JP5056052B2 - 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 motor provided with an inverter circuit.

A PWM inverter that drives a motor with an alternating voltage of variable voltage and variable frequency is basically composed of an arm in which switching elements are connected in series, and the upper switching element and the lower switching element are alternately turned on / off. The Usually, in order to prevent the upper switching element and the lower switching element from being simultaneously turned on and short-circuited, a period during which the upper and lower switching elements are simultaneously turned off during the on / off switching. Is provided. This short-circuit prevention time that turns off at the same time is called dead time. During this dead time period, the zero crossing point of the phase current and its vicinity due to incomplete turn-on of the freewheel diode connected in reverse parallel to the switching element ( Hereinafter, the output voltage becomes discontinuous in the vicinity of the zero cross point), which may cause the phase current to become discontinuous and distort the waveform. As a result, problems have arisen such that the torque of the motor as a load pulsates or the rotational speed fluctuates near the zero cross point of the phase current. In order to solve this problem, Patent Document 1 compensates for voltage distortion caused by dead time according to the polarity of the motor current.
JP 2002-95262 A

  However, in the conventional compensation method, when the compensation timing shift is large, there is a problem that the compensation effect is reduced or the voltage distortion compensation is adversely affected.

  An object of the present invention is to solve such a conventional problem, and to provide an inverter control device for driving a motor that improves the waveform to reduce the influence of the deviation between the waveform distortion and the compensation value.

In order to solve the above problems, the present invention includes a rectifier circuit that receives an AC power supply, an inverter that converts DC power into AC power, a motor and a control calculation unit that controls the operation of the inverter, The basic output voltage calculation unit for calculating the voltage to be output by the inverter necessary for maintaining the rotation of the motor, and the voltage for improving the phase current waveform distortion of the motor are shorter than the calculation cycle in the basic output voltage calculation unit The waveform improvement voltage calculation unit calculates the PWM signal for controlling the inverter based on the voltage calculated by the period, the voltage calculated by the basic output voltage calculation unit, and the voltage calculated by the waveform improvement voltage calculation unit. a PWM signal generation unit to be updated in the calculation cycle is provided, the operation of the waveform improvement voltage as a fifth-order harmonic component to the fundamental output voltage, the PWM timer Daunkau During the counting and up-counting, each is performed once, and the PWM signal generation unit superimposes it on the basic output voltage waveform obtained for each carrier cycle to generate the PWM signal, and from the PWM timer up-count to the down-count The reflection to the PWM signal is performed at the timing of transition .

  As a result, it is possible to improve the waveform distortion of the motor phase current during driving, and it is possible to realize a high-quality motor driving inverter control device with reduced torque pulsation and rotational speed fluctuation.

The inverter control device for driving a motor according to the present invention has a longer cycle than the cycle for calculating the voltage to be output by the inverter necessary for maintaining the rotation of the motor even when the waveform is distorted near the zero cross point of the phase current. By calculating the voltage that improves the phase current waveform distortion of the motor in a short cycle and reflecting it in the PWM signal that controls the inverter, it is possible to reduce the influence of the deviation between the distortion and the compensation value, and as a result, good The effect of maintaining a stable motor drive is achieved.

1st invention is provided with the rectifier circuit which inputs alternating current power supply, the inverter which converts direct-current power into alternating current power, a motor, and the control calculating part which controls the operation | movement of the said inverter, The said control calculating part contains the said motor A basic output voltage calculation unit that calculates a voltage to be output by the inverter necessary to maintain the rotation of the motor, and a voltage that improves phase current waveform distortion of the motor is greater than a calculation cycle in the basic output voltage calculation unit A waveform improvement voltage calculation unit that calculates with a short period, a PWM signal that controls the inverter based on the voltage calculated by the basic output voltage calculation unit and the voltage calculated by the waveform improvement voltage calculation unit, the waveform improvement a PWM signal generating section for updating the computation cycle of the voltage computing unit is provided, the operation of the waveform improvement voltage as a fifth-order harmonic component to the fundamental output voltage, PW During the downcounting and upcounting of the timer, each is performed once, and the PWM signal generation unit superimposes it on the basic output voltage waveform obtained for each carrier period, generates the PWM signal, and from the PWM timer upcounting The reflection to the PWM signal is performed at the timing of shifting to the down count .

