CN1980046B - motor control unit - Google Patents

Abstract

By controlling a motor that rotates randomly due to disturbances, etc., through 180-degree energization, it is possible to achieve all the goals of low cost, space saving, low vibration, and high efficiency at the same time. In an inverter circuit composed of multiple switching elements, the combined current information flowing in three phases (U phase, V phase, W phase) is detected by a shunt resistor for overcurrent detection, and the synchronous PWM signal is reproduced. The output current of the inverter thereby realizes 180-degree energization control in which the magnetic pole position of the rotor is normally estimated and driven. On the other hand, in the case of idling of the motor due to disturbance (wind) before starting, the magnetic pole position, rotation speed, and rotation direction of the motor can be directly detected before the inverter performs switching operations on the induced voltage generated by the rotation of the motor. And start.

Description

motor control unit

technical field

The present invention relates to a control device of a motor. In an inverter circuit, a resistor for overcurrent detection is used to detect the combined current of three phases (U phase, V phase, W phase), and the magnetic pole is estimated by the internal calculation of the microcomputer. position, and perform 180-degree energization control (sine wave modulation) in a position sensorless driving method during normal driving.

Background technique

Permanent magnet synchronous motors with permanent magnet rotors and stator windings are often used in home appliances such as air conditioners due to their high efficiency. The drive control of this permanent magnet synchronous motor must be performed in close relation between the magnetic pole position of the rotor and the phase of the motor current. In recent years, the efficiency of motor control has been continuously improved. Instead of using a rotor position detection sensor such as a Hall element to detect the rotor magnetic pole position, it uses a current detection through a shunt resistor for overcurrent detection, which is passed inside the microcomputer. A/D conversion infers the position of the magnetic poles, and the motor is driven by a 180-degree energization method without a position sensor.

In the 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 subsequent control is restarted, the synchronous motor rotates due to inertia, and it becomes impossible to regulate the motor pole position. In order to solve such a problem, Patent Document 1 describes a method in which a magnetic pole position sensor of a motor is set to detect the position, thereby enabling driving by an inverter.

On the other hand, Patent Document 1 also describes a sensorless driving method in which no magnetic pole position sensor is provided. It is described that when falling into the above-mentioned state, the rotation frequency before the abnormality occurs is stored in advance by utilizing the fact that the rotation speed does not drop rapidly due to the inertia of the rotor, and the operation is restarted using this position.

Patent Document 1: JP-A-2005-6453

Contents of the invention

However, in the case of driving a synchronous motor of an outdoor fan provided in an outdoor unit of an air conditioner. Sometimes there are cases where the fan spins randomly due to the wind before the inverter based motor starts. In this case, when the motor is driven by sensorless vector control in which a single shunt resistor is used to estimate the magnetic pole position, the estimation of the magnetic pole position is logically derived from the current flow in the shunt resistor at the moment when the inverter switches. Therefore, in the state where the switching elements of the inverter are not switched, it is impossible to determine what kind of current the current caused by the induced voltage of the motor is. In addition, according to the prior art, since the motor control by the inverter is not performed before starting, the rotation frequency before starting cannot be read and estimated.

In order to improve the efficiency of the motor, when the Hall element is used to detect and control the position or to perform the 180-degree energization method by setting a shunt resistor on each of the three phases (U phase, V phase, W phase), it is necessary Three shunt resistors and three current detection circuits greatly increase the number of parts, make the motor control system expensive, and require a large installation space.

The object of the present invention is to provide a motor control device, which can be detected by using a shunt resistor for overcurrent detection (U phase, V-phase, W-phase) combined current of each phase of the three phases, so that the 180-degree energization method can be applied.

The object is achieved by the following method: provide a motor control device, the motor control device is used for an inverter composed of a plurality of switching elements, a motor driven by the inverter, and a The resistance of the DC side of the inverter and the change of the voltage applied to the resistance are used to detect the rotor magnetic pole position of the motor, and a unit for detecting the line voltage of the motor is provided.

