A crane energy recovery safety control method

Abstract

This invention discloses a crane energy recovery safety control method, comprising: acquiring instantaneous voltage values ​​of the recovery circuit and instantaneous current values ​​of the power system, and calculating instantaneous feedback power; monitoring voltage and current waveform characteristics when the power exceeds the fluctuation range, and determining the main system interference risk when a transient voltage drop or preset current distortion is detected; responding to an emergency braking command under interference risk, and generating a configuration command to improve electrical isolation based on power amplitude iteration optimization; after execution, monitoring the energy status based on power accumulation, and activating the discharge backup channel when voltage saturation or abnormal temperature rise rate is detected; generating and executing a conduction timing sequence based on the discharge current decay slope and the safe operating area boundary, and outputting a collaborative control command after monitoring the power to fall back to the safe range. This invention achieves proactive management of discharge overload while ensuring the stability of the main system through power-guided waveform diagnosis, isolation optimization, and discharge timing control.

Description

Technical Field

[0001] This invention relates to the field of crane energy recovery technology, and in particular to a crane energy recovery safety control method. Background Technology

[0002] As an indispensable heavy material handling equipment in modern industry and construction, the energy consumption of cranes has always been a key indicator for measuring their economic efficiency and environmental protection. Currently, crane systems with energy recovery capabilities are gradually being applied. Their basic principle lies in converting the regenerative potential energy generated during the descent or braking of the lifting mechanism into electrical energy and storing or feeding it back, thereby replacing the traditional method of directly dissipating this energy as heat through braking resistors. Theoretically, this technology helps reduce the overall operating cost of the equipment and decrease carbon emissions.

[0003] However, under the high-frequency starting and braking conditions of cranes, the actual operational safety and reliability of energy recovery systems face severe challenges. Existing technical solutions generally focus on improving energy conversion efficiency or storage density, but lack effective dynamic management methods to address the electrical coupling interference between the recovery circuit and the crane's original power system. Specifically, during energy feedback, if the electrical isolation between the recovery circuit and the main drive bus is inadequate, harmonics and transient impacts contained in the regenerated current can easily propagate back to the power system, causing unexpected transient drops in DC bus voltage or distortion of the current waveform. This interference is not noticeable during normal stable operation, but when the crane performs emergency braking or frequent jogging operations, the energy flow changes drastically, and an imperfect isolation mechanism amplifies the risk of main system control instability.

[0004] Furthermore, existing energy discharge management often employs passive overvoltage protection logic, directly activating the discharge circuit upon detecting a voltage exceeding a fixed threshold. This crude control strategy fails to accurately identify the overload tendency of the discharge circuit itself, such as voltage saturation of the discharge resistor due to continuous high load operation, or abnormal temperature rise rates of energy storage elements due to excessively high charge / discharge rates. Once the thermal management and electrical withstand capabilities of the discharge path reach their limits, the accumulated energy cannot be dissipated in time, potentially leading not only to equipment shutdown but also to overheating damage or even safety accidents.

[0005] Therefore, how to ensure efficient electrical isolation between the recovery circuit and the main system, and achieve intelligent activation and precise control of the energy release path, under complex transient conditions, especially when dealing with emergency braking and high-frequency impacts, has become a technical bottleneck that urgently needs to be overcome in this field. Summary of the Invention

[0006] Therefore, the technical problem to be solved by the present invention is to overcome the shortcomings of the prior art in high-frequency starting and braking and emergency conditions, where the main system is affected by voltage transient drops and current waveform distortion due to imperfect electrical isolation between the recovery circuit and the power system. Furthermore, traditional discharge management cannot identify overload tendencies such as voltage saturation and abnormal temperature rise in the discharge circuit, which can easily lead to safety accidents. The present invention provides a crane energy recovery safety control method that can dynamically optimize isolation parameters by triggering waveform characteristic events and control the timing of the backup channel according to the discharge current decay slope, thereby achieving safe and reliable active management of discharge overload while ensuring the stability of the main system.

[0007] To address the aforementioned technical problems, this invention provides a crane energy recovery safety control method, comprising the following steps: Real-time acquisition of instantaneous values ​​of recovery circuit voltage and power system current during crane operation, and calculation of instantaneous feedback power; When the instantaneous feedback power exceeds the preset power fluctuation range, the waveform characteristics of the instantaneous voltage value and the waveform characteristics of the instantaneous current value are monitored in real time. In response to the detection of transient drop characteristics in the waveform of the instantaneous voltage value or preset distortion characteristics in the waveform of the instantaneous current value, it is determined that there is a risk of interference to the main system. When a risk of interference to the main system is determined, in response to the received emergency braking trigger command, the control parameters of the recovery loop are iteratively optimized and adjusted according to the current amplitude of the instantaneous feedback power to generate an isolation configuration adjustment command for improving electrical isolation. After executing the isolation configuration adjustment command, the energy accumulation status in the recovery loop is monitored based on the cumulative result of the instantaneous feedback power within the preset time window. In response to the detection of voltage saturation characteristics or abnormal temperature rise rate characteristics of the energy storage element that characterize the overload tendency of the discharge loop, the preset energy discharge backup channel is activated. Obtain the conduction status feedback of the backup energy discharge channel, and generate an energy discharge execution sequence containing the conduction timing of the discharge path based on the actual attenuation slope of the discharge current and the preset safe working area boundary conditions; The system executes an energy discharge sequence and monitors in real time whether the instantaneous feedback power falls back to the preset safety range to verify the safety of the current energy recovery management process. Finally, it outputs isolation and discharge execution commands to control the coordinated operation of the main system and the recovery loop.

[0008] In one embodiment of the present invention, the preset power fluctuation range is determined according to the rated power of the power system, and the upper limit of the power fluctuation range is positively correlated with the rated power. The power fluctuation range is also corrected based on the capacitance value of the DC bus capacitor in the recovery circuit. The larger the capacitance value of the DC bus capacitor, the greater the positive correction to the upper limit of the power fluctuation range.

[0009] In one embodiment of the present invention, in response to detecting a transient drop in the waveform of the instantaneous voltage value, a determination is made that there is a risk of interference to the main system, including: The amplitude of the instantaneous voltage value is continuously monitored over multiple consecutive sampling periods; When the amplitude at the current sampling moment is detected to decrease compared to the amplitude at the previous sampling moment, and the decrease exceeds the preset allowable drop rate, and the amplitude after the decrease is lower than the specified proportion of the rated operating voltage of the recovery circuit, a transient drop characteristic is confirmed to have occurred.

