Large-scale penetration of distributed energy resources on the existing distribution feeders impact the dynamic behavior and pose the motivation to perform a transient analysis on the distribution feeders. But, performing transient analysis based on conventional time domain approach is extremely time consuming and impractical. Besides, existing models of the PV generator in the distribution system analysis tools (OpenDSS) are just capable of supporting the snapshot and quasi-static analyses. Capturing the dynamic effects of the PV generators will be necessary for studies such as the effect of controller bandwidth, effect of multiple voltage correction devices, and anti-islanding studies. Considering an IEEE 37-bus test feeder as basis this paper proposes a mathematical approach based on differential algebraic equations (DAE) for performing dynamic analysis of distribution feeders in OpenDSS. In a detailed manner, this paper explores the use of DAE for the impact analysis of large PV generators on the existing distribution feeders. This approach models selected states as ordinary differential equations with rest of the distribution system as algebraic equations. The procedure based on DAE is effective in handling proprietary vendor-supplied models. Significant reduction in the computation time has been obtained by employing the above mentioned approach as compared with a conventional time domain technique.