Method and device for judging voltage fluctuation caused by new energy control

Abstract

The invention discloses a method and a device for judging voltage fluctuation caused by new energy control. The method comprises the steps that topological structure information of a target power grid is acquired, operation parameters of the target power grid are determined according to the topological structure information, and the operation parameters comprise operation characteristics and load distribution conditions; simplifying a new energy access point of the new energy system into a Thevenin equivalent model by adopting an equivalent transformation method according to the topological structure information and the operation parameters of the target power grid; carrying out power flow derivation according to the Thevenin equivalent model, constructing a power flow calculation equation, and constructing a relational expression of the new energy grid-connected point voltage and the output power based on the power flow calculation equation; when the new energy system performs the low voltage ride through control strategy, calculating the maximum power of the new energy according to a low voltage ride through threshold, the voltage of the new energy grid-connected point and the relational expression; and determining the voltage fluctuation condition of the target power grid according to the new energy maximum power and the output power of the new energy system.

Description

Technical Field

[0001] The present invention relates to the technical field of power system security and stability analysis, and more particularly, to a method and device for discriminating voltage fluctuations caused by new energy control. Background Art

[0002] New energy low voltage ride through (LVRT) control is the key to solving voltage drop problems, requiring the new energy system to continue grid connection during abnormal voltages and supporting grid stability through adjustment of active and reactive power control. One type of voltage fluctuation in new energy grid connection is mainly caused by the switching of control strategies. In the prior art, the switching of control strategies often leads to voltage fluctuations, especially when frequently switching between the low voltage ride through control state and the normal control state, which easily causes repeated voltage fluctuations and affects the stability of the power grid. Existing methods fail to fully consider the non-linear relationship between the power output of the new energy system and voltage fluctuations, resulting in inaccurate discrimination of voltage fluctuations. In addition, the analysis of the maximum power limit of new energy in the prior art is relatively simple, and the impact of crossing constraints on grid stability has not been systematically evaluated. Summary of the Invention

[0003] In view of the deficiencies of the prior art, the present invention provides a method and device for discriminating voltage fluctuations caused by new energy control.

[0004] According to one aspect of the present invention, there is provided a method for discriminating voltage fluctuations caused by new energy control, including:

[0005] Obtaining the topological structure information of the target power grid, and determining the operating parameters of the target power grid according to the topological structure information, where the operating parameters include operating characteristics and load distribution;

[0006] Using the equivalent transformation method, simplifying the new energy access point of the new energy system into a Thevenin equivalent model according to the topological structure information and operating parameters of the target power grid;

[0007] Performing power flow derivation according to the Thevenin equivalent model, constructing a power flow calculation equation, and constructing a relationship expression between the voltage and the output power of the new energy grid connection point based on the power flow calculation equation;

[0008] When the new energy system performs low voltage ride through control strategy, calculating the maximum power of the new energy according to the low voltage ride through threshold, the voltage of the new energy grid connection point, and the relationship expression;

[0009] Determining the voltage fluctuation situation of the target power grid according to the maximum power of the new energy and the output power of the new energy system.

[0010] Optionally, the topological structure information includes: the number of buses, the position distribution, and the parameters of the lines.

[0011] Optionally, an equivalent transformation method is adopted to simplify the new energy access point into a Thevenin equivalent model according to the topological structure information and operating parameters of the target power grid, including:

[0012] Divide the system into a new energy system and the external network of the target power grid, and determine the new energy access point;

[0013] Separate the external network and the new energy system based on the new energy access point;

[0014] Looking from the new energy access point to the external network, calculate the Thevenin equivalent parameters;

[0015] Utilize the topological structure information and operating parameters of the external network to solve the Thevenin equivalent impedance of the external network;

[0016] Disconnect the circuit at the new energy access point, solve the no-load voltage of the system, and determine the Thevenin equivalent voltage of the external network;

[0017] Combine the Thevenin equivalent voltage and the Thevenin equivalent impedance based on the Thevenin equivalent parameters to form a Thevenin equivalent model.

[0018] Optionally, utilize the topological structure information and operating parameters of the external network to solve the equivalent impedance of the external network, including:

[0019] Set the current source at the new energy access point to zero, adopt a branch admittance matrix or a circuit solving method, analyze the open-circuit voltage of the external network to the new energy access point, and calculate the Thevenin equivalent impedance.

[0020] Optionally, the relational expression is:

[0021]

[0022] In the formula, P w is the active power output of the new energy; Q w is the reactive power output of the new energy; U PCC is the voltage at the new energy grid connection point; θ pcc is the voltage phase angle at the new energy grid connection point; U 11 is the Thevenin equivalent voltage; θ 11 is the Thevenin equivalent voltage phase angle; Z 11 is the Thevenin equivalent impedance; θ z is the impedance angle of the Thevenin equivalent impedance, R 11 is the Thevenin equivalent resistance, X 11 is the Thevenin equivalent reactance.

