DC current acquisition method, system and storage medium based on shape memory alloy sensing

Abstract

This application relates to the technical field of DC current transformers, and discloses a DC current acquisition method, system, and storage medium based on shape memory alloy sensing. The method includes: a spiral shape memory alloy sensing element is installed in a current conduction cavity, with its two ends connected to a current input terminal and a moving piston, respectively; another terminal is connected to the current conduction cavity; the current conduction cavity is connected to a measuring cylinder via a medium-isolated channel, and all three are filled with measuring liquid; a measuring piston is installed inside the measuring cylinder, and an external position sensor is mounted and connected to a processor. Position data is acquired at a preset period, and fluctuation and dispersion data are calculated within the measurement time. The data is processed according to the following range: if both fluctuation and dispersion are within the preset range, the average position data is calculated and matched with a DC current; if fluctuation exceeds the range and dispersion is low, an abnormal current amplitude is indicated; if fluctuation is normal but dispersion is high, an abnormal current change is indicated. This method realizes DC current acquisition and anomaly monitoring, improving measurement reliability and stability.

Description

Technical Field

[0001] This application relates to the technical field of DC current transformers, and in particular to a DC current acquisition method, system and storage medium based on shape memory alloy sensing. Background Technology

[0002] With the rapid development of new energy technologies, DC power transmission technology, with its advantages of low loss, long transmission distance, and flexible regulation, has been widely used in grid connection of new energy sources such as wind power and photovoltaics, as well as in cross-regional power transmission. To meet the demand for large-scale energy transmission, the voltage level of DC transmission systems is constantly increasing.

[0003] In the field of high-voltage DC current measurement, opto-current transformers and zero-flux current transformers are commonly used technical solutions. Opto-current transformers utilize the magneto-optical effect of optical materials to achieve current measurement, offering advantages such as good insulation performance and strong resistance to electromagnetic interference. Zero-flux current transformers, on the other hand, achieve high-precision measurement through magnetic compensation. Both types of transformers can ensure the accuracy and stability of measurements in high-voltage DC systems, making them the mainstream choice in the industry.

[0004] However, photocurrent transformers and zero-flux current transformers have significant cost disadvantages, with a single measurement device costing tens of thousands of yuan, greatly increasing the construction and operation and maintenance costs of DC transmission systems. Furthermore, due to the characteristics of DC high voltage, the traditional AC current electromagnetic induction transformer principle is not applicable. Summary of the Invention

[0005] In order to reduce the cost of detecting DC current, this application provides a DC current acquisition method, system and storage medium based on shape memory alloy sensing.

[0006] In a first aspect, this application provides a DC current acquisition method based on shape memory alloy sensing, employing the following technical solution:

[0007] A method for acquiring DC current based on shape memory alloy sensing includes the following steps:

[0008] A spiral shape memory alloy sensing element is provided on the current conduction cavity. One end of the shape memory alloy sensing element is provided with a current input terminal, and the other end of the shape memory alloy sensing element is fixedly connected to a movable piston in the current conduction cavity. The current conduction cavity is connected to another current input terminal.

[0009] The current conduction cavity is connected to the measuring cylinder through a medium isolation channel. The medium isolation channel is located on the side of the moving piston away from the shape memory alloy sensing element. The current conduction cavity, the medium isolation channel, and the measuring cylinder are filled with measuring liquid. A measuring piston is installed inside the measuring cylinder. A position sensor for acquiring the position of the measuring piston is installed outside the measuring cylinder. The position sensor is connected to a processor.

[0010] The position data of the position sensor is acquired according to a preset acquisition cycle;

[0011] The fluctuation and discrete data of the location data are calculated within a preset measurement time.

[0012] If the fluctuation data is within a preset amplitude range and the discrete data is within a preset discrete range, then the average value of the position data is calculated; and DC current data is matched from a preset database based on the average value.

[0013] If the fluctuation data is outside the preset amplitude range and the discrete data is within the preset low discrete range, then an abnormal DC current amplitude is indicated.

[0014] If the fluctuation data is within a preset amplitude range and the discrete data is outside a preset low discrete range, then an abnormal change in DC current is indicated.

[0015] By adopting the above technical solution, a spiral shape memory alloy sensing element is set in the current conduction cavity and connected to a moving piston. A measuring cylinder is connected through a medium-isolated channel. After filling with measuring liquid, a position sensor collects the position of the measuring piston. Position data is acquired at preset intervals, and fluctuation and discrete data are calculated to determine the current state. Normal current data is matched to the measured current; abnormal current data is indicated when the amplitude or change is abnormal. This method utilizes shape memory alloy deformation and hydraulic transmission to achieve DC current measurement, significantly reducing costs compared to traditional photocurrent and zero-flux current transformers. Furthermore, multi-dimensional data processing improves measurement reliability.

