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 introduces a distributed power sharing strategy for the droop-controlled microgrids in which the power sharing errors and frequency/voltage deviations are completely eliminated based on the distributed cooperative control. The proposed strategy requires only a spare communication network in which the DG unit uses local and its neighbors’ information to execute the control algorithm. In the proposed strategy, a virtual-impedance-regulator based on the consensus algorithm is developed to eliminate the power sharing errors in the islanded microgrid in spite of the load condition changes, and a modified droop controller based on the neighbors’ power information is also introduced to cope with the frequency and voltage deviation issue. The proposed method does not use any information such as the feeder impedances, or the detailed microgrid configuration. The feasibility and effectiveness of the proposed method are also verified through digital simulation on an islanded microgrid system.

Distributed Power Sharing Strategy for Islanded Microgrids without Frequency and Voltage Deviations

In the paper, a novel analysis of carrier based PWM methods for multilevel inverters is presented The space vector PWM and carrier based PWM correlations are investigated in a nominal two-level switching diagram The obtained results will be applied to design various carrier PWM techniques In this paper, a carrier based single-state PWM technique, which reduces number of switchings and optimizes active voltage errors will be presented This technique can be advantageous in high level inverters The carrier base PWM approach shows a flexible offset control The proposed method is mathematically formulated and demonstrated by simulation and experimental results

Carrier Based Single-state PWM Technique In multilevel Inverter

This paper develops a harmonic compensation approach for the stator output voltage of a stand-alone doubly fed induction generator (DFIG) feeding a nonlinear (diode rectifier) load. This load type is characterized by a nonsinusoidal stator voltage consisting of severe harmonic components, fifth and seventh ones, which deteriorate the performance of other loads connected to the DFIG. The aim of the proposed compensation method is to eliminate these harmonics in order for the DFIG to deliver a pure sinusoidal stator voltage. To this end, the proposed compensation method is investigated in the fundamental synchronous rotating reference frame based on a proportional integral (PI) plus a resonant current controller, which is tuned at sixth resonant frequency. Therefore, the proposed control scheme has capability of eliminating both fifth and seventh harmonics without decomposing 5th negative sequence and 7th positive sequence components of the measured rotor current. The whole control scheme is implemented in the rotor-side converter (RSC). The proposed method was tested by simulations and experiments with 2.2kW DFIG feeding a nonlinear load to verify the feasibility and effectiveness in terms of harmonic compensation performance.

Elimination of voltage harmonics in a stand-alone DFIG using a PI-R controller in the fundamental reference frame

This paper proposes an adaptive virtual power rating method for state of charge (SoC) balancing among distributed battery units (BUs) in a DC microgrid The virtual power rating is flexibly determined according to the SoC to obtain the droop gain of BU, and the balanced SoC is achieved by means of the modified droop controller Because an accurate power sharing among BUs is satisfied by using only virtual power rating, SoC balancing performance is consistently ensured regardless of the line resistance difference Moreover, the voltage restoration to keep the grid voltage at a desired value is easily realized without PI controller, and the proposed control strategy is implemented based on the distributed control method with simple low-bandwidth communication The system stability is investigated, and the performance of the control method is demonstrated through both simulations and experiments

State of Charge Balancing for Distributed Battery Units Based on Adaptive Virtual Power Rating in a DC Microgrid

Maximum power point tracking techniques play an important role in improving the efficiency of photovoltaic generation system. Among various schemes, the incremental conductance (INC) method is mostly discussed in literature because of its superb tracking ability in irradiance and temperature changes. However, because the conventional INC algorithms adopt a simple duty-cycle updating law that is mainly based on the polarity information of the peak-power evaluation function, it is not possible to maximize the performance in transient as well as steady-state conditions. In order to mitigate above limitations, this paper proposes a novel regulated INC (r-INC) method. Just as a compensator in an automatic control system, it applies a digital filtering to the evaluation function and enhances the power tracking capability. Mathematical modeling of the new MPPT system also has been presented to aid the optimized design process. Comparative test results with a 120W boost peak power tracker verify the superiority of the proposed method over the conventional ones.

Hong-Hee Lee

Papers

Distributed Power Sharing Strategy for Islanded Microgrids without Frequency and Voltage Deviations

Carrier Based Single-state PWM Technique In multilevel Inverter

Elimination of voltage harmonics in a stand-alone DFIG using a PI-R controller in the fundamental reference frame

State of Charge Balancing for Distributed Battery Units Based on Adaptive Virtual Power Rating in a DC Microgrid

A regulated incremental conductance (r-INC) MPPT algorithm for photovoltaic system