[0023] Optionally, the low voltage ride-through control strategy of the new energy system includes low voltage ride-through state discrimination, active and reactive power control during and after low voltage ride-through, and

[0024] When the voltage U of the new energy grid connection point PCC is less than the low voltage ride-through threshold U L , the new energy control strategy changes from the normal control strategy to the low voltage ride-through control strategy;

[0025] When the voltage U of the new energy grid connection point PCC is greater than the low voltage ride-through exit threshold U L , the new energy control strategy changes from the control strategy during the low voltage ride-through fault to the post-fault power ramp control strategy until it returns to the normal control strategy.

[0026] According to another aspect of the present invention, there is provided a device for discriminating voltage fluctuations caused by new energy control, including:

[0027] An acquisition module, configured to acquire the topological structure information of the target power grid, and determine the operating parameters of the target power grid according to the topological structure information, where the operating parameters include operating characteristics and load distribution;

[0028] A simplification module, configured to simplify the new energy connection point of the new energy system into a Thevenin equivalent model according to the topological structure information and operating parameters of the target power grid by using the equivalent transformation method;

[0029] A construction module, configured to perform power flow derivation according to the Thevenin equivalent model, construct a power flow calculation equation, and construct a relationship expression between the voltage and the output power of the new energy grid connection point based on the power flow calculation equation;

[0030] A calculation module, configured to calculate the maximum new energy power according to the low voltage ride-through threshold, the voltage of the new energy grid connection point, and the relationship expression when the new energy system performs the low voltage ride-through control strategy;

[0031] A determination module, configured to determine the voltage fluctuation condition of the target power grid according to the maximum new energy power and the output power of the new energy system.

[0032] According to yet another aspect of the present invention, there is provided a computer-readable storage medium storing a computer program for executing the method described in any of the above aspects of the present invention.

[0033] According to yet another aspect of the present invention, there is provided an electronic device, including: a processor; a memory for storing executable instructions of the processor; the processor is configured to read the executable instructions from the memory and execute the instructions to implement the method described in any of the above aspects of the present invention.

[0034] Thus, by collecting and analyzing the topology of the power grid, operating parameters, and electrical characteristics of the new energy grid connection point, and simplifying the influence of the external power grid using the Thevenin equivalent method, the present invention accurately calculates the maximum power output of the new energy system, avoids voltage fluctuations caused by excessive power fluctuations, and thus optimizes the power control strategy during the low voltage ride-through process to ensure the safe and stable operation of the power grid after the new energy is connected to the grid. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] The exemplary embodiments of the present invention can be more fully understood by reference to the following drawings:

[0036] Figure 1 is a schematic flowchart of a method for discriminating voltage fluctuations caused by new energy control provided by an exemplary embodiment of the present invention;

[0037] Figure 2 is another schematic flowchart of a method for discriminating voltage fluctuations caused by new energy control provided by an exemplary embodiment of the present invention;

[0038] Figure 3 is a system topology diagram after Thevenin equivalence provided by an exemplary embodiment of the present invention;

[0039] Figure 4 is a schematic diagram of the operating area of new energy provided by an exemplary embodiment of the present invention;

[0040] Figure 5 is a schematic diagram of abnormal operation of new energy provided by an exemplary embodiment of the present invention;

[0041] Figure 6 is a schematic diagram of a new energy single machine infinite bus system provided by an exemplary embodiment of the present invention;

[0042] Figure 7 is a schematic diagram of the relationship between new energy output power and grid connection point voltage provided by an exemplary embodiment of the present invention;

[0043] Figure 8 is a schematic structural diagram of a device for discriminating voltage fluctuations caused by new energy control provided by an exemplary embodiment of the present invention;

[0044] Figure 9 is the structure of an electronic device provided by an exemplary embodiment of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0045] Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments of the present invention. It should be understood that the present invention is not limited by the exemplary embodiments described herein.

[0046] It should be noted that: Unless otherwise specifically stated, the relative arrangements of components and steps, numerical expressions, and numerical values set forth in these embodiments do not limit the scope of the present invention.

[0047] Those skilled in the art can understand that terms such as "first", "second", etc. in the embodiments of the present invention are only used to distinguish different steps, devices, or modules, etc., and neither represent any specific technical meaning nor indicate an inevitable logical order between them.

[0048] It should also be understood that in the embodiments of the present invention, "a plurality of" may refer to two or more, and "at least one" may refer to one, two, or more.

[0049] It should also be understood that for any component, data, or structure mentioned in the embodiments of the present invention, in the absence of a clear limitation or a contrary indication in the context, it can generally be understood as one or more.

[0050] In addition, the term "and / or" in the present invention is merely a description of the association relationship of associated objects, indicating that three relationships may exist. For example, A and / or B may represent: A exists alone, A and B exist simultaneously, and B exists alone. In addition, the character " / " in the present invention generally represents an "or" relationship between the associated objects before and after.

[0051] It should also be understood that the present invention emphasizes the differences between the various embodiments. The similarities or similarities between them can be referred to each other. For the sake of brevity, they will not be elaborated one by one.

