JP3020751B2 - Induction generator control - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an induction motor suitable for applications in which the rotational speed of a prime mover changes greatly, such as wind power generation or shaft power generation in which electric power is obtained by using surplus power of a mechanical device used during an internal combustion period. The present invention relates to a generator control device.

[0002]

2. Description of the Related Art FIG. 3 is a block diagram showing an example of a conventional control device for an induction generator.

In FIG. 1, reference numeral 1 denotes a prime mover, 2 an induction generator driven by the prime mover 1, 3 a converter for converting an AC output of the induction generator 2 to DC, 4 a capacitor for smoothing the output voltage of the converter 3, 5 Is a DC power supply, and 6 is a circuit breaker for turning on and off the power supplied from the converter 3 to the load 7.

[0004] Reference numeral 8 denotes a current detector for detecting the output current of each phase of the induction generator 2, and 9 denotes a voltage detector for detecting the output voltage of the converter 3. Reference numeral 10 denotes a power generation operation command, 11 denotes a power generation start-up control circuit, and 12 denotes a rotation detector that detects the rotation speed of the induction generator 2. Reference numeral 13 denotes a temporary frequency command value obtained by adding the rotation frequency of the induction generator 2 detected by the rotation detector 12 and a slip frequency command value provided from the start-up control circuit 11, and integrates the resultant to obtain a temporary frequency command value. This is a slip frequency control circuit that outputs an electrical angle command value of a primary current.

Reference numeral 14 denotes a three-phase current reference generator for obtaining and outputting a three-phase instantaneous current reference from the electrical angle command value output from the slip frequency control circuit 13 and the current reference 15 at startup given from the startup control circuit 11. It is a vessel. Reference numeral 16 denotes a current instantaneous value control circuit that generates a PWM signal by controlling the motor current detected by the current detector 8 to be equal to the three-phase current reference.

[0006] On the other hand, 17 is the converter 3 after the start-up is completed.
A voltage control circuit for controlling the output voltage of the motor to a voltage suitable for the load 7. After the start-up is completed, the voltage control circuit 18 compares the reference value of the current peak value output from the voltage control circuit 17 by the generation voltage control and the three-phase current of the induction motor. This is a current peak value control circuit that generates a PWM signal by comparison.

A switching circuit 19 switches a PWM signal supplied to the switching control circuit 21 from an output of the current instantaneous value control circuit 16 to an output of the current peak value control circuit 18 in response to a startup completion signal 20 output from the startup control circuit 11. It is. The switching control circuit 21 gives an on / off signal to each switching element included in the inverter 3 based on the PWM signal. The start-up completion signal 20 is also given to the circuit breaker 6, and after the start-up is completed, the load 7 is turned on.

FIG. 4 is a block diagram showing a configuration of the current peak value control circuit 18. As shown in FIG. Numeral 31 denotes a current comparison circuit which compares the command value of the current peak value with the three-phase current of the induction generator 2 and determines whether the three-phase current has exceeded the positive value of the peak value or has exceeded the negative value. And outputs a logic signal indicating whether the A commutation control circuit 32 outputs a basic electrical angle signal for commutation control of the converter 3 based on a logic signal output from the current peak value control circuit 18, and a reference numeral 33 denotes a commutation control signal output from the current comparison circuit 31. This is a PWM control circuit that generates a PWM signal based on the basic electrical angle signal output from the flow control circuit 32. Here, since the commutation control is directly related to the present invention, a detailed diagram of the current comparison circuit 31 and the commutation control circuit 32 related to the commutation control is shown.

FIG. 5 is a block diagram showing a detailed diagram of the current comparison circuit 31. As shown in FIG. In FIG. 5, I1 ^* Is the reference of the peak value of the output current of the induction generator 2, IU, IV, IW are the output currents of the induction generator 2 detected by the current detector 8, 41 to 4
3 is a detection value iIu, iIv, of the three-phase current of the induction generator 2.
A polarity reversing circuit for reversing the polarity of iIw, 44 to 49 are a three-phase current detection value, its polarity reversal value and a current peak value reference I
1 ^* And 50 to 55 are hysteresis comparators, which compare the command value of the output current peak value with the detected current and output the results as current comparison signals UP, UN, V
Output as P, VN, WP, WN.

FIG. 6 is a detailed diagram of the commutation control circuit 32.
In FIG. 6, 61 to 66 are OR circuits, 67 to 72 are AND circuits, 73 to 75 are flip-flops,
F, VF, and WF are basic electrical angle signals obtained as outputs of 73 to 75.

