Control and management of micro-grids considering renewable energy resources
Date of Issue2014
School of Electrical and Electronic Engineering
In recent years, environmental issues have become increasingly prominent. With growing demands for electricity, wind power, solar power, and other distributed power caught people's attention by their advantages of low investment, and environmental friendliness. Due to the random variations of wind speed, light intensity, temperature and other natural conditions, connecting of a large number of distributed Renewable Generators will large effect on power system operation. For example, it will affect the stable operation and power quality of the grid. Thus, the concept of micro-grid is presented to demonstrate a more rational and effective use of distributed power. The micro-grid is a controlled unit compared with large grid. The micro-grid can achieve grid-connected operation and stand-alone operation by using corresponding control strategies. In this dissertation, the control methods for each unit in the micro-gird were studied. To start, the simulation model of micro-grid was established by MATLAB/SIMULINK. Then, the simulation analysis of micro-grid is listed to verify the feasibility of the control methods. In addition, the purpose of the storage battery in two modes are studied when the load or micro-power changes. The study details are as follows. a) The basic principle and mathematical models of the PV power generation system and battery energy storage system is analyzed in this dissertation. Meanwhile, this dissertation focuses on the circuit structure of the DC/DC converter and control method of the battery energy storage system. The simulation models of these two micro-power are established in MATLAB/SIMULINK. Simulation results show that the PV system output voltage has good quality and can achieve the maximum power point tracking when external environment changes. The battery energy storage system is able to maintain a stable DC voltage. During the operation of the micro-grid, the battery energy storage system can balance the micro-grid power and play an important role in improving power quality and keeping stable operation. b) In order to make micro-grid power flows more flexibly and stably, a bidirectional DC/ AC converter is added between the AC grid and DC grid. Its control method and simulation model are designed in this dissertation. Simulation results show that power flow direction can be regulated reasonably according to the requirement of the energy management system. Meanwhile, this model can improve the energy efficiency. c) Establish the simulation model of the entire micro-grid and analyze the operating state of micro-grid in different situations. Simulation results show that this model can achieve the desired objective but there is room for improvement. Key words: micro-grid technology, bidirectional DC/DC converter, bidirectional DC/AC converter, MPPT control of PV power generation system, power balance.
DRNTU::Engineering::Electrical and electronic engineering