A partition control method based on hybrid energy storage life economy and frequency regulation limit

Abstract

A zoning control method based on the economic efficiency of hybrid energy storage life and frequency regulation limits belongs to the technical field of thermal power and energy storage combined frequency regulation. The present invention uses real-time SOC to establish a dynamic equilibrium quotation and characterize the performance of each energy storage as the upper model. At the same time, it proposes an optimal life assessment for energy-type energy storage, constructs an energy storage charge and discharge switching model, limits the frequent switching of energy-type energy storage, and extends its life. The underlying model constructs a frequency regulation limit standard for power-type energy storage, introduces multi-objective constraints, and proposes a hybrid energy storage operation plan suitable for all scenarios. Using evaluation indicators, the proposed frequency regulation control model is evaluated in terms of regulation rate, accuracy, and response time. This improves net income, reduces battery life loss and frequency offset, and is conducive to increasing the frequency regulation reliability and sustainability of regional energy storage. The method has the advantages of scientific and reasonable methods, strong applicability, and good results.

Description

Technical Field

[0001] The present invention belongs to the technical field of thermal power-energy storage combined frequency regulation, and in particular relates to a zoning control method based on hybrid energy storage life economy and frequency regulation limit. Background Art

[0002] Currently, the large-scale grid integration of renewable energy sources, represented by wind and solar power, poses a significant challenge to the frequency security of my country's power system due to their stochastic and intermittent nature. Thermal power units, currently the primary source of frequency regulation, struggle to meet frequency accuracy and speed requirements due to their inherent characteristics. Energy storage systems, with their rapid response and precise tracking, can efficiently assist thermal power units in frequency regulation. As power system requirements continue to refine, a single type of energy storage system can no longer simultaneously meet requirements for configuration flexibility, safety, response speed, service life, and economic efficiency. Consequently, hybrid energy storage systems, such as battery-flywheel hybrids, have emerged, improving the frequency regulation capabilities of energy storage while reducing battery lifespan degradation. However, current hybrid energy storage systems fail to account for the interplay between the frequency regulation performance of each type of energy storage, making it difficult to maintain frequency regulation over long timescales. This undermines the value proposition and regulatory role of hybrid energy storage. The large-scale grid integration of renewable energy sources and the inadequacy of traditional frequency regulation capabilities have led to a dilemma in balancing frequency security and the economic benefits of frequency regulation resources.

[0003] Therefore, a new technical solution is urgently needed in the existing technology to solve this problem. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide a method for controlling the life economy of hybrid energy storage and frequency regulation limit zoning to solve the technical problem that the large-scale grid connection of new energy and the lack of traditional frequency regulation capabilities lead to the inability to balance frequency safety and the economic benefits of frequency regulation resources.

[0005] A method for controlling a zoning system based on the life economy of a hybrid energy storage system and a frequency modulation limit includes the following steps, which are performed in sequence:

[0006] Step 1: Establish a hybrid energy storage combined frequency regulation system and obtain hybrid energy storage output, battery output, and flywheel output;

[0007] Step 2: Formulate a two-layer optimization allocation model for hybrid energy storage to assist thermal power unit frequency regulation, wherein the two-layer optimization allocation model includes a hybrid energy storage upper-layer scheduling model and a hybrid energy storage lower-layer control strategy;

[0008] 1) The hybrid energy storage upper-layer scheduling model performs real-time state optimization of the hybrid energy storage, including:

[0009] ① Establish a battery life loss model based on real-time energy storage state of charge (SOC) and equivalent life cycles to evaluate the optimal life of battery energy storage;

[0010] ②Provide SOC dynamic balance quotation;

[0011] ③ Characterize the hybrid energy storage performance;

[0012] 2) Based on the established hybrid energy storage underlying control strategy, combined with AGC instructions, thermal power unit output, and the real-time optimization status of hybrid energy storage, frequency modulation and zoning control are performed to obtain hybrid energy storage frequency modulation output and battery energy storage new energy dispatch output;

[0013] Step 3: Establish a hybrid energy storage transaction decision model and obtain a hybrid energy storage operation plan suitable for all scenarios by solving the model's objective function;

[0014] 1) The objective function is:

[0015]

[0016] Where: is the frequency modulation benefit at the current moment; C t neg is the electricity revenue at the current moment; C cost,t is the total cost at the current moment;

[0017] in,

[0018] Where: The cost of frequency regulation capacity for hybrid energy storage; The mileage cost of frequency regulation for hybrid energy storage;

[0019]

[0020] Where: The capacity and mileage subsidy income obtained by flywheel energy storage participating in frequency regulation during the frequency regulation period. The capacity and mileage subsidy income obtained by battery energy storage participating in frequency regulation during the frequency regulation period. is the frequency regulation capacity compensation price before correction, is the flywheel frequency modulation power at the current moment, The revised frequency adjustment mileage compensation price, To store energy in the flywheel and adjust the mileage; is the revised frequency regulation capacity compensation price, is the battery frequency modulation power at the current moment, The price of compensation for frequency adjustment mileage before correction. Frequency modulation for battery energy storage;

[0021]

[0022] Where: The electricity revenue from dispatching battery energy storage; η dc is the battery charge and discharge efficiency; ce is the grid electricity price, Charging power for the battery, is the battery discharge power;

[0023] 2) Establish constraints;

[0024] ①Battery energy storage aims to increase lifespan;

[0025] ②Battery energy storage aims to ensure grid frequency safety;

[0026] ③ Hybrid energy storage only participates in the frequency regulation service market;

[0027] ④ Other constraints, including those requiring battery energy storage to increase lifespan, ensuring grid frequency security, hybrid energy storage to participate only in the frequency regulation service market, frequency regulation power balance constraints, frequency regulation power constraints, SOC constraints, maximum charge and discharge cycle count constraints, and duration constraints for frequency regulation charge and discharge operations;

[0028] Step 4: Establish a hybrid energy storage efficiency index as an evaluation index. The hybrid energy storage efficiency index is mainly reflected in the frequency regulation performance, and the frequency regulation performance is evaluated by the AGC instructions that can be achieved by the frequency regulation assistance of the thermal power unit.

[0029] The mixed energy storage output in step 1 is specifically:

[0030] The difference between the AGC command and the output of the thermal power unit is used as the AGC command for the hybrid energy storage in this area, and then:

[0031] Where: is the hybrid energy storage frequency modulation power; P G,t Frequency modulation power for thermal power units; is the AGC instruction; P t en trading power for stored energy; It is the remaining power of hybrid energy storage at the current moment.

[0032] The battery output and flywheel output in step 1 are specifically:

[0033] The frequency modulation involves flywheel frequency modulation output and battery frequency modulation output, as well as the battery's charge and discharge energy trading to extend its life.

[0034] Where: The flywheel frequency modulation power; is the battery frequency modulation power, P is the charge and discharge power under the battery energy storage recovery SOC, dc,rate is the battery rated power, It is the frequency modulation power of hybrid energy storage.

[0035] In step 2, the optimal life of the battery energy storage is evaluated, specifically:

[0036] The throughput method is used to calculate battery life and build a battery energy storage life assessment model. The maximum number of charge and discharge cycles that can be achieved at the charge and discharge depth x is fitted into a polynomial. The relationship between the battery energy storage life assessment model is as follows:

[0037] N x =-12894x 5 +37860x 4 -42699x 3 +23528x 2 -6785.4x+12446.2; where: N x is the number of cycle life of battery energy storage under the state of charge and discharge depth x;

[0038] Calculate the maximum throughput corresponding to the battery's energy storage charge and discharge depth. Based on the maximum number of charge and discharge cycles under x and the amount of energy that can be absorbed in one charge and discharge cycle, calculate and obtain the total amount of energy that the battery can absorb when operating at x during its life cycle:

[0039] Where: E x is the total amount of electricity that the battery energy storage can handle when operating at x hours during its life cycle; E1 is the amount of electricity that the battery energy storage can handle in one charge and discharge cycle when operating at x hours; E dc,rate The rated capacity of the battery energy storage;

[0040] By quantifying the relationship between discharge depth, discharge range and equivalent cycle life, a battery energy storage life loss model based on real-time SOC state and equivalent life cycle number is constructed:

[0041] Where: N max is the number of energy storage life cycles at the maximum charge and discharge depth; x ref is the equivalent life cycle number; SOC dc,t The current SOC of the battery energy storage, SOC dc,ref is the equivalent SOC state, μ1 and μ2 are constants provided by the battery manufacturer;

[0042] Establish the equivalent life cycle number of battery energy storage at different depths of discharge (DOD) in each SOC range:

[0043] Where: n eq is the number of unit equivalent life cycles;

[0044] Through the battery energy storage life loss model, the relationship between SOC and unit transfer energy is obtained:

[0045] Where: e SOC,t Energy transferred per unit for the current SOC state; k p is a constant, and is obtained by fitting the relationship between the number of energy storage cycles and the depth of discharge using the actual operating data provided by the battery manufacturer.

