Elevator energy-saving safety device based on integration of inversion feedback and super capacitor energy storage

Abstract

The invention provides an elevator energy-saving safety device based on integration of inversion feedback and super capacitor energy storage, which comprises a traction machine frequency converter used for controlling the operation of a traction machine; the super capacitor energy storage unit is connected with a direct current bus of the tractor frequency converter in parallel and used for storing energy fed back by the tractor in the braking process; the working mechanism of the inversion feedback circuit comprises the steps that when it is detected that the voltage of the super capacitor reaches a preset threshold value, the inversion feedback circuit is started, and energy stored in the super capacitor is fed back to a power grid or other requirements; the bidirectional silicon controlled rectifier unit is connected in series between the input end of the traction machine frequency converter and an alternating current power supply, and is used for cutting off the connection with the alternating current power supply when voltage sag or short-time interruption is detected, and obtaining energy from the super capacitor energy storage unit to maintain power supply; and the control unit is used for controlling the operation of each functional unit. The invention aims to improve the energy utilization efficiency of the elevator and enhance the safe operation capability of the elevator under the condition of power grid voltage fluctuation or power failure.

Description

Technical Field

[0001] The present invention relates to the technical field of elevator systems, and particularly to an elevator energy-saving and safety device based on the integration of inverter feedback and supercapacitor energy storage. Background Art

[0002] In a 380V three-phase elevator system, the operating state of the traction machine directly affects the energy consumption and operation safety of the elevator. When the traction machine is in the electric state, the peak value of the DC bus voltage of the frequency converter is stabilized at 537V. However, in the light-load upward or heavy-load downward working conditions of the elevator, the traction machine changes to the generating state, generating excess energy. Since the input side of traditional frequency converters generally adopts the diode rectification method and cannot achieve energy feedback, the DC bus voltage of the frequency converter rises rapidly. To avoid damage to equipment due to excessive voltage, the IGBT switch of the energy consumption braking circuit conducts when the DC bus voltage reaches about 710V, and the excess energy is consumed through the braking resistor until the voltage drops to about 650V and then cuts off. This method not only causes energy waste but also increases the operating cost of the elevator.

[0003] To solve the above problems, the prior art has proposed an elevator energy feedback and energy-saving device, as Figure 1 shown. Its circuit topology structure is provided with a Boost boost voltage stabilizing circuit and a three-phase full-bridge inverter circuit in parallel on the DC bus of the elevator traction machine frequency converter. When the DC voltage of the frequency converter exceeds 560V, the inverter circuit starts, and the excess energy is fed back to the power grid. In theory, it can replace the energy consumption braking circuit and achieve the energy-saving effect. However, there are still many deficiencies in this technical solution in practical applications:

[0004] First, the energy-saving effect is not ideal: In the initial stage of elevator braking, the motor rotor speed is relatively high, generating a large induced electromotive force and induced current. These currents all flow into the DC bus of the frequency converter, resulting in a sharp increase in the feedback energy. For economic considerations, the designed power of the energy feedback inverter is often less than the peak value of the feedback power of the traction machine. As Figure 2 shown, for an elevator equipped with an energy feedback device, about 30% of the braking energy is still consumed through the braking resistor, and the energy-saving potential has not been fully exerted.

[0005] Secondly, the prior art does not have the function of treating voltage sags and short-time interruptions: According to the national standard "GB / T30137-2013 Power Quality Voltage Sags and Short-time Interruptions" and actual operation experience, when the power system suffers from faults such as lightning strikes and short circuits, voltage sags or short-time interruptions are likely to occur, and the duration can reach 10ms to 1 minute. However, the voltage tolerance of the traction machine frequency converter and the elevator controller is limited, and the longest does not exceed 20ms. Therefore, when the elevator encounters such voltage quality problems, it is prone to emergency shutdown, seriously affecting the passenger experience and safety of taking the elevator.

[0006] Finally, the prior art does not have the function of providing emergency leveling power during power outages: Elevator emergency leveling is an important measure to ensure passenger safety. However, in existing devices, due to the lack of energy storage units such as supercapacitors or batteries, it is impossible to provide emergency power for the elevator controller and actuator when the elevator encounters sudden failures such as power outages, resulting in the elevator being unable to complete the emergency leveling operation and increasing the risk of passengers being trapped in the elevator.

[0007] In summary, although the existing elevator energy feedback energy-saving technology has improved the energy-saving effect to a certain extent, there are still defects such as unsatisfactory energy saving, inability to manage voltage sags and short-term interruptions, and lack of emergency leveling function. There is an urgent need for a more efficient, safe, and reliable integrated elevator energy-saving and safety device to solve the above problems. Summary of the Invention

[0008] In order to solve the above problems existing in the prior art, the purpose of the present invention is to provide an elevator energy-saving and safety device based on the integration of inverter feedback and supercapacitor energy storage, aiming to improve the energy utilization efficiency of the elevator and enhance the safe operation ability of the elevator under power grid voltage fluctuations or power outages.

[0009] The present invention achieves the above purpose through the following technical solutions:

[0010] An elevator energy-saving and safety device based on the integration of inverter feedback and supercapacitor energy storage, comprising:

[0011] A traction machine frequency converter for controlling the operation of the traction machine;

[0012] A supercapacitor energy storage unit, connected in parallel with the DC bus of the traction machine frequency converter, for storing the energy fed back by the traction machine during braking;

[0013] An inverter feedback circuit, connected to the supercapacitor energy storage unit and the DC bus of the traction machine frequency converter, and its working mechanism includes: when it is detected that the supercapacitor voltage reaches a preset threshold, the inverter feedback circuit is started to feed back the energy stored in the supercapacitor to the power grid or to meet the operation requirements of other elevators;

[0014] A bidirectional thyristor unit, connected in series between the input end of the traction machine frequency converter and the AC power supply, for cutting off the connection with the AC power supply when a voltage sag or short-term interruption is detected, and obtaining energy from the supercapacitor energy storage unit to maintain power supply;

[0015] A control unit for controlling the operation of each functional unit.

