Alternate Arm Converters-Based HVDC Model Compatible With the CIGRE B4 DC Grid Test System

Modular multilevel converter (MMC) based high-voltage direct-current (HVDC) transmission system is a promising solution to the bulk power transmission over a long distance, especially for renewable energy integration. However, conventional half-bridge submodules MMC topology is susceptible to dc faults. In this study, dc short-circuit fault analysis and a review on recent advances in clearing dc fault current utilising different topologies are presented. Furthermore, the MMC can also work as a static synchronous compensator, producing reactive power to support the grid and improving the stability of the system when dc fault occurs. Finally, the comparison for different topologies in terms of device cost, estimated power losses, dc fault ridethrough capability, and reactive power compensation capability is given.

Section: Hybrid-cascaded Multilevel MMCmentioning

confidence: 99%

Review on topology‐based dc short‐circuit fault ride‐through strategies for MMC‐based HVDC system

Wan

Mao

Zhou

et al. 2020

“…Owing to the advantages of the AAC as aforementioned, the AAC can be potentially utilised in HVDC transmission system [32][33][34][35] and operated as a STATCOM [36]. Moreover, the AAC is also suitable for a FACTS application as analysed in [20].…”

Section: Applications Of the Aacmentioning

confidence: 99%

“…The average SM capacitor voltage ( V c ) is compared with the desired value of SM capacitor voltage (

V_{normalc}^{ref}

) to determine the energy deviation, the value of 2 α is obtained via a proportional–integral (PI) controller by considering the limit of the total number of SMs in each arm. The variable 2 α control has been employed in [6, 15, 27, 28, 34, 35, 37, 38, 44, 47, 48].…”

Section: Energy Balance Between the Upper And Lower Arms Of The Aacmentioning

confidence: 99%

Arm energy balancing control in AACs: a comparative analysis

Leow

Ooi

2020

The alternate arm converter (AAC) is an emerging state-of-the-art topology for voltage-source converter (VSC) by combining two-level converter and modular multilevel converter (MMC). The AAC performs better than the MMC in terms of the ability to block DC-side faults and ride through AC-side faults. Moreover, the number of sub-modules (SMs) per arm of the AAC is reduced by about 50% compared with the MMC. The key issue with AAC is the energy deviation during the alternate operation between the upper and lower arms. Presently, several AAC balancing techniques have been proposed, but no comparative analysis has been performed to provide insight on the effect of each balancing technique on AAC performance. In this study, five proposed balancing techniques are reviewed accordingly, followed by comparing them in terms of four parameters-the presence of DC filter, balancing capability, the presence of redundant SMs and zero-current switching control. Furthermore, a simulation work has been performed to study and compare the effects of each of the five balancing techniques. Both literature and simulation-based comparative analysis are significant to help select appropriate balancing technique as well as to provide helpful insights to improve the existing balancing techniques.

“…Thus, seamless current commutation is achievable for a limited range of power factors, and beyond which large inrush current occurs in the AAC arms. Its input dc‐link capacitors may increase the peak of dc fault current transient component [39].…”

Section: Special Multilevel Ac–dc Convertersmentioning

confidence: 99%

Review of technologies for DC grids – power conversion, flow control and protection

Adam

Vrana

et al. 2019

This article reviews dc transmission technologies for future power grids. The article emphasizes the attributes that each technology offers in terms of enhance controllability and stability, resiliency to ac and dc faults, and encourage increased exploitations of renewable energy resources (RERs) for electricity generation. Discussions of ac/dc and dc/dc converters reveal that the self-commutated dc transmission technologies are critical for better utilization of large RERs which tend to be dispersed over wide geographical areas, and offer needed controllability for operation of centralized and decentralized power grids. It is concluded that the series power flow controllers have potential to restrict the expensive isolated dc/dc converters to few applications, in which the prevention of dc fault propagation is paramount. Cheaper non-isolated dc/dc converters offer dc voltage tapping and matching and power regulation but they are unable to prevent pole-shifting during pole-to-ground dc fault. To date hybrid dc circuit breakers target dc fault isolation times ranging from 3ms to 5ms; while the resonance-based dc circuit breakers with forced current zeros target dc fault clearance times from 8ms to 12.5ms.