Overvoltage control protection method for sub-modules of symmetrical bipolar flexible direct-current power transmission system
A power transmission system, flexible direct current technology, applied in the direction of emergency protection circuit devices, emergency protection circuit devices, electrical components, etc. used to limit overcurrent/overvoltage, can solve the problem of overvoltage protection and control of sub-modules after the lockout is not applicable, Lack of problems such as MMC sub-module overvoltage
Pending Publication Date: 2021-04-20
CENT SOUTHERN CHINA ELECTRIC POWER DESIGN INST CHINA POWER ENG CONSULTING GROUP CORP
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However, this method has no effect on the transient characteristics during the fault period, and only promotes the recovery phase of the system after the fault, so this method is not suitable for the protection and control of the overvoltage of the sub-module after the blockage
[0007] In general, in the current flexible DC transmission system, there is a lack of methods that can effectively suppress and reduce the overvoltage of the MMC sub-module for the overvoltage problem generated by the bridge arm sub-module after the single-phase ground fault on the valve side is blocked.
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[0087] In this example, a ±320kV symmetrical bipolar double-terminal DC power grid is used as an example for simulation and verification. figure 2 In the simulation model shown, MMC1 and MMC2 are constant power control stations, MMC3 and MMC4 are constant voltage control stations, and the main parameters of MMC (MMC includes MMC1, MMC2, MMC3 and MMC4) are shown in Table 1. The return lines are all DC cables, the main parameters of the cables are shown in Table 2, and the structure of the cables is as follows Figure 7 shown.
[0088] Table 1 MMC main parameters
[0089]
[0090]
[0091] Table 2 Main parameters of cables
[0092] Material Thickness / m Resistivity / (Ω·m) Relative permittivity conductor 0.0239m 1.75×10 -8
/ Insulation I 0.0179m / 2.30 jacket 0.009m 2.2×10 -7
/ Insulation II 0.005m / 2.25
[0093] When the system is running in a steady state, the sending end transmits 1000MW DC power to the receivi...
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The invention discloses an overvoltage control protection method for sub-modules of symmetrical bipolar flexible direct-current power transmission system. The method comprises the following steps: step 1, replacing a valve top and a neutral line lightning arrester with controllable lightning arresters; step 2, improving a sub-module overvoltage bypass; when the converter is in an unlocked state, using a set value uset1 for the sub-module overvoltage bypass; when the converter is in a locked state, setting the set value of the sub-module overvoltage bypass to be uset2; and step 3, enabling the controllable lightning arresters and the sub-module overvoltage bypass to cooperate to carry out overvoltage control. According to the invention, the defect that the overvoltage of the MMC sub-module cannot be effectively suppressed and reduced due to the overvoltage problem generated by the bridge arm sub-module after the valve side single-phase earth fault locking occurs in the prior art is overcome; the method has the advantages that the overvoltage of the MMC sub-module can be effectively suppressed and reduced after locking, the bypass switch of the sub-module does not need to be closed, the maintenance workload of the sub-module can be reduced, and the recovery of the direct-current voltage after a fault can be accelerated.
Description
technical field [0001] The invention relates to the technical field of direct current transmission, and more specifically relates to a sub-module overvoltage control and protection method of a symmetrical bipolar flexible direct current transmission system. More specifically, it is a control and protection method for the overvoltage of the MMC sub-module after the converter station of the symmetrical bipolar flexible direct current transmission system is blocked. Background technique [0002] In recent years, with the development of power electronics technology, modular multilevel converter (MMC) has become the preferred topology for high voltage and high power transmission due to its low power consumption and few output harmonics. As a new type of Voltage Source Converter (VoltageSource Converter, VSC), the MMC-HVDC (Modular Multilevel Converter Type HVDC) system has no commutation failure problem, which is different from the traditional thyristor-based grid One of the mos...
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Login to View More IPC IPC(8): H02H9/04H02H7/26H02J3/36
CPCY02E60/60
Inventor 李浩原周国梁王刚韩毅博刘超李文津马亮曾维雯陈鹏陈晨夏泠风胡金魏来陆洲彭越梁言桥曾静
Owner CENT SOUTHERN CHINA ELECTRIC POWER DESIGN INST CHINA POWER ENG CONSULTING GROUP CORP