Input Side Research Articles

Combination of Implementation of Antiphase and Overcurrent Relays for Protection of 0.75 kW Three-Phase Induction Motor in Industry

Three-phase induction motors are the most widely used type of motor in industry. These motor operations are generally susceptible to unbalanced voltage disturbances. This interference is caused by the loss of one or two phases on the input side of the motor. This source voltage disturbance then causes an unbalanced current which flows to the coil, causing a phase shift, overheating the coil, and if left for a long time, it causes the motor to burn out. The research aims to design and implement a combination of antiphase relay (APR) and overcurrent relay (OCR) to prevent voltage drops due to failure of one or two phases and overcurrent to prevent overheating and fires in three-phase induction motor coils. Motor testing is carried out by adjusting the magnitude of the three-phase motor source voltage in three testing stages, i.e., tests A, B, and C, under no-fault conditions, 1-phase open and 2-phase open conditions respectively. The direct test results are then validated with ETAP simulations. In direct testing, A, B, and C can produce a current and relay working time of 6 A-31.04 s, 7.1 A-20.98 s, and 8.3 A-14.93, respectively. Meanwhile, testing using ETAP simulation can produce current and relay working times of 6A-31.366 s, 7A-20.599 s, and 8A-14.822 s respectively. The combination of an APR and an OCR can detect and interrupt voltage drops and overload currents in systems connected to 0.75 kW three-phase induction motors in the industry.

Design and Analysis of a Novel Bidirectional DC‐DC Converter With Ultra‐Conversion Ratio and Reduced Current Stress

ABSTRACTConventional nonisolated bidirectional DC‐DC converters are limited because of their low conversion voltage ratio. To overcome the limitation, this paper proposed a new bidirectional DC‐DC converter to introduce the novel regenerative configuration merged with the switched inductor technique for high voltage conversion applications. This design enables extreme DC‐voltage conversion with a minimal number of semiconductors and passive components. As a result, the converter's cost is reduced, and it can attain a high voltage gain with less duty ratio. In general, ultra‐gain converters suffer from high current stress across the input and output side switches in the step‐up and step‐down modes. To reduce high current stress, an active network configuration is imposed in the proposed converter. This paper describes the operating principle, steady‐state analysis of the voltage gain, and presents the performance matrices of the proposed converter. Furthermore, a comparative analysis is made with conventional and recent literature converters. Finally, a 350‐V, 500‐W, and 20‐kHz experimental prototype has been fabricated to validate the operation and corroborate the theoretical waveforms with experimental results.

A Novel Single-Stage Boost Single-Phase Inverter and Its Composite Control Strategy to Suppress Low-Frequency Input Ripples

Low-frequency pulsating ripples exist on the input side of a single-phase inverter, which bring some adverse effects and harm to the inverter and photovoltaic power generation system. In order to suppress the low-frequency pulsating ripple and reduce the filter circuit parameters, a novel single-stage boost single-phase inverter is proposed, which can suppress low-frequency ripple. And a three-closed-loop compound control strategy that can suppress input low-frequency ripples under the limitation of an energy storage inductor current and buffer capacitor voltage is proposed. The circuit topology, control strategy, key circuit parameters design, system modeling, and simulation of the inverters are deeply analyzed and studied. Simulation and experimental results show that the inverter has a good ability to suppress input low-frequency ripples.

Robust fuzzy controller design with FPGA implementation for matrix converter based induction motor drive

This paper aims to design a controller for a matrix converter fed induction motor drive providing less torque ripples and eliminating peak overshoots with good transient and steady state responses utilizing fuzzy and direct torque control. The proposed controller utilizes Direct Torque Control (DTC) strategy with space vector modulation for regulating stator flux and electromagnetic torque. Due to the superior control capabilities of the matrix converter such as bidirectional power flow, sinusoidal input/output waveforms, high power density and lesser volume, it has attracted significant research interest in the field of adjustable speed drive. Hence the proposed matrix converter based controller is developed in MATLAB/Simulink and tested in different input/output conditions. To validate simulation results, a laboratory prototype is built around the Altium Nano Board 3000 equipped with a Xilinx Spartan using Field Programmable Gate Array (FPGA) is employed. The proposed control scheme, validated through simulation and hardware testing, ensures stable, robust drive system with significant reductions in input side harmonics and enhances induction motor drive's performance.

