A novel method based on dynamic extinction angle of thyristor to mitigate commutation failure for HVDC

2021 ◽  
Author(s):  
L. Kou ◽  
Z. Mi ◽  
X. Huang
Keyword(s):  
Extinction Angle ◽  
Commutation Failure ◽  
Novel Method

Line Commutated Converter Response during Total and Partial De-Blocking of a Bipolar MTDC System

2021 ◽  
Vol 52 ◽  
pp. 49-61
Author(s):  
Oluwafemi E. Oni ◽  
Andrew G. Swanson ◽  
Rudiren Pillay Carpanen
Keyword(s):  
Dynamic Response ◽  
Direct Current ◽  
Controller Design ◽  
Dynamic Modelling ◽  
Active Power ◽  
Extinction Angle ◽  
Commutation Failure ◽  
Voltage Dependent ◽  
Operational Issues ◽  
Blocking Analysis

This paper focuses on the fault blocking analysis and operational issues associated with MTDC systems incorporated in an AC network. The dynamic modelling of a line-commutated converter based bipolar multi-terminal direct current (LCC MTDC) system are shown, and the dynamic response of the converter during a DC converter fault is discussed. The converter controller design for both rectifiers and the inverters system was modelled for a realistic active power and extinction angle (γ) control with consideration to the VI characteristics of all the converter stations. An overall power controller was modelled for both converter pole. Two operational scenarios of converter fault were simulated using PSCAD EMTDC. The converter firing angle and extinction angle, as well as the voltage-dependent current order limiter, was monitored and plotted on a graph. Results show that the MTDC link became unstable during the full deblocking stage with a continuous occurrence of commutation failure. Furthermore, the results presented in this paper show that during partial converter de-blocking showed a favourable performance, as the power system remains stable and commutation failure of the MTDC system is prevented.

Improved Extinction Angle Control for Subsequent Commutation Failure Mitigation in LCC-HVDC

2021 ◽  
Author(s):  
Quanquan Wang ◽  
Bailiang Liu ◽  
Chenyi Zheng ◽  
Rui Gu ◽  
Yurong Wang ◽  
...  
Keyword(s):  
Extinction Angle ◽  
Commutation Failure ◽  
Failure Mitigation

A Calculation Method of Pseudo Extinction Angle for Commutation Failure Mitigation in HVDC

2019 ◽  
Vol 34 (2) ◽  
pp. 777-779 ◽  
Author(s):  
Lei Liu ◽  
Sheng Lin ◽  
Peiyao Sun ◽  
Kai Liao ◽  
Xiaopeng Li ◽  
...  
Keyword(s):  
Calculation Method ◽  
Extinction Angle ◽  
Commutation Failure ◽  
Failure Mitigation

Diagnosis of Commutation Failures in HVDC System Based on Voltage or Current of the Converter Valve

2014 ◽  
Vol 960-961 ◽  
pp. 738-741
Author(s):  
Tao Liu ◽  
Tong Zhao ◽  
Liang Zou ◽  
Li Zhang ◽  
Meng Qi Liu
Keyword(s):  
Fault Diagnosis ◽  
Failure Mechanism ◽  
Accurate Diagnosis ◽  
Control Measures ◽  
Hvdc System ◽  
Depth Analysis ◽  
Commutation Failure ◽  
Novel Method ◽  
Regulatory Measures ◽  
Simulation Results

Commutation failure is one of the most common typical faults of HVDC, and it may result in subsequent commutation failures, even the outage of the HVDC system if without timely and effective regulatory measures. Trigger of the control measures depends on the rapid and accurate diagnosis of commutation failure. In-depth analysis of the commutation failure mechanism indicates its new substantive characteristics: valve voltage being continuously zero and valve current being continuous with high amplitudes, according to which a novel method for fault diagnosis of commutation failure based on voltage or current of the converter valve is proposed in this paper. Simulation results prove the accuracy and effectiveness of this method.

The removal and morphology of intact biofilms from implanted venous access devices

1995 ◽  
Vol 53 ◽  
pp. 1020-1021
Author(s):  
M.A. Gregory ◽  
G.P. Hadley
Keyword(s):  
Patient Selection ◽  
Surgical Oncology ◽  
Venous Access ◽  
Common Procedure ◽  
Indwelling Catheters ◽  
Careful Patient ◽  
Novel Method ◽  
The Subject ◽  
Vascular Catheters ◽  
Venous Access Devices

The insertion of implanted venous access systems for children undergoing prolonged courses of chemotherapy has become a common procedure in pediatric surgical oncology. While not permanently implanted, the devices are expected to remain functional until cure of the primary disease is assured. Despite careful patient selection and standardised insertion and access techniques, some devices fail. The most commonly encountered problems are colonisation of the device with bacteria and catheter occlusion. Both of these difficulties relate to the development of a biofilm within the port and catheter. The morphology and evolution of biofilms in indwelling vascular catheters is the subject of ongoing investigation. To date, however, such investigations have been confined to the examination of fragments of biofilm scraped or sonicated from sections of catheter. This report describes a novel method for the extraction of intact biofilms from indwelling catheters.15 children with Wilm’s tumour and who had received venous implants were studied. Catheters were removed because of infection (n=6) or electively at the end of chemotherapy.

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