An advanced and powerful real-time digital transient network analyser

The rapid advancement of power system technologies has significantly transformed the way electrical power quality (PQ) is monitored, managed, and improved. The increasing penetration of non-linear loads, automation systems, and renewable energy sources has intensified power quality challenges, including harmonic distortion, voltage sags, voltage fluctuations, and transient disturbances. This study aims to analyze the impact of modern technological approaches on power quality enhancement in contemporary power systems. A descriptive-analytical research methodology was employed through a systematic review of recent scientific literature, international standards, and technical reports related to power quality management. The collected data were analyzed using qualitative content analysis and comparative evaluation to assess the effectiveness of automation, machine learning, Internet of Things (IoT)-based monitoring systems, and power electronic mitigation devices. The results indicate that integrated technological solutions significantly improve power quality performance compared to conventional approaches. Machine learning techniques, particularly Artificial Neural Networks, demonstrate high accuracy in disturbance classification and adaptive control, while IoT-based systems enable real-time monitoring and rapid response to power quality deviations. Furthermore, power electronic devices such as Active Power Filters, Static Var Compensators, and Dynamic Voltage Restorers effectively mitigate harmonics and stabilize voltage. However, challenges related to implementation cost, system complexity, cybersecurity, and regulatory inconsistency remain. The study concludes that an integrated, intelligent, and data-driven framework is essential for sustainable power quality management in modern power systems.

Experiences on using a workstation cluster to implement a real-time digital transient network analyzer

The authors report results confirming the practicability of a real-time digital simulator for the bulk power transmission network using a commercially available component called a transputer. The use of the method of characteristics to model transmission lines combined with the architecture of the transputer allows a parallel processor connection topology identical to that of the network, where one or more transputers are assigned per bus. There is no theoretical limit on the size of the network. Present technology allows an integration step size in real time of about 150 mu s for a full three-phase model. >

New energy sources, storage facilities, power electronics devices, advanced and complex control concepts, economic operating doctrines, and cost-optimized construction and production of machines and equipment in power systems adversely affect small-signal stability associated with local oscillations. The objective of the article is to analyze local oscillations and the causes that affect them in order to reduce their negative impact. There are no recognized analyses of the oscillations of modern operating synchronous generators exposed to new conditions in power systems. The basic idea is to perform a numerical analysis of local oscillations of a large number of synchronous generators in the power system. The paper represents the local mode data obtained from a systematic analysis of synchronous generators in the Slovenian power system. Analyzed were 74 synchronous generators of the Slovenian power system, plus many additional synchronous generators for which data were accessible in references. The mathematical models convenient for the study of local oscillations are described first in the paper. Next, the influences of transmission lines, size of the synchronous generators, operating conditions, and control systems were investigated. The paper’s merit is the applicable rules that have been defined to help power plant operators avoid stability-problematic situations. Consequently, boundaries were estimated of the eigenvalues of local modes. Finally, experiments were performed with a laboratory-size synchronous generator to assess the regularity of the numerically obtained conclusions. The obtained results enable the prediction of local oscillations’ frequencies and dampings and will be useful in PSS planning.

The future naval surface combatant will be an all-electric medium-voltage dc integrated power and energy system; capable of supporting future dynamic loads, such as electric weapons and sensors. This system will be different from typical terrestrial distribution systems in that current carrying conductors are in close proximity to the conductive ship hull structure, and there is no well-defined ‘earth’ ground. Since this system will contain a considerable amount of power electronic devices, adoption of this system will introduce harmonic content and undesirable effects, such as common-mode (ground) current through coupling of the power system and the ship's hull. Current research under the Electric Ship Research and Development Consortium aims at development of an analytical framework to characterize and simulate megawatt scale power electronic devices. The 5 MW power hardware-in-the-loop (PHIL) testbed at the Florida State University Center for Advanced Power Systems is used to interface actual power equipment, device(s) under test (DUT), to a real-time simulated environment through power amplifiers and/or actuators. To support future PHIL endeavors, it is necessary to better understand and mitigate impacts of high switching frequencies presented to the DUTs by the amplifiers of the testbed. This paper discusses the 5 MW PHIL testbed focusing on one of the amplifiers. Results from efforts for characterization and mitigation of effects from parasitic coupling to ground are presented.

