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Records with Subject: Process Operations
Showing records 1 to 25 of 66. [First] Page: 1 2 3 Last
Study on Wear Properties of the Flow Parts in a Centrifugal Pump Based on EDEM−Fluent Coupling
Si Huang, Jiaxing Huang, Jiawei Guo, Yushi Mo
September 13, 2019 (v1)
Keywords: centrifugal pump, EDEM–Fluent coupling, numerical simulation, solid–liquid two-phase flow, wear
By using EDEM−Fluent codes and coupling the continuous fluid medium with a solid particle discrete element, the solid−liquid two-phase flow field in a centrifugal pump was simulated under the same inlet conditions of the particle volume fraction and three flow conditions of 0.7Qd, 1.0Qd and 1.3Qd. By introducing the Archard wear model, the wear was calculated, and the wear law was obtained for the pump flow parts such as the leading edge of the impeller blade, blade tip, blade pressure side, blade suction side, impeller shroud, hub and volute. The results demonstrate that the wear of volute is about 70% of the total wear of pump. The wear in the impeller mainly occurs in the blade leading edge, the junction of the hub and the trailing part of the blade pressure side, and the junction of the shroud and the rear part of the blade suction side. Under lower flow conditions, the wear in the impeller shroud is relatively considerable. As the flow rate increases, the wear in the blade pressur... [more]
Process Simulation of the Separation of Aqueous Acetonitrile Solution by Pressure Swing Distillation
Jing Li, Keliang Wang, Minglei Lian, Zhi Li, Tingzhao Du
September 5, 2019 (v1)
Keywords: acetonitrile, full-heat integration, pressure swing distillation, Water
The separation of aqueous acetonitrile solution by pressure swing distillation (PSD) was simulated and optimized through Aspen Plus software. The distillation sequence of the low pressure column (LPC) and high pressure column (HPC) was determined with a phase diagram. The pressures of the two columns were set to 1 and 4 atm, respectively. Total annual cost (TAC) was considered as the objective function, and design variables, such as the tray number, the reflux ratio, and the feeding position, were optimized. The optimum process parameters were obtained. For the reduction of energy consumption, the PSD with full-heat integration was designed. The TAC of this method is lower by 32.39% of that of the PSD without heat integration. Therefore, it is more economical to separate acetonitrile and water mixture by PSD with full-heat integration, which provides technical support for the separation design of such azeotropes.
Analysis of Dynamic Characteristics of a 600 kW Storage Type Wind Turbine with Hybrid Hydraulic Transmission
Zengguang Liu, Yanhua Tao, Liejiang Wei, Peng Zhan, Daling Yue
September 5, 2019 (v1)
Keywords: double closed loop control, energy storage system, hybrid hydraulic transmission, hydraulic wind turbine
In order to improve the efficiency and convenience of wind energy storage and solve the reproducibility of the hydraulic wind turbine, we present a storage type wind turbine with an innovative hybrid hydraulic transmission, which was adopted in the development of a 600 kW storage type wind turbine experimental platform. The whole hydraulic system of the storage type wind turbine is mainly an ingenious combination of a closed loop transmission and an open loop one, which can also be divided into three parts: hydraulic variable speed, hydraulic energy storage, power generation. For the study focusing on the capture and storage of wind energy, the mathematical model of the wind turbine except for the power generation was established under MATLAB/Simulink. A double closed loop control strategy is proposed to achieve the wind wheel speed regulation and wind energy storage. The dynamic simulations of the 600 kW storage type wind turbine experimental prototype were carried out under two diffe... [more]
Dynamic Modelling and Optimisation of the Batch Enzymatic Synthesis of Amoxicillin
Andrew B. Cuthbertson, Alistair D. Rodman, Samir Diab, Dimitrios I. Gerogiorgis
August 5, 2019 (v1)
Keywords: Amoxicillin, dynamic optimisation, enzymatic synthesis, non-isothermal modelling, parameter estimation
Amoxicillin belongs to the β-lactam family of antibiotics, a class of highly consumed pharmaceutical products used for the treatment of respiratory and urinary tract infections, and is listed as a World Health Organisation (WHO) “Essential Medicine”. The demonstrated batch enzymatic synthesis of amoxicillin is composed of a desired synthesis and two undesired hydrolysis reactions of the main substrate (6-aminopenicillanic acid (6-APA)) and amoxicillin. Dynamic simulation and optimisation can be used to establish optimal control policies to attain target product specification objectives for bioprocesses. This work performed dynamic modelling, simulation and optimisation of the batch enzymatic synthesis of amoxicillin. First, kinetic parameter regression at different operating temperatures was performed, followed by Arrhenius parameter estimation to allow for non-isothermal modelling of the reaction network. Dynamic simulations were implemented to understand the behaviour of the design s... [more]