[0016] According to an elevator energy-saving and safety device based on the integration of inverter feedback and supercapacitor energy storage provided by the present invention, the control unit is embedded with the following algorithms:

[0017] A fast voltage sag criterion algorithm based on dq decomposition method, which is configured to judge voltage anomalies when a voltage sag or short-term interruption occurs and trigger an emergency response mechanism;

[0018] A seamless switching-in control algorithm for a supercapacitor + inverter backup power supply. After a voltage sag or short-term interruption is detected, this algorithm quickly cuts off the connection with the AC power supply by forcibly turning off the bidirectional thyristor unit, and simultaneously starts the process of obtaining energy from the supercapacitor energy storage unit, and provides uninterrupted power supply for the traction machine and elevator controller with a voltage source control algorithm; during this process, the IGBT switch connected to the supercapacitor is also turned off to prevent the DC bus current of the frequency converter from flowing back in reverse due to too low voltage of the supercapacitor;

[0019] A seamless flexible exit control algorithm, which is executed when the AC power supply returns to normal after a voltage sag or short-term interruption, and smoothly switches the power supply of the elevator system from the supercapacitor + inverter backup power supply back to the normal AC power supply through a control strategy.

[0020] An elevator energy-saving and safety device based on the integration of inverter feedback and supercapacitor energy storage according to the present invention. When the traction machine brakes, the generated energy directly flows into the supercapacitor for energy storage, and this process is used to slow down the rising speed of the DC bus voltage of the traction machine frequency converter;

[0021] When the voltage of the supercapacitor rises to 1.15 times the DC bus voltage UDC of the traction machine frequency converter, the inverter feedback circuit starts to work, and the energy stored in the supercapacitor is fed back to the traction machine or the power grid. Since the braking energy of the elevator traction machine decreases with the decrease of speed, the operation of the energy feedback circuit keeps the voltage of the supercapacitor at a stable level;

[0022] When the voltage of the supercapacitor drops to 1.05 times UDC, the inverter feedback circuit stops working.

[0023] An elevator energy-saving and safety device based on the integration of inverter feedback and supercapacitor energy storage according to the present invention. When the voltage of the supercapacitor drops due to self-discharge, the supercapacitor is floatingly charged through a DC / DC converter to maintain the voltage of the supercapacitor at a set value of 1.05 times UDC, ensuring that there is sufficient energy reserve in the supercapacitor when voltage regulation or emergency leveling is required.

[0024] An elevator energy-saving and safety device based on the integration of inverter feedback and supercapacitor energy storage according to the present invention further includes an emergency leveling function control module, and its specific implementation includes:

[0025] When it is detected that the AC power supply voltage drops below the preset threshold of 0.1U1 and this low-voltage state lasts for more than 1 second, the emergency leveling function control module determines that a long-term power outage of the AC power supply has occurred;

[0026] After determining the long-term power outage, the emergency leveling function control module immediately sends a signal to the elevator controller to execute the emergency leveling function, instructing the elevator controller to start the emergency leveling operation;

[0027] The emergency leveling function control module continuously monitors the feedback signal of the elevator controller until it receives the signal indicating that the emergency leveling function has been executed by the elevator controller;

[0028] If during the execution of the emergency leveling function, the stored energy of the supercapacitor is exhausted, or the signal indicating that the emergency leveling function has been executed by the elevator controller has been received, the emergency leveling function control module stops working and ends the execution of the emergency leveling function.

[0029] According to an elevator energy-saving and safety device based on the integration of inverter feedback and supercapacitor energy storage provided by the present invention, the fault response strategy of the bidirectional thyristor unit specifically includes:

[0030] When a short-circuit fault of the bidirectional thyristor is detected: it is determined that the thyristor has lost its basic functions of forward conduction and reverse cut-off, and is equivalent to becoming a wire; the bypass contactor is controlled to close to ensure the normal power supply of the traction machine is not affected; in this fault state, the device only retains the energy-saving function and loses the functions of voltage sag and short-term interruption management;

[0031] When an open-circuit fault of the bidirectional thyristor is detected: it is determined that for the traction machine, it is equivalent to a voltage sag or short-term interruption of 50% of the effective voltage value; the voltage sag management program is immediately executed, and other normally working bidirectional thyristors are forced to turn off to prevent the fault from expanding or affecting the safe operation of the elevator; the bypass contactor is controlled to close to maintain the basic power supply of the traction machine; in this fault state, the device also only retains the energy-saving function and loses the functions of voltage sag and short-term interruption management.

[0032] According to an elevator energy-saving and safety device based on the integration of inverter feedback and supercapacitor energy storage provided by the present invention, in the voltage sag fast criterion algorithm based on the dq decomposition method, for three-phase voltage signals, their dq components can be obtained according to the dq transformation, which is expressed by the following formula:

[0033]

[0034] Where:

[0035] Then the following formula can be obtained:

[0036]

[0037] The fundamental frequency components in the three-phase voltage are converted into DC components by dq transformation, while the higher harmonics are converted into corresponding AC components; the converted dq components are filtered by setting a low-pass filter to obtain stable fundamental wave dq components; for asymmetric fault conditions, the filtered dq components are inversely transformed back into abc three-phase voltages, and single-phase voltage detection is performed based on this; among them, through the processing methods of the dq transformation and inverse transformation, the cut-off frequency of the low-pass filter can be reduced, thereby reducing the delay of the filter.

