JP2009131001A - Inverter controller for driving motor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an inverter controller for driving a motor, which satisfies even the harmonic regulation of a power supply current while being achieved in the reduction of size, weight and cost. <P>SOLUTION: In the inverter controller for driving a motor provided with a capacitor of very small capacitance between a reactor of very small capacitance and a DC bus line of the inverter, a voltage distortion amount is calculated from the time series variation of an inverter applying voltage value. An indication rotation speed is corrected corresponding to the calculated result to avoid motor abnormal stop even when a power source distortion occurs, with the continuous operation of the motor. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a motor drive inverter control device using a small capacity reactor and a small capacity capacitor.

  As a general motor drive inverter control device used in a general-purpose inverter or the like, a motor drive inverter control device as shown in FIG. 6 is well known.

  In FIG. 6, the main circuit is composed of a DC power supply device 113, an inverter 2 and a motor 3. The DC power supply device 113 is used for the AC power supply 1, the rectifier circuit 7, and the DC voltage source of the inverter 2. Are composed of a smoothing capacitor 112 for storing electrical energy and a power factor improving reactor 111 of the AC power source 1.

  On the other hand, in the control calculation unit, the PWM signal generation unit 9 that generates each phase voltage command value of the motor 3 based on the speed command of the motor 3 given from the outside, and each phase voltage generated by the PWM signal generation unit 9 The base driver 10 is configured to perform PWM control of the inverter 2 based on the command value.

  Here, when the AC power source 1 is 220 V (power frequency 50 Hz), the input of the inverter 2 is 1.5 kW, and the smoothing capacitor 112 is 1500 μF, the harmonic component of the power source current when the power factor improving reactor 111 is 5 mH and 20 mH. FIG. 7 shows the relationship between the power and the order with respect to the power frequency.

  FIG. 7 is shown together with the IEC (International Electrotechnical Commission) standard. When the power factor improving reactor 111 is 5 mH, the third harmonic component greatly exceeds that of the IEC standard. In the case of, it is understood that the IEC standard is cleared in the harmonic components up to the 40th order.

  For this reason, in order to clear the IEC standard even when the load is high, it is necessary to take measures such as further increasing the inductance value of the power factor improving reactor 111, increasing the size and weight of the inverter device, and the cost. There was an inconvenience of incurring UP.

  Therefore, for example, Patent Document 1 as shown in FIG. 8 describes a DC power supply device that suppresses an increase in inductance value of the power factor improving reactor 111 and achieves a reduction in power harmonic components and an increase in power factor. DC power supply devices have been proposed.

  In FIG. 8, the power supply voltage of the AC power supply 1 is applied to the AC input terminal of the full-wave rectifier circuit formed by bridge-connecting the diodes D1 to D4, and the output is charged to the intermediate capacitor C via the reactor Lin. The electric charge of the intermediate capacitor C is discharged to the smoothing capacitor CD, and a DC voltage is supplied to the load resistor RL.

  In this case, the transistor Q1 is connected to the positive and negative DC current path connecting the load side of the reactor Lin and the intermediate capacitor C, and the transistor Q1 is driven by the base drive circuit G1.

The circuit further includes pulse generation circuits I1 and I2 that apply a pulse voltage to the base drive circuit G1, and a dummy resistor Rdm. The pulse generation circuits I1 and I2 each detect a zero-cross point of the power supply voltage; A pulse current circuit that allows a pulse current to flow through the dummy resistor Rdm until the instantaneous value of the power supply voltage becomes equal to the voltage across the intermediate capacitor C from the detection of the zero cross point.

  Here, the pulse generation circuit I1 generates a pulse voltage in the first half of the half cycle of the power supply voltage, and the pulse generation I2 generates a pulse voltage in the second half of the half cycle of the power supply voltage.

  When the transistor Q1 is turned on and a current is forced to flow through the reactor Lin, a backflow prevention diode D5 is connected so that the charge of the intermediate capacitor C is not discharged through the transistor Q1, and further, the intermediate capacitor C A backflow prevention diode D6 and a reactor Ldc for enhancing the smoothing effect are connected in series to a path for discharging the electric charge of the current to the smoothing capacitor CD.

