Sumedha Rajakaruna

ZigBee-Based Communication System for Data Transfer Within Future Microgrids

A wireless data communication system for future microgrids (MGs) is presented in this paper. It is assumed that each MG has a central controller and each distributed generation unit in the MG has a local controller. The communication system is responsible for transmitting and receiving data amongst these controllers. This communication system is based on ZigBee technology, which is a low cost and low power consumption device. However, its main limitation is the low data transfer rate. To reduce the number of data transactions, a data management scheme is presented in this paper. The required data to be transferred are defined and a suitable coding is proposed. Finally, the number of transmitted symbols and the processing time of the proposed data management scheme are numerically analyzed. In addition, the dynamic operation of an MG is evaluated considering the delays that are imposed by this communication system.

Static Compensators (STATCOMs) in Power Systems

A static compensator (STATCOM), also known as static synchronous compensator, is a member of the flexible alternating current transmission system (FACTS) devices. It is a power-electronics based regulating device which is composed of a voltage source converter (VSC) and is shunt-connected to alternating current electricity transmission and distribution networks. The voltage source is created from a DC capacitor and the STATCOM can exchange reactive power with the network. It can also supply some active power to the network, if a DC source of power is connected across the capacitor. A STATCOM is usually installed in the electric networks with poor power factor or poor voltage regulation to improve these problems. In addition, it is used to improve the voltage stability of a network. This book covers STATCOMs from different aspects. Different converter topologies, output filters and modulation techniques utilized within STATCOMs are reviewed. Mathematical modeling of STATCOM is presented in detail and different STATCOM control strategies and algorithms are discussed. Modified load flow calculations for a power system in the presence of STATCOMs are presented. Several applications of STATCOMs in transmission and distribution networks are discussed in different examples and optimization techniques for defining the optimal location and ratings of the STATCOMs in power systems are reviewed. Finally, the performance of the network protection scheme in the presence of STATCOMs is described. This book will be an excellent resource for postgraduate students and researchers interested in grasping the knowledge on STATCOMs.

Control, operation and power sharing among parallel converter-interfaced DERs in a microgrid in the presence of unbalanced and harmonic loads

This paper demonstrates power management and control of DERs in an autonomous MG. The paper focuses on the control and performance of converter-interfaced DERs in voltage controlled mode. Several case studies are considered for a MG based on the different types of loads supplied by the MG (i.e. balanced three-phase, unbalanced, single-phase and harmonic loads). DERs are controlled by adjusting the voltage magnitude and angle in their converter output through droop control, in a decentralized concept. Based on this control method, DERs can successfully share the total demand of the MG in the presence of any type of loads. This includes proper total power sharing, unbalanced power sharing as well as harmonic power sharing, depending on the load types. The efficacy of the proposed power control, sharing and management among DERs in a microgrid is validated through extensive simulation studies using PSCAD/EMTDC.

Plug In Electric Vehicles in Smart Grids

This book focuses on the state of the art in worldwide research on applying optimization approaches to intelligently control charging and discharging of batteries of Plug-in Electric Vehicles (PEVs) in smart grids. Network constraints, cost considerations, the number and penetration level of PEVs, utilization of PEVs by their owners, ancillary services, load forecasting, risk analysis, etc. are all different criteria considered by the researchers in developing mathematical based equations which represent the presence of PEVs in electric networks. Different objective functions can be defined and different optimization methods can be utilized to coordinate the performance of PEVs in smart grids. This book will be an excellent resource for anyone interested in grasping the current state of applying different optimization techniques and approaches that can manage the presence of PEVs in smart grids.

High-Efficiency Control of Internal Combustion Engines in Blended Charge Depletion/Charge Sustenance Strategies for Plug-In Hybrid Electric Vehicles

This paper realizes a novel control strategy for the fuel consumption reduction in plug-in hybrid and hybrid electric vehicles having an internal combustion engine (ICE) and one or more motor/generators. The proposed control strategy combines power balancing and variable speed control to achieve a more efficient utilization of fossil fuel energy that is consumed over standardized drive cycles. Furthermore, a high-efficiency region in the ICE performance map is utilized to aid with energy management decisions. For the test bench, three vehicle models have been developed in ADVISOR (the software package utilized in this paper) using available measured data. After verifying the accuracy of models, the proposed control strategy is implemented in the three vehicles to demonstrate reduced fuel consumption. The proposed control strategy is applicable to parallel-connected and power-split-connected topologies.