[0052] At the same time, it should be understood that for the sake of description, the dimensions of the various parts shown in the drawings are not drawn in actual proportional relationship.

[0053] The following description of at least one exemplary embodiment is actually merely illustrative and in no way restricts the present invention and its application or use.

[0054] Techniques, methods, and devices known to those of ordinary skill in the relevant art may not be discussed in detail, but where appropriate, the techniques, methods, and devices should be regarded as part of the specification.

[0055] It should be noted that: Similar reference numerals and letters denote similar items in the following drawings. Therefore, once an item is defined in one drawing, it does not need to be further discussed in subsequent drawings.

[0056] Embodiments of the present invention can be applied to electronic devices such as terminal devices, computer systems, servers, etc., which can operate together with many other general or special computing system environments or configurations. Examples of well-known terminal devices, computing systems, environments, and / or configurations suitable for use with electronic devices such as terminal devices, computer systems, servers, etc. include, but are not limited to: personal computer systems, server computer systems, thin clients, thick clients, handheld or laptop devices, microprocessor-based systems, set-top boxes, programmable consumer electronics, network personal computers, minicomputer systems, mainframe computer systems, and distributed cloud computing technology environments including any of the above systems, and so on.

[0057] Electronic devices such as terminal devices, computer systems, servers, etc. can be described in the general context of computer system executable instructions (such as program modules) executed by a computer system. Generally, program modules can include routines, programs, target programs, components, logic, data structures, etc., which perform specific tasks or implement specific abstract data types. The computer system / server can be implemented in a distributed cloud computing environment, where tasks are executed by remote processing devices linked through a communication network. In a distributed cloud computing environment, program modules can be located on local or remote computing system storage media including storage devices.

[0058] Exemplary method

[0059] Figure 1 is a schematic flow diagram of a method for discriminating voltage fluctuations caused by new energy control provided by an exemplary embodiment of the present invention. This embodiment can be applied to an electronic device, such as Figure 1 As shown, the method 100 for discriminating voltage fluctuations caused by new energy control includes the following steps:

[0060] Step 101, obtain the topological structure information of the target power grid, and determine the operating parameters of the target power grid according to the topological structure information, where the operating parameters include operating characteristics and load distribution;

[0061] Step 102, adopt an equivalent transformation method, and simplify the new energy access point of the new energy system into a Thevenin equivalent model according to the topological structure information and operating parameters of the target power grid;

[0062] Step 103, conduct power flow derivation according to the Thevenin equivalent model, construct a power flow calculation equation, and based on the power flow calculation equation, construct a relationship expression between the voltage and the output power of the new energy connection point;

[0063] Step 104, when the new energy system performs a low voltage ride-through control strategy, calculate the maximum power of the new energy according to the low voltage ride-through threshold, the voltage of the new energy connection point, and the relationship expression;

[0064] Step 105: Determine the voltage fluctuation condition of the target power grid according to the maximum power of the new energy and the power output of the new energy system.

[0065] Specifically, the present invention accurately evaluates the maximum power output of the new energy grid connection point, avoids voltage fluctuations caused by excessive power fluctuations, thereby optimizing the power control strategy during the low-voltage ride-through process, and ensuring the safe and stable operation of the power grid after the new energy is connected to the grid.

[0066] The present invention discloses a method for discriminating voltage fluctuations caused by new energy control. Refer to Figure 2 As shown, the method includes three steps: determining the network structure parameters and new energy parameters, performing Thevenin equivalent on the system side, and determining the maximum power of the new energy that meets the crossing constraints.

[0067] Step 1: Determine the network structure parameters and new energy parameters

[0068] First, it is necessary to obtain the topological structure information of the target power grid, which includes the number of buses, their location distributions, and the parameters of the lines. Through this information, the operating characteristics and load distribution of the power grid can be clarified. At the same time, it is also necessary to conduct a detailed analysis of the key parameters of the new energy access:

[0069] When the power grid is subjected to a large disturbance impact such as a short circuit resulting in a voltage drop, most new energy installations are equipped with low-voltage ride-through control, which mainly consists of three parts, namely, low-voltage ride-through state discrimination, active and reactive power control during and after the low-voltage ride-through.

[0070] (1) Low-voltage ride-through state discrimination

[0071] Set the low-voltage ride-through threshold U L . When the voltage U PCC of the new energy grid connection point is less than the low-voltage ride-through entry threshold U L , the new energy control strategy changes from the normal control strategy to the control strategy during the low-voltage ride-through fault. When the voltage U PCC of the new energy grid connection point is greater than the low-voltage ride-through exit threshold U L , the new energy control strategy changes from the control strategy during the low-voltage ride-through fault to the post-fault power ramp control strategy until it returns to the normal control strategy.

