JP6375758B2 - Motor control device and air conditioner using the same - Google Patents

Description

  The present invention relates to a motor control device that controls driving of a brushless DC motor and an air conditioner including a compressor using the motor control device.

  Conventionally, since a sensorless brushless DC motor does not include a sensor such as a Hall element that detects the rotational position of the rotor, it has a position detection circuit that detects the rotational position of the rotor from the induced voltage of the motor.

  The brushless DC motor is driven by a three-phase (U-phase, V-phase, W-phase) bridge-connected inverter. In the position detection circuit, the other ends of the three resistors, one end of which is connected to each winding (U phase, V phase, W phase) of the stator of the brushless DC motor, are connected to each other. Another resistor is also connected to the ground. The position detection circuit compares the virtual neutral point voltage, which is the voltage at this connection point, with the reference voltage, and detects the zero cross point of the virtual neutral point voltage (the zero cross point of the induced voltage). A position detection signal for detecting the rotor position is output.

  And the control part of a motor produces | generates the inverter control signal which carries out PWM control of the inverter based on the position detection signal from a position detection circuit, and outputs it to an inverter. The upper and lower arms of each phase (U phase, V phase, W phase) of the inverter are controlled based on this inverter control signal and supply AC power to the motor.

  As this type of prior art, for example, a motor position detection operation mode shown in Patent Document 1 is known.

JP 2011-217504 A

  However, in the case of the energization switching method in the position detection by the virtual neutral point described in Patent Document 1, PWM switching (chopping) is performed between the upper and lower arms that are energized in order to detect the position of the next rotor after the energization switching. ) Is switched (so-called upper / lower arm switching). This upper and lower arm switching is performed by prediction based on the timing of position detection in the past. If the accuracy of the predicted timing is low, the rotor comes to a position where the position of the rotor is detected before the upper / lower arm switching process, and it cannot be determined from the zero cross point by PWM switching, and as a result, the zero cross indicating the rotor position is missed. Will occur.

  As a factor that causes a decrease in the prediction time accuracy, a change in the rotational speed of the motor due to a change in load applied to the motor or a change in DC voltage can be considered.

  In the brushless DC motor, when the position detection signal is missed, the position can be detected next at least after one carrier cycle (for example, 250 μsec). Therefore, every time the position detection signal is missed, the energization switching is delayed from the original timing, so that the energization switching cannot be performed at an appropriate timing, and the rotor becomes out of synchronization with the rotating magnetic field of the stator, causing a step-out. Sometimes. In particular, the probability of occurrence of step-out increases as the motor speed increases and the number of times the position detection signal is missed increases.

  The present invention has been made in view of the above, and it is possible to prevent a step-out from occurring by minimizing a detection delay even if a position detection signal is missed. An object of the present invention is to provide an air conditioner using the above.

The disclosed motor control device includes an inverter that converts DC power supplied from a DC power source into three-phase AC power by PWM control and supplies the AC power to a brushless DC motor, and a stator winding for each phase of the brushless DC motor from the inverter A position detection signal for detecting the rotational position of the rotor from the induced voltage generated in the stator winding of the non-energized phase due to the rotation of the rotor of the brushless DC motor and changing the state to a high level or a low level. In a motor control device comprising: a position detection circuit that outputs a signal; and a control unit that controls the inverter based on the position detection signal, the control unit rises or rises in the position detection signal during a predetermined period. Edge detecting means for detecting a falling edge and determining that the position is detected when the edge is detected; The level detection means for monitoring the position detection signal during the ON period of the PWM signal for controlling the inverter, detecting a change in the level state of the position detection signal, and determining that the position has been detected when the change is detected And a control signal generation means for generating a PWM signal for controlling the inverter based on the position detection results of the edge detection means and the level detection means. is there.

The disclosed air conditioner is an air conditioner using the motor control device described above.

  According to the present invention, there is provided a motor control device capable of minimizing detection delay and preventing occurrence of step-out even if a position detection signal is missed, and an air conditioner including a compressor using the motor control device. There is an effect that can be done.

