Mitigation of Voltage Sags in a Refinery with Induction Motors Using Dynamic Voltage Restorer (DVR)

Voltage sags are voltage reduction events, followed by restoration of the normal supply conditions after a short duration. Voltage sags can cause large induction motors in a continuous process industry (like a refinery) to trip, leading to costly shutdowns. The Dynamic Voltage Restorer (DVR) is a power electronic based device used to boost the voltage supplied to the loads during voltage sags. This paper introduces an industry-tailored approach for configuring and controlling DVR. Only the magnitude of the voltage is tracked and compared with reference voltage aiming at simple controller. The controller is based on feed-foreword control scheme aiming at fast response of the DVR. The DVR is controlled to operate in a standby mode for minimizing conduction losses. The industrial distribution system at Alexandria National Refining and Petrochemicals Co. (ANRPC) is taken as a case study. Simulations using the MATLAB/Simulink are carried out to confirm the validity of the proposed DVR. Simulation results have shown that the proposed DVR is an efficient tool in mitigating both sags and swells within a cycle. It can mitigate consecutive, multistage, balanced and unbalanced sags. The only shortcoming of the DVR is, being a series device, its inability to mitigate complete interruptions.