Variable Duty Cycle Research Articles

Design of digital pulse width modulator architecture with digital PID controller for DC-DC converter using FPGA

A digital pulse width modulation architecture (DPWM) along with digital proportional integral derivative (PID) controller to control the DC-DC converter is presented in this paper. Difference between the actual output voltage and the reference voltage is calculated as error value. The look up table is created for PID controller to store the duty cycle ratio and the error value of power converters. Multipliers used in conventional algorithms are replaced by look up tables in the proposed work that enable the compact and low power implementation of digital controllers. DPWM architecture is developed with gray logic against the binary logic used in traditional DPWM architectures. Usage of gray counter also leads to low power consumption in the DPWM architecture. The proposed architecture is designed using Verilog hardware language and realized using field programmable gate array. PWM signals with varying duty cycle percentage can be derived from the proposed architecture. The generated PWM signal can control the switching condition of power converter to regulate the output voltage. Duty cycle percentage ranging from 16 to 96% can be developed with the proposed architecture. Simulation and experimental results of the architecture validate the proposed architecture. PWM signal with maximum operating frequency of 59.49 MHz and 60.22 MHz for SPARTAN 3A and SPARTAN 3E respectively can be generated with the proposed architecture.

Investigation on Continuous and Modulated Microwave Plasma Filaments at Atmospheric Pressure

Microwave atmospheric pressure plasma jets continue to evolve with the growth of atmospheric plasma’s applications in sterilization, material modification, and cancer treatment. In this article, continuous and modulated microwave plasma filaments were produced by a hand-held microwave plasma jet, and then they were compared in plasma length, electron temperature, and emission spectrum. The electron temperature was measured by the emission spectroscopy diagnostic method, and the regularities of the compared parameters’ change were studied by varying duty cycles and periods of the modulating signal. The results prove that the modulated microwave can generate stable plasma filaments directly in the air without protective tubes, and it is different from the continuous microwave plasma in all compared parameters. Besides, stable dendritic tearing of plasma filaments was observed. These results imply that modulated microwave and continuous microwave plasma filaments cannot be regarded as the same, the changing manner and the reaction on the surface of the medium may be completely different even if they are the same to the naked eye in most cases. These results are helpful for the controlling and understanding of microwave plasma, and the stable tearing could be used to expand the treated area of a single plasma jet.

VTA-SMAC: Variable Traffic-Adaptive Duty Cycled Sensor MAC Protocol to Enhance Overall QoS of S-MAC Protocol

Sensing and monitoring the physical conditions are basic purposes of Wireless Sensor Networks (WSN). Sensor nodes are the building blocks of WSN and they are battery operated. Battery charging or changing is impossible in harsh areas of deployment, so battery life needs to be maximized by improving the MAC protocol. If the Duty Cycle is selected wisely, it may reduce energy utilizations of a wireless sensor network, but it may impact other factors of WSN as well. Optimum duty cycle for a specific data traffic may not be optimal for other levels of data traffic and it may negatively affect the performance of a wireless sensor network. An adaptive duty cycle algorithm, VTA-SMAC (Variable Traffic-Adaptive Duty Cycle Sensor MAC) is proposed to reduce the problem of idle listening or collisions and to reduce energy consumption of traditional S-MAC protocol. VTA-SMAC algorithm was simulated in Network Simulator NS-2 and simulation results were evaluated to assess the impact of duty cycle variation on performance of S-MAC, particularly energy conservation with condition of varying data traffic. Impact of duty cycle variation in accordance with data traffic were also evaluated on various factors like latency, throughput, collisions, delay, jitter, and packet delivery ratio etc. Trade-off between energy consumption and latency was also studied. Simulation results show that VTA-SMAC improves energy conservation by 19.9 %, 14.4 % and 20.2 % at low, medium, and high traffic, respectively. Latency is also decreased by 10.2 %, 7.5 % and 18.9 % at low, medium, and high traffic, respectively.

