Harmonic Interaction Analysis in a Grid-Connected Converter Using Harmonic State-Space (HSS) Modeling

Abstract

An increasing number of power-electronic-based distributed generation systems and loads generate not only characteristic harmonics but also unexpected harmonics. Several methods, such as impedance-based analysis, which are derived from the conventional average model, are introduced to perform research about the harmonic interaction. However, it is found that the linear-timeinvariant-based model analysis makes it difficult to analyze these phenomena because of the time-varying properties of the powerelectronic-based systems. This paper investigates a grid-connected converter by using the harmonic state-space (HSS) small-signal model, which is based on a linear time-varying periodically theory. The proposed model can include the switching behavior of the model, where it makes the model possible to analyze how harmonics are transferred into both the ac-side and dc-side circuits. Furthermore, a harmonic matrix of the grid-connected converter is developed to analyze the harmonic interaction at the steady-state behavior. Besides, the frequency-domain results are compared with time-domain simulation results by using the HSS modeling to verify the theoretical analysis. Experimental results are finally discussed to verify the proposed model and study. Index Terms-Harmonic coupling analysis, harmonic state-space (HSS) modeling, three-phase grid-connected converter. I. INTRODUCTION W ITH the increased use of power-electronic-based distributed generation (DG) Systems, the stability and the dynamic performance of the system are important issues today [2]-[6]. Particularly, various DG systems are gathered into the same grid network, where complex connections, active control, and bidirectional current flow can make it difficult to analyze the dynamics and interaction of the power-electronic-based systems [3], [7]-[11]. Besides that, even if "N" identical power converters, which operate simultaneously or independently, are connected to the same bus, the cancellation, generation,

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