KR20220020708A - Wireless Power Transfer System Based on Segmented Transmitter Line - Google Patents

Abstract

Disclosed is a system for wireless power supply. In the present embodiment, provided is a wireless power supply system using a segmented transmitter line which separates and forms a wireless power supply line for the existing railway vehicle made of a wire (copper) which does not have a core of a long length to reduce winding loss of wireless power supply and maintain safety of a human body and electronic equipment from magnetic field radiation.

Description

Wireless Power Transfer System Based on Segmented Transmitter Line

The present disclosure relates to a system for wireless power feeding. More specifically, in order to reduce the copper loss of the wireless feeding and maintain the safety of the human body and electronic equipment from magnetic field radiation, the existing wireless feeding line for railway vehicles is composed of a long core without a winding (copper). It is about a wireless power feeding system using a divided feeding line formed by dividing the

The content described below merely provides background information related to the present invention and does not constitute the prior art.

AC 25 KV or DC 1.5 KV trolly voltage is supplied to drive the MW-class large-capacity propulsion system of railway vehicles using electricity and other loads in the railway vehicle, and the railway vehicle is a pantograph ('collector'). ) is generally used to obtain electrical energy. However, the power supply line-based contact power supply method has a disadvantage in that the construction and maintenance costs of the power supply system are high and the aesthetics of the future transportation system is impaired.

In order to fundamentally overcome these shortcomings, research on a wireless power transfer (WPT) system for railway vehicles capable of transmitting electric energy to railway vehicles without contact is being actively conducted. In the WPT system, by using a long-length wireless power supply line for railway vehicles (WPT line, hereinafter 'feeding line' or 'feeding line'), not only does it provide stationary charging when the railway vehicle is stopped, but also retrograde There is an advantage that dynamic charging is possible even with large power required to drive a large-capacity propulsion system. As an example of the feed line, the feed line for high-speed trains developed in 2014 has a length of about 130 m (see Non-Patent Document 1), and the feed line for light rail developed in Korea in 2019 has a length of about 200 m.

In the WPT system including the long-length feed line illustrated in FIG. 10, in the section where the railroad car is not located, it is harmful when living things such as humans and animals approach due to the generation of a strong electromagnetic field (EMF). and may cause malfunction in the case of electronic equipment. In particular, if there is a metal foreign object in the vicinity, it may cause a serious fire due to the heat of the foreign object due to magnetic induction caused by a strong magnetic field. The feed line plays a role of passing a high-frequency current, and the reactive power of the magnetic field generated in the section of the feed line where the railroad car is not located is additional winding due to the high-frequency current even though the power is not transmitted to the receiver. The downside is that it causes losses. It is possible to cope with this disadvantage by using a separate power transfer method that shortens the length of the feed line to the length of a railroad car (see Non-Patent Document 2). Since a separate device (transmitter system, hereinafter referred to as 'Tx system') is required, it is difficult to secure an installation space and the cost increases.

Therefore, there is a need for a WPT system capable of coping with the difficulty of securing an installation space and cost increase, while reducing the winding loss of the feed line and maintaining the safety of the human body and electronic equipment from magnetic field radiation.

Non-Patent Document 1: J H Kim et al (2015) Development of 1-MW inductive power transfer system for a high-speed train, IEEE Trans Ind. Electron., 62(10), pp 6242-6250. Non-Patent Document 2: Bombardier Transportation (2010) PRIMOVE Contactless and Catenary-Free Operation, EcoActive Technologies. Non-Patent Document 3: Junsoo Shin, et al, (2014) A study on train control system for the safety and intergrity of RF-CBTC manless, Proceedings of the Korean Society for Railway, Jeju, Korea, pp 980-987.

The present disclosure provides a wireless power feed line for a conventional railway vehicle consisting of a long core without a winding (copper) in order to reduce the winding loss of the wireless power supply and maintain the safety of the human body and electronic equipment from magnetic field radiation. It is a main object to provide a wireless power feeding system using a segmented transmitter line formed by dividing.

According to an embodiment of the present disclosure, including an inverter (inverter) to generate an AC current from a DC voltage, and including two switches (switch) to control the transmission of the AC current according to the position of the receiver of the railroad car Device; and the AC current received from the power feeding device using the first or second feeding line while being divided into a first feeding line and a second feeding line in the form of a coil without a core to the induced electromotive force It provides a wireless power transfer system, characterized in that it comprises a segmented transmission line (segmented transmission line) for supplying to the receiver side in a wireless method based on the wireless power.

