Motor load variation compensation device

Abstract

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

Description

Technical Field

[0001] The present invention relates to a motor load variation compensation device, and more particularly to a motor load variation compensation device capable of reducing speed pulsation caused by periodic load variation of a motor such as one used in an electric compressor. Background Art

[0002] A motor is a device that converts electrical energy into mechanical energy. In order to drive a motor, a separate drive device is required to control the power supplied to the motor. A motor drive device is a device that controls the torque of the motor by controlling the power supplied to the motor.

[0003] Figure 1 FIG. 1 is a block diagram showing a typical example of a motor drive device. Figure 1 As shown, in order to make the rotation speed of the motor follow the set speed command value, the motor drive device includes a speed controller 11 and a current controller 12. The speed controller 11 compares the preset speed command value with the speed detection value of the motor detected by the speed detection sensor set on the motor or calculated by a preset algorithm, and outputs a current command for making the difference substantially zero. The current controller 12 outputs a voltage command value for making the current command output by the speed controller and the value of the current actually supplied to the motor the same value as each other. The motor drive device can convert DC power to control the power conversion circuit 14 that generates multi-phase AC power for driving the motor to output a voltage corresponding to the voltage command value to the motor. The power conversion circuit 14 can be an inverter 14 that converts power in a manner that performs PWM (Pulse Width Modulation) control on multiple switching elements, and the motor drive device can include a PWM controller 13 for PWM control of the switching elements of the inverter 14 based on the voltage command value.

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

[0005] Figure 2 : is a graph showing load variation characteristics corresponding to the types of common compressors. Figure 2As shown, in the case of a single-cylinder rotary compressor, each time the motor mechanically rotates one circle, a load change occurs due to the suction / compression of the refrigerant, and its size is relatively large compared to other compressors. For another example, in the case of a twin-cylinder rotary compressor, the size of the load change is greatly reduced compared to a single-cylinder rotary compressor. But it is characterized in that two load changes occur each time it rotates 360 degrees at a mechanical angle (the angle at which the motor's rotor mechanically rotates). Even in the case of a scroll compressor, a load change occurs each time it rotates 360 degrees at a mechanical angle, but its size is relatively small compared to other compressors.

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

[0007] The matters described above as background technology are only used to enhance the understanding of the background of the present invention and should not be regarded as a determination that they correspond to the prior art known to those skilled in the art. Summary of the invention

[0008] Technical issues

[0009] Therefore, the technical problem to be solved by the present invention is to provide a motor load variation compensation device which can reduce the vibration and noise of the motor by reducing the speed pulsation caused by periodic load variation of the motor such as that used in the electric compressor.

[0010] The problem to be solved by the present invention is not limited to the above-described content. Other technical problems and advantages of the present invention that are not described can be understood through the following description and will be more clearly understood through the embodiments of the present invention. In addition, those skilled in the art will easily understand that the technical solutions and advantages of the present invention can be achieved by the means shown in the claims and their combinations.

[0011] Technical Solution

[0012] As a solution to the above-mentioned technical problem, the present invention provides a motor load variation compensation device, comprising: an angle pulsation analyzer, which analyzes the characteristics of the pulsation of the rotor angle based on the detection value of the motor's rotor angle; and a speed pulsation compensator, which generates a speed pulsation compensation value for reducing the pulsation of the rotor speed based on the characteristics of the pulsation of the rotor angle analyzed by the angle pulsation analyzer.

[0013] In one embodiment of the present invention, the angle pulsation analyzer can calculate the amplitude of the cosine function and the sine function of the pulsation constituting the rotor angle.

[0014] In one embodiment of the present invention, the angle pulsation analyzer can ripple =θ m -θ * m (θ ripple : Angle pulsation value, θ m : The detected value of the rotor angle, θ * m :Through the speed command value (ω * m The angle command value obtained by integrating the angle command value) is multiplied by ω * m cosθ m (ω * m : speed command value) and ω * m sinθ m and pass each multiplication result through a low-pass filter to find the amplitude of the cosine and sine functions of the pulsation constituting the rotor angle.

[0015] In one embodiment of the present invention, the amplitude G of the cosine function and the amplitude H of the sine function constituting the pulsation of the rotor angle can be expressed as follows:

[0016] Mode as well as

[0017] Mode (A, B: the amplitudes of the cosine component and sine component of the load torque, respectively; C, D: the amplitudes of the cosine component and sine component of the motor output torque, respectively; k, γ: the magnitude and phase changes that occur when the signal passes through the first-order system corresponding to the rotating system, respectively; γ is a value in the range of [0, π / 2]).

