KR20040003700A - Method for controlling BLDC motor for inverter airconditioner - Google Patents

Abstract

PURPOSE: A control method of a BLDC(Brushless Direct Current) motor in an air conditioner is provided to smoothly execute starting in the initial starting by automatically varying PWM(Pulse Width Modulation) duty control of an acceleration range of a compressor motor according to the input voltage. CONSTITUTION: A control method of a BLDC motor in an air conditioner comprises steps of determining whether a compressor working condition is satisfied if the driving of the air conditioner is started(200); determining whether the delay time of a compressor is completed by a failure in starting of a compressor motor(210); executing control according to an acceleration range after the control of an initialization range is completed(220); detecting the voltage input to the current air conditioner through an input voltage-sensing unit before executing control according to the acceleration range(230); comparing the detected input voltage with the standard voltage and deciding output PWM signal duty based on the standard duty of the standard voltage(240); and setting up a decided signal into standard PWM signal duty if the output PWM duty is decided(250).

Description

Method for controlling BLDC motor for inverter airconditioner

The present invention relates to a control method of a BCD motor in an inverter air conditioner, and more particularly, to a BCD motor in an inverter air conditioner to compensate for a standard PWM signal for controlling the starting of the motor according to the magnitude of the input voltage. It relates to a control method of.

In general, DC motors are known to be smaller and more efficient than AC motors, and are capable of continuous variable speed operation. The BCD motor is also a type of DC motor. The brushless direct current (BLDC) motor is also referred to as a non-commutator motor. Recently, the BLC motor is used as a compressor motor in an inverter air conditioner.

The BCD motor is a motor that is switched and driven by an electronic circuit using a transistor or a MOSFET instead of a brush and a commutator which are important parts of a DC motor. The operation of the motor is to distribute the current supplied from the DC power supply to the three-phase or four-phase winding of the motor. For this purpose, the position of the rotor is detected and the current is transmitted to the three-phase winding of the motor based on the detection information. By controlling the switching operation of the transistor to turn the supply on / off to control the rotation and speed of the motor.

1 is a block diagram for controlling a BLC motor in a general inverter air conditioner.

The BCD motor of the inverter air conditioner shown is used for the compressor. In other words, the BLC motor is used for the operation of the compressor in the inverter air conditioner. The BCD motor is a sensorless type without a sensor. The sensorless BCD motor is unable to detect the position of the rotor at initial startup, and after the forced starting, the organic electromotive force is detected to detect the position of the rotor.

As shown in FIG. 1, the control configuration of the BCD motor includes a plurality of switching to switch the BCD motor 30 of the compressor having a three-phase winding and the voltage applied to each phase of the motor 30. Inverter switching unit 10 having an element, the gate drive 15 for controlling the driving of the switching element, and the current protection circuit 35 for detecting the operating current of the motor to detect the overload of the motor 30 ), A rotor position detection circuit 25 for obtaining information such as the rotational position and rotation speed of the motor rotor, and a control unit 40 for controlling the driving of the motor as a whole. In addition, a PWM control unit 20 for controlling pulse width is included between the control unit 40 and the gate drive 15, and supplies a PWM control signal to the gate drive 15 under the control of the control unit 40. The inverter switching unit 10 is composed of six transistors and six diodes.

Next, the operation of the sensorless BCD motor having the above configuration will be described in detail.

When DC power supply Vdc is supplied to the BCD motor 30 through the inverter switching unit 10, the counter electromotive force is output to the three-phase winding of the motor in accordance with the rotation of the rotor of the motor 30. At this time, the rotor position The detection circuit 25 detects the counter electromotive force of the three-phase winding of the motor and applies it to the controller 40. The rotor position detection circuit 25 detects the counter electromotive force of the three-phase winding, compares the detected counter electromotive force with a reference value, and converts the counter electromotive force into a square wave signal for output. The square wave signal according to the comparison result thus output is input to the control unit 40, and the control unit 40 detects the position of the current rotor by the input square wave signal.

