Method for starting an asynchronous generator and frequency converter system

Abstract

The application provides a starting method of an asynchronous generator, comprising the steps of: setting an auxiliary AC power supply; connecting the auxiliary AC power supply and a pre-charging loop of an AIM active interface module to limit current, rectifying by an ALM active power module and pre-charging a DC bus; connecting the auxiliary AC power supply and a main loop of the AIM active interface module, disconnecting the auxiliary AC power supply and the pre-charging loop of the AIM active interface module, rectifying by the ALM active power module and supplying power to the DC bus; starting the asynchronous generator by using the excitation energy provided by the DC bus; starting the ALM active power module and the AIM active interface module by using the electric energy generated by the asynchronous generator; disconnecting the auxiliary AC power supply and the main loop of the AIM active interface module, and connecting the main loop of the AIM active interface module and a power grid. The starting method can start the asynchronous generator without the power grid being powered. The application also provides a frequency converter system using the starting method.

Description

Technical Field

[0001] This invention relates to the field of asynchronous generator power generation, and in particular to a method for starting an asynchronous generator. The invention also relates to a frequency converter system utilizing the above-described starting method. Background Technology

[0002] When an asynchronous generator system starts up, it requires the DC bus of the frequency converter system to supply power to the motor drive module in order to obtain excitation energy. Therefore, the asynchronous generator needs to be connected to a powered grid that can provide power to the DC bus during startup, making it impossible for the asynchronous generator to be used in an islanded manner. Summary of the Invention

[0003] The purpose of this invention is to provide a method for starting an asynchronous generator, which can start the asynchronous generator without requiring power from the grid.

[0004] Another object of the present invention is to provide a frequency converter system for an asynchronous generator that can start the asynchronous generator without requiring power from the grid.

[0005] This invention provides a method for starting an asynchronous generator. The asynchronous generator is connected to the power grid through a frequency converter system. The frequency converter system includes an ALM active power module, an AIM active interface module, and a DC bus. The starting method includes the following steps:

[0006] Set up an auxiliary AC power supply;

[0007] Connect the auxiliary AC power supply and the pre-charge circuit of the AIM active interface module. Use the pre-charge circuit to limit the current of the auxiliary AC power supply. Use the IGBT power element of the AIM active power supply module to rectify the power output of the AIM active interface module and pre-charge the DC bus.

[0008] Connect the auxiliary AC power supply and the main circuit of the AIM active interface module. After bypassing the pre-charge circuit of the AIM active interface module, disconnect the auxiliary AC power supply and the pre-charge circuit of the AIM active interface module. Use the IGBT power element of the AIM active power supply module to rectify the electrical energy output by the AIM active interface module and supply power to the DC bus.

[0009] The electrical energy from the DC bus is used to provide excitation energy for the asynchronous generator and to start the asynchronous generator.

[0010] The electrical energy generated by the asynchronous generator is used to start the ALM active power module and the AIM active interface module.

[0011] Disconnect the auxiliary AC power supply and the main circuit of the AIM active interface module, and connect the main circuit of the AIM active interface module to the power grid.

[0012] The asynchronous generator starting method provided by this invention utilizes an unstarted AIM active interface module and ALM active power module in conjunction with an auxiliary AC power supply before starting the asynchronous generator. The pre-charging circuit of the AIM active interface module and the IGBT power elements of the ALM active power module function as a pre-charging circuit, pre-charging the DC bus. Then, the electrical energy from the DC bus provides excitation energy to the asynchronous generator, starting it. Therefore, the asynchronous generator can be started without grid power.

[0013] In another illustrative embodiment of the asynchronous generator starting method, after the auxiliary AC power supply and the pre-charge circuit of the AIM active interface module are connected, and the voltage of the DC bus reaches a preset value, the main circuit of the auxiliary AC power supply and the AIM active interface module is then connected.

[0014] In another illustrative embodiment of the asynchronous generator starting method, the on / off state is controlled by a first switch between the auxiliary AC power supply and the pre-charge circuit of the AIM active interface module. The on / off state is also controlled by a second switch between the auxiliary AC power supply and the main circuit of the AIM active interface module. Finally, the on / off state is controlled by a third switch between the power grid and the main circuit of the AIM active interface module.

[0015] In another illustrative embodiment of the starting method for an asynchronous generator, the first switch is the output circuit of a first relay, the second switch is the output circuit of a second relay, and the third switch is the output circuit of a third relay.

