Research on the control strategy of four-multiple grid connected converter for large-scale wind energy conversion system

This paper proposes a four-multiple pulse width modulation (PWM) converter for grid interface, which is apply to the variable-speed constant-frequency direct-drive wind turbine systems. The paper introduces the principle of PWM converter, in order to improve DC voltage utilization, space vector pulse width modulation (SVPWM) technology is adopted. Then the advantages of the multiple based on carrier phase-shifted space vector modulation (SVM) technology is presented, with the proposed method, it not only makes existing equipments apply to large-scale systems, but also reduces the current ripple amplitude, making the switching frequency of the four-multiple converter quadruple equivalently. The synchronous PI current control and the decoupling control strategy are presented subsequently. The dc voltage control loop and ac current control loop are also devised, so as to maintain constant dc link voltage and to keep sinusoidal ac current at unity power factor, the active power and reactive power can be controlled by q-axis and d-axis respectively. The static and dynamic simulation results show that the scheme is feasible and right.