KR20160059077A - Voltage compensaton apparatus for driving induction motor and voltage compensaton method usinig the same - Google Patents

Abstract

Disclosed are a voltage compensating apparatus for an induction motor to restrain voltage distortion by controlling the magnitude of compensation voltage in real time to compensate not only voltage distortion due to a time delay of turning on and turning off, but also voltage distortion due to voltage drop of a switching element and a voltage compensating method using the same. The voltage compensating apparatus for an induction motor comprises: an inverter for supplying three-phase voltage to the induction motor using a power element; and a voltage compensating control unit for controlling on and off operations of the power element by using a driving signal generated on the basis of compensating voltage which is a sum of voltage distortion amount compensating voltage and dead time compensating voltage after calculating the dead time compensating voltage by the voltage distortion amount compensating voltage and current polarity generated in the three-phase voltage.

Description

TECHNICAL FIELD [0001] The present invention relates to a voltage compensating device for driving an induction motor, and a voltage compensating method using the compensating device. [0002]

The present invention relates to a voltage compensating apparatus and a voltage compensating method, and more particularly, to a voltage compensating apparatus for driving an induction motor and a voltage compensating method using the same.

The induction motor uses a power conversion device that varies the voltage and frequency supplied from the commercial power source to meet the load conditions. The output voltage of the power converter for driving the induction motor is output in the form of PWM, and the output voltage is distorted due to the nonlinear factor due to the semiconductor switching element, so that the output voltage is different from the command voltage. Therefore, in order to keep the output voltage constant, the PWM voltage must be compensated appropriately.

Here, this PWM method is an essential component for preventing the heat loss of the amplifying transistor in the inverter by modulating the magnitude of the output voltage with an equivalent pulse width.

FIG. 1 is a schematic circuit configuration diagram of such a three-phase PWM system inverter, and FIG. 2 is a gating pulse waveform chart showing the dead time and turn-on delay time compensation in the inverter of FIG.

1 and 2, in the three-phase PWM inverter, no current flows through the same phase during a dead time (Td), for example, the transistor Ta (Ta '), which is a switching element of a-phase, The current flows only through the diode Db (Db ') or the diode Dc (Dc') on the c.

At this time, when the transistor Tc 'on c-phase Tc' is to be turned on at T1, the A-gating is first turned off at T1-Tcom and the A + The dead time Td is compensated for by turning on at -Tcom + Td.

In FIG. 2, (a) is an ideal gating pulse waveform, (b) is a gating pulse waveform when the dead time is compensated, (C) The gating pulse waveform when the delay time Ton is compensated, and (d) the equivalent waveform of (c). (A) to (d) are waveform diagrams when the current of the a phase flowing into the induction motor is greater than zero, and (e) to (g) are waveform diagrams when the current is smaller than zero.

As described above, conventionally, the distortion of the output voltage is compensated only by the compensation of the turn-on time delay and the turn-off time delay. However, the distortion of the output voltage is caused not only by the turn-on and turn-off time delays but also by the voltage drop of the switching element. Therefore, the conventional compensation method can not completely compensate for the distortion of the output voltage, and as a result, the induction motor can not be precisely controlled.

SUMMARY OF THE INVENTION The present invention has been made in order to solve the above-mentioned problems, and it is an object of the present invention to provide an apparatus and a method for compensating for voltage distortion caused by a voltage drop of a switching element as well as voltage distortion due to a time delay of turn- And a voltage compensating method using the voltage compensating apparatus. The present invention provides a voltage compensating apparatus for driving an induction motor.

According to an aspect of the present invention, there is provided an induction motor voltage compensator comprising: an inverter for supplying a three-phase voltage to an induction motor using a power device; Calculating a dead time compensation voltage according to a voltage distortion amount compensation voltage and a current polarity generated within the three-phase voltage, and outputting a driving signal generated based on a compensation voltage obtained by adding the voltage distortion amount compensation voltage and the dead time compensation voltage And a voltage compensation control unit for controlling on / off operation of the power device using the power control unit.

According to an aspect of the present invention, there is provided a voltage compensation method using an induction motor voltage compensator, comprising: determining a current polarity of a three-phase voltage output from an inverter including a plurality of power devices; A first voltage compensation generation step of generating a compensation; Calculating a current angle of each phase of the three-phase voltage, converting the current angle into a synchronous coordinate system, calculating a voltage distortion amount using the synchronous coordinate system, and generating a voltage distortion amount voltage compensation according to the voltage distortion amount, A voltage compensation generating step; A summation processing step of summing the dead time voltage compensation and the voltage distortion amount voltage compensation for each phase, and then summing the externally applied pole voltage and the summed voltage compensation; And a power device control step of controlling the ON / OFF operation of each of the plurality of power devices with the drive signal generated using the summed voltage compensation.

