Power management of islanded Self-Excited Induction Generator reinforced by energy storage systems

Self-Excited Induction Generators (SEIGs), e.g., Small-Scale Embedded wind generation, are increasingly used in electricity distribution networks. The operational stability of stand-alone SEIG is constrained by the local load conditions: stability can be achieved by maintaining the load’s active and reactive power at optimal values. Changes in power demand are dependent on customers’ requirements, and any deviation from the pre-calculated optimum setting will affect a machine’s operating voltage and frequency. This paper presents an investigation of the operation of the SEIG in islanding mode of operation under different load conditions, with the aid of batteries as an energy storage source. In this research a current-controlled voltage-source converter is proposed to regulate the power exchange between a direct current (DC) energy storage source and an alternating current (AC) grid, the converter’s controller is driven by any variation between machine capability and load demand. In order to prolong the system stability when the battery reaches its operation constraints, it is recommended that an ancillary generator and a dummy local load be embedded in the system. The results show the robustness and operability of the proposed system in the islanding mode of the SEIG under different load conditions

Design And Implementation Of Co-Operative Control Strategy For Hybrid AC/DC Microgrids

This thesis is mainly divided in two major sections: 1) Modelling and control of AC microgrid, DC microgrid, Hybrid AC/DC microgrid using distributed co-operative control, and 2) Development of a four bus laboratory prototype of an AC microgrid system. At first, a distributed cooperative control (DCC) for a DC microgrid considering the state-of-charge (SoC) of the batteries in a typical plug-in-electric-vehicle (PEV) is developed. In DC microgrids, this methodology is developed to assist the load sharing amongst the distributed generation units (DGs), according to their ratings with improved voltage regulation. Subsequently, a DCC based control algorithm for AC microgrid is also investigated to improve the performance of AC microgrid in terms of power sharing among the DGs, voltage regulation and frequency deviation. The results validate the advantages of the proposed methodology as compared to traditional droop control of AC microgrid. The DCC-based control methodology for AC microgrid and DC microgrid are further expanded to develop a DCC-based power management algorithm for hybrid AC/DC microgrid. The developed algorithm for hybrid microgrid controls the power flow through the interfacing converter (IC) between the AC and DC microgrids. This will facilitate the power sharing between the DGs according to their power ratings. Moreover, it enables the fixed scheduled power delivery at different operating conditions, while maintaining good voltage regulation and improved frequency profile. The second section provides a detailed explanation and step-by-step design and development of an AC/DC microgrid testbed. Controllers for the three-phase inverters are designed and tested on different generation units along with their corresponding inductor-capacitor-inductor (LCL) filters to eliminate the switching frequency harmonics. Electric power distribution line models are developed to form the microgrid network topology. Voltage and current sensors are placed in the proper positions to achieve a full visibility over the microgrid. A running average filter (RAF) based enhanced phase-locked-loop (EPLL) is designed and implemented to extract frequency and phase angle information. A PLL-based synchronizing scheme is also developed to synchronize the DGs to the microgrid. The developed laboratory prototype runs on dSpace platform for real time data acquisition, communication and controller implementation

Operation and Control of DC Microgrid

Power harnessing technology from the renewable energy resources has been developed over the past two decades. This technology enabled us to integrate renewable energy-based power generation to the conventional electric power grid. This study aims to improve the dynamic response and the load regulation using improved control strategies of the dc converters used to interface utility and renewable energy-based power generation. The power sharing between multiple dc microgrids/ac-dc microgrids is also investigated

Reliability Improvement of Autonomous Microgrids through Interconnection and Storage

This thesis deals with reliability and power quality improvement in autonomous microgrids. The reliability is improved through the interconnection of storage, intertying two neighbouring microgrids and interlinking of microgrids cluster through a common power exchange highway. The power quality is improved by interconnecting distributed static compensator (DSTATCOM) in the microgrid. All the proposed methods are verified through extensive digital computer simulation using PSCAD

