Method and equipment for constructing equivalent mathematical model of high-capacity network-building energy storage power station

Abstract

The invention relates to the field of power grid system modeling, and discloses a method and equipment for constructing an equivalent mathematical model of a high-capacity network energy storage power station, and the method comprises the steps: constructing a network energy storage power station system; according to different dynamic characteristics, performing grouping operation on a plurality of converters in the network construction energy storage power station system by adopting a coherent equivalent grouping criterion method; performing parameter aggregation on the grouped converters to obtain a converter equivalent to one converter; and performing single-machine equivalence according to the equivalent converter, and performing corresponding scaling on the named value of the control parameter in proportion according to the rated capacity or the rated output power to obtain a single-machine equivalence model of the network-building energy storage power station. According to the equivalent aggregation method of the high-capacity networking energy storage power station, the simulation speed is increased, the analysis difficulty is reduced, and analysis of related problems of a power system under the access of the high-capacity energy storage power station is facilitated.

Description

Technical Field

[0001] The present invention relates to the field of power grid system modeling, and in particular to a method and device for constructing an equivalent mathematical model of a large-capacity grid-building energy storage power station. Background Art

[0002] Today, energy storage technology is developing rapidly, and the scale of energy storage power stations is constantly expanding. There are even energy storage power stations of hundreds of megawatts. Energy storage power stations can be used for voltage support, reactive power control, improvement of commutation failure and frequency modulation of power grids. The rise of large-scale energy storage technology plays a powerful role in absorbing new energy and supporting the stability of power grids. Energy storage power stations have obvious technical advantages in terms of response speed, regulation accuracy and construction flexibility. At the same time, with the large-scale access of power electronic equipment, the inertia of today's power system is gradually decreasing. Today, the world is gradually adopting converter network control strategies to deal with such problems. Network control technology in the field of energy storage is gradually being widely used.

[0003] With the construction of a large number of energy storage power stations, relevant research on the application of energy storage power stations in power systems has also been gradually carried out. However, as the scale of energy storage grid connection continues to increase, the simulation model results of energy storage systems have become more complex, resulting in problems such as slow simulation speed and low efficiency, which is not conducive to actual analysis and calculation. In addition, the existing literature did not consider the detailed structure of the energy storage power station when conducting relevant analysis on the application of energy storage power stations in power systems. Generally, one converter was used for equivalent analysis, which made the accuracy and persuasiveness of the analysis results lack. Summary of the invention

[0004] The purpose of the present invention is to propose a method and device for constructing an equivalent mathematical model of a large-capacity grid-connected energy storage power station, so as to solve the problems of slow simulation speed, low efficiency, being unfavorable for actual analysis and calculation, and not considering the actual situation in the modeling and simulation of the existing power grid energy storage system.

[0005] In view of the above problems, the present invention adopts an equivalent model to replace the detailed model for simulation calculation, thereby simplifying the model, improving efficiency, and ensuring the accuracy of the analysis results when analyzing other problems.

[0006] The present invention specifically comprises the following steps:

[0007] S1: Constructing a grid-connected energy storage power station system;

[0008] S2: According to different dynamic characteristics, multiple converters in the grid-connected energy storage power station system are grouped using a grouping criterion method of coherent equivalence;

[0009] S3: aggregate parameters of the grouped converters to form a single converter.

[0010] S4: Perform single-machine equivalent according to the equivalent converter, scale the nominal value of the control parameter accordingly according to the rated capacity or rated output power, and obtain a single-machine equivalent model of the grid-connected energy storage power station.

[0011] A storage medium stores instructions and data for realizing a method for constructing an equivalent mathematical model of a large-capacity grid-connected energy storage power station.

[0012] A device for constructing an equivalent mathematical model of a large-capacity grid-connected energy storage power station comprises: a processor and the storage medium; the processor loads and executes instructions and data in the storage medium to implement a method for constructing an equivalent mathematical model of a large-capacity grid-connected energy storage power station.

