Hisham M. Soliman
Department of Electrical and Computer Engineering, Sultan Qaboos University, Muscat, Oman
Abdelsalam Elhaffar
Department of Electrical and Computer Engineering, Sultan Qaboos University, Muscat, Oman
Mohammed Albadi
Department of Electrical and Computer Engineering, Sultan Qaboos University, Muscat, Oman
In distribution systems, voltage levels of the various buses should be maintained within the permissible limits for satisfactory operation of all electrical installations and equipment. The task of voltage control is closely associated with fluctuating load conditions and corresponding requirements of reactive power compensation. The problem of load bus voltage optimization in distribution systems that have distributed generation (DG) has recently become an issue. In Oman, the distribution code limits the load bus voltage variations within ±6% of the nominal value. Several voltage control methods are employed in active distribution systems with a high share of photovoltaic systems (PV) to keep the voltage levels within the desirable limits. In addition to the constraint of targeting the best voltage profile, another constraint has to be achieved which is the minimum loss in the distribution network. An optimised solution for voltage of load busses with on-load tap-changing (OLTC) tarnsformers and PV sources is presesnted in this paper. This study addresses the problem of optimizing the injected power from PV systems associated with the facilities of tap-changing transformers, as it is an important means of controlling voltage throughout the system. To avoid violating tap-changing constraints, a method is depicted for determining the minimal changes in transformer taps to control voltage levels with distributed PV sources. The taps of a range + 5 to -15 %, can be achieved by tap-changing transformers. The OLTC operation was designed to keep the secondary bus within the voltage standard for MV networks.
[1] C. R. Sarimuthu, V. K. Ramachandaramurthy , K.R. Agileswari, Hazlie Mokhlis, A review on voltage control methods using on-load tap changer transformers for networks with renewable energy sources, renewable and Sustainable Energy Reviews, 2016, 62: 1154–1161.
[2] Konstantina Christakou, Mario Paolone, Ali Abur. Voltage Control in Active Distribution Networks Under Uncertainty in the System Model: A Robust Optimization Approach. IEEE Transactions on Smart Grid, 2018, 9(6): 5631-5642.
[3] Kashem M. Muttaqi, D. T. Le. Michael Negnevitsky, and Gerard Ledwich. A Novel Tuning Method for Advanced Line Drop Compensator and Its Application to Response Coordination of Distributed Generation With Voltage Regulating Devices. IEEE Transactions on Industry Applications, 2016, 52(2): 1842-1854.
[4] B. ULJANIĆ, et al, Voltage control in distribution networks with high share of distributed generation,C6-110, CIGRE 2014, PARIS.
[5] M. R. Salem, L. A. Talat, and H. M. Soliman. Voltage control by tap-changing transformers for a radial distribution network. IEE Proceedings Generation, Transmission and Distribution, 1997, 144(6): 517–520.
[6] H. M. Soliman, A. Elhaffar, M. Al-Harthi, A. Al-Butaini, S. Kashoub. Voltage Control in Oman Power System using Minimal Tap-Changing Transformers. GCC Power 2018 Conference, Kuwait, 2018: 11-13.
[7] Oman Electricity Transmission Company OETC Five-Year Annual Transmission capability Statement (2017-2021), 2017, available online at: https://www.omangrid.com/en/Pages/Asset-Management.aspx
[8] IEC 60038 International Electrotechnical Commission (IEC). IEC 60038:2009 Voltage Standards, 2009.
[9] M. Albadi, H. Soliman, M. Awlad Thani, A. Al-Alawi, S. Al-Ismaili, A. Al-Nabhani, H. Baalawi. Optimal Allocation of PV Systems to Minimize Losses in Distribution Networks Using GA and PSO: Masirah Island Case Study. J. Electrical Systems, 2017, 13(4): 678-688.
[10] Gajic Z., Aganovic S., Benovic J., Leci G., Gazzari S.. Using IEC 61850 analogue goose messages for OLTC control of parallel transformers. Developments in Power System Protection (DPSP 2010). Managing the Change, 10th IET International Conference on , 2010: 1-5.
