Power-to-Frequency Dependency of Residential Loads in a Wider Frequency Range: An Experimental Investigation

With decreasing rotational inertia from traditional synchronous generation, frequency is becoming more volatile. Hence, a closer assessment of frequency-dependent load behavior is required. This paper presents an experimental investigation for residential loads, including sixteen typical domestic appliances. The perturbation-based method (range 50 +/- 1 Hz) is applied to determine frequency sensitivity values as parameters for commonly used exponential and linear frequency-dependent load models. Subsequently, these models with their identified parameters are compared with the measured load behavior of four representative devices during dynamic and steady-state frequency variations. The comparison shows a significant increase in the reconstruction error beyond the 50 +/- 1 Hz range, which suggests that the model parameters identified for a small frequency range may not be the most effective for larger frequency variations. The experimental study presented in this paper also includes a PV inverter as a representative of the increasing number of distributed generator and storage systems. The frequency-dependent behavior of such systems is defined in grid codes in some countries (e.g. VDE-AR-N 4105 in Germany). The measured response from the PV inverter under test shows that there is a non-negligible response delay time, and thus modeling approaches must be upgraded in the future.