Power system short-circuit current suppression method and system based on network construction type equipment

Abstract

The invention discloses an electric power system short-circuit current suppression method and system based on network construction type equipment, and belongs to the technical field of electric power. The method comprises the following steps: establishing a power system topology and solving a steady-state operating point; establishing a converter control model based on the steady-state point, and constructing a current-limiting control logic by adopting three criteria of current, phase angle and voltage; deducing a short-circuit current analytical expression through fault analysis, and establishing a relationship between the output current of the network construction type equipment and the total short-circuit current; and dynamically adjusting the output current phase by adopting a self-adaptive saturation current angle strategy based on the relationship. The technical problems that a traditional current limiting method is difficult in parameter setting and the current limiting mode cannot be automatically quitted after a fault occurs are solved, the short-circuit current of the power system can be restrained to the maximum extent, reliable on-off of a circuit breaker is ensured, and the safety and stability of the system are improved.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of electric power, and particularly relates to a power system short-circuit current suppression method and system based on network-constructing equipment. BACKGROUND

[0002] With the continuous growth of the load demand of the power system and the continuous expansion of the power grid scale, the short-circuit capacity of the power system presents a significant upward trend. The increasing complexity of the power grid structure and the continuous improvement of the transmission voltage level make the system short-circuit current level gradually close to or even exceed the design breaking capacity limit of the existing circuit breaker. One solution is to directly replace the switching equipment, but the circuit breaker with higher breaking level is high in cost, and the large-capacity circuit breaker technology is not completely mature, and another solution is to install series reactors, adopt high-impedance transformers, and configure passive current limiting devices such as fault current limiters, but these devices will change the impedance characteristics of the system during normal operation, which may affect the power quality and system stability, and if the switching method is adopted, it may not be able to be quickly switched in under fault, and it is difficult to achieve effective suppression.

[0003] The flexible control characteristics of power electronic equipment provide a new idea for short-circuit current suppression, especially the emerging network-constructing equipment in recent years. The traditional grid-following equipment relies on the acquisition of the grid-connected point voltage to determine the phase, however, the grid-connected point voltage may be distorted or even reduced to 0 under fault, and it is difficult to phase-lock under fault, and naturally cannot output controllable current to achieve system short-circuit current suppression. In comparison, the maximum advantage of the network-constructing equipment lies in its self-synchronization characteristics, and the frequency and phase of the electrical quantity are given by the synchronization loop, and there is no phase-locking problem under fault, and it can realize operation under zero voltage, providing a feasible solution for short-circuit current support under fault.

[0004] The network-constructing equipment usually operates as a voltage source to provide frequency and voltage support for the system. However, due to the limited overcurrent capacity of the power electronic equipment, the network-constructing equipment under fault becomes a current source. The traditional current limiting strategy usually gives a constant active and reactive current, but since the phase angle under fault is constantly changing, the active and reactive current provided by the network-constructing equipment is not constant, but a current with a determined amplitude and a constantly changing phase. The current size of the signal in the first few cycles of the short circuit depends on the system topology and control parameters, and it is difficult to effectively set the parameters.

[0005] In normal operating state, grid-forming devices operate in voltage source mode to provide necessary frequency and voltage support for the system. However, due to the current tolerance capability of power electronic devices, when the system occurs short-circuit fault, the grid-forming device switches to current limiting mode operation. The traditional current limiting control strategy usually adopts the control mode of fixed active and reactive current, but due to the continuous change of the phase of the synchronous ring output under fault, the actual output is the current with constant amplitude and changing phase. Especially, within the initial several cycles after short-circuit, the amplitude and phase characteristics of short-circuit current not only depend on the control parameters of the grid-forming device itself, but also are closely related to the system network topology and operating mode, which leads to the difficulty in setting the control parameters and the difficulty in achieving the ideal current limiting effect.

[0006] Therefore, there is an urgent need for an improved control method to effectively suppress short-circuit current through grid-forming devices and solve the problem of excessive short-circuit current in power systems. SUMMARY

[0007] The technical problem to be solved by the present application is to provide a power system short-circuit current suppression method and system based on grid-forming devices to solve the technical problem of excessive short-circuit current in power systems.

[0008] The present application adopts the following technical solutions: A power system short-circuit current suppression method based on grid-forming devices, comprising the following steps: S1, for the power system to be analyzed, establish a load running system topology and a double-end power supply system topology, respectively derive system power flow equations for the load running system topology and the double-end power supply system topology, and obtain system steady-state operating points by solving the system power flow equations; S2, based on the system steady-state operating points obtained in step S1, establish a converter control model of the grid-forming device; for the grid-forming converter using direct voltage control in the converter control model, set current criterion, phase angle criterion and voltage criterion, and construct control logic for current limiting triggering and exiting, wherein the steady-state phase angle value in the phase angle criterion is determined by the system steady-state operating points obtained in step S1; S3, based on the two typical system topologies established in step S1, simulate the scene of system short-circuit fault and perform fault analysis, derive an analytical expression of short-circuit current through fault analysis; combine the converter control model established in step S2, substitute the output current parameters of the grid-forming device under fault into the analytical expression, and derive the relationship between the output current of the grid-forming device under fault and the total short-circuit current of the system; S4, based on the relationship between the output current of the grid-forming device and the total short-circuit current of the system derived in step S3, adopt a control strategy based on adaptive saturated current angle to dynamically adjust the phase of the output current of the grid-forming device under current limiting mode.

[0009] Preferably, in step S1, the system topology with load is equivalent to a three-node system, the lines are represented by admittance, the node corresponding to the grid-forming device is a PV node, the node corresponding to the upper-level power supply is a slack node, and the node corresponding to the load is a PQ node; in the topology of the double-ended power supply system, the node corresponding to the newly added power supply is a node, whose phase angle is directly given and remains unchanged under fault.

[0010] Preferably, in step S1, the system steady-state operating point is obtained by solving the system power flow equation through the Newton method; or the operating parameters of the power system to be analyzed are measured through a phasor measurement device, and a power system dispatching instruction is received, and the state variable values of the system steady-state operating point are obtained according to the measured operating parameters or the dispatching instruction.

[0011] Preferably, in step S2, the converter control model adopts a grid-forming control strategy based on a power synchronization control loop; under the normal operating state corresponding to the system steady-state operating point obtained in step S1, the grid-forming converter operates in a constant voltage control mode, and the output voltage is a preset voltage reference value; when the current limiting trigger condition is met, the grid-forming converter switches to a current limiting control mode, and the output of the current loop is taken as the terminal voltage reference value, so that the converter output current is controlled at a preset current reference value.

[0012] Preferably, in step S2, the control logic generates the control signal in the following manner: The control signal of the current criterion is 1 when the converter output current is greater than a preset current limiting value, and 0 otherwise; The control signal of the voltage criterion is 1 when the grid-connected point voltage is lower than a preset critical value, and 0 otherwise; The control signal of the phase angle criterion is 1 when the difference between the output phase angle of the power synchronization control loop and the steady-state phase angle value obtained in step S1 exceeds a set range, and 0 otherwise; The current limiting trigger condition is that the three control signals are all 1, and the current limiting exit condition is that the three control signals are all 0.

