Analytical Modeling and Control of Dual Active Bridge Converter Considering All Phase-Shifts

Abstract

In the field of power electronics-based electrical power conversion, the Dual Active Bridge (DAB) topology has become very popular in recent years due to its characteristics (e.g., bidirectional operation and galvanic isolation), which are particularly suitable to applications such as interface to renewable energy sources, battery storage systems and in smart grids. Although this converter type has been extensively investigated, its analysis and control still pose many challenges, due to the multiple control variables that affect the complex behavior of the converter. This paper presents a theoretical model of the single-phase DAB converter. The proposed model is very general, i.e., it can consider any modulation technique and operating condition. In particular, the converter is seen as composed by four legs, each capable of generating voltage on the inductor, and by the two output legs, which can steer the resulting inductor current to the load. Three variables are considered as the control inputs, i.e., the phase-shifts with respect to one leg. This approach results in a very simple yet accurate closed-form algorithm for obtaining the inductor current waveform. Moreover, a novel analytical model is proposed for calculating the average output current, based on the phase-shift values, independently of the output voltage. It is also shown that average output current can be varied cycle-by-cycle, with no further dynamics. In fact, average output current is not affected by the initial value of inductor current or by DC offset (which may arise during transients). The proposed models can be exploited at several stages of development of a DAB: during the design stage, for fast iteration, when selecting its operating points and when designing the control. In fact, based on the analytical results, a novel control loop is proposed, which adopts a “fictitious” (i.e., open-loop) inner current regulation loop, which can be applied to any modulation scheme (e.g., Single Phase-Shift, Triple Phase-Shift, etc.). The main advantage of this control scheme is that the simple dynamics of the output voltage versus the average output current can be decoupled from the complicated relationship between the phase-shifts and the output current. Moreover, a Finite Control Set (FCS) method is proposed, which selects the optimal operating points for each operating condition and control request, ensuring full Zero-Voltage Switching (ZVS) in all cases. The analytical results obtained and control methods proposed are verified through simulations and extensive experimental tests.

A Backflow Power Suppression Strategy for Dual Active Bridge Converter Based on Improved Lagrange Method

“…Based on the results of the analysis of the four working modes of the converter, it can be concluded that the Q EPS and Q SPS expressions of the backflow power are as follows: (10) Equation (10) was subjected to the unitization using (8), from which the backflow power expressions q EPS and q SPS after unitization can be obtained as follows: (11) The q EPS and q SPS three-dimensional plots plotted according to (11) are shown in Figure 5, where k was taken to be 1, 1.5, and 2, respectively. It is known from Figure 5a that there is little inhibitory effect on the backflow power under SPS modulation, and the backflow power increases as k increases.…”

“…So, a reframing of ( 14) is required. The improved Lagrange method requires that when solving (10), not for the public part η, proceed to elimination and solve for the resulting new D1 expression as follows:…”

“…The DAB converter is commonly operated using phase-shift modulation [10], which can be further categorized into single-phase-shift (SPS) modulation [11], extended-phaseshift (EPS) modulation [12], dual-phase-shift (DPS) modulation [13], and triple-phase-shift (TPS) modulation [14]. SPS modulation is the easiest to implement, as it only requires a single control variable between bridges.…”

Bidirectional Converter System in Dual Active Bridge Topology for a Hydrogen Tank

“…In this paper, the determination of phase shifts that minimise peak current has been proposed. The TPS method used for DAB converter control can be found in [11,[23][24][25]. In [23], values of phase shifts in the TPS method were first optimised using the finite control set (FCS) method using a converter model, and implemented using look-up tables.…”

“…The TPS method used for DAB converter control can be found in [11,[23][24][25]. In [23], values of phase shifts in the TPS method were first optimised using the finite control set (FCS) method using a converter model, and implemented using look-up tables. In [24], TPS phase shift selection for minimum current stress was performed using AI methods.…”