[0013] The beneficial effects provided by the present invention are:

[0014] 1. Three coherence criteria are used to make judgments together to enhance persuasiveness and ensure the correctness and accuracy of the grouping operation. At the same time, the physical quantities of the above three criteria are easy to obtain, and the results are obviously different, which is conducive to the grouping operation;

[0015] 2. Aiming at the problem that the aggregation of single-machine parameters of grid-controlled converters is incomplete and has differences, the present invention considers the converter under the control of a virtual synchronous generator, considers its internal control parameters and voltage loop and current loop control parameters as well as system filter parameters and line parameters, sorts out and compares parameter aggregation methods, and proposes an aggregation method with relatively excellent effect;

[0016] 3. For the case where the per-unit values ​​of the control parameters of the energy storage units in the energy storage power station are consistent, a corresponding aggregation equivalent method is proposed. In this case, the effect of using proportional scaling equivalent is excellent and can meet the equivalent requirements. This equivalent method is useful in practical applications, because when the same energy storage power station is established, the per-unit values ​​of the control parameters of each converter inside it should be the same, and even the rated power is likely to be the same, so this equivalent aggregation method can meet the needs of most cases, and the aggregation steps are simple. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It is a schematic flow chart of the method of the present invention;

[0018] Figure 2 It is a schematic diagram of the energy storage power station system architecture;

[0019] Figure 3 is the normalized output current curve of each energy storage unit;

[0020] Figure 4 is the normalized curve of output power of each energy storage unit;

[0021] Figure 5is the power angle curve of each energy storage unit converter;

[0022] Figure 6 It is a schematic diagram of the system after the energy storage power station is aggregated;

[0023] Figure 7 It is a verification diagram of the dynamic characteristics effect of multi-machine equivalent aggregation in energy storage power station;

[0024] Figure 8 It is a verification diagram of the effect of the equivalent aggregate impedance characteristics of multiple machines in the energy storage power station;

[0025] Fig. 9 It is a verification diagram of the dynamic characteristics of the equivalent aggregation of different single-unit parameters of the energy storage power station;

[0026] Fig.10 This is a verification diagram of the effect of the equivalent aggregate impedance characteristics of different single-unit parameters of the energy storage power station;

[0027] Fig.11 This is a schematic diagram of equivalent modeling under the same per-unit parameters inside the energy storage power station;

[0028] Fig.12 It is a verification diagram of the effect of the equivalent aggregation dynamic characteristics of a single unit with the same per unit parameters of an energy storage power station;

[0029] Fig.13 It is a verification diagram of the effect of the equivalent aggregate impedance characteristics of a single unit with the same per unit parameters of an energy storage power station;

[0030] Fig.14 It is a working schematic diagram of the hardware device of the present invention. DETAILED DESCRIPTION

[0031] In order to make the objectives, technical solutions and advantages of the present invention more clear, the embodiments of the present invention will be further described below with reference to the accompanying drawings.

[0032] Before formally describing the present invention, the scheme of the present invention is first generally described for easy understanding.

[0033] Please refer to Figure 1 , Figure 1 It is a schematic flow diagram of the method of the present invention.

[0034] The present invention provides a method for constructing an equivalent mathematical model of a large-capacity grid-connected energy storage power station, comprising the following steps:

[0035] S1: Constructing a grid-connected energy storage power station system;

[0036] Please refer to Figure 2 , Figure 2It is a schematic diagram of the energy storage power station system architecture; the grid-type energy storage power station system includes: a grid-type energy storage power station and an AC power grid; the grid-type energy storage power station and the AC power grid are electrically connected; the grid-type energy storage power station includes: multiple battery packs and corresponding multiple converters.

[0037] S2: According to different dynamic characteristics, multiple converters in the grid-connected energy storage power station system are grouped using a grouping criterion method of coherent equivalence;

[0038] It should be noted that when the dynamic characteristics and impedance characteristics of multiple converter units are greatly different, a simple single-unit equivalence cannot be performed, otherwise it will cause large errors.

[0039] When the dynamic characteristics of the converter differ greatly from the line parameters, the coherent equalization method should be adopted for aggregation. The coherent grouping criterion is:

[0040]

[0041] Among them, i p (t) represents the instantaneous value of the grid-connected current of the converter, P(t) represents the instantaneous value of the grid-connected power of the converter, and P ref Indicates the rated power of the converter, ε i Indicates the allowable error of the current criterion, ε p Represents the allowable error of power criterion, ε δ Indicates the allowable error of the power angle criterion.

[0042] As an example, in this example, the current criterion allowable error is selected as 2*10 -5 (Since it is divided by the rated power value, the error magnitude is reduced accordingly), the allowable error for power criterion is 3, and the allowable error for power angle criterion is 4°.

