JP6718356B2 - Motor control device and heat pump type refrigeration cycle device - Google Patents

Description

Embodiments of the present invention relate to a motor control device that PWM-controls a three-phase motor, and a heat pump type refrigeration cycle device including the motor control device.

For example, Patent Document 1 discloses a technique of starting a motor in a state in which the motor is rotating by an external force, so that zero vector energization is performed by an inverter circuit to stop the rotation of the motor before starting.

JP 2000-125584 A

By the way, when the motor is started from the state of being rotated by an external force, if the rotation direction and the rotor position can be determined in advance, the motor can be started without stopping the rotation. However, assuming a configuration in which the phase current of the motor is detected by one resistance element inserted in the DC portion of the inverter circuit, that is, one shunt method, there is a problem that each phase current cannot be detected by zero vector energization.

Therefore, the present invention provides a motor control device capable of discriminating the rotation direction in the state in which the motor is rotated by an external force even with a configuration in which the current is detected by the one-shunt method, and a heat pump refrigeration cycle device including the device.

The motor control device of the embodiment drives the motor through an inverter circuit that converts direct current into three-phase alternating current by performing on/off control of a plurality of switching elements connected in three-phase bridge according to a predetermined PWM signal pattern. ,
A current detection element that is connected to the DC side of the inverter circuit and that generates a signal corresponding to a current value, a rotor position determination unit that determines the rotor position based on the phase current of the motor, and to follow the rotor position. A PWM signal generator that generates a three-phase PWM signal pattern,
A current detection unit that detects a phase current of the motor based on the signal generated in the current detection element and the PWM signal pattern,
The PWM signal generation unit sets the ON time of each phase to be the same and shifts the ON timing of at least two PWM pulses, so that the current detection unit detects the currents of two phases within the carrier wave cycle of the PWM signal. Generate a three-phase PWM signal pattern corresponding to the zero vector as possible,
Before the start of the motor is started, the PWM signal generation unit is caused to output a PWM signal pattern corresponding to the zero vector, and a rotation direction determination is performed to determine the rotation direction of the motor based on the current detected at that time. Further comprises a section.
The PWM signal generation unit feedback-controls the PWM signal so that the current value detected by the current detection element becomes “0” after the rotation direction determination unit determines the rotation direction.
The rotor position determination unit determines the rotor position when the current value detected by the current detection element is zero.

The heat pump refrigeration cycle apparatus of the embodiment includes a fan motor and the above-described motor control device that controls the fan motor.

It is 1st Embodiment and is a functional block diagram which shows the structure of a motor control apparatus. The figure which shows the structure of a heat pump type refrigeration cycle device. Space vector representing the ON state of the switching elements that make up the inverter circuit The figure explaining the technique which shifts a PWM duty pulse The figure which shows an example which observed the actual waveform of the zero vector PWM pulse which shifted each phase pulse. Diagram showing the waveform of each phase current when the motor is rotating in the forward and reverse directions The flowchart which shows the processing content which estimates the rotation speed of a fan motor. State transition diagram showing processing from rotation direction determination to motor startup The figure which shows the estimated rotation speed when the motor is rotating in the forward direction, and the waveform of the U-phase current Iu. The figure which shows the estimated rotation speed when the motor is rotating in the reverse direction, and the waveform of the U-phase current Iu.

Hereinafter, one embodiment will be described with reference to the drawings. In FIG. 2, a compressor 2 constituting a heat pump type refrigeration cycle device 1 is configured by accommodating a compression unit 3 and a motor 4 in the same hermetic container 5, and a rotor shaft of the motor 4 is connected to the compression unit 3. ing. The compressor 2, the four-way valve 6, the indoor heat exchanger 7, the pressure reducing device 8, and the outdoor heat exchanger 9 are connected by a pipe serving as a heat transfer medium flow path so as to form a closed loop. The compressor 2 is, for example, a rotary type compressor, and the motor 4 is, for example, a three-phase IPM (Interior Permanent Magnet) motor or a brushless DC motor. The air conditioner E is configured to include the heat pump system 1 described above.

