Cycle Control Strategy Research Articles

Using Data-Driven Methods and Aging Information to Quantitatively Identify Microplastic Environmental Sources and Establish a Comprehensive Discrimination Index.

The global distribution of microplastics (MPs) across various environmental compartments has garnered significant attention. However, the differences in the characteristics of MPs in different environments remain unclear, and there is still a lack of quantitative analysis of their environmental sources. In addition, the inclusion of aging in source apportionment is a novel approach that has not been widely explored. In this study, we conducted a meta-analysis of the literature from the past 10 years and extracted conventional and aging characteristic data of MPs from 321 sampling points across 7 environmental compartments worldwide. We established a data-driven analysis framework using these data sets to identify different MP communities across environmental compartments, screen key MP features, and develop an environmental source analysis model for MPs. Our results indicate significant differences in the characteristics of MP communities across environments. The key features of differentiation were identified using the LEfSe method and include the carbonyl index, hydroxyl index, fouling index, proportions of polypropylene, white, black/gray, and film/sheet. These features were screened for each environmental compartment. An environmental source identification model was established based on these features with an accuracy of 75.1%. In order to accurately represent the single/multisource case in a more probabilistic manner, we proposed the MP environmental source index (MESI) to provide a probability estimation of the sample having multiple sources. Our findings contribute to a better understanding of MP migration trends and fluxes in the plastic cycle and inform effective prevention and control strategies for MP pollution.

Modulation of prey size reveals adaptability and robustness in the cell cycle of an intracellular predator

Despite a remarkable diversity of lifestyles, bacterial replication has only been investigated in a few model species. In bacteria that do not rely on canonical binary division for proliferation, the coordination of major cellular processes is still largely mysterious. Moreover, the dynamics of bacterial growth and division remain unexplored within spatially confined niches where nutrients are limited. This includes the life cycle of the model endobiotic predatory bacterium Bdellovibrio bacteriovorus, which grows by filamentation within its prey and produces a variable number of daughter cells. Here, we examined the impact of the micro-compartment in which predators replicate (i.e., the prey bacterium) on their cell-cycle progression at the single-cell level. Using Escherichia coli with genetically encoded size differences, we show that the duration of the predator cell cycle scales with prey size. Consequently, prey size determines predator offspring numbers. We found that individual predators elongate exponentially, with a growth rate determined by the nutritional quality of the prey, irrespective of prey size. However, the size of newborn predator cells is remarkably stable across prey nutritional content and size variations. Tuning the predatory cell cycle by modulating prey dimensions also allowed us to reveal invariable temporal connections between key cellular processes. Altogether, our data imply adaptability and robustness shaping the enclosed cell-cycle progression of B.bacteriovorus, which might contribute to optimal exploitation of the finite resources and space in their prey. This study extends the characterization of cell cycle control strategies and growth patterns beyond canonical models and lifestyles.

A Three-Phase Single-Stage ac/dc Converter Based on Swiss Rectifier and Three-Level LLC Topology

<italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">LLC</i> resonant converter is widely used due to its soft switching, high power density, and high efficiency. To incorporate the merits of the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">LLC</i> resonant tank into a three-phase single-stage ac/dc converter, this article proposes a three-phase single-stage ac/dc converter based on Swiss rectifier and three-level <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">LLC</i> topology. It takes advantage of the high-efficiency Swiss rectifier to convert three-phase ac voltages into three variable dc voltages and interface a three-level <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">LLC</i> resonant circuit. With help of the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">LLC</i> resonant tank, all the high-frequency three-level switches achieve soft switching. To both regulate the output voltage and achieve three-phase power factor correction, the frequency modulation in combination with the duty cycle control strategy is employed by splitting the resonant current into three parts and then forming three phase sinusoidal currents. The proposed converter's detailed operation principles, steady-state characteristics, and design considerations are given. Finally, a 10 kW experimental prototype with three-phase 220 Vac inputs and 500 Vdc output is built to verify the effectiveness and feasibility of the proposed topology and its control strategy.