Influence of Injection Timing on Performance and Exhaust Emission of CI Engine Fuelled with Butanol-Diesel Using a 1D GT-Power Model
Salman Abdu Ahmed, Song Zhou, Yuanqing Zhu, Yongming Feng, Adil Malik, Naseem Ahmad
July 31, 2019 (v1)
Keywords: bio-fuels, butanol-diesel blend, diesel engine, emission, engine performance, injection timing
Injection timing variations have a significant effect on the performance and pollutant formation in diesel engines. Numerical study was conducted to investigate the impact of injection timing on engine performance and pollutants in a six-cylinder turbocharged diesel engine. Diesel fuel with different amounts (5%, 15%, and 25% by volume) of n-butanol was used. Simulations were performed at four distinct injection timings (5°, 10°, 20°, 25°CA bTDC) and two distinct loads of brake mean effective pressure (BMEP = 4.5 bar and 10.5 bar) at constant engine speed (1800 rpm) using the GT-Power computational simulation package. The primary objective of this research is to determine the optimum injection timing and optimum blending ratio for improved efficiencies and reduced emissions. Notable improvements in engine performance and pollutant trends were observed for butanol-diesel blends. The addition of butanol to diesel fuel has greatly diminished NOX and CO pollutants but it elevated HC and CO... [more]
A High Efficiency Charging Strategy for a Supercapacitor Using a Wireless Power Transfer System Based on Inductor/Capacitor/Capacitor (LCC) Compensation Topology
Yuyu Geng, Bin Li, Zhongping Yang, Fei Lin, Hu Sun
July 26, 2019 (v1)
Keywords: charging strategy, inductor/capacitor/capacitor (LCC) compensation, quasi-constant voltage gain, supercapacitor load, wireless power transfer
In the application of rail transit vehicles, when using typical wireless power transfer (WPT) systems with series⁻series (SS) compensation supply power for supercapacitors, the output current is in an approximately inverse relationship with the duty cycle in a wide range. This renders the typical buck circuit control inappropriate. In order to help resolve the above issues, this paper designs inductor/capacitor/capacitor (LCC) compensation with new compensation parameters, which can achieve an adjustable quasi-constant voltage from the input of the inverter to the output of the rectifier. In addition, the two-port network method is used to analyze the resonant compensation circuit. The analysis shows that LCC compensation is more suitable for the WPT system using the supercapacitor as the energy storage device. In the case of LCC compensation topology combined with the charging characteristics of the supercapacitor, an efficient charging strategy is designed, namely first constant curr... [more]
Robustness Area Technique Developing Guidelines for Power System Restoration
Paulo Murinelli Pesoti, Eliane Valença de Lorenci, Antonio Carlos Zambroni de Souza, Kwok Lun Lo, Benedito Isaias Lima Lopes
July 26, 2019 (v1)
Keywords: energy function, power system restoration, power system stability, voltage stability
This paper proposes a novel energy based technique called the Robustness Area (RA) technique that measures power system robustness levels, as a helper for planning Power System Restorations (PSRs). The motivation is on account of the latest blackouts in Brazil, where the local Independent System Operator (ISO) encountered difficulties related to circuit disconnections during the restoration. The technique identifies vulnerable and robust buses, pointing out system areas that should be firstly reinforced during PSR, in order to enhance system stability. A Brazilian power system restoration area is used to compare the guidelines adopted by the ISO with a more suitable new plan indicated by the RA tool. Active power and reactive power load margin and standing phase angle show the method efficiency as a result of a well balanced system configuration, enhancing the restoration performance. Time domain simulations for loop closures and severe events also show the positive impact that the pro... [more]
Numerical Investigation of the Time-Dependent and the Proppant Dominated Stress Shadow Effects in a Transverse Multiple Fracture System and Optimization
Lei Zhou, Junchao Chen, Yang Gou, Wentao Feng
July 26, 2019 (v1)
Keywords: 3D numerical modeling, hydro-mechanical coupling, Optimization, time-dependent and proppant dominated stress shadow effect, transverse multiple fracture
