Research on efficiency optimisation of DAB converters considering current stress and soft‐switching

Abstract

To solve the problem of low efficiency of the dual active bridge (DAB) converter under the traditional single‐phase‐shift control, a natural soft‐switching current stress optimisation (NSS‐CSO) method is proposed by considering the current stress optimisation and soft‐switching operation under dual‐phase‐shift (DPS) control. This study establishes the current stress and the soft‐switching analytical models of the DPS control global mode. Based on these models, the Karush–Kuhn–Tucker (KKT) condition is used to analyse the influence of the current stress optimisation methods on the efficiency when all switches achieve controlled soft‐switching or some switches achieve natural soft‐switching. It is found that the NSS‐CSO method is more efficient. Furthermore, the optimal phase‐shift ratio combinations and the corresponding current stress extremums of the NSS‐CSO method under various ranges of transmission power and voltage conversion ratio are deduced completely. The results of this study show that the NSS‐CSO method can effectively improve the operation efficiency of the DAB converter over the entire power range when the voltage conversion ratio does not match. Finally, experimental results confirm the accuracy of the theoretical analysis and the effectiveness of the proposed optimisation method.

Optimal transformer design of DAB converters in solid‐state transformers for maximum power efficiency

“…The DC/DC power conversion in electronic devices plays an important role managing electrical power flow for various power electronic applications [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17]. Isolation-type DC/DC converters are widely used to prevent damage to either circuit side when the primary or secondary circuit is under fault conditions; hence, numerous isolation-type DC/DC converter topologies have been developed thus far, and transformers must be used to implement an electrical isolation between primary and secondary circuits.…”

“…Isolation-type DC/DC converters are widely used to prevent damage to either circuit side when the primary or secondary circuit is under fault conditions; hence, numerous isolation-type DC/DC converter topologies have been developed thus far, and transformers must be used to implement an electrical isolation between primary and secondary circuits. Among isolation-type DC/DC converters, bidirectional functions are usually required for various applications, for example, electric vehicles, distribution systems, energy storage systems, and renewable energy sys-tems [3][4][5][6][7][8][9][10][11][12][13][14][15][16][17]. Dual-active-bridge (DAB) converters are the most popular topology as an isolation-type bidirectional DC/DC converter due to a simple symmetrical structure with small size, a simple control method of phase shift modulation, and a wide control range of load voltage with zero-voltage switching (ZVS) operations [5][6][7][8][9][10][11][12][13][14][15][16][17].…”

“…Among isolation-type DC/DC converters, bidirectional functions are usually required for various applications, for example, electric vehicles, distribution systems, energy storage systems, and renewable energy sys-tems [3][4][5][6][7][8][9][10][11][12][13][14][15][16][17]. Dual-active-bridge (DAB) converters are the most popular topology as an isolation-type bidirectional DC/DC converter due to a simple symmetrical structure with small size, a simple control method of phase shift modulation, and a wide control range of load voltage with zero-voltage switching (ZVS) operations [5][6][7][8][9][10][11][12][13][14][15][16][17]. The most important issues in designing DAB converters are to increase power efficiency and to operate it by high switching frequency for high-power density [9][10][11][12][13][14][15][16][17].…”

“…Dual-active-bridge (DAB) converters are the most popular topology as an isolation-type bidirectional DC/DC converter due to a simple symmetrical structure with small size, a simple control method of phase shift modulation, and a wide control range of load voltage with zero-voltage switching (ZVS) operations [5][6][7][8][9][10][11][12][13][14][15][16][17]. The most important issues in designing DAB converters are to increase power efficiency and to operate it by high switching frequency for high-power density [9][10][11][12][13][14][15][16][17]. To increase the power efficiency of a DAB converter, novel control methods to extend the soft-switching range have been widely researched [9][10][11][12][13][14][15].…”

“…The most important issues in designing DAB converters are to increase power efficiency and to operate it by high switching frequency for high-power density [9][10][11][12][13][14][15][16][17]. To increase the power efficiency of a DAB converter, novel control methods to extend the soft-switching range have been widely researched [9][10][11][12][13][14][15]. Due to the low efficiency under light load conditions, additional circuits or modified modulation methods are adopted [9][10][11].…”