FIG. 1 is a configuration diagram of a motor control device according to the present embodiment. FIG. 2 is a diagram showing a circuit configuration of the position detection circuit of FIG. FIG. 3 is a block diagram illustrating a configuration of the control unit in FIG. 1. FIG. 4 is a diagram illustrating an example of a timing chart of the motor control device. FIG. 5 is a flowchart showing the upper and lower arm switching processing operation of the motor control device of this embodiment. FIG. 6 is a flowchart showing a subroutine of the position detection signal level confirmation timer interrupt setting process of FIG. FIG. 7 is a configuration diagram of an air conditioner including a compressor using the motor control device according to the present embodiment.

  Embodiments of an air conditioner including a motor control device according to the present invention and a compressor using the motor control device will be described below in detail with reference to the drawings. Note that the present invention is not limited to the embodiments.

(First embodiment)
FIG. 1 is a configuration diagram of the motor control device 10 according to the present embodiment, FIG. 2 is a diagram illustrating a circuit configuration of the position detection circuit 16 in FIG. 1, and FIG. 3 is a diagram of the control unit 18 in FIG. FIG. 4 is a block diagram illustrating a configuration, and FIG. 4 is a diagram illustrating an example of a timing chart of the motor control device 10. Although the motor control apparatus 10 of this embodiment demonstrates as what controls the brushless DC motor M which drives the rotor of the compressor which compresses a refrigerant | coolant in the refrigerant circuit used for an air conditioner etc., it is not necessarily limited to this.

  As shown in FIG. 1, a motor control device 10 is a sensorless drive of a three-phase four-pole brushless DC motor M of a compressor of an air conditioner by a rectangular wave energization method, and an AC power source of a commercial power source E is a DC power source. AC / DC conversion circuit 12 (rectifier circuit) for converting to, inverter 14, position detection circuit 16 for detecting the position of the rotor, and control unit 18 for controlling the inverter.

  In the inverter 14, semiconductor switching elements (transistors) 14a to 14f are three-phase (U phase, V phase, W phase) bridge connection, and diodes 14g to 14l are connected in parallel to each transistor. . The brushless DC motor M has a stator that is a stator and a rotor that is a rotor, and is driven by an inverter 14.

  The position detection circuit 16 detects the rotational position of a rotor (not shown) from the induced voltage of the brushless DC motor M, and includes resistors 16b to 16g and a comparator 16a as shown in FIG. One end of each of the resistors 16b to 16d is connected to a winding of each phase of the stator of the brushless DC motor M, and the other end of each of the resistors 16b to 16d is connected to each other. A resistor 16g is connected between a connection point of the resistors 16b to 16d and the ground, and a connection point of the resistors 16b to 16d and the resistor 16g is connected to a non-inverting input terminal of the comparator 16a. Hereinafter, the voltage at the connection point of the resistors 16b to 16d and the resistor 16g is referred to as a virtual neutral point voltage. Further, a resistor 16e and a resistor 16f are connected in series between the positive electrode P and the negative electrode N of the AC / DC conversion circuit 12, and a voltage obtained by dividing the voltage Vdc between the PNs by the resistor 16e and the resistor 16f is used as a reference voltage. It is supplied to the inverting input terminal of the comparator 16a. This reference voltage is set to be 1/2 of the applied voltage Vdc. The comparator 16a compares the virtual neutral point voltage with the reference voltage, thereby detecting the zero cross point of the virtual neutral point voltage (that is, the zero cross point of the induced voltage) and detecting the position of the rotor of the motor M (hereinafter, referred to as “comparative point”). A position detection signal for detecting the position). In FIG. 2, when the virtual neutral point voltage is higher than 1/2 of the applied voltage Vdc, a high level (H) is output, and when it is lower than 1/2 of the reference voltage Vdc, a low level (L) is output. When the zero cross is detected, the position detection signal changes from H → L or L → H.

