Abstract: With the continuous improvement of resonance frequency, the influence of the capacitance characteristics of power factor correction capacitor based on fundamental frequency design on the equivalent impedance of power grid can not be ignored. The capacitance impedance of diversified nodes with non fundamental components induces resonance, which becomes the bottleneck of improving the injecting level of renewable energy. In this paper, an IEEE 9-node regional microgrid with renewable energy group interfaced was taken as the study object. Firstly, the impedance model of regional microgrid was established, and the influence of power factor correction capacitor C_PFC on the impedance characteristics of grid side was analyzed through the Bode diagram of impedance characteristics of full frequency band. Secondly, combined with the inverter impedance, the potential resonance mechanism of grid-connected system was revealed by using the impedance matching principle in source-grid side. On this basis, an improved scheme of harmonic negative pseudo capacitor without additional detection circuit was proposed by simulating harmonic negative capacitor at point of connecting to eliminate the influence of the harmonic capacitance impedance Z_{CPFC_H} on stability. Then, the selection of the injecting node with the maximum penetration of renewable energy group in regional microgrid was researched with the limitation of harmonic resonance. Finally, the correctness and feasibility of the above research were verified by simulation and small-scale experiment.