An improved mixed AC/DC power flow algorithm in hybrid AC/DC grids with MT-HVDC systems

© 2019 by the authors. One of the major challenges on large-scale Multi-Terminal High Voltage Direct Current (MT-HVDC) systems is the steady-state interaction of the hybrid AC/DC grids to achieve an accurate Power Flow (PF) solution. In PF control of MT-HVDC systems, different operational constraints, such as the voltage range, voltage operating region, Total Transfer Capability (TTC), transmission reliability margin, converter station power rating, etc. should be considered. Moreover, due to the nonlinear behavior of MT-HVDC systems, any changes (contingencies and/or faults) in the operating conditions lead to a significant change in the stability margin of the entire or several areas of the hybrid AC/DC grids. As a result, the system should continue operating within the acceptable limits and deliver power to the non-faulted sections. In order to analyze the steady-state interaction of the large-scale MT-HVDC systems, an improved mixed AC/DC PF algorithm for hybrid AC/DC grids with MT-HVDC systems considering the operational constraints is developed in this paper. To demonstrate the performance of the mixed AC/DC PF algorithm, a five-bus AC grid with a three-bus MT-HVDC system and the modified IEEE 39-bus test system with two four-bus MT-HVDC systems (in two different areas) are simulated in MATLAB software and different cases are investigated. The obtained results show the accuracy, robustness, and effectiveness of the improved mixed AC/DC PF algorithm for operation and planning studies of the hybrid A/DC grids

A new topology of a fast proactive hybrid DC Circuit Breaker for MT-HVDC grids

© 2019 by the authors. One of the major challenges toward the reliable and safe operation of the Multi-Terminal HVDC (MT-HVDC) grids arises from the need for a very fast DC-side protection system to detect, identify, and interrupt the DC faults. Utilizing DC Circuit Breakers (CBs) to isolate the faulty line and using a converter topology to interrupt the DC fault current are the two practical ways to clear the DC fault without causing a large loss of power infeed. This paper presents a new topology of a fast proactive Hybrid DC Circuit Breaker (HDCCB) to isolate the DC faults in MT-HVDC grids in case of fault current interruption, along with lowering the conduction losses and lowering the interruption time. The proposed topology is based on the inverse current injection technique using a diode and a capacitor to enforce the fault current to zero. Also, in case of bidirectional fault current interruption, the diode and capacitor prevent changing their polarities after identifying the direction of fault current, and this can be used to reduce the interruption time accordingly. Different modes of operation of the proposed topology are presented in detail and tested in a simulation-based system. Compared to the conventional DC CB, the proposed topology has increased the breaking current capability, and reduced the interruption time, as well as lowering the on-state switching power losses. To check and verify the performance and efficiency of the proposed topology, a DC-link representing a DC-pole of an MT-HVDC system is simulated and analyzed in the PSCAD/EMTDC environment. The simulation results verify the robustness and effectiveness of the proposed HDCCB in improving the overall performance of MT-HVDC systems and increasing the reliability of the DC grids

A bidirectional power charging control strategy for Plug-in Hybrid Electric Vehicles

© 2019 by the authors. Plug-in Hybrid Electric Vehicles (PHEVs) have the potential of providing frequency regulation due to the adjustment of power charging. Based on the stochastic nature of the daily mileage and the arrival and departure time of Electric Vehicles (EVs), a precise bidirectional charging control strategy of plug-in hybrid electric vehicles by considering the State of Charge (SoC) of the batteries and simultaneous voltage and frequency regulation is presented in this paper. The proposed strategy can control the batteries charge which are connected to the grid, and simultaneously regulate the voltage and frequency of the power grid during the charging time based on the available power when different events occur over a 24-h period. The simulation results prove the validity of the proposed control strategy in coordinating plug-in hybrid electric vehicles aggregations and its significant contribution to the peak reduction, as well as power quality improvement. The case study in this paper consists of detailed models of Distributed Energy Resources (DERs), diesel generator and wind farm, a generic aggregation of EVs with various charging profiles, and different loads. The test system is simulated and analyzed in MATLAB/SIMULINK software

An improved droop-based control strategy for MT-HVDC systems

© 2020 by the authors. Licensee MDPI, Basel, Switzerland. This paper presents an improved droop-based control strategy for the active and reactive power-sharing on the large-scale Multi-Terminal High Voltage Direct Current (MT-HVDC) systems. As droop parameters enforce the stability of the DC grid, and allow the MT-HVDC systems to participate in the AC voltage and frequency regulation of the different AC systems interconnected by the DC grids, a communication-free control method to optimally select the droop parameters, consisting of AC voltage-droop, DC voltage-droop, and frequency-droop parameters, is investigated to balance the power in MT-HVDC systems and minimize AC voltage, DC voltage, and frequency deviations. A five-terminal Voltage-Sourced Converter (VSC)-HVDC system is modeled and analyzed in EMTDC/PSCAD and MATLAB software. Different scenarios are investigated to check the performance of the proposed droop-based control strategy. The simulation results show that the proposed droop-based control strategy is capable of sharing the active and reactive power, as well as regulating the AC voltage, DC voltage, and frequency of AC/DC grids in case of sudden changes, without the need for communication infrastructure. The simulation results confirm the robustness and effectiveness of the proposed droop-based control strategy

