1. Introduction
In recent years, China’s development of variable and renewable energy has been rapid. By 2019, China’s cumulative installed capacity of wind power and photovoltaics reached 210 million kilowatts and 204 million kilowatts, respectively. Non-fossil energy accounted for 15.3% of energy consumption. Despite the rapid expansion of renewable energy generation, the power system is unable to effectively accommodate the newly added green energy, leading to significant curtailment of wind and solar power in some regions.
The main reasons for these issues lie in the other two important components of the power system: the grid and electricity demand, which have failed to keep pace with the rapid expansion of generation capacity. Regarding the transmission network, on the one hand, due to the physical characteristics of electricity being generated and consumed simultaneously, the grid cannot effectively store surplus green electricity. On the other hand, the regions with abundant green energy resources may not spatially align with areas of high electricity demand. Without a robust cross-regional transmission network, excess green electricity cannot be efficiently delivered to the areas that need it. In terms of electricity demand, both the demand and variable renewable energy exhibit strong fluctuations and randomness. The peak generation of green electricity often coincides with periods of low demand, making it difficult to integrate and consume green energy effectively.
In summary, simply increasing the scale of green electricity generation is not enough to significantly increase the proportion of green electricity in the power system. It requires the coordinated development of the transmission network and electricity demand side. Additionally, the support of the power industry and power market systems is necessary to ensure the development of these three subsystems. In 2018, the National Development and Reform Commission and the National Energy Administration of China jointly issued guidance [
1] emphasizing the improvement of the power system’s regulation capacity and operational efficiency. The focus is on enhancing system flexibility and adaptability from the demand side, power source side, and grid side, addressing the challenges of renewable energy integration and promoting green development. This demonstrates China’s determination to develop a power system capable of accommodating more green energy.
To solve problems, it is essential to first identify them. To enhance the regulation capacity of a power system, it is necessary to clarify the elements involved and their relative impacts. Moreover, it is important to identify the regions where the power system requires particular attention and determine possible directions for development. Only with a clear direction can the power system be effectively developed and improved. Following this logical framework, this paper primarily aims to answer the following questions: 1. What is the essence of power system regulation capacity, and how should the evaluation system for power system regulation capacity be constructed? 2. What are the important factors influencing power system regulation capacity, and which ones have development potential and operability? 3. What is the level of power system regulation capacity in different regions of China, and how can they effectively enhance their power system regulation capacity from various aspects?
The existing research has mainly focused on evaluation systems that are similar to the concept of power system regulation capability. (1) Power system reliability: The safe operation of the power system forms the foundation for studying the power system regulation capability in this research. Early studies on the comprehensive evaluation of power systems primarily focused on power system reliability [
2,
3,
4,
5]. These evaluations considered various factors, including independent faults, common cause failures, correlated failures, weather effects, load curve models, uncertainty and correlation of bus loads, multi-area applications, fault sensitivity and repair rates, incoherence, and safety limits. (2) Power system flexibility: Building upon reliability, some studies have examined the evaluation of power system flexibility. Flexibility refers to the ability of the power system to handle changes and uncertainties in generation and demand, forming the basis for integrating variable renewable energy sources. Existing research has considered multi-objective and uncertainty factors [
6], demand-side impacts [
7], large-scale energy storage [
8], investment and operating costs of power plants [
9], among other factors. (3) Comprehensive evaluation system of power system: The power system regulation capability studied in this research is a comprehensive evaluation system of a power system. In addition to reliability and flexibility, it also encompasses economic and social factors that support power development. Existing research on comprehensive evaluation systems of power systems varies based on different research objectives, resulting in different evaluation frameworks. For example, Pu Tianjiao [
10] considered factors such as power balance adequacy, optimized resource allocation, energy conservation and emission reduction goals, to construct a power balance evaluation indicator system. Zhou Yifan [
11] depicted the regional power development level based on five aspects: economic-energy coordination, power generation level, power consumption level, power supply level, and power development potential. Shen Min [
10] evaluated the power industry environment of a country by considering the current state of power development, the sustainability of the power industry, and power development potential. Hao Yongkang [
10] established a comprehensive performance evaluation system for distribution network asset lifecycle management. Zhao Defu [
12] evaluated the power development level of 11 countries from 17 aspects. Cui Jinrui [
13] established a hierarchical evaluation system for power markets. Wang [
