Dynamical Decentralized Voltage Control of Multi-Terminal HVDC Grids

TL;DR

This paper addresses voltage control in multi-terminal HVDC systems, proposing a decentralized PI controller with deadband that ensures voltage regulation within operational limits and maintains proportional power sharing.

Contribution

It introduces a novel decentralized PI controller with deadband for MTDC systems, guaranteeing voltage regulation within operational bounds regardless of load variations.

Findings

The proposed controller always steers voltages within the operational range.

It maintains proportional power sharing under low load and resistance conditions.

Validated through MATLAB simulations.

Abstract

High-voltage direct current (HVDC) is a commonly used technology for long-distance electric power transmission, mainly due to its low resistive losses. When connecting multiple HVDC lines into a multi-terminal HVDC (MTDC) system, several challenges arise. To ensure safe and efficient operation of MTDC systems, the voltage of all terminals need to be steered to within an operational range. In this paper we study the commonly used decentralized voltage droop controller, and show that it in general does not steer the voltages to within the operational range. We propose a decentralized PI controller with deadband, and show that it always steers the voltages to within the operational range regardless of the loads. Additionally we show that the proposed controller inherits the property of proportional power sharing from the droop controller, provided that both the loads and the line resistances are sufficiently low. The results are validated through simulation in MATLAB.