Stabilization of a distributed generation unit with constant power load in islanding mode

Abstract

This paper considers stabilization of a distributed generation unit (DG) with Constant Power Load (CPL). Constant power loads impose nonlinear behavior to the grid subsystem. The constant power drawn by these loads causes a destabilizing effect known as negative incremental impedance characteristics, which is the source of instability and system degradation. In this article, a DG system with local RLC load, and a power converter driven constant power load subsystem is modeled, which results in a set of nonlinear state space equations. We use inductor and capacitor banks in the DG system as control parameters to stabilize the system in presence of constant power load. The controller design is based on Lyapunov stability theorem such that the conditions on stability are emerged as LMI conditions on system parameters. Both islanded and grid connected modes are discussed. Furthermore, numerical simulations are provided to verify the theoretical analysis.