Wide Range Of Modulation Index Research Articles

Mitigation of common mode voltage in ultra sparse matrix converters using auxiliary shoot‐through switches for wind energy systems

SummaryThis paper targets to minimize the peak common mode voltage (CMV) in ultra sparse matrix converters (USMC) by applying new zero vectors for the space vector modulation technique (SVM). Conventional zero vectors in the SVM raise the peak CMV by 42.23%. An increased magnitude of CMV is associated with the occurrence of leakage current, hence resulting in insulation degradation. So, the reduction of peak CMV is necessary for USMC. The proposed method offers suitable switching arrangements using auxiliary shoot through (AST) switches to minimize the peak‐to‐peak CMV. This proposed method holds the advantages of the conventional method, like a wide range of modulation index and zero current switching at the rectifier side, and also reduces the CMV problem. This paper also provides a comparative analysis of the existing reported methods and the proposed method. The effectiveness of the proposed method is validated through both simulation and experimental results.

Integrated Voltage Vector–Based SVPWM for Reliability and Performance Enhancement of Five-Level HANPC Inverters

Power converters are designed to operate over a wide range of voltages to meet various industrial demands. Recently, multilevel inverters have been receiving considerable attention owing to their ability to reduce the current ripple and its associated harmonic distortion. However, for applications requiring high voltage/power ratings, large electrolytic capacitors are essential, which are significantly affected by the ripple in the DC-link current. This causes a significant reduction in the lifespan and reliability of the power converter and necessitates expensive diagnosis and maintenance procedures. Therefore, an effective method of integrated voltage vector-based space vector pulse-width modulation is proposed in this study for minimizing the ripple in the DC-link and common-mode voltage of five-level hybrid active neutral-point-clamped (5L-HANPC) inverters. The proposed method uses a unique control algorithm that can smoothly select the required voltage vectors without a noticeable distortion in the output current waveforms. Moreover, the proposed method can be applied without modifying the original topology of the 5L-HANPC inverter or adding complex compensations to the control algorithm. Extensive simulation and experimental results are provided to demonstrate the capability of the proposed approach to reduce the DC-link current ripple over a wide range of modulation indices.

PSO-Optimized SHE-PWM Technique in a Cascaded H-Bridge Multilevel Inverter for Variable Output Voltage Applications

One of the problems of the selective harmonic elimination pulsewidth modulation (SHE-PWM) method is a limited range of feasible solutions. In many practical applications, the inverter is required to produce a variable output voltage within a wide range (e.g., 0.1 to 1). When the inverter operates in a low modulation index (low output voltage), the output harmonic distortion increases. This article introduces a method to use the SHE-PWM technique for a wide range of modulation indices, which allows achieving a high-quality output waveform in a cascaded H-bridge multilevel inverter. In a five-level case, a dc–dc converter regulates the dc-link voltage of only one bridge. In this way, the extra hardware requirement is reduced, and also a higher number of voltage levels is achieved, which improves the waveform quality. The particle swarm optimization algorithm is used to solve the SHE problem for different output voltage values. Two strategies are proposed to obtain the variable dc-link voltage; one of them is suitable for the lower output voltage values and the other one is more suitable for high values of the output voltage. The proposed strategies have been tested through simulation and experimental studies in different conditions. The results indicate a considerable improvement in the output waveform quality.

A single source based multilevel boost inverter with reduced peak standing voltage for renewable energy and EV applications

This paper introduces a nine-level (9L) boost inverter topology with reduced peak standing voltage (PSV) across the switches. The topology consists of a single DC source, two capacitors, a switched-capacitor (SC) and a floating capacitor (FC), and eleven power electronics switches. Due to the inherent voltage boosting capability, the proposed inverter is suitable for low-scale voltage applications such as photovoltaic (PV), fuel cell, and single battery-operated electric vehicles (EVs). A sensorless approach is introduced to stabilize the requisite voltage across the FC for any changes in input voltage. A generalized topology is also presented to obtain n-times voltage gain along with a high number of intermediate voltage levels. The PSV of the switches does not exceed the value of the input DC voltage, irrespective of increase in voltage gain. The results show that the voltage across the FC is unaffected by stepped variations in the modulation indices, power factor of load, pulse width modulation (PWM) techniques, and the operating frequency. Furthermore, when the input voltage changes, the voltage across the FC is automatically adjusted to a new requisite value within 0.6s. The topology works for a wide range of modulation indices (0–1) and loads. A thorough analysis is done to show that the proposed topology is superior to recent topologies.

