PWM Signal Measurement Issues

The real-time control of the operation of an electric vehicle made by the on-board control units requires measurements on different types of power signals from the DC power supply of the batteries to the PWM signals with which the inverter powers the engine. In particular, the voltage and current signals produced by the switching operation of the inverter are actually step signals and therefore with components that extend over a broad band (theoretically unlimited). The frequency responses of measurement devices, such as sensors or ADCs, therefore, produces systematic modifications on the measured signals with inevitable repercussions on the consequent power and energy measurements. A comprehensive analysis of measurement uncertainty requires evaluating the relationship between these deviations and the resulting errors in power measurement. This article analyzes the effects of the frequency response of the transducers and their influence on the power measurements. Moreover, a real-time compensation method that improves the transducers performances in terms of frequency response is presented and applied to a voltage divider.