A Power Circulating Suppression Method for Parallel Transient Inverters with Instantaneous Phase Angle Compensation

A unidirectional link is typically incorporated into the DC input side of an inverter to ensure the reliability and stability of the microgrid power supply. Due to impedance and control variations among inverters, circulating currents may rapidly arise during the operation of parallel transient inverters. Nonetheless, the unidirectional power circulating in a DC unidirectional link results in energy accumulation on the DC side, causing DC bus voltage pumping and affecting MGs’ operation safety and stability. This paper proposes a non-communication-based circulation suppression strategy to suppress power circulation in parallel transients based on the local information of inverters. First, a parallel transient is modeled, and the power circulation phenomenon and its influencing factors are analyzed. Then, the instantaneous power and absorbed active energy are calculated to adjust the phase of the inverter output voltage and suppress power circulation. Moreover, the output frequency is adjusted to balance the DC-side voltage of each inverter. Then, the stability of the parallel system after adding the circulation suppression control strategy is verified using the Lyapunov function method. Finally, simulation and experimental results verify the effectiveness of the proposed power circulation suppression strategy.

Measuring the effects of faults for the rotational characteristics of small plastic gears

Abstract The measurement of the recirculation torque on the input side of the gearbox is a commonly used method for gear drives. This can also be suitable for detecting the effects of periodically occurring faults on small plastic gears, for example the faults of the tooth thickness or pitch. In this article, we investigate the tooth thickness faults of small plastic gears manufactured with an SLA 3D printer. In our work, we first determine the fluctuation of chordal tooth thickness by microscopic examination. Then, using a special device, we measure the same fluctuation in the recirculation torque curve. In addition, we also examine some cases where the tooth thickness is decreased or increased with a great extent.

Adaptive complex coefficient‐filtered extended states observer type three‐phase enhanced phase‐locked loop

AbstractThis paper proposes an adaptive complex coefficient filtered (CCF) full order extended state observer (ESO) type three phase enhanced phase locked loop (EPLL), which is employed in matrix reactance frequency converter (MRFC) for rotating vectors measurement estimation. EPLL phase detector was analysed first to track not only the rad frequency and transient phase, but also the amplitude of the rotating vectors. Full order ESO can filter out more high frequency disturbance, so it can track frequency and phase more accurately than proportion and integration algorithm. CCF modules were analysed in theory to attenuate the disturbance within two times of the EPLL's cut‐off frequency. The whole adaptive CCF‐ESO‐EPLL design, including stability and parameter tuning were then interpreted. The proposed CCF‐ESO‐EPLL adapts the estimated frequency with CCF to attenuate the MRFC switching non‐linear disturbance as well as unknown disturbance by the full order ESO. The MRFC topology necessary measured vectors, as well as the input side reactive power adjustment capacity, were discussed. The theoretical conclusion has been verified on a MRFC prototype. The proposed CCF‐ESO‐EPLL has less parameter tuning, less computation resource requirement, better steady and dynamic performance, and outstanding disturbance robustness.

Analytical investigation of interleaved input/output parallel DAB converter for grid scale battery storage

With the surge of integration of intermittent renewable energy sources into the grid the installation of large scale battery energy storage is rising at a rapid rate to support the power system. The grid scale battery storage needs to be scalable with varying power system requirements. Parallel connected modular dual active bridge (DAB) converter with high frequency transformers interface can facilitate adjustable large power flow for grid scale battery storage. The high gain between LV and HV side can be achieved using isolated high frequency transformers and parallelism of the DAB converter with efficient and smooth bidirectional power transfer capability. In this paper, a generalized interleaving operation (ILO) on both input and output parallel connected DAB (IOPDAB) converter has been proposed for large energy storage capability and to enable improved quality of power flow. The generalized expressions of peak currents, average circulating current and active power flow, has been developed for the IOPDAB converter with n-parallel connected DAB modules. A detailed analytical investigation has been carried out to show the improved currents profile in both input and output sides in the interleaved mode. The operating performance of the IOPDAB converter has been shown using PSCAD/EMTDC software based simulation. The results are verified through laboratory experimental setup with two interleaved I/O parallel DAB using Spartan 3AN FPGA processor as controller. A performance comparison has been done with the non-interleaving operation (NILO) and interleaving operation (ILO) modes, and it is shown that the ILO mode has better performance in terms of efficiency, Input/output ripple current reduction, increased ripple frequency and circulating current minimization.

