An anti-islanding test device

Abstract

The utility model relates to photovoltaic power generation grid-connected detection technical field especially, it is a kind of anti-islanding test equipment, the anti-islanding test equipment, comprising: output terminal group and input terminal group, input terminal group and output terminal group between being provided with with three corresponding phase channel, a phase is set in each phase channel and is adjusted unit to make corresponding input terminal and corresponding output terminal constitute variable electric connection;Common driving part, common driving part is used to under single control output linkage driving force;Linkage transmission mechanism, linkage transmission mechanism mechanically connects common driving part with each phase adjusted unit, and linkage transmission mechanism is equal program synchronous mechanism to limit the displacement ratio of each phase adjusted unit same.

Description

Technical Field

[0001] This utility model relates to the field of photovoltaic power generation grid connection testing technology, and in particular to an anti-islanding testing device. Background Technology

[0002] With the large-scale grid-connected application of photovoltaic power generation, photovoltaic inverters have become key equipment for grid connection. To ensure the safe operation of the grid, inverters must have anti-islanding protection functions, that is, they must be able to quickly identify and cut off the output when the grid is interrupted to avoid the formation of islanding effects. Existing anti-islanding testing methods mainly include manual power outage testing, grid simulator testing, and software simulation, which are used to verify the islanding identification performance of inverters.

[0003] However, the existing methods still have shortcomings. Manual power-off is cumbersome and poses safety risks, making it difficult to simulate various voltage disturbance scenarios; grid simulators are bulky, costly, and complex to use, making them unsuitable for field applications; while software simulation facilitates algorithm verification, it lacks verification of actual hardware operating conditions. Furthermore, some existing testing devices can only provide fixed disturbance signals, lacking voltage disturbance adjustability, and also have shortcomings in overvoltage and overcurrent protection, which can easily lead to inverter damage, resulting in low repeatability and standardization of test results.

[0004] Therefore, there is an urgent need for a new anti-islanding test device that can directly simulate the grid-connected conditions of photovoltaics and has adjustable disturbance and safety protection functions, thereby improving the authenticity, accuracy and standardization of anti-islanding testing and meeting the application needs of photovoltaic inverters in the research, development, production and certification process. Utility Model Content

[0005] This utility model aims to solve at least one of the technical problems existing in the prior art. To this end, one objective of this utility model is to provide an anti-islanding test device, comprising: an output terminal group and an input terminal group, wherein a phase channel corresponding to three phases is provided between the input terminal group and the output terminal group, and each phase channel is provided with a phase adjustment unit to enable a variable electrical connection between the corresponding input terminal and the corresponding output terminal; a common drive component, which outputs a linkage drive force under single control; and a linkage transmission mechanism, which mechanically connects the common drive component to each of the phase adjustment units, wherein the linkage transmission mechanism is an equal-range synchronization mechanism to ensure that the displacement ratio of each of the phase adjustment units is the same.

[0006] In one possible implementation, the phase adjustment unit is an adjustable autotransformer used to continuously adjust the output voltage of the phase channel.

[0007] In one possible implementation, the output voltage of the autotransformer is adjustable from 0 to 500V and is equipped with a voltage limiting protection mechanism to prevent the output voltage from exceeding the set upper limit.

[0008] In one possible implementation, the common drive is a rotary mechanical handle used to drive each of the phase adjustment units.

[0009] In one possible implementation, the linkage transmission mechanism includes: a transmission rod, which is throttle-connected to the handle; three paddles, which are screwed onto the transmission rod and respectively connected to the sliding adjustment contacts of three autotransformers; and a limiting rod, which is disposed in the movement path of the paddles to limit the rotation of the paddles, so that the paddles only undergo axial displacement when the transmission rod rotates.

[0010] In one possible implementation, the input terminal group includes terminal A, terminal B, terminal C, and terminal O, and the output terminal group includes terminal a, terminal b, terminal c, and terminal O. Terminal O is a neutral terminal shared by the input and output and is used as a voltage reference for each phase channel.

[0011] In one possible implementation, terminal A is electrically connected to terminal a via a phase channel, terminal B is electrically connected to terminal b via a phase channel, terminal C is electrically connected to terminal c via a phase channel, and terminal O is directly connected between the input terminal group and the output terminal group.

[0012] In one possible implementation, a voltage and current display module is also included for displaying the voltage and current values ​​in the output terminal group, respectively.

