Improve control scheme for near 0 A references

[gabrielbrunheira]

Output current tends to become less accurate when reference is around 0 A.

On monopolar modules (FAP), it may be explained by discontinuous conduction mode (DCM) condition. On bipolar topologies (FBP and FAC), dead-time of H-bridge seems to play a role also.

Quantization and other non-linear effects may also contribute to this behavior.

An example of this behavior is shown in the image below (Ref):