JPS58218879A - Compensation of commutation lag of inverter - Google Patents

Abstract

PURPOSE:To compensate the phase error of an output current by a method wherein a DC current command, inverting angular frequency, a magnetic flux command and an exciting current command are operated to decide the commutation lag angle of an inverting circuit, and the phase angle of the driving pulse of the inverting circuit is corrected corresponding to the commutation lag angle thereof. CONSTITUTION:A circuit consisting of a torque current operating circuit 7, a DC operating circuit 8, a number of revolutions/magnetic flux converting circuit 13 and an exciting current operating circuit 14 controls a current limiting circuit 9 to control the respective thyristors of a rectifying circuit 3. A circuit consisting of an inverting angular frequency operating circuit 15, an angular frequency/ phase angle operating circuit 16, a phase angle operating circuit 17, a slip angular frequency operating circuit 22 and a torque angle operating circuit 23 decides a phase angle signal necessary to make an induction motor 2 to rotate according to a speed command, and the decided signal is supplied to a communtation lag compensating circuit 18. The commutation lag compensating circuit 18 corrects the amount of commutation lag of the phase angle command, and the corrected signal is supplied to a gate pulse operating circuit 19.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a commutation delay compensation method for an inverter that vector-controls an electric motor such as an induction motor. The present invention relates to a commutation delay compensation method for an inverter that corrects the phase angle.

Cage-shaped induction '#j, steplessly changing the rotational speed of the motive etc. 4
'4 As one of the inverters, current source input/< - evening i
) There is 1. FIG. 1 is a circuit diagram showing an example of the configuration of such a current source inverter. In this figure, 1 is a current value control circuit that controls the drive current value (input 1! current value) of the induction motor 2, and this current value control circuit 1 is a current value command S
1 and the current value detection signal 82, the conduction angle of each thyristor 3K, -a to 3T-b in the forward conversion circuit is controlled to control the output current value of the forward conversion circuit 3. Further, 4 is a frequency control circuit for controlling the driving current frequency of the induction motor 2, and this frequency control circuit 4 conducts conduction of each thyristor 5R-a to 5T-b in the inverse conversion circuit 5 based on the frequency command S3. is controlled to convert the output current of the forward conversion circuit 3 into a three-phase current with a conduction angle of 100. As a result, the inverse conversion circuit 5 outputs an R-phase current 1R55-phase current 8 and a T-phase current IT shown in FIG. In this way, the current source inverter can control the rotational speed of the induction motor 2 to an arbitrary speed by directly controlling the value and frequency of the drive current of the induction motor 2.

By the way, in such a current source inverter, a commutation delay occurs when switching conduction of each thyristor 5R-, to 5T-b of the inverse conversion circuit 5.

This will be explained below with reference to FIG. 3 and the accompanying drawings. First, when the gate pulse Qr shown in Fig. 3 (A) is supplied to the thyristor 5R-a, the R-phase current IR (see Fig. µ) flows along the path shown by the broken line Ll in Fig. 3, and At this time, commutating capacitor 6R-8 is charged to voltage -Vc with the polarity shown in FIG. Here, at time t1 shown in Fig. 1, the gate pulse G shown in Fig.
When the thyristor 58-a is made conductive at s, the thyristor 5R-a is reverse biased and becomes non-conductive.
The path of the R-phase current is switched from the path shown by the broken line L1 to the path shown by the broken line L2, and the commutation capacitor 6R-8 starts discharging. Then, from time tl, the period T - ΔT (here, T is the commutation delay period, and ΔT is the commutation heavy period)
Then, the commutating capacitor 6R-8 is charged to the voltage +Vc with the polarity opposite to that shown in Fig. 3, so the R phase current I
R is cut off, and the S-phase current Is (
(Refer to Figure (E)) is output.

On the other hand, as one of the speed controls of the induction motor, the phase of the drive current of the induction motor is also controlled.
°": i control. In the control, the drive current of the induction motor must be separated into a magnetic flux generation component and a torque generation component, and these must be controlled individually. It is necessary to accurately control not only the amplitude of the drive current but also its phase angle through the command value.Therefore, when vector control of an induction motor is performed using the current source inverter as described above, the inverse conversion circuit There is a problem in that the commutation delay causes an error in the phase angle of the excitation current, making it difficult to obtain good control characteristics.