At the time of heating, the four-way valve 6 is in the state shown by the solid line, and the high-temperature refrigerant compressed in the compression section 3 of the compressor 2 is supplied from the four-way valve 6 to the indoor heat exchanger 7 and condensed, and then the decompression device 8 Then, the pressure is reduced, and the temperature becomes low and flows into the outdoor heat exchanger 9, where it evaporates and returns to the compressor 2. On the other hand, during cooling, the four-way valve 6 is switched to the state shown by the broken line. Therefore, the high-temperature refrigerant compressed in the compression unit 3 of the compressor 2 is supplied from the four-way valve 6 to the outdoor heat exchanger 9 to be condensed, and then decompressed by the decompression device 8 to become a low temperature and the indoor heat exchange is performed. It flows to the vessel 7, where it evaporates and returns to the compressor 2. The outdoor heat exchanger 9 functions as an evaporator during heating and as a condenser during cooling operation, and the indoor heat exchanger 7 conversely functions as a condenser during heating and as an evaporator during cooling operation. There is.

Air is blown by the fans 10 and 11 to the heat exchangers 7 and 9 on the indoor side and the outdoor side, respectively, and the heat exchange between the heat exchangers 7 and 9 and the indoor air and the outdoor air is efficiently performed by the air blowing. It is designed to be well done. A fan 11 that blows air to the outdoor heat exchanger 9 is driven by a fan motor 12. The fan motor 12 is, for example, a brushless DC motor similar to the motor 4.

FIG. 1 is a functional block diagram showing the configuration of the motor control device. Although the DC power supply unit 21 is shown by the symbol of the DC power supply, when the DC power supply is generated from the commercial AC power supply, it includes a rectifying circuit, a smoothing capacitor, and the like. An inverter circuit 23 is connected to the DC power supply unit 21 via a positive side bus 22a and a negative side bus 22b, and a shunt resistor 24 which is a current detection element is inserted on the side of the negative side bus 22b. That is, the so-called one-shunt current detection method is used. The inverter circuit 23 is configured by connecting N-channel power MOSFETs 25 (U+, V+, W+, U-, V-, W-) as a switching element in a three-phase bridge connection, and the output terminal of each phase is a motor. Each of the 12 phase windings is connected.

The terminal voltage of the shunt resistor 24, which is a current detection element, is a signal corresponding to the current value and is detected by the current detection unit 27. When the current detection unit 27 A/D-converts and reads the terminal voltage, the currents Iu, Iv, and Iw of the U, V, and W phases are calculated based on the PWM signal pattern of the three phases output to the inverter circuit 3. To detect. The phase currents detected by the current detector 27 are input to the vector calculator 30.

In the vector calculation unit 30, when the rotation speed command ωref of the motor 12 is given from a functional part such as a microcomputer that sets the control condition, the torque current command Iqref is calculated based on the difference from the estimated actual rotation speed of the motor 12. Is generated. A rotor position determination unit (not shown) in the vector calculation unit 30 determines (estimates) the rotor position θ of the motor 12 from the phase currents Iu, Iv, Iw of the motor 12 and the PWM signal output at that time. The torque current Iq and the field current Id are calculated by vector control calculation using the rotor position θ. For example, the PI control calculation is performed on the difference between the torque current command Iqref and the torque current Iq to generate the voltage command Vq. The field command Id side is similarly processed to generate the voltage command Vd, and the voltage commands Vq, Vd are converted into the three-phase voltages Vu, Vv, Vw using the rotor position θ. The three-phase voltages Vu, Vv, Vw are input to the DUTY generation unit 31, and the duties U_DUTY, V_DUTY, W_DUTY for generating the PWM signal of each phase are determined.

Each phase duty U, V, W_DUTY is given to the PWM signal generation unit 32, and a two-phase or three-phase PWM signal is generated by comparing the levels of the carrier wave and the carrier. Further, a signal on the lower arm side, which is an inversion of the two-phase or three-phase PWM signal, is also generated, and a dead time is added if necessary, and then the signals are output to the drive circuit 33. The vector control unit 30 and the DUTY generation unit 31 also correspond to the PWM signal generation unit in the claims.

