Method for evaluating minimum inertia demand of multi-type energy storage power system

Abstract

The invention relates to a method for evaluating the minimum inertia demand of a multi-type energy storage power system, and the method comprises the steps: firstly, building a power system frequency response closed-loop transfer function containing electrochemical energy storage and flywheel energy storage in combination with thermal power, wind power and photovoltaic system frequency response models; then, based on the frequency response closed-loop transfer function of the power system, an initial value theorem and a final value theorem are respectively utilized to obtain an initial frequency change rate and a steady-state frequency deviation after the power system encounters disturbance; according to the initial frequency change rate and the steady-state frequency deviation, an evaluation value of the minimum inertia demand of the power system is obtained based on the initial frequency change rate security constraint and the maximum frequency deviation security constraint; and finally comparing the two evaluation values, wherein the larger value is the minimum inertia demand evaluation value. Based on a traditional system frequency response model, multiple types of energy storage and new energy units are integrated, and the actual demand of a modern novel power system for minimum inertia demand evaluation is better met.

Description

Technical Field

[0001] The invention relates to an evaluation method for minimum inertia requirements of a multi-type energy storage power system, and belongs to the field of power system automation. Background Art

[0002] With the transformation of the global energy structure and the rapid development of new energy technologies, new power systems are gradually showing the characteristics of rich resources and diversity. In particular, the access to a high proportion of new energy and power electronic equipment, as well as the development and access to new energy storage technologies, have made the frequency characteristics of the power system more complex. Compared with traditional thermal and hydropower generation, new energy power generation, such as wind power and photovoltaic power, has different dynamic characteristics, which have a significant impact on the frequency stability of the power system. In addition, the widespread use of power electronic equipment has led to a reduction in system inertia, making the system face greater challenges in frequency stability when facing large-scale faults or load changes.

[0003] In order to cope with the challenge of insufficient system inertia, new energy generators and energy storage systems have proposed a variety of control strategies, such as droop control and virtual synchronous machine control, to effectively provide the virtual inertia required by the system, but it is still weaker than the inertia support capacity of traditional synchronous generators. Therefore, considering traditional thermal power generation, wind power, photovoltaics and various types of energy storage comprehensive frequency regulation in the system is an effective means to enhance the system inertia support capacity.

[0004] In current related research, thermal power, wind turbines, photovoltaics, energy storage and other resources can participate in the inertia support and frequency regulation of the system through their typical control strategies, but the system often only considers a single type of energy storage, usually electrochemical energy storage, and does not comprehensively consider the impact of multiple types of energy storage combined with traditional thermal power and new energy units on the frequency characteristics of the power system. In addition, some studies did not further propose a minimum inertia demand assessment method based on the system frequency safety constraints when analyzing the impact of multiple frequency regulation resources on the system frequency characteristics, and could not provide a comprehensive reference for the safe and stable operation of the power system under actual working conditions. For example, the literature considers the frequency characteristics of low-inertia power systems with energy storage [J]. Zhao Qiang et al. Proceedings of the CSEE, 2023, 43(03): 904-914. The literature proposes a power system frequency response model including energy storage, but the model only includes electrochemical energy storage and traditional thermal power generation, and does not consider new energy units and multiple types of energy storage. Literature Minimum inertia evaluation of power system considering dynamic frequency constraints [J] Wang Baocai et al. Proceedings of the CSEE, 2022, 42(01): 114-127. In the established system frequency response model, both new energy units and energy storage units are uniformly classified as power electronic power sources, without considering the differences in frequency responses of various types of power electronic resources.

[0005] Therefore, how to quantitatively analyze the frequency characteristics and minimum inertia requirements of new power systems that consider multiple types of energy storage based on the system frequency response model has become an urgent problem that needs to be solved. Summary of the invention

[0006] The purpose of the present invention is to solve the problem that the minimum inertia requirement assessment method in the prior art is mainly a power system containing a single energy storage, lacks consideration of multiple types of energy storage, and provides a minimum inertia assessment method for a new power system containing multiple types of energy storage.

