At the China Electric Equipment Innovation and Development Forum, Du Hong, General Manager of Beijing North Microgrid Technology Co., Ltd., provided an in-depth overview of microgrids, covering their positioning, boundaries, capacity, and cost analysis. Below is a summary of the key points discussed:
Microgrids are considered a distribution subsystem that integrates distributed generation. Essentially, they represent an intelligent, localized power network designed to act as a bridge between renewable energy sources and the main grid. By doing so, microgrids facilitate the integration of high proportions of distributed energy resources, especially photovoltaic systems, while mitigating the impact of intermittent renewable sources on the larger grid.
In essence, microgrids serve as a critical link between large-scale grids, power sources, and distributed generation. They allow for higher access rates of distributed power, reducing waste and maximizing the value of electricity generated. This ensures better benefits for end-users by optimizing energy usage and reliability.
The current domestic boundary definitions for microgrids include voltage levels up to 35kV, such as 35kV, 10kV, and 400V. The boundary between the main grid and the microgrid substation or switching station is defined at the point of export. Internal distribution systems, monitoring, protection, metering, communication, and energy management systems are all part of the microgrid infrastructure. Energy storage systems with regulation capabilities are also included, along with the ability to connect various distributed generation sources—though not necessarily including energy storage power stations. These systems ensure safe and reliable power supply within the microgrid, even during isolation from the main grid, and can manage adjustable loads effectively.
Regarding capacity, microgrids typically range from 30kW to 50MW, covering most distributed generation scenarios. Their internal energy storage systems are matched to their capacity, and the amount of distributed generation they can accommodate depends on both their size and storage configuration. The goal is to achieve a high penetration of distributed photovoltaics, ideally above 25%, with targets like 30%, 50%, 80%, or even 100% in some cases. Through advanced energy management systems, microgrids can control energy storage, distributed generation, and load to operate safely, reliably, and efficiently.
Economic analysis of microgrids remains a challenge due to their complexity and variability. Historically, some have mistakenly compared microgrids to conventional distributed generation, leading to the misconception that they add unnecessary costs. However, this overlooks the unique role microgrids play in enhancing grid stability and enabling greater renewable integration.
To address this, the proposed approach suggests comparing microgrid costs with those of the broader power grid, particularly the distribution system, rather than just the power supply itself. In China, where the electricity market is still developing, grid costs are estimated to be about 1 to 1.5 times that of traditional power generation. The grid here refers to the full-scale system, including transmission, transformation, and distribution, whereas power supply includes thermal, hydro, and other traditional sources.
Therefore, when evaluating microgrid costs, it’s more meaningful to compare them with the cost of new energy sources and determine a reasonable ratio. This approach will help better reflect the value and economic viability of microgrids in the evolving energy landscape.
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