JP2006014388A - Inverter control device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent control performance from deteriorating, by correcting error in the offset voltage of a current sensor caused by temperature drift, or the like. <P>SOLUTION: The inverter controller comprises an inverter 2; means 4a and 4b for detecting a current flowing through a load motor 3; a means 12 for detecting the zero-cross point of current, a driving stop means 13 for turning the switching elements 5a-5f of the inverter 2 off for a predetermined time, such that the current level of the load motor 3 becomes zero; an offset voltage detecting means 14 for storing/updating the voltage level being outputted from the current detecting means 4a and 4b during a period, when the current level of the load motor 3 becomes zero; and an actual current operating means 15 for operating the current level of the load motor, 3 based on the voltage level being outputted from the current detecting means 4a and 4b and the voltage level being stored by the offset voltage detecting means 14, wherein the driving stop means 13 stops the switching elements 5a-5f at the zero-cross point of current for a predetermined time, when the switching speed of the inverter 2 is not lower than a predetermined level. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an inverter control device for controlling the operation of a motor, and more particularly to an inverter control device using a current detector and an air conditioner using the inverter control device.

  FIG. 9 shows an example of a conventional inverter control device. In FIG. 9, the control unit 110 controls the motor 103 winding current value detected by the current sensors 104a and 104b as a parameter in order to control the motor 103 to a predetermined speed based on the external speed command signal. A signal for driving the inverter 102 as a data is generated and output. In response to this drive signal, the inverter driving unit 111 drives each switching element of the inverter 102.

  The current sensors 104a and 104b generally convert the detected current value into a voltage value and output it. Here, the sensor output voltage when the amount of current is zero is referred to as an offset voltage, and a value obtained by subtracting the offset voltage from the detected sensor output voltage is a detected current value.

  By the way, an error occurs in the offset voltage of the current sensors 104a and 104b due to temperature drift due to initial variations of products, changes in ambient temperature, and the like. This gives an error to the current value to be detected, causes distortion of the current waveform of the motor 103, lowers the efficiency or steps out, and lowers the control performance.

  As a method for correcting the error of the offset voltage of the current sensor, there is a method as shown in Patent Document 1. This is to detect the offset voltage of the current sensors 104a and 104b every time the motor 103 is stopped, and to sequentially correct the offset voltage with the updated offset voltage. Thereby, it is possible to correct an error of the offset voltage due to the initial variation of the product. Further, it is possible to correct an error in the offset voltage due to a temperature drift during operation after the operation of the motor 103 is stopped.

  Furthermore, as a method for correcting an error in the offset voltage of the current sensors 104a and 104b, there is a method as shown in Patent Document 2. In this method, the offset voltage is calculated by integrating one period of the output voltage of the current sensors 104a and 104b, and the error of the offset voltage is corrected using the calculated value.

  Further, the first time when the detected current value of the output voltage of the current sensors 104a and 104b in one cycle is positive and the second time when it is negative are measured, and the ratio between the first time and the second time is measured. Based on this, an offset voltage is calculated. The calculated value is used to correct the offset voltage error.

As a result, it is possible to correct the offset voltage error due to the initial variation of the product, and it is possible to correct the offset voltage error caused by the temperature drift or the like while the motor 103 is in the operating state.
JP 7-271445 A JP-A-5-252728

For example, an inverter control device for driving a compressor motor in an air conditioner is provided in an outdoor unit, and this outdoor unit is installed outdoors. Therefore, the temperature environment of the current sensor in the inverter control device varies greatly depending on the change in the outside air temperature and the operating state of the motor.

  However, in the conventional inverter control device disclosed in Patent Document 1, the offset voltage of the current sensors 104a and 104b can be detected while the motor 103 is stopped or after the operation is stopped, and the error can be corrected. The offset voltage that fluctuates due to changes in the outside air temperature or temperature drift during the compressor motor operation cannot be corrected.

  As a result, an error occurs in the detected current value, and the control performance of the inverter control device is deteriorated.

