Discontinuous Mode Operation Research Articles

Analysis of variable speed chopper fed Brushless Direct Current motor

This paper provides the detailed analysis of the DC-DC chopper fed Brushless DC motor drive used for low-power applications. The various methods used to improve the power quality at the ac mains with lesser number of components are discussed. The most effective method of power quality improvement is also simulated using MATLAB Simulink. Improved method of speed control by controlling the dc link voltage of Voltage Source Inverter is also discussed with reduced switching losses. The continuous and discontinuous modes of operation of the converters are also discussed based on the improvement in power quality. The performance of the most effective solution is simulated in MATLAB Simulink environment and the obtained results are presented.

Predicting core losses and efficiency of SRM in continuous current mode of operation using improved analytical technique

Abstract In applications in which the high torque per ampere at low speed and rated power at high speed are required, the continuous current method is the best solution. However, there is no report on calculating the core loss of SRM in continuous current mode of operation. Efficiency and iron loss calculation which are complex tasks in case of conventional mode of operation is even more involved in continuous current mode of operation. In this paper, the Switched Reluctance Motor (SRM) is modeled using finite element method and core loss and copper loss of SRM in discontinuous and continuous current modes of operation are calculated using improved analytical techniques to include the minor loop losses in continuous current mode of operation. Motor efficiency versus speed in both operation modes is obtained and compared.

A Common Mode Voltage Reductions for Three Phase Coupled Inductor Inverter Using Multi-Carrier Interleaved PWM Strategies

This work presents multi-carrier interleaved PWM strategies to control common mode voltage (CMV) in three phase coupled inductor inverter (CII). The proposed scheme has the feature of reduced number of switches with higher output voltage level. The major problem in the coupled inductor inverter (CII) topology is power loss in inductor that is related to the magnitude of current ripple in the winding. The proposed multi-carrier interleaved PWM technique is easy to implement when compared to other PWM techniques. The additional advantage is reduction of the current ripple in inductor. The minimization of current ripple in inductor winding leads to the reduction in the common mode current participation in the (Y-Δ) connected induction motor. The common mode voltage is represented as the integration of the common mode current in each phase. The multi-carrier interleaved PWM consists of the continuous and discontinuous modes of operation. By choosing the high effective switching state with the help of Discontinuous PWM technique for inductor winding, the common mode voltage (CMV) can be reduced without degrading the performance of the inverter. The proposed scheme is applied for three-phase coupled inductor inverter (CII) to obtain the five level output. The benefit of these proposed switching strategies is reduction of the common mode voltage in the range of +Vdc/12. The simulation with 1HP induction motor drive system is set-up in MATLAB and same result is validated effectively by hardware-FPGA SPARTAN-3E processor.

Low‐voltage ride‐through concept in flyback inverter‐based alternating current–photovoltaic modules

The flyback inverter-based alternating current–photovoltaic modules’ behaviour under voltage rise/drop conditions is investigated. Specifically, the aim is to calculate the module steady-state operational characteristics of distributed generators, such us generation loss and root mean square current rise, based on the low-voltage ride-through capability requirements. The proposed analysis stands for the widely known discontinuous conduction mode of operation and it can also account for high power inverter topologies. Furthermore, the derived expressions are corroborated by means of PSPICE simulation along with the selected experimental results and insightful discussions.

Output switching noise spectral analysis and modeling in buck regulators

Useful closed-form equations for describing the spectrum of inherent steady-state switching noise at the output of buck regulators in both Continuous Conduction Mode (CCM) and Discontinuous Conduction Mode (DCM) of operation are derived. The formulas can be used by analog/RF designers to predict and account for power supply noise early in the design cycle regardless of the specific design details of the regulator itself, which can save significant development and debugging effort later in the design cycle. The theoretical formulas are verified by measuring the noise spectrum of a standard off-the-shelf buck regulator commonly used for mixed-signal SoCs and comparing these measurements to the predictions made by the proposed formulas.

Decolourization and Mineralization of Reactive Black-5 with Transition Metal Oxide Coated Electrodes by Electrochemical Oxidation

The electrochemical oxidation of reactive black -5 (RB-5) dye was investigated at thermally prepared Ti/CuOx, Ti/NiO, Ti/CoOx, Ti/AgOx electrodes. The synthetic wastewater of 100 mg/L RB- 5 was prepared as a model component for electrochemical treatment. The electro-oxidation was carried out in a discontinuous operation mode under galvanostatic conditions, equipped with a single compartment electrochemical cell. The laboratory fabricated DSA electrodes were allowed to decolorize and mineralize RB-5 at 50 mA/cm2 constant current density at acidic pH and in presence of chlorine compound. The performance of various electrodes was measured in terms of reduction of colour, COD and TOC with respect to time. This confirms that all electrodes are proved to be efficient for colour and COD reduction but not very promising for TOC reduction.

