| As the energy crisis becomes vastly more urgent, exploitation and utilization of new energy resources become a focus of research. Aiming at the electrical energy conversion technology for wind power, analysis of the common solution and the superior properties of PWM converter under quadrant operation are given, and further research on back-to-back PWM converter is made in this dissertation.First, the mathematical model in abc frame is deduced according to Kirchhoff's law. Then, coordinate transformation is used to get mathematical models in bothαβframe and dq frame with mathematics method. After current decouping and how to get target vector voltage by using SVPWM method is expounded, analyses of vector control schemes using SVPWM modulation under unit PF rectifier, unit PF connect grid, various PF connect grid operation conditions according to turbine VSI, connect grid VSI, VAR compensation in LVRT and corresponding control block diagram are given respectively.Next, wind power system with double PWM converters is analyzed and simulation models are built by MATLAB respectively for conditions: constant torque and speed, and step torque and speed. Given the simulation results.Then, based on the analyses of LVRT of wind power system, control block diagram and strategy of hysteresis adjustment around the given value of grid current is presented, and simulation are made for the condition when grid voltage falls to 40% of the rated voltage and the output power of converter changes from pure active power to lagging reactive power. Given the simulation results.Last, the overall design is given including the main hardware circuit, software flow chart, and experiment waveforms. |
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