Power assembly and converter

Abstract

The utility model provides a power assembly and a converter. The power assembly comprises a machine-side power module, a network-side power module, a positive direct-current bus conducting bar, a negative direct-current bus conducting bar and a direct-current bus capacitor, the machine side power module is connected with a motor, the network side power module is connected with a power grid, and the positive direct current bus conducting bar and the negative direct current bus conducting bar are connected between the machine side power module and the network side power module. The direct current bus capacitor is arranged between the positive direct current bus conducting bar and the negative direct current bus conducting bar; the power assembly further comprises at least one magnetic ring arranged on the positive direct current bus conducting bar and / or the negative direct current bus conducting bar. According to the power assembly and the converter, through the at least one magnetic ring arranged on the positive direct current bus conducting bar and / or the negative direct current bus conducting bar, the ripple current of the bus capacitor is prevented from being too large, the loss of the bus capacitor is reduced, and the bus capacitor is prevented from being burnt.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of converter, and particularly relates to a power assembly and a converter. BACKGROUND

[0002] In the converter, a modular design is usually adopted to integrate a DC bus capacitor and a power device into a module to save space and facilitate maintenance. However, the machine-side module and the grid-side module are connected through a copper bar bridge, and the parasitic inductance is large, which is easy to resonate with the DC bus capacitor, thereby increasing the ripple current and causing the DC bus capacitor to be damaged. CONTENT

[0003] The present application provides a power assembly and a converter to solve the problem of large ripple current in the bridge-connected power module.

[0004] In one aspect, the present application provides a power assembly, which comprises a machine-side power module, a grid-side power module, a positive DC bus conductive bar, a negative DC bus conductive bar and a DC bus capacitor.

[0005] The machine-side power module is connected with a motor, the grid-side power module is connected with a power grid, the positive DC bus conductive bar and the negative DC bus conductive bar are connected between the machine-side power module and the grid-side power module, and the DC bus capacitor is arranged between the positive DC bus conductive bar and the negative DC bus conductive bar.

[0006] The power assembly further comprises at least one magnetic ring arranged on the positive DC bus conductive bar and / or the negative DC bus conductive bar.

[0007] In one example, the magnetic ring is a magnetic ring with an air gap.

[0008] In one example, the power assembly further comprises a grid-side reactor and / or a machine-side reactor, the machine-side power module is connected with the motor through the machine-side reactor, and the grid-side power module is connected with the power grid through the grid-side reactor.

[0009] In one example, the machine-side power module and the grid-side power module each comprise a power device, and the inherent resonance frequency of the power assembly deviates from the switching frequency of the power device.

[0010] In one example, the difference between the switching frequency of the power device and the inherent resonance frequency of the power assembly is between 500Hz and 1000Hz.

[0011] In one example, the power device comprises an insulated gate bipolar transistor.

[0012] In an example, the positive DC bus conductive bar or the negative DC bus conductive bar comprises a conductive copper bar.

[0013] Another aspect of the present application provides a converter, which comprises the power assembly as described above.

[0014] The power assembly and the converter provided above avoid excessive bus capacitor ripple current, reduce bus capacitor loss, and prevent bus capacitor burnout by arranging at least one magnetic ring on the positive DC bus conductive bar and / or the negative DC bus conductive bar. BRIEF DESCRIPTION OF DRAWINGS

[0015] Figure 1 A converter schematic diagram is provided for the embodiments of the present application.

[0016] Figure 2 A grid-side and machine-side loop equivalent circuit schematic diagram is provided for the embodiments of the present application.

[0017] The implementation, functional features and advantages of the present application will be further described with reference to the accompanying drawings. DETAILED DESCRIPTION

[0018] In order to make the technical problems, technical solutions and beneficial effects of the present application more clear, specific embodiments of the present application will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application, and are not used to limit the present application.

[0019] In the description of the present application, it should be understood that the terms "center", "upper", "lower", "front", "back", "left", "right" and the like indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, and are only used to facilitate the description of the present application and simplify the description, and are not intended to indicate or imply that the device or element referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as limiting the present application. In addition, the terms "first" and "second" are only used for description purposes, and cannot be understood as indicating or implying relative importance.

[0020] As shown in FIG. 1, the converter provided by the embodiments of the present application comprises a power assembly. Figure 1

[0021] The power assembly comprises a machine-side power module, a grid-side power module, a positive DC bus conductive bar BUS+, a negative DC bus conductive bar BUS-, and a DC bus capacitor.

[0022] ​The machine-side power module is connected with the motor, the grid-side power module is connected with the power grid, the positive direct current busbar BUS+ and the negative direct current busbar BUS- are connected between the machine-side power module and the grid-side power module, and the direct current bus capacitor is arranged between the positive direct current busbar BUS+ and the negative direct current busbar BUS-.

[0023] The power assembly further comprises at least one magnetic ring arranged on the positive direct current busbar BUS+ and / or the negative direct current busbar BUS-.

[0024] In an example, the converter can be a wind power converter, and the motor can be a wind turbine.

[0025] In an example, the magnetic ring is a magnetic ring with an air gap.

[0026] In an example, the power assembly further comprises a grid-side reactor and / or a machine-side reactor, the machine-side power module is connected with the motor through the machine-side reactor, and the grid-side power module is connected with the power grid through the grid-side reactor.

[0027] In an example, the machine-side power module and the grid-side power module each comprise a power device, and the inherent resonant frequency of the power assembly deviates from the switching frequency of the power device.