[0038] According to an elevator energy-saving and safety device based on the integration of inverter feedback and supercapacitor energy storage provided by the present invention, it further includes using a three-phase software phase-locked loop to obtain phase information. The three-phase software phase-locked loop adopts synchronous rotation coordinate transformation, first transforms the three-phase stationary coordinate system into a two-phase αβ stationary coordinate system, and then obtains the corresponding phase information through rotation coordinate transformation.

[0039] Among them, the loop filter G(s) is set as a PI regulator, 1 / s represents a voltage-controlled oscillator, ω 0 is the rated angular frequency of the power grid, ω0 = 100π rad·s-1, which is used as the reference frequency of the voltage-controlled oscillator. The two transformation matrices are respectively the following formulas:

[0040]

[0041] According to an elevator energy-saving and safety device based on the integration of inverter feedback and supercapacitor energy storage provided by the present invention, in the seamless cut-in control algorithm, the voltage at the PCC point is monitored in real time to determine whether the grid voltage drops. If the grid voltage drops, triggering is stopped and switched to the island mode;

[0042] In the island mode, a modulation wave is generated according to the following formula:

[0043]

[0044] Judge whether the thyristor current reaches zero. If so, continue to stay in the island mode.

[0045] According to an elevator energy-saving and safety device based on the integration of inverter feedback and supercapacitor energy storage provided by the present invention, in the seamless flexible exit control algorithm, when a grid fault is detected or needed, it enters the island mode to maintain the independent operation of the system;

[0046] In the island mode, continuously monitor the voltage condition at the PCC point;

[0047] Judge whether the grid voltage has recovered. If not, continue to monitor the voltage at the PCC point;

[0048] If it has been restored, start the voltage linear modulation matching control, and gradually adjust the system voltage to match the grid voltage;

[0049] During the execution of the voltage linear modulation matching control, continuously judge whether the voltage matching is completed;

[0050] If it has been completed, trigger the conduction signal and perform mode switching, switching from the island mode to the state of ready to grid-connect;

[0051] After mode switching, perform a current linear transition process to smoothly adjust the system current to match the grid current;

[0052] After completing the current linear transition, exit the island mode and switch to the PQ mode to achieve synchronous grid-connected operation with the grid.

[0053] It can be seen that compared with the prior art, the present invention comprehensively improves the deficiencies of the existing elevator system in terms of energy conservation, voltage sag governance and emergency leveling power supply by adopting an innovative solution combining supercapacitor energy storage and inverter feedback technology, and has the following beneficial effects:

[0054] 1. Significantly improve the energy conservation rate: The present invention adopts a hybrid circuit of inverter feedback and supercapacitor energy storage, so that under a certain inverter feedback power, more energy generated during the braking of the traction machine can be absorbed. As an efficient energy storage element, the supercapacitor can quickly absorb and store the electric energy fed back by the traction machine, effectively avoiding the energy waste in the traditional energy-consuming braking method. This design greatly improves the energy conservation effect of the elevator system, reduces the operating cost, and conforms to the development concept of green energy conservation.

[0055] 2. Have the function of governing voltage sags and short-time interruptions: The present invention forms a stable and reliable backup power supply system through the combined design of series-connected bidirectional thyristors and parallel-connected inverters. When a voltage sag or short-time interruption occurs in the external power grid, the system can quickly respond to ensure the normal operation of the elevator is not affected. This function effectively avoids the situation of the elevator being emergently shut down due to external power grid problems, and greatly improves the comfort and safety of passengers taking the elevator.

[0056] 3. Enhance the safety of the elevator and provide emergency leveling power: The present invention adopts the supercapacitor energy storage technology to provide a reliable emergency leveling power supply for the elevator controller and the execution unit. In the case of a long-term power outage of the external power supply, the supercapacitor can release the stored electric energy to ensure that the elevator can complete the emergency leveling operation and enable passengers to safely leave the car. This design greatly enhances the response ability of the elevator in case of sudden failures and guarantees the personal safety of passengers.

[0057] In summary, by combining supercapacitor energy storage and inverter feedback technology, the present invention not only significantly improves the energy-saving effect of the elevator system, but also has the functions of managing voltage sags and short-term interruptions, provides a reliable emergency leveling power supply for the elevator, improves the overall performance of the elevator system, enhances its safety, reliability and comfort, and brings significant improvements to the development of the elevator industry and the riding experience of passengers.

[0058] The following further elaborates on the present invention in detail in conjunction with the accompanying drawings and specific embodiments. Description of the Drawings

[0059] Figure 1 is the primary circuit schematic diagram of an elevator energy feedback energy-saving device in the prior art.

[0060] Figure 2 is the schematic diagram for analyzing the energy-saving effect of an elevator energy feedback device in the prior art.

[0061] Figure 3 is the circuit schematic diagram of an embodiment of an elevator energy-saving and safety device based on the integration of inverter feedback and supercapacitor energy storage according to the present invention.

[0062] Figure 4 is the schematic diagram for analyzing the energy-saving effect of an embodiment of an elevator energy-saving and safety device based on the integration of inverter feedback and supercapacitor energy storage according to the present invention.

[0063] Figure 5 is the flow schematic diagram of the software phase-locked loop in an embodiment of an elevator energy-saving and safety device based on the integration of inverter feedback and supercapacitor energy storage according to the present invention.

[0064] Figure 6 The schematic diagram of the equivalent circuit in the seamless cut-in control algorithm mode in an embodiment of an elevator energy-saving and safety device based on the integration of inverter feedback and supercapacitor energy storage according to the present invention.

[0065] Figure 7 is the flow schematic diagram of the seamless cut-in control algorithm in an embodiment of an elevator energy-saving and safety device based on the integration of inverter feedback and supercapacitor energy storage according to the present invention.

[0066] Figure 8 is the equivalent schematic diagram in the seamless flexible exit control algorithm mode in an embodiment of an elevator energy-saving and safety device based on the integration of inverter feedback and supercapacitor energy storage according to the present invention.

