JPWO2008026269A1 - Power converter - Google Patents

Abstract

In the configuration where the operation control of the motor is continued by switching to the V / F control system when an abnormality occurs in the current measuring instrument, it is difficult to accurately control the generated torque. Inverter 2 that drives motor 1 with three-phase alternating current, current measuring devices 5a to 5c that measure the alternating current of inverter 2 for each phase, and an inverter in a rotating orthogonal coordinate system based on a command value input from the outside 2 and an inverter control unit 4 that controls the inverter 2 so as to output a voltage that matches the voltage command value. When there is an abnormality in the current measuring devices 5a to 5c, the inverter control unit 4 , The current feedback control is stopped, the output of the voltage calculation unit 10 is used as a voltage command value, and a voltage command value such that the inverter outputs a current equal to the current command value based on the circuit constant of the electric motor 1 is set to the voltage calculation unit 10. Calculates.

Description

  The present invention relates to a power conversion device that drives and controls an electric motor.

Vector control technology for electric motors is widely used in industry because torque can be controlled with high accuracy and high speed. In a conventional power conversion device, a current measuring device composed of a plurality of electronic components is provided for measuring the current of an electric motor.
If the current meter breaks down and its output signal becomes unstable or fixed, for example, an abnormal value is output, the actual current flowing through the motor cannot be measured correctly. Vector control of the electric motor becomes impossible. For example, in an electric railway system in which an electric car is driven by an electric motor, the electric motor cannot be operated due to a failure of the current measuring instrument, and the electric car is stuck on the track. Outside of electric railways, for example, in buildings, vector-controlled motors are used in air conditioners, elevators, escalators, etc., and if the motor that is the power source cannot be operated, it will have a great impact on social life. There are many things.
A configuration in which a vector control system and a V / F control system are provided side by side as a motor control system, and when an abnormality occurs in the current measuring device, the operation control of the motor is continued by switching to the V / F control system. It is shown. (For example, see Patent Document 1.)

JP 7-111708 A

In the conventional configuration shown in Patent Document 1, the voltage and frequency are raised in a preset pattern and the motor is driven in an open loop, so that the minimum required motor can be driven. The vector control used cannot be applied, and there is a problem that it is difficult to accurately control the generated torque.
In addition, a circuit for performing V / F control in preparation for failure of the current measuring device is separately provided, and there is a problem that the scale of software and hardware increases.
The present invention has been devised to solve the above-described problems, and provides a power conversion device capable of controlling torque more accurately than in the past even in a state where a current measuring instrument fails and the measurement signal cannot be used. For the purpose.

  The power conversion device according to the present invention includes an inverter that drives a motor with three-phase alternating current, a current measuring instrument that measures the alternating current of the inverter for each phase, a rotation sensor that measures the rotational state of the motor, and an external device. An inverter control unit that controls the inverter so as to obtain the voltage command value of the inverter in a rotating coordinate system that is a rotating orthogonal coordinate system based on the input command value and output an AC voltage that matches the voltage command value A coordinate conversion unit that performs coordinate conversion between the rotational coordinate system and three phases using the measurement value of the rotation sensor, and the inverter based on a command value input from the outside The current command value calculation unit that calculates the current command value that is the command value of the current to be output, the difference between the current measurement value measured by the current measuring instrument and the current command value is reduced. A current feedback control unit for controlling the voltage, a voltage calculation unit for calculating a voltage at which a sum of the output of the current feedback control unit and the voltage command value is obtained using a circuit constant of the motor and the current command value, and the voltage command A pulse generator for generating a gate pulse for controlling the inverter so as to output a value, and under a predetermined condition, the output of the voltage calculator is the voltage command value, and based on the circuit constants of the motor The voltage calculation unit calculates the voltage command value such that the inverter outputs a current equal to the current command value.