The drive circuit 33 outputs a gate signal to each gate of the six FETs 25 (U+, V+, W+, U−, V−, W−) forming the inverter circuit 23 according to the given PWM signal. The upper arm side outputs at a potential boosted by a required level. In the above, the functions of the configurations 27 to 34 excluding the drive circuit 33 are the functions realized by the hardware and software of the microcomputer including the CPU. The vector calculation unit 30 corresponds to a rotation direction determination unit.

FIG. 3 shows the ON state of the switching elements forming the inverter circuit by a method called a space vector. For example, the vector V1 (1, 0, 0) indicates that the U-phase upper switching element is on and the V-phase and W-phase upper switching elements are off, and the voltage vector has eight patterns V0 to V7. Exists. Of these, V0 (0,0,0) and V7 (1,1,1) are zero vectors.

In the present embodiment, when the fan 11 arranged in the outdoor heat exchanger 9 receives wind and the fan motor 12 is rotated by an external force, the zero vector V7 is used to determine the rotation direction before starting. (1,1,1) is used. At that time, a technique of shifting the PWM duty pulse (on-pulse) of each phase is applied.

FIG. 4A shows a three-phase PWM pulse corresponding to a general zero vector V7. In this three-phase PWM pulse, since all the three-phase pulses have the same timing and the same time width, it is impossible to detect each phase current. Therefore, in the present embodiment, in the one-shunt current detection method, as shown in FIG. 4B, the same in FIG. 4A so that the two-phase currents can be detected at the fixed two detection timings. Each on-time of the three-phase PWM pulse having a time width is not changed, and the on-timing of each PWM pulse is shifted, that is, shifted.

In this example, the V phase is left as it is at the on-timing phase, the U phase is shifted to the delayed phase side with respect to the bottom, and the W phase is shifted to the advanced phase side with respect to the bottom. As a result, two-phase currents can be detected at the two detection timings A and B shown in the figure. At this time, the PWM pulse of each phase has the same on-time, so that the output is substantially a zero vector. Although it is desirable that the ON time of the PWM pulse of each phase be the same as much as possible, a slight deviation such as control timing is allowed, and it may be substantially the same.

FIG. 5 shows an actual waveform observation result as an example. In this example, the U phase is not moved (shifted) with the bottom as a reference, the V phase is on the delayed phase side, and the W phase is on the advanced phase side. It is shifting to the side.

As shown in FIG. 6, the magnitude relationship of the phase currents detected when the three-phase motor is rotating by an external force is different in the forward direction and the reverse direction. Therefore, if each phase current can be detected at two adjacent points within at least ⅙ cycle, the rotation direction before starting can be determined from the magnitude relationship of each phase current and the increase/decrease change of each phase current. Further, at this time, since the rotational position of the rotor can be estimated to some extent from the value of each phase current, the rotational direction before the start can be discriminated also from the change in the rotational positions of two points. In the present embodiment, the rotation direction before starting is determined from the position change based on the estimation result of the rotation positions of the two rotors.

FIG. 7 is a flowchart showing a rotation speed estimation process performed before the fan motor 12 is started. First, the first zero vector is output (S1), the U, V, and W phase currents are detected (S2), and the rotor position at that time is estimated (S3). The third-phase current is calculated from the detected two-phase current. In subsequent steps S4 to S6, the same processing as steps S1 to S3 is performed corresponding to the second zero vector output.

