Research On Vector Control Strategy For Grid-connected Inverter For Wind Energy Conversion System

Wind power is the clean and renewable energy sources,wind power generation is one of the most successful solutions to global energy crisis and environmental pollution in terms of widespread take up and commercial development. This dissertation is a part of the project of developing MW-level Wind Energy Conversion System which is a key 863 program.It is mainly about the wind energy conversion system with a rated output of 1.2MW which applied to the variable speed constant frequency wind energy system(VSCF).A PWM converter applied to grid connection of wind turbine systems(WTS)and its current and voltage control strategies are researched through theoretical investigation and experimental verification.This dissertation summarizes the art-of-the-state of WTS.Comparing predominant technologies,the direct-drive system is adopted in the 1.2MW Wind Power Conversion,a dual PWM converter is employed as grid interface.Following introduction of the topology characteristics and control requirements of the system,the grid-side converter is emphasized.The topology,operation principle and mathematical modeling of PWM converter are discussed.For the real system with neutral line,the mathematical models at low and high frequency and in rotating(d-q-O)frame are given.According to the operating characteristics of Wind Power Generation System,the vector control synchronous PI current control scheme and SPWM are adopted here. Parameters in vector control are devised by employing dc steady-state and dynamic investigation.Moreover the general dc voltage controller and particular DC voltage offset compensator for the system with neutral line are also designed.The control scheme for the PWM converter is testified experimentally,following designing the hardware circuits and DSP programs of the control system.The high speed integrated control chip DSP2407 is the core of control.The PI parameters of the inner current loop,the outer voltage loop and the DC voltage offset compensation are determined in the experiment,and the closed loop control experiment is completed.At the mean time,an experiment platform of wind energy conversion system is constructed and the experimental waveforms are presented and analyzed in this paper. The results and analysis are provided demonstrating the feasibility in wind power generation and validating the theory presented before.