An elevator energy recovery system based on multiplexing bridge arms

Abstract

The utility model discloses an elevator energy recovery system based on multiplex bridge arm, including alternating current network, one -way uncontrolled rectification unit, bidirectional frequency conversion unit, motor, energy storage unit and three -phase full bridge circuit, and the output of alternating current network is connected with the input of one -way uncontrolled rectification unit through three -phase four -wire system, and the output of one -way uncontrolled rectification unit is connected with the input of bidirectional frequency conversion unit through direct current bus, and the output of bidirectional frequency conversion unit is connected with the input of motor through three -phase three -wire system, and three -phase full bridge circuit includes three bridge arms, and two semiconductor switches are connected in series on each bridge arm, and are first semiconductor switch and second semiconductor switch respectively, and the node between two semiconductor switches of each bridge arm is connected with one end of an electric reactance respectively, and the other end of one or two electric reactances is connected with phase line of three -phase four -wire system or the positive pole of energy storage unit through switching device. The utility model has the advantages of: the effective recovery of energy is realized.

Description

Technical Field

[0001] This utility model relates to the technical field of elevator traction systems, and in particular to an elevator energy recovery system based on a reused bridge arm. Background Technology

[0002] Traditional elevator traction systems mainly consist of a traction machine, traction steel cables, guide sheaves, and reversing sheaves. The traction machine's motor drives the traction sheave through a reducer. The traction sheave is connected to the car and counterweight via the traction steel cables. The friction between the traction sheave and the steel cables drives the relative movement of the car and counterweight. When the car rises, the counterweight descends; when the car descends, the counterweight rises. By controlling the forward and reverse rotation and the speed of the traction machine's motor, the elevator's vertical movement and speed can be controlled.

[0003] In traditional energy-saving braking elevator traction motor drive systems, the front stage (unidirectional uncontrolled rectifier unit) of the drive system has unidirectional energy flow, while the rear stage (bidirectional frequency converter unit) has bidirectional energy flow. Therefore, when the motor brakes, the braking energy can be fed back to the DC bus through the rear stage, raising the DC bus voltage. When the bus voltage exceeds a threshold, a braking resistor (located between the positive and negative terminals of the DC bus and connected in series with a braking discharge switch) is activated to absorb the energy fed back from the motor braking. This solution is simple, reliable, and widely used; however, because the energy is completely converted into heat, it results in significant waste. Summary of the Invention

[0004] The purpose of this invention is to address the shortcomings of the prior art by providing an elevator energy recovery system based on a reused bridge arm. This elevator energy recovery system consists of an AC power grid, a unidirectional uncontrolled rectifier unit, a bidirectional frequency converter unit, a motor, an energy storage unit, and a three-phase full-bridge circuit. By setting up the energy storage unit and the three-phase full-bridge circuit, effective energy recovery is achieved.

[0005] The objective of this utility model is achieved through the following technical solution: An elevator energy recovery system based on a reused bridge arm includes an AC power grid, a unidirectional uncontrolled rectifier unit, a bidirectional frequency converter unit, a motor, an energy storage unit, and a three-phase full-bridge circuit. The output of the AC power grid is connected to the input of the unidirectional uncontrolled rectifier unit via a three-phase four-wire system. The output of the unidirectional uncontrolled rectifier unit is connected to the input of the bidirectional frequency converter unit via a DC bus. The output of the bidirectional frequency converter unit is connected to the input of the motor via a three-phase three-wire system. The three-phase full-bridge circuit includes three bridge arms, each with two semiconductor switches connected in series. The three semiconductor switches are respectively the first semiconductor switch and the second semiconductor switch. The node between the two semiconductor switches in each bridge arm is connected to one end of the same reactor. The other end of one or two of the reactors is connected to the phase line of the three-phase four-wire system or the positive terminal of the energy storage unit through a switching device. The other end of the remaining reactors is connected to the phase line of the three-phase four-wire system. The three first semiconductor switches are respectively connected to the positive terminal of the DC bus, and the three second semiconductor switches are respectively connected to the negative terminal of the DC bus. The negative terminal of the energy storage unit is connected to the negative terminal of the DC bus.

