JPS60200790A - Drive device for ac motor - Google Patents

Abstract

PURPOSE:To eliminate to flow an excess current from a power source at a recovering time by maintaining the DC voltage of a smoothing condenser substantially constant by a regenerative control at an instantaneous power interruption time. CONSTITUTION:If a motor IM is disposed at a crossover track to instantaneously interrupt a power when the motor is operated with power, the output signal Ism of a DC voltage controller AVR increases to exceed the set level of a Schmitt circuit SH. Then, a switch circuit SW which is connected to a side so far is converted to (b) side. Accordingly, the torque command value T'e* of the motor IM becomes negative value and hence a regenerative command. Thus, the rotary energy of the motor IM is regenerated to a smoothing capacitor Cd. Thus, the DC voltage Vd of a smoothing condenser Cd does not extremely decrease, but even if a power source voltage Vs becomes reenergized state, a converter CONV can be always normally operated.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to an AC motor drive device C that combines a voltage type self-excited converter and a voltage type self-excited inverter.

[Technical background of the invention]

Voltage-type self-excited inverters have begun to be widely used to drive AC motors, such as squirrel-cage induction drives and synchronous motors. In particular, the development of switching elements with self-extinguishing capabilities, such as o'i'o (gate turn-off thyristors) and high-power transistors, has recently progressed, replacing conventional current-source inverters with forced commutation circuits. Therefore, there is a growing tendency to adopt voltage-type self-excited inverters. In other words, when a switching element with self-extinguishing ability such as GT (J) is used in a current source inverter, it is difficult to handle the energy of the circuit at turn-off. The reason for the thickness is that the energy can be easily returned to a smoothing capacitor, etc.

When driving an AC motor with Ryuo Ruinpa Yu.

A DC voltage source is required. Except when there is a DC voltage source such as a battery, it is generally
DC power is generated via a power converter.

Recently, a magnetic pressure type visually excited converter using a GTO4 self-extinguishing element has been adopted for the converter side C2.

′! FIG. 51 shows the configuration of a conventional AC motor drive device.

In the diagram, SUP is the father flow source, Ls is the AC reactor, and C0
NV is a pen pressure type self-excited converter, Cd is a DC smoothing capacitor, lNV is a voltage type self-excited inverter, M is an AC voltage type self-excited converter, C (JNT 1 is the control circuit of the converter).

cox'cr 2+t inverter if! l 8 circuit Pu#ii4. mJ m rotational speed detector, CTS
, CTL is the current detector*Cv.

CM is a comparator. 1 The inverter INV provides a variable voltage to the AC motor.

It supplies variable frequency power and its operation is as follows.

First, the rotational speed N of the electric motor M is detected by the rotational speed detector PG. Next C2, by comparator CN.

The above speed detection value N and speed command value N * & ratio axis, deviation εN
=N*-N. The control circuit C0NT2 controls the current iL supplied to the electric motor M according to the deviation εNl2, and provides the inverter INV with a gate signal necessary for the control. Generally, pulse width modulation (PW
M) The gate signal is applied so that the voltage and frequency necessary to control iL are generated from the inverter INV by a control or the like.

The electric MM frequently performs power operation and regenerative operation according to the speed control l1, but during power operation, energy is sent from the DC smoothing capacitor Cd to the motor M, and conversely, during regenerative operation, the electric motor M Energy is also transferred to the smoothing capacitor Cd.

Converter C0NV has DC voltage Vd of DC smoothing capacitor CD regardless of the above-mentioned power running 1 regeneration operation.

The value of the input current is is always controlled so that it remains approximately constant. Its operation is as follows.

First, detect the DC voltage Vd of the smoothing capacitor Cd.

A comparator Cv compares the DC voltage command value Vd. The deviation εv = Vd −Vd is determined by the control circuit C0NT.
1, and the value of the input current is is controlled according to this deviation εV (1. In other words, the peak value command I proportional to εV
sm and convert it into the power supply voltage Vs = V sm -s
input current θ〕command value + s = Ism - s
Creating inωst. The L input current iS is controlled by the one-two converter C0NV so as to match the command value iS*. Therefore, the input current is is in phase with the power supply voltage Vs (Ism 0: power running) or in reverse phase (Ism (
Controlled by a sine wave (0: regenerative operation), the power factor is always 1,
The harmonic content is low. In order to perform the above control, converter C0NV also uses a method such as pulse width modulation control.

