A low-frequency load shedding device test method and system based on RTDS

Abstract

The application discloses a low-frequency load shedding device test method and system based on RTDS, and the method comprises the following steps: constructing a power distribution network simulation model containing mixed feeders in RTDS, and setting adjustable distributed power and adjustable load in parallel for each mixed feeder; setting a feeder attribute dynamic switching mechanism, converting the power flow direction between the load and the power characteristics by adjusting the power ratio; setting a frequency drop self-adaptive generation module, generating a continuous and smooth large power grid frequency drop curve by using a variable time constant integrator, and the integrator time constant is associated with the total output proportion of the distributed power; starting the frequency drop, triggering the feeder attribute switching when the difference between the large power grid frequency and the action setting value is less than the preset threshold; transmitting the voltage, current and frequency signals to the device to be tested through the switch and receiving the tripping signal to form a hardware-in-the-loop closed-loop test; and evaluating the direction discrimination dynamic response performance of the device according to whether tripping before and after switching and the action time difference. The test efficiency is high, the scene is real, and the precision is high.

Description

Technical Field

[0001] This invention belongs to the field of power system relay protection testing technology, and particularly relates to a testing method and system for low-frequency load shedding devices based on RTDS. Background Technology

[0002] With the large-scale integration of distributed generation into distribution networks, the characteristics of traditional distribution network feeders have undergone fundamental changes, with some feeders transforming from pure load-type to hybrid "load + power source" types. In the event of a frequency collapse in the power grid, traditional low-frequency load shedding devices directly disconnect feeders, failing to distinguish between their source and load attributes, potentially leading to erroneous disconnection of distributed generation and further deteriorating system stability. To address this, new low-frequency load shedding devices have incorporated power flow direction monitoring to identify feeder attributes and achieve precise load shedding. However, efficiently and realistically simulating scenarios with a high proportion of renewable energy integration to verify this function has become a new challenge for testing technologies.

[0003] Currently, the testing of low-frequency load shedding devices mainly relies on traditional relay protection testers. This testing method simulates fault conditions by manually setting fault parameters such as voltage, current, and frequency. It has the following significant shortcomings: Low testing efficiency: A single fixed-value test takes 1 to 2 hours, which is difficult to meet the testing needs of multiple scenarios and multiple devices; Weak scenario simulation capability: It is difficult to simulate the complex dynamic behavior of the power grid under a high proportion of new energy access, such as power flow reversal and power fluctuation during frequency collapse. It does not support synchronous testing of multiple devices: it cannot simulate the coordinated response of multiple devices under system disturbances, making it difficult to verify the coordination and selectivity of the devices; Poor frequency simulation accuracy: The frequency changes output by traditional testers are actually discrete step-like changes, rather than continuous inertial changes in the real physical world, which causes the frequency tracking algorithm of the device under test to produce differential oscillation errors.

[0004] Therefore, there is an urgent need to develop a testing method for low-frequency load shedding devices that can realistically simulate the dynamic behavior of complex power grids, support parallel testing of multiple devices, and have high-precision frequency simulation capabilities. Summary of the Invention

[0005] This invention provides a test method and system for low-frequency load shedding devices based on RTDS, aiming to solve the technical problems of existing test technologies, such as the inability to simulate dynamic switching of feeder attributes, low frequency simulation accuracy, and poor test efficiency.

[0006] In a first aspect, the present invention provides a test method for a low-frequency load shedding device based on RTDS, comprising: A distribution network simulation model is constructed in the RTDS simulation platform. The distribution network simulation model includes at least one hybrid feeder, and each hybrid feeder is equipped with an adjustable distributed power source and an adjustable load in parallel. In the power distribution network simulation model, a dynamic switching mechanism for feeder attributes is set up. This mechanism adjusts the power ratio between the output of distributed power sources and the load power in the hybrid feeder, so that the feeder power flow direction switches between load characteristics and power source characteristics. A frequency sag adaptive generation module is set in the distribution network simulation model. The frequency sag adaptive generation module uses a variable time constant integrator to generate a continuous and smooth large power grid frequency sag curve. The large power grid frequency is the fundamental frequency on the bus side in the distribution network simulation model. The time constant of the variable time constant integrator is related to the proportion of total output of distributed power sources in the distribution network simulation model. During the test, the frequency drop adaptive generation module is activated to make the grid frequency decrease according to the set rate of change. When the difference between the grid frequency and the low-frequency load shedding device action setpoint is less than the preset threshold, the feeder attribute dynamic switching mechanism is triggered, causing the power flow direction of the target feeder to reverse and the feeder attribute to switch from load characteristics to power supply characteristics. The voltage, current and frequency signals output in real time by the RTDS simulation platform are transmitted to at least one low-frequency load shedding device under test via a switch, and the trip signal returned by the low-frequency load shedding device under test is received at the same time, forming a hardware-in-the-loop closed-loop test. The dynamic response performance and action accuracy of the low-frequency load shedding device under test are evaluated based on whether the device issues a trip signal before and after the feeder attribute switching, and the time difference between the time of the trip signal issuance and the time of the frequency crossover action setting in the RTDS simulation platform.

