Small Signal Stability of Synchronous Motor-Generator Pair for Power System With High Penetration of Renewable Energy

With the increase of renewable energy in power system, the usage of a large number of converters brings safety and stability issues to power system, including lack of reliable inertia response, insufficient abilities for supporting current, voltage and frequency and lack of reliable damping to restrain oscillation. To solve these instability issues, the synchronous motor-generator pair (MGP) is proposed as a new method of grid-connection. Firstly, the main structure and application scene of MGP are analyzed. Secondly, the classical model for the MGP small signal stability is derived. Theoretical deduction proves that the MGP can provide more damping than a single generator with the same mass block. Then, 5kW MGP experimental system is built. The calculation parameters of the small signal model for the experimental system are determined by fitting experimental data repeatedly. On the basis, the calculated and measured frequency responses are compared under the same disturbance. The agreements between calculations and measurements show that the MGP small signal model can reflect damping and inertia level of MGP system. Finally, same disturbance experiment is carried out on a single-generator experimental system with the same mass block. The frequency response curves of the two modes under the same disturbance show that the MGP is more conducive to system stability.