Enhanced Voltage Regulation for PV Power Conversion Using Quasi-Proportional Resonant Extended State Observer

Extended state observer (ESO) is a promising control technology thanks to its robustness against model inaccuracy. This article expands the application of an ESO-based control scheme to digitally regulate a grid-tied photovoltaic (PV) power converter. It focuses on mitigating the steady-state disturbance resulting from the dc to single-phase ac conversion and dynamic disturbances caused by solar irradiance and voltage reference changes. The development is based on an in-depth analysis of PV power systems regarding the nonlinear and time-variant features. Thanks to the disturbance rejection loop, the active damping function is naturally offered, which boosts the system damping without extra sensors or complex model-based tuning. A new ESO scheme, namely quasi-proportional resonant ESO, is developed by the frequency-domain analysis, which enables the precise tracking and rejection of fast-varying sinusoidal disturbance at the targeted frequency. The advantages include simple and intuitive tuning, easy implementation, and enhanced transient and steady-state control performance. A 1.5-kW laboratory platform is built to verify the effectiveness and practicality of the proposed control scheme.