JP2005237131A - Motor drive and air conditioner employing it - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a motor drive capable of high speed rotation in which stabilized rotation is enabled even in a state that a positional estimation error of a rotor increases at a high rate. <P>SOLUTION: Without altering a voltage saturation rate set value compared with a voltage saturation rate, i.e. the degree of the voltage saturation of a voltage command value applied to a motor 3, a speed proportional integration operation gain switching means 11 compares the voltage saturation rate with the voltage saturation rate set value and switches the gain set value of proportional integration operation for determining a command speed from the estimated number of revolutions and a target speed only when the voltage saturation rate is not lower than the voltage saturation rate set value. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an electric motor driving device that drives an electric motor such as a brushless DC motor at an arbitrary number of rotations, and an air conditioner using the electric motor driving device.

  In recent years, in an apparatus for driving an electric motor such as a compressor in an air conditioner, there is an increasing need to reduce power consumption from the viewpoint of protecting the global environment. Among them, as one of the power saving techniques, an inverter that drives a highly efficient electric motor such as a brushless DC motor at an arbitrary frequency is widely used. Furthermore, as a driving technique, a sine wave driving technique that is more efficient and can reduce noise is becoming mainstream as compared with a rectangular wave driving that is driven by a rectangular wave voltage.

  When driving an electric motor such as a compressor in an air conditioner, it is difficult to attach a sensor for detecting the position of the rotor of the electric motor. A sinusoidal drive technique has also been invented. As a method for estimating the position of the rotor, there is a method performed by estimating from the induced voltage of the motor, a method of estimating from the current flowing through the inverter bus (for example, Patent Document 1), and the method of flowing to the motor using a current sensor. A method of estimating from the current (for example, Patent Document 2) has been invented.

  FIG. 3 shows a system configuration for realizing the conventional position sensorless sine wave drive described in Patent Document 1.

  In FIG. 3, 1 is a DC power source, 2 is an inverter, 3 is a brushless motor, 4 is a stator, 5 is a rotor, and 6 is a control unit.

  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. A U-phase terminal 8u is connected to the non-connection end of the U-phase winding 4u, a V-phase terminal 8v is connected to the non-connection end of the V-phase winding 4v, and a W-phase terminal 8w is connected to the non-connection end of the W-phase winding 4w.

  The inverter 2 has three series circuits in which a pair of switching elements are connected in series in a relationship between the upstream side and the downstream side of the current, for U phase, for V phase, and for W phase. A DC voltage output from the DC power source 1 is applied to these series circuits. The U-phase series circuit includes an upstream side switching element 12u and a downstream side switching element 13u. The series circuit for V phase includes an upstream side switching element 12v and a downstream side switching element 13v. The series circuit for W phase includes an upstream side switching element 12w and a downstream side switching element 12w. Free wheel diodes 14u, 14v, 14w, 15u, 15v, and 15w are connected in parallel with the switching elements.

  In the inverter 2, the terminals 8u, 8v, 8w of the brushless motor 3 are connected to the interconnection point of the switching elements 12u, 13u, the interconnection point of the switching elements 12v, 13v, and the interconnection point of the switching elements 12w, 13w, respectively. .

  The DC voltage applied to the inverter 2 is converted into a three-phase AC voltage by a circuit such as the switching element in the inverter 2 described above, and the brushless motor 3 is thereby driven.

  In order to realize the target speed given from the outside, the PWM signal generating means 9 generates a PWM signal for driving the switching element of the inverter 2 in order to output the output voltage calculated from the error with the current speed. The switching signals 12u, 12v, 12w, 13u, 13v, and 13w operate by being converted by the base driver 10 into drive signals for electrically driving the elements.

  The control unit 6 receives the phase current of the brushless motor 3 detected by the current detection means 7 arranged on the inverter bus, the output voltage calculated by the PWM signal generation means 9 and the DC power source 1 detected by the DC voltage detection means 16. The induced voltage estimation means 17 estimates the induced voltage of the brushless motor 3 from the output DC voltage. Further, the rotor magnetic pole position and speed of the brushless motor 3 are estimated by the rotor position speed estimation means 18 from the estimated induced voltage.

