Nonlinear Feedforward Control of Three-phase Voltage Source Converter

For voltage oriented control of PWM voltage source converter (VSC), cascade scheme is usually used. However, response of conventional voltage PI controller to disturbance from load or the grid voltage is so slow that dc voltage has much larger fluctuation. Nonlinear feedforward control proposed is based on steady state power balance. Produced current reference, i.e. nonlinear feedforward signal, is directly related to load and the grid voltage. Current loop control can track disturbances and regulate ac input currents instantaneously, which maintain power balance and the dc voltage constant. Nonlinear feedforward control was implemented on a VSC prototype. The results show the strong robustness of the method for disturbance from load or the grid voltage