Low Voltage Stress Research Articles

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.

An extendable asymmetric boost multi‐level inverter with self‐balanced capacitors

AbstractThis paper proposes a basic asymmetric boost 35‐level inverter topology that can be extended to earn higher gains and levels. The proposed structure benefits from following advantages: extendibility, voltage boosting capability, natural voltage balancing of capacitors, low average voltage stress on semiconductors and large ratio of number of steps to components. The impulse charging current of capacitor(s) is suppressed by small inductor(s), which is bypassed by a diode during discharging mode. The low magnitude (accordingly small size, low price and low weight) and balanced output powers of VX and VY sources are other important profits of proposed topology. The input DC sources can be realized by batteries or combination of PVs and dc–dc converters. This paper also proposes an algorithm for deciding the magnitude of DC sources, which maximizes the number of steps. The gain and steps can be further increased by adding more cascaded switched‐capacitor cells (CSCCs). Due to large number of levels, the output voltage quality of proposed structure is high, which helps to remove or downsize the ac‐side filter. The laboratory‐scaled prototype of converter (feeding a R–L load) has been implemented. The comparison and experimental results approve superiority and correct performance of proposed topology.

Closed-Loop Control of a New High Step-Up Multi-Input Multi-Output DC-DC Converter

Abstract: A new multi-input multi-output dc-dc converter with high step-up capability for wide power ranges is proposed in this paper. The converter's number of inputs and outputs is arbitrary and independent of each other. The proposed topology combines the benefits of DC-DC boost and switched-capacitor converters. The number of input, output, and voltage multiplier stages is arbitrary and depends on the design conditions. First, the various operating modes of the proposed converter are discussed. The closed-loop control system also must be designed using state space representation and small-signal modelling. Finally, the operation of the proposed converter is derived from the simulation results. Keywords: High power converter, Low voltage stress, Multi-Input Multi-Output (MIMO) converter, Non-isolated high step-up dc-dc converter, closed loop control.

Hybrid 17‐level inverters based on T‐type flying‐capacitor and switched‐capacitor

AbstractThe purpose of this work is to use fewer components to generate more output levels for power interfaces of low dc voltage sources such as fuel cells. First, two switched‐capacitor voltage lifters (SCVLs) with similar structure and same function are summarized. Each of them uses a single capacitor and has the advantage of identical voltage stress for all components. Then, the SCVLs are combined with a T‐type unit to develop two 17‐level inverters. The SCVLs is responsible for voltage boosting, while the T‐type unit uses two flying capacitors to increase the number of output levels. In addition to the use of three capacitors, the two 17‐level inverters employ 13 and 14 semiconductor switches respectively, and all components' voltage stresses do not exceed the dc input voltage. Simple structure, reduced capacitors' count, and low components' voltage stress are the main merits of the proposed inverters compared with other 17‐level inverters. Beyond theoretical analysis, both steady‐state and dynamic performances are verified experimentally, and the highest efficiency measured by the experiment is up to 97.8%.

Improved Cascaded H-Bridge Multilevel Inverters with Voltage-Boosting Capability

This paper proposes two improved cascaded H-bridge (ICHB) multilevel inverters that feature voltage-boosting capability. The conventional H-bridge with a front-end dc–dc boost converter was restructured for single-stage operation. The developed three-level topology not only saves one power switch but also exhibits lower voltage stress across its capacitor. Extension to five-level generation was also introduced by merely adding two power switches and one capacitor. The final five-level topology outperforms the classical cascaded H-bridge (CHB) multilevel inverter with a significant reduction in the power switch count, with a 42% and 50% reduction in both the isolated dc source and inductor counts. The power efficiency was also improved without compromising the modularity feature of the classical CHB multilevel inverter. The operation and theoretical analysis of the proposed topologies were validated via simulations and experimental tests.

A High Gain AC-DC Rectifier Based on Current-Fed Cockcroft-Walton Voltage Multiplier for Motor Drive Applications

This paper proposes a novel high-gain AC-DC converter based on the Cockcroft-Walton (CW) voltage multiplier which can be utilized in motor drive systems with low input voltage. In this topology, use of the voltage multiplier and boost circuit results in the increment of converter gain which has a significant impact on the cost and efficiency of the system. Moreover, in this converter, the AC voltage is directly changed to DC voltage using the switching method in high frequency and, as well, the power factor is corrected. Besides, this high-frequency converter contributes to the reduction of output ripple. On the other hand, cost efficiency, the low voltage stress on capacitors and diodes, compactness, and the high voltage ratio, are achieved from the Cockcroft-Walton circuit. Furthermore, the hysteresis method is presented for converter switching to correct the power factor. The converter is simulated in MATLAB software to demonstrate the effectiveness of the suggested method. Lastly, a laboratory prototype of the suggested converter is built, several tests are done in order to verify the theoretical analysis, and comprehensive comparison with the state-of-the-art converter is done.

