Electricity purchasing and selling transaction method considering clock synchronization error risk and power flow

Abstract

The invention discloses an electricity purchasing and selling transaction method considering clock synchronization error risk and power flow. The method comprises the following steps: reducing flow influence of a power plant by adopting a flow tracking method; the power grid formulates a transaction strategy to reduce power sales cost and guarantee supply and demand balance; and the I ESP completes power purchase and demand response. Compared with the traditional electricity transaction, more I ESPs can enter the electricity market through the electricity transaction platform. Under the background that the power consumption is continuously increased, the method can effectively adapt to the trend that the influence of the synchronization error and the power flow is more obvious.

Description

Technical Field

[0001] The present invention relates to the technical field of power trading and smart grid applications, and in particular to a power purchase and sale trading method that takes into account clock synchronization error risks and power flow. Background Art

[0002] Under the background of the new round of power system reform, the power market has entered a period of rapid development. It is necessary to establish a business management system for power trading organizations as soon as possible, standardize and guide the orderly operation of power trading organizations, and ensure that power trading organizations are fair, just, error-free and efficient. The power trading market mainly includes medium- and long-term markets, spot markets, ancillary service markets, and capacity markets. The power plant-grid-I ESP trading market is an important part of the power market system. It plays a fundamental supporting role in the openness, competition, and orderly operation of the power market, and is also the key to coordinating market transactions and system security. Both national policies and market regularity require the power trading market to emphasize the real-time and accuracy of transactions, that is, small error in transaction volume and accurate transaction volume. Accurate power market transactions can enable trading entities to obtain information more conveniently, not only guiding the power trading behavior of market members, but also guiding the production and use of electric energy, reducing the operating costs of trading entities, promoting competition, and thus improving the operating efficiency of the entire power market.

[0003] Power flow is a term used to describe the steady-state operation of a power system. It refers to the power generated by generators in the power system, the power flowing through transmission lines, transformers and other equipment components, and the distribution of voltages on each busbar. When the power system is in operation, under the excitation of the power supply potential, the current or power flows from the power supply through the various system components into the load and is distributed throughout the power grid, which is called power flow. The power system is a system formed by connecting many power stations, substations, distribution stations, and users by transmission and distribution lines. Part of the power transmission is lost when passing through the transmission and distribution lines, substations and distribution stations, and the vast majority of the remaining power is eventually consumed by the load. In this way, from the generation of electricity to the consumption of the load, which transmission and distribution line it flows through, and what is the voltage at each node, this calculation is called power flow calculation or simply power flow calculation. The calculation and analysis of power flow is crucial to the planning, operation and maintenance of the power system, and it helps the power system optimize its operation and improve efficiency. The clock synchronization error in the power market mainly involves the time synchronization problem in the power system, which is one of the key factors to ensure the normal operation of the power market and the accuracy of transactions. Therefore, it is crucial to reduce clock synchronization errors. However, due to the inevitable information gap between power plants, power grids and users, transaction errors caused by clock errors still often occur.

[0004] At present, there is little research on clock synchronization errors and power flow in the research of power trading process, because unlike general commodity trading, the power trading mechanism is usually formulated before the actual execution of the transaction. In reality, when power plants or power grids transmit electricity, the trading power often does not match the planned amount due to inaccurate calculation of power flow. Clock synchronization errors will increase the total cost of power plants, lead to unstable electricity prices, and cause the risk of power price fluctuations. Therefore, it is necessary to establish an effective power trading mechanism in the power trading market to deal with the impact of errors and power flow. The document "Fast Calculation Method of Dynamic Optimal Power Flow of Wind Power Grid-connected System with Multi-random Variable Chance Constraints" introduces chance constraints into the traditional AC-OPF model, studies the cumulative effect of approximate conversion errors, and gives the upper and lower bounds of the error of the deterministic conversion of the overall model, but does not consider how to apply power flow calculation to power plants, and its method lacks reality; the document "Power Flow Calculation Model of Hybrid Power Transformer Based on Multi-control Modes" considers factors such as variable power flow, power flow reverse transmission, and voltage over-limit in new power systems, but does not study the traceability of power flow. Summary of the invention

[0005] The present invention proposes a method for power purchase and sale transaction that takes into account the risk of clock synchronization error and power flow. The proposed power market transaction mechanism can well cope with the impact caused by synchronization clock error and power flow.

