JP2010284013A - Inverter controller, electric compressor, and household electrical equipment - Google Patents

Abstract

The present invention provides a highly reliable inverter control device that prevents a brushless DC motor from stepping out by correcting a position detection timing while a PWM signal is off to reduce a delay in commutation time. Is.
Based on a position detection signal output from a position detection circuit unit 206 during an on period of a PWM signal, the position detection of a rotor 203b during an off period of the PWM signal is estimated, so that the PWM signal is off. This has the effect of reducing the error in detecting the position of the rotor 203b.
[Selection] Figure 1

Description

  The present invention relates to an inverter control device based on sensorless control of a brushless DC motor, and to an electric appliance for home use such as an electric compressor and a refrigerator using the inverter control device.

  Conventionally, this type of inverter control device employs a 120-degree energization method from the viewpoint of ease of control, and electric compressors do not use sensors such as hall elements from the viewpoint of use environment, reliability, and maintenance. In addition, sensorless control for detecting the rotor magnetic pole position by the induced voltage generated in the stator winding is used.

  In this case, the rotor magnetic pole position is often obtained by using an electrical angle of 60 degrees during the non-control period and observing the induced voltage appearing at the motor terminal during the OFF period of the upper and lower arm switches.

  The conventional inverter control device will be described below with reference to the drawings.

  FIG. 4 is a diagram illustrating a configuration of a conventional inverter control device described in Patent Document 1, and FIG. 5 is a diagram illustrating signal waveforms and processing contents of respective units of the conventional inverter control device.

  In FIG. 4, an inverter circuit unit 140 is configured by connecting three pairs of switching transistors Tru, Trx, Trv, Try, Trw, and Trz in series between terminals of a DC power supply 001. The brushless DC motor 105 includes a stator (not shown) and a rotor 105a. The rotor 105a has a magnet embedded structure in which permanent magnets 105α and 105β are embedded.

  The connection point between each pair of switching transistors Tru, Trx, Trv, Try, Trw, Trz is connected to the terminals of the Y-connected stator windings 105u, 105v, 105w of the brushless DC motor 105, respectively. .

  Note that protective free-wheeling diodes Du, Dx, Dv, Dy, Dw, and Dz are connected between collector-emitter terminals of the switching transistors Tru, Trx, Trv, Try, Trw, and Trz, respectively.

  The resistors 101 and 102 are connected in series between the buses 103 and 104, and the detection terminal ON as a common connection point corresponds to a neutral point voltage of the stator windings 105u, 105v, and 105w of the brushless DC motor 105. A voltage VN at a virtual neutral point that is ½ of the voltage of the DC power supply 001 to be output is output.

  The comparators 106a, 106b, and 106c have their non-inverting input terminals (+) connected to output terminals OU, OV, and OW through resistors 107, 108, and 109, respectively, and the inverting input terminals (−) are detected. Connected to terminal ON.

The output terminals of these comparators 106a, 106b and 106c are connected to input terminals I1, I2 and I3 of the microprocessor 110 which is a logic means.
The microprocessor 110 calculates a timer value per one electrical angle cycle, and determines commutation signals of the switching transistors Tru, Trx, Trv, Try, Trw, and Trz.

  Further, the microprocessor 110 performs PWM (pulse width modulation) modulation on the voltage command based on the rotation speed command, and sets a duty amount which is an ON / OFF ratio of the PWM modulation signal based on a deviation between the rotation speed command and the actual rotation speed. Control and output PWM modulation signals for three phases.

  Then, with respect to the rotational speed command, the duty is increased when the actual rotational speed is low, and conversely, the duty is decreased when the actual rotational speed is high.

  This PWM modulation signal is supplied from the output terminals O1, O2, O3, O4, O5, O6 to the drive circuit 120, and the drive circuit 120 is supplied to the base terminals of the switching transistors Tru, Trx, Trv, Try, Trw, Trz. Outputs the drive signal to be supplied.

  In FIG. 5, (A), (B), and (C) show terminal voltages Vu, Vv, and Vw of the stator windings 105u, 105v, and 105w at the time of steady operation.