In the current peak value control circuit 18, the induction generator 2
Is controlled in a trapezoidal waveform. The height of the trapezoidal wave is calculated as a peak value command value I1 ^* Give in. In FIG. 5, each phase current of the induction generator 2 and a peak value command value I1 ^* Are subtracted by the subtractors 44 to 49, and the hysteresis comparators 50 to 55 operate according to the magnitude of the deviation. If the U-phase current iu is larger than the peak value command value, the output of the subtractor 44 becomes positive, and the output UP of the hysteresis comparator 50 becomes "1". When the U-phase current iu becomes smaller than the peak value command value by the amount of hysteresis or more, UP becomes “0”. On the other hand, in the subtractor 45, when the magnitude of the signal obtained by inverting the polarity of the U-phase current iu exceeds the peak value command value, the output UN of the hysteresis comparator 51 becomes “1”. Becomes “0”. The same applies to the V phase and the W phase. That is, from the current comparison circuit 31, it is determined whether the output current of the induction generator 2 falls within the amplitude specified by the peak value command value.
It is output by the N current comparison signal.

The flip-flop 73 of the commutation control circuit 32 shown in FIG. 6 is reset when the current comparison signal UP is "1", and is set when the current comparison signal UN is "1".
When the PWM control is not performed, the output of the PWM control circuit 33 is output as it is from the commutation control circuit 32, and the switching of the converter 3 is controlled by the output of the commutation control circuit 32. Therefore, when the phase current iu is positive and becomes larger than the peak value command value, the positive-side switching element of the U-phase is turned off and the negative-side switching element is turned on, and the voltage is set to a voltage in a direction to decrease iu. . As a result, iu decreases and becomes negative, and when its absolute value exceeds the peak value command value, the U-phase negative side switching element is turned off, and the positive side switching element is turned on to increase the voltage in the direction of increasing iu. It is said.

As described above, the flip-flop 73 is set / reset each time the phase current iu changes positive or negative and its absolute value exceeds the peak value command value. The same applies to the V phase and the W phase. Thus, commutation control signals of converter 3 are obtained as outputs UF, VF, WF of flip-flops 73 to 75. If the input side of the converter 3 is not the induction generator 2 but a mere reactor, the current change rate is determined by the reactor constant and the output voltage of the converter 3. The operating frequency of converter 3 is determined by the magnitude of the high value command value.

On the other hand, when the induction generator 2 is connected as in this embodiment, an induced electromotive force is added in addition to the above.
When the magnetic flux of the induction generator 2 is established, the current flows due to the difference between the output voltage of the converter 3 and the induced electromotive force. The current change rate changes due to the change in the induced electromotive force, and when the change in the induced electromotive force is viewed in phase, the speed of change of the induction generator 2 increases because the speed of change is sinusoidal and depends on the number of rotations.
The faster the induced electromotive force changes, the faster the current change rate,
The frequency of the converter 3 automatically follows the rotation speed of the induction generator 2. This enables commutation control of the converter without the rotation detector.

FIG. 7 is a diagram showing the relationship between the phase current iu and the frequency control signals UF, VF, WF. The voltage basic electrical angle signals UF, VF, WF are "1" every 180 degrees,
It becomes a signal that repeats "0", and becomes a three-phase signal whose phase is shifted by 120 degrees. When the above-described PWM is not performed, the converter 3 is controlled by the voltage basic electrical angle signal to
Since the 80-degree energization control is performed, all of UF, VF, and WF must not be simultaneously “1” or simultaneously “0”. However, simply the hysteresis comparators 50-55
By simply setting and resetting the flip-flops 73 to 75 with the output of the above, all of them may become "1" or "0" at the same time. To prohibit this, OR circuits 61-66
And AND circuits 67 to 72 prohibit all phases from simultaneously becoming "1" or "0". At the start of the peak value control, a start-up completion signal CPL is supplied to the flip-flops 73 to 75 so that all of the flip-flops 73 to 75 are in the reset state.

Based on the voltage basic electrical angle signal output from the commutation control circuit 32 and the current comparison signal output from the current comparison circuit 31, the PWM control circuit 33 calculates the three-phase current of the induction generator 2. In each case, control is performed so as not to exceed the peak value standard. As can be seen from the operation of the commutation control circuit 32, the current and the voltage of the induction generator 2 are controlled so as to keep substantially opposite phases. That is, the phase of the induction generator 2 is locked to the power generation state by the commutation control circuit 32. The voltage basic angle signal is a three-phase signal whose phase is shifted by 120 degrees, each of which is 18
A logic signal of "0" and "1" is taken every 0 degree. Therefore, only one of the three phases has a logical value opposite to that of the other two phases. Only the phase whose logical value is inverted performs PWM based on the current comparison signal, and the other two phases perform switching control based on the voltage basic angle signal output from the commutation control circuit 32. It can be controlled within the peak value criterion.

