Research program
Renewable generation sustainable development in liberalised electric power systems: technical, economical and management aspects.
University Co-ordinator
Università degli Studi di PADOVA -
INGEGNERIA ELETTRICA - PADOVA(PD)
Research Unit Leader
Roberto CALDON
Description
The ambitious goals to increase the production of electricity from renewable energy sources for the coming decade adopted in Italy require an overall restructuring of the management of the distribution network, as well as of the intervention of the policy makers.Many measures have already been taken in the recent past to develop the renewable energy production, but many others have to be taken in order to fulfil the goals set in the documents of national and international energy policy. Increasing the renewable electricity generation of some 20 TWh in the coming ten years implies a radical change in the operation of the medium voltage network and in the procedures for the connection to the grid.The technical and regulatory development of the role of distributors will be analysed together with the required evolution of the legislation that should lead to such an increase of the role of renewables. The project aims at assessing the technical and economical aspects related to the application of the European Directive 2001/77/CE on the development of renewable energy sources.The legislative decree 29 December 2003 n. 387 has formally adopted the European directive, although many practical measures have been postponed to subsequent standards and deliberations. The work focuses on evaluating the consistency of the promoted initiatives and suggesting possible actions to be taken for the development of renewable energy sources.In particular it is intended to analyse the new role which will be played by the Distributors who, acting as the interface with the installations, may represent an obstacle for the investments if they do not assume a collaborative position.The local and regional agencies too might play an important role in this issue, and a number of actions may be suggested for stimulating local agencies to promote rather than obstacle investments in renewable energy sources.In this framework, the investigation output aims at providing valuable contributions on the following aspects:- Definition of connection criteria for the installations to the MV grid;- Definition of fare rules for the service of connection to the grid of small size installations;- Definition of fare rules for net metering of photovoltaic plants;Means for the withdrawal of energy generated by plants with P < 10 MVAPossible actions to stimulate the collaboration between distributors, producers and local agencies for an harmonic development of renewable energy sources in the territory, able to exploit the new opportunities while respecting the local environment.In most of the cases, renewable energy sources are small-medium size generation plants connected to MV or LV distribution networks which are originally designed and operated as passive systems with power flowing in one direction, from the primary sub-station to the supplied loads. This implies an operational transformation which may have a beneficial or adverse effect on the quality and safety of the supply.While the diffusion of dispersed and diversified energy sources on the system enhances its potentialities (reduction of power transfer on the transmission system, possibility of supplying local loads in case of loss of the mains), it also gives rise to a number of problems and constrains as regards the actual quality level of the supply and affects the planning strategies to be adopted for future system expansions.The research programme of the Unit is aimed at identifying suitable operational criteria for distribution network management in order to make viable at receiving and transmitting this energy. In particular, based on computer simulations and field measurement carried out on distribution networks, attention will focus on:i) the optimal sizing of generation systems based on grid-connected intermittent types of renewable sources, accounting for both technical network constrains and contractual selling agreements (with distributors, customers, GRTN, ¡K);ii) the type of connection to the MV and LV networks and interface problems such as:- re-definition and setting of protection co-ordination,- possible actions for reducing the harmonic distortion caused by inverters, through which most of the new generation technologies (micro-turbines, photovoltaic cells, wind turbines, fuell cells) are interfaced to the network,- desensitising provisions against normal network disturbances (in particular voltage sags) which may have severe consequences on small size generators,- provisions to avoid undesired islanding conditions, where dispersed generators may unconsciously supply a portion of the network which is temporarily disconnected from the rest of the grid.
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