Transaction strategy for providing inertia / primary frequency modulation auxiliary service through shared energy storage

Abstract

The invention discloses a transaction strategy for providing inertia / primary frequency modulation auxiliary service by sharing energy storage. A shared energy storage power station is configured at a wind power cluster collection position to undertake the responsibility of wind power clusters participating in frequency modulation control, a shared energy storage device compensates the grid-connected inertia weakening amount of the wind power clusters, and the frequency modulation effect is fully played for exciting shared energy storage. Market clearing and settlement compensation should be performed on a shared energy storage device equipped in a wind power plant in an electricity market, a frequency dynamic change process is comprehensively considered, a rotor motion equation is used for expression, a system frequency lowest point constraint is obtained by considering time limit and delay of each adjustment resource, and due to coupling of electric energy, inertia and PFR demands, the system frequency lowest point constraint is obtained. And the service prices are used as a whole to cooperatively perform joint clearing in the spot market, a Lagrange function of the power system joint clearing model is obtained, and all kinds of service prices are obtained by using a Lagrange multiplier. The invention provides a transaction strategy for providing inertia / primary frequency modulation auxiliary service through shared energy storage. The stability and economical efficiency of a power system can be effectively improved.

Description

Technical Field

[0001] The present invention relates to the technical field of wind power energy storage control, and particularly to a trading strategy for a shared energy storage to provide inertia / primary frequency modulation auxiliary services. Background Art

[0002] In the context of large-scale new energy grid connection, the virtual inertia control technology of wind farms faces many challenges. On the one hand, it is difficult to guarantee the control accuracy of virtual inertia because the virtual inertia of a wind farm needs to dynamically adjust the control gain according to the real-time wind speed. However, the randomness and volatility of the wind speed are relatively large, resulting in difficult precise adjustment of the control gain, which in turn affects the compensation accuracy of virtual inertia. On the other hand, the existing primary frequency modulation auxiliary services are restricted by factors such as the speed regulation range and frequency modulation dead zone of synchronous generators. After large-scale new energy grid connection, the system inertia decreases and the frequency change rate accelerates, and primary frequency modulation may not be able to respond to frequency changes in a timely and effective manner.

[0003] In recent years, although the application rate of wind farm frequency modulation control has increased to some extent, this increase is mainly due to the wind-storage combined frequency modulation system. By optimizing the charge and discharge characteristics of energy storage and the coordinated control with wind power, the wind-storage combined frequency modulation system has significantly improved the frequency modulation performance and reduced the frequency fluctuation. In contrast, the engineering application rate of the frequency modulation control of a single wind power system is still relatively low. The frequency modulation control of a wind farm needs to comprehensively consider multiple factors such as the generated power, energy storage capacity, and load demand to stimulate its enthusiasm for participating in frequency modulation. In addition, the existing single shared energy storage to provide inertia mode also faces problems. The construction and maintenance costs of energy storage devices are relatively high. At the same time, the inertia auxiliary service is highly coupled with the electrical energy and interacts with the primary frequency modulation auxiliary service. Therefore, in a power system with a high penetration rate of new energy, the application of shared energy storage technology is crucial for providing inertia and primary frequency modulation support. At the same time, how to coordinate resources and formulate trading strategies and pricing for the resources of shared energy storage to provide inertia / primary frequency modulation auxiliary services has become an urgent problem to be solved. Summary of the Invention

[0004] To solve the above technical problems, the present invention provides a trading strategy for a shared energy storage to provide inertia / primary frequency modulation auxiliary services. By configuring a shared energy storage device at the convergence point of a wind power cluster, it undertakes the responsibility of the wind power cluster to participate in frequency modulation control, making up for the shortcoming of the low engineering application rate of wind farm frequency modulation control. At the same time, the optimization problems of services such as electrical energy, inertia, and primary frequency modulation are unifiedly modeled, and the influence of constraint conditions on the system optimization objective is reflected through Lagrange multipliers, so as to reasonably determine the prices of various services.

