Multi-machine parallel system
By introducing a switching switch to control the AC filter capacitor in a multi-machine parallel system, the optimal filtering problem during redundant operation of the converter is solved, achieving better harmonic suppression and filtering effects, while reducing standby losses and costs.
Patent Information
- Application Number
- CN202423206109.9
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2024-12-23
- Publication Date
- 2025-12-12
- Estimated Expiration
- 2034-12-23
AI Technical Summary
In existing multi-machine parallel systems, the design of the number of grid-side filter capacitors did not fully consider the optimal filtering effect during redundant operation of the converter, resulting in increased costs and standby losses.
The system employs a multi-machine parallel connection, including n converters, switching switches, common connection points, AC filter circuits, and grounding blocks. The switching switches control the connection and disconnection of the AC filter capacitors to ensure optimal filtering performance during converter redundant operation.
It achieves better harmonic suppression and filtering in multi-machine parallel systems, and reduces the standby loss and cost of converters.
Smart Images
Figure CN223666046U_ABST
Abstract
Description
TECHNICAL FIELD
[0001] The present application relates to the technical field of converter, in particular to a multi-machine parallel system. BACKGROUND
[0002] Power electronic equipment such as a converter will generate abundant high-frequency harmonics due to the high-frequency operation of semiconductor switching devices. In order to reduce the harmonics injected into the power grid, an LC or LCL filter is usually added to the grid-connected port for filtering. Considering the standby state of the converter, the AC filter capacitor of the grid-side converter will generate a large amount of reactive power, resulting in increased unit loss. Therefore, a switching switch such as a contactor is added to the AC filter circuit to realize the cut-out of the AC filter capacitor in the standby state, so as to reduce the standby loss; in normal operation, the switching switch is closed to connect the AC filter capacitor, so as to realize the suppression and elimination of the grid-side high-frequency harmonics. The operation of the AC filter capacitor is related to the working state of the converter.
[0003] As the main element of the filter circuit, the capacitance value of the AC filter capacitor has a great influence on the filtering effect. Properly increasing the capacitance value of the AC filter capacitor is beneficial to achieving better grid-side harmonic filtering effect, but increasing the capacitance value will not only increase the cost and size of the converter, but also result in a large standby loss of the unit. Therefore, when designing the capacitance value of the AC filter capacitor of the converter, the influence factors of the filtering effect and economy need to be considered comprehensively. For a multi-machine parallel system, the number of AC filter capacitors is doubled, and the above conditions need to be considered.
[0004] In the existing multi-machine parallel system of the converter, when designing the number of grid-side filter capacitors, the number of single-machine filter capacitors is usually doubled according to the number of parallel units. Although this can balance the filtering effect and design economy of the grid-side converter when all the converters in the multi-machine parallel system are running, it does not fully consider how a single converter obtains the best filtering effect when the converter is running redundantly in the system. Practical new type content
[0005] Therefore, the purpose of the present application is to provide a multi-machine parallel system to ensure that the capacitance value of the input filter capacitor is large, so that the multi-machine parallel system obtains better harmonic suppression and filtering effect, and fully considers how a single converter obtains the best filtering effect when the converter is running redundantly in the multi-machine parallel system.
[0006] The technical scheme adopted by the present application to solve the above technical problems is as follows:
[0007] The application provides a multi-machine parallel system, which comprises n converters connected in parallel between a power grid and a motor, n≥2; each converter comprises a grid-side converter and a motor-side converter, an AC end of the grid-side converter is connected with the power grid, a DC end of the grid-side converter is connected with a DC end of the motor-side converter, and an AC end of the motor-side converter is connected with the motor.
[0008] The multi-machine parallel system further comprises n switching switches corresponding to the n converters, a common connection point, an AC filter circuit and a grounding row, an AC end of the grid-side converter of any one of the n converters is connected with one end of the corresponding switching switch, the other end of the corresponding switching switch is connected with the common connection point, one end of the AC filter circuit is connected with the common connection point, and the other end of the AC filter circuit is connected with the grounding row.
[0009] In an example, the switching switch comprises a contactor.
[0010] In an example, the corresponding switching switch is integrated in any one of the n converters.
[0011] In an example, the AC filter circuit comprises one three-phase AC filter capacitor or three single-phase AC filter capacitors; wherein the AC filter capacitor is in star connection or delta connection, and the neutral point of the AC filter capacitor is grounded or not grounded.