[0013] Preferably, the preset current limiting value is configured according to the overcurrent tolerance capability of the grid-forming device, and the preset critical value is configured according to the power quality requirement of the power system to be analyzed.

[0014] Preferably, in step S3, when simulating the scenario of a short-circuit fault occurring in the system, the ground impedance value of the short-circuit point is set; for the system topology with load, the short-circuit current is obtained by simplifying the fault equivalent circuit; for the topology of the double-ended power supply system, the short-circuit current is obtained by the superposition theorem.

[0015] Preferably, in step S4, when dynamically adjusting the phase of the output current of the grid-forming device in the current-limiting mode, if the ground resistance of the short-circuit fault is very small, the direction of the output current of the grid-forming device is opposite to that of the short-circuit current provided by other nodes of the system; if the ground resistance is not 0, the value of the adaptive saturated current angle is determined under the constraint condition that the short-circuit current of the specific line does not exceed the rated breaking current of the circuit breaker.

[0016] Preferably, in the topology of the double-ended power supply system, the specific line is a target line for which the short-circuit current is to be suppressed, and the adjustment direction of the adaptive saturated current angle is determined according to the short-circuit current suppression requirement on the side of the target line.

[0017] In a second aspect, an embodiment of the present application provides a power system short-circuit current suppression system based on a grid-forming device, comprising: A construction module is configured to establish a load-operated system topology and a double-ended power supply system topology for a power system to be analyzed, derive system power flow equations for the load-operated system topology and the double-ended power supply system topology, and obtain a system steady-state operating point by solving the system power flow equations. A criterion module is configured to establish a converter control model of the grid-forming device based on the system steady-state operating point obtained by the construction module, set a current criterion, a phase angle criterion, and a voltage criterion for a grid-forming converter using direct voltage control in the converter control model, and construct control logic for triggering and exiting current limiting, wherein a steady-state phase angle value in the phase angle criterion is determined based on the system steady-state operating point obtained by the construction module. An analysis module is configured to simulate a short-circuit fault scenario and perform fault analysis based on the two typical system topologies established by the construction module, derive an analytical expression of the short-circuit current through the fault analysis, and derive a relationship between the output current of the grid-forming device and the total short-circuit current of the system under fault conditions of the grid-forming device by substituting output current parameters of the grid-forming device under fault conditions into the analytical expression in combination with the converter control model established by the criterion module. A current-limiting module is configured to dynamically adjust the phase of the output current of the grid-forming device in the current-limiting mode by using a control strategy based on an adaptive saturated current angle based on the relationship between the output current of the grid-forming device and the total short-circuit current of the system derived by the analysis module.

[0018] In a third aspect, a computer device comprises a memory, a processor, and a computer program stored in the memory and executable on the processor, and the processor implements the steps of the power system short-circuit current suppression method based on the grid-forming device when executing the computer program.

[0019] In a fourth aspect, an embodiment of the present application provides a computer-readable storage medium comprising a computer program, and the computer program implements the steps of the power system short-circuit current suppression method based on the grid-forming device when executed by a processor.

[0020] In a fifth aspect, a chip is provided, which includes a memory, a processor, and a computer program stored in the memory and capable of running on the processor, and the processor implements the steps of the method for inhibiting short-circuit current of power system based on network-forming equipment when the computer program is executed.

[0021] In a sixth aspect, an electronic device is provided, which includes a computer program, and the computer program implements the steps of the method for inhibiting short-circuit current of power system based on network-forming equipment when the electronic device executes the computer program.

[0022] Compared with the prior art, the present application has at least the following beneficial effects: A method for inhibiting short-circuit current of power system based on network-forming equipment, first establishes two typical system topologies of load and double-end power supply and solves the steady-state operating point to provide a benchmark condition for subsequent analysis; then establishes a converter control model based on the steady-state operating point, innovatively uses three criteria of current, phase angle and voltage to construct a current-limiting control logic; then derives an analytical expression of short-circuit current through fault analysis, establishes a quantitative relationship between the output current of the network-forming equipment and the total short-circuit current of the system; finally, based on the relationship, adopts an adaptive saturated current angle control strategy to dynamically adjust the output current phase to achieve inhibition. A complete technical system from steady-state analysis to dynamic control is established; the current-limiting control logic of the three criteria solves the problem that the traditional method cannot automatically exit the current-limiting mode after fault removal. The adaptive saturated current angle strategy can be dynamically adjusted according to the real-time state of the system, and has better adaptability than the fixed parameter control. The entire scheme fully utilizes the self-synchronization characteristics of the network-forming equipment and can achieve accurate current phase control during the fault period, thereby achieving optimal short-circuit current inhibition effect.

[0023] Further, by specifically defining the equivalent method of the system topology and the node type, a clear technical implementation path is provided for power flow calculation. This standardized node type division facilitates the application of mature power system calculation methods, improving calculation efficiency and accuracy. The setting of the node simplifies the analysis model of the double-end power supply system and lays a solid foundation for subsequent fault analysis.

[0024] Further, a variety of feasible steady-state operating point acquisition approaches are provided, enhancing the implementation flexibility of the technical solution. Newton method is a classic method for power system power flow calculation, which has the advantages of fast convergence speed and high calculation accuracy. At the same time, considering the alternative schemes such as PMU measurement and dispatching instructions in actual engineering, the patent protection range is more comprehensive, adapting to the needs of different application scenarios.

[0025] Furthermore, the PSL-based network control strategy fully utilizes the self-synchronization characteristics of network-based equipment, eliminating phase-locking issues under fault conditions and enabling zero-voltage operation. A clear operating mode switching mechanism ensures optimal equipment performance under both normal and fault conditions, guaranteeing voltage support during normal operation and equipment safety during faults.

[0026] Furthermore, the synergistic effect of the three criteria solves the technical problem of the inability to automatically exit the current-limiting mode due to a single current criterion. The current criterion ensures overcurrent protection of the equipment, the voltage criterion reflects the system fault state, and the phase angle criterion provides a basis for mode recovery after fault clearance. The logical AND determination method ensures that the current-limiting mode is only entered under actual fault conditions, improving system reliability.

[0027] Furthermore, by rationally configuring key parameters, an optimal balance between equipment protection and system performance can be achieved. Setting current-limiting values ​​based on equipment tolerance ensures the safe operation of power electronic equipment, while setting voltage thresholds based on power quality requirements guarantees the system's power supply quality. This parameter configuration method enhances the engineering practicality of the technical solution.

[0028] Furthermore, the most suitable analysis method is adopted for different topologies to ensure computational efficiency and accuracy. The equivalent circuit simplification method is suitable for rapid analysis of simple topologies, while the superposition theorem is suitable for accurate calculation of multi-source systems. This differentiated analysis method reflects the systematic and scientific nature of the technical solution.

