High Step-up Converter Research Articles

An Improved ZVS High Step-Up Converter Based On Coupled Inductor and Built-In Transformer

A high step-up dc-dc converter with multiple magnetic devices and switched-capacitor voltage multiplier cell (SC VMC) is proposed in this article. By simultaneous implementation of a coupled inductor (CI) and a built-in transformer (BIT), the voltage gain is flexibly increased with an additional degree of freedom in comparison with the converters with only BIT or CI. To further increase the voltage gain, the secondary winding of the CI is inserted in series with the primary winding of the BIT. This new architecture leads to multiplication of the turns ratios of the CI and BIT in the voltage gain expression, as well. The SC VMC not only extends the voltage gain but also reduces the voltage stress across the MOSFETs. To have a better device utilization, the blocking capacitor is participated in voltage gain improvement. Moreover, through active clamp circuit, the leakage energy of the magnetic devices is recycled and zero voltage switching (ZVS) performance is obtained for the main and auxiliary MOSFETs. In such a case, the switching frequency can be increased to reduce the volume of the converter. Finally, a 400-W laboratory prototype with 25- 400 V voltage conversion is fabricated to demonstrate the effectiveness of the proposed converter.

Evaluation of high step-up power conversion systems for large-capacity photovoltaic generation integrated into medium voltage DC grids

With the increase of dc based renewable energy generation and dc loads, the medium voltage dc (MVDC) distribution network is becoming a promising option for more efficient system integration. In particular, large-capacity photovoltaic (PV)-based power generation is growing rapidly, and a corresponding power conversion system is critical to integrate these large PV systems into MVDC power grid. Different from traditional ac grid-connected converters, the converter system for dc grid interfaced PV system requires large-capacity dc conversion over a wide range of ultra-high voltage step-up ratios. This is an important issue, yet received limited research so far. In this paper, a thorough study of dc-dc conversion system for a medium-voltage dc grid-connected PV system is conducted. The required structural features for such a conversion system are first discussed. Based on these features, the conversion system is classified into four categories by series-parallel connection scheme of power modules. Then two existing conversion system configurations as well as a proposed solution are compared in terms of input/output performance, conversion efficiency, modulation method, control complexity, power density, reliability, and hardware cost. In-depth analysis is carried out to select the most suitable conversion systems in various application scenarios.

Bidirectional Buck-Boost and Series LC-Based Power Balancing Units for Photovoltaic DC Collection System

The input-independent and output-series (IIOS) structure is often used in the high step-up ratio converters required for medium-voltage dc (MVdc) grid interface of photovoltaic (PV) systems, which achieves high voltage gain and ensures high efficiency. However, due to the characteristics of IIOS structure, when some PV arrays are shadowed or malfunction, the generated power of these modules will be mismatched. Mismatched power will result in output capacitor voltages deviating from the rated value, which is not conducive to the standardized multimodule design. Besides, voltages of some PV arrays will deviate from their maximum power point (MPP) value, leading to a decrease in the total generated power. In order to balance the module output voltages of the IIOS structure, this article proposes bidirectional buck-boost and series <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">LC-</i> based power balancing units (LC-PBUs) for PV dc collection systems. Compared with a traditional solution, nearly half of the switches are saved and half of the inductors are displaced by small inductors. Power balance can be achieved through the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">LC</i> -PBUs by controlling the duty ratio and the phase of the pulse-width modulation (PWM) signal. Simulations and experiments are carried out to verify the effectiveness of <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">LC</i> -PBU under power sags.

A Universal ZVT Design for a Family of Multiphase Interleaved High Step-Up Converters With Minimized Voltage Stress and Wide Operating Range

Multiphase interleaved boost diode-capacitor (MIBD) converters, as the combination of multiphase interleaved input and voltage multiplier cells (VMCs), provide a preferred solution for both high voltage gain and high-efficiency application. This article proposes a universal zero-voltage transition (ZVT) circuit design method for a family of MIBD converters with different VMC structure and cell number. Compared with other soft-switching (SS) design methods, there is no extra voltage stress for all the semiconductor devices. An auxiliary circuit consisting of two low-voltage rating switches, two diodes, two capacitors, and one small inductor is integrated into the hard-switching (HS) two-phase interleaved boost diode-capacitor (TIBD) converters to provide zero-voltage switching (ZVS) turn-on and turn-off for the main switches and zero-current switching (ZCS) turn-off for all the diodes. Besides, the auxiliary switches turn on under ZCS. All the SS is accomplished within a wide duty cycle and power rating. From the comprehensive comparison, the constructed converters' performance exceeds that of ZVS converters published in the recent literature. Furthermore, the extendable high voltage gain, low input current ripple, low voltage stress, and simple parameter design characteristics of HS MIBD converters are also conserved. Finally, a 320-W laboratory prototype is implemented to validate the theoretical analysis.

