I: Wind Data Analysis.- 1. Introduction.- 1.1. Surface Wind Observation.- 1.2. General Weather Pattern.- 1.3. Outline of this Monograph.- 2. The Initial Decomposition.- 2.1. General Background.- 2.2. Robust Filtering.- 2.3. Univariate Filter Study.- 2.4. Multivariate Filter Study.- 2.5. Application to Wind Series.- 2.6. Appendix: Mathematical Details.- 3. The Geostrophic Component.- 3.1. The Geostrophic Wind.- 3.2. Estimation of the Geostrophic Wind.- 3.3. Comparison with the Geostrophic Component.- 3.4. Synoptic States.- 3.5. Appendix: Derivation of the Geostrophic Wind Equation.- 4. The Land and Sea Breeze Cycle.- 4.1. The Nature of the Circulation.- 4.2. Statistical Approach.- 4.3. Land and Sea Breeze Pattern.- 5. Short-Term Events.- 5.1. Meteorological Patterns.- 5.2. Wind Classification.- 5.3. Characteristics of Short-Term Events.- 5.4. Appendix: Removal of Storms.- II: Time Series of Directional Data.- 6. Time Series Models for Directional Data.- 6.1. Circular Variables.- 6.2. The von Mises Process.- 6.3. The Wrapped Autoregressive Process.- 7. Measures of Angular Association.- 7.1. Desirable Properties.- 7.2. Bivariate Angular Distributions.- 7.3. Review of Measures of Association.- 7.4. A Proposal for Vector Valued Time Series.- 7.5. Appendix: Non-von Mises Marginals.- 8. Comparison of Different Measures of Association.- 8.1. Independent Bivariate Directional Data.- 8.2. Time Series of Directional Data.- 9. Inference from the Wrapped Autoregressive Process.- 9.1. Introduction.- 9.2. Equating Theoretical and Empirical Circular Variance (EQ).- 9.3. Corrected EQ-Estimation (EC).- 9.4. Bayes Estimation (BA).- 9.5. Maximum Likelihood Estimation (ML).- 9.6. Characteristic Function Estimation (CF).- 9.7. Numerical Comparison of Estimators.- 10. Application to Series of Residual Wind Directions.- 11. Conclusions and Summary of Results.- List of Symbols.

The Analysis of Directional Time Series: Applications to Wind Speed and Direction

Received Jun 1, 2020 Revised Aug 1, 2020 Accepted Aug 17, 2020 This paper proposes a nearest level control method based modulation scheme for a 9-level symmetrical transistor clamped H-bridge (TCHB) inverter. The topology has gained increasing research focus due to its advantages in obtaining high-quality output while using a reduced number of electronic components. The device count for getting a 9-level output voltage is 10 switches compared to 16 switches being used in a conventional 9-level cascaded H-bridge (CHB) inverter. The significant contribution of the research is the development of the nearest level control (NLC) method that operates at the fundamental frequency, thus reducing switching losses, and able to reduce harmonic content significantly. The reduced harmonic content can lessen the power quality problem. The NLC modulation scheme shows that the overall THD is reduced without the need for filtration. The 50 values of harmonic content will be counted that follows the IEEE Standard 519. MATLAB/Simulink based simulations and experimental results obtained from the laboratory prototype of a single-phase TCHB inverter feeding an R load validate the theoretical analyses and effectiveness of the proposed modulation scheme.

/pdf/voltage-harmonics-reduction-in-single-phase-9-level-uveqnf0i3l.pdf

Voltage harmonics reduction in single phase 9-level transistor clamped H-bridge inverter using nearest level control method

This paper presents a Bilinear Time Frequency Distribution (BTFD) for recognition and detection of power quality (PQ) disturbances with power related analysis. BTFD have been intensively used to characterize and analyze non stationary signals. The bilinear TFDs offer a good time and frequency resolution and are successfully applied to various reallife problems such as radar, sonar, seismic data analysis, biomedical engineering, and automatic emission [4]. The method used in this paper is Wigner Ville Distribution. This paper will characterize the pattern for the tested power quality disturbances signals such as voltage sag, harmonics, and voltage swell in Time-frequency representation. This proposed BTFD's Time-Frequency Representation has a better insight and time resolution compared to the time domain representation or frequency domain representation alone.

