Aggregation control method and device for distributed energy storage participating in secondary frequency modulation of power grid

Abstract

The application discloses a distributed energy storage participating in secondary frequency modulation of a power grid and a method and device for aggregated control. The method first groups and aggregates each distributed energy storage unit, so that a dispatching center can schedule and manage a larger number of energy storage units; and then controls the output of each energy storage unit by solving a proposed distributed energy storage frequency modulation power double-layer optimization model considering frequency modulation cost and state of charge (SOC) difference. The first layer establishes a system layer optimization model to solve power instruction values of each aggregated energy storage, so as to achieve an economic target of minimizing a frequency modulation consumption function; and the second layer solves distributed energy storage unit power instruction values to control each distributed energy storage unit to participate in power grid frequency modulation, with the target of narrowing the SOC difference of each distributed energy storage unit in the aggregated energy storage. The variable scale and calculation amount to be considered during power distribution each time will be reduced.

Description

Technical Field

[0001] This invention belongs to the field of device technology, specifically relating to an optimized control method for distributed energy storage to participate in the secondary frequency regulation of the power grid. Background Technology

[0002] Frequency is a crucial parameter of the power grid, and frequency stability is fundamental to the stable and economical operation of the power system. In recent years, the large-scale grid connection of new energy power generation has led to the replacement of some traditional generating units in the power system. In addition, the widespread application of flexible transmission devices in the power system has made the "double high" problem of high proportion of renewable energy and high proportion of power electronic equipment in the power system increasingly prominent. This has caused a decrease in system inertia and frequency regulation resources, thereby affecting the frequency security of the power system.

[0003] Energy storage, as a high-quality active power resource, is increasingly being used to mitigate fluctuations caused by renewable energy generation and participate in grid frequency regulation. When participating in secondary grid frequency regulation, energy storage involves optimizing active power output. Currently, research on energy storage participation in grid frequency regulation by domestic and international scholars is based on a specific objective function, performing an overall optimization solution for the frequency regulation output of each energy storage device. However, with the construction of energy storage power station projects, more and more distributed energy storage units will serve grid frequency regulation in the future. If this model is still used for secondary frequency regulation at this time, it may lead to a large number of variables to be solved and a significant increase in computational load. Summary of the Invention

[0004] This invention provides a method and apparatus for aggregated control of distributed energy storage participating in secondary frequency regulation of the power grid, which reduces the solution scale of the optimization problem of energy storage participating in secondary frequency regulation, thereby greatly reducing the computational load of the dispatch center.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] A converged control method for distributed energy storage to participate in grid secondary frequency regulation includes the following steps:

[0007] S1. Group the distributed energy storage units participating in secondary frequency regulation according to their output characteristics;

[0008] S2. Aggregate the distributed energy storage units in each group to obtain the energy storage aggregation control unit model;

[0009] S3. Correct the output power range and available capacity range of the energy storage aggregation control unit by considering the state of charge of the energy storage unit;

[0010] S4. Based on the output power range and available capacity range, establish a system-level optimization model for the energy storage aggregation control unit to participate in secondary frequency regulation;

[0011] S5. Solve the system-level optimization model of secondary frequency regulation to obtain the power commands of each energy storage aggregation control unit;

[0012] S6. Based on the power commands of each energy storage aggregation control unit, establish an optimization model at the distributed energy storage unit level;

[0013] S7. Solve the optimization model at the distributed energy storage unit level to obtain the output commands of each distributed energy storage unit within the energy storage aggregation control unit, and complete the power allocation of each distributed energy storage unit according to the output commands of each distributed energy storage unit.

[0014] Furthermore, step S2 includes the following steps:

[0015] S2.1 The output characteristic expression of the energy storage aggregation control unit is determined as follows:

[0016] (1)

[0017] —The output characteristics of the energy storage aggregation control unit, including power range, available capacity range, and ramp rate range;

[0018] —Column vector elements representing the output power of the energy storage aggregation control unit during scheduling period T;

[0019] —The lower and upper limits of the output power of the energy storage aggregation control unit;

[0020] —The lower and upper limits of the available capacity of the energy storage aggregation control unit;

[0021] —The lower limit and upper limit of the ramp rate of the energy storage aggregation control unit;

[0022] Δt — Frequency modulation sampling time;

[0023] S2.2 Determine the output power range of the energy storage aggregation control unit:

[0024]

[0025] in:

[0026] —Minimum and maximum output power of the energy storage aggregation control unit i;

[0027] —Minimum and maximum output power of the j-th distributed energy storage unit within the energy storage aggregation control unit i;

[0028] n represents the number of distributed energy storage units within the energy storage aggregation control unit i.

[0029] S2.3 Determine the available capacity range of the energy storage aggregation control unit.

[0030] The minimum and maximum available capacity for overcharging and over-discharging of distributed energy storage units are as follows:

[0031]

[0032] in:

[0033] E i，j —The rated capacity of distributed energy storage unit j within the energy storage aggregation control unit i.

[0034] —Minimum and maximum available capacity of distributed energy storage unit j within energy storage aggregation control unit i.

[0035] The minimum and maximum available capacity of the energy storage aggregation control unit i are expressed as follows:

[0036]

[0037] in:

[0038] —Minimum and maximum available capacity of the energy storage aggregation control unit i.

[0039] S2.4 Determine the ramp rate range of the energy storage aggregation control unit.

[0040] For the j-th distributed energy storage unit within the energy storage aggregation control unit i, its maximum and minimum ramp rates at time t are expressed as:

[0041]

[0042]

[0043] in:

[0044] —The minimum and maximum ramp rates of the j-th distributed energy storage unit within the energy storage aggregation control unit i at time t.

[0045] —The rated minimum ramp rate and rated maximum ramp rate of the j-th distributed energy storage unit within the energy storage aggregation control unit i.

