Aiming at the slow speed of electromagnetic transient simulation of high power chain circuit STATCOM（STATic synchronous COMpensator） with a large number of modules

an equivalent modeling method for chain circuit STATCOM with cascaded H-bridge topology is proposed to improve the simulation efficiency. Firstly

the principles of classical electromagnetic transient modeling and fast equivalent modeling are compared and analyzed

and the mathematical model between voltage and current of the cascaded H-bridge converter chain are formulated. Secondly

the simulation process based on MATLAB/Simulink is designed with the mathematical model and control method of the converter chain. Then

the theoretical errors of main electrical quantities such as power module DC voltage

commutation chain current and power are analyzed. Finally

by comparing the simulation accuracy and speed of the exact model and the equivalent model

the results indicate that the simulation error between the proposed equivalent model and the exact model is less than 1.2%

while the simulation time is reduced by 80%. Therefore

the proposed electromagnetic transient fast equivalent modeling and error estimate method of high power chain circuit STATCOM greatly reduce the simulation time and accurately evaluate the model within the allowable range of accuracy

which has promising scientific and engineering application value.