In the next step S7, the rotational direction of the motor 12, the rotor rotational position and the rotational speed are estimated from the difference between the previous position in step S3 and the current position in step S6. Then, a PWM signal is output from the estimated rotation direction, rotation speed, and rotation direction of the motor 12 based on the vector-calculated phase duties U, V, and W_DUTY. As a result of supplying this PWM signal, each phase duty U, V, W_DUTY is adjusted so that each phase current becomes "0". For example, as a result of outputting a PWM signal adjusted so that each phase duty U, V, W_DUTY becomes large after the first PWM signal, if each phase current increases, then each phase duty U, V, W_DUTY gradually increases. If the current of each phase decreases, the duty U, V, W_DUTY of each phase is gradually increased from the next. By changing the duty U, V, W_DUTY of each phase in this way, the adjustment is repeated until the current becomes “0”.

That is, the inverter circuit 23 is switched by the PWM signal such that the current detected by the shunt resistor 24 becomes a vector of "0" (S8), each phase current is detected (S9), and the rotor position at that time is detected. Is estimated (S10). After that, until the time set as the rotation speed estimation time before activation elapses (S11; NO), the process returns to step S8 and the feedback control is continued.

As a result, at the time when "YES" is finally obtained in step S11, the PWM signal in which the current is "0" is output. Here, the fact that the current becomes “0” indicates that the output of the PWM signal and the external force are in balance. Therefore, it can be considered that the estimated value of the rotor position in the rotor position determining unit used in this state accurately indicates the rotor position at that time.

FIG. 8 is a state transition diagram showing processing from the determination of the rotation direction to the activation of the motor 12. When a motor start command is given from a host controller or the like, the rotation direction of the motor 12 is determined in step S7 described above before starting the start. Then, in both forward rotation and reverse rotation, when the predetermined time has passed (YES) in step S11, the rotation speed of the motor 12 is estimated based on the rotor position estimation in step S10 immediately before that, and the rotation speed is determined. From the above, it is determined whether or not the required air volume is secured. In the heat pump refrigeration cycle apparatus 1, if the amount of air required for the apparatus can be secured by the external force, that is, the outside air, the motor 12 does not need to be started and is left as it is. It also saves energy.

On the other hand, when the air volume is insufficient due to the forward rotation, the driving is started while maintaining the rotation state without stopping the rotation of the motor 12. Specifically, from the time when the predetermined time has elapsed (YES) in step S11, that is, from the state where the rotor position and the PWM signal are synchronized, the vector is set so that the motor 12 gradually increases its speed to a target rotation speed. Calculation is performed to calculate each phase duty U, V, W_DUTY, and a PWM signal according to the calculation result is output. FIG. 9 shows the estimated rotation speed and the waveform of the U-phase current Iu corresponding to this case.

On the other hand, when the air volume is insufficient due to the reverse rotation, a PWM signal for braking is output to temporarily stop the rotation of the motor 12 and then drive the motor 12 in the forward direction. Specifically, from the time when a predetermined time has passed (YES) in step S11, that is, from the state where the rotor position and the PWM signal are synchronized, vector calculation is performed so that the brake is applied so as to gradually decrease to the rotation speed. The duty U, V, W_DUTY of each phase is calculated, a PWM signal corresponding to the calculation result is output to stop the motor 12, and then each vector calculation is performed to gradually increase the target rotation speed. The phase duty U, V, W_DUTY is calculated, and the PWM signal according to the calculation result is output. FIG. 10 shows the estimated rotation speed and the waveform of the U-phase current Iu corresponding to this case.

As described above, according to the present embodiment, the current detection unit 27 determines the motor 4 based on the signal generated by the shunt resistor 24 connected to the DC side of the inverter circuit 23 in accordance with the current value and the PWM signal pattern. Of the two-phase or three-phase so as to follow the rotor position θ together with the PWM signal generator 32. Generate a PWM signal pattern.

When the fan motor 12 is started, the PWM signal generation unit 32 has the same ON period for all three phases of the PWM signal pattern of the three phases, one of the phases remains unchanged, and the other one of the phases is delayed or advanced. In any one of the two directions, the remaining one phase outputs a zero vector signal obtained by shifting the ON signal in the opposite direction to the above direction.