  These terminal voltages Vu, Vv, and Vw are supplied from the inverter circuit unit 140 with the voltages Vua, Vva, and Vwa, the induced voltages Vub, Vvb, and Vwb generated in the stator windings 105u, 105v, and 105w, and the inverter when the commutation is switched. It becomes a composite waveform with pulse-like spike voltages Vuc, Vvc, Vwc generated when any of the free-wheeling diodes Du, Dx, Dv, Dy, Dw, Dz of the circuit unit 140 becomes conductive.

  Then, the terminal voltages Vu, Vv, Vw, the virtual neutral point voltage VN which is a half voltage of the DC power supply 001, and the output signals PSu, PSv, PSw compared by the comparators 106a, 106b, 106c are (D). , (E), (F).

  In this case, the output signals PSu, PSv, PSw of the comparators 106a, 106b, 106c are the signals PSua, PSva, PSwa representing the positive and negative and the phases of the induced voltages Vub, Vvb, Vwb, and the pulse-like voltage described above. It consists of signals PSub, PSvb, PSwb corresponding to Vuc, Vvc, Vwc.

  Since the pulse-like spike voltages Vuc, Vvc, and Vwc are ignored by the wait timer, the output signals PSu, PSv, and PSw of the comparators 106a, 106b, and 106c result in the induced voltages Vub, Vvb, and Vwb. Positive and negative as well as phase are indicated.

  The microprocessor 110 recognizes F from six modes A as shown in (G) based on the states of the output signals PSu, PSv, and PSw of the comparators 106a, 106b, and 106c, and determines the levels of the output signals PSu, PSv, and PSw. The drive signals DSu, DSv, DSw, DSx, DSy, and DSz are output as shown in (J) to (O) with a delay of 30 degrees in electrical angle from the time when changes occur.

  Each time T (H) from mode A to F indicates an electrical angle of 60 degrees, and a time (I) that is 1/2 of A to F, that is, T / 2 is a delay time corresponding to 30 degrees in electrical angle. It is shown.

Thus, the position state of the rotor 105a is detected from the induced voltages Vub, Vvb, Vwb generated in the stator windings 105u, 105v, 105w according to the rotation of the rotor 105a of the brushless DC motor 105, and the induced voltage Vub, The change time T of Vvb, Vwb is detected, and the drive signal for energizing each phase stator winding 105u, 105v, 105w is determined and executed according to the energization mode and timing to the stator windings 105u, 105v, 105w. I have to.

Japanese Patent Laid-Open No. 1-8890

  However, in the above-described conventional configuration, when PWM control is performed to vary the rotation speed of the brushless DC motor 105, the input terminals of the comparators 106a, 106b, and 106c connected to the output terminals OU, OV, and OW are In order to detect the voltage on which the PWM signal is superimposed, the PWM signal is also superimposed on the detected voltage waveforms of the induced voltages Vub, Vvb, Vwb of the rotor 105a, and the microprocessor 110 outputs each comparator output while the PWM signal is on. Need to be determined as a position detection signal.

  Accordingly, when the PWM signal carrier frequency is low and the PWM signal is turned on for a long period, or when the PWM signal has a small duty value and the PWM signal is turned on for a short time, the induced voltages Vub, Vvb, and Vwb are virtually There is a high possibility that a point in time when the comparison result of the voltage VN at the sex point coincides will occur during the OFF period of the PWM signal, and then the determination result of the position detection signal output generated by turning on the PWM signal is obtained. The delay time increases.

  For this reason, commutation is delayed with respect to the position of the rotor 105a, and there is a problem that the brushless DC motor stops stepping out when the load torque increases.

  The present invention solves the above-described conventional problems, and prevents the brushless DC motor from stepping out by correcting the position detection timing during the OFF period of the PWM signal and reducing the delay in commutation time. The present invention provides a highly reliable inverter control device.

  In order to solve the above-described conventional problems, an inverter control device of the present invention includes a position detection circuit unit that detects an induced voltage of a brushless DC motor, and a PWM signal for performing PWM control that varies the rotation speed of the brushless DC motor. Of the brushless DC motor based on the induced voltage detected by the position detection circuit unit, the position detection determination unit for determining the position detection of the rotor based on the induced voltage detected by the position detection circuit unit, A position detection signal output by the position detection circuit unit during the ON period of the PWM signal, and a position detection determination means for determining the relative position of the magnetic pole center by the permanent magnet of the rotor with respect to the stator winding and outputting a position signal On the basis of the PWM signal off-period, the rotor magnetic pole position during the off-period of the PWM signal is estimated. It has an effect that it is possible to reduce the delay of error and commutation position detection data.

