Control method and control system for preventing hook sliding in case of power failure of frequency converter of hoisting equipment

Abstract

The invention discloses a frequency converter power-off anti-slip control method and system for hoisting equipment, and the method comprises the steps: triggering an emergency mode and sending a brake instruction to a brake device when detecting that the voltage is lower than a power-off judgment threshold value; controlling the motor to enter a power generation mode according to the rotation direction of the motor at the moment of power failure: if the rotation is positive rotation, outputting negative torque, and limiting the torque value in a preset negative torque interval; on the contrary, positive torque is output, the torque value is limited in a preset positive torque interval, and the output torque is dynamically adjusted to maintain the rotor frequency in a preset negative value interval; after the actual band-type brake takes effect, when the absolute value of the rotor frequency is detected to be continuously lower than the safety threshold value, it is judged that braking is completed, and the frequency converter is closed. Under the condition of no standby power supply, gravitational potential energy of a load is utilized to maintain the frequency converter to run until the brake device is completely closed, and the problem of hook slipping caused by brake response delay is solved. And gravitational potential energy is converted from a risk source to a safety braking resource, and high-risk working conditions are eliminated.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of motor control, and particularly relates to a frequency converter power-off anti-hooking control method and system for hoisting equipment. BACKGROUND

[0002] In small hoisting equipment operation, load uncontrolled falling (hooking) caused by sudden power-off of the frequency converter is a major safety hazard. Due to cost constraints, ordinary performance motor brake devices are generally used in such scenarios without a backup power supply. When the frequency converter is powered off, the load gravitational potential energy is converted into kinetic energy, causing the motor frequency to rise sharply, and the brake device cannot act immediately due to mechanical response delay; during the window period before the brake device is completely closed, the load continues to accelerate and fall, and once the falling speed exceeds the critical braking speed of the brake device, the brake distance will increase dramatically or even completely slip due to insufficient friction plate braking force. The existing solutions rely on high-performance brake devices (such as hydraulic brakes) or backup power supplies to maintain the operation of the frequency converter, but both significantly increase the cost and cannot be adapted to small hoisting scenarios. Therefore, there is an urgent need for a low-cost anti-hooking control method that can generate power using the load gravitational potential energy to maintain the operation of the frequency converter and coordinate the brake device to complete safe braking without a backup power supply and ordinary brake device. SUMMARY

[0003] Embodiments of the present application provide a frequency converter power-off anti-hooking control method and system for hoisting equipment, which can generate power using the load gravitational potential energy to maintain the operation of the frequency converter and coordinate the brake device to complete safe braking without a backup power supply and ordinary brake device in small hoisting scenarios.

[0004] To solve the above problems, according to one aspect of the present application, embodiments of the present application provide a frequency converter power-off anti-hooking control method for hoisting equipment, the hoisting equipment further comprising a motor and a brake device, the frequency converter power-off anti-hooking control method for hoisting equipment comprising:

[0005] Step one, detecting the bus voltage of the frequency converter, and triggering an emergency mode and sending a brake command to the brake device when detecting that the bus voltage is lower than a power-off judgment threshold;

[0006] Step two, controlling the motor to enter a power generation mode according to the motor rotation direction at the moment of power-off: if it is forward rotation, controlling the motor to output a negative torque and limiting the torque value in a preset negative torque range; if it is reverse rotation, controlling the motor to output a positive torque and limiting the torque value in a preset positive torque range, and dynamically adjusting the output torque of the motor to maintain the rotor frequency of the motor in a preset negative value range;

[0007] Step 3: After the actual brake takes effect, when it is detected that the absolute value of the rotor frequency continuously drops below the safety threshold, it is determined that the braking is completed and the frequency converter is turned off.

[0008] In some embodiments, the preset negative value interval in Step 2 is [f dn , f up , where f dn is the lower limit value of the preset negative value interval, and f up is the upper limit value of the preset negative value interval. Dynamically adjusting the output torque of the motor includes:

[0009] When the rotor frequency f of the motor satisfies: f up < f < 0, adjust the output torque to the lower limit value T dn _ neg of the positive torque interval;

[0010] When the rotor frequency f of the motor satisfies: f < f dn , adjust the output torque to the upper limit value T up _ neg of the positive torque interval;

[0011] When the rotor frequency f of the motor is within [f dn , f up , adjust the output torque dynamically according to a linear function.

[0012] In some embodiments, the output torque is dynamically adjusted according to a linear function, and the output torque of the motor is adjusted to be within according to the magnitude of f; where the output torque T is a linear function of the rotor frequency f, where T dn _ pos is the lower limit value of the negative torque interval, and T up _ pos is the upper limit value of the negative torque interval.

[0013] In some embodiments, the value range of f dn is -14Hz < f dn < -12Hz; the value range of f up is -8Hz < f up < -6Hz; the value range of T up _ neg is 140% < T up _ neg < 160%; the value range of T dn _ neg is 10% < T dn _ neg < 30%.

