Phase Current Reconstruction for AC Motor Drives using a DC-link Single Current Sensor and Measurement Voltage Vectors

Three-phase current measurement using only a single current sensor in the inverter dc link is appealing for ac motor drives because it minimizes the number of current sensors, thereby reducing sensor cost, weight, and volume. However, the basic dc link single current sensor technique poses special challenges because the duration of the active voltage vectors must be long enough to measure the dc link current reliably during every PWM switching interval. A new single current sensor algorithm for reconstructing the phase currents called the measurement vector insertion method (MVIM) is presented that overcomes this problem using active voltage vectors that are applied for brief measurement intervals only when needed during each fundamental frequency cycle. The insertion of measurement vectors makes it possible to reconstruct the output phase currents with minimum impact on the machine's performance and operating envelope. A combination of analytical and experimental results is provided to confirm that the MVIM algorithm offers attractive phase current reconstruction performance in comparison to alternative dc link single current sensor algorithms