[0012] In an example, the multi-machine parallel system further comprises a protection device, which is connected between one end of the AC filter circuit and the common connection point.
[0013] In an example, the protection device comprises a fuse or an air switch.
[0014] In an example, the n switching switches are not turned on at the same time.
[0015] In an example, each converter further comprises a grid-side switch, and the AC end of the grid-side converter is connected with the power grid through the grid-side switch.
[0016] In an example, each converter further comprises a motor-side switch, and the AC end of the motor-side converter is connected with the motor through the motor-side switch.
[0017] In an example, each converter further comprises a DC bus capacitor, one end of the DC bus capacitor is connected with a positive DC bus between the DC end of the grid-side converter and the DC end of the motor-side converter, and the other end of the DC bus capacitor is connected with a negative DC bus between the DC end of the grid-side converter and the DC end of the motor-side converter.
[0018] The multi-machine parallel system provided by the application ensures that the capacitance value of the input filter capacitor is large, so that the multi-machine parallel system obtains better harmonic suppression and filtering effect, and fully considers how a single converter obtains the best filtering effect when the converter is redundantly operated in the multi-machine parallel system. BRIEF DESCRIPTION OF DRAWINGS
[0019] Figure 1 A multi-machine parallel system schematic diagram provided by the embodiment of the application is provided.
[0020] Figure 2 Another multi-machine parallel system schematic diagram provided by the embodiment of the application is provided.
[0021] The implementation, functional features and advantages of the application will be further described with reference to the embodiments and the accompanying drawings. DETAILED DESCRIPTION
[0022] In order to make the technical problems, technical solutions and beneficial effects of the application more clear and explicit, the application will be further described in detail below in combination with the drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the application and not to limit the application.
[0023] As shown in the drawings, the multi-machine parallel system provided by the embodiment of the application includes n converters connected in parallel in the power grid and the motor, n≥2, for example, Q1-Qn shown in the drawings. Figure 1 Each converter includes a grid-side converter and a motor-side converter, the AC end of the grid-side converter is connected with the power grid, the DC end of the grid-side converter is connected with the DC end of the motor-side converter, and the AC end of the motor-side converter is connected with the motor. Each converter further includes a grid-side switch, and the AC end of the grid-side converter is connected with the power grid through the grid-side switch. Each converter further includes a motor-side switch, and the AC end of the motor-side converter is connected with the motor through the motor-side switch. Each converter further includes a DC bus capacitor, one end of the DC bus capacitor is connected to the positive DC bus between the DC end of the grid-side converter and the DC end of the motor-side converter, and the other end of the DC bus capacitor is connected to the negative DC bus between the DC end of the grid-side converter and the DC end of the motor-side converter.
[0024]
[0025] Taking the converter Q1 in the figure as an example, the converter Q1 comprises a grid-side converter Q11, a machine-side converter Q12, a grid-side switch K11, a machine-side switch K12, and a DC bus capacitor C1. The AC end of the grid-side converter Q11 is connected to the power grid through the grid-side switch K11. The DC end of the grid-side converter Q11 is connected to the DC end of the machine-side converter Q12. One end of the DC bus capacitor C1 is connected to the positive DC bus between the DC end of the grid-side converter Q11 and the DC end of the machine-side converter Q12. The other end of the DC bus capacitor C1 is connected to the negative DC bus between the DC end of the grid-side converter Q11 and the DC end of the machine-side converter Q12. The AC end of the machine-side converter Q12 is connected to the motor through the machine-side switch K12.
[0026] The multi-machine parallel system further comprises n switching switches (S11-S1n in the figure) corresponding to the n converters, a common connection point O, an AC filter capacitor Cz, and a grounding row (ground symbol in the figure). The AC end of the grid-side converter of any one of the n converters is connected to one end of the corresponding switching switch. The other end of the corresponding switching switch is connected to the common connection point O. One end of the AC filter capacitor Cz is connected to the common connection point O. The other end of the AC filter capacitor Cz is connected to the grounding row. The switching switch is used to realize the connection and disconnection of the AC filter circuit. The AC filter capacitor Cz is used to filter the grid-side current of the converter and can be one or multiple capacitors. The multiple capacitors can be connected in series or in parallel.
[0027] The n switching switches correspond to the n converters. For example, the switching switch corresponding to the converter Q1 is S11, the switching switch corresponding to the converter Q2 is S12, and the switching switch corresponding to the converter Qn is S1n. Taking the converter Q1 and the corresponding switching switch S11 as an example, the converter Q1 is connected to one end of the switching switch S11. The other end of the switching switch S11 is connected to the common connection point O.
