Overview of Passivity-Based Controller Applied to Grid-Tied Inverters

The high variability in power grid conditions results in a system with significant uncertainty. This uncertainty complicates the stability analysis when connecting a power electronics device to the power grid. However, designing for passivity addresses this uncertainty and ensures system stability. The feedback interconnection of stable and passive subsystems results in a system that is itself passive, which in turn guarantees global stability. The challenge of ensuring the passive behavior of a grid-connected power electronic converter up to the Nyquist frequency mainly lies on the phase shift introduced by the computation and the PWM delay at high frequencies. This challenge has been addressed through various advanced passivity-based control approaches. This paper presents an overview of passivity-based control designs and a comparison between them, including the pole-zero location in discrete time-domain and the impedance response in the frequency-domain. The methods based on proportional state-feedback tuned by optimization or by pole-placement provide the best performance in terms of passivity if components with fine tolerances are used for the filter, since they provide a phase margin greater than 0° and complete damping of the LC filter resonance peak.