Abstarct: Abstract DC microgrids have been proposed as one of the new solutions for providing energy in remote and island areas. These grids are powered by energy sources such as solar panels and batteries and can operate independently of the primary electricity grid. However, DC microgrids have challenges like input voltage and load changes. These changes can cause fluctuations in the DC bus voltage, disrupt the microgrid's performance, and eventually make the system unstable. On the other hand, the design of robust controllers is essential due to noise in the output and disturbance in the input. Among other things that cause the instability of the bus voltage, we can mention the consumer. The constant power load creates virtual negative resistance in the system output and fluctuates the bus voltage. This study considers a DC microgrid consisting of two step-up electronic power converters and two buses with a voltage of 250 V connected to power loads and a constant voltage with an energy consumption of 2 kW. A solar panel with an output voltage of 100 volts input the converters. Classical controllers such as proportional-integral-derivative control can withstand the mentioned problems and guarantee the bus voltage regulation. Considering the mentioned challenges and controlling the bus voltage optimally, a fractional order controller with a cascade structure (two loops) is proposed for the study microgrid. The cascade structure has the advantage of controlling voltage and current simultaneously. Fractional order controllers have advantages such as greater freedom, better adjustability, resistance performance, and more resistance to noise. Optimisation is required in the fractional controller due to 5 designs. For this purpose, the grey wolf optimisation algorithm has been proposed, which adjusts the control controls baxsed on the number of required conditions, such as voltage increase, convergence speed and other cases. The results show that the proposed method performs well against noise, disturbances, credit changes and constant power load fluctuations and optimises the bus voltage.