In this way, it is possible to operate an AC motor at variable speed by combining a voltage-type self-excited converter and a voltage-type self-excited inverter, but this conventional current-changing motor drive device η has the following problems. There is.

[Problems with the Prior Art] The above-mentioned conventional AC motor drive device can be applied as is to a so-called AC vehicle system that receives power supply from an AC feeder line. However, in electric railways, there are several substations that supply power to the AC feeder lines ζ2~,
Feeder lines are divided for each substation. Therefore, when a train crosses from one feeder line to the next, it has to pass through a voltage-free period of about 0.5 seconds, during which it is not possible to not only supply electricity but also regenerate it. Can not. If power supply is no longer possible, smoothing capacitor Cd
The only problem is that the energy of the motor M decreases, but the problem is that the electric motor M
This occurs when the above-mentioned no-voltage period occurs during regenerative operation. That is, the power supply 11jl is in an open state, and the energy of the smoothing capacitor Cd cannot be electrically regenerated by the converter CONV. For this reason, the DC voltage Vd of the smoothing capacitor Cd increases rapidly and eventually exceeds the withstand voltage of the device such as the GTO, causing device destruction.

To prevent this, on the AC side of converter C0NV,
A large capacity resistor is connected, and as mentioned above, when the power supply side is opened during regenerative operation, the resistor consumes energy to suppress the voltage rise of the smoothing capacitor Cd.

However, the above-mentioned resistor requires a large capacity, which has disadvantages such as increased weight and size.

This problem is not limited to AC motor drive devices for vehicles. For general industrial use, the power supply circuit may be opened due to an accident, etc., and if the circuit is opened during regenerative operation, the smoothing capacitor Cd
There is a risk that the voltage will rise and destroy the device.

Another problem arises when the power supply voltage is reestablished from the no-voltage state. That is, when the electric iM is in continuous operation and a short-term power outage occurs, most of the energy in the smoothing capacitor Cd becomes the generated torque of the electric motor M and is consumed. Therefore, the voltage Vd of the capacitor decreases, and when the power supply voltage is established again, the AC voltage that is opposite to the current voltage is applied to the converter C0.
It cannot be generated on the alternating current side of NV, and the converter experiences an uncontrollable period, albeit for a short time. This causes problems such as excessive current flowing from the power supply and destroying the elements constituting the converter.

[Purpose of the invention]

The present invention has been made in view of the above, and it is possible to control the DC voltage of the smoothing capacitor so that it does not exceed the withstand voltage of the element, and when the voltage is re-established. An object of the present invention is to provide an AC motor drive device configured to prevent excessive current from flowing from a power source.

[Summary of the invention]

The present invention relates to an AC power source and a voltage source converter connected to the AC power source via an AC reactor.

In an AC motor drive device consisting of a smoothing capacitor connected to the DC side of this converter, a voltage source self-excited inverter using this capacitor as a voltage source, and an AC motor connected to the AC output (+'ill) of this inverter, ,
Under normal operating conditions when the power supply voltage is established, the converter is controlled so that the DC voltage of the smoothing capacitor is approximately constant, but if the converter becomes uncontrollable due to a momentary power outage, etc. The above objective is achieved by controlling the inverter and the DC voltage of the smoothing capacitor to a substantially constant value, giving priority to the speed control or torque control of the AC motor. .

[Embodiments of the invention]

FIG. 2 is a configuration diagram showing an embodiment of the AC motor drive device of the present invention.

In the figure, BUS is the feeder line of the single-phase AC power supply, PAN is the pantograph, MTR is the main power transformer, Ls is the AC reactor, and C0NV is the voltage-type self-exciting converter.

