PLL-Less Active/Reactive Power Control of Photovoltaic Energy Source with Applying pq-Theory in Single-Phase Grid System

Abstract

Converter systems are applied to manage active/reactive power control of photovoltaic (PV) source during integration with the electric grid system. The control algorithm of the conventional converter system consists of a reference generation unit, a dc-link voltage control loop, two power control loops and a phase lock loop (PLL) system. PLL unit is used to lock in phase angle of the electric grid, and to perform the coordinate transformation for calculations of the active/reactive powers. However, the control algorithm has a slow dynamic response because of utilisation of a PLL structure. In addition, additional complex mathematical computations are required with the use of a PLL algorithm. Furthermore, the interaction of the PLL and the power control loops may lead power oscillation problems under weak grid, and also result in instability of the PV system. In this study, to avoid the aforementioned issues and to enhance the power flow capability of the grid-connected PV panels, a PLL-less control algorithm in pq-theory is studied for the active/reactive power management and the grid synchronization. In addition, the mathematical formulations of the current control algorithm are presented in detail. To show the effectiveness of the PLL-less controller, a PV system model with using real PV panel groups is designed and constructed in a simulation environment. The proposed control method is tested under various operation cases such as dynamic environmental conditions, reactive power support and voltage variations. The proposed method shows efficient performance under applications of the different operation situations.

Keywords

• Renewable energy systems
• Grid-connected inverter
• PLL-less control
• pq-theory
• Reactive power support

References

1. [1] R. Sharma and S. Mishra, "Dynamic Power Management and Control of a PV PEM Fuel-Cell-Based Standalone ac/dc Microgrid Using Hybrid Energy Storage," IEEE Transactions on Industry Applications, vol. PP, pp. 1-1, 09/22 2017.
2. [2] M. Büyük, A. Tan, M. Tümay, and K. Ç. Bayındır, "Topologies, generalized designs, passive and active damping methods of switching ripple filters for voltage source inverter: A comprehensive review," Renewable and Sustainable Energy Reviews, vol. 62, pp. 46-69, 2016/09/01/ 2016.
3. [3] M. Bornapour, R.-A. Hooshmand, A. Khodabakhshian, and M. Parastegari, "Optimal coordinated scheduling of combined heat and power fuel cell, wind, and photovoltaic units in micro grids considering uncertainties," Energy, vol. 117, pp. 176-189, 2016/12/15/ 2016.
4. [4] M. A. Hannan, S. Y. Tan, A. Q. Al-Shetwi, K. P. Jern, and R. A. Begum, "Optimized controller for renewable energy sources integration into microgrid: Functions, constraints and suggestions," Journal of Cleaner Production, vol. 256, p. 120419, 2020/05/20/ 2020.
5. [5] E. Kabalcı, "Review on novel single-phase grid-connected solar inverters: Circuits and control methods," Solar Energy, vol. 198, pp. 247-274, 2020/03/01/ 2020.
6. [6] B. Liu, Z. Zhang, G. Li, D. He, Y. Chen, Z. Zhang, et al., "Integration of power decoupling buffer and grid-tied photovoltaic inverter with single-inductor dual-buck topology and single-loop direct input current ripple control method," International Journal of Electrical Power & Energy Systems, vol. 125, p. 106423, 2021/02/01/ 2021.
7. [7] G. Liu, T. Caldognetto, P. Mattavelli, and P. Magnone, "Suppression of Second-Order Harmonic Current for Droop-Controlled Distributed Energy Resource Converters in DC Microgrids," IEEE Transactions on Industrial Electronics, vol. 67, pp. 358-368, 2020.
8. [8] C. Xie, K. Li, X. Zhao, J. C. Vasquez, and J. Guerrero, Reduced Order Generalized Integrators with Phase Compensation for Three-Phase Active Power Filter, 2017.

