JP2007028778A - Electric motor driver and air conditioner using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electric motor driver for providing a stable and fast rotation in the state where a position estimation error of a rotor rapidly increases. <P>SOLUTION: A load quantity detecting means 19 is used, and detects the quantity of a load in a three-phase electric motor 3. Only when the detected quantity of the load is the predetermined quantity of the load or more in the three-phase electric motor, phase currents detected in the three-phase electric motor and a torque required for attaining a target rotation speed are generated. The electric motor driver switches a proportional integral operation for determining an instruction current by using a target current, to a proportional integral-differentiation operation. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an electric motor drive device that drives an electric motor such as a brushless DC motor at an arbitrary rotation speed.

  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 technologies, 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 than a rectangular wave driving that is driven by a rectangular wave current is becoming mainstream.

  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 of estimating the rotor position, there is a method of estimating the induced voltage of the motor, and a method of estimating from the current flowing through the inverter bus (for example, Patent Document 1), or 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 position sensorless sine wave drive described in Patent Document 1. 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.

  Terminals 8u, 8v, and 8w of the brushless motor 3 are connected to an interconnection point of the switching elements 12u and 13u, an interconnection point of the switching elements 12v and 13v, and an interconnection point of the switching elements 12w and 13w in the inverter 2, 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 includes 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 inverter applied voltage detection means 16. The induced voltage of the brushless motor 3 is estimated by the induced voltage estimation means 17 from the DC voltage output from Further, the rotor magnetic pole position and speed of the brushless motor 3 are estimated by the rotor position estimating means 18 from the estimated induced voltage.

  The PWM signal generation unit 9 determines a target current for generating a torque necessary to reach the target speed based on the information on the estimated rotor magnetic pole position. Further, the command current and the command voltage are determined using proportional-integral calculation (PI control) so that the phase current of the brushless motor 3 detected by the current detection means 7 arranged on the inverter bus becomes the target current, and the inverter 2 Outputs a signal to control

  FIG. 4 shows a system configuration for realizing the position sensorless sine wave drive described in Patent Document 2. The means for detecting the phase current of the brushless motor 3 is changed from the current detection means 7 arranged on the inverter bus to the current sensors 20v and 20w. The other structure 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, there is a problem that the position estimation error increases rapidly when the load on the motor is heavy, and the step-out occurs due to the generated position estimation error. SUMMARY OF THE INVENTION An object of the present invention is to provide an electric motor drive device that prevents a step-out in a state where a rotor position estimation error increases rapidly and realizes stable driving.

  In order to solve the above-described conventional problems, the electric motor drive device of the present invention is provided with load amount detection means, and when the load detected by the load detection means exceeds a preset value, each of the detected three-phase electric motors The arithmetic expression for determining the command current from the target current that generates the phase current and the torque required to reach the target rotational speed is switched from proportional integral calculation (PI control) to proportional integral differential calculation (PID control) with a derivative term added. Thus, it is possible to improve the voltage followability applied to the inverter for realizing the target speed, and to realize an electric motor drive device capable of stable driving in a state where the increase in rotor position estimation error is fast.

  The electric motor driving device of the present invention can realize an electric motor driving device capable of stable driving in a state where the increase in rotor position estimation error is fast.

The first invention is provided with load amount detection means for detecting the load amount of the three-phase motor, and each phase of the detected three-phase motor is detected only when the load amount detected by the load amount detection means is not less than a preset value. By switching the proportional-plus-integral-derivative calculation (PID control) by adding a differential term from the proportional-integral calculation (PI control) to the calculation formula that determines the command current from the target current that generates the torque necessary to reach the current and the target rotational speed Thus, it is possible to improve the voltage followability applied to the inverter for realizing the target speed, and to realize an electric motor drive device capable of stable driving in a state where the increase in rotor position estimation error is fast.

  In the second invention, in particular, the detection of the phase current flowing through the three-phase motor of the first invention is detected using the current detection means arranged on the inverter bus, and the phase current can be generated at low cost.

  The third aspect of the invention detects the phase current flowing in the three-phase motor of the first aspect of the invention using a current sensor, and can detect the phase current with high accuracy.

  In particular, the fourth aspect of the invention uses the motor drive device of the first to third aspects of the invention in an air conditioner having pressure detection means at the discharge port and suction port of the compressor, and the discharge port and suction port of the compressor. By using the difference between the three-phase motor as a load amount, a motor drive device capable of stable driving at a low cost and with a fast increase in rotor position estimation error without newly providing load amount detection means is provided. It is realized.

  In particular, the fifth aspect of the invention uses the electric motor drive device of the first to third aspects of the invention in an air conditioner having a heat exchanger temperature detection means in each of the indoor unit and the outdoor unit, Using the indoor heat exchanger temperature detection means arranged in the heat exchanger of the machine, and during the cooling operation, using the outdoor heat exchanger temperature detection means arranged in the heat exchanger of the outdoor unit, the heat exchange detected in each operation state By using the temperature as a load amount for the three-phase motor, a motor drive device that can be driven stably at a low cost and with a fast increase in rotor position estimation error without providing a new load amount detection means is realized. To do.

  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 according to the first embodiment 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.

  Terminals 8u, 8v, and 8w of the brushless motor 3 are connected to an interconnection point of the switching elements 12u and 13u, an interconnection point of the switching elements 12v and 13v, and an interconnection point of the switching elements 12w and 13w in the inverter 2, 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 includes 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 inverter applied voltage detection means 16. The induced voltage of the brushless motor 3 is estimated by the induced voltage estimation means 17 from the DC voltage output from Further, the rotor magnetic pole position and speed of the brushless motor 3 are estimated by the rotor position estimating means 18 from the estimated induced voltage.

