## 5 Conclusions  
In this paper, the frequency fluctuation of the original system was eliminated through MAF. In the second section, under the condition of nominal parameters, we simulated and verified the stable operation state of voltage and power with one inverter DG unit, and two inverter DG units were run in parallel in the intelligent microgrid system. Secondly, on the basis of the nominal model, the problem of structural parameter uncertainty was introduced. Assuming that the new system was stable and under the initial conditions of guaranteed cost theory, the bounded range of the uncertain parameters was obtained through constraints. Finally, when the system was unstable due to parameter uncertainty, the relevant LQR controller was obtained by the Lyapunov function to give the system a certain progressive stable state. Through simulation, the purpose of optimizing the uncertain model, restraining voltage distortion, and balancing output power was achieved and ensured the stability of the power grid. At the same time, this method could analyze the parameter sensitivity of the controller, continuously adjust the filter parameters, find out the reasonable uncertainty range, verify the hypothesis, effectively simplify the model, and realize the low-cost filter.  
To better respond to the needs of the actual project, the follow-up work would consider the impact of load imbalance, faults, communication delay, interference, and other issues on the system. Considering the intermittency of distributed generation, a hardware loop simulation experiment is conducted to simulate the impact of inverter on output power between islanding and grid connected modes. In the hardware in the loop simulation experiment, the impact of the implementation of the switching system on the system performance will also be considered to make the smart microgrid more anti-interference and ensure high-quality and stable output of power.  
Conceptualization, Y.F. and Z.M.; methodology, Z.M.; software, Z.M.; validation, Y.F. and Z.M.; formal analysis, Z.M.; resources, Y.F.; data curation, Z.M.; writing--original draft preparation, Z.M.; writing--review and editing, Y.F.; supervision, Y.F.; project administration, Y.F. All authors have read and agreed to the published version of the manuscript.  
This study was funded in part by the Key Science and Technology Program of Gansu Province, China. (Grant number 20 YF8 NA059), in part by the National Natural Science Foundation of China. (Grant number 62141304).  
Not applicable.  
I want to thank my mentor, [PERSON], who is easygoing, enthusiastic, rigorous, and careful in his scholarship. In terms of writing the thesis, he always strictly requires me to adhere to \"professional standards\". From the selection of topics, the determination of topics and objectives, to the repeated modification and polishing of the thesis, [PERSON] has always seriously and responsibly given me profound and detailed guidance, helped me develop research ideas, carefully pointed out errors, and warmly encouraged me.  
Figure 12: The controller adjusts some parameters and performance to optimize and stabilize the active power and reactive power in a certain bounded range: (**a**) DG1; (**b**) DG2.