As a result, the current detection unit 27 generates a three-phase PWM signal pattern capable of detecting a two-phase current at two fixed timings within the carrier cycle of the PWM signal. The vector control unit 30 causes the PWM signal generation unit 32 to output the PWM signal pattern before starting the fan motor 12, and determines the rotation direction of the motor 12 based on the current detected at that time. Therefore, even in the configuration in which the current is detected by the one-shunt method, it is possible to determine the rotation direction when the motor 12 is rotating by the external force.

Further, the vector control unit 30 performs feedback control of the PWM signal pattern so that the current value detected by the shunt resistor 24 becomes “0” after determining the rotation direction of the motor 12. This makes it possible to more accurately estimate the rotation speed and the rotor position when the motor 12 is receiving external force and rotating.

Further, the vector control unit 30 starts the motor 12 as it is in the forward direction when the rotation direction is “forward”, and stops the rotation of the motor 12 and starts in the forward direction when the rotation direction is “reverse”. Let Therefore, when the motor 12 is rotating in the forward direction, the motor 12 can be quickly started without temporarily stopping it.

Further, the motor control device of the present embodiment is applied to the air conditioner E including the heat pump type refrigeration cycle device 1 including the compressor 2, the outdoor heat exchanger 9, the pressure reducing device 8 and the indoor heat exchanger 7. However, since the fan motor 12 is the control target, it is necessary to grasp the state in which the fan 11 arranged in the outdoor heat exchanger 9 is rotating by receiving wind before starting the fan motor 12 properly. You can

(Other embodiments)
Although the zero vector V1 is used in the above embodiment, the zero vector V0 may be used. In this case, during the PWM cycle, the output is such that the lower elements of all three phases are turned on in the same time width.
The application target of the motor control device is not limited to the air conditioner and the heat pump type refrigeration cycle device. Further, the drive target is not limited to the fan motor, and a motor that is rotated by an external force without being energized can be targeted.

Although some embodiments of the present invention have been described, these embodiments are presented as examples and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the spirit of the invention. These embodiments and their modifications are included in the scope and gist of the invention, and are also included in the invention described in the claims and the scope of equivalents thereof.

In the drawing, 1 is a heat pump type refrigeration cycle device, 7 is an indoor heat exchanger, 8 is a decompression device, 9 is an outdoor heat exchanger, 23 is an inverter circuit, 24 is a shunt resistor, 27 is a current detection unit, and 30 is a vector operation. Reference numeral 31 denotes a DUTY generator, and 32 denotes a PWM signal generator.

Claims (3)

A motor control device that drives a motor through an inverter circuit that converts direct current into three-phase alternating current by performing on/off control of a plurality of switching elements connected in a three-phase bridge according to a predetermined PWM signal pattern,
A current detection element connected to the DC side of the inverter circuit and generating a signal corresponding to a current value,
A rotor position determination unit that determines the rotor position based on the phase current of the motor;
A PWM signal generator that generates a three-phase PWM signal pattern so as to follow the rotor position;
A current detection unit that detects a phase current of the motor based on the signal generated in the current detection element and the PWM signal pattern,
The PWM signal generation unit sets the ON time of each phase to be the same and shifts the ON timing of at least two PWM pulses, so that the current detection unit detects the currents of two phases within the carrier wave cycle of the PWM signal. Generate a three-phase PWM signal pattern corresponding to the zero vector as possible,
Before the start of the motor is started, the PWM signal generation unit is caused to output a PWM signal pattern corresponding to the zero vector, and the rotation direction determination is performed to determine the rotation direction of the motor based on the current detected at that time. Further provided with
The PWM signal generation unit feedback-controls the PWM signal so that the current value detected by the current detection element becomes “0” after the rotation direction determination unit determines the rotation direction.
The motor control device, wherein the rotor position determination unit determines the rotor position in a state where the current value detected by the current detection element is zero . The direction of rotation is activated as a forward direction the motor if "forward", if the rotational direction is "reverse", claim 1 Symbol placement activates after stopping the rotation of the motor in the forward direction Motor controller. A fan motor,
The motor control device according to claim 1 or 2, wherein controlling the fan motor and a heat pump type refrigeration cycle device comprising a.

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