Hybrid high‐voltage direct current topology with line commutated converter and modular multilevel converter in series connection suitable for bulk power overhead line transmission

Abstract

In this study, a hybrid high-voltage direct current (HVDC) topology with line commutated converter (LCC) and modular multilevel converter (MMC) in series-connection is proposed, which is suitable for bulk power overhead line transmission. This topology is of operational flexibility in terms of active and reactive power controls, and is able to withstand ac and dc faults by the cooperative control of LCC and MMC. First, the operation principle and mathematical model are presented. Then, the control strategies for ac faults at rectifier and inverter side are discussed, which can prevent current cutoff under ac fault at rectifier side as well as maintain part of active power if commutation failure of LCC occurs under ac fault at inverter side. In addition, the feasibility on dealing with dc fault is theoretically demonstrated by analysing the characteristic of MMC under blocking state. A detailed control strategy for dc fault is further proposed combined with a test system. Finally, the effectiveness of the control strategy for ac and dc faults is verified and further compared with LCC-based HVDC topology through time-domain simulation.

Recent contributions and future prospects of the modular multilevel converters: A comprehensive review

“…A hybrid HVDC configuration consisting of series connected line commutated converter (LCC) and MMC is presented by Xu et al for overhead line transmission. Active/reactive power control is provided with this topology as well as withstanding AC and DC faults.…”

“…BTB, back-to-back; HVDC, high-voltage direct current; MMC, modular multilevel converter; VSC, voltage source converter Different AC and DC circuit topologies are investigated by changing cable lengths and conductor cross-sectional areas. A new chance of temperature-dependent dynamic DC voltage rating is introduced for improving grid capacity and efficiency.A hybrid HVDC configuration consisting of series connected line commutated converter (LCC) and MMC is presented by Xu et al165 for overhead line transmission. Active/reactive power control is provided with this topology as well as withstanding AC and DC faults.…”

Modeling and Analysis of an LCC HVDC System Using DC Voltage Control to Improve Transient Response and Short-Term Power Transfer Capability

“…It follows that for real-time grid frequency regulation, the proposed control scheme allows the HVDC system to respond to higher DC power references than the conventional scheme. Specifically, in the conventional scheme, the DC current and power references are normally restricted up to the rated values (i.e., 1.0 pu) [24], [25]. In contrast, the proposed control scheme enables a temporary increase in the DC voltage and consequently in DC power for a short time period when the HVDC system receives a DC power reference higher than the rated capacity of the HVDC system.…”

Electromechanical Transient Modeling of Line Commutated Converter-Modular Multilevel Converter-Based Hybrid Multi-Terminal High Voltage Direct Current Transmission Systems

“…In recent years, the hybrid HVDC systems have drawn more and more attention both from academic and industrial fields because of the combined advantages of LCC and VSC (especially the MMC) [2][3][4][5][6][7][8][9][10][11][12][13][14]. Previous studies about hybrid HVDC systems mainly focused on electromagnetic transient modeling [4][5][6][7], control protection strategies [8][9][10] and harmonic analyses [11,12], which are mainly based on the electromagnetic transient simulation platform. However, the electromagnetic transient simulation is not suitable for large-scale AC/DC power system transient stability studies.…”