Electric power converter
By combining the magnetic force of the transformer and the LCL filter, sharing magnetic components, and integrating the filter components into the transformer, the problem of high space and complexity of the electric power converter is solved, and a smaller, simpler and lower cost converter design is achieved.
Patent Information
- Application Number
- CN202411905647.9
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Priority Date
- 2023-12-28
- Filing Date
- 2024-12-23
- Publication Date
- 2025-07-01
AI Technical Summary
Existing electric power converters have problems such as large space occupation, high complexity and high cost.
By combining the transformer and the LCL filter part, sharing magnetic components, integrating the filter components into the transformer, reducing component count and space requirements.
A smaller, simpler, and lower cost electric power converters are achieved while maintaining robustness and efficiency.
Smart Images
Figure CN120237901A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to an electric power converter, in particular to an electric power converter for an MVAC / LVAC to LVDC electric power conversion drive device. The converter includes an active front end (AFE), a transformer, and an LCL filter having a grid-side choke coil (L1) and a drive device-side choke coil (L2). According to the present invention, the transformer and the LCL filter are at least partially magnetically coupled to each other.
[0002] The present invention relates to the optimization of the application of LCL filters and transformers for MVAC / LVAC to LVDC conversion. MVAC or medium voltage AC electric power conversion drive devices typically operate in a range above 1 kV and typically in a range of 3 kV to 4 kV, LVAC or low voltage AC electric power conversion drive devices typically operate in a range below 1000 V AC, and LVDC or low voltage DC electric power conversion drive devices typically operate in a range below 1500 V DC. Background Art
[0003] Such electric power converters include transformer cores and other related components, which may occupy a relatively large amount of available space. Known converters require discrete components with correspondingly higher space requirements, higher overall complexity, and more interfaces. Summary of the Invention
[0004] The object of the present invention is to provide an improved electric power converter that overcomes these problems. Specifically, the presently described electric power converter offers the advantages of reducing the overall system complexity, cost, and size.
[0005] This object is achieved by the electric power converter according to claim 1. Preferred embodiments are subject to the dependent claims.
[0006] According to claim 1, there is provided an electric power converter, preferably an electric power converter for an MVAC / LVAC to LVDC electric power conversion drive device. The electric power converter includes an active front end, a transformer, and an LCL filter having a grid-side choke coil and a drive device-side choke coil. According to the present invention, the transformer and the LCL filter are at least partially magnetically coupled to each other. Specifically, the inductive components of the LCL filter are at least partially magnetically coupled to the transformer. The coupling of the transformer and the LCL filter or at least some parts of the transformer and the LCL filter reduces the overall size of the electric power converter and the number of its components. The magnetic coupling may involve sharing magnetic components or magnetizing components between the transformer and the LCL filter such that the same magnetic component can simultaneously be part of both the transformer and the LCL filter.
[0007] Thus, the basic idea of the present invention is to integrate filter components into a transformer by partially using the same core for at least one of an inductor and a transformer, or even using the stray inductance of the transformer as an inductor. By using the stray inductance of the transformer, some of the components in some filter components can be moved to the MV side or the primary side of the transformer, where the current is much lower, and thus less material and cheaper materials are required for the corresponding components.
[0008] Overall, the power electric converter described currently provides a simpler interface than known solutions, smaller, lighter and simpler. It has better efficiency while maintaining the same robustness as the converters known in the prior art. The reduction in material requirements means a reduction in overall cost.
[0009] There are several ways to implement the combination of various power electric converter components. The following embodiments represent different degrees of integration of power electric converter components.
[0010] In a preferred embodiment of the present invention, the stray inductance of the transformer is used as only a part of the grid-side choke.
[0011] In another preferred embodiment of the present invention, the magnetic flux in the core of the grid-side choke is enclosed by a part of the magnetic yoke of the transformer, in particular by the top part of the magnetic yoke of the transformer.