[0029] Furthermore, targeted control strategies are adopted based on different fault conditions to improve the adaptability and effectiveness of control. The goal is to achieve optimal suppression during low-resistance faults, and to ensure the normal interruption of circuit breakers during non-zero resistance faults, reflecting both engineering practicality and safety considerations.

[0030] Furthermore, it enables precise current suppression for specific lines, meeting the personalized needs of different application scenarios. This targeted suppression capability is particularly suitable for mitigating excessive short-circuit currents on specific lines in complex power grid structures, and has significant engineering application value.

[0031] It is understood that the beneficial effects of the second to sixth aspects mentioned above can be found in the relevant descriptions in the first aspect mentioned above, and will not be repeated here.

[0032] In summary, this invention solves the key technical challenges in short-circuit current suppression of grid-connected equipment through multi-criteria current limiting control logic and adaptive saturation current angle strategy. It has the advantages of precise control, strong adaptability and high reliability, and provides an effective solution for short-circuit current management in power systems.

[0033] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0034] Figure 1 This is a schematic diagram of the method flow of the present invention; Figure 2 This is a system topology diagram under load conditions; Figure 3 System topology diagram for dual-ended power supply; Figure 4 The equivalent system topology diagram under power flow calculation; Figure 5 Here is the control block diagram for GFM; Figure 6 This is the short-circuit topology diagram under load conditions; Figure 7 Short-circuit topology diagram for dual-ended power supply; Figure 8 A vector diagram of a GFM converter in current-limiting mode; Figure 9 The following are simulation results of the system dynamics under fault conditions: (a) is the output voltage waveform of the network-type equipment, (b) is the short-circuit current waveform, and (c) is the output phase angle waveform of the power synchronization control loop. Figure 10 The simulation results of short-circuit current under different fault types under load are shown. Among them, (a) is the waveform of single-phase ground fault current of phase b under the traditional strategy, (b) is the waveform of single-phase ground fault current of phase b under the strategy of the present invention, (c) is the waveform of two-phase ground fault current of phases a and b under the traditional strategy, (d) is the waveform of two-phase ground fault current of phases a and b under the strategy of the present invention, (e) is the waveform of three-phase short-circuit current under the traditional strategy, and (f) is the waveform of three-phase short-circuit current under the strategy of the present invention. Figure 11 The following are simulation results of short-circuit current under different fault types in the case of dual-end power supply: (a) is the waveform of single-phase ground fault current of phase b under the traditional strategy, (b) is the waveform of single-phase ground fault current of phase b under the strategy of the present invention, (c) is the waveform of two-phase ground fault current of phases a and b under the traditional strategy, (d) is the waveform of two-phase ground fault current of phases a and b under the strategy of the present invention, (e) is the waveform of three-phase short-circuit current under the traditional strategy, and (f) is the waveform of three-phase short-circuit current under the strategy of the present invention. Figure 12 This is a schematic diagram of the system structure of the present invention; Figure 13 A schematic diagram of a computer device provided in an embodiment of the present invention; Figure 14 This is a block diagram of a chip provided according to an embodiment of the present invention.

[0035] Among them, 60. Computer equipment; 61. Processor; 62. Memory; 63. Computer program; 600. Electronic device; 610. Processing unit; 620. Storage unit; 6201. Random access memory unit; 6202. Cache memory unit; 6203. Read-only memory unit; 6204. Program / utility; 6205. Program module; 630. Bus; 640. Display unit; 650. Input / output interface; 660. Network adapter; 700. External device. Detailed Implementation

[0036] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0037] In the description of this invention, it should be understood that the terms "comprising" and "including" indicate the presence of the described features, integrals, steps, operations, elements and / or components, but do not exclude the presence or addition of one or more other features, integrals, steps, operations, elements, components and / or collections thereof.

[0038] It should also be understood that the terminology used in this specification is for the purpose of describing particular embodiments only and is not intended to limit the invention. As used in this specification and the appended claims, the singular forms “a,” “an,” and “the” are intended to include the plural forms unless the context clearly indicates otherwise.

[0039] It should also be further understood that the term "and / or" as used in this specification and the appended claims refers to any combination and all possible combinations of one or more of the associated listed items, and includes such combinations. For example, A and / or B can represent three cases: A alone, A and B simultaneously, and B alone. Additionally, the character " / " in this invention generally indicates that the preceding and following objects have an "or" relationship.

[0040] It should be understood that although terms such as first, second, third, etc., may be used in the embodiments of the present invention to describe the preset range, these preset ranges should not be limited to these terms. These terms are only used to distinguish the preset ranges from one another. For example, without departing from the scope of the embodiments of the present invention, the first preset range may also be referred to as the second preset range, and similarly, the second preset range may also be referred to as the first preset range.

[0041] Depending on the context, the word "if" as used here can be interpreted as "when," "when," "in response to determination," or "in response to detection." Similarly, depending on the context, the phrase "if determination" or "if detection (of the stated condition or event)" can be interpreted as "when determination," "in response to determination," "when detection (of the stated condition or event)," or "in response to detection (of the stated condition or event)."

[0042] The accompanying drawings illustrate various structural schematic diagrams according to embodiments disclosed in this invention. These drawings are not to scale, and some details have been enlarged for clarity, and some details may have been omitted. The shapes of the various regions and layers shown in the drawings, as well as their relative sizes and positional relationships, are merely exemplary and may deviate from reality due to manufacturing tolerances or technical limitations. Furthermore, those skilled in the art can design regions / layers with different shapes, sizes, and relative positions as needed.

[0043] This invention provides a method for suppressing short-circuit current in power systems based on grid-connected equipment. It establishes two typical system topologies: one operating under load and the other with dual-end power supply. The system power flow equations are derived, and the steady-state operating point is solved, providing a baseline operating condition for fault analysis. A converter control model is established. For grid-connected converters using direct voltage control, control logic is proposed to trigger and deactivate current limiting based on three criteria: current, phase angle, and voltage. An analytical expression for short-circuit current is derived through fault analysis, and the relationship between output current and total short-circuit current under grid-connected equipment faults is derived. A control strategy based on adaptive saturation current angle is proposed, which dynamically adjusts the phase of the output current of the grid-connected equipment under current-limiting mode to achieve maximum suppression of short-circuit current on specific lines. The method provided by this invention can effectively reduce the short-circuit current of the system using grid-connected equipment, solving the problem of excessive short-circuit current on some lines of the power grid and the inability of circuit breakers to open, thus ensuring the safe and stable operation of the power system.

[0044] Please see Figure 1 The present invention discloses a method for suppressing short-circuit current in a power system based on grid-connected equipment, comprising the following steps: S1. Establish two typical system topologies: one under load and the other with dual-end power supply. Derive the system power flow equations and solve for the steady-state operating point to provide a baseline operating condition for fault analysis.

