A method for time-limit overcurrent protection of a floating crane system and related components thereof.

Abstract

This invention discloses a time-limited overcurrent protection method and related components for a floating crane system, relating to the field of overcurrent protection. By acquiring the operating current and current frequency of the transformer in the floating crane system, it determines whether the operating current exceeds a preset current and whether the current frequency exceeds a preset frequency. If both exceed the preset current and frequency, the preset time-limited overcurrent protection is triggered; otherwise, the preset time-limited overcurrent protection is blocked. Because overcurrent protection is determined by using both current and frequency, it avoids misjudging situations of high current and low frequency that may occur during normal operation as faults. This prevents the erroneous triggering of the time-limited overcurrent protection during normal operation of the floating crane system, further preventing damage to goods and economic losses.

Description

Technical Field

[0001] This invention relates to the field of overcurrent protection, and in particular to a time-limit overcurrent protection method for a floating crane system and related components. Background Technology

[0002] Ports typically have lifting systems for loading and unloading cargo. These systems consist of multiple floating cranes, each equipped with a crane motor, a rotary motor, and a luffing motor. These motors are usually powered by the same transformer. Since the motors in a floating crane generate a large current when they start up, when multiple cranes operate simultaneously, the simultaneous starting of multiple motors can lead to excessive current. Because this current is similar to the current when a motor experiences a short circuit, it may be mistakenly identified as a short circuit, triggering the floating crane system's time-limited overcurrent protection mechanism. This results in a non-faulty power outage of the entire floating crane system, potentially damaging cargo and causing economic losses. Summary of the Invention

[0003] The purpose of this invention is to provide a time-limited overcurrent protection method for a floating crane system and its related components, which can avoid misjudging a situation of high current and low frequency that may occur during normal operation as a fault, thereby avoiding the accidental triggering of time-limited overcurrent protection during normal operation of the floating crane system, and further avoiding damage to goods and economic losses.

[0004] To solve the above-mentioned technical problems, the present invention provides a time-limit overcurrent protection method for a floating crane system, comprising:

[0005] Obtain the operating current of the transformer in the floating crane system;

[0006] Determine the current frequency of the transformer in the floating crane system;

[0007] Determine whether the operating current is greater than a preset current and whether the current frequency is greater than a preset frequency;

[0008] If all values ​​are greater than the preset time limit overcurrent protection action is triggered;

[0009] Otherwise, the preset time limit overcurrent protection action will be blocked.

[0010] Preferably, determining the current frequency of the transformer in the floating crane system includes:

[0011] Obtain N maximum current values ​​and M minimum current values ​​of the transformer within a preset time period, where N and M are both positive integers;

[0012] The intrinsic mode function of the operating current is determined using N current maxima, M current minima, and the operating current.

[0013] The phase signal of the operating current is determined based on the intrinsic mode function;

[0014] The current frequency is determined based on the phase signal.

[0015] Preferably, before determining the phase signal of the operating current based on the intrinsic mode function, the method further includes:

[0016] Determine whether the difference between the number of current maxima and current minima in the intrinsic mode function and the number of zero-crossings of the operating current within the preset time period is less than a preset difference.

[0017] If so, proceed to the step of determining the phase signal of the operating current based on the intrinsic mode function;

[0018] If not, then the new intrinsic mode function of the operating current is determined using the N current maxima, the M current minima, and the intrinsic mode function.

[0019] Preferably, determining the intrinsic mode function of the operating current using N current maxima, M current minima, and the operating current includes:

[0020] Construct N maximum envelopes corresponding to the current maxima and M minimum envelopes corresponding to the current minima;

[0021] Determine the average curve between the maximum envelope and the minimum envelope;

[0022] The intrinsic mode function of the operating current is determined based on the average curve and the operating current value.

[0023] Preferably, before determining the intrinsic mode function of the operating current based on the average curve and the operating current value, the method further includes:

[0024] Determine whether the average curve is a curve representing a mean of zero;

[0025] If so, proceed to the step of determining the intrinsic mode function of the operating current based on the average curve and the operating current value;

[0026] If not, then reconstruct the maximum envelopes corresponding to the N current maxima and the minimum envelopes corresponding to the M current minima.