Boost Chopper Behaviors in Solar Photovoltaic System

This paper investigates the behaviors of Boost DC Chopper used in Photovoltaic energy systems where the solar irradiation changes during the day time causing current and voltage changes. Varying the solar irradiation causes output chopper voltage changes in order to keep working at maximum extracted solar power. The chopper voltage changes leading to variable duty cycle operation of chopper switch and causes a significant change in switch losses in terms of the dissipated power. In addition to that the chopper behaviors are studied when the chopper voltage is boosting up to a predetermined reference value leading to a significant change in chopper current, voltage, duty cycle and occurred losses. A mathematical model for chopper performances and switch losses is derived, and a simulation model using Matlab/ Simulink platforms is conducted to follow the chopper behaviors. Simulation results for concreteSUNPOWER panel type SPR-315E-WHT-D with 315 Watts peak indicates that during the daylight time transistors are exposed to complicated changes in their current, voltage and dissipated power. Furthermore changing the output voltage according to load requirements causes heavy stress on the transistor in terms of current, oscillations and losses as well. Simulation results show that there are optimized values of irradiation, chopper voltage and duty cycle where the transistor losses are minimized. In addition to that, projecting the transistor losses over the daylight time at a given irradiation rate shows how these losses vary among the year, and the amount of energy dissipated across the main chopper switch which is around 2970 Whr/yr for the present case. Furthermore, the conducted simulation also shows the occurred in the transistor behaviors when solar irradiation changes, and can be serving for further studies.

An Ultra High Step-Up DC–DC Converter Based on the Boost, Luo, and Voltage Doubler Structure: Mathematical Expression, Simulation, and Experimental

This paper presents a novel design of step-up DC-DC converters whose merits are: (i) The continuity of the input current has been kept; (ii) The polarity of the output voltage has been kept positive which provides the same ground of the input source and load; (iii) The low voltage gain of the quadratic converters has been solved that it can increase the input voltage to 10 times more by the low value of the duty cycle; (iv) Apart from the high value of the voltage gain, the semiconductors’ voltage and current stresses were lower than the output voltage and input current of the converter which are the highest value of the voltage and current respectively and semiconductor based components do not suffer from high value of the current/voltage stresses; (v) Additionally, the voltage/current stresses are low, and the efficiency is good according to its 90 percent value. The analysis of the non-ideal voltage gain has been done and its better function has been deduced by comparing it with the recently proposed non-isolated topologies. Additionally, the non-isolated voltage gain has been studied for different output power levels. The efficiency has been extracted and discussed for varying duty cycles and output power based on ignoring some losses. Experimental results and simulation outcomes from the PLECS software have been compared along with theoretical relationships. The prototype of the topology has been tested at 100 W output power, 100 V output voltage, and 10 V input voltage.

Integrated silicon metasurface polarization beam splitter on a standard SOI substrate

Polarization beam splitters are indispensable components in on-chip polarization-division-multiplexing systems. We propose a compact integrated polarization beam splitter based on a metasurface structure with a 300 nm periodic silicon column array with a variable duty cycle on a silicon-on-insulator substrate. Simulation results indicate a low insertion loss, high extinction ratio, and a 6×12 μm2 footprint within the C+L band. The robustness of our device with respect to manufacturing tolerance and nonideal input light has also been confirmed. The proposed polarization beam splitter can be fabricated in a single lithography step with input/output waveguides, which will be advantageous for device fabrication.

Isolated Ultrafast Gate Driver with Variable Duty Cycle for Pulse and VHF Power Electronics

Ultrafast and isolated gate drivers advance the development of pulse and very high frequency power electronics for applications that include LiDAR, space systems, miniaturized hardware, and testing of emerging ultrafast devices. The isolated ultrafast gate driver in this letter achieves a gate voltage slew rate above 12 GV/s with rise and fall times below 260 ps with the proper choice of components. Magnetic isolation provides transient immunity and positive feedback enables dynamic dc restoration to allow arbitrarily long on - and off -times and preserve variable duty cycles. With the isolated ultrafast gate driver, an EPC 2038 GaN FET achieves a drain voltage slew rate of over 37 GV/s when hard-switching and improves total efficiency by 8% (including gating loss) with a careful choice of logic inverters in a symmetric 100 MHz current-mode class D (CMCD) wireless power transfer system. The ultrafast gate driver with isolation and positive feedback was implemented with a commercial radio frequency signal transformer and discrete logic inverters and validated in a hard-switching double pulse test, a narrow pulse test repeating at 165 MHz, and a 100 MHz soft-switching CMCD resonant converter.

Investigation of current-ripple for three-phase four-wire inverter-fed motors

The three-phase four-wire drive system (4wEL) has been proved to be available of realizing fault-tolerant operation. However, this type of electric drive system (EDS) still has problems of higher current ripple than traditional three-wire EDSs. For a better understanding of the current ripple, a theoretical methodology of predicting the current-ripple in 4wEL is proposed for the first time. Based on the former study on traditional three-wire EDSs, the novel ripple prediction expression for the 4wEL is obtained by the study of corresponding voltage vectors and switching sectors. It is found that the prediction of current-ripple peak in 4wEL requires less calculation effort than in traditional three-phase EDSs. Besides, the difference of the current ripple peak between 4wEL and three-wire EDSs tend to be smaller for a lower modulation rate, while the variable duty cycle of the neutral phase of 4wEL can also influence the peak of current ripple. The theoretical prediction was also validated experimentally in a practical EDS and shows a proper accuracy of the current ripple prediction for both 4wEL and three-wire EDSs, which paves the path for the application of variable-switching-frequency PWM (VSFPWM) in 4wEL.