[0005] The technical solution adopted by the present invention is as follows:

[0006] A trading strategy for a shared energy storage to provide inertia / primary frequency modulation auxiliary services, comprising the following steps:

[0007] Step 1: Configure a shared energy storage device at the convergence point of the wind power cluster, and use the shared energy storage device to compensate for the weakening of the grid connection inertia of the wind power cluster;

[0008] Step 2: The shared energy storage device is connected to the power system. Considering the dynamic change process of frequency comprehensively, the dynamic response of the power system is described by the equivalent rotor motion equation. Considering the time delay of each regulation resource time limit, the lowest point constraint of the system frequency is obtained; due to the fast response speed and good regulation performance of the energy storage, the virtual inertia response time delay of the energy storage is ignored to simplify the calculation;

[0009] Step 3: Take electric energy, inertia, and primary frequency regulation as a whole and jointly clear them in the spot market to obtain the Lagrangian function of the power system joint clearing model, and then obtain the prices of various services using Lagrange multipliers.

[0010] Step 4: The price of electric energy is determined by the Lagrange multipliers of the lowest point constraint and quasi-steady state constraint of the system frequency. The Lagrange multiplier reflects the influence of the constraint condition on the system optimization goal; the price of the auxiliary service resource of the energy storage can be calculated by the partial derivative of the Lagrange multiplier with respect to the resource demand.

[0011] In Step 1, in a power system with N synchronous generators, the grid inertia can be expressed as:

[0012]

[0013] In Equation (1): H Gi , S Gi , S sys(0) are the inertia, rated capacity of synchronous generator i, and the total rated capacity of the system respectively; H G1 , H G2 ...H GN are the inertia of synchronous generators 1, 2,... N respectively; S G1 , S G2 ...S GN are the rated capacities of synchronous generators 1, 2,... N respectively; N is the number of synchronous generators.

[0014] After a shared energy storage device with virtual inertia control technology is connected to the power system, the grid inertia becomes:

[0015]

[0016] In Equation (2): H sys(0) is the inertia before grid compensation; S sys(0) is the total rated capacity of the system; H ESS is the virtual inertia of the energy storage; S ESS is the rated capacity of the energy storage; △EESS For the compensated kinetic energy of shared energy storage; S wpc_ESS is the total rated capacity of the wind power cluster and the energy storage device.

[0017] Among them, the compensated kinetic energy △E of the shared energy storage ESS is only provided by the shared energy storage device, but the wind power cluster and the shared energy storage device constitute an overall impact on the grid inertia; after implementing the virtual inertia compensation control of the shared energy storage, the grid inertia before wind power grid connection remains unchanged. Therefore, there is:

[0018]

[0019] From this, the weakening amount of the wind power cluster is solved, that is, the compensated kinetic energy of the shared energy storage device is:

[0020] △E ESS = H ESS × S ESS = H sys(0) × S wpc_ESS (4);

[0021] Since H ESS and S ESS are the virtual inertia of the energy storage and the rated capacity that can be configured according to requirements. From Equation (4), it can be seen that if S ESS is configured smaller (lower cost), a larger virtual inertia must be configured, and vice versa. Therefore, the problem of the planning investment cost of the energy storage power station and the inertia that can be provided should be considered comprehensively.

[0022] In the said step 2, because the energy storage inertia response is rapid and the time delay of the energy storage virtual inertia response is not considered, Equation (5) is obtained:

[0023]

[0024] In Equation (5): H syn is the inertia of the system synchronous machine; H synt is the virtual inertia of the energy storage; △f is the frequency deviation; f 0 is the rated frequency, is the dynamic response power of the energy storage primary frequency regulation (PFR); △P i PFR is the dynamic response power of the synchronous machine primary frequency regulation (PFR); P loss is the disturbance power; N s is the number of shared energy storage stations configured in the power system.

