Method and device for determining capacity proportion threshold of self-synchronizing voltage source of new energy delivery system

Abstract

The invention belongs to the field of new energy sending-out systems, and provides a method and device for determining a capacity proportion threshold of a self-synchronizing voltage source of a new energy sending-out system in order to newly build or reform a new energy power supply as little as possible on the premise of ensuring stable operation of the new energy power generation sending-out system. The method comprises the following steps: constructing a multi-inverter grid-connected small signal state space model; calculating a characteristic root of the multi-inverter grid-connected small signal state space model to obtain a characteristic root distribution map; and determining a corresponding self-synchronizing voltage source capacity ratio threshold value according to the stability intensity requirement of the new energy delivery system based on the characteristic root distribution diagram. From the perspective of small disturbance stability of the new energy delivery system, a corresponding self-synchronizing voltage source capacity ratio threshold criterion is provided so as to adapt to different stability requirements.

Description

Technical Field

[0001] The present invention belongs to the field of new energy transmission systems, and in particular, relates to a method and device for determining a capacity proportion threshold of a self-synchronous voltage source of a new energy transmission system. Background Art

[0002] The statements in this section merely provide background information related to the present invention and do not necessarily constitute prior art.

[0003] At present, most new energy power sources are synchronized with the power grid through current source control based on a phase-locked loop. This control does not have the ability to actively support the voltage and frequency of the power grid. In a weak power grid with large grid impedance, the phase-locked loop will introduce negative resistance characteristics in the low-frequency region, making the inverter power supply extremely easy to become unstable under small interference, thereby endangering the stable operation of the power grid.

[0004] In order to ensure the stable operation of the power grid, self-synchronous voltage source control technology represented by virtual synchronous control has been proposed. Since self-synchronous voltage source control technology can establish frequency and voltage by itself, it can provide a synchronization reference for grid-following control, thereby enhancing the stability of the renewable energy power generation and transmission system.

[0005] For new energy power generation and transmission systems in areas with weak power grids, it is urgent to build or renovate self-synchronous voltage source power sources. However, self-synchronous voltage sources need to be equipped with energy storage or reserved power backup. Large-scale construction or renovation will require a lot of investment and operating costs, so too much renovation or construction will seriously affect the economic efficiency.

[0006] In summary, there is an urgent need for a technical solution to determine the threshold value of the proportion of the self-synchronous voltage source, so as to minimize the construction or transformation of new energy power sources while ensuring the stable operation of the new energy power generation and transmission system. Summary of the invention

[0007] In order to minimize the construction or transformation of new energy power sources while ensuring the stable operation of the new energy power generation and transmission system, the present invention provides a method and device for determining the capacity proportion threshold of a self-synchronous voltage source of a new energy transmission system. From the perspective of small disturbance stability of the new energy transmission system, it provides corresponding self-synchronous voltage source capacity proportion threshold criteria to adapt to different stability requirements.

[0008] In order to achieve the above object, the present invention adopts the following technical solution:

[0009] A first aspect of the present invention provides a method for determining a capacity proportion threshold of a self-synchronous voltage source in a new energy transmission system.

[0010] In one or more embodiments, a method for determining a capacity proportion threshold of a self-synchronous voltage source of a new energy transmission system is provided, comprising:

[0011] Constructing a node voltage model defining a grid connection point, a small signal state space model including at least one self-synchronous voltage source inverter power supply, and a small signal state space model including at least one current source inverter power supply based on a phase-locked loop;

[0012] The self-synchronous voltage source inverter power supply small signal state space model and the phase-locked loop-based current source inverter power supply small signal state space model are connected by defining a node voltage model of the grid-connected point to obtain a multi-inverter power supply grid-connected small signal state space model;

[0013] Calculating the characteristic roots of the multi-inverter grid-connected small signal state space model, and then obtaining a characteristic root distribution diagram;

[0014] Based on the characteristic root distribution diagram, the corresponding self-synchronous voltage source capacity ratio threshold is determined according to the stability strength requirements of the new energy transmission system.

[0015] A second aspect of the present invention provides a device for determining a capacity proportion threshold of a self-synchronous voltage source in a new energy transmission system.