In addition, the object is achieved by the following method: providing a motor control device, the motor control device is used for an inverter composed of a plurality of switching elements, a motor driven by the inverter, A resistor provided on the DC side of the inverter and a change in voltage applied to the resistor is used to detect the rotor pole position of the motor, which is provided with a unit for detecting the line voltage of the motor, based on the inverter The switch detects the rotation direction, rotation speed, and magnetic pole position of the rotor of the motor before driving the motor.

According to the present invention, it is possible to provide a motor control device that can detect (U phase, V-phase, W-phase) combined current of each phase of the three phases, so that the 180-degree energization method can be applied.

Description of drawings

Figure 1 is a block diagram of a motor control device for current detection and induced voltage detection of a shunt resistor.

Fig. 2 is an outdoor device diagram of the air conditioner.

FIG. 3 is a schematic diagram showing the difference between the 180-degree energization method and the 120-degree energization method.

Fig. 4 is a circuit diagram of detecting induced voltage with AD port 1 port.

Figure 5 is a flow chart of a shunt + position detection motor control.

FIG. 6 is a diagram illustrating the principle of induced voltage detection.

FIG. 7 is a schematic diagram of a detection waveform of an induced voltage.

Symbol Description

1...DC power supply, 2...Inverter circuit, 3...Synchronous motor, 4...Control circuit 4a...Microcomputer, 5...Shunt resistor, 6...Fan motor bracket, 7...Fan, 8 Fan motor 、9......Electrical products

Detailed ways

Next, an embodiment using a control device for a permanent magnet synchronous motor according to the present invention will be described with reference to FIGS. 1 to 5 .

In FIG. 2 showing the outdoor unit of the air conditioner, the outdoor unit is exposed to wind and rain because it is installed outdoors. Therefore, even if the fan motor 8 is not driven, the fan 7 rotates forward or reverse according to the wind direction, and rotates at various rotation speeds according to the wind speed.

On the other hand, it is necessary to reduce the size of the outdoor unit itself and achieve low cost. Therefore, the electrical products to be carried must also be made into cheap and efficient electrical products in a limited small space. Therefore, such a method is used: that is, the control method of the outdoor fan motor 8 is as shown in FIG. A method for detecting the over-synthesized current. Accordingly, it is not necessary to provide a magnetic pole position sensor or to provide a current detection resistor in each phase of the motor. The combined 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, so that A/D conversion is performed inside the microcomputer, and the motor current is reproduced from this value .

The details of the control are that A/D conversion is performed on the phase that does not flow DC current inside the microcomputer, and the result is combined with the A/D conversion result of the phase that flows DC current, and the output of the DC detection circuit is removed. The offset voltage changes the carrier frequency in order to increase the pulse width that can detect the pulse width of the PWM signal, and combines it with the motor current reproduced from the previously obtained DC current information to estimate the output current of the inverter at the current moment and Take control. As shown in the sensorless operation part shown in Figure 5, in (S13) a shunt resistor for overcurrent detection is used to detect the three-phase composite current at the A/D conversion port of the microcomputer, and in (S14) it is detected inside the microcomputer A/D conversion is performed, and the motor current is reproduced in (S9). In (S11), the PWM signal generated in (S10) is input to the driver based on the reproduced motor current information, and the inverter module is controlled in (S12). In this method, it is not necessary to perform position detection during normal driving, so it can be controlled by the 180-degree energization method (Fig. 3). In the 180-degree energization method, a sinusoidal voltage is applied to the motor winding to drive the motor, so that the motor current changes smoothly, so the power of the motor can be greatly improved, and high efficiency can be achieved without occurrence of The pulsation of the motor output torque generated by the 150-degree or 120-degree energized commutation. As a result, vibration and noise are reduced.

Normally, only this control method can be used to drive the motor, but in the case of the outdoor fan motor 8 of the air conditioner, the fan may rotate randomly due to disturbances such as wind before starting. In this case, since the phase and rotational frequency of the rotor at the start are not judged, the motor cannot be driven only by this control.

Therefore, by adding a circuit that detects the induced voltage of the synchronous motor 3 before the inverter circuit 2 switches, the rotor magnetic pole position, rotational speed, and rotational direction are detected. As a result, the desired rotation speed can be controlled even if there is a disturbance during start-up.

