JP2008079383A - Controller for ac excitation generator motor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a controller for an AC excitation generator motor which can be continuously operated while suppressing voltage variation, even if the voltage variation occurs in a DC circuit due to trouble in an AC power system. <P>SOLUTION: In order to operate a generator motor 2 as the AC excitation generator motor, the controller is constituted of a first power converter 4, a DC capacitor 6 connected to the DC terminal of the first power converter, a second power converter 5 for executing AC-DC conversion to excite the generator motor 2, a first control circuit 20 for the first power converter 4, and a second control circuit 30 for the second power converter 5. The first control circuit 20 adjusts the effective power of the first power converter 4 so as to allow DC voltage to coincide with a command value, and the second control circuit 30 adjusts the AC terminal voltage of the second power converter 5 so as to allow the secondary current of the generator motor 2 to coincide with the command value, thereby performing the correction control of the AC terminal voltage of the second power converter 5 so as to suppress the voltage variation at both ends of the DC capacitor corresponding to the variation component of the secondary current. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a control device for an AC excitation generator motor that excites an AC excitation generator motor connected to an AC power system with a voltage-type power converter having a DC circuit.

  An AC excitation generator motor in which a primary winding is connected to an AC power system and a power converter having a variable voltage and variable frequency output is connected to a secondary winding has an AC power system frequency and a rotor rotation speed. The system can be operated even when not synchronized, and can be operated with high efficiency in a power generation system such as hydroelectric power generation and wind power generation. Further, in the event of an AC power system failure, it is possible to obtain a power generation system that can stabilize the AC system by supplying power that matches the target value even if the frequency of the system fluctuates.

As a power converter for exciting the secondary winding of an AC excitation generator motor, a cycloconverter that converts AC of an AC power system directly into a variable voltage and variable frequency excitation output has been used. Recently, a first power converter that converts alternating current of an alternating current power system into direct current and supplies it to the direct current circuit, and second power that receives power from the direct current circuit and converts it into alternating current and supplies it to the secondary winding. A converter is used in combination. In this case, for example, if the DC voltage of the DC circuit is controlled to a constant value by the first power converter and the effective portion of the excitation current is controlled to a desired value by the second power converter, the AC power system As a result, it is possible to exchange only the active power, and the overall equipment capacity can be reduced as compared with the cycloconverter system that requires a relatively large reactive power.

  In such an AC excitation generator / motor system, when an accident occurs in the AC power system, a DC component or a reverse phase component is superimposed on the primary current of the AC excitation generator / motor, which is induced on the secondary side, and the secondary current. In addition to the excitation current component, a fluctuation component is superimposed on. The fluctuation component flows into the DC circuit and fluctuates the DC voltage. Further, when an accident occurs in the AC power system and the voltage decreases, the current capacity of the first power converter is limited, so that the convertible power also decreases. For this reason, the electric power required for suppressing the fluctuation | variation of the DC voltage of a DC circuit cannot be supplied from a 1st power converter. Therefore, the direct current voltage cannot be controlled, and there is a possibility that the system is stopped due to an overvoltage or a low voltage.

As a countermeasure for this, a technique has been proposed in which a chopper circuit composed of a resistor and a switching element is added in parallel to the DC circuit, and when the DC voltage is going to rise, the switching element is controlled to be turned on / off to control the DC voltage ( For example, see Patent Document 1.)
Japanese Patent No. 2703441 (page 3-7, FIG. 1)

  As described above, in the conventional AC excitation generator-motor system, when an AC power system accident occurs and the voltage of the DC circuit fluctuates, the DC voltage cannot be controlled and an overvoltage or an undervoltage of the DC circuit cannot be controlled. There was a problem that the system stopped. Further, according to the technique disclosed in Patent Document 1, it is possible to control a DC voltage, but it is necessary to add a chopper circuit to the DC circuit, and there is a problem that the circuit configuration becomes complicated.

  The present invention has been made to solve the above-described problems, and suppresses the occurrence of voltage fluctuations in the DC circuit due to an AC power system accident or the like with a relatively simple circuit configuration. It is an object of the present invention to provide a control device for an AC excitation generator-motor that can be continuously operated.

