Compensation of Voltage Sag and Swell in Distribution Systems using DVR based on Nine-Level Packed E-Cell (PEC9) Inverter Topology
Abstract
This paper proposes the mitigation of grid voltage disturbances using a nine-level Packed E Cells (PEC9) based dynamic voltage restorer (DVR) solution. Which regulates the injection of the compensation voltage in series and synchronism with the grid during the voltage disturbance events, the auxiliary capacitor voltage, while controlling the PEC9 output current. The nine-level PEC (PEC9) is composed of seven active switches and two dc capacitors that are shunted by a four-quadrant switch to from the E-cell, and it makes use of a single dc link. With the proper design of the corresponding PEC9 switching states, the dc capacitors are balanced using the redundant charging/discharging states. Since the shunted capacitors are horizontally extended, both capacitors are simultaneously charged or discharged with the redundant states, so only the auxiliary dc-link voltage needs to be sensed and regulated to half of the input dc source voltage, and consequently, dc capacitors' voltages are inherently balanced to one quarter of the dc bus voltage. To this end, an active capacitor voltage balancing integrated to the Nearest Level Control (NLC) has been designed based on the redundant charging/discharging states to regulate the dc capacitors voltages of PEC9. Furthermore, using the E-cell not only reduces components count but also the proposed topology permits multi ac terminal operation. The In-Phase control method is selected to control the proposed DVR and use the synchronous reference frame (SRF) method to detect the network voltage fluctuations. To verify and validate the proposed DVR performance, simulations are carried out in the MATLAB / SIMULINK software environment, and the results indicate the optimal performance and desirability of the proposed DVR to compensate for the voltage sag and swell distribution systems. Theoretical analysis and simulation results are given to show the high performance of the proposed solution.
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