Control of a PWM rectifier in the unbalanced state by robust voltage regulation

Disturbances on the network result in costly damage to converters and their loads. A method for desensitizing a PWM rectifier to network disturbances is presented. A converter model covering the unbalanced state is used to analyse the effect of a disturbance. Two robust control methods are proposed to compensate the destabilizing effects of network voltage variations on the DC voltage and the network currents. First, a three-element corrector is used to stabilize the system by positioning poles according to the α-stability method. Secondly, the use of the internal model concept allows cancelling out of oscillating disturbances due to the unbalanced network. The results presented have been verified by simulations and experiments on a power PWM rectifier using cascade digital control. The electrical load downstream from the converter is no longer disturbed by variation of the network parameters and rectifier operation is stabilized