A superconducting motor quench detection method and device based on power equivalent modulation ratio

Abstract

The application provides a superconducting motor quench detection method and device based on a power equivalent modulation ratio, and belongs to the technical field of superconducting motor quench, and comprises the following steps: collecting an excitation power actual output voltage, a DC bus voltage and an excitation operation state quantity, pre-processing the excitation power actual output voltage and normalizing to obtain an actual equivalent modulation ratio; establishing a normal equivalent output voltage model according to the excitation operation state quantity and an excitation loop health parameter, and further obtaining a normal equivalent modulation ratio; calculating a residual error between the actual equivalent modulation ratio and the normal equivalent modulation ratio, and discriminating quench according to the residual error amplitude, the duration or the change trend. The application starts from the excitation power control side, simultaneously considers the excitation current change rate and the DC bus voltage change, maps different excitation working conditions to the same dimensionless residual error, indirectly represents the abnormal increase of the equivalent resistance of the superconducting excitation winding by using the equivalent modulation ratio residual error, and improves the reliability and engineering applicability of the superconducting motor quench detection.

Description

Technical Field

[0001] This invention relates to the field of superconducting motor quench technology, and more specifically, to a method and apparatus for detecting superconducting motor quench based on the power supply equivalent modulation ratio. Background Technology

[0002] Superconducting motors utilize superconducting excitation windings to generate the main magnetic field, offering advantages such as high power density and low operating losses. They show promising application prospects in areas such as grid reactive power support, wind power generation, ship propulsion, and aviation electric propulsion. Compared to conventional motors, superconducting motor excitation windings typically operate in cryogenic environments. During normal operation, the winding resistance is extremely low, even approaching zero. However, localized areas may deviate from the superconducting state due to factors such as thermal disturbances, mechanical vibrations, electromagnetic shocks, overcurrent, abnormal cooling, or insulation defects. If quench failure is not detected and protected in time, it can lead to localized overheating of the superconducting winding, insulation damage, increased load on the cryogenic system, and even irreversible damage to the excitation winding. Therefore, quench detection and protection are among the key technologies for the safe operation of superconducting motors.

[0003] Existing quench detection methods for superconducting motors or superconducting magnets are mainly based on voltage detection. Typical schemes include the terminal voltage detection method, the bridge voltage balance method, and the differential voltage method between adjacent coils. The basic idea is to collect the analog voltage across the superconducting winding, filter and suppress interference signals, extract the resistive voltage component generated by the quench resistor, and set a threshold to determine quench.

[0004] However, for superconducting motors with closed-loop control of excitation power supply and rotating operation, traditional quench detection methods based on terminal voltage or differential voltage still have significant shortcomings.

[0005] First, the early quench signal of a superconducting winding is typically weak, with the resistive voltage possibly in the microvolt range. Interference from factors such as excitation power supply switching ripple, the inductance voltage component of the superconducting winding, electromagnetic coupling of the superconducting motor, and mechanical vibration further increases the uncertainty of the terminal voltage signal, making the direct acquisition and effective extraction of the weak quench voltage even more difficult. When the superconducting motor is under conditions such as strong excitation, excitation current regulation, or rapid demagnetization, the transient response of the excitation power supply may be much larger than the early quench voltage, easily leading to misjudgment or missed detection using traditional voltage threshold criteria. Therefore, quench detection usually requires complex filtering algorithms and operational condition detection.

[0006] Secondly, traditional quench detection methods rely on high-precision analog voltage acquisition channels, which require additional measurement lines to be arranged in low-temperature, high-pressure, strong electromagnetic interference, and rotation-related environments. This results in a complex detection system structure, difficulty in anti-interference design, and increased engineering implementation costs.

[0007] Most existing quench detection methods focus on the voltage at the superconducting winding terminals, rarely utilizing the relationship between the excitation power supply output voltage and the modulation ratio within the controller. In reality, in a closed-loop excitation current control system, when a quench occurs in the superconducting excitation winding, causing an increase in equivalent resistance, the excitation power supply needs to output a higher average voltage to maintain the same excitation current or the same rate of change of excitation current. This additional voltage demand is reflected in the actual average output voltage of the excitation power supply and can be converted into the power supply's equivalent modulation ratio through output voltage sampling, filtering, and bus voltage normalization. In other words, a quench not only manifests as a resistive voltage at the superconducting winding terminals but also as an abnormal increase in modulation output demand on the excitation power supply control side.

[0008] However, existing excitation power supply control systems typically use PWM modulation ratio, duty cycle, or voltage command as current closed-loop control quantities to generate drive signals for power switching devices. They fail to further convert the actual output voltage sample value of the excitation power supply into a measured equivalent modulation ratio, nor do they integrate this measured equivalent modulation ratio with the normal operation model, baseline bias, and quench criteria. Simply judging whether the modulation ratio or output voltage has increased is insufficient to distinguish changes caused by factors such as quench, normal excitation current regulation, forced excitation, demagnetization, bus voltage fluctuations, dead-zone effects, device voltage drop variations, and temperature drift.

[0009] Invention patent CN202010656509.7 proposes a quench detection method based on estimating the superconducting magnet loop resistance using excitation system operating parameters. This method establishes a reference curve for the loop resistance under normal operating conditions and compares the deviation between the current loop resistance and the reference value to determine quench. This method provides a useful approach for indirectly identifying superconducting magnet quench from the excitation power supply side. However, the detection object of this method is still the estimated value of the magnet loop resistance, and its normal reference is mainly obtained through loop resistance calibration under different excitation currents. When the excitation system is under conditions such as strong excitation, rapid current regulation, or dynamic changes in DC bus voltage, the actual output voltage of the excitation power supply simultaneously includes a large inductance voltage and a normal regulation voltage. Estimating only the loop resistance or the output voltage amplitude change is insufficient to directly characterize the increased modulation demand of the excitation power supply to compensate for the additional resistance required for quench compensation. Furthermore, this method does not normalize the actual output voltage of the excitation power supply to an equivalent modulation ratio based on the DC bus voltage, nor does it establish a normal modulation demand model by combining the modulation state, dead-zone voltage drop, device voltage drop, and excitation conditions of the PWM excitation power supply. Therefore, it is difficult to distinguish from the control side the output voltage change caused by normal excitation regulation and the additional modulation requirement caused by the quench additional resistance.

