Wide Input Voltage Variation Research Articles

New DC/DC Converter for Electrolyser Interfacing with Stand-Alone Renewable Energy System

Abstract This paper presents findings of a R&D project targeted to the development of a galvanically isolated step-down DC/DC converter for electrolyzer integration with renewable energy systems. The presented converter with an improved control algorithm for the full-bridge active rectifier features reduced energy circulation and switching losses. The performance can be improved under wide input voltage and load variations. The advantages of the converter were verified with a 1 kW converter prototype and the test results were in full agreement with the expected waveforms. The presented steadystate operation principle and mathematical analysis of the converter based on the simulation and experimental results can be used as design guidelines for component and parameter estimation in practical applications.

Minimum Current Operation of Bidirectional Dual-Bridge Series Resonant DC/DC Converters

This paper discusses the steady-state operation of phase-shift modulated dual-bridge series resonant converter (DBSRC) intended for dc/dc power bidirectional control over a wide range of input and output voltages. The analysis, developed here for the most general case of three independent phase-shift control angles, demonstrates the existence of minimum current trajectories in the 3-D control space along which the DBSRC cell can deliver any admissible power level with minimum tank circulating current. At nonunity conversion ratios, minimum current operation prevents the DBSRC output bridge from experiencing severe hard-switching losses, substantially reducing the effort normally required by auxiliary zero-voltage switching assistance circuitry, and outperforming the efficiency of conventional one-angle modulation approaches especially at light load. The developed approach is validated via computer simulations and experimental tests on a 1-kW DBSRC prototype. Tests performed at a nonunity voltage conversion ratio indicate a marked light-load efficiency improvement with respect to the conventional one-angle modulation, confirming the importance of the minimum current operation when the converter is expected to operate with programmable output voltages or under wide input voltage variations.

Analysis and Design of a Three-Level LLC Series Resonant Converter for High- and Wide-Input-Voltage Applications

In this paper, the analysis and design of a three-level LLC series resonant converter (TL LLC SRC) for high- and wide-input-voltage applications is presented. The TL LLC SRC discussed in this paper consists of two half-bridge LLC SRCs in series, sharing a resonant inductor and a transformer. Its main advantages are that the voltage across each switch is clamped at half of the input voltage and that voltage balance is achieved. Thus, it is suitable for high-input-voltage applications. Moreover, due to its simple driving signals, the additional circulating current of the conventional TL LLC SRCs does not appear in the converter, and a simpler driving circuitry is allowed to be designed. With this converter, the operation principles, the gain of the LLC resonant tank, and the zero-voltage-switching condition under wide input voltage variation are analyzed. Both the current and voltage stresses over different design factors of the resonant tank are discussed as well. Based on the results of these analyses, a design example is provided and its validity is confirmed by an experiment involving a prototype converter with an input of 400-600 V and an output of 48 V/20 A. In addition, a family of TL LLC SRCs with double-resonant tanks for high-input-voltage applications is introduced. While this paper deals with a TL LLC SRC, the analysis results can be applied to other TL LLC SRCs for wide-input-voltage applications.

Analysis, Design and Experimental Results of Wide Range ZVS Active-Clamped L-L Type Current-Fed DC/DC Converter for Fuel Cells to Utility Interface

A wide range zero-voltage switching (ZVS) active-clamped L-L type current-fed isolated dc-dc converter is proposed for fuel cells to utility interface application. The proposed converter maintains ZVS of all switches from full load down to very light load condition for wide input voltage variation. Detailed operation, analysis, design, simulation and experimental results for the proposed converter are presented. The auxiliary active clamping circuit absorbs the turn-off voltage spike and also assists in achieving ZVS of main switches. The ZVS of auxiliary switches and main switches is achieved by the energy stored in the boost inductors and series inductor (aided by parallel inductor), respectively. Rectifier diodes operate with zero-current switching. An experimental converter rated at 200 W has been designed, built and tested in the laboratory to verify the analysis, design and performance of the proposed converter for wide variations in input voltage and load.

