Research on Regional Spot Market Clearing Model Considering Subregional Power Exchange Constraints

The goal of the power market is to optimize the allocation of power resources. The regional power spot market can expand the space of market optimization, which makes each sub-regional demand and resource sufficiently complemented, and it is an important part of the power spot market. The difficulty of clearing the regional spot market lies in the following two aspects. One is to take into account the different power market models of each sub-region, and the other is that the regional clearing results can ensure the safety of the power system in each sub-region. This article proposes a dual-layer model that contains the power exchange constraints of the sub-region. Its boundary conditions that are based on the unit commitment results of each sub-region clearing model are used for regional spot market clearing. It is compatible with the possible power spot market model of each sub-region, but also fully considers the clearance of the sub-region. At the same time, it ensures that the regional clearing results will not affect the safe operation of the system in each sub-region. The article verifies the validity of the design area through calculation, and analyzes the clearing effect of the regional market.


Introduction
1.1 The necessity of the construction of the regional power market In the context of China's carbon peaking and carbon neutrality goals to promote and accelerate the construction of the national unified power market system, the clear model of the regional power market has become a research hot spot.At present, there are problems such as provincial transaction barriers, low market synergy efficiency, difficulties in the demand for new energy consumption, and difficulties in the demand for new energy.Therefore, it is urgent to find key links affecting regional market transactions and new energy consumption.Improve market synergy efficiency and help the realization of carbon peaking and carbon neutrality goals.In January 2021, the 22nd meeting of the Central Committee hosted by General Secretary Xi Jinping, reviewed and approved the "Guiding Opinions on Accelerating the Construction of the National Unified Electric Power Market Department", pointing out the coordination and promoting the formation of a new type of power system that is suitable for China's national conditions and has stronger new energy consumption capabilities, and aiming to create a market system with multi-level collaboration, sound basic functions, and standardized organizational operation.However, China's provincial-based model of building the power market construction has enabled provinces and regions to differentiate market construction ideas and market operating models, and gradually formed the barriers to transactions between provinces, which affect the efficiency of the twolevel market coordinated clearing and become one of the bottlenecks of its development.Therefore, in order to successfully build the regional power market, it is necessary to solve the difficulty of designing

The summary of the available spot marker clearing model
The power spot market can guide power investment, load address selection, the construction of energy storage facilities, and grid new lines through the price signals of different pricing mechanisms, to promote the construction of the power system [1] .The importance of the electric spot market is selfevident.To this end, scientific researchers at home and abroad have made unremitting efforts for the research of the model of the power market.
In the research of the domestic model of the power market, Xiao et al. [2] analyzed the clearance coordination mechanism of typical spot electric energy markets and frequency modulation auxiliary service markets at home and abroad, and gave the mathematical model of independent energy storage power station to participate in the spot electric energy market and frequency adjustment auxiliary services in turn and the mathematical model of independent energy storage power station to participate in these two markets jointly clearance.Wu [3] proposed the improvement particle group algorithm based on chaotic inertial weights, to solve unit commitment problems by improving binary and improving the integer particle group algorithm and verify the speed and effectiveness of the algorithm through the calculation examples.Peng et al. [4] first analyzed the different ways of processing the DC mixed grid and the AC grid in the power spot market model.On this basis, design the regional power spot market clearing model and verify that it can improve social welfare through a calculation example.Zhang et al. [5] introduced the newly designed transaction variety of foreign spot markets -flexible block order, and introduced the definition and characteristics of sub flexible block orders.On this basis, a new type of electric spot market considering flexible block transactions is built and verify the effectiveness and correctness of the model through an example.Hu et al. [6] built a cross-regional inter-provincial transaction network model based on power flow and transaction flow, and proposed the calculation method of transmission costs for calculation and discounts of network losses.Considering the bids and offers and regional channel security constraints, the cross-regional inter-provincial transaction optimization clearing model is proposed.The effectiveness and applicability of this model are verified through examples.Lu et al. [7] established a two-stage transaction clearing model considering the carbon emission right market, proposed an adaptive weighted sum method to solve the first phase of Pareto cutting-edge problems, and verified by validity through calculation examples.
In the study of the power market model abroad, Dimitris et al. [8] proposed a mathematical equation covering all the power market products and security constraints of the current European Electric Power Exchange, and established the European day-ahead power market clearing model.Lei et al. [9] proposed a double-layer random model to determine the strategic offer of wind power participation in the power market, established the bid model of wind power producers in the day-ahead power market, and verified the effectiveness of the model through examples.
In the above-mentioned domestic and foreign research on the modeling clearing model of the power market, no study can solve the problem of clearing problems in the regional market that exists in multilevel markets.This article innovatively proposes the transmission power constraints between the subregions which ensure the security of the sub-region and the overall sharing benefits of the regional spot market.

Regional spot market clearing methods including two-level markets
The clearing methods designed in this article containing the regional spot market of the two-level market are as follows.First of all, security constrained unit commitment (SCUC) determines the turn on/off status of units in the sub-regions.Then, based on the results of the turn on/off status of units in the subregions, the day-ahead security constrained economic dispatch recently shall be carried out to make a day-ahead generation schedule for units in each province and calculated the day-ahead LMP.The special constraints designed in this article will be introduced in the description of the clearing model below.

