Active dynamic braking solution for elevator system

Abstract

The invention relates to a method for active dynamic braking of an elevator system (100). The method includes detecting (310) a dynamic braking condition, acquiring (320) speed data representative of a speed of the elevator car (102), and activating (340) an active dynamic braking operation for dynamically braking movement of the elevator car if the acquired speed data indicates (330) that the speed of the elevator car reaches a predetermined monitored speed level. The active dynamic braking operation includes operating a motor inverter of an elevator drive unit of an elevator system by switching a high-voltage side switch and a low-voltage side switch of the motor inverter in a controlled manner such that a rotating field is generated in a stator winding of a traction motor, therefore, the rotation of the traction motor is dynamically braked, and the movement of the elevator car is braked. The invention also relates to an elevator drive unit, an elevator system, a computer program and a computer readable storage medium.

Description

Active dynamic braking solution for elevator systems Technical Field

[0001] This invention relates generally to the technical field of elevator systems. In particular, this invention relates to an active dynamic braking solution for elevator systems. Background Technology

[0002] Sometimes, in elevator systems, the traction motor is used to generate braking torque outside of normal elevator operation to perform a braking operation, thereby stopping the movement of the elevator car. For example, this braking operation may be necessary when an elevator car with passengers inside stops between floors due to a power failure. In this case, typically, a field technician arrives at the elevator location and manually engages the traction brake to allow the elevator car to move under gravity. Another situation that may require the aforementioned braking operation may occur if the braking force of the elevator traction brake is damaged for some reason. This could be caused by errors during elevator maintenance, such as improper execution during brake adjustment, or if foreign substances such as oil or grease enter the brake surfaces.

[0003] Traditionally, in the case of permanent magnet motors, braking is achieved by short-circuiting the stator windings of the traction motor. This short circuit induces an electromotive force (EMF) voltage in the windings, which in turn generates a motor torque that counteracts the rotation of the traction motor, thus braking the elevator car. This braking operation is known as dynamic braking. The problem with this traditional dynamic braking method is that it doesn't necessarily work correctly for all different traction motor models and load combinations. In some traction motor and / or load combinations, the braking torque may be insufficient, and elevator operation may become unstable (i.e., the elevator becomes uncontrollable).

[0004] Therefore, there is a need for improved dynamic braking, which can generate sufficient motor torque for various traction motors and / or load combinations, unaffected by the operating conditions and environment of the elevator system. Summary of the Invention

[0005] To provide a basic understanding of some aspects of various embodiments of the invention, a simplified overview is given below. This overview is not a detailed summary of the invention. It is neither intended to identify key or essential elements of the invention nor to depict its scope. The following overview presents only some concepts of the invention in a simplified form as a prelude to a more detailed description of exemplary embodiments of the invention.

[0006] One object of the present invention is to provide a method, elevator drive unit, elevator system, computer program, and computer-readable storage medium for active dynamic braking of an elevator system. Another object of the present invention is that the method, elevator drive unit, elevator system, computer program, and computer-readable storage medium for active dynamic braking of an elevator system enable ensuring that the traction motor generates sufficient power to maintain active dynamic braking operation, thereby dynamically braking the movement of the elevator car.

[0007] The object of the present invention is achieved by the method, elevator drive unit, elevator system, computer program and computer-readable storage medium as defined in the respective independent claims.

[0008] According to a first aspect, a method for active dynamic braking of an elevator system is provided, wherein the method includes: detecting a dynamic braking condition; acquiring speed data representing the speed of an elevator car; and activating an active dynamic braking operation for dynamically braking the movement of the elevator car if the acquired speed data indicates that the speed of the elevator car has reached a predetermined monitoring speed level; wherein the active dynamic braking operation includes operating the motor inverter of the elevator drive unit of the elevator system by controllingly switching the high-voltage side switch and the low-voltage side switch of the motor inverter, thereby generating a rotational field in the stator winding of the traction motor, thereby dynamically braking the rotation of the traction motor and thus braking the movement of the elevator car.

[0009] The method may also include adjusting the braking torque generated by the traction motor so that the speed of the elevator car does not exceed an adaptive speed limit during active dynamic braking operations, wherein the predetermined monitored speed level may be lower than the adaptive speed limit.

[0010] The method may further include: monitoring whether the supply voltage of the elevator drive unit is sufficient to power the elevator drive unit, wherein the supply voltage of the elevator drive unit can be regenerated from the traction motor; and if the current level of the monitoring of the adequacy of the supply voltage of the elevator drive unit, indicating an adaptive speed limit, is insufficient to power the elevator drive unit, then increasing the adaptive speed limit.

