Source network load storage new energy base collection system equivalent impedance modeling and order reduction method

Abstract

The invention provides an equivalent impedance modeling and order reduction method for a source network load storage new energy base collection system, and the method comprises the steps: firstly, giving a topological structure design of a large-scale new energy and energy storage large base system, and putting forward a thought that new energy electric power is subjected to the enhanced power generation through an electric heating-heat storage-steam turbine; a new energy base is constructed, and an equivalent thermal power system is constructed through source-network-load-storage integration. And thirdly, considering a convergence system impedance equivalent circuit model order reduction method of the converter cluster again, providing a convergence system impedance network based on Kron order reduction in combination with the equivalent impedance of the synchronous generator and an xy-dq reference coordinate system, and finally providing an equivalent impedance network of the whole convergence system. According to the method, a model foundation is laid for operation scheduling, control design and the like caused by source side factors such as control parameters, output levels and access modes of various types of units in a new energy base and network side factors such as power grid strength and line parameters.

Description

Technical Field

[0001] The present invention belongs to the field of energy, and particularly relates to an equivalent impedance modeling and reduction method for a source-network-load-storage new energy base aggregation system. Background Art

[0002] In recent years, the installed capacity of wind power and photovoltaic power generation has developed rapidly, and new energy bases have been rapidly deployed. However, the power load is concentrated in different places, so the power of new energy bases needs to be consumed through grid connection and transmission. Due to the volatility, intermittency and randomness of new energy, the current power system faces problems such as insufficient regulation resources, difficult peak shaving, frequency modulation and voltage regulation in weak power grids. Especially in the "desert, gobi and wasteland" new energy bases where the proportion of new energy exceeds 50%, new energy power faces problems such as difficult power transmission and low enthusiasm of receiving-end power grids to accept it.

[0003] As the cost per kilowatt-hour of wind power and photovoltaic power becomes lower and lower, new energy power is directly converted into thermal energy for storage and used for steam turbine generator units to generate electricity, or new energy power is directly converted into pumped-storage gravitational potential energy, lithium-ion battery energy storage, etc., and the energy storage is converted into power output when the power transmission demand is large. By coupling large-scale energy storage, large-scale new type of power sources for sending can be used to support the power transmission of wind power and photovoltaic bases, which will have greater flexibility and higher comprehensive benefits.

[0004] Therefore, when considering the energy storage system, traditional new energy large bases such as wind power and photovoltaic power generation are transformed into an equivalent power supply platform of source-network-load-storage integration. The flexible power output and adjustable capacity of the new energy base aggregation area for transmitting power to the external power grid are reshaped, which has a strong correlation with the spatial distribution and output characteristics of the source-network-load-storage in the aggregation area, especially synchronous generators, multiple energy storage systems and new energy. However, the electrical aggregation system design of new energy and energy storage large bases such as wind power and photovoltaic power generation is a complex project, involving multiple factors, including electrical topology, system capacity, economy, reliability, etc. At present, there is no electrical aggregation system for new energy and energy storage integration large bases that is compatible with multiple factors. Summary of the Invention

[0005] To solve the above technical problems, the present invention provides an equivalent impedance modeling and reduction method for a source-network-load-storage new energy base aggregation system, establishes an equivalent impedance network of the new energy base aggregation system, and lays a model foundation for source-side factors such as control parameters, output levels, and access methods of various types of units in the new energy base, as well as grid-side factors such as grid strength and line parameters, which cause operation scheduling, control design, etc. Furthermore, the new energy base coupled with large-scale energy storage is equivalent to a flexible adjustable virtual power plant.

[0006] To achieve the above object, the present invention adopts the following technical solutions:

[0007] An equivalent impedance modeling and reduction method for the aggregation system of a source-network-load-storage new energy base, comprising the following steps:

[0008] Step 1: Design the topological structure of the large-scale new energy and energy storage base system;

[0009] Step 2: Model the equivalent circuit of the whole network impedance of the large-scale photovoltaic and wind power aggregation system;

[0010] Step 3: Design a reduction method for the equivalent circuit model of the impedance of the aggregation system considering the converter cluster;

[0011] Step 4: Design an impedance network modeling method considering the internal potential of the synchronous generator;

[0012] Step 5: Equivalent the large-scale new energy and energy storage base to a super power plant with multiple synchronous generators and its transmission system, and conduct overall impedance modeling.

[0013] The present invention first gives the topological structure design of the large-scale new energy and energy storage base system, proposes the idea of enhancing power generation by electric heating-thermal energy storage-steam turbine for new energy power, and constructs an equivalent thermal power system for the new energy base through the integration of source-network-load-storage. Secondly, considering the reduction method for the equivalent circuit model of the impedance of the aggregation system with converter clusters, combined with the equivalent impedance of the synchronous generator and the xy-dq reference coordinate system, a Kron-based reduced impedance network of the aggregation system is proposed. Finally, the equivalent impedance network of the entire aggregation system is proposed.

[0014] Beneficial effects:

[0015] The equivalent impedance modeling and reduction method for the source-network-load-storage aggregation system of the new energy base has significant advantages in power system analysis, especially in aspects such as power flow calculation, dynamic stability analysis, and fault protection. That is, the advantages of the present invention are mainly reflected in the following aspects:

[0016] 1) The new energy base usually includes multiple new energy power generation units such as wind power and photovoltaic power, energy storage systems (such as battery energy storage), loads, and grid connections. Through equivalent impedance modeling, these complex components can be simplified into an equivalent circuit model, effectively reducing the calculation amount. This simplification enables the rapid acquisition of basic parameters such as system voltage and power during power flow calculation, providing a basis for subsequent analysis.

[0017] 2) In a large-scale new energy system, the number of state variables and equations is huge, and traditional analysis methods may lead to too long calculation time. The equivalent impedance modeling and reduction technology for the source-network-load-storage aggregation system of the new energy base can extract the main dynamic characteristics of the system, significantly shortening the calculation time. Especially under the requirements of real-time monitoring and rapid response, this advantage is particularly prominent.

