The Modeling and Advanced Controller Design of Wind, PV and Battery Inverters

Renewable energies such as wind power and solar energy have become alternatives to fossil energy due to the improved energy security and sustainability. This trend leads to the rapid growth of wind and Photovoltaic (PV) farm installations worldwide. Power electronic equipments are commonly employed to interface the renewable energy generation with the grid. The intermittent nature of renewable and the large scale utilization of power electronic devices bring forth numerous challenges to system operation and design. Methods for studying and improving the operation of the interconnection of renewable energy such as wind and PV are proposed in this Ph.D. dissertation.;A multi-objective controller including is proposed for PV inverter to perform voltage flicker suppression, harmonic reduction and unbalance compensation. A novel supervisory control scheme is designed to coordinate PV and battery inverters to provide high quality power to the grid. This proposed control scheme provides a comprehensive solution to both active and reactive power issues caused by the intermittency of PV energy. A novel real-time experimental method for connecting physical PV panel and battery storage is proposed, and the proposed coordinated controller is tested in a Hardware in the Loop (HIL) experimental platform based on Real Time Digital Simulator (RTDS).;This work also explores the operation and controller design of a microgrid consisting of a direct drive wind generator and a battery storage system. A Model Predictive Control (MPC) strategy for the AC-DC-AC converter of wind system is derived and implemented to capture the maximum wind energy as well as provide desired reactive power. The MPC increases the accuracy of maximum wind energy capture as well as minimizes the power oscillations caused by varying wind speed. An advanced supervisory controller is presented and employed to ensure the power balance while regulating the PCC bus voltage within acceptable range in both grid-connected and islanded operation.;The high variability and uncertainty of renewable energies introduces unexpected fast power variation and hence the operation conditions continuously change in distribution networks. A three-layers advanced optimization and intelligent control algorithm for a microgrid with multiple renewable resources is proposed. A Dual Heuristic Programming (DHP) based system control layer is used to ensure the dynamic reliability and voltage stability of the entire microgrid as the system operation condition changes. A local layer maximizes the capability of the Photovoltaic (PV), wind power generators and battery systems, and a Model Predictive Control (MPC) based device layer increases the tracking accuracy of the converter control. The detail design of the proposed SWAPSC scheme are presented and tested on an IEEE 13 node feeder with a PV farm, a wind farm and two battery-based energy storage systems

Sähköjärjestelmän häiriöt ydinvoimalaitoksissa ja niiden simulointivaatimukset

Electrical systems perform various functions in a nuclear power plant (NPP), and they are required for the operation of many safety systems. In normal operation, all electrical systems are connected together at the high voltage level, which creates the potential for common cause failures due to faults in the plant internal or external power system. In fact, several such incidents have been reported. This thesis reviews literature related to NPP electrical system reliability and electrical disturbances. Three particularly relevant conditions (power frequency overvoltages, open phase conditions and subsynchronous oscillations) are selected for in-depth analysis. Based on the literature review and analyses, this thesis makes recommendations about simulating these conditions in COSI. COSI is a research project which aims to develop a co-simulation platform for simulating the electrical system and NPP process systems together. This thesis notes that existing electrical simulation studies have not considered process system feedback effects and other transient dynamics in much detail, and that COSI could provide insight into their effects on nuclear safety.Sähköjärjestelmät ovat tärkeitä lukuisille ydinvoimalaitoksen toiminnoille. Muun muassa monien turvallisuusjärjestelmien toiminta riippuu sähköjärjestelmistä. Normaalissa käyttötilanteessa kaikki sähköjärjestelmät kytkeytyvät yhteen suurjännitetasolla, mistä aiheutuu mahdollinen yhteisvikariski, jos laitoksen sisäisessä tai ulkoisessa sähköverkossa tapahtuu vika. Useita tämänkaltaisia tapahtumia onkin raportoitu. Tässä diplomityössä tehdään katsaus kirjallisuuteen, joka liittyy ydinvoimalaitosten sähköjärjestelmien luotettavuuteen ja sähköjärjestelmän häiriöihin. Kolme erityisen oleellista häiriötyyppiä (verkkotaajuiset ylijännitteet, vaihekatkokset ja alisynkroniset värähtelyt) valitaan lähempään tarkasteluun. Kirjallisuuskatsauksen ja tarkastelujen perusteella annetaan suosituksia näiden häiriöiden simuloimiseen COSI-projektissa. COSI on tutkimusprojekti, jossa kehitetään kosimulaatioalusta sähköjärjestelmän ja ydinvoimalaitoksen prosessijärjestelmien yhteissimulointiin. Työn mukaan aiemmissa sähköjärjestelmien simulointitutkimuksissa ei ole tarkasti selvitetty prosessijärjestelmistä aiheutuvia takaisinkytkentöjä tai muita transienttivaikutuksia. COSI voisi parantaa ymmärrystä näiden vaikutuksista ydinturvallisuuteen