KR20210117749A - Mtpa control method of permanent magnet synchronous motor using optimization technique - Google Patents

Abstract

One embodiment of the present invention relates to a method for controlling a maximum torque per ampere (MTPA) of a permanent magnet synchronous motor by using optimization technique, which comprises the following steps of: measuring an electrical current (I_s) supplied to a stator; using the measured electrical current (I_S) to calculate a copper loss (P_cu); using the calculated copper loss to define a correction factor (Q); and applying the calculated correction factor (Q) to a gradient descent algorithm to follow each current command (β_MTPA). In accordance with the present invention, although there are errors in parameters of the motor or resolver signals for measuring the location of the rotator, an optimal current angle where the copper loss is minimized within a short time under all driving conditions can be followed. Accordingly, only the size of an electrical current supplied to the stator is used to follow the optimal current angle.

Description

MTPA control method of permanent magnet synchronous motor using optimization technique

The present invention relates to a method for controlling MTPA of a permanent magnet synchronous motor using an optimization technique. More specifically, it is to provide a method that can quickly and simply follow the optimal current angle that can minimize copper loss, which accounts for the largest proportion of losses in permanent magnet synchronous motors, only by measuring the magnitude of the stator current.

Permanent Magnet Synchronous Motor (PMSM) is used in various motor driving fields due to its high efficiency, power density and excellent dynamic characteristics.

As interest in environmental protection and depletion of energy resources increases, technologies for operating permanent magnet synchronous motors with high efficiency are being developed, and various MTPA control methods to minimize copper loss, which accounts for the largest proportion of losses in permanent magnet motors. this is being developed

In general, in order to perform MTPA control, a current command for a required output torque is derived from a mathematical model, but this method has a disadvantage in that information on constitutive numbers such as stator inductance or permanent magnet magnetic flux is required. Specifically, since the integral number of the motor varies depending on the motor load and operating temperature, there is a high possibility that accurate MTPA control cannot be performed. If (Offset) exists, the current flowing to the actual motor may have an error with the current command for MTPA control.

In order to solve this problem, three types of methods have been proposed in the prior art. 1) A method to find out fluctuations in stator inductance by estimating the inductance of an electric motor in real time to perform accurate MTPA control, 2) A method to find an MTPA operating point without using the coordinator information of a motor by injecting a high-frequency signal , 3) A method of gradually adjusting the control physical quantity so that the set objective function becomes the maximum or the minimum.

In the case of the first method, the inductance is estimated based on the magnetic flux estimation, which is vulnerable to the magnetic flux error of the stator resistance and permanent magnet. There is this.

In the second method, the MTPA operating point is estimated by injecting a high-frequency signal into the current angle and indirectly extracting the torque magnitude change information for the injected signal, which is controlled by the torque ripple caused by the injected high-frequency signal. There is a problem that this is lowered. In addition, there is a method of using a virtual high-frequency signal instead of injecting an actual signal, but information about the stator resistance is required to calculate the torque, and since the voltage command, which is the output of the current controller, is used, the voltage due to the nonlinearity of the inverter There is a limit in performing accurate MTPA control due to distortion effects.

In the third method, it takes a long time to follow the MTPA operating point because each current command is adjusted to a certain size, and there is a problem that the tracking time also varies depending on the operating conditions. In addition, there is a method of obtaining torque magnitude information indirectly from the magnitude of the high frequency component present in the rotor speed and using the ratio of the torque magnitude and the stator current magnitude, but torque ripple is generated by the injected high frequency signal to control performance. There is a problem that this is lowered.

Therefore, in the present invention, it is possible to supplement the conventional problems and follow the optimum current angle that minimizes copper loss in all operating conditions without being affected by the constant number of the motor or the error of the resolver signal using only the magnitude information of the stator current. suggest a way to

Korean Patent Registration No. 10-1693424 (2016.12.30.)

SUMMARY OF THE INVENTION It is an object of the present invention to provide a method for obtaining an optimal current angle with a minimum copper loss using only the magnitude of a stator current by applying a gradient descent algorithm.

