Discontinuous Mode Research Articles

Comparative analysis of switching losses and current ripple of continuous and discontinuous SVPWM strategies for unbalanced two‐phase four‐leg VSI Fed unsymmetrical two‐phase induction motor

This paper presents a comparative analysis of the continuous space vector pulse width modulation and the discontinuous space vector pulse width modulation in terms of the switching losses and current ripple reduction for the unbalanced two-phase four-leg voltage source inverter fed unsymmetrical two-phase induction motor. The main function of both space vector pulse width modulation strategies is to produce unbalanced two-output voltages with constant phase shift of 90° for main and auxiliary windings. The discontinuous space vector pulse width modulation principle is modified from a traditional two-phase four-leg voltage source inverter by placement of the space vectors to alternatively eliminate zero space vector in each switching sequence. As a consequence, the proposed unmodulation region or clamping zone of the discontinuous modulation strategy has 180° all the time. The experimental results illustrate the modulation waveforms of both methods, output voltage spectrum, normalized switching losses, output current ripple and inverter efficiency at high modulation index. The evaluation of the normalized average switching losses and the current ripple of the discontinuous space vector pulse width modulation method can be reduced more than that of the continuous space vector pulse width modulation method.

Post-treatment of real municipal wastewater effluents by means of granular activated carbon (GAC) based catalytic processes: A focus on abatement of pharmaceutically active compounds

Pharmaceutically active compounds (PhACs) widely present in urban wastewater effluents pose a threat to ecosystems in the receiving aquatic environment. In this work, efficiency of granular activated carbon (GAC) - based catalytic processes, namely catalytic wet peroxide oxidation (CWPO), peroxymonosulfate oxidation (PMS/GAC) and peroxydisulfate oxidation (PDS/GAC) at ambient temperature and pressure were studied for removal of 22 PhACs (ng L−1 level) that were present in secondary effluents of real urban wastewater. Concentrations of PhACs were measured using Ultra Performance Liquid Chromatography – Triple Quadrupole Mass Spectrometry (UPLC-QqQ-MS/MS). Catalytic experiments were conducted in discontinuous mode using up-flow fixed bed reactors with granular activated carbon (GAC) as a catalyst. The catalyst was characterized by means of N2 adsorption-desorption isotherm, mercury intrusion porosimetry (MIP), elemental analysis, X-ray fluorescence spectroscopy (WDXRF), X-ray diffraction (XRD), thermal gravimetry and differential temperature analyses coupled mass spectrometry (TGA-DTA-MS). Results indicate that the highest efficiency in terms of TOC removal was achieved during CWPO performed at optimal operational conditions (stoichiometric dose of H2O2; TOC removal ~ 82%) followed by PMS/GAC (initial PMS concentration 100 mg L−1; TOC removal ~73.7%) and PDS/GAC (initial PDS concentration 100 mg L−1; TOC removal ~ 67.9%) after 5 min of contact time. Full consumption of oxidants was observed in all cases for CWPO and PDS/GAC at contact times of 2.5 min, while for PMS/GAC it was 1.5 min. In general, for 18 out of 22 target PhACs, very high removal efficiencies (> 92%) were achieved in all tested processes (including adsorption) performed at optimal operational conditions during 5 min of contact time. However, moderate (40 – 70%) and poor (< 40%) removal efficiencies were achieved for salicylic acid, ofloxacin, norfloxacin and ciprofloxacin, which can be possibly attributed to insufficient contact time. Despite high efficiency of all studied processes for PhACs elimination from urban wastewater effluent, CWPO seems to be more promising for continuous operation.

Hybrid Model Predictive Control of DC–DC Boost Converters With Constant Power Load

This article presents a hybrid model predictive controller to ensure dc microgrid stability and enhance the performance of dc-dc boost converters interfaced with constant power loads (CPLs) in a hybrid system. Hybrid systems are dynamic systems with both continuous current mode and discontinuous current mode states. The main purpose in this article is to develop an advanced control technique for voltage regulation and stabilization of the converters in the presence of CPLs due to serious stability concerns, without considering the accurate modelling information of the system. In this regard, an automatic model, considering different modes of operation induced by semiconductor switches in dc-dc boost converters and highly non-linear nature of CPL is employed to design the proposed control approach. The non-linear CPL connected directly to a dc-dc boost converter is utilized to define an optimal tracking control problem by minimizing a finite-prediction horizon cost function, which is known as a finite control set MPC. The proposed controller, which is implemented in both continuous and discontinuous current modes, accounts for the regulation of output voltage within the predefined range. The effectiveness of the proposed hybrid model predictive control is verified using a comparative evaluation with discrete-time averaged model predictive control, continuous control set MPC, and the conventional PI control under experimental conditions. The results authenticate an improved dynamic performance, which can be applied to practical dc microgrids with CPLs.

