JP2000341981A - AC motor control device - Google Patents

Abstract

(57) [Problem] To control a harmonic current flowing out to a power receiving side in a motor control device including a capacitor input type inverter, and to prevent damage due to exceeding a withstand voltage of a device when regenerative power is generated from the motor. Prevent voltage rise. A capacitor connected to the DC side of a rectifier, an inverter that uses the capacitor as a voltage source to convert power into a variable frequency and feeds the power to an AC motor, a first chopper that controls a power supply current in a sine wave shape, A second chopper for controlling regenerative electric power processing from the electric motor, wherein the first or second chopper is controlled in accordance with the power running or the regenerative state of the electric motor, or the voltage across the capacitor is set to the first chopper. The control is performed by setting the second chopper higher than that of the second chopper.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a series configuration of a rectifier, a capacitor and an inverter, a first chopper connected between the rectifier and the capacitor for controlling inflow power, and also for controlling a process of regenerative power from the motor. The present invention relates to an improvement in a control device for an AC motor including a second chopper.

[0002]

2. Description of the Related Art As a control device of a motor, a control device having a configuration in which a diode rectifier and a capacitor are connected to a power receiving power source side and an inverter using a switchable control element is connected to an output side thereof has been widely used.

Although such a control device has a simple structure,
The power supply current contains many harmonic components. In other words, current flows from the power receiving power supply to the capacitor only during the period when the instantaneous value of the power supply voltage is higher than the voltage of the smoothing capacitor, and this current is a charging current of the capacitor, becomes a steep current with a narrow conduction width, and includes many harmonic components. . Therefore, when the number of such devices increases, an excessive current flows through the phase-advancing capacitor inserted into the power supply system due to the harmonic current, and the power transformer may increase in core loss and heat up. In addition, since this current distorts the power supply voltage wave, there is a possibility of adversely affecting devices connected to the system.

In order to reduce harmonics contained in the power supply current, Japanese Patent Laid-Open Publication No. Hei 8-168250 discloses a first step-up chopper called a step-up chopper in which a reactor, a control element, and a diode are combined after a rectifier constituting an inverter. A control device provided with a chopper is disclosed.

The publication also discloses a motor control device in which a resistor that consumes regenerative power from the motor and a second chopper for controlling the regenerative power processing are added between the diode rectifier and the inverter. .

[0006]

The above prior art has both a function of reducing harmonics contained in the power supply current and a function of controlling the processing of the regenerative electric power from the electric motor. Not.

That is, the first chopper has a function of boosting the DC voltage across the capacitor in order to reduce harmonics included in the power supply current, while the second chopper has a function of increasing the regenerative energy from the motor. It has a function to reduce the DC voltage at both ends. As described above, since the two choppers have opposing functions, a problem that energy from the power supply side is consumed by the regenerative power processing resistor may occur.

An object of the present invention is to provide a control device for an AC motor capable of smoothly controlling the first and second chopper means.

[0009]

SUMMARY OF THE INVENTION In one aspect, the present invention provides a capacitor connected to the DC side of a rectifier, an inverter that converts the capacitor to a variable frequency power using a voltage source to supply power to an AC motor, and an AC power supply. In a control device for an AC motor including a first chopper for controlling a power supply current from the motor in a sine wave shape and a second chopper for controlling a process of regenerative power from the motor, a DC voltage applied to the capacitor is controlled by a first chopper. Means for controlling the first chopper so that the voltage of the first chopper becomes equal to the voltage of the second chopper, and means for controlling the second chopper so that the DC voltage applied to the capacitor becomes a second voltage higher than the first voltage. Is provided.

Means for detecting the operating state of the electric motor are provided. If the result is a powering state, the first chopper is controlled. If the result is a regenerative state, the second chopper is controlled.

