This paper proposes a novel load management solution for coordinating the charging of multiple plug-in electric vehicles (PEVs) in a smart grid system. Utilities are becoming concerned about the ...potential stresses, performance degradations and overloads that may occur in distribution systems with multiple domestic PEV charging activities. Uncontrolled and random PEV charging can cause increased power losses, overloads and voltage fluctuations, which are all detrimental to the reliability and security of newly developing smart grids. Therefore, a real-time smart load management (RT-SLM) control strategy is proposed and developed for the coordination of PEV charging based on real-time (e.g., every 5 min) minimization of total cost of generating the energy plus the associated grid energy losses. The approach reduces generation cost by incorporating time-varying market energy prices and PEV owner preferred charging time zones based on priority selection. The RT-SLM algorithm appropriately considers random plug-in of PEVs and utilizes the maximum sensitivities selection (MSS) optimization. This approach enables PEVs to begin charging as soon as possible considering priority-charging time zones while complying with network operation criteria (such as losses, generation limits, and voltage profile). Simulation results are presented to demonstrate the performance of SLM for the modified IEEE 23 kV distribution system connected to several low voltage residential networks populated with PEVs.
Power quality of power systems affects all connected electrical and electronic equipment. Power quality is a measure of deviations in voltage and frequency of the particular supply system. In recent ...years, there has been a considerable increase in nonlinear loads; in particular distributed loads, such as computers, TV monitors and lighting. These draw harmonic currents which, when distorted, have detrimental effects including interference, loss of reliability, increased operating costs, equipment overheating, motor failures, capacitor failure and inaccurate power metering. This subject is pertinent to engineers involved with electric power systems, electronic equipment, computers and manufacturing equipment. This book shows readers to understand the causes and effects of power quality problems such as non-sinusoidal wave shapes, voltage outages, losses due to poor power quality, and origins of single-time events such as voltage dips, voltage reductions and outages, along with techniques to mitigate these problems.
The rapid uptake of residential photovoltaic (PV) systems is causing serious power quality issues such as significant voltage fluctuation and unbalance that are restricting the ability of networks to ...accommodate further connections. Based on the latent reactive power capability and real power curtailment of single-phase inverters, this paper proposes a new comprehensive PV operational optimization strategy to improve the performance of significantly unbalanced three-phase four-wire low voltage (LV) distribution networks with high residential PV penetrations. A multiobjective optimal power flow (OPF) problem that can simultaneously improve voltage magnitude and balance profiles, while minimizing network losses and generation costs, is defined and then converted into an aggregated single-objective OPF problem using the weighted-sum method, which can be effectively solved by the global Sequential Quadratic Programming (SQP) approach with multiple starting points in MATLAB. Detailed simulations are performed and analyzed for various operating scenarios over 24 h on a real unbalanced four-wire LV distribution network in Perth Solar City trial, Australia. Finally, smart meter readings are used to justify the validity and accuracy of the proposed optimization model and considerations on the application of the proposed PV control strategy are also presented.
This paper presents a new analysis into the impacts of various symmetrical and asymmetrical voltage sags on doubly fed induction generator (DFIG)-based wind turbines. Fault ride-through requirements ...are usually defined by the grid codes at the point of common coupling (PCC) of wind farms to the power network. However, depending on the network characteristics and constraints, the voltage sag conditions experienced at the wind generator terminals can be significantly different from the conditions at the PCC. Therefore, it is very important to identify the voltage sags that can practically affect the operation of wind generators. Extensive simulation studies are carried out in MATLAB/Simulink to investigate the transient overshoots and ripples that appear in the rotor current and dc-link voltage when the DFIG is subjected to various types of (a)symmetrical faults. For the first time, the impacts of phase-angle jump and operational constraints of circuit breakers are examined. Furthermore, the influences of sag parameters including type, initial point-on-wave instant, depth, and impedance angle are investigated. Complementary theoretical analyses are also presented to support the validity of observations made in the simulation studies.
This paper proposes a strategy for optimal integration of battery energy storage systems (BESSs) to improve the load and distributed generation (DG) hosting ability of the utility grid. An effective ...tool that determines the optimal capacity and day-ahead operation strategy for deployment of distribution network operator (DNO)-controlled BESSs is presented. It is a cost-based multiobjective optimization strategy that considers two primary factors: 1)distribution system cost; and 2)battery cycling cost. Quantitative analyses on the benefits and tradeoffs of BESS installations are carried out considering different service options. BESS is investigated for three main service options: 1)voltage regulation; 2)loss reduction; and 3)peak reduction. The performance and benefits of the optimized BESS to control one service option exclusively or multiple services simultaneously is compared. The analysis is further extended to study the effect of installation site on the size, management strategy, and the service option. Results show that optimal integration of BESSs can realize maximum operational and cost benefits while effectively elevating the load and DG hosting capability of the network. The approach is developed using MATLAB interior-point algorithm. Simulations are conducted for the medium voltage (MV) IEEE 33 bus system and a low voltage (LV) distribution network in Western Australia studied during the Perth Solar City Trial.