  As a result, even if the waveform is distorted near the zero-cross point of the phase current, the phase current waveform of the motor is shorter than the cycle for calculating the voltage that the inverter needs to maintain to rotate the motor. By calculating a voltage for improving the distortion and reflecting it in the PWM signal for controlling the inverter, it is possible to reduce the influence of the deviation between the waveform distortion and the compensation value, and as a result, it is possible to maintain good motor drive.

  According to a second aspect of the present invention, in particular, in the first aspect of the invention, a PWM signal that controls the inverter based on a calculation cycle of a voltage that should be output by the inverter necessary for maintaining the rotation of the motor in the basic output voltage calculation unit The calculation cycle of the voltage for improving the phase current waveform distortion of the motor in the waveform improvement voltage calculation unit is equal to ½ of the carrier cycle of the PWM signal for controlling the inverter.

  As a result, when the control is performed by a general motor drive microcomputer, it is possible to reduce the influence of the difference between the waveform distortion and the compensation value with a minimum processing time.

  In a third aspect of the invention, in particular, in the first or second aspect of the 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 between the buses of the inverter Is provided with a capacitor, and the combination of the reactor and the capacitor is determined so that the resonance frequency of the reactor and the capacitor is larger 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.

  4th invention has a motor and drives the said motor using the motor drive inverter control apparatus in any one of 1st to 3rd invention. 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 shows a system configuration diagram of a motor drive inverter control apparatus showing a first embodiment of the present invention.

  The motor drive inverter control device includes an AC power source 1, a diode bridge 7 for converting 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 brushless motor 3. An inverter 2 that generates and outputs a drive voltage to be supplied and a control unit 6 that controls the inverter 2 are provided.

  The 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. Yes.

  The inverter 2 has a half-bridge circuit composed of a pair of switching elements for three phases for U phase, V phase, and 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.

  The terminals 8u, 8v, and 8w of the brushless motor 3 are connected to the interconnection point between the switching element 13u and the switching element 13x in the inverter 2, the interconnection point between the switching element 13v and the switching element 13y, and the interconnection point between the switching element 13w and the switching element 13z. Each is connected.

  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 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 a basic output voltage calculation. And a waveform improvement voltage calculator 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 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 brushless motor 3 converted by the phase current conversion unit 20, the output voltage calculated by the basic output voltage calculation unit 21, and the inverter 2 detected by the inverter input voltage detection unit 16. The phase of the brushless motor 3 is estimated from information on the voltage applied to the brushless motor 3.

Further, the rotor speed detection unit 18 estimates the speed of the brushless motor 3 from the estimated phase.

  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 by using PI calculation or the like so that the rotor speed becomes the target speed. The

  The basic output voltage calculator 21 outputs an inverter necessary for maintaining the rotation of the brushless motor 3 based on deviation information between the current command value and the phase current of the brushless motor 3 converted by the phase current converter 20. Calculate the sine wave basic output voltage to be calculated.

  The waveform improvement voltage calculation unit 22 calculates a phase current waveform distortion improvement voltage based on the phase information of the brushless motor 3 estimated by the motor phase estimation unit 17.

  The PWM signal generation unit 9 generates an output voltage such that the phase current waveform becomes a sine wave without distortion by the basic output voltage obtained by the basic output voltage calculation unit 21 and the phase current waveform distortion improvement voltage obtained by the waveform improvement voltage calculation unit 22. And a PWM signal for driving the 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.

  FIG. 2 shows voltage waveforms and phase current waveforms obtained by the respective arithmetic units. FIG. 2A shows a basic output voltage waveform obtained by the basic output voltage calculation unit 21, and generates a sinusoidal output voltage based on the phase information of the brushless motor 3 estimated by the motor phase estimation unit 17. The amplitude is determined by a comparison operation between the current command value from the current command calculation unit 19 and the actual current value from the phase current conversion unit 20.

  When a PWM signal is output from the PWM signal generator 9 using only the basic output voltage waveform shown in FIG. 2A, the phase current waveform of the brushless motor 3 is distorted as shown in FIG. turn into.

  This is because the freewheel diode connected in reverse parallel to the switching element is incomplete during the dead time period for preventing the upper switching element and the lower switching element of the inverter 2 from being simultaneously turned on and short-circuited. This is because the output voltage becomes discontinuous near the zero cross point due to turn-on.

