Inverter control device

Abstract

This invention discloses an inverter control device. One embodiment of the device includes: a control unit that receives a command torque and a command voltage, and outputs a command current capable of maintaining a constant output voltage magnitude in a weak flux region; a current control unit that performs proportional-integral control on the command current and the output current of the motor, and outputs the command voltage; and a first coordinate transformation unit that converts the command voltage into three phases and provides it to the inverter.

Description

Technical Field

[0001] This invention relates to an inverter control device. Background Technology

[0002] Generally speaking, an inverter is a power conversion device that converts direct current (DC) into alternating current (AC). In industrial applications, inverters are defined as a series of devices that receive power from a commercial power source, autonomously change the voltage and frequency, and supply it to the motor to control it in a way that utilizes the motor speed efficiently.

[0003] This type of inverter can control the magnitude and frequency of AC voltage and is commonly used in systems requiring variable speed operation. Furthermore, depending on the application area based on power semiconductors, various configurations (topologies) can be implemented, with the output voltage magnitude, number of levels, and voltage synthesis method varying according to the configuration. Therefore, various inverter configurations can be achieved by configuring according to user needs.

[0004] Typically, three-phase half-bridge inverters are commonly used in industrial applications. A three-phase half-bridge inverter consists of three single-phase half-bridge inverters connected in parallel. Each half-bridge is called a pole, arm, or leg, and it forms the basic circuitry of the inverter.

[0005] In motor drive systems using this type of inverter, the motor's output power is limited by the maximum output voltage and current that the inverter can supply to the motor. The inverter's output voltage is limited by the magnitude of the DC terminal voltage and the output voltage synthesis method, while the current is typically limited by the allowable thermal ratings of the inverter or motor.

[0006] In particular, when the motor is running at high speed or the input voltage is low, the back electromotive force generated in the motor results in insufficient voltage margin to control the current and torque. Therefore, the maximum output torque of the motor cannot be fully utilized, and the operating range of the motor is relatively limited. Summary of the Invention

[0007] The problem that the invention aims to solve

[0008] The technical problem to be solved by the present invention is to provide an inverter control device whose output voltage range not only includes the linear modulation region, but also extends to the overmodulation region.

[0009] Another technical problem to be solved by the present invention is to provide an inverter control device that uses a voltage controller that performs weak flux control to linearly limit the magnitude of the output voltage, thereby generating maximum torque under the same voltage and current conditions to increase the range of operating speeds.

[0010] Another technical problem to be solved by the present invention is to provide an inverter control device that makes overmodulation operation easier by linearly limiting the magnitude of the output voltage in the overmodulation operation zone.

[0011] Technical solutions to the problem

[0012] To address the technical challenges described above, an embodiment of the present invention provides an apparatus for controlling and converting DC voltage and outputting it to a motor, which may include: a control unit that receives a command torque and a command voltage and outputs a command current capable of maintaining a constant output voltage magnitude in a weak flux region; a current control unit that performs proportional-integral control on the command current and the output current of the motor and outputs the command voltage; and a first coordinate transformation unit that converts the command voltage into three phases and provides it to the inverter.

[0013] In one embodiment of the present invention, the control unit may include: a first determining unit for determining the magnitude of the command voltage; an integrating unit for outputting a magnetic flux component command current in the command current based on the error between the magnitude of the command voltage and the limit magnitude; and a command generating unit for outputting a torque component command current in the command current based on the command torque and the magnetic flux component command current.

[0014] In one embodiment of the present invention, the limiting size can be set to... (V dc The range is 90% to 95% of the DC voltage.

[0015] In one embodiment of the present invention, the control unit may further include a first limiting unit that limits the torque component command current.

[0016] In one embodiment of the present invention, the control unit may further include a second limiting unit that limits the command current of the magnetic flux component.

[0017] In one embodiment of the present invention, the gain of the integrator can vary taking into account the weak flux state or operating state of the motor.

[0018] The apparatus of one embodiment of the present invention may further include an overmodulation unit, which corrects the modulation index of the command voltage in the overmodulation interval and generates an overmodulated command voltage based on the corrected modulation index.

[0019] In one embodiment of the present invention, the overmodulation unit may include: a correction unit that corrects the modulation index of the command voltage in the overmodulation interval and corrects the magnitude of the command voltage according to the corrected modulation index (corrected voltage command); and a generation unit that limits the corrected command voltage to a voltage limit line and generates an overmodulated voltage command (overmodulated voltage command).

