JP6165470B2 - Motor control device, heat pump system and air conditioner - Google Patents

Description

  Embodiments of the present invention provide a control device that controls a motor via an inverter circuit by PWM-controlling a plurality of switching elements connected in a three-phase bridge, a heat pump system including the control device, and an air conditioner About.

  When detecting the current of each phase of U, V, and W in order to control the motor, there is a technique of performing current detection using one shunt resistor inserted in the DC part of the inverter circuit. To detect all three-phase currents using this method, a three-phase PWM signal can be detected so that two or more currents can be detected within one cycle of a PWM (Pulse Width Modulation) carrier. It is necessary to generate a pattern. For this reason, there has been proposed a motor control device that can detect a current of two or more phases without increasing noise by shifting the phase of the PWM signal within one cycle (Patent Document 1).

JP 2012-70591 A

  When PWM control is performed on a three-phase motor, there are a three-phase modulation method and a two-phase modulation method. Since the switching loss in the inverter circuit increases in the three-phase modulation method, it is desirable to adopt the two-phase modulation method from the viewpoint of suppressing the increase in loss. However, when the current detection method disclosed in Patent Document 1 is adopted, there is a problem that it becomes difficult to detect current in the low-speed rotation region of the motor.

  Accordingly, a motor control device that can employ a current detection method using one current detection element while avoiding an increase in switching loss, and a heat pump system and an air conditioner including the control device are provided.

  According to the motor control apparatus of the embodiment, the current detection means calculates the phase current of the motor based on the signal generated by the current detection element connected to the DC side of the inverter circuit corresponding to the current value and the PWM signal pattern. Then, the rotor position determination means determines the rotor position based on the phase current, and the PWM signal generation means generates a two-phase or three-phase PWM signal pattern so as to follow the rotor position.

  At this time, the PWM signal generation means increases / decreases the duty in both directions of the delay side and the advance side of any one of the three phases with respect to any phase of the carrier wave period for the three-phase PWM signal pattern. The other one phase increases or decreases the duty in one direction on the delay side and the advance side on the basis of an arbitrary phase of the carrier wave period, and the remaining one phase increases or decreases in the opposite direction to the above direction.

As a result, the current detection means generates a three-phase PWM signal pattern so that a two-phase current can be detected at two timings fixed within the PWM signal carrier cycle. Then, the switching command output means causes the PWM signal generation means to generate a two-phase PWM signal pattern when the motor is in a high-speed rotation region where the current detection possible period by the current detection means is long , and the motor generates the current possible period. Is in a low-speed rotation region where the frequency becomes shorter , a switching command is output so as to generate a three-phase PWM signal pattern.

Functional block diagram showing the configuration of the motor control device according to the first embodiment Diagram showing the configuration of the heat pump system The figure which shows the change of the rotation speed of the motor incorporated in a compressor, and the switching of whether PWM control is performed by two-phase modulation or three-phase modulation when the operation of the air conditioner is started Flowchart schematically showing switching of the drive control method corresponding to FIG. Flow chart schematically showing switching process of modulation method during operation of air conditioner Flowchart showing interrupt processing executed for each carrier cycle when performing two-phase modulation The figure which shows the execution time image of the process shown in FIG. 6 with a PWM carrier waveform (A) is a figure which shows the phase in which a PWM duty pulse is output in the case of two-phase modulation, and the timing at which A / D conversion is performed on the terminal voltage of the resistance element, and (b) is based on orthogonal voltages Vα and Vβ. The figure which shows the table for calculating 2-phase PWM duty _, (c) is a figure which shows a sector on d (beta) coordinate Flowchart showing interrupt processing executed every half of the carrier cycle when performing three-phase modulation 7 equivalent diagram The figure which shows the output phase of each phase PWM duty pulse in three phase modulation Fig. 8 (b) equivalent diagram Flow chart mainly showing the control contents executed by the processing load monitoring unit Flow chart of interrupt processing load determination processing FIG. 9 equivalent view showing the second embodiment Figure 10 equivalent FIG. 14 equivalent diagram showing the third embodiment. (A) is an example of a table showing an increase in power consumption WSF due to strong field operation during two-phase modulation, and (b) is an example of a correction coefficient βIq for correcting the increase WSF in (a). FIG. 14 equivalent diagram showing the fourth embodiment. Flowchart for counting the current undetectable period FIG. 19 equivalent diagram showing the fifth embodiment. FIG. 14 equivalent diagram showing the sixth embodiment FIG. 5 equivalent diagram showing the seventh embodiment Fig. 9 equivalent The figure explaining the processing content of step S36b of FIG.

(First embodiment)
Hereinafter, as an example of a heat pump system, a first embodiment for driving a compressor motor of an air conditioner will be described with reference to FIGS. 1 to 14. In FIG. 2, the compressor (load) 2 constituting the heat pump system 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 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 compressor, and the motor 4 is, for example, a three-phase IPM (Interior Permanent Magnet) motor (brushless DC motor). The air conditioner E includes the heat pump system 1 described above.