[0016] In one or more embodiments, a device for determining a capacity proportion threshold of a self-synchronous voltage source of a new energy transmission system includes:

[0017] A sub-model construction module, which is used to construct a node voltage model defining a grid connection point, a small signal state space model including at least one self-synchronous voltage source inverter power supply, and a small signal state space model including at least one current source inverter power supply based on a phase-locked loop;

[0018] A multi-inverter model building module, which is used to connect the self-synchronous voltage source inverter power supply small signal state space model and the phase-locked loop-based current source inverter power supply small signal state space model by defining a node voltage model of a grid-connected point, so as to obtain a multi-inverter power supply grid-connected small signal state space model;

[0019] A characteristic root distribution diagram calculation module, which is used to calculate the characteristic roots of the multi-inverter power grid-connected small signal state space model, and then obtain a characteristic root distribution diagram;

[0020] The capacity proportion threshold determination module is used to determine the corresponding self-synchronous voltage source capacity proportion threshold based on the characteristic root distribution diagram and the stability strength requirement of the new energy transmission system.

[0021] A third aspect of the present invention provides a computer-readable storage medium.

[0022] A computer-readable storage medium stores a computer program, which, when executed by a processor, implements the steps in the method for determining the capacity proportion threshold of a self-synchronous voltage source of a new energy transmission system as described above.

[0023] A fourth aspect of the present invention provides an electronic device.

[0024] An electronic device comprises a memory, a processor and a computer program stored in the memory and executable on the processor, wherein when the processor executes the program, the steps in the method for determining the capacity proportion threshold of a self-synchronous voltage source of a new energy transmission system as described above are implemented.

[0025] Compared with the prior art, the present invention has the following beneficial effects:

[0026] (1) Based on the characteristic distribution of the small signal state space model of multi-inverter power grid-connected power sources and the stability strength requirements of the new energy transmission system, the present invention obtains the small disturbance stability operation area of ​​the new energy transmission system and determines the corresponding self-synchronous voltage source capacity ratio threshold, providing a reference for the small disturbance stability of the new energy transmission system, thereby providing a reference for the ratio of self-synchronous voltage source and phase-locked loop-based current source inverter for the planning of the new energy transmission system, and achieving the purpose of transmitting as much energy as possible while ensuring the small disturbance stability of the system.

[0027] (2) In the process of constructing a small-signal state-space model of a multi-inverter grid-connected power supply, the present invention regards the self-synchronous voltage source inverter power supply state matrix in the self-synchronous voltage source inverter power supply small-signal state-space model, the phase-locked loop-based current source inverter power supply state matrix in the phase-locked loop-based current source inverter power supply small-signal state-space model, and the inverter power supply matrix in the defined node voltage model as three independent modules for modular modeling, thereby realizing the expansion of the system small-signal state-space model, simplifying the modeling process, and effectively avoiding the problem of too many orders of the small-signal state-space model. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] The accompanying drawings in the specification, which constitute a part of the present invention, are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute improper limitations on the present invention.

[0029] Figure 1 It is a flow chart of a method for determining a capacity proportion threshold of a self-synchronous voltage source of a new energy transmission system according to an embodiment of the present invention;

[0030] Figure 2 2 is a schematic diagram of the structure of a device for determining a capacity proportion threshold of a self-synchronous voltage source in a new energy transmission system according to an embodiment of the present invention;

[0031] Figure 3is a schematic diagram of an electronic device according to an embodiment of the present invention;

[0032] Figure 4 This is a modeling idea of ​​a small signal state space model of a multi-inverter power supply grid-connected in an embodiment of the present invention;

[0033] Figure 5 This is a result diagram of characteristic roots of one VSG and one PLL according to method 1 of an embodiment of the present invention;

[0034] Figure 6 This is a result diagram of the power ratio of 5 VSGs and 5 PLL characteristic roots of method 2 of an embodiment of the present invention;

[0035] Figure 7 : is a characteristic root result diagram of N VSGs and (10-N) PLLs in capacity ratio of method 3 of an embodiment of the present invention;

[0036] Figure 8 is a characteristic root result diagram of a proportion threshold criterion according to an embodiment of the present invention;

[0037] Fig. 9 This is a result diagram of the second characteristic root of the proportion threshold criterion according to an embodiment of the present invention;

[0038] Fig.10 4 is a distribution diagram of a small disturbance stability relationship according to an embodiment of the present invention. DETAILED DESCRIPTION

[0039] The present invention will be further described below in conjunction with the accompanying drawings and embodiments.

