Design and Analysis of Digitally Controlled Algorithm-in-loop Newton-Raphson Method Based PV Emulator

Abstract

Photovoltaic (PV) sources are inherently nonlinear power devices and maximum power derivation depends on Maximum Power Point Tracking (MPPT) algorithms. The algorithms require testing in real time situation using PV source which will be troublesome due to higher dependency on environmental factors and larger space requirements for higher power rating. The increased and faster testing lead to develop a PV emulator with desired performance and lower price compare to the commercially available PV emulators. In this paper, design of a digitally controlled PV emulator with varying resistive load is proposed to replicate the behaviour of real PV sources. The power stage of the PV emulator is realized using dc-dc buck converter topology and the controller stage uses an algorithm-in-loop Newton-Raphson (NR) method. Finally, the PV emulator is tested with MPPT controlled dc-dc boost converter for battery charging. The design of the power and control stages of the PV emulator has been compared with the real PV source and it is observed that the obtained V-I characteristic is in good agreement. Moreover, an analysis is presented for different switching frequencies of the boost converter connected as load to the fixed switching frequency buck converter, i.e., PV emulator. Further, a schematic hardware circuit diagram has been given to realize the proposed digitally controlled PV emulator.