Study On Grid-side Converter And Grid-connected Technology In Direct-drive Wind Power System

Along with the great consumption of petroleum, coal and other traditional energy and the deterioration of global environment, wind energy, as the most clean, cheap, promising and renewable energy, plays an important role in today’s society with increasingly scarce resources. Grid-connected wind power system is the main force to promote the development of wind power industry, where variable speed constant frequency (VSCF) wind power system, which has easy pitch control, small mechanical stress and high wind energy utilization, is mainstream control mode. Doubly-fed type and direct-drive type are commonly used in VSCF wind power system. Compared with doubly-fed induction generator, direct-drive permanent magnet synchronous generator has more advantages and will be more widely used in the system with a small capacity. In the paper, grid-side converter and grid-connected technology were mainly studied in permanent magnet direct-drive wind power system.Firstly, this paper gave the mathematical model of grid-side converter respectively in three-phase stationary and two-phase rotating coordinate system and introduced grid voltage-oriented control strategy. Subsequently, select SVPWM as the control mode to converter and realize simulation in MATLAB R2008a/Simulink, based on the analysis and comparison of hysteresis current control, SPWM and SVPWM.Secondly, the paper introduced the principle of maximum wind energy tracking. determined the relationship between DC bus voltage and speed, obtained optimal power by using the relationship between speed and optimal power and then controlled active current to achieve maximum wind power tracking. Subsequently, in view of DC bus voltage fluctuation, active disturbance rejection control (ADRC) technique was proposed and applied in the grid-side converter control. The simulation results showed that voltage-loop with ADRC had better control quality and precision compared with PI regulator.Lastly, a set of permanent magnet direct-drive wind power grid-connected converter was designed based on TMS320F2812. Hardware design included DSP minimum system, signal acquisition circuit, zero-crossing detection and driver protection circuit. Software modules included A/D conversion module, control algorithm, SVPWM algorithm and lock-phase algorithm which was new and made grid-connected control more accurately.