Real-Time Estimation and Damping of SSR in a VSC-HVDC Connected Series-Compensated System

Abstract

Infrastructure reinforcement using high-voltage direct-current (HVDC) links and series compensation has been proposed to boost the power transmission capacity of existing ac grids. However, deployment of series capacitors may lead to subsynchronous resonance (SSR). Besides providing bulk power transfer, voltage source converter (VSC) based HVDC links can be effectively used to damp SSR. To this end, this paper presents a method for the real-time estimation of the subsynchronous frequency component present in series-compensated transmission lines-key information required for the optimal design of damping controllers. A state-space representation has been formulated and an eigenvalue analysis has been performed to evaluate the impact of a VSC-HVDC link on the torsional modes of nearby connected thermal generation plants. Furthermore, the seriescompensated system has been implemented in a real-time digital simulator and connected to a VSC-HVDC scaled-down test-rig to perform hardware-in-the-loop tests. The efficacy and operational performance of the ac/dc network while providing SSR damping is tested through a series of experiments. The proposed estimation and damping method shows a good performance both in timedomain simulations and laboratory experiments.

Experimental Validation of an Active Wideband SSR Damping Scheme for Series-Compensated Networks

“…1. Although it is arguably a simplified version of the GB system, it has been previously employed for SSR studies [13], [20], [24], [25]. Despite its simplicity, it provides sufficient information to study and understand the SSR phenomena and to elucidate key concepts by reducing system complexity while keeping an appropriate weighting of the size of generation.…”

“…This is a system of 77 differential equations linearized around an operating point (not included due to space limitations). The results shown in this section were presented in [20]; however, they are reproduced here for completeness of the SSR analysis.…”

“…Following this line, a WBD embedded in a VSC station of the HVDC is presented as an auxiliary controller to damp SSR upon occurrence. The WBD scheme presented in this section provides positive damping in a wide range of frequencies within the subsynchronous region (15)(16)(17)(18)(19)(20)(21)(22)(23)(24)(25)(26)(27)(28)(29)(30), which coincides where the TMs of turbine-generators within the GB system lie [29]. Since these modes of oscillation are fixed as long as the generator rotor or turbine blades are not replaced [38], a properly designed WBD may achieve sufficient damping for the entire frequency range of interest irrespective of changes in the configuration of the transmission network-with minimal impact on the operation of the HVDC system.…”

“…Although schemes for the real-time estimation and on-line monitoring of SSF components may relieve the aforementioned issues [18], [19], they could be computationally intensive. For instance, even when [20] represents a good attempt to experimentally damp SSR, the practical contribution of the work is limited as the time to detect SSR and the precision of frequency estimation depend on the signal processing method used for the analysis of the input signal.…”

Real-Time Hardware-in-The-Loop Platform for Hybrid AC/DC Power System Studies

“…Transient stability studies have also received significant attention. For example, [16], [17] focus on subsynchronous oscillation studies and detailed shaft models of synchronous generators, HVDC systems and series-compensated ac lines. Provision of damping using power converters to enhance power system stability has been studied in [18].…”