Ternary Imidazolium-Pyrrolidinium-Based Ionic Liquid Electrolytes for Rechargeable Li-O 2 Batteries

The conductivity and anodic stability of ternary mixed ionic liquid (IL) electrolytes consisting of pyrrolidinium [N-butyl-Nmethylpyrrolidinium + (PYR 14 + )] and imidazolium [1-butyl-3-methylimidazolium + (BMIM + )] based bis(trifluoromethylsulfonyl) imide (TFSI − ) with 0.5 M LiTFSI salt were investigated. PYR 14 TFSI ionic liquid has been reported to be stable under an oxidative environment, while BMIMTFSI provides good ionic conductivity. A conductivity study of IL electrolytes revealed a linear correlation of conductivity as a function of IL -Li salt concentration and IL volume fraction. As a result, improved battery cycling in a mixture of 4:1 (80/20 v/v%) BMIM + : PYR 14 + was observed with a specific capacity of 330 mAh.g −1 over 50 cycles at a current density of 0.1 mA.cm −2 . Also, an EIS study revealed decreasing cathode polarization by demonstrating lower impedance values for ternary mixed electrolyte than that of the pure electrolytes upon cycling. The commercial potential of Li-O 2 rechargeable batteries is tremendous due to their extremely high theoretical energy density of 12 kWh.kg −1 (excluding oxygen), which is comparable to that of gasoline. 1 For automotive applications, Li-O 2 battery technology may be viable if it can provide 1.7 kWh.kg −1 of energy to the wheels after losses from the battery chemistry. However, this technology is suffering with several issues related to electrodes and electrolyte such as lithium metal corrosion, electrolyte decomposition, wettability, cathode structure retention, catalyst selection, among others, which result in a large irreversibility and poor cycle life. 1,2 Previous reports on electrolytes 3-5 suggest that conventional carbonate based electrolyte decomposes during the discharge process to produce irreversible byproducts such as alkyl carbonates and lithium carboxylates; and during the charging process, the oxidative decomposition of these byproducts 6 lead to CO 2 , CO, and other gases instead of O 2 . It has been found that this decomposition process is favored by the highly reactive superoxide radical anion (O 2 •− ) formed through single-electron reduction of oxygen (O 2 + e − → O 2 •− ). 9-11 Another polar solvent, dimethyl sulfoxide (DMSO), is not stable against a Li anode as it can absorb moisture from the air. 20 Although PYR 14 TFSI is stable, its high viscosity (100 centipoise) and low conductivity (1.4 × 10 −3 S cm −1 ) 21 limit the diffusion rate of lithium ions in the electrolyte. On the other hand, various imidazolium based molten salts have demonstrated better cyclability compared to pyrrolidinium in lithium batteries 22 because of the higher ionic conductivity and lower viscosity. Hence, a mixed imidazolium and pyrrolidinium based IL electrolyte could provide the stability and conductivity needed for both Liair and high power Li-ion batteries (LIB). For instance, a ternary ionic liquid: 1-Ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl) imide, N-cyanoethyl-N,N,N-trimethylammonium bis(trifluoromethanesulfonyl)imide, and LiTFSI, exhibited a discharge capacity close z E-mail: [email protected] to the theoretical value with good compatibility with a LiCoO 2 cathode. 23 For Li-O 2 batteries, Cecchetto et al. investigated a mixture of PYR 14 TFSI: TEGDME-LiCF 3 SO 3 (1:1) and observed a lower overvoltage with higher conductivity for the electrolyte mixture than TEGDME alone. The present study aims to investigate ternary mixtures (IL 1 -IL 2 -Li-salt) of imidazolium and pyrrolidinium based ILs for Li-O 2 applications. BMIMTFSI was chosen as the imidazolium based IL as it has high ionic conductivity (4 mS.cm −1 ) and lower viscosity (32 centipoise), whereas, PYR 14 TFSI as a pyrrolidinium based IL as a stable solvent. Herein, different ternary mixtures of BMIMTFSI + PYR 14 TFSI + 0.5 M LiTFSI were prepared to study the effect of IL composition on ionic conductivity, electrochemical stability, lithium transference number, and Li-O 2 battery performance. It was found that 4:1 (BMIMTFSI:PYR 14 TFSI) mixed electrolyte enhanced both cyclic performance and columbic efficiency compared to BMIMTFSI or PYR 14 TFSI used alone. Experimental Ternary mixtures of electrolyte preparation.-1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl imide) (BMIMTFSI) (Sigma-Aldrich), and N-butyl-N-methylpyrrolidinium bis(trifluoromethanesulfonyl) imide (PYR 14 TFSI) (TCI America) were used as room-temperature ionic liquids. The chemical structures are shown in Conductivity measurement.-Conductivity of all pure and mixtures of ILs were determined using a digital conductivity meter (VWR International, LLC, model 2052). All tests were measured at room temperature inside the glove box. Electrochemical stability measurement.-The electrochemical stability window of the LiTFSI-IL solutions was determined by linear sweep voltammetry (LSV) using a Gamry Reference 3000 Potentiosta

