2.1 Basic Concept

Note that this section is not meant to be a comprehensive analysis of the theory of operation, rather a quick description to offer a more intuitive sense of how a DAB works.

The DAB converter works on the principle of AC power transfer. In essence, one AC voltage source/load is connected to another AC voltage source/load through an inductor. See Figure 2-1. V₁ and V₂ are AC sources with a frequency (ω) and a phase difference θ (V₁ is taken as the reference). The power transfer between V₁ and V₂ can be controlled by the phase shift, θ.

What equation governs the power transfer from V₁ to V₂ or visa-versa? First, determine the inductor current I_L(t) and then determine the average power. The instantaneous inductor current I_L(t) is defined in Equation 2-1.

Assuming a power flow from left to right, the instantaneous power flowing from V₁ to V₂ is defined in Equation 2-2.

The average power P_AVG over an AC period 1/ω is defined in Equation 2-3.

Working through the mathematics, the average power transfer is defined in Equation 2-4.

Equation 2-4 is very important. It says that depending on θ, the power transferred between the two AC sources can be modulated. The magnitude of the power can also be controlled by controlling the magnitudes of the AC waveforms (namely V₁ and V₂) and the frequency of the AC waveforms ω.