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This paper proposed a dead-time compensation method with fractional-order proportional integral (FOPI) error voltage control. The disturbance voltages caused by the power devices’ dead time and non-ideal switching characteristics are compensated for with the FOPI controller and fed to the reference voltage. In this paper, the actual error voltage is calculated based on the model and actual voltage of the permanent magnet synchronous motor. Considering the parameter error of the permanent magnet synchronous motor and the voltage error caused by the dead-time effect, a FOPI controller is used to calculate the compensation voltage. An improved particle swarm optimization (PSO) algorithm is utilized to design the parameters of the FOPI controller in order to eliminate the dead-time effect, and the optimal fitness function is designed. Compared with other optimization algorithms, the improved PSO algorithm can achieve faster convergence speed in the error voltage controller parameter design. The proposed dead-time compensation method can improve the performance of the current response and eliminate the dead-time effect. This method also eliminates all harmonic disturbances and has a good suppression effect on high-frequency harmonics. The simulation and experimental results show that the dead-time compensation method using optimal FOPI error voltage control makes the current ripple smaller and the response speed faster than that of the traditional optimal integer-order PI control, thus demonstrating the effectiveness and advantages of the proposed method.

Average switch simulation has the advantage of being much faster to simulate than the switching simulation but it lacks any harmonics or distortion on the converter current waveform. In a hardware converter, the current distortion is caused by the dead-time between high side and low side switching devices provided to avoid switch shoot-through. To improve the fidelity of average switch simulation, this paper provides a simple method to induce the distortion resulting from the dead-time. The result of average switch simulation can thus closely resemble the result of switching simulation in a fraction of the simulation time. To validate the accuracy of this average switch simulation, the result of this simulation is compared with the detail switching simulation and the waveform from actual hardware measurement.

A current-mode four-phase synchronous buck converter with a dynamic dead-time control (DDTC) method is presented in this work. A brief analysis of the multiphase buck converter power efficiency in both continuous conduction mode (CCM) and discontinuous conduction mode (DCM) is performed to provide design guidelines for minimizing power losses. In synchronous converters, the power efficiency can always be improved by optimizing the dead-time. Therefore, a gate driver with DDTC is designed to optimize the dead-time in every switching cycle, thereby improving power efficiency particularly under heavy load conditions. The proposed buck converter has the ability to deliver a maximum load current of 6.0 A at a typical output voltage of 1.2 V from a power supply of 3.0 V. A power efficiency improvement of over 1.0% is achieved when the load current is over 2.0 A, and an improvement of about 2.4% is obtained at a load current of 4.0 A. A peak power efficiency of 92.8% is measured at an output voltage of 1.8 V.

A dynamic model of surface-mounted permanent magnet synchronous motors (SPMSMs) is constructed to include the dead-time disturbance voltage of the voltage-source inverter and SPMSM parameter uncertainty. The constructed model reveals that both the disturbance voltage and the parameter uncertainty degrade the SPMSM stator current control performance. Based on this notion, a nonlinear damping compensator is designed to simultaneously compensate for the dead-time disturbance voltage and parameter uncertainty in a unified structure. The designed compensator is advantageous because it is implemented with only the static feedback of available system variables with a low computational load, which enables the compensation signal to be calculated within one sampling period without requiring a specific calculation cycle. A rigorous analysis using a Lyapunov function shows that the designed compensator achieves the global exponential ultimate boundedness of the stator current errors with arbitrarily small bounds and fast decay rates in the presence of both the dead-time disturbance voltage and parameter uncertainty. The designed compensator performance is demonstrated by performing experiments using a 750-W laboratory SPMSM drive and comparing the experimental results with those of a conventional proportional-integral controller with a feedforward compensator.

The purpose of this study was to investigate the impact of voltage drop of a three-phase voltage source inverter on driving brushless motors. This study also proposes an enhanced field-oriented control scheme that accounts for inverter voltage drop, enabling efficient driving at very low motor speeds. Experimental results are provided to verify the theoretical study and the proposed control scheme.