[0010] In one embodiment of the present invention, in response to detecting a preset distortion characteristic in the waveform of the instantaneous current value, a risk of interference to the main system is determined, including: Harmonic components are separated from the waveform of the instantaneous current value within a preset observation window to obtain the amplitude of the fundamental component and the amplitude of each harmonic component. According to the formula: The waveform distortion ratio R is calculated. in, I1 is the sum of the amplitudes of all harmonic components, and I1 is the amplitude of the fundamental component. If the waveform distortion ratio R is greater than the preset upper limit of distortion, then the preset distortion feature is confirmed to have occurred.

[0011] In one embodiment of the present invention, the control parameters of the recovery loop are iteratively optimized and adjusted based on the current amplitude of the instantaneous feedback power to generate an isolation configuration adjustment instruction for improving electrical isolation, including: Multiple sets of candidate parameter combinations, including switching frequency adjustment and duty cycle limit values, are pre-set; Using the current amplitude of instantaneous feedback power as input, the main system's suppression performance data against energy backflow interference under each set of candidate parameter combinations are obtained sequentially. From the current candidate parameter combinations, select the parameter combination that has the best suppression performance data as the preferred combination; The parameters in the preferred combination are numerically cross-substituted and randomly fine-tuned to generate a new set of candidate parameter combinations; Repeat the process of acquiring suppression performance data, selecting the best combination, and generating a new set of candidate parameter combinations until the number of repetitions reaches the preset round limit. The final selected optimal combination is converted into isolation configuration adjustment instructions for driving the power devices in the recycling loop.

[0012] In one embodiment of the present invention, monitoring the energy accumulation state in the recovery loop based on the cumulative result of instantaneous feedback power within a preset time window includes: The instantaneous feedback power at each sampling moment within the preset time window is accumulated to obtain the energy accumulation. According to the formula: The cumulative energy E is calculated, where P(t) k Let ΔT be the instantaneous feedback power at the k-th sampling time. s The sampling period is N, and the number of sampling points within the preset time window is N. If the energy accumulation E is greater than the preset energy accumulation upper limit, it is determined that the energy accumulation state in the recovery loop has an overload tendency.

[0013] In one embodiment of the present invention, in response to detecting a voltage saturation characteristic characterizing the overload tendency of the discharge circuit, a preset energy discharge backup channel is activated, including: Monitor the voltage drop across the discharge resistor connected in series with the discharge circuit; When the voltage drop across the bleed resistor remains at the preset maximum limit voltage value and the dwell time at the maximum limit voltage value exceeds the preset allowable duration, voltage saturation characteristics are confirmed to be detected. In response to the confirmation of a detected voltage saturation characteristic, a drive level signal is output to turn on the backup power switching device in the energy discharge backup channel.

[0014] In one embodiment of the present invention, in response to detecting abnormal temperature rise rate characteristics of the energy storage element, a preset energy discharge backup channel is activated, including: The temperature change of the surface of the energy storage element's outer casing between two consecutive sampling times is obtained using a temperature sensor; Obtain the change in instantaneous feedback power of the recovery loop between two consecutive sampling times; The temperature rise efficiency ratio η is calculated using the formula η=ΔT / ΔP, where ΔT is the temperature change and ΔP is the change in instantaneous feedback power. If the temperature rise efficiency ratio η is greater than the preset allowable temperature rise ratio, then an abnormal temperature rise rate characteristic is confirmed to have been detected.

[0015] In one embodiment of the present invention, an energy discharge execution sequence including the conduction timing of the discharge path is generated based on the actual attenuation slope of the discharge current and the preset safe operating area boundary conditions, including: At the initial moment after activating the backup energy discharge channel, record the peak current value in the discharge circuit; After a preset time interval, the real-time current value in the discharge circuit is recorded again. According to the formula k=【I peak The actual attenuation slope k is obtained by calculating -I(t1) / Δt, where I peakI(t1) is the peak current value, I(t1) is the real-time current value, and Δt is the preset time interval. Compare the actual attenuation slope k with the minimum permissible attenuation slope specified in the boundary conditions of the safe working area; If the actual decay slope is less than the minimum allowable decay slope, a forced shutdown interval is inserted into the energy discharge execution sequence.

[0016] In one embodiment of the present invention, real-time monitoring of whether the instantaneous feedback power falls back to a preset safe range includes: Obtain the real-time value of the instantaneous feedback power after the execution of the isolation and discharge command; Determine whether the real-time value of the instantaneous feedback power is within the preset safety range: If the real-time value is within the preset safety range, then maintain the current output state of the isolation and release execution command; If the real-time value is higher than the preset safety range, the switching frequency adjustment amount in the isolation configuration adjustment command will be corrected to a reduced direction, and the conduction period in the energy discharge execution sequence will be shortened simultaneously. If the real-time value is lower than the preset safety range, the current output state of the isolation and release execution command will be maintained, and the current control parameters will be recorded as a reference parameter group for subsequent starting and braking conditions.

[0017] The technical solution of the present invention has the following advantages over the prior art: The crane energy recovery safety control method described in this invention calculates instantaneous feedback power by real-time acquisition of instantaneous voltage and current values, monitors waveform characteristics to determine the main system interference risk when the power exceeds the range, adjusts control parameters to improve isolation in response to emergency braking commands, monitors energy accumulation status to activate the discharge backup channel, generates a discharge execution sequence and verifies safety, effectively solves the problems of dynamic electrical coupling interference and discharge circuit overload, significantly improves the safety and reliability of the crane energy recovery system, effectively avoids the main system interference risk and discharge circuit overload tendency, ensures stable operation under emergency braking and high-frequency impact conditions, thereby reducing equipment damage and unplanned downtime risks. Attached Figure Description

[0018] To make the content of this invention easier to understand, the invention will be further described in detail below with reference to specific embodiments and accompanying drawings, wherein: Figure 1 This is a flowchart of the steps of the crane energy recovery safety control method of the present invention; Figure 2 This is a flowchart of the steps in this invention to determine the risk of interference to the main system; Figure 3This is a flowchart illustrating the steps of iteratively optimizing and adjusting the control parameters of the recycling loop according to the present invention. Figure 4 This is a flowchart of the steps for monitoring the energy accumulation state in the recovery loop according to the present invention; Figure 5 This is a flowchart of the steps for activating the preset energy release backup channel in this invention; Figure 6 This is a flowchart of the steps in the present invention to generate an energy discharge execution sequence that includes the discharge path conduction timing. Detailed Implementation

[0019] The present invention will be further described below with reference to the accompanying drawings and specific embodiments, so that those skilled in the art can better understand and implement the present invention. However, the embodiments described are not intended to limit the present invention.

