Dead-time Compensation Research Articles

A novel unified method for time-varying dead-time compensation

This paper proposes an unified procedure for time-varying dead-time compensation. The method is an adapted version of the Filtered Smith Predictor (FSP), which is coupled to a delay estimation scheme and two adaptive Linear Parameter Varying (LPV) blocks. These LPV blocks allow the DTC to autonomously regulate the amount of closed-loop robustness, with respect to the (estimated) amount of delay. The method is easily adjustable and can be tuned to provide a balance between robustness and performance objectives, while being able to deal with unstable and integrative processes. A series of numerical simulations are included to illustrate the advantages of the proposed method towards reference tracking, noise attenuation, disturbance rejection and uncertainty handling. This novel DTC enables enhanced performances with respect other methods from the literature.

Model Predictive Control of LC-Filtered Voltage Source Inverters With Optimal Switching Sequence

Voltage source inverters with output LC filter enable a sinusoidal output voltage with low harmonics, suitable for islanded ac microgrid or uninterruptible power supply applications. Conventional finite-set model predictive voltage control (MPVC) applies only a single switching vector per control period, leading to a variable switching frequency and significant output ripple. This article resolves these issues by proposing an improved MPVC with optimal switching sequence (OSS-MPVC). First, an improved vector switching sequence is defined, aiming to reduce the output-voltage ripple with a constant switching frequency. Then, to tackle the difficulty in extending the OSS to high-order systems due to the coupling effect of the output filter, a generalized “one-step estimation” solution is proposed, which directly associates the control-variable gradients with the vector switching sequence. To further enhance the output-voltage tracking accuracy, intersample dynamics are taken into account in the cost function. The control delay and dead-time compensation are also considered. Simulations and experimental results verify the feasibility of the proposed method.

Current harmonic elimination method for asymmetric dual three‐phase permanent magnet synchronous motor

Four-dimension current control for asymmetric dual three-phase permanent magnet synchronous motor based on vector space decomposition approach can eliminate the harmonic currents induced by the nonlinear characteristics of inverter. This study proposes a control strategy which uses a combination of the dead-time compensation scheme and current harmonic elimination algorithm together to eliminate the harmonic currents. The dead-time compensation is calculated based on the analysis of the non-linear characteristics of the inverter. Besides, a resonant controller which takes into account the pole correction caused by the discretisation process is employed in harmonic subspace as the feedback current control loop to generate the compensation voltage. In addition the phase lag caused by the pulse width modulation update and inductive load is also considered to ensure the stability of resonant controller. The experimental results demonstrate the superior performance of the proposed scheme.

Primary-Side Regulation Scheme for LLC Resonant Converter With Improved Resonant Current Sampling Circuit

A primary-side regulation (PSR) scheme for LLC resonant converter with improved resonant current sampling circuit is presented in this letter. An RC branch together with the auxiliary winding of the transformer is added in parallel with the current sampling resistor. The transformer magnetizing current component in the sampled primary current waveform on the sampling resistor can be offset by the generated voltage waveform on the added capacitor of the RC branch. In this way, PSR control for LLC resonant converter can be realized. Detailed operation principle and deviation analysis on the proposed PSR scheme are presented. Furthermore, a deadtime compensation is introduced to improve the output current accuracy caused by the component tolerance. Finally, a 48-78 V/1.3 A half-bridge LLC prototype has been built up to verify the theoretical analysis.

Modelling and compensation of dead time in three-phase dual-active bridge DC-DC converter

ABSTRACT With growing decentralized power generation, medium-voltage (MV) dc-dc converters are becoming increasingly important. A three-phase dual-active bridge (DAB3) is a promising topology for high-power MV applications. The semiconductor devices used in such converters at multi-megawatt level tend to be slow in switching. Hence, a considerable dead time between switching instants is required to avoid shoot-through in phase legs. This dead time forces the current to commutate to the freewheeling diodes and introduces a current dependence of the phase voltages. In this work, the effects of dead time on the operation of DAB3 are analysed in detail. The derived analytical expressions are used in the control development to compensate for the effects of dead time and hence achieve superior control performance. Measurements are carried out on a small-scale laboratory prototype to validate the derived operational modes and the effectiveness of the proposed dead time compensation.

