JP7589108B2 - Ground circuit for vehicle power conversion device - Google Patents

Description

The present invention relates to a ground circuit for a vehicle power conversion device.

Track circuits are often used as signal safety devices in railway signaling systems to detect the presence of vehicles on the tracks by signal current circulating in a closed circuit consisting of a pair of rails and the wheelsets of the railway vehicle.

In the ATC (Automatic Train Control) used in Shinkansen trains, information such as signal aspects is added to the signal current and transmitted to the vehicle for use in operation control, etc. In electric railways, a pair of rails serves as the return path for the train current, so the signal protection device mentioned above needs to distinguish between the signal current and the train current (also called "return current"). For this reason, the signal protection device includes a special transformer device called an impedance bond, which functions to receive only the signal current that returns within the closed circuit mentioned above and not receive the train current that flows in balance on the pair of rails.

However, if an imbalance in the train current occurs on the rails (i.e., "a difference occurs in the amount (magnitude) of the train current flowing through a pair of rails"), it becomes impossible to distinguish between the train current and the signal current. This can lead to "track circuit malfunctions" and "equipment failures caused by receiving a large amount of train current." Furthermore, since the ATC power receiving unit on the vehicle is also configured to be able to distinguish between the signal current and the train current, the imbalance in the train current can appear as communication noise and potentially induce communication problems.

To prevent such train current imbalances from occurring (i.e., to prevent unbalanced currents (the difference in train currents flowing through a pair of rails when an imbalance in train currents occurs)), the following has been done in conventional technology:

In other words, in the grounding circuit of a railway vehicle, when the electric train current path branches toward each grounding device inside the vehicle, the electric wires from the branching point to each grounding device are designed to be equal in length and laid so that the resistance values of each electric train current path from the branching point to each grounding device are all equal.

Furthermore, to reduce the effects of communication noise, for example, Patent Document 1 discloses the following conventional technology. That is, Patent Document 1 discloses, as conventional technology, a configuration example in which the grounding wire for train current is connected to both sides of the grounding device provided at both ends of the axle. This configuration example cancels out the magnetic field of the train current flowing into the ATC receiver located near the ground circuit, reducing the effect of communication noise on the ATC receiver.

More specifically, Patent Document 1 discloses a configuration example in which "terminal blocks 110 housing grounding brushes for grounding the grounding wire 60 are disposed on both sides or in the center of the axle 72." Patent Document 1 describes that this configuration example makes it possible to equalize the effects of high-frequency noise on the ATC receivers 31, 32, thereby canceling the effects of high-frequency noise on the ATC receivers 31, 32.

JP 2007-68309 A

However, conventional technology only considers the resistance value of the ideal electric wire in the electric train current path. Conventional technology does not consider differences in resistance values due to "errors in the electric wire manufacturing process," "contact condition of the electric wire terminal," "individual differences in grounding devices," "deterioration level," and "rust on the rail surface," as well as fluctuations in contact resistance values due to "vibrations during running" and "differences in wheel load."

Generally, electric train currents are large, at several hundred amperes or more, and therefore even a slight difference in resistance between each electric train current path tends to result in a large unbalanced current, which may affect the track circuits and ATC.

The present invention has been made to address the above-mentioned problems. That is, one of the objects of the present invention is to provide a ground circuit for a vehicle power conversion device that can suppress the imbalance of the train current flowing through a pair of rails.

In order to solve the above problem, the ground circuit of the vehicle power conversion device of the present invention includes a first grounding device for flowing a train current output from a vehicle power conversion device applied to a vehicle including a bogie including an axle, a first wheel provided at one end of the axle, and a second wheel provided at the other end of the axle, via the first wheel and the axle to a first rail that is one of a pair of rails on which the vehicle runs, a second grounding device for flowing the train current via the second wheel and the axle to a second rail that is the other of the pair of rails, and a second grounding device for connecting the output of the vehicle power conversion device to each of the first grounding device and the second grounding device. A grounding wire provided downstream of the output of the power conversion device, the grounding wire being directly connected to the output of the vehicle power conversion device or connected to another conductor other than the grounding wire connected to the output, a first branching wire branching from the pre-branching wire toward the first grounding device and having one end connected to the first grounding device, and a second branching wire branching from the pre-branching wire toward the second grounding device and having one end connected to the second grounding device, the grounding wire including a first coil winding portion in which a portion of the first branching wire is wound in a coil shape and a second coil winding portion in which a portion of the second branching wire is wound in a coil shape.

The ground circuit of the vehicle power conversion device of the present invention is a first grounding device for passing a train current output from a vehicle power conversion device applied to a vehicle including a bogie including an axle, a first wheel provided at one end of the axle, and a second wheel provided at the other end of the axle, via the first wheel and the axle to a first rail that is one of a pair of rails on which the vehicle runs, a second grounding device for passing the train current via the second wheel and the axle to a second rail that is the other of the pair of rails, and a grounding wire provided downstream of the output of the vehicle power conversion device to connect between the output of the vehicle power conversion device and each of the first grounding device and the second grounding device. , the grounding electric wire includes a pre-branch electric wire that is directly connected to the output of the vehicle power conversion device or is connected to another conductor other than the grounding electric wire connected to the output, a first branch electric wire that branches from the pre-branch electric wire toward the first grounding device and has one end connected to the first grounding device, and a second branch electric wire that branches from the pre-branch electric wire toward the second grounding device and has one end connected to the second grounding device, and the grounding electric wire includes at least one of a pre-branch coil winding section in which a portion of the pre-branch electric wire is wound in a coil shape, a first coil winding section in which a portion of the first branch electric wire is wound in a coil shape, and a second coil winding section in which a portion of the second branch electric wire is wound in a coil shape.

