KR20210065572A - Apparatus for controlling inverter - Google Patents

Abstract

An inverter control device is disclosed. According to an embodiment of the present invention, the device comprises: a control unit receiving command torque and a command voltage and outputting a command current capable of maintaining a constant magnitude of an output voltage in a weak magnetic flux region; a current control unit for outputting the command voltage by proportional-integral control of the command current and an output current of a motor; and a first coordinate conversion unit that converts the command voltage into three phases and provides it to an inverter. Therefore, the inverter control device has an effect of expecting a rapid torque response without loss of magnetic flux for torque generation.

Description

Inverter control device {APPARATUS FOR CONTROLLING INVERTER}

The present invention relates to an inverter control device.

In general, an inverter is a power conversion device that electrically converts direct current (DC) into alternating current (AC). Inverters used in the industry receive power supplied from commercial power, vary the voltage and frequency, and supply it to the motor. It is defined as a set of devices that control the speed of the motor to be used with high efficiency.

Such an inverter can control the magnitude and frequency of the AC voltage, and is often used in systems requiring variable speed operation. In addition, various configurations (topologies) are possible depending on the application field based on the power semiconductor, and the size and number of levels of the output voltage and the method of voltage synthesis vary according to the configuration method. Accordingly, various inverter configurations are possible according to the user's requirements.

In industrial inverters, a three-phase half-bridge inverter is commonly used. A three-phase half-bridge inverter has a structure in which three single-phase half-bridge inverters are connected in parallel, and each half-bridge is called a pole, an arm, or a leg, and is a basic circuit constituting the inverter.

In a motor drive system using such an inverter, the output power of the motor is limited by the maximum output voltage and current that the inverter can supply to the motor. The output voltage of the inverter is limited by the size of the DC link voltage and the output voltage synthesis method, and the current is usually limited by the allowable thermal rating of the inverter or motor.

In particular, in the case of high-speed operation of the motor or when the magnitude of the input voltage is small, the voltage margin that can control the current and torque is insufficient due to the counter electromotive force generated by the motor, and the maximum output torque capacity of the motor cannot be fully utilized. There is a problem in that the operating range of the motor is relatively limited.

The technical problem to be solved by the present invention is to provide an inverter control device that increases the range of the output voltage not only in the linear modulation region but also in the over-modulation region.

Another technical problem to be solved by the present invention is to limit the magnitude of the output voltage linearly by using a voltage controller that performs weak magnetic flux control, and to increase the range of operating speed by generating maximum torque under the same voltage and current conditions. To provide an inverter control device.

Another technical problem to be solved by the present invention is to provide an inverter control device for facilitating the overmodulation operation by linearly limiting the magnitude of the output voltage in the overmodulation operation region.

In order to solve the above technical problem, the device of an embodiment of the present invention for controlling an inverter that converts a DC voltage and outputs it to an electric motor receives a command torque and a command voltage to set the magnitude of the output voltage in the weak magnetic flux region a control unit for outputting a command current that can be maintained in a stable manner; a current control unit for outputting the command voltage by proportionally and integrally controlling the command current and the output current of the motor; and a first coordinate conversion unit that converts the command voltage into three phases and provides the converted voltage to the inverter.

In an embodiment of the present invention, the control unit comprises: a first determining unit for determining the level of the command voltage; an integrator for outputting a magnetic flux-command current among the command currents from an error between the magnitude of the command voltage and the limit magnitude; and a command generator for outputting a torque-segment command current among the command currents from the command torque and the magnetic flux-related command current.

(

는 상기 직류전압임)의 90 내지 95%의 범위에서 설정될 수 있다.In one embodiment of the present invention, the limit size is,

(

is the DC voltage) may be set in the range of 90 to 95%.

In an embodiment of the present invention, the control unit may further include a first limiting unit for limiting the torque-segment command current.

In an embodiment of the present invention, the control unit may further include a second limiting unit for limiting the magnetic flux component command current.

In an embodiment of the present invention, the gain of the integrator may be varied in consideration of a weak magnetic flux state or an operating state of the electric motor.

The device according to an embodiment of the present invention may further include an over-modulation unit that corrects a modulation index of the command voltage in the over-modulation section, and generates an over-modulated command voltage from the modified modulation index.

