Additional Switching Research Articles

A General Four-Port Converter With Series LC Voltage Balancer for Bipolar DC Microgrid

To construct the bipolar DC microgrid and maintain poles voltage balanced, usually a dedicated voltage balancer (VB) is needed. In this article, a general four-port converter with series LC voltage balancer (LCVB) is proposed to replace the voltage balancer. The proposed converter is composed of two partial power processing dual-active-bridges (PDAB) and a series LC branch. The LC branch is added between the outputs of two PDABs, which is combined with half bridge circuits to form LCVB. Two PDAB inputs can realize independent bi-directional power flow according to the requirements of the connected equipment. At the same time, LCVB can also balance the bipolar voltage levels. In addition, compared with the traditional two module DAB converter, the proposed converter has no additional active switching device. Partial power processing structure improves the converter efficiency. And last, all the switches of PDAB turn on with zero-voltage switching (ZVS). Simulations and experiments are carried out to verify the validity of the converter.

Design of All-Digital Two Phase Ping-Pong Switched Capacitor Voltage Doubler Power Converter

This brief presents an all-digital two-phase Ping Pong voltage doubler with reduced reversion loss by introducing additional switches in the loss path. It is implemented using inverter logic circuits with MOM capacitors stacked on top, which is compatible with digital design flow. With varying clock conditions, the proposed circuit reduces voltage ripples down to 239.9 mV with a voltage drop of less than 20.2 mV (measured). The traditional circuit has a voltage ripple of up to 999 mV with a 171.3 mV voltage drop (simulated). The proposed circuit achieves a peak efficiency of 91.68%.

Comparative Study on Analysis of Losses and Leakage Current for Transformer-less Inverters for PV Applications: A Review

Abstract: The reduction in the Common Mode Voltage (CMV) and thermal losses in semiconductors play a crucial role in designing of a new transformer-less inverter topologies for solar powered applications. The galvanic isolation and the leakage current problem due to non-availability of transformer can be addressed either by providing additional switches on the dc side or on the ac side, but this results in more number of semiconductor devices being added into the conduction paths which are switched according to the desired output requirements which further results in high conduction and switching losses indirectly effecting the efficiency of the transformer-less inverters. Hence it is important to study the existing topologies in view of the total losses, CMV and leakage current parameters together. In this review paper H5, H6 and HERIC transformer-less inverter configurations in terms of CMV, Leakage current, Conduction and Switching losses as total losses have been analyzed using PSIM2022.2 simulation software package with the availability of the thermal module. The study of total losses with CMV and leakage current will help in noting the drawbacks of the topologies discussed in this paper.

Segment Reduction-Based Space Vector Pulse Width Modulation for a Three-Phase F-Type Multilevel Inverter with Reduced Harmonics and Switching States

An improved segment reduction-based space vector pulse width modulation (SVPWM) for an F-type three-level inverter (FT2LI) is presented in this article. The proposed SVPWM algorithm decreases the additional switching state transition of each triangle with the application of an improved nine- and three-segment reduction switching strategy. The main feature of the segment reduction technique is that it eliminates second-order harmonics in the inverter output side with good total harmonic distortion (THD), low switching losses, and minimum filter requirements when compared with carrier-based PWM (CBPWM) techniques such as multi-carrier sine PWM (MC-SPWM), sixty-degree PWM (60° PWM), and switching frequency optimal PWM (SFO PWM). The proposed modulation algorithm for FT2LI is implemented on the MATLAB/Simulink platform. The performance of the proposed segment reduction-based SVPWM algorithm is tested experimentally on an FT2LI at various amplitude and frequency modulation indices, and the experimental results are verified with the simulation results. Additionally, a comparative analysis carried out to study the relationship between the segment reduction-based SVPWM and CBPWM techniques inferred that the suggested segment reduction-based SVPWM algorithms can optimize high-order harmonic distributions and have a minimum computational burden.

Step-Current-Approximation Modulation of Multilevel-CSC With Near-Power-Frequency Switching for High-Current Variable-Voltage Application

High-current variable-voltage rectifiers with continuously adjustable output are widely applied in industrial manufacturing such as electrolysis, electrowinning, and DC arc furnaces. Multilevel-CSC is a potentially feasible solution in these scenarios. In this paper, a step-current-approximation modulation (SCAM) for Multilevel-CSC is proposed. Firstly, the topological constraint of the current-source converter is analyzed to obtain the feasible stepping-current approximation method, which is further optimized based on the gradient of reference current. Moreover, the current balancing algorithm is designed to achieve the DC current balance between modules with the least additional switching behavior. The proposed SCAM and traditional SPWM are compared by simulation, which indicates that SCAM reduces the switching frequency to less than 1/3 of SPWM and realizes the near-power-frequency switching. Finally, the feasibility of SCAM is verified in the hardware-in-the-loop experiment platform. The proposed SCAM is expected to bring the reverse-blocking devices with low on-state voltage into the application of Multilevel-CSC. Therefore, the conversion efficiency will be greatly improved, meeting the energy conversion requirements of large-scale industrial manufacturing.

