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A Methodology for the “Reactive” Ancillary Service and the Proposed Application to the Peruvian System

pubblicazioni - Memoria

A Methodology for the “Reactive” Ancillary Service and the Proposed Application to the Peruvian System

The matter of regulating the ancillary service “reactive power” is intensely discussed and led to different solutions all over the world. In particular, the possibility of adopting a market structure or simply using a remuneration scheme is one of the topics of this discussion.

The presence of a suitable remuneration for the production/withdrawal of reactive power is a basic pre- condition to the voltage stability and consequently the security and reliability of the electrical system. Indeed, the matter of reactive behaviour of the system is of especial importance for the case of Peru, where the main part of the generation, that is hydroelectric, is located in the Andes Mountains, quite far from the load centres that are close to the sea. First of all, the regulatory schemes adopted in ten systems (E&W, Sweden, Norway, Spain, PJM, California, Argentina, Brazil, Chile, Colombia) were studied, in order to compare the solutions used, that cover a wide range of possibilities. Some network studies (load flows, voltage stability analyses as well as Optimal Reactive Power Flow studies) were carried out during the activity. In particular, the ORPF analysis determined, together with the optimal voltage setting of the generating units, the Lagrange Multipliers of the reactive constraints in the optimisation problem, that represents the additional cost for supplying/absorbing reactive power in a specific bus. The evaluation of the L.M. values, together with the analysis of the characteristics of the Peruvian system, led to the proposal of adopting an OPF for voltage control and of remunerating reactive supply from generating sources with the definition of network pricing zones, after discussing a nodal solution. This choice was preferred because the characteristics of reactive power (that is a local product and that can give rise to the exercise of market power from the generating companies), in a small system like the Peruvian one, could create difficulties for the operation of a “reactive market” in Peru. Nevertheless, the proposed scheme furnishes an interesting locational signal: a higher remuneration in one zone points out the lack of local reactive support and is a signal for the system operator and the generating companies. In conclusion, the application of an optimal power flow is considered a suitable and well-established solution for voltage control and the proposed zonal solution is a suitable possibility especially for the case of longitudinal system, characterised by different local needs for reactive support. KEYWORDS Reactive Power – Electric markets – Ancillary services – Regulatory mechanisms – Optimal Power Flow – Locational signals – Voltage collapse – Must run units

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