KR20240123861A - Battery Charging System - Google Patents

Abstract

The embodiment relates to a battery charging system. The battery charging system according to the embodiment comprises: an offline charger connected to an AC power source and supplying power to a battery cell through a converter; an onboard charger connected to the battery cell to be charged; and core plugs connected to each of the offline charger and the onboard charger, wherein the core plug of the offline charger and the core plug of the onboard charger are mutually connected to charge the battery cell, and the offline charger may include a mobile unit.

Description

Battery Charging System

The embodiment relates to a battery charging system.

Self-connected battery charging method is typically borrowed from wireless charging systems. This is a magnetic induction method that uses the principle of electromagnetic induction, where a magnetic field is generated in the coil of the power transmitter, and the magnetic field is induced in the secondary coil of the receiver to supply current.

When vibratory bodies are connected to each other under resonance conditions, energy exchange occurs easily. If this is applied to wireless charging, coils are placed on each power transmitting and receiving machine, and the frequency between the transmitting and receiving parts is adjusted through the frequency, so that the transmitting and receiving parts can transmit and receive power through resonance.

Meanwhile, electric vehicles such as hybrid vehicles, electric vehicles, and forklifts are equipped with batteries as a power source. Among electric vehicles, plug-in hybrid vehicles and electric vehicles are generally provided with a function that allows the vehicle's battery to be charged via a wire from a power source outside the vehicle.

For large-capacity batteries such as those used in forklifts, this corresponds to a large-capacity battery that is approximately 10 times the battery capacity of a typical electric vehicle.

Figure 1 is a drawing for explaining a general rapid charging method.

In cases where large-capacity batteries such as forklifts are used, a high-voltage/low-current system is applied considering the battery charging scale. In such cases, if rapid charging is performed in the manner shown in Fig. 1, there is a high possibility that unbalanced charging will occur in a number of battery cells connected in series.

If a charge imbalance occurs between battery cells, the battery's chargeable capacity may be limited and its lifespan may be shortened.

However, simultaneously performing battery cell balancing during charging causes difficulties in estimating the SOC (State of Charge) between each battery cell, and also makes it difficult to predict the amount of charge.

Therefore, cell balancing and charging cannot generally be done simultaneously, and it is difficult to rapidly charge large-capacity batteries while considering cell balancing.

Figure 2 illustrates a power conversion system for a rapid charger for cell equalization charging.

The charging method of Fig. 2 is an ideal form of charging method that takes cell balancing into account in the existing charging method. In order to solve the cell balancing problem by the charging method of Fig. 1, a DC/DC power conversion device can be connected between each cell voltage as shown in Fig. 2 to charge by differentiating the charging power according to the cell charge amount.

In the method of Fig. 2, when connecting a charging connection, if a high-voltage DC terminal must be connected, a charging connector including a thick transmission line with high insulation for high power transmission is required, and when connecting a DC for cell voltage charging, each connection terminal is required, so a lot of charging connectors and wires for connecting them are required.

In addition, a capacitor is required to maintain the DC link, which requires a momentary inrush current and a large-capacity capacitor and inrush current limiting circuit to reduce it.

Therefore, it is not very effective because it is inefficient in terms of cost and size when actually implemented.

In this regard, Japanese Patent Publication No. 1994-070477 discloses a charging device for a battery forklift.

In an embodiment, a system for rapidly charging a large-capacity battery of an electric forklift is provided by using a wireless charging method.

Specifically, the present invention aims to provide a battery charging system that reduces leakage flux and improves efficiency by directly connecting coils, and does not require generation of high-power, high-frequency AC signals for power transmission between a power transmitter and receiver.

A battery charging system for a forklift may be provided, comprising: an offline charger connected to an AC power source and supplying power to a battery cell through a converter; an onboard charger connected to the battery cell to be charged; and core plugs connected to each of the offline charger and the onboard charger, wherein the core plug of the offline charger and the core plug of the onboard charger are mutually connected to charge the battery cell, and the offline charger includes a mobile unit.

