Harmonic Instability Analysis of a Single-Phase Grid-Connected Converter Using a Harmonic State-Space Modeling Method

The increasing number of renewable energy sources in the distribution grid is becoming a major issue for utility companies since grid-connected converters are operating at different operating points due to the probabilistic characteristics of the renewable energy. Usually, the harmonics and impedance from other renewable energy sources are not taken carefully into account in the installation and design of the systems. It can bring an unknown harmonic instability into a multiple power-sourced system and makes the analysis difficult due to the complexity of the grid network. This paper proposes a new model of a single-phase grid-connected renewable energy source by using the harmonic state-space modeling approach, which can identify such problems. The model can be extended to a multiple connected converter analysis. The modeling results show the harmonic impedance matrixes, which represent the harmonic coupling characteristic, as well as different dynamic characteristics. The theoretical modeling and analysis are verified by simulations, as well as experimental results.