According to the conventional induction generator control device of FIG. 3 having the above-described current comparison circuit 31, commutation control circuit 32, and PWM control circuit 33, the magnetic flux of the induction generator 2 is established. When the induced electromotive force is generated, the current of the induction generator 2 can be controlled without a rotation sensor. The establishment of magnetic flux is performed by slip frequency control. When the power generation operation command 10 is given, the start-up control circuit 11 outputs the slip at the start-up and the current reference 15 to the slip frequency control circuit 13. The three-phase current reference generator 14 outputs a three-phase AC current reference. The current instantaneous value control circuit 16 outputs a PWM signal based on the result of the instantaneous comparison between the three-phase current and its reference. By operating the converter 3 by the PWM signal, the magnetic flux of the induction generator 2 can be established. The establishment of the magnetic flux can be most easily determined by the time when the slip frequency control is performed. This is because the magnetic flux of the induction generator 2 changes according to a time constant determined by the constant of the generator 2. As a result, the start-up control circuit 11 outputs a start-up completion signal 20 to start operating the voltage control circuit 17 and to switch the switching circuit 19.
Causes the converter 3 to operate with the output signal of the current peak value control circuit 18.

The circuit breaker 6 is turned on to supply electric power to the load 7. When the load 7 is turned on and the generated voltage is about to decrease, the voltage peak value is controlled by the voltage control circuit 17 to increase the generated power of the induction generator 2 and keep the generated voltage constant. By controlling the power generated by the induction generator 2 in this manner, the output voltage of the converter 3 can be controlled to be constant irrespective of a change in the power consumption of the load 7.

[0019]

In the conventional induction generator control device described above, extremely stable control can be performed once the peak value control is started. The problem lies in switching from slip frequency control to peak value control. If the rotation speed of the prime mover 1 is low, the switching may fail. This will be described with reference to FIGS. 8 and 9
Shows waveforms of respective parts before and after switching from the slip frequency control to the peak value. U-PWM, V-PWM, W-PWM are P
Output signals of the WM control circuit, UV, VW, and WV are line voltages of the induction generator 2, iIu ^* Is the reference value at the start of the U-phase current, iIU is the U-phase current, Il ^* , -Il ^* Is a peak value reference value and its polarity inversion signal, and _eu is an induced voltage.

In FIG. 8, the magnitude of the current reference at the time of the slip frequency control and at the start of the peak value control are made equal. Time t
Although switching is performed at 1, iIu cannot be controlled within the range based on the peak value, and is protruding. At the time of switching, the flip-flops 73 to 7 of the commutation control circuit 32
5 are all in a reset state and the line voltages of the induction generator 2 are all zero, so that the current of each phase of the generator 2 increases and decreases from the current value at that time by the induced voltage. Prime mover 1
If the rotation speed of the motor is high and the induced voltage is large, the phase at which the current first reaches the peak value reference is determined by the induced voltage phase at that time, but as in this case, the rotation speed of the motor 1 is low and the induction of the generator 2 is low. If the voltage is small, the phase that first reaches the peak value reference is affected by the magnitude of the phase current at the time of switching.

FIG. 9 shows a case where the reference value of the peak value at the start of the peak value control is increased in order to avoid the influence of the magnitude of the phase current at the time of switching. However, the current cannot reach the peak value reference value. Since the commutation control cannot be maintained, both the current and the magnetic flux gradually disappear.

Although there may be a good current peak value reference value between FIG. 8 and FIG. 9, the setting of the induction generator 2 is difficult because the constant of the induction generator 2 changes depending on the operation state. Also, if large power is generated at a low rotation speed, the prime mover may stop due to the power generation brake.
I want to be able to shift to peak value control with the current peak value reference value as small as possible. An object of the present invention is to provide an induction generator control device capable of stably performing the switching from the slip frequency control to the peak value control as described above.

