JPS58139685A - Controller for ac motor - Google Patents

Abstract

PURPOSE:To shorten the synchronization acquisition time by inputting as a preliminary signal the output frequency signal of a variable voltage variable frequency power source and a rotary signal of an AC motor to a phase synchronizing loop circuit. CONSTITUTION:A phase comparator 9 applies the voltage proportional to the phase difference between the terminal voltage VM of a synchronous motor and the output AC signal VC of a voltage controlled oscillator 11 to a low pass filter 10. A switch unit 12 inputs as the input F3 of a voltage controlled oscillator 11 the output F1 of a low pass filter 10 when the phase synchronization loop is in synchronized state, the signal corresponding to the output frequency of variable voltage variable frequency power source when in asynchronous state or the preliminary signal F2 corresponding to the rotating speed of the AC motor. In this manner, the synchronization acquisition time of the phase synchronizing loop can be shortened.

Description

[Detailed Description of the Invention] (1) Description of the Technical Field The present invention relates to a control device for an AC motor, and in particular, to variable control of the terminal voltage or frequency of the current of the AC motor, and to freely change the vA tolerance from K. This relates to the control of an AC motor driven by an electric current converter.

(b) Description of the Prior Art In variable frequency operation of an AC motor, it is important to detect the waveform of the current at the terminal voltage 4L of the AC motor for its control. However, what is the control device for the AC motor in general? The waveform of the terminal voltage or current of the AC motor is a non-sinusoidal waveform, which is composed of switching elements such as Iristau transistors. If a sine wave having only a fundamental frequency component (hereinafter abbreviated as "basic liquid") can be detected from the rounded non-sinusoidal AC voltage and current waveforms, the information will be superimposed for control purposes. - For example, from the frequency of the fundamental wave of the terminal voltage waveform of a synchronous motor,
The position of the rotor can be known from the rotation speed and the phase of the fundamental wave, and this information can be used for control.

FIG. 1 shows an example of an AC motor control device to which the present invention can be applied. This example is generally called a thyristor motor, and detects and feeds back the position of a rotor of a synchronous machine to control the firing timing of a switching element that constitutes an inverter. In Fig. 1, 1 is a variable voltage DC power supply, 2 is an inverter made up of switching elements, 3 is a synchronous motor to be controlled, and 4 is a position detector fixed to the rounded motor shaft for detecting the position of the rotor. ,5
a firing angle control circuit that determines the firing timing of the switching elements constituting the inverter 2 based on the rotor position signal;
Reference numeral 6 denotes a gate circuit that controls the #distribution switching element using the output signal of the firing angle control circuit. Position detection wI4
can also be replaced by an electrical position detector 8 that detects the terminal voltage of the Mayu synchronous motor 3 using a transformer 7 and calculates the position of the rotor from the waveform. Electrical position detection 1! s8 is the above-mentioned position detection: Compared to A4, there is no mechanical moving part, so it is highly reliable. 5 Position detection error due to armature reaction is eliminated, and the position detector 4 is fixed on the motor axis. It has advantages such as no angle difference and high detection accuracy. On the other hand, a technical hurdle is that the terminal voltage of the synchronous motor 3 is generally a rounded non-sinusoidal wave as shown in FIG. It is necessary to detect the fundamental wave. FIG. 2 shows an example of a terminal voltage waveform when a six-phase thyristor inverter with load commutation is used as the inverter 2, and this gross distortion occurs when the switching elements of the inverter commutate. Therefore, even if nine different types of inverter 2 are used.

As long as switching elements are used, distortion of the terminal voltage waveform will always occur even if the waveform is different. A phase-locked loop is one of the methods for detecting a fundamental wave from a non-sinusoidal wave as shown in FIG. 12 for highly accurate rotor position detection.

FIG. 3 shows a basic configuration diagram of a phase locked loop (hereinafter abbreviated as PLL). 9 is a phase comparator which outputs a voltage proportional to the phase difference between two inputs. The output of the phase comparator 9 is inputted to a voltage controlled generator I & generator 11 through a low pass filter 10 . The voltage controlled oscillation @11 outputs an alternating current signal vc which is proportional to the input voltage and has a running wave number. The non-sinusoidal signal is input to one of the two inputs of the phase comparator 90,
When the output AC signal vc of the voltage controlled oscillator 11 is input to one of the input terminals, the PLL operates when the phase difference between the two signals - and vc becomes large. #Kinikubango■, and■. In the nine-shaped state (hereinafter abbreviated as synchronous state) where the phase difference of
The output of the low-pass filter 10 is a constant DC voltage, and this voltage value is proportional to the fundamental frequency of the non-sinusoidal wave. The output sentence tlL of the running voltage controlled oscillator 11 matches the phase and frequency of the non-sinusoidal wave (2). If the Moeki voltage controlled oscillator 11 is a sine wave excavator, the AC signal (is the fundamental wave with gold removed from the non-sinusoidal wave. In other words, the PLL shown in FIG. 3 removes the gold from the non-sinusoidal wave, It can be used as a kind of filter that extracts only the fundamental wave.

