Conventional Pulse Width Modulation Research Articles

Large-range dynamic characteristic adjustment of high-speed on-off valve for water hydraulic manipulators based on multistage voltage and double sliding mode control

High-speed on–off valves (HSVs) are highly adaptable and can control proportional flow, making them ideal for water hydraulic manipulators. In this paper, a water hydraulic HSV is specifically designed for water hydraulic manipulators. To enhance the dynamic characteristics of the HSV, a multistage voltage control combined with double sliding mode control (MVSMC) is proposed. A control system based on an H-bridge circuit is designed to implement the MVSMC algorithm. Simulations and experiments are conducted to evaluate the HSV’s rapid switching and adjustment of dynamic characteristics. The MVSMC algorithm enables quick switching of the HSV, even under fluctuating driving voltages in simulations. The sliding mode controller can control the dynamic characteristics of the HSV over a wide range by adjusting the pre-opening current and holding current. Experimental results show that, driven by the MVSMC algorithm, the opening time and closing time of the HSV are only 1.2 ms and 1.4 ms, respectively. The total non-adjustable opening time and closing time of the HSV are 0–1.2 ms and 0–1.4 ms, respectively. In other ranges, the switching time of the HSV is adjustable. Compared to conventional pulse width modulation (CPWM) control, the MVSMC algorithm offers extreme switching speed for the HSV. The MVSMC algorithm can adjust the dynamic characteristics of the HSV in a wide range, making it suitable for various working conditions requiring different dynamic characteristics.

M3D‐DPWM strategy for three‐phase four‐leg inverter with higher harmonic suppression capability

AbstractThree‐phase four‐leg inverters are widely used in power systems due to their inherent ability to handle unbalanced loads. However, with conventional 3D space vector pulse width modulation (3D‐SVPWM), high harmonics of large amplitude exist in the output voltage around the switching frequency and its integer multiples leading to noise in the load motor and limiting the application range of the inverter system. The passband amplification of conventional sinusoidal filters and their cutoff frequency vary with the load, so it is particularly important to investigate the regulation strategy with harmonic suppression. In this study, an improved 3D discontinuous pulse width modulation (M3D‐DPWM) strategy is proposed based on 3D‐SVPWM. By reducing the conventional 3D‐SVPWM switching segments and changing the vector synthesis sequence of the last half switching cycle, the output phase voltage period is reduced to half of the original one, which achieves the purpose of suppressing the output voltage at the switching frequency and its odd multiple high harmonics without changing the fundamental characteristics and adding additional circuits. In contrast, the conventional 3D‐SVPWM switching frequency is increased to 20 kHz to achieve similar performance. Finally, the effectiveness of the proposed strategy is verified by simulation and experiment.

Sample Voltage Dead-Beat Control Based on Differentiative Voltage Prediction and Switching-Cycle Extension for DC-DC Converters

In this paper, a sample voltage dead-beat control based on differentiative voltage prediction (DVP) and switching-cycle extension (SCE) is presented to achieve optimal transient response for DC-DC converters under discontinuous conduction mode (DCM) operation. Firstly, to improve load transient response, a DVP method is proposed to estimate the load. With the estimated load, the controller realizes load current feedforward and thus improves the transient response with a wide load range. Secondly, an SCE strategy is proposed to enlarge the output current range and output voltage slew rate, both of which have limited value under conventional digital pulse width modulation (DPWM). When the output current reaches the limited value, the proposed strategy increases the switching cycle to enlarge the current range without losing DCM operation. Finally, combining DVP with SCE, the converter not only achieves optimal response in large signal transients, but also doubles the load range in DCM operation.

