JP5056106B2 - Inverter control device for motor drive and equipment using the device - Google Patents

Description

  The present invention relates to a vector control inverter device for an induction motor and a DC brushless motor provided with an inverter circuit.

  A DC brushless motor including a permanent magnet rotor and a stator winding is used in an air conditioner, a refrigerator, an electric washing machine, and the like because of ease of maintenance.

  In DC brushless motor drive control, it is necessary to properly associate the rotor magnetic pole position with the position of the stator winding to be energized. In compressor motors such as air conditioners, the rotor magnetic pole position For detection, a rotor position detection sensor such as a Hall element cannot be used.

  Therefore, the method of detecting the magnetic pole position of the rotor using the counter electromotive voltage induced in the stator winding due to the interaction with the rotor magnetic pole, or detecting the motor phase current and applied voltage in advance. A method of estimating a magnetic pole position by using together a stator winding resistance value and an inductance value of a direct current brushless motor is employed.

  However, in any method, the counter electromotive voltage induced in the stator winding when the rotor rotates or is used in calculation. Thus, the rotor magnetic pole position cannot be detected.

  Therefore, when starting the DC brushless motor, positioning control is performed to move and hold the rotor magnetic pole position at a fixed position, commutation is started, synchronous operation is performed to gradually shorten the commutation interval, and the back electromotive force voltage is A method of making a transition to a drive mode based on sensorless position detection at a time point that is sufficiently necessary for detection is used in the prior art.

  With this method, if the load torque at start-up is always constant, the start-up can be performed reliably at a predetermined application voltage and timing set in advance. However, the load torque at start-up is low for compressor motors and electric washing machine motors. If the load torque is large when the commutation interval at start-up is short or the applied voltage is small, the start-up may not be possible due to a shortage of motor output torque.

  On the other hand, if the load torque is small when the commutation interval is long or the applied voltage is large, the motor current becomes large and is likely to be overcurrent. In the worst case, the inverter and the motor are damaged. That is, in the conventional low-frequency startup method, commutation is performed regardless of the rotor position during synchronous operation, and thus it is difficult to start up well when the load torque is unknown.

As a control that improves this point, a method of controlling the starting voltage is known. For example, Patent Document 1 includes a voltage adjustment unit that adjusts a startup voltage, a detection unit that detects a startup failure at startup, a counter that counts the number of startup failures, and a voltage adjustment unit for each startup failure. The voltage is sequentially increased by a predetermined voltage and restarted, and when the startup failure reaches a predetermined number of times, the system is abnormally stopped.
JP-A-10-267432

  However, in the conventional control method, the start-up voltage is sequentially increased for each start-up failure, and restart is performed. Therefore, a time loss corresponding to the number of start-up failures occurs, and the product that needs to increase the rotation speed quickly is required. Adaptation was difficult.

  The present invention solves such a conventional problem, and an inverter for driving a motor that reliably and quickly starts a DC brushless motor widely used in an air conditioner or the like even when the load torque at the time of starting is unknown. An object is to provide a control device.

In order to solve the above problems, an inverter control apparatus for driving a motor according to the present invention includes a rectifier circuit that receives an AC power supply, an inverter that converts DC power to AC power, a phase current detection that detects a phase current of the motor and the motor. And a control calculation unit for controlling the operation of the inverter, the control calculation unit includes a motor phase estimation unit for estimating the phase of the rotor during rotation of the motor, and when the motor shifts from the stop state to the rotation state. In addition, when the phase current peak value obtained by the phase current detector increases with time, a startup estimation phase correction unit that corrects the rotor phase derived by the motor phase estimation unit is provided. is there.

  According to the present invention, even when the estimated torque of the rotor is not accurate immediately after startup because the load torque is unknown and the amplitude value of the phase current increases without converging, the estimated phase of the rotor is immediately set. By making the correction, the drive mode based on the sensorless position detection can be smoothly shifted, and as a result, it is possible to prevent the product casing such as an air conditioner from starting up with large vibrations. Play.

A first invention includes a rectifier circuit that receives an AC power supply, an inverter that converts DC power into AC power, a motor, a phase current detector that detects a phase current of the motor, and a control arithmetic unit that controls the operation of the inverter The control calculation unit includes a motor phase estimation unit that estimates a phase of a rotor during rotation of the motor, and a phase current detection unit that detects when the motor shifts from a stop state to a rotation state. When the obtained phase current peak value increases with the passage of time, a startup estimation phase correction unit that corrects the phase of the rotor derived by the motor phase estimation unit is provided.

