JPH0538150A - Controller of induction generator - Google Patents

Abstract

PURPOSE:To obtain a device capable of using a low priced revolution detector without requiring accuracy and resolution for the revolution detector. CONSTITUTION:A current detector 9 detecting the output current of an induction generator 2, a revolution detector 8 detecting revolution-speeds of a prime mover 1, a slip frequency control circuit 14 outputting an instantaneous current command value based on the detection signal, a current instantaneous value control circuit 16 generating a control signal of a converter 3 based on the instantaneous current command value and output current, a current peak value control circuit 19 generating the control signal of the converter 3 based on the result comparing the peak value standard of the output current of the induction generator 2 with the output current, output of the peak value control circuit 19 and output of the current instantaneous value control circuit 16 can be switched. When the induction generator 2 starts it operation, it can be switched to the instantaneous current value control circuit 16 side, and when the magnetic flux is established by the operation of the induction generator 2, it is switched to the peak value control circuit 19 side. by a selector 20.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is suitable for applications in which the rotational speed of a prime mover such as a wind turbine and a shaft generator that obtains electric power by utilizing the surplus power of a mechanical device used in an internal combustion engine changes drastically. Control device for induction generator.

[0002]

2. Description of the Related Art FIG. 6 is a block diagram of a conventional embodiment.
In the figure, 1 is a prime mover, 2 is an induction generator driven by the prime mover 1, 3 is a converter for converting the AC output of the induction generator 2 into direct current, 4 is a capacitor for smoothing the output voltage of the converter 3, and 5 is induction generation. A DC power source for initial excitation of the machine 2, 6 is a circuit breaker for turning on / off the electric power supplied from the converter 3 to the load 7, and 7 is a load.

Reference numeral 8 is a rotation detector for detecting the rotation speed of the induction generator 2, 9 is a current detector for detecting the output current of the induction generator 2, and 10 is a voltage detector for detecting the output voltage of the converter 3. ..

Reference numeral 11 is a power generation operation command, 12 is a power generation start-up control circuit, 13 is a voltage control circuit for controlling the output voltage of the converter 3, and 14 is a rotation speed of the induction generator 2 detected by the rotation detector 8. With reference to, a slip frequency control circuit for controlling the magnitude of the output current and the slip frequency of the induction generator 2, 15 is a three-phase current command value obtained as the output of the slip frequency control circuit 14, 16 is a current control circuit, 17
Is a switching control circuit for controlling switching elements such as transistors 27 to 32 that form the converter 3.

The converter 3 is bridge-connected by diodes 21 to 26 and transistors 27 to 32. The initial excitation power supply 5 is composed of, for example, a diode 33 and a battery 34.

In the above conventional configuration, when the power generation operation command 11 is given, the start-up control circuit 12 outputs the power generation voltage command value to the voltage control circuit 13. In the voltage control circuit 13, the generated voltage command value is compared with the output voltage of the converter 3 detected by the voltage detector 10, and the magnitude of the output current of the induction generator 2 and the slip frequency are determined by the slip frequency control circuit. Controlled by 14. At the time of launch,
Since the output voltage of the converter 3 is lower than the generated voltage, the output current of the induction generator 2 is increased and the slip frequency is increased in the negative direction to increase the generated power of the induction generator 2. That is, with reference to the rotation speed of the induction generator 2 detected by the rotation detector 8 in the slip frequency control circuit 14, the instantaneous command value 15 of each phase current having an amplitude and slip corresponding to the difference in the output voltage is set. Calculate

Next, in the current control circuit 16, the instantaneous value of each phase current of the induction generator 2 detected by the current detector 9 is compared with the instantaneous command value 15 of each phase current, and the switching control circuit 17 The converter 3 is controlled to control the output current of the induction generator 2. When the output voltage of the converter 3 reaches the power generation voltage command value, the start-up control circuit 12 turns on the breaker 6 and starts supplying power to the load 7. Load 7
When the generated voltage is going to drop due to
The converter 3 is controlled by the voltage control circuit 13, the slip frequency control circuit 14, the current control circuit 16, and the switching control circuit 17 to increase the generated power of the induction generator 2 to 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 regardless of the change in the power consumption of the load 7.