[0046] The SOC dynamic balance quotation is performed in step 2, specifically:

[0047] The SOC dynamic equilibrium quotation coefficient is used to limit energy storage benefits to achieve the effect of constraining frequency regulation output. To ensure high power of flywheel energy storage, the flywheel energy storage non-limit range is set to 0.1-0.9. To ensure high capacity of battery energy storage, the battery energy storage non-limit range is set to 0.2-0.8. Based on the evaluation of the optimal life of battery energy storage, the optimal working state of energy storage SOC is set to 0.4-0.6;

[0048] The SOC dynamic balancing quotation is based on the real-time energy storage SOC dynamic response to control energy storage, which is:

[0049] When charging:

[0050]

[0051] In discharge state:

[0052] Where: SOC k,low , SOC k,high are the minimum and maximum thresholds under the optimal SOC state, is the adjustment coefficient during charging, SOC k,t is the SOC of energy storage at time t, is the adjustment coefficient during discharge.

[0053] The hybrid energy storage performance is characterized in step 2, specifically:

[0054] Frequency regulation performance is introduced to characterize the different frequency regulation characteristics of hybrid energy storage. The power characteristic coefficient is used to quantify the impact of the frequency regulation mileage of the frequency regulation resource during the frequency regulation process on the flywheel frequency regulation benefit. The capacity characteristic coefficient is used to characterize the impact of the frequency regulation demand capacity change of the frequency regulation resource during the frequency regulation process on the battery frequency regulation benefit.

[0055] The frequency regulation performance coefficients of flywheel energy storage and battery energy storage are established based on historical frequency regulation performance indicators, as shown in the following formula:

[0056]

[0057] Where: Kp is the frequency modulation factor under the historical frequency modulation performance index; k Kp is the historical frequency regulation performance index of each energy storage; sat Kp is the historical frequency modulation performance saturation index; min It is the minimum index of historical frequency modulation performance;

[0058] In the above formula, k represents the energy storage type. If k is replaced by dc, the above formula is the frequency regulation performance coefficient of battery energy storage. If k is replaced by fl, the above formula is the frequency regulation performance coefficient of flywheel energy storage.

[0059] The power characteristic coefficient of flywheel energy storage is:

[0060]

[0061] Where: δ fl is the flywheel relaxation factor; t fl is the flywheel frequency modulation response time; E fl,rate is the rated capacity of the flywheel energy storage; is the maximum output of the flywheel at the current moment, Δt is the time interval, E dc,rate The rated capacity of the battery energy storage;

[0062] Based on the power characteristic coefficient, the optimized compensation price for frequency regulation mileage at any time in the flywheel energy storage frequency regulation auxiliary service market is obtained as follows:

[0063] Where: The price for compensation of frequency adjustment mileage after correction; The price of compensation for frequency adjustment mileage before the correction;

[0064] The capacity characteristic coefficient of battery energy storage is:

[0065]

[0066] Where: δ dc is the battery relaxation factor; t dc FM response time for the battery; The maximum output of the battery at the current moment; The maximum output of the battery at the current moment; SOC dc,t The current SOC of the battery energy storage;

[0067] Based on the capacity characteristic coefficient, the optimized clearing price of frequency regulation at any time in the battery energy storage frequency regulation auxiliary service market is obtained as follows:

[0068] Where: The revised frequency regulation capacity compensation price; It is the price of frequency regulation capacity compensation before correction.

[0069] The underlying control strategy of the hybrid energy storage in step 2 is specifically as follows:

[0070] ① If flywheel energy storage is sufficient to meet frequency regulation requirements, the control strategy aims to improve battery life. Frequency regulation is performed solely on the flywheel, leveraging the advantages of power-type energy storage to meet frequency regulation requirements. Battery energy storage, based on a lifespan assessment model, participates in the electricity market and generates electricity revenue.

[0071] ② If the flywheel's remaining frequency regulation capacity is insufficient, the control strategy aims to participate in frequency regulation to ensure grid frequency security, with the dynamic balance of each energy storage SOC and the frequency regulation capacity of the hybrid energy storage as limitations. The battery energy storage is forced to participate in some small interference fluctuations, extending the overall frequency regulation capability of the hybrid energy storage.

[0072] The expressions for the hybrid energy storage frequency modulation output and battery energy storage new energy dispatch output in step 2 are as follows:

[0073] are 0-1 variables for hybrid energy storage charging and discharging, and the relationship between the two is:

[0074]

[0075] It is stipulated that battery energy storage can only work in charging state or discharging state at the same time;

[0076] The output of battery energy storage at time t is:

[0077] Where: P dc,t Total output for battery energy storage; The charging and discharging power of the battery involved in scheduling; The charging and discharging power of the battery participating in frequency modulation; A 0-1 variable to charge the battery; A 0-1 variable indicating battery discharge;

[0078] The battery energy storage response to new energy dispatch power at time t is:

[0079] Where: dispatching power for battery energy storage;

[0080] The total power of hybrid energy storage participating in new energy dispatch and frequency regulation at time t is:

[0081] Where: P t Wis the total output of hybrid energy storage; The charge and discharge power of the flywheel involved in scheduling; is a 0-1 variable for flywheel discharge; A 0-1 variable that charges the flywheel.

[0082] The constraints in step 3 are specifically:

[0083] ① Constraints on battery energy storage with the goal of increasing lifespan, specifically:

[0084] Battery energy storage bidding power constraints: At the current moment, the power of battery energy storage participating in the electric energy market and frequency regulation auxiliary service market must meet the maximum and minimum charging and discharging power and rated power constraints:

[0085]

[0086] Where: P dc,max is the remaining maximum frequency modulation power when the battery SOC limit is close to 0.9, P dc,min is the remaining maximum frequency modulation power when the battery SOC limit is close to 0.1, is the discharge power of the battery participating in the scheduling, is the frequency modulation power when the battery is discharged, P dc,rate is the battery rated power, is the charging power of the battery participating in the scheduling, FM power when charging the battery;

[0087] Battery energy storage capacity constraints:

[0088] Based on battery life assessment, set the optimal SOC limit capacity:

[0089] Where: E dc,t is the battery capacity at the current moment; Evaluate the optimal upper limit SOC for battery life; The optimal lower limit SOC for battery life evaluation; η dc The battery charging and discharging efficiency;

[0090] Battery energy storage cycle life constraint: obtained through the battery energy storage life loss model based on real-time SOC status and equivalent life cycle number;

[0091] ② Battery energy storage is constrained by the goal of ensuring grid frequency security, specifically:

[0092] Battery energy storage capacity constraints:

[0093] Where: SOC dc,max , SOC dc,min The maximum and minimum SOC states of the battery;

[0094] ③ Hybrid energy storage only participates in the frequency regulation service market, specifically:

[0095] Battery energy storage capacity constraints:

[0096]

[0097] Where: i is battery energy storage or flywheel energy storage; E i,t is the battery capacity at the current moment, SOC i,max is the maximum SOC value, SOC i,min is the minimum SOC value, E i,rate is the rated capacity, is the frequency modulation power during charging at the current moment, η i The charging and discharging efficiency of battery energy storage or flywheel energy storage;

[0098] ④Other constraints, specifically:

[0099] FM power balance constraints:

[0100]

[0101] FM power constraints:

[0102] Where: is the energy storage frequency modulation power during discharge at the current moment, The energy storage frequency modulation power during charging at the current moment, is the minimum frequency modulation power of energy storage during charging at the current moment, P k,rate is the energy storage rated power, The maximum frequency modulation power of energy storage during charging at the current moment;

[0103] SOC constraints:

[0104] Where: SOC k,min is the minimum value of energy storage SOC, SOC k,max is the maximum energy storage SOC, η k For energy storage charging and discharging efficiency, is the energy storage discharge power at the current moment, Energy storage charging power at the current moment;

[0105] Due to the characteristics of battery energy storage life, the operating duration is used as the switching charge and discharge constraint. The battery energy storage charge and discharge switching flexibility constraint is divided into the maximum charge and discharge cycle constraint and the charge and discharge duration constraint.

