Research On Control Method Of DC Microgrid Grid Connected With DC And AC Motor

Energy is vital to the development of society.With the rapid development of the economy,human demand for energy has increased.The continuous consumption of traditional fossil energy and the environmental protection problems caused by it have turned our attention to renewable energy technologies..As a kind of renewable energy,solar energy has the advantages of unlimited resources,pollution-free and sustainability,and has great development potential.Solar photovoltaic power generation technology has gradually become a popular technology.In order to solve the randomness and instability of the photovoltaic power output,people have composed photovoltaic cells and energy storage systems into a photovoltaic energy storage system,and this system is the main part to constitute a light storage DC microgrid.With the continuous development of new energy power generation technology,DC microgrid grid-connected technology has gradually become a hot spot of increasing concern.Now,the DC microgrid is interconnected by the inverter and the AC grid.The inverter has large harmonic content,high failure rate and complicated control.This paper makes full use of the advantages of long motor life,grid-connected power quality not affected by background harmonics and low operating and maintenance costs under high voltage and large capacity,and proposes a scheme for DC microgrid to realize grid-connected by DC-AC motor.The DC microgrid is simulated by the grid-connected system of DC-asynchronous motor and DC-synchronous motor.The maximum power tracking control of photovoltaic system,the constant voltage control of battery energy storage system,and the excitation control of synchronous motor The DC motor speed control has been analyzed and elaborated in detail.The main contents of this paper are as follows:Firstly,it introduces the importance of new energy power generation technology represented by photovoltaic power generation and the development history and development status of DC microgrid technology.Some shortcomings of inverters in the process of interconnecting DC microgrid through inverter and AC grid.Discussed with the shortcomings,the DC micro-grid is connected to the DC-AC motor.Secondly,the structure of the DC-infrared motor grid-connected system of the optical storage DC micro-grid is introduced.The mathematical model of the grid-connected system is built and the grid-connected control strategy is given.In the optical storage DC microgrid,the photovoltaic power supply operates in the MPPT mode,and the battery energy storage system operates in the constant voltage mode to maintain the DC bus voltage constant.The DC motor drives the three-phase asynchronous motor to rotate coaxially.The stator winding of the three-phase asynchronous motor is connected to the AC power grid.When the three-phase asynchronous motor speed is close to the synchronous speed,the grid-connected switch is closed,and the optical storage DC micro-grid is connected to the grid.The mutual conversion between DC power and AC power.Then,the mechanism of the DC-synchronous motor grid-connected system of the optical storage DC microgrid is introduced.The mathematical model of the grid-connected system is built and the control strategy is given.The optical storage DC microgrid through the DC-synchronous motor grid-connected system and the optical storage DC microgrid described above are basically the same through the DC-asynchronous motor grid-connected system structure,except that the asynchronous motor is replaced by a synchronous motor at the grid-connected structure.So,the part focuses on the judgment of the grid-connected condition of the synchronous motor and the transmission of reactive power between the DC microgrid and the AC grid.Other controls such as DC microgrid and DC bus voltage regulation are the same as the previous section.Finally,in the MATLAB/Simulink environment,the DC micro-grid is connected to the DC-asynchronous motor grid-connected system and the DC micro-grid via DC-synchronous motor grid-connected system simulation model,and the system DC bus voltage,DC motor speed,synchronous motor The key parameters waveforms such as speed,asynchronous motor speed,output active power and reactive power are analyzed and analyzed.The simulation results verify the feasibility and effectiveness of the two grid-connected schemes.