As described above, according to this embodiment, by providing a wireless power feeding system using a divided feeding line formed by dividing the existing wireless feeding line for railway vehicles composed of windings without a long core, the winding loss of wireless feeding is reduced. It has the effect of reducing and making it possible to keep the human body and electronic equipment safe from magnetic field radiation.

1 is a block diagram of a WPT system according to an embodiment of the present disclosure.
2 is a block diagram of a power feeding device according to an embodiment of the present disclosure.
3 is an exemplary view of a divided power supply line according to an embodiment of the present disclosure.
4 is a block diagram of a receiver according to an embodiment of the present disclosure.
5 is an equivalent circuit of a WPT system according to an embodiment of the present disclosure.
6 is an FEM model for a WPT system according to an embodiment of the present disclosure.
7 is an exemplary diagram illustrating a degree of magnetic coupling according to an embodiment of the present disclosure.
8 is an exemplary diagram illustrating AC-to-AC efficiency according to an embodiment of the present disclosure.
9 is an exemplary diagram illustrating EMF characteristics according to an embodiment of the present disclosure.
10 is an exemplary diagram of a WPT system including a long-length feed line.
11 is an exemplary view of a power feeding device.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described in detail with reference to exemplary drawings. In adding reference numerals to the components of each drawing, it should be noted that the same components are given the same reference numerals as much as possible even though they are indicated on different drawings. In addition, in the description of the present embodiments, if it is determined that a detailed description of a related well-known configuration or function may obscure the gist of the present embodiments, the detailed description thereof will be omitted.

Also, in describing the components of the present embodiments, terms such as first, second, A, B, (a), (b), etc. may be used. These terms are only for distinguishing the elements from other elements, and the essence, order, or order of the elements are not limited by the terms. Throughout the specification, when a part 'includes' or 'includes' a certain element, this means that other elements may be further included, rather than excluding other elements, unless otherwise stated. . In addition, the '... Terms such as 'unit' and 'module' mean a unit that processes at least one function or operation, which may be implemented as hardware or software or a combination of hardware and software.

DETAILED DESCRIPTION The detailed description set forth below in conjunction with the appended drawings is intended to describe exemplary embodiments of the present invention and is not intended to represent the only embodiments in which the present invention may be practiced.

The present disclosure relates to an apparatus for wireless power feeding. In more detail, in order to reduce the copper loss of the wireless feeding and to maintain the safety of the human body and electronic equipment from magnetic field radiation, the existing wireless feeding line for railway vehicles consisting of a long core without a winding (copper) Provided is a wireless power feeding (WPT) system using a divided feeding line formed by division.

10 is an exemplary diagram of a WPT system including a long-length feed line. The WPT system includes all or part of a power feeder (Tx system), a feed line, and a receiver unit.

The power feeding device as illustrated in FIG. 11 generates an AC current (eg, AC 500 A) from high voltage DC (eg, DC 1.5 KV or 750 V) using an inverter and delivers it to the power supply line. In addition, the power feeding device includes an inductor L _f and a capacitor C _f . The inductor L _f and the capacitor C _f act as an LC filter to generate an AC current that is a high-frequency constant current regardless of changes in the load and the surrounding environment. carry out The power supply line provides AC current to railway vehicles in a wireless manner based on induced electromotive force. The long length of the feed line is L _1,1 , L _1,2 ,… . It may be divided into m short feed lines represented by L _1,m , and a split resonance capacitor may be included between the short feed lines. In general, the feed line is located between the ground and the lower part of the railroad car.

The receiver included in the railroad car uses an AC-DC rectifier to convert the AC current received from the power supply line into a DC voltage, and then charges the electric energy or uses it to power the railroad car. On the other hand, the components included in the WPT system are not necessarily limited thereto, and as illustrated in FIG. 10 , a grid voltage (eg, AC 25 KV) is converted into a high voltage DC using a rectifier and then a power feeding device is used. It may additionally include a substation provided to.

Railroad vehicles maintain four states during operation: stop, start, drift, and regenerative brake. The operation of a WPT system with a double, long excitation feed line is related to three states: stop, run, and brake. While stationary, static charging is performed by using a power supply device, while dynamic charging is performed using a power supply device to drive the motor of the railroad car while stationary. do. A railroad car is driven by inertia after being accelerated, and although some of the charged energy is used, the involvement of the WPT system is minimized.

Hereinafter, the WPT system according to the present embodiment will be described with reference to FIGS. 1 to 4 .

1 is a block diagram of a WPT system according to an embodiment of the present disclosure.