[0020] In one embodiment of the present invention, the correction unit can correct the modulation index of the voltage command so that the modulation index of the output voltage of the inverter output by the overmodulated voltage command is linearly related to the modulation index of the overmodulated voltage command.

[0021] The apparatus of one embodiment of the present invention may further include a dynamic characteristic enhancement unit, which changes the command voltage by adding a voltage error that has been rotated by 90 degrees to the command voltage during the transition state of the motor.

[0022] In one embodiment of the present invention, the dynamic characteristic enhancement unit can change the command voltage, so that the voltage of the d-axis of the synchronous coordinate system decreases instantaneously and the voltage of the q-axis increases instantaneously.

[0023] Invention Effects

[0024] As described above, the present invention makes the output voltage range include not only the linear modulation region but also the overmodulation region, and facilitates the operation of the overmodulation region through the linear relationship between the command voltage and the output voltage in the overmodulation region.

[0025] Furthermore, the inverter control device of the present invention generates maximum torque and increases the range of operating speeds under the same voltage and current conditions by improving weak flux control.

[0026] Furthermore, the inverter control device of the present invention corrects the command voltage by instantaneously reducing the d-axis voltage of the synchronous coordinate system and instantaneously increasing the q-axis voltage during the transition state, thus enabling a rapid torque response without losing the magnetic flux used to generate torque. Attached Figure Description

[0027] Figure 1 This is a diagram used to illustrate the configuration of a typical three-phase inverter.

[0028] Figure 2 This is a detailed structural diagram of the existing inverter control unit.

[0029] Figure 3 This is an example diagram illustrating the configuration of a voltage controller that determines the variable K in the prior art.

[0030] Figure 4 This is an example graph used to illustrate the change of variable K based on voltage magnitude.

[0031] Figure 5 This is a detailed configuration diagram of an inverter control device according to an embodiment of the present invention.

[0032] Figure 6 This is an example diagram used to illustrate the overmodulation phenomenon.

[0033] Figure 7 This is an example diagram used to illustrate overmodulation.

[0034] Figure 8 yes Figure 5 A detailed structural diagram of an embodiment of the overmodulation section.

[0035] Figure 9 This is an example diagram used to illustrate the modulation index correction section's correction of the modulation index.

[0036] Figure 10 This is an example diagram used to illustrate the relationship between the command voltage and the output voltage of the modulation unit.

[0037] Figure 11 yes Figure 5 A detailed configuration diagram of an embodiment of the control unit.

[0038] Figure 12 It is used for explanation Figure 5 An example diagram illustrating the performance of the control unit and the overmodulation unit.

[0039] Figure 13 yes Figure 5 A detailed configuration diagram of an embodiment of the dynamic characteristic enhancement unit. Detailed Implementation

[0040] To fully understand the structure and effects of the present invention, preferred embodiments of the invention will be described with reference to the accompanying drawings. However, the present invention is not limited to the embodiments disclosed below and can be implemented in various forms and with various modifications. The description of these embodiments is intended to complete the disclosure of the invention and to fully inform those skilled in the art of the scope of the invention. In the drawings, for ease of explanation, the dimensions of the constituent elements are shown enlarged than actually, and the proportions of the individual constituent elements may be magnified or reduced.

[0041] To describe various elements, ordinal terms such as "first," "second," etc., may be used, but such constituent elements are not limited to these terms. These terms are intended only to distinguish one constituent element from another. For example, without departing from the scope of the invention, "first constituent element" may be named "second constituent element," and similarly, "second constituent element" may be named "first constituent element." Furthermore, unless the context clearly indicates otherwise, singular expressions include plural expressions. Unless otherwise defined, the terms used in embodiments of the invention may be interpreted in the sense that are well-known to those skilled in the art.

[0042] The following is for reference Figures 1 to 4 This describes the existing inverter control device, referring to... Figures 5 to 13The inverter control device according to an embodiment of the present invention will be described in detail.

[0043] Figure 1 This is a diagram used to illustrate the configuration of a typical three-phase inverter.

[0044] The inverter section 300 can be based on the DC terminal voltage V of the DC voltage storage section 200. dc Output three-phase AC output voltage V an v bn v cn Power is supplied to the motor 400, which is a three-phase load. The output voltage can then be determined based on the on / off state of the three-phase switches in the inverter section 300. Each phase of the inverter section 300 has two switches connected in series, allowing each phase to operate independently to generate an output voltage. The output voltages of each phase can be controlled to have a 120-degree phase difference.

