Pulse Width Modulation Voltage Research Articles

Investigation of bidirectional three-phase four-leg converter with LCL filter

A three-phase four-leg bidirectional power converter used as an input stage of an energy storage system using the inductance (L), capacitance (C), and inductance (L) or LCL filter on the grid side is considered. The article provides a variant of the three-phase four-leg bidirectional converter control system implementation based on 3D space vector pulse-width modulation and per-phase voltage control. A brief analysis of the applied control algorithms of the three-phase four-leg bidirectional converter in inverter and rectifier modes is given. A computer model has been built to investigate the operating modes of the converters of the designated class with both balanced and unbalanced load. Studies were carried out by computer modeling methods in order to optimize the parameters of the LCL filter on the grid side with bidirectional energy exchange. Optimal LCL filter parameters and modulation frequencies are determined for the developed converter, providing acceptable quality indicators when operating in bidirectional mode.

Experiment of electrothermal stress for different types of end turn grading in the inverter‐fed form‐wound windings

AbstractEnd turn grading with resistive–capacitive coupling experiences severe electrothermal stress when subjected to pulse width modulation (PWM) voltage. In this paper, several experiments and simulations were carried conducted for four types of end turn grading. First of all, the temperature rise in the end turn grading increased with a decrease in rise time. When the rise time was less than 500 ns, the temperature rise at the terminal was higher owing to the increased capacitive current coupled from the main wall insulation. Further, the current in the linear region exhibited minimal variation at different fundamental frequencies resulting in synchronized the temperature rise at the terminal and overlap. Furthermore, the jump voltage was the key factor influencing temperature rise in end turn grading, confirmed by comparing different voltage magnitudes. Finally, the transient behaviour of the maximum field in the stress grading material was determined at rise time. The experimental and simulation results indicate that balancing and interdependently addressing the electrical and thermal stress protection in end turn grading is crucial. The study aims to provide an experimental and theoretical foundation for an insulation system of inverter‐fed rotating machinery operating under PWM voltage.

Comparative study of a high‐speed permanent magnet motor when powered by different methods

AbstractThe authors present the multi‐physical field performances comparative research for a 30 kW, 30,000 r/min high‐speed permanent magnet motor (HSPMM) when the motor is powered by the sinusoidal pulse width modulation (SPWM) voltage inverter and sinusoidal voltage source, respectively. Firstly, electromagnetic performances including torque, voltage and current of the HSPMM with different driving methods are compared and analysed by the finite element method (FEM). Considering the effects of high operation frequency, power losses of the HSPMM with different driving methods under full‐load conditions are calculated and compared with the skin effect and the proximity effect considered for HSPMM winding copper loss estimation. Based on the above analysis, a prototype driven by the SPWM voltage inverter is manufactured, with its electromagnetic and thermal performances tested and verified. In addition, several influencing factors of the HSPMM rotor eddy current loss are studied, with their effects on the HSPMM under different driving methods further analysed and compared as well. A novel equivalent power supply method is proposed to effectively save the calculation time with a negligible error. Finally, in order to further improve the heat dissipation capacity of the HSPMM, a novel cooling method is intensively studied with its influencing factors further analysed. The cooling effect of the novel cooling method and the temperature of the motor components are verified and calculated by the computational fluid dynamics (CFD) method.

A Common-Mode Voltage Elimination Scheme by Reference Voltage Decomposition for Back-to-Back Two-Level Converters

Common-mode voltage (CMV) can greatly reduce the reliability and performance of back-to-back two-level converter-fed motor drive systems. To address this issue, a novel CMV elimination scheme based on reference voltage decomposition is proposed in this article. Firstly, the reference voltage of each phase is decomposed into two virtual reference voltages, resulting in six virtual reference voltages that are inter-related for back-to-back two-level converters. Then, by comparing each virtual reference voltage with a triangle carrier based on the two-level pulse width modulation (PWM), the final PWM voltage of each phase can be obtained from the differences of the corresponding two virtual PWM outputs. With the proposed method, both the amplitude and RMS value of CMV can be eliminated theoretically with satisfactory output waveform qualities. Simulations and experimental results are presented to verify the proposed method.