[0025] Among them, the virtual inertia H of the energy storage synt is expressed as:

[0026]

[0027] In Equation (6): is the virtual inertia time constant of energy storage; is the maximum discharge power of energy storage; N s is the number of shared energy storage devices configured in the power system; ei represents the ei-th shared energy storage device.

[0028] Given that the moment of the lowest frequency is t', integrating and arranging the above Equation (6), the lowest frequency is obtained as:

[0029]

[0030] In Equation (7): T 1 is the primary frequency regulation ramp-up time of energy storage; T 2 is the primary frequency regulation ramp-up time of synchronous units; T del1 is the primary frequency regulation time delay of energy storage affected by the frequency regulation dead zone and action delay; T del2 is the primary frequency regulation time delay of synchronous units affected by the frequency regulation dead zone and action delay; is the total primary frequency regulation (PFR) capacity of synchronous units; is the total primary frequency regulation (PFR) capacity of shared energy storage devices.

[0031] Among them, the range of the lowest frequency point and the range of the frequency regulation capacity are:

[0032] |△f(t')|≤△f max (8);

[0033] In Equation (8): △f(t') is the lowest frequency point; △f max is the maximum allowable frequency deviation specified by the system;

[0034]

[0035] In Equation (9): P s PFR is the total primary frequency regulation (PFR) capacity of shared energy storage devices; is the primary frequency regulation capacity of the ei-th shared energy storage device; N s represents the number of energy storage devices;

[0036]

[0037] In Equation (10): is the total primary frequency regulation (PFR) capacity of synchronous units; P i PFR is the primary frequency regulation capacity of synchronous unit i;

[0038] Since the primary frequency regulation of energy storage (PFR) can respond within a few hundred milliseconds, the general frequency will reach its lowest point after the PFR of the synchronous machine starts, and the power deficit can be fully compensated only after the synchronous generator increases its output power. At the same time, it takes about 10 - 20 s for the PFR of the synchronous machine to fully respond, that is, the lowest frequency point falls within t ∈ [T del2 ,T del2 +T 2 , where t represents the time after the power disturbance occurs; T 2 is the ramp-up time of the primary frequency regulation of the synchronous unit. Therefore, the time t' of the lowest frequency point satisfies:

[0039]

[0040] In Equation (11): P loss is the disturbance power at the time of the disturbance.

[0041] Substituting Equation (11) into Equation (7), the expression for the lowest frequency point is obtained as:

[0042]

[0043] Substituting Equation (12) into Equation (8), the constraint for the lowest frequency point is obtained as:

[0044]

[0045] In Equation (13): f 0 is the rated frequency; △f max is the maximum allowable frequency deviation specified by the system.

[0046] In Step 3, in the power system, the electricity energy market has a high coupling relationship with the inertia ancillary service and the primary frequency regulation ancillary service. Therefore, electricity energy, inertia, and primary frequency regulation are coordinated as a whole and jointly cleared in the spot market. The goal of the joint clearing is to minimize the total procurement cost of the system, including the costs of electricity energy, inertia, and primary frequency regulation resources.

[0047] The specific objective function can be expressed as:

[0048]

[0049] In Equation (14): T is the 24-hour period; N is the number of synchronous units; N s is the number of shared energy storage devices configured in the power system; is the clearing price of the electricity energy market of the synchronous generator; is the clearing price of the primary frequency regulation market of the synchronous generator; is the charging market price of the shared energy storage; is the discharging market price of the shared energy storage; is the clearing price of the primary frequency regulation market for shared energy storage; is the clearing price of the inertia market for shared energy storage; is the electric power of synchronous generator i at time t;

[0050] is the primary frequency regulation capacity of synchronous generator i at time t; is the charging power of the ei-th device of shared energy storage at time t; is the discharging power of the ei-th device of shared energy storage at time t; is the primary frequency regulation capacity of the ei-th device of shared energy storage at time t; H ei,t is the virtual inertia provided by the ei-th device of shared energy storage at time t.