[0045] This invention proposes a method for suppressing short-circuit current in a power grid by connecting grid-connected equipment. A typical system topology is as follows: Figure 2 As shown, this is a power supply system from an upstream power source to a load. The upstream line can be equivalent to a synchronous power source SG and a line with impedance. In the analysis, the equivalent synchronous machine phase angle was selected as the reference phase angle, and it was assumed that the equivalent power supply inertia was very large, and its phase angle remained essentially unchanged during the fault process. The grid-forming (GFM) equipment, through an impedance of... The line connects to the point of common connection (PCC) bus. The PCC is connected via a bus of size [missing information]. The line supplies power to the downstream load, which is equivalent to a constant impedance load, denoted as . .

[0046] Another typical system topology is Figure 3 The dual-end power supply system shown replaces the original load with a power source. Unlike... Figure 2 , Figure 3 The power supply in the system can provide short-circuit current in the event of a fault. The voltage amplitude and phase angle at the fault location are also assumed to remain unchanged in the analysis.

[0047] Under normal operation, grid-type converters require solving power flow equations to determine the steady-state operating point of the system. Figure 2 The system topology shown can be equivalent to Figure 3 The three-node system shown in the figure has its circuitry represented by admittance, where:

[0048] The power and port voltage of the GFM are controlled to reference values, therefore in power flow calculations This refers to PV nodes. Furthermore... For relaxed nodes, For nodes P and Q, the equations are as follows:

[0049] in , , , , , , For the loaded condition, supplementary equations are required.

[0050] In the case of dual-ended power supply, SG2 is considered as... The phase angle of the node is also directly given and is assumed to remain essentially unchanged under fault conditions. Supplementary equations

[0051] The final power flow equations can be solved using Newton's method to obtain the state variables. The steady-state value.

[0052] It should be emphasized that this is only one way to obtain the steady-state value of the system through calculation. In actual systems, the steady-state value of the system's operation mode and state variables may be obtained through various methods such as measurement by phasor measurement units (PMUs) and scheduling commands. All of these methods are within the scope of protection of this patent.

[0053] S2. Establish a converter control model. For grid-type converters using direct voltage control, propose control logic for current limiting triggering and exiting based on three criteria: current, phase angle, and voltage.

[0054] GFM converters employ grid-based control, outputting a constant port voltage during normal operation. Due to the weak overcurrent capability of power electronic equipment, they are typically equipped with overcurrent protection devices to switch the equipment to current source operation in case of a fault, preventing overcurrent damage. Consider a GFM converter using direct voltage control; its control block diagram is as follows... Figure 5 As shown.

[0055] The converter adopts a grid-based control strategy based on a power synchronization loop (PSL), with the output phase angle value expressed in the control equation as follows:

[0056] in, The phase angle at the converter output. For power synchronization control coefficients, and These represent the reference power and the actual power, respectively.

[0057] In the control system, the current control loop uses classic PI control. When the converter is operating normally, The current limiting unit is inactive, the current control loop is locked, and the converter operates in constant voltage control (CVC) mode, with the output voltage being a directly given reference value.

[0058] Usually given directly , . This is the amplitude of the reference voltage. When an overcurrent is detected in the converter, the current control loop in the control system engages, and the converter operates in current limiting control (CLC), reducing the output of the current loop. , As a reference value for the terminal voltage, the converter output current is controlled to the reference value:

[0059] in, and The value is given by the current saturation algorithm:

[0060] in, This is the current limiting value. It is the saturation current vector angle, which can be configured according to engineering requirements.

[0061] Since the converter entering the CLC mode behaves as a constant current source, if the overcurrent is determined by measuring the converter's output current, the converter itself will be unable to exit the CLC mode after the fault is cleared, thus remaining in CLC mode indefinitely. To address this, this invention proposes a novel switching strategy that adds phase angle and voltage criteria in addition to the current criterion. This ensures that the converter can effectively enter current-limiting mode at the moment of a fault, while smoothly exiting and resuming operation in CVC mode after the fault is cleared.

[0062] The switching logic for converter current limiting is determined by the following three control signals.

[0063]

[0064] in, This is the critical value of the grid connection point voltage. The phase angle value of the PSL output in steady state is given by the power flow calculation results in the previous section.

[0065] The final control signal is:

[0066] Under normal operating conditions, , The converter operates in CVC mode; under fault conditions, the port voltage drops below the critical value, and the current increases beyond the current limiting value. The converter enters CLC mode; after the fault is cleared, because the control is in CLC mode, therefore... The system determines whether to exit the test by detecting whether the phase angle and voltage are within the specified range. and When both are 1, The converter resumes operation in CVC mode.

[0067] S3. Derive the analytical expression of short-circuit current through fault analysis, and derive the relationship between output current and total short-circuit current under fault conditions of network-type equipment.

[0068] For operation under load, let's assume a point on the line... f A malfunction occurred, through a size of The impedance is grounded, and the line is divided into and Two segments, topology diagram as follows Figure 6 As shown. To ensure the circuit breakers on the line can disconnect normally, it is necessary to reduce... The value is not greater than the breaking current of the circuit breaker.

[0069] Because the GFM switches to current-limiting mode and operates as a current source under fault conditions, for the system, there are...

[0070] in

[0071] Typical grounding resistance The value is very small, therefore Furthermore, the reactance of transmission lines is usually much greater than their resistance, therefore there is also , This can then be further simplified to:

[0072] in, , The value has been determined. The value depends only on the location of the short-circuit point; therefore, the magnitude of the short-circuit current depends only on the short-circuit current injected during a converter fault. related.

[0073] For dual-ended power supply, the short-circuit topology is as follows: Figure 7 As shown.

[0074] Similarly, under fault conditions, the GFM switches to current-limiting mode and operates as a current source. Under short-circuit conditions, the short-circuit current at each point in the system can be obtained using the superposition theorem.

[0075]

[0076] in

[0077] When grounding resistance When the value is very small, the two formulas above can be simplified to:

[0078]

[0079] At this time, the short-circuit current on the right side of the short-circuit circuit... Uncontrollable; only the short-circuit current on the left side can be controlled. Note that they are the same, therefore the same control strategy can be used in both cases.

[0080] S4. A control strategy based on adaptive saturation current angle is proposed. By dynamically adjusting the phase of the output current of the grid-type equipment under current limiting mode, the short-circuit current on a specific line can be suppressed to the greatest extent.

[0081] Vector diagram of electrical quantities in GFM under current limiting is as follows Figure 8 As shown, therefore

[0082] Because power is difficult to deliver during a fault, therefore The PSL output power angle keeps increasing. If a traditional control strategy with a fixed saturation current vector angle is used, under fault conditions... As a variable, the fault current also changes continuously, and the effective value in the early stage of the fault may exceed the circuit breaker's capacity, making it unable to disconnect and threatening the safe operation of the power grid.

[0083] Therefore, a new rate limiting strategy is proposed, which differs from the fixed one. During a fault, the saturation current vector angle is adaptively adjusted to minimize the short-circuit current. When the short-circuit resistance is very small, this method is equivalent to solving the following problem:

[0084] generally The solution obtained at this time is This means and The directions are exactly opposite. Using this strategy, the fault current amplitude is minimized, as follows:

[0085] For cases where the grounding impedance is not zero, a similar method can be used to ensure that the short-circuit current component provided by the grid-type converter is in the opposite direction to the short-circuit current component provided by other nodes in the system. The calculated saturation current angle is then determined by the following formula.

