Dead-time Effect Research Articles

Influence of Dead-Time on the Input Current Ripple of Three-Phase Voltage Source Inverter

The DC-link capacitor in power electronic systems is one of the most vulnerable components in terms of reliability. Since a reliable design of the DC-link capacitor depends on an accurate estimation of its current ripple, this paper proposes analytical equations to model the influence of dead-time on the input current ripple of a three-phase voltage source inverter. The effect of dead-time is modeled as a delay in the rising edges of the input current waveform. The proposed analytical equations are derived and then verified by simulations and experiments. The proposed equations generally provide better accuracy in predicting the input current ripple value compared to the benchmark equations. From the simulation and experimental results, the proposed equations are optimized for dead-time values more than 0.7 μs and modulation indices less than or equal to 0.7. Limitations of the proposed equations are also discussed. For small phase displacements and high modulation indices (0.8 to 1), the accuracy decreases because of the influence of AC output current ripple. For small modulation indices (less than 0.2) and a high value of dead-time (2 μs), the accuracy also decreases due to distortion in the phase current waveforms.

Dead-Time Impact on the Harmonic Distortion and Conversion Efficiency in a Three-Phase Five-Level Cascaded H-Bridge Inverter: Mathematical Formulation and Experimental Analysis

To avoid leg short-circuit in inverters, dead time must be introduced on leg gate signals. Dead time affects the inverter output voltage fundamental harmonic amplitude, voltage harmonic distortion and inverter efficiency by introducing additional voltage drops. In this regard, dead time effects have been widely investigated for traditional two-level three-phase voltage source inverters in the literature but not extensively for multilevel topology structures. This paper provides a detailed analysis of dead time impact on the harmonic distortion and efficiency of Cascaded H-Bridges Multilevel Inverters (CHBMIs). For this purpose, a general mathematical formulation to determine voltage drop due to dead time effects, also taking into account the adopted Multicarrier PWM strategy, has been provided and experimentally validated for a five-level three-phase CHBMI structure. As a comparison tool between expected and ideal inverter output voltage, the percentage voltage error <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">e</i> % is introduced. In most of the cases, <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">e</i> % is lower than 5%, and it starts increasing for very low amplitude modulation index or for specific working points where nonlinearities occur. Furthermore, several experimental investigations have been carried out to evaluate the CHBMI performance in terms of harmonic distortion and efficiency by changing, the values of dead time, modulation index and switching frequency for ten different multi-carried PWM strategies. Experimental results confirm the strong dependency between the dead time impact on the converter performance and the adopted Multi Carrier-PWM (MC-PWM) strategy: as a way of example, converter efficiency can be reduced from 80% to 60% when dead time is increased from 0.5 μs to 1.5 μs and Phase Shifted-PWM (PS-PWM) is adopted.

Study of practical state-preparation error tolerant reference-frame-independent quantum key distribution protocol

Quantum key distribution (QKD) enables the establishment of shared keys between two distant users, Alice and Bob, based on the fundamental principles of quantum mechanics, and it has proven to possess information-theoretic security. In most of QKD systems, Alice and Bob require a shared reference frame, and real-time calibration of the reference frame increases system costs and reduces its performance. Fortunately, the reference-frame-independent QKD protocol has been proposed, overcoming reference-frame drift issues and receiving widespread attention. However, in practical QKD systems, the non-ideal characteristics of realistic devices introduce certain inconsistency between the theory and the practice. In real-world quantum key distribution systems, device imperfections can lead to security vulnerabilities, thereby reducing system security. For example, imperfections in the encoding apparatus at the source end may result in errors in the quantum states. The inherent defects in the detection part may cause after-pulse effects and dead-time effects, thus reducing the key rate. Therefore, in this work, we propose a practical state-preparation error tolerant reference-frame-independent quantum key distribution protocol by taking imperfections in both the source and the detectors into account. Moreover, a three-intensity decoy-state scheme for modeling analysis and numerical simulations is employed. In this protocol, we reduce the influence of state-preparation errors on the key rate by utilizing virtual state methods to precisely estimate the phase-error rate. Furthermore, by characterizing the effects of after-pulses and dead-time on the key rate, our protocol exhibits higher robustness and can effectively address issues related to detector imperfections. This approach can also be extended to other quantum key distribution protocols with higher security levels, such as measurement-device-independent quantum key distribution protocol and twin-field quantum key distribution, further mitigating the influence of device imperfections on practical implementation of QKD system. Therefore, our present work provide important reference value for putting the quantum key distributions into practical application.

