Inverter device

Abstract

Inverter device (12) for controlling a three-phase AC motor (10), the inverter device (12) comprising: an inverter circuit (16) arranged to supply a current to the three-phase AC motor (10); a capacitor (20) provided on an input side of the inverter circuit (16); and a control unit (13) arranged to control the inverter circuit (16) by outputting PWM signals from the phase to the inverter circuit (16), wherein the control unit (13) contains a first control mode and a second control mode each as a control mode for controlling the inverter circuit (16), the control unit (13) is arranged to: in the first control mode, Performing phase shift processing for shifting a phase of at least one of the PWM signals of three phases output to the inverter circuit (16) in the second control mode so that a time period during which polarities of output voltages of three phases output from the inverter circuit (16) are the same is shorter in the first control mode than the time period in the second control mode; Controlling the inverter circuit (16) to supply a direct current to the three-phase AC motor (10) as a d-axis current by outputting the PWM signals of the three phases, each of which has a phase after phase shift processing; and Switching the control mode from the first control mode to the second control mode when a predetermined condition regarding a temperature of the capacitor (20) is met, and the control unit (13) is arranged, in the second control mode, to control the inverter circuit (16) to supply an alternating current to the three-phase AC motor (10) by outputting the PWM signals of three phases, each of which has a phase before the phase shift processing.

Description

INVERTER DEVICE

[0001] This non-provisional application is based on Japanese patent application JP 2014-155354 A filed on July 30, 2014 with the Japan Patent Office, the entire contents of which are hereby incorporated by reference. BACKGROUND OF THE INVENTIONField of the invention

[0002] The present disclosure relates to an inverter device and, more particularly, to an inverter device for driving a three-phase alternating current (AC) motor. Description of the state of the art

[0003] Conventionally, an electric motor is driven using a PWM (pulse width modulation) control inverter device, which includes a power transistor and an IGBT (insulated gate bipolar transistor), each for a switching element. When the electric motor is driven using such an inverter device, a surge voltage is generated, which may damage a motor coil or cause electrical breakdown.

[0004] For example, Japanese Patent Publication JP H06-38543A discloses a surge suppression device having a reactor provided on the inverter output side and driving an electric motor by applying an inverter output voltage to the electric motor via a cable having a length such as to form a line reactor in the reactor.

[0005] In some inverters, smoothing capacitors may be connected in parallel between an inverter circuit formed by a combination of a plurality of semiconductor switching elements (switching elements) and a power supply (battery). In this case, the capacitor is known to have a resistance component called "equivalent series resistance (ESR)," which results from the resistance of an electrode, the characteristics of a dielectric, and the like. This ESR may be negligible at room temperature up to an elevated temperature, but it may increase to a non-negligible value when the temperature drops (e.g., 0°C or lower).

[0006] Even when the electric motor is driven using the inverter device described above, a motor current flows into and out of the capacitor, generating a surge voltage resulting from the ESR. If the surge voltage exceeds a breakdown voltage of the semiconductor switching element, etc., the semiconductor switching element may be damaged. When a motor current is supplied to the electric motor by controlling the inverter device including a capacitor on the input side of the inverter circuit, when the ambient temperature is relatively low, the influence caused by the ESR of the capacitor should be considered accordingly.

[0007] To prevent the components of the inverter device from being damaged by the surge voltage generated by the capacitor's ESR at a time when the ambient temperature is relatively low, conventionally, the maximum value (limiting motor current value) of the motor current that can be supplied to the electric motor at each temperature is produced as a map, and the inverter device is controlled based on this map. Specifically, a warm-up operation of the electric motor is performed while limiting the motor current to thereby raise the capacitor temperature, and then normal operation is performed.

[0008] DE 10 2012 213908 A1 also discloses a control unit for a multi-phase electrical machine, in which, in particular, the pulse widths of the output power remain identical. The measures for increasing the temperature of a capacitor during a warm-up phase consist of switching the alternating current between 0° and 180°. Furthermore, JP 2009 - 060776 A1 discloses corresponding measures as a d-axis current in the form of a direct current that is less than or equal to a maximum permissible motor current.

[0009] However, when the electric motor is used in a more severe low-temperature environment, the motor current that can be supplied to the electric motor is further reduced, thereby extending the warm-up period of the electric motor. This results in a problem that a longer time is required for the electric motor to start up. SUMMARY OF THE INVENTION

[0010] The present disclosure was made to solve the problems described above. An object in certain aspects is to provide an inverter device capable of further reducing the time period from the warm-up operation of the electric motor to its start-up.

