PID passivity-based droop control of power converters: Large-signal stability, robustness and performance

TL;DR

This paper reviews PID passivity-based controllers for power converters, highlighting their stability, robustness, and performance, and proposes modifications to enhance their practical applicability and robustness.

Contribution

It provides a comprehensive analysis of PID-PBC, introduces a leakage modification for improved robustness, and validates the approach with simulations on power converter applications.

Findings

PID-PBC guarantees global exponential stability with perfect knowledge of parameters.

The controller's robustness is quantified with stability margins under parameter uncertainty.

A leakage modification improves performance and robustness, interpreted as a droop control at steady-state.

Abstract

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.