Low Power Levels Research Articles

A Self-Packaged SISL Low-Power Rectifier Based on a High-Impedance Line for C-Band Applications

In this letter, a self-packaged substrate-integrated suspended line (SISL) rectifier is proposed. The rectifier consists of a quarter-wavelength high-impedance transmission line, a diode, a tuning inductor, and a dc pass filter. The lower the power is, the lower the rectifying efficiency is. At a low input power level, the diode impedance real part is almost zero. A tuning inductor is introduced to form a parallel resonator to enhance the diode voltage. A quarter-wavelength high-impedance line is presented to match the rectifying diode to the source. In addition, due to the self-packaging characteristics and air cavity of SISLs, the radiation loss and dielectric loss of the proposed rectifier are reduced. A rectifier was designed, fabricated, and measured at 5.8 GHz. The radio frequency (RF)-dc conversion efficiency reaches 3.5% at −30 dBm, which is close to its theoretical estimated efficiency at 5.8 GHz. This ultralow power rectifier may be used in energy harvesting at <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$C$ </tex-math></inline-formula> -band.

Analysis and Design of RF Energy-Harvesting Systems With Impedance-Aware Rectifier Sizing

Because of the interaction between the internal blocks of an RF energy harvesting (RFEH) system, sizing a rectifier only for high power conversion efficiency (PCE) is insufficient for improving global power harvesting efficiency (PHE). This brief analyzes and sizes the rectifier by taking its input and output impedances into account with a two-port model that combines the rectifier AC and DC characteristics. The AC characteristic in this model is used for impedance-aware rectifier sizing. We target a low input-impedance rectifier for better impedance matching between the receiver antenna and the rectifier. The DC characteristic describes the rectifier power loss allocation and estimates its maximum power point. A proposed parasitic-aware matching network sizing methodology predicts the PHE is finally limited by Ohmic loss in the matching network at a low incident power level. For overcoming this limitation, this brief also analyzes the impact of multiple rectifier stages on RFEH with a high peak-to-average power ratio (high-PAPR) incident waveform for improving the PHE. We design an RFEH prototype with a sized 28nm CMOS two-stage cross-coupled rectifier. Measurement results show sensitivity as low as −28.3 dBm with a peak PHE of 31.1% at −16.5 dBm 2.45-GHz high-PAPR incident power. It has sufficient high output impedance to prevent reverse leakage without the need for an additional self-gating circuit.

Numerical study on THz radiation of two-dimensional plasmon resonance of GaN HEMT array

The GaN high electron mobility transistor (HEMT) has been considered as a potential terahertz (THz) radiation source, yet the low radiation power level restricts their applications. The HEMT array is thought to improve the coupling efficiency between two-dimensional (2D) plasmons and THz radiation. In this work, we investigate the plasma oscillation, electromagnetic radiation, and the integration characteristics of GaN HEMT targeting at a high THz radiation power source. The quantitative radiation power and directivity are obtained for integrated GaN HEMT array with different array periods and element numbers. With the same initial plasma oscillation phase among the HEMT units, the radiation power of the two-element HEMT array can achieve 4 times as the single HEMT radiation power when the array period is shorter than 1/8 electromagnetic wavelength. In addition, the radiation power of the HEMT array varies almost linearly with the element number, the smaller array period can lead to the greater radiation power. It shows that increasing the array period could narrow the main radiated lobe width while weaken the radiation power. Increasing the element number can improve both the radiation directivity and power. We also synchronize the plasma wave phases in the HEMT array by adopting an external Gaussian plane wave with central frequency the same as the plasmon resonant frequency, which solves the problem of the radiation power reduction caused by the asynchronous plasma oscillation phases among the elements. The study of the radiation power amplification of the one-dimensional (1D) GaN HEMT array provides useful guidance for the research of compact high-power solid-state terahertz sources.

