*4.2. Vienna Rectifier Control*

The voltage equations for input side of "*n*" number of Vienna rectifier can be written as

$$\begin{aligned} \mathcal{U}\_{\mathcal{S}^h} &= L \frac{d i\_{s\mathcal{L}\\_n}}{dt} + \mathcal{U}\_{\mathcal{S}^{\mathcal{A}0}} \\\\ \mathcal{U}\_{\mathcal{S}^h} &= L \frac{d i\_{s\mathcal{U}\\_n}}{dt} + \mathcal{U}\_{\mathcal{S}^{\mathcal{B}0}} \\\\ \mathcal{U}\_{\mathcal{S}^c} &= L \frac{d i\_{s\mathcal{L}\\_n}}{dt} + \mathcal{U}\_{\mathcal{S}^c0} \end{aligned} \tag{13}$$

where *UgA*0, *UgB*0, and *UgC*0 are the input voltages of the Vienna rectifier and *n* = 1,2,3 ... .

Here, a simple current average control scheme has been implemented, where the current obtained from the voltage controller was set as a reference current *i* ∗ *l* , which further divides in NPC and interleaved Vienna rectifiers. In Figure 4, the final reference current *i* ∗ *l*\_*re f* for all interleaved rectifiers was attained by multiplying *i* ∗ *l* with sin(*wt*) . Whereas, sin(*wt*) represents the unit amplitude waveform of the generator voltage. The error obtained by taking the di fference between the reference current *i* ∗ *l* and measured current *isabc*2\_1 is taken as an input to the current control. The PI controller is also selected for the inner current control of Vienna rectifier, which gives the output, like PWM duty cycle. Additionally, the duty ratio feedforward (DFF1\_n) method has also been applied to improve the THD and waveform of the current at zero crossing. While designing the parameters of the PI controller bandwidth of the current control was kept wider than the outer voltage loop [37].