[0011] Monitoring the adequacy of the supply voltage of the elevator drive unit may include monitoring at least one of the following: the adequacy of the regenerated motor power, wherein if the regenerated motor power drops below the minimum power limit, the adaptive speed limit may be increased; the DC link voltage of the drive unit, wherein if the DC link voltage of the drive unit drops below the minimum voltage limit, the adaptive speed limit may be increased; and the magnetizing shaft current of the traction motor, wherein if the magnetizing shaft current drops below the minimum current limit, the adaptive speed limit may be increased.

[0012] The regulation of the braking torque generated by the traction motor may include operating the high-voltage side switch and the low-voltage side switch of the motor inverter.

[0013] Dynamic braking conditions can be one of the following: manually opening the traction machine brake due to a power failure; or insufficient braking force when the traction machine brake activation command is issued.

[0014] According to a second aspect, an elevator drive unit for an elevator system is provided, comprising: a motor inverter connected to the stator winding of a traction motor of the elevator system, wherein the motor inverter has a high-voltage side switch and a low-voltage side switch; and a drive controller; wherein the drive controller of the elevator drive unit is configured to cause the elevator drive unit to perform: detecting dynamic braking conditions; acquiring speed data representing the speed of the elevator car; and activating an active dynamic braking operation for dynamically braking the movement of the elevator car if the acquired speed data indicates that the speed of the elevator car has reached a predetermined monitored speed level; wherein the active dynamic braking operation includes the drive controller being configured to operate the motor inverter by controllingly switching the high-voltage side switch and the low-voltage side switch of the motor inverter, thereby generating a rotational field in the stator winding of the traction motor, thereby dynamically braking the rotation of the traction motor and thus braking the movement of the elevator car.

[0015] The elevator drive unit can also be configured to adjust the braking torque generated by the traction motor so that the speed of the elevator car does not exceed an adaptive speed limit during active dynamic braking operations, wherein the predetermined monitored speed level may be lower than the adaptive speed limit.

[0016] The elevator drive unit is also configured to: monitor whether the supply voltage of the elevator drive unit is sufficient to power the elevator drive unit, wherein the supply voltage of the elevator drive unit can be regenerated from the traction motor; and if the monitoring of the adequacy of the supply voltage of the elevator drive unit indicates that the current level of the adaptive speed limit is insufficient to power the elevator drive unit, then increase the adaptive speed limit.

[0017] To monitor the adequacy of the supply voltage of the elevator drive unit, the elevator drive unit can be configured to monitor at least one of the following: the adequacy of the regenerated motor power, wherein the elevator drive unit can be configured to increase the adaptive speed limit if the regenerated motor power drops below a minimum power limit; the DC link voltage of the drive unit, wherein the elevator drive unit can be configured to increase the adaptive speed limit if the DC link voltage of the drive unit drops below a minimum voltage limit; and the magnetizing shaft current of the traction motor, wherein the elevator drive unit can be configured to increase the adaptive speed limit if the magnetizing shaft current drops below a minimum current limit.

[0018] The elevator drive unit can be configured to operate the high-voltage side switch and the low-voltage side switch of the motor inverter to regulate the braking torque.

[0019] Dynamic braking conditions can be one of the following: manually opening the traction machine brake due to a power failure; or insufficient braking force when the traction machine brake activation command is issued.

[0020] According to a third aspect, an elevator system is provided, comprising: an elevator traction machine including a traction motor; an elevator car configured to travel along an elevator shaft; an elevator car speed measurement system configured to provide speed data representing the speed of the elevator car; and an elevator drive unit as described above.

[0021] According to a fourth aspect, a computer program is provided, wherein the computer program includes instructions that, when executed by a computer, cause the computer to perform the methods described above.

[0022] According to a fifth aspect, a computer-readable storage medium is provided, wherein the computer-readable storage medium includes instructions that, when executed by a computer, cause the computer to perform the methods described above.

[0023] When read in conjunction with the accompanying drawings, the various exemplary and non-limiting embodiments of the invention, as well as their additional objects and advantages, will be best understood from the following description of specific exemplary and non-limiting embodiments.

[0024] The verbs “comprising” and “including” are used herein as open-ended restrictions, neither excluding nor requiring the presence of any unlisted features. Features described in the dependent claims may be freely combined with each other unless expressly stated otherwise. Furthermore, it should be understood that the use of “a” or “an,” i.e., the singular form, throughout this document does not exclude a plurality. Attached Figure Description

[0025] Embodiments of the present invention are shown in the accompanying drawings by way of example rather than by way of limitation.

[0026] Figure 1 schematically illustrates an example of an elevator system.

[0027] Figure 2A schematically shows a simple example of an elevator drive unit connected to a traction motor.