Performance Characteristics of a Newly Developed Asymmetric Seven-Level Inverter Utilizing Various Hybrid Pulse Width Modulation Strategies

This study unveils a notable breakthrough in inverter technology, holding promise for substantial improvements in voltage quality and the attenuation of harmonic distortions within power systems. This study concentrates on the design and implementation of a novel Seven-Level Asymmetric Inverter (NSLAI) by incorporating various hybrid Pulse Width Modulation (PWM) techniques. The primary goal is to improve the output voltage magnitude while decreasing the Total harmonics compared to conventional PWM methods. The investigation introduces a novel Seven-Level Asymmetric Inverter (NSLAI) with innovative Hybrid Pulse Width Modulation (PWM) strategy. The purpose of this study is to investigate the distinct features of a recently developed asymmetric seven-level inverter, with a focus on exploring its characteristics through the implementation of diverse hybrid pulse width modulation strategies. Hybrid PWM methodology intricately centers on enhancing voltage quality and achieving better harmonious spectral characteristics. The gate signal producing approach for this suggested PWM technology incorporates a hybrid PWM methodology that combines trapezoidal and sinusoidal waveforms, as well as a standard triangular carrier signal enabling NSLAI. The hybrid version of PWM practices is deliberately used to generate switching signals for the NSLAI. An intensive evaluation of numerous indicators of effectiveness across multiple modulation indexes leads in the demonstrating of quantitative findings that compare the unique Hybrid PWM practice with established PWM tactics. Notably, the hybrid reference Carrier Overlapping strategy has emerged as a leading approach surpassing conventional pulse width modulation techniques. It achieves a significantly higher fundamental Root Mean Square voltage output and remarkably lower percentage of Total Harmonic Distortion values compared to all within the hybrid reference Variable Frequency strategy. The principal analytical tool used in the modeling investigation is MATLAB-SIMULINK. This study marks a watershed moment in the development of inverters, claiming significant improvements in battery power quality and distortion caused by harmonics avoidance across power systems, as evidenced by extensive simulation and prototype-based discoveries.

An analog PWM pixel circuit with shaping function for low grayscale display of Micro-LEDs

This paper presents a new analog pulse width modulation (PWM) micro light-emitting diode (LED) pixel circuit with a shaping function. The rising/falling time of PWM signal generated by the proposed pixel circuit can be greatly reduced to improve the low grayscale display quality of micro-LED. Metal oxide thin film transistors with the top-gate (TG) coplanar structure are used to realize the proposed pixel circuit on the glass substrate. It is shown that the pulse width of micro-LED current can be linearly modulated by the data voltage. Furthermore, the measured rising time and falling time of the PWM signal are 15.6 μs and 25.5 μs, respectively, which are much smaller than that of the PWM signal in the conventional analog PWM pixel circuits.

Dual-Phase-Shifted Pulsewidth Modulation of Three-Phase Modular Multilevel Converters

The modular multilevel converter (MMC) has been a crucial component for medium/high-power energy conversion systems due to its modular structure. In the literature, the harmonic analysis of MMC with different modulation methods, including the conventional carrier phase-shifted pulse width modulation (CPS-PWM) method, have been extensively investigated. However, the influence of the carrier displacement angles between three-phase legs on the output performance of an MMC is normally ignored. This paper proposes a dual-phase-shifted PWM (DPS-PWM) for a three-phase MMC which further enhances the performance of the conventional CPS-PWM scheme through proper selection of carrier displacement angles between three phases. First, the operation principle and implementation of the proposed DPS-PWM method is described. Then a two-dimensional (2D) Fourier model is derived to analyze how the carrier displacement angles between stacks and legs affect the harmonics of output voltage and circulating current. It is found that DPS-PWM can suppress specific harmonics in the line-to-line voltage by coordinating the carriers' phase shifting between the three-phase legs without affecting phase voltage and circulating current. Finally, the effectiveness of the DPS-PWM method is verified by simulation and experimental results.

