A Generalized Anti-Aliasing Algorithm for Multi-Frequency Signals used for Impedance Measurement of Nonlinear Systems

As the basis of stability analysis of power electronic systems, fast and accurate impedance measurement technology is of great significance. Multi-frequency signals can measure the impedance of multiple frequencies in one measurement period, which significantly improves the measurement speed and has attracted widespread attention. However, when measuring power electronic systems with strong nonlinearity, it stimulates complex harmonic responses, causing spectrum aliasing and reducing the accuracy. An iterative algorithm has been proposed to avoid spectrum aliasing to improve accuracy. However, this method only considers the spectrum aliasing between the different frequencies of injected signal but ignores the impact of the system's intrinsic harmonics; and the algorithm does not indicate the upper limit of the number of frequencies that can be optimized within a specified interval, which causes an infinite loop when the number is large. This article proposes a generalized anti-aliasing algorithm for multi-frequency signals and takes discrete interval binary sequence (DIBS) as an example of multi-frequency signal to measure the port impedance of the three-phase uncontrolled bridge rectifier with strong nonlinearity. The method is verified with Simulink simulation.