Principle research on suppressing harmonic instability of HVDC transmission by using an inductive filtering method

Harmonic stability is easily excited once there are non-characteristic harmonics in HVDC transmission, who operates on the unbalance condition or has disturbance of converter control system. This paper concerns the core-saturation-type harmonic instability, and presents a new concept that using inductive filtering method to solve harmonic instability fundamentally. First, the mechanism of harmonic instability generation is analyzed. Then, a new HVDC transmission based on inductive filtering method is introduced briefly, and its equivalent impedance network is established. Based on this, a frequency scanning method is presented to get the impedance-frequency characteristics of the new HVDC transmission. Besides this, for comparative study, the CIGRE HVDC benchmark model is also analyzed. Research results indicate that the application of inductive filtering method changes the resonance frequency, and it can avoid the harmonic instability caused by low-order harmonic resonance.