Load fluctuation compensation device for electric motors

Abstract

A load fluctuation compensation device for an electric motor is disclosed, which includes: an angle pulsation analyzer that analyzes characteristics of rotor angle pulsation based on a detected value of the rotor angle of the electric motor; and a speed pulsation compensator that generates a speed pulsation compensation value for reducing rotor speed pulsation based on the characteristics of the rotor angle pulsation analyzed by the angle pulsation analyzer.

Description

[Technical Field]

[0001] The present invention relates to a load fluctuation compensation device for a motor, and more particularly to a load fluctuation compensation device for a motor that can reduce speed pulsation caused by periodic load fluctuations in a motor used in an electric compressor. [Background technology]

[0002] An electric motor is a device that converts electrical energy into mechanical energy. To drive an electric motor, a separate drive device is required to control the power supplied to the electric motor. The electric motor drive device controls the torque of the electric motor by controlling the power supplied to the electric motor.

[0003] FIG. 1 is a block diagram illustrating an example of a conventional motor drive. As shown in FIG. 1, the motor drive includes a speed controller 11 and a current controller 12 to enable the rotational speed of the motor to follow a set speed command value. The speed controller 11 compares a preset speed command value with a detected speed value of the motor, which is detected by a speed detection sensor installed in the motor or calculated according to a preset algorithm, and outputs a current command to substantially eliminate the difference. The current controller 12 outputs a voltage command value to equalize the current command output by the speed controller with the value of the current actually supplied to the motor. The motor drive can control a power conversion circuit 14, which converts DC power and generates multi-phase AC power used to drive the motor, to output a voltage corresponding to the voltage command value. The power conversion circuit 14 may be an inverter 14 that converts power using a pulse width modulation (PWM) control method for multiple switching elements. The electric motor drive device may also include a PWM controller 13 for PWM-controlling the switching elements of the inverter 14 based on a voltage command value.

[0004] Meanwhile, the rotation speed of a motor is greatly affected by the characteristics of the load driven by the motor. In particular, when the load pulsates periodically in synchronization with the rotation angle of the motor, such as a compressor driven by the motor, the rotation speed of the motor also pulsates periodically.

[0005] Figure 2 is a graph showing the load fluctuation characteristics of various types of conventional compressors. As shown in Figure 2, in the case of a single-cylinder rotary compressor, a load fluctuation occurs due to the intake / compression of refrigerant every time the motor rotates mechanically, and the magnitude of this load fluctuation is relatively large compared to other compressors. As another example, in the case of a twin-cylinder rotary compressor, the magnitude of the load fluctuation is significantly smaller than that of a single rotary compressor. However, a characteristic of this compressor is that a load fluctuation occurs twice for every 360 degrees of mechanical angle (the angle at which the rotor of the motor rotates mechanically). In the case of a scroll compressor, a load fluctuation also occurs once for every 360 degrees of mechanical angle, but the magnitude of this load fluctuation is relatively small compared to other compressors.

[0006] The periodic load fluctuations described above cause speed pulsation in the motor, which can cause vibration and noise in the compressor driven by the motor.

[0007] The items described above as background art are merely intended to enhance understanding of the background of the present invention and should not be accepted as equivalent to prior art already known to those skilled in the art. Summary of the Invention [Problem to be solved by the invention]

[0008] Therefore, a technical problem to be solved by the present invention is to provide a load fluctuation compensation device for a motor that can reduce speed pulsation caused by periodic load fluctuations in a motor used in an electric compressor, thereby reducing vibration and noise of the motor.

[0009] The problems to be solved by the present invention are not limited to those described above, and other problems and advantages of the present invention not mentioned above will be understood from the following description and will become more apparent from the examples of the present invention. Furthermore, a person skilled in the art to which the present invention pertains will easily understand that the problems and advantages of the present invention can be realized by the means and combinations thereof set forth in the claims. [Means for solving the problem]

[0010] As a means for solving the above technical problems, the present invention provides:

[0011] an angle pulsation analyzer that analyzes the characteristics of the rotor angle pulsation based on the detected value of the rotor angle of the motor; and

[0012] a speed pulsation compensator that generates a speed pulsation compensation value for reducing the rotor speed pulsation based on the characteristics of the rotor angle pulsation analyzed by the angle pulsation analyzer;

[0013] The present invention provides a load fluctuation compensation device for a motor including:

[0014] In one embodiment of the present invention, the angle pulsation analyzer can determine the amplitudes of cosine and sine functions that constitute the rotor angle pulsation.

