Feasibility Region Analysis of a Single-Phase PWM Current Source Converter for Constant Power Loads in Smart Grid and Microgrid Applications

Abstract

Constant power loads (CPLs) introduce nonlinear voltage–current characteristics that can restrict the feasible operation of power-electronic converters. This paper presents a nonlinear steady-state framework for characterizing the feasible operating region of a single-phase PWM current-source converter (PWM-CSC) supplying a CPL. The averaged converter model is transformed into the synchronous dq reference frame and reduced to a nonlinear algebraic system that explicitly relates converter states, modulation variables, and active–reactive power demands. The resulting equilibrium set is mapped onto the P–Q and P–Q–m spaces to identify admissible operating points and modulation requirements. The numerical procedure evaluated 50,000 operating points with a 100% convergence rate, an average solution time of 4.168 ms per point, and residual norms below 10−6. Time-domain simulations in PSIM v9 validated representative operating points across the feasible region, with maximum deviations of approximately 0.83% in active power and 0.74% in reactive power relative to the prescribed references. Simulations also showed degraded voltage regulation near the feasibility boundary and loss of regulation for demands outside the identified region. The proposed approach provides a quantitative tool for feasibility-aware operation of PWM-CSCs supplying CPLs.