Comparative Analysis of the Fault Diagnosis in CHMLI Using k-NN Classifier Based on Different Feature Extractions

Cascaded H-bridge multilevel (CHBML) inverters usually include a large number of isolated dc-voltage sources. Some faults in the dc-voltage sources result in unequal cell dc voltages. Unfortunately, the conventional phase-shifted carrier (PSC) PWM method that is widely used for CHBML inverters cannot eliminate low frequency sideband harmonics when the cell dc voltages are not equal. This paper analyzes the principle of sideband harmonic elimination, and proposes an improved PSCPWM that can eliminate low frequency sideband harmonics under the condition of unequal dc voltages. In order to calculate the carrier phases, it is necessary to solve transcendental equations for low frequency sideband harmonic elimination. Therefore, an approach based on the artificial bee colony (ABC) algorithm is presented in this paper. The proposed PSCPWM method enhances the reliability of CHBML inverters. The proposed PSCPWM is not limited to CHBML inverters. It can also be applied to other types of multilevel inverters. Simulation and experimental result obtained from a prototype CHBML inverter verify the theoretical analysis and the achievements made in this paper.

Multilevel inverter has played a vital role in medium and high power applications in the recent years. In this paper, Reduced Switch Count Multi Level Inverter structure (RSCMLI) topology is presented with different pulse width modulation techniques. The harmonic level analysis is carried out for the reduced switch count multilevel inverter with the different PWM technique such as with Alternate Phase Opposition Disposition (APOD) method, In Phase Disposition (IPD) method and multi reference pulse width modulation method for five level, seven level , nine level and eleven level inverter. The simulation results are compared with the cascaded H Bridge Multi Level Inverter (CHBMLI). The nine level RSCMLI inverter with APOD method is used for the Distribution Static Synchronous Compensator (DSTATCOM) application in the nonlinear load connected system for power factor improvement. The result shows that the harmonic level and the number of switches required for RSCMLI is reduced compared to CHBMLI. RSCMLI employed in DSTATCOM improves the power factor and harmonic level of the system when it is connected to the nonlinear load.

Statistical imputation techniques were evaluated for infilling missing records in daily rainfall data within the Pra and Densu river basins in Ghana. The imputation techniques considered were mean, regression, multiple imputation by chain equation, k-nearest neighbour, probabilistic principal component analysis (PPCA), missForest, linear interpolation, hot deck, expectation maximization, Gaussian copula, inverse distance weighting and kriging. Different percentages of missing records (5%, 10%, 20% and 30%) were artificially introduced into the complete datasets. Then, the missing records were imputed and compared with the observed values. The root mean square error, mean absolute error, bias, coefficient of determination, similarity index and Kolmogorov-Smirnov performance statistics were used to evaluate the methods. The results were mixed depending on the performance metric used. However, the best candidates were regression, PPCA and missForest imputation techniques. These methods were better for estimating the numbers of dry and wet periods and the moderate to extreme rainfall values.

<span>In this paper, modified multilevel inverter, via addition of an auxiliary bidirectional switch, based on Newton Raphson (NR) and Particle Swarm Optimization (PSO) techniques is presented. The NR and PSO techniques were employed for selective harmonics elimination (SHE) solution in a modified Cascaded H Bridge Multilevel inverter (CHB-MLI). The Selective Harmonic Elimination Pulse-Width Modulation (SHE-PWM) is a powerful technique for harmonic minimization in multilevel inverter. The NR and PSO techniques were used to determine the switching angles by solving the non-linear equations of the output voltage waveform of the modified CHB-MLI in order to control the fundamental component and eliminate some low order harmonics. The proposed NR and PSO techniques are capable to minimize the Total Harmonic Distortion (THD) of the output voltage of the modified inverter within allowable limits. This paper aims to modeling and simulation by MATLAB of the modified topology of the CHB-MLI for a single-phase prototype for 13-levels. The inverter offers less THD and greater efficiency using PSO control algorithm compared with the NR algorithm. <br https://server9.kproxy.com/servlet/redirect.srv/sruj/snbzofspy/skvyzff/p1/> The performance of the proposed controllers based on NR and PSO techniques is verified through simulation.</span>

