Charging system for an electrically powered vehicle and method of controlling the same

Abstract

The present invention relates to a charging system for an electric vehicle and a control method thereof, the charging system including a controller that controls a duty ratio of a plurality of switching elements included in an inverter based on a duty ratio command that causes a voltage of a neutral point to follow a preset neutral point voltage command when a charging current of an external power source is supplied to the neutral point of a motor, and selectively compensates for the duty ratio command based on an error between the neutral point voltage command and the voltage of the neutral point.

Description

Technical Field

[0001] This invention relates to a charging system and control method for electric vehicles, wherein the charging system is capable of reducing the neutral point voltage resonance of the motor when charging the battery using a motor and an inverter. Background Technology

[0002] Electric vehicles (EVs) and plug-in hybrid electric vehicles (PHEVs) typically rely on external charging facilities to replenish their battery systems. The charging process involves converting electrical energy supplied from these facilities into a form suitable for storage within the battery. This conversion mechanism is crucial to ensuring that the stored energy can be used by the vehicle's electric powertrain. Charging infrastructure varies considerably. It can include home charging stations, public charging networks, and high-capacity charging stations to meet the demand for faster charging.

[0003] When an EV or PHEV is connected to a charging station, the charging system uses specific protocols to manage the flow of electricity, thereby optimally maintaining the charging level while protecting battery integrity. This conversion process typically involves the use of an on-board charger. For example, the on-board charger is responsible for converting the alternating current (AC) from the charging station into direct current (DC) suitable for charging the vehicle's battery. Furthermore, advancements in battery technology and charging standards continue to improve the efficiency and speed of this charging process, making electric mobility more widespread.

[0004] The charging of batteries in these vehicles is influenced by several factors. These factors include the type of battery chemistry (e.g., lithium-ion), the charging rate regulated by the power source, and the vehicle's state of charge. Furthermore, the integration of smart charging technology enables better energy management, allowing vehicles to charge at the optimal time, thereby reducing energy costs and minimizing the impact on the power grid.

[0005] For example, traditional fast-charging infrastructure is typically designed to provide a standardized output voltage of around 400V. However, battery technologies used in electric vehicles (EVs) today are increasingly designed to operate at higher voltage levels, such as 800V or higher. This increase in voltage specifications helps improve energy transfer efficiency and the vehicle's total driving range. As a result of this technological development, while fast-charging infrastructure still provides a voltage distribution conforming to the traditional 400V specification, next-generation vehicle batteries require voltage upgrades to meet their operational requirements. To facilitate efficient charging of these high-voltage batteries from existing charging infrastructure, integrated boost converters become crucial. These converters amplify the voltage output from charging stations, enabling efficient charging of batteries even with voltage specification differences. Therefore, the shift of EV batteries towards higher-voltage systems not only improves charging efficiency but also supports advancements in power electronics, thermal management, and lightweighting, ultimately driving the widespread adoption of electric mobility solutions.

[0006] However, realizing high-capacity boost converters capable of boosting voltage levels from 400V to 800V or higher presents significant challenges. Such converters are typically not only too heavy and bulky, making them logically difficult to integrate into the limited space of a vehicle, but also come with high manufacturing costs. These factors contribute to an overall increase in vehicle prices, which may hinder market acceptance and limit the widespread adoption of higher-voltage electric vehicle systems. Furthermore, the size and weight of these converters negatively impact vehicle efficiency and performance, and also alter their design architecture. Another obstacle is that associated costs are likely a key consideration for consumers, thus affecting manufacturers' competitive position in the evolving electric vehicle market. Addressing these challenges requires innovative engineering solutions designed to optimize the size and cost of boost converters while ensuring they meet necessary performance specifications. Therefore, an innovative charging technology is needed that can effectively increase the voltage output of existing charging infrastructure and convert the relatively low charging voltages typically associated with existing facilities to higher voltage levels. The development of such a solution will provide efficient charging for advanced battery systems and meet the growing demand for improved electric vehicle performance and range.

[0007] The background description above is intended only to enhance the understanding of the background of this invention and should not be construed as an admission that the description corresponds to prior art known to those skilled in the art. Summary of the Invention

[0008] Therefore, the present invention was made in view of the above-mentioned problems, and the object of the present invention is to provide a charging system and control method for electric vehicles, the charging system being able to reduce the neutral point voltage resonance of the motor when charging the battery using a motor and an inverter.

[0009] The purpose of this invention is not limited to the above-described purposes, and those skilled in the art will clearly understand other purposes not mentioned from the following description.