In this paper, a numerical study is conducted to investigate the stress shadow effects (stress reorientation and change) during hydraulic fracturing in a transverse multiple fracture system. A numerical model is used for the numerical study. It is a 3D model and can simulate the fracture operation from injection begin to full closure (fracture contact). Therefore, there is no need to assume the fracture geometry for the investigation of the stress shadow effects (unlike previous studies). In the numerical study, the first and second operations in a fictive transverse multiple fracture system are simulated, meanwhile the stress shadow effects and their influences on the propagation and proppant placement of the second fracture are investigated. According to the results, the following conclusions are discerned: (1) most proppants are located in the lower part of the reservoir, even below the perforation; (2) the stress shadow effects are time-dependent and proppant dominated; (3) the str... [more]
Energy-Efficient Train Driving Strategy with Considering the Steep Downhill Segment
Wentao Liu, Tao Tang, Shuai Su, Jiateng Yin, Yuan Cao, Cheng Wang
May 16, 2019 (v1)
Keywords: energy-efficient driving strategy, local optimization, rail transit, steep downhill segment, train control
Implementation of energy-efficient train driving strategy is an effective method to save train traction energy consumption, which has attracted much attention from both researchers and practitioners in recent years. Reducing the unnecessary braking during the journey and increasing the coasting distance are efficient to save energy in urban rail transit systems. In the steep downhill segment, the train speed will continue to increase without applying traction due to the ramp force. A high initial speed before stepping into the steep downhill segment will bring partial braking to prevent trains from overspeeding. Optimization of the driving strategy of urban rail trains can avoid the partial braking such that the potential energy is efficiently used and the traction energy is reduced. This paper presents an energy-efficient driving strategy optimization model for the segment with the steep downhill slopes. A numerical method is proposed to calculate the corresponding energy-efficient dr... [more]
Seepage Characteristics and Its Control Mechanism of Rock Mass in High-Steep Slopes
Hong Li, Hongyuan Tian, Ke Ma
May 16, 2019 (v1)
Keywords: fractured rock, high-steep slope, hydro-power, permeability, seepage control
In Southwest China large-scale hydropower projects, the hydraulic conductivity and fracture aperture within the rock mass of a reservoir bank slope has dramatically undergone a time series of evolution during dam abutment excavation, reservoir impounding and fluctuation operation, and discharge atomization. Accordingly, seepage control measures by hydro-structures such as drainage or water insulation curtains should be guided by scientific foundation with a dynamic process covering life-cycle performance. In this paper, the up-to-date status of studying the evolution mechanism of seepage characteristics relating to fractured rock hydraulics from experimental samples to the engineering scale of the rock mass is reviewed for the first time. Then, the experimental findings and improved practice method on nonlinear seepage flow under intensive pressure drives are introduced. Finally, the scientific progress made in fractured rock seepage control theory and optimization of the design techno... [more]
Dynamic Modeling and Control of an Integrated Reformer-Membrane-Fuel Cell System
Pravin P. S., Ravindra D. Gudi, Sharad Bhartiya
April 8, 2019 (v1)
Keywords: auto thermal reformer, multi-loop control, palladium membrane hydrogen separation, polymer electrolyte membrane fuel cell (PEMFC)
Owing to the pollution free nature, higher efficiency and noise free operation, fuel cells have been identified as ideal energy sources for the future. To avoid direct storage of hydrogen due to safety considerations, storing hydrocarbon fuel such as methane and suitably reforming in situ for hydrogen production offers merit for further investigation. Separating the resulting hydrogen in the reformate using membrane separation can directly feed pure gas to the anode side of fuel cell for power generation. Despite the numerous works reported in literature on the dynamic and steady state modeling and analysis of reformers, membrane separation units and fuel cell systems, there has been limited work on an analysis of the integrated system consisting of all the three components. This study focuses on the mathematical modeling and analysis of the integrated reformer, membrane, fuel cell system from first principles in a dynamic framework. A multi loop control strategy is developed and imple... [more]