[0086]

[0087] in, The value depends on the circuit topology. For example, for the case of S3 operating under load, it can be taken as:

[0088] For dual-ended power supply scenarios, it depends on which side's short-circuit current is being suppressed. For example, in cases where the grid on the SG2 side is stronger and the short-circuit current is larger.

[0089]

[0090] For more complex situations, a set of saturation current angle values ​​that meet the conditions can be found through the following optimization problem, ensuring that the short-circuit currents on both sides are within the circuit breaker's breaking current range.

[0091]

[0092] The objective function is not fixed; the goal is to find a solution that satisfies the constraints. This is the rated breaking current of the circuit breaker.

[0093] Please see Figure 12 In another embodiment of the present invention, a power system short-circuit current suppression system based on grid-connected equipment is provided. This system can be used to implement the above-mentioned power system short-circuit current suppression method based on grid-connected equipment. Specifically, the power system short-circuit current suppression system based on grid-connected equipment includes a construction module, a criterion module, an analysis module, and a current limiting module.

[0094] The construction module establishes a topology for the power system under load and a topology for a dual-end power supply system for the power system to be analyzed. It derives the power flow equations for the topology for the power system under load and the dual-end power supply system respectively, and obtains the steady-state operating point of the system by solving the power flow equations. The criterion module establishes a converter control model for grid-type equipment based on the steady-state operating point of the system obtained by the construction module. For grid-type converters that use direct voltage control in the converter control model, current criteria, phase angle criteria, and voltage criteria are set to construct control logic for current limiting triggering and exiting. The steady-state phase angle value in the phase angle criteria is determined by the steady-state operating point of the system obtained by the construction module. The analysis module, based on two typical system topologies established by the construction module, simulates the scenario of a short-circuit fault in the system and performs fault analysis. Through fault analysis, it derives the analytical expression of the short-circuit current. Combining the converter control model established by the criterion module, it substitutes the output current parameters under the fault of the grid-type equipment into the analytical expression and derives the relationship between the output current and the total short-circuit current of the system under the fault of the grid-type equipment. The current limiting module, based on the relationship between the output current of the network-type equipment and the total short-circuit current of the system derived from the analysis module, adopts a control strategy based on the adaptive saturation current angle. This control strategy dynamically adjusts the phase of the output current of the network-type equipment under the current limiting mode.

[0095] This invention provides a terminal device comprising a processor and a memory. The memory stores a computer program, which includes program instructions. The processor executes the program instructions stored in the computer storage medium. The processor may be a Central Processing Unit (CPU), or other general-purpose processors, graphics processing units (GPUs), tensor processing units (TPUs), digital signal processors (DSPs), application-specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. It is the computing and control core of the terminal, suitable for implementing one or more instructions, specifically suitable for loading and executing one or more instructions to achieve a corresponding method flow or corresponding function. The processor described in this embodiment can be used in the operation of a power system short-circuit current suppression method based on grid-type equipment, including: For the power system to be analyzed, a topology for a system operating under load and a topology for a two-terminal power supply system are established. The system power flow equations are derived for both topologies, and the steady-state operating point is obtained by solving these equations. Based on the obtained steady-state operating point, a converter control model for grid-connected equipment is established. For grid-connected converters using direct voltage control in the converter control model, current criteria, phase angle criteria, and voltage criteria are set, and control logic for current limiting triggering and termination is constructed. The steady-state phase angle value in the phase angle criteria is determined by the obtained steady-state operating point. Based on two established typical system topologies, a short-circuit fault scenario is simulated and fault analysis is performed. An analytical expression for the short-circuit current is derived through this analysis. Combining this with the established converter control model, the output current parameters under grid-type equipment fault conditions are substituted into the analytical expression to derive the relationship between the output current and the total short-circuit current of the system under grid-type equipment fault conditions. Based on this derived relationship, a control strategy based on adaptive saturation current angle is adopted to dynamically adjust the phase of the output current of the grid-type equipment under current-limiting mode.

[0096] Please see Figure 13The terminal device is a computer device. In this embodiment, the computer device 60 includes a processor 61, a memory 62, and a computer program 63 stored in the memory 62 and executable on the processor 61. When executed by the processor 61, the computer program 63 implements the power system short-circuit current suppression method based on grid-connected equipment in this embodiment. To avoid repetition, details are omitted here. Alternatively, when executed by the processor 61, the computer program 63 implements the functions of each model / unit in the power system short-circuit current suppression system based on grid-connected equipment in this embodiment. To avoid repetition, details are omitted here.

[0097] Computer device 60 can be a desktop computer, laptop, handheld computer, cloud server, or other computing device. Computer device 60 may include, but is not limited to, a processor 61 and a memory 62. Those skilled in the art will understand that... Figure 13 This is merely an example of computer device 60 and does not constitute a limitation on computer device 60. It may include more or fewer components than shown, or combine certain components, or different components. For example, computer device may also include input / output devices, network access devices, buses, etc.

[0098] The processor 61 may be a Central Processing Unit (CPU), or other general-purpose processors, graphics processing units (GPUs), tensor processing units (TPUs), digital signal processors (DSPs), application-specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. A general-purpose processor may be a microprocessor or any conventional processor.

[0099] The memory 62 can be an internal storage unit of the computer device 60, such as a hard disk or RAM of the computer device 60. The memory 62 can also be an external storage device of the computer device 60, such as a plug-in hard disk, smart media card (SMC), secure digital (SD) card, flash card, etc., provided on the computer device 60.

[0100] Furthermore, the memory 62 may include both internal storage units of the computer device 60 and external storage devices. The memory 62 is used to store computer programs and other programs and data required by the computer device. The memory 62 can also be used to temporarily store data that has been output or will be output.

[0101] Please see Figure 14 The terminal device is an electronic device 600, which is manifested in the form of a general-purpose computing device. The components of the electronic device may include, but are not limited to: at least one processing unit 610, at least one storage unit 620, a bus 630 connecting different platform components (including storage unit 620 and processing unit 610), a display unit 640, etc.

[0102] The storage unit stores program code, which can be executed by the processing unit 610 to perform the steps described in the method section of this specification according to various exemplary embodiments of the present invention. For example, the processing unit 610 can perform actions such as... Figure 1 The steps are shown in the figure.

[0103] Storage unit 620 may include a readable medium in the form of a volatile storage unit, such as random access memory (RAM) 6201 and / or cache memory 6202, and may further include a read-only memory (ROM) 6203.

[0104] Storage unit 620 may also include a program / utility 6204 having a set (at least one) program module 6205, such program module 6205 including but not limited to: operating system, one or more application programs, other program modules and program data, each or some combination of these examples may include an implementation of a network environment.

[0105] Bus 630 can represent one or more of several types of bus structures, including a memory cell bus or memory cell controller, a peripheral bus, a graphics acceleration port, a processing unit, or a local bus using any of the multiple bus structures.