[0016] Optionally, the method further includes the following steps:

[0017] The line power is obtained based on several recent DC current data points.

[0018] Calculate the trend curve of the correspondence between the line power and the DC current data;

[0019] The length of the measurement time is adjusted according to the slope of the corresponding trend curve; the larger the slope, the longer the measurement time; the smaller the slope, the shorter the measurement time.

[0020] By adopting the above technical solution, the measurement time is dynamically adjusted by the slope of the power and current trend curve. The slope essentially reflects the line voltage (power = current × voltage, slope = power / current = voltage). When the voltage is high, it indicates that the line power changes drastically, such as a sudden change in the load of a high-voltage transmission system. In this case, extending the measurement time can accumulate more data points, smooth out the interference of occasional fluctuations on the current measurement, and avoid misjudgment of current due to sudden voltage changes. When the voltage is low, the line power tends to be stable, and shortening the measurement time can speed up the data update frequency, capture weak current changes in a timely manner, and balance measurement efficiency and accuracy.

[0021] Optionally, the method further includes the following steps:

[0022] The position sensor is a distance sensor installed inside the measuring cylinder, used to detect the distance between the measuring piston and the end of the measuring cylinder;

[0023] The measuring piston is a metal or magnetic component;

[0024] A filter coil is provided outside the measuring cylinder body. The filter coil is connected in series with the shape memory alloy sensing element and in parallel with the conductive cylinder.

[0025] The filter coil is energized to attract the measuring piston.

[0026] By adopting the above technical solution, the position sensor, as a distance sensor installed inside the measuring cylinder, is used to detect the distance between the metal or magnetic measuring piston and the end of the cylinder. At the same time, the filter coil outside the measuring cylinder is connected in series with the shape memory alloy sensing element and in parallel with the current conduction cavity. When energized, it can attract the measuring piston. This design directly and accurately positions the piston through the distance sensor, enhances the detection stability with the metal / magnetic piston, and forms mechanical damping by the electromagnetic attraction of the filter coil, suppressing current fluctuations and external interference, achieving dual anti-interference of electrical and mechanical aspects, and improving the accuracy of current measurement.

[0027] Optionally, the method further includes the following steps:

[0028] Next to the position sensor is a distance sensor installed inside the measuring cylinder, used to detect the distance between the measuring piston and the end of the measuring cylinder;

[0029] The measuring piston is a magnetic component;

[0030] A filter coil is provided outside the measuring cylinder, and a DC driver is provided on the filter coil. The DC driver is controlled and connected to the processor.

[0031] When the filter coil is energized, it is used to attract or repel the measuring piston;

[0032] The force exerted by the filter coil on the measuring piston against gravity is adjusted according to the positive correlation of the DC current data; the larger the DC current data, the greater the force exerted by the filter coil on the measuring piston against gravity; the smaller the DC current data, the smaller the force exerted by the filter coil on the measuring piston against gravity.

[0033] By adopting the above technical solution, the measuring piston is a magnetic component, a distance sensor inside the measuring cylinder detects its distance from the cylinder end, and a filter coil outside the measuring cylinder is controlled by a processor via a DC driver, which can attract or repel the measuring piston. Through a positive correlation adjustment mechanism, a small compensation force is provided at low currents to maintain system sensitivity; at high currents, the compensation force is automatically increased to counteract mechanical resistance.

[0034] Optionally, the method further includes the following steps:

[0035] The filter coil is controlled according to a preset delay time;

[0036] The duration of the delay time is adjusted according to the positive correlation of the fluctuation data; the larger the fluctuation data, the longer the delay time; the smaller the fluctuation data, the shorter the delay time.

[0037] By adopting the above technical solution, when the current fluctuates drastically, if the filter coil operates immediately, it may oscillate due to the lack of attenuation of the interference signal, like a piston shaking back and forth. Extending the delay time allows adjustment after the interference peak has passed, improving the accuracy of the measurement data. Dynamic adjustment of the delay time can reduce the number of invalid coil actions. When the data fluctuation is small, a short delay allows the coil to respond promptly, reducing the accumulation of errors within the data acquisition cycle; when the data fluctuation is large, a long delay avoids frequent coil actions, reducing the processor's computational load and power consumption. Especially in DC systems that operate continuously for long periods, this can effectively extend the equipment's lifespan.

[0038] Optionally, the method further includes the following steps:

[0039] A pipe diameter control module is provided on the medium isolation channel;

[0040] Based on a preset delay time, the minimum inner diameter of the medium isolation channel is delayed by the pipe diameter control module.

[0041] The size of the minimum inner diameter is adjusted according to the inverse correlation of the discrete data; the larger the discrete data, the smaller the size of the minimum inner diameter; the smaller the discrete data, the larger the size of the minimum inner diameter.

