Proposed Pulse Width Modulation Technique Research Articles

A New Level Shifted Carrier Based PWM Technique for a Cascaded Multilevel Inverter Based Induction Motor Drive

The pulse width modulation (PWM) techniques are becoming the game changer for multi-pulse power converter fed multilevel inverter-based induction motor drive (IMD) due to their significant impacts on power quality. In this paper, a new level shifted carrier-based PWM technique is proposed for a 5-level cascaded H-bridge (CHB) multilevel inverter driven by a 36-pulse ac-dc converter based IMD. To meet the power quality demand of IEEE-519 at grid side, a modular transformer is used, and the transformer is coupled to form a 36-pulse ac-dc converter. A 5-level CHB multilevel inverter is utilized on the motor side, which uses the proposed carrier based PWM technique for switching action to ensure superior performance of the IMD. The proposed PWM technique is named as third-harmonic injected inverted sinusoidal carrier PWM (THI2SCPWM), which utilizes 3 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">rd</sup> harmonic injection principle with inverted sinusoidal signal to form the proposed carrier signal. The 5-level CHB inverter used in the IMD shows less power loss and total harmonic distortion (THD) with the proposed THI2SCPWM technique. Moreover, the IMD with the THI2SCPWM shows low stator voltage THD, stator current THD, and smooth dynamic response. Apart from these, the THI2SCPWM mitigates the torque ripple of the IMD. The motor drive system with the THI2SCPWM technique is modeled and its performance is simulated on MATLAB/Simulink environment. A scaled down experimental setup is utilized to validate the superiority of the proposed PWM technique.

An ampere‐second‐vector pulse width modulation technique and fault‐tolerant control for CSI11 fed five‐phase permanent magnet synchronous motor with multiple harmonic electromotive forces

AbstractWhen dealing with safety‐critical applications that involve multiphase permanent magnet synchronous motors (PMSMs), the current source inverter (CSI) is a superior choice compared with the voltage source inverter. The conventional technique of pulse width modulation (PWM) presents a challenge for CSI, particularly during faults. The fault‐tolerant control of multiphase PMSMs fed by CSIs has not been well investigated, particularly in situations involving double‐phase open‐circuit faults. Furthermore, fault‐tolerant control becomes more complex when the multiphase PMSM includes harmonic back electromotive forces (EMFs). To deal with these issues, an ampere‐second (AS) vector PWM technique is developed for a five‐phase PMSM powered by CSI11. The modulation ratio of the proposed PWM is identical to that of space vector PWM. The proposed method, however, is easier to implement. A fault‐tolerant control method using AS‐vector is proposed for single‐phase, adjacent double‐phase, and non‐adjacent double‐phase open‐circuit faults. Additionally, a method is developed to suppress the torque ripple that results from harmonic back‐EMFs during fault conditions. Compared without the torque ripple suppression method, during the speed rising, the proposed method can reduce torque ripple to 16.7%, 54.5%, and 37.5%, respectively. The experiments have confirmed the effectiveness of the proposed PWM technique and fault‐tolerant control method.

Optimal PWM in Three-Level Inverter for THD Minimization with Quarter Wave Symmetry Relaxed

Background: Previous works on total harmonic distortion (THD) minimization for multilevel inverters (MLI’s) has made a symmetrical approach that imposes Quarter Wave Symmetry (QWS) and Half Wave Symmetry (HWS) with the aim to restrict the computational difficulties to solve the finalized non-linear expressions. Objective: However, QWS constraint can be abolished, which leads to more generalized formulations and multiple solutions corresponding to minimum THD for complete modulation index-range. Methods: A systematic search approach using MATLAB in-build function is adopted to investigate ideal angles of switching related to three-level, three-phase inverter restricted to only HWS as a constraint for two and three (i.e., N= 2 and 3) switching transitions per quarter cycle. Results: On account of the effective minimization of the dominant low-order odd line voltage harmonics, the proposed pulse-width-modulation (PWM) scheme proved its superiority based on minimum THD% performance compared to the previously reported PWM techniques with both HWS and QWS being retained. Conclusion: The simulation, as well as experimental results to confirm the efficacy of the proposed non-symmetrical PWM scheme over the traditional PWM method restricted to QWS and HWS symmetries over the entire modulation-index range with added advantage of general formulation and multiple solutions.

