A cascaded dual-mode bidirectional converter

Abstract

The utility model discloses a cascade type double system bidirectional current conversion device, including 4n power unit, 4n power unit is divided into four levels, is first, second, third and fourth level power unit respectively, characterized by: the both ends of first and second level power unit's direct current side series connection, one end is connected on the positive bus, and the other end is connected on the negative bus through bipolar isolating switch QS2, the both ends of third and fourth level power unit's direct current side series connection, one end is connected on the positive bus through bipolar isolating switch QS2, and the other end is connected on the negative bus, and second level power unit is connected on third level power unit through isolating switch QS1. The utility model discloses bidirectional current conversion device, can be switched into different voltage grade bidirectional current conversion device according to the different needs of the scene, guarantees the whole power grade of device to keep invariant simultaneously, improves the integration serialization degree of bidirectional current conversion device product, and the equipment category classification and operation maintenance cost are reduced.

Description

Technical Field

[0001] This utility model relates to a cascaded dual-system bidirectional converter, and more specifically, to a cascaded dual-system bidirectional converter. Background Technology

[0002] With the rapid development of rail transit, the demand for test power supplies for rail transit has also increased to various voltage levels, among which DC3000V and DC1500V voltage levels are the most common. As an emerging power supply device, bidirectional converters can not only provide energy to the load but also feed excess energy back into the power grid, achieving bidirectional energy flow. Developing a bidirectional converter that is compatible with both DC3000V and DC1500V voltage levels, and achieving a high degree of product integration and serialization, is a problem worthy of research. Summary of the Invention

[0003] In order to overcome the shortcomings of the above-mentioned technical problems, this utility model provides a cascaded dual-system bidirectional converter.

[0004] This utility model discloses a cascaded dual-mode bidirectional converter, comprising 4n power units, each divided into four stages: a first-stage power unit, a second-stage power unit, a third-stage power unit, and a fourth-stage power unit. The DC sides of the power units in each stage are connected in parallel, and their AC sides are connected in parallel via reactors. The outputs of the four-stage power units are connected to the four secondary windings of transformer T1 via AC buffer circuits; n≥1. The invention is characterized by further including a bipolar disconnect switch QS2 and a disconnect switch QS1. The DC sides of the first-stage power unit and the second-stage power unit are connected in series, and the DC sides of the third-stage power unit and the fourth-stage power unit are connected in series. The DC side of the first-stage power unit is connected in series with the DC side of the second-stage power unit. One end of the two ends is connected to the positive bus, and the other end is connected to the negative bus via a normally open contact of the bipolar disconnect switch QS2. The DC side of the third-stage power unit is connected in series with the DC side of the fourth-stage power unit. One end of the two ends of the two ends of the two-stage power unit is connected to the positive bus via another normally open contact of the bipolar disconnect switch QS2, and the other end is connected to the negative bus. The connection point between the second-stage power unit and the bipolar disconnect switch QS2 is connected to the connection point between the third-stage power unit and the bipolar disconnect switch QS2 via a normally open contact of the disconnect switch QS1.

[0005] The cascaded dual-mode bidirectional converter of this utility model has an AC buffer circuit consisting of an AC circuit breaker, an AC buffer contactor, and an AC buffer resistor. The outputs of the first-stage power unit, the second-stage power unit, the third-stage power unit, and the fourth-stage power unit are connected to the four secondary windings of transformer T1 via the normally open contact of the AC circuit breaker. The normally open contact of the AC buffer contactor is connected in series with the AC buffer resistor and then in parallel with the normally open contact of the AC circuit breaker.

[0006] The cascaded dual-mode bidirectional converter of this utility model has a power unit with a two-level three-phase converter topology. The power unit consists of 6 IGBT devices. The two ends of the 6 IGBT devices connected in series in pairs form DC terminals, and the series connection points of the 6 IGBT devices in pairs form AC output terminals of the power unit.

[0007] The cascaded dual-mode bidirectional converter of this utility model includes a double-pole disconnect switch QS3 and a DC contactor KM9. The two normally open contacts of the double-pole disconnect switch QS3 are connected in series with the positive bus and the negative bus, respectively, and the normally open contact of the DC contactor KM9 is connected in series with the positive bus.

[0008] The cascaded dual-system bidirectional converter of this utility model has a withstand voltage rating of AC500V for each secondary winding of the transformer T1.