Performance Analysis of Three Spectrum Sensing Detection Techniques with Ambient Backscatter Communication in Cognitive Radio Networks

In wireless communications, the Ambient Backscatter Communication (AmBC) technique is a promising approach, detecting user presence accurately at low power levels. At low power or a low Signal-to-Noise Ratio (SNR), there is no dedicated power for the users. Instead, they can transmit information by reflecting the ambient Radio Frequency (RF) signals in the spectrum. Therefore, it is essential to detect user presence in the spectrum for the transmission of data without loss or without collision at a specific time. In this paper, the authors proposed a novel Spectrum Sensing (SS) detection technique in the Cognitive Radio (CR) spectrum, by developing the AmBC. Novel Matched Filter Detection with Inverse covariance (MFDI), Cyclostationary Feature Detection with Inverse covariance (CFDI) and Hybrid Filter Detection with Inverse covariance (HFDI) approaches are used with AmBC to detect the presence of users at low power levels. The performance of the three detection techniques is measured using the parameters of Probability of Detection (PD), Probability of False Alarms (Pfa), Probability of Missed Detection (Pmd), sensing time and throughput at low power or low SNR. The results show that there is a significant improvement via the HFDI technique for all the parameters.

New Load Modulation Combiner Having a Capability of Back-Off Control for Doherty Power Amplifiers

A new load modulation combiner (LMC) having the capability of back-off control is proposed for a Doherty power amplifier (DPA). The proposed LMC consists of two transmission lines tied at the combining node, and a shunt element across the other ends of the transmission lines. The shunt element of the LMC becomes virtually open-circuited at the peak power level and allows the carrier amplifier to have an arbitrary load impedance at the low power level. The operating principle and circuit structure of the DPA based on the proposed LMC are presented in detail. The proposed DPA was implemented using GaN-HEMT for the 3.5 - 4.0 GHz band. Using a 5G NR signal with a peak-to-average power ratio (PAPR) of 7.9 dB and signal bandwidth of 100 MHz, the implemented DPA showed drain efficiency (DE) of 49.6 - 54.4% and power gain of 11.1 - 13.0 dB at an average output power of 34.5 dBm. An adjacent channel leakage power ratio (ACLR) was obtained as −50.4 - −45.0 dBc at the average power level with a digital pre-distortion (DPD) technique.

Mechanisms of ensuring the accuracy and reliability of data transmission over a radio channel using relay technology and their implementation on transceivers with LoRa modulation

The article is devoted to a detailed description of the algorithms of the operation of the relay-race data transmission system over a radio channel, which ensure high reliability of transporting the results of monitoring the operation of extended objects to the central control panel. The feature of the system is operation at a low power level of transmitters, energy efficiency, which ensures a long-term operation without maintenance, the ability to replace failed elements quickly without stopping the entire system, mobility — quick installation and start-up of the system. Energy efficiency and operation of the radio channel with a low transmitter power level is ensured by the use of SX 1276 (LoRa) transceivers. The accuracy and reliability of data transmission is ensured by original algorithms, which are described in the paper. In the relay data transmission system, it is possible to use up to 255 relay nodes with their installation at a distance of up to 4 km from each other. Two options of building a system with relay-race transmission have been developed: a system with a simple handover, a system with transmission «Through one». The second option provides more reliable data transfer and higher probability of uptime. With the number of relay nodes equal to 50, the probability of failure-free operation of a simple system is 0.268, and for the system with «Through one» transmission is 0.985.

Nível de potência em dois estágios para melhoria da secagem micro-ondas-vácuo de chips reestruturados de mandioquinha-salsa

ABSTRACT The Peruvian carrot is a root that is rich in bioactive compounds. However, owing to the short shelf life of these carrots, their consumption is restricted. In the present study, we investigated the microwave vacuum drying (MWVD) of restructured Peruvian carrot chips. Two microwave power levels, namely, constant and two-stage, were considered and evaluated to determine their relationship with drying time, kinetic parameters, energy consumption, and preservation of carotenoids and phenolic compounds. At the constant microwave power level, drying time decreased with increasing drying rate, sample temperature, and energy consumption. However, it did not affect the drying rate at the end of the drying. At the two-stage microwave power level, the drying time was similar to that observed in constant power level experiments. However, sample temperature and energy consumption were decreased when drying at a lower power level. Nutritional compounds were better preserved by using the highest tested power level at the two-stage level and the lowest tested one at the one-stage power level. Page’s and Fick’s models presented an excellent fit of the experimental data. Using the two-stage microwave power level at a higher initial power level (MWVD-5-1) saved energy, decreased the drying duration, and preserved the bioactive molecules in restructured chips.