In an embodiment of the present invention, the over-modulation unit includes: a correction unit that corrects the modulation index of the reference voltage in the over-modulation section and corrects the magnitude of the reference voltage from the modified modulation index (corrected voltage command); and a generator configured to generate an over-modulated voltage command (over-modulated voltage command) by limiting the corrected command voltage to the voltage limit line.

In one embodiment of the present invention, the correction unit, the modulation index of the voltage command so that the modulation index of the output voltage of the inverter output by the overmodulation voltage command becomes linear with the modulation index of the overmodulation voltage command Can be modified.

The device according to an embodiment of the present invention may further include a dynamic characteristic improving unit for changing the command voltage by adding a voltage error rotated by 90 degrees to the command voltage in a transient state of the motor.

In an embodiment of the present invention, the dynamic characteristic improving unit may change the command voltage so that the d-axis voltage of the synchronous coordinate system is decreased and the q-axis voltage is increased.

The present invention as described above has the effect of facilitating the operation of the over-modulation region through the linear relationship between the command voltage and the output voltage in the over-modulation region by increasing the range of the output voltage not only in the linear modulation region but also in the over-modulation region. there is

In addition, the inverter control device of the present invention has the effect of improving the weak magnetic flux control to generate the maximum torque under the same voltage and current conditions and increase the operating speed range.

In addition, the inverter control device of the present invention provides a fast torque response without loss of magnetic flux for torque generation by momentarily decreasing the d-axis voltage of the synchronous coordinate system and increasing the q-axis voltage to correct the command voltage in a transient state. It has an anticipation effect.

1 is a configuration diagram for explaining a general three-phase inverter.
2 is a detailed configuration diagram of a conventional inverter control unit.
3 is an exemplary diagram for explaining the configuration of a voltage controller that determines a variable K according to the related art.
4 is an exemplary diagram for explaining a change in a variable K according to a voltage level.
5 is a detailed configuration diagram of an inverter control device according to an embodiment of the present invention.
6 is an exemplary diagram for explaining an overmodulation phenomenon.
7 is an exemplary diagram for explaining overmodulation.
FIG. 8 is a detailed structural diagram of an overmodulation unit of FIG. 5 .
9 is an exemplary diagram for explaining that the modulation-watch correction unit corrects the modulation index.
10 is an exemplary diagram for explaining the relationship between the command voltage of the overmodulation unit and the magnitude of the output voltage.]
11 is a detailed configuration diagram of an embodiment of the control unit of FIG. 5 .
FIG. 12 is an exemplary diagram for explaining the performance of the control unit and the overmodulation unit of FIG. 5 .
13 is a detailed configuration diagram of an embodiment of the dynamic characteristic improving unit of FIG. 5 .

In order to fully understand the configuration and effect of the present invention, preferred embodiments of the present invention will be described with reference to the accompanying drawings. However, the present invention is not limited to the embodiments disclosed below, and may be embodied in various forms and various modifications may be made. However, the description of the present embodiment is provided so that the disclosure of the present invention is complete, and to fully inform those of ordinary skill in the art to which the present invention belongs, the scope of the invention. In the accompanying drawings, components are enlarged in size than actual for convenience of description, and ratios of each component may be exaggerated or reduced.

Terms such as 'first' and 'second' may be used to describe various elements, but the elements should not be limited by the above terms. The above term may be used only for the purpose of distinguishing one component from another. For example, without departing from the scope of the present invention, a 'first component' may be referred to as a 'second component', and similarly, a 'second component' may also be referred to as a 'first component'. can Also, the singular expression includes the plural expression unless the context clearly dictates otherwise. Unless otherwise defined, terms used in the embodiments of the present invention may be interpreted as meanings commonly known to those of ordinary skill in the art.

Hereinafter, a conventional inverter control device will be described with reference to FIGS. 1 to 4 , and an inverter control device according to an embodiment of the present invention will be described in detail with reference to FIGS. 5 to 13 .

1 is a configuration diagram for explaining a general three-phase inverter.

