JP2019205214A - Motor controller and heat pump type refrigeration cycle device - Google Patents

Abstract

To provide a motor controller capable of reducing switching loss without reducing a current detection rate.SOLUTION: A motor controller of an embodiment drives a motor via an inverter circuit converting DC into three phase AC by performing on-off control of a plurality of switching elements in a three-phase bridge-connection according to a predetermined PWM signal pattern. The motor controller comprises a current detection part for detecting the phase current of the motor, a rotor position determination part for determining a rotor position based on the phase current of the motor, and a PWM signal generating part for generating a two-phase or three-phase PWM signal pattern so as to follow the rotor position. The PWM signal generating part generates a plurality of PWM control periods as one control unit so that the three-phase PWM signal pattern and the two-phase PWM signal pattern coexist within the control unit.SELECTED DRAWING: Figure 1

Description

  Embodiments described herein relate generally to a motor control device that performs PWM control of a three-phase motor, and a heat pump refrigeration cycle device including the motor control device.

  Patent Document 1 discloses a balance between reducing switching loss and maintaining a current detection rate in a configuration in which each phase current of a motor is detected by a single resistance element inserted in a DC portion of an inverter circuit. Therefore, a technique is disclosed in which switching is performed such that three-phase modulation is performed in a region where the motor rotates at a low speed and two-phase modulation is performed in a region where the motor rotates at a high speed.

JP 2014-171321 A

However, in the period in which the three-phase modulation is consistently performed as in Patent Document 1, the switching loss also increases.
Therefore, a motor control device that can further reduce switching loss without reducing the current detection rate, and a heat pump refrigeration cycle device including the device are provided.

The motor control device of the embodiment drives a motor via 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 detector for detecting a phase current of the motor;
A rotor position determination unit for determining a rotor position based on the phase current of the motor;
A PWM signal generator that generates a two-phase or three-phase PWM signal pattern so as to follow the rotor position;
The PWM signal generation unit generates a plurality of PWM control cycles as one control unit so that a three-phase PWM signal pattern and a two-phase PWM signal pattern are mixed in the control unit.

  The heat pump refrigeration cycle apparatus includes a fan motor that drives a fan and the motor control device.

Functional block diagram showing the configuration of the motor control device according to the first embodiment Diagram showing the configuration of the heat pump refrigeration cycle system Flowchart showing the contents of PWM interrupt processing Timing chart showing PWM duty pulse waveform Diagram showing the power consumption reduction effect according to the number of revolutions Timing chart showing the PWM duty pulse waveform according to the second embodiment

(First embodiment)
Hereinafter, a first embodiment will be described with reference to FIGS. 1 to 5. In FIG. 2, the compressor 2 constituting the heat pump refrigeration cycle apparatus 1 is configured by accommodating the compression unit 3 and the motor 4 in the same iron hermetic container 5, and the rotor shaft of the motor 4 is connected to the compression unit 3. Has been. 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 to form a closed loop by a pipe serving as a heat transfer medium flow path. The compressor 2 is, for example, a rotary 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 has the heat pump refrigeration cycle apparatus 1 described above.

  During the heating operation of the air conditioner E, the four-way valve 6 is in a state indicated by a solid line, and the high-temperature refrigerant compressed by the compression unit 3 of the compressor 2 is supplied from the four-way valve 6 to the indoor heat exchanger 7 and condensed. Thereafter, the pressure is reduced by the pressure reducing device 8, becomes a low temperature and flows to the outdoor heat exchanger 9, where it evaporates and returns to the compressor 2. On the other hand, during the cooling operation, the four-way valve 6 is switched to a state indicated by a broken line. For this reason, the high-temperature refrigerant | coolant compressed with the compression part 3 of the compressor 2 is supplied to the outdoor heat exchanger 9 from the four-way valve 6, and is condensed, and after that, it decompresses by the decompression device 8, becomes low temperature, and performs indoor heat exchange It flows to the unit 7, where it evaporates and returns to the compressor 2.

  The outdoor heat exchanger 9 functions as an evaporator during the heating operation and functions as a condenser during the cooling operation, and the indoor heat exchanger 7 conversely functions as a condenser during the heating operation and as an evaporator during the cooling operation. It has become. The indoor and outdoor heat exchangers 7 and 9 are blown by the fans 10 and 11, respectively, and the heat exchange between the heat exchangers 7 and 9 and the indoor air and outdoor air is efficient. It is structured to be performed well. A fan 11 that blows air to the outdoor heat exchanger 9 is a propeller fan, and is driven by a fan motor 12. The fan motor 12 is a brushless DC motor similar to the motor 4, for example.