  At the time of heating, 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 to be condensed, and then the decompression device. The pressure is reduced at 8 and the temperature becomes low and flows to the outdoor heat exchanger 9 where it evaporates and returns to the compressor 2. On the other hand, at the time of cooling, 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 side heat exchanger 9 from the four-way valve 6, is condensed, and is decompressed by the decompression device 8, and becomes low temperature indoor side It flows into the heat exchanger 7, where it evaporates and returns to the compressor 2. 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.

  FIG. 1 is a functional block diagram showing the configuration of the motor control device. 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 (DC AC converter) 23 is connected to the DC power source 21 via a positive bus 22a and a negative bus 22b. A shunt resistor 24, which is a current detection element, is connected to the negative bus 22b. Has been inserted. 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 four phase windings is connected.

  A terminal voltage (signal corresponding to the current value) of the shunt resistor (current detection element) 24 is detected by a current detection unit (current detection means) 27. When the current detection unit 27 performs A / D conversion and reads the terminal voltage, the current Iu, Iv of each phase of U, V, W is output based on the two-phase or three-phase PWM signal pattern output to the inverter circuit 3. , Iw is detected. Each phase current detected by the current detection unit 27 is input to a vector calculation unit (rotor position determination means, PWM signal generation means) 30.

  In the vector calculation unit 30, when the rotational speed command ωref of the motor 4 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 4. Generated. The rotor position θ of the motor 4 is determined from the phase currents Iu, Iv, and Iw of the motor 4, 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 a DUTY generation unit (PWM signal generation means) 31, and the duties U_DUTY, V_DUTY, and W_DUTY for generating the PWM signal of each phase are determined.

  Each phase duty U, V, W_DUTY is given to a PWM signal generation unit (PWM signal generation means) 32, and a two-phase or three-phase PWM signal is generated by comparing the level with the carrier. 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 drive circuit 33 outputs a gate signal to each gate of the six power MOSFETs 25 (U +, V +, W +, U−, V−, W−) constituting the inverter circuit 23 in accordance with the given PWM signal (upper). On the arm side, the voltage is output at a potential boosted by a necessary level). As a method in which the PWM signal generation unit 31 generates a three-phase PWM signal, for example, the method of the fourth embodiment disclosed in Patent Document 1 is used.

In addition, the vector calculation unit 30 outputs the torque current Iq and the excitation current Id to the power consumption calculation unit 34, calculates the estimated speed ωe based on the torque current Iq, the excitation current Id, and the excitation voltage Vd, and calculates the power consumption calculation unit. 34 and the detection method selection unit 35. The power consumption calculation unit 34 outputs the power consumption W to the detection method selection unit (switching command output means) 35 when the power consumption W is calculated by the following equation based on each input current.
W = ωe × T = ωe × P / 2 × {φ × Iq + (Ld−Lq)} × Id × Iq (1)
However, T is a motor output torque, P is the number of poles of the motor 4, φ is an electric winding interlinkage magnetic flux, Ld is a d-axis inductance, and Lq is a q-axis inductance. The power consumption calculation unit 34 will be described in the third embodiment.

  The load processing monitoring unit (switching command output means) 36 has a built-in timer 36C (for example, a free-run counter) for measuring the execution time of software processing executed every PWM control cycle or half cycle. A PWM interrupt signal from the PWM signal generation unit 32 is input to the vector calculation unit 30 and the load processing monitoring unit 36. Further, the load processing monitoring unit 36 is input with a counter value of an up / down counter used by the PWM signal generation unit 32 to generate a triangular wave carrier internally. Further, the load processing monitoring unit 36 receives a DUTY set signal that is output at a timing when the DUTY generation unit 31 sets a PWM duty pulse in the PWM signal generation unit 32. In the above, the functions of the configurations 27 to 36 (excluding the drive circuit 33) are functions realized by the hardware and software of a microcomputer including a CPU.

  Next, the operation of the present embodiment will be described with reference to FIGS. FIG. 3 shows a change in the number of rotations of the motor 4 built in the compressor 2 and a switching state of whether the PWM control is performed by two-phase modulation or three-phase modulation when the cooling operation by the air conditioner is started. Show. FIG. 4 is a flowchart schematically showing switching of the drive control method corresponding to FIG. When the compressor 2 that has started operating the air conditioner is started, PWM control is performed using three-phase modulation (S1). Since the sensorless driving method cannot be executed in the region where the rotational speed of the motor 4 is low, the motor 4 is driven by forced commutation (S2). When the rotational speed increases to some extent, the position sensorless drive system is switched (S3).

  As shown in FIG. 3, immediately after the start of the operation of the air conditioner, the rotational speed of the motor 4 is rapidly increased in order to quickly decrease the temperature in the room where the air conditioner is installed. Is detected and compared with a predetermined threshold (set temperature) (S4). While the room temperature is below the threshold value, (low) three-phase modulation is continued (S5), and when the room temperature is equal to or higher than the threshold value (high), the two-phase modulation is switched (S6).