  In order to achieve the above object, a control apparatus for an AC excitation generator-motor according to the present invention provides a first power conversion that exchanges power with an AC power system to which a primary winding of the generator-motor is connected, and performs AC / DC conversion. A DC capacitor connected in parallel to the DC terminal of the first power converter, a DC terminal connected to both ends of the DC capacitor, an AC terminal connected to the secondary winding of the generator motor, A second power converter that performs AC / DC conversion to excite the generator motor, a first control circuit that supplies a gate pulse to a switching element of the first power converter, and a second power converter A second control circuit for supplying a gate pulse to the switching element, wherein the first control circuit enables the first power converter so that the voltage across the DC capacitor matches the command value. Adjust power Current control means for adjusting the AC terminal voltage of the second power converter so that the secondary current of the generator motor matches the command value. And second DC voltage control means for correcting the output of the current control means so as to suppress voltage fluctuation across the DC capacitor according to the fluctuation component of the secondary current.

  ADVANTAGE OF THE INVENTION According to this invention, even if the voltage fluctuation of a DC circuit generate | occur | produces by the accident of an alternating current power system etc., it can provide the control apparatus of the alternating current excitation generator motor which can suppress it and can continue driving | operation. Become.

  Embodiments of the present invention will be described below with reference to the drawings.

  A control apparatus for an AC excitation generator-motor according to a first embodiment of the present invention will be described below with reference to FIGS. FIG. 1 is a block diagram of a control device for an AC excitation generator-motor according to Embodiment 1 of the present invention.

  A primary winding of a generator motor 2 is connected to the AC power system 1, and the generator motor 2 is configured to operate as both a generator and a motor. The AC power system 1 is connected to the AC terminal of the first power converter 4 via the transformer 3. The DC terminal of the first power converter 4 is connected to the DC terminal of the second power converter 5 via a DC circuit, and the AC terminal of the second power converter 5 is the secondary winding of the generator motor 2. Is connected to. A smoothing DC capacitor 6 is connected in parallel to the DC circuit.

  The first power converter 4 and the second power converter 5 are configured by bridge-connecting switching elements such as IGBTs (Insulated Gate Bipolar Transistors), for example, and each of these switching elements is a first control circuit. 20 and the gate control pulse supplied from the second control circuit 30 is ON / OFF controlled.

  The current on the AC side of the first power converter 4 is detected by the current detector 7 and given to the first control circuit 20. Similarly, the current on the AC side of the second power converter 5, that is, the secondary current of the generator motor 2 is detected by the current detector 8 and is supplied to the second control circuit 30. Further, the voltage applied to the smoothing capacitor 6, that is, the DC voltage Vdc of the DC circuit is detected by the voltage detector 9 and supplied to the first control circuit 20 and the second control circuit 30.

  The voltage phase of the AC power system 1 is detected by the phase detector 10 and supplied to the first control circuit 20 and the second control circuit 30. Further, the secondary voltage of the generator motor 2 is detected by the rotor phase detector 11 and given to the second control circuit 30.

  Hereinafter, the internal configurations of the first control circuit 20 and the second control circuit 30 will be described.

  The alternating current of the first power converter 4 detected by the current detector 7 and the voltage phase θ1 detected by the phase detector 10 are input to the coordinate converter 201. The coordinate converter 201 separates the alternating current of the first power converter 4 into an effective current component Icq and a reactive current component Icd based on the voltage phase θ1, and a current controller configured from these current components is a current controller. 202. The current controller 202 outputs a voltage command Vcref to be output by the first power converter 4 so that the current command value Icref and the current Ic coincide with each other, and supplies the voltage command Vcref to the pulse width modulator 203. Then, the pulse width modulator 203 performs on / off control of the switching element of the first power converter 4 according to the voltage command Vcref.

  On the other hand, the voltage controller 204 controls the effective current component Icq of the current command value Icref so that the DC voltage command Vdcref and the DC voltage Vdc detected by the voltage detector 9 match. For example, if the coordinate converter 201 is converted so that the effective current component Icq is positive when power flows from the AC power system 1 to the first power converter 4, the DC voltage Vdc rises. The effective current component Icq is decreased, and when the DC voltage Vdc decreases, the effective current component Icq is increased. As a result, the DC voltage Vdc of the DC circuit is controlled to coincide with the DC voltage command Vdcref. Further, by setting the command value of the reactive current component Icd to zero, the power factor on the AC power system 1 side of the transformer 3 can be controlled to be approximately 1.

  On the other hand, the current detected by the current detector 8 is given to the coordinate converter 301 and related to the reactive current component Iid related to the exciting current of the generator motor 2 and the reactive current of the primary current and the effective current of the primary current. Is separated into effective current component Iiq. The current detected by the current detector 8 is converted by the coordinate converter 301 into a current Ii including the effective current component Iiq and the reactive current component Iid with the phase θ2 as a reference. Here, the phase θ2 is obtained by subtracting the rotor phase θr detected by the rotor phase detector 11 from the phase θ1 by the subtractor 304.