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

An MTPA control method of a permanent magnet synchronous motor using an optimization technique according to an embodiment of the present invention includes measuring a current Is supplied to a stator, and using the measured current Is Loss) (Pcu), defining a correction factor (Q) by using the calculated copper loss, and applying the calculated correction factor (Q) to a gradient descent algorithm (Gradient Descent Algorithm) _MTPA ).

According to an embodiment, the calculating of the copper loss Pcu may include the copper loss Pcu according to the following [Equation 1].

[Equation 1]

where I _s is the current supplied to the stator and R _s is the stator resistance.

According to an embodiment, calculating the copper loss Pcu may include setting the copper loss Pcu as an objective function for applying the gradient descent method.

According to an embodiment, the defining of the correction factor (Q) may include, based on a ratio of copper loss (Pcu _{k ) calculated in the current control period to copper loss (Pcu k-1} ) calculated in the previous control period, The correction factor (Q) may be defined according to [Equation 2].

[Equation 2]

Here, Pcu _{k - 1} is the copper loss calculated in the previous control period, Pcu _k is the copper loss calculated in the current control period, β _{k - 1} is the current angular reference of the previous period, and β _k is the current angular reference of the current period.

According to an embodiment, in _{the step of following the current angular command β MTPA} ^{, the change relation of the current angular command β *} using [Equation 2] defining the correction factor Q is expressed in the following [Mathematics] After redefining according to Equation 3], each current command (β _MTPA ) can be followed.

[Equation 3]

Here, ρ is a parameter that controls the variation width of each current command.

According to an embodiment, the ^{changing of the current angular command β *} may further include determining whether the correction factor Q converges to zero.

According to an embodiment, the determining may return to the step of measuring the _{current I s} supplied to the stator when the correction factor Q does not converge to zero as a result of the determination. have.

_{An MTPA control device for a permanent magnet synchronous motor that follows each current command (β MTPA} ) by using the current value supplied to the stator according to another embodiment of the present invention, comprising an inverter and a processor for driving the permanent magnet synchronous motor However, the processor measures the current Is supplied to the stator, calculates a copper loss (Pcu) using the measured current Is, and a correction factor using the calculated copper loss (Q) is defined, and the calculated correction factor (Q) is applied to the gradient descent algorithm to follow _{the current angular command (β MTPA ).}

According to an embodiment, the processor may calculate the copper loss Pcu according to Equation 1 below.

[Equation 1]

where I _s is the current supplied to the stator and R _s is the stator resistance.

According to an embodiment, the processor may set the copper loss Pcu as an objective function for applying the gradient descent method.

According to an embodiment, the processor, based on the ratio of copper loss (Pcu _{k ) calculated in the current control period to copper loss (Pcu k-1} ) calculated in the previous control period, according to the following [Equation 2] A correction factor (Q) can be defined.

[Equation 2]

Here, Pcu _{k - 1} is the copper loss calculated in the previous control period, Pcu _k is the copper loss calculated in the current control period, β _{k - 1} is the current angular reference of the previous period, and β _k is the current angular reference of the current period.

According to an embodiment, the processor, using [Equation 2] defining the correction factor (Q), ^{redefines the change relational expression of each current command (β *} ) according to the following [Equation 3], Current angular command (β _MTPA ) can be followed.

[Equation 3]

Here, ρ is a parameter that controls the variation width of each current command.

According to an embodiment, the processor may determine whether the correction factor Q converges to zero.

According to an embodiment, when the correction factor Q does not converge to 0 as a result of the determination, the processor re-measures the current _{I s supplied to the stator, and each current command β MTPA} ) can be re-followed.

According to the present invention, the optimum current angle can be tracked using only the magnitude of the stator current.

According to the present invention, it is possible to follow the optimum current angle at which copper loss is minimized within a short time under all operating conditions even in a situation where an error occurs in the resolver signal for measuring the constant number of the motor or the rotor position.

According to the present invention, a Q characteristic to have a constant gradient is acquired based on the ratio of copper loss calculated in the previous control period and copper loss calculated in the current control period, and each current command is gradually adjusted according to the gradient descent method. Accordingly, each command of the finally followed current may be accurate without changing depending on the load of the objective function.