[0051] Based on equations (12)-(14), the Lagrangian function of the power system joint clearing model is obtained as follows:

[0052]

[0053] In equation (15): λ 0 is the Lagrange multiplier of the load power balance constraint; λ RoCoF is the Lagrange multiplier of the rate of change of frequency (RoCoF) constraint; λ ss is the Lagrange multiplier of the quasi-steady state constraint; λ 1 , λ 2 , and μ are all Lagrange multipliers of the frequency nadir constraint.

[0054] In step 4, from the Lagrange multipliers of the rate of change of frequency (RoCoF) and the frequency nadir constraint, the synchronous machine inertia price and the energy storage virtual inertia price

[0055]

[0056]

[0057] In the formula: β is the synchronous machine inertia self-recovery ability; α ei is the energy reservation coefficient for the energy storage to participate in the inertia market;

[0058] From the Lagrange multiplier of the load power balance constraint, the electricity price λ t E :

[0059]

[0060] In equation (18): λ 0 is the Lagrange multiplier of the load power balance constraint.

[0061] Then, from the lowest frequency point and the Lagrange multipliers of the quasi-steady state constraints, the price of primary frequency regulation (PFR) of the synchronous machine and the price of primary frequency regulation (PFR) of the energy storage

[0062]

[0063] In Equation (19): λ ss is the Lagrange multiplier of the quasi-steady state constraint.

[0064]

[0065] The trading strategy of a shared energy storage providing inertia / primary frequency regulation ancillary services in the present invention has the following technical effects:

[0066] 1) In step 1 of the present invention, starting from quantitatively characterizing the inertia weakening amount, the inertia weakening value caused by the wind power cluster is centrally compensated for this target by using the shared energy storage, thus avoiding large-scale control technology transformation of wind farms and providing a technical reference for the inertia control of the shared energy storage.

[0067] 2) In step 2 of the present invention, when the shared energy storage device is connected and the frequency dynamic change is considered, the equivalent rotor motion equation is used to describe the dynamic response. Because the response speed of the energy storage device is fast and its virtual inertia response time delay is short, the virtual inertia response time delay of the energy storage is ignored, reducing the calculation complexity and being able to accurately evaluate the supporting effect of the energy storage on the system frequency. This method can be closer to the actual operation situation and avoid the error introduced by the time delay. It can better play the fast response advantage of the energy storage device and improve the frequency stability and operation efficiency of the power system.

[0068] 3) In step 3 of the present invention, the method of jointly clearing the electricity energy market, inertia ancillary services, and primary frequency regulation ancillary services as a whole in the spot market. The joint clearing model comprehensively considers the mutual coupling effects between market services, realizes the coordinated optimization of resources, improves the system operation efficiency, and avoids the complexity and calculation burden brought by step-by-step clearing. On the premise of meeting the frequency safety constraints, the allocation of electric energy, inertia, and primary frequency regulation resources is optimized, thereby reducing the total procurement cost of the system. Using the Lagrange multiplier method to determine the prices of various services can more accurately reflect the marginal costs of different resources, make the price formation mechanism more reasonable, and encourage various resources to actively participate in the market.

[0069] 4) In step 4 of the present invention, the Lagrange multiplier method can unify the optimization problems of services such as electric energy, inertia, and primary frequency regulation for modeling. By using Lagrange multipliers, it can reflect the influence of constraint conditions on the system optimization goal. This method can more accurately quantify the marginal contribution of different constraints to resource requirements, thereby reasonably determining the prices of various services. It avoids the complex iterative optimization process, significantly improves the calculation efficiency, can flexibly reflect the resource value under different constraint conditions, and adapts to the complex operating environment of the power system. BRIEF DESCRIPTION OF THE DRAWINGS

[0070] Figure 1 It is a flowchart of an embodiment of the present invention.