[0028] Figure 2B schematically illustrates a simple example of a frequency converter.

[0029] Figure 2C schematically shows an example circuit diagram of a motor inverter.

[0030] Figure 3 schematically illustrates an example of an active dynamic braking method for an elevator system.

[0031] Figure 4 schematically illustrates another example of this method.

[0032] Figure 5 shows a schematic example of the components of the drive controller of the elevator drive unit. Detailed Implementation

[0033] Figure 1 schematically illustrates an example of an elevator system 100. The elevator system 100 includes an elevator car 102, a counterweight 108, an elevator traction machine, an elevator control unit 110, and an elevator car speed measurement system 112. The elevator car 102 is configured to travel along an elevator shaft 104 between multiple floors (i.e., landings) 106a-106n. The elevator system 100 can also form an elevator group, i.e., a group consisting of two or more elevator cars 102, each traveling along a separate elevator shaft 104, the elevator group operating as a unit serving the same landings 106a-106n. The elevator system 100 may also include one or more known elevator-related entities, such as user interface devices, elevator doors, and / or safety circuits and devices, which are not shown in Figure 1 for clarity.

[0034] An elevator traction machine is configured to drive an elevator car 102 along an elevator shaft 104 between floors 106a-106n. The elevator traction machine includes a traction motor (e.g., an electric motor such as a permanent magnet motor) 230 and a traction sheave 114 for lifting the elevator car 102. The elevator traction machine also includes a traction mechanism braking device comprising at least two traction mechanism brakes 116a, 116b that act directly on the traction sheave 114 to stop undesired movement of the elevator car 102. In the example of Figure 1, the elevator traction mechanism braking device includes two traction mechanism brakes 116a, 116b. However, the traction mechanism braking device may also include more than two traction mechanism brakes. For illustrative purposes, only the traction sheave 114 and traction mechanism brakes 116a, 116b of the elevator traction machine are shown in Figure 1.

[0035] The elevator car 102, elevator traction machine, and counterweight 108 are interconnected via a traction rope assembly 118, which is wired via a traction pulley 114 and a plurality of pulleys, which are not shown in Figure 1 for clarity. When the traction pulley 114 rotates, the elevator car 102 and counterweight 108 move. The traction rope assembly 118 includes at least one traction rope or belt.

[0036] Elevator control unit 110 is configured to control at least the operation of elevator system 100. Elevator control unit 110 may be located within machine room 120 (as shown in the example of Figure 1) or, for example, on one of floors 106a-106n in a machine room-less elevator system. Elevator control unit 110 is communicatively coupled to other entities of elevator system 100. Communication between elevator control unit 110 and other entities of elevator system 100 may be based on one or more known wired or wireless communication technologies. Elevator control unit 110 may be implemented as a standalone control entity or in a distributed control environment located among multiple standalone control entities, such as multiple servers, providing distributed control resources. Elevator control unit 110 includes elevator drive unit 122 for controlling traction motor 230 (e.g., power feed to traction motor and speed and / or torque of traction motor) to move elevator car 102 along elevator shaft 104.

[0037] Elevator drive unit 122 includes drive controller 210 and frequency converter 220. Figure 2A schematically shows a simplified example of elevator drive unit 122 connected to traction motor 230. Drive controller 210 may be, for example, a digital signal processor (DSP). Drive controller 210 is configured to generate, i.e., define, speed command values ​​and torque command values ​​for traction motor 230. The speed command value represents the speed of traction motor 230 as a function of time. The torque command value represents the torque of traction motor 230 as a function of time. Drive controller 210 is configured to provide the generated speed command values ​​and torque command values ​​to frequency converter 220. Frequency converter 220 is configured to control the speed and torque of traction motor 230 according to the speed command values ​​and torque command values.

[0038] Figure 2B schematically illustrates a simplified example of the frequency converter 220 of the elevator drive unit 122. The frequency converter 220 includes a motor inverter, i.e., an inverter bridge 240. The motor inverter 240 is connected to the stator windings of the traction motor 230. The frequency converter 220 also includes a rectifier, i.e., a rectifier bridge 242, connected to the main line 244. The motor inverter 240 is connected to the rectifier 242 via a DC link 246. The DC link 246 may, for example, include a capacitor or a set of capacitors connected in parallel with the high-voltage bus 260a and the low-voltage bus 260b. The motor inverter 240 has a high-voltage side switch 250a and a low-voltage side switch 250b. The drive controller 210 is configured to generate a rotating field in the stator windings of the traction motor 230 by switching the high-voltage side switch 250a and the low-voltage side switch 250b of the motor inverter 240. This rotating field causes the traction wheel 114 to rotate. The friction between the traction wheel 114 and the traction rope device 118 has the effect of moving the elevator car 102 when the traction wheel 114 rotates.

