Cascade closed-loop control of solar trackers applied to HCPV systems

Abstract

High concentration photovoltaic (HCPV) modules require a high precision tracking system for reaching their highest conversion efficiency. One way to accomplish this goal is by using a closed-loop mechanism and a sun sensor to track the sunlight. This paper proposes a cascade control algorithm capable of achieving a sun tracking error of 1′ for its application in high concentration photovoltaic systems. The algorithm follows an inner loop-outer loop topology. The inner loop employs a Nonlinear Proportional-Proportional Integral (NP-PI) controller and the outer loop resorts on a Proportional Integral (PI) controller. A tuning procedure for setting up the cascade controller is also described. Experiments on a laboratory prototype compare the performance of the proposed cascade controller with a PI controller not resorting on an inner loop. These outcomes show that the proposed control law provides improved tracking accuracy with less actuator wear.