  The current controller 302 adjusts the voltage command Viref of the second power converter 5 via a subtractor 306 described later so that the current command value Iiref and the current Ii match. Then, the pulse width modulator 303 performs on / off control of the switching element of the second power converter 5 according to the voltage command Viref. Here, the frequency of the secondary current of the generator motor 2 is the rate of change of the phase θ2, and is the difference frequency ω2 between the frequency ω1 of the AC power system 1 and the rotor speed ωr of the generator motor 2.

  The second control circuit 30 has a voltage controller 305 configured to input a DC voltage command Vdcref, a DC voltage Vdc, and a current Ii and correct the output of the current controller 302 by a subtractor 306. .

  FIG. 2 is a block configuration diagram for explaining the internal configuration of the voltage controller 305. After the deviation between the DC voltage command Vdcref and the DC voltage Vdc is calculated by the subtractor 305a, the deviation is amplified by the compensator 305b, and the current Ii is multiplied by the signal cut off by the filter 305c by the multiplier 305d. The output of the multiplier 305d is subtracted by a subtractor 306 so as to correct the output of the voltage controller 305 to obtain a voltage command Viref.

  Next, the operation will be described. When the AC power system 1 is in a normal state, the frequency of the secondary winding of the generator motor 2 is the difference frequency ω2 between the frequency ω1 of the AC power system 1 and the rotor speed ωr of the generator motor 2. In the coordinate converter 301, the output current of the second power converter 5 which is the secondary current of the frequency ω2 is subjected to rotational coordinate conversion with the phase θ2 related to the frequency ω2 as a reference, so that the frequency ω2 component is converted into a direct current amount. Current Ii is obtained. The current controller 302 operates so that the current command value Iiref, which is a command value corresponding to the frequency ω2, matches the current Ii. The current Ii includes two signals, an active current component Iiq and a reactive current component Iid. In this way, by separating the secondary current of the generator motor 2 into the active current component Iiq and the reactive current component Iid and controlling them independently, the generator motor 2 outputs the active current component Iiq to the AC power system 1. The reactive current component Iid is proportional to the effective current, and is proportional to the reactive current output from the generator motor 2 to the AC power system 1 and the exciting current of the generator motor 2. The effective current component Iiq and the reactive current component Iid are controlled to be constant according to the difference frequency ω2 even if the rotational speed of the generator motor 2 and the frequency of the AC power system 1 change. Therefore, it is possible to adjust the power transfer with the AC power system 1 while operating the generator motor 2 at a variable speed.

  When an accident occurs in the AC power system 1, a DC component and a negative phase component are superimposed on the primary current of the generator motor 2 along with the fluctuation of the positive phase current. This superimposed current also flows into the secondary winding of the generator motor 2 and flows to the DC circuit via the second power converter 5 to change the DC voltage Vdc. For the fluctuation component superimposed on the secondary winding, the direct current component of the primary winding is the frequency component of the rotor speed ωr, and the reverse phase component is the frequency component of the sum of the rotor speed ωr and the frequency ω1.

  FIG. 3 is a diagram schematically showing the AC power system voltage, the secondary current of the generator motor 2, the reactive current component Iid, and the active current component Iiq when an accident occurs in the AC power system 1. Assuming that an accident occurs at this time T1, the AC power system voltage drops immediately after that, as shown in the figure, fluctuations are superimposed on the secondary current, and the reactive current component Iid and the active current component Iiq are added to the DC component. AC component is superimposed. When the accident is removed at time T2, the normal state is restored.

  Since the first power converter 4 is connected to the AC power system 1 via the transformer 3, when an accident occurs in the AC power system 1 and the voltage thereof decreases, the power that can be transmitted and received is reduced to the voltage decrease level. Limited accordingly. The power that can be exchanged is the product of the input voltage of the first power converter 4 and the current of the first power converter 4, but the current that can flow depends on the facility capacity of the first power converter 4. Therefore, the power that can be transferred is limited. For this reason, the case where the electric power required for suppressing the fluctuation | variation of DC voltage Vdc by the fluctuation | variation electric current which flows in from the 2nd power converter 5 cannot be supplied from the 1st power converter 4 is assumed.

  In the voltage controller 305, when the DC voltage Vdc fluctuates, a deviation occurs from the DC voltage command Vdcref, and a signal obtained by amplifying the deviation is output to the compensator 305b. The DC component is removed from the current Ii by the low-frequency cutoff filter 305c, and only the fluctuation component is extracted. By multiplying the extracted fluctuation current by the output of the compensator 305b, an output correction signal of the voltage controller 305 is obtained. This correction signal is in phase with or out of phase with the fluctuation of the current, and the output of the compensator 305b. Is equivalent to the active component for the variable component. For example, when the deviation is positive, it means that the DC voltage Vdc is decreasing. Therefore, when the output current is positive, a voltage having a phase opposite to that of the current is output, so that the DC capacitor 6 is charged. Act on. Therefore, in FIG. 1, the output of the voltage controller 305 is subtracted by the subtractor 306, so that an antiphase voltage command is given to the pulse width modulator 303.

