Harmonic Coordination Suppression Strategy of Hybrid Grid-Connected System in Complex Grid Scenarios

With the construction and development of new power system, current-type grid-following inverters and voltage-type grid-forming inverters are widely accessed to distribution substations, but this hybrid grid-connected system will have power quality problems in complex grid scenarios where there are distortions in the grid voltage as well as access to nonlinear loads, which will seriously affect the quality of regional power supply. This paper firstly establishes a harmonic equivalent model of the hybrid control grid-connected system, analyzes the strong coupling relationship between grid voltage harmonics and grid current harmonics, and proposes a harmonic coordination suppression strategy, which realizes the effective coordination of grid harmonic voltage and current harmonics by controlling the output harmonic voltage of grid-forming inverter and reshaping the harmonic output impedance of grid-following inverter, and by adopting a method of selecting the standard value of the self-adaptive impedance and harmonic content. The effective coordinated management of grid-connected harmonic voltage and harmonic current is realized. Finally, the effectiveness and control robustness of the proposed strategy are verified by simulation.