Input has switching frequency of 50khz and i have discretize the output with a sample rate of 5e^(-8) seconds and fed to the digital Controller and if i try to decrease the sample rate to 5e^(-6) seconds the output is not correct
Hello, It's important to understand the relationship between the switching frequency, sampling frequency, and the desired performance of a digital control system. The switching frequency refers to the rate at which a power electronic converter (like a buck or boost converter) switches its states, whereas the sampling frequency refers to the rate at which the system measures the output and updates the control action.
The Nyquist-Shannon sampling theorem states that the sampling frequency should be at least twice the highest frequency component of the signal to avoid aliasing. In your case, the switching frequency is 50 kHz, so the highest frequency component of interest is likely to be around this value or somewhat lower, depending on the specific application and control strategy.
Your initial sample rate of 5e^(-8) seconds corresponds to a sampling frequency of 20 MHz, which is much higher than the minimum required sampling frequency (at least 100 kHz, based on the Nyquist criterion). With this sampling rate, the system should be able to accurately capture the dynamics of the converter and provide proper control.
However, when you decrease the sample rate to 5e^(-6) seconds, the corresponding sampling frequency becomes 200 kHz. Although this is still above the minimum required sampling frequency (100 kHz), it is much closer to the switching frequency of the converter. The reduction in the sampling rate can cause the control loop to not respond effectively to the fast dynamics of the converter, leading to performance degradation and potentially incorrect output. To ensure proper performance of your digital control system, you need to choose a sampling frequency that is significantly higher than the highest frequency component of the signal (usually above twice the switching frequency). A too-low sampling rate can lead to aliasing and poor control performance, which could be the cause of the incorrect output you're experiencing.
Regards,
Switching frequency (switching time) is the rate at which the system switches from one operation to another, while sampling frequency (sampling time) is the rate at which the system samples a signal or a set of data points. In general, sampling frequency (sampling time) must be higher than the switching frequency (switching time) in order to capture the information accurately.
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