[0045] The DC voltage storage unit 200 may include a capacitor or a battery and can be configured to maintain a constant voltage. The inverter unit 300 is a device that converts DC voltage into AC voltage, and the output voltage can be controlled by opening and closing a switch.

[0046] The inverter control unit 100 receives the speed or command torque and outputs a command voltage based on this to determine the switching state of the three phases of the inverter unit 300 to drive the motor 400.

[0047] Figure 2 This is a detailed diagram of the existing inverter control unit. As can be seen, in order to control torque, current, voltage, etc., it is formed as a structure with multiple components connected in series.

[0048] The current controller 120 outputs a command voltage by comparing the current command and the actual current to reduce current error. The current controller 120 is composed of a proportional-integral (PI) controller. At this time, the current controller 120 adjusts the phase so that the rotor flux is located on the d-axis of the synchronous coordinate system, and adds or subtracts the rotor flux through the d-axis current. There is no rotor flux on the q-axis of the synchronous coordinate system; the torque is controlled by the q-axis current.

[0049] The output voltage calculated by the current controller 120 is converted into a three-phase command voltage by the coordinate converters 130 and 130, and the inverter unit 200 applies the output voltage to the motor 400 according to the command voltage.

[0050] In existing inverter controllers, voltage controller 110 includes a flux weakening controller that limits the output voltage by reducing the flux component current command in the flux weakening operating region as follows:

[0051] [Mathematical Expression 1]

[0052]

[0053] Where NoLoadCurr is the no-load current. This is the d-axis current command in the synchronous coordinate system based on the rotor flux angle. Additionally, K is the output variable of the voltage controller 110, and F... fw This is the output variable of the weak flux controller. Observing mathematical formula 1, it can be seen that the flux component current command can be controlled through variables K and F. fw Things have changed.

[0054] Figure 3 This is an example diagram illustrating the configuration of a voltage controller that determines the variable K in the prior art. Figure 4 This is an example graph used to illustrate the change of variable K based on voltage magnitude.

[0055] If the magnitude of the input inverter's output voltage V out and the command voltage V that limits the magnitude of the maximum output voltage. out * The error between the two values ​​is then determined by the proportional-integral unit 111, which defines the variable K. At this point, the maximum value of variable K is limited to 100% by the limiting unit 112. Figure 3 The voltage controller 110, the variable K changes with the magnitude of the output voltage as follows: Figure 4 It changes as shown.

[0056] In V out * >V out Under normal operating conditions, the d-axis current in the synchronous coordinate system maintains a no-load current of 400 for the motor. Conversely, in V... out * <V out In this case, to limit the output voltage, the voltage controller 110 maintains the output voltage at the same level as the command voltage by decreasing the variable K. At this time, the d-axis current of the synchronous coordinate system decreases due to the variable K.

[0057] On the other hand, F fw It is determined by the following mathematical formula.

[0058] [Mathematical Expression 2]

[0059]

[0060] Where, ω r_base This is the reference speed, input by the user, which is a value close to the rated speed. When the motor speed is less than the reference speed, F... fwF is 1 when the motor speed is greater than the reference speed. fw The current decreases inversely to the motor speed, performing weak flux operation. Similarly, the d-axis current in the synchronous coordinate system also decreases due to F. fw And change.

[0061] The existing voltage controller using mathematical formulas 1 and 2 is an output limiting factor. It can be used uniformly regardless of the motor characteristics without considering voltage and current limiting conditions. Therefore, there is a problem that proper voltage control and weak flux operation cannot be achieved.

[0062] In particular, the existing weak flux operation method reduces the flux component current inversely proportional to the rotor speed, which leads to the problem that the motor performance cannot be fully utilized because it fails to reflect the characteristics of the motor.

[0063] In other words, existing voltage controllers cannot adequately reduce rotor flux, thus failing to fully utilize the motor's maximum output torque capability. Furthermore, because they do not consider the over-modulation region, the motor's operating range is relatively limited. On the other hand, while there are research results on over-modulation techniques, they are limited to improvements and utilization of 6-step operation, resulting in insufficient utilization of the over-modulation region between the linear modulation region and 6-step operation. Here, 6-step operation of the inverter refers to operation controlled by six equal switching intervals within one cycle of the three-phase inverter output. Under 6-step operation, the inverter outputs its maximum voltage.

