Switched model based control of dual-PWM converters in the direct-drive permanent magnet synchronous wind turbine system

Abstract

Nowadays, permanent magnet synchronous generator (PMSG) based direct drive wind power generation systems are developing rapidly and are attracting more and more attention. Dual-PWM (pulse width modulation) converters, as full power converters of the direct-drive wind power system, have excellent performance and have been widely used in recent years. The effective control of the back-to-back Dual-PWM converters plays an important role in generating the wind power efficiently. As the back-to-back Dual-PWM converters of the direct-drive wind power generation system can be considered as switched systems according to their working characteristics, this study presents one switched model based control strategy for the control of the Dual-PWM converters. First, the switched dynamic models of the converters on the PMSG side and the grid side are established, respectively. In contrast to the traditional averaged or linearized models, the proposed models can be more precise because no approximation will be introduced when the wind speed changes. Then, in order to realize the highest convergent rate, the min-projection strategy based switched control laws are derived. Furthermore, the stability analysis is done to assure the global stability of the proposed control strategy. Finally, detailed simulations and experiments are available to verify the proposed control method. The simulation and experimental results demonstrate that the proposed models and the control strategy are correct and effective. Comparing with the conventional proportional-integral control method, this paper integrates the back-to-back Dual-PWM converters as part of the proposed controller and utilizes the states of the converters as control variables, and thus, faster torque dynamics can be achieved.