[0028] In an example, the switching switch comprises a contactor.
[0029] In an example, the corresponding switching switch is integrated in any one of the n converters. For example, the switching switch S11 is integrated in the converter Q1, the switching switch S12 is integrated in the converter Q2, and the switching switch S1n is integrated in the converter Qn.
[0030] In an example, the multi-machine parallel system further comprises a protection device Z1 connected between one end of the AC filter capacitor Cz and the common connection point O. The protection device Z1 comprises a fuse or an air switch. The protection device Z1 is used for overcurrent protection of the AC filter capacitor Cz.
[0031] In an example, the n number of switching switches are not turned on at the same time. Specifically, taking n=2 as an example, the converter Q1 and the converter Q2 can be independently operated or operated at the same time. When the converter Q1 is operated, the switching switch S11 is closed to realize the AC filter capacitor Cz to be put into operation for converter harmonic suppression; when the converter Q2 is operated, the switching switch S12 is closed to realize the AC filter capacitor Cz to be put into operation for converter harmonic suppression; when the converter Q1 and the converter Q2 are operated at the same time, the switching switch S11 and the switching switch S12 can be selectively closed to one of the switching switches, realizing the AC filter capacitor Cz to be put into operation for converter harmonic suppression.
[0032] Please refer to Figure 2 As shown in the figure, the connection of the switching switch S11, the switching switch S12, the protection device Z1 and the AC filter capacitor Cz in a three-phase system when n=2 is shown. In the figure, the AC filter capacitor Cz includes one three-phase AC filter capacitor or three single-phase AC filter capacitors; wherein the AC filter capacitor Cz can be star connection or delta connection, and the neutral point of the AC filter capacitor Cz can be grounded or not. The figure shows the case of Y-type connection and the neutral point not grounded.
[0033] The above describes the preferred embodiments of the present application with reference to the accompanying drawings, and does not limit the scope of the present application. Any modification, equivalent replacement and improvement made by those skilled in the art without departing from the scope and essence of the present application shall be within the scope of the present application.
Claims
1. A multi-computer system, characterized by, The multi-machine parallel system comprises n converters connected in parallel between a power grid and an electric machine, n≥2; each converter comprises a grid-side converter and a machine-side converter, an AC end of the grid-side converter is connected with the power grid, a DC end of the grid-side converter is connected with a DC end of the machine-side converter, and an AC end of the machine-side converter is connected with the electric machine; The multi-machine parallel system further comprises n throw switches corresponding to the n converters, a common connection point, an AC filter circuit, and a grounding row, an AC end of a grid-side converter of any one of the n converters is connected with one end of a corresponding throw switch, the other end of the corresponding throw switch is connected with the common connection point, one end of the AC filter circuit is connected with the common connection point, and the other end of the AC filter circuit is connected with the grounding row.
2. The multi-computer system of claim 1, wherein, The throw switch comprises a contactor.
3. The multi-computer system of claim 1, wherein, The corresponding throw switch is integrated in any one of the n converters.
4. The multiple machine parallel system of claim 1, wherein, The AC filter circuit comprises one three-phase AC filter capacitor or three single-phase AC filter capacitors; wherein the AC filter capacitor is in star connection or delta connection, and the neutral point of the AC filter capacitor is grounded or not grounded.
5. The multiple machine parallel system of claim 1, wherein, The multi-machine parallel system further comprises a protection device, which is connected between one end of the AC filter circuit and the common connection point.
6. The multi-computer system of claim 5, wherein, The protection device comprises a fuse or an air switch.
7. The multi-computer system of claim 1, wherein, The n throw switches are not turned on at the same time.
8. The multi-computer system of claim 1, wherein, Each converter further comprises a grid-side switch, and the AC end of the grid-side converter is connected with the power grid through the grid-side switch.
9. The multi-computer system of claim 1, wherein, Each converter further comprises a machine-side switch, and the AC end of the machine-side converter is connected with the electric machine through the machine-side switch.
10. The multi-computer system of claim 1, wherein, Each converter further comprises a DC bus capacitor, one end of the DC bus capacitor is connected with a positive DC bus between the DC end of the grid-side converter and the DC end of the machine-side converter, and the other end of the DC bus capacitor is connected with a negative DC bus between the DC end of the grid-side converter and the DC end of the machine-side converter.