A transformer‐less DC–DC converter with high voltage conversion ratio adopting inverting voltage lift cell

In this work, a high voltage gain dc-dc converter is proposed based on a switched inductor cell. The proposed converter utilises an inverting switched capacitor cell at the output side to achieve high voltage gain. Extendibility of the proposed structure without applying the fundamental change to the topology is the merit of the proposed structure as well as the low voltage stress on the switches. The operation of the switches with the same duty cycle is the other advantage of the proposed converter. The steady-state analysis of the proposed converter is discussed in detail. The proposed converter is investigated under real conditions in order to compare it with its operation under ideal conditions. The proposed structure is compared with other topologies presented in the literature, previously. Finally, the experimental results are given to prove the validity of the theoretical analysis.

High gain multiphase boost converter based-on capacitor clamping structure

<p>In the last few years, the non-isolated dc converters involving high voltage gain with adequate performance are becoming quite popular in industrial applications. This is resulting in high voltage and current stress on the power device (switches and diodes), as well as a limited output voltage with a high duty cycle. This paper proposes a multi-phase non-isolated boost converter that uses capacitor clamping to increase output voltage while reducing stress across the power device. There are two stages in the proposed converter (first stage is three inductors and three switches and the second stage is clamper circuit of three capacitors and three diodes). The proposed converter is high voltage gain, with low voltage stress through switches transistors. To justify the theoretical analysis, the concept was validated through mathematical analysis and by simulation using MATLAB/SIMULINK. The results carried out the results permit the converter behavior and performance to be accurately.</p>

Quasi-Impedance-Source-Network-Based Nonisolated High-Step-Up DC–DC Converter

The high-step-up dc&#x2013;dc converter is a key for numerous renewable-energy-based applications such as photovoltaic and fuel cells. Due to the low-voltage output of these renewable sources, a high-step-up stage is required, which bridges the gap of renewable to utility state. In this article, a noncoupled high-step-up <inline-formula><tex-math notation="LaTeX">$Z$</tex-math></inline-formula>-source dc&#x2013;dc converter, utilizing a quasi-<inline-formula><tex-math notation="LaTeX">$Z$</tex-math></inline-formula>-source (QZS) network, is presented. The proposed topology is a combination of QZS structure and switched-capacitor cells, which maintains continuous input current and low-voltage stress across capacitors. In addition to these merits, the converter can achieve a high-step-up voltage at a low duty cycle, which results in lower conduction losses on semiconductor devices. The working principle, steady-state waveforms, related expressions, and comparative study are included in this article. The proposed converter can be extended for the use of a single-stage step-up <inline-formula><tex-math notation="LaTeX">$Z$</tex-math></inline-formula>-source inverter and also for hybrid output applications. Finally, experimental results are presented to verify the feasibility of the converter in both open and closed loops.

Deadbeat predictive power control for Vienna rectifier under unbalanced power grid condition

Due to the low output distortion and switch voltage stress, Vienna rectifiers have been widely utilized in high-power applications such as communication power supplies, wind power systems and electric vehicle charging piles. However, Vienna rectifiers still have to face tough challenges under unbalanced grid considering the inherit operating range limitation caused by its structure. Consequently, a deadbeat predictive power control (DBP-PC) for the Vienna rectifier under unbalanced grid is proposed. Using the positive and negative sequence double dq decoupling current control strategy, the operating range of the Vienna rectifier under unbalanced grid is analyzed. Furthermore, an improved DBP-PC for Vienna rectifiers under unbalanced grid is proposed. By the improved DBP-PC, the stable operating range can be effectively extended. Finally, the corresponding simulations and experiments are executed to demonstrate the performance of the proposed control strategy.

A novel nine‐level boost inverter with a low component count for electric vehicle applications

In electric vehicles (EVs), considerable battery cells are cascaded in series for motor driving to improve the output voltage. The series combination of battery cells causes challenges like isolation of faulty cells, voltage unbalance, and slow charge equalization. Therefore, state-of-charge (SOC) and voltage equalization circuits are often used in industries to protect the battery cells. A nine-level inverter circuit with a double voltage boost is proposed to reduce the above issues based on the switch-capacitor (SC) principle. Unique features like self-balancing, voltage boosting are attained, which cannot be achieved through traditional inverters. The proposed topology can operate at a wide range of modulation indices () to produce different voltage levels. The absence of a back-end H-bridge in the proposed circuit offers low voltage stress across the semiconductors. The operating principle, capacitor sizing, and modulation approach are presented. Further, experimental tests are conducted at different loading conditions to verify the performance of the proposed circuit.