  Further, in order to prevent the voltage applied to the brushless motor 3 from being distorted from a sine wave and increasing the estimation error of the rotor position, each phase of the brushless motor 3 determined by the PWM signal generating means 9 is prevented. A voltage saturation rate, which is a ratio at which the peak of the voltage to be applied to the DC voltage output from the DC power supply 1 detected by the DC voltage detection means 16 is compared with a preset voltage saturation rate setting value, Only when the voltage saturation rate is equal to or higher than the voltage saturation rate setting value, the voltage saturation protection means 19 performs protection control for decreasing the target rotational speed value given from the outside until the voltage saturation rate becomes smaller than the voltage saturation rate setting value. .

  The PWM signal generation means 9 determines a command speed from the rotational speed estimated by the rotor position speed estimation means 18 and the target speed using a proportional integration calculation, and controls the inverter 2 based on the determined command speed. Is output.

  FIG. 4 shows a system configuration for realizing the conventional position sensorless sinusoidal drive described in Patent Document 2, and includes a current sensor 20v, a current sensor 20v, a current detector 7 arranged on the inverter bus for detecting a phase current of the brushless motor 3. The other configuration is the same as that of the invention described in Patent Document 1.

The drive control of the brushless motor 3 is performed with the circuit configuration as described above.
JP 2003-189670 A JP 2000-350489 A

  However, in the conventional position sensorless sine wave drive based on the estimation of the induced voltage, the degree of voltage saturation of the voltage command value to be applied to the motor is prevented in order to prevent step-out due to an increase in rotor position estimation error. When a certain voltage saturation rate is equal to or higher than a preset voltage saturation rate setting value, protection control is performed to lower the target rotational speed value given from the outside until the voltage saturation rate becomes smaller than the voltage saturation rate setting value. In a heavy load, the position estimation error increases rapidly, and there is a case where the step out occurs before the protection control is performed or during the protection control operation. In addition, if the preset voltage saturation rate is reduced, step-out can be prevented when the load on the motor is heavy and the position estimation error increases rapidly, but when the load on the motor is not heavy, the rotation speed of the motor Since the protection control for lowering the target value operates quickly, there is a problem that it is difficult to rotate at high speed. SUMMARY OF THE INVENTION An object of the present invention is to solve the above-described conventional problems, and to provide an electric motor drive device that can stably rotate and can rotate at high speed even when a rotor position estimation error increases rapidly.

In order to solve the above-described conventional problems, the electric motor driving device of the present invention is configured so that the voltage saturation ratio setting value to be compared with the voltage saturation ratio which is the degree of voltage saturation of the voltage command value applied to the electric motor is changed. Compare the saturation rate with the voltage saturation setting value, and switch the gain setting value for proportional integral calculation that determines the command speed from the estimated speed and target speed only when the voltage saturation rate is equal to or higher than the voltage saturation rate setting. By improving the voltage followability applied to the inverter for realizing the speed, the motor drive device that realizes stable rotation and can rotate at high speed even when the rotor position estimation error increases rapidly is realized. It is.

  The motor drive device of the present invention can realize a stable rotation even in a state where the increase in the rotor position estimation error is fast, and can realize a motor drive device capable of high-speed rotation.

  The first invention compares the voltage saturation rate with the voltage saturation set value without changing the voltage saturation rate setting value to be compared with the voltage saturation rate which is the degree of voltage saturation of the voltage command value applied to the three-phase motor. Only when the voltage saturation rate is equal to or higher than the voltage saturation rate setting, the inverter for realizing the target speed is switched by switching the gain setting value of proportional integral calculation that determines the command speed from the estimated speed and the target speed. It is possible to improve the voltage followability to be applied, realize a stable rotation even in a state where the increase in the rotor position estimation error is fast, and realize an electric motor drive device capable of high-speed rotation.

