JP2007236188A - Inverter device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a small inverter device having small noise vibration and detecting phase current by software with few calculation processings. <P>SOLUTION: The inverter device includes a first current detector 15 for detecting a current between a lower arm switching element 3 of one phase among three phases and the negative side of a DC power supply 1 and with a second current detector 6 for detecting DC current between the DC power supply 1 and the inverter device 23. The first current detector 15 detects the phase current of the phase, and the second current detector 6 detects the phase current, other than the phase current which the first current detector 15 detects. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a phase current detection method for an inverter device that performs PWM modulation.

  Conventionally, as this type of phase current detection method, in an inverter device that drives a sensorless DC brushless motor by a sinusoidal wave drive method using PWM modulation, a method of detecting by a current sensor of a DC power supply line from the DC power supply to the inverter device is known. (For example, refer to Patent Document 1).

  This circuit will be described below. FIG. 17 shows an inverter device and its surrounding electric circuit. The control circuit 12 of the inverter device 21 detects the phase current for two phases based on the voltage from the shunt resistor 6. The phase current for the remaining one phase is calculated from the two current values (Kirchhoff's current law is applied at the neutral point of the stator winding 4). Based on these current values, an induced voltage by the magnet rotor 5 constituting the sensorless DC brushless motor 11 (hereinafter referred to as a motor) is calculated, and its position is detected. Based on a rotational speed command signal (not shown) by communication, etc., the switching element 2 (IGBT, FET, transistor, etc.) constituting the inverter circuit 10 is controlled, and the DC voltage from the battery 1 is PWM modulated. By switching at, a sinusoidal alternating current is output to the stator winding 4 constituting the motor 11. The diode 3 constituting the inverter circuit 10 serves as a return route for the current flowing through the stator winding 4. For the switching element 2, upper arm switching elements are defined as U, V, W, and lower arm switching elements are defined as X, Y, Z, and diodes corresponding to the switching elements U, V, W, X, Y, Z Is defined as 3U, 3V, 3W, 3X, 3Y, 3Z.

  Although details of phase current detection for two phases by the shunt resistor 6 are omitted, it is possible to know the phase current flowing in the power supply line (shunt resistor 6) when the upper arm switching elements U, V, W are turned on and off. . It does not flow when the upper arm switching element does not have an ON phase (de-energized, lower circulation). When only one phase is ON, the current of that phase flows (energized). When the two-phase is ON, the current of the remaining phase flows. (Energized) Does not flow when all three phases are ON (non-energized, upper circulation). Here, energization refers to a state in which power is supplied from the battery 1 to the inverter circuit 10 (motor 11), and non-energization refers to a state in which power is not supplied from the battery 1 to the inverter circuit 10 (motor 11). It is. In the non-energized state, the lower circulation is a state in which all of the lower arm switching elements X, Y, and Z are turned on and current is circulated between the lower arm and the motor 11, and the upper circulation is the upper arm switching. The elements U, V, and W are all turned on, and the current is circulating between the upper arm and the motor 11.

  FIG. 18 shows a characteristic diagram of a three-phase modulation waveform. A U-phase terminal voltage 41, a V-phase terminal voltage 42, a W-phase terminal voltage 43, and a neutral point voltage 29 are shown in 10% modulation. These terminal voltages are realized by duty (%) indicated on the vertical axis by PWM modulation. The neutral point voltage 29 is a value obtained by calculating the sum of the terminal voltages of each phase and dividing by 3. The phase voltage is a value obtained by subtracting the neutral point voltage from the terminal voltage, and is a sine wave.

  On the upper side of FIG. 19, the ON periods (Duty) of the upper arm switching elements U, V, W within one carrier (carrier cycle) at the phase of 60 degrees indicated by the broken line in FIG. 18 are displayed symmetrically from the center. ing. The ON period of the U-phase upper arm switching element U is represented by a thin solid line, the ON period of the V-phase upper arm switching element V is represented by a solid solid line, and the ON period of the W-phase upper arm switching element W is represented by a thick solid line. ing. Further, the lower circulation period (non-energization period) is indicated by a broken line arrow.

  The lower part of FIG. 19 shows the phase current flowing as a direct current in the direct current power line (shunt resistor 6) in the above state. When only the U phase is ON, the U phase current iU flows, and when the U phase and the W phase are ON, the remaining V phase current iV flows. However, the time during which these currents flow is short, and the control circuit 12 cannot detect the phase current based on the voltage from the shunt resistor 6. As a countermeasure when this phase current cannot be detected, a method of increasing or decreasing the ON period of some phases (upper arm switching elements) is shown.

  FIG. 20 shows an example of this correspondence. In the first half of the carrier cycle, the ON Δ period of the upper arm switching element U is increased and the ON period of the upper arm switching element V is decreased. As a result, the time during which the current flows becomes long, and the control circuit 12 can detect the phase current by the voltage from the shunt resistor 6. When only the U phase is ON, the phase current iU of the U phase can be detected, and when the U phase and the W phase are ON, the phase current iV of the V phase can be detected. This period is set as a detection period and is indicated by a solid line arrow, and a detectable current phase is shown in the vicinity of the solid line arrow. In this case, the detection period of the U-phase phase current iU is indicated as U, and the detection period of the V-phase phase current iV is indicated as V.

  In this way, the phase current can be detected, but the energization time becomes longer, and the current flows more than the original PWM modulation. FIG. 21 shows the increased U-phase current as ΔiU and the V-phase current as ΔiV. Due to the ΔiU and ΔiV, the power supply from the battery 1 to the inverter circuit 10 (motor 11) becomes larger than the original PWM modulation.