[0018] In one embodiment of the present invention, the speed pulsation compensator can apply gains to the amplitudes of the cosine function and the sine function of the pulsation constituting the rotor angle, respectively, and integrate the sum of the amplitudes of the cosine function and the sine function of the pulsation constituting the rotor angle to which the gains are applied, so as to generate the current command compensation value for reducing the pulsation of the rotor speed.

[0019] In one embodiment of the present invention, the speed pulsation compensator may add a first gain value to the amplitude of the cosine function of the pulsation constituting the rotor angle and a second gain value to the sine function of the pulsation constituting the rotor angle and integrate the added value to determine the amplitude of the cosine component of the output torque of the motor through the current command compensation value, and add a third gain value to the amplitude of the sine function of the pulsation constituting the rotor angle and a fourth gain value to the sine function of the pulsation constituting the rotor angle and integrate the added value to determine the amplitude of the sine component of the output torque of the motor through the current command compensation value.

[0020] In an embodiment of the present invention, the signs of the first gain, the third gain, and the fourth gain may be positive, and the sign of the second gain may be negative.

[0021] Effects of the Invention

[0022] According to the motor load variation compensation device, since the influence of periodic load variation is extracted from the angle pulsation, the phase delay occurring in the signal processing process can be limited to the range of [0,π / 2]. Accordingly, even if the sign of the gain used in the speed pulsation compensator is fixed, stable control characteristics can be obtained in all operating areas of the motor.

[0023] Furthermore, according to the motor load variation compensation device, since the bandwidth of the speed estimator is changed according to 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], the speed ripple compensator can operate stably in all operating regions.

[0024] The effects that can be obtained by the present invention are not limited to the effects described above, and those skilled in the art to which the present invention belongs will clearly understand other effects that are not described from the following description. BRIEF DESCRIPTION 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 described later, serve to facilitate understanding of the technical ideas of the present invention. Therefore, the present invention should not be interpreted limited to the matters recorded in the following drawings.

[0026] Figure 1 This is a block diagram showing a configuration of an example of a general motor drive device.

[0027] Figure 2 This is a graph showing load variation characteristics corresponding to types of general compressors.

[0028] Figure 3It is a control block diagram for realizing the speed pulsation reduction technology proposed in prior art 1.

[0029] Figure 4 It is a control block diagram for realizing the speed pulsation reduction technology proposed in the prior art 2.

[0030] Figure 5 It is a control block diagram for implementing the speed pulsation reduction technology proposed in prior art 3.

[0031] Figure 6 It is a control block diagram for realizing the speed pulsation reduction technology proposed in prior art 4.

[0032] Figure 7 and Figure 8 is shown in more detail Figure 6 Structural block diagram of speed pulsation analyzer and speed pulsation compensator.

[0033] Fig. 9 It is a structural block diagram of a motor load variation compensation device according to an embodiment of the present invention.

[0034] Fig.10 and Fig.11 It is shown Fig. 9 The structural block diagram of the structural example of the angle ripple analyzer and speed ripple compensator shown in the figure. DETAILED DESCRIPTION

[0035] The specific structural or functional descriptions of the embodiments described below are disclosed only for illustrative purposes and can be changed and implemented in various forms. Therefore, the embodiments are not limited to specific disclosed forms, and the scope of this specification includes changes, equivalents or substitutes that fall within the technical concept.

[0036] Although the terms "first" or "second" can be used to describe a plurality of components, these terms should only be interpreted for the purpose of distinguishing one component from another component. For example, a first component can be named a second component, and similarly, a second component can also be named a first component.

[0037] When it is mentioned that a certain component is “connected” to another component, it should be understood that it may be directly connected or linked to the other component, but other components may be present in between.

[0038] Unless the context clearly defines otherwise, singular expressions include plural expressions. In this specification, it should be understood that the terms "including" or "having" are intended to specify the existence of the described features, numbers, steps, actions, constituent elements, parts or combinations thereof, and do not preclude the possibility of the existence or addition of one or more other features or numbers, steps, actions, constituent elements, parts or combinations thereof.