Correction to: A ZVS high step-up converter based on an integrated boost-cuk topology

Correction to: A ZVS high step-up converter based on an integrated boost-cuk topology

An interleaved high step‐up DC–DC converter with ZVS capability for renewable energy systems applications

In this paper, an interleaved zero voltage switching high step-up converter based on active clamp, coupled inductor (CI), built-in transformer (BIT), and switched capacitor (SC) is proposed. The main novelty of the proposed converter is that the secondary winding of the CI is inserted between the primary winding of the CI and the primary winding of the BIT. Therefore, the voltage gain can be achieved in proportionate to the multiplication of the turn ratios of the CIs and BIT. The configuration of the proposed converter not only increases the voltage gain, but also reduces the current and voltage stress of the power switches and restricts the input current ripple, which decreases the conduction losses and increases the lifetime of the input source. Also, zero voltage switching turn-ON and turn-OFF conditions for all switches are achieved by employing an active clamp configuration. The voltage across the diodes clamped to the output voltage and the reverse recovery problem is reduced due to the leakage inductors. Finally, a 600 W prototype with 24–400 V voltage conversion is built to verify the performance and theoretical analysis.

Isolated ZVS-ZCS DC–DC High Step-Up Converter With Low-Ripple Input Current

This article proposes a galvanically isolated high step-up dc–dc converter for dc microgrid applications. By the use of an inductor, a transformer, a voltage multiplier, and an active clamp, the proposed converter is able to provide very high dc voltage gains along with reduced voltage stress across the semiconductors, zero-voltage and zero-current switching for the switches and the diodes, respectively, low ripple input current, and reduced component count. The analysis of the converter in continuous conduction mode (CCM) and a comparison with other previously published isolated topologies are also presented. Finally, a prototype has been built for a power of 250 W to verify the functionality of the proposed converter in CCM operation, with an input voltage range of 20–28 V and an output voltage of 400 V.

High-Gain High-Efficiency DC–DC Converter with Single-Core Parallel Operation Switched Inductors and Rectifier Voltage Multiplier Cell

This paper proposes a high step-up high-efficiency converter, comprised of an active switched coupled-inductor cell. The secondary windings are integrated into a rectifier voltage multiplier cell in a boost-flyback configuration, allowing the operation with high voltage gain with low switches duty cycle and low turn-ratios on the coupled-inductors. Both coupled-inductors are integrated into a single core due to the parallel operation of the switches. The leakage inductances of the coupled-inductors are used to mitigate the reverse recovery currents of the diodes, while regenerative clamp circuits are used to protect the switches from the voltage spikes caused by the leakage inductances. The operation of the converter is analyzed both quantitatively and qualitatively, and the achieved results are validated through experimentation of a 400 W prototype. A 97.1% CEC efficiency is also reported.

Novel High-Efficiency High Step-Up DC–DC Converter with Soft Switching and Low Component Voltage Stress for Photovoltaic System

This study developed a novel, high-efficiency, high step-up DC–DC converter for photovoltaic (PV) systems. The converter can step-up the low output voltage of PV modules to the voltage level of the inverter and is used to feed into the grid. The converter can achieve a high step-up voltage through its architecture consisting of a three-winding coupled inductor common iron core on the low-voltage side and a half-wave voltage doubler circuit on the high-voltage side. The leakage inductance energy generated by the coupling inductor during the conversion process can be recovered by the capacitor on the low-voltage side to reduce the voltage surge on the power switch, which gives the power switch of the circuit a soft-switching effect. In addition, the half-wave voltage doubler circuit on the high-voltage side can recover the leakage inductance energy of the tertiary side and increase the output voltage. The advantages of the circuit are low loss, high efficiency, high conversion ratio, and low component voltage stress. Finally, a 500-W high step-up converter was experimentally tested to verify the feasibility and practicability of the proposed architecture. The results revealed that the highest efficiency of the circuit is 98%.

