An Adaptive MMC Synchronous Stability Control Method Based on Local PMU measurements

TL;DR

This paper introduces an adaptive control method for MMC stability during faults, utilizing local PMU measurements and real-time Thevenin equivalent estimation to maximize output power and adapt to various fault conditions.

Contribution

It proposes a novel adaptive fault-current control method based on local PMU data and real-time TE estimation, eliminating the need for offline simulations.

Findings

TE estimation accurately tracks system impedance changes after faults

The control method ensures maximum MMC output power during faults

The approach adapts to different fault conditions without prior simulation

Abstract

Reducing the current is a common method to ensure the synchronous stability of a modular multilevel converter (MMC) when there is a short-circuit fault at its AC side. However, the uncertainty of the fault location of the AC system leads to a significant difference in the maximum allowable stable operating current during the fault. This paper proposes an adaptive MMC fault-current control method using local phasor measurement unit (PMU) measurements. Based on the estimated Thevenin equivalent (TE) parameters of the system, the current can be directly calculated to ensure the maximum output power of the MMC during the fault. This control method does not rely on off-line simulation and adapts itself to various fault conditions. The effective measurements are firstly selected by the voltage threshold and parameter constraints, which allow us to handle the error due to the change on the system-side. The proposed TE estimation method can fast track the change of the system impedance without depending on the initial value and can deal with the TE potential changes after a large disturbance. The simulation shows that the TE estimation can accurately track the TE parameters after the fault, and the current control instruction during an MMC fault can ensure the maximum output power of the MMC.