On Dead-Time Compensation in Repetitive Control

The note studies the stabilization problem for a SISO continuous-time plant, where the feedback loop contains a fixed infinite-dimensional repetitive element and a “primary controller” to be designed. A novel architecture of the primary controller is proposed, which reduces the stabilization problem to that for a finite-dimensional system. The architecture has a flavor of dead-time compensation, also in the structure of resulting closed-loop systems. In the minimum-phase case, an implementation scheme insensitive to the value of the delay in the repetitive block is proposed.

A Double-Modulation-Wave PWM for Dead-Time-Effect Elimination and Synchronous Rectification in SiC-Device-Based High-Switching-Frequency Converters

The adoption of fast-switching silicon carbide (SiC) devices enables power converters to operate at high switching frequencies (e.g., 100 kHz). However, as a limiting factor at high switching frequencies, the dead-time in the conventional pulsewidth modulation (PWM) can cause significant voltage losses, bring serious low-frequency voltage/current harmonics, and reduce the linear modulation region with lower dc-link voltage utilization. Using the dead-time compensation can effectively eliminate the dead-time effect but further reduce the linear modulation region. The dead-time elimination PWM essentially has no dead-time effect. But due to the abandon of drive pulses for generating synchronous rectification, it has a lower converter efficiency, as well as current jumps at zero-crossings. In this article, to overcome the drawbacks of the conventional PWM and the dead-time elimination PWM, a double-modulation-wave PWM for dead-time-effect elimination and synchronous rectification is therefore proposed, where extra drive pulses for generating synchronous rectification are added based on the dead-time elimination PWM. The added drive pulses can also help with mitigating current jumps at zero-crossings. At last, the proposed PWM is experimentally validated and compared with the conventional PWM and the dead-time elimination PWM at 100 kHz on a three-phase converter with SiC mosfets and SiC Schottky diodes, showing the merits of low voltage losses, low output harmonics, high dc-link voltage utilization, large linear modulation region, and high efficiency.

Improvement of Power Converters Performance by an Efficient Use of Dead Time Compensation Technique

The advent of renewable energy resources and distributed energy systems herald a new set of challenges of power quality, efficient distribution, and stability in the power system. Furthermore, the power electronic converters integration has been increased in interfacing alternate energy systems and industries with the transmission and distribution grids. Owing to the intermittency of renewable energy resources and the application of power electronic converters the power distribution faces peculiar challenges. The dead-time effects are among the main challenges, which leads to the distortion of third harmonics, phase angle, torque pulsation, and induction motor current, causing severe quality problems for power delivery. To tackle these problems, this paper proposes a novel dead time compensation technique for improving the power quality parameters and improving the efficiency of power converters. The proposed model is simulated in MATLAB and the parametric equations are plotted against the corresponding parametric values. Furthermore, by implementing the proposed strategy, significant improvements are attained in the torque pulsation, speed, and total harmonic distortion of the induction motor. The comparisons are drawn between with and without dead time compensation technique, the former shows significant improvements in all aspects of the power quality parameters and power converters efficiency.

Virtual shaft: Robust coupling by bidirectional and distributed prediction of coupling values

Shifting automotive powertrain development tasks to earlier phases (frontloading) increases efficiency by utilizingtest-benches as opposed to prototype vehicles (road-to-rig approach). The coupling of distributed test-benches by a virtualized shaft connection is required to reproduce interactions of automotive powertrain components. A coupling algorithm simulates a rigid connection by synchronizing the torque and speed of two distributed test-bench’s electric motors. System dead-times lead to limited stability and reduced bandwidth of the coupling algorithm. In this study, a method for a stable bidirectional coupling of speed and torque of both subsystems is described analytically and verified by simulation. All component models are calibrated based on measurements using state-of-the-art test-bench equipment. A distributed prediction algorithm is proposed for the dead-time compensation. Four Kalman predictors estimate the coupling values of both subsystems at wall-clock-time without measurement and communication latencies. A detailed drive cycle analysis is performed through simulation. This enables a Virtual Shaft Algorithm to achieve a higher bandwidth and an improved coupling robustness.

