阅读说明：本技术 电力变换装置 (Power conversion device ) 是由 赤泽奖也 小泽宽之 于 2019-10-01 设计创作，主要内容包括：为了降低从安装有构成三电平电力变换电路的半导体元件的框架漏出到电力变换装置的外部的噪声电流,通过设为将安装有构成电力变换装置所具备的三电平电力变换电路的半导体元件的框架与该三电平电力变换电路的中性点电连接的结构,将从该框架漏出的噪声电流拉回三电平电力变换电路的中性点,抑制噪声电流向电力变换装置外的流出,谋求该噪声电流的降低。(In order to reduce a noise current leaking to the outside of the power conversion device from a frame on which semiconductor elements constituting a three-level power conversion circuit are mounted, the noise current leaking from the frame is pulled back to a neutral point of the three-level power conversion circuit by a configuration in which the frame on which the semiconductor elements constituting the three-level power conversion circuit provided in the power conversion device are mounted is electrically connected to the neutral point of the three-level power conversion circuit, thereby suppressing the flow of the noise current to the outside of the power conversion device and reducing the noise current.)

1. A power conversion device including a three-level power conversion circuit, characterized in that,

the frame on which the semiconductor elements constituting the three-level power conversion circuit are mounted is electrically connected to a neutral point of the three-level power conversion circuit.

2. The power conversion device according to claim 1,

a noise absorbing core is provided on a path of a wiring electrically connecting the frame and a neutral point of the three-level power conversion circuit.

3. The power conversion device according to claim 2,

the wiring electrically connected to the frame and the wiring electrically connected to the neutral point of the three-level power conversion circuit are directly connected to each other after being wound around the noise-absorbing core a plurality of times.

4. The power conversion device according to claim 1,

a noise absorbing capacitor is provided on a path of a wiring electrically connecting the frame and a neutral point of the three-level power conversion circuit.

5. The power conversion device according to any one of claims 2 to 4,

as a wiring electrically connected to a neutral point of the three-level power conversion circuit, a ground line that reaches the ground from the neutral point via a ground resistance is used.

6. The power conversion device according to any one of claims 1 to 5,

the frame is housed in the power conversion device.

7. The power conversion device according to any one of claims 1 to 6,

the frame is also a frame of a cooler that cools the semiconductor element.

8. The power conversion device according to any one of claims 1 to 7,

the power conversion device includes at least one of an inverter that converts dc power to ac power and a converter that converts ac power to dc power.

9. The power conversion device according to any one of claims 1 to 8,

as the semiconductor element performing a switching operation, any one of an IGBT, hybrid SiC, and all SiC is used.

10. A railway vehicle is characterized in that,

a power conversion device according to any one of claims 1 to 9 is mounted thereon.

Technical Field

The present invention relates to a power converter including a three-level power conversion circuit, and is suitable as a power converter for railways.

Background

The three-level power conversion device divides a dc power supply voltage by two sets of smoothing capacitors, and can select and output three potentials of a positive potential, a negative potential, and an intermediate potential of the dc power supply voltage. Thus, the converter is used when the dc power supply voltage is high or when it is desired to reduce higher harmonics of the voltage and current supplied to the connected ac load and ac power supply.

Patent document 1 discloses a technique of providing an initial charging circuit for a smoothing capacitor provided in a power conversion device including a three-level PWM converter and a PWM inverter, and reducing the withstand voltage of a device involved in charging, thereby achieving a reduction in size and cost of the device.

Prior art documents

Patent document

Patent document 1: japanese laid-open patent publication No. 7-274529

Disclosure of Invention

Problems to be solved by the invention

As the semiconductor device constituting the main circuit is switched, a noise current flows into the frame of the power cell via a parasitic capacitance between the semiconductor device and the frame. Since the frame of the power unit is electrically connected to the power conversion device via the mounting portion, a noise current flows out to the power conversion device. Further, since the power conversion device is connected to the vehicle body via the ground circuit, the noise current flowing outside the power conversion device also flows out to the vehicle body. This noise current flows into the vehicle body, and causes a high-frequency potential variation in the vehicle body, thereby causing a problem of an obstacle to the signal equipment.

Means for solving the problems

In order to solve the above problem, a power converter according to the present invention includes a three-level power conversion circuit, and a frame on which semiconductor elements constituting the three-level power conversion circuit are mounted is electrically connected to a neutral point of the three-level power conversion circuit.

Effects of the invention

According to the present invention, the frame on which the semiconductor elements constituting the three-level power conversion circuit are mounted is electrically connected to the neutral point of the three-level power conversion circuit, and the noise current generated from the three-level power conversion circuit is pulled back to the three-level power conversion circuit, so that the noise current flowing to the outside of the power conversion device can be reduced.