  The inverter control device of the present invention reduces the rotor position detection error and commutation delay during the OFF period of the PWM signal even when the carrier frequency of the PWM signal of the inverter output voltage is low or the duty value is small. It is possible to prevent the brushless DC motor from stepping out when the load torque increases during low-speed operation.

Block diagram of the inverter control apparatus in Embodiment 1 of the present invention The figure which shows the signal waveform and processing content of each part in the embodiment Flow chart showing the operation in the same embodiment The figure which shows the structure of the conventional inverter control device The figure which shows the signal waveform and processing content of each part of the conventional inverter control apparatus

  According to the first aspect of the present invention, there is provided an inverter circuit unit for driving a brushless DC motor having a permanent magnet provided on a rotor, a position detection circuit unit for detecting an induced voltage of the brushless DC motor, and a rotational speed of the brushless DC motor. And a PWM control means for generating a PWM signal for performing PWM control to vary the magnetic field, and a magnetic pole center by a permanent magnet of the rotor with respect to the stator winding of the brushless DC motor based on the induced voltage detected by the position detection circuit unit And a commutation control means for generating a commutation signal based on the position signal from the position detection judgment means, and during the on period of the PWM signal. The position of the magnetic pole of the rotor during the OFF period of the PWM signal is estimated based on the position detection signal output by the position detection circuit unit at Even when the carrier frequency of the PWM signal of the inverter output voltage is low or the duty value is small, the rotor position detection error and commutation delay during the OFF period of the PWM signal are reduced. It is possible to prevent the brushless DC motor from stepping out when the load torque increases during low-speed operation.

  According to a second aspect of the present invention, in the first aspect of the present invention, the delay time from when the PWM signal is turned on until the position detection determining means starts determining the position detection signal is T, and the PWM signal is Assuming that the off time immediately before turning on is S, the rotor position detection is assumed to be the timing obtained by subtracting the correction time ΔT calculated by the following (Equation 1) from the detection timing of the position detection signal. Even when the signal carrier frequency is low or the duty value is small, the rotor position detection error during the OFF period of the PWM signal including the delay time for ignoring the ringing voltage generated immediately after the PWM signal is turned on In addition to the effect of the invention according to claim 1, the brushless DC can be reduced when the load torque is increased during low-speed operation. It is possible to prevent the over data to stop stepping out.

The invention according to claim 3 uses the inverter control device according to claim 1 or 2, and can prevent step-out when the load torque increases during low-speed operation, and is highly reliable electric compression. Machine can be provided.

  Invention of Claim 4 uses the inverter control apparatus as described in any one of Claim 1 to 3, It can improve a step-out tolerance at the time of the load torque increase at the time of low speed driving | operation, A highly reliable household electric appliance such as a refrigerator can be provided.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. The present invention is not limited to the embodiments.

(Embodiment 1)
FIG. 1 is a block diagram of the inverter control apparatus according to the first embodiment of the present invention, FIG. 2 is a diagram showing signal waveforms and processing contents of each part in the first embodiment, and FIG. 3 shows the operation in the first embodiment. It is a flowchart to show.

  In FIG. 1, the inverter control device 200 is connected to a commercial AC power supply 201 and an electric compressor 220, and drives a rectifying unit 202 that converts the commercial AC power supply 201 into a DC power supply, and a brushless DC motor 203 of the electric compressor 220. An inverter circuit unit 204 is provided.

  Furthermore, a drive circuit 205 that drives the inverter circuit unit 204, a position detection circuit unit 206 that detects a terminal voltage of the brushless DC motor 203, and a microprocessor 207 that controls the inverter circuit unit 204 are provided.

  The microprocessor 207 includes a position detection determination unit 208 that detects a magnetic pole position of the brushless DC motor 203 with respect to an output signal from the position detection circuit unit 206, a commutation control unit 209 that generates a commutation signal, and a position detection determination unit 208. Rotational speed detection means 210 for calculating the rotational speed with respect to the output from the output, duty setting means 211 for performing PWM modulation on the commutation signal according to the rotational speed, carrier setting means 212, PWM control means 213, and commutation Drive control means 214 for driving the drive circuit 205 by the outputs of the control means 209 and the PWM control means 213 is provided.

