Method and system for calculating frequency modulation capability of wind, fire and storage system considering elastic reserve

Abstract

The invention discloses a wind, fire and storage system frequency modulation capability calculation method and system considering elastic reserve, an interruptible load is used as the elastic reserve in a power grid for frequency modulation capability calculation, and the method comprises the following steps: obtaining scenes through Latin hypercube sampling, and obtaining a proper number of wind power generation scenes through a scene elimination technology; establishing a target function which comprehensively considers the minimum sum of the operation cost of the thermal power generating unit and the interruptible load cost; establishing a load balance constraint and a frequency modulation capacity constraint considering thermal power generation, wind power generation and energy storage, a minimum start-stop time constraint considering thermal power generation, an output upper and lower limit constraint, a climbing constraint, an energy storage system constraint and an interruptible load constraint; introducing parameter data, and solving the output of the thermal power generating unit and the energy storage unit by using a Gurobi solver in Matlab; and calculating the system frequency modulation capability according to the unit output result. The method can reasonably calculate the frequency modulation capability of the power grid under the output of thermal power generation, wind power generation and energy storage system units, thereby facilitating the reduction of the operation risk of the power grid and guaranteeing the stable operation of the system.

Description

Technical Field

[0001] The present invention relates to the field of dispatching, operation and analysis and calculation of power systems, and in particular to a method and system for calculating the frequency regulation capability of wind, fire and storage systems taking elastic reserve into account. Background Art

[0002] As the proportion of renewable energy in the power system continues to increase, the grid structure has become increasingly complex. Especially in terms of wind power, China has become the country with the largest installed wind power capacity in the world. However, due to the intermittent, uncertain and unpredictable nature of wind power output, large-scale grid connection has brought challenges to the stable operation of the power system. Therefore, how to ensure the safe and stable operation of the power grid has become an important task.

[0003] As the volatility and intermittency of renewable energy increase, the peak-to-valley difference of the power grid also increases accordingly, and the uncertainty of power grid regulation increases. This leads to the need for more frequency modulation capacity in the power grid to quickly respond to demand. If the frequency modulation capacity of the power grid is insufficient, it will affect the stability of the power grid, especially during peak load periods. Therefore, in order to ensure the stable and safe operation of the power grid, the frequency modulation capacity of the power system must be reasonably arranged.

[0004] At present, the frequency regulation capacity of the power grid is mainly provided by system generators, especially thermal power units. However, with the large-scale access of renewable energy and the rapid development of large-scale DC transmission, the form of the power grid has become more and more complex. The random uncertainty of renewable energy output and large power shortage accidents make this challenge more complicated.

[0005] In order to solve the above problems, a feasible method is to flexibly adjust the frequency regulation capacity of the system by interrupting the load. In order to cope with the frequency fluctuations in the power grid, it is necessary to reasonably arrange the frequency regulation resources according to the changes in load and renewable energy output within 24 hours. By calculating the frequency regulation capacity, it can ensure that the power grid responds quickly when frequency deviation occurs, thus ensuring the stability of the system. Summary of the invention

[0006] The technical problem to be solved by the present invention is how to calculate the frequency regulation capacity by taking the interruptible load as the elastic reserve in the power grid.

[0007] The present invention solves the above technical problems through the following technical means:

[0008] The calculation method of frequency regulation capacity of wind, fire and storage systems taking into account flexible reserve includes the following steps:

[0009] S1. Obtain the scene through Latin hypercube sampling, and obtain a suitable number of wind power generation scenes through scene elimination technology;

[0010] S2. Establishing the objective function of minimizing the sum of the operation cost of thermal power units and the cost of interruptible loads;

[0011] S3. Establish load balance constraints and frequency regulation capacity constraints for thermal power generation, wind power generation and energy storage, minimum start and stop time constraints for thermal power generation, upper and lower output limits, ramp constraints, energy storage system constraints and interruptible load constraints;

[0012] S4, input parameter data and use Gurobi solver in Matlab to solve the output of thermal power unit and energy storage unit;

[0013] S5. Calculate the system frequency regulation capability based on the unit output results.

