Research On Energy Management Strategy Of Island Operation Micro Grid With HESS

With the extensive use of distributed power such as wind energy and solar energy,as well as the wide application of micro grid composed of distributed power supply,The intermittent and random characteristics of distributed power generation and the fluctuation of micro grid load have more and more influence on the power quality and stability of micro grid.The energy storage device can play a role in restraining the fluctuation of power to a certain extent,but the single energy storage device can not meet the requirements of both power and energy.The hybrid energy storage system composed of super capacitor and battery can realize the power balance and power quality improvement of micro grid,so as to improve the reliability of power supply.This paper does research on photovoltaic micro grid and its energy management strategy with consideration of the complementary features of the battery and the super capacitor.Firstly,the photovoltaic micro grid topology is analyzed,and an equivalent model is established for the photovoltaic power generation unit The characteristics of photovoltaic cells are analyzed,the maximum power point tracking control is used to achieve maximum power and variable power output.The working characteristics and output characteristics of the battery and the super capacitor are analyzed,and the equivalent model is established respectively.Then the converter design of hybrid energy storage component is analyzed.The structure and principles of bilateral DC/DC converter are discussed.The parameter is set for the converter.Above are theoretical preparations for latter research and control on the power distribution of the battery and the super capacitor.Secondly,several connection methods of the two kinds of components for hybrid energy storage are discussed.Their advantages and drawbacks are analyzed to determine the usage of the active connection method.Various power distribution methods for hybrid energy storage are analyzed and compared.The filter method utilizes low-pass filter for the frequency measurement of the fluctuating frequency.This paper presents a power allocation method based on the state of charge instead of on the frequency.Then the paper proposes a bipolar converter structure based on the converter.The battery and the super capacitor utilize different control strategy to monitor the input/output of the system and the voltage on DC bus.Finally,the effectiveness and superiority of the proposed power distribution method is validated by simulation.Finally,an energy management strategy based on power balance and state of energy(SOC)of energy storage components is proposed.The paper utilizes hybrid energy storage system(HESS)composed of the battery and the super capacitor.The mechanism of supply and demand balance of micro grid with hybrid energy storage of islanded operation is analyzed.Based on the state of charge of the battery and super capacitor as well as the power management algorithm,a power management strategy in the islanded operation of the micro grid is proposed.Energy management of the hybrid energy storage units and photovoltaic power is done in order to maintain the energy and Power balance,ensure power quality and load requirements,and optimize the battery charge and discharge,thereby prolonging their service life.Matlab/ Simulink is used to simulate the proposed energy management strategy.The simulation results show that the proposed energy management strategy can control the flow of energy with each converter effectively in various operating conditions.The hybrid energy storage plays a great role in stabilizing power fluctuation,optimizing the process of charge and discharge of the battery,and prolonging the service life.At the same time,the smooth switching of the system in operation is achieved.