The inverter unit 300 outputs the three-phase AC output voltage (v _an , v _bn , v _{cn ) from the DC link voltage (V dc} ) of the DC voltage storage unit 200 to the motor 400 as a three-phase load. power can be supplied. In this case, the output voltage may be determined according to the on or off state of the three-phase switch of the inverter unit 300 . Two switches of each phase of the inverter unit 300 are connected in series, and each phase may operate independently of each other to generate an output voltage. The output voltages of each phase may be controlled to have a phase difference of 120 degrees from each other.

The DC voltage storage unit 200 may include a capacitor or a battery, and may be configured to maintain a constant voltage.

The inverter unit 300 is a device for converting a DC voltage into an AC voltage, and the output voltage may be controlled by turning on/off the switch.

The inverter control unit 100 may receive the speed or the command torque, output a command voltage based thereon, and determine the three-phase switching state of the inverter unit 300 to drive the motor 400 .

2 is a detailed configuration diagram of a conventional inverter control unit, and it can be seen that a plurality of components are connected in series for control of torque, current, voltage, and the like.

The current controller 120 compares the current command with the actual current, and outputs a command voltage to reduce the current error. The current controller 120 is composed of a proportional integral (PI) controller. At this time, the current controller 120 adjusts the phase so that the rotor magnetic flux is located on the d-axis of the synchronous coordinate system, and increases or decreases the rotor flux through the d-axis current of the synchronous coordinate system. There is no rotor flux in the q-axis of the synchronous coordinate system, and the torque is controlled through the q-axis current of the synchronous coordinate system.

The output voltage calculated by the current controller 120 is converted into a three-phase command voltage through the coordinate conversion of the coordinate converters 130 and 130, and the inverter unit 200 outputs an output voltage to the motor 400 according to the corresponding command voltage. to authorize

In the conventional inverter controller, the voltage controller 110 includes the weak magnetic flux controller, and reduces the magnetic flux current command as shown in the following equation in the weak magnetic flux operation region to limit the output voltage.

는 회전자 자속각 기준의 동기좌표계 d축 전류지령이다. 또, K는 전압제어기(110)의 출력변수이고,

는 약자속 제어기의 출력변수이다. 수학식 1을 보면, 변수 K와

에 의해 자속분 전류지령이 가변될 수 있음을 알 수 있다.where NoLoadCurr is the quiescent current,

is the d-axis current command in the synchronous coordinate system based on the rotor flux angle. In addition, K is an output variable of the voltage controller 110,

is the output variable of the weak flux controller. Looking at Equation 1, the variable K and

It can be seen that the magnetic flux current command can be varied by

3 is an exemplary diagram for explaining a configuration of a voltage controller that determines a variable K according to the related art, and FIG. 4 is an exemplary diagram for explaining a change of a variable K according to a voltage level.

_{When an error between the magnitude V out} of the output voltage of the inverter _{and the command voltage V out} ^* limiting the magnitude of the maximum output voltage is input, the proportional integrator 111 determines the variable K. At this time, the maximum size of the variable K is limited to 100% by the limiter 112 . By the voltage controller 110 of FIG. 3, the variable K varies as shown in FIG. 4 according to the magnitude of the output voltage.

When V _out ^* > V _out , it is a general operating state and the d-axis current of the synchronous coordinate system maintains the no-load current of the motor 400 . On the other hand, when V _out ^* < V _out , in order to limit the output voltage, the voltage controller 110 decreases the variable K to maintain the magnitude of the output voltage equal to the command voltage. At this time, the d-axis current of the synchronous coordinate system is decreased by the variable K.

는 다음 수학식에 의해 결정된다.Meanwhile,

is determined by the following equation.

는 기준속도로서, 사용자가 입력하며 정격속도 근처의 값이다. 전동기 속도가 기준속도보다 작은 경우,

는 1이고, 전동기 속도가 기준속도보다 큰 경우 전동기 속도와 반비례하게

가 감소하여 약자속 운전이 수행된다. 동일하게 동기좌표계 d축 전류도

에 의해 가변한다.here,

is the reference speed, input by the user, and is a value near the rated speed. If the motor speed is less than the reference speed,

is 1, and when the motor speed is greater than the reference speed, it is inversely proportional to the motor speed.

is reduced, so that the weak magnetic flux operation is performed. Similarly, the d-axis current diagram of the synchronous coordinate system

variable by

The conventional voltage controller using Equations 1 and 2 does not consider the voltage limit condition and the current limit condition as an output limiting factor, and applies them all at once regardless of the motor characteristics, so proper voltage control and weak magnetic flux operation are not possible. There is an impossible problem.