Further, there is provided means for calculating the electric power of the motor from the torque command signal by the speed control means of the electric motor and the rotation speed signal of the electric motor. When the electric power calculation result indicates the power running state of the electric motor, the first operation is performed. Control the chopper,
On the other hand, when the regeneration state is indicated, the voltage across the capacitor is controlled by the second chopper.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a control device for an AC motor according to the present invention will be described below with reference to FIG. In FIG. 1, reference numeral 1 denotes an AC power supply. A rectifier 2 rectifies the voltage of the AC power supply to obtain a rectified voltage, and is composed of a diode 21 having a bridge configuration. 3 is a capacitor for smoothing the rectified voltage of the rectifier. Reference numeral 4 denotes a PWM (pulse width modulation) inverter, which includes a control element 41 such as an IGBT (insulated gate bipolar transistor) and a diode. A component device including the AC power supply 1, the rectifier 2, the capacitor 3, and the inverter 4 is generally called a capacitor
It is called an input type inverter.

An AC motor 5 is supplied with variable frequency AC power converted by the PWM inverter 4 using the voltage of the capacitor 3 as a power source and driven. Reference numeral 6 denotes a speed detector for detecting the rotation speed of the electric motor 5.

Reference numerals 71 to 74 denote loads connected to the electric motor 5, and an example of the load is an elevator mechanism in which the electric motor 5 generates power and generates regenerative electric power. In the elevator mechanism, 71 is a sheave connected to the electric motor 5,
A car 72 and a counterweight 73 are suspended from the sheave via a rope 74.

Reference numerals 8 and 9 denote circuit elements which are the main points of the present invention.
Reference numeral 8 denotes a boost chopper (first chopper) that includes a reactor 81, a control element 82, and a diode 83, and controls a power supply current in a sine wave shape during power running. Reference numeral 9 denotes a resistor 91 and a control element 9.
2 is a step-down chopper (second chopper) for controlling regenerative electric power processing from the electric motor 5.

Reference numeral 10 denotes a current detector for detecting a current flowing to the AC power supply 1, and 11 denotes a current detector for detecting a current flowing to the motor 5.

Hereinafter, reference numerals 100 to 109 denote respective control means for driving the first chopper 8, the second chopper 9 and the PWM inverter 4 as block diagrams.
The control means will be described below.

Reference numeral 100 denotes a DC voltage command generating means for instructing a set value of the DC voltage of the capacitor 3. The command value E _d1 * is controlled by the first chopper 8 and the command value E _d2 * is controlled by the second chopper 9. Indicates the value.

[0019] 101 to 107 represents a control means for driving the first chopper 8, 101 voltage detecting means for detecting a DC voltage E _d of the capacitor 3, 102 DC voltage E _d is the DC voltage of the capacitor 3 A voltage control means for performing a compensation operation so as to obtain a voltage based on the command E _d1 *.
It instructs the amplitude value I _s * of the current i _s to flow to the input side of the.

Reference numeral 103 denotes a multiplier; 104, voltage phase detecting means for generating a unit sine wave | sinωt | of a voltage waveform rectified in phase with the AC power supply 1; 105, a voltage e _c to be generated by the first chopper 8 * the current control means for instructing the carrier wave generating means 106, 107 the carrier signal according to the voltage command e _c * and the carrier wave generating unit 106 by the current control means e _t *
And PWM pulse generating means for generating a PWM pulse for driving the first chopper 8 from the above.

Reference numeral 108 denotes pulse generation means for driving the second chopper 9, and reference numeral 109 denotes inverter control means for driving the PWM inverter 4.

The control device for the electric motor is composed of the above-mentioned circuit elements and control means.

Next, the operation of the motor control device shown in FIG. 1 will be described with reference to FIGS. First, the motor 5
The speed of the elevator exemplified as the load is controlled by the electric motor 5, the inverter 4 and the inverter control means 109 so that the car 72 has the acceleration α having the characteristic shown in FIG.

The elevator is designed to be balanced with the counterweight 73 when approximately half of the passengers are on the car 72, and FIG. shows the characteristic of torque T _m and the power P _m of the motor in the case where the torque-increasing operation by carrying more passengers.

