JPH0222637B2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention is an AC motor equipped with a waveform generator for smoothing a primary current and reducing torque pulsations in AC motor control, particularly vector control. This invention relates to a motor control device.

[Technical background of the invention]

Vector control is performed on induction motors or synchronous motors, and here we will discuss its application to synchronous motors.

First, FIG. 1 shows a basic control system when vector control is applied to a synchronous motor.

In FIG. 1, the rotation speed signal N _FB of the speed detector 2 directly connected to the rotor of the synchronous motor 1 and the speed reference value N _ref are added by the adder 3 with the polarity shown, and this speed error is amplified. The speed amplifier 4 obtains the amplified value |i _a | of the primary current command. A vector control circuit 5 connects the output |i _a | of the speed amplifier 4 and a magnetic flux position detector 6 directly connected to the rotor of the synchronous motor 1.
The primary current command value i _a is output based on the magnetic flux position signal φ output from the magnetic flux position signal φ. A current amplifier 7 detects the primary current of the synchronous motor 1 with a current detector 8 and supplies the synchronous motor 1 with a primary current corresponding to the output signal i _a of the vector control circuit 5 .

As described above, this device obtains the rotational speed of the synchronous motor 1 corresponding to the speed reference value _Nref .

On the other hand, devices that apply microprocessors to these controls are emerging. As this is a digital process, there is no problem of information drift due to temperature, etc., the excellent functions of a microprocessor can be easily added, new control theories can be easily added, and it is programmable, so it has a wide range of applications. Benefits include a wider space. An example of this application is shown in FIG.

Explaining FIG. 2, the microprocessor processing block 25 includes a magnetic flux position detection block 26 that outputs a digital quantity corresponding to the magnetic pole position and its timing from a magnetic pole position detector resolver signal directly connected to the synchronous motor, and a magnetic flux position detection block 26 that outputs a digital quantity corresponding to the magnetic pole position and its timing. A speed detection block 27 outputs a digital amount corresponding to the speed and its timing from the directly connected rotor rotational speed detector resolver signal, a speed command value _Nref represented by 28, and a proportional/integral value represented by 29. Constant value input and torque limit command value expressed as 30,
The armature current command value (two-phase output) of the synchronous motor is output to the current amplifier (FIG. 1, 7) using the respective digital quantities and the timing signal (CPU interrupt processing signal) as input information.

Before explaining each block, the operating principle of the resolver will be explained with reference to FIG. 3 for ease of explanation.

In the same figure, since two-phase excitation windings 200 and 201 are excited with two-phase currents of cosω ₀ t and sinω ₀ t, respectively, the detection winding 202 directly connected to the rotor of the synchronous motor has V signal is obtained.

V = Esin (ω ₀ t + φ _e (t)) ......Equation 1, where φ _e = Pφ _n /2, P: Number of resolver poles φ _e (t): Rotor electrical angle φ _n (t): Rotor Mechanical angle According to the first equation, the magnetic pole position can be detected from the phase difference between the resolver output signal and the excitation signal. Fourth
Since t ₁ and t ₂ in the figure are information corresponding to the magnetic flux position, digital quantity information of the magnetic pole position can be obtained by digitally counting t ₁ and t ₂ using the reference clock.

Further, when the frequencies of the resolver output signal and the excitation signal are respectively f and f ₀ , this deviation Δf is expressed by the following equation: Δf=f−f ₀ . From this second equation, the rotation speed of the synchronous motor is
N _FB is obtained as the third equation.

N _FB = 120Δf/P = 120 (f - f ₀ )/P = 120 (T ^-1 - f ₀ )/P _M ......3rd formula However, T = f ^-1 , P _M is the number of motor poles be.

Therefore, since the excitation frequency is known in advance, the speed N _FB can be determined from the third equation by detecting the period T of the resolver output signal.

Furthermore, it is clear that if the resolver output signal is frequency-divided by n and the period T is detected, _NFB is given by the fourth equation.

N _FB = 120 (n/T-f ₀ )/P _M . . . 4th equation Therefore, the rotational speed of the synchronous motor can be known from the digital amount information obtained by digitally counting T using the reference clock.

Next, each block in FIG. 2 and its configuration will be explained. The magnetic flux position detection block 26 includes a counter 10 that counts reference clock pulses using the zero-cross pulse signal of the excitation signal of the resolver for magnetic flux position detection as a start signal, and outputs the count value as a digital quantity, and a zero-cross pulse of the resolver output signal V〓. A latch 11 outputs the digital amount of the counter 10 by using the signal as a latch signal.
and an interrupt signal that notifies microprocessor processing block 25 that latch circuit 11 has latched a new digital quantity.