  Unlike the above method, a method of detecting the phase current with the lower arm has also been proposed (see, for example, Patent Document 2). This method will be described below.

  FIG. 22 shows an inverter device and its peripheral circuits. 17 differs from FIG. 17 in that there is no shunt resistor 6, a shunt resistor 15, a shunt resistor 16, and a shunt resistor 17 are added, and the control circuit 12 is a control circuit 13. Is the same as FIG. 17, and the symbols and the like are applied as they are. Also, functions other than current detection are applied as they are. The control circuit 13 of the inverter device 22 is provided between the U-phase lower arm and the ground, the shunt resistor 15 provided between the V-phase lower arm and the ground, and the W-phase lower arm and the ground. The phase current is calculated from the voltage from each shunt resistor 17. The current flows through the shunt resistor 15 (the current can be detected) while the lower arm switching element X is ON, and the current flows through the shunt resistor 16 (the current can be detected) when the lower arm switching element Y is ON. During the period, the current flows through the shunt resistor 17 (the current can be detected) during the ON period of the lower arm switching element Z.

In this method, the maximum current of the upper arm switching element cannot be detected, that is, the overcurrent protection of the upper arm switching element cannot be performed. When the upper arm switching element 1 phase is ON and the lower arm switching element 2 phase is ON, to detect the current of the upper arm switching element, the sum of the currents of the lower arm switching element 2 must be taken. Therefore, in order to perform overcurrent protection of the upper arm switching element, a circuit that outputs the sum of the currents of the respective phases of the lower arm switching element is required.
JP 2003-189670 A (page 2, claim 2, page 14, FIG. 1, page 15, FIG. 9) JP 2003-284374 A (page 7, FIG. 1)

  As described above, each phase current detection method for an inverter device that performs PWM modulation has problems. In the detection method using the current sensor of the DC power supply line, if the current flowing time is short and cannot be detected, it is necessary to increase or decrease the ON period of the upper arm switching elements of some phases. As a result, a current flows more than the original PWM modulation and power is supplied. Therefore, it becomes a factor of noise and noise deterioration. Therefore, the increase or decrease in the ON period of the upper arm switching elements of some phases must be minimized and minimized.

  When an electric compressor used in an air conditioner is driven by an inverter device, it is possible to use a soundproof device such as a soundproof box in a room air conditioner in order to prevent the noise, but the electric compressor used in a vehicle air conditioner In a compressor, it is difficult to use a soundproofing device due to restrictions such as mounting space and weight. Further, although vibration must be suppressed to prevent vibration transmission to the passenger compartment, it is difficult to use a vibration isolator as well. The room air conditioner is also required to be as low vibration and low noise as possible in consideration of the environment.

  Further, in order to detect the phase current by increasing or decreasing the ON period of the upper arm switching element, the control software becomes complicated and a high-performance control circuit (microcomputer) is required. That is, the calculation and execution of the time to increase or decrease and the calculation and execution of the detection timing must be performed in addition to the original PWM modulation, overcurrent protection, communication function, etc., and high-speed calculation processing is required. Depending on the control circuit (microcomputer), it will be difficult to realize. Therefore, the calculation and execution of the time to increase or decrease, and the calculation and execution of the detection timing must be minimized.

  In the method of detecting the phase current with the lower arm, there are shunt resistors in all three phases, and a circuit that outputs the sum of the currents of the lower arm switching elements for overcurrent protection is also required. Many obstacles to miniaturization. The shunt resistor is a power resistor and has a large size, and requires a printed circuit board space for heat dissipation. For example, the power consumption is 4 W when the resistance value is 10 mΩ and the current value is 20 A. For this reason, in an inverter device mounted on an electric compressor, downsizing is particularly important, which makes it difficult to realize.

  SUMMARY OF THE INVENTION The present invention solves such a conventional problem, and an object of the present invention is to provide an inverter device that can detect a phase current with software that is small in noise and vibration, small in size, and requires little arithmetic processing.

  In order to solve the above problems, an inverter device according to the present invention includes three phases of an upper arm switching element connected to the positive side of a DC power source and a lower arm switching element connected to the negative side of the DC power source. In an inverter device that outputs a sinusoidal three-phase alternating current by switching a direct current voltage by PWM modulation, a current between a lower arm switching element of one of the three phases and the negative side of the direct current power source is detected. A first current detector and a second current detector for detecting a DC current between the DC power source and the inverter device, and the first current detector detects a phase current of the phase provided with the current detector; The phase current other than the phase current detected by the first current detector is detected by the second current detector.

  With the above configuration, since the phase current for one phase is detected by the lower arm, the current sensor of the DC power supply line needs to detect only one of the remaining two phases. Therefore, the increase or decrease in the ON period of the upper arm switching elements of some phases can be reduced. Thereby, noise vibration can be reduced. Further, the calculation and execution of the time to increase or decrease and the calculation and execution of the detection timing are also reduced. As a result, the calculation processing of the control software is reduced and the implementation is facilitated.

  In addition, the second current detector that detects the direct current can detect the maximum current of the upper arm switching element and can perform overcurrent protection. Therefore, compared with the method of detecting the phase current with the lower arm, the circuit for outputting the sum of the currents of the three current detectors and the respective phases of the lower arm switching elements can be reduced to two current detectors.

  When the phase current detected by the first current detector can be detected also by the second current detector (without increasing or decreasing the ON period of the upper arm switching element of some phases) By comparing the current detection values, failure diagnosis of both current detectors can be performed. Since the second current detector has an overcurrent protection function, it is useful in terms of reliability to perform fault diagnosis.