[0010] According to one aspect of the invention, the above and other objectives can be achieved by providing a charging system for an electrified vehicle, the charging system comprising: a motor having a plurality of corresponding windings; an inverter having a plurality of branches connected to one end of each of the plurality of windings and connected to a plurality of switching elements, and a DC terminal; a battery connected to the DC terminal; a neutral point capacitor connected to the neutral point of the motor, the other ends of the plurality of windings being interconnected; and a controller configured to, when a charging current from an external power source is supplied to the neutral point of the motor, control the duty cycle of the plurality of switching elements based on a duty cycle command that causes the voltage of the neutral point to follow a preset neutral point voltage command, and selectively compensate the duty cycle command based on the error between the neutral point voltage command and the voltage of the neutral point.

[0011] According to another aspect of the present invention, a method for controlling a charging system for an electric vehicle is provided, the charging system comprising a motor having a plurality of corresponding windings, an inverter having a plurality of branches connected to one end of each of the plurality of windings and connected to a plurality of switching elements and a DC terminal, a battery connected to the DC terminal, and a neutral point capacitor connected to the neutral point of the motor interconnected with the other ends of the plurality of windings, the method comprising: when a charging current from an external power source is supplied to the neutral point of the motor, controlling the duty cycle of the plurality of switching elements based on a duty cycle command that causes the voltage of the neutral point to follow a preset neutral point voltage command, and selectively compensating the duty cycle command based on an error between the neutral point voltage command and the voltage of the neutral point. Attached Figure Description

[0012] The above and other objects, features and other advantages of the present invention will be more clearly understood from the following detailed description taken in conjunction with the accompanying drawings, wherein: Figure 1 This is a diagram illustrating the configuration of a charging system for an electrified vehicle according to an embodiment of the present invention; Figure 2 This is a diagram illustrating the zero-phase-sequence component voltage equivalent model of a charging system according to an embodiment of the present invention; Figure 3 This is a diagram illustrating the controller configuration of a charging system according to an embodiment of the present invention; Figures 4 to 6 This is a diagram illustrating the duty cycle command compensation process according to an embodiment of the present invention; and Figure 7 This is a flowchart illustrating a method for controlling a charging system according to an embodiment of the present invention. Detailed Implementation

[0013] The specific structural and functional descriptions of the embodiments of the present invention disclosed in this specification or application are merely illustrative and intended to explain the purpose of the embodiments according to the present invention. The embodiments according to the present invention can be implemented in various forms and should not be construed as limited to the embodiments described in this specification or application.

[0014] Since embodiments of the invention can be modified in various ways and have various forms, specific embodiments will be shown in the drawings and described in detail in the specification or this application. However, it is not intended to limit embodiments of the invention to a particular form of disclosure, and it should be understood to include all variations, equivalents, and alternatives contained within the spirit and technical scope of the invention.

[0015] Unless otherwise stated, all terms, including technical or scientific terms, shall have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. Commonly used terms (such as those defined in dictionaries) shall be interpreted in accordance with their meaning in relation to the relevant art, depending on the context. These terms should not be interpreted in an idealized or overly formalistic manner unless otherwise defined herein.

[0016] The embodiments disclosed herein will be described in detail below with reference to the accompanying drawings. However, the same reference numerals will be assigned to the same or similar components, and redundant descriptions will be omitted.

[0017] In the following description of the embodiments, the term "preset" means that the value of a parameter is predetermined when it is used in a process or algorithm. According to the embodiments, the value of a parameter is set at the start of the process or algorithm, or the value of a parameter is set during the execution of the process or algorithm.

[0018] The terms “module” and “unit” or “section” used to refer to components are used in this article to help understand components and should not be regarded as having a specific meaning or function.

[0019] In the following description of the embodiments disclosed in this specification, detailed descriptions of known functions and configurations included herein will be omitted where such descriptions might obscure the subject matter of the invention. Furthermore, the accompanying drawings are provided solely for the purpose of facilitating understanding of the embodiments disclosed herein and do not limit the technical spirit disclosed herein, but include all variations, equivalents, and alternative embodiments contained within the spirit and scope of the invention.

[0020] The terms "first" and / or "second" are used to describe various components, but these components are not limited by these terms. The terms are used to distinguish one component from another.

[0021] When a component is "connected" or "attached" to another component, it should be understood that the component can be directly connected or attached to the other component, and a third component may exist between the two components. When a component is "directly connected" or "directly attached" to another component, it should be understood that there are no elements between the two components.

[0022] Unless the context clearly indicates otherwise, elements described in the singular are intended to include multiple elements.

[0023] In this specification, it will be further understood that the terms "comprising" or "including" mean that the said feature, value, step, operation, component, part or combination thereof is present, but do not exclude the presence or addition of one or more other features, values, steps, operations, components or combinations thereof.

[0024] Furthermore, the term "unit" or "control unit" used in motor control unit (MCU), hybrid power control unit (HCU), etc., is merely a widely used term to name controllers that control specific functions of a vehicle and does not represent a general-purpose functional unit.