  As a result, problems have arisen such that the torque of the motor as a load pulsates or the rotational speed fluctuates near the zero cross point of the phase current.

  FIG. 2C shows the waveform improvement voltage obtained by the waveform improvement voltage calculation unit 22 for solving this problem.

  This is because, in the distorted phase current waveform shown in FIG. 2B, the waveform improvement voltage is a positive value in the phase where the current value is insufficient with respect to the sine waveform, and conversely the current value for the sine waveform. In the phase in which is excessive, the waveform improvement voltage becomes a negative value, and is obtained by calculating the fifth-order harmonic component with respect to the basic output voltage.

  FIG. 2D shows a waveform obtained by superimposing the waveform improvement voltage shown in FIG. 2C on the basic output voltage waveform shown in FIG.

  By outputting a PWM signal from the PWM signal generation unit 9 using the composite waveform shown in FIG. 2D, the phase current waveform of the brushless motor 3 is converted into a sine wave current without distortion as shown in FIG. Has been realized.

  The control timing in the control part 6 is demonstrated using FIG.

  The PWM timer is mounted on a general microcomputer for driving a motor, and repeats up-counting and down-counting (FIG. 3A). The horizontal axis in FIG. 3 means time.

  The PWM signal is repeatedly turned on and off with a period for each timing (hereinafter referred to as a valley of the PWM timer) for shifting from down-counting to up-counting as one carrier period (FIGS. 3B to 3D).

  Regarding the setting of one carrier cycle of the PWM signal, it is desirable that the setting can be made shorter (high frequency) from the viewpoint of improving controllability. On the other hand, the phase current conversion unit 20 acquires the phase current of the brushless motor 3. There is also a restriction that it must be set longer than the processing time from signal output to signal output in the PWM signal generation unit 9.

  Among them, the motor phase estimation unit 17 estimates the phase by solving the voltage equation using the resistance value and inductance value of the brushless motor 3, the current value of each phase, the applied voltage value, and the like. A relatively large amount of arithmetic processing is required.

  Therefore, as shown in FIG. 3, motor phase estimation, rotor speed detection, current command calculation, basic output voltage calculation (FIG. 3 (2)), waveform improvement from inverter applied voltage and phase current acquisition (FIG. 3 (1)) A series of arithmetic processing up to voltage calculation (FIG. 3 (3)) and PWM signal generation (FIG. 3 (4)) is within one carrier cycle, and reflected to the PWM signal at the timing of the valley of the next PWM timer (FIG. A sequence in which 3 (5)) is performed has been generally used.

  3 (1) ′ to FIG. 3 (5) ′ and FIG. 3 (1) ″ to FIG. 3 (5) ″ mean the repetition of FIG. 3 (1) to FIG. 3 (5).

  As an example, consider a case where the brushless motor 3 rotates at 100 rps in a system in which a 4-pole motor is used as the brushless motor 3 and the carrier frequency of the inverter 2 is 10 kHz.

  Since the brushless motor 3 is a quadrupole motor, the electrical frequency of the basic output voltage is 200 Hz when the mechanical angle is one rotation in two electrical angles and the rotation is 100 rps.

  In the waveform improvement voltage calculation unit 22, the phase current waveform distortion improvement voltage is calculated by calculating the fifth harmonic component with respect to the basic output voltage based on the phase information of the brushless motor 3 estimated by the motor phase estimation unit 17. (FIG. 4) is obtained, and the frequency of this waveform is 5 times 200 Hz, which is 1 kHz.

  Since the waveform improvement voltage (electric frequency 1 kHz), which is a fifth-order harmonic component, is calculated for the basic output voltage every 10 kHz of the carrier frequency, the electrical angle resolution of this waveform is 36 as shown in FIG. Therefore, the resolution is not sufficient to generate a sine waveform.

Therefore, in the first embodiment of the present invention, the control is performed in the sequence as shown in FIG. In FIG. 5, as in FIG. 3, the PWM timer (a) repeats up-counting and down-counting (FIG. 5 (a)). The PWM signal of each phase is repeatedly turned on / off every one carrier cycle (FIGS. 5B to 5D). 5 (1) 'and FIG. 5 (1) "... mean repetition of FIG. 5 (1).

