A modified nearest level control scheme for a double star chopper cell modular multilevel converter for operation at lower values of amplitude modulation index

In this article, the comparison of large signal theory and small signal theory has been done with dispersive propagation of optical signal with IMDD (Intensity Modulation Direct Detection) systems for semiconductor lasers with higher-order dispersion terms. The expressions for an exact large signal theory and small signal theory including higher-order dispersion terms for propagation of an optical wave with sinusoidal amplitude and frequency modulation in a dispersive fiber have been derived. It is observed that small signal theory is more sensitive compared to large signal theory in terms of intensity modulation/direct detection systems. Also, it is reported that for large signal analysis the higher-order effects of dispersion can be ignored, whereas for small signal theory, the higher-order effects can be ignored for lower modulation frequencies only. The variation in the transfer function for various values of modulation indices are greater for small signal analysis than for large signal analysis. Also, as the intensity modulation index is increased, there is a decrease in the value of transfer function. The large signal model approximates the small signal model for lower values of the intensity modulation index.

This paper proposes an offset voltage control scheme for the modular multilevel converter (MMC) operated in nearest level control (NLC) to improve the total harmonic distortion (THD) of AC phase voltages. Through the offset voltage control, the magnitude of each AC pole voltage maintains constant value with N+1 level in the range of whole modulation index (MI). The validity of the proposed scheme was confirmed by computer simulations for the MMC with 22.9kV/25MVA and experimental works for the scaled MMC with 380V/10kVA. It was confirmed that the proposed control scheme can generate constant pole voltages regardless the value of MI, and form phase voltages with improved THD.

This paper proposes a Dynamic Discontinuous PWM (DDPWM) strategy for Grid Tied Inverter applications utilizing 2 level Voltage Source Inverters (VSIs). DDPWM is a version of Generalized DPWM (GDPWM) optimized for usage with full range of operating power factor values and without need for current feedback signals, such that it provides minimal switching loss. Switching and Conduction Loss expressions are derived, simulated and analyzed for individual transistors and diodes inside inverter module. Simplified thermal model based on available datasheet parameters is presented and used for evaluation of thermal performance of semiconductor devices under DDPWM across full range of power factor and modulation index values. It is demonstrated that high modulation index and low power factor values produce highest overall module losses, but that the individual device temperatures are dependent on module forward and switching characteristics, as well as thermal resistances. Experimental setup is implemented to evaluate thermal performance of DDPWM.

Comparative Analysis of NR and TBLO Algorithms in Control of Cascaded MLI at Low Switching Frequency

Epilepsy, a chronic neuropsychiatric brain disorder characterized with recurrent seizures, is closely associated with abnormal neural communications within the brain. Despite that the phase-amplitude coupling (PAC) has been suggested to offer a new way to observe neural interactions during epilepsy, however, few studies pay attention to alterations of the epileptic functional brain network based on PAC, especially on the [Formula: see text] PAC. Therefore, we use scalp electroencephalography (EEG) data of epileptic patients and the [Formula: see text] PAC modulation index (MI) to construct functional brain networks to examine variations of neural interactions during different epileptic phases. Statistically, the findings show that between-channel MI values in the post-ictal period significantly increase compared to that in the pre-ictal period, and the between-channel MI value has a close association with the information of phase and amplitude provided by the channels. Importantly, in both the phase-amplitude and amplitude-phase functional brain networks, the average node degree is remarkably higher in the post-ictal period than that in the pre-ictal period, whereas the characteristic path length in the ictal and post-ictal periods is significantly lower than that in the pre-ictal period. Besides, the average betweenness centrality in the post-ictal period is remarkably higher than that in the ictal period. Interestingly, the positive correlations between within-channel MI values and between-channel MI values can be observed during the pre-ictal, ictal and post-ictal periods. These findings suggest that the [Formula: see text] PAC-based functional brain network may provide a novel perspective to understanding alterations of neural interactions during the epileptic evolution, and may contribute to effectively controlling the spread of epileptic seizures.

The adoption of an efficient approach for tuning inertia weight is one of the most effective methods of improving the performance of particle swarm optimization (PSO). Recently, the introduction of the modulation index in the nonlinearly decreasing inertia weight enhances the convergence characteristics of PSO. Economic load dispatch (ELD) is a famous optimization problem, and it is effectively solved by PSO with certain advantages. In this paper, influences of modulation index on PSO have been presented for ELD problem of IEEE 5, 14, and 30 bus systems. The minimum, maximum, average, and standard deviation of generation cost, average power loss, average iteration, and average computational time of 20 trial runs for ten different values of modulation index are computed using MATLAB program. The simulation results conclude that the value of modulation index 0.8, 0.4, and 1.8 provides high-quality solutions for IEEE 5, 14, and 30 bus systems, respectively.