[0046] P i，j，t-1 —The output power of the j-th distributed energy storage unit within the energy storage aggregation control unit i at time t-1.

[0047] The minimum ramp range of energy storage aggregation control unit i and maximum climbing range It can be represented as:

[0048]

[0049] in: —Minimum and maximum ramp range of the energy storage aggregation control unit i.

[0050] Furthermore, step S3 includes the following steps:

[0051] Define the charge / discharge correction factor a for distributed energy storage unit j within energy storage aggregation control unit i. i,j and discharge correction factor b i,j If the energy storage unit can charge and discharge normally, then a i,j =0, b i,j =0; when the SOC value reaches the lower limit of 0.1, b will be... i,j Set to 1; when the SOC value reaches the upper limit of 0.9, set a i,j Set to 1;

[0052] After considering the SOC of the energy storage unit, equations (2)-(7) in the model of step S2 are modified to obtain equations (8)-(11):

[0053]

[0054]

[0055]

[0056]

[0057] in:

[0058] —Minimum and maximum output power of the corrected energy storage aggregation control unit i;

[0059] —Minimum and maximum available capacity of distributed energy storage unit j within the corrected energy storage aggregation control unit i;

[0060] —Minimum and maximum available capacity of the corrected energy storage aggregation control unit i;

[0061] —The minimum and maximum ramp range of distributed energy storage unit j within the energy storage aggregation control unit i at time t during charging;

[0062] —The minimum and maximum ramp range of distributed energy storage unit j within the energy storage aggregation control unit i at time t during discharge;

[0063] —Minimum and maximum ramp range of the energy storage aggregation control unit i during charging;

[0064] —Minimum and maximum ramp range of the energy storage aggregation control unit i during discharge;

[0065] When the State of Charge (SOC) of a distributed energy storage unit exceeds the limit, in order not to affect the frequency regulation at the next moment, it is necessary to subtract the output power of the distributed energy storage unit that exceeded the limit at the previous moment, and at the same time update the remaining power of the energy storage aggregation control unit. That is:

[0066]

[0067] in:

[0068] —The remaining capacity of the energy storage aggregation control unit i after correction at t-1;

[0069] S i，j，t-1 —The SOC value of distributed energy storage unit j within energy storage aggregation control unit i at time t-1;

[0070] E i，j —The rated capacity of distributed energy storage unit j within energy storage aggregation control unit i;

[0071] P BEi，j，t-1 — Output power of energy storage aggregation control unit i at t-1;

[0072] P i，j，t-1 —The output power of distributed energy storage unit j within energy storage aggregation control unit i at t-1;

[0073] —The output power of the corrected energy storage aggregation control unit i at t-1.

[0074] Furthermore, in step S4, the objective function of the system-level optimization model for secondary frequency modulation is:

[0075]

[0076] Among them, D t —The first-level objective function, the frequency regulation consumption function of the energy storage aggregation control unit at time t; f c —The state of charge factor of energy storage, f d —Discharge state factor, —The coefficients of the quadratic term of the frequency modulation power consumption function during charging and the coefficients of the quadratic term of the frequency modulation power consumption function during discharging. —The coefficients of the first term of the frequency modulation power consumption function during charging and discharging, P BE,i,t —The output power of the energy storage aggregation control unit i at t, E BE,i,t-1 —The remaining capacity of the energy storage aggregation control unit i at time t-1, E ref —Reference value for the capacity of the energy storage aggregation control unit.

[0077] Furthermore, the constraints of the system-level optimization model for secondary frequency modulation are as follows:

[0078]

[0079]

[0080] In the formula: —The lower and upper limits of the charging power of the energy storage aggregation control unit during charging, P BE,i,t —The output power of the energy storage aggregation control unit i at t. —The lower and upper limits of the discharge power of the energy storage aggregation control unit during the discharge process. —Minimum and maximum output power of the corrected energy storage aggregation control unit i —The minimum and maximum ramp range of distributed energy storage unit j within energy storage aggregation control unit i at time t during discharge; Δt—frequency modulation sampling time. —The remaining capacity of the energy storage aggregation control unit i after correction at t-1, —The output power of the corrected energy storage aggregation control unit i at t-1 —Minimum and maximum available capacity of energy storage aggregation control unit i —Equivalent charging coefficient and discharging coefficient of energy storage aggregation control unit i —Minimum and maximum ramp range of the energy storage aggregation control unit i during charging.

[0081] Furthermore, in step S5, if the solution fails, the objective function is changed to minimize the error of the frequency modulation demand signal issued by the tracking system, and the system-level optimization model of the secondary frequency modulation is solved again.

[0082] Furthermore, in step S6, the objective function of the distributed energy storage unit-level optimization model is set as follows:

[0083]

[0084]

[0085] Among them, F i，t—The second-level objective function, the frequency regulation consumption function of the distributed energy storage unit within the energy storage aggregation control unit at time t, S i.j.t S i.k.t —The SOC values ​​of distributed energy storage units j and k within the energy storage aggregation control unit i at time t, S i,j,t-1 S i,k,t-1 —The SOC values ​​of distributed energy storage units j and k within the energy storage aggregation control unit i at time t-1, f c —State of charge factor, f d —and discharge state factor, P i,j,t —The output power of the j-th distributed energy storage unit within the energy storage aggregation control unit i at time t. —Charging coefficient and discharging coefficient of the k-th distributed energy storage unit within the energy storage aggregation control unit i, Δt—frequency modulation sampling time, E i，j —The rated capacity of distributed energy storage unit j within energy storage aggregation control unit i, E i,k —The rated capacity of distributed energy storage unit j within the energy storage aggregation control unit i.