[0040] It should be noted that the following detailed descriptions are all illustrative and intended to provide further explanation of the present invention. Unless otherwise specified, all technical and scientific terms used herein have the same meanings as those commonly understood by those skilled in the art to which the present invention belongs.

[0041] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit exemplary embodiments according to the present invention. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "comprising" and / or "including" are used in this specification, it indicates the presence of features, steps, operations, devices, components and / or combinations thereof.

[0042] When analyzing the influence of the proportion of different types of inverter power supplies on the system stability, it is usually based on a self-synchronous voltage source inverter power supply and a phase-locked loop-based current source inverter power supply, and a small signal state space model of two inverter power supplies in parallel is established. By adjusting the power output of the self-synchronous voltage source and the phase-locked loop-based current source, the balance point of the system changes, thereby comparing and analyzing the small disturbance stability of the system under different working conditions. This analysis method is defined as a power proportion evaluation method in the present invention.

[0043] First, define the power penetration of the phase-locked loop based current source:

[0044]

[0045] in:

[0046] η – Power penetration rate of the current source based on the phase-locked loop;

[0047] P PLL ——Active power of current source based on phase-locked loop;

[0048] P set ——active power setting value of the self-synchronous voltage source;

[0049] The active power of the current source based on the phase-locked loop can be calculated by the following formula:

[0050]

[0051] in:

[0052] E n ——Output phase voltage amplitude based on the current source of the phase-locked loop;

[0053] I dref ——The current loop input set value of the current source based on the phase-locked loop;

[0054] By setting the voltage, active power and reactive power required by the system, the equilibrium point and state space matrix under different penetration rates are obtained, the main characteristic root loci and participation factors are calculated, and the small disturbance stability of the system is analyzed.

[0055] In an actual system, there is definitely more than one self-synchronous voltage source inverter and one phase-locked loop-based current source inverter in an area. When only the above-mentioned "power share evaluation method" is used to analyze the multi-inverter system, there will be large differences.

[0056] Based on the physical meaning of the short-circuit ratio, the formula of the short-circuit ratio can be mathematically derived and transformed into:

[0057]

[0058] in:

[0059] SCR i ——The short-circuit ratio of new energy at the i-th grid connection point;

[0060] U Ni ——The nominal bus voltage value at the i-th grid connection point;

[0061] U i ——The actual bus voltage value at the i-th grid connection point;

[0062] I ii ——The magnitude of the short-circuit current provided by the ith node to the ith grid connection point;

[0063] I ij ——The magnitude of the short-circuit current provided by the jth node to the i-th grid connection point;

[0064] Z ii ——equivalent impedance at the ith and jth nodes and the ith grid connection point;

[0065] Z ij ——The equivalent impedance between the jth node and the i-th grid connection point;

[0066] From the above formula, we can see that when the system structure is fixed and the grid voltage is unchanged, SCR i It is related to the transmission capacity of each grid-connected branch, and the impedance and voltage of each line determine the weight coefficient of the influence of the transmission capacity of each grid-connected branch on the grid strength.

[0067] It can be seen that the "power share evaluation method" only uses one self-synchronous voltage source inverter and one phase-locked loop-based current source inverter to equivalent the power of the entire system. It does not consider the impact of each branch on the overall system and cannot obtain accurate results. Therefore, this analysis method needs to be improved.

[0068] Taking into account that the inverter power supply in the actual power grid is an independent power supply as an individual, the variable is the number N of self-synchronous voltage source inverter power supplies. Therefore, in order to be more in line with the actual situation, the (1+1) model of the "power share evaluation method" is changed to an N+(MN) model, where M is the number of all inverter power supplies in the new energy transmission system. The capacity share problem is evaluated by changing the number N, which is defined as a "capacity share evaluation method" in the present invention.

[0069] Figure 1 is a flow chart of a method for determining a capacity proportion threshold of a self-synchronous voltage source of a new energy transmission system in an embodiment of the present invention. Figure 1 The method for determining the capacity proportion threshold of the self-synchronous voltage source of the new energy transmission system in the embodiment shown may include:

[0070] S101, constructing a node voltage model defining a grid-connected point, a small signal state space model including at least one self-synchronous voltage source inverter power supply, and a small signal state space model including at least one current source inverter power supply based on a phase-locked loop.

