Towards a New Model of Evaluation of Transformation Losses in Solar Orchards

In this article is analyzed the economic yield that would turn out from replacing the conventional transformers currently used on solar orchards by others of higher performance. In this way, the losses would be reduced increasing at the same time the injected energy to the network. Moreover, it would have a beneficial effect in the efficiency of the global installation including the connection to the distribution network

DCOPF Contingency Analysis Including Phase Shifting Transformers

This work deals with a new formulation for the Direct Current Optimal Power Flow (DCOPF) including the corrective actions related to the phase shifting transformers. The formulation is based on the outage of generators and/or branches modelled as fictitious injections of active power. The inclusion of the sensitivities of the phase shifting transformer with respect to the injected powers is one of the novelties of this paper. By including the fictitious injections in the optimization problem, the injections are adjusted to the post-contingency state as a consequence of the corrective actions carried out by the DCOPF to bring the system back to its normal state. Consequently, when the analysis of contingencies is performed, the classical topological analysis and the subsequent analyses are avoided with this approach. The DCOPF includes as corrective control variables the rescheduling of active power generations, phase shifting transformers and, if required, permitted load shedding. The IEEE-RTS of 24 buses is used as benchmark network to assess the properties of the proposed approach.Spanish Ministry of Science and Innovation and Cooperation (Spain) ENE2011-24137Spanish Ministry of Science and Innovation and Cooperation (Spain) ENE2011-27984Junta de Andalucía PO11-TEP741

A new DC corrective OPF based on generator and branch outages modelled as fictitious nodal injections

This work deals with a new formulation for the direct current corrective optimal power flow. The formulation is based on the outage of generators and/or branches modelled as fictitious injections of active power. By including that fictitious injections in the optimization problem, the injections are adjusted to the post-contingency state as a consequence of the corrective actions carried out to bring the system back to its normal state. So, when the analysis of contingencies is performed, the classical topological analysis and the subsequent analyses are avoided with this approach. This new formulation uses the sensitivity matrix between branch power flows and powers injected in a power system. An important feature of this matrix is to remain constant during the Contingency Analysis performed for the generation-load scenario (base case) of each period of time to be analysed. The approach proposed is illustrated in the IEEE-RTS of 24buses. The results obtained in this distribution network demonstrate that the proposed methodology can assess the impact of contingencies with an acceptable accuracy and a short computation time.Spanish Ministry of Science and Innovation grant ENE2011-27984Spanish Ministry of Science and Innovation grant ENE2010-18867Junta de Andalucía TEP-517

Experimental Assessment of a Centralised Controller for High-RES Active Distribution Networks

This paper assesses the behaviour of active distribution networks with high penetration of renewable energy sources when the control is performed in a centralised manner. The control assets are the on-load tap changers of transformers at the primary substation, the reactive power injections of the renewable energy sources, and the active and reactive power exchanged between adjacent feeders when they are interconnected through a DC link. A scaled-down distribution network is used as the testbed to emulate the behaviour of an active distribution system with massive penetration of renewable energy resources. The laboratory testbed involves hardware devices, real-time control, and communication infrastructure. Several key performance indices are adopted to assess the effects of the different control actions on the system’s operation. The experimental results demonstrate that the combination of control actions enables the optimal integration of a massive penetration of renewable energy.Ministerio de Economía y Competitividad ENE2015-69597-RMinisterio de Economía y Competitividad PCIN-2015-043Ministerio de Economía y Competitividad ENE2017-84813-

Actuaciones correctoras para el control de tensiones en redes de distribución y de los flujos de potencia reactiva en los transformadores transporte/distribución

El objetivo del trabajo que se presenta en este artículo consiste en el desarrollo de técnicas para la determinación de actuaciones sobre ciertas variables de control, a disposición de los gestores de redes de distribución, para mantener las tensiones de los nudos en la red mallada de distribución y los flujos de potencia reactiva por los transformadores transporte/distribución dentro de los límites establecidos, manteniendo al mismo tiempo un adecuado margen de actuación en las variables de contro

