Simulation of 100% Inverter-Based Resource Grids With Positive Sequence Modeling

The global proliferation of inverterbased resources (IBRs) presents some interesting challenges that may be faced in planning and operating the bulk power system. The continued retirement of conventional fossil-fueled, synchronous-generator based power plants will result in a reduction in both available short circuit strength in the network and available energy injection that helps arrest the decline of frequency following a loss of generation. The impact of reduction in system strength on the behavior of IBR controls has been a topic of extensive research over the past decade. In simple terms, to inject the demanded active and reactive power, as determined by high-level controls, a conventional IBR control architecture makes use of a phase-locked loop (PLL) to track the phase-angle of the grid voltage and in turn ensure that the current injection by the IBR is synchronized with the grid. Moreover, fast inner current control regulators are used to ensure the IBR is current regulated and injecting the correct magnitude of current as demanded by its high-level controls. Since IBRs are interfaced to the grid with power electronic devices, and these power electronic devices can be damaged by excessive overcurrent in a relatively short time, the cycle of measurement and reaction must have a fast response time to prevent an extreme overcurrent condition. An inverter that can inject its share of active power (P) and reactive power (Q) successfully under normal grid conditions is said to follow the grid.