[0018] 3) The equivalent impedance modeling and reduction technology of the source-network-load-storage aggregation system is not only applicable to power flow calculation, but also can effectively support various power system analyses such as dynamic stability analysis and fault protection. By establishing a unified equivalent model, various analyses can be carried out within the same framework, improving the overall operability and analysis efficiency of the system. Brief Description of the Drawings

[0019] Figure 1 is a schematic diagram of the topological structure of a large base system of conventional power sources, large-scale new energy, and energy storage;

[0020] Figure 2 is a schematic diagram of the equivalent impedance circuit of the new energy base aggregation system;

[0021] Figure 3 is a schematic diagram of the equivalent impedance reduction circuit of the aggregation system;

[0022] Figure 4 is a relationship diagram of the dq and xy coordinate systems;

[0023] Figure 5 is a schematic diagram of the aggregation system equivalent to a multi-machine system.

[0024] Among them, the reference numerals in the drawings are: the 2nd electrical aggregation system bus 2 to the 17th electrical aggregation system bus 17, the outgoing bus 101, the equivalent synchronous generator #1 unit #1, and the equivalent synchronous generator #2 unit #2. Detailed Embodiment

[0025] In order to make the objectives, technical solutions, and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other. The present invention will be further described below with reference to the drawings and specific embodiments.

[0026] The present invention provides a method for equivalent impedance modeling and reduction of a source-network-load-storage new energy base aggregation system, including the following steps:

[0027] Step 1: Design the topological structure of the large base electrical aggregation system for large-scale new energy and energy storage, including:

[0028] The large base electrical aggregation system mainly adopts a radial topological structure and supplemented by a ring topological structure. The radial topology is simple and easy to construct, and can effectively reduce transmission losses. The large base electrical aggregation system designed by the present invention is as Figure 1 shown, including the 2nd electrical aggregation system bus 2 to the 17th electrical aggregation system bus 17, and these buses are as Figure 1The topological connection shown. The 500 kV main power grid is the external power transmission grid. The outgoing bus 101 is the sectional plane between the equivalent power source of the present invention and the external power grid, and a measuring unit can be configured to monitor the change in the output of the equivalent power source.

[0029] As Figure 1 As shown on the left, the large-scale photovoltaic power generation station is stepped up and transmitted to the 220 kV local power grid through a low-voltage transformer, a 10 / 35 kV transformer, and a 35 / 220 kV transformer; the large-scale electric heater array acts as a load in the 220 kV power grid and receives power through a 220 / 35 kV step-down transformer and a 35 / 10 kV step-down transformer; a molten salt heat storage tank is used to store the heat energy produced by the large-scale electric heater and send the heat energy into the steam unit of the thermal power plant for power generation; the steam unit generator set is stepped up through an 18 / 220 kV transformer and transmitted to the external power grid; at the same time, the large-scale photovoltaic power generation base can be directly transmitted to the external network.

[0030] Figure 1 As shown on the right, the large-scale wind power base is transmitted to the external power grid through a step-up transformer, and combined with pumped storage and electrochemical lithium-ion battery energy storage, the wind power-storage bundled transmission is implemented.

[0031] On the other hand, the power grids on the left and Figure 1 right of the present invention are interconnected through a back-to-back converter, that is, a ring topology structure is constructed to ensure that the collection system has redundancy and fault isolation capabilities, and improve the reliability of the system and the continuity of power supply. Figure 1

[0032] Step 2: Model the impedance equivalent circuit of the large-scale photovoltaic and wind power collection system, including:

[0033] For the large-scale base electrical collection system proposed by the present invention, a multi-stage step-up transformer is used for power transfer, external transmission and local consumption. When analyzing the dynamic characteristics of the electrical quantities in the collection system, especially the dynamic stability, impedance modeling is an effective method. The present invention selects 500 kV and 1000 MW of the large-scale base electrical collection system as the reference values to perform impedance modeling on the large-scale base electrical collection system. The equivalent circuit diagram is as Figure 2 shown. Figure 2 Among them, 2-17 respectively represent the bus 2 of the second electrical collection system to the bus 17 of the 17th electrical collection system, which are the same buses as those in Figure 1 . The topological connections of these buses are as Figure 2 shown, and its connection path is the same as that in Figure 1 .

[0034] ​The flexible thermal power plant is equivalent to an injected current source, and the electric heating device is equivalent to an energy-absorbing current source; the wind power and photovoltaic converters are equivalent to injected current sources. Here, it is considered that the wind power and photovoltaic converters are in the MPPT maximum power tracking mode and the grid-following control mode; the pumped-storage units and lithium-ion battery energy storage are both equivalent to bidirectional current sources; in the present invention, the connection Figure 1 on the left side and Figure 1 the back-to-back converter on the right side is equivalent to an injected and output current source.

[0035] For a large-scale photovoltaic power generation and wind power grid-connected system, the impedances of all converter units and their grid-connected branch lines are not the same. Therefore, as Figure 1 shown, it can be defined as , , , where the subscript at the lower right is the serial number of the upper-level circuit, and the superscript at the upper right is the number of the low-voltage converter unit. is the resistance of the connection line between the first-numbered low-voltage converter and the upper-level circuit, is the reactance of the connection line between the first-numbered low-voltage converter and the upper-level circuit, is the resistance of the connection line between the second-numbered low-voltage converter and the upper-level circuit, is the reactance of the connection line between the second-numbered low-voltage converter and the upper-level circuit, is the resistance of the connection line between the third-numbered low-voltage converter and the upper-level circuit, is the reactance of the connection line between the third-numbered low-voltage converter and the upper-level circuit; j represents the imaginary unit.

