JPS5843185A - Controller for voltage type pwm inverter - Google Patents

Abstract

PURPOSE:To improve the stability of a voltage type PWM inverter by detecting the output current of the inverter, inputting the signal together with a current reference signal to a current control circuit provided in a minor loop of a control system and controlling the pulse width modulation with the deviation signal from the control circuit. CONSTITUTION:When an induction motor IM is driven by a voltage type PWM inverter INV, the output current of the inverter is detected by detectors CS1, CS2, thereby obtaining an output current average value signal corresponding to the fundamental wave effective value through an absolute value converter 44 and an average circuit 45. A current reference signal IR corresponding to the voltage deviation signal as the output of a voltage control circuit 21 is calculated and is inputted to a current control circuit 46, the deviation from the circuit 46 is applied to a PWM control circuit 22, and is logically synthesized by the signal of a ring counter 28, thereby controlling the control element of an inverter. Accordingly, the motor current can be always monitored and controlled, thereby preventing the vibration in the torque and performing the stable operation.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a control device for a voltage source inverter constituting a variable voltage variable frequency control device vvvy for variable speed control of an AC motor.

Fig. 1 shows a control device for a conventional tank voltage type inverter already proposed in 4I Application No. 54-140818. A voltage source inverter is formed with a bridge configuration, a three-phase bridge configuration with a diode 7N12, and a capacitor 0 at the input end.]
, input terminal a.

;2=ko, 2=2:2j°::Nini::;;Knee is connected to the primary winding u, % W, of the visiting electric power WAxM, and the three-phase AC input B, ? The electric power input through the !1 current path Rde and whose voltage and frequency are controlled is supplied to the induction motor xM.

And each power tiger W of the above invar°)ri x Mv! The control device for controlling the pace of the printer lister has the following configuration. On the other hand, an insulated shaping circuit 19 mainly composed of RTE and the like is connected to the neutral power terminals υ, V, and W, and an output voltage average value signal uf that resonates with the fundamental wave effective value of the output power is detected. , this detection signal uf is the voltage reference signal v
Output v of the input limiting circuit that outputs a signal yaP with less steep changes even when H is input in a stepwise manner.
A calculation is performed using R/ and the indicated polarity, and the calculation result is input to the voltage control circuit 21, which outputs a voltage deviation signal U.

The voltage deviation signal U.
is input to the above reference wave generation circuit.

A reference rectangular wave or reference sine wave signal having nine amplitude values proportional to the voltage deviation signal U0 can be obtained from this reference wave generating circuit.

On the other hand, the output uI of the input limiting circuit is -W, which is input to the voltage-frequency conversion circuit 25 and converted into a clock pulse, and the clock pulse frequency divider circuit is inputted to the counting circuit 25a. Natteshi.

, 1. At this time, the count output signal of the count path 25a is inputted to the fundamental wave generation circuit and the carrier wave generation circuit 26 as an address signal.

Then, the output signal of the frequency dividing circuit d is inputted to the ring kakunta field, and this kakunta MJt) output signal and the above PI
The output signal of the FM control circuit 22O and the remote pwM control signal A are synthesized by the logic synthesis circuit 4.

The signal is transferred to the pace drive circuit 31 via the composite signal line photocoupler circuit 31, and by controlling the pace of each transistor 1-6 of the inverter INv, the inverter Hvi is driven.

This control method is known as ma/f control, and ma/f control is linear and can efficiently drive an AC motor in a variable manner, thus substituting the vvvp that drives the motor. )6・However, in Th- for the control device with the above configuration.

When driving a small load with flywheel effect, or when operating the motor alone with no load, all F)B
==00 Near the synchronous speed, the slip of the 1wJ conductive motor IM appears to change alternately between positive and negative, which causes the motor current to pulsate and cause torque oscillations, so-called. Anxiety electric phenomena may occur. To solve this problem, the rounding method is as follows:
As disclosed in No. 6, it was necessary to adopt the anti-hunt method of detecting the motor current, obtaining its differential signal, and correcting the inverter frequency according to the current differential signal.

In addition, even during normal operation, the power transistors 1 to 6 of the motor xM and inverter xNv are
It is necessary to protect the motor XM and the power transistor from overheating and destruction69, and for this purpose, in addition to detecting the DC input current of the inverter xMY, it is also necessary to detect the output current of the inverter XHV, that is, the motor current, and apply a current limit to the motor It is necessary to protect 1-6” JH rarely.

As mentioned above, it is necessary to provide anti-hunt control and overcurrent protection means in conventional inverter control equipment, and these configurations are complicated and expensive.
9. 'The present invention has been made to solve the problems of the conventional ones as described above, and it detects the motor current in a comparison section and constantly monitors and controls the current.
The present invention provides a control device for a voltage source inverter that can perform stable operation.