[0009]

In the conventional configuration described above, since the rotation detector 8 needs to be installed near the prime mover 1, the rotation detection is performed due to the bad environment of large vibration and high temperature and humidity. There were many troubles that the vessel 8 failed.
If the rotation detector 8 fails, power generation cannot be continued. Further, the output signal of the rotation detector 8 is disturbed by the vibration or electromagnetic noise of the prime mover 1, and the output current of the induction generator 2 controlled based on this is disturbed, so that stable control cannot be performed. was there. Furthermore, if the accuracy and resolution of the rotation detector 8 are low, the output current waveform of the induction generator 2 is distorted and good characteristics cannot be obtained, so an expensive rotation detector with high accuracy and resolution is required.

The present invention uses the rotation detector only at the start of power generation, does not use the rotation detector during power generation, and can continue power generation even if the rotation detector fails, and the rotation detector has accuracy and resolution. It is an object of the present invention to provide a control device for an induction generator that can use an inexpensive rotation detector without being required.

[0011]

In order to achieve the above-mentioned object, the present invention provides a rotation detector such as a slip frequency control circuit in a power generator which comprises an induction generator and a converter and obtains a direct current at the output of the converter. The output current waveform of the control circuit used and the induction generator is determined by the magnetic flux of the induction generator, the rotation speed, the impedance of the winding, the DC output voltage, and the load. Focusing on the fact that the waveform changes, the configuration is as follows.

That is, an induction generator driven by a prime mover and outputting an alternating current, a converter for converting the alternating current output of the induction generator into a direct current and supplying the converted direct current to a load, and the induction generator. Current detector that detects the output current of the motor, a rotation detector that detects the rotation speed of the prime mover, and outputs this rotation speed detection signal, and an instantaneous current command value that is output based on the detection signal of this rotation detector. A slip frequency control circuit, a current instantaneous value control circuit that generates a first control signal of the converter based on the instantaneous current command value and the output current, a peak value reference of the output current of the induction generator, and the A current peak value control circuit for generating a second control signal for the converter based on a result of comparison with an output current, an output of the peak value control circuit and a current instantaneous value control circuit. And a selector that is capable of switching the force and switches to the current instantaneous value control circuit side at the start of operation of the induction generator, and switches to the peak value control circuit side when magnetic flux is established by the operation of the induction generator. It is equipped.

[0013]

According to the present invention, when the operation of the induction generator is started, the induction generator is operated by the slip frequency control using the rotation detector, and it is detected that the magnetic flux of the induction motor is established, and the current peak value control is performed. Since the operation is switched to, the power generation can be continued even if the rotation detector fails, the rotation detector does not require accuracy and resolution, and an inexpensive rotation detector can be used.

[0014]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows the configuration of an embodiment of the present invention. Since 1 to 17 and 21 to 34 are the same as the constituent elements of the conventional example of FIG. 6, the points different from FIG. 6 will be mainly described here. .. Based on the comparison result of the current peak value reference from the voltage control circuit 13 and the output current from the current detector 9,
Current peak value control circuit 1 for generating converter control signal
9, a data selector 20 for switching the output of the peak value control circuit 19 and the output of the current instantaneous value control circuit (first converter control signal), and a switching instruction for the data selector 20. When the operation of the generator 2 is started, it is switched to the current instantaneous value control circuit 16 side, and when the induction generator 2 detects that the magnetic flux is established by the operation, it gives a command to switch to the current peak value control control circuit 19 side. That is, the raising control circuit 12 is provided.

FIG. 2 is a detailed diagram of the current instantaneous value control circuit 16, the current peak value control circuit 19, and the data selector 20 which are the main parts of the present invention in FIG. In FIG. 2, IU
^* , IV ^* , IW ^* The three-phase current command value (three-phase current reference) in slip frequency control, IU, IV, and IW are the output currents of the induction generator 2 detected by the current detector 9, 4
1, 42 and 43 are subtracters, 44, 45 and 46 are hysteresis comparators, and USF, VSF and WSF are output signals of the hysteresis comparators 44, 45 and 46, respectively.

Il ^* Is a peak value command value (peak value reference) 18 of the output current of the induction generator 2 and takes a positive value. 47
Is a polarity inversion circuit that inverts the polarity of the current peak value command value 18 to obtain a negative peak value command value, 48 to 53 are subtractors, 54 to 54
59 is a hysteresis comparator, WP, WN, VP,
VN, UP and UN are hysteresis comparators 54 to 5
Output signals 60, 61, and 62 of 9 are RS flip-flops.

