Giacomo Viganò

Hosting capacity of distribution networks: Evaluation of the network congestion risk due to distributed generation

The integration of generation units in distribution grids is one of the main research topics in the field of smart grids. Governments are supporting the connection of small/medium size generators directly to the distribution network, but the consequent growing number of energy producers poses several technical issues. For the planning and operation of a distribution network it is then important to estimate the maximum installable generation according to the limits imposed by the power quality standards. In the recent years, several methods for the evaluation of the Hosting Capacity (HC) has been proposed and designed in order to take into account different aspects related to the reliable operation of the network. However, many methods are not taking into account the effects of the grid allocation of distributed generation and, especially, the unknown position of it before the power plants realization. The paper describes a novel solution to compute the HC on the basis of the risk of network congestion. In addition to the classical voltage and current constraints, the proposed approach also integrates the stochastic allocation of distributed generation and separately evaluates their impact on the HC value.

Analysis of active power curtailment strategies for renewable distributed generation

Since the last decade, distribution networks are facing a continuously growing penetration of distributed generation, mostly thanks to the “clean energy” incentives promoted by national governments. In particular, these initiatives have enhanced the presence of renewable-based generators in electricity grids. Taking advantage of their intermittent nature, the curtailment of a small portion of production does not significantly impacts on the total injected energy but it can provide significant benefits for distribution networks. The paper analyzes some of the most common curtailment strategies applied on different kind of renewable resources, demonstrating their high potential in terms of hosting capacity increase.

Optimal Power Flow Analysis in Power Dispatch for Distribution Networks

This paper presents two applications of Optimal Power Flow analysis for active and reactive power redispatch in medium-voltage distribution networks and shows how this tool can be used to efficiently manage the selection and operation of network resources as well as the definition of a market interface with the transmission network. The description of the frameworks is complemented by the analysis of a case study for the optimal selection and operation of available devices.

Measurements placement in active distribution networks for centralized control systems

The centralized control is one of the methods proposed, also by the Italian Regulatory Authority (consultation 255/15), to integrate more renewable energy sources in the electrical networks. Due to the limited number of available measurements in the distribution system, one of the key problems for a centralized control scheme is the correct estimation of the network state. In general, the placement of the measurement devices on the network is performed in order to obtain an averagely accurate state estimation. However, the paper demonstrates how centralized controllers efficacy highly depends on the accurate monitoring of few strategic areas of the network while the impact of the global uncertainty of the state estimation in other grid nodes is marginal.

Analytical approach to identify optimal position and exchange profile of storage systems in distribution networks

The fast growth of distributed generation (DG), in particular from non-programmable renewable resources, poses many challenges on the management of MV networks. Storage systems, operated by the Distributor System Operator (DSO) or by third parties, may mitigate both the local and global effects of the DG. A major challenge is the identification of the optimal position and power exchange according to the desired objective. This paper introduces an innovative approach for the identification of the optimal position and the optimal exchange power profile for storage systems. The proposed approach, oriented to the minimization of the energy losses, has been based on simple analytical expressions, which gives a fast and immediate perception of the efficiency problem and a detailed physical explanation of the differences between the selected positions. This method could be extended from the storage system to all the local resources.

Integration of droop control functions for distributed generation in power flow simulations

The recent increase of distributed generation in distribution networks has determined the necessity of developing new control strategies for the mitigation of power quality issues. One of these functions, considered as one of the most promising solutions for the management of voltage congestions, is represented by the droop control of DG units. The traditional Power Flow formulation often does not allow an easy integration of these functionalities in the simulation environment and alternative techniques are normally used in order to study the effects of local controllers on the network electrical quantities. This paper proposes a simple modification for canonical Power Flow engines that allows the integration of local controllers for distributed generation. The described method guarantees a robust and fast solution of network simulations even for non-linear/piecewise droop control functions.

Methodology for the optimal siting and sizing of storage systems in distribution networks

Storage systems represent an important instrument to increase the renewable electricity generation, in particular in distribution networks. However, there are still many issues due to cost effectiveness of this solution, but also related to the lack of experience on the management of these devices and on their effects on the distribution network. One particular issue concerns the correlation between storage position/size and the specific objective to be achieved in supporting the operation of distribution networks. To investigate this relationship, the paper proposes a method based on Monte Carlo procedure, designed in order to be suitably integrated in network planning and operation tools. In fact, the investigated methodology can be used by DSOs or aggregators to determine the best allocation of storages systems, but it also support the study of the interactions between the energy storage and the distribution networks services.