The deregulation of the electric systems requires the definition of market procedures for the effective management of reactive resources. However, the amount of payments for participating to the voltage regulation service is a task characterized by conflicting objectives, from both the technical and the economic viewpoints. The main subjects related with the reactive power management are: maintaining an adequate security level, defining correct economic signals, providing a simple and transparent structure, ensuring market equity, and avoiding additional charges on the final energy price. After a brief review of the hierarchical voltage regulation structure developed in the Italian power system, a practicable scheme, coherent with the above mentioned requirements, is proposed: the final aim is to assign a correct economic value to the reactive resources
In a zonal market, the transmission system operator (TSO) has to compute the transfer limits among areas in advance (weeks or months) with respect to the day-ahead market session. The computation of such limits is usually made starting from some reference scenarios: this choice is arbitrary and has a strong influence on the results of the market. In this paper, a new probabilistic approach is developed to reduce such arbitrariness. A Monte Carlo method is applied to sample many different reference scenarios (in terms of generation patterns) to be adopted for the total transfer capacity (TTC) computation. Eventually, the probability density function of the TTC values is built. The proposed procedure allows the TSO to evaluate, for each possible choice of the TTC limit among areas, the maximum probability of congestion in a market framework, thus selecting the limit corresponding to the acceptable risk level. The new methodology is applied to the Italian system
The large amounts of power transfers consequent to the liberalization of energy markets has raised, among others, two issues: (i) transmission line congestions and (ii) low-damped inter-area oscillations. The method proposed in this paper simultaneously solves both problems by installing FACTS devices like TCSCs and SVCs in key points of the power system. In particular, TCSCs can eliminate the congestions by modifying the steady-state parameters of the transmission lines while SVCs and also TCSCs can assure a good damping of the inter-area modes through additional modulated signals generated by well designed Power Oscillation Dampers (PODs). As the problem is mathematically quite complex and robustness is highly required, Genetic Algorithm (GA) techniques are employed. To prove the efficiency of the method, simulations were performed on suitable test systems.
First optimization models regarding optimal dispatch of generation resources considering static and dynamic security of the network are reviewed. Given the difficulty to solve non-linear optimization problems with discrete variables, the decoupling of the active and reactive powers issues is proposed. The two resulting problems interact iteratively. A Security Verification (SV) problem is solved to identify the generation deployment in terms of real power constraints: branch flow security constraints, primary/secondary frequency control constraints to correctly identify required regulation bands and minimum inertia are here considered. The proposed linearized models are validated against real grid behavior on representative test networks. The SV solution is given to AC OPF, to optimally deploy reactive power resources.
In this paper, the problem of upgrading an electric urban distribution network is considered. Although network planning has attracted considerable attention in the field of power systems since the early 1970s, the urban distribution network of Milano (Italy) shows significant and challenging peculiarities. Due to historical reasons, there are two separate distribution networks, previously operated by two different companies, which grew up independently and in an uncoordinated way. Therefore, this paper will present a MILP approach for planning a new network configuration, called H-shaped layout, which optimally integrates the two networks already in place. In order to validate the mathematical model, computational results using a part of the whole distribution network is presented in this paper.
The flow-based methodology is a relatively new approach for the allocation of cross-border exchanges between control areas, alternative to the classical so-called NTC based methodology. At a glance, the flow-based methodology aims at determining a multi-dimensional domain where the inter-TSO energy trading is possible, taking into account the security of the transmission grid, by means of a sensitivity approach on the network elements. The flow-based methodology is particularly indicated for highly meshed power systems, where the strong interdependence among several interconnected grids, is a hindrance for the calculation of cross-border bilateral capacities. Indeed, the flow-based methodology better fits the meshed systems, as it guarantees the respecting of security constraints, in the different control area, in a simultaneous way. This paper reports the main outcomes of the analysis run on the Northern Italian interconnection applying a flow-based methodology for the assessment of cross-border power exchanges.
In this paper an optimization problem designed to calculate electric grid specific indicators to be used within model-based methodologies for the definition of alternative electricity market bidding zone configurations is designed. The approach integrates within the framework of a bidding zone review process aligned to the specifications of the Commission Regulation (EU) 2015/1222 (CACM) and Regulation (EU) 2019/943 of the European Parliament and of the Council (CEP). The calculated solution of the optimization provides locational marginal prices and allows to determine, outside the optimization problem, the power transfer distribution factors for critical elements. Both indicators can be used as inputs by specially designed clustering algorithms to identify model-based electricity market bidding zone configurations, as alternative to the current experience-based configurations. The novelty of the optimization problem studied in this paper consists in integrating the N-1 security criteria for transmission network operation in an explicit manner, rather than in a simplified and inaccurate manner, as encountered in the literature. The optimization problem is evaluated on a set of historical and significant operating scenarios of the Italian transmission network, carefully selected by the Italian transmission system operator. The results show the optimization problem capability to produce insightful results for supporting a bidding zone review process and its advantages with respect to simplified methodologies encountered in the literature.
The assessment of RES integration in the transmission network operation is of great concern for TSOs. In the paper, "ad hoc" dynamic models of the European grid with RES and storage systems have been developed and validated through security enhancements analyses on battery storage applied to both real and forecasted scenarios of renewable penetration. In particular, a detailed network of the ENTSO-E system has been adopted for carrying out the dynamic analyses and achieving reliable results. Finally, comparisons have been made in terms of frequency deviations distribution for different ranges of PV generation variability and different levels of installed storage rated power. The study results suggest that the testing-suite is appropriate not only for the validation of the new models but also for the evaluation of control strategies to mitigate the influence of RES intermittent behavior in the transmission network.
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