JPH07298670A - A.c. variable speed driving gear - Google Patents

Abstract

PURPOSE:To reduce torque ripples and enable the elimination of the tortional vibration of axes and noises, by using for excitation a brushless exciter that obtains variable direct current from a diode rectifier connected with the secondary terminal of a rotary transformer and feeds field current, and further varying the input voltage of the exciter. CONSTITUTION:The voltage of a generator 2 is determined according to the speed of a motor 4. The voltage of the generator 2 is set based on the voltage required for the motor 4 with a slight bias component allowed; the bias component is used as a control margin for controlling phase delay. In general, the voltage control for motors 2 delivers poor responsivity due to the control of the armature of the motor 4. Therefore, transient control response is performed by thyristor phase control on the armature side and a thyristor a.c. switch 20 on the field system side. This makes it possible to use control delay angles in the steady condition in regions with smaller ripples without degrading responsivity.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an AC variable speed drive system including a power converter such as an inverter, an AC motor and a generator.

[0002]

2. Description of the Related Art There are cases where it is desired to directly drive a rotating machine such as a fan or a pump by a prime mover such as a diesel engine depending on the situation of power supply. However, when it is desired to adjust the speed of a low-speed machine or a rotary machine, a variable speed drive device including a generator, a power conversion device, and an electric motor is used without directly driving a load machine by a prime mover.

An example of such a variable speed drive device is an electric propulsion system for a ship shown in FIG. That is, the prime mover 1 drives the generator 2 to generate AC power, and the power converter 3 converts the power to drive the electric motor 4 at a variable speed. A power converter for driving the electric motor 4 at a variable speed includes, for example, a load commutation inverter and a cycloconverter, and the semiconductor power converter 3 includes a load commutation inverter 31, a thyristor rectifier 32, and the like.
There is a thyristor motor system composed of a reactor 33. Further, as shown in FIG. 7, a cycloconverter is used as the power changing device.

These load commutation inverters and cycloconverters are suitable for low-speed mechanical drive because they have a large capacity and can output a low frequency with respect to the input frequency, and are controlled by the AC variable speed drive device 5 to drive the synchronous motor. It controls the primary frequency and the magnitude of the current. Here, 6 is a speed detector (SS), 13 is a voltage regulator, and 14 is a speed reference setting device.

On the other hand, the field of the synchronous motor is excited by a DC voltage to control the voltage of the motor. For example, there is a method of exciting a field by supplying a DC voltage to a rotor, which is a rotating body, by a slip ring and a brush provided on an electric motor shaft. This method is straightforward, and in order to change the exciting current, it is sufficient to control the applied DC voltage, which is simple and compact. In addition, according to such a configuration, unlike an AC variable speed drive system in which a general commercial power source is input, an electric propulsion system of a ship or a fluid machine drive of an ultra large capacity of several tens of MW or more has a machine arrangement. There are advantages such as the degree of freedom and the merit of self-sufficient power supply. However, the slip ring and brush had to be serviced, which was a major drawback.

A brushless exciter using a rotary transformer solves this drawback, and its configuration is shown in FIG. That is, the brushless exciter has the AC switch 2
0, a rotary transformer 21, a diode rectifier 22, and a field winding (FLD) 23 of the synchronous motor 1. A
The C switch 20 is provided with a circuit in which thyristors are anti-paralleled in each of the three phases, and the average voltage is controlled by firing control of the thyristors. The rotary transformer 21 is a winding type induction motor (W
It has the same structure as IM) and the primary side is AC switch 2
A voltage subjected to average voltage control is applied at 0, the secondary side is coaxial with the rotor of the synchronous engine 4, and is connected to the diode rectifier 22 which is also coaxial. The DC output voltage of the diode rectifier 22 is the field winding (F
LD) 23 is configured to pass a current.