[0007] In order to achieve the above object, the technical solution proposed by the present invention is: a method for evaluating the minimum inertia requirement of a multi-type energy storage power system, comprising:

[0008] Step 1: Combine the system frequency response models of thermal power, wind power and photovoltaic power to establish a closed-loop transfer function of the power system frequency response including electrochemical energy storage and flywheel energy storage;

[0009] Step 2: Based on the frequency response closed-loop transfer function of the power system, the initial frequency change rate and the steady-state frequency deviation of the power system after the disturbance are obtained by using the initial value theorem and the final value theorem respectively;

[0010] Step 3: According to the initial frequency change rate and the steady-state frequency deviation, the evaluation value of the minimum inertia requirement of the power system is obtained based on the initial frequency change rate safety constraint and the maximum frequency deviation safety constraint respectively, and the two evaluation values ​​are compared, and the larger value is taken as the final minimum inertia requirement evaluation value.

[0011] A further design of the above technical solution is as follows: the frequency response closed-loop transfer function of the power system is:

[0012]

[0013] Where φ(s) is the closed-loop transfer function of the system, Δf is the frequency change of the system, and ΔP L represents the disturbance size encountered by the system, G(s) represents the forward channel transfer function in the frequency response model, H(s) represents the feedback channel transfer function, H is the system equivalent inertia time constant; D is the system damping coefficient, α w , α pv , α m , α E , α v Respectively represent the proportion of wind turbines, photovoltaic units, thermal power units, electrochemical energy storage and flywheel energy storage in the power system; k pf represents the primary frequency modulation coefficient, T P represents the pitch response time constant, k df is the inertial response coefficient, T w is the inertial response time constant; kpv is the photovoltaic internal control proportional coefficient, C b is the high voltage DC capacitor, U dc is the high voltage DC voltage value, H pv is the virtual inertia time constant; k m is the mechanical power factor, F H is the work coefficient of the prime mover high pressure cylinder, T R is the reheating time constant, R is the primary frequency modulation droop coefficient; H E is the virtual inertia time constant, K E is the gain factor, T E represents the delayed response coefficient; k v represents the virtual droop coefficient, T B Represents the flywheel energy storage hysteresis coefficient, H v and D v are the virtual inertia coefficient and damping coefficient of the flywheel VSG respectively.

[0014] In the step 1, a closed-loop transfer function of the power system frequency response including electrochemical energy storage and flywheel energy storage is established, specifically including:

[0015] Step 1-1: Establish the frequency response transfer function of the grid-type electrochemical energy storage based on droop control:

[0016]

[0017] In the formula, G E (s) is the frequency response function of electrochemical energy storage, ΔP e is the change in electrochemical energy storage power, Δf e is the change in the frequency of electrochemical energy storage;

[0018] Step 1-2: Establish the flywheel energy storage frequency response transfer function based on VSG control as:

[0019]

[0020] In the formula, G v (s) is the flywheel energy storage frequency response function, ΔP v is the change in flywheel energy storage power, Δf v is the change in flywheel energy storage frequency;

[0021] Step 1-3: Establish the thermal power frequency response transfer function as follows:

[0022]

[0023] In the formula, G m (s) is the frequency response function of the traditional thermal power frequency regulation unit, ΔP m is the power change of the thermal power unit, Δfm is the frequency variation of the thermal power unit, k m is the mechanical power factor, F H is the work coefficient of the prime mover high pressure cylinder, T R is the reheating time constant, and R is the primary frequency modulation droop coefficient.

[0024] Step 1-4, wind power frequency response transfer function is:

[0025]

[0026] In the formula, G w (s) is the frequency response function of the wind turbine, ΔP w is the power change of the wind turbine, Δf w is the frequency variation of the wind turbine;

[0027] Step 1-5, the photovoltaic frequency response transfer function is:

[0028]

[0029] In the formula, G pv (s) is the frequency response function of the photovoltaic unit, ΔP pv is the power change of the photovoltaic unit, Δf pv is the frequency change of the photovoltaic unit;

[0030] Step 1-6: Combine the frequency response models of electrochemical energy storage and flywheel energy storage with the frequency response models of wind power, photovoltaic power, and thermal power to obtain a closed-loop transfer function of the system frequency response.

[0031] In step 2, the initial frequency change rate is:

[0032]

[0033] Among them, G w (s), G pv (s), G m (s), G E (s), G v (s) are the transfer functions of wind power, photovoltaic power, thermal power, electrochemical energy storage and flywheel energy storage units respectively.

