The growth of renewable energy reduces the moment of inertia for the synchronous AC grid

so the authors put forward two basic questions: 1) What is the physics insight that a synchronous AC grid needs for mechanical inertia? 2) How to provide inertial response for the power grid dominated with renewable energy? Based on Einstein's special relativity and the Lorentz transformation

these papers illustrates that the nature of the inertia of the AC grid comes from the relativity of the electromagnetic field and motion

and from the strong coupling between them. According to their nature

the inertial response of the synchronous generator is self-proven. By contrast

the converter for the grid-connection of renewable energies used various algorithms in order to provide virtual inertia. But because algorithms do not rebuild the coupling between electromagnetic fields and motion

it is doubtful whether they can provide inertia and inertial responses. Therefore

the authors propose that there is a need to build extra electromagnetic fields and motion coupling for grids with high penetration rates of renewable energy. Therefore

a new grid-connection technology via Motor-Generator Pair (MGP) is discussed. The electromagnetic-motion coupling of the MGP is analyzed

and the results of simulation and experimental studies are also reported.