A Multifunctional GPV System Using Adaptive Observer Based Harmonic Cancellation Technique

This paper presents a multipurpose three-phase double-stage grid interfaced photovoltaic (GPV) system using an adaptive nonlinear control strategy. Along with a peak power extraction from a photovoltaic array, the proposed system is capable of harmonics currents elimination, reactive power compensation, grid currents balancing, and adaptive dc-link voltage control. The fundamental and harmonics information from the polluted load current are precisely estimated using an adaptive observer. A strictly positive real Lyapunov function is used to derive update laws for an adaptive observer. The DC-link voltage is adaptively adjusted in proportion to the point of common coupling voltage to minimize switching losses in voltage source converter and to avoid its tripping in sensitive distribution grids. A feed-forward loop for PV contribution is included to improve system response under dynamic conditions. Simulated and test results depict the performance of the GPV system with aforementioned functionalities. Improved steady-state and dynamic performances are observed with the proposed nonlinear adaptive estimation based control approach. The total harmonic distortions in grid currents are found well within the limits prescribed by an IEEE-519 standard.