[0071] In the capacity ratio evaluation method, the model needs to include more inverter power supplies, and the number of self-synchronous voltage sources and phase-locked loop-based current sources can also be changed at any time, which puts higher requirements on the modeling ideas.

[0072] The biggest problem with the small signal state space model is that when the system becomes complex, the order of the model will increase rapidly, resulting in the "curse of dimensionality". In order to solve this problem, the present invention adopts a modular modeling method to simplify the process of small signal state space modeling of complex systems.

[0073] S102, connecting the self-synchronous voltage source inverter power supply small signal state space model and the phase-locked loop-based current source inverter power supply small signal state space model by defining a node voltage model of the grid-connected point to obtain a multi-inverter grid-connected small signal state space model.

[0074] During the modeling process, the small signal state space model of a single self-synchronous voltage source inverter and the small signal state space model of a current source inverter based on a phase-locked loop are obtained in a common rotating coordinate system. By defining the node voltage model of the grid-connected point, the single self-synchronous voltage source inverter, the current source inverter based on a phase-locked loop and the grid are connected.

[0075] The state matrix A of the self-synchronous voltage source inverter power supply involved INV 、The state matrix of the current source inverter based on phase-locked loop A P And define the inverter power matrix M in the node voltage model INV The three parts are considered as three independent modules for modular modeling, such as Figure 4 shown.

[0076] When the internal parameters of the inverter power supply change, only the inverter power supply state matrix A needs to be changed. INV and A P When the number of inverters changes, since the structures of the inverters are the same, the state matrix of the inverters can be universal. It only needs to expand and modify the inverter matrix M in the node voltage model. INV That is, from the perspective of the power grid, it is equivalent to adding a corresponding inverter power supply to the model, thereby realizing the expansion of the system small signal state space model, simplifying the modeling process, and effectively avoiding the problem of too many orders of the small signal state space model.

[0077] S103, calculating the characteristic roots of the multi-inverter grid-connected small signal state space model, and then obtaining a characteristic root distribution diagram.

[0078] S104, based on the characteristic root distribution diagram and in accordance with the stability strength requirement of the new energy transmission system, determining a corresponding self-synchronous voltage source capacity ratio threshold.

[0079] In order to verify that the capacity ratio evaluation method of the embodiment of the present invention is superior to the conventional power ratio evaluation method, a comparative test case is given below:

[0080] From the definition of grid strength, we can see that grid strength is related to the total capacity of the system. Therefore, when designing the comparative analysis method, we need to design the total capacity unchanged to avoid the situation where the variables are not unique. We design different scenarios (hereinafter referred to as VSG for self-synchronous voltage source inverter and PLL for current source inverter based on phase-locked loop) and compare and analyze the power proportion evaluation method and capacity proportion evaluation method.

[0081] Method 1: Power ratio - Set up 1 VSG and 1 PLL, keep the total power at 100kW, and adjust the output power of each inverter to change the ratio;

[0082] Method 2: Power ratio - Set up 5 VSGs and 5 PLLs, with a total power of 100kW, and adjust the output power of each inverter to change the ratio;

[0083] Method 3: Capacity ratio - Set N VSGs and (10-N) PLLs, keep the power at 10×10kW unchanged, and change the ratio of the number of adjustable variables N.

[0084] According to the above three methods, the corresponding small signal state space model is established, the root locus of its characteristic root is calculated, and the results of the three methods are compared and analyzed, such as Figure 5-Figure 7 shown.

[0085] according to Figure 5-Figure 7 From the characteristic root distribution diagram of the above three methods shown, it can be seen that under the weak power grid of SCR=4, method one requires that the power proportion of the self-synchronous voltage source reaches 70% for the system to be stable, and the result deviates greatly from the actual situation. Method two requires that the power proportion of the self-synchronous voltage source reaches 40% for the system to be stable. Method three requires that the capacity proportion of the self-synchronous voltage source reaches 30% for the system to be stable.

[0086] Method 3 takes into account the fact that the actual situation is based on the whole power supply as the basic unit and the variable is the number of units N, so this method is more in line with the actual transformation and the model is the most accurate. At the same time, the proportion of self-synchronous voltage source in method 3 is the lowest. In actual engineering, if it is necessary to transform the current source inverter based on the phase-locked loop into a self-synchronous power inverter, the transformation cost is the lowest and the economy is the highest. Method 3 is selected as the capacity proportion method, which is closest to reality and the analysis results are more accurate.