The ground circuit of the vehicle power conversion device of the present invention includes a first wheel set including a first axle, a first wheel provided at one end of the first axle, and a second wheel provided at the other end of the first axle, a second axle, a third wheel provided at one end of the second axle, and a fourth wheel provided at the other end of the second axle, and a bogie including a second wheel set adjacent to the first wheel set in the rail direction. The ground circuit of the vehicle power conversion device of the present invention includes a first grounding device for passing a train current output from a vehicle power conversion device applied to a vehicle including a bogie including a second wheel set adjacent to the first wheel set in the rail direction, via the first wheel and the first axle, to a first rail that is one of a pair of rails on which the vehicle runs, and a second grounding device for passing the train current via the fourth wheel and the second axle to a second rail that is the other of the pair of rails, and a grounding circuit for connecting the output of the vehicle power conversion device and the first grounding device and the second grounding device. and a grounding wire provided downstream of the output of the vehicle power conversion device to connect between each of the power converters. The grounding wire includes a pre-branching wire that is directly connected to the output of the vehicle power conversion device or is connected to another conductor other than the grounding wire connected to the output, a first branching wire that branches from the pre-branching wire toward the first grounding device and has one end connected to the first grounding device, and a second branching wire that branches from the pre-branching wire toward the second grounding device and has one end connected to the second grounding device. The grounding wire includes at least one of a pre-branching coil winding section in which a portion of the pre-branching wire is wound in a coil shape, a first coil winding section in which a portion of the first branching wire is wound in a coil shape, and a second coil winding section in which a portion of the second branching wire is wound in a coil shape.

The present invention makes it possible to suppress imbalances in train currents flowing through a pair of rails.

FIG. 1A is a schematic diagram showing paths of train currents and signal currents in an electric railway in which railway signaling devices are installed. FIG. 1B is a schematic diagram showing paths of train currents and signal currents in an electric railway in which railway signaling devices are installed. FIG. 2A is a schematic diagram showing paths of train currents and signal currents when an imbalance in train currents occurs on the rails in an electric railway equipped with railway signaling devices. FIG. 2B is a schematic diagram showing paths of train currents and signal currents when an imbalance in train currents occurs on the rails in an electric railway equipped with railway signaling devices. FIG. 3 is a schematic diagram showing an example of the configuration of the ground circuit (first ground circuit) of the vehicle power conversion device according to the first embodiment of the present invention. FIG. 4 is a diagram showing a modification of the first ground circuit. FIG. 5 is a diagram of an equivalent circuit analysis model for verifying the noise reduction effect of the first ground circuit. FIG. 6A is a graph showing the results of an equivalent circuit analysis aimed at verifying the noise reduction effect of the first ground circuit. FIG. 6B is a graph showing the results of an equivalent circuit analysis aimed at verifying the noise reduction effect of the first ground circuit. FIG. 7 is a schematic diagram showing an example of the configuration of a ground circuit (second ground circuit) of a vehicle power conversion device according to a second embodiment of the present invention. FIG. 8 is a schematic diagram showing an example of the configuration of a ground circuit (third ground circuit) of a vehicle power conversion device according to a third embodiment of the present invention. FIG. 9 is a schematic diagram showing an example of the configuration of a ground circuit (fourth ground circuit) of a vehicle power conversion device according to a fourth embodiment of the present invention. FIG. 10 is a schematic diagram showing an example of the configuration of a ground circuit (fifth ground circuit) of a vehicle power conversion device according to a fifth embodiment of the present invention.

<<Technical Background and Problems of the Invention>>
First, in order to facilitate understanding of the present invention, the technical background and problems of the present invention will be described in detail. Figures 1A and 1B are schematic diagrams showing paths of electric train currents and signal currents in an electric railway. Figure 1A is a schematic diagram showing paths of electric train currents and signal currents in an electric railway equipped with track circuits. Figure 1B is a schematic diagram showing paths of electric train currents and signal currents in an electric railway equipped with ATC.

The vehicle TR1 shown in Figures 1A and 1B is one of multiple vehicles that a train (electric train) has. In Figures 1A and 1B, only the main components of vehicle TR1 are shown for the train (the same applies to Figures 2A and 2B). Note that two adjacent axles ("a set of an axle 106 and wheels 105 provided on both ends of the axle") represent one bogie.

The main converter 100 of vehicle TR1 obtains power from the overhead line 200 through the pantograph 201 and high-voltage wire 202, and generates three-phase AC power to rotate and drive an electric motor (not shown). At this time, the current flowing through the pantograph 201 and high-voltage wire 202 is the train current. The train current flows through a pair of rails 107 and returns to the substation, which is the power source. For this reason, a ground circuit is configured starting from the main converter 100 to flow the train current to the rail 107.

The ground circuit includes a plurality of ground devices 104 (e.g., ground brushes, etc.) provided within the vehicle TR1, a ground wire DL1 that connects between the output of the main converter 100 and the ground devices 104, wheels 105, and axles 106 that are electrically connected to the wheels 105 and electrically connected to the ground devices 104.

The grounding wire DL1 includes a pre-branch wire 101 connected to the output of the main converter 100, and multiple branch wires 102 branching from the pre-branch wire 101 toward each grounding device 104. In addition, in Figures 1A and 1B, the pre-branch wire 101 is composed of a wire between the output of the main converter 100 and the branch point SP0 and a wire after branching at the branch point SP0. In other words, in this specification, the pre-branch wire 101 refers to the wire before it branches from the pre-branch wire 101 to two branch wires 102 toward the two grounding devices 104. Therefore, as shown in Figures 1A and 1B, the pre-branch wire 101 may be branched within itself.

The electric train current output from the main converter 100 flows through the pre-branch electric wire 101, the branch electric wire 102, the grounding device 104, the axle 106 and the wheels 105 to a pair of rails 107.