Improving Flexibility and Energy Efficiency of Post-Combustion CO₂ Capture Plants Using Economic Model Predictive Control
Benjamin Decardi-Nelson, Su Liu, Jinfeng Liu
April 8, 2019 (v1)
Keywords: Energy Efficiency, optimal control, post-combustion CO2 capture, time-varying operation
To reduce CO 2 emissions from power plants, electricity companies have diversified their generation sources. Fossil fuels, however, still remain an integral energy generation source as they are more reliable compared to the renewable energy sources. This diversification as well as changing electricity demand could hinder effective economical operation of an amine-based post-combustion CO 2 capture (PCC) plant attached to the power plant to reduce CO 2 emissions. This is as a result of large fluctuations in the flue gas flow rate and unavailability of steam from the power plant. To tackle this problem, efficient control algorithms are necessary. In this work, tracking and economic model predictive controllers are applied to a PCC plant and their economic performance is compared under different scenarios. The results show that economic model predictive control has a potential to improve the economic performance and energy efficiency of the amine-based PCC process up... [more]
Real-Time Velocity Optimization to Minimize Energy Use in Passenger Vehicles
Thomas Levermore, M. Necip Sahinkaya, Yahya Zweiri, Ben Neaves
March 26, 2019 (v1)
Keywords: dynamic programming, fuel, fuel consumption, Optimization
Energy use in internal combustion engine passenger vehicles contributes directly to CO 2 emissions and fuel consumption, as well as producing a number of air pollutants. Optimizing the vehicle velocity by utilising upcoming road information is an opportunity to minimize vehicle energy use without requiring mechanical design changes. Dynamic programming is capable of such an optimization task and is shown in simulation to produce fuel savings, on average 12%, compared to real driving data; however, in this paper it is also applied in real time on a Raspberry Pi, a low cost miniature computer, in situ in a vehicle. A test drive was undertaken with driver feedback being provided by a dynamic programming algorithm, and the results are compared to a simulated intelligent cruise control system that can follow the algorithm results precisely. An 8% reduction in fuel with no loss in time is reported compared to the test driver.
Operation Optimization of Steam Accumulators as Thermal Energy Storage and Buffer Units
Wenqiang Sun, Yuhao Hong, Yanhui Wang
March 15, 2019 (v1)
Keywords: minimum volume, necessary thermal energy storage capacity (NTESC), optimal operation, steam accumulator (SA), steam source (SS)
Although steam is widely used in industrial production, there is often an imbalance between steam supply and demand, which ultimately results in steam waste. To solve this problem, steam accumulators (SAs) can be used as thermal energy storage and buffer units. However, it is difficult to promote the application of SAs due to high investment costs, which directly depend on the usage volume. Thus, the operation of SAs should be optimized to reduce initial investment through volume minimization. In this work, steam sources (SSs) are classified into two types: controllable steam sources (CSSs) and uncontrollable steam sources (UCSSs). A basic oxygen furnace (BOF) was selected as an example of a UCSS to study the optimal operation of an SA with a single BOF and sets of parallel-operating BOFs. In another case, a new method whereby CSSs cooperate with SAs is reported, and the mathematical model of the minimum necessary thermal energy storage capacity (NTESC) is established. A solving progra... [more]
Risk Assessment Method of UHV AC/DC Power System under Serious Disasters
Rishang Long, Jianhua Zhang
March 15, 2019 (v1)
Keywords: chain failure, index system, risk assessment, ultra-high voltage (UHV)
Based on the theory of risk assessment, the risk assessment method for an ultra-high voltage (UHV) AC/DC hybrid power system under severe disaster is studied. Firstly, considering the whole process of cascading failure, a fast failure probability calculation method is proposed, and the whole process risk assessment model is established considering the loss of both fault stage and recovery stage based on Monte Carlo method and BPA software. Secondly, the comprehensive evaluation index system is proposed from the aspects of power system structure, fault state and economic loss, and the quantitative assessment of system risk is carried out by an entropy weight model. Finally, the risk assessment of two UHV planning schemes are carried out and compared, which proves the effectiveness of the research work.