  As a result, even if the estimated phase of the rotor immediately after start-up is not accurate and the amplitude value of the phase current increases, reliable and quick sensorless position detection is achieved by immediately correcting the estimated phase of the rotor It becomes possible to shift to the drive mode based on the above.

A second invention includes a rectifier circuit that receives an AC power supply, an inverter that converts DC power into AC power, a motor, a phase current detector that detects a phase current of the motor, and a control arithmetic unit that controls the operation of the inverter The control calculation unit includes a current phase setting unit that sets a current phase for performing flux-weakening control during high-speed operation of the motor, and when the motor shifts from a stopped state to a rotating state, When the phase current peak value obtained by the phase current detection unit increases with time, a startup current phase correction unit is provided that corrects the current phase determined by the current phase setting unit.

  As a result, even if the estimated phase of the rotor immediately after start-up is not accurate and the amplitude value of the phase current increases, the current phase setting value is immediately corrected to ensure reliable and rapid sensorless position detection. It becomes possible to shift to the drive mode based on the above.

According to a third invention, in particular, in the first or second invention, the rectifier circuit includes a diode bridge and a reactor connected to an AC input side or a DC output side of the diode bridge, and the bus of the inverter A capacitor is provided between them, and the resonance frequency between the reactor and the capacitor is greater than 40 times the AC power supply frequency.

  Thereby, the harmonic component of the power supply current can be suppressed and the IEC standard can be cleared.

  A fourth invention has a motor and drives the motor by using any one of the motor drive inverter control devices of the first to third inventions. Thereby, apparatuses, such as an air conditioner which performs favorable motor drive, a refrigerator, an electric washing machine, an electric dryer, a vacuum cleaner, a blower, and a heat pump water heater, are realizable.

  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 is a system configuration diagram of an inverter control apparatus for driving a motor, showing a first embodiment of the present invention.

  As shown in FIG. 1, the diode bridge 7 converts AC power from the AC power source 1 into DC power. The reactor 11 is connected to the DC output side of the diode bridge 7. Capacitor 12 is connected between the DC buses. The inverter 2 generates and outputs a drive voltage supplied to the DC brushless motor 3. The control unit 6 controls the inverter 2.

  The DC brushless motor 3 includes a stator 4 to which three-phase windings 4u, 4v, 4w Y-connected around a neutral point are attached, and a rotor 5 to which a magnet is attached. The U-phase terminal 8u is connected to the non-connected end of the U-phase winding 4u, the V-phase terminal 8v is connected to the non-connected end of the V-phase winding 4v, and the W-phase terminal 8w is connected to the non-connected end of the W-phase winding 4w. Has been.

  The inverter 2 has a half-bridge circuit composed of a pair of switching elements for three phases for the U phase, the V phase, and the W phase. A pair of switching elements of the half-bridge circuit are connected in series between the high-voltage side end and the low-voltage side end of the capacitor 12, and a DC voltage is applied to the half-bridge circuit.

  The U-phase half-bridge circuit includes a switching element 13u on the high voltage side (upper arm) and a switching element 13x on the low voltage side (lower arm). The V-phase half-bridge circuit includes a high-voltage side switching element 13v and a low-voltage side switching element 13y.

  The W-phase half-bridge circuit includes a high-voltage side switching element 13w and a low-voltage side switching element 13z. In addition, free wheel diodes 14u, 14v, 14w, 14x, 14y, and 14z are connected in parallel with the switching elements.

  Terminals 8u, 8v, 8w of the DC brushless motor 3 are connected to an interconnection point between the switching element 13u and the switching element 13x, an interconnection point between the switching element 13v and the switching element 13y, and an interconnection point between the switching element 13w and the switching element 13z. Are connected to each other.

The DC voltage applied to the inverter 2 is converted into a three-phase AC voltage by the switching operation of the switching element in the inverter 2 described above, whereby the DC brushless motor 3 is driven. A bus current detector 15 is arranged on the bus of the inverter 2.

  The control unit 6 includes a PWM signal generation unit 9, a base driver 10, a phase current conversion unit 20, a motor phase estimation unit 17, a rotor speed detection unit 18, a current command calculation unit 19, and an output voltage calculation unit. 21 and an activation estimated phase correction unit 22.

  The phase current converter 20 observes the inverter bus current flowing through the bus current detector 15 and converts the inverter bus current into the phase current of the DC brushless motor 3. The phase current converter 20 actually detects the current only for a predetermined period from when the inverter bus current changes.