This paper emphasizes a comparative experimental evaluation of three Smith predictor configurations. The three control schemes are tuned using different optimization algorithms; then, they are applied to an Arduino Temperature Control Lab used to test and evaluate their performance. The three deadtime compensators are compared using radial graphs. They were assessed under different conditions using various performance indices: the Integral Square Error, the Total Variations of Control Efforts, the Maximum Overshoot, and the Settling Time for tracking and disturbances changes. The Mejia et al. approach presented a better overall performance than the other two. Finally, the results showed that Smith Predictor is suitable for thermal processes with elevated dead time.

The necessary resonator employed in pulse electron paramagnetic resonance (EPR) rings after the excitation pulse and creates a finite detector dead-time that ultimately prevents the detection of signal from fast relaxing spin systems, hindering the application of pulse EPR to room temperature measurements of interesting chemical or biological systems. We employ a recently available high bandwidth arbitrary waveform generator (AWG) to produce a cancellation pulse that precisely destructively interferes with the resonant cavity ring-down. We find that we can faithfully detect EPR signal at all times immediately after, as well as during, the excitation pulse. This is a proof of concept study showcasing the capability of AWG pulses to precisely cancel out the resonator ring-down, and allow for the detection of EPR signal during the pulse itself, as well as the dead-time of the resonator. However, the applicability of this approach to conventional EPR experiments is not immediate, as it hinges on either (1) the availability of low-noise microwave sources and amplifiers to produce the necessary power for pulse EPR experiment or (2) the availability of very high conversion factor micro coil resonators that allow for pulse EPR experiments at modest microwave power.

Abstract Background Dead time may affect the accuracy of quantitative SPECT (QPSECT), and thus of dosimetry. The aim of this study was to quantify the effect of dead time on 177Lu-QSPECT and renal dosimetry following peptide receptor radionuclide therapy (PRRT) of neuroendocrine tumours. Methods QSPECT/CT was performed on days 1 and 3 during 564 personalized 177Lu-octreotate cycles in 166 patients. The dead-time data for each scanning time point was compiled. The impact of not correcting QSPECT for the dead time was assessed for the kidney dosimetry. This was also estimated for empiric PRRT by simulating in our cohort a regime of 7.4 GBq/cycle. Results The probability to observe a larger dead time increased with the injected activity. A dead-time loss greater than 5% affected 14.4% and 5.7% of QSPECT scans performed at days 1 and 3, respectively. This resulted in renal absorbed dose estimates that would have been underestimated by more than 5% in 5.7% of cycles if no dead-time correction was applied, with a maximum underestimation of 22.1%. In the simulated empiric regime, this potential dose underestimation would have been limited to 6.2%. Conclusion Dead-time correction improves the accuracy of dosimetry in 177Lu radionuclide therapy and is warranted in personalized PRRT.

This paper proposes a new concept of synthesized voltage vector to address dead-time effect issue for Finite Control Set Model Predictive Control (FCS-MPC) technique. For a voltage source inverter (VSI), dead-time is inevitably inserted between the turn off and turn on instants of power devices to avoid short circuit phenomenon. The influence of dead-time leads to output voltage vector error of three-phase inverters. Furthermore, it will result in computing deviation in cost function, and will deteriorate the performance of the system if not properly dealt with. In this paper, the problem is clearly analyzed, and the solution to this issue is proposed by introducing a synthesized voltage vector. The proposed solution is verified by Hardware-in-the-loop (HiL) test in real time, and results validate the effectiveness of the proposed solution.

Linear AC power supplies can be replaced by their nonlinear switching counterparts due to the lower voltage drops and higher efficiency and power density of switching-mode inverters. Multilevel cascaded H-bridge (CHB) converters are the preferred inverter structure because of modular configuration, control, and protection. The output voltage quality in CHB converters depends on the number of output levels. Asymmetric CHBs (ACHBs) produce an output voltage with higher number of levels with respect to CHBs for the same number of cascaded modules. This results in the reduction of power supply size, voltage drops, and losses. Considering the relative high switch counts, analysis of the effect of conduction and dead-time voltage drops on the inverter output characteristics is an important challenge in designing multilevel converters. In this paper, a generic algorithm is presented to calculate the conduction and dead-time voltage drops of ACHBs utilizing level-shifted modulation. These voltage drops give the necessary information for the design of heatsinks, switch selection, output impedance estimation, and the compensation schemes. It is shown through theoretical and simulation studies that the aforementioned voltage drops of ACHBs are to be calculated in a different manner with respect to the CHBs which mostly use the phase-shifted modulation.

