Power converter and power equipment

Abstract

The utility model relates to a power converter and electrical equipment, the power converter comprises a DC conversion circuit, an AC-DC conversion circuit, a first capacitor branch, a second capacitor branch and an impedance branch, the DC conversion circuit is connected with a first DC bus, and a DC end of the AC-DC conversion circuit is connected with a second DC bus; the first direct-current bus and the second direct-current bus are connected through the impedance branch; the first capacitor branch is connected between positive and negative electrodes of the first direct-current bus; the second capacitor branch is connected between the anode and the cathode of the second DC bus. The electrolytic capacitors are arranged in the second capacitor branch with higher access impedance, so that most noise generated by the AC / DC conversion circuit passes through the first capacitor branch with lower access impedance, the number of the electrolytic capacitors arranged on the second capacitor branch can be reduced, the reliability of the circuit is improved, and meanwhile, the cost and the occupied space are reduced.

Description

Technical Field

[0001] This application belongs to the field of power electronics technology, and in particular relates to a power converter and power equipment. Background Technology

[0002] A photovoltaic-storage grid-connected system includes a step-up / step-down DC-DC converter, a bidirectional DC-DC converter controlling battery charging and discharging, and a bidirectional AC / DC converter circuit controlling active power exchange with the grid (feeding power to or drawing power from the grid). The step-up / step-down DC-DC converter, the bidirectional DC-DC converter, and the bidirectional AC / DC converter circuit are connected via a DC bus. However, due to the large power required for AC-to-DC conversion, significant high-frequency ripple current exists. Since conventional electrolytic capacitors have relatively low ripple current, a large number of electrolytic capacitors are needed on the DC bus, resulting in large space requirements and high costs. Furthermore, electrolytic capacitors have low voltage ratings and are not heat-resistant; subjecting them to high-frequency ripple current for extended periods will further shorten their lifespan and reduce circuit reliability. Utility Model Content

[0003] The purpose of this application is to provide a power converter and power equipment that aims to solve the problem in related technologies where a large number of electrolytic capacitors need to be installed on the DC bus, which reduces the reliability of the circuit.

[0004] In a first aspect, embodiments of this application provide a power converter, including a DC-DC converter circuit and an AC-DC converter circuit. The DC-DC converter circuit is connected to a first DC bus, and the DC terminal of the AC-DC converter circuit is connected to a second DC bus. The power converter further includes:

[0005] The first capacitor branch is connected between the positive and negative terminals of the first DC bus;

[0006] The second capacitor branch is connected between the positive and negative terminals of the second DC bus; and

[0007] The impedance branch connects the first DC bus and the second DC bus. The first capacitor branch includes an electrolytic capacitor, and the second capacitor branch includes a film capacitor.

[0008] In one embodiment, the impedance branch includes a first inductor connected between the positive terminal of the first DC bus and the positive terminal of the second DC bus, or the first inductor connected between the negative terminal of the first DC bus and the negative terminal of the second DC bus.

[0009] In one embodiment, the impedance branch includes a first inductor and a second inductor, the first inductor being connected between the positive terminal of the first DC bus and the positive terminal of the second DC bus, and the second inductor being connected between the negative terminal of the first DC bus and the negative terminal of the second DC bus.

[0010] In one embodiment, the AC / DC conversion circuit is a three-phase AC / DC conversion circuit, and the DC terminal of the three-phase AC / DC conversion circuit includes a neutral point, with the first capacitor branch and the second capacitor branch both connected to the neutral point.

[0011] In one embodiment, the second capacitor branch includes a first film capacitor and a second film capacitor connected in series, the first film capacitor being connected between the positive terminal of the second DC bus and the neutral point, and the second film capacitor being connected between the negative terminal of the second DC bus and the neutral point.

[0012] In one embodiment, the first capacitor branch includes a first electrolytic capacitor and a second electrolytic capacitor connected in series, the first electrolytic capacitor being connected between the positive terminal of the first DC bus and the neutral point, and the second electrolytic capacitor being connected between the negative terminal of the first DC bus and the neutral point.

[0013] In one embodiment, the impedance branch includes a first inductor, a third inductor, and a second inductor. The first inductor is connected between the positive terminal of the first DC bus and the positive terminal of the second DC bus. The capacitor series connection point of the first capacitor branch is connected to the neutral point through the third inductor. The second inductor is connected between the negative terminal of the first DC bus and the negative terminal of the second DC bus.

