Apparatus for controlling motor and method for controlling inverter

Abstract

An apparatus for controlling a motor, according to one embodiment of the present invention, is an apparatus for controlling a motor driven by three-phase alternating current power, the apparatus comprising: an inverter for converting direct current power into the three-phase alternating current power by means of the switching operation of a plurality of switching elements, and supplying the converted three-phase alternating current power to the motor; and a control unit which generates three-phase PWM signals for controlling the inverter, and which controls that two or more of the three-phase PWM signals are shifted such that the PWM signals of the respective phases constituting the three-phase PWM signals are asymmetrical to each other.

Description

Motor control device and inverter control method

[0001] The present invention relates to a device for controlling a motor or a device and method for controlling an inverter used therein, and more specifically, to a device and method capable of suppressing the occurrence of harmonics and improving the precision of feedback control by using a shift of a PWM signal.

[0002] A three-phase AC motor is driven by three-phase AC power supplied by an inverter that converts direct current from a power source (such as a battery) into alternating current. Depending on the embodiment, if the power source is an AC resource, a converter that converts the AC power from the power source into direct current may be placed before the inverter.

[0003] The inverter includes a plurality of switching elements whose switching operation is controlled by pulse width modulation (PWM), and three-phase AC power (current) is generated by the switching operation (on / off) of these switching elements.

[0004] Typically, PWM signals are generated as a signal system for three-phase (U, V, W) control, all of which have the same frequency. Therefore, when these signals are used continuously, they exhibit overlapping behavior, which generates harmonics.

[0005] Harmonics cause electromagnetic interference (EMI), which can easily generate noise and, above all, can have negative effects such as interference with other nearby electronic components and electronic devices.

[0006] Methods for suppressing harmonics generated by electromagnetic shielding devices, shield cans, filters, etc. have been disclosed, but these are not fundamental methods because they only reduce the influence of harmonics already generated on other adjacent electronic components, and are often undesirable due to the characteristics of application devices (EVs, etc.).

[0007] The present invention was created to solve the above-described problems in the above background, and the purpose of the present invention is to provide a motor control device that can fundamentally eliminate the cause of harmonic generation by generating a PWM signal by differentially applying a shift range according to the signal, and also improve the precision of feedback control.

[0008] Other objects and advantages of the present invention can be understood through the following description and will be more clearly understood through the embodiments of the present invention. Furthermore, the objects and advantages of the present invention can be realized through the configurations and combinations of configurations set forth in the claims.

[0009] In order to achieve the above object, a motor control device according to one embodiment of the present invention is a device for controlling a motor driven by a three-phase AC power source, the device including: an inverter for converting direct current power into three-phase AC power by a switching operation of a plurality of switching elements and supplying the converted three-phase AC power source to the motor; and a control unit for generating a three-phase PWM signal for controlling the inverter. In this case, the control unit of the present invention is configured to control two or more signals among the three-phase PWM signals to be shifted so that the PWM signals of each phase constituting the three-phase PWM signal are asymmetrical to each other.

[0010] Specifically, the control unit of the present invention can control the shift range of the first signal, which is one of the two or more signals to be shifted, and the shift range of the second signal, which is another of the two or more signals to be shifted, to be different from each other.

[0011] In addition, the control unit of the present invention can control the shift range of one of the first and second signals to be smaller than the shift range of the other.

[0012] Furthermore, the control unit of the present invention controls two or more of the three-phase PWM signals to shift, and can control the shift within a certain range based on a reference frequency, and it is preferable that the shifting direction be applied differently over time.

[0013] According to an embodiment, the motor control device of the present invention may further include a detection unit that detects the output current supplied to the motor. In this case, the control unit of the present invention identifies signals of each phase using the detected output current and the signal system of the space vector sector, and controls two or more signals to shift to different ranges based on the identified signals of each phase.