Switching between foods: A potential behavioral phenotype of hedonic hunger and increased obesity risk in children

ContextReward-based eating is a trait that increases risk for eating in the absence of hunger (EAH) and obesity. Eating behaviors such as switching more frequently between different foods may increase intake during EAH by delaying the onset of sensory-specific satiation (SSS); however, this question has not been empirically tested. Objectives1) Test whether switching between foods mediates the relationship between reward-based eating and EAH intake. 2) Test whether switching between foods during EAH moderates the relationship between reward-based eating and weight status. MethodsData were analyzed from a study assessing decision-making in children (n = 63 children; 9.4 ± 1.4 years, 77.0 ± 22.4 BMI%tile). Reward-based eating was quantified using the Children's Eating Behaviour Questionnaire. EAH was assessed as the amount of palatable food consumed following ad libitum consumption of a standard meal. Videos of eating behavior were coded for eating time, number of different foods consumed, and food switches. Ordinary least squares regressions were conducted to test hypotheses. ResultsSwitching was positively associated with EAH intake for both kcal (p < 0.01) and grams (p < 0.01) such that each additional switch was associated with an increased intake of 17.0 kcal or 3.5 gs. Switching mediated the relationship between reward-based eating and EAH (p < 0.01) such that more frequent switching fully accounted for the positive association between reward-based eating and EAH (ps < 0.01). While reward-based eating was also positively associated with weight status (p < 0.01), this association was moderated by food switching (p < 0.01) such that the relationship was stronger for children who switch more frequently (p < 0.01). ConclusionsFrequent switching between foods was positively associated with EAH intake and mediated the relationship between reward-based eating and EAH. Moreover, reward-based eating was more strongly related to weight status in children who switched more frequently. Thus, food switching may contribute to overconsumption and be an important behavioral indicator of increased obesity risk in children. Studies across multiple meals and contexts will help determine if switching is a reliable behavioral phenotype.

An Integrated Power Decoupling Method for Single-Phase EV Onboard Charger in V2G Application

Instead of bulky passive filters, the active power decoupling (APD) method can be adopted to suppress the 2nd-order ripple power in the DC-bus of the single-phase electric vehicle (EV) onboard charging system. However, the traditional APD methods require additional power switches and energy storage devices, which increases the cost and significantly reduces the power conversion efficiency. To tackle these problems, an integrated method of utilizing the auxiliary power module to form a series-connected APD circuit is proposed in this paper. Without additional switches and energy storage devices, the APD circuit only needs to compensate less than 10% of the rated power, while realizing soft-switching operation. In addition, the corresponding control method can further reduce the voltage stress of the switches on the high-voltage side of the converter, and increase the efficiency of the system. Finally, a 2kW single-phase charging system prototype is built to verify the feasibility and effectiveness of the proposed method.

Analysis and Design of Bidirectional Parallel-Series DAB-Based Converter

Unprecedented expansion of renewable, energy storage and fast charger system applications has diversified the bidirectional converter designs over the past decade. This paper presents a new dual-active bridge (DAB) converter topology which employs parallel and series switches arrangements for low-voltage (LV) bridge configurations. The additional switch inclusion provides high dc conversion gain, which enables attractive fast charger applications. The performance of the proposed DAB-based converter with wide dc range has been investigated through several design techniques and comparisons. The use of use of silicon carbide devices (SiC) in higher power conversion significantly improves switching losses. However, unsupervised design will result in significant switching losses and increased electromagnetic emissions. Since the DAB-based converter's high switching frequency allows operation with smaller magnetics, the system stray capacitance plays a critical role. The common-mode current (CMC) propagated through the system's stray capacitance generates undesired electromagnetic interferences (EMI) and impacts the soft-switching achievable range. To overcome the common-mode current circulation issue, design solutions have been employed to reduce the emergence of system stray capacitance. A harmonic analysis is further discussed along with evaluation of transformer design comparisons. The experimental results show the performance of the DAB-based converter in bidirectional operation and improved common mode current generation with respect to EMI emissions. The simulation and experimental results have been performed using a 5kW rated power DAB-based converter with SiC power semiconductors.