[0007] Secondly, the present invention provides a low-frequency load shedding device testing system based on RTDS, comprising: The module is configured to build a distribution network simulation model in the RTDS simulation platform. The distribution network simulation model includes at least one hybrid feeder, and each hybrid feeder is equipped with an adjustable distributed power source and an adjustable load in parallel. The adjustment module is configured to set a dynamic switching mechanism for feeder attributes in the power distribution network simulation model. The dynamic switching mechanism for feeder attributes adjusts the power ratio between the output of distributed power sources and the load power in the hybrid feeder, so that the feeder power flow direction switches between load characteristics and power source characteristics. The generation module is configured to set a frequency drop adaptive generation module in the distribution network simulation model. The frequency drop adaptive generation module uses a variable time constant integrator to generate a continuous and smooth large power grid frequency drop curve. The large power grid frequency is the fundamental frequency on the bus side in the distribution network simulation model. The time constant of the variable time constant integrator is related to the proportion of total output of distributed power sources in the distribution network simulation model. The trigger module is configured to activate the frequency drop adaptive generation module during the test process, causing the main grid frequency to decrease according to a set rate of change. When the difference between the main grid frequency and the low frequency load shedding device action setpoint is less than a preset threshold, the feeder attribute dynamic switching mechanism is triggered, causing the power flow direction of the target feeder to reverse and the feeder attribute to switch from load characteristics to power supply characteristics. The test module is configured to transmit the voltage, current and frequency signals output in real time from the RTDS simulation platform to at least one low-frequency load shedding device under test via a switch, and at the same time receive the trip signal returned by the low-frequency load shedding device under test, forming a hardware-in-the-loop closed-loop test. The evaluation module is configured to evaluate the dynamic response performance and action accuracy of the low-frequency load shedding device under test based on whether the device issues a trip signal before and after the feeder attribute switching, and the time difference between the time of the trip signal issuance and the time of the frequency crossover action setting in the RTDS simulation platform.

[0008] Thirdly, an electronic device is provided, comprising: at least one processor, and a memory communicatively connected to the at least one processor, wherein the memory stores instructions executable by the at least one processor, the instructions being executed by the at least one processor to enable the at least one processor to perform the steps of the RTDS-based low-frequency load shedding device testing method according to any embodiment of the present invention.

[0009] Fourthly, the present invention also provides a computer-readable storage medium having a computer program stored thereon, wherein when the program instructions are executed by a processor, the processor performs the steps of the RTDS-based low-frequency load shedding device test method according to any embodiment of the present invention.

[0010] This application presents a test method and system for low-frequency load shedding devices based on RTDS. A source-load power adversarial model is constructed in RTDS. By setting a power ratio crossing script, the feeder power flow direction is triggered to switch from load characteristics to power supply characteristics within 200 milliseconds at the frequency drop critical point (approaching but not reaching the action setpoint). This mechanism achieves, for the first time, a quantitative test of whether a new type of low-frequency load shedding device with power flow direction discrimination function should switch. It can verify the correctness of the device's blocking logic and the response speed of the directional element during the dynamic change of feeder attributes. A variable time constant integrator is used to generate a continuous and smooth frequency drop curve, avoiding the stepped frequency output caused by D / A quantization in traditional testers. The integrator time constant is adaptively correlated with the total output ratio of distributed power sources. When the penetration rate of new energy increases, the time constant automatically decreases, which can realistically simulate the physical process of rapid frequency ramp-up under low-inertia power grids, thereby minimizing the differential oscillation error of the device's frequency tracking algorithm caused by test source noise. Attached Figure Description

[0011] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the following description of the embodiments will be briefly introduced. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0012] Figure 1 A flowchart illustrating a test method for a low-frequency load shedding device based on RTDS, as provided in an embodiment of the present invention; Figure 2 This is a structural block diagram of a low-frequency load shedding device testing system based on RTDS, provided in an embodiment of the present invention. Figure 3 This is a schematic diagram of the structure of an electronic device provided in an embodiment of the present invention. Detailed Implementation

[0013] 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 embodiments of the present invention, not all embodiments. 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.

[0014] Please see Figure 1 The diagram shows a flowchart of a low-frequency load shedding device test method based on RTDS according to this application.

[0015] like Figure 1As shown, the test method for low-frequency load shedding devices based on RTDS specifically includes the following steps: Step S101: Construct a distribution network simulation model in the RTDS simulation platform. The distribution network simulation model includes at least one hybrid feeder, and each hybrid feeder is equipped with an adjustable distributed power source and an adjustable load in parallel.