[0072] (2) Active and reactive power control during and after the low-voltage ride-through

[0073] For a new energy unit grid-connected inverter, when it is determined that a grid fault causes the voltage to drop below the threshold, the inverter control will switch to the low voltage ride-through control mode, and its active and reactive power controls usually adopt constant current control. Therefore, if the new energy unit enters the low voltage ride-through control state, its active power will rapidly decrease due to the reduction of the grid connection point voltage and gradually recover after the low voltage ride-through ends; its reactive power will increase during the low voltage ride-through process to raise the grid connection point voltage and stop increasing reactive power after the low voltage ride-through process ends, returning to the normal reactive power control strategy.

[0074] Specific active power control: During the low voltage ride-through period, the active current value can be specified to flexibly control the active power output of the new energy during the low voltage ride-through. During the low voltage ride-through recovery process, the active power is commonly restored to the active power value under the normal strategy in three ways: immediate recovery, specified slope recovery, and parabolic recovery. The initial value of the power ramp can also be specified at the beginning of the recovery.

[0075] Specific reactive power control measures: During the low voltage ride-through recovery process, the reactive power is commonly restored to the reactive power value under the normal strategy in four ways: immediate recovery, specified slope recovery, parabolic recovery, and maintaining a constant value for a period of time before recovery.

[0076] Regarding the above control of new energy low voltage ride-through, clarify its control form and parameters.

[0077] Step 2: Perform Thevenin equivalent on the system side

[0078] According to the topological structure and operating parameters of the power grid, using the equivalent transformation method, simplify the new energy connection point into a Thevenin equivalent model. First, divide the system into the research target (new energy system) and the external network (the part that needs to be equivalent). Determine the new energy connection point and separate the target system and the external network at this point.

[0079] Then, looking from the new energy connection point to the external network, calculate the Thevenin equivalent parameters. Use the topological structure and parameters of the external network to solve its equivalent impedance. This can be calculated by setting the current source at the new energy connection point to zero (open circuit) and analyzing the open circuit voltage of the external network at the connection point to calculate the Thevenin equivalent impedance. Usually, the branch admittance matrix of the network or direct circuit solving methods are used.

[0080] Next, to calculate the Thevenin equivalent voltage, disconnect the circuit at the new energy connection point and solve for the no-load voltage of the system. This requires analyzing the voltage at the connection point under the normal operating state of the system without including the new energy system.

[0081] Finally, combine the calculated equivalent voltage source (open circuit voltage) and equivalent impedance to form the Thevenin equivalent circuit. In this way, the influence of the external network at the new energy connection point is simplified into a series voltage source and impedance.

[0082] Through the above steps, a complex power system can be simplified into an equivalent model required for new energy system research, which is used to analyze the interaction between the new energy system and the external network subsequently.

[0083] Perform Thevenin equivalent on the system other than new energy, and equivalent it into a voltage source U 11 and an impedance Z 11 , as Figure 3 shown in

[0084] According to the power flow derivation:

[0085]

[0086] In the formula: P w is the active power output of new energy; Q w is the reactive power output of new energy; U PCC is the voltage at the new energy connection point; θ pcc is the voltage phase angle at the new energy connection point; U 11 is the Thevenin equivalent voltage; θ 11 is the Thevenin equivalent voltage phase angle; Z 11 is the Thevenin equivalent impedance; θ z is the impedance angle of the Thevenin equivalent impedance.

[0087] Respectively obtain the relationship between the new energy output power and the voltage at the connection point:

[0088]

[0089] Eliminate θ pcc -θ 11 It can be obtained:

[0090]

[0091] Solve for the voltage U at the new energy connection point PCC It can be obtained:

[0092]

[0093] According to the above formula, the relationship between the voltage at the new energy connection point and its output power can be obtained, so as to determine the power threshold that causes voltage fluctuations.

[0094] Step 3 Determine the maximum power of new energy that can cross the constraint

[0095] It can be obtained from step 1 that the low voltage ride-through threshold for new energy to enter and exit is U L , when the voltage U at the new energy connection point PCC is less than the low voltage ride-through threshold U for entry LWhen the new energy control strategy changes from the normal control strategy to the control strategy during the low-voltage ride-through fault. When the voltage U at the new energy grid connection point PCC is greater than the low-voltage ride-through threshold U L the new energy control strategy changes from the control strategy during the low-voltage ride-through fault to the post-fault power ramp control strategy until it returns to the normal control strategy.

[0096] Due to the control strategy switching behavior of the new energy system, many new types of voltage instability phenomena will occur. When the new energy switches between the normal control state and the low-voltage ride-through control state, the power system has different operating equilibrium point characteristics, which will cause the system voltage to be abnormal. Especially when the operating point switches repeatedly between different control strategies, it will lead to repeated low-ride-through phenomena, resulting in repeated voltage fluctuations at the grid connection point, affecting the safe and stable operation of the power system.

