The flexible DC transmission technology based on MMC adopts modular design, which is very easy to expand and has low switching loss, and is more suitable for HVDC transmission occasions.
Modular multilevel converter? Modular multilevel converter (MMC) was first proposed and patented by Professor R. Marquardt in 200 1 year. It is composed of several sub-modules with the same structure cascaded.
The sub-module structure can be divided into three types: half H-bridge, full H-bridge and double clamping sub-module. Modular multilevel converter MMC shows an extremely important engineering application prospect.
Technical summary:
The development of electromagnetic transient model based on 1 and MMC is still the hottest topic in the field of MMC modeling, because it covers a wide time scale and the cost of off-line simulation software is low, and the obtained results can be extended to different simulation platforms and even real-time simulation systems.
2. The MMC universal acceleration model based on controlled source has the advantages of simple implementation, strong primary system visualization, and can simulate switching device-level interpolation and faults, and is recommended for detailed simulation of large double-ended MMC-HVDC systems.
3.MMC Thevenin equivalent global model has the characteristics of high simulation accuracy and high efficiency, which has achieved a breakthrough in the computational complexity of the model and the linear growth of simulation scale.
When the simulation step is small, the whole model based on backward Euler method is recommended. When the simulation step is large, the whole model based on trapezoidal method is recommended. This model is suitable for not only considering the internal and external dynamic characteristics of the converter, but also simulating large-scale application scenarios.
4. The improved MMC average model has the ability to accurately simulate complex AC /DC operating conditions, and is suitable for the analysis of AC /DC hybrid systems that only pay attention to the external dynamic characteristics of converters and contain large-scale MMC.
5.MMC electromechanical transient real-time simulation system will gradually become a research hotspot in the future MMC modeling field, because it is closer to large-scale system analysis and engineering practice, and can better meet diverse needs.