  When the room temperature decreases due to a sudden increase in output immediately after the start of operation, the rotational speed of the motor 4 is decreased as shown in FIG. Then, the three-phase modulation is continued if the indoor temperature is stable and falls below the threshold value, and is switched to the two-phase modulation if the indoor temperature rises and exceeds the threshold value for some reason.

  Hereinafter, the switching control between the above-described two-phase modulation and three-phase modulation will be described in more detail. In FIG. 2 and FIG. 3, switching has been described using the threshold temperature in order to explain the general operation, but in actuality, control is performed as follows. FIG. 5 is a flowchart schematically showing a modulation system switching process during operation of the air conditioner. First, if the modulation method currently being executed is two-phase modulation, the process proceeds from step S11 to S12, and the cycle for generating a PWM interrupt is set to be the same as the carrier cycle. Then, current data is acquired by a current detection method according to two-phase modulation, vector control processing is performed, and a two-phase PWM signal pattern is generated and output (S13).

  On the other hand, if the modulation method currently being executed is three-phase modulation, the process proceeds from step S11 to S14, and the cycle for generating the PWM interrupt is set to every half cycle of the carrier cycle. Then, current data is acquired by a current detection method according to three-phase modulation, vector control processing is performed, and a three-phase PWM signal pattern is generated and output (S15). The selection of the modulation method in step S11 is performed based on the result of PWM processing load monitoring described later.

<Two-phase modulation processing>
Hereinafter, the two-phase modulation process will be described with reference to FIGS. FIG. 6 is a flowchart showing interrupt processing executed for each carrier cycle when performing two-phase modulation. First, when A / D converted data is extracted in the current detector 27 (S21), a three-phase current is detected based on the data (S22). Here, the A / D conversion processing of the terminal voltage of the shunt resistor 24 in the current detection unit 27 is executed twice within one carrier period separately from the processing shown in FIG. 6 (execution timing will be described later). The A / D converted data is stored in, for example, a register. Therefore, the process of step S21 reads the data stored in the register.

  Next, the rotor position (θ) of the motor 4 is estimated from the three-phase current by vector control calculation (S23), and frequency control (speed control, S24) and current control (PI control, etc.) are executed (S25). Then, when the two-phase PWM duty determined in the current arithmetic processing is output in the next cycle, it is stored in a register or memory (S26). (The two-phase PWM duty obtained here is set in the output register in step S27 of the interrupt processing in the next carrier cycle.) Then, the two-phase PWM duty determined in the previous carrier cycle is used for output. Set in the register (S27).

  FIG. 7 shows an execution time image of the interrupt process during the two-phase modulation together with the PWM carrier waveform. In the air conditioner, the motor that drives the fan 11 of the heat exchanger 9 corresponding to the outdoor unit is controlled by the single control circuit (microcomputer) in parallel with the compressor 2 (heat exchanger 7 corresponding to the indoor unit). The motor for driving the fan 10 is controlled by another control circuit, a driver IC, or the like).

  FIG. 7 shows a processing time (1) related to motor control of the compressor 2 shown in FIG. 6 in (a), and a processing time (2) related to motor (fan motor) control of the fan 11 in (b). Show. That is, when a PWM interrupt occurs at the bottom of the triangular wave that is the PWM carrier, the processing shown in FIG. 6 is executed, and then the motor current is also detected for the fan motor to perform vector control.

  FIG. 8A shows the phase at which the PWM duty pulse is output in the case of two-phase modulation, and the timing at which the current detection unit 27 performs A / D conversion on the terminal voltage of the shunt resistor 24. In this example, U and V phase duty pulses are output so that the bottom of the triangular wave is the center phase. The first A / D conversion is executed at the bottom timing. The current detected at this time is a W-phase negative current. Then, the second A / D conversion is executed when a minute time α that further considers the switching delay has passed after the passage of the time D2 from the bottom. The current detected at this time is a U-phase positive current. The V-phase current is obtained by calculation based on the above two A / D conversion results.

FIG. 8B is a table for calculating the two-phase PWM duty based on the orthogonal voltages Vα and Vβ obtained in the vector control process. As shown in the left side of FIG. 8B and FIG. 8C, sectors 0 to 5 are determined according to the magnitude relationship between the voltages Vα and Vβ, and the pulse width values D1 and D2 are determined for each sector. Is determined based on the voltages Vα and Vβ and the correction value H. The correction value H is a term for correcting the duty pulse width in accordance with the DC voltage that is the voltage of the DC power supply unit 21 and is expressed by the following equation.
H = √3 × (PWM register maximum value) × 32768 / (DC voltage) (2)
The “PWM register maximum value” is 65535 if the register is 16 bits, for example.

  PWMa, PWMb, and PWMc shown on the right side of FIG. 8B correspond to the three-phase voltages Vu, Vv, and Vw output from the vector calculation unit in FIG. 1, and the pulse width value D1 corresponds to each sector. , D2 or only the pulse width value D2, or “0”.