[0013] In one possible implementation, the voltage and current display module includes a red digital tube for displaying voltage and a green digital tube for displaying current.

[0014] In one possible implementation, three sets of overcurrent protection units are also included, which are respectively set between the A end, B end, C end and the corresponding phase channel. Each set of overcurrent protection units achieves current limiting protection by means of fuse breaking.

[0015] Additional aspects and advantages of this invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Based on the above technical solution, the anti-islanding test equipment provided by this utility model sets up a three-phase channel between the input terminal group and the output terminal group, and configures a phase adjustment unit in each phase channel. Simultaneously, it utilizes a common drive component and a synchronous linkage transmission mechanism to achieve synchronous variable adjustment of the three-phase voltage. Specifically, the operator only needs to adjust through a single common drive component to drive each phase adjustment unit to maintain the same displacement ratio, thereby ensuring the consistency and symmetry of the three-phase voltage during the change process.

[0016] The aforementioned structure can directly simulate the actual grid-connected operation of photovoltaic systems: when voltage disturbances are applied, the three-phase voltages can be adjusted proportionally and synchronously, thus forming test conditions highly consistent with actual grid disturbances. This solves the problem of asynchronous three-phase voltage regulation and difficulty in accurately simulating grid conditions in existing anti-islanding test devices. Therefore, this invention can improve the realism, accuracy, and standardization of anti-islanding testing, meeting the application needs of photovoltaic inverters in research and development, production, and certification processes. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in the embodiments of this utility model or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this utility model. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0018] Figure 1 A schematic diagram of the anti-islanding test equipment provided in this embodiment of the utility model; Figure 2 for Figure 1 A schematic diagram of the second perspective in the device shown; Figure 3 for Figure 1 A schematic diagram of the third-person perspective in the device shown; Figure 4 for Figure 1 A schematic diagram of the internal structure of the device shown.

[0019] Explanation of reference numerals in the attached figures: 1. Output terminal group; 2. Input terminal group; 3. Common drive component; 4. Linkage transmission mechanism; 5. Transmission rod; 6. Paddle; 7. Limit rod; 8. A end; 9. B end; 10. C end; 11. O end; 12. a end; 13. b end; 14. c end; 15. Voltage and current display module; 16. Overcurrent protection unit. Detailed Implementation

[0020] To make the objectives, technical solutions, and advantages of the embodiments of this utility model clearer, the technical solutions of the embodiments of this utility model will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this utility model, not all embodiments. Based on the embodiments of this utility model, all other embodiments obtained by those skilled in the art without creative effort are within the protection scope of this utility model.

[0021] In the description of this utility model, it should be understood that the terms "center," "longitudinal," "transverse," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," and "circumferential," etc., indicating the orientation or positional relationship shown in the accompanying drawings, are only for the convenience of describing this utility model and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this utility model. Furthermore, features defined with "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this utility model, unless otherwise stated, "a plurality of" means two or more.

[0022] In the description of this utility model, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "joining" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this utility model based on the specific circumstances.

[0023] The embodiments of this utility model are described in detail below. Examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain this utility model, and should not be construed as limiting this utility model.

[0024] Figure 1 A schematic diagram of the anti-islanding test equipment provided in this embodiment of the utility model; Figure 2 for Figure 1 A schematic diagram of the second perspective in the device shown; Figure 3 for Figure 1 A schematic diagram of the third-person perspective in the device shown; Figure 4 for Figure 1A schematic diagram of the internal structure of the device shown.

[0025] Please see Figure 1-4 In one possible implementation, it includes: an output terminal group 1 and an input terminal group 2, wherein a phase channel corresponding to three phases is provided between the input terminal group 2 and the output terminal group 1, and a phase adjustment unit is provided in each phase channel so that the corresponding input terminal and the corresponding output terminal form a variable electrical connection; it also includes a common drive 3, which is used to output a linkage drive force under a single operation; a linkage transmission mechanism 4 mechanically connects the common drive 3 to each phase adjustment unit, and the linkage transmission mechanism 4 is an equal-stroke synchronization mechanism to limit the displacement ratio of each phase adjustment unit to be the same.