The magnetic flux position detection block 26 outputs magnetic flux position information as a digital quantity to the microprocessor processing block in a time-division manner.

The speed detection block 27 receives the resolver output signal
A frequency divider circuit 14 which divides the frequency of V〓 by n, a counter 12 which uses this pulse as a start reset pulse to count the reference clock pulse and outputs a digital quantity, and a counter 12 which uses the output pulse of the frequency divider circuit 14 as a latch signal. A latch circuit 13 latches and outputs the count value of , and an interrupt signal notifies the microprocessor processing block 25 that the latch circuit 13 has latched a new digital quantity.

The speed detection block 27 outputs information on the period T of the fourth equation necessary for the microprocessor processing block 25 to detect the speed as a digital quantity to the microprocessor processing block in a time-division manner.

Next, the microprocessor processing block 25 will be explained. The T/N _FB conversion circuit 16 inputs the digital quantity T of the fourth equation from the speed detection block 27 in a time-division manner using an interrupt pulse, and calculates the digital quantity corresponding to the speed N _FB according to the fourth equation. .
The adder 17 receives the digital quantity N _ref of the speed command 28
and the digital quantity N _FB of the T/N _FB conversion circuit 16
are added with the sign shown in the figure, this error is amplified by the speed amplifier 18, and a digital quantity corresponding to the amplitude command |i〓 _a |' of the primary current is calculated. This amplification is performed using information on the proportionality/integral constant 29 given from the outside.

The torque limiting circuit 19 uses a torque limiting command given from the outside as information, and outputs |i〓 _{a |} in which |i〓 a |' is limited. On the other hand, the T/φ conversion circuit 15 inputs the digital quantity corresponding to the magnetic flux position from the magnetic flux position detection block 26, converts it into address information of the memory table 20 having data of sinφ and cosφ, and converts it into memory table 20 having data of sinφ and cosφ. table 20
outputs two-phase digital information corresponding to this address information.

The multipliers 21 and 22 are connected to the torque limiting circuit 19.
The primary current amplitude command |i _a | which is _the output of
Output to 4. The D/A conversion circuits 23 and 24 are
The phase is converted into an analog quantity, and the current amplifier 7 in FIG.
Output to.

Figure 5 shows the microprocessor processing block 25.
An example of a flowchart is shown below. Within the controller of the main program in this diagram, the three main routines on the right are required. The first is a routine that detects the magnetic flux position and obtains phase information of two phases of the primary current command, the second is a routine that obtains speed information from the period of the resolver output frequency, and the third is a routine that obtains torque from the speed information.
This is a routine that calculates the primary current amplitude and obtains the primary current command information from the phase information.

The first and second routines are executed for each time-division sampling by an interrupt signal to the microprocessor processing block that indicates that new digital information has been generated from the magnetic flux position detection block 26 or velocity detection block 27 in FIG. , 3rd
The routine is executed based on new information after it is processed in the first and second routines.

Furthermore, each routine requires calculations and processing such as division and multiplication, so data is sampled at a certain time _T1 to control the primary current command i _a1 , and then at the next time _T2 , the primary current command i _{a2 is} Time to control Δt
(T ₂ −T ₁ ) requires several milliseconds. In other words,
i _a1 controlled by sampling the data at T ₁ is
It is fixed until data is sampled and controlled at T ₂ , resulting in so-called discontinuous control.

Therefore, when the synchronous motor is operating at low speed, Δt is sufficiently small with respect to the period of the primary current, so it is not a big problem, but when the synchronous motor is operating at high speed, Δt cannot be ignored with respect to the period of the primary current, and the next The following problems arise.

It becomes impossible to maintain the orthogonal relationship between magnetic flux and primary current, resulting in torque pulsation, torque reduction, and response delay.

The harmonic components of the primary current increase, resulting in increased loss, decreased power factor, and vibration noise.

[Purpose of the invention]

The present invention solves these conventional problems and
While retaining the smooth characteristics of the conventional analog control method, it also uses a microprocessor that does not have the drawbacks of analog circuits, such as temperature drift and troublesome adjustments, to achieve the excellent functions inherent in microprocessors. The purpose is to fully demonstrate the

[Structure of the invention]