A Modified Reference Saturated Third Harmonic Injected Equal Loading PWM for VSC-Based Renewable Energy Systems

Mitigation of excessive heat due to high frequency switching of voltage source converter (VSC) is always an industrial concern for superconducting magnetic energy storage (SMES) or high temperature superconducting (HTS) material based power conditioning system with grid-tied renewable energy interface. The pulse width modulation (PWM) technique employed for the switching of the VSC has a significant impact on joules heating, switching and conduction power losses, total harmonic distortion (THD) profile of the VSC output, and conversion efficiency in the SMES/HTS based grid-tied power system. In this paper, a modified reference saturated third harmonic injected equal loading PWM technique is proposed for a VSC-based grid-tied photovoltaic (PV) system, which offers lower THD and reduced power conversion losses. The proposed PWM technique employed in the VSC can be used in a PV-based SMES/HTS integrated power system to improve the performance of the power conditioner. To prove the superiority of the proposed PWM technique, a simulation in MATLAB/Simulink was carried out and the simulation results were validated by laboratory tests.

A Five-Level Converter in a Three-Level Mode for Common-Mode Leakage Current Suppression in PV-Generation Systems

Power generation systems (PGSs) based on renewable energy sources are finding ever-widening applications, and many researchers work on this problem. Many papers address the problem of transformerless PGSs, but few of them aimed at conducting research on structures with multilevel converter topologies as part of a PGS. In this paper a grid-tied transformerless PV-generation system based on a multilevel converter is discussed. There are common-mode leakage currents (CMLCs), which act as a parasitic factor. It is also known that common-mode voltage is the main cause of the common-mode leakage current in grid-tied PV-generation systems. This paper considers the space vector pulse-width modulation (PWM) technique, which is used to suppress or reduce common-mode leakage current. The proposed PWM technique with the reduction of common-mode leakage current for a generation system based on the multilevel converter controlled with a PWM technique was verified experimentally. The experimental results accurately confirmed the mathematical model and the compensation achieved without errors. In the experiment, there was an approximately six-fold decrease in the common-mode leakage current (10.3 mA in rejection mode and 61 mA in non-rejection current). This can lead to the elimination of CMLC in a multilevel semiconductor converter only by changing the modulation mode. This suggests the possibility of using these devices as part of transformerless generation systems. Suppression of CMLC can only be carried out by changing the PWM algorithm. Both considered topologies can implement this mode of operation. The proposed converter has a higher efficiency up to a frequency multiplicity of 2000.

A novel PWM technique to eliminate common-mode voltage for single-phase three-level T-NPC inverter

This paper presents a new pulse width modulation (PWM) technique in order to eliminate common mode voltage for a single-phase full H-bridge T-NPC inverter. Three-level NPC inverters are commonly used in grid connected applications or as UPS backup power for industry. In addition to abilities such as to withstand high voltage, and reach output voltage and current with low harmonic distortion, three-level NPC inverter is advantageous for mitigating common mode voltage and leakage current. The new proposed PWM technique is based on the switching state table of the three-level H-bridge T-NPC inverter that containing many switching states with zero common mode voltage. Furthermore, implementation of PWM control for single-phase three-level T-NPC inverter configuration can decrease voltage stress on the output and reduce output voltage distortion compared with bipolar PWM control technique for two-level H-bridge inverter. In this paper, the sine wave carrier PWM technique is analyzed, designed and modelled based on the switching table. The analytical analysis will be evaluated using MATLAB/SIMULINK. Simulation results of the proposed PWM technique for three-level T-NPC inverter are compared with conventional techniques without common mode voltage elimination; the quality of the three-level T-NPC inverter is also compared to that of traditional two-level inverter. The power loss content is evaluated using PLECS software. The obtained results confirm the advantages of the eliminated common mode voltage PWM technique in the three-level T-NPC inverter configuration.

