Technical Presentations

Study of Sub-synchronous Resonance for thermal power plants connected on Vietnamese grid using EMTP®867

Abstract
Study of Sub-synchronous Resonance for Thermal Power Plants Connected on Vietnamese Grid Using EMTP

Tag(s): Synchronous Machine, Subsynchronous Ressonance, Undamped Oscillations, FACTs, Series Compensation, TCSC, STATCOM

Real Case of a Resonance in a Power Plant851

Abstract
Overvoltages were identified on the MV and LV networks of a Hydro Power Plant as the cause of the trip of the LV maximum voltage protection, compromising the normal operation of the system. Following ... see morethis event, measurements were conducted and the presence of a very high 23rd harmonic, potentially responsible for the various overvoltages, was identified associated to the operation of the Plant’s Synchronous Machine Frequency Control System (FCS). It was concluded then that this harmonic would have its origin in the FCS and would be amplified due to a possible resonance in the Power Plant internal network. A digital simulation study, using EMTP, was conducted to identify and characterize the resonance in the system and to propose mitigation solutions. The simulation models were developed using the equipment data and the system characteristics. The models were duly validated with measurements made both in time and frequency domains and it was possible to identify the origin of the overvoltages and their propagation in the system. It was concluded that the resonance occurred between a 30/11 kV Power Transformer and a 30 kV cable with 850 m.

This conclusion was supported by the results obtained in the measurements. Several alternatives were analyzed as mitigation solutions: - Installation of capacitors; - Different bonding techniques of the 30 kV cable sheaths; - Changing the 30 kV cable length; - Installation of a harmonic filter; The advantages and disadvantages of each solution were weighed also considering the ease of implementation, namely the available room. It was concluded that the installation of capacitors would be the best option. Measurements were conducted after the capacitor’s installation confirming the success of this solution.

Tag(s): harmonics, power uality, resonance

Influence of HVDC Controls on Transient Stability of Synchronous Machines747

Abstract
<h2 class="title">EMTP Europe User Conference 2019 </h2> <p class="tagline"><b>The EMTP User Conference pres... see moreentations are now available online!</b></p> <p id="text-intro"><b>Influence of HVDC Controls on Transient Stability of Synchronous Machines</b><br> With the energy transition in France and in Europe, the transmission grid is strongly impacted by the forthcoming connection of power electronics devices, such as offshore wind farms and HVDC interconnections. These new devices use power electronics converters that generate transients which are usually more complex to analyzed than for standard AC devices, in particular during faults. These phenomena can have an impact on the grid stability.<br> The presentation will focus on the transient stability studies of synchronous generator influenced by power electronics devices. The objective is to compare the critical fault clearing time for different fault locations, fault conditions and different HVDC converter fault ride through control strategies. Generic test cases as well as real scenarios are considered. In this study, the critical time is obtained with bisection method thanks to the new parameter sweep toolbox.