[0039] Figure 2C schematically illustrates an example circuit diagram of a motor inverter 240. The high-side switch 250a and low-side switch 250b of the motor inverter 240 form an inverter bridge. In the example of Figure 2B, each high-side switch 250a and each low-side switch 250b of the motor inverter 240 includes a semiconductor switch connected in parallel with an anti-parallel diode. This semiconductor switch may be, for example, an insulated-gate bipolar transistor (IGBT), a metal-oxide-semiconductor field-effect transistor (MOSFET), a gallium nitride (GaN) transistor, or a silicon carbide (SiC) transistor. The high-side switch 250a is connected to the high-voltage bus 260a of the DC link 246, and the low-side switch 250b is connected to the low-voltage bus 260b of the DC link 246. The high-voltage side switch 250a and the low-voltage side switch 250b are connected on one side between the two buses 260a and 260b of the DC link 246, and on the other side to the feed line of the traction motor 230. For a standard three-phase elevator motor, which is preferably a permanent magnet motor, the feed line is a three-phase feed line.

[0040] The elevator car speed measurement system 112 is configured to provide speed data representing the speed of the elevator car 102. The elevator speed measurement system may include a motor encoder indicating the rotational speed of the traction motor 230. Additionally or alternatively, the elevator speed measurement system 112 may include a sensor providing a direct indication of the speed of the elevator car 102. The sensor providing the direct indication may be, for example, but not limited to, an acceleration sensor attached to the elevator car 102, an encoder mounted to a rope pulley of the elevator car 102, or a measuring device attached to the elevator car 102 adapted to measure one or more targets attached to a fixed structure in the elevator shaft 104. In the example of FIG. 1, the elevator car speed measurement system 112 is implemented using a measuring device attached to the elevator car 102; however, this is merely one example implementation of the elevator car speed measurement system 112 discussed.

[0041] During normal elevator operation, the elevator car 102 moves according to a desired elevator drive curve, allowing it to smoothly depart from the departure floor, accelerate to its maximum speed (i.e., rated speed), and then decelerate from the rated speed, thus smoothly reaching the destination floor. When the elevator car 102 reaches the destination floor, the elevator control unit 110 executes a stop operation to halt the movement of the elevator car 102 and maintains the elevator car 102 stationary in the elevator shaft 104 by activating the traction brake 116. Normal elevator operation may also include, for example, inspection operations. During an inspection operation, the elevator car 102 moves at a low speed along the elevator shaft 104 according to a manual drive command issued by a maintenance technician. Outside of normal elevator operation, there may be situations requiring dynamic braking of the elevator car 102. The active dynamic braking operation discussed below can be used to dynamically brake the movement of the elevator car 102 in such cases.

[0042] Next, an example of a method for active dynamic braking of an elevator system 100 will be described with reference to Figure 3, which schematically illustrates the method as a flowchart. This method is executed by the elevator drive unit 122.

[0043] In step 310, the elevator drive unit 122 detects a dynamic braking condition. A dynamic braking condition can be a situation outside of normal elevator operation in which active dynamic braking is to be used. A dynamic braking condition can be, for example, at least one of the following: the traction brake 116 is manually engaged due to a power failure; or insufficient braking force is detected when a traction brake activation command is issued. For example, a dynamic braking condition can be detected when a field technician manually engages the traction brake 116 in the event of a power failure, causing the elevator car 102 to begin moving under gravity. Alternatively, a dynamic braking condition can also be detected, for example, if a braking activation command is issued at the end of the elevator car 102's journey but the braking force of the traction brake 116 is insufficient and the elevator car 102 continues to move. A dynamic braking condition can also be any other situation outside of normal elevator operation in which active dynamic braking can be utilized. The detection of a dynamic braking condition can be performed directly by the elevator drive unit 122 itself, or indirectly by obtaining detection information (from the elevator drive unit 122) indicating that a dynamic braking condition has been detected.

[0044] In step 320, the elevator drive unit 122 acquires speed data representing the speed of the elevator car 102. More specifically, the drive controller 210 of the elevator drive unit 122 acquires the speed data. The speed data is acquired from an elevator speed measurement system 112 configured to provide the speed data discussed above. The elevator drive unit 122 can acquire speed data continuously.