Detecting the fundamental wave from a non-sinusoidal wave using a PLL has both advantages and disadvantages, such as high precision in its construction, stable output signal, and ease of subsequent signal processing. One of the disadvantages of this is the synchronization pull-in time of the PLL. PLL
When there is no input signal, it oscillates at a frequency # (free-running 8 wave numbers) specific to the PLL.

When an input signal having a certain frequency is applied from this state, it takes time until the output AC signal of the PLL becomes synchronized with the input signal. Generally this time (synchronization pull-in time)
is determined by the difference between the frequency of the input signal and the free-running frequency and the initial phase when the input signal is applied, but if the frequency difference is large, it may take a very long time and may not be synchronized forever.

This property of PLL is similar to the control device of AC motor.
This is a major drawback for devices that need to start up quickly.

On the other hand, if the control device for the AC motor is configured with switching elements, it may be difficult to detect the terminal voltage of the AC motor itself when starting at a low frequency. In this case, after the l1lIlflL number of the terminal voltages increases to a certain extent and becomes detectable, it becomes necessary to perform synchronization of the PLL. In addition, if the control device itself does not have the ability to start the tributary motor, or if the AC motor itself cannot start the tributary motor due to the circumstances of the AC motor itself, it is possible to The electric motor may be started and then switched to the control i11 side for operation.

In this case as well, after the terminal voltage or current frequency of the AC motor increases to a certain degree, the PLL must be synchronously pulled in. Furthermore, the terminal voltage or current frequency of the AC motor during synchronous pull-in is not always maintained at a constant value. Considering the characteristics of the AC motor side equipment as described above, it is possible to shorten the synchronization pull-in time of the PLL by some means and synchronize the PLL promptly regardless of the operating state of the AC motor. An object of the present invention is to provide a control device for an AC electric IIIJ machine using a PLL that can change the state.

(a) Structure of the Invention FIG. 4 shows an example of the structure of the present invention. In FIG. 4, the phase ratio afiI9. Low pass filter 10. Voltage controlled oscillation m
1ll is the ninth explanation of the same function as the explanation of Fig. 3. 1
Reference numeral 2 denotes a switch for switching the input signal Wt of the voltage control oscillator 11. The output y1 of the low-pass filter 10 indicates the fundamental frequency I11 of the input signal - when the PLL is in a synchronous state,
This signal F1 is directly used as the input signal 4 of the voltage controlled oscillator in the switching device. When the nine PLLs are in an asynchronous state, the preliminary signal 4 is switched to the input nine of the voltage controlled oscillator 11. In other words, when the PLL is in an asynchronous state, the switch 120 operates the voltage control generator (n1l) 11 using a preliminary signal as F when the PLL is in an asynchronous state, switches to 9-Fm from the switching command CK, and thereafter switches the PLL to a synchronous state. It lies in holding.

(@) Effect of the Invention Here, the preliminary signal F is a signal that resonates with the operating frequency of the control device constituted by the switching element or a signal that resonates with the rotational speed of the AC motor. The meaning of inputting the preliminary signal r, when the PLL is an asynchronous layer, is that when the switching command C is given, the input signal V, O fundamental wave frequency 11 when running.
The synchronization pull-in time of the PLL can be minimized by reducing the difference between the number of free-running cycles of the PLL and the number of free-running cycles of the PLL.

Tsut! Even in the asynchronous state, the PLL always operates at a frequency that is the same as or close to the fundamental frequency and number of the input signal (2) due to the preliminary signal (4). Thereby, the switching command C is given, and the synchronization pull-in time during running can be shortened. switching! 12 is not limited to the III era explanation, and can take various actions. For example, when the PLL is in an asynchronous state, F, =F.

As a reserve II! The voltage control generator 4tii is activated by the signal, and the two inputs are added by the control IC, r, =F, +F.

However, it is possible to maintain synchronization.

Hold the preliminary signal F according to the Kakyukiriso command C and send r@
The same holds true for =F, +F, -F, +K ([=constant m).

(f) Other examples FIG. 5 shows one of the different embodiments of the invention.

Phase comparator9. Low pass filter 10. The voltage-controlled oscillating hot water 11 has the same function as that described in FIG. 3, so a description thereof will be omitted. The function of switch 120 is basically the same as switch 1112 in FIG. 4, but in this example it is voltage controlled oscillation! i! The difference is that the output AC signal vc1 of No. 11 and the preliminary AC signal VCI are switched. Preliminary AC signal V. , is an alternating current signal that is composed of the switching element and is consistent with the operating frequency of the control device or an alternating current signal that is consistent with the number of revolutions of the alternating current motor,
The only difference from the example shown in FIG. 4 is that it is an intersection tlL signal. Switching except for this! Function 4 required for If 2 is the same as the 4th example.