[0014] In some embodiments, the T up pos T up pos T dn pos T dn pos T

[0015] In some embodiments, the power-off determination threshold V threshold e threshold e e wherein the V

[0016] In some embodiments, when the absolute value of the rotor frequency continuously falls below the preset safety threshold and maintains for a preset duration in step three, it is determined that the braking is completed and the frequency converter is turned off.

[0017] In some embodiments, after the emergency mode is triggered in step one, the frequency converter output frequency is set to zero.

[0018] According to another aspect of the present application, embodiments of the present application provide a power-off anti-slip hook control system for a frequency converter of a hoisting device. The control system is used to execute the control method described above, and comprises a frequency converter and a brake device and an encoder connected thereto. The frequency converter comprises:

[0019] a main control module for detecting bus voltage and executing control logic;

[0020] a voltage detection module for real-time monitoring of bus voltage value;

[0021] a brake control module for receiving brake instruction issued by the main control module and controlling the action of the brake device;

[0022] an encoder feedback module for real-time acquisition of motor rotor frequency;

[0023] ​​​​​​​​The control system is configured to trigger an emergency mode when the voltage detection module detects that the bus voltage is lower than a power-off determination threshold, the main control module sends a brake engagement instruction to the brake engagement control module, the brake engagement control module controls the brake device to act, the main control module controls the motor to enter a power generation mode according to the motor rotation direction fed back by the encoder at the moment of power-off, if the rotation direction is forward, the motor outputs a negative torque and the torque value is limited in a negative torque interval, if the rotation direction is reverse, the motor outputs a positive torque and the torque value is limited in a preset positive torque interval, and the output torque of the motor is dynamically adjusted to maintain the rotor frequency in a preset negative value interval, and when it is detected that the rotor frequency continuously is lower than a safety threshold, the main control module determines that the braking is completed and the frequency converter is turned off.

[0024] In some embodiments, the frequency converter is equipped with a brake resistor for consuming the excess power generated in the power generation braking process.

[0025] Compared with the prior art, the crane frequency converter power-off anti-slip hook control method has at least the following beneficial effects:

[0026] The crane frequency converter power-off anti-slip hook control method provided by the application comprises the following steps: step one, detecting the bus voltage of the frequency converter, triggering an emergency mode and sending a brake engagement instruction to the brake device when it is detected that the bus voltage is lower than a power-off determination threshold; step two, controlling the motor to enter a power generation mode according to the motor rotation direction at the moment of power-off, if the rotation direction is forward, controlling the motor to output a negative torque and limiting the torque value in a preset negative torque interval, if the rotation direction is reverse, controlling the motor to output a positive torque and limiting the torque value in a preset positive torque interval, and dynamically adjusting the output torque of the motor to maintain the rotor frequency of the motor in a preset negative value interval; and step three, when it is detected that the absolute value of the rotor frequency continuously is lower than a safety threshold after the actual brake engagement braking takes effect, determining that the braking is completed and turning off the frequency converter.

[0027] The crane frequency converter power-off anti-slip hook control method provided by the application comprises the following steps: step one, detecting the bus voltage of the frequency converter, triggering an emergency mode and sending a brake engagement instruction to the brake device when it is detected that the bus voltage is lower than a power-off determination threshold; step two, controlling the motor to enter a power generation mode according to the motor rotation direction at the moment of power-off, if the rotation direction is forward, controlling the motor to output a negative torque and limiting the torque value in a preset negative torque interval, if the rotation direction is reverse, controlling the motor to output a positive torque and limiting the torque value in a preset positive torque interval, and dynamically adjusting the output torque of the motor to maintain the rotor frequency of the motor in a preset negative value interval; and step three, when it is detected that the absolute value of the rotor frequency continuously is lower than a safety threshold after the actual brake engagement braking takes effect, determining that the braking is completed and turning off the frequency converter.

[0028] The above description is only a summary of the technical scheme of the application, in order to more clearly understand the technical means of the application and can be implemented according to the content of the specification, the following is a preferred embodiment of the application and the detailed description is as follows. BRIEF DESCRIPTION OF DRAWINGS

[0029] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings needed in the embodiment description will be briefly introduced. Obviously, the drawings in the following description are some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor.

[0030] Figure 1 is a flow chart of a frequency converter power-off anti-slip hook control method of a hoisting equipment provided by an embodiment of the present application;

[0031] Figure 2 is a structural schematic diagram of the frequency converter in state 1 in the frequency converter power-off anti-slip hook control method of a hoisting equipment provided by an embodiment of the present application;

[0032] Figure 3 is a structural schematic diagram of the frequency converter in state 2 in the frequency converter power-off anti-slip hook control method of a hoisting equipment provided by an embodiment of the present application;

[0033] Figure 4 is a structural schematic diagram of the frequency converter in state 3 in the frequency converter power-off anti-slip hook control method of a hoisting equipment provided by an embodiment of the present application;

[0034] Figure 5 is a waveform diagram of power-off in the frequency converter power-off anti-slip hook control method of a hoisting equipment provided by an embodiment of the present application;

[0035] Figure 6 is a system block diagram of a frequency converter power-off anti-slip hook control system of a hoisting equipment provided by an embodiment of the present application.