[0020] Reference Figure 1 As shown, this invention proposes a safety control method for energy recovery in cranes, representing a systematic improvement to address the pain points of existing technologies. Firstly, it collects the instantaneous voltage values ​​of the recovery circuit and the instantaneous current values ​​of the power system in real time, and then calculates the instantaneous feedback power through multiplication. This physical quantity accurately reflects the real-time intensity of energy return, providing a unified and precise benchmark for all subsequent judgments and adjustments.

[0021] Furthermore, this invention does not rely on a single voltage threshold for protection. Instead, it uses the instantaneous feedback power exceeding a preset fluctuation range as a precondition. Under this condition, it monitors the waveform characteristics of voltage and current in real time, focusing on detecting whether the voltage waveform exhibits transient drop characteristics or whether the current waveform exhibits preset distortion characteristics. This event-triggered mechanism based on physical waveform characteristics can accurately capture electrical coupling interference caused by inadequate isolation. Compared to traditional threshold comparisons, it has a faster response speed and stronger anti-interference capability, and can determine the existence of main system interference risk at the nascent stage of interference generation.

[0022] It should be noted that in practical applications, the preset power fluctuation range is determined based on the crane's design parameters, the electrical system's tolerance, and operational experience. This represents the power range within which the system can operate stably and safely. If the preset power fluctuation range fails to fully consider the actual operating characteristics of the crane's power system and the energy storage capacity of the recovery circuit, it may lead to inaccurate judgment of instantaneous feedback power fluctuations, thus affecting the timeliness and accuracy of risk identification. For example, a fixed power fluctuation range may not be suitable for power systems with different rated power, nor may it reflect the buffering capacity of the DC bus capacitor in the recovery circuit for power fluctuations, potentially leading to misjudgments or omissions. Therefore, this embodiment further proposes a scheme for dynamically adjusting the preset power fluctuation range: the preset power fluctuation range is determined based on the rated power of the power system, and the upper limit of the power fluctuation range is positively correlated with the rated power; the power fluctuation range is also corrected based on the capacitance value of the DC bus capacitor in the recovery circuit, with a larger DC bus capacitor value resulting in a greater positive correction to the upper limit of the power fluctuation range.

[0023] The rated power of a crane's power system is a crucial indicator of its overall energy handling capacity. During crane operation, the range of power fluctuations the power system can withstand is typically directly related to its rated power. A system with a higher rated power exhibits stronger tolerance and buffering capabilities against instantaneous power fluctuations; therefore, the upper limit of its permissible power fluctuation range should be correspondingly higher. This positive correlation can be established by consulting the technical specifications provided by the power system manufacturer, conducting system performance tests, or fitting parameters based on empirical models. For example, the upper limit of the power fluctuation range can be set as a percentage of the rated power, or determined through a linear or nonlinear functional relationship.

[0024] The DC bus capacitor in the recovery circuit is mainly used to smooth DC voltage, absorb instantaneous power fluctuations, and provide energy buffering. The larger the capacitor value, the stronger its energy storage capacity, and the more significant its absorption and buffering effect on instantaneous power fluctuations. This results in smaller transient changes in voltage and current when the system withstands the same power fluctuations, leading to higher system stability. Therefore, the DC bus capacitor value should be taken into consideration when determining the power fluctuation range. When the DC bus capacitor value is large, the system's tolerance to power fluctuations increases, allowing for a positive correction to the upper limit of the power fluctuation range—that is, appropriately relaxing the upper limit—to avoid unnecessary risk misjudgments. This correction can be achieved through preset correction coefficients, lookup tables, or dynamic models based on the capacitor's charging and discharging characteristics.

[0025] When the risk is confirmed and an emergency braking trigger command is received simultaneously, this method does not immediately cut off energy recovery. Instead, it iteratively optimizes the control parameters of the recovery loop based on the current amplitude of the instantaneous feedback power, dynamically generating configuration commands to improve electrical isolation. The core value of this logic lies in its recognition that energy recovery and system safety are not absolutely contradictory under emergency conditions. By using the real-time power amplitude as the optimization benchmark, it can accurately match the isolation level required by the current energy impact intensity, thus avoiding interference from energy backflow to the main system braking while maximizing the preservation of recovery efficiency.

[0026] At the energy discharge management level, this invention introduces an active monitoring mechanism for the health status of the discharge circuit itself. After executing the isolation configuration adjustment command, this method monitors the energy accumulation status based on the cumulative result of the instantaneous feedback power within a preset time window. This cumulative amount directly corresponds to the total energy load that the discharge circuit needs to bear. Furthermore, it pays particular attention to voltage saturation characteristics or abnormal temperature rise rate characteristics of energy storage elements that characterize the overload tendency of the discharge circuit. This judgment method directly corresponds to the boundary conditions of the physical limits of the discharge components, rather than simply comparing current magnitudes. When the above overload tendency characteristics are detected, the system actively activates the preset energy discharge backup channel, realizing dynamic expansion of the discharge capacity.

[0027] After activating the backup channel, its conduction status feedback is obtained, and an energy discharge execution sequence is generated based on the actual attenuation slope of the discharge current and the boundary conditions of the safe operating area. This technical feature ensures the safety of the discharge process from the perspective of circuit physics, because the current attenuation slope directly reflects the impedance matching of the discharge path. Controlling the conduction sequence based on the slope can effectively avoid electromagnetic stress shocks and secondary heat accumulation caused by sudden current changes.