Integration of distributed generation using energy storage systems

New challenges in grid reliability are coming up with the increasing penetration of renewable energies and distributed generation (DG). The use of Energy Storage Systems (ESS) is proposed in this thesis as solution for different problems related to these new challenges. The development and current state of ESS are described in this thesis. This description permits to choose the best solution for the different scenarios that are analyzed. The analysis of electrical grids is carried out by means of simulation tools. For this purpose a dynamic power calculation is proposed. The modeling of electrical components and their implementation in the proposed simulation tool permits to analyze the frequency and voltage stability of power systems. These two are the most important parameters for grid operation and therefore the most important parameters to analyze the integration of DG. Some applications related to the use of ESS as a solution for a certain problem related to the high penetration of DG are analyzed in the present work. Voltage regulation, restoration of large frequency deviations, primary frequency regulation and the control of the power dispatch of a wind farm are proposed as applications for ESS. The design of an application combining these functionalities is discussed. Hybrid ESS that combines different ESS technologies is proposed as a single solution for all the applications analyzed during the course of this thesis.Energia berriztagarrien eta Sorkuntza Barreiatuaren (SB) erabilera azkorrak erronkau berriak aurkezten ditu sare elektrikoen sinesgarritasunari begira. Tesi honetan Energia Metatzeko Sistemen (EMS) erabilera eztabaidatzen da aipatutako erronketatik eratorritako zenbait arazo konpontzeari begira. EMSen garapena eta egungo egoera azaltzen dira tesi honetan. Deskribapen honek tesi honetan aztertzen diren egoera desberdinentzat konponbide egokiena hautatzea ahalbideratzen du. Sare elektrikoen azterketa simulaziorako tresnen bidez egiten da. Helburu hau betetzeko potentzia fluxuen kalkulu dinamikoa proposatzen da. Osagai elektrikoen modelatzeak eta beren inplementazioak proposaturiko simulazio tresnan potentziako sistemen tentsio eta frekuentziaren azterketa egitea ahalbideratzen du. Bi parametro hauek dira garrantzitsuenak sare elektrikoaren operazioaren ikuspegitik eta honenbestez parametro garrantzitsuenak dira SBren integrazioa aztertzeko orduan. Lan honetan EMSen erabileraren inguruko hainbat aplikazio aztertzen dira, SBren sarrera handiarekin erlazionatutako zenbait arazori konponbidea bilatzeko. Tentsioaren erregulazioa, frekuentziaren desbideratze handien berreskurapena, frekuentziaren erregulazio primarioa eta parke eolikoen despatxu kontrolatua EMSentzako aplikazio bezala proposatzen dira. Funtzio guzti hauek beteko lituzken aplikazio baten diseinua eztabaidatzen da. EMS Hibrido bat proposatzen da EMS teknologia desberdinak konbinatuko dituena, lan honetan aztertu diren aplikazio desberdinentzako soluzio bezala.La creciente penetración de energías renovables y Generación Distribuida (GD) presentan nuevos retos en la fiabilidad de las redes eléctricas. El uso de Sistemas de Almacenamiento de Energía (SAE) se propone en esta tesis como solución a diferentes problemas derivados de los mencionados retos. El desarrollo y el actual estado de los SAE se describen en esta tesis. Esta descripción permite elegir la mejor solución ante los diferentes escenarios que se analizan. El análisis de las redes eléctricas se realiza mediante herramientas de simulación. Con este objetivo se propone el cálculo dinámico de los flujos de carga. El modelado de componentes eléctricos y su implementación en la herramienta de simulación propuesta permite analizar la estabilidad del voltaje y la frecuencia en los sistemas de potencia. Estos dos parámetros son los más importantes para operación de la red eléctrica y por consiguiente son los parámetros más importantes para analizar la integración de la GD. En este trabajo se analizan varias aplicaciones relacionadas con el uso de los SAE como solución a ciertos problemas relacionados con la alta penetración de la GD. Regulación de voltaje, restitución de grandes desviaciones de frecuencia, regulación primaria de frecuencia y el despacho controlado de los parques eólicos se proponen como aplicaciones para SAE. Se debate el diseño de una aplicación que combine estas funcionalidades. Se propone un SAE Híbrido que combine diferentes tecnologías de SAE como solución única para todas las aplicaciones analizadas durante el curso de esta tesis

