Recent changes in the electric utility infrastructure have created opportunities for many technological innovations, including the employment of distributed generation (DG) to achieve a variety of benefits. After a brief discussion of the benefits, this paper proposes a general approach and a set of indices to assess some of the technical benefits in a quantitative manner. The indices proposed are: 1) voltage profile improvement index; 2) line-loss reduction index; 3) environmental impact reduction index; and 4) DG benefit index. Simulation results obtained using a simple 12-bus test system and a radial system are presented and discussed to illustrate the value and usefulness of the proposed approach.

An approach to quantify the technical benefits of distributed generation

Ancillary services for distributed generation (DG) systems become a challenging issue to smartly integrate renewable-energy sources into the grid. Voltage control is one of these ancillary services which can ride through and support the voltage under grid faults. Grid codes from the transmission system operators describe the behavior of the energy source, regulating voltage limits and reactive power injection to remain connected and support the grid under fault. On the basis that different kinds of voltage sags require different voltage support strategies, a flexible control scheme for three-phase grid-connected inverters is proposed. In three-phase balanced voltage sags, the inverter should inject reactive power in order to raise the voltage in all phases. In one- or two-phase faults, the main concern of the DG inverter is to equalize voltages by reducing the negative symmetric sequence and clear the phase jump. Due to system limitations, a balance between these two extreme policies is mandatory. Thus, over- and undervoltage can be avoided, and the proposed control scheme prevents disconnection while achieving the desired voltage support service. The main contribution of this work is the introduction of a control algorithm for reference current generation that provides flexible voltage support under grid faults. Two different voltage sags have been experimentally tested to illustrate the behavior of the proposed voltage support control scheme.

Flexible Voltage Support Control for Three-Phase Distributed Generation Inverters Under Grid Fault

Assessing the contribution of microgrids to the reliability of distribution networks

Recently, the new concept of microgrid (muG) has been emerging on distribution networks as a way to ease the integration of micro generation in LV networks and increase reliability. A muG is an association of a low voltage distribution network, small modular generation systems (micro-generators), loads and storage devices having some local coordinated functions. This entity can operate in two different modes: interconnected or emergency. In the first mode, the microgrid is connected with the distribution network, importing or exporting electricity and/or ancillary services. When in emergency mode, the microgrid operates isolated from the distribution network and uses local resources, changing from power control to frequency control and, if necessary, shedding load. A micro grid will only be established if its promoters achieve sufficient advantages that justify the incurred costs, namely the investment, operation and maintenance costs. The main purpose of this paper is to identify all the relevant costs and benefits and build a decision model for the situation, taking into account the regulatory framework, which is essential for the definition of some of the benefits. The paper also shows how to include in the evaluation the risk associated to the uncertainties in data and parameters. An illustrative example is included that shows a possible situation of equilibrium between global costs and benefits

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Economic Analysis of Microgrids Including Reliability Aspects

Regulation of microgeneration and microgrids

Utility power systems are faced to an increasing number of small size producers requiring interconnection particularly to the low voltage (LV) network. Since most distribution systems are not designed to "receive" large scale power injections, these small generation units may impact these networks specifically in terms of quality of the energy delivered, reliability and safety of the whole distribution system from LV to medium voltage (MV) levels. In this paper, a methodology, based on a parametric study, is proposed to investigate distributed generation (DG) impacts when interconnected to distribution networks. The proposed methodology has been validated for a particular case of voltage profile (LV/MV). The test system used for this study is a real urban network containing 11 feeders with 2 transformers of 36 MVA.

Impact assessment of LV distributed generation on MV distribution network

The article discusses the behavior of the distributed generation (DG) in order to increase the EPS (electric power system) robustness. Special attention is paid to the DG influence during emergency states such as the propagation of cascading failures or other major events. In one hand, a high amount of DG can improve the system response to these disturbances but, on other hand, a massive DG insertion could endanger the system operation. The article proposes a methodology to define the robustness and risk of a system operating point through the evaluation of a robustness index. Furthermore, EPS robustness could be enhanced by new emergency strategies such as intentional islanding operation. This would require new ICT components (information and communication technologies) in order to share and analyze the information and then, elaborate decisions to avoid total blackouts.

http://ieeexplore.ieee.org/iel5/9893/32012/01489669.pdf

On the use of distributed generation to increase EPS robustness

https://www.crisp.ecn.nl/deliverables/D1.1.pdf

Functional Specifications of electric Networks with high degrees of distributed generation

The dependence of present societies on the electricity supply does that the electric power system (EPS) is one of the critical points in the normal life and defence of a country. The absence of electricity provokes problems for daily life and so, EPS constitutes a critical infrastructure for societies.

/pdf/limiting-the-dg-insertion-a-deterministic-criterion-5dxjiglfd9.pdf

Limiting the DG insertion: A deterministic criterion

New era of information and communication technologies (ICT) is changing traditional works and solving challenges for human activities. Progress and advances in different fields are being carried out in order to improve the quality o f operations and perform automations.

/pdf/integration-of-new-icts-for-eps-in-the-scope-of-utilities-1y1q9oyxd2.pdf

Christophe Andrieu

Papers

Impact assessment of LV distributed generation on MV distribution network

On the use of distributed generation to increase EPS robustness

Functional Specifications of electric Networks with high degrees of distributed generation

Limiting the DG insertion: A deterministic criterion

Integration of new ICTS for EPS in the scope of utilities services