[0097] As Figure 4 shown in the figure is the operating state of the new energy. The shaded area is the change process of the active and reactive power of the new energy (the specific change process is determined by the parameters in step one): After the new energy unit enters the low-ride-through, it generates reactive power, so it will leave a movement trajectory on the Q-axis; when it exits the low-ride-through, the reactive power drops to 0, and the active power starts to recover from 0 according to the slope, so it will leave a movement trajectory on the P-axis. The black curve represents the low-voltage ride-through threshold curve. When the threshold curve intersects with the operating trajectory, the new energy unit will change between the normal control strategy and the low-ride-through control strategy during operation, resulting in voltage fluctuation phenomena caused by new energy control. Therefore, it is necessary to avoid the intersection of the threshold curve and the power operating trajectory.

[0098] Therefore, it is set that when the voltage U at the new energy grid connection point PCC is equal to the low-voltage ride-through threshold U L it is the limit case. At this time, as Figure 4 shown, at this time, the operating power of the new energy does not intersect with the low-ride-through operating curve, and the operating power of the new energy is all in the normal control strategy, and there will be no control strategy change, so there will be no repeated voltage fluctuation phenomenon. Therefore, according to Equation (5), when its voltage is equal to the threshold U L the maximum power of the new energy that can pass through the constraint can be calculated.

[0099] When the output power P1 of the new energy is greater than the calculated maximum power of the new energy that can pass through the constraint, as Figure 5 shown. When the output power of the new energy is P1, at this time, the voltage U at the new energy grid connection point PCC is less than the low-voltage ride-through threshold U L Therefore, the new energy control strategy will change to the low-voltage ride-through control strategy, and the new energy will reduce the active power output and generate reactive power. As shown by the arrow, the power output by the new energy will change from P1 to Q1. When the output power of the new energy is P1, at this time, the voltage U at the new energy grid connection point PCC is greater than the low-voltage ride-through threshold UL Therefore, the new energy control strategy will change to the normal control strategy. As shown by the arrow, the power output from the new energy will change from Q1 to P1 through P0. At this time, the voltage U at the new energy grid connection point PCC will be less than the low voltage ride-through threshold U L , resulting in voltage fluctuations in a cycle.

[0100] Based on Figure 6 the single-machine infinite bus equivalent system shown, the effectiveness of the proposed method is verified.

[0101] The new energy side is equivalent to a power source, and its output active power is P W , and the reactive power is Q W

[0102] According to Equation (5), when the new energy unit is connected to the infinite power grid, the relationship between the new energy output power and the grid connection point voltage can be obtained, as Figure 7 shown:

[0103] The curved surface shows the relationship between the new energy grid connection point voltage and the new energy output power (per unit value) when the access impedance is j0.1 after the new energy is connected. As can be seen from the figure, the red plane is the new energy in and out of the low voltage ride-through threshold (taking the in and out low voltage ride-through thresholds both being 0.9 as an example). When the curved surface is above the red threshold plane, the new energy grid connection point voltage is above the in and out low voltage ride-through thresholds, which is the normal control strategy; when the curved surface is below the red plane, the new energy grid connection point voltage is below the in and out low voltage ride-through thresholds, which is the low voltage ride-through control strategy.

[0104] Therefore, the power at the intersection of the curved surface and the red plane is the maximum power of the new energy under the crossing constraint. By comparing the new energy output power with the calculated maximum power, it is judged whether the new energy will cause voltage fluctuations due to control switching.

[0105] Thus, the present invention collects and analyzes the topological structure of the power grid, operating parameters, and electrical characteristics of the new energy grid connection point, simplifies the influence of the external power grid by combining the Thevenin equivalent method, accurately calculates the maximum power output of the new energy system, avoids voltage fluctuations caused by excessive power fluctuations, and thus optimizes the power control strategy during low voltage ride-through to ensure the safe and stable operation of the power grid after the new energy is connected to the grid.

[0106] Exemplary device

[0107] Figure 8 is a schematic structural diagram of a voltage fluctuation discrimination device caused by new energy control provided by an exemplary embodiment of the present invention. As Figure 8 shown, the device 800 includes:

[0108] An acquisition module 810, configured to acquire the topological structure information of a target power grid, and determine the operating parameters of the target power grid according to the topological structure information, where the operating parameters include operating characteristics and load distribution;

[0109] A simplification module 820, configured to simplify the new energy access point of the new energy system into a Thevenin equivalent model according to the topological structure information and operating parameters of the target power grid by using an equivalent transformation method;

[0110] A construction module 830, configured to perform power flow derivation according to the Thevenin equivalent model, construct a power flow calculation equation, and construct a relationship expression between the new energy connection point voltage and the output power based on the power flow calculation equation;

[0111] A calculation module 840, configured to calculate the maximum new energy power according to the low voltage ride-through threshold, the new energy connection point voltage, and the relationship expression when the new energy system performs a low voltage ride-through control strategy;

[0112] A determination module 850, configured to determine the voltage fluctuation condition of the target power grid according to the maximum new energy power and the output power of the new energy system.

[0113] Optionally, the topological structure information includes: the number of buses, the location distribution, and the parameters of the lines.