[0006] The steps of the power purchase and sale transaction method considering the risk of clock synchronization error and power flow are as follows:

[0007] Step 1: Use the power flow tracking method to reduce the impact of power flow in the power plant;

[0008] Step 2: The power grid formulates a trading strategy to reduce the cost of electricity sales and ensure the balance between supply and demand;

[0009] Step 3: I ESP completes electricity purchase and demand response.

[0010] The present invention also discloses a power purchase and sale transaction system that takes into account the risk of clock synchronization errors and power flow. The system includes a non-volatile storage medium, which is characterized in that: the non-volatile storage medium includes a stored program, wherein when the program is running, the device where the non-volatile storage medium is located is controlled to execute the above method.

[0011] The present invention also discloses an electronic device, which is characterized by comprising a processor and a memory; the memory stores computer-readable instructions, and the processor is used to execute the computer-readable instructions, wherein the computer-readable instructions execute the above method when executed.

[0012] Beneficial Effects

[0013] The present invention proposes a power purchase and sale transaction mechanism that takes into account the risk of clock synchronization error and power flow. Compared with traditional power transactions, more I ESPs can enter the power market through the power trading platform; and the entire power market transaction steps are completed based on the power flow tracking method, normally distributed clock synchronization error, and comprehensive demand response. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 The basic structure diagram of the power market transaction of the present invention;

[0015] Figure 2 This is a diagram of specific electricity market transaction steps. DETAILED DESCRIPTION

[0016] The present invention proposes a power purchase and sale transaction mechanism that takes into account the risk of clock synchronization errors and power flow. Compared with traditional power transactions, more I ESPs can enter the power market through the power trading platform. The entire power spot market transaction steps include: power plants reduce the impact of power flow, power grids formulate trading strategies, and I ESPs complete demand response. The entire power market transaction steps are completed based on power flow tracking, normally distributed clock synchronization errors, and comprehensive demand response. Step 1 plays a role of constraint and calculation, and can effectively track the source and destination of each current, thereby effectively calculating the power consumption and power purchase cost in the subsequent steps. In step 2, based on step 1, the power grid obtains the source and value of the power generation, and then formulates its own power purchase and sale cost function. In step 3, I ESP completes its own power purchase and demand response based on the response amount issued by the power grid due to the imbalance between supply and demand. According to the attached Figure 1 Specific electricity market transaction steps diagram.

[0017] The steps of the power purchase and sale transaction method considering the risk of clock synchronization error and power flow are as follows:

[0018] Step 1: Use the power flow tracking method to reduce the impact of power flow in the power plant.

[0019] The core idea of ​​power flow tracking is the principle of proportional sharing, that is, the power of the outgoing branch is provided by the incoming branches according to the power ratio, and the power of the incoming branch is also distributed by the outgoing branches according to the power ratio. The basic principle of power flow tracking is: the generator supplies local loads first, and the remaining power supplies non-local loads. Each node in the power grid can be regarded as a mixer of power flow, and the power flow of each output branch is composed of the power flow of each input branch. On the basis of power flow calculation, the lossy network is equivalent to a lossless network, and then calculated according to the principle of proportional sharing. The total injected power of any incoming node can be expressed as:

[0020]

[0021] Where: Pi is the total injected power of any incoming node i; P Gi Inject active power into the generator of node i; is the incoming line set of node i; P ij is the power flowing from node j to node i on branch ij;

[0022] In a lossless network, there is |P ij |=|P ji |, let C ij =|P ji | / P j , substituting into formula (1) we get:

[0023]

[0024] P ji The power flowing from node i to node j is expressed in matrix form as:

[0025] A u P=P G (3)

[0026] Where: P G is the generator power column vector; P is the total injected power column vector of n nodes; A u is an n×n order traceback matrix, whose elements are:

[0027]

[0028] if If exists, then formula (4) can be transformed into:

[0029]

[0030] For the outgoing load node P L ,exist:

[0031] P L =diag(B)P (6)

[0032] Where B i is a row vector of load factors, whose elements are:

[0033]

[0034] Where: α L is the load node set; P Li is the load of the outgoing node i. Therefore, the final outgoing load Li power consumption can be expressed as a linear combination of the output of each generator set:

[0035]

[0036] The essential principle of the power flow tracking method of the present invention is based on Kirchhoff's law and proportional sharing principle in the circuit. It constructs a tracking matrix, uses the line flow results and node flow results of the power grid flow calculation, and calculates the distribution coefficient of a single source or a single flow through matrix decomposition and forward back substitution technology, so that the flow direction of each current can be well traced. The present invention provides a reliable basis for calculating power consumption and electricity charges through the construction of the current model matrix and the construction of the load factor, thereby promoting the perfect conduct of power purchase and sale transactions. Tracking the flow of electricity at the same time can improve the reliability and safety of power dispatching. Flow tracking also provides transparency of power flow, which helps market participants understand power flow and cost allocation, and can effectively reduce various uncertain information brought by the flow, such as not knowing which power plant a certain current comes from, being unable to calculate electricity charges, and being unable to know the flow direction of this current, where it comes from and where it goes. These functions can be better and more accurately realized through the current flow tracking model of this article.

[0037] Step 2: The power grid develops a trading strategy to reduce electricity sales costs and ensure supply and demand balance.

[0038] For the power grid, energy trading strategy has become the core issue of its operation. In the model proposed by the present invention, the strategy formulated by the power grid includes the battery market (PM), renewable energy (photovoltaic (PV) system and wind turbine (WT)), energy storage system ESS, and the strategy formulated by the power grid IESP considers electric vehicles (EV) and demand response plan (DRP) in addition to the daily power purchase business to reduce the cost of power sales and ensure the balance of supply and demand. The demand response plan is defined as IESP guiding users to change their electricity demand in a specific period of time through electricity prices or incentives to achieve the balance of supply and demand of electric energy, which is manifested as the change of user electricity consumption in a unit period of time. The electricity price is the ladder electricity price in daily life. The final electricity price is determined by the amount of electricity consumption. The more the user uses, the higher the electricity price. The present invention adopts incentive demand response. When the supply and demand of the power grid is unbalanced, IESP gives users money to let users use more or less electricity. In this way, if users consume more or less electricity, the electricity can be balanced, and the power grid will not have the situation of supply and demand imbalance. As for the energy storage system and battery market, they can discharge when the power grid is insufficient and charge when the power grid is sufficient; however, photovoltaic and wind power are uncertain. They generate electricity when there is sun and wind, and do not generate electricity when there is no sun and wind, which will lead to unbalanced power in the grid. Therefore, the above-mentioned demand response, energy storage and other methods are used to achieve balance among all parties through final optimization. In the model of the present invention, the objective functions are established from the perspectives of the grid and IESP respectively.

[0039] (1) Battery Market Model

[0040] The electricity purchase cost in the battery market is given by formula (9):

[0041]

[0042] Where C pm is the cost of purchasing batteries, p,t Battery price, P t PM is the amount of electricity purchased from the battery market; t represents the current time period, and T represents the entire time period.

