JPS62114488A - Electric motor speed control method - Google Patents

Abstract

PURPOSE:To perform speed control having excellent response and high precision by learning the drift section of a speed detecting value by a tachometer generator system by using a rotor-position detector and compensating the speed detecting value on the basis of the result of the learning. CONSTITUTION:An output from a first detecting system consisting of a tachometer generator (TG) 10 and an A/D converter 11 is introduced to a comparator 14a, and a reaching to approximately rated speed is detected. Consequently, changeover switches 13a, 13c are turned ON and ones 13b, 13d are turned OFF, and an error at that time is memorized to a memory 12 as a drift section. Accordingly, the so-called drift learning period is formed. The drift section is memorized to the memory 12 after the learning, and introduced to an adder 7c through the switch 13c, thus compensating the output from the first detecting system by the introduction to the adder 7c of the drift section, then starting predetermined speed-alignment control.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a control method for controlling the speed of an electric motor via a power conversion device.

[Conventional technology]

Conventionally, as this type of control system, the ones shown in FIGS. 2 and 3 are known. In these figures, l is a digital arithmetic unit, 2 is a power converter consisting of a converter 2a and an inverter 2b, 3 is a synchronous motor,
4 is a rotor position detector (PD), and 6 is a speed feedback loop. This speed feedback loop 6 includes a pulse generator (PLO) 8 and a digital speed detector 9 in FIG. 2, and a speed generator (TO) 10 and an analog/digital (
A/D) converters 11, respectively.

That is, the PD 4 and the PLG (Figure 2) or TG (Figure 3) as speed detection means are coupled to the rotor shaft of the synchronous machine 30, and the former is connected to the digital speed detector 9, and the latter is connected to the A/ Each of the signals is converted into a digital quantity by the D converter 11, and feedback control is performed.

Although this is used as a PDVi magnetic flux position detection means to control an inverter, it is also conceivable to use it as a speed detection means as shown in FIG.

[Problem that the invention seeks to solve]

However, as shown in Figure 2, PLO is used as a speed detection means.
Using PLO, it is possible to perform control with high precision and high-speed response, but there are cases where PLO cannot be used due to structural constraints of the synchronous machine used or constraints on the installation environment. Although the system using TG has good responsiveness, there is a problem in that the accuracy of static speed control is poor because the output voltage and the circuit that converts it into a total digital quantity are subject to temperature drift, aging, etc. Furthermore, as shown in Figure 4 (PD
In the method using the PD, since the number of teeth in the PD is smaller than that in the PLG, a relatively long measurement time is required to obtain a sufficient speed detection means, resulting in a problem of poor response. There is.

Therefore, this invention is a speed detection means as a speed detection means!
The purpose of this study is to particularly improve accuracy when using a machine (TG).

[Means for solving problems]

A speed generator that detects the speed of the motor driven via a power converter whose phase is controlled based on the output from the position detector, and a signal converter that converts the speed generator output voltage into a digital quantity. and speed detection means for digitally detecting the motor speed from the output of the position detector;
Error detection means for determining the detection error of the speed detection value by the speed generator and signal converter from this speed detection value and its command value (or the speed detection value by the speed generator), and a memory for recording this detection error: shall provide means.

[Effect]

In the above configuration, while maintaining the speed command value at a predetermined value,
When the motor speed detection value matches the command value for a predetermined period of time or more, drift learning is performed in which the output obtained from the error detection means is stored in the storage means as a drift amount. By correcting the speed detected by the speed generator and signal converter using the learning results and performing feedback control, it is possible to achieve the same coordination and accuracy as when a pulse generator (PLO) is used in the speed detection system. to ensure that

[Jibu baeng]

Figure 1 shows the actuality of this invention I? FIG. 2 is a configuration diagram showing an example of lji.

In the same figure, 12 is a memo! j, 13a to 13d are changeover switches, 14a is a comparator, 14b is a timer, and the other parts are the same as those in Figure 3. Note that f(t)−Δ
f is a speed command value when controlling the speed of the synchronous machine 3 in synchronization with the source.

Δf indicates the slip frequency component of the synchronous machine.

Further, % floo is a constant speed command value.

