JP5193421B2 - Electric motor control device - Google Patents

Description

  According to the present invention, in an inverter circuit, a composite current of three phases (U phase, V phase, W phase) is detected by a single overcurrent detection resistor, and a magnetic pole position is estimated by a microcomputer internal calculation to perform normal driving. The present invention relates to a motor control device that performs 180-degree energization control (sinusoidal modulation) in a position sensorless drive system.

  A permanent magnet synchronous motor including a permanent magnet rotor and a stator winding is often used for home appliances such as an air conditioner because of its high efficiency. The drive control of the permanent magnet synchronous motor needs to be performed by closely relating the magnetic pole position of the rotor and the phase of the motor current. In recent years, motor control has become more efficient, and current detection is performed with a single overcurrent detection shunt resistor without detecting the rotor magnetic pole position using a rotor position detection sensor such as a Hall element. A position sensorless driving method is adopted in which the magnetic pole position is estimated by A / D conversion and the motor is driven by a 180-degree energization method.

  By the way, in a washing machine, when a predetermined abnormality occurs in the control system, the drive of the motor by the inverter is temporarily stopped, but when the control is resumed after that, the synchronous motor is rotating by inertia and the magnetic pole position of the rotor Cannot be identified. In order to solve such a problem, Patent Document 1 describes that by providing a magnetic pole position sensor of a motor, the position is detected and driving by an inverter becomes possible.

  On the other hand, this Patent Document 1 also describes a sensorless driving method in which no magnetic pole position sensor is provided. When it falls into the state as described above, utilizing the fact that the rotational speed does not decrease rapidly due to the inertia of the rotor, the rotational frequency immediately before the occurrence of the abnormality is stored, and the operation is resumed using this position. It is described.

Japanese Patent Laid-Open No. 2005-6453

  However, in the case of a synchronous motor that drives an outdoor fan provided in an outdoor unit of an air conditioner, the fan may rotate freely by wind before the motor is started by an inverter. In such a case, if the motor is driven by sensorless vector control in which the magnetic pole position is estimated with one shunt resistor, the estimation of the magnetic pole position flows from the current switching timing to the current shunt resistance. Since this is a control that logically derives what current is, it is not possible to specify what current is generated by the induced voltage of the motor when the switching element of the inverter is not turned on or off. Further, unlike the prior art, since the motor control by the inverter is not executed immediately before, it is impossible to read and estimate the immediately preceding rotation frequency.

  The hall element was used to improve the motor efficiency and control was performed by detecting the position (U phase / V phase / W phase). In this case, since three shunt resistors and three current detection circuits are required, the number of parts is greatly increased, the motor control system becomes expensive, and a large mounting space is required.

  The purpose of the present invention is to detect the combined current of each of the three phases (U phase, V phase, W phase) for one motor that is used in applications where the motor may rotate freely due to disturbance. An object of the present invention is to provide an electric motor control device capable of applying a 180-degree energization method by detecting the shunt resistance.

The above object is an air conditioner including an outdoor unit having an outdoor fan,
An inverter composed of a plurality of switching elements, an electric motor driven by the inverter by a 180-degree energization method, driving the outdoor fan, a resistor provided on the DC side of the inverter, and a three-phase of the electric motor The line voltage of the three-phase of the motor is converted to an analog value based on a change in voltage applied to the resistor generated by rotation of the outdoor fan due to disturbance before driving the motor. And detecting the rotation direction, rotation speed, and magnetic pole position of the rotor of the electric motor before driving the electric motor by switching of the inverter .

Further, the above object is achieved by providing a motor control device that detects the analog value at the same port of the microcomputer by switching a switch provided for each phase of the three-phase line voltage of the motor .

  According to the present invention, the combined current of each of the three phases (U phase, V phase, W phase) is detected for one overcurrent even with respect to the motor used for applications where the motor may rotate freely due to disturbance. Therefore, it is possible to provide a motor control device that can apply the 180-degree energization method by detecting the shunt resistance.

  Hereinafter, an embodiment of a motor control device using the permanent magnet synchronous motor of the present invention will be described with reference to FIGS.

