KR20130119313A - Apparatus for controlling inverter current and method for operating the same - Google Patents

Abstract

PURPOSE: A current control apparatus of an inverter reduces manufacturing cost by simplifying a circuit by directly detecting current flowing in a switching element without an extra current detection sensor. CONSTITUTION: An inverter (100) converts input DC into three-phase AC and outputs it to a motor. The inverter comprises multiple current detecting switching elements (Pu) capable of detecting current which is switched and then outputted. An AD converter (210) converts output current of an output part of the current detecting switching element into a detecting signal value of digital form. A control unit (200) outputs a driving signal controlling the on/off of multiple switching elements by using the detecting signal value. A driving circuit (400) produces a gate signal directly controlling the on/off of the current detecting switching element. [Reference numerals] (200) Control unit; (210) AD converter; (211) Sigma delta modulation unit; (212) First filter unit; (213) Second filter unit; (300) Motor; (400) Driving circuit; (600) Converter

Description

Apparatus for controlling inverter current and Method for operating the same}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a current control device for an inverter, and more particularly, to a current control device for controlling a current of a switching element of an inverter for outputting a three-phase alternating current.

In a vehicle such as a hybrid car or an electric vehicle, a high voltage battery is used to drive a driving motor or a compressor motor, and a low voltage battery is used to communicate with an audio device or a local interconnect network (LIN) or controller area network (CAN). Drive a communication device to In such a configuration, for example, when the motor control unit for controlling the operation of the inverter device and the communication control unit for controlling the operation of the communication device transmit and receive signals with each other, the signal is transmitted and received through the photocoupler.

In general, an apparatus for driving a motor by controlling an inverter includes a high voltage battery 10, a voltage converter converting a voltage of the high voltage battery into another voltage, and the converted voltage. A smoothing unit 30 (filter capacitor) for storing and smoothing voltage, an inverter 40 for converting a DC voltage of the smoothing unit into an alternating voltage, and an AC voltage of the inverter And a control unit 50 for controlling the motor 60 and the output frequency.

The inverter 40 connects and uses a switching device, and generally uses a semiconductor device called an insulated gate bipolar transistor (IGBT) having excellent characteristics as a switching device.

When an output short circuit or an arm short circuit occurs in the inverter 40 and a short circuit current flows in the switching element IGBT, the short circuit current of the switching element is allowed by the gate-emitter voltage VGE applied to the switching element. The current rises and the collector-emitter voltage VCE of the switching element rises in proportion to the current. As described above, due to the short-circuit current, when an uncontrolled current (hereinafter, referred to as an 'accident current') flows in the IGBT element, which is a switching element in the inverter, it is necessary to take appropriate action.

To this end, conventionally, a separate detection for performing current control and short-circuit current detection using current values detected by phase output current detection sensors 70 (70a, 70b, 70c) installed in a phase ouptut for current control purposes. I had to put a dedicated circuit.

For example, in the normal case, when the switching element is turned on, the input voltage VCC is connected to GND through a pull-up resistor, current limiting resistor, blocking diode, switching element. At this time, only the turn-on voltage of the switching element is detected to perform normal operation. On the contrary, when the switching element is shorted, the turn-on voltage of the switching element rises in proportion to the magnitude of the short-circuit current, and compared with the reference voltage of the comparison unit to determine the presence or absence of a short circuit detection and transmit a failure signal to the control unit.

However, the inverter control apparatus with the current detection sensor having the short-circuit current detection function according to the prior art has a problem that the cost increases because it requires a separate current detection sensor. In addition, there is a problem in that the load of the controller is increased because a separate current detection sensing has to be performed. In addition, there is a problem that the short-circuit detection level cannot be adjusted only by the conventional current detection sensor.

Korea Patent Publication 10-2011-0126857

An object of the present invention is to detect a current flowing in the switching element without a separate current detection sensor. Another object of the present invention is to provide an inverter current control device and a current control method without a separate current detection sensor. In addition, the technical problem of the present invention is to directly detect the current flowing in the switching element to protect the inverter current control system. In addition, the technical problem of the present invention is to shorten the digital modulation time of the detected current.

The present invention includes a plurality of current detection switching device capable of detecting the current output by switching, the inverter for converting the DC current into a three-phase alternating current by turning on and off the current detection switching device, respectively, and outputs to the motor; An AD converter which directly receives an output current of an output terminal of the current detection switching element as a detection current and converts the signal into a digital detection signal value; It includes a control unit for output.