Generic Dynamically Reconfigurable Battery With Integrated Auxiliary Output and Balancing Capability

Modular multilevel converters (MMC) and cascaded H-bridge (CHB) converters are established concepts in ultra-high-voltage systems. In combination with batteries, these circuits allow dynamically changing the series/parallel configuration of the battery modules, also known as reconfigurable batteries. A large body of research discusses applications of such systems in grid-storage and electromobility with a single load, such as an electric drive. However, most studies neglect the presence of auxiliary loads, which require additional voltage levels and isolation from the high-voltage battery. This paper proposes a decoupling method that can fork a second (galvanically isolated) output off a reconfigurable dc battery without negatively affecting the main output by exploiting the many control degrees of freedom in the modular circuit. The proposed system provides a nonisolated port for the dc link of the motor-drive inverter(s), while generating an additional isolated output at another voltage for auxiliaries. The auxiliary output benefits from the interleaving effect, which increases the operating frequency of the transformer and reduces the filter size. The solution does not require additional active switches for the auxiliary port and can operate with a wide range of voltages. The integrated auxiliary circuit can also balance the modules during idling and charge/discharge cycles. Both simulation and experiments validate the analysis.

Difference Between the PWM and Standard DC Power Cycling Tests Based on the Finite-Element Simulation

PWM power cycling, which has complex control strategies and high testing costs, received a lot of attention in recent years due to the test conditions are closer to the application of power modules than standard DC power cycling. Therefore, the root difference of the failure modes and lifetime of IGBT power modules between DC and PWM power cycling is the concern in this paper, based on the finite element simulation. For stimulating the PWM power cycling with high accuracy and fast speed, an IPWM power cycling is proposed and verified by a simple model. Then an electro-thermo-mechanical coupled model of a single chip is established for comparison. Mainly focus on the current distribution, temperature distribution and stress distribution. The current distribution comparison results show no difference while a higher temperature gradient is shown in PWM power cycling due to the additional switching losses. However, the stress distribution results show chip solder layer is still the main failure mechanism both in DC and IPWM power cycling. Therefore, a conclusion can be obtained that there is no difference in failure mechanism and lifetime between DC and PWM power cycling. And the same bond wire failure and similar lifetime of DC and PWM power cycling tests further verify this conclusion.

Dual-Circulant Modulation for Modular Multilevel DC/DC Converters With Inherent Balance Capability

Modular multilevel DC/DC converters (MMDC) have emerged recently for medium-voltage dc applications. Under single circulant modulation, the sub-module (SM) capacitor voltages in MMDC are found to be evenly divided only at some specific modulation coefficients. To obtain the inherent balance capability under all modulation coefficients and expand the application range of circulant modulation, a simple dual circulant modulation is proposed in this letter. On the basis of single circulant modulation, the self-balancing of the SM capacitor voltages is realized by using the additional switching patterns generated by a simple circulant permutation method. The theoretical analysis of the proposed method is presented, and the inherent balance capability of MMDC under the dual circulant modulation method is verified by experiments.

Geometric Phase Flat Optical Gratings with High Diffraction Angle Based on Dual‐Frequency Nematic Liquid Crystal

AbstractDiffractive optical elements (DOEs) are increasingly used as lightweight and compact solutions in photonic devices. Steering of light and manipulation of the polarization can be efficiently obtained with the help of photo‐aligned liquid crystal (LC) devices. 1D LC diffraction gratings are studied that are based on the geometric phase principle and demonstrate that the optical functionality can be substantially broadened by using dual frequency LC. Switching between a highly efficient diffractive and a transmissive state is obtained by adjusting the frequency of the applied electric field. Compared to commonly studied 1D nematic LC diffraction gratings, the steering efficiency over large diffraction angles is strongly increased. By using an appropriate electric‐field treatment, the efficiency for first‐order diffraction of red light over an angle of 12.6° increases from 60% to 90%. Moreover, additional switching phenomena are observed at intermediate voltage treatments, leading to enhanced tunability of the DOEs. The origin of this behavior is explained with the help of finite element Q‐tensor simulations for the director configuration.

Smoothed Online Combinatorial Optimization Using Imperfect Predictions

Smoothed online combinatorial optimization considers a learner who repeatedly chooses a combinatorial decision to minimize an unknown changing cost function with a penalty on switching decisions in consecutive rounds. We study smoothed online combinatorial optimization problems when an imperfect predictive model is available, where the model can forecast the future cost functions with uncertainty. We show that using predictions to plan for a finite time horizon leads to regret dependent on the total predictive uncertainty and an additional switching cost. This observation suggests choosing a suitable planning window to balance between uncertainty and switching cost, which leads to an online algorithm with guarantees on the upper and lower bounds of the cumulative regret. Empirically, our algorithm shows a significant improvement in cumulative regret compared to other baselines in synthetic online distributed streaming problems.