[0015] In one embodiment of the present invention, the angular pulsation analyzer is JPEG2025529439000002.jpg827(θ ripple :Angular pulsation value, θ m : The detected value of the rotor angle, θ * m :Speed ​​command value (ω * m ) is an angle command value obtained by integrating JPEG2025529439000003.jpg820(ω * m : speed command value) and JPEG2025529439000004.jpg819, and passing each multiplication result through a low-pass filter, the amplitudes of the cosine function and sine function that make up the pulsation of the rotor angle can be obtained.

[0016] In one embodiment of the present invention, the amplitude (G) of the cosine function and the width (H) of the sine function constituting the rotor angle pulsation are respectively

[0017] formula JPEG2025529439000005.jpg1474; and

[0018] formula JPEG2025529439000006.jpg1471 (A, B: the amplitude of the cosine and sine components of the load torque, respectively; C, D: the amplitude of the cosine and sine components of the motor output torque, respectively; k, γ: the magnitude and phase change of the signal generated while passing through the primary system corresponding to the rotating system, respectively; γ is a value within the range [0, π / 2]).

[0019] In one embodiment of the present invention, the speed pulsation compensator may apply gains to the amplitudes of a cosine function and a sine function constituting the rotor angle pulsation, respectively, and integrate the sum of the amplitudes of the cosine function and the sine function constituting the rotor angle pulsation to which the gains have been applied, thereby generating the current command compensation value for reducing the rotor speed pulsation.

[0020] In one embodiment of the present invention, the speed pulsation compensator may determine the amplitude of the cosine component of the output torque of the motor according to the current command compensation value by summing a value obtained by applying a first gain to the amplitude of a cosine function constituting the rotor angle pulsation and a value obtained by applying a second gain to a sine function constituting the rotor angle pulsation and integrating the summed value, and may determine the amplitude of the sine component of the output torque of the motor according to the current command compensation value by summing a value obtained by applying a third gain to the amplitude of a sine function constituting the rotor angle pulsation and a value obtained by applying a fourth gain to the sine function constituting the rotor angle pulsation and integrating the summed value.

[0021] In one embodiment of the present invention, the first gain, the third gain, and the fourth gain may have a positive sign, and the second gain may have a negative sign. [Effects of the Invention]

[0022] According to the load fluctuation compensator for a motor, the influence of periodic load fluctuations is extracted from angle pulsation, so that the phase delay occurring in the signal processing process can be limited to within the range of [0, π / 2]. As a result, even if the sign of the gain used in the speed pulsation compensator is fixed, stable control characteristics can be obtained in all operating ranges of the motor.

[0023] In addition, according to the load fluctuation compensator for a motor, the bandwidth of the speed estimator is changed depending on the operating speed so that the phase delay between the actual speed and the estimated speed is always within the range of [π / 2, π], so that the speed pulsation compensator can operate stably in all operating regions.

[0024] The effects obtained by 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 to which the present invention pertains from the following description. [Brief explanation of the drawings]

[0025] The following drawings attached to this specification illustrate preferred embodiments of the present invention and, together with the detailed description of the invention to be given later, serve to make the technical concept of the present invention easier to understand. Therefore, the present invention should not be interpreted as being limited only to the matters shown in the following drawings.

[0026] [Figure 1] FIG. 1 is a block diagram showing an example of a typical electric motor drive device.

[0027] [Figure 2] 1 is a graph showing load fluctuation characteristics depending on the type of a typical compressor.

[0028] [Figure 3] FIG. 1 is a control block diagram for implementing the speed pulsation reduction technology proposed in Prior Art 1.

[0029] [Figure 4] FIG. 1 is a control block diagram for realizing the speed pulsation reduction technique proposed in Prior Art 2.

[0030] [Figure 5] FIG. 10 is a control block diagram for realizing the speed pulsation reduction technique proposed in Prior Art 3.

[0031] [Figure 6] FIG. 10 is a control block diagram for realizing the speed pulsation reduction technique proposed in Prior Art 4.

[0032] [Figure 7] FIG. 7 is a block diagram showing the speed pulsation analyzer and the speed pulsation compensator of FIG. 6 in more detail. [Figure 8] FIG. 7 is a block diagram showing the speed pulsation analyzer and the speed pulsation compensator of FIG. 6 in more detail.

[0033] [Figure 9] 1 is a block diagram of a load fluctuation compensation device for a motor according to an embodiment of the present invention;

[0034] [Figure 10] FIG. 10 is a block diagram showing an example of the configuration of the angle pulsation analyzer and the speed pulsation compensator shown in FIG. 9. [Figure 11] FIG. 10 is a block diagram showing an example of the configuration of the angle pulsation analyzer and the speed pulsation compensator shown in FIG. 9. DETAILED DESCRIPTION OF THE INVENTION

[0035] The specific structural or functional descriptions for each embodiment described below are disclosed for illustrative purposes only and may be modified and implemented in various forms. Therefore, each embodiment is not limited to the specific disclosed form, and the scope of this specification includes modifications, equivalents, or alternatives included in the technical idea.