A switched-capacitor and floating-capacitor (SCFC) based multilevel boost inverter with a single DC power supply and sensor-less voltage balancing method

This paper introduces a nine-level (9L) boost inverter with reduced number of components. The proposed 9L topology comprises a single DC source, eight switches, and two capacitors, namely a switched-capacitor (SC) and a floating capacitor (FC). The topology consists of two converter units: the SC unit and the FC unit. Both units are cascaded to achieve nine voltage levels with a voltage gain of 2. The inherent voltage boosting capability of the proposed topology makes it suitable for low-scale voltage applications like photovoltaics (PV) and electric vehicles (EVs). A sensorless method is introduced to stabilize the requisite voltage across the FC for any undesirable changes in input voltage. The performance reveals that the voltage across the FC does not deviate with changes in the modulation index, power factor of load, pulse width modulation (PWM) methods, or the operating frequency. And, when the input voltage fluctuates, the voltage across the FC is naturally adjusted to the new desired value within 0.6 s. The topology operates over a wide range of modulation indices (0 to 1) and different types of loads. A generalized topology is also developed to get a high output voltage along with a higher number of intermediate voltage levels. A comprehensive analysis is presented to show the effectiveness of the proposed topology over the recent topologies.

Space Vector PWM Based DTC Scheme With Reduced Common Mode Voltage for Five-Phase Induction Motor Drive

In multiphase induction motor drives, lowering the common-mode voltage (CMV) reduces motor insulation degradation and the existence of destructive bearing current. For this investigation, a five-phase two-level voltage source inverter (FPTL-VSI) fed five-phase induction motor (FPIM) drive is used. FPTL-VSI produces increased CMV, which cannot be totally removed. Moreover, CMV can be reduced by 80% in contrast to its peak-to-peak value with suitable selection of small and large voltage vectors in a space vector pulsewidth modulation (SVPWM) scheme. Direct torque control (DTC) combined with the SVPWM scheme can accomplish such reduced CMV performance at constant switching frequency. To provide better speed and torque control, two virtual vector (VV) based SVPWM-DTC (DTC1 and DTC2) methods are proposed in this study. Over a wide range of modulation index, the influence of each voltage VV on motor drive speed and torque response is investigated. The proposed DTC1 and DTC2 schemes are validated under steady-state and dynamic conditions over a wide range of speed fluctuations using a high-power laboratory prototype of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$3.8\,\text{{k}W}$</tex-math></inline-formula> FPIM drive. The efficacy of the proposed DTC1 and DTC2 is compared to the current literature by evaluating the effectiveness of CMV and the switching frequency.

A novel nine‐level boost inverter with a low component count for electric vehicle applications

In electric vehicles (EVs), considerable battery cells are cascaded in series for motor driving to improve the output voltage. The series combination of battery cells causes challenges like isolation of faulty cells, voltage unbalance, and slow charge equalization. Therefore, state-of-charge (SOC) and voltage equalization circuits are often used in industries to protect the battery cells. A nine-level inverter circuit with a double voltage boost is proposed to reduce the above issues based on the switch-capacitor (SC) principle. Unique features like self-balancing, voltage boosting are attained, which cannot be achieved through traditional inverters. The proposed topology can operate at a wide range of modulation indices () to produce different voltage levels. The absence of a back-end H-bridge in the proposed circuit offers low voltage stress across the semiconductors. The operating principle, capacitor sizing, and modulation approach are presented. Further, experimental tests are conducted at different loading conditions to verify the performance of the proposed circuit.