[0106] The maximum number of charge and discharge cycles is constrained to:

[0107] In the formula: σ is the charge and discharge symbol; k is the charge and discharge time; is the change of discharge state; To change to a discharge state; The charging state changes; is changed to charging state; N0 is the maximum number of charge and discharge cycles;

[0108] Frequency modulation charging and discharging operation duration constraints:

[0109] Where: T c 、T d It is the time limit for charging and discharging; is the time adjustment factor; TC and TD are the duration of charge and discharge; They are respectively changed into charging state and changed into discharging state; They are respectively the duration of charging and the duration of discharging;

[0110] The regulation performance in step 4 includes three factors: regulation rate, regulation accuracy and response time;

[0111] The evaluation index expression is as follows:

[0112] Where: It is an evaluation index to measure the regulation performance of the i-th unit during the j-th regulation process; and are the adjustment rate, accuracy and response time of the jth adjustment of the i-th unit respectively;

[0113] The frequency regulation performance evaluation of the AGC instructions that can be achieved by the thermal power unit frequency regulation assistance is carried out as follows:

[0114] ① FM rate

[0115] The regulation rate refers to the rate at which the unit responds to the setpoint command, which is divided into rising rate and falling rate. The calculation process of the j-th regulation rate of the i-th unit is as follows:

[0116] The actual regulation rate calculation formula is as follows:

[0117]

[0118] Where: v i,j is the jth actual regulation rate of unit i, in MW / minute; P Ei,j is the output at the end of the response process, in MW; P Si ,j is the output when it starts to move, in MW; T Ei,j It's time to end, T Si,j It's time to start, Pdi,j is the critical power of the start-stop grinding mill of the jth adjustment, in MW; T di,j is the actual time consumed by the jth adjustment of starting and stopping the grinding mill;

[0119] If the unit does not meet the typical AGC setpoint control process, that is, the unit fails to enter the target dead zone, the regulation rate is the unit output at the end of the instruction minus the active power change at the time of crossing the dead zone, divided by the required time;

[0120] The calculation formula for regulating rate regulation index is:

[0121]

[0122] Where: v N,i is the standard regulation rate of unit i, in MW / min;

[0123] ②Adjustment accuracy

[0124] The regulation accuracy refers to the difference between the actual output and the set point output after the unit response is stable. The method to obtain it is: integrate the absolute value of the difference between the actual output and the command, and then divide the integral by the integration time to obtain the value from T Si,j to T Ei,j The adjustment deviation of the time period is as follows:

[0125]

[0126] Where: P i,j (t) is the actual output during the period, P i,j Obtaining a setpoint command value for the period;

[0127] If the unit fails to enter the target dead zone, the regulation accuracy is the minimum value of the deviation between the actual output and the target output during the period from the moment the unit steps out of the dead zone in the same direction to the moment the command ends:

[0128]

[0129] Where: The allowable deviation of regulation is 1% of the rated active power of the unit;

[0130] ③Response time

[0131] Response time refers to the time it takes for the unit to reliably step out of the frequency regulation dead zone consistent with the regulation direction at the original output point after the EMS system issues a command. The formula is as follows:

[0132]

[0133] Where: is the time for the i-th unit to leave the initial adjustment dead zone during the j-th adjustment process, T1 is the time to leave the adjustment dead zone, T0 is the time when the unit starts to output, is the time when the i-th unit leaves the last adjustment dead zone during the j-th adjustment process, T6 is the time when it leaves the grinding stop point, T5 is the time when the AGC control program issues a new set point command to the unit, and t i,j is the response time of the jth AGC unit of the i-th unit; the standard AGC response time of thermal power units is less than 1 minute;

[0134] The above and If the calculated value is less than 0.1, it is taken as 0.1 and the evaluation index is used. Calculation of and If one of the calculated values ​​is greater than 2, then none of the three calculated values ​​will be evaluated. calculation; assessment and If the calculated values ​​are all within the range of [0.1, 2], the evaluation index is Calculation.

[0135] Through the above design scheme, the present invention can bring the following beneficial effects:

[0136] The present invention uses real-time SOC to establish dynamic equilibrium quotation and each energy storage performance characterization as the upper model, and at the same time proposes the optimal life assessment of energy-type energy storage, constructs an energy storage charge and discharge switching model, limits the frequent switching of energy-type energy storage, and extends its life; the underlying model constructs the power-type energy storage frequency regulation limit standard, introduces multi-objective constraints, and proposes a hybrid energy storage operation plan suitable for all scenarios. The evaluation indicators are used to evaluate the frequency regulation effect of the proposed frequency regulation control model from the perspective of regulation rate, accuracy and response time, which improves the net profit, reduces battery life loss and frequency offset, and is conducive to increasing the frequency regulation reliability and sustainability of regional energy storage; it has the advantages of scientific and reasonable methods, strong applicability, and good effects.

[0137] The present invention effectively solves the problem in the prior art that the mutual influence between the life loss of battery energy storage and the frequency regulation performance of each energy storage is not fully considered, the frequency regulation mode of hybrid energy storage cannot be maintained on a long time scale, and the value law and regulatory role of hybrid energy storage are not fully reflected. BRIEF DESCRIPTION OF THE DRAWINGS

[0138] The present invention will be further described below with reference to the accompanying drawings and specific embodiments:

[0139] Figure 1 A schematic diagram of a hybrid energy storage frequency modulation structure in a hybrid energy storage life economy and frequency modulation limit zoning control method according to the present invention;

[0140] Figure 2 This is a double-layer control framework diagram of hybrid energy storage in a hybrid energy storage life economy and frequency modulation limit partition control method according to the present invention;

[0141] Figure 3 This is a flow chart of a hybrid energy storage control strategy in a hybrid energy storage life economy and frequency regulation limit zoning control method according to the present invention;

[0142] Figure 4 The frequency modulation power diagram of Model 1 and Model 2 in the example analysis of the present invention;

[0143] Figure 5 The hybrid energy storage power diagram of Model 1 and Model 2 in the example analysis of the present invention;

[0144] Figure 6 This is the SOC dynamic balance quotation diagram in the example analysis of the present invention;

[0145] Figure 7 The SOC change diagram of Model 1 and Model 2 in the example analysis of the present invention;

[0146] Figure 8 This is a diagram showing the frequency modulation output and SOC changes of different energy storage configuration schemes in the example analysis of the present invention. DETAILED DESCRIPTION

[0147] The present invention will be further described in detail below in conjunction with specific embodiments. The following examples are used to illustrate the present invention, but it should be understood that the scope of protection of the present invention is not limited by the specific embodiments.