[0036] Although terms such as "first" or "second" may be used to describe various components, these terms should be construed only to distinguish one component from another. For example, a first component may be designated as a second component, and similarly, a second component may be designated as a first component.

[0037] When a component is said to be "coupled" to another component, it should be understood that the component may be directly coupled or connected to the other component, but there may also be other components in between.

[0038] The singular expression includes the plural expression unless the context clearly dictates otherwise. In this specification, the terms "comprise" or "have" and the like are intended to specify the presence of stated features, numbers, steps, operations, components, parts, or combinations thereof, and should be understood as not precluding the presence or possibility of addition of one or more other features, numbers, steps, operations, components, parts, or combinations thereof.

[0039] Unless otherwise defined, all terms used herein, including technical or scientific terms, have the same meaning as commonly understood by a person of ordinary skill in the art. Each predefined general term should be interpreted to have a meaning consistent with the context of the relevant art, and should not be interpreted in an idealized or overly formal sense unless expressly defined herein.

[0040] In a compressor driven by an electric motor, to reduce speed pulsation caused by load pulsation that periodically fluctuates with the rotation of the motor, the speed controller 11 (Figure 1) must generate a current command that can offset the load pulsation. To eliminate speed pulsation caused by periodic load pulsation using a conventional feedback-type speed controller, the speed controller's bandwidth must be set large. However, in actual motor drive systems, increasing the speed controller's bandwidth can cause the control system to become unstable, limiting the ability of feedback-type speed controllers to compensate for periodic speed pulsation. Most electric compressors use permanent magnet synchronous motors (PMSMs), which, due to their structural characteristics, are controlled using a sensorless control method that does not use a rotor position detection sensor. When driving a motor using sensorless control, increasing the speed controller's bandwidth can cause the control system to become unstable and even lead to the motor stalling. Therefore, when using a sensorless control method, the bandwidth of the speed controller is generally set to a low value, and in this case, the speed controller alone has very little effect in reducing the speed pulsation caused by periodic load fluctuations. Various methods have been proposed to solve this problem.

[0041] In the following, in order to facilitate a clearer and easier understanding of the present invention, first, specific conventional control techniques for reducing pulsation in a motor (Prior Art 1 to Prior Art 4) will be specifically described.

[0042] Prior art 1: Speed ​​pulsation reduction technology for electric motors using a lookup table (Cho, Kwan-yuhl, "Sensorless control for a PM synchronous motor in a single piston rotary compressor." Journal of Power Electronics 6.1 (2006): 29-37.)

[0043] FIG. 3 is a control block diagram for implementing the speed pulsation reduction technique proposed in Prior Art 1.

[0044] Prior Art 1 provides a control method for reducing speed pulsation due to periodic load fluctuations in a single-cylinder rotary compressor. As shown in Figure 3, the control method proposed in Prior Art 1 reduces the rotor angle (θ m The current command value capable of compensating for load fluctuations due to changes in the rotor angle is stored in a look-up table 21 in advance, and the current command value stored in the look-up table is read according to the rotor angle and applied to the output of the speed controller as feedforward compensation. Because the load applied to the compressor driving motor varies depending on the refrigeration cycle to which the compressor is connected, creating a look-up table that reflects various load conditions is challenging. Therefore, the periodic speed pulsation reduction method using the look-up table 21 has a drawback in that its performance is significantly affected by load fluctuations in the refrigeration cycle. Furthermore, when estimating the rotor angle of the compressor driving motor using a sensorless control method, errors in the estimated rotor angle can occur due to errors in the control constants used in the estimator. Such rotor angle estimation errors actually cause errors when reading the compensation value stored in the look-up table synchronized with the rotor angle. As a result, the performance of reducing speed pulsation due to load fluctuations can be significantly reduced.

[0045] For reference, in the drawings attached to this specification, reference numeral "11" denotes a speed controller for controlling the speed of the motor. As described above, the speed controller 11 can output a current command (command value) for substantially zeroing the error between a set speed command (command value) and an actual measured speed value or an estimated speed value (a value corresponding to the actual speed of the motor).

