In this letter, a novel ultra-large gain step-up coupled inductor DC/DC converter with asymmetric voltage multiplier network is presented for a sustainable energy system. The proposed converter contains one boost converter, one voltage multiplier network and one passive lossless clamped circuit. In order to achieve a ultra-large voltage gain, one of the two capacitors is charged by the primary side and secondary side of coupled inductor, then it together with the secondary side of coupled inductor provide its energy for the other capacitor in voltage multiplier network. Besides, the passive lossless clamped circuit not only recycles leakage energy but also effectively reduces the voltage stress on the main switch. By this way, the efficiency of the conversion can be improved. Moreover, the reverse-recovery problem of the diodes in the leakage inductor is alleviated. The operating principles and steady-state analyses are illustrated in detail. Then, the performance of proposed converter is compared with existing converters. Finally, a prototype circuit at 50 kHz switching frequency with 20-V input voltage, 200-V output voltage, N = 2, and 200-W output power is established in the laboratory to verify the performance of the proposed converter.

In this paper, a novel high step-up interleaved DC-DC converter is presented, which is composed of an interleaved structure, an asymmetric voltage multiplier cell (AVMC) and a passive lossless clamped circuit. Compared to the classical interleaved boost converter, the proposed converter has higher voltage gain owing to the employment of the AVMC and the coupled inductor. Besides, the input current ripple is limited at low values with the help of the interleaved structure, which gives more life time of the input power source. The voltage stresses of main switches are substantially low so that the MOSFETs with low-voltagerated and on-resistance ( DS (ON) R ) can be used. In addition, the voltage stresses and the reverse recovery problems of diodes are improved dramatically. Moreover, the zero-current-switching (ZCS) turn-on of switches and the ZCS turn-off of the clamp diodes are realized to reduce the switching losses. The leakage inductor energy is recycled and the voltage spikes are improved greatly by the passive lossless clamped circuit so that the efficiency can be upgraded further. Finally, a 400W 40V-input 400V-output prototype is established to demonstrate the performance of this converter. The highest efficiency is about 97.3% and the full-load efficiency is approximate 97%.

In this article, a novel passive lossless clamped circuit composed of two capacitors and one diode is proposed. One of the two capacitors is used to construct a flowing path for the energy of leakage inductor and the other is used to store the leakage energy. Compared with a classical passive lossless clamped circuit, the novel circuit structure is more flexible and versatile, and the number of the extra capacitor and diode is consistent to the classical circuit for recycling the energy. Moreover, an idea of using more capacitors in series instead of a single output capacitor to reduce voltage stress and volume is presented. In order to extend their application scope and demonstrate their practical value, the novel clamped circuits and the idea are integrated into a family of cascade dc–dc converters based on the popular boosting cell, such as voltage-lift cell, symmetric voltage multiplier cell and asymmetric voltage multiplier cell. As a representative, a novel cascade converter, which integrates the novel passive lossless clamped circuit and the idea is analyzed in detail. The proposed converter has a high voltage gain and low ripple input current. The voltage stresses of an output diode and output capacitor can be effectively reduced. Its output capacitor adopts a 20-uF polypropylene (CBB) capacitor rated at 250 V to replace the higher rated electrolytic capacitor. A prototype circuit in the laboratory is established to verify its performances.

A voltage sensorless control of low-complexity model predictive direct power control (LC-MPDPC) for pulse width modulation (PWM) rectifier is proposed. The conventional LCMPDPC adopts one or two voltage vectors during one control period, which achieve good steady-state performance and quick dynamic response. Besides, based on the mathematical model of the real system, the conventional method only requires one prediction to find the optimal voltage vector, which reduces the control complexity and computational burden. However, the use of one or two vectors during one sampling interval present abundant current harmonics and high power ripples. In order to solve these problems, whilst preserving all the advantages of conventional LC-MPDPC, this paper presents a novel control scheme, with the aim of operating at a constant-switching frequency and obtaining an excellent steady-state performance at a low switching frequency. The proposed method is based on an optimal application of three voltage vectors in a symmetrical way, which takes advantage of advanced pulse width modulation techniques. Furthermore, the virtual flux based control scheme is introduced to achieve voltage sensorless control. The proposed strategy is compared with the conventional MPDPC methods and its effectiveness is confirmed by both simulation and experimental results from a three-phase PMW rectifier under 1000-W operation condition.

This study presents a novel step‐up DC–DC converter with the coupled inductor and low switch voltage stress, which reduce diode voltage stress. The presented converter contains single switch, four diodes, four capacitors and one coupled inductor. When switch is turned ON, the primary side of coupled inductor is charged by the input source. Besides, the primary and secondary side of the coupled inductor is discharged in series with the input source and two capacitors to realise the high step‐up voltage gain when the switch is turned OFF. Furthermore, the clamped circuit which adopts two capacitors negative pole connection not only recycles leakage energy and obtains the high voltage conversion gain, but also is realised to reduce the voltage stress of the diode, which can be use low‐voltage rated devices with low on‐resistance. In addition, the three diodes are working on the zero‐current‐switching turn‐off, therefore, the loss is reduced and the reverse‐recovery problem is avoided. The current falling rate of the output diode is effectively restricted for the leakage inductor, therefore, its reverse‐recovery problem is effectively alleviated. Finally, a 40 V input voltage, 380 V output voltage and 400 W output power prototype circuit is established in the laboratory to verify the performance.