[0036] Reference signs:

[0037] 1, main control module; 2, voltage detection module; 3, band brake control module; 4, encoder feedback module. DETAILED DESCRIPTION

[0038] In order to further illustrate the technical means and effects taken by the present application to achieve the predetermined purposes, the specific embodiments, structures, features and effects according to the present application will be described in detail below in combination with the drawings and preferred embodiments. In the following description, different "an embodiment" or "embodiments" do not necessarily refer to the same embodiment. In addition, the specific features, structures or characteristics in one or more embodiments can be combined in any suitable form.

[0039] In the description of the present application, it is necessary to make it clear that the terms "first", "second" and the like in the specification and claims of the present application and the above-mentioned drawings are used to distinguish similar objects, and do not have to be used to describe a specific order or sequence; the terms "vertical", "transverse", "longitudinal", "front", "back", "left", "right", "up", "down", "horizontal" and the like indicate the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present application, and do not mean that the devices or elements referred to must have a particular orientation or position, so it cannot be understood as a limitation on the present application.

[0040] In the description of the present application, it is necessary to make it clear that the terms "installation", "connection", "connection" should be understood broadly, for example, it can be fixed connection, or detachable connection, or integral connection; it can be mechanical connection, or electrical connection; it can be directly connected, or indirectly connected through intermediate medium. For those skilled in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0041] In order to better understand the above technical solutions, the above technical solutions will be described in detail in combination with the drawings and specific embodiments of the specification.

[0042] Embodiment 1

[0043] The present embodiment provides a frequency converter power-off anti-hooking control method of a hoisting equipment, as shown in Figure 1 The frequency converter power-off anti-hooking control method of the hoisting equipment comprises:

[0044] Step one, detecting the bus voltage of the frequency converter, when detecting that the bus voltage is lower than the power-off judgment threshold, triggering the emergency mode and sending the brake device with the brake command;

[0045] Step two, according to the motor rotating direction at the moment of power-off, control the motor to enter the power generation mode: if it is forward rotation, control the motor to output negative torque, and limit the torque value in the preset negative torque interval; if it is reverse rotation, control the motor to output positive torque, limit the torque value in the preset positive torque interval, and dynamically adjust the output torque of the motor to maintain the rotor frequency of the motor in the preset negative value interval;

[0046] Step three, after the actual brake brake takes effect, when detecting that the absolute value of the rotor frequency is continuously lower than the safety threshold, it is judged that the brake is completed and the frequency converter is closed.

[0047] Specifically, step one involves real-time detection of frequency converter power failure and emergency response. When the bus voltage detection value is lower than the preset power failure determination threshold, the frequency converter immediately triggers the emergency mode, synchronously issues the brake command and sets the output frequency to zero. The key role of this step is to use the residual amount of bus capacitor to establish a short time buffer (about tens to hundreds of milliseconds) to create a response window for subsequent power generation braking, and to start the mechanical action of the brake device in advance to shorten the braking air window period. Step two performs directional power generation braking according to the motor rotation direction at the moment of power failure. If the motor is rotating in the forward direction (lifting the load) at the moment of power failure, the control outputs negative torque to make the motor enter the second quadrant power generation mode (positive speed / negative torque), limits the torque within the preset negative value range, and converts the gravitational potential energy into electrical energy to feed back to the bus; if the motor is rotating in the reverse direction (lowering the load) at the moment of power failure, the control outputs positive torque to make the motor enter the fourth quadrant power generation mode (negative speed / positive torque), limits the torque within the preset positive value range, and dynamically adjusts the output torque to stabilize the rotor frequency within the preset negative value range. The core role of this step is to achieve energy autonomous circulation through quadrant switching: the gravitational potential energy drives the motor to generate power to maintain the operation of the frequency converter, while the precise torque restriction and speed closed-loop control suppress the load acceleration and descent, so that the system continues to operate under the condition of no external power supply. Step three determines the braking completion state. When the rotor frequency feedback by the encoder is continuously lower than the preset safety threshold and maintains for a set time, it is determined that the brake device has physically stopped the load, and the frequency converter output is turned off. This step verifies the speed and time to exclude transient interference, ensures safe shutdown after mechanical braking takes effect, and avoids the risk of secondary vehicle sliding.

[0048] To visually illustrate the energy conversion mechanism of the power generation mode, the embodiment is described in combination with the motor working state diagram shown in FIG. 1. Figures 2-4 Figures 2-4 The three working modes are shown in the horizontal direction.

