Emulation of Grid-Following Inverters for Impedance-Based Stability Analysis regarding Outer Control Loops

With an increasing share of converter based devices in power grids, numerous investigations on the overall system stability have been tackled in recent years to understand their interplay with the existing grid. Here, impedance based studies enable screening studies over a broad frequency range. Whereas interaction studies considering a grid impedance only represent a snapshot of the system, passivity studies enable classification of several sensitivities with respect to the damping behaviour of the considered device. Therefore, a test setup is proposed within this contribution to analyse the frequency-dependent characteristic of a converter at its output terminal up to 10 kHz. Hence, the behaviour of an arbitrary voltage source converter with an arbitrary controller implementation is replicated by a converter emulation setup. Utilizing the introduced test setup, the impedance characteristic related to different controller structures and operation points are received and evaluated.