[0148] like Figures 1 to 3 As shown, the present invention provides a zoning control method based on the life economy of hybrid energy storage and frequency regulation limit. First, a hybrid energy storage combined with frequency regulation system is established. Second, a hybrid energy storage two-layer optimization allocation strategy is constructed. Then, the real-time state optimization layer and the frequency regulation zoning control layer are designed respectively. Finally, a hybrid energy storage transaction decision model is constructed. By designing the constraint conditions of the zoning control layer, the model is solved to finally obtain the hybrid energy storage frequency regulation output and battery power output. The specific steps are as follows:

[0149] Step 1: Establish a hybrid energy storage combined with frequency regulation system

[0150] A hybrid energy storage combined frequency regulation system is established to realize the distribution of AGC commands between thermal power units and hybrid energy storage. The AGC commands distributed by the hybrid energy storage are then divided into the flywheel frequency regulation output and battery frequency regulation output participating in frequency regulation. The specific relationship between the battery's charge and discharge energy trading to extend its life is as follows:

[0151] Where: is the hybrid energy storage frequency modulation power; PG,t Frequency modulation power for thermal power units; is the AGC instruction; P t en trading power for stored energy; The remaining power of the hybrid energy storage at the current moment; The flywheel frequency modulation power; is the battery frequency modulation power, Restore the charge and discharge power under SOC for battery energy storage.

[0152] See the relationship diagram described in step 1. Figure 1 .

[0153] Step 2: Construct a two-layer optimization allocation strategy for hybrid energy storage;

[0154] First, design the real-time status optimization layer;

[0155] The first step is to establish a battery life assessment model by fitting a polynomial of the maximum number of charge and discharge cycles that the battery storage can achieve at the charge and discharge depth x to historical data:

[0156] N x =-12894x 5 +37860x 4 -42699x 3 +23528x 2 -6785.4x+12446.2 (4); Where: N x is the number of cycles of battery energy storage when the depth of charge and discharge is x; the total amount of electricity that the battery can handle when operating at x during its life cycle can then be calculated:

[0157]

[0158] Where: E x is the total amount of electricity that the battery energy storage can handle when operating at x hours during its life cycle; E1 is the amount of electricity that the battery energy storage can handle in one charge and discharge cycle when operating at x hours; E dcrate is the rated capacity of the battery energy storage; in order to solve the problem that different discharge intervals of the battery energy storage discharge cycle will also reduce the energy storage life, a battery life loss model considering the real-time SOC state and the number of equivalent life cycles is proposed:

[0159] Where: n eq The unit equivalent life cycle number.

[0160] Based on the real-time SOC state and the battery life loss model of equivalent life cycle, the relationship between SOC and unit transfer energy is obtained.

[0161] Where: e SOC,t Energy transferred per unit for the current SOC state; k p is a constant and can be obtained by fitting the relationship between the number of energy storage cycles and the depth of discharge using the actual operating data provided by the battery manufacturer.

[0162] The second step is to design a SOC dynamic equilibrium quotation strategy, which is to compare the real-time SOC state of the energy storage with the optimal SOC working state of the energy storage, and set the optimal SOC working state of the battery energy storage to 0.4-0.6, and the optimal SOC working state of the flywheel energy storage to 0.1-0.9. When the AGC instruction is in the charging state, when the energy storage SOC state is less than the minimum limit of the SOC optimal working state, the energy storage power demand is positively correlated with the frequency regulation state, and takes priority over the energy storage charging, while participating in the frequency regulation service, taking into account the recovery of the energy storage SOC; and when the SOC state of the energy storage is greater than the minimum limit of the SOC optimal working state and less than the maximum limit of the SOC optimal working state, the energy storage is in the optimal state, and the energy storage cost and benefit caused by the SOC are not considered. When the SOC state is greater than the maximum limit under the optimal state, the energy storage power demand is negatively correlated with the frequency regulation state, and continuous charging will cause the energy storage to reach an over-limit state. Therefore, at this stage, coordinated cooperation between hybrid energy storage is required. Conversely, the situation is similar under the discharge state. Specifically:

[0163] Discharge status:

[0164]

[0165] Charging status:

[0166] Where: SOC k,low , SOC k,high These are the minimum and maximum thresholds under the optimal SOC state.

[0167] The third step is to establish the performance characterization of hybrid energy storage. The frequency regulation benefits of hybrid energy storage are mainly frequency regulation mileage and frequency regulation capacity benefits. In order to solve the problem of reasonable compensation of fast and slow frequency regulation resources, the frequency regulation performance is introduced to characterize the different frequency regulation characteristics of hybrid energy storage. Flywheel energy storage has high power, and the power characteristic coefficient is used to quantify the impact of frequency regulation mileage on flywheel frequency regulation benefits; battery energy storage has high capacity, and the capacity characteristic coefficient is used to characterize the impact of frequency regulation demand capacity changes on battery frequency regulation benefits. The performance coefficients of flywheel energy storage and battery energy storage are established based on historical frequency regulation performance indicators, as shown in the following formula:

[0168] Where: Kp is the frequency modulation factor under the historical frequency modulation performance index; kis the historical frequency regulation performance index of each energy storage; k is the energy storage type; Kp sat Kp is the historical frequency modulation performance saturation index; min It is the minimum indicator of historical frequency modulation performance.

[0169] The energy storage type k in the formula can be replaced. Replacing k with dc indicates battery energy storage, and replacing k with fl indicates flywheel energy storage.

[0170] The power characteristic coefficient of flywheel energy storage expresses the frequency regulation response speed of the system. Based on the characteristics of flywheel energy storage, the pricing mechanism is mainly optimized through time scale and historical average frequency regulation performance.

[0171] Where: δ fl is the flywheel relaxation factor; t fl is the flywheel frequency modulation response time; E fl,rate is the rated capacity of the flywheel energy storage; is the maximum output of the flywheel at the current moment; E dc,rate The rated capacity of the battery energy storage;

[0172] Based on the power characteristic coefficient, the optimized compensation price for frequency regulation mileage at any time in the flywheel energy storage frequency regulation auxiliary service market is:

[0173] Where: The price for compensation of frequency adjustment mileage after correction; This is the price for compensation for frequency adjustment mileage before correction.

[0174] The capacity characteristic coefficient of battery energy storage is an expression of the system's frequency regulation response capacity, reflecting the impact of changes in the capacity of battery energy storage participating in frequency regulation demand on the frequency regulation price in the frequency regulation ancillary service market.

[0175] Where: δ dc is the battery relaxation factor; t dc FM response time for the battery; The maximum output of the battery at the current moment, SOC dc,t The current SOC of the battery energy storage;

[0176] The optimized clearing price of the battery energy storage frequency regulation auxiliary service market at any time based on the capacity relaxation coefficient is:

[0177] Where: The revised frequency regulation capacity compensation price; It is the price of frequency regulation capacity compensation before correction.

[0178] Secondly, the frequency modulation partition control layer is designed;

[0179] The frequency modulation control center needs to follow the following principles during the frequency modulation signal distribution process: 1) The output of the coordinated system should minimize the deviation from the AGC signal; 2) The flywheel energy storage can frequently switch between charge and discharge states; 3) The battery should not frequently switch between charge and discharge states.

[0180] Hybrid energy storage can participate in frequency regulation while restoring SOC through electric energy charging and discharging. Specifically: ① When the flywheel energy storage is sufficient to meet the frequency regulation demand, the control strategy takes improving battery life as the main goal, and uses the flywheel alone for frequency regulation output, so that it can give full play to the advantages of power-type energy storage and quickly meet the frequency regulation demand. Battery energy storage participates in the electric energy market based on the optimal life assessment model in this article and obtains electric energy benefits. ② When the flywheel's remaining frequency regulation capacity is insufficient, the control strategy takes participating in frequency regulation to ensure grid frequency security as the main goal, and is limited by the dynamic balancing strategy of each energy storage SOC and the frequency regulation capacity of the hybrid energy storage. Battery energy storage is forced to participate in some small interference fluctuations, extending the overall frequency regulation capability of the hybrid energy storage.

[0181] Combine Figure 1 With the proposed underlying control strategy, the hybrid energy storage frequency regulation output and battery energy storage new energy dispatch output are expressed as follows:

[0182] are 0-1 variables for hybrid energy storage charging and discharging, and the relationship between the two is:

[0183]

[0184] It is stipulated that at the same time, the main goal of controlling battery energy storage to ensure the safety of grid frequency is that battery energy storage can only operate in charging or discharging state.