The above AC power source is a three-phase power source and can be connected to the core plug of the offline charger through an AC/AC converter or an AC/DC converter.

The above offline charger can have a conversion frequency selected from the converter for optimal output of the core plug of the offline charger.

When the offline charger has multiple core plugs, the frequency for control can be selected according to the length of the core plugs of the multiple offline chargers.

The core plug of the above onboard charger is configured in a form in which a plurality of cores, each having a different length, are joined, and each of the plurality of cores can be joined to a converter.

The above plurality of cores may have equal areas in contact with the core plugs of the offline charger, and may have equal distances from the battery rows to which the battery cells are connected.

The above-mentioned moving unit can be provided in the offline charger in a form that can move up, down, left, and right.

The core plug of the offline charger and the core plug of the onboard charger are connected to each other in a ring shape, and can be compressed when the core plug of the offline charger and the core plug of the onboard charger are connected.

In an offline charger, an AC power source; a converter; and a core plug are provided, wherein the AC power source is connected to the core plug through the converter, and is directly connected to the core plug of an onboard charger of a forklift through the core plug to supply power of the AC power source to a battery cell to be charged.

In an onboard charger of a forklift, an onboard charger may be provided, comprising: a core plug configured in a form in which a plurality of cores having different lengths are joined; and a plurality of converters, wherein the core plug is connected to the plurality of converters, the plurality of converters are connected to each battery row of battery cells to be charged, and the onboard charger receives AC power by directly connecting to the core plug of an offline charger through the core plug to charge the battery cells.

According to an embodiment of the invention, a system for rapidly charging a large-capacity battery of an electric forklift can be provided by using a wireless charging method.

Specifically, by directly connecting the coils, leakage flux can be reduced, efficiency can be improved, and a battery charging system can be provided that does not require generating a high-power, high-frequency AC signal for power transmission between a power transmitter and a receiver.

Figure 1 is a drawing for explaining a general rapid charging method.
Figure 2 illustrates a power conversion system for a rapid charger for cell equalization charging.
FIG. 3 is a drawing for explaining the configuration of a battery charging system in an embodiment.
FIG. 4 is a drawing for explaining a method of connecting a charging system for a forklift, in an embodiment.
FIG. 5 illustrates the configuration of an onboard charger in an embodiment.
Figure 6 is a drawing for explaining the configuration of an offline charger in an embodiment.

Hereinafter, embodiments will be described in detail with reference to the attached drawings. However, since various modifications may be made to the embodiments, the scope of rights of the patent application is not limited or restricted by these embodiments. It should be understood that all modifications, equivalents, or substitutes to the embodiments are included in the scope of rights.

The terms used in the examples are for the purpose of description only and should not be construed as limiting. The singular expression includes the plural expression unless the context clearly indicates otherwise. In this specification, the terms "comprises" or "has" and the like are intended to specify the presence of a feature, number, step, operation, component, part or combination thereof described in the specification, but should be understood to not exclude in advance the possibility of the presence or addition of one or more other features, numbers, steps, operations, components, parts or combinations thereof.

Unless otherwise defined, all terms used herein, including technical or scientific terms, have the same meaning as commonly understood by one of ordinary skill in the art to which the embodiments belong. Terms defined in commonly used dictionaries, such as those defined in common dictionaries, should be interpreted as having a meaning consistent with the meaning they have in the context of the relevant art, and will not be interpreted in an idealized or overly formal sense unless expressly defined in this application.

In addition, when describing with reference to the attached drawings, the same components will be given the same reference numerals regardless of the drawing numbers, and redundant descriptions thereof will be omitted. When describing an embodiment, if it is determined that a specific description of a related known technology may unnecessarily obscure the gist of the embodiment, the detailed description thereof will be omitted.