  However, in the inverter control device shown in Patent Document 2, when the motor winding current waveform has a smooth sine wave shape, due to changes in the outside air temperature during operation of the compressor motor, temperature drift, etc. Although it is possible to calculate the offset voltage that fluctuates and correct the error, it is not possible to calculate an accurate offset voltage with the current waveform on which the switching frequency component of the inverter is superimposed. The offset voltage that fluctuates due to changes in outside air temperature, temperature drift, etc. cannot be corrected.

In this case as well, there is a problem that an error occurs in the detected current value and the control performance of the inverter control device is deteriorated.
The present invention solves such a conventional problem, and even if the current waveform is superimposed with the switching frequency of the inverter, the offset voltage due to the change in the outside air temperature or the temperature drift during the operation of the motor. It is an object of the present invention to provide an inverter control device that can detect a fluctuation and correct an error thereof, and does not deteriorate control performance.

  In order to solve the above-described problems, an inverter control device according to the present invention includes an inverter configured of a plurality of switching elements, which converts direct current into alternating current and supplies the alternating current to a load motor. The switching speed for turning on / off multiple switching elements is changed, and the pulse duty output according to the load driven by the load motor is changed to detect the current value flowing through the load motor and convert it to a voltage value. Output current detection means, zero cross detection means for detecting zero cross points of a plurality of phases of current flowing through the load motor, and at least one of the switching elements of the inverter so that the value of current flowing through the load motor is zero. Driving stop means for turning off the inverter for a predetermined time, and the drive stopping means turns off the switching element of the inverter. Thus, the offset voltage detection means for storing and updating the voltage value output by the current detection means during the period when the current value flowing through the load motor becomes zero, and the voltage value output by the current detection means and the offset voltage detection means are stored. An actual current calculating means for calculating a current value flowing through the load motor from the voltage value, and the drive stopping means switches the inverter at the zero cross point of the current detected by the zero cross detecting means when the inverter switching speed is equal to or higher than a predetermined value. The element is stopped for a predetermined time.

  The inverter device of the present invention can correct the fluctuation of the offset voltage of the current detecting means while operating the inverter.

  The first invention includes an inverter, current detection means, zero cross detection means, drive stop means, offset voltage detection means, and actual current calculation means, and the drive stop means has a predetermined inverter switching speed. When the value is equal to or greater than the value, the switching element of the inverter is stopped for a predetermined time at the zero cross point of the current detected by the zero cross detecting means.

  As a result, even when the inverter switching frequency component is superimposed on the current waveform of the load, the fluctuation error of the offset voltage of the current detection means due to temperature drift during operation can be reliably corrected. it can. In particular, when the switching speed of the inverter is below a predetermined value, the offset voltage of the current sensor is not detected, so that the operation of the motor can be stabilized, and the inverter control apparatus with low vibration and low noise and high reliability. Can be realized.

  In the second invention, particularly in the first invention, when the inverter is changing the switching speed, the drive stopping means stops the switching element of the inverter for a predetermined time at the zero cross point of the current detected by the zero cross detecting means. I don't do it.

  Thus, even when the inverter switching frequency component is superimposed on the current waveform of the load, the fluctuation error of the offset voltage of the current detecting means due to temperature drift during operation can be reliably corrected. . In particular, since the offset voltage of the current sensor is not detected while the switching speed of the inverter is being changed, the motor operation can be stabilized, and a low-vibration, low-noise and reliable inverter control device can be realized. it can.

  In a third aspect of the invention, particularly in the first aspect of the invention, the drive stop means stops the switching element of the inverter for a predetermined time at the zero cross point of the current detected by the zero cross detection means when the pulse duty output by the inverter is not more than a predetermined value. Is.

  As a result, even when the inverter switching frequency component is superimposed on the current waveform of the load, the fluctuation error of the offset voltage of the current detection means due to temperature drift during operation can be reliably corrected. it can. In particular, when the output pulse duty of the inverter is greater than or equal to a predetermined value, the offset voltage of the current sensor is not detected, so the motor operation can be stabilized, and the inverter control is reliable with low vibration and low noise. An apparatus can be realized.

  In the fourth invention, particularly in the first invention, when the drive stop means is changing the pulse duty output by the inverter, the switching element of the inverter is stopped for a predetermined time at the zero cross point of the current detected by the zero cross detection means. The operation is not performed.