The track circuit shown in Figure 1A detects the presence or absence of a train in a specific track circuit section by passing a signal current through a closed circuit consisting of a pair of rails 107 and the wheels 105 and axles 106 of the electric railway (vehicle TR1). However, as mentioned above, the train current flows on the rails 107 and returns to the substation, so the track circuit must be able to distinguish between this train current and the signal current.

The function of distinguishing between train current and signal current is realized by impedance bonds 203 installed at both ends of a specified track circuit section. Impedance bonds 203 transmit only the current flowing in one direction through the coil included in impedance bond 203 to the track presence detection device 204 side, which includes a coil that is magnetically coupled to the coil.

The track presence detection device 204 includes a track presence detection relay 204a in its circuit. The track presence detection device 204 fires the track presence detection relay 204a when it detects a signal current transmitted from the other end of a specified track circuit section. In contrast, the track presence detection device 204 drops the track presence detection relay 204a when the track circuit is short-circuited by the wheels 105 and axles 106 of the train (vehicle TR1) and the signal current does not reach the track presence detection device 204. When the track presence detection relay 204a is in a dropped state, it is determined that a train is on the track.

On the other hand, the train current flows along a path that propagates from the midpoint MP1 of the coil in the impedance bond 203 to the adjacent track circuit side. Ideally, train current flows in equal amounts and in opposite directions on each of the pair of rails 107, so the magnetic flux due to the train current is cancelled out in the coil in the impedance bond 203 and is not transmitted to the track presence detection device 204.

In an electric railway equipped with the ATC device shown in FIG. 1B, a pair of power receivers 205 that detect the signal current on the rails 107 and an ATC power receiving unit 206 that demodulates the received signal current are arranged on the vehicle TR1. The pair of power receivers 205 are differentially connected and input to the ATC power receiving unit 206, so that the receiving voltage of the signal current flowing in the opposite direction is amplified by superposition, and the receiving voltage of the train current flowing in the same direction is offset and input to the ATC power receiving unit 206.

Figures 2A and 2B are schematic diagrams showing the paths of train currents and signal currents when a difference occurs in the amount of train current on a pair of rails 107. Note that Figure 2A shows the paths of train currents and signal currents in a track circuit, and Figure 2B shows the paths of train currents and signal currents in ATC.

As shown in FIG. 2A, in an electric railway equipped with track circuits, when the train current on the rail 107 at the front side of the drawing increases, a difference occurs in the amount of train current flowing above and below the midpoint MP1 in the coil in the impedance bond 203. As a result, the magnetic flux due to the train current is not canceled out by the coil in the impedance bond 203, and the difference is transmitted to the track presence detection device 204. Since train currents are generally very large, at several hundred amperes or more, a bias in the train currents on the rail 107 (unbalanced train currents) can cause saturation of the impedance bond 203 and malfunction of the track presence detection device 204.

As shown in FIG. 2B, in the ATC as well, when a train current imbalance (unbalanced train current) occurs on the rail 107, the receiving voltage of the train current cannot be offset even by the differential connection of each receiver 205 (even if the train current is leveled to some extent by the wheelsets in front of the ATC power receiving unit 206, the receiving voltage of the train current cannot be offset even by the differential connection of each receiver 205). For this reason, even in the ATC, the train current imbalance (unbalanced train current) on the rail 107 may appear as communication noise and induce communication failures, etc. The present invention has been made to solve these problems described above.

Each embodiment of the present invention will be described in detail below with reference to the drawings. Note that in each embodiment, the form of a ground circuit of a vehicle power conversion device having a specific configuration will be described, but the present invention is not limited to each embodiment. The configuration of the ground circuit of each embodiment may be appropriately changed within the scope of the present invention depending on the configuration and arrangement of the devices and electric wires mounted on the vehicle. Vehicles to which the ground circuit of each embodiment is applied are not limited to vehicles that run on power obtained from an overhead line or a third rail. The ground circuit of each embodiment may be applied to any vehicle that uses a pair of rails as a return path for the train current.

<<First embodiment>>
A ground circuit of a vehicle power conversion device according to a first embodiment of the present invention (hereinafter, may be referred to as a "first ground circuit") will be described.

<Configuration>
Fig. 3 is a schematic diagram showing an example of the configuration of a railway signaling system to which the first ground circuit is applied. Note that the vehicle TR2 shown in Fig. 3 is one of a plurality of vehicles equipped in a train (electric train). Fig. 3 shows only the main components of the vehicle TR2 with respect to the train.

As described above, the main converter 100 obtains power from the overhead line 200 through the pantograph 201 and the high-voltage wire 202, and generates three-phase AC power to drive an electric motor (not shown). At this time, the electric train current flowing through the pantograph 201 and the high-voltage wire 202 flows to the rail 107 through the first ground circuit.

The first grounding circuit includes a grounding wire DL1, a first grounding device 104a, a second grounding device 104b, an axle 106 electrically connected to the first grounding device 104a and the second grounding device 104b, and two wheels 105 electrically connected to the axle 106.

The grounding wire DL1 is a grounding wire for passing the train current obtained from the overhead line 200 to a pair of rails 107. The grounding wire DL1 includes a pre-branch wire 101 connected to the output of the main converter 100, and a first branch wire 102a and a second branch wire 102b branching from the pre-branch wire 101.

The first branch electric wire 102a branches from the pre-branch electric wire 101 toward the first grounding device 104a at the branch point SP1, and one end of the first branch electric wire 102a is connected to the first grounding device 104a. The second branch electric wire 102b branches from the pre-branch electric wire 101 toward the second grounding device 104b at the branch point SP1, and one end of the second branch electric wire 102b is connected to the second grounding device 104b.

