KR20140009941A - Power cabel breaking detection method of inverter system - Google Patents

Abstract

A power cable breaking detection method for an inverter system according to an embodiment of the present invention comprises a step of detecting the voltage of a battery; a step of detecting a DC link voltage; a step of detecting the breaking of a power cable based on the difference between the battery voltage and the DC link voltage; and a step of stopping a motor when the breaking of the power cable is detected. Also, the power cable breaking detection method for an inverter system according to the embodiment of the present invention comprises a step of checking the driving speed of the motor; a step of determining if the driving speed of the motor is higher than a reference level; a step of determining if a phase current command value for driving the motor is higher than a first reference value when the driving speed of the motor is higher than the reference level; a step of determining if an actual phase current supplied to the motor is lower than a second reference value when the phase current command value is higher than the first reference value; and a step of stopping the motor when the actual phase current is lower than the second reference value. [Reference numerals] (160) Inverter controller

Description

Detect detection of power cable in inverter system {POWER CABEL BREAKING DETECTION METHOD OF INVERTER SYSTEM}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an inverter, and more particularly, to a method of detecting a non-engagement of a high voltage cable included in an inverter.

Inverter system, a motor controller used in eco-friendly vehicles, is an ESA (Electric / Electronic Sub Assembly) that converts high voltage DC power into AC or DC power for motor control. Belong to the main parts.

As described above, the permanent magnet motor is applied to the eco-friendly vehicle as a driving means. The motor applied as a driving means to the eco-friendly vehicle is driven by a phase current transmitted through a first high voltage power cable from an inverter for converting a DC voltage into a three phase voltage by a PWM signal of a controller.

In addition, the inverter converts the DC link voltage transmitted through the second high voltage power cable into a three-phase voltage by opening and closing the main relay.

Therefore, when any one of the first power cable connecting the inverter and the motor or the second power cable connecting the high voltage battery and the inverter is disconnected, the motor is not smoothly driven and high voltage / high current is applied to the system. A fatal problem arises that is abandoned and damages the entire inverter system.

1 is a view showing the separation detection device of the power cable in the inverter system according to the prior art.

Referring to FIG. 1, a conventional separation detection apparatus for a power cable is connected to a power cable 10 and the power cable 10 to detect a separation that transmits a signal according to whether the power cable 10 is disconnected to a controller. Device 20.

The separation detection device 20 is connected to the power cable 10, and transmits a digital signal to a controller according to whether the power cable 10 is connected.

That is, in the related art, there is a device for confirming whether the power cable 10 is separated separately from the power cable 10 by hardware, and checking whether the power cable is disconnected in real time using a digital signal output from the device. It was.

However, since the separation detection device of the power cable as described above detects in hardware whether or not the power cable is disconnected, there is a problem not only in terms of price but also in space.

In addition, there is a problem that the separation detection device for power cables as described above has a possibility of malfunction due to external factors.

The embodiment provides a method of detecting the separation of a power cable in an inverter system capable of detecting whether or not a power cable is disconnected (non-fastened) by software without the hassle of adding additional hardware.

Further, in the embodiment, it is provided a method of detecting a separation of a power cable capable of verifying whether or not the hardware operates normally in a system equipped with hardware capable of detecting the separation of the power cable.

It is to be understood that the technical objectives to be achieved by the embodiments are not limited to the technical matters mentioned above and that other technical subjects not mentioned are apparent to those skilled in the art to which the embodiments proposed from the following description belong, It can be understood.

In the inverter system according to the embodiment, the separation detection method of the power cable may include detecting a battery voltage; Detecting a DC link voltage; Detecting whether a power cable is disconnected based on the difference value between the detected battery voltage and the DC link voltage; And if it is detected that the power cable is disconnected, stopping the motor drive.

The detecting of the disconnection may include calculating a difference value between the battery voltage and the DC link voltage, comparing the calculated difference value with a predetermined reference value, and the difference value being the reference value. If greater than the value, detecting that the power cable is disconnected; and if the difference is less than the reference value, detecting that the power cable is normally connected.

The power cable is a DC link power cable for supplying DC power charged from the battery to the inverter.

The method may further include checking a state of the main relay that regulates the DC power supplied to the inverter. The detecting of the disconnection of the power cable may be performed when the state of the main relay is turned on. Is performed.

The stopping of the motor driving may include changing a state of the main relay to an off state and forcibly discharging a capacitor included in the inverter.

The step of forcibly discharging may include applying a d-axis current, which is a magnetic flux component current, to 0 and a q-axis current, which is a torque component current, to the motor.