Abstract Background Personalization of 177Lu-based radionuclide therapy requires implementation of dosimetry methods that are both accurate and practical enough for routine clinical use. Quantitative single-photon emission computed tomography/computed tomography (QSPECT/CT) is the preferred scanning modality to achieve this and necessitates characterizing the response of the camera, and calibrating it, over the full range of therapeutic activities and system capacity. Various methods to determine the camera calibration factor (CF) and the deadtime constant (τ) were investigated, with the aim to design a simple and robust protocol for quantitative 177Lu imaging. Methods The SPECT/CT camera was equipped with a medium energy collimator. Multiple phantoms were used to reproduce various attenuation conditions: rod sources in air or water-equivalent media, as well as a Jaszczak phantom with inserts. Planar and tomographic images of a wide range of activities were acquired, with multiple energy windows for scatter correction (double or triple energy window technique) as well as count rate monitoring over a large spectrum of energy. Dead time was modelled using the paralysable model. CF and τ were deduced by curve fitting either separately in two steps (CF determined first using a subset of low-activity acquisitions, then τ determined using the full range of activity) or at once (both CF and τ determined using the full range of activity). Total or segmented activity in the SPECT field of view was computed. Finally, these methods were compared in terms of accuracy to recover the known activity, in particular when planar-derived parameters were applied to the SPECT data. Results The SPECT camera was shown to operate as expected on a finite count rate range (up to ~ 350 kcps over the entire energy spectrum). CF and τ from planar (sources in air) and SPECT segmented Jaszczak data yielded a very good agreement (CF < 1% and τ < 3%). Determining CF and τ from a single curve fit made dead-time-corrected images less prone to overestimating recovered activity. Using triple-energy window scatter correction while acquiring one or more additional energy window(s) to enable wide-spectrum count rate monitoring (i.e. ranging 55–250 or 18–680 keV) yielded the most consistent results across the various geometries. The final, planar-derived calibration parameters for our system were a CF of 9.36 ± 0.01 cps/MBq and a τ of 0.550 ± 0.003 μs. Using the latter, the activity in a Jaszczak phantom could be quantified by QSPECT with an accuracy of 0.02 ± 1.10%. Conclusions Serial planar acquisitions of sources in air using an activity range covering the full operational capacity of the SPECT/CT system, with multiple energy windows for wide-spectrum count rate monitoring, and followed by simultaneous determination of CF and τ using a single equation derived from the paralysable model, constitutes a practical method to enable accurate dead-time-corrected QSPECT imaging in a post-177Lu radionuclide therapy setting.

High efficiency and high output power quality of converters are always two goals pursued in power electronic systems. In this paper, the conventional discontinuous pulse width modulation (DPWM) for switching-loss reduction and a modified time-based dead-time compensation for reducing output current harmonics are investigated. And a combined DPWM for switching-loss reduction and dead-time compensation is proposed, where the amplitude adjustment and the zero-sequence injection in modulation waves are carried out separately in different current intervals related to polarities of three-phase currents. Moreover, in order to detect accurate polarities of the three-phase currents with ripples and harmonics, the second-order generalized integrator frequency-locked loop (DSOGI-FLL) is adopted and inserted into the combined DPWM. Finally, a combined DPWM based on DSOGI-FLL is proposed for switching-loss reduction and dead-time compensation. The comparison of experimental results with several PWM schemes verifies that, the proposed PWM scheme can both effectively reduce the switching loss and compensate the dead-time, simultaneously enhancing the efficiency and the output power quality of the converter.

