Development of improved curve tracer for photovoltaic system under partial shaded conditions

Solar Photovoltaic (PV) systems have non linear characteristics. Maximum power point tracking (MPPT) is a challenging task when they are interfaced with load. When the PV panels in an array receive non-uniform insolation/partially shaded, anti-parallel diodes called bypass diodes are used across a group of cells to avoid the damage of low illuminated cells/panels. This further makes the task of MPPT more difficult as the characteristics have multiple peaks. Curve tracers can be used to assist the software-based MPPT techniques. In this paper, a load self-adaptive PV panel characteristics curve tracer by applying a hysteretic self-controlled duty-modulated load resistor (DMLR) to a boost converter I-V curve tracer is presented. Several advantages are achieved, such as simple structure, cost-efficient implementation and no tracing limitation near the V_oc. A circuit for a 72 W PV panel is simulated and implemented to verify the feasibility of the proposed curve tracer using PSpice.