Improved Power Quality Transformerless Single-Stage Bridgeless Converter Based Charger for Light Electric Vehicles

In this article, a bridgeless switched inductor Cuk (BSIC) converter based charger is presented to provide the low-cost and reduced-size charging solution for the light electric vehicles, i.e., LEVs, with enhanced performances at the supply side. Generally, the chargers of LEVs such as E-Rickshaws, E-Bike, and E-Cycle, are equipped with an additional converter to charge the batteries at low voltages (24–72 V). The switched inductor configuration improves the step-down dc voltage gain of the charger with only one stage and also improves the reliability at such low voltages. It is noteworthy that the cost associated with the sensors along with the size of the magnetic components is considerably reduced by operating the charger in discontinuous current mode condition. Moreover, the high-gain transformerless configuration further improves the cost, size, and efficiency of the charger. The effectiveness of the charger is tested on a laboratory prototype, for an 850 W rating with 220 V, 50 Hz nominal supply voltage conditions. The steady state and dynamic behaviors of the charger are analyzed under different operating conditions. Moreover, the behaviors of the charger during the initialization of charging process are analyzed for ensuring the soft starting of the charger. A basic comparison of the presented charger configuration with existing LEVs chargers is presented to highlight its advantages over the existing one.

Verification of irregularities in a reinforced concrete tall structure

Building plans with simple, regular and compact arrangements are preferred to perform well during the occurrence of earthquakes. In practice, planning a regular layout may not be possible in all occasions due to irregular shape of building sites in the plan as well as in elevation due to uneven ground conditions. It is a challenge both for the architect and structural designer to plan and design such buildings. Further, the planning is to be made in compliance with the rules and regulations of the local approving authorities, which sometimes may lead to irregular shapes both in plan and elevation. Most of the times, the owner’s and / or builder’s requirement is to be fulfilled such that the project is viable to them. This is a challenge for the practising professionals designing the structures that are built in earthquake zones of III, IV and V. The earthquake resistant design code i.e., IS 1893 (Part 1) was revised in the year 2016 and adopting the provisions of building irregularities with more restrictions on their allowable limits. This paper addresses the identification or verification of the existence of building irregularities in a 17 storey multipurpose tall structure with two parking, two commercial and 13 residential floors. From the results, it is opined that there is a need for a review of the procedure and some of the limits set on irregular building configurations particularly Stiffness, Excessive openings, Out-of-plane offsets, Strength, In-plane discontinuity and Irregular modes of oscillation.

A Scalar Decoupled PWM Technique for a Three-Level Symmetrical Dual Inverter Fed OEWIM Drive for Electric Vehicle

Induction motor is employed in electric vehicle to control the speed. Dual inverter fed drives are used for this purpose. Even though it finds application in many applications, high common-mode voltage (CMV) becomes a major problem and it results in EMI problems. Hence, to overcome this problem, this work introduced a novel PWM generation technique named scalar decoupled PWM topology to control a three-level symmetrical DI fed OEWIM. In this proposed topology, switching signals of the inverter 1 and 2 can be generated and controlled separately. To examine the efficiency of the proposed topology, its operation is examined under both continuous and discontinuous modes of operation and is carried out in both simulation and experimental set up. From the acquired results, it is concluded that this proposed topology exhibits reduced CMV and harmonics when compared to traditional PWM topology.

A novel impedance source inverter topology with active front-end for AC drives

A unique impedance Source Inverter with an Active Front-End is proposed in this paper, that can be used for controlling AC Drives. There are a number of modulation schemes that may be used with the three-phase impedance source inverters, ultimate reduction in the switching losses makes the discontinuous modulation schemes seem most appropriate. The discontinuous modulation schemes are differentiated into two classes based on the technique used for achieving shoot-through (ST) state: single-phase-leg ST-based and three-phase-leg ST-based (3P) discontinuous modulation schemes. In this paper, we discuss the improvements in Single Phase Maximum Boost Discontinuous Space Vector modulation (1P/MB/DSVM) scheme under similar operating conditions, by simplifying gate signal generation and improving the conversion efficiency. A simulated analysis and comparison of the conventional and the enhanced 1P/MB/DSVM schemes is also discussed using PLECS. Lastly, verification of the simulation outcomes and reported analysis is carried out by making use of a three-phase quasi-Z-source inverter (qZSI) prototype which demonstrates improvement in conversion efficiency, utilizing the refined 1P/MB/DSVM scheme.

