Nonlinear PI current control for a high-precision HIL photovoltaic emulator with real-time I–V characterization

Accurate and flexible photovoltaic emulation is essential for the experimental validation of maximum power point tracking algorithms and photovoltaic (PV)-interfaced power converters. This paper presents a real-time hardware-in-the-loop (HIL) photovoltaic emulator (PVE) that combines numerical PV modeling with physical power hardware to achieve high-fidelity source emulation. A single-diode PV model is executed in real time on a dSPACE DS1104 platform and coupled to a DC-DC buck converter operating as the power stage, with output current regulated to reproduce realistic PV behavior. A nonlinear Proportional-Integral (NLPI) current controller is proposed to overcome the dynamic limitations of conventional linear Proportional-Integral (PI) regulation. By adapting controller gains according to the tracking error, the NLPI simultaneously improves transient response and steady-state stability. In addition, a converter-based I-V tracer enables continuous and stable extraction of I-V and P-V characteristics under changing irradiance conditions. Comprehensive HIL experiments under standard test conditions and variable irradiance demonstrate that the proposed approach significantly enhances emulation accuracy, reduces output ripple, and ensures reliable curve reproduction. The developed HIL photovoltaic emulator provides a robust experimental platform for the development and validation of advanced PV control and energy conversion systems.