[0071] Figure 2 It is a schematic structural diagram of a virtual inertia compensation control system for a shared energy storage in a wind power cluster.

[0072] Figure 3 It is a schematic diagram of the wind power output and load prediction of the system.

[0073] Figure 4 It is a schematic diagram of the time-of-use electricity price for the shared energy storage to buy and sell electricity to the power grid.

[0074] Figure 5 It is a schematic diagram of the electricity settlement price of the shared energy storage.

[0075] Figure 6 It is a schematic diagram of the settlement price of the virtual inertia of the shared energy storage.

[0076] Figure 7 It is a schematic diagram of the settlement price of the frequency regulation of the shared energy storage. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0077] A trading strategy and pricing method for a shared energy storage to provide inertia / primary frequency regulation ancillary services. A shared energy storage device (shared energy storage power station) is configured at the convergence point of a wind power cluster (such as a substation) to undertake the responsibility of the wind power cluster participating in frequency regulation control, and the shared energy storage device is used to compensate for the weakening of the grid-connected inertia of the wind power cluster. To encourage the shared energy storage to fully play its role in frequency regulation, market clearing and settlement compensation are carried out for the shared energy storage devices equipped in wind farms in the power market; comprehensively considering the dynamic process of frequency change, expressed by the rotor motion equation, and considering the time-delay of each regulation resource time limit, the lowest point constraint of the system frequency is obtained. Due to the coupling of electric energy, inertia, and PFR demand, they are jointly cleared in the spot market as a whole, and thus the Lagrangian function of the lowest point constraint of the frequency is obtained, and then the Lagrange multipliers of the lowest point of the frequency and the quasi-steady state constraint are obtained. The prices of each ancillary service resource of the synchronous machine and the energy storage are obtained.

[0078] During the clearing process, the prices of various services can be obtained using Lagrange multipliers, and the settlement price is represented by the derivative of the Lagrangian function with respect to the required services. Given that the example system has 10 thermal power units and 2 wind farms, the reference on-grid electricity price for wind power is set at 259.5 yuan / (unit: MWh). Figure 3 is the predicted curve of wind power output and load for the system. As Figure 3 can be seen, the output of the wind turbines is affected by the wind, and the output of the wind turbines is relatively large during the period from 0:00 to 12:00. The load is at its peak during the period from 19:00 to 24:00.

[0079] Table 1 Thermal Power Unit Parameter Settings

[0080]

[0081]

[0082] Table 1 shows the parameter settings of the thermal power units. Since the penetration rate of the asynchronous power source is less than 40%, and the load rate of the synchronous units is greater than 40%, according to the "Implementation Rules for the Management of Power Auxiliary Services in the Southern Region", the inertial support of the synchronous units to the system is an inherent obligation for them to obtain power generation benefits, and there is no need to consider the benefits of synchronous machine inertia compensation anymore. The electricity purchase and sale prices between the energy storage and the power grid are set with reference to the scope of the notice on optimizing the peak-valley time-of-use electricity price mechanism in this region, as Figure 4 shown. Figure 4 Shows the changes in the electricity price during the peak-valley periods of the energy storage charging and discharging. The electricity price increases during the peak period and decreases during the valley period.

[0083] Table 2 Energy Storage Parameters

[0084]

[0085] The parameters of the shared energy storage power station are shown in Table 2. Take the rated frequency f 0 as 50 Hz, the maximum frequency deviation △f max as 0.5 Hz, the energy storage is subject to the frequency modulation dead zone and the action delay T del1 as 0.3 s, and the synchronous units are subject to the frequency modulation dead zone and the action delay T del2 as 2.5 s; the primary frequency modulation ramp-up time T1 of the energy storage is 0.75 s, and the primary frequency modulation ramp-up time T2 of the synchronous units is 7 s.