Design and development of a new three‐phase AC‐DC single‐stage wind energy conversion system

The prevalent use of the diode bridge rectifier in three phase wind energy conversion systems decreases the efficiency of the power generation. In standalone wind energy generation, bridgeless converters can address this problem by eliminating the front-end diode bridge rectifier. This work presents a novel single-stage three-phase bridgeless AC to DC c̀uk converter for wind energy conversion systems. The proposed converter is designed to work in discontinuous inductor current mode because of its inherent power factor correction and less harmonic distortion. Using body-diodes of the MOSFETs per phase component reduction is also done in this converter. A unique maximum power point tracking technique is developed for this converter using three-phase voltages and currents, instead of the DC link states. A wind energy emulation system using a DC motor and self excited induction generator is used to test the laboratory prototype of the proposed converter.

Multimode Constant Power Control Strategy for LCC Resonant Capacitor Charging Power Supply Based on State Plane Analysis

A novel constant power charging strategy is proposed for LCC resonant capacitor charging power supply (CCPS) in this article, which combines the advantages of discontinuous current mode (DCM) and continuous current mode (CCM) to increase the charging speed of capacitor and the utilization of input grid capacity. In order to implement the multimode constant power control (CPC) strategy, a steady-state model of LCC series-parallel resonant converter is built by state plane analysis, and the analytical expressions for output voltage, average output current, and switching frequency are derived. By the analytical expressions, this control strategy directly determines the relationship of the output voltage and the switch frequency, so the frequency control curve of the pulse frequency modulation could be realized easily. Accordingly, the converter operating along the control curve can take advantage of high average and low peak current of CCM, small switching loss of DCM. Finally, the accuracy of LCC state plane model and the effectiveness of multimode CPC are verified by the simulation and a 2-kW CCPS experiment.

A Constant Current Digital Control Method for Primary-Side Regulation Active-Clamp Flyback Converter

Constant current controlled flyback converter is widely used in low power applications for its simple structure and low cost. In order to further improve the output power and the efficiency, active-clamp flyback converter with soft-switching technique is always used. To avoid the nonlinearity and temperature drift of opto-coupler in the feedback circuit, a constant current digital control method is proposed for a primary-side regulation active-clamp (PSRAC) flyback converter in this article. Soft-switching technique is realized in discontinuous conduction modulation mode with a modified active-clamp technique. To compensate the nonlinearity of the secondary diode current with primary-side regulation, a new output current estimation algorithm is put forward based on the charge balance principle. The output current is predicted from primary current and the auxiliary winding voltage, and constant output current control is realized with primary peak current control method. The cost is low as only one low speed digital-to-analog converter, three comparators and a digital controller are required. The proposed control scheme was verified by a field-programmable gate array controlled 5.4-10.8 V/1.80 A PSRAC flyback converter. The output current accuracy is within in 1.2% in different input and output condition and the peak efficiency is improved by 3.6% after active-clamp technique is used.

Bidirectional single-loop current sensorless control applied to NPC multi-level converter considering conduction losses

The current feedback is considered as unavoidable part of most control system driving power electronic converters. However, it is possible to eliminate the use of current sensor, if properly calculated volt-second balance is applied to input inductor. This paper describes the implementation of current sensorless control technique applied to neutral point clamped multi-level converter, where only voltage control-loop is used to stabilize internal capacitors voltage, while inductor’s current is shaped by means of current sensorless control block in both discontinuous and continuous current modes. The capacitor voltage balancing is implemented by means of delta-controller that selects alternative capacitor in respect to main switching scheme. Finally, the analytical study of proposed solution is verified with simulation results.

Fast Motion Speed Alters the Sit-to-Walk Spatial and Temporal Pattern in Healthy Young Men.