  The brushless DC motor 203 includes a three-phase winding stator 203a and a rotor 203b.

  The stator 203a includes stator windings 203u, 203v, and 203w, and the rotor 203b has permanent magnets 203α, 203β, 203γ, 203δ, 203ε, and 203ζ arranged therein.

  The inverter circuit unit 204 is composed of six switching transistors Tru, Trx, Trv, Try, Trw, Trz connected in a three-phase bridge, and free-wheeling diodes Du, Dx, Dv, Dy, Dw, Dz connected in parallel with each other. It is configured.

  The position detection circuit unit 206 includes a comparator (not shown) and the like, and obtains a position detection signal by comparing a terminal voltage signal based on the induced voltage of the brushless DC motor 203 with a reference voltage using a comparator.

  The position detection determination unit 208 obtains the position detection signal of the rotor 203b from the output signal of the position detection circuit unit 206 and generates a position signal.

  The commutation control means 209 calculates the commutation timing based on the position signal of the position detection determination means 208, and generates commutation signals for the switching transistors Tru, Trx, Trv, Try, Trw, Trz.

  The rotation speed detection unit 210 calculates the rotation speed of the brushless DC motor 203 by counting the position signal from the position detection determination unit 208 for a certain period or measuring the pulse interval.

  The duty setting means 211 performs a duty addition / subtraction operation based on the deviation between the rotation speed obtained from the rotation speed detection means 210 and the command rotation speed, and outputs the duty value to the PWM control means 213. When the actual rotational speed is low with respect to the rotational speed command, the duty is increased. Conversely, when the actual rotational speed is high, the duty is decreased.

  The carrier output means 212 sets a carrier frequency for switching the switching transistors Tru, Trx, Trv, Try, Trw, Trz.

  The PWM control unit 213 outputs a PWM modulation signal from the duty value set by the duty setting unit 211 and the carrier frequency set by the carrier output unit 212.

  The drive control unit 214 synthesizes the commutation signal and the PWM modulation signal, generates a drive signal for turning on / off the switching transistors Tru, Trx, Trv, Try, Trw, and Trz, and outputs the drive signal to the drive circuit 205. The drive circuit 205 performs ON / OFF switching of the switching transistors Tru, Trx, Trv, Try, Trw, and Trz based on the drive signal to drive the brushless DC motor 203.

  Next, various waveforms of the inverter control device shown in FIG. 2 will be described.

  In FIG. 2, (A), (B), and (C) are the terminal voltages Vu, Vv, and Vw of the U-phase, V-phase, and W-phase of the brushless DC motor 203, and the phases are shifted by 120 degrees. It changes with the state.

  These terminal voltages Vu, Vv, and Vw are supplied from the inverter circuit unit 204 with the voltages Vua, Vva, and Vwa, the induced voltages Vub, Vvb, and Vwb generated in the stator windings 203u, 203v, and 203w, and the inverter when the commutation is switched. A combined waveform with pulse-like spike voltages Vuc, Vvc, Vwc generated when any of the free-wheeling diodes Du, Dx, Dv, Dy, Dw, Dz of the circuit unit 204 is turned on.

  Then, these terminal voltages Vu, Vv, Vw are compared with a voltage VN at a virtual neutral point that is ½ of the DC power supply voltage 1, and output signals PSu, PSv, PSw output from the comparator are (D). , (E), (F).

  The output signals PSu, PSv, PSw are PSua, PSva, PSwa corresponding to the supply voltages Vua, Vva, Vwa, PSuc, PSvc, PSwc corresponding to the spike voltages Vuc, Vvc, Vwc, and the induced voltages Vub, Vvb, This is a combined signal of Vsub and PSub, PSvb, PSwb corresponding to the period during comparison of the voltage VN of the virtual neutral point.

  Here, the pulse-like spike voltages Vuc, Vvc, and Vwc are equal to the waiting time (G) in the same manner as the first timer 122 and the second timer 123 that are wait timers in the conventional inverter control device described in Patent Document 1. Therefore, the output signals PSu, PSv, PSw of the comparator show the positive and negative values and the phase of the induced voltages Vub, Vvb, Vwb as a result.