In particular, since the conventional weak magnetic flux operation reduces the magnetic flux current in inverse proportion to the rotor speed, there is a problem in that it is difficult to sufficiently use the motor performance because the characteristics of the motor are not reflected.

That is, the conventional voltage controller cannot adequately reduce the rotor magnetic flux, so the maximum output torque capability of the motor cannot be fully utilized, and since the overmodulation region is not considered, there is a problem in that the motor operation region is relatively limited. On the other hand, there are research results on the overmodulation technique, but it is limited to the improvement and utilization of 6-step operation, and there is a problem that the utilization of the overmodulation area between the linear modulation area and the 6-step operation is insufficient. Here, the 6-step operation of the inverter refers to controlling the 3-phase inverter so that six equal switching sections exist in one cycle of the output, and in the case of the 6-step operation, the inverter maximum voltage is output.

According to the inverter control device of an embodiment of the present invention, the voltage range of the output voltage is increased not only in the linear modulation region but also in the over-modulation region by applying the over-modulation technique, and output using a voltage controller that performs including control of the weak magnetic flux In addition to limiting the magnitude of the voltage linearly, it is possible to generate maximum torque under the same voltage and current conditions and increase the range of operating speed.

In addition, by linearly limiting the magnitude of the output voltage in the over-modulation operation region, the over-modulation operation between the linear modulation region and the six-step operation is facilitated.

5 is a detailed configuration diagram of an inverter control device according to an embodiment of the present invention, in which a three-phase command voltage output from the inverter control device 1 may be applied to the inverter unit 300, and The phase output voltage may be applied to the motor 400 serving as a load.

As shown in the drawing, the inverter control device 1 according to an embodiment of the present invention includes a control unit 10, a magnetic flux control unit 15, and a current control unit 20 for receiving a command torque and performing weak magnetic flux control and voltage control. ), a dynamic characteristic improving unit 25 , coordinate transformation units 30 , 35 , 40 , 50 , 55 , 60 , and an overmodulation unit 45 .

First, the operation of the overmodulation unit 45 will be described.

The three-phase half-bridge inverter as shown in FIG. 1 has a limited range of voltages that can be linearly output. 6 is an exemplary diagram for explaining an overmodulation phenomenon.

The limiting range of the output voltage of the inverter is a hexagon 6A formed by a dotted line in FIG. 6 , and the linear modulation region corresponds to a circle 6B. The inverter can output the same voltage for the command voltage within the circle 6B, but synthesis of the output voltage is required for the command voltage in the overmodulation region.

The command voltage 6C of FIG. 6 corresponds to the over-modulation region, and the over-modulation unit 45 may limit the command voltage 6C within the voltage range of the hexagon 6A.

7 is an exemplary diagram for explaining overmodulation, and is for explaining switching state maintenance overmodulation.

이 스위칭 상태 유지 과변조에 의해

으로 이동할 수 있다. The switching state maintenance overmodulation of FIG. 7 is a method of maintaining the switching state as much as possible by preferentially selecting a voltage vector closest to the command voltage vector. command voltage vector

By this switching state maintenance overmodulation

can move to

과

중 근접한 유효전압

의 스위칭 상태를 유지하고, 나머지 스위칭 시간에 다른 유효전압

을 출력하는 방식이다. 이 방식은 지령전압 벡터가 커질수록 가장 근접한 유효전압 벡터를 출력하므로 6-스텝 운전으로 운전절환이 용이하다.This is the effective voltage to output the command voltage vector within a certain switching time.

and

close to the effective voltage

maintains the switching state of , and other effective voltages for the rest of the switching time

method to output. In this method, as the command voltage vector increases, the closest effective voltage vector is output, so it is easy to switch to 6-step operation.