[0011] According to a specific embodiment, an inverter device for controlling a three-phase AC motor is provided. The inverter device includes: an inverter device configured to supply a current to the three-phase AC motor; a capacitor provided on an input side of the inverter circuit; and a control unit configured to control the inverter circuit by outputting PWM signals of the three phases to the inverter circuit. The control unit includes a first control mode and a second control mode, each as a control mode for controlling the inverter circuit.The control unit is configured to: in the first control mode, perform phase shift processing to shift a phase of at least one of the PWM signals of the three phases output to the inverter circuit in the second control mode so that a time period during which polarities of output voltages of the three phases output from the inverter circuit are the same is shorter in the first control mode than the time period in the second control mode; control the inverter circuit to supply a direct current to the three-phase AC motor as a d-axis current by outputting the PWM signals of the three phases, each of which has a phase after the phase shift processing; and switch the control mode from the first control mode to the second control mode when a predetermined condition regarding a temperature of the capacitor is satisfied.The control unit is configured, in the second control mode, to control the inverter circuit to supply an alternating current to the three-phase AC motor by outputting the PWM signals of the three phases each having one phase before the phase shift processing.

[0012] According to another embodiment, an inverter device for controlling a three-phase AC motor is provided. The inverter device includes: an inverter circuit configured to supply a current to the three-phase AC motor; a capacitor provided on an input side of the inverter circuit; and a control unit configured to control the inverter circuit by outputting PWM signals of the three phases to the inverter circuit. The control unit includes a first control mode, a second control mode, and a third control mode, each as a control mode for controlling the inverter circuit.The control unit is configured to: in the first control mode, perform phase shift processing to shift a phase of at least one of the PWM signals of the three phases output to the inverter circuit in the third control mode so that a time period during which polarities of output voltages of the three phases output from the inverter circuit are the same in the first control mode is shorter than the time period in the third control mode; control the inverter circuit to supply a direct current to the three-phase AC motor as a d-axis current by outputting the PWM signals of the three phases, each of which has a phase after the phase shift processing; and switch the control mode from the first control mode to the second control mode when a predetermined condition regarding a temperature of the capacitor is satisfied.The control unit is configured to, in the second control mode, control the inverter circuit to supply alternating current to the three-phase AC motor by outputting the PWM signals of the three phases, each of which has a phase after phase shift processing. The control unit is configured to: in the third control mode, estimate a rotor position of the three-phase AC motor based on a voltage or a current applied to three phases of the three-phase AC motor; and perform sensorless control to rotate the rotor based on the estimated rotor position and control the inverter circuit by outputting the PWM signals of the three phases, each of which has a phase from the phase shift processing, to which the phase is returned after the phase shift processing.

[0013] The foregoing and other objects, features, aspects and advantages of the present invention will become more apparent from the following detailed description of the present invention when considered in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF THE ILLUSTRATIONS Fig. 1 is a circuit diagram showing the configuration of an inverter device for controlling an electric motor according to the present invention. Fig. 2 is a functional block diagram of a control unit. Fig. 3 is a figure showing the relationship between a capacitor temperature and a maximum allowable motor current value. Fig. 4A and Fig. 4B are schematic diagrams showing an output voltage waveform of an inverter circuit before and after phase shifting. Fig. 5 is a flowchart showing warm-up control processing performed by the control unit. Fig. Figure 6 is a waveform diagram showing two phases (a U phase and a W phase) of voltage waveforms of an AC motor. DESCRIPTION OF PREFERRED EMBODIMENTS

[0014] The following describes the present embodiment in detail with reference to the figure. Note that the same or corresponding portions of the figures are denoted by the same reference numerals and will not be described repeatedly. Overall configuration

[0015] Fig. 1 is a circuit diagram showing a configuration of an inverter device for controlling an electric motor according to the present embodiment. The electric motor is, for example, an electric motor for an electric compressor. Note that the electric motor may be an electric motor controlled by an inverter and capable of being used in a low-temperature state. The electric motor may be, for example, an electric motor used for a vehicle and an electric motor for a machine tool.

[0016] With reference to Fig. 1, an inverter device 12 for controlling an alternating current (AC) motor 10 as the electric motor includes a control unit 13, an inverter circuit 16, a coil 17, current sensors 18a, 18b, a voltage sensor 19, a capacitor 20, and a temperature sensor 21. A resistor Rs connected in series with the capacitor 20 indicates an equivalent series resistance (ESR) of the capacitor 20.

[0017] The inverter device 12 is connected to a high-voltage battery 14, which is a DC power supply, via a fuse 15. It receives electric power from the high-voltage battery 14 and controls the driving of the AC motor 10. The AC motor 10 is a three-phase synchronous motor. The AC motor 10 is used, for example, as a motor for a vehicle air conditioner (a motor for an air conditioner compressor).