(Invited) Battery Durability and Reliability Under Electric Utility Grid Operations

Battery Energy Storage Systems (BESSs) show promise to help renewable energy sources integration onto the grid. These systems are expected to last for a decade or more, but the actual battery degradation under different real-world conditions is still largely unknown.In this work we analyzed different types of usage for batteries similar to deployed 1MW and 2MW BESS in the Hawaiian archipelago. These batteries are used for a mix of different applications such as voltage smoothing, curtailment, reserve and frequency regulation. With different usages come different battery degradation. A new protocol encompassing all those applications was designed to be able to test the cells and assess their durability in the field. We investigated the impact of frequency regulation duty cycles with different SOC ranges, depth of discharge and temperatures. We also investigated cells with varying duty cycles and temperatures to decipher whether the degradation can be predicted from a laboratory experiment.Based on the BESS representative usage profiles, we designed cycle-aging and calendar-aging experiments to test the degradation in a controlled fashion. The frequency regulation duty cycle was extracted from a 3 years usage analysis of a previous generation lithium titanate BESS in operation in Hawai'i since 2012. Laboratory testing was used to investigate the degradation in detail to improve remaining useful life predictions. The degradation mechanisms, and their path dependency, were analyzed using incremental capacity analysis and mechanistic modeling. It was found that despite the fact that most of the cells did less than 0.5% capacity after more than 400 days of testing, they actually degraded significantly. Cell temperature had the strongest impact on the loss of lithium inventory whereas duty cycle had a big impact on the loss of positive electrode material. Interestingly, the impact of SOC in the calendar aging experiments, was found to be counterintuitive as batteries lost capacity faster at low SOCs than at high. Based on our results we established a 20 year forecast of the BESS degradation under different usages.

DC Motor Control Using Laboratory Virtual Instrumentation Engineering Workbench

Motor has an important role in everyday life. Both are used on a home scale and in the industrial world. To regulate a motor, a good control system is needed. Laboratory Virtual Instrumentation Engineering Workbench abbreviated as LabVIEW is defined as a system engineering software that is used for the needs of testing, measuring, and controlling quickly on accessing hardware in which there is data needed. LabVIEW uses a graphics-based programming language or block diagram while other programming languages use a text base. This study aims to obtain a value of DC motor control. The method used in this research is to assemble the DC motor hardware with the driver followed by connecting it to a myRIO 1900 board controller. By providing variations in frequency and duty cycle, the results of current and voltage and rotation are obtained to determine its effect. The results of this study indicate that by giving a duty cycle of more than 50%, current and voltage are obtained and the motor rotation is linear and forms a horizontal line. The 100 Hz frequency is the best frequency that can produce the highest motor rotation.

Measuring and modeling quasicontinuous wave operation of quantum cascade lasers for enhanced average brightness

Quasicontinuous wave operation of midinfrared quantum cascade lasers are shown to have increased average output power with good beam quality. The ability to enhance average power by a significant fraction of CW power motivates the development of a model to estimate and project performance at varying duty cycles based on a previously developed continuous wave power projection model. The model takes into account pulse to pulse changes in temperature profile to project a transient steady-state temperature distribution. This temperature distribution is used to project both peak and average power in agreement with measurements. Preliminary model projections suggest that high average brightness may be achieved using a reduced number of stages and a greater scaling of core width than would be permissible for CW lasing.

Cumulative Damage Modeling with Recurrent Neural Networks

Maintenance of engineering assets (for example, aircraft, jet engines, and wind turbines) is a profitable business. Unfortunately, building models that estimate remaining useful life for large fleets is daunting due to factors such as duty cycle variation, harsh environments, inadequate maintenance, and mass production problems that cause discrepancies between designed and observed lives. We model cumulative damage through recurrent neural networks. Besides architectures such as long short-term memory and gated recurrent unit, we introduced a novel physics-informed approach. Essentially, we merge physics-informed and data-driven layers. With that, engineers and scientists can use physics-informed layers to model well understood phenomena (for example, fatigue crack growth) and use data-driven layers to model poorly characterized parts (for example, internal loads). A numerical experiment is used to present the main features of the proposed physics-informed recurrent neural network. The problem consists of predicting fatigue crack length for a fleet of aircraft. The models are trained using full input observations (far-field loads) and very limited output observations (crack length data for only a portion of the fleet). The results demonstrate that our proposed physics-informed recurrent neural network can model fatigue crack growth even when the observed distribution of crack length does not match the fleet distribution.

