A communication infrastructure is an essential part to the success of the emerging smart grid. A scalable and pervasive communication infrastructure is crucial in both construction and operation of a smart grid. In this paper, we present the background and motivation of communication infrastructures in smart grid systems. We also summarize major requirements that smart grid communications must meet. From the experience of several industrial trials on smart grid with communication infrastructures, we expect that the traditional carbon fuel based power plants can cooperate with emerging distributed renewable energy such as wind, solar, etc, to reduce the carbon fuel consumption and consequent green house gas such as carbon dioxide emission. The consumers can minimize their expense on energy by adjusting their intelligent home appliance operations to avoid the peak hours and utilize the renewable energy instead. We further explore the challenges for a communication infrastructure as the part of a complex smart grid system. Since a smart grid system might have over millions of consumers and devices, the demand of its reliability and security is extremely critical. Through a communication infrastructure, a smart grid can improve power reliability and quality to eliminate electricity blackout. Security is a challenging issue since the on-going smart grid systems facing increasing vulnerabilities as more and more automation, remote monitoring/controlling and supervision entities are interconnected.

https://digitalcommons.unl.edu/cgi/viewcontent.cgi?article=1315&context=electricalengineeringfacpub

A Survey on Smart Grid CommunicationInfrastructures: Motivations, Requirements andChallenges

A recurrent neural network based health indicator for remaining useful life prediction of bearings

Electrifying transportation is a promising approach to alleviate the climate change issue. The adoption of electric vehicle into market has introduced significant impacts on various fields, especially the power grid. Various policies have been implemented to foster the electric vehicle deployment and the increasing trend of electric vehicle adoption in the recent years has been satisfying. The continual development of electric vehicle power train, battery and charger technologies have further improved the electric vehicle technologies for wider uptake. Despite the environmental and economical benefits, electric vehicles charging introduce negative impacts on the existing network operation. Appropriate charging management strategies can be implemented to cater for this issue. Furthermore, electric vehicle integration in the smart grid can bring many potential opportunities, especially from the perspective of vehicle-to-grid technology and as the solution for the renewable energy intermittency issue. This paper reviews the latest development in electric vehicle technologies, impacts of electric vehicle roll out and opportunities brought by electric vehicle deployment.

A review on the state-of-the-art technologies of electric vehicle, its impacts and prospects

This paper reviews state of the art maximum power point tracking (MPPT) algorithms for wind energy systems. Due to the instantaneous changing nature of the wind, it is desirable to determine the one optimal generator speed that ensures maximum energy yield. Therefore, it is essential to include a controller that can track the maximum peak regardless of wind speed. The available MPPT algorithms can be classified as either with or without sensors, as well as according to the techniques used to locate the maximum peak. A comparison has been made between the performance of different MPPT algorithms on the basis of various speed responses and ability to achieve the maximum energy yield. Based on simulation results available in the literature, the optimal torque control (OTC) has been found to be the best MPPT method for wind energy systems due to its simplicity. On the other hand, the perturbation and observation (P&O) method is flexible and simple in implementation, but is less efficient and has difficulties determining the optimum step-size.

A review of maximum power point tracking algorithms for wind energy systems

Impedance networks cover the entire of electric power conversion from dc (converter, rectifier), ac (inverter), to phase and frequency conversion (ac-ac) in a wide range of applications. Various converter topologies have been reported in the literature to overcome the limitations and problems of the traditional voltage source, current source as well as various classical buck-boost, unidirectional, and bidirectional converter topologies. Proper implementation of the impedance-source network with appropriate switching configurations and topologies reduces the number of power conversion stages in the system power chain, which may improve the reliability and performance of the power system. The first part of this paper provides a comprehensive review of the various impedance-source-networks-based power converters and discusses the main topologies from an application point of view. This review paper is the first of its kind with the aim of providing a “one-stop” information source and a selection guide on impedance-source networks for power conversion for researchers, designers, and application engineers. A comprehensive review of various modeling, control, and modulation techniques for the impedance-source converters/inverters will be presented in Part II.