In view of the above points, the present invention provides an inverter commutation delay compensation method that can compensate for the phase error of the output current due to the commutation delay of the inverse conversion circuit and obtain good control characteristics. In the invention, a commutation lag angle is calculated by calculating a DC current command obtained based on a speed command, an inverse conversion angular frequency obtained by driving the motor, a magnetic flux command, and an excitation current command, and this commutation lag angle is The first invention is characterized in that the phase angle of the gate pulse of the inverse conversion circuit is corrected according to the phase angle of the gate pulse of the inverse conversion circuit. Detect the output current of the inverse conversion circuit, calculate the output current, the voltage of each of the commutation capacitors, and the inverse conversion angular frequency i obtained by driving the motor to obtain the commutation delay angle, and calculate the commutation delay angle. The present invention is characterized in that the phase angle of the gate pulse of the inverse conversion circuit is corrected accordingly.

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

FIG. 3 is a block diagram showing a seventh embodiment of a speed control device to which this inverter commutation delay compensation method using the output BAVc is applied. The block diagram shown in this figure shows the seventh invention 1. In this figure, 7 is an adder 7a.
The torque current calculation circuit 7 includes a torque current component (torque current command) of a current that drives the induction motor 2 based on a speed command ωr and a speed feedback signal ωmTIc. 1qs) and supplies it to the DC' current calculation circuit 8.

The DC current calculation circuit 8 is composed of multipliers 8a and 8b, an adder 8C, and a square root section 8d, and drives the induction motor 2 based on the torque current commands iqs and ↓ and the excitation current command ids. A current value (DC'IM, current command value) is determined and supplied to the current control circuit 9.

The current control circuit 9 is composed of an adder section 9a and a current control section 9b, and includes the DC current command unit and current transformer 10. Each thyristor of the forward conversion circuit 3 is controlled based on the current feedback signal If obtained by the rectifier circuit 11. Further, 12 is a speed detector for detecting the rotational speed of the induction motor 2, and this speed detector 12 performs a detection operation V and sends the obtained speed feedback signal ωm to the torque current calculation circuit 7 and the rotational speed/magnetic flux. Conversion circuit 13
Supply Vc. The rotation speed/magnetic flux conversion circuit 13 is composed of a magnetic flux calculation section 13a, and calculates a required magnetic flux value (magnetic flux command ψ) of the induction motor 2 from the speed feedback signal ωm and supplies it to the excitation current calculation circuit 14. The exciting current calculation circuit 14 is composed of an adder 14a and a magnetic flux controller 14b, and calculates the exciting current component of the current that drives the induction motor 2 based on the magnetic flux command ψ and the magnetic flux feedback signal φS. (Excitation current commands i, ds) are determined and the DC 'rη is supplied to the current circuit 8Vc. That is, the torque current calculation circuit 7 to the rectifier circuit 11 and the speed detector 12 to the excitation current calculation circuit 14 are connected to each other. Motive 2
This is to control the drive current value.

The output of the speed detector 12 is also supplied to an inverse conversion angular frequency calculation circuit 15. The inverse conversion angular frequency calculation circuit 15 consists of an adding section 15a, and calculates the speed feedback signal ωm based on the multi-angular frequency signal ωS.
is corrected to obtain the inverse conversion angular frequency command ω0) and the angular frequency/
The signal is supplied to the phase angle conversion circuit 16. Angular frequency/phase browning i
The circuit 16 includes a phase angle calculation section 16a, which obtains a phase angle signal 0o based on the inverse conversion angular frequency command ω0 and supplies it to a phase angle calculation circuit 17. The phase angle calculation circuit 17 includes an adder 17a, which corrects the phase angle signal θ0 based on the vector angle signal θi to obtain a phase angle θC and supplies it to the commutation delay compensation circuit 18. The commutation delay compensation circuit 18 includes an adder 18B, and a phase angle box θp that compensates for the commutation delay by correcting the phase angle signal θC based on the commutation delay angle signal θ6.
is determined and supplied to the gate pulse calculation circuit 19Vc. The gate pulse calculation circuit 19 controls each phase risk of the inverse conversion circuit 5 based on the phase angle command θp.

