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By the negative influence of parasitic parameters from the components, the voltage step-up capacity of basic dc-dc converters is limited at extremely high duty cycle. Which makes the traditional dc-dc converters are difficult to be applied to renewable energy generation systems such as fuel cell and photovoltaic (PV) systems. In this study, a single-switch high step-up Zeta converter is proposed based on the basic Zeta converter and corresponding coat circuit. By using the coat circuit, the proposed converter not only can achieve higher voltage gain, but also acquire lower voltage stress on the semiconductor devices. Therefore, the devices with lower conduction resistances can be used to improve the efficiency. Furthermore, the coat circuit is composed of passive components, which does not change the continuous output current characteristic of the basic Zeta converter. And the proposed converter has only one active switch, the drive and control circuits are simple. The operation principle and the performance analysis of the proposed Zeta converter are described in detail, and a 300 W closed-loop experimental prototype has been developed for verification.

An interleaved zero-voltage zero-current switching (ZVZCS) high step-up DC-DC converter is proposed for modern photovoltaic power generation systems. The proposed converter can achieve high voltage conversion gain without operating under extreme duty cycles. The voltage conversion gain can be readily adjusted by selecting different numbers of the diode-capacitor multiplier (DCM) cells in the circuit at the design stage. Moreover, with the passive snubber circuit in the proposed converter, all power switches and diodes in the DCMs can achieve zero-voltage turn-off and zero-current turn-on, which effectively reduces switching losses and increases the overall converter efficiency. The operational principles and analysis of the performance analysis with two DCMs are presented for demonstrative purpose. The effectiveness of the proposed ZVZCS DC-DC converter is validated using an 800W experimental prototype.

Voltage multipliers (VMs) are widely used in applications with the high-voltage-gain rectifiers and dc/dc converters with the capability of increasing voltage conversion ratio. Currently, all the existing VM circuits are designed with two input terminals, while the optimal design on the voltage conversion ratio and voltage stress on the semiconductor devices of the converters with VMs can be achieved by varying the number of basic VM units. However, as the number of its input terminals is fixed and, thus, the current stress on the semiconductor devices are not adjustable at the design stage, such circuits have limited applications in today's high-power energy conversion systems. In order to address such drawbacks of the conventional VMs, a multiple input-terminal VM (MIVM) circuit is proposed in this article. The analysis of the operation principles and the performance characteristics of the proposed MIVM circuit are presented in detail. As an example, the application of the MIVM with the traditional boost converters is presented and discussed, and the efficacy of the theoretical analysis is validated experimentally.

The voltage conversion ratio of basic dc/dc converters is limited due to the influence of parasitic elements of circuits and components. In this article, a family of passive circuits termed as “coat circuits” are proposed for conventional dc/dc converters. Not only voltage step-up capacity can be improved but also the voltage stress of components can be decreased by adding coat circuits to basic dc/dc converters. Moreover, no additional active switches are needed in the coat circuits, that means the control and driver circuits of the converters are not changed. The Cuk converter with the coat circuit has been analyzed as an example, and a 200 W experimental prototype has been built to verify the validity of the theoretical analysis.

The conventional buck-boost converter has the advantages of simple structure, low cost, and the capability to achieve both voltage step-up and down. However, due to the negative impacts of the parasitic parameters of the device, the voltage conversion gain of the conventional buck-boost converter is greatly limited. A low-voltage stress buck-boost converter with a high voltage conversion gain based on a coat circuit is proposed in this paper to address the problem. Similar to a coat that can enhance human’s resistance to cold weather, by adding the proposed coat circuit to the conventional buck-boost converter, not only the range for the voltage conversion can be extended, but also the voltage stresses of the semiconductor components are effectively reduced. In this work, comprehensive analysis on the working principles and performance characteristics of the coat converter are provided. Experimental results are obtained and analyzed to validate of the theoretical analysis based on a 300W closed-loop prototype platform.

A single-switch high step-up boost converter based on a novel voltage multiplier (VM) has been proposed in this study. Compared to traditional boost converter, not only the voltage conversion ratio has been increased, but also voltage stress across semiconductor devices has been decreased. Moreover, the voltage conversion ratio and voltage stress of switch of the proposed converter can be adjusted by the number of the VM cells. The control and drive circuits for the proposed converter is as simple as boost converter as there are no additional switches. Working principles and performance characteristics of the proposed converter have been analysed in detail. A 200 W experimental prototype with three VMs has been built to validate the theoretical analysis.

This study presents a high step-up scalable voltage multiple cell (SVMC)-based DC/DC converters, which have the features of high gain, low and adjustable components stresses and automatic input-current sharing in each input phase. In virtue of the above features, the converter is applicable for the DC collection grids for offshore wind farms. In this study, the converter in terms of working principle and property characteristics are analysed with four input phases and three SVMCs. The converter has also been evaluated in terms of the component stress and voltage conversion ratio against some other converters for high-power occasions. Moreover, a 2.5 MW simulation model and a 1.2 kW prototype were constructed for verification.

