JPS593119B2 - Control method of inverter device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a control system for an inverter device that converts direct current to alternating current to drive an induction machine, and particularly relates to a control system for an inverter device that converts direct current into alternating current to drive an induction machine, and in particular controls current that contributes to field generation of an induction machine and current that contributes to torque generation. An inverter system that can control both independently.

Regarding the control method of the FIG. 1 shows a route map of an example of an inverter device to which the present invention is applied.

In FIG. 1, 1 is an AC power supply, 2 is a phase-controllable rectifier composed of transistors, thyristors, etc.;
3 is a DC reactor 5 that smoothes the current, 4 is an inverter that converts DC to variable frequency AC, which is composed of transistors, thyristors, etc., 5 is an induction machine to be controlled, and 6 is an induction machine. , 7 is a speed control circuit, 8 is a field control circuit, 9 is a current reference calculation circuit, 10 is a current control circuit, 11 is a rectifier gate signal generation circuit,
12 is a current reference vector calculation circuit, 13 is a current vector calculation circuit, 14 is a commutation signal generation circuit, 15 is an inverter gate signal generation circuit, and 16 is a field calculation circuit.

15 Below, regarding the operation of the inverter device shown in Fig. 1,
The outline will be explained below.

The rectifier 2 rectifies the alternating current supplied from the alternating current power supply 1 to obtain a direct current.

The magnitude of the direct current can be changed by controlling the phase of the rectifier 2. After the direct current is smoothed by the direct current reactor 3, it is converted into alternating current by the inverter 4 and supplied to the induction machine 5. The rotation speed ω and phase of the current vector supplied to the induction machine 5 can be controlled by the inverter 4. The rotational speed ω of the induction machine 5 is detected by a rotational speed detection device 6&C such as a tachometer or a pulse generator directly connected to the axis of the induction machine 5, and compared with the rotational speed reference ω, the deviation thereof is determined by a speed control circuit T.

The deviation becomes a reference 11q for the current that contributes to torque generation (hereinafter referred to as "torque component current").

'j0 Also, the field φ outputted from the field arithmetic circuit 16, which will be described later, and the field reference φ* are compared, the deviation thereof is determined by the field control circuit 8, and the electric current, * current ( Hereinafter referred to as "field component current") reference 11d, *.

Torque component current reference 11q and field component current, * *■5
Since there is an orthogonal relationship with the reference 11d, the current reference 11 can be determined by the following formula.

Ha=(i杏d)'+(i-shoq)' Haku* The current reference 1 is obtained by performing the above calculation using the current reference calculation circuit 9.

Next, the current reference 1T and the detected current value 11 are compared, and the current control circuit 10 obtains the phase control signal PHC.

The rectifier gate signal generation circuit 11 receives the phase control signal PHC and generates a control signal for the rectifier 2. On the other hand, the current reference vector calculation circuit 12 uses the torque component current reference 1
With Fq and field component current reference 1rd as input, current reference vector i↑ is output. Current vector calculation circuit 1
3 outputs a current vector I by directly detecting the output current of the inverter 4 or by calculating it from the output signal of the inverter gate signal generation circuit 15. The commutation signal generation circuit 14 has a current reference vector IT and a current vector i1.
A commutation signal 1NV is output which determines the commutation timing of the inverter. Inverter gate signal generation circuit 1
5 generates a control signal for the inverter 4 by inputting the commutation signal 1NV. Finally, the field calculation circuit 16 calculates the field generated inside the induction machine 5 from the current vector i1, or directly detects it with a magnetic sensor installed inside the induction machine 5, so that the field φ Output. Next, a method for determining the commutation signal 1NV of the inverter 4 will be explained using FIGS. 2 to 5.

FIG. 2 shows an example of the configuration of the inverse converter 4 in a block diagram.

U, V, W, X, Y, and Z are thyristors, C is a commutating capacitor, and D is a series diode, which constitutes a current-type inverter. The current vector I, which can be output by the inverter having the above configuration, can take six positions as shown in FIG. In FIG. 3, vector UZ indicates the current vector I, which is obtained when the thyristors U and Z are on. Vector VZ, VX, WX, WY, UY
The current vectors I, obtained when the thyristor, Z, V (5' However, in the inverter as shown in Fig. 2, it is not possible to take a current vector i1 other than the above six vectors.Therefore, when one of the above thyristors is commutated, the current vector I, becomes 6'. For example, by commutating from the thyristor U to the thyristor U, the current vector i1 moves from the UZ position to the VZ position.On the other hand, the current base vector IP moves smoothly at the angular velocity ω. It is clear that this can be achieved by 2π by supplying a sinusoidal current of frequency f (=1) to the induction machine 5ω.

The above operation will be explained on coordinates rotating at the same angular velocity ω as the current reference vector i (referred to as dq coordinates) as shown in FIG. 4.

