A compound current limiter and circuit breaker

© 2019 by the authors. Licensee MDPI, Basel, Switzerland. The protection of sensitive loads against voltage drop is a concern for the power system. A fast fault current limiter and circuit breaker can be a solution for rapid voltage recovery of sensitive loads. This paper proposes a compound type of current limiter and circuit breaker (CLCB) which can limit fault current and fast break to adjust voltage sags at the protected buses. In addition, it can act as a circuit breaker to open the faulty line. The proposed CLCB is based on a series L-C resonance, which contains a resonant transformer and a series capacitor bank. Moreover, the CLCB includes two anti-parallel power electronic switches (a diode and an IGBT) connected in series with bus couplers. In order to perform an analysis of CLCB performance, the proposed structure was simulated using MATLAB. In addition, an experimental prototype was built, tested, and the experimental results were reported. Comparisons show that experimental results were in fair agreement with the simulation results and confirm CLCB’s ability to act as a fault current limiter and a circuit breaker

A fast-acting protection scheme for series compensators in a medium-voltage network

In recent 20 years medium voltage networks have been becoming one of the important interfaces between the power plants and loads due to the increasing load demand as well as number of distributed generators connected to the network. This is the reason, managing the power flow, and voltage profile of the network at the lowest possible power losses and also price are of the utmost importance. The series compensators such as a static synchronous series compensator are of the most cost effective power compensators that also have the high efficiency in controlling the power flow and voltage profile. However, their drawback is their vulnerability against the short circuit. This thesis presents a new protection scheme for an SSSC in an MV network by using a varistor and thyristors to eliminate this weakness. The DC offset phenomenon is one of the main uncertainties that has been studied in the thesis. This phenomenon could cause a delay in the circuit breakers’ performance. In this thesis, the parameters of the machines that have most influence on the time when the fault current will pass the zero point have been analysed. Besides, the impact of the DC offset in the medium voltage network has been studied. Furthermore, the thermal issues have always been one of the most challenging problems for the power electronics devices. This thesis investigates a new packaging style by using the phase change material to improve the thermal managing of a press-pack thyristor during a short circuit. This packaging style is able to absorb the heat as much as required and also could decrease the thermal resistance

Analysis and Modeling of Advanced Power Control and Protection Requirements for Integrating Renewable Energy Sources in Smart Grid,

Attempts to reduce greenhouse gas emissions are promising with the recent dramatic increase of installed renewable energy sources (RES) capacity. Integration of large intermittent renewable resources affects smart grid systems in several significant ways, such as transient and voltage stability, existing protection scheme, and power leveling and energy balancing. To protect the grid from threats related to these issues, utilities impose rigorous technical requirements, more importantly, focusing on fault ride through requirements and active/reactive power responses following disturbances. This dissertation is aimed at developing and verifying the advanced and algorithmic methods for specification of protection schemes, reactive power capability and power control requirements for interconnection of the RESs to the smart grid systems. The first findings of this dissertation verified that the integration of large RESs become more promising from the energy-saving, and downsizing perspective by introducing a resistive superconducting fault current limiter (SFCL) as a self-healing equipment. The proposed SFCL decreased the activation of the conventional control scheme for the wind power plant (WPP), such as dc braking chopper and fast pitch angle control systems, thereby increased the reliability of the system. A static synchronous compensator (STATCOM) has been proposed to assist with the uninterrupted operation of the doubly-fed induction generators (DFIGs)-based WTs during grid disturbances. The key motivation of this study was to design a new computational intelligence technique based on a multi-objective optimization problem (MOP), for the online coordinated reactive power control between the DFIG and the STATCOM in order to improve the low voltage ride-through (LVRT) capability of the WT during the fault, and to smooth low-frequency oscillations of the active power during the recovery. Furthermore, the application of a three-phase single-stage module-integrated converter (MIC) incorporated into a grid-tied photovoltaic (PV) system was investigated in this dissertation. A new current control scheme based on multivariable PI controller, with a faster dynamic and superior axis decoupling capability compared with the conventional PI control method, was developed and experimentally evaluated for three-phase PV MIC system. Finally, a study was conducted based on the framework of stochastic game theory to enable a power system to dynamically survive concurrent severe multi-failure events, before such failures turn into a full blown cascading failure. This effort provides reliable strategies in the form of insightful guidelines on how to deploy limited budgets for protecting critical components of the smart grid systems

