A Prediction-Based Current Sampling Scheme Using Three Resistors for Induction Motor Drives

In the traditional three-resistor-based current sampling scheme, the sampled currents will become inaccurate when the duration of zero-voltage vectors of an inverter is too short, which leads to a limited modulation index (MI). To overcome this problem, an improved three-resistor sampling method is proposed by establishing a predictive current model of an inverter load, which is that of an induction motor on the synchronous rotating frame for the demonstration purpose in this paper. The principle of this method is detailed in the paper. Then a simulation model of a vector-controlled induction motor drive that utilizes the proposed current sampling scheme is built in the Simulink environment. Finally, the experiment on the new sampling scheme is performed in both steady-state and dynamic conditions. The results verify that the existing current sampling problems can be solved effectively and the motor can perform well with higher MI under the new scheme. As a result, the loading capacity of the system can be enhanced notably.