Conversion Loss Research Articles

The Modeling and Simulation of Non-Isolated DC–DC Converters for Optimizing Photovoltaic Systems Applied in Positive Energy Districts

DC–DC converters are critical for energy management in positive energy districts (PEDs) because they allow for efficient conversion between different voltage levels, enabling the integration of various renewable energy sources, energy storage systems, and loads. The demand for high-voltage gain DC–DC converters in photovoltaic power systems has surged in recent times. Despite the numerous converter topologies reported, there is a focused effort to streamline components, particularly switching devices, passive elements, and overall converter losses. This paper introduces the single switching impedance network (SSIN)-based converter as a unique DC–DC converter topology, designed in both one-stage and double-stage configurations for photovoltaic applications. One of the main characteristics of the SSIN converter is that it needs just one switch and three capacitors for the n-stage. A comparative analysis with conventional boost converter topology demonstrates the SSIN-based converter’s capability to achieve a desirable output voltage that closely approximates an ideal sine waveform. Furthermore, the application of advanced control strategies to the proposed converter highlights its superior performance and robustness in maintaining output voltage stability under varying conditions. These characteristics make the SSIN-based converter particularly well-suited for PED applications, where efficiency, reliability, and the seamless integration of renewable energy sources are crucial.

Calculation and measurement of motor and converter losses according to IEC 61800-9-2 ED2

Calculated and measured motor and converter losses are compared using the example of a four-pole asynchronous motor with a rated output of 110 kW, operated on a standard converter. The determination of the motor losses using the polynomial approach to describe the motor losses in the field weakening range shows a clear deviation from the measurements. To calculate the converter losses, an equation for calculating the losses in DC link chokes was shown. The polynomial approach to describe the motor losses as a function of torque and speed can also be used for converters in the constant flux range. The semi-analytical model for calculating the converter losses shows satisfactory accuracy even when the motor is operated in the field weakening range.

Techno-economic performance of different DC power distribution networks in official buildings based on a real-time analysis method

The integration of photovoltaic (PV) and energy storage systems into official buildings has garnered considerable attention, which are recognized as DC power sources. Notably, DC power can satisfy the majority of electrical demands in official buildings. The primary objective of this research is to enhance overall system efficiency by efficiently utilizing renewable energy through direct current (DC) power distribution compared to alternating current (AC) systems. This study proposes a techno-economic analysis framework to guide designers in selecting system configuration and voltage levels. The analysis covers various PV capacities, load compositions, and battery capacities, with the aim of optimizing power distribution efficiency and achieving a more competitive levelized cost of energy (LCOE). The proposed model integrates the dynamic efficiency of actual converters and wire gauges, enabling real-time computation of the energy supply–demand balance within the power distribution system, including associated conversion and transmission losses. The results indicate that conversion loss accounts for approximately 80% of the overall energy loss within power distribution networks. The implementation of DC power distribution significantly improves system efficiency and economic viability. Specifically, the DC375 system exhibits superior techno-economic performance in scenarios involving high PV and battery capacities. In scenarios with limited PV and battery capacity, the building power distribution system should employ a hybrid AC-DC topology to efficiently distribute the available PV output to building loads powered by DC

Power Quality Enhancement in Grid-Connected Solar PV Systems Using Adaptive Control and Multilevel Inverter Topologies Under Dynamic Grid Conditions

This paper introduces a control strategy that uses an integrator-based positive sequence estimator to improve the power quality of a grid-connected double-stage solar PV system. The control extracts positive sequence components from distorted and unbalanced grid voltages to calculate unit templates and grid reference currents during grid anomalies like distortion, unbalance, sag/swell, and DC offset. A feedforward term is introduced to the photovoltaic array to ensure rapid transient response, and the DC-link voltage is adaptively regulated to reduce the voltage source converter (VSC) losses during weak grid conditions. The paper compares the performance of two-level and three-level inverters in this system configuration, highlighting the differences in power quality improvement, harmonic reduction, and system efficiency under various grid disturbances and intermittent solar conditions. Simulation results, performed in MATLAB, validate the superior performance of the three-level inverter in terms of lower total harmonic distortion (THD) in grid currents, in compliance with IEEE standard 519, while demonstrating the satisfactory response of both inverter types during challenging grid conditions like intermittent solar irradiation, DC offset, voltage distortions, unbalance, and voltage sag/swell.

Demonstration of 400 Gbit/s/λ wireless transmission for a photonic-assisted SISO integration system at 220 GHz.

