Efficient Dynamic Simulation of Unbalanced Distribution Grids with Distributed Generators

As modern active distribution systems (DSs) host high penetration of distributed generators (DGs), interesting and significant dynamics can be observed on the distribution level. Hence, it becomes necessary to develop computationally efficient methods to solve the dynamics of practical-sized unbalanced active power distribution grids with high penetration of DGs for effective control and protection. In this context, this paper presents dynamic modeling of unbalanced distribution grid with DGs. The resulting differential-algebraic equations (DAEs) are solved using direct sequential integration (DSI) method adopting fourth-order Runge-Kutta (RK4). However, the DSI could be computationally inefficient for large DSs with high penetration of DGs; therefore, this paper also presents Waveform Relaxation with windowing (WRW) based distributed approach of solving the system of DAEs. The proposed dynamic modeling and WRW based parallel dynamic simulation is applied to the IEEE 123-node test system with twenty-four DGs, and case studies demonstrate that the solve time of the proposed WRW approach is more than two times faster than the DSI method.