[0042] By employing the above technical solution, the hydraulic oil flow exhibits a certain lag in the media-isolated channel, especially with a large pipe diameter, where rapid current changes may cause piston response delays or fluctuations. By controlling the timing of pipe diameter adjustment through delay time and dynamically adjusting the pipe diameter based on discrete data, the dynamic response and stability of the hydraulic system can be balanced, reducing measurement lag errors. When the discrete data is small, increasing the pipe diameter ensures smooth hydraulic oil flow, allowing the measuring piston to more accurately follow the minute deformations of the shape memory alloy sensing element, improving the sensitivity of low-current measurements. Simultaneously, a larger pipe diameter reduces hydraulic oil flow resistance, lowers noise generated by pipe friction, and further improves the quality of the measurement signal. When the discrete data is large, reducing the pipe diameter creates a throttling effect, mechanically filtering the hydraulic oil flow and suppressing piston vibration caused by interference.

[0043] Optionally, the method further includes the following steps:

[0044] The control speed at which the pipe diameter control module adjusts the minimum inner diameter is obtained;

[0045] The control speed is adjusted according to the inverse correlation of the fluctuation data; the larger the fluctuation data, the smaller the control speed; the smaller the fluctuation data, the larger the control speed.

[0046] By adopting the above technical solution, the control speed of the minimum inner diameter adjustment module is obtained by acquiring the pipe diameter control module, and the adjustment is made inversely based on the fluctuation data. When the current fluctuation is large, the adjustment speed can be reduced to suppress the resonance and oscillation of the hydraulic system and avoid over-response to high-frequency interference. When the fluctuation is small, the adjustment speed can be increased to quickly respond to load changes, balance measurement accuracy and real-time performance, and reduce mechanical stress and energy consumption.

[0047] Optionally, the guide ring on the movable piston is a conductive metal component;

[0048] Alternatively, a conductive metal contact is fixedly connected to the guide ring on the movable piston, with one end of the conductive metal contact electrically connected to the movable piston and the other end electrically connected to the current conduction cavity;

[0049] Alternatively, an elastic conductive element may be provided on the movable piston or the shape memory alloy sensing element, with one end of the elastic conductive element fixedly connected to the movable piston and the other end of the elastic conductive element abutting against the inner wall of the current conduction cavity.

[0050] Alternatively, an elastic conductive element may be provided on the movable piston or the shape memory alloy sensing element, with the middle part of the elastic conductive element fixedly connected to the movable piston, one end of the elastic conductive element abutting against the shape memory alloy sensing element, and the other end of the elastic conductive element abutting against the inner wall of the current conduction cavity.

[0051] By adopting the above technical solutions, by setting conductive metal guide rings or conductive metal contacts on the moving piston, or setting elastic conductive parts on the moving piston / shape memory alloy sensing element, the current path can be optimized, the contact resistance can be reduced to improve measurement accuracy, parasitic capacitance and electromagnetic interference can be eliminated, electrochemical corrosion can be reduced and the system life can be extended through frictional self-cleaning, and stable conductivity can be maintained in high temperature environments, and dynamic current can be responded to quickly, thereby enhancing the system's adaptability and stability.

[0052] Secondly, this application provides a DC current acquisition system based on shape memory alloy sensing, which adopts the following technical solution:

[0053] A DC current acquisition system based on shape memory alloy sensing includes a processor, wherein the processor executes the steps of the DC current acquisition method based on shape memory alloy sensing as described in any one of the preceding claims.

[0054] Thirdly, this application provides a storage medium, which adopts the following technical solution:

[0055] A storage medium storing a program, which, when executed by a processor, implements the steps of the DC current acquisition method based on shape memory alloy sensing described above.

[0056] In summary, this application includes at least one of the following beneficial technical effects: This application sets a spiral shape memory alloy sensing element in the current conduction cavity and connects it to a moving piston. It communicates with the measuring cylinder through a medium-isolated channel. After filling with measuring liquid, a position sensor collects the position of the measuring piston, acquires position data according to a preset cycle, calculates fluctuation and discrete data to determine the current state, matches the current data when normal, and indicates abnormal amplitude or change when abnormal. It achieves DC current measurement based on the deformation characteristics of the shape memory alloy and the hydraulic transmission principle. Compared with traditional photocurrent transformers and zero-flux transformers, the cost is significantly reduced. Furthermore, the reliability of the measurement is further improved through multi-dimensional data processing. Simultaneously, by dynamically adjusting the measurement time, filter coil delay, and pipe diameter control strategies, combined with conductive path optimization and gravity compensation design, low-cost, high-precision, and interference-resistant DC current measurement is achieved. Attached Figure Description

[0057] Figure 1 This is a flowchart illustrating the steps of a DC current acquisition method based on shape memory alloy sensing.

[0058] Figure 2 This is a schematic diagram of a DC current acquisition device.

