Grid Reduction Method Considering Electromagnetic Loop and Local Accommodation Effect for the Dynamic Equivalent

Keeping the invariability of power flow and dynamic characteristics of generators rotor angles before and after the equivalent is an essential evaluation indicator for dynamic equivalence, which is necessary to electromagnetic transient modeling and simulation. A novel dynamic equivalent method is proposed for large-scale power systems electromagnetic transient modeling, which could reflect the characteristics of power alternation via electromagnetic loop and local accommodation among generators and loads in the equivalent network. The key method is to determine an equivalent bus for each node located in the equivalent section firstly, calculate the equivalent bus voltage(magnitude and phase) as well as the impedance of the equivalent tie branch follow the principle of unchanged of power flow and total current of the boundary transmission sections based on the initial operation point of the original power grids, then compute the effective sending power ability of equivalent coherent generators, and the effective receiving power ability for each equivalent bus. The effective load is summed finally for every equivalent bus. The real power system cases equivalent results demonstrate the accuracy and effectiveness of the method.