  The power conversion device according to the present invention includes an inverter that drives a motor with three-phase alternating current, a current measuring instrument that measures the alternating current of the inverter for each phase, a rotation sensor that measures the rotational state of the motor, and an external device. An inverter control unit that controls the inverter so as to obtain the voltage command value of the inverter in a rotating coordinate system that is a rotating orthogonal coordinate system based on the input command value and output an AC voltage that matches the voltage command value A coordinate conversion unit that performs coordinate conversion between the rotational coordinate system and three phases using the measurement value of the rotation sensor, and the inverter based on a command value input from the outside The current command value calculation unit that calculates the current command value that is the command value of the current to be output, the difference between the current measurement value measured by the current measuring instrument and the current command value is reduced. A current feedback control unit for controlling the voltage, a voltage calculation unit for calculating a voltage at which a sum of the output of the current feedback control unit and the voltage command value is obtained using a circuit constant of the motor and the current command value, and the voltage command A pulse generator for generating a gate pulse for controlling the inverter so as to output a value, and under a predetermined condition, the output of the voltage calculator is the voltage command value, and based on the circuit constants of the motor Since the voltage calculation unit calculates the voltage command value such that the inverter outputs a current equal to the current command value, the measured current value of the inverter measured by the current measuring instrument cannot be used. Even in the state, there is an effect that the torque can be controlled more accurately than in the past.

It is a figure which shows the structural example of the power converter device in Embodiment 1 which concerns on this invention. It is a figure which shows the simulation result of the torque command value, the torque of an electric motor, and the rotor frequency of an electric motor in case the current measuring device abnormality detection part in the structure of Embodiment 1 which concerns on this invention has determined normally. It is a figure which shows the simulation result of the torque command value, the torque of an electric motor, and the rotor frequency of an electric motor in case the current measuring device abnormality detection part in the structure of Embodiment 1 which concerns on this invention has determined abnormality.

Explanation of symbols

40: Power converter 1: Electric motor 2: Inverter 3: Filter capacitor 4: Inverter control unit 5a: Current measuring device 5b: Current measuring device 5c: Current measuring device 6: Rotation sensor 7: Current command value calculating unit 8: Three-phase dq axis coordinate converter (coordinate converter)
9: current feedback control unit 10: voltage calculation unit 11D: adder 11Q: adder 12: slip angular velocity calculation unit 13: angular velocity phase angle calculation unit 14: dq-axis three-phase coordinate converter (coordinate conversion unit)
15: Pulse generator 16: Current measuring device abnormality detector 17D: Switch 17Q: Switch

Embodiment 1 FIG.
FIG. 1 is a diagram showing a configuration example of a power conversion device 40 according to Embodiment 1 of the present invention. As shown in FIG. 1, the power converter 40 includes an inverter 2 that drives a motor 1 by converting direct current into three-phase alternating current of an arbitrary frequency, and a direct current side of the inverter 2 in order to smooth fluctuations in direct current voltage. And an inverter control unit 4 that controls the inverter 2. In addition, as the electric motor 1, although demonstrated below by the structural example using an induction motor, the fundamental structural concept of this invention is applicable also when using a synchronous motor.
The inverter control unit 4 measures the torque command value Tm * and the secondary magnetic flux command value Φ2 * generated by an external control device, and current measuring devices 5a to 5c that measure the alternating current of the inverter 2 for each phase. The U-phase current Iu, the V-phase current Iv, the W-phase current Iw, and the motor rotation angular velocity ωr that is the output of the rotation sensor 6 attached to the shaft end of the motor 1 are input. The inverter control unit 4 calculates the three-phase voltage command values Vu *, Vv *, and Vw * that the inverter 2 should output, and configures the inverter 2 so that the inverter 2 outputs a voltage that matches the voltage command value. A gate pulse to a switching element (not shown) is generated.

  The configuration of the inverter control unit 4 will be described below. A so-called vector control for performing control on a dq axis rotation coordinate system defined by a d axis that is an axis that rotates in accordance with the secondary magnetic flux axis of the electric motor 1 and a q axis that is an axis orthogonal to the d axis. It is the structure to perform. The inverter control unit 4 is divided into a part that realizes vector control by current feedback similar to the conventional one and a part that is used when a voltage command value is calculated in a feedforward manner when the alternating current of the inverter 2 cannot be measured. .