Terahertz Metamaterial Absorber Based on Ni–Mn–Sn Ferromagnetic Shape Memory Alloy Films

Terahertz absorbers have been extensively investigated by researchers due to their applications in thermophotovoltaic energy conversion and sensors, but a key factor limiting their development is the lack of vital and versatile materials. Ferromagnetic shape memory alloys (FSMAs) offer a novel remedy for tunable metamaterials due to their brilliant recovery of deformation, remote control, and transient response. In this study, we propose a tunable absorber based on magnetic field tuning, consisting of Ni–Mn–Sn ferro-magnetic shape memory alloy films in fractal geometry and optically excited Si plates. Numerical analysis shows that the proposed absorber has an absorbance bandwidth of 1.129 THz above 90% between 1.950 THz and 3.079 THz. The absorber geometry can be regulated by an external magnetic field, allowing dynamic switching between broadband and narrowband absorption modes, the latter showing an ultra-narrow bandwidth and a high-quality factor Q of ~25.8. The proposed terahertz absorber has several advantages over current state-of-the-art bifunctional absorbers, including its ultra-thin structure of 10.39 μm and an additional switching function. The absorption can be continuously tuned from 90% to 5% when the light-excited silicon plate is transferred from the insulator state to the metal state. This study presents a promising alternative strategy for developing actively regulated and versatile terahertz-integrated devices.

An IoT-Based Multimodal Real-Time Home Control System for the Physically Challenged: Design and Implementation

Physical impairments affect a significant proportion of the global populace, emphasizing the need for assistive technologies to increase the ability of these individuals to perform daily activities autonomously. This study discusses the development and implementation of a multimodal home control system, designed to afford physically challenged individuals greater control over their home environments. This system utilizes the Internet of Things (IoT) for its functionality. The system is primarily based on the utilization of the Amazon Alexa Echo Dot, which facilitates speech-based control, and a sequential clap recognition system, both made possible through an internet connection. These methods are further supplemented by an additional manual switching option, thereby ensuring a diverse range of control methods. The processing core of this system consists of an Arduino Uno and an ESP32 Devkit module. In conjunction with these, a sound detector is employed to discern and process a variety of clap patterns, which is set to function at a predefined threshold. The Amazon Alexa Echo Dot serves as the primary interface for voice commands and real-time information retrieval. Furthermore, an Android smartphone, equipped with the Alexa application, provides alternate interfaces for appliance control, through both soft buttons and voice commands. Based on an analysis of this system, it is suggested that it is not only viable but also effective. Key attributes of the system include rapid response times, aesthetic appeal, secure operation, low energy consumption, and most importantly, increased accessibility for physically disabled individuals.

RESEARCH OF VALVE MOTOR CONVERTER CONTROL METHODS

A technique for selecting the electrical equipment of a valve motor with machine commutation has been developed, which takes into account the ways of controlling the inverter. The installed capacity of the electrical equipment of the valve motor (VD) is determined by technological requirements and depends on the structure of the converter, the method of commutation of the converter keys and the methods of controlling the inverter. The use of autonomous inverters with artificial switching, the keys of which are switched due to the reactive energy accumulated in additional switching devices, increases the utilization factor of the synchronous machine. However, in this case, the circuit becomes more complicated and the installed power of the converter increases. The use of IGBT transistors and IGCT thyristors leads to a significant increase in the cost of the equipment.&#x0D; To reduce the influence of the rectifier VD on the network and match the drive voltage with the supply voltage, a matching transformer and reactive power compensation device may be needed. The amount of power of this equipment is affected by the method of controlling the rectifier, the nature of the engine load and the range of speed changes.&#x0D; Voltage regulation of the rectifier can be symmetrical or asymmetrical. Several methods of asymmetric regulation are known, among which one of the most expedient is alternating. In the case of alternating control in the three-phase bridge circuit, an artificial zero circuit is created, as a result of which the duration of the current flowing through the secondary windings of the transformer becomes less than 2/3 of the half-cycle of the supply voltage. In addition, the energy indicators also increase, in particular, the reactive power consumption decreases and the shift and power coefficients increase.

