PWM output voltage measurement apparatus and method

摘要

Output voltage feedback systems and methods are provided for controlling voltage source inverter output voltages using low bandwidth buffer circuitry and low A/D converter sample rates to sense and sample PWM output voltage waveforms to provide an estimated volt-second value for phase voltage or line-line voltage as feedback for controlling the voltage source inverter.

主权项

1. A method for estimating output voltages of a pulse width modulated inverter, the method comprising:
individually low pass filtering a plurality of output voltage signals of a pulse width modulated inverter using a corresponding plurality of low pass filter circuits having low pass filter cut off frequencies lower than an output voltage waveform frequency corresponding to a maximum rise or fall rate of output voltage waveforms of the output voltage signals; individually buffering the low pass filtered output voltage signals using a corresponding plurality of analog buffer circuits to provide a plurality of buffered voltage signals; sampling at least some of the buffered voltage signals at a sampling frequency above the low pass filter cut off frequencies to provide a plurality of sampled values; averaging at least some of the sampled values corresponding to the phase voltage or line-line voltage of interest over a pulse width modulation period to compute the estimated volt-second value using the at least one processor, by:
accumulating at least some of the sampled values corresponding to the phase voltage or line-line voltage of interest over the pulse width modulation period to provide an accumulation total value for the pulse width modulation period using the at least one processor, andrefraining from accumulating sampled values that fall within a predefined range that includes values representing positive and negative voltages, anddividing the accumulation total value by a number of samples for the pulse width modulation period to provide the estimated volt-second value for the phase voltage or line-line voltage of interest using the at least one processor; and using at least one processor, determining an estimated volt-second value for a phase voltage or line-line voltage of interest according to at least some of the sampled values.