One-Dimensional Optimization for Proportional-Resonant Controller Design Against the Change in Source Impedance and Solar Irradiation in PV Systems

The variation in source impedance and solar irradiation effects on photovoltaic (PV) system control performance is investigated. A proportional-resonant (PR) controller in a stationary frame in place of a proportional-integral controller in a synchronous frame was adopted to modulate a single-phase grid-tied inverter for PV systems. Although the PR controllers have gained some momentum lately due to advantages such as instantaneous tracking capability and low-cost computational resources, the tracking performance may decline due to changes in source impedance and solar irradiation where the conventional PR design rule is void. To adapt PR controllers over diverse operating conditions without incurring excessive tracking error, a one-dimensional optimization (ODO) algorithm that dictates the quality of the tracking performance is proposed to search for an appropriate factor chi between the real part of dominant and nondominant eigenvalues for the PV systems. The control gains of the PR controller can be then altered in light of the optimal chi through a simple algebraic conversion. The experimental results confirm the performance of the proposed strategy.