  As a result, even when the inverter switching frequency component is superimposed on the current waveform of the load, the fluctuation error of the offset voltage of the current detection means due to temperature drift during operation can be reliably corrected. it can. In particular, since the offset voltage of the current sensor is not detected while changing the output pulse duty of the inverter, the motor operation can be stabilized, and a low-vibration, low-noise and highly reliable inverter control device is realized. be able to.

  According to a fifth aspect of the invention, the inverter control device according to any one of the first to fourth aspects is used in an air conditioner. As a result, an air conditioner having high control performance and reliability, low vibration and low noise can be realized without increasing the size of the apparatus and increasing the cost.

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

(Embodiment 1)
FIG. 1 is a control block diagram showing an embodiment of an inverter control apparatus according to the present invention. In FIG. 1, reference numeral 1 denotes a DC power source, 2 denotes an inverter which is composed of a plurality of switching elements and outputs a variable voltage / variable frequency AC voltage from the DC power source 1, and 3 is a motor whose speed is controlled by the inverter 2. For example, a brushless DC motor, an induction motor, a reluctance motor, or the like is used.

  Further, 4a and 4b are current sensors for detecting current values flowing in the respective phase windings of the motor 3. Here, current values Iv and Iw provided in the V phase and the W phase are detected. The U-phase current value Iu is calculated from Iu = −Iv−Iw (Equation 1).

  Reference numeral 12 denotes a zero-cross detection unit that detects a zero-cross point of a current waveform flowing in each phase of the motor 3. In this embodiment, the zero-cross detection unit 12 detects a current value calculated by an actual current calculation unit 15 described later.

  Further, 13 is a drive stop unit for stopping the drive signal of the inverter 2 for a predetermined time so that the current value flowing in each phase of the motor 3 becomes zero at the zero cross point of the current waveform detected by the zero cross detection unit 12. It is. Here, reference numeral 20 denotes a stop interval measuring unit which determines a time interval at which the drive stop unit 13 stops the drive signal of the inverter 2. 14 is an offset voltage detection unit that stores and updates the output voltage of the current sensors 4a and 4b as an offset voltage during a period when the drive stop unit 13 stops the drive signal of the inverter 2 and the current value becomes zero. This is an actual current calculation unit that calculates an actual current value from the output voltages of the current sensors 4 a and 4 b during operation of the motor 3 and the offset voltage stored in the offset voltage detection unit 14.

  Reference numeral 10 denotes a control unit which includes a command current calculation unit 16, a current error calculation unit 17, and a drive signal creation unit 18. Reference numeral 11 denotes an inverter drive unit that receives the inverter drive signal output from the control unit 10 and drives the inverter 2.

  Based on the external speed command, the command current calculation unit 16 calculates a command current value for controlling the motor 3 to a predetermined speed. An error between the command current value calculated by the command current calculation unit 15 and the actual current value calculated by the actual current calculation unit 15 is obtained by the current error calculation unit 17, and the drive signal creation unit 18 uses this error value. A drive signal to be output to the inverter 2 is created and output. The inverter drive unit 11 performs switching of the inverter 2 based on this drive signal to control the speed of the motor 3.

  Here, the current sensors 4a and 4b convert the detected current value into a corresponding voltage value and output it. In particular, an output voltage value when the current is zero is referred to as an offset voltage, and a value obtained by subtracting the offset voltage from the detection voltage is a current value.

  The offset voltages of the current sensors 4a and 4b usually have characteristics that vary due to initial variations of products, temperature drifts during operation of the motor 3, and the like. As a result, an error occurs in the current value detected by the current sensors 4a and 4b, and control using this value causes a decrease in control performance.

  Hereinafter, a method for correcting the offset voltage error of the current sensor 4a in the inverter control apparatus of the present invention will be described in detail with reference to FIGS.

  The current sensor 4a is provided in the V phase of the motor 3, and detects a current value Iv flowing in the V phase. In the steady operation state of the motor 3, the zero cross detector 12 detects the zero cross point of the V-phase current waveform from the actual current calculator 15. At this time, if the measured value at the stop interval measuring unit 20 is equal to or greater than a predetermined value, the drive stopping unit 13 is connected to the V-phase winding of the motor 3 via the drive signal generating unit 18 as shown in FIG. The switching elements 5b and 5e of the inverter 2 are stopped for a predetermined time.

