Adjoint least mean square control for solar photovoltaic array grid-connected energy generating system

Abstract

This study deals with a new control for a double-stage grid-integrated solar photovoltaic array (SPVA)-based energy generation system, which is based on adjoint least mean square (ALMS) control. This ALMS control algorithm has some new features: (1) it provides a fast rate of convergence, (2) harmonics mitigation ability, and (3) ease of implementation. The solar PV energy generating system includes a DC–DC boost converter, a voltage source converter (VSC), a ripple filter, a three-phase grid, and local non-linear loads. The VSC is controlled for feeding the active power from the solar array to the grid and three-phase non-linear loads. Moreover, VSC control is used to improve the grid current quality. A DC–DC boost converter is coupled between the photovoltaic array and the DC-link capacitor, which tracks the maximum SPVA power from the SPV array by using perturb & observe algorithm. Here, the main goals of SPVA generating system are to eradicate power quality problems caused by unbalanced and non-linear loads and to provide sinusoidal grid currents at solar PV array irradiance variation. Moreover, a comparison of ALMS control is made with other control algorithms. Performance of this ALMS control is studied at varying non-linear loads and under different environmental conditions on a developed prototype in the laboratory. The simulated results of the system are validated with test results. Detailed behaviour of the grid-integrated SPV system and harmonics spectrum of grid currents are given here while meeting the IEEE 519 Standard.