Fourth-Order Buck Converter for Maximum Power Point Tracking Applications

Photovoltaic arrays (PVAs) need an intermediate maximum power point tracker as their v-i characteristics are nonlinear. Application of switch-mode dc-dc converters are popular in this area and the buck topology is widely used in these power tracking applications. However, the buck converter with an input L-C filter, with insufficient damping, will exhibit unwanted oscillations, or it may operate at suboptimal power points for certain solar insolations. Suitable damping must be designed otherwise the maximum power point (MPP) becomes unstable. Because of the variable impedance characteristic of PVA the design of optimal damping, suitable for all solar insolations, is a complex task. In order to eliminate these problems a fourth-order buck converter, which will track maximum power (MP) at all solar insolations, is proposed for the photovoltaic (PV) power tracking applications. Mathematical models of the proposed converter are formulated and then boundary conditions, under which the converter capable of tracking MP, are obtained. The combined PV power tracking scheme is simulated in PSIM and then power tracking performance characteristics are generated. Performance of the proposed topology is compared with the buck converter with input filter. The proposed converter effectiveness, in power tracking applications, is verified through experimental studies. Micro-controller, dsPIC30F6010, is employed in the real-time implementation of the perturb and observe (P & O) tracking algorithm.