When the position of the rotor is detected in this way, the controller 40 controls the gate drive 15 through the PWM controller 20 to control the current supplied to each phase of the motor 30. At this time, the inverter switching unit 10, the six transistors on / off operation, to control the rotational speed of the motor 30 while the current is always supplied to the two-phase winding of the three-phase winding of the motor 30. do.

In addition, the controller 40 receives the current value detected by the current protection circuit 35 detecting the current from the inverter switching unit 10, detects the surge current and the overcurrent, and achieves stable operation of the motor.

That is, in the case of a DC type motor, it is driven by detecting the position of the rotor and controlling the current to be supplied to the two-phase winding of the three-phase winding of the motor 30 by the detected position of the rotor.

The BCD motor is composed of three coils and a rotor of U phase, V phase, and W phase, and the motor has high, low, and open phase voltages alternately with the three coils. While being applied, the magnetic force generated in the coil by the voltage is driven by rotating the rotor of the motor. Therefore, the controller 40 can accurately control the voltage applied to the three-phase coil only by accurately detecting the position of the current rotor.

On the other hand, in the drive control of the sensorless BCD motor, the position of the rotor is detected using the counter electromotive force detected by the rotor position detection circuit 25. The counter electromotive force is a function related to the rotational speed of the rotor, and it is impossible to detect the counter electromotive force at the stop or low speed rotation through the rotor position detection circuit 25. Therefore, in general, the driving circuit of the sensorless BCD motor performs control to arbitrarily rotate the motor to a speed at which the rotor position detection circuit 25 can stably detect counter electromotive force.

For this control, the motor 30 is controlled by the pattern as shown in FIG.

That is, the driving step of the motor 30 is composed of an initialization section, an acceleration section and a sensorless section. The initialization section is a section that does not know the position of the stationary rotor. The acceleration section is a section in which it is difficult to recognize the position of the rotor because the counter electromotive force detected by the rotor position detection circuit 25 is small. Therefore, in the acceleration section, the motor is accelerated up to a speed at which the rotor position detection circuit 25 can stably detect counter electromotive force. Finally, the sensorless section is a section in which the position of the rotor is detected by the detected back EMF. Therefore, the normal control of the rotor is performed from entering the sensorless section.

On the other hand, the initialization section is a section for outputting a signal so that the rotor can come to a fixed position because the position of the stationary rotor is not known. Therefore, the controller 40 performs the PWM control according to the initialization section on the three-phase winding of the motor 30 in a predetermined pattern.

When the initialization section is progressed and the position of the rotor is fixed to the preset position, the next step is to control the acceleration section to gradually increase the motor RPM by varying the magnitude of the voltage supplied to the motor.

In the sensorless section, the position of the rotor is detected based on the counter electromotive force detected from the compressor motor started in the acceleration section, and the rotation of the compressor motor is controlled according to the detected position of the rotor.

However, the conventional BLC motor control method has the following problems.

In the acceleration section of the conventional BCD motor, the switching operation of the six switching elements of the inverter switching unit 10 is controlled by the PWM duty determined for each frequency regardless of the input voltage.

That is, the controller 40 performs the control of rotating the rotor in the stationary state while proceeding from the initialization section to the acceleration section. At this time, the control unit 40 controls the acceleration section while gradually increasing the frequency, and the frequency is continuously increased until the constant value is reached. When performing such control, the controller 40 controls on / off switching of the switching element with a duty determined for each frequency.

By the way, the duty determined for each frequency conventionally is the duty value at the standard voltage. Therefore, when the input voltage is lower than the standard voltage, the output current of the motor 30 is lowered according to the duty value at the standard voltage, and conversely, when the input voltage is higher than the standard voltage, the switching is made by the duty value at the standard voltage. When the device operates, the output current of the motor increases.