  The inverter device of the present invention is small in noise and vibration, small in size, and can detect a phase current with software with little arithmetic processing.

  The first invention comprises three phases of an upper arm switching element connected to the positive side of the DC power source and a lower arm switching element connected to the negative side of the DC power source, and switches the DC voltage of the DC power source by PWM modulation. 1st current detector and DC power supply which detect the current between the lower arm switching element of one phase among the three phases and the negative side of the DC power supply in the inverter device which outputs a sinusoidal three-phase AC current And a second current detector for detecting a direct current between the inverter devices, the phase current of the phase provided with the current detector is detected by the first current detector, and the second current detector A phase current other than the phase current detected by the first current detector is detected.

  With the above configuration, since the phase current for one phase is detected by the lower arm, the current sensor of the DC power supply line needs to detect only one of the remaining two phases. Therefore, the increase or decrease in the ON period of the upper arm switching elements of some phases can be reduced. Thereby, noise vibration can be reduced. Further, the calculation and execution of the time to increase or decrease and the calculation and execution of the detection timing are also reduced. As a result, the calculation processing of the control software is reduced and the implementation is facilitated. In addition, the second current detector that detects the direct current can detect the maximum current of the upper arm switching element and can perform overcurrent protection. Therefore, compared with the method of detecting the phase current with the lower arm, the circuit for outputting the sum of the currents of the three current detectors and the respective phases of the lower arm switching elements can be reduced to two current detectors.

  As a result, an inverter device that is small in noise vibration, small in size, and capable of detecting the phase current with simple control software can be obtained.

  According to a second aspect of the present invention, in the inverter device of the first aspect, the same ON period is reduced from the ON period of the upper arm switching element in all three phases within the carrier cycle, whereby the first current detector Thus, the phase current of the phase provided with the current detector is detected. Accordingly, an ON period can be provided even in a phase where the lower arm switching element of the phase in which the first current detector is provided is not turned ON by 100% modulation, and the current is detected by the first current detector. The phase current of the phase provided with the detector can be detected. The present invention can also be applied to a case where the lower arm switching element has a short ON period or a case where the lower arm switching element is close to 100% modulation such as 95% modulation. According to the above method, since the phase current of the phase provided with the current detector can always be detected by the first current detector, the consistency of the software can be maintained.

  At this time, the same ON period is reduced in all three phases, and the ON period of only a part of the phases (upper arm switching elements) is not increased or decreased. The PWM modulation does not change. That is, no current flows beyond the PWM modulation. In addition, since the energization period is divided into the first half and the second half in the carrier cycle and the PWM modulation becomes fine, the current becomes smooth and noise vibration is reduced.

  The third invention comprises three phases of an upper arm switching element connected to the positive side of the DC power source and a lower arm switching element connected to the negative side of the DC power source, and switches the DC voltage of the DC power source by PWM modulation. 1st current detector and DC power supply which detect the current between the upper arm switching element of one phase among the three phases and the positive side of the DC power supply in the inverter device which outputs sinusoidal three-phase AC current And a second current detector for detecting a direct current between the inverter devices, the phase current of the phase provided with the current detector is detected by the first current detector, and the second current detector A phase current other than the phase current detected by the first current detector is detected.

  With the above configuration, since the phase current for one phase is detected by the upper arm, only one of the remaining two phases needs to be detected by the current sensor of the DC power supply line. Therefore, the increase or decrease in the ON period of the upper arm switching elements of some phases can be reduced. Thereby, noise vibration can be reduced. Further, the calculation and execution of the time to increase or decrease and the calculation and execution of the detection timing are also reduced. As a result, the calculation processing of the control software is reduced and the implementation is facilitated. In addition, the second current detector that detects the direct current can detect the maximum current of the upper arm switching element and can perform overcurrent protection. Therefore, compared with the method of detecting the phase current with the lower arm, the circuit for outputting the sum of the currents of the three current detectors and the respective phases of the lower arm switching elements can be reduced to two current detectors.

  As a result, an inverter device that is small in noise vibration, small in size, and capable of detecting the phase current with simple control software can be obtained.

  According to a fourth invention, in the inverter device of the third invention, the same ON period is added to the ON period of the upper arm switching element in all three phases in the carrier cycle, whereby the first current detector Thus, the phase current of the phase provided with the current detector is detected. Accordingly, an ON period can be provided even in a phase where the upper arm switching element of the phase in which the first current detector is provided is not turned ON by 100% modulation, and the current is detected by the first current detector. The phase current of the phase provided with the detector can be detected. The present invention can also be applied to a case where the ON period of the upper arm switching element is small, or a case where the upper arm switching element is close to 100% modulation such as 95% modulation. By the above method, consistency of software can be maintained.

  At this time, the same ON period is added to all three phases, and the ON period of only a part of the phases (upper arm switching elements) is not increased or decreased. The PWM modulation does not change. That is, no current flows beyond the PWM modulation. In addition, since the energization period is divided into the first half and the second half in the carrier cycle and the PWM modulation becomes fine, the current becomes smooth and noise vibration is reduced.

  According to a fifth aspect of the present invention, in the inverter device according to the first to fourth aspects of the invention, the phase current detection by the second current detector has a smaller ON period adjustment of the upper arm switching element required for the phase current detection. The phase current is detected. Thereby, ON period adjustment can be suppressed small. Therefore, noise vibration can be reduced.