On the other hand, the disconnection detection method of the power cable in the inverter system according to the embodiment includes the steps of checking the drive speed of the motor; Determining whether a driving speed of the checked motor exceeds a reference speed; If the driving speed exceeds a reference speed, determining whether a phase current command value for driving the motor is greater than a first reference value; If the phase current command value is greater than the first reference value, determining whether the actual phase current supplied to the motor is less than a second reference value; And if the actual phase current is less than the second reference value, stopping the motor driving.

In addition, the actual phase current is a current flowing through the three-phase power cable to transfer the three-phase AC power converted through the inverter to the motor.

The stopping of the motor may include determining that the three-phase power cable is disconnected when the actual phase current is less than the second reference value, and as the three-phase power cable is disconnected. Stopping the drive.

In addition, if the actual phase current is greater than the second reference value, and confirming that the three-phase power cable is normally connected, and further comprising the step of continuously supplying drive power to the motor.

In addition, the driving of the motor may include stopping the q-axis current as the torque component current to 0 and applying the d-axis current as the magnetic flux component current to force discharging a capacitor included in the inverter. do.

According to the embodiment, by attaching a hardware device to a conventionally used power cable, it can be diagnosed by software, rather than a method of detecting the non-fastening state of the power cable, so that not only the effect in terms of price Therefore, malfunctions that may be caused by external factors can be prevented in advance.

1 is a view showing the separation detection device of the power cable in the inverter system according to the prior art.
2 is a view showing the configuration of an inverter system according to an embodiment.
3 is a diagram illustrating a first power cable according to an embodiment.
4 is a diagram illustrating a second power cable according to an embodiment.
5 is a diagram illustrating a separation detection method of a first power cable according to an exemplary embodiment.
6 is a diagram illustrating a separation detection method of a second power cable according to an embodiment.

The following merely illustrates the principles of the invention. Thus, those skilled in the art will be able to devise various apparatuses which, although not explicitly described or shown herein, embody the principles of the invention and are included in the concept and scope of the invention. Furthermore, all of the conditional terms and embodiments listed herein are, in principle, only intended for the purpose of enabling understanding of the concepts of the present invention, and are not to be construed as limited to such specifically recited embodiments and conditions do.

It is also to be understood that the detailed description, as well as the principles, aspects and embodiments of the invention, as well as specific embodiments thereof, are intended to cover structural and functional equivalents thereof. It is also to be understood that such equivalents include all elements contemplated to perform the same function irrespective of the currently known equivalents as well as the equivalents to be developed in the future, i.e., the structure.

2 is a view showing the configuration of an inverter system according to an embodiment.

Referring to FIG. 2, the inverter system includes a battery 110, a main relay 120, an inverter 130, a motor 140, a battery management system (BMS), and an inverter controller 160.

The battery 110 supplies driving power to an electric vehicle (not shown).

In particular, the battery 110 supplies DC power to the capacitor C provided in the inverter 130 inside the inverter system.

The battery 110 may be a high voltage battery, and may be formed of a plurality of unit cells.

The plurality of unit cells may be managed by a battery management system (BMS) 150 to maintain a constant voltage, and the battery 110 emits a constant voltage under the control of the battery management system 150. can do.

For example, the battery management system 150 may detect the voltage of the battery 110 and transfer it to the inverter controller 160.

In addition, when the voltage of the battery 110 falls below a predetermined lower limit, the inverter controller 160 may supply DC power stored in a capacitor included in the electric vehicle to the battery 110.

On the contrary, when the voltage of the battery 110 rises above the upper limit, the inverter controller 160 may supply the DC power stored in the battery 110 to the capacitor in the electric vehicle.

The battery 110 may be a secondary battery that can be changed into a charged state and a discharged state according to an operating state.

The main relay 120 is connected to a predetermined power line connected to the battery 110 to intercept the DC power output through the battery 110.

Although only one main relay is disposed in the power line in the drawing, this is only an example, and the number of the main relays may be increased.

For example, the main relay may include a first main relay connected to the positive terminal for interrupting the direct current power, and a second main relay connected to the negative terminal for interrupting the direct current power.

The inverter 130 receives DC power from the battery 110 according to the switching state of the main relay 120.

In addition, the inverter 130 converts the DC power supplied from the battery 110 into AC power and supplies it to the motor 140.

AC power converted by the inverter 130 is preferably a three-phase AC power.

In particular, the inverter 130 is made of an Insulated Gate Bipolar Transistor (IGBT), and is supplied from the battery 110 by executing PWM (Pulse Width Modulation) switching according to a control signal applied from the inverter controller 160 to be described later. Phase power is converted to drive the motor 140.