As can be seen from the figure, the motor is in a mode in which a power running torque (positive area) is generated during acceleration and constant speed running, and a regenerative torque (negative area) is generated from the start of deceleration to immediately before the stop. Therefore, power is supplied from the AC power supply 1 to the motor 5 via the control device (positive region) during a period in which power running torque is required, and power is supplied from the motor 5 to the control device during a period in which regenerative torque is generated. (Negative region).

Under such conditions, the control device having the configuration shown in FIG. 1 operates as follows. First, when an activation of the elevator is instructed (not shown), the DC voltage command generating means 100 causes the peak value E _SP (= √2 · E) of the AC power supply 1 to be obtained.
_S, E _S; supply voltage effective value) than the high DC voltage is set to a value command E _d1 *, emits E _d2 *. Among them, the voltage command E _d1 *
The first chopper 8, the other of the voltage command E _d2 * assigned as a command value for controlling the DC voltage applied to the capacitor 3 by the second chopper 9.

The relation between the command values is set in advance as E _SP <E _d1 * <E _d2 *.

In this state, assuming that the voltage applied to the capacitor 3 is initially charged to the peak value of the AC power supply 1,
The control system of the first chopper 8 operates as follows.

The voltage control means 102 receives the DC voltage command E _d1 *
Performs compensation calculation so that the voltage E _d of the capacitor 3 and a voltage feedback value becomes a voltage based on the DC voltage command E _d1 * and,
It emits a signal I _s * which instructs the amplitude value of the input current i _s to flow to the input side of the rectifier 2.

The amplitude signal I _s * and the voltage phase detecting means 10
Unit sine wave from 4 | sin .omega.t | calculated and in the multiplication means 103, to obtain an input current command i _s *, such as shown in the following equation.

[0031] _{i s * = I s * ·} | sinωt | the input current command i _s * controls the input current i _s sinusoidally, as a reference signal for adjusting the phase to the supply voltage.
This aspect is shown in FIG.

Next, the current control means 105 performs a compensation operation based on the input current command i _s * and the current feedback value.
(B-1), (b -2) a sinusoidal arc by the size of the power P _m required motor as shown in changes modulated signal e
emit _c *.

The PWM pulse generating means 107 compares the modulated wave signal e _c * with the carrier signal e _t *, and generates the following PWM pulse for driving the control element 82 of the first chopper 8.

[0034] e _c *> e by _t * pulse said pulse to turn off the pulse e _c * ≦ e _t * control element 82 when turning on the control element 82 when, during the on control element 82 is an AC power source 1
Rectifier 2-reactor 81-control element 82-rectifier 2-current flows through the route of AC power supply 1, and when it is off, current corresponding to the energy stored in the reactor is supplied to reactor 81-diode 83-capacitor 3, PWM inverter 4. -A current flows through the route of the rectifier 2-the AC power supply 1-the rectifier 2-the reactor 81. As a result, the input current i _s
3 involves a ripple of the frequency (= 1 / carrier signal period) accompanying the switching of the control element 82 as shown in FIG. 3, but has a substantially sinusoidal waveform.

The ripple is determined by the switching frequency and the inductance of the reactor 81, and can be set to a very small level by selecting a constant.

Therefore, as compared with the case where the input section is constituted only by a rectifier using a diode, the harmonic component is greatly reduced, and the power factor is greatly improved (almost 1.0) with the reduction of the harmonic. It becomes a waveform.

The above operation corresponds to t ₁ during the powering period shown in FIG.
Continued until As a result, (c), input current i _s as shown in (d) of FIG. 2 is made magnitude current control in accordance with the power P _m, the DC voltage E _d is constant control to the command value E _d1 * You.

On the other hand, the second chopper 9 during the powering period
Works as follows.

[0039] generating a pulse for driving the DC voltage command E _d2 * and a control device 92 compares the voltage feedback value E _d from DC voltage command generating means 100 in the pulse generating means 108 consisting of hysteresis comparator.