  According to a sixth invention, in the inverter devices of the first to fourth inventions, the second current detector detects a phase current for two phases other than the phase current detected by the first current detector, and the 2 The phase current value of the remaining phase calculated from the phase current of the phase is compared with the detection value of the first current detector. Thereby, failure diagnosis of the first current detector, the second current detector, and the current detection related circuit can be performed.

  According to a seventh invention, in the inverter device of the first to fourth inventions, the phase current detected by the first current detector is also detected by the second current detector, and the detection value of the first current detector is detected. Is to be compared. Thereby, failure diagnosis of the first current detector, the second current detector, and the current detection related circuit can be performed.

  According to an eighth invention, in the inverter device of the first to seventh inventions, the current detector is a shunt resistor, which is smaller and has improved vibration resistance as compared with a current detector using a Hall element. Can do.

  A ninth aspect of the invention is the inverter device of the first to eighth aspects of the invention, wherein the three-phase alternating current is output to the motor of the electric compressor. Electric compressors used in air conditioners and refrigerators have a long operation time and are greatly affected by noise and vibration because they are indoors. Therefore, the present low-noise, low-vibration inverter device is useful.

  A tenth aspect of the invention is the inverter device according to the ninth aspect of the invention, which is mounted on an electric compressor. The inverter device mounted on the electric compressor is limited in installation space, needs to be downsized, and requires vibration resistance against vibrations from the motor. Therefore, this inverter is small and can drive the motor with low vibration. The device is useful.

  An eleventh aspect of the invention is the inverter device according to the first to tenth aspects of the invention, which is mounted on a vehicle. In the case of a vehicle, the mounting space is limited and it is necessary to reduce the size, and it is difficult to install a soundproofing device and a vibrationproofing device due to weight and other constraints, and this inverter device having a small size, low noise, and low vibration is useful.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. Note that the present invention is not limited to the embodiments.

(Embodiment 1)
FIG. 1 shows an inverter device 23 according to Embodiment 1 of the present invention and an electric circuit around it. 22 in the background art is that the shunt resistor 16 and the shunt resistor 17 are not provided, the shunt resistor 6 is added, and the control circuit 13 is the control circuit 14. This is the same as FIG. 22, and the symbols and the like are applied as they are. Also, functions other than current detection are applied as they are.

  The shunt resistor 15 can detect the U-phase current iU. This will be described with reference to FIG. FIG. 2 is a characteristic diagram showing a lower arm ON period and a lower circulation period in a phase of 30% to 90 degrees of 10% three-phase modulation. Each phase waveform in 10% three-phase modulation is as shown in FIG. The ON period of the U-phase lower arm switching element X is represented by a thin solid line, the ON period of the V-phase lower arm switching element Y is represented by a solid solid line, and the ON period of the W-phase lower arm switching element Z is represented by a thick solid line. ing. Further, the lower circulation period is indicated by a broken line arrow. However, in order to simplify the display, a dead time for preventing a short circuit between the upper arm switching element and the lower arm switching element is omitted. The phase of 60 degrees corresponds to a period obtained by subtracting the upper arm ON period shown in FIG. 19 within the carrier period. The ON period of the lower arm switching element X is ensured in each phase (iU and iV in the first half of the carrier cycle in FIG. 20), and the U-phase phase current iU can be detected by the shunt resistor 15.

  Since the phase current iU of the U phase can be detected, it is sufficient that the phase current for one phase other than the U phase (the phase current iV of the V phase or the phase current iW of the W phase) can be detected by the shunt resistor 6. The remaining phase current is determined by applying Kirchhoff's current law at the neutral point of the stator winding 4. The effect of the phase current detection for only one phase will be described with reference to FIGS. FIG. 3 shows a state in which the ON period of the upper arm switching element V is reduced so that only the V-phase current iV can be detected in FIG. FIG. 4 shows the phase current ΔiV of the V phase thus increased. Compared to FIG. 21, there is no increased phase current ΔiU for the U phase. Therefore, compared with the case where the phase current for two phases is detected (FIG. 20), the noise vibration in the case where the phase current for only one phase is detected (FIG. 3) is assumed to be approximately half.

  Next, other phases and modulation will be considered. FIG. 5 is a characteristic diagram showing the modulation of each phase waveform in 10% three-phase modulation. Check each phase indicated by the broken line. FIG. 6 shows the ON period, the detection period, and the lower circulation period of the upper arm in the phase of 30 degrees to 90 degrees. 7 shows the same for the phases 150 to 210 degrees, and FIG. 8 shows the same for the phases 270 to 330 degrees.

  The case of the present invention will be described with reference to FIGS. 6 to 8, the downward circulation period is sufficiently long. As a result, a sufficient ON period of the lower arm switching element X is secured (iU, iV time or more in the first half of the carrier cycle in FIG. 20), so that the U-phase phase current iU can be detected by the shunt resistor 15. Therefore, the shunt resistor 6 only needs to detect the V-phase phase current iV or the W-phase phase current iW.

  In FIG. 6, since iV can be detected at a phase of 30 degrees, it is not necessary to adjust (increase or decrease) the ON period of the upper arm switching element. Since iV and iW cannot be detected at a phase of 45 degrees, it is necessary to adjust (increase or decrease) the ON period of the upper arm switching element. Therefore, the phase current to be detected increases. As in this case, an increase in the phase current generated for detecting one phase current is set as Δi (as an average value). IV and iW cannot be detected even at a phase of 60 degrees, a phase of 75 degrees, and a phase of 90 degrees. Therefore, Δi occurs respectively. Thereby, with respect to FIG. 6, in the case of the present invention, a phase current increase of 4Δi occurs. However, iU can be detected at a phase of 90 degrees. Therefore, compared with iU detected by the shunt resistor 15, failure diagnosis of the shunt resistor 15, the shunt resistor 6 and the current detection related circuit can be performed based on the magnitude of the comparison result. In this case, the shunt resistor 6 detects phase currents for two phases.