[0059] Figure 3 This is a schematic diagram of the structure of a current conduction cavity.

[0060] Figure 4This is a schematic diagram of a DC current acquisition device with an added filter coil and pipe diameter control module.

[0061] Reference numerals: 1. Current input terminal; 2. Main current transmission cable; 3. Shape memory alloy sensing element; 4. Current conduction cavity; 5. Moving piston; 6. Medium isolation channel; 7. Measuring cylinder; 8. Measuring piston; 9. Processor; 10. Position sensor; 11. Housing; 12. Cylinder component; 13. Guide ring; 14. Seal; 15. Piston rod; 16. Pipe diameter control module; 17. Filter coil. Detailed Implementation

[0062] The embodiments of this application are described in detail below, and examples of the embodiments are shown in the accompanying drawings.

[0063] In the description of this specification, the references to "certain embodiments," "one embodiment," "some embodiments," "illustrative embodiment," "example," "specific example," or "some examples" refer to specific features, structures, materials, or characteristics described in connection with the described embodiment or example, which are included in at least one embodiment or example of this application. 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.

[0064] This application discloses a DC current acquisition method based on shape memory alloy sensing, relying on a DC current acquisition device, and referring to... Figure 1 and Figure 2 It includes the following steps:

[0065] A spiral spring-shaped shape memory alloy sensing element 3, made of nickel-titanium alloy, is disposed on the current conduction cavity 4. One end of the shape memory alloy sensing element 3 is provided with a current input terminal 1 for connecting to the DC circuit under test; the other end of the shape memory alloy sensing element 3 is fixedly connected to a moving piston 5 inside the current conduction cavity 4, which is connected to another current input terminal 1, also for connecting to the DC circuit under test. When current passes through the shape memory alloy sensing element 3, its temperature rises due to the Joule heating effect, triggering a linear deformation caused by the shape memory effect. The deformation is positively correlated with the magnitude of the current, thereby pushing the moving piston 5 to move axially within the cylinder.

[0066] The current conduction cavity 4 is connected to the measuring cylinder 7 via a dielectric isolation channel 6, which is located on the side of the moving piston 5 away from the shape memory alloy sensing element 3. The dielectric isolation channel 6 is made of high-strength insulating materials such as polytetrafluoroethylene (PTFE). The current conduction cavity 4, the dielectric isolation channel 6, and the measuring cylinder 7 are filled with a measuring liquid, which is a high-purity liquid insulating oil, such as silicone oil, forming a closed hydraulic transmission system. (Refer to...) Figure 3 The current conduction cavity 4 includes a cylinder body 12, a moving piston 5, and a piston rod 15. The moving piston 5 is equipped with a seal 14 and a guide ring 13. A measuring piston 8 is housed within the measuring cylinder 7. The displacement of the moving piston 5 is transmitted to the measuring piston 8 within the measuring cylinder 7 via hydraulic oil, causing the measuring piston 8 to move synchronously. A high-precision position sensor 10, such as a laser displacement sensor or a Hall sensor, is mounted on the outer wall of the measuring cylinder 7 to acquire the position of the measuring piston 8. The position sensor 10 is connected to a processor 9, and the sensor signal is input to the processor 9, such as an ARM chip. The shape memory alloy sensing element 3 and the current conduction cavity 4 are installed inside the housing 11. A medium isolation channel 6 passes through the housing 11 and connects to the measuring cylinder 7 outside the housing 11.

[0067] The position data of the position sensor 10 is acquired according to the preset acquisition cycle; sampling is performed according to the preset acquisition cycle, the typical value of which is 10ms, and data processing is performed within the preset measurement time window; the preset measurement time window is such as 100ms-1s.

[0068] Within a preset measurement time, fluctuating and discrete data of the location data are calculated. Fluctuating data is the sum of the cumulative fluctuations of the location data, reflecting the overall stability of the signal. Discrete data is the average of the absolute values ​​of the differences between adjacent detection values, characterizing the rate of signal change.

[0069] When the fluctuation data is within the preset amplitude range (e.g., ±0.5mm) and the discrete data is within the preset discrete range (e.g., ≤0.1mm / ms), the processor 9 takes the average value of the position data and matches the corresponding DC current value from the preset database (which stores the position-current mapping relationship) by looking up a table.

[0070] If the fluctuation data is outside the preset amplitude range (i.e., fluctuation data > 0.5 mm or < -0.5 mm) and the discrete data is within the preset low discrete range (i.e., discrete data ≤ 0.1 mm / ms), and the rate of change is normal, then the DC current amplitude is abnormal.

[0071] If the fluctuation data is within the preset amplitude range, i.e., the fluctuation data ∈ [-0.5mm, 0.5mm], and the discrete data is outside the preset low discrete range, i.e., the discrete data > 0.1mm / ms, and the rate of change is abnormal, then an abnormal change in DC current is indicated.

