Adaptive Observer Based Control for Rooftop Solar PV System

Abstract

In this paper, the multifunctional adaptive observer-based control scheme is proposed for double-stage grid interacted solar energy conversion system with distribution static compensator (DSTATCOM) abilities. The adaptive observer based control scheme facilitates the manifold power quality (PQ) functionalities in the distribution grid such as grid currents balancing, unity power factor, harmonics compensation, adaptive dc-link voltage regulation, etc. The dc-link voltage is varied adaptatively in proportion to the common coupling point voltage to reduce switching losses in the voltage source converter and to evade its tripping in weak distribution grid. The global asymptotic stability of the adaptive observer is demonstrated with zero steady-state error using passivity, Lyapunov stability theory, and LaSalle's invariance principle. To verify the effectiveness of the proposed control scheme, an experimental prototype is realized in the laboratory under manifold dynamic conditions such as load currents imbalancing, variation of solar irradiations, DSTATCOM-SPVA (solar photovoltaic array) mode, SPVA-DSTATCOM mode, under voltage, over voltage distorted grid conditions. The experimental comparative performances of the system, are demonstrated to validate the effectiveness of the proposed control strategy over conventional control scheme under distorted grid voltages and dynamic operating conditions. Moreover, the loss analysis between adaptive and fixed dc-link voltages is analyzed for double stage SPVA system.