Current Reduction Method for Dual Active Bridge Converter in Non-linear Dead-time Compensation Method

Current Reduction Method for Dual Active Bridge Converter in Non-linear Dead-time Compensation Method

Buck–boost derived interleaved hybrid converter for residential nanogrid applications

This study proposes a novel buck-boost based interleaved hybrid converter (BIHC), which can supply both AC and DC loads simultaneously. This topology uses two buck-boost derived hybrid converters where the DC outputs of the individual converters are interleaved and the AC voltage is the differential voltage tapped between the two source (of the MOSFETs) nodes of the individual converters. This converter uses only two switches which is lower than similar converters reported in literature, hence reducing the switching losses. In BIHC, there is no possibility of shoot through and no dead time compensation is required. BIHC will find application in hybrid nanogrids supplying residential loads powered by solar photovoltaic. The principle of operation of individual converters is augmented sinusoidal pulse width modulation with AC references for individual converters phase shifted by 180°. This results in line frequency components in the inductor currents and hence the buck-boost stage inductors are relatively larger. However, reduction in number of switches offsets this increase in size. The circuit has been extensively simulated in MATLAB and an experimental prototype of 100 W is tested in the laboratory.

Novel Multicarrier PWM Scheme for a Reconfigurable Single-Phase Inverter to Achieve Manifold Higher Effective Switching Frequency

Inverter operation at higher switching frequency brings several advantages. The article presents a novel multicarrier pulsewidth modulation (PWM) scheme along with a reconfigurable single-phase inverter topology. The combination facilitates multiple times higher effective switching frequency (ESF) at the inverter output. The novel reconfigurable topology incorporates additional pairs of series-connected switches in the conventional full-bridge inverter. The proposed PWM scheme uses multiple modified carrier waves to generate gate pulses for the various switches. Consequently, the switches operate in such a coordinated manner that ESF increases multiple times compared to the actual switching frequency of its switches. Thus, the scheme offers several advantages like reduced filter requirements, reduced overall size, weight, and cost. Moreover, the distortion in the output waveforms caused by the dead time is eliminated by a modified dead-time compensation technique, incorporated with the proposed PWM scheme. The proposed scheme is demonstrated here by configuring the proposed inverter topology as an eight-switch topology to achieve four times higher ESF. It is shown through analysis, simulations, and experimental results that in spite of including additional switches, a high-frequency operation can be achieved with a low cost. The proposed scheme may serve as an alternative to using wide bandgap devices, thereby saving cost and efforts.

A Combined DPWM Based on DSOGI-FLL for Switching-Loss Reduction and Dead-Time Compensation

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.

Fractional-Order Predictive PI Controller for Dead-Time Processes With Set-Point and Noise Filtering

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.

CSPS: an interactive tool for control design and analysis of processes with industrial characteristics

Abstract This work presents an user friendly interactive tool for control design, simulation and analysis of systems with characteristics commonly found in industry, such as dead time, constraints and measurement noise. The tool is able to validate and compare, in a simple and intuitive way, the performance and robustness of the three control structures most widely used in industrial applications: proportional-integral-derivative (PID), dead-time compensators (DTC), and model predictive control (MPC). Furthermore, the tool provides several options of techniques for handling input and output process constraints. A case study is used to illustrate some of the features of the tool.

