An investigation into the current state of the operation of medium voltage distribution grids and the integration of distributed generation (DG) of renewable resources has led researchers to conclude that smart grids represent an R&D opportunity for China.
In their study published in Science China Technological Sciences, the researchers outline the contours of power distribution grids in terms of the practical distribution asset utilization, load compositions and characteristics, along with urban reliability and the integration of distributed generations of renewable resources.
According to the authors, a smart grid is an evolving goal as a key development strategy across China and constant research is needed to forecast fluctuating demand and to estimate changing costs and benefits.
But the smart grid can only be constructed based on the existing power system, they point out. Only through a very profound understanding of existing weaknesses of current power grids and by fully tapping their potential can the system realize maximum benefits with minimum costs. Yet research on this important point is limited at present.
The researchers noted that distribution assets involving the investment up to trillions of Chinese yuan accounted for more than half of the entire grid of China. Among 40 Chinese cities studied, the annual average utilization rates of major 10kV equipment were below 40 percent, far below the comparable levels in developed countries.
The customer average interruption duration index (CAIDI) of urban 10kV users in China was 7.01 hours in 2011; during the same period this index averaged 74 minutes for urban and rural users in the U.S. The index ranged from 40 to 70 minutes in developed European countries and was less than five minutes in Japan and Singapore.
Tianjin Universitys Professor Yu Yixin, co-author of the paper, said that major equipment deployed across distribution grids in most Chinese cities is running with low loads and that 10kV distribution grids are operated with a relatively large margin.
Integrating renewable energy generations into the distribution grids of load centers under an active distribution network mode is a better alternative to the centralized long-distance power transmission mode in the form of wind power and thermal power bundling for large-scale wind power in terms of minimizing the full social costs.
Prof. Yu Yixin said that the current distribution grids in China should improve the economic efficiency of construction and operation, especially the asset utilization rates. Under the current system, the reliability of power supply and the power quality cannot meet the requirement of the upcoming digital society.
Efforts to seize these R&D opportunities should be aimed at the models and topologies of network infrastructure, communication and interconnection methods and related technologies and the function of self-healing and operation optimization and voltage management.
Likewise, R&D should be targeted at utilizing demand response and load control and improving electrical efficiency, as well as related laws and regulations on the power market and smart grid investment.
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