[0049] Figure 2 State 1 (electric mode forward rising): The external power source drives the motor to rotate forward, the torque direction is the same as the speed direction, and the electrical energy is converted into mechanical energy to lift the load; Figure 3 State 2 (power generation mode forward rising): After power failure, the load begins to descend under the action of gravity, dragging the motor to rotate forward but outputting reverse negative torque, converting the gravitational potential energy into electrical energy to feed back to the bus (the arrow in the figure shows the energy reverse path of load potential energy→motor power generation→frequency converter); Figure 4 State 3 (power generation mode reverse descending): If the load is in the lowering state at the moment of power failure, the motor reverses to output positive torque, also achieving the conversion of gravitational potential energy into electrical energy (the energy flow direction is the same as that of state 2 but the rotation direction is opposite).

[0050] Figures 2-4 ​The core comparison of the three states proves that in state 2 and state 3, the electromagnetic field direction of the motor (the "F" / "G" polarity marked in the conical base in the figure) and the rotation direction of the rotor form a reverse coupling relationship, realizing the "second / fourth quadrant power generation mode". Especially in Figure 3 State 2 of the electromagnetic device marked current reverse arrow (comparing Figure 2 State 1) verifies the essence of the invention of "gravity potential energy driving motor power generation".

[0051] The power-off anti-slip hook control method of the hoisting equipment provided by the embodiment forms a closed loop in three steps: step one realizes instantaneous response in power-off, step two converts the gravity potential energy into control energy through the second / fourth quadrant power generation mode and dynamically suppresses the load acceleration, and step three confirms that the mechanical brake is completed. After the three are coordinated, under the condition of no standby power supply, the gravity potential energy of the load itself is used to maintain the operation of the frequency converter to the complete closing of the brake device, completely solving the problem of slip hook caused by the response delay of ordinary brake devices. The embodiment breaks through the risk source and converts the gravity potential energy into a safe braking resource, eliminating the high-risk working conditions described in the background technology at zero hardware cost.

[0052] Motor four-quadrant refers to the division of four working states of the motor according to the polarity combination of motor speed and torque. The first quadrant corresponds to the positive rotation motor mode of the motor, in which mode the motor rotates positively, and the electromagnetic torque is also positive (i.e. the torque direction is consistent with the rotation direction), which is the most typical motor driving state. The second quadrant corresponds to the positive rotation power generation mode of the motor, in which mode the motor rotates positively, but the electromagnetic torque is negative (i.e. the torque direction is opposite to the rotation direction). This is a braking state, and the motor works like a generator. The third quadrant corresponds to the reverse rotation motor mode of the motor, in which mode the motor rotates reversely, and the electromagnetic torque is also negative (i.e. the torque direction is consistent with the rotation direction). This is a reverse motor driving state. The fourth quadrant corresponds to the reverse rotation power generation mode of the motor, in which mode the motor rotates reversely, but the electromagnetic torque is positive (i.e. the torque direction is opposite to the rotation direction). This is a reverse braking state, and the motor works like a generator when it reverses. The embodiment mainly aims at the second quadrant and the fourth quadrant, and converts the gravity potential energy into control energy through the second and fourth quadrant power generation modes and dynamically suppresses the load acceleration.

[0053] In specific embodiments, the preset negative value interval in step two is [f dn , f up ], where f dn is the lower limit value of the preset negative value interval, and f up is the upper limit value of the preset negative value interval. The dynamic adjustment of the output torque includes:

[0054] When the rotor frequency f satisfies: f upWhen <0, the output torque is adjusted to the positive torque interval lower limit value T dn . neg ;

[0055] When the rotor frequency f satisfies: f < f dn , the output torque is adjusted to the positive torque interval upper limit value T up . neg ;

[0056] When the rotor frequency f is between [f dn , f up ], the output torque is dynamically adjusted according to a linear function.

[0057] When the rotor frequency f is between f up and 0, it indicates that the load lowering speed is lower than the target interval lower limit. At this time, the output torque is adjusted to T dn . neg (the positive torque lower limit value), part of the gravitational potential energy is released by reducing the braking intensity, so that the load is accelerated to the effective power generation interval. This operation prioritizes power generation to avoid bus voltage collapse due to excessively low frequency, while reserving kinetic energy for subsequent braking. When the rotor frequency f is lower than f dn , it indicates that the load lowering speed exceeds the safety threshold. At this time, the output torque is immediately adjusted to T up . neg (the positive torque upper limit value) to quickly absorb gravitational potential energy. This operation forces the load to decelerate to prevent the brake device from failing due to excessive speed. When the rotor frequency f is between [f dn , f up ], the output torque is dynamically adjusted according to the value of f. When the frequency increases, the output torque increases to enhance the braking effect, and when the frequency decreases, the output torque decreases to release gravitational potential energy. This linear adjustment forms a closed-loop negative feedback, stabilizing the load speed within the target interval.