We experimentally demonstrate a dual-polarized, single-input single-output (SISO) photonic-electronic integrated system, achieving a single-wavelength data rate of 400 Gbit/s at 220 GHz. This system is based on a self-developed IQ mixer, orthomode transducers (OMTs), and a dual-polarized multiplexing antenna (DPMA). The IQ mixer front-end exhibits a conversion loss of over 14 dB within a 30 GHz bandwidth, and cross talk between IQ channels is better than 15 dB for most frequency points. The OMT achieves a polarization isolation of over 30 dB and an insertion loss (IL) of less than 3 dB across the entire WR-4 band (170-260 GHz). The DPMA operates in the WR-4 band, with measured in-band return loss characteristics better than 15 dB. The 50 GBaud DP-16QAM modulation is successfully transmitted over a 20 km SSMF and a 1 m wireless link. Additionally, a 125 Gbit/s real-time transparent fiber-THz-fiber SISO transmission system is demonstrated, marking a significant advancement in the development of large-bandwidth, high-speed 6G photonic-electronic systems.

A 24–30‐GHz Modified Gilbert‐Cell Downconverter With High Linearity and Isolation

ABSTRACTThis paper introduces a downconverter mixer employing a modified double‐balanced Gilbert‐cell topology, designed using IHP's 0.13‐m SiGe BiCMOS technology. Distinct from the conventional topology, a resonator was employed at the emitter of the transconductance stage, which enables the utilization of transconductance stage as an active balun, allowing for direct feeding of the single‐ended input without sacrificing the advantageous of the double‐balanced topology. The integration of the resonator reduces the amplitude and phase errors within the active balun segment, thereby enhancing port‐to‐port isolation. The area occupied by the resonator is approximately 1.7 times smaller than that of an RF transformer balun typically employed in conventional double‐balanced topologies. The LO and IF differential signals are converted to single‐ended ones through transformer baluns for measurement purposes. The frequencies of operation for RF, LO, and IF are 24–30, 18–24, and 6 GHz, respectively. The conversion loss is 7.7 dB at 26 GHz, with port‐to‐port isolations exceeding 35 dB. The input 1‐dB compression point is 5.7 dBm, while the circuit consumes 65‐mW power from a 3.3‐V voltage supply. Excluding the pads, the active area of the design spans 1 mm2.

Solar PV powered DC charger for electric vehicles with reconfigurable power electronic interface

ABSTRACT Global expansion of the EV market has led to widespread DC charging infrastructure. Consumers prefer DC charging over AC to reduce charging time per kilometer. However, grid-connected DC chargers can cause issues such as grid instability, power quality problems, demand imbalance, and conversion losses. This paper proposes an off-grid photovoltaic (PV) fed DC charger for EVs along with a battery energy storage system (BESS) to mitigate these challenges. The work aims to increase the use of clean energy for EV charging, to ensure uninterrupted EV charging with minimum power conversion stages, and to improve PV utilization. BESS serves as a backup power source that charges or discharges based on PV availability. Additionally, the system powers the non-critical adjustable loads of domestic/industrial sites with the available PV power when both EV and BESS are fully charged. The system can be reconfigured to operate in six distinct modes using two DC-DC converters and five relays. Among six modes, four modes operate in single-stage power conversion. A buck converter is used to extract power from PV. A bidirectional buck-boost converter is used to charge and discharge the BESS. The proposed system is validated through hardware prototype for both steady-state and transient conditions.

Modal phase-matching in thin-film lithium niobate waveguides for efficient generation of entangled photon pairs.

Thin-film lithium niobate (TFLN) waveguides have emerged as a pivotal platform for on-chip spontaneous parametric down-conversion (SPDC), serving as a crucible for the generation of entangled photon pairs. The periodic poling of TFLN, while capable of generating high-efficiency SPDC, demands intricate fabrication processes that can be onerous in terms of scalability and manufacturability. In this work, we introduce a novel approach to the generation of entangled photon pairs via SPDC within TFLN waveguides, harnessing the principles of modal phase-matching (MPM). To address the challenge of efficiently exciting pump light typically in a higher-order mode, we have engineered a mode converter that couples two asymmetrically dimensioned waveguides. This converter adeptly transforms the fundamental mode into a higher-order mode, demonstrating a conversion loss of 1.55 dB at 785 nm with a 3 dB bandwidth exceeding 30 nm. Subsequently, we have showcased the device's capabilities by characterizing the pair generation rate (PGR), coincidences-to-accidentals ratio (CAR), and spectral profile of the entangled photon source. Our findings present a simplified and versatile method for the on-chip generation of entangled photon sources, which may pave the way for the application in the realms of quantum information processing and communication technologies.