[0043] (2) Renewable energy model

[0044] Wind power generation: Wind turbines convert the kinetic energy of wind into electrical energy. The maximum output energy produced by WT at time t is a function of wind speed. The power limit that the grid can obtain from WT at time t is given by:

[0045]

[0046] P t wind ≤P t wind,max (11)

[0047] Where p r is the rated power of WT, represents wind speed, v ci represents the wind speed at WT, v r Indicates the rated wind speed of WT, v co Indicates the wind speed of WT, P t wind Indicates WT power generation, P t wind,max Indicates the maximum power generation. This paper considers the cost function of wind power and models it as formula (12), where k wind Indicates the operation and maintenance cost coefficient:

[0048]

[0049] Where C wind represents the operating cost of WT, k wind represents the cost coefficient of WT.

[0050] Photovoltaic system: Solar energy is converted into electrical energy through the photovoltaic system. The available power of the photovoltaic system in this paper can be expressed as formula (13). The power limit used by the retailer from PV at time t is formula (14):

[0051] P t pv,max =η p ×s p ×φ t ×(1-0.005×(T t-25)) (13)

[0052] P t pv ≤P t pv,max (14)

[0053] Where P t pv,max is the maximum photovoltaic output, η p represents the conversion efficiency, s p represents the photovoltaic array area, φ t represents the solar irradiance, T t Indicates the ambient temperature, P t pv k represents the photovoltaic power generation. This paper considers the cost function of the photovoltaic system and models it as formula (15). pv The cost factor representing operation and maintenance is:

[0054]

[0055] Where C pv is the photovoltaic operation cost, k pv is the photovoltaic cost coefficient.

[0056] (3) Energy storage system model

[0057] The initial energy of the ESS is given by equation (16). Furthermore, the charging power and discharging power are respectively limited to the predefined range of the facility. As can be seen from equation (19), charging and discharging cannot be performed simultaneously. In addition, the available energy of the ESS at time t depends on the energy at the previous moment and the charging and discharging conditions at that moment. Equation (21) represents the actual energy range of the ESS.

[0058]

[0059] In the formula is the initial energy of ESS, represents the energy storage at the start time, P t ch , P t disc represents the charging and discharging power of ESS, A binary variable representing the charge and discharge of ESS, Indicates the upper limit of the charge and discharge power of EES. represents the ESS charging and discharging efficiency, represents the energy storage at time t, represents the energy storage at the previous moment t, represents the upper and lower limits of ESS capacity, assuming that the ESS cost is a linear function of the absolute value of the charge and discharge power at time t:

[0060]

[0061] Where C ess is the operating cost of ESS, m ess 、n ess Represents the cost coefficient of ESS.

[0062] (4) Electric vehicle model

[0063] Equations (25)-(29) provide technical constraints related to EVs. The initial state of charge (SOC) of an EV is given by Equation (25). In addition, the charging power limit of an EV is given by Equation (26). The lower and upper limits of the SOC in an EV are given by Equation (28). Finally, Equation (29) is used to constrain the EV from leaving with an SOC that exceeds expectations:

[0064]

[0065] SOC leace,v ≥SOC exp,v (27)

[0066] In the formula represents the electric vehicle capacity at the beginning, Indicates the initial charging state of the electric vehicle, Indicates the upper and lower limits of electric vehicle charging power, Pc t,v Indicates the electric vehicle power at time t; Uc t,v is a binary variable for the charging method of electric vehicles, Indicates the charging efficiency of electric vehicles, SOC t,v represents the electric vehicle reserve at time t, SOC t-1,v represents the electric vehicle reserve at time t-1, Indicates the upper and lower limits of the state of charge of electric vehicles, SOC leace,v Indicates the power of the electric vehicle when it leaves, SOC exp,v It represents the expected value of the SOC of the electric vehicle at the time of departure, assuming that the charging cost of the electric vehicle is the product of the charging power and the unit price.

[0067]

[0068] R ev represents the benefit brought by charging, r ev Electric vehicle unit charging price, Pc t,c Indicates the charge level.