The first branch electric wire 102a includes a first coil winding portion 102a1, a part of which is wound in a coil shape. The second branch electric wire 102b includes a second coil winding portion 102b1, a part of which is wound in a coil shape.

The first coil winding section 102a1 and the second coil winding section 102b1 are a single coil winding formed integrally, and the branch point SP1 is located at the midpoint of this single coil winding. That is, the axial length of the first coil winding section 102a1 (the length from the branch point SP1 to one end of the first coil winding section 102a1 opposite the branch point SP1) is equal to the axial length of the second coil winding section 102b1 (the length from the branch point SP1 to one end of the second coil winding section 102b1 opposite the branch point SP1). Therefore, the number of turns of the first coil winding section 102a1 is equal to the number of turns of the second coil winding section 102b1.

Furthermore, the coil winding direction of the first coil winding portion 102a1 and the coil winding direction of the second coil winding portion 102b1 are the same direction. Furthermore, the first coil winding portion 102a1 and the second coil winding portion 102b1 are magnetically coupled. It can be said that the first coil winding portion 102a1 and the second coil winding portion 102b1 constitute an autotransformer.

Therefore, the mutual induction effect between the first coil winding portion 102a1 and the second coil winding portion 102b1 has the effect of leveling out the electric train current flowing through the first coil winding portion 102a1 and the second coil winding portion 102b1. In other words, the mutual induction effect between the first coil winding portion 102a1 and the second coil winding portion 102b1 has the effect of causing the same amount of current to flow through the first coil winding portion 102a1 and the second coil winding portion 102b1. Hereinafter, for convenience of explanation, this effect may also be referred to as the "autotransformer effect" in this specification.

The branch point SP1 does not have to be located at the midpoint of one coil winding. In this case, for example, the branch point SP1 may be located within a central range between "a first position a predetermined distance away to the left of the midpoint of one coil winding" and "a second position a predetermined distance away to the right of the midpoint of one coil winding" in the axial direction of one coil winding. This predetermined distance is, for example, 5% of the axial length of one coil winding. On the other hand, in order to obtain a greater autotransformer effect, it is preferable that the branch point SP1 is located at the midpoint of one coil winding.

Even if the branch point SP1 is not located at the midpoint of one coil winding, in order to obtain the autotransformer effect, it is preferable that the number of turns of the first coil winding portion 102a1 is equal to the number of turns of the second coil winding portion 102b1.

The length of the first branch electric wire 102a (length from branch point SP1 to first grounding device 104a) and the length of the second branch electric wire 102b (length from branch point SP1 to second grounding device 104b) may be the same or different. From the viewpoint of further reducing the difference between the impedance of the current path from branch point SP1 to first grounding device 104a and the impedance of the current path from branch point SP1 to second grounding device 104b, it is more preferable that the lengths of the first branch electric wire 102a and the second branch electric wire 102b are the same.

Furthermore, as shown in FIG. 4, the first coil winding portion 102a1 and the second coil winding portion 102b1 do not have to be a single coil winding formed integrally. That is, the first coil winding portion 102a1 may be wound starting from a position on the first branch electric wire 102a that is a predetermined first distance away from the branch point SP1. The second coil winding portion 102b1 may be wound starting from a position on the second branch electric wire 102b that is a predetermined second distance away from the branch point SP1. In this case, from the viewpoint of obtaining an autotransformer effect, it is preferable that the first coil winding portion 102a1 and the second coil winding portion 102b1 are magnetically coupled.

Furthermore, as will be described in detail later, it is preferable that the resistance value of the axle 106 is larger in order to obtain a larger autotransformer effect and thereby reduce unbalanced current. Therefore, it is particularly preferable that the axle 106 is an insulating axle having insulating properties.

＜Effects＞
As described above, in the first grounding circuit, the grounding wire DL1 includes the first coil winding portion 102a1 and the second coil winding portion 102b1. This allows the first grounding circuit to increase the impedance to high-frequency current in the current paths between the output of the main converter 100 and the first grounding device 104a and the second grounding device 104b. This allows the first grounding circuit to increase the impedance to high-frequency current in the current path between the output of the main converter 100 and the grounding device, relative to the impedance fluctuation (and the difference in impedance to high-frequency current (impedance difference caused by the impedance fluctuation occurring in each path)) caused by various factors between the train current path from the branch point SP1 through the first grounding device 104a to the rail 107 and the train current path from the branch point SP1 through the second grounding device 104b to the rail 107. Therefore, the first grounding circuit can suppress the imbalance of the train current. In order to obtain such an effect, it is sufficient that the grounding wire DL1 includes a coil winding portion in which a portion of the grounding wire DL1 is wound in a coil shape. In the following, for convenience of explanation, the train current path in which the train current passes from the branch point SP1 through the first grounding device 104a to the rail 107 may also be referred to as the "first train current path." The train current path in which the train current passes from the branch point SP1 through the second grounding device 104b to the rail 107 may also be referred to as the "second train current path.").

Furthermore, the first ground circuit can obtain the effect of trying to pass the same current through the first electric train current path and the second electric train current path due to the autotransformer effect, so the first ground circuit can further suppress the imbalance in the electric train currents (further reduce the unbalanced currents).

These effects are described in more detail below. In a typical vehicle configuration, in order to equalize the amount of train current flowing from the vehicle onto the pair of rails 107, electric wires are laid that are designed to have equal lengths to each grounding device 104 so that the resistance values of the train current paths branching out toward each grounding device 104 inside the vehicle are all equal.

