Stability analysis of the main converter supplying a constant power load in a multi-converter system considering various parasitic elements

Abstract

Multi-converter power electronic system is nowadays popular in mobile vehicular applications. Different converters behave as Constant Power Loads (CPL) in a multi-converter system. These offer a negative impedance characteristic which results in a destabilizing effect on a converter driving them. Researchers have analyzed that the Buck converter supplying a CPL is unstable, but stability can be achieved by considering Constant Voltage Load (CVL) and parasitics of converter components in the system. In this paper, the effect of CVL in parallel with CPL and parasitic of switch, diode and inductor of main converter is mathematically evaluated on system stability. Then capacitor internal resistance is considered for the further analysis and the generalized expression is derived with consideration of parasitics of switch, diode, inductor, capacitor and CVL connected in the system and consistency of the generalized expression is verified with the established cases in the literature. The effect of the equivalent series resistance of capacitor on stability is analysed and compared with the stability due to parasitic elements of switch, diode and inductor. Further minimum and maximum range of parasitic of capacitor is derived to obtain the desired stability limit for given operating condition.

Keywords

• Constant Power Load (CPL)
• Negative impedance characteristics
• Parasitic elements
• Stability