JP2005176505A - Control device for generator and starting method of induction type generator - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a technology that enables safe starting by preventing an excessive current from flowing to an induction type generator. <P>SOLUTION: In starting the induction type generator, a voltage and a frequency of rotating magnetic field generating AC power fed to the induction type generator are controlled, a frequency at which a current of the AC power becomes minimum is obtained by decreasing the frequency in a state that the voltage is lowered below a voltage at a normal time, and a generation operation is started with a position of the obtained frequency as a starting point. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a starting technique for an induction generator.

  As a prior art related to the present invention, for example, there is one described in Japanese Patent Application Laid-Open No. 11-41986 (Patent Document 1). In this publication, when a plurality of drives equipped with induction motors are restarted from a running state, a motor frequency is estimated for the induction motor in one drive as a technique for preventing the generation of unnecessary overcurrent and torque. Based on this, a technique is described in which the inverter in each of the plurality of drives is controlled to raise the motor magnetic flux of the induction motor. In estimating the motor frequency, the phase current supplied to the induction motor is detected, and the inverter frequency that makes the magnitude of the phase current calculated based on the detection result zero or minimized is set to the motor frequency (rotation of the induction motor). Frequency).

Japanese Patent Laid-Open No. 11-41986

For example, the prior art described in the above publication is a technique for restarting an induction motor, and is not a technique for starting (starting) an induction generator. Further, in the case where the conventional technique is used for starting an induction generator, when obtaining an inverter frequency at which the magnitude of the phase current is zero or minimum, the inverter frequency is determined from the rotational frequency when the induction motor is driven. It is also possible to obtain an inverter frequency value at which the magnitude of the phase current is zero or minimum by increasing from a low frequency value. In this case, however, the phase current during the start-up preparation period is at a high level. There is a risk that. Moreover, in this prior art, the calculation means for calculating a phase current based on a detected value is needed.
In view of the state of the prior art, the problem of the present invention is that, as a control technique at the time of starting the induction generator, when the rotor of the induction generator is rotated by an external force such as a turbine, the induction generator This is to prevent excessive current from flowing through the stator.
An object of the present invention is to provide a control technique capable of solving the above-described problems and safely starting an induction generator.

  In order to solve the above-described problems, the present invention controls the voltage and frequency of the rotating magnetic field generating AC power supplied to the induction generator at the start of the induction generator, so that the voltage is more stable than the steady state. By reducing the frequency in the lowered state, the frequency at which the current of the AC power is substantially minimum (including the minimum) is obtained, and the power generation operation is started from the obtained frequency position.

  According to the present invention, the induction generator can be safely started.

The best mode for carrying out the present invention will be described below with reference to the drawings.
1-4 is explanatory drawing of embodiment of this invention. 1 is a configuration diagram of a generator control device as an embodiment of the present invention, FIG. 2 is a characteristic example diagram of current exchanged between the generator control device of FIG. 1 and an induction generator, FIG. 3 is a diagram for explaining the operation of the generator control device of FIG. 1, and FIG. 4 is a diagram showing currents transferred between the generator control device of FIG. 1 and the induction generator under conditions different from those in FIG. FIG.

  In FIG. 1, 100 is a generator control device for controlling an induction generator, 101 is a control computer, 102 is a control unit, 103 is an induction generator, and 104 is an induction generator for power generation. Turbine turbine for rotating the rotor of the machine 103 (induction type rotor), 105 an AC power supply system, and 106 a current exchanged between the generator control device 100 and the induction generator 103. A current detection unit 121 serving as a current detection means for detecting supplies alternating-current power for generating a rotating magnetic field to a stator coil (not shown) of the induction generator 103 and a rotor (not shown) of the induction generator 103. The first inverter 122 that converts the AC power generated in the stator coil by the rotation of (none) into DC power and outputs it, 122 is a smoothing capacitor as a smoothing means for smoothing the DC power, 123 A second inverter for outputting the AC power supply system 105 side as regenerative power to convert the DC power smoothed into AC power. The generator control device 100 excites the induction generator to generate power to obtain regenerative power. The control computer 101 controls the control unit 102. At the time of starting the induction generator 103, the control computer 101 controls the first inverter 121 in the control unit 102, and the rotation supplied from the first inverter 121 to the stator coil of the induction generator. Controls the frequency value and voltage value of AC power for magnetic field generation. The frequency value and the voltage value are set by the control computer 101.