  In FIG. 2 which shows the outdoor unit of an air conditioner, since the outdoor unit is installed outdoors, it is exposed to wind. For this reason, even if the fan motor 8 is not driven, the fan 7 rotates forward or backward depending on the wind direction, and rotates at various rotational speeds depending on the wind speed.

  On the other hand, it is necessary to reduce the size of the outdoor unit itself and realize low cost. For this reason, it is necessary to produce inexpensive and highly efficient electrical products in a limited small space. Therefore, as shown in FIG. 1, the control method of the outdoor fan motor 8 is a method of detecting the combined current flowing in each of the three phases of the inverter module (U phase, V phase, W phase) by using one overcurrent detection shunt resistor. Is used. This eliminates the need to provide a current detection resistor in each phase of the magnetic pole position sensor and the electric motor. The synthesized current is amplified by a differential amplifier composed of an operational amplifier and several resistors, and the value is input to the A / D port of the microcomputer to perform A / D conversion inside the microcomputer. Reproduce the current.

The details of the control include A / D conversion of the phase in which no DC current flows inside the microcomputer, and the result is combined with the A / D conversion result in the phase in which DC flows, and is included in the output of the DC current detection circuit In order to remove the offset voltage and expand the pulse width of the PWM signal so that it can be detected, the carrier frequency is changed, or the motor current reproduced from the DC current information obtained in the past is combined with the current The output current of the inverter is estimated and controlled. As shown in the sensorless driving section shown in FIG. 7, a three-phase combined current is detected by a microcomputer A / D port from one overcurrent detection shunt resistor in (S13), and A / D conversion is performed in the microcomputer in (S14). The motor current is reproduced in (S9). The PWM signal generated in (S10) based on the reproduced motor current information is input to the driver in (S11), and (S12) the inverter module is controlled. Since this method does not require position detection during normal driving,
Control is possible by the 180-degree energization method (FIG. 3). The 180-degree energization method is a method in which a sine wave voltage is applied to the motor winding and driven, and the motor current is smoothly changed. Therefore, the power factor of the motor can be greatly improved, and high efficiency can be realized. Or pulsation of motor output torque does not occur with commutation as in the case of 120-degree energization. As a result, vibration and noise were reduced.

  Normally, it is possible to drive the motor only with this control method, but in the case of the outdoor fan motor 8 of the air conditioner, there are cases where the fan is in a state of being turned freely by a disturbance such as wind before starting. In that case, since the phase and rotational frequency of the rotor at the time of starting are not known, the motor cannot be started only by this control.

  Therefore, the rotor magnetic pole position, the rotation speed, and the rotation direction are detected by adding a circuit for detecting the induced voltage of the synchronous motor 3 before the inverter circuit 2 is switched. This makes it possible to control the rotation speed to a desired level even when a disturbance occurs during startup.

As the magnetic pole position detection method, several methods have been conventionally employed.
Japanese Patent No. 36519 discloses that the induced voltage generated by the rotation of the motor is passed through a primary filter to be converted into three triangular wave signals having a phase relationship of approximately 90 degrees with respect to the induced voltage. Conduct the wavy signal through a star-connected resistor, compare the neutral voltage of the star connection with these triangular wave signals using a comparator, and control the motor drive according to the pulse signal obtained from the comparator. doing.

  This has the problem that when the induced voltage is detected using a primary filter, the phase difference becomes large when the motor rotation speed is low, and Japanese Patent Application Laid-Open No. 2000-14187 discloses a comparison using a comparator. In order to stabilize the voltage, the rotor magnetic pole position detection signal of each phase is formed by comparison with a voltage that is half the DC power supply voltage, and motor drive control is performed.

  However, in either case, the 120-degree energization or 150-degree energization method is adopted, and the rotor magnetic pole position is detected during start-up and normal operation by detecting the induced voltage between the lines by the position detection circuit shown above in the non-energization section. To control. In the 120-degree energization or 150-degree energization method, there is a non-energization section in each phase. At startup, the induced voltage can be detected because the inverter module is not ON. During normal driving, it is possible to detect an induced voltage generated by rotation of the motor that occurs in a phase in which no current flows (phase in a non-energized section). In this way, the motor control is performed by detecting the magnetic pole position of the rotor, the rotational speed and the rotational direction.

