Company Name: Henan Xinchaoda Cable Co., Ltd.
Contact: Manager Guo
Address: Xibaishui Village, Xitao Town, Wuzhi County
Marketing Center: 1812, Building B, Building 3, Shenglong Plaza, Zhengdong New District, Zhengzhou
As fossil power becomes increasingly dry and environmental carrying capacity is weakened, China urgently needs to adjust the power strategy structure led by traditional fossil power and gradually increase the proportion of renewable power. The DC grid provides an ineffective solution for the processing of a high percentage of renewable power grid-connected and consumption results. Considering the distribution characteristics of renewable power such as wind power and photovoltaic in China, overhead line networking will still be the mainstream method of DC grids in the future, and the use of overhead line transmission methods will inevitably lead to the addition of fragmentary fault probability, so it is urgent to break overhead lines to use DC Remedy maintenance related technologies.
1. The results and significance of the dissertation
Due to the low damping characteristics of the DC power grid, its DC faults have the characteristics of rapid development and wide range of influence, and it is very easy to form "partial faults, and the entire network will be shut down." In order to solve the performance of overhead line DC grid maintenance and improve the reliability of DC grid operation, this paper combines the development status of DC grid main equipment and maintenance technology from the perspective of the fragmented configuration of DC grid, taking a typical four-terminal ring grid as an example. The technical characteristics of two typical overhead line DC grid maintenance schemes based on DC circuit breakers and fault self-cleaning converters are analyzed in comparison, and they provide originality for the follow-up maintenance strategy discussion and fragmented design of the DC grid.
The "half-bridge MMC converter + DC circuit breaker" solution is similar to the AC system. The fault removal and restart does not affect the continuous operation of the system. The voltage and power disturbances are extremely small. The "Self-cleaning converter + DC rapid switching" solution requires the converter station to be globally blocked, and the power transmission time is very long. Regarding the access to a high proportion of renewable power, it can cause large fluctuations in the frequency and voltage of weak winds, such as wind farms, resulting in wind farm outages and failure to complete fault crossing. Receiving end converter station under two schemes
2. The main points of the thesis
The dissertation analyzes and discusses the achievements in the following aspects: (1) the requirements for measurement, positioning, fault current suppression / cut-off, and maintenance coordination of overhead line DC grid relay maintenance; (2) equipment level, DC fragmentation, and AC grid The requirements for DC grid maintenance at each level; (3) The basic flow and functional characteristics of the DC grid maintenance program based on DC circuit breakers and fault self-cleaning converters.
Overhead line DC grid line maintenance solution based on "half-bridge MMC converter + DC circuit breaker" can complete rapid fault line removal and piecemeal restart, and can still achieve a minimum of about 23% of power transmission in the one-station blocking period. The impact on AC fragmentation is small, but it is necessary to deal with technical problems such as ultra-high-speed relay maintenance technology.