Research On Control System Of Automatic Capacity And Voltage Regulating Distribution Transformer

The loads of rural areas,industrial parks and development zones in the city of our country have such characteristics,seasonal load changing greatly,obvious difference between peak and valley.As a result,the annual average load rate of distribution transformers is low and its loss is great.In addition,voltage fluctuation problem in the distribution network is serious.On-load capacity and voltage regulating distribution transformer have such characteristics,its capacity and voltage can be changed automatically according to the real time load.It can efficiently decrease the lose and improve electric power quality.However,the technology of automatic capacity and voltage regulating distribution transformer,and the control system of capacity and voltage regulating can not meet the requirements for intelligence of on-load capacity and voltage regulating distribution transformer.Therefore,it is important to develop a intelligent control system that contain all kinds of functions,such as capacity and output voltage regulation,date sampling,GPRS communication.And the intelligent control system is applicable in the distribution power line communication network and efficiently decrease the lose and improve electric power quality.In this paper,intelligent controller of capacity and voltage regulating is researched and designed.The intelligent controller of capacity and voltage regulating studied in this paper is discussed from the following aspects.(1)This chapter first describes the development history of on-load capacity and voltage regulating distribution transformer and its important functions of saving energy and improving electric power quality.Then the structure of on-load capacity and voltage regulating distribution transformer is described from three aspects such as capacity and voltage regulating distribution transformer body,intelligent controller and capacity and voltage regulating switch.And analysis the principles of capacity and voltage regulating and reducing energy loss.Two capacity regulation methods are introduced,including series-parallel capacity regulation and D-Y capacity regulation.Finally the principles of monostable permanent magnetic actuator and bistable permanent magnetic actuator are studied,as power of capacity and voltage regulating switch.(2)The economic operation mode of capacity regulating transformers is described.In order to solve the problem of irrationality of selecting the best capacitive set-point in actual application,a method based on fuzzy decision is presented to select the best capacitive set-point of on-load capacity regulating transformer.Different capacitive set-points of on-load capacity regulating transformer are chosen as evaluation target.The loss of on-load capacity regulating transformer and switching times are chosen as evaluated factors.Then the best object is selected by calculating of mathematical optimization value.The method was verified by case analysis.(3)This chapter particularly discusses the hardware design process of the intelligent controller of on-load capacity and voltage regulating.Firstly,the overall design scheme of hardware is introduced,and then all the function modes are designed based on functional requirements of the intelligent controller,including the selection of main chip,the design of power module,switch input and output processing module,communication module and human-machine interaction module.(4)This chapter first discusses the software programming method and flow of the intelligent controller of on-load capacity and voltage regulating.And then the overall design scheme of software is introduced.This paper has designed the software part of intelligent controller based on FreeRTOS platform and with modular design method as follows: the program design of main control based on LPC4078,the design of communication module program and human-machine interaction module program.(5)The experiment and test on hardware and software of the device are carried out by using the standard source,three-phase power and capacity and voltage regulating switch,including wirelessly transferring date to the server by communication module,keyboard scanning and text display by human-machine interaction module,detecting the situation of capacity and voltage regulating switch and switch shifting function by switch input and output processing module.