[0086] Scenario Analysis:

[0087] Scenario 1: A shared energy storage power station is configured at the wind farm collection point. The energy storage does not participate in frequency modulation and inertial auxiliary services, and the wind farm pays the energy storage charging and discharging service fees according to a fixed price;

[0088] Scenario 2: A shared energy storage power station is configured at the wind farm collection point. The energy storage participates in frequency modulation and inertial auxiliary services.

[0089] Based on this, the market settlement fees are as shown in Table 3:

[0090] Table 3 Market Settlement Fees

[0091]

[0092] From the Lagrange multipliers of the load power balance constraint, the energy settlement price of the energy storage can be obtained as Figure 5 shown. From Figure 5 it can be seen that when the wind turbine output is large and the load is small, the energy storage discharge price is low and stable. When the load is large, the energy storage electricity price fluctuates frequently and is high, and it is greatly affected by the load.

[0093] From the rate of change of frequency RoCoF and the frequency nadir constraint, the virtual inertia settlement price of the energy storage is obtained as Figure 6 shown.

[0094] From Figure 6 it can be seen that during low load periods, the system's demand for the energy storage to provide inertia is small, and the virtual inertia price of the energy storage is small at this time. During high load periods, the system has high requirements for inertial response. At this time, the virtual inertia price of the energy storage is high and fluctuates frequently with the load.

[0095] From the Lagrange multipliers of the frequency nadir and quasi-steady state constraints, the frequency modulation settlement price of the energy storage can be obtained, as Figure 7 shown. From Figure 7 it can be seen that the primary frequency modulation price of the energy storage is affected by market demand and supply. During low load periods, the synchronous machine frequency modulation reserve capacity is high and the frequency modulation demand is low. Therefore, the primary frequency modulation price of the energy storage is low. During high load periods, the synchronous machine frequency modulation reserve capacity is small, and the primary frequency modulation price of the energy storage increases due to the influence of frequency modulation demand.

[0096] Table 3 shows the market settlement fees. In Plan 1, the grid inertia and frequency modulation ancillary services are all borne by the synchronous generator sets. To meet the inertia safety, small-capacity and high-cost units are started, resulting in an increase in the total grid clearing cost. In Plan 2, during the periods when the wind turbine output is large and the load is high (0:00 - 12:00 and 19:00 - 24:00), there are grid inertia differences and frequency safety risks. The shared energy storage power station purchases electricity at a low price from the wind farm and uses it to participate in grid frequency modulation and inertia ancillary services. While increasing the income of the shared energy storage power station, it reduces the inertia and frequency modulation capacity of the synchronous generator sets, effectively reducing the switching of small-capacity and high-cost units and reducing the overall clearing cost.

Claims

1. A trading strategy for shared energy storage to provide inertia / primary frequency regulation auxiliary services, characterized in that The following steps are involved: Step 1: Configure a shared energy storage device at the gathering point of the wind power cluster, and use the shared energy storage device to compensate for the weakening of the wind power cluster's grid-connected inertia; Step 2: The shared energy storage device is connected to the power system, and the dynamic frequency change process is comprehensively considered. The dynamic response of the power system is described by the equivalent rotor motion equation, and the time delay of each regulation resource is considered to obtain the system frequency minimum point constraint; Step 3: Electric energy, inertia, and primary frequency regulation are coordinated as a whole to be jointly cleared in the spot market, so as to obtain the Lagrangian function of the power system joint clearing model, and the prices of various services are then obtained using Lagrangian multipliers.

2. According to claim 1, a trading strategy for shared energy storage to provide inertia / primary frequency regulation auxiliary services is characterized by: It also includes step 4: the price of electricity is determined by the Lagrange multipliers of the system frequency minimum point constraint and the quasi-steady-state constraint. The Lagrange multipliers reflect the impact of the constraints on the system optimization objectives; the price of the auxiliary service resources of energy storage is calculated by the partial derivative of the Lagrange multiplier with respect to the resource demand.