[0027] Preferably, constructing the maximum envelopes corresponding to the N current maxima and the minimum envelopes corresponding to the M current minima includes:

[0028] The envelope of the maximum current is obtained by connecting N current maxima using cubic spline fitting;

[0029] The envelope of the minimum current is obtained by connecting M minimum current values ​​using cubic spline fitting.

[0030] Preferably, before obtaining the N maximum current values ​​and M minimum current values ​​of the transformer within a preset time period, the method further includes:

[0031] Determine the working cycle of each floating crane in the floating crane system;

[0032] A preset time period is determined based on each of the aforementioned work cycles, and the length of the preset time period is N times the length of the aforementioned work cycle, where N is a positive integer greater than 2.

[0033] Preferably, after determining whether the operating current is greater than a preset current and whether the current frequency is greater than a preset frequency, the method further includes:

[0034] If the operating current is greater than the preset current and the current frequency is less than the preset frequency, then determine whether the operating current is greater than the preset current for a preset time period.

[0035] If so, the preset time limit overcurrent protection action will be triggered.

[0036] This application also provides a time-limit overcurrent protection device for a floating crane system, comprising:

[0037] Memory, used to store computer programs;

[0038] A controller is used to implement the steps of the time-limit overcurrent protection method for the floating crane system as described above when executing the computer program.

[0039] This application also provides a computer-readable storage medium storing a computer program, which, when executed by a processor, implements the steps of the time-limit overcurrent protection method for the floating crane system described above.

[0040] This invention provides a time-limited overcurrent protection method and related components for a floating crane system, relating to the field of overcurrent protection. By acquiring the operating current and current frequency of the transformer in the floating crane system, it determines whether the operating current exceeds a preset current and whether the current frequency exceeds a preset frequency. If both exceed the preset current and frequency, the preset time-limited overcurrent protection is triggered; otherwise, the preset time-limited overcurrent protection is blocked. Because overcurrent protection is determined by using both current and frequency, it avoids misjudging situations of high current and low frequency that may occur during normal operation as faults. This prevents the erroneous triggering of time-limited overcurrent protection during normal operation of the floating crane system, further preventing damage to goods and economic losses. Attached Figure Description

[0041] To more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings used in the prior art and embodiments will be briefly introduced below. Obviously, the 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.

[0042] Figure 1 A flowchart of a time-limit overcurrent protection method for a floating crane system provided in this application;

[0043] Figure 2 A flowchart of the working cycle of a floating crane is provided for this application;

[0044] Figure 3 This is a structural schematic diagram of a time-limit overcurrent protection device for a floating crane system provided in this application. Detailed Implementation

[0045] The core of this invention is to provide a time-limited overcurrent protection method for a floating crane system and its related components, which can avoid misjudging a situation of high current and low frequency that may occur during normal operation as a fault, thereby avoiding the accidental triggering of time-limited overcurrent protection during normal operation of the floating crane system, and further avoiding damage to goods and economic losses.

[0046] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0047] Please refer to Figure 1 , Figure 1 A flowchart of a time-limit overcurrent protection method for a floating crane system provided in this application includes:

[0048] S1: Obtain the operating current of the transformer in the floating crane system;

[0049] S2: Determine the current frequency of the transformer in the floating crane system;

[0050] S3: Determine whether the operating current is greater than the preset current and whether the current frequency is greater than the preset frequency; if both are greater, proceed to S4; otherwise, proceed to S5.

[0051] S4: Triggers the preset time limit overcurrent protection action;

[0052] S5: Lockout preset time limit overcurrent protection action.