Analysis and design of a hybrid phase modulated converter

High-frequency transformer isolated DC-to-DC converters are widely used for power conversion in alternate energy and other applications. In such applications, it is important for the converter to operate with wide variations in input voltage. A hybrid phase modulated converter (HPMC) can achieve this with soft-switching characteristics. This paper presents the analysis of such a hybrid phase modulated DC-to-DC converter for different modes of operation. A systematic design procedure is illustrated with a design example. PSIM simulation results obtained for the design example are presented for varying input voltage and load conditions. A 200 W experimental converter with 22 to 41 V input and 350 V output switching at 100 kHz, has been built to verify the performance of the designed converter.

Small signal analysis and closed loop control design of active-clamped zero-voltage switched two inductor current-fed isolated DC–DC converter

This study presents detailed small signal analysis and a closed loop control design of zero-voltage switched two inductor active-clamped current-fed isolated DC–DC converter. State-space averaging technique is used to derive the small signal model. A two-loop average current controller is designed for fixed frequency duty cycle modulation and works for wide input voltage and load variation. A complete design procedure is presented. A simple analogue controller is implemented. Experimental results for step-change in load are presented at different input voltage conditions.

Small Signal Modeling and Closed Loop Control Design of ZVS Current-fed Half-Bridge L-L Type Dc/Dc Converter with Active-Clamp

This paper presents the small signal model and closed loop control design using average current control for an L-L type active-clamped zero-voltage switching (ZVS) current-fed isolated DC-DC converter. State-space averaging technique is used to derive the small signal model. The controller is designed for fixed-frequency duty cycle modulation and works for wide input voltage and load variation. A complete design procedure is presented. Frequency response curves are obtained at different input voltage and load conditions to verify the stability and design, and to evaluate the performance of the controller. Simulation results for step changes in load are given to check the transient response of the converter.

A Novel DC/DC Converter Resonant Architecture for Traction Power Supplies

A novel method to reduce the effect of wide input voltage variation in soft-switched DC/DC converters for high-power and high-voltage traction applications is presented in this paper. To enhance high conversion efficiency together with high reliability and cost reduction, the document addresses the use of a power architecture whose front-end is a three-level half-bridge converter in differential configuration. Thanks to a structured control methodology based on the possibility to use either a two-level or a three-level modulation strategy according to the input voltage level, it is possible to optimize the converter performance over the whole input voltage range.First, the soft-switching implementation of the converter which allows ZVS (Zero Voltage Switching) operation in the entire load range by using the magnetizing inductance of the transformer is discussed. Then, the operation of the converter at both two-level and three-level operation is addressed. Concluding, experimental results obtained in the specified input voltage range are presented to confirm the validity of the theoretical analysis.

Design aspects of a switch-mode transformer under wide input voltage variation

Proposed is a discrete switch-mode fly-back power supply that combines part of its resonance topology into its switch-mode transformer (SMT). The resonant action is generated by the snubber circuit, and an expensive tank circuit is avoided. The "minimum switch on" circuit from the proposed SMT primary and lower auxiliary winding is designed in such a way that it provides a delay of half-resonant cycle before the driver circuit switches on the biasing circuit. This paper presents some practical design aspects of a series of SMTs intended to be used in developed and developing countries where the ac mains voltage is expected to fluctuate from very narrow to wide ranges, respectively.

A 28 Volt, 0 to 150 AMP Power Supply Incorporating a Multi-Section Morgan Chopper

A novel technique has been developed which enables a Morgan Chopper to be used in a system having wide input voltage and load current variations. A multi-section Morgan Chopper is programmed as a function of these variables to maintain a more constant chopping frequency. This and other special circuit techniques have been incorporated in a production 28 volt power supply which regulates better than ± 1% over wide input voltage and load current variations. One version of this supply having output capability of 4200 watts is packaged in a full ATR case and weight 75 pounds (figure 1).