A method of negative sequence compensation based on YNd transformer and static var generator is proposed from the perspective of compensation with active reactive power. The general mathematical model of negative sequence compensation is constructed; meanwhile

the YNd11 transformer is taken as an example

and the topology of negative sequence compensation is divided into compensation modes I and II based on the mathematical model. The mathematical models of reactive capacity and current of static var generator for cophase and out of phase power supply are constructed

respectively

and a method to determine the scheme of negative sequence compensation is proposed. A double-closed-loop control strategy for compensation modes I and II under the conditions of co-phase power supply and out-of-phase power supply is proposed

which can achieve the purposes of stabilizing voltage and ensuring response speed

and can realize satisfaction of compensation of negative sequence. By taking the data of a traction substation as an example

the determination method of the negative sequence compensation scheme is illustrated

and the results show that the proposed scheme can meet the requirements of the national standard on reducing the capacity of the compensation device. The effectiveness and accuracy of the control strategy of compensation mode I and II for the negative sequence compensation are verified by simulation.