The motor 140 includes a stator (not shown) that is fixed without rotation, and a rotating rotor (not shown). The motor 140 receives AC power supplied through the inverter 130.

The motor 140 may be, for example, a three-phase motor. When a voltage variable / frequency variable each phase AC power is applied to the coil of the stator of each phase, the rotation speed of the rotor is changed according to the applied frequency.

The motor 140 may be in various forms, such as an induction motor, a BLDC motor, a reluctance motor, and the like.

On the other hand, one side of the motor 140 may be provided with a drive gear (not shown). The drive gear converts the rotational energy of the motor 140 according to the gear via. The rotational energy output from the drive gear is transmitted to the front and / or rear wheels to make the electric vehicle move.

Although not shown in the drawings, the electric vehicle may further include an electronic controller for controlling electronic devices throughout the electric vehicle. An electronic control unit (not shown) controls the operation and display of each device. It is also possible to control the above-described battery management system.

The electronic control unit includes an inclination angle sensing unit (not shown) for sensing the inclination angle of the electric vehicle, a speed sensing unit (not shown) for sensing the speed of the electric vehicle, a brake sensing unit (not shown) (Driving mode, reverse mode, neutral mode, parking mode, and the like) based on a detection signal from an accelerator sensor (not shown) or the like depending on the operation of the pedal. The operation command value at this time may be, for example, a torque command value or a speed command value.

Meanwhile, the electric vehicle according to the embodiment of the present invention may be a concept including a hybrid electric vehicle using a battery and a motor while using an engine as well as a battery and a motor.

At this time, the hybrid electric vehicle may further include a transmission and a transmission capable of selecting at least one of a battery and an engine. On the other hand, a hybrid electric vehicle can be divided into a serial system in which the mechanical energy output from the engine is converted into electric energy to drive the motor, and a parallel system in which the mechanical energy output from the engine and the electric energy in the battery are used simultaneously.

The battery management system 150 allows the plurality of unit cells to maintain a constant voltage when the battery 110 includes a plurality of unit cells.

In addition, the battery management system 150 causes the voltage charged in the battery 110 to be discharged to the inverter 130 by the main relay 120.

The inverter controller 160 controls the operation of the inverter 130.

For example, the inverter controller 160 calculates a driving value for driving the motor 140 by using a current (three-phase current) supplied to the motor 140, and according to the calculated driving value. A switching signal (PWM signal) for controlling the inverter 130 is generated.

Accordingly, the inverter 130 selectively performs an on-off operation according to a switching signal generated through the inverter controller 160 to convert the DC power into AC power.

On the other hand, the inverter controller 160 determines the state of the power cable supplied with the DC power and AC power, and controls the power supplied to the motor 140.

In this case, the power cable includes a first power cable to which the DC power is supplied, and a second power cable to which the AC power is supplied.

3 is a diagram illustrating a first power cable according to an embodiment, and FIG. 4 is a diagram illustrating a second power cable according to an embodiment.

Referring to FIG. 3, the inverter system 100 includes a first power cable 200 that receives a DC power source (obviously, a DC-link voltage) from the battery 110 and supplies it to the inverter 130. do.

The first power cable 200 is connected to the positive terminal (+) and the negative terminal (-) of the battery 110, respectively, and accordingly the DC power supplied through the connected battery 110 is connected to the inverter ( 130).

At this time, if a problem occurs in the first power cable 200 (for example, disconnection, non-fastening, disconnection, etc. of the cable), the inverter 130 is not supplied with the normal DC power, and thus the motor 140 may cause a problem in driving.

Accordingly, the inverter controller 160 detects whether the first power cable 200 is disconnected, and if it is detected that the first power cable 200 is disconnected, the inverter controller 160 passes through the inverter 130 and the motor 140. Shut off the power supply.

The separation detection method of the first power cable 200 and the power cutoff method will be described in more detail below.

Next, referring to FIG. 4, the inverter system 100 includes a second power cable 300 for supplying the AC power converted through the inverter 130 to the motor 140.

That is, the inverter 130 supplies the converted three-phase AC power to the motor 140 through the second power cable 300-three-phase cable.

The second power cable 300 may be divided into three cables, respectively. Alternatively, three cables may be provided in one cable.

In addition, when a problem occurs in the second power cable 300 like the first power cable 200 (disconnected, disconnected, not fastened, etc.), the three-phase AC power converted through the inverter 130 is It may not be normally supplied to the motor 140, which may cause a great problem in the operation of the electric vehicle.

Accordingly, the inverter controller 160 detects whether the second power cable 300 is disconnected, and when it is detected that the second power cable 300 is disconnected, the power supplied to the motor 140. To block.