In this embodiment, the WPT system 100 wirelessly supplies electric energy to the railroad vehicle using a divided power supply line. The WPT system 100 includes all or part of the power feeding device 110 , the divided feeding line 120 , and the receiving unit 130 , but is not necessarily limited thereto, and a sub-station providing high voltage DC power to the power feeding device. (not shown) may be additionally included.

1 is an exemplary configuration according to the present embodiment, and various components including other components or different connections between components according to the structure and operation of the power feeding device, the structure and operation of the receiving unit, and the structure and operation of the substation implementation is possible.

2 is a block diagram of a power feeding device according to an embodiment of the present disclosure.

The power feeding device 110 converts high voltage DC into AC current and supplies it to the divided power feeding line 120 . The power supply 110 includes an inverter, an inductor L _f and a capacitor C _f , and all or part of two switches. The inverter converts high-voltage DC into high-frequency AC current, and the inductor L _f and the capacitor C _f act as an LC filter to generate an AC current that is a high-frequency constant current regardless of changes in the load and surrounding environment. The reason for generating the high-frequency AC current is that the induced electromotive force applied to the receiver 130 can be increased in proportion to the frequency. The two switches serve to control the transfer of AC current to the two divided feed lines of the split feed line 120 . Here, the switch may be a bidirectional switch or a relay through which an AC current can pass.

3 is an exemplary view of a divided power supply line according to an embodiment of the present disclosure.

For a conventional feed line having a long length as illustrated in (a) of FIG. 3, as illustrated in (b) of FIG. 3, the divided feed line 120 according to this embodiment is located in the center The AC current is provided to the railway vehicle in a wireless manner based on the induced electromotive force while being divided into a first feeding line and a second feeding line around the power feeding device 110 . The first feeding line located on the left side of the power feeding device 110 and the second feeding line located on the right side of the power feeding device 110 may be symmetrically formed as lines of the same shape and size, but are not limited thereto. In addition, by dividing into two as illustrated in (b) of FIG. 3, the difference in length between the railroad car and each power supply line can be reduced.

In order to further reduce the difference in length between the railroad car and each feed line, it may be considered to divide the feed line into three as illustrated in FIG. There are problems such as generation of EMF and increase in thickness in a crossed section. Therefore, in the present embodiment, as in the example of Figure 3 (b), the divided divided feed line 120 is used.

Meanwhile, as shown in FIGS. 1 and 2 , the characteristics of each feeding line may be expressed as inductance and capacitance added for resonance.

4 is a block diagram of a receiver according to an embodiment of the present disclosure.

The receiver 130 is included in a railroad car, and includes all or part of an AC-DC rectifier, a bidirectional DC-DC converter, a propulsion inverter, a rechargeable battery, and a motor of the railroad car. The receiver 130 converts the AC current received from the power supply line into a DC voltage using a rectifier, and then charges the electric energy to the battery side using a bidirectional converter. The receiver 130 may drive the motor of the railway vehicle using a propulsion inverter based on the output of the rectifier or the output of the bidirectional converter converted from the charged electric energy. In addition, the receiver 130 is Electric energy can be charged to the battery side by using the process in which the motor of the railway vehicle is decelerated during regenerative braking. Except for selectively receiving AC current from the first and second feeding lines constituting the divided feeding line 120, the structure and operation of the receiving unit 130 is the same as the conventional method shown in FIG. assumed to be the same.

Meanwhile, in FIG. 4 , C ₂ and L ₂ represent inductance and resonance capacitance of the receiver 130 .

1 , the railway vehicle including the receiving unit 130 is expressed as being located in the region of the first feeding line.

The power feeding device 110 supplies AC current to the section of the first feeding line by using two switches when the stopped railroad car reaches the section of the second feeding line by going backwards in the section of the first feeding line. can be stopped, and AC current supply to the section of the second feed line can be started.

For switching of this AC current supply, the position of the rolling stock during retrograde must be determined. In order to determine which zone of the first feeding line area or the second feeding line area the railway vehicle is located in, the WPT system 100 may use an infrared sensor or a camera image sensor.

In another embodiment of the present disclosure, the WPT system 100 uses a CBTC (Communication Based Train Control) and a wayside transmitter (see Non-Patent Document 3), the area of the first feed line or the second feed line. It is possible to determine in which section of the section of the road the railroad car is located.

5 is an equivalent circuit of a WPT system according to an embodiment of the present disclosure.

Hereinafter, a process of inducing power delivered to the rectifier output of the receiver 130 and AC-to-AC efficiency using an equivalent circuit as shown in FIG. 5 will be described.