[0086] Furthermore, in step S6, the constraints of the optimization model at the distributed energy storage unit level are:

[0087]

[0088]

[0089]

[0090]

[0091] Among them, P BE,i,t — Output power of energy storage aggregation control unit i at time t, n — Number of distributed energy storage units within energy storage aggregation control unit i —The minimum and maximum output power of the j-th distributed energy storage unit within the energy storage aggregation control unit i. —The minimum and maximum available capacity of distributed energy storage unit j within energy storage aggregation control unit i. —The rated minimum ramp rate and rated maximum ramp rate of the j-th distributed energy storage unit within the energy storage aggregation control unit i.

[0092] An aggregation control device for distributed energy storage participating in secondary frequency regulation of the power grid includes:

[0093] The grouping module is used to group the distributed energy storage units participating in secondary frequency regulation according to their output characteristics;

[0094] The aggregation module is used to aggregate the distributed energy storage units in each group to obtain the energy storage aggregation control unit model;

[0095] The correction module is used to correct the output power range and available capacity range of the energy storage aggregation control unit by taking into account the state of charge of the energy storage unit.

[0096] The first modeling module is used to establish a system-level optimization model for the energy storage aggregation control unit to participate in secondary frequency regulation based on the output power range and available capacity range.

[0097] The first solution module is used to solve the system-level optimization model of secondary frequency regulation and obtain the power commands of each energy storage aggregation control unit;

[0098] The second modeling module is used to establish an optimization model at the distributed energy storage unit level based on the power commands of each energy storage aggregation control unit.

[0099] The second solution module is used to solve the optimization model at the distributed energy storage unit level, obtain the output commands of each distributed energy storage unit within the energy storage aggregation control unit, and complete the power allocation of each distributed energy storage unit according to the output commands of each distributed energy storage unit.

[0100] A computer device is characterized by comprising an electrically connected memory and a processor, wherein the memory stores a computer program executable on the processor, and the processor, when executing the computer program, implements the steps of the method described above.

[0101] Compared with the prior art, the present invention has at least the following beneficial technical effects:

[0102] This invention first groups and aggregates distributed energy storage units to facilitate scheduling and management of a large number of units by the dispatch center. This reduces the scale of the optimization problem for energy storage participation in secondary frequency regulation, thereby significantly reducing the computational load on the dispatch center. Then, it controls the output power of each distributed energy storage unit by solving a proposed two-layer optimization model for distributed energy storage frequency regulation power that considers frequency regulation costs and state of charge (SOC) differences. The first layer establishes a system-level optimization model to solve for the power command values ​​of each energy storage aggregation control unit, aiming to minimize the economic objective of the frequency regulation cost function. The second layer aims to reduce the SOC differences among distributed energy storage units within the energy storage aggregation control unit to obtain the power command values ​​of the distributed energy storage units, thereby controlling their participation in grid frequency regulation. This hierarchical optimization achieves both the cost of energy storage participation in grid frequency regulation and the SOC differences among distributed energy storage units, ensuring the economy and sustainability of distributed energy storage participation in grid frequency regulation. Attached Figure Description

[0103] Figure 1It is a response model for energy storage participating in regional power grid frequency regulation;

[0104] Figure 2 This is a flowchart of the distributed energy storage frequency regulation power dual-layer optimization control method of the present invention;

[0105] Figure 3 A schematic diagram of the module structure of the control device provided by the present invention;

[0106] Figure 4 The load curve of a regional power grid subjected to a continuous disturbance for 2000 seconds over a certain period of time;

[0107] Figure 5 This is the system frequency deviation curve. Detailed Implementation

[0108] To make the objectives and technical solutions of this invention clearer and easier to understand, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. The specific embodiments described herein are for illustrative purposes only and are not intended to limit the invention.

[0109] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., indicating orientation or positional relationships based on the orientation or positional relationships shown in the accompanying drawings, are only for the convenience of describing the invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the invention. Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined with "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this invention, unless otherwise stated, "a plurality of" means two or more. In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0110] Figure 1A response model for distributed energy storage participating in regional power grid frequency regulation is presented. The system's power demand signal is divided, with traditional generating units handling relatively low-frequency power signals and energy storage devices handling relatively high-frequency power signals. The specific frequency thresholds for this division can be set by operators based on the actual energy storage capacity configuration and load changes.

[0111] In the picture: T CH F is the time constant of the speed controller. HP For the reheater gain; T RH T is the time constant of the reheater; G ΔF(s) represents the time constant of the steam turbine; M represents the system moment of inertia; ΔF(s) represents the system frequency deviation; ΔP represents the system frequency deviation. L (s) represents the power disturbance in the system; D is the load damping coefficient; R is the droop coefficient; B is the droop coefficient; K I It is the integration constant; The secondary frequency modulation power signal is handled by traditional generating units; The secondary frequency modulation power signal is provided for energy storage; P i P represents the output power of the i-th energy storage aggregation control unit. i，j T represents the output power of the j-th distributed energy storage unit within the i-th energy storage aggregation control unit; i，j Let be the response time constant of the j-th distributed energy storage unit within the i-th energy storage aggregation control unit.

[0112] Reference Figure 2 A method for aggregated control of distributed energy storage units participating in secondary frequency regulation of the power grid, the specific process of which is shown in the attached figure. Figure 2 As shown, it includes the following steps:

[0113] Step 1: Each distributed energy storage unit reports its output power and remaining capacity from the previous moment to the dispatch center;

[0114] Step Two: After grouping the distributed energy storage units according to their output characteristics (this grouping can be done manually), the dispatch center aggregates the distributed energy storage units in each group to obtain the model of each energy storage aggregation control unit. The specific method is as follows:

[0115] (1) Determine the output characteristic expression of the energy storage aggregation control unit.