Machine Learning and Wavelet Transform: A Hybrid Approach to Predicting Ammonia Levels in Poultry Farms.

Ammonia (NH3) is a major pollutant in poultry farms, negatively impacting bird health and welfare. High NH3 levels can cause poor weight gain, inefficient feed conversion, reduced viability, and financial losses in the poultry industry. Therefore, accurate estimation of NH3 concentration is crucial for environmental protection and human and animal health. Three widely used machine learning (ML) algorithms-extreme learning machine (ELM), k-nearest neighbor (KNN), and random forest (RF)-were initially used as base algorithms. The wavelet transform (WT) with ten levels of decomposition was then applied as a preprocessing method. Three statistical metrics, including the mean absolute error (MAE) and the correlation coefficient (R), were used to evaluate the predictive accuracies of algorithms. The results indicate that the RF algorithms perform robustly individually and in combination with the WT. The RF-WT algorithm performed best using the air temperature, relative humidity, and air velocity inputs with a MAE of 0.548 ppm and an R of 0.976 for the testing dataset. In summary, applying WT to the inputs significantly improved the predictive power of the ML algorithms, especially for inputs that initially had a low correlation with the NH3 values.

Optimization Control Strategy for Light Load Efficiency of Four-Switch Buck-Boost Converter

The four-switch buck-boost (FSBB) converter usually adopts a pseudo-continuous conduction mode (PCCM) soft switching (ZVS) control strategy, but there is a problem with the low efficiency of FSBB converters under light loads. Firstly, the constraints that the control variables of the FSBB converter need to satisfy are analyzed, and it is pointed out that the fixed frequency constraint is not necessary. Then, the switching frequency is used to control the degree of freedom, and the quantitative relationship between the FSBB converter loss and the switching frequency is obtained. Finally, for different input voltages and loads, the switching frequency corresponding to the minimum power loss is calculated offline. By optimizing the switching frequency, the light-load efficiency of the FSBB converter is improved. A prototype with an input voltage range of 210 V–330 V, an output voltage of 270 V, and an output power of 3 kW was developed. The loss was reduced by 15% at 20% load, and the peak efficiency of the converter reached 99.23%. The experimental results verified the effectiveness of the proposed control strategy.

An ultra-high gain boost converter with low switching stress for integrated multi-energy storage systems

In this paper, a high-gain low-switching-stress coupled-inductor with high voltage step-up voltage multiplier cells quadratic boost converter (VMC-QBC) is proposed. The turn ratio of the coupled inductors and the switch duty cycle increase the dynamic gain, and the two degrees of freedom adjustment and modularity of the voltage multiplier cells (VMC) make the structure more flexible. The use of the same drive signal for both switches makes control easier. While achieving multi-stage boosting and multiplication boosting from low to medium duty cycle, the passive clamping circuit absorbs the energy leaked by the coupled inductor, thus reducing the stress on the switching tube and alleviating the diode reverse recovery problem. A non-ideal model with parasitic parameters is developed to analyse the real voltage gain and the converter losses to give design guidelines. A 300 W prototype is designed and tested. The state space model of the converter is established and the working principle is analysed. Compared to other high-gain quadratic boost converters, the proposed converter has continuous input current, common ground characteristics, and high voltage gain at low to medium duty cycles to accommodate integrated multi-energy storage systems.

Optimal‐droop voltage‐restorer for zonal dc distribution system with simultaneous consideration of dynamic current balance and power loss reduction

AbstractA dc voltage restorer (dc‐VR) with optimal droop control is developed to reduce the power loss and solve the dynamic current imbalance simultaneously of the zonal dc distribution system integrating multi‐parallel energy storage. Firstly, the power loss model composed of line loss and converter loss is built and it is proved to be a strictly convex function with respect to droop coefficients, which indicates the power loss can be mitigated by optimizing the current distribution. Thus, an image‐based droop optimization method is proposed to search for the optimal droop coefficients. Then, the economy of voltage compensation on power loss reduction is investigated and an ESS‐combined dc‐VR is designed, including an interleaved parallel architecture and a capacitor‐integrated electric spring (C‐ES). Unified virtual inertia is proposed for interleaved parallel bridge arms to make their dynamic performance consistent. And the newly introduced C‐ES can keep the bus voltage at the rated level to reduce the system cost. Therefore, the problem of dynamic currents imbalance is addressed from the points of converter structure (dc‐VR) and control system (unified inertia), and the power loss can be reduced by voltage recovery (C‐ES) and optimizing the current reallocation which is achieved by updating sharing coefficients from the image‐based droop optimization method. Finally, the simulation cases validate the effectiveness of the proposed optimal‐droop dc‐VR on dynamic current balance and power loss reduction, and hardware in the loop experiment results prove the consistent dynamic characteristics of the dc‐VR's arms.