[0010] Therefore, it is necessary to propose a new method and system for detecting superconducting motor quench. Starting from the excitation power supply control side, this method considers both the excitation current change rate and the DC bus voltage change, and maps different excitation conditions to the same dimensionless residual. The equivalent modulation ratio residual is used to indirectly characterize the abnormal increase in the equivalent resistance of the superconducting excitation winding, thereby improving the reliability and engineering applicability of superconducting motor quench detection. Summary of the Invention

[0011] To address the aforementioned problems, this invention provides a method and apparatus for detecting superconducting motor quench based on the equivalent modulation ratio of the power supply. Starting from the excitation power supply control side, this invention simultaneously considers the excitation current change rate and DC bus voltage variation, and maps different excitation conditions to the same dimensionless residual. The equivalent modulation ratio residual is used to indirectly characterize the abnormal increase in the equivalent resistance of the superconducting excitation winding, thereby improving the reliability and engineering applicability of superconducting motor quench detection.

[0012] To achieve the above objectives, the technical solution adopted by the present invention is as follows: This invention provides a superconducting motor quench detection method based on the equivalent modulation ratio of the power supply, comprising: acquiring the actual output voltage of the excitation power supply, the DC bus voltage, and the excitation operating status variables; preprocessing the actual output voltage of the excitation power supply to obtain the equivalent average output voltage, and calculating the actual equivalent modulation ratio based on the equivalent average output voltage and the DC bus voltage; establishing a normal equivalent output voltage model based on the excitation current, the excitation current change rate, and the health parameters of the excitation circuit, and normalizing it according to the DC bus voltage to obtain the normal equivalent modulation ratio; calculating the equivalent modulation ratio residual between the actual equivalent modulation ratio and the normal equivalent modulation ratio; judging whether the superconducting excitation winding has an abnormal increase in equivalent resistance based on the equivalent modulation ratio residual and its duration or trend, and outputting corresponding warning or protection commands.

[0013] In some implementations, the difference between the actual output voltage of the pre-processed excitation power supply and the normal equivalent output voltage can be directly used to construct the equivalent voltage residual, which can be used as an auxiliary detection quantity for the equivalent modulation ratio residual.

[0014] Furthermore, the excitation operating state quantities include the excitation current i f Excitation current setpoint i f * , excitation current change rate di f / dt and excitation condition commands.

[0015] Furthermore, the health parameters of the excitation circuit include at least the superconducting excitation winding inductance L. f The normal equivalent resistance R0 of the excitation circuit, and may further include the equivalent voltage V corresponding to the dead-time effect of the excitation power converter. dead, Switching device on-state voltage drop V sw and system normal baseline offset V base One or more of them.

[0016] Furthermore, the preprocessing employs one or more of the following: analog low-pass filtering, digital low-pass filtering, PWM period averaging, PWM period integer multiple window averaging, sliding window averaging, synchronous sampling reconstruction, median filtering combined with low-pass filtering, and window mean calculation after removing switching spikes.

[0017] Furthermore, the normal equivalent output voltage is calculated based on the excitation operating state parameters and the excitation circuit health parameters, and the calculation method is as follows: ; Among them, L f di is the inductance value of the superconducting excitation winding. f / dt is the rate of change of excitation current; i f R0 is the excitation current; R0 is the normal equivalent resistance of the excitation circuit; V dead The equivalent output voltage error caused by the dead-time effect of the excitation power converter; V sw V is the on-state voltage drop of the switching device. base This is the normal baseline offset for the system.

[0018] Furthermore, construct the equivalent voltage residual V res As an auxiliary detection quantity for the equivalent modulation ratio residual, the equivalent voltage residual V res The calculation method is as follows: ; Among them, V out，avg This is the actual output voltage of the pre-processed excitation power supply, i.e., the equivalent average output voltage.

[0019] Furthermore, the equivalent modulation ratio residual m res The calculation method is as follows: ; ; ; Among them, V dc V is the DC bus voltage. out，avg This is the actual output voltage of the pre-processed excitation power supply, i.e., the equivalent average output voltage.

[0020] Furthermore, trend prediction is performed on the equivalent modulation ratio residual based on a sliding window.

[0021] Compared with directly using the actual output voltage of the excitation power supply as the quench criterion, the equivalent modulation ratio is normalized by the DC bus voltage, so that the detected quantity reflects the relative modulation output actually required by the excitation power supply under the current bus voltage condition. This can reduce the influence of changes in the DC bus voltage level and dynamic changes in the bus voltage on the fixed voltage threshold, and give the detected quantity under different excitation conditions a unified dimensionless expression form.

[0022] Furthermore, when the excitation power supply is in the modulation saturation condition during the strong excitation process, the normal equivalent output voltage is still calculated based on the excitation current change rate, wherein the excitation winding inductance voltage term L is retained. f di f / dt; When the superconducting excitation winding generates an additional resistance voltage, the excitation current change rate decreases relative to the healthy operating condition, causing the normal equivalent modulation ratio to be lower than the actual equivalent modulation ratio, and generating a positive equivalent modulation ratio residual, based on which quench judgment is performed.