Particularly, the control of multilevel inverters at medium voltage and higher power levels have technical challenges like higher switching losses and high %THD. Control of multilevel inverters at low switching frequency is highly desirable at higher power levels and this can be achieved by Selective Harmonic Elimination (SHE) technique. Solving the non-linear transcendental SHE equations set at various values of modulation index as to attain feasible values of switching angles to control MLI is quite complex which involves a lot of computational effort. In order to interface DC source solar panels using SHE technique is quite complex because the solar panels may give slight variation in the output voltage. To find feasible switching angles as to control the MLI is a challenging task while in particular handling with unequal DC sources. In this paper, Modified Species based PSO algorithm has been used to find the optimum switching angles which are formed in control of three-phase CHB 7-level inverter with unequal dc sources by using selective harmonic elimination technique. MATLAB programming and SIMULINK environment have been used to validate the proposed approach. This research work enlightened, the %THDs obtained at various values of modulation indices are better and complies with IEEE 519-1992 harmonic guidelines too.

The electric vehicles (EVs) operated from induction motor need clean, harmonic free AC supply for efficient operation, also the fault tolerant operation of inverter gives additional reliability to EV system. This paper presents a fault tolerant multilevel inverter for EV application. The harmonic profile of output voltage generated by fault tolerant T-type cross-connected source (TTCCS) inverter depends upon the value of gain for nearest level control (NLC) technique and modulation index for phase opposition disposition sinusoidal pulse width modulation (PODSPWM) technique. This paper presents the application of particle swarm optimization (PSO) algorithm to select the optimal gain for NLC technique and modulation index for PODSPWM technique to operate the nine-level (9L) symmetric fault tolerant TTCCS inverter with better harmonic profile. The presented simulation work is carried out in R2017b version of MATLAB. With the application of PSO, optimal value of gain and modulation index is calculated.KeywordsEV applicationFault tolerant control (FTC)Nine-level (9L) inverterParticle swarm optimization (PSO)T-type cross-connected source (TTCCS) inverter

The paper proposes a new topology named Improved Current Fed Switched Inverter which is derived from the current fed switched inverter. The new topology improves the value of modulation index from its previous topology where the value of modulation index was restricted. The improved current fed switched inverter is suitable for the renewable applications as it draws continuous input current. This paper describes about the inverter for the UPS application. Pulse width modulation (PWM) control strategy is used for the proposed inverter. The MATLAB/ SIMULINK is used to simulate the inverter and the performance parameters are also presented in this paper.

The parallel-hybrid converter (PHC) is a promising high-power topology. Smaller capacitor size, lower capacitor and switch counts, and low-energy storage requirement are some of its important features. However, it requires a large dc-filter inductor to filter the dc-side harmonics. Moreover, since its dc and ac sides are strongly coupled, only a single stable operating point in terms of a fixed modulation-index (MI) value is possible. Even with an additional dedicated control effort, the obtained MI variation remains still limited. This article proposes the PHC-static compensator (STATCOM) configuration that eliminates the dc-filter inductor requirement and can also operate at any MI value without necessitating additional control efforts. A detailed power analysis of the PHC-STATCOM for balanced and unbalanced grid conditions (UGCs) is performed in this article. A new control technique for PHC-STATCOM is proposed, which effectively balances the capacitor voltages of its chain-links even during UGCs. The energy storage requirement of PHC-STATCOM is evaluated to obtain the capability curve and determine its capacitor size. The PHC-STATCOM is compared with the popular STATCOM configurations in terms of the capacitor and switch counts. The proposed principles of PHC-STATCOM for several three-phase balanced and UGCs are verified using simulation and experimental studies.

The new simple space vector PWM (SVPWM) technique for single-phase multilevel voltage source inverters (MLVSIs) of any arbitrary topologies with any odd numbers of the levels (an even number of the generated equal DC voltage steps and the zero level) is proposed. Due to a reasonable and simple approach to the choice of the sampling positions, of the frequency modulation index, and of the action order at the PWM cycle period of the two voltage space vectors (SVs) nearest to the reference one, the resultant voltage waveforms always have the quarter-wave symmetry. This, in addition to enough low switching frequency of power switches in this technique, makes it possible to obtain the required quality of the output voltage and current by harmonic composition even at comparatively low values of the frequency modulation index. Employing integer and fractional parts values of the reference voltage normalized value provides fast and easy calculating of the two modulating SVs’ coordinates and duty cycles. The PSIM model of the seven-level cascaded H-bridge inverter with the proposed SVPWM modulator is presented. The simulated waveforms, spectra and few curves of dependences of the THD and first-order weighted THD values on the amplitude modulation index are obtained for two variants of reference voltage sampling.

