Hardware lab tests on dynamic frequency support by converters applying different inertia constants

Today's electrical power systems are facing a continuous loss of conventional power plants and their mechanical inertia stabilizing the grid frequency during the first seconds of disturbance. Renewables and energy storages are usually converter connected and do not inherently provide any frequency support. Therefore, new converter control methods are required to maintain frequency stability despite increasing renewable penetration. This paper proposes a P(f)-droop control strategy for converters in which the droop parameters directly relate to the inertia constant in the grid. In this regard, high renewable penetration implies high frequency support by converters and vice versa. The concept was implemented and tested in a hardware lab with energy storages and converters and power ratings up to 100 kW. The test cases involved grid emulation with different inertia constants in order to analyze the impact of P(f)-droop-controlled converters on frequency dynamics. The test results showed that dynamic frequency deviations after a disturbance are significantly reduced with higher renewable penetration levels, when the loss of inertia is compensated by the proposed frequency support strategy.

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