  The motor phase estimation unit 17 includes the phase current of the DC brushless motor 3 converted by the phase current conversion unit 20, the output voltage calculated by the output voltage calculation unit 21, and the inverter 2 detected by the inverter input voltage detection unit 16. The phase of the DC brushless motor 3 is estimated based on the information on the voltage applied to the DC brushless motor 3.

  The startup estimation phase correction unit 22 stores the peak value of the phase current of the DC brushless motor 3 converted by the phase current conversion unit 20 immediately after startup, and the phase current peak value increases with time. In this case, a startup estimated phase correction value for correcting the phase estimated by the motor phase estimation unit 17 is derived. The rotor speed detection unit 18 estimates the speed of the DC brushless motor 3 from the phase estimated by the motor phase estimation unit 17.

  The current command calculation unit 19 derives a current command value to be energized based on deviation information between the estimated speed of the rotor 5 and the target speed using the PI calculation or the like so that the rotor speed becomes the target speed. Is done.

  In the output voltage calculation unit 21, an inverter necessary for maintaining the rotation of the DC brushless motor 3 is based on deviation information between the current command value and the phase current of the DC brushless motor 3 converted by the phase current conversion unit 20. A sinusoidal output voltage to be output is calculated while using the phase estimated by the motor phase estimating unit 17 and the estimated startup phase correction value derived by the estimated startup phase correcting unit 22 together.

  Based on the output voltage obtained by the output voltage calculation unit 21, the PWM signal generation unit 9 obtains an output voltage such that the phase current waveform becomes a sine wave without distortion, and a PWM signal for driving the DC brushless motor 3 is generated. .

  Finally, the PWM signal is output to the base driver 10, and the switching elements 13u, 13v, 13w, 13x, 13y, and 13z are driven in accordance with the PWM signal to realize a sine wave drive in which a sine wave phase current flows.

  Next, the operation of the activation estimation phase correction unit 22 will be described in detail with reference to FIG. FIG. 2 is a flowchart showing an operation flow of the activation estimation phase correction unit 22.

  In step 1, the value of the inflection point at which the phase current of the DC brushless motor 3 shifts from increase to decrease is detected as the phase current peak value.

  In Step 2, it is determined whether or not the phase current peak value exceeds 7.5 A as a threshold value. If it exceeds the threshold value, the number of times the threshold value is exceeded is counted in Step 3. Increment the counter to +1. If it does not exceed the threshold value, the counter is cleared in step 11, then 0 deg is set as the estimated phase correction value in step 12, and the series of processing ends.

  In step 4, it is determined whether or not the counter for counting the number of times the threshold value has been exceeded has exceeded the prescribed number of times. That is, in the flow so far, it is determined whether or not the phase current peak value of the DC brushless motor 3 has continuously exceeded the threshold value (7.5 A) a prescribed number of times (six times).

  If it is determined in step 4 that the counter for counting the number of times the threshold is exceeded exceeds the prescribed number of times, the counter is once cleared in step 5. If it is not determined in step 4 that the counter for counting the number of times of exceeding the threshold exceeds the prescribed number of 6 times, 0 deg is set as the estimated phase correction value in step 12, and the series of processes is terminated.

  In step 6, it is determined whether the estimated phase correction value is a positive value or a negative value based on whether the positive correction flag is set.

  If the plus correction flag is set in step 6, the process proceeds to step 7 to set −5 deg as the estimated phase correction value. After step 7, the process proceeds to step 8, the plus correction flag is cleared, and the series of processes is terminated.

  If the plus correction flag is not set in step 6, the process proceeds to step 9, and +5 deg is set as the estimated phase correction value.

  After step 9, the process proceeds to step 10, the plus correction flag is set, and the series of processes is terminated.

  That is, when the phase current of the DC brushless motor 3 immediately after startup increases without converging in the processing from step 6 onward, −5 deg is given as the estimated phase correction value, the estimated phase is corrected, and normal sensorless Transition to driving.

  Further, when the estimated phase correction direction is reversed and the phase current of the DC brushless motor 3 further increases, the estimated phase correction value is switched to +5 deg to shift to normal sensorless driving.

  FIG. 3 is a waveform diagram showing the state of the phase current when the DC brushless motor 3 is successfully started without any abnormality. As shown in FIG. 3, after a direct current is passed through the U-phase winding 4u as a positioning process, the phase current is driven while converging.

  On the other hand, FIG. 4 is a waveform diagram showing the state of the phase current when the DC brushless motor 3 fails to start and stops due to an overcurrent abnormality. As shown in FIG. 4, when shifting from positioning to driving, the phase current continues to diverge, an excessive current flows, and a stop operation works to protect the parts.

