Relay protection analysis modeling method under control strategy of network construction type energy storage converter

Abstract

The invention discloses a relay protection analysis modeling method under a control strategy of a network construction type energy storage converter, and the method comprises the steps: building an operation equivalent circuit model of the network construction type converter based on a synchronous operation control strategy and a fault ride-through control strategy of the network construction type converter; on the basis of the network construction type converter equivalent circuit model, the network following type converter equivalent circuit model and the relay protection function model, constructing a power system overall model; and based on the overall model of the power system, evaluating fault electrical characteristics and protection action characteristics in combination with different fault working conditions. According to the method, various protections of mainstream configuration in a current power transmission line are fully considered, a control strategy of the network-building type converter is combined, and a specific construction method of the network-building type converter model and the system model thereof under different operation conditions is provided.

Description

Technical Field

[0001] The present invention belongs to the technical field of relay protection of electric power systems, and in particular relates to a relay protection analysis modeling method under a grid-type energy storage converter control strategy. Background Art

[0002] Energy storage is an important technology and basic equipment for building a new power system. The application of energy storage technology in the power system is the key to ensuring the large-scale development of clean energy and the safe and economical operation of the power grid. Energy storage technology can make up for the missing storage and release functions in the power system, change the mode of synchronous completion of power production, transmission and use, and make the rigid power system with real-time balance more flexible. In particular, it can smooth out the volatility caused by the access of large-scale clean energy power generation to the power grid, and improve the safety, economy and flexibility of power grid operation.

[0003] Electrochemical energy storage stores electrical energy in batteries, and when it needs to be discharged, it is output through converters and other links. Due to the existence of power electronic converters and control links, its characteristics during faults are affected by the current carrying capacity of the device and the control strategy, which is significantly different from the traditional power grid. The current grid-type energy storage control strategy can effectively improve the stability of the new power system and provide a new solution for building a stable and highly reliable system. In recent years, domestic and foreign scholars have proposed various types of energy storage converter control technologies, but their research has mostly focused on improving the stability of the access system, and has rarely involved how to build a reasonable model for the analysis of relay protection. Relay protection mainly focuses on the differences in external characteristics presented by the control strategy under various types of operating conditions. Analogous to the synchronous generator system, it is expected to simplify the description of its corresponding physical equivalent circuit, thereby building a system-level model that can evaluate the action behavior of various types of relay protection. Summary of the invention

[0004] The purpose of the present invention is to provide a relay protection analysis modeling method under the control strategy of a grid-type energy storage converter. The method fully considers various protections configured in the mainstream of current transmission lines, and combines the control strategy of the grid-type converter to propose a specific construction method of the grid-type converter model and its system model under different operating conditions.

[0005] In order to achieve the above object, the solution of the present invention is:

[0006] A relay protection analysis modeling method under a grid-type energy storage converter control strategy includes:

[0007] Based on the synchronous operation control strategy and fault ride-through control strategy of the grid-connected converter, an operation equivalent circuit model of the grid-connected converter is established;

[0008] Based on the grid-forming converter equivalent circuit model, the grid-following converter equivalent circuit model and the relay protection function model, an overall model of the power system is constructed. Based on the overall model of the power system, the fault electrical characteristics and the protection action characteristics are evaluated in combination with different fault conditions.

[0009] Among them, the synchronous operation control strategy based on the grid-connected converter includes:

[0010] Based on the synchronous operation control strategy of the grid-connected converter, an equivalent circuit model under normal operation is constructed.

[0011]

[0012] In the formula, are the voltage and current at the common coupling point on the grid side of the converter, is the converter equivalent voltage source, Z IBR is the equivalent system impedance.

[0013] Among them, the fault ride-through control strategy based on grid-connected converter includes:

[0014] During the fault ride-through period, the output current is limited by current limiting, including a method of directly setting the output current and a method of introducing impedance limiting;

[0015] Among them, for the method of directly giving the output current, the fault ride-through period is equivalent to the form of a controlled current source connected in parallel with a large impedance;

[0016] Among them, for the method of introducing impedance limiting, the fault ride-through period is equivalent to the form of a voltage source and an impedance in series.

