A Linear Time-Invariant Approach to Dc-Dc Boost Converter Control for Two-Stage Grid-Connected Photovoltaic Systems

The nonlinear relationship between the photovoltaic (PV) voltage and current presents significant challenges for the control and operation of grid-interfacing inverters. In two-stage grid-connected PV systems, conventional control methods typically rely on linearising the system around a specific PV operating point. These methods perform adequately with classical maximum power point tracking (MPPT) or flexible power point tracking (FPPT) algorithms, where PV voltage references change incrementally. However, advanced PV algorithms introduces large PV voltage reference steps, which, for conventional control methods, can lead to overshoot and oscillations during transients, depending on the linearisation point. This paper proposes an alternative state-space representation for the dc-dc stage that eliminates the need for PV-curve linearisation. A linear control law, independent of the operating point, is developed, to ensure consistent responses, enhancing compatibility with advanced PV algorithms requiring large voltage steps. The effectiveness of the proposed control is verified through MATLAB/Simulink simulations and experimental tests, demonstrating superior transient performance compared to conventional state-feedback control.