[0106] Electronic device 600 can also communicate with one or more external devices 700 (e.g., keyboard, pointing device, Bluetooth device, etc.), and with one or more devices that enable a user to interact with electronic device 600, and / or with any device that enables electronic device 600 to communicate with one or more other computing devices (e.g., router, modem). This communication can be performed via input / output interface 650. Furthermore, electronic device 600 can also communicate with one or more networks (e.g., local area network, wide area network, and / or public network, such as the Internet) via network adapter 660. Network adapter 660 can communicate with other modules of electronic device 600 via bus 630. It should be understood that, although not shown in the figures, other hardware and / or software modules can be used in conjunction with electronic device 600, including but not limited to: microcode, device drivers, redundant processing units, external disk drive arrays, RAID systems, tape drives, and data backup storage platforms.

[0107] Example 4 This invention also provides a storage medium, specifically a computer-readable storage medium, which is a memory device in a terminal device for storing programs and data. It is understood that the computer-readable storage medium here can include both built-in storage media in the terminal device and extended storage media supported by the terminal device; it can be any tangible medium containing or storing a program that can be used by or in conjunction with an instruction execution system, apparatus, or device. The computer-readable storage medium provides storage space that stores the terminal's operating system. Furthermore, the storage space also stores one or more instructions suitable for loading and execution by a processor, which can be one or more computer programs (including program code). More specific examples of the computer-readable storage medium include: an electrical connection with one or more wires, a portable disk, a hard disk, random access memory, read-only memory, erasable programmable read-only memory, optical fiber, portable compact disk read-only memory, optical storage device, magnetic storage device, or any suitable combination thereof.

[0108] Computer-readable storage media also include data signals propagated in baseband or as part of a carrier wave, carrying readable program code. Such propagated data signals can take various forms, including but not limited to electromagnetic signals, optical signals, or any suitable combination thereof. A readable storage medium can also be any readable medium other than a readable storage medium that can send, propagate, or transmit a program for use by or in connection with an instruction execution system, apparatus, or device. The program code contained on the readable storage medium can be transmitted using any suitable medium, including but not limited to wireless, wired, optical fiber, radio frequency, etc., or any suitable combination thereof.

[0109] Program code for performing the operations of this invention can be written in any combination of one or more programming languages, including object-oriented programming languages ​​such as Java and C++, and conventional procedural programming languages ​​such as C or similar languages. The program code can execute entirely on the user's computing device, partially on the user's computing device, as a standalone software package, partially on the user's computing device and partially on a remote computing device, or entirely on a remote computing device or server. In cases involving remote computing devices, the remote computing device can be connected to the user's computing device via any type of network, including a local area network (LAN) or a wide area network (WAN), or it can be connected to an external computing device (e.g., via the Internet using an Internet service provider).

[0110] One or more instructions stored in a computer-readable storage medium can be loaded and executed by a processor to implement the corresponding steps of the power system short-circuit current suppression method based on grid-type equipment in the above embodiments; one or more instructions in the computer-readable storage medium are loaded and executed by the processor to perform the following steps: For the power system to be analyzed, a topology for a system operating under load and a topology for a two-terminal power supply system are established. The system power flow equations are derived for both topologies, and the steady-state operating point is obtained by solving these equations. Based on the obtained steady-state operating point, a converter control model for grid-connected equipment is established. For grid-connected converters using direct voltage control in the converter control model, current criteria, phase angle criteria, and voltage criteria are set, and control logic for current limiting triggering and termination is constructed. The steady-state phase angle value in the phase angle criteria is determined by the obtained steady-state operating point. Based on two established typical system topologies, a short-circuit fault scenario is simulated and fault analysis is performed. An analytical expression for the short-circuit current is derived through this analysis. Combining this with the established converter control model, the output current parameters under grid-type equipment fault conditions are substituted into the analytical expression to derive the relationship between the output current and the total short-circuit current of the system under grid-type equipment fault conditions. Based on this derived relationship, a control strategy based on adaptive saturation current angle is adopted to dynamically adjust the phase of the output current of the grid-type equipment under current-limiting mode.

[0111] The databases involved in the embodiments provided in this application may include at least one type of relational database and non-relational database. Non-relational databases may include, but are not limited to, blockchain-based distributed databases. The processors involved in the embodiments provided in this application may be general-purpose processors, central processing units, graphics processing units, digital signal processors, programmable logic devices, quantum computing-based data processing logic devices, etc., and are not limited to these.

[0112] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0113] The effectiveness of the proposed strategy was verified using PSCAD / EMTDC. The circuit topology and control strategy are consistent with those described above, and the main parameters of the simulation model are shown in Figure 1. To highlight the impact of the converter strategy on the short-circuit current, the current limit value was set to 2.0 pu.

[0114] Table 1. Main parameters of the simulation model

[0115] The simulation time is set to 1 second, at which point a three-phase-to-ground short circuit occurs at 1 / 5 of the downstream line, and the fault is cleared after 0.3 seconds. The short circuit point meets the following conditions. =0.1pu and =0.4pu, grounding resistance is The system dynamics under fault conditions are shown in the following figure: In the diagram, subscript 1 indicates the use of the traditional strategy, and subscript 2 indicates the use of the proposed short-circuit suppression strategy. In comparison, although the traditional strategy allows for faster system recovery after a fault, its short-circuit current is larger, such as... Figure 9 As shown in (b), the short-circuit current pulse value at the moment of the fault reaches 8.7 pu, and the steady-state value is 5.2 pu. When the proposed strategy is adopted, the short-circuit current pulse value can be reduced to 6.2 pu, ensuring the rapid and effective operation of the circuit breaker.

[0116] Furthermore, its effectiveness under single-phase and two-phase fault conditions was also verified, such as... Figure 10 As shown. Here, to ensure that the GFM enters current-limiting mode under asymmetrical faults, the trigger value for current limiting is reduced to 1.2 pu. By comparing the three-phase short-circuit current waveforms of the traditional current-limiting strategy (left column (a), (c), (e) sub-figures) with those of the proposed strategy (right column (b), (d), (f) sub-figures), the improvement effect can be clearly observed. Specifically, under the single-phase-to-ground short-circuit condition of phase b, as Figure 10 (a) and Figure 10 (b) Under the traditional strategy, the maximum peak-to-peak short-circuit current is 14.1 pu, and the maximum peak pulse current is 8.6 pu; while with the proposed strategy, the maximum peak-to-peak short-circuit current is reduced to 9.3 pu, and the maximum peak pulse current is reduced to 6.8 pu. Similarly, Figure 10 Figures (c) and (d) show the case of a two-phase ground fault between phases a and b. The proposed strategy can reduce the peak-to-peak value of the short-circuit current from 12.1 pu to 9.6 pu, while effectively suppressing the peak value of the pulse current. Figure 10 (e) Figure 10 (f) The case where both sub-diagrams represent a three-phase short circuit, and Figure 8 The analysis in the previous section corresponds to this, and will not be repeated here. These waveforms verify that the proposed strategy can not only effectively reduce the short-circuit current under three-phase short circuits, but also suppress the short-circuit current under asymmetrical faults.