This is because the DC link voltage supplied to the motor changes depending on the magnitude of the input voltage. Accordingly, the position of the initial rotor may vary due to the lowered current value and the higher current value depending on the input voltage. In this case, the position of the rotor may not be detected in the sensorless section performed after the control of the acceleration section is completed. Cause the phenomenon. In addition, since the current value is not constant at the time of initial startup, compressor start noise may be generated.

Accordingly, an object of the present invention is to control the PWM duty control of the acceleration section of the compressor motor in the inverter air conditioner automatically changes according to the magnitude of the input voltage to control the BCD motor in the inverter air conditioner to control the smooth start at the initial start-up In providing.

1 is a motor control configuration diagram of a typical inverter air conditioner,

2 is a control state diagram of a general BCD motor,

3 is an operation flowchart illustrating a control method of a BCD motor in an inverter air conditioner according to the present invention;

4A to 4D are output waveform diagrams for driving control of a BCD motor according to the present invention;

5 is a configuration diagram for the control of the BCD motor in the inverter air conditioner according to the present invention.

Explanation of symbols on the main parts of the drawings

110: inverter switching unit 115: gate drive

120: PWM control unit 125: rotor position detection circuit

130: BCD motor 135: current protection circuit

140: control unit 150: input voltage detection unit

In order to achieve the above object, a control method of a BCD motor in an inverter air conditioner according to the present invention includes: outputting a signal having a predetermined pattern so that a motor rotor in a stationary state can move to a predetermined position; Adjusting the standard PWM signal duty to be inversely proportional to the magnitude of the input voltage, and gradually accelerating the speed of the motor to a predetermined value according to the adjusted standard PWM signal duty value; And adjusting the speed of the motor in accordance with the position signal of the motor rotor.

Hereinafter, a control method of a BCD motor in an inverter air conditioner according to the present invention will be described in detail with reference to the accompanying drawings.

In the inverter air conditioner according to the present invention, the control method of the BCD motor, as shown in Figure 4a, do not know the position of the stationary rotor, the initialization section for controlling to move the rotor to a predetermined position with the output of a predetermined pattern And an acceleration section for controlling the recognition of the position of the rotor by the counter electromotive force generated while the motor rotates, and a sensorless section for controlling the rotation and speed of the motor while detecting the position of the rotor by the detected back electromotive force. .

In particular, the acceleration section is characterized in that the duty of the PWM signal for controlling the output current of the acceleration section in accordance with the magnitude of the input voltage. The PWM signal is a signal for controlling the on / off operation of six switching elements included in the inverter switching unit. Therefore, when the input voltage is higher than the standard voltage, the duty of the PWM signal is smaller, and when the input voltage is lower than the standard voltage, the duty of the PWM signal is increased.

In order to make the above operation more detailed, the control configuration of the BCD motor will be described with reference to FIG.

As shown, there is provided a BCD motor 130 having a three-phase winding, and an inverter switching unit 110 having a plurality of switching elements to switch the voltage applied to each phase of the motor 130. . The inverter switching unit 110 is composed of six transistors and six diodes. The six switching elements included in the inverter switching unit 110 are driven by the gate drive 115. The gate drive 115 is controlled by the PWM controller 120 which outputs a PWM signal under the control of the controller 410 to be described later.

The controller 140 controls the initial starting of the motor 130 in the starting pattern as shown in FIG. 4B. Therefore, the controller 140 should store the startup pattern of FIG. 4B. The start pattern of FIG. 4B illustrates an initialization section in which the position of the stopped rotor is not known. Accordingly, the controller 140 controls the PWM controller 120, the gate drive 115, and the inverter switching unit 110 to perform PWM control according to the pattern.

In addition, the controller 140 controls the acceleration section of the rotor with the starting pattern shown in FIG. 4D. Therefore, the controller 140 must store the output waveform of each phase as shown in FIG. 4D.

As illustrated in FIG. 4C, the controller 140 stores the starting duty for each frequency in the acceleration section of the rotor. The value is the PWM signal duty value determined at the standard voltage. Therefore, in the present invention, it is necessary to perform a control to automatically vary the start-up duty for each frequency according to the magnitude of the input voltage. At this time, the base value uses the standard duty shown in FIG. 4C.