  This is because the calculation result of the estimated phase in the motor phase estimator 17 immediately after startup is different from the actual one, and the voltage applied to the inverter 2 is not given at regular timing.

  5 and 6 are waveform diagrams when the control flow shown in FIG. 2 operates in the motor drive inverter control apparatus of the present invention.

As shown in FIG. 5, the direct current brushless motor 3 is moved from the positioning state to driving.
Since the phase current peak value of the current exceeded 7.5 A as the threshold value six times in succession, -5 deg is derived in the start estimation phase correction unit 22 at the timing shown in (I) and calculated by the motor phase estimation unit 17 The estimated phase thus corrected is corrected, and as a result, the phase current converges and the startup is successful.

  As shown in FIG. 6, the phase current peak value of the direct current brushless motor 3 exceeded the threshold value of 7.5 A for six consecutive times when shifting from the positioning state to driving, so the timing shown in (II) In -5, -5 deg was derived in the startup estimated phase correction unit 22 and the estimated phase calculated by the motor phase estimation unit 17 was corrected, but the phase current still did not converge, so 7.5 A was exceeded six times in succession ( Correction of +5 deg is performed at the timing of III), and as a result, the phase current converges and the startup is successful.

  As described above, the motor drive inverter control device according to the present invention can surely and quickly start the DC brushless motor even when the load torque is unknown, and realize a high-quality device with high reliability. Can do.

(Embodiment 2)
FIG. 7 is a system configuration diagram of an inverter control device for driving a motor according to the second embodiment of the present invention.

  In FIG. 7, an AC power source 1, a diode bridge 7 that converts AC power into DC power, a reactor 11 connected to the DC output side of the diode bridge 7, a capacitor 12 between the DC buses, and a drive supplied to the DC brushless motor 3. The inverter 2 that generates and outputs a voltage and the control unit 6 that controls the inverter 2 are the same as those in FIG.

  The control unit 6 includes a PWM signal generation unit 9, a base driver 10, a phase current conversion unit 20, a motor phase estimation unit 17, a rotor speed detection unit 18, a current command calculation unit 19, and an output voltage calculation unit. 21, a startup current phase correction unit 23, and a current phase setting unit 24.

  The startup current phase correction unit 23 stores the peak value of the phase current of the DC brushless motor 3 converted by the phase current conversion unit 20 immediately after startup, and the phase current peak value increases with time. In this case, the starting current phase for correcting the setting value of the current phase (the advance value of the inverter output voltage with respect to the induced voltage of the DC brushless motor 3) for performing the flux weakening control during the high speed operation set by the current phase setting unit 24 A correction value is derived.

  Next, the operation of the startup current phase correction unit 23 will be described in detail with reference to FIG. FIG. 8 is a flowchart showing an operation flow of the startup current phase correction unit 23.

  In step 1, the value of the inflection point at which the phase current of the DC brushless motor 3 shifts from increase to decrease is detected as the phase current peak value.

  In Step 2, it is determined whether or not the phase current peak value exceeds 7.5 A as a threshold value. If it exceeds the threshold value, the number of times the threshold value is exceeded is counted in Step 3. Increment the counter to +1. If it does not exceed the threshold value, the counter is cleared in step 11, then 0 deg is set as the current phase correction value in step 12, and the series of processing ends.

  In step 4, it is determined whether or not the counter for counting the number of times the threshold value has been exceeded has exceeded the prescribed number of times. That is, in the flow so far, it is determined whether or not the phase current peak value of the DC brushless motor 3 has continuously exceeded the threshold value (7.5 A) a prescribed number of times (six times).

  If it is determined in step 4 that the counter for counting the number of times the threshold is exceeded exceeds the prescribed number of times, the counter is once cleared in step 5. If it is not determined in step 4 that the counter for counting the number of times of exceeding the threshold exceeds the prescribed number of 6 times, 0 deg is set as the current phase correction value in step 12, and the series of processes is terminated.

  In step 6, it is determined whether the current phase correction value is set to a positive value or a negative value based on whether or not the positive correction flag is set. In step 6, if the plus correction flag is set, the process proceeds to step 7, and -5 deg is set as the current phase correction value.

  After step 7, the process proceeds to step 8, the plus correction flag is cleared, and the series of processes is terminated.

  In step 6, if the plus correction flag is not set, the process proceeds to step 9, and +5 deg is set as the current phase correction value.

  After step 9, the process proceeds to step 10, the plus correction flag is set, and the series of processes is terminated.

  That is, when the phase current of the direct current brushless motor 3 immediately after startup increases without converging in the processing from step 6 onward, -5 deg is given as the current phase correction value, and the current phase is corrected to correct normal sensorless. Transition to driving.