[0116] The output characteristics of the energy storage aggregation control unit, which consists of various distributed energy storage units, can be expressed as:

[0117] (1)

[0118] in:

[0119] —The output characteristics of the energy storage aggregation control unit, including power range, available capacity range, and ramp rate range;

[0120] —The column vector elements that constitute the output power of the energy storage aggregation control unit during the scheduling period T.

[0121] —The lower limit and upper limit of the output power of the energy storage aggregation control unit.

[0122] —The lower limit and upper limit of the available capacity of the energy storage aggregation control unit.

[0123] —The lower limit and upper limit of the ramp rate of the energy storage aggregation control unit.

[0124] Δt—frequency modulation sampling time, which can usually be taken as 1 second;

[0125] (2) Determine the output power range of the energy storage aggregation control unit.

[0126] The minimum and maximum power ranges of an energy storage aggregation control unit depend on the output power of all its distributed energy storage units. Let n be the number of energy storage units in energy storage aggregation control unit i, then:

[0127]

[0128] in:

[0129] —Minimum output power and maximum output power of the energy storage aggregation control unit i.

[0130] —The minimum and maximum output power of the j-th distributed energy storage unit within the energy storage aggregation control unit i.

[0131] (3) Determine the available capacity range of the energy storage aggregation control unit.

[0132] To prevent overcharging and over-discharging of distributed energy storage units, their minimum and maximum available capacities are specified as follows:

[0133]

[0134] in:

[0135] E i，j —The rated capacity of distributed energy storage unit j within the energy storage aggregation control unit i.

[0136] —Minimum and maximum available capacity of distributed energy storage unit j within energy storage aggregation control unit i.

[0137] The minimum and maximum available capacity of the energy storage aggregation control unit i can be expressed as:

[0138]

[0139] in:

[0140] —Minimum and maximum available capacity of the energy storage aggregation control unit i.

[0141] (4) Determine the ramp rate range of the energy storage aggregation control unit.

[0142] The ramp rate of a distributed energy storage unit is affected not only by its rated ramp rate range, but also by its rated output power and the output power at the previous moment. For the j-th distributed energy storage unit within the energy storage aggregation control unit i, its maximum and minimum ramp rates at time t can be expressed as:

[0143]

[0144]

[0145] in:

[0146] —The minimum and maximum ramp rates of the j-th distributed energy storage unit within the energy storage aggregation control unit i at time t.

[0147] —The rated minimum ramp rate and rated maximum ramp rate of the j-th distributed energy storage unit within the energy storage aggregation control unit i.

[0148] P i，j，t-1 —The output power of the j-th distributed energy storage unit within the energy storage aggregation control unit i at time t-1.

[0149] The minimum ramp range of energy storage aggregation control unit i and maximum climbing range It can be represented as:

[0150]

[0151] in:

[0152] —Minimum and maximum ramp range of the energy storage aggregation control unit i.

[0153] Step 3: Correct the output power range and available capacity range of the aggregation control unit by considering the SOC of the energy storage unit. The specific method is as follows:

[0154] Define the charge / discharge correction factor a for distributed energy storage unit j within energy storage aggregation control unit i. i,j and discharge correction factor b i,j If the energy storage unit can charge and discharge normally, then a i,j =0, b i,j =0; when the SOC value reaches the lower limit of 0.1, b will be... i,j Set to 1; when the SOC value reaches the upper limit of 0.9, set a i,j Set to 1. Considering the SOC of the energy storage unit, the equations (2)-(7) in the model of step two are modified to obtain equations (8)-(11):

[0155]

[0156]

[0157]

[0158]

[0159] in:

[0160] —Minimum and maximum output power of the corrected energy storage aggregation control unit i.

[0161] —The minimum and maximum available capacity of distributed energy storage unit j within the corrected energy storage aggregation control unit i.

[0162] —Minimum and maximum available capacity of the corrected energy storage aggregation control unit i.

[0163] —The minimum and maximum ramp range of distributed energy storage unit j within the energy storage aggregation control unit i at time t during charging.

[0164] —The minimum and maximum ramp range of distributed energy storage unit j within the energy storage aggregation control unit i at time t during discharge.

[0165] —Minimum and maximum ramp range of the energy storage aggregation control unit i during charging.

[0166] —Minimum and maximum ramp range of the energy storage aggregation control unit i during discharge.

[0167] When the State of Charge (SOC) of a distributed energy storage unit exceeds the limit, in order not to affect the frequency regulation at the next moment, it is necessary to subtract the output power of the distributed energy storage unit that exceeded the limit at the previous moment, and at the same time update the remaining power of the energy storage aggregation control unit. That is:

[0168]

[0169] in:

[0170] —The remaining capacity of the energy storage aggregation control unit i after correction at t-1.

[0171] S i，j，t-1 —The SOC value of distributed energy storage unit j within energy storage aggregation control unit i at time t-1.

[0172] E i，j —The rated capacity of distributed energy storage unit j within the energy storage aggregation control unit i.

[0173] P BE，i，t-1 — Output power of energy storage aggregation control unit i at t-1.

[0174] P i，j，t-1 — Output power of distributed energy storage unit j within energy storage aggregation control unit i at t-1.

[0175] —The output power of the corrected energy storage aggregation control unit i at t-1.

[0176] Step 4: Establish a system-level optimization model for the energy storage aggregation control unit participating in secondary frequency regulation, including the objective function and constraints. The specific method is as follows.

[0177] From the power balance equation, we have:

[0178]

[0179] in:

[0180] P AGC，t —The power demand signal issued by the power grid AGC at time t.

[0181] —The power demand signal allocated to the traditional unit at time t.

[0182] —The power demand signal allocated to all energy storage aggregation control units at time t.