[0072] A spiral shape memory alloy sensing element 3 is arranged in the current conduction cavity 4 and linked with the moving piston 5. A hydraulic transmission link is constructed through the medium isolation channel 6 to connect to the measuring cylinder 7. The measuring liquid is used as the displacement transmission medium, and the dynamic position of the measuring piston 8 is captured in real time by the position sensor 10. Position data is collected at a preset frequency. A three-dimensional current state discrimination method is constructed by calculating the fluctuation data and discrete data: when the data characteristics meet the normal threshold, the current is accurately converted by averaging and matching with the database; if the fluctuation data exceeds the limit but the rate of change is normal, an abnormal amplitude is warned; if the rate of change exceeds the limit but the fluctuation is stable, the risk of current sudden change is indicated. The method of this application relies on the thermal deformation characteristics of shape memory alloy and the hydraulic transmission principle to realize DC current measurement. The hardware cost is reduced compared with the traditional photocurrent / zero flux transformer, and the measurement reliability is improved through multi-dimensional data processing.

[0073] The method also includes the following steps:

[0074] Based on recent DC current data, the line power is obtained; the line power P and the DC current I satisfy P=U×I, where U is the line voltage.

[0075] Calculate the trend curve of the correspondence between line power and DC current data; in the time series, the slope k of the power-current trend curve is approximately equal to U, which serves as the equivalent characterization of real-time voltage.

[0076] The measurement time is adjusted based on the positive correlation between the slope of the trend curve and the slope; the larger the slope, the longer the measurement time; the smaller the slope, the shorter the measurement time. The mapping function between measurement time T and slope k is defined as: T = T0 + a × k; where a is the adjustment coefficient.

[0077] By dynamically adjusting the measurement time, the problems of data lag or noise amplification that occur when the voltage changes drastically with traditional fixed measurement cycles are avoided. Dynamically adjusting the measurement time can reduce the continuous working time of components such as position sensor 10 and processor 9. Especially in long-term DC transmission systems, this can extend the service life of equipment by reducing power consumption and further reduce operation and maintenance costs.

[0078] The method also includes the following steps:

[0079] A laser distance sensor is axially mounted on the inner wall of the measuring cylinder 7, directly aligned with the end face of the measuring piston 8, forming a non-contact displacement detection. The measuring piston 8 is either a metal or magnetic component. The sensor emits a laser beam, which is reflected by the piston surface and the receiver calculates the time of flight, converting it into the real-time distance between the piston and the end of the cylinder. The metal piston is made of 316L stainless steel, while the magnetic piston has an embedded neodymium iron boron permanent magnet, which improves the sensor signal strength compared to traditional non-metallic pistons.

[0080] Reference Figure 4A filter coil 17 is installed outside the measuring cylinder 7. The filter coil 17 is connected in series with the shape memory alloy sensing element 3 and in parallel with the conductive cylinder. The filter coil 17 is tightly wound around the outer wall of the measuring cylinder 7. The circuit connection is as follows: after being connected in series with the shape memory alloy sensing element 3, it is then connected in parallel with the current conduction cavity 4 to form a current-magnetic field linkage circuit. When the primary current passes through the shape memory alloy, part of the current is diverted to the filter coil 17, generating a magnetic field strength proportional to the current.

[0081] After the filter coil 17 is energized, it is used to attract the measuring piston 8. The attraction force of the measuring piston 8 is calculated using a mechanical model of electromagnetic damping.

[0082] A distance sensor inside the measuring cylinder 7 is used to detect the distance between the metal or magnetic measuring piston 8 and the end of the cylinder. Simultaneously, a filter coil 17 is installed outside the measuring cylinder 7, connected in series with the shape memory alloy sensing element 3 and in parallel with the current conduction cavity 4. When energized, this coil generates an attractive force on the measuring piston 8. The distance sensor enables direct and precise positioning of the piston, the metal / magnetic piston enhances detection stability, and the electromagnetic attraction of the filter coil 17 creates mechanical damping, effectively suppressing current fluctuations and external interference. This constructs a dual anti-interference system, combining electrical and mechanical methods, significantly improving the accuracy of current measurement.

[0083] The method also includes the following steps:

[0084] The measuring piston 8 inside the measuring cylinder 7 uses neodymium iron boron permanent magnet material, which is axially magnetized and parallel to the cylinder axis. A distance sensor is installed at the end of the cylinder to detect the distance between the piston end face and the sensor in real time. A filter coil 17 is wound around the outside of the measuring cylinder 7, powered by a PWM DC driver. The driver is controlled by the DA output channel of the processor 9, forming a closed-loop control link. When the filter coil 17 is energized, it attracts or repels the measuring piston 8. Forward current generates an attractive force, and reverse current generates a repulsive force. The DC driver outputs a polarity-adjustable current (±5A), and the coil generates a controllable magnetic field. The magnetic field strength is proportional to the square of the current, providing a continuously adjustable electromagnetic force of 0-10N.

