Dynamic Phasor Model of Modular Multilevel Converters High Voltage DC transmission

When conducting system-level research, it is unacceptable to adopt a detailed MMC electromagnetic transient model to bring about the amount of calculation. Although the use of electromechanical transient simulation and electromagnetic transient hybrid simulation technology or electromagnetic transient and dynamic phasor hybrid simulation technology can retain high simulation accuracy, it is not conducive to the model mechanism analysis and the control operation. In addition, the MMC average model is also used for AC and DC transient simulation. The average modeling uses controlled power sources to describe the average response of the converter, which can also be employed to the transient simulation. Due to the modeling properties of the ABC coordinate system, the average model is only suitable for time-domain simulation. The dynamic phasor modeling method employs the d−q axis coordinate system to analyze the MMC steady-state and research the small-signal stability. The order of each component in the d−q axis coordinate system model can be selected according to the required accuracy. Thus, the MMC dynamic phasor modeling scheme has widespread application in MMC-HVDC stability research, electromechanical transient simulation and controller design, etc. This article will establish an MMC dynamic phasor model to analyze the dynamic characteristics of system circulation.