FIG. 6 shows one of the different embodiments of the invention.

Phase comparator9. - One-pass filter 10. The voltage controlled oscillator 11 chimes because it has the same function as explained in FIG.

The function of the switch 120 is the same as that of the switch 12 shown in FIG. 5, except that in this example, it switches between the input signal V and the preliminary AC signal VMt. The preliminary AC signal V is the same as the preliminary AC signal VCI in FIG.

This is one of the application examples of the present invention for the 711th Fi odorant.

111th! In the control device for the synchronous motor described in IK, the electrical position detector 8 is a round one using the PLL implementing the present invention as shown in FIG. 4. All the components in FIG. It has the same function as the nine explained in FIG. The case where the synchronous motor is accelerated to a certain number of revolutions by some means, and then the PLL is set to the synchronous state 11i1Vc to detect the position of the rotor will be explained as follows. First, the (b) rotation a of the synchronous motor is detected or calculated by some means and input into preliminary information 4. This allows P
LL operates at a chest wave number that is equal to or close to the terminal voltage of the synchronous motor 3 at that time. However, the phase is completely fish-related. Next, when the switching command C is input, the switching voltage control #oscillation control is input 11 to the switching device 12! No. 4 is switched from the preliminary signal F to the output signal F of the p-bus filter 1o. At this time, the terminal voltage v of the synchronous motor 3
The frequencies of M and the preliminary signal F are rounded to be approximately equal, and the PLL becomes a synchronous layer in a short time. As long as the synchronous layer is maintained, the terminal voltage of the synchronous motor 3 - and the output signal of the voltage controlled oscillator 11 ■. The frequency is the same and the phase is in line. Therefore, this output signal c can be used to detect the position of the rotor, and the firing angle control circuit 5 allows the inverter 2t-
It becomes possible to calculate the firing timing of the constituent switching elements.

In the above example, a synchronous motor was used as the motor.

However, the scope of application of the present invention is not limited to this.

- Can also be used for conductive motors.

In general, the electric power supply device that supplies power to an induction motor uses a forced commutation inverter or a natural commutation cycloconverter, and both scissors and the terminal voltage or current line of the induction motor are supplied with a non-sinusoidal wave. . The present invention is also applicable to detecting the base liquid from these non-sinusoidal waves.
1's output becomes a sine wave.However, in principle, there is no need for a PLL to operate with a sine wave. For example, voltage controlled launch! When the output of Ill is a square wave signal, the phases of the fundamental wave of this square wave and the fundamental wave of the input signal - are aligned.

-) Effects of the Invention As explained above, according to the present invention, the fundamental wave is detected from the terminal voltage or current of an AC motor using a phase-locked loop. becomes possible.

[Brief explanation of drawings]

Figure 1 shows the control of an AC motor to which the present invention can be applied! Fig. 2 is a diagram showing an example of the terminal voltage waveform when a synchronous motor is operated by a thyristor inverter; Fig. 3 is a basic configuration diagram of a phase-locked loop;
Figure 5 is a block diagram showing one embodiment of the present invention. Figure 6 is a block diagram showing different pond embodiments of the present invention.
The figure shows a specific application example of the present invention. l... DC power supply with variable temperature pressure 2... Inverter 3 composed of switching elements... Synchronous motor to be controlled 4... Rotor position detector 5... Negative ignition control #(b) Path 6... Gate circuit 7... Transformer 8... Electrical position detector 9... Phase comparator 10... Low pass filter - 11... Voltage controlled oscillator 12...・Off WS - Input signal of phase-locked loop (non-sinusoidal signal) v
c...Output signal of voltage controlled oscillator C...Switching command Fl...Output signal of low-pass filter -j)F,...
Preliminary signal F, . . . input signal VCI of the voltage controlled oscillator . . . output signal VI of the voltage controlled oscillator! ... Preliminary AC signal VCS ... Input signal of phase comparator ■Yo, ... Preliminary AC signal 7M, ... Input signal of phase-locked loop (7317) Agent Masu Shioji Norichika (tt or 1 person) Figure 1 2 Figure 3 J Figure 5 Figure 6 Figure 7 [1 3

Claims (1)

[Claims] The output signal of the phase-locked loop circuit is used as a signal to control the Machi-hen-voltage Machi-hengang-tIL-Shuden-6Ili device, and the alternating current motor is driven by the Machi-Jaku voltage variable frequency control device, wherein the phase-locked loop circuit is An AC motor which uses the output wave number signal of the variable voltage variable chest wave number electric* device or the rotation signal of the AC motor or a signal corresponding to these signals as a backup signal. control device.