Multi‐input multi‐phase transformerless large voltage conversion ratio DC/DC converter

Abstract

This paper proposes a two-input transformerless DC-DC converter. The proposed converter has large voltage conversion ratio with low-voltage and current stress on semiconductors and low input current ripple. It can transfer energy as two-phase converter with three and four input voltage sources to increase the availability of the input voltage of the converter. Despite the capability of extending the number of the input sources up to four, the range of operating duty cycle for the switches and the voltage conversion ratio are remained the same as the values for two-input topology of the proposed converter. By increasing diode-capacitor (D-C) cells in upper and lower modules, not only the amount of transferred energy will be increased, but also the voltage stress on semiconductors would be decreased. In this paper, theoretical analysis for continuous current mode (CCM), analysis under discontinuous current mode (DCM), voltage gain and voltages and currents of all of the elements are calculated. Finally, the performance of the proposed converter is confirmed by implemented prototype which converts two 40-V input voltages to output voltage of 600 V with the power of 400 W.high-voltage gain, low-voltage stress on semiconductors, non-isolated converter, two phase dc-dc converter | INTRODUCTIONDC-DC boost converters have different applications, such as, photovoltaic cells, fuel cells, electrical vehicles, hybrid renewable energy systems, uninterruptable power supplies (UPS), battery energy supplies and so on. [1][2][3][4][5][6] There are several methods to improve the input voltage level in dc-dc boost converters. The first approach to achieve high ranges of voltages in conventional boost converters is to apply wider ranges of duty cycles close to unity. 7 However, through this method, several drawbacks, such as large voltage spikes on semiconductor components, may occur; consequently, the conduction losses would be increased. Therefore, there must be some components added to the conventional dc-dc boost converters to obtain higher ranges of voltages. In Liu et al., Babaei et al., Wu et al., Cheng et al. and Babaei and Saadatizadeh,[8][9][10][11][12] several dc-dc converters with high voltage gain are presented which have coupled inductors in their structures like flyback converters or converters with transformers. The converters with transformers in their structures are isolated which enhance their safety comparing to non-isolated converters. Even though, by increasing secondary turns ratio of the couple inductor in the implemented circuit, the voltage conversion ratio of the converter would be

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“…The LF transformerless converter attracts attention in the field of power electronics technology for years 8,9 . There are two types of such system configurations: (1) the back‐to‐back (BTB) connection of a NPC PWM rectifier and inverter, 10 and (2) a front‐end diode rectifier connected with NPC PWM inverter 11,12 .…”

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