According to the present invention, it may be possible to efficiently drive to minimize copper loss in the field of traction motors including electric vehicles and railway vehicles, or in the fields of electric motors such as air conditioners and washing machines.

According to the present invention, in the field of driving a motor using a limited energy source, the driving efficiency is improved by minimizing copper loss, thereby improving the period of use during one-time charging of the battery.

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

1 is a diagram showing the configuration of a PMSM speed control system according to an embodiment of the present invention.
2 is a diagram illustrating a flow of an MTPA control method of a permanent magnet synchronous motor using an optimization technique according to an embodiment of the present invention.
3 is a view for explaining the principle of the gradient descent method to be applied to the PMSM speed control system according to an embodiment of the present invention.
4 is a diagram for explaining a case in which the tracking performance of the copper loss (Pcu), which is an objective function, is changed in the PMSM speed control system according to an embodiment of the present invention.
5 is a view for explaining a change in copper loss (Pcu) according to a load condition in the PMSM speed control system according to an embodiment of the present invention.
6A and 6B are diagrams for explaining the tracking performance of the copper loss (Pcu) using the modified gradient descent method of the PMSM speed control system according to an embodiment of the present invention.
7 is a view showing a result of applying the MTPA control method of the present invention in a situation in which a conventional constitutive error exists.
8 is a diagram illustrating a result of applying the MTPA control method of the present invention in a situation where an offset exists in a conventional resolver signal.
9 is a view showing a result of using the MTPA control method in the PMSM speed control system of the present invention.
10 and 11 are diagrams showing the results of applying the MTPA control method of the present invention in an IPMSM system under different conditions.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. Advantages and features of the present invention, and a method for achieving them will become apparent with reference to the embodiments described below in detail in conjunction with the accompanying drawings. Like reference numerals refer to like elements throughout.

Unless otherwise defined, all terms (including technical and scientific terms) used herein may be used with the meaning commonly understood by those of ordinary skill in the art to which the present invention belongs. In addition, terms defined in a commonly used dictionary are not to be interpreted ideally or excessively unless clearly defined in particular. The terminology used herein is for the purpose of describing the embodiments and is not intended to limit the present invention. As used herein, the singular also includes the plural unless specifically stated otherwise in the phrase.

As used herein, “comprises” and/or “comprising” refers to a referenced component, step and/or action indicating the presence or addition of one or more other components, steps and/or actions. do not exclude

Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.

FIG. 1 is a diagram showing the configuration of a PMSM speed control system 1000 according to an embodiment of the present invention, and FIG. 2 is a flow of an MTPA control method of a permanent magnet synchronous motor using an optimization technique according to an embodiment of the present invention. is a diagram showing

Referring to FIG. 1 , the PMSM speed control system 1000 may include a permanent magnet synchronous motor 100 and an MTPA control device 200 of the permanent magnet synchronous motor.

The MTPA control device 200 of the permanent magnet synchronous motor uses the current value supplied to the stator and the newly applied Gradient Descent Algorithm to obtain the optimal current angular command (β _MTPA ), and accordingly, the permanent magnet synchronization The motor 100 may be controlled, and for this purpose, an inverter 210 and a processor 220 may be included.

The inverter 210 for a permanent magnet synchronous motor connected to the permanent magnet synchronous motor 100 may be a pulse width modulation (PWM) inverter according to an embodiment.

_{The processor 220 is a d-axis and q-axis current (i ds} ^r ) to minimize copper loss in an IPMSM (Interior Permanent Magnet Synchronous Motor) (embedded PMSM) that must efficiently output a reluctance torque component. You can select (i _qs ^r ) to use it as a current reference.