[0039] Unless otherwise defined, all terms used herein, including technical or scientific terms, have the same meaning as those generally understood by those of ordinary skill in the art. Terms defined in commonly used dictionaries should be interpreted as having a meaning consistent with the meaning in the context of the relevant technology, and unless clearly defined in this specification, shall not be interpreted in an idealized or overly formalized sense.

[0040] In order to reduce the speed pulsation caused by the load pulsation that periodically changes according to the rotation of the motor, such as in a motor-driven compressor, Figure 1 A current command capable of offsetting load pulsation is generated in the speed controller 11 of the general feedback type. In order to eliminate the speed pulsation caused by the periodic load pulsation, the bandwidth of the speed controller should be set larger. However, in the actual motor drive system, increasing the bandwidth of the speed controller will cause the control system to become unstable, so the feedback type speed controller has limitations in compensating for the periodic speed pulsation. As the driving motor of most electric compressors, a permanent magnet synchronous motor (PMSM) is used. Due to the structural characteristics of the compressor, the motor is controlled by a sensorless control method without using the rotor position detection sensor of the motor. When the motor is driven by the sensorless control method, increasing the bandwidth of the speed controller will cause the control system to become unstable, and the motor drive may stop. Therefore, when the sensorless control method is used, the bandwidth of the speed controller is usually set to a lower value. At this time, the effect of reducing the speed pulsation caused by the periodic load change is small only by the action of the speed controller. In order to solve such a problem, a variety of methods have been proposed.

[0041] In the following, in order to facilitate a clearer and easier understanding of the present invention, specific existing control technologies for reducing the pulsation of a motor (prior art 1 to prior art 4) are first described in detail.

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

[0043] Figure 3It is a control block diagram for realizing the speed pulsation reduction technology proposed in prior art 1.

[0044] Prior art 1 provides a control method for reducing speed pulsation caused by periodic load changes in a single-cylinder rotary compressor. Figure 3 As shown, the control technology proposed in the prior art 1 has the following structure: the rotor angle θ corresponding to the compressor drive motor can be compensated in advance in the look-up table 21 (Look-Up Table) m The structure is to read the current command value stored in the lookup table according to the rotor angle according to the current command value of the load change, and perform feedforward compensation on the output of the speed controller. Since the load applied to the compressor drive motor has the characteristic of changing depending on the refrigeration cycle to which the compressor is connected, there are many difficulties in creating a lookup table that reflects various load conditions. Therefore, the disadvantage of the periodic speed pulsation reduction method using the lookup table 21 is that its performance is greatly affected by the load changes of the refrigeration cycle. In addition, when the rotor angle of the compressor drive motor is estimated by the sensorless control method, due to the error of the control constant used in the estimator, the estimated rotor angle may have an error. Such a rotor angle estimation error will cause an error in reading the compensation value stored in the lookup table in synchronization with the actual rotor angle. As a result, this may cause the speed pulsation reduction performance corresponding to the load change to be greatly reduced.

[0045] For reference, in the drawings attached to this specification, reference numeral "11" refers to 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 making the error between the set speed command (command value) and the actual motor speed measurement value or speed estimation value (value corresponding to the actual motor speed) substantially "0".

[0046] In addition, reference numeral "100" refers to a motor system that operates based on a current command output by the speed controller 11. Strictly speaking, reference numeral "100" includes a control mechanism that compares a current command with a drive current actually supplied to the motor and controls the error to be substantially "0", a power conversion mechanism that supplies the drive current to the motor, and a motor that operates by receiving the drive current, but since the technology of current control or power conversion corresponds to the known technology necessary for driving the motor, reference numeral "100" can be understood as a motor that operates based on a current command.

[0047] In addition, reference numeral “161” indicates a first-order system representing a rotating system composed of inertia J and viscous friction coefficient B, and a speed value ω of the motor corresponding to the torque value in the rotating system can be derived. mReference numeral "162" refers to an integrator, which is an integrator for the motor (rotor of the motor) speed ω m ) is integrated and outputs the motor (motor rotor) angle θ m The reference numerals "161" and "162" are for deriving the rotor angle θ of the motor. m Explanation of the applied system, the actual rotor angle θ m It may be a detection value detected by a well-known position detection sensor such as a resolver or an encoder.