This paper focuses on the development of open and closed loop system for nine level cascaded H-Bridge multilevel inverter (CHBMLI). Inverters are often used to provide power to electronics in case of a power outage where no power is available. An inverter converts a DC voltage into an AC voltage. But main drawbacks of these inverters are high harmonic content and limited power applications. This is the main problem identified in conventional system. In order to overcome this problem, a new topology of CHBMLI is presented, which increases the level number of output waveform and thereby reduces the low-order harmonics and THD. The proposed system consists of a PV module, DC-DC converter with capacitor filter and DC-AC multilevel inverter. In this paper, an equal pulse width modulation (E-PWM) technique, applicable for proposed CHBMLI is presented. The proposed nine level cascaded H-bridge multilevel inverter achieves higher power ratings, and also enables the use of renewable energy sources in an efficient manner. Simulation results are compared with theoretical results.Index terms- cascaded H-bridge multilevel inverter (CHBMLI); Equal pulse width modulation (EPWM); Total harmonic distortion (THD); Photovoltaic (PV); Separate DC sources (SDCS).

We review the most common topology of multi-level inverters. As is known, the conventional inverters are utilized to create an alternating current (AC) source from a direct current (DC) source. The two-level inverter provides various output voltages [(Vdc/2) and (−Vdc/2)] of the load. It is a successive method, but it makes the harmonic distortion of the output side, Electromagnetic interference (EMI), and high dv/dt. We solve this problem by constructing the sinusoidal voltage waveform. This is achieved by a “multilevel inverter” (MLI). The multilevel inverter creates the output voltage with multiple DC voltages as inputs. Many voltage levels are combined to produce a smoother waveform. During the last decade, the multilevel inverter has become very popular in medium and high-power applications with some advantages, such as the reduced power dissipation of switching elements, low harmonics, and low EMIs. We introduce the information about several multilevel inverters such as the diode-clamped multilevel inverter (DC-MLI), cascaded H-bridge multilevel inverter (CHB-MLI), and flying-capacitor multilevel inverter (FC-MLI) with Power systems CAD (PSCAD) simulation. It is shown that THD is 28.88% in three level FC-MLI while THD is 18.56% in five level topology. Therefore, we can decrease the total harmonic distortion adopting the higher-level topology.

Cascaded H-bridge Multilevel Inverter (CHMI) is widely used in industrial applications thanks to its many advantages. However, the reliability of a CHMI is decreased with the increase of its levels. Fault diagnosis techniques play a key role in ensuring the reliability of a CHMI. The performance of a fault diagnosis method depends on the characteristics of the extracted features. In practice, some extracted features may be very similar to ensure a good diagnosis performance at some H-bridges of CHMI. The situation becomes even worse in the presence of noise. To fix these problems, in this paper, signal denoising and data preprocessing techniques are firstly developed. Then, a Principal Components Rearrangement method (PCR) is proposed to represent the different features sufficiently distinct from each other. Finally, a PCR-based fault diagnosis strategy is designed. The performance of the proposed strategy is compared with other fault diagnosis strategies, based on a 7-level CHMI hardware platform.

This paper discusses gate open-circuit fault detection and diagnosis method in SPWM modulated symmetric cascaded H-bridge multilevel inverter. First, an output voltage modelling under fault condition in cascaded H-bridge multilevel inverter is presented. Further, simulations of fault conditions have been carried out for the development of the fault detection and diagnosis method. Based on fault modelling and simulations, a fault detection and diagnosis method have been proposed based on the mean values of the bridge voltages as the diagnostic feature. Further, the proposed method has been validated experimentally on a 5-level symmetric sine pulse width modulated cascaded H-bridge multilevel inverter.

Nowadays, a multilevel inverter is one of the important devices that provides a practical approach device in power system industries because of its features which are less switching losses, lower electromagnetic interference, reduced harmonic distortion, higher DC link voltages, and improved output voltage and current waveforms. Among all existed multilevel inverter, cascaded H-bridge multilevel inverter is the most attractive because of the technology development with megawatt power level. So, the cascaded H-bridge multilevel inverter has been tested and proven as a suitable DC/AC device for medium and high power applications such as renewable energy systems, electric vehicles, and motor drive applications. In this paper, the project is focusing on the combination of a nine-level cascaded H-bridge multilevel inverter connected to photovoltaic (PV) sources and a hybrid powerfilter. This project aims to study and to analyze the results of the proposed system. Thebehaviour and the performance of the designed system have shown that the system offered330V peak output AC voltage with an efficiency of 93.96% and a 5% reduction of THD.This project will be carried out only in Matlab/Simulink software.