[0087] The small signal state space model determines whether the system is stable by the positive or negative real part of the characteristic root, but the state of the actual system will not remain fixed, so a certain margin needs to be left when determining the proportion threshold.

[0088] In step S104, if the new energy transmission system is required to maintain a stable state under a set small disturbance state, a first threshold value of the self-synchronous voltage source capacity proportion corresponding to the new energy transmission system is determined according to the characteristic root distribution diagram.

[0089] The criterion for determining the first threshold value of the capacity proportion of the self-synchronous voltage source corresponding to the new energy transmission system is criterion one (for example, ensuring that the new energy transmission system can operate stably under ±10% disturbance).

[0090] By Figure 8 From the characteristic root distribution diagram of the criterion 1 shown, it can be seen that in the case of weak AC power grid, when the capacity of the self-synchronous voltage source accounts for 30% and the capacity of the current source based on the phase-locked loop accounts for 70%, the new energy transmission system will be unstable when subjected to a disturbance of ±10%, so the proportion threshold needs to be further increased. When the capacity of the self-synchronous voltage source accounts for 40% and the capacity of the current source based on the phase-locked loop accounts for 70%, the new energy transmission system is subjected to a disturbance of ±10%, and the new energy transmission system remains stable. Therefore, the capacity of the self-synchronous voltage source accounts for 40% and the capacity of the current source based on the phase-locked loop accounts for 70%, which are the capacity proportion thresholds of the criterion 1.

[0091] In step S104, if the difference between the stability of the new energy transmission system and the stability of all inverters being current source inverters based on phase-locked loops under strong power grid conditions is required to be within a preset range, the second threshold value of the self-synchronous voltage source capacity proportion corresponding to the new energy transmission system is determined based on the characteristic root distribution diagram.

[0092] The criterion for determining the second threshold value of the self-synchronous voltage source capacity proportion corresponding to the new energy transmission system is criterion 2. Fig. 9From the characteristic root distribution diagram of criterion 2 shown in the figure, it can be seen that in the case of strong AC power grid, the stability of 10 current source inverters based on phase-locked loops is equivalent to the stability of 60% capacity of self-synchronous voltage source and 40% capacity of current source based on phase-locked loops. Therefore, 60% capacity of self-synchronous voltage source and 40% capacity of current source based on phase-locked loops are the capacity proportion thresholds of criterion 2. According to the thresholds of criterion 1 and criterion 2, a small interference stability relationship distribution diagram is drawn, as shown in Fig.10 shown.

[0093] Aiming at the new energy transmission system, the present invention proposes a capacity share evaluation method and a small signal modular modeling method based on the small signal state space model, designs three methods to compare and analyze the traditional power share evaluation method and the capacity share evaluation method, and proposes two proportion threshold judgment criteria, and obtains the small disturbance stability operation area of ​​the system, thereby determining the stability threshold under different working conditions, and providing a reference for the small disturbance stability of the new energy transmission system.

[0094] In one or more embodiments, the method for determining the capacity proportion threshold of the self-synchronous voltage source of the new energy transmission system further includes:

[0095] According to the relationship f between the self-synchronous voltage source capacity proportion S%, the power grid strength SCR and the characteristic root real part RE, a small interference stable operation area diagram is constructed; where RE = f(S%, SCR);

[0096] The small disturbance stable operation area map consists of three parts: unstable area, weak grid small disturbance stable area and approximately strong grid stable area;

[0097] The weak grid small interference stable area is an area where the new energy transmission system is subject to a set small interference state and the new energy transmission system remains stable;

[0098] The approximate strong power grid stability area is an area where the difference between the stability of the new energy transmission system and the stability of all inverter power supplies under strong power grid conditions, which are current source inverter power supplies based on phase-locked loops, does not exceed a preset range.

[0099] Among them, the real parts of the characteristic roots RE in the unstable region are all greater than zero.

[0100] Figure 2 Schematic diagram of a device for determining a capacity ratio threshold of a self-synchronous voltage source in a new energy transmission system according to an embodiment of the present invention. Figure 1 The new energy transmission system self-synchronous voltage source capacity ratio threshold determination method corresponds to, for example Figure 2 As shown, the device for determining the capacity proportion threshold of the self-synchronous voltage source of the new energy transmission system in this embodiment may include:

[0101] The sub-model construction module 201 is used to construct a node voltage model defining a grid-connected point, a small signal state space model including at least one self-synchronous voltage source inverter power supply, and a small signal state space model including at least one current source inverter power supply based on a phase-locked loop.