  As shown in FIG. 1, the control unit 18 generates an inverter control signal based on the position detection signal from the position detection circuit 16 and outputs the inverter control signal to the inverter 14. U phase upper arm (14a, 14g), V phase upper arm (14c, 14i), W phase upper arm (14e, 14k), U phase lower arm (14b, 14h), V phase lower arm (14d, 14j), the W-phase lower arms (14f, 14l) are switched (chopped) based on the inverter control signal.

  As shown in FIG. 3, the control unit 18 includes an edge detection unit 18a, a level detection unit 18b, a control signal generation unit 18c, a storage unit 18d, and a timer unit 18e. The edge detection unit 18a changes the state of the position detection signal output from the position detection circuit 16 from a low (L) level to a high (H) level or from a high (H) level to a low (L) level. Edge detecting means for detecting a rising or falling edge of the signal and determining that the position is detected when the edge is detected and outputting a position signal. In the level detection unit 18b, the level of the position detection signal output from the position detection circuit 16 during the on period of the PWM signal for controlling the inverter is changed from low (L) level to high (H) level or high (H) level. Level detecting means for detecting a change in state from a low to a low (L) level and determining that the position has been detected when the change is detected and outputting a position signal. The control signal generator 18c is a control signal generator that generates an arm switching and PWM signal for controlling the inverter based on the position signal output from the edge detector 18a or the level detector 18b. Further, the control signal generation unit 18c notifies the level detection unit 18b that the level detection unit 18b detects the level of the position detection signal, that is, the on period of the PWM signal for controlling the inverter. The storage unit 18d stores an arithmetic expression for predicting the measured position detection time (time) and the next position detection timing. The timer unit 18e is for setting a position detection time measurement, a timer interruption time, and the like.

  The controller 18 predicts the next position detection timing based on the time from the previous position detection to the current position detection in order to reliably detect the rotor position. Actually, the next position detection timing to be predicted is the position detection timing of the same section one rotation ahead. This utilizes the fact that the load regularly fluctuates in each section during one rotation of the compressor. For example, if the rotor is a four-pole motor, the zero cross of the induced voltage indicating position detection is output 12 times with one rotation of the rotor (mechanical angle of 360 degrees and electrical angle of 720 degrees). One rotation can be divided into 12 sections based on the zero cross. Based on the predicted position detection timing (corresponding to an electrical angle of 60 degrees), the control unit 18 performs an upper / lower arm switching process for switching an arm that performs PWM switching (chopping) between the upper and lower arms to which the inverter 14 is energized. A timing to perform (an electrical angle of 60 degrees, for example, an electrical angle of 45 degrees) is set. An inverter control signal for switching energization of the stator winding of the brushless DC motor M is generated based on the first detected position detection after the upper and lower arm switching processing.

  The drive control of the brushless DC motor M is performed as shown in the timing chart of FIG. In order from the top of FIG. 4, (a) the waveform of the induced voltage of the motor M at the virtual neutral point of the position detection circuit 16, (b) the output waveform of the position detection circuit 16, (c) position detection and energized phase switching processing timing (D) Inverter upper / lower arm switching processing timing, (e) U-phase upper arm drive signal waveform, (f) V-phase upper arm drive signal waveform, (g) W-phase upper arm drive signal waveform, (h ) U-phase lower arm drive signal waveform, (i) V-phase lower arm drive signal waveform, (j) W-phase lower arm drive signal waveform, and (k) 10 to 3 sections. Each number is shown.