According to the embodiment of the present invention, the amount of voltage distortion is calculated and compensated during the operation of the electric motor, so that the quality of the output current can be maintained even when the operation condition is changed, and the torque vibration of the electric motor can be minimized.

In addition, not only the voltage distortion due to the turn-on and turn-off time delays but also the voltage distortion due to the voltage drop of the switching element is compensated, so that a precise output voltage can be obtained, Providing the advantage of precise control.

1 is a schematic circuit diagram of a general PWM type inverter.
FIG. 2 is a graph showing a gating pulse waveform diagram showing compensation of dead time and turn-on delay time in the inverter of FIG. 1. FIG.
3 is a block diagram illustrating a voltage compensation apparatus for an induction motor according to an embodiment of the present invention.
4 is a block diagram showing the voltage distortion amount voltage compensation generating unit shown in FIG.
5 is a flowchart illustrating a voltage compensation method using a voltage compensating apparatus for an induction motor according to an embodiment of the present invention.
FIG. 6 is a flowchart showing the second calculation step shown in FIG. 5 in more detail.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. However, the embodiments of the present invention can be modified into various other forms, and the scope of the present invention is not limited to the embodiments described below. The shape and the size of the elements in the drawings may be exaggerated for clarity and the same elements are denoted by the same reference numerals in the drawings.

3 is a block diagram illustrating a voltage compensation apparatus for an induction motor according to an embodiment of the present invention. 4 is a block diagram showing the voltage distortion amount voltage compensation generating unit shown in FIG.

3, the voltage compensating apparatus 100 for driving an induction motor according to an embodiment of the present invention includes an inverter 200 and a voltage compensation controller 300. [

The inverter 200 functions to supply three-phase power to operate the induction motor.

More specifically, the inverter 200 converts the direct-current voltage into an alternating-current voltage according to the drive signal output from the voltage compensation controller 300, and applies the alternating-current voltage to the coils of the induction motor to generate a magnetic field.

For reference, three coils (three phases) are distributed in the stator located inside the induction motor, and the inverter 200 can generate a rotating magnetic field by sequentially applying a voltage to the stator. The rotating magnetic field is called a rotating field, and when this rotating field is coupled to the rotor conductor, an electromotive force is induced in the shorted rotor conductor, thereby causing a current to flow. A torque is generated by the interaction between the rotor current and the stator rotating system, and the rotor rotates.

Meanwhile, the inverter 200 may include a power source, a plurality of power devices Q1 to Q6, and a plurality of diodes D1 to D6.

Here, the power source functions to supply electric energy to be converted into rotational force of the induction motor in the form of voltage and current, and the plurality of power devices include a plurality of upper power devices (Q1 to Q3) connected to the + And a plurality of lower power devices (Q4 to Q6) provided between power terminals.

Here, the contacts of the upper power devices Q1 to Q3 and the lower power devices Q4 to Q6 are connected to three coils (a phase, b phase, and c phase) connected to the motor.

Each of the plurality of power devices Q1 to Q6 is connected in parallel to the diodes D1 to D6 and performs switching operation in accordance with a drive control signal provided by the voltage compensation controller 300, Into an alternating-current voltage having two phases.

At this time, the plurality of power devices Q1 to Q6 may be IGBTs or FETs considering power capacity, switching time, and the like.

Hereinafter, an example of driving operation of the inverter will be described.

For example, when the upper power elements Q1 to Q3 of the inverter 200 are sequentially turned on, the lower power elements Q4 to Q6 perform the ON / OFF operation as opposed to the upper power elements Q1 to Q3.

At this time, when the power device Q1 is turned on, a positive voltage is applied to the a-phase coil of the induction motor, and the power device Q6 is turned on, - voltage is applied.

Thus, a magnetic force of opposite polarity is generated between the a-phase coil and the c-phase coil, and the rotor rotates by 60 degrees due to the magnetic interaction. Subsequently, the power element Q1 is turned OFF, and the power element Q2 is turned ON, so that a magnetic force having a polarity opposite to that of the magnetic force generated in the c-phase coil is generated in the b-phase coil, Rotate.

Similarly, while the power element Q2 is in the ON state, the power element Q6 is turned OFF and the power element Q4 is turned ON, so that a magnetic force having a polarity opposite to the magnetic force of the b-phase coil is generated in the a- The person turns 60 more.

