Power Quality Improvement in Microgrids using STATCOM under Unbalanced Voltage Conditions

Document Type : Original Article


Department of Electrical Engineering, Razi University, Kermanshah, Iran


A large number of single-phase loads and sources create unbalanced voltage in microgrids. Voltage unbalance reduces the power quality, which results in misoperation or failure of customer equipment and microgrid. Also, voltage unbalance negatively impacts induction motors, power electronic converters, and adjustable speed drives.  Static synchronous compensator (STATCOM), as an influential segment of the Flexible Alternative Current Transmission Systems (FACTS), has been extensively utilized as shunt compensators for controlling reactive power and regulation voltage in transmission and distribution networks. Under unbalanced conditions, an oscillating couple between the positive and negative sequence components of control loops emerge in the d-q frame. This paper suggests an innovative point of common coupling (PCC) voltage controller in Decoupled Double Synchronous Reference Frame (DDSRF) to compensate for an unbalanced PCC voltage and reduce the oscillating couple using STATCOM. Implementation of the proposed DDSRF involves several steps. Firstly, unbalance signals are rotated counterclockwise to split up the positive sequences. Secondly, those signals are rotated clockwise to separate negative sequences. Finally, by utilizing mathematical equations, the proposed DDSRF is introduced, which enables independent control of positive and negative sequence components. This study controls DC capacitor voltage for unbalanced conditions. Furthermore, the regulation voltage at PCC is performed. The control system scheme is also designed under unbalanced conditions, and simulation results guarantee the suggested control strategy.


  1. Han, Yang, Pan Shen, Xin Zhao, and Josep M. Guerrero. "Control strategies for islanded microgrid using enhanced hierarchical control structure with multiple current-loop damping schemes." IEEE Transactions on Smart Grid, Vol. 8, No. 3, (2015), 1139-1153, DOI:10.1109/TSG.2015.2477698.
  2. Baghaee, Hamid Reza, Mojtaba Mirsalim, Gevork B. Gharehpetian, and Heidar Ali Talebi. "Three-phase AC/DC power-flow for balanced/unbalanced microgrids including wind/solar, droop-controlled and electronically-coupled distributed energy resources using radial basis function neural networks." IET Power Electronics, Vol. 10, No. 3, (2017), 313-328, DOI: 10.1049/iet-pel.2016.0010.
  3. Guerrero, Josep M., Poh Chiang Loh, Tzung-Lin Lee, and Mukul Chandorkar. "Advanced control architectures for intelligent microgrids—Part II: Power quality, energy storage, and AC/DC microgrids." IEEE Transactions on Industrial Electronics, Vol. 60, No. 4, (2012), 1263-1270, DOI: 10.1109/TIE.2012.2196889.
  4. Aghaei, J., M. Gitizadeh, and M. Kaji. "Placement and operation strategy of FACTS devices using optimal continuous power flow." Scientia Iranica Vol. 19, No. 6, (2012), 1683-1690, DOI: 10.1016/j.scient.2012.04.021.
  5. Subramanian, Sridhar Bala, Sibin Mohan, Mohammad Akbari, Hesamaldin Maleki, Reza Salehi, Wayne H. Litzenberger, and Rajiv K. Varma. "Control of STATCOMs–A review." In 2018 IEEE Power & Energy Society General Meeting (PESGM), IEEE, (2018), 1-5, DOI:10.1109/PESGM.2018.8586479.
  6. Hatano, Nobuhiko, and Toshifumi Ise. "Control scheme of cascaded H-bridge STATCOM using zero-sequence voltage and negative-sequence current." IEEE Transactions on Power Delivery, Vol. 25, No. 2, (2010), 543-550, DOI:10.1109/TPWRD.2009.2035221.
  7. Wang, Keyou, and Mariesa L. Crow. "Power system voltage regulation via STATCOM internal nonlinear control." IEEE Transactions on Power Systems, Vol. 26, No. 3, (2010), 1252-1262, DOI:10.1109/TPWRS.2010.2072937.
  8. Hysa, Azem. "Modeling and simulation of the photovoltaic cells for different values of physical and environmental parameters." Emerging Science Journal, Vol. 3, No. 6, (2019), 395-406, DOI: 10.28991/esj-2019-01202.
  9. Slavova, Miglena, Elena Mihaylova-Dimitrova, Emiliya Mladenova, Borislav Abrashev, Blagoy Burdin, and Daria Vladikova. "Zeolite Based Air Electrodes for Secondary Batteries." Emerging Science Journal, Vol. 4, No. 1, (2020), 18-24, DOI: 10.28991/esj-2020-01206.
  10. Sani, Mahnaz Jabbarzadeh. "Spin-Orbit Coupling Effect on the Electrophilicity Index, Chemical Potential, Hardness and Softness of Neutral Gold Clusters: A Relativistic Ab-initio Study." HighTech and Innovation Journal, Vol. 2, No. 1, (2021), 38-50, DOI: 10.28991/HIJ-2021-02-01-05.
  11. Sagar, G. V. R., and T. Debela. "Implementation of optimal load balancing strategy for hybrid energy management system in dc/ac microgrid with pv and battery storage." International Journal of Engineering, Transactions A: Basics, Vol. 32, No. 10, (2019), 1437-1445, DOI: 10.5829/ije.2019.32.10a.13.
  12. Somasundaram, Deepa, and Samuel Rajesh Babu. "A robust statcom controller using particle swarm optimization." International Journal of Engineering, Transactions B: Applications, Vol. 27, No. 5, (2014), 731-738, DOI:10.5829/idosi.ije.2014.27.05b.08.
  13. Song, Qiang, and Wenhua Liu. "Control of a cascade STATCOM with star configuration under unbalanced conditions." IEEE Transactions on Power Electronics, Vol. 24, No. 1 (2009), 45-58, DOI: 10.1109/TPEL.2008.2009172.
  14. Miao, Zhixin, Lakshan Piyasinghe, Javad Khazaei, and Lingling Fan. "Dynamic phasor-based modeling of unbalanced radial distribution systems." IEEE Transactions on Power Systems, Vol. 30, No. 6, (2015), 3102-3109, DOI:10.1109/TPWRS.2014.2388154.
  15. Shuai, Zhikang, Yelun Peng, Josep M. Guerrero, Yong Li, and Z. John Shen. "Transient response analysis of inverter-based microgrids under unbalanced conditions using a dynamic phasor model." IEEE Transactions on Industrial Electronics, Vol. 66, No. 4 (2018), 2868-2879, DOI:10.1109/TIE.2018.2844828.
  16. Wessels, Christian, Sönke Grunau, and Friedrich W. Fuchs. "Current injection targets for a STATCOM under unbalanced grid voltage condition and the impact on the PCC voltage." Proc. EPE Joint Wind Energy TD Chapters Sem (2011).