[0016] In this step, each hybrid feeder in the distribution network simulation model is connected to the bus via a circuit breaker and a current transformer. Each hybrid feeder contains a set of adjustable distributed power sources and a set of adjustable loads. The power distribution network simulation model also includes: a large power grid simulation power source connected to the bus via a circuit breaker; a voltage transformer for measuring the three-phase voltage of the bus; a switch control module for simulating manual tripping, manual closing, protection tripping, and protection closing operations; and an input / output module for outputting voltage, current, and switching signals generated by the RTDS simulation platform to the low-frequency load shedding device under test, and receiving action signals from the low-frequency load shedding device under test.

[0017] In one specific embodiment, a distribution network simulation model suitable for testing low-frequency load shedding devices is first built in RTDS (Real-Time Digital Simulator). The distribution network simulation model uses RTDS's GPC (General Purpose Processor Card) and PB5 (Processor Backplane) for real-time calculations, with the simulation step size set to 50 microseconds to ensure accurate simulation of power system transient processes.

[0018] The topology of the power distribution network simulation model is as follows: (a) Busbar Configuration The distribution network simulation model has two busbars: a 110kV busbar (main grid side) and a 10kV busbar (distribution network side). The 110kV busbar and the 10kV busbar are connected by a three-phase double-winding transformer with a capacity of 50MVA, a turns ratio of 110kV / 10kV, a Yd11 connection method, and a short-circuit impedance percentage of 10.5%.

[0019] (II) Large power grid simulation power source The large power grid simulation power supply (src0) is connected to the 110kV bus side, using the standard voltage source of RTDS, with a rated voltage of 110kV and a rated frequency of 50Hz. The voltage amplitude, frequency, and phase angle of this power supply can all be adjusted in real time through the RTDS runtime parameter adjustment interface. The large power grid simulation power supply is connected to the 110kV bus via a 110kV transmission line (line impedance parameters: positive sequence resistance 0.05Ω / km, positive sequence reactance 0.35Ω / km, line length 10km) and a circuit breaker. By controlling the opening and closing of BRK0, the grid connection and disconnection operations of the large power grid can be simulated.

[0020] (III) Hybrid feeder configuration The distribution network simulation model includes eight hybrid feeders (feeders 1 to 8), each connected to a 10kV bus. Each hybrid feeder is equipped with a set of adjustable distributed generation sources and a set of adjustable loads connected in parallel, as follows: Each feeder is connected to the 10kV busbar via a circuit breaker. The circuit breaker can be controlled to open and close by simulation software through logic control signals, or it can be tripped by receiving the open contact signal (trip command) from the low-frequency load shedding device under test.

[0021] Each feeder is equipped with a set of current transformers with a transformation ratio of 600A / 5A and an accuracy class of 0.2S, used to collect feeder current and output it to the low-frequency load shedding device under test.

[0022] Each feeder's distributed power source adopts the "adjustable power source" model of RTDS, capable of outputting active and reactive power in real time. The active power output adjustment range is 0–10MW, and the reactive power output adjustment range is -2–+2MVar. The distributed power source is controlled in PQ mode, with the active power setpoint P adjusted via the runtime interface. ref and reactive power setpoint Q ref .

[0023] Each feeder load uses RTDS's "adjustable parallel load" feature, with an active load adjustment range of 0–10MW and a reactive load adjustment range of 0–2MVar. The active power P of the load can be changed via the operating interface. set and reactive power Q set .

[0024] (iv) Voltage transformer configuration A three-phase voltage transformer with a transformation ratio of 10kV / 100V and an accuracy class of 0.2 is installed on the 10kV bus side to measure the three-phase voltage of the bus. The secondary output of the voltage transformer is converted into an analog signal by the analog output module of RTDS, which is used to supply the voltage sampling input terminal of the low-frequency load shedding device under test.

[0025] (v) Switch control module The switch control module is implemented in the RTDS model using custom logic control elements. This module includes the following functions: Manual tripping / closing button: The virtual button on the RTDS runtime interface can simulate the manual control of any circuit breaker by the operator.

[0026] Protection tripping / closing logic: Based on the tripping signal returned by the low-frequency load shedding device under test (received through the digital input module of RTDS), the corresponding feeder circuit breaker is automatically controlled to trip.

[0027] Timing control logic: used to implement a preset power ratio crossover script, automatically adjusting the output of distributed power sources and load power at specified times or frequencies.

[0028] The output signal of the switch control module is connected to the control terminal of each circuit breaker. The control level is 24V DC and the action time constant is less than 1 millisecond.