[0006] The switching device includes a first switch and a second switch. The two ends of the first switch are respectively connected to the phase line and the reactor of the three-phase four-wire system, and the two ends of the second switch are respectively connected to the positive terminal of the energy storage unit and the reactor.

[0007] The first switch and the second switch are mechanical switches or semiconductor switches.

[0008] The first switch and the second switch are controlled by a control unit configured to control the closing and opening of the first switch and the second switch, and to ensure that the two switches cannot be closed at the same time.

[0009] The first semiconductor switch and the second semiconductor switch are IGBT switches or MOSFET switches.

[0010] The two ends of the neutral wire of the three-phase four-wire system are connected to the output end of the AC power grid and the input end of the unidirectional uncontrolled rectifier unit, respectively.

[0011] The advantages of this utility model are: 1. Effective energy recovery methods can stabilize DC bus voltage and are economical; 2. Further improve economic efficiency by utilizing peak-valley arbitrage of energy storage units; 3. The final energy outlet is the grid side, and meters can be installed after the inverter unit to make the revenue visible; 4. The energy storage media are diverse, which can provide backup power for elevator systems, and energy storage units can also be selected to reduce initial installation costs; 5. The energy storage medium can provide a DC interface, which facilitates the access of new energy sources and enhances the system's scalability; 6. The bridge arm in the inverter system is reused to realize energy storage access, reducing costs and simplifying the system; 7. The reuse method is flexible. Depending on the different energy storage ratios, single or double arm reuse can be selected, or double arms can be used in staggered parallel connection, etc. 8. It can achieve automatic switching without manual operation; 9. Compatible with two modes, allowing for more flexible selection and connection of energy storage units. Attached Figure Description

[0012] Figure 1 This is a flowchart of the elevator energy recovery system based on a reused bridge arm, which is an embodiment of the present invention. Figure 2 This is a flowchart of the elevator energy recovery system based on a reused bridge arm, which is embodiment 2 of this utility model. like Figures 1-2 As shown in the figure, the labels represent: AC power grid 10, unidirectional uncontrolled rectifier unit 20, bidirectional frequency converter unit 30, motor 40, energy storage unit 50, three-phase full bridge circuit 60, three-phase four-wire system 70, DC bus 80, three-phase three-wire system 90; Phase line A, phase line B, phase line C, neutral line N, DC bus positive terminal DC+, DC bus negative terminal DC-, phase line U, phase line V, phase line W, first semiconductor switch PS1, second semiconductor switch PS2, first semiconductor switch PS3, second semiconductor switch PS4, first semiconductor switch PS5, second semiconductor switch PS6, reactance L1, reactance L2, reactance L3, first switch SW1, second switch SW2, first switch SW3, second switch SW4. Detailed Implementation

