JP2021125980A - Motor drive device - Google Patents

Abstract

To provide a motor drive device capable of reducing a rotational frequency of a motor and an over shoot of a current flowing in a torque or the motor, and achieving a stable driving.SOLUTION: A motor drive device includes: a first mode that performs a PI operation of a difference between a command value of a current required for driving a motor 5 in a desired load state and a detection value from a current detection part 7, and generates a voltage command applied to the motor 5; and a second mode that uses the command value of the current required for driving the motor 5 in the desired load state, and generates the voltage command from a predetermined voltage command calculation formula. In a regeneration state that a power is supplied to any one of a capacitor 3, a rectification circuit 2, and an AC power supply 1 from the motor 5, the voltage command applied to the motor 5 is generated in the second mode.SELECTED DRAWING: Figure 1

Description

The present invention relates to a motor drive device.

Patent Document 1 discloses a technique for reducing the capacity of a capacitor of a motor drive device for the purpose of miniaturization or cost reduction of the motor drive device.

Patent Document 2 estimates or detects the speed at which the rotor of the motor is rotating and the current flowing through the motor in a configuration in which the capacitor of the motor drive device is reduced in capacity, and the speed or current. A technique is disclosed in which the deviation from the command value of is calculated by PI (speed control or current control), and the voltage required to drive the motor with a load such as a desired rotation speed or torque is applied to the motor.

In the regenerative state, Patent Documents 3 and 4 regenerate so that the deviation does not increase in the speed control system in the process of generating the voltage command required to drive the motor with a load such as a desired rotation speed or torque. A technique for driving an electric motor without taking the deviation into consideration is disclosed from the stage before the state or the regenerative state is reached.

JP-A-2002-51589 Japanese Unexamined Patent Publication No. 2003-164179 JP-A-2007-159263 Japanese Unexamined Patent Publication No. 2007-181335

The present disclosure provides a motor drive device capable of stably driving by reducing the rotation speed of the motor, torque, and overshoot of current flowing through the motor.

The electric motor drive device in the present disclosure includes an AC power supply, an AC voltage detection unit that detects an AC voltage from the AC power supply, a rectifying circuit that converts AC power from the AC power supply into DC power, and the rectifying circuit. The capacity is set so that the output voltage of the AC power supply pulsates at a frequency approximately twice that of the AC power supply, and a capacitor connected in parallel to the output side of the rectifier circuit and a voltage applied to the AC power supply are input as desired. An inverter that converts to AC voltage, an electric motor provided on the output side of the inverter, a DC voltage detector that detects the voltage applied to the capacitor, and a current detector that detects the current flowing through the electric motor. At least a control unit that transmits information necessary for driving the electric motor with a desired load based on information from the AC voltage detection unit, the DC voltage detection unit, and the current detection unit to the inverter. The control unit performs PI calculation of the difference between the command value of the current required to drive the electric motor under a desired load state and the detected value from the current detection unit, and generates a voltage command to be applied to the electric motor. The first mode is to generate a voltage command from a predetermined voltage command calculation formula by using the command value of the current required to drive the electric motor under a desired load state. In the regenerated state in which power is supplied from the electric motor to any one of the capacitor, the rectifying circuit, and the AC power supply, a voltage command to be applied to the electric motor is generated in the second mode.

The motor drive device in the present disclosure can reduce the rotation speed of the motor, the torque, and the overshoot of the current flowing through the motor, and can drive the motor stably.

Configuration diagram of the motor drive device according to the first embodiment (A) A diagram relating to current command generation by the speed control unit in the first embodiment (b) A diagram in which the output of PI calculation corresponding to the output of the speed control unit in the first embodiment is a current command. The figure regarding the set advance angle in the advance angle control unit in Embodiment 1. (A) A diagram illustrating the operation of the regenerative state determination unit in the first embodiment (b) A diagram when the regenerative state determination unit in the first embodiment determines that the regenerative state is in a regenerative state.

(Knowledge, etc. that was the basis of this disclosure)
In the conventional configuration, in the configuration in which the capacitor of the motor drive device is reduced in capacity, the power on the motor side becomes higher than that on the rectifier circuit or the AC power supply side in the vicinity of the phase where the AC voltage from the power supply voltage becomes zero. Since the electric power is supplied from the electric motor to the capacitor side in a regenerated state, the electric motor cannot be stably controlled with a desired load.

