Charging device capable of reducing low-frequency leakage current

Abstract

A charging device capable of reducing a low-frequency leakage current, the charging device comprising: a filter (11) which has two input terminal Y capacitors (C CM11 , C CM12 ) which are connected in series to input terminals into which alternating current (AC) power provided by an external charging device is input, and of which a connection node is connected to ground, a power factor correction converter (13) having a switching element (Q1 to Q4), correcting the power factor of the AC power supplied from the external charging system through the filter (11) by on / off control of the switching element to convert the AC power into direct current (DC) power, and outputting the DC power, a DC link capacitor (C link), which is connected to both ends of the power factor correction converter (13) and forms a DC voltage, a non-isolating DC-DC converter (15) which reduces the level of the DC voltage generated by the DC link capacitor (C link ) into a voltage level required by an energy storage device to be charged, two output terminal Y capacitors (C CM31 , C CM32 ), which are connected to an output terminal of the DC-DC converter (15) and are connected in series with each other and whose connection node is connected to ground, and a duty ratio control device (100) which controls the duty ratio of the switching element in the power factor correction converter (13) on the basis of the level of a common mode component of an AC voltage of the AC power supplied from the external charging system, the level of the DC voltage supplied by the DC link capacitor (C link ) and a leakage current flowing from the connection node of the input terminal Y capacitors (C CM11 , C CM12 ) and the connection node of the output terminal Y capacitors (C CM31 , C CM32 ) flows from the ground.

Description

Background1. Field of InterestThe present invention relates to a charging device for charging an energy storage device, and more particularly to a charging device capable of reducing a low-frequency leakage current resulting from a Y capacitor provided at input / output terminals of the charging device due to a common mode component included in an alternating current (AC) system power.2. Description of the Related ArtIn general, electric vehicles or plug-in hybrid vehicles include an energy storage device (for example, a battery) that is supplied with alternating current (AC) system power using a charging facility and stores the power. To charge an energy storage device, a vehicle includes a charging device that converts an AC system power supplied from an external charging facility to a desired (voltage) level of a direct current (DC) power.A charging device installed in a vehicle is generally referred to as an on-board charger (OBC) and includes a power factor correction converter for generating a DC voltage by correcting the power factor of an input AC power, and a DC-DC converter for converting the level of a voltage output from the power factor correction converter to a voltage level required for charging the battery. In addition, Y capacitors are provided at input and output terminals of the in-vehicle charging device to eliminate noise components. Generally, a Y capacitor (e.g., suppression capacitor circuit(s) having one or more (class)Y capacitors) installed at the output terminal is manufactured to have a higher capacitance than that of a Y capacitor installed at the input terminal.AC power provided by a charging facility external to a vehicle may be symmetric or asymmetric depending on the type of charging equipment or the type of power grid of each country. With unbalanced AC power, there is a common mode component. This common mode component acts as a source of low frequency (system power frequency) noise.Specifically, when a DC-DC converter included in an in-vehicle charging device is an insulated type having a transformer, an input terminal and an output terminal of the DC-DC converter are insulated from each other, and thus a Y capacitor at the output terminal is not affected by system power (e.g., grid power) input to the in-vehicle charging device. However, when a non-insulated DC-DC converter is included in an in-vehicle charging device, an electrical connection path is formed between input and output terminals of the DC-DC converter, and thus a common mode component of an input system power acts as low-frequency noise (noise having the standard frequency of the system power), thereby generating a leakage current flowing to the ground through an output terminal Y capacitor having a high capacitance. Although slight, a low frequency leakage current also originates from an input terminal Y capacitor.An external charging system that supplies system power for a vehicle includes a residual current detection device (RCD) device (RCD), which switches off supplied system power for safety if the value of a leakage current exceeds a certain level. The level of low frequency leakage current resulting from an input terminal Y capacitor is significant compared to a reference leakage current level used by the RCD device to determine whether system power is to be turned off.Not only a low-frequency leakage current due to an output terminal Y capacitor but also a low-frequency leakage current due to an input terminal Y capacitor needs to be managed appropriately to prevent interruption of charging by the RCD device during charging.The foregoing details mentioned in this Background Art Description are only for the purpose of enhancing understanding of the background of the present disclosure and are not to be construed as corresponding to the related art already known to those skilled in the art.Furthermore, the publication "A transformerless single-phase utility interface converter to attenuated common-mode voltage for DC microgrid" by F. Chen, R. Burgos and D. Boroyevich, published in 2017 IEEE 314-International Future Energy Electronic Conference and ECCE Asia (IFEEC 2017-ECCE Asia), discloses an active regulation of the common-mode current to the network, wherein the DC / DC actuator assumes the regulation of the common-mode current and for this purpose the potential