Analysis and Simulation of a Single Phase Nine Level Inverter with Reduction in Power Switching Devices

This paper present analysis and modelling of single phase nine level inverter, a Wide range of Modulation index (M) varied between 0.05-1.05 is achieved by two switching strategies (Optimized harmonic stepped waveform (OHSW), (Optimal minimization of total harmonic distortion (OTHD)) the first strategy focusses on harmonic elimination and the other on reducing output voltage total harmonic distortion (THD). Calculation of switching angles for both equal and unequal dc sources is done by Genetic Algorithm (GA). simulation in Matlab, PSpice and PSIM is presented in this work.

A Voltage Balancing Scheme for Modular Multilevel Converter Based on Charge Variation in Each Cycle

This article presents a voltage balancing scheme for a modular multilevel converter (MMC) based on capacitor charge variation in each fundamental cycle. An in-depth theoretical analysis of stored charge variation for the concept is described. A new hybrid pulsewidth modulation (PWM) sequence is proposed based on a rotation strategy to achieve capacitor voltage balancing without sensing the capacitor voltages or arm currents. The rotation strategy provides the freedom of finding the best possible sequence to achieve capacitor voltage balancing. This reduces hardware, software burden and overall cost of the design implementation. The functionality and performance of the balancing strategy with new hybrid PWM sequence are carried out over wide range of modulation index (M) for three-phase five-level MMC in MATLAB/Simulink. A hardware prototype of single-phase five-level MMC is designed for experimental validation. The proposed hybrid PWM sequence is implemented on an Altera/Cyclone I series (EP1C12Q240C8N) field-programmable gate array using alternate phase opposition disposition PWM method. Simulation and experimental results are presented.

Optical millimeter-wave generation via frequency octupling circuit based on two parallel dual-parallel polarization modulators

In this paper, a filterless optical millimeter-wave (mm-wave) generation by frequency octupling based on two parallel dual-parallel polarization modulators circuit is proposed. From the theoretical analysis, ± 4th order optical sidebands can be generated by proper adjustment of the phases of the radio-frequency (RF) drive signals and polarizer angle. Since there is no need for an optical filter to suppress the optical carrier or unwanted harmonics, the system is suitable for the optical generation of highly stable and tunable mm-waves. Theoretical analysis is verified by computer simulation. From the obtained results, it is shown that the optically generated mm-wave signal from the proposed circuit has a high optical sideband suppression ratio (OSSR) and radio-frequency spurious suppression ratio (RFSSR) for a wide range of modulation index. This range of modulation index extends, theoretically, from 1.8 up to 7.3. For instance, at a modulation index of 5.318, an 80 GHz can be generated from a 10 GHz RF drive signal with an OSSR of 68.4 dB and an RFSSR of 62 dB. Furthermore, the effects of non-ideal system parameters on the OSSR and RFSSR are investigated.

Classical Control for Unequal DC Sources Five-Level Inverter-Based SHE Technique

This study proposes a classical control algorithm for solving the transcendental set of equations for the unequal DC sources of five-level multilevel inverters (MLIs). Such sources can be generated from renewable energy sources. Two DC sources with different values are used to produce an output voltage with five levels. Then, a set of two transcendental equations is formulated with two targeted functions to control the fundamental component and cancel the stipulated single harmonic order. The proposed solution uses a simple classical proportional control with two loops to generate two switching angles. The first switching angle is assigned with an initial value, whereas the second one is calculated from the inner loop. The outer loop is used to cancel the specified harmonic by sending the error signal to the proposed proportional control that tunes the switching angles. The proposed algorithm is easy, fast, and accurate, and has a wide-range solution in terms of modulation index (MI ) and input DC source ratio (x=V1V2≤1). The proposed algorithm is tested for a wide range of MI and x to verify its feasibility. Moreover, several simulation and laboratory tests are presented to further validate the applicability of the proposed approach.

Discontinuous Space Vector Modulation Schemes for Modular Multilevel Converters

In this article, a new, simple, and generalized discontinuous pulse width modulation (PWM)-based submodule capacitor voltage balancing approach is proposed and generated within the carrier-based PWM for modular multilevel converters (MMCs). In this scheme, different variants of zero-sequence voltage (ZSV) component is injected into the pulse width modulator so that each arm of the MMC is virtually clamped to positive or negative dc bus during a specific interval to achieve discontinuous modulation. A simple approach based on the location of the voltage vector mapping to a two-level space-vector diagram is presented to determine various ZSV components. The effectiveness of the proposed scheme with a voltage balancing algorithm is demonstrated through PLECS simulations and experimentally verified using a hardware-in-the-loop-based system. The performance of MMC with different ZSV injections is holistically evaluated to determine the best possible sequence over a wide range of modulation index.