[0114] Optionally, the simplification module 820 includes:

[0115] A determination sub-module, configured to divide the system into a new energy system and the external network of the target power grid, and determine the new energy access point;

[0116] A separation sub-module, configured to separate the external network and the new energy system based on the new energy access point;

[0117] A calculation sub-module, configured to calculate the Thevenin equivalent parameters when looking from the new energy access point to the external network;

[0118] A solution sub-module, configured to solve the Thevenin equivalent impedance of the external network by using the topological structure information and operating parameters of the external network;

[0119] A solution sub-module, configured to disconnect the circuit at the new energy access point, solve the no-load voltage of the system, and determine the Thevenin equivalent voltage of the external network;

[0120] A formation sub-module, configured to combine the Thevenin equivalent voltage and the Thevenin equivalent impedance based on the Thevenin equivalent parameters to form a Thevenin equivalent model.

[0121] Optionally, the solution sub-module includes:

[0122] A calculation unit is used to set the current source of the new energy access point to zero, and by using the branch admittance matrix or the circuit solution method, it analyzes the open-circuit voltage of the new energy access point by the external network and calculates the Thevenin equivalent impedance.

[0123] Optionally, the relational expression is:

[0124]

[0125] In the formula, P w is the active power output by the new energy; Q w is the reactive power output by the new energy; U PCC is the voltage at the new energy grid connection point; θ pcc is the phase angle of the voltage at the new energy grid connection point; U 11 is the Thevenin equivalent voltage; θ 11 is the phase angle of the Thevenin equivalent voltage; Z 11 is the Thevenin equivalent impedance; θ z is the impedance angle of the Thevenin equivalent impedance, R 11 is the Thevenin equivalent resistance, X 11 is the Thevenin equivalent reactance.

[0126] Optionally, the low voltage ride-through control strategy of the new energy system includes low voltage ride-through state discrimination, active and reactive power control during and after low voltage ride-through, and

[0127] When the voltage U PCC at the new energy grid connection point is less than the low voltage ride-through threshold U L , the new energy control strategy changes from the normal control strategy to the low voltage ride-through control strategy;

[0128] When the voltage U PCC at the new energy grid connection point is greater than the low voltage ride-through exit threshold U L , the new energy control strategy changes from the control strategy during the low voltage ride-through fault to the post-fault power ramp control strategy until it returns to the normal control strategy.

[0129] Exemplary electronic device

[0130] Figure 9 is the structure of the electronic device provided by an exemplary embodiment of the present invention. As Figure 9 shown, the electronic device 90 includes one or more processors 91 and a memory 92.

[0131] The processor 91 can be a central processing unit (CPU) or other forms of processing units with data processing capabilities and / or instruction execution capabilities, and can control other components in the electronic device to perform desired functions.

[0132] The memory 92 may include one or more computer program products, and the computer program products may include various forms of computer-readable storage media, such as volatile memory and / or non-volatile memory. The volatile memory may include, for example, random access memory (RAM) and / or cache memory, etc. The non-volatile memory may include, for example, read-only memory (ROM), hard disk, flash memory, etc. One or more computer program instructions may be stored on the computer-readable storage media, and the processor 91 may run the program instructions to implement the methods of the software programs of the various embodiments of the present invention described above and / or other desired functions. In one example, the electronic device may further include: an input device 93 and an output device 94, and these components are interconnected through a bus system and / or other forms of connection mechanisms (not shown).

[0133] In addition, the input device 93 may further include, for example, a keyboard, a mouse, and so on.

[0134] The output device 94 may output various information to the outside. The output device 94 may include, for example, a display, a speaker, a printer, and a communication network and its connected remote output devices, and so on.

[0135] Of course, for simplicity, Figure 9 only some of the components related to the present invention in the electronic device are shown, and components such as buses, input / output interfaces, etc. are omitted. In addition, according to specific application scenarios, the electronic device may further include any other appropriate components.

[0136] Exemplary computer program product and computer-readable storage medium

[0137] In addition to the above methods and devices, embodiments of the present invention may also be computer program products, which include computer program instructions that, when run by a processor, cause the processor to execute the steps in the methods according to various embodiments of the present invention described in the "Exemplary Methods" section above of this specification.

[0138] The computer program products may be written in any combination of one or more programming languages to write program codes for performing the operations of the embodiments of the present invention. The programming languages include object-oriented programming languages, such as Java, C++, etc., and also include conventional procedural programming languages, such as the "C" language or similar programming languages. The program codes may be executed entirely on the user computing device, partially on the user device, executed as an independent software package, partially on the user computing device and partially on a remote computing device, or entirely on a remote computing device or server.

[0139] In addition, an embodiment of the present invention may also be a computer-readable storage medium storing computer program instructions, which, when run by a processor, cause the processor to execute the steps in the methods according to various embodiments of the present invention described in the above "Exemplary Methods" section of this specification.