[0043] In the τ time after the fault occurs, as long as the two converters meet the three synchronization criteria, they can be judged to be synchronized and divided into a subgroup. If the judgment is not strict, it is allowed to meet two synchronization criteria to judge the synchronization.

[0044] In this example, the per-unit parameters of the six converters are set to be different, and the above grouping operation is performed. Figure 3 , Figure 4 , Figure 5 They are the normalized output current curve of each energy storage unit, the normalized output power curve of each energy storage unit, and the power angle curve of each energy storage unit converter. After analysis and comprehensive judgment, the six converters were finally divided into two synchronous groups. Group 1 includes GFM1, GFM2, and GFM3, and Group 2 includes GFM4, GFM5, and GFM6. Within the group, the dynamic characteristics and impedance characteristics of the converters are similar, with no significant differences. Figure 6It is a schematic diagram of the internal equalization of the system energy storage power station.

[0045] The present invention selects three coherence criteria for grouping determination, proposes a power criterion, and performs certain normalization processing on the current criterion and the power criterion, thereby achieving optimization, being beneficial to the actual grouping operation, and making the result more obvious and accurate.

[0046] S3: aggregate parameters of the grouped converters to form a single converter.

[0047] It should be noted that after the converters inside the energy storage power station are synchronized and grouped, the single-machine aggregation operation is performed in each group according to the following formula:

[0048]

[0049] P eq Indicates the equivalent rated output active power after equalization within the group, Q eq Indicates the equivalent rated output reactive power after equalization within the group.

[0050]

[0051] Where, J represents the active damping coefficient, J eq represents the active damping coefficient of the converter after equal value aggregation, D p Denotes the inertia coefficient, D peq represents the inertia coefficient of the converter after equal value aggregation, K represents the reactive integral coefficient, K eq Represents the reactive power integral coefficient of the converter after equal value aggregation, D q Indicates voltage virtual inertia, D qeq Represents the converter voltage virtual inertia after equal value aggregation.

[0052]

[0053] Among them, k Pv Represents the voltage loop proportional gain coefficient, k Iv Represents the voltage loop integral gain coefficient, k Pi Represents the current loop proportional gain coefficient, k Ii represents the current loop integral gain coefficient, c i represents the rated power weight of the i-th converter, and n represents the number of converters in the cluster performing aggregation operation.

[0054]

[0055] L represents the inductance inside the converter, R represents the resistance inside the converter, and C represents the capacitance inside the converter. The above LRCs all include filtering and line impedance devices, that is, the filtering devices and line impedance devices are aggregated and equalized in parallel using the method of equalization.

[0056] After the two groups are equalized, the equalization effect is verified. Figure 7 The solid line in the middle is the detailed model result, and the dashed line is the response result after equalization. Figure 8 The solid line in the middle is the detailed model admittance result, and the dashed line is the coherent equivalent admittance result. Figure 7 It can be seen that the dynamic characteristic curves before and after the equal value are in good agreement. Figure 8 This shows that the admittance characteristics before and after the equivalence are in good agreement, with only a certain difference in the amplitude-frequency characteristics near 10 Hz. Overall, the admittance characteristics before and after the equivalence are not much different, and can meet the equivalence requirements.

[0057] If the six GFMs are directly aggregated into single machines without coherent grouping, the results will be compared with the coherent equivalent effect. Fig. 9 , Fig.10 When the six GFM inverters with large differences in control parameters and not belonging to the same group are directly aggregated into one GFM, a large error will occur, and the dynamic characteristics and impedance characteristics cannot match, so it is impossible to directly aggregate them using single-machine equivalence, which also shows the superiority and necessity of synchronous equivalence.

[0058] S4: Perform single-machine equivalent according to the equivalent converter, scale the nominal value of the control parameter accordingly according to the rated capacity or rated output power, and obtain a single-machine equivalent model of the grid-connected energy storage power station.

[0059] It should be noted that the single-machine equivalent method is applicable to the case where the per-unit values ​​of the control parameters of the energy storage unit converters within the energy storage power station are the same. The energy storage converter is equivalent to a large-capacity converter with the same per-unit value of the control parameters, and the nominal value of the control parameter is scaled accordingly according to the rated capacity or rated output power.

