An investigation of solar active power filter based on direct power control for voltage quality and energy transfer in grid-tied photovoltaic system under unbalanced and distorted conditions
This paper discusses a renewable energy system connected to a dual-function power grid through a parallel active power filter for simultaneously improving the power quality and injecting photovoltaic energy to the power grid in the presence of non-linear load. The rejection of disturbances affecting the electrical network supplying the non-linear load in the presence of the photovoltaic system is provided by the proposed direct power control (DPC) command. The combination of a fractional order PID controller for the regulation of the DC bus voltage with an intelligent method of tracking the maximum power point articulated on the fuzzy logic, reserved to solve the problem of quickly changing weather conditions, are proposed for the DPC strategy. The quality of energy offered by the improved DPC resides in the elimination of the undesirable harmonics of the source currents, thus operating the studied system under a power factor very close to the unit with a satisfactory rate of harmonic distortion, in agreement with the international standard IEEE-519. The overall control of the presented system has been the object of an assessment under different states of the power source behavior: balanced, unbalanced and distorted by simulation using MATLAB/Simulink software. The obtained simulations results demonstrate the performance, robustness and feasibility of proposed methods compared to the existing techniques in the literature.
Key words: active power filter; direct power control; disturbance rejection; fractional order PID regulator; fuzzy logic MPPT controller.