As can be seen in FIG. 6 , it is difficult to synthesize the output voltage corresponding to the command voltage in the overmodulation region, and the actual output voltage decreases. Therefore, the overmodulation unit 45 of the present invention increases the voltage modulation index (MI) to generate an output voltage equal to the command voltage on average.

The modulation index is shown in Equation 3 below.

MI in Equation 3 above is the ratio of the voltage level to the maximum output voltage level of the three-phase half-bridge inverter.

이 될 때이며, 이때의 변조지수는 0.9067이 된다. 따라서, MI가 0.9067보다 큰 영역에서 도 6의 6C와 같은 과변조 현상이 발생하게 된다. 6 and the definition of Equation 3, at the moment when the overmodulation region starts, the magnitude of the command voltage is

At this time, the modulation index becomes 0.9067. Accordingly, in a region where the MI is greater than 0.9067, an overmodulation phenomenon as shown in 6C of FIG. 6 occurs.

The over-modulation unit 45 of an embodiment of the present invention extends the linearity of the output voltage with respect to the command voltage by maximizing the inverter output voltage in the over-modulation section. Unlike the conventional method of instantaneously correcting the command voltage, In consideration of one cycle time unit, the over-modulation method for maintaining the switching state is modified to generate the over-modulation command voltage.

FIG. 8 is a detailed structural diagram of an overmodulation unit of FIG. 5 .

As shown in the drawing, the overmodulation unit 45 according to an embodiment of the present invention may include a modulation index correction unit 451 and an overmodulation command voltage generation unit 452 .

The modulation index correction unit 451 may correct the modulation index of the initial reference voltage and output a virtual modified reference voltage modulation index. FIG. 9 is an exemplary diagram for explaining that the modulation watch correcting unit corrects the modulation index.

For example, assuming a situation where the modulation index of the initial command voltage is 0.95, linearity is secured when the modulation index of the output voltage output by the inverter is also 0.95. For this, according to an embodiment of the present invention, the command voltage It can be provided to the inverter by modifying the modulation index of 0.989 instead of 0.95. As a result, the modulation index of the output voltage becomes 0.95, which can coincide with the modulation index of the actual command voltage.

When the modulation index of the initial reference voltage is corrected by the modulation index correction unit 451, the magnitude of the reference voltage may be modified by Equation (3).

The overmodulation command voltage generating unit 452 may generate an overmodulated command voltage such that the modified command voltage is limited to the voltage limit line by using the amended magnitude of the command voltage. This may be generated by the minimum distance overmodulation of FIG. 7 or the reference voltage may be generated by overmodulation maintaining the switching state.

In this way, the output voltage equal to the command voltage is synthesized on average in the over-modulation region as well as the linear modulation region by the over-modulation unit 45 of the embodiment of the present invention, and a maximum of 6-step operation is possible. 10 is an exemplary diagram for explaining the relationship between the command voltage of the overmodulation unit 45 and the magnitude of the output voltage.

As shown in the figure, according to an embodiment of the present invention, since the modulation index of the output voltage becomes the same as the linearity reference line, it can be seen that the linearity of the output voltage of the inverter is secured.

The operation of the control unit 10 of the present invention will be described.

11 is a detailed configuration diagram of an embodiment of the control unit 10 of the present invention.

As shown in the figure, the control unit 10 according to an embodiment of the present invention is capable of maintaining a constant level of the output voltage in the weak magnetic flux region by the voltage feedback method, and the size determination unit 101, the first error It may include a determining unit 102 , an integrating unit 103 , a limiting unit 104 , a second error determining unit 105 , a command generating unit 106 , and a limiting unit 107 .

를 결정할 수 있다. The magnitude determination unit 101 calculates the magnitude of the output voltage from the command voltage that is the output of the current control part 20 to determine the magnitude of the command voltage.

can be decided

와 지령전압 제한크기

의 오차를 결정하고, 적분부(103)는 이를 적분하여 지령자속을 출력할 수 있다. 이때 제한부(104)에 의해 최소 자속크기를 확보할 수 있다. The first error determining unit 102 determines the magnitude of the command voltage.

and command voltage limit size

may determine the error of , and the integrator 103 may integrate it to output the command magnetic flux. At this time, it is possible to secure the minimum magnetic flux size by the limiter 104 .

