High Voltage Direct Current Converter Station Research Articles

Energy Efficiency Evaluation of HVDC Converter Station Based on Deep Neural Network Model

Abstract This paper introduces a new idea of energy efficiency evaluation of high voltage direct current (HVDC) converter based on deep neural networks. This paper analyzes the leading operating indicators and finds the main influencing factors in constructing the energy-saving hands of each converter table. Then this paper uses the deep neural network method to establish the converter table's energy efficiency model. The deep neural network for energy efficiency evaluation of the converter table is obtained. In this paper, PSCAD/EMTDC was used for simulation to evaluate the energy-saving effect. The research shows that the method of energy efficiency evaluation based on deep neural networks is feasible.

Availability assessment of voltage source converter HVDC grids using optimal power flow‐based remedial actions

This study proposes a methodology for assessing the availability of voltage source converter high-voltage direct current (HVDC) grids based on the enumeration methodology of contingency analysis with N − 2 criteria and makes contributions in the computation of remedial actions and the definition and computation of reliability indices applied for HVDC grids. Thus, this study proposes the computation of remedial actions based on an optimal power flow, looking to maintain power exchanges between HVDC and high-voltage alternating current grids, when a contingency occurs on the HVDC grid and converter stations or HVDC lines are out of their operating limits. On the other hand, an HVDC grid has the function of injecting and extracting power from AC interconnected zones, and then traditionally used nodal reliability indices must be modified to indices that reflect the performance of the HVDC network to fulfil its function of interconnection of systems. This study defines two sets of availability indices applicable to HVDC grids: (i) loss of power and energy extracted from the DC grid to the AC zones and (ii) loss of power and energy injected to AC zones from the DC grid. The proposed methodology is applied to perform the availability assessment of the CIGRE B4 DC grid test system and the results are presented.

Power‐system level classification of voltage‐source HVDC converter stations based upon DC fault handling capabilities

To date, numerous concepts for converter station designs for use in voltage source converter (VSC)-based high-voltage direct current (HVDC) systems have been proposed. These differ not only in converter circuit topology, sub-module design, and control scheme but also in AC-or-DC switchgear and other auxiliary equipment. In the main, the existing literature categorises these converter stations according to just the converter circuit technologies and controls. However, for the development of network codes and to enable systematic network studies, a system-focused and technology-independent classification is needed. As such a classification does not yet exist, this study proposes a new framework, which categorises VSC station designs according to their capabilities during a DC-side fault and the method by which post-fault restoration may be achieved, given that these are the main differentiating factors from a system perspective. The classification comprises six converter station types and three time-intervals through which to fully characterise a design. Many well-known forms of converters are used as case studies, and simulation results are used to exemplify the classification framework. The outcome is a generic and technology-independent way of characterising converter station designs that is useful in wider power-system analysis but also for putting proposed converter stations into context.

Modeling of Acoustic Emission Generated by Filter Capacitors in HVDC Converter Station

The acoustic noise generated by filter capacitors in a high voltage direct current (HVDC) converter station will have a serious negative impact on the residents' lives and the ecological environment. Though accurate enough, traditional modeling methods based on either boundary element method (BEM) or finite element method (FEM) are almost impossible to reconstruct sound field for whole HVDC station filter array because of their extremely high demand for computing resources. To deal with this problem, this paper proposes a novel Tikhonov Regularization Equivalent Source Method (TRESM)-based filter capacitor acoustic model. By constructing multiple point-sound source models, the acoustic characteristics of the actual filter capacitor are simulated and the original sound field is reconstructed. The accuracy of the proposed model is verified by the experimental results and the sound field distribution characteristics of the three-phase filter capacitor array are observed and analyzed using the proposed model.

Master self‐tuning VDCOL function for hybrid multi‐terminal HVDC connecting renewable resources to a large power system

To take advantage of line commutated converter (LCC) and voltage source converter high-voltage, direct current (HVDC) technologies a hybrid multi-terminal HVDC (MTDC) is designed to exploit the power from renewable resources. A previous study showed that the voltage dependent current order limiter (VDCOL), an emergency function to reduce the current order of an HVDC converter station when voltage is depressed, should be installed in all of the LCC stations of the hybrid MTDC. This study presents a design for a master self-tuning VDCOL function implemented in a hybrid multi-terminal HVDC system. This controller aims to generate an adaptive current reference for each LCC station of the VDCOL in a low-voltage condition. The parameter of this adaptive VDCOL can be chosen according to the summary table of practical experiences; therefore, no tuning technique is required. The developed HVDC control algorithm is implemented on the simplified South East (SE) Australian 14 generator system using DIgSILENT PowerFactory. The simulation results demonstrate the effectiveness of the proposed control function in reducing the complexity of the control system and operation along with improving system transient stability.