[0067] Figure 9 is the flow schematic diagram of the seamless flexible exit control algorithm in an embodiment of an elevator energy-saving and safety device based on the integration of inverter feedback and supercapacitor energy storage according to the present invention. Specific Embodiments

[0068] To make the objectives, technical solutions and advantages of the present invention more clear, the following will, in conjunction with the accompanying drawings of the present invention, clearly and completely describe the technical solutions in the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all of the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the scope of protection of the present invention.

[0069] As used herein, the term "embodiment" means that a particular feature, structure or characteristic described in connection with the embodiment may be included in at least one embodiment of the present application. The phrase appears in various places in the specification and does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment mutually exclusive with other embodiments. Those skilled in the art will explicitly and implicitly understand that the embodiments described herein may be combined with other embodiments.

[0070] See Figures 3 to 9 , this embodiment provides an elevator energy-saving and safety device based on the integration of inverter feedback and supercapacitor energy storage, including:

[0071] A traction machine frequency converter for controlling the operation of the traction machine.

[0072] A supercapacitor energy storage unit, connected in parallel with the DC bus of the traction machine frequency converter, for storing the energy fed back by the traction machine during braking.

[0073] An inverter feedback circuit, connected to the supercapacitor energy storage unit and the DC bus of the traction machine frequency converter, whose working mechanism includes: when it is detected that the supercapacitor voltage reaches a preset threshold, start the inverter feedback circuit to feed back the energy stored in the supercapacitor to the power grid or for meeting the operation requirements of other elevators.

[0074] A bidirectional thyristor unit, connected in series between the input end of the traction machine frequency converter and the AC power supply, for disconnecting the connection with the AC power supply when a voltage sag or short-term interruption is detected, and obtaining energy from the supercapacitor energy storage unit to maintain power supply.

[0075] A control unit for controlling the operation of each functional unit.

[0076] In this embodiment, the control unit is embedded with the following algorithms:

[0077] A fast voltage sag criterion algorithm based on the dq decomposition method, which is configured to judge the voltage anomaly when a voltage sag or short-term interruption occurs and trigger an emergency response mechanism;

[0078] Seamless switching-in control algorithm for supercapacitor + inverter backup power supply. After voltage sag or short interruption is detected, the algorithm quickly cuts off the connection with the AC power supply by forcibly turning off the bidirectional thyristor unit, and simultaneously starts the process of drawing energy from the supercapacitor energy storage unit, and provides uninterrupted power supply for the traction machine and elevator controller with the voltage source control algorithm; during this process, the IGBT switch connected to the supercapacitor is turned off simultaneously to prevent the reverse injection of the DC bus current of the frequency converter due to too low voltage of the supercapacitor.

[0079] Seamless flexible switching-out control algorithm, which is executed when the AC power supply returns to normal after voltage sag or short interruption. Through the control strategy, the power supply of the elevator system is smoothly switched from the supercapacitor + inverter backup power supply back to the normal AC power supply, ensuring the continuity and stability of elevator operation, and at the same time reducing the voltage impact on the traction machine and elevator controller.

[0080] It can be seen that the control unit, as the core of the device, is responsible for controlling the operation of all the above units. The control unit is embedded with a fast voltage sag criterion algorithm based on dq decomposition method, a seamless switching-in control algorithm for supercapacitor + inverter backup power supply, and a seamless flexible switching-out control algorithm to ensure the stable operation of the device under various working conditions.

[0081] In this embodiment, the seamless flexible switching-out control algorithm is configured to smoothly transition back to the normal operation control strategy when the AC power supply returns to normal, ensuring the continuity and stability of elevator operation. While executing the seamless flexible switching-out control algorithm, monitor the voltage level of the supercapacitor. When it is confirmed that the voltage of the supercapacitor has recovered above the safety threshold and the AC power supply is stable and reliable, re-enable the IGBT switch to allow the normal interaction of the DC bus current of the frequency converter and the AC power supply; through the continuous monitoring and adjustment of the voltage source control algorithm, ensure that the supply voltage of the traction machine and elevator controller is stable during the process of switching back to the AC power supply, and avoid the adverse impact on elevator operation caused by voltage fluctuation.

[0082] The seamless flexible switching-out control algorithm is also configured to dynamically adjust the control strategy according to the current operating state of the elevator and the preset safety parameters during the switching process to ensure that the elevator can safely and smoothly transition to the normal power supply mode.

[0083] In this embodiment, when the traction machine is in the electric traction mode, the peak value U of the DC bus voltage of the frequency converter DC is equal to 1.414 times the AC power supply voltage U 1 , assuming U 1 is 380V, then U DC is 537V.

[0084] When the traction machine brakes, energy is quickly poured into the DC bus of the frequency converter through the freewheeling diodes of the inverter bridge, causing the DC voltage to rise. The overvoltage protection action setting value of the DC bus of the elevator frequency converter is generally 810V. The on-voltage of the IGBT switch in the energy consumption braking circuit is generally 660V, and the cut-off voltage is generally 620V. IGBT belongs to a power electronic device and supports high-frequency repeated on-off. In fact, during the braking process of the elevator, to maintain the relative stability of the DC bus voltage, the IGBT switch conducts and cuts off very frequently.

[0085] When the traction machine brakes, the generated energy directly flows into the super capacitor for energy storage. This process is used to slow down the rising speed of the DC bus voltage of the traction machine frequency converter; when the voltage of the super capacitor rises to 1.15 times the DC bus voltage UDC of the traction machine frequency converter (618V), the inverter feedback circuit starts to work and returns the energy stored in the super capacitor to the traction machine or the power grid. Since the braking energy of the elevator traction machine decreases as the speed decreases, the operation of the energy feedback circuit keeps the voltage of the super capacitor at a stable level; when the voltage of the super capacitor drops to 1.05 times UDC (564V), the inverter feedback circuit stops working.