[0023] This invention also provides a superconducting motor quench detection system, comprising: a signal acquisition module for acquiring the actual output voltage of the excitation power supply, the DC bus voltage, and excitation operating status parameters; a calculation module for calculating the actual equivalent modulation ratio based on the pre-processed actual output voltage of the excitation power supply and the DC bus voltage, calculating the normal equivalent modulation ratio based on the excitation operating status parameters and excitation circuit health parameters, and calculating the equivalent modulation ratio residual between the actual equivalent modulation ratio and the normal equivalent modulation ratio; a prediction module for trend prediction and discrimination of the equivalent modulation ratio residual; and an early warning module for adaptively adjusting the quench criterion according to the excitation operating conditions, and outputting a quench warning or protection command based on the quench criterion.

[0024] The present invention also provides a superconducting motor quench detection device, including a memory and a processor; the memory is used to store program code and transmit the program code to the processor; the processor is used to execute the above-mentioned quench detection method according to the instructions in the program code.

[0025] The beneficial effects of the technical solution provided by the embodiments of this invention include: the essence of this invention is to transform the quench detection object from "weak quench voltage at the end of the rotating superconducting winding" to "equivalent modulation ratio residual on the excitation power supply side". Its significance lies in: First, reducing the reliance on direct acquisition of the weak differential voltage at the end of the superconducting winding, and reducing the influence of rotating leads, electromagnetic coupling, mechanical vibration, and external simulation measurement links on the detection results. Second, by acquiring the actual output voltage of the excitation power supply and filtering it, an equivalent average output voltage reflecting the actual output capability of the excitation power supply is obtained. Third, by normalizing according to the DC bus voltage, the equivalent modulation ratio of the power supply is obtained, transforming the detected quantity from a dimensional output voltage to a dimensionless modulation demand characteristic, facilitating unified discrimination under different bus voltage levels and different operating conditions. Fourth, by eliminating inductor voltage, normal resistance voltage drop, dead zone voltage drop, device voltage drop, and system baseline bias through a normal equivalent modulation ratio model, the residual mainly reflects the additional voltage demand caused by the abnormal increase in the equivalent resistance of the superconducting excitation winding. Fifth, by retaining the inductor voltage term corresponding to the excitation current change rate in the normal equivalent modulation ratio model, quench detection can be performed using a unified equivalent modulation ratio residual for both steady-state and dynamic excitation processes. Under steady-state excitation conditions, the quench additional resistance mainly manifests as an increase in the actual equivalent modulation ratio relative to the normal equivalent modulation ratio; under modulation saturation conditions during strong excitation, the quench additional resistance causes the excitation current change rate to decrease relative to the healthy trajectory, thereby causing the normal equivalent modulation ratio to decrease relative to the actual equivalent modulation ratio. Positive equivalent modulation ratio residuals are formed in both cases, thus achieving unified quench detection under different excitation conditions. In summary, this invention does not require the power switching device to output or distinguish minute duty cycle changes, nor does it simply compare the absolute changes in the actual output voltage of the excitation power supply. Instead, it achieves quench detection and protection for superconducting motors by high-precision sampling of the actual output voltage of the excitation power supply, filtering to obtain the equivalent average output voltage, normalizing to obtain the power supply's equivalent modulation ratio, and identifying abnormal increases in the equivalent resistance of the superconducting excitation winding based on the equivalent modulation ratio residual. Attached Figure Description

[0026] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0027] Figure 1 This is a flowchart of the superconducting motor quench detection method based on power equivalent modulation ratio provided in Embodiment 1 of the present invention; Figure 2 This is a block diagram of the superconducting motor quench detection system based on power supply equivalent modulation ratio provided in Embodiment 1 of the present invention; Figure 3 The original data of the excitation power supply output current and voltage provided in Embodiment 2 of the present invention; Figure 4 The equivalent average output voltage of the filtered excitation power supply provided in Embodiment 2 of the present invention; Figure 5 This describes the process of change in the equivalent modulation ratio of the excitation power supply provided in Embodiment 2 of the present invention; Figure 6 This is a graph showing the change in the actual output voltage of the excitation power supply over time as provided in Embodiment 3 of the present invention. Figure 7 This is a graph showing the equivalent modulation ratio over time as provided in Embodiment 3 of the present invention. Figure 8 This is a graph showing the change of the equivalent modulation ratio residual over time, provided in Embodiment 3 of the present invention. Figure 9 The graph shows the actual output voltage of the excitation power supply provided in Embodiment 3 of the present invention as a function of time. Detailed Implementation

[0028] To make the objectives, technical solutions, and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0029] Example 1 This invention provides a method for detecting quench in superconducting motors based on the power supply equivalent modulation ratio, such as... Figure 1 As shown, it includes: S1. Collect the actual output voltage of the excitation power supply, the DC bus voltage, and the excitation operating status. S2. Preprocess the actual output voltage of the excitation power supply and calculate the actual equivalent modulation ratio based on the equivalent average output voltage and the DC bus voltage. S3. Calculate the normal equivalent output voltage and normal equivalent modulation ratio based on the excitation operating status and excitation circuit health parameters, and calculate the equivalent modulation ratio residual between the actual equivalent modulation ratio and the normal equivalent modulation ratio. S4. Based on the equivalent modulation ratio residual and its duration or trend of change, perform quench detection and output quench warning or protection command.

[0030] In some implementations, the difference between the actual output voltage of the pre-processed excitation power supply and the normal equivalent output voltage can be directly used to construct the equivalent voltage residual, which can be used as an auxiliary detection quantity for the equivalent modulation ratio residual.