Optimal Decoupled Discontinuous Modulation for StatComs Based on the Cascaded H-Bridge Converter

Conventional discontinuous pulse width modulation (DPWM) strategies for cascaded H-bridge static compensators suffer from poor inter-phase capacitor voltage balance control during unbalanced grid voltage conditions. Specifically, the logic-based algorithm that calculates the zero-sequence voltage (ZSV) for discontinuous operation interacts with the closed-loop capacitor voltage control. This paper proposes an optimal DPWM strategy based on a finite-set optimization that chooses the best ZSV candidate that minimizes the control interactions while clamping a converter voltage. Furthermore, the effect of the different ZSV candidates on the switching loss is also considered within the optimization. Extensive experimental study is provided to demonstrate the effectiveness of the proposed approach.

A novel programmed hybrid modulation for electromagnetic interference mitigation and current ripple control in miniaturised synchronous machine drives

AbstractA novel programmed hybrid spreading spectrum modulation method to mitigate electromagnetic interference (EMI) emission and bearing current in the context of miniaturised and lightweight synchronous machine drives is proposed. The proposed method adopts the combination of conventional pulsewidth modulation (PWM) and low common mode voltage PWM. The offline look‐up table for switching frequency is acquired by analysing the root mean square voltage values at different modulation indices and angles. By adjusting the switching frequency according to this table, the spectrum can be spread into the sidebands of the switching frequency, and the harmonic spike can be suppressed. To address the challenge of increased current ripple and harmonic distortion in high torque density motors under overload conditions, a motor model that considers the cross‐saturation and slotting effect is presented. This motor model is used to derive the switching frequency correction factors, aiming to mitigate the influence of saturation and slotting effect on harmonic amplification. The proposed method is well‐suited for controlling synchronous motors using three‐phase two‐level voltage source inverters. The simulation and experimental results validate the effectiveness of the proposed method, showcasing its advantages in terms of computational complexity reduction and significant attenuation of peak EMI currents.

A Novel Hybrid PWM Technique for Asymmetric Inverter

Multi-Level Inverters (MLIs) are achieving broad popularity owing to the rapid development of power semiconductor devices. The capability of MLIs became recognized as a significant aspect of a system heavily reliant on Pulse Width Modulation(PWM) strategy. The conventional high frequency PWM techniques suffer from significant Total Harmonic Distortion (THD) along with power loss difficulties. This work recommends a hybrid PWM technique for lowering the THD and power loss of VSI adding the benefits of level-shift PWM and Phase-shift PWM. A novel form of carrier signals is employed in the proposed hybrid PWM technique. In contrast to existing PWM techniques, the proposed hybrid PWM technique minimizes switching and conduction power losses. In this work, the proposed PWM scheme is employed for asymmetric multilevel inverter. The proposed configuration is also examined using PLECS software to estimate losses and efficiency. The simulation work is done in the MATLAB/Simulink environment and the OPAL-RT(OP4510) test platform is employed to evaluate topology performance.

Modified SPWM technique for single phase variable voltage nine level inverter for PV system

<span lang="EN-US">Multilevel inverters are widely popular because they boost the overall staging of the network with low harmonic distortion, less strain, and simply create highest possible development in industrial and electrical vehicle applications. Here a hybrid multilevel inverter having few switches compare to traditional multi-level inverters has been implemented. It has the capability to operate as a 3-level, 5-level, 7-level and 9-level inverter with different magnitudes of output voltage by varying the modulation index without changing of circuit topology and switching sequences. A new variable amplitude phase opposition disposition sinusoidal pulse width modulation (VAPODPWM) technique is proposed to control the inverter. In this concept unsymmetrical carrier wave form, i.e. A single triangular wave is divided into three triangular waves of different magnitude was chosen. it reduces the volt-sec of output due to that it gives less total harmonic distortion (THD) compare to other conventional space pulse width modulation (SPWM) techniques and conventional space vector pulse width modulation (CSVPWM) control techniques. The ease of conversion capability with less count of switches and operation with less THD shows the effectiveness of the converter. The converter is simulated by using MATLAB/Simulink and results are discussed.</span>

