Prospects for the construction and development of new power systems

The second meeting of the Central Committee for Comprehensively Deepening Reform held on the afternoon of July 11 reviewed and approved the "Guiding Opinions on Deepening the Reform of the Electric Power System and Accelerating the Construction of a New Power System" and other documents.

The meeting pointed out that it is necessary to deepen the reform of the power system and accelerate the construction of a new power system that is clean and low-carbon, safe and abundant, economical and efficient, coordinated between supply and demand, and flexible and intelligent, so as to better promote the revolution in energy production and consumption and ensure national energy security. The meeting emphasized that it is necessary to scientifically and rationally design the construction path of a new power system, and on the basis of safe and reliable substitution of new energy, there are plans to gradually reduce the proportion of traditional energy. It is necessary to improve the system and mechanism adapted to the new power system, and promote the strengthening of power technology innovation, market mechanism innovation, and business model innovation. It is necessary to promote better integration of effective markets with promising governments, continuously improve the policy system, and do a good job in the supply of basic public services for electricity. This paper intends to discuss and prospect the construction and development of new power system.

Scientific and reasonable design of new power system construction path

In the process of energy clean and low-carbon transition, large-scale access of new energy such as wind power and photovoltaic power generation has brought great challenges to the operation and control of power system. The randomness, intermittence and volatility of new energy make the power balance in power system planning and operation probabilistic, which reduces the reliability of power supply to a certain extent, and the single "source with load" (I. e., adjusting the power generation according to the load change) mode of traditional power system will be transformed into a friendly interaction mode of "source-load interaction.

The stability characteristics of the power system after being disturbed are dominated by the traditional electromechanical mode to the electromechanical-electromagnetic multi-mode coupling interaction, and the system stability analysis and control problems have received extensive attention. The characteristics of low inertia and low short-circuit ratio on the power supply side are prominent, the security and stability support capacity is constantly weakened, the dynamic characteristics of the load side are becoming more and more complex, and the coupling between AC and DC and multi-DC on the grid side is closer.

In recent years, there have been several blackouts induced by power grid equipment failures abroad, which have aroused heated discussions. On September 28, 2016, a 50h statewide blackout occurred in Australia's South Australia power grid. About 1 million people were affected by the massive blackout in the UK on August 9, 2019. From February 15 to 19, 2021, a blackout occurred in Texas, USA, affecting a maximum of 4.5 million people. The Texas power grid entered a level 3 emergency state with a maximum load cut of 20 million kW and a real-time market price of more than 9000 USD/(MW · h).

It can be seen that in order to ensure the safe and reliable supply of electricity, traditional energy still needs to play a supporting and regulating power supply for a long time. Energy transition can not be achieved overnight, only a planned step by step to gradually reduce the proportion of traditional energy.

Improve the system and mechanism to adapt to the new power system

Under the goal of "double carbon", with the access of high proportion of intermittent renewable energy, it is necessary to improve the institutional mechanism to adapt to the new power system. In the traditional design of power wholesale market based on real-time electricity price theory, due to the characteristics of near zero marginal cost of photovoltaic and wind power, the market clearing price is reduced or even negative, and the traditional thermal power and nuclear power are squeezed out in the bidding transaction based on marginal cost. Therefore, thermal power and nuclear power are difficult to survive, resulting in imbalance of power supply structure and reducing the safety and flexibility of power system. At the same time, the randomness, intermittency, and volatility of photovoltaics and wind power bring major challenges to the operation and control of power systems, and the demand for system flexibility has increased dramatically, requiring sufficient economic incentives for flexible resources.

Under the goal of "double carbon", it is very important to design a new market mechanism that correctly reflects the value of different quality electric energy. In the new power system, as the foothold of the "source-load interaction" operation mode, new technologies and business models such as flexible load and virtual power plant have received extensive attention.

Flexible load includes adjustable load or transferable load with demand toughness, electric vehicle with two-way adjustment capability, energy storage, energy storage and distributed power supply, microgrid, etc., and its power behavior can respond flexibly to price signals, which is an important source of power system flexibility. In large cities where power supply cannot meet the growth of electricity demand, the peak-cutting and valley-filling effect of flexible loads can also play a key role in ensuring the safe operation of the power grid. With the advancement of power market reform, the conditions for flexible load and virtual power plant to participate in the power spot market and auxiliary service market are gradually met, and the business model is gradually formed.

Promote better integration of effective markets with promising governments.