[0028] Finally, the actual effect of the closed-loop management throughout the entire process is verified by monitoring in real time whether the instantaneous feedback power falls back to the preset safety range, and coordinated control commands are output. This includes: obtaining the real-time value of the instantaneous feedback power after the execution of the isolation and discharge execution commands; determining whether the real-time value of the instantaneous feedback power is within the preset safety range: if the real-time value is within the preset safety range, the output state of the current isolation and discharge execution commands is maintained; if the real-time value is higher than the preset safety range, the switching frequency adjustment amount in the isolation configuration adjustment command is corrected to a decreasing direction, and the conduction period in the energy discharge execution sequence is shortened simultaneously; if the real-time value is lower than the preset safety range, the output state of the current isolation and discharge execution commands is maintained, and the current control parameters are recorded as a reference parameter set for subsequent starting and braking conditions.

[0029] In summary, the technical solution of this invention establishes a complete logical link by introducing instantaneous feedback power as a state perception and control benchmark, encompassing power over-limit trigger waveform diagnosis, power amplitude-guided isolation optimization, power accumulation early warning of discharge overload, and power fallback verification management closed loop. Its beneficial effects are as follows: Instantaneous feedback power runs throughout the entire control process, ensuring a high degree of consistency between the judgment criteria and control objectives of each step, avoiding potential logical conflicts and response lags between multiple independent thresholds; the combination of waveform characteristic triggering mechanism and discharge slope feedback control, while ensuring the electromagnetic compatibility and stability of the main system, proactively prevents the risk of thermal overload in the discharge circuit, thereby achieving safer, more reliable, and faster-responding energy recovery management under complex transient conditions.

[0030] In practical applications, refer to Figure 2 As shown, the present invention provides two methods for determining the presence of main system interference risk, including: responding to the detection of transient drop characteristics in the waveform of instantaneous voltage value or preset distortion characteristics in the waveform of instantaneous current value.

[0031] A method for determining the risk of main system interference in response to a detected transient drop in the waveform of an instantaneous voltage value includes continuously monitoring the amplitude of the instantaneous voltage value over multiple consecutive sampling periods. Specifically, the system uses a voltage sensor configured in the recovery loop to continuously acquire the instantaneous voltage value at a preset sampling frequency and stores this continuous sampled data in the controller to provide a continuous data basis for trend analysis and comparison.

[0032] When the voltage amplitude at the current sampling moment is detected to decrease compared to the amplitude at the previous sampling moment, and the decrease exceeds the preset allowable sag rate, the system identifies a rapid decline in voltage amplitude. After acquiring the instantaneous voltage value at the current sampling moment, the controller compares it with the instantaneous voltage value at the previous sampling moment to calculate the actual sag rate. The actual sag rate is then compared with the preset allowable sag rate to exclude normal, slow voltage fluctuations, ensuring that only abnormal situations of rapid decline are monitored.

[0033] It should be further clarified that the preset allowable sag rate refers to the maximum allowable decrease in the instantaneous voltage value per unit time, and its physical meaning is the threshold of the voltage change rate. In crane energy recovery scenarios, transient sags in DC bus voltage are usually caused by isolation failure between the energy feedback loop and the main system. When the isolation is insufficient, the recovered energy will instantly impact the DC bus, causing the voltage to drop rapidly beyond the normal range.

[0034] The permissible drop rate is determined based on the following factors: (1) Capacitance of DC bus in recovery circuit: The larger the capacitance of DC bus, the stronger the bus's ability to smooth voltage fluctuations and the smaller the voltage change rate under normal operating conditions. Therefore, the allowable drop rate can be set to a smaller value. Conversely, the smaller the capacitance, the more sensitive the bus voltage is to the impact response. The allowable drop rate should be set to a larger value to avoid misjudging normal fluctuations as transient drops.

[0035] (2) Rated power level of the power system: The higher the rated power level, the greater the power fluctuation amplitude generated by the crane during the starting and braking process, and the greater the corresponding voltage change rate. Therefore, the allowable drop rate should be positively correlated with the rated power level.

[0036] In practical implementation, the allowable drop rate can be determined as follows: Under the stable no-load operation of the crane, simulate different levels of energy feedback impact, record the maximum normal rate of change of the DC bus voltage, and take 1.2 to 1.5 times this maximum normal rate of change as the allowable drop rate. For example, for a crane with a rated power of 50kW and a DC bus capacitance of 4700μF, if the measured voltage change rate under normal operating conditions does not exceed 80V / ms, then the allowable drop rate can be set to 100V / ms to 120V / ms.

[0037] Simultaneously, a transient voltage drop is only confirmed when the voltage amplitude after the drop falls below a specified proportion of the rated operating voltage of the recovery circuit. This means that even if the voltage drops rapidly, if the final voltage amplitude remains within a safe range, it does not pose a serious risk. Therefore, the system further checks whether the instantaneous voltage value at the current sampling moment is lower than the rated operating voltage of the recovery circuit multiplied by a preset proportional coefficient. Only when the voltage amplitude simultaneously meets both the conditions of rapid drop and falling below a safe threshold is a transient voltage drop finally confirmed.

[0038] It should be further clarified that the specified percentage of the rated operating voltage refers to the lower limit percentage of the amplitude used to determine whether a voltage drop constitutes a transient sag characteristic. When the instantaneous amplitude of the DC bus voltage drops below a certain percentage of the rated operating voltage, it indicates that the voltage drop has become severe enough to affect the normal operation of the main system, and a transient sag characteristic should be confirmed at this point.

[0039] The prescribed ratio is determined based on the following factors: (1) Voltage tolerance of power devices in power system: Power devices usually allow the input voltage to fluctuate within a certain range. When the voltage is lower than the lower limit of the range, the power device may not be able to switch normally or the output torque may be insufficient. This lower limit is usually 85% to 90% of the rated operating voltage.

[0040] (2) Undervoltage protection threshold of control circuit in power system: In order to prevent the control circuit from resetting or malfunctioning due to low voltage, an undervoltage protection threshold is usually set. This threshold is generally 80% to 85% of the rated operating voltage.

[0041] Taking the above factors into consideration, the specified ratio is usually set to a value between 80% and 90% of the rated operating voltage. In specific implementation, it can be determined according to the actual undervoltage protection parameters of the crane drive system. For example, if the undervoltage protection threshold of a crane drive system is 85% of the rated operating voltage, then the specified ratio can be set to 85%, that is, when the instantaneous voltage value drops below 85% of the rated operating voltage, a transient drop characteristic is confirmed.

