PN admittance characterisation of grid supporting VSC controller with negative sequence regulation and inertia emulation

This work presents an analysis of converter output admittance for grid supporting VSC controllers in the positive – negative frame (pn-frame). Previously discovered issues in other reference frames are explored to prove the efficacy of analysis in the pn-frame The effect of negative sequence control is often overlooked and the pn-frame offers a useful method for observing the result. The impact of control parameters such as PLL bandwidth was explored which decreased network damping and increased regions of negative incremental impedance. Reduction of unwanted admittance components was achieved by the addition of appropriately tuned voltage feedforward filters. The equivalence of inertia and droops has been documented previously but not utilising converter impedance. Analogous traces of impedances were obtained for each structure with a similar response obtained when changing the respective associated gain indicating an equivalence.