[0185] The output of battery energy storage at time t is:

[0186] Where: P dc,t Total output for battery energy storage; The charging and discharging power of the battery involved in scheduling; The charging and discharging power of the battery participating in frequency modulation; A 0-1 variable to charge the battery; A 0-1 variable indicating battery discharge;

[0187] The battery energy storage response to new energy dispatch power at time t is:

[0188] Where: Dispatching power for battery energy storage.

[0189] The total power of hybrid energy storage participating in new energy dispatch and frequency regulation at time t is:

[0190] Where: P t W is the total output of hybrid energy storage; It is the charging and discharging power of the flywheel involved in scheduling.

[0191] Step 3: Construct a hybrid energy storage transaction decision model;

[0192] The first step is to construct the objective function that maximizes the net benefit of frequency modulation, specifically:

[0193] Where: is the frequency modulation benefit at the current moment; C t neg is the electricity revenue at the current moment; C cost,t is the total cost at the current moment.

[0194] The total cost in the objective function is specifically: the total cost is composed of the frequency regulation capacity cost of energy storage and the frequency regulation mileage cost of energy storage:

[0195] Where: The cost of frequency regulation capacity for hybrid energy storage; The mileage cost of hybrid energy storage frequency regulation.

[0196] The frequency regulation capacity cost of energy storage includes the opportunity cost caused by the energy storage participating in the frequency regulation auxiliary service at time t instead of participating in the electricity energy market and the initial investment cost of the energy storage, which is not taken into account under joint clearing.

[0197] Where: Regulating opportunity costs for the market; is the initial investment cost of hybrid energy storage.

[0198] The initial investment cost of hybrid energy storage is composed of the initial investment costs of flywheel energy storage and battery energy storage:

[0199] Where: Initial investment cost for battery energy storage; is the initial investment cost of flywheel energy storage; c cap is the unit capacity cost of battery energy storage; s is the number of dispatches, and the time scale is seconds; r dc is the discount rate of energy storage; Tk,float is the floating charge life of energy storage; c pcs is the flywheel unit power cost; P fl,rate is the flywheel rated power; c fess is the cost of a single flywheel device; c p is the flywheel unit power operation and maintenance cost; c e The unit capacity operation and maintenance cost of the flywheel is almost 0.

[0200] The mileage cost of energy storage frequency regulation includes the energy loss cost caused by continuous charging and discharging of energy storage and the cycle life loss cost caused by the depth of energy storage discharge.

[0201] Where: Energy loss cost caused by charging and discharging; The cost of battery energy storage cycle life is reduced.

[0202] The life depreciation cost of hybrid energy storage refers to the fact that during actual operation, battery energy storage is affected by its characteristics. Charging and discharging will reduce its life, resulting in life depreciation costs. At the same time, its long-term operation will also lead to replacement costs. By simplifying it to the depreciation cost of each unit of battery energy storage in each settlement cycle, the original cost is replaced by the depreciation cost, including the life depreciation of participating in the electric energy market and the life depreciation of participating in the frequency regulation auxiliary service market. Flywheel energy storage has a small failure rate and capacity loss during its life, so it does not require additional replacement costs and maintenance costs.

[0203] Where: The life loss cost of batteries in different markets; op is the loss cost coefficient; η dc It is the battery charge and discharge efficiency.

[0204] The energy loss cost of hybrid energy storage charging and discharging is the cost of electricity loss caused by the charging and discharging efficiency not being 1 when the flywheel energy storage exchanges energy with the system. The expression is:

[0205] Where: Energy loss costs of hybrid energy storage for charging and discharging; is the energy loss cost; η fl is the flywheel charge and discharge efficiency.

[0206] The benefits in the objective function are specifically: the frequency regulation benefits obtained by hybrid energy storage participating in frequency regulation and the electricity benefits of hybrid energy storage scheduling. The frequency regulation benefits of hybrid energy storage can be divided into the frequency regulation benefits obtained by flywheel participation in frequency regulation and the frequency regulation benefits obtained by battery participation in frequency regulation:

[0207] Where Ccap for the net benefit of hybrid energy storage; is the frequency modulation benefit at the current moment; C t neg is the electricity revenue at the current moment; is the FM power at the current moment; To store energy in the flywheel and adjust the mileage; To store energy in the battery and increase mileage.

[0208] The electricity revenue from hybrid energy storage scheduling only includes the electricity revenue from battery energy storage scheduling:

[0209] Where: The electricity revenue from dispatching battery energy storage; η dc The battery charging and discharging efficiency;

[0210] The second step is to design constraints. Since hybrid energy storage needs to participate in the auxiliary frequency regulation market and the electric energy market, and the battery energy storage life is shorter than that of flywheel energy storage, the frequency regulation limit of flywheel energy storage is introduced to describe the trading boundary between the two markets and battery energy storage.

[0211] Compared with battery energy storage, flywheel energy storage has a higher reaction rate to meet the grid frequency security. When only flywheel energy storage participates in frequency regulation, flywheel energy storage can meet the grid frequency fluctuation and maintain the grid frequency within the range allowed by the system. The maximum equivalent load fluctuation is called the flywheel energy storage frequency regulation limit, which is denoted as F. N .

[0212] When the maximum frequency regulation capacity of flywheel energy storage alone cannot meet the frequency regulation power requirements, battery energy storage will be needed to meet the frequency regulation power shortfall, even if the battery energy storage lifespan is significantly depleted. As the definition of the flywheel frequency regulation limit indicates, calculating the flywheel frequency regulation limit is to determine the maximum equivalent load fluctuation that the flywheel energy storage can withstand at any given moment.

[0213] F N =min(P fl,rate ,P fl,re ) (33);

[0214]

[0215] Where: P fl,re is the remaining frequency modulation power of the flywheel; SOC fl,t is the current SOC of the flywheel; SOC fl,max The maximum SOC state of the flywheel; SOC fl,min is the minimum SOC state of the flywheel; η fl is the flywheel charge and discharge efficiency.

[0216] The design of the frequency regulation partition control layer shows that different objectives are used to constrain different intervals: ① When the grid frequency fluctuation meets the set power-type energy storage frequency regulation, the main goal is to improve the life of the battery energy storage, including the frequency regulation constraints of the hybrid energy storage, the SOC state constraints of the hybrid energy storage, and the upward and downward frequency regulation constraints of the battery energy storage.

[0217] Battery energy storage bidding power constraints: At the current moment, the power of battery energy storage participating in the electric energy market and frequency regulation auxiliary service market meets the maximum, minimum charging and discharging power and rated power constraints.

[0218] Where: P dc,max is the remaining maximum frequency modulation power when the battery SOC limit is close to 0.9, P dc,min It is the maximum remaining frequency modulation power when the battery SOC limit is close to 0.1.

[0219] Battery energy storage capacity constraint: Set the optimal SOC limit capacity based on battery life assessment.

[0220] Where: E dc,t is the battery capacity at the current moment; Evaluate the optimal upper limit SOC for battery life; Optimal lower limit SOC for battery life evaluation.

[0221] Battery energy storage cycle life constraint: The battery energy storage cycle life constraint is given by step 2.

[0222] ② When the grid frequency fluctuation exceeds the set flywheel energy storage frequency regulation limit, with the main goal of ensuring grid frequency safety, the hybrid energy storage power station participating in the frequency regulation auxiliary service market needs to consider the frequency regulation capacity limitations of flywheel energy storage and battery energy storage, as well as their charging and discharging capacity constraints.

[0223] Battery energy storage capacity constraints:

[0224] Where: SOC dc,max , SOC dc,min The maximum and minimum SOC states of the battery.

[0225] ③ Hybrid energy storage only participates in the frequency regulation service market. When the grid frequency fluctuation exceeds the set hybrid energy storage frequency regulation limit, with the main goal of ensuring grid frequency safety, all hybrid energy storage is only used in the frequency regulation auxiliary service market, increasing the opportunity cost caused in the objective function.

[0226] Battery energy storage capacity constraints:

[0227]

[0228] ④Other constraints, specifically:

[0229] FM power balance constraints:

[0230]

[0231] FM power constraints:

[0232]

[0233] SOC constraints:

[0234]

[0235] Due to the characteristics of battery energy storage life, frequent control of energy storage for charge and discharge switching is not conducive to reducing life attenuation. Therefore, this paper uses the operating duration as the switching charge and discharge constraint to improve the decision-making transformation of battery energy storage for potential future situations. The battery energy storage charge and discharge switching flexibility constraints are divided into the maximum charge and discharge cycle number constraint and the charge and discharge duration constraint.