[0026] In the above embodiment, three phase channels are arranged side-by-side within the chassis, corresponding to phases A, B, and C of the three-phase power grid. The phase adjustment unit within each phase channel changes the equivalent output of that channel via a sliding tap or equivalent adjustment component, creating a continuously variable electrical connection between the input and output terminals. The operator only needs to perform single-point control on the common drive unit 3, and the linkage transmission mechanism 4 synchronously distributes the driving force to the three sets of phase adjustment units. Due to the use of an equal-range synchronization mechanism, the three sets of adjustment units achieve a consistent stroke ratio under the same angular or linear displacement, thus ensuring that the three-phase output changes in phase amplitude and remains consistent between phases, avoiding test errors caused by inconsistencies in amplitude or phase. For applications using a three-phase four-wire system, the N terminal can be used as a voltage reference terminal. This reference terminal does not participate in the equal-range linkage and is only used to provide a unified measurement and loop reference.

[0027] The three-phase equal-range synchronous adjustment achieved by a single common drive component 3 can significantly reduce the risk of phase imbalance caused by separate adjustments, and improve the accuracy and repeatability of the testing process. Equal-range synchronization limits the phase deviation of mechanical coupling error, so that the three-phase outputs change with the same amplitude and distance, reducing false triggering or missed triggering. The unified mechanical linkage structure simplifies the human-machine interface and calibration steps, shortens preparation time and reduces operational intensity. The phase adjustment unit and linkage mechanism adopt a detachable connection, which facilitates maintenance and replacement, and improves the overall reliability and maintainability of the machine.

[0028] In one possible implementation, the phase adjustment unit is an adjustable autotransformer used to continuously adjust the output voltage of the corresponding phase channel; the three phase channels are respectively equipped with an A-phase autotransformer, a B-phase autotransformer and a C-phase autotransformer, and their rotating shafts (or sliding contact drive shafts) are connected to the common drive unit 3 via a linkage transmission mechanism 4, so that the three-phase adjustment is equal and synchronous.

[0029] In the above embodiment, the autotransformer for each phase channel adopts a single-winding structure, with the core preferably being a toroidal or EI laminated silicon steel sheet, and the insulation class not lower than F. One end of the winding is connected to the corresponding input phase terminal (phase A, phase B, phase C), and the reference terminal of the winding is connected to the N terminal as a voltage reference. The sliding contact serves as the variable output terminal (a, b, c) for that phase channel. This forms a phase-to-ground adjustable output with the N terminal as the reference, and the voltages of a-N, b-N, and c-N of output terminal group 1 continuously change across the entire range as the sliding contact position changes. The relationship between the mechanical travel of the autotransformer and the voltage regulation is calibrated through a dial scale, for example, linearly mapping the rotation angle 0° to θmax to an output of 0 to k·Uin (where k is determined by the tap structure and turn ratio of the autotransformer) to quickly set the target voltage. To ensure uniform stroke synchronization, the effective stroke, shaft end connection dimensions, and contact pressure of the three autotransformers are kept consistent. The linkage transmission mechanism 4 outputs the same angular displacement across the three shaft ends. During assembly, the three-phase zero position is corrected using stop pins and reference markings, ensuring consistent three-phase output ratios at any angle of the common drive component 3. The contact material can be a silver-graphite / copper alloy composite. The contact pressure is set within the required range for stable conduction via a spring or spring mechanism. The sliding path surface is refined to reduce contact resistance and noise. To suppress high-frequency ripple and transients introduced by sliding contact, small-capacity suppression capacitors (e.g., nF-level film capacitors with voltage margins set according to the highest possible output) can be connected in parallel between the a, b, and c output terminals and the N terminal, without significantly affecting the amplitude setting accuracy within the low-frequency bandwidth. Considering the requirements for three-phase consistency and repeatability in anti-islanding testing, the rated capacity, DC resistance, and leakage inductance parameters of the three autotransformers are selected to be as consistent as possible. After assembly, three-phase deviation calibration is performed under both no-load and load conditions, and the scale-voltage correspondence table is recorded for reference during testing. For three-phase three-wire applications, scenarios without a neutral (N) terminal can be modified to a series (or step-up / step-down) connection to achieve phase-to-phase adjustment: the two ends of the winding are connected to the phase line and the output phase terminal, and the sliding contacts are connected in parallel to the compensation branch to achieve amplitude adjustment, while ensuring that the three phases remain synchronously equal. To improve reliability, the autotransformer adopts a replaceable shaft end connection (spline or key connection) for easy maintenance and setting; a transparent protective cover and mechanical limiter are installed on the outside to limit contact overtravel and prevent accidental contact.

