A Comparative Study of Flexible Power Point Tracking Strategies Operating at Left and Right Sides of Photovoltaic Systems

With the continuous increase of photovoltaic (PV) penetration rate in the grid, the frequency modulation capability decreases and inertia is insufficient. In order to reduce the adverse effects of high permeability of PV, the power system has put forward relevant requirements for PV to participate in peak and frequency modulation. A method to solve the problem of PV peak and frequency modulation is to use Flexible Power Point Tracking (FPPT) strategy which is photovoltaic power generation system (PVPGS) operates below the maximum Power Point, with active Power reserve. Most of FPPT strategies operates in the right-sides of Photovoltaic system, instead of the left-side. However, the right-sides operation mode has its defects, and the left-sides operation mode has its advantages. In this paper, the FPPT strategy of photovoltaic power generation system is classified and briefly described, and the tracking performance of FPPT strategy in different working conditions is studied, and its principles are analyzed, which provides a benchmark for researchers and engineers to choose suitable FPPT operation mode for specific applications. The simulation results show that the PVPGS is more stable when running on the left side of the photovoltaic characteristic curve, while it is difficult to give consideration to the corresponding dynamic speed and steady-state accuracy when running on the right side. The single-stage PV system have the problem of power reverse peak when running on the left side of the PV characteristic curve.