3. According to claim 1, a trading strategy for shared energy storage to provide inertia / primary frequency regulation auxiliary services is characterized by: In step 1, in a power system containing N synchronous units, the grid inertia can be expressed as: In formula (1): H Gi , S Gi , S sys(0) are the inertia, rated capacity and total rated capacity of the system of synchronous unit i respectively; H G1 , H G2 ...H GN are the inertia of synchronous unit 1, synchronous unit 2, ... synchronous unit N respectively; S G1 , S G2 ...S GN They are the rated capacities of synchronous unit 1, synchronous unit 2, ... synchronous unit N respectively; N is the number of synchronous units; After the shared energy storage device equipped with virtual inertia control technology is connected to the power system, the grid inertia becomes: In formula (2): H sys(0) is the inertia before grid compensation; S sys(0) is the total rated capacity of the system; H ESS is the virtual inertia of energy storage; S ESS is the rated capacity of energy storage; △E ESS Compensation kinetic energy for shared energy storage; S wpc_ESS is the total rated capacity of the wind power cluster and energy storage device; Among them, the compensation kinetic energy of shared energy storage △E ESS It is only provided by the shared energy storage device, but the wind power cluster and the shared energy storage device form a whole that affects the grid inertia; after implementing the virtual inertia compensation control of the shared energy storage, the grid inertia before the wind power is connected to the grid is maintained unchanged, so there is: The weakening amount of the wind power cluster, that is, the compensation kinetic energy of the shared energy storage device, is solved as follows: △E ESS =H ESS ×S ESS =H sys(0) ×S wpc_ESS (4); Due to H ESS and S ESS is the virtual inertia and rated capacity of energy storage that can be configured according to demand. From formula (4), we can see that if S ESS A smaller configuration requires a larger virtual inertia.

4. According to claim 1, a trading strategy for shared energy storage to provide inertia / primary frequency regulation auxiliary services is characterized by: In step 2, because the energy storage inertia responds quickly, the virtual inertia response time delay of the energy storage is not considered, and equation (5) is obtained: In formula (5): H syn is the system synchronous machine inertia; H synt is the virtual inertia of energy storage; △f is the frequency deviation; f0 is the rated frequency, is the dynamic response power of energy storage primary frequency modulation (PFR); △P i PFR is the dynamic response power of the synchronous machine primary frequency modulation (PFR); P loss is the disturbance power; N s The number of shared energy storage stations configured in the power system; Among them, the energy storage virtual inertia H synt It is expressed as: In formula (6): is the virtual inertia time constant of energy storage; is the maximum discharge power of energy storage; N s is the number of shared energy storage devices configured in the power system; ei represents the ei-th shared energy storage device; It is known that the lowest frequency point is at t'. By integrating and sorting the above formula (6), the lowest frequency point is obtained as: In formula (7): T1 is the primary frequency regulation ramp-up time of energy storage; T2 is the primary frequency regulation ramp-up time of synchronous unit; T del1 T is the frequency modulation delay time of the energy storage affected by the frequency modulation dead zone and action delay; del2 It is the primary frequency regulation delay time of the synchronous unit affected by the frequency regulation dead zone and action delay; P is the total primary frequency regulation capacity of synchronous units; s PFR It is the total primary frequency regulation capacity of the shared energy storage device.

5. According to claim 4, a trading strategy for shared energy storage to provide inertia / primary frequency regulation auxiliary services is characterized by: The frequency minimum point range and frequency modulation capacity range are: |△f(t')|≤△f max (8); In formula (8): △f(t') is the lowest frequency point; △f max Specify the maximum frequency deviation allowed for the system; In formula (9): P s PFR The total primary frequency regulation capacity of the shared energy storage device; is the primary frequency regulation capacity of the ei-th shared energy storage device; N s Indicates the number of energy storage devices; In formula (10): P is the total primary frequency regulation capacity of synchronous units; i PFR is the primary frequency regulation capacity of synchronous unit i.