Smart Grid is a cyber-physical system that incorporates Information and Communication Technologies (ICT) into the physical power system, which introduces vulnerabilities to the grid and opens the door to cyber attacks. Wide area protection is one of the most important smart grid applications that aims at protecting the power system against faults and disturbances, which makes it an attractive target to cyber attacks, aiming at compromising the reliability of the power system. Understanding the interaction between the cyber and physical components of the smart grid and analyzing the damage that cyber-attacks can do to wide area protection is very important as it helps in developing effective mitigation approaches. This paper evaluates the impact of cyber attacks on a wide area distance relay backup protection scheme in real-time, through the development of a co-simulation platform based on Real Time Digital Simulator (RTDS) and network simulator 3 (NS3) and using the IEEE-14 bus power system model.

Due to power system oscillations induced by complex interconnections, power system stability has been a major concern and will continue to be a major concern in power system operations. For improving power system stability, efforts have been directed toward damping power system oscillations. The small signal stability is the instability that has been influenced by complex interconnections. Small signal stability can be dampened with power system stabilisers (PSS). PSS, on the other hand, have certain disadvantages, such as significant variations in voltage profiles and the potential for leading power factor operations, which may reduce system stability in the face of severe disturbances. In wide multi machine power systems, using only traditional PSS can not be enough to dampen inter-area oscillations and the effect of voltage profile variation. Power electronic devices known as Flexible Alternating Current Transmission System (FACTS) devices, on the other hand, are good at damping inter-area oscillations and can handle voltage variations. As a result, based on computational intelligence techniques, this paper provides a thorough analysis and evaluation of PSS and FACTS power oscillation damping (POD) controllers in reducing low frequency oscillations. The importance of technical paper publications on PSS and FACTS-based controller design, optimum location, and parameter tuning is highlighted. Finally, the potential future research directions for novel PSS and FACTS devices is proposed as a reference for interested researchers.

Development of digital simulators for transient analysis of electric power systems has been the subject of many research works during the last four decades. In most studies, the simulation can be done off-line but in some particular situations, usually equipment testing, it may be mandatory to have the simulation executed in real time so that the interaction with real equipments can be studied. Digital Real Time Power System Simulators, DRTPSS for short, became a mandatory tool to ensure the quality of power systems. Most of the DRTPSSs in use nowadays are based on high performance parallel processors using last generation technology. Recently, some works have proposed new architectures based on the use of FPGAs ("Field Programmable Gate Arrays") as a mean to increase the simulator's processing power without increasing its cost too much. This work shows how FPGAs can be used to implement a DRTPSS capable of simulating large electrical networks including high frequency power electronic devices.

As the power system develops towards a high proportion of renewable energy sources and power electronic devices, the power system suffers from poor frequency stability due to the lack of synthetic inertia. The grid-forming energy storage can not only improve the frequency dynamic response of the generator and enhance inertia support capability but can also realize the peak regulation and valley filling of the power system. But its relatively high configuration cost restricts its development and construction. Therefore, how to rationally configure the grid-forming energy storage and grid-following energy storage within the power system by means of corresponding technical approaches has become the focal point of academic research. This study proposes a method for evaluating the inertia distribution characteristics of the power system based on the network equations of the power system. Furthermore, the demand for grid-forming energy storage at each node of the power system under different operation scenarios can be quantified according to this method. Finally, an optimization configuration method for an energy storage system that can improve the inertia distribution characteristics of the power system is proposed, and its effectiveness is verified through the 39-bus system.

Electromagnetic transients are the tidal waves of electric power systems. These momentary voltage surges generally lasting only fractions of a second can be powerful enough to disrupt normal operations and even cause serious damage to major pieces of equipment, such as transformers. Created by lightning, line faults, substation switching functions, and other sudden events along a utility network, transients must be taken into account both in choosing equipment ratings for a power system and in setting its operating parameters. Like the builders of a seawall that must withstand the highest expected waves from the ocean, engineers trying to guard against damage from transients face an extraordinary design task. Most of the huge computer simulation codes related to power systems either model steady-state conditions or deal with system stability problems. The analysis of electromagnetic transients, on the other hand, requires a much more detailed examination of how some critical portion of a power system will react to conditions that can change greatly in microseconds. For many years, simulation of transient effects was performed by special-purpose analog computers called transient network analyzers (TNAs). These machines, which are still in use, recreate a portion of the power system in miniature, complete with voltage sources representing generators and various kinds of capacitive or inductive loads. TNAs are generally adequate but relatively inflexible, tedious to set up, and cumbersome to use. Once a system configuration is modeled, many simulations can be performed. Given the need to manually reconfigure TNA circuits to represent changes in a system, however, the analyzers can also be quite expensive to use. During the late 1960s, Herman Dommel of the Bonneville