[0036] Step 3: Design a method for reducing the order of the equivalent circuit model of the collection system impedance considering the converter cluster, including:

[0037] Based on Kirchhoff's voltage law and the circuit phasor model, establish the voltage-current correlation equations of all converter equivalent current sources, the synchronous generator equivalent current source, and the impedance network as follows:

[0038] (1)

[0039] Among them, the second bus is the grid-connected bus, and the fourteenth bus is the synchronous generator equivalent current source bus. , respectively represent the voltages of the synchronous generator, the equivalent current source of the sixteenth bus and the grid-connected bus. , , are the voltages between the first converter equivalent current source branches of the fifth bus, the seventh bus, and the eighth bus of the equivalent current source and the grid-connected bus. , , respectively represent the loop impedance between the equivalent current source of the synchronous generator and the 3rd bus, the loop impedance between the 2nd bus and the 3rd bus, the loop impedance between the 2nd bus and the 5th bus, etc. , respectively represent the branch impedances of the first and second converter equivalent current sources of the 5th bus. , respectively represent the branch impedances of the first converter equivalent current sources of the 7th bus and the 8th bus. , are respectively the input currents of the equivalent current sources of the synchronous generator and the converter of the 16th bus. represents the output current of the first converter equivalent current source branch of the 5th bus. , respectively represent the input currents of the first converter equivalent current source branches of the 7th bus and the 8th bus. , respectively represent the branch impedances of the second and third converter equivalent current sources of the 7th bus. , , , respectively represent the branch impedances of the second, third, and fourth converter equivalent current sources of the 8th bus. , , , are respectively the loop impedance between the 2nd bus and the 4th bus, the loop impedance between the 2nd bus and the 6th bus, the loop impedance between the 2nd bus and the 7th bus, and the loop impedance between the 2nd bus and the 8th bus. , , are the voltages between the second converter equivalent current source branches of the 5th bus, 7th bus, and 8th bus of the equivalent current source and the grid-connected bus. , are the voltages between the third converter equivalent current source branches of the 7th bus and the 8th bus of the equivalent current source and the grid-connected bus. is the voltage between the fourth converter equivalent current source branch of the 8th bus of the equivalent current source and the grid-connected bus. represents the output current of the second converter equivalent current source branch of the 5th bus. , respectively represent the input currents of the second converter equivalent current source branches of the 7th bus and the 8th bus. , respectively represent the input currents of the third converter equivalent current source branches of the 7th bus and the 8th bus. represents the input current of the fourth converter equivalent current source branch of the 8th bus.

[0040] Meanwhile, the current sources equivalent to each converter and the current sources equivalent to the synchronous generators are simplified and combined, and their current relationships satisfy the following equations:

[0041] (2)

[0042] Wherein, represents the output current of the first converter equivalent current source branch of the 5th bus, , respectively represent the input currents of the first converter equivalent current source branches of the 7th bus and the 8th bus represents the output current of the second converter equivalent current source branch of the 5th bus, , respectively represent the input currents of the second converter equivalent current source branches of the 7th bus and the 8th bus. , respectively represent the input currents of the third converter equivalent current source branches of the 7th bus and the 8th bus. represents the sum of the output currents of the first and second converter equivalent current source branches of the 5th bus. represents the sum of the input currents of the first, second, and third converter equivalent current source branches of the 7th bus. represents the sum of the input currents of the first, second, and third converter equivalent current source branches of the 7th bus.

[0043] Furthermore, substituting Equation (2) into Equation (1), Equation (1) can be simplified to:

[0044] (3)

[0045] Wherein, the 2nd bus is the grid-connected bus, and the 14th bus is the synchronous generator equivalent current source bus, , respectively represent the voltages of the synchronous generator, the equivalent current source of the 16th bus, and the grid-connected bus, , , are the voltages between the first converter equivalent current source branches of the 5th, 7th, and 8th buses of the equivalent current source and the grid-connected bus. , , etc. respectively represent the loop impedances between the synchronous generator equivalent current source and the 3rd bus, the loop impedance between the 2nd bus and the 3rd bus, the loop impedance between the 2nd bus and the 5th bus, etc., , respectively represent the branch impedances of the first and second converter equivalent current sources of the 5th bus, , respectively represent the branch impedances of the equivalent current sources of the first converters of the 7th bus and the 8th bus. and are respectively the input currents of the synchronous generator and the equivalent current source of the converter of the 16th bus, represents the output current of the branch of the equivalent current source of the first converter of the 5th bus, and respectively represent the input currents of the branches of the equivalent current sources of the first converters of the 7th bus and the 8th bus,

[0046] and respectively represent the branch impedances of the equivalent current sources of the first and second converters of the 5th bus. and respectively represent the branch impedances of the equivalent current sources of the second and third converters of the 7th bus, , , , respectively represent the branch impedances of the equivalent current sources of the second, third, and fourth converters of the 8th bus, , , , , respectively the loop impedances between the 2nd bus and the 4th bus, between the 2nd bus and the 6th bus, between the 2nd bus and the 7th bus, and between the 2nd bus and the 8th bus. , , are the voltages between the branches of the equivalent current sources of the second converters of the 5th, 7th, and 8th buses and the grid-connected bus. , are the voltages between the branches of the equivalent current sources of the third converters of the 7th and 8th buses and the grid-connected bus. is the voltage between the branch of the equivalent current source of the fourth converter of the 8th bus and the grid-connected bus. represents the sum of the output currents of the branches of the first and second converters of the 5th bus. represents the sum of the input currents of the branches of the first, second, and third converters of the 7th bus. represents the sum of the input currents of the branches of the first, second, and third converters of the 7th bus.

[0047] Since on the same bus, such as the buses of the branches connected to the 5th bus, the 7th bus, or the 8th bus, their voltage values are nearly equal, satisfying the following formula:

[0048] (4)

[0049] Among them, 、 、 are the voltages between the equivalent current source branch of the first converter of the 5th bus, 7th bus, and 8th bus of the equivalent current source and the grid-connected bus. , , are the voltages between the equivalent current source branch of the second converter of the 5th bus, 7th bus, and 8th bus of the equivalent current source and the grid-connected bus. , are the voltages between the equivalent current source branch of the third converter of the 7th bus and 8th bus of the equivalent current source and the grid-connected bus. is the voltage between the equivalent current source branch of the fourth converter of the 8th bus of the equivalent current source and the grid-connected bus.

