By Wenpeng Luan, Huishi Liang, Hui Yu
Due to the effectiveness and efficiency in promoting renewable energy utilization, distributed generation and microgrids have been gaining attention in China, a country experiencing rapid industrialization and urbanization development and under the threat of exhaustion of energy resources and environmental pollution. Great efforts aiming to boost distributed generation and microgrids development have been made in China during the past decade.
The priority of developing distributed generation and microgrids vary in different countries, due to different national conditions. In China, the biggest impetus to develop microgrids is the rapid-growing, diverse demands for energy and the difficulty in making maximum use of renewable energy in an efficient way. During the past five years, work has been done in microgrids research and construction by power companies, universities and research institutes. Dozens of microgrids demonstration projects have been established, of which the main objectives are to verify the newly-developed technologies of microgrids, to demonstrate microgrids’ capability in safe and sustainable operation, acceptable power quality supply, seamless transition from grid-connected to islanded mode and plug-and-play operation. These projects can be divided into three categories: urban microgrids, rural microgrids and the island microgrids.
Urban microgrids are intended to utilize distributed energy to provide a diverse, high quality and reliable power supply. The Tianjin Ecological City Microgrid Project, containing 100kW solar photovoltaic (PV) and 1.5-megawatt CCHP (combined cooling, heating & power), is one of such implementation.
Rural microgrids solve the problem of power supply to remote areas while enhancing the power quality in these areas. The East Inner Mongolia Rural Microgrid Project uses 110kW of PV, 50 kilowatts of wind power and a 50-kW lithium-ion ferrous phosphate battery.
To provide a relatively low cost power supply to an isolated island, in contrast with power supplied by a submarine cable or diesel delivery, the Zhejiang Nanji Island Microgrid Project features 1 MW wind power, 660 kW PV, a 1,700-kW diesel generator, a 4,000-kWh battery and 1MW×15s super-capacitor.
Standardization work also plays a noticeable role in microgrids development in China. As an emerging market with huge potential, standards are urgently needed to guide and support the microgrids technology development, addressing various microgrids applications in different supply and operation modes. Eight national standards and six industrial standards have been established to preliminarily constitute the domestic microgrids standard system with the coverage of:
- Microgrid integration requirements
- Connection requirements of micro-sources into microgrid
- Commissioning, and conformance & acceptance test
- Protection, monitoring and control
- Information and communication
- Operation and maintenance
- Microgrid black start
- Coordinated operation with main grid
- Participation in ancillary service
- Tech-economic evaluation
China has also taken an active part in the establishment of international standards. State Grid Corporation of China (SGCC), the largest power utility in the world, started the IEC ad hoc group on Microgrid (ahG53) in 2012 and later IEC Systems Evaluation Group on Non-conventional Distribution Networks/Microgrids (SEG6) in 2014to lead the setting of strategic planning of microgrids in IEC. Two IEEE standards, establishment of IEEE 2030.3 and IEEE 2030.9 are also led by SGCC.
Since microgrids are still in their adolescence in China, a mature business operation model, which has become the most important restricting factor of microgrids’ practical application, still needs to be developed. From a perspective of microgrids and distribution generation investment operation body, currently the operation mode of microgrids in China can fall into three classes: unified purchase and sale mode, self-generation-self-consumption mode, contract energy management mode. The unified purchase and sale mode, in which the output of distributed generations is totally sold to the utility, and the self-generation-self-consumption mode, in which the output of distributed generations is used by their owners in priority and the surplus is sent to the utility, are the two main modes of microgrids operation in China.
The next five years, which is in China's 13th Five Year National Plan, would show a more promising vision for distributed generation and microgrids development in China, due to the more rapid and massive growth of renewable energy exploration and the constant descending of distributed generation and storage cost. An important programmatic national development plan called Innovative action plan for energy technology revolution (2016-2030) was officially published by National Energy Administration in Jun 2016, marking a new stage of energy exploration and utilization in China. Distributed generation and microgrids, listed among the 15 preferential key technologies according to the plan, will be strongly supported by national policy and funding during the next 15 years.
The rise of a new concept, energy interconnection, which is considered a promising development direction of smart grid, also facilitates the development of microgrids. According to the vision of energy interconnection, microgrids is the elementary unit of energy internet. The future energy internet in China is like a sophisticated organism: ultra-high voltage power transmission system plays the role of aorta, whereas microgrids are indispensable blood capillaries ensuring efficient green energy utilization at the end of the grid. Internet and information technology could be adopted in the future renewable energy microgrids construction to realize multi-party participation in the electricity markets and intelligent matching for energy production and consumption, so that a new platform of more efficient and clean energy utilization could be formed.
Wenpeng Luan, an IEEE Senior Member, has extensive academic and industrial experience in power system analysis, power system planning, smart grid applications, and distributed generation integrations. Currently, he works with China Electric Power Research Institute as Chief Expert. His special fields of interest include smart sensing, data analytics, distribution system analysis, renewable energy resource integration, and utility advanced applications. He is a member of CIGRE and is a professional engineer registered at the Association of Professional Engineers and Geoscientists of British Columbia, Canada. Also, he is Convener for IEC SMB System Evaluation Group SEG6: Nontraditional Distribution Networks/Microgrids, Chair for IEEE WG P2030.9 Recommended Practice for the Planning and Design of the Microgrid, leading and making efforts for microgrid standardization. He received a B.Sc. degree from Tsinghua University, Beijing, China, in 1986, an M.Sc. degree from Tianjin University, Tianjin, China, in 1989, and a Ph.D. degree from Strathclyde University, Glasgow, UK, in 1999, all in electrical engineering.
Huishi Liang has been working at the China Electric Power Research Institute since 2009. Her special research field is distribution system planning, distributed generation and microgrid, in which she has extensive academic and industrial experience. She is a member of IEEE P2030.9. She received B.Sc. and M.Sc. degrees in biomedical engineering and in electrical engineeringfrom Tsinghua University, Beijing, China.
Hui Yu is a senior engineer at the China Electric Power Research Institute. Her research interests include the research and applications of microgrid and distributed generation integration, as well as the standardization. She is the member of IEC SEG6，IEEE P2030.3, and IEEE P2030.9. She received an MS in electrical engineering from North China Electric Power University, Beijing in 2003.
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