<Three-phase modulation processing>
Hereinafter, the three-phase modulation process will be described with reference to FIGS. FIG. 9 is a flowchart showing interrupt processing executed every half cycle of the carrier cycle when three-phase modulation is performed. Steps S31 to S35 are executed in the same manner as steps S21 to S25 shown in FIG. 6, but in the subsequent step S36, a three-phase PWM duty is output. The subsequent steps S37 to S39 are performed in the DUTY generation unit 31. With reference to the value of the carrier counter provided from the PWM signal generation unit 32, it is determined whether the count is up or down (S37). If up counting is in progress, D_Pwm_set2 () is set (S38), and if down counting is in progress, D_Pwm_set1 () is set (S39). These will be described with reference to FIGS.

  FIG. 10 is a diagram corresponding to FIG. 7, but in the case of three-phase modulation, a PWM interrupt occurs at the peak and bottom of the triangular wave. In the processes (1) to (4) indicated by circled numbers in the figure, the processes (1) and (3) correspond to steps S31 to S37, and the processes (2) and (4) correspond to steps S38 and S39, respectively. It corresponds. In this case, the fan motor control (5) is performed after the processing (4) is executed.

  FIG. 11 shows the output phase of each phase PWM duty pulse in the case of three-phase modulation. As described above, the method disclosed in Patent Document 1 is used. That is, for any one of the three phases, the duty is increased or decreased in both directions of the delay side and the advance side with reference to the bottom of the triangular wave. For the other one phase, for example, the duty is increased or decreased on the leading phase side with respect to the bottom, and for the remaining one phase, the duty is increased or decreased on the delayed phase side with respect to the bottom. By determining the output phase of the three-phase duty pulse in this way, the current detection unit 27 can detect a two-phase current at two fixed timings within the carrier cycle.

  In the example shown in FIG. 11, the duty of the U-phase pulse is increased or decreased in both directions from the center phase of the carrier cycle, the duty of the V-phase pulse is increased or decreased from the center phase in the advance direction, and the W-phase pulse is increased to the center. The duty is increased or decreased from the phase in the delay direction. When an interrupt occurs at the peak of the triangular wave, the carrier counter is counting down, so the D_Pwm_set2 () outputs a duty pulse in the first half of the current carrier cycle.

  For the U phase, a pulse with a duty of 1/2 is output in the period from the timing after the interruption at the peak to the bottom. For the V phase, if the duty is less than 50%, the pulse is output in the period from the timing after the interruption at the peak to the bottom as in the U phase. For the W phase, when the duty exceeds 50%, the excess pulses are output during the period from when the interrupt at the peak occurs until the bottom is reached. Therefore, these pulses are output by D_Pwm_set2 ().

  On the other hand, when an interrupt occurs at the bottom of the triangular wave, the carrier counter is counting up, so the D_Pwm_set1 () outputs a duty pulse for the latter half of the current carrier cycle. As for the U phase, as in the first half, a pulse having a duty of 1/2 is output in the period from the timing to the peak after the interruption at the bottom occurs. For the V phase, when the duty exceeds 50%, the excess pulses are output during the period from the timing when the interruption at the bottom occurs until the peak is reached. For the W phase, if the duty is less than 50%, the pulse is output in the period from the timing to the peak after the bottom interruption occurs, as in the U phase. Therefore, it is these pulses that are output by D_Pwm_set1 ().

  The two A / D conversion timings in the three-phase modulation are immediately before and after the triangular wave reaches the bottom. A W-phase current is obtained at the former timing, and a V-phase current is obtained at the latter timing. As for the former, even if A / D conversion is performed at the timing that coincides with the bottom, it is possible to obtain the W-phase current due to the timing of each control, signal delay, and the like.

  FIG. 12 is a diagram corresponding to FIG. 8B, but conditions 1 to 3, sectors, D1, and D2 are exactly the same as those in the case of two-phase modulation, and only the determined portions of PWMa, PWMb, and PWMc are different. . These determinations include not only the pulse width values D1 and D2 but also the maximum value PD of the PWM register described in the explanation of the correction value H.

<Modulation method switching process>
Next, details of control for switching between two-phase modulation and three-phase modulation will be described with reference to FIGS. FIG. 13 is a flowchart mainly showing the control contents executed by the processing load monitoring unit 36. Here, switching from the three-phase to the two-phase in the process of increasing the rotational speed of the motor 4 at the start-up described with reference to FIG. 3 and the rotation from the state where the motor 4 is rotating at high speed and performing two-phase modulation. When the number decreases, it is determined whether or not switching to three-phase modulation that increases the software processing load is possible.

  When a PWM interrupt occurs every carrier cycle, the processing load monitoring unit 36 reads and acquires the counter value (1) of the timer 36C at that time (S41). The subsequent “interrupt processing execution” in step S42 is the processing shown in FIG. 6 or FIG. 9 described above, and is executed by the vector computing unit 30 or the like (when three-phase modulation is executed, every half cycle, two-phase modulation is executed). (When executed, every cycle). When step S27 is executed, the Dutyset signal output from the DUTY generator 31 becomes active. Thereby, the processing load monitoring unit 36 reads and acquires the counter value (2) of the timer 36C again (S43).