[0023]

According to one aspect of the present invention, an induction generator driven by a prime mover and a converter for converting a three-phase AC output of the induction generator into a direct current are provided. And a current detector that detects each phase output current of the induction generator and outputs a current detection signal,

The current detection signal is compared with a commutation timing level command value common to each phase of the induction generator to determine whether or not the current detection signal exceeds a positive value of the commutation timing command value. A current comparison circuit composed of two comparators for each phase for outputting whether or not a negative value has been exceeded; and an output signal of the current comparison circuit being used as a commutation timing for each phase voltage of the induction generator at 180 degrees. Invert the logical value to 3
Current peak value control comprising: a commutation control circuit for generating a phase voltage synchronization signal; and a PWM control circuit for generating a switching signal for the converter based on the voltage synchronization signal and an output signal of the current comparison circuit. A circuit, a rotation detector that determines the rotation frequency of the induction generator,

Slip is added to the rotation frequency obtained from the rotation detector and integrated to obtain an electrical angle signal of the operating frequency of the converter, and a current reference instantaneous value obtained from the DC current reference and the electrical angle signal. A slip frequency control circuit that controls the current of the induction generator based on

Switching means for controlling the converter by the output of the slip frequency control circuit to switch the operation of the converter by the output of the current peak value control circuit after the magnetic flux of the induction generator is established;

Means for starting the control of the converter with the output of the current peak value control circuit after providing a period for controlling the converter so that the current of the induction generator becomes zero when the switching means is switched; It is a control device of the induction generator provided with.

According to a second aspect of the present invention, a commutation timing level command value at the start of control by the current peak value control circuit is set to a DC current reference at the time of control by the slip frequency control circuit. The control device for an induction generator according to claim 1, wherein the control device is made smaller.

[0029]

According to the first and second aspects of the present invention, the induced voltage of the induction generator changes only by the time constant determined by the constant of the generator. That is, it cannot change rapidly. On the other hand, the generator current can be rapidly controlled.
The present invention has been made by paying attention to this point, and controls the current to zero once at the time of switching from the slip frequency control to the peak value control, and the flip-flop of the commutation control circuit according to the magnitude of the current at the time of switching. While preventing mistakes in the first set, the initial value of the peak value reference value when switching the peak value control is made smaller than the current reference value during the start-up control,
Even when the induced voltage that cannot be measured is small, it is possible to stably shift to the peak value control.

[0030]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows the configuration of the first embodiment of the present invention. In FIG. 1, reference numerals 1 to 10 and 12 to 21 are the same as those of the conventional example shown in FIG. As the start-up control circuit 11A, one that outputs the start-up current reference 15 and outputs a current zero command 24 and a current weakening command 25 is used. The current zero command 24 is a switching sequence signal for temporarily setting the magnitude of the current reference to zero when switching from the start-up control to the generation voltage control. The current weakening command 25 is a signal for weakening the initial value of the output of the voltage control circuit 17 from the rising current reference 15 when the power generation voltage is started after the completion of the rising control circuit 11A.

The multiplication is performed between the output side of the start-up control circuit 11A and the input side of the three-phase current reference generator 14, and between the output side of the start-up control circuit 11A and the input side of the voltage control circuit 17, respectively. Units 22 and 23 are connected, and a multiplier 2
A rising current reference 15 is provided to one side of the inputs 2 and 23, respectively. On the other input side of the multiplier 22,
A current zero command 24 is provided, and a current weakening command 25 is provided to the other input side of the multiplier 23. In the multiplier 22, the start-up current reference 15 and the current zero command 24 are multiplied, and as a result, the current reference 15 is set to zero.
In addition, it is input to the three-phase current reference generator 14. The multiplier 23 multiplies the start-up current reference 15 and the current weakening command 25 and inputs the multiplied value to the voltage control circuit 17.

Next, the operation of the embodiment apparatus configured as described above will be described with reference to the time chart of FIG.
The slip frequency control is performed for a predetermined time, and at time t1 when the magnetic flux is established, the start-up control circuit 11 outputs a current zero command 24. Then, in the multiplier 22, the current reference 15 given to the three-phase current reference generator 14 is set to zero, and based on this, the current instantaneous value control is performed.

In this case, as shown in FIG.
The detected value iIu of the three-phase current flows only for the ripple. However, during this time, the induced voltage changes sinusoidally. At time t2, a start-up completion signal is provided, and peak value control is started. At this time, in the output of the voltage control circuit 17, a current peak value smaller than the current value at the time of startup is initially set by the current weakening command 25 given from the startup control circuit 11A. However, since the current is controlled to be zero, the flip-flops 73 to 75 set first in the commutation control circuit 32 (FIG. 4)
(FIG. 6) is determined by the induced voltage phase, and has shifted to the peak value control stably.

