Abstract: Voltage source converter(VSC) is widely used in grid-connected areas such as distributed generation and energy storage units, and the VSC system seriously affects the stable operation of grid-connected system. The development of health state monitoring and early observation and identification of potential faults in grid-connected VSCs is of great significance to ensure the continuous safe, stable and reliable operation of the converter. First, the main circuit structure and common electrical faults of the grid-connected VSC are summarized and analyzed, including DC-link capacitor faults, insulated gate bipolar transistor(IGBT) faults, filter inductor faults, AC-side current and voltage sensor faults, etc. The fault occurrence mechanisms and fault characteristics are also explained. Secondly, with the grid-connected VSC condition monitoring and fault diagnosis methods as the core, the relevant researches of scholars at home and abroad are classified and summarized, and the advantages and shortcomings of different condition monitoring and fault diagnosis methods are compared and summarized. Finally, the future research direction of the grid-connected VSC condition detection and fault diagnosis technology is prospected.