The economy and security of the power system are two sides of the same body, and the economy is based on the security. Without the security, the economy of the power system is out of the question. For a long time, my country's power system has insisted on safety first, but not enough attention has been paid to economy. The operation of the power grid has retained a high safety margin, and there is a phenomenon of excessive investment for safety. The reform of the power market reflects the great importance of the CPC Central Committee and the State Council on the efficiency and economy of the power system, which has opened a new page for the development of China's power industry and brought unprecedented opportunities.

In the design, operation and supervision of the power market, the safety of the power system still needs to be considered as a prerequisite from time to time. In the non-commercial links in the power market, we should pay full attention to the role of planning methods (including government intervention and power grid planning management), so that the "visible hand" of the plan and the "invisible hand" of the market can be divided and coordinated, learn from each other's strengths, and give full play to the advantages of the public ownership of my country's power industry as the main body and the socialist market economic system.

Specifically, in situations where security is dominant, natural monopolies and public services are suitable for the introduction of planned management; in situations where economy is dominant (efficiency is preferred), market regulation is suitable; and some links are in between, depending on the circumstances. Effective markets and active governments should clarify their reasonable boundaries. Only by allowing the government to manage public services and ensure the security of the power grid can market transactions be more free and smooth, and truly play a decisive role in the allocation of resources.

Construction of a new power system with hierarchical cluster

The production, transmission, and consumption of electricity and energy often need to be carried out through various types of networks, such as power grids, heat grids, and gas grids. Because of the nature of these networks are the transfer of energy, but in different forms, so collectively referred to as the energy network. The energy network consists of subnetworks of different types of energy (electricity, heating, gas, etc.), which are connected by energy conversion devices (such as generators, pumps, air conditioners, water heaters, etc.).

Due to the rapid development of information and communication technology (information communication technology,ICT), on the basis of the energy network at the physical level, information networks based on traditional automation, Internet technology and emerging technologies such as "cloud mass transfer intelligence chain" can be established to regulate and control energy production, storage, transportation and utilization equipment. The actual operation of transactions and value transmission of electricity and energy commodities forms a value network. Value network is the basis of electricity and energy price system, and is restricted by the physical law of energy network. Therefore, the new energy system and the new power system will present the form of "energy-information-value" three-layer network architecture, which is closely coupled and interrelated.

In the new power system, renewable clean energy such as wind and light will exist everywhere, which means that the power supply will be spread throughout the entire power system, and the structure of the power system will undergo major changes. Academician Yu Yixin of Tianjin University and others proposed a hierarchical cluster grid architecture, that is, "the system is broken down into clusters (clusters) hierarchy and global coordination" and "each cluster (cluster) maintains its own net power balance and local self-optimization". For the sake of clarity, this paper refers to the power system with this structural feature as a "new power system with hierarchical clusters", and further discusses its operation and control problems.

The new power system of hierarchical cluster also presents a "energy-information-value" three-layer network architecture and is closely connected with other energy systems. The planning and operation problems of the new power system with hierarchical cluster can be divided into three levels: physical mechanism ("energy network" level), operation control ("information network" level) and market transaction ("value network" level). It is a typical multi-disciplinary cross-cutting problem that needs to be solved through multi-disciplinary and multi-industry joint research.

In the traditional power system, large-capacity generator sets are often built in areas rich in primary energy resources and transmitted to the load center through ultra/UHV long-distance transmission technology. The transformation process from the traditional power grid to the future new power system, according to the national "double carbon" goal and the requirements of ensuring energy security, the gradual withdrawal of traditional energy must be based on the safe and reliable substitution of new energy. With the gradual increase in the penetration rate of low-carbon and carbon-free energy and load, the transformation of the power system will be a process of establishing first and then breaking.

In the process of power system transformation, power enterprises and other market players will gradually improve the utilization rate of distributed power supply in the power system, especially in the user side and distribution network, and develop distributed smart grid. This means that the form and function of the distribution network will undergo major changes, especially distributed power, electric vehicles, energy storage, flexible loads, etc. will be connected in large numbers.

Taking photovoltaic power generation as an example, the total installed capacity of photovoltaic in China is increasing rapidly year by year. Since 2016, the new and cumulative installed capacity is the first in the world. In order to achieve stable energy supply in the vast desert, desert, industrial and mining wasteland, rural areas of the development of photovoltaic ecology, agricultural and light complementarity, should improve its flexibility and convenience, greatly reduce the impact on the existing power generation and transmission and distribution equipment planning and operation.