[0025] Before describing the method of controlling the charging system according to the implementation scheme below, the charging system for electric vehicles according to the implementation scheme will be described first.

[0026] Figure 1 This is a diagram illustrating the configuration of a charging system for an electrified vehicle according to an embodiment of the present invention. Figure 2 This is a diagram illustrating the zero-phase-sequence component voltage equivalent model of a charging system according to an embodiment of the present invention.

[0027] First, refer to Figure 1 The charging system according to an embodiment of the present invention includes a motor 20, an inverter 30, a battery 40, and a neutral point capacitor C. n DC link capacitor C dc And controller 100, and can charge battery 40 via motor 20 and inverter 30. However, Figure 1 The main components described are shown in relation to one implementation scheme, and the actual charging system can be implemented by including more or fewer components.

[0028] Generally, the system for driving the motor 20 may include a battery 40 and an inverter 30, wherein the battery 40 is an energy storage device for storing electricity for driving the motor 20, and the inverter 30 converts the direct current stored in the battery 40 into three-phase alternating current and supplies it to the motor 20.

[0029] Inverter 30 is connected to one end of motor 20, which has multiple corresponding windings, and is connected to battery 40 via DC terminals D1 and D2. Inverter 30 has multiple branches S1-S4, S3-S6, and S5-S2. Among the multiple switching elements S1 to S6, two switching elements (two of S1 to S6) are connected in series with each other in each branch S1-S4, S3-S6, and S5-S2, and one phase of drive power is supplied to motor 20 from the connection nodes of the multiple switching elements. In this way, in Figure 1 In this process, the energy used to drive the motor 20 flows from the battery 40 to the motor 20.

[0030] Therefore, one winding of the multiple windings of the motor 20 and the switching elements S1 to S6 in branches S1-S4, S3-S6, and S5-S2 of the inverter 30 connected to the motor 20 can constitute a boost circuit. In other words, the motor 20 and the inverter 30 can form a circuit in which the corresponding boost circuits are connected in parallel between the neutral point N of the motor 20 and the battery 40.

[0031] In an embodiment of the invention, unlike the energy flow described above for driving the motor, external charging power from an external power source 10, including a charging facility such as an electric vehicle power supply device (EVSE), is supplied to the neutral point N of the motor 20 to the inverter 30 to the respective corresponding branches S1-S4, S3-S6, and S5-S2. The switching elements S1 to S6 of the branches S1-S4, S3-S6, and S5-S2 are controlled to boost the external charging power and then supply the power to the battery 40 to charge the battery 40.

[0032] In other words, in various embodiments of the present invention, the motor 20 side connection terminal of the inverter 30 can be the input terminal of the inverter 30, and the battery 40 side connection terminal of the inverter 30 can be the output terminal of the inverter 30.

[0033] More specifically, the charging system according to an embodiment of the present invention may include a motor 20 having a plurality of corresponding windings, an inverter 30 having a plurality of branches S1-S4, S3-S6 and S5-S2 (which are connected to one end of each of the plurality of windings and have a plurality of switching elements S1 to S6) and DC terminals D1 and D2, a battery 40 connected to DC terminals D1 and D2, and a neutral point capacitor C connected to the neutral point N of the motor 20 (at the neutral point N, the other ends of the plurality of windings are interconnected). n And controller 100.

[0034] When charging power is supplied to charge the battery 40 through the neutral point N of the motor 20, if the voltage V of the neutral point N, which is the input terminal, is not properly controlled during the charging process...n If this happens, charging may stop, or in severe cases, the system may be damaged. Therefore, it is necessary to stably control the neutral point voltage V of motor 20. n .

[0035] Therefore, when the charging current of the external power supply 10 is supplied to the neutral point N of the motor 20 (i.e., when the voltage of the external power supply 10 is boosted through the motor 20 and the inverter 30 to charge the battery 40), the controller 100 according to the embodiment can stably control the voltage V of the neutral point N by controlling the duty cycles of multiple switching elements S1 to S6 based on duty cycle commands. n The duty cycle command causes the voltage V at neutral point N to... n Follow the preset neutral point voltage command.

[0036] refer to Figure 2 The zero-phase-sequence component voltage equivalent model of the charging system according to the implementation scheme can be obtained by controlling the output voltage V of the voltage controller that controls the voltage at the neutral point N. xn The stator resistance R of motor 20 s The leakage inductance L of motor 20 lk and neutral point capacitor C n The capacitance C is used to represent this. In this case, the impedance component seen from the external power supply side is very small in a specific frequency band. Therefore, when the input is subjected to a current disturbance of a specific frequency, the neutral point voltage V... n It may resonate at that frequency. If the neutral point voltage V n If the resonance does not decay rapidly, the durability of the charging system may be affected, and charging may stop. Here, the current disturbance includes the current I input from the EVSE. EVSE The current flows into the vehicle. Therefore, the charging current I branches off from the neutral point and flows to the motor. CHG and the flow to the neutral point capacitor C n Neutral point capacitor current I np-cap This includes current disturbance components, and the impedance component L along the path of these current disturbance components. lk When C is present, it will affect the neutral point voltage.