[0064] According to an embodiment of the inverter control device of the present invention, overmodulation technology is used to increase the voltage range of the output voltage to include not only the linear modulation region but also the overmodulation region. Furthermore, it is possible not only to linearly limit the magnitude of the output voltage using a voltage controller that performs flux weakening control, but also to generate maximum torque and increase the range of operating speeds under the same voltage and current conditions.

[0065] In addition, by linearly limiting the output voltage in the overmodulation operation region, overmodulation operation between the linear modulation region and the 6-step operation becomes easier.

[0066] Figure 5 This is a detailed configuration diagram of an inverter control device according to an embodiment of the present invention. The three-phase command voltage output from the inverter control device 1 can be applied to the inverter section 300, and the three-phase output voltage of the inverter section 300 can be applied to the motor 400, which serves as the load.

[0067] As shown in the figure, an inverter control device 1 according to an embodiment of the present invention may include a control unit 10, a flux control unit 15, a current control unit 20, a dynamic characteristic enhancement unit 25, coordinate transformation units 30, 35, 40, 50, 55, 60, and an overmodulation unit 45, which receive command torque to perform weak flux control and voltage control.

[0068] First, the operation of the modulation unit 45 has been explained.

[0069] like Figure 1 The three-phase half-bridge inverter shown has a limited range of linearly output voltages. Figure 6 This is an example diagram used to illustrate the overmodulation phenomenon.

[0070] The output voltage limit range of the inverter is Figure 6 The hexagon 6A formed by the dashed lines corresponds to circle 6B as the linear modulation zone. For command voltages within circle 6B, the inverter can output the same voltage; however, for command voltages outside the modulation zone, the output voltage needs to be synthesized.

[0071] Figure 6 The command voltage 6C corresponds to the overmodulation region, and the overmodulation unit 45 can limit the command voltage 6C to the voltage range of the hexagon 6A.

[0072] Figure 7 This is an example diagram used to illustrate overmodulation, showing how the switching state is maintained under overmodulation.

[0073] Figure 7 Switch-state holding overmodulation is a method of maximizing the holding of the switching state by preferentially selecting the voltage vector closest to the command voltage vector. Command voltage vector V * Overmodulation can be maintained by switching state.

[0074] This is a method that maintains the switching state of the effective voltage V2, which is closer to the effective voltage V1, in order to output the command voltage vector within a specified switching time, and outputs the other effective voltage V1 during the remaining switching time. Because this method outputs the closest effective voltage vector as the command voltage vector increases, it facilitates easy switching operation using a 6-step operation.

[0075] Figure 6 It can be confirmed that it is difficult to synthesize an output voltage corresponding to the command voltage in the overmodulation region, and the magnitude of the actual output voltage decreases. Therefore, the overmodulation unit 45 of the present invention generates an output voltage that is the same as the average command voltage by increasing the voltage modulation index (MI).

[0076] The following mathematical formula 3 is the modulation index.

[0077] [Mathematical Expression 3]

[0078]

[0079] In the above mathematical formula 3, MI is the ratio of the voltage magnitude to the maximum output voltage of the three-phase half-bridge inverter.

[0080] pass Figure 6 According to the definition in mathematical formula 3, the moment when the modulation zone begins is when the magnitude of the command voltage is... At that moment, the modulation index is 0.9067. Therefore, in regions where the modulation index (MI) is greater than 0.9067, events such as... Figure 6 The overmodulation phenomenon seen in 6C.

[0081] In one embodiment of the present invention, the overmodulation unit 45 maximizes the inverter output voltage in the overmodulation interval to expand the linearity of the output voltage to the command voltage. Unlike the existing method of instantaneously correcting the command voltage, it considers a period of time to change the switching state to maintain the overmodulation mode in order to generate an overmodulated command voltage.

[0082] Figure 8 yes Figure 5 A detailed structural diagram of an embodiment of the overmodulation section.

[0083] As shown in the figure, the overmodulation unit 45 of one embodiment of the present invention may include a modulation index correction unit 451 and an overmodulation command voltage generation unit 452.

[0084] The modulation index correction unit 451 can output a hypothetical corrected modulation index of the command voltage by correcting the modulation index of the initial command voltage. Figure 9 This is an example diagram used to illustrate the modulation index correction section's correction of the modulation index.