[0013] The features and other related features of this utility model will be further described in detail below with reference to the accompanying drawings and embodiments, so as to facilitate the understanding of those skilled in the art: Example 1: As Figure 1As shown, this embodiment relates to an elevator energy recovery system based on a reused bridge arm. The elevator energy recovery system mainly includes an AC power grid 10, a unidirectional uncontrolled rectifier unit 20, a bidirectional frequency converter unit 30, a motor 40, an energy storage unit 50, a three-phase full-bridge circuit 60, a three-phase four-wire system 70, a DC bus 80, and a three-phase three-wire system 90. The output end of the AC power grid 10 is connected to the input end of the unidirectional uncontrolled rectifier unit 20 through the three-phase four-wire system 70. The three-phase four-wire system 70 includes three phase wires (phase wire A, phase wire B, and phase wire C) and one neutral wire (neutral wire N). The two ends (input and output ends) of phase wire A / phase wire B / phase wire C / neutral wire N are respectively connected to the output end of the AC power grid 10 and the input end of the unidirectional uncontrolled rectifier unit 20. The output of the unidirectional uncontrolled rectifier unit 20 is connected to the input of the bidirectional frequency converter unit 30 via a DC bus 80. The DC bus 80 includes a positive DC+ terminal and a negative DC- terminal. The two ends (input and output) of the positive DC+ and negative DC- terminals are connected to the output of the unidirectional uncontrolled rectifier unit 20 and the input of the bidirectional frequency converter unit 30, respectively. The output of the bidirectional frequency converter unit 30 is connected to the input of the motor 40 via a three-phase three-wire system 90. The three-phase three-wire system 90 includes three phase wires (phase wire U, phase wire V, and phase wire W). The two ends (input and output) of phase wires U, V, and W are connected to the output of the bidirectional frequency converter unit 30 and the input of the motor 40, respectively. The three-phase full-bridge circuit 60 includes three bridge arms: phase A, phase B, and phase C. Each bridge arm has two semiconductor switches connected in series: a first semiconductor switch and a second semiconductor switch. Specifically, phase A has a first semiconductor switch PS1 and a second semiconductor switch PS2, phase B has a first semiconductor switch PS3 and a second semiconductor switch PS4, and phase C has a first semiconductor switch PS5 and a second semiconductor switch PS6. In this embodiment, the first and second semiconductor switches are IGBT (Insulated Gate Bipolar Transistor) switches or MOSFET (Metal-Oxide-Semiconductor Field-Effect Transistor) switches.Each node between the two semiconductor switches in each bridge arm is connected to one end of a reactor (three in total, namely reactor L1, reactor L2, and reactor L3). The other end of reactor L3 is connected to a phase line (phase line C) of the three-phase four-wire system 70 or the positive terminal of the energy storage unit 50 via a switching device. The other ends of reactors L1 and L2 are connected to phase lines (phase lines A and B) of the three-phase four-wire system 70. The switching device includes a first switch (first switch SW1) and a second switch (second switch SW2). SW1 is connected to phase line C and reactance L3 of the three-phase four-wire system 70 at both ends, and the second switch SW2 is connected to the positive terminal and reactance L3 of the energy storage unit 50 at both ends. The first switch SW1 and the second switch SW2 are mechanical switches or semiconductor switches. The first switch (SW1) and the second switch (SW2) are controlled by a control unit configured to control the closing and opening of the first switch (SW1) and the second switch (SW2), ensuring that they cannot be closed simultaneously. First semiconductor switches PS1, PS3, and PS5 are connected to the positive terminal DC+ of the DC bus, and second semiconductor switches PS2, PS4, and PS6 are connected to the negative terminal DC- of the DC bus. The negative terminal of the energy storage unit 50 is connected to the negative terminal DC- of the DC bus.

[0014] In addition, this embodiment also has the following operating modes: 1. Working mode one: First switch SW1 is closed, and second switch SW2 is open.

[0015] When the elevator is in operation (consuming power): the unidirectional uncontrolled rectifier unit 20 draws power from the AC power grid 10 to supply the DC bus 80. The three-phase full-bridge circuit 60 operates in inverter mode, converting the DC power into variable frequency and voltage three-phase AC power to drive the motor 40. Current direction: AC power grid 10 → unidirectional uncontrolled rectifier unit 20 → DC bus positive terminal DC+ → bidirectional frequency converter unit 30 → motor 40.

[0016] When the elevator brakes (generates power): Motor 40 becomes a generator, and the three-phase full-bridge circuit 60 operates in rectifier mode, rectifying the three-phase AC power generated by Motor 40 into DC power, which is then fed back to the DC bus 80. If charging the energy storage is not required at this time or the energy storage is full, and the first switch SW1 is closed, the three-phase full-bridge circuit 60 can also act as an active inverter, converting excess braking energy on the DC bus 80 into AC power that is in phase and frequency with the AC grid 10, and feeding it back to the grid. Current direction: Motor 40 → Bidirectional frequency converter 30 → DC bus positive terminal DC+ → Three-phase full-bridge circuit 60 → AC grid 10.

[0017] When energy storage discharge is required to assist drive: Although the second switch SW2 is open, the energy storage unit 50 can release energy to the DC bus 80 through other paths (usually a dedicated DC-DC converter) (to boost the bus voltage or provide power), and then the bidirectional frequency converter 30 drives the motor 40. At this time, the three-phase full-bridge circuit 60 may be in inverter mode (drawing power from the AC grid 10) or in a non-operating state (powered only by the energy storage unit 50). Current direction: Energy storage unit 50 → DC-DC converter → DC bus positive DC+ → bidirectional frequency converter 30 → motor 40.

