Microgrid includes the process of generating, storing, and using electricity. This section analyzes the key technologies and technological development level of microgrid based on the characteristics of microgrid power supply types and operation modes.
- Microgrid optimization planning technology
Microgrid optimization planning and design is a scientific microgrid energy storage composition and topology design under the premise of meeting the reliability requirements of differentiated users’ power supply. Its core includes optimization planning and design methods, comprehensive evaluation index system and decision support system. The optimal planning and design of the microgrid is of great significance to improve the efficiency of distributed energy utilization and ensure the safe and reliable operation of the microgrid. In the planning and design of the microgrid, the intermittent nature of the output of the distributed power supply and the diversity of the operation modes of the microgrid components increase the complexity of the microgrid power flow calculation, reliability assessment, and weak link identification. Complex constraints and optimization objectives (energy efficiency, renewable energy utilization, energy cost, etc.) need to be taken into account, and the computational complexity is large.
At present, although Europe and the United States and other countries have carried out researches such as microgrid operation and transaction mode analysis, investment and benefit evaluation, etc., the research on the comprehensive evaluation index system of microgrid is still in the primary research stage. In terms of microgrid planning and design software, there are already some software for research and use in the world, such as: HOMER, Hy-brid2 and RETScreen, etc. However, these planning and design software generally have component models that are too simple, cannot take into account load growth, and cannot reflect microgrids. Due to the defects of the actual network structure inside the power grid, these softwares have not been widely used in practical engineering. China’s research on microgrid evaluation, planning and design is still in its infancy, and the research in method and theory is still lacking in depth, and it is still blank in terms of quantitative evaluation system and planning and design tools. Although there are many microgrid demonstration projects in China, it has not been able to optimize the energy composition and topology of the microgrid from the perspective of energy optimization and reliability improvement, and there is also a lack of quantitative evaluation and analysis.
- Microgrid information collection and communication technology
Information collection and two-way communication platform are the basic support of microgrid. The information collection and communication technology of the microgrid reads the real-time operation data of the microgrid through monitoring equipment installed in distributed power sources, loads, transformers, etc., and transmits it to the control processing microgrid monitoring platform for statistics and analysis, and sends out corresponding control and dispatch instructions to monitor the operation of the microgrid. Advanced applications such as microgrid operation control, energy optimization, and response to distribution network scheduling all need to rely on information collection and two-way communication platforms. The information collection and communication of microgrid should meet the following requirements:
1) Open: The network architecture based on open technology provides a platform that can realize “plug and play”, securely connect various network devices, and allow intercommunication and collaboration between them;
2) Standard: The main components of communication and the way of interaction between them must be clearly specified;
3) Expansion: There should be sufficient bandwidth to support current and future microgrid functional requirements;
4) Real-time: The communication speed must meet the real-time requirements of microgrid operation control;
5) Integration: Integrate various real-time data to provide reliable and timely microgrid operation and electricity demand information for the microgrid analysis system.
At present, there is still a lack of unified standards for information collection and communication of microgrids in China. The microgrid control communication protocol extension conforming to 1EC61850 and the microgrid information model extension conforming to IEC 61970, and the fusion technology of 1EC61970 and 1EC61850 are still to be studied. In the microgrid demonstration projects that have been built in China, the design of most of the system information and communication architectures is still difficult to meet the real-time and open requirements of microgrids.