[0037] Therefore, the controller 100 according to the implementation scheme transmits the neutral point voltage command V. n *With neutral point voltage V n The error compensation duty cycle command between the two is used to suppress resonance caused by current disturbances from the external power supply 10, thereby improving charging stability.

[0038] Meanwhile, the external power supply 10, such as EVSE, can operate in either current control mode or voltage control mode, thus enabling the external power supply 10 to be configured such that the voltage V at the neutral point of the motor 20, which serves as the charging power input terminal, is such that... n It is controlled by an external power supply. However, since the external power supply 10 often operates in current control mode under normal charging conditions, embodiments of the present invention can use a controller 100 to control the neutral point voltage V. n Furthermore, the external power supply 10 implements current control.

[0039] In the following text, reference will be made to Figure 3 The charging control method via the controller according to the implementation scheme is described in more detail.

[0040] Figure 3 This is a diagram illustrating the controller configuration of a charging system according to an embodiment of the present invention.

[0041] refer to Figure 3 The controller 100 of the charging system according to the embodiment may include a voltage controller 110, a nonlinear compensator 130, a current imbalance reduction controller 150, a signal output unit 170, and a damping controller 190, and may further include a communication device for communicating with other controllers or sensors to control the functions of the controller 100, a memory for storing operating system or logic instructions and input / output information, and one or more processors for determining, calculating, making decisions, etc., required to perform the functions of the controller 100. Figure 3 The main components shown are those associated with the description of one implementation, and the actual controller 100 may include more or fewer components.

[0042] First, when the charging current of the external power supply 10 is supplied to the neutral point N of the motor 20, the voltage controller 110 can generate a voltage V for the neutral point N. n Follow the preset voltage command V n The duty cycle command of * causes the voltage V at neutral point N to... n It can be continuously controlled to the neutral point voltage command V. n *

[0043] The nonlinear compensator 130 can be based on the current I at the neutral point N. n and the voltage V between DC terminals D1 and D2 dc To generate the compensation duty cycle D used to compensate for the nonlinearity of inverter 30 comp1* Here, the nonlinearity of inverter 30 refers to the difference between input and output caused by the dead time of switching elements S1 to S6 for safe operation of inverter 30, the turn-on / turn-off delay time of inverter drive circuit, and the characteristics of switching elements S1 to S6. This nonlinearity of inverter 30 may lead to differences between the duty cycle and voltage of inverter 30 calculated by the control algorithm and the actual output duty cycle and inverter voltage, which may result in control errors, reduced dynamic characteristics, etc. Therefore, in one embodiment, a compensation duty cycle D generated by nonlinear compensator 130 is used. comp1 *To compensate for the duty cycle command generated by the voltage controller 110, the nonlinearity of the inverter 30 can be compensated during the charging process of the battery 40.

[0044] The current imbalance reduction controller 150 can be based on the compensated duty cycle command D. com * and the phase current I flowing through each of the multiple windings of motor 20 abc This generates a duty cycle command for individually controlling the duty cycles of multiple switching elements S1 to S6 connected to multiple branches S1-S4, S3-S6, and S5-S2. In this case, the compensated duty cycle command D... com * refers to the duty cycle of multiple boost circuits that are applied together to each phase of motor 20 and inverter 30.

[0045] The current imbalance reduction controller 150 can be based on the compensated duty cycle command D. com * and the phase current I flowing through each of the multiple windings of motor 20 abc To generate duty cycle command D for individually controlling the duty cycles of multiple switching elements S1 to S6. abc * to eliminate imbalances with each corresponding boost circuit.

[0046] More specifically, the current imbalance reduction controller 150 can control the duty cycle of the switching elements S1 to S6 that constitute the boost circuit, so that the phase current flowing through each of the multiple windings of the motor 20 follows the average value of the phase current.

[0047] Therefore, the current of the same magnitude flows to the corresponding boost circuits of each phase, thus eliminating the imbalance between the motor 20 and the inverter 30, thereby preventing torque from being generated in the motor 20 due to the imbalance of each phase during charging.

