Harmonic Power Flow Calculation Based on Unified Harmonic State-Space Model of Converter

With the developments of distributed renewable energy and direct current (DC) based loads in recent years, the power electronic converter has been widely used in the distribution network. However, due to the lack of a harmonic model suitable for different types of converters, the evaluation of harmonics caused by large-scale converter integration is limited in the distribution network. In this paper, a unified harmonic model for converters based on the harmonic state-space (HSS) modeling is proposed to realize the steady-state harmonic characteristic analysis for various types of converters. The proposed model could capture the coupling relationship, which is independent of the harmonic distortion degrees of the connected network. Thus, the proposed model could significantly improve the accuracy of harmonic evaluation. Then, based on the proposed unified HSS model, a novel harmonic power flow (HPF) calculation method is developed in this paper to overcome high computational complexity and non-convergence issues caused by the change of converter operating condition. Simulation verifications are performed on a modified IEEE 13-bus system. The simulation results indicate the unified HSS model and HPF calculation method have high accuracy and good performance.