[0053] A floating crane consists of multiple motors, including a hoisting motor, a rotary motor, and a luffing motor. Each motor starts and stops at different times within a working cycle of the floating crane to perform loading and unloading operations. Please refer to [the relevant documentation / reference]. Figure 2 , Figure 2 The flowchart of the working cycle of a floating crane provided in this application describes how, when goods need to be moved from point A to point B using the floating crane, such as moving goods from a cargo ship to land, if the default position of the floating crane is at point A, the floating crane first needs to lower its grab bucket to pick up the goods; after picking up the goods, the grab bucket rises back for subsequent movement; then the floating crane rotates around its own axis of rotation to move the goods from above point A to above point B; at this time, the grab bucket is lowered again to place the goods at point B; the grab bucket releases the goods and then rises back; finally, the floating crane rotates around its own axis of rotation again to return to its default position. The above steps constitute one working cycle of the floating crane's loading and unloading operations. In each step of one working cycle, the working time of each motor corresponding to the floating crane is different. For example, the lifting motor starts when the grab bucket begins to descend or begins to rise and stops when the descent or rise ends, while the rotation motor starts when the floating crane begins to rotate around its own axis of rotation and stops when the floating crane stops rotating around its own axis of rotation. It is evident that the starting and stopping times of the various motors in a floating crane are different. When multiple floating cranes in a lifting system are working simultaneously, multiple floating cranes may start rotating or raising their grab buckets at the same time. This will cause multiple motors to start simultaneously. Since the motors generate a large starting inrush current when they first start, the starting current may overlap, resulting in an excessive current in the transformer of the lifting system. This may lead to the system being mistakenly identified as a fault, causing an incorrect overcurrent protection action and resulting in a power outage of the floating crane. This could lead to serious economic losses such as damage to the cargo.

[0054] To address the aforementioned technical issues, this application considers that the total current generated by multiple floating cranes operating simultaneously under normal working conditions is approximately the same as the current when one floating crane malfunctions. Relying solely on whether the transformer's operating current is excessive to trigger overcurrent protection could easily misjudge normal working conditions as faults, leading to incorrect overcurrent protection actions. Therefore, in addition to determining the transformer's operating current, it is also necessary to determine the current frequency. The current frequency of a floating crane operating normally differs significantly from that during a fault. When a floating crane is operating normally, even if multiple floating cranes operate simultaneously, causing excessive current, the transformer's current frequency will remain within the normal range. However, when a floating crane malfunctions, not only will the current be excessive, but the current frequency will also increase. Based on this, the application uses both operating current and current frequency for judgment. Only when both the current frequency and operating current are excessive will a preset time-limited overcurrent protection action be executed, thus avoiding misjudging situations where the operating current is excessive but the current frequency is normal as faults.

[0055] To accurately determine the preset current and frequency, a simulated working scenario and a simulated fault scenario can be pre-established. In the simulated working scenario, different working cycles are set for each floating crane in the floating crane system, so that these floating cranes simulate the situation of each floating crane working individually in the actual scenario, and the operating current and frequency of the transformer are detected in real time to obtain the operating current range and current frequency range of the transformer under normal working conditions. Similarly, in the simulated fault scenario, combined with the working conditions of the floating cranes in the simulated working scenario, multiple sub-scenarios can be set up to correspond to the failure of each floating crane and the failure at different time points, and the operating current and current frequency of the transformer are detected to obtain the operating current range and current frequency range of the transformer when different floating cranes fail and when failures occur at different time points. Furthermore, by establishing multiple simulated working scenarios and multiple simulated fault scenarios, accurate operating current ranges and current frequency ranges can be obtained. Finally, based on the ranges under normal working conditions and the ranges under fault conditions, accurate preset current and preset frequency can be determined.

[0056] In summary, by acquiring the operating current and frequency of the transformer in the floating crane system, and then determining whether the operating current exceeds a preset current and whether the current frequency exceeds a preset frequency, the preset time-limited overcurrent protection is triggered. Otherwise, the preset time-limited overcurrent protection is blocked. Because overcurrent protection is determined using both current and frequency, it avoids misjudging situations of high current and low frequency occurring during normal operation as faults. This prevents the erroneous triggering of time-limited overcurrent protection during normal operation of the floating crane system, further preventing damage to cargo and resulting economic losses.

[0057] Based on the above embodiments:

[0058] As a preferred embodiment, determining the current frequency of the transformer in the floating crane system includes:

[0059] Obtain N maximum current values ​​and M minimum current values ​​of the transformer within a preset time period, where N and M are both positive integers;

[0060] The intrinsic mode function of the operating current is determined using N current maxima, M current minima, and the operating current.

[0061] The phase signal of the operating current is determined based on the intrinsic mode function;

[0062] The current frequency is determined based on the phase signal.