[0007]

By the way, the speed and the voltage of the synchronous motor are in a proportional relationship, and there is a so-called V / f constant relationship. In addition, the synchronous motor increases in speed due to the armature reaction, and as the load increases, the field current,
Since the voltage also increases, it is necessary to output a small voltage in both the power converter that controls the armature of the electric motor and the brushless exciter that controls the field in the low speed region. However, since the thyristor rectifier and the thyristor AC switch both control the average voltage by firing phase control, the ripple voltage and current increase as the voltage decreases, so the ripple voltage and current increase as the motor speed decreases. As a result, the torque ripple becomes large, and problems such as shaft torsional vibration and noise occur.

The output voltage of the cycloconverter is
As shown in FIGS. 9A and 9B, the ripple includes 6 times the power supply voltage, and this ripple increases as the voltage of the motor decreases. This is because the cycloconverter is composed of a thyristor rectifier by controlling the ignition phase of the control delay angle α of the thyristor. That is, the firing phase angle is increased (the phase is narrowed) in order to reduce the output voltage. Therefore, as the motor speed becomes slower, the ripple voltage becomes larger, and as a result, the torque ripple becomes larger, causing problems such as shaft torsional vibration and noise. Such vibration noise becomes a serious problem when it is installed in a place near the human living environment such as a passenger ship, and quietness is required.

The present invention has been made to solve the above problems, and its purpose is to reduce the torque ripple generated in the low speed operation region of the electric motor, thereby eliminating the torsional vibration and noise of the shaft. The purpose is to supply a quiet AC variable speed drive device.

[0010]

In order to achieve the above-mentioned object, the first aspect of the present invention is to convert AC power generated by a generator driven by a prime mover into arbitrary AC power by a semiconductor power converter. Then, in the AC variable speed drive device that drives the synchronous motor at a variable speed, the output voltage of the generator has a proportional relationship with the operating frequency of the synchronous motor in the steady state excluding the transient state in which the speed is changing. The field of the synchronous motor is varied, and the primary voltage of the rotary transformer is varied by the ignition control of the AC switch, and the variable DC voltage is obtained by the diode rectifier connected to the secondary terminal of the rotary transformer to obtain the field current. Is used as a power source for the generator that excites a brushless exciter for flowing a current and varies the input voltage of the brushless exciter.

According to a second aspect of the present invention, there is provided an AC variable speed drive device for converting AC power generated by a generator driven by a prime mover into arbitrary AC power by a semiconductor power converter to control the AC motor at a variable speed. If the setting change of the speed command of the electric motor is an acceleration, the speed of the electric motor is accelerated to the set value after previously raising the voltage of the generator to the required voltage at the changed new speed command value, and When the setting change of the speed command of the electric motor is deceleration, the voltage of the generator is reduced to a voltage corresponding to the current speed after the electric motor speed is decelerated to the set speed.

According to a third aspect of the present invention, there is provided an AC variable speed drive device for converting AC power generated by a generator driven by a prime mover into arbitrary AC power by a semiconductor power converter to control the AC motor at a variable speed. If the speed command setting change of the electric motor is acceleration, the speed is changed after detecting the voltage settling.If the speed command setting change of the electric motor is deceleration, the voltage is reduced after the speed settling is detected. However, when the deceleration rate is such that the regenerative operation is further performed, the voltage setting in the deceleration direction is set to the maximum value in advance.

[0013]

In the present invention (corresponding to claim 1), when the output voltage Vo, the input voltage Va, and the control delay angle α are both the thyristor rectifier and the thyristor AC switch, the output voltage is represented by the equation (1). Vo = K · Va · cosα ··· (1) K is a constant. For example, in the case of a thyristor rectifier with a three-phase Glets connection, the coefficient is 1.35, which is the equation (2). Vo = 1.35 × Va × cos α (2) According to the above equation (2), since Va is constant at the commercial voltage, the control delay angle α is the delay direction (90) in order to reduce the voltage. The output becomes 0), and the ripple becomes larger as α becomes closer to the delay direction (90 °). This is the same for the field thyristor AC switch. The reason why the ripple component becomes large in the region where the voltage is low in both the armature and the field, that is, in the low speed region is that the output voltage control is performed only by the control delay angle α. Therefore, by controlling the generator voltage in proportion to the speed of the electric motor (2)
The value of α in the equation can be fixed to a value with less ripple.