High Gain PWM Method and Active Switched Boost Z-source Inverter With Less Voltage Stress on the Devices

This article presents a new circuit topology for high voltage gain active switched boost quasi Z-source inverter (qZSI) and a pulsewidth modulation (PWM) technique. The higher boosting capability with a lower number of elements, the continuous source current, the less voltage stress across the devices, and having the common ground are the main advantages of the proposed structure. The voltage gain of the proposed inverter is twice that of the conventional capacitor-assisted qZSI (sCA-qZSI). Other benefits of the proposed inverter over the sCA-qZSI are the reduction of Z-source passive components and shoot-through current. Compared to the conventional active switched inductor boost qZSI, the proposed inverter has higher output voltage and also lower shoot-through current, while it has fewer components (one fewer inductor, two fewer diodes, but one more capacitor). The boost factor of the proposed inverter is more than twice that of the classic ones. Besides, a high gain PWM technique is proposed, which can be applied to any types of Z-source inverters. Both the simulation and experimental results of the proposed inverter under the proposed PWM technique are examined to validate their operation.

A Hysteresis Current Controller PWM Scheme Applied to 3-Level NPC Inverter for Distributed Generation Interface

In this article, a novel pulsewidth modulation (PWM) technique is proposed for an existing space vector hysteresis current controller (SVHCC) scheme. A three-level neutral-point-clamped (NPC) inverter is used for dual purpose of shunt active power filtering and solar photovoltaic (PV) power integration to a distribution grid. This dual-purpose NPC inverter utilizes the proposed PWM technique for solving the neutral-point voltage-balancing issue in a unique way. Due to the inherent advantages of the SVHCC, the current control is characterized by fast action and optimal switching. A single reference current required for both filtering and maximum PV power integration is generated using instantaneous power theory, where a diode bridge rectifier load is considered to demonstrate the controller performance while compensating nonlinear current components. Thus, not only a unique space-vector-based PWM technique is adopted for fast-tracking of currents, but also a sliding current error boundary is used for the first time. This sliding technique tackles the dc-link balance issue of the NPC inverter while controlling the output currents simultaneously. The simulation and hardware results prove the aforementioned performance and demonstrate the efficacy of the proposed PWM current controller.

A New Modulation Technique to Improve the Power Loss Division Performance of the Multilevel Inverters

Multilevel inverters (MLIs) have offered significant contributions toward the implementation of energy conversion units used in industry and renewable energy applications. However, the switching devices in MLIs are associated with power loss division problems. The pulsewidth modulation (PWM) techniques greatly influence the peak, average, and ripple values of the device junction temperature. Thermal tension in the devices may be raised due to increased power loss caused by additional switching or uneven distribution of losses due to unbalanced gate pulses. Higher thermal stress accelerates the life degradation process of the power devices, and, eventually, leads to permanent damage of the MLI. Therefore, a new loss balancing two-pole clamped PWM technique for a single-phase MLI is proposed in this article. In the proposed PWM technique, in each half line cycle, symmetrical and equal duration of nonswitching zone is placed on the two reference signals alternately. Due to symmetrical and equal duration of clamping action, the unbalanced gate pulses become balanced after each half line cycle. The proposed technique extends the reliability of the power devices by improving the loss division performance and the junction temperature characteristics. Moreover, the reduction of neutral point potential swing reduces the output total harmonic distortion. The improved performance of the proposed technique is validated by simulation in MATLAB/Simulink and experimental results from downscale laboratory prototype test platform.

