Analysis And Controller Design Of Subsynchronous Oscilliation In HVDC Transmission System

With the implementation of China’s "west to East" project, in order to realize the long-distance and large capacity transmission, HVDC transmission technology and series compensation technology has been widely used in China. AC transmission system with series capacitor compensation and HVDC transmission system may cause torsional vibration generator(subsynchronous oscillations, SSO). Therefore, it is very important significance to research subsynchronous oscillation problem caused by HVDC and how to effectively control.This paper first introduces the research background and research method about the subsynchronous oscillation, and elaborates the generating mechanism of the subsynchronous oscillation caused by series compensation and HVDC transmission system, analysis of Electrical disturbance transfer characteristics. Then analysis the generator shafting based on the IEEE SSR first model. And then as the basis of the CIGRE high voltage direct current transmission model, establish the subsynchronous oscillation model and small signal mathematic linear model, analysis of the value in the characteristic modes of1-5and the modal damping ratio in generator. And using the time domain simulation method and complex torque method to analysis the electrical damping in the MATLAB/SIMULINK, and obtained that the parameters of the controller, the triggering angle will have some effect on the damping. Last, by changing the Equivalent impedance of AC side to analysis and verify influences of AC and DC coupling strength on subsynchronous oscillation in the PSCAD/EMTDC, and analysis of the generator speed by FFT, verify the different modal frequency of the shafting oscillation. In addition, establish the subsynchronous oscillation model in AC/DC parallel transmission system, analysis and compare the electrical damping characteristic of different series compensation degree, the parameters of the controller and the trigger angle. Then analysis subsynchronous oscillation by means of time domain simulation method, last compare similarities and differences of the two kinds of subsynchronous oscillation.For subsynchronous oscillation phenomenon, based on the generator angular velocity and frequency deviation as the feedback signal, using single modal and multi-modal control method designed three additional damping controllers. Finally, compare and verify the inhibitory effect of the designed controller through analysising the electrical damping and time domain simulation of small disturbance. At the same time, based on the same principle to design a controller for AC/DC power system subsynchronous oscillation, and verify its effectiveness.