JPH0452717B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a control device for a thyristor motor.

FIG. 1 shows a conventional control device for a thyristor motor driven by a naturally commutated inverter. In the figure, 100 is a power transformer,
Secondary winding 10H, 10 whose output has a phase difference of 30 degrees
It has an L. 11H and 11L are three-phase bridge converters, each with a secondary winding of 10
It receives AC power from H and 10L, and together they form a 12-phase rectifier circuit. 12H and 12L are DC reactors, and 13H and 13L are three-phase bridge natural commutation type inverters, which send out AC power with a phase difference of 30 degrees to the converters 11H and 11H, respectively, through the DC reactors 12H and 12L. 11
Connected to L. 14H and 14L are thyristor switches, each of which is a converter 11H.
and converter 11L, inverters 13H and 13L
inserted in between. 15H and 15L are current detectors, and converters 11H and 11L respectively.
detects an AC input and sends a DC signal (current detection signal) corresponding to the AC input. A synchronous motor 101 has two sets of windings, and a position detector 102 and a speed detector 103 for detecting the rotor position are connected to its rotating shaft. 104 is a speed controller which receives the output signal of the speed detector 103 as a speed feedback signal and sends out an output corresponding to the deviation between this and the speed reference signal. 10
Reference numerals 5H and 105L are current reference devices that receive the output signal of the speed controller 104 and the low speed control pulse signals P1 and P2 output from the logic circuit device 109 and output a current reference signal. The logic circuit device 109 receives the output of the position detector 102 and the output of the speed controller 104 and sends out a conduction signal for the inverters 13H and 13L, and also receives the low speed determination signal output from the speed comparator 108 and switches the thyristor switches 14H and 13L. 1
The 4L alternating conduction signal and the low-speed control pulse signals P1 and P2 synchronized with the alternating conduction signal are sent out.
The speed comparator 108 generates the low speed determination signal when the speed of the synchronous motor 101 falls below a predetermined speed. Reference numerals 106H and 106L are current controllers, respectively, and output signals corresponding to the deviation between the outputs of the current detector 15H and the current reference device 105H, and the deviation between the outputs of the current detector 15L and the current reference device 105L, respectively. 107H, 107L are gate pulse generators, and current controllers 106H, 106
Converter 11 receives the output signal of L.
H, sends a conduction signal to converter 11L.

In this configuration, inverters 13H, 13
In the speed range (load commutation range) of the synchronous motor where L can be commutated by the induced voltage of the synchronous motor 101, the thyristor switches 14H and 14L are not conductive.
Converter 11H, 11L group and inverter 13
H, 13L group is DC reactor 12H, 12L
Converters and inverters are alternately and sequentially connected in series to form a closed loop.

However, when the speed of the synchronous motor 101 drops to a low speed and the induced voltage of the synchronous motor 101 is no longer able to commutate the inverters 13H and 13L well,
The speed comparator 108 outputs and the logic circuit device 109
A conduction signal is alternately supplied from the thyristor switches 14H and 14L to the thyristor switches 14H and 14L, and low-speed control pulse signals P1 and P2 as shown in FIG. 2 are inputted to the current reference devices 105H and 105L in synchronization with the conduction signal. These low-speed control pulse signals P1 and P2 are generated simultaneously and with opposite polarities at intervals of 30 degrees based on the frequency of the synchronous motor 101, coinciding with the commutation timing of the inverters 13H and 13L. Pulse signals, P1 and P2 are current reference device 10
5H, while being input to the current reference device 105L,
The current reference signals output by the current reference devices 105H and 105L are controlled to zero level or double level.

For example, at time _t1 , the low speed control pulse signals P1, P
2 is input to the current reference devices 105H and 105L with the illustrated polarity, the current reference signal of the current reference device 105H becomes zero level, the current reference signal of the current reference device 105L becomes twice the level, and the thyristor switch 14L becomes conductive. However, a closed loop is formed of the thyristor switch, converter 11L, DC reactor 12L, and inverter 13L, and a current doubled from before time _t1 is sent to the closed loop. During this time, since the current reference signal of the current reference device 105H is zero, commutation is possible until no current flows into the inverter 13H. 30 from time t ₁
At time _t2 , which is delayed by 1.5 degrees, the thyristor switch 14H becomes conductive, contrary to the above, and the thyristor switch 14H becomes conductive.
A closed loop consisting of converter 11H, inverter 13H, and DC reactor 12H is formed, during which commutation of inverter 13L is performed.

In this way, conventional control devices require two current controllers and two current standards, which not only increases the cost, but also makes it difficult to equalize the DC currents of both converters in the load commutation region. However, there was a problem in that it was not easy to balance the outputs of both current controllers.

This invention has been made in view of the above problems, and includes a common current controller that receives a current reference signal to control the gate pulse generator of each converter, and also allows the current controller to control the current of each converter. The sum of the outputs of the individually detected current detectors is given as a current feedback signal, and the output of the current controller is synchronized with the low-speed control pulse signal to reduce the input of the gate pulse generator of one converter and generate the gate pulse of the other converter. The present invention provides a thyristor motor control device that can be made cheaper than conventional ones and has improved control characteristics by having a configuration in which the input is supplied to each gate pulse generator through an input device that increases the input of the generator. The purpose is to provide.

An embodiment of the present invention will be described below with reference to the drawings.