[0048] In addition, reference numeral "163" refers to a speed estimator that estimates the speed of the motor. In the description of the various embodiments of the present invention, the speed estimator 163 may receive the angle of the motor (the rotor of the motor) derived from a rotor position detection sensor (resolver, encoder, etc.) provided on the motor and perform processing corresponding to differentiation to derive an estimated value (measured value) of the speed of the motor (the rotor of the motor). Or receive the angle of the motor estimated by the sensorless control method and perform processing corresponding to differentiation to derive an estimated value of the speed of the motor (the rotor of the motor)

[0049] Prior art 2: Technology using 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] Figure 4 It is a control block diagram for realizing the speed pulsation reduction technology proposed in the prior art 2.

[0051] like Figure 4 As shown, the prior art 2 is proposed to make up for the shortcomings of the lookup table method. It is a technology that uses a load torque observer (Load Torque Estimator) 31 to estimate the load torque and feed-forward compensate the speed controller output with the estimated load torque to reduce the periodic speed pulsation.

[0052] In order to construct the load torque observer 31, accurate numerical information of the mechanical inertia (Inertia) of the compressor, the viscous friction coefficient (Viscous Friction Coefficient), and the torque output by the motor is required. The mechanical inertia of the compressor is determined by the inertia of the rotating body and the inertia of the refrigerant. Since the value of the inertia of the refrigerant changes with the temperature, it is difficult to obtain the accurate inertia of the compressor in real time. Since the output torque of the motor also has the characteristic of changing according to the internal temperature of the motor and the magnitude of the current supplied to the motor, it is also difficult to accurately predict the output torque of the motor. For this reason, the performance of the periodic speed pulsation reduction method using the load torque observer 31 is greatly affected by the mechanical parameter and electrical parameter errors of the system. Therefore, when the parameter error is large, there is a problem that the speed pulsation reduction performance will also be greatly reduced.

[0053] Prior Art 3: Technology using a resonant controller and an iterative controller (Jeong Seong-min, Lee Jeong-ho, Choi Jong-woo, "Reducing the periodic speed pulsation of a motor using a resonant controller and an iterative controller," Journal of the Korean Institute of Electrical Engineers, Vol. 67, No. 11, pp. 1434-1446, 2018.)

[0054] Figure 5 It is a control block diagram for implementing the speed pulsation reduction technology proposed in prior art 3.

[0055] like Figure 5 As shown, prior art 3 proposes a technique for compensating periodic speed pulsation by adding a resonant controller 311 and an iterative controller 312 in parallel to the speed controller 10. The resonant controller 311 and the iterative controller 312 do not require the mechanical parameters and electrical parameters of the motor, and thus can overcome the disadvantages of prior art 2.

[0056] In the iterative controller 312, the error that occurs periodically in synchronization with the rotor position is accumulated and stored in the memory in the form of an array according to the rotor position of the motor, and an instruction for compensating the periodic pulsation is created using the values ​​stored in the array. At this time, the value of the index used when reading the value stored in the array is determined in consideration of the phase delay of the motor drive system.

[0057] In the case of an electric compressor, the phase characteristics of the periodic torque pulsation to the speed pulsation will change according to conditions such as the operating speed, temperature or pressure. Therefore, if the phase change characteristics cannot be correctly reflected when using the iterative controller 312, the speed pulsation reduction performance may be greatly reduced. In addition, when estimating the rotor angle of the compressor drive motor by sensorless control, errors in the control constants used in the estimator may cause errors in the estimated rotor angle. Such rotor angle estimation errors will cause errors when reading the values ​​stored in the array that constitutes the iterative controller, which becomes a cause of the degradation of the action performance of the iterative controller. Therefore, the method of using a lookup table in prior art 1 and the method of using an iterative controller in prior art 3 are sensorless control methods, and their common disadvantage is that when estimating the rotor angle of the compressor drive motor, they are greatly affected by the rotor angle estimation error.

[0058] The resonance controller 311 reduces the speed pulsation by increasing the gain of the frequency band corresponding to the periodic speed pulsation. Similarly, for the resonance controller 311, when the phase delay of the input signal is large, the stability of the controller decreases.

[0059] When the magnitude of the periodic speed pulsation is greater than the output torque of the motor, the output saturation of the speed controller 11 occurs. When the output of the speed controller 11 is saturated, the resonance controller 311 and the iteration controller 312 may diverge, which may cause the problem of decreased control stability. In particular, under the condition of saturation of the output of the speed controller, such as the overload operation of a single-cylinder rotary compressor, the speed pulsation reduction method using the resonance controller 311 and the iteration controller 312 cannot show stable control performance.