Cd is a smoothing capacitor, INV is a voltage type self-excited inverter, IM is a squirrel cage conductive motor, P (J is a rotation speed detector,
CTs, CTU, CTv, CTw are current detectors, Is is an alternating current voltage detector, ISO is an insulation increaser I
M unit, AVH・ is a DC voltage control circuit, ASLj is a speed control circuit, KT is an operational amplifier, SH is a Schmitt circuit, S
W is a switch circuit, TEC is a torque control circuit, AD is an adder, PTG is a three-phase half-phase sine wave generator, ML, , M
L2 is the power nq>, ACLLl, ACR2c current controll
il road, PWM, .

P~'VIXA are pulse width modulation control circuits.

The voltage source self-exciting converter C0NV includes gate turn-off thyristors (GTOs) S, , ~S14 and diodes I
)11 to DI4, and the current is supplied from the power supply so that the DC voltage Vd of the smoothing capacitor Cd is constant.
til control.

The voltage source self-excited inverter INV includes a gate turn-off thyristor (GTO) S2. ~S2° and diode 021
~I) 3-phase current i composed of 26 and supplied to the motor IM
o, iv, iw.

First, a method for controlling the current supplied to the electric @machine IM will be explained.

First, the rotational speed N of the electric machine M is detected by the speed detector PG. The speed control circuit As compares the detected speed value N and the speed command value Z, amplifies or integrates the deviation εN-N''-N, and determines the generated torque command value Te of the electric motor M.
Output.

Normally 2, the circuit SW is connected to the a side.

The generated torque command value Te is determined by the following torque control circuit TE.
It is input to C. The torque control circuit TEC gives peak value commands It, m of the supply currents iu, iv, iw and a slip frequency setting value fsl so that the electric motor IM outputs the required generated torque Te=Te. The slip frequency set value fsl and the rotational frequency fm obtained from the one-rotation speed detector PG are added to the adder AD to obtain the output frequency of the inverter INV (primary frequency of the motor IM) fO.

fo = fm + fsl ・・・・・・・・・・・・
... (1) If fSl is a positive value, the electric motor IM generates a positive torque and becomes a power running operation. Conversely, if fsl is a negative value, the electric motor IM generates negative torque and regenerative braking is applied.

The three-phase half-phase sine wave generator PTG generates three-phase half-phase sine waves Pu, Pv, and Pw having the output frequency fO.

Ptr=sin ωat・・・・・・・・・・・・・・・
... (2) Pv = sin (ω01-2π/3)
・・・・・・・・・・・・・・・ (3) Pw = s
in CωO1+2π/3) ・・・・・・・・・・・・
・・・・・・ (4) ω0−2πfO・・・・・・・・・
... (5) This unit sine wave PU, Pv,
L'w and the above-mentioned wave 1, 6-value finger It, +n are combined with each other to calculate the next supply current command value IL (iu, iv, +w).

lu = ILm −sinωot ・・・・・・・・・
...” (61tv = It, m − sin (ωo
1-2π/3)...(7)iw*=ILm
-sin (ωat-4-2π/3) --------
(8) Current control circuit Act compares the detected current value iL (iu, iv, iw) supplied to the motor iM with the above current command value IL, and amplifies the deviation 5: IL-iL to calculate the primary PWM control circuit PWM21m control gogo e2 (
ezu, e2v, ezw).

PW? The vi control circuit PWM2 is constructed by known means, and receives the control input signals e2 (ezu, e
zv, ezw) (two proportional voltages VU, VV, VW
is generated from inverter iNV, so that inverter I
Control NV.

The slip frequency Qfsl of the electric motor IM is as follows.

It is set to a positive value, and when regenerative braking is set to a negative value,
(Method of controlling the edge frequency fsl=constant.

■Method of changing according to the current peak value command IIt, m.

(2) Furthermore, there is a method of changing the C two-slip frequency fsl so as to control the 121st order current vector so that the excitation current of the motor IM and the secondary current maintain an orthogonal relationship. Here, in order to simplify the explanation, fsl is assumed to be constant, and only the sign changes during power travel and regeneration. Accordingly, the value of the generated torque Te of the electric motor IM is determined by the magnitude of the current peak value command ILm.

