KR102494526B1 - Offset estimator in indcution motor and estimation method thereof - Google Patents

Abstract

An offset estimator and an offset estimation method for an induction motor are disclosed. The offset estimation method includes calculating a first subtracted value obtained by subtracting the stator back EMF estimation offset fed back from the stator back EMF, calculating a first estimated stator flux and a second estimated stator flux from the calculated subtraction value, an estimated stator flux calculation step, Calculating a second subtraction value obtained by subtracting the calculated second estimated stator flux from the calculated first estimated stator flux, and calculating a stator EMF estimation offset by PI-controlling the calculated second subtraction value.

Description

Induction motor offset estimator and offset estimation method {OFFSET ESTIMATOR IN INDCUTION MOTOR AND ESTIMATION METHOD THEREOF}

The present invention relates to an induction motor offset estimator and an offset estimation method, and more particularly, to an induction motor offset estimator and an offset estimation method for estimating an offset of a stator counter electromotive force of an induction motor.

Induction motors are used in many industrial fields due to their advantages such as high durability and low maintenance cost. Vector control enables instantaneous torque control of AC motors and is applied to many fields requiring high-performance driving of motors. In vector control, magnetic flux information is essential to obtain a control angle. A Hall sensor for measuring magnetic flux is not used because of durability problems, and in most cases, a method of estimating magnetic flux from a magnetic flux estimator using an induction motor model equation is used. Therefore, it is very important to design a high-performance flux estimator for high-performance driving of an induction motor.

A lot of research has been done on the voltage model magnetic flux estimator, which has a simple structure and is robust to parameter errors. In the voltage model, magnetic flux can be estimated by integrating back EMF. However, it is difficult to implement a voltage model including a pure integration operation due to a voltage offset due to the nonlinear characteristics of the inverter and a current measurement offset. A lot of research has been done to solve these problems. A method of implementing a voltage model using a low pass filter (LPF) has been studied, but in this method, the effect of offset always remains. Therefore, there is a need for an offset estimator capable of estimating the offset.

The present invention is to solve the above problems, and an object of the present invention is to provide an offset estimator and an offset estimation method for estimating an offset to improve flux estimation of an induction motor.

According to an embodiment of the present invention for achieving the above object, an offset estimation method includes calculating a first subtraction value obtained by subtracting a feedbacked stator back EMF estimation offset from a stator back EMF, and calculating a first subtraction value from the calculated subtraction value. An estimated stator flux calculation step of calculating an estimated stator flux and a second estimated stator flux; calculating a second subtraction value obtained by subtracting the calculated second estimated stator flux from the calculated first estimated stator flux; and The method may include calculating the stator EMF estimation offset by PI-controlling the second subtraction value.

Here, the second subtraction value may finally be zero.

Meanwhile, the step of calculating the estimated stator flux may include calculating a stator flux command value by low-pass filtering the magnitude of the estimated stator flux input, rotating the calculated stator flux command value by a preset angle, and rotating the stator flux command value. Calculating a third subtraction value obtained by subtracting the estimated stator magnetic flux calculated from , outputting an output value obtained by applying a preset cut-off angle frequency to the third subtraction value, and adding the output value to the stator counter electromotive force. Calculating and integrating the addition value to calculate the estimated stator magnetic flux.

In the calculating of the estimated stator flux, the first estimated stator flux may be calculated based on the first cutoff angle frequency, and the second estimated stator flux may be calculated based on the second cutoff angle frequency.

According to an embodiment of the present invention for achieving the above object, the offset estimator includes a first operator for calculating a first subtraction value obtained by subtracting the estimated offset of the stator back EMF fed back from the stator back EMF, and a second subtraction value from the calculated subtraction value. 1 first flux estimator for calculating estimated stator flux, second flux estimator for calculating second estimated stator flux from the calculated subtraction value, subtracting the calculated second estimated stator flux from the calculated first estimated stator flux A second calculator for calculating a second subtraction value and a controller for calculating the stator EMF estimation offset by PI-controlling the calculated second subtraction value.

Here, the second subtraction value may finally be zero.