  As a result, as shown in FIG. 3, the value of the current flowing in the V phase does not increase and maintains a zero state. The offset voltage detector 14 detects, updates, and stores the output voltage value of the current sensor 4a during this period as an offset voltage.

  Here, current sensors 4a and 4b using Hall elements generally have magnetic characteristics as shown in FIG. That is, when the current flowing through the motor 3 changes from positive to negative, even if the current value flowing through the motor 3 is zero, the holding voltage has the first offset voltage (Voff1). Further, when the current flowing through the motor 3 changes from negative to positive, the second offset voltage (Voff2) is held as the holding voltage even if the value of the current flowing through the motor 3 is zero.

  Therefore, if the true offset voltage (Voff) of the current sensors 4a and 4b is to be detected accurately, the first offset voltage (Voff1) and the second offset voltage (Voff2) are detected and Voff = (Voff1 + Voff2) / 2 ... It is necessary to calculate from (Expression 2).

  Therefore, as shown in FIG. 5, the zero-cross detection unit 12 detects the zero-cross point from negative to positive and the zero-cross point from positive to negative of the V-phase current waveform from the actual current calculation unit 15. At this time, if the measurement value in the stop interval measurement unit 20 is equal to or greater than a predetermined value, the drive stop unit 13 stops the switching elements 5b and 5e of the inverter 2 through the drive signal generation unit 18 for a predetermined time.

  As a result, voltage values corresponding to the first and second offset voltages in FIG. 4 can be detected, so that the true offset voltages of the current sensors 4a and 4b can be detected according to (Equation 2).

  Then, the actual current calculation unit 15 calculates the actual current value using the detected offset voltage value and the voltage value obtained from the current sensor 4a.

  The offset voltage used for this calculation is a value that always includes fluctuations due to temperature drift during operation of the motor 3 and errors due to the magnetic characteristics of the current sensors 4a and 4b. Therefore, the actual current value obtained by the actual current calculation unit 15 can be obtained as a true value without being affected by the fluctuation error of the offset voltage.

  The current sensor 4b is provided in the W phase of the motor 3, and detects a current value Iw flowing in the W phase. The correction method of the offset voltage of the current sensor 4b can be performed in the same manner as in the case of the current sensor 4a.

  Here, the inverter 2 changes the switching speed according to the speed of the motor 3 as shown in FIG. When the switching speed is low, the number of pulses in FIG. 3 is small and the influence of one pulse is large, and the loss of one pulse leads to an increase in noise and vibration. Therefore, it is not preferable to stop the switching of the inverter 2 in order to detect the offset voltage of the current sensors 4a and 4b at this time. Therefore, in the present embodiment, when the inverter 2 has a switching speed equal to or lower than a predetermined value, the offset voltage of the current sensors 4a and 4b is not detected, and only when the switching speed of the inverter 2 is equal to or higher than the predetermined value. The offset voltage of 4b is detected.

  Thereafter, the method of creating a drive signal for the inverter 2 using this actual current value and the command current calculated by the command current calculation unit 16 to control the motor 3 is as described above.

With the above operation, according to the inverter control apparatus of the present embodiment, even when the switching frequency component of the inverter 2 is superimposed on the current waveform of the motor 3, the temperature during operation is Since the fluctuation error of the offset voltage of the current sensors 4a and 4b due to drift or the like can be reliably corrected, a highly reliable inverter control device can be realized without deteriorating the control performance.

  Furthermore, in the inverter control apparatus of the present embodiment, offset voltage detection is performed at the zero cross point of the current waveform of the motor 3, so that distortion of the current waveform can be minimized.

  Moreover, when the switching speed of the inverter 2 is equal to or lower than a predetermined value, the switching is not stopped by detecting the offset voltage, so that the distortion of the current waveform can be further suppressed, and an inverter control device with extremely little noise and vibration is realized. Can do.

  In addition, since the control method of the present embodiment can be performed entirely by software by using a microcomputer or the like in the control unit 10 without requiring addition of a new circuit or the like, the number of parts can be increased and the size of the apparatus can be increased. Can realize cost prevention.

