A non‐isolated quasi‐Z‐source‐based high‐gain DC–DC converter

Abstract

To overcome the problems associated with Z-source-based DC-DC converters, a quasi-Z-source (QZS)-based high-gain DC-DC boost converter with switched capacitors is proposed in this work. Z-source-based DC-DC converters have problems like low-voltage gain, discontinuous input current, and high-voltage stress on the active and passive components. The proposed converter can produce a high-voltage gain of more than 10 times for a duty cycle of less than 0.5. The converter has other desirable features like reduced voltage stress across the switching components and continuous input current (CIC). It comprises a QZS cell made up of switched inductors and a voltage multiplier cell (VMC) made up of switched capacitors. The power loss analysis is done using PLECS software by incorporating the real parameters of switches and diodes from the datasheet. A hardware prototype of 200 W is developed in the laboratory to verify the working of the converter. In experimental results for an output power of 200 W, the converter is operated with a source voltage of 33 V at a duty ratio of 0.4 providing an output voltage of 395 V. The converter performance is good in open-loop conditions and is verified through experimental results. K E Y W O R D S duty ratio (λ), quasi-Z-source (QZS), voltage multiplier cell (VMC), voltage stress | INTRODUCTIONNowadays, gain DC-DC converters have found applications in electric vehicles (EVs), DC microgrids, switch-mode power supplies, and robotics to name a few. The power range of these high-gain converters varies from few milliwatts to a kilowatt range. The main objective is to build a topology with a high gain and reduced number of components. Desirable features like low voltage and current stress, common ground with low ripple in input current make the highgain converter an attractive choice for renewable energy applications. Conventional step-up converters and their variants need to be operated at a high duty ratio (λ) to obtain high-voltage gain. Consequently, the efficiency decreases, and the stress across the components increases. Moreover, the low and fluctuating output voltage of the PV panel cannot be fed to the inverter directly; it must be boosted with reduced ripple using a high-gain converter. 1,2 In Figure 1, it is depicted that a high-gain DC-DC converter can effectively boost the voltage from various sources like fuel cells, solar PV modules, battery, and an ultra-capacitor. These converters are used at the front end of a grid-connected inverter to maintain the DC-link voltage. The DC-DC converters have isolated and non-isolated structures. The isolated structures

Nonisolated high gain hybrid switched‐inductor DC‐DC converter with common switch grounding

“…As depicted in Figure 9, for the duty ratio D 1 = 0.6 and D 2 = 0.35 the theoretical voltage gain attained by HSL-CSG converter is 39, whereas the gain of the converters in previous studies 34,38 are 32 and 33, respectively. These voltage gains are far superior to those of the converters in previous studies 13,15,19 which provide a voltage gain of 4 and 3.5 for the same operating conditions stated above and among the previous studies [31][32][33] ; only Mahmood et al 33 is in par interms of the voltage gain for the aforementioned conditions. The normalized voltage stress across various elements of different converters in comparison with the proposed converter are presented in Table 1 and as shown in Figure 10A-C.…”

“…34,38 The inductor and capacitor counts are equal to the converters in previous studies 13,15,34 and this count is less than the converters in previous studies. 19,[31][32][33] The switches S 2 , S 3 will have high voltage stress and this is permissible because of the facts that split in overall duty and The intermediate switch S 3 will have the highest current stress compared to all elements because it has to carry the entire input current for a time period of D 2 T s as shown in Figure 11. The current stress profile of the HSL-CSG converter is better than the converters in previous studies.…”

“…The current stress profile of the HSL-CSG converter is better than the converters in previous studies. [31][32][33] F I G U R E 1 1 Peak current stress versus duty ratio of switches…”

“…10 Recent dual active bridge topologies are capable of achieving zero voltage switching by the integration of resonant converters at fixed or variable frequency modulation. Some of the aforementioned demerits in isolated topologies can be overcome by adopting rectifiers, voltage doublers-quadruplers at the secondary side and more over reverse power flow, circulating currents can also completely eliminated as mentioned in Mustafa et al 11 Numerous voltage amplification techniques based on conventional boost converters, 12 switched inductors, [13][14][15] switched capacitors, [16][17][18][19] coupled inductors, [20][21][22][23] cascaded connections, 24,25 quadratic boost, 26 voltage lift, 27,28 voltage multiplier with capacitor-diode combination, 29,30 hybrid switched inductor with intermediate capacitor, 31,32 and quasi Z source type 33 are used for nonisolated converters. The merits of nonisolated converters such as simple in structure and low cost are preferable in applications where galvanic isolation is not necessary.…”

“…Numerous voltage amplification techniques based on conventional boost converters, 12 switched inductors, 13–15 switched capacitors, 16–19 coupled inductors, 20–23 cascaded connections, 24,25 quadratic boost, 26 voltage lift, 27,28 voltage multiplier with capacitor‐diode combination, 29,30 hybrid switched inductor with intermediate capacitor, 31,32 and quasi Z source type 33 are used for nonisolated converters. The merits of nonisolated converters such as simple in structure and low cost are preferable in applications where galvanic isolation is not necessary.…”