Further, each of the first magnetic flux estimator and the second magnetic flux estimator includes a low-pass filter for calculating a stator flux command value by low-pass filtering the magnitude of the estimated stator flux input, and a low-pass filter for rotating the calculated stator flux command value at a preset angle. A third operator, a fourth operator that calculates a third subtraction value by subtracting the estimated stator flux calculated from the rotated stator flux command value, and a fifth operator that outputs an output value obtained by applying a predetermined cut-off angle frequency to the third subtraction value. It may include an operator, a sixth operator that calculates an addition value obtained by adding the output value to the stator counter electromotive force, and an integrator that calculates an estimated stator magnetic flux by integrating the addition value.

Meanwhile, the first estimated stator magnetic flux may be calculated based on a first cutoff angle frequency, and the second estimated stator magnetic flux may be calculated based on a second cutoff angle frequency.

As described above, according to various embodiments of the present disclosure, an offset estimator and an offset estimation method of an induction motor can accurately estimate an offset.

In addition, since the offset estimated by the offset estimator and the offset estimation method of the induction motor is removed from the stator counter electromotive force, more accurate magnetic flux estimation can be performed.

The effects of the present invention are not limited to the effects mentioned above, and other effects not mentioned will be clearly understood by those skilled in the art from the description below.

1 is a block diagram of an offset estimator according to an embodiment of the present invention.
2 is a block diagram of a magnetic flux estimator used in an offset estimation method according to an embodiment of the present invention.
3 is a diagram illustrating a root locus of an offset estimator according to an embodiment of the present invention.
4 is a block diagram of a magnetic flux estimator of an induction motor to which an offset estimator according to an embodiment of the present invention is applied.
5 is a flowchart of an offset estimation method according to an embodiment of the present invention.
6 is a diagram showing experimental results for a speed of 300 r/min in a no-load state in the Lorentz model according to an embodiment of the present invention.
7 is a view showing experimental results for a speed of 200 r/min in a full load state in the Lorentz model according to an embodiment of the present invention.
8 is a diagram showing experimental results for a speed of 300 r/min in a no-load state in the Ohtani model according to an embodiment of the present invention.
9 is a diagram showing experimental results for a speed of 200 r/min in a full load state in the Ohtani model according to an embodiment of the present invention.

Hereinafter, various embodiments will be described in more detail with reference to the accompanying drawings. The embodiments described in this specification may be modified in various ways. Particular embodiments may be depicted in the drawings and described in detail in the detailed description. However, specific embodiments disclosed in the accompanying drawings are only intended to facilitate understanding of various embodiments. Therefore, the technical idea is not limited by the specific embodiments disclosed in the accompanying drawings, and it should be understood to include all equivalents or substitutes included in the spirit and technical scope of the invention.

Terms including ordinal numbers, such as first and second, may be used to describe various components, but these components are not limited by the above terms. The terminology described above is only used for the purpose of distinguishing one component from another.

In this specification, terms such as "comprise" or "having" are intended to indicate that there is a feature, number, step, operation, component, part, or combination thereof described in the specification, but one or more other features It should be understood that the presence or addition of numbers, steps, operations, components, parts, or combinations thereof is not precluded. It is understood that when an element is referred to as being "connected" or "connected" to another element, it may be directly connected or connected to the other element, but other elements may exist in the middle. It should be. On the other hand, when an element is referred to as “directly connected” or “directly connected” to another element, it should be understood that no other element exists in the middle.

In the description of the present invention, the order of each step should be understood as non-limiting, unless the preceding step logically and temporally necessarily precedes the subsequent step. That is, except for the above exceptional cases, even if the process described as the later step is performed before the process described as the preceding step, the essence of the invention is not affected, and the scope of rights must also be defined regardless of the order of the steps. And, in this specification, "A or B" is defined to mean not only selectively indicating either one of A and B, but also including both A and B. In addition, in this specification, the term “including” has a meaning encompassing further including other components in addition to the elements listed as included.

In this specification, only essential components necessary for the description of the present invention are described, and components not related to the essence of the present invention are not mentioned. And it should not be interpreted as an exclusive meaning that includes only the mentioned components, but should be interpreted as a non-exclusive meaning that may include other components.