[0034] In step 2, the steady-state frequency deviation is:

[0035]

[0036] In step 2, the estimated value of the minimum inertia requirement of the power system obtained based on the initial frequency change rate safety constraint is:

[0037]

[0038] Among them, H min represents the minimum equivalent inertia time constant of the system, f N is the system rated frequency, S N is the total rated capacity of the system, ΔP max Indicates the maximum value of the disturbance, r max Indicates the maximum limit of the frequency change rate.

[0039] In step 2, the evaluation value of the minimum inertia requirement of the power system obtained based on the maximum frequency deviation safety constraint is:

[0040]

[0041] Where ΔP max Indicates the maximum value of the disturbance, f N is the system rated frequency, S N is the total rated capacity of the system, R is the synchronous modulation coefficient, f0 represents the primary frequency modulation dead zone, usually 0.033Hz, f min Indicates the value at which the frequency drops to the lowest point.

[0042] The beneficial effects of the present invention are:

[0043] Compared with the existing technology, the present invention constructs a power system frequency response model that incorporates multiple types of energy storage and new energy units based on the traditional system frequency response model, which is more in line with the actual needs of modern new power systems for minimum inertia demand assessment.

[0044] The method of the present invention realizes the quantitative analysis of frequency characteristics and quantitative calculation of inertia requirements of new power systems containing multiple types of energy storage and new energy units, providing a reference for the minimum inertia evaluation method and frequency safety and stability analysis of new power systems containing multiple types of energy storage. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] Figure 1 is an overall flow chart of the method of the present invention;

[0046] Figure 2 A frequency response model for a system that includes thermal power, wind power, photovoltaic power, and multiple types of energy storage;

[0047] Figure 3 The system frequency response model built in Matlab / Simulink;

[0048] Figure 4 The frequency characteristic curve of the system when the electrochemical energy storage and flywheel energy storage have different capacity ratios;

[0049] Figure 5 The system frequency response curve generated after the system frequency response model is run;

[0050] Figure 6 It is a three-dimensional surface diagram based on the maximum frequency change rate constraint;

[0051] Figure 7 It is a three-dimensional surface plot based on the maximum frequency deviation constraint. DETAILED DESCRIPTION

[0052] The present invention is described in detail below with reference to the accompanying drawings and specific embodiments.

[0053] Embodiment 1

[0054] Minimum inertia requirement assessment method for power systems with multiple types of energy storage, such as Figure 1 As shown, the method of the present invention specifically comprises the following steps:

[0055] Step 1: Combine the system frequency response models of thermal power, wind power and photovoltaic power to establish a closed-loop transfer function of the power system frequency response including electrochemical energy storage and flywheel energy storage;

[0056] Step 2: Based on the frequency response closed-loop transfer function of the power system, the initial frequency change rate and the steady-state frequency deviation of the power system after the disturbance are obtained by using the initial value theorem and the final value theorem respectively;

[0057] Step 3: According to the initial frequency change rate and the steady-state frequency deviation, the evaluation value of the minimum inertia requirement of the power system is obtained based on the initial frequency change rate safety constraint and the maximum frequency deviation safety constraint respectively. The two evaluation values ​​are compared, and the larger value is the minimum inertia requirement evaluation value to ensure the safety and stability of the power system frequency.

[0058] Embodiment 2

[0059] This embodiment is further designed on the basis of the first embodiment. Figure 1 As shown, including:

[0060] In step 1, based on the traditional system frequency response model containing a single energy storage, a power system frequency response model containing two types of energy storage, electrochemical energy storage and flywheel energy storage, is established. In this model, various resources provide frequency support for the system according to their own frequency response principles. Based on this model, the frequency response closed-loop transfer function expression of the system is obtained. Specifically:

[0061] Step 1-1: The inertia of the energy storage system directly affects the system's initial frequency response capability to disturbances. The frequency response transfer function of the grid-type electrochemical energy storage based on droop control is:

[0062]

[0063] Step 1-2: The rotor motion equation of the flywheel energy storage based on virtual synchronous machine control can be expressed as:

[0064]

[0065] Where, T vm , T ve are the mechanical torque and electromagnetic torque of flywheel energy storage VSG, J v , K DV are the inertia coefficient and damping coefficient respectively; ω, ω0, ω′ are the rotation angular frequency, rated rotation angular frequency and per unit value of rotation angular frequency of flywheel energy storage VSG respectively; δ is the power angle of flywheel energy storage VSG.

