Research And Design Of Intelligent Capacitor With Reactive Power Compensation In Low Voltage Distribution Network

In recent years,with the widespread application of power electronic devices and inductive loads in distribution networks,the problem of insufficient reactive power in grid systems has become increasingly prominent.In order to solve this problem,reactive power compensating devices are generally required.However,the conventional compensating devices composed of hardware electronic circuit have some problems such as low compensation accuracy,slow compensation speed,and unreasonable switching mode.Therefore,the development of intelligent reactive power compensation devices with high intelligence,high speed,and high reliability has very important significance for reactive power compensation of low-voltage distribution networks.In this paper,a low-voltage intelligent capacitor based on TMS320F28335 is designed under the background of reactive power compensation,power factor improvement and power quality improvement in distribution networks.First of all,the working principle of smart capacitors is studied and discussed,including principals of capacitor reactive power compensation,determination of compensation capacity,zero-crossing switching technology,capacitor switching control method and grid parameter calculation method.Then,based on the design criteria and standards of the smart capacitor,the overall design of the smart capacitor is determined under consideration of economy and reliability.In the switching mode,the voltage and reactive eleven-domain map switching control method is selected to avoid the appearance of a capacitor “switching oscillation” phenomenon.In order to meet the real-time requirements of signal monitoring,the grid parameters are calculated using a sliding FFT algorithm.The content of the design mainly includes hardware circuit design and software program design.The hardware design includes signal sampling and conditioning circuits,auxiliary power supply circuits,composite switch circuits,human-machine interface interfaces,temperature detection circuits,CAN bus communication circuits,and DSP peripheral circuits.The software design adopts CCS3.3 development environment to compile the program,and through the modular design idea,the software design is more simple to understand and easier to write and debug.Thesoftware design mainly includes the design of the main program of the system and the design various subroutines,and gives the corresponding flow charts and carries on the detailed explanation to them.Finally,the MATLAB/Simulink simulation verification of reactive power compensation system composed of intelligent capacitors.