[0031] This invention acquires the actual output voltage of the excitation power supply, obtains the equivalent average output voltage through low-pass filtering or periodic averaging, and obtains the power supply equivalent modulation ratio by normalizing it according to the DC bus voltage; establishes a normal equivalent modulation ratio model based on the excitation current, excitation current change rate, normal equivalent resistance, dead zone voltage drop, device voltage drop, and system baseline bias; obtains the residual by subtracting the power supply equivalent modulation ratio from the normal equivalent modulation ratio model, and outputs overrun warning or protection command by combining excitation condition identification and sliding window trend judgment.

[0032] In existing technologies, direct measurement of weak quench voltage is difficult. The early quench voltage amplitude of superconducting windings is small and easily affected by power switch ripple, inductor voltage, mechanical vibration, and zero drift. Especially in rotating superconducting motors, it is difficult to resist interference when directly collecting weak quench voltage at the winding ends, and the quench characteristics are easily submerged by noise. The reliability of the fixed voltage threshold criterion under excitation transient is insufficient. During strong excitation, rapid demagnetization, and changes in excitation current, the voltage at the excitation winding ends contains a large inductor voltage and the transient response of the excitation power supply, the amplitude of which may be much larger than the early quench resistor voltage. If a fixed terminal voltage threshold or a simple differential voltage threshold is still used for judgment, false positives or false negatives are likely to occur. Traditional analog measurement links are complex, and traditional quench detection relies on high-precision differential voltage sampling, weak signal isolation and amplification, filtering and conditioning, and synchronous sampling. Additional analog measurement links increase the complexity of the superconducting motor signal system, the difficulty of anti-interference design, and the engineering implementation cost. Existing quench detection methods do not fully utilize the equivalent relationship between the actual output voltage of the excitation power supply and the modulation ratio. They mainly focus on the terminal voltage of the superconducting winding and rarely utilize the equivalent modulation relationship between the output voltage of the excitation power supply and the DC bus voltage. In fact, after the quench causes the equivalent resistance of the superconducting excitation winding to rise, the excitation power supply needs to output a higher average voltage in order to maintain the same excitation current or the same rate of change of excitation current. This additional voltage requirement can be reflected by acquiring the actual output voltage of the excitation power supply, filtering out the switching ripple, and normalizing it to the power supply equivalent modulation ratio. However, the lack of a digital discrimination mechanism for the power supply equivalent modulation ratio residual means that the sampling channel of the traditional excitation power supply controller mainly serves current closed-loop control and conventional protection. It usually does not have a high-precision sampling, filtering, normalization, and residual discrimination design for small equivalent output voltage changes. The technical solution proposed in this invention does not require power switching devices to output or distinguish minute duty cycle changes, nor does it rely solely on the bit width of a PWM counter to identify microvolt-level overvoltage. Its core lies in observing, through a high-precision sampling system, how much equivalent voltage the excitation power supply actually outputs to maintain the excitation current, and converting this equivalent voltage into a digitized equivalent modulation ratio. The residual of this equivalent voltage relative to the normal equivalent modulation ratio is then compared in the digital domain. This reduces the reliance on direct analog acquisition of the weak differential voltage at the ends of the rotating superconducting winding, shifting the detection focus to the output voltage on the excitation power supply side, and using the normalized equivalent modulation ratio residual for discrimination. This normalization process weakens the influence of bus voltage fluctuations, different bus voltage levels, and different excitation conditions on the output voltage amplitude, transforming the detected quantity into a dimensionless control-side characteristic representing the modulation requirements of the excitation power supply, thereby improving the integration and anti-interference capability of the detection system.

[0033] Specifically, in step S1, the actual output voltage V of the excitation power supply in the superconducting motor excitation system is collected. out DC bus voltage V dcand excitation operating status quantities; the excitation operating status quantities include excitation current i f Excitation current setpoint i f * , excitation current change rate di f / dt and excitation condition commands.

[0034] Wherein, the actual output voltage V of the excitation power supply out This refers to the voltage at the output terminal of the excitation power conversion unit, used to characterize the actual output voltage applied to the excitation circuit by the excitation power supply. The sampled object is the output voltage on the excitation power supply side, not the weak quench voltage at the end of the superconducting winding, nor the differential voltage between adjacent superconducting coils.

[0035] The excitation current change rate di f / dt can be calculated from the sampled value of the excitation current. In specific implementations, the excitation current change rate can be calculated using methods such as adjacent sampling point difference, sliding window linear fitting, multi-cycle average difference, or band-limited differential algorithm.

[0036] The preprocessing is either filtering or averaging. Because the actual output voltage V of the excitation power supply... out Typically, the actual output voltage of the excitation power supply includes PWM switching ripple, switching spikes, and high-frequency noise. Therefore, filtering or averaging the acquired actual output voltage of the excitation power supply yields the pre-processed actual output voltage V of the excitation power supply. out，avg That is, the equivalent average output voltage.

[0037] The filtering process includes one or more of the following methods: Analog low-pass filtering, digital low-pass filtering, PWM period averaging, PWM period integer multiple window averaging, sliding window averaging, synchronous sampling reconstruction, median filtering and low-pass filtering combination, and window mean calculation after removing switching spikes.

[0038] In a preferred embodiment, the actual output voltage of the excitation power supply is synchronously averaged using the PWM period or an integer multiple of the PWM period as a window, so as to reduce the impact of switching ripple on the subsequent calculation of the equivalent modulation ratio.

[0039] The actual equivalent modulation ratio of the excitation power supply is calculated based on the preprocessed equivalent average output voltage and DC bus voltage. Specifically, for the case where the equivalent average output voltage and the bus voltage satisfy a linear equivalence relationship, the following definition can be made: ; Where, m eq The equivalent modulation ratio of the power supply is calculated from the equivalent average output voltage.

