Time-optimal switching surface for photovoltaic MPPT

The dynamic response of photovoltaic (PV) power converters plays a critical role to perform fast Maximum Power Point Tracking (MPPT). Among different options, linear controllers are a very popular choice to control power converters due to their design simplicity and basic implementation. However, the simplicity of the controller comes with a sacrifice in the speed and performance given the extremely large operating range in PV applications (V_OC to I_SC). For example, in the boost topology, the Right-Half-Plane Zero induces overshoot and the severe inability to handle extreme operating points. In this paper, a non-linear controller based on phase-plane analysis is implemented for a boost converter for PV-battery charging applications. The novel proposed controller provides a number of advantages, including: 1) Faster transient response, close to the physical limit; 2) Overshoot elimination; 3) Minimization and tight handling of disturbances caused by changes in environmental conditions. The combination of these benefits translates into faster MPPT algorithms and a minimization of the losses during the MPPT scan process. A comparative analysis is presented to demonstrate the characteristic features of the controller, showing significant improvements over the traditional dual-loop linear controller tuned by an optimal method.