9. [9] P. Verma, T. Kaur, and R. Kaur, "Power control strategy of an integrated PV system for active power reserve under dynamic operating conditions," Sustainable Energy Technologies and Assessments, vol. 45, p. 101066, 2021/06/01/ 2021.
10. [10] J. P. Roselyn, C. P. Chandran, C. Nithya, D. Devaraj, R. Venkatesan, V. Gopal, et al., "Design and implementation of fuzzy logic based modified real-reactive power control of inverter for low voltage ride through enhancement in grid connected solar PV system," Control Engineering Practice, vol. 101, p. 104494, 2020/08/01/ 2020.
11. [11] D. Çelik and M. E. Meral, "A novel control strategy for grid connected distributed generation system to maximize power delivery capability," Energy, vol. 186, p. 115850, 2019/11/01/ 2019.
12. [12] M. M. Savrun and M. İnci, "Adaptive neuro-fuzzy inference system combined with genetic algorithm to improve power extraction capability in fuel cell applications," Journal of Cleaner Production, vol. 299, p. 126944, 2021/05/25/ 2021.
13. [13] S. Gu, X. Du, Y. Shi, Y. Wu, P. Sun, and H. Tai, "Power control for grid-connected converter to comply with safety operation limits during grid faults," in 2016 IEEE Energy Conversion Congress and Exposition (ECCE), 2016, pp. 1-5.
14. [14] A. Q. Al-Shetwi, M. A. Hannan, K. P. Jern, M. Mansur, and T. M. I. Mahlia, "Grid-connected renewable energy sources: Review of the recent integration requirements and control methods," Journal of Cleaner Production, vol. 253, p. 119831, 2020/04/20/ 2020.
15. [15] P. Rodríguez, A. Luna, I. Candela, R. Mujal, R. Teodorescu, and F. Blaabjerg, "Multiresonant Frequency-Locked Loop for Grid Synchronization of Power Converters Under Distorted Grid Conditions," IEEE Transactions on Industrial Electronics, vol. 58, pp. 127-138, 2011.
16. [16] B. Wen, D. Boroyevich, R. Burgos, P. Mattavelli, and Z. Shen, "Analysis of D-Q Small-Signal Impedance of Grid-Tied Inverters," IEEE Transactions on Power Electronics, vol. 31, pp. 675-687, 2016.
17. [17] Y. Gui, X. Wang, F. Blaabjerg, and D. Pan, "Control of Grid-Connected Voltage-Source Converters: The Relationship Between Direct-Power Control and Vector-Current Control," IEEE Industrial Electronics Magazine, vol. 13, pp. 31-40, 2019.
18. [18] K. M. Tsang, W. L. Chan, and X. Tang, "PLL-less single stage grid-connected photovoltaic inverter with rapid maximum power point tracking," Solar Energy, vol. 97, pp. 285-292, 2013/11/01/ 2013.
19. [19] K. S. R. Sekhar and M. A. Chaudhari, "Reactive Power Enhancement of a PLL less PV inverter for AC Micro-grids," in 2020 IEEE First International Conference on Smart Technologies for Power, Energy and Control (STPEC), 2020, pp. 1-6.
20. [20] S. Dedeoglu and G. C. Konstantopoulos, "PLL-Less Three-Phase Droop-Controlled Inverter with Inherent Current-Limiting Property," in IECON 2019 - 45th Annual Conference of the IEEE Industrial Electronics Society, 2019, pp. 4013-4018.
21. [21] P. Patel, U. Mali, and G. Patel, "PLL less strategy for grid tied inverter with different load conditions," in 2017 Third International Conference on Advances in Electrical, Electronics, Information, Communication and Bio-Informatics (AEEICB), 2017, pp. 251-254.
22. [22] X. Li and R. S. Balog, "PLL-less robust active and reactive power controller for single phase grid-connected inverter with LCL filter," in 2015 IEEE Applied Power Electronics Conference and Exposition (APEC), 2015, pp. 2154-2159.
23. [23] S. Deo, C. Jain, and B. Singh, "A PLL-Less Scheme for Single-Phase Grid Interfaced Load Compensating Solar PV Generation System," IEEE Transactions on Industrial Informatics, vol. 11, pp. 692-699, 2015.
24. [24] A. Khan, M. Hosseinzadehtaher, and M. B. Shadmand, "Single Stage PLL-less Decoupled Active and Reactive Power Control for Weak Grid Interactive Inverters," IFAC-PapersOnLine, vol. 53, pp. 12390-12395, 2020/01/01/ 2020.
25. [25] A. Khan, M. Easley, M. Hosseinzadehtaher, M. B. Shadmand, H. Abu-Rub, and P. Fajri, "PLL-less Active and Reactive Power Controller for Grid-Following Inverter," in 2020 IEEE Energy Conversion Congress and Exposition (ECCE), 2020, pp. 4322-4328.
26. [26] E. Heydari, A. Y. Varjani, and D. Diallo, "Fast terminal sliding mode control-based direct power control for single-stage single-phase PV system," Control Engineering Practice, vol. 104, p. 104635, 2020/11/01/ 2020.
27. [27] G. C. Konstantopoulos, Q. Zhong, and W. Ming, "PLL-Less Nonlinear Current-Limiting Controller for Single-Phase Grid-Tied Inverters: Design, Stability Analysis, and Operation Under Grid Faults," IEEE Transactions on Industrial Electronics, vol. 63, pp. 5582-5591, 2016.
28. [28] R. Chen, "DC Capacitor Minimization of Single Phase Power Conversion and Applications," PhD, Michigan State University., 2016, PhD Thesis.
29. [29] H. Cha and T. Vu, "Comparative analysis of low-pass output filter for single-phase grid-connected Photovoltaic inverter," in 2010 Twenty-Fifth Annual IEEE Applied Power Electronics Conference and Exposition (APEC), 2010, pp. 1659-1665.
30. [30] Ö. Çelik, A. Tan, M. İnci, and A. Teke, "Improvement of energy harvesting capability in grid-connected photovoltaic micro-inverters," Energy Sources, Part A: Recovery, Utilization, and Environmental Effects, pp. 1-25, 04/24 2020.
31. [31] C. Kalavalli, P. Meenalochini, P. Selvaprasanth, and S. Syed Abdul Haq, "Dual loop control for single phase PWM inverter for distributed generation," Materials Today: Proceedings, vol. 45, pp. 2216-2219, 2021/01/01/ 2021.
32. [32] M. Talha, S. R. S. Raihan, and N. A. Rahim, "PV inverter with decoupled active and reactive power control to mitigate grid faults," Renewable Energy, vol. 162, pp. 877-892, 2020/12/01/ 2020.
33. [33] S. Roy, P. Kumar Sahu, S. Jena, and A. Kumar Acharya, "Modeling and control of DC/AC converters for photovoltaic grid-tie micro-inverter application," Materials Today: Proceedings, vol. 39, pp. 2027-2036, 2021/01/01/ 2021.
34. [34] L. Hassaine and B. Mohamed Rida, "Control technique for single phase inverter photovoltaic system connected to the grid," Energy Reports, vol. 6, 11/01 2019.
35. [35] M. İnci, "Active/reactive energy control scheme for grid-connected fuel cell system with local inductive loads," Energy, vol. 197, p. 117191, 2020/04/15/ 2020.