基于置信间隙决策的输电网络不确定性最优传输切换

Uncertain Optimal Transmission Switching in Transmission Networks Based on Confidence Gap Decision

最优传输切换(OTS)是一种应用较为广泛的通过改变网络拓扑结构提高输电网络灵活性的控制机制。然而,输电网络中往往存在不确定风电及负荷需求,这使得常规最优传输切换方案无法达到预期效果。为此,提出将置信间隙决策理论(CGDT)应用于寻求不确定条件下的鲁棒最优传输切换方案。该文分别采用高斯混合模型和正态分布对风电出力及负荷需求预测误差的概率分布函数进行拟合,将不确定性纳入最优传输切换,并以总发电成本最优为目标,建立了基于置信间隙决策理论的输电网络最优传输切换鲁棒优化模型。采用改进的IEEE 24节点系统进行仿真实验,结果表明,使用所提方法求取的最优传输切换方案具有较强的鲁棒性。

Optimal Transmission Switching(OTS)is a control mechanism that improves the transmission network's flexibility by changing the network's topology.OTS is widely used in transmission networks.OTS schemes are usually determined in the day-ahead scheduling stage.However,there are often uncertain wind power and load demands in the transmission network,which makes OTS schemes unable to achieve the desired effect.In order to solve these problems,this paper proposes to apply the Confidence Gap decision theory(CGDT)to find the OTS scheme under the condition of uncertainty and improve its robustness of OTS scheme.Firstly,the Gaussian mixture model and normal distribution are used to fit the probability distribution function of wind power output and load demand prediction errors,and the uncertainty is incorporated into the OTS model of the transmission network.Secondly,CGDT based on the robust drive is introduced to solve the uncertainty,and a robust optimization method based on CGDT is proposed to solve the uncertainty OTS scheme.A mixed integer nonlinear programming model based on CGDT for OTS robust optimization of the transmission network is constructed to minimize the total generation cost as the optimization goal.Thirdly,the chance constraints in the model are transformed into equivalent deterministic constraints according to the uncertainty theory.Finally,this paper uses the improved IEEE 24 node power network to analyze the proposed CGDT-based OTS robust optimization model.In the proposed OTS robust optimization method,the influence of uncertainty parameters on OTS optimization results is maximized by maximizing the confidence level to provide a robust OTS scheme.According to the OTS solution,the transmission network topology is changed.The operation results show that the proportion of the power generation of coal-fired units in the total power output of the power network is reduced from 84.96%to 60.13%.The power output of generating units that meet the load demand is transferred from thermal power units to gas units with high generation efficiency and wind turbines with low generation cost,which improves the power generation structure of the system and reduces the total power generation cost by 3.9%.In wind power and load demand robust range using the Monte Carlo method in extracting 1000 groups of random wind power and load demand scenario,the total cost by probability distribution results show that the approximate probability distribution is normal,the corresponding scenarios of the total cost is less than the set value.Thus the solving scheme of OTS has good adaptability.Under the same operation condition,CGDT,IGDT,and multi-scene methods are used to obtain the corresponding OTS scheme.One thousand scenarios were randomly selected within the fluctuation range of wind power and load demand prediction errors to solve the total power generation cost corresponding to different scenarios.The statistical results show that the CGDT method has a relatively short computation time,its corresponding maximum,mean,and median values are optimal,and the OTS scheme is more robust.In addition,this method can give a robust fluctuation interval of uncertain parameters,which is of great significance to decision makers and has good scalability in practical applications.The following conclusions can be drawn from the example analysis:(1)Using the CGDT method to obtain the OTS scheme can optimize the topology structure of the transmission network,reduce the total generation cost of the system,and improve the stability of the operation of the wind power transmission network with uncertainty.(2)Compared with the other methods to calculate the uncertainty OTS,in this paper,based on the proposed CGDT robust optimization method to calculate the uncertainty of OTS using probability and confidence interval to describe uncertainty,more fully reflect the actual distribution of the uncertain parameters,to avoid caused by uncertain parameters to describe humble OTS on defects of poor feasibility.(3)The robust optimization method based on CGDT is more efficient to obtain OTS under uncertain conditions,and the obtained OTS scheme has good robustness and adaptability to fluctuations of uncertain variables of wind power output and load demand.