Research On The Home Energy Management System

DC micro-grid is an important method to solve the problems of large-scale distributed energy integrations,improve the power quality and enhance the reliability and security of grid systems.Therefore,it is a significant component of the future intelligent power distribution system.With the development of smart power grids and rooftop solar technologies,the home DC micro-grid that includes the solar power generation and the battery storage has received more and more attention.Home energy management system is the kernel controller of the home DC micro-grid.Under the background of smart grids,it can optimize the energy distribution of the home,and improve the power usage effectiveness and the comfort of users to reach the purpose of energy conservation and consumption reduction by using the detection equipment,control methods and optimum scheduling methods.The research on the home energy management system mainly focuses on the optimization scheduling algorithms and network communications.However,the studies on the operation state and structure of home energy management system are not enough.This thesis considers two different DC micro-grids which under grid-connected operation mode and independent operation mode,and studies the corresponding home energy management system.It can achieve the goals of improving power quality and energy conservation and consumption reduction.The main research contents are as follows.(1)This thesis introduced the basic construction of DC micro-grid,and studied the equivalent circuit model,operating principle and control method of the photovoltaic power generation system and battery energy storage system.Besides,it also introduced three kinds of maximum power point tracking control methods for the photovoltaic power generation system,and proposed an improved incremental conductance method based on the PI control.Compared with the incremental conductance method,the proposed method is simpler.(2)This thesis constructed the home DC micro-grid under grid-connected operation mode and studied its home energy management system.It can be divided into two layers,one is the basic control layer of the converter and the other is the scheduling layer.The basic control layer can receive the control signal from the scheduling layer to control the convers.The scheduling layer based on the demand response strategy schedules the battery to provide electric power during load peaks,and charge during load valley.This method can achieve the goals of load transfer and peak load shifting.In order to response the schedule of HEMS,this thesis also modeling the home AC loads.At last,the effectiveness of the proposed schedule method is verified through the MATLAB software.(3)The home DC micro-grid under independent operation mode is constructed in this thesis.The diesel power generation system is considered as a schedulable power supply system because of the absence of AC grid,and its operation principle and control system are also studied.The DC/AC converter adopts the modular multilevel converter for improving the quality of electric energy.Compared with the two-level converter,the output voltage of MMC has higher quality and lower loss.It also omits the filter device.However,the control strategy of MMC is more complicated.Therefore,the modulation strategy and capacitor voltage balance control strategy are studied.(4)This thesis studied the home energy management under independent operation mode.The goal of HEMS is to enhance the stability and reliability of the whole system.When the energy of battery is insufficient,the HEMS started to adjust the operation mode of the diesel power generation system and the battery energy storage system.Then the load can operate normally and the home DC micro-grid can operate steadily.