of the intermediate circuit is evaluated with respect to the ground potential.Explanation Of ExplanationIt is an object of the present disclosure to provide a charging device capable of reducing a low-frequency leakage current generated from a Y capacitor provided at input / output terminals of the charging device due to a common mode component arising in alternating current (AC) system power.In order to solve the above problems, the present disclosure provides a charging device capable of reducing a low-frequency leakage current, the charging device including: a filter including two input terminal Y capacitors connected in series to input terminals to which alternating current (AC) power supplied from an external charging equipment is input, and a connection node of which is connected to ground (e.g., grounded); a power factor correction converter including a switching element that corrects the power factor of the AC power supplied from the external charging equipment through the filter by on / off controlling the switching element to convert the AC power to direct current (DC) power, A DC power output device includes a DC link capacitor connected to both ends of the power factor correction converter and forming a DC voltage, a non-insulating DC-DC converter that converts the level of the DC voltage (e.g., DC voltage level) formed by the DC link capacitor into a voltage level required by a power storage device to be charged, two output terminal Y capacitors connected to an output terminal of the DC-DC converter and connected in series to each other and having the connection node connected to ground (e.g., grounded), and a duty controller (hereinafter, referred to as a duty controller), which determines (e.g., determines) the operation ratio (hereinafter, briefly: operation ratio, duty) of the switching element in the power factor correction converter based on the level of a common mode component of an AC voltage of the AC power supplied from the external charger, the level of the DC voltage formed by the DC link capacitor, and a leakage current flowing from the connection node of the input terminal Y capacitors and the connection node of the output terminal Y capacitors to the ground.According to an exemplary embodiment of the present disclosure, the operation portion controller may calculate the common mode component of the AC voltage of the AC power using the following equation: where v g_CM denotes the common mode component of the AC voltage of the AC power, v Y-Cap_in denotes a voltage value applied to one of the input terminal Y capacitors, and v g denotes the AC voltage of the AC power.According to an exemplary embodiment of the present disclosure, the operation share control means may include: a standard operation share generator that determines (e.g., determines) a first operation share value (hereinafter, abbreviated: duty value) for controlling the switching element so that the power factor correction converter outputs a preset voltage level; a minimum leakage current adjustment control means that calculates a gain for compensating a level of the AC voltage of the AC power and outputs the gain at preset time intervals, wherein the minimum leakage current adjustment control means calculates an average value of the leakage current, which flows out to the ground from the connection node of the input terminal Y capacitors and the connection node of the output terminal Y capacitors at the preset time intervals, and detects and outputs a currently output gain according to a change in the previously input average value of the leakage current and a change in the gain, a multiplier (e.g., multiplier) which outputs the level of the common mode component of the AC voltage of the AC power multiplied by the gain output from the minimum leakage current adjustment controller, and a divider (e.g., divider), which can generate a common mode compensation duty value by dividing the output value of the multiplier with the level of the DC voltage formed by the DC link capacitor, and supply a value equal to the common mode compensation duty value plus a respective one of the first duty value and a value complementary to the first duty value as a duty value for on / off control of the switching element.According to an exemplary embodiment of the present disclosure, the minimum leakage current adjustment controller may: compare, at the preset time intervals, a currently input average leakage current value with a latest (e.g., latest) input average leakage current value, and compare a latest calculated gain with a gain calculated immediately before the latest calculated gain, output a value equal to the latest calculated gain minus a preset gain variation Δ as an actual gain when the currently input average leakage current value is larger than the latest input average leakage current value and the latest calculated gain is larger than the gain calculated immediately before the latest calculated gain, output a value equal to the latest calculated gain plus the preset gain variation Δ as the actual gain, when the currently input average leakage current value is larger than the last input average leakage current value and the latest calculated gain is smaller than the gain calculated immediately before the latest calculated gain, outputs a value equal to the latest calculated gain k' plus a preset gain variation Δ as the present gain when the currently input average leakage current value is smaller than the latest input average leakage current value and the latest calculated gain is larger than the gain calculated immediately before the latest calculated gain, and outputs a value equal to the latest calculated gain k' minus a preset gain variation Δ as the present gain when the currently input average leakage current value is smaller than the latest input average leakage current value and the latest calculated gain is smaller than the gain calculated immediately before the latest calculated gain.According to an exemplary embodiment of the present disclosure, the power factor correction converter may include a first arm including a first switching element and a second switching element directly connected to each other, and a second