As described above, except for the transient states of the electric motor and the field, the voltage and the speed are in a substantially proportional relationship, so that by supplying only the required voltage from the generator, the phase control of the thyristor is the state with the smallest ripple. You can drive at.

In the present invention (corresponding to claims 2 and 3),
The output voltage of the cycloconverter is the same as the thyristor rectifier, the voltage command coefficient K, the output voltage Vo, the output angular frequency ω.
The output voltage is expressed by equation (3), where o, generator voltage Va, and control delay angle α. Vo = K · sinωot ····· (3) The electric motor changes the voltage and frequency according to the speed, and Vo / fo
Operate while changing K so as to keep the ratio constant. (In the DC motor, sinωot = 1)

On the other hand, the expression (3) becomes the expression (4) when expressed by the phase control of the thyristor rectifier. Vo = 1.35 × Va × cos α (4) The following equation (5) is obtained from the equations (3) and (4). K · sin ωot = 1.35 × Va × cos α · (5) According to the above formula (5), since Va is constant at the commercial voltage, the control delay angle α is α cos ⁻¹ (K · sin
Since ωot) is controlled, K is reduced in order to reduce the voltage, and α is in the delay direction. The ripple becomes larger as α becomes closer to the delay direction (90 °). FIG. 9A shows a state in which the maximum voltage is output, and FIG. 9B shows a state in which half of the maximum voltage is output. Thus, the smaller the output voltage, the larger the ripple.

On the other hand, if Va can be varied, K
By controlling the generator voltage so that
The control delay angle α is α = cos ⁻¹ (sinωot) = ωo
It becomes t + 90 °, and it can be operated with less ripple. That is, it means that the vehicle can always be operated in the state of FIG.

However, when considering the voltage control of the electric motor, since there is one control target and two control systems, there are cases where stable control cannot be performed due to mutual interference. Further, since the responsiveness of the voltage control of the generator is slower than that of the thyristor phase control, the control response may be limited. Therefore, when controlling by both, it is necessary to give priority. That is, in the present invention, when the speed command of the electric motor is set in the speed increasing direction with respect to the current speed command, the voltage of the generator is increased to the required voltage at the changed new speed command value, and after the increase is completed. Accelerate the motor speed to the set value. Thus, the variable voltage of the generator does not change the speed of the electric motor, but the speed is changed after the generator voltage is set to a voltage corresponding to the target speed in advance. Therefore, the phase control of the thyristor controls the torque and speed response required for acceleration. Similarly, when the setting change of the speed command is deceleration, the voltage of the generator is reduced to the voltage corresponding to the current speed after decelerating the motor speed to the set speed.

When operated in this manner, the thyristor phase control can be used in the range with the smallest ripple, and stable operation can be achieved without interfering with the voltage control of the generator.

[0020]

Embodiments of the present invention will now be described with reference to the drawings. (First Embodiment) FIG. 1 is a block diagram of the first embodiment of the present invention. As shown in the figure, the prime mover 1 drives the generator 2 to generate AC power, and the power is converted by the semiconductor power converter 3 which is a load commutation inverter to drive the electric motor 4 at a variable speed. The electric motor 4 has a speed command 16 and a speed detector (SS) 6
The feedback signal from the speed operational amplifier (SC) 7
Then, the signal is transmitted to the current operational amplifier (CC) 8 by the comparison operation. The current operational amplifier 8 controls a current for receiving a torque command to generate a torque required for the electric motor, and generally constitutes a closed loop control system by current feedback, but it is omitted here. The next phase control circuit (PHC) 9 calculates the ignition timing of the thyristor in synchronization with the power supply and generates an ignition pulse. The load commutation inverter is self-controlled by the β control circuit 11 according to the position signal from the position sensor 10, but this is omitted here because it is a function of a general thyristor motor.