[0014] Furthermore, the objective function in step 2 is:

[0015]

[0016] Where F is the total operating cost; T is the total number of time periods in the entire unit scheduling cycle; n is the number of units participating in the unit; F1(p i (t)) is the fuel cost at time t, p i (t) is the active power of unit i at time t; I i (t) is the on / off state of unit i at time t, where 1 represents the on state and 0 represents the off state; cu i (t) is the startup cost of unit i at time t; cd i (t) is the shutdown cost of unit i at time t, which is generally independent of the startup time of the unit. Here it is approximately 0; F IL is the interruptible load cost.

[0017] Furthermore, the fuel cost expression at time t is:

[0018]

[0019] Where a i , b i 、c i are the fuel cost characteristic curve parameters of unit i respectively.

[0020] Furthermore, the startup cost expression of unit i at time t is:

[0021]

[0022] Where hc i ,cc i are the hot and cold start-up costs of unit i, respectively; is the continuous shutdown time of unit i in period t; Ti cold is the cold start time of unit i; T i off is the maximum downtime of unit i.

[0023] Furthermore, the interruptible load cost expression is:

[0024]

[0025] Where C IL is the cost coefficient corresponding to the load reduction in period t; p IL (t) is the load reduction corresponding to period t.

[0026] Furthermore, the constraints in step 3 are:

[0027] Load balancing constraints:

[0028]

[0029]

[0030] In the formula is the active power output of thermal power unit i in time period t in scenario s; is the active power output of wind turbine i in time period t in scenario s; p w,i (t) is the active power of the wind farm in all scenarios Active power output in a scenario obtained using probability distribution; p d (t), p c (t) are the discharge power and charging power of the energy storage system respectively; D(t) is the load of the system in time period t;

[0031] Minimum start and stop time constraints for units:

[0032]

[0033] In the formula T is the time that unit i has been turned on and off continuously; i on (t), T i off (t) is the minimum startup and shutdown time of unit i;

[0034] Unit output upper and lower limit constraints:

[0035] I i (t)p imin <=p i (t)<=I i (t)p imax

[0036]

[0037] Where p imin 、p imax are the upper and lower limits of the output of unit i respectively;

[0038] Frequency regulation capacity constraints:

[0039]

[0040] Where R(t) represents the capacity requirement of frequency modulation capacity in time period t, which can generally be set to R(t) = 0.1D(t)

[0041] Hill climbing constraints:

[0042] -DR i <=p i (t)-p i (t-1)<=UR i ,I i (t)-I i (t-1)=0(t>=2)

[0043]

[0044] In the formula, m i It is the level at which the thermal power unit can be quickly adjusted in a short time, which can generally be set to m i =0.1p imax ;

[0045] Energy storage system inherent constraints:

[0046] Initial storage energy of the energy storage system:

[0047]

[0048] In the formula is the initial storage energy of the energy storage system; is the maximum storage energy of the energy storage system; w is the discharge coefficient of the energy storage system

[0049] The charging and discharging energy of the energy storage system in time period t:

[0050] C c (t) = ∫αp c (t)dt

[0051] C d (t) = ∫βp d (t)dt

[0052] Where α and β are the charging and discharging efficiency coefficients of the energy storage system respectively;

[0053] Energy storage of the energy storage system in time period t:

[0054]

[0055] Interruptible load constraints:

[0056] 0<=p IL (t)<=p IL,max (t)

[0057] Where p IL,max (t) is the maximum interruption amount of the interruptible load.

[0058] Furthermore, the upper and lower limits of energy storage of the energy storage system in time period t are:

[0059]

[0060] In the formula are the maximum and minimum values ​​of energy that can be stored in the energy storage system respectively;

[0061] Charge and discharge constraints:

[0062]

[0063] Where k is the discharge coefficient of the energy storage system, t c ,t d The period when charging and discharging of the energy storage system is completed;

[0064] Energy storage system maximum charge and discharge power limit constraints:

[0065]

[0066] In the formula The maximum power for charging (discharging) the energy storage system.

