Three Phase Power Flow for Distribution Systems with Dispersed Generation

This paper describes the development of a three phase distribution system power flow program. The program is developed without any radial topology assumptions and thus can be used to solve both radial as well as meshed networks without any restrictions. Distributed generation, any combination of different types of loads including constant power, constant current and constant impedance with floating or grounded neutral can be modelled at a given bus. Voltage regulators are also modelled by three phase tap changing transformers, where taps on individual phases can be adjusted independently to satisfy the desired voltage correction along the feeder. The program can handle unbalanced loads and generation as well as un-transposed lines and missing phases. Modelling details for all system components, computational issues involved in factorizing the Jacobian having a special structure and in adjusting the control variables are described. Different size systems ranging from 14 to 155 buses are used to demonstrate the performance of the program under different operating conditions involving unbalanced loads, voltage regulator settings, different combinations of load types, remote generation and different network topologies such as meshed versus radial systems.