KR20240040205A - Method for selecting pulse mode conversion criteria of synchronous pulse width modulation relative to switching loss - Google Patents

Abstract

The present invention relates to a method for selecting a synchronous pwm pulse mode switching reference considering switching loss. According to the present invention, a method for selecting a synchronous pwm pulse mode switching reference considering a switching loss comprises the steps of: (a) manufacturing a loss analysis table by using a voltage modulation index and current information; (b) determining an initial pulse multiple and determining a pulse multiple downshift according to a result of checking the switching loss; and (c) checking the switching loss and re-determining the pulse multiple.

Description

Method for selecting synchronous PWM pulse mode conversion criteria considering switching loss {METHOD FOR SELECTING PULSE MODE CONVERSION CRITERIA OF SYNCHRONOUS PULSE WIDTH MODULATION RELATIVE TO SWITCHING LOSS}

The present invention relates to a method for selecting a synchronous PWM pulse mode switching standard.

According to the prior art, the pulse conversion standard for harmonic loss reduction analyzes the harmonic distortion rate according to the pulse multiple and pulse pattern, and the pulse multiple and pulse pattern with small harmonic loss are preferentially used for control because the harmonic distortion is small.

In this case, the larger the pulse multiple, the smaller the harmonic distortion, but as the number of switching times during one cycle of the inverter's output voltage increases, switching loss increases.

The present invention was proposed to solve the above-mentioned problem, and sets an efficient standard for switching the number of pulses in a situation where a synchronous PWM is driven in consideration of switching loss, compared to the pulse switching standard method for reducing harmonic loss according to the prior art. The purpose is to provide a method for selecting a synchronous PWM pulse mode switching standard that can reduce energy consumption by minimizing the switching loss of the inverter during operation and reduce the stress of the inverter, thereby increasing the replacement period of power semiconductors.

The synchronous PWM pulse mode switching system considering switching loss according to the present invention includes an input unit that receives voltage modulation index and current magnitude information, and a program that generates a loss analysis table for pulse multiple switching using the voltage modulation index and current magnitude information. It includes a processor that executes the stored memo and program, and the processor performs synchronous PWM pulse mode switching considering switching loss using a loss analysis table.

The processor normalizes the voltage modulation index to create the loss analysis table in preset units, and divides the rated torque into preset sections to create the loss analysis table for the current corresponding to the torque.

The processor performs control by selecting a preset initial pulse multiplier from among the set of pulse multipliers, considering the harmonic distortion rate in a region where the back electromotive force and output voltage are smaller than the preset size.

The preset initial pulse multiplier is the maximum pulse multiplier that can be selected among the pulse multiplier set.

When the switching loss reaches a preset maximum switching loss during control using a constant pulse multiplier, the processor switches to a pulse multiplier one level lower than the constant pulse multiplier among the pulse multiplier sets.

When the constant pulse multiple is the maximum pulse multiple among the pulse multiple convergence, the maximum switching loss is the maximum switching loss in the asynchronous PWM control section.

During control using a constant pulse multiplier, if the processor determines that the maximum switching loss will not be reached even if switching to a pulse multiplier one level higher than the constant pulse multiplier, it switches to a pulse multiplier one level higher than the constant pulse multiplier among the pulse multiplier sets. .

When the voltage modulation index or the size of the current decreases and the switching loss decreases, the processor checks whether the maximum switching loss will not be reached even if the pulse multiplier is switched to one level higher than the constant pulse multiplier.

The present invention relates to a method for selecting a synchronous PWM pulse mode switching standard considering switching loss.

The method of selecting a synchronous PWM pulse mode switching standard considering switching loss according to the present invention includes the steps of (a) creating a loss analysis table using voltage modulation index and current information, (b) determining the initial pulse multiple, and switching loss It includes the step of determining the pulse multiplier downshift according to the results of checking and (c) re-determining the pulse multiplier by checking the switching loss.

In step (a), the voltage modulation index is normalized to produce the loss analysis table in preset units, and the rated torque is divided into preset sections to produce the loss analysis table for the current corresponding to the torque.

In step (b), the maximum selectable pulse multiplier from the set of pulse multipliers is selected by considering the harmonic distortion rate in a region where the back electromotive force and output voltage are smaller than the preset size.