A ZVS high step-up converter based on an integrated boost-cuk topology

A ZVS high step-up converter based on an integrated boost-cuk topology

A ZVT Auxiliary Circuit for High Step-Up Multi-Input Converters with Diode-Capacitor Multiplier

In this paper, a Zero-Voltage Transition (ZVT) non-isolated high step-up multi-input DC-DC converters is proposed which employs an auxiliary cell and diode-capacitor multiplier. The auxiliary cell has only one switch and is suitable for high step converters with diode-capacitor multiplier. In the proposed converter, all semiconductor devices operate under fully soft switching condition. The main switches turn on and turn off under Zero Voltage Switching (ZVS) condition whereas the auxiliary switch turns on under Zero Current Switching (ZCS) condition and turns off under zero Voltage and Zero Current Switching (ZVZCS) condition. Also, ZCS condition at turn-off is provided for all diodes to eliminate reverse recovery issue. The structure of the proposed converter includes two boost cells, one diode-capacitor multiplier cell, and one ZVT auxiliary circuit. Soft switching conditions for all main switches are provided by only one auxiliary circuit. The proposed converter has high step-up conversion gain without any coupled inductor. Soft switching conditions, continuous current of input sources, high efficiency, expansion capability of input sources, returning the energy of the auxiliary circuit to the diode-capacitor multiplier and low-voltage stress on switches are the main advantages of the proposed converter. The steady-state analysis of the converter and operation modes are discussed. A 160-W prototype of the proposed converter is designed and implemented. Experimental results confirm that the theoretical and the efficiency of the proposed converter reaches 96.4% at the nominal load.

High Step-Up Converter Based on Non-Series Energy Transfer Structure for Renewable Power Applications.

In this paper, a high step-up boost converter with a non-isolated configuration is proposed. This configuration has a quadratic voltage gain, suitable for processing energy from alternative sources. It consists of two boost converters, including a transfer capacitor connected in a non-series power transfer structure between input and output. High power efficiencies are achieved with this arrangement. Additionally, the converter has a common ground and non-pulsating input current. Design conditions and power efficiency analysis are developed. Bilinear and linear models are derived for control purposes. Experimental verification with a laboratory prototype of 500 W is provided. The proposed configuration and similar quadratic configurations are compared experimentally using the same number of components to demonstrate the power efficiency improvement. The resulting power efficiency of the prototype was above 95% at nominal load.

An Interleaved ZVS High Step-Up Converter for Renewable Energy Systems Applications

A novel zero voltage switching (ZVS) interleaved high step-up converter for renewable energy systems is proposed in this article. By applying a switched capacitor mixed with coupled inductor and built-in transformer, the proposed converter achieves high voltage gain and minimized voltage stress across power switches. Both of the voltage gain and the voltage stress can be adjusted by the turns ratio of the coupled inductor and built-in transformer, which gives an extra degree of freedom for the converter design. Hence, operating at high duty cycles is avoided and low voltage rated semiconductors can be adopted, which reduce conduction losses and improve the circuit performance. Furthermore, an active clamp scheme is utilized to guarantee ZVS turn- <sc xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">on</small> for the power <sc xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">MOSFET</small> s and the leakage inductances of the magnetic means help to provide zero current switching of the diodes. In such a case, switching losses are minimized and the reverse current recovery is alleviated. Accordingly, the proposed converter with reduced counterparts is a suitable candidate for high step-up and high power applications. Finally, a 600-W prototype with 24 to 480 V voltage conversion is built to demonstrate the performance of the proposed converter.

Generalized Flexible Voltage Pumping Module for Extra High Voltage Gain Converters in Electric Vehicles

This study proposes a generalized voltage pumping module (GVPM) and a GVPM-enabled converter design approach for electric vehicles. The designed GVPM has high flexibility and can be applied to most high step-up converters for extra voltage pumping yet with low component stresses. The proposed GVPM design method is presented, rationalized and analyzed in a generalized structure, which is followed by eight specific application examples, where typical step-up converters are employed to be structurally coupled with the proposed GVPM design approach for design guideline and methodological validation. Through theoretical analyses and experimental verification, the proposed voltage pumping approach is proven to be able to work synergistically with most types of DC-DC converters, demonstrating its advantageous features and wide applicability for voltage pumping of step-up converters.

Design And Analysis Of Different Multi-Level Inverter Topologies For Single Phase Im Drive

A PWM technique can be used to increase the level of the converter voltage. The duty ratio of PWM controller plays a major role in controlling the step-up converter operation to obtain the required output level. The output of the boost converter is converter into AC by using the Inverter and fed to the induction motor (IM). The operation of the IM is mainly based on the suitable choice of converter-inverter system. Inverter operation is controlled by a PWM switching technique. This paper mainly deals with the photovoltaic (PV) integration of Voltage Multiplier circuit and an inverter fed IM drive. Solar energy from the renewable resource is the primary source for the converter circuit. In renewable energy applications, a new high step-up converter is used to boost up the input variable low-voltage. Converter doubles the input voltage by using a voltage multiplier circuit. The proposed model is designed and simulation is done and the output waveforms are plotted.

