Comparative Analysis of Second Order and First Order Filter-Based Inertia Emulation Control for Low-Inertia Power Systems

This article makes a comparative analysis between the classic first-order filter-based inertia emulation method and the more recent second-order filter-based approach, which manages to emulate the electrodynamic behaviour of the synchronous machine. The dynamics of the interactions between the control techniques, the filter capacitance, and the parasitic grid inductance are analysed assuming ideal and real phase-locked-loops (PLL) and current control loops. The results reveal how electromagnetic oscillatory modes between the controllers and the LC elements of the grid are excited, which in the case of the first-order filter-based inertia emulation methods impose severe restrictions on the maximum inertia that can be emulated, including the bandwidth of the converter current controllers and the PLL. The second-order filter-based inertia emulation approach relaxes these restrictions, improving the system response. These results are validated through simulations on the IEEE 9-bus low-inertia power system. Hardware in the loop experimental results are presented to support this application research.