  FIG. 4A shows a waveform of the induced voltage of the brushless DC motor M at the virtual neutral point of the position detection circuit shown in FIG. 2, and the voltage value is a value obtained by dividing the sum of the voltages of each phase by 3. Become. Accordingly, one of the three phases is Vdc, one phase is zero volts, and the remaining one phase generates an induced voltage. The voltage range is from zero to Vdc, so the maximum voltage is 2 Vdc / 3 and the minimum voltage is Vdc / 3 Further, the reflux section shown in FIG. 4A refers to a section in which a reflux current flows through the diode (14g to 14l in FIG. 1) by the back electromotive force generated when the energized phase is switched. The motor control device 10 configured as described above detects the rotor position at the timing when the induced voltage at the virtual neutral point crosses Vdc / 2, that is, the zero cross point of the induced voltage, as shown in FIG. The energized phase of the brushless DC motor M is switched at the timing (see FIG. 4C). Further, when the induced voltage at the virtual neutral point is in the direction of increasing with time, the rising induced voltage is defined as, for example, the induced voltage after the upper and lower arm switching processing in the section 11 in FIG. When detecting the zero-cross point of the rising induced voltage, PWM switching is performed by the upper arm (see FIG. 4E). Further, when the induced voltage is in the direction of decreasing with time, the falling induced voltage is defined as, for example, the induced voltage after the upper and lower arm switching processing in the section 10 in FIG. When detecting the zero-cross point of the falling induced voltage, the lower arm (see FIG. 4 (i)) performs PWM switching to detect the induced voltage zero-cross indicating position detection.

  As shown in FIG. 4A, the zero-cross point of the induced voltage includes an induced voltage zero-cross generated by PWM switching in addition to the induced voltage zero-cross indicating the rotor position detection. The timing of the induced voltage zero crossing indicating position detection is such that the position detection signal in FIG. 4B is changed from the low level (L) to the high level (H) after the arm switching process in FIG. ) To the low level (L), on the other hand, the zero cross caused by the PWM switching occurs after the energized phase switching process in FIG. 4 (c) and before the arm switching process in FIG. 4 (d). The position detection signal is a zero-crossing of the induced voltage generated between them, and as shown in FIG. 4B, the position detection signal is an induced voltage indicating position detection because the virtual neutral point voltage after the recirculation period always repeats high and low by PWM switching. Will be erroneously detected as the zero cross point. Therefore, even if the position detection circuit 16 detects a zero cross of the induced voltage that occurs between the energized phase switching process and before the arm switching process, the control unit 18 receives a signal from the position detection circuit 16 by performing masking. I try not to. Then, after detecting the zero cross of the induced voltage indicating the rotor position detection and switching the energized phase, the upper arm and the lower arm of the phase that performs PWM switching before the zero cross point of the induced voltage indicating the next position detection comes. The arm switching process for switching is performed. For example, in the section 10 of FIG. 4, the arm that performs PWM switching is switched from the U-phase upper arm that is performing PWM switching between the energized U-phase upper arm and V-phase lower arm to the V-phase lower arm. Thus, it is possible to detect the zero cross point of the induced voltage indicating the position detection of the falling edge.

  As described above, the position detection of the rotor is output from the position detection circuit 16 when the induced voltage at the virtual neutral point after the upper and lower arm switching processing shown in FIG. 4A crosses half the voltage of the reference voltage Vdc. Edge detection when the position detection signal level changes from high level (H) to low level (L) or from low level (L) to high level (H) (see FIG. 4B). The timing detected by the unit 18a is used. However, if the timing indicating the position detection of the rotor is before the upper / lower arm switching process, it may not be detected by the mask process of the control unit 18 or the edge detection unit 18a may miss the edge of the position detection signal. . For this reason, the motor control apparatus 10 according to the first embodiment includes the level (high (H) / low (L)) of the position detection signal output from the position detection circuit 16 in addition to the edge detection of the position detection signal. By providing the level detection unit 18b that detects the presence or absence of the zero cross of the induced voltage indicating the position detection, even if the edge detection unit 18a misses the edge of the position detection signal output from the position detection circuit 16, the level detection unit The position detection delay can be minimized by detecting the position at 18b. Hereinafter, the operation according to the first embodiment will be described with reference to the flowcharts of FIGS. 5 and 6.

  FIG. 5 is a flowchart showing the position detection interrupt setting processing operation by the external interrupt of the motor control device of this embodiment, and FIG. 6 is a flowchart showing the subroutine of the position detection signal level confirmation timer interrupt setting processing of FIG. is there. As shown in FIG. 5, the control signal generation unit 18c of the control unit 18 performs an upper and lower arm switching process for switching the switching of the upper and lower arm PWMs in order to detect the zero cross of the induced voltage indicating the position detection to be detected next ( Step S1). Then, by performing position detection interrupt setting processing by external interrupt (step S2), the position detection signal output from the position detection circuit 16 after the edge detection unit 18a performs the upper and lower arm switching processing is changed from high level (H) to low level. (L) or an edge when the level is inverted from a low level (L) to a high level (H) is detected, and when the edge is detected, it is determined that the position is detected, and a position signal is output to the control signal generator 18c. Upon receipt of the position signal, the control signal generator 18c switches the energized phase.