[0046] Furthermore, reference symbol "100" refers to the motor system that operates based on a current command output from the speed controller 11. Strictly speaking, reference symbol "100" includes all of the following: a control means that compares the current command with the drive current actually provided to the motor and controls the difference to be substantially "0," a power conversion means that provides the drive current to the motor, and the motor that operates based on the drive current; however, current control and power conversion technologies correspond to well-known technologies that are essential for driving a motor, so reference symbol "100" can be understood as the motor that operates based on the current command.

[0047] Also, reference numeral 161 denotes a primary system that indicates a rotational system composed of inertia (J) and a viscous friction coefficient (B), and the speed value (ω) of the motor corresponding to the torque value in the rotational system. m Reference numeral "162" denotes an integrator, which is a circuit that derives the motor (motor rotor) speed (ω m ) and integrate the motor (rotor) angle (θ m ) is a system that outputs the rotor angle (θ m ) and the actual rotor angle (θ m ) can be a detected value detected by a known position detection sensor such as a resolver or an encoder.

[0048] Also, reference numeral "163" denotes a speed estimator that estimates the speed of the motor. In the description of many embodiments of the present invention, the speed estimator 163 receives the angle of the motor (rotor of the motor) derived by a rotor position detection sensor (resolver, encoder, etc.) installed in the motor, and performs processing equivalent to differentiation to obtain an estimated value (measured value) ( JPEG2025529439000007.jpg88), or by receiving the motor angle estimated by the sensorless control method and performing a process equivalent to differentiation, an estimated value of the motor (rotor) speed ( JPEG2025529439000008.jpg88) can be derived.

[0049] Prior art 2: Technique using a load torque observer (Chen, Wen-Hua, et al., "Disturbance-observer-based control and related methods—An overview." IEEE Transactions on Industrial Electronics 63.2 (2015): 1083-1095.)

[0050] FIG. 4 is a control block diagram for implementing the speed pulsation reduction technique proposed in Prior Art 2.

[0051] As shown in FIG. 4, Prior Art 2 was proposed to overcome the drawbacks of the look-up table method, and is a technology that reduces periodic speed pulsation by estimating the load torque using a load torque estimator 31 and feeding the estimated load torque into the output of the speed controller as feedforward compensation.

[0052] To configure the load torque observer 31, accurate numerical information on the compressor's mechanical inertia, viscous friction coefficient, and the torque output by the motor is required. The compressor's mechanical inertia is determined by the inertia of the rotor and the inertia of the refrigerant. Because the inertia of the refrigerant changes with temperature, it is difficult to accurately determine the compressor's inertia in real time. The motor's output torque also changes depending on the motor's internal temperature and the magnitude of the current supplied to the motor, making it difficult to accurately predict the motor's output torque. For these reasons, the performance of a periodic speed pulsation reduction method using the load torque observer 31 is significantly affected by errors in the system's mechanical and electrical parameters. Therefore, a large parameter error significantly reduces the speed pulsation reduction performance.

[0053] Prior Art 3: Technique using resonant controller and repetitive controller (Jeon Sungmin, Lee Jeongho, Choi Jeongwoo, "Reduction of Periodic Speed ​​Pulsation of Electric Motor Using Resonant Controller and Repetitive Controller," Transactions of the Institute of Electrical Engineers of Japan, Vol. 67, No. 11, pp. 1434-1446, 2018.)

[0054] FIG. 5 is a control block diagram for implementing the speed pulsation reduction technique proposed in Prior Art 3.

[0055] As shown in Fig. 5, prior art 3 proposes a technique for compensating for periodic speed pulsation by adding a resonance controller 311 and a repetition controller 312 in parallel to the speed controller 10. The resonance controller 311 and the repetition controller 312 do not require the mechanical and electrical parameters of the motor, and therefore can overcome the shortcomings of prior art 2.

[0056] The repetitive controller 312 accumulates and stores the error that occurs periodically in synchronization with the rotor position in the form of an array in a memory for each rotor position of the motor, and generates a command to compensate for the periodic pulsation using the values ​​stored in the array. At this time, the index value used to read the values ​​stored in the array is determined taking into account the phase delay of the motor drive system.

[0057] In the case of an electric compressor, the phase characteristics of the effect of periodic torque pulsation on speed pulsation vary depending on conditions such as operating speed, temperature, and pressure. Therefore, if the phase fluctuation characteristics are not accurately reflected when using a repetitive controller 312, the speed pulsation reduction performance can be significantly reduced. Furthermore, when estimating the rotor angle of the compressor drive motor using a sensorless control method, errors in the control constants used in the estimator can cause errors in the estimated rotor angle. Such rotor angle estimation errors cause errors when reading values ​​stored in the arrays that make up the repetitive controller, thereby degrading the performance of the repetitive controller. Therefore, both the method using a lookup table (Conventional Art 1) and the method using a repetitive controller (Conventional Art 3) share the disadvantage of being significantly affected by rotor angle estimation errors when estimating the rotor angle of the compressor drive motor using a sensorless control method.

