Microgrid Power Sharing Framework for Software Defined Networking and Cybersecurity Analysis

Hierarchical control is a widely used strategy that can increase resilience and improve the reliability of the electrical network based on microgrid global variables. Large amounts of data required during transitions prompt the use of more reliable and flexible communications to achieve the control objectives. Such communications can involve potential cyber vulnerabilities and latency restrictions, which cannot be always addressed in real-time. To accurately capture the system’s overall operation, this paper proposes a co-simulation framework driven by flexible communications and a resilient control algorithm to regulate the frequency and voltage deviations in a networked microgrids. Model-based predictive control has been implemented, to avoid slow transient response associated with linear hierarchical control. Software-Defined Networking (SDN) is responsible for increasing the communication intelligence during the power-sharing process. The effects of critical communications and overall system performance are reviewed and compared for different co-simulation scenarios. Graphical Network Simulator (GNS3) is used in combination with model-based predictive control and SDN, to provide latency below 100 ms, as defined in IEC 61850. Testing of the proposed system under different cyber attack scenarios demonstrate its excellent performance. The novel control architecture presented in the paper provides a reference framework for future cloud computing-based microgrids

Self-powered, remotely controlled machines and tools for safety improvement in mining

This paper addresses the problem of meeting the safety requirements of mining industry for implementation of control and monitoring equipment without external wiring. Local power generation and accumulation combined with remote control and wireless data transmission are suggested as an appropriate way to make the implementation of such devices safe and convenient, which in its turn would facilitate their wider application for automation and safety improvement. A rope shovel dipper trip system is discussed in detail as an example of a self-powered remotely-controlled system. Other possible applications of the concept are also identified, such as Armoured Face Conveyor (AFC) and water jet drilling operation monitoring

Space harmonics analysis of the main air gap flux of an induction motor and its applicability to detect faults

Condition monitoring of an induction motor may be based on measuring the electrical signals, such as stator current, electromagnetic flux etc. or mechanical signals such as vibration, noise etc. from the motor. Most of the existing electrical techniques of condition monitoring and fault diagnostics are based on the stator current and/or leakage flux measurement outside the motor. Besides, most of these methods only concentrate on the time harmonics analysis of the acquired signal. But the main air gap flux consists of both time and space harmonics. The latter is overlooked by most of the existing researches. We propose to analyse the space harmonics of the main air gap electromagnetic flux along with the time domain analysis. But to do so, a thorough knowledge of the space harmonics of the stator flux, the rotor flux and their insights is needed to be obtained. To this aim, we present the space harmonics analysis of the main air gap flux of a healthy induction in this paper. Then the applicability of the space harmonics analysis to detect the faults is discussed. Two types of rotor faults, i.e. eccentricity and the broken rotor bar fault are discussed

The use of feedback quantizer PWM for shaping inverter noise spectrum

There has been a continuous development of PWM strategies addressing different inverter topologies, as well as requirements of efficiency and minimal distortion. One of such strategies recently proposed by the authors is Feedback Quantizer PWM (FBQ-PWM). In this paper we briefly describe FBQ-PWM and its fundamental differences from other PWM techniques. We then present a detailed study of FBQ-PWM application to inverter noise shaping as to avoid a particular frequency or a number of frequencies in the harmonic spectrum of the output voltage. We illustrate our study with detailed simulations in physics-based Saber environment. The paper is concluded by a summary of its main findings and notes on practical implementation

Fault diagnostics of induction motors based on internal flux measurement

A new fault diagnosis scheme based on the monitoring of main air gap flux of squirrel cage induction motors is proposed. Most of the existing flux monitoring techniques are based on the leakage or stray flux measurement outside of the motor. A few methods, however, use the main air gap flux as the fault signature, where search coils are used to monitor the derivative of the flux, which eventually introduces noise in the signal. Moreover, the diagnosis methods are mainly based on detecting a fault, whereas very little initiative has been taken to locate a fault precisely. To address these problems, a sophisticated yet robust condition monitoring and fault diagnosis method is needed. To this aim, we propose to monitor the main air gap flux using Hall Effect Flux Sensors (HEFS) at all the stator slots of an induction motor, which can be used to address the stator and rotor slot effects not only through frequency analysis of the magnetic flux, but also by magnitude and phase shift comparison of sensors located at different geometric positions around the stator. We have successfully detected the stator turn-to-turn fault at a very incipient stage and detected the location of the fault precisely. Promising results have been obtained through simulation in the case of broken rotor bar faults as well