[0069] Therefore, the objective function model of the power grid is:

[0070] Q dw =R re +R ev-C pm -C wind -C pv -C ess (29)

[0071] Where Q dw is the total benefit of the power grid. The power balance constraint is as follows:

[0072] P L +P t PM +P t wind +P t PV +P t ch +P t disc =P t IESP +Pc t,c (30)

[0073] Where P t IESP Indicates the amount of electricity sold to IESP.

[0074] Step 3: IESP completes power purchase and demand response

[0075] The demand response strategy of IESP is considered to meet the energy demand of IESP and ensure the balance between supply and demand. At the same time, in order to prevent clock synchronization errors, the risk cost caused by the errors is taken into account in the model to make its strategy more accurate and in line with reality.

[0076] (1) Demand response model

[0077] When there is an imbalance between supply and demand in the power grid, the power grid will issue subsidies to IESP to let it find ways to balance the electricity. IESP's method is to issue incentives to users, which is money, to encourage users to use less electricity during peak hours and more during off-peak hours. The incentives issued by IESP to users are less than the subsidies given by the power grid, and IESP earns the difference. The cost of incentives issued by IESP to users is R DRP for:

[0078] R DRP =q t ×|DRP t | (31)

[0079] Where DRP t Represents the response quantity, q t Indicates the incentive price.

[0080] Although the power grid will issue subsidies to IESP to help it balance electricity, IESP also needs to purchase electricity from the power grid. The difference IESP earns is the difference between the subsidy from the power grid to IESP and the incentives IESP gives to users. Therefore, the power purchase cost of IESP is expressed as formula (32):

[0081]

[0082] Where SP t,re Represents the unit electricity purchase price. In order to prevent clock synchronization errors, the risk cost caused by the error is taken into account in the model. According to the actual situation, the error obeys the normal distribution. Assuming the clock synchronization error value is δ, it obeys the normal distribution δ~N(μ,σ). At the same time, according to Markowitz MVT theory, the risk cost model caused by the error is:

[0083]

[0084] Where R tick represents the risk cost caused by synchronization error, represents the MVT theoretical coefficient, which represents the relationship between δ and P t IESP +|DRP t |relationship.

[0085] Therefore, the total cost model of IESP is:

[0086] Q IESP =R re +R tick -R DRP (35)

[0087] Finally, the YALMIP / CPLEX12.8 commercial solver in MATLABR2018b is used to solve the power grid and IESP optimization models, and finally the optimal optimization solution is obtained.

[0088] Since the present invention includes the two quantities of IESP power purchase and demand response in formulas 29, 30 and 35, through iterative solution of the two formulas 29 and 35, the power grid and IESP finally reach their respective optimizations and complete power purchase and sale and demand response.

[0089] The present invention proposes a power purchase and sale transaction mechanism that considers the risk of clock synchronization error and power flow. The power flow tracking method is applied to power market transactions, which reduces the impact of losses, calculation errors, transaction volume errors and other problems in the power transmission process, and can accurately calculate the actual transaction volume; adding demand response to transactions can effectively improve the balance of power supply and demand, and enhance the enthusiasm of IESP to participate in power transactions, ensure the stable operation of the transaction mechanism, and effectively deal with the transaction default risk of IESP in the transaction process; the synchronization clock error is considered in the IESP cost model, which can effectively reduce the risk caused by the error and reduce the uncertainty of the clock synchronization error to the transaction. Therefore, the power market transaction mechanism of the present invention can be well applied to a variety of scenarios.

[0090] The above shows and describes the basic principles, main features and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The above embodiments and descriptions only describe the principles of the present invention. The present invention may be subject to various changes and improvements without departing from the spirit and scope of the present invention. These changes and improvements fall within the scope of the present invention. The scope of protection claimed by the present invention is defined by the attached claims and their equivalents.

Claims

1. A power purchase and sale transaction method considering the risk of clock synchronization error and power flow, which is characterized by: Step 1: Use the power flow tracking method to reduce the impact of power flow in the power plant; Step 2: The power grid formulates a trading strategy to reduce the cost of electricity sales and ensure the balance between supply and demand; Step 3: IESP completes electricity purchase and demand response.

