Wave Function and Multiscale Modeling of MMC-HVdc System for Wide-Frequency Transient Simulation

Abstract

The detailed modeling of power electronic (PE) devices poses challenging problems to efficient transient simulation of large-scale PE-dominated power systems. As PE paradigm, a multi-scale modeling methodology of the modular multilevel converter (MMC) for simulating diverse transients from lowfrequency oscillations up to high-frequency switching events in an MMC high-voltage direct current (HVDC) system is developed, implemented and validated. The novelty lies in a creation of wave propagation function (WPF) that describes the MMC submodule (SM) transient behavior, and then the SM Fourier seriesbased shifted-frequency phasor (SFP) is developed to accelerate computation speed of the system-level dynamics. These efforts serve as the basis for multi-scale modeling of the MMC where a multiple-frequency shifting is achieved. By implementing seamless model interface with the control systems, the multi-scale modeling is applicable to an MMC-HVDC transmission system. The multi-scale model is validated through case studies that cover dc fault, MMC internal fault, power oscillations and wind power fluctuations. The computational accuracy and efficiency of the model is verified through comparison of the results with those from the full electromagnetic transient (EMT) model.

Equivalent model of nearest level modulation for fast electromagnetic transient simulation based on DC voltage control loops of sub‐modules in modular multilevel converter

“…In the average model, if the sub-module of each phase is equivalent to a controllable voltage source, the variable characteristics of the switching model can be better preserved. For example, in [16,17], the ac side of MMC submodule is equivalent to a controllable voltage source, and the dc side is equivalent to the parallel connection of a controllable current source and a capacitor. This equivalence can eliminate the influence of switching devices and improve the simulation speed.…”

Real-Time Simulation Modeling Method of Multiphase Converters Based on High-Order Approximation in Micro-grid

“…The scholars at home and abroad have conducted a lot of research on the modeling of multiphase converters, which can be divided into the following categories: detailed models (Chen et al, 2020;Pan et al, 2020;Ye et al, 2021), switching function models (Dimitrov et al, 2020;Jiang et al, 2021), average-value models (Hengsi Qin and Kimball, 2012;Peralta et al, 2012;Zhang et al, 2017;Feng et al, 2021), and other models (Andres, 2018;HuangXin et al, 2018). In the studies by (Chen et al, 2020;Pan et al, 2020;Ye et al, 2021), the authors present the application scope of the detailed models, switching function models, and average-value models of the controllable inverter. The detailed model is high in accuracy but low in efficiency, especially the converters with hundreds of switches.…”