  In FIG. 7, since iW can be detected at a phase of 150 degrees and iV can be detected at a phase of 210 degrees, it is not necessary to adjust (increase or decrease) the ON period of the upper arm switching element. IV and iW cannot be detected at 165 degrees, 180 degrees, and 195 degrees. Therefore, Δi occurs respectively. Accordingly, with respect to FIG. 7, in the case of the present invention, a phase current increase of 3Δi occurs. In phase 165 degrees, phase 180 degrees, and phase 195 degrees, either iV or iW may be detected, but it is preferable to detect the smaller ON period adjustment of the upper arm switching element. That is, it is preferable to detect iV by reducing the ON period of the upper arm switching element W at phase 165 degrees and adding the ON period of the upper arm switching element V at phase 195 degrees. At the phase of 165 degrees, the ON period of the upper arm switching element V can be added to detect iV, but the additional amount for iV detection is larger than the reduction amount for iW detection. Further, at the phase of 195 degrees, the ON period of the upper arm switching element W can be reduced to detect iW, but the reduction amount for iW detection is larger than the additional amount for iV detection. Therefore, the ON period adjustment of the upper arm switching element can be reduced. Therefore, noise vibration can be reduced. Both are the same at the phase of 180 degrees.

  In FIG. 8, since iW can be detected at a phase of 330 degrees, it is not necessary to adjust (increase or decrease) the ON period of the upper arm switching element. IV and iW cannot be detected at 270 degrees, 285 degrees, 300 degrees, and 315 degrees. Therefore, Δi occurs respectively. Thus, with respect to FIG. 8, in the case of the present invention, a phase current increase of 4Δi occurs. However, iU can be detected at a phase of 270 degrees. Therefore, compared with iU detected by the shunt resistor 15, failure diagnosis of the shunt resistor 15, the shunt resistor 6 and the current detection related circuit can be performed based on the magnitude of the comparison result. In this case, the shunt resistor 6 detects phase currents for two phases.

  From the above, with respect to FIGS. 6 to 8, it can be considered that an increase in the phase current of 11Δi occurs in the present invention.

  Next, the conventional case shown in the examples of FIGS. 17 and 20 will be described with reference to FIGS. Since there is no shunt resistor 15 for detecting the current of the lower arm, it is necessary to detect the phase current for two phases with the shunt resistor 6.

  In FIG. 6, since iV can be detected at a phase of 30 degrees and iU can be detected at a phase of 90 degrees, the ON period adjustment (increase or decrease) of the upper arm switching element is required for one phase. As a result, a phase current increase of Δi occurs. Since even one phase cannot be detected at 45 degrees, 60 degrees, and 75 degrees, it is necessary to adjust (increase or decrease) the ON period of the upper arm switching element for two phases. As a result, a phase current increase of 2Δi occurs. Thereby, with respect to FIG. 6, in the conventional case, an increase in phase current of 8Δi occurs.

  Similarly in FIG. 7, an increase in phase current of 8Δi occurs. The same applies to FIG. 8, and an increase in phase current of 8Δi occurs. 6 to 8, it can be considered that a phase current increase of 24Δi occurs in the conventional case.

  Therefore, with respect to FIGS. 6 to 8 (10% three-phase modulation), in the case of the present invention, it is considered that the increase in phase current, that is, noise vibration is about half (11 ÷ 24) compared to the conventional case.

  Next, consider 50% modulation. FIG. 9 is a characteristic diagram showing the modulation of each phase waveform in 50% three-phase modulation. Check each phase indicated by the broken line. FIG. 10 shows the upper arm ON period, the detection period, and the lower circulation period in the phase of 30 to 90 degrees. FIG. 11 shows the same for the phase of 150 to 210 degrees, and FIG. 12 shows the same for the phase of 270 to 330 degrees.

  The case of the present invention will be described with reference to FIGS. 10 to 12, the downward circulation period is sufficiently long. As a result, a sufficient ON period of the lower arm switching element X is secured (iU, iV time or more in the first half of the carrier cycle in FIG. 20), so that the U-phase phase current iU can be detected by the shunt resistor 15. Therefore, the shunt resistor 6 only needs to detect the V-phase phase current iV or the W-phase phase current iW.

  In FIG. 10, since iV can be detected at a phase of 30 degrees, a phase of 45 degrees, a phase of 60 degrees, and a phase of 75 degrees, it is not necessary to adjust (increase or decrease) the ON period of the upper arm switching element. IV and iW cannot be detected at a phase of 90 degrees. Therefore, Δi occurs. Thus, with respect to FIG. 10, in the case of the present invention, a phase current increase of 1Δi occurs. However, iU can be detected at 45 degrees, 60 degrees, 75 degrees, and 90 degrees. Therefore, compared with iU detected by the shunt resistor 15, failure diagnosis of the shunt resistor 15, the shunt resistor 6 and the current detection related circuit can be performed based on the magnitude of the comparison result. In these cases, the shunt resistor 6 detects phase currents for two phases.

In FIG. 11, since iW or iV can be detected in any phase, it is not necessary to adjust (increase or decrease) the ON period of the upper arm switching element. Accordingly, with respect to FIG. 11, in the case of the present invention, no increase in phase current occurs. Both iW and iV can be detected at a phase of 165 degrees, a phase of 180 degrees, and a phase of 195 degrees. If both are detected, iU can be calculated. The calculated iU and the iU detected by the shunt resistor 15 are compared, and a failure diagnosis of the shunt resistor 15, the shunt resistor 6 and the current detection related circuit can be performed based on the comparison result. For example, if the difference in the comparison result is within the variation range of the shunt resistance, it is diagnosed as normal, and if it is outside the variation range, the failure is diagnosed.