[0014] In one embodiment, the impedance branch includes a first inductor and a second inductor, with the first inductor connected between the positive terminals of the first DC bus and the second DC bus, and the second inductor connected between the negative terminals of the first DC bus and the second DC bus.

[0015] Secondly, embodiments of this application also provide a power device, including a power converter as described above. The DC input terminal of the power converter is used to connect to a DC power supply. The DC input terminal is connected to a first terminal of the DC conversion circuit of the power converter. The second terminal of the DC conversion circuit is connected to a first DC bus. The DC terminal of the AC-DC conversion circuit of the power converter is connected to a second DC bus. The AC terminal of the AC-DC conversion circuit is connected to the AC terminal of the power converter. The AC terminal of the power converter is used to connect to the power grid and / or a load.

[0016] The beneficial effects of this application embodiment compared with related technologies are: by placing the electrolytic capacitor in the second capacitor branch with higher path impedance, most of the noise generated by the AC-DC conversion circuit goes through the first capacitor branch with lower path impedance, which reduces the number of electrolytic capacitors placed in the second capacitor branch, improves the reliability of the circuit, and reduces cost and space occupation. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the structure of a power converter provided in an embodiment of this application;

[0018] Figure 2 This is a schematic diagram of the circuit structure of a power converter provided in an embodiment of this application;

[0019] Figure 3 This is a schematic diagram of the circuit structure of a power converter provided in an embodiment of this application;

[0020] Figure 4 This is a schematic diagram of the circuit structure of a power converter provided in an embodiment of this application;

[0021] Figure 5 This is a schematic diagram of the circuit structure of a power converter provided in an embodiment of this application. Detailed Implementation

[0022] To make the technical problems, technical solutions, and beneficial effects to be solved by this application clearer, 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 and are not intended to limit the scope of this application.

[0023] It should be noted that when a component is referred to as being "fixed to" or "set on" another component, it can be directly on or indirectly on that other component. When a component is referred to as being "connected to" another component, it can be directly connected to or indirectly connected to that other component.

[0024] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this application, "multiple" means two or more, unless otherwise explicitly specified.

[0025] like Figure 1 As shown, one embodiment of this application provides a power converter, including a DC-DC converter 100 and an AC-DC converter 200. The DC-DC converter 100 is connected to a first DC bus, and the DC terminal of the AC-DC converter 200 is connected to a second DC bus. The power converter also includes a first capacitor branch 300, a second capacitor branch 400, and an impedance branch 500.

[0026] The first capacitor branch 300 is connected between the positive and negative terminals BUS1+ / BUS1- of the first DC bus. The second capacitor branch 400 is connected between the positive and negative terminals BUS2+ / BUS2- of the second DC bus. The first and second DC buses are connected through an impedance branch 500. The first capacitor branch 300 includes an electrolytic capacitor, and the second capacitor branch 400 includes a film capacitor.

[0027] Because the AC-to-DC conversion has a large power output, significant high-frequency noise (i.e., high-frequency ripple current) flows from the AC-DC converter 200 to the DC converter 100. The impedance of the high-frequency noise in the path containing the first capacitor branch 300 is the sum of the impedance of the first capacitor branch 300 itself and the impedance of the impedance branch 500. The impedance in the path containing the second capacitor branch 400 is the impedance of the second capacitor branch 400 itself. By placing the electrolytic capacitor in the first capacitor branch 300, which has a higher path impedance, and separating the first capacitor branch 300 and the second capacitor branch 400 by the impedance branch 500, most of the high-frequency noise generated by the AC-DC converter 200 flows through the second capacitor branch 400, which has a lower path impedance. This reduces the number of electrolytic capacitors required in the first capacitor branch 300, improving circuit reliability and reducing space requirements.

[0028] like Figure 2 As shown, in one embodiment, the impedance branch 500 includes a first inductor L1. The first inductor L1 is connected between the positive terminal BUS1+ of the first DC bus and the positive terminal BUS2+ of the second DC bus, or the first inductor L1 is connected between the negative terminal BUS1- of the first DC bus and the negative terminal BUS2- of the second DC bus. Taking a single-phase power converter as an example, an inductor is provided on one of the positive and negative terminals of the DC bus, and the first inductor L1 is provided between the first capacitor branch 300 and the second capacitor branch 400. The provision of the inductor can increase the impedance of the high-frequency noise generated by the AC-DC conversion circuit 200 flowing from the second DC bus to the first DC bus. Therefore, most of the high-frequency noise flows through the second capacitor branch 400 with lower impedance, which reduces the number of electrolytic capacitors provided on the first capacitor branch 300.