In this embodiment, by setting the current reference 15 of the current instantaneous value control circuit 16 to zero, the induction generator 2
Current is zero. As described above, in this embodiment, the current of the induction generator 2 may be set to zero, and there are other means. For example, the base may be cut off to turn off all the switching elements constituting the converter 3. In this case, since the current becomes almost zero, the current peak value reference value at the start of the peak value control can be further reduced as compared with the present embodiment.

According to the embodiment described above, it is possible to start power generation at a lower rotational speed than in the prior art. In a system that generates electric power by using the surplus power of a prime mover, the rotational speed of the prime mover may be reduced due to its intended use, but even in such a case, the power generation can be performed stably. As a result, the applications of the power generation device based on the peak value control that can continue the power generation control without the rotation detector are expanded, and the generation stop due to the trouble of the rotation detector such as the system using only the slip frequency control is eliminated. Further, since the closed loop of the rotation speed is eliminated from the power generation control, and the influence on the accuracy of the rotation speed detection and the control of the response speed is eliminated, high-speed and stable power generation control becomes possible.

[0036]

According to the present invention, it is possible to provide a control device for an induction generator which can stably switch from slip frequency control to wave height control.

[Brief description of the drawings]

FIG. 1 is a configuration diagram illustrating a first embodiment of a control device for an induction generator according to the present invention.

FIG. 2 is a time chart for explaining the operation of the embodiment of FIG. 1;

FIG. 3 is a configuration diagram showing an example of a conventional induction generator control device.

FIG. 4 is a configuration diagram of a current peak value control circuit of FIG. 3;

FIG. 5 is a configuration diagram of the current comparison circuit of FIG. 3;

FIG. 6 is a configuration diagram of a commutation control circuit of FIG. 3;

FIG. 7 is a time chart for explaining the operation of the commutation control circuit of FIG. 3;

FIG. 8 is a time chart for explaining the operation of FIG. 3;

FIG. 9 is a time chart for explaining the operation of FIG. 3;

[Explanation of symbols]

REFERENCE SIGNS LIST 1 motor, 2 induction generator, 3 converter, 4 capacitor, 5 DC power supply, 6 circuit breaker, 7 load, 8
... current detector, 9 ... voltage detector, 10 ... power generation operation command,
11, 11A ... raising control circuit, 12 ... rotation detector,
13: slip frequency control circuit, 14: three-phase current reference generator, 15: starting current reference, 16: current instantaneous value control circuit, 17: voltage control circuit, 18: current peak value control circuit, 19: switching circuit , 20 ... Startup complete signal, 2
1: switching control circuit, 22-23: polarity inverter,
24: current zero command, 25: current weakening command, 31: current comparison circuit, 32: commutation control circuit, 33: PWM control circuit, 41 to 43: polarity inversion circuit, 44 to 49: subtractor,
50-55 ... hysteresis comparator, 61-66 ...
OR circuit, 67-72 ... AND circuit, 73-75 ... flip-flop.

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) H02P 9/00 H02P 9/10 H02M 7/12

Claims (2)

(57) [Claims] 1. An induction generator driven by a prime mover, a converter for converting a three-phase alternating current output of the induction generator to a direct current, and detecting a current of each phase of the induction generator to output a current detection signal. A current detector that compares the current detection signal with a commutation timing level command value common to each phase of the induction generator to determine whether the current detection signal exceeds a positive value of the commutation timing command value. And a current comparison circuit comprising two comparators for each phase for outputting whether or not a negative value has been exceeded. An output signal of the current comparison circuit is used as a commutation timing to calculate the phase voltage of each phase of the induction generator. A commutation control circuit that generates a three-phase voltage synchronization signal that inverts a logical value every 180 degrees, and a PWM that generates a switching signal of the converter based on the voltage synchronization signal and an output signal of the current comparison circuit A current peak value control circuit including a control circuit; a rotation detector that determines the rotation frequency of the induction generator; and a slip added to the rotation frequency obtained from the rotation detector, integrated, and integrated to operate the converter. A slip frequency control circuit that obtains a frequency electrical angle signal and controls the current of the induction generator based on a current reference instantaneous value obtained from the DC current reference and the electrical angle signal; and an output of the slip frequency control circuit. Switching means for controlling the converter to operate the converter according to the output of the current peak value control circuit after the magnetic flux of the induction generator is established; and the current of the induction generator when the switching means is switched. Means for starting the control of the converter with the output of the current peak value control circuit after providing a period for controlling the converter so that is zero, An induction generator control device comprising: 2. The induction according to claim 1, wherein a commutation timing level command value at the start of control by the current peak value control circuit is smaller than a DC current reference at the time of control by the slip frequency control circuit. Generator control device.