Safety charging system for electric vehicle and safety charging method thereof

Abstract

The present application provides a safe charging system for an electric vehicle and a safe charging method thereof. The safe charging system includes a motor and an inverter that raise a voltage from a fast battery charger for charging a high-voltage battery, a current variation amount sensor configured to detect a variation amount of a current flowing into a motor coil from the fast battery charger, and a controller configured to determine that a rotor of the motor rotates when the variation amount of the current detected in the current variation amount sensor is greater than a reference value and perform control to interrupt a charging process.

Description

Technical Field

[0001] This invention relates to a safe charging system and method for electric vehicles. More specifically, this invention relates to a safe charging system and method for electric vehicles that can safely perform the battery charging process, for example, by operating an inverter and a motor as boost converters, to increase the charging voltage. Background Technology

[0002] Generally speaking, hybrid vehicles and electric vehicles are types of environmentally friendly cars, which include high-voltage batteries, drive motors powered by high-voltage batteries, and inverters that convert alternating current (AC) to direct current (DC) during the charging and discharging of high-voltage batteries.

[0003] In particular, environmentally friendly vehicles include a charging circuit system that converts power from an external power source (e.g., a fast battery charger) into rechargeable DC power, thereby generating a charging current for the high-voltage battery.

[0004] For reference, a system that rapidly charges a high-voltage battery by increasing the charging voltage (e.g., from 400V to 800V) is called a multi-charger system. Using a multi-charger system, a vehicle's 800V high-voltage battery can be rapidly charged from a 400V fast battery charger.

[0005] Figure 1 Showing according to such Figure 1 The example of a charging circuit in a prior art multi-charging system is shown, in which a controller turns on and off a relay 12 to form a fast charging path when an external fast battery charger 10 is connected to the charging circuit of a vehicle that is in a stopped state.

[0006] The voltage (e.g., 400V) supplied from the fast battery charger 10 is then boosted (e.g., 800V) by the motor 20 and inverter 30, which act as boost converters, so that the capacitor 40 and the high-voltage battery 50 can be charged quickly.

[0007] Figure 1 The motor 20 shown illustrates the equivalent circuit of a three-phase motor and can be represented by an a-phase inductor La, a b-phase inductor Lb, and a c-phase inductor Lc.

[0008] Therefore, when the charging current from the fast battery charger 10 passes through the motor 20, the three-phase currents Ia, Ib, and Ic flow in the motor coils via a pulse width modulation (PWM) control method to generate a three-phase force (torque) that moves the rotor. However, the sum of the three-phase forces becomes "zero," causing the rotor of the motor 20 to not move, thus keeping the vehicle stationary for safe charging.

[0009] However, the amount of current of each phase is varied due to a design deviation problem of a motor coil and an error or a failure of a current sensor, and when the amount of current is varied, the sum of three-phase forces does not become "zero", so the rotor of the motor moves. Therefore, the vehicle moves during charging due to the movement of the rotor of the motor, thereby threatening the safety of a user.

[0010] In general, the rotation of the motor, i.e., the movement of the rotor of the motor, can be known through a sensing value of a position sensor. However, in the case where the position sensor fails, it is not known whether the rotor of the motor moves.

[0011] Accordingly, there is a need for a method of determining whether the motor rotates during charging and interrupting the charging to secure safety when it is determined that the motor rotates thereafter, regardless of a position sensor. SUMMARY

[0012] The present application is directed to solving the above problems associated with the prior art.

[0013] In one aspect, the present application provides a safe charging system for an electric vehicle and a safe charging method thereof, which is capable of interrupting charging to secure safety when the movement of the rotor of the motor is detected, in the case where an inverter and a motor operate as a boost converter to raise a charging voltage and charge a battery.

[0014] The objects of the present application are not limited to the above-mentioned objects, other objects of the present application which are not mentioned can be understood from the following description, and will also be obvious to those skilled in the art to which the present application pertains by the embodiments of the present application. Furthermore, the objects of the present application can be achieved by the means described in the appended claims and combinations thereof.