[0066] Virtual rotor kinetic energy W of flywheel energy storage VSG k and virtual inertia coefficient H v The relationship can be expressed by the following formula:

[0067]

[0068] Where T vn Represents the torque of the virtual rotor of the flywheel energy storage. From the above formula, we can get:

[0069]

[0070] The frequency response transfer function of flywheel energy storage based on VSG control is:

[0071]

[0072] Steps 1-3: The traditional thermal power frequency modulation unit uses the classic low-order transfer function to be equivalent:

[0073]

[0074] In the formula, k m is the mechanical power factor; F H T is the work coefficient of the high pressure cylinder of the prime mover; R is the reheat time constant; R is the primary frequency modulation droop coefficient.

[0075] Step 1-4: The source-side wind power control mode adopts the inertia response and variable pitch primary frequency modulation control strategy, and the frequency response transfer function is:

[0076]

[0077] k pf represents the primary frequency modulation coefficient, T P represents the pitch response time constant, k df is the inertial response coefficient, T w is the inertial response time constant.

[0078] Step 1-5: When the grid frequency is disturbed, the photovoltaic system simulates the release of the rotor kinetic energy of the synchronous generator by adjusting its DC bus voltage. This adjustment can be achieved by controlling the power output of the DC / DC and DC / AC converters. The photovoltaic frequency response transfer function is:

[0079]

[0080] In the formula, k pv is the photovoltaic internal control proportional coefficient, C b is the high voltage DC capacitor, U dc is the high voltage DC voltage value, H pv is the virtual inertia time constant.

[0081] Step 1-6: Combine the frequency response models of electrochemical energy storage and flywheel energy storage with the frequency response models of wind power, photovoltaic power, and traditional thermal power to establish a system frequency response model that includes multiple types of energy storage, and obtain a closed-loop transfer function of the system frequency response:

[0082]

[0083] Where G(s) represents the forward channel transfer function in the frequency response model, and H(s) represents the feedback channel transfer function. w , α pv , α m , α E , α v They respectively represent the proportion of wind turbines, photovoltaic turbines, thermal power units, electrochemical energy storage and flywheel energy storage in the power system.

[0084] In step 2, the power system frequency response model containing two types of energy storage in step 1 is used to derive the expressions of the initial frequency change rate and steady-state frequency deviation after the system encounters a disturbance using the initial value theorem and the final value theorem. The above expressions can be used to analyze the influencing factors of the dynamic frequency characteristics of the system. Specifically:

[0085] Step 2-1, according to the initial value theorem:

[0086]

[0087] The expression of the initial frequency change rate r is obtained:

[0088]

[0089] In the formula, φ(s) represents the closed-loop transfer function of the system, U(s) represents the system input, and the system disturbance is usually represented by a step signal, so the input complex domain expression is ΔP LIndicates the disturbance amplitude. Substituting the closed-loop transfer function of the system into the derivation, we can get:

[0090]

[0091] Among them, G w (s), G pv (s), G m (s), G E (s), G v (s) are the transfer functions of wind power, photovoltaic power, thermal power, electrochemical energy storage and flywheel energy storage units, that is, the active power-frequency response relationship. Since s tends to infinity, the influence of the system's damping coefficient on the initial frequency change rate can be ignored. It can be seen from the above formula that the system's initial frequency change rate is related to the disturbance size, the total inertia of the system, and the relevant parameters of each unit.

[0092] Step 2-2: The steady-state frequency error (SSE) after the system encounters a disturbance can be obtained using the final value theorem, which can be expressed as:

[0093]

[0094] In the formula, φ(s) represents the closed-loop transfer function of the system, and U(s) represents the input signal of the system. The steady-state frequency deviation of the system can be further expressed as:

[0095]

[0096] It can be seen from the above formula that the steady-state deviation frequency of the system is related to the disturbance size encountered by the system, the system damping coefficient, and the parameters of each unit. The delay response coefficient T in each frequency regulation resource model is E , T B Parameters such as have almost no effect on the steady-state frequency. It can be seen that the above expression can be used to analyze the influencing factors of the system steady-state frequency deviation.