arm including a third switching element and a fourth switching element directly connected to each other, wherein the first arm and the second arm may be connected to two input terminals of input terminals of the DC-DC converter in parallel, a connection node of the first switching element and the second switching element may be connected to one terminal of the input terminals to which the AC power is supplied, and a connection node of the third switching element and the fourth switching element may be connected to the other terminal of the input terminals to which the AC power is supplied.According to an exemplary embodiment of the present disclosure, the duty control means may provide a value equal to the first duty value plus the common mode compensation duty value as a duty value for on / off controlling the first switching element, provide a value complementary to the value equal to the first duty value plus the common mode compensation duty value as a duty value for on / off controlling the second switching element, provide a value equal to a value complementary to the first duty value plus the common mode compensation duty value as a duty value for on / off controlling the third switching element, and provide a value complementary to the value, which is equal to the value (in turn) complementary to the first duty value plus the common mode compensation duty value, provide, as a duty value for on / off control of the fourth switching element.The charging device capable of reducing the low-frequency leakage current can reduce a low-frequency leakage current due to a common mode component of a DC power source having an unbalanced structure occurring in the charging device.In particular, the charging device capable of reducing the low-frequency leakage current can reduce not only a low-frequency leakage current due to an output terminal Y capacitor having a high capacitance but also a low-frequency leakage current due to an input terminal Y capacitor having a low capacitance.Accordingly, the charging device capable of reducing the low-frequency leakage current can reduce a leakage current to less than the level detected by a power recovery (RCD) device provided in a charging facility, thereby preventing interruption of charging.The effects that can be achieved by the present disclosure are not limited to the above-mentioned effects, and other non-mentioned effects will be clearly understood by those skilled in the art from the following description.Brief Description of the DrawingsThe above and other aspects, features and advantages of the present disclosure will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings, wherein: FIG. 1 is a circuit diagram illustrating a charging device capable of reducing a low-frequency leakage current according to an exemplary embodiment of the present disclosure, FIG. 2 is a block diagram illustrating an example of an operation portion control device of a charging device capable of reducing a low-frequency leakage current in more detail according to an exemplary embodiment of the present disclosure, FIG. 3 is an equivalent circuit diagram illustrating a connection relationship between a common mode component and a Y capacitor of a charging device capable of reducing a low-frequency leakage current according to an exemplary embodiment of the present disclosure, FIG. 4 illustrates one type of external charging device AC system power supply structure, FIG. 5 illustrates another type of external charger AC system power supply structure, FIG. 6 illustrates another type of external charging device AC system power supply structure; and FIG. 7 is a table illustrating an operation in which a minimum leakage current adjustment controller in the operation portion controller shown in FIG. 2 detects a feed-forward compensation gain.Detailed DescriptionHereinafter, a charging device capable of reducing a low-frequency leakage current according to various exemplary embodiments will be described in detail with reference to the accompanying drawings.FIG. 1 is a circuit diagram illustrating a charging device capable of reducing a low-frequency leakage current according to an exemplary embodiment of the present disclosure.Referring to FIG. 1, the charging apparatus capable of reducing a low-frequency leakage current according to the exemplary embodiment of the present disclosure may include a filter 11 for removing high-frequency noise of the AC power (v g, i g), input from an external charging equipment (e.g., a charging station), a power factor correction (PFC) converter 13, a DC link capacitor C link for forming a DC voltage at an output terminal of the PFC converter 13, A DC-DC converter 15 for converting the level (e.g., level) of the voltage V link of the DC link capacitor C link into a charge voltage level for charging a battery 17, output terminal Y capacitors C CM31 and C CM32, which are connected to an output terminal of the DC-DC converter 15, and a duty controller (Duty controller) 100.The filter 11 is an element for eliminating a high-frequency noise component included in the power supplied from an external charger, and may include two Y capacitors C CM11 and C CM12 connected in series to an input terminal to which an AC voltage is applied from the external charger. A connection node of the two Y capacitors C CM11 and C CM12( e.g., a connection point located between the two Y capacitors C CM11 and C CM12 ) may be connected to ground.In FIG. 1, the filter 11 may include two inductors L CM, which form a transformer, and additional input terminal Y capacitors C CM21 and C CM22, which are connected to the two inductors L CM but this structure may be changed as needed. A connection node of the two additional Y capacitors C CM21 and C CM22( e.g., a connection point located between the two additional Y capacitors C CM21 and C CM22 ) may also be connected to ground.Leakage currents i CG1 and i CG2 due to a common mode component of the input AC power may occur at the connection node of the two Y capacitors C CM11 and C CM12 and at the connection node of the two Y capacitors C CM21 and C CM22 in the filter 11.The PFC converter 13 receives AC power (system power, for example. Grid power) v g, which