[0085] The force exerted by the filter coil 17 on the measuring piston 8 against gravity is adjusted according to the positive correlation of the DC current data; the larger the DC current data, the greater the force exerted by the filter coil 17 on the measuring piston 8 against gravity; the smaller the DC current data, the smaller the force exerted by the filter coil 17 on the measuring piston 8 against gravity.

[0086] When the DC current increases from 10A to 5000A, the electromagnetic force (the force exerted by the filter coil 17 on the measuring piston 8 to overcome gravity) smoothly increases from 0.5N to 5N, which is proportional to the square of the current, ensuring the gravity compensation effect under high current.

[0087] The method also includes the following steps:

[0088] The filter coil 17 is controlled according to the preset delay time. When the current fluctuates drastically, if the filter coil 17 acts immediately, it may cause oscillation due to the lack of attenuation of the interference signal, such as the piston shaking back and forth. Extending the delay time allows the adjustment to be made after the interference peak has passed, thereby improving the accuracy of the measurement data.

[0089] The delay time is adjusted based on the positive correlation with the fluctuation data; the larger the fluctuation data, the longer the delay time; the smaller the fluctuation data, the shorter the delay time. The initial delay time is a preset fixed time, such as 5ms.

[0090] Small fluctuation scenario: Fluctuation data: F=0.03mm (normal measurement noise); Corresponding delay time: 5ms (basic value).

[0091] Medium fluctuation scenario: Fluctuation data: F = 0.2mm (e.g., current fluctuation caused by converter valve triggering); Corresponding delay time: Td is 18ms. Delay time Td = Initial delay time + b1 × ((F - F0) / (F1 - F0)) b2 In this embodiment, F0 is the minimum fluctuation threshold of 5ms; F1 is the maximum fluctuation threshold of 50ms; b1 and b2 are adjustment coefficients. F0=0.05mm corresponds to a signal-to-noise ratio (SNR) > 20dB; F1=0.5mm corresponds to an SNR < 5dB; b1=45ms, b2=1.8, enhancing the response sensitivity to large fluctuations; thus, based on F=0.2mm, Td can be calculated to be 18ms.

[0092] Large fluctuation scenario: Fluctuation data: F=0.6mm (such as oscillation after DC system fault recovery); Corresponding delay time: 50ms (upper limit).

[0093] By dynamically adjusting the delay time, the system reduces invalid actions during large fluctuations while maintaining a fast response during small fluctuations, achieving a dual optimization of measurement accuracy and energy efficiency.

[0094] The method also includes the following steps:

[0095] A pipe diameter control module 16 is provided on the medium isolation channel 6. The pipe diameter control module 16 includes a conical valve core or a ball valve provided on the medium isolation channel 6. The angle of the conical valve core or ball valve is controlled by a stepper motor, thereby changing the minimum inner diameter of the medium isolation channel 6 to ultimately regulate the flow rate of the insulated pipe.

[0096] Based on a preset delay time, the minimum inner diameter of the control medium isolation channel 6 is delayed by the pipe diameter control module 16. The preset delay time is T0 = 10ms. By using the preset delay time, the timing of pipe diameter adjustment is precisely controlled, avoiding system oscillations caused by adjusting too early or too late.

[0097] The minimum inner diameter is adjusted based on the inverse correlation of discrete data. Larger discrete data results in a smaller minimum inner diameter, and vice versa. Adjusting the minimum inner diameter based on the discrete data corresponds to adjusting the flow rate of the media isolation channel 6. When the data is large, the inner diameter is reduced; for example, when the discrete data is 80%, the cone valve core is adjusted to 6mm to throttle and suppress piston vibration. When the data is small, the inner diameter is increased; for example, when the discrete data is 5%, it is adjusted to 11.5mm to reduce flow resistance and improve the sensitivity of low-current measurements, balancing accuracy and stability.

[0098] The method also includes the following steps:

[0099] The control speed at which the pipe diameter control module 16 adjusts the minimum inner diameter is obtained;

[0100] The control speed is adjusted based on the inverse correlation of the fluctuation data; the larger the fluctuation data, the smaller the control speed; the smaller the fluctuation data, the larger the control speed.

[0101] Based on the inverse correlation of fluctuation data, the control speed is adjusted using a segmented, stepped control method.

[0102] During the stable phase, the fluctuation data is F≤0.1mm; the control speed is v1=12mm / s, achieving a rapid response.

[0103] During the transition phase, the fluctuation data is: 0.1mm < F ≤ 0.3mm; the control speed is: v2 = 6mm / s, balancing the response and stability.

[0104] During the disturbance phase, the fluctuation data is: F > 0.3 mm; the control speed is: v3 = 2 mm / s, with low speed suppressing oscillations.