[0030] Please see Figure 1-4 In one possible implementation, the common drive component 3 is a rotary mechanical handle, which is used to output torque to the linkage transmission mechanism 4 under a single operation, thereby simultaneously driving the adjustment units of each phase A, phase B, and phase C to achieve equal-range synchronous adjustment.

[0031] In the above embodiment, the mechanical handle is fixed to the input shaft end and coaxially positioned with the main shaft of the linkage transmission mechanism 4 via a spline or key connection. The operator rotates the handle clockwise and counterclockwise, and the angular displacement of the input shaft is proportionally distributed to the drive shafts of the three phase adjustment units via the linkage transmission mechanism 4, ensuring that all three phases achieve the same effective stroke. An indicator needle and dial scale are provided at the handle end, with an angle range of, for example, 0° to θmax, corresponding to a linear (or quasi-linear) change in the three-phase output from lowest to highest. Mechanical stops are provided at the 0° and θmax positions to prevent overtravel. To improve operational stability, the handle incorporates a built-in friction damping or ratchet differential structure, allowing small angular displacements to be stably maintained. The handle length and grip diameter are selected according to ergonomic parameters to provide sufficient torque margin during full-load adjustment and to prevent sudden slippage. An insulating sleeve and protective cover are installed between the handle and the housing to ensure protection against electric shock and accidental contact in high-voltage environments.

[0032] This solution achieves three-phase linkage through a simple and intuitive rotary human-machine interface, enabling continuous adjustment without the need for a power supply and control system, thus reducing system complexity and potential failure points. The clear correspondence between rotary input and scale facilitates quick and repeated setting of target voltage and recording of test points. Mechanical stops and damping structures suppress over-adjustment and rebound, improving setting stability and test repeatability. The highly versatile handle structure facilitates assembly, maintenance, and replacement, ensuring overall machine reliability and maintainability.

[0033] Please see Figure 4 In one possible implementation, the linkage transmission mechanism 4 includes: a transmission rod 5 that is connected to a rotary mechanical handle; three paddles 6, which are respectively screwed onto the transmission rod 5 and connected to the sliding adjustment contacts of three autotransformers; and a limiting rod 7 disposed in the movement path of the paddles 6 to limit the rotation of the paddles 6 so that the paddles 6 only undergo axial displacement when the transmission rod 5 rotates.

[0034] In the above embodiment, the transmission rod 5 is a lead shaft with a uniform pitch trapezoidal thread along its entire length, and the pitch p is consistent. It undergoes surface hardening treatment to improve wear resistance. The three paddles 6 are threaded slider components, arranged at intervals along the axial direction of the transmission rod 5. The paddles 6 are connected to the sliding adjustment contacts of the corresponding autotransformer via connecting rods or flexible belts. A limiting rod 7 is arranged parallel to one side of the transmission rod 5. Guide grooves that mate with the limiting rod 7 are formed on the bodies of the three paddles 6. The guide grooves are either interference-fitted or clearance-fitted with the limiting rod 7, so that when the paddles 6 are driven by the transmission rod 5, their rotation is suppressed by the limiting rod 7, and they only make linear displacements along the direction of the transmission rod 5. When the transmission rod 5 rotates around its axis by an angle Δθ, each paddle 6 obtains the same axial displacement Δx = p·Δθ / 2π, thus the three sliding adjustment contacts move synchronously in an equal-distance manner. To ensure consistent start and end points for the three phases, during assembly, the three levers 6 are moved to the zero-position reference and positioned with stop pins. The effective lengths of the three connecting rods are then fixed to ensure that the start and end points of the three-phase contact stroke correspond to the same output voltage range. A universal or ball joint structure is installed at the junction of the lever 6 and the connecting rod to absorb minor non-parallelism of the autotransformer contact rails. A PTFE or bronze wear-resistant insert is added between the lever 6 and the guide groove to reduce friction and improve sliding stability. Bearing supports and mechanical stops are provided at both ends of the transmission rod 5 to prevent overtravel. A scale and reference line are provided at the end of the transmission rod 5 for easy reading of the lever 6 stroke percentage and alignment with the output voltage scale. To reduce transmission backlash, the lever 6 employs an elastic anti-loosening structure (such as a lateral pressure plate or spring washer). If necessary, preload is introduced between the threads of the transmission rod 5 and the internal threads of the lever 6 to ensure that the three-phase synchronization is not affected by load changes.