Fault diagnosis of induction motors by space harmonics analysis of the main air gap flux

A new fault diagnosis scheme based on the monitoring of main air gap flux of the three phase squirrel cage induction motor is proposed. Most of the existing electrical techniques of condition monitoring are based on the stator current and/or leakage flux measurement outside the motor. Besides, most of these methods only concentrate on the time harmonics analysis of the acquired signal. We propose to analyse the space harmonics of the main air gap electromagnetic flux along with the time domain analysis. To this aim, we propose to monitor the main air gap flux using Hall Effect Flux Sensors (HEFS) at all the stator slots of an induction motor, which can be used to address the stator and rotor slot effects not only through frequency analysis of the time varying magnetic flux, but also by magnitude and phase shift comparison of sensors located at different geometric positions around the stator. Moreover, by using HEFS in all the stator slots, the flux density along the circumference of the stator can be acquired and the space harmonics of the flux can be analysed, which shown promising results in detecting and locating different faults. In this paper, we concentrate on detecting different types of rotor faults such as broken rotor bar fault and eccentricity

Advanced noise shaping and filter design with feedback quantizer PWM

There has been a continuous development of PWM strategies addressing different inverter topologies, as well as requirements of efficiency and minimal distortion. One of such strategies recently proposed by the authors is Feedback Quantizer PWM (FBQ-PWM). In this paper we briefly describe FBQ-PWM. We present a detailed study of different feedback filter options for noise spectrum shaping. We illustrate our study with detailed simulations and experimental results. The paper is concluded by a summary of its main findings and notes on potential applications

Introducing feedback quantizer - a novel pulse-width modulation strategy for voltage source inverters

There has been a continuous development of PWM strategies addressing different inverter topologies, as well as requirements of efficiency and minimal distortion. In this paper we present a novel PWM strategy for a voltage source inverter for AC drives which is based on the use of a Feedback Quantizer (FBQ).We begin with a simple implementation with a three phase two level inverter and show that it yields an excellent harmonic performance compared with existing methods. We then gradually introduce embellishments that add desirable properties to the FBQ-PWM, such as improved reference tracking, harmonic rejection and extended range of linear modulation. We back up our conclusions with extensive simulations in the Saber environment. Further directions of development of the proposed strategy conclude the paper

Frame alignment stability issues in natural field orientation

Natural field orientation (NFO) is a technique for generating a rotating reference frame position for an induction machine aligned with the stator flux. The term "natural" is applied because there is an implicit tendency for the rotating frame to realign with the correct stator flux frame position if there is a perturbation away from this position. However, under regeneration conditions this realignment property does not occur, and the frame position, if perturbed, will move the control reference frame away from stator flux alignment. This paper examines this frame alignment stability problem and proposes a solution that retains the features and simplicity of the NFO concept

Energy efficient trajectories of industrial machine tools with parallel kinematics

Mechanisms with parallel kinematics are receiving growing attention in industrial applications including flexible machine tools, due to superior positioning and faster performance as compared to series kinematic schemes. In addition to a precise contour forming by a PKM-based machine, its redundant degrees of freedom (DOFs) can be used to improve its energy efficiency. A new approach of tool trajectory planning is proposed in this paper which utilizes redundant DOFs to so position the tool relative to the workpiece during the contour forming that non-regenerative drives involved in the cutting process primarily stay in motoring mode. This excludes energy losses on nonregenerative breaking and significantly improves energy efficiency of milling operation. As the proposed approach reduces the order of the optimization problem, its solution included in the paper is obtained partially analytically and partially numerically. The solution is independent of inaccuracies of dynamic modeling and ensures high accuracy contour forming and stable drive operation. The paper findings are supported by experimental results obtained with the help of an industrial PKM-based machine KIM-1000