Hybrid PFM and SPWM Control Scheme for DCM Single-Leg-Integrated Boost Inverter

Under the conventional pulse width modulation (PWM) + sinusoidal pulse width modulation (SPWM) hybrid control, the discontinuous conduction mode (DCM) single-leg-integrated boost (SLIB) inverter confronts an over-modulation problem under a wide change in load, leading to the distorted output waveform. One approach to address this issue is to keep the boost-leg duty cycle constant and regulate load power. However, it is not suitable for standalone or PV grid-connected power systems. Therefore, a pulse frequency modulation (PFM) + SPWM hybrid control scheme is proposed to overcome the shortcomings in this paper. Under the proposed scheme, the boost-leg of the inverter works in PFM while the other leg works in SPWM. Since the DC-link voltage is controlled by frequency, instead of load power or duty cycle, the inverter can avoid over-modulation for a wide load range and be applied on occasions where the load power is non-adjustable, which is more practical in comparison with the counterpart. The feasibility of the proposed hybrid control is verified by experiment through a 500 W prototype.

A unified duty-cycle modulation algorithm for a three-level NPC inverter

In this paper, it is a kind of challenge to simplify the conventional pulse width modulation (PWM) algorithms for a three-level neutral-point-clamped inverter. Thus, the unified duty-cycle modulation (UDM) algorithm is presented. It is more attractive than the carrier-based PWM (CBPWM), space-vector PWM (SVPWM), and unified PWM algorithms with a simpler calculation by utilizing the usefulness of the SVPWM algorithm to synthesize the duty cycles in time-domain and the CBPWM algorithm to synthesize the duty cycles in frequency-domain with the lesser conditions and the blankness of the lookup tables, switching sequence design, and zero-sequence component finding. Besides, it is outstanding with three outcomes: (1) comprehensive mathematical models of the dwell times, (2) permanent mathematical models of the duty cycles in time-domain, and (3) simplified PWM algorithm, which has a better workflow with the reduction of the computation burden. As it is very easy to implement as the sinusoidal PWM technique while its performance is equivalent to the SVPWM algorithm, this makes the proposed UDM algorithm a good candidate to optimize between the performance and the cost. Both the simulation and experimental results can confirm the feasible practicability and performance. The comparison with the conventional algorithms can evidently emphasize the superiority.

A new floor function single‐carrier‐based modulated model predictive current control technique for single‐phase PUC5 inverter topology

SummaryIn this paper, a new floor function (F2) single‐carrier (SC)‐based modulated model predictive current control technique (M2PC2T) has been proposed by considering the conventional single‐phase five‐level packed U‐cell (PUC5) inverter topology. Generally, to regulate the output current, the finite control set‐based MPC technique without a modulator inherently operates with variable switching frequency, and it is unsuitable for industrial applications. To alleviate this, authors have implemented M2PC2T, which provides constant switching frequency of operation. In this technique, generally, the predictive algorithm has been integrated with any modulation stage. However, while the implementation of pulse width modulation (PWM) techniques, most authors have used conventional PWM techniques which further increases the control complexity as the level number increases. In this manuscript, a simple and generalized F2‐SC‐PWM technique has been proposed and integrated with the predictive algorithm. This PWM technique implementation process is very simple as compared with all conventional PWM techniques since even if the level number increases, the number of modulating and carrier signals is always only one. Finally, the complete closed‐loop control technique is called a generalized F2‐SC‐M2PC2T which is suitable for all stiff direct current (dc) sources and switched capacitor‐type multilevel inverter (MLI) topologies. The proposed control technique (PCT) has been experimentally verified with different transient and steady‐state case studies by considering resistive‐inductive load.