[0042] A specific method for determining the risk of main system interference in response to the detection of a preset distortion feature in the waveform of an instantaneous current value includes harmonic component separation of the waveform of the instantaneous current value within a preset observation window to obtain the amplitude of the fundamental component and the amplitudes of each harmonic component; according to the formula: The waveform distortion ratio R is calculated, where, I1 is the sum of the amplitudes of all harmonic components, and I1 is the amplitude of the fundamental component. If the waveform distortion ratio R is greater than the preset upper limit of distortion, then the preset distortion feature is confirmed to have occurred.

[0043] Specifically, to accurately quantify the distortion of the current waveform, digital signal processing techniques such as Fast Fourier Transform (FFT) or wavelet transform can be used. First, continuously acquired instantaneous current values ​​are sampled within a preset observation window. Then, these sampled data are input into the FFT algorithm, which uses spectral analysis to decompose the complex current waveform into a fundamental frequency (usually the power frequency component) and a series of higher harmonics. The FFT algorithm can calculate the amplitude and phase of each frequency component. The amplitude I1 of the fundamental frequency component represents the main effective component of the current, while the amplitudes of each harmonic component reflect the nonlinear distortion of the waveform. The length of the preset observation window should be determined based on the system power frequency and the required harmonic analysis accuracy, typically an integer multiple of the power frequency period, to avoid spectral leakage.

[0044] Based on this, to provide a quantitative indicator to measure the degree of distortion of the current waveform, this application uses the total harmonic distortion (THD) as the waveform distortion ratio R. After obtaining the amplitude I1 of the fundamental component and the amplitudes of each harmonic component (e.g., I2, I3, ..., I...),... n After that, first calculate the sum of the amplitudes of all higher harmonic components, that is... Then, dividing this value by the amplitude I1 of the fundamental component yields the waveform distortion ratio R. The higher this ratio R is, the greater the harmonic content in the current waveform and the more severe the waveform distortion.

[0045] To establish a clear judgment criterion, the quantified distortion ratio R is compared with a preset safety threshold to automatically and objectively identify anomalies in the current waveform. The preset upper limit for allowable distortion is a key parameter, which needs to be determined based on the crane's power system design specifications, operating environment, and tolerance to interference from the main system. For example, relevant power quality standards (such as IEEE 519 or IEC 61000 series standards) can be referenced for setting this limit. When the calculated waveform distortion ratio R exceeds this upper limit, the system considers the current waveform to have undergone significant distortion, which is usually a clear signal of interference in the main system (such as nonlinear loads, switching power supplies, grid fluctuations, etc.). This judgment result will trigger subsequent risk assessment procedures.

[0046] When the system determines that there is a risk of interference to the main system and receives an emergency braking trigger command, it needs to adjust the control parameters of the recovery loop based on the current amplitude of the instantaneous feedback power to generate an isolation configuration adjustment command to improve electrical isolation. However, the control parameters of the recovery loop (such as switching frequency and duty cycle) have a complex and nonlinear impact on electrical isolation. Simple or preset adjustment strategies may not achieve the best interference suppression effect under varying operating conditions, thereby affecting the stable operation of the main system and the efficiency of energy recovery.

[0047] Reference Figure 3 As shown, this application further proposes a method for iteratively optimizing the control parameters of the recovery loop based on the current amplitude of the instantaneous feedback power to generate isolation configuration adjustment instructions for improving electrical isolation. This method includes: pre-setting multiple sets of candidate parameter combinations containing switching frequency adjustment amounts and duty cycle limit values. The switching frequency adjustment amount refers to the magnitude or direction of adjusting the switching frequency of the power converter (such as a DC-DC converter or inverter) in the recovery loop. By changing the switching frequency, the switching losses of the power devices, the design requirements of the filters, and the impact on grid harmonics can be altered. For example, in some cases, increasing the switching frequency can move harmonic components away from the fundamental frequency, facilitating filtering; while in other cases, decreasing the switching frequency may help reduce switching losses. The duty cycle limit value refers to the limitation on the ratio of the power device's on-time to the switching cycle. The duty cycle directly affects the output voltage or current of the power converter, thus affecting the amplitude and waveform of the energy feedback. By limiting the range of the duty cycle, it is possible to prevent the power devices from operating in unsafe areas or to prevent excessive current surges. These candidate parameter combinations can be pre-defined based on theoretical calculations, simulation analysis, or historical operating data to form an initial parameter search space.

[0048] Secondly, using the current amplitude of the instantaneous feedback power as input, the suppression performance data of the main system against energy return interference under each combination of candidate parameters are obtained sequentially. The current amplitude of the instantaneous feedback power reflects the real-time intensity of energy feedback and is an important basis for assessing interference risk and the effectiveness of adjustment strategies. Energy return interference refers to the negative impacts on the main system, such as voltage fluctuations, current harmonics, and electromagnetic interference, that may occur when the recovery loop feeds energy back to the main system. Suppression performance data are quantitative indicators that measure the interference suppression effect of the recovery loop on the main system under different parameter combinations. For example, the total harmonic distortion (THD), current ripple coefficient, electromagnetic compatibility (EMC) index, or voltage sag / overshoot amplitude on the main system side can be measured. These data can be obtained through simulation models, hardware-in-the-loop (HIL) test platforms, or controlled testing of actual systems.

[0049] Next, from the current candidate parameter combinations, the one with the best suppression performance data is selected as the optimal combination. The definition of "optimal" depends on the specific optimization objective. For example, it could be the combination that minimizes the total harmonic distortion of the main system voltage, the combination that minimizes current ripple, or the combination that maximizes energy feedback efficiency while meeting a certain safety margin. By comparing the suppression performance data of each candidate parameter combination, the parameter combination that performs best at the current stage can be quantitatively selected.

[0050] Subsequently, numerical crossover and random fine-tuning are performed on the parameters in the preferred combinations to generate a new set of candidate parameter combinations. Numerical crossover is a method that simulates the "crossover" operation in genetic algorithms, where some parameters from two or more preferred combinations are exchanged to generate new parameter combinations, thereby exploring new possibilities in the parameter space. Random fine-tuning introduces small-scale random perturbations into the parameters of the preferred combinations, simulating a "mutation" operation to avoid getting trapped in local optima and further refine the search. These operations aim to expand the search range while maintaining the depth of exploration of the current optimal solution, in order to find a more globally optimal solution.