An X-shaped-switching-network high-step-up converter for grid integration of renewable energy sources

Power converters play a pivotal role in forming modern renewable energy sources integrated power grids. Among all grid-forming converters, high step-up converters with great nonlinear dynamic responses and fault recovery abilities have been sought after and developed in recent decades. This study proposes a novel X-shaped switching network (X-net)-based high-step-up converter. Specifically, an X-shaped switching network is designed to realize energy conversion of the converter, which, different from traditional impedance networks, only comprises switches and diodes. With this radically new X-shaped network, the proposed X-net converter is able to realise additional voltage pumping and low capacitor stress, hence improving dynamic responses and system reliability. In this study, the theory, analysis and simulation and prototype experiments of the proposed X-net converter with additional voltage pumping are presented in detail. Extensive comparisons between the X-net converter and its traditional counterparts are also presented which verifies the superiority of the proposition. The proposed X-net based high step-up converter bears significant potential as future grid-forming converters.

Controllability Analysis and Verification for High-Order DC–DC Converters Using Switched Linear Systems Theory

Output voltages of renewable energy sources, such as photovoltaic units and fuel cells, are normally low, and multistage boost converters or single-stage high step-up converters are usually employed to increase the output voltage to be connected to the electric grid. Among all converter technologies, single-stage high-order dc–dc converters with multiple cells have gained significant popularity in recent years due to their high power density, low cost, and high efficiency. With an increased number of cells, the number of switching variables and dynamic components in multicell converters also increases, leading to control difficulties and consequently system malfunction. In order to understand and ensure the controllability of these converter systems, in this article, we establish high-order mathematical models for typical single-stage multicell high-order dc–dc converters and study their controllability using switched linear systems theories. The structure controllability, state controllability, and output controllability of the converters are analyzed in detail based on the proposed mathematical model. The theoretical analysis is substantiated by simulation and experimental verification on the improved four-cell switched-inductor dc–dc converter. The outcome of this article will provide a theoretical framework and useful references for parameter and control designs for high-order converters in practical applications.

An Efficient and Robust Current Control for Polymer Electrolyte Membrane Fuel Cell Power System

Taking into account the restricted ability of polymer electrolyte membrane fuel cell (PEMFC) to generate energy, it is compulsory to present techniques, in which an efficient operating power can be achieved. In many applications, the PEMFC is usually coupled with a high step-up DC-DC power converter which not only provides efficient power conversion, but also offers highly regulated output voltage. Due to the no-linearity of the PEMFC power systems, the application of conventional linear controllers such as proportional-integral (PI) did not succeed to drive the system to operate precisely in an adequate power point. Therefore, this paper proposes a robust non-linear integral fast terminal sliding mode control (IFTSMC) aiming to improve the power quality generated by the PEMFC; besides, a digital filter is designed and implemented to smooth the signals from the chattering effect of the IFTSMC. The stability proof of the IFTSMC is demonstrated via Lyapunov analysis. The proposed control scheme is designed for an experimental closed-loop system which consisted of a Heliocentric hy-Expert™ FC-50W, MicroLabBox dSPACE DS1202, step-up DC-DC power converter and programmable DC power supplies. Comparative results with the PI controller indicate that a reduction of 96% in the response time could be achieved using the suggested algorithm; where, up to more than 91% of the chattering phenomenon could be eliminated via the application of the digital filter.

Resonant Push–Pull Converter With Flyback Regulator for MHz High Step-Up Power Conversion

With the trend toward achieving high efficiency, high power density and high operating frequency in power converters, a galvanic isolated circuit architecture is proposed in this article for high step-up applications with wide input-voltage range. This converter consists of a current-fed resonant push-pull (PP) converter as a dc transformer (dcX) dealing with most of the power with high efficiency and an active clamp flyback converter (ACF) as a regulator within a large conversion range. As a single-stage converter, the ACF regulator is paralleled with PP converter to share the total power and regulates the high output voltage. An experimental prototype with an input-voltage range of 24-32 V and output 400 V/400 W is built under 1 MHz switching frequency. A peak efficiency of 97.1% and a power density of 210 W/in <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> (or 13 W/cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> ) are achieved. Experimental result validates the correctness of the analysis and proves the feasibility of the proposed converter for MHz high step-up dc-dc conversion.

MPPT-based backstepping control for a grid connected fuel cell system using high step-up converter

MPPT-based backstepping control for a grid connected fuel cell system using high step-up converter