New regulation strategies study of solar aided liquid air energy storage system under off-design conditions

Liquid air energy storage (LAES) is a large-scale physical energy storage system with high energy storage density. At present, the coupling matching regulation mechanism of the cold and thermal cycles is unclear under off-design conditions, which makes the stable and efficient operation of the LAES system difficult. New multivariable control strategies for cold and thermal cycles are proposed based on the solar aided liquid air energy storage (SA-LAES) system. The study results show the “equal proportion cold recovery” strategy is superior to other strategies, improving the system performance and meeting the demand of the maximum capacity of the charging process. When the liquid air mass flow ratios are 0.7 and 0.4, the air liquefaction ratios increase by 20.20% and 86.43%, and the round-trip efficiency (RTE) values increase by 19.44% and 84.86%, respectively. The new thermal cycle control strategy achieves a good heat coupling matching and maximizes the discharging time and RTE in the zero-carbon environment. Under 70% load and 40% load, the discharging time increase by 16.26% and 53.83%. RTE values increase by 16.28% and 53.84%, respectively. Finally, the operation domains of SA-LAES at different molten salt temperatures are obtained with the optimal cold and thermal cycle strategies. The achievements in this paper will provide valuable reference for the stable operation of SA-LAES under off-design conditions.

Duty Cycle Control Strategy for Dual-Side LCC Resonant Converter in Wireless Power Transfer Systems

The dual-side inductor–capacitor–capacitor (LCC) topology circuit has been widely adopted in wireless power transfer (WPT) systems due to its constant output current characteristic. However, most conventional control methods need specific synchronization techniques between the primary and secondary sides to avoid the oscillation in the system, which increases the cost and control complexity. To solve this issue, this article proposes a new duty cycle control (DCC) strategy for a dual-side LCC resonant converter with a semibridgeless active rectifier (SAR). With such a control strategy, gate signals of the primary- and secondary-side circuits do not need to be synchronized, which could reduce the complexity and the cost of the WPT system. Besides, the switching frequency of the secondary side can be decreased significantly. This article first presents the modal analysis of phase shift control (PSC) and DCC. Then, generalized state-space averaging (GSSA) modeling with PSC and the hybrid average modeling with DCC are performed. In addition, controllers’ design for both strategies is conducted to achieve the constant output voltage. Finally, the eigenvalues’ analysis is used to determine the stability region of the WPT system. The theoretical analysis has been validated by both simulation and experimental results.

Model predictive duty cycle control for three‐phase Vienna rectifiers

The Vienna rectifiers are widely used in industrial applications. The computationally efficient optimal switching sequence model predictive control directly optimizes the switching sequences. Thus, it requires to store the switching states of 25 voltage vectors, which increases the memory usage. Moreover, the neutral-point (NP) voltage is regulated by redundant vector preselection. As only one redundant vector is applied during the whole sampling period, the NP voltage ripple is relatively large, and the grid current performance is still not satisfactory. To overcome these drawbacks, this paper proposes a model predictive duty cycle control strategy for three-phase Vienna rectifiers, which directly optimizes three-phase duty cycles. The three-phase duty cycles are first obtained by predicting the effects of three-phase duty cycles on instantaneous current variations and minimizing a cost function. To guarantee the grid current performance, a novel three-phase duty cycles modification method is proposed by considering the structural characteristics of the Vienna rectifier. To suppress the NP voltage ripple, the obtained three-phase duty cycles are further optimized. With the proposed method, low memory usage, low harmonic distortion in the grid current, and low NP voltage ripple are achieved simultaneously. Experiments are conducted to verify the effectiveness of the proposed method.

Model Predictive Based Direct Torque Control for Induction Motor Drives by Sole-Evaluation of Two Parameter Independence Duty Ratios for Each Voltage Vector

Due to importance of duty cycle based model predictive torque control (MPTC), it has been accepted as an effective and common alternative control strategy for industry. Since its major drawback is great dependency on duty ratio parameter, the robustness and the complexity of control system has been respectively decreased and increased. A duty-ratio set considering limited members can be replaced with continuous and dependent parameters form duty cycle relationship. Hence, this paper proposes a new and applicable discrete duty cycle control strategy to reduce both the torque and flux ripples appeared in MPTC method. In the proposed method, after preselecting around half of all admissible voltage vectors based on the torque sign or speed variation and the stator flux position, two duty ratios have just been selected for the preselected active voltage vectors. These two duty ratios are achieved based on the equivalent voltage concept with independent motor parameter. Then, the model predictive control method is employed to select the optimum active voltage vector and its relevant duty ratio among the reduced feasible voltage vectors which reduces both the flux and torque ripples, especially in low speed ranges. The simulation results have confirmed the performance of the proposed method in order to reduce the torque and flux ripples, and the experimental results have accordingly validated its performance. Since the number of voltage vectors and duty ratios is significantly decreased, the execution time of the proposed method is further reduced, and virtually worked with a constant switching frequency for all speed ranges.