An Improved Mixed AC/DC Power Flow Algorithm in Hybrid AC/DC Grids with MT-HVDC Systems

One of the major challenges on large-scale Multi-Terminal High Voltage Direct Current (MT-HVDC) systems is the steady-state interaction of the hybrid AC/DC grids to achieve an accurate Power Flow (PF) solution. In PF control of MT-HVDC systems, different operational constraints, such as the voltage range, voltage operating region, Total Transfer Capability (TTC), transmission reliability margin, converter station power rating, etc. should be considered. Moreover, due to the nonlinear behavior of MT-HVDC systems, any changes (contingencies and/or faults) in the operating conditions lead to a significant change in the stability margin of the entire or several areas of the hybrid AC/DC grids. As a result, the system should continue operating within the acceptable limits and deliver power to the non-faulted sections. In order to analyze the steady-state interaction of the large-scale MT-HVDC systems, an improved mixed AC/DC PF algorithm for hybrid AC/DC grids with MT-HVDC systems considering the operational constraints is developed in this paper. To demonstrate the performance of the mixed AC/DC PF algorithm, a five-bus AC grid with a three-bus MT-HVDC system and the modified IEEE 39-bus test system with two four-bus MT-HVDC systems (in two different areas) are simulated in MATLAB software and different cases are investigated. The obtained results show the accuracy, robustness, and effectiveness of the improved mixed AC/DC PF algorithm for operation and planning studies of the hybrid A/DC grids

An Improved Droop-Based Control Strategy for MT-HVDC Systems

This paper presents an improved droop-based control strategy for the active and reactive power-sharing on the large-scale Multi-Terminal High Voltage Direct Current (MT-HVDC) systems. As droop parameters enforce the stability of the DC grid, and allow the MT-HVDC systems to participate in the AC voltage and frequency regulation of the different AC systems interconnected by the DC grids, a communication-free control method to optimally select the droop parameters, consisting of AC voltage-droop, DC voltage-droop, and frequency-droop parameters, is investigated to balance the power in MT-HVDC systems and minimize AC voltage, DC voltage, and frequency deviations. A five-terminal Voltage-Sourced Converter (VSC)-HVDC system is modeled and analyzed in EMTDC/PSCAD and MATLAB software. Different scenarios are investigated to check the performance of the proposed droop-based control strategy. The simulation results show that the proposed droop-based control strategy is capable of sharing the active and reactive power, as well as regulating the AC voltage, DC voltage, and frequency of AC/DC grids in case of sudden changes, without the need for communication infrastructure. The simulation results confirm the robustness and effectiveness of the proposed droop-based control strategy

A fast fault detection and identification approach in power distribution systems

© 2019 IEEE. In this paper, a Modified Multi-Class Support Vector Machines (MMC-SVM) technique is developed to simultaneously detect and classify different types of open-circuit faults in power distribution systems. This technique is capable of detecting and identifying open-circuit faults considering the impact of variations in the voltage of different nodes in power distribution systems. The RMS (Root Mean Square) voltage of the power grid is used as the input signal to diagnose the faults. Simulations are carried out on the IEEE 13-node test system considering temporary open-circuit faults in MATLAB software. The simulation results show the accuracy, effectiveness, and robustness of the proposed method

Modeling, simulation, and analysis of hybrid electric vehicle using MATLAB/simulink

© 2019 IEEE. Carbon dioxide (CO2) emissions from automotive vehicles are tremendous problems for the climate. The automotive industries are confronting significant issues to reduce greenhouse gases emissions, which have a direct impact on the environment. The automotive industries are manufacturing Hybrid Electric Vehicles (HEVs) and Full Electric Vehicles (FEVs) with less carbon emission to reduce the effect of carbon dioxide emissions. This paper mainly focuses on modeling, simulation, and analysis of a parallel HEV to improve the fuel economy and reduce the overall emission, as well as enhancing the performance of the HEV by optimizing the efficiency of the battery pack. Moreover, technical considerations to minimize the mechanical and electrical power losses, as well as maximizing the energy absorption from the braking system, are investigated. ADVISOR, which is a MATLAB/Simulink-based software, is used for the simulation and analysis of the HEV

A Real-Time Cloud-Based Intelligent Car Parking System for Smart Cities

© 2019 IEEE. Nowadays, parking space shortages and traffic congestion are two issues that all drivers are facing in large cities around the world. Due to the growing number of vehicles and the mismanagement of available parking spaces, heavy traffic in crowded cities are severe. Therefore, there is a compelling urge for an intelligent and efficient car parking system which can be used for managing the limited parking spaces, thereby saving on time, cost, and fuel. In this paper, a secure and reliable cloud-based intelligent car parking system based on Internet-of-Things (IoT) technology for smart cities is presented. Integrated on-site data collection using wireless sensors along with real-time and streaming data analytics on data from IoT are investigated to dynamically check the availability of parking spaces in different parking areas and address the above-mentioned challenges