is input from the outside, converts the AC power into DC power and outputs the DC power. The PFC converter 13 thereby corrects the power factor of the AC power. Specifically, the PFC converter 13 may be configured using a line-coupled inverter topology including a plurality of switching elements Q 1 to Q 4.More specifically, the PFC converter 13 that realizes the grid-coupled inverter topology may include a first arm including a first switching element Q 1 and a second switching element Q 2, which are directly connected to each other, and a second arm including a third switching element Q 3 and a fourth switching element Q 4, which are directly connected to each other. The first arm and the second arm may be connected in parallel with two input terminals of input terminals of the DC-DC converter (e.g., connected in parallel with the input terminals of the DC-DC converter). That is, the first switching element Q 1 and the second switching element Q 2 may be sequentially connected in series between a positive (+) terminal and a negative (-) terminal of the output terminals of the PFC converter 13, and the third switching element Q 3 and the fourth switching element Q 4 may be sequentially connected in series between the positive (+) terminal and the negative (-) terminal of the output terminals of the PFC converter 13.Further, the PFC converter 13 may include a first inductor (e.g., first input inductor) L ac1, the respective ends of which are connected to one end of the input AC power or the filter 11 and to a connection node of the first switching element Q 1 and the second switching element Q 2 and a second inductor (e.g., second input inductor) L ac2, the respective ends of which are connected to the other end of the input AC power and to a connection node of the third switching element Q 3 and the fourth switching element Q 4 respectively.The on / off states of the switching elements Q 1 to Q 4 of the PFC converter 13 may be controlled according to an operation fraction value obtained by the operation fraction controller 100 described later. In the control of the switching elements Q 1 to Q 4, for example, a period may be divided into an operation portion (e.g., duty cycle, duty cycle) and a non-operation portion (e.g., a duty cycle).AC power filtered by the filter 11 may be input to an input terminal of the PFC converter 13. AC power may have a symmetric structure or a symmetric structure depending on the country or specification of a charging facility. AC power provided in the balanced structure does not have a common mode component, but single-phase AC power provided in the unbalanced structure may be variously changed depending on the configuration or the provided structure thereof.The PFC converter 13 converts AC power input from an AC power source into DC power by correcting the power factor of the AC power and outputs the DC power. A DC link capacitor C link, which has two ends connected to respective connection points of the output terminal of the PFC converter 13, is charged with power output from the PFC converter 13 to form a certain level of DC link voltage v link.The non-insulating DC-DC converter 15 may convert the DC voltage v link of the DC link capacitor C link, which is connected to both output terminals of the PFC converter 13, into a desired DC voltage level, and may output the (resultant) DC voltage. Since various exemplary embodiments of the present disclosure relate to a charging device that generates DC power for charging the battery 17 of a vehicle or the like, the non-insulating DC-DC converter 15 may be controlled to output a DC voltage level for charging the battery 17.The non-insulating DC-DC converter 15 applied to various exemplary embodiments of the present disclosure may employ various structures known in the art, and a method of controlling the DC-DC converter is also known in the art. Therefore, additional description of the DC-DC converter 15 will be omitted.Output terminal Y capacitors C CM31 and C CM32 are connected to output terminals of the non-insulating DC-DC converter 15, and a connection node of the two output terminal Y capacitors C CM31 and C CM32 is grounded. More specifically, the one ends (e.g., first ends) of the first and second output terminal Y capacitors C CM31 and C CM32 may be connected to a positive (+) terminal and a negative (-) terminal of the output terminals of the DC-DC converter 15 (i.e., an output terminal of the charging device), respectively, and the other ends (e.g., second ends) thereof may be connected together with the ground (chassis ground in a vehicle).Generally, since the first and second output terminal Y capacitors C CM31 and C CM32, which are provided at the output terminal of the charger, have a much larger capacitance than the input terminal Y capacitors C CM11, C CM12, C CM21 and C CM22, which are present in the filter 11 of the charger, a leakage current i CG3, which constitutes a large part of a low frequency leakage current i CG, which is due to a common mode component, flows out to the ground through the output terminal Y capacitors C CM31 and C CM32.Various embodiments of the present disclosure provide a technique (particularly, a method) for appropriately controlling the operation of a switching element in the PFC converter 13 to calculate the total leakage current detected by an RCD in consideration of not only the low-frequency leakage current i CG3 from the output terminal Y capacitors C CM31 and C CM32, which occurs due to the common mode component of the input system power, but also the low-frequency leakage currents i CG1 and i CG2( fundamental wave components of the leakage currents) from the input terminal Y capacitors C CM11, C CM12, C CM21 and C CM22.FIG. 2 is a block diagram illustrating an example of an operation portion control device of a charging device capable of reducing a low-frequency leakage current in more detail according to an exemplary embodiment of the present disclosure.The duty controller 100 may include a standard duty generator 101 for determining (e.g., determining, setting) a first duty value (e.g., a duty ratio, a duty value) d 1 for controlling the switching elements Q 1 to Q 4 in the PFC converter 