A Modified SVPWM Strategy for Reducing PWM Voltage Noise and Balancing Neutral Point Potential

PWM (pulse width modulation) is the most widely applied current conversion technology, but the high-frequency harmonics it causes have a significant negative impact on inverter system performance. This paper focuses on the three-phase T-type three-level inverter as the research object and addresses existing PWM voltage noise and midpoint potential imbalance issues by proposing an improved random SVPWM strategy, named Neutral Point Potential Balance Random Space Vector PWM (NPB–RSVPWM). The NPB–RSVPWM strategy includes three main steps: (1) introducing a midpoint potential balancing control loop to adjust the synthesis timing of the effective vectors to generate pulse signals, optimizing midpoint potential balance; (2) employing a randomly varying carrier frequency in place of the carrier used in the SVPWM strategy to generate the driving signals for switching devices; and (3) controlling the inverter through the driving pulse signals. This strategy optimizes the synthesis sequence of traditional SVPWM strategy vectors and incorporates random frequency modulation techniques. The mathematical model analyzes PWM harmonic expressions corresponding to fixed switching frequencies, and a random frequency carrier is chosen to suppress these PWM harmonics. The effective vector’s equivalent circuit is analyzed, proposing a technique for optimized vector synthesis timing. The simulation and experimental results verify that the NPB–RSVPWM technique can disperse PWM harmonic energy, reduce voltage noise, and optimize midpoint potential balance. Under the NPB–RSVPWM strategy, the line voltage spectrum becomes uniform, the maximum harmonic content is greatly reduced, and the fluctuation in the DC side midpoint potential is significantly improved. Compared with the traditional SVPWM strategy and random PWM strategy, the NPB–RSVPWM strategy has a lower voltage noise, smaller total harmonic distortion, and a more stable midpoint potential. The effectiveness and feasibility of the NPB–RSVPWM strategy are verified by simulation and experimental results.

A Switched-Capacitor Multilevel Inverter With Modified Pulsewidth Modulation and Active DC-Link Capacitor Voltage Balancing

Although switched-capacitor (SC) multilevel inverters (MLIs) offer self-voltage balancing of flying capacitors and voltage gain higher than unity, the advantages come at the cost of high current stress and power loss in the SC circuit and DC source. Moreover, the voltage balancing is often restricted to a limited range of modulation index. Another problem of MLIs with neutral-point clamped (NPC) front end is with DC-link capacitor voltage balancing under unbalanced load conditions, imploring sensor-based closed-loop control. This paper proposes a unity gain five-level active-NPC SC-MLI with inrush charging current attenuation and actively balanced DC-link capacitor voltages under all load conditions and over the entire range of modulation index and power factor. The modified pulse-width modulation results in most switches operating at a low switching frequency, minimizing switching losses in the SC circuit. The proposed MLI attains a maximum efficiency of 98.04% at an output power of 510 W. Experiments on a 2 kVA laboratory prototype validate the theoretical analysis. Results from transformerless grid-connected solar PV system show that the proposed MLI can inject power into the grid with a unity power factor under conditions of varying irradiance and provide the grid with reactive power as well.

Development of Novel Hydraulic 3D Printed Actuator Using Electrorheological Fluid for Robotic Endoscopy

Endoscopy has made a significant and noteworthy contribution to the field of medical science and technology. Nevertheless, its potential remains constrained due to the limited availability of rigid or flexible endoscopes. This paper introduces a novel hydraulic actuator based on electrorheological fluid (ERF) as a pivotal advancement in bridging the existing gap within the realm of endoscopy. Following a comprehensive introduction that briefly outlines the electrorheological effect, the subsequent section is dedicated to the elucidation of the actuator’s development process. Challenges arise, particularly in terms of miniaturization and the realization of a hydraulically sealed system with integrated valve electrodes. An internal electrorheological valve system consisting of four valves that are controlled using a pulse-width modulated high voltage was suitable for position control of the antagonistic hydraulic actuators. High-precision stereolithography (SLA) printing has proven practical for manufacturing actuator components. For functional testing, a test bench was set up in which the actuator follows a setpoint through a PI control loop. The control deviation ranged from 0.6 to 1 degree, with a response time between 6 and 8 s. The experiments have demonstrated that through the use of ERF and integrated valve electrodes, a miniaturized functional actuator can be constructed.