Failure analysis and maintenance of a surge capacitor on the neutral bus in a ±500 kV HVDC converter station

This study analyses a surge capacitor failure on the neutral bus in a ±500 kV high voltage direct current (HVDC) converter station. Both overvoltage and insulation of the surge capacitor are investigated through simulation, practical record data analysis, and experimentation. A highly accurate HVDC model is established on the basis of the topological structure and parameters of the HVDC project. Using this model, the failure process is simulated by combining neutral bus overvoltage record analysis and voltage divider performance test. Results indicate that the 246 kV uncharacteristically high overvoltage on the neutral bus is a measurement error caused by voltage divider fault. From the field test, difference equation of the voltage divider is derived to reconstruct the actual overvoltage, the amplitude of which is 73 kV. The amplitude is significantly lower than that of the switching impulse withstand level of the surge capacitor, which should not cause capacitor failure. Therefore, the primary cause of capacitor failure is insulation damage rather than overvoltage. Finally, maintenance measures are proposed and applied in the station.

HVDC시스템 적용을 위한 Triple-tuned 필터 설계방법 연구

The ac side current of a line commutated converter(LCC) high voltage direct current (HVDC) is characterized by highly non-sinusoidal waveform. If the harmonic current is allowed to flow in the connected ac network, it may cause unacceptable levels of distortion. Therefore, ac side filters are required as part of the total HVDC converter station, in order to reduce the harmonic distortion of the ac side current and voltage to acceptably low levels. The ac filters are also employed to compensate the requested reactive power because LCC HVDC also consume substantial reactive power. Among different types of filters, triple-tuned filters have been widely utilized for HVDC system. This paper presents two design methods of triple-tuned filter; equivalent method and parametric method. Using a parametric method, in particular this paper proposes a design algorithm for a triple tuned filter. Finally, the performance of the design algorithm is evaluated for a 250kV HVDC system in Jeju island. The results cleary demonstrate the effectiveness of proposed design method in harmonics reduction.

Research on the Whole Condition Loaded Noise Measurement Circuit of Power Capacitor

Power capacitor is one of the key equipments of the high-voltage direct current (HVDC) transmission system. It is also the main noise source difficult to control. Presently in the world, there are none explicit requirement and regulation on the evaluation and measurement of the noise generated by the power capacitor, which has seriously restricted the development of the further research on the noise control in power capacitor. So the research on the noise measurement method and technology has extremely important significance in scientifically evaluating the noise of power capacitor. Power capacitor in HVDC Converter Station under practical conditions has apparent fundamental frequency and rich harmonic frequency components. In order to simulate this condition, a whole condition loaded bridge circuit of noise measurement on power capacitor has been designed and studied. Two arms of the bridge are used to load fundamental frequency and a parallel resonance compensation inductance is used to reduce the fundamental current, while the other two arms are used to load harmonic frequency. The harmonic frequency load power supply composed of harmonic signal generator and power amplifier which can simultaneously load any combination of harmonics under 48th to simulate the various actual working conditions. The tests indicated that the noise spectrum measured under the designed circuit completely accorded with the one in HVDC Converter Station.

HVDC System 적용 Double-tuned 필터의 설계 방법 연구

The ac side current of an high voltage direct current (HVDC) converter is characterized by highly non-sinusoidal waveform. If the harmonic current is allowed to flow in the connected ac system, it may cause unacceptable levels of distortion. Therefore, ac side filters are required as part of the total HVDC converter station, in order to reduce the harmonic distortion of the ac side current and voltage to acceptably low levels. The ac side filters are also employed to compensate network requested reactive power because HVDC converters also consume substantial reactive power. Among different types of filters, double-tuned filters have been widely utilized for HVDC system. This paper presents two design methods of double-tuned filter; equivalent method and parametric method. Using a parametric method, in particular the paper proposes a new design algorithm for a realistic system. Finally, the performance of the design algorithm is evaluated for a 80㎸ HVDC system in Jeju island with PSCAD/EMTDC program. The results cleary demonstrate the effectiveness of proposed design method in harmonics elimination and steady-state stability.

AC/DC interconnectors stability and torsional interaction

Higher levels of power transfers across AC transmission circuits (also called interconnectors when they connect two electrical systems or companies) can result in system stability issue (rotor angle and voltage stability) and prevent the use of circuits’ full thermal capacity. Due to increased amount of renewables there is also a need to reinforce the thermal capacity of such circuits. A high voltage direct current (HVDC) link parallel to these circuits can resolve the stability issue as well as provide the required additional transmission capacity. However the current controller of HVDC converters can introduce negative damping under certain operating conditions. If there are thermal generators close to the HVDC converter stations, and the negative damping exceeds the positive damping of generators, there will be a risk of sub-synchronous torsional interaction (SSTI) between the electrical and mechanical shaft system of the turbine-generators. When such an interaction is not mitigated, generators shafts could be damaged, putting generators out of service and possible loss of supply to customers – a major cost implication for power stations and system operator. This study discusses the above issues, and present ideas that have been considered in this project to enhance system stability, thermal capacities, and mitigate the SSTI issue.

