Effects of stiffness factor on bus voltage variations in the presence of intermittent distributed generation

Electrical distribution systems are experiencing increased penetration levels of distributed generation thanks to economic incentives and technology cost reductions. Analyzing the effects of distributed generation on planning and operation of distribution system is typically done based on steady-state simulations; output variability of renewable dispersed generation units implies the need for more dynamic evaluation of their effects on the system and for the introduction of mitigating measures. The authors previous work has shown the advantages of select meshed configuration of distribution systems for accommodating higher levels of distributed generation considering steady-state voltage and current limitations. In this paper, after introducing stiffness factor and its relation to Thevenin equivalent impedance, the effects of intermittent photovoltaic systems on bus voltages are investigated. The IEEE 34-node test feeder in its radial and in different meshed configurations is used as test case. Results of the study verify the superior performance of select meshed configuration for accommodating intermittent renewable resources in distribution systems.