[0029] (vi) Input / output module The input / output module is implemented using RTDS's GTAO (analog output card) and GTDI (digital input card) hardware. Analog output: The three-phase voltage (stepped down by PT1 and amplified by power amplifier), three-phase current and mains frequency signal (calculated by frequency measurement module) of each hybrid feeder, a total of 3×8=24 analog signals, are output to the external power amplifier through the GTAO card. The amplified signals are used to drive the analog sampling port of the low-frequency load shedding device under test.

[0030] Digital inputs: The GTDI card receives 8 input signals from the low-frequency load shedding device under test, with each signal corresponding to one feeder. The trip signal is in the form of a passive contact, which is input to the RTDS after optocoupler isolation to control the tripping of the corresponding feeder circuit breaker.

[0031] Digital output: The GTDO card outputs 8 output signals to the low-frequency load shedding device under test to simulate the position status (closed / open) of the circuit breaker for the device to perform status judgment.

[0032] (vii) Model Validation After completing the model construction, a model verification test is conducted: Close the main power grid circuit breaker BRK0, set the main power grid frequency to 50.00Hz, and the 10kV bus voltage to the rated value of 10kV. Sequentially close each feeder circuit breaker, setting the distributed generation output of odd-numbered feeders (1, 3, 5, 7) to 0MW and the load power to 5MW; and the distributed generation output of even-numbered feeders (2, 4, 6, 8) to 5MW and the load power to 0MW. Read the measured values ​​of each current transformer and voltage transformer through the RTDS runtime monitoring interface, confirming that the measurement errors are all within ±0.5%. After the distribution network simulation model stabilizes, proceed to step S102.

[0033] Step S102: In the power distribution network simulation model, a dynamic switching mechanism for feeder attributes is set. The dynamic switching mechanism for feeder attributes adjusts the power ratio between the output of distributed power sources and the load power in the hybrid feeder, so that the feeder power flow direction switches between load characteristics and power source characteristics.

[0034] Step S103: In the distribution network simulation model, a frequency drop adaptive generation module is set up. The frequency drop adaptive generation module uses a variable time constant integrator to generate a continuous and smooth large power grid frequency drop curve. The large power grid frequency is the fundamental frequency on the bus side in the distribution network simulation model. The time constant of the variable time constant integrator is related to the proportion of total output of distributed power sources in the distribution network simulation model.

[0035] In this step, the target value for the rate of change of frequency, the lower limit of frequency, and the integrator time constant T are set; The integrator time constant T is correlated with the proportion of total output of distributed power sources η, and the correlation is T = T0 × (1 - η) + T min ×η, where η is the proportion of the total output of distributed generation to the total load of the distribution network, with a value range of 0≤η≤1, and T0 is the reference time constant under pure load conditions. min It represents the minimum time constant under high new energy penetration rates; The variable time constant integrator continuously integrates the target value of the frequency change rate based on the integrator time constant T, and outputs the large power grid frequency value that decreases continuously and smoothly over time, thus obtaining the large power grid frequency drop curve.

[0036] Step S104: During the test process, the frequency drop adaptive generation module is activated to reduce the grid frequency according to the set rate of change. When the difference between the grid frequency and the low-frequency load shedding device action setpoint is less than the preset threshold, the feeder attribute dynamic switching mechanism is triggered to reverse the power flow direction of the target feeder and switch the feeder attribute from load characteristics to power supply characteristics.

[0037] In this step, the preset threshold is set to 0.2Hz to 0.5Hz; The initial power ratio of the hybrid feeder is set such that the output of the distributed power source is less than the load power, so that the feeder exhibits load characteristics and the power flow direction is from the bus to the feeder. When the difference between the main grid frequency and the initial action setting of the low-frequency load shedding device is less than the preset threshold, the distributed power output will ramp up from the first power value to the second power value within 200 milliseconds, while the load power will ramp down from the third power value to the fourth power value, so that the ratio of distributed power output to load power changes continuously from less than 1 to greater than 1, and the power flow direction of the feeder will switch from the bus to the feeder to the feeder to the bus.

[0038] Step S105: The voltage, current and frequency signals output in real time by the RTDS simulation platform are transmitted to at least one low-frequency load shedding device under test via a switch. At the same time, the tripping signal returned by the low-frequency load shedding device under test is received to form a hardware-in-the-loop closed-loop test.

[0039] In this step, the three-phase voltage, three-phase current and main grid frequency signal under the same fault scenario are synchronously output to the switch using the multi-channel analog output channel of RTDS. The switch transmits the received signals to N low-frequency load shedding devices under test, where N≤8; Each low-frequency load shedding device under test independently performs low-frequency load shedding logic judgment based on the received voltage, current and frequency signals, and returns the trip signal to the input / output module of the RTDS simulation platform.

[0040] Step S106: Based on whether the low-frequency load shedding device under test issues a trip signal before and after the feeder attribute switching, and the time difference between the time of the trip signal issuance and the time of the frequency crossover action setting in the RTDS simulation platform, evaluate the direction discrimination dynamic response performance and action accuracy of the low-frequency load shedding device under test.