From this, in the regenerated state, in the process of generating the voltage command required to drive the motor with a load such as a desired rotation speed and torque, the command value and the detected value or the estimated value in the speed control system or the current control system are used. In each control system after the end of the regeneration state, each control system works steeply in an attempt to eliminate the deviation, so that overshoot occurs in the rotation speed and torque of the motor or the current flowing through the motor, causing the motor to operate. It is possible that it cannot be driven stably.

However, since only countermeasures for the speed control system are generally known, in the current control system, the deviation between the command value and the detected value in the speed control system or the current control system, or the command value and the estimated value is dealt with. No measures were taken.

Therefore, there is a problem that the deviation between the command and the detection in the current control system increases after the end of the regenerative state, an overshoot occurs in the current or torque flowing through the motor, and the motor cannot be driven stably.

Therefore, the inventors have come to construct the subject matter of the present disclosure in order to solve the problem.

The present disclosure provides an electric motor drive device capable of stably driving by reducing the rotation speed of the electric motor, torque, and overshoot of current flowing through the electric motor.

Hereinafter, embodiments will be described in detail with reference to the drawings. However, more detailed explanation than necessary may be omitted. For example, detailed explanations of already well-known matters or duplicate explanations for substantially the same configuration may be omitted. This is to avoid unnecessarily redundant explanations below and to facilitate the understanding of those skilled in the art.

It should be noted that the accompanying drawings and the following description are provided for those skilled in the art to fully understand the present disclosure, and are not intended to limit the subject matter described in the claims.

(Embodiment 1)
Hereinafter, the first embodiment will be described with reference to FIGS. 1 to 4.

[1-1. composition]
As shown in FIG. 1, the electric motor drive device according to the first embodiment is composed of an AC power source 1, an AC voltage detection unit 10 for detecting an AC voltage from the AC power source 1, and an AC power source connected in series to the AC power source 1. The AC current detection unit 11 that detects the AC current, the rectifying circuit 2 that converts the AC power from the AC power supply 1 into DC power as an input, and the output voltage of the rectifying circuit 2 at a frequency that is approximately twice that of the AC power supply 1. A capacitor 3 whose capacitance is set so as to pulsate and connected in parallel to the output side of the rectifier circuit, an inverter 4 that converts the voltage applied to the capacitor 3 into a desired AC voltage as an input, and an inverter 4 on the output side of the inverter 4. An electric motor 5 provided, a DC voltage detection unit 6 for detecting the voltage applied to the capacitor 3, a current detection unit 7 for detecting the current flowing through the electric motor 5, an AC voltage detection unit 10, and the DC voltage detection unit 10. 6. A control unit 8 for transmitting information necessary for driving the electric motor 5 with a desired load to the inverter 4 based on the information from the current detection unit 7 is provided.

In addition, in order to reduce the peak of the charge / discharge current to the capacitor 3, the reactor 9 may be provided in series between the AC power supply 1 and the rectifier circuit 2.

Further, the control unit 8 includes a position / speed estimation unit 8a, a speed control unit 8b, an advance angle control unit 8c, a current control unit 8d, a two-phase / three-phase conversion unit 8e, and a PWM signal generation unit 8f. , A three-phase / two-phase modulation unit 8g, a zero-cross detection unit 8h, an AC power supply phase / period measurement unit 8i, and a regeneration state determination unit 8j.

[1-2. motion]
Next, each operation will be described below.

First, the AC power supply phase / cycle measuring unit 8i determines the period and phase of the AC voltage from the AC power supply 1 based on the information from the zero cross detection unit 8h that measures the timing when the AC voltage from the AC power supply 1 becomes zero. measure.

In the position / speed estimation unit 8a, the current flowing in each phase of the motor 5 detected by the current detection unit 7, the PWM signal applied to each phase of the motor 5 from the PWM signal generation unit 8f, and the DC voltage detection unit Based on the DC voltage detection value from 6 and the information from, the rotor magnetic pole position and the rotation speed of the motor 5 are estimated.

The speed control unit 8b performs PI calculation on the difference between the indicated speed at which the rotor of the motor 5 is desired to be driven and the speed of the rotor of the motor 5 estimated by the position / speed estimation unit 8a.