[0236] Constraints on the maximum number of charge and discharge cycles:

[0237] In the formula: σ is the charge and discharge symbol; k is the charge and discharge time; is the change of discharge state; To change to a discharge state; The charging status changes; To change to charging state;

[0238] Frequency modulation charging and discharging operation duration constraints:

[0239] From the perspective of the energy storage element itself, the duration of its charge and discharge operation is affected by its capacity-to-power ratio and the current state of charge. However, when participating in frequency modulation operation, in order to avoid the impact of frequent switching on the energy storage life, a strict charge and discharge duration constraint model is proposed. Its expression is:

[0240] Where: T c 、T d It is the time limit for charging and discharging; is the time adjustment factor; TC and TD are the duration of charge and discharge.

[0241] The third step is to construct a hybrid energy storage efficiency index. The hybrid energy storage efficiency index is mainly reflected in the frequency regulation performance. The frequency regulation performance is evaluated by evaluating the AGC instructions that can be achieved by the thermal power unit frequency regulation assistance. The regulation performance evaluation is mainly reflected in the comprehensive evaluation index of frequency regulation performance by considering the three factors of regulation rate, regulation accuracy and response time. The comprehensive evaluation index expression is as follows:

[0242] K P,i =K 1,i K 2,i K 3,i (44); where: K P,i To measure the degree of regulation performance during the i-th regulation process; K 1,i , K 2,i and K 3,i are the adjustment rate, accuracy and response time of the i-th adjustment of the system frequency modulation respectively.

[0243] The frequency regulation performance evaluation of the AGC instructions that can be achieved by the thermal power unit frequency regulation assistance is carried out as follows:

[0244] ① FM rate

[0245] The regulation rate refers to the rate at which the unit responds to the setpoint command, which can be divided into rising rate and falling rate. The calculation process of the j-th regulation rate assessment index of the i-th unit is as follows:

[0246] The actual regulation rate calculation formula is as follows:

[0247]

[0248] Where: v i,j is the jth regulation rate of unit i (MW / min), P Ei,j is the output (MW) at the end of the response process, P Si ,j is the output (MW) when it starts to move, T Ei,j It's time to end, T Si,j It's time to start, P di,j is the critical power of the start-stop grinding mill of the jth adjustment (MW), T di,j It is the actual time consumed by adjusting the start and stop of the grinding mill for the jth time.

[0249] When the unit does not meet the typical AGC set point control process (fails to enter the target dead zone), the adjustment rate is the unit output at the end of the instruction minus the active change of the output at the time of crossing the dead zone divided by the required time.

[0250] The calculation formula for regulating rate regulation index is:

[0251]

[0252] If K1 i If the calculated value of ,j is less than 0.1, it is taken as 0.1.

[0253] Where: v N,i is the standard regulation rate of unit i, in MW / minute. If the unit enters deep regulation condition below 50% of rated output, the AGC regulation rate is required to be 80% of the normal regulation.

[0254] ②Adjustment accuracy

[0255] The regulation accuracy refers to the difference between the actual output and the set point output after the unit response is stable. Integrate the absolute value of the difference between the actual output and the command, and then divide the integral by the integration time to obtain the value from T Si,j to T Ei,j The adjustment deviation amount for the time period.

[0256] Where: P i,j (t) is the actual output during the period, P i,j If the unit fails to enter the target dead zone, the regulation accuracy is the minimum deviation between the actual output and the target output during the period from the moment the unit exits the dead zone in the same direction to the moment the command ends.

[0257] Where: The allowable deviation of regulation is 1% of the rated active power of the unit. When the unit enters the deep regulation condition with the rated output below 50%, the AGC regulation accuracy requirement is 125% of the normal regulation.

[0258] ③Response time

[0259] Response time refers to the time it takes for the unit to reliably step out of the frequency regulation dead zone consistent with the regulation direction at the original output point after the EMS system issues a command.

[0260]

[0261] The AGC response time of a thermal power unit should be less than 1 minute. When the unit enters deep regulation mode with rated output below 50%, the AGC response time is 125% of that of a conventional unit.

[0262] The above and If the calculated value is less than 0.1, it is taken as 0.1 and the evaluation index is used. Calculation of and If one of the calculated values ​​is greater than 2, then none of the three calculated values ​​will be evaluated. calculation; assessment and If the calculated values ​​are all within the range of [0.1, 2], the evaluation index is Calculation.

[0263] The process described in step 3 is shown in Figure 3 ;

[0264] The fourth step is to use the control method of the present invention to simulate and analyze a specific example:

[0265] The rated capacity of the unit is set to 330MW, the battery energy storage system parameters are 5MW / 2.5MWh, the charge and discharge efficiency is 0.9, the flywheel energy storage system parameters are 5MW / 0.5MWh, the charge and discharge efficiency is 0.85, and the energy storage SOC is 0.5. Simulation analysis is performed in the MATLAB / Simulink simulation environment.

[0266] In order to verify the advantages of the solution of the present invention, Model 1 is set as the response model proposed by the present invention that gives economy and SOC recovery; Model 2 only considers the frequency regulation economy without considering various constraints of battery energy storage life. Figure 4 It can be seen that Model 1 is more effective in following AGC instructions and has a better degree of following. The frequency deviation of Model 1 is better than that of Model 2, and the practicality of Model 1 is more obvious. Figure 5 It can be seen that the flywheel output of model 1 is more obvious, which reflects the high power and long life of flywheel energy storage, and solves the problem of frequent charging and discharging of battery energy storage and shortening its life. Figure 6 It can be seen that compared with the frequent fluctuations of flywheel energy storage, the life loss of battery energy storage is effectively reduced, reflecting the long life and cycle life characteristics of flywheel energy storage and the large capacity characteristics of battery energy storage. Figure 7 It can be seen that compared with model 2, model 1 has more concentrated fluctuations and is more gentle in life assessment, which is more conducive to long-term frequency regulation and protection of battery energy storage from exceeding the SOC limit. The present invention designs four schemes: scheme 1 has no energy storage, scheme 2 and scheme 3 are single battery energy storage and single flywheel energy storage frequency regulation schemes with the same total configuration power, respectively, and scheme 4 is a hybrid energy storage scheme. Figure 8 It can be seen that Scheme 4 has the best performance in terms of frequency regulation performance improvement. Compared with the scheme containing only flywheel and battery, the hybrid energy storage scheme has a significant effect on improving frequency regulation performance.

[0267] The embodiments of the present invention are not exhaustive and do not limit the scope of protection of the claims. Those skilled in the art can conceive of other substantially equivalent alternatives based on the inspiration gained from the embodiments of the present invention without creative work, and all of them are within the scope of protection of the present invention.