  First, a part having the same configuration as that of the conventional vector control will be described. The inverter control unit 4 includes a current command value calculation unit 7 that calculates current command values for the d-axis and the q-axis from the torque command value Tm * and the secondary magnetic flux command value Φ2 *, a U-phase current Iu, a V-phase current Iv, W A three-phase dq-axis coordinate converter 8 that converts the phase current Iw into a value in the dq-axis rotating coordinate system, a d-axis and q-axis current measurement value and a current command value converted by the three-phase dq-axis coordinate converter 8; The current feedback control unit 9 performs feedback control by separating the d axis and the q axis so that the deviation becomes smaller, and calculates the d axis and q axis voltages from the current command value using the circuit constants of the motor. Voltage calculator 10, adders 11D, 11Q, and current command values, which are the sum of the output of current feedback controller 9 and the output of voltage calculator 10 for each of the d-axis and q-axis, and are used as voltage command values for inverter 2 To the motor circuit constants Sliding angular velocity calculating unit 12 for calculating the angular velocity, angular velocity phase angle calculating unit 13 for calculating the rotational angular velocity ω of the dq coordinate axis and the phase angle θ of the voltage command vector on the dq coordinate axis from the sliding angular velocity and the motor rotational angular velocity ωr, an adder The three-phase signals converted by the dq-axis three-phase coordinate converter 14 and the dq-axis three-phase coordinate converter 14 that convert the voltage command value on the dq-axis coordinate system of the inverter 2 that is the output of 11D and 11Q into a three-phase alternating current. And a pulse generator 15 for controlling the inverter 2 by generating a gate pulse so that the output voltage of the inverter 2 matches the voltage command value. In the three-phase dq-axis coordinate converter 8 and the dq-axis three-phase coordinate converter 14 which are coordinate conversion units, the coordinate conversion is performed using the phase angle θ calculated by the angular velocity phase angle calculation unit 13. Moreover, the voltage calculation part 10 calculates a voltage also using angular velocity (omega).

  The part used when calculating the voltage command value in a feed forward manner when the alternating current of the inverter 2 cannot be measured is as follows. The current measuring device abnormality detecting unit 16 that monitors the current measured by the current measuring devices 5a to 5c and detects an abnormality, and the output signal CS of the current measuring device abnormality detecting unit 16 determines the current for each of the d axis and the q axis. Switches 17D and 17Q for switching whether to input the output of the feedback control unit 9 to the adders 11D and 11Q are added. Here, the switches 17D and 17Q are for switching between the output of the current feedback control unit 9 and the zero signal. Further, when the output signal CS of the current measuring device abnormality detecting unit 16 is also input to the voltage calculating unit 10 and the current measuring device abnormality detecting unit 16 detects an abnormality, the voltage calculating unit 10 changes the output.

  The inverter 2 is a voltage-type three-phase PWM inverter, which is a known technique, but a switching element having a self-protection function against overcurrent is applied as a built-in switching element. The switching element having a self-protection function is, for example, an intelligent power module (IPM) or a power module combined with a gate driver having an overcurrent protection function. A switching element with a self-protection function against overcurrent is detected automatically by a measurement circuit built in the switching element when an overcurrent flows due to a short circuit or ground fault of the motor 1 or wiring. After the switching operation is turned off, it has a function of notifying the external system (corresponding to the inverter control unit 4 in the present invention) and does not pass through the current measuring devices 5a to 5c and the inverter control unit 4 at high speed. A protection operation against current is possible.

Next, the operation will be described. The current command value calculation unit 7 calculates the q-axis (in the following equations (1) and (2) from the torque command value Tm *, the secondary magnetic flux command value Φ2 *, and the circuit constants of the motor 1 that are input from an external system. Torque) Current command value Iq * and d-axis (excitation) current command value Id * are calculated. The differential operator is expressed by p.
Iq * = (Tm * / (Φ2 * × PP)) × (L2 / M) (1)
Id * = Φ2 * / M + L2 / (M × R2) × pΦ2 * (2)

Here, the following is used as the circuit constant of the induction motor. M: Mutual inductance value. l1: Primary leakage inductance value. L1: Primary self-inductance value. L1 = M + l1 is established. l2: Secondary leakage inductance value. L2: Secondary self-inductance value. L2 = M + l2 holds. σ: leakage coefficient. σ = 1−M ² / (L1 × L2). R1: Primary resistance value. R2: Secondary resistance value. PP: Number of pole pairs.

