JPH0810996B2 - Motor control device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a motor control device using a voltage source inverter. 2. Description of the Related Art Many motor control devices using voltage source inverters are constructed as shown in FIG. 1 is a three-phase AC power supply, 2 is a forward converter that receives power from the power supply 1 and rectifies it, 3 is a capacitor that smoothes the output of the forward converter 2, 4
Is a main circuit portion of an inverse converter that receives the DC power smoothed by the capacitor 3, converts the DC power into three-phase AC, and supplies the three-phase AC to the motor 5.
6 is a switching control circuit forming a part of the inverse converter,
Reference numeral 7 is a shunt resistor as a current detecting means for detecting the magnitude of the input current of the inverse converter. The main circuit 4 of the inverse converter includes transistors Q1 to Q6 as main switching elements,
It is composed of flywheel elements D1 to D6 connected in anti-parallel to the respective main switching elements. The transistors Q1 and Q2, Q3 and Q4, Q5 and Q6 are connected in series, and both ends thereof are connected to both terminals of the capacitor 3. One terminal of the electric motor is connected to each of the serial connection points P1, P2 and P3. The switching control circuit 6 has a built-in speed command means, and is configured to control each main switching element so that the output voltage and the output frequency of the inverse converter become the values according to the output of the speed command means. There is. Further, the switching control circuit 6 uses the current detection means 7
Is configured to make each of the main switching elements Q1 to Q6 non-conductive when a current equal to or more than a certain value is detected. When
A regenerative operation of a motor control device configured in this way
To detect the state, the conventional output voltage, the phase difference of the output voltage
It can be detected from the status and the output power of the voltage source inverter can be calculated.
Since it was calculated and calculated, the configuration became complicated and the regenerative condition
It takes longer to detect the condition, which causes problems in control response.
It was the title. A device provided with a current detecting means on the input side of an inverse converter is known from Japanese Patent Laid-Open No. 57-78372. SUMMARY OF THE INVENTION The present invention has been made in view of the above points, and an object thereof is to detect a regenerative state of an electric motor with a simple structure. Well
Equipped with a regeneration mode detection means with little time delay in
This is to configure the machine control device. [0005] SUMMARY OF THE INVENTION That rate in the present invention
A command and a slow acceleration / deceleration command means for gently changing the command
Based on the output of the speed command and the slow acceleration / deceleration command means.
Equipped with regeneration mode detection means to detect the regeneration state based on
Things. The above speed command is the slow acceleration / deceleration command during the forward rotation operation.
It becomes smaller than the output of the means.
Can be detected. Also, this regeneration mode detection is based on the speed command.
Therefore, the detection speed in the regenerative mode becomes faster. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS First, a first embodiment of the present invention will be described with reference to FIGS. The main circuit configuration is the same as that shown in FIG. This embodiment is characterized by the switching control circuit 6, which will be described below. In this embodiment, a mode detecting means 10 for detecting the regenerative mode is provided, and when the mode detecting means 10 detects the regenerative mode, the off control means 11 is operated so that all the main switching elements Q1 to Q6 are temporarily operated at the same time. It is configured to be turned off. Reference numeral 101 is speed command means for commanding the speed of the electric motor 5, and reference numeral 102 is slow acceleration / deceleration command output means for softening abrupt changes in the output of the speed command means. Reference numeral 103 is a voltage command means for commanding a voltage having a magnitude matching the output of the slow acceleration / deceleration command output means 102, and 104 is a frequency command means for similarly commanding a frequency having a magnitude matching the output of the slow acceleration / deceleration command output means 102. Is. Reference numeral 105 is a sine wave generating means for generating a sine wave having a voltage suitable for the output of the voltage command means 103 and having a frequency suitable for the output of the frequency command means 104, and 106 is a carrier wave generating means. 107 is a sine wave generating means 105
Is a pulse width modulation circuit that compares the output of the carrier wave generator 106 with the output of the carrier wave generator 106 to modulate the pulse width. Reference numeral 108 is a logic circuit that logically operates the output of the pulse width modulation circuit 107 and the output of the off control means 11, and this output becomes the base signal of the main switching element Q1. 109 is an inverting circuit that inverts the output of the pulse width modulation circuit 107, and 110 is a logic circuit that logically operates the output of the inverting circuit 109 and the output of the off control means 11, and this output is the base signal of the main switching element Q2. Become. Main switching element Q3〜
The circuitry that produces the base signal to Q6 is not shown in this figure. They receive the output of the voltage command means 103 and the output of the frequency command means 104, and are provided with sine wave generating means having a phase difference of 120 degrees and 240 degrees in electrical angle with respect to the output of the sine wave generating means 105, respectively. Consider that there are two more sets of identically configured circuits. In this case, the carrier wave generation means 106 and the off control means 11 are commonly used for all phases. The mode detection means 10 is the speed command means 1
01, the slow acceleration / deceleration command output means 102, and a comparator 111 for comparing the output of the speed command means 101 and the output of the slow acceleration / deceleration command output means 102. This comparator 111
Determines that the regeneration mode is set when the output of the speed command unit 101 is smaller than the output of the slow acceleration / deceleration command output unit 102. The off control means 11 is a sawtooth wave generation circuit 11
