Calculation and Theory
EasyPower calculates three-phase power flows using a newly developed Current Injection method (CI). The CI method is more robust than either the Fast De-coupled, Gauss-Seidel, or similar hybrid arrangements, and an order of magnitude faster than the Newton-Rhapson method. The CI method uses the nodal admittance network and the latest in sparse vector solutions to obtain solution accuracies within one kVA. The system is modeled in the form given below. Refer to Reference1 for additional details.
Note: Many programs offer two or three solution techniques. This is done because most solutions cannot solve a variety of problems ranging from the simple to the difficult. The CI method is the most robust algorithm available to the industry and does not require user-specified backup analysis, voltage profiles or starter solutions.
Reference:
1 Robust Power Flow Solutions For Distribution Management Systems, W.F. Tinney, T.G. Nowak, R. Bacher, K.I. Geisler, IEEE/PES Summer 1984
Impact Motor Starting
EasyPower uses the constant impedance method for calculating impact motor starting conditions. Impact conditions are modeled at time equals 0+ and are considered the worst case voltage for motor starting. This method models each existing load as a constant impedance, and generation as a constant voltage source behind its subtransient impedance. Starting motors are also considered as constant impedance loads based on the motors starting MVA and power factor.
This method is very robust and works for all systems and voltage drop levels. Up to 10 motors can be started at once.