[0016] In another illustrative embodiment of the asynchronous generator starting method, the input circuits of the first, second, and third relays, as well as the input circuit of the resistive relay in the pre-charge circuit of the AIM active interface module, are automatically controlled by a programmable logic controller.

[0017] This invention also provides a frequency converter system for an asynchronous generator, including a DC bus, an ALM active power module, an AIM active interface module, a first switch, a second switch, and a third switch. The DC bus is used to provide excitation energy to the asynchronous generator or to obtain electrical energy from the asynchronous generator. The ALM active power module is connected to the DC bus. The AIM active interface module is connected to the ALM active power module. The first switch is located between the pre-charge circuit of the AIM active interface module and an auxiliary AC power supply. The second switch is located between the main circuit of the AIM active interface module and the auxiliary AC power supply. The third switch is located between the main circuit of the AIM active interface module and the power grid.

[0018] The frequency converter system for the asynchronous generator provided by this invention utilizes an unstarted AIM active interface module and ALM active power module in conjunction with an auxiliary AC power supply before the asynchronous generator starts. The pre-charging circuit of the AIM active interface module and the IGBT power elements of the ALM active power module function as a pre-charging circuit, pre-charging the DC bus. Then, the electrical energy from the DC bus provides excitation energy to the asynchronous generator and starts it. Thus, the asynchronous generator can be started without grid power.

[0019] In another illustrative embodiment of the frequency converter system for the asynchronous generator, the first switch is the output circuit of a first relay, the second switch is the output circuit of a second relay, and the third switch is the output circuit of a third relay.

[0020] In another illustrative embodiment of the inverter system for the asynchronous generator, the inverter system further includes a programmable logic controller that connects to and controls the input circuits of the first, second, and third relays, as well as the input circuit of the resistive relay in the pre-charge circuit of the AIM active interface module.

[0021] In another illustrative embodiment of the inverter system for the asynchronous generator, the programmable logic controller is configured to first control the output circuits of the first relay and the resistor relay to close, then control the output circuit of the second relay to close, then control the output circuits of the first relay and the resistor relay to open, after the asynchronous generator starts, control the output circuit of the second relay to open, and then control the output circuit of the third relay to close.

[0022] In another illustrative embodiment of the inverter system for the asynchronous generator, the programmable logic controller is configured to detect the voltage of the DC bus, and after controlling the output circuits of the first relay and the resistor relay to close, and after the voltage of the DC bus reaches a preset value, control the output circuit of the second relay to close, and then control the output circuits of the first relay and the resistor relay to open. Attached Figure Description

[0023] The following figures are for illustrative purposes only and do not limit the scope of the invention.

[0024] Figure 1 This is a schematic flowchart illustrating one embodiment of an asynchronous generator starting method.

[0025] Figure 2 This is a schematic diagram illustrating an implementation method for starting an asynchronous generator.

[0026] Figure 3 This is a schematic diagram illustrating another implementation method for starting an asynchronous generator.

[0027] Label Explanation

[0028] 10 DC bus

[0029] 20 ALM Active Power Module

[0030] 30 AIM Active Interface Module

[0031] 32 Pre-charge resistor

[0032] 33. Resistor Relay

[0033] 40 Programmable Logic Controller

[0034] 50 Asynchronous Generator

[0035] 60 Auxiliary AC power supply

[0036] 70 Power Grid

[0037] K11 First Switch

[0038] K21 Second Switch

[0039] K31 Third Switch

[0040] K12 Input circuit of the first relay

[0041] K22 Input Circuit of the Second Relay

[0042] K32 Third Relay Input Circuit Detailed Implementation

[0043] To provide a clearer understanding of the technical features, objectives, and effects of the invention, specific embodiments of the invention are now described with reference to the accompanying drawings. In the drawings, the same reference numerals indicate components with the same or similar structures but the same function.

[0044] In this document, “illustrative” means “serving as an example, illustration or description”, and any illustration or implementation described herein as “illustrative” should not be construed as a more preferred or advantageous technical solution.

[0045] Figure 1 This is a schematic flowchart illustrating one embodiment of an asynchronous generator starting method. Figure 2 This is a schematic diagram illustrating an implementation method for starting an asynchronous generator. (Refer to...) Figure 1 and Figure 2 The asynchronous generator 50 is connected to the power grid 70 via a frequency converter system, which includes a Siemens ALM active power module 20, an AIM active interface module 30, and a DC bus 10. The startup method includes the following steps:

[0046] Step S10: Set up an auxiliary AC power supply 60. The auxiliary AC power supply 60 is a low-power AC power supply on site, used to provide the electrical energy required for starting the asynchronous generator 50.