Dodecagonal Voltage Space Vector Based PWM Techniques for Switching Loss Reduction in a Dual Inverter Fed Induction Motor Drive

The dodecagonal space vector generation scheme eliminates the most dominant lower order harmonics fifth and seventh for the entire modulation range, thereby improving the quality of the output waveform and eliminates the sixth harmonic torque pulsations. By considering this advantage, a group of dodecagonal space vector pulsewidth modulation (PWM) techniques is proposed in this article. These techniques improve the harmonic profile of the output waveform further at higher modulation indices compared to conventional dodecagonal space vector PWM. In this article, a generalized closed-form expression for harmonic distortion of various dodecagonal space vector PWM schemes is derived and the analytical results are compared. The proposed PWM techniques are simulated in MATLAB/Simulink environment and validated experimentally on a laboratory prototype. Also, a detailed switching loss analysis for various dodecagonal space vector PWM schemes are obtained and it is shown that the proposed PWM techniques yield lower inverter switching power losses than the conventional scheme throughout the power factor range.

Voltage-Injected PWM Variants for a Dual Two-Level Inverter-Fed Open-End Winding Induction Motor Drive

In this article, three new pulsewidth modulation (PWM) methods are proposed for a dual-inverter-fed open-end winding induction motor (OEWIM) drive aimed at reducing voltage harmonic distortions in the inverter output. The proposed PWM variants are devised using appropriate voltage injection to the modulating signals. The proffered PWM variants for the dual inverter are analyzed through rigorous harmonic analysis to arrive at complete harmonic description using double Fourier integral approach (DFIA) to obtain their characteristics. For all the PWM variants, optimal values of voltage injection are also obtained, which yields lower voltage harmonics at the output of the dual inverter. The analytical solutions thus obtained are verified through simulations and experimental results, and the improved harmonic performance compared to the existing PWM techniques is also presented. Identifying the shortcoming of reduced limits of linear modulation of the proposed PWM techniques, a solution to smoothly slide-over to the phase-disposed PWM techniques is also demonstrated. Besides, the impact of the proposed PWM variants on improved motor current ripple and torque ripple performance when used with field-oriented control is presented and compared with some existing PWM methods to showcase their superior performance characteristics and also the usefulness of the envisaged PWM methods.

Enhanced Performance Modified Discontinuous PWM Technique for Three-Phase Z-Source Inverter

Various industrial applications require a voltage conversion stage from DC to AC. Among them, commercial renewable energy systems (RES) need a voltage buck and/or boost stage for islanded/grid connected operation. Despite the excellent performance offered by conventional two-stage converter systems (dc–dc followed by dc–ac stages), the need for a single-stage conversion stage is attracting more interest for cost and size reduction reasons. Although voltage source inverters (VSIs) are voltage buck-only converters, single stage current source inverters (CSIs) can offer voltage boost features, although at the penalty of using a large DC-link inductor. Boost inverters are a good candidate with the demerit of complicated control strategies. The impedance source (Z-source) inverter is a high-performance competitor as it offers voltage buck/boost in addition to a reduced passive component size. Several pulse width modulation (PWM) techniques have been presented in the literature for three-phase Z-source inverters. Various common drawbacks are annotated, especially the non-linear behavior at low modulation indices and the famous trade-off between the operating range and the converter switches’ voltage stress. In this paper, a modified discontinuous PWM technique is proposed for a three-phase z-source inverter offering: (i) smooth voltage gain variation, (ii) a wide operating range, (iii) reduced voltage stress, and (iv) improved total harmonic distortion (THD). Simulation, in addition to experimental results at various operating conditions, validated the proposed PWM technique’s superior performance compared to the conventional PWM techniques.