First, r _1a and r ₂ added to the illustration of FIG. 5A represent the internal resistance of the first feed line and the receiver 130, respectively, and in the case of the first feed line, represent a winding loss, and a ferrite core is applied. In the case of the receiving unit 130, which includes both a core loss and a winding loss. Since the first feeding line and the receiving unit 130 are magnetically coupled, the inductance in FIG. 5A has a relationship as shown in Equation (1).

Here, L _ma is the magnetic inductance between the first feeding line (or the second feeding line) and the receiver 130, n is the turn ratio, L _l1a and L _l2 are the leakage inductance ( leakage inductance).

As described above, the inductor L _f and the capacitor C _f act as a filter to generate a constant current. The magnitude of the constant current source I _1a indicated by the Norton equivalent circuit shown in FIG. 5B may be adjusted using the inductance L _f .

In addition, when the resonance condition as shown in Equation 3 is satisfied, the magnitude of the Norton equivalent resistance Z _f becomes infinite, so that the constant current source I _1a is completely transferred to the first feeding line.

In the case of the receiver 130 shown in Figure 5b, the output voltage and output resistance of the rectifier V _L and R _L (= V _L /I _L ) is the output voltage of the bidirectional converter V _b and duty (duty) operating conditions , and when the target voltage and target power of the converter output side are determined, V _L and R _L may be determined. The rectifier may be equivalent to an auto-transformer driven in a continuous conduction mode (CCM), in which case the load resistance R _L and the load voltage V _L may be expressed as in Equation (4).

Next, using the Thevenin equivalent circuit, the diagram of FIG. 5B can be represented as the diagram of FIG. 5C. Here, capacitors C ₁ and C ₂ are applied to the first feeding line and the receiving unit 130 to compensate the inductance to cause resonance. In this case, the equivalent voltage V _2a and the current I ₂ of the receiver 130 may be expressed as in Equation 5.

Here, n is a ratio between N1 which is the number of turns of the first feeding line and N2 which is the number of turns of the receiver 130 .

Using Equations 4 and 5, the output power P _L and the AC-to-AC efficiency η _ac may be expressed as Equations 6 and 7 .

As shown in Equation 7 , in this embodiment, in order to analyze the coil-to-coil characteristics, only r _1a , which is the winding loss of the feed line, and r ₂ , which is the sum of the winding loss of the receiver and the core loss, is However, it is assumed that inverter switching loss and conduction loss, AC/DC rectifier loss and DC/DC converter loss, and loss due to parasitic resistance of the LC filter are all ignored.

Hereinafter, an experimental example for confirming the performance of the WPT system 100 according to the present embodiment will be described.

In the experimental example, in order to confirm the bar shown in Equation 7, a simulation was performed using a finite element method (FEM) model as shown in FIG. 6 . In the experimental example, the length of the existing feed line was assumed to be 9.0 m, and the length of each of the two proposed split feed lines was assumed to be 4.5 m, which is half of 9.0 m. The receiver has a size of 0.5m×1.5m, and the total thickness of the applied ferrite core is 40 T (Thickness, unit is mm), and is designed to receive 250 kW power. The number of turns N2 of the receiver is 4, and the number of turns N1 of the feed line is 2. It was assumed that the distance between the feed line and the receiver was 7 cm and the operating frequency was 60 kHz. In order to apply a high-capacity high-frequency current of 500 A class to the feeding line, the winding thickness of the feeding line is 120 sq (cross-sectional area, unit is mm ² ), and 120 sq is set in consideration of the same level of large-capacity high-frequency current in the receiver. became

The parameter analysis results according to the simulation are shown in Table 1, and for the L _f (= 358 μH) value set to supply a constant current, the C _f value that satisfies the resonance condition as shown in Equation 3 is also recorded in Table 1 did In addition, the values of the capacitors satisfying the resonance condition as shown in Equation 5 are also listed in Table 1.

Here, the subscripts 1a and 1b each indicate a first feeding line and a second feeding line with a length of 4.5 m, and the subscript 1c indicates an existing feeding line with a length of 9.0 m.

7 and 8 are exemplary views illustrating efficiency characteristics according to an embodiment of the present disclosure. In the experimental example, it was assumed that the receiver moves from the area of the first feed line (see the example of FIG. 6 ) to the area of the second feed line (see the example of FIG. 6 ) (-4.5 m < d _y < 4.5 m) .

First, the bar illustrated in FIG. 7 is a simulation result for a magnetic coupling factor. Here, k _a1 , k _b1 , and k _c1 represent the degree of magnetic coupling with respect to the 4.5 m first feed line, the 4.5 m second feed line, and the 9.0 m existing feed line, respectively. When the receiver is completely included in the feed line, the magnetic coupling of the 4.5 m feed line according to this embodiment is increased by about 42% compared to the 9.0 m feed line.