Radiometric Correction Model and Land Cover Classification of Snow-Covered Terrains for ICESat-2 Photon-Counting Lidar

The signal strength is a fundamental parameter in radiometric applications for satellite lidars. Different from full-waveform lidars, photon-counting lidars cannot record the returned signal strength but only respond to the presence of the photon event and may miss some returned photons due to the dead time effect, i.e., introduce radiometric distortion. Based on the lidar equation and the response mechanism of photon-counting detectors, we propose a radiometric correction model to remove the impact of the nonlinear response and dead time of detectors for the photon-counting lidar borne on ICESat-2. The returned signal photon number is corrected by the proposed model with respect to the photon event number per shot (PNPS) and surface slope derived from ATL03/ATL08 products. Then, the optical throughput calibration factor of ICESat-2 is obtained from ATL06 products over high Antarctic plateau where has given reflectance and clear atmosphere, which is generally equal to 0.52. The atmospheric attenuation induced by the molecular, cloud, and aerosol is calculated from ATL09 products. In addition, the corrected radiometric parameters including the calculated surface reflectance and apparent surface reflectance (ASR) are applied to classify land cover types along laser tracks over snow-covered terrains. The results indicate that the signal strength and calibration constant are reliable after corrections, but the atmospheric attenuation is sometimes inaccurate, which further influences the derived surface reflectance. In classifications, the overall accuracy and Kappa coefficient based on the corrected ASR can achieve the best classification results with 88.80% and 0.69. The proposed radiometric correction model is very essential to radiometric applications for photon-counting lidars such as ICESat-2, especially for data captured on ice and bare land with relatively high reflectance.

Stability Analysis and Design of Common Phase Shift Control for Input-Series Output-Parallel Dual Active Bridge With Consideration of Dead-Time Effect

Input-series output-parallel (ISOP) connected dual-active-bridge (DAB) converters allow the use for occasions requiring high input voltage and galvanic isolation with bidirectional power capability. However, when DAB converters are ISOP connected, the traditional analysis without consideration of the dead time cannot effectively explain the reason why the ISOP converter system is stable under common phase shift control (CPSC) when parameters are mismatched. In this article, it is first revealed that the stability of the ISOP DAB converter under common phase ratio control can be ensured by consideration of the dead time. Based on the analysis of the DAB power transmission characteristics with consideration of dead time, a new model is derived for the ISOP DAB converter, which can reveal the reason why the converter can operate stably under CPSC when the design parameters of the individual module are mismatched. Then, based on the derived model, the stability analysis and the parameters design are further performed. Finally, the effectiveness of the working principle and analysis is verified through results from a two-module ISOP experimental prototype.