[0041] In this step, if the feeder exhibits load characteristics before the switch and power characteristics after the switch, and the low-frequency load shedding device under test issues a trip signal before the switch but does not issue a trip signal after the switch, the direction discrimination function is determined to be correct; otherwise, it is determined to be incorrect. The RTDS simulation platform records the time T of the frequency crossover action setpoint in real time. RTDS And the time T when the target feeder power crosses zero. zero ; The time T of the displacement of the internal directional element of the low-frequency load shedding device under test is recorded. dir and the time T when the trip message is sent action ; Calculate the dynamic response time Δt for direction discrimination response =T dir -T zero And calculate the motion time error Δt action =T action -T RTDS ; If Δt response Less than the first preset threshold and Δt action If the value is less than the second preset threshold, the dynamic response performance and action accuracy of the direction discrimination device are deemed acceptable.

[0042] In summary, the method of this application constructs a distribution network simulation model in RTDS that includes hybrid feeders, with each hybrid feeder connected in parallel with adjustable distributed generation and adjustable loads; it sets up a dynamic switching mechanism for feeder attributes, adjusting the power ratio to switch the power flow direction between load and power characteristics; it sets up a frequency sag adaptive generation module, using a variable time constant integrator to generate a continuous and smooth large-scale power grid frequency sag curve, with the integrator time constant correlated with the total output ratio of distributed generation; it initiates frequency sag, triggering feeder attribute switching when the difference between the large-scale power grid frequency and the action setpoint is less than a preset threshold; it transmits voltage, current, and frequency signals to the device under test via a switch and receives trip signals, forming a hardware-in-the-loop closed-loop test; it evaluates the device's directional dynamic response performance based on whether it trips before and after the switching and the time difference of the action; the test is highly efficient, realistic, and accurate.

[0043] Please see Figure 2 The diagram shows a structural block diagram of a low-frequency load shedding device test system based on RTDS according to this application.

[0044] like Figure 2 As shown, the low-frequency load shedding device test system 200 includes a construction module 210, an adjustment module 220, a generation module 230, a trigger module 240, a test module 250, and an evaluation module 260.

[0045] The system includes a construction module 210 configured to construct a distribution network simulation model in an RTDS simulation platform. This model includes at least one hybrid feeder, with each feeder connected in parallel to an adjustable distributed generation source and an adjustable load. An adjustment module 220 is configured to set a dynamic switching mechanism for feeder attributes in the distribution network simulation model. This mechanism adjusts the power ratio between the output of the distributed generation source and the load power in the hybrid feeder, causing the feeder power flow direction to switch between load characteristics and power generation characteristics. A generation module 230 is configured to set an adaptive frequency sag generation module in the distribution network simulation model. This module uses a variable time constant integrator to generate a continuous and smooth large-scale grid frequency sag curve. The large-scale grid frequency is the fundamental frequency on the bus side of the distribution network simulation model, and the time constant of the variable time constant integrator is related to the proportion of the total output of the distributed generation source in the distribution network simulation model. Trigger module 240 is configured to, during the test process, activate the frequency drop adaptive generation module to cause the main grid frequency to decrease according to a set rate of change. When the difference between the main grid frequency and the low-frequency load shedding device's action setpoint is less than a preset threshold, trigger the feeder attribute dynamic switching mechanism to reverse the power flow direction of the target feeder and switch the feeder attribute from load characteristics to power supply characteristics. Test module 250 is configured to transmit the voltage, current, and frequency signals output in real time from the RTDS simulation platform to at least one low-frequency load shedding device under test via a switch, and simultaneously receive the trip signal returned by the low-frequency load shedding device under test, forming a hardware-in-the-loop closed-loop test. Evaluation module 260 is configured to evaluate the direction discrimination dynamic response performance and action accuracy of the low-frequency load shedding device under test based on whether the low-frequency load shedding device under test issues a trip signal before and after the feeder attribute switching, and the time difference between the time of the trip signal issuance and the time of the frequency crossover action setpoint in the RTDS simulation platform.

[0046] It should be understood that Figure 2 The modules and references described in the document Figure 1 The steps described in the text correspond to those in the method described above. Therefore, the operations, features, and corresponding technical effects described above also apply to the method described in the text. Figure 2 The various modules in the document will not be described in detail here.

