scholarly journals Convex Model for Estimation of Single-Phase Photovoltaic Impact on Existing Voltage Unbalance in Distribution Networks

2020 ◽  
Vol 10 (24) ◽  
pp. 8884
Author(s):  
Verner Püvi ◽  
Matti Lehtonen
Keyword(s):  
Single Phase ◽  
Low Voltage ◽  
Distribution Networks ◽  
Mixed Integer ◽  
Convex Model ◽  
Phase Selection ◽  
Voltage Unbalance ◽  
Integer Quadratic Programming ◽  
Mixed Integer Quadratic Programming ◽  
Photovoltaic Plants

Due to the increasing adoption of solar power generation, voltage unbalance estimation gets more attention in sparsely populated rural networks. This paper presents a Monte Carlo simulation augmented with convex mixed-integer quadratic programming to estimate voltage unbalance and maximum photovoltaic penetration. Additionally, voltage unbalance attenuation by proper phase allocation of photovoltaic plants is analysed. Single-phase plants are simulated in low-voltage distribution networks and voltage unbalance is evaluated as a contribution of measured background and photovoltaic-caused unbalance. Voltage unbalance is calculated in accordance with EN 50160 and takes into account 10-minute average values with 5% tolerance condition. Results of the optimization revealed substantial unbalance attenuation with optimal phase selection and increased potential of local generation hosting capacity in case of higher background unbalance.

scholarly journals A Comprehensive Analysis of the Voltage Unbalance Factor in PV and EV Rich Non-Synthetic Low Voltage Distribution Networks

Energies ◽  
2020 ◽  
Vol 14 (1) ◽  
pp. 117
Author(s):  
Tomislav Antić ◽  
Tomislav Capuder ◽  
Martin Bolfek
Keyword(s):  
Power System ◽  
Single Phase ◽  
Low Voltage ◽  
Negative Impact ◽  
Renewable Energy Sources ◽  
Electric Energy ◽  
Distribution Networks ◽  
End Users ◽  
Low Carbon ◽  
Voltage Unbalance

With the development of technology and the decrease in prices, power systems are facing a strong growth in the number of end-users with photovoltaics (PVs), battery storages and electric vehicles (EVs). A penetration of low carbon (LC) technologies has an impact not only on the financial aspect, but also on parameters of the power quality (PQ) in the power system. Since most of end-users with renewable energy sources (RES) are connected to a low-voltage (LV) distribution network, there is a high number of single-phase loads and distributed generators (DG) that can cause unwanted effects in LV networks. According to standards, electric energy must be of a certain quality in order to avoid harmful effects on the power system, being both the network or the end-users equipment. One of the PQ parameters is the voltage unbalance. Voltage unbalance occurs in networks with the high share of single-phase loads and generators. Since most loads in households are connected to the only one phase, the voltage unbalance is constantly present in the network, even without LC technologies. Single-phase connected PVs, residential battery storages and EV charging stations can increase voltage unbalance in the system. This paper systematically analyzes a real-world LV network and different stages and shares of connected PVs, residential battery storages and EVs to different phases. The value of the voltage unbalance factor (VUF) is observed for one week in January and August in 10-min intervals. It is shown that connected systems can significantly increase the VUF and potentially cause negative impact on the equipment and the power system as a whole. In turn we analyze a three-phase connection of these new LC technologies and demonstrate how in all analyzed cases PQ values remain within boundaries defined by the EN 50160 and the IEC 61000-3-13.

scholarly journals An Approximate Mixed-Integer Convex Model to Reduce Annual Operating Costs in Radial Distribution Networks Using STATCOMs

Electronics ◽  
2021 ◽  
Vol 10 (24) ◽  
pp. 3102
Author(s):  
Oscar Danilo Montoya ◽  
Lázaro Alvarado-Barrios ◽  
Jesus C. Hernández
Keyword(s):  
Optimal Power Flow ◽  
Large Scale ◽  
Location Problem ◽  
Reactive Power ◽  
Programming Model ◽  
Search Algorithm ◽  
Distribution Networks ◽  
Mixed Integer ◽  
Convex Model ◽  
Integer Quadratic Programming

