A Novel Asymmetric Three-Phase Cascaded 21 Level Inverter Fed Induction Motor Using Multicarrier PWM with PI and Fuzzy Controller

Multilevel inverters are gaining popularity in high power applications. This paper proposes a new ladder type structure of cascaded three-phase multilevel inverter with reduced number of power semiconductor devices which is used to drive the induction motor. The ultimate aim of the paper is to produce multiple output levels with minimum number of semiconductor devices. This paper uses only 11 switches along with 3 diodes and 4 asymmetrical sources to produce an output voltage of 21 levels. The modulation technique plays a major role in commutation of the switches. Here we implement the multicarrier level shifting pulse width modulation technique to produce the commutation signals for the inverter. The proposed multilevel inverter is used to drive the three-phase induction motor. The mathematical modeling of three-phase induction motor is done using Simulink. Furthermore the PI and fuzzy logic controllers are also used to produce the reference waveform of the level shifting technique which in turn produces the commutation signals of the proposed multilevel converter. The controllers are used to control the speed of the induction motor. The effectiveness of the proposed system is proved with the help of simulation. The simulation is performed in MATLAB/Simulink. From the simulation results, it shows that the proposed multilevel inverter works properly to generate the multilevel output waveform with minimum number of semiconductor devices. The PI and fuzzy logic controller performances are evaluated using the results which indicate that with the help of controllers the harmonics has been reduced and the speed control of induction motor is achieved under different loading conditions.

Currentless Multiple Switch Open-Circuit Faults Diagnosis for Modular Multilevel Converters with Nearest Level Modulation in HVDC Systems

Due to the large number of submodules(SMs),and modular multilevel converters(MMCs)in high-voltage applications,they are usually regulated by the nearest level modulation(NLM).Moreover,the large number of SMs causes a challenge for the fault diagnosis strategy(FDS).This paper proposes a currentless FDS for MMC with NLM.In FDS,the voltage sensor is relocated to measure the output voltage of the SM.To acquire the capacitor voltage and avoid increasing extra sensors,a capacitor voltage calculation method is proposed.Based on the measurement of output voltages,the faults can be detected and the number of different-type switch open-circuit faults can be confirmed from the numerous SMs in an arm,which narrows the scope of fault localization.Then,the faulty SMs and faulty switches in these SMs are further located without arm current according to the sorting of capacitor voltages in the voltage balancing algorithm.The FDS is independent of the arm current,which can reduce the communication cost in the hierarchical control system of MMC.Furthermore,the proposed FDS not only simplifies the identification of switch open-circuit faults by confirming the scope of faults,but also detects and locates multiple different-type faults in an arm.The effectiveness of the proposed strategy is verified by the simulation results.

Static loading and vertical displacement at southern Siberia

Seismic method is usually used for elastic parametric estimation. This is why this method presents dynamic parameters of Earth. Frequency seismic range changes greatly from geodynamic modelling time. Now we have opportunity to use geodesy result for some years for elastic parameters estimation. Static solution from elastic theory may be used for the interpretation of long term results. It presents static elastic parameter. The inverse problem for different types of vertical surface loading on one year period is calculated. Two cases of loading with maximal and minimal area are presented. Results are determined by space geodesy and leveling methods. Current relation between atmospheric pressure and vertical displacements was estimated at the center of Siberian Anti Cyclone with size varied from 2000 km to 3000 kin. Pressure-displacement coefficients （PDC） can be achieved by three years obser- vation （0.997 mm/mbar for NVSK GPS station）. It is used for elastic module study of geology medium with maximum thickness up to 600 km. In the context of elastic model, the modulus of rigidity is estimated to be 113 GPa. Vast expanse of anti-cyclone may relate with rheology of crust and upper mantle. Smaller size of surface loading - local loading is seasonal variation of water reservoir. Annual vertical changes were obtained by leveling near the dam of the reservoir. PDC ratio was 1.15 mm/bar for these places. In elastic theory, the Young modulus E = 80 GPa （Poisson ratio = 0.25, the modulus of rigidity - 32 GPa） was calculated by sixteen years of leveling measurements. This result can effectively be represented for upper crust. Our results were checked by solution for coseismic displacement of Chyia- Altai earthquake （Sep. 27, 2003, M = 7.3）. Coseismic results calculated by static modules agree with experimental coseismic GPS data at 10% level.

Reducing energy loss via tuning energy levels of polymer acceptors for efficient all-polymer solar cells

The open-circuit voltage(Voc) of all-polymer solar cells(all-PSCs) is typically lower than 0.9 V even for the most efficient ones.Large energy loss is the main reason for limiting Voc and efficiency of all-PSCs. Herein, through materials design using electron deficient building blocks based on bithiophene imides, the lowest unoccupied molecular orbital(LUMO) energy levels of polymer acceptors can be effectively tuned, which resulted in a reduced energy loss induced by charge generation and recombination loss due to the suppressed charge-transfer(CT) state absorption. Despite a negligible driving force, all-PSC based on the polymer donor and acceptor combination with well-aligned energy levels exhibited efficient charge transfer and achieved an external quantum efficiency over 70% while maintaining a large Voc of 1.02 V, leading to a 9.21% efficiency. Through various spectroscopy approaches, this work sheds light on the mechanism of energy loss in all-PSCs, which paves an avenue to achieving efficient all-PSCs with large Voc and drives the further development of all-PSCs.

Gorenstein AC-Projective and AC-Injective Modules over Formal Triangular Matrix Rings

Let A and B be rings and U a(B,A)-bimodule.If BU is flat and UA is finitely generated projective(resp.,BU is finitely generated projective and UA is flat),then the characterizations of level modules and Gorenstein AC-projective modules(resp.,absolutely clean modules and Gorenstein AC-injective modules)over the formal triangular matrix ring T=(A0 UB)are given.As applications,it is proved that every Gorenstein AC-projective left T-module is projective if and only if each Gorenstein AC-projective left A-module and B-module is projective,and every Gorenstein AC-injective left T-module is injective if and only if each Gorenstein AC-injective left A-module and B-module is injective.Moreover,Gorenstein AC-projective and AC-injective dimensions over the formal triangular matrix ring T are studied.

The inhibitory activities of Urtica fissa to BPH

In the present study, the BPH inhibitory activities of Urtica fissa were systematically investigated. Firstly, inhibitory activities of 5α reductase of the alcoholic extracts from different parts(root, stem, leaf, flower and fruit) were evaluated. The results indicated that the root possessed the most significant action. Subsequently, U. fissa root(UFR) was subjected to further pharmacological evaluation using the benign prostate hyperplasia(BPH) model rats induced by testosterone propionate. The results revealed that UFR could significantly decrease the prostate index, alter the hyperplasia tissue morphology, suppress the prostatic growth factors of VEGF, EGF, bF GF and KGF, decrease the inflammation factor levels of TNF-α, IL-1β and IL-6, improve the activities of GSH-Px, CAT and SOD and decrease the MDA level in the prostate of the model rats. Moreover, UFR also significantly suppressed the hormone levels of testosterone and dihydrotestosterone. These results indicated that the possible BPH inhibitory mechanisms of UFR were growth factor suppression, hormone level modulation, anti-inflammation, and anti-oxidative stress.