[0047] In other embodiments, the present invention also provides a computer-readable storage medium having a computer program stored thereon, wherein when the program instructions are executed by a processor, the processor performs the RTDS-based low-frequency load shedding device test method in any of the above method embodiments. In one embodiment, the computer-readable storage medium of the present invention stores computer-executable instructions, which are configured as follows: A distribution network simulation model is constructed in the RTDS simulation platform. The distribution network simulation model includes at least one hybrid feeder, and each hybrid feeder is equipped with an adjustable distributed power source and an adjustable load in parallel. In the power distribution network simulation model, a dynamic switching mechanism for feeder attributes is set up. This mechanism adjusts the power ratio between the output of distributed power sources and the load power in the hybrid feeder, so that the feeder power flow direction switches between load characteristics and power source characteristics. A frequency sag adaptive generation module is set in the distribution network simulation model. The frequency sag adaptive generation module uses a variable time constant integrator to generate a continuous and smooth large power grid frequency sag curve. The large power grid frequency is the fundamental frequency on the bus side in the distribution network simulation model. The time constant of the variable time constant integrator is related to the proportion of total output of distributed power sources in the distribution network simulation model. During the test, the frequency drop adaptive generation module is activated to make the grid frequency decrease according to the set rate of change. When the difference between the grid frequency and the low-frequency load shedding device action setpoint is less than the preset threshold, the feeder attribute dynamic switching mechanism is triggered, causing the power flow direction of the target feeder to reverse and the feeder attribute to switch from load characteristics to power supply characteristics. The voltage, current and frequency signals output in real time by the RTDS simulation platform are transmitted to at least one low-frequency load shedding device under test via a switch, and the trip signal returned by the low-frequency load shedding device under test is received at the same time, forming a hardware-in-the-loop closed-loop test. The dynamic response performance and action accuracy of the low-frequency load shedding device under test are evaluated based on whether the device issues a trip signal before and after the feeder attribute switching, and the time difference between the time of the trip signal issuance and the time of the frequency crossover action setting in the RTDS simulation platform.

[0048] Computer-readable storage media may include a stored program area and a stored data area, wherein the stored program area may store an operating system and an application program required for at least one function; the stored data area may store data created based on the use of the RTDS-based low-frequency load shedding device test system, etc. Furthermore, the computer-readable storage medium may include high-speed random access memory, and may also include memory, such as at least one disk storage device, flash memory device, or other non-volatile solid-state storage device. In some embodiments, the computer-readable storage medium may optionally include memory remotely configured relative to a processor, which can be connected to the RTDS-based low-frequency load shedding device test system via a network. Examples of such networks include, but are not limited to, the Internet, corporate intranets, local area networks, mobile communication networks, and combinations thereof.

[0049] Figure 3 This is a schematic diagram of the structure of the electronic device provided in the embodiment of the present invention, such as... Figure 3As shown, the device includes a processor 310 and a memory 320. The electronic device may also include an input device 330 and an output device 340. The processor 310, memory 320, input device 330, and output device 340 can be connected via a bus or other means. Figure 3 Taking a bus connection as an example, the memory 320 is the computer-readable storage medium described above. The processor 310 executes various server functions and data processing by running non-volatile software programs, instructions, and modules stored in the memory 320, thereby implementing the RTDS-based low-frequency load shedding device testing method described in the above embodiment. The input device 330 can receive input digital or character information and generate key signal inputs related to user settings and function control of the RTDS-based low-frequency load shedding device testing system. The output device 340 may include a display screen or other display device.

[0050] The aforementioned electronic device can execute the method provided in the embodiments of the present invention, and has the corresponding functional modules and beneficial effects for executing the method. Technical details not described in detail in this embodiment can be found in the method provided in the embodiments of the present invention.

[0051] In one implementation, the above-described electronic device is used in an RTDS-based low-frequency load shedding device testing system as a client, comprising: at least one processor; and a memory communicatively connected to the at least one processor; wherein the memory stores instructions executable by the at least one processor, the instructions being executed by the at least one processor to enable the at least one processor to: A distribution network simulation model is constructed in the RTDS simulation platform. The distribution network simulation model includes at least one hybrid feeder, and each hybrid feeder is equipped with an adjustable distributed power source and an adjustable load in parallel. In the power distribution network simulation model, a dynamic switching mechanism for feeder attributes is set up. This mechanism adjusts the power ratio between the output of distributed power sources and the load power in the hybrid feeder, so that the feeder power flow direction switches between load characteristics and power source characteristics. A frequency sag adaptive generation module is set in the distribution network simulation model. The frequency sag adaptive generation module uses a variable time constant integrator to generate a continuous and smooth large power grid frequency sag curve. The large power grid frequency is the fundamental frequency on the bus side in the distribution network simulation model. The time constant of the variable time constant integrator is related to the proportion of total output of distributed power sources in the distribution network simulation model. During the test, the frequency drop adaptive generation module is activated to make the grid frequency decrease according to the set rate of change. When the difference between the grid frequency and the low-frequency load shedding device action setpoint is less than the preset threshold, the feeder attribute dynamic switching mechanism is triggered, causing the power flow direction of the target feeder to reverse and the feeder attribute to switch from load characteristics to power supply characteristics. The voltage, current and frequency signals output in real time by the RTDS simulation platform are transmitted to at least one low-frequency load shedding device under test via a switch, and the trip signal returned by the low-frequency load shedding device under test is received at the same time, forming a hardware-in-the-loop closed-loop test. The dynamic response performance and action accuracy of the low-frequency load shedding device under test are evaluated based on whether the device issues a trip signal before and after the feeder attribute switching, and the time difference between the time of the trip signal issuance and the time of the frequency crossover action setting in the RTDS simulation platform.

