JP2009077526A - Inverter device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an inverter device capable of changing the operation frequency of a motor at a maximum rise rate permitted depending on the status of a load. <P>SOLUTION: The inverter device 3 converts a DC voltage into an AC voltage and controls the operation frequency of the electrically-driven compressor motor 1. The inverter device 3 has a control section 9 determining the operation frequency of the electrically-driven compressor motor 1 on the basis of a specified control input. The control section 9 maximizes the rate of rise of the operation frequency within a range where the value of a current flowing to the electrically-driven compressor motor 1 or the output value of the motor is an allowable value or less. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an inverter device that controls the operation of, for example, a motor of an electric compressor.

In recent air conditioners for air conditioning, the frequency of the operation of the motor of the electric compressor is controlled by an inverter. In this case, the inverter device increases or decreases the operating frequency of the motor based on a predetermined control input calculated from the indoor set temperature and the current temperature. For example, it was about 2 Hz / sec. This is a sufficient value for air conditioners used at home, but car air conditioners for electric vehicles (including hybrid cars) that have become popular in recent years are required to quickly lower the temperature in the passenger compartment in summer. Therefore, it is necessary to raise the operating frequency of the electric compressor used in the car air conditioner at an early stage (see, for example, Patent Document 1).
Japanese Patent No. 3477759

  Here, when the operating frequency of the motor driving the electric compressor is increased, the value of the current flowing through the motor changes as shown in FIG. 10 depending on the increasing speed (the changing speed of the operating frequency). The current on the vertical axis is the current value that flows through the motor. The input current value that flows through the inverter device (the value of the total DC current that flows through the switching unit of the inverter device) and the phase current value (the current that flows through each phase of the switching unit). Value). In FIG. 10, the load torque (torque applied to the motor) is constant, and is increased from a certain low operating frequency to a higher operating frequency at an increasing rate of 8 Hz / sec, 4 Hz / sec, and 2 Hz / sec. The change in the input current value in each case is shown.

  The value of the current that flows through the motor is initially consumed by the output to oppose the inertia of the motor, so it starts to rise at any speed and then suddenly rises. It can be seen that the peak value is highest at the higher 8 Hz / sec, the peak is lowered at the lower 4 Hz / sec, and the peak value is lowest at the lower 2 Hz / sec.

  FIG. 11 shows, for each load torque (torque applied to the motor at that time), how the input current value flowing in the motor changes when the speed of increase (change speed) of the operating frequency of the motor is constant. . From this figure, it can be seen that the larger the load torque, the higher the peak value of the change in the current value when the operating frequency is increased.

  As described above, when the operating frequency of the motor of the electric compressor is increased, the value of the current flowing through the motor varies depending on the increasing speed and the load torque. That is, in an operating state where the load torque is large, the value of the current flowing through the motor increases as the operating frequency is changed at a higher speed. Therefore, if the operating frequency is increased too quickly, the current value will be the current of the motor winding. The allowable value and the current allowable value of a switching element (for example, IGBT) constituting the switching unit of the inverter device are exceeded, and there is a risk of causing winding burnout and destruction of the switching element.

  In fear of this, in the past, according to these permissible values (determined by the inverter device and motor), a constant ascending speed that is set in advance so that this permissible value is not exceeded in all possible operating states (load torque states). The operating frequency of the motor was changed at 20 Hz / sec (for example, in the case of a car air conditioner). For this reason, for example, there is a limit even if the temperature in the passenger compartment of an automobile is quickly reduced.

  The present invention has been made to solve the conventional technical problems, and provides an inverter device capable of changing the operating frequency of the motor at the maximum ascent rate allowed by the load condition. It is.

  An inverter device of the present invention controls a motor operating frequency by converting a DC voltage into an AC voltage, and includes a control unit that determines a motor operating frequency based on a predetermined control input. Is characterized in that the speed of increase of the operating frequency is maximized within a range where the current value supplied to the motor or the output value of the motor is less than the allowable value.

  In the inverter device of the invention according to claim 2, the control unit monitors the current value or the output value in the above, and based on the comparison between the allowable value and the current value or the current output value, the operating frequency It is characterized in that the rising speed of the is determined.

  In the inverter device of the invention according to claim 3, in the above, the control unit determines an increase speed of the operating frequency by PID control based on a deviation between the allowable value and the current value or the output value, When the current value or the output value of the PID control approaches the allowable value, the gain of the PID control is lowered.