  Next, with reference to the value of the carrier counter given from the PWM signal generation unit 32, it is determined whether or not the counter is counting up (S44). If it is counting up (YES), the interrupt processing time (3) is set. A difference between the counter values (2) and (1) is obtained (S45). Then, the interrupt processing time (3) is compared with the maximum allowable processing time; MAX load A. If the interrupt processing time (3) exceeds the MAX load A (S46: YES), the interrupt processing time (3) Is set to the MAX load A (S47). If the interrupt processing time (3) is equal to or less than the MAX load A (S45: NO), the processing shown in FIG.

  On the other hand, if the counter is counting down in step S44 (NO), the interrupt processing time (4) is obtained as the difference between the counter values (1) and (2) (S48). Then, the interrupt processing time (4) is compared with the maximum allowable processing time; MAX load B. If the interrupt processing time (4) exceeds the MAX load B (S49: YES), the interrupt processing time (4) Is set to the MAX load B (S50). If the interrupt processing time (4) is equal to or less than the MAX load B (S45: NO), the processing is terminated. For example, if the carrier cycle is 100 μs and the threshold value is set to 50 μs, which is 50%, the MAX load A (50 μs) is set when the interrupt processing time (3) exceeds 50 μs, and NG determination It becomes.

  Here, the interrupt processing times (3) and (4) correspond to “the length of the current processing time”. The MAX loads A and B are threshold values for evaluating and determining the interrupt processing times (3) and (4), but these may be set to values that are ½ or less of the carrier period.

  FIG. 14 is a flowchart of the interrupt processing load determination process performed by the detection method selection unit 35 and the processing load monitoring unit 36. In step S51, a determination is made based on whether the interrupt processing time (3) is set to the MAX load A or whether the interrupt processing time (4) is set to the MAX load B, and the MAX load A or B is determined. If it is set to (NG), if the three-phase modulation is being executed, the mode is switched to the two-phase modulation (S54).

  On the other hand, if the MAX load A or B is not set (OK), the maximum and minimum duty difference (Maxduty-Mindity) is compared with the threshold for the duty pulse (S52). In other words, during the three-phase modulation, if the above-mentioned duty difference becomes equal to or greater than the threshold value due to a certain increase in the rotation speed of the motor 4, a sufficient period for detecting the current for two phases within the carrier cycle can be secured (current detection is possible). The drive control of the motor 4 can be performed in a stable state. Therefore, the process proceeds to step S54. Further, if the duty difference is less than the threshold value, it is difficult to secure a period during which the current for two phases can be detected within the carrier cycle (the current detectable period is short). Therefore, a three-phase modulation method that basically has a merit of high current detection rate is maintained (S53).

  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 either of the delay side and the advance side with respect to the bottom of the carrier cycle with respect to the three-phase PWM signal pattern, Is to increase or decrease the duty in one direction on the delay side and the advance side with respect to the bottom, and in the remaining one phase in the direction opposite to the direction.

  Thus, the current detection unit 27 generates a three-phase PWM signal pattern so that a two-phase current can be detected at two timings fixed within the PWM signal carrier cycle. The detection method selection unit 35 causes the DUTY generation unit 31 and the PWM signal generation unit 32 to generate a two-phase PWM signal pattern when the motor 4 is in the high-speed rotation region, thereby suppressing an increase in switching loss. When 4 is in the low speed rotation region, a switching command is output so as to generate a three-phase PWM signal pattern with a high current detection rate. Therefore, it is possible to improve control accuracy while suppressing switching loss.

Further, the detection method selection unit 35 and the processing load monitoring unit 36 refer to the result of referring to the duty ratio of the PWM signal, the length of the interrupt processing time within the carrier cycle, or the length of the current detectable period within the carrier cycle. Based on this, a switching command is output. Therefore, switching between the two-phase modulation method and the three-phase modulation method can be performed appropriately based on the interrupt processing time and the length of the current detectable period.
In addition, when performing two-phase modulation, an interrupt is generated every carrier cycle, and when generating three-phase modulation, an interrupt is generated every half of the carrier cycle. For modulation, the novel three-phase modulation method presented in Patent Document 1 can be easily introduced.

  Further, the processing load monitoring unit 36 measures the time required for the PWM interrupt processing during execution of the two-phase modulation method, and if the interrupt processing time is less than a threshold value set to ½ or less of the carrier cycle, the processing load monitoring unit 36 If the interrupt processing time is equal to or greater than the threshold, a switching command is output so as to maintain the two-phase modulation method. Therefore, it is possible to evaluate the time required for the PWM interrupt processing and shift to the case where the three-phase modulation method can be surely executed.