[0183] Referring to the frequency regulation consumption function of the traditional unit in Equation (14), the frequency regulation consumption function of energy storage is defined as shown in Equation (15):

[0184]

[0185]

[0186] In the formula:

[0187] D G,t —Frequency regulation consumption of a traditional generator unit at time t.

[0188] P G,t — Output power of a traditional unit at time t.

[0189] a G —The weighting coefficient for the consumption of traditional units.

[0190] D i,t — Frequency regulation consumption of energy storage aggregation control unit i at time t.

[0191] a s —Weighting coefficients of the real-time power influence consumption function of the energy storage aggregation control unit.

[0192] b s —Weighting coefficients of the consumption function for the capacity deviation of the energy storage aggregation control unit.

[0193] P BE,i,t — Output power of energy storage aggregation control unit i at time t.

[0194] E BE,i,t —The remaining capacity of the energy storage aggregation control unit i at time t.

[0195] E ref —The capacity reference value of the energy storage aggregation control unit is 0.5 times the rated capacity in this invention.

[0196] The real-time remaining power of the energy storage aggregation control unit is further expressed as:

[0197]

[0198] In the formula:

[0199] E BE，i，t-1 —The remaining capacity of the energy storage aggregation control unit i at time t-1.

[0200] —Equivalent charging coefficient and discharging coefficient of energy storage aggregation control unit i.

[0201]

[0202] In the formula:

[0203] —The charging coefficient and discharging coefficient of the j-th distributed energy storage unit within the energy storage aggregation control unit i.

[0204] Substituting equations (16) and (17) into the energy storage frequency regulation consumption function defined in equation (15), the variables in the energy storage frequency regulation consumption function are represented only by the output power of the energy storage aggregation control unit. After each frequency regulation cycle, the power of the energy storage aggregation control unit is updated according to the real-time information reported by each distributed energy storage unit.

[0205]

[0206] in:

[0207] —The quadratic coefficient of the frequency modulation consumption function during charging and the quadratic coefficient of the frequency modulation consumption function during discharging.

[0208] —The coefficients of the first term of the frequency modulation consumption function during charging and the coefficients of the first term of the frequency modulation consumption function during discharging.

[0209] To better distinguish the charge and discharge states of energy storage, a state-of-charge factor f is introduced. c and discharge state factor f d And by adding the objective functions of the frequency regulation consumption of each energy storage, we get equations (19)-(20).

[0210]

[0211]

[0212] in:

[0213] D t —The first-level objective function is the frequency regulation consumption function of the energy storage aggregation control unit at time t;

[0214] Substituting equations (8)-(12) and (16) into the constraints expressed in equation (1), we can finally obtain the power constraints for the energy storage aggregation control unit during the frequency regulation process:

[0215]

[0216]

[0217] In the formula:

[0218] —The lower limit and upper limit of the charging power of the energy storage aggregation control unit during the charging process.

[0219] —The lower limit and upper limit of the discharge power of the energy storage aggregation control unit during the discharge process.

[0220] Therefore, a system-level quadratic programming model for energy storage aggregation control unit participating in secondary frequency regulation was established, including the objective function of equation (20) and the constraints of equations (21)-(22).

[0221] Step 5: Solve the above quadratic programming model using the CPLEX solver to obtain the output power command P issued by the power grid dispatch center to each energy storage aggregation control unit. BE,i,t .

[0222] In actual operation, the above model may fail to solve. The main reason is that the current power or capacity of all energy storage devices is insufficient to meet the power demand, or the energy storage capacity is sufficient, but the ramp-up constraint cannot meet the power demand. In this case, after the solution fails, the objective function is changed to minimizing the error of the frequency regulation demand signal issued by the system, i.e.:

[0223]

[0224] The model is solved again, which ensures that the energy storage aggregation control unit can meet the grid frequency regulation requirements to the greatest extent possible based on its own situation after the dispatch center issues a signal.

[0225] Step Six: After the energy storage aggregation control unit obtains the required output power, an optimization model at the distributed energy storage unit level is established to obtain the output power of each distributed energy storage unit within the energy storage aggregation control unit. This model aims to minimize the difference in SOC values ​​among the distributed energy storage units, that is, to achieve SOC balance among the energy storage units as much as possible. Its objective function is set as follows:

[0226]

[0227]

[0228] in:

[0229] F i，t —The second-level objective function (the number depends on the number of energy storage aggregation control units), the frequency regulation consumption function of the distributed energy storage units in the energy storage aggregation control unit at time t;

[0230] P i，k，t —The output power of the kth distributed energy storage unit within the energy storage aggregation control unit i at time t.

[0231] —The charging coefficient and discharging coefficient of the kth distributed energy storage unit within the energy storage aggregation control unit i.

[0232] S i.j.t S i.k.t —The SOC values ​​of distributed energy storage units j and k within the energy storage aggregation control unit i at time t.

[0233] S i,j,t-1 S i,k,t-1 —The SOC values ​​of distributed energy storage units j and k within the energy storage aggregation control unit i at time t-1.

[0234] E i,k —The rated capacity of distributed energy storage unit j within the energy storage aggregation control unit i.

[0235] Meanwhile, the equality constraints that need to be satisfied are shown in equations (26)-(29), and the inequality constraints include power range, capacity range and ramp range.

[0236]

[0237]

[0238]

[0239]

[0240] Step 7: Solve the above distributed energy storage unit level optimization model using the CPLEX solver to obtain the output command P of each distributed energy storage unit within the energy storage aggregation control unit. i,j,t The power allocation of each distributed energy storage unit is completed according to the output command of each distributed energy storage unit.