The slip angular velocity calculation unit 12 calculates a slip angular velocity command value ωs * to be generated by the motor 1 from the following equation (3) from the d-axis current command value Id *, the q-axis current command value Iq * and the circuit constants of the motor 1. Calculate.
ωs * = (Iq * / Id *) × (R2 / L2) (3)

The slip angular velocity command value ωs * calculated by the equation (3) and the motor rotation angular velocity ωr that is the output of the rotation sensor 6 attached to the shaft end of the motor 1 are input to the angular velocity phase angle calculation unit 13, and Thus, the inverter angular velocity ω and the phase angle θ, which are the angular velocities of the AC voltage output from the inverter 2, are calculated.
The slip angular velocity is a difference between the rotational angular velocity of the secondary magnetic flux (same as the inverter angular velocity ω) and the motor rotational angular velocity ωr, and the following holds.
ω = ωs * + ωr (4)
Since the phase angle θ is obtained by integrating the angular velocity ω, the following holds. The phase angle θ is based on the U phase.
θ = ∫ωdt (5)

In the three-phase dq-axis coordinate converter 8, the q-axis on the dq-coordinate that calculates the U-phase current Iu, the V-phase current Iv, and the W-phase current Iw measured by the current measuring devices 5a to 5c by the following equation (6). Conversion into current Iq and d-axis current Id.

The current feedback control unit 9 performs proportional-integral control with the same gain on the deviation between the command value and the measured value independently on the q-axis and the d-axis. The d-axis control amount ΔId0 and the q-axis control amount ΔIq0, which are outputs of the current feedback control unit 9, are expressed by the following equations (7) and (8). Here, K1 is a proportional gain, and K2 is an integral gain.
ΔIq0 = (K1 + K2 / p) × (Iq * −Iq) (7)
ΔId0 = (K1 + K2 / p) × (Id * −Id) (8)
Note that the control operation of the vector control using the current feedback control unit 9 is the same as the known vector control, and a detailed description thereof is omitted.

The current measuring device abnormality detection unit 16 monitors the current of each phase and detects whether or not an abnormal state such as an unstable or fixed current value occurs for each phase. When there is even one phase that is not normal, the current measuring device abnormality detection unit 16 outputs an abnormality as the output signal CS, and outputs normal when all phases are normal.
Since the sum of the three-phase alternating currents becomes zero, if the number of abnormal phases is one in the current measuring devices 5a to 5c, the current of the abnormal phase is calculated from the currents of the other phases. For example, a case where the number of abnormal phases is two or more may be determined as abnormal.

When the output signal CS of the current measuring device abnormality detection unit 16 is normal, the switches 17D and 17Q output the d-axis and q-axis outputs of the current feedback control unit 9 to the adders 11D and 11Q, respectively. The output of the switch 17D is called a d-axis voltage compensation value and is expressed by a variable de. Similarly, the output of the switch 17Q is a q-axis voltage compensation value qe. If the signal CS is abnormal, the switches 17D and 17Q output a zero signal to the adders 11D and 11Q.
In summary, the switches 17D and 17Q switch between the d-axis voltage compensation value de and the q-axis voltage compensation value qe as follows.
(When current meter is normal)
qe = ΔIq0 (9-1)
de = ΔId0 (10-1)
(When the current meter is abnormal)
qe = 0 (9-2)
de = 0 (10-2)
Note that the q-axis voltage compensation value qe and the d-axis voltage compensation value de can be instantaneously zeroed, but in order to reduce the torque fluctuation at this time, it is more preferable to provide a function of gradually narrowing to zero. desirable.

The voltage calculation unit 10 calculates the q-axis feedforward voltage Eq * and the d-axis feedforward voltage Ed * by switching between the following two calculation formulas according to the output signal CS from the current measuring device abnormality detection unit 16. And output.
(When current meter is normal)
Eq * = ω × L1 × σ × Id * + (ω × M) / (L2 × Φ2 *) (11-1)
Ed * = − ω × L1 × σ × Iq * + (M / L2) × pΦ2 * (12-1)
(When the current meter is abnormal)
Eq * = (pL1 × σ + R1) × Iq *
+ Ω × L1 × σ × Id * + (ω × M) / (L2 × Φ2) (11-2)
Ed * = (pL1 × σ + R1) × Id *
−ω × L1 × σ × Iq * + (M / L2) × pΦ2 (12-2)

  Expressions (12-2) and (11-2) when the current measuring instrument is abnormal are the output voltages in the dq coordinate system of the inverter 2 necessary for supplying the current command values Id * and Iq * to the motor 1. Means. By doing so, the current feedback control is stopped when the current measuring instrument is abnormal, but the vector control can be performed in a feedforward manner to drive the electric motor 1.