Fault-Ride through Strategy for Permanent-Magnet Synchronous Generators in Variable-Speed Wind Turbines
Mohamed Abdelrahem, Ralph Kennel
February 27, 2019 (v1)
Keywords: fault-ride through, Model Predictive Control, permanent-magnet synchronous generator, wind turbine
Currently, the electric power production by wind energy conversion systems (WECSs) has increased significantly. Consequently, wind turbine (WT) generators are requested to fulfill the grid code (GC) requirements stated by network operators. In case of grid faults/voltage dips, a mismatch between the generated active power from the wind generator and the active power delivered to the grid is produced. The conventional approach is using a braking chopper (BC) in the DC-link to dissipate this active power. This paper proposes a fault-ride through (FRT) strategy for variable-speed WECSs based on permanent magnet synchronous generators (PMSGs). The proposed strategy exploits the rotor inertia of the WECS (inertia of the WT and PMSG) to store the surplus active power during the grid faults/voltage dips. Thus, no additional hardware components are requested. Furthermore, a direct model predictive control (DMPC) scheme for the PMSG is proposed in order to enhance the dynamic behavior of the WE... [more]
Structural Dynamic Analysis of Semi-Submersible Floating Vertical Axis Wind Turbines
Jeremiah Ishie, Kai Wang, Muk Chen Ong
February 27, 2019 (v1)
Keywords: coupled non-linear time domain simulation, fatigue analysis, finite element method, semi-submersible substructure, Simo-Riflex-DMS, structural dynamics, wind turbine
The strong and stable wind at offshore locations and the increasing demand for energy have made the application of wind turbines in deeper water surge. A novel concept of a 5 MW baseline Floating Vertical Axis Wind Turbine (FVAWT) and a 5 MW optimised FVAWT with the DeepWind Darrieus rotor and the optimised DeepWind Darrieus rotor, respectively, were studied extensively. The structural responses, fatigue damages, platform global motions and mooring line dynamics of the FVAWTs were investigated comprehensively during normal operating conditions under steady wind and turbulent wind conditions, using a coupled non-linear aero-hydro-servo-elastic code (the Simo-Riflex-DMS code) which was developed by Wang et al. for modeling FVAWTs. This coupled code incorporates the models for the turbulent wind field, aerodynamics, hydrodynamics, structural dynamics, and generator controller. The simulation is performed in a fully coupled manner in time domain. The comparison of responses under different... [more]
Modeling and Mitigation for High Frequency Switching Transients Due to Energization in Offshore Wind Farms
Yanli Xin, Bo Liu, Wenhu Tang, Qinghua Wu
February 27, 2019 (v1)
Keywords: high frequency (HF), offshore wind farm (OWF), overvoltage mitigation, prestrikes, switching transient, vacuum circuit breaker (VCB)
This paper presents a comprehensive investigation on high frequency (HF) switching transients due to energization of vacuum circuit breakers (VCBs) in offshore wind farms (OWFs). This research not only concerns the modeling of main components in collector grids of an OWF for transient analysis (including VCBs, wind turbine transformers (WTTs), submarine cables), but also compares the effectiveness between several mainstream switching overvoltage (SOV) protection methods and a new mitigation method called smart choke. In order to accurately reproduce such HF switching transients considering the current chopping, dielectric strength (DS) recovery capability and HF quenching capability of VCBs, three models are developed, i.e., a user⁻defined VCB model, a HF transformer terminal model and a three-core (TC) frequency dependent model of submarine cables, which are validated through simulations and compared with measurements. Based on the above models and a real OWF configuration, a simulati... [more]
