| As a kind of pollution-free and green renewable energy, wind power not only can relieve the energy crisis, but also beneficial to environmental protection. In recent years, as wind power industry develops rapidly, direct-wind power system attracted wide attention for many advantages; it becomes an important research direction in wind generation technology area. In Directly-driven Permanent Magnet Synchronous Generator (D-PMSG) wind turbine systems, the full-scale system power control system is the core part of the whole control system. After the comparative analysis of some current common topological structure of D-PMSG wind turbine systems converter, the paper choose the topological structure of back-to-back PWM converter as research focus.Firstly, the paper analyzes the work principle of the D-PMSG wind turbine systems based on the double PWM converter and establishes the mathematical model of D-PMSG wind turbine systems, including the model of wind turbine, D-PMSG model and the mathematical model of back-to-back PWM converter, etc.Secondly, it analyzes the principle of maximum wind energy capture and Space Vector Modulation (SVPWM) technique and focus on the on the research of the control strategy of the double of PWM. Based on the technique of vector control, the generator-side converter uses the zero d-axis current vector control policy. The particular method is double-loop control model, the outer loop of speed, the inner loop of current. The aim of the control is to regulates the speed of wind turbine and achieve the maximum wind energy capture. On the basis of the voltage-oriented vector control principle, to realize unit power of factor control of the grid current and keep DC-side voltage constant, the grid-side converter adopts the double-loop control model, the outer loop of voltage, the inner loop of current. Then the whole system simulation model is set up and simulated in Matlab/Simulink. And the correctness and effectiveness of the control strategy is proved by the simulation results.Finally, the paper analyzes the control strategy to realize the LVRT of wind generator system. It mainly studies on the power dissipative Crowbar circuit on the dc side. The validity and correctness of the control is confirmed through the Matlab/Simulink simulation. |
