General Classification and Comprehensive Performance Assessment of Multi-Objective DC Voltage Control in Multi-Terminal HVDC Networks

Sawsan S Sayed,Ahmed M Massoud

doi:10.1109/access.2021.3060935

Sawsan S Sayed, Ahmed M Massoud

Open Access

https://doi.org/10.1109/access.2021.3060935

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Abstract

The recent massive global movement towards green energy in power systems has raised the efforts of integrating large-scale Renewable Energy Sources (RESs) through Multi-Terminal HVDC (MTDC) systems. The configuration of the MTDC system and the possibility of transnational interconnection impose some challenges and raise the potential of single or multi-objective control for the DC voltage control. Additional requirements from the Transmission System Operator (TSO) and/or AC grids may influence the action taken for the DC voltage control. In this paper, a generalized classification for the DC voltage control methods in an MTDC system is delivered. The DC voltage control methods are classified into conventional control (i.e., reference voltage-based control) and non-conventional control (i.e., virtual resistance-based control) methods. The DC voltage control objective may cover a range of the following targets: power-sharing based on converters' rating capacity, ratio priority of the power distribution, available headroom, and/or loading factor. The control objective may include transmission losses minimization of the MTDC system with optimal or sub-optimal power flow. The design approaches of the control methods for post-contingency operation are presented. The control methods are evaluated and simulated with a 4-terminal radial MTDC network during normal and abnormal system operation. A comprehensive performance assessment is also presented considering the control methods from the perspective of the control method and objective, system efficiency, grid-code violation, communication requirement, and design complexity and flexibility.

Highlights

Renewable Energy Sources (RESs) are the modern advances in mainstream high-power transmission systems
For an Multi-Terminal High-Voltage Direct Current (HVDC) (MTDC) network with m Wind-Side Converters (WSCs) and n Grid-Side Converters (GSCs), with GSC1 acting as the master converter, while the rest of the Voltage Source Converters (VSCs) acting as slave converters, (1) must be guaranteed for balanced power flow during any disturbance event
CASE STUDIES: RESULTS AND DISCUSSION case studies are presented for the DC voltage control methods covered in the previous sections

Summary

Introduction

Renewable Energy Sources (RESs) are the modern advances in mainstream high-power transmission systems. The uninterruptible power supply and clean generation nature of the RESs embolden their steadfastness alongside the worldwide electricity demand and the United Nations’ (UN) 2030 sustainable development goals [1], [2]. Due to the nature of the high-power RESs, its installation location is commonly in isolated off-load lands. With the development of fast control power electronics and lowloss high-voltage DC cables, High-Voltage Direct Current (HVDC) and Multi-Terminal HVDC (MTDC) networks with Voltage Source Converters (VSCs) have been the superlative technology for long-distance RESs and transnational power transmission systems [3]. The intermittent power supply nature from the RESs requires extensive and regular AC/DC power/voltage management [4], [5]

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