A Novel Zero-Sequence Current Elimination PWM Scheme for an Open-Winding PMSM With Common DC Bus

This paper introduces a novel pulsewidth modulation (PWM) scheme for an open-winding permanent magnet synchronous machine (OW-PMSM) driven by dual two-level three-phase inverter with common dc bus, which can effectively deal with the inherent zero-sequence current (ZSC) problem. Based on the conventional symmetrical unipolar double-frequency sinusoidal PWM scheme with an appropriate phase shift, the common mode voltage (CMV) of two inverters remains same and cancel out each other to eliminate the modulated zero-sequence voltage (ZSV) disturbance source. In this case, the double-frequency effect can be retained to reduce the ac side current ripple and suppress both corresponding motor vibration and acoustic noise, which is advantageous to improve the synthetic performance of motor. The dc-bus voltage utilization of the novel PWM scheme is proved to reach the same maximum value comparing to the conventional modulated ZSV elimination scheme. Meanwhile, a zero-sequence controller is designed to suppress ZSC by further adjusting the two CMVs to counteract other zero-sequence disturbance sources. To verify the analysis, the proposed PWM technique associated with the control method is implemented in an OW-PMSM experimental setup to validate the superiority of the proposed method.

An Instantaneous Power Balancing Technique for an Open-End IM Drive Using Carrier-Based Modulation for Vehicular Application

A multilevel drive can be realized by using an open-ended machine, fed from dual two-level inverters. The topology supplied from isolated dc sources is suitable for transportation electrification. In vehicular systems, it is essential that the isolated dc sources, comprising of battery packs, should discharge uniformly and maintain balanced dc voltage at the dc-link terminal. A simple carrier-based pulsewidth modulation (PWM) technique is presented in this paper, which can effectively regulate the power drawn between the two two-level inverters while maintaining the multilevel operation of the drive. The modulation technique can balance the instantaneous state of charge of independent battery packs and dynamically equalize the power flow from the two inverters, based on drive requirement. This will enhance the reliability of the propulsion system in electric vehicles. The operation of the proposed PWM technique has been validated through detailed simulation and experimental tests.

Optimized Switching PWM Technique With Common-Mode Current Minimization for Five-Phase Open-End Winding Induction Motor Drives

This paper presents a novel approach to derive a pulsewidth modulation (PWM) technique for the generalized multi-phase drive. This novel approach is called a phase traversing principle. The given phase traversing principle is applied to the proposed PWM technique for five-phase open-end winding induction motor drive fed from a single dc source. The proposed PWM technique has the benefits of phase clamping, symmetrical operation of inverters, and common-mode current (CMC) elimination. Thus, it reduces the switching losses and also minimizes the issue of the CMC. The symmetrical operation of dual inverters further helps in the even distribution of losses. Also, the proposed PWM technique gives a good harmonic performance. The performance of the proposed PWM technique is analyzed using the switching loss function and harmonic flux trajectory methods. The first analysis gives justification of the reduced switching losses. While the second analysis gives the deviations in the motor flux with respect to variation in. modulation indices The proposed PWM technique is verified with both simulation and hardware results.

Space vector PWM technique for a two‐level asymmetrical six‐phase drive

A space vector pulse-width modulation (PWM) technique for a two-level asymmetrical six-phase drive is proposed for the first time in this study. The PWM technique is developed based on the modified vector space decomposition approach. The details regarding the process of choosing the switching sequences and the calculation of dwell times are presented. The PWM technique is verified through simulation using PLECS software and is further validated experimentally. Obtained results show the validity of the proposed PWM technique.

PWM Switching Technique for Three-Phase Bidirectional Grid-Tie DC–AC–AC Converter With High-Frequency Isolation