That is, the digital arithmetic unit 1 controls the speed of the synchronous machine 3 via the power converter 2. The rotor shaft of the synchronous machine 30 has a position detector (PD) 4 and a speed generator (TG) 1.
0 is connected. The output of the PD 4 is given to a digital calculator 1 and a digital speed detector 9, and the former controls the phase of the power converter 20, while the latter converts the detected speed value into a digital quantity. on the other hand,
Equal speed command value f - Δf, which is obtained by subtracting the desired slip frequency Δf from the power system frequency f, and the synchronous machine rated frequency command value '10
0 is input to adders 7a and 7b via changeover switches 13a and 13b'l, respectively.

The output of the digital speed detector 9 is introduced into the adder 7b with the polarity shown, and the output of the adder 7b is input to the switch 13d.
'e to the memory 12.

The output of the memory 12 is input to the adder 7C via the switch 13 (l), and the output of the A/D converter 11 is also introduced to this adder 7C.
a and a comparator 14a, and the output of the adder 7a is given to the digital arithmetic unit 1, while the output of the comparator 14a is given to the timer 14b, and the changeover switches 133 to 13d are driven by the output.

In such a configuration, the switch 13a.

Assuming that 13C is off and 13b and 13d are on, the speed of the synchronous machine 3Vi is controlled based on a constant speed command f100. At this time, the rotation speed of the synchronous machine 30 is determined by the first detection system consisting of the TGIO and the A/D converter 11, and the FD4.
and a second detection system consisting of the digital speed detector 9. By the way, in the first detection system, the detected value is affected by drift components, etc.
An error will occur between the speed command value fl 00 or the output of the second detection system. Therefore, in this case, the adder 7b adds the speed command value fl00 and the output from the digital speed detector 9 with the polarity shown, thereby extracting the error, that is, the drift amount. Note that if such an operation is performed before the motor speed reaches the rated speed floO, an erroneous detection will occur, so in this embodiment, the output of the first detection system obtained via the adder 7Ct is introduced into the comparator 14a. Detection of the above-mentioned error is started by completely detecting that the speed has reached approximately the rated speed. At this time, as mentioned earlier, the second detection system takes a relatively long time to detect the speed.
Therefore, after securing this measurement time with timer 14b,
Turn on the changeover switches 13a and 13c, 13b and 13d'
t off, and the error at that point is stored in the memory 12 as a triad. In this way, a so-called drift learning period is formed. After this drift learning, the drift amount is stored in the memory 12 and introduced into the adder 7C via the switch 13C'e, so that the output of the first detection system is corrected and predetermined speed equalization control is started. Ru.

Note that, although the above description has mainly been given to the case where a synchronous machine is controlled, the present invention can be similarly applied to other electric motors. Furthermore, it goes without saying that the present invention is not limited to the case where uniform speed control is performed.

〔Effect of the invention〕

According to this invention, at an appropriate time such as when the motor starts operating,
The existing rotor position detector (FD) is used to learn the drift of the speed detection value due to the speed generator system, and based on this learning result, the speed detection value is corrected and speed control is performed. This provides the advantage of being able to perform speed control with good response and high static control accuracy.

[Brief explanation of drawings]

Figure @1 is a block diagram showing an embodiment of the present invention, Figure 2 is a block diagram showing a conventional example of the speed control method, Figure @3 is a block diagram showing another conventional example of the speed control method, and Figure 4 is a block diagram showing another conventional example of the speed control method. FIG. 2 is a configuration diagram showing still another conventional example of a speed control method. Description of symbols 1...Digital calculator, 2...Power converter, 3...Synchronous motor, 4...Rotor position detector (PD), 6... Speed feedback loop, 7a to 7C... Adder, 8... Pulse generator (PLG), 9... Digital speed detector, 10・・・・・・Related generator (TG)-11,
-----・A/D converter, memory for 12-, 13a
~13d...Switch, 14a...Comparator, 14b...Timer. Figure 11I Figure 2 L−+ −−+j Figure 3

Claims (1)

[Claims] A speed generator that detects the speed of an electric motor driven via a power conversion device whose phase is controlled based on the output from a position detector, and a signal converter that converts the output voltage of the speed generator into a digital quantity. and speed detection means for digitally detecting the motor speed from the output of the position detector;
Error detection means for determining a detection error of the speed detection value via the speed generator and the signal converter from the speed detection value and its command value or the speed detection value by the speed generator, and storage means for storing the detection error. and when the speed command value is held at a predetermined value and a state in which the detected motor speed value substantially matches the command value continues for a predetermined time or more, the output obtained from the error detection means at that time is A speed control method for an electric motor, characterized in that by performing learning stored in a storage means in advance, a speed detection value via the speed generator and the signal converter is corrected based on the learning result to perform feedback control.