In addition, the current detection switching device is connected to two insulated gate bipolar transistor (IGBT) devices in parallel. In addition, the current detection switching device is implemented by a first insulated gate bipolar transistor and a second insulated gate bipolar transistor, wherein the first insulated gate bipolar transistor includes a first collector connected to an input terminal to which the DC current is input, and a control current is inputted. A first emitter connected to the motor and a first emitter connected to the motor, wherein the second insulated gate bipolar transistor comprises: a second collector connected to a node between an input terminal and the first collector; And a second gate to which the same signal is input and a second emitter which is a second output terminal for outputting the detection current.

The AD converter also includes a sigma delta modulator which converts the digital signal into a digital signal through correction using an error between the predicted value predicted in advance and the detected current detected. The AD converter further includes a first order filter unit for performing filtering to block aliasing of the converted digital signal, and a second order filter unit for low pass filtering a down-sampled digital signal.

In addition, the first-order filter performs downsampling after aliasing filtering, and the second-order filter performs downsampling after low pass filtering the signal input from the first-order filter unit.

In addition, the primary filter is characterized in that the comb filter (comb filter) that is a comb filter, the second filter is characterized in that the finite impulse response filter (FIR Filter).

According to the embodiment of the present invention, a circuit can be simplified by directly detecting a current flowing through the switching element without a separate current detection sensor. Therefore, the cost can be reduced when implementing the inverter current control device. Further, according to the embodiment of the present invention, rapid current control can be achieved by directly detecting the current flowing through the switching element. In addition, according to the embodiment of the present invention, it is possible to directly and accurately detect whether the switching element is abnormal. In addition, according to the embodiment of the present invention, it is possible to minimize the digital modulation time by using sigma-delta modulation to reduce the load of the controller to facilitate the implementation of other additional control operations and to facilitate resource allocation.

1 is a view showing a device for driving a motor by controlling a conventional inverter.
2 is a diagram illustrating a short circuit current detection circuit of an inverter according to an exemplary embodiment of the present invention.
3 is a diagram illustrating a current detection switching device integrated as a structure of a TCS-IGBT according to an embodiment of the present invention.
4 illustrates a detailed configuration of each of the sigma-delta modulator, the first-order filter unit, and the second-order filter unit of the AD converter according to an embodiment of the present invention.
5 is a diagram illustrating the sigma delta modulation principle.
6 is a diagram illustrating an example of a filtering band of a comb filter.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. It will be apparent to those skilled in the art that the present invention may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, It is provided to let you know. Wherein like reference numerals refer to like elements throughout.

2 is a diagram illustrating a short circuit current detection circuit of an inverter according to an exemplary embodiment of the present invention.

Referring to FIG. 2, a current control device for controlling an inverter to drive a motor includes a high voltage battery 500, a voltage conversion unit 600 for converting a voltage of the high voltage battery into another DC voltage, and a converted voltage. And a smoothing unit 700 (filter capacitor) for storing and smoothing a voltage, and a plurality of current detection switching elements for converting a DC voltage of the smoothing unit into an alternating voltage, capable of detecting a current that is switched and output. Inverter 100 for converting direct current into three-phase alternating current and outputting the motor 300 by switching the current detecting switching element on and off, and directly receiving the output current of the output terminal of the current detecting switching element as a detection current. An AD converter 210 for converting to a detection signal value in a digital form, and a driving signal for outputting a driving signal for controlling on and off a plurality of switching elements using the detection signal value. Fisherman 200. In addition, a drive circuit 400 for generating a gate signal for directly controlling the on and off of the current detection switching element according to the control signal of the control unit.

The inverter 100 is used to drive a compressor motor mounted on a vehicle such as a hybrid vehicle or an electric vehicle. The inverter includes a plurality of current detection switching elements, and the plurality of current detection switching elements are turned on and off, respectively, thereby converting the input DC voltage into three-phase AC and outputting it to the motor. For example, the inverter 100 is connected in series with each other and connected to the n-channel first current detection switching element Pu and the second current detection switching element Nu, which output U phases, and are connected in series to each other. The n-channel third current detection switching element Pv and the fourth current detection switching element Nv of the n-channel output are connected in series with each other, and the fifth current detection switching element Pw and the sixth n-channel current outputting phase W are outputted. The current detection switching element Nw is configured to be connected in parallel to the high voltage battery 500. The first current detection switching device Pu, the third current detection switching device Pv, and the fifth current detection switching device Pw are switching devices that output three-phase currents of positive U, V, and W, respectively. , The second current detection switching element Nu, the fourth current detection switching element Nv, and the sixth current detection switching element Nw are switching elements which output negative U, V, and W three-phase currents, respectively. . For reference, a diode D for blocking current is connected in parallel between the collector C and the emitter E in each of the current detection switching elements Pu, Pv, Pw, Nu, Nv, and Nw.