[0058] The resonant controller 311 reduces the speed pulsation by increasing the gain of the frequency band corresponding to the periodic speed pulsation. Even in the resonant controller 311, if a large phase delay occurs in the input signal, the stability of the controller decreases.

[0059] If the magnitude of the periodic speed pulsation is greater than the output torque of the motor, the output of the speed controller 11 becomes saturated. When the output of the speed controller 11 becomes saturated, the resonant controller 311 and the repetitive controller 312 may experience a problem of reduced control stability due to the possibility of divergence. In particular, under conditions where the output of the speed controller becomes saturated, such as when a single-cylinder rotary compressor is operating under overload, the speed pulsation reduction method using the resonant controller 311 and the repetitive controller 312 no longer exhibits stable control performance.

[0060] Prior Art 4: Technique using a speed ripple observer (JW Choi, S L Lee, S Y Yu and S J Jang, "Novel Periodic Torque Ripple Compensation Scheme in Vector Controlled AC Motor Drives," Applied Power Electronics Conference and Exposition, pp. 81-85, 1998.)

[0061] FIG. 6 is a control block diagram for implementing the speed pulsation reduction technique proposed in Prior Art 4.

[0062] As shown in FIG. 6, Prior Art 4 proposes a method for reducing periodic speed pulsation by analyzing each speed pulsation component using a speed pulsation observer 413, determining the magnitude of the cosine and sine components of the speed pulsation based on a specific mechanical angle of the motor, and generating a torque command that compensates for the cosine and sine components of the speed pulsation using a speed pulsation compensator 412.

[0063] Prior Art 4 adds an anti-windup controller to the integrator used in the controller, thereby solving the problem of divergence when the output is saturated, which is a drawback of Prior Art 3. Also, unlike Prior Art 2, it does not use the parameters of the electric motor and mechanical system.

[0064] However, the technique presented in Reference 4 does not take into account the phase delay that may occur in the speed measurement (or estimation), which may cause the periodic speed pulsation compensation controller to operate in the wrong direction and diverge.

[0065] In FIG. 6, the load torque, which varies with the same frequency as the electrical angular frequency of the motor, can be defined as in the following Equation 1.

[0066]

[0067]

number

[0068] In the above formula 1, A and B represent the amplitudes of the cosine function and the sine function, respectively, and θ m means the mechanical angle of the motor. In Figure 6, the load torque (T L ) to compensate for the motor output torque (T e ) can be given by the following formula 2:

[0069]

[0070]

number

[0071] In the above equation 2, C and D represent the amplitudes of the cosine function and the sine function, respectively.

[0072] In FIG. 6, the signal at node (N1) indicating the difference between the motor output torque and the load torque is given by Equation 3 below.

[0073]

[0074]

number

[0075] In Equation 3, if the values ​​of C and D are set so that the conditions C=-A and D=-B are satisfied, the torque pulsation component input to the first-order system (1 / (Js+B)) 161 consisting of inertia (J) and viscous friction coefficient (B) becomes zero, and as a result, the speed pulsation due to periodic load fluctuation becomes zero.

[0076] In a typical motor drive system that does not use an expensive torque sensor, the values ​​A and B, which correspond to the amplitudes of the cosine and sine components of periodic torque pulsation, cannot be directly measured. Therefore, as shown in Figure 6, a method is used in which the speed ripple component is analyzed using a speed ripple analyzer 411, and the speed ripple compensator 412 uses the analysis results to generate a current command that satisfies the conditions C = -A and D = -B.

[0077] In Figure 6, when a signal at node N1 passes through first-order system (1 / (Js+B)) 161, a phase delay occurs within the range of [0, π / 2] depending on the frequency of the input signal. Since speed estimator 163 generally has low pass filter characteristics, a phase delay generally occurs within the range of [0, π / 2] when the signal passes through speed estimator 163. Therefore, in Figure 6, when the signal at node N1 expressed by Equation 3 passes through first-order system (1 / (Js+B)) 161, integrator (1 / s) 163, and speed estimator 163 and arrives at node N2, the signal can be expressed as Equation 4 below.

[0078]

[0079]

number

[0080] In Equation 4, k and β respectively represent the magnitude and phase change of the signal generated while passing through the first-order system (1 / (Js+B)) 161 and the speed estimator 163. The values ​​of k and β vary depending on the frequency of the input signal. In particular, the value of β is determined by the phase delay of the first-order mechanical system (1 / (Js+B)) 161 and the phase delay of the speed estimator 163, and generally has a value that varies within the range of [0, π].

