Research On Coordinated Control Optimization Model And Method Of Low-voltage Active Distribution Network

In order to achieve China’s major goal of "carbon peak and carbon neutral",renewable energy will be more and more widely connected to the low voltage distribution network(LVDN)in the form of distributed generation.However,the random fluctuations of renewable energy generation and the single-phase access of power supply will increase the difficulty of LVDN regulation,direct and full consumption of the above power output will also bring adverse effects to the operation of power grid.With the development of control technology,the increase of flexible loads,such as electric vehicles,and the maturity of new energy storage technologies,LVDN has more and more schedulable resources,which provides opportunities for the research on coordinated control of low-voltage active distribution network.Based on the LVDN power flow constraint of three-phase four-wire system,this paper studies the coordinated control method of low-voltage active distribution network considering the interaction of "sourcestorage-load" dispatching resources.The main work contents are as follows:Firstly,this paper models the low-voltage active distribution network,puts forward the basic structure and composition of the low-voltage active distribution network,and analyzes the characteristics of "source-storage-load".Based on the three-phase four-wire system node admittance matrix,the three-phase modeling is carried out for each LVDN component,and Newton Raphson three-phase power flow model with injection current as the correction is introduced.The ground state model of low-voltage active distribution network is built and the power flow analysis is carried out to study the variation rules of voltage,network loss and threephase imbalance degree after photovoltaic access,and the possible impacts after photovoltaic access to LVDN are revealed,which provides a basis for the formulation of "source-storageload" coordinated control strategy.Secondly,in view of the phenomenon that single-phase photovoltaic access may exacerbate three-phase imbalance and the applicability of traditional three-phase balance optimization in three-phase four-wire LVDN,this article analyzes the positive effect of photovoltaic inverter reactive power regulation on LVDN.The basic process of photovoltaic phase selection,and the feasibility of the device are studied.Based on this,the three-phase imbalance optimization model of LVDN including photovoltaic and energy storage is established.The three-phase four-wire power flow model is used to model LVDN,the uncertainty of photovoltaic output is described by interval number,the interval constraint level is used to transform the interval constraint,and the complementary constraint is constructed to carry out continuous processing on discrete variables.The results of calculation examples show that the three-phase imbalance degree of LVDN can be effectively reduced through photovoltaic phase selection,photovoltaic inverter reactive power regulation and energy storage active power regulation,and the proposed algorithm has good convergence and improves the solution efficiency.Finally,on the basis of the above-mentioned grid side regulation resources,taking the load side regulation capacity as the key point,the price-based demand side response mechanism is added as a regulation means.The basic framework of cooperation between grid and load is put forward,and the dual objective optimal scheduling model with minimum distribution network operation cost and minimum user energy consumption cost is established.The ε-constraint method and the entropy weight double base point method with subjective weight correction are used to solve the dual objective optimal scheduling model and select the compromise solution.The simulation results show that the regulation flexibility of LVDN is increased after the demand-side response participates in regulation,and the selection of the compromise solution of the dual objective can effectively balance the demand of the distribution network side to improve the power quality and the user’s demand to reduce the energy cost.