Physics Insight of the Inertia of Power Systems and Methods to Provide Inertial Response

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.