Cascaded H-bridge multilevel inverters are becoming increasingly used in applications such as distribution systems, electrical traction systems, high voltage direct conversion systems, and many others. Despite the fact that multilevel inverters contain a large number of control switches, detecting a malfunction takes a significant amount of time. In the fault switch configurations diode included for freewheeling operation during open-fault condition. During short circuit fault conditions are carried out by the fuse, which can reveal the freewheeling current direction. The fault category can be identified independently and also failure of power switches harmed by the functioning and reliability of cascaded H-bridge multilevel inverters. This paper investigates the effects and performance of open and short switching faults of multilevel inverters. Output voltage characteristics of five level MLI are frequently determined from distinctive switch faults with modulation index value of 0.85 is used during simulation analysis. In the simulation study, with the modulation index value of 0.85, one second open and short circuit faults are generated for the location of the defective switch. Fault is identified automatically by means of artificial neural network technique using sinusoidal pulse width modulation based on distorted total harmonic distortion and managed by its own. The proposed topology is to be design and evaluate using MATLAB/Simulink platform.

SummaryIn general, cascaded H‐bridge multilevel inverters (CHB‐MLI) are typically operated with either symmetrical or asymmetrical input DC sources, set at predefined specific ratios such as binary (1:2) or trinary (1:3) in the case of asymmetry, to achieve the desired output voltage waveform. However, if any DC source fails to provide the predefined voltage magnitude, or CHB‐MLIs with unspecified DC source ratios are utilized, the output voltage waveform may exhibit unequal magnitudes between consecutive levels, thereby causing a significant increase in total harmonic distortion (THD). Conventionally, to mitigate this effect, the corresponding H‐bridge is bypassed through zero voltage switching, which leads to an additional burden on the remaining H‐bridges to serve the same load. To reduce the burden on the remaining cells and improve the THD profile of the inverter, this article proposes a novel method for CHB‐MLI with varying DC magnitudes. It aims to enhance the quality of the output voltage waveform by strategically selecting optimum voltage levels rather than utilizing all available levels when CHB‐MLI has unspecified or variable DC sources. This approach can achieve a more balanced distribution of voltage magnitudes across successive levels by eliminating redundant states. Moreover, the proposed technique can reduce switch losses and enhance the converter's efficiency. The proposed method is validated through MATLAB/Simulink software simulations, followed by experimental verification.

SummaryIn this study, a comprehensive control scheme for cascaded H‐bridge multilevel inverter (CHBMLI)‐based grid integrated bulk wind energy conversion system (WECS) addressing the problem of deviation of wind speeds among windmills like a partial shading condition of PV system is presented. The proposed control scheme uses independent dc links with reduced voltages that makes such a topology an ideal candidate for high and medium power WECS with improved reliability. Inconsistency of wind speeds at each turbine causes distinct voltage conditions among the isolated dc links of the CHBMLI H‐bridge cells (HBC) leading to unstable power generation. The projected scheme along with maximum and efficient energy conversion has the ability of dc link capacitor voltage balancing in each HBC of CHBMLI during the above said power generation mismatch conditions and also maintains power quality in the grid side voltage and injected currents as per standards. Moreover, the modelling analysis of the adopted CHBMLI for the grid integrated WECS application has also been derived. The system performance under inconsistent wind speed environment has been tested and analysed by using MATLAB simulation and validated by using FPGA‐based real‐time simulator (Opal‐RT‐OP5700).

Motor bearings play an important role in industrial production. Regular inspection and fault diagnosis can provide reliable guarantee for the normal operation of the motor. If the potential or early bearing failures are not detected in time, they will bring safety hazards to production operations. In this thesis, distance measure method for feature extraction and KNN (k-nearest neighbor) algorithm for recognition are combined for the purpose of diagnosis of motor bearing. Through experimental verification, the medium KNN algorithm has the most obvious improvement, and the accuracy has increased from 39. 1% to 99. 8% with the help of the proposed feature extraction. Using the KNN algorithm, the effect of time domain feature extraction, frequency domain feature extraction and distance feature extraction are verified. After comparison, it is concluded that the distance feature extraction method can effectively improve the accuracy rate and speed up the training speed of the model.

Improved Sparse Representation based Robust Hybrid Feature Extraction Models with Transfer and Deep Learning for EEG Classification

Soft sensor modeling with a selective updating strategy for Gaussian process regression based on probabilistic principle component analysis