The magnetic pole position detection method currently adopts several methods. For example, in Japanese Patent Publication No. 59-36519, the induced voltage generated due to the rotation of the motor is converted into a phase having a phase of approximately 90 degrees by passing the induced voltage generated by the rotation of the motor through a primary filter. The three triangular wave signals of the relationship, make these three triangular wave signals conduct in the star-connected resistors, use a comparator to compare the star-connected neutral point voltage with these triangular wave signals, according to the pulse obtained from the comparator signal for motor drive control.

Here, when the induced voltage is detected by primary filtering, there is a problem that the phase difference becomes large when the rotation speed of the motor is low. Stable, compared with the 1/2 voltage of the DC power supply voltage, the detection signal of the rotor magnetic pole position of each phase is formed, and the motor drive control is performed.

However, in any case, the 120-degree energization method or the 150-degree energization method is adopted, and the induced voltage between the lines is detected by the position detection circuit shown above in the non-energized interval, and the rotor is detected during startup and normal operation. Magnetic pole position detection and control. In the 120-degree energization or 150-degree energization method, a non-energization period exists in each phase. At start-up, the inverter module is not turned on so that the induced voltage can be detected. During normal driving, it is possible to detect an induced voltage generated by the rotation of the motor occurring in a phase to which no current flows (a phase in a non-energized period). In this way, the magnetic pole position detection, rotation speed, and rotation direction of the rotor are detected and motor control is performed.

In this embodiment, the detection circuit of the induced voltage is made in such a way that after directly inputting the induced voltage generated in the three phases (U phase, V phase, W phase) to the A/D port of the microcomputer, A/D conversion is performed, thereby, based on the reproduced motor current, the rotor magnetic pole position, rotation speed, and rotation direction of the motor are calculated.

However, when the number of A/D ports of the microcomputer 4a is insufficient, detection can be performed with one A/D port by using a triode and a diode by the circuit shown in FIG. 4 .

The detection principle will be described using FIG. 6 . Even when the fan rotates due to wind force and the synchronous motor 3 rotates randomly, an induced voltage is generated due to the magnet of the rotor crossing the stator winding, and a current flows through the inverter circuit 2 due to the voltage. For example, when a voltage as shown in the figure is generated, the current from the U-phase winding passes through the U-phase return diode of the inverter, the power supply, and the shunt resistor, flows through the W-phase lower arm return diode, and reaches the W-phase winding. Similarly, the current from the V-phase winding reaches the W-phase winding through the V-phase return diode of the inverter, the power supply, the shunt resistor, and the W-phase lower arm return diode.

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

In Fig. 4 and Fig. 6, if Tr1 is turned off through the I/O port, the U-phase induced voltage Vun detected by R1 can be detected by the A/D port through the diode of D1. At this time, the W-phase of the synchronous motor 3 serves as a reference voltage (ground), and the combined induced voltage of the W-phase winding and the U-phase winding is detected. Next, when Tr1 is turned on and Tr2 is turned off, the combined induced voltage of the W-phase winding and the V-phase winding whose terminal of the W-phase becomes a reference voltage is detected. Next, when Tr2 is turned on and Tr3 is turned off, this potential becomes the ground potential due to the conduction of the reflux diode of the W-phase lower arm of the inverter circuit 2. No current flows through the detection resistor R1 and it is detected as 0 voltage. In this state, in FIG. 7( a ), it is a period from 270 degrees to 30 degrees. The reason why there are two peaks in the voltage waveform of each phase is that in Figure 7(b), the negative pole is from 270 degrees to 30 degrees. The resultant voltage of the phase windings, so the line voltage can be sensed. The terminal of the W-phase is a ground potential, and the line voltage is detected based on this ground, so the reference potential changes with the temporal change of the W-phase terminal voltage of the synchronous motor 3 . That is, since the W-phase terminal voltage that changes in a sinusoidal wave is taken as 0 potential, the U-phase and V-phase terminal voltages that are composite voltages change as shown in FIG. 7( a ).