[0047] Step S20: Connect the auxiliary AC power supply 60 and the pre-charge circuit of the AIM active interface module 30, use the pre-charge circuit to limit the current of the auxiliary AC power supply 60, and use the IGBT power element of the AIM active power supply module 20 to rectify the power output of the AIM active interface module 30 and pre-charge the DC bus 10.

[0048] Those skilled in the art will understand that if the auxiliary AC power supply 60 is directly connected without a pre-charging circuit, the components connected to the DC bus 10 may be damaged due to excessive instantaneous current. Therefore, current limiting of the auxiliary AC power supply 60 is necessary. In a specific embodiment, the AIM active interface module 30 has a pre-charge circuit, which includes a pre-charge resistor 32. By setting a first switch K11 between the auxiliary AC power supply 60 and the pre-charge circuit of the AIM active interface module 30 to control the on / off state, when the AIM active interface module 30 is not activated, the first switch K11 and the resistor relay 33 in the pre-charge circuit are closed. Power is first supplied to the AIM active power module 20 through the pre-charge circuit of the AIM active interface module 30. At the same time, the IGBT power elements of the AIM active power module 20 are used to rectify the power and pre-charge the DC bus 10, causing the voltage on the DC bus 10 to gradually increase.

[0049] Step S30: Connect the auxiliary AC power supply 60 and the main circuit of the AIM active interface module 30. After bypassing the pre-charge circuit of the AIM active interface module, disconnect the auxiliary AC power supply 60 and the pre-charge circuit of the AIM active interface module 30. Use the IGBT power element of the AIM active power supply module 20 to rectify the power output of the AIM active interface module 30 and supply power to the DC bus 10. Specifically, a second switch K21 is set between the auxiliary AC power supply 60 and the main circuit of the AIM active interface module 30 to control the on / off state. After the voltage of the DC bus 10 reaches the preset value, close the second switch K21 to bypass the pre-charge resistor 32, and then disconnect the first switch K11 and the resistor relay 33 in the pre-charge circuit. At this time, the auxiliary AC power supply 60 directly charges the DC bus 10 through the main circuit of the AIM active interface module 30 and the AIM active power supply module 20.

[0050] Step S40: Use the electrical energy from the DC bus 10 to provide excitation energy for the asynchronous generator 50 and start the asynchronous generator 50. The motor module of the asynchronous generator 50 is connected to the DC bus 10, and can obtain electrical energy from the DC bus 10 to generate excitation energy, thereby starting the asynchronous generator 50 to generate electricity.

[0051] Step S50: Use the electrical energy generated by the asynchronous generator 50 to start the ALM active power module 20 and the AIM active interface module 30. After starting, the asynchronous generator 50 provides electrical energy to the DC bus 10, which in turn provides the ALM active power module 20 and the AIM active interface module 30 with the power needed for startup. The ALM active power module 20 and the AIM active interface module 30 are fully started and perform their functions.

[0052] Step S60: Disconnect the auxiliary AC power supply 60 and the main circuit of the AIM active interface module 30, and connect the main circuit of the AIM active interface module 30 to the power grid 70. Specifically, a third switch K31 is set between the power grid 70 and the main circuit of the AIM active interface module 30 to control the on / off state. The auxiliary AC power supply 60 is disconnected by opening the second switch K21, and the main circuit of the AIM active interface module 30 is connected to the power grid 70 by closing the third switch K31.

[0053] The asynchronous generator starting method provided by this invention utilizes the unstarted AIM active interface module 30 and ALM active power module 20 in conjunction with an auxiliary AC power supply 60 before starting the asynchronous generator 50. The pre-charging circuit of the AIM active interface module 30 and the IGBT power elements of the ALM active power module 20 pre-charge the DC bus 10. Then, the electrical energy from the DC bus 10 provides excitation energy to the asynchronous generator 50, starting the asynchronous generator 50. Thus, the asynchronous generator can be started without requiring grid power.

[0054] In the illustrative embodiment, refer to Figure 2 The first switch K11 is the output circuit of a first relay, the second switch K21 is the output circuit of a second relay, and the third switch K31 is the output circuit of a third relay. This allows for centralized configuration of the input circuits K12 (first relay), K22 (second relay), and K32 (third relay), enabling remote centralized control.