가 지령전압 제한크기

보다 크지 않도록 회전자 지령자속

을 출력할 수 있으며, 지령자속

와 회전자 자속

의 오차를 제2오차결정부(105)가 출력할 수 있다.The first error determining unit 102 and the integrating unit 103 may perform proportional-integration control, that is, the magnitude of the command voltage.

Command voltage limit size

Rotor command flux so as not to be greater than

can be output, and the command flux

and rotor flux

The second error determining unit 105 may output an error of .

In this case, the d-axis current of the synchronous coordinate system may be output instead of the command flux depending on the control method or the type of the motor 400 .

은 상수가 아니라 약자속 운전과 전동기(400)의 운전상태 또는 인버터 제어장치(1)의 응답성을 고려하여 선정될 수 있을 것이다. 이때

가 크면 적분부(103)의 응답성이 빨라지고,

가 작으면 적분부(103)의 응답성이 느려질 수 있다. gain of integrator 103

is not a constant, but may be selected in consideration of the weak magnetic flux operation and the operating state of the electric motor 400 or the responsiveness of the inverter control device 1 . At this time

If is large, the responsiveness of the integrator 103 increases,

If is small, the responsiveness of the integrator 103 may be slow.

에 의해 인버터의 출력전압이 제한될 수 있다. 선형 변조영역까지 출력전압을 사용하는 경우, 지령전압 제한크기

는

의 90 내지 95%로 설정할 수 있다. 이는, 전동기(400)의 임피던스에 의한 전압강하를 고려한 것이다. 만약, 과변조 영역까지 출력전압을 사용하는 경우, 지령전압 제한크기는 그 이상으로 설정될 수도 있다.On the other hand, in an embodiment of the present invention, the command voltage limit size

may limit the output voltage of the inverter. When using the output voltage up to the linear modulation range, the command voltage limit size

is

It can be set to 90 to 95% of This is in consideration of the voltage drop due to the impedance of the electric motor 400 . If the output voltage is used up to the overmodulation region, the command voltage limit size may be set higher than that.

In this way, the size determining unit 101, the first error determining unit 102, the integrating unit 103, the limiting unit 104, and the second error determining unit 105 of the control unit 10 according to an embodiment of the present invention. can determine the degree of attenuation of the rotor flux.

과 제2오차결정부(105)의 출력으로부터 토크분 전류지령

을 생성할 수 있고 제한부(107)는 동기좌표계 d축 전류의 크기에 따라 토크분 전류지령을 제한하여 출력할 수 있다.The command generation unit 106 is a command torque

and the torque equivalent current command from the output of the second error determining unit 105

can be generated, and the limiter 107 may limit and output the torque-related current command according to the magnitude of the d-axis current of the synchronous coordinate system.

The control unit 10 according to an embodiment of the present invention satisfies the voltage limit condition by the command voltage limit magnitude, and satisfies the current limit condition by the limiter 107, and outputs the maximum torque within the limited voltage and current range. can do.

FIG. 12 is an exemplary diagram for explaining the performance of the control unit 10 and the overmodulation unit 45 of FIG. 5 .

In Fig. 12, 12C shows the torque-speed performance curve of the conventional method, 12A shows the torque-speed performance curve when overmodulation and weak magnetic flux control are performed, and 12B shows the torque when the weak magnetic flux control is performed. - It shows the speed performance curve.

As shown in the figure, it can be seen that when the weak magnetic flux control is performed, the performance is improved compared to the conventional method, and when the overmodulation control is performed, the performance is further improved.

In addition, 12A and 12B can be adjusted according to the magnitude of the command voltage of the control unit 10. As the command voltage is selected smaller, the voltage limit condition becomes smaller, so that the operating range of the motor is reduced.

As an example of application of the present invention, when the DC link voltage is reduced due to input power failure, etc., the command voltage limit size of the control unit 10 of the present invention is increased, and the inverter voltage is output without the influence of the input power state to the motor performance can be maintained

As described above, according to the control unit 10 according to an embodiment of the present invention, the existing system can be improved by appropriately adjusting the command voltage limit size.