[0048] Signal output unit 170 can generate and output a separate duty cycle command D generated by current imbalance reduction controller 150. abc*Corresponding drive signals, and pulse width modulation can be performed for this purpose. During the process of boosting the voltage of the external power supply through the motor 20 and inverter 30 to charge the battery 40, in order to improve charging efficiency, the signal output unit 170 can control the duty cycle of the switching elements by utilizing drive signals generated by pulse width modulation for sequentially turning multiple branches S1-S4, S3-S6, and S5-S2 on and off. In this case, turning on a branch can mean that the upper switching elements S1, S3, and S5 connected to branches S1-S4, S3-S6, and S5-S2 are turned on and the lower switching elements S2, S4, and S6 are turned off, and turning off a branch can mean the opposite.

[0049] The pulse width modulation used to sequentially connect and disconnect multiple branches S1-S4, S3-S6, and S5-S2 can be represented as interleaved pulse width modulation. According to this interleaved pulse width modulation, dq-axis voltage ripple exists, but the ripple of the zero-phase-sequence component voltage can be reduced. In this case, the dq-axis inductance is greater than the zero-phase-sequence component inductance, therefore it has no significant effect on the phase current ripple. During charging, only the zero-phase-sequence component current flows through the neutral point capacitor C. n Therefore, the ripple of the dq-axis voltage and current will not affect the neutral point capacitor C. n The capacitor. Therefore, current ripple can be reduced, which in turn reduces the iron loss of motor 20 during charging and improves charging efficiency.

[0050] In addition to the voltage controller 110, nonlinear compensator 130, current imbalance reduction controller 150 and signal output unit 170 mentioned above, the controller 100 according to the embodiment may further include a damping controller 190, which is used to suppress resonance caused by current disturbances on the external power supply 10 side.

[0051] The damping controller 190 can be based on the neutral point voltage V n and the voltage V between DC terminals D1 and D2 dc To generate the compensation duty cycle D comp2 *, and can utilize the generated compensation duty cycle D comp2 * Compensation duty cycle command to quickly attenuate resonance caused by current disturbances.

[0052] This duty cycle command compensation can be performed when the charging current from the external power supply is supplied to the neutral point N (i.e., during boost charging), and further, it can be performed on the neutral point capacitor C. n Execution is performed after the voltage reaches the voltage of the external power supply 10 and the initial charging is completed.

[0053] On the other hand, during the charging operation when the voltage of the external power supply 10 is directly applied to the battery 40, since it is not necessary to control the voltage of the neutral point N for boosting, the duty cycle command compensation can be omitted.

[0054] The following will refer to Figure 4 A detailed description of the duty cycle compensation process used to suppress resonance is given.

[0055] Figures 4 to 6 This is a diagram used to describe the duty cycle command compensation process according to an embodiment of the present invention.

[0056] Figure 4 The voltage control and damping control processes during the boost charging process are shown.

[0057] First, the damping controller 190 can be based on the neutral point voltage V. n The extracted voltage signal contained in the preset frequency band is used to determine the compensation duty cycle D. comp2 * and for this purpose, acquire the voltage signal V contained in the preset frequency band. n2 and the voltage V between DC terminals D1 and D2 dc .

[0058] More specifically, the controller 100 may include a first low-pass filter 191 and a high-pass filter 192, and the first low-pass filter 191 and the high-pass filter 192 may be able to draw voltage V from the neutral point N. n Extract the ripple component.

[0059] First, the first low-pass filter 191 can obtain the voltage V at the neutral point N. n As an input signal, a first voltage signal V with a frequency lower than a preset first cutoff frequency is output from the input signal. n1 In this case, the voltage V at the neutral point N n It can be connected to the neutral point capacitor C n The voltage is obtained from the voltage sensors at both ends.

[0060] For example, the first cutoff frequency could be 10kHz, so that the neutral point voltage V n This minimizes noise while fully detecting ripple components. Furthermore, the first low-pass filter can be implemented as a hardware filter with a first cutoff frequency set via analog circuitry, thus minimizing the voltage V at the neutral point N. n It can achieve a high processing speed when performing preliminary filtering.

[0061] Furthermore, the controller 100 may further include a high-pass filter 192, which receives the first voltage signal V. n1 As the input signal, and outputting the first voltage signal Vn1 The second voltage signal V with a frequency exceeding the second cutoff frequency n2 The second cutoff frequency is lower than the first cutoff frequency. The high-pass filter 192 can suppress the first voltage signal V that has passed through the first low-pass filter 191. n1 A signal with a frequency lower than the second cutoff frequency, and a second voltage signal V with an output frequency exceeding the second cutoff frequency. n2 .