Mathematical proof of a harmonic elimination procedure for multilevel inverters

In this paper, a single phase cascaded H-bridge inverter with s variable dc sources (s≥2), l=2s+1 levels has been considered. A mathematical proof is presented to demonstrate that, under a particular choice of the switching angles, which number corresponds to the number of dc sources i.e. s, and of the dc voltages, all harmonics are eliminated from the output voltage waveform, except those of order n=4p⋅s±1, p=1,2,… . With this method, the dc voltage sources vary linearly according to the modulation index m, while the switching angles do not depend on m. The resulting output voltage has low total harmonic distortion, that remains independent on m. Compared to a conventional selective harmonic elimination procedure and to a pulse amplitude method, the proposed procedure reduces distortion in a wide range of modulation index.

A Seven-Level Inverter With Self-Balancing and Low-Voltage Stress

Based on the switched-capacitor (SC) principle, a seven-level inverter is proposed, which can synthesize seven levels containing a single dc source. Moreover, it can further generate more levels by a cascaded extension. Meanwhile, the proposed topology does not require any sensor due to the use of SC technology. Furthermore, the capacitor voltage is self-balanced without utilizing the complicated control strategy and additional control circuits. The phase disposition pulsewidth modulation is adopted to reduce the total harmonic distortion. The topology can generate different levels with a wide range of modulation index. In addition, the topology can also work in overmodulation. Compared with the traditional SC multilevel inverter, the absence of H-bridge makes low-voltage stress in proposed topology. The voltage stress of all switches is not more than the input voltage. Operational principles, modulation strategy, and voltage stress analysis are discussed. Simulation and experiment are conducted in low power to verify the feasibility of the proposed topology.

A Modified Finite Control Set Model Predictive Control for 3L−NPC Grid−Connected Inverters Using Virtual Voltage Vectors

In order to improve the performance of a 3−level neutral point clamped (3L−NPC) grid−connected inverter with finite control set model predictive control (FCS−MPC), this paper proposes a modified FCS−MPC algorithm based on the rearranged control set (MFCS−MPC). By adding synthetic virtual voltage vectors to rearrange the finite control set (FCS) of the 3L−NPC inverter, the frequency spectrum of output leg voltage becomes concentrated, which is benefited for decreasing total harmonic distortion (THD) of grid currents and makes it easier to design output filters for the grid−connected inverter. Moreover, based on switching state sequences of virtual voltage vectors, the modified predictive model of the proposed method is established considering capacitor voltage difference. Besides, according to the location of the reference output voltage vector, a preselection step is incorporated into MFCS−MPC to narrow the control set for predictions, which avoids evaluating all candidate voltage vectors in the control set, and hence, the online computational burden is significantly reduced. A prototype of 3L−NPC grid−connected inverter is established to validate the proposed MFCS−MPC method and the experimental results show that this method has excellent static and dynamic performance, with a low THD for a wide range of modulation indexes.

A full-duplex 40 GHz radio-over-fiber transmission system based on frequency octupling

A 10 Gbps full-duplex 40 GHz radio-over-fiber (RoF) communication system is presented in this paper. A 5 GHz input Radio Frequency signal is octupled to 40 GHz using cascaded parallel Mach–Zehnder modulators (MZMs) operating at lower modulation index (m) range of 2.5–3.5. The ROF transmission system employs symmetrical inline dispersion compensation technique using tDCF and frequency re-use concept for upstream transmission. Full-duplex transmission distance of 180 kms can be achieved with quality factor (Q) ≥ 7 for wide range of modulation index (2.5–3.5) of MZMs, reflecting that system is tolerant to biasing variations. The transmission length can be increased to 210 kms for relatively reduced modulation index range of 3.2–3.5.

