Research On Key Technologies Of Non-Grid-Connected Direct Drive Pmsg Wind Power System

With the burden of serious energy crisis and deteriorated environmental problem, the society of human beings is facing a horrible dilemma. To develop and utilize the new energy has been recognized among different countries. Therefore, the wind power technology has been developing rapidly in recent years. This paper focus on the non-grid-connected direct drive PMSG wind power system that aiming at changing the situation of the remote area lack of power, the low-speed generator and control strategy of converters are researched in this paper.Firstly, on the basis of comprehensive elaboration of the features about the PMSG used in wind power system. The design of low-speed multipole PMSG, inprovement of the waveform quality of back-EMF, reduction of the voltage regulation rate and control of short-circuit current are regarded as the key factors in the design and check of generator. Based on the finite element analysis, reasonable parameters and slot-pole match are chosen due to those factors. Then, a type of nonuniform thickness tile shape is designed to optimize the quality of back-EMF. The voltage regulation rate is reduced by conventional means and demagnetising working point is checked to confirm the short-circuit current proper. Through these measures, the performance of PMSG is promoted.Secondly, based on the analysis of Aerodynamics model of wind turbine, conventional MPPT strategy is discussed and improved in this paper. An improved method based on the combination of table lookup and power signal feedback is proposed. Through this new way, the power of DC link is regarded as the output power of wind turbine, the wind velocity is devided into several regions and the tables about optimal power curve and RPM-Power curve are formed in this method, the optimal working point is found out by the pattern of undifined length.Thirdly, the rectifier of the generator side is designed and researched.To realize the convert of power from AC to DC, MPPT, charging for the battery, the rectifier based on the PWM strategy is introduced to the wind power system. Two closed loop is constituted by RPM(obtained through MPPT strategy) and current. The proposed strategy is proved correct and effective through simulation and wind field experiment.Finally, the inverter for the users is analysised and designed. The OCC(one cycle control) is imported into single phase inverter in this paper. Based on the detailed analysis about the principle, simulation and experiment platforms are built, the output voltage has a good performance and lower THD. The inverter controlled by OCC strategy is fit for wind power technology, revealed by the simulation and experiment results.