[0097] In step 3, the inertia time constant H is used to characterize the inertia of the system. Based on the relationship between the inertia time constant and the frequency characteristic quantity, the minimum inertia evaluation expression required by the system is proposed based on the maximum frequency deviation safety constraint and the initial frequency change rate safety constraint. These two formulas can be substituted into the corresponding values ​​for calculation, and finally two evaluation values ​​are obtained. The larger value is the minimum inertia requirement evaluation value that can ensure the safety and stability of the system frequency. Specifically:

[0098] Step 3-1: The inertia of the power system is usually characterized by the inertia time constant. The relationship between the equivalent inertia of a system containing multiple types of resources and the inertia time constant can be expressed as:

[0099]

[0100] Where, E represents the theoretical inertia value of the system; E m 、E w 、E pv 、E E 、E v They represent the inertia of traditional thermal power units and the virtual synchronous inertia values ​​of wind turbines, photovoltaic units, electrochemical energy storage units and flywheel energy storage units respectively; H xi Represents the inertia time constant of each type of inertia resource unit; S xi Represents the capacity of each type of inertia resource unit; Z xi Represents the on / off status of each type of inertia resource unit.

[0101] From the above formula, the equivalent inertia time constant of the system can be obtained as:

[0102]

[0103] Step 3-2: When the system encounters a disturbance, the minimum inertia value required to keep the initial rate of change of the system frequency from exceeding the safety threshold can be expressed as:

[0104]

[0105] H min represents the minimum equivalent inertia time constant of the system, f N is the system rated frequency, S N is the total rated capacity of the system, ΔP max Indicates the maximum value of the disturbance, r max Indicates the maximum limit of the frequency change rate.

[0106] Step 3-3: The minimum inertia value required to keep the system maximum frequency deviation below the safety threshold (generally set to 49Hz) can be expressed as:

[0107]

[0108] Where ΔP max Indicates the maximum value of the disturbance, f N is the system rated frequency, S N is the total rated capacity of the system, R is the synchronous modulation coefficient, f0 represents the primary frequency modulation dead zone, usually 0.033Hz, f min Indicates the value at which the frequency drops to the lowest point.

[0109] Step 3-4: When estimating the minimum inertia requirement of the system, in order to ensure that the initial frequency change rate and the maximum frequency deviation of the system are within the safe and stable range, it is necessary to select the larger value of equation (17) and equation (18). Let the minimum inertia requirement value of equation (17) be The minimum inertia requirement of formula (18) is

[0110]

[0111] Application Examples

[0112] This example uses the above-mentioned embodiment method to evaluate and simulate the minimum inertia requirement.

[0113] Use Figure 2 The method shown in the figure is used to build an equivalent frequency response model of a system including thermal power, wind and solar power, and two types of energy storage in Matlab / Simulink. The effect of the built model is as follows Figure 3 The system frequency in the model is set to 50Hz, the load type is constant power load, the total system rated capacity is set to 1000MW, the load disturbance is set to 100MW, and the per-unit disturbance value is set to 0.1pu. Other important parameters are given in the table below.

[0114] Table 1 Important parameters of system frequency response model

[0115]

[0116] The derivation of the closed-loop transfer function of the system can quantitatively analyze the frequency characteristics of the system. The simulation can intuitively show the relationship between various input parameters and the system frequency characteristics. Figure 4 The frequency characteristics of the system are shown when the electrochemical energy storage and flywheel energy storage have different capacity ratios.

[0117] The method of the present invention adopts a quantitative analysis method to dynamically characterize the minimum inertia requirement of the system by using the system equivalent inertia time constant. The estimated minimum inertia requirement value can enable the system to meet the dual frequency index constraints. When different system equivalent inertia time constants are set, the frequency characteristic quantity of the system is also different. When the system equivalent inertia time constant is less than the minimum inertia requirement of the system, the initial frequency change rate and the maximum frequency deviation may exceed the safety constraint range, such as Figure 5 shown.