Hereinafter, with reference to FIG. 2 , a method in which the _{processor 220 of the MTPA control device 200 follows the optimal current angular command β MTPA will be described.}

Referring to FIG. 2 , the processor 220 measures the current Is supplied to the stator ( S110 ). Here, the current Is may be formed by a combination of the d-axis and q-axis currents i _ds ^r (i _qs ^{r ) that output torque of the same magnitude.}

After step S110, the processor 220 calculates a copper loss (Pcu) using the measured current Is (S120). Specifically, copper loss (Pcu) due to the d-axis and q-axis current may be proportional to the square of the stator current magnitude (Is) as shown in Equation 1 below.

where I _s is the current supplied to the stator and R _s is the stator resistance.

Meanwhile, the magnitude (Is) of the stator current with respect to the output torque command (T _e ^* ) of the PMSM is a function of the current angle (b), and copper loss (Pcu) may also vary according to the current angle (b). In general, the current angle (b) at which the copper loss (Pcu) becomes the minimum is obtained as shown in [Equation 2], but in the present invention, the time to obtain the current angle (b) is shortened, and the final followed angle is the error. It is possible to obtain the optimal current angle reference (β _MTPA ) by applying the gradient descent algorithm so as not to be affected.

3 is a diagram for explaining the principle of the gradient descent method to be applied to the PMSM speed control system 1000 according to an embodiment of the present invention.

Referring to FIG. 3 , the gradient descent method uses the gradient in the opposite direction (the direction in which the value decreases) of f(x) as in [Equation 2] to find the minimum of the objective function f(x). ) can move as much as it is proportional to its size.

In the process of following the minimum point of f(x), if x moves by a certain amount, the tracking time increases in proportion to the moving distance, but when using the gradient descent method as in [Equation 2], the gradient size Since it moves in proportion to , the tracking time can be shortened.

Accordingly, the processor 220 may set the copper loss Pcu calculated as in [Equation 1] in step S120 as an objective function for applying the gradient descent method. It is possible to follow the optimal current angular reference (β _{MTPA ) by using the newly defined gradient descent method.}

Before describing this, the gradient descent method to Equation 3] inclination, that is the current cycle, and then the slope is zero for each command (β ^* _{k +1)} the current of the current period, as each command (β _k ^* ) is followed by a point having the same value (a point at which copper loss (Pcu) is the minimum).

Here, ρ is a parameter for adjusting the variation width of each current command, and may be referred to as a step size. The objective function, copper loss (Pcu), is a continuous quadratic function proportional to the square of the current (Is), and can be expressed as in [Equation 4] by discretizing [Equation 3].

At this time, in the case of following the optimal current angular command (β _MTPA ) through [Equation 4], the tracking performance (required time, accuracy) is determined by the parameter (ρ) controlling the fluctuation range, this parameter ( If ρ) is not properly selected, the tracking performance may deteriorate.

For example, when the parameter (ρ) is set to a small value, since the magnitude of Δβ becomes small, it takes a long time for _{the current angular reference (β k} ^* ) of the current period to converge to the optimal current angular reference (β _{MTPA ).} In the section where the magnitude of the slope is small, the magnitude of Δβ has a very small value close to 0 before _{the current angular command (β k} ^* ) of the current cycle converges to the optimal current angular command (β _{MTPA ).} This may end.

Conversely, when the parameter ρ is selected as a large value, since the slope is very large at the beginning of the tracking, _{a problem in which each current command β k} ^{* in} the current period vibrates or diverges may occur. Accordingly, it is important to appropriately select the value of the parameter ρ, but the slope value of the copper loss Pcu may vary depending on the load condition.

4 is a view for explaining a case in which the tracking performance of the copper loss (Pcu), which is an objective function, is changed in the PMSM speed control system 1000 according to an embodiment of the present invention, and FIG. 5 is an embodiment of the present invention. It is a diagram for explaining a change in copper loss (Pcu) according to a load condition in the PMSM speed control system 1000 according to the present invention.

Referring to (a) and (b) of Figure 4, when the load conditions are 100% and 50%, respectively, the initial current angular command is 90°, and the same parameter (ρ=1.2x10 ^-5 ), the optimal current angle The time required to follow the instruction β _MTPA may be different as follows.