In step (b), when the switching loss reaches a preset maximum switching loss during control using the maximum pulse multiplier, the pulse multiplier is switched to a pulse multiplier one level lower than the constant pulse multiplier among the pulse multiplier sets.

In step (c), switching loss is checked during control with the downshifted pulse multiplier, and when the maximum switching loss is reached, the pulse multiplier is switched to a pulse multiplier one level lower than the downshifted pulse multiplier.

In step (c), while controlling the downshifted pulse multiplier, the voltage modulation index or the magnitude of the current decreases, thereby reducing the switching loss, so that the maximum switching loss is not reached even if the pulse multiplier is switched to a pulse multiplier one level higher than the downshifted pulse multiplier. If it is confirmed that this will not be the case, control is performed to reduce the size of the current and torque ripple by switching to a pulse multiplier one step higher than the downshifted pulse multiplier.

According to the present invention, the switching loss of the inverter is minimized when operating a railway vehicle, thereby saving energy consumption, reducing the stress of the inverter, and increasing the replacement period of power semiconductors.

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

Figure 1a shows a propulsion system for a railway vehicle using an induction motor according to the prior art.
Figure 1b shows a propulsion system for a railway vehicle using a permanent magnet synchronous motor according to the prior art.
Figure 2 shows the switching frequency relationship according to fundamental frequency and pulse number.
Figure 3 shows a comparison of Weighted Total Harmonic Distortion Factor (WTHD0) according to pulse multiplier and control method.
Figure 4 shows a pulse pattern selection process according to the prior art.
Figure 5 shows the space voltage vector distribution when P = 9 and N = 9 in Mode 1 (SVPWM, Space Vector PWM).
Figure 6 shows the spatial voltage vector distribution when P = 7 and N = 9 in Mode 2 (DPWM, Discontinuous PWM).
Figure 7 shows the spatial voltage vector distribution when P = 5 and N = 6 in Mode 3 (a mode that reduces the number of switching through vector sequence modification).
Figure 8 shows a synchronous PWM pulse mode switching system considering switching loss according to an embodiment of the present invention.
Figure 9 shows a method for selecting a synchronous PWM pulse mode switching standard considering switching loss according to an embodiment of the present invention.
Figure 10 shows a retrograde section loss analysis 3D table (21, 15, 9, total pulse multiple) according to an embodiment of the present invention.
Figure 11 shows a regenerative section loss analysis 3D table (21, 15, 9, total pulse multiple) according to an embodiment of the present invention.
Figure 12 shows a pulse multiplier selection process using a loss analysis table according to an embodiment of the present invention.
Figure 13 shows a simulation waveform to which a pulse multiplier conversion standard considering switching loss is applied in the retrograde/regenerative section according to an embodiment of the present invention.
Figure 14 shows a simulation waveform to which a pulse multiple conversion criterion considering switching loss is applied in the retrograde section according to an embodiment of the present invention.
Figure 15 shows a simulation waveform to which a pulse multiplier conversion standard considering switching loss is applied in the regenerative section according to an embodiment of the present invention.
Figure 16 is a block diagram showing a computer system for implementing a method according to an embodiment of the present invention.

The above-mentioned object and other objects, advantages and features of the present invention, and methods for achieving them will become clear by referring to the embodiments described in detail below along with the accompanying drawings.

However, the present invention is not limited to the embodiments disclosed below and can be implemented in various different forms. The following embodiments are merely intended to convey to those skilled in the art the purpose of the invention, It is only provided to easily inform the configuration and effect, and the scope of rights of the present invention is defined by the description of the claims.

Meanwhile, the terms used in this specification are for describing embodiments and are not intended to limit the present invention. As used herein, singular forms also include plural forms, unless specifically stated otherwise in the context. As used in the specification, “comprises” and/or “comprising” means that the mentioned element, step, operation and/or element precludes the presence of one or more other elements, steps, operations and/or elements. Or it is not excluded that it is added.

A traction motor is an electric motor installed to traction (drive) a vehicle by receiving voltage supplied from the main generator or catenary. Depending on the type of traction motor, the propulsion system of a railway vehicle is largely divided into an induction motor and a permanent magnet synchronous motor (IPMSM).

