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AC-BASED RENEWABLE ENERGY NANOGRID
Increasing environmental and economic problems on one side, and lower cost and higher availability of smaller generating systems (i.e. solar cells, wind turbines) on the other, have opened new opportunities for electricity users to generate power on-site. Along these lines, the so-called microgrid is a widely known and accepted concept that comprises energy storage and a larger number of generating units in order to get the most from the naturally available renewable energy sources [56]. Although its structure is more complex, and for the meantime a more expensive one, it provides unparalleled flexibility for the residential house applications. On the other hand, Plug-in Hybrid Electrical Vehicles (PHEV) present a promising, emerging technology for the future home since in general, the average personal vehicle is parked at the house for approximately 15 hours per day, which makes them potentially available for Vehicle-to-Grid (V2G) operation more than 60% of the time. An intelligent synergy of these two concepts combined with an advanced system control can provide a great platform for developing a residential house renewable energy solution at the lower power level.
AC Nanogrid
Utilizing PHEV, nanogrid has the ability to isolate a house from the utility grid (or microgrid), intentionally due to a fault or other abnormal grid conditions, work in the stand-alone mode, synchronize and reconnect to the utility grid, without load power interruptions. PHEV, with a built-in bidirectional power converter, presents the opportunity for demand-response operation in the grid connected mode, whereas in the islanded mode, it can perform frequency and voltage regulation of the power bus. The basic idea behind the V2G technology is that electric vehicles can provide power to the grid when parked and plugged in [57], and in order to function in V2G mode, PHEV must be equipped with a bidirectional power converter and additional battery pack. Having this, a two way energy flow is possible – when the power demand is low, PHEV‟s batteries can be charged and when high, batteries can be discharged and thus perform voltage and frequency regulation by matching generation with the load demand.
System Description
The proposed home uninterruptible renewable energy system is shown in Figure 2.2,with the essential components. The house can have a photovoltaic and/or small wind turbine interconnected into the Integrated Power Hub (IPH) – an integrated solution with all of the equipment enclosed in a single cabinet. The IPH can comprise an internal single or three phase bus-bar for interconnection of available renewable sources, PHEV, power meter, synchronization contactor, circuit breakers and system controller. The basic idea of introducing the IPH is to develop a system that can be easily installed in the house, without any substantial modifications and rewiring. As shown in Figure 2.2,The PHEV comprises the Bidirectional Power Converter (BPC) interconnected to the additional vehicle‟s battery. The BPC can perform a full, four-quadrant demand-response service according to the commands received from the power system operator as routed to the BPC from the Power Hub Controller (PHC). The BPC can perform an advanced active algorithm for islanding detection, and island the house when a grid outage occurs. In islanded operation, the BPC can supply power to keep all high priority loads and renewable sources to continue functioning in the stand-alone mode [60,61]. The proposed system also includes a supervisory control and data acquisition unit called the Power Hub Controller (PHC) as a main part of the IPH. One of the PHC‟s most important functions is the monitoring of system components by gathering data (current, voltage, THD and other) over communication lines. The collected data is fed to the web-based graphical user interface and used for additional control algorithms.
The PHC also captures data and commands from the power system operator for the V2G service, and transmits them to the vehicle.
Table of contents :
List of Figures
List of Tables
Chapter 1. Introduction
1.1. Motivation and Objectives
1.1.1. Electrical System Architecture
1.1.2. DC Systems
1.1.3. Terminal Behavioral Modeling
1.2. Thesis Outline
Chapter 2. AC-Based Renewable Energy Nanogrid
2.1. AC Nanogrid
2.1.1. System Description
2.1.2. Modes of Operation
2.1.3. System Realization
2.1.4. Experimental Results
2.1.5. Conclusion
Chapter 3. DC-Based Renewable Energy Nanogrid
3.1. Contemporary Home Electrical Architecture
3.2. DC Nanogrid
3.3. The Main Characteristics of the DC Nanogrid System
3.4. Static Operation of a DC Nanogrid
Chapter 4. Modeling and Operation of a DC Nanogrid
4.1. Average Model
Chapter 5. Terminal Behavioral Modeling
5.1. Open- and Closed-loop Converter Model
5.2. Terminal identification of general behavioral model for dc-dc converters
5.3. Verification of the terminal behavioral modeling with the regulated buck and regulated boost converter
5.4. Experimental Validation of the Terminal Behavioral Modeling
5.5. Terminal Behavioral Model of Sources and Loads
5.6. System Level Terminal Behavioral Models
Chapter 6. Non-linear, Hybrid Terminal Behavioral Models
6.1. Hybrid model of dc-dc converters
6.1.1. Static Model
6.1.2. Dynamic Model
6.1.3. Hybrid Model
6.2. Generic Hybrid Model of the Source and Load
6.2.1. Generic static model of the source and load
6.2.2. Generic Dynamic Model of the Source and Load
6.2.3. Generic Hybrid Model of the Source and Load
6.3. Verification of Hybrid Models in the System Level Simulation
Chapter 7. Conclusions and Future Work
Appendix. Matlab Codes Used for Identification in the Frequency Domain
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