| Firstly, the study backgrounds and the development status at home and abroad of small wind power generator system are introduced in this thesis. Then the characteristics of common stand-alone small wind power generator, such as DC generator, permanent magnet synchronous generator, silicon rectifier self-excited synchronous generator and capacitor self-excited induction generator, are analyzed. The advantages of switched reluctance generator for wind power generation are summarized.Secondly, the structure of small wind power switched reluctance generator system is introduced, and the circuit scheme is determined by analyzing the function of SRG control unit, energy storage unit and inverter unit. According to the energy flow state of system and the relationship between power and load, the system is divided into two operating modes. On the basis of energy storage unit is in the maximum charge or discharge status, each operating mode is divided into two operating states. Then the control modes of each unit in different operating states are discussed.Thirdly, combined with the advantages of the power signal feedback method and the climbing search method, the maximum power point tracking method in stages is given. Then the realization process of maximum power tracking when the system starts and the wind speed changes is analyzed. In order to achieve the power balance of the system, the maximum power point tracking method, the voltage loop method and the power loop method are combined. Then the control method of battery energy storage unit is designed. With the DC bus voltage as the control target, this method combines the two-stage method to realize the control of battery charging process. And then the voltage loop control methods of the boost circuit and the voltage instantaneous value PI control method of the inverter circuit are determined.Fourthly, the power main circuit and control circuit of the generator control unit, energy storage unit and inverter unit are designed. According to the control requirement of the system, the independent digital controller is selected for each unit. Combined with the control strategy, the timer interrupt program, ADC interrupt program, capture interrupt program, MPPT subroutine and the corresponding program flow chart of the system are given.Finally, the experiment platform is constructed and the control strategy is validated. The experiment result shows that the maximum power point tracking method in stages can quickly achieve maximum wind energy capture and limit power within safe limits. Power balance control method can effectively ensure the stability of the DC bus voltage. The battery’s recharge and discharge control method can well maintain the power balance of system, and control the charge process of battery. Inverter unit has good static and dynamic performance. |
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