[0040] Compared with directly using the actual output voltage of the excitation power supply as the quench criterion, the equivalent modulation ratio is normalized by the DC bus voltage, so that the detected quantity reflects the relative modulation output actually required by the excitation power supply under the current bus voltage condition. This can reduce the influence of changes in the DC bus voltage level and dynamic changes in the bus voltage on the fixed voltage threshold, and give the detected quantity under different excitation conditions a unified dimensionless expression form.

[0041] For bipolar H-bridge, two-phase interleaved H-bridge, multi-level excitation power supply or other excitation power supply topologies, the power supply equivalent modulation ratio can be normalized and defined according to the specific topology and modulation method.

[0042] It should be noted that the power supply equivalent modulation ratio meq is not simply the PWM command modulation ratio, nor is it the result of the actual small duty cycle change of the power switching device. Instead, it is a digital equivalent modulation ratio obtained by filtering, averaging, and normalizing the actual output voltage of the excitation power supply.

[0043] According to the excitation current i f , excitation current change rate di f / dt, excitation current setpoint i f * The system identifies the current operating condition of the excitation system by monitoring the DC bus voltage change rate, excitation condition commands, modulation limit status, and protection status signals.

[0044] The excitation condition command includes one or more of the following: Constant current excitation condition, slow excitation condition, strong excitation condition, rapid demagnetization condition, and current loop saturation condition.

[0045] For example, when the DC bus voltage is stable, the current loop is not saturated, and there are no strong excitation or demagnetization commands, the system can be determined to be in constant current excitation mode or low excitation rate mode; when the excitation current setpoint i f * When the excitation current rises rapidly, the strong excitation command is valid, the DC bus voltage increases, or the modulation amount approaches the upper limit, the system can be determined to be in strong excitation mode; when the excitation current setpoint i f * When the system experiences a rapid descent, a valid demagnetization command, or a reversal of the output voltage polarity, it can be determined that the system is in a rapid demagnetization state.

[0046] A normal equivalent modulation ratio model is established based on the excitation current, excitation current change rate, DC bus voltage, normal equivalent resistance, excitation winding equivalent inductance, dead zone voltage drop, device voltage drop, system baseline bias, and excitation conditions.

[0047] Under normal, non-quenching conditions, the required normal equivalent output voltage of the excitation power supply is calculated as follows: ; Among them, L f di is the inductance value of the superconducting excitation winding. f / dt is the rate of change of excitation current; i f R0 is the excitation current; R0 is the normal equivalent resistance of the excitation circuit; V dead The equivalent output voltage error caused by the dead-time effect of the excitation power converter; V sw V is the on-state voltage drop of the switching device. base This is the normal baseline offset for the system.

[0048] Among them, R0, L f V dead V sw and V base These are health parameters of the excitation circuit and can be obtained through design parameters, offline calibration, online measurement, or parameter identification.

[0049] The operating conditions of the excitation system are determined in the following way: based on the excitation current i f Excitation current setpoint i f * , excitation current change rate di f The system uses / dt, DC bus voltage change rate, excitation condition command, modulation limit status, and protection status signal to identify the current operating condition of the excitation system.

[0050] The excitation condition commands include one or more of the following: constant current excitation condition, slow excitation condition, strong excitation condition, rapid demagnetization condition, and current loop saturation condition. When the DC bus voltage is stable, the current loop is not saturated, and there are no strong excitation or demagnetization commands, the system can be determined to be in constant current excitation condition or low excitation rate condition; when the excitation current setpoint i f * When the excitation current rises rapidly, the strong excitation command is valid, the DC bus voltage increases, or the modulation amount approaches the upper limit, the system can be determined to be in strong excitation mode; when the excitation current setpoint i f * When the system experiences a rapid descent, a valid demagnetization command, or a reversal of the output voltage polarity, it can be determined that the system is in a rapid demagnetization state.

[0051] This invention uses the equivalent modulation ratio residual as the primary detection quantity to determine whether an early warning or protection command is triggered; in some embodiments, an equivalent voltage residual can also be constructed as an auxiliary detection quantity. The actual equivalent modulation ratio of the excitation power supply is calculated based on the pre-processed actual output voltage and DC bus voltage. Specifically, the equivalent voltage residual V... res The calculation method is as follows: ; Among them, V out，avgThis is the actual output voltage of the pre-processed excitation power supply, i.e., the equivalent average output voltage.

[0052] Specifically, the equivalent modulation ratio residual m res The calculation method is as follows: ; ; ; Among them, V dc This is the DC bus voltage.

[0053] The equivalent modulation ratio residual and the equivalent voltage residual satisfy the following: .

[0054] Trend prediction and discrimination are performed on the equivalent modulation ratio residual; in the embodiment using equivalent voltage residual, auxiliary discrimination can also be performed on the equivalent voltage residual.

[0055] The equivalent modulation ratio residual will be used as an example for explanation.

[0056] For the equivalent modulation ratio residual m res Perform moving averages, moving integrals, slope estimations, or multi-time-window comparisons to identify whether there is a persistent positive shift and increasing trend in the residuals.

[0057] As a preferred implementation, the average value of the equivalent modulation ratio residual is calculated using both short and long time windows: ; Where, N s The short window length is 20 ms, and N is the value of N. l The length of the long window is 100 ms, and N is... s < N l k is the number of equivalent modulation ratio residual points collected within the window, which is not specifically limited here.

[0058] When the mean residual of the short-term window exceeds the set threshold, and the mean residual of the short-term window continues to increase relative to the mean residual of the long-term window, the equivalent modulation ratio residual is considered to have an increasing trend.

[0059] It should be noted that the calculation method using short and long time windows is one implementation method, and it is only for illustration.

