JP4489238B2 - Electric motor control device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a motor control device that controls driving of an AC motor (synchronous motor, induction motor).
[0002]
[Prior art]
FIG. 8 is a circuit diagram showing an example of a conventional motor control device called a battery-driven servo amplifier. This is a bridge connection of a 12V or 24V low voltage battery (E) 1, a DC / AC converter 24 that creates an AC 100V or 200V power source from the DC voltage of the battery 1, and diodes D21 to D26 that rectify the AC voltage of the converter 24. The converter unit 25 and the converter unit 25 convert the DC voltage of the converter unit 25 into an AC voltage and apply it to the AC motor (M) 6, and bridge the switch elements such as IGBTs (insulated gate bipolar transistors) T3 to T8. An inverter unit 4 composed of diodes D3 to D8 connected to each IGBT and connected in reverse parallel to each other, a smoothing capacitor for smoothing the output DC voltage of the converter unit 25, such as an electrolytic capacitor 3, and an input side of the inverter unit 4 The regenerative energy of the AC motor 6 is connected between the output sides of the converter unit 25. The series circuit of the resistor 27 to be consumed and the switch element, for example, the IGBT 28, and the IGBTs T3 to T8 and the IGBT 28 of the inverter unit 4 are turned on / off, or the torque command, speed command, or position command from the outside is received, It comprises a control unit 26 for controlling the AC motor 6 by controlling the switch element to vary the voltage applied to the AC motor 6.
[0003]
Thus, in the example of FIG. 8, the converter unit 25 formed by bridge-connecting the diodes D21 to D26 for rectifying the AC voltage is interposed to connect the battery 1 and the inverter unit 4 of the battery-driven servo amplifier. The regenerative energy of the inverter unit 4 cannot be regenerated in the battery 1 when the AC motor 6 is decelerated or is rotated by the rotational force from the load driven by the AC motor 6.
[0004]
FIG. 9 is a circuit diagram showing another example of a conventional motor control device called a battery-driven servo amplifier. This example is a series circuit of the DC / AC converter 24, the converter unit 25, the resistor 27 and the IGBT 28 of FIG. Is removed. With this configuration, the regenerative energy of the inverter unit 4 can be regenerated in the battery 1 when the AC motor 6 is decelerated or when being rotated by the rotational force from the load driven by the AC motor 6. In this case, the battery 1 has a similar configuration in which, for example, a high voltage battery in which a number of low voltage batteries as shown in FIG. 8 are connected in series is directly connected to the inverter unit.
[0005]
[Problems to be solved by the invention]
In the configuration of FIG. 8 described above, since the regenerative energy in the inverter unit 4 from the AC motor 6 cannot be regenerated in the battery 1, the regenerative energy of the inverter unit 4 is connected between the power supply buses PN of the converter unit 25. Although stored in the electrolytic capacitor 3, when the voltage of the regenerative energy exceeds a specified value, energy is wasted because the resistor 27 and the IGBT 28 are used to consume the heat generated by the resistor 27. In addition, when the regenerative energy is large, the resistor 27 has a large capacity, so that the size is increased and the mounting area and cost are increased.
[0006]
In FIG. 9, there are the following problems. In general, most IGBTs are devices with a 600V withstand voltage specification on the assumption that AC200V is connected to a rectified and smoothed DC power supply. For this reason, the servo amplifier and the inverter unit 4 that use the battery power supply use the battery with a high battery voltage in order to use the IGBT efficiently. Therefore, there is a danger in battery charging work and replacement work. In order to increase the voltage, many low-voltage batteries 1 must be connected in series or a special battery connected in series inside must be used.
[0007]
For this reason, in order to lower the battery voltage, there is a method of using a low-breakdown-voltage power MOSFET instead of the IGBT as the switch element constituting the inverter unit 4 in FIG. 9, but this is disadvantageous for the following reason. There are many points and it is not realistic.
