Voltage Stability in Converter-interfaced Power System: a Monotone Systems Approach

This paper reports some preliminary results on the asymptotic stability of the equilibrium point of reactive power subsystem. First, we show that the Jacobian matrix of converter-interfaced power system model has certain structural properties, most notably, the submatrix associated with voltage regulation has sign pattern. Then, based on the small-gain theorem for interconnected input-output monotone systems, we quantify the stability condition of the equilibrium point and the effect of control parameters on the stability of subsystems, revealing the voltage regulation mechanism of modern power systems. A case study, using a two-area system with renewable energy generators, has been carried out. The results show that the interconnection of grid-following converters in general deteriorates the voltage stability of the power grid, while the interconnection of grid-forming converters with reasonable parameter configuration can enhance the voltage stability of the power grid.