  FIG. 1 is a functional block diagram showing a configuration of a motor control device that drives the fan motor 12. The DC power supply unit 21 is indicated by a DC power supply symbol, but includes a rectifier circuit, a smoothing capacitor, and the like when a DC power supply is generated from a commercial AC power supply. An inverter circuit 23 is connected to the DC power source 21 via a positive bus 22a and a negative bus 22b, and a shunt resistor 24, which is a current detection element, is inserted on the negative bus 22b side. The inverter circuit 23 is configured by connecting, for example, N-channel type power MOSFETs 25 (U +, V +, W +, U−, V−, W−) as switching elements in a three-phase bridge, and the output terminals of each phase are motors. Each of the 12 phase windings is connected.

  A terminal voltage between both ends of the shunt resistor 24 that is a current detection element is a voltage signal corresponding to the current value, and is detected by the current detection unit 27. When the current detection unit 27 performs A / D conversion and reads the terminal voltage, the current of each phase of U, V, and W is output based on the three-phase PWM signal pattern output from the drive circuit 33 to the inverter circuit 23 at that time. Iu, Iv, and Iw are detected. Each phase current detected by the current detection unit 27 is input to the vector calculation unit 30.

  In the vector calculation unit 30, when the rotational speed command ωref of the motor 12 is given from a functional part such as a microcomputer that sets the control conditions, the torque current command Iqref is calculated based on the difference from the estimated actual rotational speed of the motor 12. Generated. Here, the rotational speed command ωref of the motor 12 is data supplied from a control device (not shown) of the air conditioner E, and is determined in the control device from the state of the refrigeration cycle and the operating state of the air conditioner E. The rotation speed of the fan motor 12 desired as the air conditioner E.

  The rotor position θ of the motor 12 is determined from the phase currents Iu, Iv, and Iw of the motor 12, and the torque current Iq and the excitation current Id are calculated by vector control calculation using the rotor position θ. For example, a PI control calculation is performed on the difference between the torque current command Iqref and the torque current Iq, and a voltage command Vq is generated. The excitation current Id side is similarly processed to generate a voltage command Vd, and the voltage commands Vq and Vd are converted into three-phase voltages Vu, Vv and Vw using the rotor position θ. The three-phase voltages Vu, Vv, and Vw are input to the DUTY generator 31, and the duties U_DUTY, V_DUTY, and W_DUTY for generating the PWM signals of the respective phases are determined.

  Each phase duty U, V, W_DUTY is given to the PWM signal generation unit 32, and the two-phase modulated PWM signal or the three-phase modulated signal PWM signal is generated by comparing the levels of the carrier and the carrier. The Hereinafter, the two-phase modulated PWM signal is also referred to as a two-phase PWM signal, and the three-phase modulated signal PWM signal is also referred to as a three-phase PWM signal. Further, a signal on the lower arm side obtained by inverting the two-phase or three-phase PWM signal is also generated, and after a dead time is added as necessary, they are output to the drive circuit 33. The detection method selection unit 35 receives a PWM interrupt signal from the PWM signal generation unit 32 and sends a “switching flag” as a signal to the current detection unit 27, the DUTY generation unit 31, and the PWM signal generation unit 32, which will be described in detail later. Output. The vector calculation unit 30 and the DUTY generation unit 31 also correspond to the PWM signal generation unit.

  The drive circuit 33 outputs a gate signal to each gate of the six FETs 25 (U +, V +, W +, U−, V−, W−) constituting the inverter circuit 23 according to the given PWM signal. For the upper arm side, output is performed at a potential boosted by a necessary level. In the above, the functions of the configurations 27 to 35 excluding the drive circuit 33 are functions realized by the hardware and software of the microcomputer including the CPU.

  Furthermore, this embodiment will be described with reference to FIGS. In the present embodiment, as shown in FIG. 4, the vector calculation unit 30 and the DUTY generation unit 31 handle, for example, four PWM carrier cycles as one control unit. Since the control is repeatedly executed with this control unit as one cycle, this is hereinafter simply referred to as “control cycle”.

  In the inverter circuit for driving the compressor 2, a load fluctuation of suction-compression-discharge occurs during one rotation, and a large load fluctuation of a refrigeration cycle such as a defrosting operation occurs during the operation. Since it is necessary to improve the response of the output torque and the carrier frequency is low, the PWM signal is generated with one PWM carrier period as one control period. In comparison, when driving the fan motor 12, there is no load fluctuation during one rotation, the load fluctuation during operation is small, and the carrier cycle is short, that is, the frequency is high. It is common to operate as a cycle. No new current detection or vector calculation is executed within this control cycle, and the duties U_DUTY, V_DUTY, and W_DUTY determined before the start of the control cycle are used as they are during the control cycle. That is, the vector calculation is executed every control cycle, and is not executed every carrier cycle.