Below, one embodiment of the present invention will be explained based on FIG. 2, in which the same parts as in FIG. 1 are denoted by the same reference numerals. The present invention is characterized in that relatively simple current detection means and current control means are provided in the minor loop to perform average value current control of the output current of inverter XN'Y. That is, in order to detect and shape the three-phase alternating current input to the electric motor M and relatively easily obtain the current feedback signal if, the following means is provided in FIG.

First, the output terminal U%W of inverter XNV and electric fi1
M+2) Current detectors aS1 and a are connected between the primary windings u and v.
1. A 9-hole OT or the like is applied by applying a shunt resistance 0-tehole element as a ζ, 0 current detector, and 1. Detector OB, and os.

An insulated amplifier circuit 41 and a catfish are respectively connected to the insulated amplifier circuits 41 and 42, and the p-section current detection signal 41u and the W-phase current detection signal 1W obtained by the isolation amplifier circuits 41 and 42 are inputted to the arithmetic circuit 43, and the V-phase current detector, signal Try to get 1v.

Next, each current detector No. 1 1u, *ma, iv is inputted to the absolute value conversion circuit 44, and its absolute value signal l iv
l.

11ma 1.11w1 is obtained, which is further input to the average value circuit 45, and an output current average value signal 1f corresponding to the fundamental wave effective value of the output current of the inverter XNV is obtained as an output of 1,000. The output of the circuit 21 is calculated according to the current reference signal IR corresponding to the voltage deviation signal 6 and the illustrated polarity, and the result is input to the current control circuit 46 so that the error amplification signal and the current deviation signal 1Δt% are generated ( The amplitude value of the reference sine wave or reference rectangular wave that is input to the fundamental wave generation circuit of the PWM control circuit n and output from the fundamental wave generation circuit O is used as the current deviation signal 1Δ't.
By changing it accordingly? ), change the modulation rate of PWM control! The magnitude of the motive current is controlled.

ζ Here, the above performance! - Road 43% absolute value conversion circuit shop.

and average value circuit 45. The filamentous structure of is shown in FIG. First, the arithmetic circuit 43 is an adder circuit mainly composed of an operational amplifier 43a (Table 9 (431) to 436 are resistors), and the absolute value conversion circuit Kaede is a similar circuit for the U phase s v @ w phase silver. In addition, the absolute value conversion circuit 4417 of the phase
are two operational amplifiers 441Ta, 441T'b and two diodes 44U., 44ff+1. and resistance 4417
・The J4t7kt is equipped with an average value circuit section.

It mainly consists of an adder circuit consisting of an operational amplifier 45a, a resistor 451) #45f, and a capacitor 45g.The capacitor 45g is removed and the output terminal of the amplifier 45a is connected to the output terminal of the amplifier 45a. It can also be used as a circuit to obtain the average value output by connecting an active filter (Cubus filter).

In the above-mentioned configurations of FIGS. 2 and 8, the U-phase current 1u
and the W-phase current 1W are detected, and the V-phase current 1W is calculated based on this. Now, the output current is 1u, iv,
When iv· is approximated to a perfect sine wave, it can be expressed as follows.

Winter u = cIm 51m1lt −”=””
-(1)'it = Xm5is+ (#t-, -yr
)・Fist・−−−−−−−−(8) Therefore, 1u + 1 shrine m (sinu− 7u (@t−Tπ))=m
2xIB@BSho#tgoo)・閘(100K)=-IBssi
Since i(St-7g)=-1v=(4).

1v=-(1ma+1v) -・・・・・・・1 old・・
-(5) and perform the operation of equation (6) K, 6v
The phase current it can be determined, and the arithmetic circuit 43 has this arithmetic function. Therefore, as shown in FIG. 4(1), when the main phase signal 1v shown by the broken line is obtained based on the detection signals 4u and iw, 6 is obtained.

In addition, the absolute value conversion circuits 44υ, 447, and 44W convert the current signals 1u, 1ma, and iw into half-waves, as shown in Figure 1...). 1 Keyaki Shi9 absolute value signal 11ul, liv I, 11w
1, and furthermore, the average value circuit 46 has obtained an average value signal 1f of the output current as shown in FIG. The motor current can always be controlled to a predetermined value by inputting the average value signal 1f as a feedback signal to the current required control circuit 46 to perform feedback control.

Further, even if the average value signal if' changes due to load fluctuation, the deviation signal 1Δ is small, so that the modulation force is reduced and the motor current is controlled to be constant based on the reference value xB. Therefore, even if load fluctuation occurs, pulsation of the motor current can be suppressed, and the inverter INV can be stably controlled.

Furthermore, FIG. 6 shows a modification of the present invention, which differs from the configuration in FIG. 2 in that the insulation shaping circuit 19 is removed without detecting the output voltage σf of the inverter xMv, and the replacement]K
A speed generator TG is provided at the shaft end of the load motor, a gain adjustment circuit 47 is connected to this, and a speed detection signal nf is fed back. Here, the speed reference signal NJi is used as the reference signal, and the signal NRF is obtained through the input control circuit in the same manner as in FIG. 2 and is applied to the control system.

