scholarly journals A Hybrid MMC Topology with dc Fault Ride-Through Capability for MTDC Transmission System

2015 ◽  
Vol 2015 ◽  
pp. 1-11
Author(s):  
Xinhan Meng ◽  
Ke-Jun Li ◽  
Zhuodi Wang ◽  
Wenning Yan ◽  
Jianguo Zhao
Keyword(s):  
Short Circuit ◽  
Harmonic Distortion ◽  
Transmission System ◽  
Simulation Software ◽  
Power System Simulation ◽  
Multilevel Converter ◽  
Harmonic Content ◽  
Dc Fault ◽  
Fault Ride Through ◽  
Short Circuit Fault

This paper proposes a hybrid modular multilevel converter (MMC) topology based on mismatched-cascade mechanism. The blocking conditions of different submodule (SM) structures under dc fault are analyzed and a series double submodule is presented. With series-double submodules and mismatched-cascade submodules, the proposed hybrid MMC can ride-through the dc side short-circuit fault and provide an output voltage with the feature of low harmonic content. This hybrid MMC topology can be used in the VSC based multiterminal dc (VSC-MTDC) transmission system. The dc fault ride-through properties of the new structure and the total harmonic distortion (THD) are analyzed compared with the previous full-bridge and clamp-double architectures. An appropriate fault blocking procedure is presented, and a typical four-terminal dc transmission simulation system is given in the power system simulation software. Finally, simulation of steady-state and dc bipolar short-circuit fault verifies that the MTDC system based on this new hybrid MMC topology is stabilized and can block the dc fault and return the nonfault parts to normal.

scholarly journals Simulation Test of a DC Fault Current Limiter for Fault Ride-Through Problem of Low-Voltage DC Distribution

Energies ◽  
2020 ◽  
Vol 13 (7) ◽  
pp. 1753 ◽  
Author(s):  
Bing Han ◽  
Yonggang Li
Keyword(s):  
Fault Detection ◽  
Low Voltage ◽  
Short Circuit ◽  
Distribution Network ◽  
Fault Current ◽  
Fault Current Limiter ◽  
Dc Fault ◽  
Fault Ride Through ◽  
Current Limiter ◽  
Short Circuit Fault

The low voltage direct current (LVDC) distribution networks are connected with too many kinds of loads and sources, which makes them prone to failure. Due to the small damping value in the DC lines, the fault signal propagates so fast that the impact current with the wave front of millisecond and the transient voltage pose great challenges for fault detection. Even worse, some faults with small currents are difficult to detect and the communication is out of sync, resulting in protection misoperation. These problems have severely affected the new energy utilization. In view of this, a DC fault current limiter (FCL) composed of inductance, resistance, and power electronic switch was designed in this paper. The rising speed of fault current can be decreased by the series inductance and the peak value of the fault current can be limited by series impedance, thus in this way the running time can be gained for fault detection and protection. For distributed energy access, by deducing the short circuit fault characteristic expression of LVDC distribution network, the feasibility of FCL was verified. Based on the structure of the bridge-type alternating current (AC) current limiter, the structure and parameters of the DC FCL were determined according to the fault ride-through target. Then, a low voltage ride-through strategy based on DC FCL was proposed for the bipolar short-circuit fault of LVDC distribution network. Finally, MATLAB/Simulink simulation was used to verify the rationality of the proposed FCL and its ride-through strategy.

scholarly journals Hybrid Cascaded Modular Multilevel Converter With DC Fault Ride-Through Capability for the HVDC Transmission System

2015 ◽  
Vol 30 (4) ◽  
pp. 1853-1862 ◽  
Author(s):  
Rui Li ◽  
Grain Philip Adam ◽  
Derrick Holliday ◽  
John E. Fletcher ◽  
Barry W. Williams
Keyword(s):  
Transmission System ◽  
Modular Multilevel Converter ◽  
Multilevel Converter ◽  
Hvdc Transmission ◽  
Dc Fault ◽  
Fault Ride Through

scholarly journals A DC Short-Circuit Fault Ride Through Strategy of MMC-HVDC Based on the Cascaded Star Converter

Energies ◽  
2018 ◽  
Vol 11 (8) ◽  
pp. 2079 ◽  
Author(s):  
Yingjie Wang ◽  
Bo Yang ◽  
Huifang Zuo ◽  
Haiyuan Liu ◽  
Haohao Yan
Keyword(s):  
Control Method ◽  
Short Circuit ◽  
Normal Operation ◽  
Zero Crossing ◽  
High Voltage Direct Current ◽  
Fault Ride Through ◽  
Power Load ◽  
Constant Power Load ◽  
Short Circuit Fault ◽  
Balancing Control

A modular multilevel converter based high voltage direct current (MMC-HVDC) with DC fault self-clearing is adopted to deal with the DC short-circuit fault. However, the constant power load characteristic of the sub-modules causes capacitor voltages to diverge and the converter to go out of hot standby. To address this problem, a novel DC short-circuit fault ride through strategy is proposed. According to the polarities of grid voltages, the working or blockage of the upper and lower bridge arms is chosen according to six sections to obtain a cascaded star converter. The capacitor voltages of MMC sub-modules are maintained and balanced through the control similar to the cascaded star converter. Moreover, in order not to change zero crossing, a cluster balancing control method by scaling the amplitudes of the modulated waves is proposed to balance the capacitor voltages between phase clusters. The strategy also achieves the DC Bus line-to-line equipotential and no fault current generated. With the switches of two modes (normal operation and fault ride through operation) after the fault is cleared, the power transfer of MMC-HVDC can be recovered quickly. Finally, the effectiveness of the proposed fault ride through strategy is demonstrated on the 21-level MMC-HVDC simulation model in PSCAD/EMTDC.

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