  According to a fourth aspect of the present invention, there is provided an inverter device according to the second aspect, wherein the control unit has a maximum value of an increase rate of the operating frequency based on the difference between the allowable value and the current value or the output value and the inertia of the motor. It is characterized by determining.

  According to a fifth aspect of the present invention, there is provided the inverter device according to the first aspect, wherein the control unit maintains a correlation between the current value or the output value and the maximum value of the increase speed of the operating frequency at which they are equal to or less than the allowable value. The current value or the output value is monitored, and the maximum value of the rising speed of the operating frequency is determined from the correlation based on the current value or the output value.

  An inverter device according to a sixth aspect of the invention is characterized in that the operating frequency determined in any one of the second to fifth aspects is set as an upper limit value, and the control unit increases the operating frequency of the motor.

  According to the present invention, the operating frequency of the motor can be accelerated at the maximum rising speed without damaging the motor and the switching element. In particular, if the current value supplied to the motor and the output value of the motor are monitored as in claim 2 and the rate of increase in the operating frequency is determined by comparison with the allowable values, the load frequency is not affected. The operating frequency can be changed at the maximum allowable climbing speed, and the response to fluctuations in load is improved. For example, in a car air conditioner using an electric compressor, the cooling performance in the passenger compartment is remarkably improved. Is possible.

  Further, when the speed of increase of the operation frequency is determined by PID control based on the deviation between the allowable value and the current value or the output value as in claim 3, the current value or the current output is determined. If the value of the PID control is lowered when the value approaches the allowable value, the maximum increase speed of the motor operating frequency can be accurately obtained below the allowable value of the current value or output value.

  If the maximum value of the increase speed of the operating frequency is determined based on the difference between the allowable value and the current value or the output value and the inertia of the motor as in the invention of claim 4, the motor Thus, it is possible to eliminate the inconvenience that the current value and the output value exceed the allowable values.

  Further, as in the invention of claim 5, a correlation between the current value or output value and the maximum value of the rising speed of the operating frequency at which they are below the allowable value is obtained in advance, and the current value or If the output value is monitored, and the maximum value of the rising speed of the operation frequency is determined from the correlation based on the current value or the current output value, the invention of claim 2 to claim 4 Thus, the maximum allowable rising speed can be obtained without calculating the rising speed every time.

  As in the sixth aspect of the present invention, even if the control unit increases the operating frequency of the motor by setting the increasing speed of the operating frequency determined in any of the second to fifth aspects as the upper limit, It is possible to obtain the maximum ascent rate according to. In particular, when controlling the motor of an electric compressor, the rising speed is limited due to the problem of oil discharge from the compressor, which is effective.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the following embodiments, an inverter device that controls a motor that drives an electric compressor of a car air conditioner has been described. However, the present invention is not limited to this, and the present invention is effective as long as the motor operating frequency is controlled. .

  In FIG. 1, reference numeral 1 denotes a motor for driving an electric compressor, and the electric compressor itself constitutes a part of a refrigerant circuit of a car air conditioner (not shown). The electric compressor motor 1 is controlled by an inverter device 3 of the present invention using a battery 2 (DC power supply) of an electric vehicle (including a hybrid vehicle) as a power source. The inverter device 3 is connected to the battery 2 via an input circuit 4, and includes a switching unit 7 composed of six switching elements 6 made of, for example, an IGBT, and a drive circuit 8 that drives the switching elements 6 of the switching unit 7. A control unit 9 as a control means for controlling the drive circuit 8, a power source unit 10 for generating a power source (for example, DC 5V) for the control unit 9 and the drive circuit 8, and the like. 1 is connected.

  The control unit 9 receives the value of the input voltage Vdc from the voltage detection unit 13 including the voltage dividing resistors 11 and 12, and the control unit 9 monitors the value of the input voltage Vdc. Further, the control unit 9 receives the shunt resistors 13 and 14 and the amplifier circuits 16 and 17 for detecting the phase current (for two phases) If of the switching unit 7 and the input current Idc which is the total DC current flowing into the switching unit 7. The values of the phase current If and the input current Idc are input from the current detection unit 21 including the shunt resistor 18 and the amplifier circuit 19 for detection, and the control unit 9 monitors the values of the phase current If and the input current Idc. Yes.

  The controller 9 also receives outputs from a temperature sensor 22 that detects the temperature of the substrate provided with the electric circuit and a temperature sensor 23 that detects the temperature of the discharge gas (refrigerant) of the electric compressor. The control unit 9 receives a control signal from the air conditioner controller AC via the communication circuit 24. The air conditioner controller AC is provided with a temperature sensor and a solar radiation sensor in the vehicle interior, and the air conditioner controller AC is a control signal related to the operating frequency of the electric compressor motor 1 for making the vehicle interior comfortable based on the input and set temperature from them. Is generated.

