FPGA based direct measurement of PWM voltage and inverter disturbance

Inverter disturbance has been widely discussed to improve the performance of AC motor control, with the very high nonlinearity and uncertainty of power electronic devices, it is still very difficult to be estimated and compensated accurately; therefore, the performances of most AC motor observers are affected by the inaccurate terminal voltage estimation. In this paper, the principle of PWM (pulse width modulation) is discussed to better understand the definition of inverter disturbance. Based on high speed ADC and FPGA, a direct measurement for accurately obtaining the inverter output voltage and inverter disturbance online is proposed. Because physical models and parameters are not needed, the proposed method can be used for all PWM voltage measurements. The experimental results of voltage measurements are provided, the feasibility of the proposed method is validated, and the blanking time, the modulation ratio and the fundamental frequency are selected as three key parameters to evaluate the impact of parametric variation on the inverter disturbance.