[0067] Furthermore, the system frequency modulation capability calculation process in step 5 is:

[0068]

[0069] Where f N is the grid frequency, σ1% is the regulation coefficient of the thermal power unit, and σ2% is the regulation coefficient of the energy storage unit.

[0070] The present invention also provides a frequency regulation capacity calculation system for wind, fire and storage systems taking into account flexible reserve, which is characterized by comprising:

[0071] Wind power generation scenario construction module: obtain scenarios through Latin hypercube sampling, and obtain a suitable number of wind power generation scenarios through scenario elimination technology;

[0072] Objective function construction module: establish an objective function that comprehensively considers the minimum sum of the operating cost of thermal power units and the cost of interruptible loads;

[0073] Yushu condition construction module: Establish load balance constraints and frequency regulation capacity constraints for thermal power generation, wind power generation and energy storage, minimum start and stop time constraints for thermal power generation, output upper and lower limit constraints, climbing constraints, energy storage system constraints and interruptible load constraints;

[0074] Solution module: Input parameter data and use Gurobi solver in Matlab to solve the output of thermal power units and energy storage units;

[0075] System frequency regulation capability calculation module: Calculates the system frequency regulation capability based on the unit output results.

[0076] Furthermore, the objective function is:

[0077]

[0078] Where F is the total operating cost; T is the total number of time periods in the entire unit scheduling cycle; n is the number of units participating in the unit; F1(p i (t)) is the fuel cost at time t, p i (t) is the active power of unit i at time t; I i (t) is the on / off state of unit i at time t, where 1 represents the on state and 0 represents the off state; cu i (t) is the startup cost of unit i at time t; cd i (t) is the shutdown cost of unit i at time t, which is generally independent of the startup time of the unit. Here it is approximately 0; F IL is the interruptible load cost.

[0079] The advantages of the present invention are:

[0080] 1. The present invention discloses a method for calculating the frequency regulation capacity of wind, fire and storage systems taking elastic reserve into account, which calculates the frequency regulation capacity by taking interruptible load as elastic reserve in the power grid, thereby improving the frequency regulation capacity of the power grid and improving the economy and reliability of the system.

[0081] 2. The present invention introduces a wind turbine generator set and an energy storage system into a traditional thermal power generator set system, thereby expanding the application field of the system.

[0082] 3. The present invention adds elastic reserve to the wind and thermal storage systems, improves the system's objective function, load balance constraints, frequency regulation capacity constraints and interruptible load constraints, and reasonably increases the grid's reserve capacity, which will help reduce grid operation risks, effectively alleviate conventional reserve pressure, and ensure stable system operation. BRIEF DESCRIPTION OF THE DRAWINGS

[0083] Figure 1 It is a flowchart of the method in the embodiment of the present invention. DETAILED DESCRIPTION

[0084] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described below in combination with the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0085] This embodiment discloses a method for calculating the frequency regulation capability of wind, thermal, and storage systems taking into account elastic reserve, and calculating the frequency regulation capability by taking the interruptible load as the elastic reserve in the power grid, including the following steps:

[0086] Step 1: Obtain wind power generation scenarios through Latin hypercube sampling, and obtain a suitable number of wind power generation scenarios through scenario elimination technology.

[0087] Step 2: Setting and collecting parameters related to thermal power units, wind power units, energy storage and variable loads: a. i , b i 、c i are the fuel cost characteristic curve parameters of thermal power unit i; T i on (t), T i off (t) is the minimum startup and shutdown time of thermal power unit i; p imin 、p imax are the upper and lower limits of the output of thermal power unit i respectively; are the maximum and minimum values ​​of energy that can be stored in the energy storage system respectively; w is the discharge coefficient of the energy storage system; β is the charging and discharging efficiency coefficient of the energy storage system; k is the discharge coefficient of the energy storage system; The maximum power of charging (discharging) the energy storage system; C IL is the cost coefficient corresponding to the load reduction in period t; p IL (t) is the load reduction corresponding to the period t; p IL,max (t) is the maximum interruption amount of the interruptible load.