14] summarized the theories and methods applicable to national economic evaluation of UHV power grid. Han [
15] established an overall concept for the estimation of environmental impacts from PCPP under nominal and partial loads with combined thermodynamic analysis and life cycle assessment (LCA) methodology. He [
16] constructed a comprehensive evaluation index system for the level of clean energy development by considering policies and regulations, energy supply, environmental impact, energy consumption, technology, economy and so on. Held [
17] presented a Qualitative Comparative Analysis (QCA) of e-mobility policies in 15 European cities in order to identify policy configurations on the national and local, urban level. Ioannidis [
18] estimated energy supply diversity and concentration for 44 islands in order to provide an island specific benchmark approach for energy supply security. Kucukvar [
19] investigated material footprints of Turkey’s and UK’s national energy development plans by applying a global, multiregional input–output (GMRIO) model. Li [
20] build the evaluation indicator system of the energy saving and emission reduction effects for electricity retailers and gained the combination weights by means of analytic hierarchy process and entropy weight method. Li [
21] constructed a regional electrical energy substitution potential evaluation index system, based on comprehensive consideration of the influencing factors and regional differences in the potential of electrical energy substitution. Lin [
22] proposed a risk identification and analysis model of NEPS based on the D numbers theory and decision making trial and evaluation laboratory (DEMATEL) method. Ji [
23] considered four parts, the technical performance, economic benefit, ecological impact, and social benefit, and designed a multi-angle evaluation index system of the wind-PV-ES and transmission system.
Extant research is characterized by the following problems. First, most studies incorporate some indicators related to power system regulation capacity into the evaluation system. As a part of the overall evaluation goal, few studies focus on the problems related to power system regulation capacity, such as power peak shaving, green power consumption, and power system flexibility. Second, the existing studies lack richness in terms of data and fail to provide a comprehensive characterization and evaluation of multiple indicators in various regions. Third, the existing research index weights are mostly determined by a subjective weighting method, and the use of an objective weighting method is lacking. Fourth, most of the existing studies involve evaluations and comparisons between countries; however, few have been evaluated and analyzed within the context of Chinese provinces and regions.
Compared with previous studies, the advantages of this paper are as follows: First, we clarified the conceptual category of power system regulation capacity and constructed a hierarchical multi-index evaluation system by focusing on power system regulation flexibility carrying out a comprehensive assessment from the supply side, grid side, load side, and support system side. Compared to the research on the reliability and flexibility of power systems, the definition in this study is more comprehensive, with reliability and flexibility being sub-concepts studied in this paper. In contrast to other research on the comprehensive evaluation of power systems, the focus of this study is specifically on the regulation capability of the power system. Second, 34 different types of datasets from Chinese provinces were selected to characterize and evaluate the regulation capacity of power systems in each region. Compared to previous studies, this paper has made efforts to obtain a larger amount of industry data whenever possible. Third, the objective weighted entropy method was used to construct the evaluation system, which avoids the subjective bias caused by human factors. Fourth, from the regional perspective, this paper comprehensively considered factors such as coordinated development, resource endowment constraints and advantageous conditions, and provides suggestions for a development strategy for each region. While previous studies often focused on specific regions or countries as their research subjects, this study considers the relationships and variations among multiple regions.
The paper makes contributions in both technological innovation and practical problem-solving. In terms of technological innovation, it proposes a methodology for constructing an index system, identifying key indicators, and recognizing potential areas for improvement. This methodology enhances the accuracy and relevance of the evaluation method. The paper first constructs an index system and employs the entropy weight method to determine objective weights. Then, by considering objective weights as one dimension and incorporating a subjective dimension of importance based on reality, it jointly selects key indicators. Finally, based on the key indicators, clustering methods are utilized to identify potential areas for improvement. This methodology combines the objectivity of the entropy weight method with real-world information, resulting in a more accurate evaluation method. In addressing practical problems, the paper focuses on evaluating the regulation capability of a regional power system. It analyzes the concept and connotation of the power system regulation capability and constructs a three-level evaluation index system based on this analysis. By employing the entropy weight method, the paper identifies key indicators that affect the regulation capability of power systems. Additionally, it utilizes clustering methods to analyze potential key areas for improving and enhancing the regulation capability of power systems in different regions of China. The findings of this paper provide valuable guidance for the development of regulation capability in China’s power systems.