  In the above configuration, when the induction generator 103 is started, the control computer 101 controls the first inverter 121 in a state where the rotor of the induction generator 103 is rotationally driven by the turbine turbine 104. The frequency value and voltage value of the rotating magnetic field generating AC power are controlled. That is, the frequency value is gradually decreased in a state where the voltage value is lower than that in the steady state, and the current between the first inverter 121 and the induction generator 103 including the current of the rotating magnetic field generating AC power is reduced. A frequency position where the energization current is substantially minimum (including the minimum) is obtained. At this time, the control computer 101 may keep the ratio of the voltage value lowered from the steady state and the gradually decreasing frequency value substantially constant, or the voltage lowered from the steady state. The value may be kept constant regardless of the change in the frequency value. The control computer 101 causes the control unit 102 to start a power generation operation starting from a frequency position where the energization current is substantially minimum. That is, the control computer 101 controls the first inverter 121, further reduces the frequency value of the rotating magnetic field generating AC power output from the first inverter 121, and increases the voltage value to a steady-state value. Then, AC generated power from the induction generator 103 is received.

  After starting the induction generator 103, the AC generated power from the induction generator 103 is converted into DC power by the first inverter 121, and then smoothed by the smoothing capacitor 122. It is converted into AC power by the inverter 123 and supplied to the AC power supply system 105 side as regenerative power.

  FIG. 2 is a characteristic example diagram of current exchanged between the generator control device 100 and the induction generator 103 of FIG. This characteristic is when the ratio between the voltage and the frequency is kept substantially constant. Hereinafter, the same reference numerals as those in FIG. 1 are used for the components in FIG.

In FIG. 2, A is a case where the ratio between the voltage value V _{1 of the} rotating magnetic field generating AC power supplied to the stator coil of the induction generator 103 and the frequency value f is constant (constant value c ₁ ), that is, V _1. Current characteristic in the case of / f = c ₁ , B is a constant ratio of the voltage value V ₂ (<V ₁ ) and the frequency value f of the AC power for generating the rotating magnetic field (constant value c ₂ (<c ₁ )) (I) is a region where the induction generator 103 operates as a generator (hereinafter referred to as a generator operating region), and (b) is a current characteristic when V ₂ / f = c _2. A region in which the power generator 103 operates as a motor (hereinafter referred to as a motor operation region), f ₀ is a rotation frequency of the rotor of the induction generator 103. When starting the induction generator 103, the frequency f of the rotating magnetic field generating AC power supplied from the first inverter 121 to the induction generator 103 is set in advance in the motor operating region (b). A certain frequency (hereinafter referred to as a set frequency) f _{max is} gradually lowered according to the current characteristic B. When the frequency value of the rotating magnetic field generating AC power is gradually lowered, the current detection unit 106 detects the current value, and obtains a frequency at which the current value is substantially minimum (hereinafter referred to as the minimum current frequency). Thereafter, the operation shifts to the operation of the generator operation region, and the generator operation is started. The minimum current frequency is the rotational frequency f ₀ at which the rotor of the induction generator 103 is driven to rotate by the turbine for turbines 104.