Next, while the power device Q2 is turned OFF, the power device Q3 is turned ON, and a magnetic force of opposite polarity is generated in the a-phase coil and the c-phase coil, and the induction motor is further rotated by 60 DEG, (Q4) is turned off, the power device (Q5) is turned on, and the rotor rotates again by 60 degrees by the magnetic force of the a-phase coil and the b-phase coil.

As the process is repeated, the rotor continues to rotate, and the induction motor is operated. The above-described processes are repeated by the control of the inverter 200 according to the drive control signal, I can do it.

Next, the voltage compensation controller 300 calculates a dead time compensation voltage according to the amount of voltage distortion and the current polarity generated in the three-phase voltage, and then calculates a pulse width modulation based on the voltage distortion amount and the dead time compensation voltage And controls the ON / OFF operation of the power devices Q1 to Q6 using a drive control signal.

More specifically, the voltage compensation controller 300 includes a first voltage compensation generator 310, a second voltage compensation generator 320, an operation unit 330, and a driving signal generator 340.

The first voltage compensation generator 310 generates the dead time voltage compensation of the three-phase voltage through determination of the current polarity of the three-phase voltage.

The second voltage compensation generator 320 calculates a current angle of each phase of the three-phase voltage, converts the current angle into a synchronous coordinate system, calculates a voltage distortion amount using the synchronous coordinate system, Thereby generating a voltage distortion compensation amount voltage compensation according to the following equation.

The second voltage compensation generation unit 320 includes a coordinate transformation unit 321 and a voltage distortion amount voltage compensation generation unit 322.

The current angle-of-orthogonal transformation unit 321 calculates a current angle of the three-phase voltage, and performs a coordinate transformation on the basis of the synchronous coordinate system.

At this time, the synchronous coordinate system is derived by the following equation (1).

[Equation 1]

,

는 a상 전류를 기준으로 하는 d, q축 동기좌표계 고정자 전류,

는 기본파 전류의 크기,

은 n차 고조파 전류의 크기,

는 a상 전류의 위상각,

,

,

는 a상, b상, c상 전류를 나타낸다.
here,

,

D and q axis synchronous coordinate system stator current based on a phase current,

The magnitude of the fundamental wave current,

The magnitude of the n-th order harmonic current,

Phase angle of the a-phase current,

,

,

Represents the a-phase, b-phase, and c-phase currents.

The voltage distortion amount voltage compensation generator 322 extracts fifth and seventh harmonics of the d-axis component current, which is the amount of voltage distortion of each phase, using the synchronous coordinate system, and then converges the magnitude of the harmonics to zero And outputs a compensation voltage Vcomp.

More specifically, the voltage distortion amount voltage compensation generator 322 may include a first operator 322a, a second operator 322b, and a PI controller 322c.

The first operator 322a multiplies the voltage distortion amount of each phase by a sine function having a predetermined current angle, and then performs filtering through the low-pass filter to extract the harmonic components.

Here, the first operator 322a extracts the harmonic components using Equation (2) described below.

&Quot; (2) "

,

는 a상 전류를 기준으로 하는 d, q축 동기좌표계 고정자 전류를 나타낸다.
here,

,

Represents the stator current of the d and q axis synchronous coordinate system based on the a-phase current.

The second operator 322b performs a function of converging the magnitude of the harmonic component to 0 through an add / subtract operation.

The PI controller 322c generates a voltage distortion compensation voltage for each phase using the result of the second operator 322b.

Next, the operation unit 330 adds up the dead time voltage compensation and the voltage distortion amount voltage compensation corresponding to each phase, and then calculates the pole voltages (Van, Vbn, Vcn) applied from the outside and the summed voltage compensation (Vdac, Vdbc, Vdcc).

The driving signal generator 340 generates a driving signal that is a pulse width modulation signal for controlling ON / OFF operations of the power devices Q1 to Q6 using the voltage compensation summed in the operation unit 330. [

Accordingly, the inverter 200 can provide a three-phase voltage (current) uniformly in real time to the induction motor from power elements driven through different drive signals for each phase provided by the voltage compensation controller 300. [

Hereinafter, a voltage compensation method using the voltage compensating apparatus for an induction motor according to an embodiment of the present invention will be described.

5 is a flowchart illustrating a voltage compensation method using a voltage compensating apparatus for an induction motor according to an embodiment of the present invention. FIG. 6 is a flowchart showing the second calculation step shown in FIG. 5 in more detail.

5, the voltage compensation method S100 using the voltage compensating apparatus for an induction motor according to an embodiment of the present invention includes a first voltage compensation generating step S10, a second voltage compensation generating step S20, A summation processing step S30, and a power device control step S40.