6. According to claim 5, a trading strategy for shared energy storage to provide inertia / primary frequency regulation auxiliary services is characterized by: Since the energy storage primary frequency regulation can respond within 100 milliseconds, the frequency will reach the lowest point after the synchronous machine primary frequency regulation is started. The synchronous generator can only fully make up for the power shortage after increasing power. At the same time, it takes about 10 to 20 seconds for the synchronous machine primary frequency regulation to fully respond, that is, the lowest frequency point falls at t∈[T del2 ,T del2 +T2], t represents the time after the power disturbance occurs; T2 is the frequency ramp-up time of the synchronous unit, so the lowest frequency point time t' satisfies: In formula (11): P loss is the disturbance power when disturbance occurs; Substituting formula (11) into formula (7), the expression of the lowest frequency point is obtained as follows: Substituting equation (12) into equation (8), the frequency minimum point constraint is obtained as: In formula (13): f0 is the rated frequency; △f max Specifies the maximum frequency deviation allowed for the system.

7. According to claim 6, a trading strategy for shared energy storage to provide inertia / primary frequency regulation auxiliary services, characterized in that: In step 3, in the power system, the electric energy market has a highly coupled relationship with the inertia auxiliary service and the primary frequency regulation auxiliary service. Therefore, the electric energy, inertia and primary frequency regulation are coordinated as a whole to be jointly cleared in the spot market. The goal of the joint clearing is to minimize the total procurement cost of the system, including the cost of electric energy, inertia and primary frequency regulation resources. The specific objective function is expressed as: In formula (14), T is the 24-hour period; N is the number of synchronous units; N s The number of shared energy storage devices configured in the power system; clearing prices for the market for electricity from synchronous generators; It is the clearing price of the synchronous generator primary frequency regulation market; charging market prices for shared energy storage; The market price for shared energy storage discharge; Clearing prices for the primary frequency regulation market for shared energy storage; Clearing prices for the shared energy storage inertia market; is the electric power of synchronous generator i at time t; is the primary frequency regulation capacity of synchronous generator i at time t; is the charging power of the shared energy storage device ei at time t; is the discharge power of the shared energy storage device ei at time t; H is the frequency regulation capacity of the shared energy storage device ei at time t; ei,t The virtual inertia provided by the shared energy storage device ei at time t.

8. According to claim 7, a trading strategy for shared energy storage to provide inertia / primary frequency regulation auxiliary services is characterized by: Based on equations (12)-(14), the Lagrangian function of the power system joint clearing model is obtained as follows: In formula (15), λ0 is the Lagrange multiplier of load power balance constraint; λ RoCoF is the Lagrange multiplier for the rate of change of frequency (RoCoF) constraint; λ ss is the Lagrange multiplier of the quasi-steady-state constraint; λ1, λ2, and μ are all Lagrange multipliers of the frequency minimum point constraint.

9. According to claim 2, a trading strategy for shared energy storage to provide inertia / primary frequency regulation auxiliary services, characterized in that: In step 4, the inertia price of the synchronous motor is obtained by the Lagrange multiplier constrained by the frequency change rate and the frequency minimum point. Virtual inertia price of energy storage Where: β is the inertia self-recovery capacity of the synchronous machine; α ei Energy reservation coefficient for energy storage participating in the inertia market; The Lagrange multiplier constrained by the load power balance constraint gives the electricity price In formula (18), λ0 is the Lagrange multiplier of the load power balance constraint.

10. A trading strategy for shared energy storage to provide inertia / primary frequency regulation auxiliary services according to claim 9, characterized in that: The Lagrange multiplier of the lowest frequency point and the quasi-steady-state constraint is used to obtain the price of the synchronous machine primary frequency regulation. and energy storage primary frequency regulation price In formula (19): ss is the Lagrange multiplier for the quasi-steady-state constraint;

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