[0060] Prior Art 4: Technology using a speed ripple observer (JW Choi, SSLee, SY Yu, SJ Jang, "Novel Periodic Torque Ripple Compensation Scheme in Vector Controlled AC motor drives", Applied Power Electronics Conference and Expo, pp. 81-85, 1998.)

[0061] Figure 6 It is a control block diagram for implementing the speed pulsation reduction technology proposed in prior art 4.

[0062] like Figure 6As shown, in the prior art document 4, a method is proposed in which a speed pulsation component is analyzed by a speed pulsation observer 413, the speed pulsation magnitude of the cosine component and the sine component based on a specific mechanical angle of the motor is calculated, and a torque instruction is generated in a speed pulsation compensator 412 to compensate for the speed pulsation of the cosine component and the sine component, thereby reducing the periodic speed pulsation.

[0063] In the prior art 4, the disadvantage of the prior art 3, namely, the problem of divergence under the condition of output saturation, can be solved by adding an anti-windup controller in the integrator used in the controller. In addition, unlike the prior art 2, it has the feature of not using the parameters of the motor and the mechanical system.

[0064] However, since the technology proposed in the prior art document 4 does not take into account the phase delay that may occur in the speed measurement (or estimation), the action of the periodic speed pulsation compensation controller may run in the wrong direction and diverge.

[0065] exist Figure 6 In the equation (1), the load torque (Load Torque) that changes at the same frequency as the electrical angular frequency of the motor can be defined as shown in the following equation.

[0066] [Formula 1]

[0067] T L = -Acosθ m -Bsinθ m

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

[0069] [Formula 2]

[0070] T e =Ccosθ m +Dsinθ m

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

[0072] exist Figure 6 In the equation 3, the signal at the node N1 representing the difference between the output torque of the motor and the load torque is as shown in the following equation 3.

[0073] [Formula 3]

[0074] T e -T L =(A+C)cosθ m +(B+D)sinθ m

[0075] In the above formula 3, if the values ​​of C and D are set to satisfy the conditions of C=-A, D=-B, the pulsating component of the torque input to the first-order system (1 / (Js+B))(161) composed of inertia J and viscous friction coefficient B is 0, and as a result, the speed pulsation caused by periodic load changes is 0.

[0076] In a general motor drive system that does not use an expensive torque sensor, it is impossible to directly measure the values ​​of A and B corresponding to the amplitudes of the cosine component and the sine component of the periodic torque pulsation. Figure 6 As shown, a method is adopted in which a speed ripple analyzer (Speed ​​Ripple Analyzer) 411 analyzes the ripple component of the speed, and a speed ripple compensator (Speed ​​Ripple Compensator) 412 generates a current command under the conditions of C=-A and D=-B using the analysis result.

[0077] exist Figure 6 In the example, when the signal at the node N1 passes through the first-order system (1 / (Js+B)) (161), a phase delay occurs in the range of [0, π / 2] according to the frequency of the input signal. Since the speed estimator (Speed ​​Estimator) 163 generally has the characteristics of a low pass filter, a phase delay generally occurs in the range of [0, π / 2] when passing through the speed estimator 163. Therefore, when Figure 6 The signal at the node N1 represented by Formula 3 passes through the first-order system (1 / (Js+B)) 161, the integrator (1 / s) 163, and the speed estimator 163 and reaches the signal at the node N2 can be expressed as shown in Formula 4 below.

[0078] [Formula 4]

[0079] ω ripple = k{(A+C)cos(θ m -β)+(B+D)sin(θ m -β)} In Formula 4, k and β respectively represent the magnitude and phase changes that occur when the signal passes 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].

[0080] In formula 4, ω ripple The speed pulsation component can be calculated by subtracting the speed command from the estimated speed. To find out. Solve equation 4, as shown in equation 5 below.

[0081] [Formula 5]

[0082] ω ripple =k{[(A+C)cosβ-(B+D)sinβ]cosθ m +[(A+C)sinβ+(B+D)cosβ]sinθ m}

[0083] Speed ​​pulsationω ripple is a measurable (estimated) value. Therefore, for ω ripple By performing appropriate signal processing, we can find the components of ω ripple The cosine function (cosθ m ) and the sine function (sinθ m ) amplitude.

[0084] Figure 7 and Figure 8 is shown in more detail Figure 6 Structural block diagram of speed pulsation analyzer and speed pulsation compensator.

