This article briefly introduces the two topological architecture ideas of the microgrid. The first is a topology system based on the plug-and-play modular concept of the microgrid, and the second is a topology system based on the power electronic transformer.
As a powerful supplement to the centralized large-scale power grid, the micro-grid is a good breakthrough for solving the impact of distributed energy access to the distribution network by realizing the local consumption of new energy. With the introduction of national policies, the development of microgrids has been greatly promoted, but how does the microgrid that has entered the fast lane break the existing dilemma and promote the rapid and good development of clean energy? .
The development of microgrid is now facing the following problems:
1. The support policy has not been clarified and the market mechanism has not been established;
2. Commercialization operation model needs to be explored, and commercialization demonstration is insufficient;
3. The micro-grid topology system is not clear and lacks the necessary literature standards;
4. Lack of overall planning for industrial development;
5. Difficulties in network distribution.
Based on the third point above, this article briefly introduces the two topologies of the microgrid and provides a reference for the development of the microgrid project.
First of all, the first microgrid topology architecture introduced is a modular topology architecture system based on the plug-and-play function of the microgrid. The topology architecture system is shown in Figure 1:
Figure 1 Modular microgrid topology based on Energy Internet
Modular micro-grid is divided into DC micro-grid subsystem and AC micro-grid subsystem. The entire micro-grid can achieve AC and DC inclusion. The micro-grid includes two variable-current parts: the first part of the grid-side rectification part is AC / DC rectification, which can achieve the entire micro-grid and distribution network; the second part of the micro-grid side rectification part is DC / AC rectification, which can realize DC micro The connection of the power grid subsystem and the AC micro-grid subsystem to achieve multi-energy interconnection. The DC subsystem of the microgrid is composed of a DC bus and a subordinate energy storage system of the bus, a DC load, and a DC distributed power supply. In order to achieve DC bus voltage stability and smooth distributed energy output, the energy storage system includes flywheel energy storage or supercapacitor energy storage or superconducting energy storage and battery energy storage, with fast response energy storage such as flywheel energy storage and large power density energy storage The battery provides power / energy support for the DC bus, and the battery pack is managed by a DC / DC chopper, providing backup energy support for fast-responsive battery packs such as flywheel energy storage, while taking advantage of the battery's energy density and reducing its charge and discharge Response frequency. The micro-grid AC subsystem is composed of an AC bus and the AC bus lower-level AC distributed power supply and AC load.
Based on the concept of energy internet, the micro gas turbine power generation system was introduced, and the natural gas clean fuel was used to realize the micro gas turbine power generation and supply to the micro-grid system. The waste heat of the turbine power generation was provided by the phase change heat storage device to provide hot water, and the absorption lithium bromide unit was used The demand for cooling can also provide high-quality steam through the waste heat boiler. From the perspective of the economic operation of the microgrid, hot spot cogeneration can effectively improve system efficiency. By reasonably combining the state of gas turbine power generation and energy storage batteries, coordinating the operation status of micropower and energy storage batteries can effectively reduce the initial energy storage of energy storage batteries cost.
Next, the second microgrid topology is introduced. This microgrid system is based on advanced power electronic transformers (SST) to achieve energy integration in the microgrid. The topology architecture system is shown in Figure 2.
Figure 2 Micro-grid topology based on power electronic transformer
SST, as the core module of the future microgrid, has always been a hot topic in the field of microgrid research. Its advanced control concept and electronic technology can cope with the effects of distributed energy access, such as the introduction of large numbers of power electronic devices. Harmonic control problems brought about, voltage imbalance on the grid side, voltage drop, disturbance on the load side. Therefore, the research of micro-grid topology system based on SST is very beneficial to the development of micro-grid.
For solid-state transformers, the general structure can be divided into three parts:
The first part is the input stage, which can achieve access and rectification with the grid side;
The second part is the isolation stage, which contains three modules: DC / AC rectification, isolation transformer, AC / DC rectification, which can achieve controllable voltage and harmonic isolation;
The third part is the inverter stage, which can realize DC to AC rectification, and build a bridge between the DC microgrid and the AC microgrid.
SST-based microgrids mainly use solid-state transformers as energy routers to connect energy grids, DC microgrids, and AC microgrids as relay points to achieve energy interconnection. The DC and AC microgrid units in Fig. 2 are the same as the above-mentioned first microgrid DC and AC units, so they are not discussed.
The development of the microgrid is constantly progressing, and the continuous innovation of technology and control theory has led to a variety of microgrid topologies. The two mentioned in this article are just a drop in the ocean. reference.
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