[0050] Among them, when the power supply voltage values in the same bus are basically the same, further simplifying the equivalent impedance network of the collection system, we can obtain:

[0051] (5)

[0052] Among them, , , , the superscript T represents the transpose of the matrix. Further, , , , are the intermediate matrices for mathematical derivation, which are respectively:

[0053] , , , ;

[0054] Among them, the superscript on the upper right of Z’ indicates that it is , , , the elements in the intermediate matrix;

[0055] Simplifying the above formula, we can obtain the reduced-order equation:

[0056] (6)

[0057] Further, formula (6) can be expanded into the voltage impedance loop equation as follows:

[0058] (7)

[0059] Among them, Z’ is the intermediate matrix , , , the elements in is the grid-connected bus voltage, , , , , are the equivalent current source voltages of the synchronous generator, the 16th bus, the 5th bus, the 7th bus, and the first branch converter of the 8th bus. The impedance matrix is the recombination of the impedances after equivalent voltage merging in Equation (3). the input current of the synchronous generator, represents the sum of the output currents of the equivalent current source branches of the first and second converters of the 5th bus. represents the sum of the input currents of the equivalent current source branches of the first, second, and third converters of the 7th bus. represents the sum of the input currents of the equivalent current source branches of the first, second, and third converters of the 7th bus. is the grid-connected bus voltage.

[0060] Step 4: Design an impedance network modeling method considering the internal electromotive force of the synchronous generator, including:

[0061] In the new energy base collection system, by coupling the synchronous generator with the new energy grid-connected system, on the one hand, it improves the active inertia support ability of the new energy base for the external power grid, and on the other hand, it improves the anti-interference ability of the new energy grid-connected system, such as the ability to resist short-circuit currents in the external power grid. Therefore, based on the impedance network in Step 3 of the present invention, the internal electromotive force of the synchronous generator is further considered. The internal electromotive force of the synchronous generator is represented by and is assumed to be a constant, where the angle is the actual power angle of the internal electromotive force of the synchronous generator. On the other hand, if the effect of forced excitation is considered, only the differential equation of the excitation system needs to be added to calculate the value at each moment.

[0062] The present invention takes the generator as a current source. Now the relationship with the stator current of the generator can only establish the voltage balance relationship along the d and q axes respectively as follows:

[0063] (8)

[0064] Among them, , and , are respectively the q and d axis components of the bus generator terminal voltage and current. represents the Internal resistance of the busbar synchronous generator Denote the internal electromotive force of the busbar synchronous generator , and denote the d-axis and q-axis components of the internal reactance of the busbar synchronous generator by respectively.

[0065] Write Equation (8) in matrix form:

[0066] (9)

[0067] where , and , are the q-axis and d-axis components of the terminal voltage and current of the busbar generator respectively. Denote the internal resistance of the busbar synchronous generator by , denote the internal electromotive force of the busbar synchronous generator by , and denote the d-axis and q-axis components of the internal reactance of the busbar synchronous generator by respectively. In the power flow calculation during normal operation and the network calculation during transient processes, all voltage and current phasors are referenced to the common coordinate system, i.e., the reference coordinate. Further assume that the angle between the axis of the generator rotor and the axis is Figure 4 . , coordinates of the generator set and the relationship with the synchronous rotating

[0068] For any phasor in the figure, the , components and the , components have the following relationship:

[0069] (10)

[0070] where the angle between the q-axis of the motor rotor and the x-axis is . is the component of on , is the component of on , Component in the q-axis is the th busbar's component in the d-axis

[0071] Therefore, as long as the , and , are respectively the q- and d-axis components of the busbar generator terminal voltage and current, and are converted into the form of Equation (10) as , and , , which are respectively the x- and y-axis components of the busbar generator terminal voltage and current, that is, we obtain the relationship between , coordinates and the terminal voltage and current components is:

[0072] (11)

[0073] where it is assumed that the angle between the generator rotor axis and the axis is . , and , are respectively the x- and y-axis components of the busbar generator terminal voltage and current, represents the internal electromotive force of the th busbar synchronous generator, . respectively represent the d- and q-axis components of the internal reactance of the th busbar synchronous generator. represents the internal resistance of the th busbar synchronous generator

[0074] Furthermore, we obtain:

[0075] (12)

[0076] where it is assumed that the angle between the generator rotor axis and the axis is . is the th busbar's component in the q-axis, is the th busbar's Component on the d-axis Indicates the Internal electromotive force of the bus synchronous generator 、 And 、 Are respectively The x- and y-axis components of the bus generator terminal voltage and current , Respectively represent the d- and q-axis components of the internal reactance of the bus synchronous generator Indicates the Internal resistance of the bus synchronous generator

[0077] In fact ,Assume = 0, Then Equation (12) can be further simplified and substituted into Equation (7) to obtain:

[0078] (13)

[0079] Where 、 、 、 Are the equivalent current source voltages of the converters of the first branch of the 16th bus, the 5th bus, the 7th bus, and the 8th bus Input current of the synchronous generator Is the grid-connected bus voltage Represents the sum of the output currents of the equivalent current source branches of the first and second converters of the 5th bus Represents the sum of the input currents of the equivalent current source branches of the first, second, and third converters of the 7th bus Represents the sum of the input currents of the equivalent current source branches of the first, second, and third converters of the 7th bus Represents the d-axis component of the internal reactance of the bus synchronous generator

[0080] Step 5: Conduct overall impedance modeling for the large-scale new energy and energy storage base system, including:

[0081] Similar to the modeling process in Step 3, conduct impedance modeling for the other side of the grid connection. Based on Kirchhoff's voltage law and the circuit phasor model, establish the voltage-current correlation equations for all converter equivalent current sources, synchronous generator equivalent current sources, and impedance networks as follows

[0082] (14)