FITEVT: A FORTRAN program for arrival-time analysis of nuclear-decay events

FITEVT is a FORTRAN program designed to analyze recorded arrival times of nuclear-decay events affected by dead-time. The primary goal of the program is precise and accurate determination of half-lives. Its method involves imposition of a known sufficiently long extending dead-time to the recorded event sequence, so that the original dead-time effects are completely obliterated and the remaining live-times of the survived events are known exactly. Upon completion of the analysis, the arrival-time spectrum and the live-time spectrum are predicted and compared to those constructed from the survived events. Program summaryProgram title: FITEVTLicensing provisions: MITCPC Library link to program files:https://doi.org/10.17632/scg6p9jxjk.1Programming language: FORTRAN (using double precision)Nature of problem: Accurate determination of the ideal event rate from the observed event rate in a nuclear decay can be a challenging task due to the inevitable presence of detection system's dead-time, whose nature and extent are typically unknown. Consequently, the results of nuclear half-life measurements may depend on the method used to correct for event losses due to dead-time. Therefore, there is a need for an exact method of data analysis and the means to apply it in order to ensure reproducibility, accuracy and optimized precision of the results.Solution method: FITEVT performs arrival-time analysis of the recorded events, in which a known, sufficiently large extending dead-time is imposed by means of software, so that in the resulting set of survived events the original dead-time effects are completely replaced by the effects of the imposed dead-time. As a result, the dead-time following each survived event and the remaining live-time preceding each surviving event are known exactly. This allows for application of the maximum-likelihood method of estimation, in which the half-lives as well as the other parameters of the ideal-decay-rate function can be accurately determined.Additional comments including restrictions and unusual features: In its original form the program can handle contributions from a constant event rate (i.e., a typical background) plus up to 4 different exponentially-decaying event rates. One of these 4 contributions is allowed to be negative, so that the program can be applied to the general case involving a single two-component decay chain. The employed method of analysis produces accurate results even when the product of the ideal event rate (ρ) and the extending dead-time parameter (τe) is as large as 51.2 [1]. Example used in the present paper involves simulated events having initial rate of 105 s−1, to which extending dead-time of 64 μs is imposed.Data analysis is based on maximum-likelihood principle, in which minimization of the deviance involves calculations in double precision and determination of its derivatives is based on analytical expressions. This is done in order to optimize precision and accuracy of the results as well as the program execution time.With the provided input data and a typical contemporary laptop computer, the program execution typically lasts about 5 minutes. Reducing the imposed dead-time to zero increases the number of survived events approximately by a factor of 6, but the program execution time increases by about a factor of 3.

Minimum Current Optimization of DBSRC Considering the Dead-Time Effect

In a dual-bridge series resonant converter (DBSRC) working at a high switching frequency, the dead-time effect is a serious issue. When the minimum current trajectory (MCT) method is applied, the inductor current cannot be minimized due to the dead-time effect, and the range of the soft switching is reduced. Considering the dead-time, this paper first presents a theoretical analysis of the transmission power and the soft-switching characteristics based on the fundamental harmonic approximation (FHA) approach. Then, a minimum current trajectory method considering the dead-time (MCT-d) is proposed to achieve the minimum inductor current by compensating for the dead-time. This method can extend the soft-switching range as well. Finally, the experimental results validate the theoretical analysis and the improvement of the converter’s efficiency.

Optimal Design of Resonant Network for Resonant Converter

The dc transformer based on <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">CLLC</i> resonant converter is widely researched in the dc microgrid due to its excellent bidirectional power transfer capacity. Many resonant network design methods assume that the resonant current is constant during the deadtime. It may lead to hard switching or large conduction loss. Besides, the effects of deadtime on soft switching have not been closely analyzed. This article proposes an optimized design method to minimize conduction losses while achieving zero voltage switching, and it can easily obtain the optimal region and deadtime selection range. Parametric design and deadtime selection principles are derived based on the time-domain models, and then the design method and corresponding procedure are developed. Finally, a 4-kW 500-kHz <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">CLLC</i> resonant converter prototype is built to verify the feasibility of the proposed optimal design method.

