Voltage regulation of photovoltaic arrays: small-signal analysis and control design

This study deals with the regulation of the output voltage of photovoltaic (PV) arrays. As a case study, the DC-DC buck converter is used as an interface between the PV array and the load, but other types of converters can be used for the same purpose. The input voltage of the converter is controlled in order to regulate the operating point of the array. Besides reducing losses and stress because of the bandwidth-limited regulation of the converter duty cycle, controlling the converter input voltage reduces the settling time and avoids oscillation and overshoot, making easier the functioning of maximum power point tracking (MPPT) methods. The voltage regulation problem is addressed with a detailed analysis that starts with the modelling of the PV array and the converter. This analysis is followed by study, design, simulation and practical experiments of three closed-loop control strategies for the buck converter. Control stability and implementation considerations are presented.