With the above configuration, by turning on the transistor Q1 in part or all of the phase interval in which the instantaneous value of the power supply voltage does not exceed the voltage across the intermediate capacitor C, harmonic components can be maintained while suppressing the increase in size of the device. Reduction and high power factor can be achieved (see, for example, Patent Document 1 and Non-Patent Document 1).
JP-A-9-266684 Inverter Drive Handbook Editorial Committee, “Inverter Drive Handbook”, published by Nikkan Kogyo Shimbun, first edition in 1995

  However, the above-described conventional configuration still has the smoothing capacitor CD having a large capacity and the reactor Lin (described in the simulation result at 1500 μF and 6.2 mH in Patent Document 1), and further the intermediate capacitor. C, transistor Q1, base drive circuit G1, pulse generation circuits I1 and I2, dummy resistor Rdm, backflow prevention diodes D5 and D6, and a reactor Ldc that enhances the smoothing effect, thereby increasing the size of the device and the number of parts. There was a problem of incurring a cost increase accompanying the increase.

  The present invention solves such a conventional problem, and provides a high-grade motor drive inverter control device that is small, light, and low in cost and does not deteriorate the drive performance of the motor. Objective.

  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 operation unit that controls the operation of the inverter. It consists of a diode bridge and a very small capacity reactor connected to the AC input side or DC output side of the diode bridge, and an extremely small capacity capacitor and inverter applied voltage detection means are arranged between the DC buses of the inverter. The control calculation unit includes an instruction rotation number determination unit that determines an instruction rotation number of the motor, and an inverter application that calculates a voltage distortion amount from a time-series change of an inverter application voltage value obtained by the inverter application voltage detection unit. The command rotation number obtained by the voltage distortion amount calculation unit and the command rotation number determination unit is set as the inverter applied voltage distortion amount. It is provided with a command rotational speed correction unit for correcting in accordance with the voltage distortion amount obtained by the calculation unit.

  As a result, a small, lightweight, and low cost motor drive inverter control device can be realized by using a small capacitor and small capacitor, and even when power supply voltage distortion occurs, the motor can be stopped abnormally and operated. Can be maintained.

  The motor drive inverter control device of the present invention can realize a small, light, and low cost motor drive inverter control device by using a small-capacity reactor and a small-capacitance capacitor, and can rotate the motor even if power supply voltage distortion occurs. Since the operation can be maintained, when the present control device is applied to the compressor drive of an air conditioner, it is possible to maintain the comfort by avoiding the abnormal stop of the compressor motor.

  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 rectifier circuit is a diode bridge, It is composed of an extremely small capacity reactor connected to the AC input side or DC output side of the diode bridge, and a capacitor and inverter applied voltage detection means are arranged between the DC buses of the inverter. An instruction rotation number determination unit that determines an instruction rotation number of the motor, an inverter applied voltage distortion amount calculation unit that calculates a voltage distortion amount from a time-series change of an inverter application voltage value obtained by the inverter application voltage detection unit, and an instruction A rotational speed correction unit is provided, and the commanded rotational speed obtained by the commanded rotational speed determination unit in the commanded rotational speed correction unit It is corrected in accordance with the voltage distortion amount obtained by inverter application voltage distortion amount calculating unit.

  As a result, it is possible to realize a highly reliable inverter control device for driving a motor that is capable of avoiding abnormal motor stop even when power supply distortion occurs while being small, light, and low cost.

  According to a second aspect, in the first aspect, the amount of voltage distortion obtained by the inverter applied voltage distortion amount calculation unit is decreased from an increase in inverter applied voltage value or increased from a decrease in every half cycle of the AC power supply. This is the number of changes.

  As a result, even when a sudden distortion that does not occur every cycle of the AC power supply voltage occurs, it is possible to realize a motor drive inverter control device that is small, light, and low in cost but highly reliable.

  According to a third aspect of the present invention, in the first aspect, the voltage distortion amount obtained by the inverter applied voltage distortion amount calculation unit is obtained by calculating the maximum value or the minimum value of the inverter applied voltage values for each half cycle of the AC power supply. This is the amount of change in the time interval.

  As a result, a highly reliable inverter control apparatus for driving a motor can be realized even in the case where distortion occurs such that the periodic interval of the AC power supply voltage, that is, the frequency becomes irregular.

  4th invention determines the combination of a reactor and a capacitor | condenser so that the resonant frequency of a reactor and a capacitor | condenser may become larger than 40 times the power supply frequency in any one invention of 1-3. The harmonic component of the power supply current can be suppressed and the IEC standard can be cleared.

