Pre-charging circuit and converter
By introducing the control of the first pre-charge switch, the second pre-charge switch, and the switching switch in the converter, the problem of overheating of the resistor in the pre-charge circuit is solved, and soft-start charging of the DC bus capacitor and filter capacitor is realized, reducing cost and space requirements.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- XIAN BORUN ELECTRIC CO LTD
- Filing Date
- 2025-05-30
- Publication Date
- 2026-05-15
AI Technical Summary
In existing pre-charge circuits, the resistance value of the pre-charge resistor is too small, which leads to excessive current and easy overheating failure. In addition, the use of multiple switching contactors or air contactors increases cost and space requirements.
A pre-charge circuit including a first pre-charge switch, a second pre-charge switch, and a switching switch is adopted. By controlling the conduction and disconnection of these switches, soft-start charging of the DC bus capacitor and filter capacitor is achieved, avoiding the problem of resistor overheating.
It enables soft-start charging of DC bus capacitors and filter capacitors, avoiding resistor overheating and reducing cost and space requirements.
Smart Images
Figure CN224249376U_ABST
Abstract
Description
Technical Field
[0001] This application relates to the field of converter technology, and more particularly to a pre-charging circuit and a converter. Background Technology
[0002] As the power of wind power converters increases, the capacity of grid-side filter capacitors also increases. When the converter is in standby mode, owners generally do not allow the capacitors to be connected to the grid. Therefore, a switching contactor or air contactor is needed at the capacitor front end to disconnect the AC filter capacitors when the converter is in standby mode.
[0003] If switching contactors are used, multiple switching contactors need to be connected in parallel because of their limited capacity, which requires more cabinet space and increases costs.
[0004] If an air contactor is used, a pre-charge resistor is required to prevent excessive inrush current when the contactor engages. In common pre-charge circuits, the pre-charge resistor is typically very small in value to ensure the DC bus voltage reaches the predetermined value. The problem with this pre-charge circuit is that the excessively small resistance leads to excessive current flowing through the resistor, making it prone to overheating and failure. Utility Model Content
[0005] This application provides a pre-charging circuit and a converter to avoid the problems existing in existing pre-charging circuits.
[0006] This application provides a pre-charging circuit for a converter, the converter including a grid-side converter and a DC bus capacitor connected to the DC terminal of the grid-side converter; the pre-charging circuit includes a grid-side switch, a first pre-charging switch, a pre-charging resistor, a second pre-charging switch, a switching switch, and a filter capacitor;
[0007] One end of the first pre-charge switch is connected to one end of the grid-side switch and the power grid. The other end of the first pre-charge switch is connected to one end of the pre-charge resistor and one end of the second pre-charge switch. The other end of the pre-charge resistor is connected to the other end of the grid-side switch. The other end of the second pre-charge switch is connected to one end of the switching switch and the filter capacitor. The other end of the switching switch is connected to the other end of the grid-side switch and the AC terminal of the grid-side converter.
[0008] This application also provides a converter, including the aforementioned pre-charge circuit and a controller, the controller being used to control the on or off of the first pre-charge switch, the second pre-charge switch and the switching switch.
[0009] The pre-charge circuit and converter provided in this application can sequentially realize the soft-start charging of the DC bus capacitor and the soft-start charging of the filter capacitor through the first pre-charge switch, the second pre-charge switch and the switching switch; thus avoiding the problem that the current flowing through the resistor is too large due to the resistance value of the pre-charge resistor being too small, which makes the resistor easily overheat and fail. Attached Figure Description
[0010] Figure 1 A schematic diagram of a converter provided in an embodiment of this application;
[0011] Figure 2 This is a schematic diagram of the pre-charging of the converter provided in an embodiment of this application;
[0012] Figure 3 Another pre-charge schematic diagram of the converter provided in the embodiments of this application.
[0013] The realization of the purpose, functional features and advantages of this application will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Implementation
[0014] To make the technical problems, technical solutions, and beneficial effects to be solved by this application clearer and more understandable, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of this application and are not intended to limit the scope of this application.
[0015] In the description of this application, it should be understood that the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.
[0016] like Figure 1 As shown, this application provides a converter including a grid-side converter LSC, a machine-side converter MSC connected to the grid-side converter LSC via a positive DC bus BUS+ and a negative DC bus BUS-, and a DC bus capacitor C1 connected between the positive DC bus BUS+ and the negative DC bus.
[0017] The converter also includes a pre-charging circuit, which includes a grid-side switch Q10, a first pre-charging switch K1, a pre-charging resistor R0, a second pre-charging switch K2, a switching switch K3, and a filter capacitor C2.
[0018] One end of the first pre-charge switch K1 is connected to one end of the grid-side switch Q10 and the power grid. The other end of the first pre-charge switch K1 is connected to one end of the pre-charge resistor R0 and one end of the second pre-charge switch K2. The other end of the pre-charge resistor R0 is connected to the other end of the grid-side switch Q10. The other end of the second pre-charge switch K2 is connected to one end of the switching switch K3 and the filter capacitor C2. The other end of the switching switch K3 is connected to the other end of the grid-side switch Q10 and the AC terminal of the grid-side converter LSC.
[0019] In one example, the AC terminal of the turbine-side converter MSC is connected to the rotor of the wind turbine, and the other terminal of the grid-side switch Q10 is connected to the stator of the wind turbine. For example... Figure 1 The doubly fed wind turbine G in the middle has a stator and a rotor.