[0008]
1) In order to reduce the induced voltage of the AC motor 6, it is necessary to increase the amateur current. For this reason, the switching element of the inverter unit 4 is enlarged, and the electric wire between the inverter unit 4 and the AC motor 6 is thickened. Must.
[0009]
2) Since the rate of decrease of the inductance ωLI with respect to the battery voltage increases, the inductance ωLI of the AC motor 6 must be made as small as possible. Therefore, the switching frequency must be increased, and the switching loss increases.
[0010]
3) Since the ratio of the voltage drop of the inductance ωLI and the voltage drop of the switch element is increased with respect to the battery voltage, the voltage applied to the AC motor 6 is reduced. This also causes an increase in amateur current.
[0011]
4) Due to the inductance of the DC power supply line, the ratio of the voltage drop at the current change rate di / dt to the DC voltage increases. This causes a decrease in the voltage applied to the AC motor 6.
[0012]
The present invention has been made to eliminate the above-described problems. A high-voltage battery is not required to control an electric motor with a high voltage, and the safety at the time of battery replacement is improved and the maintainability is improved. An object of the present invention is to provide an electric motor control device that enables energy saving and reduction in size and weight.
[0013]
[Means for Solving the Problems]
In order to achieve the above object, the invention corresponding to claim 1 is a low-voltage battery (E) 1 of 12V or 24V and a DC voltage of the battery 1 is converted into a three-phase AC voltage, and a three-phase AC motor (M ) Inverter section comprising six diodes D3 to D8, which are applied to 6 and bridge-connect six IGBTs (Insulated Gate Bipolar Transistors) T3 to T8 and are connected in antiparallel to each IGBT. 4 and
An electrolytic capacitor 3 for smoothing the output DC voltage of the battery 1;
The collector of the first IGBTTT1 and the source of the second IGBTTT2 are connected, the first diode D1 is connected in antiparallel to the source and collector of the first IGBTTT1, and the source and collector of the second IGBTTT2 are reversed. A second diode D2 is connected in parallel, and one end of a reactor L is connected to a connection point between the first and second diodes D1 and D2 and a connection point between the first IGBTTT1 and the second IGBTTT2, Both of the other ends of the reactor L are connected to the anode of the battery 1 and the cathode of the battery 1 is connected to the collector of the second IGBTTT 2 and the anode of the second diode D2 to boost the DC voltage of the battery 1. Directional boost chopper 2;
A converter unit 11 formed by bridge-connecting a diode D17 for rectifying alternating current from a power generation device including an automobile engine 14 and a dynamo 15 or diodes D11 to D16 for rectifying alternating current from a commercial power source;
The current detected by the current detector 7 from the battery 1 to the chopper unit 2 is used as a current feedback value, which is supplied to one input terminal of the first comparator 13 and supplied to the electrolytic capacitor 3. The applied voltage is supplied to one input terminal of the second comparator 12 as a voltage feedback value PN, a PN voltage command is supplied to the other input terminal of the second comparator 12, and the second comparator 12 2 is supplied to a controller 8 having a PI controller and a limiter, and a current command obtained by the controller 8 is supplied to the other input terminal of the first comparator 13. The current deviation obtained by the first comparator 13 is amplified by the PI controller 9, and this is supplied to the IGBT of the chopper unit 2 via the power amplifier 10 . Comparator 3 is an input terminal and can be switched between a current command and a charging current command which are output from the controller 8, and a normally closed contact 18b provided on the side to which the current command is provided and the current command A two-link switch 18 comprising a normally open contact 18a provided on a side different from the given side;
A switch 19 which is provided between the normally open contact 18a and the first comparator 13 and which is always open;
A first comparator 16 having an inverting input terminal for inputting and inverting the voltage feedback value PN and an input terminal for inputting a PN clamp voltage;
The output of the first comparator 16 and the monitor signal of the AC voltage are input, the logical product of both is obtained, this is given to the two interlocking switch 18, the normally open contact 18a is closed, and the normally closed contact 18b is An AND circuit 17 to be opened;
A second comparator for inputting the voltage of the battery 1 and having an inverting input terminal for inverting the voltage and an input terminal for inputting an overcharge clamp voltage, and closing the switch 19 when a deviation between them occurs. A control unit 5;
And when the AC motor 6 rotates to a rotational speed of up to 3000 (1 / min), the necessary PN voltage is lowered and the PN voltage command is varied according to the speed of the AC motor 6. In addition, when the rotational speed of the AC motor 6 exceeds 3000 (1 / min), the PN voltage does not exceed a set value.