[0055] Figure 3 This is a schematic diagram illustrating another implementation of the starting method for an asynchronous generator. (Refer to...) Figure 3 , and Figure 2 The similarities and similarities in the startup methods shown will not be repeated here. The difference lies in the fact that a programmable logic controller automatically controls the input circuits K12 of the first relay, K22 of the second relay, K32 of the third relay, and the input circuit of the resistive relay 33 in the pre-charge circuit of the AIM active interface module 30. This achieves automatic process control.

[0056] The present invention also provides a frequency converter system for an asynchronous generator, with reference to... Figure 2 The inverter system includes a DC bus 10, an ALM active power module 20, an AIM active interface module 30, a first switch K11, a second switch K21, and a third switch K31.

[0057] DC bus 10 is used to provide excitation energy to the motor module of asynchronous generator 50, or to obtain electrical energy from asynchronous generator 50. ALM active power module 20 is connected to DC bus 10. AIM active interface module 30 is connected to ALM active power module 20. First switch K11 is located between the pre-charge circuit of AIM active interface module 30 and an auxiliary AC power supply 60. Second switch K21 is located between the main circuit of AIM active interface module 30 and the auxiliary AC power supply 60. Third switch K31 is located between the main circuit of AIM active interface module 30 and the power grid 70.

[0058] When the asynchronous generator 50 starts, the inverter system provided by this invention first controls the first switch K11 and the resistor relay 33 in the pre-charge circuit to close, connecting the auxiliary AC power supply 60 and the pre-charge circuit of the AIM active interface module 30. The pre-charge circuit limits the current of the auxiliary AC power supply 60, and the IGBT power element of the AIM active power supply module 20 rectifies the electrical energy output by the AIM active interface module 30 and pre-charges the DC bus 10. After the voltage of the DC bus 10 reaches a preset value, the second switch K21 is controlled to close to bypass the pre-charge circuit of the AIM active interface module 30. Then, the first switch K11 and the resistor relay 33 in the pre-charge circuit are controlled to open, connecting the auxiliary AC power supply 60 and the main circuit of the AIM active interface module 30. The IGBT power element of the AIM active power supply module 20 rectifies the electrical energy output by the AIM active interface module 30 and supplies power to the DC bus 10. The DC bus 10 provides excitation energy to the asynchronous generator 50, starting the generator 50. The asynchronous generator 50 then supplies power to the DC bus 10 in reverse. The ALM active power module 20 and the AIM active interface module 30 are fully started. At this time, the second switch K21 is opened, and the third switch K31 is simultaneously closed, connecting the main circuit of the AIM active interface module 30 to the power grid 70. The inverter system provided by this invention can start the asynchronous generator without requiring power from the grid.

[0059] In the illustrative embodiment, refer to Figure 2The first switch K11 is the output circuit of a first relay, the second switch K21 is the output circuit of a second relay, and the third switch K31 is the output circuit of a third relay. This allows for centralized configuration of the input circuits K12 (first relay), K22 (second relay), and K32 (third relay), enabling remote centralized control.

[0060] In another illustrative embodiment, refer to Figure 3 , and Figure 2 The similarities and differences between the inverter systems described above will not be elaborated upon. The key difference lies in the inclusion of a programmable logic controller (PLC) 40. This PLC 40 connects to and controls the input circuits of the first relay (K12), the second relay (K22), and the third relay (K32), as well as the input circuit of the resistor relay 33 in the pre-charge circuit of the AIM active interface module 30. The PLC 40 is configured to first close the output circuits of the first relay and the resistor relay 33. After the voltage on the DC bus 10 reaches a preset value, it then closes the output circuit of the second relay, followed by opening the output circuits of the first relay and the resistor relay 33. After the asynchronous generator 50 starts, it opens the output circuit of the second relay, then closes the output circuit of the third relay. This achieves automatic process control during the startup of the asynchronous generator 50.

[0061] It should be understood that although this specification is described according to various embodiments, not every embodiment contains only one independent technical solution. This way of describing the specification is only for clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment can also be appropriately combined to form other implementation methods that can be understood by those skilled in the art.

[0062] The detailed descriptions listed above are merely specific descriptions of feasible embodiments of the present invention and are not intended to limit the scope of protection of the present invention. All equivalent implementation schemes or modifications made without departing from the spirit of the present invention, such as combinations, divisions or repetitions of features, should be included within the scope of protection of the present invention.