  In the second invention, in particular, by switching only the proportional term gain of the gain setting value of the proportional integral calculation of the first invention and improving the voltage followability applied to the inverter for realizing the target speed, It is possible to realize a motor drive device that can achieve stable rotation and can rotate at a high speed while the position estimation error increases rapidly.

  In particular, the third invention detects the phase current flowing through the three-phase motor of the first or second invention using current detection means arranged on the inverter bus, and detects the phase current at low cost. can do.

  In the fourth aspect of the invention, in particular, the detection of the phase current flowing through the three-phase motor of the first or second aspect of the invention is detected using a current sensor, and the phase current can be detected with high accuracy.

  In the fifth aspect of the invention, in particular, the motor drive device according to the first to fourth aspects of the present invention is used in an air conditioner, and an air conditioner that makes use of the effects of the respective motor drive devices can be realized.

  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 block diagram showing the configuration of the electric motor drive apparatus according to Embodiment 1 of the present invention.

  1 is a DC power source, 2 is an inverter, 3 is a brushless motor, 4 is a stator, 5 is a rotor, and 6 is a control unit.

  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. A U-phase terminal 8u is connected to the non-connection end of the U-phase winding 4u, a V-phase terminal 8v is connected to the non-connection end of the V-phase winding 4v, and a W-phase terminal 8w is connected to the non-connection end of the W-phase winding 4w.

  The inverter 2 has three series circuits in which a pair of switching elements are connected in series in a relationship between the upstream side and the downstream side of the current, for U phase, for V phase, and for W phase. A DC voltage output from the DC power source 1 is applied to these series circuits. The U-phase series circuit includes an upstream side switching element 12u and a downstream side switching element 13u. The series circuit for V phase includes an upstream side switching element 12v and a downstream side switching element 13v. The series circuit for W phase includes an upstream side switching element 12w and a downstream side switching element 12w. Free wheel diodes 14u, 14v, 14w, 15u, 15v, and 15w are connected in parallel with the switching elements.

  In the inverter 2, the terminals 8u, 8v, 8w of the brushless motor 3 are connected to the interconnection point of the switching elements 12u, 13u, the interconnection point of the switching elements 12v, 13v, and the interconnection point of the switching elements 12w, 13w, respectively. .

  The DC voltage applied to the inverter 2 is converted into a three-phase AC voltage by a circuit such as the switching element in the inverter 2 described above, and the brushless motor 3 is thereby driven.

  In order to realize the target speed given from the outside, the PWM signal generating means 9 generates a PWM signal for driving the switching element of the inverter 2 in order to output the output voltage calculated from the error with the current speed. The switching signals 12u, 12v, 12w, 13u, 13v, and 13w operate by being converted by the base driver 10 into drive signals for electrically driving the elements.

  The control unit 6 receives the phase current of the brushless motor 3 detected by the current detection means 7 arranged on the inverter bus, the output voltage calculated by the PWM signal generation means 9 and the DC power source 1 detected by the DC voltage detection means 16. The induced voltage estimation means 17 estimates the induced voltage of the brushless motor 3 from the output DC voltage. Further, the rotor magnetic pole position and speed of the brushless motor 3 are estimated by the rotor position speed estimation means 18 from the estimated induced voltage.

  Further, in order to prevent the voltage applied to the brushless motor 3 from being distorted from a sine wave and increasing the estimation error of the rotor position, each phase of the brushless motor 3 determined by the PWM signal generating means 9 is prevented. A voltage saturation rate, which is a ratio at which the peak of the voltage to be applied to the DC voltage output from the DC power supply 1 detected by the DC voltage detection means 16 is compared with a preset voltage saturation rate setting value, Only when the voltage saturation rate is equal to or higher than the voltage saturation rate setting value, the voltage saturation protection means 19 performs protection control for decreasing the target rotational speed value given from the outside until the voltage saturation rate becomes smaller than the voltage saturation rate setting value. .