A Study on Effects of Deadtime in a Single-phase Multilevel Inverter Using Circuit Topology and the Modulation Method

A Study on Effects of Deadtime in a Single-phase Multilevel Inverter Using Circuit Topology and the Modulation Method

High-precision measurement of the He6 half-life

The half-life of $^{6}\mathrm{He}$ has been measured using a low-energy radioactive beam implanted in an ${\mathrm{YAlO}}_{3}$ Ce-doped inorganic scintillator and recording decay events in a $4\ensuremath{\pi}$ geometry. Events were time-stamped with a digital data acquisition system enabling a reliable control of dead-time effects and detector gain variations. The result, ${T}_{1/2}=(807.25\ifmmode\pm\else\textpm\fi{}0.{16}_{\mathrm{stat}}\ifmmode\pm\else\textpm\fi{}0.{11}_{\mathrm{sys}}$) ms, provides the most precise value obtained so far and is consistent with the only previous measurement having a precision smaller than 0.1%. This resolves the long-standing discrepancy previously observed between two sets of measurements.

Multiple Synchronous Rotating Frame Transformation-Based 12th Current Harmonic Suppression Method for an IPMSM

In order to solve the problem that the three-phase current of the interior permanent magnet synchronous motor (IPMSM) contains the 11th and 13th current harmonics, a multiple synchronous rotating frame transformation (MSRFT)-based current harmonic suppression method is established. Firstly, the influencing factors of current harmonics in IPMSM vector control are analyzed, and the influence mechanism of the inverter’s dead-time effect and the permanent magnet flux linkage harmonics on the current harmonics is described. Secondly, a simple current harmonic extraction method is proposed by optimizing the traditional current harmonic extraction method based on MSRFTs. The proposed method achieves the accurate extraction of the current harmonic components. Thirdly, a harmonic voltage generation method is established and is combined with the proposed current harmonic extraction method to form a current harmonic suppression strategy. Finally, the feasibility and effectiveness of the proposed method are verified via MATLAB/Simulink simulations and experiments. The simulation and experimental results show that the proposed current harmonic extraction method can extract the current harmonic components accurately, and the proposed current harmonic suppression strategy can suppress the 11th and 13th current harmonics effectively.

Dark current and single photon detection by 1550 nm avalanche photodiodes: dead time corrected probability distributions and entropy rates.

Single photon detectors have dark count rates that depend strongly on the bias level for detector operation. In the case of weak light sources such as novel lasers or single-photon emitters, the rate of counts due to the light source can be comparable to that of the detector dark counts. In such cases, a characterization of the statistical properties of the dark counts is necessary. The dark counts are often assumed to follow a Poisson process that is statistically independent of the incident photon counts. This assumption must be validated for specific types of photodetectors. In this work, we focus on single-photon avalanche photodiodes (SPADs) made for 1550 nm. For the InGaAs detectors used, we find the measured distributions often differ significantly from Poisson due to the presence of dead time and afterpulsing with the difference increasing with the bias level used for obtaining higher quantum efficiencies. We find that when the dead time is increased to remove the effects of afterpulsing, it is necessary to correct the measured distributions for the effects of the dead time. To this end, we apply an iterative algorithm to remove dead time effects from the probability distribution for dark counts as well as for the case where light from an external weak laser source (known to be Poisson) is detected together with the dark counts. We believe this to be the first instance of the comprehensive application of this algorithm to real data and find that the dead time corrected probability distributions are Poisson distributions in both cases. We additionally use the Grassberger-Procaccia algorithm to estimate the entropy production rates of the dark count processes, which provides a single metric that characterizes the temporal correlations between dark counts as well as the shape of the distribution. We have thus developed a systematic procedure for taking data with 1550 nm SPADs and obtaining accurate photocount statistics to examine novel light sources.