Review of PHEV and HEV operation and control research for future direction

This paper identifies recent plug-in hybrid electric vehicle (PHEV) and hybrid electric vehicle (HEV) literature for the purpose of analysis in determining future direction. The authors have utilized and expanded on a procedure for analyzing control strategies which is found in Wirasingha et al. The existing procedure allocates control strategies into the four categories previously determined optimization based blended control, rule based blended control, multi-mode control, and hybrid only control and is given the heading control paradigms in this paper. Extending on this control strategy classification in the identification of the control paradigms, the ranking of individual controllers is undertaken in the control schemes section of this paper, to scrutinize the advantages and disadvantages of each system. This ranking system identifies three control strategies of significant interest to PHEV and HEV operation; predictive optimization, adaptive equivalent consumption minimization strategy (A-ECMS), and online optimization controllers. Additionally the analysis completed identifies a comparison of selected controller performance attributes namely: accuracy, computational complexity, a priori knowledge and portability, which determine the potential outcomes of integrating control systems with the respective strategies. From the analysis of existing literature the summary of this article realizes the PHEV and HEV operation and control design criteria that have shown significant improvements to performance and that are of particular importance for future design integration and implementation.

Secondary Control in Microgrids for Dynamic Power Sharing and Voltage/Frequency Adjustment

This paper discusses the operation of the central controller for a microgrid. The central controller is responsible to maintain the voltage and frequency of the microgrid within the acceptable ranges while the distributed energy resources supply the required power demand of the loads based on the droop control. The desired ratio among the output active power of the distributed energy resources is determined by the distribution network tertiary controller. To achieve a dynamic variation for the output active power ratios among the distributed energy resources, the central controller has to adjust the references of the rated active power and the droop control coefficients. As this may lead to unacceptable voltage and frequency in the microgr-id, the central controller has to adjust the references of the voltage and frequency consequently. The proposed central controller strategy for the microgrid is validated through PSCAD/EMTDC simulations.

Autonomous operation of multiple interconnected microgrids with self-healing capability

This paper shows how multiple interconnected microgrids can operate in autonomous mode in a self-healing medium voltage network. This is possible if based on network self-healing capability, the neighbour microgrids are interconnected and a surplus generation capacity is available in some of the Distributed Energy Resources (DERs) of the interconnected microgrids. This will reduce or prevent load shedding within the microgrids with less generation capacity. Therefore, DERs in a microgrid are controlled such that they share the local load within that microgrid as well as the loads in other interconnected microgrids. Different control algorithms are proposed to manage the DERs at different operating conditions. On the other hand, a Distribution Static Compensator (DSTATCOM) is employed to regulate the voltage. The efficacy of the proposed power control, sharing and management among DERs in multiple interconnected microgrids is validated through extensive simulation studies using PSCAD/EMTDC.

Operation and Control of a Hybrid AC-DC Nanogrid for Future Community Houses

A hybrid AC-DC nanogrid (NG) can be considered as the power supply system for future community houses. In this paper, the operation and control of a NG are presented. The NG consists of an AC bus and a DC bus, interconnected through a tie-converter. Each bus may have several loads and micro sources. The NG should have an adequate generation capacity to supply its loads in off-grid mode as well as the capability of exchanging power with the utility grid. The tie-converter exchanges the power between two buses and regulates bus voltage in both buses in the case of off-grid operation. Several case studies are presented using PSCAD/EMTDC to verify the NG dynamics.

Design and modeling of a hundred percent renewable energy based suburban utility

This paper presents the complete system modelling, designing and controlling of an islanded minigrid power supply to the town of Carnarvon, Western Australia. Carnarvon power system is an isolated network supplying power to approximately 5000 people via 205km of distribution lines. The existing power system is supplied by a number of large centralized 21MW Diesel Generators. The objective of this paper is to report the design, development and installation of a Photovoltaic (PV) diesel hybrid-power system such that the operating cost can be minimized and the load on the aging generators could be significantly reduced. The proposal includes the installation of two 25kW DC variable speed diesel generators and a suitably sized advanced battery bank at each suburban transformer to ensure hundred percent penetration of solar power by residential customers in the local area. This method of control is modelled and simulated in HOMER, PSpice and Matlab. The different modes of control used to integrate maximum solar energy, reduce diesel consumption and also the methodology imposed to store excess renewable energy for operation during the night.