Abstract: The evolution of global energy industry has promoted the transformation of power electronics in the power system. The proportion of synchronous machines in renewable-rich power system is low, and the system shows low inertia and weak damping characteristics, causing a series of operational issues. The grid-forming converter is a voltage source in essence, which can actively construct voltage frequency, provide inertia for the system, consequently, improve system stability. It is an effective means to improve the power ability of new energy and has become a research hotspot in recent years. Starting from the operational issues of renewable-rich power system, this article summarizes the implementation principles and internal connections of grid-forming control strategies such as droop control and virtual synchronous generator control, and establishes a unified mathematical model for grid-forming strategies; by comparing the voltage and frequency construction principles of synchronous generator and grid-forming converters under steady-state conditions, the physical essence of grid-forming converters is revealed. The characteristics of grid-forming converters are explained from the perspectives of voltage and frequency construction, inertia damping support, synchronization mechanism, etc., providing theoretical reference for the stability and control of grid-forming converters.