Drawings

Fig. 1 is a diagram showing the overall configuration of a power conversion device according to embodiment 1 of the present invention.

Fig. 2 is a diagram illustrating connection between a part of a power conversion circuit provided in the power conversion device according to embodiment 1 and a vehicle body.

Fig. 3 is a diagram showing a semiconductor element of the power conversion device according to embodiment 1 and a frame of a power unit on which the semiconductor element is mounted.

Fig. 4 is a diagram showing an example of wiring and components of a noise absorbing core used in the power converter according to example 1.

Fig. 5 is a diagram showing connection between a part of the power conversion circuit according to embodiment 2 of the present invention and a vehicle body.

Detailed Description

Hereinafter, examples 1 and 2 according to the present invention will be described with reference to the drawings as a mode for carrying out the present invention.

Example 1

Fig. 1 is a diagram showing an example of the overall configuration of a power conversion device according to embodiment 1 of the present invention. Although fig. 1 shows a power converter mounted on a railway vehicle, the present invention is widely applicable not only to electric vehicles but also to power converters used in power electronics related fields such as industrial use.

The power conversion device 1 includes a converter power unit 2 and an inverter power unit 3 as a three-level power conversion circuit. The power conversion device 1 is mounted on, for example, an ac vehicle and used, and takes in single-phase ac power by reducing a voltage from an ac overhead line through a pantograph (pantographic) 15 and a vacuum ac contactor 14 by a main transformer 13.

The ac power taken into the power conversion device 1 is rectified by the converter power unit 2 through the electromagnetic contactor 9 or 10. The rectified dc power is taken into the inverter power unit 3, and the converted ac power is supplied to the main motor 4 to control the same.

In the power conversion device 1, the inverter power unit 3 and the converter power unit 2 are three-level circuits, and the neutral point is grounded. The neutral point is grounded via a ground resistor 11 and a ground (ground) switch 12 in fig. 1. Here, the ground switch 12 is turned on in a normal state including a driving state, and is turned off in a special state such as a withstand voltage test.

As semiconductor elements constituting the converter power unit 2 and the inverter power unit 3, a semiconductor element 5 and a clamp diode 6, which perform a switching operation as a main circuit, are mounted on a frame of the power unit. Meanwhile, the cooler for the power unit is generally mounted on a frame of the power unit as shown in fig. 3 described later, for example.

In addition, as the semiconductor elements constituting the converter power cells and the inverter power cells, IGBTs, hybrid SiC (a combination of IGBTs and SiC schottky barrier diodes), or all SiC are used as the semiconductor elements that perform switching operations as main circuits.

Further, fig. 1 shows the configuration of the power conversion device in the case of an ac vehicle that takes in single-phase ac power from an ac overhead wire, but the present invention can be applied to a power conversion device in the case of taking in dc power from a dc overhead wire, as a matter of course, and the power conversion device in this case includes an inverter power unit of a three-level circuit.

Fig. 2 is a diagram illustrating connection between a part of a power conversion circuit provided in the power conversion device according to embodiment 1 and a vehicle body.

The power conversion device 17 (a frame of a solid line shown in fig. 2) is attached to the vehicle body 16. The neutral point 27 of the three-level inverter is electrically connected to the frame 18 (frame of the broken line shown in fig. 2) of the power unit on which the semiconductor devices 19 to 22 and the clamp diodes 23 and 24 constituting one phase of the inverter are mounted. Here, as shown in fig. 3, the frame 18 of the power unit also serves as a frame of a cooler for the power unit.

Specifically, as shown in fig. 2, the neutral point 27 of the three-level inverter is connected to the vehicle body 16 (i.e., the ground) via the ground resistor 11 and the noise absorbing core 29, and the frame 18 of the power unit (and the cooler) is connected to the ground via the ground switch 12 via the noise absorbing core 29.

Here, the present invention is configured such that a frame on which semiconductor elements constituting a three-level power conversion circuit are mounted is electrically connected to a neutral point of the three-level power conversion circuit, and a noise current generated from the three-level power conversion circuit is drawn back to the three-level power conversion circuit, thereby preventing the noise current from flowing out of the power conversion device. The configuration shown in fig. 2 can be said to be a configuration in which the basic configuration according to the present invention described above is added to a conventional ground circuit (ground via a ground resistor and a ground switch). The noise-absorbing core 29 is provided to further reduce the noise current and improve the effect.