Sub-regional Energy Market clearing models
The model description is as follows: The target function.The goal of maximizing social benefits is as follows: In the equation,  means the social benefits of each sub-region;  means the utility of electricity efficiency for users of each sub-region;  means the total cost of power generation based on the market offers of the each sub-region;  means the upper limit of the market offers; D , means the ultra-short-term prediction load of S node at T time;  , , and  , , respectively mean the declaration price and the output of the award of the bid for section B of the unit I at the time of T;  and  respectively mean the idling load and start-stop costs of the unit I;  , means the start-stop status of the unit I at the time of T, a value of 1 indicates the startup status, while a value of 0 indicates the shutdown status; η , means the startup state transition variable, if and only if  , = 1 and  , = 0 hold simultaneously,  , = 1; otherwise,  , = 0;  means the total number of time periods;  means the total number of units;  means the total number of nodes of the network;  means the total number of segments in the offer method;  means the power exchange plan between the sub-region and the external at a certain time.
The overall output of the units can be expressed as: 2) Constraint conditions.The constraints of the SCUC model are shown in Equations ( 3) -(11).① Power balance constraint at all times: ② System reserve capacity constraint: In the equation,  means the upper limit of the unit I;  means the system reserve capacity rate requirements.
③ Unit output upper and lower limit constraint: In the equation,  means the lower limit of the unit I. ④ Unit segmented output constraint: In the equation,  , means the lower limit for section B of the unit I. ⑤ Unit ramp constraint: In the equation,  and  mean respectively the ramp up and ramp down capacity for section B of the unit I.
⑥ Minimum start-off time constraint of units: In the equation, X , means the run time of unit I; T means the minimum start-off time limit for the unit I.
⑦ Least on-running time constraint of units: In the equation,  , means the shutdown time of unit I; T means the minimum start-on time limit for unit I.
⑧ Forward (reverse) line power flow constraints: In the equation,  means the transmission capacity limit of line L;  and  mean respectively the distribution factor of generator transfer between unit I and node S on line L.

Regional spot market clear model
The establishment of the SCED model of the regional electrical energy market is to fix the binary 0-1 variables - , and  , of the SCUC model in the sub-region to  , * and  , * , and no need to consider the Equations ( 9)-(10).Functions can change to minimize the power generation costs because under general circumstances, the utility  of various provinces remains unchanged.The model description is as follows.
The goal is to minimize the cost of power generation, which shows as follows: The regional market clearing system constraints and unit technical and economic characteristics constraints are consistent with each sub-region.Based on the above model, the innovative constrained conditions of this article are proposed as follows.
⑨ Import change quantity constraints: NESP-2023 Journal of Physics: Conference Series 2592 (2023) 012069 In the equation,  means the power exchange plan of sub-region i at a certain time t before the optimization of the regional market. , , means the power exchange plan of sub-region i at a certain time t after optimization of the regional market.

Simulation scene introduction
This article takes a simulation verification of the effectiveness of the design of the model of the regional power market to clear models and the effectiveness of the sub-regional exchange power constraint on regional optimization results.There are four sub-regions in this area, which use the actual market clearing results of the sub-region as the boundary.The power constraint value of the sub-regional exchanges of the sub-regional growth is compared with the regional clearing model verification and optimization results.The calculations conducted continuous clearing verification of the market throughout the year 2022.It counted the exchanges of the entire region when the steps were selected by the steps of different sub-regions when the power constraints of different sub-regions were selected.The three typical daily experiences of the typical scenes of spring (Tomb Sweeping Day), the typical scenes of autumn (China National Day) and the typical scene of winter (China Spring Festival) analyzed the effects of the power constraints of sub-regional exchange on the effectiveness of the regional market optimization.Affect analysis includes optimization of changes in new energy abandonment, changes in new energy abandonment, and changes in regional total power generation costs.
The specific simulation process is as figure 1 simulation process: According to the actual power exchange value settings of the sub-regions, the 24 times throughout the day power exchange value of the typical day in each sub-region is displayed as table 1~table3. The settings of the sub-regional power exchange constraints of regional spot market clearance.
Combined with the security constraints of the sub-region in the region of calculation examples, the constraint values shall be set by not exceeding 10%, 20%, and 30% settings of the original power exchange value according to the power exchange value in the sub-regions.In practice, suitable constraint values shall be set according to the security constraints of the target sub-region itself.

Results and analysis
 Continuously market clearing verification and results analysis throughout the year The article made a full-year simulation of the 2022 calculation region to verify the effectiveness of the clearing models.Examples prove that the clearing model designed in this article is valid, and now the regional market optimization benefits and retrograde display are based on the regional market design designed in this article.Shown as table 4.

Reduced by 532
Reduced by 63 Reduced by 621 better regional sharing benefits, but it will also cause more challenges to the sub-regional security.The less power exchange constraint value of the sub-regions means better sub-regional security, but it also means the damping of regional sharing benefits.
For regional markets including two-level or muti-level markets, when setting the clearing models, the introduction of the sub-regional power exchange constraint is a good means to ensure the safety of the sub-regions.When setting the power exchange constraint value of the sub-region power exchange, we should take into account the safety of the sub-regions and the regional sharing benefits, and to achieve a balance between the two.

Figure 1 .
Figure 1.Simulation process 3.2 Parameter preparation  Power grid topology structure of calculation examples Examples are simplified to form a topological structure based on the actual situation in East China.The examples include a total of five sub-regions of A, B, C, D, and E. The power connection line between the sub-regions is shown in the figure below.Examples do not consider the internal network topology constraints.The original power exchange value of the sub-regions.

Table 1 .
The power exchange value of the five regions in the Tomb Sweeping Day.

Table 2 .
The power exchange value of the five regions on National Day.

Table 4 .
The annual electricity exchange situation in each scenic region in 2025 (Unit: 100 million kilowatt-hours) Market clearing verification and results analysis in typical days For typical scenarios in spring, autumn, and winter, this article further conducted detailed simulations and analyzed the regional sharing benefits from three dimensions: changes in quantity of abandoned new energy, changes in rate of abandoned new energy, and changes in power generation costs.Shown as table 5~table 7.

Table 5 .
Sharing Benefits under Power Exchange Constraints in Different Sub-regions in Spring Scene