[0086] When the voltage of the super capacitor drops due to self-discharge, the super capacitor is floating charged through a DC / DC converter to maintain the voltage of the super capacitor at the set value of 1.05 times UDC, ensuring that there is sufficient energy reserve in the super capacitor when voltage regulation or emergency leveling is required.

[0087] When a voltage sag or short interruption of no more than 1 second occurs in the AC power supply, the duration of the voltage sag is equal to the time of the relay protection device + switch to cut off the fault, which is at most about 300ms. The short interruption of the voltage is actually the switching time of the elevator dual-power switch ATS, which is at most about 400ms. Therefore, the energy in the super capacitor should be equal to the energy required for the traction machine power + elevator controller power to work continuously for 1 second. If the elevator controller has an emergency leveling function, the energy of the super capacitor should be equal to the energy required for emergency leveling (the energy required for the emergency leveling function must be greater than the energy required to handle the voltage sag or short interruption for 1 second).

[0088] When a voltage sag or short interruption occurs, the controller adopts the fast criterion algorithm and seamless cut-in control algorithm of this embodiment, quickly cuts off the connection with the AC power supply by forcibly turning off the bidirectional thyristor, and draws energy from the super capacitor to supply power to the traction machine and elevator controller with the voltage source control algorithm. At the same time as the criterion is obtained, the IGBT switch of the super capacitor is turned off to prevent the DC bus current of the frequency converter from flowing into due to too low voltage of the super capacitor. After the voltage sag or short interruption ends, the seamless flexible exit control algorithm of this embodiment is adopted to return to the operation control strategy when the AC power supply is normal.

[0089] In this embodiment, an emergency leveling function control module is also included, and its specific implementation includes:

[0090] When the AC power supply is cut off for a long time and the elevator controller has an emergency leveling function: when the AC power supply voltage is detected to drop below the preset threshold value 0.1U1 and the low voltage state lasts for more than 1 second, the emergency leveling function control module determines that the AC power supply is cut off for a long time.

[0091] After determining that the power is off for a long time, the emergency leveling function control module immediately sends a signal to the elevator controller to execute the emergency leveling function, instructing the elevator controller to start the emergency leveling operation.

[0092] The emergency leveling function control module continuously monitors the feedback signal of the elevator controller until receiving a signal from the elevator controller indicating that the emergency leveling function has been executed.

[0093] If the energy storage capacity of the supercapacitor is exhausted during the execution of the emergency leveling function, or a signal indicating that the emergency leveling function has been completed is received from the elevator controller, the emergency leveling function control module stops working and ends the execution of the emergency leveling function.

[0094] In this embodiment, the device can be regarded as two parts: a series bidirectional thyristor and a parallel inverter power supply. If a partial fault in the parallel inverter power supply is detected, the control signal is output, the contactor in the feedback metering is disconnected, the fault information is reported, and maintenance personnel are waiting. The parallel partial fault has no effect on the operation of the elevator. The following focuses on the response strategy for the series bidirectional thyristor fault.

[0095] Specifically, the fault response strategies for the bidirectional thyristor unit include:

[0096] When a short circuit fault is detected in the bidirectional thyristor: it is determined that the thyristor has lost its basic functions of forward conduction and reverse cutoff, which is equivalent to becoming a wire; the bypass contactor is controlled to close to ensure that the normal power supply of the traction machine is not affected; in this fault state, the device only retains the energy-saving function, and loses the function of controlling voltage sags and short-term interruptions.

[0097] When a short circuit fault of the bidirectional thyristor is detected: it is determined that for the traction machine, a voltage sag or short interruption equivalent to 50% of the effective value of the voltage has occurred; the voltage sag control procedure is immediately executed to force the shutdown of other normally operating bidirectional thyristors to prevent the fault from expanding or affecting the safe operation of the elevator; the bypass contactor is controlled to close to maintain the basic power supply to the traction machine; in this fault state, the device also only retains the energy-saving function, and loses the function of controlling voltage sags and short interruptions.

[0098] Moreover, the execution of the above-mentioned fault detection, determination, and countermeasure strategies is automatically completed by the fault countermeasure strategy module within the device without manual intervention, ensuring the safe and stable operation of the elevator in case of faults.

[0099] In this embodiment, as Figure 4 shown, when the elevator traction machine operates in the braking power generation state, the present invention is equivalent to simultaneously absorbing it with the inverter power and the supercapacitor power. The energy-saving effect is much better than that of the conventional elevator inverter feedback energy-saving device. It not only improves the energy-saving effect but also enhances the stability of the system and extends the service life of the equipment, having significant application value. Among them, the supercapacitor has the characteristics of fast charge and discharge, and can efficiently absorb the electric energy generated when the traction machine generates electricity and store it. The inverter power is responsible for feeding back part of the electric energy to the power grid to achieve the maximum utilization of energy. This combination method significantly improves the energy-saving effect. The energy storage function of the supercapacitor can alleviate the impact brought by the concentrated feedback of electric energy to the power grid and improve the stability of the power grid. By effectively absorbing and storing electric energy, the energy consumption and wear of other components in the elevator system are reduced, thereby extending the service life of the equipment.

[0100] In this embodiment, in the fast voltage sag criterion algorithm based on the dq decomposition method, for the three-phase voltage signal, its dq components can be obtained according to the dq transformation, expressed as the following formula:

[0101]

[0102] Where:

[0103] Then the following formula can be obtained:

[0104]

[0105] The fundamental frequency components in the three-phase voltage are converted into DC components by using the dq transformation, and at the same time, the high-order harmonics are converted into corresponding AC components; the transformed dq components are filtered by setting a low-pass filter to obtain stable fundamental wave dq components; for the asymmetrical fault situation, the filtered dq components are inversely transformed back to the abc three-phase voltage, and single-phase voltage detection is performed based on this; among them, through the processing methods of the dq transformation and inverse transformation, the cut-off frequency of the low-pass filter can be reduced, thereby reducing the delay of the filter.