Typically.

The output voltage of the PfM inverter is in the form of a PfM series.

Moreover, since surge voltage is superimposed, it is difficult to accurately detect the speed detection signal vf, but in the configuration shown in FIG. 6, the speed generator! Since G is used, accurate speed detection can be performed, and control accuracy can therefore be improved compared to the configuration shown in FIG.

6 is a partial improvement of the configuration of FIG. 2, in which an arithmetic circuit mallet is inserted between the voltage control □ circuit 21 and the current control circuit 46 in FIG. 2, and the current reference signal IR and The excitation current setting standard Io is input to the above-mentioned arithmetic circuit mallet, and this arithmetic circuit calculates the primary current reference signal I.
.

The above current reference signal IR is originally a torque, that is, -
The output current signal 1f corresponds to the secondary current H, while the output current signal 1f corresponds to the primary current 1. The result obtained by detecting h
;bej÷, therefore, the above calculation circuit Ml/C0(j
℃1 animal - 70 performances! If the primary current is controlled based on the primary current reference work and the kettle response key ``λ,'' then good control characteristics can be obtained as in the configuration shown in *g. When carrying out the operation i', a pattern circuit may be provided that reduces the excitation current setting standard 1. as the speed increases.

　　.

Furthermore, in the embodiment shown in FIG. 6 described above, the calculation circuit 48 is inserted between the speed control circuit 21 and the current control circuit 21 and the same calculation is performed. Based on this, the primary current can be controlled and the control characteristics can be improved.

In addition, in the above-mentioned round can embodiment, the load is a synchronous motor and a % speed counterfeit generator! It is possible to replace G with a pulse generator P()K to achieve the same effect.

Further, the effective value of the fundamental wave of the output current is obtained with equal constraints using the ζ table for calculating the average value of the output current, but the calculation normal of the effective value of the fundamental wave is not limited to this.

As described above, according to the present invention, the control device for a voltage type PWM inverter is capable of detecting the motor current relatively easily and constantly monitoring and controlling the motor current to perform stable operation. is obtained.

[Brief explanation of the drawing]

Fig. 1 is a block diagram showing a conventional inverter control device, Fig. 2 is a block diagram of a control device according to an embodiment of the present invention, Fig. 8 is a partial detailed configuration diagram of Fig. 1s2, and Fig. l1r4 is Fig. 8. FIG. 6 is a waveform diagram showing operation waveforms of each part of FIG. 6, and FIG. 6 is a block diagram showing another embodiment of the present invention. XHv-inverter, Rν... rectifier circuit, X-...
Induction motor: is=・-insulated shaping circuit s 2om's
Input limit circuit, 21-voltage control circuit%22-”P W
M control circuit.蓼... Fundamental wave generation circuit, 24... Comparison circuit, 25.
-vy conversion circuit, '2s*a/carrier generation circuit, 27
***Divider circuit. 4.-Linda counter, 29.-Logic synthesis circuit, 31
-...Pace drive circuit, am(, as,...Current detector. 1u, 1ma, iW-phase current detection signal, 43--Arithmetic circuit. 45--Average value circuit, 46--Current control Circuit. Applicant's agent, Inomata Kiyoma 6 Figure

Claims (1)

[Claims] 1.1! In a voltage source inverter consisting of a reverse parallel q connection between a bridge configuration of power control rectifiers and a bridge configuration of power rectifiers, an output voltage detection signal above the average value of the inverter output voltage is output. A deviation signal is obtained from the voltage ItlIJ# circuit, which inputs the voltage detection signal and the voltage reference signal, and is used as a current reference signal.In addition, the output current of the inverter is detected, the basic a effective value is calculated, and the output current detection signal is generated. year. The current reference signal and the output current detection signal are applied to the current control circuit provided in the minor loop of the control system, and pulse width modulation control is performed according to the current-difference signal between them, and the voltage reference signal is A control flJ device for a voltage source PfM inverter, characterized in that it controls an output frequency according to the frequency. Of the three-phase output of the above inverter, the output current for three phases is detected, inputted to the engineering calculation circuit, and the above three phases are added up.
The output current of the other one phase is determined by reversing the current, and the output current of each phase is input to the effective value circuit to obtain the fundamental wave effective value, and this fundamental wave effective value is used for the current control described above. Feedback control by inputting to the circuit'elf
A control device for a voltage-type P1M inverter according to claim 1, wherein: Tortoise A secondary-to-primary conversion calculation means is provided between the voltage control circuit and the current control circuit, and the current reference signal and the excitation electroparalysis setting signal are inputted to calculate the primary current reference.
Feedback control is performed by inputting the next current reference and the output current reference inverse effective value signal to the current control circuit t%
A control device for a voltage-type PIFM inverter according to claim 41 or 2.