The connection point node between the first current detection switching element Pu and the second current detection switching element Nu and the U phase of the motor 300 are connected, and the third current detection switching element Pv and the fourth current detection switching element ( The connection point node between Nv and the V phase of the motor 300 are connected, and the connection point node of the fifth current detection switching element Pw and the sixth current detection switching element Nw and the W phase of the motor 300 are connected. When the IGBTs (Pu, Pv, Pw, Nu, Nv, and Nw) are sequentially turned on and off, a plurality of alternating currents flow through the motor 300 to rotate the rotor of the motor 300.

On the other hand, each of the current detection switching elements Pu, Pv, Pw, Nu, Nv, and Nw constituting the inverter switches the current input to the input collector terminal and outputs it as an output current to the emitter. An embodiment of the present invention provides a method of directly detecting the output current value output to the emitter without a separate detection sensor and providing it to the controller. To this end, each current sensing switching element is implemented as a parallel combination of two IGBT Insulated Gate Bipolar Transistors to detect the output current value. For reference, only two emitters are illustrated in FIG. 2 to show parallel coupling of two insulated gate bipolar transistors.

In detail, the parallel coupling of two insulated gate bipolar transistors is implemented by integrating a current detection switching element as a structure of the on-chip current sense-insulated gate bipolar transistor (TCS-IGBT) as shown in FIG. 3. The TCS-IGBT device is implemented by combining two insulated gate bipolar transistors IGBT1 and IGBT2 in parallel, so that the first insulated gate bipolar transistor IGBT1 provides an output current to the motor 300 and the other second. The insulated gate bipolar transistor IGBT2 outputs the same value as the output current provided to the motor and provides it to the AD converter 210.

To this end, the first insulated gate bipolar transistor IGBT1 includes a first collector C1 connected to an input terminal through which the DC current is input, a first gate G1 through which a control current is input as a gate signal, and a motor. It includes a first emitter (E1) which is a first output terminal. In addition, the second insulated gate bipolar transistor IGBT2 includes a second collector C2 connected to a node between the input terminal and the first collector C1, and a second gate G2 to which the same control current as the first gate is input. And a second emitter E2 which is a second output terminal for outputting a detection current.

Therefore, the input current i _L input to the current detection switching element is input to both input terminals of the collector C1 (first collector) of the first insulated gate bipolar transistor and the collector C2 (second collector) of the second insulated gate bipolar transistor. The gate signal i _G , which is the same and is a control signal input to the current detection switching element, includes a gate G1 of the first insulated gate bipolar transistor and a gate G2 of the second insulated gate bipolar transistor; The same is input to both sides of the second gate). Therefore, the current i _E1 flowing in the emitter E1 (first emitter), which is the output terminal of the first insulated gate bipolar transistor, and the current flowing in the emitter E2 (second emitter, E2), which is the output terminal of the second insulating gate bipolar transistor, i _E2 ) will have the same value. The current i _E1 output through the emitter (first emitter) of the first insulated gate bipolar transistor is provided to the motor and used as a driving source, and the emitter (second emitter) of the second insulated gate bipolar transistor is used. The current i _E2 output through is provided to the AD converter as the detection current.

Meanwhile, in the above embodiment, the integrated insulated gate bipolar transistors IGBT1 and IGBT2 are illustrated as being provided on both the positive and negative sides, but various modifications are possible, such as being provided on the negative side to measure a phase current. Do.

In the above description of the embodiment, an example of using an insulated gate bipolar transistor (IGBT) element as the current detection switching element in the inverter has been described. However, not limited to this, it will be apparent that embodiments of the present invention can be applied to various switching devices. For example, in addition to the insulated gate bipolar transistor (IGBT), each current detection switching element constituting the inverter may be a MOSFET (Metal Oxide Semiconductor Field Effect Transistor) connected in parallel with a diode, and the like is not limited to the IGBT.