[0052] Through the above description of the embodiments, those skilled in the art can clearly understand that each embodiment can be implemented by means of software plus necessary general-purpose hardware platforms, and of course, it can also be implemented by hardware. Based on this understanding, the above technical solutions, in essence or the part that contributes to the prior art, can be embodied in the form of a software product. This computer software product can be stored in a computer-readable storage medium, such as ROM / RAM, magnetic disk, optical disk, etc., including several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute the methods of various embodiments or some parts of embodiments.

[0053] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A test method for low-frequency load shedding devices based on RTDS, characterized in that, include: A distribution network simulation model is constructed in the RTDS simulation platform. The distribution network simulation model includes at least one hybrid feeder, and each hybrid feeder is equipped with an adjustable distributed power source and an adjustable load in parallel. In the power distribution network simulation model, a dynamic switching mechanism for feeder attributes is set up. This mechanism adjusts the power ratio between the output of distributed power sources and the load power in the hybrid feeder, so that the feeder power flow direction switches between load characteristics and power source characteristics. A frequency sag adaptive generation module is set in the distribution network simulation model. The frequency sag adaptive generation module uses a variable time constant integrator to generate a continuous and smooth large power grid frequency sag curve. The large power grid frequency is the fundamental frequency on the bus side in the distribution network simulation model. The time constant of the variable time constant integrator is related to the proportion of total output of distributed power sources in the distribution network simulation model. During the test, the frequency drop adaptive generation module is activated to make the grid frequency decrease according to the set rate of change. When the difference between the grid frequency and the low-frequency load shedding device action setpoint is less than the preset threshold, the feeder attribute dynamic switching mechanism is triggered, causing the power flow direction of the target feeder to reverse and the feeder attribute to switch from load characteristics to power supply characteristics. The voltage, current and frequency signals output in real time by the RTDS simulation platform are transmitted to at least one low-frequency load shedding device under test via a switch, and the trip signal returned by the low-frequency load shedding device under test is received at the same time, forming a hardware-in-the-loop closed-loop test. The dynamic response performance and action accuracy of the low-frequency load shedding device under test are evaluated based on whether the device issues a trip signal before and after the feeder attribute switching, and the time difference between the time of the trip signal issuance and the time of the frequency crossover action setting in the RTDS simulation platform.

2. The test method for a low-frequency load shedding device based on RTDS according to claim 1, characterized in that, in, In the power distribution network simulation model, each hybrid feeder is connected to the bus via a circuit breaker and a current transformer. Each hybrid feeder contains a set of adjustable distributed power sources and a set of adjustable loads. The power distribution network simulation model also includes: The large power grid simulates a power source, which is connected to the busbar via a circuit breaker; Voltage transformers are used to measure the three-phase voltage of a busbar; The switch control module is used to simulate manual opening, manual closing, protection opening, and protection closing operations; The input / output module is used to output voltage, current and switching signals generated by the RTDS simulation platform to the low-frequency load shedding device under test, and to receive action signals from the low-frequency load shedding device under test.

3. The test method for a low-frequency load shedding device based on RTDS according to claim 1, characterized in that, The frequency drop adaptive generation module uses a variable time constant integrator to generate a continuous and smooth large power grid frequency drop curve, including: Set the target value for the rate of change of frequency, the lower limit of frequency, and the integrator time constant T; The integrator time constant T is correlated with the proportion of total output of distributed power sources η, and the correlation is T = T0 × (1 - η) + T min ×η, where η is the proportion of the total output of distributed generation to the total load of the distribution network, with a value range of 0≤η≤1, and T0 is the reference time constant under pure load conditions. min It represents the minimum time constant under high new energy penetration rates; The variable time constant integrator continuously integrates the target value of the frequency change rate based on the integrator time constant T, and outputs the large power grid frequency value that decreases continuously and smoothly over time, thus obtaining the large power grid frequency drop curve.

