Hunan urgently needs to break the deadlock in the power system and give full play to the value of energy storage according to local conditions

China Energy Storage Network: Small hydropower accounts for a large proportion in Hunan, and most of them do not have peak-shaving capabilities. At the same time, after the large-scale entry of electricity instead of coal, the load characteristics of Hunan are becoming increasingly complex, making it more urgent to build a new power system.

"As the receiving power grid in the central and eastern regions, the Hunan power grid has obvious characteristics of a 'double high' power system. After the introduction of ultra-high voltage AC and DC into Hunan, the power supply structure, grid structure and load characteristics will change significantly, bringing many challenges to the operation of the Hunan power grid. Therefore, Hunan must establish a new power system to break the deadlock in power grid operation, and energy storage is the key." A relevant person in charge of the Hunan power grid revealed at the Hunan Battery Expo and the first China International New Energy Storage Technology and Engineering Application Conference a few days ago.

Previously, Hunan Province has clearly focused on developing independent energy storage on the grid side, with the construction of large-scale centralized shared energy storage as the main line, coordinating project site selection, and centrally planning and building a number of grid-side energy storage power stations, striving to build more than 1.5 million kilowatts/3 million kilowatt-hours of electrochemical energy storage power stations by 2023.

Hunan power grid faces great peak load regulation pressure

Zhou Guandong, deputy director of the Energy Storage Special Office of State Grid Hunan Electric Power Company, believes that "During the 14th Five-Year Plan period, Hunan's new energy installed capacity is expected to be 2.4 times that of the 13th Five-Year Plan period, and Hunan will officially enter a power system dominated by new energy."

What challenges will the access of a high proportion of new energy bring to the Hunan power grid?

Zhou Guandong told reporters that at present, the absorption capacity of new energy is limited, and it has anti-peaking characteristics, and there is a serious mismatch between load and power supply. In addition, since small hydropower accounts for a large proportion in Hunan, and most of them do not have peak-shaving capabilities, the peak-shaving pressure faced by the Hunan power grid is very high.

Zhou Weihua, director of the Electric Power Research Institute of Hunan Electric Power Company, said that the traditional power grid is built on the basis of steady-state and quasi-steady-state mathematical models, and it is difficult to adapt to the new power system that requires access analysis and simulation of corresponding DC systems such as new energy, energy storage, and distribution networks, and faces many uncertainties in the planning of the power grid.

"At the same time, due to too many parameters and limited modeling, there are many problems that need to be solved urgently." Zhou Weihua told reporters, "First, the peak-to-valley difference of Hunan power grid ranks among the highest in the country all year round, with the highest load of 33 million kilowatts and the lowest load of 8 million kilowatts. The peak-to-valley difference is more than 60%, and the peak-to-peak pressure is huge; secondly, Hunan is facing a shortage of conventional power sources, and it is necessary to promote the joint transformation of thermal power infrastructure, prompt the planned thermal power units to be quickly put into operation, and play a basic peak-shaving role; finally, Hunan power grid must further improve the peak-shaving mechanism, and basically form a thermal power regulation capacity of more than 24 million kilowatts and a hydropower regulation capacity of more than 1 million kilowatts by 2035."

The increasing diversity of load structures brings challenges

"From the perspective of power supply structure, new energy has strong uncertainty and weak controllability. The future power grid will be a large AC/DC hybrid power grid, microgrid and load regulation coexisting power grid. From the perspective of characteristics, it will be real-time balance and integrated operation." Zhou Guandong believes that under the new power system based on new energy, the power structure, grid form and operating characteristics have brought new changes.

"Hunan Power Grid faces challenges and pressures in voltage, short circuit resistance, power balance, regulation capability and energy storage in order to achieve the coordinated development of 'source, grid, load and storage'," Zhou Guandong said. "As new energy becomes the main power source, there are many difficulties and challenges. Therefore, energy storage must take on the mission of ensuring the consumption of clean energy and providing safe and high-quality electricity services."

Zhou Weihua said that Hunan's current wind power is distributed mountain wind power, which has no advantages in scale, and the utilization hours of photovoltaic power are also low. "In addition, Hunan's load characteristics are also very complex. After the large-scale entry of electricity-to-coal load, Hunan's electricity accounted for 17% of terminal energy, which is still lower than the national average of 27%. As the power potential of end users is released, the demand for electricity will increase."

Zhou Weihua believes that after the diversification of Hunan's load structure in the future, the load will participate in two-way energy interaction on the power supply side, the scope of power supply utilization will be widely extended, and the load characteristics will become more complex. Therefore, energy storage must be the support of Hunan's source-grid-load-storage interaction and multi-energy complementary system, and is the key to a clean, low-carbon, safe, controllable, flexible, efficient, open and interactive power system.

Taking local conditions into consideration to maximize the value of energy storage

Hunan's emphasis on energy storage can be seen from the province's intensive release of energy storage policies. "In addition to the overall planning and layout, the country's only grid-side energy storage power station has also landed in Hunan, and we strive to build more than 1.5 million kilowatts/3 million kilowatt-hours of electrochemical energy storage power stations across the province by 2023," the Hunan power grid expert told reporters.

He said that Hunan Power Grid will also consider making full use of energy storage power stations to simulate the rotational inertia of traditional generators to further improve the stability of power grid operation.

With the rapid development of electrochemical energy storage, it is imperative to fully grasp the safe and stable performance of energy storage operation and accurately evaluate the support capacity of energy storage for the power grid.

Zhou Guandong said that Hunan Power Grid also has its own thoughts on the use of energy storage. "The reactive resources of wind turbines have not been well utilized yet. After wind power is equipped with energy storage, the voltage support of wind farms, how to support the friendly, safe and efficient grid connection of new energy, and how to coordinate control have also prompted the power grid to think and explore."

In response to this, Hunan Power Grid proposed the coordinated control concept of integrating the booster station, energy storage station and wind farm into one to achieve unified coordination of active and reactive resources of the three stations. Zhou Guandong believes that this can effectively prevent wind turbines from going offline, save primary frequency regulation investment, and achieve efficient full-power power generation.