Elimination of Dead Time Effects on Common Mode Voltage in an Open-End Winding Induction Motor Drive Under Low Speed Operation Using a Simplified Model Predictive Control

In this article, a simplified model predictive current control (MPCC) for a three-level open-end winding induction motor drive mitigating the dead time effects on common mode voltage (CMV) in the low speed operation of the motor is proposed. The traditional current based objective function is replaced with an equivalent voltage based objective function, and an additional term indicating the nonzero CMV during dead time is added to achieve complete CMV elimination. Further, a sector-based selection of candidate switching states is employed to reduce the computational burden. It is also shown that the constraint on eliminating the dead time effect on CMV heavily deteriorates the performance of the drive at higher speeds and a smooth transition with and without the constraint is also demonstrated. The envisaged MPCC is simulated in MATLAB and is experimentally verified using TMS320F28377S launchpad. The proposed MPCC gives a massive reduction in the computational burden compared to the conventional MPCC without sacrificing the motor drive performance.

A PWM Method of H-Bridge Converter With Temperature Rise Balancing and Minimization Based on Periodically Alternating Employment of Power Devices

Aiming at the temperature rise and thermal control issues of power devices in H-bridge converters under conventional pulsewidth modulation (PWM) methods, a novel PWM method of H-bridge converter with temperature rise balancing and minimization based on periodically alternating employment of power devices is proposed. In the proposed method, two novel operation mechanisms of power devices are alternately applied into the eight regions with the identical and opposite polarities of reference voltage and input current, which are composed of two fundamental frequency periods. All active switches and antiparallel diodes in H-bridge converters are made to work alternately in these eight regions, each of them is designed to keep in <sc xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">on</small> -state in one region, operate in switching state in another two regions, and inactive in the left other five regions. This way, the power dissipation and temperature rise of all the devices are balanced and minimized, and H-bridge converters no longer suffer from the dead-time effect on current quality and dc-bus voltage utilization. The implementation strategy of the proposed modulation method is discussed in detail. Simulation and experimental results are presented that verify the effectiveness of the proposed method and the corresponding implementation strategy at different operating points.

Improved PWM Methods to Reduce the Common Mode Voltage of the Five-Phase Open-Winding Drive Topology

With the phase angle and shape modifications for carriers, two improved carrier-based pulse width modulation (CPWM) methods with common-mode voltage (CMV) suppression effects for the five-phase open-winding drive topologies are introduced. Theoretical analysis reveals that, by employing reversed triangular carriers for two inverters under the carrier-reversed PWM (CRPWM), CMV contributions of two bridge legs belonging to the same phase can be cancelled, realizing the zero CMV effect. By dynamically employing positive and negative sawtooth carriers for all bridge legs under the carrier-switching PWM (CSPWM), the CMV contribution of each inverter can be reduced, decreasing both the amplitude and step frequency of the CMV. Current qualities and dead-time effects on CMV under the above PWM methods are analyzed. Moreover, performances of two PWM methods are verified by experiments implemented on a five-phase open-winding topology with the induction motor load.

Effective Dead Time of Two Non-Paralyzable Detector Components in Series

Detector dead time losses, caused by both physical components in the detection system and the electronic data acquisition system, are perhaps the most prominent effect in non-ideal detector behavior. Most mathematical modeling methods consider the detector as a single unit with a single dead time parameter, while a true physical detector is often comprised of several serially connected components, each suffering from independent dead time losses. In this study, we develop new formulas for evaluating the dead time losses in a detection system with two serially connected components, each component with a non paralyzing dead time, while assuming that the original count rate has a Poisson distribution. The analytic results obtained are first compared with numeric simulations (showing a very good correspondence) and are then used for numeric investigation of global boundaries of the dead time effect in serially connected systems.