A high efficient 33 level inverter for electric vehicle application using PMSM

The permanent magnet synchronous motor (PMSM) avoids commutation-related torque ripples and produces smooth torque. Its great handling capacity and better efficiency make it an excellent choice for high-demand applications. A typical PM motor drive fed with pulse width-modulated voltages may cause the motor insulation to break down if rapid voltages (dv/dt) occur across the motor terminals. Applying variable voltage with low dv/dt and implementing multiple inverter topology can solve this issue. Multilevel converters have minimal switching losses, better power quality and the ability to operate at both fundamental and higher switching frequencies. In this study, a three phase stacked multilevel inverter-based FOC driven PMSM drive design is proposed. Here, the neutral point is a capacitor intermediate point on DC side, where current is naturally balanced throughout a switching cycle. This makes it possible to use downstream batteries and even lower voltage equipment, greatly increasing efficiency, improved performance and smother control at low speed. Therefore, direct-battery-driven electric vehicles will be able to use this. A 33 level inverter-based PMSM drive was used to implement the FOC, and the simulation results were used to validate it. The Matlab/Simulink tool is used to simulate the entire system.

Developing a novel personal thermoelectric comfort system for improving indoor occupant’s thermal comfort

Personal comfort systems (PCSs), which target to condition only the occupied zones of indoor space, have received considerable interest due to their validity in thermal comfort improvement and building energy saving. Recently, the thermoelectric module (TEM) has been utilized in the design of PCS for its high reliability, small size and noise-free operation. However, the PCSs using the TEM generally lack the effective control strategy with occupant’s feedback, thus reducing their actual effectiveness on improving thermal comfort. In this paper, a novel personal thermoelectric comfort system (PTCS) is developed with a feedback control framework embedded into it. The PTCS is mainly composed of a thermoelectric conversion unit, a micro blower, control/drive modules and a tube network. A thermal comfort feedback control strategy is proposed for the PTCS. In this strategy, a thermal comfort feedback table is established based on offline experiments, and the tube outlet airflow velocity and temperature setpoints are obtained simultaneously through the table look-up method. Then, the neuron PID control algorithm and pulse width modulation (PWM) of voltage are adopted to adjust the tube outlet airflow velocity and temperature for tracking the obtained setpoints. Experimental results validate the effectiveness of the thermal comfort feedback control strategy. Thermal imaging results on human body demonstrate the availability of the developed PTCS. Performance comparison with other PCSs is also provided, which indicates the potential for practical applications.

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 Simulation Analysis of Grid-Connected DSTATCOM with PWM Voltage Control and Hysteresis Current Control for Power Quality Improvement

Abstract The DTSTACOM is a power quality compensator that can be used in the distribution grid to compensate the demand of reactive power, which can be produced by different linear and non-linear loads. In this process, the control method of DSTATCOM is one of the key factors influencing the performance of DSTATCOM. This study aims to analyse the effect of two modulation schemes, Pulse Width Modulation (PWM) and Hysteresis Current Control (HCC), under several conditions. The proposed modelling approach and Synchronous Reference Frame (SRF) theory are used to verify reactive power compensation and total harmonic distortion (THD). Further, PWM and Hysteresis Current Control (HCC) with proportional-integral (PI) controller simulated in MATLAB for different cases, and percentage THD was calculated to prove the effectiveness of the proposed method for the control of reactive power and THD with grid-connected DSTATCOM. The results presented here justify that the HCC controller can be better than the PWM method to generate the PWM pulses for reduction of harmonics under various conditions of DTSTACOM to compensate the reactive power. Additionally, the simulation was performed to check the efficacy of the projected method to reduce THD by varying the current control band of HCC.

High-accuracy control of variable blank holding force driven by electromagnetics based on pulse width modulation with grading voltage and mode matching

Using variable blank holding force, which is conventionally achieved by hydraulic or mechanical drive, can effectively reduce defects in the forming process. To overcome the obstacles of low response and high complexity of conventional drives, this paper proposes a holding system for variable blank holding force driven by the electro-permanent magnet. Focusing on the variable electromagnetic force, a control method based on grading voltage pulse width modulation and mode matching is addressed. The model of the transient electromagnetic force is first established, the relationship between electromagnetic force and current is obtained, and the migration law of the working point of the magnet with the change of current is analyzed. Then, the grading voltage pulse width modulation control, which regulates current by the pulse width and its amplitude, is developed for continuously increasing or decreasing force control. When force variations occur, mode matching is introduced to identify the working point and allocate matching parameters for better control. To validate the feasibility of the control method, the co-simulation based on Simulink-Simplorer-Maxwell and the experiment bench are built. Results of electromagnetic force show that the step response time is 0.13 s and the mean relative error is less than 1% for a given variable blanking force. The control method can reduce the thickness variations of sheet metal by 14–20% compared to the existing electro-permanent magnet blank holder. This work assists in realizing the loading of variable blank holding force driven by electromagnetics to improve the forming quality of parts.