However, in this case, only the resistance values of the ideal electric wires that make up the electric train current paths will be equal. Therefore, the following may occur. That is, in the electric train current paths, impedance fluctuation factors such as "errors in wire manufacturing," "contact condition of the electric wire terminals," "individual differences and deterioration of the grounding devices," "differences in resistance values due to rust on the rail surface," and "fluctuations in contact resistance values due to vibrations and/or wheel load differences during running" may occur. In this case, impedance fluctuations may occur in each electric train current path (impedance fluctuations may occur, and the amount of fluctuation may differ). Therefore, in this case, impedance differences may occur between each electric train current path. This may cause an imbalance in the electric train current.

In order to reduce the influence of the above-mentioned impedance fluctuation factors in the ground circuit, the first ground circuit includes a first coil winding portion 102a1 and a second coil winding portion 102b1 in the ground wire DL1. This allows a sufficiently large inductance (large impedance for relatively large high-frequency currents (signals)) to be added to the portion of the ground wire DL1 where the first coil winding portion 102a1 and the second coil winding portion 102b1 are formed, compared to the impedance of the ground circuit. Therefore, in each electric train current path of the ground circuit, the impedance fluctuation (and the resulting impedance difference between each electric train current path) can be reduced relative to the impedance of the ground circuit, so that the imbalance of the electric train current can be suppressed (the unbalanced current can be reduced).

The inductance values of the first coil winding section 102a1 and the second coil winding section 102b1 (one coil winding) are preferably set based on the target frequency and the impedance of the ground circuit. For example, when the target frequency is 50 Hz, which is one of the track circuit signal frequencies, the impedance of the ground circuit usually fluctuates at a level lower than 0.1 mΩ, so if the inductance of one coil winding is set to 0.5 mH or more, an impedance of 5 times or more can be obtained. In other words, depending on the value of the ratio of the inductance to the impedance fluctuation level of the ground circuit corresponding to the target signal current frequency (= "inductance" / "impedance fluctuation level") (the larger the ratio value), a greater effect of reducing the unbalanced current (the effect of suppressing the unbalanced train current) can be obtained.

Furthermore, the first ground circuit includes the first coil winding section 102a1 and the second coil winding section 102b1 as a single integrated coil winding on the ground electric wire DL1. In this way, by configuring the first coil winding section 102a1 and the second coil winding section 102b1 as an autotransformer in which the coil winding directions of both are the same and are magnetically coupled, the first ground circuit can obtain the following effect. That is, the first ground circuit can obtain the effect of leveling the currents flowing through the first coil winding section 102a1 and the second coil winding section 102b1 by the mutual induction effect (autotransformer effect). Therefore, the first ground circuit can further reduce the unbalanced current. As a result, the first ground circuit can prevent malfunctions and failures of the track circuit and communication failures of the ATC.

<Test Example>
In order to confirm the effect of the first ground circuit described above, an equivalent circuit analysis was carried out based on the configuration shown in FIG.

Example 1-1: A constant current source S1 was provided upstream of the pre-branch electric wire 101, and at the branch sections SA1 and SA2 indicated by dotted lines in FIG. 5, an autotransformer was installed in which the first coil winding section 102a1 and the second coil winding section 102b1 were each configured with a 1 mH coil winding, as shown in FIG. 3. The axle 106 was configured as a low resistance axle.

Example 1-2: Example 1-2 was a first ground circuit with the same configuration as Example 1-1, except that the axle 106 was an insulated axle (open).

Comparative Example 1: Comparative Example 1 was a ground circuit with the same configuration as Example 1-1, except that no autotransformers consisting of 1 mH coil windings were installed at the branches SA1 and SA2 in the dotted lines in Figure 5.

The following evaluations were performed for Example 1-1, Comparative Example 1-2, and Comparative Example 1.

The earthing device resistance value and the wheel-rail contact resistance value were randomly assigned within the range of 0% to 50% of 100 mΩ in the circuit, and the impact on the track circuit on-track detection device was evaluated using ammeter 300a (Figure 6A), and the impact on ATC was evaluated using the difference between ammeters 300b and 300c (Figure 6B). The evaluation results are shown in Figures 6A and 6B.

As shown in Figure 6A, by adding an autotransformer to the ground wire branch, even for a normal low resistance axle (Example 1-1), a reduction effect of 1 to 3 dB was obtained compared to the conventional configuration (Comparative Example 1) in the track circuit frequency band of 20 to approximately 1 kHz. As shown in Figure 6B, a reduction effect of 40 dB was obtained compared to the conventional configuration in the 20 kHz band, which is the ATC frequency band.

Furthermore, as shown in Figure 6A, when an insulated axle was used (Example 1-2), an unbalanced current suppression effect of 20 to 40 dB or more was obtained in the track circuit frequency band.

As shown in Figure 6B, when an insulated axle was used (Example 1-2), an unbalanced current suppression effect of 80 dB was achieved in the ATC frequency band.

The reason for the difference in reduction effect (unbalanced current suppression effect) between Example 1-1 and Example 1-2 is thought to be as follows. That is, when the resistance value of the axle 106 connected via the branch electric wire 102 by the autotransformer is smaller than the contact resistance value between the wheel 105 and the rail 107, both parallel output ports of the autotransformer are close to a short-circuit connection (that is, the first coil winding portion 102a1 and the second coil winding portion 102b1 only function as inductors). For this reason, it is thought that the reason is that in Example 1-1, the effect of making the impedance fluctuation appear relatively small and the mutual induction effect of the autotransformer (autotransformer effect) are reduced compared to Example 1-2.

For this reason, the higher the resistance value of the axle that constitutes the ground circuit for the train current, the more desirable it is. On the other hand, even with a typical low-resistance axle such as that of Example 1-1, a sufficient noise reduction effect can be obtained for the ATC (see comparison between Example 1-1 and Comparative Example 1 in Figure 6B), and a certain level of noise reduction effect can also be obtained for the track circuit (see comparison between Example 1-1 and Comparative Example 1 in Figure 6A).

