Analytical Analysis on DC Capacitance Voltage Dip Amplitude of AC Adjustable-Speed Drives

With the development of society, the frequency of Adjustable-Speed Drives (ASD) usage among industrial users has surged. ASDs are highly sensitive to voltage dips, when the DC capacitance voltage drops below a certain threshold, the ASD low voltage protection is triggered. However, this threshold is set based on voltage tolerance curve (VTC) and is subjective, quantitative analysis on the amplitude of DC capacitor voltage dips in ASDs is lacking. Therefore, this paper constructs a dynamic model of the ASD grid-connected system on a transient time scale and obtains an approximate analytical solution for the power absorbed by the ASD from the grid. Furthermore, by establishing a dynamic model of the capacitor voltage during speed regulation and grid voltage dips caused by the single line-to-ground fault, and based on the Fourier expansion method, the approximate analytical solution for the amplitude of ASD capacitor voltage dips is obtained. Finally, the effectiveness of the algorithm is validated by simulation and calculation.