[0045] In step 340, if the acquired speed data indicates that the speed of the elevator car 102 has reached a predetermined (i.e., preset) monitoring speed level, the elevator drive unit 122 activates the active dynamic braking operation of the elevator system 100 to dynamically brake the movement of the elevator car 102. In other words, when dynamic braking is detected and the acquired speed data indicates that the speed of the elevator car 102 has reached a predetermined monitoring speed level, the active dynamic braking operation can be activated. For example, the predetermined monitoring speed level may be, but is not limited to, 0.20 m / s. The active dynamic braking operation may, for example, be referred to as active dynamic motor braking (ADMB) operation.

[0046] The active dynamic braking operation of the elevator system 100 involves the elevator drive unit 122 operating the motor inverter 240 by controlling the switching of the high-voltage side switch 250a and the low-voltage side switch 250b of the motor inverter 240. This generates a rotational field in the stator windings of the traction motor 230, which is used to brake the rotation of the traction motor 230 and thus the movement of the elevator car 102. The drive controller 210 of the elevator drive unit 122 can generate control signals to the high-voltage side switch 250a and the low-voltage side switch 250b of the motor inverter 240 to switch the high-voltage side switch 250a and the low-voltage side switch 250b of the motor inverter 240 during the active dynamic braking operation. Using the active dynamic braking operation, sufficient braking torque can be generated for various traction motor models and various load combinations to dynamically brake the movement of the elevator car 102. Controlled switching of the high-voltage side switch 250a and low-voltage side switch 250b of the motor inverter 240 may include, for example, switching the high-voltage side switch 250a and low-voltage side switch 250b so that a sinusoidal rotating field can be generated in the motor windings with minimal distortion. The switching can be controlled using any suitable modulation technique. For example, pulse width modulation (PWM) can be used. However, any other suitable modulation technique, such as space vector modulation or any other suitable modulation technique, can also be employed. This modulation produces a switching mode with a switching frequency between, for example, 5-10 kHz.

[0047] During active dynamic braking operation, for safety reasons, the elevator drive unit 122 and traction motor 230 are preferably disconnected from the main line. The elevator drive unit 122 and traction motor 230 can be disconnected from the main line, for example, via a contactor, so that the main line power supply is not used to generate driving torque (i.e., acceleration torque) in the traction motor 230. Therefore, only the braking torque of the traction motor 230 can be generated during active dynamic braking operation. The elevator drive unit 122 can receive its supply voltage from the regenerative power of the traction motor 230. The drive controller 210 of the elevator drive unit 122 can convert the regenerative power of the traction motor 230 into the supply voltage of the elevator drive unit 122. For example, a DC / DC converter connected to the DC link 246 of the frequency converter 220 can be used to generate a suitable voltage, for example, 24V, to supply the control electronics of the elevator drive unit 122. Using the regenerative power of the traction motor 230 as the supply voltage of the elevator drive unit 122 eliminates the need for an additional backup power supply (e.g., a battery) in the event of a power failure. Therefore, active dynamic braking can be used in a variety of operating conditions and environments (such as in the event of a power failure) without requiring an external power source.

[0048] According to one example, in addition to active dynamic braking, a dynamic braking operation (i.e., conventional dynamic braking) can also be used. In (conventional) dynamic braking, the stator windings of the traction motor 230 are short-circuited to generate braking torque, thereby dynamically braking the movement of the elevator car 102. The dynamic braking operation is preferably self-awakening, such that it is initiated when the traction motor 230 begins to rotate, causing the DC link voltage of the elevator drive unit 122 to rise. The rise in DC link voltage is caused by the electromotive force (EMF) of the traction motor 230, which is rectified from the stator windings of the traction motor 230 to the DC link 246 of the elevator drive unit 122 via anti-parallel connected diodes of the motor inverter 240. Preferably, the stator windings of the traction motor 230 are short-circuited once the traction motor 230 begins to rotate, so that the movement of the elevator car 102 is dynamically braked before the active dynamic braking operation is activated. As discussed above, if the acquired speed data indicates that the speed of the elevator car 102 has reached a predetermined monitored speed level (step 330), the active dynamic braking operation is activated. However, the dynamic braking operation is activated before the active dynamic braking operation is activated. This self-awakening dynamic braking operation has been disclosed in document WO2008 / 031915 A1.