[0017] Among them, the operation equivalent circuit model of the grid-connected converter is established, including:

[0018] Set the equivalent circuit model according to different operating conditions;

[0019] Among them, when Assuming that the grid-connected converter is in normal operation, the equivalent circuit model under the synchronous operation control strategy is adopted; where, is the rated voltage, k is the coefficient, and its value range is 0.7~0.9;

[0020] Among them, when Assume that the grid-connected converter is in the fault ride-through period. At this time,

[0021] When the current limiting mode is a mode of directly giving the output current, an equivalent circuit model of a controlled current source connected in parallel with a large impedance is adopted;

[0022] When the current limiting method is to introduce impedance limiting, a voltage source and an impedance are connected in series.

[0023] The grid-following converter equivalent circuit model is modeled by a voltage-controlled current source method.

[0024] Wherein, the relay protection function model includes:

[0025] For collector line protection, an overcurrent protection model is constructed;

[0026] For transformer protection, differential protection model and overcurrent protection model are constructed;

[0027] For transmission line protection, differential protection model, distance protection model and zero-sequence overcurrent protection model are constructed.

[0028] A computer device comprises a memory, a processor, and a computer program stored in the memory and executable on the processor; when the processor executes the computer program, the steps of the relay protection analysis modeling method under the control strategy of the grid-type energy storage converter as described above are implemented.

[0029] A computer-readable storage medium stores a computer program; when the computer program is executed by a processor, the steps of the relay protection analysis modeling method under the control strategy of a grid-type energy storage converter as described above are implemented.

[0030] After adopting the above scheme, the present invention first analyzes the synchronous operation control strategy and fault crossing control strategy of the grid-type converter, and establishes the fault equivalent circuit of the grid-type converter; then, based on the equivalent circuit of the grid-type converter, the equivalent circuit of the grid-type converter and the models of various functions of relay protection, the overall system model is constructed to evaluate the fault electrical characteristics and protection action characteristics. The relay protection analysis modeling method under the control strategy of the grid-type energy storage converter proposed in the present invention can combine the system operating conditions and control characteristics to accurately evaluate the relay protection operation performance of the new energy transmission system containing the grid-type energy storage converter. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 It is a schematic diagram of a new energy transmission grid including a grid-type converter;

[0032] Figure 2 It is a schematic diagram of the equivalent circuit model of the grid-type converter;

[0033] Among them, (a) is the equivalent circuit model corresponding to normal control, (b) is the equivalent circuit model corresponding to limited current fault ride-through, and (c) is the equivalent circuit model corresponding to impedance limiting fault ride-through. DETAILED DESCRIPTION

[0034] The technical solutions and beneficial effects of the present invention will be described in detail below with reference to the accompanying drawings.

[0035] like Figure 1 As shown, the present invention is directed to a system relay protection device for collecting and transmitting new energy and a grid-type energy storage inverter. The system includes a grid-following wind power inverter, a grid-following photovoltaic inverter, a grid-type energy storage inverter, and various types of relay protection devices configured in the system, wherein R1, R2, and R3 are collector line protections, R4 is transformer protection, and R5 and R6 are transmission line protections.

[0036] To build Figure 1 The system model shown needs to propose the equivalent circuit of the grid-connected converter in combination with different operating conditions, and build a complete system model in combination with the overall system situation. The specific steps include:

[0037] Step 1: Analyze the synchronous operation control strategy and fault ride-through control strategy of the grid-connected converter, and establish a fault equivalent circuit model of the grid-connected converter;

[0038] Step 2: Based on the equivalent circuit model of the grid-forming converter, the equivalent circuit model of the grid-following converter, and the models of various functions of relay protection, the overall system model is constructed. Combined with different fault conditions, the fault electrical characteristics and protection action characteristics are evaluated.

[0039] Furthermore, in step 1, the synchronous operation control strategy of the grid-connected converter determines the equivalent circuit construction method under normal operation, which is specifically described as follows:

[0040] The grid-type converter achieves active and reactive power regulation by controlling the port voltage amplitude and phase. Different control strategies have different regulation methods, but the goal is to control the port voltage. Under steady-state conditions, its equivalent circuit is in the form of port potential series loop impedance, such as Figure 2 The equivalent circuit model corresponding to the normal control in (a) is as follows:

[0041]

[0042] In the above formula: are the voltage and current at the common coupling point P on the grid side of the converter, is the converter equivalent voltage source, Z IBR is the equivalent system impedance.