2. Purpose and Direction of Power System Regulation in China
Based on the theoretical framework of power system composition and the practical needs of developing the power system in China [
1], this paper provides the following definition for power system regulation capability:
Power system regulation capability refers to the ability of a power system to adjust the balance quickly and effectively between power generation and electricity consumption in the face of the variability and uncertainty of renewable energy and electricity load. It encompasses coordinated measures from the power generation side, power grid side, load side, and supporting systems, aiming to accommodate a greater amount of renewable energy, ensure electricity demand satisfaction, and maintain the safe and stable operation of the system.
According to this definition, this paper elaborates on the connotations of power system regulation capability from the perspectives of supply side, grid side, load side, and support system side.
Supply side: The development of power generation-side regulation capability needs to consider existing thermal power units, newly added flexible generation units, and the overall power generation scale. Improving the flexibility of existing thermal power units and enhancing their regulation capability can enable them to better cope with the variability of renewable energy. Optimizing the power generation mix and increasing the proportion of flexible power sources can provide more dispatchable electricity resources. Additionally, increasing the overall capacity can ensure that the system has sufficient generation capacity to balance supply and demand.
Grid side: To enhance the grid-side regulation capability, several aspects need to be considered, including coordinated development between power sources and the grid, interregional transmission capacity, and grid infrastructure. By strengthening the coordinated development between power sources and the grid, ensuring synchronized planning, implementation, and commissioning, it is possible to avoid investment and resource waste. Enhancing grid infrastructure, improving transmission stability, and focusing on the construction of power grids in key areas for renewable energy and ultra-high voltage transmission, as well as establishing interprovincial and interregional transmission corridors, can contribute to enhancing the grid’s regulation capability. Simultaneously, undertaking distribution network construction and renovation, promoting the development of smart grids, can further improve the grid’s flexibility and controllability. Developing shared peak-shaving and reserve resources within regional grids and expanding the space for renewable energy generation are also important measures to enhance the grid’s regulation capability.
Load side: To enhance the load-side regulation capability, two main aspects need to be considered: flexible loads and load-side energy storage. Developing various types of flexible loads and advancing reforms on the demand side of electricity sales can enable rapid and flexible demand response, making the load more controllable. Improving the intelligence level of electric vehicle (EV) charging infrastructure and exploring the utilization of EV energy storage can not only promote the development of EVs but also provide potential for energy storage and flexible regulation. By increasing the deployment of flexible loads, such as demand response programs and smart appliances, and implementing reforms that allow consumers to actively participate in load management, the load-side regulation capability can be enhanced. Additionally, leveraging the role of EVs as mobile energy storage units can contribute to load balancing and grid stability.
Support system side: To achieve development in the aforementioned three areas, it is essential to concurrently develop the supporting systems, which mainly include the power equipment industry, compensation for ancillary services, and the power market. Improving the level of efficient and intelligent power equipment and promoting the development of key equipment technologies can enhance the performance and reliability of critical equipment for regulation capabilities. Enhancing the compensation mechanism for ancillary services and establishing a sharing mechanism for the participation of power generation companies and users in ancillary services can provide more flexible support to the power system’s regulation needs. Establishing a power market that combines medium- to long-term contracts and spot market trading can leverage an elastic pricing mechanism to unleash the flexibility of the system. This facilitates optimized resource allocation and the effective operation of the market.
5. Key Indicators, Regional Potential Areas, and Enhancement Strategies
5.1. Key Indicators Identification
Considering that the entropy weight method completely ignores the subjective judgements associated with the index weight, all indexes are divided into two categories according to development potential with the actual situation. The judgment principles mainly included: (1) whether development was significantly affected by resource endowment. Indexes such as Gas-Fired Power Generation Investment, Pumped Storage Capacity, and Coal Mine Density are difficult to develop in areas with poor resource endowment, even with high economic and human costs; and (2) whether the economic utility of further investment is low. With the vigorous development of China’s power infrastructure, some indexes have reached a high level in most provinces (e.g., Power Purchase Cost, Reliability of Power Supply), and income from further development of these indexes is relatively low. In addition, it is important to consider whether the index represents the new development direction of power system regulation capacity. Fields like electric vehicle energy storage and the power market are developing rapidly and show obvious differences among regions, which means that backward areas have substantial catch-up space. According to the above principles, the indexes were determined based on whether or not they had development potential. They were then separated by the median weight to obtain the four-quadrant diagram shown in
Figure 3.