  1. Nejabatkhah, Farzam, Yun Wei Li, and Bin Wu. "Control strategies of three-phase distributed generation inverters for grid unbalanced voltage compensation." IEEE Transactions on Power Electronics, Vol. 31, No. 7, (2015), 5228-5241, DOI: 10.1109/TPEL.2015.2479601.
  2. Mishra, Priyanka, Ashok Kumar Pradhan, and Prabodh Bajpai. "Voltage control of PV inverter connected to unbalanced distribution system." IET Renewable Power Generation, Vol. 13, No. 9, (2019), 1587-1594, DOI: 10.1049/iet-rpg.2018.6219.
  3. Zhenglong, Xia, Shi Liping, and Yang Xiaodong. "Control strategy of cascade STATCOM under unbalanced grid conditions." IETE Technical Review, Vol. 31, No. 2, (2014), 177-185, DOI: 10.1080/02564602.2014.892741.
  4. Bakhshizadeh, Mohammad Kazem, Jesper Hjerrild, Łukasz Kocewiak, Bo Hesselbæk, Xiongfei Wang, Frede Blaabjerg, and Claus Leth Bak. "Small-signal model of a decoupled double synchronous reference frame current controller." In 2016 IEEE 17th Workshop on Control and Modeling for Power Electronics (COMPEL), 1-6. IEEE, 2016, DOI: 10.1109/COMPEL.2016.7556713.
  5. Reyes, Manuel, Pedro Rodriguez, Sergio Vazquez, Alvaro Luna, Remus Teodorescu, and Juan Manuel Carrasco. "Enhanced decoupled double synchronous reference frame current controller for unbalanced grid-voltage conditions." IEEE Transactions on Power Electronics, Vol. 27, No. 9, (2012), 3934-3943,DOI:10.1109/TPEL.2012.2190147.
  6. Misra, Himanshu, and Amit Kumar Jain. "Enhanced DDSRF based vector control of grid side converter using single AC side current sensor under unbalanced grid conditions." In 2016 IEEE International Conference on Power Electronics, Drives and Energy Systems (PEDES), 1-6. IEEE, 2016,DOI:10.1109/PEDES.2016.7914355.
  7. Rodríguez, Pedro, Josep Pou, Joan Bergas, J. Ignacio Candela, Rolando P. Burgos, and Dushan Boroyevich. "Decoupled double synchronous reference frame PLL for power converters control." IEEE Transactions on Power Electronics, Vol. 22, No. 2, (2007), 584-592, DOI:10.1109/TPEL.2006.890000.
  8. Vasquez, Juan C., Josep M. Guerrero, Mehdi Savaghebi, Joaquin Eloy-Garcia, and Remus Teodorescu. "Modeling, analysis, and design of stationary-reference-frame droop-controlled parallel three-phase voltage source inverters." IEEE Transactions on Industrial Electronics, Vol. 60, No. 4, (2012), 1271-1280, DOI:10.1109/TIE.2012.2194951.
  9. Yazdani, Amirnaser, and Reza Iravani. Voltage-sourced converters in power systems. Vol. 39. Hoboken, NJ, USA: John Wiley & Sons, 2010, DOI: 10.1002/9780470551578.
  10. Savaghebi, Mehdi, Alireza Jalilian, Juan C. Vasquez, and Josep M. Guerrero. "Secondary control scheme for voltage unbalance compensation in an islanded droop-controlled microgrid." IEEE Transactions on Smart Grid, Vol. 3, No. 2, (2012), 797-807, DOI:10.1109/TSG.2011.2181432.