To keep the balance between generation and consumption power, frequency regulation plays a significant role. The Thermostatically Controlled Loads (TCLs), like heating systems, refrigerators, and air conditioning units can be employed as the regulation tool to address the problem of distribution system fluctuation since these loads can be managed without compromising customer comfort due to their flexible operation. The task of research is to create a suitable controller by regulating the combined TCLs to work with conventional generators to maintain the consistency in the frequency of a single area system and then by using the model of proportional-integral (PI) control method, a transfer function approach must be formulated. The simulated results show that the suggested approach and models are adequate for providing frequency control to enable higher renewable energy penetrations and could be done by analyzing and comparing the system frequency response.