Особенности желудочковой экстрасистолии на фоне коморбидной патологии у юных спортсменов

Aim: to assess the role of autonomic disorders and undifferentiated connective tissue dysplasia (UCTD) of the heart in children with ventricular extrasystoles (VE) engaged in sports. Patients and Methods: the study included 52 athlete boys with newly diagnosed cardiac arrhythmia in the form of ventricular extrasystoles. The study group (n=34) consisted of children with moderate VE severity co-existing with asympaticotonic type of autonomic dysfunction syndrome (ADS) amid undifferentiated connective tissue dysplasia mostly affecting the heart (UCTDH). The study group was split into two subgroups: subgroup 1 (n=11) – children with monotopic VE persisting at load and subgroup 2 (n=23) – children with occasionally appearing VE which reduced in the vertical position and/or at load. The control group (n=18) consisted of children with moderate VE amid UCTDH without ADS manifestations. A comprehensive clinical and laboratory assessment was performed in all patients. Results: on Holter monitoring (HM), in patients of the study group, subgroup 1, a sinus rhythm was recorded with the presence of 9,000- 15,000 VE per day (single or paired). The power spectral analysis of heart rate variability (HRV) in the subgroup 1 children demonstrated that in most cases (10 (90.9%)) there were low levels of the total power (TP) (р&lt;0.05) and high values of the high-frequency component (HF) (p&lt;0.05) as compared to those in the control group children. Also, a significant decrease in creatine phosphokinase-MB activity in the blood serum was found in children of the study group, subgroup 1, as compared to the reference values (р&lt;0.05). The VE development in the study group, subgroup1, children was caused by the combined exposure to sport loads and the autonomic control of cardiovascular function amid UCTDH. In the study group, subgroup 2, children the laboratory testing did not demonstrate any statistically significant changes in creatine phosphokinase-MB activity in the blood serum as compared to the reference values (р&gt;0.05). On HM, in most of the subgroup 2 children, a sinus rhythm was recorded with the presence of 6,000-9,000 VE per day. The changes in HRV parameters and their spectrogram in 19 (82.6%) cases were common for asympaticotonic type. As compared to the values in the control group children, TP was slightly lower (р&gt;0.05) along with a high HF level (р&gt;0.05). A half of the control group children had a moderate increase in creatine phosphokinase-MB activity in the blood serum (р&lt;0.05), while in other cases its values did not differ considerably from the normal range. On HM, in most cases a normal sinus rhythm with usually single EV, 300-5,000 per day, was recorded. The main measurements of the power spectral analysis of HRV and spectrogram indicators suggested that children of this group had sufficient body energy supply. The presence of VE in the control group children was associated with the impact of sport loads on the heart with dysplasia. Conclusion: the authors have distinguished the clinical variants of heart rhythm disorders in young athletes with different levels of body energy supply, VE patterns, etc. In young athletes, ventricular extrasystoles are characterized by a persisting occurrence in cases with asympaticotonic type of autonomic disorders amid UCTDH. They are associated with a decrease in energy supply of the body, in particular, the myocardial muscle. Occasionally occurring VE were recorded in athletes without significant disturbances in energy supply. KEYWORDS: ventricular extrasystoles, autonomic dysfunction syndrome, undifferentiated connective tissue dysplasia of the heart, energy supply, athletes. FOR CITATION: Cherkasov N.S., Doronina T.N., Prakhov A.V., Semenova I.A. Characteristics of ventricular extrasystoles co-occurring with comorbidities in young athletes. Russian Journal of Woman and Child Health. 2023;6(1):45–49 (in Russ.). DOI: 10.32364/2618-8430-2023-6-1-45-49.