Here, the difference between the right side of equation (11-2) and the right side of (11-1) is expressed by a variable ΔEq *, and the difference between the right side of equation (12-2) and the right side of (12-1) is expressed as When expressed by the variable ΔEd *, it is as follows.
ΔEq * = (pL1 × σ + R1) × Iq * (13)
ΔEd * = (pL1 × σ + R1) × Id * (14)
Expressions (13) and (14) mean that the difference in the output of the voltage calculation unit 10 between when the current measuring instrument is normal and when it is abnormal corresponds to a voltage drop in the primary side circuit of the electric motor 1. To do.

When the current measuring instrument is normal and the current feedback control unit 9 is operating, the current feedback control unit 9 shares ΔEq * and ΔEd *. That is, the following formula is established. Here, the symbol “≈” means that the values coincide when there is no disturbance, control error, or current command value fluctuation, and that the difference is small even when there is a disturbance.
ΔIq0≈ΔEq * (15)
ΔId0≈ΔEd * (16)

  As shown in the equations (13) and (14), ΔEq * is determined only from the current command value Iq *, and ΔEd * is determined only from the current command value Id *. Can be separated and controlled in principle. Therefore, the current feedback control unit 9 performs proportional-integral control on the deviation between the command value and the measured value independently on the d-axis and the q-axis. The proportional gain K1 and the integral gain K2 in the equations (7) and (8) are appropriately set in consideration of the magnitude of the voltage component shared and compensated by the current feedback control unit 9 and the response characteristics to be realized. The voltage component that is shared and compensated by the current feedback control unit 9 is the sum of a term determined by the current command value Iq * and a constant term (may be omitted), and the d-axis represents the current command value Id *. As long as the sum of the term determined by (1) and a constant term (which may be omitted) may be calculated by a formula different from formulas (13) and (14).

The outputs of the adders 11D and 11Q are voltage command values Vd * and Vq *, respectively. The adder 11D takes the sum of the output for the d-axis of the voltage calculation unit 10 and the output of the switch 17D, and the adder 11Q takes the sum of the output for the q-axis of the voltage calculation unit 10 and the output of the switch 17Q. Vq * and Vd * are calculated by the following equations.
Vq * = Eq * + qe (17)
Vd * = Ed * + de (18)

  The voltage command values Vq * and Vd * are converted into three-phase voltage command values Vu *, Vv * and Vw * by the dq-axis three-phase coordinate converter 14 and input to the pulse generator 15. The pulse generator 15 controls the inverter 2 by generating a gate pulse based on the three-phase voltage command value so that the output voltage of the inverter 2 matches the voltage command value.

  The effect by the operation | movement demonstrated as mentioned above is shown by the simulation result at the time of changing torque command value Tm * of an electric motor in steps. FIG. 2 shows simulation results of the torque command value Tm *, the torque Tm of the electric motor 1 and the rotor frequency FM of the electric motor 1 when the current measuring instrument abnormality detecting unit 16 in the configuration of the first embodiment determines normal. FIG. FIG. 3 shows simulation results of the torque command value Tm *, the torque Tm of the electric motor 1 and the rotor frequency FM of the electric motor 1 when the current measuring instrument abnormality detecting unit 16 in the configuration of the first embodiment makes an abnormality determination. FIG. The rotor frequency FM has a relationship of FM = ωr / 2π with the rotational angular velocity ωr.

Comparing FIG. 2 and FIG. 3, even in FIG. 3 when current cannot be measured and the current feedback control is stopped, control similar to FIG. 2 when current feedback control is operating is possible. I understand that.
In FIG. 3, since the signals of the current measuring devices 5a to 5c are not used for control, when the torque command value Tm * is started (near t = 0.8 s), the torque Tm of the electric motor 1 is the torque command value Tm *. The rise time constant is about 30 ms, which is about 1/10 of several hundred ms, which is a time constant that can be generally realized by V / F control, and a high-speed response is obtained. I understand that This is because the V / F control does not consider the secondary magnetic flux to be constant, and it takes several hundreds of milliseconds until the secondary magnetic flux settles constant.
In the steady state (t = 1.5 s or later), the torque Tm of the electric motor 1 has a slight error from the torque command value Tm *, but there is no practical problem, and the rotor frequency FM of the electric motor 1 is linear. It is increasing and it can be seen that it can be accelerated stably.

