Control Strategy to Eliminate Impact of Voltage Measurement Errors on Grid Current Performance of Three-Phase Grid-Connected Inverters

Abstract

This study proposes an advanced current control strategy for three-phase grid-connected inverters to reject the impact of the dc offsets and scaling errors in the grid voltage measurement on the grid current performance. The proposed current controller designed in the synchronous ( d-q ) reference frame is developed with a proportional integral (PI) plus three vector PI controllers. The PI controller regulates the fundamental current to follow its reference, meanwhile, three vector PI controllers tuned at the fundamental grid frequency ( ${\omega _s}$ ), $2{\omega _s}$ , $6{\omega _s}$ are employed to eliminate the dc, unbalance, harmonic components in the grid current. As a result, the three-phase grid currents are controlled to be balanced, sinusoidal, and extremely low dc component despite the presence of the dc offset and scaling errors in the grid voltage measurement and distorted grid voltage conditions. The main advantage of the proposed control scheme is that it is developed without the need of additional hardware circuit, dc extraction, and harmonic detection scheme so that it can be integrated into the existing grid-connected inverter system without extra cost. The effectiveness of the suggested solution is verified by experimental results under various grid voltage conditions and the grid voltage measurement errors.