Passivity-Based Harmonic Stability Analysis of Voltage Source Converters Considering the Impact of Sequence Decomposition Algorithms

Sequence decomposition algorithm (SDA) serves as the basis of the positive- and negative-sequence current control of voltage source converters (VSCs), but its impact on the system's stability has not been addressed. This paper investigates the impact of two typical SDAs, i.e., delay-based SDA and second-order generalized integrator (SOGI)-based SDA, on the high-frequency stability of VSC. It is found out that comparing with the SOGI-based SDA, the delay-based SDA will enlarge the negative-real-part region of the output impedance of VSC, and thus, introduce a higher risk of instability. Time-domain simulations are given to verify the theoretical analysis.