In this way, by switching the ON and OFF actions of the triode at high speed, one A/D port can be used to detect the instantaneous induced voltage of the three phases, and by tracking the induced voltage of the three phases, a graph as shown in Figure 7(a) can be drawn. of the graph. Thereby, the rotational direction, rotational speed, and magnetic pole position of the rotor can be detected.

The rotation direction can be judged by the order of appearance of UVW, the rotation speed can be judged by the frequency of these waveforms, and the magnetic pole position can be judged by the respective phases.

This flow will be described based on FIG. 5 . The line induced voltage is detected in (S1) by the position detection unit, and the noise is removed by installing a noise filter with an RC structure in (S2). Although it is a detection circuit that can sufficiently reduce noise, there is a limit to the amount of noise that can be removed by a filter, and there may be some deviation in the detected data due to noise remaining in the detected induced voltage. Therefore, detection values below a certain value are determined as noise so as not to make false determinations.

In addition, in (S5) (S6), the α, β conversion of the voltage is performed to calculate the voltage phase. From this data, the phase difference is calculated (S7), and the direction of rotation is judged as (S3) when the phase sum value Δφsum is positive, it is in the forward rotation state, when it is 0, it is in the stop state, and when it is negative in reverse state. The rotor phase is determined in ( S8 ) from the determination value in ( S3 ) and the calculated value in ( S6 ). In addition, cycle conversion is performed in (S4) based on the determination value in (S3), and the number of revolutions is detected. When the number of rotations calculated here is judged to be stopped or slightly rotated, the positioning of the rotor is performed, and the position of the rotor is fixed once before starting. In addition, when the calculated rotation direction is judged to be reverse rotation, the brake is applied by control, and the motor is moved to forward rotation and driven at a desired rotation speed.

Also, when the calculated rotation direction is judged to be forward rotation, PWM energization is started in conjunction with the position of the rotor without stopping even once, and the drive is driven at a desired number of rotations.

By combining the current detection method using the single overcurrent detection shunt resistor and the induced voltage method, it is possible to realize a motor drive circuit that can control the outdoor fan motor of the air conditioner that may be idling due to noise. Less installation space, low cost, high efficiency, and low vibration control to the desired rotation speed.

As described above in this embodiment, in this control mode, during normal operation, a shunt resistor is used to detect the combined current of each phase of the three phases (U phase, V phase, W phase) to perform 180-degree energization control, In the state where the fan rotates randomly due to interference, the induced voltage is detected only at startup before the inverter switches, and the rotor magnetic pole position, rotational peripheral speed, and rotational direction are calculated, and 180-degree energization control is performed in combination with its phase.

For motors used in applications where there is a possibility of the rotor idling due to the above-mentioned disturbance, etc., the current obtained by combining the currents flowing in each of the three phases (U phase, V phase, W phase) passes through an overcurrent detection A motor control method that combines the method of detecting the shunt resistance with the method of detecting the induced voltage before the inverter switches at startup, and calculating the rotor magnetic pole position, rotational peripheral speed, and rotational direction. It can be installed in a small space, cheap and efficient, low vibration, stable starting motion and desired rotational speed.

In addition, in Fig. 1, the reason for detecting the induced voltage and converting it into a current is that the motor current is generated by the vector control of the 180-degree energization, and the rotor motion of the induced voltage is grasped by using it.

In addition, in order to detect the rotor magnetic pole position in the case of the rotor idling due to disturbance, etc., the induced voltage of the three phases (U phase, V phase, W phase) generated is connected to one port of the A/D port of the microcomputer. The method of detection has been described, but even if the induced voltage of three phases (U phase, V phase, W phase) is directly input to the A/D port, the A/D conversion inside the microcomputer will have the same effect.

Claims (1)

1. the control device of a motor is used for inverter institute drive electric motor, and described inverter is made of a plurality of switch elements, at described inverter direct-flow side one resistance is set, the variation of the voltage by being applied to this resistance detects the rotor magnetic pole position of described motor, it is characterized in that

Be provided with the unit of the line voltage that detects described motor, before the driving of the described motor that carries out switch by described inverter, detect rotation direction, velocity of rotation and the position of magnetic pole of the rotor of described motor, thereby can be suitable for 180 degree step modes.

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