Next, a bar exemplified in FIG. 8 is a simulation result for AC-to-AC efficiency. The efficiency of the 4.5m feeding line according to this embodiment was 98.5%, which was improved by about 0.6% compared to the 97.9%, which is the efficiency of the 9.0m feeding line. In addition, the theoretical efficiency can be calculated using Equation 7 while adjusting R _L for each d _y position so that P _L = 250 kW. On the other hand, the 0.6% gain in efficiency removes the heat loss corresponding to about 1.6 kW in the winding of the 4.5m feeding line, so the improvement effect is large in terms of heat dissipation.

9 is an exemplary diagram illustrating EMF characteristics according to an embodiment of the present disclosure.

Here, the EMF characteristic represents the magnetic flux density measured at a position (d _z ) 10 cm and 100 cm away from the feed line vertically. The measurement range is 0~4.5 m in the area where no railroad cars are located. As shown in Fig. 9a, when the vertical position d _z is 10 cm, in all areas of the 9.0 m feed line, the International Radiation Protection Association (ICNIRP) guideline recommends more than 27 μT, which is the allowable standard for the human body. However, the 4.5m feed line showed EMF characteristics below the allowable standard in the region of d _y > +2.2 m. On the other hand, as shown in FIG. 9b, when the vertical position d _z is 100 cm, in the 9.0 m feed line, it was 27 μT or more in all areas, but in the 4.5 m feed line, the EMF characteristics were below the allowable standard in the d _y > +1.5 m area. showed

As described above, according to this embodiment, by providing a wireless power feeding system using a divided feeding line formed by dividing the existing wireless feeding line for railway vehicles composed of windings without a long core, the winding loss of wireless feeding is reduced. It has the effect of reducing and making it possible to keep the human body and electronic equipment safe from magnetic field radiation.

Various implementations of the systems and techniques described herein may be implemented in digital electronic circuitry, integrated circuitry, field programmable gate array (FPGA), application specific integrated circuit (ASIC), computer hardware, firmware, software, and/or combination can be realized. These various implementations may include being implemented in one or more computer programs executable on a programmable system. The programmable system includes at least one programmable processor (which may be a special purpose processor) coupled to receive data and instructions from, and transmit data and instructions to, a storage system, at least one input device, and at least one output device. or may be a general-purpose processor). Computer programs (also known as programs, software, software applications or code) contain instructions for a programmable processor and are stored on a "computer-readable recording medium".

The above description is merely illustrative of the technical idea of this embodiment, and a person skilled in the art to which this embodiment belongs may make various modifications and variations without departing from the essential characteristics of the present embodiment. Accordingly, the present embodiments are intended to explain rather than limit the technical spirit of the present embodiment, and the scope of the technical spirit of the present embodiment is not limited by these embodiments. The protection scope of this embodiment should be interpreted by the following claims, and all technical ideas within the scope equivalent thereto should be interpreted as being included in the scope of the present embodiment.

100: WPT system 110: feeding device
120: split feed line 130: receiver

Claims (6)

a power feeding device that generates AC current from DC voltage including an inverter and controls transmission of the AC current according to a position of a receiving unit of the railroad car including two switches; and
Based on the induced electromotive force, the AC current received from the power feeding device using the first or second feed line is divided into a first feed line and a second feed line in the form of a coil without a core. A segmented transmission line that supplies the receiver side in a wireless way
A wireless power transfer system comprising a. According to claim 1,
The power feeding device is located in the center of the divided feeding line, and the first feeding line and the second feeding line of the divided feeding line located on both sides of the feeding device are formed as lines having the same shape and size as each other. wireless feeding system. According to claim 1,
The power supply device,
When the railway vehicle reaches the section of the second feed line after going backward from the section of the first feed line, using the two switches, the supply of AC current to the first feed line is stopped, and the second feed line is stopped. 2 Wireless power feeding system, characterized in that starting the AC current supply to the feed line. According to claim 1,
The two switches are
A wireless power feeding system, characterized in that it is a bidirectional switch or relay through which the AC current can pass. According to claim 1,
Wireless power feeding system, characterized in that by using an infrared sensor or a camera image sensor, it is characterized in that the railway vehicle is located in either a section of a first feed line or a section of a second feed line of the divided feed line. According to claim 1,
It is characterized in that by using CBTC (Communication Based Train Control) and a wayside transmitter, it is characterized in that the railway vehicle is located in which zone of the first feeding line or the second feeding line of the divided feeding line. A wireless power supply system with

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