[0106] In this embodiment, it also includes using a three-phase software phase-locked loop to obtain phase information. The three-phase software phase-locked loop adopts synchronous rotation coordinate transformation, first transforms the three-phase stationary coordinate system into a two-phase αβ stationary coordinate system, and then obtains the corresponding phase information through rotation coordinate transformation, as Figure 5 shown.

[0107] Among them, the loop filter G(s) is set as a PI regulator, 1 / s represents a voltage-controlled oscillator, ω 0 is the rated angular frequency of the power grid, ω 0 = 100π rad·s-1, which is used as the reference frequency of the voltage-controlled oscillator. The two transformation matrices are respectively the following formulas:

[0108]

[0109] The dq decomposition method has the advantages of less computational complexity, better anti-interference characteristics, and fast response speed.

[0110] Specifically, in the seamless switching-in mode, the supercapacitor + inverter backup power supply forcibly turns off the bidirectional thyristor and ensures that the amplitude and duration of the transient voltage fluctuation at the PCC2 point caused are small enough so that the impact on the traction machine frequency converter and elevator controller can be ignored. For the convenience of analysis, the equivalent circuit of the seamless switching-in process is as Figure 6 shown. Considering that the line load is usually inductive, the load current is approximately treated as a current source in a short time, and the influence of the instantaneous discharge of the filter capacitor is ignored at the same time, then there is the following relationship:

[0111] i l = i g + i f

[0112] Δi l / Δt ≈ 0

[0113] In the formula, i l is the load current, i g is the grid-side current, and i f is the inverter output current.

[0114] It can be seen from the above formula that the change rate Δi f of the filter inductor current i f is approximately equal to the change rate Δi m of the current i g of the small reactance L g , that is, Δi f / Δt ≈ -Δi g / Δt. Therefore, in the voltage control mode, by controlling the voltage difference Δu across the filter inductor L f , the change rate of its current can be controlled, and then the current drop rate of the small reactance current i g can be controlled. Its relationship can be expressed as:

[0115]

[0116] In the formula, u INV is the output voltage of the inverter bridge arm port, and u PCC2 is the voltage at the PCC2 point.

[0117] The effect of seamless switching mainly depends on the forced turn-off time T of the thyristor s which can be evaluated according to the following formula:

[0118]

[0119] In the formula, i gmax represents the peak value of the thyristor current at the starting moment of turn-off.

[0120] Meanwhile, the forced turn-off also needs to satisfy the following two constraint conditions:

[0121] u INV | ≤ U dc

[0122]

[0123] In the formula, represents the maximum allowable current change rate of the selected thyristor device, and U dc represents the rated DC voltage value of the PWM inverter. Therefore, the criterion for the seamless switching process is:

[0124]

[0125] In this embodiment, the steps of the seamless switching algorithm control algorithm are as Figure 7 shown, specifically including:

[0126] In the seamless switching control algorithm, the voltage at the PCC point is monitored in real time to determine whether the grid voltage drops. If the grid voltage drops, the triggering is stopped and the system switches to the island mode;

[0127] In the island mode, the modulation wave is generated according to the following formula:

[0128]

[0129] It is judged whether the thyristor current reaches zero. If so, the system continues to stay in the island mode.

[0130] Specifically, the seamless flexible exit control algorithm of the supercapacitor + inverter backup power supply is implemented as follows:

[0131] Before triggering the bidirectional thyristor, the output voltage of the PWM inverter should be controlled to match the grid-side voltage, and then the thyristor is triggered to conduct. At the same time, after the thyristor is triggered to conduct, if the commutation between the PWM converter and the grid line is completed instantaneously, a large voltage drop will be generated on the equivalent reactance L of the line g causing u PCC2Severe spikes occur. Therefore, the commutation processes of the two must be smoothed. Here, the complete control process including voltage matching and commutation smoothing is called the flexible exit process.

[0132] The equivalent circuit diagram in the flexible exit mode is as Figure 8 (a) shown. In the initial state, the thyristor T 1 is turned off, the grid-side current i g = 0, and the load-side voltage u PCC2 does not match the grid-side voltage u PCC1 . For the conventional voltage matching algorithm, first, the frequencies and phases of u PCC1 and u PCC2 are phase-locked respectively, and the voltage amplitudes of the two are calculated; then phase-shift control is performed on u PCC2 to make the phases of the two gradually approach until the thyristor is triggered and turned on when the phase difference is less than a certain threshold. Its disadvantage is that the phase-locking and phase-shift calculations are relatively cumbersome, especially when the system voltage is unbalanced, and even when the phases are the same, it cannot ensure that the voltage amplitudes are the same.

[0133] To overcome the above problems, this embodiment proposes a voltage matching algorithm based on instantaneous value linear modulation, which is simple in calculation and high in accuracy. The principle is as follows:

[0134] Assume that at the initial moment of voltage matching, the control reference voltage of the backup power supply of the supercapacitor + inverter for point PCC2 is u PCC2_ref0 , then the difference between the voltage at point PCC1 and u PCC2_ref0 at this moment is:

[0135] Δv = u PCC1 -u PCC2_ref0

[0136] For the linear modulation voltage matching method, the core idea is to linearly divide the instantaneous voltage difference Δv between two points into N segments, and gradually "approach" u PCC2_ref0 to the voltage at point PCC1 according to the whole period of Δv. The phasor relationships are as Figure 8 (b) shown. The reference voltage of the supercapacitor + inverter during this process can be expressed as:

[0137]

[0138] In the formula, N is a positive integer, usually selected between 5 and 20.