[0051] Next, the processes of acquiring suppression performance data, selecting the optimal combination, and generating a new set of candidate parameter combinations are repeated until the preset maximum number of iterations is reached. This step describes an iterative optimization process. By repeatedly performing the above steps, the system can gradually converge to a better parameter combination. The preset maximum number of iterations is to control the computational cost and time of the optimization process, ensuring feasibility in practical applications. When the maximum number of iterations is reached, it is considered that a sufficiently good approximate optimal solution has been found.

[0052] Finally, the selected optimal combination is converted into isolation configuration adjustment instructions for driving the power devices in the recycling loop. The final selected optimal combination includes specific switching frequency adjustments and duty cycle limits. These values ​​need to be converted into actual control signals, such as the frequency and duty cycle of a pulse-width modulation (PWM) signal, to drive the power semiconductor devices (such as IGBTs, MOSFETs, etc.) in the recycling loop. These instructions will directly act on the power converter in the recycling loop, changing its operating state and thus improving electrical isolation.

[0053] Reference Figure 4 As shown, this application further proposes monitoring the energy accumulation status in the recovery loop based on the cumulative result of instantaneous feedback power within a preset time window, including: accumulating the instantaneous feedback power at each sampling moment within the preset time window to obtain the energy accumulation. This step aims to quantify the total energy flowing into the recovery loop within a specific time period. Instantaneous feedback power only reflects the energy flow rate at a certain moment, while components such as capacitors and bleeder resistors in the recovery loop accumulate energy over time. By accumulating the instantaneous feedback power within the preset time window, the actual energy storage level in the recovery loop or the energy stress on the components can be more accurately assessed. In specific implementation, a digital signal processor (DSP) or microcontroller can be used with a fixed sampling period ΔT. s Real-time acquisition of instantaneous feedback power P(t) k The values ​​of the sampled data are calculated and summed within a preset time window. The length of this preset time window can be set according to the thermal time constant or electrical response characteristics of the key energy storage components in the recovery loop to ensure that the accumulated results can effectively reflect the energy carrying capacity of the components.

[0054] Based on this, according to the formula The cumulative energy E is calculated, where P(t) k Let ΔT be the instantaneous feedback power at the k-th sampling time. s Let N be the sampling period and N be the number of sampling points within a preset time window. This formula provides a method for accurately calculating the cumulative energy in a digital control system, which is essentially an approximation of the discrete integral of the power-time function. This is achieved by using the instantaneous feedback power P(t) at each sampling moment... k Multiply by the sampling period ΔT s The total energy accumulation E within a preset time window is obtained by summing all sampling points within that window. The control unit (e.g., an embedded controller or a field-programmable gate array FPGA) is responsible for performing this calculation. After each sampling period, the latest P(t) is calculated. k value multiplied by ΔT sAnd add it to the current cumulative sum. To implement the concept of a preset time window, a sliding window mechanism can be used, for example, using a circular buffer to store P(t) of the most recent N sampling points. k The energy accumulation E is always reflected in the energy status within the latest time window. Each time the value is updated, a new sample value is added and the oldest sample value is removed, thus ensuring that the energy accumulation E always reflects the energy status within the latest time window.

[0055] Furthermore, if the accumulated energy E exceeds the preset upper limit, it is determined that the energy accumulation state in the recovery loop has an overload tendency. This step identifies potential overload risks in the recovery loop by setting an energy threshold. The calculated accumulated energy E is compared with the preset upper limit. Once E exceeds this upper limit, it indicates that critical components in the recovery loop (such as DC bus capacitors, bleed resistors, or energy storage elements) may be approaching their electrical or thermal load limits due to excessive energy accumulation. This upper limit is typically determined during the system design phase based on factors such as the rated parameters, safety margins, and expected operating life of each component in the recovery loop. For example, it can be associated with indicators such as the maximum allowable energy storage of the DC bus capacitor and the maximum allowable energy dissipation of the bleed resistor within a specific time period. When the accumulated energy E is detected to exceed this upper limit, the control system immediately triggers corresponding warning or protection mechanisms, such as activating the energy bleed backup channel, to prevent component damage or system failure.

[0056] In practical applications, refer to Figure 5 As shown, the present invention provides two methods for activating a preset energy discharge backup channel, including responding to the detection of voltage saturation characteristics or abnormal temperature rise rate characteristics of energy storage elements that characterize the overload tendency of the discharge circuit.

[0057] The step of activating a preset energy discharge backup channel in response to the detection of a voltage saturation characteristic that characterizes the overload tendency of the discharge circuit includes: monitoring the voltage drop across the discharge resistor connected in series with the discharge circuit; confirming the detection of a voltage saturation characteristic when the voltage drop across the discharge resistor is maintained at a preset maximum limit voltage value and the dwell time at the maximum limit voltage value exceeds a preset allowable duration; and outputting a drive level signal for turning on the backup power switching device in the energy discharge backup channel in response to the confirmation of the voltage saturation characteristic.

[0058] Specifically, a bleeder circuit typically includes one or more bleeder resistors to dissipate excess electrical energy as heat. By connecting the bleeder resistor in series in the bleeder circuit and monitoring the voltage drop across it, the magnitude of the current flowing through the bleeder circuit and the power consumption of the bleeder resistor can be indirectly reflected. When the bleeder circuit carries excessive energy, causing an increase in current, the voltage drop across the bleeder resistor will also increase accordingly, thus providing basic data for determining the load status of the bleeder circuit. This voltage drop can be acquired in real time using a high-precision voltage sensor or a voltage divider circuit.

[0059] Furthermore, the above technical solution aims to accurately identify the overload tendency of the discharge circuit. The preset maximum limiting voltage value is determined comprehensively based on the rated power and heat dissipation capacity of the discharge resistor, as well as the safe operating boundary conditions of the discharge circuit. It represents the upper limit of voltage that the discharge circuit can withstand under normal operating conditions. When the monitored voltage drop reaches and remains at this maximum limiting voltage value, it indicates that the discharge circuit is operating under high load. Based on this, the preset allowable duration is used to filter out brief voltage spikes or transient fluctuations, ensuring that only when the discharge circuit is in this high-load state for an extended period—that is, when energy cannot be effectively dissipated and may lead to overheating or damage—is it confirmed as a true voltage saturation characteristic. The setting of this duration must consider the thermal inertia of the discharge circuit, its response speed, and the system's tolerance to false alarms.