  FIG. 3 is a flowchart showing the contents of PWM interrupt processing that occurs every carrier cycle. First, it is determined whether or not the current detection within the control period can be completed by the PWM signal in the two-phase modulation scheduled to be output in the next control period (S1), and if it is determined that the current detection cannot be completed (NO). Each phase duty pulse is set to execute three-phase modulation (S4). At this time, the detection method selection unit 35 sets the “switching flag” shown in FIG. Based on this “switching flag”, the DUTY generating unit 31 and the PWM signal generating unit 32 set the output data of the PWM signal pattern corresponding to the three-phase modulation (S3), and perform switching of the inverter circuit 23.

  When performing three-phase modulation, as shown in FIG. 4, as in Patent Document 1, each current is detected so that the current can be reliably detected and the supply voltage in the PWM carrier cycle matches the original instruction value. Shifts the phase duty pulse. Furthermore, a current detection timing signal is output from the PWM signal generation unit 32 to the current detection unit 27 at a fixed timing before and after the bottom of the carrier waveform that is an intermediate phase of the PWM carrier cycle. At this timing, the current detection unit 27 detects a two-phase current. For example, in the first carrier cycle, which is the leftmost carrier cycle shown in FIG. 4, V and U phase currents are detected. If the V and U phase currents can be detected, the W phase current can be calculated by calculation, and the motor current for three phases can be detected.

  When the current detection is completed in the first cycle as described above, the next time, that is, in the interrupt processing after the second carrier cycle, “YES” is determined in step S1, the two-phase modulation output is selected (S2), and step S3 is performed. Execute. When the two-phase modulation output is selected, the “switching flag” is reset. The two-phase modulation output is set, for example, by setting the duty of the phase having the minimum duty in the three-phase modulation output to zero and subtracting the minimum value from the other two-phase duties. The carrier period in the subsequent control period, that is, the third and fourth carrier periods all follow such a process, and a two-phase modulated two-phase PWM signal having the same waveform as the second period is output. .

  As a result, as shown in FIG. 4, three-phase modulation is executed in the first carrier period in the control period, and two-phase modulation is executed in the second to fourth carrier periods. When the second current detection is performed in the first carrier cycle, the current detection unit 27 causes the vector calculation unit 30 to generate a current detection completion interrupt as shown in FIG. It is good also as a trigger which starts vector control calculation.

  In the case of two-phase modulation, the upper switching element is fixed off in any one phase in each PWM carrier cycle. Therefore, the switching element in the inverter circuit 23 is compared with three-phase modulation in which all switching elements are turned on and off. The number of times of turning on / off can be reduced. Conventionally, in a state where current cannot be detected, three-phase modulation has been performed in all PWM carrier periods in the control period. On the other hand, in this embodiment, three-phase modulation for current detection is performed only in one PWM carrier period in the control period, and a two-phase modulation signal is output in the other PWM carrier period, thereby improving efficiency. Can be planned.

  FIG. 5 shows an example of the power consumption reduction amount for each rotation speed when the modulation system switching control according to this embodiment is applied. The object of comparison is a conventionally considered method of performing three-phase modulation in all PWM carrier periods in the control period when current reading cannot be performed with a two-phase modulation PWM waveform. FIG. 5 shows the improvement effect based on the method. According to the present embodiment, since at least three of the four PWM carrier periods in one control period are always two-phase modulation, the operation rate by efficient two-phase modulation is increased, and as a result, the number of revolutions is approximately It can be seen that there is an effect of reducing power consumption in the entire area. From the figure, it can be seen that the power consumption is reduced by about 0.5 W to 1.6 W at about 200 rpm or more. FIG. 5 shows a test result in which a fan driving motor having a rated power of 70 W is applied as the motor 12.

  As described above, according to the present embodiment, the current detection unit 27 is configured so that the motor 4 is based on the signal generated by the shunt resistor 24 connected to the DC side of the inverter circuit 23 corresponding to the current value and the PWM signal pattern. The phase calculation unit 30 determines the rotor position θ based on the phase current, and together with the PWM signal generation unit 32, the two-phase or three-phase currents Iu, Iv, Iw are detected. A PWM signal pattern is generated. At this time, the PWM signal generation unit 32 increases or decreases the duty in both directions of the delay side and the advance side with respect to the bottom of the carrier cycle for any one of the three-phase PWM signal patterns. With respect to the bottom, the duty is increased or decreased in one direction on the delay side and the advance side, and the remaining one phase is increased or decreased in the direction opposite to the above direction.

  As a result, the current detection unit 27 generates a three-phase modulation PWM signal pattern that enables detection of a two-phase current at two fixed timings within the PWM carrier period. Then, the detection method selection unit 35 sets four PWM carrier cycles as one control cycle, and within the control cycle, the DUTY generation unit 31 and the PWM signal generation unit 32 provide a three-phase PWM signal pattern and a two-phase PWM signal. It was made to generate so that a pattern might be mixed.