Here, assuming that the hysteresis value in the pulse generation means 108 is ΔE _d *, the control element 92 is turned on by a pulse E _d2 * −ΔE _d * ≧ E _d for turning on the control element 92 when E _d2 * ≦ E _d. A pulse is generated that turns off.

The DC voltage E _d of the capacitor 3 during the powering period
Is maintained as E _d = E _d1 * (; E _d1 * <E _d2 * −ΔE _d * <E _d2 *) by the first chopper 8 as described above. Therefore, during the powering period, the pulse generating means 108 continues to emit off-pulses.

As described above, during the powering period, the first chopper 8
While supplying from an AC power source 1 to the input current i _s sinusoidal in magnitude corresponding to the power to be supplied to the electric motor 5 by,
Controls to keep the DC voltage E _d of the capacitor 3 to the voltage command value E _d1 *. At this time, the control element 92 constituting the second chopper 9 operates to keep being turned off.

Next, the operation of the control device during the regeneration mode period will be described with reference to FIG.

At t ₁ immediately after the start of deceleration, the mode shifts from the powering mode to the regeneration mode. In the regenerative mode, the electric power generated by the motor is supplied to the capacitor 3 via the inverter 4 because the input of the control device is constituted by a rectifier.
It is supplied to raise the DC voltage E _d.

This voltage rise causes the DC voltage command E _d1 *
And when the relationship between the voltage feedback value E _d becomes E _d1 * <E _d, the voltage control unit 101 input current i to flow to the input side of the rectifier 2
Instructs the amplitude of _s to be zero. As a result, the control elements 82 that constitute the first chopper 8 by the subsequent control means
Operate to turn off.

Meanwhile, the DC voltage E _d is further increased by the regenerative power from the motor, exceeds the DC voltage command E _d2 * and _{(E d2 * ≦ E d)} , the pulse generating means 108 as previously described first The second chopper 9 generates an ON signal for the control element 92.

The energy stored in the regenerative power or capacitor 3 from the motor by turning on the control element 92 is consumed by the resistor 91, to lower the DC voltage E _d.

[0048] The voltage E _d is E _d2 * -ΔE _d * below (; E
_{d2 * -ΔE d * ≦ E d} ) becomes the pulse generating means 108 generates a clear signal to the control device 92 which constitutes the second chopper 9. Therefore, the DC voltage E _d starts to rise by regenerative power from again motor.

Thereafter, this operation is repeated during the regenerative mode, and the DC voltage E _d is maintained at E _d2 * −ΔE _d * ≦ E _d ≦ E _d2 *.

As a result, during the period in which the regenerative torque of the electric motor is generated, the regenerative electric power is processed in the apparatus, so that a voltage rise that exceeds the withstand voltage of the equipment and may cause damage is prevented.

Next, the operation after t _{3 when the} mode shifts from the regeneration mode to the powering mode will be described. In FIG. 2, at time t ₃ , the regenerative electric power from the electric motor disappears, and the electric power for generating the power running torque is supplied from the capacitor 3. Therefore, the DC voltage E _d of the capacitor starts to descend. At this time, the control element 92 keeps off.

On the other hand, until now (during the regeneration period), the input current i
Voltage control means 101 that instructed _s to be zero
E _{d 1} is the relationship between the voltage feedback value E _d and the DC voltage command E _d1 *
*> Becomes the E _d, performs compensation operation so that the voltage based on the DC voltage command E _d1 * emits an amplitude signal I _s * of the input current i _s.

[0053] Consequently, while again supplied from the first AC power supply a sinusoidal input current chopper 8 in a size corresponding to the power supplied to the electric motor, the voltage command value DC voltage E _d of the capacitor 3 E _d1 * Control to keep in.

As described above, the input current is controlled to be substantially sinusoidal during the power running period, and the regenerative electric power is processed in the apparatus during the regeneration period.

