Flux Balancing of Isolation Transformers and Application of “The Magnetic Ear” for Closed-Loop Volt–Second Compensation

Dual loop control for eliminating DC-bias in a DC-DC dual active bridge converter

“…Dc bias in the transformer current can be observed under various operating conditions. Non-ideal behavior of the system components, i.e., different turn-on and turn-off times, semiconductor voltage drops, gate driving signal delays, etc., [5,6], harmonics in the PWM reference signal [7] can lead to dc bias in the transformer current. It can also be observed during transients, when the converter operates under asymmetrical PWM signal [8].…”

“…The above conditions result in a dc bias in the transformer current leading to its saturation. Under saturation, the conduction and switching losses in the converter are increased leading to the reduction in the efficiency of the converter and higher operating temperatures for the semiconductor switches and the transformer which could lead to failure in the operation of the converter [5,6].…”

“…But, the saturation cannot be avoided when the dc bias is very high. [3,5,6,9] have proposed various methods to eliminate dc bias in the transformer in order to prevent magnetic saturation of the transformer. [9] has proposed three different predictive controllers.…”

“…Third, a predictive equal area mode controller controls duty ratio of both the bridges and makes the current in the transformer a perfect AC. [5,6] proposes a flux density measurement principle called the "Magnetic Ear" where an auxiliary core with a winding is attached to the main core so as to share the magnetic path. The output of the auxiliary circuit is fed to a closed loop controller in order to calculate the additional duty cycle required to increase or decrease the dc voltage applied to the primary winding.…”

Fast Transient Modulation for a Step Load Change in a Dual-Active-Bridge Converter with Extended-Phase-Shift Control

“…Additionally, there are some research works focusing on the modeling and closed-loop control of a DAB converter. Comparatively, there are only a few works reported concerning the transient performance of a DAB converter, especially the step-change of phase-shift angles [25][26][27][28][29][30][31]. When a step load change is requested in a DAB converter, one or more phase-shift angles are to be adjusted…”