Research On Methodologies And Expansion Application For Transmission Loss Allocation

As one of the basic problems under the operation of electricity market, the application of transmission loss allocation has expanded even further, from the initial application in recovering the costs of losses, to loss modification to generation biddings before the auction, and the issue of purchasing transmission loss compensation ancillary service and so on. All these issues not only relate to the economic interests of market participants close, but also have important impact on the system and market operations. So they should be solved effectively. However, the loss allocation problem is not an easy one due to its nonlinearity. There are different opinions existing both in theoretical researches and practical applications. Now this issue has become a difficult problem desiderated to be solved during the construction of electricity market in our country.As the theory is the foundation for practice, this paper firstly researches further on the methodologies for loss allocation, including the following three elements.The circuit-based methods have received great attentions due to their specific foundation on circuit theories. This paper presents a new circuit-based method for branch loss allocation using the concept of orthogonal projection. Also the reasonableness of the two equivalence modes of power injections is discussed. Analysis and numerical results show that, the method is explicit and intuitionistic, and the obtained branch power flow decomposition and branch loss allocation results are stable and valid. Conclusion on which equivalence mode is more reasonable is also given.The power flow tracing method is found in practical application that the method may produce unreasonable loss allocation due to not directly reflecting the electrical distances between buses. Therefore this paper presents a new power flow tracing method considering the electrical distances. It takes the equivalent impedance of the pair of terminals to evaluate the electrical distance between buses, then partitions the network into several sub-networks, finally calculates the loss allocation from two levels, the exterior and interior of sub-networks. Numerical results show that, the method keeps the property of nonnegative loss allocation of power flow tracing method, and reflects the electrical distances among buses better.This paper analyses the cause of negative loss allocation from the view of power flow, and then proposes a modification method to avoid it. The method exploits the concept of load center and generator center to modify loss sensitivities of generator and load buses separately. The calculation is simplified through the derivation of the given relation that loss sensitivities referred to different slack buses satisfy. Numerical examples illustrate that the method could not only avoid allocating negative or zero results to nonzero power injections, which will be more acceptable, but also it keeps the economical signals for operation efficiency.Then the proposed three methods are compared from following aspects: the maximum of social benefit, the equilibrium of individual interests, stableness, consistency, and simplicity. The comparisons would help to make the characteristics and capabilities of the proposed methods clear. This would provide reference to theoretical research and practical applications.Based on the research on methodologies for loss allocation, this paper also works on two expansion applications of loss allocation, loss modification for generation biddings and modes of purchasing transmission loss compensation ancillary service. For the problem of loss modification for generation biddings in the Northeast regional electricity market, the two methods for selected, the power flow tracing method and the power flow perturbation method, are compared in four aspects, namely loss modification factors, modification extent to generation biddings, optimizing direction of network loss and balance between income and expenditure for network loss expense. The work shows that, the power flow tracing method is suitable to loss modification for generation biddings of long-term whole electricity quantity in Northeast regional electricity market. For the modes of purchasing transmission loss compensation ancillary service, this paper discusses the three existing modes from the view of management, to make their characteristics and distinctions represented during implementation clear. Then preliminary discussion on the suitable mode for electricity markets of our country is given with reference to the experiences of typical electricity markets in abroad.To sum up, for the problem of loss allocation, there still is development space in theoretical research, and there might be new issues coming out during the development of electricity market. So this paper probes into the problem of loss allocation further and more deeply from two aspects, methodologies research and expansion application. In theoretical research, three different methods are proposed based on the summaries and reviews of the existing research results, and their characteristics and capabilities are evaluated from many aspects. In expansion application, the paper pinpoints that the power flow tracing method is suitable to loss modification for generation biddings in initial Northeast regional electricity market. It also makes characteristics of the existing purchasing transmission loss modes clear from the view of management. The above work is expected to provide theoretical reference to the construction and operation of electricity market in our country.