A comparator 114 which compares the two signals with the binary level signal generating circuit 113 and these signals and generates a signal only when the output of the sawtooth wave generating circuit 112 is larger than the output of the binary level signal generating circuit 113. It consists of and. The binary level signal generating circuit 113 always outputs the sawtooth wave generating circuit 1 when the mode detecting means 10 does not output the signal indicating the regeneration mode.
When a signal larger than the output of 12 is output and a signal indicating the regeneration mode is output, a signal between the output of the sawtooth wave generation circuit 112 and the maximum value and the minimum value is output. Reference numeral 115 is a change stop command circuit for temporarily stopping the output change of the slow acceleration / deceleration command output means when the output of the current detection means 7 is a certain value or more. The construction of this is disclosed in Japanese Patent Publication No. 59-20274. It is described in detail. Now, in the structure configured as described above,
In the powering mode, the mode detection means 10 sends no signal to the off control means. Therefore, as shown in FIG. 2, the output a of the binary level signal generating circuit 113 is always larger than the output b of the sawtooth wave generating circuit 112, so that the output of the comparator 114 is always "L" as shown by c. Therefore, the logic circuit 108 outputs the output of the pulse width modulation circuit 107 as it is as the base signal of the main switching element Q1, and the logic circuit 110 outputs the output of the inverting circuit 109 as it is as the base signal of the main switching element Q2. d is a current flowing through the current detecting means 7. In the regenerative mode, the mode detecting means 10
Outputs to the off control means a signal indicating that it is in this mode. Therefore, the output of the binary level signal generation circuit 113 becomes a value smaller than the maximum value of the output b of the sawtooth wave generation circuit 112 as indicated by a ′, and the comparator 114 outputs the pulsed signal indicated by c ′. It will output.
Therefore, the logic circuits 108 and 110 are the pulse width modulation circuit 1
07 and the output of the inverting circuit 109, the comparator 114
Outputs the "H" signal, the base signals of Q1 and Q2 are cut off. As described above, the output of the off control means 11 acts in common on the circuits that generate the base signals of the other main switching elements Q3 to Q6, so that all the main switching elements Q1 to Q6 are temporarily turned off at the same time. Become. Since the electric motor 5 includes a reactance component, the circulating current tends to grow with a certain time constant as time passes. However, in the present invention, the circulating current is temporarily cut off, so it decreases at the time of this interruption and increases again when the interruption is released. Therefore, an increase in circulating current can be suppressed. Note that all the main switching elements Q1 to Q6 are temporarily cut off, and the circulating current is d1 in FIG.
As shown by d2 and d3, the flow path is changed to flow into the current detecting means 7. FIG. 4 is a different embodiment of the present invention. The difference from the embodiment shown in FIG. 1 is that all the switching elements Q1 in the embodiment shown in FIG.
.About.Q6 are cut off, whereas in the configuration shown in FIG. 4, all the switching elements Q1 to Q6 are cut off when the current detecting means 7 detects a current value above a certain value. is there. Therefore, a comparator 111 'for comparing the output of the current detection means 7 with the set value is provided, and the comparator 11' is provided.
1'is configured to output the signal "L" when the output of the current detection means 7 is smaller than the set value, and to output the signal "H" when the output is larger than the set value. Also, the binary level signal generation circuit 1
13 is a constant value larger than the maximum value of the sawtooth wave generation circuit 112 when the output of the comparator 111 ′ is “L”, and is a maximum value and a minimum value of the sawtooth wave generation circuit 112 when it is “H”. It is configured to output the signal between. Although the case where a transistor is used as the main switching element has been described above, the present invention can be implemented when a thyristor is used. According to the present invention, as is clear from the above description, it is possible to detect the regenerative state with a simple circuit, and the regenerative state can be detected.
Mode detection is performed based on the speed command, so regenerative mode
This has the effect of increasing the detection speed of the monitor.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram showing an embodiment of a control device of the present invention. FIG. 2 is a time chart used for explaining the operation of the embodiment shown in FIG. FIG. 3 is a time chart used for explaining the operation of the embodiment shown in FIG. FIG. 4 is a block diagram showing a different embodiment of the control device of the present invention. FIG. 5 is a circuit diagram showing a conventional control device. [Description of Reference Signs] 2 is a forward converter, 3 is a capacitor, 4 is an inverse converter, 7 is a current detecting means, 10 is a mode detecting means, and 11 is an off control means.

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Yuichiro Nagato             7-1, 1-1 Higashi Narashino, Narashino City, Chiba Prefecture             Narashino Factory, Hitachi, Ltd.              (56) References Japanese Patent Laid-Open No. 62-107699 (JP, A)

Claims (1)

Claims: A DC power source and an electric motor for receiving the power of the DC power source and converting the power into an AC current.
To the inverter, speed setting means for instructing the speed of the electric motor , and variable output frequency of the inverse converter based on the speed command.
Motor equipped with a control circuit for controlling the acceleration and deceleration of the motor
In the machine control device, the speed command is received in the control circuit by receiving the speed command.
Slow acceleration / deceleration command means for softening sudden changes, and the speed
The speed command is received in response to a command and the output of the slow acceleration / deceleration command means.
And the magnitude of the output of the slow acceleration / deceleration command means are compared.
Characterized by having a mode detection means for detecting the mode
Electric motor control device.