[0118] Minimum inertia requirement evaluation method based on initial frequency change rate safety constraint and system rated frequency f N 、Total rated capacity of the system S N , the maximum disturbance ΔP max , Maximum limit of frequency change rate r max Set the system rated frequency to 50Hz, the disturbance size to 100MW to 300MW, the frequency change rate to 0.5Hz / s to 2Hz / s, the total system rated capacity to 1000MW, and the system minimum inertia requirement calculation results are as follows: Figure 6As shown. When the frequency change rate constraint r max When the disturbance value is kept at a fixed value, the system minimum inertia requirement evaluation value is positively correlated with the disturbance size. The larger the disturbance value, the higher the minimum inertia value required by the system. When the disturbance size is kept at a fixed value, the system minimum inertia requirement evaluation value is positively correlated with r max The constraints are negatively correlated. The stricter the constraints, the higher the required minimum inertia value. According to the parameter settings in Table 1, the disturbance value is 0.1pu, and the maximum frequency change rate of the system is 0.625Hz / s. If this value is used as the maximum frequency change rate constraint, H min The calculated value is 4s. When the equivalent inertia time constant of the system is set to this value, the system meets the maximum frequency change rate constraint.

[0119] Minimum inertia requirement evaluation and maximum disturbance ΔP based on maximum frequency deviation constraint max , system rated frequency f N , total rated capacity of the system S N , synchronous modulation coefficient R, primary frequency modulation dead zone limit f0 and lowest frequency f min f0 is usually 0.033Hz, and the maximum frequency deviation range is 0.4Hz to 0.7Hz. The calculation result of the minimum inertia requirement of the system is as follows: Figure 7 As shown. When the maximum frequency deviation constraint is kept at a fixed value, the system minimum inertia requirement evaluation value is positively correlated with the disturbance size. The larger the disturbance value, the higher the minimum inertia value required by the system. When the disturbance size is kept at a fixed value, the system minimum inertia requirement evaluation value is negatively correlated with the maximum frequency deviation constraint. The lower the maximum frequency deviation constraint value, the stricter the constraint, and the higher the minimum inertia value required by the system. Still according to the parameter settings in Table 1, the disturbance value is 0.1pu, and the maximum frequency deviation value of the system is 0.554Hz. If this value is used as the maximum frequency deviation constraint, H min The calculated value is 4.8s. When the equivalent inertia time constant of the system is set to this value, the system meets the maximum frequency deviation constraint. The larger the system H value, the higher the frequency stability. When the system meets the larger minimum inertia requirement, the frequency can remain stable.

[0120] Comparing the sizes of the above two evaluation values, the larger value is the minimum inertia requirement evaluation value to ensure the safety and stability of the power system frequency.

[0121] It can be seen that the present invention is applicable to the current "double-high" new power system background with multiple types of energy storage access, and has guiding significance for the system frequency stability analysis and inertia demand quantitative calculation including new energy units, traditional thermal power units and multiple types of energy storage.

[0122] The technical solutions of the present invention are not limited to the above-mentioned embodiments, and any technical solutions obtained by equivalent replacement methods fall within the scope of protection required by the present invention.

Claims

1. A method for evaluating the minimum inertia requirement of a multi-type energy storage power system, characterized in that: include: Step 1: Combine the system frequency response models of thermal power, wind power and photovoltaic power to establish a closed-loop transfer function of the power system frequency response including electrochemical energy storage and flywheel energy storage; Step 2: Based on the frequency response closed-loop transfer function of the power system, the initial frequency change rate and the steady-state frequency deviation of the power system after the disturbance are obtained by using the initial value theorem and the final value theorem respectively; Step 3: According to the initial frequency change rate and the steady-state frequency deviation, the evaluation value of the minimum inertia requirement of the power system is obtained based on the initial frequency change rate safety constraint and the maximum frequency deviation safety constraint respectively, and the two evaluation values ​​are compared, and the larger value is taken as the final minimum inertia requirement evaluation value.