[0022]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0023]
FIG. 1 is a circuit diagram showing a first embodiment of an electric motor control device according to the present invention. The prior art of FIG. 9 is composed of a reactor L, switching elements such as IGBTTT1, T2 and diodes D1, D2. the bidirectional step-up chopper unit 2 is obtained by adding disposed between the battery 1 Doo electrolytic capacitors 3.
[0024]
FIG. 2 is a circuit diagram for explaining the relationship between the bidirectional boost chopper unit 2 and the control unit 5 of the IGBTTT1, T2. Specifically, as shown in FIG. 2, the bidirectional boost chopper unit 2 connects the collector of the IGBTTT1 and the source of the IGBTTT2, connects the diode D1 in antiparallel to the source and collector of the IGBTTT1, and connects the source of the IGBTTT2 The diode D2 is connected in reverse parallel to the collector, one end of the reactor L is connected to the connection point between the diodes D1 and D2 and the connection point between the IGBTTT1 and T2, and the other end of the reactor L is connected to the anode of the battery 1 Is connected to the collector of IGBTTT2 and the anode of diode D2.
[0025]
A current (current feedback value) obtained by detecting a current flowing through the battery 1 by a current detector, for example, a current transformer 7 is input to the control unit 5, and a voltage (voltage feedback value) applied to the electrolytic capacitor 3 is input. The control unit 5 gives a gate signal to the gates of IGBTTT1 and IGBTTT2 by PWM control.
[0026]
FIG. 4 is a block diagram for explaining details of the control unit 5 in FIG. 3, and a voltage feedback signal is input to the comparator 12 in order to control the PN voltage to an arbitrary voltage command. Thereby, the fall of the PN voltage at the time of the power running of the electric motor 6 and the PN voltage rise at the time of motor regeneration can be suppressed, and the voltage can be stabilized.
[0027]
The PN voltage deviation that is the output of the comparator 12 is input to a controller 8 having a PI controller and a limiter, and a current command is obtained in the controller 8, and the current command and the current feedback signal are sent to the comparator 13. The current deviation input and obtained by the comparator 13 is input to the power amplifier 10 via the PI controller 9. By providing a limiter for the current command in this way, overcurrent of the IGBTTT1, IGBTTT2 and the battery 1 can be prevented.
[0028]
Here, the ON / OFF duty of the IGBTTT1 and IGBTTT2 is determined by the output value of the PI controller 9. The portion of the power amplifier 10 corresponds to IGBTTT1 and IGBTTT2. For example, when the inverter unit 4 is powered, a current flows out from the electrolytic capacitor 3 between the PNs, the voltage decreases, and an error from the PN voltage command occurs. The error is amplified by the PI controller 9, and the electrolysis between the battery 1 and the PN is performed. A current command to the capacitor 3 is generated, an error from the current feedback is amplified by the next PI controller 9, the ON duty of the IGBTTT 2 is widened, and more current is supplied to the electrolytic capacitor 3.
[0029]
When the motor rotation speed indicated by W1 in FIG. 4 is low, the necessary PN voltage may be low. If the PN voltage is low, the switching loss is reduced. Therefore, if the method of changing the PN voltage command according to the speed of the electric motor 6 (lowering the PN voltage at low speed) is used, the switching loss of the inverter unit 4 as well as the bidirectional chopper unit can be reduced, and energy saving can be achieved. Become. When the motor rotation speed indicated by W2 in FIG. 4 is high, the PN voltage is prevented from exceeding a set value, and the IGBT withstand voltage is protected.