Hereinafter, the separation detection method of the first power cable 200 and the second power cable 300 and the operation of the inverter system 100 according to the separation detection will be described in more detail.

5 is a diagram illustrating a separation detection method of a first power cable according to an exemplary embodiment.

Referring to FIG. 5, the battery management system 150 checks the state of the main relay 120 (step 101).

That is, the battery management system 150 is a state in which the DC power stored in the battery 110 is being supplied to the inverter 130 as the electric vehicle is currently being driven, or as stopped, to the inverter 130. It is determined whether the DC power is not supplied.

Subsequently, the battery management system 150 determines whether the checked state of the main relay 120 is in an on state (step 102).

As a result of the determination (step 102), if the state of the main relay 120 is on, the battery management system 150 checks the voltage of the battery 110 (step 104).

That is, when the main relay 120 is in an on state, the battery management system 150 checks a voltage (for example, a rated voltage or output voltage of the battery) output from the battery 110.

Thereafter, the battery management system 150 detects a voltage, that is, a DC-link voltage, supplied to the inverter 130 through the first power cable 200 (step 105).

Thereafter, when the battery voltage and the DC-link voltage are detected, the battery management system 150 transmits the detected battery voltage and the DC link voltage to the inverter controller 160.

The inverter controller 160 detects a difference value between the battery voltage and the DC link voltage provided from the battery management system 150 and determines whether the detected difference value is greater than a preset reference value (step 106).

In other words, when the first power cable 200 is normally connected, the battery voltage and the DC link voltage should be equal to each other.

However, when the first power cable 200 is abnormally connected (disconnected, not fastened, disconnected, etc.), a difference occurs in the battery voltage and the DC link voltage.

In this case, a detection error may occur in the process of detecting the DC link voltage, and a difference may occur between the DC link voltage actually flowing through the first power cable 200 and the detected DC link voltage.

Accordingly, the error range according to the detection error is set as the reference value, and accordingly, it is determined whether a difference value between the battery voltage and the DC link voltage is greater than the reference value.

As a result of the determination (step 106), if the difference value is greater than the reference value, the inverter controller 160 determines that the first power cable 200 is abnormally connected (step 107).

That is, if the difference value is smaller than the reference value, the inverter controller 160 has a difference between the battery voltage and the DC link voltage, but this difference is due to a detection error generated during the detection of the DC link voltage. Be aware.

However, if the difference value is greater than the reference value, the inverter controller 160 recognizes that the difference is due to abnormal connection of the first power cable 200, not the difference due to the detection error.

In operation 108, the inverter controller 160 performs a forced discharge.

The forced discharge means forced discharge of power stored in a capacitor (DC capacitor) included in the inverter 130.

To this end, the inverter controller 160 changes the state of the main relay 120 to the off state. That is, the power supplied from the battery 110 is not transmitted to the inverter 130 according to the separation of the first power cable 200.

Thereafter, the inverter controller 160 forcibly discharges the power charged in the capacitor by the power previously supplied to the battery 110.

To this end, the inverter controller 160 controls the q-axis current which is the torque component current to 0 to the motor 140, and applies only the d-axis current which is the magnetic flux component current to discharge the voltage remaining in the capacitor.

As described above, when the state of the main relay is on, the inverter controller 160 activates a detection process of disconnecting the first power cable 200.

Thereafter, the inverter controller 160 compares the battery voltage with the DC link voltage, and accordingly determines that the first power cable 200 is disconnected when the error according to the comparison result is equal to or greater than a predetermined reference value. As a result, the forced discharge as described above is performed.

If the difference between the battery voltage and the DC link voltage is within the reference value (step 106), the inverter controller 160 determines that the first power cable 200 is normally connected.

6 is a diagram for describing a method of detecting a separation of a second power cable according to an exemplary embodiment.

Referring to FIG. 6, first, the inverter controller 160 checks the speed of the motor 140 (step 201).

The speed of the motor 140 is determined according to the frequency. When the frequency of the motor 140 is close to zero, the current of any one of three phase currents supplied to the motor 140 is within a range close to zero. A changing situation occurs.

Accordingly, the inverter controller 160 detects whether the second power cable 300 is disconnected only when the speed of the motor 140 is greater than or equal to a predetermined speed.

The inverter controller 160 determines whether the checked speed of the motor 140 exceeds a reference speed, which is a condition for detecting whether the second power cable 300 is disconnected (step 202).

As a result of the determination (step 202), if the speed of the motor 140 is less than or equal to the reference speed, the controller waits for a predetermined time (step 203) and returns to the step (201).

