Analysis of DC Power Systems Containing Multiple Induction Motor-Drive Loads

An analytical method used for conducting a power flow analysis on a DC power system containing multiple motor-drive loads is presented. The method is fast, simplistic, easy to implement, and produces results that are comparable to software packages such as PSPICE and Simulink. The method presented utilizes a simplified model of a voltage source inverter-fed induction motor that is based on the steady-state T-type harmonic equivalent circuit model of the induction motor and the input-output relationships of the inverter. In the simplified model, a V-I load characteristic curve is established that allows the inverter, motor, and load to be replaced by a current-controlled voltage source. The simplified model can be utilized in the analysis of a multiple-bus DC power system containing motor-drive loads by incorporating the V-I load characteristic curve of each motor-drive load into an iterative procedure based on the Newton-Raphson method. The analytical method presented is capable of analyzing DC power systems containing induction motor-drive loads fed from voltage source inverters with various types of switching schemes. The speed advantage of the analytical method presented versus simulation packages such as PSPICE is apparent when analyzing multiple motor-drive systems.