[0030]
The operation of the switch element during power running will be described. When the IGBTTT 2 is turned on, a current flows from the battery 1 to the reactor L. Thus, when the current continues to increase and reaches a certain value, when the IGBTTT2 is turned off, a counter electromotive voltage is generated in the reactor L so that the current continues to flow, and flows into the electrolytic capacitor 3 between the power supply bus PN through the diode D1. Even if the PN voltage is high, a back electromotive voltage corresponding to the PN voltage is generated, so that boosting is possible. If the on period and the off period of IGBTTT2 are varied, the voltage between PNs can be controlled to an arbitrary value.
[0031]
At the time of regeneration, a current flows from the inverter unit 4 to the electrolytic capacitor 3 and the voltage between the PNs rises. However, when the IGBTTT1 is turned on, a current flows from the electrolytic capacitor 3 through the IGBTTT1 and the reactor L and flows into the battery 1. Although the current continues to increase, when the IGBTTT1 is turned off at a certain value, the current flows into the battery 1 through the diode D2. At this time, the current continues to decrease. If the on period and off period of the IGBTTT 1 are varied, the average current can be controlled and the PN voltage can be controlled to an arbitrary value even during regeneration.
[0032]
According to the embodiment described above, since the bidirectional boost chopper 2 is additionally provided as shown in FIG. 1, the following operational effects can be obtained.
[0033]
(1) If the voltage of the battery 1 is boosted using the bidirectional boost chopper unit 2, the voltage applied to the AC motor 6 can be increased (the inverter circuit portion of the general-purpose servo amplifier and the general-purpose AC servo motor remain as they are. Can be used.)
(2) When the motor is decelerated or rotated by force from the load, the inverter unit 4 accumulates electric power in the electrolytic capacitor 3 between the power supply buses PN. Therefore, if the capacity of the electrolytic capacitor 3 is not increased, the power supply bus PN The voltage between rises above a certain limit. This is consumed by the resistor 27 using the resistor 27 and the switching element such as the IGBT 28 as in the prior art of FIG. 8 to suppress the voltage rise. There is no increase in the DC voltage for charging, and the resistor 27 and the IGBT 28 for suppressing the increase are not required.
[0034]
(3) Since power is regenerated in the battery 1, the smoothing capacitor, for example, the electrolytic capacitor 3, does not have to have a large capacity.
[0035]
(4) The high-voltage AC motor 6 is controlled without the need for the high-voltage battery 1, and the safety at the time of replacement of the battery 1 is increased and the maintainability is improved.
[0036]
FIG. 5 is a circuit diagram for explaining a second embodiment of the motor control device of the present invention. In the motor control device of FIG. 1, a converter unit comprising diodes D11 to D16 so that a commercial power source can be used. 11 is added, and the configuration of the control unit 5 is as follows. With this configuration, the battery 1 and the commercial power supply can be used in two ways, increasing the practicality.
[0037]
FIG. 6 is a block diagram showing the configuration of the control unit 5 in FIG. 5. The control unit 5 in FIG. 3 has two interlocks including comparators 16 and 20, an AND circuit 17, a normally open contact 18a and a normally closed contact 18b. A switch 18 and a switch 1a are added.
[0038]
Specifically, a voltage feedback value and a PN clamp voltage command (= PN voltage command + α) are input to the comparator 16, and a deviation between the two is input to one input terminal of the AND circuit 17. When the commercial power supply voltage monitoring signal from the commercial power supply voltage monitoring means (not shown) is input to the other input terminal of both, and both signals are present, the logical product condition is established, and the operation of the two interlock switch 18 is switched. A charging current command is input to the normally open contact 18a that is closed when a signal is output from the AND circuit 17, and a normally closed contact 18b that is opened when a signal is output from the AND circuit 17 is provided. A connection point between the controller 8 and the comparator 13 is connected.