  The PWM signal generation means 9 determines a command speed from the rotational speed estimated by the rotor position speed estimation means 18 and the target speed using a proportional integration calculation, and controls the inverter 2 based on the determined command speed. Is output. In the speed proportional integral calculation gain switching means 11, the voltage saturation protection means 19 detects whether the voltage saturation rate is greater than or equal to the voltage saturation rate set value and when the voltage saturation rate is less than the voltage saturation rate set value. The proportional term gain and integral term gain used in the proportional integral calculation that determines the speed are switched. Switching between the proportional term gain and integral term gain is determined that if the voltage saturation rate is greater than or equal to the voltage saturation set value, the load of the brushless motor 3 is heavy, so that the rotor position estimation error increases rapidly and is likely to step out. Since the proportional term gain and the integral term gain are increased, the voltage applied to the inverter 3 for realizing the target speed to be lowered by the voltage saturation protection means 19 can easily follow, so that stable rotation can be obtained. Furthermore, since it is not necessary to change the voltage saturation setting value, high-speed rotation is possible.

  Further, since the integral term gain used in the proportional integral calculation is used to eliminate the residual deviation when the command speed approaches the target speed, it is possible to only switch the proportional term gain.

(Embodiment 2)
FIG. 2 is a block diagram showing the configuration of the electric motor driving apparatus according to the second embodiment of the present invention. From the current detection means 7 to the current sensor 20v, the detection means for the phase current flowing through the brushless motor 3 according to the first embodiment is arranged on the inverter bus. 20w, and the other configuration and operation are the same as those in the first embodiment, and thus the description thereof is omitted.

  As described above, the electric motor drive device of the present invention realizes stable rotation in a state where the increase in the rotor position estimation error is fast, and enables high-speed rotation, so that it is other than an air conditioner using a brushless DC motor. It can be widely used for applications such as air-conditioning equipment, refrigeration equipment, and industrial equipment.

Configuration block diagram of electric motor drive device according to Embodiment 1 of the present invention Configuration block diagram of an electric motor drive device in Embodiment 2 of the present invention Configuration block diagram of a conventional current sensorless motor drive device Configuration block diagram of a conventional motor drive unit with a current sensor

Explanation of symbols

DESCRIPTION OF SYMBOLS 2 Inverter 3 Brushless motor 6 Control part 7 Current detection means 9 PWM signal generation means 10 Base driver 11 Speed proportional integral calculation gain switching means 16 DC voltage detection means 17 Induced voltage estimation means 18 Rotor position speed estimation means 19 Voltage saturation protection means 20v, 20w current sensor

Claims (5)

A three-phase motor, an inverter, a current detection means for detecting a phase current flowing in the three-phase motor, a DC voltage detection means of a DC power source connected to the inverter, a voltage value output from the inverter and the current detection Induced voltage estimating means for estimating the induced voltage of the motor from the current value detected by the means, and rotor position speed for estimating the rotor magnetic pole position and the rotational speed of the motor based on the estimated induced voltage estimated value An estimation means, a PWM signal generation means for determining a command speed from the estimated rotation speed and a target rotation speed using a proportional integral calculation, and generating a PWM signal for controlling the inverter from the command speed; and the DC voltage detection The voltage saturation rate that is the degree of voltage saturation is calculated from the output of the means and the voltage command value applied to the electric motor, and compared with a preset voltage saturation rate setting value, Only when the pressure saturation rate is equal to or higher than the voltage saturation rate set value, the motor drive device is constituted by voltage saturation protection means for reducing the target rotational speed value given from the outside until the voltage saturation rate becomes smaller than the voltage saturation rate set value. The motor drive device according to claim 1, wherein when the voltage saturation rate is equal to or higher than a voltage saturation rate set value, a proportional term gain and an integral term gain used in the proportional integration calculation are switched. 2. The electric motor drive device according to claim 1, wherein when the voltage saturation rate is equal to or higher than the voltage saturation rate set value, the proportional term gain used in the proportional integration calculation is switched. 3. The motor driving device according to claim 1, wherein the phase current of the three-phase motor is detected from the inverter bus. 3. The motor driving device according to claim 1, wherein the phase current of the three-phase motor is detected using a current sensor. An air conditioner using the electric motor drive device according to any one of claims 1 to 4.

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