A Control Strategy to Improve Voltage Sag Ride-Through in Single-Phase Multilevel Active Rectifier

Voltage sags are one of the most important power quality problems, affecting industrial and commercial customers. These events are usually associated with a fault somewhere on the supplying power system. Industrial processes are particularly sensitive to relatively small voltage sags; therefore, customers will have to improve the ride-through capability of the system equipment in their facilities. This paper presents the application of a control strategy to a single-phase multilevel active rectifier in order to achieve a fast compensation and a small ripple in the DC bus during the voltage sag, maintaining the other benefits (power factor correction and input current harmonic components reduction). The proposed strategy is based on a classical PI voltage controller which parameters are modified when voltage sag occurs. The single-phase DQ theory is used to detect voltage sag and to make the compensation by means of a power estimator. Simulation and experimental results have been carried out in a 1 kVA, single-phase power converter