The data selector 20 receives the respective outputs of the current instantaneous value control circuit 16 and the current peak value control circuit 19 as data input, and the current instantaneous value control is performed by the switching signal 63 output from the rising control circuit 11. Circuit 1
6 or the output signal of the current peak value control circuit 19
Output as WM signals U, V, W.

The operation of this structure will be described below. First, the operation of the current peak value control circuit 19 will be described with reference to FIG. In FIG. 3, IU, IV, and IW are output current waveforms of the induction generator 2, and thin lines are U-phase currents IU and
The broken line represents the V-phase current IV and the alternate long and short dash line represents the W-phase current IW. This current waveform is a waveform when the induction generator 2 is operated by the converter 3 and the frequency is not so low and PWM control is not performed (this state is hereinafter referred to as a 180-degree conduction mode). At this time, converter 3
The output voltage of each phase has a waveform in which the U-phase voltage is USL in FIG. 3, the V-phase voltage is VSL, and the W-phase voltage is WSL. In order to understand the phase relationship with the current waveform, vertical dotted lines are inserted at every 60 electrical angle in FIG. Also, in the same column as the current waveform, a solid line indicates I1 ^* , -I1 ^* Is drawn.

Looking at the relationship between the current waveform and the voltage waveform, U
In terms of phase, the U-phase current increases and I1 ^* When
The U-phase voltage changes from high level to low level, the U-phase current decreases, and the current becomes -I1 ^*. When it reaches, the U-phase voltage changes from low level to high level. The same applies to the V phase and the W phase. When the induction machine is operated to generate electricity by the voltage source converter, the relationship between the induction machine output current and each phase voltage in the 180-degree conduction mode is always as shown in FIG. This also applies to the slip frequency control circuit 14 described in the above-mentioned conventional example. Considering from now on, DC level I1 ^* And-
I1 ^* It is likely that the output current can be controlled like IU, IV, and IW by comparing the phase currents and controlling the converter switch based on the result. It is actually possible when you try it, and this is the principle of current peak value control.

However, this is because the induction generator 2
Only when the magnetic flux is established and the induced voltage is generated. If there is no induced voltage, the current flows only by the terminal voltage and the impedance of the winding of the generator 2.
The frequency has nothing to do with the rotation speed of. On the other hand, when the magnetic flux is established, an induced voltage is generated, and the current flows due to the voltage difference between the terminal voltage and the induced voltage. The frequency of the induced voltage depends on the rotation speed and the power generation state at that time. I1 ^* for peak value control , -I1 ^* Then, the magnitude of the current of the induction generator 2 is determined, and the power generation state is determined by this. That is, the frequency is determined without the rotation sensor. Once the current peak value control is established, the frequency of the current automatically follows the change in rotation speed even if the rotation speed of the induction generator changes. This is because the frequency of the induced voltage changes depending on the rotation speed.

As described above, the current peak value control cannot be established unless the magnetic flux of the induction generator 2 is established. In the present invention, the magnetic flux of the induction generator 2 is established by the slip frequency control and switched to the current peak value control.

In FIG. 2, I1 ^* The current crest value reference 18 having the magnitude of and the signal obtained by making the current crest value reference 18 negative by the polarity reversing circuit 47 are input to the subtractors 48 to 52. The output current of the induction generator 2 detected by the current detector 9 is also input to the subtractors 48 to 52, and I1 ^* Or -I1 ^* And the difference is taken. The outputs of the subtracters 48 to 52 are converted into logic signals by the hysteresis comparators 54 to 59. The subtractor 48 has -I1 ^* Since the W-phase current IW is subtracted from the output of the hysteresis comparator 54, IW is I1 ^*. When it becomes larger than "1", it becomes "0" otherwise. This is indicated by WP in FIG.