[0062] In this case, in order to obtain the voltage V from the neutral point N n After removing the DC component, the second cutoff frequency can be 0Hz, and the second voltage signal V passes through the first low-pass filter 191 and the high-pass filter 192. n2 This includes ripple components with values ​​between the first and second cutoff frequencies. Therefore, the damping controller 190 can be based on a second voltage signal V contained in the frequency band between the first and second cutoff frequencies. n2 To generate the compensation duty cycle D for resonance suppression. comp2 *

[0063] Meanwhile, unlike the first low-pass filter, the high-pass filter can be implemented as a software filter with a second cutoff frequency set via a software algorithm. Therefore, the cutoff frequency can be precisely set to remove the DC component. Furthermore, by combining the first low-pass filter 191 (a hardware filter) and the high-pass filter (a software filter), the first low-pass filter 191 can quickly remove voltage signals exceeding the first cutoff frequency, reducing the computational load on the high-pass filter 192. The high-pass filter 192 can then filter only the initially filtered first voltage signal V. n1 Filtering is performed instead of filtering the entire neutral point voltage V. n Filtering is performed to ensure fast and accurate extraction of frequency components.

[0064] Furthermore, based on the neutral point voltage V after passing through the first low-pass filter 191 and the high-pass filter... n (That is, the second voltage signal V) n2 When compensating for the duty cycle command D*, it is compared with the neutral point voltage command V, which is reflected in the calculation. n Compared to methods that calculate ripple components, offset errors can be reduced, and the frequency component that is only the resonant target can be effectively used as a control input value.

[0065] The damping controller 190 is based on a second voltage signal V that has passed through a first low-pass filter 191 and a high-pass filter 192. n2 and the voltage V of DC terminals D1 and D2 dc Generate compensation duty cycle D comp2 * and subtract the compensation duty cycle D from the duty cycle instruction D*.comp2 *, thereby compensating for the duty cycle instruction D*.

[0066] Therefore, the damping controller 190 can apply the proportional gain Kp to the second voltage signal V. n2 And it can be achieved by applying a second voltage signal V with a proportional gain Kp. n2 Divide by the voltage V of DC terminals D1 and D2 dc To generate the compensation duty cycle D comp2 *

[0067] The voltage controller 110 can be based on the neutral point voltage command V n *With the first voltage signal V n1 The error between them is used to generate the duty cycle command D*, thereby generating the neutral point voltage V. n Follow the neutral point voltage command V n The duty cycle instruction D*.

[0068] Furthermore, the controller 100 may further include a second low-pass filter 193, which acquires the first voltage signal V. n1 As the input signal, and outputting the first voltage signal V n1 The third voltage signal V with a frequency lower than the third cutoff frequency n3 If the value of the third cutoff frequency (e.g., 100Hz) is lower than the first cutoff frequency and higher than the second cutoff frequency, in this case, the voltage controller 110 can base its operation on the neutral point voltage command V. n *With the third voltage signal V n3 The error between them generates a duty cycle instruction D*. In one implementation, unlike the first low-pass filter 191, the second low-pass filter 193 can be implemented as a software filter with a third cutoff frequency set by a software algorithm. This allows for precise setting of the cutoff frequency.

[0069] Furthermore, by combining a first low-pass filter 191, which functions as a hardware filter, and a second low-pass filter 193, which functions as a software filter, the first low-pass filter 191 quickly removes voltage signals exceeding the first cutoff frequency, thereby reducing the computational load on the second low-pass filter 193. The second low-pass filter 193 only processes the filtered first voltage signal V. n1 Filtering is performed instead of filtering the entire neutral point voltage V. n Filtering is performed to ensure fast and accurate extraction of frequency components.

[0070] The third voltage signal V after passing through the second low-pass filter n3 It can be input to voltage controller 110 and used for voltage control of neutral point N. In this case, voltage controller 110 can control the voltage based on neutral point voltage command V.n *With the third voltage signal V n3 The error between them generates the duty cycle instruction D*.

[0071] refer to Figure 5 According to the implementation scheme, controller 100 can activate / deactivate duty cycle compensation via damping controller 190 based on the determination of resonance degradation. More specifically, the damping controller 190 compensates for the duty cycle D. comp2 During the compensation process for the duty cycle command, when resonance degradation is detected, the controller 100 can disable damping control to stop duty cycle compensation, and can activate damping control to perform duty cycle compensation when resonance degradation is determined to be resolved. This is to prevent the current control bandwidth of the external power supply 10 from being affected during the compensation period of the duty cycle command for resonance suppression, thereby preventing a larger resonance component from appearing on the external power supply 10 side. In particular, since it is impossible to check in advance whether the resonance will deteriorate due to duty cycle compensation before actual charging is performed, the following method is proposed in the implementation: monitoring the resonance occurrence trend, and automatically releasing the damping control performed by duty cycle command compensation when resonance degradation occurs, to prevent charging instability or damage to the vehicle and charging device.