[0083] Among them, the second bus is the grid-connected bus, and the 15th bus is the synchronous generator equivalent current source bus. 、 respectively represent the voltages of the synchronous generator, the equivalent current source of the 17th bus, and the grid-connected bus. 、 are the voltages between the equivalent current source of the 13th bus, the first converter equivalent current source branch of the 12th bus, and the grid-connected bus. 、 、 etc. respectively represent the loop impedance between the synchronous generator equivalent current source and the 9th bus, the loop impedance between the 2nd bus and the 9th bus, the loop impedance between the 2nd bus and the 13th bus, etc. 、 respectively represent the branch impedances of the first and second converter equivalent current sources of the 13th bus. 、 、 respectively represent the branch impedances of the three converter equivalent current sources of the 12th bus. represents the input / output current of the synchronous generator. is the output current of the converter equivalent current source of the 17th bus. represents the input / output current of the first converter equivalent current source branch of the 13th bus. represents the input current of the first converter equivalent current source branch of the 12th bus. At the same time, the current sources equivalent to each converter and the current source equivalent to the synchronous generator are simplified and combined, and their current relationships satisfy the following equations:

[0084] (15)

[0085] Among them, is the voltage between the second converter equivalent current source branch of the 12th bus of the equivalent current source and the grid-connected bus. is the voltage between the third converter equivalent current source branch of the 12th bus of the equivalent current source and the grid-connected bus. represents the input current of the second converter equivalent current source branch of the 12th bus. represents the input current of the third converter equivalent current source branch of the 12th bus. represents the input / output current of the second converter equivalent current source branch of the 13th bus. represents the input / output current of the sum of the first and second converter equivalent current source branches of the 13th bus. represents the input current of the sum of the first, second, and third converter equivalent current source branches of the 12th bus. is the output reactance of the converter equivalent current source of the 17th bus. , respectively represent the loop impedance between the second bus and the tenth bus of the synchronous generator equivalent current source, and the loop impedance between the second bus and the twelfth bus.

[0086] Further, substituting Equation (15) into Equation (14), Equation (14) can be simplified to:

[0087] (16)

[0088] where and respectively represent the voltages of the synchronous generator, the equivalent current source of the 17th bus and the grid-connected bus, and are the voltages between the equivalent current source branch of the first converter of the 13th bus, the 12th bus and the grid-connected bus. and and etc. respectively represent the loop impedance between the synchronous generator equivalent current source and the 9th bus, the loop impedance between the second bus and the 9th bus, the loop impedance between the second bus and the 13th bus, etc., and respectively represent the branch impedances of the first and second converter equivalent current sources of the 13th bus, and and respectively represent the branch impedances of the three converter equivalent current sources of the 12th bus. represents the input / output current of the synchronous generator, is the output current of the converter equivalent current source of the 17th bus, is the voltage between the equivalent current source branch of the second converter of the 12th bus and the grid-connected bus. is the voltage between the equivalent current source branch of the third converter of the 12th bus and the grid-connected bus. is the output reactance of the converter equivalent current source of the 17th bus. , respectively represent the loop impedance between the second bus and the tenth bus of the synchronous generator equivalent current source, and the loop impedance between the second bus and the twelfth bus. represents the input / output current of the sum of the first and second converter equivalent current source branches of the 13th bus. represents the input current of the sum of the first, second and third converter equivalent current source branches of the 12th bus.

[0089] Since at the same bus, such as the buses of each branch connected to the 12th bus and the 13th bus, their voltage values are nearly equal, satisfying the following formula:

[0090] (17)

[0091] Among them, is the voltage between the equivalent current source branch of the first converter of the 12th bus of the equivalent current source and the grid-connected bus. is the voltage between the equivalent current source branch of the second converter of the 12th bus of the equivalent current source and the grid-connected bus. is the voltage between the equivalent current source branch of the third converter of the 12th bus of the equivalent current source and the grid-connected bus. is the voltage between the equivalent current source branch of the first converter of the 13th bus of the equivalent current source and the grid-connected bus. is the voltage between the equivalent current source branch of the second converter of the 13th bus of the equivalent current source and the grid-connected bus.

[0092] Among them, when the power supply voltage values in the same bus are basically the same, the equivalent impedance network of the collection system can be further simplified to obtain:

[0093] (18)

[0094] Among them, , , is the intermediate matrix, that is , , , , , and are also intermediate matrices in the formula derivation process. The reduced-order equation can be obtained by simplifying the above formula:

[0095] (19)

[0096] Furthermore, similar to formula (6), the voltage impedance loop equation is obtained as follows:

[0097] (20)

[0098] Among them, is the grid-connected bus voltage, , , , are the equivalent current source voltages of the synchronous generator, the 17th bus, the 13th bus, and the first branch converter of the 12th bus. The impedance matrix is the recombined impedance after equivalent voltage merging in formula (14). represents the input / output current of the synchronous generator, is the output current of the equivalent current source of the converter of the 17th bus, Represents the input / output current of the sum of the equivalent current source branches of the first converter and the second converter of bus No. 13. Represents the input current of the sum of the equivalent current source branches of the first converter, the second converter, and the third converter of the 12th bus.

[0099] Figure 3 for Figure 1 The equivalent circuit diagram of the left half of the collection system, Figure 3 The numbers in Figure 1 The same reference numerals in the drawings represent the same components. Figure 3 The connection relationship and function of each component are as follows: the 2nd bus is the grid-connected bus, and the 14th bus is the synchronous generator equivalent current source bus. Represents the equivalent impedance between bus 2 and bus 101, Represents the equivalent impedance between busbar 2 and busbar 3, Represents the equivalent impedance between the third busbar and the synchronous generator grid connection point, Represents the equivalent impedance between busbar 3 and busbar 4, Represents the equivalent impedance between bus 4 and bus 5, Represents the equivalent impedance between bus 4 and bus 6, represents the equivalent impedance between busbar 4 and the interconnected converter, Represents the equivalent impedance between busbar 6 and busbar 7, Represents the equivalent impedance between busbar 6 and busbar 8. , They represent the equivalent impedance between the equivalent current source of the 1st and 2nd branch converters of bus No. 5 and bus No. 5 respectively; , , They represent the equivalent impedance between the equivalent current source of the 1st, 2nd and 3rd branch converters of the 7th bus and the 6th bus respectively; , , , They respectively represent the equivalent impedance between the equivalent current source of the 1st, 2nd, 3rd and 4th branch converters of the 8th bus and the 8th bus.

