The Use of System in the Loop, Hardware in the Loop, and Co-modeling of Cyber-Physical Systems in Developing and Evaluating New Smart Grid Solutions

This paper deals with two issues: development of some advanced smart grid applications, and implementation of advanced testbeds to evaluate these applications. In each of the development cases, the role of the testbeds is explained and evaluation results are presented. The applications cover the synchrophasor systems, interfacing of microgrids to the main grid, and cybersecurity solutions. The paper hypothesizes that the use of the advanced testbeds is beneficial for the development process since the solution product-to-market cycle may be shortened due to early real-life demonstrations. In addition, solution users’ feedback to the testbed demonstration can be incorporated at an early stage when making the changes is not as costly as doing it at more mature development stages

Real time adaptive relay settings for Microgrid protection verified using Hardware in Loop

Microgrids with penetration of renewables is imposing new challenges for system protection. Renewables are characterized with high source impedance which limit the short circuit current. The value of short-circuit current is limited due to converters used which limit the current to a maximum of 1.1 to 1.5 times maximum rated load current. This can result in faults during the islanded mode of microgrid to go unnoticed if the relay settings are not adapted to account for it. The presence of such uncleared faults in the microgrid can result in exposing it to overcurrent for a long time which can damage the equipment. One solution is to have different protection element pickup settings for different modes of operation. This report discusses the development of an algorithm to switch these settings upon microgrid state changes and test the algorithm using OPAL-RT hardware in loop real-time testing with SEL-351S relay as the hardware

On the importance of characterizing virtual pmus for hardware‐in‐the‐loop and digital twin applications

open5noThis research was funded by EdgeFLEX, grant number 883710. This project received funding from the European Union’s Horizon 2020 research and innovation program.In recent years, the introduction of real‐time simulators (RTS) has changed the way of researching the power network. In particular, researchers and system operators (SOs) are now ca-pable of simulating the complete network and of making it interact with the real world thanks to the hardware‐in‐the‐loop (HIL) and digital twin (DT) concepts. Such tools create infinite scenarios in which the network can be tested and virtually monitored to, for example, predict and avoid faults or energy shortages. Furthermore, the real‐time monitoring of the network allows estimating the status of the electrical assets and consequently undertake their predictive maintenance. The success of the HIL and DT application relies on the fact that the simulated network elements (cables, gener-ation, accessories, converters, etc.) are correctly modeled and characterized. This is particularly true if the RTS acquisition capabilities are used to enable the HIL and the DT. To this purpose, this work aims at emphasizing the role of a preliminary characterization of the virtual elements inside the RTS system, experimentally verifying how the overall performance is significantly affected by them. To this purpose, a virtual phasor measurement unit (PMU) is tested and characterized to understand its uncertainty contribution. To achieve that, firstly, the characterization of a virtual PMU calibrator is described. Afterward, the virtual PMU calibration is performed, and the results clearly highlight its key role in the overall uncertainty. It is then possible to conclude that the characterization of the virtual elements, or models, inside RTS systems (omitted most of the time) is fundamental to avoid wrong results. The same concepts can be extended to all those fields that exploit HIL and DT capa-bilities.openMingotti A.; Costa F.; Cavaliere D.; Peretto L.; Tinarelli R.Mingotti A.; Costa F.; Cavaliere D.; Peretto L.; Tinarelli R

A review on protective relays’ developments and trends

One of the most complex disciplines in electrical engineering is power system protection which requires not only the proper understanding of the different components of a power system and their behaviours but also a good knowledge and analysis of the abnormal circumstances and failures that can occur in any element of a power system. Moreover, the rapid changing and development in relays principles as well as in their technologies are additional factors that oblige those people working in the field to expand and update continuously their knowledge. In this paper, we shed light in the evolution of protective relays since the onset of electrical energy to currently. We try also to foresee the future prospects and trends in this area

A review on protective relays’ developments and trends

One of the most complex disciplines in electrical engineering is power system protection which requires not only the proper understanding of the different components of a power system and their behaviours but also a good knowledge and analysis of the abnormal circumstances and failures that can occur in any element of a power system. Moreover, the rapid changing and development in relays principles as well as in their technologies are additional factors that oblige those people working in the field to expand and update continuously their knowledge. In this paper, we shed light in the evolution of protective relays since the onset of electrical energy to currently. We try also to foresee the future prospects and trends in this area