[0063] To determine the current frequency of the transformer, this application uses the intrinsic mode function of the operating current to determine the current frequency. Specifically, the time corresponding to the simulated working scenario and the simulated fault scenario can be used as a preset time period. Multiple simulated working scenarios and simulated fault scenarios are traversed in advance to determine the current maximum and current minimum values ​​in each simulated scenario. In practical applications, the current maximum and current minimum values ​​in the original current signal of the transformer can be obtained based on the determined current maximum and current minimum values ​​in the simulated scenarios. Then, at the current moment, multiple current maximum and current minimum values ​​from a period of time before the current moment are used, that is, N current maximum values ​​and M current minimum values ​​within the preset time period, plus the original current signal of the transformer itself, to determine the intrinsic mode function of the operating current.

[0064] When determining the phase signal through the eigenmode function, specifically, let the eigenmode function be imf(t), where t is the current time and τ is the integration variable. Performing a time-frequency domain transformation on the eigenmode function, we have:

[0065]

[0066] c(t) is the time-frequency domain transformed imf(t). Based on this, and further analyzing c(t), we have:

[0067]

[0068] Where a(t) is the amplitude signal and θ(t) is the phase signal, specifically:

[0069]

[0070]

[0071] Finally, when calculating the current frequency, it is calculated based on the phase signal θ(t), specifically:

[0072]

[0073] ω(t) is the current frequency. Based on this, the current frequency of the transformer can be accurately determined using the phase signal.

[0074] As a preferred embodiment, before determining the phase signal of the operating current based on the intrinsic mode function, the method further includes:

[0075] Determine whether the difference between the number of current maxima and current minima in the intrinsic mode function and the number of zero crossings of the operating current within a preset time period is less than a preset difference.

[0076] If so, proceed to the step of determining the phase signal of the operating current based on the intrinsic mode function;

[0077] If not, then the new intrinsic mode function of the operating current is determined by using the N current maxima, M current minima, and intrinsic mode functions.

[0078] To ensure the accuracy of the intrinsic mode function (IMF), this application requires that some parameters of the IMF meet specific requirements before it can be used. Specifically, since the IMF is obtained through current maxima and minima, the acquisition of extrema may result in more than N extrema due to low accuracy. Therefore, it is necessary to determine the difference between the number of extrema and the number of zero-crossings of the current signal. Under normal circumstances, since the current is a periodically changing waveform, it needs to pass through a zero-crossing before reaching each extremum. Therefore, the number of extrema should be consistent with the number of zero-crossings. Based on this, a preset difference can be set to 1. When the difference between the number of extrema and the number of zero-crossings of the current is less than or equal to 1, the IMF meets the requirements; otherwise, it does not meet the requirements.

[0079] Furthermore, considering that multiple eigenmode functions may be calculated in practical applications, the first eigenmode function can be determined by comparing the eigenmode function obtained this time with the eigenmode function obtained last time. Specifically, let the eigenmode function obtained this time be imf1(t), and the eigenmode function obtained last time be imf2(t), then:

[0080]

[0081] If the final arithmetic sum S is less than the preset constant ε, then imf1(t) can be used as the first eigenmode function.

[0082] When the intrinsic mode functions (IMFs) do not meet the requirements, new IMFs need to be determined. Since the IMFs are calculated using N current maxima, M current minima, and the operating current itself, the previous IMF can be used to replace the operating current. Then, the extreme points are redefined and recalculated to obtain new IMFs. This process is repeated until the IMFs meet the requirements, allowing subsequent calculations to be performed using compliant IMFs. This ensures the accuracy of the IMFs.

[0083] As a preferred embodiment, the intrinsic mode function of the operating current is determined using N current maxima, M current minima, and the operating current, including:

[0084] Construct the maximum envelopes corresponding to N current maxima and the minimum envelopes corresponding to M current minima;

[0085] Determine the average curve between the maximum and minimum envelopes;

[0086] The intrinsic mode function of the operating current is determined based on the average curve and the operating current value.