Power electronic devices such as HVDC and FACTS can be used to improve the damping of poorly damped inter-area modes in large power systems. This involves the use of wide-area feedback signals, which are transmitted via communication networks. The performance of the closed-loop system is strongly influenced by the delay associated with wide-area signals. The random nature of this delay introduces a switched linear system model. The stability assessment of such a system requires linear matrix inequality based approaches. This makes the stability analysis more complicated as the system size increases. To address this challenge, this paper proposes a delay-processing strategy that simplifies the modelling and analysis in discrete-domain. In contrast to the existing stability assessment techniques, the proposed approach is advantageous because the stability, as well as damping performance, can be accurately predicted by a simplified analysis. The proposed methodology is verified with a case study on the 2-area 4-machine power system with a series compensated tie-line. The results are found to be in accordance with the predictions of the proposed simplified analysis.

With the increasing penetration of wind and solar renewable energy into modern power systems, grids exhibit ‘dual-high’ (i.e., a high proportion of both renewable energy and power electronic devices) and ‘dual-low’ (i.e., low equivalent rotational inertia and low short-circuit capacity) structural characteristics. This leads to critical challenges, notably insufficient short-circuit capacity, declining voltage and frequency stability, and weakened system damping. To address the stability requirements of new power systems, this study proposes and systematically investigates a variable-speed synchronous condenser based on AC excitation technology. The research encompasses the operational principles, starting mechanisms, and control strategies of the device, with a particular focus on analyzing its stator-flux-oriented vector control method and active–reactive power decoupling regulation mechanism. By independently adjusting the frequency, amplitude, and phase of the AC excitation on the rotor side, the system achieves a millisecond-level dynamic reactive power response, rapid frequency support, and self-starting capability without the need for external starting devices. To validate the effectiveness of the theoretical analysis and engineering practicality, this study presents grid-connected operational tests using a 3600 kVar engineering prototype at a wind farm. The test results demonstrate that the variable-speed synchronous condenser performs excellently in speed regulation, dynamic reactive power response, and primary frequency modulation. It effectively provides short-circuit capacity, enhances system damping, and significantly improves the voltage and frequency stability of power grids with high penetration of renewable energy. This study offers innovative technical pathways and empirical evidence for constructing a stability support system that meets the developmental needs of new power systems. It holds significant theoretical value and engineering guidance for promoting the smooth transition of power grids from synchronous machine-dominated to power electronics-based architectures.

With the increasing demands of modern industrial society on the capacity and reliability of the power supply system, distributed power supply system control technology has emerged. In the context of a large number of mature power electronics technologies, power systems are gradually evolving into power electronics, and more and more power electronic devices are emerging in power systems. In today's power technology transformation field, multi-inverter parallel operation control technology has become a research trend. It can not only expand the power supply capacity but also makes the system more stable and reliable. Firstly, this paper introduces the main problem of parallel operation of multi-inverter, namely the circulation between inverters. According to the analysis of the circulation problem, the control method of the parallel operation of a multi-inverter is introduced. The non-interconnected control technology of drooping control has obvious advantages and development potential. Finally, according to the principle of drooping control, some new improved control methods are introduced, and it is pointed out that drooping control technology will become the mainstream of the development of parallel control technology of inverter in the future, and the development trend of this kind of control technology is forecasted.

Bridge rectifier of three-phases is has widely applications in power systems. This rectifier consummates a wave form that has been shaped by a non-linear of the input current, though in the power system. The harmonic parts caused by such power electronic devices have critical effects on a number of aspects of power networks, particularly, on distribution. In accumulation, the value of Total Harmonic Distortion (THD) is high; it causes unwanted distortion on the sinusoidal figure of the wave for the input current. The outcomes propose a new circuit for a three-phase rectifier, making use of harmonic current injection method. The MATLAB software has been used to simulate the proposed circuit. A prototype has been developed to prove the actual results and compare them with the simulation results of the proposed circuit. The proposed circuit applies active harmonic current injection method with a capacitor bank, which, compared to conventional circuits, is not sophisticated. The model has been verified with feedback injection harmonic current to demonstrate the strength of the system. The evaluation of the simulation results and experimental outcomes from the prototype represents an unimportant difference. The proposed circuit has minimized the THD drawn from the input current supply down to 5.5%.

Chapter 31 - Power Electronics Applications in Smart Grid