[0100] Figure 5 This is a schematic diagram of the aggregation system equivalent to a multi-machine system. Figure 5 The numbers 101, 2 and Figure 1 The same numbers in the figures represent the same parts. Figure 5 The #1 and #2 represent the equivalent synchronous generator units #1 and #2 respectively.

Claims

1. A method for equivalent impedance modeling and order reduction of a collection system for a new energy base integrating power sources, the grid, loads, and energy storage, characterized in that It includes the following steps: Step 1: Design the topological structure of the large-scale new energy and energy storage base system; Step 2: Model the equivalent impedance circuit of the whole network with a large-scale photovoltaic and wind power collection system; Step 3: Design a method for reducing the order of the equivalent impedance circuit model of the collection system considering the converter cluster; Step 4: Design a method for impedance network modeling considering the internal potential of the synchronous generator; Step 5: Equivalent the large-scale new energy and energy storage base to a super power plant with multiple synchronous generators and its transmission system, and conduct overall impedance modeling.

2. The equivalent impedance modeling and reduction method for the source-network-load-storage new energy base collection system according to claim 1, wherein In Step 1, the electrical collection system of the large base is mainly of a radial topological structure and supplemented by a ring topological structure.

3. The equivalent impedance modeling and order reduction method for the source-network-load-storage new energy base aggregation system according to claim 1, characterized in that Step 2 includes: For large-scale photovoltaic power generation and wind power grid-connected systems, the impedances of all converter units and their grid-connected branches are different, which are defined as and and , where the subscript at the lower right is the serial number of the upper-level circuit, and the superscript at the upper right is the number of the low-voltage converter unit. is the resistance of the connecting line between the first-numbered low-voltage converter and the upper-level circuit. is the reactance of the connecting line between the first-numbered low-voltage converter and the upper-level circuit. is the resistance of the connecting line between the second-numbered low-voltage converter and the upper-level circuit. is the reactance of the connecting line between the second-numbered low-voltage converter and the upper-level circuit. is the resistance of the connecting line between the third-numbered low-voltage converter and the upper-level circuit. is the reactance of the connecting line between the third-numbered low-voltage converter and the upper-level circuit; j represents the imaginary unit.

4. The equivalent impedance modeling and order reduction method for the source-network-load-storage new energy base collection system according to claim 1, wherein Step 3 includes: Based on Kirchhoff's voltage law and the circuit phasor model, establish the voltage-current correlation equations of all converter equivalent current sources, synchronous generator equivalent current sources, and impedance networks as follows: （1） Among them, the second bus is the grid-connected bus, and the fourteenth bus is the equivalent current source bus of the synchronous generator. , respectively represent the voltages of the synchronous generator, the equivalent current source of the sixteenth bus, and the grid-connected bus. , , are the voltages between the first converter equivalent current source branches of the fifth, seventh, and eighth buses of the equivalent current source and the grid-connected bus; , , etc. respectively represent the loop impedances between the equivalent current source of the synchronous generator and the third bus, between the second bus and the third bus, between the second bus and the fifth bus, etc. , respectively represent the branch impedances of the first and second converter equivalent current sources of the fifth bus. , respectively represent the branch impedances of the first converter equivalent current sources of the seventh and eighth buses; , respectively are the input currents of the synchronous generator and the converter equivalent current source of the sixteenth bus. represents the output current of the first converter equivalent current source branch of the fifth bus. , respectively represent the input currents of the first converter equivalent current source branches of the seventh and eighth buses; , respectively represent the branch impedances of the second and third converter equivalent current sources of the seventh bus. , , respectively represent the branch impedances of the second, third, and fourth converter equivalent current sources of the eighth bus. , , , , respectively, are the loop impedances between the second bus and the fourth bus, between the second bus and the sixth bus, between the second bus and the seventh bus, and between the second bus and the eighth bus; , , are the voltages between the second converter equivalent current source branches of the fifth, seventh, and eighth buses of the equivalent current source and the grid-connected bus; , are the voltages between the third converter equivalent current source branches of the seventh and eighth buses of the equivalent current source and the grid-connected bus; is the voltage between the fourth converter equivalent current source branch of the eighth bus of the equivalent current source and the grid-connected bus; represents the output current of the second converter equivalent current source branch of the 5th busbar, , respectively represent the input currents of the second converter equivalent current source branches of the 7th busbar and the 8th busbar; , respectively represent the input currents of the third converter equivalent current source branches of the 7th busbar and the 8th busbar; represents the input current of the fourth converter equivalent current source branch of the 8th busbar.

