Research And Suppression Of Subsynchronous Oscillation In Power System

With the rapid economic development, the demand for electricity further more, economic measure to solve this problem is to improve the transmission capacity of the original high-voltage transmission lines. Series compensation technology can improve the stability of the system and substantial increase transmission capacity of the line. However, disturbance in power systems with series capacitors compensated in transmission lines would raise the danger of subsynchronous resonance (SSR). Full controlled devices and high-speed deflector static synchronous compensator (STATCOM) as a new device can effectively inhibit the sub-synchronous oscillation.Firstly, the paper studies the sub-synchronous oscillation theory, analysis Tubogenerator shaft model. Detailed derivation of Generator rotor subjected to mechanical disturbance, changed current in the stator-side generates the electrical damping to the mechanical disturbance. Draw the calculated electrical damping torque coefficient formula. Electrical resonant frequency current in the stator side causing the sub-synchronous frequency electromagnetic torque in the rotor side, which vias a series of mechanical and electrical interaction produces damp effact to mechanical disturbance is proved. Electrical resonant frequency current in the stator side causing the super-synchronous frequency electromagnetic torque in the rotor side, which vias a series of mechanical and electrical interaction produces damp effact to mechanical disturbance. The qualitative analysis of the impact of sub-synchronous frequency and super-synchronous frequency mechanical oscillations. Verify the conclusions vias test signal method.Then, study the inhibition of sub-synchronous oscillation, design sub-synchronous damping controller (SSDC) which dynamically generates modal complementary current, Explioting STATCOM to real-time tracking compensation current to achieve the purpose of sub-synchronous oscillation suppression. Detailed introduction the procedure of designing Supplementary Subsynchronous Damping Controller (SSDC) and the STATCOM control systems design. Research damping characteristics of subsynchronous damping controller (SSDC) which design by different filters. The study found that different filters affect the inhibitory effect of sub-synchronous damping controller. Based on different filters designed three synchronous damping controllers, among which proposes a new controller design method, according to this method designing narrow band-pass sub-synchronous damping controller. Increasing a narrow band-pass sub-synchronous damping controller channel in the sub-modal sub-synchronous damping controller to get a new sub-synchronous damping controller, which realizes positive electrical damping in all frequence bands. The new controller has a strong adaptability, when the parameters of the generator are not accurate, inhibitory effect not affected. Analyze the electrical damping characteristics of three different sub-synchronous damping controllers in IEEE SSR first benchmark model. Simulation verify the effectiveness of synchronous damping controllers in inhibiting sub-synchronous oscillation. Compared the inhibitory effect of different damping controller providing different electrical damping. The sub-synchronous damping controller which design according to the proposed method has a better effact. Finally, consider the impact of STATCOM capacity to Suppression sub-synchronous oscillation.