6E analysis and particle swarm optimization of a novel ultra-high temperature solar cogeneration system fusing thermochemical energy storage and multistage direct heat transfer

The reshaping of the energy development model depends on the penetration of renewable energy on the input side and the substitution of electrical energy on the supply side. Therefore, this research proposes a novel solar cogeneration system in which the Brayton cycle possesses triple pressure and can be flexibly coupled directly to each subsystem under supercriticality without intermediate exchangers. Firstly, a series of research tasks are executed sequentially, including model establishment, cycle potential comparison, operating parameter analysis, and multi-objective particle swarm optimization. Secondly, the exergy flow rate, consumption rate, and 6E (energy, exergy, exergoeconomic, exergoenvironmental, emergoeconomic, and emergoenvironmental) performances of each subsystem and subcomponent are thoroughly discussed. Lastly, the operating performance, economic benefits, and regional characteristics of each subsystem and the cogeneration system are explored. After optimization, the exergy efficiency, average advanced exergy-emergy factor, and advanced exergy-emergy impact difference of the system are 22.72 %, 56.17 %, and 23.97 %. Compared with similar research, the energy efficiency of the system is improved by 8.2 %, which can repay the capital cost in 8.83 years, and the economic benefit reaches $5,503,086 for the entire service year. The system embodies excellent 6E performance, aligns with the goals of reshaping the energy development model, and provides guidelines for the development of ultra-high temperature solar cogeneration.

A composite control method of PWM and phase shift for a three-level DC-DC converter

Abstract This research introduces a control strategy for the Three Level Active Half Bridge (TL-DAHB) DC-DC converter that integrates PWM combined with phase-shift control. This composite control method precisely regulates the output voltage by adjusting the phase-shift duty cycle between the input and output sides. Additionally, the application of the PWM control loop optimizes the duty cycle of the switches, effectively reducing the current stress on the converter during operation, improving transmission efficiency, and decreasing conduction losses of the switches. These enhancements boost the overall performance and the reliability of the converter. With its excellent voltage regulation capabilities and safety features, this converter is an ideal choice in the field of power conversion, especially in applications that demand high levels of stability and safety.

Cleaner production promotion law and pollution: Firm level evidence from China

Using the formulation and implementation of China's Cleaner Production Promotion Law (CPPL) in 2003 as a quasi-natural experiment and a unique combined dataset of Annual Survey of Industrial Production Database and China Industrial Enterprise Pollution Emissions Database over 1998–2013, we investigate the impact of ex-ante prevention policies on firm pollution emissions. Our DID and DDD results show that: 1) The CPPL has significantly reduced firm's per unit of output emissions of SO2 and COD; 2) China's CPPL reduced firm pollution emissions intensity by reducing resource consumption, increasing firms' TFP and the number of green patents (Porter effect), and increasing the total amount of pollutants removal per unit of output; 3) The impact of CPPL on pollution shows modest firm heterogeneity, with larger effects on SOEs and on large-scale enterprises. The conclusions of this paper reveal that China's CPPL, as a formal rule of law regulation and ex-ante prevention policy, not only reduces the pollution intensity of enterprises from the input side, but also stimulate the Porter effect, and reduces the pollution removal level.

A bidirectional power converter connecting electric vehicle battery and DC microgrid

One way to increase electric vehicle (EV) battery utilization is to connect it to a dc microgrid. The EV battery can assume the role of an energy storage from the grid point of view. A bidirectional DC-DC converter will be needed to transfer power between them back and forth. This paper proposes the converter design considering its functional objective, including interleaved phase number determination. Efficiency performance evaluation is presented by power loss analysis with the parasitic-parameters consideration of the components. Finding optimum switching frequency based on power loss analysis is performed independently between input and output sides of the converter. Finally, experiments using a scaled-down prototype are shown to verify the analytical analysis of the converter. The experimental results properly validate the power loss analytic analysis carried out in this paper with a maximum error of 2.04% at 1131-watt, 60 V battery voltage, and 140 V grid voltage. Maximum efficiency 96.97% is obtained at 301-watt, 130 V battery voltage, and 151 V grid voltage. Overall, the converter has a simple structure, capable to be operated in various levels of input and output voltages with a minimum battery side current ripple.