Further, the field of the electric motor 4 constitutes a brushless excitation device 24 having a current control function, an AC switch 20 in which a thyristor is connected in antiparallel is provided for each of the three phases, and ignition control of the thyristor is performed. The average voltage is controlled by and is applied to the primary side of the rotary transformer 21. The secondary side is coaxial with the rotor of the synchronous motor 4, and is connected to the diode rectifier 22 which is also coaxial. The DC output voltage of the diode rectifier 22 is the field winding 2 of the synchronous motor.
Apply current to 3. The voltage of the electric motor 4 is input to the voltage operational amplifier (VC) 12 by voltage feedback, further passes through the field current operational amplifier 8 and the AC switch phase control circuit (PHC) 9, and the AC of the brushless exciter 24 is supplied.
A field current is input to the switch 20, and thereafter, a field current is caused to flow through the field winding 23 of the synchronous motor via the rotary transformer 21 and the diode rectifier 22 as described above. The output voltage of the generator 2 is closed-group controlled by the voltage regulator 13. The speed command, the motor voltage command, and the generator voltage command are generated by the reference generator 14.

In the present embodiment constructed as described above, the voltage of the generator 2 is also determined according to the speed of the electric motor 4, and the relationship between the voltage of the electric motor and the voltage of the electric generator is proportional to that shown in FIG. Can be set to The voltage of the generator is set with a slight bias for the voltage required by the electric motor, which is used as a control margin for controlling the phase delay. Generally, the voltage control of the generator is slower in response than the armature control of the motor, so that the transient control response is controlled by the thyristor phase control on the armature side and the thyristor AC on the field side.
Since the switch responds, the control delay angle in the steady state can be used in the region of small ripple without impairing the responsiveness.

(Second Embodiment) FIG. 3 is a block diagram of the second embodiment of the present invention. As shown in the figure, the prime mover 1 drives the generator 2 to generate AC power, and the semiconductor power converter 3 converts the power to drive the electric motor 4 at a variable speed. The semiconductor power conversion device 3 is a cycloconverter and is controlled by the speed control device 5. The speed control device 5 compares and calculates the speed command signal and the feedback signal from the speed detector 6 of the electric motor 3 by the speed calculation amplifier (ASR) 7, and transmits the signal to the torque calculation control circuit (TC) 8a. The torque calculation control circuit 8a controls a current and a phase thereof for receiving a torque command and generating a torque required for the electric motor based on a vector control theory or the like. The next phase control circuit (PHC) 9 calculates the ignition timing of the thyristor in synchronization with the power supply and generates an ignition pulse. The above configuration is the same as the general AC variable speed drive system configuration.

The voltage of the generator 2 is closed-loop controlled by the voltage regulator 13 with the voltage command 15 as a target value. The voltage command 15 and the speed command 16 are generated by the reference setter 14. The speed setting signal 19 becomes a voltage command 15 and a speed command 16 through the hold circuit 17. Hold circuit 1
7 is operated by the timing circuit 18. The timing circuit 18 monitors the change of the speed setting signal 19, and the voltage command 15 is output without a time delay with respect to the change in the speed increasing direction, the speed command 16 is held as the current signal, and after the time delay, The hold is released and a new speed command signal is output. When the speed setting signal 19 changes in the deceleration direction, the voltage command 15 is held,
After a time delay, a new voltage command is output and speed command 1
6 is output without a time delay.

This situation is shown in FIG. That is, in FIG. 4, when the speed setting changes from 0 to 1 notch, the voltage of the generator immediately generates a voltage corresponding to 1 notch.
After that, the motor accelerates to the speed of one notch with a delay.
When the speed setting is changed to 2 notches, the generator voltage immediately produces a voltage corresponding to 2 notches. Then, with a delay, the motor accelerates to a speed of 2 notches. Similarly, when the speed setting changes from 2 notches to 1 notch, the electric motor decelerates to 1 notch speed, and after a delay, the generator voltage drops to 1 notch voltage. As described above, the generator voltage is high in the transient short-time region of the speed setting, but in the steady state, the generator can output the minimum voltage required by the electric motor.

(Other Embodiment) In the second embodiment, the time relationship between the voltage command and the speed command, that is, the hold time is a fixed time by a timer or the like. However, in the speed-up direction, after the voltage settling is detected. Change speed. Similarly, in the deceleration direction, it is also effective to reduce the voltage after detecting the speed settling to reduce the time.