[0081] In Equation 4, ω ripple is a speed pulsation component, and is a calculation for subtracting the speed command from the estimated speed ( JPEG2025529439000013.jpg817). Equation 4 can also be expressed as Equation 5.

[0082]

[0083]

number

[0084] Speed ​​pulsation (ω ripple ) is a measurable (estimated) value. Therefore, ω ripple By applying appropriate signal processing to ω ripple The cosine function (cosθ m ) and the sine function (sinθ m ) can be calculated as follows:

[0085] 7 and 8 are block diagrams showing the speed pulsation analyzer and speed pulsation compensator of FIG. 6 in more detail.

[0086] As shown in the speed pulsation analyzer in Figure 7, cosθ m After multiplying by and passing it through a low-pass filter, ω ripple The cosine function (cosθ m The amplitude (E) of the signal (V) is calculated using the following equation (6):

[0087]

[0088]

number

[0089] Similarly, sinθ in Equation 5 m After multiplying by and passing it through a low-pass filter, The sine function (sinθ m The amplitude (F) of the signal (F) is calculated using the following equation (7):

[0090]

[0091]

number

[0092] If the value of the phase delay (β) is in the range [0, π / 2], JPEG2025529439000018.jpg716, Therefore, if the value of E calculated through Equation 6 is positive, the value of E can be converged to 0 when the magnitude of C is adjusted to decrease and the magnitude of D is adjusted to increase.

[0093] Similarly, if the value of F obtained through Equation 7 is positive, the magnitude of C must be adjusted to a decreasing direction, and the magnitude of D must be adjusted to a decreasing direction.

[0094] In summary, if the values ​​of C and D are adjusted to increase or decrease depending on the signs of E and F obtained through Equation 6 and Equation 7, respectively, the values ​​of C and D that satisfy the condition CA, D = -B can be obtained.

[0095] In Fig. 7, k1, k2, k3, and k4 in the speed pulsation compensator are gains multiplied by the signal input to the integrator (1 / s). In Fig. 7, two integrators (1 / s) 421 and 422 create the magnitude (amplitude) of the cosine and sine functions that make up the signal that compensates for load torque fluctuations.

[0096] In Figure 7, when the value of the phase delay (β) is within the range [0, π / 2], only the sign of k4 is positive, and the signs of k1, k2, and k3 are negative. If this condition is not met, the speed pulsation compensator may operate to increase torque pulsation due to load fluctuations.

[0097] If the value of the phase delay (β) is in the range [π / 2, π], JPEG2025529439000020.jpg716, Therefore, if the value of E obtained through Equation 6 is positive, the magnitude of C must be increased and the magnitude of D must be increased.

[0098] Similarly, if the value of F obtained through Equation 7 is positive, the magnitude of C should be adjusted to decrease, and the magnitude of D should be adjusted to increase.

[0099] That is, as shown in FIG. 8, when only the gain (k2) used in the speed pulsation compensator has a negative value and the remaining k1, k3, and k4 have positive values, a signal that compensates for torque pulsation due to load fluctuations is reliably generated.

[0100] As shown in Figure 8, the signs of the gains (k1, k2, k3, k4) used in the speed pulsation compensator have different values ​​compared to when the phase delay (β) value is within the range [0, π / 2] (Figure 7). In the method proposed in Prior Art 4, since the signs of the gains used in the speed pulsation compensator are fixed, there is a problem that the operation of the torque pulsation compensator may diverge depending on the region in which the phase delay (β) value is located.

[0101] To summarize the above, in Prior Art 1, current command values ​​that can compensate for load fluctuations based on the rotor angle of the motor are stored in a lookup table, so there is no effect from phase delays that occur in speed detection. However, as explained above, there are limitations to expressing fluctuating load characteristics using a lookup table.

[0102] The methods described in Prior Art 2 to Prior Art 4 can overcome the shortcomings of Prior Art 1. However, all of the methods described in Prior Art 2 to Prior Art 4 have a structure that generates a control input that compensates for periodic speed pulsation from the speed pulsation component.