[0060] Based on the identified operating conditions of the excitation system, adjust the equivalent modulation ratio residual threshold and the criterion duration.

[0061] Under constant current excitation or low excitation rate conditions, a high-sensitivity equivalent modulation ratio residual criterion is enabled. In this embodiment of the invention, the equivalent modulation ratio residual criterion can be set to 0.1 ppm.

[0062] For operating conditions with rapid changes in excitation current such as strong excitation, this invention preferentially retains the inductor voltage term L in the normal equivalent output voltage model. f di f / dt allows the normal equivalent modulation ratio to be updated in real time with the excitation dynamics. Especially when the excitation power supply enters modulation saturation, the actual equivalent modulation ratio can approach its saturation value. When the superconducting excitation winding experiences quench, the newly added resistive voltage occupies part of the actual output voltage of the excitation power supply, reducing the rate of change of the excitation current relative to the healthy trajectory. This leads to a decrease in the normal equivalent modulation ratio, while the actual equivalent modulation ratio remains at a high level, thus forming a positive equivalent modulation ratio residual. Therefore, under the aforementioned strong excitation dynamic conditions, it is not necessary to rely solely on the fixed terminal voltage threshold or to block quench detection; instead, quench identification can continue based on the equivalent modulation ratio residual.

[0063] When the excitation transient is too strong, or the model error or measurement noise exceeds the preset range, the residual criterion threshold can be further increased and the criterion duration can be extended. If necessary, the quench criterion based on the equivalent modulation ratio residual can be temporarily blocked to reduce misjudgment caused by the excitation transient process.

[0064] Under conditions of rapid excitation current changes, such as strong excitation and rapid demagnetization, or bus voltage switching, the actual output voltage of the excitation power supply itself will change significantly, and the inductor voltage and power supply transient response may increase significantly. If a highly sensitive equivalent modulation ratio residual criterion is still used under these conditions, the risk of transient misjudgment may increase. Therefore, this invention adaptively adjusts the residual threshold, criterion duration, and criterion weight according to the excitation condition, and temporarily blocks the quench criterion or reduces the weight of the modulation ratio residual criterion when necessary.

[0065] By identifying operating conditions, the modulation ratio change caused by normal excitation regulation can be distinguished from the additional resistance requirement caused by quench, thereby improving the reliability of detection.

[0066] When the equivalent modulation ratio residual meets one or more of the following conditions, it is determined that there is a risk of abnormal increase in the equivalent resistance of the superconducting excitation winding: ; Among them, M th ΔM is the equivalent modulation ratio residual threshold. th It is the threshold for the difference between the mean of the equivalent modulation ratio residuals for short and long time windows.

[0067] Furthermore, the duration of the above conditions exceeds the set time T. hold .

[0068] It should be noted that, apart from the values ​​already given, the thresholds and setting parameters in this invention can be determined based on empirical data, obtained through summarizing and analyzing historical data, or calculated by simulating quench and normal state data under different working conditions in experiments.

[0069] When a suspected loss of protection is detected, a loss of protection warning signal is output; when the residual amplitude, residual growth trend or duration further meets the protection threshold, a protection command is output.

[0070] The protection commands include one or more of the following: blocking strong excitation command, limiting the excitation current change rate, blocking PWM pulse, shutting off excitation power supply, and rapid demagnetization.

[0071] This invention also provides a superconducting motor quench detection system, comprising: a signal acquisition module for acquiring the actual output voltage of the excitation power supply, the DC bus voltage, and excitation operating status parameters; a calculation module for calculating the actual equivalent modulation ratio based on the pre-processed actual output voltage of the excitation power supply and the DC bus voltage, calculating the normal equivalent modulation ratio based on the excitation operating status parameters and excitation circuit health parameters, and calculating the equivalent modulation ratio residual between the actual equivalent modulation ratio and the normal equivalent modulation ratio; a prediction module for trend prediction and discrimination of the equivalent modulation ratio residual or the equivalent voltage residual; and an early warning module for adaptively adjusting the quench criterion according to the excitation operating conditions, and outputting a quench warning or protection command based on the quench criterion.

[0072] The signal acquisition module includes an actual output voltage acquisition module for the excitation power supply, a bus voltage acquisition module, and an excitation current acquisition module. The calculation module includes an output voltage filtering module, a power supply equivalent modulation ratio calculation module, an excitation condition identification module, a normal equivalent modulation ratio model module, and an equivalent modulation ratio residual calculation module. The prediction module includes a trend discrimination module. The early warning module includes a protection and control module.

[0073] like Figure 2 As shown, specifically, the circuit module includes: an actual output voltage acquisition module for the excitation power supply, a bus voltage acquisition module, an excitation current acquisition module, an output voltage filtering module, a power supply equivalent modulation ratio calculation module, an excitation condition identification module, a normal equivalent modulation ratio model module, an equivalent modulation ratio residual calculation module, a trend discrimination module, and a protection and control module.

[0074] ① The excitation power supply actual output voltage acquisition module is used to acquire the output voltage of the excitation power supply power conversion unit (i.e., the actual output voltage of the excitation power supply) V. out This module is preferably located on the excitation power supply side to obtain the actual output voltage of the excitation power supply, rather than directly acquiring the weak quench voltage at the end of the superconducting winding.

[0075] ② The bus voltage acquisition module is used to acquire the DC bus voltage V of the excitation power supply. dc It is then provided to the power supply equivalent modulation ratio calculation module and the normal equivalent modulation ratio model module.

[0076] ③ The excitation current acquisition module is used to acquire the excitation current i of the superconducting excitation winding. f And calculate the excitation current change rate di f / dt.

[0077] ④ The output voltage filtering module is used to filter the actual output voltage V of the excitation power supply. out After performing low-pass filtering, the actual output voltage V of the pre-processed excitation power supply is obtained. out，avg That is, the equivalent average output voltage.