Similarly, IW is -I1 ^* When it goes in the negative direction, it becomes "1" otherwise it becomes "0". The same applies to the U phase and V phase, and the signals indicated by UP, UN, VP, and VN in FIG. 3 are output from the respective hysteresis comparators. The RS of the W-phase signals WP and WN is input to the flip-flop 60. Since the RS flip-flop 60 is reset by WP and set by WN, it has a waveform as shown by WSL in FIG. That is, IW changes from positive to negative, and -I1 ^* When going to the more negative direction, WN becomes "1" and WSL becomes "0" to "
1 ”. After that, in FIG.
It becomes "0" and becomes "1" again, but at that time, the RS flip-flop has already been set and therefore the output does not change. When WSL is "1", the data selector 20
And the W of the converter via the switching control circuit 7.
The transistor 27 on the positive side of the phase is turned on, and the transistor 28 on the opposite side is turned off. As a result, a positive voltage is applied to the W phase, and the W phase current changes as shown in FIG. 3IW to change from negative to positive, and finally I1 ^* Reach the level of.

As a result, WP becomes "1", the RS flip-flop 60 is reset, and WSL changes from "1" to "0". This causes the transistor 27,
28 is turned on and off in reverse, a negative voltage is applied to the W phase, the W phase current changes as shown by IW to change from positive to negative, and finally −I1 ^* Reach The same applies to the U phase and V phase. When controlling as described above, the voltage between the U phase and V phase, between V phase and W phase, and between W phase and U phase of the induction machine is UV in FIG.
The waveforms are UW and WU.

4 and 5 are waveforms showing the process of operating the induction generator by slip frequency control to establish the magnetic flux, raising the generated voltage to the command value, switching to the current peak value control and turning on the load. It is a figure. 4 and 5, i1 is U-phase current, v2 is U-phase-V phase voltage, and v3 is U-phase-V.
Induced voltage between phases, i4 is U phase current reference during slip frequency control, and I1 ^{* for} current peak value control ^. Is represented. i5 is a U-phase current like i1. t6 is a torque generated by the induction generator, which is negative in the direction of deceleration of the prime mover 1. p7 is the power generated by the induction generator, and p8 is the power consumption of the load. The generated voltage, that is, the converter output voltage, rises due to the generated power p7 of the induction generator and decreases due to the power consumption p8 of the load.
The generated power is positive and the power consumption of the load is negative.
v9 is the command value of the power generation voltage, and v10 is the power generation voltage.

In FIG. 2, when the operation command 11 is input to the rising control circuit 12, the rising control circuit 12 outputs a negative slip to the slip frequency control circuit 14, and at the same time, the data input of the data selector 20 is changed to a current. It is set on the instantaneous value control circuit 16 side. Since the slip is negative, the induction generator 2 operates as a generator. The instantaneous current value control circuit 16 operates so that the U-phase current i5 follows the U-phase current reference i4 having a frequency lower than the rotation frequency only by the slip frequency. In FIG. 3, the output USF of the hysteresis comparator 44 changes depending on the magnitude relationship between the U-phase current and the U-phase current reference. Based on this signal USF, by controlling the converter 3 via the data selector 20 and the switching control circuit 17, the U-phase current is controlled so as to follow the U-phase current reference. At first, the induced voltage v3 is zero because there is no magnetic flux, but the magnetic flux gradually increases due to the current flowing by the slip frequency control circuit 14, so that the amplitude of the induced voltage v3 increases. Further, the torque t6 also gradually increases to a value determined by the magnitude of the slip and the current, and the generated power also increases. As a result, the power generation voltage v10 increases. As the induced voltage v3 increases, the U-phase current waveform i1 changes due to the influence, and the current followability improves as the induced voltage v3 increases.

FIG. 5 is a continuation of FIG. 4, but is adapted for PWM. When the current followability is improved, the instantaneous current value control circuit 16 automatically performs PWM control.

The rising control circuit 12 compares the power generation voltage v10 with the power generation voltage reference v9, and turns on the circuit breaker 6 at a time point t1 when the power generation voltage v10 exceeds the power generation voltage reference v9 to turn on the negative voltage. At the same time, the voltage control circuit 13 is activated, and the data input of the data selector 20 is set in the voltage peak value control circuit 19. The current peak value control circuit 19 described with reference to FIG. 3 is the simplest circuit example, and since PWM control is not performed, the current waveform i1 becomes a 180-degree conduction mode waveform as shown in FIG. In FIG. 5, the current reference i after t1
Reference numeral 4 represents a current peak value reference 18. When the generated voltage v10 decreases due to the load 7 being turned on, the current peak value reference 18 output from the voltage control circuit 13 increases.
In FIG. 5, it is indicated by i4. As a result, the generated voltage approaches the reference value. Thereafter, the load control is automatically controlled by the voltage control circuit 13, and the rotation fluctuation of the prime mover 1 is automatically controlled by the current peak value control.

