Article

Influence characteristics of high voltage direct current transmission on geomagnetic observation

July 2014

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High voltage direct current transmission (HVDC) failure can affect the geomagnetic observation data in a large range and causes much trouble to data processing. With the number of HVDC projects growing, the problem has become even more acute in recent years. In order to produce reliable geomagnetic observation data, the relationship between HVDC failure and its characteristics on geomagnetic observation data should be known, although it is difficult to identify interferences from the HVDC failure. By conducting a comprehensive analysis on the large data set, four characteristics were obtained and introduced in this paper, which would provide an effective method for the observer to identify and judge the interferences on geomagnetic observation data caused by the HVDC failure.

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Article

Study on Operational Tests of Voltage Source Converter Valve Based on MMC

September 2018 · Gaoya Dianqi/High Voltage Apparatus

With the development of the HVDC-flexible technology, the performance advantages of voltage source converter have been more widely recognized, voltage source converter technology based on modular multi-level converter(MMC)has been widely used in China, Nan'ao, Zhou'shan multi-terminal HVDC-flexible project and Lu'xi asynchronous interconnection HVDC-flexible project have been completed and put ... [Show full abstract] into operation, ±420 kV Yu'e back-to-back interconnection project, ±500 kV Zhang'bei renewable energy HVDC-flexible demonstration project has started construction, ±800 kV Wu'dongde to Guang'dong and Guang'xi multi-terminal HVDC project has entered the implementation stage of the project. The modular multi-level converter (MMC) valve is one of the main devices of the HVDC-flexible transmission system. To ensure safe and reliable operation of the HVDC-flexible transmission system, the converter valve must be strictly examined in the type test. The operational test, as one of the important items in type tests, examine the adequacy of the converter valve with regard to current, voltage and temperature stress in conducting state and at turn-on or turn-off moments under the worst repetitive stress condition. According to the actual operational condition of voltage source converter valve based on MMC, this study proposed an operational test method, and constructed a test circuit to conduct operational tests of the MMC valve for actual HVDC-flexible project. The results show that the proposed test method and test circuit can carry out operational tests of the voltage source converter valve, and the test results meet the relevant standards of IEC 62501:2017, GB/T 33348-2016, and DL/T 1513-2016. © 2018, Xi'an High Voltage Apparatus Research Institute Co., Ltd. All right reserved.

Article

Control of Modular Multilevel Converters Under Singular Unbalanced Voltage Conditions With Equal Pos...

January 2016 · Power Systems, IEEE Transactions on

This paper focuses on the control of Modular Multilevel Converters (MMC) for High Voltage DC (HVDC) applications during unbalanced AC grid voltage sags where positive and negative sequence voltages are equal. The control scheme is based on six arm energy regulators, six independent current controllers, and two reference calculation stages that convert the power references into grid and inner ... [Show full abstract] current references. Conventional inner AC currents reference calculation fails if the amplitude of the positive and the negative sequence AC grid voltages are equal, a state which is referred to in this paper as singular voltage condition. This paper discusses the types of network faults that cause this condition and proposes three different solutions to operate the converter in such scenarios. The adequacy of the proposed solutions is validated through simulations considering each of the problematic fault scenarios.

Article

A Transient Harmonic Current Protection Scheme for HVDC Transmission Line

October 2012 · IEEE Transactions on Power Delivery

Based on the boundary characteristic of a dc transmission line, the response of transient harmonic current in the line-commutated converter HVDC transmission system is analyzed under various fault conditions in this paper. A new transient harmonic current protection scheme is proposed. The discrete Fourier transform is used to extract transient harmonic currents at both terminals of the dc ... [Show full abstract] transmission line and the type of fault can be identified by the transient harmonic currents. Two main factors including fault resistance and fault location that affect performance of the protection are also discussed in this study. The test system is modeled based on the CIGRE benchmark including distributed parameters of the dc transmission line. Comprehensive test studies show that the performance of the transient harmonic current protection scheme is encouraging. It can not only identify internal faults and external faults correctly and quickly, but also can respond to high ground resistance faults.

Article

Decentralized Control of Uncertain Structures Using Luenberger Observer

February 2017 · Structural Engineering International

Multiplicity of the required sensors in the centralized control of large-scale structures, leads to excessive data transmission and resulting system lags. On the other hand, decentralized control, as an alternative approach, offers sub-optimal responses. In this paper, an innovative estimation procedure to compensate for the mentioned deficiency is presented. In this method, a substructure is ... [Show full abstract] equipped with an embedded Luenberger observer, which estimates the whole state of the structure based on the available ones. Then, the actuator commands are locally calculated by the estimated states. To evaluate the proposed method, fully decentralized control of a three storey frame structure and semi-decentralized control of a 20 storey one are investigated. Comparison of the estimated states with the measured ones indicates the acceptable accuracy of the utilized estimator. Precision of the structural responses controlled by the estimated states introduces the proposed method as an appropriate alternative for the centralized one. The approach provides an efficient decentralized control by eliminating numerous sensors and excessive data communication.

Conference Paper

Thermal-hydraulic analysis of high-voltage bushings in HVDC transmission systems suitable for the 15...

October 2014

Article

Full-text available

Current Rating Considerations in Designing HVDC Cable Installations

February 2018 · IEEE Transactions on Power Delivery

Ampacity calculations for High Voltage Direct Current (VHDC) cables are more difficult than the AC cables because of absence of suitable analytical formulas. The current carrying capability of such cables is not only limited by the operating temperature, but also by the electrical stress within the insulation. The IEC60287 standard considers only the thermal limitations of the conductor current ... [Show full abstract] and, therefore, cannot be used for some HVDC applications because it fails to include the analytical derivations of the stress-limited rating equations. However, applications of the HVDC cables becomes more common and there is a need to extend the IEC standard methodology so that ampacity calculations can be performed for such installations. This paper considers various aspects of the HVDC cable design and how they influence cable rating. It focuses on the temperature rise across the electrical insulation and the entire cable as a means of representing the maximum dielectric stress as the current limiting factor when calculating ratings for HVDC cables.