[0015] According to one exemplary embodiment of the present application, a safe charging system for an electric vehicle includes a motor and an inverter which raise a voltage for charging a high-voltage battery from a fast battery charger, a current variation amount sensor configured to detect a variation amount of current flowing into a motor coil from the fast battery charger, and a controller configured to determine that the rotor of the motor rotates when the variation amount of current detected in the current variation amount sensor is greater than a reference value, and perform a control of interrupting a charging process.

[0016] In particular, to control the interrupting of the charging process, the controller can be configured to compare three-phase current values Ia, Ib, and Ic flowing in the motor coil, and when the difference between the three-phase current values Ia, Ib, and Ic is similar to each other within a reference range, the controller can be configured to simultaneously turn off three-phase current control by a pulse width modulation (PWM) control method.

[0017] According to another exemplary embodiment of the present application, a safe charging method for an electric vehicle includes: a charging operation of raising a voltage supplied from a fast battery charger by a motor and an inverter, and charging a high voltage battery with the raised voltage; detecting an amount of change in current flowing in a motor coil by a current change amount sensor during the charging operation; comparing, by a controller, a reference value with the amount of change in current detected in the current change amount sensor; determining, by the controller, that a rotor of the motor rotates when the amount of change in current is greater than the reference value as a result of the comparison, and performing a control of interrupting the charging operation.

[0018] In particular, the control of interrupting the charging operation can include comparing three-phase current values Ia, Ib and Ic flowing in the motor coil, and simultaneously turning off three-phase current control by a pulse width modulation (PWM) control method when differences between the three-phase current values Ia, Ib and Ic are similar to each other within a reference range.

[0019] When the amount of change in current is less than the reference value, the control method can further include determining, by the controller, that the rotor of the motor does not rotate and maintaining the charging operation.

[0020] Other aspects and preferred embodiments of the present application are discussed below.

[0021] It should be understood that the term "vehicle" or "vehicular" or other similar terms used herein generally include motor vehicles, such as passenger vehicles including sport utility vehicles (SUV), buses, trucks, various commercial vehicles, passenger vehicles including minivans, boats, and ships including pleasure boats and naval vessels, seacraft, aircraft, and the like, and includes hybrid vehicles, electric vehicles, plug-in hybrid electric vehicles, hydrogen-powered vehicles, and other alternative fuel vehicles (e.g., those powered by fuels other than petroleum products). As used herein, a hybrid vehicle is a vehicle having two or more sources of power, such as a vehicle having both gasoline power and electric power.

[0022] The above and other features of the present application are discussed below. BRIEF DESCRIPTION OF DRAWINGS

[0023] The above and other features of the present application are discussed below.

[0024] Figure 1 is a diagram illustrating a charging circuit of a multiple charging system according to the related art;

[0025] Figure 2 is a block diagram illustrating a safe charging system for an electric vehicle according to the present application;

[0026] Figure 3is a flowchart illustrating a safety charging method for an electric vehicle according to the present application; and

[0027] Figure 4 is a waveform diagram illustrating an example of detecting a motor current variation amount during charging.

[0028] It is to be understood that the drawings are not drawn to scale, but are schematically simplified to present various preferred features to show the basic principles of the present application. The specific design features of the present application disclosed herein, including, for example, specific dimensions, directions, positions, and shapes, will be determined in part by the specific circumstances of the application and use.

[0029] In these drawings, the reference numerals represent the same or equivalent parts of the present application throughout the drawings. DETAILED DESCRIPTION

[0030] Hereinafter, exemplary embodiments of the present application will be described in detail with reference to the accompanying drawings.

[0031] As described above with reference to Figure 1 the voltage supplied from the fast battery charger 10 as an external power source (for example, 400V) is raised (for example, 800V) by the motor 20 and the inverter 30 as a boost converter, so that the capacitor 40 and the high-voltage battery 50 can be quickly charged.

[0032] Therefore, when the charging current from the fast battery charger 10 passes through the motor 20, three-phase currents Ia, Ib, and Ic flow in the motor coil by a pulse width modulation (PWM) control method to generate a three-phase force (torque) of the moving rotor. However, the sum of the three-phase forces becomes "zero" so that the rotor of the motor 20 does not move, and thus the vehicle remains in a stationary state for safety charging.