[0014] According to another aspect of the present invention, a method for controlling an inverter converting direct current power into three-phase alternating current power by a switching operation of a switching element and supplying the converted three-phase alternating current power to a motor is provided, the method comprising: a signal generation step of generating a three-phase PWM signal for switching control of the switching element, wherein two or more signals among the three-phase PWM signals are shifted so that the PWM signals of each phase constituting the three-phase PWM signal are asymmetrical to each other; an output step of outputting the three-phase PWM signal to the inverter; a characteristic value input step of receiving the detected output current from a detection unit that detects the output current supplied to the motor; and a control step of identifying signals of each phase using a signal system of the output current and a space vector domain, and controlling the two or more signals to be shifted to different ranges based on the identified signals of each phase.

[0015] According to one embodiment of the present invention, each signal constituting a PWM signal is shifted to be asymmetrical to each other, and further, each signal is shifted with a differential size, so that the generation of harmonics due to overlapping of the same frequency can be effectively prevented.

[0016] According to one embodiment of the present invention, by controlling the directionality of the shift to be randomly or irregularly variable, the possibility of signals overlapping can be significantly reduced, thereby further increasing the reliability of output current detection as well as feedback control using the same.

[0017] In one embodiment of the present invention, in feedback control using the detected output current, each signal is effectively identified, and shift processing having a differential size is cyclically applied based on the identified signal, so that not only can the generation of harmonics be suppressed in the entire series of processes for controlling the motor, but also the precision of the feedback control can be effectively improved.

[0018] The following drawings attached to this specification illustrate preferred embodiments of the present invention, and together with the detailed description of the invention described below, serve to more effectively understand the technical idea of ​​the present invention, and therefore the present invention should not be interpreted as being limited to the matters described in these drawings.

[0019] Figure 1 is a block diagram showing the configuration of a motor control device according to a preferred embodiment of the present invention.

[0020] Fig. 2 is a block diagram showing the detailed configuration of the motor control device illustrated in Fig. 1.

[0021] FIG. 3 is a drawing explaining a frequency shift according to one embodiment of the present invention;

[0022] Figure 4 is a drawing explaining the sector configuration of a space vector.

[0023] FIG. 5 is a diagram explaining a frequency shift according to an embodiment of the present invention using characteristic values ​​of output current, etc.

[0024] Figure 6 is a flowchart explaining the processing process of a control method according to a preferred embodiment of the present invention.

[0025] Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the attached drawings. Prior to this, it should be noted that the terms and words used in this specification and claims should not be construed as limited to their conventional or dictionary meanings. Based on the principle that the inventor can appropriately define the concept of a term to best explain his or her invention, they should be interpreted in a way that conforms to the technical spirit of the present invention.

[0026] Therefore, the embodiments described in this specification and the configurations illustrated in the drawings are only the most preferred embodiments of the present invention and do not represent all of the technical ideas of the present invention. Therefore, it should be understood that there may be various equivalents and modified examples that can replace them at the time of filing this application.

[0027]

[0028] FIG. 1 is a block diagram showing the configuration of a motor control device (100) according to a preferred embodiment of the present invention, FIG. 2 is a block diagram showing the detailed configuration of the motor control device (100) shown in FIG. 1, and FIG. 6 is a flowchart explaining the processing process of an inverter control method according to a preferred embodiment of the present invention.

[0029] As illustrated in FIG. 1, a motor control device (100) according to one embodiment of the present invention may be configured to include an inverter (110), a control unit (120), and a detection unit (130).

[0030] Before going into a detailed description of the present invention, it should be understood that each component of the motor control device (100) of the present invention illustrated in FIG. 1 is a logically distinct component rather than a physically distinct component.

[0031] That is, since each component corresponds to a logical component for realizing the technical idea of ​​the present invention, even if each component is configured integrated or separated, if the function performed by the logical component of the present invention can be realized, it should be interpreted as being within the scope of the present invention, and of course, if it is a component that performs the same or similar function, it should be interpreted as being within the scope of the present invention regardless of whether or not there is consistency in the name.

[0032] The control method of the present invention is implemented as a set or algorithm of processing related to data processing, handling, operation, etc., and therefore, it can be implemented in the form of software that is driven by a control unit (120) implemented as a processor that can be composed of an MCU, memory, electronic chip, etc., or is installed and driven by this processor, etc.