[0078] ⑤ The power supply equivalent modulation ratio calculation module is used to calculate the equivalent average output voltage V after preprocessing the excitation power supply. out，avg and DC bus voltage V dc Calculate the power supply equivalent modulation ratio m eq For different excitation power supply topologies, the power supply equivalent modulation ratio calculation module can also perform normalization conversion based on the topology state and modulation method.

[0079] ⑥ The excitation condition identification module is used to identify the current operating condition of the excitation system based on the excitation current, the excitation current change rate, the excitation current setpoint change rate, the DC bus voltage change rate, the excitation condition command, and the modulation limit status.

[0080] ⑦ The normal equivalent modulation ratio model module is used to calculate the normal equivalent modulation ratio m based on the excitation current, excitation current change rate, DC bus voltage, normal equivalent resistance, excitation winding equivalent inductance, dead zone voltage drop, device voltage drop, system baseline bias, and excitation system operating conditions. normal .

[0081] ⑧ The equivalent modulation ratio residual calculation module is used to calculate the power supply equivalent modulation ratio m eq Compared with the normal equivalent modulation ratio m normal By subtracting the values, we obtain the equivalent modulation ratio residual m. res .

[0082] ⑨ The trend discrimination module is used to perform moving average, moving integral, slope estimation or multi-time window comparison on the equivalent modulation ratio residual to determine whether there is a continuous positive offset and growth trend.

[0083] ⑩ The protection control module is used to output a quench warning signal or protection command when the equivalent modulation ratio residual satisfies the quench warning or quench protection criterion.

[0084] The protection commands include one or more of the following: reducing the excitation current setpoint, limiting the excitation current change rate, blocking forced excitation, rapid demagnetization, engaging the protection resistor, shutting off the excitation power supply, blocking the PWM pulse, or outputting an alarm signal.

[0085] The above methods and systems can be implemented by DSPs, microcontrollers, FPGAs, high-speed data acquisition units, industrial controllers, or combinations thereof.

[0086] In a preferred embodiment, a high-precision ADC is used to acquire the actual output voltage of the excitation power supply, and an FPGA, a high-speed digital processing unit or an embedded controller is used to realize output voltage sampling triggering, digital filtering, PWM period averaging, synchronous acquisition of bus voltage and excitation current, equivalent modulation ratio calculation, residual calculation, trend judgment and protection action output.

[0087] It should be noted that the FPGA or high-speed digital processing unit is not intended to require the power switching device to output or distinguish minute duty cycle changes, but rather to perform high-speed and high-precision sampling control, digital filtering, equivalent modulation ratio conversion, and residual criterion calculation on the actual output voltage of the excitation power supply, thereby identifying in the digital domain the additional equivalent output voltage required by the excitation power supply to maintain the excitation state.

[0088] This invention also provides a superconducting motor quench detection device, including a memory and a processor; the memory is used to store program code and transmit the program code to the processor; the processor is used to execute the above-described quench detection method according to the instructions in the program code.

[0089] The memory may include random access memory (RAM) or read-only memory (ROM). The memory can be used to store instructions, programs, code, code sets, or instruction sets. The memory may include a program storage area and a data storage area. The program storage area may store instructions for implementing an operating system, instructions for implementing at least one function, instructions for implementing the various method embodiments described above, etc. The data storage area may also store data created during the use of the electronic device.

[0090] A processor may include one or more processing cores. The processor connects various parts within the electronic device using various interfaces and lines, and performs various functions and processes data by running or executing instructions, programs, code sets, or instruction sets stored in memory, and by calling data stored in memory. Optionally, the processor may be implemented using at least one hardware form of Digital Signal Processing (DSP), Field-Programmable Gate Array (FPGA), or Programmable Logic Array (PLA). The processor may integrate one or more of a Central Processing Unit (CPU) and a modem. The CPU primarily handles the operating system and applications; the modem handles wireless communication. It is understood that the modem may also be implemented separately as a communication chip, without being integrated into the processor.

[0091] Those skilled in the art will further recognize that the units and algorithm steps of the various examples described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, computer software, or a combination of both. To clearly illustrate the interchangeability of hardware and software, the components and steps of the various examples have been generally described in terms of functionality in the foregoing description. Whether these functions are implemented in hardware or software depends on the specific application and design constraints of the technical solution. Those skilled in the art can implement the described functions using different methods for each specific application, but such implementations should not be considered beyond the scope of the invention.

[0092] Example 2 Taking the 15 Mvar high-temperature superconducting phase converter prototype as an example, its rotor adopts a superconducting structure, consisting of two superconducting coils connected in series. The inductance parameter of a single superconducting coil is 9 H. The stator uses conventional copper windings. The excitation system operates under a constant current excitation of 243 A, and the excitation power supply bus voltage is 50 V.

[0093] Figures 3-5 The test demonstrated the simulation of a single superconducting coil losing quench in a two-panel 9H superconducting coil under a constant current excitation mode of 243 A, starting at 1.5 seconds. The test stopped when the equivalent resistance voltage drop caused by the additional resistor reached about 10 mV. The output current of the excitation power supply, the actual output voltage of the excitation power supply, the equivalent average output voltage of the filtered excitation power supply, and the change process of the equivalent modulation ratio of the excitation power supply were detected.

[0094] Example 3 Taking the forced excitation process of a superconducting phase modulator as an example, the excitation current setpoint is set to 300 A, and the maximum DC bus voltage is 2500 V. During forced excitation, the excitation power supply enters a high modulation ratio operating state, and the excitation current rises rapidly. Therefore, the normal equivalent output voltage model retains L. f di f / dt item.

