Modeling of Power Electronics Systems and PWM Modulators in Harmonic-State Space

Abstract

Modeling and simulation of the converter dominated systems have recently emerged as a monumental challenge. These simulations are useful for predicting instability and system's harmonic content, consequently assisting in developing better control and filters. But, as more and more converters are incorporated into the system, time-domain simulation models have a tradeoff of either limited accuracy or fewer simulated converters. On the contrary, frequency-domain modeling methods like linear time-invariant models cannot capture the system's time-varying nature and complex converter interactions. The recently developed harmonic state space (HSS) modeling approach has emerged to provide an alternate avenue to model and simulate these converter-dominated systems. HSS models, while accurate, until recently have not been able to reliably model the non-linear pulse width modulator. This paper solves this challenge and develops a new modulator model for harmonic domain models, including HSS. The proposed large-signal modulator is computationally less demanding and can reliably capture the harmonic spectrum of complex multi-converter systems till converter switching frequencies. Several optimization methods are introduced to utilize the unique multi-harmonic nature of HSS, making simulations faster than conventional time-domain methods. Results are verified with extensive simulations and experiments. The application, challenges, and future scope for this method are also highlighted.