Bridgeless single stage flyback converter-based computer power supply

A power factor corrected (PFC) bridgeless converter-based computer power supply (CPS) using multioutput flyback dc-dc converter is presented in discontinuous conduction mode (DCM) of operation. In place of the conventional diode bridge to convert ac voltage into uncontrolled dc voltage, two multioutput flyback converters are connected in anti-series across the single phase ac supply. The diode bridge at the front end is eliminated and the outputs of the two flyback converters are connected to two high frequency transformers, HFT-1 and HFT-2 respectively. Two multi-output flyback converters are operating alternately in positive and negative half cycles of the ac mains respectively to avoid the diode bridge at the front end. The proposed configuration of CPS offers low total harmonic distortion (THD) of supply current, low conduction losses due to the absence of diode bridge, high efficiency and good power factor (PF) with very simple control at full load as well as light load conditions. The performance of the proposed CPS meets the guidelines of international standards.

Using the Discrete Element Method for Predicting the Mixing Behavior of Gravity Blenders in Different Operation Modes

AbstractThe application of residence time density distributions gained with discrete element method (DEM) simulations for predicting the mixing behavior of gravity blenders in different operation modes is presented. Knowing these distributions, the performance of a blender can be predicted during different blending tasks in continuous and discontinuous operation mode. Up to now, the residence time distributions needed for these predictions could only be measured. It will be explained how a gravity blender containing more than 1 million of particles is mapped to simulation considering the computational effort as well as the quantitative validity of the results. Based on these data, the discontinuous blending behavior is predicted. The results indicate good agreement between simulations and experimental data and can serve as a basis for designing gravity blenders.

에너지저장 커패시터의 최적 충전을 위한 직렬공진형 컨버터의 운용 모드 비교

In this paper, charging modes of series resonant converter for a high voltage energy storage capacitor are compared in terms of charging time, peak resonant current, normalized peak resonant current and voltage in each operation mode. Operating principles of the full bridge series resonant converter with capacitor load are explained and analyzed in discontinuous and continuous operation mode. Based on the analysis and simulation result, 0.6ω_r<ω_s<0.75ω_r and 1.3ω_r<ω_s<1.4ω_r are evaluated to the best range of switching frequency for charging of an high voltage energy storage capacitor. 1.8 kJ/s SRC prototype is assembled with TI 28335 DSP controller and 40 kJ, 7 kV energy storage capacitor. Design rules based on the comparative analysis are verified by experiment.

Electrochemical Degradation of a Real Pharmaceutical Effluent

In this work, the electrochemical treatment of an effluent from the pharmaceutical industry with boron-doped diamond electrodes was investigated. The electrolyses were carried out in a discontinuous operation mode under galvanostatic conditions, using a bench-scale plant equipped with a single-compartment electrochemical flow cell. The effect of operating conditions, such as current density (from 25.7 to 179.4 mA cm2) and flow rate (from 104.8 to 564.7 cm3 min−1), at residence times between 0 and 570 min, was studied. Design of experiments was used for optimizing the process. The global contribution of operative parameters and evolution of the residence time in TOC removal was studied, and a time of 77 min was obtained in order to evaluate the highest influence of the operative parameters. For this time, ANOVA test reported significance for four of the five involved variables. The current density was found to have a considerable positive effect on TOC removal, whereas the flow rate was found to have a moderate negative effect on target variable.

Series Resonant Multiinverter with Discontinuous-Mode Control for Improved Light-Load Operation

Operation under light-load conditions is a general issue when developing power converters as it can lead to system instability and/or decreased performance. This topic is particularly important for resonant converters as their efficiency significantly reduces when their operation point is set outside their resonant conditions. Considering the importance of efficiency for power converter reliability, environmental impacts, and regulation concerns, a major effort to improve the operation under light-load conditions is justified. Domestic induction heating is an application where variable loads and output power requirements imply operation under a wide range of conditions, including long-term light-load operation. The aim of this paper is to propose an improved control scheme for series resonant multiinverters, which are a cost-effective topology for supplying multiple inductive loads, based on discontinuous-mode operation. Two different control strategies are proposed: regenerative control and direct conduction control. An analytical study is performed, and the main simulation results are presented. An experimental series resonant multiinverter prototype is used to validate the simulation results.