[0241] This invention reports real-time information from distributed energy storage units to a dispatch center. The dispatch center then groups and aggregates these distributed energy storage units into several energy storage aggregation control units. At the start of frequency regulation, the dispatch center issues power commands to the energy storage aggregation control units through optimization solutions. After receiving the power commands from the dispatch center, the energy storage aggregation control units redistribute power among their constituent distributed energy storage units. This reduces the scale of variables and computational load that the dispatch center needs to consider each time power is allocated.

[0242] Reference Figure 3 This invention provides a distributed energy storage aggregation control device for participating in the secondary frequency regulation of the power grid, such as... Figure 3 As shown, it includes:

[0243] The grouping module is used to group the distributed energy storage units participating in secondary frequency regulation according to their output characteristics;

[0244] The aggregation module is used to aggregate the distributed energy storage units in each group to obtain the energy storage aggregation control unit model;

[0245] The correction module is used to correct the output power range and available capacity range of the energy storage aggregation control unit by taking into account the state of charge of the energy storage unit.

[0246] The first modeling module is used to establish a system-level optimization model for the energy storage aggregation control unit to participate in secondary frequency regulation based on the output power range and available capacity range.

[0247] The first solution module is used to solve the system-level optimization model of secondary frequency regulation and obtain the power commands of each energy storage aggregation control unit;

[0248] The second modeling module is used to establish an optimization model at the distributed energy storage unit level based on the power commands of each energy storage aggregation control unit.

[0249] The second solution module is used to solve the optimization model at the distributed energy storage unit level, obtain the output commands of each distributed energy storage unit within the energy storage aggregation control unit, and complete the power allocation of each distributed energy storage unit according to the output commands of each distributed energy storage unit.

[0250] The present invention provides a computer device comprising an electrically connected memory and a processor, wherein the memory stores a computer program that can run on the processor, and when the processor executes the computer program, it implements the above-described aggregation control method for distributed energy storage to participate in the secondary frequency regulation of the power grid.

[0251] Specific application examples

[0252] The proposed method was applied to a regional power grid using MATLAB / Simulink simulation. The total installed capacity of the regional power grid is 1000MW, and the unit ramp rate is 200MW / h. Among them, the renewable energy account for 100MW, and 56MW / 20MW·h of distributed energy storage is configured. The energy storage configured in the grid consists of three types of energy storage, including supercapacitors, lithium batteries, and lead-acid batteries.

[0253] Table 1 shows the relevant parameters of the regional power grid. Table 2 shows the parameters of the distributed energy storage units in the regional power grid, including output power, ramp range, rated capacity, charge / discharge efficiency, and response time. Table 3 shows the initial SOC value of each distributed energy storage unit. The column number corresponds to the first digit of the distributed energy storage unit number, and the row number corresponds to the second digit of the distributed energy storage unit number. According to this rule, it can be seen from the table that the initial SOC value of distributed energy storage unit numbered 24 in Table 2 is 0.45.

[0254] Table 1 Relevant Parameters of Regional Power Grid

[0255]

[0256] Table 2 Parameters of Distributed Energy Storage Units

[0257]

[0258]

[0259] Table 3 Initial SOC values ​​for distributed energy storage units

[0260] serial number 1 2 3 4 5 1 0.7 0.3 0.4 0.6 — 2 0.8 0.75 0.4 0.45 0.6 3 0.7 0.65 0.6 0.55 0.45

[0261] Based on the parameters in the table above, four strategies are constructed for comparison:

[0262] Strategy 1 directly uses the output power of each energy storage unit as a variable to establish a global optimization model, serving as a comparison method for this invention. Based on the method proposed in this invention, distributed energy storage units participating in frequency regulation in the power grid can be aggregated into several energy storage aggregation control units, reducing the problem scale when distributed energy storage units participate in power grid frequency regulation optimization. Furthermore, different distributed energy storage units can be artificially classified, thereby expanding the frequency regulation modes. Therefore, strategies 2, 3, and 4 adopt the distributed energy storage participation in secondary frequency regulation control method proposed in this invention. Strategy 2's division method is based on the fact that the rated output power and rated capacity of each energy storage aggregation control unit are roughly the same; Strategy 3's division is based on the level of charging and discharging efficiency (the average of charging efficiency and discharging efficiency); and Strategy 4's division is based on the energy storage response characteristics (energy storage type). The proposed method is applied to strategies 2, 3, and 4 and compared with strategy 1 to verify the effectiveness of the distributed energy storage unit aggregation method proposed in this invention. The specific distributed energy storage unit composition of each energy storage aggregation control unit in strategies 2, 3, and 4 is shown in Table 4.

[0263] Table 4 Initial SOC values ​​for distributed energy storage units

[0264]

[0265] Figure 4 To simulate and compare the load curve of a regional power grid subjected to a continuous disturbance for 2000 seconds over a certain period of time, under the condition that each strategy adopts the same secondary frequency regulation signal distribution mode, strategies 1, 2, 3, 4 and the case where the generator unit alone bears all the secondary frequency regulation signals are simulated and compared.

[0266] Figure 5The table shows the frequency deviation curve of the system after experiencing continuous step disturbances. Firstly, compared to a system where only traditional generating units handle all secondary frequency regulation signals, the system with energy storage exhibits a better overall frequency deviation curve after continuous disturbances, and the frequency recovers quickly after decreasing. Secondly, when the system has energy storage, the frequency deviation curves of Strategy 1 and Strategy 2, 3, and 4 (using the method described in this invention) are basically consistent. Table 5 shows that when energy storage controlled by Strategy 4 participates in frequency regulation, the average frequency deviation of the system is the smallest. Furthermore, the frequency deviation curves show that the method of aggregating into three energy storage aggregation control units for system frequency regulation does not reduce the frequency regulation capability of the original energy storage units, because compared to Strategy 1, its average frequency deviation is essentially zero throughout the entire frequency regulation process, thus verifying the correctness of the strategy proposed in this invention. After adopting the method described in this invention, the dispatch center only performs optimization calculations on the power commands of the energy storage aggregation control units at the beginning of each frequency regulation, thereby reducing the scale of variable solutions and the computational requirements during optimization.