  As described above, in the first embodiment of the present invention, even if the charging / discharging of the DC capacitor 6 by the first power converter 4 is restricted when an accident occurs in the AC power system 1, the second power Since charging / discharging can be performed using the fluctuating current flowing into the converter 5, it is possible to prevent overvoltage and undervoltage of the DC circuit and to continue operation without stopping the system.

  FIG. 4 is a circuit configuration diagram of a control device for an AC excitation generator-motor according to Embodiment 2 of the present invention. In the second embodiment, the same parts as those in the circuit configuration diagram of the control device for the AC excitation generator-motor according to the first embodiment shown in FIG. The second embodiment is different from the first embodiment in that a filter 307 is provided on the output side of the coordinate converter 301, and the current Ii related to the second power converter 5 is given to the current controller 302 via the filter 307. This is the configuration.

  Next, the operation will be described. When an accident occurs in the AC power system 1, a fluctuation component is superimposed on the secondary winding current of the generator motor 2 as shown in the schematic diagram of FIG. In addition to the DC component, an AC component is superimposed on the reactive current component Iid and the effective current component Iiq. The filter 307 is composed of a low-pass filter, and removes the AC component and inputs the reactive current component Iid and the effective current component Iiq to the current controller 302. Current control by the current controller 302 has a transient characteristic in which the current Ii follows the change in the current command value Iiref with a delay and compensates for the change in the current Ii with a delay. For this reason, when the voltage command Viref is corrected in response to the AC fluctuation component superimposed on the current Ii, the fluctuation may not be suppressed. In addition, the generator motor 2 mainly passes a current to the inductance component. However, when the fluctuation component is suppressed, the voltage required for the suppression increases as the frequency increases, and the voltage of the second power converter 5 increases. May be saturated and the follow-up characteristic of the current command value Iiref may be deteriorated.

  On the other hand, according to the invention of the second embodiment, by removing the fluctuation component by the filter 307, there is an effect of improving the follow-up characteristic with respect to the current command value Iiref. Thereby, the current controller 302 operates so as to follow the current command value Iiref which is mainly a DC component, and the voltage controller 305 operates so as to control the DC voltage Vdc of the DC circuit 6 using the current fluctuation component. Therefore, there is an effect that interference between the current controller 302 and the voltage controller 305 can be suppressed.

  FIG. 5 is a block diagram of a voltage controller used in the controller for an AC excitation generator-motor according to the third embodiment of the present invention. About each part of this Example 3, the same part as each part of the block block diagram of the voltage controller used for the control apparatus of the alternating current excitation generator-motor according to Example 1 of FIG. The third embodiment is different from the first embodiment in that a dead band 305e is provided on the output side of the subtractor 305a and a voltage deviation signal is provided to the compensator 305b via the dead band 305e.

  Next, the operation will be described. In the dead zone 305e, zero is output when the deviation of the DC voltage Vdc from the DC voltage command Vdcref is within the dead zone, and a signal corresponding to the input is output when the dead zone is exceeded. When the AC power system 1 is healthy, the DC voltage Vdc of the DC circuit is controlled by the first power converter 4 and the first control circuit 20. At this time, the voltage control operation by the voltage controller 305 is unnecessary, and the second control circuit 30 desirably performs only the operation of controlling the secondary current.

  Therefore, by adopting the above configuration, the voltage controller 204 operates during normal operation without interference between the two voltage controllers 204 and 305, and the voltage controller 305 also operates when the AC power system 1 has an accident. It becomes possible to operate and control the DC voltage Vdc.

  As described above, according to the third embodiment of the present invention, it is possible to obtain a stable control device for an AC excitation generator-motor that can prevent interference between two voltage controllers.

  FIG. 6 is a block diagram of a voltage controller used in the controller for an AC excitation generator-motor according to Embodiment 4 of the present invention. The same parts as those in the block configuration diagram of the voltage controller used in the control device for the AC excitation generator-motor according to the first embodiment shown in FIG. 2 are denoted by the same reference numerals and the description thereof will be omitted. The fourth embodiment is different from the first embodiment in that a BP filter 305f that is a bandpass filter is used instead of the filter 305e.