Specifically, (a) shows that under the 100% load condition, _{it takes 0.285 seconds for the current angular command (β k} ^* ) of the current cycle to be adjusted from 90° to the final value of 120.9°, which minimizes copper loss (Pcu) within a short time. Although the optimal current angular reference (β _MTPA ) can be obtained, in (b) _{it takes 1.193 seconds for the current angular reference (β k} ^* ) of the current cycle to be adjusted from 90° to the final value of 113.6° under the 50% load condition. .

That is, in the case of 50% load, the current angle command (β _k ^* ) of the current cycle must be adjusted to the optimal current angle command (β _MTPA ), even though the size (current angle of the vertical axis) is small It takes longer time, and _{the tracking is terminated before reaching the optimum current angular reference (β MTPA} ), and an accurate value cannot be obtained.

That is, as shown in FIG. 5 , as the load increases in the current command (β)-copper loss (Pcu) graph, the slope increases at the same Δβ, and the tracking speed can be increased.

It will be described again with reference to FIG. 2 .

After step S120 , the processor 220 calculates a correction factor (Q) using copper loss (Pcu) in order to use a constant gradient regardless of the load condition, that is, to compensate for the problem of the conventional gradient descent method described above. Define (S130). Specifically, the processor 220 is based on the ratio of the copper loss (Pcu _{k ) calculated in the current control period to the copper loss (Pcu k-1} ) calculated in the previous control period, according to the following [Equation 5], the correction factor ( Q) can be defined.

Here, Pcu _{k - 1} is the copper loss calculated in the previous control period, Pcu _k is the copper loss calculated in the current control period, β _{k - 1} is the current reference in the previous period, and β _k is the current reference in the current period. .

The processor 220 substitutes the correction factor (Q) defined in step S130 to [Equation 4] at which the copper loss (Pcu) can be obtained the minimum point, and redefines the gradient descent method as shown in [Equation 6] below. can do.

Here, since _{the ratio of Pcu k - 1} and Pcu _k has a value of 1 or more when copper loss (Pcu) decreases, the positive (+)/negative (-) sign of the correction factor (Q) can be determined using this have. For example, the correction factor Q _{has a positive value when the current angular command (β k} ^* ) increases and the copper loss (Pcu) decreases, and the current angular command (β _k ^* ) is When increasing, when copper loss (Pcu) decreases, it may have a negative (-) value.

If change as shown in [Equation 6] according to the current angle command (β _k *) a correction factor (Q) jeongoe the current cycle, since the variation amount of copper loss (Pcu) group shown in the ratio, the formula 3 ] Unlike ∂Pcu / ∂β represented in does not occur, an error caused by the load, it is possible to follow the optimal current angle command (β _MTPA).

In addition, the larger the difference between the current angular command (β _k ^* ) and the optimal current angular command (β _MTPA ) of the current period, the larger the change rate of copper loss (Pcu), and the larger the ratio of _{Pcu k - 1 to Pcu k} Therefore, the correction factor Q may have a large value. That is, the magnitude of Δβ in [Equation 6] _{becomes larger as the difference between the current angular command (β k} ^* ) and the optimal current angular command (β _MTPA ) of the current period increases, and is optimal using [Equation 6]. In the case of following each current command β _{MTPA of} , the tracking speed can be improved.

After step S130 , the processor 220 applies the calculated correction factor Q to the gradient descent method _{to follow the current angular command β MTPA} ( S140 ). Specifically, the processor 220 may determine whether the correction factor (Q) converges to 0 (S150), and if the correction factor (Q) converges to 0, each current command (β _k ^* ) can be understood as the optimal current angular reference (β _{MTPA ).}

In step S150, if the correction factor Q does not converge to 0, the processor 220 may return to step S110 of measuring the current Is supplied to the stator, and the objective function copper loss (Pcu) ) can be recalculated.

6A and 6B are diagrams for explaining the tracking performance of the copper loss (Pcu) using the modified gradient descent method of the PMSM speed control system 1000 according to an embodiment of the present invention.