[0049] During active dynamic braking operation of elevator system 100, elevator drive unit 122 can adjust (step 350) the braking torque generated by traction motor 230 such that the speed of elevator car 102 does not exceed an adaptive speed limit. A predetermined monitored speed level is below the adaptive speed limit. An initial value can be set for the adaptive speed limit. The initial value of the adaptive speed limit can be, for example, but not limited to, 0.28 m / s. The adaptive speed limit can be adjusted (e.g., increased) according to the supply voltage of elevator drive unit 122, as described later in this disclosure. Adjusting the braking torque may include operating the high-voltage side switch 250a and the low-voltage side switch 250b of motor inverter 240. The adjustment of the braking torque can be by increasing and / or decreasing the braking torque according to the speed of elevator car 102. In a permanent magnet motor, motor torque is generated by supplying current along the direction of the torque axis (i.e., the q-axis in the dq coordinate system). In practice, the q-axis is located in a direction orthogonal to the magnetization axis (i.e., the d-axis), which is in the direction of the permanent magnet. Depending on the polarity of the q-axis current, a driving torque or a braking torque is generated. The elevator drive unit 122 measures the motor current, for example, through a current control loop, and regulates the supply voltage in the motor windings by operating the high-voltage side switch 250a and the low-voltage side switch 250b of the motor inverter 240, thereby controlling the q-axis current and thus also the braking torque.

[0050] As discussed, during active dynamic braking operation of elevator system 100, elevator drive unit 122 can adjust the braking torque in traction motor 230 such that the speed of elevator car 102 does not exceed an adaptive speed limit. However, there may be situations where the current adaptive speed limit is insufficient to power elevator drive unit 122. For example, when the regenerative power of traction motor 230 is insufficient to provide sufficient supply voltage to elevator drive unit 122. If the adaptive speed limit is insufficient to power the elevator drive unit, active dynamic braking will cease. Therefore, to maintain active dynamic braking operation, it may be necessary to adjust (e.g., increase) the adaptive speed limit. In other words, during active dynamic braking operation, the speed of elevator car 102 can be adaptively limited to adequately power elevator drive unit 122. The adaptive speed limit for active dynamic braking operation ensures that traction motor 230 generates sufficient power (i.e., regenerative power) to maintain the operation of elevator drive unit 122, thereby enabling active dynamic braking to dynamically brake the movement of elevator car 102.

[0051] Next, we will discuss the adaptive speed limit for active dynamic braking operation with reference to Figure 4, which schematically illustrates the adaptive speed limit as a flowchart.

[0052] In step 410, the elevator drive unit 122 may monitor whether the supply voltage of the elevator drive unit 122 is sufficient to power the elevator drive unit 122. In other words, the elevator drive unit 122 monitors whether the supply voltage of the elevator drive unit 122 is sufficient to power the elevator drive unit 122 at the current level where the speed of the elevator car 102 follows an adaptive speed limit. For example, the adequacy of the supply voltage can be monitored by monitoring the adequacy of the regenerated motor power. Alternatively or additionally, the adequacy of the supply voltage can be monitored, for example, by monitoring the DC link voltage of the drive unit 122. According to a non-limiting example, the predetermined voltage limit can be 300VDC. Alternatively or additionally, monitoring the adequacy of the supply voltage of the elevator drive unit 122 may include, for example, monitoring the magnetizing shaft current (I) of the traction motor 230. d ).

[0053] If the monitoring indication of the adequacy of the supply voltage to the elevator drive unit 122 (step 420) indicates that the current level of the adaptive speed limit is insufficient to power the elevator drive unit 122, then the adaptive speed limit of the elevator drive unit 122 is increased (step 430). In other words, it is detected that the speed of the elevator car 102 needs to be higher than the current adaptive speed limit in order to adequately power the elevator drive unit 122 through the supply voltage of the elevator drive unit 122 (i.e., the regenerative power of the traction motor 230). The increase in the adaptive speed limit allows for an increase in the supply voltage of the elevator drive unit 122, which in turn allows for maintaining an adequate power supply to the elevator drive unit 122 and thus maintaining active dynamic braking operation. For example, if the regenerative motor power is monitored and drops below the minimum power limit, the adaptive speed limit can be increased. In other words, the regenerative motor power is monitored, and if the monitored regenerative motor power drops below the minimum power limit, the adaptive speed limit is increased. According to another example, when the DC link voltage of drive unit 112 is monitored, if the DC link voltage of drive unit 122 drops below the minimum voltage limit, the adaptive speed limit can be increased. In other words, the DC link voltage is monitored, and if the monitored DC link voltage drops below the minimum voltage limit, the adaptive speed limit is increased. According to yet another example, when the magnetizing shaft current is monitored, if the monitored magnetizing shaft current drops below the minimum current limit, the adaptive speed limit can be increased. In other words, the magnetizing shaft current of traction motor 230 is monitored, and if the monitored magnetizing shaft current drops below the minimum current limit, the adaptive speed limit is increased.

[0054] The adaptive speed limit is preferably lower than the buffer impact speed. Therefore, the use of active dynamic braking ensures that the speed of the elevator car 102 does not exceed the buffer impact speed even when the braking force is insufficient when the traction brake activation command is issued. Thus, active dynamic braking can also serve as a solution to meet the safety requirements of other braking devices (OBMs).