[0072] In this case, whether the resonance has deteriorated can be determined by the neutral point voltage command V. n *With neutral point voltage V n The determination is made based on whether the error between them exceeds a preset threshold, and further, it can be based on the neutral point voltage command V. n *With neutral point voltage V n The number of times the error exceeds a preset threshold is used to determine this.

[0073] More specifically, see reference Figure 6 The controller 100 can receive the neutral point voltage command V n * and neutral point voltage V n When the voltage ripple corresponding to the error exceeds the preset threshold a at time point t1, damping control for reducing resonance is activated (ON). In this case, damping control can be performed by compensating the duty cycle generated by the damping controller 190 to the duty cycle command.

[0074] Controller 100 can begin responding to neutral point voltage command V n * and neutral point voltage V n The number of times the error exceeds a preset threshold 'a' is counted, and after the counting start time t2, the neutral point voltage command V... n * and neutral point voltage V nWhen the number of times the error exceeds the preset threshold a exceeds the preset reference number b, the controller 100 can stop compensating for the duty cycle command by disabling (OFF) the damping control.

[0075] Voltage command V n * and neutral point voltage V n The process of comparing the error between the two values ​​with a preset threshold a can be repeated according to a preset first cycle, and the first cycle can be, for example, 1ms.

[0076] Furthermore, the controller 100 can variably apply a threshold value for the amplitude of the voltage ripple, and for this purpose, can, according to a preset second cycle, output the neutral point voltage command V that occurs within the second cycle. n *With neutral point voltage V n The maximum value of the error between the two periods is stored as a new threshold and reset. In this case, the second period can be set to be shorter than the first period, for example, 33 μs. In this way, whether resonance degradation is determined according to the first period, and the threshold is reset and stored according to the relatively short second period, it is possible to detect ripple in the resonant frequency band while reducing the computational load on the controller 100.

[0077] In the above description, whether the damping control is activated (ON) is determined by the neutral point voltage command V. n *With neutral point voltage V n The error between them is determined by whether it exceeds a preset threshold α. However, according to another implementation, when the neutral point current I flowing into the motor from neutral point N... n Damping control can be activated when the current is less than the preset first reference current value. (See below for further details.) Figure 7 Describe the first reference current value.

[0078] The following will describe a method for controlling the charging system according to the above description.

[0079] Figure 7 This is a flowchart illustrating a method for controlling a charging system according to an embodiment of the present invention.

[0080] refer to Figure 7 First, the controller 100 can determine whether to execute the voltage control mode (step S701). Here, the voltage control mode is a mode in which the voltage of the neutral point N is controlled by receiving charging current from an external power source via the neutral point N to perform charging, and can be controlled by, for example, the voltage V of the neutral point N. n Determine whether to execute voltage control mode.

[0081] When the neutral point current I flows into the motor from the neutral point N nWhen the current is less than the preset first reference current value (e.g., -30A) (yes in step S703), the controller 100 can operate as a compensation duty cycle command (S704).

[0082] During the compensation period of the duty cycle command, if the neutral point current I... n If the second reference current value (e.g., -20A) is exceeded (which exceeds the first reference current value) (step S705 is yes), then the controller 100 can stop the duty cycle command compensation and wait (step S702) until the neutral point current I... n It becomes less than the preset first reference current value. On the other hand, if the neutral point current I... n If the current does not exceed the second reference current value (No in step S705), the controller 100 can determine that the resonance suppression is not complete and can continue to compensate for the duty cycle command (step S704).

[0083] During the operation of damping control via duty cycle compensation (step S706 is yes), controller 100 can determine whether the voltage ripple exceeds a preset threshold (step S707). In this case, the neutral point voltage command V can be used. n *With neutral point voltage V n The difference between them determines the voltage ripple.

[0084] The controller 100 can count the number of times the voltage ripple exceeds the threshold (step S708). If the number of counts exceeds the preset reference number as the count accumulates (step S709 is yes), the damping control can be terminated when resonance degradation is determined (step S710).

[0085] In the above description, the first and second reference values ​​for the neutral point current are negative. It should be noted that this is because the inverter senses a positive current flowing from the motor to the neutral point, but during charging, current flows from the neutral point to the motor, therefore the neutral point current is considered negative. Therefore, from a different perspective, if the charging current flowing from the neutral point to the motor during charging is positive, the concepts of exceeding and falling below the reference values ​​in the above description should be reversed.

[0086] Meanwhile, in the above implementation, the start and stop of compensation are determined by comparing the neutral point current with the first and second reference values. On the other hand, other implementations may allow continuous compensation to be performed regardless of the reference values.

[0087] According to various embodiments of the present invention as described above, when the battery voltage is higher than the voltage supplied from an external charging facility, the battery can be charged by using a motor and an inverter to boost the supplied voltage without the need for an additional boost converter.