  The control unit 9 of the inverter device 3 receives a control signal from the air conditioner controller AC, and outputs a switching signal to the drive circuit 8 so as to drive the electric compressor motor 1 at an operation frequency based on the control signal. 8, the switching element 6 of the switching unit 7 is switched to convert it to a variable frequency or variable AC voltage. Note that the control unit 9 uniquely limits the operating frequency of the electric compressor motor 1 in preference to the control signal from the air conditioner controller AC also by the outputs from the temperature sensors 22 and 23.

  Next, an embodiment of the control for increasing the operating frequency of the electric compressor motor 1 by the control unit 9 will be described with reference to FIGS. As described above, the control unit 9 of the inverter device 3 receives a control signal from the air conditioner controller AC, and increases or decreases the rotational speed (operation frequency) of the electric compressor motor 1 so as to obtain an operation frequency based on the control signal. However, the speed at which the operating frequency is increased is determined based on the output from the current detection unit 21.

  In the following description, the rising speed is determined based on the input current Idc detected by the current detection unit 21 as the current flowing through the electric compressor motor 1, but in addition, the current flowing through the electric compressor motor 1 is determined. The phase current If may be used as an index of the output, or the output value of the electric compressor motor 1, that is, Idc × Vdc corresponding to the output value may be used. However, in these cases, the following allowable values are replaced with allowable values of phase current values or allowable values of output values.

  FIG. 2 shows a control block diagram for determining the rising speed of the operating frequency of the electric compressor motor 1. In the case of this embodiment, the control unit 9 includes a frequency increase speed determination unit 31 that performs PID control and a switching signal generation unit 32. Then, the frequency increase speed determination unit 31 compares the allowable value (current allowable value) −α of the input current Idc with the current value of the input current Idc input from the current detection unit 21, and sets the deviation e. Based on this, the proportional (P), integral (I), and differential (D) calculations are performed in the direction of reducing the deviation e, and the operating frequency increase speed as the operation amount is determined and output to the switching signal generator 32.

  Thus, the frequency increase speed determination unit 31 determines the increase speed of the operation frequency so that the current value of the input current Idc approaches the allowable value −α, that is, the increase speed is determined by the value of the input current Idc. It will be the maximum within a range that is less than the allowable value.

  When the operating frequency of the electric compressor motor 1 is increased, the switching signal generator 32 increases the operating frequency at the determined increasing speed based on the increasing speed of the operating frequency determined by the frequency increasing speed determining unit 31. A switching signal is generated so as to be accelerated. The generated switching signal is input to the drive circuit 8 (not shown in FIG. 2), the switching element 6 of the switching unit 7 is switched, and the electric compressor motor 1 is accelerated. Then, the operation frequency is finally set based on the control input from the air conditioner controller AC.

  FIG. 3 shows a change in the operating speed of the electric compressor motor 1 (lower stage) and a change in the input current Idc (upper stage) under the control of the control unit 9. As is apparent from this figure, it can be seen that the input current Idc changes approximately approximating to the change in the operating frequency rise rate, and converges to the allowable value −α by the PID control. Here, the target value in the frequency increase speed determining unit 31 is set to the allowable value −α in order to allow a margin under the allowable value so that the input current Idc does not exceed the allowable value due to overshoot. is there. The value of α is determined with the minimum necessary by the apparatus.

  In this way, the control unit 9 monitors the value of the input current Idc (which may be phase current If or Idc × Vdc corresponding to the output value) supplied to the electric compressor motor 1 and the value of the input current Idc is less than the allowable value. Within this range, the operating speed of the electric compressor motor 1 is maximized, so that the operating frequency of the electric compressor motor 1 is accelerated at the maximum ascending speed without damaging the electric compressor motor 1 and the switching element 6. Will be able to.

  In particular, the operating frequency of the electric compressor motor 1 can be changed at the maximum allowable rising speed regardless of the load condition of the electric compressor (motor 1) constituting the refrigerant circuit, and the load fluctuation can be prevented. The responsiveness is improved, and in the car air conditioner using the electric compressor as in the embodiment, it is possible to remarkably improve the cooling performance (cool down performance) in the passenger compartment.

  In the first embodiment, not only the above-described PID control but also the allowable value (or allowable value -α) is compared with the input current Idc, and the rising speed is determined in a direction to reduce the difference. For example, other control methods (for example, a third embodiment described later) may be used.

