An Effective Solution to Minimize The Dc Component In Grid Connected Pv Inverters

Abstract

The main aim of project is dc component is a special issue in transformer less grid-connected photovoltaic (PV) inverter systems and may cause problems regarding system operation and safety. This paper has proposed an effective solution to minimize the dc component in three-phase ac currents and developed a software-based approach to mimic the blocking capacitors used for the dc component minimization, the so-called virtual capacitor.. A proportional integral-resonant controller is further designed to regulate the dc and line-frequency component in the current loop to provide precise control of the dc current. The proposed method has been validated on a 10-kVA experimental prototype, where the dc current has been effectively attenuated to be within 0.5% of the rated current. The total harmonic distortion and the second-order harmonic have also been reduced as well as the dc-link voltage ripple. Grid connected photovoltaic (PV) systems often include a line transformer between the power converter and the grid. The transformer guarantees galvanic isolation between the grid and the PV systems, thus fulfilling safety standards. Furthermore, it ensures that no direct current (dc) is injected to the grid . However, the low-frequency (50 or 60 Hz) transformer is bulky, heavy, and expensive and its power loss brings down the overall system efficiency.