*4.3. Control of DC-Link Voltage*

In Figure 5, the DC-link voltage controller is depicted, which aims to maintain a constant DC-link voltage during any disturbances or instabilities.

**Figure 5.** Schematic of controller of DC-link voltage.

The DC-link voltage error can be given by:

$$V\_{dc\\_error} = (V\_{dc}^\*)^2 - (V\_{dc})^2\tag{25}$$

where, *Vdc \** is the reference of *Vdc*.

To generate the DC current reference *Idcref*, this error signal was sent to the PI controller to the ensure DC bus voltage constant value. The DC current reference *Idcref* is given by:

\_

$$I\_{dcref} = K\_{p,dc} \left( (V\_{dc} \, ^\ast)^2 - (V\_{dc} \, ^\ast)^2 \right) + K\_{i,dc} \int\_0^t \left( (V\_{dc} \, ^\ast)^2 - (V\_{dc} \, ^\ast)^2 \right) dt \tag{26}$$

0

22 2 <sup>2</sup>

2 22 3 33

*α β*

αβ

2

2

33 3

where, *Kp,dc* and *Ki,dc* are the PI controller gains. In Appendix A Table A2, the PI controller gain values for DC-link voltage controller are presented.