Exploiting the use of DC SCOPF approximation to improve iterative AC SCOPF algorithms

This paper focuses on improving the solution techniques for the AC SCOPF problem of active power dispatch by using the DC SCOPF approximation within the SCOPF algorithm. Our approach brings two benefits compared to benchmark SCOPF algorithms: it speeds-up the solution of an iterative AC SCOPF algorithm thanks to a more efficient identification of binding contingencies, and allows improving the objective by an appropriate choice of a limited number of corrective actions for each contingency. The proposed approach is illustrated on 5 test systems of 60, 118, 300, 1203, and 2746 buses

Optimal Location of Distributed Energy Resources Considering Investment Costs, Use of Resources and Network Constraints

The consideration of distributed energy resources as non-wires alternatives for the elimination of overloads and voltage problems poses new challenges for their location and management. Traditional location methodologies approach the problem from the distribution system operator perspective, who tries to correct overload and voltage outside margins while minimizing other possible negative impacts in the network. The approach presented in this paper also considers the investor's point of view, seeking the most appropriate technology alternative, the maximum use of the available resource, and the minimum investment. Those aspects are explicitly taken into account in the formulation of the model, which takes the form of a mixed-integer nonlinear optimization problem. The proposed methodology is tested in two different scenarios using the medium-voltage distribution system benchmark of CIGRE. The results show that the interests of the distribution system operator and the investors can be jointly satisfied, achieving an effective, safe and realistic integration of new distributed resources

Optimal Scheduling of Controllable Resources in Energy Communities: An Overview of the Optimization Approaches

In recent years, there has been a growing interest in the study of energy communities. This new definition refers to a community sharing energy resources of different types to meet its needs and reduce the associated costs. Optimization is one of the most widely used techniques for scheduling the operation of an energy community. In this study, we extensively reviewed the mathematical models used depending on the objectives and constraints considered. The models were also classified according to whether they address uncertainty and the inclusion of flexibility constraints. The main contribution of this study is the analysis of the most recent research on the mathematical formulation of optimization models for optimal scheduling of resources in energy communities. The results show that the most commonly used objectives are profit maximization and cost minimization. Additionally, in almost all cases, photovoltaic generation is one of the main energy sources. Electricity prices, renewable generation, and energy demand are sources of uncertainty that have been modeled using stochastic and robust optimization. Flexibility services using demand response are often modeled using interruptible loads and shiftable loads. There is still considerable room for further research on the distribution of benefits among the participants of the energy community and the provision of flexibility services to the electricity grid

A hybrid methodology for optimal var dispatch in the western algerian power system

This paper describes the methodology adopted for the optimal var dispatch (OVD) integrating a particle swarm optimization (PSO) algorithm and the interior point method (IPM). The proposed hybrid method can be mainly divided in two parts. The first part is to solve the OVD with the IPM based on the logarithmic- barrier primal- dual algorithm (LB-PDA), for non linear programming (NLP) by relaxing the discrete variables. In the second part, the PSO algorithm is used to solve the discrete variables with the continuous variables being fixed, whereas the IPM solves the continuous optimization with the discrete variables being constant. The optimal solution can be obtained by solving the two sub-problems alternately. Numerical simulation on the Western Algerian power system illustrate this proposed hybrid method

Steady-state model for the three-leg shunt-series ac-link power flow controller

Shunt-series ac links constitute a class of so-called vector switching converters, capable of controlling power flows by synthesising an adjustable series voltage. A novel steady-state model for the recently introduced three-leg shunt-series ac link, suitable for power flow studies, is developed in this study. The new model is then applied in two optimal power flow problems arising in distribution systems, namely, power loss reduction and integration of distributed generation, where the performance of the three-leg topology is compared with that of the conventional four-leg scheme. The CIGRE Task Force C06.04.02 benchmark network is used as case study.Junta de Andalucía TEP-07411Ministerio de Economía y Competitividad ENE2011-2413