6A and 6B, when the load conditions are 100% and 50%, respectively, the initial current angular command is 90°, and the same parameter (ρ=1.2x10 ^-5 ), the current angular command (β _k ^* ) Changes may appear as follows:

Specifically, in Fig. 6a, _{it took 0.221 seconds for the current angular command (β k} ^* ) of the current cycle to be adjusted from 90° to the final value of 120.9° under the 100% load condition, and Fig. 6b shows the current cycle under the 50% load condition. It takes 0.213 seconds for the current angle reference (β _k ^* ) to be adjusted from 90° to the final value of 114.3°.

That is, by using the modified gradient descent method of the present invention, it is possible to obtain the optimal current angular command (β _MTPA ) that minimizes copper loss (Pcu) within a short time even when the load conditions are changed.

In addition, in [Equation 5], the correction factor (Q) has a _{larger value as the difference between the current angular command (β k} ^* ) and the optimal current angular command (β _MTPA ) of the current period increases, It can be seen that the magnitude of the reference (β _k ^* ) to be adjusted to obtain the optimal current angular reference (β _MTPA ) is larger than that of (a) in (b), but there is no significant difference in the follow-up time. In other words, by reflecting the correction factor Q, it is possible to ensure almost equal tracking performance in all load conditions.

So far, the PMSM speed control system 1000 of the present invention and the MTPA control method of a permanent magnet synchronous motor using the same have been described. _{According to the present invention, it is possible to determine the optimal current angular command (β MTPA} ) for MPTA control using only the magnitude information of the stator current, so that it is not affected by the constitutive error of PMSM or the rotor position offset. Precise control can be achieved.

Hereinafter, changed experimental results appearing when the MTPA control method of the present invention is applied to the existing MTPA control method will be described, thereby verifying the effectiveness of the present invention.

7 is a view showing the result of applying the MTPA control method of the present invention in a situation where there is a conventional constitutive error, and FIG. 8 is a view showing the result of applying the MTPA control method of the present invention in a situation where an offset exists in the conventional resolver signal. 9 is a diagram showing a result of using the MTPA control method in the PMSM speed control system 1000 of the present invention.

Before describing FIGS. 7 to 9 , simulations for verifying effectiveness were performed using Matlab/Simulink. [Table 1] below means the constitutive number of 210 kW IPMSM used in the simulation, and [Table 2] below means the constitutive number of the 800 W IPMSM used in the simulation. In addition, the switching frequency was applied to 2kHz for 210kW IPMSM and 5kHz for 800W IPMSM.

Parameter Value Parameter Value _rated 210kW P 6poles T _rated 1925N*m R _s 32.42mΩ I _rated 335A (peak) L _ds 2.49mH V _rated 1500V L _qs 5.56mH ω _rated 1000r/min φ _f 0.9595Wb

Parameter Value Parameter Value _rated 800kW P 8poles T _rated 3.18N*m R _s 1.8mΩ I _rated 4A(peak) L _ds 7.8mH V _rated 220V L _qs 14.5mH ω _rated 1000r/min φ _f 0.13 Wb

와 같이 변동된 경우(

는 PMSM 시스템(1000)의 제어기가 인지하고 있는 q축 인덕턴스), 초기에 전류 각 지령(β_k ^*)이 103.1°에서 운전 중인 것을 알 수 있다. 여기서, 본 발명의 MTPA 제어 방법을 적용할 경우, 약 0.125초 후에 114.8°로 조정되고, 이로 인해 고정자 전류의 크기(Is)가 199.9A에서 194.7A로 감소하고, 동손(Pcu)는 1295W에서 1229W로 감소함을 확인할 수 있다.Referring to FIG. 7 , at 210kW IPMSM, speed 500r/min, and 50% load condition, there is a quadrature error, so that the q-axis inductance is

If it is changed like (

is the q-axis inductance recognized by the controller of the PMSM system 1000), _{it can be seen that the initial current angle command (β k} ^* ) is operating at 103.1°. Here, when the MTPA control method of the present invention is applied, it is adjusted to 114.8° after about 0.125 seconds, whereby the magnitude (Is) of the stator current is reduced from 199.9A to 194.7A, and the copper loss (Pcu) is from 1295W to 1229W can be seen to decrease.

