Penetration Of Dispersed Generation Research Articles

Planning of flexible power sources in power distribution systems with high penetration of dispersed generation

With the wide application of dispersed generations (DG), power distribution systems are transferring from passive to active. Acting as important composition of DG, wind turbine (WT) and photovoltaic (PV) are developing quickly in these years for their clean and renewable. In high penetration scenarios, as the power outputs of WT and PV are uncontrollable, the volatility and intermittency of WT and PV power make the net load curve a ‘duck curve’, and the flexibility and ramping needs become significant, which may threaten the security and reliability of power system operation. Thus, to allocate enough flexible power sources are essential. Based on the definition of power system flexibility, the characteristics of power system flexibility and flexible sources are first analysed. Then, a quantitative evaluation model of power system flexibility, which appears in a probability form, is proposed and solved using Monte Carlo simulation method. After that, on the basis of flexibility improvement, the siting and sizing problems of flexible sources are discussed. Finally, case studies are made on the IEEE 33-bus test system to verify the validity of the model and method proposed, and several conclusions are obtained.

Enel Distribuzione projects for renewable energy sources integration in distribution grid

The integration of the dispersed generation, based on constantly increasing renewable energy sources, is one of the biggest challenges of the modern distribution system operator.Enel Distribuzione, that operate the 85% of the Italian distribution grid with 33 million customers, connected more than 25GW of dispersed generations, mainly based on renewable energy sources, in Italy up to 2013; these numbers are most impressive taking into account that the consumption peak for medium voltage and low voltage distribution networks was 40GW during the 2007 (the period before the economical crisis and with very small dispersed generation connected).The original design of Enel Distribuzione networks is radial and does not consider interconnection of any generation with significant size. In a radial feeder, the power flows unidirectionally from a single source to the loads. The penetration of dispersed generation into the feeder can cause a flow reversal. This flow reversal violates the concept of “radial design” and has a significant impact on the operation of the feeder and, in particular, on the protection systems and on the voltage regulation.In this scenery, Enel Distribuzione implemented and is implementing several large area demonstrations to test innovative smart grid technologies, in particular for dispersed generation integration. In this paper, two of these projects are presented focusing on the innovative solutions for voltage regulation and dispersed generation dispatching.

The Italian Regulatory Framework for Developing Smart Distribution Grids

Abstract The integration of Dispersed Generation (DG) is by far the most important and challenging issue that modern power systems are facing nowadays, and is the only way of exploiting Renewable Energy Sources (RES) for electric production. This revolution is running particularly fast in Europe, where significant incentive schemes have been promoted by many Member States in order to match the targets decided by the European institutions. As a consequence of the important share of RES already connected (especially to low voltage and medium voltage networks), new technical challenges have to be faced both at a distribution network level and at a transmission system level. Some of these challenges are covered by Smart grids that represent a new framework for improved management of distribution and transmission networks with attention to interoperability, security, resilience problems, and quality of service (QoS). It is recognized that an intelligent use of Information and Communication Technology (ICT), as enabling technology, is the only approach able to solve new problems arising on energy networks due to larger DG penetration, without hindering system security and QoS.The paper focuses on the Italian case and in particular on the Italian regulatory framework for developing Smart Grids, and describes the technical foundations of the regulatory innovations introduced by the Italian energy regulatory authority (Autorità per l’energia elettrica e il gas - AEEG). After a selection process based on cost/benefit assessment, some demonstration projects for Smart Grid proposed by Distribution System Operators have been awarded with special capital cost remuneration (extra WACC of 2% for 12 years, on top of the ordinary WACC equal to 7% for distribution investments). The smart grid demonstration projects founded by AEEG introduce and test a new advanced management of DG in order to avoid the problems coming from reverse power flowing and maintain the necessary level of security, availability and quality of service.

New Approaches for Very Short-term Steady-State Analysis of An Electrical Distribution System with Wind Farms

Distribution networks are undergoing radical changes due to the high level of penetration of dispersed generation. Dispersed generation systems require particular attention due to their incorporation of uncertain energy sources, such as wind farms, and due to the impacts that such sources have on the planning and operation of distribution networks. In particular, the foreseeable, extensive use of wind turbine generator units in the future requires that distribution system engineers properly account for their impacts on the system. Many new technical considerations must be addressed, including protection coordination, steady-state analysis, and power quality issues. This paper deals with the very short-term, steady-state analysis of a distribution system with wind farms, for which the time horizon of interest ranges from one hour to a few hours ahead. Several wind-forecasting methods are presented in order to obtain reliable input data for the steady-state analysis. Both deterministic and probabilistic methods were considered and used in performing deterministic and probabilistic load-flow analyses. Numerical applications on a 17-bus, medium-voltage, electrical distribution system with various wind farms connected at different busbars are presented and discussed.

Analysis of distribution network protection issues in presence of dispersed generation

The presence of a significant dispersed generation (DG) capacity in existing distribution systems would cause in most cases some conflicts with correct network operation. This is mainly due to conceiving a distribution system as a “passive” radial network, with neither generators operating in parallel nor power flow control. Issues such as voltage regulation, system protection, and, generally speaking, power quality are still being investigated by researchers in order to maintain adequate service to customers in presence of DG. The present paper illustrates an analysis of the relevant malfunctioning problems that may take place in distribution networks protection schemes in presence of DG. In particular, operation conflicts between distribution protection and DG are discussed with reference to unforeseen increase in short circuit currents, lack of coordination in protection schemes, ineffectiveness of line reclosing after a fault using automatic reclosing devices, undesired islanding and untimely tripping of DG interface protections. The present study aims at highlighting the need for changes, with respect to current distribution protection philosophies, which should be made by planners and distribution operators in order to increase DG penetration in distribution networks and to provide improved service continuity to customers. The presented analysis is preliminary to the development of a research project, carried out in collaboration with ENEL Distribuzione S.p.A. (Italy), which analyses possible innovative solutions for operation conflicts between distribution network protections and DG.