Three-Level Converter Driving For PMSG-based Direct-Drive Wind Power Generator

Harnessing the power of the wind is one of the effective ways to solve the energy and environment problems which influence the survival and development of human beings. In recent years, studying on the multi-level converter is one of the important research directions along with the enlargement of capacity of wind turbine. On the basis of vector control for permanent magnet synchronous generator by employing three-level converter, the main work achieved in this thesis is as follows.Firstly, a three-level SVPWM algorithm and a method for the neutral-point potential balance are present. In the three-level SVPWM algorithm, with the reference voltage simplified into that of two-level, the gating time of each converter arm is calculated by the correlation between carrier-based PWM and SVPWM. For the neutral-point potential balance, the dwelling times of the positive small vectors and the negative small vectors are adjusted in the light of the voltage of the neutral-point.Secondly, the mathematical models of PMSG in three-phase stationary coordinates and dq synchronous rotational coordinates are set up; the operating characteristic of PMSG under steady state is analyzed; several vector control strategies for PMSG are described; the block diagram of system based on the control strategy of Maximum torque per ampere is depicted.Thirdly, speed sensor-less control strategy of PMSG is introduced. In view of the operating features of PMSG in wind turbines, a scheme of the rotor position observation based on the fundamental excitation is adopted. The scheme is composed of an extended-flux observer and a phase-lock-loop control to get the position with the observed flux. The observer, where the parameters of PMSG are utilized in the simplest manner, has the minimum order without any approximation on its mathematical model.At last, the simulations are built by employing matlab and the corresponding experiments are done by using dsp28335. The results of the simulations and the experiments testify the feasibility of the theories.