[0117] The short-circuit current suppression effect under dual-ended power supply was also verified through electromagnetic transient simulation. The line parameters in the model are consistent with those in Table 1. The phase angle is given as .

[0118] Figure 11 This paper presents a comparison between the traditional strategy (left column sub-graphs (a), (c), and (e)) and the proposed strategy (right column sub-graphs (b), (d), and (f)) under dual-power supply conditions. Under the single-phase-to-ground short-circuit condition of phase b, as shown... Figure 11 (a) and (b), under the traditional strategy, the maximum peak-to-peak short-circuit current is 14.2 pu, and the maximum pulse current peak occurs in the second pulse cycle at 8.9 pu; while under the proposed strategy, the peak-to-peak short-circuit current drops to 7.6 pu, and the maximum pulse current peak, also occurring in the second pulse cycle, drops to 5.7 pu. Similarly, Figure 11 Figures (c) and (d) illustrate a two-phase-to-ground short circuit between phases a and b. The proposed strategy reduces the maximum peak-to-peak short-circuit current from 13.9 pu to 6.7 pu and the peak pulse current from 9.7 pu to 6.8 pu. Sub-figures (e) and (f) show a three-phase short circuit, where the peak pulse current is reduced from 9.4 pu to 6.2 pu. The comparison of experimental results clearly demonstrates the effectiveness of the proposed strategy, verifying its applicability to dual-terminal power supply systems.

[0119] The invention demonstrates significant technical effectiveness through simulation verification. Under load operation, the proposed strategy can reduce the three-phase short-circuit current pulse value from 8.7 pu in the traditional strategy to 6.2 pu; the steady-state value is effectively suppressed from 5.2 pu. During a single-phase ground fault, the maximum peak-to-peak value decreased from 14.1 pu to 9.3 pu, and the peak pulse current decreased from 8.6 pu to 6.8 pu. During a two-phase ground fault, the peak-to-peak value decreased from 12.1 pu to 9.6 pu. The effect was even more significant in a dual-ended power supply system, where the maximum peak-to-peak value decreased from 14.2 pu to 7.6 pu and the peak pulse current decreased from 8.9 pu to 5.7 pu during a single-phase ground fault; the maximum peak-to-peak value decreased from 13.9 pu to 6.7 pu and the peak pulse current decreased from 9.7 pu to 6.8 pu during a two-phase ground fault; and the peak pulse current decreased from 9.4 pu to 6.2 pu during a three-phase short circuit. These results indicate that the present invention can not only effectively reduce the three-phase short-circuit current but also has a good suppression effect on asymmetrical faults, significantly improving the circuit breaker's breaking success rate and ensuring the safe and stable operation of the power system. This method is highly adaptable and exhibits superior performance under different topologies and fault types, making it of significant engineering application value.

[0120] In summary, this invention provides a method and system for suppressing short-circuit current in power systems based on grid-connected equipment. It establishes system models under steady-state and fault conditions, analyzes the impact of the output current of the grid-connected equipment on the total short-circuit current of the system, proposes a switching strategy for the grid-connected equipment using direct voltage control, and presents a control scheme for the adaptive saturation current vector angle. This effectively improves the short-circuit current level in the system and achieves short-circuit current suppression, demonstrating significant effectiveness in electromagnetic transient simulation results.

[0121] Those skilled in the art will clearly understand that, for the sake of convenience and brevity, the above-described division of functional units and modules is merely an example. In practical applications, the above functions can be assigned to different functional units and modules as needed, that is, the internal structure of the device can be divided into different functional units or modules to complete all or part of the functions described above. The functional units and modules in the embodiments can be integrated into one processing unit, or each unit can exist physically separately, or two or more units can be integrated into one unit. The integrated unit can be implemented in hardware or as a software functional unit. Furthermore, the specific names of the functional units and modules are only for easy differentiation and are not intended to limit the scope of protection of this application. The specific working process of the units and modules in the above system can be referred to the corresponding process in the foregoing method embodiments, and will not be repeated here.

[0122] In the above embodiments, the descriptions of each embodiment have different focuses. For parts that are not described in detail or recorded in a certain embodiment, please refer to the relevant descriptions of other embodiments.

[0123] Those skilled in the art will recognize that the units and algorithm steps of the various examples described in conjunction with the embodiments disclosed in this invention can be implemented in electronic hardware, or a combination of computer software and electronic hardware. Whether these functions are implemented in hardware or software depends on the specific application and design constraints of the technical solution. Those skilled in the art can use different methods to implement the described functions for each specific application, but such implementations should not be considered beyond the scope of this invention.

[0124] In the embodiments provided by this invention, it should be understood that the disclosed devices / terminals and methods can be implemented in other ways. For example, the device / terminal embodiments described above are merely illustrative. For instance, the division of modules or units is only a logical functional division, and in actual implementation, there may be other division methods. For example, multiple units or components may be combined or integrated into another system, or some features may be ignored or not executed. Furthermore, the coupling or direct coupling or communication connection shown or discussed may be through some interfaces; the indirect coupling or communication connection between devices or units may be electrical, mechanical, or other forms.

[0125] The units described as separate components may or may not be physically separate. The components shown as units may or may not be physical units; that is, they may be located in one place or distributed across multiple network units. Some or all of the units can be selected to achieve the purpose of this embodiment according to actual needs.

[0126] Furthermore, the functional units in the various embodiments of the present invention can be integrated into one processing unit, or each unit can exist physically separately, or two or more units can be integrated into one unit. The integrated unit can be implemented in hardware or as a software functional unit.

[0127] If the integrated module / unit is implemented as a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, all or part of the processes in the methods of the above embodiments can also be implemented by a computer program instructing related hardware. The computer program can be stored in a computer-readable storage medium, and when executed by a processor, it can implement the steps of the various method embodiments described above. The computer program includes computer program code, which can be in the form of source code, object code, executable files, or certain intermediate forms. The computer-readable medium can include: any entity or device capable of carrying the computer program code, recording media, USB flash drives, portable hard drives, magnetic disks, optical disks, computer memory, read-only memory (ROM), random-access memory (RAM), electrical carrier signals, telecommunication signals, and software distribution media, etc. It should be noted that the content included in the computer-readable medium can be appropriately added or removed according to the requirements of legislation and patent practice in the jurisdiction. For example, in some jurisdictions, according to legislation and patent practice, computer-readable media do not include electrical carrier signals and telecommunication signals.

[0128] This application is described with reference to flowchart illustrations and / or block diagrams of methods, apparatus, and computer program products according to embodiments of this application. It will be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, special-purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, generate instructions for implementing the flowchart... Figure 1 One or more processes and / or boxes Figure 1 A device that provides the functions specified in one or more boxes.