A 34.16–39.6 GHz low phase noise VCO for frequency‐modulated continuous‐wave radar in a 28‐nm CMOS

AbstractA dual‐core voltage‐controlled oscillator (VCO) using harmonic resonance is presented in this letter. Without an additional switch capacitor bank, harmonic resonance implemented in VCO is realized by only a single control voltage, satisfying the requirement of frequency‐modulated continuous‐wave radar. Two pairs of varactors are added to the transformer‐based tank, which ensures a constant ratio between the two resonant frequencies of the tank in the entire tuning range. Robustly single‐frequency oscillation is obtained by increasing the coupling coefficient of the transformer and the coupling capacitor's capacitance. Implemented in a 28‐nm complementary metal–oxide–semiconductor, the VCO shows a 14.75% frequency tuning range covering 34.16–39.6 GHz. The measured results show it exhibits −102.13 dBc/Hz phase noise at a 1 MHz offset from the 34.16 GHz. The oscillator core draws 21–28 mA from a 0.9 V supply.

A Thyristor-Based Auto-Passing Neutral Section Scheme With Auxiliary Transformers for AC Electrified Railway

The further development of high-speed and heavy-haul railways is restricted by the existence of neutral sections. Traditional thyristor-based auto-passing neutral section schemes can make the train pass through neutral sections with power supply and reduce its speed loss. However, the electric locomotive still exists a power interruption time of several milliseconds and may confront with the problem of inrush current. To address the issues of traditional thyristor-based schemes and transfer the neutral section voltage more smoothly, a modified thyristor-based scheme is proposed in this paper. By adding auxiliary transformers and additional switches, two intermediate voltages with unchanged amplitude are introduced. The neutral section voltage is switched step by step between the voltages of two feeders, with a smaller phase change each time. The total power interruption time of the train is further shortened and the inrush current is effectively avoided. The construction idea and the working characteristics of the proposed scheme are introduced. Furthermore, the effectiveness and the superiority are verified by the simulation and experimental results. The proposal of the modified thyristor-based scheme provides a new thought to deal with the problem of train passing neutral section in AC electrified railway.

A Novel Active Neutral Point-Clamped Five-Level Inverter With Single-Stage-Integrated Dynamic Voltage Boosting Feature

Application of mid-point-clamped multilevel inverters, e.g., active neutral point-clamped (ANPC) or stacked multicell (SMC) converters, have been significantly broadened in recent years due to better performance, reduced common-mode voltage and leakage current, bidirectional power flow capability and simplicity in circuit design. Nonetheless, the dc-link voltage utilization factor is only 50% (i.e., the peak of the ac output voltage is half of the dc-link voltage), which requires additional front-end boost integrated circuit to accommodate low and wide varying input voltage. In this article, a single-stage ANPC-based five-level (5 L) boost integrated inverter is proposed, which is able to meet the peak amplitude of the grid voltage even when the dc-link voltage is low and wide varying. The proposed topology is comprised of two boost inductors, four capacitors, and 10 power switches, which can be assembled with two standard T-Type modules and two additional discrete power switches. Compared with the conventional two-stage ANPC and/or SMC-5 L inverters with a front-end bidirectional boost converter, the proposed topology requires the same number of power switches, whilst providing more flexible/dynamic voltage conversion gain with a reduced total standing voltage across the switches. Operating principles, circuit analysis and modulation strategy of the proposed topology are discussed. Finally, a comparative study supported by closed-loop grid-tied experimental results are presented to confirm the potentiality and feasibility of this proposal.

A Family of IPT Battery Chargers With Small Clamp Coil for Configurable and Self-Sustained Battery Charging Profile

To self-sustain the constant current (CC) output to constant voltage (CV) output transition for inductive power transfer (IPT) chargers, the clamp coil assisted IPT battery chargers are better than the existing solutions due to the merits of no additional switching components, sensors, and control circuits. However, the clamp coil of these IPT chargers is bulky and hard to design, as the mutual inductances between the clamp coil and the main coupler coils are significant to the output performances. To facilitate the small clamp coil in the transmitter, this paper proposes a family of IPT battery chargers with a proper secondorder compensation network on the secondary side. The output thresholds of the IPT charger with the proper compensation can be readily configured to cope with the desired charging profile, and the clamp coil can be designed very small to decrease the corresponding cost and size. In addition, the proposed threecoil IPT charger still features automatic and smooth CC-to-CV transition to eliminate wireless communication, near unity power factor to minimize voltage-ampere (VA) ratings, soft switching to improve transfer efficiency, and open-circuit protection during CC charging. An experimental prototype of a 48 V/2.5 A battery charger is built to verify the analysis.