Frequency-dependent Control of the Active Power Consumption of Converter-fed Loads for Grid Support

Loads are more often equipped with converter-based grid interfaces, e.g. for energy saving reasons. This type of load has a reduced or no dependency of its active and reactive power consumption on changes in grid voltage and frequency (load self-regulation) compared to conventional consumers. A variety of additional control structures have been proposed to improve their contribution to power system stability. This paper discusses the dimensioning of an additional control for a pump drive in a heating system. The active power consumption is changed according to the locally measured grid frequency. A detailed nonlinear and a linear model is presented. The steady-state behaviour, the influence regarding power system modal stability and the small-signal stability of the load itself are addressed.