5. The equivalent impedance modeling and order reduction method for the source-network-load-storage new energy base aggregation system according to claim 4, wherein Simplify and combine the current sources equivalent to each converter and the current sources equivalent to the synchronous generator, and their current relationship satisfies the following equation: （2） Among them, represents the output current of the first converter equivalent current source branch of the 5th busbar, , respectively represent the input currents of the first converter equivalent current source branches of the 7th busbar and the 8th busbar represents the output current of the second converter equivalent current source branch of the 5th busbar, , respectively represent the input currents of the second converter equivalent current source branches of the 7th busbar and the 8th busbar; , respectively represent the input currents of the third converter equivalent current source branches of the 7th busbar and the 8th busbar; represents the sum of the output currents of the first and second converter equivalent current source branches of the 5th busbar; represents the sum of the input currents of the first, second, and third converter equivalent current source branches of the 7th busbar; represents the sum of the input currents of the first, second, and third converter equivalent current source branches of the 7th busbar; Substitute Equation (2) into Equation (1), and Equation (1) is simplified to: （3） Among them, the second bus is the grid-connected bus, and the fourteenth bus is the equivalent current source bus of the synchronous generator. 、 respectively represent the voltages of the synchronous generator, the equivalent current source of the sixteenth bus, and the grid-connected bus. 、 、 are the voltages between the first converter equivalent current source branches of the fifth, seventh, and eighth buses of the equivalent current source and the grid-connected bus. 、 、 etc. respectively represent the loop impedances between the equivalent current source of the synchronous generator and the third bus, the loop impedance between the second bus and the third bus, the loop impedance between the second bus and the fifth bus, etc. 、 respectively represent the branch impedances of the first and second converter equivalent current sources of the fifth bus. 、 respectively represent the branch impedances of the first converter equivalent current sources of the seventh and eighth buses. 、 are respectively the input currents of the equivalent current sources of the synchronous generator and the sixteenth bus converter. represents the output current of the first converter equivalent current source branch of the fifth bus. 、 respectively represent the input currents of the first converter equivalent current source branches of the seventh and eighth buses. 、 respectively represent the branch impedances of the first and second converter equivalent current sources of the fifth bus. 、 respectively represent the branch impedances of the second and third converter equivalent current sources of the seventh bus. , , respectively represent the branch impedances of the second, third, and fourth converter equivalent current sources of the eighth bus. , , , respectively are the loop impedances between the second bus and the fourth bus, the loop impedance between the second bus and the sixth bus, the loop impedance between the second bus and the seventh bus, and the loop impedance between the second bus and the eighth bus. , , are the voltages between the second converter equivalent current source branches of the fifth, seventh, and eighth buses of the equivalent current source and the grid-connected bus. , is the voltage between the equivalent current source branch of the third converter of the 7th bus and the 8th bus of the equivalent current source and the grid-connected bus; is the voltage between the equivalent current source branch of the fourth converter of the 8th bus of the equivalent current source and the grid-connected bus; represents the sum of the output currents of the equivalent current source branches of the first converter and the second converter of the 5th bus; represents the sum of the input currents of the equivalent current source branches of the first converter, the second converter, and the third converter of the 7th bus; represents the sum of the input currents of the equivalent current source branches of the first converter, the second converter, and the third converter of the 7th bus.

6. The equivalent impedance modeling and reduction method for the aggregation system of the source-network-load-storage new energy base according to claim 5, characterized in that Since the voltage values of each branch bus are nearly equal at the same bus, it satisfies the following equation: （4） Among them, , , are the voltages between the first converter equivalent current source branches of the 5th, 7th, and 8th buses of the equivalent current source and the grid-connected bus; , , are the voltages between the second converter equivalent current source branches of the 5th, 7th, and 8th buses of the equivalent current source and the grid-connected bus; , are the voltages between the third converter equivalent current source branches of the 7th and 8th buses of the equivalent current source and the grid-connected bus; is the voltage between the fourth converter equivalent current source branch of the 8th bus of the equivalent current source and the grid-connected bus; Among them, when the power supply voltage values in the same bus are basically the same, further simplify the equivalent impedance network of the collection system to obtain: （5） Among them, , , , the superscript T represents the transpose of the matrix; Further, , , , are intermediate variables in the process of deriving the formula, and are respectively: ， ， ， ； Among them, the superscript on the upper right of Z’ indicates that it is , , , the elements in the intermediate matrix; the reduced-order equation is obtained by simplifying the above formula: （6） Furthermore, Equation (6) is extended to the voltage impedance loop equation as follows: （7） Among them, Z’ is the intermediate matrix , , , are the elements in; is the grid-connected bus voltage, , , , , are the equivalent current source voltages of the synchronous generator, the 16th bus, the 5th bus, the 7th bus, and the first branch converter of the 8th bus. The impedance matrix is the recombined impedance after equivalent voltage merging in Equation (3); is the input current of the synchronous generator, represents the sum of the output currents of the first and second converter equivalent current source branches of the 5th bus; represents the sum of the input currents of the first, second, and third converter equivalent current source branches of the 7th bus; represents the sum of the input currents of the first, second, and third converter equivalent current source branches of the 7th bus; is the grid-connected bus voltage.

7. The equivalent impedance modeling and reduction method for the source-network-load-storage new energy base aggregation system according to claim 1, characterized in that Step 4 includes: Taking the generator as a current source, the internal electromotive force in the synchronous generator as a constant The relationship with the stator current of the motor can only establish the voltage balance relationship separately according to the d-axis and q-axis directions as follows: （8） Among them, , and , are respectively the q- and d-axis components of the terminal voltage and current of the busbar generator; represents the internal resistance of the busbar synchronous generator, represents the internal electromotive force of the busbar synchronous generator, , respectively represent the d- and q-axis components of the internal reactance of the busbar synchronous generator; Write Equation (8) in matrix form: （9） Among them, , and , are respectively the q- and d-axis components of the busbar generator terminal voltage and current; represents the internal resistance of the th busbar synchronous generator, represents the internal electromotive force of the th busbar synchronous generator, , respectively represent the d- and q-axis components of the internal reactance of the th busbar synchronous generator; For any phasor of 、 components sum 、 components have the following relationship: （10） where the angle between the q-axis of the motor rotor and the x-axis is ; is the component of on ; is the component of the th busbar in the q-axis component, is the th busbar in the d-axis component, so as long as the and in Equation (9) are respectively the q-axis and d-axis components of the busbar generator terminal voltage and current, and are converted into and and in the form of Equation (10), which are respectively the x-axis and y-axis components of the busbar generator terminal voltage and current, that is, the relationship between and the terminal voltage expressed in the network and coordinates and the current component is: ​ （11） It is assumed that the generator rotor Axis and The angle between the axes is , , and , They are The x- and y-axis components of the voltage and current at the bus generator terminal, Indicates The electromotive force inside the busbar synchronous generator, , Respectively represent The d- and q-axis components of the internal reactance of the busbar synchronous generator; Indicates Internal resistance of busbar synchronous generator; Furthermore, obtain: （12） Among them, assume that the generator rotor axis and the included angle of the axis is ; is the component of the on the q-axis of the nth busbar, is the component of the on the d-axis of the nth busbar, represents the internal electromotive force in the nth busbar synchronous generator, ; , and , are respectively the x-axis and y-axis components of the terminal voltage and current of the nth busbar generator, , respectively represent the d-axis and q-axis components of the internal reactance of the nth busbar synchronous generator; represents the internal resistance of the nth busbar synchronous generator; Assume that = 0, then Equation (12) is further simplified and substituted into Equation (7) to obtain: （13） Among them, , , , are the equivalent current source voltages of the converters of the first branch of the 16th bus, the 5th bus, the 7th bus, and the 8th bus; is the input current of the synchronous generator; is the grid-connected bus voltage; represents the sum of the output currents of the equivalent current source branches of the first and second converters of the 5th bus; represents the sum of the input currents of the equivalent current source branches of the first, second, and third converters of the 7th bus; represents the sum of the input currents of the equivalent current source branches of the first, second, and third converters of the 7th bus; represents the d-axis component of the internal reactance of the synchronous generator of the bus.

