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Virtual Impedance Based Selective Harmonic Compensation (VI-SHC) PWMNi, Ruoshui Unknown Date
No description available.
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Power quality and inverter-generator interactions in microgridsPaquette, Andrew Donald 22 May 2014 (has links)
This research addresses some of the difficulties faced when operating voltage controlled inverters with synchronous generators in microgrids. First, an overview of microgrid value propositions is provided, and the problems faced when attempting to use microgrids to provide improved power quality are discussed. Design considerations for different types of microgrids are provided to enable microgrids to deliver the desired functionality without adding unnecessary cost. The main body of this research investigates the poor transient load sharing encountered between voltage controlled inverters and synchronous generators in islanded operation. Poor transient load sharing results in high peak inverter rating requirements and high cost. The tradeoff between power quality and power sharing is highlighted, and methods to improve transient load sharing are proposed. The use of current limiting to protect inverters during faults and overloads is also investigated. Stability problems are identified when using simple inverter current limiting methods when operating in parallel with synchronous generators. Virtual impedance current limiting is proposed to improve transient stability during current limiting. The methods proposed in this thesis for mitigating inverter overloads and faults will allow for more reliable and cost effective application of inverter based distributed energy resources with synchronous generators in microgrids.
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Large Scale Analysis of Massive Deployment of Converter-based Generation equipped with Grid- forming StrategiesJimenez Saldana, Cristhian Carim January 2020 (has links)
To mitigate the carbon footprint and the need to fulfil the energy goals in terms of sustainability, it is required to deploy a large integration of green energies. Therefore, in the previous and the coming years, there will be a high research and technological interest in the high penetration of converter-based generation. With the replacement and integration of power converters into the bulk power grid, new challenges and issues must be faced to maintain the system´s stability and reliability in terms of procedures for the transmission system operators. The main objective of this thesis project is to analyze and to implement the current- limiting techniques implemented in voltage source converters, which are equipped with grid-forming functionalities so that these electronic devices are safeguarded during a severe transient event as three-phase short-circuit and remain connected to the grid during the fault scenario. The model of the voltage source converter with grid-forming strategies is described as well as the grid-forming strategies (droop control, virtual synchronous machine (VSM) and dispatchable virtual oscillator control (dVOC)) utilized in the outer loop. The low-inertia and zero-inertia system in the IEEE 9-Bus test system were exhibited to be resilient towards 3-phase fault events, and their behavior shows neither significant oscillations during and after the incident of the fault nor noticeable difference in their performance regarding the location. In this test system model, the current-limiting techniques were validated and analyzed results display good effectiveness for the current and frequency. The Hydro-Québec network model was employed to have a more practical approach in the behavior of the current limitation strategies in the power converters in a real power system. The fault location and the percentage of participation of the voltage source converters in the energy generation were the two main scenarios, in which the proposed control strategies for restricting the current work but simultaneously, it is required an appropriate control to keep the system´s stability. / För att minska koldioxidutsläppet och uppnå energimålen med avseende på hållbarhet krävs integrering av hållbara energikällor. Därmed, under de föregående och kommande åren kommer stort fokus riktas mot forskning kring ökad penetration av kraftelektronikomriktare i kraftsystemet. När kraftelektronikomriktare ersätter traditionella generationsenheter uppkommer nya utmaningar och problem som behöver lösas för att upprätthålla systemets stabilitet och pålitlighet med avseende på tillvägagångssätt för systemansvariga för överföringssystemet. Avhandlingens huvudmål är att analysera och implementera strömbegränsande metoder för kraftelektronikomriktare av typen voltage source converters med en nätformande (”grid- forming”) funktionalitet. Strömbegränsaren ska säkerställa att kraftelektronikomriktaren skyddas under allvarliga transienta händelser och att kraftelektronikomriktaren förblir ansluten till nätet under händelsen. Modellen av kraftelektronikomriktaren med nätformande egenskaper är beskrivna tillsammans med nätformande kontrollstrategier, virtuella synkronmaskniner (VSM) och användande av avsändande virtuell oscillerande kontroll i den yttre slingan. Den låga trögheten och noll-tröghetssystemet i IEEE 9-Bus test-system visade sig vara motståndskraftig mot trefasfel eftersom testsystemets beteende visade varken signifikanta oscillationer under och efter felet eller märkbar förändring i dess prestanda beroende på var felet inträffade. I denna testsystemsmodell var strömbegränsande tekniker validerade och de analyserande resultaten visade på god effektivitet för strömmen och för frekvensen. Hydro-Québec nätverks-modellen användes för att få en mer praktisk inriktning med hänsyn till beteendet hos strömbegränsarna där olika strategier har använts. Felpositionen och andelen av kraftelektronikomriktare i energigenereringen var två huvudsakliga scenarion, där de föreslagna kontrollstrategierna för att begränsa strömmen fungerade men kräver samtidigt att en lämplig kontroll för att behålla systemets stabilitet.
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Consensus Control for Power Sharing in an Islanded Microgrid Using an Adaptive Virtual Impedance ApproachAlsafran, Ahmed Sulaiman, . January 2020 (has links)
No description available.
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