PV-assisted modified Z-source inverter for multiport EV charging infrastructure: Access with PV2V

A solar photovoltaic system with its sustainability and cost-effectiveness, emerges as an important source in powering Electric Vehicle (EV) charging stations. Also, the multiport EV charging allows multiple EVs to charge simultaneously from a single station, optimizing time and resources. For integrating multiple sources and creating multiport charging option, the charging station required an efficient inverter topology. In this work, a modified Z-source inverter (MZSI) is developed for the multiport EV charging station using PV and grid. The proposed MZSI is connected between the input and output sides to boost the voltage as per the demand at the battery side. This developed converter topology operates the systems in five different modes like PV-Grid, PV-battery, grid-Battery and battery-grid, PV to grid and battery. The performance of the proposed work has been validated using MATLAB/Simulink® and in the experimental setup. The experimental measurement has been developed with two charging ports for obtaining 1 kW at each charger end which cumulatively produces 2 kW output across both chargers with an efficiency of 90.18%. With this evaluation, the proposed MZSI can be the best solution for the EV charging station with multiple charging ports.

Investigation of a power factor correction converter utilizing SEPIC topology with input current switching

The single-ended primary-inductor converter (SEPIC) is a popular converter topology that can be employed in diverse application fields where the needed output voltage is greater or lesser than the input voltage. The non-inverted output voltage of a SEPIC converter provides additional advantages when compared to a buck-boost or Ćuk converter. Furthermore, the position of the capacitor in the SEPIC converter provides inherent isolation and circuit safety. One drawback in the conventional bridge-diode SEPIC AC-DC converter is the lack of controllability which can be overcome by adding extra active switch(es) or by replacing the passive diode(s) with active switch(es). However, introducing more active switches increases the control complexity and may increase the requirement for additional driver circuits. To address this trade-off, this article proposes a single-phase AC to DC modified SEPIC converter with input current-switching capability without adding any extra active switch(es). The existing active switch of the DC-DC SEPIC converter was shifted towards the input side and thus no additional switch has been introduced. This allows the option of input-current switching without any additional complexity in the control or driver circuit. The circuit topology, principles of operation, and ideal voltage gain equations for the suggested circuit have been derived and included in this research work. The proposed circuit has been simulated in both open-loop conditions and closed-loop control with varying duty cycles and output load. Results from the simulation show that the proposed converter provides better efficiency (∼90 %) and lower total harmonic distortion (THD) (10 %) for varying duty cycles when compared to a conventional converter. The converter also shows good dynamic response. A low-power 15V hardware prototype has been built to experimentally validate the performance of the proposed converter. Experimental results illustrate that the suggested converter can improve the power factor by up to 0.968 while operating at an efficiency above 75 %. This converter topology can be suitable for applications where high output voltage gain, high power factor, and lower THD are needed without isolation requirements.

Empirical Investigation of a Single-phase Input Switched AC-DC Boost Converter with Improved Power Quality

The Boost converter topology is most widely used for power factor correction (PFC) converters. The conventional passive Boost PFC converter inherently suffers from the lack of controllability and non-ideal characteristics of the diode-bridge rectifier. Replacing diodes with active switch(es) offers viable solutions but increases the circuit complexity. Addressing this trade-off, a novel design of a single–phase input switched AC to DC Boost converter has been presented in this article. The active switch of the Boost DC converter is shifted to the input side of the full-bridge diode rectifier which provides more control on the input current without increasing much of the circuit complexity. Two Boost inductors and two output split capacitors are used for providing higher step-up operation compared to the conventional. The converter has been simulated both in open-loop and closed-loop conditions using the PSIM software. The simulation results show that the proposed converter provides good dynamic response and can maintain a constant stable output voltage during sudden load change. Furthermore, to evaluate the experimental performance of the suggested converter, a prototype converter has been developed. A scaled-down experiment has been performed which shows that the converter can achieve up to 85.2 % efficiency and an input power factor of 0.9.

A single-stage variable output AC-DC converter with PFC and soft-switching for renewable energy integration

This study introduces a versatile variable-output isolated AC-DC converter design distinguished by its incorporation of soft-switching and a novel control algorithm. The converter configuration comprises two full-bridge diode rectifiers, positioned at both input and output sides, complemented by a full-bridge isolated resonant DC–DC converter. By providing soft-switching across all semiconductor components, the proposed design could achieve a significant power density increase while still preserving the power conversion efficiency in an acceptable range. The novel control algorithm concurrently governs power factor and output voltage, employing the duty cycle as the primary control variable and the phase shift as an auxiliary parameter. Using this synergistic method fulfills more efficiency, increases power density, and improves power factor performance. The effectiveness and reliability of the converter were carefully confirmed by experiments done on a prototype, which provided the capacity to provide over 400 watts in its maximum state of operation. Notably, the converter's adaptability makes it an ideal candidate for a wide variety of applications, with a specific emphasis on integrating renewable energy sources into power systems.