[0058] The embodiment achieves the following effects through frequency partition control: starting maximum braking to prevent hooking at high speed, maintaining power generation to ensure system operation at low speed, and precisely stabilizing speed within the target interval. The hooking distance is controlled within a very short range, completely solving the high-risk working condition.

[0059] In specific embodiments, the output torque is dynamically adjusted according to a linear function, and the output torque is limited to be between T , according to the size of f; wherein the output torque T is a linear function of the rotor frequency f, wherein T dn . pos is the negative torque interval lower limit value, and T up . pos is the negative torque interval upper limit value.

[0060] When the rotor frequency f is at [f dn f up When the frequency f is within the specified range, the output torque T changes linearly with frequency f, and its mathematical expression is: This formula essentially constructs a closed-loop negative feedback between frequency and torque: when f increases, T increases proportionally to enhance braking strength and absorb more gravitational potential energy; when f decreases, T decreases synchronously to release gravitational potential energy and maintain power generation.

[0061] This embodiment first uses linear feedback to precisely lock the load speed within a safe range, preventing overspeed slippage or low-speed power failure; secondly, it realizes the on-demand conversion of gravitational potential energy, enhancing the power generation feedback bus when the frequency increases and releasing potential energy to maintain system operation when the frequency decreases; finally, it works in conjunction with the braking resistor to form a complete energy management closed loop, ensuring stable power generation to support the inverter operation until the brake is engaged.

[0062] In a specific embodiment, the f dn The value range is -14Hz <f dn <-12Hz; the f up The value range is -8Hz <f up <-6Hz; the T up _ neg The value range is 140%. <T up _ neg <160%; the T dn _ neg The value range is 10%. <T dn _ neg <30%.

[0063] Lower limit of power generation frequency f dn The default setting is -13Hz, which is slightly below the lower limit of the target power generation range. Its core function is to establish a speed buffer boundary. When the frequency is below -13Hz, the system determines that the power generation is insufficient and immediately reduces the torque to the lower limit value T. dn _ neg This prevents the busbar from losing power by releasing gravitational potential energy. The upper limit of the power generation frequency f... up The default setting is -7Hz, which serves as the upper speed limit for the power generation range. This value ensures that the load release frequency does not exceed the critical point of the braking capacity of the brake device, preventing excessive speed from causing wear on the friction plates and making it difficult to stop the vehicle. Setting it to -7Hz keeps the maximum kinetic energy under heavy load conditions within the braking capacity of the friction plates, preventing overspeeding and hook slippage. (Reverse maximum torque T) up _ negThe default value is 150%. This parameter relates to the maximum transient overload capacity of the strain gauge and is specifically designed for heavy-load and overspeed conditions. The upper limit of the reverse operation output torque should be greater than the torque required by the rated maximum load of the lifting equipment. The 150% setting covers extreme conditions of 150% of the rated load, ensuring that all gravitational potential energy can be absorbed during emergency braking. Minimum reverse torque T dn _ neg The default value is 20%, which serves as the lower limit of torque under light load conditions. This value ensures that the minimum power generation can still be maintained when the hook is empty or under light load. It also ensures that the load can be accelerated normally under light load conditions, thus avoiding power outages caused by light load stalls and preventing excessive acceleration beyond the control range.

[0064] In a specific embodiment, the negative torque range is [T dn _ pos T up _ pos ], wherein the T up _ pos The value range is -12%. <T up _ pos <-8%, the T dn _ pos The value range is -60%. <T dn _ pos <-40%.

[0065] In this embodiment, the percentage range is based on the rotor's rated torque, where T up _ pos The default setting is -10%, which serves as the upper limit for the positive generating braking torque, indicating a mild braking intensity. Its core function is to prevent mechanical shock caused by sudden reverse torque during load increases, while ensuring sufficient generating power to maintain the bus voltage. The output negative torque should not be too large; the -10% setting ensures a smooth deceleration process under heavy load conditions, preventing damage from instantaneous overload of the gearbox. dn _ pos The default setting is -50%, which serves as the lower limit for the positive braking torque. This value provides basic power generation capability. In the event of a sudden power outage during heavy load lifting, the -50% torque can force the gravitational potential energy to be converted into sufficient electrical energy, preventing the bus voltage from collapsing. The -50% setting has been verified to enable a 2-ton load to generate 4kW of power, meeting the minimum operating requirements of the frequency converter.

[0066] In a specific embodiment, the power outage determination threshold V threshold The value range is 1.1V. e <V threshold <1.3V e , where V e This is the rated voltage of the motor.

[0067] Power outage detection threshold V thresholdThe default value is 1.2Ve, i.e. 120% of the rated voltage of the motor, which is the core design principle to match the discharge characteristics of the bus capacitor. After power failure, the residual energy of the capacitor can maintain the bus voltage for tens to hundreds of milliseconds. The threshold of 1.2Ve is set to trigger detection at the initial voltage drop. The advantages are: 1. The 200ms buffer period of capacitor discharge is used to complete the brake command sending and power generation mode switching; 2. Higher than the rated voltage but lower than the full charge voltage of the capacitor (usually 1.3-1.4Ve), avoiding false operation caused by power grid fluctuations; 3. Adapt to different rated voltage systems such as 380V / 480V without hardware modification.