[0103] When detecting the speed of a motor using a speed detection device such as a tachometer, there is very little phase difference between the actual speed of the motor and the detected speed. However, when measuring the rotor angle using an encoder or resolver and re-calculating the speed from the measured angle, a phase delay inevitably occurs between the actual speed of the motor and the detected speed. In particular, even in applications that use a sensorless control method that does not use a position detection sensor, such as an electric compressor, a phase delay exists between the actual speed of the motor and the estimated speed. Each of the methods presented in Prior Art 2 to Prior Art 4 is affected by a phase delay that occurs in speed detection. Therefore, the degree of phase delay in speed detection can significantly affect the operation of a controller that reduces periodic speed pulsation, and the value of the phase delay can cause problems such as divergence in the operation of a speed pulsation compensator.

[0104] Many embodiments of the present invention propose new techniques for compensating for periodic speed pulsations in electric motor drives that overcome the limitations and shortcomings of the prior art discussed above.

[0105] Many embodiments of the present invention employ a method of detecting pulsation not in the rotational speed of a motor but in the rotational angle of the motor and using this to reduce periodic speed pulsation. When detecting pulsation in the rotational angle of the motor, speed information is not used, so the phase delay value described above may be limited to the range of [0, π / 2]. In this case, the sign of the gain used in the speed pulsation compensator can be fixed to a constant value. Therefore, by detecting pulsation in the rotational angle of the motor and configuring a speed pulsation compensator using this, a controller that reduces periodic speed pulsation in all operating ranges can be configured to operate stably without divergence, regardless of the operating conditions of the motor.

[0106] FIG. 9 is a block diagram of a motor load fluctuation compensation device according to one embodiment of the present invention, and FIGS. 10 and 11 are block diagrams showing examples of the configuration of the angle pulsation analyzer and speed pulsation compensator shown in FIG. 9.

[0107] 9 and 10, the load fluctuation compensation device for a motor according to an embodiment of the present invention detects the rotor angle of the motor ( JPEG2025529439000022.jpg85) or estimated value ( JPEG2025529439000023.jpg87), and a speed pulsation compensator 512 that generates a speed pulsation compensation value for reducing rotor speed pulsation based on the rotor angle pulsation characteristics analyzed by the angle pulsation analyzer 511.

[0108] The angle pulsation analyzer 511 analyzes the characteristics of angle pulsation from the angle information of the electric motor 100, and the speed pulsation compensator 512 can generate a torque control signal to compensate for periodic load fluctuations using the characteristics analyzed by the angle pulsation analyzer 511.

[0109] In Figure 9, the load torque (T L ) and the motor output torque (T e ) respectively. JPEG2025529439000024.jpg841' and ' JPEG2025529439000025.jpg841', the signal at the node (N1) can be expressed as in the following Equation 8.

[0110]

[0111]

number

[0112] In FIG. 9, when the signal at node (N1) passes through the first-order system (1 / (Js+B)) 161 indicating the rotation system and the integrator (1 / s) and reaches node (N3), the signal can be expressed as the following Equation 9.

[0113]

[0114]

number

[0115] Equation 9 can also be expressed as the following Equation 10.

[0116]

[0117]

number

[0118] In Equation 9 and Equation 10, k and γ respectively represent the magnitude and phase change of the signal generated through the first-order system (1 / (Js+B)) 161. Here, γ is limited within the range [0, π / 2].

[0119] In Fig. 10, the angular pulsation (θ ripple ) is ω ripple This corresponds to the integral of and can be calculated as shown in the following formula 11.

[0120]

[0121]

number

[0122] In Equation 11, θ * m is the preset speed command (ω * m ) can be obtained by integrating θ ripple can be limited to the range [-π, π]. ripple ) is the angle command (θ * m ) can be obtained by subtracting θ ripple ω * m cosθ m and ω * m sinθ m and pass each multiplication result through a low-pass filter, ripple The cosine function (cosθ m ) and the sine function (sinθ m ) can be obtained. That is, the following Equations 12 and 13 can be derived from Equation 9.

[0123]

[0124]

number

[0125]

[0126]

number

[0127] In one embodiment of the present invention, the angle detection value (θ m) is used to analyze pulsation, so only the phase delay (γ) due to the first-order system of the rotating system (1 / (Js+B))161 can be considered, and the value of the phase delay (γ) is limited within the range [0, π / 2]. JPEG2025529439000032.jpg715, The condition JPEG2025529439000033.jpg716 is always met.

[0128] If the value of G obtained through Equation 12 is positive, the magnitude of C should be increased and the magnitude of D should be increased. Similarly, if the value of H obtained through Equation 13 is positive, the magnitude of C should be decreased and the magnitude of D should be increased. The angle pulsation analyzer and speed pulsation compensator 512 configured to satisfy these conditions are shown in FIG. 10.

[0129] That is, as shown in FIG. 10, among the multiple gains used in the speed pulsation compensator 512, only the gain (k2) has a negative value, and the remaining gains k1, k3, and k4 have positive values, so that the signal that compensates for torque pulsation due to load fluctuations does not diverge.

