Phase Current Sensing Method Using Three Shunt Resistors to Eliminate Immeasurable Area in Voltage Vector Plane

This paper proposes a current sensing method to eliminate the immeasurable areas in three-phase inverters using the shunt resistors. Conventional shunt resistor-based current sensing methods have immeasurable areas in the voltage vector plane. Since motor control performance is degraded by the immeasurable area, various current reconstruction techniques have been proposed to expand the measurement range. Nevertheless, the software algorithm is quite complex, and the reconstruction ability is still unsatisfactory. In the proposed method, shunt resistors are located in series with the inverter output lines to obtain the motor phase currents. Both ends of the shunt resistors are at the high-potential as the dc-link voltage. High-potential voltages are lowered to the common-mode voltage level of the analog amplifier using voltage divider, and voltage drops across shunt resistors are detected by instrumentation amplifiers. Immeasurable areas are completely eliminated because phase currents can be detected directly through line shunt resistors. Simulations and experiments are carried out to verify the effectiveness of the proposed current sensing method.