Furthermore, due to the mutual induction effect of the autotransformer, the difference in train current flowing through the pair of grounding devices (first grounding device 104a and second grounding device 104b) that make up the first grounding circuit is kept below 0.5 dB even in the above equivalent circuit analysis. Therefore, the first grounding circuit can suppress the variation in deterioration of the grounding devices, and achieve effective maintenance.

In addition, even if the coil winding is in the order of mH to obtain a low-frequency reduction effect (unbalanced current reduction effect), the inductance seen from the main motor side can be made to appear extremely low due to the magnetic flux cancellation effect of the branched current flowing in the opposite direction inside the autotransformer, so it can function as a low-impedance ground circuit. Furthermore, the presence of a large inductance (first coil winding portion 102a1 and second coil winding portion 102b1) that constitutes the autotransformer at the branch makes it possible to suppress the absorption of train currents from other vehicles flowing on the rail 107.

<<Second embodiment>>
A ground circuit (hereinafter referred to as a "second ground circuit") of a vehicle power conversion device according to a second embodiment of the present invention will be described. Fig. 7 is a schematic diagram showing an example of the configuration of a railway signaling system to which the second ground circuit is applied. Note that vehicle TR3 shown in Fig. 7 is one of a plurality of vehicles included in a train (electric train). Fig. 7 shows only the main configuration of vehicle TR3 with respect to the train.

The vehicle TR3 includes a three-phase electric wire 108 that transmits the three-phase AC power generated by the main converter 100, an electric motor 109 that is driven to rotate by the three-phase AC power, and a gearbox 110 that transmits the rotational power of the electric motor 109 to the axle 106. One end of the pre-branch electric wire 101 opposite the branch point SP1 is connected to the frame of the electric motor 109. Other than the above configuration, it is the same as the first ground circuit.

＜Effects＞
The second grounding circuit has the same effect as the first grounding circuit, and the second grounding circuit can reduce the unbalanced current regardless of the presence or absence of a return line that starts from the frame of the motor 109 and returns to the main converter 100.

When the second ground circuit is applied to a vehicle TR3 that does not have the return line, the unbalanced current reduction effect is more effective than when the second ground circuit is applied to a vehicle TR3 that does have the return line. The reason for this is explained below.

In other words, in conventional configurations, especially in vehicles that do not have the return line, the motor frame is often connected to only one grounding device on the axle to prevent floating voltages and other issues from occurring and to prevent noise currents from flowing through unintended paths such as the gearbox.

However, in the past, little consideration was given to the unbalanced current that flows onto the rails and returns to the main converter. Because the switching noise current generated by the main converter has a wide range of frequency components, the unbalanced current of this noise on the rails is highly likely to affect various signaling devices.

In contrast, the second grounding circuit is configured to pull out the pre-branch electric wire 101 starting from the frame of the electric motor 109, and connect the first branch electric wire 102a and the second branch electric wire 102b after branching via an autotransformer (first coil winding section 102a1 and second coil winding section 102b1) to the first grounding device 104a and the second grounding device 104b on both sides of the axle 106, respectively.

With this configuration, even if impedance fluctuations occur in each electric train current path (in both the first electric train current path and the second electric train current path), the mutual induction effect makes it possible to distribute and level the noise currents in a wide frequency range that appear on the frame of the motor 109 to the first electric train current path and the second electric train current path. Therefore, the second ground circuit can reduce the unbalanced current that flows onto the rail 107.

Therefore, when the second ground circuit is applied to a vehicle TR3 that does not have the return line, the effect of reducing the unbalanced current is more effective (is more effective) than when the second ground circuit is applied to a vehicle TR3 that has the return line.

<<Third embodiment>>
A ground circuit of a vehicle power conversion device according to a third embodiment of the present invention (hereinafter referred to as a "third ground circuit") will be described. Fig. 8 is a schematic diagram showing an example of the configuration of a railway signaling system to which the third ground circuit is applied. Note that vehicle TR4 shown in Fig. 8 is one of a plurality of vehicles provided in a train (electric train). Fig. 8 shows only the main configuration of vehicle TR4 with respect to the train.

The third ground circuit is provided with a resistor axle 111 that has a resistance between both ends of the axle of 100 mΩ or more as the axle that constitutes the third ground circuit. Apart from the above, it is similar to the first ground circuit. Therefore, the following explanation will focus on this difference.

As mentioned above, the above test example shows that the higher the resistance value at both ends of the axle that constitutes the first ground circuit, the greater the effect of suppressing unbalanced currents on the rails, and therefore the greater the reduction in the amount of noise transmitted to the signaling device.

In view of this, the third ground circuit includes a resistor axle 111 that, as an axle that constitutes the ground circuit, has a resistance value between both ends of the axle of 100 mΩ or more. This resistance value is based on the results of a test example that shows that if the resistance value is five or more times greater than the resistance of each grounding device and the contact resistance between the wheel and the rail, it is possible to obtain the effect of reducing a certain unbalanced current caused by an autotransformer.

For example, a variable-length axle having a movable part within the axle is used as the resistor axle 111. Alternatively, an axle made of an alloy that exhibits the above-mentioned electrical resistance value may be used as the resistor axle 111. Furthermore, an axle made of a high-resistance or insulating metal may be used as the resistor axle 111, and a grounding device 104 may be connected to the wheel 105.

＜Effects＞
Since the third grounding circuit has a resistance value between both ends of the axle that is higher than the resistance of the grounding device and the contact resistance between the wheel and the rail, it can provide a greater autotransformer effect, thereby further reducing unbalanced currents.