Near infrared tunable diode laser spectroscopy for aero engine related applications

Tunable diode laser spectroscopy is a widely used technique for recovering quantitative gas information in a range of industrial applications. Established methods often use readily available, robust and low cost optoelectronic hardware in the near-infrared, with output wavelengths that coincide with the absorption spectra of several important gas species of interest, providing a versatile platform for gas analysis instrumentation. In this work the challenges associated with the recovery of gas information from harsh detection environments, particularly for aero engine diagnostics, are considered. For stand-alone instrumentation, calibration-free direct absorption measurements are highly advantageous yet calibrated techniques employing wavelength modulation spectroscopy are often favoured due to their significantly higher sensitivities. Recent developments have enabled calibration-free line shape recovery using lock-in amplifier detection of the residual amplitude modulation in wavelength modulated signals. These techniques have significant potential in harsh environments, but the overall sensitivity is limited by distortions to the recovered line shapes at high modulation amplitudes and by large background signals that saturate the detection electronics. In this thesis, solutions to these two problems are proposed, investigated and validated. A correction function is derived that is able to account for line shape distortions at arbitrarily high modulation indices. Application of the function depends upon knowledge of the experimental modulation index and two methods for extracting this information directly from the experimental signals are described. The full correction procedure has been experimentally validated. An investigation was made into the use of autobalanced photoreceivers, typically used for common mode noise cancellation, for direct absorption measurements and in a different configuration for nulling of the residual amplitude modulation (RAM) in wavelength modulation spectroscopy. Initial measurements suggest that removal of the background RAM can increase the lock-in detection sensitivity by over an order of magnitude. In addition an external amplitude modulator has been iv shown to be an effective method for producing sensitive absorption signals that are free of distortions, recoverable at frequencies that are outside the bandwidth of most environmental noise sources. A temperature sensor based on ratio thermometry of ambient water vapour absorption was designed and evaluated. The sensor is intended to provide accurate intake gas temperature information during aero engine ground testing when misting conditions prevent standard thermocouples from providing reliable data. Direct detection and second harmonic wavelength modulation spectroscopy experiments were undertaken in an environmental chamber, over the range 273-313K, to test the potential accuracy of the proposed system. Using a second harmonic peak height method, temperature information based on a calibration was able to recover temperature measurements with precision of ±0.4K however the overall accuracy suffered from a problematic calibration drift. Three engine test campaigns are described in which a range of recovery methods and potential optical system layouts are evaluated for the purposes of intake and exhaust mounted test bed sensor systems. The effects of extreme noise conditions were observed on a variety of measurements and favourable detection and modulation options were identified for the purpose of planning proposed future engine tests. Exhaust plume measurements of high temperature water vapour on the Rolls-Royce Environmentally Friendly Engine demonstrator established the viability of temperature and concentration measurements up to 850K.Tunable diode laser spectroscopy is a widely used technique for recovering quantitative gas information in a range of industrial applications. Established methods often use readily available, robust and low cost optoelectronic hardware in the near-infrared, with output wavelengths that coincide with the absorption spectra of several important gas species of interest, providing a versatile platform for gas analysis instrumentation. In this work the challenges associated with the recovery of gas information from harsh detection environments, particularly for aero engine diagnostics, are considered. For stand-alone instrumentation, calibration-free direct absorption measurements are highly advantageous yet calibrated techniques employing wavelength modulation spectroscopy are often favoured due to their significantly higher sensitivities. Recent developments have enabled calibration-free line shape recovery using lock-in amplifier detection of the residual amplitude modulation in wavelength modulated signals. These techniques have significant potential in harsh environments, but the overall sensitivity is limited by distortions to the recovered line shapes at high modulation amplitudes and by large background signals that saturate the detection electronics. In this thesis, solutions to these two problems are proposed, investigated and validated. A correction function is derived that is able to account for line shape distortions at arbitrarily high modulation indices. Application of the function depends upon knowledge of the experimental modulation index and two methods for extracting this information directly from the experimental signals are described. The full correction procedure has been experimentally validated. An investigation was made into the use of autobalanced photoreceivers, typically used for common mode noise cancellation, for direct absorption measurements and in a different configuration for nulling of the residual amplitude modulation (RAM) in wavelength modulation spectroscopy. Initial measurements suggest that removal of the background RAM can increase the lock-in detection sensitivity by over an order of magnitude. In addition an external amplitude modulator has been iv shown to be an effective method for producing sensitive absorption signals that are free of distortions, recoverable at frequencies that are outside the bandwidth of most environmental noise sources. A temperature sensor based on ratio thermometry of ambient water vapour absorption was designed and evaluated. The sensor is intended to provide accurate intake gas temperature information during aero engine ground testing when misting conditions prevent standard thermocouples from providing reliable data. Direct detection and second harmonic wavelength modulation spectroscopy experiments were undertaken in an environmental chamber, over the range 273-313K, to test the potential accuracy of the proposed system. Using a second harmonic peak height method, temperature information based on a calibration was able to recover temperature measurements with precision of ±0.4K however the overall accuracy suffered from a problematic calibration drift. Three engine test campaigns are described in which a range of recovery methods and potential optical system layouts are evaluated for the purposes of intake and exhaust mounted test bed sensor systems. The effects of extreme noise conditions were observed on a variety of measurements and favourable detection and modulation options were identified for the purpose of planning proposed future engine tests. Exhaust plume measurements of high temperature water vapour on the Rolls-Royce Environmentally Friendly Engine demonstrator established the viability of temperature and concentration measurements up to 850K

