Compensation of Voltage Sag and Swell in Distribution Systems using DVR based on Nine-Level Packed E-Cell (PEC9) Inverter Topology
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.
 G. Lee, M. Sidorov, C. S. Lim, N. R. N. Idris, and Y. E. Heng, "Hybrid cascaded multilevel inverter (HCMLI) with improved symmetrical 4-level submodule", IEEE Trans. Power Electron., vol. 33, no. 2, pp. 1932-1935, Feb 2018.
 A. Elnady and M. Salama, “Duall Role CDSC based Dual Vector Control for Effective Operation of DVR with Harmonic Mitigation” IEEE Transactions on Industrial Electronics, Vol. 16, No. 8, pp. 2614-2625, Nov 2018.
 H. Vahedi and K. Al-Haddad, “Real-Time Implementation of a Seven-Level Packed U-cell Inverter a Low-Switching-Ferquency voltage Regulator” IEEE Trans. Power Electron, Vol. 31, No. 8, pp. 5967-5973, Aug 2016.
 K. Gupta and A. Ranjan, “Multilevel inverter topologies with reduced device count a review” IEEE Trans. Power Electron, Vol. 31, No. 1, pp. 234-247, July2017.
 Y. Ounejjar and K. Al-Haddad, “Packed E-cell (PEC) Converter Topology Operation and Experimental Validation” IEEE Trans. Ind. Electron, Vol. 23, No. 6, pp. 8421-8432, July 2019.
 A. M. Rauf and V. Khadkikar, "An Enhanced Voltage Sag Compensation Scheme for Dynamic Voltage Restorer," IEEE Transactions on Industrial Electronics, vol. 62, no. 5, pp. 2683-2692, May 2015.
 E. Samadaei, S. A. Gholamian, A. Sheikholeslami, and J. Adabi “An envelope type (E-type) module: Asymmetric Multilevel inverters with reduced components” IEEE Trans. Ind. Electron., vol. 63, no. 11, pp. 7148-7156, Nov 2016.
 P. M. Meshram, V. B. Borghate and F. Nugater “A simplified nearest level control (NLC) voltage balancing method for modular multilevel converter (MMC)” IEEE Trans. Power Electron, Vol. 30, No. 1, pp. 450-462, Aug 2017.
 P. Jayaprakash, and K. Al-Haddad, "Control of reduced-rating Dynamic Voltage Restorer with a battery energy storage system," IEEE Transactions on Industry Application, vol. 50, no. 2, pp. 1295-1303, Mar 2015.