The indexes located in the first quadrant, which have a high weight and great development potential, indicate key areas in which the regulation capacity of the power system can be improved. All provinces, particularly those that are rich in resources, should pay attention to these areas. The indexes located in the second quadrant have a low weight but high development potential, which indicates that these fields may represent foundations for further improving power system regulation capacity. Although the indexes in the fourth quadrant have a high weight, they are subject to resource endowment. Provinces with rich natural resources can focus on flexible peak shaving power supply, while provinces with poor resources should prioritize other areas. The indexes in the third quadrant have low weights and offer little development potential. Most of them reflect the level of power supply infrastructure and offer little potential in terms of improvement because of high costs and low marginal incomes; therefore, development is not a high priority.
5.2. Identification of Potential Areas for Regional Power System Regulation Capability
As mentioned above, from the connotation of the entropy weight method, the weight reflects the information variation of data, and indexes with high weights are generally discrete. Therefore, the scores of provinces and regions on each index can be classified by means of cluster analysis, which allows for the identification of potentially weak areas in each province, so as to propose targeted improvement strategies. Because the three indexes in the fourth quadrant (Gas-Fired Power Generation Investment, Pumped Storage Capacity, and Coal Mine Density) are subject to resource endowment and offer little development potential, the indexes in the first quadrant with higher weights and greater development potential were selected. A cluster analysis was carried out to assess 30 regions, and each index was classified into three categories. To identify areas with development potential, the indicators that fall into the lower range of the third category in each region’s score are summarized and consolidated.
Table 5 shows the index of each province that had the lowest score in the cluster analysis. It can be seen that first, the number of provinces in the third category comprising five indexes (Charging Points, Decommissioning Capacity Of Thermal Power Units, Remaining Utilization Hours Of Thermal Power, Electric Vehicle Quantity, and Power Distribution Capacity) exceeded 25. Less than five provinces rank at the top of these indexes and a significant gap can be observed between the remaining provinces and provinces with higher scores. This shows that there is substantial room for improvement countrywide with respect to the five areas of power system regulation capacity construction reflected by these market and grid indexes (i.e., electric vehicle energy storage, thermal power flexibility, regional power grid regulation, electric vehicle construction). Second, more than half of the provinces fall into the third category composed of seven indexes (i.e., Uhv Access, Power Ancillary Service Compensation Cost, Electrical Machinery and Equipment Innovation, Internet Development, Renewable Energy Power Consumption, Inter-provincial power output and Electrical Machinery and Equipment Scale). This shows that some development has been undertaken in these fields, but the development potential of about half of the provinces has yet to be tapped. Less than half of the provinces fall into the third category which is composed of three indexes, including Power Distribution Capacity, Capacity-Load Ratio, and Power Market Scale. This shows that many provinces have made some progress in these fields, but there is still room for development in some provinces, which could be addressed by investing resources to compensate for shortcomings and narrow the gap relative to other provinces.
5.3. Enhancement Strategies for Power System Regulation Capability
Based on the identification of potential areas for each region as mentioned above, this paper presents specific enhancement strategies for each indicator.
Power side: Some provinces are weak in thermal power flexibility. Provinces with low scores in Decommissioning Capacity of Thermal Power Units should accelerate efforts to eliminate backward production capacity and promote the flexible transformation of thermal power units. They should also close and retire some old 300,000 kW thermal power units and focus on launching 600,000 kW and above supercritical and ultra-supercritical units. On the other hand, other provinces are weak in power capacity. Compared with other regions, the installed capacity of the power supply in these provinces still lags; therefore, these provinces should focus on accelerating power construction to improve overall capacity. In terms of construction planning, an emphasis should be placed on the development of renewable energy, and the self-use coal power planning and the coal power capacity scales should be strictly controlled.
Grid side: There are two kinds of provinces that need to improve their grid side ability. The first kind of provinces are weak in grid construction. UHV Access had the highest weight and is key to improving both grid construction and the overall power system regulation capacity. In most of the relatively backward provinces, the construction of the UHV power grid has not been carried out. To plan smart grid use, the UHV grid is necessary as it acts as the backbone grid. It is also important to coordinate the development of power grids at all levels so as to promote the cross-regional consumption of surplus renewable power. The other three indexes of grid construction reflect the construction of the basic regional power grid (except the UHV grid). Provinces that lag behind should strengthen their efforts to plan and build the main grid of the regional transmission network and coordinate power grids of various voltage levels. The second kind of provinces are weak in grid regulation. In terms of peak shaving with renewable energy, these provinces show weak potential. On the basis of controlling the total installed capacity of thermal power, the flexible transformation of thermal power units and the construction of new peak shaving power stations should be promoted to improve the regulation capacity of the regional power grid.