In most of the industrial process plants, PI/PID controllers have been widely used because of its simple design, easy tuning, and operational advantages. However, the performance of these controllers degrades for the processes with long dead-time and variation in set-point. Up next, a PPI controller is designed based on the Smith predictor to handle dead-time processes by compensation technique, but it failed to achieve adequate performance in the presence of external noise, large disturbances, and higher-order systems. Furthermore, the model-based controllers structure is complex in nature and requires the exact model of the process with more tunable parameters. Therefore, in this research, a fractional-order predictive PI controller has been proposed for dead-time processes with added filtering abilities. The controller uses the dead-time compensation characteristics of the Smith predictor and the fractional-order controller's robustness nature. For the high peak overshoot, external noise, and disturbance problems, a new set-point and noise filtering technique is proposed, and later it is compared with different conventional methods. In servo and regulatory operations, the proposed controller and filtering techniques produced optimal performance. Multiple real-time industrial process models are simulated with long dead-time to evaluate the proposed technique's flexibility, set-point tracking, disturbance rejection, signal smoothing, and dead-time compensation capabilities.

An on-line compensation for the dead time strategy without the knowledge of the current direction is proposed for PMSM drive based on a current observer. The modifications of the motor reference voltages are achieved by an uncomplicated current observer working in conjunction with the feedforward dead time voltage estimator. Therefore, the distortions on phase currents and torque due to dead time are greatly reduced. The proposed method does not require look-up table and coordinate transformations. It also does not need phase current polarity information or calculation of dead time period. Since the proposed scheme requires no extra hardware and time consuming signal processing algorithms, it is appropriate to use in real-time implementation of AC drives. The proposed scheme has been validated in simulation and implemented using TMS320F28335 DSP. Simulation and practical results validate the effectiveness and the feasibility of the proposed scheme.

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.

Grid-tied inverter is the prominent component of the three-phase dual-stage photovoltaic (PV) grid-tied power generation system. However, the disturbances caused by dead time effect will pose the reduction of grid-tied current quality and even cause the imbalance of inverter itself or other circuit devices. In this paper, a current control strategy is proposed to damp dead time effect for the three-phase dual-stage PV grid-tied inverter system, and its design, stability analysis, and implementation are carried out. First, the inverter model is modified by regarding the dq reference frame coupling terms, uncertainties, and external and internal disturbances as an unknown lumped disturbance. Then, a current control scheme based on compensation of equivalent input disturbance is introduced, and it estimates and compensates the unknown lumped disturbance, which effectively realizes the inverter model decoupling and comprehensive disturbance rejection. Last, simulation results demonstrate the effectiveness and superiority of the proposed current controller.

Sensorless control based on high-frequency square-wave voltage injection (HFSVI) is one of the most common sensorless control methods for synchronous reluctance motors (SynRMs). However, the injection frequency for SynRMs cannot be too high due to various factors. As the injection frequency decreases, the dead-time harmonic current will greatly affect the separation of high frequency signals. This paper analyzes the effect of dead-time harmonic current on the HFSVI-based sensorless control performance of SynRMs and proposes a source of position estimation error. Then, a dead-time compensation method suitable for filter-free HFSVI is proposed. It can estimate current vector spatial orientation without any low-pass filters (LPFs) and effectively compensate the impact of dead-time setting. The correctness of the theoretical analysis and the feasibility of the proposed methods in this paper are verified by experiments.

Double electron-electron resonance spectroscopy (DEER, also known as PELDOR) is used to study spin-spin dipolar interactions between spin labels, at the nanoscale range of distances. The DEER effect is obtained as a signal generated by echo-forming microwave (mw) pulses with an additional mw pump pulse applied at a different frequency. It is important to carry out measurements without artefacts induced by overlap of the pulses in the time scale. Such an experiment without the dead-time effect is achieved using the 4-pulse (4p) DEER method. The analysis of the literature performed here shows however that the 3-pulse (3p) DEER can also be free of the dead time problem, for which there are two possibilities. The first occurs using a specially designed bimodal resonator, for which the two frequencies are completely decoupled. The second possibility, which can be implemented for any commercial spectrometer, involves the signal correction based on an additional “blank” measurement with the pump pulse applied outside the EPR resonance. A detailed comparison of the 3p and 4p DEER data obtained previously by Milov et al. [Appl. Magn. Reson. 41 (2011) 59–67] shows that 3p and 4p approaches give similar results. The advantages of the 3p DEER techniques are discussed.