[0139] To avoid the sudden change of the reference voltage at PCC2, the change of the k value in Equation (2-16) should be selected at the zero-crossing moment of Δv. Further, to ensure the symmetry of the positive and negative half-cycles of the reference voltage at PCC2 within one cycle, the k value is changed only when Δv crosses zero and its derivative is positive until k = N is satisfied. Thereafter, if the absolute value of the instantaneous voltage difference between the PCC2 point and the PCC1 point of each phase is within the preset value vth for n consecutive samplings (n is a positive integer within 10), the bidirectional thyristor of this phase is re-triggered, and the PWM inverter is switched from the voltage control mode to the current control mode.

[0140] For the subsequent commutation slow change control, the reference current of the supercapacitor + inverter backup power supply is expressed as follows:

[0141]

[0142] In the formula, M is a positive integer, usually selected between 5 and 20.

[0143] To avoid the sudden change of the reference current, the change of the j value in the above formula should be selected at the zero-crossing moment of i ref . Further, to ensure the symmetry of the positive and negative half-cycles of the reference current within one cycle, the j value is changed only when i ref crosses zero and its derivative is positive until j = M is satisfied.

[0144] In this embodiment, the steps of the flexible exit algorithm are as Figure 9 shown, specifically including:

[0145] In the seamless flexible exit control algorithm, when a grid fault is detected or needed, enter the island mode to maintain the independent operation of the system;

[0146] In the island mode, continuously monitor the voltage condition of the PCC point;

[0147] Judge whether the grid voltage has recovered. If not, continue to monitor the voltage of the PCC point;

[0148] If it has recovered, start the voltage linear modulation matching control to gradually adjust the system voltage to match the grid voltage;

[0149] During the execution of the voltage linear modulation matching control, continuously judge whether the voltage matching is completed;

[0150] If it has been completed, trigger the conduction signal and perform mode switching, switching from the island mode to the state of ready to connect to the grid;

[0151] After the mode switching, perform a current linear transition process to smoothly adjust the system current to match the grid current;

[0152] After completing the linear transition of the current, exit the islanding mode and switch to the PQ mode to achieve synchronous grid-connected operation with the power grid.

[0153] In summary, by combining the supercapacitor energy storage and inverter feedback technologies, this embodiment not only significantly improves the energy-saving effect of the elevator system, but also has the functions of dealing with voltage sags and short-time interruptions, provides a reliable emergency leveling power supply for the elevator, improves the overall performance of the elevator system, enhances its safety, reliability and comfort, and brings significant improvements to the development of the elevator industry and the elevator riding experience of passengers.

[0154] Furthermore, this embodiment adopts a hybrid circuit of inverter feedback and supercapacitor energy storage, so that under a certain inverter feedback power, more energy generated during the braking of the traction machine can be absorbed. As an efficient energy storage element, the supercapacitor can quickly absorb and store the electric energy fed back by the traction machine, effectively avoiding the energy waste in the traditional energy consumption braking method. This design greatly improves the energy-saving effect of the elevator system and reduces the operating cost, which conforms to the development concept of green energy conservation.

[0155] Furthermore, through the combined design of series-connected bidirectional thyristors and parallel-connected inverters, this embodiment forms a stable and reliable backup power supply system. When there is a voltage sag or short-time interruption in the external power grid, this system can respond quickly to ensure the normal operation of the elevator is not affected. This function effectively avoids the situation of the elevator being emergently shut down due to external power grid problems, and greatly improves the comfort and safety of passengers taking the elevator.

[0156] Furthermore, this embodiment adopts the supercapacitor energy storage technology to provide a reliable emergency leveling power supply for the elevator controller and the execution unit. In the case of a long-term power outage of the external power supply, the supercapacitor can release the stored electric energy to ensure that the elevator can complete the emergency leveling operation and enable passengers to leave the car safely. This design greatly enhances the elevator's response ability in case of sudden failures and ensures the personal safety of passengers.

[0157] The above embodiments are only the preferred embodiments of the present invention and cannot be used to limit the scope of protection of the present invention. Any non-substantive changes and substitutions made by those skilled in the art based on the present invention fall within the scope of protection required by the present invention.

Claims

1. An elevator energy-saving safety device based on the integration of inverter feedback and supercapacitor energy storage, characterized in that: include: Traction machine inverter, used to control the operation of the traction machine; The supercapacitor energy storage unit is connected in parallel with the DC bus of the traction machine inverter to store the energy fed back by the traction machine during braking; The inverter feedback circuit is connected to the DC bus of the supercapacitor energy storage unit and the traction machine inverter, and its working mechanism includes: when it is detected that the supercapacitor voltage reaches a preset threshold, the inverter feedback circuit is started to feed back the energy stored in the supercapacitor to the power grid or to meet the operation requirements of other elevators; The bidirectional thyristor unit is connected in series between the input terminal of the traction machine inverter and the AC power supply, and is used to cut off the connection with the AC power supply when a voltage sag or short-term interruption is detected, and obtain energy from the supercapacitor energy storage unit to maintain power supply; The control unit is used to control the operation of each functional unit.

2. The device according to claim 1, characterized in that The control unit has the following algorithms embedded in it: A voltage sag fast judgment algorithm based on the dq decomposition method, which is configured to judge voltage abnormality when a voltage sag or short-term interruption occurs and trigger an emergency response mechanism; The seamless cut-in control algorithm of the supercapacitor + inverter backup power supply, when a voltage sag or short-term interruption is detected, quickly cuts off the connection with the AC power supply by forcibly shutting down the bidirectional thyristor unit, and simultaneously starts the process of extracting energy from the supercapacitor energy storage unit, using the voltage source control algorithm to provide uninterrupted power supply for the traction machine and elevator controller; in this process, the IGBT switch connected to the supercapacitor is also shut down to prevent the reverse injection of the inverter DC bus current due to the supercapacitor voltage being too low; Seamless flexible exit control algorithm, which is executed when the AC power returns to normal after the voltage sag or short interruption ends. Through the control strategy, the power supply of the elevator system is smoothly switched from the supercapacitor + inverter backup power supply to the normal AC power supply.