  The microprocessor 207 recognizes the six modes A to F as shown in (H) based on the states of the output signals PSu, PSv, and PSw of the respective comparators, and according to the states of the output signals PSu, PSv, and PSw, ( As shown in (I) to (N), drive signals DSu, DSv, DSw, DSx, DSy, and DSz are output.

  That is, the elapsed time in each of the modes A to F shown in (H) indicates the occurrence interval of the state change of the position detection signal recognized by the microprocessor 207, that is, the position detection interval (O).

  Next, a detailed operation will be described with reference to a flowchart showing the operation of the position detection determination unit 208 in FIG.

  First, in step 101, the correction time is calculated as ½ of the total delay time from when the PWM signal is turned off and when the detection of the position detection signal is started after the PWM signal is turned on.

Here, the delay time will be described. In general, the induced voltage waveform on which the PWM signal is superimposed causes ringing immediately after the PWM signal is turned on. Therefore, the detected voltage waveform of the position detection circuit unit 206 has a voltage value equal to the induced voltages Vub, Vvb, and Vwb while causing vibration. Converge.

  For this reason, when the amplitude of the oscillating voltage due to ringing exceeds the voltage VN at the virtual neutral point, the output signals PSu, PSv, PSw of the comparator cause chattering, so that the position detection determination unit 208 cannot perform normal determination. Become.

  Therefore, the ringing voltage is neglected by providing a delay time from when the PWM signal is turned on until the position detection signal is determined.

  That is, when the delay time from when the PWM signal is turned on until the position detection signal determination is started is T, and when the off time immediately before the PWM signal is turned on is S, the correction time ΔT is expressed by the above equation (1). calculate.

  Next, in step 102, the state of the PWM signal is determined. When the PWM signal is OFF, the position detection determination unit 208 ends the operation as it is. On the other hand, if the PWM signal is on, the process proceeds to step 103.

  Step 103 determines whether the delay time has elapsed after the PWM signal is turned on. If it is less than the delay time, the position detection determination unit 208 ends the operation as it is. On the other hand, if the delay time has elapsed, the process proceeds to step 104.

  In step 104, the states of the output signals PSu, PSv, PSw from the position detection circuit unit 206 are detected, and the output states of the switching transistors Tru, Trx, Trv, Try, Trw, Trz, that is, the operation mode ( The detection detection of the position detection signal is performed according to the states of the output signals PSu, PSv, PSw corresponding to the state of H).

  As an example, when the operation mode (H) in FIG. 2 is A, rising of the U-phase terminal voltage Vu is detected by detecting PSu at H level, PSv at L level, and PSw at H level. Similarly, also in other operation mode states, by detecting the states of PSu, PSv, and PSw, rising detection or falling detection of each terminal voltage Vu, Vv, Vw with respect to the virtual neutral point voltage VN is performed.

  Here, the rising detection or falling detection of each terminal voltage Vu, Vv, Vw occurs six times during one period of the terminal voltage Vu, Vv, Vw, and therefore the electric voltage is measured by measuring the detection interval of the position detection signal. An elapsed time corresponding to 60 degrees in angle can be obtained.

  When the position detection signal is not detected, the position detection determination unit 208 ends the operation as it is. On the other hand, if a position detection signal is detected, the process proceeds to step 105.

  Subsequently, in step 105, it is determined whether or not the detection time point of the position detection signal coincides with the delay time.

  When the position detection signal detection time coincides with the delay time, that is, when the position detection signal is detected simultaneously with the end of the delay time, either the PWM signal OFF time or the delay time after the PWM signal is turned ON During this period, it is determined that the position detection signal has already been generated, and the routine proceeds to step 106.

In step 106, a value obtained by subtracting the correction value from the timer value counting the detection interval of the position detection signal and adding a history value to be described later is calculated as the position detection interval. Thereafter, in step 107, the correction value reduced in the previous step is updated as a history value.

  On the other hand, if the detection time of the position detection signal does not coincide with the delay time at step 105, that is, if the position detection signal is detected after the end of the delay time, it is determined that the position detection signal is generated during the on time of the PWM signal. Then go to step 108.

