A coordinated control hybrid MPPT algorithm for a grid-tied PV system considering a VDCIQ control structure

Abstract

In this paper, a new coordinated maximum power point tracking (MPPT) algorithm has been developed for a grid-tied PV system, whose inverter follows a VDCIQ control scheme. The control objectives of this system are shared between 2 converters: a DC boost converter which performs MPPT of the PV plant, and an inverter which is responsible for DC voltage setpoint control, specific reactive current injection under request and reduced harmonic content of AC grid currents. The proposed algorithm operates upon a proper switching amongst conventional MPPT algorithms, namely perturb and observe (P&O) and incremental conductance (IC) algorithms, to take advantage of the best characteristics of each MPPT method with a different step size and considering the influence of the inverter control constants. Two coordination schemes are proposed for this algorithm to prioritise the improvement of different performance aspects over others. The impact of the proposed algorithm according to the 2 coordination schemes is evaluated and compared with the impact of conventional MPPT algorithms according to the trackability of power, the impact on DC voltage and on the AC grid side. The results are analysed by simulations conducted in MATLAB-Simulink.