The development of renewable energy can effectively alleviate the energy crisis and promote the low-carbon process of the power system, but also have an impact on the safe and stable operation of the power system [
4]. Due to the access to renewable energy, the energy structure of the power system is changed, and various departments of the power system usually adopt a variety of flexible resources and joint regulation measures, such as improving the rapid climbing start-stop capacity of thermal power units, energy storage, and multi-network interconnection, to cope with the fluctuations of renewable energy [
5]. More detailed on the energy supply side of the power system, the research of international scholars is more focused on improving the performance of thermal power units, rationally using virtual synchronous machines and other ways to strengthen the flexibility of the power system, including Lu Q. et al. [
6] taking 300 MW and 200 MW cogeneration unit as an example, by analyzing that the hot water storage device can increase the peak-load capacity of the unit from 16% to 37% and from 13% to 27%, respectively, the possibility of improving the flexibility of the power system by improving the capacity of peak regulation of the unit is verified. Jaber A. et al. [
7] used the swing equation of synchronous motor to express the virtual inertia characteristics in their research on VSG design and could control the swing equation parameters of VSG in real time to enhance the fast response of the virtual machine tracking steady frequency. This study improves the ability of the power system to resist disturbance. On the grid side of the power system, the measures to improve the flexibility of the power system are mainly to improve the transmission capacity of the power network, including the adoption of Uhv AC-DC(Ultra-high voltage Alternating Current/Direct Current) technology and flexible HVDC (High Voltage Direct Current) technology, such as Zhou J. et al. [
8] made a comparative study of UHV AC and DC technologies and proposed the applicability of each technology, which is conducive to the construction planning of improving the flexibility of power grid in various regions. On the load side, the way to improve the flexibility of the power system is to increase the flexibility load, including the application of virtual power plants, multi-energy complementarity, and “vehicle network coordination” of EVs (electric vehicles), etc. In this regard, Li J. et al. [
9] study the market mechanism of virtual power plants participating in peak and frequency regulation and sum up the experience of various countries. Xu H. et al. [
10] put forward a comprehensive electricity/heat demand response mechanism based on multi-energy complementing, which can tap the response potential of users and achieve a win-win situation for both the power grid and users. Sun J. et al. [
11] study the influence of EV charging and discharging behavior on power grid load variation rules under natural charging and orderly charging strategies, and proposed a demand-side management strategy for EVs, which can be better used for peak cutting and valley filling. In terms of energy storage, an energy storage device converts electrical energy into mechanical energy, chemical energy, and other forms to achieve energy storage as an important way to improve the power system’s flexibility. Energy storage can be placed in each link of electricity production and transmission, such as power supply, grid and load, it can realize the imbalance regulation of electricity on multiple time scales, and undertake many auxiliary tasks such as peak regulation, frequency modulation, consumption of renewable energy and seasonal electricity balance. Yuan B. et al. [
12] propose the application scenarios of energy storage in power supply, power grid, and user side, showing the role of energy storage in improving the flexibility of the power system. Sperstad I.B. et al. [
13] account for uncertainties due to distributed wind and solar photovoltaic power generation beyond the planning horizon in an AC (alternating current) MPOPF (multi-period optimal power flow) model for distribution systems with energy storage systems and prove the effectiveness of the strategy. Hosseini S.M. et al. [
14] develop a robust optimization framework for the day-ahead energy scheduling of a grid-connected residential user and confirm that scheduling the RES (renewable energy source) and ESS (energy storage system), power grids are becoming more secure and efficient in the electricity market. Moreover, Microgrids are often used to facilitate the use of distributed energy, and then improve the capacity of the power system to receive renewable energy. Raffaele C. et al. [
15] built a multi-carrier microgrid with an energy storage system, adopted an innovative RMPC algorithm and proposed a modeling framework for a microgrid energy management system, including heat and electricity, to solve the interference of uncertainty in the system model. Li Q. et al. [
16] put forward a kind of electric–hydrogen hybrid energy storage based on DP-MPC micro grid real-time energy management method, this method can allocate batteries, fuel cells, cell energy, and the network, the output of distributed power supply can be maximally realized while ensuring the power balance and cost optimization of the system.
It can be seen that there are many ways to improve the flexibility of the power system from the power source, power grid, load, and storage. Therefore, many scholars have studied the effects of various ways to improve the flexibility of the power system. Generally speaking, it includes the following two types. The first one is to construct the power system flexibility index to evaluate the operating characteristics of the system. Such as “IRRE” (insufficient ramping resource expectation) and “TUSFI-TEUSFI” (Technical Uncertainty Scenarios Flexibility Index-Technical Economic Uncertainty Scenarios Flexibility Index) proposed by Xiao D. et al. [
17] respectively represent the probability expectation that the power system cannot cope with the load change of the grid and the flexibility change of the system caused by the power flow capacity change. Also, the flexibility margin distribution and the probability of insufficient flexibility proposed by Lu Z. et al. [
18] establish the quantitative relationship between flexibility, the level of renewable energy consumption, and the risk of load loss. The second is dynamic simulation evaluation, that is, several scenarios are set to optimize scheduling and production simulation, and the flexibility of the system is often judged according to whether there is a load loss or a renewable energy power limit. Tang X. et al. [
19] establish a multi-time scale optimization scheduling strategy considering multi-energy flexibility, it can effectively improve the flexibility of the system without significantly reducing the economic efficiency. Hussam N. et al. [
20] establish the system flexibility demand and supply model under the time scale of 1 h, and analyzed the system flexibility supply and demand balance in the short-term operational planning.
However, most of the current research on the flexibility of power system focuses on the micro level, that is, studying a specific measure to improve the flexibility of the power system or optimizing the operation of the constructed micro power system. Few of them can expand the research scope to the regional level and carry out the simulation of the real power system. In this paper, the Flextool model is used to simulate the system flexibility changes when the power system in Northwest China changes the status of different flexible resources through hourly system scheduling and operation simulation at the regional level.