Also, in describing components of the embodiments, terms such as first, second, A, B, (a), (b), etc. may be used. These terms are only intended to distinguish the components from other components, and the nature, order, or sequence of the components are not limited by the terms. When it is described that a component is "connected," "coupled," or "connected" to another component, it should be understood that the component may be directly connected or connected to the other component, but another component may also be "connected," "coupled," or "connected" between each component.

Components included in one embodiment and components that have common functions will be described using the same names in other embodiments. Unless otherwise stated, descriptions made in one embodiment may be applied to other embodiments, and specific descriptions will be omitted to the extent of overlap.

FIG. 3 is a drawing for explaining the configuration of a battery charging system in an embodiment.

As illustrated, it may include an offline charger (310) and an onboard charger (320), and the transmission power of the offline charger (310) may be transmitted to a battery cell connected to the onboard charger via a core plug (330).

The core plug (330) is provided in a form that is separated and connected to each of the offline charger (310) and the onboard charger (320), and the core plugs connected to each of the offline charger (310) and the onboard charger (320) can be connected to each other. By using the core plug (330), it is possible to enable equal charging of the battery cells through direct connection between cores.

The offline charger (310) can provide AC power to the onboard charger (320) through an AC/AC converter. The AC/AC converter can deliver power to one side of the core plug (330), that is, the core plug (330) connected to the offline charger (310), and when the core plug (330) acts as a plug and is connected to the core plug of the onboard charger (320), power can be supplied to each battery cell.

The onboard charger (320) may include multiple AC/DC converters, each AC/DC converter connected to a respective battery cell.

By providing a battery charging system capable of evenly charging battery cells through direct connection between cores using a core plug (330), the insulation/current capacity of the plug for large-capacity power transmission does not need to be considered, and in case of evenly charging between cells, only connection of ports for magnetic circuits is required without the need for a plurality of power lines, so that a battery charging system with a simple structure can be provided.

Additionally, since a large DC link is unnecessary, a large capacitor or inrush current limiting circuit is also unnecessary.

The offline charger (310) can be responsible for PFC (Power Factor Correction) control of the AC source and frequency modulation for efficient power transmission of the multi-winding transformer.

In the case of an onboard charger (320) mounted on an electric forklift, non-isolated power conversion devices with low power output can transmit power to each cell through a multi-winding transformer. Insulation between each cell is obtained through a multi-winding method of the core, and the AC/DC converter of the onboard charger (320) can control the charging power according to the charging status of each battery cell sent from a BMS (Battery Management System).

FIG. 4 is a drawing for explaining a method of connecting a charging system for a forklift, in an embodiment.

A connection method applicable to an electric forklift may be provided. In an embodiment, in order to connect the coil of an offline charger and the core plug of an onboard charger, an offline charger equipped with an AC/AC converter may first be provided in a movable form. For example, it may include wheels or a moving unit for moving up, down, left, and right.

The core plug of an offline charger may be configured to remain retractable within the charger while charging is not taking place.

The battery charging system may further include a core bonding unit to secure the core in the correct position when the offline charger moves to bond with the core for the onboard charger.

The core joining unit may utilize a light-receiving/light-emitting sensor to enable the offline charger core to be joined at an accurate location via the moving unit, and the moving unit of the offline charger may be moved to a location for core plug joining using the sensor. Alternatively, the moving unit may be moved automatically based on the sensor value.

The moving unit of the offline charger is configured to enable the core to move up, down, left, and right, and for this purpose, the connection between the offline charger core winding and the output line of the AC/AC converter can be connected via a wire.

The core joint shape of the core joint unit can be configured in a ring shape so that the core plugs can be firmly fixed together. In addition, an appropriate position can be placed on the core joint unit in the transformer design, and in this case, a crimping device or the like that can firmly fix the two core plugs can be utilized.

FIG. 5 illustrates the configuration of an onboard charger in an embodiment.

Figure 5(a) illustrates a side view of the onboard charger, and Figure 5(b) illustrates a top plan view of the onboard charger.

When power transmitted through the core plug of the offline charger is input through the core plug of the onboard charger, charging of the battery cell connected to the core of the onboard charger can occur.