  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 generates an AC power supply 1, a diode bridge 7 for converting AC power into DC power, a small capacity reactor 11 of 2 mH or less, a small capacity capacitor 12 of 100 μF or less, and a drive voltage supplied to the brushless motor 3. The inverter 2 for output and the control unit 6 for controlling 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 small-capacitance 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 of the switching element 13u and the switching element 13x in the inverter 2, the interconnection point of the switching element 13v and the switching element 13y, and the interconnection point of 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 can be configured by a microcomputer, a system LSI, or the like, and 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. Each block includes a function block 19, a command speed determination unit 21, a command speed correction unit 22, and an inverter applied voltage distortion amount calculation unit 23.

  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 motor phase estimation unit 17 outputs the phase current of the brushless motor 3 converted by the phase current conversion unit 20, the output voltage calculated by the PWM signal generation unit 9, and the inverter 2 detected by the inverter applied voltage detection unit 16. The phase of the brushless motor 3 is estimated based on the applied voltage information. Further, the rotor speed detector 18 estimates the speed of the brushless motor 3 from the estimated phase.

In the current command calculation unit 19, the current command execution value to be energized so that the rotor speed becomes the target speed based on the deviation information between the estimated speed of the brushless motor 3 and the target speed is calculated using PI calculation or the like. The PWM signal generation unit 9 generates a PWM signal for driving the brushless motor 3.

  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 generate a sinusoidal alternating current.

  Thus, in the present embodiment, the sine wave drive of the brushless motor 3 is realized by flowing a sine wave phase current.

  Furthermore, the target speed of the brushless motor 3 will be described. The target speed of the brushless motor 3 is normally determined by the instruction rotation speed determination unit 21, but in the embodiment of the present invention, the target speed is corrected by the instruction rotation speed correction unit 22 based on the result of the inverter applied voltage distortion amount calculation unit 23. It was set as the structure to do.

  This target speed can be corrected by adding a filter calculation and optimizing the control gain, etc., and constructing a control system that is as robust as possible to disturbances, and then distorting the inverter applied voltage that exceeds its limits. It is intended to be taken as a countermeasure against.

  FIG. 2 shows a first operation result of the motor drive inverter control apparatus of the present invention, and shows a power supply voltage waveform of the AC power supply 1, an inverter applied voltage, and a motor phase current waveform during the operation of the brushless motor 3. is there.

  Since the capacitor 12 of the present invention has a very small capacity, when a current flows through the brushless motor 3, the voltage applied to the inverter pulsates greatly with a cycle (= 10 msec) twice the power supply frequency fs (= 50 Hz).

  Furthermore, since the capacitor 12 has a very small capacity, if the power supply voltage waveform is distorted as shown in FIG. 3, the distortion appears directly in the inverter applied voltage. This distortion of the voltage applied to the inverter can be a factor that degrades the control stability of the system.

  For example, as described above, the information on the voltage applied to the inverter 2 detected by the inverter applied voltage detection means 16 is used for the estimation calculation of the phase of the brushless motor 3 in the motor phase estimation unit 17. When distortion of a frequency component higher than the power supply frequency occurs, the phase estimation calculation result may become unstable and deviate from the actual one.

  If an error occurs in the phase estimation calculation result in the motor phase estimation unit 17, excitation at each timing of the brushless motor 3 at the optimum timing cannot be performed, and the brushless motor 3 can be rotated at high speed in such an unstable state. Attempting to perform high torque rotation will result in an abnormal stop due to overcurrent.

  Therefore, in order to solve the above-described problem, the target speed is corrected by the command rotation speed correction unit 22 based on the result of the inverter applied voltage distortion amount calculation unit 23, and the brushless motor 3 is in a high speed rotation or high torque rotation region. When it is recognized that the inverter applied voltage is distorted during driving, the correction is performed to lower the target speed determined by the indicated rotational speed determination unit 21.

  As a result, even when a distortion of a frequency component higher than the power supply frequency occurs in the inverter applied voltage, the drive can be maintained without causing the brushless motor 3 to be abnormally stopped due to an excessive current or the like.

  This is because, for example, when this inverter control device is adapted to the compressor motor drive of an air conditioner, it avoids a situation where comfort is lost due to an abnormal stop of the compressor motor, and the cooling or heating capacity is reduced. Can continue to be in a state where comfort is not compromised.

