Research on EPS Modulation Strategy of DAB Converter with Low Surge Current

Aiming at the problem that the Dual Active Bridge (DAB) converter has a relatively large surge current under the traditional modulation strategy, an improved extended phase shifted (EPS) modulation strategy is proposed. By introducing additional phase-shift angle control, this strategy increases the control degrees of freedom, enabling more precise regulation of the converter’s operating state. The working principle, operating modes, and power transmission characteristics of the improved EPS modulation strategy are elaborated in detail. The mathematical model of the converter is established. Theoretical analysis and simulation verification demonstrate that the new EPS modulation strategy can effectively reduce the surge current of the DAB converter during startup and abrupt phase-shift angle changes, enhancing the converter’s stability and reliability. It can also maintain high efficiency and excellent performance under working conditions such as light load and wide voltage input. Experimental verification shows that under 20% rated load, the peak surge current of the improved EPS is 1.1 A, a 47.12% reduction compared with the traditional EPS. When the load suddenly increases from 20% to 80%, the output voltage recovery time is only 20 ms, superior to the 50 ms of the traditional EPS.