[0033] However, due to a design deviation problem of the motor coil and an error or failure of the current sensor, the amount of current of each phase is varied, and when the amount of current is varied, the sum of the three-phase forces does not become "zero", so that the rotor of the motor moves. Therefore, due to the movement of the rotor of the motor, the vehicle moves during charging, thereby threatening the safety of the user.

[0034] Accordingly, the present application focuses on determining whether the motor rotates when the motor and the inverter work as a boost converter to raise the voltage supplied from the fast battery charger, and when the movement of the rotor of the motor is detected, the charging can be interrupted to prevent safety accidents.

[0035] Figure 2 is a block diagram illustrating a safety charging system for an electric vehicle according to the present application, Figure 3 is a flowchart illustrating a safety charging method for an electric vehicle according to the present application.

[0036] As shown in Figure 2 The safety charging system for an electric vehicle according to the present application includes a quick battery charger 10 as an external power source, a motor 20 and an inverter 30 as a boost converter configured to raise a voltage (e.g., 400V) supplied from the quick battery charger 10 to a voltage (e.g., 800V), a capacitor 40 and a high-voltage battery 50 as a target of charging of the raised voltage, a current variation amount sensor 60 for detecting a current variation amount flowing in a motor coil during charging, and a controller 70 for determining whether the motor rotates based on the detected current variation amount and performing control to interrupt the charging process.

[0037] The current variation amount sensor 60 can include a current sensor that detects a variation amount of a current flowing from the quick battery charger 10 into the motor coil. The current variation amount sensor 60 can detect a variation amount of an output current flowing between the motor 20 and the inverter 30.

[0038] The controller 70 is configured to compare the variation amount of the current detected by the current variation amount sensor 60 with a reference value for determining rotation of the motor. When the detected current variation amount is greater than the reference value, the controller 70 is configured to determine that a rotor of the motor is rotating to perform control to interrupt the charging process.

[0039] In other words, the controller 70 is configured to compare all of the variation amounts of three-phase currents flowing in the motor coil (as a variation amount of a parent current detected by the current variation amount sensor 60) with a reference value for determining rotation of the motor, and when the detected current variation amount is greater than the reference value, the controller 70 is configured to determine that a rotor of the motor is rotating to perform control to interrupt the charging process.

[0040] In particular, to control the interruption of the charging process, the controller 70 is configured to compare three-phase current values Ia, Ib, and Ic flowing in the motor coil, and when the three-phase current values Ia, Ib, and Ic fall within a reference range close to zero and are similar to each other, the controller 70 is configured to simultaneously turn off three-phase current control by a pulse width modulation (PWM) control method.

[0041] Hereinafter, a safety charging method of the present application based on the above-described configuration will be described in detail.

[0042] First, the motor 20 and the inverter 30 as a boost converter raise a voltage (e.g., 400V) supplied from the quick battery charger 10 as an external power source to a voltage (e.g., 800V), and quickly charge the capacitor 40 and the high-voltage battery 50.

[0043] During the above charging process, the current variation sensor 60 monitors and detects the variation amount of the current flowing in the motor coil (step S101).

[0044] Subsequently, the controller 70 compares the reference value with the variation amount of the current detected in the current variation sensor 60 (step S102).

[0045] That is, the controller 70 compares the reference value for determining the rotation of the motor with all the variation amounts of the three-phase current flowing in the motor coil, which is the variation amount of the current detected by the current variation sensor 60.

[0046] In this case, during the charging process, the current value applied to the motor (i.e., the coil of the three-phase motor) is constant. However, as the inductance value of the motor coil changes due to the magnetic flux of the permanent magnet of the rotor of the motor when the rotor of the motor rotates, and the current value flowing in the motor coil also changes over time.

[0047] Therefore, during the charging process, when the current value applied to the motor (i.e., the coil of the three-phase motor) is constant, it can be determined that the non-rotating state in which the rotor of the motor does not rotate, however, when the variation amount of the current flowing in the motor coil and changing over time is greater than the reference value, it can be determined that the rotor of the motor rotates.

[0048] Therefore, as a result of the comparison in S102, when the variation amount of the current is greater than the reference value, the controller 70 determines that the rotor of the motor is rotating (step S103), and in order to prevent the movement of the vehicle due to the rotation of the motor, performs control to interrupt the charging process (step S104).