This letter proposes a proportional-integral-derivative (PID) design method for second-order plus dead time models based on a desired closed-loop transfer function for load disturbance changes. Also, tuning rules for single integrating first-order plus dead time models are provided. Using a two-degree-of-freedom control scheme, the design problem considers load disturbance rejection, robustness to model uncertainties, and setpoint tracking. Three examples are used to assess the performance of the proposed method. Finally, the results are compared to two popular PID control design methodologies, skogestad internal model control or skogestad IMC (SIMC) and improved SIMC (iSIMC). [ABSTRACT FROM AUTHOR]

The paper deals with hardware solution of a fully digital dead-time generator. The circuit is applicable to the H-bridges based on any type of semiconductor switching devices including SiC, IGBT, Si-MOSFET and up-to-date GaN HEMTs. The generation of dead-times is ensured by commercially available silicon delay lines. High temperature stability is obtained by self-compensation of propagation delay of logic elements thanks to the symmetry of design topology. The circuit can be set-up to generate dead-times in the range from 10 ns to 500 ns. Longer dead-times are also available by simple cascading of the silicon delay lines. The key motivation for development of the circuit was unavailability of ready to use integrated solutions on the market. Moreover, contrary to the other solutions the proposed circuit is immune to prospective oscillations of an input PWM signal. The paper brings a detailed analysis of the circuit principle, results of the verification of a sample solution and an example of practical application as well.

The purpose of this study was to investigate the impact of voltage drop of a three-phase voltage source inverter on driving brushless motors. This study also proposes an enhanced field-oriented control scheme that accounts for inverter voltage drop, enabling efficient driving at very low motor speeds. Experimental results are provided to verify the theoretical study and the proposed control scheme. [ABSTRACT FROM AUTHOR]

Objective: Quantitative values derived from PET brain images are of high interest for neuroscientific applications. Insufficient DT correction (DTC) can lead to a systematic bias of the output parameters obtained by a detailed analysis of the time activity curves (TACs). The DTC method currently used for the Siemens 3T MR BrainPET insert is global, i.e., differences in DT losses between detector blocks are not considered, leading to inaccurate DTC and, consequently, to inaccurate measurements masked by a bias. However, following careful evaluation with phantom measurements, a new block-pairwise DTC method has demonstrated a higher degree of accuracy compared to the global DTC method., Approach: Differences between the global and the block-pairwise DTC method were studied in this work by applying several radioactive tracers. We evaluated the impact on [11C]ABP688, O-(2-[18F]fluoroethyl)-L-tyrosine (FET), and [15O]H2O TACs., Results: For [11C]ABP688, a relevant bias of between -0.0034 and -0.0053 ml/ (cm3 • min) was found in all studied brain regions for the volume of distribution (VT) when using the current global DTC method. For [18F]FET-PET, differences of up to 10% were observed in the tumor-to-brain ratio (TBRmax), these differences depend on the radial distance of the maximum from the PET isocenter. For [15O]H2O, differences between +4% and -7% were observed in the GM region. Average biases of -4.58%, -3.2%, and -1.2% for the regional cerebral blood flow (CBF (K1)), the rate constant k2, and the volume of distribution VT were observed, respectively. Conversely, in the white matter region, average biases of -4.9%, -7.0%, and 3.8% were observed for CBF (K1), k2, and VT, respectively., Conclusion: The bias introduced by the global DTC method leads to an overestimation in the studied quantitative parameters for all applications compared to the block-pairwise method., Significance: The observed differences between the two DTC methods are particularly relevant for research applications in neuroscientific studies as they affect the accuracy of quantitative Brain PET images., Competing Interests: The authors have declared that no competing interests exist., (Copyright: © 2024 Issa et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.)

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.

Aiming at the issue of the sliding mode observer (SMO) being sensitive to the motor model parameters at low speeds, a rotor position observation method based on resistance adaptive SMO and considering the influence of inverter dead time is designed in this paper. In this method, the online resistance identification is introduced into the conventional SMO, the resistance parameters of the SMO are modified in real-time, and the online resistance identification algorithm is designed by using the Lyapunov function. An enhanced linear dead time compensation method is proposed to improve the resistance adaptive SMO and eliminate the voltage error between the estimated and the actual motor models in order to address the impact of inverter dead time on the voltage parameters in the estimation model at low speeds. Simulation results show that the online resistance identification and dead time compensation can significantly improve the accuracy of sensorless speed control at low speeds, and the dead time compensation can also improve the accuracy of online resistance identification.