[0105] Fluctuation data reflects the overall fluctuation intensity of the current signal, i.e., the sum of cumulative fluctuations. When the fluctuation data is large, such as when the system suffers a lightning strike or short circuit fault, it indicates the presence of high-frequency interference or drastic changes in the current. In this case, the pipe diameter adjustment speed should be reduced to avoid resonance or oscillation in the hydraulic system caused by rapid pipe diameter adjustment. For example, at the moment of a short circuit in a DC system, the current fluctuation data surges. The system slows down the pipe diameter adjustment speed to ensure a smooth transition of hydraulic oil flow, preventing piston overshoot due to sudden pipe diameter changes and ensuring the reliability of the measurement data.

[0106] When the fluctuation data is small, such as with stable load operation, it indicates that the current signal is stable. In this case, increasing the pipe diameter adjustment speed allows the system to respond quickly to load changes or minor faults. For example, in renewable energy grid-connected scenarios, photovoltaic output power changes slowly with light intensity, resulting in small fluctuation data. Rapidly adjusting the pipe diameter can promptly adjust the hydraulic damping, ensuring that the measuring piston 8 follows the shape memory alloy deformation, thereby improving the system's dynamic response speed.

[0107] The conductive connection between the movable piston 5 and the current conduction cavity 4 can be implemented in the following ways:

[0108] The first type: the guide ring 13 on the moving piston 5 is a conductive metal part; the conductive metal part is made of copper-based alloy, such as C17200 beryllium bronze, with a hardness ≥360HV and conductivity ≥50%IACS; surface treatment: electroless nickel-phosphorus alloy plating (thickness 5-8μm) to improve wear resistance and corrosion resistance.

[0109] The second type: A conductive metal contact is fixedly connected to the guide ring 13 on the moving piston 5. One end of the conductive metal contact is electrically connected to the moving piston 5, and the other end is electrically connected to the current conduction cavity 4. The conductive metal contact is made of Au90Ag10 alloy, and the surface treatment is: a 0.5μm thick electroless palladium plating layer as a diffusion barrier. Multiple conductive metal contacts can be provided and are evenly distributed along the circumference of the guide ring 13.

[0110] The third type: An elastic conductive element is provided on the moving piston 5 or the shape memory alloy sensing element 3. One end of the elastic conductive element is fixedly connected to the moving piston 5, and the other end of the elastic conductive element abuts against the inner wall of the current conduction cavity 4. The elastic conductive element is made of nickel-titanium shape memory alloy.

[0111] The fourth type: An elastic conductive element is provided on the moving piston 5 or the shape memory alloy sensing element 3. The elastic conductive element is made of nickel-titanium shape memory alloy. The middle part of the elastic conductive element is fixedly connected to the moving piston 5, one end of the elastic conductive element abuts against the shape memory alloy sensing element 3, and the other end of the elastic conductive element abuts against the inner wall of the current conduction cavity 4, forming a current shunt design.

[0112] By configuring a conductive metal guide ring 13 and contacts on the moving piston 5, or by adding an elastic conductive element between the moving piston 5 and the shape memory alloy sensing element 3, the current transmission path can be optimized.

[0113] This application also discloses a DC current acquisition system based on shape memory alloy sensing, including a processor, wherein the processor executes the steps of the DC current acquisition method based on shape memory alloy sensing as described in any of the above embodiments.

[0114] This application also discloses a storage medium storing a program, which, when executed by a processor, implements the steps of the DC current acquisition method based on shape memory alloy sensing described above.

[0115] Although embodiments of this application have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting this application. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of this application.

Claims

1. A method for acquiring DC current based on shape memory alloy sensing, characterized in that, Includes the following steps: A spiral shape memory alloy sensing element (3) is provided on the current conduction cavity (4). One end of the shape memory alloy sensing element (3) is provided with a current access terminal (1). The other end of the shape memory alloy sensing element (3) is fixedly connected to the moving piston (5) inside the current conduction cavity (4). The current conduction cavity (4) is connected to another current access terminal (1). The current conduction cavity (4) is connected to the measuring cylinder (7) through the medium isolation channel (6). The medium isolation channel (6) is located on the side of the moving piston (5) away from the shape memory alloy sensing element (3). The current conduction cavity (4), the medium isolation channel (6) and the measuring cylinder (7) are filled with measuring liquid. A measuring piston (8) is provided inside the measuring cylinder (7). A position sensor (10) for collecting the position of the measuring piston (8) is provided outside the measuring cylinder (7). The position sensor (10) is connected to a processor (9). The position data of the position sensor (10) is acquired according to a preset acquisition cycle; The fluctuation and discrete data of the location data are calculated within a preset measurement time. If the fluctuation data is within a preset amplitude range and the discrete data is within a preset discrete range, then the average value of the position data is calculated; and DC current data is matched from a preset database based on the average value. If the fluctuation data is outside the preset amplitude range and the discrete data is within the preset low discrete range, then an abnormal DC current amplitude is indicated. If the fluctuation data is within a preset amplitude range and the discrete data is outside a preset low discrete range, then an abnormal change in DC current is indicated.

