The invention discloses a series compensation device. The device comprises at least two voltage source current converters, at least two three-phase transformers, and at least one three-phase electric reactor; the voltage source current converters are connected to a multi-loop line in series through the three-phase transformers, and the AC sides of the voltage source current converters are connected with one another through the three-phase electric reactors, thereby realizing the function of equally dividing system flow by the plurality of current converters. The device scheme provided by the application can be independently installed in a power transmission system to be used as a static synchronous series compensator, and can also be used as a component of a unified flow controller, a convertible static compensator, an inter-line flow controller and a unified power quality regulator to be connected to a power transmission system device in series. The device is capable of saving the capacity of the current converters, the application efficiency of the series compensation device is improved, and the cost and the floor area are reduced.