If the speed command N* is larger than the actual speed N, the deviation εN
=N''-N becomes a positive value, increases the wave height values I, t, and m, and increases the torque generated by the electric motor IM.

Conversely, in the case of N'' (N, the deviation tN becomes a negative value, reducing the above-mentioned peak value ILm and reducing the generated torque of IM. Therefore, finally, N=N- and settles down.

If N*<N, the slip frequency gfsl is made negative and regenerative braking is applied. At this time, since ft and m do not need to be negative values, IIr and rnl are provided through an absolute value circuit.

When the slip frequency fsl>O, the motor IM is in the row mode (motor mode), and the motor IM+2 electric power is supplied from the constant voltage source 1 negative current smoothing capacitor→no Cd. Also, when the inverse f two slip frequency gfsl<-0, the motor IM becomes the regeneration mode (generator mode) and the motor IM
From the DC smoothing capacitor CdI: electric power is regenerated and the regenerative brake is applied to the motor IM (7J).

Next, a method of controlling the input current is from the power supply by the voltage type self-exciting converter CONV will be explained.

First, the DC voltage Vd of the smoothing capacitor Cd is insulated amplified 1
Detected via IsO. DC cage pressure control circuit A V L
L compares the detected voltage value Vd and the voltage command value Vd, and amplifies or integrates the deviation εv=Vd - Vd.
, create an input current peak value command 1sm.

On the other hand, the power supply voltage Vs = Vsm by the transformer PTs
・Unit sine wave Ps = sin synchronized with sinωst
ωst is detected and input to the multiplier ML.

The multiplier ML multiplies the input current peak value command Ism by the unit sine wave Ps=sinωst.

The next input 'grain flow command value IS' is created.

Is = Ism - sinωst ・・・・・・・・・
(9) The current detector C'I's detects the input current is supplied from the power supply and inputs it to the current control circuit CR. The current control circuit ACR compares the input current command value Is with the input current detection value is, inverts and amplifies the deviation εl5=IS-Is, and provides control input to the primary PWM control circuit PWL'A. Give signal e□.

1'WM control circuit PWM, which is also achieved by known means, connects the converter C(,)N so as to generate a voltage Vc on the AC side of the converter C0NV proportional to the control input 1, e. Control V.

Difference voltage V between power supply voltage Vs and converter AC side voltage Vc
LS = Vs - Vc is applied to AC reactor Ls.

The input terminal is is determined by the difference voltage VLS as follows.

■ 'S = f YLs dt ・・・・・・・・・・・・
.... Qs Therefore, C and C that control the value of VLS = Vs - Vc
Second, human power! It is possible to control lN and tS7J)
Ru.

−, ts ) Is, the deviation εIs −= Is
-Is becomes a positive value, and control human power 1d e to PWMt
, is a negative value.

Therefore, Vc decreases and the differential voltage, VLS = Vs −
Vc increases, increasing the input terminal is. To the connoisseur, i
In the case of s (Is), the deviation εIS becomes a negative value,
The control human power signal e1 takes a positive value. Therefore, Vc increases,
Vr, s = Vs - Decrease Vc and decrease lS. Finally (two is ball is).

When the DC voltage Vd becomes smaller than the command value Vd'', the input terminal peak value Ism is increased. Since the input '-current is is controlled so that it matches the command value 1s = Ism - sinωsH, It is in phase with the power supply voltage (power factor = 1), and only the effective force component is always supplied from the power supply.Therefore, an increase in l5In means an increase in the active power supplied from '-Ei. equally.

The effective power is converted into energy in the smoothing capacitor Cd in °C.
It will be stored. Therefore, the direct current voltage Vd is distorted and becomes Vd-, ;Vd.

When reverse C2 Vd > Vd*, the input current wave height (
BiIsm decreases and even becomes a negative value. Late C2,
This time, the input current 1s=1s is in reverse phase with the power supply voltage Vs (
power factor = 1), and the active power is regenerated to the power supply (
Two people.

Therefore, the energy of the smoothing capacitor Cd is 75 (
As a result, the DC voltage Vd decreases. Final (2 Vd
It settles down to ≠Vd*.

