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This study presents how to improve the short-term forecast of photovoltaic plant's output power by applying the Long Short-Term Memory, LSTM, neural networks for industrial-scale solar power plants in Vietnam under possible curtailment operation. Since the actual output power does not correspond to the available power, new techniques (Global Horizontal Irradiance - GHI interval division, P/GHI factor addition (P - Power)) have been designed and applied for processing errors and missing data. The prediction model (LSTM network, structure of hidden layers, number of nodes) has been developed by the authors in a previous work. In this new version of the model, the training technique is improved by using validation and experiments to determine the appropriate relevant parameters. The forecast results show that the proposed new method is more efficient than the old method, as the MAPE (Mean Absolute Percentage Error) forecast error is reduced by 6.059% and the RMSE (Root Mean Square Error) is reduced by 6.710%.

In this work, the minimum losses optimal power dispatch problem for islanded microgrids with distributed energy resources (DER) is solved by means of a distributed heuristic approach. Optimal power management is performed almost in real time, with a predefined schedule, i.e. every 5 min, and the solution is applied to generators when the current operating solution violates voltage or current constraints or when the current configuration produces too large power losses. The operating point of both inverter-interfaced generation units as well as rotating production systems can be modified simply using local information. The latter are voltage measurements and power injections or loads data of local and nearby nodes, therefore information processed at each bus derive from communications between adjacent nodes. The distributed algorithm is iterative but also fast and easy to understand, since it is based on the use of power flow equations. It can be employed for small and medium size networks showing tens of nodes and test results prove that convergence happens in few iterations.

The paper presents a study, conceived within the GEYSER FP7 co-funded European research project, on the ancillary services that Green Data Centres (GDCs) can provide, focusing, in particular, on spinning reserve. More in detail, the main contribution of the paper is to show how GDCs can be involved in the secondary frequency regulation process of a smart distribution grid, for contrasting the disturbing effects of unexpected variation of the energy production. With this aim, a real data centre, owned by Engineering S.p.A., is simulated as connected to the Medium Voltage IEEE 14-bus test grid where some RES-based generators are supposed to exist. Simulations are carried out in order to evaluate the impact of power management actions to be executed by the data centre during under-frequency transients, due to an event of renewable energy facilities power production decrease. During this event, the effects of the spinning reserve provided by the data centre are deeply analysed.

The paper presents a method for the study of large interconnected earthing systems in High Voltage networks. The mathematical model proposed for calculating the distribution of the Single-line-to-Earth fault current is useful for a methodical and accurate analysis of complex systems having meshed configuration and more sources, and has practical application for the Transmission System Operator. Two case studies are provided. The first one considers a fault occurring inside and outside a station in a real 220 kV transmission network. In the second example, the proposed methodology is compared with the classical “Double-sided elimination” method.

This paper proposes an efficient solution to the problem of reactive power flow tracing in electrical transmission networks. For such systems, the tracing techniques used for active power flows cannot be used straightforwardly, due to reactive power variations induced by the line reactances, these variations often being comparable to the powers delivered to the loads. In other words, as is well known, in transmission systems the reactive flows are strongly influenced by the inductive and capacitive effects of the network, making the tracing of power flow and allocation of losses more critical. In this paper, after discussing some methodological aspects, an approach based on the use of transmission line models differentiated on the basis of the reactive behaviour of the lines is proposed. These models allow the power contributions due to reactive losses to be evaluated separately and compared to the flows exchanged between generators and loads; moreover, their application does not require the introduction of nodes or additional links, as is the case with other methods proposed in the literature. The proposed tracing technique is then presented; the method is straightforward and does not require the creation or inversion of matrices of participation factors. The paper concludes with two applications, a 4 node system and the IEEE test system with 30 nodes.

Service continuity is one of the major aspects in the definition of the quality of the electrical energy, for this reason the research in the field of faults diagnostic for distribution systems is spreading ever more. Moreover the increasing interest around modern distribution systems automation for management purposes gives faults diagnostics more tools to detect outages precisely and in short times. In this paper, the applicability of an efficient fault location and characterization methodology within a centralized monitoring system is discussed. The methodology, appropriate for any kind of fault, is based on the use of the analytical model of the network lines and uses the fundamental components rms values taken from the transient measures of line currents and voltages at the MV/LV substations. The fault location and identification algorithm, proposed by the authors and suitably restated, has been implemented on a microprocessor-based device that can be installed at each MV/LV substation. The speed and precision of the algorithm have been tested against the errors deriving from the fundamental extraction within the prescribed fault clearing times and against the inherent precision of the electronic device used for computation. The tests have been carried out using Matlab Simulink for simulating the faulted system.

In this paper, a new backward/forward (b/f) methodology for the analysis of distribution systems with constant power loads is presented. In the proposed method, at each iteration, the loads are considered as constant impedances; in the backward sweep all the network variables (bus voltages and branch currents) are evaluated considering a scaling factor which is determined at the end of the backward phase. Indeed the forward sweep is eliminated and the node voltages calculation does not demand the sequentiality needed in the b/f methodology. The developed method, although deriving conceptually from the b/f methodology, presents only the backward phase in which all the network variables are evaluated considering a scaling factor. Moreover the load simulation as impedances is particularly important when the network shows PV nodes for which the voltage displacement and the reactive power are the unknowns. The condition of 90° displacement between the PV node voltage and the current injected by the apparatus for voltage regulation is not usually satisfied in networks solved by methods using constant current load models. The possibility to solve, at each iteration, a network made up of impedances allows to evaluate the reactance that must be inserted into the PV node in order to set the voltage at the prescribed value. In this way the value of this reactance is updated at each iteration and, at the end of the iterative process, whatever it is the displacement of the PV node voltage, the current circulating into the voltage regulating apparatus will be at 90° from it. In the paper, after a description of the PV nodes models reported in the b/f analysis literature, the new method is presented. The way in which the constant power loads are represented by means of a constant impedance model is also illustrated as well as the method for the evaluation of the unknown reactance to be installed at the PV nodes. The results of the executed applications show the efficiency of the model in terms of precision in the calculation of the reactive power required to sustain the voltage at the PV nodes.