[0029] like Figure 3 As shown, in one embodiment, the impedance branch 500 includes a first inductor L1 and a second inductor L2. The first inductor L1 is connected between the positive terminal BUS1+ of the first DC bus and the positive terminal BUS2+ of the second DC bus, and the second inductor L2 is connected between the negative terminal BUS1+ of the first DC bus and the negative terminal BUS2- of the second DC bus. Taking a single-phase power converter as an example, inductors are provided at both the positive and negative terminals of the DC bus to further increase the impedance of the high-frequency noise generated by the AC / DC conversion circuit 200 flowing from the second DC bus to the first DC bus.

[0030] like Figure 3As shown, in one embodiment, the first capacitor branch 300 includes a first electrolytic capacitor C1 connected between the positive terminal BUS1+ and the negative terminal BUS1- of the first DC bus, and the second capacitor branch 400 includes a first thin film capacitor C2 connected between the positive terminal BUS2+ and the negative terminal BUS2- of the second DC bus.

[0031] like Figure 4 As shown, in one embodiment, the AC / DC converter 200 is a three-phase AC / DC converter 200, meaning the power converter can also be a three-phase power converter. The DC terminal of the three-phase AC / DC converter 200 includes a neutral point BUSN, and both the first capacitor branch 300 and the second capacitor branch 400 are connected to the neutral point BUSN. In this case, the noise generated by the AC / DC converter 200 will flow from the second DC bus through the second capacitor branch 400 to the neutral point BUSN.

[0032] like Figure 4 As shown, in one embodiment, the second capacitor branch 400 includes a first film capacitor C2 and a second film capacitor C3 connected in series. The first film capacitor C2 is connected between the positive terminal BUS2+ of the second DC bus and the neutral point BUSN, thereby forming a first high-frequency noise path. The second film capacitor C3 is connected between the negative terminal BUS2- of the second DC bus and the neutral point BUSN, thereby forming a second high-frequency noise path.

[0033] The impedance of the first high-frequency noise path is:

[0034]

[0035] ESR C2 Let C2 be the equivalent series resistance of the first thin-film capacitor. Let C2 be the capacitive reactance of the first thin-film capacitor.

[0036] like Figure 4 As shown, in one embodiment, the first capacitor branch 300 includes a first electrolytic capacitor C1 and a second electrolytic capacitor C4 connected in series. The first electrolytic capacitor C1 is connected between the positive terminal BUS1+ of the first DC bus and the neutral point BUSN. The second electrolytic capacitor C4 is connected between the negative terminal BUS1- of the first DC bus and the neutral point BUSN.

[0037] like Figure 4As shown, in one embodiment, the impedance branch 500 includes a first inductor L1 and a second inductor L2. The first inductor L1 is connected between the positive terminals of the first DC bus BUS1+ and the second DC bus BUS2+, and the second inductor L2 is connected between the negative terminals of the first DC bus BUS1- and the second DC bus BUS2-. It is understood that the power converter can be a single-phase or three-phase power converter, and inductors can be respectively installed on the positive and negative DC buses.

[0038] like Figure 5 As shown, optionally, the impedance branch 500 is also connected to the neutral point BUSN. In one embodiment, the impedance branch 500 includes a first inductor L1, a second inductor L2, and a third inductor L3. The first inductor L1 is connected between the positive terminals of the first DC bus BUS1+ and the second DC bus BUS2+. The capacitor series connection point of the first capacitor branch 300 (i.e., the series connection node of the first electrolytic capacitor C1 and the second electrolytic capacitor C4) is connected to the neutral point BUSN through the third inductor L3. The second inductor L2 is connected between the negative terminals of the first DC bus BUS1- and the second DC bus BUS2-.

[0039] In this embodiment, the second DC bus positive terminal BUS2+, the first inductor L1, the first DC bus positive terminal BUS1+, the first electrolytic capacitor C1, the third inductor L3, and the neutral point BUSN form the second high-frequency noise path.

[0040] The impedance of the second high-frequency noise path is:

[0041]

[0042] ESR C1 This is the equivalent series resistance of the first electrolytic capacitor C1. JwL1 and JwL3 are the capacitive reactance of the first electrolytic capacitor C1, and the inductive reactances of the first inductor L1 and the third inductor L3, respectively.

[0043] Assume the total high-frequency noise generated by the AC / DC converter circuit 200 is Iripple.