[0087] To obtain the intrinsic mode functions, this application connects the maxima and minima in a certain order, such as time sequence, to obtain the maximum and minimum envelopes of the operating current. This ensures that all maxima and minima lie on the maximum and minimum envelopes, thus determining the current range of the operating current. Let the maximum envelope be Xmax(t) and the minimum envelope be Xmin(t). The average curve between the two envelopes is calculated as follows:

[0088]

[0089] Where m(t) is the average curve, and when determining the intrinsic mode functions, we have:

[0090] imf(t) = x(t) - m(t)

[0091] Where imf(t) is the intrinsic mode function, and x(t) is the original current signal of the operating current. At this point, imf(t) can be used to describe x(t). First, subtract imf(t) from x(t) to obtain the residual sequence r(t). Then, replace x(t) with r(t) and perform the subtraction of imf(t) from x(t) again to obtain a new r(t). Repeat this step multiple times until the final r(t) is a monotonic function or a constant less than a preset value. At this point, the earliest x(t) can be expressed as:

[0092]

[0093] Based on this, the intrinsic mode functions can be obtained simply and accurately using the average curve method.

[0094] As a preferred embodiment, before determining the intrinsic mode function of the operating current based on the average curve and the operating current value, the method further includes:

[0095] Determine whether the average curve represents a curve with a mean of zero;

[0096] If so, proceed to the step of determining the intrinsic mode function of the operating current based on the average curve and the operating current value;

[0097] If not, then reconstruct the maximum envelopes corresponding to the N current maxima and the minimum envelopes corresponding to the M current minima.

[0098] To ensure the accuracy of the intrinsic mode functions (EMFs), this application considers the current as a periodically changing waveform, typically resembling a sine wave. Its extreme characteristics are that the absolute value of the maximum equals the absolute value of the minimum; therefore, the sum of the maximum and minimum values ​​is zero. Based on this, since points on the maximum envelope are all maximum points, and points on the minimum envelope are all minimum points, the average curve obtained should represent a stable current of zero—that is, a curve parallel to the X-axis (time) and with the Y-axis (current value) at zero. If the actual obtained average curve does not represent a zero mean, it indicates that an incorrect extreme point was obtained when acquiring the current maximum or minimum. In this case, it is necessary to reconstruct the envelope and re-determine the average curve to ensure the accuracy of the subsequently obtained EMFs.

[0099] As a preferred embodiment, constructing the maximum envelope corresponding to N current maxima and the minimum envelope corresponding to M current minima includes:

[0100] By using cubic spline fitting to connect N current maxima, the maximum envelope is obtained;

[0101] By using cubic spline fitting to connect M current minima, the minimum envelope is obtained.

[0102] When constructing the envelope, the original current signal of the transformer can be considered as a sine function on a coordinate system. Obtaining N current maxima and M current minima is equivalent to obtaining discrete points on the coordinate system. To draw a maximum and minimum envelope, it is necessary to connect these extreme points. However, considering the potential for current fluctuations in practical applications, interpolation methods often fail to accurately represent the actual current situation. Therefore, the envelope may not necessarily pass through all extreme points, but rather approximate them in some way; this method is called fitting. Thus, cubic spline functions can be used to fit the extreme points. The function values, first derivative, and second derivative of a cubic spline function are continuous at each extreme point, exhibiting clear geometric and mechanical significance. Furthermore, the cubic spline fitting method results in smooth and symmetrical continuity at each extreme point; that is, the spline function at each extreme point is a small arc with the same radius of curvature at each extreme point. Therefore, since cubic spline fitting is simple to construct, easy to use, and accurate in fitting, and can approximate complex shapes in curve fitting and interactive curve design, it can accurately obtain the maximum and minimum envelopes.

[0103] As a preferred embodiment, before obtaining the N maximum current values ​​and M minimum current values ​​of the transformer within a preset time period, the method further includes:

[0104] Determine the working cycle of each floating crane in the floating crane system;

[0105] The preset time period is determined based on each work cycle. The length of the preset time period is N times the work cycle, where N is a positive integer greater than 2.

[0106] To obtain accurate current maximum and minimum values, this application determines the required preset time period for acquiring these values ​​based on the working cycle of each floating crane. Specifically, when determining the preset time period, first, the duration of one complete working cycle for each floating crane is determined, i.e., the time required for each floating crane to pick up cargo and finally lower and reset the cargo. Then, within one complete working cycle, the start and stop times of various motors, such as the crane motor or rotary motor, corresponding to that floating crane are determined. These start and stop times are calculated using the start time of the complete working cycle as zero, i.e., determining how long after the start of the complete working cycle these motors will start and how long after they will stop. Considering that the motor start and stop times in each complete working cycle in actual application scenarios will deviate from the standard start and stop times, this deviation can be represented by a normal distribution with an expected value of 0 and a standard deviation of te. Specifically:

[0107]

[0108] Where f(xt; σt) represents the deviation, σt is the range of the time deviation, and xt is the actual random deviation value of the motor. Based on this, the start-up and stop-down time ranges of each motor in each floating crane can be determined, which is equivalent to determining the approximate start-up and stop-down times of each motor after the start of the floating crane's complete working cycle. Multiple time nodes can be set according to this time range to correspond to the start-up and stop times of each motor. Specifically:

[0109] ti = tin + xt

[0110] Where xt is the random deviation value mentioned above, ti is the possible time node of the motor in actual application, and tin is the standard time node corresponding to that time node.

[0111] After determining the complete working cycle of each floating crane, a working scenario library for the entire lifting system under normal operating conditions is constructed based on the complete working cycles of each floating crane. Specifically, assuming the lifting system contains n floating cranes, the total number of working scenarios to be generated (randomly combined) is determined to be q. Then, the number of floating cranes in operation for each scenario is generated according to a uniform distribution U(0~n), forming a quantity matrix [q, n-1]. Based on the working cycle of a single floating crane, the total duration of each scenario is set. This total duration needs to cover multiple complete working cycles of each floating crane to ensure the accuracy of the scenario simulation. Furthermore, the shorter the total duration, the higher the efficiency of the scenario simulation; the longer the total duration, the wider the actual situation the scenario can cover. This application does not limit the actual total duration. Then, in each scenario, the start and stop events of each motor are generated, and the first start time tj of each floating crane is generated according to a uniform distribution U(0~t), where t is the total duration. By setting each floating crane and performing scenario simulations multiple times, a complete working scenario library is obtained.

[0112] In addition, a fault scenario library can be constructed. Based on the number of power supply buses nb corresponding to each floating crane, the fault bus corresponding to each working scenario is generated according to the uniform distribution U (0~nb) on the basis of the working scenario library, and the occurrence time of each fault is generated according to the uniform distribution U (0~t), thereby simulating the possible time points and locations of each fault in actual applications.

[0113] Based on the working scenario library and the fault scenario library, the preset time period can be accurately calculated, thereby obtaining the accurate current maximum and current minimum values.

[0114] In a preferred embodiment, after determining whether the operating current is greater than a preset current and whether the current frequency is greater than a preset frequency, the method further includes:

[0115] If the operating current is greater than the preset current and the current frequency is less than the preset frequency, then determine whether the operating current is greater than the preset current throughout the preset time period.

[0116] If so, the preset time limit overcurrent protection action will be triggered.

[0117] To protect the transformer and the entire lifting system, this application, while indicating that no floating crane malfunctions and the high current is simply due to multiple motors starting simultaneously, suggests that the operating current exceeds the preset current and the current frequency is below the preset frequency, the transformer's temperature will rapidly increase with the current. Therefore, even without a fault, the transformer still faces risks after prolonged exposure to high current. Based on this, after determining that the operating current exceeds the preset current and the current frequency is below the preset frequency, the duration of this excessive current is monitored in real time. If the current remains above the preset current for a continuous period, it indicates a potential risk, necessitating the triggering of the preset time-limited overcurrent protection. For example, the preset duration can be set to 5 seconds. If, after determining that the operating current exceeds the preset current and the current frequency is below the preset frequency, the operating current remains above the preset current for the next 5 seconds, the preset time-limited overcurrent protection should be triggered to prevent potential risks. This approach better protects the transformer and the entire lifting system.

[0118] Please refer to Figure 3 , Figure 3 A schematic diagram of a time-limit overcurrent protection device for a floating crane system provided in this application includes:

[0119] Memory 21 is used to store computer programs;

[0120] The controller 22 is used to implement the steps of the time-limit overcurrent protection method for the floating crane system as described above when executing a computer program.

[0121] For a detailed description of the time-limited overcurrent protection device for a floating crane system provided in this application, please refer to the embodiments of the time-limited overcurrent protection method for the floating crane system described above. This application will not repeat the details here.

[0122] This application also provides a computer-readable storage medium storing a computer program, which, when executed by a processor, implements the steps of the time-limit overcurrent protection method for the floating crane system described above.