[0018] A positive electrode terminal of the high-voltage battery 14 is connected to one terminal of the capacitor 20 and a positive electrode power line of the inverter circuit 16. A negative electrode terminal of the high-voltage battery 14 is connected to the other terminal of the capacitor 20 and a negative electrode power line of the inverter circuit 16. The inverter circuit 16 is supplied with a direct current from the high-voltage battery 14 via the capacitor 20. Although not shown, it should be noted that the high-voltage battery 14 may be a power source that supplies electric power to drive a motor for traveling, which is included in an electric vehicle or a hybrid vehicle.

[0019] The inverter circuit 16 includes switching elements Q1 to Q6 and diodes D1 to D6. Examples of the switching elements Q1 to Q6 used herein include an IGBT (Insulated Gate Bipolar Transistor), a MOSFET (Metal Oxide Semiconductor Field Effect Transistor), a bipolar transistor, or the like.

[0020] The switching elements Q1, Q2 for a U-phase are connected in series between the positive electrode power line and the negative electrode power line. The switching elements Q3 and Q4 for a V-phase are connected in series between the positive electrode power line and the negative electrode power line. The switching elements Q5, Q6 for a W-phase are connected in series between the positive electrode power line and the negative electrode power line. The diodes D1 to D6 are connected in anti-parallel to the switching elements Q1 to Q6, respectively. A U-phase coil 6, a V-phase coil 7, and a W-phase coil 8, corresponding to their respective phases of the AC motor 10, are connected to a connection node of the switching elements Q1, Q2, a connection node of the switching elements Q3, Q4, and a connection node of the switching elements Q5, Q6, respectively. The U-phase coil 6, the V-phase coil 7, and the W-phase coil 8 are Y-connected.

[0021] Current sensors 18a, 18b are provided between the inverter device 12 and the AC motor 10. The current sensors 18a and 18b detect voltage values ​​Iu, Iw of the two phases (in the present embodiment, U-phase and W-phase) and current values ​​Iu, Iv, Iw of the phase currents supplied to the AC motor 10. The current sensors 18a and 18b input the detected current values ​​Iu and Iw to the control unit 13. It should be understood that the sum of instantaneous values ​​of the current values ​​Iu, Iv, Iw of the three phase currents is 0. Therefore, the current sensors only need to be arranged to detect current values ​​of two phase currents. The control unit 13 can also calculate the current value Iv of the remaining one phase current based on the current values ​​Iu, Iw.

[0022] Instead of the current sensors 18a, 18b, the current values ​​Iu, Iw may be detected based on the voltage of a shunt resistor connected to a switching element for a U-phase and a switching element for a W-phase.

[0023] The voltage sensor 19 is provided on an input side of the inverter circuit 16. The voltage sensor 19 detects an input voltage value V and inputs the input voltage value V to the control unit 13.

[0024] Capacitor 20 is provided on the input side of inverter circuit 16 and is connected in parallel to high-voltage battery 14. Capacitor 20 is, for example, an electrolytic capacitor. Switching elements Q1, Q3, and Q5 are connected to a positive electrode terminal side of capacitor 20. Switching elements Q2, Q4, and Q6 are connected to a negative electrode terminal side of capacitor 20.

[0025] The temperature sensor 21 detects a temperature to estimate the temperature of the capacitor 20 and inputs the detected temperature to the control unit 13. The temperature sensor 21 can be arranged at a position where the temperature sensor 21 can detect the temperature to estimate the temperature of the capacitor 20 and does not need to be located near the capacitor 20. In the present embodiment, the temperature sensor 21 is arranged on a substrate on which the switching element is formed. For example, the temperature sensor 21 can be arranged on a surface or the like of a casing for accommodating the inverter device 12.

[0026] The control unit 13 includes a CPU (central processing unit) 22 and a memory 23. The control unit 13 controls the inverter circuit 16 by outputting PWM signals of three phases of the inverter circuit 16.

[0027] The CPU 22 controls the inverter circuit 16 by reading and executing a program stored in the memory 23. Specifically, the CPU 22 implements each processing (step) of the control unit, which will be described later, by executing the program.

[0028] The memory 23 is implemented by a RAM (Random Access Memory), a ROM (Read-Only Memory), and the like. The memory 23 stores programs to be executed by the CPU 22, data to be used by the CPU 22, and the like.

[0029] The CPU 22 is connected to a gate as a control terminal of each of the switching elements Q1 to Q6 via a drive circuit (not shown). The CPU 22 is connected to the current sensors 18a, 18b and the voltage sensor 19 via an input interface (not shown).

