Research On Operation Optimization Of Distributed Photovoltaic Access Power Distribution Systems

Photovoltaic power generation system is green low-carbon energy;it is significant for environmental protection and efficient for economic benefits.At present,with the development of new energy sources such as photovoltaic power generation,it is one of the most effective means to solve the environmental problems such as haze.According to the WWF study,it is shown that the installation of 1 square meter photovoltaic power generation system,which is equivalent to greening 100 square meters.At the same time according to China's different regions of the average daily solar radiation intensity,photovoltaic power generation system output 1 kilowatts can produce 1200 kWh annual energy output,it can effectively reduce the standard amount of coal used about 400 kg,it reduce carbon dioxide emissions by about 1 ton.Therefore,photovoltaic power generation is high-quality green energy,in the future,the high penetration trend will become increasingly apparent in the distribution network,and the work mode of photovoltaic power generation system in the active distribution network should be transformed into conventional energy.However,there are uncertainties factors including the intermittent and seasonal factors,which impact the capacity of the photovoltaic power generation.The PV grid operation technology in the distribution network is important,it is put forward higher requirements.This paper presents the theory,which merges the interval forecast of centralized power plant.output into the interval optimization of decentralized photovoltaic power generation grid,in connection with random fluctuation characteristics of PV power generation,it researches on interval optimization of distributed PV grid-connected system,it realizes the predictive modeling of output power in the photovoltaic power generation system and interval optimization modeling of the photovoltaic grid-connected system.Therefore,this paper mainly completes the two problems that need to be solved urgently in the photovoltaic power generation system:First,the short-term interval prediction of photovoltaic power generation:it realizes the stochastic fluctuation characteristic analysis of photovoltaic power generation using statistical theory;it combines the linear regression analysis with the weighted Markov;it finishes the prediction modeling of Photovoltaic power generation system.It supplies the interval adjustable range for PV generation grid-conneted.Then,the deterministic optimization and interval optimization of the photovoltaic power generation system:it completes the deterministic optimization based on ideal situation of reducing the active loss in the distribution network,which is called "2/3 principle";it proposes the grid theory of active power matching adjustment;in other words,it achieves the nonlinear modeling of interval optimization in the photovoltaic power grid system,due to active power regulation.It is the mainstream trend in the distribution network planning;it injects new energy power generation system into traditional distribution network.In the future,it develops the broader space for new energy in the active distribution system.It is necessary to operate photovoltaic power generation grid-connected system in view of active power adjustment.It combines the predictable adjustability of the Photovoltaic power with the constraint grid-connected power regulation.The paper raises the short-term interval prediction modeling based on stochastic fluctuation characteristics of photovoltaic power generation system,and analyzes the non-linear modeling of interval optimization in photovoltaic power generation system.The main research contents and achievements of the paper are as follows:(1)Stochastic fluctuation characteristics analysis of PV power output:Due to the basic statistical theory,it analyzes the stochastic fluctuation characteristics of the photovoltaic power plant output power by the theory of the descriptive statistical analysis;it describes the random distribution trend of the photovoltaic power plant output power including the distribution curve and normal distribution test of the random characteristic;it finishes the single factor analysis of variance against the external factors(Such as ambient temperature,irradiation intensity,wind direction,etc.)That influent the characteristic of the PV power output power;it clears the significance analysis of the random fluctuation in terms of PV power output power from the influencing factors;it uses the influence factors as the independent variables by filtering,the output of the photovoltaic power plant as the dependent variable,and it sets up the multiple linear regression model;it achieves the linear regression model of the output of photovoltaic power plants and many affecting factors;it completes the linear prediction of photovoltaic power plant output,and appears the trend of random fluctuation characteristics in regard to PV power plants output power.(2)Realize the short-term interval prediction of the output power of PV power plant by using the method of Least Squares Method and Weighted Markov Chain:it uses the linear fitting curve of least squares method to replace the traditional classification method of K-means Order clustering;it achieves linear fitting relation of the photovoltaic power plant output power and solar irradiance;it completes the state partition of the photovoltaic power plant output power daily,in the light of using the parallel fitting curve as a symmetric center;it makes use of PV plants output power in different delay periods to describe the autocorrelation coefficient and the weight analysis,and sets up the state transition probability matrix of different steps(delay time),it founds the prediction model of the weighted Markov chain,thus defines the state of the prediction interval,on the basis of the principle "probability of the largest" which the autocorrelation coefficient of different steps are weighted sums.Accordingly,it determines the short-term forecast interval range of the photovoltaic power plant output power.(3)The deterministic optimization of the grid connection of the photovoltaic power generation system based on the active power regulation:It ensures the location of the initial configuration node in the photovoltaic grid-connected system,and it refers to the ideal loss reduction the "2/3 principle" of the distribution network;it takes active power loss as optimization goal,and completes the optimal configuration scheme of the location and capacity in the photovoltaic grid-connected system,finally applies the theoretical foundation for the active grid when the new energy pour into the traditional distribution network;it obtains the static analysis data of the photovoltaic grid-connected system in the steady-state operation,it bases on the load flow calculation of Newton-Raphson method;it acquires the sensitivity matrix of the grid nodes voltage-power in the photovoltaic grid-connected system from the Jacobian matrix,and puts forward the constraint condition of the steady-state operation that the whole network nodes need to demand the limit of grid conditions;it realizes the deterministic optimization the photovoltaic power generation system in view of the multi-node PV access into grid,it adopts the active power matching adjustment of the PV injection node for the photovoltaic power generation system.(4)Utilize the interval optimization(interval optimization,IO)method to realize the distributed system power operation that distributed photovoltaic access to mains:it uses the power source capacity of the photovoltaic power grid node as the objective function,and the distribution network branch power characteristics as the constraint conditions,at last it creates a nonlinear model of the interval optimization in regard to the photovoltaic power generation system.It brings out the optimization configuration scheme of the photovoltaic power grid;it takes into account the interval uncertainty of the new energy output of the power system and the interval constraints of the grid node voltage.It is the optimal solution to satisfy the robustness.It is verified by the simulation of IEEE 33 node power distribution system,the terminal node voltage is promoted by 3.3%?11.8%;the system active loss is reduced by 63.8%?66.8%,and the head end power optimization target is[30.446,354.59],it achieves the maximum peak load of 354.59KW.The method has high precision solution and fast Convergence characteristics.(5)Design the visual simulation platform of photovoltaic power generation grid-connected system:It can completes the regulation and display of the distributed multi-node distributed PV access power distribution system:?it demonstrates the topological structure of the power systems and the power flow distribution of the steady-state system through real-time online display,as long as it accepts the known parameter information by operator input information of the power systems,there are the network node voltage and feeder branch power and active power loss in the power flow distribution;?it implements dynamic search for reasonable location and capacity of the photovoltaic power generation system grid-connected the mains by the initial operating state of the system,It carries out dynamic addressing of bifurcation feeder,and runs dynamic demonstration of the situation when the photovoltaic power generation system is connected grid with one node;?It presents the changeable trends of node voltage and feeder branch power in the system operation interface,in the light of the different situation of multi-node photovoltaic power generation system into power system;It adjusts the capacity of the active power which the photovoltaic power generation system into power system,according to the interval constraints of the node voltage and the smallest of the power grid active power loss.