[0123] For a detailed description of the computer-readable storage medium provided in this application, please refer to the embodiments of the time-limit overcurrent protection method for the floating crane system described above; further details will not be repeated here.

[0124] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on its differences from other embodiments. Similar or identical parts between embodiments can be referred to interchangeably. For the apparatus disclosed in the embodiments, since it corresponds to the method disclosed in the embodiments, the description is relatively simple; relevant parts can be referred to the method section.

[0125] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A time-limit overcurrent protection method for a floating crane system, characterized in that, include: Obtain the operating current of the transformer in the floating crane system; Determine the current frequency of the transformer in the floating crane system; Determine whether the operating current is greater than a preset current and whether the current frequency is greater than a preset frequency; If all values ​​are greater than the preset time limit overcurrent protection action is triggered; Otherwise, the preset time limit overcurrent protection will be disabled. Determining the current frequency of the transformer in the floating crane system includes: Obtain N maximum current values ​​and M minimum current values ​​of the transformer within a preset time period, where N and M are both positive integers; The intrinsic mode function of the operating current is determined using N current maxima, M current minima, and the operating current. The phase signal of the operating current is determined based on the intrinsic mode function; The current frequency is determined based on the phase signal.

2. The time-limit overcurrent protection method for a floating crane system as described in claim 1, characterized in that, Before determining the phase signal of the operating current based on the intrinsic mode function, the method further includes: Determine whether the difference between the number of current maxima and current minima in the intrinsic mode function and the number of zero-crossings of the operating current within the preset time period is less than a preset difference. If so, proceed to the step of determining the phase signal of the operating current based on the intrinsic mode function; If not, then the new intrinsic mode function of the operating current is determined using the N current maxima, the M current minima, and the intrinsic mode function.

3. The time-limit overcurrent protection method for a floating crane system as described in claim 1, characterized in that, Determining the intrinsic mode function of the operating current using N current maxima, M current minima, and the operating current includes: Construct N maximum envelopes corresponding to the current maxima and M minimum envelopes corresponding to the current minima; Determine the average curve between the maximum envelope and the minimum envelope; The intrinsic mode function of the operating current is determined based on the average curve and the operating current value.

4. The time-limit overcurrent protection method for a floating crane system as described in claim 3, characterized in that, Before determining the intrinsic mode function of the operating current based on the average curve and the operating current value, the method further includes: Determine whether the average curve is a curve representing a mean of zero; If so, proceed to the step of determining the intrinsic mode function of the operating current based on the average curve and the operating current value; If not, then reconstruct the maximum envelopes corresponding to the N current maxima and the minimum envelopes corresponding to the M current minima.

5. The time-limit overcurrent protection method for a floating crane system as described in claim 3, characterized in that, Constructing the maximum envelopes corresponding to N current maxima and the minimum envelopes corresponding to M current minima, including: The envelope of the maximum current is obtained by connecting N current maxima using cubic spline fitting; The envelope of the minimum current is obtained by connecting M minimum current values ​​using cubic spline fitting.

6. The time-limit overcurrent protection method for a floating crane system as described in claim 1, characterized in that, Before obtaining the N maximum current values ​​and M minimum current values ​​of the transformer within a preset time period, the process also includes: Determine the working cycle of each floating crane in the floating crane system; A preset time period is determined based on each of the aforementioned work cycles, and the length of the preset time period is N times the length of the aforementioned work cycle, where N is a positive integer greater than 2.

7. The time-limit overcurrent protection method for a floating crane system as described in any one of claims 1 to 6, characterized in that, After determining whether the operating current is greater than a preset current and whether the current frequency is greater than a preset frequency, the method further includes: If the operating current is greater than the preset current and the current frequency is less than the preset frequency, then determine whether the operating current is greater than the preset current for a preset time period. If so, the preset time limit overcurrent protection action will be triggered.

8. A time-limit overcurrent protection device for a floating crane system, characterized in that, include: Memory, used to store computer programs; A controller is configured to implement the steps of the time-limit overcurrent protection method for a floating crane system as described in any one of claims 1 to 7 when executing the computer program.

9. A computer-readable storage medium, characterized in that, The computer-readable storage medium stores a computer program that, when executed by a processor, implements the steps of the time-limit overcurrent protection method for a floating crane system as described in any one of claims 1 to 7.

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