First, the present invention detects speed and magnetic flux position as digital quantities by a detector directly connected to the rotor of an AC motor, and adjusts the speed and magnetic flux position according to the deviation between these detected values and a speed command and a position command. AC motor 1
In an AC motor control device that calculates a primary current command value and applies this primary current command value to an electric amplifier to control an AC motor, a binary value corresponding to the rotational speed of the AC motor detected by the detector is used. A pulse generator that outputs a pulse train obtained by dividing a reference clock pulse using a digital quantity as a frequency division ratio, and a reset signal that is input every time the magnetic flux position is sampled. a counter that resets the digital output; a digital adder that adds the counter output to a digital amount corresponding to the magnetic flux position output every time the magnetic flux position is sampled;
This digital adder output is used as the address input for 2
A memory table that outputs the digital quantity of the phase waveform, and each output of this memory table and 1
Multipliers 1 and 2 multiply the primary current amplitude by a digital quantity corresponding to the primary current amplitude, and the primary current command value expressed by the digital quantity obtained by the multipliers 1 and 2 is converted into an analog quantity and the D/A output to current amplifier
The second aspect of the invention relates to an AC motor control device characterized by comprising a converter, and a second aspect of the invention is to detect speed and magnetic flux position as digital quantities by a detector directly connected to the rotor of the AC motor; An AC motor control device that calculates a primary current command value of the AC motor according to deviations between these detected values and a speed command and a position command, and controls the AC motor by giving this primary current command value to an electric amplifier. , a pulse generator that generates a pulse with a period of 1/n of the magnetic flux position sampling period Δt of the AC motor, a counter that counts the pulses of the pulse generator and is reset each time the magnetic flux position is sampled, and this counter. a digital multiplier that digitally multiplies the output of the counter by a digital amount corresponding to the rotation speed; a digital adder that adds the counter output and the digital amount of the magnetic flux position output for each magnetic flux position detection sampling; n in a period of Δt using the device output as address input.
A memory table that detects rotational speed information and outputs a digital quantity of a two-phase waveform obtained by interpolating the magnetic flux position n times during a Δt period from this speed information, and the respective outputs of this memory table and the primary current amplitude. Multiplying circuits 1 and 2 that multiply by a digital quantity corresponding to
and a D/A converter that converts the primary current command value expressed in digital quantities obtained by the multipliers 1 and 2 into an analog quantity and outputs it to the current amplifier. This relates to an AC motor control device.

〔Example〕

The present invention will be explained below based on the embodiment shown in FIG. In this figure, parts having the same or similar functions as those in FIG. 2 are designated by the same reference numerals. The magnetic flux position interpolation block 36 in FIG.
From the T/φ conversion circuit 15, data corresponding to the magnetic flux position is time-divided into a digital quantity, the timing at which new data is input, and the T/N _FB conversion circuit 16 is further time-divided into a digital quantity corresponding to the speed N _FB . The address information of the memory table 20 having two-phase data corresponding to the magnetic flux position is time-divided and outputted in a time-divided manner smaller than Δt.

The primary current command calculation block 37 inputs the output of the magnetic flux position interpolation block 36 and the primary current amplitude command value | _ia |, and calculates the two-phase primary current command value as a digital quantity.

Magnetic flux position interpolation block 36 which is the gist of the present invention
The operations of the primary current command calculation block 37 will be explained.

The magnetic flux position interpolation block 36 divides the clock of the reference clock generator 33 according to the rotational speed _NFB , and uses the counter 34 to generate pulses from the pulse generator 32, which generates pulses with a frequency proportional to the digital amount of _NFB . Count. The contents of the counter 34 are reset by the timing signal 31 output every time a new digital quantity of magnetic flux position is output from the T/φ converter. Digital adder 3
5 digitally adds the digital amounts of the counter 34 and the T/φ converter 15. In other words, the magnetic flux position interpolation block 36 maintains a constant speed during the period Δt from when the digital quantity of the T/φ converter 15 is output to when the next new digital quantity is output, and uses the digital quantity of the T/φ converter 15 as the base. The magnetic flux position is interpolated using the digital value of the counter 34 as an offset.

The primary current command calculation block 37 takes in the magnetic flux position information interpolated by the magnetic flux position interpolation block 36 into the memory table 20 as address information.

Hereinafter, the primary current command value is generated in the same manner as explained based on FIG.

FIG. 8 shows another embodiment of the magnetic flux position interpolation block 36. This is to perform n interpolations for the cycle Δt of magnetic flux position detection of the T/φ converter 15, and to briefly explain the operation, τ=Δt/n
The counter 41 counts the pulses of the pulse generator 42 which generates the pulses, outputs a digital value, and is reset by the signal 31 from the T/φ converter 15 in FIG. Furthermore, the speed signal _NFB and the output of the counter 41 are multiplied by a multiplier 40 to obtain an offset for magnetic flux position interpolation.

Further, the magnetic flux position interpolation block 36 and the primary current command calculation circuit 37 may be performed by a microprocessor separate from the microprocessor processing block 25.