Integrating photovoltaic systems into remote diesel generator powered networks

This thesis aims to research the effects of multiple ascending levels of photovoltaic (PV) power penetration on a prototype diesel generator powered network that has a PV power system integrated into it. First the effects of this additional photovoltaic penetration were documented then some ways to mitigate the effects of solar intermittency were investigated. This project relates to the Power and Water Corporation’s (PWC) proposed roll out of 10 megawatt of solar throughout more than 30 of the remote communities they service in the Northern Territory. This thesis is concerned with instantaneous PV power penetration and studying the effects levels of instantaneous penetration higher than 30 per cent may have on an individual network. To conduct this study, literature about solar irradiance data and previous trials in the Northern Territory was studied to make sensible simulation event estimates for a mock network. A network model was created and used in simulations to approximate the network’s response to cloud shading during various levels of penetration. The simulations confirmed that photovoltaic penetration of 30 per cent and even 45 per cent could easily be implemented without the need for upgrading the existing infrastructure. Both 60 and 70 per cent penetration level simulations suggested that there would likely be a need to raise the nominal generated voltage and or apply shunt capacitor banks to the load buses. The significance of these results is that they confirm the Power and Water Corporations premise that 30 per cent penetration is a safe starting point and also suggest that higher levels of photovoltaic penetration can be achieved with little to no costly infrastructure upgrades, depending on the level of penetration implemented

Requirements to Testing of Power System Services Provided by DER Units

The present report forms the Project Deliverable ‘D 2.2’ of the DERlab NoE project, supported by the EC under Contract No. SES6-CT-518299 NoE DERlab. The present document discuss the power system services that may be provided from DER units and the related methods to test the services actually provided, both at component level and at system level

Power Management Strategies for Islanded Microgrids

The focus of this thesis is on developing power management strategies for islanded microgrids, at the primary and the secondary hierarchal control layers. At the Primary Control Layer, the main objective of the proposed strategies is to achieve decentralized power management of Photovoltaic (PV) and battery storage in islanded microgrids. In contrast to the common approach of controlling the PV unit as a current source, in the proposed strategies, the PV unit is controlled as a voltage source that follows a multi-segment adaptive power/frequency characteristic curve. The strategies are implemented locally at the units using multi-loop controllers without relying on a central management system and communications, as most of the existing algorithms do. At the Secondary Control Layer, strategies are developed to improve reactive power sharing in islanded microgrids. The proposed controllers are shown to still outperform conventional droop technique during communication failures. In addition, the reactive power sharing accuracy based on the proposed strategy is immune to the time delay in the communication channel. The sensitivity of the tuned controller parameters to changes in the system operating point is also explored. The net control action of the proposed controllers is demonstrated to have a negligible effect on the microgrid bus voltage. The proposed strategies are validated using experimental results from a 4.0 kVA prototype microgrid

European White Book on Real-Time Power Hardware in the Loop Testing : DERlab Report No. R- 005.0

The European White Book on Real-Time-Powerhardware-in-the-Loop testing is intended to serve as a reference document on the future of testing of electrical power equipment, with specifi c focus on the emerging hardware-in-the-loop activities and application thereof within testing facilities and procedures. It will provide an outlook of how this powerful tool can be utilised to support the development, testing and validation of specifi cally DER equipment. It aims to report on international experience gained thus far and provides case studies on developments and specifi c technical issues, such as the hardware/software interface. This white book compliments the already existing series of DERlab European white books, covering topics such as grid-inverters and grid-connected storag