[0033] A three-phase AC motor (hereinafter referred to as a “motor”) driven by a three-phase AC power source is a type of AC motor that is driven by a method in which a rotor rotates relative to a stator that forms a rotating magnetic field (RMF), and can stably produce high output and torque with a simple structure, so it is widely used in various electric and electronic applications, including electric vehicles (EVs).

[0034] The inverter (110) of the present invention is configured to convert direct current power provided from a power supply unit (50) into three-phase alternating current power and output the converted three-phase alternating current power to a motor (M).

[0035] As illustrated in FIG. 2, the inverter (110) is provided with a plurality of switching elements (S) inside, and converts the direct current power of the power supply unit (50) into three-phase (U, V, W) AC power by the switching operation (ON / OFF) of these multiple switching elements (S) and the circuit connection of the inverter (110), and supplies the converted three-phase AC power to the motor (M).

[0036] The switching operation of a plurality of switching elements (S) is controlled by a pulse width modulation signal ('PWM signal') generated and output by the control unit (120) (processor) of the present invention. This PWM signal used to control the switching elements has a pulse form in which high and low are repeated at a predetermined cycle, and the duty cycle or duty ratio, which means the ratio of the high section of the PWM signal, is controlled, thereby adjusting the amount of power provided to the motor.

[0037] The high and low sections of the PWM signal correspond to sections in which the switching element (S) is turned on / off by the PWM signal. The control signal according to the pulse width modulation method can be configured to be converted into a gate drive signal and input to the gate of each switching element (S) in the inverter (110).

[0038] In the case of conventional technology, PWM signals that are generated as a signal system for three-phase (U, V, W) control and whose duty ratio is time-variant are all of the same frequency (f a , is configured to have a (see Fig. 3(a)).

[0039] In this case, when each of the three-phase PWM signals has the same frequency, the possibility of errors occurring in output current detection for feedback control is low, but since multiple signals have the same frequency, the possibility of harmonics occurring due to signal overlap increases.

[0040] In order to solve this problem, when the driving of the motor (M) is started (S600, see FIG. 6), the control unit (120) of the present invention generates a three-phase PWM signal for controlling a plurality of switching elements (S) provided in the inverter (110) (S610) and outputs it to the inverter (110) (S620), and controls two or more signals among the three-phase PWM signals to shift so that the PWM signals of each phase constituting the three-phase PWM signal are asymmetrical to each other (S610).

[0041] As illustrated in FIG. 3(b), the control unit (120) of the present invention can control the frequency (f1, f2,..., see FIG. 3(b)) of the PWM signal to change over time by controlling the shifting time to be advanced or delayed, that is, by controlling the PWM signal to be shifted to the left or right based on the signal modification illustrated in FIG. 3.

[0042] In the case of the embodiment of the present invention as described above, since the three-phase PWM signals have different frequencies, the generation of harmonics due to overlapping signals of the same frequency, which occurs in the prior art, can be effectively prevented.

[0043] In order to further minimize the possibility of PWM signal overlap, it is preferable that the control unit (120) of the present invention be configured to apply the shift direction of the PWM signal differently over time. In this case, it is preferable that the shift direction be configured to change arbitrarily or irregularly through the application of an algorithm or the like.

[0044] If the frequencies of the three-phase PWM signals are not matched, errors may occur in the generation of the three-phase current (U-phase current, V-phase current, W-phase commutation). Therefore, it is desirable that the shift range be limited to a certain range based on the frequency for matching (reference frequency).

[0045] For example, as illustrated in Fig. 3(b), it is preferable that the phase shift (ps) be configured to be a random value in the range of 2 to 5% with respect to the center (horizontal direction) of the PWM signal having the reference frequency.

[0046] According to an embodiment, the control unit (120) of the present invention is preferably configured to shift at least two signals among the three-phase PWM signals so that the frequencies of at least two signals among the three-phase PWM signals vary within a certain range based on a reference frequency, and to apply the shifting direction differently over time.

[0047] In addition, when the control unit (120) of the present invention controls the three-phase PWM signal to shift as described above, it can control the shift range (hereinafter referred to as the 'first range') of one of the two or more signals to be shifted (hereinafter referred to as the 'first signal') to be different from the shift range (hereinafter referred to as the 'second range') of the other of the two or more signals to be shifted (hereinafter referred to as the 'second signal').