In addition, when the determination result (step 202), the speed of the motor 140 exceeds the reference speed, the command value for the phase current to be supplied to the motor 140 is checked (step 204).

Thereafter, the inverter controller 160 compares the checked phase current command value with a predetermined first reference value (step 205).

The first reference value is a theoretical current command value corresponding to the torque command, and may be substantially a value belonging to 50% of the theoretical current command value.

As a result of the comparison (step 205), if the phase current command value is less than or equal to the first reference value, the inverter controller 160 returns to step (203), where the phase current command value is greater than or equal to the first reference value. Wait until this happens.

In addition, when the comparison result (step 205), the phase current command value is greater than or equal to the first reference value, the inverter controller 160 detects the actual phase current flowing through the second power cable 300 (step 206). ).

In operation 207, the inverter controller 160 determines whether the detected actual phase current is equal to or less than a second reference value.

In this case, the second reference value may be a value near zero, and preferably, an error range may be set, and may be a value as large as 0 to the error range.

That is, when the second power cable 300 is abnormally connected, the actual phase current is zero. In this case, the actual phase current may have a value slightly larger than 0 even when the second power cable 300 is abnormally connected due to the residual current remaining in the second power cable 300 itself.

As a result, the inverter controller 160 sets the second reference value to a value near zero, which is greater than zero, with the above error range.

As a result of the determination (step 207), if the actual phase current is less than or equal to the second reference value, the inverter controller 160 determines that the second power cable 300 is abnormally connected (step 208).

In addition, the inverter controller 160 performs a forced discharge operation.

The forced discharge means forced discharge of power stored in a capacitor (DC capacitor) included in the inverter 130.

To this end, the inverter controller 160 changes the state of the main relay 120 to the off state. That is, the power supplied from the battery 110 is not transmitted to the inverter 130 according to the separation of the second power cable 300.

Thereafter, the inverter controller 160 forcibly discharges the power charged in the capacitor by the power previously supplied to the battery 110.

To this end, the inverter controller 160 controls the q-axis current which is the torque component current to 0 to the motor 140, and applies only the d-axis current which is the magnetic flux component current to discharge the voltage remaining in the capacitor.

On the other hand, if the determination result (step 207), the actual current is greater than the second reference value, the inverter controller 160 determines that the current operating state that the second power cable 300 is normally connected. (Step 210).

As described above, according to the embodiment, it is possible to install a hardware device in a conventionally used power cable, so that the diagnosis can be made by software rather than a method of detecting a non-fastening state of the power cable. In addition to the effect of, it is possible to prevent malfunctions that may be caused by external factors in advance.

The image processing method according to the present invention described above may be stored in a computer-readable recording medium that is produced as a program for execution on a computer, and examples of the computer-readable recording medium include ROM, RAM, CD-ROM, Magnetic tapes, floppy disks, optical data storage devices, and the like, and also include those implemented in the form of carrier waves (eg, transmission over the Internet).

The computer readable recording medium may be distributed over a networked computer system so that computer readable code can be stored and executed in a distributed manner. And, functional programs, codes and code segments for implementing the above method can be easily inferred by programmers of the technical field to which the present invention belongs.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed exemplary embodiments, but, on the contrary, It will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the present invention.

100: inverter system
110: Battery
120: Main relay
130: inverter
140: motor
150: battery management system
160: inverter controller
200: first power cable
300: second power cable

Claims (5)

Checking the driving speed of the motor;
Determining whether a driving speed of the checked motor exceeds a reference speed;
If the driving speed exceeds a reference speed, determining whether a phase current command value for driving the motor is greater than a first reference value;
If the phase current command value is greater than the first reference value, determining whether the actual phase current supplied to the motor is less than a second reference value;
If the actual phase current is less than the second reference value, stopping the motor driving; And
And forcibly discharging a capacitor provided in the inverter. The method of claim 1,
The actual phase current is,
Separation detection method of a power cable in the inverter system which is a current flowing through the three-phase power cable to transfer the three-phase AC power converted through the inverter to the motor. 3. The method of claim 2,
Stopping the motor drive,
If the actual phase current is less than the second reference value, confirming that the three-phase power cable is disconnected;
And stopping the motor drive as the three-phase power cable is disconnected. 3. The method of claim 2,
And if the actual phase current is greater than the second reference value, confirming that the three-phase power cable is normally connected, and continuously supplying driving power to the motor. The method of claim 1,
Discharging the forced discharge
And setting the q-axis current as the torque component current to 0 and applying the d-axis current as the magnetic flux component current to the motor.

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