와 같이 변동된 경우(

는 PMSM 시스템(1000)의 제어기가 인지하고 있는 회전자 위치), 초기에 전류 각 지령(β_k ^*)이 120.9°에서 운전 중인 것을 알 수 있다. 여기서, 본 발명의 MTPA 제어 방법을 적용할 경우, 약 0.123초 후에 110.4°로 조정되고, 이로 인해 고정자 전류의 크기(Is)가 343.3A에서 335.2A로 감소하고, 동손(Pcu)는 3823W에서 3642W로 감소함을 확인할 수 있다.Referring to FIG. 8 , at 210kW IPMSM, speed 1000r/min, 100% load condition, there is an offset in the resolver signal installed for measuring the rotor position, so that the position of the rotor is

If it is changed like (

is the rotor position recognized by the controller of the PMSM system 1000), _{it can be seen that the current angular command (β k} ^* ) is being operated at 120.9° initially. Here, when the MTPA control method of the present invention is applied, it is adjusted to 110.4° after about 0.123 seconds, whereby the magnitude (Is) of the stator current is reduced from 343.3A to 335.2A, and the copper loss (Pcu) is from 3823W to 3642W can be seen to decrease.

_{Referring to FIG. 9 , it can be seen that the current angular command (β init} ) initially controls 90°, that is, the d-axis current to 0 under the 800W IPMSM, speed 2000r/min, and 100% load condition. Here, when the MTPA control method of the present invention is applied, it is adjusted to 101° after about 0.123 seconds, whereby the magnitude (Is) of the stator current is reduced from 4.077A to 3.996A, and the copper loss (Pcu) is at 41.55W. It can be confirmed that the decrease to 39.92W.

Hereinafter, the feasibility of the present invention will be described with the experimental results of the IPMSM driving system using the digital controller. The specifications of the 800W IPMSM used in the experiment are the same as in [Table 2], and the switching frequency of the inverter is 5kHz.

10 and 11 are diagrams showing results of applying the MTPA control method of the present invention in an IPMSM system under different conditions, respectively.

), 회전자 속도(

), 고정자 전류의 크기(Is) 및 전류 각 지령(β^*)을 나타낸다.In both FIGS. 10 and 11, in the process of controlling the initial current command to be 90°, that is, the d-axis current to 0, the torque calculated when the MTPA control method of the present invention is used (

), rotor speed (

), the magnitude of the stator current (Is), and the current command (β ^* ).

Referring to FIG. 10, when the MTPA control method of the present invention is applied at a speed of 1000r/min and a load condition of 75%, the current angle command (β ^* ) was adjusted from 90° to 98.2° in 0.125 seconds, and the current angle As the command (β ^* ) is adjusted, it can be seen that the magnitude (Is) of the stator current decreases.

11, when the MTPA control method of the present invention is applied at a speed of 2000r/min and 100% load condition, the current angle command (β ^* ) was adjusted from 90° to 101.6° in 0.125 seconds, and the current angle As the command (β ^* ) is adjusted, it can be seen that the magnitude (Is) of the stator current decreases.

Although embodiments of the present invention have been described with reference to the accompanying drawings, those of ordinary skill in the art to which the present invention pertains can realize that the present invention can be implemented in other specific forms without changing the technical spirit or essential features. you will be able to understand Therefore, it should be understood that the embodiments described above are illustrative in all respects and not restrictive.

1000: PMSM speed control system
100: permanent magnet synchronous motor, PMSM
200: MTPA control device
210: inverter
220: processor

Claims (14)