  In FIG. 12, since iW can be detected at phase 285 degrees, phase 300 degrees, phase 315 degrees, and phase 330 degrees, it is not necessary to adjust (increase or decrease) the ON period of the upper arm switching element. IV and iW cannot be detected at a phase of 270 degrees. Therefore, Δi occurs. Accordingly, with respect to FIG. 12, in the case of the present invention, a phase current increase of 1Δi occurs. However, iU can be detected at 270 degrees, 285 degrees, 300 degrees, and 315 degrees. Therefore, compared with iU detected by the shunt resistor 15, failure diagnosis of the shunt resistor 15, the shunt resistor 6 and the current detection related circuit can be performed based on the magnitude of the comparison result. In these cases, the shunt resistor 6 detects phase currents for two phases.

  From the above, with respect to FIGS. 10 to 12, it can be considered that a phase current increase of 2Δi occurs in the present invention.

  A conventional case will be described with reference to FIGS. Since there is no shunt resistor 15 for detecting the current of the lower arm, it is necessary to detect the phase current for two phases with the shunt resistor 6. In FIG. 10, since the phase currents (iU, iV) for two phases can be detected at the phase of 45 degrees, the phase of 60 degrees, and the phase of 75 degrees, the ON period adjustment (increase or decrease) of the upper arm switching element is not necessary. At 30 degrees and 90 degrees, only one phase can be detected. Therefore, Δi occurs respectively. Accordingly, with respect to FIG. 10, in the conventional case, a phase current increase of 2Δi occurs.

  Similarly in FIG. 11, a phase current increase of 2Δi occurs. The same is true in FIG. 12, and a phase current increase of 2Δi occurs. From the above, with respect to FIGS. 10 to 12, it can be considered that a phase current increase of 6Δi occurs in the conventional case.

  Accordingly, with respect to FIGS. 10 to 12 (50% three-phase modulation), it is considered that the increase in phase current, that is, noise vibration, is approximately 1/3 (2 ÷ 6) in the present invention as compared with the conventional case.

  As described above, in the present invention, since the phase current iU for one phase can be detected by the shunt resistor 15 of the lower arm, only one of the remaining two iV and iW needs to be detected by the shunt resistor 6 of the DC power supply line. . Therefore, the increase or decrease in the ON period of the upper arm switching elements of some phases can be reduced. Thereby, noise vibration can be made small (half, 1/3). Further, the calculation and execution of the time to increase or decrease and the calculation and execution of the detection timing are also reduced. As a result, the calculation processing of the control software is reduced and the implementation is facilitated.

  Further, the maximum current of the upper arm switching element can be detected by the shunt resistor 6 that detects a direct current on the direct current power line, and overcurrent protection can be performed. Therefore, compared with the method of detecting the phase current with the lower arm, the shunt resistor 2 is generated from a circuit that outputs the sum of the currents of the three phases of the shunt resistors (shunt resistor 15, shunt resistor 16, shunt resistor 17) + lower arm switching element. It can be reduced to individual pieces (shunt resistor 15, shunt resistor 6). As a result, it is possible to obtain an inverter device that is small in noise vibration, small in size, and capable of detecting a phase current with software with little arithmetic processing.

  In addition, when the phase current iU detected by the shunt resistor 15 can be detected also by the shunt resistor 6 (without increasing or decreasing the ON period of some phases of the upper arm switching elements), the current detection values of both are compared. Thus, failure diagnosis of the shunt resistor 15, the shunt resistor 6, and the current detection related circuit can be performed. Since the shunt resistor 6 has an overcurrent protection function, it is useful in terms of reliability to perform failure diagnosis.

  In the above embodiment, the shunt resistor 15 (U phase) is indispensable in FIG. 1, but a shunt resistor 16 (V phase) and a shunt resistor 17 (W phase) may be provided. . One lower arm shunt resistor is required, but any of the shunt resistor 15 (U phase), the shunt resistor 16 (V phase), and the shunt resistor 17 (W phase) may be used. The current can be detected in the first half of the carrier cycle, but it may be in the second half. Further, both the first half and the second half may be used. Although three-phase modulation has been described, the same applies to two-phase modulation.

  Furthermore, the ON period adjustment (increase or decrease) of the upper arm switching elements of some phases to enable detection of current is shown in FIG. 3 as an example, but it is longer than the minimum time required to detect current. Should be set. Although the specific phases of FIGS. 5 and 9 are shown, the same is true for the other phases as well. Although a shunt resistor is shown as the current detector, the present invention is not limited to this, and a current detector using a Hall element, a method of detecting a forward voltage of a diode, or the like may be used. Although the case where a shunt resistor is provided between the lower arm switching element of one phase and the negative side of the DC power supply among the three phases is shown, it may be arranged on the upper side of the lower arm switching element. That is, it is only necessary to detect the value of the current flowing between the lower arm switching element and the negative side of the DC power supply.

  Although the case where current is detected in the lower circulation has been described as an example, the present invention can also be applied to a case where current is detected in an upper circulation period in which all the upper arm switching elements near the center of the carrier cycle are ON. In this case, a current detector (shunt resistor) for detecting a current flowing between the upper arm and the positive side of the power supply is provided for one phase.