[0140] The computer-readable storage medium may adopt any combination of one or more readable media. The readable media may be a readable signal medium or a readable storage medium. The readable storage medium may, for example, include but is not limited to an electrical, magnetic, optical, electromagnetic, infrared, or semiconductor system, apparatus, or device, or any combination of the above. More specific examples (a non-exhaustive list) of the readable storage medium include: an electrical connection with one or more wires, a portable disk, a hard disk, a random access memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or flash memory), an optical fiber, a portable compact disk read-only memory (CD-ROM), an optical storage device, a magnetic storage device, or any suitable combination of the above.

[0141] The basic principles of the present invention have been described above in conjunction with specific embodiments. However, it should be noted that the advantages, benefits, effects, etc. mentioned in the present invention are only examples and not limitations. It cannot be considered that these advantages, benefits, effects, etc. are essential for each embodiment of the present invention. In addition, the above-disclosed specific details are only for illustrative purposes and for ease of understanding, rather than limitations. The above details do not limit the present invention to necessarily adopt the above specific details for implementation.

[0142] Each embodiment in this specification is described in a progressive manner. The key point of each embodiment is to illustrate the differences from other embodiments. The same or similar parts among the embodiments can be referred to each other. For system embodiments, since they basically correspond to method embodiments, the description is relatively simple. For the relevant parts, refer to the description of the method embodiments.

[0143] The block diagrams of the devices, systems, equipment, and systems involved in the present invention are only illustrative examples and do not intend to require or imply that they must be connected, arranged, and configured in the manner shown in the block diagrams. As those skilled in the art will recognize, these devices, systems, equipment, and systems can be connected, arranged, and configured in any manner. Words such as "including", "comprising", "having", etc. are open-ended terms, meaning "including but not limited to", and can be used interchangeably with each other. The words "or" and "and" used herein refer to the word "and / or", and can be used interchangeably with each other unless the context clearly indicates otherwise. The word "such as" used herein refers to the phrase "such as but not limited to", and can be used interchangeably with each other.

[0144] The methods and systems of the present invention can be implemented in many ways. For example, the methods and systems of the present invention can be implemented by software, hardware, firmware, or any combination of software, hardware, and firmware. The above order of the steps for the methods is for illustration only, and the steps of the methods of the present invention are not limited to the specific order described above, unless otherwise specifically stated. In addition, in some embodiments, the present invention can also be implemented as a program recorded in a recording medium, and these programs include machine-readable instructions for implementing the methods according to the present invention. Therefore, the present invention also covers a recording medium storing a program for executing the methods according to the present invention.

[0145] It should also be noted that in the systems, devices, and methods of the present invention, each component or each step can be decomposed and / or recombined. These decompositions and / or recombinations should be regarded as equivalent solutions of the present invention. The above description of the disclosed aspects is provided to enable any person skilled in the art to make or use the present invention. Various modifications to these aspects are very obvious to those skilled in the art, and the general principles defined herein can be applied to other aspects without departing from the scope of the present invention. Therefore, the present invention is not intended to be limited to the aspects shown herein, but to the widest scope consistent with the principles and novel features disclosed herein.

[0146] The above description has been given for purposes of illustration and description. In addition, this description is not intended to limit the embodiments of the present invention to the forms disclosed herein. Although multiple example aspects and embodiments have been discussed above, those skilled in the art will recognize certain variations, modifications, alterations, additions, and sub-combinations thereof.

Claims

1. A method for distinguishing voltage fluctuation caused by new energy control, characterized in that: include: Acquire topological structure information of the target power grid, and determine operating parameters of the target power grid according to the topological structure information, wherein the operating parameters include operating characteristics and load distribution; Using an equivalent transformation method, according to the topological structure information and the operating parameters of the target power grid, a new energy access point of the new energy system is simplified into a Thevenin equivalent model; Derivation of power flow is performed according to the Thevenin equivalent model, a power flow calculation equation is constructed, and based on the power flow calculation equation, an expression for the relationship between the voltage and the output power at the new energy grid connection point is constructed; When the new energy system performs a low voltage ride-through control strategy, the new energy maximum power is calculated according to the low voltage ride-through threshold, the new energy grid connection point voltage and the relationship expression; The voltage fluctuation of the target power grid is determined according to the maximum power of the new energy and the output power of the new energy system.

2. The method according to claim 1, characterized in that The topology information includes: the number and location distribution of busbars and line parameters.

3. The method according to claim 1, characterized in that Using an equivalent transformation method, according to the topological structure information and the operating parameters of the target power grid, the new energy access point is simplified into a Thevenin equivalent model, including: Dividing the system into a new energy system and an external network of the target power grid, and determining a new energy access point; Separating the external network and the new energy system based on the new energy access point; Calculating a Thevenin equivalent parameter looking from the new energy access point toward the external network; Utilizing the topological structure information and the operating parameters of the external network, solving the Thevenin equivalent impedance of the external network; Disconnect the circuit at the new energy access point, solve the no-load voltage of the system, and determine the Thevenin equivalent voltage of the external network; The Thevenin equivalent voltage and the Thevenin equivalent impedance are combined based on the Thevenin equivalent parameter to form the Thevenin equivalent model.