[0102] The multi-inverter model construction module 202 is used to connect the self-synchronous voltage source inverter power supply small signal state space model and the phase-locked loop-based current source inverter power supply small signal state space model by defining the node voltage model of the grid-connected point to obtain a multi-inverter power supply grid-connected small signal state space model.

[0103] During the modeling process, the small signal state space model of a single self-synchronous voltage source inverter and the small signal state space model of a current source inverter based on a phase-locked loop are obtained in a common rotating coordinate system. By defining the node voltage model of the grid-connected point, the single self-synchronous voltage source inverter, the current source inverter based on a phase-locked loop and the grid are connected.

[0104] The state matrix A of the self-synchronous voltage source inverter power supply involved INV 、The state matrix of the current source inverter based on phase-locked loop A P And define the inverter power matrix M in the node voltage model INV The three parts are considered as three independent modules for modular modeling, such as Figure 4 shown.

[0105] When the internal parameters of the inverter power supply change, only the inverter power supply state matrix A needs to be changed. INV and A P When the number of inverters changes, since the structures of the inverters are the same, the state matrix of the inverters can be universal. It only needs to expand and modify the inverter matrix M in the node voltage model. INV That is, from the perspective of the power grid, it is equivalent to adding a corresponding inverter power supply to the model, thereby realizing the expansion of the system small signal state space model, simplifying the modeling process, and effectively avoiding the problem of too many orders of the small signal state space model.

[0106] The characteristic root distribution diagram calculation module 203 is used to calculate the characteristic roots of the multi-inverter grid-connected small signal state space model, and then obtain a characteristic root distribution diagram.

[0107] The capacity proportion threshold determination module 204 is used to determine the corresponding self-synchronous voltage source capacity proportion threshold based on the characteristic root distribution diagram and the stability strength requirement of the new energy transmission system.

[0108] During the specific implementation process, in the capacity proportion threshold determination module 204, if the new energy transmission system is required to maintain a stable state under a set small interference state, the first threshold value of the self-synchronous voltage source capacity proportion corresponding to the new energy transmission system is determined according to the characteristic root distribution diagram.

[0109] In the capacity proportion threshold determination module 204, if the new energy transmission system is required to maintain a stable state under a set small disturbance state, the small disturbance stability relationship between the self-synchronous voltage source capacity proportion S%, different grid strengths SCR, and the real part of each characteristic root RE is: RE=f(S%, SCR); wherein f is a known function.

[0110] In the capacity proportion threshold determination module 204, if the difference between the stability of the new energy transmission system and the stability of all inverter power supplies being current source inverter power supplies based on a phase-locked loop under strong power grid conditions is required to be within a preset range, then the second threshold value of the capacity proportion of the self-synchronous voltage source corresponding to the new energy transmission system is determined based on the characteristic root distribution diagram.

[0111] In one or more embodiments, the new energy transmission system self-synchronous voltage source capacity proportion threshold determination system further includes:

[0112] A small-disturbance stable operation region map construction module is used to construct a small-disturbance stable operation region map according to the relationship f between the self-synchronous voltage source capacity proportion S%, the power grid strength SCR and the characteristic root real part RE; wherein RE = f(S%, SCR);

[0113] The small disturbance stable operation area map consists of three parts: unstable area, weak grid small disturbance stable area and approximately strong grid stable area;

[0114] The weak grid small interference stable area is an area where the new energy transmission system is subject to a set small interference state and the new energy transmission system remains stable;

[0115] The approximate strong power grid stability area is an area where the difference between the stability of the new energy transmission system and the stability of all inverter power supplies under strong power grid conditions, which are current source inverter power supplies based on phase-locked loops, does not exceed a preset range.

[0116] Among them, the real parts of the characteristic roots RE in the unstable region are all greater than zero.

[0117] It should be noted here that the various modules in a device for determining a threshold value for the capacity proportion of a self-synchronous voltage source in a new energy transmission system in an embodiment of the present invention correspond one by one to the various steps in the above-mentioned method for determining a threshold value for the capacity proportion of a self-synchronous voltage source in a new energy transmission system, and the specific implementation process is the same and will not be repeated here.