Taxonomic and functional characterization of biofilms from a photovoltaic panel reveals high genetic and metabolic complexity of the communities.

Biofilms are complex microbial cell aggregates that attach to different surfaces in nature, industrial environments, or hospital settings. In photovoltaic panels (PVs), biofilms are related to significant energy conversion losses. In this study, our aim was to characterize the communities of microorganisms and the genes involved in biofilm formation. In this study, biofilm samples collected from a PV system installed in southeastern Brazil were analyzed through shotgun metagenomics, and the microbial communities and genes involved in biofilm formation were investigated. A total of 2030 different genera were identified in the samples, many of which were classified as extremophiles or producers of exopolysaccharides. Bacteria prevailed in the samples (89%), mainly the genera Mucilaginibacter, Microbacterium, Pedobacter, Massilia, and Hymenobacter. The functional annotation revealed >12 000 genes related to biofilm formation and stress response. Genes involved in the iron transport and synthesis of c-di-GMP and c-AMP second messengers were abundant in the samples. The pathways related to these components play a crucial role in biofilm formation and could be promising targets for preventing biofilm formation in the PV. In addition, Raman spectroscopy analysis indicated the presence of hematite, goethite, and ferrite, consistent with the mineralogical composition of the regional soil and metal-resistant bacteria. Taken together, our findings reveal that PV biofilms are a promising source of microorganisms of industrial interest and genes of central importance in regulating biofilm formation and persistence.

A Broadband Low Conversion Loss Single-Ended Resistive Mixer With an Innovative Topology

A Broadband Low Conversion Loss Single-Ended Resistive Mixer With an Innovative Topology

State Space Average Modeling, Small Signal Analysis, and Control Implementation of an Efficient Single-Switch High-Gain Multicell Boost DC-DC Converter with Low Voltage Stress

This paper presents the closed-loop control of a single-switch high-gain multicell boost DC-DC converter working in a continuous conduction mode (CCM). This converter is particularly designed for applications in photovoltaic systems. One of the main advantages of the proposed converter is that it only employs one active semiconductor switch, which decreases the converter losses and cost, increases the efficiency, and simplifies the control circuit. Moreover, the multicell nature of the proposed converter offers the possibility of obtaining the required voltage gain by selecting the number of cells. State space average (SSA) modeling and small-signal analysis are used to model the switching converter power stages of the proposed converter. The parasitic series resistances of the passive elements of the converter circuit are considered to improve the accuracy of the modeling. Small-signal analysis is used to derive the open-loop transfer functions, input-to-output and control-to-output transfer functions of the proposed converter to examine its dynamic performance. The stability of the converter is analyzed to design the parameters of the voltage controller using the proposed modeling method. The experimental prototype of the proposed single-switch two-cell boost DC-DC converter was implemented. The simulation and experimental results proved the effectiveness of the proposed boost DC-DC converter under different working conditions. It has a fast dynamic response without overshoots. A comprehensive comparison between the proposed converter and previous boost converters is provided. It guarantees a required variable and constant high voltage gain with a wider duty ratio range. It compromises between the required performance, the low number of components, low voltage stress on the components, and cost-effectiveness. The experimental efficiency of the proposed converter is about 96% at a 100 W load.

Cascaded partitioned phase modulation for cross-connection of orbital angular momentum mode and polarization multiplexing channels.

Multi-dimensional orbital angular momentum (OAM) mode multiplexing provides a promising route for enlarging communication capacity and establishing comprehensive networks. While multi-dimensional multiplexing has gained advancements, the cross-connection of these multiplexed channels, especially involving modes and polarizations, remains challenging due to the needs for multi-mode interconversion and on-demand polarization control. Herein, we propose an OAM mode-polarization cross-transformation solution via cascaded partitioned phase modulation, which enables the divergently separated OAM modes to be independently phase-imposed within distinct spatial regions, leading to the synergistic conversion operation of mode and polarization channels. In demonstrations, we implemented the cross-connection of three OAM modes and two polarization multiplexed channels, achieving the mode purity that exceeds 0.951 and polarization contrast up to 0.947. The measured mode insertion losses and polarization conversion losses are below 3.42 and 3.54 dB, respectively. Consequently, 1.2 Tbit/s quadrature phase shift keying signals were successfully exchanged, yielding the bit-error-rates close to 10-6. Incorporating with increased partitioned phase treatments, this approach shows promise in accommodating massive mode-polarization multiplexed channels, which hold the potential to augment networking capability of large-scale OAM mode multiplexing communication networks.