  Furthermore, since the switching element built in the inverter 2 is a switching element having a self-protection function against overcurrent, this is detected when an overcurrent flows due to a short circuit or ground fault of the motor 1 or wiring. Thus, the switching operation can be automatically turned off. For this reason, even when the signals from the current measuring devices 5a to 5c cannot be used, the inverter 2 can be protected and stopped, and the inverter 2 is not damaged.

By stopping the current feedback control, it becomes impossible to compensate for a control error caused by an ON voltage of the switching element of the inverter 2 or an error in switching timing. Therefore, the torque Tm generated by the electric motor 1 is slightly different from the torque command value Tm *. Although an error occurs, the operation of the electric motor 1 can be continued even when the current cannot be measured correctly, and the situation where the power conversion device 40 stops can be avoided.
Even when the current feedback control is stopped, since the vector control is performed in a feedforward manner from the output signals of the slip angular velocity calculation unit 12 and the voltage calculation unit 10, the control performance of the torque Tm generated by the motor 1 is conventionally Better than the example. The reason for this is that even in feedforward vector control, the slip angular velocity at which vector control conditions (conditions for matching the d-axis with the secondary magnetic flux axis) are established from the d-axis current command value Id * and the q-axis current command value Iq *. The command value ωs * is calculated by the slip angular velocity calculation unit 12, and then, the d-axis feedforward voltage Ed * and the q-axis feedforward voltage Eq * can be applied to the motor 1, and the applied voltage amplitude to the motor 1 is determined. This is because the phase can be controlled on an instantaneous value basis.

As described above, according to the configuration of the first embodiment of the present invention, regarding the power conversion device that can drive the electric motor in a state where the current measuring device fails and the measurement signal cannot be used, additional parts and The generated torque can be controlled more accurately and at a higher speed than the conventional example without increasing the cost, increasing the scale of software and hardware, and without using the signal of the current measuring instrument.
In addition, in an electric railway system that drives an electric vehicle with an electric motor, even if the signal from the current measuring instrument cannot be used due to a failure of the current measuring instrument, the electric motor can be operated with practically sufficient performance. It is possible to avoid a situation where the vehicle is stuck on the track, and a stable railway system can be configured.
When the inverter drives a synchronous motor, the synchronous motor rotates in synchronization with the power supply frequency, and the torque is determined by the phase difference between the rotating magnetic field and the applied voltage, so the rotation sensor measures the phase angle of the synchronous motor. become. The rotation speed and phase angle are called a rotation state.

Note that the configurations shown in the above embodiments are examples of the contents of the present invention, and can be combined with other known techniques, and a part thereof is omitted without departing from the gist of the present invention. It is also possible to configure by changing.
Furthermore, in the present specification, the description of the invention is carried out in consideration of the power conversion device to the electric railway field, but the application field is not limited to this, and various types of vehicles such as automobiles, elevators, electric power systems, etc. Application to related fields is possible.

The power conversion device according to the present invention includes an inverter that drives an induction motor with three-phase alternating current, a current measuring instrument that measures the alternating current of the inverter for each phase, a rotation sensor that measures the rotational state of the induction motor, Based on a command value input from the outside, the voltage command value of the inverter is obtained as a voltage vector in a rotating coordinate system by a d-axis coinciding with the secondary magnetic flux axis of the induction motor and a q-axis orthogonal thereto. An inverter control unit that controls the inverter to output an AC voltage that matches the command value, and the inverter control unit uses the measurement value of the rotation sensor to coordinate between the rotating coordinate system and the three phases. A coordinate conversion unit that performs conversion, and a current command value calculation that calculates a current command value that is a current command value to be output from the inverter based on a command value input from the outside A slip angular velocity calculating section always calculated using the circuit constants of the slip angular velocity as the d-axis coincides the current command value and the induction motor secondary flux axis of the induction motor, measured by the current measuring device A current feedback control unit for controlling the difference between the measured current value and the current command value to be small, and a voltage at which the sum of the output of the current feedback control unit and the voltage command value becomes the circuit constant of the induction motor And a voltage calculation unit that calculates using the current command value, and a pulse generation unit that generates a gate pulse that controls the inverter so as to output the voltage command value . The voltage calculation unit calculates a voltage such that the inverter outputs a current equal to the current command value based on a circuit constant, and outputs the voltage calculation unit to the voltage command. It is characterized in that a.

