Research On Photovoltaic Generation Planning And Coordinated Optimal Operation Technology Of Power Grid In The Marketization Environment Of Distributed Generation

Distributed photovoltaic generation has the characteristics of clean and environmentally friendly,widely distributed,low cost and nearby utilization,which has been one of the main forms of power generation in the distribution network.Moreover,distributed photovoltaic generation would be an important support for my country to promote energy structure reform and one of the technologies to achieve the "30·60" strategic goal.For the healthy,stable and sustainable development of distributed power generation represented by photovoltaic power generation,the National Development and Reform Commission and the National Energy Administration jointly issued the policy document "the Notice on Carrying out Pilot Programs on Distributed Generation Market Trading" at the end of 2017.Since then,the construction of distributed power generation market has been promoted.For more than three years,the marketoriented transaction policy of distributed power generation has provided diversified market transaction models for distributed photovoltaic power generation,and promoted the rapid development of distributed photovoltaic power generation.However,the distributed power generation market has the characteristics of different interest demands,complex interactions,and diverse transaction modes.On the one hand,the market has profoundly changed the investment behavior and profit model for distributed photovoltaic generation companies,and put forward new requirements for planning technology of distributed photovoltaic generation;On the other hand,the market has affected the power supply structure of grid,changed the relationship between grid and power users,brought new challenges to the economy and safety of grid.Therefore,it is necessary to deeply analyze operation mechanism of distributed generation market,explore reasonable planning methods of distributed photovoltaic generation,and propose coordinated and optimized operation strategies to grid for distributed generation market.These are important theoretical research value and engineering practical significanc to improve distributed photovoltaic generation to access the grid friendly,promote the efficient consumption of distributed photovoltaic generation,realize the high-standard construction of the distributed generation market,and ensure the safe and stable operation of power system.Therefore,this article conducts indepth research on photovoltaic generation planning and power grid coordinated and optimized operation technology in the marketization environment of distributed generation.The main contents are as follows:(1)To solve the problem of evaluating the power grid hosting capacity of distributed photovoltaic generation accessed to the grid,a method for evaluating the power grid hosting capacity of distributed photovoltaic power generation considering harmonic coupling constraints was proposed.This method would lay a constraining foundation for subsequent distributed photovoltaic generation planning and coordinated and optimized operation of grid.Firstly,according to the harmonic voltage and current coupling relationship of distributed photovoltaic generation grid connection point,the frequency coupling matrix was derived,and the harmonic coupling constraint model of distributed photovoltaic generation was established.Secondly,on this basis,a model for evaluating the power grid hosting capacity of distributed photovoltaic generation accessed to the grid was established,which aimed to maximize the installed capacity of distributed photovoltaics.Thirdly,considering the problem of harmonic coupling constraint non-convexity,the convex relaxation conversion method was used for relaxation processing.Finally,the original non-convex model was converted into a positive semi-definite programming model that can be solved by mature solving software,which realized the efficient and fast solution.The results are as follows: in the evaluation model of power grid hosting capacity of distributed PV accessed to network,it is not only necessary to consider harmonic coupling constraints,but also can effectively reduce grid operation risks.Besides,it can provide reasonable evaluation results for grid companies and government departments.(2)For the problem of distributed photovoltaic optimization planning with multi-type transaction mode,a distributed photovoltaic optimization planning method considering the needs of distributed photovoltaic generation collaborative planning was proposed.Firstly,based on the multi-type transaction mechanism introduced by the distributed generation marketoriented transaction policy,the distributed generation market-oriented constraint was established.Secondly,taking into account the actual engineering needs of the coordinated planning of poverty alleviation photovoltaic and ordinary distributed photovoltaic power generation,a distributed photovoltaic bi-level optimization planning model with multi-type transaction mechanism was constructed.The lower level model aimed at maximizing the revenue of distributed photovoltaic generation companies,and distribution PV construction capacity was decided.The upper level model considers the multiple types of operation requirements of power grid,and the distributed PV access mode was decided.Thirdly,for the non-convex constraints with the multiplication terms of the decision variables,the convex relaxation method was taken to perform convex hull substitution.Finally,Karush-Kuhn-Tucker Conditions was used to convert bi-level model with the multi-low-level independent into a single-level model,which could realize the efficient and rapid solution.The results are as follows: The proposed method improves the income of distributed generators and reduces the economic losses of grid.At the same time it also effectively improves the grid operation level and more bearing capacity of PVs.(3)On the basis of the research of distributed photovoltaic generation planning,in view of the optimal operation of grid in the marketization environment of distributed generation,an optimization operation technology of active distribution network for the distributed generation market was proposed.Firstly,according to the characteristics of multiple participants in the distributed generation market,the response behavior models of distributed generation companies,power customers,government agencies and grid companies in the marketization environment of distributed generation were established respectively.Secondly,considering the characteristics of the action sequence of the response behavior of the distributed generation market,a bi-level model with multi-low-level interacting was established,whose upper model was the response behavior model of the distributed power generation company.Moreover,the optimality condition was taken to prove the effectiveness of the model conversion method.Thirdly,the multi-objective evolutionary algorithm was used to further obtain the Pareto optimal solution set of the model.Finally,the response behavior of each entity was analyzed,and the impact of different grid operation strategies on the distributed generation market and other entities was studied.The results are as follows: there is an interactive relationship of competition and cooperation interests between the various entities in the marketization environment of distributed generation.Compared with the optimization goal of the minimum economic operation cost,the grid enterprise aims to maximize the consumption of distributed generation,which can be effective reduce the operating costs of distributed power generation companies and power customers,and promote further increase of distributed generation market trading electricity.(4)With the continuous increase of the scale of distributed photovoltaic generation in the distribution network,the problem of coordinated and optimized operation of the transmission and distribution network for high proportion of distributed photovoltaic access has become prominenter.Therefore,based on the AC optimal power flow,a non-iterative coordination optimization algorithm for transmission and distribution network was proposed.Firstly,a twolevel grid coordination model for transmission and distribution network was established.On this basis,the convexity of the original model was solved by using the second-order cone relaxation method.Secondly,considering the complexity of quadratic inequality constraint derivation of the relaxed model,a polyhedron approximation method was adopted to realize the linear expression of the second-order cone constraints.Thirdly,based on the derivation of optimality condition transformation and linear expression method,the distribution network operation objective function and root node reactive power were respectively expressed as piecewise linear functions about the root node active power.Finally,the original model was transformed into a mixed integer programming model that can be solved by a mature algorithm,which can realize the efficient and rapid solution.The results are as follows: compared with the traditional optimization algorithm,the algorithm proposed in this paper has a better performance in terms of solution efficiency and accuracy.