A Coordinated Optimization Method of SNOP and Tie Switch Operation Simultaneously Based on Cost in Active Distribution Network

Soft Open Point (SOP) refers to a power electronic device installed in place of a normally-open point in a distribution network. The application of SOP will greatly promote the economy, flexibility and controllability of the distribution network. However, due to the high investment of SOP and operation cost of switch, the coordinated operation of SOP and switch needs to be considered. In this paper, a coordinated optimization method of SOP and tie switch operation simultaneously based on cost is proposed for the operation of active distribution system. Firstly, this paper builds a coordinated operation optimization model for SOP and switch considering action costs. Then, a conic model conversion is proposed and mixedinteger second-order cone programming is used to solve the model with efficiency and convergence. Finally, case studies on IEEE 33-node test feeder are used to verify the proposed coordinated optimization method. INTRODUCTION The development and application of smart distribution network and renewable resource generation technologies is pushing forward the reform of distribution & utilization pattern and operation management mechanism [1]. As a novel power electronic device, Soft Open Point (SOP), emerges to replace the normally-open point in distribution network. Compared with traditional tie switch, the power flow controlled by SOP is in an accurate and flexible way. It can realize real-time active power flow optimization and reactive power compensation, which effectively responds to the volatility brought by DG and load. However, traditional tie switch cannot be completely replaced by SOP in a short time in terms of the high investment. The operation optimization of distributed network containing both of them needs to be taken into account. Considering the power losses and current surge caused by switching events, the traditional tie switch can’t operate frequently. By contrast, SOP is capable of changing transmitted power and operation state, which offers a feasible solution to overvoltage and overload. In this case, the time series model of coordinated optimization of traditional tie switch and SOP is needed. Foundation item: Support by the Science & Technology Projects of CSG ( KY2014-2-0024 ). Reference [2] studied the basic principle and model of the SOP, while reference [3, 4] carried on the simulation analysis of steady-state and transient characteristics of SOP, respectively, which will provide a foundation for the coordinated optimization for SOP and tie switch. This paper proposes a coordinated optimization method for SOP and tie switch considering action costs. The conic programming is employed to convert the original model into a mixed integer second order conic programming model. The effectiveness of the optimization model and algorithm is verified on the modified IEEE 33-node system. MODELING OF DISTRIBUTION NETWORK COORDINATED OPERATION WITH SOP AND TIE SWITCHES In this section, considering the action costs of tie switch and power losses of SOP, the mathematical model of distribution network coordinated operation with SOP and tie switch is formulated. Objective function This paper takes the minimization of active power losses as the objective function, which is formulated as   SWI,loss NET,loss SOP,loss min min f W W W    (1) The overall active power losses of distribution network are composed of the following three parts. 1) W SWI,loss : equivalent losses of action costs caused by switches