Galvanic isolation based high-frequency transformers have become very attractive in bidirectional dc/ac converters. This paper presents a new pulse width modulation (PWM) switching technique for controlling a bidirectional isolated dc–ac–ac converter employing a high-frequency link transformer. The proposed PWM technique has the ability to control the input dc current and to inject a sinusoidal three-phase current to the grid at unity power factor. The primary-side is an H-bridge converter used to convert the dc voltage to a high-frequency square-wave single-phase voltage. The secondary side is a matrix converter used to convert the grid three-phase voltage to a high-frequency single-phase waveform. The dc–ac–ac converter utilizes a high-frequency link transformer for the galvanic isolation between the H-bridge and matrix converters as alternative for the bulky line-frequency transformers (50/60 Hz). The bidirectional power flow is controlled by the phase shift angle between the primary and secondary voltages of the high-frequency transformer. The mathematical model and the circuit operational modes are presented along with the voltage controllable limit. The feasibility of the proposed PWM switching technique and the accuracy of the mathematical model are demonstrated experimentally by using a 200 V/1 kW laboratory prototype system.

Soft-Switching PWM Technique for Grid-Tie Isolated Bidirectional DC–AC Converter With SiC Device

Soft-switching techniques have become very attractive in bidirectional grid-tie dc–ac converters utilizing high-frequency link transformers for galvanic isolation. This paper presents a new pulse-width modulation (PWM) switching technique for controlling a bidirectional isolated dc–ac–ac converter along with its soft-switching method. The proposed PWM technique has the ability to control the input dc current and to inject a sinusoidal three-phase current to the grid at unity power factor. In the first stage, an H-bridge converter is used to convert the dc voltage to a high-frequency square-wave single-phase voltage. In the second stage, a matrix converter is used to convert the high-frequency voltage waveform to conventional three-phase voltage synchronized with the grid. Therefore, a single-phase high-frequency transformer is used to link the H-bridge output voltage to the matrix converter input voltage. The proposed soft-switching technique is achieved by connecting shunt ceramic capacitors across all converter switches. The mathematical model and the circuit operation for soft-switching are presented along with the voltage controllable limits. The effectiveness of the proposed technique has been verified experimentally using a laboratory prototype.

Space vector based random pwm algorithms for acoustic noise and harmonics reduction for voltage source inverter fed ac drive

Conventional Space vector based Pulse Width Modulation (PWM) method is superior to Sinusoidal PWM technique in terms of its better DC bus utilization as well as harmonic reduction. But it doesn’t give solution to reduce acoustic noise which is more annoyance to the driver and the passenger or the human beings in certain applications such as electric propulsion or accessory drives. This paper presents space vector based random PWM techniques - a solution to reduce the acoustic noise as well spread spectrum resulting in low harmonic distortion as suppression of peak sound pressure levels. The techniques employed for a VSI fed Induction motor drive are 1) Random Zero vector PWM 2) Dual Zero Random PWM and 3) Variable Delay Random PWM. The spectrum plots of stator current demonstrate the effectiveness of the proposed PWM techniques. The feasibility of the proposed PWM techniques has been confirmed in terms of acoustical noise and harmonic distortion is presented in this paper.

A Highly Efficient and Reliable Inverter Configuration Based Cascaded Multilevel Inverter for PV Systems

This paper presents an improved cascaded multilevel inverter (CMLI) based on a highly efficient and reliable configuration for the minimization of the leakage current. Apart from a reduced switch count, the proposed scheme has additional features of low switching and conduction losses. The proposed topology with the given pulse width modulation (PWM) technique reduces the high-frequency voltage transitions in the terminal and common-mode voltages. Avoiding high-frequency voltage transitions achieves the minimization of the leakage current and reduction in the size of electromagnetic interference filters. Furthermore, the extension of the proposed CMLI along with the PWM technique for 2 m + 1 levels is also presented, where m represents the number of photovoltaic (PV) sources. The proposed PWM technique requires only a single carrier wave for all 2 m + 1 levels of operation. The total harmonic distortion of the grid current for the proposed CMLI meets the requirements of IEEE 1547 standard. A comparison of the proposed CMLI with the existing PV multilevel inverter topologies is also presented in the paper. Complete details of the analysis of PV terminal and common-mode voltages of the proposed CMLI using switching function concept, simulations, and experimental results are presented in the paper.