At this time, when the input voltage is low, the controller 140 increases the duty of the PWM signal to increase the output current of the acceleration section. When the input voltage is high, the controller 140 decreases the duty of the PWM signal to decrease the output current of the acceleration section. At the same time, it controls to maintain a constant initial starting current regardless of the magnitude of the input voltage.

For this control, the controller 140 adjusts the duty of the output PWM signal according to the magnitude of the input voltage as in Equation 1 below.

Output PWM Signal Duty = Standard PWM Signal Duty * (Standard Voltage / Input Voltage) ..... Equation 1

In the above, the standard PWM signal duty represents the optimum acceleration section start PWM duty at the standard voltage.

As described above, the present invention includes an input voltage detecting unit 150 for detecting the magnitude of the input voltage for the variable control of the PWM signal according to the magnitude of the input voltage. The input voltage sensed by the input voltage detector 150 is provided to the controller 140. The controller 140 recognizes the magnitude of the input voltage sensed by the input voltage detector 150 and performs variable control of the PWM signal duty accordingly.

And the present invention is provided with a current protection circuit 135 for detecting the operating current of the motor in order to detect the overload of the motor 130, 125 is a rotor position detection circuit. The rotor position detection circuit 125 detects back EMF generated when the motor 130 rotates, and outputs a square wave signal in a high or low state by comparing the detected back EMF with a reference value. The square wave signal output from the rotor position detection circuit 125 is input to the control unit 140, and the control unit 140 detects the position of the rotor by the square wave signal, The control signal for controlling the rotation and speed of the motor based on the position is output to the PWM controller 120.

Next, the control method of the BCD motor according to the present invention having the above configuration will be described in detail.

3 is an operation flowchart for controlling the BC motor in the present invention.

When driving of the product is started according to a user driving signal input or the like, the controller 140 determines that the compressor operating condition is satisfied (step 200). At this time, the power input to the product is generated as a DC power of a predetermined size through a process such as a predetermined power factor correction. The DC power generated in this way is described in the present invention as the DC voltage Vdc charged in the capacitor.

When the compressor operation condition is performed in operation 200, the controller 140 determines whether the compressor delay time (generally 2 minutes) is completed due to a failure in starting the compressor motor due to various causes (operation 210).

When the condition of step 210 is satisfied, the controller 140 performs control in a pattern as shown in FIG. 4A to rotate the compressor motor.

Meanwhile, the BCD motor 130 may control the motor to rotate by applying an appropriate voltage to the three-phase coil of the motor 130 only if the rotor position is known. However, in the case of the sensorless BCD motor as in the present invention, since a sensor for knowing the position of the rotor is not provided, the control of detecting the position of the rotor must be performed before the motor is driven.

Therefore, when the DC voltage for driving the compressor is charged to the capacitor (Vdc), the controller 140 controls the initial driving of the BC motor 130 (step 260). First, the controller 140 controls the current to be supplied to the motor 130 in a pattern determined in the initialization section shown in FIG. 4B.

The initialization section is also divided into two alignment sections. In the first alignment section 1, the U phase, Y phase, and Z phase are turned off, the X phase is turned on, and the V and W phases are turned on and off with a constant duty. Control to continue. When the motor is controlled by the controller 410 in the pattern, the PWM control unit 120 outputs a PWM control signal according to the pattern, and the PWM control signal is output to the inverter switching unit 110 through the gate drive 115. The operation of the six switching elements of the control.

In addition, after the operation of the first alignment 1 section is performed, the control unit 140, as in the second alignment 2 section, the U phase, V phase, Y phase, Z phase is off, and X phase is on And control the W phase to continue on / off switching at a constant duty. At this time, the duty ratio of the on / off switching of the W phase is set differently from the duty ratio in the first alignment 1 interval. When the control unit 140 controls the motor to be driven in the pattern, the PWM control unit 120 outputs a PWM control signal according to the pattern, and the PWM control signal is transferred through the gate drive 115 to the inverter switching unit 110. The operation of the six switching elements of the control.