Claims

1. A method for controlling hybrid energy storage life economy and frequency modulation limit zoning, characterized by: The following steps are included and are performed in sequence: Step 1: Establish a hybrid energy storage combined frequency regulation system and obtain hybrid energy storage output, battery output, and flywheel output; Step 2: Formulate a two-layer optimization allocation model for hybrid energy storage to assist thermal power unit frequency regulation, wherein the two-layer optimization allocation model includes a hybrid energy storage upper-layer scheduling model and a hybrid energy storage lower-layer control strategy; 1) The hybrid energy storage upper-layer scheduling model performs real-time state optimization of the hybrid energy storage, including: ① Establish a battery life loss model based on real-time energy storage state of charge (SOC) and equivalent life cycles to evaluate the optimal life of battery energy storage; ②Provide SOC dynamic balance quotation; ③ Characterize the hybrid energy storage performance; 2) Based on the established hybrid energy storage underlying control strategy, combined with AGC instructions, thermal power unit output, and the real-time optimization status of hybrid energy storage, frequency modulation and zoning control are performed to obtain hybrid energy storage frequency modulation output and battery energy storage new energy dispatch output; Step 3: Establish a hybrid energy storage transaction decision model and obtain a hybrid energy storage operation plan suitable for all scenarios by solving the model's objective function; 1) The objective function is: Where: is the frequency modulation benefit at the current moment; C t neg is the electricity revenue at the current moment; C cost,t is the total cost at the current moment; in, Where: The cost of frequency regulation capacity for hybrid energy storage; The mileage cost of frequency regulation for hybrid energy storage; Where: The capacity and mileage subsidy income obtained by flywheel energy storage participating in frequency regulation during the frequency regulation period. The capacity and mileage subsidy income obtained by battery energy storage participating in frequency regulation during the frequency regulation period. is the frequency regulation capacity compensation price before correction, is the flywheel frequency modulation power at the current moment, The revised frequency adjustment mileage compensation price, To store energy in the flywheel and adjust the mileage; is the revised frequency regulation capacity compensation price, is the battery frequency modulation power at the current moment, The price of compensation for frequency adjustment mileage before correction. Frequency modulation for battery energy storage; Where: The electricity revenue from dispatching battery energy storage; η dc is the battery charge and discharge efficiency; ce is the grid electricity price, Charging power for the battery, is the battery discharge power; 2) Establish constraints; ①Battery energy storage aims to increase lifespan; ②Battery energy storage aims to ensure grid frequency safety; ③ Hybrid energy storage only participates in the frequency regulation service market; ④ Other constraints, including battery energy storage's goal of increasing lifespan, battery energy storage's goal of ensuring grid frequency security, hybrid energy storage's participation in the frequency regulation service market only, frequency regulation power balance constraints, frequency regulation power constraints, SOC constraints, maximum charge and discharge cycle count constraints, and frequency regulation charge and discharge operation duration constraints; Step 4: Establish a hybrid energy storage efficiency index as an evaluation index. The hybrid energy storage efficiency index is mainly reflected in the frequency regulation performance, and the frequency regulation performance is evaluated by the AGC instructions that can be achieved by the frequency regulation assistance of the thermal power unit.

2. The method for controlling hybrid energy storage life economy and frequency modulation limit zoning according to claim 1 is characterized by: The mixed energy storage output in step 1 is specifically: The difference between the AGC command and the output of the thermal power unit is used as the AGC command for regional hybrid energy storage, and then: Where: is the hybrid energy storage frequency modulation power; P G,t Frequency modulation power for thermal power units; is the AGC instruction; P t en trading power for stored energy; It is the remaining power of hybrid energy storage at the current moment.

3. The method for controlling hybrid energy storage life economy and frequency modulation limit zoning according to claim 1 is characterized by: The battery output and flywheel output in step 1 are specifically: The frequency modulation involves flywheel frequency modulation output and battery frequency modulation output, as well as the battery's charge and discharge energy trading to extend its life. Where: The flywheel frequency modulation power; is the battery frequency modulation power, P is the charge and discharge power under the battery energy storage recovery SOC, dc,rate is the battery rated power, It is the hybrid energy storage frequency modulation power.

4. The method of claim 1, wherein the method is characterized by: In step 2, the optimal life of the battery energy storage is evaluated, specifically: The throughput method is used to calculate battery life and build a battery energy storage life assessment model. The maximum number of charge and discharge cycles that can be achieved at the charge and discharge depth x is fitted into a polynomial. The relationship between the battery energy storage life assessment model is as follows: N x =-12894x 5 +37860x 4 -42699x 3 +23528x 2 -6785.4x+12446.2; where: N x is the number of cycle life of battery energy storage under the state of charge and discharge depth x; Calculate the maximum throughput corresponding to the battery's energy storage charge and discharge depth. Based on the maximum number of charge and discharge cycles under x and the amount of energy that can be absorbed in one charge and discharge cycle, calculate and obtain the total amount of energy that the battery can absorb when operating at x during its life cycle: Where: E x is the total amount of electricity that the battery energy storage can handle when operating at x hours during its life cycle; E1 is the amount of electricity that the battery energy storage can handle in one charge and discharge cycle when operating at x hours; E dc,rate The rated capacity of the battery energy storage; By quantifying the relationship between discharge depth, discharge range and equivalent cycle life, a battery energy storage life loss model based on real-time SOC state and equivalent life cycle number is constructed: Where: N max is the number of energy storage life cycles at the maximum charge and discharge depth; x ref is the equivalent life cycle number; SOC dc,t The current SOC of the battery energy storage, SOC dc,ref is the equivalent SOC state, μ1 and μ2 are constants provided by the battery manufacturer; Establish the equivalent life cycle number of battery energy storage at different depths of discharge (DOD) in each SOC range: Where: n eq is the number of unit equivalent life cycles; Through the battery energy storage life loss model, the relationship between SOC and unit transfer energy is obtained: Where: e SOC,t Energy transferred per unit for the current SOC state; k p is a constant, and is obtained by fitting the relationship between the number of energy storage cycles and the depth of discharge using the actual operating data provided by the battery manufacturer.

5. The method of claim 1, wherein the method is characterized by: The SOC dynamic balance quotation is performed in step 2, specifically: The SOC dynamic equilibrium quotation coefficient is used to limit energy storage benefits to achieve the effect of constraining frequency regulation output. To ensure high power of flywheel energy storage, the flywheel energy storage non-limit range is set to 0.1-0.

9. To ensure high capacity of battery energy storage, the battery energy storage non-limit range is set to 0.2-0.

8. Based on the evaluation of the optimal life of battery energy storage, the optimal working state of energy storage SOC is set to 0.4-0.6; The SOC dynamic balancing quotation is based on the real-time energy storage SOC dynamic response to control energy storage, which is: When charging: In discharge state: Where: SOC k,low , SOC k,high are the minimum and maximum thresholds under the optimal SOC state, is the adjustment coefficient during charging, SOC k,t is the SOC of energy storage at time t, is the adjustment coefficient during discharge.

6. The method of claim 1, wherein the method is characterized by: The hybrid energy storage performance is characterized in step 2, specifically: Frequency regulation performance is introduced to characterize the different frequency regulation characteristics of hybrid energy storage. The power characteristic coefficient is used to quantify the impact of the frequency regulation mileage of the frequency regulation resource during the frequency regulation process on the flywheel frequency regulation benefit. The capacity characteristic coefficient is used to characterize the impact of the frequency regulation demand capacity change of the frequency regulation resource during the frequency regulation process on the battery frequency regulation benefit. The frequency regulation performance coefficients of flywheel energy storage and battery energy storage are established based on historical frequency regulation performance indicators, as shown in the following formula: Where: Kp is the frequency modulation factor under the historical frequency modulation performance index; k Kp is the historical frequency regulation performance index of each energy storage; sat Kp is the historical frequency modulation performance saturation index; min It is the minimum index of historical frequency modulation performance; In the above formula, k represents the energy storage type. If k is replaced by dc, the above formula is the frequency regulation performance coefficient of battery energy storage. If k is replaced by fl, the above formula is the frequency regulation performance coefficient of flywheel energy storage. The power characteristic coefficient of flywheel energy storage is: Where: δ fl is the flywheel relaxation factor; t fl is the flywheel frequency modulation response time; E fl,rate is the rated capacity of the flywheel energy storage; is the maximum output of the flywheel at the current moment, Δt is the time interval, E dc,rate The rated capacity of the battery energy storage; Based on the power characteristic coefficient, the optimized compensation price for frequency regulation mileage at any time in the flywheel energy storage frequency regulation auxiliary service market is obtained as follows: Where: The price for compensation of frequency adjustment mileage after correction; The price of compensation for frequency adjustment mileage before the correction; The capacity characteristic coefficient of battery energy storage is: Where: δ dc is the battery relaxation factor; t dc FM response time for the battery; The maximum output of the battery at the current moment; SOC dc,t The current SOC of the battery energy storage; Based on the capacity characteristic coefficient, the optimized clearing price of frequency regulation at any time in the battery energy storage frequency regulation auxiliary service market is obtained as follows: Where: The revised frequency regulation capacity compensation price; It is the price of frequency regulation capacity compensation before correction.