  In parallel with this, in the motor control device 10 according to the present embodiment, a position detection signal level confirmation timer interrupt setting process is performed (step S3). FIG. 6 shows a subroutine of the position detection signal level confirmation timer interrupt setting process. That is, the control unit 18 of the motor control device according to the present embodiment, as shown in FIGS. 3 and 6, generates a zero cross of the induced voltage indicating the position detection of the next rotor from the position detection signal output from the position detection circuit 16. It is determined whether the edge direction is rising or falling (step S31). As a method for this determination, after the upper / lower arm switching process, when the induced voltage at the virtual neutral point is in the direction of increasing with time, the rising induced voltage is used, and the position detection signal output from the position detection circuit 16 is low level. (L), the edge direction is determined to be rising, and conversely, the position detection signal output by the position detection circuit 16 is defined as the falling induced voltage when the induced voltage at the virtual neutral point is in the direction of decreasing with time. Becomes a high level (H), and the edge direction is determined to fall. In other words, the PWM switching arm based on the inverter control signal generated by the control signal generator 18c after the upper / lower arm switching process is the rising direction when the upper arm is used, and the falling direction when the lower arm is used. When the control signal generation unit 18c determines that the detection edge is in the rising direction (Yes in step S31), the level detection unit 18b is an inverter control signal generated by the control signal generation unit 18c. The presence or absence of a zero cross indicating position detection is detected based on the level (high (H) / low (L)) of the position detection signal output from the position detection circuit 16 during the ON period (step S32). If the level of the position detection signal is high (H) (Yes in step S32), it is determined that there is a zero cross indicating position detection, and the result is transmitted to the control signal generator 18c to switch the energized phase. A position detection process (step S34) is performed, and the process returns to the main routine of FIG.

  In step S32, when the level detection unit 18b detects that the level of the position detection signal is low (L) (No in step S32), it is determined that there is no zero cross of the induced voltage indicating position detection, and the control signal generation unit 18c A timer interrupt for checking the position detection signal level is set (step S33). In this position detection signal level confirmation timer interrupt setting, the timer interrupt time is set again, the timer interrupt is performed after a predetermined time, and the position is detected by the level detection signal level (high (H) / low (L)) in the level detection unit 18b. The detection is re-detected.

  As described above, in addition to detecting the edge of the position detection signal in step S2 by the edge detection unit 18a, the level detection unit 18b periodically monitors a change in the level state of the position detection signal. Even if the edge detection unit 18a misses the edge of the position detection signal, is there a zero cross indicating position detection by checking the high (H) level / low (L) level state of the position detection signal by the level detection unit 18b? Since it can be confirmed whether or not the motor control is performed using this, it becomes possible to minimize the delay in detecting the position of the rotor and to prevent the occurrence of step-out.

  When the control unit 18 of the motor control device according to the present embodiment determines that the next detected edge is not in the rising direction in step S31 of FIG. 6 (No in step S31), the level detection unit 18b detects the detected edge. It is determined whether or not the position detection signal level is a low level (L) (step S35). If the position detection signal level is low (L) (Yes in step S35), it is determined that there is a zero cross indicating position detection, and a position detection process (step S34) for switching the energized phase is performed. Return to the main routine.

  In step S35, when the level of the position detection signal detects a high level (H) (No in step S35), the level detection unit 18b determines that there is no zero cross indicating position detection, and the control signal generation unit 18c detects the position. A signal level confirmation timer interrupt is set (step S36). This position detection signal level confirmation timer interrupt setting is to re-detect the position detection by setting the timer interruption time again, performing a timer interruption after a predetermined time, and the high (H) / low (L) position detection signal. It is.