Further, the processing load monitoring unit 36 obtains a difference between the maximum value and the minimum value for the three-phase PWM duty during the execution of the three-phase modulation method, and performs two-phase modulation if the duty difference is equal to or greater than a predetermined threshold value. A switching command is output so as to shift to the method. Therefore, the current detection rate can be evaluated and a transition can be made when the two-phase modulation method can be reliably executed.
Furthermore, about the air conditioner provided with the heat pump system 1 provided with the compressor 2, the outdoor side heat exchanger 9, the decompression device 8, and the indoor side heat exchanger 7, the motor 4 which comprises the compressor 2 is controlled object. Therefore, the operation efficiency of the heat pump system 1 and the air conditioner can be improved.

(Second Embodiment)
FIGS. 15 and 16 are views corresponding to FIGS. 9 and 10 showing the second embodiment. The same parts as those of the second embodiment are denoted by the same reference numerals, the description thereof is omitted, and different parts will be described below. As shown in FIG. 15, in 2nd Embodiment, step S30, S35a, S36a is added to the flowchart shown in FIG. 9, and the location which performs step S36 is changed. That is, when step S35 is executed, the flag M_Int_flg is set to “1” (S35a). The above flag indicates that the processing of steps S31 to S35 has already been executed in the half cycle of the carrier.

Then, in step S30 the beginning, it is determined whether the flag M_Int_flg = 0 (reset), perform a "1 (Se Tsu g)" if (NO) step S36, the flag M_Int_flg to "0" (S36a). If step S35a, 36a is performed, it will transfer to step S37. That is, in the second embodiment, in the PWM interrupt processing when performing three-phase modulation, steps S30 to S35a and S37 to S39 are executed in the first half of the cycle, and steps S30, S36, S36a, and S37 to are executed in the second half of the cycle. S39 is executed.

  As a result, the interrupt processing times (1) and (3) shown in FIG. 16 are slightly shorter than those in FIG. Since the fan motor control process (5) of the outdoor unit is also executed in the second half of the carrier cycle, the processing time in the second half of the cycle can be provided by dividing the interrupt processing as described above. The process of dividing the first half and the second half is not limited to the above example, and may be set as appropriate.

(Third embodiment)
17 and 18 show a third embodiment. FIG. 17 is a diagram corresponding to FIG. 14, and step S55 for making a determination based on the rotational speed and power consumption is added between steps S52 and S53. In step S55, the power corresponding to the switching loss in the three-phase modulation is compared with the power consumption in the strong field operation in the two-phase modulation determined from the table shown in FIG. Branches to select the modulation method. The reason why the strong field operation is performed is that when the rotational speed of the motor 4 is low, the excitation current Id is increased to increase the current detection rate.

The electric power W3sW corresponding to the increase in switching loss at the time of three-phase modulation with reference to the two-phase modulation is a predetermined power obtained by an experiment or the like in advance to the power consumption W calculated by the power consumption calculator 34 as described above. It is obtained by multiplying the coefficient αloss (for example, 5%, etc.) by the switching period ratio 0.33 for performing only three-phase modulation.
W3sW = W × αloss × 0.33 (3)

  FIG. 18A is an example of a table showing an increase WSF in power consumption due to the strong field operation during two-phase modulation. FIG. 18B is an example of a correction coefficient βIq for correcting the increase in power consumption WSF in FIG. 18A based on the case of the torque current Iq = 2.8 A. That is, if the load of the motor 4 becomes heavy, the output torque needs to be increased accordingly, and the torque current Iq increases, so the duty increases. Since the exciting current Id that does not contribute to the torque can be reduced by that amount, correction is made so as to reduce the increase in power consumption.

Therefore, the power W2sW corresponding to the switching loss during the two-phase modulation is calculated as follows.
W2sW = WSF × βIq (4)
In step S55, the modulation method with the smaller value is selected from the powers W3sw and W2Sw.
As described above, according to the third embodiment, the detection method selection unit 35 instructs to switch between the two-phase modulation method and the three-phase modulation method based on the result of referring to the power W consumed by the motor 4. , The modulation method can be switched so that the power consumption is reliably reduced.

(Fourth embodiment)
19 and 20 show a third embodiment. FIG. 19 is a diagram corresponding to FIG. 14, in which step S <b> 56 is arranged instead of step S <b> 52, and it is determined whether or not the current detection rate is equal to or greater than a threshold value. FIG. 20 is a flowchart showing a process of counting the number of carrier periods in which current detection is impossible (current detection impossible period), which is used to calculate the current detection rate. In the flowchart shown in FIG. 6 or FIG. , S27 or between steps S36 and S37.

  In each of the determination steps S61 to S63, the two-phase simultaneous on-time D2 and the one-phase on-time D1, (MAaxduty-Midduty) are each compared with a threshold value determined as the minimum time required for current detection. If it is less than the threshold, the detection impossible counter is incremented (S64). However, the threshold value is a doubled value for the phase in which the duty pulse is arranged at the center of the carrier period.