[0055] Next, a non-restrictive example equation is given to define the adaptive speed limit. Motor torque T M It can be defined by the following equation: , where P mech It is the motor's nominal mechanical power and ω mech This is the mechanical angular velocity of the motor. Mechanical angular velocity can be defined by the following equation: RPM refers to the nominal speed of the motor, measured in RPM.

[0056] Next, the motor power loss P M It can be defined by the following equation: , where r s It is the stator resistance of the motor, and I M This is the motor's nominal current.

[0057] Total loss P TOT Then it can be defined by the following equation: , where P D This represents the estimated loss of drive unit 122.

[0058] Minimum angular velocity ω in active dynamic braking operation min It can be defined using the following equation: T N It is the motor's nominal torque.

[0059] Minimum value v of the adaptive speed limit min For example, it can be defined using the following equation: D ts It is the diameter of the traction sheave 114, and roping is the rope winding ratio of the elevator traction rope assembly 118 (e.g., 1, 2, 4, etc.). The adaptive speed limit needs to have at least a minimum value v. min To keep the elevator drive unit 122 in operation during active dynamic braking operations.

[0060] Figure 5 shows a schematic example of the components of the drive controller 210 of the elevator drive unit 122. The drive controller 210 may be a standalone unit or may be included in or part of other units; for example, the frequency converter 220 and / or the drive controller 210 may be included in or part of the elevator control unit 110. The drive controller 210 may also be distributed across more than two locations or more than two units. The drive controller 210 may include one or more processors 510, one or more volatile or non-volatile memories 520 for storing portions of computer program code 525 and any data values, one or more communication interface units 530, and, if possible, one or more user interface units 540. The aforementioned components may be communicatively connected to each other using, for example, an internal bus. The processor 510 may be configured to execute at least some portions of the computer program code 525 stored in the memory 520, causing the processor 510 and thus the drive controller 210 to perform desired tasks, such as the operation of the drive controller 210 and / or the method steps described above. Therefore, processor 510 can be configured to access memory 520 and retrieve or store any information therein. For clarity, processor here refers to any unit suitable for processing information and controlling the operation of drive controller 210, as well as other tasks. These operations can also be implemented using a microcontroller solution with embedded software. Similarly, memory 520 is not limited to a specific type of memory, but any type of memory suitable for storing the described information can be applied in the context of this invention. Communication interface unit 530 provides an interface for communicating with any external unit, such as elevator car speed measurement system 112, elevator control unit 110, one or more databases, and / or any other unit. The communication interface unit can be based on one or more known communication technologies, whether wired or wireless, for exchanging information. One or more user interface units 540 may include one or more input / output (I / O) devices, such as buttons, keyboards, touchscreens, microphones, speakers, displays, etc., for receiving input and output information. The computer program 525 may be a computer program product, which may be contained in a tangible, non-volatile (non-transient) computer-readable medium carrying embedded computer program code 525 for use with a computer, namely the drive controller 210 of the elevator drive unit 122.

[0061] The specific examples provided in the above description should not be construed as limiting the applicability and / or interpretation of the appended claims. The list and groups of examples provided in the above description are not exhaustive unless otherwise expressly stated.

Claims

1. A method for active dynamic braking of an elevator system (100), the method comprising: Detect (310) the dynamic braking status; acquire (320) speed data representing the speed of the elevator car (102); And if the acquired speed data indicates (330) that the speed of the elevator car (102) reaches a predetermined monitored speed level, then an active dynamic braking operation for dynamically braking the movement of the elevator car (102) is activated (340), wherein the active dynamic braking operation includes operating the motor inverter (240) of the elevator drive unit (122) of the elevator system (100) by controlling the switching of the high-voltage side switch (250a) and the low-voltage side switch (250b) of the motor inverter (240) to generate a rotational field in the stator winding of the traction motor (230), thereby dynamically braking the rotation of the traction motor (230) and thus braking the movement of the elevator car (102).

2. The method according to claim 1, further comprising: Adjust (350) the braking torque generated by the traction motor (230) such that the speed of the elevator car (102) does not exceed an adaptive speed limit during the active dynamic braking operation, wherein the predetermined monitored speed level is lower than the adaptive speed limit.

3. The method according to claim 2, further comprising: The system monitors (410) whether the supply voltage of the elevator drive unit (122) is sufficient to power the elevator drive unit (122), wherein the supply voltage of the elevator drive unit (122) is regenerated from the traction motor (230); and if the monitoring of the adequacy of the supply voltage of the elevator drive unit (122) indicates (420) that the current level of the adaptive speed limit is insufficient to power the elevator drive unit (122), the system raises (430) the adaptive speed limit.

