Control strategy for hardware simplification of voltage source converter-based power applications

A hardware simplification control strategy for three-phase voltage-source-converter-based power applications is presented. The main goal of the proposal is to reduce the number of sensors needed to implement the controller while maintaining the high performance of the system. To this end, ac-voltage and dc-current sensors are replaced by software sensors based on state observers. Consequently, a more rugged, smaller and cheaper realisation can be accomplished. Regarding the voltage source converter controller, an energy function and the reactive power of the converter are considered as outputs for constructing a feedback law based on the feedback linearisation technique. In this way, internal dynamics is avoided. In order to improve controller performance, estimates of the load power and its time derivative are feedforwarded. The ac-voltages and load power estimates are obtained by designing a reduced-order non-linear observer. Several tests, with a realistic voltage source converter model that takes into account the switching power devices, validate the proposed technique. They evaluate the system performance in the presence of parameter uncertainties and disturbances in the AC input voltage.