The current detection rate is obtained by the following equation for each electrical angle cycle.
(Current detection rate) = {(Counter value corresponding to one electrical angle period) − (Counter value not detectable)}
/ (1 electrical angle cycle equivalent counter value) (5)
For example, if the electrical angular frequency is 20 Hz and the PWM carrier frequency is 4 kHz, the counter value corresponding to one electrical angular cycle is “200”. If there are 20 current non-detectable periods within the electrical angle period,
(Current detection rate) = (200−20) /200=0.9=90 (%)
It becomes.

  In step S56, it is determined whether or not the current detection rate is equal to or greater than a threshold value set for the detection rate. If the current detection rate is less than the threshold value, the three-phase modulation method is executed. Execute the method.

  As described above, according to the fourth embodiment, the detection method selection unit 35 obtains a current detection rate for each electrical angle cycle, and determines whether the current detection rate is equal to or greater than a threshold value. Since a command for switching between the phase modulation schemes is output, a modulation scheme capable of reliably detecting the three-phase current can be selected.

(Fifth embodiment)
FIG. 21 is a view corresponding to FIG. 19 showing the fifth embodiment, in which step S55 of the third embodiment is added to the flowchart shown in FIG.

(Sixth embodiment)
FIG. 22 is a view corresponding to FIG. 14 showing the sixth embodiment. In addition to making the determinations in steps S51, S52, and S55, and determining “NG” in step S51, the determinations in steps S56 and S57 are made. Same as S55. In subsequent step S58, the carrier period is changed to be lower. That is, when the interrupt processing load is heavy but the power consumption is smaller in the three-phase modulation, the carrier period is lowered (for example, 5 kHz → 4.5 kHz), and the processing time is ensured and the process returns.

  As described above, according to the sixth embodiment, when the detection method selection unit 35 determines that the interrupt processing time exceeds the threshold and the power consumption of the three-phase modulation is smaller than the power consumption of the two-phase modulation, Adjustment is made to make the carrier period longer without switching the modulation method. Therefore, an increase in power consumption can be suppressed.

(Seventh embodiment)
23 to 25 show the seventh embodiment. FIG. 23 is a diagram corresponding to FIG. 5. In S16 instead of Step S12, an interrupt is generated every half cycle of the carrier period even in the two-phase modulation method. FIG. 24 is a diagram corresponding to FIG. 9, but by adding steps S36a and S36b between steps S36 and S37, the processing is common to two-phase modulation and three-phase modulation. That is, when step S36 is executed, it is determined whether the modulation method being executed is two-phase or three-phase (S36a), and if it is three-phase modulation (NO), the process proceeds to step S37. On the other hand, in the case of two-phase modulation (YES), the three-phase PWM duty obtained in step S36 is converted into a two-phase PWM duty (S36b), and the process proceeds to step S37.

  FIG. 25 illustrates the processing content of step S36b. It is assumed that the three-phase PWM duty is obtained as shown in FIG. Among these, the minimum duty is set to MINduty (U phase in this example). Then, the two-phase PWM duty is obtained by subtracting (MINduty + τ) from the duty of the other phases (V, W). Here, τ is the dead time equivalent time, but the duty is of course zero for the U phase. Therefore, in this case, the two-phase modulation is performed by the V and W phases. By converting the PWM pattern of the three-phase modulation method into the pattern of the two-phase modulation method in this manner, the two-phase modulation method can be set at 2 fixed timings as in the three-phase modulation method. The phase current can be detected.

  As described above, according to the seventh embodiment, in both cases of two-phase modulation and three-phase modulation, processing is performed by generating a PWM interrupt every half cycle of the carrier cycle. In other words, with conventional two-phase modulation, it is common to perform interrupt processing every carrier cycle, so a new three-phase that performs interrupt processing every half cycle in the two-phase modulation control already performed If modulation is combined, the first embodiment and the like are easier to introduce.

  On the other hand, if it is assumed that a program corresponding to the control of the above combination is created on a zero basis, the PWM interrupt generation pattern is changed in both two-phase modulation and three-phase modulation. It can be said that it is more efficient to create programs. In addition, when generating the two-phase PWM signal pattern, the DUTY generating unit 31 generates a three-phase PWM signal pattern, and sets the duty of the phase having the smallest duty among these three phases to zero, The two-phase PWM signal pattern is obtained by subtracting the minimum phase duty from the other two-phase duty. As a result, as shown in FIG. 24, it is possible to make the interrupt processing performed by the two-phase modulation and the three-phase modulation as common as possible, and at the two fixed timings in any modulation method, the two-phase modulation is performed. Current can be detected.

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 process shown in FIG. 14 of the first embodiment, the process for evaluating the duty difference may be deleted.
In the third embodiment, the reference of the correction coefficient βIq shown in FIG. 18B is not limited to 2.8 A, and may be changed as appropriate according to the individual design.