[0085] For example, assuming the modulation index of the initial command voltage is 0.95, and the modulation index of the inverter's output voltage is also 0.95 to ensure linearity, according to an embodiment of the present invention, the modulation index of the command voltage can be corrected from 0.95 to 0.989 and provided to the inverter. Thus, the modulation index of the output voltage becomes 0.95, which can be consistent with the modulation index of the actual command voltage.

[0086] If the modulation index of the initial command voltage is corrected by the modulation index correction unit 451, the magnitude of the command voltage can be corrected by mathematical formula 3.

[0087] The overmodulated command voltage generation unit 452 can generate the overmodulated command voltage using the magnitude of the corrected command voltage, thereby limiting the corrected command voltage to the voltage limit line. This can also be achieved through... Figure 7The minimum distance overmodulation generation, or the overmodulation generation command voltage can be maintained by the switching state.

[0088] As described above, the overmodulation unit 45 of one embodiment of the present invention can synthesize an output voltage that is the same as the average of the command voltage not only in the linear modulation region but also in the overmodulation region, enabling a maximum of 6-step operation. Figure 10 This is an example diagram used to illustrate the relationship between the command voltage and the output voltage of the modulation unit 45.

[0089] As shown in the figure, it can be seen that the modulation index of the output voltage according to an embodiment of the present invention is the same as the linearity baseline, thus ensuring the linearity of the inverter's output voltage.

[0090] The operation of the control unit 10 of the present invention will be described.

[0091] Figure 11 This is a detailed configuration diagram of an embodiment of the control unit 10 of the present invention.

[0092] As shown in the figure, the control unit 10 of one embodiment of the present invention can maintain the magnitude of the output voltage constant in the weak magnetic flux region by means of voltage feedback. It may include a magnitude determination unit 101, a first error determination unit 102, an integration unit 103, a limiting unit 104, a second error determination unit 105, an instruction generation unit 106, and a limiting unit 107.

[0093] The magnitude determination unit 101 can calculate the magnitude of the output voltage based on the command voltage output as the current control unit 20, and thus determine the magnitude of the command voltage.

[0094] The first error determination unit 102 determines the magnitude of the command voltage. and command voltage limit size The integrator 103 can integrate the error to output the command flux. At this time, the limiting unit 104 can ensure the minimum flux size.

[0095] The first error determination unit 102 and the integrator unit 103 can perform proportional-integral control, that is, they can control the magnitude of the command voltage. Not greater than the command voltage limit Output rotor command flux in the manner The second error determination unit 105 can output command magnetic flux. and rotor flux The error.

[0096] At this time, depending on the control method or the type of motor 400, the synchronous coordinate system d-axis current can be output instead of the command flux.

[0097] Gain K of integrator 103ifw It is not a constant, but rather selected considering the operation of the weak magnetic flux and the operating state of the motor 400 or the responsiveness of the inverter control device 1. In this case, if K... ifw If K is large, the response of the integral part 103 may be faster. ifw If the size is small, the responsiveness of the integrator 103 may be slower.

[0098] On the other hand, in one embodiment of the present invention, the output voltage of the inverter may be limited by the command voltage. The limitation. When the output voltage is used in the linear modulation region, the command voltage limitation size. It can be set in 90% to 95%. This takes into account the voltage drop caused by the impedance of the motor 400. If the output voltage is used in the overmodulation zone, the command voltage limit can also be set above it.

[0099] As described above, the size determination unit 101, first error determination unit 102, integration unit 103, limiting unit 104, and second error determination unit 105 of the control unit 10 of an embodiment of the present invention can determine the degree of attenuation of the rotor magnetic flux.

[0100] The command generation unit 106 can generate commands based on the command torque. The output of the second error determination unit 105 generates a torque component current command. The limiting unit 107 can limit and output torque component current commands based on the magnitude of the d-axis current in the synchronous coordinate system.

[0101] In one embodiment of the present invention, the control unit 10 satisfies the voltage limiting condition by commanding the voltage limit size and satisfies the current limiting condition by limiting unit 107, thereby enabling the output of maximum torque within a limited voltage and current range.

[0102] Figure 12 It is used for explanation Figure 5 An example diagram of the performance of the control unit 10 and the overmodulation unit 45.

[0103] exist Figure 12 In the figure, 12C represents the torque-speed performance curve of the conventional method, 12A represents the torque-speed performance curve of the case with over-modulation and flux weakening control, and 12B represents the torque-speed performance curve of the case with flux weakening control.

