Online Monitoring and Early Warning of Subsynchronous Oscillation Using Levenberg–Marquardt and Backpropagation Algorithm Combined with Sensitivity Analysis and Principal Component Analysis

Table 1

Main factors and their influencing degrees.

Influence factor	Influence degree	Description
Degree of series compensation	★★★	One of the critical factors to determine whether SSO occurs in a system
Grid line impedance	★★★	Affect the SSO characteristics by affecting the degree of series compensation
Natural frequency of torsional vibration mode of shafting	★★★	The risk increases when it is close to complementary to the electrical resonance frequency
Control system parameters of DFIG	★★★	The current loop proportional coefficient significantly impacts the subsynchronous resonance damping
Electrical parameters of DFIG	★★	It affects the equivalent series compensation of the system
Mechanical damping of unit shafting	★★	It affects all aspects of SSO
Unit combination mode	★★	The number and type of grid-connected units affect the external equivalent series compensation of the torsional mode of the unit
Grid operation mode	★★	It affects the equivalent series compensation of the system
Electrical parameters of synchronous	★★	The subtransient impedance more significantly impacts the global equivalent capability
Synchronous machine control system and its parameters	★	The speed regulation or excitation control system may have a feedback control effect on the subsynchronous signal
Control system parameters of HVDC	★	The current gain and time constant of the control system have a certain influence on the subsynchronous resonance damping