In the first embodiment described above, the switching timing from the slip frequency control to the current peak value control,
That is, the timing at which the magnetic flux of the induction generator 2 is established and the current peak value control is established is detected by comparing the levels of the generated voltage. However, various detection methods can be considered depending on the power generation system. In the case of the system shown in FIG. 2, it is necessary to raise the power generation voltage from the initial excitation DC power supply voltage to the voltage supplied to the load, and therefore, only the level comparison of the power generation voltage is performed. As another power generation system, for example, the DC voltage for initial excitation may be equal to the load voltage. In this case, the system is such that the diode 33 is omitted in the initial excitation DC power supply of FIG. In such a system, it is not necessary to raise the generated voltage. Immediately after the breaker is inserted, power is supplied from the battery 34 to the load. The electric power generated by the induction generator 2 is the electric power for charging the battery 34 and the electric power required by the load. The establishment of the magnetic flux of the induction generator 2 can be detected by the time when the slip frequency is performed. This is because the magnetic flux changes with a time constant determined by the equivalent circuit constant of the induction generator 2.

Further, if the system is provided with a current detector for detecting the generated current of the DC portion of the output of the converter 3, it is also possible to compare the current levels. When the induction generator 2 is excited by the slip frequency control and the generated current increases to a value determined by the slip at that time and the magnitude of the current, it may be considered that the magnetic flux has been established.

[0031]

According to the control apparatus for an induction generator of the present invention described above, the rotation detector is used only at the start of power generation, and when the current peak value control is performed, the rotation detector is used. Since the rotation detector is not used, power generation can be continued even if the rotation detector fails, and since the rotation detector is not required to control the generated power, the rotation detector does not require accuracy and resolution, and an inexpensive rotation detector can be used. Can be used.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing an embodiment of the present invention.

FIG. 2 is a detailed circuit diagram of a main part of FIG.

3 is an operation explanatory diagram of an example of a current peak value control circuit 19 of FIG.

FIG. 4 is an operation waveform diagram for explaining the operation of a process from the start of power generation operation by slip frequency control according to the present invention to the power generation operation by current peak value control to supply power to a load.

FIG. 5 is an operation waveform diagram for explaining the operation of the process from the start of power generation operation by slip frequency control according to the present invention to the power generation operation by current peak value control to supply power to a load.

FIG. 6 is a configuration diagram of a conventional example.

[Explanation of symbols]

1 ... motor, 2 ... induction generator, 3 ... converter, 4 ... capacitor, 5 ... DC power supply for initial excitation, 6 ... breaker, 7
... load, 8 ... rotation detector, 9 ... current detector, 10 ... voltage detector, 11 ... operation command, 12 ... rising control circuit, 1
3 ... Voltage control circuit, 14 ... Slip frequency control circuit, 15
... 3-phase current reference, 16 ... Current instantaneous value control circuit, 17 ... Switching control circuit, 18 ... Current peak value reference, 19 ... Current peak value control circuit, 20 ... Data selector, 21-26
... Tioode, 27-32 ... Transistor, 33 ... Diode, 34 ... Battery.

Claims (1)

Claim: What is claimed is: 1. An induction generator driven by a prime mover to output an alternating current, and an alternating current output of the induction generator is converted into a direct current.
A converter that supplies this converted direct current to a load, a current detector that detects the output current of the induction generator, a rotation detector that detects the rotation speed of the prime mover, and outputs this rotation speed detection signal, A slip frequency control circuit that outputs an instantaneous current command value based on the detection signal of the rotation detector, and an instantaneous current value that generates a first control signal for the converter based on the instantaneous current command value and the output current. A control circuit, a current peak value control circuit for generating a second control signal of the converter based on a comparison result of the peak value reference of the output current of the induction generator and the output current, and a peak value control circuit for the peak value control circuit The output and the output of the current instantaneous value control circuit can be switched, and when the operation of the induction generator is started, it is switched to the current instantaneous value control circuit side, and by the operation of the induction generator. Control for an induction generator which anda selector switch to the peak value control circuit side when the flux is established.