13 so that the PFC converter 13 outputs a preset voltage level, and a divider 150 for generating a common mode compensation operating portion value obtained by dividing a common mode component v g_CM a system AC voltage v g by the level of a DC link voltage v link.The standard duty generator 101 in the duty controller 100 may acquire and output the duty value d 1 to control the switching elements Q 1 to Q 4 such that the PFC converter 13 outputs the preset voltage level. That is, the standard duty generator 101 may determine the first duty value d 1 of the switching elements Q 1 to Q 4 in the PFC converter 13, so that the level of the DC link voltage v link may be / become the preset voltage level.More specifically, the standard duty generator 101 may generate a reference current value for the DC link voltage V link to follow the preset voltage by comparing the DC link voltage V link with the preset voltage, generate a d / q axis voltage control value for an input current to follow the reference current value by comparing a value obtained by d / q transformation of the input current with the reference current value on the basis of phase information of an input voltage, and then generate the first duty value d 1 by inverse d / q transformation of the d / q axis voltage control value. Since a method by which the standard operation share generator 101 generates the first operation share value d 1 is a known technique applied to a PFC control structure using inverter type topology, a detailed description thereof will be omitted.The divider 150 performs a process of dividing the common mode component v g_CM the system AC voltage v g by the level of the DC link voltage v link and may generate the common mode compensation duty value d CM for controlling the switching elements Q 1 to Q 4 of the PFC converter 13, so that the output of the divider 150 compensates a leakage current due to the output terminal Y capacitors C CM31 and C CM32.FIG. 3 is an equivalent circuit diagram illustrating a connection relationship between a common mode component and a Y capacitor of a charging device capable of reducing a low-frequency leakage current according to an exemplary embodiment of the present disclosure.In FIG. 3, a voltage indicated by v AB_CM is a common mode component of a voltage v AB, which is formed between the connection node A of the first switching element Q 1 and the second switching element Q 2, which form the first arm of the PFC converter 13, and the connection node B of the third switching element Q 3 and the fourth switching element Q 4, which form the second arm.The equivalent circuit shown in FIG. 3 is an equivalent circuit designed by considering only a part related to the described low-frequency common mode component in the circuit of FIG. 1. In the circuit of FIG. 1, the inductances L ac have an insignificant impedance with respect to a low frequency component and can thus be disregarded. The non-insulating DC-DC converter 15 transmits the low-frequency common mode component to the output terminal, and thus can be disregarded. Further, since it is easy to analyze the output terminal Y capacitors based on a negative (-) DC line in analyzing the equivalent circuit, it is appropriate to express a low-frequency common mode path through the second Y capacitor C in CM32. Considering these aspects in FIG. 1, an equivalent circuit diagram associated with the common mode component may be derived as shown in FIG. 3.As illustrated in FIG. 3, it is possible to adjust a leakage current due to a common mode component v g_CM of an AC power source flowing into a Y capacitor (the second Y capacitor C CM32 in FIG. 2 ) when the common mode component v AB_CM of the voltage between the node A and the node B is controlled. Here, the voltage between the node A and the node B may be determined by controlling the on / off duty value ("on / off duty value") of the switching elements Q 1 to Q 4 using a grid-coupled inverter topology.That is, in order to reduce the low-frequency leakage current of the Y capacitors C CM31 and C CM32, which is due to the common mode component of the AC power source, the on / off duty value of the switching elements Q 1 to Q 4 is controlled so that the common mode component v g_CM of the AC power source is compensated by the common mode component v AB_CM of the voltage between the node A and the node B. That is, the on / off duty value of the switching elements Q 1 to Q 4 is obtained so that the voltage of the Y capacitors C CM31 and C CM32 is converted into DC voltage (DC).Since the Y capacitors C CM31 and C CM32 have substantially infinite impedance with respect to a DC component, the DC component of the current i CG, which flows out to the ground through the Y capacitors C CM31 and C CM33 can be disregarded.Thereby, a DC component of the common mode component voltage v AB_CM between the node A and the node B shown in FIG. 3 can be disregarded, and only an AC component can be controlled to be equal to the common mode component v g_CM of the system power source, thereby eliminating the low-frequency leakage current due to the common mode component.To this end, in an exemplary embodiment of the present disclosure, a second duty value d CM may be generated by dividing the common mode component v g_CM the AC voltage v g the AC power by the DC link voltage V link and added to the first duty value d 1 thereby controlling the switching elements Q 1 to Q 4 of the PFC converter 13.In this equation, v Y-cap_p denotes the voltage of the Y capacitor C CM31, which is connected to the positive (+) terminal of the output terminal of the DC-DC converter 15, v bat denotes the voltage of an energy storage device, which is connected to the output terminal of the DC-DC converter 15, and v link denotes the DC link voltage of the input terminal of the DC-DC converter 15. Further, α is a constant set to a range of 0 to 1, which may preferably be a value close to 0.5, and more preferably 0.5.According to this equation, the voltage of the Y capacitor C CM32, which is connected to the negative (-) terminal of the output terminal of the DC-DC converter 15, always has a level of -αv link.The DC component of the common mode component