Small Wind Power Converter Control System

As the output voltage and power of wind power generation present unstable changes with the variations of wind speed, how to improve the power factor of system and the stability of the output voltage has been an important topic. Based on the100w small wind power generation system as the research object, this paper discusses the control technology such as how to improve the power factor and the battery charge and discharge.Current distortion occurs in the process of rectification of the three-phase diode rectifier, the total harmonic content is over30%and the power factor is low, generally between0.50.7. Aiming at this problem, this paper improves a single switch three phase rectifier and carries out specific analysis on its topological structure and working state combined with PFC technology. Only using voltage monocyclic control by boost converter, we can make the output voltage stable and reduce the input current harmonic in DCM mode. Combining with the five times harmonic trap filter, we can further reduce the harmonic content of the input current. What’s more, the output voltage fluctuation is within1%, the total harmonic content of the current can be reduced down to0.57%, and the power factor is close to1through the simulation.According to the power distribution, this paper determines whether the power of system reaches equilibrium using the judgment of DC-side voltage. When the output power of wind power generation system is larger than the demand of load, the voltage of DC-side rises due to the principle of conservation of energy; conversely, declines,which can be regarded as the basis of battery charging and discharging. Using bidirectional de converter for battery charging and discharging, the charging control method of two-section rated current and voltage is optimized in order to control the current of battery charging and discharging, shorten the time of battery charging and prolong the life of battery. Through the battery charging and discharging control, we can maintain the voltage of the load as a fixed value and adjust the power of system into balance.The inverter adopts full bridge type structure combining with unipolar PWM switching to deduce its mathematical model. The PID controller based on pole assignment is optimized, the state feedback of the controller contains three three state variables which are the instantaneous value of the output voltage, the rate of change and the integral value, comparing with the voltage and current double loop control of the traditional inverter, its structure is more simple. The PID controller parameters of low pass filter is designed, and the simulation is carried out in each case with the resistance load as the research object, the harmonic content of voltage waveform is lower than0.39%, the error is less than0.67%, and when the load changes, the steady-state and dynamic performance are fine.