Robust Static Quadratic Optimization for Fast Active and Reactive Power Control in Grid-Tied PV-Fuel Cell Hybrid Systems

This paper proposes a new modified P–Q control scheme with a simple design using Static Quadratic Optimization (SQO) concept for a grid-connected hybrid system of photovoltaic (PV) and Fuel Cell (FC) sources. Contrary to traditional design practices involving voltage-oriented control (VOC) employing proportional-integral (PI) controllers or existing predictive strategies involving quadratic optimization by iterative computation, this proposed design of SQO directly computes an analytical expression of dq-axis current references as the optimal solution of a static-quadratic cost minimization problem. The proposed design enables optimal real and reactive power control simultaneously in a single step. The design of an efficient voltage-oriented current controller effectively utilizes measured values of grid current and voltage, as well as reference powers, which allows optimal bidirectional reactive controlled supply or absorption of reactive powers according to grid needs. The simulation of the grid-connected system has been performed in a MATLAB/Simulink environment. The simulation outcome verified the proposed P-Q voltage-oriented current controller design with a power factor of ۰.۹۹۸, phase displacement of ۰.۱۲°, total harmonic distortion (THD) levels of ۱.۲% for current and ۰.۳۹% for voltage, strictly within the IEEE-۵۱۹ standards.

Keywords:

Grid-tied inverter , photovoltaic- fuel cell hybrid system , active and reactive power control , power factor correction , smart grid integration