A Self-Powered Synchronous Switch Energy Extraction Circuit for Electromagnetic Energy Harvesting Enhancement

Previous studies have shown that the synchronous switch energy extraction (SSEE) solutions could enhance the energy harvesting capability of vibration energy harvesters with capacitive output impedance, such as piezoelectric ones. These circuits use a synchronous switch inductive branch to compensate for the capacitive source. Some studies have also shown that an inductive source can be compensated by a synchronous switch capacitive branch. Yet, the controls were all carried out by external bulky and power-hungry controllers, which is unrealistic in a self-contained and self-sustainable system. This paper proposes a self-powered SSEE (SP-SSEE) circuit for inductive electromagnetic energy harvesting (EMEH) sources. The sampling, synchronization, and switch control are implemented with a small series sampling inductor, a comparator, and some digital gates, respectively. The SSEE circuit carries out two rounds of the switch on/off actions in each vibration cycle to make the current through the induced equivalent voltage source in phase with its voltage. By improving the power factor of the induced voltage source, it enlarges the harvested power under the same excitation. It uses fewer switching actions than the conventional pulse-width modulation (PWM) ac-dc rectifier designs. Moreover, the self-powered design makes the SSEE solution a passive ac-dc rectifier, which is more convenient to be utilized in real applications. The detailed working principle and experimental validation of the SP-SSEE circuit are provided in this paper. The results show that, under the tested frequencies, SP-SSEE outperforms the benchmark standard energy harvesting (SEH) diode-bridge rectifier by 62.1% to 96.4% percent under different excitation frequencies, in terms of harvested power.

Design and Analysis of Universal Natural Fault-Tolerant SVPWM Strategy With Simplified Fault Diagnosis for Multiphase Motor Drives

Conventional space vector pulse width modulation (SVPWM) would degrade the operating performance of the multiphase motor drives under open-phase fault. To resolve this issue, existing solutions require the reconfiguration of transformation matrices. However, for the variable positions of faulty phases, the structure of matrices needs to be redefined, which is a restraint to the industrial implementation of such technologies. This study examined the offset of the voltage vectors after fault occurrence. Accordingly, a universal fault-tolerant SVPWM strategy is proposed for the purpose of natural fault-tolerance, as well as a simplified fault detection scheme. Compared with conventional fault-tolerant SVPWM, it is highlighted with the characteristics of minimum reconfiguration, torque-ripple free operation, and applicability to handle various types of open-phase faults using a single transformation matrix. Besides, proposed strategy eliminates the redundant controllers and also reduces the degree of difficulty for fault diagnosis. Finally, the effectiveness of proposed approach is evaluated experimentally with a seven-phase induction machine, which shows that the torque ripple could be reduced by about 40% in the presence of multiple faults compared to the conventional SVPWM strategy.

Multiaverage Random Switching Frequency Space Vector Pulsewidth Modulation Strategy for High-Order Harmonics Dispersion

A multi-average random switching frequency space vector pulse width modulation (MARSF-SVPWM) strategy is proposed in this paper, in order to further disperse the high-order harmonics concentrated at the switching frequency and its integer multiplies in the output voltage of the inverter. The proposed strategy divides the fundamental period equally, with different stages corresponding to different average switching frequencies and spread-spectrum ranges, in contrast with the conventional random switching frequency space vector pulse width modulation (RSF-SVPWM), under the premise of maintaining the same overall average switching frequency and spread-spectrum range. The simulation and experimental results demonstrate that, even in the case of a narrow spread-spectrum range, the proposed MARSF-SVPWM strategy can obtain a better effect of high-order harmonic dispersion.