The first voltage compensation generation step (S10) may be a step of determining the current polarity of the three-phase voltage output from the inverter composed of a plurality of power devices, and then generating the dead time voltage compensation.

The second voltage compensation generation step (S20) calculates a current angle of each phase of the three-phase voltage, converts the current angle into a synchronous coordinate system, calculates a voltage distortion amount using the synchronous coordinate system, , And may include a coordinate transformation step (S21) and a voltage distortion amount voltage compensation generation step (S22).

The coordinate transformation step S21 may be a step of calculating a current angle of each phase of the three-phase voltage and then performing coordinate transformation on the basis of the synchronous coordinate system, and the step S22 of generating the voltage distortion amount voltage compensation may include: And extracting the fifth and seventh harmonics of the d-axis component current, which is the amount of voltage distortion of each phase, and outputting the compensating voltage whose harmonic amplitude converges to zero.

At this time, the coordinate transformation step S21 transforms each phase current into a synchronous coordinate system using the following equation (1).

[Equation 1]

,

는 a상 전류를 기준으로 하는 d, q축 동기좌표계 고정자 전류,

는 기본파 전류의 크기,

은 n차 고조파 전류의 크기,

는 a상 전류의 위상각,

,

,

는 a상, b상, c상 전류를 나타낸다.
here,

,

D and q axis synchronous coordinate system stator current based on a phase current,

The magnitude of the fundamental wave current,

The magnitude of the n-th order harmonic current,

Phase angle of the a-phase current,

,

,

Represents the a-phase, b-phase, and c-phase currents.

Referring to FIG. 6, in the voltage distortion amount voltage compensation generation step S22, the voltage distortion amount of each phase current is multiplied by a sine function having a predetermined current angle, and then filtered using a low-pass filter, A second calculation step (S22b) for converging the magnitude of the harmonic component extracted through the addition / subtraction operation to 0, and a second calculation step (S22b) for adding the result value of the second calculation step (S22b) And a PI control step (S22c) for generating a current distortion compensation voltage corresponding to each phase current.

Here, the first calculation step (S22a) extracts the harmonic components using Equation (2) described below.

&Quot; (2) "

,

는 a상 전류를 기준으로 하는 d, q축 동기좌표계 고정자 전류,

는 a상 전류의 위상각을 나타낸다.here,

,

D and q axis synchronous coordinate system stator current based on a phase current,

Represents the phase angle of the a-phase current.

Next, the summing processing step S30 is a step of summing the dead-time voltage compensation and the voltage-distortion amount voltage compensation for each of the phases, and then adding the externally applied pole voltages Van, Vbn, Vcn and the summed voltage May be a step of summing the compensation (Vdac, Vdbc, Vdcc).

The power device control step S40 may be a step of controlling the ON / OFF operation of each of the plurality of power devices Q1 to Q6 with the drive signal generated using the summed voltage compensation.

Therefore, according to an embodiment of the present invention, the amount of voltage distortion of the three-phase voltage provided to the induction motor is calculated and compensated in real time, so that the quality of the output current can be maintained even when the operating condition of the induction motor fluctuates, This provides the advantage that the torque vibration of the induction motor can be minimized.

In addition, not only the voltage distortion due to the time delay due to the turn-on / off operation of the power device but also the voltage distortion due to the voltage drop of the power device can be compensated simultaneously, thereby obtaining a precise output voltage, Control is possible.

The present invention is not limited to the above-described embodiments and the accompanying drawings. 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 invention as defined by the appended claims. It will be self-evident.

100: Voltage compensator for induction motor 200: Inverter
300: Voltage compensation control unit 310: First voltage compensation generation unit
311: current polarity discrimination unit 312: dead time voltage compensation generation unit
320: Second voltage compensation generation unit 321: Coordinate transformation unit
322: Voltage Distortion Amount Voltage Compensation Generation Unit 322a:
322b: second arithmetic unit 322c: PI control unit
330: Summing unit 340: Driving signal generating unit

Claims (10)