[0030] The CPU 22 outputs a drive waveform signal (PWM signal) to each of the switching elements Q1 to Q6 via the drive circuit based on detection signals from the current sensors 18a, 18b, the voltage sensor 19, and the temperature sensor 21. The PWM signal is used to control the AC motor 10 to achieve a target output. This PWM signal controls the operation of turning on / off each of the switching elements Q1 to Q6 of the inverter circuit 16. Through this control, a direct current from the high-voltage battery 14 is converted into a three-phase alternating current, and the converted three-phase alternating current is supplied to each of the coils 6, 7, 8 of the respective phases of the alternating current 10. The AC motor 10 is driven by this three-phase alternating current. <funktionskonfiguration>

[0031] Fig. 2 is a functional block diagram of the control unit 13. With reference to Fig. 2, the control unit includes, as its main functional configuration, a temperature estimation unit 102, an allowable current calculation unit 104, a rotor position estimation unit 106, a command current calculation unit 108, a command voltage calculation unit 110, a PWM signal generation unit 112, and a phase shift unit 114. These functions are mainly implemented by, for example, the CPU 22 of the control unit 13, which executes the program stored in the memory 23.

[0032] In the present embodiment, the control unit 13 has a warm-up control mode for controlling a direct current to be supplied as a d-axis current to the AC motor 10, and a normal control mode for controlling an alternating current to be supplied to the AC motor 10. The control unit 13 switches the control mode from the warm-up control mode to the normal control mode when the predetermined condition regarding the temperature of the capacitor 20 is satisfied. In the present embodiment, the predetermined condition is considered satisfied when the temperature of the capacitor 20, detected based on the detection signal from the temperature sensor 21, becomes equal to or greater than a predetermined temperature A, which will be described later.

[0033] The temperature estimation unit 102 estimates the temperature of the capacitor 20 based on the detection signal (detected temperature) from the temperature sensor 21. Specifically, the memory 23 stores information (e.g., a relationship expression or a table) that describes the relationship between the temperature at the position where the temperature sensor 21 is provided and the temperature of the capacitor 20.

[0034] Since the temperature sensor 21 in the present embodiment is disposed on a substrate in which a switching element is formed, the memory 23 stores the relationship expression showing the relationship between the temperature of this substrate and the temperature of the capacitor 20. This relationship expression is established by performing a simulation in advance or actually driving the AC motor 10. Accordingly, the temperature estimation unit 102 can estimate the temperature of the capacitor 20 based on the temperature detected by the temperature sensor 21 and this relationship expression.

[0035] The allowable current calculation unit 104 calculates the maximum allowable motor current value at the temperature estimated by the temperature estimation unit 102 based on the information (e.g., a map shown in FIG. 10.10). Fig. 3), which shows a relationship between the temperature of the capacitor stored in the memory 23 and the maximum allowable motor current value. It should be understood that the maximum allowable motor current value is the maximum value of the motor current at which the components of the inverter device 12 are not damaged by the surge current caused by an equivalent series resistance Rs of the capacitor 20.

[0036] Fig. Figure 3 is a diagram showing the relationship between the capacitor temperature and the maximum allowable motor current. With reference to Fig. 3, the figure (map) shows this relationship between the temperature of the capacitor and the maximum allowable motor current value, and the current value required to generate a torque required to start the AC motor 10. It is also shown that the maximum allowable motor current value becomes equal to or greater than a current value required to generate a torque required to start the AC motor 10 when the capacitor exhibits a temperature equal to or greater than the prescribed temperature A.

[0037] Again with reference to Fig. 2, the rotor position estimation unit 106 estimates the position (a phase angle θ) and the speed of the rotor based on the output signals from the current sensors 18a, 18b and the voltage sensor 19. Specifically, the rotor position estimation unit 106 calculates a voltage pulse to be applied based on the voltage value detected by the voltage sensor 19, applies the calculated voltage pulse to the U-phase, the V-phase, and the W-phase of the AC motor 10, and detects a value of the current flowing through a junction of each of the U-phase, the V-phase, and the W-phase through the current sensors 18a and 18b. Then, the rotor position estimation unit 106 estimates the position of the rotor based on the data stored in the memory 23, the current values ​​detected by the current sensors 18a and 18b, and the voltage value detected by the voltage sensor 19.The data stored in the memory 23 is, for example, a program for estimating the position of the rotor based on the current values ​​detected by the current sensors 18a, 18b and the voltage value detected by the voltage sensor 19.

[0038] The command current calculation unit 108 sets a command d-axis current value and a command q-axis current value based on the torque command value of the AC motor 10 and the maximum allowable motor current value calculated by the allowable current calculation unit 104.

[0039] The command voltage calculation unit 110 calculates a detected d-axis current value and a detected q-axis current value, each indicating a detected value of the current flowing through the AC motor 10, based on the current flowing through each connection of the current sensors 18a and 18b using the U-phase, V-phase, and W-phase, and also on the phase θ calculated by the rotor position estimation unit 106. Then, the command voltage calculation unit 110 calculates a command d-axis voltage value based on the difference between the command d-axis current value and the detected d-axis current value, and also calculates a command q-axis voltage value based on the difference between the command q-axis current value and the detected q-axis current value.