Small-signal modeling comparison of dual active bridge converter

The dual active bridge (DAB) converter is a versatile DC-DC converter, which has AC components in the high-frequency transformer within the converter topology as well as DC components at the input and output sides. These AC components are constructed from infinite sinusoids of multiples of the converter's switching frequency. Different approaches have been proposed to model the DAB converter. The generalized averaging modeling (GAM) includes only the first order harmonic of the inductor current with the DC components of the input and output voltages and currents. For better model accuracy, harmonic-domain models have been employed, where the model includes all the harmonics of all the model state variables up to an arbitrary harmonic index. While the harmonic model provides a systematic approach to include the harmonics, this increases the model complexity. To avoid this complexity, the flexible harmonic model is used where harmonics can be selected per each state variable without needing to be in successive order. The aforementioned modeling approaches have been implemented on the DAB converter. This paper aims to compare between the dynamic performance of GAM and the harmonic modeling approaches under different disturbances, where the GAM approach provided a simple model with acceptable results that can be used for controller design, while the LTP model provided a more complex model with better accuracy that is suitable for harmonic studies. The models have been validated and compared using simulations executed on MATLAB /Simulink environment.

An analytical design and analysis of a high gain switched inductor voltage multiplier cell power converter

The proposed modified higher gain boost converter employs switched Inductor and multiplier cell-based voltage boosting techniques, as the paper represents. This converter is modelled to enhance the static gain and efficiency. As the designed topology has an incessant source current at its input side, it is ideal for solar PV applications. With a power capacity of 100 W, the proposed topology is designed to work on 24 V source input and 200 V load/output voltage. The load voltage is maintained by a PI controller, which achieves the highest efficiency of 92% under rated load conditions. The converter’s transient performance with the controller is investigated under various situations, including supply voltage variation, reference voltage variation, and load power variation. Finally, the designed converter’s experimental model is created to evaluate the simulated and conceptual results.

ДИНАМІЧНА МОДЕЛЬ РЕЗОНАНСНОГО ПЕРЕТВОРЮВАЧА ДЛЯ ВПЛИВУ ЗІ СТОРОНИ ЖИВЛЕННЯ

In the paper, a discrete dynamic model of a full-bridge resonant converter with a symmetrical operating mode has been obtained, which describes the resonant converter as a transfer link with an supply voltage input side and a load current output side. The dynamic model is based on a linear mathematical model of the resonant converter built according to the superposition principle. The structure of the resonant converter with the processes outline function is given and analyzed. The structure of the discrete dynamic model of the resonant converter of the nth order is presented. It is proved that the transfer function of the discrete dynamic model for the outline function can be determined by the transfer function of the continuous system. The resulting dependencies describing the discrete transfer functions of the resonant converter are used to obtain the discrete dynamic model of the double-circuit transformer resonant converter in a synchronous rectifier. For this, the sequence of actions is defined: definition of the transfer function of the continuous dynamic model; obtaining the system of equations in vector-matrix form describing electromagnetic processes in the converter; definition of the system of discrete equations; definition of the transfer function of the circuit. The obtained theoretical results were verified by means of simulation modeling of the considered double-circuit resonant converter. The proposed dynamic model makes it possible to analyze the influence of instability and low-frequency fluctuations of the supply voltage of the resonant converter on the output values. The presented results can be used in the development and improvement of single- or multi-circuit bridge high-frequency resonant converters as the secondary power sources and converters used in ship demagnetization systems. References 25, figures 8, tables 2.

OECD 고등교육 재정의 국제 비교

In this article we compare the higher education finance of advanced countries using OECD’s “Education at a Glance” data from 1998~2018. We first investigate the relationship among input side variables such as relative size of number of college students, relative size of per student expenditure, the portion of public expenditure in higher education finance. We find fundamental trade-off between the quality and quantity, as captured by the negative correlation between the per student expenditure-GDP per capita ratio and the number of college students compared to the total population. We also investigate the relationship between the input and outputs of higher education. The major findings are that the higher the portion of public expenditure in higher education finance, the lower the chance of having world’s top research universities. Meanwhile, the youth unemployment tends to be lower in countries that governments’ portion of higher education finance are large.