[0267] Table 5 Average Frequency Deviation Index

[0268]

[0269] The above content is only for illustrating the technical concept of the present invention and should not be construed as limiting the scope of protection of the present invention. Any modifications made to the technical solution based on the technical concept proposed in this invention shall fall within the scope of protection of the claims of this invention.

Claims

1. A method for aggregated control of distributed energy storage participating in secondary frequency regulation of the power grid, characterized in that, Includes the following steps: S1. Group the distributed energy storage units participating in secondary frequency regulation according to their output characteristics; S2. Aggregate the distributed energy storage units in each group to obtain the energy storage aggregation control unit model; S3. Correct the output power range and available capacity range of the energy storage aggregation control unit by considering the state of charge of the energy storage unit; S4. Based on the output power range and available capacity range, establish a system-level optimization model for the energy storage aggregation control unit to participate in secondary frequency regulation; S5. Solve the system-level optimization model of secondary frequency regulation to obtain the power commands of each energy storage aggregation control unit; S6. Based on the power commands of each energy storage aggregation control unit, establish an optimization model at the distributed energy storage unit level; S7. Solve the distributed energy storage unit level optimization model to obtain the output commands of each distributed energy storage unit inside the energy storage aggregation control unit, and complete the power allocation of each distributed energy storage unit according to the output commands of each distributed energy storage unit. In step S4, the objective function of the system-level optimization model for secondary frequency modulation is: in, —The first-level objective function, the energy storage aggregation control unit in t Frequency modulation consumption function at time; f c —The state of charge factor of energy storage f d —Discharge state factor, , —The coefficients of the quadratic term of the frequency modulation power consumption function during charging and the coefficients of the quadratic term of the frequency modulation power consumption function during discharging. , —The coefficients of the first term of the frequency modulation power consumption function during charging and the coefficients of the first term of the frequency modulation power consumption function during discharging. P BE,i,t —Energy Storage Aggregation Control Unit i exist t 'output power' E BE,i,t-1 —Energy Storage Aggregation Control Unit i exist t-1 Remaining capacity at any given time E ref —Reference value for the capacity of the energy storage aggregation control unit; In step S6, the objective function of the distributed energy storage unit-level optimization model is set as follows: in, —The second-level objective function, the distributed energy storage units within the energy storage aggregation and control unit, t Frequency modulation consumption function at time t, , —Energy Storage Aggregation Control Unit i Internal distributed energy storage unit j and k exist t SOC value at time t, S i,j,t-1 , S i,k,t-1 —Energy Storage Aggregation Control Unit i Internal distributed energy storage unit j and k exist t The SOC value at time -1 f c —State of Charge Factor ，f d — and discharge state factor, P i,j,t —Energy Storage Aggregation Control Unit i Inner j Taiwan distributed energy storage unit in t Output power at any moment , —Energy Storage Aggregation Control Unit i Inner k The charging coefficient and discharging coefficient of the distributed energy storage unit in Taiwan. —Frequency modulation sampling time, —Energy Storage Aggregation Control Unit i Internal distributed energy storage unit j Rated capacity, E i,k —Energy Storage Aggregation Control Unit i Internal distributed energy storage unit j Rated capacity.

2. The aggregation control method for distributed energy storage participating in secondary frequency regulation of the power grid according to claim 1, characterized in that, Step S2 includes the following steps: S2.1 The output characteristic expression of the energy storage aggregation control unit is determined as follows: (1) —The output characteristics of the energy storage aggregation control unit, including power range, available capacity range, and ramp rate range; —Energy storage aggregation control unit during the scheduling cycle T The column vector elements representing the output power at each time step; , —The lower and upper limits of the output power of the energy storage aggregation control unit; , —The lower and upper limits of the available capacity of the energy storage aggregation control unit; , —The lower limit and upper limit of the ramp rate of the energy storage aggregation control unit; —Frequency modulation sampling time; S2.2 Determine the output power range of the energy storage aggregation control unit: (2) in: , —Energy Storage Aggregation Control Unit i Minimum output power, maximum output power; , —Energy Storage Aggregation Control Unit i Inner j The minimum and maximum output power of the distributed energy storage unit; n Energy storage aggregation control unit i The number of internal distributed energy storage units; S2.3 Determine the available capacity range of the energy storage aggregation control unit. The minimum and maximum available capacity for overcharging and over-discharging of distributed energy storage units are as follows: (3) in: —Energy Storage Aggregation Control Unit i Internal distributed energy storage unit j Rated capacity; , —Energy Storage Aggregation Control Unit i Internal distributed energy storage unit j Minimum available capacity and maximum available capacity; Then the energy storage aggregation control unit i The minimum and maximum available capacities are expressed as follows: (4) in: , —Energy Storage Aggregation Control Unit i Minimum available capacity and maximum available capacity; S2.4 Determine the ramp rate range of the energy storage aggregation control unit. Energy storage aggregation control unit i Inner j For distributed energy storage units in Taiwan, their t The maximum and minimum climbing rates at any given time are expressed as: (5) (6) in: , —Energy Storage Aggregation Control Unit i Inner j Taiwan distributed energy storage unit in t Minimum and maximum climbing rates at any given time; , —Energy Storage Aggregation Control Unit i Inner j The rated minimum ramp rate and rated maximum ramp rate of the distributed energy storage unit; —Energy Storage Aggregation Control Unit i Inner j Taiwan distributed energy storage unit in t Output power at time -1; Then the energy storage aggregation control unit i Minimum climbing range and maximum climbing range Represented as: (7) in: , —Energy Storage Aggregation Control Unit i Minimum and maximum climbing range.