FIG. 3 is an explanatory diagram of the operation at the start of the generator control device 100 of FIG.
In FIG.
(1) Start preparation operation is started by an instruction from the control computer 101 (step S301). At this time, it is assumed that the rotor of the induction generator 103 is rotationally driven by an external force from the turbine for turbines 104.
(2) The control computer 101 sets the frequency f of the rotating magnetic field generating AC power supplied from the first inverter 121 to the induction generator 103 to the set frequency f _max in the motor operation region (step S302). The set frequency f _max may be read out in advance as stored in a memory or the like.
(3) The control computer 101 controls the first inverter 121, and the voltage V of the rotating magnetic field generating AC power supplied to the induction generator 103 is a value lower than that in the normal state and has a frequency f. Is set to V _{2 at} which the ratio is constant (step S303).
(4) While decreasing the frequency f, the voltage V ₂ is applied to the stator coil of the induction generator 103 according to the current characteristic B of FIG. 2, ie, V ₂ / f = c ₂ (constant) (step S 304). .
(5) The current detector 106 detects the absolute value of the current i of the rotating magnetic field generating AC power (step S305).
(6) The control computer 101 compares the absolute value of the detected current i with the absolute value of the current detected last time in the detection operation, and the absolute value of the current detected current is the absolute value of the previous detected current. It is discriminated whether or not there is an increase (step S306).
(7) As a result of the determination, if the absolute value of the current detected current i has increased with respect to the absolute value of the previous detected current, the frequency f has already reached the rotation of the rotor of the induction generator 103. Assuming that the frequency f ₀ is decreasing, ie, exceeding the current minimum frequency, the control computer 101 adds the excess decreasing frequency Δf to the frequency f at that time to obtain the current minimum frequency (step S308).
(8) At the obtained current minimum frequency, the control computer 101 controls the first inverter 121 to increase the voltage V of the rotating magnetic field generating AC power supplied to the induction generator 103 (step S309).
(9) The preparation for starting the induction generator 103 is completed (step S310). Thereafter, the generator operation in the generator operation region is started from the obtained minimum current frequency as a starting point.
(10) If the absolute value of the detected current i has not increased with respect to the absolute value of the previous detected current as a result of the determination in step S306, the current of the rotating magnetic field generating AC power is decreasing and the frequency f Has not yet reached the minimum current frequency (rotation frequency f ₀ of the rotor of the induction generator 103), the control computer 101 controls the first inverter 121, and the frequency f of the AC power for generating the rotating magnetic field is determined. Is further decreased by Δf, and the operation returns to the operation of step S303 (step S307).

According to the above-described embodiment of the present invention, when the induction generator 103 is started, the voltage of the rotating magnetic field generating AC power supplied to the stator coil is lowered, and the frequency f is rotated by the rotation of the induction generator 103. The induction generator 103 is fixed in order to obtain a minimum current frequency (= rotation frequency f ₀ of the rotor of the induction generator 103) by gradually decreasing from a frequency higher than the rotation frequency f _{0 of the} child. It is possible to prevent an excessive current from flowing through the child, and the induction generator 103 can be started safely.

In the above description, the relationship between current and frequency in FIG. 2 is used. This is when the voltage and frequency of the AC power for generating the rotating magnetic field are in a proportional relationship. However, it is not always necessary to maintain a proportional relationship between frequency and voltage. For example, FIG. 4 shows the relationship between current and frequency when the voltage is maintained at a certain constant value regardless of the frequency. FIG. 5 shows the relationship between current and frequency when the voltage V is proportional to the square of the frequency. 4 and 5, C and D are current characteristics, respectively. Further, (A) is a generator operating region, (B) is an electric motor operating region, f ₀ is a rotation frequency of the rotor of the induction generator 103, and f _max is a set frequency. If the voltage is suppressed to a sufficiently low value in this way, the voltage and the frequency may have an arbitrary relationship.

  For example, in the method of FIG. 3, for determining the frequency that gives the minimum value of the current, the frequency that gives the substantially minimum value is determined by comparing the magnitudes of the detected currents. However, the present invention is not limited to this, and other methods may be used. For example, the value of the current change ratio Δi / Δf with respect to the frequency change may be used. That is, Δi / Δf is positive or almost close to 0 in the region (b), but changes to a negative value when the region (b) is entered beyond the region (b). That is, it can be determined that the current is at a frequency at which the current becomes substantially the minimum value when Δi / Δf becomes a certain value or less.