[0035] The above structure converts the angular displacement of the handle into the equal linear displacement of the three paddles 6 via the transmission rod 5, and uses the limit rod 7 to achieve anti-rotation constraint, avoiding additional torque on the contact side; the equal pitch and common lead ensure that the three-phase displacement ratio is strictly consistent, significantly improving the consistency and repeatability of three-phase synchronous adjustment; the guide and preload design reduces backlash and creep, and small angle adjustments can be stably maintained, which is conducive to obtaining higher voltage setting resolution; the three paddles 6 have the same force and kinematic relationship on the same transmission rod 5, and the manufacturing and calibration process is unified, which facilitates batch assembly and maintenance.

[0036] Please see Figure 1-3 In one possible implementation, input terminal group 2 includes terminal A 8, terminal B 9, terminal C 10, and terminal O 11, and output terminal group 1 includes terminal a 12, terminal b 13, terminal c 14, and terminal O 11, wherein terminal O 11 is the neutral terminal shared by input and output, and is used as the voltage reference for each phase channel. To be consistent with industry-standard markings, "O / N" can be marked on both the panel and the wiring diagram, and the instruction manual should clearly state that "terminal O 11 is equivalent to the neutral terminal N," and the two are considered to be the same electrical node.

[0037] In the above embodiment, the input terminal group 2 and the output terminal group 1 use the same type of shielded anti-electric shock terminals (such as shielded terminal blocks or insulated through-wall terminals). Terminals A 8, B 9, and C 10 are clearly distinguished from terminals a 12, b 13, and c 14 by phase color or letter (e.g., L1=brown, L2=black, L3=gray; O / N=blue). The terminal crimping torque and conductor cross-section are selected according to the rated current (e.g., 6-25 mm² copper conductor, depending on the autotransformer capacity). Terminal O 11 forms a "neutral busbar" inside the machine through a low-impedance copper busbar. This busbar is led to the input O terminal 11 and the output O terminal 11 in a star topology to avoid reference drift caused by series voltage drop. Independent test points and fuse-type maintenance terminals are set on the busbar for easy measurement and isolation. To prevent accidental connection of the protective ground PE to terminal O11, a clear mechanical isolation and color-coded distinction are provided between terminal O11 and the PE terminal. PE is only connected to the chassis protective ground and not electrically connected to terminal O11. Voltage measurements and voltage limiting sampling (if any) for each phase channel use terminal O11 as a common reference to ensure consistent amplitude determination for the three phases relative to the neutral wire. When the equipment is used in a three-phase three-wire system, terminal O11 on the output side can be covered and marked "unused," while the internal neutral busbar remains intact for compatibility with four-wire applications. To reduce loop noise, the shortest path wiring is used between the O11 busbar and each phase output terminal on the panel. If necessary, small-capacity high-voltage film capacitors (nF level) are connected in parallel at a-O, b-O, and c-O to suppress spikes. Anti-loosening pads and anti-twisting structures are installed near the terminals to improve long-term connection reliability. During the manufacturing and inspection phases, the neutral continuity test and voltage drop test confirm that the input O terminal 11 and the output O terminal 11 are at the same potential point, and that their DC resistance and voltage drop under rated current meet the design limits. The O / N terminals are identified with uniform symbols on the nameplate and wiring diagram, and wiring examples are provided to reduce the risk of incorrect wiring during use.

[0038] This implementation uses the O terminal 11 structure as a shared neutral reference for input and output, providing a unified and stable measurement benchmark, which is beneficial for the consistent evaluation and repeated setting of the three-phase relative neutral voltage; the star-shaped neutral busbar and short-path wiring reduce the measurement deviation caused by neutral circulating current and voltage drop, improving test accuracy; clear terminal markings and physical isolation of PE / O reduce the probability of accidental contact and incorrect wiring, enhancing operational safety and maintainability; the terminals on both the input and output sides have uniform specifications, facilitating quick field replacement and standardized wiring.

[0039] In one possible implementation, terminal A 8 is electrically connected to terminal a 12 via the corresponding A-phase channel, terminal B 9 is electrically connected to terminal b 13 via the corresponding B-phase channel, and terminal C 10 is electrically connected to terminal c 14 via the corresponding C-phase channel; terminal O 11 is directly connected between input terminal group 2 and output terminal group 1, and terminal O 11 is equivalent to the neutral line N terminal, which is uniformly marked as "O / N" on the panel.

