Analyze the Sub-synchronous Resonance Risk of Thermal Power Plants and Take an Effective Solution to Suppress: A Case Study for Vietnamese Power System

Abstract

This paper presents an entirely new subject to prevent SSR in thermal power plants. The SSR phenomenon is firstly analyzed by using the frequency scanning method in the frequency domain under considering other operating conditions for operating grid-configurations, and then the SSR due to the self-excitation and the transient phenomenon is analyzed to provide the inputs for working out an effective solution. Three devices, namely the thyristor controlled series capacitor (TCSC), static synchronous compensator (STATCOM), and blocking filter (BL) are considered as a proposed choice, and the control strategy for each mentioned device is developed to mitigate the SSR. For TCSC, the control strategy is designed based on two PI controllers for the voltage and current regulator, respectively; besides, the auxiliary sub-synchronous damping controller is proposed to provide a supplementary signal of dynamic current on the input signal that is chosen the generator rotor speed deviation. For STATCOM, two PI controllers, using for the DC and connected point voltage regulator, proposed; besides, the auxiliary sub-synchronous damping controller is proposed to provide a supplementary signal of dynamic current on the input signal that is chosen the generator rotor speed deviation. For BL, the natural torsional vibration frequency of models to ensure that SSR due to torsional interaction (TI), torque amplification (TA), and induction generator effect (IEG) are prevented. The effectiveness of this study is verified via a time-domain simulation of the Vietnam Quang-Tri electric power system connected to the 500/220 kV transmission system using EMTP-RV and PSS/E programs. The obtained results show that the frequency scanning method is chosen as a useful method to analyze SSR and the effective solution can be applied to immediately solve the difficulties encountering in the Vietnamese power system to be BL.