4. The test method for a low-frequency load shedding device based on RTDS according to claim 1, characterized in that, When the difference between the main grid frequency and the low-frequency load shedding device's operating setpoint is less than a preset threshold, a dynamic switching mechanism for feeder attributes is triggered, causing the power flow direction of the target feeder to reverse, and the feeder attribute to switch from load characteristics to power supply characteristics, including: Set the preset threshold to 0.2Hz to 0.5Hz; The initial power ratio of the hybrid feeder is set such that the output of the distributed power source is less than the load power, so that the feeder exhibits load characteristics and the power flow direction is from the bus to the feeder. When the difference between the main grid frequency and the initial action setting of the low-frequency load shedding device is less than the preset threshold, the distributed power output will ramp up from the first power value to the second power value within 200 milliseconds, while the load power will ramp down from the third power value to the fourth power value, so that the ratio of distributed power output to load power changes continuously from less than 1 to greater than 1, and the power flow direction of the feeder will switch from the bus to the feeder to the feeder to the bus.

5. The test method for a low-frequency load shedding device based on RTDS according to claim 2, characterized in that, The process of transmitting the voltage, current, and frequency signals output in real time from the RTDS simulation platform to at least one low-frequency load shedding device under test via a switch, and simultaneously receiving the tripping signal returned by the low-frequency load shedding device under test, forming a hardware-in-the-loop closed-loop test, includes: By utilizing the multi-channel analog output of RTDS, the three-phase voltage, three-phase current and main grid frequency signals under the same fault scenario are synchronously output to the switch. The switch transmits the received signals to N low-frequency load shedding devices under test, where N≤8; Each low-frequency load shedding device under test independently performs low-frequency load shedding logic judgment based on the received voltage, current and frequency signals, and returns the trip signal to the input / output module of the RTDS simulation platform.

6. The test method for a low-frequency load shedding device based on RTDS according to claim 1, characterized in that, The evaluation of the direction discrimination dynamic response performance and action accuracy of the low-frequency load shedding device under test, based on whether the device issues a trip signal before and after the feeder attribute switching, and the time difference between the trip signal issuance time and the frequency crossover action setpoint time in the RTDS simulation platform, includes: When the feeder exhibits load characteristics before the switch and power supply characteristics after the switch, if the low-frequency load shedding device under test issues a trip signal before the switch but does not issue a trip signal after the switch, the direction discrimination function is determined to be correct; otherwise, it is determined to be incorrect. The RTDS simulation platform records the time T of the frequency crossover action setpoint in real time. RTDS And the time T when the target feeder power crosses zero. zero ; The time T of the displacement of the internal directional element of the low-frequency load shedding device under test is recorded. dir and the time T when the trip message is sent action ; Calculate the dynamic response time Δt for direction discrimination response =T dir -T zero And calculate the motion time error Δt action =T action -T RTDS ; If Δt response Less than the first preset threshold and Δt action If the value is less than the second preset threshold, the dynamic response performance and action accuracy of the direction discrimination device are deemed acceptable.

7. A test system for low-frequency load shedding devices based on RTDS, characterized in that, include: The module is configured to build a distribution network simulation model in the RTDS simulation platform. The distribution network simulation model includes at least one hybrid feeder, and each hybrid feeder is equipped with an adjustable distributed power source and an adjustable load in parallel. The adjustment module is configured to set a dynamic switching mechanism for feeder attributes in the power distribution network simulation model. The dynamic switching mechanism for feeder attributes adjusts the power ratio between the output of distributed power sources and the load power in the hybrid feeder, so that the feeder power flow direction switches between load characteristics and power source characteristics. The generation module is configured to set a frequency drop adaptive generation module in the distribution network simulation model. The frequency drop adaptive generation module uses a variable time constant integrator to generate a continuous and smooth large power grid frequency drop curve. The large power grid frequency is the fundamental frequency on the bus side in the distribution network simulation model. The time constant of the variable time constant integrator is related to the proportion of total output of distributed power sources in the distribution network simulation model. The trigger module is configured to activate the frequency drop adaptive generation module during the test process, causing the main grid frequency to decrease according to a set rate of change. When the difference between the main grid frequency and the low frequency load shedding device action setpoint is less than a preset threshold, the feeder attribute dynamic switching mechanism is triggered, causing the power flow direction of the target feeder to reverse and the feeder attribute to switch from load characteristics to power supply characteristics. The test module is configured to transmit the voltage, current and frequency signals output in real time from the RTDS simulation platform to at least one low-frequency load shedding device under test via a switch, and at the same time receive the trip signal returned by the low-frequency load shedding device under test, forming a hardware-in-the-loop closed-loop test. The evaluation module is configured to evaluate the dynamic response performance and action accuracy of the low-frequency load shedding device under test based on whether the device issues a trip signal before and after the feeder attribute switching, and the time difference between the time of the trip signal issuance and the time of the frequency crossover action setting in the RTDS simulation platform.

8. An electronic device, characterized in that, include: At least one processor, and a memory communicatively connected to the at least one processor, wherein the memory stores instructions executable by the at least one processor to enable the at least one processor to perform the method according to any one of claims 1 to 6.

9. A computer-readable storage medium having a computer program stored thereon, characterized in that, When the program is executed by a processor, it implements the method described in any one of claims 1 to 6.

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