In addition, in describing the present invention, if it is determined that a detailed description of a related known function or configuration may unnecessarily obscure the subject matter of the present invention, the detailed description thereof will be abbreviated or omitted. Meanwhile, each embodiment may be implemented or operated independently, but each embodiment may be implemented or operated in combination.

In the present invention, each variable is defined as follows.

v: voltage, i: current, λ: magnetic flux

ω _r : rotor angular velocity, ω _e : synchronous angular velocity

: 미분기

: differentiator

Bold: Complex vector (e.g. x = x _d + jx _q )

*: command value

| |: the size of the vector

Subscript: stator (s), rotor (r) (e.g., R _s : stator resistance, R _r : rotor resistance)

Superscript: stationary coordinate system (s), synchronous coordinate system (e), rotor coordinate system (r)

σL _s : stator transient inductance, L _m : mutual inductance, L _s : stator inductance, L _r : rotor inductance

: 고정자 역기전력

: Stator back emf

: 회전자 역기전력

: Rotor back EMF

: 고정자 역기전력 추정 옵셋(offset)

: stator counter emf estimation offset

1 is a block diagram of an offset estimator according to an embodiment of the present invention.

Referring to FIG. 1 , the offset estimator 100 may include a first operator 110, a first magnetic flux estimator 120a, a second magnetic flux estimator 120b, a second operator 130, and a controller 140. there is.

)을 입력받고, 산출된 고정자 역기전력 추정 옵셋(

)을 피드백으로 입력받을 수 있다. 제1 연산기(110)는 입력된 고정자 역기전력(

)으로부터 고정자 역기전력 추정 옵셋(

)을 감산한 제1 감산 값을 출력할 수 있다.The first operator 110 is a stator counter electromotive force (

) is input, and the calculated stator EMF estimation offset (

) can be input as feedback. The first calculator 110 is input stator counter electromotive force (

) from the stator back EMF estimation offset (

) may be subtracted to output a first subtraction value.

) 및 제2 추정 고정자 자속(

)을 산출할 수 있다.The first magnetic flux estimator 120a and the second magnetic flux estimator 120b may each receive the first subtracted value output from the first operator 110 . As an example, the first magnetic flux estimator 120a and the second magnetic flux estimator 120b may be of a low pass filter type. In the present invention, the offset of the back electromotive force can be estimated using the property that the effect of the offset component exists in the magnetic flux estimator of the low pass filter type. The first magnetic flux estimator 120a and the second magnetic flux estimator 120b each have a first estimated stator magnetic flux (

) and the second estimated stator flux (

) can be calculated.

)으로부터 제2 추정 고정자 자속(

)을 감산한 제2 감산 값을 산출할 수 있다. 산출된 제2 감산 값은 제어기(140)로 입력될 수 있다.The second operator 130 calculates the first estimated stator magnetic flux (

) from the second estimated stator flux (

) may be subtracted to calculate a second subtraction value. The calculated second subtraction value may be input to the controller 140 .

)을 산출할 수 있다. 산출된 고정자 역기전력 추정 옵셋(

)은 메인 자속 추정기로 입력되는 고정자 역기전력에 적용됨으로써 메인 자속 추정기는 정확한 최종 자속을 추정할 수 있다.The controller 140 PI-controls the second subtracted value to obtain a stator EMF estimation offset (

) can be calculated. Calculated stator EMF estimation offset (

) is applied to the stator counter electromotive force input to the main magnetic flux estimator, so that the main magnetic flux estimator can accurately estimate the final magnetic flux.

So far, the block diagram of the offset estimator has been described. Below, the operation of the offset estimator will be described based on the equation.

축 상에서, 유도 전동기의 쇄교 자속식은 다음과 같다.rotating at an arbitrary speed ω

On shaft, the flux linkage equation of an induction motor is:

(Equation 1)

(Equation 2)

(Equation 3)

(Equation 4)

The voltage model magnetic flux estimator may be obtained by integrating the back electromotive force. From the above model equation, the stator flux can be obtained from (Equation 5) and the rotor flux from (Equation 6).