Figure 1a shows a propulsion system for a railway vehicle using an induction motor according to the prior art, and Figure 1b shows a propulsion system for a railway vehicle using a permanent magnet synchronous motor according to the prior art.

An induction motor operates on the principle that when alternating current electricity generates a rotating magnetic field and an induced current is generated in the rotor of a conductor, the rotor receives electromagnetic force and rotates in response to the rotating magnetic field. Since the rotating magnetic field of an induction motor is formed according to the magnetic flux current output by the propulsion inverter, there is no need to sense the rotor position, so it is possible to drive multiple traction motors with a single propulsion inverter.

On the other hand, a permanent magnet synchronous motor must directly rotate the rotor shaft, so the position of each traction motor must be sensed and individual control must be performed.

Figure 2 shows the switching frequency relationship according to fundamental frequency and pulse number.

Several algorithms are required to drive a traction motor up to high-speed range using a propulsion inverter, and among them, the synchronous PWM method is essential for smooth torque control. The synchronous PWM method is a method of determining the number of propulsion inverter switching pulses according to the speed of the traction motor. If you want to drive a traction motor in the entire speed range with asynchronous PWM, you basically need a very high switching frequency or a high-performance/expensive controller.

Figure 3 shows a comparison of Weighted Total Harmonic Distortion Factor (WTHD0) according to pulse multiplier and control method.

If the switching frequency is selected using a high pulse multiplier in the synchronous PWM control method, the number of switching times during one cycle of the inverter's output voltage fundamental wave increases as much as the pulse multiplier. Therefore, compared to when the switching frequency is selected using a small pulse multiplier, the size of the current ripple is small, and the harmonic distortion (THD) is small.

In addition, when controlling using a constant pulse multiplier, the number of switching times is reduced when using a discontinuous modulation technique (DPWM, Discontinuous PWM) compared to when using a general space vector modulation technique (SVPWM, Space Vector PWM). Switching loss is reduced, but the size of the current ripple increases, resulting in a higher harmonic distortion rate for the discontinuous modulation technique than for the space vector modulation technique.

Therefore, in terms of reducing harmonic loss, control is performed with a pulse multiplier with a small harmonic distortion rate, and when the switching frequency increases and exceeds the switching frequency limit, the pulse multiplier is sequentially switched in the order of the smallest harmonic distortion rate throughout the entire operation section. Control is possible to keep the harmonic distortion rate small.

Referring to FIG. 3, WTHD0 is the Weighted Total Harmonic Distortion Factor normalized to the DC-link voltage, which can represent the absolute size of the harmonics and can be derived through [Equation 1] and [Equation 2] below.

As shown in FIG. 3, in a section where the voltage modulation index (MI) is small, WTHD0 in the case of discontinuous modulation control using a multiple of 27 pulses is larger than WTHD0 in the case of space vector modulation control using a multiple of 21 pulses. This means that in the case of discontinuous modulation control using a multiple of 27 pulses, the number of switching times during one cycle of the actual inverter output voltage is reduced to 19 times instead of 27, and the number of switching times is 21 in the case of space vector modulation control using a multiple of 21 pulses. This is because the number of switching times becomes smaller than the number of times, so the size of the output ripple increases and WHTD0 becomes relatively large.

However, in the section where the voltage modulation index is large, WTHD0 in the case of discontinuous modulation control through a multiple of 27 pulses is smaller than WHTD0 in the case of space vector modulation control through a multiple of 21 pulses. Therefore, pulse pattern selection can be performed by considering voltage modulation index (MI), pulse multiplier limit due to switching frequency limit, and WTHD0, as shown in FIG. 4.

Referring to FIG. 4, the pulse multiplier selection limit can be expressed using the switching frequency limit and the fundamental wave frequency of the inverter output voltage (i.e., the armature frequency of the electric motor), as shown in [Equation 3] below.

The switching frequency limit is determined by the volume limitations of the thermal design of the propulsion system. This is a limited frequency to secure the minimum time required for control operations.

