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Vlachos A.G.,Regulatory Authority for Energy RAE | Biskas P.N.,Aristotle University of Thessaloniki
2011 16th International Conference on Intelligent System Applications to Power Systems, ISAP 2011 | Year: 2011

As electricity markets emerge, power exchanges and wheeling transactions become a common operating practice in most power systems. This paper considers an interim system which transfers power between two neighboring systems and presents a methodology to estimate the maximum secure wheeling transaction that the interim system is capable to support. By reactive or active power rescheduling actions, the interim system can significantly increase the size of transfer capability, thus offer support services to accommodate the wheeling transaction. The method utilizes an Optimal Power Flow algorithm, in order to calculate the maximum active power that can be transferred, subject to security constraints, as well as the support services provided by the host system. An AC-OPF model is used and a variety of formulations are examined to model the host system actions. The method is intended for application in real time procedures, utilizing the intra-day electricity market processes. An illustrative study case of the methodology is presented for a 26-bus power system supporting wheeling transaction between two neighboring systems. © 2011 IEEE.


Vlachos A.G.,Regulatory Authority for Energy RAE | Biskas P.N.,Aristotle University of Thessaloniki
IEEE Transactions on Power Systems | Year: 2011

The integration of the spot electricity markets in Europe shall lead to multi-area power exchanges that will substitute the local markets. In such scheme, market prices are affected by physical (e.g., network) constraints, yet they should sometimes follow regulatory policy rules, which do not necessarily reflect or depend on physical characteristics. In some cases, complex pricing rules should be implemented, which impose price discrimination for supply and demand entities within the same area. The methodology presented in this paper enables the balancing of supply and demand in a multi-area market considering energy and reserve bids, under complex pricing rules, which mix energy and reserve prices. A demand bid corresponds to the whole cost a demand entity is willing to pay for its participation in the energy market, including the cost for the procurement of the necessary reserves. The approach attains price integration of energy and reserves markets, simultaneous settlement of energy and reserves, and significant decrease of the payments through the uplift accounts. The main principle is the formulation of a mixed complementarity problem for the system equilibrium conditions, in which supply and demand are associated to explicitly or implicitly defined prices, which may be different even in the same zone. © 2006 IEEE.


Vlachos A.G.,Regulatory Authority for Energy RAE | Biskas P.N.,Aristotle University of Thessaloniki
IEEE Transactions on Power Systems | Year: 2011

Market clearing has always been an issue of great interest and research as liberalized electricity markets evolved over time in many countries. As trading in electricity evolves rapidly, multi-area power exchanges appear to substitute the local markets. The tie-lines constitute a significant parameter in multi-area power exchanges, since congestion leads to price differentiation. Prices are affected by physical (e.g., network) constraints, yet they should sometimes follow regulatory policy rules, which do not necessarily reflect or depend on physical characteristics. Until now, all approaches in clearing a multi-area power dispatch (or a multi-area market) are based on a zonal or nodal pricing model, which is applied uniformly to both production and demand within the same zone (or at each node). These approaches are not able to deal with complex pricing rules, which impose price discrimination for supply or demand entities within the same area. This paper presents a mathematical approach for the solution of a multi-area dispatch, in which production and demand of the same area may be cleared in different prices. The main principle is the formulation of a mixed complementarity problem for the system equilibrium conditions, in which supply and demand are associated to explicitly or implicitly defined prices. Illustrative implementations and test results for a simple five-zone system and the 73-bus IEEE RTS-96 are presented. © 2011 IEEE.


Vlachos A.G.,Regulatory Authority for Energy RAE | Biskas P.N.,Aristotle University of Thessaloniki
Electric Power Systems Research | Year: 2014

Since the 90s various policies have been applied for supporting the development of Renewable Energy Sources (RES), including quota or amount-based systems and price-based systems (feed-in tariffs or "FiT"). In both cases, there is a political stress when there is a need to increase the renewable uplift charge rates (out-of-market mechanism), in order to finance the RES projects. This issue is resolved by adopting a novel market framework, in which the demand entities' clearing price entails the whole cost they are willing to pay for their participation in the energy market, including energy prices, reserve prices and the RES uplift price. A Mixed Complementarity Problem is utilized for clearing the market, in which the demand clearing prices are implicitly defined by mixing the explicit prices for energy, reserves and the RES uplift. The model retains the consistency of the supply (energy and reserves) and demand cleared quantities with the respective bids and the clearing prices, and attains a significant decrease of the payments through the relevant uplift accounts. The efficiency of the proposed model is demonstrated on a 24-h day-ahead market simulation using the IEEE RTS-96, defining endogenously the RES uplift under a system-wide FiT and a Green Certificate mechanism. © 2014 Elsevier B.V.


Asimakopoulou G.E.,National Technical University of Athens | Vlachos A.G.,Regulatory Authority for Energy RAE | Hatziargyriou N.D.,National Technical University of Athens
IEEE Transactions on Power Systems | Year: 2015

This paper presents a bilevel model for describing the interdependence of decisions between a retailer/aggregator and the distributed resources owners that the former serves and represents. Decision making is performed in a hierarchical fashion. The retailer performs the energy management of various resources indirectly; price signals are used as incentives for inducing the entities owning the distributed resources in a behavior that optimizes the operation and economic profit of the microgrid that they compose. The two-level interaction is formulated mathematically as a mathematical programming problem with complementarity constraints, while nonlinearities are replaced by equivalent linear expressions. The results of a characteristic case study indicate the efficiency and scalability of the proposed model. © 2014 IEEE.

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