(Embodiment 2)
FIG. 13 shows the modulation of each phase waveform in 100% three-phase modulation. Here, at the phase of 90 degrees indicated by the broken line, the upper arm switching element U has a 100% duty, so that the lower arm switching element X has a 0% duty. Therefore, the phase current iU cannot be detected by the shunt resistor 15. This is the same even in the vicinity of the phase of 90 degrees.

  This correspondence is shown below. On the upper side of FIG. 14, the ON period of the upper arm, the detection period, and the lower circulation period at the phase of 90 degrees indicated by the broken line in FIG. The lower circulation period is zero. From this state, the same ON period is reduced from the ON periods of the upper arm switching elements U, V, and W in all three phases. A downward circulation period is secured. Since the same ON period is reduced for all three phases, the upper circulation period in which all three phases in the center of the carrier cycle are ON decreases, and the lower circulation period increases accordingly. Therefore, the length of the energization period (U phase) does not change. That is, the PWM three-phase modulation does not change.

  FIG. 15 shows the ON period of the lower arm corresponding to FIG. On the upper side of FIG. 15, the U-phase lower arm switching element X has 0% duty, but on the lower side of FIG. 15, the ON period is secured (iU and iV in the first half of the carrier cycle in FIG. 20 or more). Is). Thereby, the phase current iU can be detected by the shunt resistor 15. Although the phase current iU can be detected by the shunt resistor 6, the above method can maintain the software consistency that the phase current iU is detected by the shunt resistor 15 regardless of the phase.

  Further, as shown in the lower side of FIG. 14, in the carrier period, the energization period is divided into the first half and the second half, and the PWM modulation becomes finer. Therefore, the current becomes smooth and noise vibration is reduced. As shown in FIGS. 6 to 8 and FIGS. 10 to 12, in the three-phase modulation, the upper arm is turned on for the three phases in the center period in the carrier period, and the non-energization period (up circulation period) is entered. There are also non-energization periods (down circulation periods) at the front end and the rear end in the carrier period. Therefore, there are energization periods in the first half and the second half in the carrier cycle. This is because the two-phase modulation has one phase fixed, so there is no upper circulation period, and the carrier period is half that of the single cycle (the carrier frequency is twice). It becomes fine. However, at the 100% modulation phase of 90 degrees, there is no non-energization period (lower circulation period) at the front and rear ends in the carrier period, and therefore, the energization period is continuous with the preceding and succeeding carrier periods. For this reason, the energization period in the carrier cycle is two times. As a result, the energization period is one time per carrier cycle, and the above effect cannot be obtained. According to the present invention, the above effects can be obtained. However, in reducing the same ON period from the ON periods of the upper arm switching elements U, V, and W, the upper circulation period must be eliminated.

  When the upper circulation period and the lower circulation period (the sum of the front end and the rear end) are equal, the energization timing is equalized. Therefore, the current of three-phase modulation becomes smoother. Also, the same ON period can be reduced when there is a phase in which the ON period of the lower arm switching element in the carrier period is close to 0% or 0%, such as around the 90% phase of 100% three-phase modulation (lower circulation). This is only necessary when the period is short and the minimum time required to detect the current cannot be secured. Therefore, in many cases, it is not necessary to reduce the same ON period, and the control is simple.

  In the above embodiment, the phase of 90% of 100% three-phase modulation is shown. However, when iV is detected by the lower arm, the phase is around 210 degrees, and when iW is detected by the lower arm, the phase is around 330 degrees. It becomes a target. Although the case where current is detected in the lower circulation has been described as an example, the present invention can also be applied to a case where current is detected in an upper circulation period in which all the upper arm switching elements near the center of the carrier cycle are ON. In this case, a current detector (shunt resistor) for detecting the current between the upper arm and the positive side of the power supply is provided for one phase, and in 100% three-phase modulation, the same ON period is added for all three phases. become. In this case, the same effect can be obtained. When iU is detected by the upper arm, the phase is around 270 °, when iV is detected, the phase is around 30 °, and when iW is detected, the phase is around 150 °.

(Embodiment 3)
FIG. 16 is a diagram in which the inverter device 23 is attached in close contact with the right side of the electric compressor 40. The compression mechanism 28, the motor 11, and the like are installed in the metal casing 32. The refrigerant is sucked from the suction port 33 and compressed by driving the compression mechanism portion 28 (scroll in this example) by the motor 11. The compressed refrigerant cools the motor 11 when passing through the motor 11 and is discharged from the discharge port 34.

  The inverter device 23 uses the case 30 so as to be attached to the electric compressor 40. The inverter circuit unit 10 serving as a heat source is cooled by the low-pressure refrigerant through the low-pressure pipe 38. In order to prevent condensation due to this cooling, the inverter device 23 is arranged below the suction pipe 38, and the ambient temperature of the inverter circuit unit 10 is also lowered so that the temperature difference is reduced. A terminal 39 connected to the winding of the motor 11 inside the electric compressor 40 is connected to the output unit of the inverter circuit unit 10. The connection line 36 fixed to the inverter device 23 by the holding unit 35 includes a power line to the battery 1 and a signal line to an air conditioner controller (not shown) that transmits a rotation speed signal.

  In such an inverter device-integrated electric compressor, since the inverter device 23 is small and receives vibration from the motor, it is necessary to be able to drive the motor of the electric compressor with low vibration. Is preferred.

  In each of the above embodiments, the DC power source is a battery. However, the present invention is not limited to this, and a DC power source obtained by rectifying a commercial AC power source may be used. Although the motor is a sensorless DC brushless motor, it can also be applied to an induction motor or the like. In addition, as a vehicle, a quiet effect is significant in a vehicle having no engine noise such as an electric vehicle, a hybrid vehicle, and a fuel cell vehicle. Although the case of three phases has been described as an example, the present invention can also be applied to multiphase.