[0118] Reference Figure 3 , a schematic diagram of an electronic device is given. It should be noted that, Figure 3 The electronic device 300 shown is only an example and should not bring any limitation to the functions and scope of use of the embodiments of the present invention.

[0119] like Figure 3 As shown, the electronic device 300 includes a central processing unit (CPU) 301, which can perform various appropriate actions and processes according to the program stored in the read-only memory (ROM) 302 or the program loaded from the storage part 308 into the random access memory (RAM) 303. In the RAM 303, various programs and data required for system operation are also stored. The central processing unit 301, the ROM 302 and the RAM 103 are connected to each other through a bus 304. An input / output (I / O) interface 305 is also connected to the bus 304.

[0120] The following components are connected to the I / O interface 305: an input section 306 including a keyboard, a mouse, etc.; an output section 307 including a cathode ray tube (CRT), a liquid crystal display (LCD), etc., and a speaker, etc.; a storage section 308 including a hard disk, etc.; and a communication section 309 including a network interface card such as a local area network (LAN) card, a modem, etc. The communication section 309 performs communication processing via a network such as the Internet. A drive 310 is also connected to the I / O interface 305 as needed. A removable medium 311, such as a magnetic disk, an optical disk, a magneto-optical disk, a semiconductor memory, etc., is installed on the drive 310 as needed so that a computer program read therefrom is installed into the storage section 308 as needed.

[0121] When the central processing unit 301 in the electronic device of this embodiment executes the program, the following is achieved: Figure 1 The steps in the method for determining the capacity proportion threshold of the self-synchronous voltage source of the new energy transmission system are shown.

[0122] In particular, according to an embodiment of the present application, the process described above with reference to the flowchart can be implemented as a computer software program. For example, an embodiment of the present application includes a computer program product, which includes a computer program carried on a computer readable medium, the computer program including a computer program for executing Figure 1 In such an embodiment, the computer program can be downloaded and installed from the network through the communication part 309, and / or installed from the removable medium 311. When the computer program is executed by the central processing unit 301, various functions defined in the apparatus of the present application are executed.

[0123] in, Figure 1The computer program instructions corresponding to the method shown may also be stored in a computer-readable memory capable of directing a computer or other programmable data processing device to operate in a specific manner, so that the instructions stored in the computer-readable memory produce a product including an instruction device, which implements the process Figure 1 A process or multiple processes and / or boxes Figure 1 A function specified in one or more boxes.

[0124] A person skilled in the art can understand that all or part of the processes in the above-mentioned embodiments can be implemented by instructing the relevant hardware through a computer program, and the program can be stored in a computer-readable storage medium, and when the program is executed, it can include the processes of the embodiments of the above-mentioned methods. The storage medium can be a disk, an optical disk, a read-only memory (ROM) or a random access memory (RAM), etc.

[0125] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for determining a capacity proportion threshold of a self-synchronous voltage source in a new energy transmission system, characterized in that: include: Constructing a node voltage model defining a grid connection point, a small signal state space model including at least one self-synchronous voltage source inverter power supply, and a small signal state space model including at least one current source inverter power supply based on a phase-locked loop; The self-synchronous voltage source inverter power supply small signal state space model and the phase-locked loop-based current source inverter power supply small signal state space model are connected by defining a node voltage model of the grid-connected point to obtain a multi-inverter power supply grid-connected small signal state space model; Calculating the characteristic roots of the multi-inverter grid-connected small signal state space model, and then obtaining a characteristic root distribution diagram; Based on the characteristic root distribution diagram, the corresponding self-synchronous voltage source capacity ratio threshold is determined according to the stability strength requirements of the new energy transmission system.

2. The method for determining the capacity proportion threshold of the self-synchronous voltage source of the new energy transmission system according to claim 1, characterized in that: If the new energy transmission system is required to maintain a stable state when subjected to a set small disturbance state, a first threshold value of the self-synchronous voltage source capacity proportion corresponding to the new energy transmission system is determined according to the characteristic root distribution diagram.

3. The method for determining the capacity proportion threshold of the self-synchronous voltage source of the new energy transmission system according to claim 1, characterized in that: If the difference between the stability of the new energy transmission system and the stability of all inverter power supplies based on phase-locked loop current source inverter power supplies under strong power grid conditions is required to be within a preset range, then the second threshold value of the proportion of the self-synchronous voltage source capacity corresponding to the new energy transmission system is determined based on the characteristic root distribution diagram.