The harmonics-related performance characteristics of the common-mode-voltage-eliminating space vector pulse width modulation (CMVE-SVPWM) technique for three-phase multilevel voltage source inverter (MLVSI), based on the recently offered quarter-wave-symmetric space vector pulse width modulation (QWS-SVPWM) algorithm, are investigated. Namely, the dependences of the output voltage THD and three low-order weighted THDs values on the phase voltage amplitude modulation index are obtained by LabVIEW simulation for the three low, multiple of 12, values of frequency modulation index and the considerably extended range of the amplitude modulation index. Like the baseline QWS-SVPWM algorithm, the CMVE-SVPWM technique keeps the quarter-wave symmetry of the star (phase-to-neutral) and delta (phase-to-phase) voltages and is intended for MLVSI of any arbitrary topology with any arbitrary number of generated equal voltage levels. The zero-common-mode-voltage MLVSI space vectors are being applied, producing the zero value of the voltage across the neutral point of the load and the inverter system ground point. To this end, relative values of the MLVSI phase load voltages, referred to the three-phase load common star point (phase-to-neutral load voltages) are being set as the reference ones and being processed.

Multilevel inverters are finding wide application in electric drives, traction, flexible AC transmission systems (FACTS) and renewable energy systems. A cascaded H-bridge type multilevel inverter (CHBMLI) produces a near sinusoidal output voltage with lower switching stress and a higher conversion efficiency than the other types of MLIs. The Selective Harmonic Elimination (SHE) strategy is used to eliminate lower-order harmonic profiles and to regulate the fundamental component in the output voltage. SHE has the advantages of low switching frequency, low switching losses and low stress. In this paper, the modulation index and input voltage values are also considered as optimization variables along with the conventional switching angles to analyze the performance improvement in selective harmonic elimination. Heterogeneous Comprehensive Learning Particle Swarm Optimization (HCLPSO) and Gravitational Search Algorithm (GSA) algorithms are used to find the optimal switching angles, modulation index and input voltage source values for minimizing the lower-order harmonics present in the output voltage of seven-level and eleven-level CHBMLIs, while maintaining the fundamental component of the output voltage. The results obtained from MATLAB simulations and an experimental setup clearly indicate that the proposed HCLPSO-based multilevel inverter provides better performance when compared with GSA, firefly and Differential Search Algorithm (DSA)-based MLIs.

A new Symmetric Solar Fed Inverter (SSFI) proposed with a reduced number of components compared to the classical, modified, conventional type of Multilevel Inverter (MLI). The objective of this architecture is to design fifteen-level SSFI, this circuit uses a single switch with minimizing harmonics, and Modulation Index (MI) values. Power Quality (PQ) is developed by using the optimization algorithms like as Particle Swarm Optimization (PSO), Genetic algorithm (GA), Modified Firefly Algorithm (MFA). It’s determined to generate the gating pulse and finding optimum firing angle values calculate as per the input of MPP intelligent controller schemes. The proposed circuit is solar fed inverter used for optimization techniques governed by switching controller approach delivers a major task. The comparison is made for different optimization algorithm has significantly reduced the harmonic content by varying the modulation index and switching angle values. SSFI generates low distortion output uses through without any additional filter component through utilizing MATLAB Simulink software (2020a). The SSFI circuit assist Xilinx Spartan 3-AN Filed Program Gate Array (FPGA) tuned by optimization techniques are presented for the effectiveness of the proposed model.

Multilevel converter technology has emerged recently as a very important alternative in the area of high-power medium-voltage energy control. The advantages of multilevel converters are lower switching losses, improved power quality, better electromagnetic compatibility, and higher voltage capability. Several topologies for multilevel inverters have been proposed over the years; the most popular cascaded H-bridge apart from other multilevel inverters is the capability of utilizing different dc voltages on the individual H-bridge cells which results in splitting the power conversion amongst higher-voltage lower-frequency and lower-voltage higher-frequency inverters. In this paper Sinusoidal and third harmonic injected carrier based PWM technique i.e. phase shifted carrier PWM (PSCPWM) and level shifted carrier PWM (LSCPWM) are implemented and analysed the THD levels for different values of modulation index and switching frequency. In level shifted carrier PWM, in phase disposition (IPD), alternative phase opposite disposition (APOD) and phase opposite disposition (POD) modulating technique is analysed using MATLAB/ SIMULINK. Finally better modulating technique is applied to drive the five level cascaded-H Bridge fed Permanent Magnet Synchronous Motor drive