[0039]
The overcharge clamp voltage command and the voltage of the battery 1 are inputted to the two input terminals of the comparator 20, and one end of the switch 1a opened by the output from the comparator 20 is the other end of the normally open contact 18a ( The other end of the switch 19 is connected to a connection point between the normally closed contact 18 b and the comparator 13.
[0040]
Since the control unit 5 is configured in this way, the battery 1 can be charged with an arbitrary current command. Further, when it is detected that a commercial power source is connected, the voltage control loop can be disconnected and the battery 1 can be charged with an arbitrary current command. Further, when the PN voltage rises and exceeds a certain voltage due to deceleration of the electric motor 6 or the like, voltage control can be started and controlled to an arbitrary voltage. Moreover, in order to prevent the overcharge of the battery 1, the voltage of the battery 1 can be monitored and the charge current command can be cut off. As described above, the battery 1 can always be charged with the commercial power source not only when the motor is stopped but also during operation of the motor.
[0041]
The embodiment in FIG. 5 is directed to an alternating current (AC) 200V as a commercial power source, for example. However, in the case of an alternating current 100V, it is possible to replace the converter unit 11 in FIG. 5 with a voltage doubler rectifier circuit.
[0042]
As a modification of the embodiment of FIG. 5, for example, by connecting a power generation device including an automobile engine 14 and a dynamo 15 to the power supply buses P and N via a diode D <b> 17, the commercial power supply of FIG. The power generated by the power generation device can also be used.
[0043]
FIG. 7 is a circuit diagram showing a third embodiment of the present invention, in which a DC power source of AC 200 V inverter units 41 and 42 and AC 400 V inverter unit 43 is shared by using a bidirectional step-up chopper unit 2 and an inverter unit AC200V AC motors 61 and 62 and AC400V AC motor 63 connected to 41, 42 and 43, respectively, can be operated.
[0044]
In this case, a rectified power supply of AC 200 V or a battery DC 280 V is used as the DC power supply 21, and a large capacity is provided between the output side of the DC power supply 21 and the input side of the bidirectional boost chopper unit 2 and the inverter units 41 and 42. A capacitor such as an electrolytic capacitor (CE) 22 is connected.
[0045]
In such a configuration, the bidirectional boost chopper 2 boosts the DC voltage of about 280V to a voltage obtained by rectifying and smoothing the AC 400V (about 560V). 3 is used as the control unit in this case, when the AC 400V motor 63 is regenerated, the electrolytic capacitor 22 is charged with energy, and the AC 200V motors 61 and 62 are used as energy during powering. it can.
[0046]
Conversely, even when the electric motor 63 is in powering and the electric motors 61 and 62 are in regeneration, it can be used as regenerative energy. On the other hand, in the conventional technique that does not use the bidirectional step-up chopper unit 2 as in this embodiment, a separate converter unit is required because a transformer that boosts the voltage to AC 400 V is required. Energy will be consumed.
[0050]
【The invention's effect】
As described above in detail, according to the present invention, a high-voltage battery is not required to control a high-voltage motor, safety at the time of battery replacement is improved, maintainability is improved, energy saving and reduction in size and weight are achieved. An electric motor control device that can be provided can be provided.
[Brief description of the drawings]
FIG. 1 is a main circuit diagram of an electric motor control device according to a first embodiment of the present invention.
FIG. 2 is a circuit diagram for explaining the bidirectional boost chopper section of FIG. 1;
FIG. 3 is a circuit diagram for explaining a control unit in FIG. 1;
FIG. 4 is a characteristic diagram of a motor rotation speed and a PN voltage for explaining the operation and effect of the embodiment of FIG. 1;
FIG. 5 is a main circuit diagram of an electric motor control device according to a second embodiment of the present invention.