[0009] The beneficial effects of this utility model are as follows: The cascaded dual-mode bidirectional converter of this utility model has 4n power units evenly distributed to form four levels of power units. The DC sides of the power units in each level are connected in parallel, and the AC sides are connected in parallel via reactors. The output of each power unit is connected to a secondary winding of transformer T1. The two ends of the DC sides of the first and second level power units connected in series are respectively connected to the positive bus and to the negative bus via the normally open contact of the bipolar disconnect switch QS2. The two ends of the DC sides of the third and fourth level power units connected in series are respectively connected to the negative bus and to the positive bus via the normally open contact of the bipolar disconnect switch QS2. Furthermore, the DC sides of the second and third level power units... The bidirectional converter is connected to the normally open contact of the disconnector QS1. Thus, when the bidirectional converter needs to operate at DC 1500V, simply close the normally open contact of the double-pole disconnector QS2 and keep the normally open contact of the disconnector QS1 open to allow the combination of the first and second stage power units, or the combination of the third and fourth stage power units, to operate at DC 1500V. When the bidirectional converter needs to operate at DC 3000V, simply close the normally open contact of the disconnector QS1 and keep the normally open contact of the double-pole disconnector QS2 open to allow the combination of the first, second, third, and fourth stage power units to operate at DC 3000V.

[0010] As can be seen, the cascaded dual-mode bidirectional converter of this utility model can automatically switch to different voltage levels of bidirectional converter according to different field requirements, while ensuring that the overall power level of the device remains unchanged. It can be said that it achieves compatibility with multiple field operating voltage levels, improves the integration and serialization of bidirectional converter products, reduces equipment category classification, and greatly reduces equipment development costs and operation and maintenance costs to a certain extent. Attached Figure Description

[0011] Figure 1 This is a circuit diagram of the cascaded dual-mode bidirectional converter of this utility model; Figure 2 This is the circuit schematic diagram of the power unit in this utility model; Figure 3 This is the circuit diagram of the cascaded dual-mode bidirectional converter of this utility model operating under DC1500V conditions. Figure 4 This is a circuit diagram of the cascaded dual-mode bidirectional converter of this utility model operating under DC 3000V conditions.

[0012] In the diagram: 1 Power unit, 2 First-stage power unit, 3 Second-stage power unit, 4 Third-stage power unit, 5 Fourth-stage power unit, 6 Positive bus, 7 Negative bus, 8 Transformer T1, 9 AC buffer circuit, 10 Reactor; QS1 isolating switch, QS2 and QS3 are both double-pole isolating switches, KM1, KM3, KM5 and KM7 are all AC buffer contactors, KM2, KM4, KM6 and KM8 are all AC circuit breakers, KM9 is a DC contactor, R1 to R9 are AC buffer resistors. Detailed Implementation

[0013] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0014] like Figure 1 The circuit diagram of the cascaded dual-mode bidirectional converter of this utility model is shown. It consists of 4n (n≥1) power units 1, double-pole disconnect switches QS2, QS3, and QS1, and a DC contactor KM9. The 4n power units 1 are divided into four levels: first-level power unit 2, second-level power unit 3, third-level power unit 4, and fourth-level power unit 5. The DC sides of the n power units in each level are connected in parallel, and the AC sides are connected in parallel via reactor 10. The outputs of the four power units are connected to the four secondary windings of transformer T1 via AC buffer circuit 9, and the primary winding of transformer T1 outputs AC power. Figure 1In the first-stage power unit 2, the DC sides of the power units 11, ..., 1n shown in the figure are connected in series, while the AC sides are connected in parallel after being connected to the reactor 10.

[0015] The DC side of the first-stage power unit 2 is connected in series with the DC side of the second-stage power unit 3, and the DC side of the third-stage power unit 4 is connected in series with the DC side of the fourth-stage power unit 5. One end of the series connection between the DC side of the first-stage power unit 2 and the DC side of the second-stage power unit 3 is connected to the positive bus 6, and the other end is connected to the negative bus 7 via a normally open contact of the bipolar disconnect switch QS2; for example, for... Figure 1 For the first and second stage power units, after the DC side of the first stage power unit 2 is connected in series with the DC side of the second stage power unit 3, one end of the first stage power unit 2 is connected to the positive bus 6, and the other end of the second stage power unit 3 is connected to the negative bus 7 through a normally open point of the bipolar isolation switch QS2.

[0016] The DC side of the third-stage power unit 4 is connected in series with the DC side of the fourth-stage power unit 5. One end of the series connection is connected to the negative bus 7, and the other end is connected to the positive bus 6 via the other normally open contact of the bipolar disconnect switch QS2. For example, for... Figure 1 For the third and fourth power units, the DC side of the third power unit 4 is connected in series with the DC side of the fourth power unit 5. The end of the fourth power unit 5 is connected to the negative bus 7, and the end of the third power unit 4 is connected to the positive bus 6 through the normally open contact of the bipolar isolation switch QS2.

[0017] The second-stage power unit 3 is connected to the normally open point of the double-pole disconnector Q2 via the normally open point of the disconnector QS1, and then to the third-stage power unit 4 connected to the normally open point of the double-pole disconnector Q2.

[0018] Thus, when the cascaded dual-mode bidirectional converter of this utility model needs to operate under DC 1500V conditions, it is only necessary to close the normally open contact of the double-pole disconnector QS2 while keeping the normally open contact of the disconnector QS1 open. Figure 3 As shown, this can be achieved by combining the first-stage power unit 2 and the second-stage power unit 3, or by combining the third-stage power unit 4 and the fourth-stage power unit 5.