The above describes the normal θ) operation when the power supply voltage Vs is established.

In an AC train, when passing from one feeder line to the next σ) feeder line, the electric line BUS is in an open state (two iJ, voltage Vs) or zero. Therefore (the output of the two-transformer PTs, the unit positive bow Genba sinωst, also becomes zero, and as a result, the multiplier ML, σ)
The input current command value Is, which is li(')J, also becomes zero.

Therefore, the DC voltage command value Vd* and the actual voltage Vd 75(;
The input terminal is becomes zero again.

When the electric motor IM is running in the direction of 1 (2. When approaching the upstream wire crossing, the DC voltage VJ decreases, so Vd*:>Vcl, and the output 1 of the DC voltage converting IJ control circuit AVR The 100th Ism increases with a positive value.However, since the unit sine wave sinω5t, which is the other input of the 1st multiplier ML, is 0°C, the input current remains 1s = 1s = 0. .

Here, the output signal I of the DC voltage control circuit AVI (,
sm is connected to the b-side terminal of the switch circuit SW via the operational amplifier KT.The operational amplifier KT inverts the output signal Ism of the AVR and multiplies it by a constant.
e'' gives another torque command value.

In addition, the output signal Ism of AVIt is output from the Schmitt circuit 5.
)((2 is also input. The Schmitt circuit SH generates a signal to switch the f-switch circuit SW to the b side when the absolute value of the signal Ism exceeds a set level.

Therefore, when Ism increases and exceeds the setting level of the Schmitt circuit SH, the switch circuit S
W, which had been connected to the a side, is now switched to the b side. Therefore, the torque command value of the electric motor IM' is given to the operational amplifier by the output signal Te of the motor. The new torque command value Te is T'e*= -
kT・Ism ・・・・・・・・・・・・・・・ (I
Since Ism is a positive value, the torque '* command value +11e is a negative value, that is, a regeneration command.

Therefore, the rotational energy of the electric Pa I M is regenerated into the smoothing capacitor Cd, and the DC type! EVd is rising. If the Schmitt circuit SH has a hysteresis characteristic, Vd becomes Vd, and the AVR output signal Is
Even if the value of m becomes small, the switch circuit SW is not immediately returned to the a side, so that instability phenomena accompanying switching of the switch circuit SW can be avoided.

Moreover, even if the electric motor IM is operated continuously at 100°C and comes across a feeder line, the DC voltage Vdli of the smoothing capacitor Cd does not drop significantly.

Next, even if the power supply voltage Vs is turned on again, the converter C0Nv is always in a state where it can operate normally, and an excessive rush current will not flow from the power supply.

At this time, there is a concern that the electric MIM will be forced to go from a state of continuous operation to a second regenerative operation, so the first regenerative brake will be applied and decelerate. Energy is not that large, and once it is charged, the energy consumption is just enough to compensate for the circuit loss.Therefore, the deceleration of the electric 51M is extremely small.

Next, when the electric motor IM is in regenerative operation.

Explain what would happen if you were forced to cross a shortcut line.

Similarly, the input terminal is becomes zero.

In this case, it becomes Vd)Vd*, and the output signal Ism of VR to the DC voltage control circuit increases again with a negative value.

When the absolute value of l sm exceeds the set level of the Schmitt circuit SH, the switch circuit SW is switched from the a side to the b side f2. Since Ism is a negative value, the new torque command value T;* becomes Te:>o, and the engine is in continuous operation.

Therefore, the energy of the smoothing capacitor Cd is the energy of the motor I, M
The DC voltage Vd decreases to Vd#Vd.

Therefore, the DC voltage Vd will not become an excessive voltage,
Breakdown of the elements can be prevented without threatening the withstand voltage of the elements constituting the converter C0NV and the inverter INV.

Incidentally, in the embodiment shown in FIG. 2, the switching of the switch circuit SW is performed by the output signal Ism of the AVR.

It may also be switched depending on the value of the DC voltage Vd.

It is also possible to detect the presence or absence of the power supply voltage and switch accordingly.

