Switching Noise Propagation and Suppression in Multisampled Power Electronics Control Systems

This article addresses switching noise propagation and its suppression in current-controlled systems with multisampled pulsewidth modulation (MS-PWM). MS-PWM enables very high control bandwidths by reducing digital delays. However, when the sampling instants occur near the commutation ones, system performance is prone to being impaired by switching noise. It is analyzed how using the typically considered moving average filters (MAFs) in feedback may have an adverse effect, especially when the number of the noise-corrupted samples is high compared with the number of averaged samples. It is also shown that, without any filters, MS-PWM on its own may mask the negative impact of noise, due to modulator-related nonlinear effects. However, these nonlinearities can lead to an undesirable response to transients and output waveform distortion. Hence, this article proposes MS-PWM with median-based feedback filtering. To avoid ranking within median filter (MED) being affected by the switching ripple, repetitive ripple removal (RRR) is added before MED. The effectiveness of the proposed strategy in suppressing the switching noise is verified in simulations and experiments, during dc and ac operations. RRR+MED successfully suppresses noise-sensitive operating point regions that appear with MAF. Finally, it is shown that, even with added RRR+MED, MS-PWM still retains dynamic improvements over the standard DS-PWM without any filters, offering better reference tracking and disturbance rejection.