Optimal Allocation of Available Transfer Capability in Operating Horizon

When there are transmission service requests for a specific sink/source pair in a transmission system, the ISO must allocate the available transfer capacity (ATC) of that pair to the requests. Since the requests could have different types, tariffs and time frames, the allocation must be accomplished in a sound and fair manner that incorporates various aspects of the requests. This paper proposes a comprehensive approach to allocation of ATC to transmission service requests. The proposed method considers types, tariffs, and priority of requests in a mixed-integer nonlinear optimization which incorporates the allocation rules. The solution to the optimization problem gives the amount of accepted requests and their priority to the system operator while an emergency could result in the curtailment of certain transmission services. The proposed method is applied to a test system and its performance is evaluated and compared with that of existing methods through a series of studies.

I. Introduction

IN the restructured electric power environment, ISO must calculate available transfer capability (ATC) [1] for the both transmission types of non-recallable and recallable and post non-recallable available transfer capability (NATC) and recallable available transfer capability (RATC) on the Open Access Same-Time Information System (OASIS) [2]. By definition, a transmission service is called recallable, or non-firm, “when the transmission provider has the right to interrupt all or part of the service for any reasons, including economics, which are consistent with the transmission provider's transmission service tariffs or contract provisions” [1]. For non-recallable transmission services, referred to also as firm, the service is to be curtailed only in cases when the system reliability is threatened or emergency conditions exist.