  As described above, the inverter device according to the present invention can be applied to various consumer products and various industrial devices because it is small in noise and vibration, small in size, and capable of detecting phase current with software with little arithmetic processing. The load can be applied to AC devices other than motors.

The inverter apparatus which concerns on Embodiment 1 of this invention, and its surrounding electric circuit diagram Characteristic chart showing lower arm ON period and lower circulation period in 30% to 90 degrees phase of 10% 3-phase modulation Characteristic diagram showing upper arm ON period, detection period, lower circulation period, and direct current when upper arm ON period is reduced at the same phase of 60 degrees Characteristic diagram showing increased DC current due to reduction of ON period of arm Characteristic chart showing modulation of each phase waveform in 10% 3-phase modulation The characteristic diagram which shows the ON period of the upper arm, the detection period, and the lower circulation period in the phase of 30% to 90 degrees of the same 10% three-phase modulation Characteristic chart showing upper arm ON period, detection period, and lower circulation period at 150% to 210 degrees of 10% three-phase modulation Characteristic chart showing upper arm ON period, detection period, and lower circulation period in phase 270 to 330 degrees of 10% three-phase modulation Characteristic diagram showing the modulation of each phase waveform in 50% 3-phase modulation The characteristic diagram which shows the ON period of the upper arm, the detection period, and the lower circulation period in the phase of 30% to 90 degrees of the 50% three-phase modulation The characteristic diagram which shows the ON period of the upper arm, the detection period, and the lower circulation period in the phase of 150 to 210 degrees of the 50% three-phase modulation Characteristic chart showing upper arm ON period, detection period, and lower circulation period in phase 270 to 330 degrees of 50% three-phase modulation The characteristic view which shows the modulation | alteration of each phase waveform in the 100% three phase modulation which concerns on Embodiment 2 of this invention Explanatory diagram of the effect of reducing the same upper arm ON period for all three phases at the same phase of 90 degrees Explanatory drawing of effects in the lower arm Sectional drawing of the inverter apparatus integrated electric compressor which concerns on Embodiment 3 of this invention. Inverter device that detects phase current with shunt resistance of power line and electrical circuit diagram around it Characteristic diagram showing modulation of each phase waveform in 10% 3-phase modulation Characteristic diagram showing upper arm ON period, lower circulation period, DC current at 60% phase of 10% 3-phase modulation Fig. 19 is a characteristic diagram in which the detection period is added by increasing and reducing the upper arm ON period. FIG. 19 to FIG. 20 are characteristic diagrams showing the increased direct current. Inverter device for detecting phase current with lower arm and surrounding electric circuit diagram

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Battery 2 Switching element 3 Diode 4 Stator winding 5 Magnet rotor 6 Shunt resistance for DC current detection 10 Inverter circuit 11 Sensorless DC brushless motor 15 Shunt resistance for U-phase current detection 23 Inverter device 40 Electric compressor

Claims (11)

Three phases of an upper arm switching element connected to the positive side of the DC power source and a lower arm switching element connected to the negative side of the DC power source are provided, and the DC voltage of the DC power source is switched by PWM modulation to form a sine wave In the inverter device that outputs the three-phase alternating current, the first current detector that detects the current between the lower arm switching element of one phase of the three phases and the negative side of the direct current power source, and the direct current power source, A second current detector for detecting a direct current between the inverter devices, the phase current of the phase provided with the current detector is detected by the first current detector, and the second current detector An inverter device that detects a phase current other than the phase current detected by the first current detector. By reducing the same ON period from the ON period of the upper arm switching element in all three phases within the carrier cycle, the phase current of the phase provided by the current detector is reduced by the first current detector. The inverter device according to claim 1 to be detected. Three phases of an upper arm switching element connected to the positive side of the DC power source and a lower arm switching element connected to the negative side of the DC power source are provided, and the DC voltage of the DC power source is switched by PWM modulation to form a sine wave In the inverter device that outputs the three-phase alternating current, the first current detector that detects the current between the upper arm switching element of one of the three phases and the positive side of the direct current power source, and the direct current power source, A second current detector for detecting a direct current between the inverter devices, the phase current of the phase provided with the current detector is detected by the first current detector, and the second current detector An inverter device that detects a phase current other than the phase current detected by the first current detector. In all three phases in the carrier cycle, by adding the same ON period to the ON period of the upper arm switching element, the phase current of the phase in which the current detector is provided is obtained by the first current detector. The inverter device according to claim 3 to be detected. 5. The phase current detection by the second current detector detects a phase current having a smaller ON period adjustment of the upper arm switching element required for the phase current detection. The inverter device described in the paragraph. The second current detector detects phase currents for two phases other than the phase current detected by the first current detector, and the phase current values of the remaining phases calculated from the phase currents for the two phases The inverter apparatus as described in any one of Claims 1-4 which compares the detected value of a said 1st electric current detector with a 1st. The phase current detected by the first current detector is also detected by the second current detector and is compared with a detection value of the first current detector. The inverter device described in the paragraph. The inverter device according to any one of claims 1 to 7, wherein the current detector is a shunt resistor. The inverter device according to any one of claims 1 to 8, wherein the three-phase alternating current is output to a motor of an electric compressor. The inverter apparatus of Claim 9 mounted in the said electric compressor. The inverter apparatus as described in any one of Claims 1-10 mounted in a vehicle.

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