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In the past few decades, the scale of the power grid has continued to expand, and it has gradually developed into a super-large interconnected network system with centralized power generation and long-distance transmission. However, the continuous increase of long-distance power transmission makes the power grid increasingly dependent on external power, the stability and security of power grid operation tend to decline, and it is difficult to meet diversified power supply needs. On the other hand, there are more and more distributed power sources such as small photovoltaic energy storage. In order to coordinate the contradiction between large power grids and distributed power sources, and make full use of the value and benefits that distributed power sources bring to the power grid and users, a microgrid is proposed. the concept of. Micro-grid, also known as micro-grid, refers to a small power generation and distribution system composed of distributed power sources, energy storage devices, energy conversion devices, loads, monitoring and protection devices, etc. It can run independently and is an effective way to exert the performance of distributed power.

The proposal of microgrid aims to realize the flexible and efficient application of distributed power, and solve the problem of grid connection of a large number and various forms of distributed power. The development and extension of microgrid can fully promote the large-scale access of distributed power and renewable energy, and achieve highly reliable supply of various forms of energy to loads. Smart grid transition.

Due to the distributed and intermittent characteristics of wind power, photovoltaic power generation and other distributed power sources, it will adversely affect the power quality, control and protection, and operation reliability of the power grid. With the advancement of energy storage and operation control technologies, wind power, photovoltaic power The controllable energy storage system composed of power generation, energy storage and load can be smoothly connected to the large power grid. Microgrids have the following four basic characteristics:

1. Micro: The voltage level of the micro grid is generally below 10kV, and the system scale is generally below the megawatt level. It is connected to the end user and the electric energy is used locally.

2. Clean: The distributed power supply in the microgrid is mainly based on clean energy, or in the form of power generation with the goal of comprehensive utilization of energy. The power input is mainly photovoltaic, wind power, hydrogen energy, natural gas, biogas and other mature power generation technologies.

3. Autonomy: The internal power of the microgrid can achieve basic self-balancing, and the power exchange with the external power grid is small. The smart microgrid dispatching system belongs to the horizontal multi-energy complementary optimal dispatching technology, which can fully exploit and utilize the direct complementary alternatives of different energy sources. Energy exchange for cold, wind/electricity, direct/AC. Various types of energy are layered in the source-storage-load links to achieve orderly and cascade optimal scheduling to achieve optimal energy utilization efficiency.

4. Friendly: Microgrid supports the large power grid, can provide users with high-quality and reliable power, and can achieve smooth switching between grid-connected/off-grid modes. The microgrid can fully and effectively exert the potential of distributed clean energy, reduce the unfavorable factors such as small distributed power generation capacity, unstable power generation, and low reliability of independent power supply, and ensure the safe operation of the power grid. The distributed development of energy plays a key role.

Composing various distributed power sources to operate in the form of a micro-grid has many advantages. For example, it is beneficial to improve the acceptance capacity of the distribution network for distributed power sources; it can effectively improve the utilization rate of intermittent renewable energy, and it can be used according to the actual situation. Provide a variety of power quality services according to user needs; it can reduce the loss of the distribution network and optimize the operation mode of the distribution network; it can ensure the power supply of key loads in the state of grid failure, and improve the reliability of the power supply of the network; it can be used to solve remote areas, deserts or Electricity problems for users in the island. Microgrid has become a friendly carrier to solve the barrier-free access of distributed power.

Microgrids often integrate advanced information technology, control technology and power technology to provide reliable power supply and meet the various needs of users, while ensuring the maximization of energy, economic and environmental benefits. At the same time, the microgrid can play the role of grid support, energy efficiency improvement, energy conservation and consumption reduction, earthquake prevention and disaster mitigation, and rural electrification in conventional power grids. Determined by various advantages of microgrid, microgrid will be an indispensable part of smart grid construction, and the comprehensive development of microgrid technology is an objective requirement for realizing smart grid construction.

Vigorously developing micro-grid technology to make it cooperate with the current power system to form a more flexible power supply pattern can effectively strengthen the safety and reliability of my country's power system, and point out an effective way to improve the power supply capacity and power quality of the current power system. It also provides theoretical support for optimizing the current power system structure and building a strong and fully controllable smart grid.

In the future, the microgrid will develop into an integrated energy network, which will bundle resources such as electricity, gas, water, heat, and energy storage into overall resources, realize the coupling of the electricity network, the heating network and the cooling network, and uniformly solve the effective utilization of energy and energy storage. peaking problem. Compared with the hot network and the cold network, the electric network has the characteristics of easy interconnection, low loss, and fast transmission. It will become the core of the future comprehensive energy network and bring opportunities for the development of the power grid.

Author: Liu Jimao Guo Jun