Sit-to-Walk (STW) is a critical task for daily independence, yet its two inherent destabilizing events (seat-off, walking initiation) may diminish postural stability under fast motion speed (FS). This study aimed at the FS effect on the STW spatial and temporal patterns, with a specific interest in the relative STW temporal pattern. The STW kinetics and kinematics were recorded (n=18 men, 20.7±2.0 years) at preferred and FS. Statistics included One-Way repeated measures ANOVA (SPSS 25.0, p≤0.05). The FS spatial pattern reveals a discontinuous mode of the forward ground reaction force, indicating a balance rather than a propulsive strategy during the Rising phase. The FS relative temporal pattern reveals the prolongation of the Leaning phase (most possibly due to the feet repositioning), the shortening of the Rising and the Walking phases, and a relative delay in the spatial variables (p≤0.05). Overall, the results do not allow the STW consideration at FS as a “magnified” with respect to force, or a “shrinked-in” with respect to time, copy of the preferred motion speed. As more generic and versatile than the absolute one, the relative temporal pattern may be used as a reference for a variety of populations.

Improvement of laccase biosynthesis by various feeding strategies and in situ integration of biomass separation

In this paper the process of biosynthesis of fungal laccases is addressed with the investigation of methods for improvement of the enzyme’s production efficiency and prolongation of the culture’s performance. The research is focused on improving the biosynthesis results through repeated discontinuous fed-batch cultures, and in situ integration of the process with the first step of downstream processing – biomass separation via specially constructed rotating filter. Four different strategies were applied with varied frequency of feeding and whether the filter was used or not. Based on obtained results, it is claimed that biosynthesis of laccase conducted in repeated discontinuous fed-batch mode provides satisfactory improvement in terms of laccase production per run. The total laccase recovery in the process with daily refills was more than 6 times higher than in the batch mode performed in the same bioreactor.

Simple discontinuous PWM strategies to reduce the switching losses of an indirect matrix converter

This work proposes the new discontinuous pulse width modulation (DPWM) schemes for an indirect matrix converter (IMC) to reduce the switching losses. The use of discontinuous modulation signals reduces the switching losses of the IMC by reducing the switching counts per cycle of the output converter. The key feature of the proposed schemes is the easy implementation as compared to existing DPWM schemes of the IMC. The major drawback of the existing DPWM schemes is the absence of zero current commutation (ZCC). In the absence of ZCC, the switchings of the input converter are accomplished through four-step commutation which adds the difficulties to the implementation. The proposed scheme overcomes above limitation by using the triangular carrier instead of the sawtooth carrier for the modulation of input converter. Consequently, the ZCC is enabled on the input converter which allows the use of two-step commutation. The two-step commutation simplifies the implementation to a great extent. The presented scheme provides the required input/output performance similar to continuous PWM (CPWM) schemes. The proposed work is verified by the simulation and experimental results. The reduction in the switching losses of the IMC by the new scheme is verified based on the comparison with the CPWM scheme.

Travelling through the emotions: staging the erotic

Este artigo discute a tradução para a performance como um esforço humanista impulsionado pelo desejo de conexão com a alteridade. A partir das ideias de Gabriel Marcel, Georges Bataille e Slavoj Žižek, entre outros, ele descreve a tradução teatral nos termos de uma nostalgia pelo humano ausente, como uma prática preocupada em recuperar a conexão perdida, uma continuação do ser que vai além dos limites e restrições do racional. Nesse sentido, argumenta que há algo comum à promessa mantida pela tradução e pela experiência erótica. Em última análise, talvez o que acenda essa promessa seja o contraste com a posse de si mesmo, o antídoto para nosso modo descontínuo de existência como indivíduos definidos e separados.

High Gain Switched-Inductor-Double-Leg Converter With Wide Duty Range for DC Microgrid

In a dc microgrid, efficient high gain converters are needed to raise the voltage level of low voltage power sources such as photovoltaic, fuel cells, etc. In this article, a high-gain switched-inductor-double-leg converter for dc microgrid is proposed. The proposed converter is capable of providing higher gain devoid of using any transformer, coupled inductor, and multiple voltage lifting techniques, e.g., triple lift, quadruple lift, super lift, etc. The operating modes of the converter are controlled using three switches in double duty mode. Compared to single duty converter, the double duty converter provides a flexibility in selection of duty cycle for switch to achieve desired output voltage and controlling inductor current ripple magnitude by selecting appropriate duty cycles. Moreover, two duty cycles make the converter capable of achieving high gain with wide duty range and an individual switch does not need to operate at very large duty cycle to achieve high voltage gain. The topological description, operating principles, steady-state voltage gain analysis during continuous conduction mode and discontinuous continuous mode, boundary condition, and voltage and current analysis, efficiency analysis, comparison and design of the proposed are presented. The proposed converter is tested in laboratory to validate its feasibility and performance.