Numerical Study of the Dynamic Response of Heat and Mass Transfer to Operation Mode Switching of a Unitized Regenerative Fuel Cell
Hong Xiao, Hang Guo, Fang Ye, Chongfang Ma
February 27, 2019 (v1)
Keywords: heat transfer, mass transfer, mode switching, transient response, unitized regenerative fuel cells
Knowledge concerning the complicated changes of mass and heat transfer is desired to improve the performance and durability of unitized regenerative fuel cells (URFCs). In this study, a transient, non-isothermal, single-phase, and multi-physics mathematical model for a URFC based on the proton exchange membrane is generated to investigate transient responses in the process of operation mode switching from fuel cell (FC) to electrolysis cell (EC). Various heat generation mechanisms, including Joule heat, reaction heat, and the heat attributed to activation polarizations, have been considered in the transient model coupled with electrochemical reaction and mass transfer in porous electrodes. The polarization curves of the steady-state models are validated by experimental data in the literatures. Numerical results reveal that current density, gas mass fractions, and temperature suddenly change with the sudden change of operating voltage in the mode switching process. The response time of... [more]
Global Maximum Power Point Tracking (MPPT) of a Photovoltaic Module Array Constructed through Improved Teaching-Learning-Based Optimization
Kuei-Hsiang Chao, Meng-Cheng Wu
February 27, 2019 (v1)
Keywords: maximum power point tracking, partial module shading, photovoltaic module array, teaching-learning-based optimization
The present study proposes a maximum power point tracking (MPPT) method in which improved teaching-learning-based optimization (I-TLBO) is applied to perform global MPPT of photovoltaic (PV) module arrays under dissimilar shading situations to ensure the maximum power output of the module arrays. The proposed I-TLBO enables the automatic adjustment of teaching factors according to the self-learning ability of students. Incorporating smart-tracking and self-study strategies can effectively improve the tracking response speed and steady-state tracking performance. To evaluate the feasibility of the proposed I-TLBO, a HIP-2717 PV module array from Sanyo Electric was employed to compose various arrays with different serial and parallel configurations. The arrays were operated under different shading conditions to test the MPPT with double, triple, or quadruple peaks of power-voltage characteristic curves. Boost converters were employed with TMS320F2808 digital signal processors to test the... [more]
Novel Auto-Reclosing Blocking Method for Combined Overhead-Cable Lines in Power Networks
Ricardo Granizo Arrabé, Carlos Antonio Platero Gaona, Fernando Álvarez Gómez, Emilio Rebollo López
February 5, 2019 (v1)
Keywords: distribution protections, electrical distribution networks, ground faults, protection
This paper presents a novel auto-reclosing blocking method for combined overhead-cable lines in power distribution networks that are solidly or impedance grounded, with distribution transformers in a delta connection in their high-voltage sides. The main contribution of this new technique is that it can detect whether a ground fault has been produced at the overhead line side or at the cable line side, thus improving the performance of the auto-reclosing functionality. This localization technique is based on the measurements and analysis of the argument differences between the load currents in the active conductors of the cable and the currents in the shields at the cable end where the transformers in delta connection are installed, including a wavelet analysis. This technique has been verified through computer simulations and experimental laboratory tests.
