Enhanced droop control for off-grid and grid-tied scenarios in renewable energy systems

Abstract

The control methods of Grid-forming (GFM) inverters are discussed and reviewed. Then, the droop control method’s weak points are modified to have better load sharing performance and improving the lifetime of the inverters when the system has light load situations. Also, the effects of the coupling reactance on stability and reliability are investigated. This control method is applied to three different scenarios in order to see frequency and voltage stability and load sharing between three Inverter Based Resources (IBRs) and the grid. The first case is that the voltage and frequency regulation control algorithm is presented when the IBRs have equal power ratings during the off-grid. Then, the second case is also performed in islanding mode where the load sharing control algorithm is determined based on the different power ratings of the IBRs. Lastly, this setup examined the load sharing status during the grid-tied scenario when the IBRs are not capable of supplying enough power to the load. In all cases, loads are added to and removed from the system to ensure that the frequency and voltages are in the range of continuous operation.

Keywords

• Droop control
• Inverter based resources
• Load sharing
• Renewable energy systems

Kaynakça

1. [1] Lasseter R H, Chen Z, Pattabiraman D. Grid-Forming Inverters: A Critical Asset for the Power Grid. IEEE Journal of Emerging and Selected Topics in Power Electronics 2020; 8(2): 925-935.
2. [2] Rathnayake D B, Akrami M, Phurailatpam C, Me S P, Hadavi S, Jayasinghe G, Zabihi S, Bahrani B. Grid Forming Inverter Modeling, Control, and Applications. IEEE Access 2021; 9: 114781-114807.
3. [3] Unruh P, Nuschke M, Strauß P, Welck F. Overview on grid-forming inverter control methods. Energies 2020;13 (10): 2589.
4. [4] Rezaii R, Ghosh S, Safayatullah M, Milad T S, Batarseh I. Quad-Input Single-Resonant Tank LLC Converter for PV Applications. IEEE Transactions on Industry Applications 2023; 59(3): 3438-3457.
5. [5] Nilian M, Rezaii R, Safayatullah M, Gullu S, Alaql F, Batarseh I. A Three-port Dual Active Bridge Resonant Based with DC/AC Output. IEEE Energy Conversion Congress and Exposition (ECCE) Nashville, TN, USA, 2023.
6. [6] Rezaii R, Nilian M, Ghosh S, Batarseh I, Safayatullah M. Design and Implementation of a Multiport System for Solar EV Applications. IEEE Applied Power Electronics Conference and Exposition (APEC) Orlando, FL, USA, 2023.
7. [7] Rezaii R, Ghosh S, Safayatullah M, Batarseh I. Design and Implementation of a Five-Port LLC Converter for PV Applications. IEEE Applied Power Electronics Conference and Exposition (APEC) Orlando, FL, USA, 2023.
8. [8] Rezaei M H, Akhbari M. Power decoupling capability with PR controller for Micro-Inverter applications. International Journal of Electrical Power & Energy Systems 2022; 136: 107607.

9. [9] Rezaei M H, Akhbari M. An active parallel power decoupling circuit with a dual loop control scheme for micro-inverters. International Journal of Electrical Power & Energy Systems 2021; 49(12): 3994-4011.
10. [10] Matevosyan J, Badrzadeh B, Prevost T, Quitmann E, Ramasubramanian D, Urdal H, Achilles S, MacDowell J, Huang S H, Vital V, O’Sullivan J. Grid-Forming Inverters: Are They the Key for High Renewable Penetration?. IEEE Power and Energy Magazine 2019; 17(6): 89-98.
11. [11] Song G, Cao B, Chang L. Review of Grid-forming Inverters in Support of Power System Operation. Chinese Journal of Electrical Engineering 2022; 8(1): 1-15.
12. [12] Tayyebi A, Groß D, Anta A, Kupzog F, Dörfler F. Frequency Stability of Synchronous Machines and Grid-Forming Power Converters. IEEE Journal of Emerging and Selected Topics in Power Electronics 2020; 8(2): 1004-1018.
13. [13] California Public Utilities Commission, Recommendations for Updating the Technical Requirements for Inverters in Distributed Energy Resources. Smart Invert. Work. Gr. Recomm. 2014. https://www.cpuc.ca.gov/-/media/cpuc-website/divisions/energydivision/documents/rule21/smart-inverter-working-group/siwgworkingdocinrecord.pdf
14. [14] IEEE Standard for Interconnection and Interoperability of Distributed Energy Resources with Associated Electric Power Systems Interfaces – Redline. IEEE Std 1547-2018, 2018.
15. [15] Gkountaras A, Dieckerhoff S, Sezi T. Evaluation of current limiting methods for grid forming inverters in medium voltage microgrids. IEEE Energy Conversion Congress and Exposition (ECCE) Montreal, QC, Canada, 2015.
16. [16] Du W, Chen Z, Schneider K P, Lasseter R H, Nandanoori S P, Tuffner F K. A Comparative Study of Two Widely Used Grid-Forming Droop Controls on Microgrid Small-Signal Stability. IEEE Journal of Emerging and Selected Topics in Power Electronics 2020; 8(2): 963-975.
17. [17] Li M, Wang Y, Xu N, Liu Y, Wang W, Wang H. A novel virtual synchronous generator control strategy based on improved swing equation emulating and power decoupling method. IEEE Energy Conversion Congress and Exposition (ECCE) Milwaukee, WI, USA, 2016.
18. [18] Brabandere D K, Bolsens B, Van den Keybus J, Woyte A, Driesen J, Belmans R. A Voltage and Frequency Droop Control Method for Parallel Inverters. IEEE Transactions on Power Electronics 2007; 22(4): 1107-1115.
19. [19] Chandorkar M C, Divan D M, Adapa R. Control of parallel connected inverters in standalone AC supply systems. IEEE Transactions on Industry Applications 1993; 29(1): 136-143.
20. [20] Karimi-Davijani H, Ojo O. Dynamic operation and control of a multi-DG unit standalone Microgrid. ISGT Anaheim, CA, USA, 2011.
21. [21] Singhal A, Vu T L, Du W. Consensus Control for Coordinating Grid-Forming and Grid Following Inverters in Microgrids. IEEE Transactions on Smart Grid 2022; 13(5): 4123-4133.
22. [22] Nasirian V, Shafiee Q, Guerrero J M, Lewis F L, Davoudi A. Droop-Free Distributed Control for AC Microgrids. IEEE Transactions on Power Electronics 2016; 31(2): 1600-1617.
23. [23] Du W, Lasseter R H, Khalsa A S. Survivability of Autonomous Microgrid During Overload Events. IEEE Transactions on Smart Grid 2019; 10(4): 3515-3524.