(Equation 5)

(Equation 6)

In the voltage model, integration saturation may occur in pure integration (1/s) due to the offset component included in the voltage and current of the back EMF. In addition, DC drift may be generated by the condition of the initial value of the integral. As an example, a voltage model using a low-pass filter may prevent integral saturation. The low-pass filter model for the phase- and magnitude-compensated rotor flux is as follows.

(Equation 7)

Here, ω _c is the cutoff angular frequency.

Since there is no pure integration in this model, integration saturation or DC drift problems do not occur. However, since it is a first-order filter, the offset included in the back EMF cannot be completely removed. The higher the cut-off angle frequency, the smaller the effect of the offset, but the cut-off angle frequency cannot be set infinitely high because of the stability of magnetic flux estimation.

The Ohtani model using the magnetic flux command of the low-pass filter type is as follows.

(Equation 8)

)은 동기좌표계 자속 지령치(

)에 최종적으로 추정된 자속(

)의 위상(

)을 이용하여 산출될 수 있다. 오타니 모델도 차단각 주파수가 높을수록 옵셋의 영향이 작아질 수 있다. 그러나, 차단각 주파수가 높을수록 위생 왜곡이 심해지므로 차단각 주파수는 무한정 높게 설정될 수 없다.Command flux (

) is the magnetic flux command value of the synchronous coordinate system (

) to the final estimated magnetic flux (

) of the phase (

) can be calculated using In the Ohtani model, the higher the cutoff angle frequency, the smaller the effect of the offset. However, since sanitary distortion increases as the cutoff angle frequency increases, the cutoff angle frequency cannot be set infinitely high.

)은 상술한 모델방정식으로부터 유도될 수 있다.The Lorentz model is: current model (

) can be derived from the above-described model equation.

(Equation 9)

,

here,

,

Since this model is in the form of a second-order filter, the offset included in the back EMF can be completely canceled in a steady state. The offset in the transient state can be reduced as much as possible by increasing the cutoff angle frequency. However, the higher the cutoff angle frequency, the higher the utilization rate of the current model. Since the current model is sensitive to the errors of the parameters R _r , L _r , and L _m , the frequency of cut-off angle should be reduced to reduce the frequency of use of the current model. In addition, since the Lorentz model has more severe phase distortion than the Ohtani model, which is a first-order filter type, the cut-off angle frequency should be designed to be lower.

The effect of the offset on the magnetic flux estimator of the low-pass filter type of (Equation 7) and (Equation 8) described above can be obtained as follows.

(Equation 10)

는 역기전력에 포함된 옵셋 성분이고,

는 옵셋에 의한 자속의 직류 성분이다.here,

Is an offset component included in the back EMF,

is the DC component of the magnetic flux due to the offset.

Since the offset included in the counter-EMF has a much slower variation than the AC component, it can be regarded as a DC with a constant value. (Equation 10) can be expressed as follows in the time domain.

(Equation 11)

의 자속의 직류 성분이 존재한다.in normal condition

There is a direct current component of the magnetic flux of

In the case of the Lorentz model of (Equation 9), the DC flux due to the offset is as follows.

(Equation 12)

This can be expressed in the time domain as:

(Equation 13)

으로 옵셋에 의한 영향은 없다. 그러나, (식 13)과 같이 과도 상태의 영향은 존재한다.DC magnetic flux may gradually monotonically decrease to '0' while oscillating in a transient state. in normal condition

, there is no effect by offset. However, as shown in (Equation 13), the effect of the transient state exists.

2 is a block diagram of a magnetic flux estimator used in an offset estimation method according to an embodiment of the present invention.

The magnetic flux estimator is affected by the offset of back EMF. The present invention relates to an offset estimator and an offset estimation method for estimating an offset to improve the performance of a magnetic flux estimator. As an embodiment, the present invention may use the Ohtani model flux estimator for stator flux. Here, the property that a DC magnetic flux component due to offset exists can be used. The magnetic flux estimator is shown below.