Application of SMES Unit in Improving the Performance of an AC/DC Power System

This paper investigates the use of a superconducting magnetic energy storage (SMES) unit to improve the performance of an ac/dc power system. In this context, investigations have been conducted on a large turbine-generator unit connected to a high-voltage direct current (HVDC) system. The impact of HVDC converter station faults on the torsional torques induced in turbine-generator shafts with and without using an SMES unit is elaborated. Faults considered are fire-through, misfire, short circuit across the inverter station, flashover, and a three-phase short circuit in the ac system. These investigations are studied using an electromagnetic transient program power system simulation/electromagnetic transients including DC (PSCAD/EMTDC) and the results are presented in the form of typical time responses as well as harmonic analysis.

Reliability assessment of 3-phase three winding converter transformer of HVDC transmission system

High voltage direct current (HVDC) is today recognized as an effective and efficient means of transmitting bulk power over long distances through over head lines or cables. The reliability of HVDC links have always been of primary concern in planning and operating of power systems. The existence of spares and maintenance practices do affect the availability of HVDC stations. The HVDC converter transformer plays a relevant roll in HVDC converter station, not only due to the direct cost associated to them but also causes its availability affects the HVDC transmission capability (or) capacity. In this paper the effect of converter transformer failure rate, repair time on expected capacity level of three phase three winding converter transformer with and without spares is analyzed and compared. It also effect of number of spares on expected capacity level is presented. Key words: HVDC transmission system, converter transformer, unavailability, Morkov modeling.

Electromagnetic interference and shielding of valve hall in HVDC converter station

The electromagnetic interference (EMI) from the valve hall as an important consideration in the design of high voltage direct current (HVDC) converter stations is analyzed by electromagnetic field numerical method and measurements. By using moment method, the EMI filed strength level as well as radio interference level (RIL) of the valve hall during the normal operation are computed after an antenna model is built for the valve tower. According to the character of EMI obtained, the practical shielding measures for valve hall are discussed to satisfy the relative standards. The test results for the ±500 kV converter station show that both the numerical method and shielding technique used in this paper are practical.

Evaluation of the effectiveness of shielding and filtering of HVDC converter stations

The application of the Numerical Electromagnetic Code (NEC) to the problem of EMI (electromagnetic interference) from HVDC (high-voltage direct current) converter stations is investigated, with particular emphasis on evaluating the effectiveness of valve hall shielding and filtering. It is shown that valve hall shielding alone is not effective in reducing the EMI of converter stations. Appropriate combinations of shielding and filtering produce EMI attenuation of the order of 20 to 30 dB. In order to reduce the EMI, the length of busbars and other connecting elements should be reduced to a minimum, both inside and outside valve halls. The location of filters should be chosen to minimize the length of high-frequency return-current paths. >

Measurement of the electromagnetic environment of HVDC converter stations

The results of an experimental study on the electromagnetic environment of HVDC (high-voltage direct-current) converter stations are presented. Transient EMI (electromagnetic interference) as well as steady-state RI (radio interference) and TVI (television interference) measurements were made at the Arnott station of BC Hydro and the Chateaguay station of Hydro-Quebec. The maximum values of the electric and magnetic fields measured inside the valve halls of Arnott station are 1.8 kV/m and 3.2 A/m; outside, they are 0.28 kV/m and 0.4 A/m respectively. These values cover the range of normal operation, including start-up and stopping of the converter station. During normal operation of the Chateauguay station, maximum electric and magnetic fields of 0.7 kV/m and 1.1 A/m are measured inside the valve hall; outside, they are below the sensitivity of the measuring system. It is recommended that immunity testing be carried out on electronic equipment to be used either inside or outside the valve halls of converter stations at transient electric and magnetic field levels of 5 kV/m and 10 A/m, respectively, with approximately 1 mu s risetime and 10 mu s duration.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Insulation coordination process for HVDC converter stations: preliminary and final designs

The authors provide step-by-step procedures for determining the appropriate surge arrester characteristics and insulation levels for both transmission and back-to-back HVDC (high-voltage direct current) systems. Information is included on insulation coordination practices in existing HVDC systems, such as typical system voltage and insulation withstand levels. Two different design procedures with specific design objectives are presented: preliminary insulation coordination and final insulation coordination. The proposed procedures concentrate on the use of gapless metal oxide arresters for insulation protection.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Measurement of the Electromagnetic Environment of HVDC Converter Stations

The results of an experimental study on the electromagnetic environment of HVDC (high-voltage direct-current) converter stations are presented. Transient EMI (electromagnetic interference) as well as steady-state RI (radio interference) and TVI (television interference) measurements were made at the Arnott station of BC Hydro and the Chateaguay station of Hydro-Quebec. The maximum values of the electric and magnetic fields measured inside the valve halls of Arnott station are 1.8 kV/m and 3.2 A/m; outside, they are 0.28 kV/m and 0.4 A/m respectively. These values cover the range of normal operation, including start-up and stopping of the converter station. During normal operation of the Chateauguay station, maximum electric and magnetic fields of 0.7 kV/m and 1.1 A/m are measured inside the valve hall; outside, they are below the sensitivity of the measuring system. It is recommended that immunity testing be carried out on electronic equipment to be used either inside or outside the valve halls of converter stations at transient electric and magnetic field levels of 5 kV/m and 10 A/m, respectively, with approximately 1 mu s risetime and 10 mu s duration. >