Abstract: The primary frequency regulation capacity of the power grid is continuously decreasing due to the rapid expansion of new energy installed capacity. The utilization of flywheel energy storage technology is beneficial for improving the frequency stability and reliability of the power grid. In This paper, we propose a coordinated control method for flywheel energy storage array (FESA) in primary frequency regulation of the power grid. Firstly, the droop control coefficient is improved based on the state of charge (SOC) of FESA. The required frequency regulation power of FESA is obtained by introducing the droop additional coefficient and additional output power. An optimization strategy is subsequently proposed for power proportion distribution within fixed time period. The flywheels are grouped based on the SOC of flywheel unit, while the load allocation is carried out on the grouped flywheels according to the power proportion within the fixed time period. The maximum output constraint is taken into account to prevent power from exceeding the limit. Under the premise of meeting the primary frequency regulation power requirements, the power allocation of each flywheel unit is ensured to be relatively balanced. Meanwhile, a self recovery strategy is designed for the flywheel unit SOC. The proposed coordinated control method is ultimately validated through simulation cases and compared with traditional load allocation strategies. The results indicate that the proposed method enables a more reasonable load allocation to various flywheel units, thereby enhancing the energy utilization efficiency of FESA. Additionally, it can better respond to frequency changes in power grids, contributing to ensuring the safe and stable operation of the power grid.