Improvement of power utilisation capability for a three‐phase seven‐level CHB inverter using an improved selective harmonic elimination–PWM scheme by sharing a desired proportion of power among the H‐bridge cells

An improved selective harmonic elimination-pulse width modulation (SHE-PWM) scheme has been proposed for a three-phase seven-level cascaded H-bridge (CHB) inverter that enhances the power utilisation capability of the inverter by sharing the desired amount of power among the H-bridge cells and also eliminates both 5th- and 7th-order harmonic components from the inverter output voltage maintaining the desired fundamental voltage component for a wide range of modulation index. Compared to conventional SHE-PWM, this scheme introduces two additional switching in the first cell, while the second and the third cells are switched at advanced switching angles. The differential search algorithm (DSA) technique has been applied to solve the proposed SHE-PWM scheme, and it exhibited comparatively better performance than the algorithm based on genetic algorithm, BEE algorithm and particle swarm optimisation. The effectiveness of the proposed scheme has been verified by both simulation and experimental study on a seven-level CHB inverter. Finally, the proposed scheme has been applied to the closed-loop constant V/f control of the induction motor drive application. It has been established that the proposed scheme is independent of the load power factor angle, and it improved the power conversion efficiency of the conventional SHE-PWM scheme.

General Mathematical Solution for Selective Harmonic Elimination

This article proposes a general mathematical solution for a selective harmonic elimination (SHE) technique. The proposed procedure is valid for both symmetrical and unsymmetrical multilevel inverter (MLI) inverter configurations with a wide range of modulation indexes (mi). The proposed procedure eliminates the targeted number of harmonics “ $l$ ” for switching angles $\text {NS}= 2^{l}$ regardless to the MLI output waveform levels. The proposed procedure receives the values and ratios of the dc sources, and then, it calculates the NS values to generate a suitable set of harmonic equations. In this proposed algorithm, the nonlinear transcendental harmonic equations were transformed into a linear system of equations ( $A X=B$ ); the resulting equations can be solved online easily by formulating matrix A and matrix B and then multiplying the inversion of matrix A by matrix B. It has been found that only the last element in matrix B needs to be updated for each change in the modulation index or in the ac output fundamental component, resulting in reduced computation time. The proposed technique generates the switching angles $\alpha _{1}, \alpha _{2}, \ldots, \alpha _{k}$ based on a preset objective functions. The simulation and experimental results in some selected cases are provided to validate the proposed algorithms.

A dual-mode cascaded H-bridge multilevel inverter for improving THD

Conventionally, multilevel inverters utilise multi-carrier pulse width modulation or multi-stepped (staircase) modulation to produce high-power quality waveforms. Though multi-carrier modulation schemes reduce total harmonic distortion (THD), they lead to considerable switching loss at higher modulation indexes. The staircase modulation, which operates at low switching frequencies, has a limitation of excessive high THD at low modulation indexes, making it unsuitable at lower modulation indexes. The proposed modulation technique blends the advantages of multi-carrier pulse width modulation and staircase modulation to improve the THD and reduce the switching losses over a wide range of modulation indexes. The proposed multilevel inverter employs a modified level-shifted multi-carrier modulation at lower modulation indexes and shifts to sinusoidally approximated multi-stepped at moderate and higher modulation indexes. The carrier frequency of the multi-carrier modulation is varied according to the switching loss analysis to further enhance the THD. A 1 KW prototype was built to confirm the practicality of the proposed method.

Filterless frequency octupling circuit using dual stage cascaded polarization modulators

ABSTRACTThis paper demonstrates the photonic generation of millimetre-wave carriers by frequency octupling of a radio frequency (RF) carrier using a circuit with two parallel arms each containing two polarization modulators in series. The low RF drive power required and the absence of optical filters make this architecture suitable for generating highly stable and tunable optical millimetre-waves. A transfer function representation is used to analyse the operation and a simulation using Virtual Photonic Inc. software package is presented as a proof of concept. The simulation results show very high unwanted optical and electrical side harmonic suppression ratio for a wide range of modulation index compared to the prior art. Further, considering the practical scenario, operating tolerance against the imbalances in the key parameters is established. The unwanted RF sidebands are more than 19 dB and 30 dB below the desired signal power even when a deviation of ±3° is considered in individual RF phase and polarizer angle respectively.