Control and Interfacing of a Grid-Connected Small-Scale Wind Turbine Generator
ABSTRACT An ac/dc/ac power converter is an important device used to extract power from variable speed permanent magnet wind generators and feed it into the grid. This paper describes how these converters incorporate maximum power point tracking based on its power feed to the grid at different wind speeds. Using the permanent magnet generator voltage, grid current, and grid voltage samples, the proposed system achieves an enhanced dynamic behavior. This feature effectively prevents the grid from “boost” charging the dc side of the H-bridge inverter at the start of operation. Since small wind turbines normally do not have expensive pitch control mechanisms, a thyristor-based “dump-load circuit” is employed to protect the turbine from high wind speed operation when disconnected from the grid. The thyristor controller also protects the inverter from high dc voltage input from the wind generator at high wind speed. Preliminary results are included using a laboratory 2-kW prototype converter.
Conference Proceeding: A self-tuning PID control for a wind energy conversion system based on the Lyapunov approach[show abstract] [hide abstract]
ABSTRACT: Nonlinear characteristics of wind turbines and electric generators necessitate that grid connected wind energy conversion systems (WECS) use nonlinear controls. In this paper, we will propose a self-tuning PID control based on Lyapunov approach for WECS control. This self-tuning PID control is founded on the combination of two controllers, i.e. a self-tuning PID controller, which drives the tracking error to zero with user specified dynamics, and a supervisory controller, based on crude bounds of the systempsilas nonlinearities. The supervisory controller guarantees the stability of closed-loop nonlinear PID control system. The form of the supervisory control and the adaptation law are derived from a Lyapunov analysis of stability. The results are applied to a typical WECS, presenting the ability of the proposed method.Universities Power Engineering Conference, 2008. UPEC 2008. 43rd International; 10/2008
Conference Proceeding: Flicker study on variable speed wind turbines with permanent magnet synchronous generator[show abstract] [hide abstract]
ABSTRACT: Grid connected wind turbines are fluctuating power sources that may produce flicker during continuous operation. This paper presents a simulation model of a MW-level variable speed wind turbines with a permanent magnet synchronous generator (PMSG) and a full-scale converter developed in the simulation tool of PSCAD/EMTDC. Flicker emission of this system is investigated during continuous operation. The dependence of flicker emission on wind characteristics (mean speed, turbulence intensity), 3p torque oscillations due to wind shear and tower shadow effects and grid conditions (short circuit capacity, grid impedance angle) are analyzed. Flicker mitigation is realized by output reactive power control of the variable speed wind turbines with PMSG. Simulation results show the output reactive power control is an effective measure to mitigate the flicker during continuous operation of grid connected wind turbines.Power Electronics and Motion Control Conference, 2008. EPE-PEMC 2008. 13th; 10/2008
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ABSTRACT: The energy capacitor system (ECS), composed of power electronic devices and electric double layer capacitor to enhance the low voltage ride through (LVRT) capability of fixed speed wind turbine generator system (WTGS) during network disturbance, is discussed. Control scheme of ECS is based on a sinusoidal pulse width modulation voltage source converter and DC-DC buck/boost converter composed of insulated gate bipolar transistors. Two-mass drive train model of WTGS is adopted because the drive train system modelling has great influence on the characteristics of wind generator system during network fault. Extensive analysis of symmetrical fault is performed with different voltage dip magnitudes and different time durations. Permanent fault because of unsuccessful reclosing is also analysed, which is one of the salient features of this study. A real grid code defined in the power system is considered and LVRT characteristic of WTGS is analysed. Finally, it is concluded that ECS (20 MW) can significantly enhance the LVRT capability of grid connected WTGS (50 MW) during network disturbance, where simulations have been carried out by using PSCAD/EMTDC.IET Renewable Power Generation 04/2009; · 1.72 Impact Factor