The operation of the dynamic characteristic improving unit 25 of FIG. 5 will be described.

에 의해 결정되는데,

는 약자속 상태, 또는 전동기의 운전상태 등을 고려하여 가변할 수 있으나 응답성을 빠르게 하기 위해 충분히 크게 하는 것은 어렵다. 따라서, 제어부(10)가 충분히 과도상태를 벗어나기 전까지 토크특성을 제한하게 되는데, 이때 동특성 향상부(25)는 과도상태에서 토크특성을 확보하기 위한 것이다. 이를 위해 동특성 향상부(25)는 순시적으로 d축 전류 또는 지령자속을 적절하게 감소시킬 수 있다. The responsiveness of the control unit 10 is the gain of the integrator 103 .

is determined by

can be varied in consideration of the weak magnetic flux state or the operating state of the motor, but it is difficult to make it large enough to speed up the responsiveness. Accordingly, the control unit 10 limits the torque characteristic until it sufficiently leaves the transient state. At this time, the dynamic characteristic improving unit 25 is for securing the torque characteristic in the transient state. To this end, the dynamic characteristic improving unit 25 may temporarily reduce the d-axis current or the command magnetic flux appropriately.

13 is a detailed configuration diagram of an embodiment of the dynamic characteristic improving unit of FIG. 5 .

As shown in the figure, the dynamic characteristic improving unit 25 according to an embodiment of the present invention may change the command voltage by adding a voltage error rotated by 90 degrees to the command voltage. This can be expressed as a mathematical expression as follows.

Accordingly, in the case of the induction motor, the d-axis voltage of the synchronous coordinate system may decrease instantaneously and the q-axis voltage may increase. The torque is generated in proportion to the magnetic flux and the torque current, and the magnetic flux current may decrease due to the instantaneous decrease of the d-axis voltage of the synchronous coordinate system, and the torque current may increase due to the increase of the q-axis voltage of the synchronous coordinate system. However, since the magnetic flux is instantaneously constant, a fast torque response can be expected without loss of magnetic flux for torque generation.

The operation of the overall inverter control device of FIG. 5 will be described.

와 전류제어부(20)의 출력인 지령전압이 입력되면, 약자속 운전을 사용하여 출력전압의 크기를 일정하게 하는 지령자속

또는 자속분 전류지령

과, 토크분 전류지령

을 출력할 수 있다. Command torque to control unit (10)

When the command voltage, which is the output of the eddy current control unit 20, is input, the command magnetic flux to make the magnitude of the output voltage constant by using the weak magnetic flux operation.

or magnetic flux current command

Over and torque equivalent current command

can be printed out.

When the control unit 10 outputs the magnetic flux current command, the magnetic flux control unit 15 may not be required.

When the control unit 10 outputs the command magnetic flux, the magnetic flux control unit 15 outputs the magnetic flux current command through proportional integral control of the estimated magnetic flux of the electric motor 400 estimated by the magnetic flux estimation unit 50 and the command magnetic flux. can do. The magnetic flux estimating unit 50 may estimate the magnetic flux from the coordinate conversion unit 60 converting the output current of the inverter unit 300 into d-axis and q-axis current, and may output a magnetic flux angle.

When the magnetic flux angle output by the magnetic flux estimating unit 50 is coordinate-converted by the converting unit 40 to determine the output current in the synchronous coordinate system, the current control unit 20 receives the current command and the output current and performs proportional integral control by Current command can be output.

As described above, the dynamic characteristic improving unit 25 is for securing the torque characteristic in the transient state, and changes the command voltage by adding the voltage error rotated by 90 degrees to the command voltage, and thereby the d-axis voltage of the synchronous coordinate system instantaneously. The command voltage can be corrected by decreasing the q-axis voltage and increasing the q-axis voltage. In this case, the output command voltage of the over-modulation unit 45 may be converted into a synchronous coordinate system by the coordinate conversion unit 30 in the dynamic characteristic improving unit 25 , and may be input to the dynamic characteristic improving unit 25 .