In this way, the speed detector 12 and the inverse conversion angular frequency calculation circuit 15 to the gate pulse calculation circuit 19 operate the induction motor 2
The drive current frequency is controlled. Still, 20 is a magnetic flux detector that detects the magnetic flux inside the induction motor 2, and this magnetic flux detector 20 detects the magnetic flux detection signal φα, which is obtained by the detection operation.
pβ is supplied to the magnetic flux amplitude calculation circuit 21. The magnetic flux amplitude calculation circuit 21 determines the magnetic flux amplitude (Vφα2+φβ2) in the induction motor 2 based on the magnetic flux detection signals φα and φβ, and outputs a magnetic flux feedback signal φf corresponding to this magnetic flux amplitude to adjust the excitation current. It is supplied to the arithmetic circuit 14 and the angular frequency arithmetic circuit 22. The total polygonal frequency calculation circuit 22 is composed of a dividing section 22a and a minimum angular frequency calculation section 22b, and calculates the total angular frequency of the induction motor 2 based on the torque current command 1qs and the magnetic flux feedback signal φf. (subjective angular frequency signal ω8) is obtained and supplied to the inverse conversion angular frequency calculation circuit 15. Here, M shown in the Besi angular frequency calculation section 22b
is the mutual inductance (H) between the 7th winding and the secondary winding of the induction motor 2, Lr is the secondary winding self-inductance (H) of the induction motor 2, and Rr is the 7th line resistance (H) of the induction motor 2. Ω) Yes. Reference numeral 23 denotes a vector angle calculation circuit composed of a division section 23a and a vector angle calculation section 23b. is determined and supplied to the phase angle calculation circuit 17. Further, 24 is a commutation delay calculation circuit for calculating the commutation delay angle of the thyristor generated in the inverse conversion circuit 5.

Here, the calculation contents of this commutation delay self-calculation circuit 24 will be explained in detail. First, commutation delay period T (vth
(see figure) is equal to the period during which the voltage of the commutating capacitor changes from -VC to +Vc, so 2C" vc(sec) -・-= (1)T
−−] (However, ■ is the value of the drive current supplied to the induction motor 2 (
A) and C are the capacitance (F) of the commutation capacitor. Also, the commutation delay angle O11 is (however, ω0 is the inverse conversion angular frequency), so if we substitute equation (1) into equation (2) and eliminate the commutation delay period T, we get . On the other hand, the commutating capacitor voltage Vc is given by the following equation. However, L is commutation inductance (H)
, Em is the peak value 'ff) of the voltage between the power supply input terminals of the induction motor 2, and ψ is the power factor angle. Therefore, by substituting the formula into (3) and eliminating the commutating capacitor voltage vc, the voltage drop caused by Bieder's fault is so small that it can be ignored, so the voltage between the terminals of the induction motor 2, Em, becomes Em= ω
0φ can be expressed by the equation (6). Further, as is clear from the vector diagram shown in FIG. 6, the iIJ power ratio angle ψ is ds ψ=□ (7)■. In the figure, id8 is the excitation current vector, i4s is the torque current vector, Φ is the magnetic flux vector,
Em is the voltage vector, ■ is the current vector (v/i d
s2-1-iqs2).

Here, by substituting the above equations (6) and (7) into the above equation (5) and rearranging, the following is obtained. That is, the commutation delay control circuit 24 outputs the output of the DC current calculation circuit 8 (DC current command), the output of the rotation speed/magnetic flux conversion circuit 13 (magnetic flux command ρ), and the output of the excitation current calculation circuit 14 (excitation current command). Current command 1ds) Output of the inverse conversion angular frequency calculation circuit 15 (inverse conversion angular frequency command ω0) and constant commutation inductance and 1 commutation capacitor capacity tC
Based on Vc, the calculation shown in equation (8) is performed to obtain the commutation delay angle θε, which is supplied to the commutation delay compensation circuit 18.

Next, the operation of the embodiment having the above configuration will be explained.