The definitions of the voltage modulation index (MI) shown in FIG. 3, the pulse pattern in the WTHD0 graph, and the pulse pattern in FIG. 4 are as shown in [Equation 4] below.

In [Equation 4], P is the number of pulses of the voltage actually output during one cycle of the fundamental wave of the inverter output voltage (i.e., the number of switching times during one cycle of the fundamental wave), and N is the number of pulses output during one cycle of the fundamental wave when not clamped. It is the number of pulses. Mode indicates the control used in the selected pulse multiple, mode 1 refers to space vector modulation control, mode 2 refers to discontinuous modulation control, and mode 3 refers to reducing the number of switching by modifying the vector sequence. Examples of control methods for each mode using space vectors are shown in Figures 5 to 7.

Figure 5 shows the space voltage vector distribution when P = 9, N = 9 in Mode 1 (SVPWM, Space Vector PWM), and Figure 6 shows the distribution of space voltage vectors when P = 7, N = 9 in Mode 2 (DPWM, Discontinuous PWM). Figure 7 shows the spatial voltage vector distribution when P = 5 and N = 6 in Mode 3 (a mode that reduces the number of switching through vector sequence modification).

The subscript +/- indicates the clamping direction in the section. If +, it is clamped to the positive bus, and if -, it is clamped to the negative bus. Additionally, the subscript indicates the direction of the vector that appears at the starting point of the pulse pattern and means starting with a rising-vector or starting with a falling-vector.

The pulse switching standard for reducing harmonic loss described above is a method of analyzing the harmonic distortion rate according to the pulse multiplier and pulse pattern, and preferentially using the pulse multiplier and pulse pattern with small harmonic loss for control because the harmonic distortion is small. As described above, the larger the pulse multiple, the smaller the harmonic distortion, but as the number of switching times during one cycle of the inverter's output voltage increases, the switching loss increases.

Below, a method for selecting a synchronous PWM pulse mode switching standard considering switching loss according to an embodiment of the present invention will be described. The present invention is applicable to the field of controlling inverter systems that drive traction motors and to propulsion systems for all railway vehicles.

When selecting a pulse multiplier considering only switching loss, it is desirable to select a small pulse multiplier to reduce switching loss by reducing the number of switching times during one cycle of the inverter's output voltage. However, when performing control with a small pulse multiple selected, the harmonic distortion rate increases, and the magnitude of current and torque ripple also increases. Therefore, in low-speed areas where the back electromotive force is small and the output voltage is small, control is performed by selecting a large pulse multiple considering the harmonic distortion rate, and when the switching loss due to the selected pulse multiple reaches the maximum switching loss, a pulse smaller than the selected pulse multiple is used. It is desirable to perform control to reduce switching loss by switching to multiples, taking into account the increase in harmonic distortion rate.

According to an embodiment of the present invention, in order to switch pulse multiples when the maximum switching loss is reached, a loss analysis table (LUT, Look Up Table) is constructed for each pulse multiple used for control. Using the switch element used for control, loss analysis is performed according to the voltage modulation index (MI) and pulse multiple according to control, and a loss analysis table is created and used for control.

According to an embodiment of the present invention, the switch element used for control is the FMF750DC-66A product, which has a rated voltage of 3300V and a rated current of 750A and is used in traction motors and inverters of large-capacity industrial machines. In addition, it is a full SiC module composed of two SiC MOSFETs, and both switches are SiC elements.

According to an embodiment of the present invention, in order to perform pulse multiplier switching considering switching loss, a loss analysis table (LUT) is created using the FMF750DC-66A switch element, and the voltage modulation index (MI) is normalized to 0.3-1.1547. It progressed in 0.1 increments, and the current was divided into 7 sections by dividing the rated torque and proceeded at each current corresponding to the torque. The parameters of the interior permanent magnet synchronous motor (IPMSM) used in the loss analysis according to the embodiment of the present invention are shown in [Table 1] below.

specification value Motor Rate Voltage 612V Motor Rate Frequency 95 Hz Motor Rate Speed 1900 rpm Motor Rate Current 240A d-axis Inductance 1.833 mH q-axis Inductance 5.335 mH Stator Resistance 0.039Ω Pole 6 Pole

Figure 8 shows a synchronous PWM pulse mode switching system considering switching loss according to an embodiment of the present invention.