[0085] like Figure 7 As shown in the speed pulsation analyzer, multiply equation 5 by cosθ m , and pass it through a low-pass filter, then ω ripple The cosine function cosθ m The amplitude E can be calculated as follows:

[0086] [Formula 6]

[0087] E=k{(A+C)cosβ-(B+D)sinβ}

[0088] Similarly, multiplying equation 5 by sinθ m , and pass it through a low-pass filter, then ω ripple The sine function sinθ m The amplitude F is calculated as follows:

[0089] [Formula 7]

[0090] F=k{(A+C)sinβ+(B+D)cosβ}

[0091] When the phase delay β is in the range of [0,π / 2], the conditions of sinβ≥0 and cosβ≥0 are met. Therefore, if the value of E obtained by equation 6 is positive, the value of C should be adjusted in the decreasing direction and the value of D should be adjusted in the increasing direction so that the value of E can converge to 0.

[0092] Similarly, if the value of F obtained by Formula 7 is a positive value, the size of C should be adjusted in a decreasing direction, and the size of D should be adjusted in a decreasing direction.

[0093] In summary, by adjusting the values ​​of C and D in the direction of increase or decrease according to the signs of E and F obtained by equations 6 and 7 respectively, the values ​​of C and D that satisfy the condition CA, D = -B can be obtained.

[0094] Figure 7 In the speed ripple compensator, k1, k2, k3, and k4 are gains multiplied by the signal inserted into the integrator (1 / s). Figure 7 In FIG. 4 , two integrators (1 / s) 421 and 422 create the magnitude (amplitude) of the cosine function and the sine function constituting the signal compensating for the load torque variation.

[0095] exist Figure 7 In the equation, when the phase delay β is in the range of [0, π / 2], only k4 has a positive sign, while k1, k2, and k3 have negative signs. If this condition does not hold, the speed pulsation compensator may act in a direction that increases the torque pulsation caused by load fluctuations.

[0096] When the phase delay β is in the range of [π / 2,π], the conditions of sinβ≥0 and cosβ≤0 are satisfied. Therefore, if the value of E obtained by equation 6 is positive, the size of C should be increased, and the size of D should be adjusted in the direction of increasing.

[0097] Similarly, if the value of F obtained by equation 7 is a positive value, the size of C should be adjusted in a decreasing direction, and the size of D should be adjusted in an increasing direction.

[0098] That is, Figure 8 As shown, only the gain k2 used in the speed ripple compensator is a negative value, while the remaining k1, k3, and k4 should be positive values ​​in order to properly create a signal that compensates for the torque ripple caused by load changes.

[0099] like Figure 8 As shown in the figure, it can be seen that the signs of the gains k1, k2, k3, k4 used in the speed ripple compensator and the value of the phase delay β are in the range of [0, π / 2] ( Figure 7In the method proposed in the prior art 4, since the sign of the gain used in the speed pulsation compensator is fixed, there is a problem that the action of torque pulsation compensation may diverge depending on the region where the value of the phase delay β is located.

[0100] In summary, in the prior art 1, since the current command value that can compensate for the load variation based on the rotor angle of the motor is stored in the lookup table, it is not affected by the phase delay that occurs in the speed detection. However, as mentioned above, there are limitations in using the lookup table to express the variable load characteristics.

[0101] The methods described in prior arts 2 to 4 can overcome the disadvantages of prior art 1. However, the methods described in prior arts 2 to 4 all have a structure of creating a control input that compensates for periodic speed pulsation from the pulsating component of the speed.

[0102] When the speed of the motor is detected using a speed detection device such as a tachometer, the phase difference between the actual speed of the motor and the detected speed is very small. However, when the rotor angle is measured by an encoder or a rotary transformer, and the speed is calculated from the measured angle, a phase delay will inevitably occur between the actual speed of the motor and the detected speed. In particular, even in the case of the application of a sensorless control method such as an electric compressor that does not use a position detection sensor, there will be a phase delay between the actual speed of the motor and the estimated speed. The methods proposed in Prior Art 2 to Prior Art 4 are affected by the phase delay that occurs in speed detection. Therefore, the action of the controller that reduces periodic speed pulsation may be greatly affected depending on the degree of phase delay in speed detection, and depending on the value of the phase delay, the problem of action divergence of the speed pulsation compensator may occur.