[0044] The ripple current of the first thin-film capacitor C2 is:

[0045]

[0046] The ripple current of the first electrolytic capacitor C1 is:

[0047]

[0048] When the frequency is relatively high, i.e., w is relatively large, R2 is much larger than R1. Therefore, most of the high-frequency noise generated by the AC / DC converter circuit 200 passes through the first film capacitor C2, which reduces the number of first electrolytic capacitors C1. Of course, to meet performance requirements, the first electrolytic capacitor C1 and the second electrolytic capacitor C4 can each be composed of multiple electrolytic capacitors connected in parallel.

[0049] Please continue reading. Figure 1 This application also provides a power device including the power converter described above. The DC input terminal of the power converter is connected to a DC power supply, and the DC input terminal is connected to a first terminal of the DC-DC conversion circuit 100 of the power converter. The second terminal of the DC-DC conversion circuit 100 is connected to a first DC bus. The DC terminal of the AC-DC conversion circuit 200 of the power converter is connected to a second DC bus, and the AC terminal of the AC-DC conversion circuit 200 is connected to the AC terminal of the power converter. The AC terminal of the power converter is used to connect to the power grid and / or a load.

[0050] In some embodiments, the power device may be a photovoltaic inverter or an energy storage inverter.

[0051] The above-described embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of this application, and should all be included within the protection scope of this application.

Claims

1. A power converter, characterized by, The power converter includes a DC-DC converter and an AC-DC converter. The DC-DC converter is connected to a first DC bus, and the DC terminal of the AC-DC converter is connected to a second DC bus. The power converter also includes: The first capacitor branch is connected between the positive and negative terminals of the first DC bus; The second capacitor branch is connected between the positive and negative terminals of the second DC bus; and The impedance branch connects the first DC bus and the second DC bus. The first capacitor branch includes an electrolytic capacitor, and the second capacitor branch includes a film capacitor.

2. The power converter of claim 1, wherein, The impedance branch includes a first inductor, which is connected between the positive terminal of the first DC bus and the positive terminal of the second DC bus, or the first inductor is connected between the negative terminal of the first DC bus and the negative terminal of the second DC bus.

3. The power converter of claim 1, wherein, The impedance branch includes a first inductor and a second inductor. The first inductor is connected between the positive terminal of the first DC bus and the positive terminal of the second DC bus, and the second inductor is connected between the negative terminal of the first DC bus and the negative terminal of the second DC bus.

4. The power converter of claim 1, wherein, The AC / DC conversion circuit is a three-phase AC / DC conversion circuit. The DC terminal of the three-phase AC / DC conversion circuit includes a neutral point, and the first capacitor branch and the second capacitor branch are both connected to the neutral point.

5. The power converter of claim 4, wherein, The second capacitor branch includes a first film capacitor and a second film capacitor connected in series. The first film capacitor is connected between the positive terminal of the second DC bus and the neutral point, and the second film capacitor is connected between the negative terminal of the second DC bus and the neutral point.

6. The power converter of claim 4, wherein, The first capacitor branch includes a first electrolytic capacitor and a second electrolytic capacitor connected in series. The first electrolytic capacitor is connected between the positive terminal of the first DC bus and the neutral point, and the second electrolytic capacitor is connected between the negative terminal of the first DC bus and the neutral point.

7. The power converter of claim 6, wherein, The impedance branch includes a first inductor, a third inductor, and a second inductor. The first inductor is connected between the positive terminal of the first DC bus and the positive terminal of the second DC bus. The capacitor series connection point of the first capacitor branch is connected to the neutral point through the third inductor. The second inductor is connected between the negative terminal of the first DC bus and the negative terminal of the second DC bus.

8. The power converter of claim 6, wherein, The impedance branch includes a first inductor and a second inductor. The two ends of the first inductor are connected between the positive terminal of the first DC bus and the positive terminal of the second DC bus, and the second inductor is connected between the negative terminal of the first DC bus and the negative terminal of the second DC bus.

9. An electric power device, characterized by The device includes a power converter as described in any one of claims 1 to 8, wherein the DC input terminal of the power converter is used to connect to a DC power supply, the DC input terminal is connected to a first terminal of the DC conversion circuit of the power converter, the second terminal of the DC conversion circuit is connected to a first DC bus, the DC terminal of the AC-DC conversion circuit of the power converter is connected to a second DC bus, and the AC terminal of the AC-DC conversion circuit is connected to the AC terminal of the power converter; the AC terminal of the power converter is used to connect to the power grid and / or a load.

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