Research On Generator-side Three-level Converter And Its Control Technology For Direct-driven Wind Power Generation System

Full-scale power converter is a key part of the direct-driven wind power generationsystem, and its rated power and voltage levels are becoming higher and higher with theincrease of single wind turbine capacity. In order to lay a theoretical and technicalfoundation for the application of the high voltage and high power three-level converter todirect-driven wind power generation system, a three-level generator-side converter isdesigned, its control technologies are investigated, and the correctness and feasibility ofproposed control technologies are verified by simulation in this dissertation.Firstly, the background, purpose and significance of the project as well as the maintopologies of three-level converter are introduced in brief. The research status ofdirect-driven wind power generation system at home and abroad is overviewed from thethree aspects of typical topologies for wind power generation system, the topologies andcontrol strategies of direct-driven wind power generation system.Secondly, the working principle of neutral-point-clamped three-level converter isbriefly analyzed. The main circuit and drive circuit of the converter are designed based onthe actual parameters of a direct-driven wind power generation system. The algorithm ofthree-level space vector pulse width modulation (SVPWM) is derived in detail, and then itscorrectness is verified by simulation based on three-level SVPWM inverter model built inMATLAB/Simulink.Thirdly, the rotor flux-oriented vector control strategy with id=0and the design methodof its PI controllers are investigated based on mathematical models of wind turbine, PMSGand three-level generator-side converter. In order to improve the reliability and reduce thecost of direct-driven wind power generation system, a control strategy without rotorposition sensors is put forward to achieve sensor-less control of PMSG, in which thesliding mode observer and software phase locked-loop (SMO-SPLL) are used to estimatethe rotor speed and position of PMSG.Finally, simulation model for generator-side part of the direct-driven wind powergeneration system is build up, and simulation research is carried out in Matlab/Simulink.Simulation results show that SMO-SPLL is able to accurately estimate speed and rotor position of PMSG, and the rotor flux-oriented vector control based on it can achieve highperformance control of PMSG.