(Embodiment 2)
A method of correcting the offset voltage error of the current sensors 4a and 4b according to the present embodiment will be described in detail with reference to FIGS. In addition, since description about the code | symbol in a figure is the same as Embodiment 1, it abbreviate | omits.

  The operation of the motor 3 is started by the inverter 2. The current sensor 4a is provided in the V phase of the motor 3, and detects a current value Iv flowing in the V phase.

  In the operation state of the motor 3, as shown in FIG. 5, the zero cross detection unit 12 detects the zero cross point from negative to positive and the zero cross point from positive to negative of the V-phase current waveform from the actual current calculation unit 15. At this time, if the measurement value in the stop interval measurement unit 20 is equal to or greater than a predetermined value, the drive stop unit 13 stops the switching elements 5b and 5e of the inverter 2 through the drive signal generation unit 18 for a predetermined time.

  As a result, voltage values corresponding to the first and second offset voltages in FIG. 4 can be detected, so that the true offset voltages of the current sensors 4a and 4b can be detected according to (Equation 2).

  Then, the actual current calculation unit 15 calculates the actual current value using the detected offset voltage value and the voltage value obtained from the current sensor 4a. The offset voltage used for this calculation is a value that always includes fluctuations due to temperature drift during operation of the motor 3 and errors due to the magnetic characteristics of the current sensors 4a and 4b. Therefore, the actual current value obtained by the actual current calculation unit 15 can be obtained as a true value without being affected by the fluctuation error of the offset voltage.

  The current sensor 4b is provided in the W phase of the motor 3 and detects the current value Iw flowing in the W phase. The correction method of the offset voltage of the current sensor 4b can be performed in the same manner as in the case of the current sensor 4a.

  Here, the inverter 2 changes the switching speed according to the speed of the motor 3 as shown in FIG. During the switching speed change, the behavior of the motor 3 such as sound and vibration becomes unstable as compared with the steady state. At this time, it is preferable to stop the switching of the inverter 2 in order to detect the offset voltage of the current sensors 4a and 4b. Absent. Therefore, in this embodiment, when the inverter 2 is changing the switching speed, the detection of the offset voltage of the current sensors 4a and 4b is not performed.

Thereafter, using this actual current value and the command current calculated by the command current calculation unit 16, the inverter 2 is used.
The method for generating the driving signal and controlling the motor 3 is as described above.

  With the above operation, according to the inverter control apparatus of the present embodiment, even when the switching frequency component of the inverter 2 is superimposed on the current waveform of the motor 3, the temperature during operation is Since the fluctuation error of the offset voltage of the current sensors 4a and 4b due to drift or the like can be reliably corrected, a highly reliable inverter control device can be realized without deteriorating the control performance.

  Furthermore, in the inverter control apparatus of the present embodiment, offset voltage detection is performed at the zero cross point of the current waveform of the motor 3, so that distortion of the current waveform can be minimized.

  Moreover, when the switching speed of the inverter 2 is being changed, the switching of the inverter 2 is not stopped by detecting the offset voltage, so that the distortion of the current waveform can be further suppressed, and the inverter control apparatus with extremely low noise and vibration and stable operation. Can be realized.

  In addition, since the control method of the present embodiment can be performed entirely by software by using a microcomputer or the like in the control unit 10 without requiring addition of a new circuit or the like, the number of parts can be increased and the size of the apparatus can be increased. Can realize cost prevention.

(Embodiment 3)
A method of correcting the offset voltage error of the current sensors 4a and 4b according to the present embodiment will be described in detail with reference to FIGS. In addition, since description about the code | symbol in a figure is the same as Embodiment 1, it abbreviate | omits.

  The operation of the motor 3 is started by the inverter 2. The current sensor 4a is provided in the V phase of the motor 3, and detects a current value Iv flowing in the V phase.

  In the operation state of the motor 3, as shown in FIG. 5, the zero cross detection unit 12 detects the zero cross point from negative to positive and the zero cross point from positive to negative of the V-phase current waveform from the actual current calculation unit 15. At this time, if the measurement value in the stop interval measurement unit 20 is equal to or greater than a predetermined value, the drive stop unit 13 stops the switching elements 5b and 5e of the inverter 2 through the drive signal generation unit 18 for a predetermined time.

