Residential Micro-grid Energy Management Control System

With the gradually depletion of fossil fuels and pollution of the global environment, the exploitation and utilization of solar energy attracts attention all over the world. There have already been some exemplary or research projects in Many countries including china. The application and research show that micro-grid based solar energy, which can merge renewable generating and utility together to form smart grid and smart city in the future, is one of the important mode with broad applicable prospect and actual significance. Taking residential photovoltaic micro-grid system as the research object the dissertation did some research works deeply as to related technology.The main contents and contributions are as follows:1. One model based 4 parameters of PV(photovoltaic) generating was brought forward after analyzing the operation principle and output characteristics of photovoltaic array. Analyzed algorithm of MPPT like as HC(Hill Climbing), PO(Perturbation and Observation) and IC(Incremental Conductance) combined with Boost converter. Especially application of FCA(fuzzy control algorithm) in MPPT was studied. Simulation also was carried out and the results show that FCA speeds up MPPT.A way of electricity quantity prediction of PV generating united in the PV model with 4 parameters and Irradiance prediction model(Hottel) built according to geographic information and meteorological data was propose. The availability was verified by experimental data.2. The charge and discharge characteristics of the lithium iron phosphate ion(LIP) battery group were discussed with experimental data and general battery models were analyzed to ascertain two order RC equivalent circuit as the model of the LIP battery group. The principles and border parameters of the battery group for charging and discharging were set with discoursing the ways of SOC estimation and correction of battery group. The model parameters of the battery group were identified experimentally with the help of the technology of MATLAB curve fitting then to build the model completely. The coordination strategy based frequency decoupling and fuzzy logic between the battery group and the super capacitor group applied in micro-grid was talked over as well as its validity and effectiveness. The mathematics models of bidirectional DC/DC converter operated in Buck mode and Boost mode were established respectively and the control strategies as to different running mode were presented. Simulation and test have been carried out and the results show that the proposed model, control scheme and control strategy are available so that to settle the foundation to control of the micro-grid.3. The important sub-systems of the micro-grid like as the photovoltaic generating sub-system and the energy storage sub-system were analyzed about their function and ways of control then the strategies of the system and energy management were proposed. How to achieve the two main control objects of power balance and stabilize of DC bus voltage was discussed. In control, the system power error is decoupled according to frequency considering the SOC of the battery group and fuzzy logic algorithm to form the power reference of the battery group and the super capacitor group respectively. That means the low frequency error will be balanced by the battery group and the residual will be balanced by the super capacitor group to realize system control objects. As to DC bus voltage control, a segment control is applied in which traditional PI control, load control and drop control is applied respectively according to different segment of DC bus voltage to keep the bus voltage among the designed scope.4. Simulation and experiment micro-grid system were carried out. The results show that the system is good at load tracking and benign to keep the bus voltage not beyond the referenced value under varied irradiance, temperature and load to verify the validity of the proposed strategy. The strategy can make micro-grid operate steadily, make full use of solar energy and prolong the battery group circulating life with excellent dynamic property.5. The system monitoring and control software have been finished. The key of the software is the algorithm of energy management. Besides that, there are several functional modules like as user login management module, manual operation module, auto operation module, data base management module, photovoltaic generating test module, battery group charge & discharge test module, super capacitor charge & discharge test module and etc. The electric cabinet has also been designed and finished in which every component of the system was fixed to build system experimental platform. The system overall debugging and experiment & test were carried through depending the platform. The results show that both functionality and security of the platform were attained that agree with the system’s design objects so that make the foundation for further researching of micro-grid in experiment and theory.