Modeling and Analysis of Voltage Harmonic for Three-Level Neutral-Point-Clamped H-Bridge Inverter Considering Dead-Time

The advantages of three-level neutral-point-clamped (NPC) H-bridge inverters, such as simple topological structure, low device voltage stress, high equivalent switching frequency, and highly expansible capacity, have made them the preferred choice for inverters matching with medium voltage high-capacity multi-phase open-end winding vessel propulsion motors. To quantitatively evaluate the propulsion motors’ harmonics, electromagnetic vibration, and noise caused by pulse-width modulation (PWM) and device dead-time, it is necessary to research the mathematical modeling of pulse-width modulated output voltage harmonics in consideration of dead-time. In this paper, the principle of the phase-disposition PWM method of the 3L-NPC H-bridge inverters was firstly introduced. Then, the analytical models of output voltage harmonics with and without considering the effect of dead-time were established based on the double Fourier series approach and the harmonic distribution of the dead-time effect was accurately characterized. On the basis of the above, the experimental platform was established to verify the proposed analytical model. Simulation and experimental results are consistent with the theoretical analysis in low and high-frequency output voltage harmonics, which proves the correctness and the feasibility of the analytical modeling method researched by this paper. This will provide a theoretical basis for subsequent studies, which include the quantitative analysis and the suppression of output harmonics of the H-bridge inverter considering dead-time.

Modeling and Analysis of Multiple Inverters With Dual-Loop-Based Virtual Oscillator Control

Virtual oscillator control (VOC) is an emerging decentralized control technique for grid-forming inverter applications. In contrast to conventional phasor-based droop control or virtual synchronous machine control, VOC is a time-domain controller designed to emulate the dynamics of a nonlinear oscillator. VOC is a current-controlled voltage source, lacking the ability to regulate the inverter terminal voltage, which will result in significant voltage deviations caused by dead-time effects, nonideal semiconductor devices, and output filter voltage drops. In this article, a voltage and current dual-loop control structure augments the VOC to compensate for these voltage deviations and regulate the inverter output variables directly. A complete small-signal model for a multiple inverter-based microgrids with the proposed control structure is presented in order to assess system stability using eigenvalue and participation factor analysis. Analytical results show that the parameter related to the frequency regulation and the integral gain of the voltage controller affect the location of the system’s dominant modes significantly. The stability margin is determined by modifying these control parameters. Experimental results on a laboratory test microgrid verify the predication from the small-signal analysis and time-domain simulations.

A Simple Method for Stator Inductance and Resistance Estimation for PMSM at Standstill

An accurate stator resistance and inductance are necessary for high-performance permanent magnet synchronous motor (PMSM) control. The stator resistance and inductance can be estimated during motor standstill operation. This study proposes a standstill estimation method for the determination of dq-axis inductances and resistance of a PMSM drive system fed by a conventional voltage source inverter (VSI). The proposed method estimates both inductance and the rotor's position using the same algorithm, and knowledge of its initial position is not required. The d- and q-axis inductances were estimated by applying three short-time voltage pulses and measuring phase current peak values. The stator's resistance is estimated by monitoring the exponential decay process of the direct axis current. The method was verified by simulation and experiments conducted on two different PM synchronous motors. A good agreement of simulation and experimental results was obtained. Moreover, the proposed method is relatively simple and can identify stator resistance and inductance at any motor load condition. Compared to the existing parameter estimation strategies, the proposed estimation scheme has a relatively faster estimation time. Additionally, it is shown that the method accounts for the dead-time effect as well.

Benchmarking a New Digital Data Acquisition System for Fast Neutron Metrology

The application of a CAEN DT5730 digitizer unit for fast neutron metrology is explored. Measurements were made at the Accelerator for Metrology and Neutron Applications in External Dosimetry (AMANDE) monoenergetic neutron facility of the IRSN, France, over a neutron energy range from 1.2 to 7.0 MeV using a BC501A scintillator. The DT5730 digitizer and an analog system based on NIM electronics and an MPA-3 multichannel analyzer acquisition unit were used, under identical beam conditions, for data acquisition. Several observables were compared between the two systems including the quality of pulse shape discrimination (PSD), neutron energy distribution derived from unfolding analyses, and deadtime effects over a range of beam currents from 0.1 to <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$5.1~\mu \text{A}$ </tex-math></inline-formula> . The suitability of the digital system for fast neutron metrology measurements both in the laboratory and in workplace fields is discussed.