Hybrid predictive control of a DC–DC boost converter in both continuous and discontinuous current modes of operation

AbstractDeveloping efficient and appropriate modeling and control techniques for DC–DC converters is of major importance in power electronics area and has attracted much attention from automatic control theory. Since DC–DC converters have a complex hybrid nature, recently several techniques based on hybrid modeling and control have been introduced. These techniques have shown better results as compared with conventional averaging‐based schemes with limited modeling and control abilities. But the current works in this field have not considered all possible dynamics of the converters in both continuous and discontinuous current modes (CCM, DCM) of operations. These dynamics are results of controlled and uncontrolled switching phenomena in DC–DC converters. This paper proposes a new switching scheme for modeling and controlling a DC–DC boost converter. The converter is represented as a hybrid automaton by considering the all three possible modes. The hybrid automaton is translated into the mixed logical dynamical (MLD) mathematical framework. The switching among these modes is generated by hybrid predictive control method which is calculated by Mixed Integer Quadratic Programming (MIQP). Using the exact model of the converter, the proposed switching algorithm can globally control the converter in all operation regimes, including CCM and DCM operations, considering all constraints in the physical plant, such as maximum inductor current and capacitor voltage limits. The switching algorithm is applied to a real converter circuit, modeled with various parasitic components. Simulation results are provided to show the advantages of the proposed control scheme. Copyright © 2010 John Wiley &amp; Sons, Ltd.

Averaged Modeling of Non-ideal Boost Converter Operating in DCM

The averaged model of non-ideal Boost converter operating in discontinuous mode (DCM) circuit was studied based on the switching elements model, the equivalent circuit method, and the energy conservation law, in which the duty ratio constraint was introduced to improve the model. The open-loop transfer function was derived to build the small signal model, by adding a voltage-controlled feedback loop, the closed-loop transfer function was also derived. The simulation results showed the correctness of the model at last.

Control Scheme for Sensorless Operation and Detection of CCM and DCM Operation Modes in Synchronous Switching Power Converters

Switching power converters with synchronous rectification utilize transitioning between inductor's current continuous and discontinuous conduction operation modes (CCM and DCM) in order to achieve improved power efficiency across wide load and input voltage ranges. The inductor current zero crossing is sensed in order to detect the operation modes transition point between CCM and DCM. The challenges associated with this include inductor current zero crossing point sensing accuracy, noise effect near the zero crossing point, and the sensing circuitry speed and power loss. Moreover, additional hardware such as analog-to-digital converter is required if the controller used is a fully digital controller. In this letter, a control scheme for sensorless operation and detection of CCM and DCM in a switching power converter is presented. The presented controller utilizes dual control loops and does not require sensing the inductor current or any current in the converter, which eliminates or reduces challenges associated with inductor current sensing for the zero point detection. The presented controller is discussed, and proof-of-concept experimental prototype results are presented.

A Practical Algorithm for Simulation of Transient Performance of Chopper-Controlled R-L and Dc Drive Loads

This paper presents a practical algorithm for obtaining transient response of chopper-controlled active and passive loads. Core algorithm given for simulating transient response of chopper-controlled R-L load is extended to chopper-controlled DC drive, covering both the continuous and discontinuous current modes of operation. Although chopper-controlled loads are taken as case studies, with a little effort the core algorithm can be readily extended to handle the transient response of the other system which manifests periodic discontinuous forcing functions of different types. Transient current and speed responses of chopper-controlled DC drive, which are obtained from application of the proposed algorithm are compared with their counterparts obtained from detailed numerical solution of the state-space model of the drive using fourthorder Runge-Kutta method, and the advantages of proposed algorithm are discussed.

Modelling and experimental model validation for a pusher-type reheating furnace

The slab reheating process turns out to play a key role in dealing with the steadily increasing demands on the quality of hot rolled steel plates. Improvements both in the throughput of the furnace as well as the accurate realization of reheating paths for the slabs require to incorporate modern model-based control design techniques into the furnace automation. For this, suitable mathematical models with manageable dimension and complexity have to be determined for the furnace and slab dynamics. In this contribution, first principles are applied for the derivation of a physics-based model of the reheating process in a so-called pusher-type reheating furnace. Thereby, a discontinuous mode of furnace operation is considered, which is characterized by a varying number of slabs with variable geometry being discontinuously moved through the furnace. This, in particular, results in a hybrid structure of the mathematical model. The accuracy of the mathematical model is validated by a comparison with experimental data obtained from a measurement campaign with a test slab performed at an industrial pusher-type reheating furnace.