[0040] In the above embodiment, terminals A (8), B (9), and C (10) are respectively connected to the fixed terminals of three phase adjustment units (preferably autotransformers). The sliding contacts of the three phase adjustment units are respectively led to terminals a (12), b (13), and c (14) to achieve continuous adjustable output relative to the O / N terminals. The conductors or copper busbars of each phase channel are selected according to the rated current and transitioned using crimp terminals or through-wall terminals. The terminal markings correspond one-to-one with the phase colors to prevent incorrect connection. The O / N terminal uses a low-impedance copper busbar as a "neutral busbar" to directly connect the input O / N terminal and the output O / N terminal at the same potential. No fuses, relays, or any active / passive adjustment devices are connected in series in between to ensure that the neutral reference is not affected by the adjustment branch. The two ends of the busbar are crimped with double bolts and spring washers to prevent loosening. The cross-section of the busbar is selected according to the highest operating current and allowable voltage drop (e.g., ≥10×3 mm copper busbar or equivalent cable). To reduce loop voltage drop and noise, the wiring of a-O, b-O, c-O and the corresponding measurement points adopts the shortest path. The O / N busbar is led out in a star topology to the common reference point of each sampling / display circuit. Before leaving the factory, the continuity and insulation tests of the three phase channels A→a, B→b, and C→c are performed, and the DC resistance and potential consistency of the O / N direct connection are verified to ensure the correctness of the phase correspondence and the direct connection of the neutral line.

[0041] This connection ensures a one-to-one correspondence between the three input phases and the three output phases, avoiding phase sequence confusion caused by cross-phase or cross-wiring. The direct connection between the O / N terminals and the outputs provides a stable and unified reference potential for all adjustable outputs, ensuring that the a-O, b-O, and c-O voltages are only affected by the adjustment of their respective phase channels and are not affected by the additional voltage drop on the neutral side, thus improving measurement consistency and adjustment repeatability. The clear phase-terminal correspondence facilitates on-site wiring according to the diagram and quick troubleshooting, reducing the risk of misoperation.

[0042] Please see Figure 1-4 In one possible implementation, the system further includes a voltage and current display module 15, used to display the voltage and current values ​​of each phase of the output terminal group 1. This display module uses terminals a, b, c, and O / N of the output terminal group 1 as measurement points. The voltage measurement channels are connected to a-O / N, b-O / N, and c-O / N respectively; the current measurement channels are connected in series in the loop from terminal a 12, terminal b 13, and terminal c 14 to the external load, or are fitted onto the corresponding phase conductors in a through-hole manner. The display module's panel has independent voltage and current reading windows, supporting cyclic display of phases A, B, and C, or parallel display of the three channels. The module is powered by an isolated low-voltage power supply. The creepage distance and clearance requirements between the power supply and the measured high voltage are met under a 500V range. The signal link uses optical / magnetic isolation to improve anti-interference and personal safety.

[0043] In this implementation, voltage measurement uses a high-resistance voltage divider sampling method for each phase (total resistance on the order of several MΩ, withstand voltage margin ≥630V) combined with RC anti-aliasing filtering before input to an isolation amplifier or isolation ADC to achieve true RMS measurement of 0–500V. Current measurement can use a low-resistance shunt with isolation amplification (four-terminal lead-out to reduce lead wire error), or a switchable Hall sensor / current transformer to achieve non-intrusive measurement. After multi-channel synchronous sampling, the three-phase signals are calculated by a microcontroller and displayed with decimal places. The sampling rate is, for example, ≥1 kS / s / phase, and the value update rate is approximately 2–4 times / second. A minimum / maximum hold and instantaneous value display mode switching is set. When the voltage / current reading exceeds a set threshold, the corresponding alarm indicator light is illuminated to indicate over-limit or wiring abnormality. The measurement reference is uniformly taken from the O / N terminals, and all voltage values ​​are phase voltages relative to the neutral wire. When the equipment is used in a three-phase three-wire system, the display logic automatically switches to phase-to-phase conversion or only indicates "neutral wire not connected" to avoid misreading. To ensure consistency, each phase and range is calibrated at two or more points and the calibration coefficients are recorded at the factory. The unit “V” and “A” of each window are silkscreened on the panel.