The problem of optimal siting and sizing of distribution static compensators (STATCOMs) is addressed in this research from the point of view of exact mathematical optimization. The exact mixed-integer nonlinear programming model (MINLP) is decoupled into two convex optimization sub-problems, named the location problem and the sizing problem. The location problem is addressed by relaxing the exact MINLP model, assuming that all the voltages are equal to 1∠0∘, which allows obtaining a mixed-integer quadratic programming model as a function of the active and reactive power flows. The solution of this model provides the best set of nodes to locate all the STATCOMs. When all the nodes are selected, it solves the optimal reactive power problem through a second-order cone programming relaxation of the exact optimal power flow problem; the solution of the SOCP model provides the optimal sizes of the STATCOMs. Finally, it refines the exact objective function value due to the intrinsic non-convexities associated with the costs of the STATCOMs that were relaxed through the application of Taylor’s series expansion in the location and sizing stages. The numerical results in the IEEE 33- and 69-bus systems demonstrate the effectiveness and robustness of the proposed optimization problem when compared with large-scale MINLP solvers in GAMS and the discrete-continuous version of the vortex search algorithm (DCVSA) recently reported in the current literature. With respect to the benchmark cases of the test feeders, the proposed approach reaches the best reductions with 14.17% and 15.79% in the annual operative costs, which improves the solutions of the DCVSA, which are 13.71% and 15.30%, respectively.

Single-Phase Generation Headroom in Low-Voltage Distribution Networks Under Reduced Circuit Characterization

2015 ◽  
Vol 30 (2) ◽  
pp. 1006-1011 ◽  
Author(s):  
Pedro M. S. Carvalho ◽  
Luis A. F. M. Ferreira ◽  
Joao J. E. Santana
Keyword(s):  
Single Phase ◽  
Low Voltage ◽  
Distribution Networks ◽  
Voltage Distribution

scholarly journals Combinatorial Optimization of Service Order and Overtaking for Demand-Oriented Timetabling in a Single Railway Line

2018 ◽  
Vol 2018 ◽  
pp. 1-21 ◽  
Author(s):  
Dewei Li ◽  
Shishun Ding ◽  
Yizhen Wang
Keyword(s):  
Travel Time ◽  
High Speed ◽  
Cost Benefit ◽  
Theory And Practice ◽  
Mixed Integer ◽  
High Speed Rail ◽  
Railway Line ◽  
Integer Quadratic Programming ◽  
Total Travel Time ◽  
Mixed Integer Quadratic Programming

Train timetabling is crucial for passenger railway operation. Demand-oriented train timetable optimization by minimizing travel time plays an important role in both theory and practice. Most of the current researches of demand-oriented timetable models assume an idealized situation in which the service order is fixed and in which zero overtaking exists between trains. In order to extend the literature, this paper discusses the combinatorial effect of service order and overtaking by developing four mixed-integer quadratic programming timetabling models with different service order as well as overtaking conditions. With the objective of minimizing passengers’ waiting time and in-vehicle time, the models take five aspects as constraints, namely dwell time, running time, safety interval, overtaking, and capacity. All four models are solved by ILOG CPLEX; and the results, which are based on Shanghai-Hangzhou intercity high-speed rail data, show that either allowing overtaking or changing service order can effectively optimize the quality of timetable with respect to reducing the total passengers’ travel time. Although optimizing train overtaking and service order simultaneously can optimize the timetable more significantly, compared to overtaking, allowing the change of service order can help passengers save total travel time without extending the train travel time. Moreover, considering the computation effort, satisfying both of the conditions in the meantime, when optimizing timetable has not got a good cost benefit.

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