3. The aggregation control method for distributed energy storage participating in secondary frequency regulation of the power grid according to claim 2, characterized in that, Step S3 includes the following steps: Define energy storage aggregation control unit i Internal distributed energy storage unit j Charge / discharge correction factor a i,j and discharge correction factor b i,j If the energy storage unit can charge and discharge normally, then a i,j =0, b i,j =0; when the SOC value reaches the lower limit of 0.1, it will... b i,j Set to 1; when the SOC value reaches the upper limit of 0.9, a i,j Set to 1; After considering the SOC of the energy storage unit, equations (2)-(7) in the model of step S2 are modified to obtain equations (8)-(11): (8) (9) (10) (11) in: , —Corrected energy storage aggregation control unit i Minimum output power, maximum output power; , —Corrected energy storage aggregation control unit i Internal distributed energy storage unit j Minimum available capacity and maximum available capacity; , —Corrected energy storage aggregation control unit i Minimum available capacity and maximum available capacity; , —Energy storage aggregation control unit during charging i Internal distributed energy storage unit j exist t Minimum and maximum climbing range at any given time; , —Energy storage aggregation control unit during discharge i Internal distributed energy storage unit j exist t Minimum and maximum climbing range at any given time; , —Energy storage aggregation control unit during charging i Minimum climbing range, maximum climbing range; , —Energy storage aggregation control unit during discharge i Minimum climbing range, maximum climbing range; When the State of Charge (SOC) of a distributed energy storage unit exceeds the limit, in order not to affect the frequency regulation at the next moment, it is necessary to subtract the output power of the distributed energy storage unit that exceeded the limit at the previous moment, and at the same time update the remaining power of the energy storage aggregation control unit. That is: (12) in: —Corrected energy storage aggregation control unit i exist t- 1. Remaining capacity; —Energy Storage Aggregation Control Unit i Internal distributed energy storage unit j exist t SOC value at time -1; —Energy Storage Aggregation Control Unit i Internal distributed energy storage unit j Rated capacity; —Energy Storage Aggregation Control Unit i exist t- 1. Output power; —Energy Storage Aggregation Control Unit i Internal distributed energy storage unit j exist t- 1. Output power; —Corrected energy storage aggregation control unit i exist t- 1. Output power.

4. The aggregation control method for distributed energy storage participating in secondary frequency regulation of the power grid according to claim 1, characterized in that, The constraints of the system-level optimization model for secondary frequency modulation are: (21) (22) In the formula: , —The lower and upper limits of the charging power of the energy storage aggregation control unit during the charging process. P BE,i,t —Energy Storage Aggregation Control Unit i exist t 'output power' , —The lower and upper limits of the discharge power of the energy storage aggregation control unit during the discharge process. , —Corrected energy storage aggregation control unit i Minimum output power, maximum output power , —Energy storage aggregation control unit during discharge i Internal distributed energy storage unit j exist t Minimum and maximum climbing range at any given time. —Frequency modulation sampling time, —Corrected energy storage aggregation control unit i exist t- 1. Remaining capacity —Corrected energy storage aggregation control unit i exist t- 1's output power , —Energy Storage Aggregation Control Unit i Minimum available capacity, maximum available capacity, , —Energy Storage Aggregation Control Unit i The equivalent charging coefficient and discharging coefficient, , —Energy storage aggregation control unit during charging i Minimum and maximum climbing range.

5. The aggregation control method for distributed energy storage participating in secondary frequency regulation of the power grid according to claim 1, characterized in that, In step S5, if the solution fails, the objective function is changed to minimize the error of the frequency modulation demand signal issued by the tracking system, and the system-level optimization model of the secondary frequency modulation is solved again.

6. The aggregation control method for distributed energy storage participating in secondary frequency regulation of the power grid according to claim 1, characterized in that, In step S6, the constraints of the distributed energy storage unit-level optimization model are: in, P BE,i,t —Energy Storage Aggregation Control Unit i At any moment t 'output power' n —Energy Storage Aggregation Control Unit i The number of internal distributed energy storage units. , —Energy Storage Aggregation Control Unit i Inner j The minimum and maximum output power of the distributed energy storage unit. , —Energy Storage Aggregation Control Unit i Internal distributed energy storage unit j Minimum available capacity, maximum available capacity, , —Energy Storage Aggregation Control Unit i Inner j The rated minimum ramp rate and rated maximum ramp rate of the distributed energy storage unit.

7. A convergence control device for distributed energy storage participating in secondary frequency regulation of the power grid, used to implement the method of claim 1, characterized in that, include: The grouping module is used to group the distributed energy storage units participating in secondary frequency regulation according to their output characteristics; The aggregation module is used to aggregate the distributed energy storage units in each group to obtain the energy storage aggregation control unit model; The correction module is used to correct the output power range and available capacity range of the energy storage aggregation control unit by taking into account the state of charge of the energy storage unit. The first modeling module is used to establish a system-level optimization model for the energy storage aggregation control unit to participate in secondary frequency regulation based on the output power range and available capacity range. The first solution module is used to solve the system-level optimization model of secondary frequency regulation and obtain the power commands of each energy storage aggregation control unit; The second modeling module is used to establish an optimization model at the distributed energy storage unit level based on the power commands of each energy storage aggregation control unit. The second solution module is used to solve the optimization model at the distributed energy storage unit level, obtain the output commands of each distributed energy storage unit within the energy storage aggregation control unit, and complete the power allocation of each distributed energy storage unit according to the output commands of each distributed energy storage unit.

8. A computer device, characterized in that, The method includes an electrically connected memory and a processor, wherein the memory stores a computer program that can run on the processor, and when the processor executes the computer program, it implements the steps of the method according to any one of claims 1-6.

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