Load side: Provinces that need to improve their load side ability are weak in electric vehicle energy storage. These provinces can lower the threshold of the electric vehicle charging service market, reform the electric vehicle charging price mechanism, implement policies such as green certificates and carbon credits to encourage orderly charging and discharging, carry out pilot operations of electric vehicle energy storage, and explore the interaction mechanism between electric vehicles and the power grid, so as to take full advantage of the energy storage potential of electric vehicles.
Support side: There are three kinds of provinces that need to improve their support side ability. The first kind of provinces are weak in power equipment industry development. These provinces should actively promote supply side structural reform, improve industrial technology competitiveness, promote the coordinated development of power generation, transmission, and distribution equipment, and transform the power equipment industry from follower to leader. The second kind of provinces are weak in power ancillary service compensation. These provinces should promote the establishment and improvement of the provincial frequency modulation ancillary service market and the inter-provincial standby ancillary service market and continuously optimize the transaction varieties of ancillary services, so as to consume more renewable energy. The third kind of provinces are weak in power market. In the development of power trading in these provinces, there are often some problems, such as a lack of marketization confidence, working mechanisms that fail to satisfy the requirements of power trading, a conflict between trading and renewable energy consumption, inter-provincial barriers, and contract transfer barriers. Therefore, these provinces should deepen their understanding of the resource allocation aspect of market-oriented transactions, perfect the medium-and-long-term power transaction price mechanism, strengthen the coupling of transaction information and promote the competition among trading institutions, to achieve a high proportion of medium-and-long-term power contracts.
6. Conclusions and Policy Implications
Improving the power system regulation capacity is critical to resolving the problem of renewable energy consumption. Accurate analysis and measurement of the power system regulation capacity and its regional differences and shortcomings are of great practical significance for promoting and improving power system regulation capacity. Based on defining the connotation of power system regulation capacity, this paper constructed an evaluation index system that took into account four factors; that is, the power supply, power grid, power load, and support system, which facilitated a quantitative investigation of China’s power system regulation capacity, and produced the following main conclusions: (1) the national average power system regulation capacity score was 0.18, which is at a low level. Less than one third of provinces scored higher than the average. (2) The contribution of each dimension to the power system regulation capacity is obviously different. In terms of the weight of each dimension, the results were as follows: the power side (0.315), the grid side (0.298), the load side (0.213), and the support side (0.172). (3) Obvious regional heterogeneity was observed in the development of power system regulation capacity, which is stronger in the east, weaker in central China, and the most backward in the west. This weakness may be explained by the lack of development in areas corresponding to the key indexes.
The main policy implications of the above conclusions are as follows: First, on the whole, policy makers should focus on improving load side and support side regulation capacity, while consolidating and improving the regulation capacity of the power side and grid side. Second, policy makers should improve power system regulation capacity according to local conditions. For the power side, backward thermal power production capacity should be gradually eliminated, and thermal power units should be flexibly transformed. Pumping storage peak shaving and gas peak shaving power stations should be planned and constructed to develop flexible regulation power reserves. For the grid side, the construction of smart grids with a UHV grid as the backbone grid should be promoted, along with the coordination of power grids at all levels. Shared peak shaving and standby resources in regional power grids should be developed to enhance the space for renewable energy power generation. For the load side, policy makers should promote the construction of electric vehicles, charging piles, and vehicle networking, explore electric vehicle energy storage, build the charging intelligent service platform through the “Internet plus charging infrastructure”, and promote a two-way interaction between energy and information in relation to electric vehicles and the smart grid. For the support side, policy makers should promote supply side structural reform, improve industrial technology, and establish an innovative application system in which enterprises, research institutions, and universities can participate. The compensation mechanism should be improved in the case of power auxiliary services and the direct cost and opportunity cost of flexible thermal power operations, pumped storage power and new energy storage power. The construction of the power market should be accelerated to increase the power market-oriented trading volume and establish a market-oriented system.