The d axis is in the direction of the field φ created inside the induction machine 5, and the q axis is
The axis is assumed to be at a position 90 degrees ahead of the d-axis. In other words, since the field φ is created by the current vector I, it rotates at the same angular velocity ω. Since the d-q coordinate and the current reference vector IF are rotating at the same angular velocity ω, the d-q
In the coordinate system, the current reference vector i'F is stationary. The current reference vector IF is stationary. Current reference vector IF (7) The d-axis component is the current that contributes to field generation, that is, the aforementioned field component current reference 1Fd, and the q-axis component is the current that contributes to torque generation, that is, the aforementioned torque component current reference. It is 1Fq. Therefore, the current vector i1 is
As shown in FIG. 2, when two specific thyristors are turned on, their positions are fixed, so they rotate at an angular velocity ω on the dq coordinates.

Therefore, the angle θ between the current reference vector IF and the current vector i1 is constantly changing. As mentioned above, since there are only six output current vectors 11 of the inverter having the configuration shown in FIG.
The current vector I, closest to the table is selected and a given thyristor is turned on. In Fig. 4, the current vector VZ
is closest to the current reference vector IP, so thyristors V and Z are turned on.

As described above, since the current vectors i1 are spaced at 60° intervals, the commutation signal 1NV is output when the angle θ reaches 30°. FIG. 5 shows an example of the vector diagram.

In Fig. 5, the current vector UZ is rotating clockwise at an angular velocity ω, and the angle θ with the current reference vector i =
3', a commutation signal 1NV is output. As a result, commutation occurs from thyristor U to V, and the current vector jumps 6' to the current vector VZ. Thereafter, commutation is performed in the same manner as the current vector I rotates l. By the way, as is clear from the above explanation, the inverse conversion device 4 having the configuration as shown in FIG.
The d-axis component of the current vector i1 supplied to the induction conductor 5, q
The axial component is constantly changing, and G↓ changes suddenly during commutation. Normally, fluctuations in the d-axis component, that is, the field component current 11d, have a large inductance of the induction machine 5, and have little effect on the field φ. Therefore, the field φ is the field component current 1
A constant value corresponding to the field component current reference 1d, which is the average value of 1d, is maintained. However, fluctuations in the q-axis component, that is, the torque component current 11q, directly appear as fluctuations in the induction machine generated torque. This state is shown in FIGS. 6A, b and 7A, b. FIG. 6a shows comparatively the generated torque of the induction machine 5.
*When the torque component current reference 11q is large and the torque component current reference 11q is large, the fluctuation of the torque component current 11q varies from a maximum of 1}q to a minimum of 1rq.

When this change is viewed on the time axis, it becomes as shown in Figure 6b. After one commutation, the transition to a sine wave with a delayed phase occurs. Assuming that the field φ is constant, the waveform shown in FIG. 6b is also the torque generated by the inducer 5. Next, FIG. 7a shows a case where the torque generated by the induction machine 5 is relatively small, and since the torque component current reference q is smaller than the field component current base 91Fd, the minimum value 1τq of the torque component current 11q is is a negative value.

This means that the induction machine 5 temporarily generates negative torque as shown in FIG. 7b. The generation of negative torque adversely affects not only the induction machine 5 but also the load device connected thereto, such as vibration and noise. This phenomenon is not unique to the inverter device described in FIG. 1 or the inverter device described in FIG. 2, but is an essential drawback of inverter devices that cannot obtain a sine wave output. The present invention has been made in view of these drawbacks of inverter devices, and provides a control method for inverter devices that can extend the state in which the induction motor does not generate negative torque even temporarily, even during light loads. The purpose is to FIG. 8 shows a process diagram of one embodiment of the present invention.

In the drawings from FIG. 8 onwards, elements given the same numbers as in FIG. 1 have the same functions. The difference between FIG. 8 and FIG. 1 is that a field weakening control circuit 17 is provided which inputs the current reference vector IF and outputs the field reference φ*.

As mentioned above, the induction machine 5 generates negative torque when the load is light and the torque component current reference 1Tq is the field component current reference 1F.
Since it is small compared to d, the current reference vector Ir
When the angle .theta. between the d-axis and the d-axis becomes smaller than a predetermined angle, the generation of negative torque can be prevented by performing field-weakening control to reduce the field component current reference d. FIG. 9 shows a vector diagram representing this principle. When the angle θ blue between the current reference vector IF and the d-axis is small,
The field component current reference 1' is set by the field weakening control circuit 17.
IF Fd! decreases to d. As a result, the torque generated by the induction machine 5 decreases, and to compensate for this, the torque component current reference 1Fq increases to i'F'q. : Le = W: 7 Tei: 1
::↓Shatter=T can be done.

Normally, there is a limit to weakening the field of the induction machine 5, so
When the load is extremely light, it becomes difficult to increase the angle θ.

