A control method for a passive MMC station to be integrated into DC power grids of different voltage levels
A technology of DC power grid and voltage level, applied in power transmission AC network, circuit devices, wind power generation, etc., can solve problems such as affecting DC power grid, staying, damaging sub-module capacitors and other key equipment, etc.
Active Publication Date: 2020-07-07
NORTH CHINA ELECTRIC POWER UNIV (BAODING)
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Problems solved by technology
Relevant research results only focus on the start-up control method of a certain converter station and the start-up control method of the entire system in double-terminal and multi-terminal HVDC transmission systems
In the process of offline MMC stations being integrated into DC grids of different voltage levels online, the DC / DC converter needs to be started smoothly, and for passive MMC stations, it cannot charge its sub-modules through its own AC side system , so only the charging power of the DC / DC converter and the passive MMC station can be provided by the DC grid
If a reasonable control method for connecting passive MMC stations to DC grids of different voltage levels cannot be adopted, the inrush current generated when passive MMC stations are incorporated will be too large, damage sub-module capacitors and other key equipment, and affect the entire DC grid safe and stable operation
Method used
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[0016] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention more clear, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention.
[0017] The initial state is figure 1 The upper DC grid shown in is in normal operation, figure 1 The schematic diagram of the specific wiring method of the single-ended flexible straight line with DC / DC converter in the lower layer shown in image 3 as shown, figure 1 The schematic diagram of the positive pole topology of the DC / DC converter shown in figure 2 as shown, figure 2 and image 3 The DC / DC converter and the passive MMC station are shown as locked, image 3 Each switch shown is open, the main steps are as follows:
[0018] Step 1: Close image 3 The DC bus bar of the original DC grid shown in the figure is connected to the DC isolating switc...
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The invention, which belongs to the field of flexible direct-current transmission, discloses a control method of merging of a passive modular multilevel converter (MMC) station into true bipolar direct-current grids with different voltage levels. The method comprises: with constant alternating-current voltage and frequency control, a port 1 of a DC / DC converter is unlocked is unlocked and direct-current voltage matching control is carried out; a port 2 is unlocked by constant direct-current voltage and reactive power controlling and a direct-current voltage control instruction is adjusted; theport 2 is connected with a passive MMC station, the passive MMC station is unlocked by using constant alternating-current voltage and frequency controlling, and direct-current voltage matching control is carried out; and then a passive system is connected and a power reference value is changed to adapt to investment of the passive system. According to the invention, an effective method is provided for merging of an MMC station into true bipolar direct-current grids with different voltage levels; the smoothness of the merging process of the passive MMC station is ensured; the impact on the original direct-current grid system is low; and the engineering practicalness is high.
Description
technical field [0001] The invention belongs to the technical field of flexible direct current transmission, and in particular relates to a control method for a passive MMC station to be integrated into direct current grids of different voltage levels. Background technique [0002] The flexible DC system based on power electronics technology has become the mainstream trend of DC grid development due to its advantages of independent power control and no commutation failure. Modular multilevel converter (MMC) is a new type of power transmission technology. The topology of the bridge arm of the converter station adopts sub-module cascading. The system-level active power control of the converter station includes DC voltage Control, active power control and frequency control, reactive power control includes reactive power control and AC voltage control, the control mode and specific control parameters need to be adjusted according to different working conditions. MMC has many ad...
Claims
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IPC IPC(8): H02J3/36H02J3/38
CPCH02J3/36H02J3/386Y02E10/76Y02E60/60
Inventor 贾秀芳韩乃峥许建中赵成勇
Owner NORTH CHINA ELECTRIC POWER UNIV (BAODING)