voltage v AB_CM between the node A and the node B is half of the DC link voltage V link(0,5 v link), and the voltage of the Y capacitor C CM32 always has a level of -αv link according to Equation 1. that is, regardless of whether the voltage of the DC-DC converter 15 is boosted or decreased, it is possible in consideration of FIG. 3 and Equation 1 if α=0.5, generating the second operation portion value d CM for eliminating the common mode component by adjusting only the AC component of the common mode component voltage v AB_CM between the node A and the node B without considering the DC component.Since the voltage of each node A and B is determined by the switching element operation portion (d A and d B) of each arm (V A= d A V link V B= d B V link) the common mode component voltage v AB_CM between the node A and the node B can be determined according to Equation 2.Further, referring to the equivalent circuit in FIG. 3, when the common mode component voltage of the AC power is equal to the sum of the common mode component voltage v AB_CM between the node A and the node B and the voltage of the Y capacitor C CM32 the leakage current can be eliminated. Therefore, since a DC offset (DC offset) component can be disregarded, particularly when the voltage of the Y capacitor C is CM32-0.5 v link Equation 3 can be derived.The switching element operation amount (d A and d B) of each arm is determined based on an operation amount (e.g., duty ratio, duty ratio) determined to have a value complementary to 0.5, and thus includes an offset value of 0.5. Since the sum of the operation amounts for controlling the switching elements of each arm is set to be always 1, by the first operation amount d 1, which is a standard operation amount for generating the switching element operation amount (d A and d B) of each arm, generated by the standard operation amount generator 101, that is, the operation amount d CM, which corresponds to the common mode component by subtracting 0.5 from the value which can be obtained by dividing the sum of the switching element operation components (d A and d B) of each arm generated based on the standard operation component by 0.5, which is represented by Equation 4.According to Equation 3 and Equation 4, the operation corresponding to the common mode component can be obtained using Equation 5.That is, the common mode component v g_CM of the AC voltage v g is divided by the voltage of a DC link terminal connecting the PFC converter 13 and the DC-DC converter 15, thereby deriving the operation portion for controlling the common mode component.The common mode component v g_CM of the AC voltage v g can be theoretically determined by detecting an input voltage according to the type of the AC power. The method for detecting a common mode component of an AC voltage according to the type of AC power supply will be described with reference to FIGS. 4 to 6.FIGS. 4-6 illustrate various types of external charger AC system power supply structures.FIG. 4 shows the AC power supply structure of an in-cable control box (ICCB) used in Korea, Europe and North America, which is an unbalanced structure for supplying an AC voltage between one of three phases and a grounded neutral point. In the system power supply structure shown in FIG. 4, 1 / 2 of the supplied AC power v g may be a common mode component. In the system structure of FIG. 4, in particular, when a connection line of two lines L 1 and L 2 and an input terminal of a vehicle-mounted charging device are reversed, -1 / 2 of the supplied AC power v g may be a common mode component.FIG. 5 shows a system structure applied in North America, which is a non-symmetrical structure in which a voltage between two lines having different phases is provided as an AC voltage v g and a neutral point between the two lines is grounded. In the structure shown in FIG. 5, a phase angle difference between the two lines of +120 degrees or -120 degrees indicates different common mode components.FIG. 6 is a symmetric structure applied to the electric vehicle supply infrastructure (EVSE) in North America. In this case, a common mode component is zero.In the system power supply systems shown in FIGS. 4 to 6, a common mode voltage may be represented by the average value, i.e., 1 / 2, of voltages between each of the two terminals of the input terminal to which the AC voltage v g is input and the ground.Specifically, when a voltage applied to a Y capacitor C CM11 is detected in the presence of the Y capacitors C CM11 and C CM12, which are connected to the input terminal of the filter 11, the common mode component of the AC voltage may be defined by the following equation.Using Equation 6, the operation portion controller 100 may calculate and provide the common mode component v g_CM of the input AC voltage.Referring back to FIG. 2, the operation share controller 100 may include a complementary value calculator 160 for calculating a value obtained by subtracting the first operation share value d 1 from the value complementary to the first operation share value d 1, which is generated by the standard operation share generator 101, i.e., 1, a first adder 170 for generating an operation portion d A for controlling the first switching element Q 1 of the PFC converter 13 by adding the first operation portion value d 1 and the common mode compensation operation portion value d CM and a second adder 180 for generating an operation portion d B for controlling the second switching element Q 2 by adding the value output from the complementary value calculator 160 and the common mode compensation operation portion value d CM. Since the third switching element Q 3, which is included in the same arm as the first switching element Q 1 is turned on / off in a complementary relationship to the first switching element Q 1 the third switching element Q 3 can be controlled with an operation ratio of 1-d A. In addition, since the fourth switching element Q 4, which is included in the same arm as the second switching element Q 2 is turned on / off in a complementary relationship to the second switching element Q 2 the fourth switching element Q 4 can be controlled with an operation proportion of 1-d B.In addition, the