[0048] Preferably, the control unit (120) of the present invention can control one of the first range of the first signal and the second range of the second signal to be smaller than the other.

[0049] According to an embodiment, the first range and the second range can be controlled to vary over time, in which case the first range and the second range can be controlled to vary over time while maintaining a state in which the first range (second range) is smaller than the second range (first range).

[0050] By applying the shifted range differentially in this way and configuring the ranges to have different sizes, the possibility of signal overlap can be more effectively reduced, and the efficiency of distinguishing or identifying each signal can be increased in the process of detecting output current for feedback control.

[0051] The embodiment of the present invention described above corresponds to an embodiment of shifting two signals among three-phase PWM signals. However, since the technical idea of ​​the present invention is to prevent harmonics from being generated due to signal overlapping, it goes without saying that it can be configured to shift all three-phase PWM signals in order to control the frequencies of each of the three-phase PWM signals to be different from each other.

[0052] Control of the motor (M) can be performed based on a control signal input from an external source (such as a user input signal, torque command, command signal input from a linkage device or module, etc.).

[0053] The control unit (120) of the present invention compares the current state of the motor (M) with an external control signal, calculates the difference between them, and generates a PWM signal (S610) to offset the difference using PI control or PID control, and outputs the signal to the inverter (110) (S620). This process can of course be performed cyclically to ensure continuous feedback control.

[0054] For such feedback control, a device or system for controlling a motor may be equipped with a detection unit that detects the driving current of each phase supplied to the motor. Depending on the embodiment, a measuring device such as a Hall sensor that detects the rotational speed, position, angle, etc. of the motor may also be equipped.

[0055] For feedback control, each phase's output current supplied to the motor can be individually detected, and the output currents of two phases can also be detected using three-phase balance. The detection means for detecting the output current can be located between the inverter and the motor, and a current transfer (CT) or shunt resistor can be used for current detection.

[0056] When shunt resistors are used, three shunt resistors may be placed between the inverter and the motor, or one end of the shunt resistor may be connected to the lower arm switching element of the inverter.

[0057] In the case of this 3-shunt method, since additional voltage amplifiers, A / D ports, etc. must be provided, the circuit configuration becomes complex and it may be inefficient in terms of manufacturing cost and size of the motor control device.

[0058] In contrast, in the case of the 1-shunt method, the phase current supplied to the motor can be detected in a sensorless manner using a single shunt resistor element (R), so it can have advantages such as low manufacturing cost and compact implementation of the motor control device (100).

[0059] The motor control device (100) of the present invention may include a sensing unit (130) that detects the characteristic value of the output current supplied to the motor (M) for feedback control, and in this case, the control unit (120) of the present invention controls the switching element (S) using a parameter including the characteristic value of the output current input from the sensing unit (130) and a space vector-based PWM (SVPWM).

[0060] In the case of the 1-shunt method, the phase current detected from the shunt resistor (R) in the space vector-based control cycle is converted into a signal through an ADC, and the three-phase current can be estimated using the corresponding current sector among the vector and space vector sectors (see Fig. 4) corresponding to the converted value.

[0061] The control unit (120) of the present invention can identify (distinguish) the signals of each phase (U, V, W) by using the signal system of the corresponding sector among the 6 sectors of the space vector shown in FIG. 4 (S640) when the output current detected at a specific detection time is input from the detection unit (130) by applying this method.

[0062] Once the signals of each phase are identified in this manner, the control unit (120) of the present invention controls two or more signals to shift to different ranges based on the identified signals of each phase (S650). Various methods described above can be applied as specific shifting methods.

[0063] As a specific example, as illustrated in Fig. 5(a), when the current sector corresponds to Sector 0, the V-phase and W-phase signals can be controlled to shift based on the first detected U-phase signal.

[0064] From a corresponding viewpoint, if the current sector corresponds to Sector 4, the U-phase signal and the V-phase signal can be controlled to shift based on the W-phase signal as illustrated in Fig. 5(b).

