Research On Optimal Dispatching And Voltage Control Strategy Of Virtual Power Plant For Active Power Distribution Network

With the rapid development of renewable smart grid,the penetration rate of clean and pollution-free energy resources integrated into distribution network,such as photovoltaic and wind power,is getting higher and higher.As a means of efficient aggregation and coordinated optimal control of distributed generation,virtual power plant has gradually attracted the attention of scholars at home and abroad.However,the stochastic volatility and intermittence of output power of distributed generation in virtual power plant will have great influence on the static voltage stability of active distribution network directly.Conventional voltage stability assessment methods and voltage control strategies cannot cope with the stochastic uncertainties of active distribution network with virtual power plant.At the same time,the stochastic uncertainties of distributed generation in virtual power plants will further increase the uncertainties in power system optimal dispatch operations.The conventional economic optimal scheduling strategy often ignores the effect of the voltage stability on optimal scheduling process.In view of the above problems,based on consulting a large number of domestic and foreign literatures and relevant information,this paper focuses on the probabilistic evaluation of voltage stability and the calculation of voltage stability probabilistic indicators of active distribution network operating at the virtual power plant mode,voltage control strategy and multi-objective economic optimal scheduling model of virtual power plants has been studied systematically and deeply,considering the characteristics of the virtual power plant and the voltage stability.The main contents and achievements of this paper are as follows:(1)The probabilistic evaluation model of static voltage stability of active distribution network operating at the virtual power plant mode is studied.Based on the stochastic volatility of distributed generation,a probabilistic model of output power of the main components in virtual power plant is established,and the probabilistic power flow and voltage distribution characteristics of an active distribution network operating at the virtual power plant mode are calculated based on the forward-backward substitution method and the two-point estimation method.The proposed method is compared with the traditional Monte Carlo method to verify the results.After obtaining the power flow solution and voltage distribution of the power system,the catastrophe theory is applied to establish the corresponding static voltage stability probabilistic index model,and the impact of different load models on the static voltage stability of power system is further analyzed.The results are compared with traditional voltage stability indices.Based on the above research contents,a probabilistic evaluation model for static voltage stability of active distribution network operating at the virtual power plant mode is constructed.(2)The multi-objective economic optimal dispatching model of active power distribution network with voltage stability margin is studied.Based on the multi-scenario analysis method,the uncertain prediction model of output power of distributed generation in scheduling cycle is established;the voltage stability index based on catastrophe theory proposed in this paper is taken as the optimization objective,and the environmental pollution cost is included in the objective function,and the corresponding multi-objective economic optimal dispatching model is established.An improved multi-objective grey wolf optimization algorithm is proposed based on traditional grey wolf optimization algorithm.The objective function in the scheduling model is solved to determine the optimal output value of distributed energy in the scheduling cycle of each sub-virtual power plant,and the corresponding Pareto optimal solution set is obtained.Based on the above research contents,a multi-objective economic optimal dispatching model for active distribution network under the virtual power plant model with voltage stability margin is constructed.(3)Voltage control strategy of virtual power plant based on multi-agent distributed model predictive control is studied.Based on the model predictive control theory,this paper analyzes the advantages of the distributed model predictive control method compared with other control methods,establishes its voltage control optimization model based on the distributed model predictive control theory,and analyzes the objective function and constraints in the quadratic programming problem,and establishes the voltage sensitivity matrix.Based on the theory of multi-agent technology and the distributed model predictive voltage control optimization model,a multi-agent hierarchical distributed voltage coordination control system for active power distribution network operating at virtual power plant mode is established to achieve the goal of voltage stability control.Based on the above research contents,a voltage control strategy of virtual power plant based on multi-agent technology distributed model predictive control is synthetically constructed.