Design, analysis and implementation of a new three‐port DC‐DC converter with bidirectional capability

The proposed converter here is a dual-input DC-DC converter with bidirectional power flow. One of the inputs is unidirectional, while the other is a bidirectional port for a battery. The proposed converter can combine two alternating sources with different characteristics. The demanded power of the load can be provided by each input source individually or simultaneously. What is more, the unidirectional port can charge the battery as well as power the output load. Due to the bidirectional capability, the energy returned from the output can be stored in the battery which is suitable for electric vehicle (EV) applications. Step-up capability, the low voltage stress on semiconductors, and the smaller number of passive elements are the other advantages of the converter. Depending on the battery usage status, four different operation scenarios are defined in the proposed converter. The converter operation is described in each scenario and the mathematical analysis is presented. Based on these, the experimental prototype is conducted to verify the characteristics and feasibilities of the converter.

Transformer-Less Switched-Capacitor Quasi-Switched Boost DC-DC Converter

In this article, a quasi-switched boost converter based on the switched-capacitor technique with high step-up voltage capability is dealt with and analyzed. The proposed converter offers a simple structure and low voltage stress on the semiconductor elements with intrinsic small duty cycle. An inductor of the proposed converter is connected in series with the input voltage source; therefore, continuous input current ripple is attainable. In addition, the efficiency of the proposed converter is also improved. A detailed steady-state analysis is discussed to identify the salient features of the switched-capacitor-based quasi-switched boost DC-DC converter. The performance of the converter is compared against similar existing high boost DC-DC converters. Finally, the switched-capacitor-based quasi-switched boost DC-DC converter is investigated by experimental verification.

An Embedded Half-Bridge Γ-Z-Source Inverter with Reduced Voltage Stress on Capacitors

In this paper, an embedded half-bridge Z-source inverter based on gamma structure is proposed. In contrast with the classical half-bridge inverter, the proposed inverter can generate zero voltage levels in output. High voltage gain and low voltage stress on capacitors are the main advantages of the proposed converter. The value of the boost factor in the proposed structure is increased by changing both the shoot-through (ST) duty cycle and turns ratio of the transformer. The operating principle of the proposed converter in four operating modes is presented. We also calculate the critical inductance and compare the proposed converter with conventional topologies. In addition, power loss and THD analysis are presented. Finally, PSCAD/EMTDC software is used to verify the correct operation of the proposed inverter and the experimental results.

Solar photovoltaic based dynamic voltage restorer with DC-DC boost converter for mitigating power quality issues in single phase grid

ABSTRACT A new topology of photovoltaic (PV) based transformerless dynamic voltage restorer (TDVR) with high gain DC-DC boost converter is proposed to mitigate voltage sag and swell, interruptions, and unbalanced outages in single-phase grid. The proposed PV-DVR high DC-DC boost converter is comprised of one MOSFET switch and three inductors with second order generalized integrator (SOGI) based unit vector template (UVT) control to enhance the effectiveness of the system for grid-connected renewable applications. The high voltage (HV) gain is achieved by this proposed converter through its soft-switching ability and coupled inductor arrangement with continuous conduction mode (CCM). In the proposed high gain DC-DC converter, the MOSFET IRFP260 power switch is preferably used for low voltage stress and also minimum on-state resistance. The mathematical analysis of the proposed converter is also discussed in this paper. The proposed converter is interfaced with an SOGI-PLL controller with input voltage (24 V), output voltage (230 V), and power rating as 250 W with less number of both passive and active switches. Moreover, to validate the performance and advantage of the proposed converter, the system was simulated by using MATLAB-SIMULINK and laboratory 250 W prototype results are presented to show the effectiveness of the design to limit the voltage sag – 0.1 pu and swell – 1.9 pu and also THD% level within in ceiling limit prescribed in IEEE STD at the load side.

