Abstract
Available transfer capability (ATC) is the transfer capability remaining in the physical transmission network for further commercial activity over and above already committed uses which needs to be posted in the electricity market to facilitate competition. ATC evaluation is a complicated task including the determination of total transfer capability (TTC) and existing transfer capability (ETC). In the deregulated electricity market, ETC is decided by the independent system operator’s (ISO’s) economic dispatch (ED). TTC can then be obtained by a continuation power flow (CPF) method or by an optimal power flow (OPF) method, based on the given ED solutions as well as the ETC. In this paper, a bi-level optimization framework for the ATC evaluation is proposed in which ATC results can be obtained simultaneously with the ED and ETC results in the deregulated electricity market. In this bi-level optimization model, ATC evaluation is formulated as the upper level problem and the ISO’s ED is the lower level problem. The bi-level model is first converted to a mathematic program with equilibrium constraints (MPEC) by recasting the lower level problem as its Karush-Kuhn-Tucher (KKT) optimality condition. Then, the MPEC is transformed into a mixed-integer linear programming (MILP) problem, which can be solved with the help of available optimization software. In addition, case studies on PJM 5-bus, IEEE 30-bus, and IEEE 118-bus systems are presented to demonstrate the proposed methodology.
Highlights
In the deregulated electricity market, effectively and efficiently coordinating the security and economic concern in the system operation has become a significant issue for market participants—especially the system and market operators
It is defined as a total transfer capability (TTC) minus: existing transfer capability (ETC), capacity benefit margin (CBM), and transmission reliability margin (TRM)
By solving this bi-level optimization model, available transfer capability (ATC) results are obtained with economic dispatch (ED) results together at a given system condition and the change of the system condition such as load change and N-1 tie-line outages is modeled in the ATC evaluation model and ED simultaneously
Summary
In the deregulated electricity market, effectively and efficiently coordinating the security and economic concern in the system operation has become a significant issue for market participants—especially the system and market operators. The system operators need to do numerous simulations to consider uncertainties within the system conditions, including load variations and N-1 line outages This two-step evaluation may be inefficient shown in Figure 1; an integrated method is proposed to evaluate ATC that considers the change of base case due to the system demand variation and N-1 tie-line outages and obtain ATC result with the ED results simultaneously. ATC evaluation is formulated as an upper-level optimization problem, and the ISO’s ED is a lower-level problem for generation cost minimization By solving this bi-level optimization model, ATC results are obtained with ED results together at a given system condition and the change of the system condition such as load change and N-1 tie-line outages is modeled in the ATC evaluation model and ED simultaneously.
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