(Embodiment 2)
In the second embodiment of the present invention, in the motor drive inverter control apparatus of the first embodiment, the voltage distortion amount obtained by the inverter applied voltage distortion amount calculation unit 23 is the inverter application for each half cycle of the AC power supply 1. The number of changes from increasing to decreasing or from decreasing to increasing was used.

  A method of calculating the distortion amount of the inverter applied voltage in the inverter applied voltage distortion amount calculation unit 23 will be described with reference to the flowchart of FIG.

  When the inverter application voltage Vinv (n) detected by the inverter application voltage detection means 16 is input (S1), the previously stored inverter application voltage Vinv (n-1) stored next time is loaded (S2). .

  The Vinv increase flag for storing whether or not the inverter printing pressure is increasing is set (Yes in S3), and the inverter detected voltage Vinv (n) detected this time is the previous detected inverter If it is equal to or higher than the applied voltage Vinv (n-1) (Yes in S4), the Vinv increase flag is reset because it is continuously increasing (S5).

  When the Vinv increase flag is set (Yes in S3) and the inverter applied voltage Vinv (n) detected this time is less than the previously detected inverter applied voltage Vinv (n-1) (No in S4) Since the inverter applied voltage has started to decrease, the Vinv increase flag is cleared (S6), and the Vinv distortion counter indicating the amount of distortion of the inverter applied voltage is incremented (S7).

  When the Vinv increase flag is cleared (No in S3) and the detected inverter applied voltage Vinv (n) is equal to or higher than the previously detected inverter applied voltage Vinv (n-1) (Yes in S8). Since the inverter applied voltage has started to increase from the state where the inverter applied voltage is decreasing, the Vinv increase flag is set (S9), and the Vinv distortion counter indicating the amount of distortion of the inverter applied voltage is incremented (S10).

  When the Vinv increase flag is cleared (No in S3), and the inverter applied voltage Vinv (n) detected this time is less than the previously detected inverter applied voltage Vinv (n-1) (No in S8). Resets the Vinv increase flag again because it is decreasing (S11).

  Finally, the inverter applied voltage Vinv (n) detected this time is stored for the next calculation (S12).

  The Vinv distortion counter is cleared every time that is a half cycle of the AC power supply 1 (S13, S14), and the distortion amount of the inverter applied voltage during this period is updated as needed.

  In addition, after the inverter application voltage Vinv (n) detected by the inverter application voltage detection means 16 is input, the control stability can be improved by inserting a low-pass filter operation to remove noise components. Is possible.

  As a result, it is possible to realize a highly reliable inverter control device for driving a motor that can avoid abnormal motor stop even when sudden distortion that does not always occur every cycle of the AC power supply voltage occurs.

(Embodiment 3)
In the third embodiment of the present invention, in the motor drive inverter control device of the first embodiment, the voltage distortion amount obtained by the inverter applied voltage distortion amount calculation unit 23 is the inverter application for each half cycle of the AC power supply 1. The amount of change in the time interval between the maximum values or the minimum values of the voltage values is used.

  A method of calculating the distortion amount of the inverter applied voltage in the inverter applied voltage distortion amount calculation unit 23 will be described with reference to the flowchart of FIG.

  When the inverter application voltage Vinv (n) detected by the inverter application voltage detection means 16 is input (S1), the previously detected inverter application voltage Vinv (n-1) stored next time and the inverter detected the previous time The applied voltage Vinv (n-2) is loaded (S2).

  The inverter detected voltage Vinv (n-1) detected last time is equal to or higher than the inverter applied voltage Vinv (n-2) detected last time (Yes in S3), and the inverter applied voltage Vinv (n) detected this time is detected last time. If the inverter applied voltage Vinv (n-1) is less than the calculated value (Yes in S4), the inverter applied voltage Vinv stored last time is determined from the count value of the free-run timer provided in the inverter applied voltage distortion amount calculation unit 23. The value interval is subtracted, and the result is set as the distortion amount of the inverter applied voltage (S5).

  Further, after the amount of distortion of the inverter applied voltage is calculated, the count value of the free-run timer is stored as the inverter applied voltage Vinv maximum value interval measured this time (S6), and the count value is cleared (S7).

  In the above description, the example in which the inverter applied voltage Vinv maximum value interval is measured is used. However, the minimum value of the inverter applied voltage may be captured and the time interval may be measured.

  As a result, it is possible to realize a highly reliable inverter control device for driving a motor capable of avoiding abnormal motor stop even in the case where distortion occurs such that the frequency interval of the AC power supply voltage, that is, the frequency becomes irregular. .