For reference, the IGBT can only take advantage of the MOSFET and Bipolar transistor. IGBTs can actually be seen as replacements for MOSFETs. Since the MOSFET is a device driven by one type of carrier (electron or hole), there is a limit in increasing the breakdown voltage or the amount of current. Because of this, IGBTs can compensate for these disadvantages of MOSFETs and achieve high breakdown voltages and currents. However, IGBT has the disadvantage of being slower than MOSFET. Briefly describing the features of the IGBT device, the IGBT has the same voltage control scheme as the MOSFET and has low ON-resistance, making it widely used in high power devices. Comparing the difference in voltage-dependent ON-resistance between the MOSFET and the IGBT, the conduction resistance in the IGBT is lower than in the MOSFET over a wide voltage range. Comparing the characteristics of switching devices IGBT, MOS FET and TR, the input type is controlled by voltage, IGBT and MOS FET by voltage, BJT by current, and input resistance is very high while IGBT and MOS FET are low, but BJT is low. . In addition, the operating frequency is medium IGBT, MOS FET is high, BJT is low, switching speed is medium, IGBT is medium, MOS FET is very fast and BJT is the slowest.

The control unit 200 obtains the current position of the rotor of the motor 300 based on the three-phase currents Iu, Iv, and Iw, and inputs the current position of the motor rotor and the command message inputted from outside. The phase voltages of the U phase, V phase, and W phase are obtained based on the command message, and the switching elements Pu, Pv, Pw, Each control signal for controlling each of On, Off of Nu, Nv, and Nw) is generated. In addition, the control unit 200 transmits and receives a signal to and from a device that controls the operation of a communication device that communicates, such as LIN and CAN.

In addition, the controller 200 may receive a digital output value of each current detection switching element provided from the AD converter, and quickly detect whether an abnormal state such as a short circuit current has occurred by comparing whether the current of each current detection switching element flows normally. have. For example, when a short circuit current flows through each current detection switching element, the controller may detect whether the output current value provided from each current detection switching element is a short circuit current value and detect that the short circuit state is short. For reference, the current detected in each current detection switching element may be used for current control of each switching element through the detected current as well as used for short-circuit current detection.

The drive circuit 400 generates and outputs a control signal output from the control unit 200 as a gate signal input to the gate of each current detection switching element. That is, the drive circuit generates a current signal conforming to the device operation specification of each current detection switching element (Pu, Pv, Pw, Nu, Nv, Nw) and provides the current signal to the gate terminal of each current detection switching element, thereby turning on and off. The switching operation is made.

The AD converter 210 directly receives the output current of each output terminal of the current detection switching elements Pu, Pv, Pw, Nu, Nv, and Nw as a detection current, and converts the detection current into digital detection signal values for each detection current. Provided at 200. To this end, the AD converter 210 includes a sigma delta modulator 211 for converting a digital signal for each phase through a correction using an error between a predicted value predicted in advance and an actually detected detection current. In addition, the apparatus may further include a first-order filter unit performing filtering to block aliasing of the converted digital signal, and a second-order filter unit performing low pass filtering on the down-sampled digital signal.

In addition to the sigma delta modulator, the first and second filter units may be sequentially connected and subjected to sigma-delta modulation, an aliasing blocking process, and a low pass filtering process. FIG. 4 shows a detailed configuration of each sigma-delta modulator 211, the first order filter part 212, and the second order filter part 213 of the AD converter.

The sigma delta modulator 211 is an analog-to-digital conversion method derived from a delta_modulation method. It is easy to implement with low cost CMOS process and is widely used due to the development of semiconductor technology.

The sigma delta modulation principle is to roughly predict the value of a signal as shown in FIG. 5 (a) to find an error, and then correct the error using the accumulated error and convert it into a digital signal. According to this principle, if the cumulative error value is finite, the average value of the input signal and the average value of the output signal are equal. The number of integrators determines the order of sigma delta modulation. 5B is an example of second-order sigma delta modulation. First-order modulation is stable, but the higher the order, the more attention should be paid to stability. By applying the sigma delta modulator in the embodiment of the present invention as described above, only two insulated channel lines are required for data input and high resolution can be achieved.

On the other hand, after the conversion to the digital signal by the sigma delta modulator can be output through the first and second filter unit for stabilizing the signal.

The first-order filter unit 212 performs filtering to block aliasing of the converted digital signal, and the first-order filter unit uses a comb filter. Aliasing is a signal distortion phenomenon in which the sampling frequency is less than twice the maximum frequency of the signal or the filtering is inadequate when the analog signal is sampled, so that adjacent spectra overlap each other. To avoid this, increase the sampling frequency to more than twice the maximum frequency of the signal, and use low pass filters to remove signals above the maximum frequency before sampling. The primary filter unit filters out the aliasing by using a comb filter.

