Multi-objective Optimal Active Power Dispatch With Intermittent Energy Integration And Operation Security

Active power dispatch is one of the most important parts to ensure the security, economy, energy conservation, and high efficiency of power system operation. In recent years, energy crisis and environmental pollution are growing concerns, many blackouts happened around the world. The traditional optimal active power dispatch method which only considers minimizing the total fuel cost can not meet the requirements of power grid dispatching operation in the new situation. Therefore, multi-objective optimal active power dispatch with intermittent energy integration and operation security is analyzed in this dissertation.A general framework for solving power system multi-objective optimization problems is proposed. The solving process involves two stages. At the first stage, a self-adaptive multi-objective differential evolution algorithm is proposed to obtain the Pareto front, the valuable tradeoff information between objectives can be provided. At the second stage, if the Pareto-optimal set is large, the data clustering method is applied first to classify the Pareto optimal solutions into several clusters with similar properties. Then, within each cluster, the compromise solution is selected according to the operation characteristics of power system or through using multiple attribute decision making theory.Integrating the power generated by large-scale wind farm into power grid introduces an extra factor of uncertainties for power system operation. Based on chance-constrained programming, an environmental/economic dispatch model is formulated for the system incorporating wind farm. In this model, Weibull distribution is used to describe the stochastic behavior of wind power, minimizing both the fuel cost and emission of atmospheric pollutants of thermal generators are considered as objective functions, the up spinning reserve and the down spinning reserve constraints are introduced to deal with the influence of wind power on economic dispatch. According to the cumulative distribution function of wind power, the stochastic optimization problem is transformed to a deterministic one. Numerical experiments demonstrate the effectiveness of the proposed dispatching approach.The widespread adoption of plug-in hybrid electric vehicles (PHEVs) will bring new challenges to the secure and economical operation of power systems. A multi-objective dynamic economic dispatch model with large-scale PHEVs penetration is formulated to minimize the fuel cost and to improve the load characteristic. In this model, the PHEVs charging loads and the generator outputs of each time period are selected as decision variables, the driving behavior of PHEVs is taken into account. To demonstrate the effectiveness of the proposed method, the generation scheduling problem is performed on the ten-unit system. At last, the emission-reduction strategies of PHEVs-penetrated power systems are discussed.In view of the uncertainties exist in the operation of power grid and the drawback of traditional deterministic security criterion, the risk theory is introduced into the optimal generation dispatch. The operation risk index is defined based on branch overload and bus voltage violation, the utility function is employed to measure the severity in order to reflect relative severity between different contingencies. Risk-based multi-objective economic dispatch model is formulated, minimizing both the operation risk and fuel cost are considered as objective functions, and the normal state constraints are taken into account. In addition, the post-contingency set comprises both single fault and multiple faults. The proposed generation dispatch approach is tested on IEEE RTS-79test system, the results obtained show that the quantitative index that reflects security level can be provided, and vulnerable parts of power grid can be identified.Since undesirable protective relay operation played a major role in voltage collapse, a voltage stability constrained optimal power flow model considering the operation characteristics of distance protection is formulated. Minimizing the fuel cost, active power loss and maximizing the static voltage stability margin are selected as objective functions. Operation margin of zone3impedance relay constraint is included in the model. Numerical results on IEEE30-bus test system are provided to validate the accuracy of the proposed model, the risk of mal-operation can be reduced in stressed power systems.