Therefore, harmonics are greatly reduced, and the power factor can be greatly improved (approximately 1.0) as the harmonics are reduced. Further, it is possible to prevent a voltage rise exceeding the breakdown voltage of the device.

In the above embodiment, two DC voltage control levels are provided so that the switching between the choppers can be performed smoothly. However, the DC voltage control level is set to one, and the power generated by the motor is reduced. Switching may be performed in response.

FIG. 5 shows that the operating state of the electric motor is determined by, for example, electric power,
13 shows another embodiment for switching the second chopper. 5, parts corresponding to those in FIG. 1 are denoted by the same reference numerals, and redundant description will be omitted.

Reference numerals 1091 to 1095 denote the configuration of the inverter control means 109 described above. 1091 is an elevator speed command generating means, 1092 is a car speed ω.
Speed control means for instructing the torque T _m * to be output by the electric motor 5 so that the (rotation angular velocity) follows the velocity command ω * (rotation angular velocity command). The 1093 converts the torque command T _m * into a motor current command. Current control means for calculating a voltage command for instructing a voltage to be output by the PWM inverter 4 from the current command and the feedback current;
Reference numeral 5 denotes a PWM pulse generating means of the PWM inverter 4.

Reference numeral 100 denotes a DC voltage command generating means, which outputs a DC voltage command in two levels in the embodiment shown in FIG. 1, but has one level in the present configuration.

Reference numeral 200 denotes a motor operating condition detecting means for judging a power running or a regenerative condition. In this embodiment, the electric power required for driving the elevator is calculated, and the electric power for generating the signal S1 for instructing the driving of the first chopper 8 or the signal S2 for instructing the driving of the second chopper 9 is calculated from the calculation result. It is an arithmetic means. Other elements are the same as those in FIG.

In the motor control device having the above-described structure, first, when an elevator start command (not shown) is issued, the speed command generating means 1091 causes the car 72 to move to the position shown in FIG.
The speed command ω * is issued so that the speed becomes as shown in FIG.
The speed control means 1092 calculates a torque command T _m * necessary for driving the elevator from the speed command ω * and the rotation speed ω of the electric motor, and converts the torque command T _m * into the current control means 10.
At 93, it is converted into a motor current command. Further, the current control means 1093 calculates a voltage command indicating a voltage to be output by the PWM inverter 4 from the current command and the feedback current. The PWM pulse generating means 1095 compares the voltage command with the carrier wave, and drives the PWM inverter 4 by PWM.
_{Emit a} pulse GPI.

As a result, electric power of a variable frequency is supplied to the motor using the DC voltage of the capacitor 3 as a voltage source, and the motor generates a driving torque. As a result, the elevator is operated so as to follow the speed command ω *.

During this time, the electric power calculating means (operating state detecting means) 200 outputs the torque command T _m * and the rotational speed ω of the electric motor.
The power P _m (= T _m * × ω *) necessary for driving is continuously calculated from the above. When the calculation result is P _m ≧ 0 (power running state), the first
A signal S1 for driving the chopper 8 is generated.
Then, the second chopper 9 is set in the suppressed state. When the calculation result is P _m <0 (regeneration state), the second chopper 9
Is generated, and the first chopper 8 is put into a suppressed state by the signal S2.

Thus, while controlling the DC voltage to the same level of DC voltage in accordance with the DC voltage command E _d * in both the power running and the regenerative states, the first voltage is maintained during the power running period, similarly to the operation described in the previous embodiment. The chopper 8 works to make the input current substantially sinusoidal, and the second chopper 9 works to process the regenerative power in the device during the regeneration period. During this time, the operation of the first and second choppers is switched smoothly.

Although the motor operating state detecting means determines the power running or the regenerative state from the torque command and the motor rotational speed, the operating state may be calculated from the motor voltage / current, power factor and the like.

[0066]

According to the present invention, stable control of an AC motor from power running to regeneration of the motor can be performed.

