The power distribution system is undergoing changes and the need for real-Time control is increasing. This paper uses AC power flow equations (ACPF) to find the relationship between voltage change and Renewable Energy Sources (RES) penetration. A modified Newton-Raphson based approach is proposed in this paper to approximate ACPF into time-dependent linear equations. Since the changes to the distribution system operating conditions are small during normal operations, the change in voltage between two-Time steps are assumed to be linear. Optimal RESs outputs are calculated using the developed model. IEEE four node distribution test system is used to evaluate the proposed model. The results show that voltage violations can be avoided with the proposed method.