One Cycle Control of a PWM Rectifier a New Approach

This paper analyzes a Digital Signal Processor (DSP) based One Cycle Control (OCC) strategy for a Power Factor Corrector (PFC) rectifier with Common-mode Voltage (CMV) immunity. It is proposed a strategy that utilizes an emulated-resistance-controller in closed-loop configuration to set the dc-link voltage to achieve unity power factor (UPF). It is shown that if the PFC can achieve UPF condition and if the phase voltage is only affected by CMV, then phase current is free from CMV, as well as a lead-lag compensator (LLC) to average phase current.

Experimental analysis of reverse cycle defrosting and control strategy optimization for transcritical carbon dioxide heat pump water heater

The heating performance of air source transcritical carbon dioxide heat pump will be dramatically reduced with frost formation when operating in cold regions. Although reverse cycle defrosting is widely used, no information is available in the transcritical carbon dioxide system. In this paper, the reverse cycle defrosting was experimentally investigated in a transcritical carbon dioxide heat pump with a microchannel evaporator. The effect of water flow rate, initial water tank temperature, compressor frequency and electronic expansion valve opening are respectively studied, and an optimized control strategy is proposed considering the defrosting time and stability. Results show that thermal energy is considerably affected by water side parameters, and stability is more sensitive to the water temperature and electronic expansion valve opening. With the optimized reverse cycle defrosting, defrosting time and total energy consumption are reduced by 95 s and 21.8% compared with the pre-set basic control strategy, and the total energy consumption is also saved by 38.6% compared with the other defrosting method. The optimized reverse cycle defrosting is verified to be preferable for the transcritical carbon dioxide system, and the presented discussion is beneficial for the application of reverse cycle defrosting in the air-to-water heat pump.

A Robust Simplified Dynamic Observer-Based Backstepping Control of Six-Phase Induction Motor for Marine Vessels Applications

This article presents a robust simplified dynamic observer-based backstepping control (RSDO-BSC) and direct torque control (DTC) synthesized with duty cycle control strategy of a six-phase induction motor (6PIM) for marine vessels applications. RSDO-BSC and DTC are employed to estimate the rotor speed, while the DTC is utilized to accomplish enhanced steady-state torque performance via accurate inputs applied to the switching table of the six-phase inverter. Furthermore, by using the duty cycle control approach, the loss components in the subspace are disregarded via the appropriate choice of virtual voltage vectors. Consequently, the 6PIM torque ripples and the current harmonics are significantly reduced. First, both the flux and the torque are decoupled using Lyapunov theory on a 6PIM two-axis mathematical model represented in the stationary reference frame. The 6PIM actual stator voltages are acquired from the dc-link voltage via the space vector pulsewidth modulated inverter. Subsequently, when the 6PIM is loaded under the rated speed, a rapid search approach is used to maximize the 6PIM efficiency. A 750-W 6PIM drive test setup employs a dSPACE 1104 for real-time implementation. The proposed RSDO-BSC performance is experimentally investigated at different speed commands, load disturbance, and low speed command with low load torque conditions.

Process variation tolerant wide-band fast PLL with reduced phase noise using adaptive duty cycle control strategy

ABSTRACT This paper presents the effects of manufacturing process variations on the phase-locked loop (PLL) performances like lock time, lock range and phase noise. At higher operating frequencies, due to process variations, there is a shift in the duty cycle of the divider output to phase-frequency detector, which leads to lock failure. To alleviate this problem an adaptive duty cycle control (ADCC) strategy is proposed and used in the frequency divider present in the feedback path of PLL. The proposed technique makes the PLL process variation tolerant and lock at higher frequencies where otherwise PLL was out of lock. It assists the PLL to lock faster and achieve low phase noise at all frequencies under nominal conditions. The operating temperature range is also enhanced to −50° to 50o C. Simulation studies in Cadence design environment on a 3.5 GHz PLL reveals the lock range improvement of 40% and phase noise improvement of 15%.

Model Predictive Flux Control of Semicontrolled Open-Winding PMSG With Circulating Current Elimination

In this article, an improved finite-control-set model predictive flux control (FCS-MPFC) is developed and implemented to eliminate the circulating current in the semicontrolled open-winding permanent magnet synchronous generator supplied by a single dc power. First, the references of torque, flux, and zero-sequence current are combined into the stator flux vector reference along with the implementation of maximum torque per ampere control to eliminate the weighting factors of the cost function in the conventional finite-control-set model predictive torque control. Then, to further improve the steady-state performance, a developed double-vector method based on the uncontrollable side voltage vector adjustment is conducted, which has the advantage of low computation burden. Moreover, a modified duty cycle control strategy is presented, in a manner where the reference value of flux is superseded with the measurement one to effectively calculate the duration of the optimal vector. Finally, experimental results verify the effectiveness and superiority of the proposed FCS-MPFC scheme.