[0040] The PWM signal generation unit 112 generates command voltage values ​​Vu, Vv, and Vw for the coils 6, 7, and 8 of the three phases of the AC motor 10 based on the command d-axis voltage value and the command q-axis voltage value, and then generates a PWM signal required to obtain the command voltage values ​​Vu, Vv, and Vw.

[0041] In the warm-up control mode, the phase shift unit 114 shifts a phase of at least one of the three-phase PWM signals generated by the PWM signal generation unit 112 (phase shift processing) and outputs the PWM signals after phase shift processing to the inverter circuit 16. The phase shift processing unit 114 outputs the PWM signals generated by the PWM signal generation unit 112 to the inverter circuit 16 without shifting the phase. By this PWM signal, each of the switching elements Q1 to Q6 of the inverter circuit 16 is driven to be on / off.

[0042] Then, the positive-phase and negative-phase PWM signals for each of the U-phase, V-phase, and W-phase are output to the inverter circuit to control the AC motor 10. The positive-phase PWM signal and the negative-phase PWM signal are complementary to each other. When one of these positive-phase and negative-phase PWM signals is at an active level, turning on the switching elements, the other of these PWM signals is generally at an active level, turning off the switching elements. It should be understood that a dead time may occur where the positive-phase and negative-phase PWM signals are each at an inactive level.

[0043] Accordingly, the PWM signal of one phase in the present embodiment is represented by a concept that includes a positive-phase PWM signal and a negative-phase PWM signal. Specifically, the PWM signal of a U phase includes a positive-phase and negative-phase PWM signal supplied to the switching elements Q1 and Q2, respectively. Similarly, the PWM signal of a V phase includes positive-phase and negative-phase PWM signals supplied to the switching elements Q3 and Q4, respectively. The PWM signal of a W phase includes positive-phase and negative-phase PWM signals supplied to the switching elements Q5 and Q6, respectively.

[0044] Specifically, in the warm-up control mode, the phase shift unit 114 shifts the phase of at least one of the PWM signals of the three phases output to the inverter in the normal control mode, so that the time period during which polarities of output voltages of the three phases output from the inverter circuit 16 are equal is shorter in the warm-up control mode than in the normal control mode. With reference to Fig. 4A and Fig. 4B, the phase shift processing is described in detail below.

[0045] Fig. 4A and Fig. 4B are schematic diagrams showing an output voltage waveform of the inverter circuit 16 before and after a phase shift. In particular, Fig. 4A shows an output voltage waveform after a phase shift, while Fig. 4B shows an output phase waveform before a phase shift. In addition, "H" indicates each of the Fig. 4A and Fig. 4B indicates that the output voltage is at a high voltage level (high polarity), and "L" indicates that the output voltage is at a low voltage level (low polarity).

[0046] The PWM signal, which is a pulse-width-controlled square wave signal, is used to control the output voltage output from the inverter circuit 16. The PWM signals corresponding to the U-phase, V-phase, and W-phase are output to the inverter circuit 16. The PWM signals of the three phases have their respective prescribed phases and operating conditions.

[0047] As in Fig. 4A and Fig. 4B when the output voltage waveform is before a phase shift ( Fig. 4B) and the output voltage waveform after a phase shift ( Fig. 4A), it turns out that the electrical conduction time of the AC motor 10 after the phase shift is relatively longer than before the phase shift in one period of the PWM carrier (carrier wave). In particular, the time period during which a voltage is applied between the UW phases and the V phase and between the U phase and the VW phases is longer after the phase shift than before the phase shift. In other words, the time period during which the polarities of the output voltages of the three phases (a U phase, a V phase, a W phase) are the same (each phase has a high polarity or a low polarity) is shorter after the phase shift than before the phase shift (the same polarity time period: the time period indicated by each hatched area in Fig. 4A and Fig. 4B).

[0048] Accordingly, when the switching elements Q1 to Q6 are operated to switch based on the PWM signals after the phase shift, the current flowing into and out of the capacitor 20 is increased compared to the case before the phase shift. Therefore, the rate at which the temperature of the capacitor 20 is raised can be increased, with the result that the warm-up operation can be completed sooner.

[0049] Further, based on the phases and duty ratios of the PWM signals of the three phases output to the inverter in the normal control mode, the PWM signal generation unit 112 performs phase shift processing so that the same polarity time period is the shortest in the warm-up control mode. In the examples of Fig. 4A and Fig. 4B, the phase of the output voltage of the V-phase is shifted, for example ( Fig. 4A) by shifting the phase of the PWM signal of a V-phase from the state before the phase shift ( Fig. 4B), so that the same polarity time period is the shortest. It should be noted that a phase of at least one of the PWM signals of the three phases only needs to be shifted, which can be such a configuration as the state after which the phase shift in Fig. 4A is implemented by shifting phases of the PWM signals of the two or three phases from the state before the phase shift to Fig. 4B.