Offline chargers can supply charging power to the battery through an AC/DC converter connected to each battery cell.

At this time, in the form of a general single core, the line length between each cell to the battery will be different. In particular, the battery row located on the closest core and the battery row located farthest can have a significant difference in impedance according to the line length depending on the battery size and the number of parallel connections. In addition, since the internal temperature of the electric forklift fluctuates greatly and the thermal environment is poor, the difference can be greater due to the increase in resistance caused by heat.

The core of the offline charger may be configured in the form of a single large core, and the form of the onboard charger core may be configured in the form of bonding separate cores, unlike the core of the offline charger. In addition, the core of the offline charger may also be configured as a separate core according to each onboard charger core. This is the same as the configuration of Fig. 6(c) and Fig. 6(d).

The area of the part in contact with the offline charger core is taken equally, and the cores connected to each battery row are arranged as separated cores according to the number of batteries connected in parallel, as shown in Fig. 5(a) and Fig. 5(b), so that the distance between each battery row and the core can be arranged as evenly as possible.

Figure 6 is a drawing for explaining the configuration of an offline charger in an embodiment.

The offline charger can supply power by connecting a three-phase AC power source in the form of Fig. 6(a) to Fig. 6(d). Power conversion devices can be connected in various forms as shown in Fig. 6.

In the embodiment, as shown in Fig. 6(a), a three-phase AC power source is connected to an AC/DC converter in three phases, and since the AC/DC converter has a large capacity, PFC control is performed. A power conversion device can be configured to transmit power to the core plug of an offline charger through an optimal frequency from a connected DC/AC inverter.

Fig. 6(b) illustrates a power conversion device that performs PFC power control for AC power using an AC/AC converter and controls the frequency for optimal output in accordance with the high frequency of the core plug.

Fig. 6(c) illustrates a form in which PFC power control of a three-phase AC power source is performed through an AC/AC converter, and three AC conversions are performed for the three-phase core plugs according to the frequency of each core plug.

In the diagram (d), a structure of a power conversion device can be provided that operates in a manner that applies a DC/AC inverter to each of the three-phase AC power sources, shares the DC voltage, and controls it at a frequency optimized for each core plug connected to the DC/AC inverter.

There are two main ways to consider when connecting a three-phase power supply. First, the ratio of the number of turns of the transformer must be considered, but among them, the ratio of the primary voltage to the secondary voltage is the most important. The secondary voltage standard can be set based on the battery cell voltage.

The power conversion device configuration for AC/AC conversion can be applied to an AC-DC-AC conversion method, an AC/AC conversion method for single-phase output for three-phase input power, and an AC/AC power conversion method for three-phase output for three-phase input power. Among these, in the case of a three-phase output power method for three-phase input power, it can be configured in a manner in which the core plugs of three offline chargers are respectively connected to the core plugs of three onboard chargers. Therefore, in this case, three onboard charger cores of the type shown in Fig. 5 are required. This three-phase output is also possible in the structure of AC-DC-AC conversion.

In the case of controlling a power conversion device connected to a three-phase input power supply, PFC control is performed, and in the case of output power, the frequency that is efficient for charging each battery cell can be selected and controlled. The converter can be controlled by changing to the optimal frequency according to the operating situation. In the case of a three-phase output, the optimal conversion frequency considering the core length of each cell group can be selected and controlled.

The method according to the embodiment may be implemented in the form of program commands that can be executed through various computer means and recorded on a computer-readable medium. The computer-readable medium may include program commands, data files, data structures, etc., alone or in combination. The program commands recorded on the medium may be those specially designed and configured for the embodiment or may be those known to and usable by those skilled in the art of computer software. Examples of the computer-readable recording medium include magnetic media such as hard disks, floppy disks, and magnetic tapes, optical media such as CD-ROMs and DVDs, magneto-optical media such as floptical disks, and hardware devices specially configured to store and execute program commands such as ROMs, RAMs, flash memories, etc. Examples of the program commands include not only machine language codes generated by a compiler but also high-level language codes that can be executed by a computer using an interpreter, etc. The hardware devices described above may be configured to operate as one or more software modules to perform the operations of the embodiment, and vice versa.