  As a result, voltage values corresponding to the first and second offset voltages in FIG. 4 can be detected, so that the true offset voltages of the current sensors 4a and 4b can be detected according to (Equation 2).

  Then, the actual current calculation unit 15 calculates the actual current value using the detected offset voltage value and the voltage value obtained from the current sensor 4a. The offset voltage used for this calculation is a value that always includes fluctuations due to temperature drift during operation of the motor 3 and errors due to the magnetic characteristics of the current sensors 4a and 4b. Therefore, the actual current value obtained by the actual current calculation unit 15 can be obtained as a true value without being affected by the fluctuation error of the offset voltage.

  The current sensor 4b is provided in the W phase of the motor 3 and detects the current value Iw flowing in the W phase. The correction method of the offset voltage of the current sensor 4b can be performed in the same manner as in the case of the current sensor 4a.

Here, the inverter 2 changes the pulse duty to be output according to the load of the motor 3 as shown in FIG. When the pulse duty is large, the influence of one pulse becomes large, and the loss of this pulse leads to an increase in noise and vibration. Therefore, it is not preferable to stop the switching of the inverter 2 in order to detect the offset voltage of the current sensors 4a and 4b at this time. Therefore, in the present embodiment, when the pulse duty output from inverter 2 is greater than or equal to a predetermined value, the offset voltage of current sensors 4a and 4b is not detected, and the pulse duty output from inverter 2 is less than or equal to the predetermined value. Only the offset voltage of the current sensors 4a and 4b is detected.

  Thereafter, the method of creating a drive signal for the inverter 2 using this actual current value and the command current calculated by the command current calculation unit 16 to control the motor 3 is as described above.

  With the above operation, according to the inverter control apparatus of the present embodiment, even when the switching frequency component of the inverter 2 is superimposed on the current waveform of the motor 3, the temperature during operation is Since the fluctuation error of the offset voltage of the current sensors 4a and 4b due to drift or the like can be reliably corrected, a highly reliable inverter control device can be realized without deteriorating the control performance.

  Furthermore, in the inverter control apparatus of the present embodiment, offset voltage detection is performed at the zero cross point of the current waveform of the motor 3, so that distortion of the current waveform can be minimized.

  In addition, when the pulse duty output by the inverter 2 is greater than or equal to a predetermined value, the switching is not stopped by detecting the offset voltage, so that the distortion of the current waveform can be further suppressed, and the operation is extremely stable with little noise and vibration. A control device can be realized.

  In addition, since the control method of the present embodiment can be performed entirely by software by using a microcomputer or the like in the control unit 10 without requiring addition of a new circuit or the like, the number of parts can be increased and the size of the apparatus can be increased. Can realize cost prevention.

(Embodiment 4)
A method for correcting the offset voltage error of the current sensors 4a and 4b according to the present embodiment will be described in detail with reference to FIGS. The description of the reference numerals in the figure is the same as that of the first embodiment, and will be omitted.

  The operation of the motor 3 is started by the inverter 2. The current sensor 4a is provided in the V phase of the motor 3, and detects a current value Iv flowing in the V phase.

  In the operation state of the motor 3, as shown in FIG. 5, the zero cross detection unit 12 detects the zero cross point from negative to positive and the zero cross point from positive to negative of the V-phase current waveform from the actual current calculation unit 15. At this time, if the measurement value in the stop interval measurement unit 20 is equal to or greater than a predetermined value, the drive stop unit 13 stops the switching elements 5b and 5e of the inverter 2 through the drive signal generation unit 18 for a predetermined time.

  As a result, voltage values corresponding to the first and second offset voltages in FIG. 4 can be detected, so that the true offset voltages of the current sensors 4a and 4b can be detected according to (Equation 2).

  Then, the actual current calculation unit 15 calculates the actual current value using the detected offset voltage value and the voltage value obtained from the current sensor 4a. The offset voltage used for this calculation is a value that always includes fluctuations due to temperature drift during operation of the motor 3 and errors due to the magnetic characteristics of the current sensors 4a and 4b. Therefore, the actual current value obtained by the actual current calculation unit 15 can be obtained as a true value without being affected by the fluctuation error of the offset voltage.