[0068] In specific embodiments, when the absolute value of the rotor frequency is continuously lower than the preset safety threshold and is maintained for a preset time length, it is determined that the braking is completed and the frequency converter is turned off in step three; wherein the safety threshold is 0.5 Hz, and the preset time length is at least 1 second, and it is determined that the braking is completed and the frequency converter is turned off.

[0069] The feature sets double determination conditions for brake completion: frequency threshold 0.5Hz superimposed with duration 1 second. Its core advantage is to strictly match the physical characteristics of mechanical braking. The 0.5Hz threshold is much lower than the lower limit of the braking interval (-7Hz), ensuring that the load kinetic energy has been completely absorbed by the brake pad. If only relying on single speed detection, load instantaneous jitter may cause misjudgment, while the 1 second duration requires the speed to be stable and close to zero, confirming from the physical level that the friction plate has been completely closed and engaged. The 1 second duration covers the entire brake action period. After the brake is closed, the load may have residual shaking of 0.3-0.8Hz, and if the machine is stopped too early, it will cause the gravitational potential energy to be released again, causing secondary hooking. Continuous monitoring for 1 second ensures that the system stops after mechanical braking takes effect, completely blocking the energy transmission path.

[0070] As Figure 5 Under heavy load conditions, it takes 0.6 seconds from brake action to speed stabilization below 0.5Hz, and the load displacement tends to zero when continuously monitored for 1 second; under light load conditions, continuous monitoring can filter the ±0.4Hz speed fluctuations caused by wind load. The essence is to build an absolute criterion for braking completion through time-speed double threshold, to completely eliminate the "braking empty window period hooking" hidden danger at zero hardware cost.

[0071] In specific embodiments, the frequency converter output frequency is set to zero after the emergency mode is triggered in step one.

[0072] The core advantage of immediately setting the frequency converter output frequency to zero in emergency mode is: first, eliminating residual driving risk: immediately terminating the original output command at the moment of power failure, preventing the residual energy of the bus capacitor from continuing to drive the motor; second, establishing a braking reference point: providing a zero frequency reference for subsequent power generation braking, allowing the torque control to quickly switch to the second / fourth quadrant mode.

[0073] The essence of frequency zeroing is to seize the control window: use the tens of milliseconds of residual energy of the capacitor to force the control system into a braking preparation state, and avoid the initial risk of "load out-of-control acceleration at the moment of power failure" described in the background art.

[0074] The crane frequency converter power failure anti-slip hook control method provided by the embodiment first detects the bus voltage in real time, triggers the emergency mode immediately when the bus voltage is lower than 1.2 times the rated voltage, synchronously sends the brake engagement command and sets the output frequency to zero to seize the control response window; then, according to the motor direction at the moment of power failure, the power generation mode is switched, when rotating forward, the output negative torque is limited to the [-50%, -10%] interval to enter the second quadrant to generate power, and when rotating reversely, the output positive torque is limited to the [20%, 150%] interval to enter the fourth quadrant to generate power, and the torque-frequency is dynamically adjusted through frequency partition control: when the frequency is higher than -7Hz, 20% minimum torque is enabled to release potential energy, when the frequency is lower than -13Hz, 150% maximum torque is enabled to brake urgently, and in the [-13Hz, -7Hz] interval, the power generation and braking are dynamically balanced according to a linear function; finally, the rotor frequency is continuously monitored, and when the rotor frequency is lower than 0.5Hz and maintains 1s, it is determined that the mechanical brake is completed, and the frequency converter output is turned off. The embodiment converts the gravitational potential energy into control energy to radically eliminate the risk of load slip hooking with zero additional hardware cost.

[0075] Figure 5 In the middle ①, the bus voltage V dc drops to V threshold Hereinafter, it is determined that the frequency converter is powered off, enters the emergency mode, the current rotor frequency f is positive, rapidly outputs negative torque to generate power, and maintains the bus voltage. Figure 5 In the middle ②, the rotor frequency f crosses zero, the output torque is adjusted to be positive, and power generation is continued to maintain the bus voltage. During ②-③, the output torque changes with the rotor frequency f, and the rotor frequency f is controlled within a safe range until the brake engagement action. Figure 5 In the middle ③, the load is stopped after the brake engagement device acts, the output torque is automatically adjusted to the lower limit, and the frequency converter continues to run. Figure 5 In the middle ④, the speed is lower than 0.5Hz and maintains 1s, and the frequency converter considers that the brake engagement device has stopped the load, and then the frequency converter is stopped.

[0076] Multiple tests on site show that whether it is a heavy load with an output torque of 150% or a light load with an output torque of 20%, the frequency converter can generate power to maintain operation with a very small slip after power failure, support the brake engagement action time, and then rely on the external brake engagement device to stably stop the load, thereby greatly reducing the safety risk of frequency converter running power failure.

