Constant Power Loads and Negative Impedance Instability in Automotive Systems: Definition, Modeling, Stability, and Control of Power Electronic Converters and Motor Drives

TLDR

Power electronic converters and electric motor drives are increasingly used in advanced automobiles, yet their multivoltage hybrid AC/DC and electromechanical systems exhibit nonlinear, time‑dependent dynamics and stability problems that remain poorly understood. This paper assesses the negative‑impedance instability of constant power loads in automotive power systems and proposes design criteria for controllers to mitigate it. The authors analyze and control these systems using sliding‑mode and feedback‑linearization techniques, supported by large‑signal phase‑plane analysis, to stabilize converters and motor drives with CPLs.

Abstract

Power electronic converters and electric motor drives are being put into use at an increasingly rapid rate in advanced automobiles. However, the new advanced automotive electrical systems employ multivoltage level hybrid ac and dc as well as electromechanical systems that have unique characteristics, dynamics, and stability problems that are not well understood due to the nonlinearity and time dependency of converters and because of their constant power characteristics. The purpose of this paper is to present an assessment of the negative impedance instability concept of the constant power loads (CPLs) in automotive power systems. The main focus of this paper is to analyze and propose design criteria of controllers for automotive converters/systems operating with CPLs. The proposed method is to devise a new comprehensive approach to the applications of power electronic converters and motor drives in advanced automotive systems. Sliding-mode and feedback linearization techniques along with large-signal phase plane analysis are presented as methods to analyze, control, and stabilize automotive converters/systems with CPLs