Study On Optimal Power Flow Problem For Micro-grid Based On The Sequence Component

With the distributed power generation technology matures, more and more distributed generation(DG) in the form of grid connected micro grid. Optimal power flow of micro-grid is the effective tool for planning and operation of micro-grid electricity system to realize micro-grid safe, economy, stabile operation of the comprehensive optimization.It is widely used in the aspects of micro-grid security economic dispatch, market economic operation, voltage stability, electricity market, and so on. The optimal power flow of micro-grid is the same as that of conventional power system, is also a multi-variable, high dimension, multi-constrained, non-convex, non-linear programming problem. However, due to the complexity and diversity of distributed generations,micro-grid and asymmetry operating characteristics of micro-grid, the study of micro-grid optimal power flow will bring new opportunities and challenges, and it would propose more new requirements to the traditional optimal power flow algorithms. This paper taken the micro-grid optimal power flow as the research object, and proposed study on optimal power flow of micro-grid based on sequence components.In this paper, firstly, the order component model of each power element in micro-grid was established, and the DG was classified according to the different forms of grid connected. Considering the operation characteristics of the micro-grid, the DG sequence component model by full power converter and power grid were established; and an equivalent sequence component model of asymmetric lines was established based on the sequence current compensation; then considering the phase shift of the transformer connection mode, the sequence component model of the three phase transformer was established. According to the characteristics of various types of loads, and considering the asymmetry, the preface component models were established.To attain higher efficient calculation requirements of micro-grid optimal power flow, a new method based on sequence component using semi-definite programming to solve optimal power flow(OPF) problems was presented. The proposed method is based on sequence component modeling a three decoupling sequence optimal power flow of micro-grid, which is considering the micro-grid may contain a high proportion of distributed power and asymmetric load. In the sequence network model, by means of leading in auxiliary variables the non-convex estimation problem is equivalently turned into a semi-definite programming problem, which is a convex problem, and then solved byprimal-dual interior point method. Furthermore, the sequence components method and the SDP sparsity technique can greatly improve the efficiency of storage and computing. The testing of the proposed method is performed by unbalance 6-bus systems, IEEE 13-bus system, IEEE 37-bus system, and IEEE 123-bus system, and simulation results of these tests systems show that the proposed method is available.