The current sensor 4b is provided in the W phase of the motor 3 and detects the current value Iw flowing in the W phase. The correction method of the offset voltage of the current sensor 4b can be performed in the same manner as in the case of the current sensor 4a.

  Here, the inverter 2 changes the pulse duty to be output according to the load of the motor 3 as shown in FIG. Since the behavior of the motor 3 such as sound and vibration becomes unstable when the inverter 2 is changing the pulse duty speed, the switching of the inverter 2 is performed at this time in order to detect the offset voltage of the current sensors 4a and 4b. It is not preferable to stop it. Therefore, in the present embodiment, when the pulse duty output from the inverter 2 is being changed, the offset voltage of the current sensors 4a and 4b is not detected.

  Thereafter, the method of creating a drive signal for the inverter 2 using this actual current value and the command current calculated by the command current calculation unit 16 to control the motor 3 is as described above.

  With the above operation, according to the inverter control apparatus of the present embodiment, even when the switching frequency component of the inverter 2 is superimposed on the current waveform of the motor 3, the temperature during operation is Since the fluctuation error of the offset voltage of the current sensors 4a and 4b due to drift or the like can be reliably corrected, a highly reliable inverter control device can be realized without deteriorating the control performance.

  Furthermore, in the inverter control apparatus of the present embodiment, offset voltage detection is performed at the zero cross point of the current waveform of the motor 3, so that distortion of the current waveform can be minimized.

  In addition, when the pulse duty output by the inverter 2 is greater than or equal to a predetermined value, the switching is not stopped by detecting the offset voltage, so that the distortion of the current waveform can be further suppressed, and the operation is extremely stable with little noise and vibration. A control device can be realized.

  In addition, since the control method of the present embodiment can be performed entirely by software by using a microcomputer or the like in the control unit 10 without requiring addition of a new circuit or the like, the number of parts can be increased and the size of the apparatus can be increased. Can realize cost prevention.

(Embodiment 5)
FIG. 8 shows an example of the configuration of an air conditioner to which one of the inverter control devices of the present invention is applied. 8, the same components as those in FIG. 1 are denoted by the same reference numerals, and detailed description thereof is omitted. Hereinafter, the air conditioner of the present invention will be described with reference to FIG.

  As shown in FIG. 8, the air conditioner uses the motor control device of the invention shown in the first embodiment as a compressor drive device, and in addition to the inverter device 81 and the electric compressor 82, the indoor unit 92, A refrigeration cycle comprising an outdoor unit 95 and a four-way valve 91 is provided.

  The indoor unit 92 includes an indoor heat exchanger 93 and an indoor fan 94, and the outdoor unit 95 includes an outdoor heat exchanger 96, an outdoor fan 97, and an expansion valve 98.

  During the refrigeration cycle, a refrigerant that is a heat medium circulates. The refrigerant is compressed by the electric compressor 82, and heat is exchanged with the outdoor air by blowing from the outdoor blower 97 in the outdoor heat exchanger 96, and indoor air is blown from the indoor blower 94 in the indoor heat exchanger 93. And heat exchange. Indoor air conditioning is performed by the air after heat exchange in the indoor heat exchanger 93. Switching between cooling and heating is performed by reversing the direction of refrigerant circulation by a four-way valve 91.

  The circulation of the refrigerant in the refrigeration cycle as described above is performed by driving the electric compressor 82 by the inverter device 81, and the control method of the inverter device 81 and the electric compressor 82 is the inverter of the first embodiment. It is performed using a data control device. Since the configuration and operation of the inverter control device are as described above, description thereof is omitted.

  With the above configuration, it is possible to suppress a decrease in control performance such as a decrease in efficiency in the air conditioner.

  In this embodiment, the air conditioner using the inverter control device of the invention shown in the first embodiment as the compressor driving device has been described. However, the inverter of the other invention as shown in the second or fourth embodiment is used. -Even if it uses an inverter control apparatus, the air conditioner which had the effect which the inverter control apparatus of each invention has similarly can be provided.

  Therefore, the effect of the inverter control device of the present invention can be maximized by using it particularly for an air conditioner having a severe operating temperature environment.