[0103] Various embodiments of the present invention provide a new technology that can overcome the limitations and shortcomings of the aforementioned prior art in compensating for periodic speed pulsations in motor drives.

[0104] In the manner adopted by multiple embodiments of the present invention, the pulsation in the rotational angle of the motor is not detected, but the pulsation in the rotational angle of the motor is detected and used to reduce the periodic speed pulsation. When detecting the pulsation in the rotational angle of the motor, the speed information is not used, so the value of the previous phase delay can 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 for use. Therefore, by detecting the pulsation in the rotational angle of the motor and configuring the speed pulsation compensator using it, the controller that reduces the periodic speed pulsation in all operating areas without being affected by the operating conditions of the motor can be operated stably without divergence.

[0105] Fig. 9 is a structural block diagram of a motor load variation compensation device according to an embodiment of the present invention. Fig.10 and Fig.11 It is shown Fig. 9 The structural block diagram of the structural example of the angle ripple analyzer and speed ripple compensator shown in the figure.

[0106] Reference Fig. 9 and Fig.10 The motor load variation compensation device of one embodiment of the present invention may include: an angle pulsation analyzer 511, which is based on the detected value θ of the rotor angle of the motor m or estimated value to analyze the characteristics of the pulsation of the rotor angle; and a speed pulsation compensator 512, which generates a speed pulsation compensation value for reducing the pulsation of the rotor speed based on the characteristics of the pulsation of the rotor angle analyzed by the angle pulsation analyzer 511.

[0107] The angle pulsation analyzer 511 may analyze the characteristics of the angle pulsation from the angle information of the motor 100 , and the speed pulsation compensator 512 may generate a torque control signal for compensating for periodic load variation using the characteristics analyzed by the angle pulsation analyzer 511 .

[0108] exist Fig. 9 If the load torque T L and the motor output torque T e Set as "T L = -A cosθ m -B sinθ m ” and “T e =Ccosθ m +Dsinθ m ", the signal at the node N1 can be expressed as follows:

[0109] [Formula 8]

[0110] T e -T L =(A+C)cosθ m +(B+D)sinθ m exist Fig. 9 In the example, the signal at the node N1 passes through the first-order system (1 / (Js+B)) 161 representing the rotating system and the integrator 1 / s to reach the signal at the node N3, which can be expressed as follows in Equation 9.

[0111] [Formula 9]

[0112]

[0113] Solving equation 9, we get equation 10.

[0114] [Formula 10]

[0115]

[0116] In equations 9 and 10, k and γ represent the magnitude and phase changes that occur when the signal passes through the first-order system (1 / (Js+B)) 161. Here, γ is limited to the range of [0, π / 2].

[0117] exist Fig.10 In the case of angle pulsation θ ripple Corresponding to ω ripple The integral of can be calculated as follows:

[0118] [Formula 11]

[0119] θ ripple =∫ω ripple dt=θ m -θ * m

[0120] In Equation 11, θ* m The preset speed command ω* m Integrate to find, θ ripple Can be limited to the range [-π,π]. Angle ripple θ ripple The angle command θ* can be obtained by subtracting the integral of the speed command from the measured motor rotor angle m Therefore, if Fig.10 As shown in the angle pulse analyzer 511, by changing θ ripple Multiply by ω* m cosθ m and ω* m sinθ m , and pass each multiplication result through a low-pass filter, then we can find the components that make up θ ripple The cosine function cosθ m and the sine function sinθ m The amplitudes G and H. That is, the following equations 12 and 13 can be derived from equation 9.

[0121] [Formula 12]

[0122]

[0123] [Formula 13]

[0124]

[0125] One embodiment of the present invention uses the angle detection value θ mTo analyze the pulsation, we can only consider the phase delay γ of the first-order system (1 / (Js+B))161 of the rotating system, and since the value of its phase delay γ is limited to the range of [0, π / 2], the conditions of sinγ≥0 and cosγ≥0 always hold.

[0126] If the value of G obtained by equation 12 is positive, the size of C should be adjusted in the direction of increase, and the size of D should be adjusted in the direction of increase. Similarly, if the value of H obtained by equation 13 is positive, the size of C should be adjusted in the direction of decrease, and the size of D should be adjusted in the direction of increase. If the angle pulsation analyzer and the speed pulsation compensator 512 are configured to satisfy such conditions, then Fig.10 shown.