[0088] Step 3: By setting the relevant parameters of the thermal power unit in step 1, determine the minimum sum of the operating cost of the thermal power unit and the interruptible load cost of the objective function

[0089]

[0090] Step 4: By setting the objective function in step 3, determine the load balance constraints and frequency regulation capacity constraints of thermal power generation, wind power generation and energy storage as in step 4 of the claim, the minimum start and stop time constraints of thermal power generation, the upper and lower limit constraints of output, the climbing constraints, the constraints of the energy storage system itself and the interruptible load constraints;

[0091] Step 4.1: Load Balancing Constraints:

[0092]

[0093] In formula (24) is the active power output of thermal power unit i in time period t in scenario s; is the active power output of wind turbine i in time period t in scenario s; p w,i (t) is the active power of the wind farm in all scenarios Active power output in a scenario obtained using probability distribution; p d (t), p c (t) are the discharge power and charging power of the energy storage system respectively; D(t) is the load of the system in time period t.

[0094] Step 4.2: Minimum start and stop time constraints for units:

[0095]

[0096] In formula (26) T is the time that unit i has been turned on and off continuously; i on (t), T i off (t) is the minimum startup and shutdown time of unit i.

[0097] Step 4.3: Upper and lower limits of unit output:

[0098] I i (t)p imin <=p i (t)<=I i (t)p imax (4)

[0099]

[0100] In formula (27), p imin 、p imax are the upper and lower limits of the output of unit i respectively.

[0101] Step 4.4: Frequency regulation capacity constraints:

[0102]

[0103] In formula (29), R(t) represents the capacity requirement of frequency modulation capacity in time period t, which can generally be set to R(t) = 0.1D(t)

[0104] Step 4.5: Hill Climbing Constraints:

[0105] -DR i <=p i (t)-p i (t-1)<=UR i ,I i (t)-I i (t-1)=0(t>=2) (8)

[0106]

[0107] In formula (32), m i It is the level at which the thermal power unit can be quickly adjusted in a short time, which can generally be set to m i =0.1p imax .

[0108] Step 4.6: Energy storage system constraints:

[0109] Initial storage energy of the energy storage system:

[0110]

[0111] In formula (33) is the initial storage energy of the energy storage system; is the maximum storage energy of the energy storage system; w is the discharge coefficient of the energy storage system.

[0112] The charging and discharging energy of the energy storage system in time period t:

[0113] C c (t) = ∫αp c (t)dt (11)

[0114] C d (t) = ∫βp d (t)dt (12)

[0115] In formulas (34) and (35), α and β are the charging and discharging efficiency coefficients of the energy storage system, respectively.

[0116] Energy storage of the energy storage system in time period t:

[0117]

[0118] Step 4.6.1: Energy storage upper and lower limit constraints:

[0119]

[0120] In formula (37) are the maximum and minimum values ​​of energy that the energy storage system can store, respectively.

[0121] Step 4.6.2: Charge and discharge constraints (to prevent the energy storage system from being frequently charged and discharged and affecting the life of the energy storage system):

[0122]

[0123]

[0124] In formulas (38) and (39), k is the discharge coefficient of the energy storage system, t c ,t d It is the period when charging and discharging of the energy storage system are completed.

[0125] Step 4.6.3: Energy storage system maximum charge and discharge power limit constraints:

[0126]

[0127] In formula (40), The maximum power for charging (discharging) the energy storage system.

[0128] Step 4.7: Interruptible load constraints:

[0129] 0<=p IL (t)<=p IL,max (t) (19)

[0130] In formula (42), p IL,max (t) is the maximum interruption amount of the interruptible load.

[0131] Step 5: Taking a typical 10-machine system as an example, assume that the system has 10 thermal power generating units and 10 wind power generating units. In order to illustrate that the present invention reasonably calculates the power grid frequency regulation capability under the output of thermal power generation, wind power generation and energy storage system units, it helps to reduce the risk of power grid operation and ensure the stable operation of the system. The system frequency regulation capability considering elastic reserve is discussed.

