The quantum‐mode regulated power point tracking in a photovoltaic array for application under the quantised converter duty ratio

Abstract

The objective of this work is to develop a realistic control technique for stably regulating the power output of a photovoltaic array. The associated process is referred to as the regulated power point tracking (RPPT). Ideally, the converter duty ratio is expected to be a continuous variable so that the photovoltaic power output can be freely adjusted. However, such a continuous-mode RPPT is possible only with the help of an analogue pulse-width-modulation (PWM) control. In contrast, the modern digital PWM control causes a duty ratio quantisation. As a result, the photovoltaic power output can, practically, be adjusted only at some discrete power levels. Therefore, existing RPPT control techniques, which optimistically assume a continuous power production range, may lead to persistent low-frequency power oscillations because of the digital PWM. To overcome the particular problem, a quantum-mode RPPT control technique is proposed in this paper. The quantum-mode RPPT basically limits its search only to the practically attainable discrete power levels by suitably modifying the given power reference command. Thus, the power tracking can always reach a converged state. For the faster RPPT, the perturbation step size is dynamically adapted. The proposed RPPT control technique is verified via both simulations and hardware experiments.