Further, in deceleration, if the deceleration rate is such that regenerative operation is performed, an accident due to commutation failure may occur unless a necessary commutation voltage is secured. In such a system, in order to secure the commutation voltage. Generator voltage may require maximum voltage. This case can be dealt with by setting the voltage setting in the deceleration direction to the maximum value in advance as shown in FIG.

[0028]

As described above, according to the present invention,
By controlling the voltage of the generator according to the operating speed command, both the armature and the field of the motor can be operated with the smallest current ripple, and the torque ripple generated in the low speed operation range can be reduced. As a result, it is possible to supply a quiet variable speed drive device by solving the problem of torsional vibration of the shaft and reducing noise.

[Brief description of drawings]

FIG. 1 is a configuration diagram of a first embodiment of the present invention.

FIG. 2 is a characteristic diagram for explaining the operation of FIG.

FIG. 3 is a configuration diagram of a second embodiment of the present invention.

FIG. 4 is a diagram for explaining the operation of FIG.

FIG. 5 is a diagram for explaining an operation when the deceleration rate in FIG. 3 is large.

FIG. 6 is a configuration diagram of a thyristor motor system that is a variable speed drive device of an AC electric motor.

FIG. 7 is a configuration diagram of a conventional variable speed drive device.

FIG. 8 is a configuration diagram of a conventional brushless excitation device.

FIG. 9 is an output waveform diagram of the cycloconverter.

[Explanation of symbols]

1 ... motor, 2 ... generator, 3 ... electric power converter, 4 ... motor, 5 ... variable speed drive controller, 6 ... speed detector, 7 ... speed operational amplifier, 8 ... current operational amplifier, 8a ... torque arithmetic control Circuit, 9 ... Phase control circuit, 10 ... Position center, 11 ... β control circuit, 12 ... Voltage operational amplifier, 13 ...
Voltage regulator, 14 ... Speed reference setting device, 15 ... Voltage command,
16 ... Speed command, 17 ... Hold circuit, 18 ... Timing circuit, 19 ... Speed setting signal, 20 ... AC switch, 2
DESCRIPTION OF SYMBOLS 1 ... Rotation transformer, 22 ... Diode rectifier, 23 ... Field winding, 24 ... Brushless exciter, 31 ... Inverter, 32 ... Rectifier, 33 ... Reactor.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical indication H02P 9/14 F

Claims (3)

[Claims] 1. An AC variable speed drive device for converting an AC power generated by a generator driven by a prime mover into an arbitrary AC power by a semiconductor power conversion device to drive a synchronous motor at a variable speed. The output voltage is varied so as to have a proportional relationship with the operating frequency of the synchronous motor in the steady state except for the transient state where the speed is changing, and the field of the synchronous motor is rotated by the ignition control of the AC switch. The primary voltage is varied, a variable DC voltage is obtained by the diode rectifier connected to the secondary terminal of the rotary transformer, and a brushless exciter that causes a field current to flow is excited and the input voltage of the brushless exciter is varied. An AC variable speed drive device characterized by being used as a power source of the generator. 2. In an AC variable speed drive device for converting AC power generated by a generator driven by a prime mover into arbitrary AC power by a semiconductor power conversion device to control the AC motor at a variable speed, the speed of the electric motor. When the command setting is changed to speed up, the voltage of the generator is raised in advance to the required voltage at the changed new speed command value, and then the speed of the electric motor is accelerated to the set value. When the setting change of the command is deceleration, the AC variable speed drive device is characterized in that, after decelerating the motor speed to a set speed, the voltage of the generator is lowered to a voltage corresponding to the current speed. 3. An AC variable speed drive device for converting AC power generated by a generator driven by a prime mover into arbitrary AC power by a semiconductor power conversion device to control the AC motor at a variable speed, wherein the speed of the electric motor. When the setting change of the command is acceleration, the speed is changed after detecting the voltage settling, and when the setting change of the speed command of the motor is deceleration, the voltage is reduced after the setting of the speed is detected, and An AC variable speed drive device characterized in that the voltage setting in the deceleration direction is set to a maximum value in advance when the deceleration rate is such that regenerative operation is performed.