The synchronous PWM pulse mode switching system considering switching loss according to an embodiment of the present invention includes an input unit 810 that receives voltage modulation index and current magnitude information. It includes a memory 820 storing a program that generates a loss analysis table for pulse multiplier conversion using voltage modulation index and current magnitude information, and a processor 830 that executes the program, and the processor 830 generates a loss analysis table. It performs synchronous PWM pulse mode switching considering switching loss.

The processor 830 normalizes the voltage modulation index to create a loss analysis table in preset units, and divides the rated torque into preset sections to create a loss analysis table for the current corresponding to the torque.

The processor 830 performs control by selecting a preset initial pulse multiplier from among the set of pulse multipliers, considering the harmonic distortion rate in a region where the back electromotive force and output voltage are smaller than the preset size. At this time, the preset initial pulse multiplier is the maximum pulse multiplier that can be selected among the pulse multiplier set.

When the switching loss reaches a preset maximum switching loss during control using a constant pulse multiplier, the processor 830 switches to a pulse multiplier one level lower than the constant pulse multiplier among the pulse multiplier sets. When a constant pulse multiple is the maximum pulse multiple, the VSI is controlled using an asynchronous PWM control method in the low speed region, so the maximum switching loss is selected as the maximum switching loss in the asynchronous PWM control section.

During control using a constant pulse multiplier, if it is determined that the maximum switching loss will not be reached even if the processor 830 switches to a pulse multiplier one level higher than the constant pulse multiplier, it switches to a pulse multiplier one level higher than the constant pulse multiplier during the set of pulse multipliers. Switch. At this time, the processor 830 checks whether the maximum switching loss will not be reached even if switching to a pulse multiplier that is one step higher than the constant pulse multiplier when the voltage modulation index or the size of the current decreases and the switching loss decreases.

Figure 9 shows a method for selecting a synchronous PWM pulse mode switching standard considering switching loss according to an embodiment of the present invention.

The method for selecting a synchronous PWM pulse mode switching standard considering switching loss according to an embodiment of the present invention includes the steps of creating a loss analysis table using the voltage modulation index and current information (S910), determining the initial pulse multiple, and switching loss. It includes a step of determining a pulse multiplier downshift (S920) and a step of re-determining the pulse multiplier by checking switching loss (S930).

In step S910, the voltage modulation index is normalized to create a loss analysis table in preset units, and the rated torque is divided into preset sections to create a loss analysis table for the current corresponding to the torque.

In step S920, among the pulse multiplier sets (21, 15, and 9), the maximum pulse multiplier (21) that can be selected from the pulse multiplier set is selected by considering the harmonic distortion rate in a region where the back electromotive force and output voltage are smaller than the preset size.

In step S920, when the switching loss reaches the preset maximum switching loss during control using the maximum pulse multiplier, the pulse multiplier is switched (downshifted) to the pulse multiplier 15, which is one step lower than the constant pulse multiplier among the pulse multiplier sets.

In the low-speed region, the VSI is controlled using the asynchronous PWM control method, so the preset maximum switching loss to be compared during control using the maximum pulse multiple is the maximum switching loss in the asynchronous PWM control section.

In step S930, while controlling the 15-pulse multiple, the switching loss is checked, and when the maximum switching loss is reached, it is switched to a 9-pulse multiple. On the other hand, in step S930, during the 15-pulse multiple control, if it is confirmed that the switching loss is reduced due to a decrease in the voltage modulation index or the size of the current and the maximum switching loss is not reached even if switched to the 21-pulse multiple, the switching is switched to the 21-pulse multiple. Control is performed to reduce the size of current and torque ripple while accepting losses.

Figure 10 shows a retrograde section loss analysis 3D table (21, 15, 9, total pulse multiple) according to an embodiment of the present invention, and Figure 11 shows a regenerative section loss analysis 3D table (21, 15, 9, total pulse multiple), and Figure 12 shows the pulse multiple selection process using a loss analysis table according to an embodiment of the present invention.