Modeling toolkit for comparing AC vs. DC electrical distribution efficiency in buildings, A

2021 Summer.Includes bibliographical references.An increasing proportion of electrical devices in residential and commercial buildings operate from direct current (DC) power sources. In addition, distributed power generation systems such as solar photovoltaic (PV) and energy storage natively produce DC power. However, traditional power distribution is based on an alternating current (AC) model. Performing the necessary conversions between AC and DC power to make DC devices compatible with AC distribution results in energy losses. For these reasons, DC distribution may offer energy efficiency advantages in comparison to AC distribution. However, reasonably fast computation and comparison of electrical efficiencies of AC-only, DC-only, and hybrid AC/DC distributions systems is challenging because DC devices are typically (nonlinear) power-electronic converters that produce harmonic content. While detailed time-domain modeling can be used to simulate these harmonics, it is not computationally efficient or practical for many building designers. To address this need, this research describes a toolkit for computation of harmonic spectra and energy efficiency in mixed AC and DC electrical distribution systems, using a Harmonic Power Flow (HPF) methodology. The toolkit includes a library of two-port linear and nonlinear device models which can be used to construct and simulate an electrical distribution system. This dissertation includes a description of the mathematical theory and framework underlying the toolkit, development and fitting of linear and nonlinear device models, software implementation in Modelica, verification of the toolkit with laboratory measurements, and discussion of ongoing and future work to employ the toolkit to a variety of building designs

Jet mixing optimization using machine learning control

We experimentally optimize mixing of a turbulent round jet using machine learning control (MLC) following Li et al (2017). The jet is manipulated with one unsteady minijet blowing in wall-normal direction close to the nozzle exit. The flow is monitored with two hotwire sensors. The first sensor is positioned on the centerline 5 jet diameters downstream of the nozzle exit, i.e. the end of the potential core, while the second is located 3 jet diameters downstream and displaced towards the shear-layer. The mixing performance is monitored with mean velocity at the first sensor. A reduction of this velocity correlates with increased entrainment near the potential core. Machine Learning Control (MLC) is employed to optimize sensor feedback, a general open-loop broadband frequency actuation and combinations of both. MLC has identified the optimal periodic forcing with a small duty cycle as the best control policy employing only 400 actuation measurements, each lasting for 5 seconds. This learning rate is comparable if not faster than typical optimization of periodic forcing with two free parameters (frequency and duty cycle). In addition, MLC results indicate that neither new frequencies nor sensor feedback improves mixing further-contrary to many of other turbulence control experiments. The optimality of pure periodic actuation may be attributed to the simple jet flapping mechanism in the minijet plane. The performance of sensor feedback is shown to face a challenge for small duty cycles. The jet mixing results demonstrate the untapped potential of MLC in quickly learning optimal general control policies, even deciding between open- and closed-loop control.Comment: 15 pages, 14 figure