Design of Self-Powered Solid-State Fault Current Limiters for VSC DC Grids

Abstract-Fault current limiters (FCLs) can suppress the rise of short-circuit fault currents in voltage source converter (VSC) based DC grids. However, the power electronic switches of FCLs need extra source equipment to supply the required power, which increases complexity and cost. This paper presents three kinds of self-powered solid-state FCLs (SSFCLs). The proposed self-powered SSFCLs detect short-circuit faults by sensing fault current increases and draw energy from the fault DC line to automatically drive the power electronic switches. The self-powered SSFCLs are equipped with a self-powered supply system (SPSS). The SPSS obtains energy from the magnetic field induced by short-circuit fault current using magnetic-coupling mutual inductance coils. In PSCAD/EMTDC, the proposed self-powered SSFCLs are placed directly on the DC line without external power supply equipment. When a short-circuit fault occurs, the simulation results verify that the proposed self-powered SSFCLs can rapidly acquire power to drive the power electronic switches and then suppress the rise of the fault current. The proposed self-powered SSFCL prototypes provide a solution for decreasing the cost and complexity associated with installing extra source equipment.

Extended hybrid cross-switched multilevel inverter circuit topology

Purpose Multilevel inverters (MLIs) have been studied widely over the past two decades because of their inherent advantages and interesting features. However, most of the newly introduced structures suffer from the increased standing voltage of the switches, which is defined as the maximum off-state voltage on the switches, losing modularity and increased number of direct current (DC) voltage sources. The purpose of this study is to propose a new hybrid MLI topology to alleviate the mentioned problems. Design/methodology/approach The proposed approach in this study includes using the advantage of two different topologies and combine them in a way that the advantages of both of the topologies are achieved. Therefore, the approach is to design a hybrid topology from two existing topologies so that a new topology has resulted. Findings This paper proposes a new hybrid MLI with lower power electronic switches and lowers DC voltage sources in comparison with the classic structures. The proposed MLIs maintain a balance between the number of switches, the standing voltage on the switches and the number of DC sources. The topology description, modulation method and comparative study have been presented. Also, another more reduced structure is presented for higher power factor operation. The MATLAB simulation and experimental results of a nine-level inverter have been presented to verify its operation. Originality/value The hybrid topology has a new structure that has not been presented before. It is important to emphasize that the topology combination and achieving the hybrid topology is wisely accomplished to improve some features of the MLI.

Design, simulation and testing of an array of nano electro mechanical switches (NEMS)

Electro mechanical switches used for multi-purposs applications with ultra small size in nano meter scale, operating in very small voltage in millivolts, approximately zero leakage current due to air gap separation between electrodes with three terminals that easy to control it. Nano electro mechanical switches are electronic switches similar to those used by conventional semiconductor switches in application as they can be used as relays, logic devices. The basic principle of nano electro mechanical switches is electronic switches operation is fundamentally different from semiconductor switches. They have many advantages over conventional semiconductor switches such as low-power digital logic applications, ability to work with very small voltage signals for low dynamic energy consumption, and durability against hostile environments such as high temperatures and radiation contaminated spaces. In this article, we will design, implement, and test a matrix of nano electro mechanical switches by on line test using the superposition theory. The simulations of these switches were implemented using the MATLAB-Simulink and ORCAD Pspice environments. Also, controlling the flow of current was achieved by means of a nanometer movement to make or break the physical contact between the electrodes.

HVDC Breaker Power Loss Reduction by Bridge-Type Hybrid Breakers

Several types of high voltage direct current (HVDC) breakers have been introduced and commercialized. Each of them has advantages and disadvantages. Among them, the hybrid HVDC breaker is highly successful. One of the most important concerns that the hybrid HVDC breaker has faced is high power loss throughout its fault current breaking process. The hybrid HVDC breaker comprises a high voltage bidirectional main HVDC breaker. A significant number of electronic switches need to be connected in a series where anti-parallel diodes are essentially embraced. During fault inception, a number of series solid-state switches and a number of series diodes dramatically increase the power loss of the main breaker. This study, firstly, studies the power loss of the hybrid HVDC breaker and later develops a structure of a full-bridge hybrid breaker (FBHB) to reduce the losses of the current structure both in the normal and fault protection states. In this paper simulations are done based on PSCAD. In addition to the analytical study and simulations, we show that the developed structure substantially decreases the amount of power lost during the normal operation and fault current breaking stage.

Multilevel level single phase inverter implementation for reduced harmonic contents

<p>Selective harmonic elimination technique SHE is adopted in this work to reduce the harmonic contents in single phase cascaded multilevel inverter. The firing instants for the electronic switches MOSFETs in the inverter are calculated off line for five level to thirteen level inverter. An Arduino microcontroller is programmed to cope with different topologies of the multilevel inverter. The implemented multi-level (MLI) inverter results are compared with Simulink simulation program and are found very close to each other. SHE technique works at system frequency (50 Hz or 60 Hz) and the switching losses are very small. The sinusoidal pulse width modulation SPWM requires a carrier frequency not less 20 times the system frequency so SHE approach is found to be superior compared with SPWM. Also, SHE technique shows significant reduction in THD as the number of levels increased. Results for the output voltages and currents along with their frequency spectrum are shown and compared with traditional SPWM.</p>

A simulation energy management system of a multi-source renewable energy based on multi agent system

<p>The intermittent nature of renewable energies sources makes their control difficult. One of the solutions to overcome this handicap is to promote hybridization (multi-source system). To ensure continuity of service, a storage system must be coupled to the system. To do so, artificial intelligence based models are developed to respond optimally to the dilemma of energy supply and demand. These models allow the management of the energy flow between the sources (photovoltaic, wind, battery, super capacitor, and generator) and the variable loads by controlling electronic switches according to the availability of the sources. The artificial intelligence algorithm used in this study is multi agent system (MAS). The simulation results and validation tests shows the effectivenes of the proposed approach.</p>

Structural Reorganization of Imidazolium Ionic Liquids Induced by Pressure-Enhanced Ionic Liquid—Polyethylene Oxide Interactions

Mixtures of polyethylene oxide (PEO, M.W.~900,000) and imidazolium ionic liquids (ILs) are studied using high-pressure Fourier-transform infrared spectroscopy. At ambient pressure, the spectral features in the C–H stretching region reveal that PEO can disturb the local structures of the imidazolium rings of [BMIM]+ and [HMIM]+. The pressure-induced phase transition of pure 1-butyl-3-methylimidazolium bromide ([BMIM]Br) is observed at a pressure of 0.4 GPa. Pressure-enhanced [BMIM]Br-PEO interactions may assist PEO in dividing [BMIM]Br clusters to hinder the aggregation of [BMIM]Br under high pressures. The C–H absorptions of pure 1-hexyl-3-methylimidazolium bromide [HMIM]Br do not show band narrowing under high pressures, as observed for pure [BMIM]Br. The band narrowing of C–H peaks is observed at 1.5 GPa for the [HMIM]Br-PEO mixture containing 80 wt% of [HMIM]Br. The presence of PEO may reorganize [HMIM]Br clusters into a semi-crystalline network under high pressures. The differences in aggregation states for ambient-pressure phase and high-pressure phase may suggest the potential of [HMIM]Br-PEO (M.W.~900,000) for serving as optical or electronic switches.