Article

Full-text available

Model, Characterization, and Analysis of Steady-State Security Region in AC/DC Power System with a L...

August 2017 · Energies

A conventional steady-state power flow security check only implements point-by-point assessment, which cannot provide a security margin for system operation. The concept of a steady-state security region is proposed to effectively tackle this problem. Considering that the commissioning of the increasing number of HVDC (High Voltage Direct Current) and the fluctuation of renewable energy have ... [Show full abstract] significantly affected the operation and control of a conventional AC system, the definition of the steady-state security region of the AC/DC power system is proposed in this paper based on the AC/DC power flow calculation model including LCC/VSC (Line Commutated Converter/Voltage Sourced Converter)-HVDC transmission and various AC/DC constraints, and hence the application of the security region is extended. In order to ensure that the proposed security region can accurately provide global security information of the power system under the fluctuations of renewable energy, this paper presents four methods (i.e., a screening method of effective boundary surfaces, a fitting method of boundary surfaces, a safety judging method, and a calculation method of distances and corrected distance between the steady-state operating point and the effective boundary surfaces) based on the relation analysis between the steady-state security region geometry and constraints. Also, the physical meaning and probability analysis of the corrected distance are presented. Finally, a case study is demonstrated to test the feasibility of the proposed methods.

Article

Study of turn-on test method for high-voltage thyristor valve

February 1993 · IEEE Transactions on Power Delivery

Digital simulations have been conducted to analyze the thyristor valve turn-on phenomenon while a valve arrester is conducting, which gives the most severe turn-on stress for the valve. The effects of various other parameters have also been clarified. Based on this analysis, two test methods are proposed that verify a valve turn-on during arrester conduction, and their effectiveness is described. ... [Show full abstract] The nonrepetitive turn-on test given in the IEC Std Pb. 700 and IEEE Std 857 is studied, and a new test voltage level based on these analyses is proposed

Conference Paper

Fault Current limiting in VSC-HVDC systems with MMC converters

June 2016

High Voltage Direct Current (HVDC) transmission systems are playing an important role due to their economical and technical benefits in the countries where the electric grid is expanding fast. However, fault current interruption is still an unsolved challenge in these HVDC grids. In order to interrupt undesirable currents, DC circuit breakers can be used, but their capability is limited. With ... [Show full abstract] that scenario, Fault Current Limiters (FCL) arise as a good approach in order to reduce fault currents to a more manageable level allowing to increase the transmission ratings of an electrical system, without changing the equipment. Thus, the existing equipment would be able to handle the new currents and protect properly the system. In this paper, the general characteristics and classification of FCLs are explained. After that, a Solid State FCL is applied on a VSC-HVDC system with MMC converters. A simulation case of its optimal behavior is presented.

Conference Paper

High voltage VLF test equipment with sinusoidal waveform

May 1999

Richard Reid

The problems associated with testing field aged XLPE cable using HVDC are now well documented. AC test equipment for field tests at power frequency also presents problems. The equipment required for such tests is large, heavy and expensive even with resonant test sets. Equipment producing very low frequency (VLF) high voltage has been used to some extent in the past. Typically this equipment ... [Show full abstract] produced 0.1 Hz voltage having a variety of waveforms. Squarewaves, triangular waves, etc. have been available. Such nonstandard waveforms complicate efforts to correlate VLF techniques with the results of power frequency tests. This paper describes AC test equipment utilizing a new approach to high voltage VLF in the range of 0.02 to 0.1 Hz. The equipment generates a sinusoidal waveform directly, without the additional complexity, cost and weight of HV filters. This not only saves weight and reduces cost but also simplifies its use in diagnostic tests such as partial discharge detection and site location. The design concept and application of the equipment to both voltage withstand testing and partial discharge testing are discussed

Article

Steady-state Error Calibration Technology for HVDC Current Transformer

September 2018 · Gaoya Dianqi/High Voltage Apparatus

Accurate measurement of DC current is very important for safe and stable operation of HVDC transmission project. Considering the mainstream high voltage DC current transformer and the national standard, this study proposed a design scheme of steady-state error calibration system for DC current measurement device, and built an error calibration system. Experiment and comparison were performed, and ... [Show full abstract] the validity of the present steady-state error calibration system for DC current transformer was proved. It is concluded that this system meets the requirements of practical application. © 2018, Xi'an High Voltage Apparatus Research Institute Co., Ltd. All right reserved.

Article

Influence of Wind and Conductor Potential on Distributions of Electric Field and Ion Current Density...

May 1982 · IEEE Transactions on Power Apparatus and Systems

Lateral profiles of electric field and ion current density at ground level were measured precisely in a unipolar/bipolar line to plane geometry under different wind conditions and different dc voltages. Furthermore, the relationship between the field and current density is discussed. In the case of unipolar line in still air, the normalized profiles are approximately independent of the magnitude ... [Show full abstract] of the applied voltage and the linear dimensions of the gap, but they are strongly influenced in the bipolar case. The wind effect on the current profile is greatest at voltages close to corona onset for each experimental arrangemeht. The experimental results suggest that the usual wind extends the region of the ionic current flowing . e. the right-of- ay required for HVDC transmis-sion lines) by a factor of two or more as compared with that with no wind.

Last Updated: 05 Jul 2022