As shown in Figure 10, loss analysis during reverse operation was conducted in the reverse operation section of the 21, 15, and 9 pulse multiplier electric motors used for control, and each table is shown combined. According to the pulse multiple conversion method using the loss analysis table, during control by selecting the 21 pulse multiple located in the upper left corner of the integrated loss analysis table in Figure 10, when the switching loss of the 21 pulse multiple reaches the maximum switching loss. By controlling the pulse multiple switching to a 15-pulse multiple located in the upper right corner rather than the 9 pulse multiple located in the lower left corner, it is possible to perform control so as not to exceed the maximum switching loss and not significantly increase the size of the current ripple. do.

Since the size of the current flowing through the switch and diode in the retrograde operation section and the regenerative operation section varies depending on the operation, loss analysis was performed separately in the retrograde operation section and the regenerative operation section, and the conditions for performing loss analysis in the regenerative operation section were: It is the same as the loss analysis conditions in the operation section.

In the same way that pulse switching was performed using a loss analysis table in the retrograde operation section, in the regenerative section, the loss analysis table was used to select the largest pulse multiple among the selectable pulse multiples by considering the current and MI. Control to minimize torque ripple while not exceeding maximum switching losses. When the size of the current or voltage increases and reaches the maximum switching loss at the switching frequency based on the pulse multiplier used for control, control is performed by switching the pulse multiplier to another pulse multiplier that does not exceed the maximum switching loss.

Using the above-described 3D loss analysis table, it is possible to predict the switching loss occurring in the switch depending on the current size, voltage size, and pulse multiple.

Figure 12 shows a sequence of pulse multiplier selection using a loss analysis table considering the magnitude of current and magnitude of voltage (MI) in actual inverter control. It is controlled by selecting the maximum selectable pulse multiplier, but if the switching loss exceeds the maximum switching loss, pulse multiplier switching is performed to another pulse multiplier. During control by selecting the 9 pulse multiple, the voltage modulation index (MI) or the size of the current decreases and the switching loss decreases. If it is determined that the maximum switching loss will not be exceeded even if the 15 pulse multiple is selected, the 15 pulse multiple is used. converted.

Figure 13 shows a simulation waveform to which a pulse multiplier conversion standard considering switching loss is applied in the retrograde/regenerative section according to an embodiment of the present invention.

An example of a simulation in which a permanent magnet synchronous motor (IPMSM, Interior Permanent Magnet Synchronous Motor) is controlled using the IPMSM with the parameters shown in Table 1 and the previously loss-analyzed LUT is shown. The current and voltage were changed by changing the torque command during the entire operation section in which the fundamental wave frequency of the inverter output voltage rose and fell.

First, in the low-speed region in the retrograde section, the VSI is controlled using an asynchronous PWM control method, and when entering the medium-speed region, the magnitude of the voltage increases, so a multiple of 21 pulses is selected to reduce switching loss. At this time, the maximum switching loss is selected as the maximum switching loss in the asynchronous PWM control section. As the asynchronous PWM control is converted to the 21 pulse multiple synchronous PWM control, the switching loss is reduced as shown in (D) of FIG. 13. If the maximum switching loss is reached due to an increase in voltage or current while performing synchronous PWM control with a 21-pulse multiple, switch to a 15-pulse multiple or 9-pulse multiple to reduce switching loss.

During synchronous PWM control with a multiple of 9 pulses within the retrograde section, if the size of the current decreases and it is determined that the maximum switching loss is not exceeded even during synchronous PWM control using a multiple of 15 pulses, then multiple of 15 pulses, and then 21. By switching to pulse multipliers, you sacrifice increased switching losses (as long as they do not exceed maximum switching losses) and reduce the magnitude of current ripple and torque ripple.

The operation in the retrograde section is enlarged as shown in Figure 14. Figure 14 shows a simulation waveform to which a pulse multiplier conversion criterion considering switching loss is applied in the retrograde section according to an embodiment of the present invention.

In the front part of the waveform, as the speed (A) of the motor increases, the back electromotive force increases and the size of the inverter output voltage increases, but as the output torque command decreases, the size of the inverter output current (E) also decreases. The controller considers both decreasing current and increasing voltage through the loss analysis table and maintains control at a 9-pulse multiple. If it is determined that the maximum switching loss does not exceed even if switched to a 15-pulse multiple, it switches to a 15-pulse multiple. Control is performed to reduce the size of current and torque ripple while accepting increasing switching losses (in the area where the maximum switching loss is not exceeded).

