A soft-switched dual-boost coupled-inductor-based converter is proposed which possesses an intrinsic advantage, in terms of transferring the energy directly to output to provide the essential voltage and power for load. The fabulous characteristic of the proposed structure, the combination of forward and flyback converter, makes it possible to utilise one magnetic core for two coupled inductors, advancing the power density. Another implication of proposed converter is the fact that leakage inductances pave the way for the zero-current-switching implementation by confining the diodes current slope during turn-off period. As regards the voltage conversion ratio, the secondary windings of the coupled inductors operate in series with the capacitors of both voltage-doubler stage and capacitordiode stages; consequently, designer is under no obligation to use coupled inductors with extreme turn ratio. Concerning the mentioned features of converter besides its high-efficiency power conversion over a broad range of input voltage, the proposed structure is well suited for the purpose of high step-up dc-dc converter. Lastly, the results of laboratory prototype, working with switching frequency of 50 kHz and output voltage 380 V, are convincingly in line with the mathematical analysis.

This study describes a duty-cycle-controlled resonant dual-half-bridge converter with multifunctional capacitors for enhancing the voltage level of fuel cell and photovoltaic sources to 380 V. Owing to the incorporation of dc-link capacitors and leakage inductance into two various resonant circuits, both switches turn-on under the zero-voltageswitching circumstance and turn-off with low current because of quasi-resonant operation. Since the currents of diodes are controlled by the leakage inductances of transformers, it is not obligatory for a designer to employ the diodes with reverse-recovery current specification; consequently, less expensive diodes can be adopted. The complementary effects of series-connected secondary windings of transformers and switched-capacitor circuits result in forming the balanced voltage multiplier stage, augmenting the voltage conversion ratio substantially without the need for utilising a transformer having higher turns ratio; so, one of the magnificent factors of growth of the conduction losses has been avoided. Ultimately, the results of the laboratory prototype operating with 58 kHz switching frequency, 18 V input voltage, 380 V output voltage, and 500 W output power prove that the proposed topology would be proficient to fulfil its function in systems using distributed generation resources.

SUMMARYThis paper presents a high step-up soft switched dc-dc converter having the feature of current ripple cancelation in the input stage that is specialized for power conditioning of fuel cell systems. The converter comprises a special half-bridge converter and a rectifier stage based upon the voltage-doubler circuit, in which the coupled-inductor technology is amalgamated with switched-capacitor circuit. The input current with no ripple is the principal characteristics of this topology that is achieved by utilizing a small coupled inductor. In addition, the low clamped voltage stress across both power switches and output diodes is another advantage of the proposed converter, which allows employing the metal-oxide-semiconductor field-effect transistors with minuscule on-state resistance and diodes with lower forward voltage-drop, and thereby, the semiconductors' conduction losses diminish considerably. The inherent nature of this topology handles the switching scheme based on the asymmetrical pulse width modulation in order for switches to establish the zero voltage switching, leading to lower switching losses. Besides, because of the absence of the reverserecovery phenomenon, all diodes turn off with zero current switching. At last, a 250-W laboratory prototype with the input voltage 24 V and output voltage 380 V is implemented to verify the especial features of the proposed converter.

No abstract

This paper proposes a current-fed quasi-resonant converter with soft switching method. Input current ripple is reduced by employing two boost circuits at the input, which makes this converter appropriate for fuel cell application.Current stress on switches is reduced because of the resonance in switches, and also, as a result of zero voltage switching in switches, switching losses will be reduced in this proposed converter. In the output, the reverse recovery problem of diodes is alleviated by zero current switching, so there is no need for fast diodes anymore. The reduction of losses improves the efficiency, and in a wide range of load, efficiency is high. Experimental results on a 1-kW prototype are provided to validate the proposed concept.

In developing a neural network technique for a finite element model updating, researchers have been shown that the number of training samples and their quality, significantly affect the accuracy of the NN predication. In this study, based on the genetic algorithm (GA) method, we reduce the number of analyses required to develop the training pairs and reduce the amount of time for training the NN. In the other words, a uniform distribution of design points inside the design space will be obtained by means of this approach. To validate the efficiency of GA sample selection, random generation (RG) method is used for comparison. Two comparisons are made based on a numerical and experimental example. One is updated from 10 degrees of freedom lumped parameters system and the other is updated from a free-free beam using test data. The results indicate that the GA sample selection can reduce the number of training samples without affecting the accuracy of the NN predication. In our present study, also, the advantages of using frequency response function (FRF) data as input to the NN are kept and the drawback of having too many frequency points is overcome by the application of principal component analyses (PCA).

No abstract