Puesta a punto de dispositivos para ensayos de digestión anaeróbica

La Digestión Anaeróbica (DA) permite tratar residuos orgánicos y transformarlos en productos con valor agregado: el biogás y el digerido. En el presente trabajo se confeccionaron y testearon dispositivos para ensayos de DA en modalidad discontinua de 530 ml (Dispositivo tipo 1) y semi-continua de 5.62 L (Dispositivo tipo 2). El Dispositivo 1 logró validarse por medio de ensayos con orujo de manzana, realizados por triplicado, con una producción de biogás de 142 ± 6.6 ml y de CH4 de 102.7 ± 9.8 ml y se corroboró que el agregado de cáscara de huevo mejora en un 43.06% la generación de CH4. Otro estudio, realizado con orujo de manzana y macroalgas en distintas proporciones, mostró los valores más altos de CH4 para la DA con 100% orujo (224.33 ± 21.59 ml), seguido por 50-50% orujo-macroalgas (92.5 ± 14.73 ml) y por último, 100% macroalgas (6.17 ± 2.93 ml). En el Dispositivo tipo 2 se realizaron pruebas de generación de inóculo a partir de lodo anaeróbico de río, y estudios con orujo de manzana y purín de cerdo, que permitieron testear la aptitud del diseño y sugerir mejoras.

Model-Based Control for Grid-Tied Inverters Operated in Discontinuous Current Mode With Low Harmonic Current Distortion

Low-power grid-tied inverters can be designed to operate in a discontinuous current mode (DCM) with a model-based feedforward control, which can be advantageous for further increasing the switching frequency to achieve high power density. However, current distortions can be generated due to the parasitic capacitance of the devices. To address the issue, an improved modulation for the DCM is proposed in this article. We describe the proposed modulation and, then, demonstrate its improved performance by a time-domain simulation. We also discuss the proposed modulation in comparison with another method that has been proposed previously. The proposed method is also verified by experiments using a 400-W laboratory prototype. A significant improvement in the current harmonics by the improved modulation has been confirmed.

A Fast Processing Discontinuous Control Strategy for Vienna Rectifier

In this paper, Vienna rectifier has been inspected as one of the prominent topologies among three-level switched-mode rectifiers. A fast processing discontinuous modulation strategy has been proposed with the aim of improving the rectifier’s performance. The proposed method not only takes advantage of special properties available in three-phase three-level rectifiers, but also reduces the control design complexity and the switching loss. Moreover, neutral point voltage balancing is inherently realized. To achieve these goals, the rectifier is decoupled into two 2-level boost converters in every defined region, leading to simple modulation algorithm and fast processing control strategy. The validity of the proposed technique has been verified via simulation and experimental results conducted on a laboratory prototype.

Ion-exchange medium coated with abundant small zwitterions for the purification of soluble proteins

A new ion-exchange medium was prepared from magnetic particles of ∼1.0 µm through coating with small zwitterions and then functionalizing with ampholytic groups for the isoelectric point of ∼6.4 and denoted MSP-ZEWB. With Meyerozyma guilliermondii uricase (MGU) as the model of soluble proteins, the purification of a protein via ion-exchange was compared between MSP-ZEWB through elution in discontinuous mode and Toyopearl SP-650C as a classical ion-exchange medium through elution in continuous mode. MGU was adsorbed at pH 7.6 or 8.0 and eluted via competitive displacement by NaCl or electrostatic repulsions with an elution buffer at pH 10 to reverse the type of net charges of MGU. From MSP-ZEWB, MGU was eluted more rapidly with the elution percentages higher than those from Toyopearl SP-650C. For yielding a unit of MGU activity, MSP-ZEWB gave the elution solution volumes that were ∼50% of those obtained with Toyopearl SP-650C. The yields of MGU of the highest purity from MSP-ZEWB were higher than those from Toyopearl SP-650C, but the highest purification folds with both media were comparable. MSP-ZEWB regenerated for 16 times still showed the consistent purification efficacy. Therefore, the ion-exchange media bearing small zwitterion coats showed great promise for the purification of soluble proteins.