In the case of a regenerative state in which power is supplied from the motor 5 to the AC power supply 1, the rectifier circuit 2, or the capacitor 3, based on the information from the regenerative state determination unit 8j described later, it is desired to drive the rotor of the motor 5. The PI calculation is performed assuming that there is no difference between the indicated speed and the speed of the rotor of the motor 5 estimated by the position / speed estimation unit 8a.

Further, after the PI calculation, as shown in FIG. 2A, in order to effectively supply power from the AC power supply 1 or the rectifier circuit 2 to the electric motor 5, based on the information from the AC power supply phase / period measurement unit 8i. , The current command is generated so that the cycle is synchronized with the half cycle of the AC power supply 1 and the area is equivalent to the area of the PI calculation result during the half cycle of the AC power supply 1.

In the regenerated state in which electric power is supplied from the electric motor 5 to the AC power supply 1, the electric motor 5 to the rectifier circuit 2, or the electric motor 5 to the capacitor 3, the torque of the electric motor 5 cannot be controlled according to the current command. It may be omitted from the area calculation.

Further, when the current command of the motor is generated as shown in FIG. 2A, the current flowing through the motor momentarily increases in the vicinity of the phase where the AC voltage from the AC power supply 1 peaks.

Therefore, in a load state near the rated current of each component constituting the motor drive device or the demagnetization current of the motor 5, it is necessary to limit the rotation speed and torque of the motor 5 even if the rated torque has a margin. It is believed that there is.

Therefore, when the load for driving the motor 5 is near the rated current of each component constituting the motor drive device or the demagnetizing current of the motor 5, the output of the speed control unit 8b is as shown in FIG. 2 (b). The output of the corresponding PI operation may be used as a current command.

Further, based on the advance angle value from the advance angle control unit 8c, the current commands are distributed to the d-axis and the q-axis. The advance value is set to a predetermined value in advance according to the speed of the motor 5 or a load such as torque.

Further, in order to effectively supply the electric power from the AC power source 1 to the electric motor 5, the phase in which the electric power is regenerated is set in the vicinity of the phase where the AC power source in which the electric power is easily regenerated from the electric motor 5 to the inverter 4 or the AC power source 1 becomes zero. As shown in FIG. 3, it is desirable to set the advance angle so that it becomes shorter and to minimize the current required to output the torque in the vicinity of the phase where the AC voltage peaks. The advance value may be changed within half a cycle of the power supply.

In the current control unit 8d, the current command values distributed to the d-axis and the q-axis corresponding to the output of the speed control unit 8b and the current flowing in each phase of the motor 5 detected by the current detection unit 7 are three-phase. / It has a first mode in which the difference between the current detection values of the d-axis and the q-axis converted by the two-phase conversion unit 8h is calculated by PI, and the voltage commands of the d-axis and the q-axis are generated.

Further, the second current command value distributed to the dq axis corresponding to the output of the speed control unit 8b and the voltage command of the d-axis and the q-axis are generated by using the equations (1) and (2). Has a mode.

The explanation of each variable of the formula (1) and the formula (2) is shown below.

ここで、Ｒは電動機の各相抵抗、Ｌｄはｄ軸のインダクタンス、Ｌｑはｑ軸のインダクタンス、Ｉｄｒｅｆはｄ軸の電流指令値、Ｉｑｒｅｆはｑ軸の電流指令値、ωｅｓｔは電動機の回転子の推定速度、φは電動機の起電力乗数である。

Here, R is the resistance of each phase of the motor, Ld is the inductance of the d-axis, Lq is the inductance of the q-axis, Idref is the current command value of the d-axis, Iqref is the current command value of the q-axis, and ωest is the rotor of the motor. The estimated speed, φ, is the electromotive force multiplier of the motor.

The regeneration state determination unit 8j determines whether or not the current is in a regeneration state in which power is supplied from the motor 5 to the condenser 3, the motor 5 to the rectifier circuit 2, or the motor 5 to the AC power supply 1. Information from the detection unit 7, the DC voltage detection unit 6, or the AC current detection unit 11, or the estimated speed of the motor 5 calculated by the position / speed estimation unit 8a is used.

For example, when the current detected by the current detection unit 7 is flowing from the inverter 4 to the capacitor 3, or the estimated speed of the electric motor 5 calculated by the position / speed estimation unit 8a is a value preset with respect to the indicated speed. When the speed is reduced by the above, or when the AC current is not flowing in the AC current detection unit 11, or when the increase amount of the DC voltage per detection cycle in the DC voltage detection unit 6 is equal to or more than a preset value. It is determined that the current state is regenerated.