Synthesis of structured lipids by two enzymatic steps: Ethanolysis of fish oils and esterification of 2-monoacylglycerols

This paper studies the synthesis of structured triacylglycerols (STAGs), rich in polyunsaturated fatty acids (PUFAs) by a two-step enzymatic process: (i) alcoholysis of fish oils (cod liver and tuna oils) with ethanol to obtain 2-monoacylglycerols (2-MAGs), catalyzed by 1,3 specific lipases and (ii) esterification of these 2-MAGs with caprylic acid (CA, 8:0), also catalyzed by a 1,3 specific lipase, to produce STAGs of structure CA–PUFA–CA. As regards the alcoholysis reaction, three factors have been studied: the influence of the type of lipase used (lipase D from Rhizopus oryzae, immobilized on Accurel MP1000, and Novozym 435 from Candida antarctica), the operational mode of a stirred tank reactor (STR operating in discontinuous and continuous mode) and the intensity of treatment (IOT = lipase amount × reaction time/oil amount). Although higher 2-MAG yields were obtained with lipase D, Novozym 435 was selected due to its greater stability in the operational conditions. The highest 2-MAG yield (63%) was attained in the STR operating in discontinuous mode at an IOT of 1 g lipase × h g oil −1 (at higher IOT the 2-MAGs were degraded to glycerol). This system was scaled up to 100 times the initial volume, achieving a similar yield (65%) at the same IOT. The 2-MAGs in the final alcoholysis reaction mixture were separated from ethyl esters by solvent extraction using solvents of low toxicity (ethanol and hexane); the 2-MAG recovery yield was over 90% and the purity was approximately 87–90%. Regarding the esterification of the 2-MAGs, the following factors were studied: the influence of the lipase type used, the presence or absence of solvent (hexane) and the reaction time or intensity of treatment (IOT = lipase amount × reaction time/2-MAG amount). Of the five lipases tested, the highest STAG percentages (over 90%) were attained with lipases D and DF, immobilized on Accurel MP1000. These STAGs contain 64% CA, of which 98% is at positions 1 and 3. Position 2 contains 5% CA and 45% PUFAs, which means that all the PUFAs that were located at position 2 in the original oil remain in that position in the final STAGs. The lipase D immobilized on Accurel MP1000 is stable in the operational conditions used in the esterification reaction. Finally the purification of STAGs was carried out by neutralization of free fatty acids with hydroethanolic solution of KOH and extraction of STAGs with hexane. By this method purity was over 95% and separation yields were about 80%.

Analyses of vibration-based piezoelectric power generator in discontinuous operation mode

Vibration energy can be converted into electrical energy using piezoelectric power generator. The electrical energy is usually collected in a storage capacitor. The storage capacitor discharges to the load only when enough energy is harvested for the required operation. The time interval between successive required operations depends on several parameters: characteristics of piezoelectric power generator and vibration magnitude, energy requirement and voltage interval, and value of the storage capacitor. In this paper, theoretical and experimental analyses of these parameters are performed to choose appropriate values of the voltage interval and storage capacitor to minimize the time interval. Theoretical analyses are well conformed by the experimental results. Analysis results are instructive for applications of both macro and MEMS-based piezoelectric power generator.

Study on Bifurcation and Chaos in Boost Converter Based on Energy Balance Model

Based on boost converter operating in discontinuous mode, this paper proposes an energy balance model (EBM) for analyzing bifurcation and chaos phenomena of capacitor energy and output voltage when the converter parameter is varying. It is found that the capacitor energy and output voltage dynamic behaviors exhibit the typical period-doubling route to chaos by increasing the feedback gain constant K of proportional controller. The accurate position of the first bifurcation point and the iterative diagram of the capacitor energy with every K can be derived from EBM. Finally, the underlying causes for bifurcations and chaos of a general class of nonlinear systems such as power converters are analyzed from the energy balance viewpoint. Com-paring with the discrete iterative model, EBM is simple and high accuracy. This model can be easily devel-oped on the nonlinear study of the other converters.

Global hybrid modeling and control of a buck converter: A novel concept

AbstractSeveral attempts have been made to design suitable controllers for DC–DC converters. However, these designs suffer from model inaccuracy or their inability to desirably function in both continuous and discontinuous current modes. This paper presents a novel switching scheme based on hybrid modeling to control a buck converter using mixed logical dynamical (MLD) methodologies. The proposed method is capable of globally controlling the converter in both continuous and discontinuous current modes of operation by considering all constraints in the physical plant such as maximum inductor current and capacitor voltage limits. Different loads and input voltage disturbances are simulated in MATLAB and results are presented to demonstrate the suitability of the controller. The transient and steady‐state performance of the closed‐loop control over a wide range of operating points shows satisfactory operation of the proposed controller. Copyright © 2008 John Wiley &amp; Sons, Ltd.