[0104] As shown in the figure, it can be seen that the performance is improved compared with the existing method when weak flux control is performed, and the performance is further improved when overmodulation control is performed.

[0105] In addition, 12A and 12B can be adjusted by the magnitude of the command voltage of the control unit 10. The voltage limit condition becomes smaller as the command voltage is selected, thus reducing the operating range of the motor.

[0106] As an application example of the present invention, when the DC terminal voltage decreases due to reasons such as input power supply failure, the inverter voltage can be output without being affected by the input power supply state by increasing the command voltage limit of the control unit 10 of the present invention, thereby maintaining the motor performance.

[0107] As described above, the control unit 10 according to an embodiment of the present invention can improve the existing system by appropriately adjusting the command voltage limit size.

[0108] right Figure 5 The operation of the dynamic characteristic enhancement unit 25 will be explained.

[0109] The responsiveness of the control unit 10 is determined by the gain K of the integrator 103. ifw It is determined that, considering factors such as the weak magnetic flux state or the operating state of the motor, K ifw The torque characteristics can be varied, but it's difficult to make them large enough to significantly improve responsiveness. Therefore, the control unit 10 limits the torque characteristics until the transition state is completely out of control, at which point the dynamic characteristic enhancement unit 25 ensures the torque characteristics during the transition state. To this end, the dynamic characteristic enhancement unit 25 can instantaneously and appropriately reduce the d-axis current or command flux.

[0110] Figure 13 yes Figure 5 A detailed configuration diagram of an embodiment of the dynamic characteristic enhancement unit.

[0111] As shown in the figure, the dynamic characteristic enhancement unit 25 of one embodiment of the present invention can change the command voltage by adding a voltage error rotated by 90 degrees to the command voltage. Its mathematical expression is shown below.

[0112] [Mathematical Expression 4]

[0113]

[0114]

[0115] Therefore, in the case of an induction motor, the d-axis voltage of the synchronous coordinate system can decrease instantaneously, and the q-axis voltage can increase instantaneously. Torque is generated proportionally to the magnetic flux and the torque component current; the magnetic flux component current may decrease due to the instantaneous decrease of the d-axis voltage of the synchronous coordinate system, while the torque component current increases due to the increase of the q-axis voltage of the synchronous coordinate system. However, since the magnetic flux is instantaneously constant, a rapid torque response can be expected without losing the magnetic flux used to generate torque.

[0116] right Figure 5The overall operation of the inverter control device will be explained.

[0117] If the command torque When the command voltage, which is the output of the current control unit 20, is input to the control unit 10, the weak flux operation can be used to output a command flux that keeps the magnitude of the output voltage constant. Or magnetic flux component current command and torque component current command

[0118] When the control unit 10 outputs a magnetic flux component current command, the magnetic flux control unit 15 may not be needed.

[0119] When the control unit 10 outputs a command flux, the flux control unit 15 can output a flux component current command by proportional-integral control of the estimated flux of the motor 400 and the command flux estimated by the flux estimation unit 50. The flux estimation unit 50 can estimate the flux by converting the output current of the inverter unit 300 into d-axis and q-axis currents through the coordinate transformation unit 60, and can output a flux angle.

[0120] If the conversion unit 40 performs coordinate transformation on the flux angle output by the flux estimation unit 50 to determine the output current in the synchronous coordinate system, then the current control unit 20 can receive the current command and output the current, and can output the current command through proportional-integral control.

[0121] As previously described, the dynamic characteristic enhancement unit 25 is used to ensure torque characteristics during transition states. It adds a 90-degree rotational voltage error to the command voltage to change the command voltage. Therefore, the command voltage can be corrected by instantaneously decreasing the voltage on the d-axis of the synchronous coordinate system and instantaneously increasing the voltage on the q-axis. At this time, for the dynamic characteristic enhancement unit 25, the output command voltage of the overmodulation unit 45 can be converted into the synchronous coordinate system by the coordinate transformation unit 30 and input to the dynamic characteristic enhancement unit 25.

[0122] As described above, the command voltage corrected by the dynamic characteristic enhancement unit 25 is transformed into a command voltage in the static coordinate system by the coordinate transformation unit 35 and input to the overmodulation unit 45. In order to maximize the inverter output voltage in the overmodulation range and thus expand the linearity of the output voltage of the command voltage, the overmodulation unit 45 outputs a hypothetical corrected command voltage modulation index by correcting the modulation index of the command voltage. The overmodulated command voltage can be output using the magnitude of the corrected command voltage to limit the corrected command voltage to the voltage limit line. However, when it is not in the overmodulation range, the output of the coordinate transformation unit 35 can be input to the coordinate transformation unit 55 without the correction of the command voltage.

