3.2.2. Control Design

The block scheme control of the DC/DC converter is shown in Figure 5.

The current of every coil is measured and multiplied by the *Rvirtual*, getting the emulation effect of a real resistance in the LC filter. A PI control has been chosen in order to ge<sup>t</sup> no voltage error in the steady state output capacitor voltage. The output of the PI regulator is subtracted in every branch by the previous calculation of the *Rvirtual* gain, and then divided by the input voltage *Vdc* to obtain the duty cycle in every branch. After that, a carrier phase-shift is implemented in order to obtain 120° phase in each branch PWM.

The gain of this integrator has been calculated to have a cut-off frequency to 16.7 Hz, which gives a step response of the system close to 3 ms. Figure 6 shows the step response of the system to a 40 V instantaneous set-point change.

**Figure 4.** Bode diagram of the DC output filter with the selected *Rvirtual* = 1 Ω.

**Figure 5.** EVE output voltage control block diagram of the DC/DC converter. The carrier of the three gate signals has the same sample time in order to keep constant the phase between them.

**Figure 6.** Output voltage response of the DC/DC converter to a step of 40 V in the set-point.