That is, in the initialization section, the BCD motor 130 is controlled to the output waveform determined as described above. At this time, the rotor reaches a predetermined position by the rotation operation according to the predetermined pattern in the stationary state.

Next, after the initialization section is controlled (step 220), the controller 140 performs control according to the acceleration section. In the acceleration section, the supply of current to each phase is controlled by the output waveform of each phase shown in FIG. 4D, and the on / off switching operation of the switching element is performed by the PWM duty for each frequency shown in FIG. 4C.

In the acceleration section, the frequency of the motor 130 is increased until the rotor position signal can be detected by the rotor position detection circuit 125. At this time, the frequency of the motor 130 continues to rise until it reaches a fixed value.

On the other hand, during the operation of the product, the magnitude of the DC voltage is also changed according to the magnitude of the input voltage supplied to the product. In other words, if the input voltage of the product is lower than the standard rated voltage, the magnitude of the generated DC voltage is also small. On the contrary, if the input voltage of the product is higher than the standard rated voltage, the generated DC voltage is large. Therefore, in order to maintain a constant starting current of the motor even when the magnitude of the DC voltage is changed, it is necessary to adjust the PWM signal duty for controlling the switching operation of the switching element.

Therefore, the control unit 140 detects the magnitude of the voltage currently input to the product through the input voltage detecting unit 150 before performing the control according to the acceleration section (step 230). The input voltage detected in step 230 is compared with the standard voltage to determine the output PWM signal duty based on the standard duty at the standard voltage (step 240).

That is, in step 240, when the input voltage is low, the output current PWM duty of the acceleration section is increased. On the contrary, when the input voltage is high, the output current PWM duty of the acceleration section is reduced. With this control, step 240 is to adjust the duty value to generate a constant initial starting current regardless of the input voltage.

When the output PWM signal duty is determined in step 240, the determined signal is set as the standard PWM signal duty (step 250), and the controller 140 controls the inverter switching unit according to the standard PWM signal duty set in step 250. The switching operation of 110 is controlled.

That is, in the acceleration section, the frequency of the motor 130 is increased until the rotor position signal can be detected by the rotor position detection circuit 125 by the changed PWM signal duty. When the compressor motor 130 is normally rotated by the control of the operation and the position detection signal according to the counter electromotive force is detected by the rotor position detection circuit 125, the controller 140 operates the sensorless operation based on the detected position detection signal. The section is controlled.

As described above, the present invention is characterized in that the initial duty current is kept constant regardless of the input voltage by automatically varying the PWM duty of the acceleration section according to the input voltage. With this control, the present invention can prevent the compressor from failing due to the change of the initial starting current due to the change of the DC link voltage.

The present invention described above can obtain the following effects.

The present invention automatically varies the PWM duty of the acceleration section according to the magnitude of the input voltage in order to suppress the change in the initial starting current generated while the DC link voltage is varied according to the input voltage. Therefore, the present invention can keep the initial starting current constant regardless of the magnitude of the input voltage.

In addition, the present invention can suppress the compressor starting noise by the stability of the initial starting current during the initial start-up. In addition, the present invention can smoothly start the compressor by constantly controlling the position of the rotor in the sensorless section due to the constant initial starting current. In this regard, the present invention provides an effect of quickly providing the user with the effect of heating and cooling in the inverter air conditioner.

Claims (1)

Outputting a signal of a predetermined pattern so that the motor rotor in a stationary state can move to a predetermined position; Adjusting the standard PWM signal duty to be inversely proportional to the magnitude of the input voltage, and gradually accelerating the speed of the motor to a predetermined value according to the adjusted standard PWM signal duty value; And controlling the speed of the motor according to the position signal of the motor rotor.