Detection and analysis of power quality disturbances using Bilinear Time-Frequency Distribution

Multilevel inverters (MLI) play an important role in AC applications and are undergoing continuous development in topology and control. In higher levels inverters, conventional MLIs have high components count which calls for modification of these topologies to obtain the same number of levels with fewer components to reduce cost and size. Balancing of the capacitors voltages is crucial for the operation of the MLI and it becomes more challenging in higher levels. This paper presents an active voltage balancing strategy for a reduced switch count five-leve topology which is the asymmetric stacked multilevel inverter (ASMLI). The ASMLI uses fewer components than the conventional MLIs when used in their five-levelconfiguration. The proposed active voltage balancing strategy uses simple measurements and logic to assure a balanced capacitors voltages during steady state and transients. The performance was examined and compared based on two modulation techniques with LCL filter and RL load using MATLAB/Simulink. The results show that the active voltage balancing strategy can trace all capacitors voltages to the reference value simultaneously with less than 1% voltage error, fast dynamic response, and an acceptable total harmonic distortion (THD) which allows the proposed setup to be an available option for medium voltage applications.

/pdf/active-voltage-balancing-strategy-of-asymmetric-stacked-3pe7sk98cr.pdf

Active voltage balancing strategy of asymmetric stacked multilevel inverter

This paper introduces a modified multilevel inverter topology with asymmetrical dc sources combination. The significant features of the proposed circuit are the reduced number of switches and low total standing voltage (TSV). Proposed topology utilizes ten switches to produce 13 level output with per unit TSVp.u of 5.33. An additional feature of the proposed topology is the inherent negative level generation as there is no requirement of an H-bridge for the polarity reversals. Nearest level control (NLC) technique is used as the modulation strategy. Performance of the proposed topology is validated through extensive analysis using Simulink and PLECS software. Detailed circuit analysis and its power loss, as well as efficiency studies, have been carried out under constant and dynamic load conditions. Results obtained shows that the proposed topology is working well, producing an output of 13-level with total harmonic distortion of 6.36% and inverter efficiency of 98.8%. The topology is extended to n-level structure, and its generalized expressions for different parameters were formulated. The comparison of the generalized structure with other existing topology is carried out, and it is found that the proposed topology outperform other topologies on many parameters.

https://ijpeds.iaescore.com/index.php/IJPEDS/article/download/21033/13306

Modified asymmetrical 13-level inverter topology with reduce power semiconductor devices

Multilevel inverters are gaining special interest among researchers and in the industry due to their widespread applications and numerous merits. Obtaining high quality, more reliable output while using a reduced number of electronic components is the main purpose of most of the research conducted in this area of study. The purpose of this study is to apply the nearest level control (NLC) method to a 13-level transistor-clamped H-bridge (TCHB) inverter with unequal DC voltage supplies. The NLC method operates at the fundamental frequency, thus reducing switching losses, and can reduce the harmonic content significantly. The adopted multilevel inverter consists of two TCHB cells supplied with two asymmetrical DC input sources with a voltage ratio of 1:2. This structure reduces the number of electronic components, and the asymmetry in the DC input voltages results in a higher number of levels. The adopted topology and its proposed control method were simulated in Matlab/Simulink, and the simulation results were verified through experiments using an Altera field-programmable gate array (FPGA) board. The results showed that the topology and its control method are efficient in obtaining a high-quality output with an improved total harmonic distortion (THD).

https://ijpeds.iaescore.com/index.php/IJPEDS/article/download/20700/13189

Harmonic minimization of a single-phase asymmetrical TCHB multilevel inverter based on nearest level control method

Power quality has become a great concern to all electricity consumers. Poor power quality can cause equipment failure, data and economical losses. An automated monitoring system is needed to ensure signal quality, reduce diagnostic time and rectify failures. This paper presents the analysis of power quality signals using frequency domain smooth-windowed Wigner-Ville distribution (FDSWWVD). The power quality signals focused are swell, sag, interruption, harmonic, interharmonic and transient based on IEEE Std. 1159–2009. The TFD represents signal jointly in time-frequency representation (TFR) with good frequency and time resolution. Thus, it is very appropriate to analyze the signals that consist of multi-frequency components and magnitude variations. However, there is no fixed kernel of the TFD can be used to remove cross-terms for all types of signals. A set of performance measures is defined and used to compare the TFRs to identify and verify the TFD that operated at optimal kernel parameters. The result shows that FDSWWVD offers good performance of TFR and appropriate for power quality analysis.

Nurul Ain Mohd Said

Papers

Harmonic minimization of a single-phase asymmetrical TCHB multilevel inverter based on nearest level control method

Voltage harmonics reduction in single phase 9-level transistor clamped H-bridge inverter using nearest level control method

Power quality analysis using frequency domain smooth-windowed Wigner-Ville distribution