[0020] Furthermore, the converter also includes a grid-connected switch SC, one end of which is connected to the other end of the grid-side switch Q10, and the other end of which is connected to the stator of the wind turbine.
[0021] In one example, the pre-charge circuit further includes a protector FU, one end of which is connected to the other end of the grid-side switch Q10, and the other end of the protector FU is connected to the other end of the switching switch K3 and the AC terminal of the grid-side converter LSC.
[0022] In one example, the protector FU includes a fuse.
[0023] In one example, the converter further includes a grid-side filter inductor L1, one end of which is connected to the AC terminal of the grid-side converter LSC, and the other end of which is connected to the other end of the switching switch K3.
[0024] In one example, the converter further includes a machine-side filter inductor L2, one end of which is connected to the AC terminal of the machine-side converter MSC, and the other end of which is connected to a wind turbine, for example, to the rotor of a doubly-fed wind turbine G.
[0025] In one example, the first precharge switch K1 includes a contactor.
[0026] In one example, the second precharge switch K2 includes a contactor.
[0027] In one example, the switching switch K3 includes a contactor.
[0028] In one example, the converter further includes a controller that can control the on / off state of the first pre-charge switch K1, the second pre-charge switch K2, and the switching switch K3, thereby sequentially achieving soft-start charging of the DC bus capacitor C1 and the filter capacitor C2. Specifically:
[0029] In one example, such as Figure 2 As shown, when grid-side switch Q10 is in the open state, if the controller receives a start-up command (shown as ARE in the figure), the controller first controls the first pre-charge switch K1 to turn on. The grid charges the DC bus capacitor C1 through the first pre-charge switch K1, pre-charge resistor R0, protector FU, grid-side filter inductor L1, and grid-side converter LSC. When the voltage between the positive DC bus BUS+ and the negative DC bus BUS- reaches a predetermined value, the controller controls the grid-side switch Q10 to turn on and controls the first pre-charge switch K1 to turn off. Then, the controller controls the second pre-charge switch K2 to turn on, and the grid charges the filter capacitor C2 through the grid-side switch Q10, pre-charge resistor R0, and the second pre-charge switch K2. Finally, the controller controls the switching switch K3 to turn on and controls the second pre-charge switch K2 to turn off.
[0030] In another example, such as Figure 3 As shown, when grid-side switch Q10 is in the ON state, if the controller receives a start-up command (shown as ARE in the figure), the controller first controls the second pre-charge switch K2 to turn on. The grid charges the filter capacitor C2 through grid-side switch Q10, pre-charge resistor R0, and the second pre-charge switch K2. The controller then controls the switching switch K3 to turn on and controls the second pre-charge switch K2 to turn off.
[0031] The preferred embodiments of this application have been described above with reference to the accompanying drawings, but this does not limit the scope of the claims. Any modifications, equivalent substitutions, and improvements made by those skilled in the art without departing from the scope and spirit of this application shall be within the scope of the claims.
Claims
1. A pre-charging circuit for a converter, the converter comprising a grid-side converter and a DC bus capacitor connected to the DC terminal of the grid-side converter; characterized in that, The pre-charge circuit includes a grid-side switch, a first pre-charge switch, a pre-charge resistor, a second pre-charge switch, a switching switch, and a filter capacitor. One end of the first pre-charge switch is connected to one end of the grid-side switch and the power grid. The other end of the first pre-charge switch is connected to one end of the pre-charge resistor and one end of the second pre-charge switch. The other end of the pre-charge resistor is connected to the other end of the grid-side switch. The other end of the second pre-charge switch is connected to one end of the switching switch and the filter capacitor. The other end of the switching switch is connected to the other end of the grid-side switch and the AC terminal of the grid-side converter.
2. The pre-charging circuit according to claim 1, characterized in that, The pre-charging circuit also includes a protector, one end of which is connected to the other end of the grid-side switch, and the other end of which is connected to the other end of the switching switch and the AC terminal of the grid-side converter.
3. The pre-charging circuit according to claim 2, characterized in that, The protector includes a fuse.
4. The pre-charging circuit according to claim 1, characterized in that, The first pre-charge switch includes a contactor.
5. The pre-charging circuit according to claim 1, characterized in that, The second pre-charge switch includes a contactor.
6. The pre-charging circuit according to claim 1, characterized in that, The switching switch includes a contactor.
7. A converter, characterized in that, The invention includes the pre-charging circuit and controller according to any one of claims 1-6, wherein the controller is used to control the first pre-charging switch, the second pre-charging switch and the switching switch to be turned on or off.
8. The converter according to claim 7, characterized in that, The converter also includes a machine-side converter connected to the grid-side converter. The AC terminal of the machine-side converter is connected to the rotor of the wind turbine, and the other terminal of the grid-side switch is connected to the stator of the wind turbine.
9. The converter according to claim 8, characterized in that, The converter also includes a grid-connected switch, one end of which is connected to the other end of the grid-side switch, and the other end of which is connected to the stator of the wind turbine.
10. The converter according to claim 8, characterized in that, The converter also includes a grid-side filter inductor and a machine-side filter inductor; One end of the grid-side filter inductor is connected to the AC terminal of the grid-side converter, and the other end of the grid-side filter inductor is connected to the other end of the switching switch. One end of the machine-side filter inductor is connected to the AC terminal of the machine-side converter, and the other end of the machine-side filter inductor is connected to the wind turbine.