On nonlinear observers applied to three-phase voltage source converters

This paper deals with the estimation problem in power converters using nonlinear observers. In general, most of the schemes used to control the three-phase voltage source inverter (3/spl phi/-VSI) assume the exact full state information provided by a set of sensors. However, from a practical point of view, it results in exploring the possibility of reducing the number of sensors, or even using these soft sensors as redundants for security purposes. On the basis of some structural properties of the converter, we show mathematically that is possible to design such estimators for two particular cases even in the presence of singular inputs. In this light, we propose two nonlinear observers: a sliding mode observer and a Kalman-like estimator. Finally, the performance of these soft sensors are investigated by simulations in a control-loop which is based on the dead-beat space vector modulation technique.