The conversion from 15 pulse multiple to 21 pulse multiple is performed in the same manner as described above. As the motor speed (A) continues to increase as it progresses to the latter part of the waveform, the size of the inverter output voltage also gradually increases. Additionally, because the torque command is increased, the magnitude of the current (E) also increases. Therefore, the controller maintains control at a multiple of 21 pulses through the loss analysis table, but switches to a multiple of 15 pulses when the magnitude of the current and voltage increases and the switching loss reaches the maximum switching loss.

Figure 15 shows a simulation waveform to which a pulse multiplier conversion standard considering switching loss is applied in the regenerative section according to an embodiment of the present invention.

In the regenerative section, pulse multiple conversion is performed by selecting an appropriate pulse multiplier using a loss analysis table in the same way as in the retrograde section. When entering the regenerative section at the front of the waveform, the speed (A) of the motor is rotating at 3000 [rpm], so the size of the inverter output voltage is large due to back electromotive force, but as the size of the current gradually increases from 0, it is a multiple of 21 pulses. Even if you select and control, the switching loss is small, so select a multiple of 21 pulses for control.

As the magnitude of the current gradually increases, if the switching loss of the control selecting the 21 pulse multiple exceeds the maximum switching loss, the pulse multiple conversion is performed to the 15 pulse multiple, and then to the 9 pulse multiple in the same manner.

As the motor decelerates as it progresses to the latter part of the waveform, the size of the inverter output voltage decreases. During control with a multiple of 9 pulses, if it is determined that the switching loss of the control with a multiple of 15 pulses selected does not exceed the maximum switching loss, , pulse multiple conversion is carried out with a pulse multiple of 15.

Figure 16 is a block diagram showing a computer system for implementing a method according to an embodiment of the present invention.

Referring to FIG. 16, the computer system 1300 includes a processor 1310, a memory 1330, an input interface device 1350, an output interface device 1360, and a storage device 1340 that communicate through a bus 1370. ) may include at least one of Computer system 1300 may also include a communication device 1320 coupled to a network. The processor 1310 may be a central processing unit (CPU) or a semiconductor device that executes instructions stored in the memory 1330 or the storage device 1340. Memory 1330 and storage device 1340 may include various types of volatile or non-volatile storage media. For example, memory may include read only memory (ROM) and random access memory (RAM). In embodiments of the present disclosure, the memory may be located inside or outside the processor, and the memory may be connected to the processor through various known means. Memory is various forms of volatile or non-volatile storage media, for example, memory may include read-only memory (ROM) or random access memory (RAM).

Accordingly, embodiments of the present invention may be implemented as a computer-implemented method or as a non-transitory computer-readable medium storing computer-executable instructions. In one embodiment, when executed by a processor, computer readable instructions may perform a method according to at least one aspect of the present disclosure.

The communication device 1320 can transmit or receive wired signals or wireless signals.

Additionally, the method according to an embodiment of the present invention may be implemented in the form of program instructions that can be executed through various computer means and recorded on a computer-readable medium.

The computer-readable medium may include program instructions, data files, data structures, etc., singly or in combination. Program instructions recorded on the computer-readable medium may be specially designed and configured for embodiments of the present invention, or may be known and usable by those skilled in the art of computer software. A computer-readable recording medium may include a hardware device configured to store and perform program instructions. For example, computer-readable recording media include magnetic media such as hard disks, floppy disks, and magnetic tapes, optical media such as CD-ROMs and DVDs, and floptical disks. It may be the same magneto-optical media, ROM, RAM, flash memory, etc. Program instructions may include not only machine language code such as that created by a compiler, but also high-level language code that can be executed by a computer through an interpreter, etc.

Although the embodiments of the present invention have been described in detail above, the scope of the present invention is not limited thereto, and various modifications and improvements made by those skilled in the art using the basic concept of the present invention defined in the following claims are also possible. It falls within the scope of rights.