[0012] In another preferred embodiment of the present invention, at least one of the chokes and the transformer use the same core.
[0013] In another preferred embodiment of the present invention, the grid-side choke and capacitor of the LCL filter are arranged on the primary side or the higher voltage side of the transformer.
[0014] In another preferred embodiment of the present invention, the circuit breaker is arranged on the primary side of the transformer, before or after the LC part filter. In this embodiment, the LCL filter can be divided into an LC part and an L part, or the LCL filter can only include the LC part.
[0015] In another preferred embodiment of the present invention, the drive device side choke is arranged on the secondary side of the transformer. Alternatively, the drive device side choke can be arranged on the primary side of the transformer.
[0016] In another preferred embodiment of the present invention, the drive device side choke and the secondary winding of the transformer share the same secondary winding. Description of the Drawings
[0017] Other details and advantages of the present invention are described with reference to the embodiments shown in the accompanying drawings. The drawings show:
[0018] Figure 1a : A schematic diagram of an electric power converter having an active front end and an LCL filter;
[0019] Figure 1b : A typical application of the electric power converter;
[0020] Figure 2a : A perspective view of a core shared between a transformer and a choke;
[0021] Figure 2b : An embodiment of the present invention;
[0022] Figure 3a : Another embodiment of the present invention; and
[0023] Figure 3b : A perspective view of how windings can be arranged to obtain sufficient stray inductance between the primary and secondary sides of a transformer. Detailed Description
[0024] Figure 1a is a schematic diagram of an electric power converter having an active front end AFE and an LCL filter. The electric power converter is provided for, for example, electric power conversion drives such as MVAC / LVAC to LVDC. The electric power converter includes an active front end AFE, a transformer 10, and an LCL filter having a grid-side choke L1 and a drive-side choke L2.
[0025] The LCL filter can be arranged between the transformer 10 and the AFE. According to the present invention, the transformer 10 and the LCL filter are at least partially magnetically coupled to each other. In particular, the inductive components of the LCL filter are at least partially magnetically coupled to the transformer 10, i.e., they share some common magnetic components.
[0026] The coupling of the transformer 10 and the LCL filter or the coupling of at least some parts of the transformer 10 and the LCL filter reduces the overall size of the electric power converter and the number of its components.
[0027] The coupling of the transformer 10 and the LCL filter allows the stray inductance of the transformer 10 to be used as part of only the grid-side choke L1 of the LCL filter.
[0028] Figure 1bShows a typical application of an electric power converter. In this case, a dedicated transformer 10 is used together with an AFE drive device. The common coupling point of the transformer 10 and the LCL filter is on the primary side of the transformer 10. The common coupling point is the point where the entire device including both the filter and the transformer 10 is connected to the power grid, and is also the point where other similar devices can be connected. The currently used term "LCL filter" is understood in a broad sense, and thus actually only refers to the CL part of the LCL filter.
[0029] Figure 1a The shown grid-side choke L1 can be omitted. Instead, only the natural stray inductance of the transformer 10 can be used as the corresponding inductance.
[0030] Figure 2a Shows a perspective view of core sharing between the transformer 10 and the choke. In this setup, the drive-side choke L2 can be mounted on top of the core of the transformer 10, and the drive-side choke L2 does not have its own separate lower yoke. The magnetic flux in the core of the drive-side choke L2 is enclosed by the top part of the yoke of the transformer 10.
[0031] Several chokes can be mounted on top of the transformer 10, thereby optimizing the amount of core material required. Any yoke can be shared between the transformer 10 and the chokes L1, L2.
[0032] Generally, at least one of the chokes L1, L2 and the transformer 10 can use the same core or a part of the same core.
[0033] The transformer 10 can include three transformer yokes 3, and the chokes L1, L2 can be arranged between the three transformer yokes 3. The grid-side choke L1 and the capacitor C can be separate components on the medium voltage MV side of the transformer 10.