[0044] By configuring an independent voltage and current display module 15 on the output side, the output amplitude and load current of each phase channel can be obtained in real time and intuitively, which facilitates the operator to accurately stop and repeat the setting during the linkage adjustment process, and reduces the error caused by reading lag or mismatch of external instrument range; the unified measurement caliber with O / N terminal as reference improves the comparability of three-phase data; the isolated sampling and high-resistance voltage divider design meet the wide range of 0-500V while taking into account safety and anti-interference ability, improving the stability and reliability of test results; the integrated display reduces external instruments and wiring, improves deployment efficiency and reduces the probability of field errors.

[0045] Please see Figure 1-4In one possible implementation, in the voltage and current display module 15, the voltage reading is displayed using a red LED digital tube, and the current reading is displayed using a green LED digital tube. The two are independently arranged in the upper and lower or left and right areas of the panel, and are distinguished by silkscreened "V" and "A" and their corresponding units. Preferably, each window uses a 4-digit 7-segment digital tube (including a decimal point). The voltage channel displays the phase voltages a-O / N, b-O / N, and c-O / N in the format "XXX.X" or "XXX", and the current channel displays the corresponding phase loop current in the format "XX.XX" or "XXX.X". The specific decimal places are automatically switched by the microcontroller according to the range and resolution. The digital tube is either a common anode or common cathode structure, using constant current drive or a current-limiting resistor + multiplexing scanning scheme. To ensure readability, the refresh rate is not less than 100 Hz, and the brightness is adjustable from 10% to 100% via PWM, automatically increasing when the ambient light is strong. To enhance readability from a distance, the voltage window uses a red filter or a red full-character frame, while the current window uses a green filter or a green full-character frame. Physical separators are placed between the two windows to prevent visual crosstalk. To improve reliability, current limiting and overvoltage protection are added to the digital tube segment drive terminals, and decoupling capacitors and series resistors are arranged on the row and column lines to reduce EMI. When the entire unit loses power or the protection system activates, the display module flashes or goes out to indicate that it is currently unreadable. The panel is uniformly marked with A-phase, B-phase, and C-phase switching buttons or knobs, and the current channel is confirmed by the corresponding indicator light. In three-phase three-wire systems, the display interface displays "Neutral wire not connected" or automatically switches to a phase-to-phase voltage / current conversion display to avoid misreading.

[0046] Employing a color-coded scheme of "voltage—red, current—green," it can quickly match information in situations with strong light, at long distances, or with multiple instruments in parallel, reducing the probability of misreading and misoperation. The combination of red and green color separation and unit silkscreen further enhances the intuitiveness and consistency of readings. Multiplexing and constant current drive balance power consumption, brightness consistency, and lifespan, while automatic brightness adjustment improves readability and user experience in different environments. Separating ribs and electromagnetic compatibility design reduce crosstalk and flicker, which is conducive to long-term stable operation.

[0047] Please see Figure 1-3In one possible implementation, three sets of overcurrent protection units 16 are further included, respectively disposed between terminal A 8, terminal B 9, and terminal C 10 and their corresponding phase channels. Each set of overcurrent protection units 16 uses a fuse to achieve current limiting protection. Specifically, each set of overcurrent protection units 16 consists of a finger-type or tubular fuse and a fuse holder with anti-electric shock protection. The rated voltage is preferably not less than 690 Vac, the breaking capacity is not less than 100 kA, and the fusing characteristic is selected as gG / gL time-delay type to take into account both the inrush current of the autotransformer and the requirements for rapid short-circuit disconnection. The three fuses are connected in series on the input side of terminal A 8 → phase A channel, terminal B 9 → phase B channel, and terminal C 10 → phase C channel, respectively. The O / N terminals are not connected in series with fuses and are electrically isolated from the protective earth PE of the chassis. The fuse holder features a mechanical indicator and a micro-motion auxiliary contact. When any phase blows, the "Overcurrent / Fused" indicator illuminates on the panel, simultaneously interlocking the control circuit and tripping the input contactor K1 to prevent the equipment from operating in a single-phase state. To reduce contact temperature rise and the risk of loose wiring, the fuse holder uses spring-loaded terminals or double-screw crimping with anti-loosening washers. Three-phase fuses are arranged in the same row on the inside of the panel and clearly marked with phase colors (brown for phase A, black for phase B, and gray for phase C) and silkscreen printing. A transparent protective cover is installed in front to meet the requirements for live-line protection and visual inspection. The fuse is calibrated by selecting the rated current Ifuse based on the autotransformer's rated current Ir and the maximum operating current Imax of the tested circuit. Ifuse ≥ 1.25 × Imax, and its I²t current-limiting energy does not exceed the allowable thermal withstand capacity I²t_adm of the autotransformer and conductors. To ensure selectivity, time-current coordination is performed with upstream protection (such as upstream distribution fuses / circuit breakers) to ensure that the downstream operates before the upstream. Factory inspection includes tests on contact resistance, temperature rise, and disconnection indicator interlock function, and a spare fuse of the same specification and replacement instructions are attached to the inside of the door.