Analysis of the effects of the transitional period on performance parameters in young soccer players

Purpose: The transitional period has been shown to produce detraining effects in soccer players and could increase the risk of injury. The primary purpose of this study was to analyse the impact of the transitional period (4-6 weeks) on lower body power levels by vertical and horizontal jumping in young players and compare them with the first part of the regular season, using the peak height velocity (PHV) as a covariate. Methods: Eighteen elite youth players (15.73 ± .25 years) belonging to a professional soccer club that competes in national U-16 categories were evaluated before starting the transitional period (M1: end of the season) and at the end of it (M2: end of transitional period), as well as in the middle of the regular season (M3). The variables analyzed in the study were the vertical jump (e.g., CMJ) and horizontal jump. Results: Improvements were observed in all the variables during the transitional period. They were also like those of the first part of the season. When analysing responders and non-responders to the PHV between M1, M2 and M3, all the vertical jump variables show significant differences (P &lt; .05). In contrast, no significant differences were found in the horizontal jump (P &gt; .05). Conclusions: It is shown that the transitional period (7 weeks) does not have detraining effects on young players because they are in a moment of muscular development. In addition, the responder players have higher values in power levels and have produced more tremendous changes during study time than the non-responder players. Keywords: Transitional period; power; adolescent players; soccer; peak height velocity.

Enhancing the power level harvested by rectenna systems based on focusing metasurfaces for ambient environments

Electromagnetic (EM) RF (radio frequency) energy harvesting in dynamic ambient environments is a challenge for conventional energy harvesting systems such as rectennas. The main challenges are the low efficiency of the collector and low ambient power levels, which makes it hard to consider in industrial applications. Several research works have focused on the design of high-efficiency antennas to achieve an efficient and maximum possible level of RF EM energy harvesting. Their main objective is to improve the EM energy harvesting system by overcoming the low efficiency of the collector, which is the main part of the rectenna system. In this work, we propose and investigate a methodology in terms of EM energy harvesting based on the concentration and focusing of EM energy in a small zone where it can be easily collected and transferred indirectly to the rectenna system. It consists of a focusing device and a methodology to associate the latter with existing RF energy harvesting systems. We demonstrate a focusing metasurface design implemented alongside an off-the-shelf rectenna device at 900 MHz, where an enhanced energy harvested power level up to a linear gain of 8 is achieved compared to the case when only the rectenna is used. Numerical results as well as measurements results in an anechoic chamber are shown. Experimental power received levels are given both in the focusing plane and in time for the validation of the concept.

Lead-Free HIFU Transducers.

High-intensity focused ultrasound transducers operating at 4 MHz based on lead-free piezoceramics from the sodium bismuth titanate (NBT) family are described. First, the piezoelectric material (Pz12X) is evaluated from the standpoint of transducer design and its important characteristics, including temperature dependance of several parameters such as dielectric and mechanical coefficients. Then, the performance of six transducers of the same design is evaluated in terms of electro-acoustic efficiency and its dependency on the operating acoustic power level up to 30 W. Overall, the initial electro-acoustic efficiency of three independent transducers is approximately 50% at low acoustic power levels and slightly drops down to 42% as the input electric power reaches 10 W. This process is stable and fully reversible. Moreover, the stability of electro-acoustic efficiency over extended power burst cycling is studied using another two transducers up to 95×103 power bursts of 250-ms duration and acoustic power of 10 W. This protocol is beyond the typical clinical use of similar devices in practice. No significant changes in electro-acoustic performance are noted. Additionally, the input electric power and the output acoustic power, together with the temperature of the piezoelectric component, are evaluated simultaneously over the period of one power burst. It is found that the maximum operating temperature over a high-input electric power burst of 600 J is below 60°C, which defines the operational limit for such devices, as the de-poling temperature of the lead-free material is around 85°C. It is found that the lead-free material from the NBT family is also a promising alternative to lead-based PZT-type materials in high-power therapeutic ultrasound.