[0043] Furthermore, in step 1, the grid-connected converter needs to limit the output current during the fault ride-through period, and the fault current limiting strategy determines the construction method of the equivalent circuit model during the ride-through period, which is specifically described as follows:

[0044] During the identification of fault ride-through, a current limiting method is adopted, which is divided into a method of directly giving the output current and a method of introducing impedance limiting.

[0045] For the method of directly giving the output current, the fault ride-through period is equivalent to a controlled current source connected in parallel with a large impedance, such as Figure 2 The equivalent circuit model corresponding to the limited current fault ride-through in (b) is as follows:

[0046]

[0047] Depends on the impedance of the external system, is the converter equivalent current source.

[0048] For the method of introducing impedance limiting, the fault ride-through period is equivalent to the form of a voltage source and an impedance in series, such as Figure 2 The equivalent circuit model corresponding to the impedance limiting fault ride-through in (c) is as follows:

[0049]

[0050] is the voltage formed under the control of synchronous operation strategy before the fault, Z IBR The corresponding impedance value is the accumulated value taking into account the control limit and the actual impedance in the system.

[0051] Furthermore, in step 1, the equivalent circuit model setting under each operating condition is specifically expressed as follows:

[0052] when Assume that the grid-connected converter is in normal operation and adopt the equivalent circuit model in synchronous operation; where: is the rated voltage, k is the coefficient, and its value range is 0.7 to 0.9; preferably, the coefficient can be set to 0.85.

[0053] when Assume that the grid-connected converter is in the fault ride-through period.

[0054] When the fault current limiting strategy is to directly set the output current, an equivalent circuit model of a controlled current source in parallel with a large impedance is adopted;

[0055] When the fault current limiting strategy is to introduce impedance limiting, a voltage source and an impedance are connected in series.

[0056] Furthermore, in step 2, the specific contents are as follows:

[0057] The equivalent circuit model of the grid-type converter under different operating conditions is set according to the above-mentioned combination of operating voltage and control strategy; the equivalent circuit model of the grid-type converter corresponds to Figure 1 The grid-following wind power converter and grid-following photovoltaic converter are modeled using a general voltage-controlled current source method; the functional models of various protections, for collection line protection, the protection models that need to be constructed include overcurrent protection; for transformer protection, the protection models that need to be constructed mainly include differential protection and overcurrent protection; for transmission line protection, the protection models that need to be constructed mainly include differential protection, distance protection, and zero-sequence overcurrent protection.

[0058] An embodiment of the present invention further provides another computer device, including a processor and a memory configured to store a computer program that can be run on the processor; wherein, when the processor is configured to run the computer program, the method steps in the aforementioned embodiment are executed.

[0059] In practical applications, the processor includes a field programmable gate array (FPGA), and the processor may be a central processing unit (CPU) or a digital signal processor (DSP). It is understandable that for different devices, the electronic device used to implement the function of the processor may be other, and the embodiment of the present invention does not specifically limit it.

[0060] The above-mentioned memory can be a volatile memory (volatile memory), such as a random access memory (RAM); or a non-volatile memory (non-volatile memory), such as a read-only memory (ROM), a flash memory, a hard disk (HDD) or a solid-state drive (SSD); or a combination of the above-mentioned types of memory, and provide instructions and data to the processor.

[0061] In an exemplary embodiment, an embodiment of the present invention further provides a computer-readable storage medium for storing a computer program.

[0062] Optionally, the computer-readable storage medium can be applied to any one of the methods in the embodiments of the present invention, and the computer program enables the computer to execute the corresponding processes implemented by the processor in each method in the embodiments of the present invention. For the sake of brevity, they are not described here.

[0063] In the several embodiments provided by the present invention, it should be understood that the disclosed devices and methods can be implemented in other ways. The device embodiments described above are only schematic. For example, the division of the units is only a logical function division. There may be other division methods in actual implementation, such as: multiple units or components can be combined, or can be integrated into another system, or some features can be ignored or not executed. In addition, the coupling, direct coupling, or communication connection between the components shown or discussed can be through some interfaces, and the indirect coupling or communication connection of the devices or units can be electrical, mechanical or other forms.