As shown in FIG. 4B, when it is determined that the state is regenerative, the voltage commands of the d-axis and the q-axis calculated in the second mode of the current control unit 8d are output, and it is determined that the state is not regenerative. In this case, the d-axis and q-axis voltage commands calculated in either the first mode or the second mode of the current control unit 8d are output.

When it is determined that the current is in the regenerated state, the same effect as when the voltage command is generated in the second mode can be obtained. The currents distributed to the d-axis and the q-axis corresponding to the output of the speed control unit 8b are obtained. It is assumed that there is no difference between the command value and the d-axis and q-axis current detection values obtained by converting the current flowing through each phase of the motor 5 detected by the current detection unit 7 by the three-phase / two-phase conversion unit 8h. A voltage command may be generated in one mode.

In the two-phase / three-phase conversion unit 8f, each phase of the motor 5 is based on information from the d-axis and q-axis voltage commands from the regeneration state determination unit 8j and the estimated position from the position / velocity estimation unit 8a. Generates (U, V, W phase) voltage commands.

In the PWM signal generation unit 8g, each of the motors 5 is based on the information from the voltage command of each phase of the motor 5 from the two-phase / three-phase conversion unit 8f and the DC voltage detection value from the DC voltage detection unit 6. Generates a phase PWM signal.

Each switching element of the inverter 4 can drive the motor 5 at a desired rotation speed and torque by switching according to the PWM signal from the PWM signal generation unit 8g.

[1-3. Effect, etc.]
As a result, in the motor drive device having a smaller capacity of the capacitor, the motor drive device can be driven more stably by reducing the overshoot of the torque and the current flowing through the motor 5 in addition to the rotation speed of the motor 5.

The motor drive device of the present disclosure can reduce the overshoot of the motor speed, torque, and current flowing through the motor, and therefore can be driven more stably. Therefore, for air conditioners, refrigerators, vacuum cleaners, washing machines, etc. It can be applied to drive electric motors of electrical equipment.

1 AC power supply 2 Rectifier circuit 3 Condenser 4 Inverter 5 Motor 6 DC voltage detector 7 Current detector 8 Control unit 9 Reactor 10 AC voltage detector 11 AC current detector

Claims (2)

AC power supply and
An AC voltage detector that detects the AC voltage from the AC power supply,
A rectifier circuit that converts AC power from the AC power supply into DC power as an input,
A capacitor whose capacitance is set so that the output voltage of the rectifier circuit pulsates at a frequency approximately twice that of the AC power supply and is connected in parallel to the output side of the rectifier circuit.
An inverter that uses the voltage applied to the capacitor as an input and converts it to a desired AC voltage.
An electric motor provided on the output side of the inverter and
A DC voltage detector that detects the voltage applied to the capacitor,
A current detection unit that detects the current flowing through the motor, and
At least a control unit that transmits information necessary for driving the motor with a desired load to the inverter based on information from the AC voltage detection unit, the DC voltage detection unit, and the current detection unit. Prepare,
The control unit
A first mode in which the difference between the command value of the current required to drive the motor under a desired load state and the value detected from the current detection unit is calculated by PI to generate a voltage command to be applied to the motor.
It has a second mode in which a voltage command is generated from a predetermined voltage command calculation formula using a command value of a current required to drive the motor under a desired load state.
In the regenerative state in which electric power is supplied from the electric motor to any one of the capacitor, the rectifier circuit, and the AC power supply, the electric motor that generates a voltage command to be applied to the electric motor in the second mode. Drive device. In the control unit, information from any one of an AC current detection unit that detects an AC current from an AC power source, the current detection unit, and the DC voltage detection unit, or estimation of the electric motor calculated by the control unit. The speed is used to determine whether or not the state is regenerated, and when a current is flowing from the electric motor to any one of the capacitor, the rectifier circuit, and the AC power supply, the control unit calculates the current. When the estimated speed of the electric motor is lower than the indicated speed by a predetermined speed, when no AC current is flowing in the AC current detection unit, or when the increase amount of the DC voltage in the DC voltage detection unit is equal to or more than a predetermined value. The electric motor drive device according to claim 1, wherein in any of the cases, the regenerative state is determined.

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