Control And Optimization Of AC/DC Hybrid Microgrid Based On Renewable Energy Generation

The report of the 20 th National Congress of the Communist Party of China states that it is necessary to actively and steadily promote carbon peaking and carbon neutrality.To achieve this,it is important to coordinate the reduction of carbon,pollution,and expansion of greenery,and improve the control of total energy consumption and intensity.There should be a focus on controlling the consumption of fossil energy,gradually shifting to the "dual control" system of carbon emissions and intensity,and actively participating in global governance to address climate change.Traditional biofuels must be reduced and replaced with cleaner and pollution-free renewable energy sources to achieve this goal.Consequently,China’s demand for renewable energy,such as solar,wind,and tidal energy,is becoming more urgent.However,clean energy generation has some drawbacks.When new energy is connected to the grid,it may encounter problems of access and absorption.Microgrids can be an effective solution to these problems.Microgrids can operate in two modes: island mode and grid-connected mode.In traditional control mode,the system runs relatively smoothly and maintains stable output,but there are significant system disturbances when the microgrid disconnects from the grid.Additionally,new energy generation is volatile and the load is time-varying,resulting in a high total harmonic distortion(THD)in the system.This can damage system components and distort the output voltage and current waveform,seriously affecting the power quality of the system.To address these problems,a faster control method is needed.This paper proposes an optimized method for microgrid system control called the Model Predictive Control(MPC)algorithm,which predicts the next state of the microgrid and controls the state ahead of time with a faster response rate.This keeps the microgrid in a lower THD state and reduces the impact on the power quality of the main grid.When the microgrid is in island mode,frequency and power allocation errors occur due to droop control characteristics.As the local load increases,the frequency and voltage gradually decrease.If the frequency and voltage drop too much,connecting the microgrid to the main grid will cause grid connection failure due to the mismatch of parameters between the two.After the microgrid is connected to the grid,introducing the MPC algorithm will make the reactive power in the system difficult to maintain stable.Therefore,reactive power feedback control needs to be added to the grid connection control.Adding secondary switching control can restore the voltage and frequency of the microgrid after grid connection to the rated value,and ensure stable reactive power in the system.This paper focuses on the following issues based on the AC/DC hybrid microgrid of wind power generation with energy storage devices:Firstly,this paper presents the microgrid’s structure and builds a model of an AC/DC hybrid microgrid with energy storage devices for wind power generation.The impact of wind speed and other parameters on wind power generation is analyzed,and the model is simulated in MATLAB/Simulink.The simulation demonstrates the microgrid’s stable operation both in island mode and grid-connected mode,as well as its smooth transition when leaving the grid.Besides,the microgrid’s output voltage and current remain within a stable range,meeting the microgrid system’s operating standards.Secondly,there are many harmful harmonics in the microgrid during normal operation and grid disconnection switching,which will damage the components in the system and reduce the output power quality of the microgrid.By introducing the MPC module in the simulation,the THD in the microgrid system is significantly reduced,and the performance and power quality are greatly improved.However,the microgrid can only maintain the stability of the reactive power through the droop control strategy,which makes it impossible for the microgrid to operate normally,so it is necessary to introduce secondary control to ensure the stability of the reactive power.Then,in order to solve the problem that the microgrid can only maintain the stability of the reactive power through the droop control strategy,this paper introduces secondary switching control based on the droop control.By comparing the real-time voltage and frequency in the system with their rated values,the voltage and frequency of the system can be effectively restored,reducing the deviation of the microgrid output and greatly improving the performance of the system.The simulation results show that the combination of secondary switching control and MPC can effectively suppress harmonics,reduce THD in the system,improve the output power quality,and ensure the stability of the reactive power.Finally,based on simulations and comparisons in MATLAB/Simulink,the proposed methods can improve the response speed and maintain the stability of microgrid parameters,while also being highly applicable and accurate.By introducing MPC and secondary switching control,the system can effectively reduce THD in output voltage and current,improve power quality,and adjust frequency and voltage deviation to prepare for the next grid connection.The comprehensive analysis of AC/DC voltage characteristics and microgrid control performance verifies the feasibility and effectiveness of the proposed methods.