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

A standard repetitive controller (RC) is theoretically able to replace a bank of resonant controllers in harmonic signals tracking applications. However, the traditional RC has some drawbacks such as a poor dynamic response and a complex structure to compensate grid frequency deviations for an effective unified power quality conditioner (UPQC) control scheme. In order to solve these problems, an improved RC with an outstanding dynamic response and a simplified grid frequency adaptive scheme is proposed for UPQC control systems in this paper. The control strategy developed for the UPQC has delay time, i.e., one-sixth of a fundamental period (Tp/6), repetitive controllers. As a result, the UPQC system can provide a fast dynamic response along with good compensation performance under both nonlinear and unbalanced loads. Furthermore, to guarantee the excellent performance of the UPQC under grid frequency deviations, a grid frequency adaptive scheme was developed for the RC using a simple first order Pade’s approximation. When compared with other approaches, the proposed control method is simpler in structure and requires little computing time. Moreover, the entire control strategy can be easily implemented with a low-cost DSP. The effectiveness of the proposed control method is verified through various experimental tests.

/pdf/versatile-upqc-control-system-with-a-modified-repetitive-47qmg8tlym.pdf

Versatile UPQC Control System with a Modified Repetitive Controller under Nonlinear and Unbalanced Loads

This paper introduces a simple grid-voltage-sensorless control scheme for single-phase power factor correction (PFC) boost converters. The grid voltage waveform is obtained based on the dc output voltage, the switching duty ratio, and a phase-lead compensator. In addition, the duty ratio feedback is utilized to obtain the unity input power factor and the zero harmonic current. The proposed control scheme is designed and mathematically analyzed based on a small-signal model of PFC boost converters. To verify the effectiveness of the proposed control scheme, several simulations and experiments are carried out in two applications: an industrial power system with a 60 Hz grid frequency and a commercial aircraft application with a 400 Hz grid frequency.

/pdf/a-simple-grid-voltage-sensorless-control-scheme-for-pfc-560gycc7di.pdf

A Simple Grid-Voltage-Sensorless Control Scheme for PFC Boost Converters

This paper introduces a low cost, high efficiency, high performance three-phase unified power quality conditioner (UPQC) by using four-switch three-phase inverters (FSTPIs) and an extra capacitor in the shunt active power filter (APF) side of the UPQC. In the proposed UPQC, both shunt and series APFs are developed by using FSTPIs so that the number of switching devices is reduced from twelve to eight devices. In addition, by inserting an additional capacitor in series with the shunt APF, the DC-link voltage in the proposed UPQC can also be greatly reduced. As a result, the system cost and power loss of the proposed UPQC is significantly minimized thanks to the use of a smaller number of power switches with a lower rating voltage without degrading the compensation performance of the UPQC. Design of passive components for the proposed UPQC to achieve a good performance is presented in detail. In addition, comparisons on power loss, overall system efficiency, compensation performance between the proposed UPQC and the traditional one are also determined in this paper. Simulation and experimental studies are performed to verify the validity of the proposed topology.

/pdf/low-cost-and-high-performance-upqc-with-four-switch-three-y8co4wbjcw.pdf

Low cost and high performance UPQC with four-switch three-phase inverters

In this paper, we optimize a hybrid energy storage system that includes a supercapacitor and a battery storage system for economical dispatching of the intermittent wind power source. In the optimal hybrid energy storage system, based on the technical merits of each storage, the supercapacitor is used to compensate a short-term wind power fluctuation, whereas the battery plays as a long-term one to dispatch a stable power into grid. In order to allocate optimally the power flow between two storages, the supercapacitor power is effectively determined based on a zero-phase low-pass filter, and the battery power commits an average dispatching method to stabilize the power dispatch. To obtain the optimal capacity in hybrid energy storage system (HESS), the smoothing time constant of the zero-phase low-pass filter in each dispatching interval is optimized by using the particle swarm optimization (PSO) method. In order to evaluate the proposed optimal system, a numerical example is performed using a 3-MW wind turbine generator with a real wind speed data.

An optimal hybrid supercapacitor and battery energy storage system in wind power application

This paper introduces a low cost high performance three-phase unified power quality conditioner (UPQC) by using four-switch three-phase inverters. In the proposed UPQC, both shunt and series active power filters (APFs) are developed by using four-switch three-phase inverters so that the number of switching devices in the proposed topology is reduced from twelve in the traditional UPQC down to eight devices. In addition, by inserting an additional capacitor in series with the shunt APF, the DC-link voltage in the proposed UPQC can also be greatly lessened. As a consequence, by using a smaller number of power switches with lower rating voltage in the proposed UPQC system, we can greatly reduce the system cost of the UPQC without degrading the harmonic compensation performance. Design of passive components for the proposed UPQC to achieve a good performance is discussed in detail in this paper. Simulation studies are performed to verify the effectiveness of the proposed topology.

Hong-Hee Lee

Papers

Versatile UPQC Control System with a Modified Repetitive Controller under Nonlinear and Unbalanced Loads

A Simple Grid-Voltage-Sensorless Control Scheme for PFC Boost Converters

Low cost and high performance UPQC with four-switch three-phase inverters

An optimal hybrid supercapacitor and battery energy storage system in wind power application

A low cost high performance UPQC for current and voltage harmonics compensations