[0123] As described above, the overmodulation command voltage output from the overmodulation unit 45 can be output as a three-phase command voltage through the coordinate transformation unit 55, which can be applied to the inverter unit 300 and converted into a motor input voltage.

[0124] As described above, the inverter control device of the present invention performs overmodulation through the overmodulation unit 45, which can extend the range of the output voltage beyond the linear modulation region to include the overmodulation region. That is, in the overmodulation region, the operation of the overmodulation region can be facilitated by the linear relationship between the command voltage and the output voltage.

[0125] Furthermore, the inverter control device of the present invention generates maximum torque under the same voltage and current conditions and can increase the range of operating speeds by improving the weak flux control.

[0126] Furthermore, the inverter control device of the present invention corrects the command voltage by instantaneously reducing the d-axis voltage of the synchronous coordinate system and instantaneously increasing the q-axis voltage during the transition state, thus enabling a rapid torque response without losing the magnetic flux used to generate torque.

[0127] While embodiments of the present invention have been described above, they are merely exemplary, and those skilled in the art will understand that various modifications and equivalent embodiments can be made to the embodiments. Therefore, the true scope of protection of the present invention should be determined by the scope of the appended claims.

[0128] Industrial applicability

[0129] This invention relates to an inverter control device that increases the range of the output voltage to include the overmodulation region, including the linear modulation region, and therefore has industrial applicability.

Claims

1. An inverter control device, which controls an inverter that converts DC voltage and outputs it to a motor, wherein, include: The control unit receives command torque and command voltage, and outputs command current that can maintain the output voltage constant in the weak magnetic flux region; The current control unit performs proportional-integral control on the command current and the output current of the motor, and outputs the command voltage. as well as The first coordinate transformation unit converts the command voltage into three phases and provides it to the inverter. The control unit includes: The first determining unit determines the magnitude of the command voltage; The integrator outputs the flux component of the command current based on the error between the magnitude of the command voltage and the limit magnitude; and The command generation unit outputs the torque component command current from the command current based on the command torque and the magnetic flux component command current. The gain of the integrator varies taking into account the weak flux state or operating state of the motor.

2. The inverter control device according to claim 1, wherein, The limit size is set at Within the range of 90% to 95%, of which V dc The DC voltage is referred to here.

3. The inverter control device according to claim 1, wherein, The control unit also includes a first limiting unit that limits the torque component command current.

4. The inverter control device according to claim 1, wherein, The control unit also includes a second limiting unit that limits the command current of the magnetic flux component.

5. The inverter control device according to claim 1, wherein, It also includes an overmodulation unit, which corrects the modulation index of the command voltage in the overmodulation interval and generates an overmodulated command voltage based on the corrected modulation index.

6. The inverter control device according to claim 5, wherein, The overmodulation unit includes: The correction unit corrects the modulation index of the command voltage in the over-modulation range, and corrects the magnitude of the command voltage based on the corrected modulation index, i.e., corrects the voltage command; and The generation unit limits the corrected command voltage to the voltage limit line, generating an overmodulated voltage command, i.e., an overmodulated voltage command.

7. The inverter control device according to claim 6, wherein, The correction unit corrects the modulation index of the voltage command so that the modulation index of the inverter's output voltage output through the overmodulated voltage command is linearly related to the modulation index of the overmodulated voltage command.

8. An inverter control device, which controls an inverter that converts DC voltage and outputs it to a motor, wherein, include: The control unit receives command torque and command voltage, and outputs command current that can maintain the output voltage constant in the weak magnetic flux region; The current control unit performs proportional-integral control on the command current and the output current of the motor, and outputs the command voltage. as well as The first coordinate transformation unit converts the command voltage into three phases and provides it to the inverter. It also includes a dynamic characteristic enhancement unit, which changes the command voltage by adding a voltage error that has been rotated by 90 degrees to the command voltage during the transition state of the motor.

9. The inverter control device according to claim 8, wherein, The dynamic characteristic enhancement unit changes the command voltage, causing the voltage on the d-axis of the synchronous coordinate system to decrease instantaneously and the voltage on the q-axis to increase instantaneously.

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