4. The method according to claim 3, characterized in that Solving the equivalent impedance of the external network by using the topology information and the operating parameters of the external network includes: The current source of the new energy access point is set to zero, and the open circuit voltage of the external network to the new energy access point is analyzed by using a branch admittance matrix or a circuit solving method, and the Thevenin equivalent impedance is calculated.

5. The method according to claim 1, characterized in that The relational expression is: Where P w Output active power for new energy; Q w Output reactive power for new energy; U PCC is the voltage at the grid-connected point of new energy; θ pcc is the voltage phase angle of the new energy grid connection point; U 11 is the Thevenin equivalent voltage; θ 11 is the Thevenin equivalent voltage phase angle; Z 11 is the Thevenin equivalent impedance; θ z is the Thevenin equivalent impedance angle, R 11 is the Thevenin equivalent resistance, X 11 is the Thevenin equivalent reactance.

6. The method according to claim 1, characterized in that The low voltage ride through control strategy of the new energy system includes low voltage ride through state determination, active and reactive power control during and after the low voltage ride through, and When the voltage U PCC Less than the low voltage ride-through threshold U L When the new energy control strategy changes from the normal control strategy to the low voltage ride-through control strategy; When the voltage U PCC Greater than the exit low voltage ride-through threshold U L When the fault occurs, the new energy control strategy changes from the low voltage ride-through fault control strategy to the post-fault power ramp-up control strategy until it returns to the normal control strategy.

7. A voltage fluctuation identification device caused by new energy control, characterized in that: include: An acquisition module, used to acquire topological structure information of a target power grid, and determine operating parameters of the target power grid according to the topological structure information, wherein the operating parameters include operating characteristics and load distribution; A simplification module, configured to simplify a new energy access point of a new energy system into a Thevenin equivalent model according to the topological structure information and the operating parameters of the target power grid by adopting an equivalent transformation method; A construction module is used to derive power flow according to the Thevenin equivalent model, construct a power flow calculation equation, and construct a relationship expression between the voltage and the output power of the new energy grid connection point based on the power flow calculation equation; A calculation module, used for calculating the maximum power of the new energy according to the low voltage ride-through threshold, the voltage of the new energy grid connection point and the relational expression when the new energy system performs the low voltage ride-through control strategy; The determination module is used to determine the voltage fluctuation of the target power grid according to the maximum power of the new energy and the output power of the new energy system.

8. The device according to claim 7, characterized in that The topology information includes: the number and location distribution of busbars and line parameters.

9. The device according to claim 7, characterized in that Simplified modules, including: A determination submodule is used to divide the system into a new energy system and an external network of the target power grid, and determine a new energy access point; A separation submodule, used for separating the external network and the new energy system based on the new energy access point; A calculation submodule, used for calculating the Thevenin equivalent parameter from the new energy access point to the external network; A solution submodule, used to solve the Thevenin equivalent impedance of the external network by using the topology information and the operating parameters of the external network; A solution submodule, used for disconnecting the circuit at the new energy access point, solving the no-load voltage of the system, and determining the Thevenin equivalent voltage of the external network; A submodule is formed, which is used to combine the Thevenin equivalent voltage and the Thevenin equivalent impedance based on the Thevenin equivalent parameter to form the Thevenin equivalent model.

10. The device according to claim 9, characterized in that Solving submodules, including: The calculation unit is used to set the current source of the new energy access point to zero, adopt a branch admittance matrix or a circuit solving method to analyze the open circuit voltage of the external network to the new energy access point, and calculate the Thevenin equivalent impedance.

11. The device according to claim 7, characterized in that The relational expression is: Where P w Output active power for new energy; Q w Output reactive power for new energy; U PCC is the voltage at the grid-connected point of new energy; θ pcc is the voltage phase angle of the new energy grid connection point; U 11 is the Thevenin equivalent voltage; θ 11 is the Thevenin equivalent voltage phase angle; Z 11 is the Thevenin equivalent impedance; θ z is the Thevenin equivalent impedance angle, R 11 is the Thevenin equivalent resistance, X 11 is the Thevenin equivalent reactance.

12. The device according to claim 7, characterized in that The low voltage ride through control strategy of the new energy system includes low voltage ride through state determination, active and reactive power control during and after the low voltage ride through, and When the voltage U PCC Less than the low voltage ride-through threshold U L When the new energy control strategy changes from the normal control strategy to the low voltage ride-through control strategy; When the voltage U PCC Greater than the exit low voltage ride-through threshold U L When the fault occurs, the new energy control strategy changes from the low voltage ride-through fault control strategy to the post-fault power ramp-up control strategy until it returns to the normal control strategy.

13. A computer-readable storage medium, characterized in that: The storage medium stores a computer program, and the computer program is used to execute the method according to any one of claims 1 to 6.

14. An electronic device, characterized in that: The electronic device comprises: processor; a memory for storing instructions executable by the processor; The processor is used to read the executable instructions from the memory and execute the instructions to implement the method described in any one of claims 1 to 6.

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