  Next, FIG. 4 and FIG. 5 show another embodiment (embodiment 2) of control for increasing the operating frequency of the electric compressor motor 1 by the controller 9. In this figure, the same reference numerals as those in FIGS. 2 and 3 indicate the same or similar functions. In this case, the allowable value −β is set further below the allowable value −α of the input current Idc in the frequency increase speed determining unit 31 of the control unit 9 in the control block of FIG. 4 (α <β). When the value of the input current Idc is smaller than this allowable value −β, the PID control gain (PID calculation coefficient) is increased (PID gain: large), and the input current Idc value approaches the allowable value. When the value is equal to or greater than the allowable value −β, the gain is switched to be lowered (PID gain: small). The other control is the same as in FIG.

  Thus, if the gain of the PID control is lowered when the current value of the input current Idc approaches the permissible value, so-called overshoot is further suppressed, and the electric compressor can be accurately performed below the permissible value of the input current Idc. It becomes possible to obtain the maximum rising speed of the operating frequency of the motor 1.

  Next, FIGS. 6 and 7 show still another embodiment (embodiment 3) of the control of the speed increase of the operating frequency of the electric compressor motor 1 by the control unit 9. FIG. In this case, the control unit 9 determines the maximum value of the increase speed of the operating frequency based on the difference between the allowable value of the input current Idc and the current value of the input current Idc and the inertia (inertia) of the electric compressor motor 1. To do.

  As described above, when the electric compressor motor 1 is accelerated, the input current Idc increases as the operating frequency increases, but if the difference between the allowable value and the current input current Idc is large, the increasing speed is increased. It can be said that there is enough room for the increase. Moreover, when accelerating the electric compressor motor 1, the larger the inertia, the greater the output required to face it.

  Therefore, every time the operating frequency of the electric compressor motor 1 increases by, for example, Δa, the control unit 9 is based on a calculation formula of maximum frequency increase speed = ((allowable value−current input current Idc value) / inertia) × K. The rising speed is determined, and the operating frequency of the electric compressor motor 1 is increased at the determined speed. K is a coefficient.

  That is, FIG. 6 shows a flowchart in that case. The control unit 9 determines the maximum value of the rising speed of the operating frequency of the electric compressor motor 1 using the above calculation formula in step S1 of FIG. In step S2, it is determined whether the operating frequency has increased by Δa. If it has increased, the process returns to step S1, and this is repeated. From the calculation formula, it can be seen that the greater the difference between the allowable value and the current input current Idc, the greater the maximum value of the ascending speed, and the greater the inertia of the electric compressor motor 1, the more the maximum value of the ascending speed is limited. . When the operating frequency of the electric compressor motor 1 is increased, the control unit 9 accelerates at the determined maximum increase rate.

  FIG. 7 shows how the input current Idc is changed by such control. In FIG. 7, the frequency is raised from a certain low operating frequency to a higher operating frequency. In the course of this increase, the input current Idc increases rapidly in order to cope with the load torque and inertia, but it can be seen that the peak value is kept below the allowable value. Then, the rising speed of the operating frequency of the electric compressor motor 1 is set to the maximum value within the suppressed range.

  In this way, if the speed of increase in the operating frequency is determined based on the difference between the allowable value of the input current Idc and the current value of the input current Idc and the inertia of the electric compressor motor 1, the electric compressor motor 1 Thus, the disadvantage that the value of the input current Idc exceeds the allowable value can be solved by the inertia.

  Next, FIGS. 8 and 9 show still another embodiment (embodiment 4) of the control of the speed increase of the operating frequency of the electric compressor motor 1 by the controller 9. FIG. In this case, the correlation between the current value of the input current Idc in the device and the maximum value of the increase speed of the operating frequency of the electric compressor motor 1 at which the input current Idc falls below the allowable value when the value is the value (FIG. 9). ) Is obtained in advance by experiments, and stored (held) in the control unit 9.

  Therefore, the control unit 9 uses the current value of the input current Idc every time the operating frequency of the electric compressor motor 1 increases by Δa, for example, and uses the stored correlation (FIG. 9) to determine the maximum value of the increasing speed. And the operating frequency of the electric compressor motor 1 is increased at the determined speed.