operation portion controller 100 may include a plurality of limiters 191, 192, and 193 for limiting an input value to a certain range. For example, a limiter 191 may limit the output value from the divider 150 to a range ranging from -0.5 to 0.5, another limiter 192 may limit the output value from the first adder 170 to a range ranging from 0 to 1, and another limiter 193 may limit the output value from the second adder 180 to a range ranging from 0 to 1. These limiters can be applied to the required locations by suitably and selectively setting their upper and lower limits.In an exemplary embodiment of the present disclosure, the operation fraction controller 100 may further include a minimum leakage current adjustment controller 130 that generates a feed-forward compensation gain of the AC voltage v g the system AC power before division by the DC link voltage v link in the calculation of the common mode compensation operation fraction value d CM to adjust the operation fraction of the PFC converter 13 such that a leakage current generated in the input terminal Y capacitors C CM11, C CM12, C CM21 and C CM22 of the filter 11, reduced.The minimum leakage current adjustment controller 130 may provide an appropriate compensation gain k according to the change in the leakage current i CG, which flows from the connection node of the two input terminal Y capacitors C CM11 and C CM12, the connection node of the two input terminal Y capacitors C CM21 and C CM22 and the connection node of the two output terminal Y capacitors C CM31 and C CM32 to the ground. The gain k is multiplied with the common mode component v g_CM the AC voltage v g the system AC power by a multiplier 140 before division by the DC link voltage V link by the divider 150, thereby achieving feedforward compensation (English: feedforward compensation) of the AC voltage v g of the system AC power.Specifically, the minimum leakage current adjustment controller 130 calculates the gain k at preset time intervals. The minimum leakage current adjustment controller 130 may receive an average leakage current value i CG_avg at preset time intervals, and may determine and output a currently output gain according to a change in the previously input average leakage current value and a change in the gain.FIG. 7 is a table illustrating an operation in which a minimum leakage current adjustment controller in the operation portion controller shown in FIG. 2 detects a feed-forward compensation gain.Referring to FIG. 7, the minimum leakage current adjustment controller 130 compares a currently input average leakage current value i CG _ avg with a latest input average leakage current value i CG_avg' and compares a latest calculated gain k' with a gain k" calculated immediately before the latest calculated gain k' at preset time intervals.When the currently input average leakage current value i CG _ avg is equal to the latest input average leakage current value i CG_avg' the minimum leakage current adjustment controller 130 outputs the latest calculated gain k' as the present gain.When the currently input average leakage current value i CG _ avg is larger than the most recently input average leakage current value i CG_avg' and the most recently calculated gain k' is larger than the gain k" calculated immediately before the most recently calculated gain k', the minimum leakage current adjustment controller 130 outputs a value equal to the most recently calculated gain k' minus a preset gain variation Δ as a present gain. When the currently input average leakage current value i CG _ avg is larger than the latest input average leakage current value i CG_avg' and the latest calculated gain k' is smaller than the gain k" calculated immediately before the latest calculated gain k', the minimum leakage current adjustment controller 130 outputs a value equal to the latest calculated gain k' plus the preset gain variation Δ as an actual gain.Further, when the currently input average leakage current value i CG _ avg is smaller than the latest input average leakage current value i CG_avg' and the latest calculated gain k' is larger than the gain k" calculated immediately before the latest calculated gain k', the minimum leakage current adjustment controller 130 outputs a value equal to the latest calculated gain k' plus a preset gain variation Δ as an actual gain. When the currently input average leakage current value i CG _ avg is smaller than the most recently input average leakage current value i CG_avg' and the most recently calculated gain k' is smaller than the gain k" calculated immediately before the most recently calculated gain k', the minimum leakage current adjustment controller 130 outputs a value equal to the most recently calculated gain k' minus the preset gain variation Δ as a present gain.As described above, in an exemplary embodiment of the present disclosure, a common mode compensation duty value d CM may be calculated in consideration of a variation in leakage current arising at the connection node of the two input terminal Y capacitors C CM11 and C CM12, the connection node of the two input terminal Y capacitors C CM21 and C CM22 and the connection node of the two output terminal Y capacitors C CM31 and C CM32, which are disposed at the input / output sides of the charging device, thereby fundamental wave components of leakage current arising from a common mode component of an AC power, Thus, the charging can be eliminated and thus interruption by a remaining current detection (RCD) device of an external charging facility can be prevented.In FIG. 2, reference numerals 110 and 120 indicate elements for generating an average leakage current value, 110 indicates an element for calculating the absolute value of a leakage current i CG and 120 indicates a low-pass filter for generating an average leakage current value i CG _ avg by performing low-pass filtering of the absolute value of a leakage current.Although the present disclosure has been shown and described with reference to the specific exemplary embodiments, it will be understood by those skilled in the art that various changes and modifications may be made to the present disclosure within the scope of the claims.