Level vector pulse width modulation for multilevel inverters

SummaryIn this paper, a novel method named as level vector pulse width modulation (LVPWM) is proposed for multilevel inverters. Similar to the conventional space vector pulse width modulation (SVPWM), the proposed method is a vector‐based method in the α–β frame. Unlike the SVPWM, the variables of each of the α and β axes are considered separately. Instead of space vectors, level vectors are considered for the synthesis of the reference vectors. There is no need to consider multiple switching states, vectors, and large lookup tables in the algorithm. The appropriate switching states for the synthesis of the reference vectors are determined using simple computations at each sampling time. Generality for different inverter topologies, online implementation, simplicity of the algorithm and computations, independency of the algorithm complexity from the number of switching states, and easy extension to overmodulation region are the advantages of the proposed method. Implementation of the LVPWM in different inverter topologies is studied. The validation of the proposed modulation strategy is carried out by simulation and experimental results.

P‐9: LTPO TFTs Based PWM Pixel Circuit for AM‐Micro‐LED Display with Falling‐time <10μs

A pulse‐width‐modulation (PWM) pixel circuit for Micro‐LED display based on low‐temperature poly‐silicon and oxide (LTPO) thin‐film transistor (TFT) is proposed. The PWM falling‐time is reduced to 10 μs, which is only 1/10 of conventional PWM pixel schematics, thanks to the high gain dynamic CMOS inverter for converting data voltage to PWM waveforms and an independent diode‐connected compensation structure for generating constant driving current. The maximum error of PWM conversion and driving current of Micro‐LED is less than 1%, despite VTH shift of oxide TFT ±2 V or VTH variation of LTPS TFT ±1 V. Furthermore, high display resolution above 270 PPI is obtained as the pixel layout reduced to 94 μm×94 μm due to the simplified pixel structure.

A Modified PWM Scheme to Improve the Power Quality of NPC Inverter Based Solar PV Fed Induction Motor Drive for Water Pumping

This paper proposes a modified modulating signal-based pulse width modulation (PWM) scheme for a neutral point clamped (NPC) inverter-based induction motor drive (IMD) for enhancing the efficiency of solar photovoltaic (PV) fed water-pumping systems. During the previous several decades, the use of sustainable source-based power generation systems has benefited water pumps in household life, irrigation-based activities, and industrial sectors, especially in areas where the electric grid is less available. A critical concern has long been the power quality, speed, and torque of an induction motor used in solar PV-powered water pumping. This paper focuses on the improvement of power performance by minimizing total harmonic distortions (THDs), switching losses and conduction losses, and torque ripples in the induction motor driving the PV-fed water pump by using a modified PWM scheme that generates symmetrical and balanced gate driving signals for the NPC inverter employed in the IMD. The IMD with the suggested PWM switching strategy has been tested in all feasible induction motor operating situations. To demonstrate the effectiveness of the suggested PWM scheme, a performance comparison of the proposed PWM scheme with conventional PWM schemes is performed, and also the IMD with the suggested PWM switching strategy is tested in all feasible induction motor operating situations using the MATLAB/Simulink platform.

Hybrid Active Modulation Strategy for Three-Level Neutral-Point-Clamped Converters in High-Speed Aerospace Drives

In the aircraft electric starter/generator system, the three-level neutral-point-clamped converters play a crucial role in driving turbofan engines and delivering onboard electrical power. However, the conventional pulsewidth modulation (PWM) strategies face the challenge of capacitor voltage deviation, large common-mode voltage (CMV), and extra switching losses. Regarding the characteristics of the studied wide-speed range aerospace drives, the modulation scheme needs to be designed according to its operating conditions. To tackle the above demerits, a hybrid active modulation approach is, hence, proposed in this article. By the coordinate-based PWM, the nearest-three-vector is used in the startup process as the neutral-point (NP) voltage balance can be realized with fewer switching intervals; when the drives run in generation mode, an enhanced carrier-based virtual-space-vector modulation technique is involved, which aims to eliminate NP voltage fluctuation, suppress CMV, and simplify the modulation process. With the help of bias-offset injection in the time and voltage domain, capacitor voltages can be effectively kept at a balanced state even though the imbalance exists. The validity of the presented algorithm is proved by simulation and experimental results obtained from a 45 kW, 32 kr/min aircraft starter/generator test rig.