Aiming at renewable energy generation system with storage elements. A multi-operating mode and multi-port DC/DC converter with high step-up voltage gain has been presented in this paper, the proposed converter interfaces a unidirectional input power port, a bidirectional port for storage elements and a load port into a unified structure, which features single stage power conversion among any two electrical ports. It has the advantages of high step-up voltage gain, smoothly switching between any working modes and low voltage stress on switching devices. The working principles of the converter were analyzed in this paper, and then the performances and characteristics of the converter were deduced. Finally, an experimental prototype with a rated power of 200W was set up to verify the theoretical analysis.

Voltage multipliers (VMs) are widely used to combine with traditional DC/DC converter to achieve high voltage conversion gain. However, the input-terminals of existing VM circuits are unchangeable to two which make these converters are not suitable for high power/current applications. In this paper, a high power high step-up DC/DC converter based on multiple input-terminal voltage multiplier (MIVM) is presented. Analysis of the operation principles and the performance characteristics of the proposed converter are presented in detail. And an experimental prototype with a rated power of 800W was built to verify the correctness of the theory.

Voltage multipliers (VMs) are widely used not only in high voltage gain rectifier applications but also some traditional dc/dc converters to improve voltage conversion ratio. However, as the fixed number of its input-terminals, it is hard to traditional VM circuits to make a balance between the voltage and current stress on capacitors. In order to address such drawback of traditional VMs, a multiple input-terminal VM (MIVM) circuit is presented in this paper. The design flexibility of the proposed MIVM is better than traditional VMs. Analysis of the operation principles and the performance characteristics of the proposed MIVM circuit are presented in detail. And the efficacy of the theoretical analysis is validated experimentally.

This study presents a non-isolated high step-up DC/DC converter based on a high degree of freedom voltage gain cell (HDF-VGC). Both voltage stress of components and conversion ratio of the proposed converter could be adjusted by the number of the HDF-VGC, the current stress of the semiconductor devices can also be adjusted by the input phase numbers of the converter. Moreover, the input current of each phase are automatically balanced. These characteristics make the proposed converter very suitable for high-power and high-voltage applications, such as offshore wind power high-voltage DC transmission system. In this study, the topology construction of the proposed converter has been discussed. The operation principle and performance characteristics of the converter are analysed with four input phases and five HDF-VGCs, then the converter is simulated and a 400 W experimental prototype has been built to verify the correctness of the theoretical analysis.

This study proposes a kind of high step-up dc/dc converter with a novel voltage multiplier cell (VMC). The proposed VMC sharply reduces voltage stress on switches and diodes. Therefore, the conversion efficiency can be improved significantly. The converter also provides a wide range of voltage conversion ratios including fractional as well as VMC numbers and switch duty cycle. The topologies, operation principles, working characteristics and voltage conversion ratio are analysed in detail. A 500 W experimental prototype with two VMCs has been developed to validate the effectiveness of the theoretical analysis, and the highest efficiency is 93.8%.

A multi-input-port bidirectional DC/DC converter is proposed in this paper for the energy storage systems in DC microgrid. The converter can connect various energy storage batteries to the DC bus at the same time. The proposed converter also has the advantages of low switch voltage stress and high voltage conversion gain. The working principle and performance characteristics of the converter were analyzed in detail, and a 200 W, two-input-port experimental prototype was built. The experimental results are consistent with the theoretical analysis.

The modeling and control system design of high step-up DC/DC converters based on voltage multipliers (VMs) are difficult, due to the various circuit topologies and the presence of large number of capacitors in VMs. This paper proposes a generic approach to reduce the model order of such converters by replacing the VM capacitors with voltage sources controlled by the output voltage of the converter. Theoretical analysis and simulation results show that the derived models can accurately represent the low frequency response of the converter which is valuable for obtaining a small-signal AC model for control system design. The detailed modeling and controller design process are demonstrated for the converter, and the obtained simulation results are verified experimentally on a 400 W prototype.

A high step-down multiple-output LED driver is proposed in this paper. Firstly, the derivation of the driver with dual-output is presented and its operation principle and steady state performance are analyzed in detail. Secondly, a high step-down N-channel LED driver is proposed and its current auto-balance characteristic and step-down ratio are analyzed. Finally, an experimental prototype is built and the experimental results are given. The theoretical analysis and experimental results show that the proposed driver has the following virtues: First, if load balancing is achieved, the voltage gain is 1/N that of a Buck driver, where N is the number of channels. Second, each output automatically has an equal output current, without requiring more current close-loop control circuits than a Buck driver. Last, the voltage stresses of the switches and diodes are lower than those of a Buck driver, meaning that lower voltage switches and diodes can be used, and a higher efficiency can be expected.