Coordination of protection system and VSC-HVDC to mitigate cascading failures

The rapid development of the global economics has made power systems allover the world become large-scale interconnected grids. This increases the capabilityof power grids to transfer power over the long distance to serve the desiredpower demand with the minimum cost of operation. Unfortunately, it alsoenables the propagation of local failures into global networks. In other words,if a blackout happens in a power system, the size and the damage may significantlyincrease. One of the main ways in which blackouts become widespread is cascadingfailures. This type of failure originates after a critical component of the systemhas been removed fromthe service by protective relaying. As a consequence, theload handled by the failed component needs to be redistributed which mightcause an overloading on other components in the system. On the other hand, the high power electronics controllable devices suchas Voltage Source Converters-based High Voltage Direct Current (VSC-HVDC)transmission are recently developed. These electronics devices have the potentialadvantages such as the ability to independently control active and reactivepower, and maintain voltage to be at acceptable level. Therefore, they are consideredto be the promising devices that with an appropriately designed controlstrategy, they can substantially improve the performance and reliability of thepower system. This thesis presents the possibility to consider protection system status inthe control of VSC-HVDC link. A great deal of this research is development ofcoordination between this power electronic device and protection system which normally are considered separately. The derivation of protection system has been selected to determine the operation of VSC-HVDC. The methodology isbased on utilizing the signal created from a logical evaluation of relay and simplificationsof certain parameters. By introducing information from the relays tothe VSC-HVDC link via Central Control Unit (CCU), the modulation of transmitted power is devised in order to reduce the risk of system-wide failures. In turn,this means an avoided blackout.Furthermore, this thesis also includes the preliminary suggestion to selectthe location of VSC-HVDC. The methodology is based on predicting voltage instabilityusing voltage stability indices and related parameterswhich are derivedby using Singular ValueDecomposition method. The solutions indicate an effectivelocation for applying corrective action such as load shedding. This optimallocation is selected to reinforce the control strategy of VSC-HVDC in order toprevent cascading failures in the more encompassing systems.QC2010061

Power System Protective Relaying : basic concepts, industrial-grade devices, and communication mechanisms

QC 2011121

"All-in-one" test system modelling and simulation for multiple instability scenarios

QC 2011121

Power System Protective Relaying : basic concepts, industrial-grade devices, and communication mechanisms

QC 2011121

Modeling Adequacy for Cascading Failure Analysis

This paper describes the mechanisms of cascading failure as the cause of severe blackouts. The severe blackouts that occurred in 2003 affecting large metropolitan areas around the globe are first reviewed. Then the probable root cause of each blackout events is identified in order to seek effective corrective preventive solutions. Several of the well-known techniques for cascading failure analysis and correction are discussed and characterized based on their fundamental features. Thereupon a new model power system component is proposed for simulating cascading failure in actual networks.QC 20111213</p

Calculation of magnetic interaction forces between particles in a magnetorheological suspension

Daudzas magnetoreoloģisko šķidrumu īpašības var izskaidrot ar magnētisko spēku palīdzību. Šajā darbā aplūkotas magnētiskās mijiedarbības starp sfēriskām daļiņām. Aprēķiniem izstrādāta programma, kas ar trīsdimensionālas galīgo elementu metodes palīdzību risina magnetostatisku problēmu. Programmā implementāts arī mijiedarbības spēku un vidējās magnetizācijas aprēķins. Minētā programma var tikt izmantota arī citas formas ķermeņiem.Many of MR fluids’ properties can be explained by magnetic forces. In this thesis are researched the magnetic interactions between two spherical particles. For this purpose there is created a program, that solves the magnetostatic problem with finite elements method. Program has optional interaction force and average magnetization calculation subroutines included as well. This software can be used for solving different problems with different shape objects