A low cost fuzzy logic active rectifier

This paper presents a current-sensorless active rectifier specifically designed for low cost applications. Both the control and the modulation use fuzzy logic. A simple model of the system is given in order to explain the current feedforward control using fuzzy logic and the fuzzy logic-based modulation. In this paper, the new algorithm has been deeply analysed looking to obtain the highest performance with the smallest passive elements and the lowest switching frequency. Performance has been compared with those of a closed loop PI-based rectifier with space-vector modulation. This comparison has been carried out either considering the whole systems or a combination of their components (PI control + fuzzy modulation or fuzzy feedforward control + SVM). The results show that, even without current sensors, the low frequency distortion of line currents and the DC voltage oscillations produced by the proposed system are very limited ensuring performance similar to those of more expensive PI-based, closed loop active rectifiers.