[0034] Figure 2b Shows an embodiment of the present invention, in which a circuit breaker CB is provided on the primary side of the transformer 10, before or after the LC part filter. The LCL filter can be separated such that its LC part is located between the transformer 10 and the power grid 11, and its drive-side choke L2 is provided between the transformer 10 and the AFE. In the shown embodiment, two drive-side chokes L and L2 are provided. The circuit breaker CB can be provided between the LCL filter and the power grid 11.
[0035] The grid-side choke L1 and the capacitor C of the LCL filter are provided on the primary and higher voltage side of the transformer 10.
[0036] The main advantage of this embodiment is that the components used in the LCL filter can be separated on both sides of the transformer 10, that is, separated on the grid side and the AFE side of the transformer 10. The grid-side choke L1 and the capacitor C can be arranged on the primary side of the system. Since the required current rating is lower, a large amount of cost can be saved in terms of system-level design. In addition, the circuit breaker CB between the system and the grid 11 can be designed according to a current rating lower than that required on the secondary side of the transformer 10.
[0037] Figure 3a Another embodiment of the present invention is shown. Here, the transformer 10 is designed such that the drive device-side choke L2 or the AFE-side choke and the secondary winding of the transformer 10 share the same secondary winding. Therefore, the drive device-side choke L2 can be arranged on the secondary side of the transformer 10. Since the specification of the stray inductance of the transformer 10 is set to be the same as the inductance value of the drive device-side choke L2, there is no separate drive device-side choke L2 component.
[0038] Figure 3b is a simplified diagram of how the windings can be arranged to obtain sufficient stray inductance between the primary side and the secondary side of the transformer 10. The transformer 10 includes two magnetic yokes 3 connected to the primary side 1 and the secondary side 2 of the transformer 10, thereby forming a transformer core 6. The primary winding 4 of the grid-side choke L1 is arranged on the primary side 1 of the transformer 10, while the secondary winding 5 of the drive device-side choke L2 is arranged around both the primary side 1 and the secondary side 2 of the transformer 10. For better understanding, the primary winding ends 4a, 4b and the secondary winding ends 5a, 5b are shown. The transformer assembly 100 can include the transformer and any other components of the power electric converter currently described. The transformer assembly 100 introduces a method of integrating the choke L2 into the transformer 10 without the need for any additional windings for the choke L2. Instead, the core geometry is changed to increase the leakage inductance between the primary winding 4 and the secondary winding 5.
Claims
1. An electric power converter, in particular an electric power converter for a MVAC / LVAC to LVDC electric power conversion drive device, the electric power converter comprising an active front end (AFE), a transformer (10) and an LCL filter having a grid-side choke (L1) and a drive-side choke (L2), characterized in that: The transformer (10) and the LCL filter are at least partially magnetically coupled to each other.
2. The electric power converter according to claim 1, characterized in that: The stray inductance of the transformer (10) is used as only a part of the grid-side choke (L1).
3. Electric power converter according to the preceding claim, characterized in that The magnetic flux in the core of the line-side inductor (L1) is enclosed by a portion of the yoke of the transformer (10).
4. An electrical power converter according to any one of the preceding claims, characterized in that At least one of the choke coils (L1, L2) and the transformer (10) use the same core.
5. An electrical power converter according to any one of the preceding claims, characterized in that The grid-side choke (L1) and capacitor (C) of the LCL filter are arranged on the primary side of the transformer (10).
6. An electrical power converter according to any one of the preceding claims, characterized in that A circuit breaker (CB) is arranged on the primary side of the transformer (10), before or after the LC partial filter.
7. An electrical power converter according to any one of the preceding claims, characterized in that The drive device side choke (L2) is arranged on the secondary side of the transformer (10).
8. Electric power converter according to the preceding claim, characterized in that The drive device side choke (L2) and the secondary winding of the transformer (10) share the same secondary winding.