(Equation 14)

이 존재하므로 이를 이용할 수 있으나, 회전자 자속 기준에서는

이 존재하지 않는다. 그러므로, 본 발명에서는 (식 14)에서 최종 추정된

의 크기를 이용한다. 옵셋에 의해서 |

|는 리플이 존재하므로 저역 통과 필터로 필터링하고, 이 값을

로 사용한다. 하지만, |

|를 필터링하면 값이 ‘0’에서 시작하여, 정상 상태에 도달하기까지 시간이 소요된다. 따라서, 다음과 같이 저역 통과 필터 출력의 초기값을 아래와 같이 계산하여 설정할 수 있다. 모델방정식으로부터 아래의 쇄교자속식이 성립한다.In the stator flux reference control, the synchronous coordinate system stator flux command value

exists, so it can be used, but in terms of rotor flux

this doesn't exist Therefore, in the present invention, the final estimate in (Equation 14)

use the size of by offset |

| has a ripple, so it is filtered with a low-pass filter, and this value is

use as However, |

When | is filtered, the value starts at '0' and it takes time to reach a steady state. Therefore, the initial value of the low-pass filter output can be calculated and set as follows. From the model equation, the following flux-linkage equation is established.

(Equation 15)

으로 일정하게 제어되고 있으므로 회전자 자속 기준 동기좌표계 고정자 자속은Rotor flux based on rotor flux

Since it is constantly controlled by , the stator magnetic flux in the synchronous coordinate system based on the

(Equation 16)

Therefore, the magnitude of the stator flux is

(Equation 17)

의 초기값으로 설정한다. 도 2에는 상술한 자속 추정기가 도시되어 있다. 즉, 도 2에 도시된 바와 같이, 자속 추정기(120)는 저역 통과 필터(121), 제3 연산기(122), 제4 연산기(123), 제5 연산기(124), 제6 연산기(125) 및 적분기(126)을 포함할 수 있다.this value

set to the initial value of 2 shows the above-described magnetic flux estimator. That is, as shown in FIG. 2, the magnetic flux estimator 120 includes a low pass filter 121, a third operator 122, a fourth operator 123, a fifth operator 124, and a sixth operator 125 and an integrator 126 .

)를 필터링하여 회전자 자속 기준 동기좌표계 고정자 자속 지령치(

)를 산출할 수 있다. 제3 연산기(122)는 산출된 회전자 자속 기준 동기좌표계 고정자 자속 지령치(

)를 기 설정된 각도로 회전시킬 수 있다. 제4 연산기(123)는 회전된 회전자 자속 기준 고정자 자속 지령치로부터 산출된 추정 고정자 자속(

)을 감산한 감산 값을 산출할 수 있다. 제5 연산기(124)는 감산 값에 기 설정된 차단각 주파수(ω_c)를 적용한 출력 값을 출력할 수 있다. 제6 연산기(125)는 고정자 역기전력(

)에 제5 연산기(124)로부터 출력된 출력 값을 가산한 가산 값을 산출할 수 있다. 적분기(126)는 제6 연산기(125)로부터 산출된 가산 값을 적분하여 추정 고정자 자속(

)을 산출할 수 있다. 상술한 바와 같이, 산출된 추정 고정자 자속(

)은 피드백되어 제3 연산기(122)로 입력될 수 있다.The low-pass filter 121 is the magnitude of the estimated stator magnetic flux input (

) to filter the rotor flux reference synchronous coordinate system stator flux command value (

) can be calculated. The third calculator 122 calculates the stator magnetic flux command value of the synchronous coordinate system based on the rotor flux (

) can be rotated at a preset angle. The fourth calculator 123 calculates the estimated stator flux (calculated from the reference stator flux reference value of the rotated rotor flux)

) can be calculated by subtracting the subtraction value. The fifth calculator 124 may output an output value obtained by applying a predetermined cut-off angle frequency ω _c to the subtraction value. The sixth operator 125 is a stator counter electromotive force (

An addition value obtained by adding the output value output from the fifth operator 124 to ) can be calculated. The integrator 126 integrates the addition value calculated from the sixth operator 125 to obtain the estimated stator flux (

) can be calculated. As described above, the calculated estimated stator flux (

) may be fed back and input to the third calculator 122.