2. The method for evaluating the minimum inertia requirement of a multi-type energy storage power system according to claim 1, characterized in that: The frequency response closed-loop transfer function of the power system is: Where φ(s) is the closed-loop transfer function of the system, Δf is the frequency change of the system, and ΔP L represents the disturbance size encountered by the system, G(s) represents the forward channel transfer function in the frequency response model, H(s) represents the feedback channel transfer function, H is the system equivalent inertia time constant; D is the system damping coefficient, α w , α pv , α m , α E , α v Respectively represent the proportion of wind turbines, photovoltaic units, thermal power units, electrochemical energy storage and flywheel energy storage in the power system; k pf represents the primary frequency modulation coefficient, T P represents the pitch response time constant, k df is the inertial response coefficient, T w is the inertial response time constant; k pv is the photovoltaic internal control proportional coefficient, C b is the high voltage DC capacitor, U dc is the high voltage DC voltage value, H pv is the virtual inertia time constant; k m is the mechanical power factor, F H is the work coefficient of the prime mover high pressure cylinder, T R is the reheating time constant, R is the primary frequency modulation droop coefficient; H E is the virtual inertia time constant, K E is the gain factor, T E represents the delayed response coefficient; k v represents the virtual droop coefficient, T B Represents the flywheel energy storage hysteresis coefficient, H v and D v are the virtual inertia coefficient and damping coefficient of the flywheel VSG respectively.

3. The method for evaluating the minimum inertia requirement of a multi-type energy storage power system according to claim 2, characterized in that: In the step 1, a closed-loop transfer function of the power system frequency response including electrochemical energy storage and flywheel energy storage is established, specifically including: Step 1-1: Establish the frequency response transfer function of the grid-type electrochemical energy storage based on droop control: In the formula, G E (s) is the electrochemical energy storage frequency response function, ΔP e is the change in electrochemical energy storage power, Δf e is the change in the frequency of electrochemical energy storage; Step 1-2: Establish the flywheel energy storage frequency response transfer function based on VSG control as: In the formula, G v (s) is the flywheel energy storage frequency response function, ΔP v is the change in flywheel energy storage power, Δf v is the change in flywheel energy storage frequency; Step 1-3: Establish the thermal power frequency response transfer function as follows: In the formula, G m (s) is the frequency response function of the traditional thermal power frequency regulation unit, ΔP m is the power change of the thermal power unit, Δf m is the frequency variation of the thermal power unit, k m is the mechanical power factor, F H is the work coefficient of the prime mover high pressure cylinder, T R is the reheating time constant, and R is the primary frequency modulation droop coefficient. Step 1-4, wind power frequency response transfer function is: In the formula, G w (s) is the frequency response function of the wind turbine, ΔP w is the power change of the wind turbine, Δf w is the frequency change of the wind turbine; Step 1-5, the photovoltaic frequency response transfer function is: In the formula, G pv (s) is the frequency response function of the photovoltaic unit, ΔP pv is the power change of the photovoltaic unit, Δf pv is the frequency change of the photovoltaic unit; Step 1-6: Combine the frequency response models of electrochemical energy storage and flywheel energy storage with the frequency response models of wind power, photovoltaic power, and thermal power to obtain a closed-loop transfer function of the system frequency response.

4. The method for evaluating the minimum inertia requirement of a multi-type energy storage power system according to claim 3 is characterized by: In step 2, the initial frequency change rate is: Among them, G w (s), G pv (s), G m (s), G E (s), G v (s) are the transfer functions of wind power, photovoltaic power, thermal power, electrochemical energy storage and flywheel energy storage units respectively.

5. The method for evaluating the minimum inertia requirement of a multi-type energy storage power system according to claim 4 is characterized in that: In step 2, the steady-state frequency deviation is:

6. The method for evaluating the minimum inertia requirement of a multi-type energy storage power system according to claim 5, characterized in that: In step 2, the estimated value of the minimum inertia requirement of the power system obtained based on the initial frequency change rate safety constraint is: Among them, H min represents the minimum equivalent inertia time constant of the system, f N is the system rated frequency, S N is the total rated capacity of the system, ΔP max Indicates the maximum value of the disturbance, r max Indicates the maximum limit of the frequency change rate.

7. The method for evaluating the minimum inertia requirement of a multi-type energy storage power system according to claim 6 is characterized by: In step 2, the evaluation value of the minimum inertia requirement of the power system obtained based on the maximum frequency deviation safety constraint is: Among them, ΔP max Indicates the maximum value of the disturbance, f N is the system rated frequency, S N is the total rated capacity of the system, R is the synchronous modulation coefficient, f0 represents the primary frequency modulation dead zone, usually 0.033Hz, f min Indicates the value at which the frequency drops to the lowest point.

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