Claims

A charging device capable of reducing a low-frequency leakage current, the charging device comprising: a filter (11) having two input terminal Y capacitors (C CM11, C CM12) connected in series to input terminals to which alternating current (AC) power supplied from an external charger is input, and a connection node of which is connected to ground; a power factor correction converter (13) having a switching element (Q 1 to Q 4) that corrects the power factor of the AC power supplied from the external charger through the filter (11) by on / off control of the switching element, In addition, in order to convert the AC power into direct current (DC) power and output the DC power, a DC link capacitor (C link), which is connected to both ends of the power factor correction converter (13) and forms a DC voltage, a non-insulating DC-DC converter (15) which converts the level of the DC voltage formed by the DC link capacitor (C link) into a voltage level required by a power storage device to be charged, two output terminal Y capacitors (C CM31, C CM32), which are connected to an output terminal of the DC-DC converter (15) and connected to each other in series and whose connection node is connected to ground, and an operation portion controller (100) which controls the operation portion of the switching element in the power factor correction converter (13) on the basis of the level of a common mode component of an AC voltage of the AC power supplied from the external charging equipment, the level of the DC voltage formed by the DC link capacitor (C link) and a leakage current formed by the connection node of the input terminal Y capacitors (C CM11, C CM12) and the connection node of the output terminal Y capacitors (C CM31, C CM32) from flowing to the ground.The charging apparatus according to claim 1, wherein the operation portion controller (100) calculates the common mode component of the AC voltage of the AC power using the following equation: v g _ C M = 0.5 [v Y - C a p _ i n + { - ( v g - v Y - C a p _ i n ) } ] = v Y - C a p _ i n - 0.5 v g wherein v g_CM denotes the common mode component of the AC voltage of the AC power, v Y-Cap_in denotes a voltage value applied to one of the input terminal Y capacitors (C CM11, C CM12), and v g denotes the AC voltage of the AC power.The charging apparatus according to claim 1 or 2, wherein the duty controller (100) comprises: a standard duty generator (101) that determines a first duty value (d 1) for controlling the switching element so that the power factor correction converter (13) outputs a preset voltage level; a minimum leakage current adjustment controller (130) that calculates a gain for compensating a level of the AC voltage of the AC power and outputs the gain at preset time intervals, wherein the minimum leakage current adjustment controller determines an average value of the leakage current generated from the connection node of the input terminal Y capacitors (C CM11, C CM12) and the connection node of the output terminal Y capacitors (C CM31, C CM32) flowing out to the ground, receiving at the preset time intervals, and obtaining and outputting a currently output gain (k') according to a change in the previously input average value of the leakage current and a change in the gain, a multiplier (140) outputting the level of the common mode component of the AC voltage of the AC power multiplied by the gain output from the minimum leakage current adjustment controller, and a divider (150), which generates a common mode compensation duty value by dividing the output value of the multiplier with the level of the DC voltage formed by the DC link capacitor, and supplies a value equal to the common mode compensation duty value plus a respective one of the first duty value and a value complementary to the first duty value as a duty value for on / off control of the switching element.The charging apparatus according to claim 3, wherein the minimum leakage current adjustment controller (130): compares, at the preset time intervals, a currently input average leakage current value (i CG_avg) with a latest input average leakage current value (i CG_avg') and compares a latest calculated gain (k') with a gain (k") calculated immediately before the latest calculated gain, outputs a value equal to the latest calculated gain (k') minus a preset gain variation Δ as an instantaneous gain when the currently input average leakage current value (i CG_avg) is larger than the latest input average leakage current value (i CG_avg') and the latest calculated gain (k') is larger than the gain (k") calculated immediately before the latest calculated gain, a value equal to the latest calculated gain (k') plus the preset gain variation Δ outputs as the present gain when the present input average leakage current value (i CG_avg) is larger than the latest input average leakage current value (i CG_avg') and the latest calculated gain (k') is smaller than the gain (k") calculated immediately before the latest calculated gain, outputs a value equal to the latest calculated gain k' plus a preset gain variation Δ as the present gain, when the currently input average leakage current value (i CG_avg) is smaller than the latest input average leakage current value (i CG_avg') and the latest calculated gain (k') is larger than the gain (k") calculated immediately before the latest calculated gain, and outputs a value equal to the latest calculated gain (k') minus the preset gain variation Δ as the present gain when the currently input average leakage current value (i CG_avg) is smaller than the latest input average leakage current value (i CG_avg') and the latest calculated gain (k') is smaller than the gain (k") calculated immediately before the latest calculated gain.The charging apparatus according to claim 4, wherein the power factor correction converter (13) includes: a first arm including a first switching element (Q 1) and a second switching element (Q 2), which are directly connected to each other; and a second arm including a third switching element (Q 3) and a fourth switching element (Q 4), which are directly connected to each other, the first arm and the second arm being connected to two input terminals of input terminals of the DC-DC converter (15) in parallel; a connection node of the first switching element (Q 1) and the second switching element (Q 2) to one terminal of the input terminals, to which the AC power is supplied, and a connection node of the third switching element (Q 3) and the fourth switching element (Q 4) is connected to the other terminal of the input terminals to which the AC power is supplied.The charging apparatus according to claim 5, wherein the duty control means (100) supplies a value equal to the first duty value plus the common mode compensation duty value as a duty value for on / off controlling the first switching element (Q 1) supplies a value complementary to the value equal to the first duty value plus the common mode compensation duty value as a duty value for on / off controlling the second switching element (Q 2) supplies a value equal to a value complementary to the first duty value plus the common mode compensation duty value, as an operation share value for on / off controlling the third switching element (Q 3) and a value complementary to the value equal to the value complementary to the first operation share value plus the common mode compensation operation share value, as an operation share value for on / off controlling the fourth switching element (Q 4).

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