[0077] Embodiment 2

[0078] The embodiment provides a frequency converter power failure anti-slip hook control system for a crane, which comprises a frequency converter and a brake engagement device. Figure 6As shown, the control system is used to execute the control method described in Embodiment 1, and the control system comprises a frequency converter and a brake device, an encoder connected thereto; the frequency converter comprises:

[0079] A main control module 1 is used to detect the bus voltage and execute the control logic;

[0080] A voltage detection module 2 is used to monitor the bus voltage value in real time;

[0081] A brake control module 3 is used to receive the brake command issued by the main control module 1 and control the brake device to act;

[0082] An encoder feedback module 4 is used to collect the motor rotor frequency in real time;

[0083] The control system is configured to: when the voltage detection module detects that the bus voltage is lower than the power-off determination threshold, trigger the emergency mode; the main control module sends the brake command to the brake control module, and the brake control module controls the brake device to act; the main control module controls the motor to enter the power generation mode according to the motor rotation direction fed back by the encoder at the moment of power-off: if the rotation direction is forward, controls the motor to output negative torque and limits the torque value in the negative torque interval, if the rotation direction is reverse, controls the motor to output positive torque and limits the torque value in the preset positive torque interval, and dynamically adjusts the output torque of the motor to maintain the rotor frequency of the motor in the preset negative value interval; when it is detected that the absolute value of the rotor frequency continuously is lower than the safety threshold, the main control module determines that the braking is completed and the frequency converter is turned off.

[0084] In this embodiment, the frequency converter serves as the core control unit, the main control module 1 thereof is connected with the voltage detection module 2 (which collects the bus voltage in real time) and the encoder feedback module 4 (which receives the rotor frequency signal transmitted by the encoder) through an internal bus; the brake control module 3 drives the external brake device to act through a relay output circuit after receiving the main control command; the encoder is directly installed on the motor rotor and transmits the frequency signal to the encoder feedback module 4 of the frequency converter through a cable. The brake device is coupled with the motor shaft through a mechanical linkage mechanism. Among them, the frequency converter is responsible for overall energy conversion and logic control, and switches to the power generation mode to maintain operation at the moment of power-off; the brake device stops the load by generating mechanical braking force through the friction plate; the encoder monitors the motor rotor frequency in real time and feeds back data; the main control module 1 executes the anti-slip hook algorithm and dynamically adjusts the torque according to the voltage and frequency signal; the voltage detection module 2 continuously monitors the bus voltage and triggers the power-off emergency response; the brake control module 3 converts the main control command into a relay action signal to control the brake device to release / engage the brake; the encoder feedback module 4 processes the original frequency signal to provide accurate frequency data for closed-loop control.

[0085] When the voltage detection module 2 identifies that the bus voltage is lower than the threshold value, the main control module 1 immediately triggers the emergency mode: the brake control module 3 starts the pre-brake of the braking device, and the motor enters the power generation mode based on the rotor direction feedback of the encoder, if the rotor rotates forward (lifts the load), the output is limited negative torque, if the rotor rotates reversely (drops the load), the output is limited positive torque. The main control module 1 dynamically adjusts the torque to stabilize the rotor frequency in the preset interval (such as -13Hz to -7Hz), and uses the gravitational potential energy of the load to generate electricity to maintain the bus voltage. When the frequency feedback by the encoder continuously falls below the safety threshold, the main control module 1 determines that the braking is completed and stops. This cooperation realizes three effects: 1. When there is no standby power supply, the frequency converter is maintained through energy conversion; 2. The load speed is controlled in the effective braking range of the brake, avoiding high-speed sliding; 3. Redundant protection is formed for low-performance brake devices, significantly reducing the risk of hook sliding in case of sudden power failure.

[0086] In specific embodiments, the frequency converter is equipped with a braking resistor for consuming excess power generated during power generation braking.

[0087] The provision of the braking resistor enables the frequency converter to actively consume the excess power converted from the gravitational potential energy of the load by the motor during power generation braking, which has three main effects: 1. When the generated power exceeds the power required for the frequency converter to maintain its operation, the bus voltage is prevented from being damaged by overvoltage due to energy accumulation by consuming power through the resistor; 2. In the process of load gravitational potential energy fluctuation or torque adjustment, a buffer channel is provided for dynamic energy balance to ensure that the bus voltage is stable within a safe range and avoid interruption of power generation mode; 3. As a supplementary guarantee for torque control strategy, even when the load suddenly decreases and the power generation increases, the resistor can timely release the energy to maintain the stability of the frequency control loop, thereby ensuring the continuous and reliable operation of the entire anti-hook sliding control process until the brake is completed.