[0088] In addition, it can reduce resonance caused by current disturbances from the external charging device during battery charging, thereby stabilizing battery charging and reducing durability damage to the motor and inverter during charging.

[0089] The effects that can be obtained from the present invention are not limited to those described above, and those skilled in the art can clearly understand other effects not mentioned from the following description.

[0090] Although preferred embodiments of the invention have been disclosed for illustrative purposes, those skilled in the art will understand that various modifications, additions, and substitutions may be made without departing from the scope and spirit of the invention as disclosed in the appended claims.

Claims

1. A charging system for an electric vehicle, comprising: An electric motor, which includes multiple corresponding windings; An inverter comprising multiple branches connected to one end of each of a plurality of windings and to a plurality of switching elements, and a DC terminal. The battery is connected to the DC terminal. A neutral point capacitor is connected to the neutral point of a motor in which the other ends of multiple windings are interconnected. as well as The controller is configured to: when the charging current of the external power supply is provided to the neutral point of the motor, control the duty cycle of multiple switching elements based on the duty cycle command that makes the voltage of the neutral point follow the preset neutral point voltage command, and selectively compensate the duty cycle command based on the error between the neutral point voltage command and the voltage of the neutral point.

2. The charging system for electric vehicles according to claim 1, wherein, The controller uses a voltage signal extracted from the neutral point voltage and contained in a preset frequency band to compensate for the duty cycle command.

3. The charging system for electric vehicles according to claim 1, wherein, The controller includes a first low-pass filter, which is configured to receive the voltage of the neutral point as an input signal and output a first voltage signal in the input signal with a frequency lower than a preset first cutoff frequency.

4. The charging system for electric vehicles according to claim 3, wherein, The first cutoff frequency includes 10 kHz.

5. The charging system for electric vehicles according to claim 3, wherein, The first cutoff frequency is set using analog circuitry.

6. The charging system for electric vehicles according to claim 3, wherein, The controller further includes a high-pass filter configured to receive a first voltage signal as an input signal and output a second voltage signal in the first voltage signal whose frequency exceeds a second cutoff frequency, wherein the value of the second cutoff frequency is lower than the first cutoff frequency.

7. The charging system for electric vehicles according to claim 6, wherein, The second cutoff frequency includes 0Hz.

8. The charging system for electric vehicles according to claim 6, wherein, The second cutoff frequency is set using a software algorithm.

9. The charging system for electric vehicles according to claim 6, wherein, The controller compensates for the duty cycle command based on the voltage between the second voltage signal and the DC terminal.

10. The charging system for electric vehicles according to claim 9, wherein, The controller generates a duty cycle command based on the error between the neutral point voltage command and the first voltage signal.

11. The charging system for electric vehicles according to claim 1, wherein, During the duty cycle command compensation period, if the error between the neutral point voltage command and the neutral point voltage exceeds a preset threshold, the controller stops compensating for the duty cycle command.

12. The charging system for electric vehicles according to claim 11, wherein, During the duty cycle command compensation period, if the number of times the error between the neutral point voltage command and the neutral point voltage exceeds the preset threshold exceeds a preset reference number, the controller stops compensating for the duty cycle command.

13. The charging system for electric vehicles according to claim 12, wherein, When compensating for the duty cycle command, the controller compares the error between the neutral point voltage command and the neutral point voltage with the preset threshold according to a preset first cycle.

14. The charging system for an electrified vehicle according to claim 13, wherein, The controller resets the maximum value of the error between the neutral point voltage command generated in the second cycle and the neutral point voltage to a threshold according to a preset second cycle, the second cycle being shorter than the preset first cycle.

15. The charging system for electric vehicles according to claim 1, wherein, The controller compensates for the duty cycle command based on the voltage and charging current between the DC terminals.

16. The charging system for electric vehicles according to claim 1, wherein, The controller individually controls the duty cycle of multiple switching elements connected to each of the multiple branches based on duty cycle commands and the phase current flowing through each of the multiple windings.

17. The charging system for electric vehicles according to claim 1, wherein, The controller controls the duty cycle of the switching elements by pulse width modulation that sequentially turns multiple branches on and off.

18. A method for controlling a charging system for an electrified vehicle, the charging system comprising a motor having a plurality of corresponding windings, an inverter having a plurality of branches connected to one end of each of the plurality of windings and connected to a plurality of switching elements and a DC terminal, a battery connected to the DC terminal, and a neutral point capacitor connected to the neutral point of the motor interconnected with the other ends of the plurality of windings, the method comprising: When the charging current of the external power supply is provided to the neutral point of the motor, the duty cycle of multiple switching elements is controlled based on the duty cycle command that makes the voltage of the neutral point follow the preset neutral point voltage command. Based on the error between the neutral point voltage command and the neutral point voltage, the duty cycle command is selectively compensated.

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