<<Fourth embodiment>>
A ground circuit of a vehicle power conversion device according to a fourth embodiment of the present invention (hereinafter referred to as a "fourth ground circuit") will be described. Fig. 9 is a schematic diagram showing an example of the configuration of a railway signaling system to which the fourth ground circuit is applied. Note that a vehicle TR5 shown in Fig. 9 is one of a plurality of vehicles provided in a train (electric train). Fig. 9 shows only the main configuration of vehicle TR5 with respect to the train.

The fourth ground circuit is similar to the first ground circuit, except for the points described below. As shown in FIG. 9, the vehicle TR5 includes a bogie BO1. The bogie BO1 includes a first wheel set WL1 and a second wheel set WL2 adjacent to the first wheel set WL1 in the longitudinal direction of the rail 107. The first wheel set WL1 is a set of a first axle 106a and two wheels 105a provided at both ends of the first axle 106a, and the second wheel set WL2 is a set of a second axle 106b and two wheels 105b provided at both ends of the second axle 106b.

When the rear side of the drawing is the front of the bogie BO1, the first grounding device 104a is installed at the left end of the second axle 106b, and the second grounding device 104b is installed at the right end of the first axle 106a. Therefore, the first grounding device 104a and the second grounding device 104b are located diagonally within the bogie BO1 (at the second wheel set WL2 and the first wheel set WL1).

In the fourth ground circuit, one end of the first branch electric wire 102a branching off from the pre-branch electric wire 101 is connected to the first ground device 104a. One end of the second branch electric wire 102b branching off from the pre-branch electric wire 101 is connected to the second ground device 104b diagonally opposite to the first ground device 104a. Therefore, in the fourth ground circuit, the electric current path (length of the electric wire) from the branch point SP1 to the first ground device 104a and the electric current path (length of the electric wire) from the branch point SP1 to the second ground device 104b are longer than in the first ground circuit, so that the impedance of the fourth ground circuit is larger than that of the first ground circuit.

Therefore, the fourth ground circuit can enhance the effect of relatively reducing the impedance fluctuations of the first electric train current path and the second electric train current path compared to the first ground circuit. As a result, the fourth ground circuit can further reduce the unbalanced current generated in the rail 107 compared to the first ground circuit.

＜Effects＞
As described above, the fourth ground circuit can further reduce the unbalanced current generated in the rail 107.

<<Fifth embodiment>>
A ground circuit of a vehicle power conversion device according to a fifth embodiment of the present invention (hereinafter referred to as a "fifth ground circuit") will be described. Fig. 10 is a schematic diagram showing an example of the configuration of a railway signaling system to which the fifth ground circuit is applied. Note that a vehicle TR6 shown in Fig. 10 is one of a plurality of vehicles provided in a train (electric train). Fig. 10 shows only the main configuration of vehicle TR6 with respect to the train.

As shown in FIG. 10, the fifth ground circuit is similar to the first ground circuit, except that a magnetic sensor 112 and a magnetic flux detection unit 113 are added to the first ground circuit.

The magnetic sensor 112 is, for example, a Hall element, and is installed near the midpoint (branch point SP1) of the first coil winding portion 102a1 and the second coil winding portion 102b1. The magnetic flux detection unit 113 receives information (for example, output (voltage)) generated by the magnetic sensor 112 according to the magnetic flux density, and determines (detects) the amount of magnetic flux in the first coil winding portion 102a1 and the second coil winding portion 102b1. The magnetic flux detection unit 113 determines the occurrence of an imbalance in the train current flowing out to each rail 107 based on the amount of magnetic flux in the first coil winding portion 102a1 and the second coil winding portion 102b1. That is, near the midpoint of the first coil winding section 102a1 and the second coil winding section 102b1 (autotransformer), if the magnitude of the current on each of the first coil winding section 102a1 and the second coil winding section 102b1 is equal, the magnetic flux generated by each is canceled out, and nothing is detected by the magnetic sensor 112 and the magnetic flux detection section 113 (the amount of detected magnetic flux is small). Therefore, for example, if the detected magnetic flux amount is equal to or greater than a predetermined threshold magnetic flux amount, the magnetic flux detection section 113 determines that an imbalance in the train current has occurred. In contrast, for example, if the detected magnetic flux amount is less than the predetermined threshold magnetic flux amount, the magnetic flux detection section 113 determines that an imbalance in the train current has not occurred.

＜Effects＞
The fifth ground circuit has the same effect as the first ground circuit. Furthermore, the fifth ground circuit makes it possible to detect and trace (analyze and record) the timing of occurrence of train current imbalance (abnormality) by a simple method. Therefore, the fifth ground circuit can be used for investigation and analysis when a malfunction occurs and for determining maintenance of the grounding device.

<<Modifications>>
The present invention is not limited to the above-described embodiments, and various modifications can be made within the scope of the present invention. Furthermore, the features of the above-described embodiments can be combined with each other without departing from the scope of the present invention.

For example, in each embodiment, a ferrite core may be inserted into the first coil winding portion 102a1 and the second coil winding portion 102b1 to reduce leakage magnetic flux. For example, in each embodiment, the pre-branch electric wire 101 may include a pre-branch coil winding portion, a portion of which is wound in a coil shape. For example, in each embodiment, either the first coil winding portion 102a1 or the second coil winding portion 102b1 may be omitted. For example, in each embodiment, both the first coil winding portion 102a1 and the second coil winding portion 102b1 may be omitted, and the pre-branch electric wire 101 may include a pre-branch coil winding portion.