This paper proposes enhanced hysteresis-based current regulators in the field-oriented vector control of doubly fed induction generator (DFIG) wind turbines. The proposed control scheme is ...synchronized with the virtual grid-flux space vector, readily extractable by a quadrature phase-locked loop (QPLL) system. Identical equidistant-band vector-based hysteresis current regulators (VBHCRs) are then used to control the output currents of the rotor-side and grid-side converters. The proposed hysteresis-based technique has excellent steady-state performance and reveals several advantages in comparison with the commonly used proportional-integral (PI) current regulator, including very fast transient response, simple control structure, and intrinsic robustness to the machine parameters variations. Moreover, the fixed hysteresis bands in VBHCRs are replaced with equidistant bands to limit the instantaneous variations of the switching frequency and reduce the maximum switching frequencies experienced in the converters. Extensive simulation studies are carried out for a 1.5 MW DFIG-based wind turbine to examine the operation of the proposed vector control scheme under changing wind speed and compare its transient and steady-state performances with the conventional PI current regulators.
This paper introduces an innovative approach to Wind Turbine Blade (WTB) inspection through the synergistic use of thermal and RGB imaging, coupled with advanced deep learning techniques. We curated ...a unique dataset of 1000 thermal images of healthy and faulty blades using a FLIR C5 Compact Thermal Camera, which is equipped with Multi-Spectral Dynamic Imaging technology for enhanced imaging. This paper focuses on evaluating 35 deep learning classifiers, with a standout ensemble model combining Vision Transformer (ViT) and DenseNet161, achieving a remarkable 100% accuracy on the dataset. This model demonstrates the exceptional potential of deep learning in thermal diagnostic applications, particularly in predictive maintenance within the renewable energy sector. Our findings underscore the synergistic combination of ViT’s global feature analysis and DenseNet161’s dense connectivity, highlighting the importance of controlled environments and sophisticated preprocessing for accurate thermal image capture. This research contributes significantly to the field by providing a comprehensive dataset and demonstrating the efficacy of several deep learning models in ensuring the operational efficiency and reliability of wind turbines.
A new analysis into the steady-state operation and derating of three-phase transformers under nonsinusoidal and asymmetric operating conditions is proposed. The combined effects of transformer core ...and load asymmetry, nonlinearity, and harmonics, as well as nonsinusoidal input excitation are examined. A time-domain nonlinear model for three-phase three-leg transformers is implemented. Transformer derating is estimated by modeling additional power losses due to harmonics generated by the iron core, nonsinusoidal excitation, and nonlinear (rectifier and electric drive) loading. Laboratory tests are performed to verify simulated waveforms. The contribution of this paper is a nonlinear transformer modeling technique for steady-state operation under unbalanced, asymmetric, and nonsinusoidal operation, capable of computing derating factors.
The integration of wind turbines into modern power grids has significantly increased during the last decade. Wind turbines equipped with doubly fed induction generators (DFIGs) have been dominating ...wind power installation worldwide since 2002. In this paper, a superconducting magnetic energy storage (SMES) unit is proposed to improve the dynamic performance of a wind energy conversion system equipped with DFIG during voltage sag and voltage swell events. The converter and the chopper of the SMES unit are controlled using a hysteresis current controller and a fuzzy logic controller, respectively. Detailed simulation is carried out using MATLAB/SIMULINK software to highlight the impact of the SMES unit in improving the overall system performance under voltage sag and voltage swell conditions.
Controlling residential thermal loads and thermal energy storage is a viable tactic to engage end-users in demand response programs (DRPs). This paper focuses on the development of an optimal ...real-time thermal energy management system (TEMS) for smart homes to respond to DRP for peak-load shifting. The proposed TEMS combines two model predictive controllers to manage two thermal energy storage systems, a water storage tank (WST) and the building thermal mass, to schedule residential heat pump loads to off-peak periods. The intention is to manage the operation of a ground source heat pump (GSHP) to produce the desired amount of thermal energy by controlling the volume and temperature of the stored water in the WST while optimizing the operation of the heat distributors to control indoor temperature. The primary contributions are the development of a new control strategy for GSHPs coupled with WST based on building identification to minimize total energy consumption and cost. This paper also proposes a real-time indoor dynamic temperature set-point strategy based on real-time pricing tariffs for enhancing peak-load shifting of heat pump loads with an acceptable variation in thermal comfort. Simulation and experimental results demonstrate that the proposed TEMS has significant potential for real-time peak-load shifting.
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