Study On Operation Control And Energy Coordination Control Of Microgrid In Urban Rail Station

In recent years,the rapid development of urban rail transit has brought great convenience to people's travel.However,due to its large volume of the total energy consumption and higher proportion of urban electricity load,it becomes the city's largest monomer load.In order to realize the sustainable development of energy saving and emission reduction in urban rail transit,a micro-grid composed of new energy and other clean energy distributed power sources,regenerative braking energy feedback unit,supercapacitor energy storage unit is proposed for urban rail stations to provide green power for stations.Therefore,the thesis takes the micro-grid of urban rail station as the research object,mainly carries out the following aspects of research,including the basic structure of micro-grid of urban rail station,the operation control method of micro-grid,the coordinated control strategy of micro-grid energy,and so on.To be specific,the further study is shown as follow:(1)To begin with,regarding the regenerative braking energy feedback syste as a special distributed power supply,a basic structure of station microgrid composed of distributed power supply,braking energy feedback unit and energy storage unit is proposed.The impact and intermittence of braking energy can be solved by using the autonomy and self-balancing characteristics of microgrid.According to the relative position between urban rail station and ground,the station is divided into elevated station and underground station.In view of the different forms of new energy available in elevated station and underground station,photovoltaic power generation and fuel cell are selected as the distributed power supply of microgrid in elevated station and underground station respectively.(2)For the operation control of micro-grid in urban rail station,the braking energy feedback control based on saturated PI regulator is proposed,and the braking energy is quickly feedback according to the catenary voltage;Considering the high amplitude,short time and large impact of regenerative braking energy,the charge or discharge of supercapacitors are controlled by active disturbance rejection control(ADRC),and the impact and intermittence of regenerative braking energy are suppressed by high current and fast non-overshoot charging and discharging;In order to improve the efficiency of photovoltaic power generation and avoid component mismatch,distributed maximum power point tracking(MPPT)control is adopted for photovoltaic power generation;Considering that the fuel of the fuel cell can be stored when the energy storage device is out of operation,the fuel cell still works as a standby power supply,and the fuel cell adopts constant DC bus voltage control;Because of the short distance between stations and the high density of stations in urban rail transit,the grid-connected inverters adopt virtual synchronous generator(VSG)control to realize the automatic power apportioning without tie-line between stations' micro-grid groups,(3)In order to coordinate the VSG control of grid-connected inverters with the former distributed power supply and supercapacitor energy storage,aiming at the elevated station and underground station,energy coordination control strategies are respectively designed to make the supercapacitor energy storage unit provide inertia and primary frequency modulation energy for the inverters,the intermittent and impact regenerative braking energy and the fluctuation of photovoltaic power generation are also suppressed,and the state of charge is controlled in a safe and controllable range.At the same time,photovoltaic power generation outputs maximum power tracking power and fuel balance of fuel cell fuel cell is adjustable.(4)Finally,a simulation model is built on the Matlab/Simulink simulation platform to verify the effectiveness and feasibility of the operation control and energy coordination control of the microgrid in the elevated station and the underground station.