  In this embodiment, the induced voltage detection circuit directly inputs the induced voltages generated in the three phases (U phase, V phase, W phase) into the A / D port of the microcomputer, and performs A / D conversion inside the microcomputer. Thus, the rotor magnetic pole position, rotational speed, and rotational direction of the motor are calculated from the motor current reproduced.

  However, when the number of A / D ports of the microcomputer 4a is insufficient, it is possible to detect with one A / D port by using transistors and diodes by the circuit shown in FIG. .

  The detection principle will be described with reference to FIG. Even when the fan is rotated by the wind and the synchronous motor 3 is rotating freely, an induced voltage is generated because the magnet of the rotor crosses the stator winding, and the current is passed through the inverter circuit 2 for this voltage. Flows. For example, when a voltage is generated as shown in the drawing, the current from the U-phase winding passes through the W-phase lower arm free-wheeling diode via the U-phase free-wheeling diode, power supply and shunt resistor of the inverter, and the W-phase winding. To the line. Similarly, the current from the V-phase winding reaches the W-phase winding through the V-phase return diode of the inverter, the power source, the shunt resistor, and the return diode of the W-phase lower arm.

  At this time, only one transistor Tr1, Tr2, Tr3 is turned off in a predetermined order. That is, the other two are turned on. This is performed at a frequency sufficiently higher than the rotational frequency of the synchronous motor 3. Therefore, when the turn-off operation is sequentially performed in the order of Tr1, Tr2, and Tr3, the instantaneous induced voltage can be detected.

4 and 6, if Tr1 is turned off by the I / O port, the U-phase induced voltage Vun detected by R1 can pass through the diode D1 and be detected by the A / D port. In this case, the W phase of the synchronous motor 3 becomes the reference voltage (ground), and the combined induction voltage of the W phase winding and the U phase winding is detected. Next, when Tr1 is turned on and Tr2 is turned off, a combined induction voltage of the W-phase winding and the V-phase winding in which the W-phase terminal becomes the reference potential is detected. Next, when Tr2 is turned on and Tr3 is turned off, this potential becomes the ground potential because the return diode of the W-phase lower arm of the inverter circuit 2 is turned on, and no current flows through the detection resistor R1, and 0 voltage is detected. Will be. This state is a period from 270 degrees to 30 degrees in FIG. The reason why there are two peaks in the voltage waveform of each phase is that, in FIG. 7B, the 270 to 30 degrees of the W phase is a negative electrode. For example, the voltage appearing in the U phase that is the positive electrode is Since this is the combined voltage of the U-phase winding, the line voltage is detected. The W-phase terminal is at ground potential, and the line voltage is detected with reference to this ground, so the reference potential changes according to the time change of the W-phase terminal voltage of the synchronous motor 3. That is, since the W-phase terminal voltage that changes sinusoidally is set to 0 potential, the combined U-phase and V-phase terminal voltages change as shown in FIG. 7A.

  By switching the ON / OFF operation of the transistor at a high speed in this way, it is possible to detect an instantaneous induced voltage of three phases with one A / D port, and by tracing this three-phase induced voltage, Then, a graph as shown in FIG. 7A can be drawn. Thereby, the rotation direction, rotation speed, and magnetic pole position of the rotor can be detected.

  The rotation direction can be determined by the appearance order of UVW, the rotation speed by the frequency of these waveforms, and the magnetic pole position by each phase.

  This flow will be described with reference to FIG. In the position detection unit, the line induced voltage is detected in (S1), and in (S2), a noise filter is provided by an RC configuration to remove noise. However, although it is a detection circuit that sufficiently reduces noise, there is a limit to the noise that can be removed by the filter, and there is a possibility that the detected data is slightly shifted due to noise on the detected induced voltage. For this reason, a detection value equal to or smaller than a certain value is determined to be noise, and erroneous determination is not performed.

