摘要 :
With the development of economy and the increased demand of power energy, it is unavoidable that high-voltage direct current (HVDC) and high-voltage alternating current (HVAC) transmission lines are in the same corridor. In order ...
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With the development of economy and the increased demand of power energy, it is unavoidable that high-voltage direct current (HVDC) and high-voltage alternating current (HVAC) transmission lines are in the same corridor. In order to minimise the land resource and meet the requirements of the electromagnetic environment, it is necessary to accurately predict the hybrid electric field under the hybrid transmission lines. The ±800 kV HVDC and 750 kV HVAC parallel transmission lines of parallel erection are chosen to be analysed. The corridor width with a different separation distance is calculated, and the minimum corridor width under this voltage-level combination is obtained according to the control value of the hybrid electric field recommended at home and abroad in a non-residential area. Increasing the height of DC or AC lines can reduce the corridor width. At a fixed separation distance, the minimum height of the AC line can be obtained when the height of the DC line is set at a certain value. Meanwhile the change of the corridor width is analysed with different heights of DC lines and AC lines. Based on the above analysis, the reasonable arrangement is made.
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摘要 :
In order to solve the problem of power supply shortage in certain region of Nanjing city, a high-voltage direct current (HVDC) flexible transmission project needs to be constructed. It could be the first project with ±380 kV DC ...
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In order to solve the problem of power supply shortage in certain region of Nanjing city, a high-voltage direct current (HVDC) flexible transmission project needs to be constructed. It could be the first project with ±380 kV DC and real bipolar connection in the world. Two new converter stations will be built with 1500 MW transmission capacity. The system design scheme has been proposed including the main connection mode of converter stations, the operation mode, the control strategy, parameters design for main circuit and determination of converter station's power operation range. This technical solution can provide complete design method for future HVDC flexible transmission project, which is of great significance to the development and engineering application of the HVDC flexible technology in China.
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This study proposes a novel transverse differential protection for voltage sourced converter-high-voltage, direct current (VSC-HVDC) to clear faults on DC-line fast. The proposed scheme depends on the transient current of positive...
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This study proposes a novel transverse differential protection for voltage sourced converter-high-voltage, direct current (VSC-HVDC) to clear faults on DC-line fast. The proposed scheme depends on the transient current of positive pole and negative pole at the same side. Transverse differential current can be used to distinguish DC and AC faults, novel criteria are built using the ratio of difference and sum current of bipolar. According to the variation characteristics of transient fault current, internal faults and external faults can be detected. The scheme can protect the whole transmission line without dead zone, simplify the algorithm and improve the speed of operation. A typical VSC-HVDC model in PSCAD/EMTDC is built. The tolerance to grounding resistance of the scheme is researched in simulation. The results demonstrate the feasibility and reliability of the proposed scheme. The scheme can be used as supplementary criteria for primary protection or backup protection for VSC-HVDC transmission lines.
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摘要 :
The hybrid high-voltage direct current (HVDC) system, in which the rectifier is made up of the line commutated converter (LCC) and the inverter is composed of the modular multilevel converter (MMC), has quite different fault chara...
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The hybrid high-voltage direct current (HVDC) system, in which the rectifier is made up of the line commutated converter (LCC) and the inverter is composed of the modular multilevel converter (MMC), has quite different fault characteristics from the symmetrical LCC–HVDC and MMC–HVDC systems. Therefore, it is necessary to analyse the applicability of the existing line protection principles to the hybrid HVDC system. First, the fault characteristics of the travelling wave on both ends of the hybrid HVDC line are obtained by analysing the boundary characteristics. The applicable conditions of travelling wave protection to the hybrid HVDC line are given based on the criteria of travelling wave protection and the fault characteristics. Second, an electromagnetic transient simulation model of the hybrid HVDC system is established in Power System Computer-Aided Design/Electromagnetic Transients including DC (PSCAD/EMTDC) in order to verify the theoretical analysis results. A large amount of simulation results show that the travelling wave protection has good applicability in the hybrid HVDC system, but it has poor sensitivity for high-resistance grounding faults; an appropriate sampling rate should be chosen according to the parameters of the boundary element for a better performance of the protection.
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摘要 :
Multi-terminal high voltage direct current (MTDC) has many features including multiple sending ends, multiple receiving ends, and high transmission capacity. These make it highly competitive in both technical and economic terms. I...
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Multi-terminal high voltage direct current (MTDC) has many features including multiple sending ends, multiple receiving ends, and high transmission capacity. These make it highly competitive in both technical and economic terms. In designing a MTDC system, the calculation of the main circuit steady-state parameter plays a fundamental role. However, existing researches mainly focus on parallel multi-terminal DC transmission systems (P-MTDC), few looks into series multi-terminal DC transmission systems (S-MTDC). Therefore, this study researches into the calculation of the main circuit steady-state parameters for S-MTDC transmission systems. First of all, the two types of MTDC transmission systems, S-MTDC and P-MTDC, are briefly introduced and compared. Then, the calculation of the steady-state parameter of the main circuit for two-terminal high voltage direct current (HVDC) transmission systems is explained. Based on this calculation method, research on the main circuit steady-state parameter for S-MTDC transmission systems is conducted and the design of calculation of steady-state parameter of the main circuit is presented in detail. Finally, this study designs a series four-terminal HVDC systems and verifies the calculation method of the steady-state parameter of the main circuit.
