Circuit Theory Based Load Flow Tracing Method Considering Counter Flow Contribution

new method to trace the power flow based on the converged AC power flow solution is proposed in this paper. The method is formulated by using the transmission network structure, the equivalent-current-injection and the load- equivalent-admittances from the engineering viewpoint where all the electrical circuit theories are satisfied. Four steps are used to trace the relationship between each line flow and each generator injection power without any assumptions, and the power distribution of each generator to each load can also be determined. Besides, the line loss also can be allocated to each generator. This tracing algorithm can calculate power contributions effectively, and can be integrated into the existent tariffs of charging for transmission losses and services.

Recent years have seen a worldwide trend towards deregulation and unbundling of services provided by utilities throughout the world, especially in power market. This trend separates the traditional vertical-integrated power system structure into generation, transmission and distribution independently companies. And, the goal is always lowering of the average consumer price and introduction of competition. While competition is introduced in generation and retail, it is widely agreed that transmission network is a natural independent and monopoly. Therefore, the transmission network company should remain neutrality and centrally controlled to make the market is operating fairly. Transparency is one of the most important ingredients in the operation of the transmission system. It is necessary to find accurate and indisputable answers to questions as “which GENCOs are using this transmission line?” or “which GENCOs are supplying this load?” In other words, the network operating company or ISO must find out the capacity usage of individual transactions happening at the same time, and then a fair use-of-transmission charge can be allocated to individual GENCO. This problem relates to how to allocate the total cost of transmission between all electrical users in an equitable and non-discriminatory manner, which also provides a correct, market-based economical signal to every participant at the same time. In order to determinate usage-of-transmission, we need to know the contributions of individual participants to the line flow and loss, and how participants utilize the system by the AC power flow tracing. Several papers have been published on this subject traced the contributions of generators and line flows using a proportionality assumption. In , the authors used the state graph concept to represent the system structure according to line flow directions. With the reactive power being usually much smaller than the active power, the contributions were either neglected or approximated solely on the basis of line active power. On the other hand, neglecting the effect of active power flow when dealing with reactive power is not persuasive either. discussed the reactive flow tracing by using the same concept as active flow tracing method. In, the authors proposed a decomposition of complex power flows in relation to individual transaction, but the flows can’t allocate to each participant independently. The couplings between the active and reactive power have not been well addressed. Methods were also proposed to determine the active and reactive power contribution by tracing the real and imaginary current networks, which is accurate only for the reactive flow.

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