Analysis on Instability Mechanism of Angle/Voltage Interaction Considering Dynamic Characteristic of Photovoltaic Generators

Under the background of centralized access of large-capacity high-voltage direct current (HVDC) transmission and high-penetration renewable energy (RE) generation, this paper studied the instability mechanism of angle/voltage interaction considering the dynamic characteristic of photovoltaic generators (PVG). Firstly, the motion equations of the generator rotor and the motor load of the two-machine equivalent system were derived in theory. Then, the physical mechanism of system instability resulted by angle/voltage interaction after HVDC large disturbance was analyzed. Finally, the impact of different active/reactive power characteristics of PVG during low-voltage ride through (LVRT) process on system stability was studied. The results were verified through simulation of the practical Changji-Guquan (Giquan) HVDC sending-side system in China. The study results showed that the system instability was eventually resulted by the vicious circle between the increase of generator rotor angle and the drop of motor load voltage (i.e. the decrease of motor load resistance). Moreover, the impact of PVG LVRT characteristic on system stability should be comprehensively analyzed by theory combined with simulation.