First, a circuit consisting of a torque current calculation circuit 7, a DC current calculation circuit 8, a rotation speed/magnetic flux conversion circuit 13, and an excitation current calculation circuit 14 commands the induction motor 2 to a speed ωr based on a speed feedback signal ωm and an excitation feedback signal ρf. The DC current command required to rotate at the rotational speed shown by is determined, and the current control circuit 9 is controlled based on this DC current command to control the conduction angle of each thyristor in the forward conversion circuit 3. In addition, in parallel with such current value control operation, an inverse conversion angular frequency calculation circuit 15, an angular frequency/phase angle calculation circuit 16, a phase angle calculation circuit 17, a T-berry angular frequency calculation surface path 22, a vector angle calculation circuit 2
The circuit consisting of 3 is a torque current command iqs, an excitation current command ids, a magnetic flux feedback signal Of, :AA
Phase angle signal θ necessary to rotate the induction motor 2 at the speed command ωr based on the good feedback signal ωnl
0 is determined and supplied to the commutation delay 11 sleeve compensation circuit 18. On the other hand, along with these operations, the flow delay self-calculation circuit 24 Get t
(8) above based on DC current command, excitation current command i d s, magnetic flux command y7 conversion angular frequency command ω0
The commutation delay tLjf of the trace conversion circuit 5 is calculated by performing the operation n shown in the equation.
4tlε is determined and supplied to the commutation delay n compensation circuit 18. The commutation delay compensation circuit 18 corrects the commutation delay n of the phase angle command IO based on this commutation delay n angle θε, and supplies the n75 phase angle command lp obtained thereby to the gate pulse calculation circuit 19. Tru. As a result, the phase of the output (gate pulse) of the gate pulse calculation circuit 19 is advanced by the commutation delay of the inverse conversion circuit 50, and the phase of the output (gate pulse) of the gate pulse calculation circuit 19 is advanced by the commutation delay of the inverse conversion circuit 50. The current is output 8 old.

FIG. 7 is a block diagram showing an example of a specific circuit of the commutation delay angle calculation circuit 24 shown in FIG. 3. In this diagram,
Reference numeral 25 denotes an absolute value detection circuit for determining the absolute value of the inverse conversion angular frequency command ω0.The output of this absolute value detection circuit 25 is supplied to the eleventh multipliers 26a and 26b of the arithmetic circuit 26. Further, 27 is a forward/reverse detection circuit for detecting the polarity of the inverse conversion angular frequency command ω0.
1" is output, and conversely, when it indicates a reversal, "-1" is output.
is output and supplied to the third multiplier 26c of the arithmetic circuit 26. The arithmetic circuit 26 includes first to ≠ multipliers 26a to 26d.
1 Seventh to third division sections 26e to 26g and addition section 26
f, and the absolute value detection circuit 25
output, output of forward/reverse detection circuit 27, magnetic flux command ρ, DC current command, excitation current command ids, constant tan, 2 JT
Based on M, the calculation shown in equation (8) is performed to find the commutation delay angle θe.

1 and 2 are block diagrams showing a second embodiment of a commutation delay self-computing circuit to which the inverter commutation delay compensation method according to the present invention is applied. Note that the Prozok diagram shown in this figure shows the second invention. In these figures, 28 is an isolation amplifier that detects the voltage between the terminals of the commutating capacitor 6R-8, and the output ([voltage V (!('R-8)) of this isolation amplifier 28 is one absolute value. The signal is supplied to the detection circuit 29.

The absolute value detection circuit 29 detects the voltage EEV c (R-'8
), this absolute value detection circuit 2
9's output (l V(! (R-s) l ) Iti
Nt University 4B,? The output circuit 30 is supplied with +18. Also, 3
1 is an isolation amplifier that detects the voltage between the terminals of the commutating capacitor 6B-T, and the output of this isolation amplifier 31 (voltage VC
(8-T)) is supplied to the other absolute value detection circuit 32,
Here, the absolute value (the value is lVc (8-T)I)vc is converted and supplied to the maximum value detection circuit 30&C. The maximum value detection circuit 30 selects the larger value of the outputs of the absolute value detection circuits 29 and 32, and uses this as the commutating capacitor voltage vc.
The signal is supplied to the first multiplier 33aK of the arithmetic circuit 33 as a signal.