[0049] Therefore, when the motor is determined to be rotating, the controller 70 can interrupt the charging process to prevent safety accidents from occurring due to the movement of the vehicle during charging.

[0050] In this case, the charging interruption controlled by the controller 70 can be achieved by interrupting control of the three-phase current flowing in the motor coil through the PWM control method.

[0051] However, in the case where the control of the three-phase current is interrupted and thus there is a large difference in the value of the three-phase current, when the control of the three-phase current is turned off in a random order, additional rotation of the motor can occur.

[0052] Therefore, the control of interrupting the charging process includes comparing the three-phase current values Ia, Ib and Ic flowing in the motor coil (step S105), determining whether the differences of the three-phase current values Ia, Ib and Ic fall within a reference range close to zero and are similar to each other (step S106). When the differences between the three-phase current values Ia, Ib and Ic are similar to each other within the reference range close to zero, the three-phase current control by the PWM control method is simultaneously turned off (step S107).

[0053] As described above, when the differences between the three-phase current values Ia, Ib and Ic flowing in the motor coil are similar to each other within the reference range close to zero, the three-phase current control by the PWM control method is simultaneously turned off to prevent the occurrence of the additional rotation of the motor.

[0054] As a result of the comparison of step S102, when the amount of change of the current is less than the reference value, the controller 70 determines that the rotor of the motor is in a non-rotating state in which the rotor of the motor does not rotate, to maintain the charging process.

[0055] As described above, in the electric vehicle in which the motor and the inverter operate as a step-up converter to increase the charging voltage and charge the battery, the amount of change of the current of the motor coil is monitored to detect whether the motor rotates, and when it is determined that the motor rotates, the charging is interrupted, so that a safety accident can be prevented from occurring due to the movement of the vehicle during the charging process.

[0056] The present application provides the following effects through the above-described problem solving method.

[0057] According to the present application, in the electric vehicle in which the motor and the inverter operate as a step-up converter to increase the charging voltage and charge the battery, the amount of change of the current of the motor coil is monitored to detect whether the motor rotates, and when it is determined that the motor rotates, the charging is interrupted, so that a safety accident can be prevented from occurring due to the movement of the vehicle during the charging process.

[0058] Although embodiments of the present application have been described in detail, the scope of the present application is not limited to the embodiments, and various modifications and improvements further belong to the scope of the present application using the basic concept of the present application defined by the appended claims designed by those skilled in the art.

Claims

1. A safe charging system for electric vehicles, comprising: A motor and an inverter that amplify the voltage from a fast battery charger used for charging a high-voltage battery. A current change sensor configured to detect the change in current flowing into the motor coil from a fast battery charger; as well as The controller is configured as follows: When the change in current detected by the current change sensor is greater than the reference value, it is determined that the motor rotor is rotating. Control the interruption of the charging process.

2. The safe charging system for electric vehicles according to claim 1, wherein: The controller is configured to compare the three-phase current values ​​flowing in the motor coils. When the difference between the three-phase current values ​​is within the reference range, the controller is configured to disable three-phase current control via pulse width modulation control.

3. The safe charging system for electric vehicles according to claim 1, wherein: The controller is configured to determine that the motor rotor does not rotate when the change in current is less than a reference value, and to maintain an increase in the voltage supplied from the fast battery charger.

4. A safe charging method for electric vehicles, comprising: The motor and inverter boost the voltage supplied from the fast battery charger and use the boosted voltage to charge the high-voltage battery, wherein boosting the voltage includes detecting the change in current flowing from the fast battery charger into the motor coil via a current change sensor. The controller compares the reference value with the change in current. When the change in current is determined to be greater than the reference value, the controller determines that the motor rotor is rotating and executes a control to interrupt the charging operation.

5. The safe charging method for electric vehicles according to claim 4, wherein, The control for performing the interrupted charging operation includes: Compare the three-phase current values ​​flowing in the motor coils; When it is determined that the difference between the three-phase current values ​​is within the reference range, the three-phase current control performed by the pulse width modulation control method is turned off.

6. The safe charging method for electric vehicles according to claim 4, further comprising: When the change in current is determined to be less than the reference value, the controller determines that the motor rotor will not rotate and maintains the voltage supplied from the fast battery charger.

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