7. The method of claim 1, wherein the method is characterized by: The underlying control strategy of the hybrid energy storage in step 2 is specifically as follows: ① If flywheel energy storage is sufficient to meet frequency regulation requirements, the control strategy aims to improve battery life. Frequency regulation is performed solely on the flywheel, leveraging the advantages of power-type energy storage to meet frequency regulation requirements. Battery energy storage, based on a lifespan assessment model, participates in the electricity market and generates electricity revenue. ② If the flywheel's remaining frequency regulation capacity is insufficient, the control strategy aims to participate in frequency regulation to ensure grid frequency security, with the dynamic balance of each energy storage SOC and the frequency regulation capacity of the hybrid energy storage as limitations. The battery energy storage is forced to participate in some small interference fluctuations, extending the overall frequency regulation capability of the hybrid energy storage.

8. The method of claim 1, wherein the method is characterized by: The expressions for the hybrid energy storage frequency modulation output and battery energy storage new energy dispatch output in step 2 are as follows: are 0-1 variables for hybrid energy storage charging and discharging, and the relationship between the two is: It is stipulated that battery energy storage can only work in charging state or discharging state at the same time; The output of battery energy storage at time t is: Where: P dc,t Total output for battery energy storage; The charging and discharging power of the battery involved in scheduling; The charging and discharging power of the battery participating in frequency modulation; A 0-1 variable to charge the battery; A 0-1 variable indicating battery discharge; The battery energy storage response to new energy dispatch power at time t is: Where: dispatching power for battery energy storage; The total power of hybrid energy storage participating in new energy dispatch and frequency regulation at time t is: Where: P t W is the total output of hybrid energy storage; The charge and discharge power of the flywheel involved in scheduling; is a 0-1 variable for flywheel discharge; A 0-1 variable that charges the flywheel.

9. The method of claim 1, wherein the method is characterized by: The constraints in step 3 are specifically: ① Constraints on battery energy storage with the goal of increasing lifespan, specifically: Battery energy storage bidding power constraints: At the current moment, the power of battery energy storage participating in the electric energy market and frequency regulation auxiliary service market must meet the maximum and minimum charging and discharging power and rated power constraints: Where: P dc,max is the remaining maximum frequency modulation power when the battery SOC limit is close to 0.9, P dc,min is the remaining maximum frequency modulation power when the battery SOC limit is close to 0.1, is the battery discharge power, P dc,rate is the battery rated power, Charging power for the battery, The charging and discharging power of the battery participating in frequency modulation; Battery energy storage capacity constraints: Based on battery life assessment, set the optimal SOC limit capacity: Where: E dc,t is the battery capacity at the current moment; S dc_ The best upper limit SOC for battery life evaluation; S dc_ Evaluate the optimal lower limit SOC for battery life; η dc is the battery charge and discharge efficiency; E dc,rate The rated capacity of the battery energy storage; Battery energy storage cycle life constraint: obtained through the battery energy storage life loss model based on real-time SOC status and equivalent life cycle number; ② Battery energy storage is constrained by the goal of ensuring grid frequency security, specifically: Battery energy storage capacity constraints: Where: SOC dc,max , SOC dc,min is the maximum and minimum SOC state of the battery; Δt is the time interval; ③ Hybrid energy storage only participates in the frequency regulation service market, specifically: Battery energy storage capacity constraints: Where: E dc,t is the battery capacity at the current moment, E dc,rate is the rated capacity, is the frequency modulation power during discharge at the current moment, η dc is the battery charge and discharge efficiency; ④Other constraints, specifically: FM power balance constraints: FM power constraints: Where: is the battery frequency modulation power, is the energy storage frequency modulation power during discharge at the current moment, The energy storage frequency modulation power during charging at the current moment, is the maximum frequency modulation power of energy storage during discharge at the current moment, P k,rate is the energy storage rated power, The maximum frequency modulation power of energy storage during charging at the current moment; SOC constraints: Where: SOC k,min is the minimum value of energy storage SOC, SOC k,max is the maximum energy storage SOC, η k For energy storage charging and discharging efficiency, is the energy storage discharge power at the current moment, Energy storage charging power at the current moment; Due to the characteristics of battery energy storage life, the operating duration is used as the switching charge and discharge constraint. The battery energy storage charge and discharge switching flexibility constraint is divided into the maximum charge and discharge cycle constraint and the charge and discharge duration constraint. The maximum number of charge and discharge cycles is constrained to: In the formula: σ is the charge and discharge symbol; k is the charge and discharge time; is the change of discharge state; To change to a discharge state; The charging status changes; is the change to charging state; N0 is the maximum number of charge and discharge cycles; t is the current time; Frequency modulation charging and discharging operation duration constraints: Where: T c 、T d It is the time limit for charging and discharging; is the time adjustment factor; TC and TD are the duration of charge and discharge; They are respectively changed into charging state and changed into discharging state; They are respectively the duration of charging and the duration of discharging.

10. The method for controlling hybrid energy storage life economy and frequency modulation limit zoning according to claim 1 is characterized by: The regulation performance in step 4 includes three factors: regulation rate, regulation accuracy and response time; The evaluation index expression is as follows: Where: It is an evaluation index to measure the regulation performance of the i-th unit during the j-th regulation process; and are the adjustment rate, accuracy and response time of the jth adjustment of the i-th unit respectively; The frequency regulation performance evaluation of the AGC instructions that can be achieved by the thermal power unit frequency regulation assistance is carried out as follows: ① FM rate The regulation rate refers to the rate at which the unit responds to the setpoint command, which is divided into rising rate and falling rate. The calculation process of the j-th regulation rate of the i-th unit is as follows: The actual regulation rate calculation formula is as follows: Where: v i,j is the actual adjustment rate of the i-th unit for the jth time, in MW / minute; P Ei,j is the output at the end of the response process, in MW; P Si ,j is the output when it starts to move, in MW; T Ei,j It's time to end, T Si,j It's time to start, P di,j is the critical power of the start-stop grinding mill of the jth adjustment, in MW; T di,j is the actual time consumed by the jth adjustment of starting and stopping the grinding mill; If the unit does not meet the typical AGC setpoint control process, that is, the unit fails to enter the target dead zone, the regulation rate is the unit output at the end of the instruction minus the active power change at the time of crossing the dead zone, divided by the required time; The calculation formula for regulating rate regulation index is: Where: v N,i is the standard regulation rate of unit i, in MW / min; ②Adjustment accuracy The regulation accuracy refers to the difference between the actual output and the set point output after the unit response is stable. The method to obtain it is: integrate the absolute value of the difference between the actual output and the command, and then divide the integral by the integration time to obtain the value from T Si,j to T Ei,j The adjustment deviation of the time period is as follows: Where: P i,j (t) is the actual output during the period, P i,j Obtaining a setpoint command value for the period; If the unit fails to enter the target dead zone, the regulation accuracy is the minimum value of the deviation between the actual output and the target output during the period from the moment the unit steps out of the dead zone in the same direction to the moment the command ends: Where: The allowable deviation of regulation is 1% of the rated active power of the unit; ③Response time Response time refers to the time it takes for the unit to reliably step out of the frequency regulation dead zone consistent with the regulation direction at the original output point after the EMS system issues a command. The formula is as follows: Where: is the time for the i-th unit to leave the initial adjustment dead zone during the j-th adjustment process, T1 is the time to leave the adjustment dead zone, T0 is the time when the unit starts to output, is the time when the i-th unit leaves the last adjustment dead zone during the j-th adjustment process, T6 is the time when it leaves the grinding stop point, T5 is the time when the AGC control program issues a new set point command to the unit, and t i,j is the response time of the jth AGC unit of the i-th unit; the standard AGC response time of thermal power units is less than 1 minute; The above and If the calculated value is less than 0.1, it is taken as 0.1 and the evaluation index is used. Calculation of and If one of the calculated values ​​is greater than 2, then none of the three calculated values ​​will be evaluated. calculation; assessment and If the calculated values ​​are all within the range of [0.1, 2], the evaluation index is Calculation.

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