  Computation of the waveform improvement voltage that is a fifth-order harmonic component with respect to the basic output voltage, which requires relatively little processing time, is performed once during the down-counting and up-counting of the PWM timer (FIG. 5A). (FIG. 5 (3) and FIG. 5 (6)), the PWM signal generator 9 generates a PWM signal by superimposing it on the basic output voltage waveform obtained for each carrier cycle (FIG. 5 (4) and FIG. 5). (7)) and the reflection to the PWM signal (FIG. 5 (5) and FIG. 5 (8)) is performed at the timing of the valley and peak of the PWM timer (shift from up-count to down-count). The electrical angle resolution of the waveform of the phase current waveform distortion improving voltage was doubled compared to that shown in FIG. 3 (FIG. 6).

  In the above example, a system in which a 4-pole motor is used as the brushless motor 3 and the carrier frequency of the inverter 2 is 10 kHz, when the brushless motor 3 is rotating at 100 rps, the waveform improvement voltage is as shown in FIG. The electrical angle resolution is 18 °, and the improvement accuracy to the sine waveform is improved.

  Note that the phase information of the brushless motor 3 used for the waveform improvement voltage calculation (FIG. 5 (6)) while the PWM timer in FIG. 5 is counting up is the change in phase estimated by the motor phase estimation unit 17 for each carrier period. It is assumed that 1/2 of the amount is added to the previous estimation result.

  As a result, in the inverter control apparatus for driving a motor of the present invention, it is possible to improve the waveform distortion in the vicinity of the zero cross point of the motor phase current during driving in a state where the influence of the deviation from the compensation value is reduced to the maximum. It is possible to maintain good motor drive with reduced torque pulsation and rotational speed fluctuation.

(Embodiment 2)
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 improve the distortion of the motor phase current with high accuracy by compensating the phase shift, and can supply a stable current while maintaining high efficiency. Therefore, it can be widely used for AV equipment (particularly small equipment) that requires a small motor starting device.

1 is a system configuration diagram of an inverter control device for driving a motor according to Embodiment 1 of the present invention. The figure which shows the operation result in Embodiment 1 of this invention. The figure which shows the control timing of the general motor drive inverter control device The figure which shows the waveform improvement voltage in the control shown in FIG. The figure which shows the control timing in Embodiment 1 of this invention. The figure which shows the waveform improvement voltage in the control shown in FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 AC power supply 2 Inverter 3 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 to 14w, 14x to 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 Basic output Voltage calculator 22 Waveform improvement voltage calculator

Claims (4)

A rectifier circuit that receives an AC power supply, an inverter that converts DC power into AC power, a motor, and a control calculation unit that controls the operation of the inverter,
In the control calculation unit, a basic output voltage calculation unit that calculates a voltage to be output by the inverter necessary for maintaining the rotation of the motor;
A waveform improvement voltage calculation unit that calculates a voltage that improves the phase current waveform distortion of the motor in a cycle shorter than a calculation cycle in the basic output voltage calculation unit;
A PWM signal for updating the PWM signal for controlling the inverter based on the voltage calculated by the basic output voltage calculation unit and the voltage calculated by the waveform improvement voltage calculation unit at a calculation cycle in the waveform improvement voltage calculation unit. And generating a waveform improvement voltage, which is a fifth-order harmonic component with respect to the basic output voltage, once each during the down-counting and up-counting of the PWM timer, and the PWM signal generating unit , Superimposed on the basic output voltage waveform obtained every carrier cycle, generates the PWM signal, and is reflected in the PWM signal at the timing of shifting from the up-count to the down-count of the PWM timer Inverter control device. The calculation period of the voltage to be output by the inverter necessary for maintaining the rotation of the motor in the basic output voltage calculation unit coincides with the carrier period of the PWM signal for controlling the inverter, and in the waveform improvement voltage calculation unit 2. The inverter control apparatus for driving a motor according to claim 1, wherein a calculation cycle of a voltage for improving phase current waveform distortion of the motor coincides with a half of a carrier cycle of a PWM signal for controlling the inverter. 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 set. The motor drive inverter control device according to claim 1 or 2, wherein a combination of the reactor and the capacitor is determined to be greater than 40 times the AC power supply 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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