  We present a full review of PID passivity-based controllers (PBC) applied to
power electronic converters, discussing limitations, unprecedented merits and
potential improvements in terms of large-signal stability, robustness and
performance. We provide four main contributions. The nominal case is first
considered and it is shown, under the assumption of perfect knowledge of the
system parameters, that the PID-PBC is able to guarantee global exponential
stability of a desired operating point for any positive gains. Second, we
analyze robustness of the controller to parameters uncertainty for a specific
class of power converters, by establishing precise stability margins. Third, we
propose a modification of the controller by introducing a leakage, in order to
overcome some of the intrinsic performance and robustness limitations.
Interestingly, such controller can be interpreted at steady-state as a droop
between the input and the passive output, similar to traditional primary
controllers. Fourth, we robustify the design against saturation of the control
input via an appropriate monotone transformation of the controller. The
obtained results are thoroughly discussed and validated by simulations on two
relevant power applications: a dc/dc boost converter and an HVDC grid-connected
voltage source converter.