African Swine Fever Virus: An Emerging DNA Arbovirus.

African swine fever virus (ASFV) is the sole member of the family Asfarviridae, and the only known DNA arbovirus. Since its identification in Kenya in 1921, ASFV has remained endemic in Africa, maintained in a sylvatic cycle between Ornithodoros soft ticks and warthogs (Phacochoerus africanus) which do not develop clinical disease with ASFV infection. However, ASFV causes a devastating and economically significant disease of domestic (Sus scrofa domesticus) and feral (Sus scrofa ferus) swine. There is no ASFV vaccine available, and current control measures consist of strict animal quarantine and culling procedures. The virus is highly stable and easily spreads by infected swine, contaminated pork products and fomites, or via transmission by the Ornithodoros vector. Competent Ornithodoros argasid soft tick vectors are known to exist not only in Africa, but also in parts of Europe and the Americas. Once ASFV is established in the argasid soft tick vector, eradication can be difficult due to the long lifespan of Ornithodoros ticks and their proclivity to inhabit the burrows of warthogs or pens and shelters of domestic pigs. Establishment of endemic ASFV infections in wild boar populations further complicates the control of ASF. Between the late 1950s and early 1980s, ASFV emerged in Europe, Russia and South America, but was mostly eradicated by the mid-1990s. In 2007, a highly virulent genotype II ASFV strain emerged in the Caucasus region and subsequently spread into the Russian Federation and Europe, where it has continued to circulate and spread. Most recently, ASFV emerged in China and has now spread to several neighboring countries in Southeast Asia. The high morbidity and mortality associated with ASFV, the lack of an efficacious vaccine, and the complex makeup of the ASFV virion and genome as well as its lifecycle, make this pathogen a serious threat to the global swine industry and national economies. Topics covered by this review include factors important for ASFV infection, replication, maintenance, and transmission, with attention to the role of the argasid tick vector and the sylvatic transmission cycle, current and future control strategies for ASF, and knowledge gaps regarding the virus itself, its vector and host species.

New Technologies for Studying Negative-Strand RNA Viruses in Plant and Arthropod Hosts.

The plant viruses in the phylum Negarnaviricota, orders Bunyavirales and Mononegavirales, have common features of single-stranded, negative-sense RNA genomes and replication in the biological vector. Due to the similarities in biology, comparative functional analysis in plant and vector hosts is helpful for understanding host-virus interactions for negative-strand RNA viruses. In this review, we will highlight recent technological advances that are breaking new ground in the study of these recalcitrant virus systems. The development of infectious clones for plant rhabdoviruses and bunyaviruses is enabling unprecedented examination of gene function in plants and these advances are also being transferred to study virus biology in the vector. In addition, genome and transcriptome projects for critical nonmodel arthropods has enabled characterization of insect response to viruses and identification of interacting proteins. Functional analysis of genes using genome editing will provide future pathways for further study of the transmission cycle and new control strategies for these viruses and their vectors.

A Dynamic Priority Factor Loop for Fast Voltage Equalization Applied to High Power Density DC–DC Converter System

A fast output voltage equalization control strategy applied to 10-kV/100-kW high power density photovoltaic dc–dc converter system is proposed in this paper. The converter modules in the system have two dynamic priority factor loops for fast response with an inconsistent voltage between modules and a soft start-up circuit to precharge output capacitance for solving inrush current problem in boost circuit. The proposed strategy can realize fast voltage equalization control under inconsistent leakage inductance and parasitic resistance parameters condition between modules compared to the traditional unified duty cycle control strategy. The fast equalization performance is verified by 10-kV/100-kW photovoltaic dc–dc converter system. The converter system adopts an isolated boost full-bridge topology and input parallel output series structure, which meets high conversion ratio and high-power density requirements.

A Novel Vector Control Strategy for a Six-Phase Induction Motor with Low Torque Ripples and Harmonic Currents

In this paper, a new vector control strategy is proposed to reduce torque ripples and harmonic currents represented in switching table-based direct torque control (ST-DTC) of a six-phase induction motor (6PIM). For this purpose, a new set of inputs is provided for the switching table (ST). These inputs are based on the decoupled current components in the synchronous reference frame. Indeed, using both field-oriented control (FOC) and direct torque control (DTC) concepts, precise inputs are applied to the ST in order to achieve better steady-state torque response. By applying the duty cycle control strategy, the loss subspace components are eliminated through a suitable selection of virtual voltage vectors. Each virtual voltage vector is based on a combination of a large and a medium vector to make the average volt-seconds in loss subspace near to zero. Therefore, the proposed strategy not only notably reduces the torque ripples, but also suppresses the low frequency current harmonics, simultaneously. Simulation and experimental results clarify the high performance of the proposed scheme.

