A bidirectional high voltage ratio DC–DC topology for energy storage systems in microgrid

Abstract

This study proposes a bidirectional DC–DC converter with low voltage stress on its semiconductor elements and high voltage gain. Bidirectional DC–DC converters play a crucial role in DC microgrid systems, and they have been used for many applications such as power flow management, battery storage systems, voltage regulation, and electric vehicle (EV) charging systems. This paper proposes a novel non‐isolated, bidirectional DC–DC converter with an improved voltage gain conversion ratio. In the structure of the proposed converter, the coupled inductor provides high voltage gain and is employed to reduce the overall voltage stress across the main switches. Additionally, a filter inductor on the input‐low voltage side of the converter reduces current ripple. In addition, a single switch is used in boost mode, which simplifies control of the converter. Furthermore, two power switches receive simultaneous pulses for adjusting the buck stage voltage gain. Also, in the following, the mathematical calculations and the small signal analysis for the proposed converter are provided. Furthermore, a 200 W prototype is finally implemented, and its results are validated by the theoretical analysis.

A high step‐up high step‐down coupled inductor based bidirectional DC–DC converter with low voltage stress on switches

“…Under the same duty cycle and turns ratio of 2.5 for coupled inductors presented in other literature, the proposed converter has a lower NVS/S than those in [18,19,22,26,28] and [30]. Converters in [20,24] and [27] have exactly the same NVS/S as the proposed converter and structures in [23,25] and [29] have a slightly lower NVS/S under extreme duty cycles. The structure presented in [21] manages to get better performance regarding NVS/S under extreme duty cycles, which reduces the efficiency of the converter.…”

“…2. Under the same duty cycle and turns ratio of 2.5 for coupled inductors presented in other literatures, the proposed converter shows a better performance regarding voltage gain in buck operation than those presented in other literature, but the converters presented in [21] and [29] manage to get better performance under duty cycles that are higher than 0.6. However, as stated before, an extreme duty cycle also increases conduction losses and reduces the efficiency of the converter.…”

“…1. Under the same duty cycle and turns ratio of 2.5 for coupled inductors presented in other literature, the proposed converter has a higher voltage gain in boost operation than those in [19][20][21][22][23][24][25][26][27][28][29][30], but lower than that of [18] under extreme duty cycles. However, extreme duty cycle also increases conduction losses and reduces the efficiency of the converter.…”

“…6. The proposed converter has a smaller power switch count compared to those in [18,19,23,26,28,30] and the proposed one also has a lower LC component count compared to that in [18][19][20] and [22][23][24][25][26]29]. The converter in [21], has a slightly lower LC component count but it utilizes two coupled inductors which increases the cost and the size of the structure.…”

“…Table 1 illustrates the features of the proposed converter and other topologies in terms of voltage gain, normalized current and voltage stress across semiconductors (NVS/S and NCS/S), efficiency, soft switching capability, common ground feature, rated power and the number of components. The other topologies mainly include the bidirectional DC-DC converter in [18], a threephase interleaved bidirectional DC-DC converter in [19], a bidirectional DC-DC converter with a coupled inductor in [20], an interleaved bidirectional DC-DC converter in [21], a quadratic bidirectional DC-DC converter in [22], a hybrid switched-capacitor/switched-quasi-Z-source bidirectional DC-DC converter in [23], a switched-capacitor bidirectional DC-DC converter in [24], a switched-quasi-Z-source bidirectional DC-DC converter in [25], an interleaved switched-capacitor bidirectional DC-DC converter in [26], a switched capacitor and coupled inductor based bidirectional DC-DC converter in [27], a switched capacitor based bidirectional DC-DC converter in [28], a bidirectional DC-DC converter in [29] and dual-input interleaved bidirectional DC-DC converter in [30]. The voltage gain and sum of NVS/S and NCS/S against the duty cycle curves of these converters in boost operation mode are plotted in Figure 9.…”