[0132] Step 5.1: Table 1 shows the setting and collection of thermal power unit parameters; Table 2 shows the load and wind power generation parameters; Table 3 shows the energy storage system parameters; Table 4 shows the interruptible load parameters.

[0133] Table 1: Thermal power unit parameters

[0134]

[0135] Table 2: Load and wind power generation parameters

[0136]

[0137]

[0138] Table 3: Energy storage system parameters

[0139]

[0140] Table 4: Parameters of interruptible loads

[0141]

[0142] Step 5.2: According to the objective functions and constraints listed in Step 2 and Step 3 in the manual and the parameter data in Step 5.1, real-time simulation is performed in Matlab. The solution method directly uses the Gurobi solver to solve, thereby obtaining the frequency regulation capability of the power grid considering the elastic reserve. The data results are shown in Table 5.

[0143] Table 5: Frequency modulation capability

[0144]

[0145] According to the table shown in Table 5, it can be seen that the frequency regulation capacity of wind, thermal and storage systems taking into account flexible reserve is within a reasonable range, proving the rationality of the frequency regulation capacity calculation method. At the same time, increasing the frequency regulation capacity of the power grid will help reduce the risk of power grid operation and ensure the stable operation of the system.

[0146] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that the technical solutions described in the aforementioned embodiments may still be modified, or some of the technical features may be replaced by equivalents. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for calculating the frequency regulation capacity of wind, fire and storage systems taking into account flexible reserve, characterized in that: The following steps are involved: S1. Obtain the scene through Latin hypercube sampling, and obtain a suitable number of wind power generation scenes through scene elimination technology; S2. Establishing the objective function of minimizing the sum of the operation cost of thermal power units and the cost of interruptible loads; S3. Establish load balance constraints and frequency regulation capacity constraints for thermal power generation, wind power generation and energy storage, minimum start and stop time constraints for thermal power generation, upper and lower output limits, ramp constraints, energy storage system constraints and interruptible load constraints; S4, input parameter data and use Gurobi solver in Matlab to solve the output of thermal power unit and energy storage unit; S5. Calculate the system frequency regulation capability based on the unit output results.

2. The method for calculating the frequency regulation capability of wind, fire and storage systems taking into account flexible reserve according to claim 1 is characterized in that: The objective function in step 2 is: Where F is the total operating cost; T is the total number of time periods in the entire unit scheduling cycle; n is the number of units participating in the unit; F1(p i (t)) is the fuel cost at time t, p i (t) is the active power of unit i at time t; I i (t) is the on / off state of unit i at time t, where 1 represents the on state and 0 represents the off state; cu i (t) is the startup cost of unit i at time t; cd i (t) is the shutdown cost of unit i at time t, which is generally independent of the startup time of the unit. Here it is approximately 0; F IL is the interruptible load cost.

3. The method for calculating the frequency regulation capability of wind, fire and storage systems taking into account elastic reserve according to claim 2 is characterized in that: The fuel cost expression at time t is: Where a i , b i 、c i are the fuel cost characteristic curve parameters of unit i respectively.

4. The method for calculating the frequency regulation capability of wind, fire and storage systems taking into account elastic reserve according to claim 2 is characterized in that: The startup cost expression of unit i at time t is: Where hc i ,cc i are the hot and cold start-up costs of unit i, respectively; is the continuous shutdown time of unit i in time period t; is the cold start time of unit i; is the maximum downtime of unit i.

5. The method for calculating the frequency regulation capability of wind, fire and storage systems taking into account flexible reserve according to claim 2 is characterized in that: The interruptible load cost expression is: Where C IL is the cost coefficient corresponding to the load reduction in period t; p IL (t) is the load reduction corresponding to period t.

