scholarly journals System Unbalance Analyses and Improvement for Rooftop Photovoltaic Generation Systems in Distribution Networks

Energies ◽  
2020 ◽  
Vol 13 (8) ◽  
pp. 1996
Author(s):  
Rong-Ceng Leou ◽  
Jen-Hao Teng ◽  
Yun-Fang Li ◽  
Wei-Min Lin ◽  
Yu-Hung Lin
Keyword(s):  
Distribution Networks ◽  
Test Results ◽  
Photovoltaic Generation ◽  
Distribution Transformers ◽  
Flow Limit ◽  
Line Flow ◽  
Tap Changer ◽  
Load Tap Changer ◽  
Current Unbalance ◽  
Phase Arrangement

This paper studies the system unbalance caused by rooftop Photovoltaic Generation Systems (PVGSs) in distribution networks and proposes an improved method. The voltage and current unbalance studies for three extreme cases considering all rooftop PVGSs being connected to one single phase and then the stochastic analyses for the integration cases of rooftop PVGSs are considered. These three extreme cases lead to severe system unbalance problems. An improving method that combines the On Load Tap Changer (OLTC) and the optimal phase arrangement of distribution transformers is proposed in this paper to mitigate the system unbalance. The OLTC-based improving method is applied first. If the system unbalance is still out of range, the optimal phase arrangement of distribution transformers is further used to mitigate the system unbalance problem. The objective function of optimal phase arrangement is to minimize the system unbalance with the constraints of voltage limits, line flow limit, etc. Test results show that the proposed method can improve the system unbalance significantly even under very extreme cases.

scholarly journals Accurate Assessment of Decoupled OLTC Transformers to Optimize the Operation of Low-Voltage Networks

Energies ◽  
2019 ◽  
Vol 12 (11) ◽  
pp. 2173
Author(s):  
Álvaro Rodríguez del Nozal ◽  
Esther Romero-Ramos ◽  
Ángel Luis Trigo-García
Keyword(s):  
Distributed Generation ◽  
Optimization Problem ◽  
Low Voltage ◽  
Optimal Solution ◽  
Distribution Networks ◽  
Voltage Regulation ◽  
Rigorous Approach ◽  
Tap Changer ◽  
Load Tap Changer ◽  
Active Distribution Networks

Voltage control in active distribution networks must adapt to the unbalanced nature of most of these systems, and this requirement becomes even more apparent at low voltage levels. The use of transformers with on-load tap changers is gaining popularity, and those that allow different tap positions for each of the three phases of the transformer are the most promising. This work tackles the exact approach to the voltage optimization problem of active low-voltage networks when transformers with on-load tap changers are available. A very rigorous approach to the electrical model of all the involved components is used, and common approaches proposed in the literature are avoided. The main aim of the paper is twofold: to demonstrate the importance of being very rigorous in the electrical modeling of all the components to operate in a secure and effective way and to show the greater effectiveness of the decoupled on-load tap changer over the usual on-load tap changer in the voltage regulation problem. A low-voltage benchmark network under different load and distributed generation scenarios is tested with the proposed exact optimal solution to demonstrate its feasibility.

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