Synchronous Motor-Generator Pair to Enhance Small Signal and Transient Stability of Power System With High Penetration of Renewable Energy.

A synchronous generator is a key element in maintaining stability in the traditional power system and performs well. However, the high penetration of renewable energy will challenge the stable operation of the future power system, because the characteristics of converter-based resources differ from those of a synchronous generator. As a result, a weak grid caused by a lack of short circuit capacity and inertia, damping, and fault ride-through abilities become important issues for grid stability. To solve these problems, the synchronous motor-generator pair (MGP) was proposed as a possible approach. In this paper, first, state equations considering different frequencies on both sides of the MGP are established. The model for small signal stability is further modified to include the wind generator. On this basis, two systems are tested to investigate the performance of the MGP in small signal stability, torsional modes, rotor angle stability, and voltage support. Finally, on the basis of proposed control strategy, a closed-loop active power control of the MGP is realized by the 3-kW experimental system. The results show that the active power of the system is controllable. The MGP can provide sufficient inertia for frequency stability, restrain oscillation, and maintain rotor angle stability by higher damping and support the voltage.