  That is, FIG. 8 shows a flowchart in that case. The control unit 9 determines the maximum value of the rising speed of the operating frequency of the electric compressor motor 1 using the above correlation in step S3 of FIG. Then, in step S4, it is determined whether the operating frequency has increased by Δa. If it has increased, the process returns to step S3 and is repeated. As shown in FIG. 9, the smaller the value of the input current Idc, the larger the maximum value of the operating frequency increase rate (maximum frequency increasing rate), and the larger the value of the input current Idc, the smaller the maximum value tends to be. .

  As described above, the correlation between the value of the input current Idc and the maximum value of the increase rate of the operating frequency at which they are below the allowable value is obtained in advance, and the current value of the current input current Idc is monitored by monitoring the input current Idc. Based on the above, if the maximum value of the rising speed of the operating frequency is determined from the above-described correlation, the maximum allowable rising speed can be obtained without calculating the rising speed each time as in the above-described embodiment. Will be able to.

  In each of the above embodiments, the controller 9 maximizes the operating frequency of the electric compressor motor 1 within the allowable input current Idc (which may be a phase current value or an output value). However, the present invention is not limited to this, and the rising speed determined in each embodiment is set as an upper limit value, and the rising speed is determined within a range equal to or lower than the upper limit value to accelerate the electric compressor motor 1. Also good.

  For example, in the case of a car air conditioner, if the electric compressor motor 1 is accelerated rapidly, the amount of oil discharged from the electric compressor increases. Therefore, it is necessary to limit the rising speed of the operating frequency. However, if the rising speed determined in the above-described embodiment is set as the upper limit value as in this embodiment, the maximum allowable value is considered in consideration of oil discharge restriction. You will be able to gain ascending speed.

It is an electric circuit diagram of the inverter apparatus to which the present invention is applied. FIG. 3 is a block diagram illustrating control for determining an increase speed of the operating frequency of the electric compressor motor by the control unit of the inverter device of FIG. 1 (Example 1). It is a figure which shows the mode of the change of the value of the input current by the control of FIG. 2, and the raise speed of an operating frequency. (Example 2) which is another block diagram explaining the increase speed determination control of the operating frequency of the electric compressor motor by the control part of the inverter apparatus of FIG. It is a figure which shows the mode of the change of the value of the input current by the control of FIG. 4, and the raise speed of an operating frequency. (Example 3) which is a flowchart explaining the increase speed determination control of the operating frequency of the electric compressor motor by the control part of the inverter apparatus of FIG. It is a figure which shows the mode of the change of the value of input current by control of FIG. (Example 4) which is another flowchart explaining the increase speed determination control of the operating frequency of the electric compressor motor by the control part of the inverter apparatus of FIG. It is a figure which shows the correlation with the value of the present input current used for control of FIG. 8, and the maximum value of the raise speed of the operating frequency of an electric compressor motor in which an input current is less than an allowable value when it is the said value. It is a figure which shows the change of the input electric current value in each raising speed at the time of raising the driving frequency of a motor by making load torque constant. It is the figure which showed the mode of the change of the input electric current value which flows into a motor at the time of making the raise speed of the operating frequency of a motor constant for every load torque.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Electric compressor motor 2 Battery 3 Inverter apparatus 6 Switching element 7 Switching part 8 Drive circuit 9 Control part 13 Voltage detection part 21 Current detection part 31 Frequency rise speed determination part 32 Switching signal generation part

Claims (6)

In the inverter device that controls the motor operating frequency by converting DC voltage to AC voltage,
A control unit that determines an operating frequency of the motor based on a predetermined control input, the control unit being within a range in which a current value energized to the motor or an output value of the motor is equal to or less than an allowable value; An inverter device characterized by maximizing the rising speed of the operating frequency.   The control unit monitors the current value or the output value, and determines an increase rate of the operation frequency based on a comparison between the allowable value and the current value or the output value. The inverter device according to claim 1.   The control unit determines an increase rate of the operating frequency by PID control based on a deviation between the allowable value and the current value or output value, and the current value or output value is The inverter device according to claim 2, wherein when approaching the allowable value, the gain of the PID control is lowered.   The control unit determines a maximum value of an increase speed of the operating frequency based on a difference between the allowable value and the current value or output value and an inertia of the motor. The inverter device described in 1.   The control unit holds a correlation between the current value or the output value and the maximum value of the increase speed of the operating frequency at which they are less than or equal to the allowable value, and the current value or the output value The inverter device according to claim 1, wherein the maximum value of the rising speed of the operating frequency is determined from the correlation based on the current value or the output value.   6. The inverter device according to claim 1, wherein the controller raises the operating frequency of the motor using the rising speed of the operating frequency determined in any one of claims 2 to 5 as an upper limit value.

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