[0018] 2. Working mode two: First switch SW1 is open, and second switch SW2 is closed.

[0019] At this time, the C-phase bridge arm (first semiconductor switch PS5 / second semiconductor switch PS6) is connected to the energy storage unit 50 through the reactor L3 and the first switch SW2, and is no longer directly connected to the phase line C. The A-phase bridge arm (first semiconductor switch PS1 / second semiconductor switch PS2) and the B-phase bridge arm (first semiconductor switch PS3 / second semiconductor switch PS4) are still connected to the phase lines A and B through the reactors L1 and L2, respectively.

[0020] Elevator braking and energy storage charging: Motor 40 generates electricity, and bidirectional frequency converter 30 rectifies the AC power into DC power, boosting the voltage of DC bus 80. Phase C bridge arm (first semiconductor switch PS5 / second semiconductor switch PS6) now operates as a bidirectional DC-DC converter, controlling the charging of energy storage unit 50. It can step down the higher voltage (from braking energy) on DC bus 80 to charge energy storage unit 50. If there is excessive energy on DC bus 80 (charging power less than braking power), phase A and phase B bridge arms (first semiconductor switch PS1 / second semiconductor switch PS2, first semiconductor switch PS3 / second semiconductor switch PS4) can act as a two-phase active inverter, converting the excess energy into AC power to feed back to phase lines A and B. Current direction (main path): Motor 40 → Bidirectional frequency converter 30 → DC bus positive (DC+) → First semiconductor switch PS5 / second semiconductor switch PS6 → Energy storage unit 50 positive → Energy storage unit 50 negative → DC bus negative (DC-). Current direction (excess energy feedback): DC bus positive terminal DC+ → first semiconductor switch PS1 / second semiconductor switch PS2 & first semiconductor switch PS3 / second semiconductor switch PS4 → reactance L1 / reactance L2 → phase line A / phase line B → neutral line N → unidirectional uncontrolled rectifier unit 20 → DC bus negative terminal DC-.

[0021] Energy storage discharge and elevator drive: When the elevator needs to be driven and requires energy storage, or when energy storage is needed to stabilize the bus voltage, the C-phase bridge arm (first semiconductor switch PS5 / second semiconductor switch PS6) operates in boost mode as a bidirectional DC-DC converter. It boosts the lower voltage of the energy storage unit 50 to the DC bus 80 voltage level. The boosted energy is then supplied to the DC bus 80. If this energy is used to drive the elevator, the bidirectional inverter unit 30 operates in inverter mode, converting the DC power into AC power to drive the motor 40. Current direction: positive terminal of energy storage unit 50 → first semiconductor switch PS5 / second semiconductor switch PS6 → DC bus positive terminal DC+ → bidirectional inverter unit 30 → motor 40. Simultaneously, the AC power grid 10 may also provide some energy through the A-phase bridge arm / B-phase bridge arm. If this energy is used to stabilize the bus or supply other loads, it flows directly into the DC bus 80. In energy storage connection mode, phase A and phase B bridge arms can still work: when power needs to be drawn from AC grid 10 (e.g., when the drive power demand is large): phase A and phase B bridge arms work in active rectification mode; when energy needs to be fed back to AC grid 10 (e.g., when the energy storage charging power is insufficient or peak shaving is required): phase A and phase B bridge arms work in active inverter mode.

[0022] 3. Working mode three: First switch SW1 is open, and second switch SW2 is open.

[0023] The C-phase bridge arm (first semiconductor switch PS5 / second semiconductor switch PS6) is not working, while the A-phase bridge arm (first semiconductor switch PS1 / second semiconductor switch PS2) and the B-phase bridge arm (first semiconductor switch PS3 / second semiconductor switch PS4) are working to achieve the energy feedback function.