6. The method for calculating the frequency regulation capability of wind, fire and storage systems taking into account flexible reserve according to any one of claims 1 to 5, characterized in that: The constraints in step 3 are: Load balancing constraints: In the formula is the active power output of thermal power unit i in time period t in scenario s; is the active power output of wind turbine i in time period t in scenario s; p w,i (t) is the active power of the wind farm in all scenarios Active power output in a scenario obtained using probability distribution; p d (t), p c (t) are the discharge power and charging power of the energy storage system respectively; D(t) is the load of the system in time period t; Minimum start and stop time constraints for units: In the formula The time that unit i has been continuously turned on and off; is the minimum startup and shutdown time of unit i; Unit output upper and lower limit constraints: I i (t)p imin <=p i (t)<=I i (t)p imax Where p imin 、p imax are the upper and lower limits of the output of unit i respectively; Frequency regulation capacity constraints: Where R(t) represents the capacity requirement of frequency modulation capacity in time period t, which can generally be set to R(t) = 0.1D(t) Step 4.5: Hill Climbing Constraints: -DR i <=p i (t)-p i (t-1)<=UR i ,I i (t)-I i (t-1)=0(t>=2) In the formula, m i It is the level at which the thermal power unit can be quickly adjusted in a short time, which can generally be set to m i =0.1p imax ; Energy storage system inherent constraints: Initial storage energy of the energy storage system: In the formula is the initial storage energy of the energy storage system; is the maximum storage energy of the energy storage system; w is the discharge coefficient of the energy storage system The charging and discharging energy of the energy storage system in time period t: C c (t)=∫αp c (t)dt C d (t)=∫βp d (t)dt Where α and β are the charging and discharging efficiency coefficients of the energy storage system respectively; Energy storage of the energy storage system in time period t: Interruptible load constraints: 0<=p IL (t)<=p IL,max (t) Where p IL,max (t) is the maximum interruption amount of the interruptible load.

7. The method for calculating the frequency regulation capability of wind, fire and storage systems taking into account flexible reserve according to claim 6 is characterized in that: The upper and lower limits of energy storage in the energy storage system at time period t are: In the formula are the maximum and minimum values ​​of energy that can be stored in the energy storage system respectively; Charge and discharge constraints: Where k is the discharge coefficient of the energy storage system, t c ,t d The period when charging and discharging of the energy storage system is completed; Energy storage system maximum charge and discharge power limit constraints: In the formula The maximum power for charging (discharging) the energy storage system.

8. The method for calculating the frequency regulation capability of wind, fire and storage systems taking into account flexible reserve according to any one of claims 1 to 5, characterized in that: The system frequency modulation capability calculation process in step 5 is: Where f N is the grid frequency, σ1% is the regulation coefficient of the thermal power unit, and σ2% is the regulation coefficient of the energy storage unit.

9. A frequency regulation capacity calculation system for wind, fire and storage systems taking into account flexible reserve, characterized in that: include: Wind power generation scenario construction module: obtain scenarios through Latin hypercube sampling, and obtain a suitable number of wind power generation scenarios through scenario elimination technology; Objective function construction module: establish an objective function that comprehensively considers the minimum sum of the operating cost of thermal power units and the cost of interruptible loads; Constraint construction module: Establish load balance constraints and frequency regulation capacity constraints for thermal power generation, wind power generation and energy storage, minimum start and stop time constraints for thermal power generation, upper and lower output limits, ramp constraints, energy storage system constraints and interruptible load constraints; Solution module: Input parameter data and use Gurobi solver in Matlab to solve the output of thermal power units and energy storage units; System frequency regulation capability calculation module: Calculates the system frequency regulation capability based on the unit output results.

10. The frequency regulation capacity calculation system of wind, fire and storage systems taking into account flexible reserve according to claim 9 is characterized in that: The objective function is: Where F is the total operating cost; T is the total number of time periods in the entire unit scheduling cycle; n is the number of units participating in the unit; F1(p i (t)) is the fuel cost at time t, p i (t) is the active power of unit i at time t; I i (t) is the on / off state of unit i at time t, where 1 represents the on state and 0 represents the off state; cu i (t) is the startup cost of unit i at time t; cd i (t) is the shutdown cost of unit i at time t, which is generally independent of the startup time of the unit. Here it is approximately 0; F IL is the interruptible load cost.

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