  Also in this case, in addition to detecting the edge of the position detection signal by the edge detection unit 18a, the level detection unit 18b periodically monitors the change in the level state of the position detection signal, so that the position of the position detection signal is temporarily detected by the edge detection unit 18a. Even if the detection signal edge is missed, the level detector 18b can detect the presence or absence of a zero cross indicating position detection. By using this, motor control can be performed to minimize the detection delay of the rotor. The occurrence of step-out can be prevented.

  The timer interrupt setting performed by the control signal generation unit 18c of the control unit 18 described above is set by the timer unit 18e shown in FIG. 3, but here it is not a fixed time, for example, after an electrical angle of 5 degrees, Set a timer interrupt by setting the time according to the angle.

(Second Embodiment)
FIG. 7 is a configuration diagram of an air conditioner including a compressor using the motor control device according to the present embodiment. In 2nd Embodiment, as shown in FIG. 7, the motor control apparatus 10 concerning 1st Embodiment is used as a control apparatus of the brushless DC motor which rotates the rotor of the compressor 20 of an air conditioner. The motor control device 10 is provided in the outdoor unit 30 of the air conditioner and controls the drive of the compressor 20. The compressor 20 constitutes a refrigerant circuit together with the four-way valve 34, the outdoor heat exchanger 32, the expansion valve 36, the indoor unit 40, the indoor heat exchanger 42, and the refrigerant pipe 38 connecting them. FIG. 1 is a block diagram of the motor control device 10 in FIG. 7, and an AC / DC conversion circuit 12, an inverter 14, a position detection circuit 16, and a control for converting an AC power source of a commercial power source E into a DC power source. The compressor 18 having the brushless DC motor M is driven and controlled.

  As described above, the motor control apparatus according to the embodiment of the present invention includes a conventional edge detection unit 18a that detects the presence or absence of a rising or falling edge of the position detection signal in order to detect the rotational position of the rotor. In addition, a level detection unit 18b that monitors the level of the position detection signal during the on period of the PWM signal in the inverter control signal and detects the position based on the presence or absence of the level change enables the conventional edge detection unit 18a to detect the position. Even if it is missed, it is possible to minimize the detection delay and prevent the motor from stepping out.

10 Motor control device 12 AC / DC conversion circuit (rectifier circuit)
14 Inverter 14a-14f Switching element (transistor)
14g to 14l Diode 16 Position detection circuit 16a Comparator 16b to 16g Resistance 18 Control unit 18a Edge detection unit (edge detection means)
18b Level detection unit (level detection means)
18c Control signal generator (control signal generator)
18d Storage unit 18e Timer unit 20 Compressor 30 Outdoor unit 32 Outdoor heat exchanger 34 Four-way valve 36 Expansion valve 40 Indoor unit 42 Indoor heat exchanger M Brushless DC motor E Commercial power supply

Claims (2)

An inverter that converts DC power supplied from a DC power source into three-phase AC power by PWM control and supplies the AC power to a brushless DC motor;
The inverter is energized to the stator winding of each phase of the brushless DC motor, and the rotational position of the rotor is detected from the induced voltage generated in the stator winding of the non-energized phase by the rotation of the rotor of the brushless DC motor. A position detection circuit that outputs a position detection signal whose state changes to high or low level,
A control unit for controlling the inverter based on the position detection signal;
In a motor control device comprising:
The control unit detects an edge of a rising edge or a falling edge of the position detection signal in a predetermined period, and an edge detection unit that determines that the position is detected when the edge is detected;
The position detection signal is monitored during an ON period of a PWM signal for controlling the inverter, a first state in which the level of the position detection signal changes from the low level to the high level, and from the high level to the low level Level detection means for trying to detect a second state that changes to a level and determining that the position has been detected when the first state or the second state is detected;
Control signal generating means for generating a PWM signal for controlling the inverter based on the result of position detection of each of the edge detecting means and the level detecting means;
A motor control device comprising:   An air conditioner using the motor control device according to claim 1.

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