With the above configuration, the noise current flowing to the frame 18 of the power unit (and the cooler) accompanying the potential variation due to the switching operation of the semiconductor elements 19 to 22 constituting the main circuit flows to and from the noise absorbing core 29 and then flows to the neutral point 27 of the three-level inverter via the ground resistor 11, as shown by the broken line with arrows in fig. 2. This prevents the noise current from actively flowing to the power conversion device 17 and the vehicle body 16, and reduces the noise current to the vehicle body, thereby reducing communication failure to the signal device.

The noise absorbing core 29 is a ferrite core, and when a current flows through the core, magnetic energy generated by the noise current is converted into heat and consumed by the core, thereby reducing the noise current.

As described above, it is an effective method to cause the noise current flowing to the frame 18 of the power unit (and the cooler) to flow to the neutral point 27 of the three-level inverter using the noise absorbing core 29 in order to reduce the noise current. However, the noise absorbing core 29 is not an essential component, and if a configuration in which the frame 18 of the power unit (and the cooler) is connected to the neutral point 27 of the three-level inverter is adopted to the minimum, it is possible to prevent a noise current from flowing to the power conversion device 17 and the vehicle body 16.

Fig. 3 is a diagram showing semiconductor elements (semiconductor elements and clamp diodes constituting a main circuit) of the power conversion device according to example 1 and a frame of a power unit on which the semiconductor elements are mounted.

In addition to the power unit, the frame 34 of the power unit is configured such that the semiconductor element 32 is mounted on one surface side and the power unit cooler 33 is mounted on the remaining one surface side. The present invention positively prevents a noise current from flowing out to a vehicle body by connecting a frame of a power unit to a neutral point of a three-level inverter when the noise current flows to the frame of the power unit via a parasitic capacitance between a semiconductor element constituting a main circuit and the frame in accordance with a potential variation caused by a switching operation of the semiconductor element.

Fig. 4 is a diagram showing an example of wiring and components of a noise absorbing core used in the power converter according to example 1.

Fig. 4 (a) shows an example of wiring for electrically connecting the neutral point 27 of the three-level inverter shown in fig. 2 to the frame 18 of the power unit (and the cooler) having the semiconductor element mounted thereon, and wiring for the noise absorption core 29. A wiring 28 (shown by a solid line) electrically connected to a neutral point 27 of the three-level inverter and a wiring 30 (shown by a broken line) electrically connected to a frame 18 of a power unit (and a cooler) on which a semiconductor element is mounted are wound a plurality of times around a noise absorbing core 29 and directly connected to each other. That is, the connection structure except that the wiring 28 and the wiring 30 are wound around the noise-absorbing core 29 a plurality of times is the same as the connection structure shown in fig. 2.

In this way, by winding the wiring 30 electrically connected to the frame 18 and the wiring 28 electrically connected to the neutral point 27 of the three-level inverter around the noise absorbing core 29 a plurality of times with respect to the noise current flowing to the frame 18, the attenuation effect by the noise absorbing core 29 can be improved, and the noise can be further reduced.

Fig. 4 (b) is a perspective view showing an example of a member used as a noise-absorbing core.

Example 2

Fig. 5 is a diagram showing connection between a part of the power conversion circuit according to embodiment 2 of the present invention and a vehicle body. The same elements as those of the structure shown in fig. 2 are denoted by the same reference numerals.

As a difference in structure of example 1, in example 1, a core is used for reducing noise, but in example 2, a capacitor is used instead of the core. That is, as shown in fig. 2, one end of the noise absorbing capacitor 31 is connected to the neutral point 27 side of the three-level inverter, and the other end of the noise absorbing capacitor 31 is connected to the frame 18 side of the power unit (and the cooler).

With the above configuration, the noise current flowing to the frame 18 of the power unit (and the cooler) flows to the neutral point 27 of the three-level inverter via the ground resistor 11 through the noise absorbing capacitor 31 as shown by the dotted line with an arrow in fig. 5. This prevents the noise current from actively flowing to the power conversion device 17 and the vehicle body 16, and reduces the noise current to the vehicle body, thereby reducing communication failure to the signal device. That is, the same effects as in example 1 can be obtained by adopting the configuration according to example 2.

Description of the reference numerals

1. 17: power conversion device, 2: converter power unit, 3: inverter power unit, 4: main motor, 5, 19 to 22, 32: semiconductor element, 6, 23, 24: clamp diode, 7, 25, 26: filter capacitor, 8: preparatory charging resistor, 9: electromagnetic contactor for preliminary charging, 10: electromagnetic contactor, 11: grounding resistor, 12: grounding switch, 13: main transformer, 14: vacuum contactor, 15: pantograph, 16: vehicle body, 18: frame of power unit, 27: neutral point of three-level inverter, 28, 30: wiring, 29: noise-absorbing core, 31: noise absorption capacitor, 33: power unit cooler, 34: a power unit and a frame of a cooler.