In this way, the command voltage corrected by the dynamic characteristic improvement unit 25 is changed to a command voltage on the stationary coordinate system by the coordinate conversion unit 35 and input to the over-modulation unit 45, and the over-modulation unit 45 is overmodulated. In order to maximize the inverter output voltage in the section and expand the linearity of the output voltage with respect to the reference voltage, the modulation index of the reference voltage is corrected, the virtual modified reference voltage modulation index is output, and the size of the modified reference voltage is used. Thus, the overmodulated command voltage can be output so that the corrected command voltage is limited to the voltage limit line. However, when it is not in the over-modulation region, the output of the coordinate transformation unit 35 may be input to the coordinate transformation unit 55 without correction of the command voltage.

In this way, the over-modulation command voltage output from the over-modulation unit 45 may be output as a three-phase command voltage by the coordinate conversion unit 55, and is applied to the inverter unit 300 to be converted into a motor input voltage. will be able

As described above, the inverter control device of the present invention can increase the range of the output voltage not only in the linear modulation region but also in the over-modulation region by performing over-modulation by the over-modulation unit 45 . That is, it is possible to facilitate the operation of the over-modulation region through the linear relationship between the command voltage and the output voltage in the over-modulation region.

In addition, the inverter control device of the present invention can improve the weak magnetic flux control to generate maximum torque under the same voltage and current conditions and increase the operating speed range.

In addition, the inverter control device of the present invention provides a fast torque response without loss of magnetic flux for torque generation by momentarily decreasing the d-axis voltage of the synchronous coordinate system and increasing the q-axis voltage to correct the command voltage in a transient state. can be expected

Although the embodiments according to the present invention have been described above, these are merely exemplary, and those of ordinary skill in the art will understand that various modifications and equivalent ranges of embodiments are possible therefrom. Accordingly, the true technical protection scope of the present invention should be defined by the following claims.

Claims (11)

A device for controlling an inverter that converts a DC voltage and outputs it to an electric motor,
a control unit receiving the command torque and the command voltage and outputting a command current capable of maintaining a constant magnitude of the output voltage in the weak magnetic flux region;
a current control unit for outputting the command voltage by proportionally and integrally controlling the command current and the output current of the motor; and
Inverter control device including a first coordinate conversion unit for converting the command voltage into three phases to provide to the inverter.
According to claim 1, wherein the control unit,
a first determining unit that determines the level of the command voltage;
an integrator for outputting a magnetic flux component command current among the command current from an error between the command voltage and the limit magnitude; and
and a command generation unit for outputting a torque component command current among the command current from the command torque and the magnetic flux component command current.
According to claim 2, wherein the limit size,

(

is the DC voltage) in the range of 90 to 95% of the inverter control device.
According to claim 2, wherein the control unit,
The inverter control device further comprising a first limiting unit for limiting the torque-segment command current.
According to claim 2, wherein the control unit,
Inverter control device further comprising a second limiter for limiting the magnetic flux command current.
The inverter control device according to claim 2, wherein the gain of the integrator is variable in consideration of a weak magnetic flux state or an operating state of the electric motor.
According to claim 1,
The inverter control device further comprising an over-modulation unit for correcting the modulation index of the command voltage in the over-modulation section, and generating an over-modulated command voltage from the modified modulation index.
The method according to claim 7, wherein the overmodulation unit comprises:
a correction unit that corrects the modulation index of the reference voltage in the over-modulation section and corrects the magnitude of the reference voltage from the modified modulation index (correction voltage command); and
An inverter control device including a generator configured to generate an overmodulated voltage command (overmodulated voltage command) by limiting the corrected command voltage to a voltage limit line.
The method of claim 8, wherein the correction unit,
The inverter control device for correcting the modulation index of the voltage command so that the modulation index of the output voltage of the inverter output by the overmodulation voltage command becomes linear with the modulation index of the overmodulation voltage command.
According to claim 1,
In the transient state of the motor, the inverter control device further comprising a dynamic characteristic improving unit for changing the command voltage by adding a voltage error rotated by 90 degrees to the command voltage.
11. The method of claim 10, wherein the dynamic characteristic improving unit,
An inverter control device for changing the command voltage so that the d-axis voltage of the synchronous coordinate system is instantaneously decreased and the q-axis voltage is increased.

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