Research On The Strategy Of Doubly-fed Wind Power Grid Connected Control With Unbalance Input Voltage

Wind energy is rich and clean energy. Because wind farm is build in the more remote areas, and the grid system is weak, wind energy has the characteristics of intermittent and unbalance. The most important research is able to provide continuous and stable energy. In this paper, we mainly research the grid connected control strategy of doubly-fed wind power with unbalance input voltage. We design the turbine side and net measure current loop in unbalance input voltage in order to improve the operation capacity of DIFG wind power generation system of unbalanced voltage.First, this paper analyses the unbalance grid adopted the symmetrical component method and the positive and negative sequence component method. When the grid voltage is normal, our back-to-back converter adopts classical vector control strategy with simulate the traditional vector control system of balanced input voltage and unbalanced input voltage. The results show that the current’s 2 frequency multiplication of the stator and rotor, DC bus voltage ripple, the changes of system active power and reactive power.Second, it is hard that the traditional phase locked loop eliminates two frequency components in unbalanced power grid. This paper puts forward an improved DDSRF-PLL algorithm which based on inverse Park transform DDSRF-PLL algorithm can make the grid phase locked loop more accurate in unbalance input voltage. We build the mathematical model of doubly-fed induction generator and the mathematical model of the grid converter under the condition of two phase rotating coordinate in decoupling double synchronous coordinate system. On turbine side, two control strategies for the current loop which is double DQ current loop and reference value decoupling network current loop have been adopted. On line side, the current loop of notch filter and the DDSRF-PLL current loop of reference and error decoupling feedback have been adopted.This paper do the simulation research on vector control strategy ofdoubly-fed wind power generation system under the condition of unbalanced input voltage. The results show that the Machine side and Network side converter can effectively achieve control objectives and eliminate the phenomenon of failure adopted the control method. The experiment programs the control algorithm based on the 5KW simulation of the double fed wind power generation platform, it verifies the correctness and effectiveness the cooperative control strategy between Machine side and Network side of unbalanced voltage.