  Specifically, three-phase modulation is performed in the first carrier period within the control period, and two-phase modulation is performed in the second to fourth carrier periods. Thus, the switching loss can be further reduced by reliably detecting the two-phase current when performing the three-phase modulation and performing the other two-phase modulation. If the current can be detected once in one control period, the duty in the next control period can be determined. Therefore, in the last carrier period in the control period or in the middle one carrier period, the current of three-phase modulation can be detected. A PWM signal may be output.

  Moreover, the motor control apparatus of this embodiment is applied to the air conditioner E provided with the heat pump refrigeration cycle apparatus 1 provided with the compressor 2, the outdoor heat exchanger 9, the decompression device 8, and the indoor heat exchanger 7. And since the fan motor 12 is made into control object, the operating efficiency of the heat pump refrigerating-cycle apparatus 1 and the air conditioner E can be improved.

(Second Embodiment)
Hereinafter, the same parts as those in the first embodiment are denoted by the same reference numerals, description thereof is omitted, and different parts are described. As shown in FIG. 6, in the second embodiment, although not shown, each phase current is a three-shunt method in which a shunt resistor is inserted into each source of FETs 25U−, 25V−, and 25W− that are lower arms of the inverter circuit 23. Applies to configurations that detect In this case, it is not necessary to detect current at two fixed detection timings as in Patent Document 1, and each phase current can be detected while the FET 25 of the lower arm of each phase is on.

(Other embodiments)
As a method for generating a three-phase PWM signal by the PWM signal generation unit 32, for example, the method of the fourth embodiment disclosed in Patent Document 1 may be used. It is only necessary to generate a three-phase PWM signal pattern capable of detecting a two-phase current at a predetermined timing.
The control unit period does not necessarily have to be set to 4 periods of the PWM carrier, and if it is 2 periods or more, a power reduction effect can be obtained.
In addition, the number of executions of three-phase modulation in the control unit period may be two or more, but the number of executions of three-phase modulation is set to be smaller than the number of executions of two-phase modulation from the viewpoint of reducing switching loss. Is desirable.

As in Patent Document 1, the first embodiment may be applied to control in the low speed region in a configuration in which only three phase modulation is performed in the low speed region and only two phase modulation is performed in the high speed region. .
The application target of the motor control device is not limited to an air conditioner or a heat pump refrigeration cycle device. Further, the driving target is not limited to the fan motor, and any motor control device that performs PWM driving using a plurality of carrier cycles as one control cycle is applicable.

  Although several embodiments of the present invention have been described, these embodiments have been presented by way of example 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 scope of the invention. These embodiments and modifications thereof are included in the scope and gist of the invention, and are included in the invention described in the claims and the equivalents thereof.

  In the drawings, 1 is a heat pump 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 detector, and 30 is a vector calculation. , 31 is a DUTY generator, 32 is a PWM signal generator, and 35 is a detection method selector.

Claims (6)

In a motor control device that drives a motor via 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 detector for detecting a phase current of the motor;
A rotor position determination unit that determines a rotor position based on the phase current of the motor;
A PWM signal generator that generates a two-phase or three-phase PWM signal pattern so as to follow the rotor position;
The PWM signal generator generates a plurality of PWM control cycles as one control unit, and generates a three-phase PWM signal pattern and a two-phase PWM signal pattern in the control unit.   2. The PWM signal generation unit reduces a generation ratio of a three-phase PWM signal pattern to a generation ratio of a two-phase PWM signal pattern when three or more PWM control cycles are set as one control unit. Motor control device. The current detection unit includes a current detection element that is connected to a DC side of the inverter circuit and generates a signal corresponding to a current value. The motor is based on the signal generated in the current detection element and the PWM signal pattern. Phase current of
3. The motor control device according to claim 1, wherein the PWM signal generation unit generates a PWM signal pattern capable of detecting a two-phase current at a predetermined timing as the three-phase PWM signal pattern. The PWM signal generation unit increases or decreases the duty in either of the delay side and the advance side with respect to any phase of the carrier wave period for any one of the three-phase PWM signal patterns,
For the other one phase, the duty is increased or decreased in one direction on the lag side and the advance side on the basis of an arbitrary phase of the carrier wave period,
For the remaining one phase, the current detection unit is fixed in two points within the carrier period of the PWM signal by increasing or decreasing the duty in the direction opposite to the direction with respect to an arbitrary phase of the carrier period. The motor control device according to claim 3, wherein a three-phase PWM signal pattern is generated so that a two-phase current can be detected at the timing.   The motor control device according to any one of claims 1 to 4, wherein the motor is applied to a device that drives a fan that blows air. A fan motor that drives the fan;
A heat pump refrigeration cycle apparatus comprising the motor control device according to claim 5.

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