Advanced Materials Research Vols. 354-355

Abstract: To meet the demand of that the waveform control welding machine controlling the waveform of the arc voltage and arc current, need to further improve the working frequency of the inverter power source and reduce switching loss, switching stress and electromagnetic interference. The parameters of soft-switching inverter’s main circuit, witch make the working state with zero-voltage and zero-current switching, is designed. First, the working principle of the FB-ZVZCS-PWM inverter is analyzed. And the constraint equation of the main circuit’s parameters is obtained, it provide the basis for the calculation of the main circuit’s parameters. According to the requirements of the working condition of inverter and the time sequence of PWM, the value of the block capacitor Cx is obtained. And the satiable inductor, witch improve the rise speed of the short circuit current and the descending speed of the necking current, is designed. Second, the simulation model of the satiable inductor is designed. And the simulation model of the FB-ZVZCS-PWM inverter is established. It verified the correctness of the theoretical analysis and the parameter design.

Abstract: The power electronic devices are difficult to model due to their switching behavior. Conventional quasi-static models are difficult to reflect the dynamic behavior of the switching adequately. Electro-magnetic transient analysis based on time-domain models can offer improved accuracy, but their nonlinear time-varying nature is impractical to analyze the large power system. A model for single phase inverter on the basis of dynamic phasors is established in order to improve the accuracy of simulation and reduce computation. By comparing the dynamic phasor (DP) model and the detailed time domain electromagnetic transient (EMT) model of single phase inverter, the simulation results show that the DP method could ensure simulation accuracy and reduce computational cost.

Abstract: Wastewaters discharged from oil refineries and coal coking plants often contain large amounts of toxic monocyclic phenolic compounds (MCPC_s), mainly including phenol, cresols and xylenols, polluting soils and surface water. In this work, crude phenols or 12 individual MCPC_s were used as the enrichment medium and the later strategy was discovered for the first time to be more effective in finding more and competent MCPC-degrading strains. Phylogenetic analysis and multiple MCPC degradation tests revealed that phylogenetically close microbes generally exhibited similar MCPC-degrading spectra.

Abstract: This paper proposes a nonlinear Lyapunov-based control method of the single-phase shunt active power filter (APF). The system is modeled firstly and then the compensated current of the APF is calculated. The energetic like Lyapunov function is constructed and the control output is determined through ensuring the differential of the Lyapunov function negative, which grantee the convergence of the APF system. Considering that the time-varying load may cause greater fluctuations in DC voltage, an average value is used to calculate the control output. A globally stable control is possible and it is insensitive to the parameter uncertainties and robustness to the disturbances. Simulation results are obtained using Matlab/ Simulink. These results verify the correct operation of the proposed control method.

Abstract: IGCT is a kind of new type power electronic device which developed from GTO and IGBT . In this paper, Author based on analysis of the internal structure of GTO, shows how GTO development IGCT through technical methods.Through simulation of its off and on performance, the work curve and comparing results of the two devices are given. Then on two components of the inverter circuits are analyzed and compared. Thinking in large power AC drive locomotive, IGCT inverter is greatly simplifier than GTO inverter circuit, and superior performance,it will become the main converter for AC driving locomotive.

Abstract: To be used for voltage regulator, An AC-AC direct converter with small bulk has been researched. The paper has proposed an isolated Cuk Three-Level AC-AC Converter. It is produced by applying TL AC switch unit in Isolated Cuk converter which is put forward by Slobodan Cuk. Because the two-level converter usually isn’t used in high voltage and heavy load situation, the paper proposed the cascaded type of isolated Cuk AC-AC converter. Besides, the operating principle and the control strategy of isolated Cuk Three-Level AC-AC Converter are investigated. Transient voltage feedback control is used in the converter and principle diagram of control circuit is given. By experiment results, the correctness of operating principle and control strategy of isolated Cuk Three-Level AC-AC Converter have been proved.

Abstract: Hilbert-Huang transform (HHT) is a new time-frequency-domain analysis method, which is suitable for non-stationary and nonlinear signals. In this paper, endpoint continuation and ensemble empirical mode decomposition (EEMD) decomposition method are introduced to improve the HHT, which solve the endpoint winger and modal aliasing problem. The improved HHT (IHHT) is used for analyzing the harmonic signal and detecting the fault signal of power system. Simulation results show that IHHT is feasible and effective for harmonic analysis and fault detection.