3. The device according to claim 1, characterized in that: When the traction machine is braked, the generated energy flows directly into the supercapacitor for energy storage. This process is used to slow down the rising speed of the DC bus voltage of the traction machine inverter. When the supercapacitor voltage rises to 1.15 times the DC bus voltage UDC of the traction machine inverter, the inverter feedback circuit starts to work and feeds back the energy stored in the supercapacitor to the traction machine or the power grid. Since the braking energy of the elevator traction machine decreases as the speed decreases, the energy feedback circuit works to maintain the supercapacitor voltage at a stable level. When the supercapacitor voltage drops to 1.05 times of UDC, the inverter feedback circuit stops working.

4. The device according to claim 3, characterized in that: When the supercapacitor voltage drops due to self-discharge, the supercapacitor is float-charged through the DC / DC converter to maintain the supercapacitor voltage at 1.05 times the UDC set value, ensuring that there is sufficient energy reserve in the supercapacitor when voltage regulation or emergency leveling is required.

5. The device according to claim 1, characterized in that It also includes an emergency leveling function control module, the specific implementation of which includes: When it is detected that the AC power supply voltage drops below the preset threshold value 0.1U1, and the low voltage state lasts for more than 1 second, the emergency leveling function control module determines that the AC power supply has been disconnected for a long time; After determining that the power is off for a long time, the emergency leveling function control module immediately sends a signal to the elevator controller to execute the emergency leveling function, instructing the elevator controller to start the emergency leveling operation; The emergency leveling function control module continuously monitors the feedback signal of the elevator controller until receiving a signal returned by the elevator controller indicating that the emergency leveling function has been executed; If the energy storage capacity of the supercapacitor is exhausted during the execution of the emergency leveling function, or a signal indicating that the emergency leveling function has been completed is received from the elevator controller, the emergency leveling function control module stops working and ends the execution of the emergency leveling function.

6. The device according to claim 1, characterized in that: The fault response strategy of the bidirectional thyristor unit specifically includes: When a short-circuit fault of the bidirectional thyristor is detected: it is determined that the thyristor has lost its basic functions of forward conduction and reverse cutoff, which is equivalent to becoming a wire; the bypass contactor is controlled to close to ensure that the normal power supply of the traction machine is not affected; in this fault state, the device only retains the energy-saving function, but loses the function of controlling voltage sag and short-term interruption; When a short circuit fault of the bidirectional thyristor is detected: it is determined that for the traction machine, a voltage sag or short interruption equivalent to 50% of the effective value of the voltage has occurred; the voltage sag control procedure is immediately executed to force the shutdown of other normally operating bidirectional thyristors to prevent the fault from expanding or affecting the safe operation of the elevator; the bypass contactor is controlled to close to maintain the basic power supply to the traction machine; in this fault state, the device also only retains the energy-saving function, and loses the function of controlling voltage sags and short interruptions.

7. The device according to claim 2, characterized in that: In the voltage sag fast judgment algorithm based on the dq decomposition method, for the three-phase voltage signal, its dq component can be obtained according to the dq transformation, which is expressed as the following formula: Then we can get the following formula: The fundamental frequency component in the three-phase voltage is converted into a DC component by using dq transformation, and the higher harmonics are converted into corresponding AC components; the converted dq component is filtered by setting a low-pass filter to obtain a stable fundamental dq component; for asymmetric fault conditions, the filtered dq component is inversely transformed and converted back to the abc three-phase voltage, and single-phase voltage detection is performed based on this; wherein, through the processing method of the dq transformation and inverse transformation, the cutoff frequency of the low-pass filter can be reduced, thereby reducing the delay of the filter.

8. The device according to claim 7, characterized in that: It also includes using a three-phase software phase-locked loop to obtain phase information. The three-phase software phase-locked loop uses synchronous rotating coordinate transformation to first transform the three-phase stationary coordinate system into a two-phase αβ stationary coordinate system, and then obtains the corresponding phase information through rotating coordinate transformation. The loop filter G(s) is set as a PI regulator, 1 / s represents a voltage-controlled oscillator, ω0 is the rated angular frequency of the power grid, ω0=100πrad·s-1, which is the reference frequency of the voltage-controlled oscillator. The two transformation matrices are as follows:

9. The device according to claim 2, characterized in that: In the seamless switching control algorithm, the voltage at the PCC point is monitored in real time to determine whether the grid voltage drops. If the grid voltage drops, the triggering stops and switches to the island mode. In island mode, the modulation wave is generated according to the following formula: Determine whether the thyristor current reaches zero, if so, continue to stay in island mode.

10. The device according to claim 2, characterized in that: In the seamless flexible exit control algorithm, when a grid fault is detected or required, the system enters the island mode to maintain independent operation; In island mode, the voltage condition of the PCC point is continuously monitored; Determine whether the grid voltage has recovered. If not, continue to monitor the PCC point voltage; If it has been restored, the voltage linear modulation matching control is started to gradually adjust the system voltage to match the grid voltage; During the process of executing the voltage linear modulation matching control, continuously judging whether the voltage matching is completed; If it has been completed, the conduction signal is triggered and the mode is switched from the island mode to the state of preparing for grid connection; After the mode is switched, a current linear transition process is performed to smoothly adjust the system current to match the grid current; After completing the current linear transition, exit the island mode and switch to the PQ mode to achieve synchronous grid-connected operation with the power grid.

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