Synchronous Voltage Reversal control of TCSC – impact on SSR conditions Hailian Xie Lennart Ängquist EME/ETS, Royal Institute of Technology, Stockholm

Series compensation  capacitor bank inserted in series with transmission line  aims to increase the power transfer capacity of high-voltage transmission line  fixed capacitor bank may cause a Torsional Interaction Sub-Synchronous Resonance (TI- SSR) problem with thermal power generators  Thyristor Controlled Series Capacitor (TCSC) may solve this problem EME/ETS, Royal Institute of Technology, Stockholm

TCSC main circuit and generic waveforms EME/ETS, Royal Institute of Technology, Stockholm Line current Valve current Capacitor voltage Apparent reactance

About this paper  describes the laboratory setup of a TCSC model with the SVR (Synchronous Voltage Reversal) control scheme  presents the result from an investigation concerning the impact of the SVR controlled TCSC on SSR in the real-time simulator EME/ETS, Royal Institute of Technology, Stockholm

Diagram of the real-time simulator EME/ETS, Royal Institute of Technology, Stockholm Infinite bus u 2 Source 1 impedance u1u1 Line Fixed Impedance capacitor TCSC inductance TCSC capacitor Thyristor valve

SVR Control scheme EME/ETS, Royal Institute of Technology, Stockholm SVR idea: control capacitor voltage zero-crossing instant

TCSC capacitor SVR boost control system overview EME/ETS, Royal Institute of Technology, Stockholm PLL Boost controller u c (measured) k Bref + k Bm _ pulses -X C0 Re Im SVR trig pulse generation TCSC inductance Thyristor valve i l (measured) Apparent Z evaluation Phasor estimation 

Method to analyze the system damping EME/ETS, Royal Institute of Technology, Stockholm K el D el T el iLiL LP filter Calculate the electrical torque In DSPIn Matlab Calculate the spring constant and damping coefficient Generate system voltage u1u1 Control modulation Re(ΔT el ) Im(ΔT el )

Electrical damping curve (1) system with fixed series compensation EME/ETS, Royal Institute of Technology, Stockholm

Electrical damping curve (2) system with SVR controlled TCSC EME/ETS, Royal Institute of Technology, Stockholm

Electrical damping curve (3) Comparison between SVR and  control EME/ETS, Royal Institute of Technology, Stockholm

Electrical damping curve (4) SVR control with different parameters EME/ETS, Royal Institute of Technology, Stockholm

Conclusions  at low boost factor, SVR controlled TCSC can provide much better damping than conventional control scheme that controls the firing angle directly  the damping characteristic of SVR controlled TCSC with respect to SSR is almost independent of the boost factor  the tuning of the boost controller and PLL makes no critical difference on the TCSC SSR behavior EME/ETS, Royal Institute of Technology, Stockholm

Thank you! EME/ETS, Royal Institute of Technology, Stockholm