PWM Voltage-Based Modeling for PM Machines With Interturn Short Circuit Fault Considering the Effect of Drives

This paper presents a novel analytical fault model based on PWM voltage rather than ideal sinewave phase voltage for permanent magnet (PM) machines with inter-turn short circuit fault. This model is important because PM machines are usually driven by the pulse width modulation (PWM) inverter. In addition, main contributors to the accuracy of the fault model such as (i) the cables between the inverter and the machine, (ii) the precision of the rotor position estimation and (iii) the inverter, in particular the metal-oxide semiconductor field-effect transistors (MOSFETs) have been considered. Therefore, this developed model can fully account for the effects of PWM harmonics and accurately predicts the machine's behaviors (particularly the fault current) under fault conditions considering the effect of the drives. This has rarely been studied in the literature as most existing fault modelling methods adopt sinewave phase voltage as inputs, which cannot account for the PWM harmonics in the fault currents. However, the investigations in this paper showed that the PWM harmonic component could be close to 25% of the fundamental component in the fault current, and hence cannot be neglected. The accuracy of the proposed fault model has been validated by a series of experimental tests.

Non-Intrusive Efficiency Estimation of Inverter-Fed Induction Motors

The use of inverter supplies over sinusoidal supplies for induction motors is growing considerably. Inverter supplies enable effective and robust control of induction motors in many automated systems. However, this benefit features at the expense of additional harmonic motor losses due to pulse-width modulated (PWM) voltages and currents produced by inverter supplies. The quantification of these additional harmonic losses and the estimation of efficiency in a non-intrusive manner can be quite challenging. This paper proposes a non-intrusive efficiency estimation technique for inverter–fed induction motors that is based on harmonic regression analysis, harmonic equivalent circuit parameter estimation and harmonic loss analysis using limited measured data. The efficiency results from the proposed technique are comparable to those obtained using the IEC 60034-2-3 Standard up to 1% accuracy when tested on three different inverter-fed motors at different loads.

Cascaded Inverters Increasing the Number of Levels and Effective Switching Frequency in Output Using Coupled Inductors

In this paper, a new coupled-inductor based modular multilevel cascaded inverter using a new phase-shift control is presented. The proposed inverter can generate a high output ac voltage using standard low voltage rating devices. The number of levels in the output pulse width modulation (PWM) voltage and the effective switching frequency of the output filter are increased using coupled inductors and phase-shift control. The switching signals of the cascaded units in the proposed inverter are phase-shifted by 360°/4n, where n is the number of cascaded units. The proposed phase-shift control results in (4n+1) levels in the output PWM voltage of the proposed inverter and increases the effective switching frequency of the output filter by 4n times of the actual switching frequency fsw. As a result, the output waveforms can be generated with better quality and less distortion. In addition, the output filter can be decreased dramatically in size. Besides, fewer coupled inductors are used to reduce the footprints, the number of inductors, and magnetic volume. Moreover, the proposed inverter is exceptionally reliable due to no short-circuit risk in the circuit.

Characterization and calculation of losses in soft magnetic composites for motors with SVPWM excitation

This study investigates the impact of space vector pulse width modulation (SVPWM) voltage excitation on the magnetic properties and losses of soft magnetic composite materials (SMCs) used in motors. This research aims to comprehend how SVPWM voltage excitation affects the magnetic properties and losses of SMCs. SVPWM voltage waveform has apparent voltage harmonics that can affect the core losses of soft magnetic materials. To measure the magnetic properties of SMCs, a test system is established that uses a range of carrier frequencies from 0 kHz to 100 kHz during SVPWM voltage excitation. The test results show that the hysteresis loop of SMCs exhibits minor loops on the major loop, which results in at least a 5.554% increase in losses when compared to sinusoidal excitation. To better predict and understand these losses, a neural network-based model is proposed for estimating losses under SVPWM excitation in SMCs. The proposed model optimizes the application of SMCs in motors and can contribute to the optimization of motor design.