An inverter for supplying a three-phase voltage to the induction motor using a power device;
Calculating a dead time compensation voltage according to a voltage distortion amount compensation voltage and a current polarity generated within the three-phase voltage, and outputting a driving signal generated based on a compensation voltage obtained by adding the voltage distortion amount compensation voltage and the dead time compensation voltage And a voltage compensation control unit for controlling the on / off operation of the power device using the voltage compensation control unit.
The apparatus of claim 1, wherein the voltage compensation controller comprises:
A first voltage compensation generator for determining a current polarity of the three-phase voltage and generating a dead time voltage compensation;
Calculating a current angle of each phase of the three-phase voltage, converting the current angle into a synchronous coordinate system, calculating a voltage distortion amount using the synchronous coordinate system, and generating a voltage distortion amount voltage compensation according to the voltage distortion amount, A voltage compensation generator;
An operation unit for summing the dead time voltage compensation and the voltage distortion amount voltage compensation for each phase, and then summing the externally applied pole voltage and the summed voltage compensation; And
And a drive signal generator for generating a drive signal for controlling the on / off operation of the power device using the voltage compensation summed in the operation unit.
The apparatus of claim 2, wherein the second voltage compensation generator comprises:
Calculating a current angle of each phase of the three-phase voltage, and then performing coordinate conversion on the synchronous coordinate system; And
Calculating a synchronous coordinate system of each phase, extracting fifth and seventh harmonics of the d-axis component current, which is the amount of voltage distortion of each phase, and outputting a voltage compensating voltage having a magnitude of the harmonic converged to 0 And a compensation generating unit. The method of claim 3,
Wherein the current angular coordinate conversion unit comprises:
And the synchronous coordinate system of each phase is generated by using the following equation (1).
[Equation 1]

here,

,

D and q axis synchronous coordinate system stator current based on a phase current,

The magnitude of the fundamental wave current,

The magnitude of the n-th order harmonic current,

Phase angle of the a-phase current,

,

,

Represents the a-phase, b-phase, and c-phase currents.
The voltage-distortion compensating apparatus as claimed in claim 3,
A first operator for multiplying the voltage distortion amount of each phase by a sin function having a predetermined current angle, and then filtering the harmonic components to extract the harmonic components;
A second operator for converging the magnitude of the harmonic component to zero through an add / subtract operation; And
And a PI control unit for generating a current distortion compensation voltage for each phase of the result of the operator.
6. The method of claim 5, wherein the first operator
The voltage compensating device for an induction motor for extracting the harmonic component by using Equation (2) described below.
&Quot; (2) "

here,

,

Represents the stator current of the d and q axis synchronous coordinate system based on the a-phase current.
A first voltage compensation generation step of determining a current polarity of a three-phase voltage output from an inverter composed of a plurality of power devices and then generating a dead time voltage compensation;
Calculating a current angle of each phase of the three-phase voltage, converting the current angle into a synchronous coordinate system, calculating a voltage distortion amount using the synchronous coordinate system, and generating a voltage distortion amount voltage compensation according to the voltage distortion amount, A voltage compensation generating step;
A summation processing step of summing the dead time voltage compensation and the voltage distortion amount voltage compensation for each phase, and then summing the externally applied pole voltage and the summed voltage compensation; And
And a power device control step of controlling the ON / OFF operation of each of the plurality of power devices with the drive signal generated by using the summed voltage compensation method. The voltage compensation method of an industrial inverter using the voltage compensation device for an induction motor .
The method of claim 7, wherein the second voltage compensation generation step
A coordinate conversion step of calculating a current angle of each phase of the three-phase voltage and then performing coordinate conversion with the synchronous coordinate system; And
Calculating a synchronous coordinate system of each phase, extracting fifth and seventh harmonics of the d-axis component current, which is the amount of voltage distortion of each phase, and outputting a voltage compensating voltage having a magnitude of the harmonic converged to 0 And a compensating step of compensating the voltage of the induction motor.
9. The method of claim 8,
Wherein the coordinate transformation step comprises:
A method of compensating an inverter voltage of an induction motor using a voltage compensator for an induction motor in which the currents of the respective phases are coordinate-converted into a synchronous coordinate system by using the following equation (1).
[Equation 1]

here,

,

D and q axis synchronous coordinate system stator current based on a phase current,

The magnitude of the fundamental wave current,

The magnitude of the n-th order harmonic current,

Phase angle of the a-phase current,

,

,

Represents the a-phase, b-phase, and c-phase currents.
9. The method of claim 8, wherein the step of generating the voltage distortion amount voltage compensation comprises:
A first calculation step of multiplying the amount of voltage distortion of each phase current by a sine function having a predetermined current angle and then filtering using a low band pass filter to extract the harmonic component;
A second calculation step of converging the magnitude of the harmonic component extracted through the add / subtract operation to zero; And
And a PI control step of generating a current distortion compensation voltage corresponding to each phase current in a result of the second calculation step,
Wherein the first calculating step comprises:
A method for compensating an industrial inverter voltage using an induction motor voltage compensator for extracting the harmonic components using Equation (2) described below.
&Quot; (2) "

here,

,

Represents the stator current of the d and q axis synchronous coordinate system based on the a-phase current.

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