A High Step-up DC-DC Converter Based on the Voltage Lift Technique for Renewable Energy Applications

High gain DC-DC converters are getting popular due to the increased use of renewable energy sources (RESs). Common ground between the input and output, low voltage stress across power switches and high voltage gain at lower duty ratios are desirable features required in any high gain DC-DC converter. DC-DC converters are widely used in DC microgrids to supply power to meet local demands. In this work, a high step-up DC-DC converter is proposed based on the voltage lift (VL) technique using a single power switch. The proposed converter has a voltage gain greater than a traditional boost converter (TBC) and Traditional quadratic boost converter (TQBC). The effect of inductor parasitic resistances on the voltage gain of the converter is discussed. The losses occurring in various components are calculated using PLECS software. To confirm the performance of the converter, a hardware prototype of 200 W is developed in the laboratory. The simulation and hardware results are presented to determine the performance of the converter in both open-loop and closed-loop conditions. In closed-loop operation, a PI controller is used to maintain a constant output voltage when the load or input voltage is changed.

A New Three-Winding Coupled Inductor Nonisolated Quasi-Z-Source High Step-Up DC–DC Converter

This article presents a new three-winding coupled inductor high step-up quasi-Z-source dc–dc converter with single magnetic core and voltage multiplier techniques. Conventional quasi-Z-source-based dc–dc converters not only suffer limited voltage gain and high voltage stresses on semiconductors but also have utilized two or more magnetic cores in their structures. However, the suggested converter shares high voltage gain with continuous input current, low normalized voltage stresses on switch and diodes, low total voltage stresses on semiconductors, and common ground between input energy source and load. Also, this converter with single power switch and magnetic core has not limited the duty cycle. Furthermore, the proposed converter has good efficiency at high output voltage, and hence it is suitable for high voltage dc bus of three-phase inverters in renewable energy applications. The mathematical analysis, operating principle for the proposed converter, and comparison with other Z-source-based converters are provided. At last, a 400-W prototype is built in the laboratory, which has validated the accuracy of the proposed converter.

Family of Transformerless Active Switched Inductor and Switched Capacitor Ćuk DC–DC Converter for High Voltage Gain Applications

This article presents a family of transformerless active switched inductor and switched capacitor Ćuk high voltage gain dc–dc converters. The configuration of this family has the advantages of nonpulsating output current, high step-up voltage gain, low voltage, and current stress across the component. Thus, conduction losses are decreased owing to the low-voltage-rating of the semiconductors. The Ćuk converter with two switched-capacitor cells is evaluated in detail. The experimental results are provided to verify the theoretical analysis.

Zero Inductor-Voltage Multilevel Bus Converter

A novel topology to achieve 4:1 voltage step down, aimed at 48 V to 12 V conversion in data center applications, is presented. The so-called dc-transformer topologies have become a very active area of research to improve the overall efficiency of data centers in response to a shift from a 12 Vdc bus architecture to a 48 Vdc bus architecture. In particular, switched-capacitor topologies have been investigated due to their high power density, efficiency, and low reliance on magnetics. However, switched-capacitor topologies have challenges associated with the hard-charging of capacitors and are often forced to make design compromises that reduce their overall performance. The proposed topology maintains many of the advantages of a switched capacitor topology, such as reduced component stresses, and very low reliance on magnetics, while also inherently avoiding any hard-charging of the flying capacitors. This allows the converter to operate at a very low frequency, such as 60 kHz, with a small inductor, such as 100 nH, and use low voltage stress devices to achieve a peak efficiency of more than 99% for 48 V to 12 V conversion and a power density of 800 W/in <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> .

Design of a High Step-Up DC-DC Converter with Voltage Doubler and Tripler Circuits for Photovoltaic Systems

In this paper, a high step-up DC-DC interleaved boost converter is proposed for renewable sources with low voltages such as photovoltaic module and fuel cell. The proposed converter uses interleaving method with an additional voltage doubler and tripler circuit. In the proposed converter, the inductor at all phases is operated to gain high voltage through voltage doubler and tripler circuit capacitors with suitable duty cycle. The proposed topology operates in six switching states in one period. The steady-state analysis and operating principle are examined comprehensively which shows numerous improvements over the traditional boost converter. These improvements are high-voltage gain and low-voltage stress across switches. The proposed DC-DC interleaved boost converter has a gain/conversion ratio four times that of the conventional interleaved boost converter and four times less-voltage stress across the main switches. Simulation has been done in Matlab Simulink on a 70% duty cycle, and results are compared with conventional interleaved boost converter. For an input voltage of 15 volts, the proposed converter is able to generate an output voltage of 200 volts at 70% duty cycle with a voltage stress of 50 volts across main switches, whereas traditional interleaved boost converter generates 200 volts from same input voltage at 92.5% duty cycle with voltage stress of 200 volts across switches. From simulation results, it is clear that the proposed converter has better performance as compared to conventional interleaved boost converter for same design parameters.