  In addition, since the offset voltage correction control described above can be realized by software, it can be incorporated in the control unit 10 and has a very great effect that it can be performed without adding components or increasing costs.

  In the first to fifth embodiments of the present invention, the constituent elements included in the control unit 10 are not limited to the combinations shown in the above-described embodiments, and other constituent elements 11 to 15 in FIGS. One part or all may be included.

  In the first to fourth embodiments, the initial variation of the offset voltage of the current sensors 4a and 4b can be corrected by detecting the sensor output voltage in advance as the offset voltage before starting the motor 3. .

  Furthermore, in the first to fourth embodiments, the offset voltage is detected from the average of the voltage at the point where the current waveform changes from negative to positive and the point voltage where the current waveform changes from positive to negative. You may obtain | require only from the voltage of the point from which it becomes only from the voltage of a certain point, or from positive to negative.

  The inverter control device of the present invention can be applied to applications such as a refrigerator and a freezer using a motor driven by an inverter because it can correct the offset error of the current sensor and suppress distortion of the current waveform.

1 is a control block diagram showing an embodiment of an inverter control device according to the present invention. The inverter circuit block diagram in one Embodiment of the inverter control apparatus of this invention The figure which shows the offset voltage detection in one Embodiment of the inverter control apparatus of this invention FIG. 6 is a characteristic diagram of a current sensor in an embodiment of an inverter control device of the present invention. The figure which shows the offset voltage detection in one Embodiment of the inverter control apparatus of this invention The figure which shows the switching speed with respect to the motor speed in other embodiment of the inverter control apparatus of this invention. The figure which shows the pulse duty with respect to the motor speed in other embodiment of the inverter control apparatus of this invention. The block diagram of the structure which shows one embodiment of the air conditioner of this invention Control block diagram in a conventional inverter control device

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 DC power supply 2 Inverter 3 Motor 4a, 4b Current sensor 5a, 5b, 5c, 5d, 5e, 5f Switching element 10 Control part 11 Inverter drive part 12 Zero cross detection part 13 Drive stop part 14 Offset voltage detection Section 15 Actual current calculation section 16 Command current calculation section 17 Current error calculation section 18 Drive signal creation section 20 Stop interval measurement section 81 Inverter device 82 Electric compressor 91 Four-way valve 92 Indoor unit 93 Indoor heat exchanger 94 Indoor blower 95 Outdoor unit 96 Outdoor heat exchanger 97 Outdoor blower 98 Expansion valve

Claims (5)

An inverter composed of a plurality of switching elements, which converts DC to AC and supplies the load motor to the load motor, and the inverter changes a switching speed for turning on / off the plurality of switching elements according to the speed of the load motor. And a current detection means for changing a pulse duty to be output in accordance with a load driven by the load motor, detecting a current value flowing through the load motor, converting it to a voltage value, and outputting the voltage value to the load motor. Zero-cross detection means for detecting zero-cross points of flowing currents of a plurality of phases, and drive stop means for turning off at least one of the switching elements of the inverter for a predetermined time so that the current value flowing through the load motor becomes zero And when the drive stop means turns off the switching element of the inverter, Offset voltage detection means for storing and updating the voltage value output by the current detection means during the period when the current value flowing through the data becomes zero, and the voltage value output by the current detection means and the offset voltage detection means An actual current calculation means for calculating a current value flowing through the load motor from a voltage value, and the drive stop means detects the zero cross point of the current detected by the zero cross detection means when the switching speed of the inverter is equal to or higher than a predetermined value. In the inverter control device, the switching element of the inverter is stopped for a predetermined time. The drive stop means does not perform an operation of stopping the switching element of the inverter for a predetermined time at the zero cross point of the current detected by the zero cross detection means when the inverter is changing the switching speed. The inverter control device described. The drive stop means stops the switching element of the inverter for a predetermined time at the zero cross point of the current detected by the zero cross detection means when the pulse duty output by the inverter is equal to or less than a predetermined value. Inverter control device. The drive stop means does not perform an operation of stopping the switching element of the inverter for a predetermined time at the zero cross point of the current detected by the zero cross detection means when the pulse duty output by the inverter is being changed. The inverter control device according to 1. An air conditioner comprising the inverter control device according to any one of claims 1 to 4.

Images