  In step 108, a value obtained by adding a later-described history value to a timer value counting the detection interval of the position detection signal is calculated as the position detection interval. Thereafter, in step 109, the history value is cleared.

  After step 107 or 109, the count operation is started after the timer for counting the detection interval of the position detection signal is cleared in step 110, and the position detection determination means ends the operation.

  The position detection determination unit 208 repeatedly executes the above-described operation.

  Therefore, the position detection interval corrected by the position detection determination unit 208 with respect to the timer value measured when the position detection signal is detected, that is, the actual elapsed time from the time when the previous position detection signal was detected. Is shortened by the amount obtained by subtracting the aforementioned correction value. That is, it is recognized that the position detection signal has been detected by looking back in time from the time when the actual position detection signal is detected.

  By the way, when the correction value is subtracted from the timer value, the timer value measured at the time of the next generation of the position detection signal is insufficient in the count value by the reduced correction value. For this reason, the correction value of this time is stored as a history value, and when calculating the position detection interval at the detection time of the next position detection signal, the correction is performed by adding the history value to the measured timer value. Do. That is, the correction value subtracted from the timer value in the detection detection of the position detection signal is always stored as a history value, and the position value is determined by adding the previous history value to the newly measured timer value. Calculate the detection interval.

  Based on the detection information of the position detection signal from the position detection determination unit 208 obtained as described above, the commutation control unit 209 calculates the commutation timing, and the switching transistors Tru, Trx, Trv, Try, Trw. , Trz commutation signals are generated. That is, the commutation control means 209 sets the commutation time from position detection to commutation based on the corrected position detection interval.

  As an example, when the conduction angle is 120 degrees and the advance angle is 0 degrees, the commutation time corresponding to the electrical angle of 30 degrees is calculated with respect to the electrical angle of 60 degrees obtained by the corrected position detection interval. The detection point of the position detection signal, which is the base point for timing setting, is set retroactively by the amount obtained by subtracting the correction value from the detection point of the actual position detection signal. A commutation signal is output when the timer value has passed the commutation time.

  Therefore, even when the carrier frequency of the PWM signal of the inverter output voltage is low or the duty value is small, the error in detecting the position of the rotor 203b and the commutation delay during the OFF period of the PWM signal can be reduced. It is possible to prevent the brushless DC motor from stepping out when the load torque during operation is increased.

Moreover, even if the inverter control device 200 is used for the electric compressor 220, good operation is possible, and even when the inverter control device 200 is used for household electric appliances such as a refrigerator, good system operation is possible. .

  As described above, the inverter control device according to the present invention can reduce the error in detecting the position of the rotor while the PWM signal is off, and can be operated satisfactorily. It is useful for household electric appliances and electric vehicles.

200 Inverter control unit 203 Brushless DC motor 203b Rotor 203α, 203β, 203γ, 203δ, 203ε, 203ζ Permanent magnet 204 Inverter circuit unit 206 Position detection circuit unit 208 Position detection determination unit 209 Commutation control unit 213 PWM control unit

Claims (4)

An inverter circuit unit for driving a brushless DC motor having a permanent magnet provided on the rotor, a position detection circuit unit for detecting an induced voltage of the brushless DC motor, and PWM control for varying the rotation speed of the brushless DC motor Based on the PWM control means for generating the PWM signal and the induced voltage detected by the position detection circuit unit, the relative position of the magnetic pole center by the permanent magnet of the rotor is determined with respect to the stator winding of the brushless DC motor. And a commutation control means for generating a commutation signal based on the position signal from the position detection determination means, and the position detection circuit section outputs the PWM signal during the ON period of the PWM signal. An inverter that estimates the magnetic pole position of the rotor during the OFF period of the PWM signal based on the position detection signal. Motor controller. When the delay time from when the PWM signal is turned on until the position detection determination means starts determining the position detection signal is T, and when the OFF time immediately before the PWM signal is turned on is S, the rotor position detection is The inverter control device according to claim 1, wherein the inverter control device estimates that the correction timing ΔT calculated by the following (Equation 1) is subtracted from the detection timing of the position detection signal.
An electric compressor using the inverter control device according to claim 1. Home electric appliances, such as a refrigerator, using the inverter control device according to any one of claims 1 to 3.