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摘要 :
This study presents the results of technical and economic analysis of high-voltage direct current (HVDC) transmission system and high-voltage alternating current transmission system for bulk transmission over very long distances. ...
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This study presents the results of technical and economic analysis of high-voltage direct current (HVDC) transmission system and high-voltage alternating current transmission system for bulk transmission over very long distances. The last is a point-to-point transmission that does not need reactive compensation and does not have intermediate substations, the half-wavelength transmission (HWL). Special attention is paid to reliability and ways to meet the - 1 criteria regarding security and adequacy. Single-circuit lines instead of double-circuit ones are considered for economic and environmental reasons ensuring the same reliability when clearing the most frequent line-to-ground (or single-pole) fault. For this, single-circuit line with reserve phase for HWL and quadripolar single-circuit line for HVDC are proposed. The analysed system considered Brazilian electrical system conditions: 6000 MW transmission over 2500 km. This study highlights the advantages of applying a reserve phase for HWLs and a third converter substation increase to cope with system security with minimum cost. It is shown that the single-circuit HWL with reserve phase has an investment 30\% lower than that for HVDC, resulting in a total yearly cost 15\% lower.
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摘要 :
Here, the response characteristics of high-voltage DC (HVDC) control system are studied in the case that fault occurs in the sending-end AC system. Then the characteristics of DC system which is equivalent to power-frequency varia...
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Here, the response characteristics of high-voltage DC (HVDC) control system are studied in the case that fault occurs in the sending-end AC system. Then the characteristics of DC system which is equivalent to power-frequency variation impedance in the fault super-imposed network are analysed by mathematical derivation and verified by simulations on PSCAD/EMTDC. The result shows that the equivalent power-frequency variation impedance of HVDC system is affected by the rated capacity and the parameters of HVDC control system. The power-frequency variation impedance becomes capacitive under certain fault conditions, which reduces the zone of distance protection based on power-frequency variation and even leads to the operation failure.
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摘要 :
This study presents a comprehensive analysis and a suppression method of sub-modules' (SMs') voltage stress in the hybrid modular multilevel converters when riding through zero DC voltage faults in high-voltage direct-current (HVD...
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This study presents a comprehensive analysis and a suppression method of sub-modules' (SMs') voltage stress in the hybrid modular multilevel converters when riding through zero DC voltage faults in high-voltage direct-current (HVDC) systems. First, the general DC fault ride through (FRT) strategy considering the redundancy of the arm voltage generation scheme under a reduced dc-link voltage is derived. Then full-bridge sub-modules (FBSMs') voltage stress for the conventional DC-FRT schemes with and without common-mode voltage injection are analysed. Finally, on the basis of the available full-bridge SM capacitor energy control strategy, an improved method implemented by energy interaction between half-bridge sub-modules and FBSMs is presented. The proposed DC-FRT scheme can make all SM capacitor voltages balanced at their rated values during the zero DC voltage conditions. Simulated results are provided to demonstrate the validity of the analytical results and the feasibility of the proposed DC-FRT scheme.
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摘要 :
In this paper, two standard VSC HVDC dynamic models are proposed. The full system model, consisting of the converter and its controllers, DC circuit equations, and coupling equations, is derived mathematically. Special attention i...
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In this paper, two standard VSC HVDC dynamic models are proposed. The full system model, consisting of the converter and its controllers, DC circuit equations, and coupling equations, is derived mathematically. Special attention is given to the filter and phase-locked loop (PLL), often neglected in VSC HVC modelling. A reduced order model is then derived from the full model by neglecting the smallest time constants, resulting in a reduced set of differential equations that can be integrated with a larger time step. The models are implemented in MatDyn, a Matlab based stability program. Simulations validate the proposed models.
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摘要 :
The abnormal heating phenomena of contact terminal in large DC current loop of the ultra-high voltage direct current (UHVDC) converter station became one of the most serious problems, which caused serious impact on the operation r...
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The abnormal heating phenomena of contact terminal in large DC current loop of the ultra-high voltage direct current (UHVDC) converter station became one of the most serious problems, which caused serious impact on the operation reliability of the power grid. Based on existing codes and standards of contact terminal temperature rise and the results of large current temperature rise test, the design principle of the contact terminal in large DC current loop of DC voltage ±800 kV, capacity 10,000 MW converter station is put forward and introduced detailedly in this study. Then, taking the design of three typical contact terminals in large DC current loop of Taizhou ±800 kV converter station as an example, the infrared temperature measurement results of contact terminals on the large current operation condition are analysed. The infrared temperature measurement results indicate that the design principle of the contact terminal in large DC current loop proposed in this study is able to meet the requirements of existing codes and standards of the temperature (temperature rise) limit of the contact terminal. This design principle is significant to improve the maintenance ability and operation reliability of the UHVDC converter station.
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