The above embodiment is about a synchronous motor, but
The same effect can be obtained for induction motors by performing interpolation in a similar manner.

〔Effect of the invention〕

As described above, according to the present invention, the primary current command value is also interpolated by predicting and interpolating the magnetic flux position from the speed information during the period Δt in which the magnetic flux position is sampled, and the primary current is smoothed. Therefore, it is possible to solve problems such as primary current distortion, torque pulsation, loss, torque reduction, vibration noise, and power factor drop, which were considered drawbacks of conventional control using a microprocessor. can.

[Brief explanation of drawings]

Figure 1 is a block diagram showing a basic control system when vector control is applied to a synchronous motor, Figure 2 is a block diagram showing an example of the configuration of a vector control system using a microprocessor, and Figure 3 is a position diagram. An explanatory diagram showing the principle of detection by a resolver as a detector,
Figure 4 is a waveform diagram showing the phase relationship between the two phases of the excitation current of the resolver, Figure 5 is a flowchart showing the control routine by the microprocessor, and Figure 6 is the detected waveform and analog waveform by conventional microprocessor control. A waveform diagram showing a comparison of detected waveforms by control, FIG. 7 is a block diagram showing a configuration example of the present invention,
FIG. 8 is a block diagram showing another example of the microprocessor. 1: Synchronous motor, 2: Speed detector, 3: Adder, 4: Speed amplifier, 5: Vector controller, 6:
Magnetic flux position detector, 7: Current amplifier, 8: Current detector, 10, 12: Counter, 11, 13: Latch circuit, 14: Frequency dividing circuit, 15: T/φ conversion circuit,
16: T/N _FB conversion circuit, 17: Adder, 18:
Speed amplifier, 19: Torque limiting circuit, 20: Memory table, 21, 22: Multiplier, 23, 2
4: D/A converter, 25: Microprocessor processing block, 26: Magnetic flux position detection block, 2
7: Speed detection block, 28: Speed command value, 2
9: Proportional/integral constant value input, 30: Torque limit command value, 31: Timing signal, 32: Pulse generator, 33: Reference clock generator, 34: Counter, 35: Digital adder, 36: Magnetic flux position interpolation block , 37: Primary current command calculation block, 3
8: Microprocessor processing block, 40: Multiplier, 41: Counter, 42: Pulse generator.

Claims (1)

[Claims] 1. Speed and magnetic flux position are detected as digital quantities by a detector directly connected to the rotor of an AC motor,
An AC motor control device that calculates a primary current command value for the AC motor according to deviations between these detected values and a speed command and a position command, and controls the AC motor by supplying this primary current command value to a current amplifier. a pulse generator that outputs a pulse train obtained by dividing a reference clock pulse using a binary digital quantity corresponding to the rotational speed of the AC motor detected by the detector as a frequency division ratio; and an output pulse train of this pulse generator. A counter that counts and outputs it as a digital quantity and resets the digital output by a reset signal input every time the magnetic flux position is sampled, and a digital quantity that corresponds to the output of this counter and the magnetic flux position that is output every time the magnetic flux position is sampled. a digital adder that adds up the output of the digital adder, a memory table that uses the output of this digital adder as an address input and outputs a digital amount of a two-phase waveform, and a digital amount that corresponds to each output of this memory table and the primary current amplitude. multipliers 1 and 2 for multiplying the value of An AC motor control device characterized by comprising: 2 A detector directly connected to the rotor of the AC motor detects the speed and magnetic flux position as digital quantities,
An AC motor control device that calculates a primary current command value for the AC motor according to deviations between these detected values and a speed command and a position command, and controls the AC motor by supplying this primary current command value to a current amplifier. , a pulse generator that generates a pulse with a period of 1/n of the magnetic flux position sampling period Δt of the AC motor; a counter that counts the pulses of the pulse generator and is reset each time the magnetic flux position is sampled; a digital multiplier that digitally multiplies the output of the counter by a digital amount corresponding to the rotation speed; a digital adder that adds the counter output and the digital amount of the magnetic flux position output for each magnetic flux position detection sampling; The speed information is detected n times during the Δt period using the device output as the address input, and the magnetic flux position is interpolated n times during the Δt period from this speed information.
A memory table that outputs a digital amount of a phase waveform, multiplier circuits 1 and 2 that multiply each output of this memory table by a digital amount corresponding to the primary current amplitude, and these multipliers 1 and 2. an AC motor control device comprising: a D/A converter that converts a primary current command value expressed in a digital quantity obtained by the above-described method into an analog quantity and outputs the converted quantity to the current amplifier;