2. The DC current acquisition method based on shape memory alloy sensing according to claim 1, characterized in that, The method also includes the following steps: The line power is obtained based on several recent DC current data points. Calculate the trend curve of the correspondence between the line power and the DC current data; The length of the measurement time is adjusted according to the slope of the corresponding trend curve; the larger the slope, the longer the measurement time; the smaller the slope, the shorter the measurement time.

3. The DC current acquisition method based on shape memory alloy sensing according to claim 1, characterized in that, The method also includes the following steps: The position sensor (10) is a distance sensor installed inside the measuring cylinder (7) for detecting the distance between the measuring piston (8) and the end of the measuring cylinder (7); The measuring piston (8) is a metal part or a magnetic part; A filter coil (17) is provided outside the measuring cylinder (7). The filter coil (17) is connected in series with the shape memory alloy sensing element (3) and in parallel with the conductive cylinder. When the filter coil (17) is energized, it is used to attract the measuring piston (8).

4. The DC current acquisition method based on shape memory alloy sensing according to claim 1, characterized in that, The method also includes the following steps: Next to the position sensor (10) is a distance sensor installed inside the measuring cylinder (7), used to detect the distance between the measuring piston (8) and the end of the measuring cylinder (7); The measuring piston (8) is a magnetic component; A filter coil (17) is provided outside the measuring cylinder (7), and a DC driver is provided on the filter coil (17). The DC driver is controlled and connected to the processor (9). When the filter coil (17) is energized, it is used to attract or repel the measuring piston (8); The force exerted by the filter coil (17) on the measuring piston (8) to overcome gravity is adjusted according to the positive correlation of the DC current data. The larger the DC current data, the greater the force exerted by the filter coil (17) on the measuring piston (8) against gravity; the smaller the DC current data, the smaller the force exerted by the filter coil (17) on the measuring piston (8) against gravity.

5. The DC current acquisition method based on shape memory alloy sensing according to claim 4, characterized in that, The method also includes the following steps: The filter coil (17) is controlled to be delayed according to a preset delay time; The duration of the delay time is adjusted according to the positive correlation of the fluctuation data; the larger the fluctuation data, the longer the delay time; the smaller the fluctuation data, the shorter the delay time.

6. The DC current acquisition method based on shape memory alloy sensing according to claim 1, characterized in that, The method also includes the following steps: A pipe diameter control module (16) is provided on the medium isolation channel (6); Based on a preset delay time, the minimum inner diameter of the medium isolation channel (6) is delayed by the pipe diameter control module (16); The size of the minimum inner diameter is adjusted according to the inverse correlation of the discrete data; the larger the discrete data, the smaller the size of the minimum inner diameter; the smaller the discrete data, the larger the size of the minimum inner diameter.

7. The DC current acquisition method based on shape memory alloy sensing according to claim 6, characterized in that, The method also includes the following steps: The control speed at which the pipe diameter control module (16) adjusts the minimum inner diameter is obtained; The control speed is adjusted according to the inverse correlation of the fluctuation data; the larger the fluctuation data, the smaller the control speed; the smaller the fluctuation data, the larger the control speed.

8. The DC current acquisition method based on shape memory alloy sensing according to claim 1, characterized in that, The guide ring (13) on the movable piston (5) is a conductive metal part; Alternatively, a conductive metal contact is fixedly connected in the guide ring (13) on the movable piston (5), one end of the conductive metal contact is electrically connected to the movable piston (5), and the other end is electrically connected to the current conduction cavity (4); Alternatively, an elastic conductive element may be provided on the movable piston (5) or the shape memory alloy sensing element (3), one end of the elastic conductive element being fixedly connected to the movable piston (5), and the other end of the elastic conductive element abutting against the inner wall of the current conduction cavity (4). Alternatively, an elastic conductive element may be provided on the movable piston (5) or the shape memory alloy sensing element (3), with the middle part of the elastic conductive element fixedly connected to the movable piston (5), one end of the elastic conductive element abutting against the shape memory alloy sensing element (3), and the other end of the elastic conductive element abutting against the inner wall of the current conduction cavity (4).

9. A DC current acquisition system based on shape memory alloy sensing, characterized in that, Includes a processor, wherein the steps of the DC current acquisition method based on shape memory alloy sensing as described in any one of claims 1-8 are executed.

10. A storage medium, characterized in that, The medium stores a program that, when executed by a processor, implements the steps of the DC current acquisition method based on shape memory alloy sensing as described in any one of claims 1-8.

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