[Brief description of the drawings]

FIG. 1 is a block diagram of a motor control device according to an embodiment of the present invention.

FIG. 2 is an explanatory diagram of each chopper operation period of the present invention.

FIG. 3 is an explanatory diagram of the operation of the first chopper of the present invention.

FIG. 4 is an explanatory diagram of an operation of a second chopper according to the present invention.

FIG. 5 is a block diagram of a motor control device showing another embodiment of the present invention.

[Explanation of symbols]

1: AC power supply, 2: Rectifier, 3: Capacitor, 4: PW
M inverter, 5 ... AC motor, 8 ... first chopper,
9: second chopper, 100: DC voltage command generating means,
E _d1 *: voltage command of the first chopper, 102: voltage control means of the first chopper, 108: pulse generation means (control means) of the second chopper, E _d2 *: voltage command of the second chopper,
109 ... Inverter control means, 200 ... Power calculation means (motor operation state detection means), 1092 ... Speed control means, _Tm * ... Torque command, ω ... Speed (rotation angular speed).

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Hiroshi Nagase 1070 Ma, Hitachinaka City, Ibaraki Prefecture Inside Mito Plant, Hitachi, Ltd. (72) Inventor Naoto Onuma 1070 Ma, Hitachinaka City, Ibaraki Prefecture Hitachi, Ltd. Inside the Mito Plant (72) Inventor Toshiki Kajiyama 1070 Ma, Hitachinaka-shi, Ibaraki Prefecture Inside the Mito Plant, Hitachi, Ltd. F-term (reference) 5H007 AA17 BB06 CA01 CB02 CB05 CC12 CC23 DA05 DA06 DC01 DC02 DC03 DC05 EA15 FA01 FA13 FA18 5H576 AA07 BB06 CC05 DD02 DD04 EE11 GG02 GG04 GG05 HA04 HB02 JJ09 JJ29 KK28 LL28 LL22 LL22 LL22 LL22 LL22

Claims (3)

[Claims] 1. A rectifier for rectifying AC power, a capacitor connected to the DC side of the rectifier, an inverter for converting DC power of the capacitor into AC power of a variable voltage and a variable frequency, and an output power of the inverter. Motor, a first chopper connected between the rectifier and the capacitor to control a current flowing into the rectifier, and a regenerative power from the motor connected between the rectifier and the capacitor. A control device for an electric motor, comprising: a second chopper for controlling a process; a means for controlling the first chopper so that a DC voltage applied to the capacitor becomes a first voltage; AC means for controlling the second chopper so that the DC voltage becomes a second voltage higher than the first voltage. Motor control device. 2. A rectifier for rectifying AC power, a capacitor connected to the DC side of the rectifier, an inverter for converting DC power of the capacitor into AC power of a variable voltage and a variable frequency, and an output side of the inverter. An AC motor connected to the rectifier, the first chopper connected between the rectifier and the capacitor, and controlling the power flowing through the rectifier so that the voltage across the capacitor becomes a predetermined value; and A second chopper that is connected between the capacitor and the capacitor and controls regenerative power from the motor so that a voltage between both ends of the capacitor becomes a predetermined value, wherein an operation state of the motor is detected. Means for controlling the first chopper when the detection result indicates that the motor is in a power running state; A control device for an AC motor, further comprising means for controlling the second chopper when in a state. 3. A rectifier for rectifying an AC power supply and outputting a rectified voltage, a capacitor connected to a DC output of the rectifier, and converting the AC motor into a variable frequency power using the capacitor as a voltage source. An inverter to drive,
A first chopper for controlling a power supply current of the AC power supply in a sine wave shape, a second chopper for controlling regenerative electric power processing from the motor, and a speed control unit for generating a torque command for the motor. In the control device, a unit that determines a power running or a regenerative state of the motor from a signal related to the torque command and a signal related to the rotation speed of the motor, and controls the first chopper when the motor is in a power running state. And a control unit for controlling the second chopper when the motor is in a regenerative state.