[0060] Once the system detects voltage saturation characteristics, indicating an overload tendency in the discharge circuit, it immediately triggers the activation of the backup energy discharge channel. Specifically, the control unit generates and outputs a drive level signal, which is sent to the backup power switching device in the backup energy discharge channel. The backup power switching device is typically a high-power semiconductor device, such as an IGBT or MOSFET. Upon receiving the drive level signal, it quickly turns on, thereby activating or enhancing the discharge capacity of the backup energy discharge channel to rapidly reduce the load on the discharge circuit and prevent overload damage.

[0061] In response to the detection of an abnormal temperature rise rate in the energy storage element, a preset energy discharge backup channel is activated. The method includes: acquiring the temperature change of the energy storage element's outer casing surface between two consecutive sampling moments using a temperature sensor. The temperature sensor can be a thermistor, thermocouple, or infrared temperature sensor, which is tightly mounted on the outer casing surface of the energy storage element to monitor the actual operating temperature of the energy storage element in real time and accurately. Between two consecutive sampling moments, the system records and calculates the temperature change ΔT on the outer casing surface of the energy storage element, which directly reflects the heat load accumulation of the energy storage element in a short period. Simultaneously, the system acquires the change ΔP of the instantaneous feedback power of the recovery circuit between two consecutive sampling moments. The instantaneous feedback power is calculated based on the real-time acquired instantaneous values ​​of the recovery circuit voltage and the power system current; its change ΔP characterizes the magnitude of energy change input to the recovery circuit within the same sampling period.

[0062] Based on this, the temperature rise efficiency ratio η is calculated using the formula η=ΔT / ΔP. The temperature rise efficiency ratio η quantifies the temperature change of the energy storage element caused by a unit instantaneous change in feedback power, and is a key indicator for evaluating the thermal management performance and potential thermal runaway risk of the energy storage element. If the calculated temperature rise efficiency ratio η is greater than the preset allowable temperature rise ratio, an abnormal temperature rise rate is detected. The preset allowable temperature rise ratio is a safety threshold pre-set based on factors such as the material characteristics, heat dissipation conditions, expected lifespan, and safety margin of the energy storage element, through experimental testing or simulation analysis. When the actual temperature rise efficiency ratio exceeds this threshold, it indicates that the temperature rise rate of the energy storage element is too fast, posing a risk of thermal runaway or overload.

[0063] In crane energy recovery safety control methods, when an overload tendency is detected in the recovery circuit and the backup energy discharge channel is activated, ensuring that the energy discharge process is efficient and safe, and avoiding secondary damage to the system due to improper attenuation of the discharge current, is a problem requiring meticulous management. Simply activating the discharge channel cannot fully guarantee that the conduction timing of the discharge path matches the actual system state, which may lead to insufficient discharge efficiency or the risk of component overheating.

[0064] Reference Figure 6As shown, this application further proposes to generate an energy discharge execution sequence that includes the conduction timing of the discharge path, based on the actual attenuation slope of the discharge current and the preset safe operating area boundary conditions. Specifically, at the initial moment after activating the backup energy discharge channel, the system records the peak current value in the discharge circuit. This peak current value represents the maximum current load borne by the circuit at the start of energy discharge and is a key parameter for evaluating the initial state of the discharge process. Subsequently, after a preset time interval, the system records the real-time current value in the discharge circuit again. This preset time interval is a short time window determined by system design and testing to observe the initial attenuation of the current.

[0065] Based on the recorded current values, the system calculates the current using the formula k = [I]. peak The actual attenuation slope k is obtained by calculating -I(t1) / Δt, where I peak Here, I(t1) represents the peak current value, I(t1) represents the real-time current value, and Δt represents the preset time interval. This calculation formula intuitively reflects the average rate of decrease of the discharge current within the preset time interval, i.e., the speed of energy dissipation. The actual attenuation slope k is a key indicator for measuring discharge efficiency and component load.

[0066] The system then compares the calculated actual attenuation slope k with the minimum permissible attenuation slope defined in the safe operating area boundary conditions. The safe operating area boundary conditions are pre-set based on the withstand capabilities and heat dissipation characteristics of components such as power devices and discharge resistors in the discharge circuit, as well as the overall system safety requirements. These conditions include the minimum current attenuation rate required to ensure that components do not overheat, break down, or experience other faults. The minimum permissible attenuation slope is a specific quantitative indicator within these boundary conditions, used to determine whether the current discharge process is within a safe range.

[0067] If the actual attenuation slope is less than the minimum allowable attenuation slope, it indicates that the current discharge current is decaying too slowly, which may cause the components in the discharge circuit to be under high load for an extended period, posing a risk of overheating or damage. To avoid such risks, the system inserts a forced shutdown interval into the energy discharge execution sequence. This forced shutdown interval temporarily interrupts the conduction of the discharge path, allowing the components in the discharge circuit to cool or recover, thereby effectively reducing the thermal stress on the components and preventing irreversible damage caused by continuous overload.

[0068] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A safety control method for energy recovery in cranes, characterized in that, Includes the following steps: Real-time acquisition of instantaneous values ​​of recovery circuit voltage and power system current during crane operation, and calculation of instantaneous feedback power; When the instantaneous feedback power exceeds the preset power fluctuation range, the waveform characteristics of the instantaneous voltage value and the waveform characteristics of the instantaneous current value are monitored in real time. In response to the detection of transient drop characteristics in the waveform of the instantaneous voltage value or preset distortion characteristics in the waveform of the instantaneous current value, it is determined that there is a risk of interference to the main system. When a risk of interference to the main system is determined, in response to the received emergency braking trigger command, the control parameters of the recovery loop are iteratively optimized and adjusted according to the current amplitude of the instantaneous feedback power to generate an isolation configuration adjustment command for improving electrical isolation. After executing the isolation configuration adjustment command, the energy accumulation status in the recovery loop is monitored based on the cumulative result of the instantaneous feedback power within the preset time window. In response to the detection of voltage saturation characteristics or abnormal temperature rise rate characteristics of the energy storage element that characterize the overload tendency of the discharge loop, the preset energy discharge backup channel is activated. Obtain the conduction status feedback of the backup energy discharge channel, and generate an energy discharge execution sequence containing the conduction timing of the discharge path based on the actual attenuation slope of the discharge current and the preset safe working area boundary conditions; The system executes an energy discharge sequence and monitors in real time whether the instantaneous feedback power falls back to the preset safety range to verify the safety of the current energy recovery management process. Finally, it outputs isolation and discharge execution commands to control the coordinated operation of the main system and the recovery loop.

