This paper presents an inverter average input power estimation algorithm in the low-frequency modulation index such as a low sampling to operating frequency ratio. When the current sampling frequency to operating frequency is low, the error between the sampled phase current and the average phase current is large. This results in an error of the inverter average input power estimation, because it is calculated with the sampled phase current. Thus, in this paper, the average phase currents are calculated for every voltage vector duration within a current sampling period. The average phase currents are multiplied by the phase voltages to estimate the inverter average input power. Then, the inverter average input power is estimated as the sum of the three phases in the active voltage durations. Simulation and experimental results are presented to verify the proposed inverter average input power estimation.
