Research On Probabilistic Load Flow Calculation And Optimization Of AC/DC Distribution Network With Energy Router

As a new power electronic equipment,energy router can realize the flexible distribution of electric energy in the power system.It is vital to analyze the influence of energy router on the system and study the power flow calculation method of AC-DC hybrid distribution network with energy router as the distribution hub.The energy router can realize the efficient access of energy in different forms to the distribution network,while the intermittent energy grid connection brings a lot of uncertainties to the grid,and the traditional deterministic power flow calculation is difficult to evaluate the impact of such uncertainties.Due to the influence of weather and other factors,distributed generator cannot always maintain its rated power output.For distributed generator in the same system,its environment is similar,so there is a correlation between light intensity and wind speed.In order to get a more suitable operation state of actual power grid,it is necessary to study probabilistic load flow calculation of AC/DC power distribution network with energy router and uncertainties.At the same time,in order to play a better role in the overall regulation and operation optimization of the energy router,this paper combined the traditional optimal power flow theory on the basis of probabilistic power flow calculation,and carried out a probabilistic optimal load flow study with uncertainty and correlation.Firstly,this paper summarizes the research status of energy routers,the system structure and characteristics of common energy routers.Then this paper focuses on the structure and control strategy of general standardized three-level energy routers.This paper concludes the current research status of AC and DC power flow calculation methods,and summarizes the characteristics and application scenarios of probabilistic power flow calculation methods.Then it analyzes the current power flow calculation and power flow optimization of AC/DC distribution network with energy routers.Secondly,based on the improved alternating iteration method,the steady state power flow model of the energy router is established in this paper,and the DC port of the energy router is used to droop control strategy,combined with the traditional decoupling method,an AC-DC decoupling iterative power flow calculation method suitable for the power distribution network including the energy router is proposed.The convergence and effectiveness of the proposed method are verified by simulating the improved IEEE14-node system.In order to analyze the influence of the energy router on the system operation and verify the superiority of droop control,the simulation calculation of IEEE14-node system in different scenarios is compared to prove that the energy router can support the node voltage of the DC distribution network and improve the system operation.Then,on the basis of AC/DC decoupling iterative power flow calculation,the probability theory is introduced to the AC/DC distribution network with energy router,and the uncertainty of random variables is simulated.The probabilistic distributions of wind power plant,photovoltaic power plant and load are established.The Monte Carlo simulation method and three-point estimation method are used to calculate the probabilistic power flow with distributed energy.By comparing the simulation calculation of IEEE14-node system,the accuracy of Monte Carlo simulation is proved to be higher.In view of the difficulty in obtaining the joint probability density function between wind speeds in the actual electric field,this paper introduces Nataf transform to deal with the wind speed correlation in AC/DC distribution network.In this paper,a 14-node IEEEsystem with two wind plants is simulated based on Nataf transform.The results show that the correlation between wind speeds has a significant effect on the node voltage and branch power of AC distribution network.Finally,in order to give full play to the regulation and optimization function of the energy router,a probabilistic load flow multi-objective optimization method taking uncertainty into account is proposed based on the calculation of the probabilistic load flow with the correlation between wind speeds.A multi-objective optimal power flow model of AC/DC hybrid system with the energy router is established,and the multi-objective optimization model is constructed by using the multi-objective particle swarm optimization algorithm.Solve the Pareto solution set.Then,the fuzzy membership degree method is used to make decisions on the Pareto solution set,and the compromise solution with the highest satisfaction is found.The simulation analysis of the improved IEEE-69 node system shows that the correlation has obvious influence on the Pareto front obtained by multi-objective optimization,and the optimization effect of the two objectives is negatively correlated.Then,the influence of wind velocity correlation on probabilistic load flow optimization in IEEE-69 node system is further studied.The results show that: The probabilistic load flow optimization based on multi-objective particle swarm optimization can increase the voltage amplitude of the node of the meter and correlation system.In addition,the correlation between wind speeds can affect the network loss of the system.The probabilistic load flow optimization based on multi-objective particle swarm optimization can reduce the network loss of the correlation system.Finally,the compromise solution is compared with the single objective particle swarm optimization scheme,and it is proved that the probabilistic load flow multi-objective optimization method taking uncertainty into account adopted in this paper can improve the comprehensive performance of the system better.