, θ는 출력단에 최종 추정된

로부터 다음과 같이 연산될 수 있다.here,

, θ is the final estimated

From can be calculated as:

(Equation 18)

의 계산을 위한 별도의 연산은 필요 없으며, 동기좌표계 고정자 자속 지령치를 그대로 이용할 수 있다. 저역 통과 필터의 시정수 ι는 50 ~ 200 ms 범위 내에서 설정될 수 있다.From the stator flux standard

There is no need for a separate operation for the calculation of , and the synchronous coordinate system stator flux command value can be used as it is. The time constant ι of the low-pass filter can be set within the range of 50 to 200 ms.

, 제2 자속 추정기:

)로 구현될 수 있다. 차단각 주파수가 다르더라도, 두 자속 추정기에서 추정되는 자속의 교류 성분은 동일하다. 그러나, (식 10)과 같이 직류 성분은 다를 수 있다. 제1 자속 추정기에서 추정된 제1 자속(

)과 제2 자속 추정기에서 추정된 제2 자속(

)의 차는 아래와 같다.In the present invention, two different cut-off angle frequencies (first magnetic flux estimator:

, the second flux estimator:

) can be implemented. Even if the cut-off angle frequencies are different, the AC component of the magnetic flux estimated by the two magnetic flux estimators is the same. However, as shown in (Equation 10), the DC component may be different. The first magnetic flux estimated by the first magnetic flux estimator (

) and the second magnetic flux estimated by the second magnetic flux estimator (

) is as follows.

(Equation 19)

가 ‘0’이 되도록 제어하면 옵셋

를 추정할 수 있다.That is, only the term for the offset component included in the counter electromotive force remains.

is controlled to be '0', the offset

can be estimated.

에 대한 추정 옵셋

의 전달 함수는 다음과 같다.The actual offset from the offset estimator 100 shown in FIG. 1 of the present invention

estimated offset for

The transfer function of is:

(Equation 20)

를 만족한다. PI 이득은 다음과 같이 구현될 수 있다.Since G(0) = ∞, in the steady state

satisfies The PI gain can be implemented as follows.

(Equation 21)

k ₀ is a gain of the offset estimator, and z ₀ is defined as a zero point. For stability and proper response in the transient state, we design ω _c2 > ω _c1 > z ₀ > 0, and k ₀ can be set to a value lower than 1.

3 is a diagram illustrating a root locus of an offset estimator according to an embodiment of the present invention.

Referring to FIG. 3, the root locus of the transfer function of (Equation 20) according to the gain k0 is shown. As an embodiment, ω _c1 = 2π, ω _c2 = 6π, z ₀ = 6, and k ₀ = 0.1. In the above example, a vibration response may not appear because there are no imaginary terms at the three poles.

4 is a block diagram of a magnetic flux estimator of an induction motor to which an offset estimator according to an embodiment of the present invention is applied.

)으로부터 필터링된 추정 옵셋(

)을 제거할 수 있다. 메인 자속 추정기(300)는 추정 옵셋(

)이 제거된 고정자 역기전력(

)으로부터 자속을 추정할 수 있다. 즉, 본 발명의 옵셋 추정기(100)는 옵셋 보상기(200)에 포함되어 정확한 옵셋을 추정할 수 있다. 그리고, 옵셋 보상기(200)는 고정자 역기전력으로부터 추정된 옵셋을 제거할 수 있다. 따라서, 옵셋 추정기(100)를 포함하는 유도 전동기(1000)는 정확한 자속을 추정할 수 있다.Referring to FIG. 4 , an induction motor 1000 may include an offset estimator 100 , an offset compensator 200 and a main magnetic flux estimator 300 . The offset compensator 200 may include a low pass filter 10 and an operator 20 of the offset compensator. The offset estimator 100 may estimate an offset of the stator counter electromotive force. The low-pass filter 10 may appropriately filter the output of the offset estimator 100 for stability. The operator 20 of the offset compensator calculates the stator counter electromotive force (

), the estimated offset (filtered from

) can be removed. The main magnetic flux estimator 300 provides an estimated offset (

) is removed, the stator back emf (

), the flux can be estimated from That is, the offset estimator 100 of the present invention may be included in the offset compensator 200 to estimate an accurate offset. Also, the offset compensator 200 may remove the offset estimated from the stator counter electromotive force. Therefore, the induction motor 1000 including the offset estimator 100 can accurately estimate magnetic flux.

