Vector current controlled grid connected voltage source converter-influence of nonlinearities on the performance

In the literature, the influence of nonlinearities occurring due to the effects of blanking time, the valves and the nonideal grid filter on the dynamic performance of current control are usually not described. In this paper, small-signal analysis is used to study the influence of nonlinearities for a vector current controlled VSC connected to a grid. To show the influence of nonlinearities, measured frequency responses are compared with responses from analytical models. Measured responses are presented for operation in rectifier and inverter operation as well as static VAr operation. As displayed, the frequency dependent losses in the grid filter affect the dynamic performance at high frequencies. A method for compensating for nonlinearities due to blanking-time and nonideal valves is implemented. The compensation method improves the performance.