Impedance-Source Networks for Electric Power Conversion Part I: A Topological Review

This paper presents an enhanced control algorithm for stand-alone DFIG system under unbalanced load condition with reduced current sensors at stator side. The unbalanced load regularly causes the stator current/voltage unbalance and the rotor current contains harmonic components. In order to overcome this problem, a control method is investigated based on the load side converter (LSC). In this control method, the negative sequence components of the line current of LSC are generated to compensate the unbalanced stator current. In addition, only the rotor current is used as the feedback signal to compensate the unbalanced stator current. Thus, the current sensors installed at load and stator side are totally removed, so that the number of current sensors employed in system is reduced. The simulation and experimental results are provided to verify the effectiveness of the proposed method.

An enhanced control algorithm for stand-alone DFIG system feeding unbalanced loads with reduced current sensors

This paper investigates a multilevel combined NPC converter for medium-and high-power energy storage systems and active power filters. The proposed multilevel NPC converter is composed of a parallel connection of multiple NPC converters using the current sharing reactors and involves the phase shifted PWM strategy for better energy quality performance. Using the switching function-based mathematical model, the proposed multilevel converter is evaluated to show the energy quality performance and fault tolerance of an energy storage system or active power filter. In addition, the switching frequency of circulating currents is analyzed to obtain its relationship with the converter parameters and maximum sharing reactor current ripple. The performance of the proposed multilevel converter is verified by simulation.

Multilevel NPC Converters in Parallel Connection for Power Conditioning Systems

This paper proposes an enhanced control strategy for unified power quality conditioner (UPQC) including a series and a shunt active power filter (APF) to compensate harmonics in the distorted supply voltage and nonlinear load current. In the series APF control scheme, a proportional-integral (PI) controller and a resonant controller tuned at six multiple of the fundamental frequency of the network (6 ω S ) are performed to compensate harmonics in distorted source, meanwhile a PI controller and three resonant controllers tuned at 6nω S (n=1, 2, 3) are designed in the shunt APF control scheme to mitigate harmonic currents produced by nonlinear loads. Thereby, the load voltage and the supply current are regulated to be sinusoidal waveforms. Performance of the UPQC is significantly improved compared to the conventional control strategy thanks to the superiority of resonant controllers. The feasibility of the proposed UPQC control scheme is validated through the simulation.

Improvement of power quality under distorted source and nonlinear load conditions

This paper develops the low-cost drive system of the small-size electric vehicles (EVs) driven by the brushed dc motor. The power circuit for driving the dc motor is designed by considering both the cost and efficiency. Some MOSFET and diodes at the power converter are connected in parallel for reducing the conduction loss. In order to change smoothly the rotating direction of dc motor, an operating sequence for both the field current and the armature voltage according to the accelerator pedal angle is suggested. Through the simulation studies and experimental results with the low-cost 8-bit AVR, the performances of the proposed methods are verified.

Development of low-cost drive system of a small-size electric vehicles

This paper proposes an enhanced control strategy for three-phase unified power quality conditioners (UPQCs) under the distorted source and nonlinear load conditions The proposed controller consists of a proportional-integral and a repetitive controller (RC), which is developed on both the series and the shunt APFs of the UPQC to compensate (6n±1) (n=1, 2, 3) harmonic voltages in distorted source voltage and those harmonic currents produced by nonlinear loads As a result, the load voltage and the supply current are compensated to be sinusoidal In the proposed RC, the delay time is reduced to be one-sixth of the fundamental period which is much shorter than that of the traditional RC, ie, one fundamental period Hence, the proposed RC provides a much faster dynamic response compared to the traditional RC The proposed control strategy is analyzed and design of the RC for the UPQC is presented in detail The feasibility of the proposed control strategy is verified through simulations

Hong-Hee Lee

Papers

An enhanced control algorithm for stand-alone DFIG system feeding unbalanced loads with reduced current sensors

Multilevel NPC Converters in Parallel Connection for Power Conditioning Systems

Improvement of power quality under distorted source and nonlinear load conditions

Development of low-cost drive system of a small-size electric vehicles

A repetitive control scheme to improve performance of UPQC under distorted source and nonlinear load conditions