Design and Measurement of a Frequency Converter with SPWM Modulation of Output Voltage for a Two-Phase Induction Motor

This paper deals with the design, implementation, and measurements of a frequency converter with bipolar sinusoidal pulse width modulation (SPWM) of output voltage for two-phase induction motors. The paper is dedicated to an analysis of the operation of a two-phase frequency converter and its implementation. The inverter has a single-phase H-bridge topology with split DC link and bipolar switching to minimise the number of components. Insulated gate bipolar transistors (IGBTs) are used in the realisation of the inverter power section. The inverter is controlled using a digital signal processor (DSP) TMS320F28335. Measurements with a 0.12 kW two-phase induction motor were performed to verify the correct operation of the inverter. The influence of the switching frequency on the motor current ripple is measured for frequencies of the first harmonic up to 100 Hz.

A Control Scheme for a Quasi-Z Source Three-Phase Inverter

This paper presents a novel control scheme for a three-phase quasi-z source inverter (qZSI) using a capacitor voltage and input current-based sinusoidal pulse width modulation (SPWM) technique. The proposed scheme combines the advantages of both qZSI and SPWM techniques to achieve improved performance. The SPWM technique utilizes a sinusoidal modulation signal, which is compared with a high-frequency triangular carrier wave and two shoot-through (ST) references to determine the switching states for the three-phase qZSI. The positive and negative ST references are obtained from the capacitor voltages and input current, allowing for control of the DC bus voltage and ST states of the inverter. Additionally, the proposed control scheme generates the three-phase modulation signal through decoupling control in the dq reference frame. The detailed analysis of the control scheme includes its operating principle, transient state, steady-state responses, and the effects of parameter variations. Simulation studies are conducted using MATLAB/Simulink to assess the performance of the three-phase qZSI under the proposed control scheme. The simulation results demonstrate the effectiveness of the control scheme in terms of output voltage quality, DC bus voltage control, and robustness against reference variations. Overall, the proposed capacitor voltage and input current-based SPWM control scheme for the three-phase qZSI shows promising performance improvements and robustness, as confirmed through comprehensive simulation studies.

Influence of mixed-frequency medium-voltage and environmental stress on the aging of epoxy

Recent developments in power electronic technologies lead to new challenges for insulation systems. This contribution aims to clarify the influence of a broad range of mixed-frequency (MF) medium-voltage and environmental stress parameters on the aging of epoxy insulation. For this purpose, test samples are stressed with an AC (50 Hz) or a DC voltage, superimposed with a pulse-width-modulated (PWM) voltage (kHz range). An analysis of the samples’ health state is carried out after the aging by the evaluation of potential aging markers (AC breakdown strength, dielectric permittivity, glass transition temperature, Fourier-transform infrared spectroscopy spectra). Although the main focus of this work is on aging below the inception of partial discharges (PDs), it was first confirmed that PD-related aging depends mainly on the peak voltage stress. In contrast, the results obtained by aging below PD inception suggests a dependence on the root-mean-square of the applied voltage stress, and consequently on the energy dissipation. Aging in the PD-free regime was only observed at alternating electric field stress and high relative humidity or elevated temperatures. No influences of space charge and of the slew rate of the PWM voltage were observed. Remarkably, higher PWM frequencies lead to less insulation aging. This might be attributed to the increasing hindrance of polymer side chain movement at higher frequencies, as observed by dielectric spectroscopy. In addition, it is indicated that the aging mechanisms under MF voltage stress result from superimposed single-frequency aging mechanisms and that aging is activated after a latency period. Of the investigated potential aging markers, only the residual breakdown strength revealed aging effects, which correlates with lifetime observations in the PD-free voltage stress regime. It is hypothesized that the aging mechanism is associated with a rearrangement of the free volume in the polymer, followed by a localized breaking of van der Waals bonds.

Transient modelling and simulation of a switched reluctance machine in different operating modes

An appropriate numerical computational method and simplest model captures the performance of Switched Reluctance Machines (SRMs). Several papers and computer software-based simulation models are reported in the literature. Each model has its own merits and demerits. This paper proposes a mathematical model, based on a combination of voltage and mechanical equations, suitable for the transient running of a switched reluctance machine. The simulation results of current, torque and speed profile of SRM are produced under current chopping control and voltage pulse width modulation control. The proposed work has used experimental data of flux linkage and static torque in the mathematical model for best performance and control of the machine. The obtained simulation results are verified with experimental results. This model can be extended to a range of rotor position where the machine can be switched at decreased and increased inductance region which gives motoring and generating operation mode.