The software may include a computer program, code, instructions, or a combination of one or more of these, which may configure a processing device to perform a desired operation or may independently or collectively command the processing device. The software and/or data may be permanently or temporarily embodied in any type of machine, component, physical device, virtual equipment, computer storage medium or device, or transmitted signal wave, for interpretation by the processing device or for providing instructions or data to the processing device. The software may also be distributed over network-connected computer systems and stored or executed in a distributed manner. The software and data may be stored on one or more computer-readable recording media.

Although the embodiments have been described with limited drawings as described above, those skilled in the art can apply various technical modifications and variations based on the above. For example, appropriate results can be achieved even if the described techniques are performed in a different order than the described method, and/or components of the described system, structure, device, circuit, etc. are combined or combined in a different form than the described method, or are replaced or substituted by other components or equivalents.

Therefore, other implementations, other embodiments, and equivalents to the claims are also included in the scope of the claims described below.

Claims (11)

In a battery charging system for a forklift,
An offline charger that is connected to AC power and supplies power to the battery cells through a converter;
An onboard charger connected to said battery cell to be charged; and
Core plugs connected to each of the above offline charger and the above onboard charger
Including,
The core plug of the above offline charger and the core plug of the above onboard charger are mutually connected to charge the battery cell,
The above offline charger comprises a mobile unit,
Battery charging system.
In the first paragraph,
The above AC power is a three-phase power supply,
Connected to the core plug of the above offline charger via an AC/AC converter or an AC/DC converter,
Battery charging system.
In the first paragraph,
The above offline charger is,
In the above converter, the conversion frequency is selected for maximum efficiency of the core plug of the offline charger.
Battery charging system.
In the third paragraph,
If the above offline charger has multiple core plugs,
The frequency for control is selected according to the length of the core plug of the above multiple offline chargers.
Battery charging system.
In the first paragraph,
The core plug of the above onboard charger is,
It is composed of multiple cores, each having a different length, joined together,
The above multiple cores are each connected to a converter,
Battery charging system.
In paragraph 5,
The above multiple cores are,
The contact area of the core plug of the above offline charger is the same,
Equalizing the distance between the battery cells and the battery rows at different locations;
Battery charging system.
In the first paragraph,
The above moving unit is,
Equipped in the offline charger in the form of the above-mentioned up, down, left, and right movement,
Battery charging system.
In the first paragraph,
The core plug of the above offline charger and the core plug of the above onboard charger are mutually connected in a ring shape,
When the core plug of the above offline charger and the core plug of the above onboard charger are joined,
Battery charging system.
For offline chargers,
AC power;
converter; and
Core plug
Including,
The above AC power is connected to the above core plug through the above converter,
The core plug is directly connected to the core plug of the onboard charger of the forklift through the core plug, and supplies power from the AC power to the battery cell to be charged.
Offline charger.
For onboard chargers in forklifts,
A core plug comprising a plurality of cores each having a different length joined together; and
Multiple converters
Including,
The above core plug is connected to the above multiple converters,
The above plurality of converters are connected to each battery row of battery cells to be charged,
By directly connecting the core plug of the offline charger through the above core plug, AC power is received to charge the battery cell.
Onboard charger.
In the power conversion device of the offline charger,
3 phase AC power; and
A converter device connected to the above three-phase AC power supply;
One or more core plugs for transmitting the converted power of the above converter to the onboard charger.
Including,
The above converter device,
Consists of an AC/DC converter and one or more DC/AC inverters;
It consists of an AC/AC converter,
The core plug is directly connected to the core plug of the onboard charger through the core plug, and the converted power of the three-phase AC power is transmitted to the onboard charger.
Power conversion device.

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