2. The crane energy recovery safety control method according to claim 1, characterized in that: The preset power fluctuation range is determined based on the rated power of the power system, and the upper limit of the power fluctuation range is positively correlated with the rated power. The power fluctuation range is also corrected based on the capacitance value of the DC bus capacitor in the recovery circuit. The larger the capacitance value of the DC bus capacitor, the greater the positive correction to the upper limit of the power fluctuation range.

3. The crane energy recovery safety control method according to claim 1, characterized in that: In response to the detection of transient drop characteristics in the waveform of the instantaneous voltage value, a risk of main system interference is determined, including: The amplitude of the instantaneous voltage value is continuously monitored over multiple consecutive sampling periods; When the amplitude at the current sampling moment is detected to decrease compared to the amplitude at the previous sampling moment, and the decrease exceeds the preset allowable drop rate, and the amplitude after the decrease is lower than the specified proportion of the rated operating voltage of the recovery circuit, a transient drop characteristic is confirmed to have occurred.

4. The crane energy recovery safety control method according to claim 1, characterized in that: In response to the detection of a preset distortion characteristic in the waveform of an instantaneous current value, a risk of main system interference is determined, including: Harmonic components are separated from the waveform of the instantaneous current value within a preset observation window to obtain the amplitude of the fundamental component and the amplitude of each harmonic component. According to the formula: The waveform distortion ratio R is calculated. in, I1 is the sum of the amplitudes of all harmonic components, and I1 is the amplitude of the fundamental component. If the waveform distortion ratio R is greater than the preset upper limit of distortion, then the preset distortion feature is confirmed to have occurred.

5. The crane energy recovery safety control method according to claim 1, characterized in that: The control parameters of the recovery loop are iteratively optimized based on the current amplitude of the instantaneous feedback power to generate isolation configuration adjustment instructions for improving electrical isolation, including: Multiple sets of candidate parameter combinations, including switching frequency adjustment and duty cycle limit values, are pre-set; Using the current amplitude of instantaneous feedback power as input, the main system's suppression performance data against energy backflow interference under each set of candidate parameter combinations are obtained sequentially. From the current candidate parameter combinations, select the parameter combination that has the best suppression performance data as the preferred combination; The parameters in the preferred combination are numerically cross-substituted and randomly fine-tuned to generate a new set of candidate parameter combinations; Repeat the process of acquiring suppression performance data, selecting the best combination, and generating a new set of candidate parameter combinations until the number of repetitions reaches the preset round limit. The final selected optimal combination is converted into isolation configuration adjustment instructions for driving the power devices in the recycling loop.

6. The crane energy recovery safety control method according to claim 1, characterized in that: The energy accumulation status in the recovery loop is monitored based on the cumulative results of instantaneous feedback power within a preset time window, including: The instantaneous feedback power at each sampling moment within the preset time window is accumulated to obtain the energy accumulation. According to the formula The cumulative energy E is calculated, where P(t) k Let ΔT be the instantaneous feedback power at the k-th sampling time. s The sampling period is N, and the number of sampling points within the preset time window is N. If the energy accumulation E is greater than the preset energy accumulation upper limit, it is determined that the energy accumulation state in the recovery loop has an overload tendency.

7. The crane energy recovery safety control method according to claim 1, characterized in that: In response to the detection of voltage saturation characteristics that indicate an overload tendency in the discharge circuit, a preset energy discharge backup channel is activated, including: Monitor the voltage drop across the discharge resistor connected in series with the discharge circuit; When the voltage drop across the bleed resistor remains at the preset maximum limit voltage value and the dwell time at the maximum limit voltage value exceeds the preset allowable duration, voltage saturation characteristics are confirmed to be detected. In response to the confirmation of a detected voltage saturation characteristic, a drive level signal is output to turn on the backup power switching device in the energy discharge backup channel.

8. The crane energy recovery safety control method according to claim 1, characterized in that: In response to the detection of abnormal temperature rise rate characteristics of the energy storage element, a preset energy discharge backup channel is activated, including: The temperature change of the surface of the energy storage element's outer casing between two consecutive sampling times is obtained using a temperature sensor; Obtain the change in instantaneous feedback power of the recovery loop between two consecutive sampling times; The temperature rise efficiency ratio η is calculated using the formula η=ΔT / ΔP, where ΔT is the temperature change and ΔP is the change in instantaneous feedback power. If the temperature rise efficiency ratio η is greater than the preset allowable temperature rise ratio, then an abnormal temperature rise rate characteristic is confirmed to have been detected.

9. The crane energy recovery safety control method according to claim 1, characterized in that: Based on the actual attenuation slope of the discharge current and the preset safe operating area boundary conditions, an energy discharge execution sequence containing the conduction timing of the discharge path is generated, including: At the initial moment after activating the backup energy discharge channel, record the peak current value in the discharge circuit; After a preset time interval, the real-time current value in the discharge circuit is recorded again. According to the formula k=【I peak The actual attenuation slope k is obtained by calculating -I(t1) / Δt, where I peak I(t1) is the peak current value, I(t1) is the real-time current value, and Δt is the preset time interval. Compare the actual attenuation slope k with the minimum permissible attenuation slope specified in the boundary conditions of the safe working area; If the actual decay slope is less than the minimum allowable decay slope, a forced shutdown interval is inserted into the energy discharge execution sequence.

10. The crane energy recovery safety control method according to claim 1, characterized in that: Real-time monitoring of whether the instantaneous feedback power drops back to the preset safety range, including: Obtain the real-time value of the instantaneous feedback power after the execution of the isolation and discharge command; Determine whether the real-time value of the instantaneous feedback power is within the preset safety range: If the real-time value is within the preset safety range, then maintain the current output state of the isolation and release execution command; If the real-time value is higher than the preset safety range, the switching frequency adjustment amount in the isolation configuration adjustment command will be corrected to a reduced direction, and the conduction period in the energy discharge execution sequence will be shortened simultaneously. If the real-time value is lower than the preset safety range, the current output state of the isolation and release execution command will be maintained, and the current control parameters will be recorded as a reference parameter group for subsequent starting and braking conditions.

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