[0127] That is, Fig.10 As shown, it can be configured that among the multiple gains used in the speed ripple compensator 512, only the gain k2 is a negative value, and the remaining k1, k3, and k4 are positive values ​​to prevent the signal for compensating the torque ripple caused by load variation from diverging.

[0128] In one embodiment of the present invention, since the value of the phase delay γ is always limited to the range of [0,π / 2] regardless of the motor operating conditions, the sign of the gain used in the speed ripple compensator can be used as follows: Fig.10 The fixed value shown, and the speed ripple compensator can exhibit non-divergent stable control characteristics even when the operating conditions change.

[0129] on the other hand, Fig.11 The figure shows a case where the electric compressor adopts a sensorless method without using a position detection sensor. The actual angle θ of the motor rotor m Angle with estimation ) may have errors. Assuming θ m and The error between is δ, then the periodic load change T expressed by formula 1 is L It can be expressed as the following formula 14.

[0130] [Formula 14]

[0131]

[0132] Equation 14 can be re-expressed as the following equation 15.

[0133] [Formula 15]

[0134]

[0135] Equation 15 means that in the sensorless control method, when there is an estimated position error, the periodic load variation can be expressed as and Therefore, when using sensorless control, if the cosθ m and sinθ m Respectively changed to and If used, a controller can be configured that compensates for periodic load variations independently of the influence of sensorless angle estimation errors. In this case, too, since the value of the phase delay γ is always limited to range, so the speed ripple compensator has stable control characteristics.

Claims

1. A motor load variation compensation device, characterized in that: include: An angle pulsation analyzer that analyzes the characteristics of the pulsation of the rotor angle based on the detected value of the rotor angle of the motor; as well as A speed pulsation compensator generates a speed pulsation compensation value for reducing the pulsation of the rotor speed based on the characteristics of the pulsation of the rotor angle analyzed by the angle pulsation analyzer.

2. The motor load variation compensation device according to claim 1, characterized in that: The angle pulsation analyzer calculates the amplitudes of the cosine function and the sine function of the pulsation constituting the rotor angle.

3. The motor load variation compensation device according to claim 2, characterized in that: The angle ripple analyzer will be through the formula θ ripple =θ m -θ * m (θ ripple : Angle pulsation value, θ m : The detected value of the rotor angle, θ * m :Through the speed command value (ω * m The angle command value obtained by integrating the angle command value) is multiplied by ω * m cosθ m (ω * m : speed command value) and ω * m sinθ m and pass each multiplication result through a low-pass filter to find the amplitude of the cosine and sine functions of the pulsation constituting the rotor angle.

4. The motor load variation compensation device according to claim 2, characterized in that: The amplitude of the cosine function (G) and the amplitude of the sine function (H) constituting the pulsation of the rotor angle are respectively expressed as follows: Mode as well as Mode (A, B: the amplitudes of the cosine component and sine component of the load torque, respectively; C, D: the amplitudes of the cosine component and sine component of the motor output torque, respectively; k, γ: the magnitude and phase changes that occur when the signal passes through the first-order system corresponding to the rotating system, respectively; γ is a value in the range of [0, π / 2]).

5. The motor load variation compensation device according to any one of claims 2 to 4, characterized in that: The speed pulsation compensator applies gains to the amplitudes of the cosine function and the sine function of the pulsation constituting the rotor angle, respectively, and integrates the sum of the amplitudes of the cosine function and the sine function of the pulsation constituting the rotor angle to which the gains are applied, so as to generate a current command compensation value for reducing the pulsation of the rotor speed.

6. The motor load variation compensation device according to claim 5, characterized in that: The speed pulsation compensator adds a value obtained by applying a first gain to the amplitude of the cosine function of the pulsation constituting the rotor angle and a value obtained by applying a second gain to the sine function of the pulsation constituting the rotor angle and integrates the added value to determine the amplitude of the cosine component of the output torque of the motor by the current command compensation value. The value of the third gain applied to the amplitude of the sinusoidal function of the pulsation constituting the rotor angle and the value of the fourth gain applied to the sinusoidal function of the pulsation constituting the rotor angle are added and the added value is integrated to determine the amplitude of the sinusoidal component of the output torque of the motor through the current command compensation value.

7. The motor load variation compensation device according to claim 6, characterized in that: The signs of the first gain, the third gain, and the fourth gain are positive, and the sign of the second gain is negative.

Images