Permanent Magnet Fault Current Limiters for Electrical Power Protection Systems

The main aim of this work is to design and test a permanent magnet fault current limiter (PMFCL) to limit the fault current in electrical power system network. The (fit and forget) device presented in this thesis is based on two important aspects; the best selection of the state of the art soft and hard magnetic materials and the design topology of PMFCL. Rare earth material is used as a permanent magnet, which is the main source of excitation to keep the non-oriented silicon steel iron core in magnetic saturation state. During the normal operation of the device the saturated core offers low impedance to the grid and during the fault state the core inherently rushed to high impedance state that limits the high short circuit current. A commercial Finite Element software (FEM) was used in the device modelling techniques from the commencement till the end of the final design. The work commenced with the verifications and investigations of a recently reported model in 2D (FEM). Then, a prototype of small scale, in two design configurations of the same PMFCL specifications, was built and tested at the electrical laboratory of Sheffield Hallam University to verify the simulation results and to access the design of the PMFCL device. After that, the 11-kV PMFCL for substation distribution transformer was designed. Finally, the low voltage toroidal core PMFCL was proposed for the existing renewable energy and future wind-photovoltaic (wind-PV) step-up transformer. The dry type PMFCL current-inductance profiles were obtained by 3D (FEM) magneto static solver to predict the behaviour of the devices in the abnormal condition. The calculated RMS current, using 3D (FEM) time saving inductance-current approach, agreed with the peak transient currents obtained by the lengthy computation process time-step solver. The current limitation capability has been calculated in comparison with the air-cored of similar specifications as the PMFCL device and a useful reduction in the fault current has been achieved. The simulation results proved that the proposed PMFCL topologies (toroidal and square-shaped) can protect the renewable energy generator-transformer and real power grids from the fault current. Both the toroidal and full scale PMFCL devices initial and energy cost over an expected service of life have been evaluated. The merit of the PMFCL device is that it reduces downtime during power system’s outages by mitigating the severe fault current in the first half cycle

A Review on Superconducting Magnetic Energy Storage System Applications

Superconducting Magnetic Energy Storage is one of the most substantial storage devices. Due to its technological advancements in recent years, it has been considered reliable energy storage in many applications. This storage device has been separated into two organizations, toroid and solenoid, selected for the intended application constraints. It has also been used in many industries, such as transportation, renewable energy utilization, power system stabilization, and quality improvement. This chapter discusses various SMES structures and their applications in electric and power systems. Here, the authors try to deliver a comprehensive view for scholars whose research is related to the SMES by examination of the published articles while providing a brief guideline of this modern technology and its applications

Power Inductors: Design, Modeling and Analysis

Power inductors, or reactors as they are called in the power industry, are one of the fundamental components of a power system. They serve various purposes in both conventional and emerging power systems including: power flow control, fault current limitation, reactive power compensation, harmonic filtering, and others. This dissertation explores the design and applications of conventional power inductors and ways to overcome their shortcomings and expand their functionalities. In addition, novel inductor designs are proposed and analyzed to address power system challenges. A series of inductors, including traditional constant reactance inductor, gapless ferromagnetic core reactor (GFCR) (both costant and variable reactance), and magnetic amplifier-based variable reactance reactor (both single-phase and three-phase), are considered and examined. The various unique inductor designs have been analyzed, both analytically and numerically, and their potential assessed for applications in modern power systems using novel simulation frameworks. A finite element analysis (FEA) based numerical modeling has been carried out for all inductors for accurate representation and analysis. On the other hand, analytical modeling based on magnetic equivalent circuit (MEC) has been presented, to complement the FEA-based approach and overcome its shortcomings. A comparative analysis of the processes provides insights into the effectiveness and accuracy of the proposed analytical models. Also, an advanced data-intensive machine learning (ML) approach to understanding the working of magnetic amplifier technology has been proposed. Additionally, a unique optimal power flow (OPF) formulation with variable reactance because of the power magnetic devices like a magnetic amplifier in a power system is presented. This dissertation covers the presentation of novel inductor designs and their advantages, analyses, and assessments to the broad scientific community and the industry. This kind of research is expected to pave the pathway for future innovations in inductor technologies for applications in modern power systems to make them more reliable, resilient, and efficient