Dynamic duty cycle control strategy for surface nuclear magnetic resonance sounding system.

The surface nuclear magnetic resonance (SNMR) technique exploits the NMR phenomenon to quantitatively determine the subsurface distribution of water. In the SNMR sounding system, deeper regions are probed by increasing the pulse moment (the product of the current amplitude and pulse duration). However, the amplitude of the current in the transmitter coil inevitably decays due to the energy loss in the storage capacitor. In practical application, the maximum amplitude of the current in one transmission process is recorded and used as the current amplitude. However, this approach results in errors in calculating the pulse moment and the sensitivity kernel function. In this paper, we build a simulation of the transmission process and the current decay phenomenon appears. From the simulation results, the current amplitude at the end of the pulse is 83% of the maximum. We present a dynamic duty cycle control strategy for a constant excitation current. We calculate the 1D sensitivity kernel function based on the two cases of constant and decaying excitation current, respectively. We observe that the maximum difference between them is greater than 200 nV/m. The inversion results based on a 1D aquifer model containing two aquifers show that the decaying excitation current results in aquifers deeper than the model and the water content of the second aquifer is 50% of the model. A comparative experiment between the decaying excitation current system and the constant excitation current system was conducted in a field experiment. Compared with traditional SNMR instruments, our new system can effectively avoid the phenomenon of excitation current decay in field experiments, and the new SNMR sounding system enables accurate inversion of aquifers.

Operating Flexibility of Natural Gas Combined Cycle Power Plant Integrated with Post-Combustion Capture

This study reports key findings from a rigorous technical assessment of the performance of a natural gas fired power station fully integrated with a post-combustion MEA based capture unit. Behaviour at full load and at part load, during solvent storage operation and during regeneration of previously stored rich solvent, is characterised. Two different part load power cycle and capture unit control strategies are assessed during additional regeneration of stored solvent using alternative steam extraction strategies: (1) floating IP/LP crossover pressure; and (2) throttled IP/LP crossover. In practise these strategies could be used in combination. In contrast to previous literature the operating limits are described in detail. Additionally, a variable speed integrally geared centrifugal compressor model is deployed to predict the off design performance and operating limits of the compression unit.

Control of flash gas bypass MAC system with emphasis on start-ups and transients

Most of the previous research on flash gas bypass (FGB) focused on performance improvement in steady state and demonstrated that compared to direct expansion mode (DX), FGB mode have better performance. However, the control strategy of flash gas bypass system and dynamic behavior during start-ups and transients were not yet clearly defined and investigated. In this paper, a novel control strategy has been proposed for an automobile air conditioning system operating in flash gas bypass mode with R134a as the refrigerant. The proposed control strategy utilized an electronic expansion valve (EV) for the control of subcooling from condenser outlet and a bypass valve (BV) for superheat from compressor inlet. Both start-up and transient system behaviors were studied. The experimental results showed that the proposed cycle control strategy was found to be able to provide reliable control to the system. In addition, proper sizing of bypass valve and flash gas bypass tank have also been studied.

Improved Cycle Control and Sizing Scheme for Wind Energy Storage System Based on Multiobjective Optimization

This paper proposes an improved control and sizing scheme for a wind energy storage system for wind smoothing. Considering the trading rules in the electricity market, a cycle control strategy with progressive cycle period including one charge and discharge period is proposed. To determine the reference output and time duration of each cycle control period, a multiobjective optimization model is presented considering both the maximum of time duration of each cycle control period and the minimum of power variation between adjacent charge and discharge intervals. In the proposed control strategy, wind power is smoothed with flexible reference output and self-adjustable battery state of charge ranges, and then, the battery can be utilized without overdischarge. Meanwhile, the smoothed wind power with longer average interval duration can better benefit the wind power trading in electricity market. Besides, the charge/discharge switch can be significantly decreased to prolong the battery lifetime. Afterward, based on the presented control strategy, the sizing methodology is proposed according to the cumulative probability function of the charge/discharge power and energy. Moreover, the impact of wind power forecast error is also considered in the real-time operation. By using actual wind power data, case studies are fulfilled to validate the performance of the proposed cycle control and sizing strategy.