[0050] Additionally, the rotor position estimation unit 106 is used to enable sensorless control for rotation control of the rotor of the AC motor 10 based on the estimated position and speed of the rotor. Sensorless control is performed to rotate the motor based on the estimated values ​​obtained by estimating the rotation speed of the rotor from an input voltage, a motor current, and the like, without using a rotation speed sensor, such as a coordinate converter, to detect the rotation position of the motor. <verarbeitungsprozedur>

[0051] Fig. 5 is a flowchart showing warm-up control processing executed by the control unit 13. Fig. 6 is a waveform diagram showing two phases (a U phase and a W phase) of current waveforms of the AC motor 10. Fig. 6 shows that the control unit 13 performs control in the warm-up control mode from time T1 to time T2 and then performs control in the normal control mode at and after time T2. The normal control mode is further divided into a forced synchronization control mode (from time T2 to time T3) and a sensorless control mode (at and after time T3).

[0052] When the inverter device 12 is started, the CPU 22 of the control unit 13 estimates the temperature of the capacitor 20 based on the detection signal input from the temperature sensor 21 (step S10). Then, the CPU 22 determines whether the estimated temperature of the capacitor 20 (the estimated temperature of the capacitor 20) is equal to or greater than the prescribed temperature A (step S12). As shown in Fig. 3, the prescribed temperature A corresponds to a current value at which a torque required to start the AC motor 10 can be generated. In other words, the CPU 22 determines whether the maximum allowable motor current value at the estimated temperature of the capacitor 20 is less than a value at which a torque required to start the AC motor 10 can be generated.

[0053] Again with reference to Fig. 5, when the estimated temperature of the capacitor 20 is equal to or greater than the prescribed temperature A (YES in step S12), the CPU 22 performs control in the normal control mode in which an alternating current is supplied to the AC motor 10 to drive the AC motor 10 (step S24).

[0054] Specifically, the CPU 22 outputs the PWM signals of the three phases to control the inverter circuit 16 and adjusts the current value supplied to the AC motor 10 so that the AC motor 10 achieves a target speed and torque, while the d-axis current and the q-axis current are each set to a value equal to or less than the maximum prescribed motor current value. Accordingly, the rotor of the AC motor 10 starts to rotate. In this case, the current waveform in the normal control mode corresponds to the current waveform at and after T2 shown in Fig. 6, and thus it turns out that the alternating current is supplied to the AC motor 10.

[0055] On the other hand, if the estimated temperature of the capacitor 20 is lower than the prescribed temperature A (NO in step S12), the CPU 22 executes the process from step S14 onwards to perform control in the warm-up control mode in which a direct current is supplied as a d-axis current. In this case, the current waveform in the warm-up control mode corresponds to the current waveform from T1 to T2 shown in Fig. 6, and thus it turns out that a direct current is supplied to the alternating current motor 10.

[0056] Then, the CPU 22 calculates the maximum allowable motor current value at the estimated temperature of the capacitor 20 based on the Fig. 3 and stored in the memory 23 (step S14). Then, the CPU 22 estimates the position (a phase θ) of the rotor based on the detection signals of the current sensors 18a, 18b and the voltage sensor 19 (step S16).

[0057] Then, the CPU 22 determines the command d-axis voltage value and the command q-axis voltage value based on the detection signals of the current sensors 18a, 18b and the phase θ, and then generates PWM signals of the three phases so that the d-axis motor current value and the q-axis motor current value assume a command d-axis current value (the maximum allowable motor current value) and a command q-axis current value (0A), respectively (step S20). Since the CPU 22 controls the command q-axis current value to be set to 0A in the warm-up control mode, the command d-axis current value is the maximum allowable motor current value. Accordingly, a direct current of the maximum allowable motor current value flows through the AC motor 10, and this direct current is caused to flow into and out of the capacitor 20 by the switching operation of the switching elements Q1 to Q6. The temperature of the capacitor 20 increases as the direct current flows into and out of the capacitor 20.

[0058] Then, the CPU 22 shifts a phase of at least one of the generated three-phase PWM signals and outputs the PWM signals after phase shift processing to the inverter circuit 16 (step S22). Specifically, the CPU 22 shifts a phase of at least one of the three-phase PWM signals output from the inverter circuit 16 in the normal control mode so that a time period during which the polarities of output voltages of the three phases output from the inverter 16 are equal is shorter than that in the normal control mode. Then, the CPU 22 outputs the shifted phases to the inverter circuit 16.

