Research On Voltage Control Technology Of Microgrid

Compared with the traditional infinite grid,microgrid has many advantages such as simple structure,fast establishment and flexible control.Clean energy sources such as solar and wind power generation can be established as islanded grid,which has higher applicability in places with geographical restrictions such as islands and deserts.Additionally,it can also be connected to infinite grid and transmit clean energy,resulting in higher economy.Therefore,the research on microgrid is of great significance.However,the control of microgrid needs to solve the challenges of unstable power supply and sudden load change.Compared with infinite grid,microgrid has a small power level and is more vulnerable to these uncontrollable factors.On the premise of ensuring islanded and grid-connected operation,it is of great significance to study the voltage control of microgrid to deal with the disturbance of power fluctuation and sudden load change.This paper mainly studies the control method to realize stable active and reactive power output and ensure stable output voltage when microgrid fluctuates due to changes in natural conditions such as light intensity and wind speed.Firstly,the composition of microgrid,inverter modulation and other related basic contents are introduced,and then the current typical grid control strategies are analyzed,including PQ control strategy,U/f control strategy and droop control strategy.Secondly,as an important part of microgrid,taking solar power generation as a typical example and MATLAB/Simulink as a simulation environment,the simulation system model of storage battery and photovoltaic power generation system is established,including MPPT control to realize maximum power output and storage battery bidirectional DC/DC control DC bus voltage.The model adopts voltage-current double closed-loop PI control,and controls the output of grid-connected inverter through SVPWM space vector modulation.Through reasonable design,it has the functions of current harmonic maintenance and voltage control.Aiming at the stability problem of microgrid,according to the voltage deviation and frequency deviation in the system,the corresponding controllers are designed corresponding to the P-f and Q-V characteristic curves.Based on separate control,the control models can be smoothly switched according to the operation state.Finally,a microgrid grid-connected voltage regulating system including permanent magnet direct drive wind power generation,photovoltaic power generation and storage battery is established,and its working performance in islanded,grid-connected and switching modes is verified respectively.Wind power and photovoltaic adopt MPPT to control the output maximum power,storage battery to control the voltage stability of DC bus,and islanded-grid-connected control adopts voltage and current double closed-loop control to ensure the stability of output voltage amplitude and frequency.The simulation results show that the designed microgrid voltage control system has good anti-interferenceand stability,and can realize fast and reliable voltage control for disturbances such as power fluctuation,load abrupt change,grid-connected closing.