Position Control with Predictor-based Dead Time Compensation for Hydraulic Actuators of Excavators

Position Control with Predictor-based Dead Time Compensation for Hydraulic Actuators of Excavators

An Adaptive Strategy to Compensate Nonlinear Effects of Voltage Source Inverters Based on Artificial Neural Networks

In motor drives, distortions of phase voltages and currents are often caused by nonlinear effects of inverters such as dead time, turn-on delay, turn-off delay and voltage drop of power devices. To eliminate these distortions, the dead-time compensation voltage is usually investigated. Furthermore, the relationship between the dead-time compensation voltage and phase currents is nonlinear, which is related to not only the parameters mentioned above, but also the snubber and parasitic capacitance of inverters. A nonlinear function is constructed to model the nonlinear relationship in this paper. To identify the nonlinear function, a method based on artificial neural networks is proposed without inverter parameters. According to the criterion that the trajectory of voltage vector in $\alpha - \beta $ coordinate system is a circle, an adaptive law is constructed to modify the parameters of the nonlinear function. Therefore, the nonlinear dead-time compensation voltage model is obtained accurately, where the distortions of voltages and currents are reduced without any additional hardware. Applying this method to the current predictive control, the bandwidth of a current loop is increased by 500Hz. Effectiveness of the method is verified by experiments.

Adaptive Selective Harmonic Elimination Model Predictive Control for Three-Level T-Type Inverter

In this work, an adaptive selective harmonic elimination model predictive control (ASHEMPC) method for a 3L-T type inverter is proposed. This algorithm is based on model predictive control (MPC), introduces adaptive selective harmonic elimination (ASHE) algorithm, and performs digital delay compensation through two-step prediction. Compared with the harmonic suppression strategies based on PI or PR controller, ASHE-MPC significantly improves the current loop bandwidth, speeds up the dynamic response, and greatly increases the harmonic order that can be eliminated. Compared with the harmonic suppression strategies based on the deadbeat model predictive control (DB-MPC), ASHE-MPC can eliminate low-order harmonics caused by multiple factors (including dead-time and grid background harmonics), and can easily eliminate multiple harmonics (5 th -31 th in this paper). The proposed ASHE-MPC method for the first time achieves adaptive selective harmonic elimination in model predictive control. The ASHE-MPC method is novel, simple and efficient. A three-level T-type grid-connected inverter for dead-time compensation is used as an example to verify the feasibility of this method.

Dead-time Compensation Method Based on Field Oriented Control Strategy

This paper analyzed a dead-time effect and zero-current clamping phenomenon in FOC control strategy, and then proposed corresponding compensation measures. The Field Oriented Control (FOC) strategy of brushless motor is improved according to this Dead-time Compensation measure. On the basis of the existing FOC control theory, a dead-time hysteresis loop is added near the current zero-crossing point to prevent current fluctuation and zero-point clamping from causing errors. The dead-time compensation is carried out in each PWM cycle according to the principle that the actual volt-second area is equal. Finally, the feasibility of the method was verified by experiments, the results showed that the compensation method effectively improves the current waveform and improves the stability of the motor operation, and it proved to be of good use value.

Modeling and Observer-Based Monitoring of RAFT Homopolymerization Reactions

Reversible addition–fragmentation chain–transfer (RAFT) polymerization of methyl methacrylate (MMA) is modeled and monitored using a multi-rate multi-delay observer in this work. First, to fit the RAFT reaction rate coefficients and the initiator efficiency in the model, in situ 1 H nuclear magnetic resonance (NMR) experimental data from small-scale (<2 mL) NMR tube reactions is obtained and a least squares optimization is performed. 1 H NMR and size exclusion chromatography (SEC) experimental data from large-scale (>400 mL) reflux reactions is then used to validate the fitted model. The fitted model accurately predicts the polymer properties of the large-scale reactions with slight discordance at late reaction times. Based on the fitted model, a multi-rate multi-delay observer coupled with an inter-sample predictor and dead time compensator is designed, to account for the asynchronous multi-rate measurements with non-constant delays. The multi-rate multi-delay observer shows perfect convergence after a few sampling times when tested against the fitted model, and is in fair agreement with the real data at late reaction times when implemented based on the experimental measurements.