[0065] The processing of the present invention, which distinguishes signals of each phase using output current and space vector sectors and applies differential shift control based on the distinguished signals, is performed cyclically according to feedback control. Through this cyclic control, it is possible to induce the mutual frequency asymmetry of each signal constituting the PWM signal to be continuously maintained.

[0066] In addition, according to the embodiment of the present invention, the signals of each phase can be continuously induced so as not to overlap with each other during the detection time for detecting the output current, thereby further improving the reliability of the output current detection and the driving precision of the feedback control using the same.

[0067] It goes without saying that the processing for the control method of the present invention described above can be applied cyclically if a preset termination condition such as a forced termination, system down, or occurrence of an emergency event is not met (S660).

[0068]

[0069] Although the present invention has been described above with reference to limited embodiments and drawings, the present invention is not limited thereto, and it is obvious that various modifications and variations are possible within the scope of the technical idea of ​​the present invention and the equivalent scope of the patent claims to be described below by a person having ordinary skill in the art to which the present invention pertains.

[0070] In the description of the present invention described above, modifiers such as first and second are merely instrumental conceptual terms used to relatively distinguish components from each other, and should be interpreted as not being terms used to indicate a specific order, priority, etc.

[0071] The drawings attached for the purpose of explaining the present invention and illustrating embodiments thereof may be illustrated in a somewhat exaggerated form to emphasize or highlight the technical contents of the present invention. However, it should be interpreted that it is obvious that various modified application examples may be possible at the level of a person skilled in the art in consideration of the contents described above and matters illustrated in the drawings.

[0072] The control method of the present invention described above can be implemented as computer-readable code on a computer-readable recording medium. The computer-readable recording medium includes all types of recording devices (CD-ROMs, RAMs, ROMs, floppy disks, magnetic disks, hard disks, magneto-optical disks, etc.) that store data that can be read by a computer, and also includes servers for wired and wireless Internet transmission.

Claims

1. A device that controls a motor driven by a 3-phase AC power source, An inverter that converts direct current power into three-phase alternating current power by switching operations of multiple switching elements and supplies the converted three-phase alternating current power to the motor; and It includes a control unit that generates a three-phase PWM signal for controlling the above inverter, The above control unit, A motor control device characterized in that two or more signals among the three-phase PWM signals are shifted so that the PWM signals of each phase constituting the three-phase PWM signal are asymmetrical to each other.

2. In the first paragraph, the control unit, A motor control device characterized in that the shift range of a first signal, which is one of the two or more signals to be shifted, and the shift range of a second signal, which is another of the two or more signals to be shifted, are controlled to be different from each other.

3. In the second paragraph, the control unit, A motor control device characterized in that the shift range of one of the first and second signals is controlled to be smaller than the shift range of the other.

4. In paragraph 1, the control unit, A motor control device characterized in that it controls two or more of the three-phase PWM signals to shift, and controls them to shift within a certain range based on a reference frequency.

5. In paragraph 4, the control unit, A motor control device characterized by applying a shifting direction differently over time.

6. In paragraph 1, It further includes a detection unit that detects the output current supplied to the above motor, The above control unit, A motor control device characterized in that it identifies signals of each phase using the signal system of the detected output current and space vector sector, and controls two or more signals to shift to different ranges based on the signals of each identified phase.

7. A method for controlling an inverter that converts direct current power into three-phase alternating current power by the switching operation of a switching element and supplies the converted three-phase alternating current power to a motor. A signal generation step for generating a three-phase PWM signal for switching control of the above switching element, wherein two or more signals among the three-phase PWM signals are shifted so that the PWM signals of each phase constituting the three-phase PWM signal are asymmetrical to each other; An output stage for outputting the above three-phase PWM signal to the inverter; A characteristic value input step for receiving the detected output current from a detection unit that detects the output current supplied to the motor; and An inverter control method characterized by including a control step of identifying signals of each phase using the signal system of the output current and space vector domain, and controlling two or more signals to shift to different ranges based on the identified signals of each phase.

8. A computer-readable recording medium having recorded thereon a program for performing the method described in Article 7.

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