The comb filter is a band pass filter in which a plurality of comb shapes (corrugated curves) appear in accordance with frequency characteristics as shown in FIG. 6. Therefore, when passing through the comb filter having the frequency of the corresponding phase of the detection current of the channel received from each current detection switching element as a comb band, the detection current of each channel is selectively attenuated by the comb band. After the first filtering is performed through the comb filter to the comb band, it is downsampled and transferred to the second filter unit.The downsampling is performed by a decimator, which is a clock of the converted digital signal. Downsamples the frequency to a sampling rate that can be processed by the digital processor. To this end, the frequency of the clock is divided by a sampling factor N to downsample at a specific sampling rate.

The second filter unit 213 low-pass filters the digital signal and outputs the digital signal. Through low pass filtering of the second filter unit, a compensation filter function for compensating for pass band dropping by the comb filter may be performed. The secondary filter unit is implemented as a finite impulse response filter (FIR filter) to stabilize the digital signal through band filtering. The finite impulse response filter is a digital filter having a continuous duration of an impulse response, and is implemented as a two-stage finite impulse response filter having two bands in the embodiment of the present invention. Two low-pass filters are performed in two stages of finite impulse response filters. The low pass filtering of the second stage is only to obtain the desired low frequency band signal, the filtering order may be variously applicable. On the other hand, after the second filtering is similarly downsampled and output. This down sampling can be done by a decimator.

By using the emitter current of the integrated isolated gate bipolar transistor as described above and using an AD converter that performs sigma-delta modulation, the system can be directly used by using a signal detected from the isolated gate bipolar transistor by excluding a separate current detection sensor. It can protect the circuit. At the same time, sigma-delta modulation can be used to minimize the digital modulation time, thereby reducing the load on the controller to facilitate other additional control operations and to facilitate resource allocation.

Although the present invention has been described with reference to the accompanying drawings and the preferred embodiments described above, the present invention is not limited thereto but is limited by the following claims. Accordingly, those skilled in the art will appreciate that various modifications and changes may be made thereto without departing from the spirit of the following claims.

100: inverter 200: control unit
210: AD converter 211: sigma delta modulator
212: primary filter unit 213: secondary filter unit
300: motor 400: drive circuit
Pu, Pv, Pw: positive phase current generating switching element
Nu, Nv, Nw: Negative phase current generating switching device

Claims (10)

An inverter which has a plurality of current detection switching elements capable of detecting a current which is switched and output, and which converts a DC current into a three-phase alternating current by turning on and off the current detection switching elements, respectively, and outputs it to a motor;
An AD converter which directly receives an output current of an output terminal of the current detection switching element as a detection current and converts the detected current into a digital detection signal value;
A control unit outputting a driving signal for controlling on / off of a plurality of switching elements by using the detection signal value;
Current control device of the inverter comprising a. The current control device of claim 1, wherein the current detection switching device is implemented by two insulated gate bipolar transistor (IGBT) devices connected in parallel. The method of claim 2, wherein the current detection switching device is implemented with a first insulated gate bipolar transistor and a second insulated gate bipolar transistor,
The first insulating gate bipolar transistor,
A first collector connected to an input terminal to which the DC current is input;
A first gate through which a control current is input;
And a first emitter which is a first output terminal connected to the motor.
The second insulated gate bipolar transistor is,
A second collector connected to a node between the input terminal and the first collector;
A second gate to which the same signal as the control current is input;
A second emitter which is a second output terminal for outputting the detection current;
Current control device of the inverter comprising a. The apparatus of claim 1, wherein the AD converter includes a sigma delta modulator for converting the digital signal into a digital signal through correction using an error between a predicted value predicted in advance and a detected current detected. The method according to claim 4, wherein the AD converter,
A first order filter unit to perform filtering to block aliasing of the converted digital signal;
A second order filter unit for low-pass filtering the down-sampled digital signal;
Current control device of the inverter comprising a. The apparatus of claim 5, wherein the first filter performs down sampling after aliasing filtering. The apparatus of claim 5, wherein the second filter performs down sampling after low pass filtering the signal input from the first filter unit. The apparatus of claim 5, wherein the first filter is a comb filter, which is a comb-shaped filter. The apparatus of claim 5, wherein the secondary filter is a finite impulse response filter. 10. The apparatus of claim 9, wherein the finite impulse response filter is a low pass filter of two stages.

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