Further, although the embodiment shown in FIG. 2 has been described using an AC train as an example, it goes without saying that it can be similarly applied to general industrial power outages, etc.

Further, although the converter C0NV has been described in the case of a single-phase power supply, a three-phase power supply or the like C2 can be similarly applied.

FIG. 3 shows another embodiment of the device of the present invention, which differs from FIG. 2 in that the switch circuit SW is switched depending on the presence or absence of the power supply voltage.

In other words, the voltage Vs at the receiving end of the AC power supply is
One is input to the multiplier ML as a unit sine wave sinωst, as mentioned above.

The other voltage is input to the rectifier DS to convert the current into direct current, and the voltage is output to the Schmitt circuit SH+. When the power supply voltage Vs becomes zero due to a momentary power outage or the like, the output voltage of the rectifier DS also becomes zero. The Schmitt circuit SH+2 detects that Vs has fallen below a certain set level,
Switch the switch circuit SW from the a side to the b side. Once the switch is made to the side, the switch is turned off until the power supply '71 voltage is restored.
is connected to the b side, the DC voltage Vd is controlled by the new torque command Te'' to match the command value Vd, and the deviation εv−Vd−Vd becomes a small value. remains on the b side.Therefore, the advantage of this embodiment is that the stability of DC voltage control during momentary power outages is better than that of the embodiment shown in FIG.

When the power supply voltage Vs is restored, the ℃ switch S field is returned to the a side f2 again via the Schmitt circuit SH which also indicates a high output voltage of the rectifier DS. After this, it becomes normal operation mode.

That is, DC voltage control is performed by converter C0NV, and speed control is performed by inverter INV.

〔Effect of the invention〕

As described above, according to the AC motor and drive device of the present invention, the bending voltage Vd of the flat/loaf capacitor Cd is maintained almost constant even in the event of a momentary power outage, etc., and when the power is turned on again, an excessive rush Current no longer flows in, and there is still the effect of preventing element destruction due to a DC voltage increase during regenerative operation, which has been a problem in the past. It is no longer necessary to install a large-capacity resistor on the AC side of the converter, and it is possible to provide an AC motor drive device that is economical, compact, and lightweight.

[Brief explanation of the drawing]

Figure 1 shows conventional AC power! I1 Machine drive configuration M. FIGS. 2 and 3 are configuration diagrams showing an embodiment of the AC motor and drive device of the present invention. BUS...Single-phase AC power supply feeder line 1'AN...Pantograph MT It,...Main power transformer Ls...AC reactor C0NV 0. Voltage-type self-excited converter Cd...smoothing capacitor INV, ・Voltage-type self-excited inverter IM...cage shadow line conductive motor i) G...rotational speed detector CTs, CTU, CTv, C'J"w −'
% flow detector P'l's...AC heavy pressure, detector ISO...insulation amplifier AVa..., DC'7 pressure control circuit A, SR, -...speed control circuit Kq゛...calculation Amplifier SH... Schmitt circuit DS... Rectifier SW... Switch circuit TEC,... Torque, 1. irish circuit AD... adder PT (J... 3 phase

Claims (1)

[Scope of Claims] An AC power supply, a voltage-type self-exciting converter connected to the AC power supply via an AC reactor, a smoothing capacitor connected to the DC side of this converter, and a voltage to be used as the voltage source of this capacitor. a self-excited inverter, an AC motor connected to the AC output side of the inverter, a DC voltage control circuit that controls the DC voltage of the smoothing capacitor, and a DC voltage iti! M depending on the output No. 100 from the control circuit
An input current control circuit that controls input from an AC power supply (DC). a first PWM control circuit that performs pulse width modulation control of the converter in accordance with an output signal C2 of the input current control circuit;
@Distribution A torque control circuit that controls the generated torque of the AC motor, an output current control circuit that controls the current supplied to the AC motor by the output signal from the torque control circuit, and a a second PWM control circuit that pulse-width modulates the inverter according to the output signal; and a torque command for the AC motor so that the DC voltage of the smoothing capacitor does not become too large or too small when the AC power supply fails. An alternating current motor drive device comprising means for providing.