Grid forming controlled modular multilevel converter gains attentions in the interconnection of weak AC system and integration of renewable energy sources. Different from the traditional power control from AC side of modular multilevel converter, this article proposed a power control based on the DC side control. The proposed control includes three parts. The first part is the cascaded voltage current loop, tracking the reference of voltage reference and imitating the voltage source characteristic of synchronous machine (SM). The second part is the capacitor voltage synchronization control, realizing the inertia support from the capacitor like rotor of SM. If grid frequency is constant, the capacitor voltage is constant with the synchronization control. The third part is the inserted submodule number to obtain certain DC voltage to form the appropriate DC current and DC power, imitating the governor of SM. Considering the coupling between frequency and voltage, the feedforward control between frequency and voltage for stability enhancement is proposed and the dynamic phasor model is constructed for the parameter selection and stability analysis. Finally, electromagnetic transient simulations are performed using Simulink to verify our proposed strategy.