Experimental study of pressure pulsation in a large-scale hydropower plant with Francis turbine units and a common penstock

The effects of partial load operation on pressure pulsation and pressure pulsation propagation to off-operation units are significant • Pressure pulsation measurements are provided for an actual hydropower plant. • Rotor-stator interactions and draft tube vortex rope were studied simultaneously. • Pressure pulsation propagates from operating units to off-operation units. • In partial loads, the most significant wave in waterway is draft tube vortex rope. • The turbine rotor-stator interaction waves are localized and flow rate dependent. As a limiting factor in power generation, especially in part-loads, turbulence is considered an important phenomenon in hydropower plants. In this study, the pressure pulsation measurements are done for Darian Hydropower Plant in Iran, which is composed of three 70 MW units with a common penstock. The frequency spectrum for different features such as rotor-stator interactions, draft tube vortex rope, and surge tank fluctuations is obtained and discussed in detail. Pressure pulsation measurements were obtained while one of the units (i.e., Unit I) was in operation, and the other units (Units II, III) were out of operation. In addition to the in-operation units, the effect of pressure pulsation on the out of operation units is also studied comprehensively. The results show that to avoid the destructive effect of pressure pulsation, the output power of the in-operation unit should not be lower than 55 MW (i.e., a part load lower than 78% of the full load). Results demonstrate that at lower power levels pressure pulsation is significant likely because the flow characteristics are rather significantly different than the conditions considered for the design of the plant. Moreover, it is found that most of the pressure waves generated by the turbulent flow of the in-operation unit waterway have considerable impacts on the neighboring units. A very good agreement between the expected theoretical frequencies and measured frequencies are observed for various pressure pulsation phenomena, as well.

LoRa-based IoT applications on campus: experimental demonstrations and performance evaluation

Lora technology is widely used in solving many IoT problems because of its long-range capability and low-cost. However, the model which works in the 2.4GHz frequency and without regional limitations is a novelty and its full capabilities are unknown. In this research the device is test for its transmission capabilities on a university campus because this is the conditions with high 2.4GHz interference from Wi-Fi, Bluetooth, etc. The authors also try to find the packet delivery rate and define at what distance LoRa end-node starts to lose connection with its gateway. Along the way receiving signal strength indicator is registered in order to understand the device power level. All of it is done by placing the gateway in the middle of the campus so that it equally reaches the furthermost points, connecting it with a LoRa-based end-node and testing this connection by placing the end-node device in different spots within the area and analysing the connection. LoRa 2.4GHz has shown lower effectiveness in terms of distance in comparison with its sub-GHz counterparts. Receiving signal strength indicator also demonstrated a lower power level in comparison with the mentioned device specifications. However, the LoRa technology still provides bigger distance than Wi-Fi or Bluetooth and is cheaper than other protocols used in IoT. Higher results can be achieved by using a better antenna and by eliminating physical obstacles.

Thermodynamic analysis of Tesla turbine in Organic Rankine Cycle under two-phase flow conditions

In the field of clean energy, Organic Rankine Cycle (ORC) is considered a vital method to utilize low-grade waste heat effectively. Due to certain application advantages in low power level ORC systems, the Tesla turbine is considered one of the essential choices for the core components of ORC systems. Given the inadequacy of the current research on the performance of the Tesla turbine under two-phase flow conditions, a one-dimensional model of the Tesla turbine was constructed in this paper to make it equally applicable to the two-phase flow conditions of wet working fluids. A model of the Tesla turbine and ORC system was constructed from the thermodynamic point of view, and five typical wet working fluids (R22, R417a, R134a, R152a, and R290) were selected to study the effects of the five wet working fluids on the thermal performance of Tesla turbine and ORC system. The effects of the changes in key structural parameters of the Tesla turbine on the performance of the Tesla turbine and the ORC system were further analyzed when different wet working fluids were used in the ORC system. The results showed that the highest turbine efficiency of 42.0 % was achieved when the Tesla turbine used R22 as the working fluid under the design conditions, while the highest turbine output power and the highest system thermal efficiency of 1.19 kW and 3.96 % were achieved when R417a was used as the working fluid. The analysis of the key structural parameters of the system showed that for the five different wet working fluids, the turbine efficiency, turbine output power, and system thermal efficiency increased monotonically with increasing rotor inlet radius. For each of the five wet working fluids, an optimum rotor speed, rotor outlet radius, and rotor gap distance exist, resulting in optimal turbine efficiency and system performance. The related work provides an important reference for the optimal design of Tesla turbines with wet working fluids.