[0064] It will be appreciated by those skilled in the art that embodiments of the present invention may be provided as methods, systems, or computer program products. Therefore, the present invention may take the form of a complete hardware embodiment, a complete software embodiment, or an embodiment combining software and hardware. Moreover, the present invention may take the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program codes. The schemes in the embodiments of the present invention may be implemented in various computer languages, for example, object-oriented programming language Java and literal scripting language JavaScript, etc.

[0065] The present invention is described with reference to flowcharts and / or block diagrams of methods, devices (systems), and computer program products according to embodiments of the present invention. It should be understood that each process and / or block in the flowchart and / or block diagram, as well as the combination of processes and / or blocks in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to produce a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the processes in the flowchart and / or block diagram. Figure 1 A process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0066] These computer program instructions 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 an article of manufacture comprising 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.

[0067] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operating steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing instructions for implementing the process. Figure 1 A process or multiple processes and / or boxes Figure 1 The steps for the functions specified in one or more boxes.

[0068] Although the preferred embodiments of the present invention have been described, those skilled in the art may make other changes and modifications to these embodiments once they have learned the basic creative concept. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications that fall within the scope of the present invention.

[0069] Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include these modifications and variations.

Claims

1. A relay protection analysis modeling method under a grid-type energy storage converter control strategy, characterized in that: include, Based on the synchronous operation control strategy and fault ride-through control strategy of the grid-connected converter, an operation equivalent circuit model of the grid-connected converter is established; Based on the grid-forming converter equivalent circuit model, the grid-following converter equivalent circuit model and the relay protection function model, an overall model of the power system is constructed. Based on the overall model of the power system, the fault electrical characteristics and the protection action characteristics are evaluated in combination with different fault conditions.

2. The method according to claim 1, characterized in that: The synchronous operation control strategy based on the grid-connected converter includes: Based on the synchronous operation control strategy of the grid-connected converter, an equivalent circuit model under normal operation is constructed. In the formula, are the voltage and current at the common coupling point on the grid side of the converter, is the converter equivalent voltage source, Z IBR is the equivalent system impedance.

3. The method according to claim 1, characterized in that: The fault ride-through control strategy based on grid-connected converter includes: During the fault ride-through period, the output current is limited by current limiting, including a method of directly setting the output current and a method of introducing impedance limiting; Among them, for the method of directly giving the output current, the fault ride-through period is equivalent to the form of a controlled current source connected in parallel with a large impedance; Among them, for the method of introducing impedance limiting, the fault ride-through period is equivalent to the form of a voltage source and an impedance in series.

4. The method according to claim 3, characterized in that: Establish the operation equivalent circuit model of the grid-connected converter, including: Set the equivalent circuit model according to different operating conditions; Among them, when Assume that the grid-connected converter is in normal operation and adopt the equivalent circuit model under the synchronous operation control strategy; where, is the rated voltage, k is the coefficient, and its value range is 0.7~0.9; Among them, when Assume that the grid-connected converter is in the fault ride-through period. At this time, When the current limiting mode is a mode of directly giving the output current, an equivalent circuit model of a controlled current source connected in parallel with a large impedance is adopted; When the current limiting method is to introduce impedance limiting, a voltage source and an impedance are connected in series.

5. The method according to claim 1, characterized in that: The grid-following converter equivalent circuit model is modeled by using a voltage-controlled current source method.

6. The method according to claim 1, characterized in that: The relay protection function model includes: For collector line protection, an overcurrent protection model is constructed; For transformer protection, differential protection model and overcurrent protection model are constructed; For transmission line protection, differential protection model, distance protection model and zero-sequence overcurrent protection model are constructed.

7. A computer 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 computer program, the steps of the relay protection analysis and modeling method under the grid-type energy storage converter control strategy as described in any one of claims 1 to 6 are implemented.

8. A computer-readable storage medium storing a computer program; characterized in that: When the computer program is executed by a processor, the steps of the relay protection analysis and modeling method under the grid-type energy storage converter control strategy as described in any one of claims 1 to 6 are implemented.

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