Ensuring the stability and security of autonomous microgrids (MG) supplied by renewable energy sources (RES) represents an issue of great importance, which can be tackled from several perspectives. Besides implementing various control techniques, mainly based on energy storage systems, improving the response of RES-based generators and increasing the controllability at the consumption level are among the most discussed techniques to achieve high levels of reliability and robustness for the future MG. On this topic, the current paper presents a control solution for active loads (AL), which can be developed based on non-critical loads, in order to provide dynamic support during fast frequency variations. The study shows that implementing a frequency controller based on the derivative of the estimated frequency provides an improvement of the MG transitory behaviour, but due to the difficulty of accurately measuring the MG frequency, the method can also worsen the AL input current distortion. Therefore, the paper presents an original harmonic compensation technique, which can mitigate the current distortions in certain limits. The presented results show that the dynamic frequency response is improved by the action of AL, the feature being optimally used along with the proposed harmonic compensation technique.