Research on the power flow calculation method and the influence of voltage violation in distribution networks with hybrid access of grid-following/grid-forming inverters

• Developed a new GFM inverter power flow model including virtual reactance and line reactance effects. • Proposed a power flow calculation method for hybrid GFL/GFM networks that captures soft current limiting. • Revealed the effects of line parameters, control modes, and new energy penetration on voltage violations. The distribution network with a high penetration rate of new energy integration presents a more severe and complex new situation in the voltage violation problem due to the randomness, volatility of new energy power, and factors such as the grid-following(GFL)/grid-forming(GFM) inverters. Research on the power flow calculation method and the influence of the voltage violation in the distribution network with hybrid access of GFL/GFM inverters is crucial for voltage stability. Firstly, this paper analyzes the characteristics of the connection nodes of droop/VSG-controlled inverters, proposes a power flow mathematical model for GFM inverters, and then proposes a power flow calculation method in the distribution network with hybrid access of GFL/GFM inverters. The correctness and advantages of this power flow calculation method have been validated through the construction of a simulation model and a comparative analysis with existing methods. Secondly, the influence mechanism of factors such as new energy access scenarios with different penetration rates, line parameters, and GFL/GFM inverters on the voltage violation of the distribution network is studied. Finally, a comprehensive simulation analysis was conducted on the factors affecting voltage violation in the distribution network, such as new energy penetration rate, line parameters and GFL/GFM control mode, using a standard IEEE33-node distribution system based on the proposed power flow calculation method. At the same time, convergence analysis of the algorithm is performed using the IEEE69-node and IEEE123-node distribution systems. The research results can provide an important basis for the voltage analysis of the distribution network with hybrid access of GFL/GFM inverters.