However, under such a light load, the current 11 decreases,
The generated torque is also small, and even if negative torque occurs, it is reduced to such an extent that it does not pose a practical problem. FIGS. 10 to 12 show route maps of different embodiments of the present invention.

In FIG. 10, 18 is a field weakening control circuit which inputs the tortor component current reference 1Fq and outputs the reference φ*.

By inputting torque component current reference table 1 q and performing field weakening control when it becomes less than a predetermined value, generation of negative torque can be prevented. In Figure 11,
19 is a field weakening control circuit which inputs the current vector i1 and outputs the field reference φ*.

When the q-axis component 11q of the current vector i1 is input and becomes negative or approaches negative, generation of negative torque can be prevented by performing field weakening control. In FIG. 12, 20 is a torque sensor that detects the torque generated by the induction machine, and 21 is a field weakening control circuit that receives the output signal of the torque sensor and outputs a field reference φ*.

The generated torque of the induction machine 5 is detected by the torque sensor 20, and when a negative torque is generated or when the generated torque approaches a negative value, field weakening control is performed to prevent the generation of negative torque. Note that the inverter 4 to which the present invention is applied is not limited to having the configuration shown in FIG. is not limited to this.

As explained above, according to the present invention, the generation of negative torque at light loads, which was an essential drawback when driving an induction machine with a non-sinusoidal current, can be replaced with a current that contributes to the torque generation of the induction machine. This can be prevented or reduced by using an inverter device that can independently control the current that contributes to field generation.

[Brief explanation of the drawing]

Figure 1 is a route diagram of an example of an inverter device to which the present invention is applied, Figure 2 is a block diagram of an example of an inverter, and Figure 3 is a vector diagram of the current that can be output by the inverter shown in Figure 2. ,
Figures 4 and 5 are vector diagrams of output current seen on the d-q coordinates, Figures 6A and b are output current vector diagrams and torque component current waveforms at heavy loads, and Figures 7 a and b are for light loads. Output current vector diagram and torque component current waveform during load, 8th
9 is a vector diagram for explaining the principle of the present invention, and FIGS. 10 to 12 are route diagrams of different embodiments of the present invention. 1... AC power supply, 2... Phase controllable rectifier, 3... DC reactor, 4...
...Inverse converter, 5...Induction machine, 6...
Rotation speed detection device, 7...Speed control circuit, 8...
...Field control circuit, 9...Current reference calculation circuit, 10...Current control circuit, 11...
Rectifier gate signal generation circuit, 12... Current reference vector calculation circuit, 13... Current vector calculation circuit, 14... Commutation signal generation circuit, 15...
...Inverse converter gate signal generation circuit, 16...
Field calculation circuit, 17, 18, 19... Field weakening control circuit, 20... Torque sensor, 21...
...field weakening control circuit, ωr...induction*machine rotation speed, ωr...induction machine rotation speed reference, φ...
...Field*Magnetic, φ ...Field reference, Ilq...
...Torque component current, IFq...Torque component current reference, Ild...Field component current, IFd
......Field component current reference, i1...Current vector, i...Current reference vector, I,...
...Current (absolute value), IF...Current (absolute value) reference, PHC...1...Phase control signal, INV...
... Commutation signal, U,, W, X, Y, Z...
・Thyristor that makes up the inverter, D...Series diode that makes up the inverter, C...Commuting capacitor that makes up the inverter, UZ...Thyristor The i1 vector obtained by turning on U and Z, VZ・
...I obtained by turning on thyristors V and Z,
Vector, VX... i1 vector obtained by turning on thyristors V and X, WX... i1 vector obtained by turning on thyristors W and X, WY...
... i1 vector obtained by turning on thyristors W and Y, UY ... I vector obtained by turning on thyristors U and Y, θ ... i vector and I vector angle with, ω...Rotational angular velocity of i1 vector, i/, Ir...vector indicating the change range of i1 vector, i/Q, irq...
The maximum and minimum values of Ilq, IT(...Ird
New current reference vector when weakening, i/D, i doq...
...The d-axis and q-axis components of the i store, :-゜]::Angle with the ゛1゛゜01゛ axis, θ*d...Angle between i1* and the d-axis.

Claims (1)

[Claims] 1. Reduce the current that contributes to field generation by using an inverter device configured to independently control the current that contributes to torque generation of the induction machine and the current that contributes to field generation. A control method for an inverter device that is characterized by preventing or reducing negative torque generated by an induction machine during light loads. 2 Claims that are configured to reduce the current that contributes to field generation when the reference value or detected value of the current component that contributes to torque generation among the current supplied to the induction machine falls below a predetermined value A control method for the inverter device according to item 1. 3. Claim 1 is configured to detect the generated torque of the induction machine and reduce the current contributing to field generation when negative torque is generated or when the generated torque approaches negative torque. control method for inverter equipment.