Measuring the current (Is) supplied to the stator (stator);
calculating copper loss (Pcu) using the measured current (Is);
defining a correction factor (Q) using the calculated copper loss; and
applying the calculated correction factor (Q) to the gradient descent algorithm to follow _{the current angular command (β MTPA );} MTPA control method of a permanent magnet synchronous motor using an optimization technique comprising a. According to claim 1,
The step of calculating the copper loss (Pcu),
MTPA control method of a permanent magnet synchronous motor using an optimization technique, calculating the copper loss (Pcu) according to the following [Equation 1].
[Equation 1]

where I _s is the current supplied to the stator and R _s is the stator resistance. 3. The method of claim 2,
The step of calculating the copper loss (Pcu),
setting the copper loss (Pcu) as an objective function for applying the gradient descent method; MTPA control method of a permanent magnet synchronous motor using an optimization technique comprising a. 4. The method of claim 3,
The step of defining the correction factor (Q),
Based on the ratio of the copper loss (Pcu _{k ) calculated in the current control period to the copper loss (Pcu k-1} ) calculated in the previous control period, the correction factor (Q) is defined according to the following [Equation 2], optimization MTPA control method of permanent magnet synchronous motor using technique.
[Equation 2]

Here, Pcu _{k - 1} is the copper loss calculated in the previous control period, Pcu _k is the copper loss calculated in the current control period, β _k-1 is the current angular reference in the previous period, and β _k is the current angular reference in the current period. 5. The method of claim 4,
The step of following each current command (β _{MTPA ) is,}
Using [Equation 2] that defines the correction factor (Q), ^{the change relational expression of each current command (β *} ) is redefined according to the following [Equation 3], and then each current command (β _MTPA ) is followed. , MTPA control method of permanent magnet synchronous motor using optimization technique.
[Equation 3]

Here, ρ is a parameter that controls the variation width of each current command. 6. The method of claim 5,
The step of changing each current command (β ^{* ) is,}
determining whether the correction factor (Q) converges to zero; MTPA control method of a permanent magnet synchronous motor using an optimization technique further comprising a. 7. The method of claim 6,
The determining step is
As a result of the determination, if the correction factor Q does not converge to 0, _{returning to the step of measuring the current I s} supplied to the stator MTPA control method of a permanent magnet synchronous motor using an optimization technique . An MTPA control device for a permanent magnet synchronous motor that follows _{each current command (β MTPA} ) using a current value supplied to a stator, comprising:
an inverter and a processor for driving the permanent magnet synchronous motor; including,
The processor is
Measure the current (Is) supplied to the stator, calculate the copper loss (Pcu) using the measured current (Is), define a correction factor (Q) using the calculated copper loss, , MTPA control device of a permanent magnet synchronous motor that follows _{the current angular command (β MTPA} ) by applying the calculated correction factor (Q) to the gradient descent algorithm. 9. The method of claim 8,
The processor is
MTPA control device of a permanent magnet synchronous motor, which calculates the copper loss (Pcu) according to the following [Equation 1].
[Equation 1]

where I _s is the current supplied to the stator and R _s is the stator resistance. 10. The method of claim 9,
The processor is
An MTPA control device for a permanent magnet synchronous motor, which sets the copper loss (Pcu) as an objective function for applying the gradient descent method. 11. The method of claim 10,
The processor is
Based on the ratio of the copper loss (Pcu _{k ) calculated in the current control period to the copper loss (Pcu k-1} ) calculated in the previous control period, the correction factor (Q) is defined according to Equation 2 below. MTPA control unit for magnet synchronous motors.
[Equation 2]

Here, Pcu _{k - 1} is the copper loss calculated in the previous control period, Pcu _k is the copper loss calculated in the current control period, β _k-1 is the current angular reference in the previous period, and β _k is the current angular reference in the current period. 12. The method of claim 11,
The processor is
Using [Equation 2] that defines the correction factor (Q), ^{the change relational expression of each current command (β *} ) is redefined according to the following [Equation 3], and then each current command (β _MTPA ) is followed. , MTPA control device for permanent magnet synchronous motors.
[Equation 3]

Here, ρ is a parameter that controls the variation width of each current command. 13. The method of claim 12,
The processor is
MTPA control apparatus of a permanent magnet synchronous motor, which determines whether the correction factor (Q) converges to zero. 14. The method of claim 13,
The processor is
As a result of the determination, if the correction factor (Q) does not converge to 0, the current (I _s ) supplied to the stator (stator) is re-measured, and the current each command (β _MTPA ) is re-followed, permanent magnet synchronization MTPA control unit for electric motors.

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