A Self-Perturbation Impedance Measurement Method for Grid-Connected Inverters

When assessing the interaction stability between the grid-connected inverter (GCI) and the grid by applying the impedance-based stability theory, the GCIs' impedance is recognized as key information that has to be known. To measure the impedance, a costly commercial frequency response analyzer (FRA) and special power amplifier (PA) for generating perturbation signals are often needed. In this paper, a cost-effective method for measuring the impedance of the GCI through perturbation signals generated by itself is proposed. Therefore, it can help GCI manufacturers conveniently learn the impedance information about their products. The theoretical principle and method for measuring impedance are explained in detail. Finally, both simulations and experiments of the impedance measurement are carried out on a 110V/1.1 kVA three-phase GCI involving different control schemes. The results show the effectiveness of the proposed method in measuring the GCI's impedance.