4. The method for determining the capacity proportion threshold of the self-synchronous voltage source of the new energy transmission system according to claim 1, characterized in that: The method for determining the capacity proportion threshold of the self-synchronous voltage source of the new energy transmission system further includes: According to the relationship f between the self-synchronous voltage source capacity proportion S%, the power grid strength SCR and the characteristic root real part RE, a small interference stable operation area diagram is constructed; where RE = f(S%, SCR); The small disturbance stable operation area map consists of three parts: unstable area, weak grid small disturbance stable area and approximately strong grid stable area; The weak grid small interference stable area is an area where the new energy transmission system is subject to a set small interference state and the new energy transmission system remains stable; The approximate strong power grid stability area is an area where the difference between the stability of the new energy transmission system and the stability of all inverter power supplies under strong power grid conditions, which are current source inverter power supplies based on phase-locked loops, does not exceed a preset range.

5. A device for determining a capacity proportion threshold of a self-synchronous voltage source in a new energy transmission system, characterized in that: include: A sub-model construction module, which is used to construct a node voltage model defining a grid connection point, a small signal state space model including at least one self-synchronous voltage source inverter power supply, and a small signal state space model including at least one current source inverter power supply based on a phase-locked loop; A multi-inverter model building module, which is used to connect the self-synchronous voltage source inverter power supply small signal state space model and the phase-locked loop-based current source inverter power supply small signal state space model by defining a node voltage model of a grid-connected point, so as to obtain a multi-inverter power supply grid-connected small signal state space model; A characteristic root distribution diagram calculation module, which is used to calculate the characteristic roots of the multi-inverter power grid-connected small signal state space model, and then obtain a characteristic root distribution diagram; The capacity proportion threshold determination module is used to determine the corresponding self-synchronous voltage source capacity proportion threshold based on the characteristic root distribution diagram and the stability strength requirement of the new energy transmission system.

6. The device for determining the capacity ratio threshold of the self-synchronous voltage source of the new energy transmission system according to claim 5, characterized in that: In the capacity proportion threshold determination module, if the new energy transmission system is required to remain in a stable state under a set small interference state, the first threshold value of the self-synchronous voltage source capacity proportion corresponding to the new energy transmission system is determined according to the characteristic root distribution diagram.

7. The device for determining the capacity proportion threshold of the self-synchronous voltage source of the new energy transmission system according to claim 5, characterized in that: In the capacity proportion threshold determination module, if the difference between the stability of the new energy transmission system and the stability of all inverter power supplies based on phase-locked loop current source inverter power supplies under strong power grid conditions is required to be no more than a preset range, then the second threshold value of the capacity proportion of the self-synchronous voltage source corresponding to the new energy transmission system is determined according to the characteristic root distribution diagram.

8. The device for determining the capacity proportion threshold of the self-synchronous voltage source of the new energy transmission system according to claim 5, characterized in that: The new energy transmission system self-synchronous voltage source capacity proportion threshold determination system also includes: A small-disturbance stable operation region map construction module is used to construct a small-disturbance stable operation region map according to the relationship f between the self-synchronous voltage source capacity proportion S%, the power grid strength SCR and the characteristic root real part RE; wherein RE = f(S%, SCR); The small disturbance stable operation area map consists of three parts: unstable area, weak grid small disturbance stable area and approximately strong grid stable area; The weak grid small interference stable area is an area where the new energy transmission system is subject to a set small interference state and the new energy transmission system remains stable; The approximate strong power grid stability area is an area where the difference between the stability of the new energy transmission system and the stability of all inverter power supplies under strong power grid conditions, which are current source inverter power supplies based on phase-locked loops, does not exceed a preset range.

9. A computer-readable storage medium having a computer program stored thereon, characterized in that: When the program is executed by a processor, the steps in the method for determining the capacity proportion threshold of a self-synchronous voltage source of a new energy transmission system as described in any one of claims 1 to 4 are implemented.

10. An electronic device comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, characterized in that: When the processor executes the program, the steps in the method for determining the capacity proportion threshold of a self-synchronous voltage source of a new energy transmission system as described in any one of claims 1 to 4 are implemented.

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