Reduction of DC Component in Three Phase Grid Connected Inverter Based On Virtual Capacitor and PIR Controller

Abstract

The dc component is a special issue in transformer-less grid-connected photo -voltaic (PV) inverter systems and may cause problems regarding system operation and safety. The dc component can cause line-frequency power ripple, dc-link voltage ripple, and a further second-order harmonic in the ac current. This paper has proposed an successful solution to make light of the dc component in three-phase ac currents and developed a software-based move toward to take off the blocking capacitors used for the dc component minimization, the so-called virtual capacitor The design of the control parameters based on virtual capacitor was proposed in a grid-connected inverter with LCL filter. A method for accurate extraction of the dc component based on double time integral, as a key to achieve the control and approved effective even under grid-frequency variation and harmonic conditions.