The power conversion device according to the present invention includes an inverter that drives an induction motor with three-phase alternating current, a current measuring instrument that measures the alternating current of the inverter for each phase, a rotation sensor that measures the rotational state of the induction motor, Based on a command value input from the outside, the voltage command value of the inverter is obtained as a voltage vector in a rotating coordinate system by a d-axis coinciding with the secondary magnetic flux axis of the induction motor and a q-axis orthogonal thereto. An inverter control unit that controls the inverter to output an AC voltage that matches the command value, and the inverter control unit uses the measurement value of the rotation sensor to coordinate between the rotating coordinate system and the three phases. A coordinate conversion unit that performs conversion, and a current command value calculation that calculates a current command value that is a current command value to be output from the inverter based on a command value input from the outside A slip angular velocity calculating section always calculated using the circuit constants of the slip angular velocity as the d-axis coincides the current command value and the induction motor secondary flux axis of the induction motor, measured by the current measuring device A current feedback control unit for controlling the difference between the measured current value and the current command value to be small, and a voltage at which the sum of the output of the current feedback control unit and the voltage command value becomes the circuit constant of the induction motor And a voltage calculation unit that calculates using the current command value, and a pulse generation unit that generates a gate pulse that controls the inverter so as to output the voltage command value . The voltage calculation unit calculates a voltage such that the inverter outputs a current equal to the current command value based on a circuit constant, and outputs the voltage calculation unit to the voltage command. Because they are characterized by a, even when the measured value of the current of the inverter, which is measured by the current measuring device is not used, a feed forward manner can drive the electric motor implemented vector control, torque accurately than conventional There is an effect of being controllable.

Claims (6)

An inverter that drives an electric motor with three-phase alternating current;
A current measuring device for measuring the alternating current of the inverter for each phase;
A rotation sensor for measuring a rotation state of the electric motor;
An inverter that controls the inverter so as to obtain the voltage command value of the inverter in a rotating coordinate system that is a rotating orthogonal coordinate system based on a command value input from the outside, and to output an AC voltage that matches the voltage command value A control unit,
The inverter control unit should output a coordinate conversion unit that performs coordinate conversion between the rotating coordinate system and three phases using the measurement value of the rotation sensor, and the inverter based on a command value input from the outside A current command value calculation unit that calculates a current command value that is a current command value; a current feedback control unit that controls the difference between the current measurement value measured by the current measuring instrument and the current command value; A voltage calculation unit that calculates a voltage that is the sum of the output of the current feedback control unit and the voltage command value using the circuit constant of the motor and the current command value, and the inverter to output the voltage command value Having a pulse generator for generating a gate pulse to be controlled;
The voltage calculation unit outputs the voltage command value such that the inverter outputs a current equal to the current command value based on a circuit constant of the motor under a predetermined condition. The power converter characterized by calculating. A current measuring device abnormality detection unit that monitors whether the current measuring device can measure current normally,
The power converter according to claim 1, wherein the predetermined condition is satisfied when the number of the current measuring devices that cannot normally measure the current is equal to or greater than a predetermined number. The power conversion device according to claim 1, wherein the switching elements constituting the inverter have a self-protection function against overcurrent. The inverter control unit includes a switch that switches and outputs the output of the current feedback control unit and a zero signal, and an adder that adds the output of the switch and the output of the voltage calculation unit to obtain the voltage command value. The power converter according to claim 1, comprising: The electric motor is an induction motor, one axis of the rotational coordinate system is matched with a secondary magnetic flux axis, a torque command value and a secondary magnetic flux command value are input from the outside,
The power converter according to claim 1, wherein the inverter control unit includes a slip angular velocity calculation unit that calculates a slip angular velocity command value from the current command value. The power converter according to claim 1, wherein the current feedback control unit performs feedback control by sharing a voltage drop on a primary side of the electric motor.

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