[0130] In one embodiment of the present invention, the value of the phase delay (γ) is always limited within the range [0, π / 2] regardless of the operating conditions of the motor. Therefore, a fixed value can be used for the sign of the gain used in the speed pulsation compensator, as shown in FIG. 10. This allows the speed pulsation compensator to exhibit stable control characteristics that do not diverge even when the operating conditions change.

[0131] On the other hand, Figure 11 shows the case where a sensorless method is used, which does not use a position detection sensor, as in an electric compressor. JPEG2025529439000034.jpg85) and the estimated angle ( There may be errors between the image and the image quality (JPEG2025529439000035.jpg87). JPEG2025529439000036.jpg85 and If the error between JPEG2025529439000037.jpg87 is δ, the periodic load fluctuation (T L ) can be expressed as the following Equation 14.

[0132]

[0133]

number

[0134] Equation 14 can be re-expressed as Equation 15 below.

[0135]

[0136]

number

[0137] According to Equation 15, when there is an estimated position error in the sensorless control method, the periodic load fluctuation is JPEG2025529439000040.jpg817 and Therefore, when using the sensorless control method, the angle pulsation analyzer and the speed pulsation compensator are used. JPEG2025529439000042.jpg812 and JPEG2025529439000043.jpg812 respectively JPEG2025529439000044.jpg817 and If we change it to JPEG2025529439000045.jpg816 and use it, we can configure a controller that compensates for periodic load fluctuations regardless of the influence of sensorless angle estimation errors. In this case, too, the value of the phase delay (γ) is always [0, JPEG2025529439000046.jpg126] range, the speed pulsation compensator has stable control characteristics.

Claims

1. an angle pulsation analyzer that analyzes the characteristics of the rotor angle pulsation based on the detected value of the rotor angle of the motor; and a speed pulsation compensator that generates a speed pulsation compensation value for reducing the rotor speed pulsation based on the characteristics of the rotor angle pulsation analyzed by the angle pulsation analyzer; A load fluctuation compensation device for an electric motor including:

2. The angular pulsation analyzer comprises:

2. The load fluctuation compensation device for an electric motor according to claim 1, wherein the amplitudes of the cosine function and the sine function constituting the pulsation of the rotor angle are calculated.

3. The angular pulsation analyzer comprises: Formula (θ ｒｉｐｐｌｅ : angle pulsation value, θ ｍ : the detected value of the rotor angle, θ ＊ ｍ : Speed ​​command value (ω ＊ ｍ ) is an angle command value obtained by integrating (ω ＊ ｍ : speed command value) and and passing the multiplication results through a low-pass filter to obtain the amplitudes of the cosine function and sine function that constitute the pulsation of the rotor angle.

4. The amplitude (G) of the cosine function and the width (H) of the sine function that constitute the pulsation of the rotor angle are respectively formula and formula 3. The load fluctuation compensation device for an electric motor according to claim 2, wherein A and B are the amplitudes of the cosine and sine components of the load torque, respectively; C and D are the amplitudes of the cosine and sine components of the output torque of the electric motor, respectively; k and γ are the magnitude and phase change of the signal generated while passing through a primary system corresponding to the rotating system, respectively; and γ is a value within the range of [0, π / 2].

5. The speed pulsation compensator includes:

5. The load fluctuation compensator for an electric motor according to claim 2, wherein gains are applied to amplitudes of a cosine function and a sine function constituting the rotor angle pulsation, respectively, and a sum of the amplitudes of the cosine function and the sine function constituting the rotor angle pulsation to which gains have been applied is integrated to generate the current command compensation value for reducing the rotor speed pulsation.

6. The speed pulsation compensator includes: summing a value obtained by applying a first gain to the amplitude of a cosine function constituting the pulsation of the rotor angle and a value obtained by applying a second gain to a sine function constituting the pulsation of the rotor angle, integrating the summed value, and determining the amplitude of a cosine component of the output torque of the electric motor according to the current command compensation value; 6. The load fluctuation compensation device for an electric motor according to claim 5, wherein a value obtained by applying a third gain to the amplitude of a sine function constituting the pulsation of the rotor angle and a value obtained by applying a fourth gain to the sine function constituting the pulsation of the rotor angle are summed, and the summed value is integrated to determine the amplitude of a sine component of the output torque of the electric motor based on the current command compensation value.

7. 7. The load fluctuation compensation device for an electric motor according to claim 6, wherein the first gain, the third gain, and the fourth gain have positive signs, and the second gain has a negative sign.

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