5 is a flowchart of an offset estimation method according to an embodiment of the present invention.

Referring to FIG. 5 , the offset estimator may calculate a first subtracted value obtained by subtracting the fed back stator counter electromotive force estimation offset from the stator counter electromotive force (S510). The offset estimator may calculate the first estimated stator flux and the second estimated stator flux from the calculated subtraction values (S520). Each of the first and second estimated stator fluxes can be calculated as follows. Each of the first and second flux estimators calculates a stator flux command value by low-pass filtering the magnitude of the estimated stator flux input, rotates the calculated stator flux command value by a preset angle, and estimates the calculated stator flux command value from the rotated stator flux command value. A third subtraction value obtained by subtracting the stator flux may be calculated.

Each of the first and second magnetic flux estimators may output an output value obtained by applying a predetermined cut-off angle frequency to the third subtraction value. For example, each of the first and second flux estimators may calculate the estimated stator flux based on different cutoff angle frequencies. Further, each of the first and second magnetic flux estimators may calculate an addition value obtained by adding an output value to the stator counter electromotive force, and may calculate the estimated stator flux by integrating the addition value.

The offset estimator may calculate a second subtraction value obtained by subtracting the calculated second estimated stator flux from the calculated first estimated stator flux (S530). Meanwhile, the second subtraction value may be 0 in a steady state. The offset estimator may calculate the stator EMF estimation offset by PI-controlling the calculated second subtraction value (S540). The calculated estimated offset can remove the offset of the stator EMF.

Below, the magnetic flux estimation experiment results by applying the offset estimator of the present invention are shown. The magnetic flux estimator used for the vector control used the Ohtani model and the Lorentz model, and sensorless vector control based on rotor flux was performed. 6 to 9 show waveforms of the estimated speed, the actual speed measured by the speed sensor, the d-axis current (magnetic flux component current), and the q-axis current (torque component current).

6 is a view showing experimental results for a speed of 300 r/min in a no-load state in the Lorentz model according to an embodiment of the present invention, and FIG. It is a diagram showing the experimental results for r/min speed. In the Lorentz model, the cutoff frequency was set to 3.14 rad/s (cutoff angle frequency 0.5 Hz).

Referring to FIG. 6 , the Lorentz model in the form of a second-order filter has an offset effect in a transient state, but no offset effect in a steady state. During transients where the speed changes, there is significant ripple in the speed and current. In FIG. 6 (a), the offset estimation method of the present invention is applied from the offset compensation time point at the midpoint. After the method of the present invention is applied, it can be seen that the speed and current ripple are gradually reduced. Comparing FIG. 6(b) and FIG. 6(c), the effect of offset compensation on the transient response can be confirmed. 7 is an experimental result for 200 r/min under full load (applying 100% rated torque load). As in FIG. 6 , the offset compensation effect to which the present invention is applied can be confirmed.

8 is a view showing experimental results for a speed of 300 r/min in a no-load state in the Ohtani model according to an embodiment of the present invention, and FIG. It is a diagram showing the experimental results for r/min speed. In the Ohtani model, the cutoff frequency was set to 6.28 rad/s (cutoff angle frequency 1 Hz).

8 shows the results of the experiment at a speed of 300 r/min without load. It can be seen that the Ohtani model, which is a first-order filter type, always has the effect of offset in the steady state, so there is a significant ripple in the speed and current. After the offset estimation method is applied in FIG. 8(a), the ripple in the speed and current gradually decreases. In FIGS. 8(b) and 8(c), a difference before and after offset compensation can be confirmed. 9 is an experimental result of 200 r/min under full load, and the same offset compensation effect as the result of FIG. 8 can be confirmed.

The offset estimation method according to various embodiments described above may be provided as a computer program product. The computer program product may include a S/W program itself or a non-transitory computer readable medium in which the S/W program is stored.