[0060] As a specific embodiment, please refer to Fig.11 , Fig.11 This is a schematic diagram of equivalent modeling under the same per-unit parameters inside the energy storage power station;

[0061] The single machine equivalent method is as follows:

[0062]

[0063] P=kP base ,Q=kQ base

[0064]

[0065] Where k is the power proportional coefficient, which is used to characterize the parameter scaling ratio, P rated Indicates the rated power of a single converter, P base Indicates the selected reference active power, Q base Indicates the selected reference reactive power, L f , C f Represents the filter inductance and filter capacitance of the grid-connected converter, R d , L c represents the converter line parameters, k Pi represents the proportional gain parameter of the current loop in the network control, k Ii Current loop integral gain parameter, k Pu Voltage loop proportional gain parameter, k Iu represents the proportional integral parameter of the voltage loop, J represents the inertia coefficient, D p Represents the active damping coefficient, D q represents the voltage virtual inertia, and K represents the reactive integral coefficient. l Indicates the scaling factor of each converter inside the energy storage power station, Represents the aggregation scaling factor.

[0066] In the process of energy storage power station equivalence, it is only necessary to determine the aggregation scaling coefficient of the energy storage power station, and then scale it according to the parameter scaling method to obtain the aggregated equivalent model. Fig.12 As shown in Figure 1, a three-phase grounding fault is set at 1s in the time domain model, and the fault is removed at 1.05s. The equivalent effect is verified by comparing the dynamic characteristics of equivalent aggregation. Fig.13 As shown, the impedance characteristics before and after equalization are verified using the small signal impedance model. Fig.12 In the figure, the solid line is the power input to the grid by the six converters before equalization, and the dotted line is the power response of the converter input to the grid after equalization. It can be clearly seen that the two are basically consistent, indicating that the dynamic characteristics do not change much before and after equalization. Fig.13 The solid line in the middle is the sum of the admittances of the six converters before being equalized, and the dotted line is the admittance of the converter after being equalized. It can be seen that the results are very consistent.

[0067] In summary, the effect of using proportional scaling in this case is excellent and can meet the equivalent requirements. This equivalent method is useful in practical applications, because when the same energy storage power station is established, the per-unit values ​​of the control parameters of each converter inside it should be the same, and even the rated power is likely to be the same, so this equivalent aggregation method can meet the needs of most cases.

[0068] See also Fig.14 , Fig.14It is a schematic diagram of the working of the hardware device of an embodiment of the present invention, and the hardware device specifically includes: an equivalent mathematical model construction device 401 of a large-capacity grid-connected energy storage power station, a processor 402 and a storage medium 403.

[0069] An equivalent mathematical model construction device 401 for a large-capacity grid-connected energy storage power station: The equivalent mathematical model construction device 401 for a large-capacity grid-connected energy storage power station implements an equivalent mathematical model construction method for a large-capacity grid-connected energy storage power station.

[0070] Processor 402: The processor 402 loads and executes the instructions and data in the storage medium 403 to implement the method for constructing an equivalent mathematical model of a large-capacity grid-connected energy storage power station.

[0071] Storage medium 403: The storage medium 403 stores instructions and data; the storage medium 403 is used to implement the method for constructing an equivalent mathematical model of a large-capacity grid-connected energy storage power station.

[0072] The beneficial effects of the present invention are:

[0073] When analyzing the access of a grid-connected energy storage power station to a power system, a simplified model is generally used or a converter is used to equivalently replace the entire energy storage power station, without considering the differences in its internal parameters and line impedance, resulting in insufficient accuracy of the analysis results. Or a detailed model is considered but the result is too complex, which is not conducive to simulation analysis and calculation. The present invention considers studying the internal topological structure of a grid-connected energy storage power station, and proposes an equivalent aggregation method for a large-capacity grid-connected energy storage power station to improve the simulation speed and reduce the difficulty of analysis. According to this method, the grid-connected energy storage power station is simplified, which is conducive to the analysis of power system-related issues under the access of a large-capacity energy storage power station.

[0074] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for constructing an equivalent mathematical model of a large-capacity grid-connected energy storage power station, characterized in that: Methods include: S1: Constructing a grid-connected energy storage power station system; S2: According to different dynamic characteristics, multiple converters in the grid-connected energy storage power station system are grouped using a coherent and equivalent grouping criterion method; S3: aggregate parameters of the grouped converters to make them equivalent to one converter; S4: Perform single-machine equivalent according to the equivalent converter, scale the nominal value of the control parameter accordingly according to the rated capacity or rated output power, and obtain a single-machine equivalent model of the grid-connected energy storage power station.