[0019] When the cascaded dual-mode bidirectional converter of this utility model needs to be operated under DC 3000V conditions, it is only necessary to close the normally open contact of the disconnecting switch QS1 while keeping the normally open contact of the double-pole disconnecting switch QS2 in the open state. Figure 4The diagram shows the circuit schematic of the cascaded dual-mode bidirectional converter of this invention operating under DC 3000V conditions. At this time, the first-stage power unit 2, the second-stage power unit 3, the third-stage power unit 4 and the fourth-stage power unit 5 are connected in series, which can meet the insulation withstand voltage requirements of DC 3000V and can operate under DC 3000V conditions.

[0020] The power unit 1 in this invention adopts a two-level three-phase converter topology, such as... Figure 2 The circuit diagram of the power unit in this utility model is shown. The power unit consists of 6 IGBT devices. The two ends of the 6 IGBT devices connected in series in pairs form DC terminals, and the series connection points of the 6 IGBT devices in pairs form AC output terminals of the power unit.

[0021] The AC buffer circuit 9 connecting each power unit to transformer T1 consists of an AC circuit breaker, an AC buffer contactor, and an AC buffer resistor. The outputs of the first-stage power unit 2, the second-stage power unit 3, the third-stage power unit 4, and the fifth-stage power unit 5 are connected to the four secondary windings of transformer T1 via the normally open contact of the AC circuit breaker. The normally open contact of the AC buffer contactor is connected in series with the AC buffer resistor and then in parallel with the normally open contact of the AC circuit breaker. For example, for the first-stage power unit 2, its output is connected to one secondary winding of transformer T1 via the normally open contact of AC circuit breaker KM2. The normally open contact of AC buffer contactor KM1 is connected in series with the AC buffer resistors (R1, R2, R3) and then in parallel with the normally open contact of AC circuit breaker KM2.

[0022] The two normally open contacts of the double-pole disconnector QS3 shown are connected in series with the positive bus 6 and the negative bus 7, respectively. The normally open contact of the DC contactor KM9 is connected in series with the positive bus to control the on / off state of the positive bus 6 and the negative bus 7.

Claims

1. A cascaded dual-mode bidirectional converter, comprising 4n power units, each of which is divided into four stages: a first-stage power unit (2), a second-stage power unit (3), a third-stage power unit (4), and a fourth-stage power unit (5). The DC sides of the power units in each stage are connected in parallel, and the AC sides are connected in parallel via reactors (10). The outputs of the four-stage power units are connected to the four secondary windings of transformer T1 (8) via AC buffer circuits (9); n≥1; characterized in that: It also includes bipolar disconnect switches QS2 and QS1, with the DC side of the first-stage power unit connected in series with the DC side of the second-stage power unit, and the DC side of the third-stage power unit connected in series with the DC side of the fourth-stage power unit. The two ends of the DC side of the first-stage power unit and the DC side of the second-stage power unit connected in series are connected to the positive bus (6) at one end and to the negative bus (7) at the other end via a normally open point of the bipolar disconnect switch QS2. The two ends of the DC side of the third-stage power unit and the DC side of the fourth-stage power unit connected in series are connected to the positive bus at one end via another normally open point of the bipolar disconnect switch QS2 and to the negative bus at the other end. The position where the second-stage power unit is connected to the bipolar disconnect switch QS2 is connected to the position where the third-stage power unit is connected to the bipolar disconnect switch QS2 via a normally open point of the disconnect switch QS1.

2. The cascaded dual-mode bidirectional converter according to claim 1, characterized in that: The AC buffer circuit (9) consists of an AC circuit breaker, an AC buffer contactor, and an AC buffer resistor. The outputs of the first-stage power unit (2), the second-stage power unit (3), the third-stage power unit (4), and the fourth-stage power unit (5) are connected to the four secondary windings of the transformer T1 (8) via the normally open contact of the AC circuit breaker. The normally open contact of the AC buffer contactor is connected in series with the AC buffer resistor and then in parallel with the normally open contact of the AC circuit breaker.

3. The cascaded dual-mode bidirectional converter according to claim 1 or 2, characterized in that: The power unit (1) is a two-level three-phase converter topology. The power unit consists of 6 IGBT devices. The two ends of the 6 IGBT devices connected in series form DC terminals, and the AC output terminals of the power unit are formed at the series connection points of the 6 IGBT devices connected in series.

4. The cascaded dual-mode bidirectional converter according to claim 1 or 2, characterized in that: It includes a double-pole disconnector QS3 and a DC contactor KM9. The two normally open contacts of the double-pole disconnector QS3 are connected in series on the positive bus (6) and the negative bus (7), respectively. The normally open contact of the DC contactor KM9 is connected in series on the positive bus.

5. The cascaded dual-mode bidirectional converter according to claim 1 or 2, characterized in that: The withstand voltage rating of each secondary winding of the transformer T1 (8) is AC500V.

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