A non-transitory readable medium is not a medium that stores data for a short moment, such as a register, cache, or memory, but a medium that stores data semi-permanently and can be read by a device. Specifically, the various applications or programs described above may be stored and provided in non-transitory readable media such as CD, DVD, hard disk, Blu-ray disk, USB, memory card, ROM, and the like.

In addition, although the preferred embodiments of the present invention have been shown and described above, the present invention is not limited to the specific embodiments described above, and the technical field to which the present invention belongs without departing from the gist of the present invention claimed in the claims. Of course, various modifications are possible by those skilled in the art, and these modifications should not be individually understood from the technical spirit or perspective of the present invention.

The present invention does not require additional hardware and can remove the offset component included in the stator EMF by estimating the offset component with a simple structure. The present invention can be used for all induction motor flux estimators using counter-electromotive force, and can be used for both stator flux-based control and rotor flux-based control. In particular, if the present invention is applied to sensorless control that does not use a speed sensor, flux estimation performance of an induction motor can be further improved.

100: offset estimator
110: first calculator 120a, 120b: magnetic flux estimator
130: second calculator 140: controller

Claims (8)

Calculating a first subtraction value obtained by subtracting the fed back stator back electromotive force estimation offset from the stator back electromotive force;
an estimated stator flux calculation step of calculating a first estimated stator flux and a second estimated stator flux from the calculated subtraction values;
calculating a second subtraction value obtained by subtracting the calculated second estimated stator flux from the calculated first estimated stator flux; and
calculating the stator EMF estimation offset by performing PI control on the calculated second subtraction value;
In the step of calculating the estimated stator flux,
The first estimated stator flux is calculated based on a first cutoff angle frequency, the second estimated stator flux is calculated based on a second cutoff angle frequency, and the first estimated stator flux and the second estimated stator flux are A method for estimating induction motor offsets calculated in parallel. According to claim 1,
The second subtraction value is,
A method for estimating an induction motor offset that is ultimately zero. According to claim 1,
In the step of calculating the estimated stator flux,
Calculating a stator flux command value by low-pass filtering the magnitude of the estimated stator flux input;
rotating the calculated stator flux command value at a preset angle;
calculating a third subtraction value obtained by subtracting the estimated stator flux calculated from the rotated stator flux command value;
outputting an output value obtained by applying a predetermined cut-off angle frequency to the third subtracted value;
calculating an addition value obtained by adding the output value to the stator counter electromotive force; and
Calculating an estimated stator magnetic flux by integrating the addition value; including, an induction motor offset estimation method. delete a first operator calculating a first subtraction value obtained by subtracting the feedback stator counter electromotive force estimated offset from the stator counter electromotive force;
a first flux estimator calculating a first estimated stator flux from the calculated subtraction value;
a second flux estimator calculating a second estimated stator flux from the calculated subtraction value;
a second operator calculating a second subtraction value obtained by subtracting the calculated second estimated stator flux from the calculated first estimated stator flux; and
a controller for calculating the stator EMF estimation offset by PI-controlling the calculated second subtraction value;
The first magnetic flux estimator and the second magnetic flux estimator are connected in parallel,
The first estimated stator flux is calculated based on a first cutoff angle frequency, the second estimated stator flux is calculated based on a second cutoff angle frequency, and the first estimated stator flux and the second estimated stator flux are An induction motor offset estimator, computed in parallel. According to claim 5,
The second subtraction value is,
Finally zero, induction motor offset estimator. According to claim 5,
Each of the first magnetic flux estimator and the second magnetic flux estimator,
a low-pass filter for calculating a stator flux reference value by low-pass filtering the magnitude of the estimated stator flux input;
a third operator for rotating the calculated stator flux command value at a preset angle;
a fourth operator calculating a third subtraction value obtained by subtracting the estimated stator flux calculated from the rotated stator flux command value;
a fifth operator for outputting an output value obtained by applying a preset cut-off angle frequency to the third subtraction value;
a sixth operator calculating an addition value obtained by adding the output value to the stator counter electromotive force; and
An integrator for integrating the addition value to calculate the estimated stator magnetic flux; including, an induction motor offset estimator. delete

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