[0048] This solution uses a three-phase independent, front-end series-connected fuse-type current limiting unit to suppress fault current peaks and energized I²t energy. It provides rapid and reliable disconnection and isolation for faults such as autotransformer starting contact short circuits, external load short circuits, and incorrect wiring, while maintaining the three-phase equal-range synchronous regulating mechanism unaffected. The high breaking capacity of the fuses, combined with mechanical / electrical dual interlocking, reduces the risk of arc and thermal damage, improving equipment and personnel safety. The non-fusing arrangement at the O / N terminals maintains a stable neutral line reference, avoiding reading distortion caused by an open neutral line. The modular fuse holder facilitates quick on-site replacement, resulting in low maintenance costs and short downtime.

[0049] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "illustrative embodiment," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0050] Although embodiments of the present invention have been shown and described, those skilled in the art will understand that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the present invention, the scope of which is defined by the claims and their equivalents.

Claims

1. An anti-islanding testing device, characterized in that, include: The system includes an output terminal group and an input terminal group, with a corresponding phase channel between the input terminal group and the output terminal group. Each phase channel is equipped with a phase adjustment unit to enable a variable electrical connection between the corresponding input terminal and the corresponding output terminal. A common drive unit, which is used to output a linkage driving force under a single operation; A linkage transmission mechanism is provided, which mechanically connects the common drive component to each of the phase adjustment units. The linkage transmission mechanism is an equal-stroke synchronization mechanism to ensure that the displacement ratio of each of the phase adjustment units is the same.

2. The anti-islanding testing equipment according to claim 1, characterized in that, The phase adjustment unit is an adjustable autotransformer used to continuously adjust the output voltage of the phase channel.

3. The anti-islanding testing equipment according to claim 2, characterized in that, The output voltage of the autotransformer is adjustable from 0 to 500V and is equipped with a voltage limiting protection mechanism to prevent the output voltage from exceeding the set upper limit.

4. The anti-islanding testing equipment according to claim 1, characterized in that, The common drive component is a rotary mechanical handle used to drive each of the phase adjustment units.

5. The anti-islanding testing equipment according to claim 4, characterized in that, The linkage transmission mechanism includes: A transmission rod, which is throttle-connected to the handle; Three levers are screwed onto the transmission rod and are respectively connected to the sliding adjustment contacts of three autotransformers; A limiting rod is provided in the movement path of the paddle to limit the rotation of the paddle, so that the paddle only undergoes axial displacement when the transmission rod rotates.

6. The anti-islanding testing equipment according to claim 1, characterized in that, The input terminal group includes terminal A, terminal B, terminal C and terminal O, and the output terminal group includes terminal a, terminal b, terminal c and terminal O. Terminal O is the neutral terminal shared by input and output and is used as the voltage reference for each phase channel.

7. The anti-islanding testing device according to claim 6, characterized in that, Terminal A is electrically connected to terminal a via a phase channel, terminal B is electrically connected to terminal b via a phase channel, terminal C is electrically connected to terminal c via a phase channel, and terminal O is directly connected between the input terminal group and the output terminal group.

8. The anti-islanding testing equipment according to claim 1, characterized in that, It also includes a voltage and current display module for displaying the voltage and current values ​​in the output terminal group, respectively.

9. The anti-islanding testing equipment according to claim 8, characterized in that, The voltage and current display module includes a red digital tube for displaying voltage and a green digital tube for displaying current.

10. The anti-islanding testing equipment according to claim 6, characterized in that, It also includes three sets of overcurrent protection units, which are respectively set between the A end, the B end, the C end and the corresponding phase channel. Each set of overcurrent protection units achieves current limiting protection by means of fuse breaking.

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