100...Main converter, 101...Pre-branch electric wire, 102a...First branch electric wire, 102b...Second branch electric wire, 102a1...First coil winding section, 102b1...Second coil winding section, 104a...First grounding device, 104b...Second grounding device, 105...Wheels, 106...Axles, 107...Rails, 200...Overhead line, 201...Pantograph, 202...High-voltage electric wire

Claims (10)

a first grounding device for causing a train current output from a vehicle power conversion device applied to a vehicle including a bogie including an axle, a first wheel provided at one end of the axle, and a second wheel provided at the other end of the axle, to flow through the first wheel and the axle to a first rail that is one of a pair of rails on which the vehicle runs;
a second grounding device for passing the electric train current through the second wheel and the axle to a second rail which is the other of the pair of rails;
a ground wire provided downstream of the output of the vehicle power conversion device to connect the output of the vehicle power conversion device to each of the first grounding device and the second grounding device;
Including,
The ground wire is
A pre-branch electric wire that is directly connected to an output of the vehicle power conversion device or is connected to another conductor other than the ground electric wire that is connected to the output;
a first branch wire branching from the pre-branch electric wire toward the first grounding device and having one end connected to the first grounding device;
a second branch wire branching from the pre-branch electric wire toward the second grounding device and having one end connected to the second grounding device;
Including,
The ground wire is
a first coil winding portion in which a portion of the first branch electric wire is wound in a coil shape, and a second coil winding portion in which a portion of the second branch electric wire is wound in a coil shape,
A ground circuit for a vehicle power conversion device. 2. The ground circuit of the vehicle power conversion device according to claim 1,
the first coil winding portion and the second coil winding portion are magnetically coupled to each other.
A ground circuit for a vehicle power conversion device. 3. The ground circuit of the vehicle power conversion device according to claim 2,
The number of turns of the first coil winding portion is the same as the number of turns of the second coil winding portion.
A ground circuit for a vehicle power conversion device. 4. The ground circuit of the vehicle power conversion device according to claim 3,
the first coil winding portion and the second coil winding portion constitute a single integral coil winding,
a branch point at which the pre-branch electric wire branches into the first branch electric wire and the second branch electric wire is located at a midpoint in the axial direction of one of the coil windings.
A ground circuit for a vehicle power conversion device. 2. The ground circuit of the vehicle power conversion device according to claim 1,
a resistance value between both ends of the axle is larger than a resistance of the first grounding device, a contact resistance between the first wheel and the rail, a resistance of the second grounding device, and a contact resistance between the second wheel and the rail;
A ground circuit for a vehicle power conversion device. 2. The ground circuit of the vehicle power conversion device according to claim 1,
the one end of the pre-branch electric wire is directly connected to the output of the vehicle power conversion device,
A ground circuit for a vehicle power conversion device. 2. The ground circuit of the vehicle power conversion device according to claim 1,
the other conductor includes a frame of an electric motor driven by three-phase power generated by the vehicle power conversion device,
The one end of the pre-branch electric wire is connected to the frame.
A ground circuit for a vehicle power conversion device. 5. The ground circuit of the vehicle power conversion device according to claim 4,
a magnetic sensor for acquiring information for detecting an amount of magnetic flux generated in the one coil winding;
a magnetic flux detection unit that acquires the information from the magnetic sensor and determines whether or not an imbalance has occurred in the train currents flowing through the pair of rails based on the amount of magnetic flux calculated based on the information; and
Further comprising:
A ground circuit for a vehicle power conversion device. a first grounding device for causing a train current output from a vehicle power conversion device applied to a vehicle including a bogie including an axle, a first wheel provided at one end of the axle, and a second wheel provided at the other end of the axle, to flow through the first wheel and the axle to a first rail that is one of a pair of rails on which the vehicle runs;
a second grounding device for passing the electric train current through the second wheel and the axle to a second rail which is the other of the pair of rails;
a ground wire provided downstream of the output of the vehicle power conversion device to connect the output of the vehicle power conversion device to each of the first grounding device and the second grounding device;
Including,
The ground wire is
A pre-branch electric wire that is directly connected to an output of the vehicle power conversion device or is connected to another conductor other than the ground electric wire that is connected to the output;
a first branch wire branching from the pre-branch electric wire toward the first grounding device and having one end connected to the first grounding device;
a second branch wire branching from the pre-branch electric wire toward the second grounding device and having one end connected to the second grounding device;
Including,
The ground wire is
The branch electric wire includes at least one pre-branch coil winding section in which a portion of the pre-branch electric wire is wound in a coil shape, a first coil winding section in which a portion of the first branch electric wire is wound in a coil shape, and a second coil winding section in which a portion of the second branch electric wire is wound in a coil shape.
A ground circuit for a vehicle power conversion device. a first wheel set including a first axle, a first wheel provided at one end of the first axle, and a second wheel provided at the other end of the first axle, a second axle, a third wheel provided at one end of the second axle, and a fourth wheel provided at the other end of the second axle, the first grounding device configured to cause a train current output from a vehicle power conversion device applied to a vehicle including a bogie including a second wheel set adjacent to the first wheel set in a rail direction to flow via the first wheel and the first axle to a first rail that is one of a pair of rails on which the vehicle runs;
a second grounding device for causing the electric train current to flow through the fourth wheel and the second axle to a second rail which is the other of the pair of rails;
a ground wire provided downstream of the output of the vehicle power conversion device to connect the output of the vehicle power conversion device to each of the first grounding device and the second grounding device;
Including,
The ground wire is
A pre-branch electric wire that is directly connected to an output of the vehicle power conversion device or is connected to another conductor other than the ground electric wire that is connected to the output;
a first branch wire branching from the pre-branch electric wire toward the first grounding device and having one end connected to the first grounding device;
a second branch wire branching from the pre-branch electric wire toward the second grounding device and having one end connected to the second grounding device;
Including,
The ground wire is
The branch electric wire includes at least one pre-branch coil winding section in which a portion of the pre-branch electric wire is wound in a coil shape, a first coil winding section in which a portion of the first branch electric wire is wound in a coil shape, and a second coil winding section in which a portion of the second branch electric wire is wound in a coil shape.
A ground circuit for a vehicle power conversion device.

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