[0088] The above is only a specific embodiment of the present application, but the protection scope of the present application is not limited thereto, any skilled person in the art can easily think of various equivalent modifications or replacements within the technical range disclosed by the present application, and these modifications or replacements should be covered within the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the protection scope of the claims.

Claims

1. A method for controlling the anti-hook slippage of a frequency converter in lifting equipment during power failure, characterized in that, The lifting equipment also includes a motor and a braking device, and the inverter power failure anti-hook control method of the lifting equipment includes: Step 1: Detect the inverter bus voltage. When the bus voltage is detected to be lower than the power failure threshold, trigger the emergency mode and send a brake command to the braking device. Step 2: Based on the motor's rotation direction at the moment of power failure, control the motor to enter the generator mode: if it rotates in the forward direction, control the motor to output negative torque and limit the torque value to a preset negative torque range; if it rotates in the reverse direction, control the motor to output positive torque and limit the torque value to a preset positive torque range, and dynamically adjust the motor's output torque to maintain the motor's rotor frequency within a preset negative range. Step 3: After the actual holding brake takes effect, when the absolute value of the rotor frequency is detected to be continuously lower than the safety threshold, the braking is determined to be completed and the frequency converter is shut down.

2. The method for controlling the anti-hook slippage of the frequency converter in lifting equipment according to claim 1, characterized in that, The preset negative value range in step two is [f dn f up ], where f dn f is the lower limit of the preset negative value range. up The dynamic adjustment of the motor's output torque, based on the upper limit of the preset negative range, includes: When the rotor frequency f of the motor satisfies: f up < f < 0, the output torque is adjusted to the lower limit value T dn _ neg ; When the rotor frequency f of the motor satisfies: f <f dn When this occurs, the output torque is adjusted to the upper limit value T of the positive torque range. up _ neg ; When the rotor frequency f of the motor is in [f dn f up When the torque is between [a certain value], the output torque will be dynamically adjusted according to a linear function.

3. The method for controlling the anti-hook slippage of the frequency converter in lifting equipment according to claim 2, characterized in that, Dynamically adjusting the output torque according to a linear function includes: Adjust the motor's output torque according to the size limit of f. Between; wherein, the output torque T is a linear function of the rotor frequency f, Where T dn_pos T is the lower limit of the negative torque range. up_pos This is the upper limit of the negative torque range.

4. The method for controlling the anti-hook slippage of the frequency converter in lifting equipment according to claim 2, characterized in that, The f dn The value range is -14Hz <f dn <-12Hz; the f up The value range is -8Hz <f up <-6Hz; the T up _ neg The value range is 140%. <T up _ neg <160%; the T dn _ neg The value range is 10%. <T dn _ neg <30%.

5. The inverter power failure anti-hook control method according to claim 3, characterized in that, The T up _ pos The value range is -12%. <T up _ pos <-8%, the T dn _ pos The value range is -60%. <T dn _ pos <-40%.

6. The method for controlling the anti-hook slippage of the frequency converter in lifting equipment according to claim 1, characterized in that, The power outage determination threshold V threshold The value range is 1.1V. e <V threshold <1.3V e , wherein, the V e This is the rated voltage of the motor.

7. The method for controlling the anti-hook slippage of the frequency converter in lifting equipment according to claim 1, characterized in that, In step three, when the absolute value of the rotor frequency remains below the preset safety threshold for a preset duration, braking is deemed complete and the inverter is shut down.

8. The method for controlling the anti-hook slippage of the frequency converter in lifting equipment according to claim 1, characterized in that, After triggering the emergency mode in step one, the inverter output frequency is set to zero.

9. A frequency converter power failure anti-hook control system for lifting equipment, characterized in that, The control system is used to execute the control method according to any one of claims 1-8, and the control system includes a frequency converter and a braking device and an encoder connected thereto; the frequency converter includes: The main control module is used to detect the bus voltage and execute control logic; The voltage detection module is used to monitor the bus voltage value in real time. The brake control module is used to receive the brake command issued by the main control module and control the braking device to operate. Encoder feedback module, used to acquire motor rotor frequency in real time; The control system is configured as follows: when the voltage detection module detects that the bus voltage is lower than the power failure threshold, it triggers an emergency mode; the main control module sends a brake command to the brake control module, which then controls the braking device to operate; the main control module controls the motor to enter a generator mode based on the motor rotation direction fed back by the encoder at the moment of power failure: if rotating in the forward direction, it controls the motor to output negative torque and limits the torque value to the negative torque range; if rotating in the reverse direction, it controls the motor to output positive torque and limits the torque value to the preset positive torque range, while dynamically adjusting the motor's output torque to maintain the motor's rotor frequency within the preset negative range; when the absolute value of the rotor frequency is detected to be continuously lower than the safety threshold, the main control module determines that braking is complete and shuts down the frequency converter.

10. The frequency converter power failure anti-hook control system for lifting equipment according to claim 9, characterized in that, The frequency converter is equipped with a braking resistor to dissipate excess electrical energy generated during the regenerative braking process.

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