(Embodiment 4)
A specific method for determining the specifications of the small-capacity capacitor and small-capacity reactor 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 small capacitor and the small reactor is set to the power frequency in order to suppress the harmonic component of the power current and clear the IEC standard. The combination of the small capacitor and the small reactor is determined so as to be larger than 40 times fs.

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

That is, the combination of the small-capacitance capacitor and the small-capacity reactor 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 small-capacity capacitor and the small-capacity reactor, the harmonic component of the power supply current can be suppressed and the IEC standard can be cleared.

  Note that the present invention described in the first to third embodiments can be applied to a motor driving inverter control device that drives a motor using an inverter circuit. For example, an air conditioner equipped with an inverter circuit, a refrigerator, an electric washing machine, an electric dryer, an electric vacuum cleaner, a blower, a heat pump water heater and the like. In any product, the motor drive inverter device can be reduced in size and weight, so that the degree of freedom in product design can be improved and an inexpensive product can be provided.

  As described above, the motor drive inverter control device according to the present invention can realize a motor drive inverter control device that is small, light, and low cost by using a small-capacity reactor and a small-capacitance capacitor, resulting in power supply distortion. Even in cases, it is possible to avoid abnormal motor stop and save time loss of restart sequence execution by maintaining the drive. For information equipment (especially storage units such as hard disks) that require a small motor drive Can also be widely used.

The system block diagram of the inverter control apparatus for motor drive which shows Embodiment 1 of this invention The figure which shows the 1st operation result in Embodiment 1 of this invention. The figure which shows the 2nd operation result in Embodiment 1 of this invention. Control flowchart in inverter applied voltage distortion amount calculation unit in Embodiment 2 of the present invention Control flowchart in inverter applied voltage distortion amount calculation unit in Embodiment 3 of the present invention System configuration diagram of a general motor drive inverter control device The diagram which showed the relationship between the harmonic component of power supply current in the motor drive inverter apparatus of FIG. 6, and the order with respect to power supply frequency System configuration diagram of conventional DC power supply

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 Small capacity reactor 12 Small capacity capacitor 13u-13w Upper arm Switching element 13x to 13z Lower arm switching element 14u to 14w, 14x to 14z Free wheel diode 15 Bus current detector 16 Inverter applied voltage detection means 17 Motor phase estimation unit 18 Rotor speed detection unit 19 Current command calculation unit 20 Phase current conversion Unit 21 Instructed rotation speed determination unit 22 Instructed rotation speed correction unit 23 Inverter applied voltage distortion amount calculation unit 111 Reactor 112 Smoothing capacitor 113 DC power supply device D1 to D6 Diode Lin, Ldc Reactor C Intermediate capacitor D smoothing capacitor Q1 transistor G1 base driving circuit I1, I2 pulse generating circuit RL load resistance Rdm dummy resistor

Claims (4)

A rectifier circuit having an AC power supply as input, an inverter for converting DC power into AC power, a motor and a control operation unit for controlling the operation of the inverter, the rectifier circuit having a diode bridge and an AC of the diode bridge Consists of a reactor connected to the input side or the DC output side, a capacitor and an inverter applied voltage detection means are arranged between the DC buses of the inverter, and the control calculation unit is instructed to determine the indicated rotational speed of the motor A rotation speed determination unit, an inverter applied voltage distortion amount calculation unit that calculates a voltage distortion amount from a time-series change in an inverter application voltage value obtained by the inverter application voltage detection unit, and an instruction rotation obtained by the instruction rotation number determination unit An instruction rotation speed correction unit that corrects the number according to the voltage distortion amount obtained by the inverter applied voltage distortion amount calculation unit; Only motor drive inverter control apparatus. The voltage distortion amount obtained by the inverter applied voltage distortion amount calculation unit is defined as the number of times the inverter applied voltage value increases or decreases or decreases to increase in each half cycle of the AC power supply. Inverter control device for motor drive. The voltage distortion amount obtained by the inverter applied voltage distortion amount calculation unit is defined as a change amount of a time interval between maximum values or minimum values of inverter application voltage values in each half cycle of the AC power supply. Motor drive inverter control device. The motor drive inverter according to any one of claims 1 to 3, wherein a combination of the reactor and the capacitor is determined so that a resonance frequency between the reactor and the capacitor is larger than 40 times the power supply frequency. Control device.