Research On Voltage Evaluation And Regulation Method Of Medium-voltage Distribution Network Considering The Voltage Characteristics Of Transformer Areas

With the change of load structure and power consumption pattern,the problems of high voltage,low voltage,and voltage fluctuation in medium-voltage distribution network are becoming complicated.The current voltage regulation strategies are not only rigid and rough,but also have not realized the potential of grid-side resources,which leads to a deterioration of voltage quality in all transformer areas along a feeder.The planning and renovation measures,such as line rebuild and the installation of new compensation equipment,are not likely to be resolved anytime soon due to the high cost and huge works.In view of this and focusing on the operation level,this paper studies a voltage evaluation and regulation method for medium-voltage distribution network considering the voltage characteristics of transformer areas,which can maximize the voltage quality of medium-voltage distribution network by improving the voltage regulation strategies based on the voltage conditions of transformer areas.Firstly,considering the mechanism of line voltage loss,this paper summarizes the main factors that affect the voltage of feeder nodes,and numerous feeders can be classified into limited categories based on the physical properties of feeders and load characteristics.The potential voltage problems of each category are analyzed,so the corresponding voltage quality improvement measures are selected.This section extends and supplements the conventional voltage control theory of distribution network,and typical feeders are screened out for the regulation in the following chapters.Then,aiming at the ossified voltage regulation scheme of medium-voltage bus which ignoring the actual demands of transformer areas,a voltage regulation method of medium-voltage bus considering the voltage characteristics of all transformer areas along the feeder is designed.A set of evaluation index system of all transformer areas is established based on the overall voltage characteristics,voltage limit and line loss,the voltage quality of the all transformer areas are evaluated by efficiency coefficient method and the sequence relation method..Adjusting the bus voltage according to this evaluating result,the overall voltage quality of transformer areas can be improved effectively without any extra devices.This method not only makes a beneficial inquiry for precision management,but also provides the voltage class objective function for the following chapters.Next,in view of the shortage of reactive power resources in distribution network,which cannot meet the demand of all transformer areas,an evaluation method of medium-voltage bus voltage regulation considering the transformer areas priority is proposed.The definition of the transformer area priority is designed to represent the importance of different transformer areas to power suppliers.The priority evaluation indexes are built,the index weights are determined by an improved entropy value method,and the transformer area priority calculation method is designed.The concept and calculation method of bus voltage regulation benefit is put forward.The regulation of bus voltage based on the benefit can satisfy and guarantee the voltage quality of important transformer areas first,and the overall voltage quality of the transformer areas can be improved to the greatest extent at the same time,so the limited regulation means are being fully used.Finally,an optimal voltage regulation method for medium-voltage distribution network with distributed photovoltaic is proposed.The objective function of two objective functions are processed by weighting the voltage quality estimation of all transformer areas and the line loss rate.The improved particle swarm optimization(PSO)algorithm is adopted to optimize the operation schemes of main transformer gears and capacitor banks in each period of time within the change of photovoltaic output and load in 24 hours.The optimized operation schemes obtained by this method can improve the voltage quality and operating economy greatly,and achieve great regulating effect.