Nonlinear Modeling and Transient Stability Analysis of SG–PV Infeed Systems

ABSTRACT

For hybrid systems with a synchronous generator (SG) and photovoltaic (PV), this paper investigates the impact of PV penetration on transient (synchronization) stability by considering the complete low voltage ride through (LVRT) process of PV converters. The LVRT process is divided into 4 stages (including pre‐fault stage 1, during‐fault stage 2, early fault recovery stage 3 and late fault recovery stage 4), with the corresponding transient nonlinear models established separately. Four major instability modes based on either SG or PV becoming unstable first are classified under various parameters. The transient stability is analysed by using the transient energy function (TEF) method. The results show that to be compared with the most appearing SG instability mode, the phase‐locked loop (PLL) instability mode occurs under weaker grids and larger values of active current output in stage 2 and active current recovery in stage 3. Additionally, the TEF exhibits switching discontinuity. The system stability can be judged by comparing the TEF value with the critical energy at the initial state of stage 3, no necessary to wait until stage 4. This study provides a system‐level physical picture and a fast transient stability criterion for the SG–PV infeed systems and it also offers important theoretical guidance and technical support for reliable operation of high‐renewable systems.