Research On Emergency Power Support Control Strategy For HVDC

In recent years,research and application of HVDC(High Voltage Direct Current Transmission)with high voltage and large capacity technology has been developed considerably.HVDC transmission system has better controllability,adjusting the transmission power with its fast regulation and control performance is an effective way to improve the stability of AC/DC hybrid system.In order to realize the rapid power adjustment of HVDC technology to improve the stability of AC/DC hybrid system,the analyze of the factors to influence the power operation of MMC-HVDC(High Voltage Direct Current Transmission based on Modularized Multilevel Converter)system,the improvement of the adjusting rate of the fast power control and the design of emergency power support control strategy in AC/DC hybrid power system.In this paper,the topological structure and mathematical model of MMC-HVDC is established,then study its operational principle and operation characteristics and got the affecting factors of converter power operation interval,optimize control to improve the operating characteristic of converter,and then expand the power range of operation.Design the fast power control method of HVDC converter,abc three-phase components are converted to the dq rotating coordinate system through the transform,use PID control to control the dq component of inner loop current,then improve PID controller parameters to improve the dynamic characteristic of converter inner loop current control,so as to enable the converter to track the reference power fast and accurately,establish foundation for emergency power support of HVDC.Analyze the stability under the transient fault of AC/DC hybrid system with HVDC emergency power support through static SEEAC method.The results show that the emergency power support can improve the stability of the system,on this basis,emergency power regulation control strategy of AC/DC parallel operation system is designed to improve the system transient stability after fault AC transmission line.Based on the analysis of the structure of MMC-HVDC system and mathematical model,method is put forward to expand the operating range of the power,control method based on PID control is designed to improve the converter's performance of fast power control,propose the emergency power support control strategy of AC/DC hybrid system.AC/DC transmission simulation system is established based on PACAD and RT-lab simulation platform to test the capability of controller and performance of the system under transient fault,the simulation results show that the power interval optimization controller and the fast power controller designed have excellent performance,and the emergency power support strategy can improve the transient stability of the system.