ISM 2.4 GHz Band Antenna Model for RF Energy Harvesting Systems

In today’s world many technological devices can operate with very low power levels. Despite this situation, these devices need to be fed with a sustainable energy source and constantly charged. This low level power need can be attained from ambient electromagnetic waves from any radio frequency sources. Radio frequency energy harvesting systems can be offered to feed these type of devices and these systems have been used in many areas in recent years. In this study, an antenna designment that can be used in RF energy harvesting systems is emphasized. Within the scope of this study, an RF energy harvesting antenna operating at 2.4 GHz frequency has been modeled. The electromagnetic performance and antenna fundamental parameters of the RF energy harvesting antenna are numerically calculated using a commercial 3D based on a transmission line matrix (TLM) and the finite integration technique (FIT). The physical extents of the antenna are 35 x 28 x 1.6 mm. The proposed RF energy harvesting antenna has 2.1 dBi directivty and %98.1 radiation efficiency performance parameters. The antenna proposed here can be have usage areas such as an RF energy harvesting antenna for low-power medical devices, self sustainable wireless devices in Internet of Things (IoT), Wireless Body Sensor Network (WBSN) devices.

Steady-state thermal hydraulic modelling and turbine trip transient simulation of the NuScale integral pressurised water reactor using the ASTEC code

A steady state model of the NuScale reactor has been built using the thermal hydraulic module CESAR of the severe accident code ASTEC. Construction of the model was achieved through iterations based on convergence towards data provided by NuScale pertaining to important operating properties—core temperatures, coolant mass flow rate and secondary steam temperature—at 100% power (160 MW) and also at lower power levels. Good agreement with reference values was achieved to within 3% deviation. With a similar methodology, the previous model was adjusted to give a second steady state model meant to provide conservative initial conditions from which a turbine trip transient simulation would be performed. Sound agreement with literature was achieved, with maximum deviations of less than 1.8% for monitored parameters. Lastly, a turbine trip transient was simulated and compared to reference data from analyses performed with NRELAP5 and RELAP5/SCDAPSIM. The most important system behaviors and event timings are well captured and reproduced, with discrepancies arising from inevitable estimates made due to lack of information.

Development and testing of a low-current applied-field magnetoplasmadynamic thruster with a rectangular discharge channel

This study explores the possibility of miniaturizing magnetoplasmadynamic thrusters (MPDTs) to significantly lower power and discharge current levels compared to most conventional MPDTs. A design alternative for MPDTs using a discharge channel with a rectangular cross-section is presented that enables the implementation of strong external magnetic fields to increase the applied-field Lorentz force. The thruster concept uses heaterless calcium aluminate electride (C12A7:e-) hollow cathodes as the electron source. A prototype of the concept intended for the low-amp current range generates thrust in the low millinewton range with a specific impulse ranging between 400 s and 1200 s at power levels below 500 W but shows high thermal power losses to the anode. A further miniaturized version of the concept intended for the sub-amp current range is thermally more sustainable but requires high mass flow rates to achieve a stable discharge, limiting the achievable specific impulse.