Ultra-low-energy operation of electromagnetic bi-stable actuator under restricted energy supply

During the periodic drug administration for chronic diseases, unexpected battery depletion can be significantly problematic for the patients. While body heat harvesting utilizing the wearable thermoelectric generator (WTEG) shows the significant potential in continuous drug delivery systems (DDSs) by providing ceaseless power source, the power and the voltage output might not be sufficient to drive micropump actuators in such drug delivery systems. The continuous actuating current also imposes an additional challenge in developing efficient and compact voltage boosting circuits. In this paper, we propose an ultra-low-energy operating method of the WTEG-powered electromagnetic micropump system. In combination with our electromagnetic bi-stable actuator (EBA) where the energy demand is discretized, we present (1) the dedicated high-efficient charge pumps (CPs) (2) and the actuating pulse control method to prevent redundant energy waste. The proposed 10-stage charge pump is designed to reduce the conversion loss by utilizing multiple flying-capacitor switching structure, and the 2-stage series–parallel charge pump (SPCP) is fabricated with flexible thin-film super-capacitors (TFSCs) to realize the high boosting performance within compact and wearable features. Applying the proposed control method with the 10-stage CP in our WTEG-powered micropump system, we significantly reduce the charging time per actuation by 88.8% compared to the commercial boosting circuit. Also, the 2-stage SPCP achieves 84.0% reduction in the charging time while utilizing flexible and wearable features, showing a significant potential for self-powered wearable healthcare applications.

Low‐latency and power‐efficient row‐based binary‐weighted compensator for fixed‐width Booth multiplier

AbstractFixed‐width Booth multiplier (FWBM) plays a significant role in the arouse of approximate computing (AC) field. In this paper, a row‐based binary‐weighted compensator (RBC) for fixed‐width Booth multiplication is proposed. The derived binary‐weighted close‐form minimizes the conversion loss and hardware cost. With the proposed close‐form, the partial product array can be reduced dramatically. Consequently, the compact FWBM with the proposed RBC not only shortens the critical path to at least 24% but also minimizes the power dissipation to at least 44%. Moreover, the proposed RBC outperforms the state‐of‐art with a maximum merit improvement of 39%. By implementing the proposed RBC‐FWBM in the FIR filter, we manage to demonstrate the practicality of the proposed design with a significant reduction in power‐dissipation and delay while maintaining high accuracy.

Compact Switched-Inductor Power Supplies: Design Optimization with Second-Order Core Loss Model

Expressing switched-inductor converter losses simply as a function of design variables is key for designers. Power losses in switched-inductor power supplies are varied in nature, and optimization schemes in the literature fail to account for all of them. Available core loss models are mostly empirical or rely on measurements or variables beyond the reach of power supply designers. Specifically, a simple core loss model is missing. This work offers complete design optimization of switched-inductor power supplies with a quadratic model of core loss that relies solely on design variables known to the designers—inductance and switching frequency (or inductor peak current). This model alleviates the burden of performing complex measurements to characterize the inductor—measurements that, moreover, require geometric data about the core, such as its size, which are often not disclosed by the manufacturer. Predicted minimum losses without approximation are within 3.2% of measured minimum losses, and predicted minimum losses with approximation are within 2.2% of measured minimum losses.

A mixer architecture using GaN-based split-gate nanowire transistor

Frequency mixer is an essential block in radio-frequency signal processing for frequency translation and phase comparison. The most common mixers are fabricated using passive elements which suffer from significant conversion loss and low isolation. Mixers using active devices are used less frequently and rather less matured on GaN technology. Here, we demonstrate a mixer based on GaN split-gate nanowire transistor, allowing low conversion loss and high isolation. A constriction is formed by electrostatic modulation of the effective gate width. The threshold voltage of the transistor is modified by one of the gate voltages through the width variation, while the other gate voltage biases the transistor in the saturation region. The nonlinear dependency of the transistor characteristics on the two gate voltages facilitates frequency translation. The mixing characteristics of this architecture are verified both experimentally and theoretically. The output power spectral density peaks at the difference frequency with a minimal conversion loss. Extremely high isolation is measured using three-port S-parameter measurements. The proposed architecture shows multiple benefits, additionally facilitating monolithic mixers on the GaN platform.