Methods to model grid-connected VSC systems in order to study the instability phenomena used in the literature are impedance-based and state-space modelling. Impedance-based is based on the impedance characterization of a system which can be expressed as a transfer function in the s-domain. On the other hand, state-space represents it as a system of linear equations in the time domain, resulting in a state transition matrix which relates the inputs and the outputs of a system.