Voltage vector correction based on a novel coordinate transformation for motor current detection using a single shunt resistor

A method of detecting current using a single shunt resistor is required for motor-drive systems in home-electrical appliances to reduce the cost of inverters. This paper proposes a method of correcting the voltage reference vector by converting coordinates from a rotating reference frame into a fixed reference frame. It also proposes a new method of transforming coordinates that is appropriate for the correction. We focused on areas that cannot be detected every 60 degrees in alpha-beta coordinates. When the alpha-beta coordinates in an npi/3 rotation are defined as alphan-betan, the alphan-axis can be defined as the central axis in an undetectable area. We propose a method of transforming coordinates that converts the voltage vector in the d-q coordinates into UVW phase voltages through alphan-betan coordinates to correct it. This method corrects the voltage vector by using a very simple algorithm that limits the alphan-betan elements. The effectiveness of the proposed approach was confirmed through simulation and an experiment. Currents were clearly detected by using the proposed method. This demonstrated that the new method is suitable for position sensor-less drives in permanent-magnet synchronous motors.