Validation of a generalized laser safety analysis method for irregular pulse trains

The current laser safety standards do not address specifically how to account for repetitively pulsed lasers with irregular pulse trains. Variations in peak power, pulse duration, and duty cycle within a pulse train pose a number of problems when it comes to product classification or to assess the hazard of a given exposure. This study proposes to analyze irregular pulse trains by generalizing the determination of the number of pulses N used in the IEC 60825-1 or n in the ANSI Z136.1 standard. The proposed method for the determination of N applies to emission durations longer than 5 μs and was validated by generating a large number of theoretical pulse patterns and by comparing the retinal injury threshold, determined with a computer model, with the applicable emission limit. For 18 000 different pulse patterns, the ratio of the injury threshold to the emission limit was never less than 2, which is commonly considered as a sufficient safety margin. The smallest safety margin found for regular pulse patterns also equals 2. This study validates an analysis method for irregular pulse trains that can be included in the standards by simple generalization of the determination of the parameter N.

Evaluation of patient specific quality assurance of gated field in field radiation therapy technique using two-dimensional detector array

Introduction: Gated tangential field-in-field (FIF) technique is used to lower the dose to organs at risk for breast cancer radiotherapy (RT). In this study, the authors investigated the accuracy of the delivered treatment plan with and without gating using a two-dimensional detector array for patient-specific verification purposes.Methods: In this study, a 6MV beams were used for the merged FIF RT (forward Intensity Modulated Radiation Therapy). The respiration signals for gated FIF delivery were obtained from the one-dimensional moving phantom using the real-time position management (RPM) system (Varian Medical Systems, Palo Alto, CA). RPM system used for four-dimensional computed tomography scanner light-speed, GE is based on an infrared camera to detect motion of external 6-point marker. The beams were delivered using a Clinac iX (Varian Medical Systems, Palo Alto, CA) with the multileaf collimator Millennium 120. The MapCheck2 (SunNuclear, Florida) was used for the evaluation of treatment plans. MapCheck2 was validated through a comparison with measurements from a farmer-type ion chamber. Gated beams were delivered using a maximum dose rate with varying duty cycles and analyzed the MapCheck2 data to evaluate treatment plan delivery accuracy.Results: Results of the gamma passing rate for relative and absolute dose differences for all ungated and gated beams were between 95.1% and 100%.Conclusion: Gated FIF technique can deliver an accurate dose to a detector during gated breast cancer RT. There is no significance between gated and ungated patient-specific quality assurance (PSQA); one can use ungated PSQA for verification of treatment plan delivery

Design and experimental performance of an off-grid ice storage system driven by distributed wind energy

To expand the use of wind energy, this paper proposed an off-grid ice storage system driven by distributed wind energy using ice storage to partly replace batteries with wind-electric-cold conversion. The current research aimed to achieve stable and efficient conversion of wind-electric-cold through control method. A system energy transfer model was established to study the energy utilizing efficiencies between the variable speed compressor direct drive mode and the battery floating charge mode under different wind conditions. An optimized variable step-size duty cycle maximum power point tracking (MPPT) algorithm based on the system impedance variation was proposed, then the average wind-electric conversion efficiency increased from 31.6% to 40.58%. Mode-switching control based on the parameters of the wind condition definition was designed to improve electric-cold conversion efficiency to 205.8% on the premise of reducing the battery charge and discharge loss by switching the battery on or off in advance. The superiority of the control method was verified by experiments, finally, the system energy efficiency ratio (EER) reached 0.59 in the case of continuous and stable operation under outdoor wind conditions.

Modeling and simulation of DC to DC boost converter using single phase matrix converter topology

The main objective of this work is to model and simulate DC to DC Boost Converter using Single Phase Matrix Converter (SPMC) topology using MATLAB/Simulink (MLS). The output voltage is controlled by using Pulse Width Modulation (PWM) technique. Four pairs of Insulated Gate Bipolar Transistor (IGBT) is used as the switching device where for each pair, it is located in parallel and opposite direction. Safe commutation technique is performed in preventing voltage spike at the output. Through the simulation, at switching frequency of 25kHz, the model is able to step up its input voltage about two times larger and all of the results achieved a good agreement with the principle of four quadrant operation. It is also realized that without the implementation of safe commutation technique, spikes were generated and the model is unable to boost its input voltage. All of the selected results from the analysis which includes variation of quadrant, switching frequency, duty cycle and resistive load are presented in this paper.

