wind turbine (WT) which supplies an autonomous system in cooperation with a small hydro power unit. The WT consists of a synchronous generator (SG) with two three-phase stator windings displaced by 300, so as the torque distortions due to the wind fluctuations to be limited. The SG operates in variable speed mode in order to maximize the power absorbed from the wind and minimize the amount of water consumed by the hydro power unit. The requirements from the control schemes are to deliver the total power from the WT to the isolated load under constant voltage and frequency and adjust suitably the power from the hydro unit at the same time. There are two controllers: the rectifier controller, which drives the WT at such value of mechanical velocity that maximum power from the wind is absorbed and the inverter controller, which passes this amount of power to the load under constant voltage. There are two schemes presented in this paper: the first includes two PID controllers and the second includes a robust controller for the rectifier pulsation and a state-feedback controller for the inverter pulsation.