34- is an isolation amplifier that detects the value of the drive current supplied to H2j-motor 2Vc, and this isolation amplifier 34
The output (signal indicating the current value ■) is supplied to the division section 33d of the arithmetic circuit TN133. Further, 35 is a forward/reverse detection circuit for detecting the polarity of the inverse conversion angular frequency command ω0 obtained in the same manner as the inverse conversion angular frequency command ω0 shown in FIG.
The output of this forward/reverse detection circuit 35 (r+IJ or "-1"
is supplied to the first multiplier 33bK of the arithmetic circuit 33. The arithmetic circuit 33 is composed of first to third multipliers 33a to 33c and a divider 33d. Inverse conversion frequency ω0 and the forward/reverse detection circuit 3
Based on the output of step 5, the calculation shown in equation (3) is performed to find the commutation delay angle 0ε. In this way, in the second embodiment as well, the commutation delay angle θε
is determined, and each size ! in the inverse conversion circuit 5 is determined based on this commutation delay angle θε. The phases of the firing angles of J stars 5R-a to 5T-b are corrected.

As explained above, the method for compensating commutation delay for an inverter current according to the first invention calculates the direct weight 1'4!4, inverse conversion, angular frequency, magnetic flux command, and excitation current command to convert the inverse conversion circuit. The commutation delay compensation method for an inverter according to the first invention involves determining the commutation delay angle and correcting the phase angle of the drive pulse of the inverter according to this commutation delay angle. At the same time as detecting the voltage of each commutating capacitor of the 2゛ phase, the output current of the inverse conversion circuit is detected, and the inverse conversion angular frequency obtained by driving this output current, each of the commutating capacitor voltage and the rust conduction motor is calculated. The commutation delay angle of the inverse conversion circuit is calculated and the phase angle of the driving pulse of the inverse conversion circuit is corrected according to this commutation delay angle. Accordingly, it is possible to compensate for the phase error of the output current due to the commutation delay of the inverse conversion circuit without using a particularly high-speed thyristor, and it is possible to obtain good control characteristics.

[Brief explanation of the drawing]

FIG. 7 is a circuit diagram showing one configuration example of a current source inverter, FIG. 2 is a waveform diagram for explaining FIG. 1, and FIG. 3 is for explaining commutation delay of the inverse conversion circuit 50 shown in FIG. 7. FIG. 5 is a block diagram showing a seventh embodiment of a speed control device to which the invar 1 commutation delay compensation method according to the present invention is applied. , FIG. 6 is a vector diagram for explaining the same embodiment, FIG. 7 is a block diagram showing the details of the commutation delay angle wave calculation circuit 24 shown in the J column, and FIGS. FIG. 2 is a block diagram showing a first implementation example of a commutation delay angle calculation circuit to which the inverter commutation delay compensation method is applied. 3... Forward conversion circuit, 5... Inverse conversion circuit 56u-s. 6B-T”・・・Commuting capacitor, 8・・・・・・
DC current calculation circuit, 13... Rotation speed/magnetic flux conversion circuit, 14... Excitation current calculation circuit, 15...
... Inverse conversion angular frequency calculation circuit, 18 ... Commutation delay compensation circuit, 24 ... Commutation delay angle wave calculation circuit,
26... Arithmetic circuit, 28, 31° 34...
...Isolated amplifier, 33... Arithmetic circuit.

Claims (2)

[Claims] (1) In an inverter that has a forward conversion circuit and an inverse conversion circuit, separates the input current of the electric motor (load) into a magnetic flux generation portion and a torque generation portion, and controls these magnetic flux generation portion and torque generation portion individually. The commutation delay angle of the inverse conversion circuit is calculated by calculating the DC current command, the inversion angular frequency, the magnetic flux command, and the excitation current command, and the phase of the drive pulse of the inversion circuit is determined according to the commutation delay angle of the inversion circuit. An inverter commutation delay compensation method characterized by correcting the angle. (2) In an inverter that has a forward conversion circuit and an inverse conversion circuit, separates the input current of a motor, which is a load, into a magnetic flux generation component and a torque generation component, and controls these magnetic flux generation component and torque generation component individually. , detecting the voltages of the commutating capacitors of the seventh phase and the second phase in the inverse conversion circuit, and detecting the output current of the inverse conversion circuit, and detecting the output current,
calculating a commutation delay angle by calculating each commutation capacitor voltage and an inverse conversion angular frequency obtained by driving the motor;
A method for compensating for commutation delay of an inverter, characterized in that a phase angle of a drive pulse of the inverse conversion circuit is corrected according to this commutation delay angle.