Stability Analysis of DC-DC Converters Applying Lie Algebra

ABSTRACT Stability analysis of switched DC-DC converters is necessary because instability enhances current ripple and causes converter operation at unwanted voltage/current level. In the present study, stability analysis of switched converters using Lie Algebra has been performed considering the switched linear model of DC-DC converters. The switched linear system is asymptotically stable if the Lie bracket formed by the state matrices of the system is commutative. The Lie Algebra is generated and its derived series is also computed. The Lie Algebra is found to be solvable, consequently the switched system is exponentially stable under arbitrary switching. The effect of duty cycle variation and load resistance of DC-DC converters, working in continuous conduction mode (CCM) on the decay constant and decay coefficient, has also been studied. The decay coefficient and decay rate of this exponentially stable system are observed to increase with an increase in the duty cycle for a specific load resistance.

RETRACTED ARTICLE: An effective compensation of power quality issues using MPPT-based cuckoo search optimization approach

Power quality becomes the most significant concerns for many reasons as the dependence of electricity is increasing in this modern society. In fact that less quality of power will generate some considerable losses in terms of economy in few moments. The potential power quality issues were flicker, voltage dips, supply and harmonic interruptions. The quality of power might be enhanced with the use of some filtering approaches and some compensators. This work presents a unique framework of optimal utilization of the unified power flow controller (UPFC). The UPFC’s inverter series is then controlled so as to perform the following functions: load reactive power sharing with the shunt inverter and compensation of voltage sag/swell. A cuckoo search optimization-based maximum power point tracking algorithm is employed for providing best fitness function for varying duty cycles. The approach of active power filter is widely employed in the harmonic compensation of voltage swell/sag. The proposed system also provides low rate of total harmonic distortion. MATLAB/Simulink-based simulation results are discussed to support the developed concept.

Battery Durability and Reliability Under Electric Utility Grid Operations

Battery Energy Storage Systems (BESSs) show promise to help renewable energy sources integration onto the grid. These systems are expected to last for a decade or more, but the actual battery degradation under different real-world conditions is still largely unknown.In this work we analyzed different types of usage for batteries similar to deployed 1MW and 2MW BESS in the Hawaiian archipelago. These batteries are used for a mix of different applications such as voltage smoothing, curtailment, reserve and frequency regulation. With different usages come different battery degradation. A new protocol encompassing all those applications was designed to be able to test the cells and assess their durability in the field. We investigated the impact of frequency regulation duty cycles with different SOC ranges, depth of discharge and temperatures. We also investigated cells with varying duty cycles and temperatures to decipher whether the degradation can be predicted from a laboratory experiment.Based on the BESS representative usage profiles, we designed cycle-aging and calendar-aging experiments to test the degradation in a controlled fashion. The frequency regulation duty cycle was extracted from a 3 years usage analysis of a previous generation lithium titanate BESS in operation in Hawai'i since 2012. Laboratory testing was used to investigate the degradation in detail to improve remaining useful life predictions. The degradation mechanisms, and their path dependency, were analyzed using incremental capacity analysis and mechanistic modeling. It was found that despite the fact that most of the cells did less than 0.5% capacity after more than 400 days of testing, they actually degraded significantly. Cell temperature had the strongest impact on the loss of lithium inventory whereas duty cycle had a big impact on the loss of positive electrode material. Interestingly, the impact of SOC in the calendar aging experiments, was found to be counter-intuitive as batteries lost capacity faster at low SOCs than at high.

Time series analysis of duty cycle induced randomness in thermal lens system

The present work employs time series analysis, a proven powerful mathematical tool, for investigating the complex molecular dynamics of the thermal lens (TL) system induced by the duty cycle (C) variation. For intensity modulation, TL spectroscopy commonly uses optical choppers. The TL formation involves complex molecular dynamics that vary with the input photothermal energy, which is implemented by varying the duty cycle of the chopper. The molecular dynamics is studied from the fractal dimension (D), phase portrait, sample entropy (S), and Hurst exponent (H) for different duty cycles. The increasing value of C is found to increase D and S, indicating that the system is becoming complex and less deterministic, as evidenced by the phase portrait analysis. The value of H less than 0.5 conforms the evolution of the TL system to more antipersistent nature with C. The increasing value of C increases the enthalpy of the system that appears as an increase in full width at half maximum of the refractive index profile. Thus the study establishes that the sample entropy and thermodynamic entropy are directly related.