Allocating the costs of reactive power purchased in an ancillary service market by modified Y-bus matrix method

In an open accessed transmission system, the costs of each ancillary service will be unbundled. This paper proposes a straightforward method of allocating the costs of reactive power purchased by contract or from a bidding market. This method uses basic circuit theory and partitions the Y-bus matrix to decompose the voltage of the load buses with a view to calculating the reactive power sharing. This method is derived from the system equations without such assumptions as the proportional flow or lossless transmission line.