[0024] The beneficial technical effects of this embodiment are as follows: 1. Effective energy recovery methods can stabilize DC bus voltage and are economical; 2. Further improve economic efficiency by utilizing peak-valley arbitrage of energy storage units; 3. The final energy outlet is the grid side, and meters can be installed after the inverter unit to make the revenue visible; 4. The energy storage media are diverse, which can provide backup power for elevator systems, and energy storage units can also be selected to reduce initial installation costs; 5. The energy storage medium can provide a DC interface, which facilitates the access of new energy sources and enhances the system's scalability; 6. The bridge arm in the inverter system is reused to realize energy storage access, reducing costs and simplifying the system; 7. The reuse method is flexible. Depending on the different energy storage ratios, single or double arm reuse can be selected, or double arms can be used in staggered parallel connection, etc. 8. It can achieve automatic switching without manual operation; 9. Compatible with two modes, allowing for more flexible selection and connection of energy storage units.

[0025] Example 2: As Figure 2 As shown, this embodiment relates to an elevator energy recovery system based on a reused bridge arm. Except for the other end of reactor L2 being connected to a phase line (phase line B) of the three-phase four-wire system 70 or the positive terminal of the energy storage unit 50 via a switching device, everything else is the same as in Embodiment 1, and therefore will not be described in detail here. The switching device corresponding to reactor L2 includes a first switch SW3 and a second switch SW4. The two ends of the first switch SW3 are connected to phase line B of the three-phase four-wire system 70 and reactor L2, respectively. The two ends of the second switch SW4 are connected to the positive terminal of the energy storage unit 50 and reactor L2, respectively. The energy storage unit 50 is connected by reusing two bridge arms (phase B and phase C), and the remaining bridge arm (phase A) releases energy to the grid side.

[0026] Although the above embodiments have described the concept and embodiments of the present invention in detail with reference to the accompanying drawings, those skilled in the art will recognize that various improvements and modifications can still be made to the present invention without departing from the scope of the claims, and therefore will not be elaborated here.

Claims

1. An elevator energy recovery system based on a reused bridge arm, characterized in that... The elevator energy recovery system includes an AC power grid, a unidirectional uncontrolled rectifier unit, a bidirectional frequency converter unit, a motor, an energy storage unit, and a three-phase full-bridge circuit. The output of the AC power grid is connected to the input of the unidirectional uncontrolled rectifier unit via a three-phase four-wire system. The output of the unidirectional uncontrolled rectifier unit is connected to the input of the bidirectional frequency converter unit via a DC bus. The output of the bidirectional frequency converter unit is connected to the input of the motor via a three-phase three-wire system. The three-phase full-bridge circuit includes three bridge arms, each with two semiconductor switches connected in series, namely the first semiconductor switch and the second semiconductor switch. The bridge arm comprises a body switch and a second semiconductor switch. The nodes between the two semiconductor switches in each arm are respectively connected to one end of a reactor. The other end of one or two of the reactors is connected to the phase line of the three-phase four-wire system or the positive terminal of the energy storage unit through a switching device. The other end of the remaining reactors is connected to the phase line of the three-phase four-wire system. The three first semiconductor switches are respectively connected to the positive terminal of the DC bus, and the three second semiconductor switches are respectively connected to the negative terminal of the DC bus. The negative terminal of the energy storage unit is connected to the negative terminal of the DC bus.

2. The elevator energy recovery system based on a reused bridge arm as described in claim 1, characterized in that... The switching device includes a first switch and a second switch. The two ends of the first switch are respectively connected to the phase line and the reactor of the three-phase four-wire system, and the two ends of the second switch are respectively connected to the positive terminal of the energy storage unit and the reactor.

3. The elevator energy recovery system based on a reused bridge arm as described in claim 2, characterized in that... The first switch and the second switch are mechanical switches or semiconductor switches.

4. The elevator energy recovery system based on a reused bridge arm as described in claim 1, characterized in that... The first semiconductor switch and the second semiconductor switch are IGBT switches or MOSFET switches.

5. An elevator energy recovery system based on a reused bridge arm as described in claim 1, characterized in that... The two ends of the neutral wire of the three-phase four-wire system are connected to the output end of the AC power grid and the input end of the unidirectional uncontrolled rectifier unit, respectively.

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