8. The equivalent impedance modeling and order reduction method for the source-network-load-storage new energy base aggregation system according to claim 1, characterized in that Step 5 includes: According to the modeling process of Step 3, conduct impedance modeling on the other side of the grid connection; based on Kirchhoff's voltage law and the circuit phasor model, establish the voltage-current correlation equations of all converter equivalent current sources, synchronous generator equivalent current sources, and impedance networks as follows: （14） Among them, the second bus is the grid-connected bus, and the 15th bus is the equivalent current source bus of the synchronous generator. and respectively represent the voltages of the synchronous generator, the equivalent current source of the 17th bus, and the grid-connected bus. and are the voltages between the equivalent current source branch of the first converter of the 13th bus and the 12th bus and the grid-connected bus. and and etc. respectively represent the loop impedance between the equivalent current source of the synchronous generator and the 9th bus, the loop impedance between the 2nd bus and the 9th bus, the loop impedance between the 2nd bus and the 13th bus, etc. and respectively represent the branch impedances of the first and second converter equivalent current sources of the 13th bus. and and respectively represent the branch impedances of the three converter equivalent current sources of the 12th bus. represents the input / output current of the synchronous generator, is the output current of the converter equivalent current source of the 17th bus. represents the input / output current of the first converter equivalent current source branch of the 13th bus. represents the input current of the first converter equivalent current source branch of the 12th bus. At the same time, the current sources equivalent to each converter and the current source equivalent to the synchronous generator are simplified and combined, and their current relationships satisfy the following equations: （15） Among them, is the voltage between the equivalent current source branch of the second converter of the 12th bus of the equivalent current source and the grid-connected bus; is the voltage between the equivalent current source branch of the third converter of the 12th bus of the equivalent current source and the grid-connected bus; represents the input current of the second equivalent current source branch of the converter of the 12th bus, represents the input current of the third equivalent current source branch of the converter of the 12th bus, represents the input / output current of the second equivalent current source branch of the converter of the 13th bus, represents the input / output current of the sum of the equivalent current source branches of the first and second converters of the 13th bus; represents the input current of the sum of the equivalent current source branches of the first, second, and third converters of the 12th bus; is the output reactance of the converter equivalent current source of the 17th bus; , respectively represent the loop impedance between the 2nd bus and the 10th bus, and the loop impedance between the 2nd bus and the 12th bus of the synchronous generator equivalent current source; Furthermore, substitute Equation (15) into Equation (14), and Equation (14) is simplified to: （16） Among them, , respectively represent the voltages of the synchronous generator, the equivalent current source of the 17th bus, and the grid-connected bus, , are the voltages between the first converter equivalent current source branches of the 13th bus and the 12th bus of the equivalent current source and the grid-connected bus; , , etc. respectively represent the loop impedances between the equivalent current source of the synchronous generator and the 9th bus, between the 2nd bus and the 9th bus, between the 2nd bus and the 13th bus, etc., , respectively represent the branch impedances of the first and second converter equivalent current sources of the 13th bus, , , respectively represent the branch impedances of the three converter equivalent current sources of the 12th bus; represents the input / output current of the synchronous generator, is the output current of the converter equivalent current source of the 17th bus, is the voltage between the second converter equivalent current source branch of the 12th bus of the equivalent current source and the grid-connected bus; is the voltage between the third converter equivalent current source branch of the 12th bus of the equivalent current source and the grid-connected bus; is the output reactance of the converter equivalent current source of the 17th bus; , respectively represent the loop impedances between the 2nd bus and the 10th bus, between the 2nd bus and the 12th bus of the equivalent current source of the synchronous generator; represents the input / output current of the sum of the first and second converter equivalent current source branches of the 13th bus; represents the input current of the sum of the first, second, and third converter equivalent current source branches of the 12th bus; Since the voltage values are nearly equal at the same bus, it satisfies the following equation: （17） Among them, is the voltage between the equivalent current source branch of the first converter of the 12th bus of the equivalent current source and the grid-connected bus; is the voltage between the equivalent current source branch of the second converter of the 12th bus of the equivalent current source and the grid-connected bus; is the voltage between the equivalent current source branch of the third converter of the 12th bus of the equivalent current source and the grid-connected bus; is the voltage between the equivalent current source branch of the first converter of the 13th bus of the equivalent current source and the grid-connected bus; is the voltage between the equivalent current source branch of the second converter of the 13th bus of the equivalent current source and the grid-connected bus; Among them, when the power supply voltage values in the same bus are basically the same, further simplify the equivalent impedance network of the collection system to obtain: （18） Among them, , , is the intermediate matrix, that is , , , , and are also intermediate matrices in the formula derivation process; the reduced-order equation is obtained by simplifying the above formula: （19） Furthermore, similar to Equation (6), obtain the voltage impedance loop equation as follows: （20） Among them, is the grid-connected bus voltage, , , , are the equivalent current source voltages of the synchronous generator, the 17th bus, the first branch converter of the 13th bus, and the 12th bus; the impedance matrix is the recombined impedance after equivalent voltage merging in Equation (14); represents the input / output current of the synchronous generator, is the output current of the equivalent current source of the 17th bus converter, represents the input / output current of the sum of the equivalent current source branches of the first converter and the second converter of the 13th bus; represents the input current of the sum of the equivalent current source branches of the first converter, the second converter, and the third converter of the 12th bus.

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