Claims

1. A method of starting an asynchronous generator connected to an electrical grid through a frequency converter system comprising an ALM active power supply module, an AIM active interface module and a DC bus, characterized in that, The starting method comprises the following steps: setting up an auxiliary AC power supply; connecting the auxiliary AC power supply and the pre-charge circuit of the AIM active interface module, using the pre-charge circuit to limit the current of the auxiliary AC power supply, using the IGBT power element of the ALM active power module to rectify the electric energy output by the AIM active interface module and pre-charge the DC bus; connecting the auxiliary AC power supply and the main circuit of the AIM active interface module, disconnecting the auxiliary AC power supply and the pre-charge circuit of the AIM active interface module after bypassing the pre-charge circuit of the AIM active interface module, using the IGBT power element of the ALM active power module to rectify the electric energy output by the AIM active interface module and supply power to the DC bus; using the electric energy of the DC bus to provide excitation energy for the asynchronous generator and start the asynchronous generator; using the electric energy generated by the asynchronous generator to start the ALM active power module and the AIM active interface module; and disconnecting the auxiliary AC power supply and the main circuit of the AIM active interface module, connecting the main circuit of the AIM active interface module and the power grid.

2. The method of starting an asynchronous generator of claim 1, wherein, In the starting method, after connecting the auxiliary AC power supply and the pre-charge circuit of the AIM active interface module, and the voltage of the DC bus reaches a preset value, the auxiliary AC power supply and the main circuit of the AIM active interface module are connected.

3. The method of starting an asynchronous generator of claim 2, wherein, In the starting method, a first switch is set between the auxiliary AC power supply and the pre-charge circuit of the AIM active interface module to control the on-off; a second switch is set between the auxiliary AC power supply and the main circuit of the AIM active interface module to control the on-off; and a third switch is set between the power grid and the main circuit of the AIM active interface module to control the on-off.

4. The method of starting an asynchronous generator of claim 3, wherein, The first switch is the output circuit of a first relay, the second switch is the output circuit of a second relay, and the third switch is the output circuit of a third relay.

5. The method of starting an asynchronous generator of claim 4, wherein, In the starting method, a programmable logic controller is used to automatically control the input circuit of the first relay, the input circuit of the second relay, the input circuit of the third relay, and the input circuit of the resistance relay in the pre-charge circuit of the AIM active interface module.

6. A frequency converter system for an asynchronous generator, characterized in that It comprises: a DC bus (10) for providing excitation energy for the asynchronous generator or obtaining electric energy from the asynchronous generator; an ALM active power module (20) connected to the DC bus (10); an AIM active interface module (30) connected to the ALM active power module (20); a first switch (K11) set between the pre-charge circuit of the AIM active interface module (30) and an auxiliary AC power supply; a second switch (K21) set between the main circuit of the AIM active interface module (30) and the auxiliary AC power supply; and a third switch (K31) set between the main circuit of the AIM active interface module (30) and the power grid.

7. The variable frequency drive system for an asynchronous generator of claim 6, wherein, The first switch (K11) is an output circuit of a first relay, the second switch (K21) is an output circuit of a second relay, and the third switch (K31) is an output circuit of a third relay.

8. The variable frequency drive system for an asynchronous generator of claim 7, wherein, The frequency converter system further comprises a programmable logic controller (40) connected to and controlling the input circuits of the first relay, the second relay, and the third relay, and the input circuit of a resistor relay (33) in the pre-charge circuit of the AIM active interface module (30).

9. The variable frequency drive system for an asynchronous generator of claim 8, wherein, The programmable logic controller (40) is configured to control the output circuits of the first relay and the resistor relay (33) to be closed first, then control the output circuit of the second relay to be closed, then control the output circuits of the first relay and the resistor relay (33) to be disconnected, then control the output circuit of the second relay to be disconnected after the asynchronous generator is started, and then control the output circuit of the third relay to be closed.

10. The variable frequency drive system for an asynchronous generator of claim 9, wherein, The programmable logic controller (40) is configured to detect the voltage of the DC bus (10), and after controlling the output circuits of the first relay and the resistor relay (33) to be closed, and after the voltage of the DC bus (10) reaches a preset value, then control the output circuit of the second relay to be closed, and then control the output circuits of the first relay and the resistor relay (33) to be disconnected.

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