[0028] In an example, the difference between the switching frequency of the power device and the inherent resonant frequency of the power assembly is between 500 Hz and 1000 Hz.

[0029] In an example, the positive direct current busbar or the negative direct current busbar comprises a conductive copper bar.

[0030] In an example, the power device comprises an insulated gate bipolar transistor.

[0031] Taking the grid-side and machine-side loop equivalent circuit as an example, in actual design, the differential mode magnetic ring can be designed according to the direct current bus capacitor capacity, the busbar (busbar conductive bar) parasitic inductance and other parameters, so that the inherent resonant frequency of the system deviates from the switching frequency of the power device, such as IGBT, and the ripple voltage is avoided. Figure 2

[0032] The frequency of the ripple voltage is determined by the switching frequency, and the direct current bus capacitor capacity generally does not change. Adjusting the busbar parasitic inductance to make the resonant frequency avoid the switching frequency is a relatively effective method.

[0033] If the busbar ripple current of the system has resonance, the grid-side and machine-side capacitor capacities and the switching frequency of the power device are known, and the parasitic inductance L1 of the busbar can be calculated by using the following formula:

[0034]

[0035] ​Adding magnetic ring on DC bus can increase inductance, so that the resonant frequency of the system deviates from the switching frequency f sw . The difference between the switching frequency f sw and the resonant frequency f is between 500Hz-1000Hz. At this time, the inductance in the loop is:

[0036]

[0037] Therefore, the inductance of the magnetic ring is

[0038] L=L1'-L1

[0039] The specifications of the magnetic ring are as follows

[0040]

[0041] Wherein,

[0042] N is the number of turns of the coil, the bus passes through the magnetic ring, and the number of turns can be 1;

[0043] μ is the magnetic permeability, which is related to the material of the magnetic ring;

[0044] S is the cross-sectional area of the magnetic ring.

[0045] The selection of the magnetic ring needs to pay attention to the problem of magnetic saturation. Magnetic saturation is a physical property of ferromagnetic materials. The more saturated the magnetic circuit is, the lower the magnetic permeability is, and the smaller the equivalent inductance is. Increasing the air gap between the magnetic rings, because the magnetic permeability of air is much smaller than that of ferromagnetic materials, the magnetic resistance is very large, so the magnetic potential is mainly on the air gap, so increasing the air gap can effectively prevent magnetic saturation.

[0046] Hl=NI

[0047]

[0048] Wherein, H is the magnetic field strength;

[0049] l is the length of the magnetic circuit loop;

[0050] N is the number of turns of the coil;

[0051] I is the coil current;

[0052] B is the magnetic induction intensity;

[0053] μ is the magnetic permeability.

[0054] For example, the saturation magnetic density of iron-based amorphous material is 1.56T, assuming the length of the magnetic circuit loop l=500mm, the number of turns of the coil is 1, and if there is no air gap, the magnetic ring will be saturated by a current of 2.5A.

[0055]

[0056] So must add air gap, set air gap 1mm, add air gap after the magnetic ring can pass 1242A current, greatly enhanced the magnetic saturation capacity.

[0057]

[0058] In an example, the net side bus capacitance C1, the machine side bus capacitance C2, the switching frequency f sw As follows:

[0059] C1 = C2 = 300 * 24 = 7200 μF

[0060] f sw = 3000 Hz

[0061] According to the above formula, the loop parasitic inductance is

[0062] L1 = 0.78 μH

[0063] The loop natural resonance frequency is shifted to 2000 Hz, and the loop inductance is adjusted to

[0064] L1' = 1.76 μH

[0065] The increased magnetic ring inductance is about 1 μH, and if two magnetic rings are used in each positive and negative busbar, the single magnetic ring inductance required is 0.25 μH.

[0066] The preferred embodiments of the present application are described above with reference to the accompanying drawings, and are not limited to the scope of the present application. Any modifications, equivalent replacements and improvements 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 power component, characterized in that, This includes machine-side power modules, grid-side power modules, positive DC bus conductors, negative DC bus conductors, and DC bus capacitors; The machine-side power module is connected to the motor, the grid-side power module is connected to the power grid, the positive DC bus and the negative DC bus are connected between the machine-side power module and the grid-side power module, and the DC bus capacitor is disposed between the positive DC bus and the negative DC bus. The power assembly further includes at least one magnetic ring disposed on the positive DC bus conductor and / or the negative DC bus conductor.

2. The power component according to claim 1, characterized in that, The magnetic ring is a magnetic ring with an air gap.

3. The power component according to claim 1, characterized in that, The power assembly further includes a grid-side reactor and / or a generator-side reactor. The generator-side power module is connected to the motor through the generator-side reactor, and the grid-side power module is connected to the power grid through the grid-side reactor.

4. The power component according to claim 1, characterized in that, Both the machine-side power module and the grid-side power module include power devices, and the inherent resonant frequency of the power components deviates from the switching frequency of the power devices.

5. The power component according to claim 4, characterized in that, The difference between the switching frequency of the power device and the inherent resonant frequency of the power component is between 500Hz and 1000Hz.

6. The power component according to claim 4, characterized in that, The power device includes an insulated gate bipolar transistor.

7. The power component according to claim 1, characterized in that, The positive DC bus conductor or the negative DC bus conductor includes a conductive copper bus.

8. A converter, characterized in that, The converter includes the power component as described in any one of claims 1-7.

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