4. The method according to claim 3, wherein, Monitoring the adequacy of the supply voltage of the elevator drive unit (122) includes monitoring at least one of the following: the adequacy of the regenerated motor power, wherein if the regenerated motor power drops below the minimum power limit, the adaptive speed limit is increased; the DC link voltage of the drive unit (122), wherein if the DC link voltage of the drive unit (122) drops below the minimum voltage limit, the adaptive speed limit is increased; and the magnetizing shaft current of the traction motor (230), wherein if the magnetizing shaft current drops below the minimum current limit, the adaptive speed limit is increased.

5. The method according to any one of claims 2 to 4, wherein, Adjusting (350) the braking torque generated by the traction motor (230) includes operating the high-voltage side switch (250a) and the low-voltage side switch (250b) of the motor inverter (240).

6. The method according to any one of the preceding claims, wherein, The dynamic braking situation is one of the following: the traction brake (116) is manually opened due to a power failure; or the braking force is insufficient when the traction brake activation command is issued.

7. An elevator drive unit (122) for an elevator system (100), wherein, The elevator drive unit (122) includes: a motor inverter (240) connected to the stator winding of the traction motor (230) of the elevator system (100), wherein the motor inverter (240) has a high-voltage side switch (250a) and a low-voltage side switch (250b); and a drive controller (210), wherein the drive controller (210) of the elevator drive unit (122) is configured to enable the elevator drive unit (122) to perform: detecting dynamic braking conditions; acquiring speed data representing the speed of the elevator car (102); and if the acquired speed data indicates that the elevator car... When the speed of the elevator car (102) reaches a predetermined monitoring speed level, an active dynamic braking operation is activated to dynamically brake the movement of the elevator car (102). The active dynamic braking operation includes the drive controller (210) being configured to operate the motor inverter (240) by controlling the switching of the high-voltage side switch (250a) and the low-voltage side switch (250b) of the motor inverter (240) to generate a rotational field in the stator winding of the traction motor (230), thereby dynamically braking the rotation of the traction motor (230) and thus braking the movement of the elevator car (102).

8. The elevator drive unit (122) according to claim 7, wherein, The elevator drive unit (122) is also configured to adjust the braking torque generated by the traction motor (230) such that the speed of the elevator car (102) does not exceed an adaptive speed limit during the active dynamic braking operation, wherein the predetermined monitored speed level is lower than the adaptive speed limit.

9. The elevator drive unit (122) according to claim 8, wherein, The elevator drive unit (122) is also configured to: monitor whether the supply voltage of the elevator drive unit (122) is sufficient to power the elevator drive unit (122), wherein the supply voltage of the elevator drive unit (122) is regenerated from the traction motor (230); and if the monitoring of the adequacy of the supply voltage of the elevator drive unit (122) indicates that the current level of the adaptive speed limit is insufficient to power the elevator drive unit (122), then increase the adaptive speed limit.

10. The elevator drive unit (122) according to claim 9, wherein, In order to monitor the adequacy of the supply voltage of the elevator drive unit (122), the elevator drive unit (122) is configured to monitor at least one of the following: the adequacy of the regenerated motor power, wherein the elevator drive unit (122) is configured to increase the adaptive speed limit if the regenerated motor power drops below the minimum power limit; the DC link voltage of the drive unit (122), wherein the elevator drive unit (122) is configured to increase the adaptive speed limit if the DC link voltage of the drive unit (122) drops below the minimum voltage limit; and the magnetizing shaft current of the traction motor (230), wherein the elevator drive unit (122) is configured to increase the adaptive speed limit if the magnetizing shaft current drops below the minimum current limit.

11. The elevator drive unit (122) according to any one of claims 8 to 10, wherein, The elevator drive unit (122) is configured to operate the high-voltage side switch (250a) and low-voltage side switch (250b) of the motor inverter (240) to adjust the braking torque.

12. The elevator drive unit (122) according to any one of claims 7 to 11, wherein, The dynamic braking situation is one of the following: the traction brake (116) is manually opened due to a power failure; or the braking force is insufficient when the traction brake activation command is issued.

13. An elevator system (100), comprising: An elevator traction machine, the elevator traction machine including a traction motor (230). An elevator car (102) is configured to travel along an elevator shaft (104); An elevator car speed measurement system (112) is configured to provide speed data representing the speed of the elevator car (102); And the elevator drive unit (122) according to any one of claims 7 to 12.

14. A computer program (525) comprising instructions that, when executed by a computer, cause the computer to perform the method according to any one of claims 1 to 6.

15. A computer-readable storage medium comprising instructions that, when executed by a computer, cause the computer to perform the method according to any one of claims 1 to 6.

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