Claims (14)

An input unit that receives voltage modulation index and current magnitude information;
a memory storing a program that generates a loss analysis table for pulse multiple conversion using the voltage modulation index and current magnitude information; and
Includes a processor that executes the program,
The processor performs synchronous PWM pulse mode switching considering switching loss using the loss analysis table.
Synchronous PWM pulse mode switching system considering switching losses.
According to paragraph 1,
The processor normalizes the voltage modulation index to produce the loss analysis table in preset units, and divides the rated torque into preset sections to produce the loss analysis table for the current corresponding to the torque.
Synchronous PWM pulse mode switching system considering switching losses.
According to paragraph 1,
The processor performs control by selecting a preset initial pulse multiplier from among the set of pulse multipliers, considering the harmonic distortion rate in a region where the back electromotive force and output voltage are smaller than the preset size.
Synchronous PWM pulse mode switching system considering switching losses.
According to paragraph 3,
The preset initial pulse multiplier is the maximum pulse multiplier that can be selected among the pulse multiplier set.
A synchronous PWM pulse mode switching system that considers switching losses, featuring:
According to paragraph 1,
During control using a constant pulse multiplier, if the switching loss reaches a preset maximum switching loss, the processor switches to a pulse multiplier one level lower than the constant pulse multiplier during the set of pulse multipliers.
Synchronous PWM pulse mode switching system considering switching losses.
According to clause 5,
If the constant pulse multiple is the maximum pulse multiple among the pulse multiple convergence, the maximum switching loss is the maximum switching loss in the asynchronous PWM control section.
A synchronous PWM pulse mode switching system that considers switching losses, featuring:
According to paragraph 1,
During control using a constant pulse multiplier, if the processor determines that the maximum switching loss will not be reached even if switching to a pulse multiplier one level higher than the constant pulse multiplier, it switches to a pulse multiplier one level higher than the constant pulse multiplier during the set of pulse multipliers. thing
Synchronous PWM pulse mode switching system considering switching losses.
In clause 7,
When the voltage modulation index or the size of the current decreases and the switching loss decreases, the processor checks whether the maximum switching loss will not be reached even if the pulse multiplier is switched to one level higher than the constant pulse multiplier.
Synchronous PWM pulse mode switching system considering switching losses.
(a) creating a loss analysis table using voltage modulation index and current information;
(b) determining the initial pulse multiplier and determining the pulse multiplier downshift according to the results of confirming the switching loss; and
(c) re-determining the pulse multiplier by checking the switching loss;
Method for selecting synchronous PWM pulse mode switching criteria considering switching loss including.
According to clause 9,
In step (a), the voltage modulation index is normalized to produce the loss analysis table in preset units, and the rated torque is divided into preset sections to produce the loss analysis table for the current corresponding to the torque.
Method for selecting synchronous PWM pulse mode switching criteria considering switching losses.
According to clause 9,
Step (b) is to select the maximum selectable pulse multiplier from the set of pulse multipliers by considering the harmonic distortion rate in the area where the back electromotive force and output voltage are smaller than the preset size.
Method for selecting synchronous PWM pulse mode switching criteria considering switching losses.
According to clause 11,
In step (b), when the switching loss reaches a preset maximum switching loss during control using the maximum pulse multiplier, switching to a pulse multiplier one level lower than a certain pulse multiplier during pulse multiplier set.
Method for selecting synchronous PWM pulse mode switching criteria considering switching losses.
According to clause 9,
Step (c) checks the switching loss during control with the downshifted pulse multiplier, and when the maximum switching loss is reached, switches to a pulse multiplier one level lower than the downshifted pulse multiplier.
Method for selecting synchronous PWM pulse mode switching criteria considering switching losses.
According to clause 9,
In step (c), while controlling the downshifted pulse multiplier, the voltage modulation index or the magnitude of the current decreases, thereby reducing the switching loss, so that the maximum switching loss is not reached even if the pulse multiplier is switched to a pulse multiplier one level higher than the downshifted pulse multiplier. If it is confirmed that this will not be the case, control is performed to reduce the size of the current and torque ripple by switching to a pulse multiplier one step higher than the downshifted pulse multiplier.
Method for selecting synchronous PWM pulse mode switching criteria considering switching losses.

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