In (S5) and (S6), α / β conversion of the voltage is performed to calculate the voltage phase. From the data, (S7) determining calculates the phase difference (S3) and in which case stop state and negative when the reverse rotation state when the phase sum value .DELTA..PHI _SUM is positive forward state-0 the direction of rotation. The rotor phase is determined in (S8) from the determination value in (S3) and the calculated value in (S6). Further, frequency conversion is performed in (S4) from the determination value in (S3), and the rotation speed is detected. When it is determined that the rotation speed calculated here is stopped or slightly rotated, the rotor is positioned, and the rotor position is fixed once before starting. If it is determined that the calculated rotation direction is reverse rotation, the brake is applied by control, shift to normal rotation, and drive at a desired rotation speed.

  Further, when it is determined that the calculated rotation direction is normal rotation, the rotor position is aligned as it is without stopping once, PWM energization is started, and driving is performed at a desired rotation speed.

  By adopting a combination of the current detection method using an overcurrent detection shunt resistor and the induced voltage method, an outdoor fan motor that may run idle due to the disturbance of the air conditioner can be reduced in a small mounting space and at a low cost. A motor drive circuit that can be controlled to a desired rotation speed with high efficiency and low vibration can be realized.

  As described above in this embodiment, in this control method, during normal operation, 180 energization control is performed by detecting the combined current of each of the three phases (U phase, V phase, W phase) with one single shunt resistor. In the state where the fan is rotating freely due to disturbance, etc., the induced voltage is detected before the inverter is switched only at the time of startup, and the rotor magnetic pole position, rotational peripheral speed and rotational direction are calculated and 180 degrees according to the phase. Conduct energization control.

  For motors used in applications where the rotor may be idle due to the disturbance shown above (U-phase / V-phase / W-phase), one overcurrent detection is made by combining the currents flowing through the three phases. A small space is achieved by a motor control method that combines a detection method using a shunt resistor for the motor and a combination of two methods that detect the induced voltage before switching the inverter only at startup and calculate the rotor magnetic pole position, rotation peripheral speed and rotation direction. It is possible to mount to a low-cost, high-efficiency, low-vibration stable start and control to a desired rotational speed.

  In FIG. 1, the reason for detecting the induced voltage and replacing it with the current is that the motor current is created by vector control with 180-degree conduction, and the rotor movement caused by the induced voltage is utilized. Is to grab.

  In the above, in order to detect the magnetic pole position of the rotor when the rotor is idling due to disturbance or the like, the induced voltage of the generated three phases (U phase, V phase, W phase) is used as the A / D port 1 of the microcomputer. Although the detection method using the port has been explained, it is also effective if the induced voltage of 3 phases (U phase, V phase, W phase) is directly input to the A / D port of the microcomputer and A / D conversion is performed inside the microcomputer. Is the same.

The block diagram of the motor control apparatus of the electric current detection by one shunt resistance, and an induced voltage detection. The outdoor unit figure of an air conditioner. The figure which shows the difference between a 180 degree energization system and a 120 degree energization system. The circuit diagram which detects an induced voltage by AD port 1 port. The flowchart of 1 shunt + position detection motor control. The figure explaining the principle of an induced voltage detection. The figure which shows the detection waveform of an induced voltage.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... DC power source, 2 ... Inverter circuit, 3 ... Synchronous motor, 4 ... Control circuit, 4a ... Microcomputer, 5 ... Shunt resistance, 6 ... Fan motor support, 7 ... Fan, 8 ... Fan motor, 9 ... Electrical goods.

Claims (2)

An air conditioner equipped with an outdoor unit having an outdoor fan,
An inverter composed of a plurality of switching elements;
While being driven at 180-degree energization method by the inverter, and a motor for driving the outdoor fan,
A resistor provided on the DC side of the inverter ;
It means for detecting an analog value line voltages of three phases before Symbol motor,
By detecting an analog value of a three-phase line voltage of the electric motor from a change in voltage applied to the resistance caused by rotation of the outdoor fan due to disturbance before driving the electric motor, the electric motor of the electric motor by switching of the inverter is detected . rotational direction of the rotor of the motor before driving, and a control device of the motor for detecting the rotational speed and the magnetic pole position,
Air conditioner equipped with.   2. The motor control device according to claim 1, wherein the analog value is detected at the same port of the microcomputer by switching a switch provided for each phase of the three-phase line voltage of the motor.

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