2. The method for constructing an equivalent mathematical model of a large-capacity grid-connected energy storage power station according to claim 1, characterized in that: The grid-type energy storage power station system comprises: a grid-type energy storage power station and an AC power grid; the grid-type energy storage power station and the AC power grid are electrically connected; the grid-type energy storage power station comprises: a plurality of battery packs and a corresponding plurality of converters.

3. The method for constructing an equivalent mathematical model of a large-capacity grid-connected energy storage power station according to claim 1, characterized in that: In step S2, the grouping criteria are as follows: Among them, i p (t) represents the instantaneous value of the inverter grid-connected current, P(t) represents the instantaneous value of the inverter grid-connected power, P ref Indicates the rated power of the converter, ε i Indicates the allowable error of the current criterion, ε p Represents the allowable error of power criterion, ε δ Indicates the allowable error of the power angle criterion.

4. A method as claimed in claim 3, characterized in that: During the τ time after the fault occurs, as long as the two converters meet three or two grouping criteria, they can be judged to be synchronous and divided into one group.

5. The method for constructing an equivalent mathematical model of a large-capacity grid-connected energy storage power station according to claim 4, characterized in that: Step S3 is as follows: After the converters inside the energy storage power station are synchronized and grouped, the single-machine aggregation operation is performed in each group according to the following formula: P eq Indicates the equivalent rated output active power after equalization within the group, Q eq Indicates the equivalent rated output reactive power after equalization within the group; Where, J represents the active damping coefficient, J eq represents the active damping coefficient of the converter after equal value aggregation, D p Denotes the inertia coefficient, D peq represents the inertia coefficient of the converter after equal value aggregation, K represents the reactive integral coefficient, K eq Represents the reactive power integral coefficient of the converter after equal value aggregation, D q Indicates voltage virtual inertia, D qeq It represents the converter voltage virtual inertia after equal value aggregation; Among them, k Pv Represents the voltage loop proportional gain coefficient, k Iv Represents the voltage loop integral gain coefficient, k Pi Represents the current loop proportional gain coefficient, k Ii represents the current loop integral gain coefficient, c i represents the rated power weight of the i-th converter, and n represents the number of converters in the cluster for aggregation operation; L represents the inductance inside the converter after equivalent, R represents the resistance inside the converter, and C represents the capacitance inside the converter. The above LRCs all include filtering and line impedance devices, that is, the filtering devices and line impedance devices are aggregated and equalized in a parallel manner.

6. The method for constructing an equivalent mathematical model of a large-capacity grid-connected energy storage power station according to claim 5, characterized in that: The single machine equivalent method in step S4 is as follows: P=kP base ,Q=kQ base Where k is the power proportional coefficient, which is used to characterize the parameter scaling ratio, P rated Indicates the rated power of a single converter, P base Indicates the selected reference active power, Q base Indicates the selected reference reactive power, L f , C f Represents the filter inductance and filter capacitance of the grid-connected converter, R d , L c represents the converter line parameters, k Pi represents the proportional gain parameter of the current loop in the network control, k Ii Current loop integral gain parameter, k Pu Voltage loop proportional gain parameter, k Iu represents the proportional integral parameter of the voltage loop, J represents the inertia coefficient, D p Represents the active damping coefficient, D q represents the voltage virtual inertia, K represents the reactive integral coefficient; k l Indicates the scaling factor of each converter inside the energy storage power station, Represents the aggregation scaling coefficient; the aggregation scaling coefficient of the energy storage power station is calculated, and then scaled according to the parameter scaling method to obtain the aggregated equivalent model.

7. A storage medium, characterized in that: The storage medium stores instructions and data for implementing the method for constructing an equivalent mathematical model of a large-capacity grid-connected energy storage power station as described in any one of claims 1 to 6.

8. An equivalent mathematical model construction device for a large-capacity grid-connected energy storage power station, characterized in that: include: Processor and storage medium; the processor loads and executes instructions and data in the storage medium to implement the method for constructing an equivalent mathematical model of a large-capacity grid-connected energy storage power station as described in any one of claims 1 to 6.

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