[0059] Then, the CPU 22 repeats the process from step S10 to step S22 until the estimated temperature of the capacitor 20 becomes a temperature equal to or greater than the prescribed temperature A. When the estimated temperature of the capacitor 20 becomes equal to or greater than the prescribed temperature A (YES in step S12), the CPU 22 then ends the warm-up control mode and proceeds to the normal control mode (switches the mode). Specifically, the CPU 22 controls the inverter circuit 16 to supply an alternating current to the three-phase AC motor by outputting the PWM signals of the three phases without performing the phase shift processing described above. In other words, these PWM signals of the three phases each have one phase before the phase shift processing described above. <Effekte der Ausführungsform>

[0060] According to the present embodiment, by shifting a phase in the warm-up control mode, the electrical conduction time of the AC motor is extended more in this warm-up control mode than in the case where a phase is not shifted. Thereby, the ripple amount of the input current or the motor current is increased, so that the current input to or output from the capacitor can be increased. Accordingly, the temperature of the capacitor can rise more quickly, with the result that the warm-up operation can be completed sooner. On the other hand, the ripple amount of the input current or the motor current is smaller in the normal control mode than in the warm-up control mode. This can prevent deterioration of motor control and efficiency.

[0061] Furthermore, according to the present embodiment, the inverter circuit is controlled so that the current flowing into the AC motor is equal to or less than a maximum allowable motor current value. Accordingly, the components of the inverter device can be prevented from being damaged by the surge voltage caused by the capacitor's ESR at a relatively low temperature. <modifikation>(Switching control mode)

[0062] In the above-described embodiment, the configuration was described in which the temperature of the capacitor 20 is estimated based on the detection signal by the temperature sensor 21, and the control mode is switched from the warm-up control mode to the normal control mode when the estimated temperature reaches the prescribed temperature A, but the present embodiment is not limited to this configuration.

[0063] For example, since the current flowing through the capacitor 20 increases in accordance with the elapsed time from the start of the warm-up control mode, the temperature of the capacitor 20 rises. Accordingly, the control unit 13 may be configured to measure the elapsed time from the start of the warm-up control mode using a timer (not shown) or the like, and then switch the control mode from the warm-up control mode to the normal control mode when the measured time becomes 1 or longer than a predetermined time. The predetermined time means a period of time from the start of the warm-up control mode until the temperature of the capacitor 20 reaches the prescribed temperature A.

[0064] In this case, the memory 20 stores a relationship (or table) showing the relationship between the elapsed time from the start of the warm-up control mode and the temperature of the capacitor 20. This relationship is established by performing a simulation in advance or an actual operation of the AC motor 10. The control unit 13 can estimate the temperature of the capacitor 20 based on the elapsed time and the relationship. If the measured elapsed time is equal to or longer than an elapsed time during which the temperature of the capacitor 20 reaches the prescribed temperature A, then the control unit 13 switches the control mode from the warm-up control mode to the normal control mode. (phase shift)

[0065] In the above-described embodiment, a configuration was explained in which the phase shift processing is executed only in the warm-up control mode, but the embodiment is not limited to this configuration. For example, the control unit 13 may be configured to output PWM signals of the three phases after the phase shift processing during a period from the start of the warm-up control mode to the start of sensorless control (from T1 to T3 in Fig. 6).

[0066] In particular, with reference to Fig. 6 the phase shift processing executed in the warm-up control mode (from T1 to T2 in Fig. 6) and the forced synchronization control mode (from T2 to T3 in Fig. 6), but is not used in the sensorless control mode (at and after T3 in Fig. 6). The forced synchronization control mode is designed to forcibly increase the speed of the rotor at a prescribed acceleration during a period of time from the time the rotor starts rotating until the rotor reaches a speed at which excellent phase calculation accuracy is achieved.

[0067] In this case, the control unit 13 performs phase shift processing to shift a phase of at least one of the three-phase PWM signals output to the inverter in the sensorless control mode, so that a time period during which the polarities of the three-phase output voltages output from the inverter circuit 16 are the same is shorter in the warm-up control mode than in the sensorless control mode. Then, the control unit 13 controls the inverter circuit 16 to supply a direct current to the AC motor as the d-axis current by outputting the three-phase PWM signals each having one phase after the phase shift processing.

[0068] In the forced synchronization control mode, the control unit 13 further controls the inverter circuit 16 to supply an alternating current to the AC motor by outputting the PWM signals of the three phases each having one phase after the phase shift processing, while forcibly increasing the speed of the rotor at the prescribed acceleration.

[0069] Then, in the sensorless control mode, the control unit 13 estimates the position of the rotor of the AC motor 10 based on the voltage or current applied to the three phases of the AC motor 10, performs sensorless control to rotate the rotor based on the estimated rotor position, and controls the inverter circuit 16 by outputting the PWM signals of the three phases, each of which has a phase before phase shift processing. In addition, the control mode is switched from the forced synchronization control mode to the sensorless control mode when the rotor speed becomes equal to or greater than the prescribed speed. Other embodiments

[0070] Although the configuration for performing sensorless control was described in the above embodiment, the embodiment is not limited to this configuration. The rotor position of the motor can be detected by using a rotation speed sensor, such as a coordinate converter, provided in the inverter device 12, without estimating the position of the rotor based on the current values ​​detected by the current sensors 18a, 18b and the voltage value detected by the voltage sensor 19.