  The PWM signal generation unit 9 determines a target current for generating a torque necessary to reach the target speed based on the information on the estimated rotor magnetic pole position. Further, the command current and the command voltage are determined using proportional-integral calculation (PI control) so that the phase current of the brushless motor 3 detected by the current detection means 7 arranged on the inverter bus becomes the target current, and the inverter 2 Outputs a signal to control In the command rotation number calculation switching means 11, an arithmetic expression for determining the command speed is determined when the load amount detected by the load amount detection means 19 for detecting the load amount of the brushless motor 3 is greater than or less than a preset value. Switching between proportional integral calculation (PI control) or proportional integral differential calculation (PID control) with a differential term added. Switching between proportional integral calculation (PI control) and proportional integral derivative calculation (PID control) is determined that if the load amount is greater than or equal to a preset value, the rotor position estimation error increases quickly and is likely to step out. Proportional-integral-derivative calculation (PID control) is performed, and the voltage applied to the inverter 2 for realizing the target rotational speed can easily follow, so that stable rotation can be obtained.

(Embodiment 2)
FIG. 2 is a block diagram in the second embodiment of the present invention, which detects the phase current flowing through the brushless motor 3 using the current sensors 20v and 20w, thereby accurately detecting the phase current. Since other configurations and operations are the same as those in the first embodiment, description thereof is omitted.

(Embodiment 3)
FIG. 3 is a block diagram according to the third embodiment of the present invention. 21 is an outdoor unit of the air conditioner, 22 is a compressor, 23 is a discharge port pressure detection means arranged at the discharge port of the compressor, and 24 is a suction port pressure detection means arranged at the suction port of the compressor.

  By calculating the difference between the pressures detected by the discharge port pressure detection means 23 and the suction port pressure detection means 24 and using the calculated pressure difference as the load amount, the load amount detection means 19 is not newly provided, and it is inexpensive. In addition, an electric motor drive device capable of stable driving in a state where the increase in rotor position estimation error is fast is realized.

(Embodiment 4)
FIG. 4 is a block diagram according to the fourth embodiment of the present invention. 25 is an indoor unit of the air conditioner, 26 is an AC power source, 27 is a DC voltage generating unit that converts an AC voltage supplied from the indoor unit 25 into a DC voltage, and 28 is a heat exchanger of the indoor unit 25. The indoor heat exchanger temperature detecting means 29 is an outdoor heat exchanger temperature detecting means arranged in the heat exchanger of the outdoor unit 21.

  By using the outdoor heat exchanger temperature detected by the outdoor heat exchanger temperature detecting means 29 during the cooling operation and the indoor heat exchanger temperature detected by the indoor heat exchanger temperature detecting means 28 during the heating operation as the load amount, the load amount detecting means Without newly providing 19, it is possible to realize an electric motor drive device that can be stably driven at a low cost and in a state where the increase in the rotor position estimation error is fast.

  As described above, the electric motor drive device of the present invention can be stably driven in a state where the increase in the rotor position estimation error is fast, so that it can be used for industrial equipment, products, and the like using the position sensorless brushless DC motor. Can also be used.

The block diagram of the electric motor drive device in Embodiment 1 of this invention Block diagram of an electric motor drive device according to Embodiment 2 of the present invention The block diagram of the air conditioner in Embodiment 3 of this invention The block diagram of the air conditioner in Embodiment 4 of this invention Block diagram of a conventional current sensorless motor drive device Block diagram of a conventional motor drive unit with a current sensor

Explanation of symbols

2 Inverter 3 Brushless motor (three-phase motor)
6 Control section 7 Current detection means 9 PWM signal generation means 10 Base driver 11 Command rotation speed calculation switching means 16 Inverter applied voltage detection means 17 Induced voltage estimation means 18 Rotor position speed estimation means 19 Load amount detection means

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 Based on detection means, information on the estimated rotor magnetic pole position, a target current for generating a torque necessary for the rotation speed of the three-phase motor to reach a target rotation speed by proportional-integral calculation, and the current detection means A PWM signal generating means for determining a command current from the detected current value and generating a PWM signal for controlling the inverter, and a load amount of the three-phase motor When the load detected by the load detection means is greater than or equal to a preset value, the proportional integral calculation that determines the command current is performed as a proportional integral differential calculation. An electric motor drive device characterized by switching to The motor drive device according to claim 1, wherein the phase current of the three-phase motor is detected from the inverter bus. The motor driving device according to claim 1, wherein the phase current of the three-phase motor is detected using a current sensor. The outdoor unit of the air conditioner includes pressure detection means for detecting the pressure of the refrigerant at each of the discharge port and the suction port of the compressor, and the pressure difference between the discharge port and the suction port is set as a load amount of the three-phase motor. An air conditioner using the electric motor drive device according to claim 1. The air conditioner indoor unit heat exchanger has an indoor heat exchanger temperature detecting means for detecting the heat exchanger temperature, and the outdoor unit heat exchanger has an outdoor heat exchanger temperature detecting means for detecting the heat exchanger temperature. In the heating operation, the indoor heat exchanger temperature detection means arranged in the indoor unit is detected, and in the cooling operation, the outdoor heat exchanger temperature detection means arranged in the outdoor unit is used to detect each heat exchanger temperature, An air conditioner using the motor drive device according to claim 1, wherein the detected heat exchanger temperature is a load amount of the three-phase motor.

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