新能源电力系统并网设备小扰动稳定分析(二)：导出机理与稳定性分类探讨

p>From the perspective of stability equivalence, nominal performance and robustness, a quantitative evaluation index of stability criterion is proposed in Part . In addition, the rationality of the evaluation index is explained from the physical concept. In Part II, the adaptation of the existing stability criteria and derivation mechanism are analyzed for the typical equipment in power system, such as synchronous machines, doubly-fed induction generators (DFIG) and converters. Thereby we propose the stability classification of the renewable power system. Firstly, aiming at low-frequency and sub-synchronous oscillation (SSO) of synchronous machine, we verify the rationality of the existing stability analysis methods and physical interpretation by using the proposed evaluation indexes. Secondly, we analyze the multi-timescale frequency oscillation of converters and the SSO of DFIG, which the adaptive stability criteria as well as the derivation mechanism are further be discussed. Finally, we extend the traditional phasor-based dynamic model to the instantaneous vector-based dynamic model, so that the stability classification in power system can be unified from the perspective of output stability in polar coordinates. Therefore, we classify the stability problems of renewable power system as phase-dominant synchronization stability, amplitude-dominant voltage stability and amplitude-phase combined vector stability. Synchronization stability includes the low frequency oscillation and SSO caused by shafting of synchronous machine, as well as oscillation caused by phase-locked loop of converter and DFIG. Voltage stability includes the instability caused by outer loop of converter and LCC. Vector stability includes the LC circuit resonance, the SSO caused by series compensation capacitor of synchronous machine and DFIG, and high frequency oscillation caused by converter inner loop as well as feedforward.</p