[0129] These computer program instructions may also be stored in a computer-readable storage medium that can direct a computer or other programmable data processing device to function in a particular manner, such that the instructions stored in the computer-readable storage medium produce an article of manufacture including instruction means, which are implemented in a process Figure 1 One or more processes and / or boxes Figure 1 The function specified in one or more boxes.

[0130] These computer program instructions may also be loaded onto a computer or other programmable data processing equipment to cause a series of operational steps to be performed on the computer or other programmable equipment to produce a computer-implemented process, thereby providing instructions that execute on the computer or other programmable equipment for implementing the process. Figure 1 One or more processes and / or boxes Figure 1 The steps of the function specified in one or more boxes.

[0131] The above content is only for illustrating the technical concept of the present invention and should not be construed as limiting the scope of protection of the present invention. Any modifications made to the technical solution based on the technical concept proposed in this invention shall fall within the scope of protection of the claims of this invention.

Claims

1. A method for suppressing short-circuit current in a power system based on grid-connected equipment, characterized in that, Includes the following steps: S1. For the power system to be analyzed, establish the topology of the system operating under load and the topology of the dual-end power supply system. Derive the system power flow equations for the system operating under load and the dual-end power supply system topology respectively. The steady-state operating point of the system is obtained by solving the system power flow equations. S2. Based on the steady-state operating point of the system obtained in step S1, establish a converter control model for the grid-type equipment; for the grid-type converter using direct voltage control in the converter control model, set current criteria, phase angle criteria and voltage criteria, and construct control logic for current limiting triggering and exiting. The steady-state phase angle value in the phase angle criteria is determined by the steady-state operating point of the system obtained in step S1. S3. Based on the two typical system topologies established in step S1, simulate the scenario of a short-circuit fault in the system and perform fault analysis. Derive the analytical expression of the short-circuit current through the fault analysis. Combined with the converter control model established in step S2, substitute the output current parameters under the fault of the grid-type equipment into the analytical expression to derive the relationship between the output current and the total short-circuit current of the system under the fault of the grid-type equipment. S4. Based on the relationship between the output current of the network-type equipment and the total short-circuit current of the system derived in step S3, a control strategy based on the adaptive saturation current angle is adopted to dynamically adjust the phase of the output current of the network-type equipment under the current limiting mode.

2. The power system short-circuit current suppression method based on grid-type equipment according to claim 1, characterized in that, In step S1, the topology of the system operating under load is equivalent to a three-node system. Lines are represented by admittance, the nodes corresponding to network-type equipment are PV nodes, the nodes corresponding to the upstream power supply are slack nodes, and the nodes corresponding to the load are PQ nodes. In the dual-end power supply system topology, the nodes corresponding to the newly added power supply are... The node has a phase angle that is directly given and remains unchanged under fault conditions.

3. The power system short-circuit current suppression method based on grid-type equipment according to claim 1, characterized in that, In step S1, the steady-state operating point of the system is obtained by solving the power flow equations of the system using Newton's method; or the operating parameters of the power system to be analyzed are measured by a phasor measurement device, and the power system dispatch instructions are received. The state variable values ​​of the steady-state operating point of the system are obtained based on the measured operating parameters or dispatch instructions.

4. The power system short-circuit current suppression method based on grid-type equipment according to claim 1, characterized in that, In step S2, the converter control model adopts a grid-type control strategy based on the power synchronization control loop. Under the normal operating state corresponding to the steady-state operating point of the system obtained in step S1, the grid-type converter operates in constant voltage control mode, and the output voltage is the preset voltage reference value. When the current limiting trigger condition is met, the grid-type converter switches to current limiting control mode, and uses the output of the current loop as the terminal voltage reference value, so that the converter output current is controlled at the preset current reference value.

5. The power system short-circuit current suppression method based on grid-type equipment according to claim 1, characterized in that, In step S2, the control logic generates control signals in the following manner: The control signal for the current criterion is: 1 when the converter output current is greater than the preset current limit value, and 0 otherwise; The control signal for the voltage criterion is: 1 when the grid connection point voltage is lower than the preset threshold value, and 0 otherwise; The control signal for the phase angle criterion is: 1 when the difference between the output phase angle of the power synchronization control loop and the steady-state phase angle obtained in step S1 exceeds the set range, and 0 otherwise; The current limiting is triggered when all three control signals are 1, and the current limiting is deactivated when all three control signals are 0.

6. The power system short-circuit current suppression method based on grid-connected equipment according to claim 5, characterized in that, The preset current limit value is configured based on the overcurrent tolerance capability of the grid-type equipment, and the preset critical value is configured based on the power quality requirements of the power system to be analyzed.

7. The power system short-circuit current suppression method based on grid-type equipment according to claim 1, characterized in that, In step S3, when a short-circuit fault occurs in the simulated system, the grounding impedance value of the short-circuit point is set; for the topology of the system operating under load, the short-circuit current is obtained by simplifying the fault equivalent circuit; for the topology of the dual-power supply system, the short-circuit current is obtained by superposition theorem.

8. The power system short-circuit current suppression method based on grid-type equipment according to claim 1, characterized in that, In step S4, when dynamically adjusting the phase of the output current of the network-type equipment under the current limiting mode, if the grounding resistance of the short-circuit fault is very small, the output current of the network-type equipment is made to be opposite in direction to the short-circuit current provided by other nodes in the system; if the grounding resistance is not 0, the value of the adaptive saturation current angle is determined with the constraint that the short-circuit current of a specific line does not exceed the rated breaking current of the circuit breaker.

9. The power system short-circuit current suppression method based on grid-type equipment according to claim 1, characterized in that, In a dual-ended power supply system topology, a specific line is the target line for suppressing short-circuit current. The adjustment direction of the adaptive saturation current angle is determined based on the short-circuit current suppression requirements on the target line side.

10. A power system short-circuit current suppression system based on grid-connected equipment, characterized in that, include: The module constructs a topology for the power system under analysis, including a topology for a system operating under load and a topology for a system with two-terminal power supply. It then derives the power flow equations for both systems and derives the steady-state operating point of the system by solving the power flow equations. The criterion module establishes a converter control model for grid-type equipment based on the steady-state operating point of the system obtained by the construction module. For grid-type converters that use direct voltage control in the converter control model, current criteria, phase angle criteria, and voltage criteria are set to construct control logic for current limiting triggering and exiting. The steady-state phase angle value in the phase angle criteria is determined by the steady-state operating point of the system obtained by the construction module. The analysis module, based on two typical system topologies established by the construction module, simulates the scenario of a short-circuit fault in the system and performs fault analysis. Through fault analysis, it derives the analytical expression of the short-circuit current. Combining the converter control model established by the criterion module, it substitutes the output current parameters under the fault of the grid-type equipment into the analytical expression and derives the relationship between the output current and the total short-circuit current of the system under the fault of the grid-type equipment. The current limiting module, based on the relationship between the output current of the network-type equipment and the total short-circuit current of the system derived from the analysis module, adopts a control strategy based on the adaptive saturation current angle. This control strategy dynamically adjusts the phase of the output current of the network-type equipment under the current limiting mode.

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