About the system of 7th Embodiment, you may implement 2nd-6th embodiment similarly.
In addition, the seventh embodiment is not limited to generating a three-phase PWM pattern and then converting it to a two-phase PWM pattern, and a two-phase PWM pattern as shown in FIG. 8 may be generated from the beginning.
The first to third embodiments of Patent Document 1 may be applied to the method for determining the arrangement of each phase duty pulse.
The power consumption W is not limited to the value calculated by the equation (1), but may be determined by directly measuring the voltage and current.

The peak of the triangular wave carrier may be the center of the cycle.
The present invention is not limited to an air conditioner, and is not limited to other heat pump systems or heat pump systems, and can be applied as long as the motor is driven and controlled by switching between a two-phase modulation method and a three-phase modulation method.

  In the drawings, 1 is a heat pump system, 2 is a compressor (load), 4 is a motor, 7 is an indoor heat exchanger, 8 is a decompressor, 9 is an outdoor heat exchanger, 23 is an inverter circuit, and 24 is a shunt resistor. (Current detection element, current detection unit), 27 is a current detection unit (current detection unit), 30 is a vector calculation unit (PWM signal generation unit), 35 is a detection method selection unit (switching command output unit), and 36 is load processing. A monitoring part (switching command output means) is shown.

Claims (10)

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 detection element connected to the DC side of the inverter circuit and generating a signal corresponding to a current value;
Rotor position determining means for determining the rotor position based on the phase current of the motor;
PWM signal generating means for generating a two-phase or three-phase PWM signal pattern so as to follow the rotor position;
Current detection means for detecting a phase current of the motor based on a signal generated in the current detection element and the PWM signal pattern;
The PWM signal generating means, for any one phase of the PWM signal pattern of the three phases, side delay any phase of carrier wave period as a reference, the advanced side bidirectionally increasing or decreasing the duty,
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, wherein the said direction relative to the arbitrary phase of the carrier wave period by increasing or decreasing the duty in the reverse direction, the current detecting means, is fixed in a carrier wave period before Symbol P WM signal A three-phase PWM signal pattern is generated so that a two-phase current can be detected at two timings,
When the motor is in a high-speed rotation region where the current detection period of the current detection unit is long , the PWM signal generation unit generates a two-phase PWM signal pattern, and the motor shortens the current detection period. A motor control device comprising switching command output means for outputting a switching command so as to generate a three-phase PWM signal pattern when in a low-speed rotation region. At least a part of each means is a function realized by a microcomputer,
The switching command output means includes a power value consumed by the motor, a duty ratio of the PWM signal, a length of a current processing time by the microcomputer within the carrier wave period, and a current detectable period within the carrier wave period. The motor control device according to claim 1, wherein the switching command is output based on a result of referring to any one or more of the lengths. At least a part of each means is a function realized by a microcomputer,
When generating the two-phase PWM signal pattern in the PWM signal generating means, generating an interrupt for causing the microcomputer to execute processing for each carrier cycle to generate a three-phase PWM signal pattern The motor control device according to claim 1, wherein the interrupt is generated every ½ of the carrier wave period. At least a part of each means is a function realized by a microcomputer,
The interrupt is generated every ½ of the carrier wave period in both cases where the PWM signal generation unit generates the two-phase PWM signal pattern and the three-phase PWM signal pattern. The motor control device according to claim 1 or 2, wherein   When generating the two-phase PWM signal pattern, the PWM signal generating means generates the three-phase PWM signal pattern, and sets the duty of the phase having the smallest duty among the three phases to zero. 5. The motor control device according to claim 4, wherein the two-phase PWM signal pattern is obtained by subtracting the minimum phase duty from the other two-phase duty.   The switching command output means measures an interrupt processing time executed by the microcomputer when the PWM signal generation means generates a two-phase PWM signal pattern, and the interrupt processing time is 1 / of the carrier wave period. If it is less than a predetermined threshold set to 2 or less, the PWM signal generation means generates a three-phase PWM signal pattern, and if the interrupt processing time is equal to or greater than the threshold, the PWM signal generation means The motor control device according to claim 3, wherein the switching command is output so as to generate a PWM signal pattern.   When the switching command output means determines that the interrupt processing time exceeds the threshold value and the power consumption of the control by the three-phase PWM signal pattern is smaller than the control by the two-phase PWM signal pattern, the switching command output means The motor control device according to claim 6, wherein adjustment is performed so that the period of the carrier wave is made longer without outputting a command.   The switching command output means obtains a difference between a maximum value and a minimum value for the three-phase PWM duty when the PWM signal generation means generates a three-phase PWM signal pattern, and the difference is a predetermined threshold value. The motor control device according to any one of claims 1 to 7, wherein the switching command is output so that the PWM signal generation unit generates a two-phase PWM signal pattern if the above is true. A compressor, an outdoor heat exchanger, a decompressor, and an indoor heat exchanger;
The motor which comprises the said compressor is controlled by the motor control apparatus as described in any one of Claim 1 to 8, The heat pump system characterized by the above-mentioned.   An air conditioner comprising the heat pump system according to claim 9.

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