Research and analysis of the effect between the power level and economy on the lead-based modular nuclear power reactor

The fast reactor is gradually being paid attention to in nuclear power due to a better breeding effect, and its economy is also directly followed. Due to the restriction of the core power density, the core power level is directly related to the volume of the core active area. When the power level and the volume of the core gradually increase, the mass of uranium and 235U in the core at the beginning of life will gradually increase on the basis of a critical uranium inventory. At the same time, due to the gradual increase in the breeding effect, the utilization rate of uranium resources at the end of life will gradually increase. Due to the characteristics of the large critical uranium mass and high breeding effect, the mass of uranium and 235U in the low power level core at the beginning of life cannot be further reduced because of the critical uranium inventory. The lifetime of the high power level core should be extended to use the wealthy reactivity of the core because of the improvement in the breeding effect. However, due to the requirements of the nuclear power refuel time and the limitation to fuel consumption, the breeding effect brought by the improvement in the core power level and the size of the active zone may be less effective. In this article, the power level and economy of lead-based modular nuclear power are analyzed, and the economy of different power level fast reactors with 2,000 EFPD lifetime such as 100 MWt, 300 MWt, 500 MWt, 700 MWt, and 1000 MWt thermal power is designed and analyzed. By analyzing the invention of uranium and 235U and the fuel utilization of different core schemes, the best economic analysis of the single reactor power of the current lead-based modular reactor is proposed and the foundation of the lead-based modular nuclear power is provided.

A Review of Compensation Topologies and Control Techniques of Bidirectional Wireless Power Transfer Systems for Electric Vehicle Applications

Owing to the constantly rising energy demand, Internal Combustion Engine (ICE)-equipped vehicles are being replaced by Electric Vehicles (EVs). The other advantage of using EVs is that the batteries can be utilised as an energy storage device to increase the penetration of renewable energy sources. Integrating EVs with the grid is one of the recent advancements in EVs using Vehicle-to-Grid (V2G) technology. A bidirectional technique enables power transfer between the grid and the EV batteries. Moreover, the Bidirectional Wireless Power Transfer (BWPT) method can support consumers in automating the power transfer process without human intervention. However, an effective BWPT requires a proper vehicle and grid coordination with reasonable control and compensation networks. Various compensation techniques have been proposed in the literature, both on the transmitter and receiver sides. Selecting suitable compensation techniques is a critical task affecting the various design parameters. In this study, the basic compensation topologies of the Series–Series (SS), Series–Parallel (SP), Parallel–Parallel (PP), Parallel–Series (SP), and hybrid compensation topology design requirements are investigated. In addition, the typical control techniques for bidirectional converters, such as Proportional–Integral–Derivative (PID), sliding mode, fuzzy logic control, model predictive, and digital control, are discussed. In addition, different switching modulation schemes, including Pulse-Width Modulation (PWM) control, PWM + Phase Shift control, Single-Phase Shift, Dual-Phase Shift, and Triple-Phase Shift methods, are discussed. The characteristics and control strategies of each are presented, concerning the typical applications. Based on the review analysis, the low-power (Level 1/Level 2) charging applications demand a simple SS compensation topology with a PID controller and a Single-Phase Shift switching method. However, for the medium- or high-power applications (Level 3/Level 4), the dual-side LCC compensation with an advanced controller and a Dual-Side Phase-Shift switching pattern is recommended.

Self-induced transparency in a perfectly absorbing chiral second-harmonic generator

Transparency and perfect absorption are two contradictory terms; a perfect absorber never permits waves to transmit through. However, this statement only remains true in the linear regime, where the nonlinearity has been omitted and the physical system like the perfect absorber is not affected by the incoming waves. Here we experimentally demonstrate an intriguing self-induced transparency effect in a perfectly absorbing optical microcavity, which perfectly absorbs any incoming waves at the low power level, but allows a portion of waves to be transmitted at the higher power due to the nonlinear coupling between the fundamental and its second harmonic modes. Moreover, the asymmetric scattering nature of the microcavity enables a chiral and unidirectional reflection in one of the input ports, this leads to asymmetric and chiral coherent control of the perfect absorption states through phase varying. More importantly, such chiral behaviors also empower the chiral emission of second-harmonic generation with a high distinct ratio in the transparency state. These results pave the way for controllable transparency in a wide range of fields in optics, microwaves, acoustics, mechanics, and matter waves.