  When an accident occurs in the AC power system 1, the fluctuation current flowing in the secondary winding of the generator motor 2 is such that the DC component of the primary winding is the rotor speed ωr component, and the reverse phase component of the primary winding is the rotor. This is a sum component of the speed ωr and the frequency ω1 of the AC power system 1. Therefore, if the BP filter 305 is composed of bandpass filters whose center frequencies are in the vicinity of the rotor speed ωr and in the vicinity of ωr + ω1, only the fluctuation component can be extracted. In this case, since other frequency components are removed, there is an effect that the influence of noise included in the current Ii can be removed. Note that the vicinity in the above is usually within a range of plus or minus 5%, although it depends on the frequency characteristics of the bandpass filter.

  In particular, in applications where the rotor speed ωr is operated near the frequency ω1 of the AC power system 1, the center frequency may be set in the vicinity of the frequency ω1 of the AC power system 1 and in the vicinity of twice the frequency ω1.

The block block diagram of the control apparatus of the alternating current excitation generator motor which concerns on Example 1 of this invention. The block block diagram of the voltage controller in Example 1 of this invention. The schematic diagram of each part waveform for demonstrating operation | movement of this invention. The block block diagram of the control apparatus of the alternating current excitation generator motor which concerns on Example 2 of this invention. The block block diagram of the voltage controller in Example 3 of this invention. The block block diagram of the voltage controller in Example 4 of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 AC power system 2 Generator motor 3 Transformer 4 1st power converter 5 2nd power converter 6 DC capacitor 7 Current detector 8 Current detector 9 Voltage detector 10 Phase detector 11 Rotor phase detector

20 First control circuit 30 Second control circuit

201 Coordinate converter 202 Current controller 203 PWM controller 204 Voltage controller

301 Coordinate converter 302 Current controller 303 PWM controller 304 Subtractor 305 Voltage controller 305a Subtractor 305b Compensator 305c Filter 305d Multiplier 305e Dead band 305f BP filter 306 Subtractor 307 Filter

Claims (8)

A first power converter that exchanges power with an AC power system to which a primary winding of a generator motor is connected;
A DC capacitor connected in parallel to a DC terminal of the first power converter;
A DC terminal connected to both ends of the DC capacitor, an AC terminal connected to a secondary winding of the generator motor, and a second power converter that excites the generator motor by performing AC / DC conversion;
A first control circuit for supplying a gate pulse to the switching element of the first power converter;
A second control circuit for supplying a gate pulse to the switching element of the second power converter,
The first control circuit includes:
First DC voltage control means for adjusting the effective power of the first power converter so that the voltage across the DC capacitor matches a command value;
The second control circuit includes:
Current control means for adjusting an AC terminal voltage of the second power converter so that a secondary current of the generator motor matches a command value;
AC excitation power generation characterized by comprising second DC voltage control means for correcting the output of the current control means so as to suppress voltage fluctuation across the DC capacitor in accordance with the fluctuation component of the secondary current. Electric motor control device. The second control circuit includes:
Coordinate conversion means for decomposing the secondary current of the generator motor into an active component and an ineffective component;
The current control means includes
2. The AC excitation generator motor according to claim 1, wherein an AC terminal voltage of the second power converter is adjusted so that the effective component and the ineffective component coincide with respective command values. 3. Control device.   A filter for removing current fluctuation components is provided at the output of the effective component and the ineffective component, and the AC terminal voltage of the second power converter is adjusted so that the respective outputs of the filter coincide with the respective command values. The control apparatus for an AC excitation generator-motor according to claim 2, wherein the control apparatus is configured as described above. The second DC voltage control means includes:
Compensation means for amplifying the deviation between the voltage across the DC capacitor and its command value;
Multiplying means for multiplying the output of the compensating means and the fluctuation component of the secondary current,
The control apparatus for an AC excitation generator-motor according to any one of claims 1 to 3, wherein the output of the current control means is corrected in accordance with the output of the previous multiplication means. The compensation means includes
5. The control apparatus for an AC excitation generator motor according to claim 4, further comprising a dead zone that does not respond when a deviation between a voltage at both ends of the DC capacitor and a command value thereof is a predetermined value or less.   The control device for an AC excitation generator-motor according to claim 4 or 5, wherein the fluctuation component of the secondary current is extracted by a low-frequency elimination filter.   6. The control apparatus for an AC excitation generator motor according to claim 4, wherein the fluctuation component of the secondary current is extracted by a band pass filter.   8. The control device for an AC excitation generator motor according to claim 7, wherein a center frequency of the bandpass filter is set in the vicinity of a main frequency component of the fluctuation component.

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