Three-phase Pwm Rectifier Control Strategy Research Of Direct-Drive Wind Power System

In direct-drive wind power generation system, the permanent magnet synchronous wind generator whose the advantages include little mechanical wear and tear, high operating efficiency, low maintenance cost has become another important wind turbine models instead of the double-fed induction. To get the power CVCF electricity finally, firstly VVVF three-phase AC should be converted into suitable inverter grid and stability DC. In order to reduce the harmonic pollution on the grid, carry out the generator side current sinusoidal and run at unity power factor status, this paper have chosen the three-phase voltage source PWM rectifier (VSR) as the motor side of the power electronic converter circuit and design the controller, the main work is as follows:Firstly, the paper analyzes the wind power converter technology status, on the basis of comparing to advantages and disadvantages of current direct-drive wind power converter topology, and selects the generator side of the three-phase voltage source PWM rectifier as the object of study; analysis basic composition and working principle of the three-phase voltage source PWM rectifier, and establish the mathematical model of three-phase stationary coordinate system (a, b, c) and the mathematical model the grid fundamental frequency synchronization coordinate system (d, q).Secondly, for strong nonlinear, time-varying system of the three-phase the VSR system, this chapter presents a fuzzy fractional PIλDμ controller based on fuzzy control and fractional control. Compared with the conventional integer order PID controller, fractional order PIλDμ controller adds two adjustable parameters, namely, the integral order of λ and the differential order of μ. The λ mainly affects the steady-state accuracy and the μ mainly affects the system overshoot. It is due to the two degree of freedom increased, the design of the controller becomes more flexible and the performance of the controller becomes more superior. The fuzzy controller can track the error signal and change dynamically the parameters of PIλDμ controller. Consequently, the system robustness is improved.Then, in wind power generation system, because randomicity of the wind, the mechanical loss and outside interference, a nonlinear adaptive backstepping control algorithm is proposed. Theoretical analysis and simulation studies have shown that the designed controller can guarantee that it achieves network-side current sinusoidal and phase control, the DC side of the output voltage can be fast, no overshoot and reach steady state, and has a very good adaptability and robustness, in the case of systems with uncertain parameters, which are the load resistance, IGBT equivalent resistance, inductance impedance and frequency of the AC side,Finally, taking into account the controller can be realized in the actual operation of the process, this paper presents a method based on linear active-disturbance rejection control (LADRC) algorithm for voltage and current double closed-loop control. The ADRC control technology does not rely on the accurate mathematical model of control object and the disturbance and implement simply. the controller will turn all kinds of uncertainty in the system classified as total disturbance. The linear extended state observers observe and compensate the total disturbance, which LADRC adopts the parameterization method based on observer bandwidth and closed-loop bandwidth. It solves difficult problems of the nonlinear ADRC with amounts of parameters and tuning.