Control of three-phase voltage-source converters with reduced number of sensors

An AC-voltage sensorless control strategy for three-phase voltage-source grid-side converters (VSCs) is presented. The main goal of the proposal is to reduce the number of sensors needed to implement the controller. To this end, AC-voltages and DC-current sensors are replaced by software sensors based on observers. An energy function and the reactive power of the VSC are considered as outputs for constructing a feedback law based on Feedback Linearization technique. In this way, internal dynamics is avoided. In order to improve the 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 nonlinear observer. Simulation results taking into account PWM switching, measurement filter delays, and parameters uncertainties are presented.