[0071] The configuration shown as an embodiment described above, which is only one example of the configuration of the present invention, may be combined with another known technique or may also be configured by a modification such as partial omission within a range not deviating from the feature of the present invention.

[0072] Also in the embodiment described above, an appropriate combination of the configurations described in the modification may be used for implementation.

[0073] Although the present invention has been described and illustrated in detail, it should be clearly understood that the same is for the purpose of illustration only and should not be taken in a limiting sense, with the scope of the present invention being interpreted by the terms of the appended claims.< / modifikation> < / verarbeitungsprozedur> < / funktionskonfiguration>

Claims

[1] Inverter device (12) for controlling a three-phase AC motor (10), the inverter device (12) comprising: an inverter circuit (16) arranged to supply a current to the three-phase AC motor (10); a capacitor (20) provided on an input side of the inverter circuit (16); and a control unit (13) arranged to control the inverter circuit (16) by outputting PWM signals from the phase to the inverter circuit (16), wherein the control unit (13) contains a first control mode and a second control mode each as a control mode for controlling the inverter circuit (16), the control unit (13) is arranged to: in the first control mode, Performing phase shift processing for shifting a phase of at least one of the PWM signals of three phases output to the inverter circuit (16) in the second control mode so that a time period during which polarities of output voltages of three phases output from the inverter circuit (16) are the same is shorter in the first control mode than the time period in the second control mode; Controlling the inverter circuit (16) to supply a direct current to the three-phase AC motor (10) as a d-axis current by outputting the PWM signals of the three phases, each of which has a phase after phase shift processing; and Switching the control mode from the first control mode to the second control mode when a predetermined condition regarding a temperature of the capacitor (20) is met, and the control unit (13) is arranged, in the second control mode, to control the inverter circuit (16) to supply an alternating current to the three-phase AC motor (10) by outputting the PWM signals of three phases, each of which has a phase before the phase shift processing. [2] The inverter device (12) according to claim 1, further comprising a temperature sensor (21) configured to detect a temperature for estimating the temperature of the capacitor (20), wherein the control unit (13) is configured to: Estimating the temperature of the capacitor (20) based on the detected temperature; Determining that the predetermined condition is satisfied when the estimated temperature becomes equal to or greater than a predetermined temperature; and Switching the control mode from the first control mode to the second control mode. [3] Inverter device (12) according to claim 1, wherein the control unit (13) is arranged to: Measuring an elapsed time from a start of control of the inverter circuit (16) in the first control mode; Determining that the predetermined condition is satisfied when the measured elapsed time becomes equal to or longer than a predetermined time; and Switching the control mode from the first control mode to the second control mode. [4] The inverter device (12) according to any one of claims 1 to 3, wherein the control unit (13) is arranged to perform the phase shift processing so that the time period in the first control mode is the shortest, based on phases and duty ratios of the PWM signals of the three phases output to the inverter circuit (16) in the second control mode. [5] Inverter device (12) for controlling a three-phase AC motor (10), the inverter device (12) comprising: an inverter circuit (16) arranged to supply a current to the three-phase AC motor (10); a capacitor (20) provided on an input side of the inverter circuit (16); and a control unit (13) arranged to control the inverter circuit (16) by outputting PWM signals of three phases to the inverter circuit (16), wherein the control unit (13) includes a first control mode, a second control mode and a third control mode each as a control mode for controlling the inverter circuit (16), the control unit (13) is arranged to: in the first control mode, Performing phase shift processing for shifting a phase of at least one of the PWM signals of three phases output to the inverter circuit (16) in the third control mode so that a time period during which polarities of output voltages of three phases output from the inverter circuit (16) are the same is shorter in the first control mode than the time period in the third control mode; Controlling the inverter circuit (16) to supply a direct current to the three-phase AC motor (10) as a d-axis current by outputting the PWM signals of three phases each having one phase after the phase shift processing; and Switching the control mode from the first control mode to the second control mode when a predetermined condition regarding a temperature of the capacitor (20) is met, the control unit (13) is arranged, in the second control mode, to control the inverter circuit (16) to supply an alternating current to the three-phase AC motor (10) by outputting the PWM signals of the three phases, each of which has a phase after the phase shift, and the control unit (13) is designed to: in the third control mode, Estimating a position of a rotor of the three-phase AC motor (10) based on a voltage or a current applied to three phases of the three-phase AC motor (10); and performing sensorless control to rotate the rotor based on the estimated position of the rotor; and controlling the inverter circuit (16) by outputting the PWM signals of three phases, each of which has a phase before the phase shift processing to which the phase returns after the phase shift processing.

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