Further, in the example of FIG. 3 described above, the frequency is scanned in a direction lower by Δf from the set frequency f _max , and the frequency at which the current is substantially minimum is detected. However, the present invention is not limited to this, and other general methods may be used. For example, if the Newton-Raphson method is used, the frequency can be detected more quickly. For example, when the Newton-Raphson method is used in the relationship between the current and the frequency in FIG. 5, the frequency at which the current becomes substantially minimum is detected without trying the frequency below f ₀ by giving f _max as an initial value. be able to.

It is a block diagram of the control apparatus for generators as embodiment of this invention. It is a characteristic example figure of the electric current between the control apparatus for generators of FIG. 1, and an induction type generator. It is operation | movement explanatory drawing of the control apparatus for generators of FIG. It is another characteristic example figure of the electric current between the control apparatus for generators of FIG. 1, and an induction type generator. It is another characteristic example figure of the electric current between the control apparatus for generators of FIG. 1, and an induction type generator.

Explanation of symbols

100 ... Generator control device,
101 ... Control computer,
102 ... control unit,
103 ... induction type generator,
104: Turbine turbine,
105 ... AC power supply system,
106 ... a current detector,
121 ... first inverter,
122 ... smoothing capacitor,
123: Second inverter.

Claims (5)

A generator control device for generating regenerative power by exciting an induction generator to generate power,
The AC power for generating the rotating magnetic field is supplied to the stator coil of the induction generator, and the AC power generated in the stator coil due to the rotation of the rotor is converted into DC power and converted into AC power again. An inverter that outputs as
A control computer for controlling the inverter to control the frequency and voltage of the rotating magnetic field generating AC power;
When the induction generator is started, the frequency of the alternating-current power is reduced while the voltage of the alternating-current power for generating the rotating magnetic field is lower than that in the steady state, and the induction generator is energized from the inverter. A generator control device characterized in that a power generation operation is started from a frequency at which a current is substantially minimum. A generator control device for generating regenerative power by exciting an induction generator to generate power,
A first inverter that supplies AC power for generating a rotating magnetic field to the stator coil of the induction generator, and that converts AC power generated in the stator coil by rotation of the rotor into DC power and outputs the DC power;
Smoothing means for smoothing the DC power;
A second inverter that converts the smoothed DC power into AC power and outputs it as regenerative power;
Current detection means for detecting an energization current between the first inverter and the induction generator;
A control computer that controls the first inverter based on a preset program and controls the frequency and voltage of the AC power for generating the rotating magnetic field;
A current of the rotating magnetic field generating AC power detected by the current detecting means by reducing the frequency in a state where the voltage of the rotating magnetic field generating AC power is lower than that at the normal time when starting the induction generator The first frequency at which the level is substantially minimum is obtained, the voltage is increased at the first frequency, and the power generation operation is started as the second frequency lower than the first frequency. A generator control device.   The generator computer according to claim 2, wherein the control computer controls the first inverter so that a ratio of the voltage to the frequency becomes substantially constant when the frequency of the rotating magnetic field generating AC power is decreased. Control device. A method for starting an induction generator,
A first step of reducing the frequency value of the rotating magnetic field generating AC power in a state where the voltage of the rotating magnetic field generating AC power supplied to the induction generator is lower than that in a steady state;
A second step of obtaining a frequency at which the current level of the rotating magnetic field generating AC power is substantially minimum;
A third step of increasing the voltage of the rotating magnetic field generating AC power and further reducing the frequency;
And starting the induction generator via the induction method.   5. The induction generator starting method according to claim 4, wherein in the first step, a ratio between a voltage value and a frequency value in the rotating magnetic field generating AC power is substantially constant.

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