Grid-Connected Research On Direct-Drive Wind Power Generation System With Energy Storage Under Non Ideal Grid

With the rapid development of global economy, the traditional fossil energy is becoming depleted, at the same time, the human living environment is deteriorating. Under this background, the wind power generation technology has become the focus of the development strategy in the various countries. Because of the permanent magnet direct-drive synchronous motor (PMSG) wind power generation system has a simple structure, high wind energy utilization and the characteristics of stable and reliable, thus become the research hot spot.Traditional researches of PMSG wind power generation system are mainly under the ideal grid, which are not suitable for grid voltage unbalance conditions. The grid voltage unbalance and voltage flicker down will cause mutations in grid-connected power, which affectes the dc bus voltage. This paper focused on the grid-connected research of direct-drive wind power generation system with energy storage under non-ideal grid.Firstly, this paper analysed the direct-drive wind power grid-connected generation system, the mathematical models of generator and PWM converter were established, the control strategies in the ideal grid conditions of the rectifier and inverter were introduced in detail. The PI regulator parameters were designed and the system was verified and analyzed through simulation, that laid the foundation for the analysis and research of the system under the unbalanced grid voltage.Secondly, in the case of non ideal grid, the dc bus voltage fluctuation and pumping mechanism was deduced on the basis of the mathematical model, the control strategy of positive negative sequence decomposition and the direct power control strategy of inverter were introduced, used the decoupled double synchronous reference frame (DDSRF) method for positive and negative sequence decomposition and phase locked, the proportional integral resonant controller of direct power control strategy was analyzed and designed, based on results of the simulation, two kinds of the control strategy were compared.Then, the hybrid energy storage system of direct-drive grid-connected wind power generation system was introduced, second harmonic fluctuation and high frequency DC power was absorpted by super capacitor and used battery to absorb excess energy to stabilize bus voltage. The electrical model and selection of battery and super capacitor was calculated, the mathematical model of Bi-directional DC/DC converter was established, and the PI controller parameters was designed, combined the hybrid energy storage system with inverter control strategies and simulation tested.Finally, the hybrid energy storage system and network side inverter experimental platform were introduced, the platform hardware circuit and software programming based on TMS320F2812 digital signal processor were designed, through the analysis of the experimental waveforms, proved the correctness of the above control strategy.