6 is a circuit diagram for explaining a control unit in FIG. 5;
FIG. 7 is a main circuit diagram of an electric motor control device according to a third embodiment of the present invention.
FIG. 8 is a main circuit diagram of a conventional motor control device of a first example.
FIG. 9 is a main circuit diagram of a conventional motor control device of a second example.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Battery 2 ... Bidirectional step-up chopper part 3 ... Smoothing capacitor, for example, decomposition | disassembly capacitor | condenser 4,41,42,43 ... Inverter part 11 ... Converter part 5 ... Control part 6,61,62,63 ... AC motor 7 ... Current detection For example, current transformer 8 ... PI controller + limiter 9 ... PI controller 10 ... power amplifier

Claims (1)

A 12V or 24V low voltage battery (E) 1 and a DC voltage of the battery 1 are converted into a three-phase AC voltage and applied to a three-phase AC motor (M) 6, which includes six IGBTs (insulated gates) (Bipolar transistor) Inverter section 4 comprising six diodes D3 to D8 that bridge-connect T3-T8 and are connected in antiparallel to each IGBT,
An electrolytic capacitor 3 for smoothing the output DC voltage of the battery 1;
The collector of the first IGBTTT1 and the source of the second IGBTTT2 are connected, the first diode D1 is connected in antiparallel to the source and collector of the first IGBTTT1, and the source and collector of the second IGBTTT2 are reversed. A second diode D2 is connected in parallel, and one end of a reactor L is connected to a connection point between the first and second diodes D1 and D2 and a connection point between the first IGBTTT1 and the second IGBTTT2. The other end of the reactor L is connected to the anode of the battery 1, and the cathode of the battery 1 is connected to the collector of the second IGBTTT 2 and the anode of the second diode D2 to boost the DC voltage of the battery 1. Directional boost chopper 2;
A converter unit 11 formed by bridge-connecting a diode D17 that rectifies alternating current from a power generation device including an automobile engine 14 and a dynamo 15 or diodes D11 to D16 that rectify alternating current from a commercial power supply;
The current detected by the current detector 7 from the battery 1 to the chopper unit 2 is set as a current feedback value, which is supplied to one input terminal of the first comparator 13 and supplied to the electrolytic capacitor 3. The applied voltage is supplied as a voltage feedback value PN to one input terminal of the second comparator 12, a PN voltage command is supplied to the other input terminal of the second comparator 12, and the second comparator 12 2 is supplied to a controller 8 having a PI controller and a limiter, and a current command obtained by the controller 8 is supplied to the other input terminal of the first comparator 13. The current deviation obtained by the first comparator 13 is amplified by the PI controller 9, and this is supplied to the IGBT of the chopper unit 2 via the power amplifier 10 . Comparator 3 is an input terminal and can be switched between a current command and a charging current command which are output from the controller 8, and a normally closed contact 18b provided on the side to which the current command is provided and the current command A two-link switch 18 comprising a normally open contact 18a provided on a side different from the given side;
A switch 19 which is provided between the normally open contact 18a and the first comparator 13 and is always open;
A first comparator 16 having an inverting input terminal for inputting and inverting the voltage feedback value PN and an input terminal for inputting a PN clamp voltage;
The output of the first comparator 16 and the monitor signal of the AC voltage are input, the logical product of both is obtained, this is given to the two interlocking switch 18, the normally open contact 18a is closed, and the normally closed contact 18b is An AND circuit 17 to be opened;
A second comparator for inputting the voltage of the battery 1 and having an inverting input terminal for inverting the voltage and an input terminal for inputting an overcharge clamp voltage, and closing the switch 19 when a deviation between them occurs. A control unit 5;
And when the AC motor 6 rotates to a rotational speed of up to 3000 (1 / min), the necessary PN voltage is lowered and the PN voltage command is varied according to the speed of the AC motor 6. In addition, when the rotational speed of the AC motor 6 exceeds 3000 (1 / min), the PN voltage does not exceed a set value.

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