Operational Modal Analysis of a Spar-Type Floating Platform Using Frequency Domain Decomposition Method
Carlo Ruzzo, Giuseppe Failla, Maurizio Collu, Vincenzo Nava, Vincenzo Fiamma, Felice Arena
January 31, 2019 (v1)
Keywords: damping of offshore structures, Frequency Domain Decomposition, output-only system identification
System identification of offshore floating platforms is usually performed by testing small-scale models in wave tanks, where controlled conditions, such as still water for free decay tests, regular and irregular wave loading can be represented. However, this approach may result in constraints on model dimensions, testing time, and costs of the experimental activity. For such reasons, intermediate-scale field modelling of offshore floating structures may become an interesting as well as cost-effective alternative in a near future. Clearly, since the open sea is not a controlled environment, traditional system identification may become challenging and less precise. In this paper, a new approach based on Frequency Domain Decomposition (FDD) method for Operational Modal Analysis is proposed and validated against numerical simulations in ANSYS AQWA v.16.0 on a simple spar-type structure. The results obtained match well with numerical predictions, showing that this new approach, opportunely... [more]
A Modified Bird-Mating Optimization with Hill-Climbing for Connection Decisions of Transformers
Ting-Chia Ou, Wei-Fu Su, Xian-Zong Liu, Shyh-Jier Huang, Te-Yu Tai
January 31, 2019 (v1)
Keywords: and voltage deviation, bird-mating optimization, voltage imbalance
This paper endeavors to apply a hybrid bird-mating optimization approach to connection decisions of distribution transformers. It is expected that with the aid of hybrid bird-mating approach, the voltage imbalance and deviation can be mitigated, hence ensuring a satisfactory supplying power more effectively. To evaluate the effectiveness of this method, it has been tested through practical distribution systems with comparisons to other methods. Test results help confirm the feasibility of the approach, serving as beneficial references for the improvement of electric power grid operations.
Capacitor Current Feedback-Based Active Resonance Damping Strategies for Digitally-Controlled Inductive-Capacitive-Inductive-Filtered Grid-Connected Inverters
Iman Lorzadeh, Hossein Askarian Abyaneh, Mehdi Savaghebi, Alireza Bakhshai, Josep M. Guerrero
January 30, 2019 (v1)
Keywords: active resonance damping, current control, discrete-time domain, grid-connected inverter, Inductive-capacitive-inductive (LCL)-filter
Inductive-capacitive-inductive (LCL)-type line filters are widely used in grid-connected voltage source inverters (VSIs), since they can provide substantially improved attenuation of switching harmonics in currents injected into the grid with lower cost, weight and power losses than their L-type counterparts. However, the inclusion of third order LCL network complicates the current control design regarding the system stability issues because of an inherent resonance peak which appears in the open-loop transfer function of the inverter control system near the control stability boundary. To avoid passive (resistive) resonance damping solutions, due to their additional power losses, active damping (AD) techniques are often applied with proper control algorithms in order to damp the LCL filter resonance and stabilize the system. Among these techniques, the capacitor current feedback (CCF) AD has attracted considerable attention due to its effective damping performance and simple implementa... [more]
Partial Discharge Measurement under an Oscillating Switching Impulse: A Potential Supplement to the Conventional Insulation Examination in the Field
Ming Ren, Ming Dong, Chongxing Zhang, Jierui Zhou
January 30, 2019 (v1)
Keywords: gas insulated switchgear, impulse voltage, insulation diagnosis, partial discharge, power apparatus, SF6
Partial discharge (PD) detection under oscillating switching impulse (OSI) voltage was performed on three types of insulation defects, including a protrusion on a conductor, a particle on an insulator surface, and a void in an insulator, which are three kinds of the common potential insulation hazards in gas insulated power apparatus. Experiment indicated that the PD sequences under OSI were composed of various combinations of the single pulse, the multiple pulses, and the reverse polarity pulse. The difference between the PD inception voltage (PDIV) and the breakdown voltage (BDV) under OSI voltage was greater than that under alternating current (AC) voltage in some cases, which can provide a more sufficient margin below the BDV for PD diagnosis. The OSI voltage also showed a better performance for exciting PDs with detectable magnitudes from small-scale defects, of which the AC voltage was incapable under our test conditions. The different PD activities with different interfaces unde... [more]
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