In FIG. 3, 206 is a current controller, and the output signal ih of the current detector 15H and the current detector 15L correspond to the output signal Vs of the speed controller 104.
outputs a current control signal Is corresponding to the deviation of the sum from the output signal il. 210H and 210L are polarity converters, and the former exchanges the polarity of the current control signal Is and inputs it to the gate pulse generator 107H, and also inputs it to the polarity converter 210 via a switch 211H.
The output of L is input. The latter is the current control signal Is
The polarity of the signal is inverted and inputted to the gate pulse generator 107L, and at the same time, the output of the polarity converter 210H is inputted via the switch 211L. switch 21
1H and 211L are turned on and off in response to low-speed control pulse signals p1 and p2, which will be described later, output from the logic circuit device 109. Polarity converter 210H, 21
0L, switches 211H, and 211L constitute an input device for the gate pulse generator. Note that the gate pulse generators 107H and 107L have a phase characteristic in which the output phase of the gate pulse to be output is approximately 180° when the input is zero, and advances from this approximately 180° phase as the input increases in the positive direction.

In this configuration, in the load commutation region described above, the low speed control pulse signals p1 and p2 are applied to the logic circuit device 1.
Since there is no output from 09, logic switch 211
H, 211L and thyristor switch 14H, 1
4L is open, converters 11H and 11L
The converters and the inverters 13H, 13L are connected in series alternately and sequentially via the DC reactors 12H, 12L to form a closed loop.

When the speed of the synchronous motor 101 falls below the predetermined speed, the logic circuit device 109 outputs low speed control pulse signals p1 and p2 shown in FIG.
These low-speed control pulse signals p1 and p2 coincide with the commutation timing of the inverters 13H and 13L,
Occurs every 30 degrees based on the frequency of the synchronous motor 101, and alternately and when the thyristor switches 14L, 14
Switches 211H and 21 are activated in synchronization with the H conduction signal.
1L is supplied.

Now, at time _t1 , if the switch 211L receives the low-speed control pulse signal p2 and closes the circuit, the input of the polarity converter 210L receives the current control signal Is and the output of the polarity converter 210H which converted the polarity of the current control signal Is. is given, the output of the polarity converter 210L decreases to zero level. At this time, a conduction signal is also given to the thyristor switch 14H at the same time. For this reason, the converter 11L has a phase control angle of approximately
As the current is controlled at 180°, the output current level decreases toward the zero level, and the output of the current detector 15L decreases accordingly, so the output level of the current controller 206 increases. When the output current of converter 11L becomes zero, converter 11H, DC reactor 12H, and inverter 13
H, the level of the current flowing through the DC closed loop of the thyristor switch 14H doubles from the level before time _t1 . In this way, while the low-speed control pulse signal p2 is being generated, the output of the converter 11L is reduced to zero, so that commutation of the inverter 13L can be performed. At time _t2 , the thyristor 14L becomes conductive and the thyristor switch 14L, converter 11L,
A DC closed loop consisting of an inverter 13L and a DC reactor 12L is formed, and a polarity converter 210H
The output of converter 11H becomes below zero level.
The output of converter 11L is reduced to zero, and the output of converter 11L is doubled.

In the above embodiment, the case of a converter and an inverter constituting a 12-phase rectifier circuit has been described, but the present invention can also be practiced to obtain the same effect even in the case of a multi-phase rectifier circuit configuration. Can be done. Although an analog configuration is shown, it can be easily converted to a digital configuration using a microprocessor.

Furthermore, in the above embodiment, the DC current of one converter is controlled to double when the synchronous motor runs at low speed, but the current reference and current feedback gain are adjusted to adjust the current between 1 and 2 times. Good too. Alternatively, the DC current of the converter may be detected and provided as the current feedback signal. Further, the DC reactors may be coupled to each other.

As described above, according to the present invention, the gate pulse generators of a plurality of converters can be controlled by one current controller, so the cost of the device can be reduced compared to the conventional one, and In the load commutation region, the outputs of the plurality of converters are easily balanced, so that control characteristics can be improved.

[Brief explanation of the drawing]

Fig. 1 is a block diagram of a conventional thyristor motor control device, Fig. 2 is an operation waveform diagram for explaining the operation of the above control device, and Fig. 3 is an embodiment of the thyristor motor control device according to the present invention. The block diagram and FIG. 4 are operational waveform diagrams for explaining the operation of the above embodiment. 11H, 11L...Converter, 13H, 13
L...Inverter, 14H, 14L...Thyristor switch, 15H, 15L...Current detector, 1
02...Position detector, 103...Speed detector, 1
07H, 107L...Gate pulse generator, 10
8...Speed comparator, 109...Logic circuit device, 2
06... Current controller, 210H, 210L... Polarity converter, 211H, 211L... Switch. In addition, in the figures, the same reference numerals indicate the same or corresponding parts.

Claims (1)

[Scope of Claims] 1. A synchronous motor driven by the AC output of the inverter of a polyphase rectifier circuit configured by connecting two converters and inverters in series alternately to form a closed loop circuit, A control device for a thyristor motor having a thyristor switch in between, which controls the output of the converter based on a current reference signal and a current feedback signal, and generates a low speed control pulse signal when the speed of the synchronous motor drops below a predetermined speed. The thyristor switches are alternately turned on in response to the low-speed control pulse signal, and power is transferred through the turned on thyristor switches. In a device that naturally commutates an inverter that reduces the output and transfers power to and from the other converter, each of the converters has a common current controller that receives a current reference signal and controls the gate pulse generator of each of the converters. A signal representing the sum of the currents is given as a current feedback signal, and the difference between the output of the current controller and the input to the gate pulse generator of the one converter is applied to the gate of the other converter in synchronization with the low-speed control pulse signal. A control device for a thyristor motor, characterized in that the output of the current controller is distributed and supplied to each of the gate pulse generators through an input device that inputs input to the pulse generator. 2. The input device has a polarity converter corresponding to each of the gate pulse generators, and these polarity converters receive the output of the other polarity converter via a switch, and these switches synchronize with the low-speed control pulse signal. 2. The thyristor motor control device according to claim 1, wherein the thyristor motor is controlled to open and close alternately.