A possible configuration with motor-generator pair for renewable energy integration

High penetration rates of renewable energy will bring stability problems for the future power grid. One of the critical issues is lack of inertia. In this paper, a synchronous motor-generator pair (MGP) system is proposed as a possible solution for renewable energy integration to enhance inertia and improve grid stability. First, feasibility studies of MGP on inertia, damping, efficiency, and cost are presented. Second, an analytical model is established based on its rotor angle relation. An active power control scheme based on voltage phase difference between renewable energy source and grid is then proposed, and state equations of MGP are derived for small signal stability. Next, two experiments are designed and implemented to verify stable operation and active power regulation of the MGP system. A single-machine infinite bus system is tested to investigate small signal stability and frequency response of MGP. The results show that the MGP system has a solid base in physics and is a feasible solution for providing enough inertia and improving small signal performance in the power grid with high penetration of renewable energy. The paper concludes with a discussion on future research directions to gain a better understanding of MGP.