2. The method for purchasing and selling electricity considering the risk of clock synchronization error and power flow according to claim 1 is characterized in that: The step 1 includes the following contents: the principle of the power flow tracking method is: the generator supplies the local load first, and the remaining power supplies the non-local load; each node in the power grid can be regarded as a power flow mixer, and the power flow of each output branch is composed of the power flow of each input branch; on the basis of power flow calculation, the lossy network is equivalent to a lossless network, and then calculated according to the proportional sharing principle, and the total injected power of any incoming node can be expressed as: Where: P i is the total injected power of any incoming node i; P Gi Inject active power into the generator of node i; is the incoming line set of node i; P ij is the power flowing from node j to node i on branch ij; In a lossless network, there is |P ij |=|P ji |, let C ij =|P ji | / P j , substituting into formula (1) we get: P ji The power flowing from node i to node j is expressed in matrix form as: A u P=P G (3) Where: P G is the generator power column vector; P is the total injected power column vector of n nodes; A u is an n×n order traceback matrix, whose elements are: if If exists, then formula (4) can be transformed into: For the outgoing load node P L ,exist: P.S L diag(B)P (6) Where B i is a row vector of load factors, whose elements are: Where: α L is the load node set; P Li is the load of the outgoing node i. Therefore, the final outgoing load Li power consumption can be expressed as a linear combination of the output of each generator set:

3. The method for purchasing and selling electricity considering the risk of clock synchronization error and power flow according to claim 1 is characterized in that: The step 2 includes the following contents: the strategy formulated by the power grid includes the battery market (PM), renewable energy, energy storage system ESS, electric vehicle (EV) and demand response plan (DRP) to reduce the cost of electricity sales and ensure the balance between supply and demand.

4. The method for purchasing and selling electricity considering the risk of clock synchronization error and power flow according to claim 1 is characterized in that: The step 3 includes the following contents: IESP adjusts its electricity consumption according to the time-of-use electricity price proposed by the grid; by considering DRP, IESP shifts its load from expensive hours to cheaper hours, thereby reducing its electricity purchase costs; IESP's electricity purchase cost R re It is expressed as formula (33): Where SP t,re Represents the unit electricity purchase price, P t IESP represents the amount of electricity purchased by IESP. In order to prevent clock synchronization errors, the risk cost caused by the errors is taken into account in the model. According to the actual situation, the clock synchronization error value is δ, which obeys the normal distribution δ~N(μ,σ). According to Markowitz MVT theory, the risk cost model caused by the error is: Where R tick represents the risk cost caused by synchronization error, Represents the Markowitz MVT theory coefficient, representing μ-δ 2 With P t IESP +|DRP t |; In the model, the purpose of IESP is to minimize the power purchase cost, risk cost, and negative utility of load transfer; γ represents the trade-off between reducing the power purchase cost and reducing the negative utility cost: Where γ represents a 0-1 parameter, DRP t Indicates the response amount, SP t represents the selling price, μ dis represents the disutility cost coefficient; During a complete cycle, the load increases and decreases equally: Therefore, the total cost model of IESP is: s is the incentive issued to IESP: Q IESP =R re +R tick -s·DRP t (35) Finally, the YALMIP / CPLEX12.8 commercial solver in MATLABR2018b was used to solve the two-layer optimization model, and finally the optimal optimization solution was obtained.

5. A power purchase and sale transaction system considering clock synchronization error risk and power flow, the system comprising a non-volatile storage medium, characterized by: The non-volatile storage medium includes a stored program, wherein the program controls the device where the non-volatile storage medium is located to execute the method according to any one of claims 1 to 4 when the program is executed.

6. An electronic device, characterized by: It comprises a processor and a memory; the memory stores computer-readable instructions, and the processor is used to execute the computer-readable instructions, wherein the computer-readable instructions execute the method described in any one of claims 1 to 4 when executed.

Images