Research On Energy Management And Operation Control Of DC Distribution Network Based On Virtual Storage

The operation control technology of DC microgrid with distributed energy has developed rapidly in recent years.Intermittent energy sources such as wind energy and solar energy have strong randomicity.They are always an important factor threatening the safe and stable operation of the system.As a special micro power source in microgrid,energy storage unit plays a role of energy storage.Energy storage technology is also the most commonly used way to suppress power fluctuation in recent years.At present,energy storage devices include energy-based energy storage elements based on storage batteries and functional energy storage elements based on supercapacitors.The hybrid energy storage devices composed of storage batteries and supercapacitors can complement the advantages of them,and have the advantages of large capacity,high power and long service life.Active load can achieve economic benefits by changing the load size to match the demand response strategy of power operators.Active load with energy storage capacity can cooperate with energy storage unit to suppress power fluctuation.So it can be regarded as a virtual energy storage device.Firstly,the structure of DC microgrid based on hybrid energy storage is analyzed,and the mathematical models of wind turbine,hybrid energy storage unit,interconnected converter and active load are established.The energy management model of DC distribution network when the economy is maximized is proposed.The genetic algorithm is used to solve the management model,and the power distribution when the system obtains the maximum benefit is obtained.The virtual storage capacity of asynchronous motor is evaluated,and two important parameters of asynchronous motor as virtual capacitor are deduced: virtual capacitance value and virtual charging state.The priority order of three types of energy storage input is analyzed from the angle of economy and response speed.Secondly,a control strategy based on hybrid energy storage is proposed.According to the different charging states of three kinds of energy storage components,the system is operated in different control zones.When virtual energy storage is used,the reference value of angular speed of asynchronous motor is determined from the angle of energy.The speed of asynchronous motor is regulated by frequency conversion control.At least one end of the converter is guaranteed to maintain voltage stability by sagging control under each area control.Finally a simulation model is built in Matlab/Simulink to verify the effectiveness of the proposed power coordination control strategy.