  Further, when the current phase correction direction is reversed and the phase current of the DC brushless motor 3 further increases, the current phase correction value is switched to +5 deg to shift to normal sensorless driving.

  As described above, the same effect as that of the first embodiment can also be obtained by correcting the set value in the current phase setting unit 24.

(Embodiment 3)
A specific method for determining the specifications of the capacitor 12 and the reactor 11 according to the present invention will be described below.

In the motor drive inverter control device of the present invention, the resonance frequency f _LC (LC resonance frequency) of the capacitor 12 and the reactor 11 is set to the power supply frequency fs in order to suppress the harmonic component of the power supply current and clear the IEC standard. Eleven combinations of capacitor 12 and reactor are determined so as to be larger than 40 times.

Here, when the capacitance of the capacitor 12 is C [F] and the inductance value of the reactor 11 is L [H], the LC resonance frequency f _LC is expressed by the following equation.

That is, the combination of the capacitor 12 and the reactor 11 is determined so as to satisfy f _LC > 40 fs (because the IEC standard defines the 40th harmonic in the harmonic component of the power supply current).

  As described above, by determining the combination of the capacitor 12 and the reactor 11, it is possible to suppress the harmonic component of the power source current and clear the IEC standard in the inverter control device for motor drive that realizes small size, light weight and low cost. It becomes possible.

  In addition, the inverter control apparatus for motor drive of this invention is a motor drive which drives a motor using an inverter circuit, such as an air conditioner, a refrigerator, an electric washing machine, an electric dryer, a vacuum cleaner, a blower, and a heat pump water heater. In any case, it can contribute to the realization of a highly reliable product.

  As described above, the motor drive inverter control device according to the present invention can reliably and quickly start the DC brushless motor even when the load torque is unknown. It can also be widely used for required AV equipment (particularly small equipment).

1 is a system configuration diagram of an inverter control device for driving a motor according to Embodiment 1 of the present invention. The flowchart which shows the flow of operation | movement in Embodiment 1 of this invention. Operation waveform diagram in a general motor drive inverter control device Operation waveform diagram in a general motor drive inverter control device Operation waveform diagram in Embodiment 1 of the present invention Operation waveform diagram in Embodiment 1 of the present invention The system block diagram of the inverter control apparatus for motor drive in Embodiment 2 of this invention The flowchart which shows the flow of operation | movement in Embodiment 2 of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 AC power supply 2 Inverter 3 DC brushless motor 4 Stator 4u-4w Winding 5 Rotor 6 Control part 7 Diode bridge 8u-8w Terminal 9 PWM signal generation part 10 Base driver 11 Reactor 12 Capacitor 13u-13w Upper arm switching element 13x ˜13z Lower arm switching element 14u˜14z Free wheel diode 15 Bus current detector 16 Inverter input voltage detector 17 Motor phase estimator 18 Rotor speed detector 19 Current command calculator 20 Phase current converter 21 Output voltage calculator 22 Startup estimated phase correction unit 23 Startup current phase correction unit 24 Current phase setting unit

Claims (4)

A rectifier circuit that receives an AC power supply, an inverter that converts DC power into AC power, a motor, a phase current detector that detects a phase current of the motor, and a control calculation unit that controls the operation of the inverter,
The control calculation unit includes a motor phase estimation unit that estimates a phase of a rotor during rotation of the motor,
The phase of the rotor derived by the motor phase estimation unit when the phase current peak value obtained by the phase current detection unit increases with time when the motor transitions from the stopped state to the rotation state. A startup estimated phase correction unit for correcting
An inverter control device for driving a motor. A rectifier circuit that receives an AC power supply, an inverter that converts DC power into AC power, a motor, a phase current detector that detects a phase current of the motor, and a control calculation unit that controls the operation of the inverter,
In the control calculation unit, a current phase setting unit that sets a current phase for performing flux-weakening control during high-speed operation of the motor; and
Corrects the current phase determined by the current phase setting unit when the phase current peak value obtained by the phase current detection unit increases with time when the motor shifts from the stopped state to the rotation state. A starting current phase correction unit to
An inverter control device for driving a motor. The rectifier circuit includes a diode bridge and a reactor connected to an AC input side or a DC output side of the diode bridge, a capacitor is provided between the buses of the inverter, and a resonance frequency between the reactor and the capacitor is The inverter control apparatus for motor drive according to claim 1 or 2, wherein the inverter control apparatus is greater than 40 times the AC power frequency. The apparatus which has a motor and drives the said motor using the motor drive inverter control apparatus of any one of Claims 1-3.

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