[0095] Figures 6-9 This demonstrates that under healthy excitation conditions, the actual equivalent modulation ratio remains essentially consistent with the normal equivalent modulation ratio. When the simulated superconducting excitation winding experiences partial quench at t0 = 2.8 s during the excitation process, the additional resistor voltage causes the excitation current rate of change to decrease relative to the healthy trajectory. Consequently, the normal equivalent modulation ratio calculated from the normal model decreases, while the actual equivalent modulation ratio calculated from the actual output voltage of the excitation power supply remains at a relatively high level. This results in a positive equivalent modulation ratio residual, which is reflected at t0 = 2.8 s. q = 2.88 s. The set criterion was exceeded for the first time.

[0096] In this embodiment, when the residual exceeds the set criterion and continues to reach the first time threshold T1 = 10 ms (t1 = 2.89 s), a failure warning is output; when it continues to reach the second time threshold T2 = 20 ms (t2 = 2.9 s), the forced excitation is terminated; if the residual continues to exist and reaches the third time threshold T3 = 40 ms (t3 = 2.92 s), the excitation power supply is shut off and rapid demagnetization is performed.

[0097] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for detecting quench in a superconducting motor based on the power supply equivalent modulation ratio, characterized in that, include: Collect the actual output voltage of the excitation power supply, the DC bus voltage, and the excitation operating status parameters; The actual output voltage of the excitation power supply is preprocessed to obtain the equivalent average output voltage, and the actual equivalent modulation ratio is calculated based on the equivalent average output voltage and the DC bus voltage. The normal equivalent output voltage is calculated based on the excitation operating status and excitation circuit health parameters, and the normal equivalent modulation ratio is calculated based on the normal equivalent output voltage and the DC bus voltage; the equivalent modulation ratio residual between the actual equivalent modulation ratio and the normal equivalent modulation ratio is calculated. Based on the equivalent modulation ratio residual, determine whether there is an abnormal increase in the equivalent resistance of the superconducting excitation winding, and output a quench warning or protection command based on the judgment result.

2. The quench detection method according to claim 1, characterized in that, The excitation operating state parameters include the excitation current i f Excitation current setpoint i f * , excitation current change rate di f / dt and excitation condition commands.

3. The quench detection method according to claim 1, characterized in that, The health parameters of the excitation circuit include at least the superconducting excitation winding inductance L. f The normal equivalent resistance R0 of the excitation circuit, and may further include the equivalent voltage V corresponding to the dead-time effect of the excitation power converter. dead , Switching device on-state voltage drop V sw and system normal baseline offset V base One or more of them.

4. The quench detection method according to claim 1, characterized in that, The preprocessing employs one or more of the following: analog low-pass filtering, digital low-pass filtering, PWM period averaging, PWM period integer multiple window averaging, sliding window averaging, synchronous sampling reconstruction, median filtering and low-pass filtering combination, and window mean calculation after removing switching spikes.

5. The quench detection method according to claim 1, characterized in that, The normal equivalent output voltage is calculated based on the excitation operating state parameters and the health parameters of the excitation circuit. The calculation method is as follows: ； Among them, L f di is the inductance value of the superconducting excitation winding. f / dt is the rate of change of excitation current; i f R0 is the excitation current; R0 is the normal equivalent resistance of the excitation circuit; V dead The equivalent output voltage error caused by the dead-time effect of the excitation power converter; V sw V is the on-state voltage drop of the switching device. base This is the normal baseline offset for the system.

6. The quench detection method according to claim 5, characterized in that, Constructing the equivalent voltage residual V res As an auxiliary detection quantity for the equivalent modulation ratio residual, the equivalent voltage residual V res The calculation method is as follows: ； Among them, V out，avg This is the actual output voltage of the pre-processed excitation power supply, i.e., the equivalent average output voltage.

7. The quench detection method according to claim 5, characterized in that, The equivalent modulation ratio residual m res The calculation method is as follows: ； ； ； Among them, V dc V is the DC bus voltage. out，avg This is the actual output voltage of the pre-processed excitation power supply, i.e., the equivalent average output voltage.

8. The quench detection method according to claim 1, characterized in that, Trend prediction of equivalent modulation ratio residuals based on sliding window.

9. The quench detection method according to claim 1, characterized in that, When the excitation power supply is in the modulation saturation condition during the strong excitation process, the normal equivalent output voltage is still calculated based on the excitation current change rate, wherein the excitation winding inductance voltage term L is retained. f di f / dt; When the superconducting excitation winding generates an additional resistance voltage, the rate of change of the excitation current decreases relative to the healthy operating condition, causing the normal equivalent modulation ratio to be lower than the actual equivalent modulation ratio, and generating a positive equivalent modulation ratio residual, based on which quench detection is performed.

10. A superconducting motor quench detection system, characterized in that, include: The signal acquisition module is used to acquire the actual output voltage of the excitation power supply, the DC bus voltage, and the excitation operating status. The calculation module is used to calculate the actual equivalent modulation ratio based on the actual output voltage of the pre-processed excitation power supply and the DC bus voltage, calculate the normal equivalent modulation ratio based on the excitation operating status and excitation circuit health parameters, and calculate the equivalent modulation ratio residual between the actual equivalent modulation ratio and the normal equivalent modulation ratio. The prediction module is used to predict and determine the trend of the equivalent modulation ratio residual; The early warning module is used to adaptively adjust the overrun criterion according to the excitation conditions, and output overrun early warning or protection command based on the overrun criterion.

11. A superconducting motor quench detection device, characterized in that, Including memory and processor; The memory is used to store program code and transmit the program code to the processor; The processor is configured to execute the timeout detection method according to any one of claims 1 to 9 according to the instructions in the program code.

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