CA2022375C - Ac-excited rotary electric machine system - Google Patents
Ac-excited rotary electric machine systemInfo
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- CA2022375C CA2022375C CA 2022375 CA2022375A CA2022375C CA 2022375 C CA2022375 C CA 2022375C CA 2022375 CA2022375 CA 2022375 CA 2022375 A CA2022375 A CA 2022375A CA 2022375 C CA2022375 C CA 2022375C
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- 238000004804 winding Methods 0.000 claims abstract description 26
- 238000001514 detection method Methods 0.000 claims abstract description 6
- 230000005284 excitation Effects 0.000 claims description 16
- 230000008859 change Effects 0.000 claims description 5
- 230000004044 response Effects 0.000 abstract description 3
- 230000001360 synchronised effect Effects 0.000 description 13
- 238000010586 diagram Methods 0.000 description 9
- 230000001105 regulatory effect Effects 0.000 description 4
- 230000004907 flux Effects 0.000 description 3
- 230000014509 gene expression Effects 0.000 description 3
- 238000013459 approach Methods 0.000 description 2
- 230000003247 decreasing effect Effects 0.000 description 2
- 238000010304 firing Methods 0.000 description 2
- 238000000034 method Methods 0.000 description 2
- 230000003111 delayed effect Effects 0.000 description 1
- 230000008034 disappearance Effects 0.000 description 1
- 230000002708 enhancing effect Effects 0.000 description 1
- 230000006698 induction Effects 0.000 description 1
- 239000003607 modifier Substances 0.000 description 1
- 230000008569 process Effects 0.000 description 1
- 230000010349 pulsation Effects 0.000 description 1
- 230000002441 reversible effect Effects 0.000 description 1
- 239000004065 semiconductor Substances 0.000 description 1
- 230000007704 transition Effects 0.000 description 1
- 230000001960 triggered effect Effects 0.000 description 1
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Abstract
An AC-excited rotary electric machine system includes an AC-excited rotary machine having a primary winding connected to an AC power line and a secondary winding connected to a frequency converter. A primary current detector detects a current flowing through a primary winding of an AC-excited rotary machine. In response to a detection value detected by the primary current detector, a secondary current controller changes the range of a command value for the current flowing through the secondary winding of the AC-excited rotary machine to a predetermined range.
Description
2~223~
Field of the Invention The present invention relates generally to a speed-variable AC-excited rotary electric machine set or system which includes a synchronous machine operated by AC excitation. More particularly, the present invention is concerned with an AC-excited rotary electric machine system which is advantageously suited for a load regulator and a rotary phase modifier for enhancing the stability of an AC power system.
With progress in the technical field of semi-conductor power converters, there is employed increasingly and extensively in practical applications the AC-excited rotary electric machine system which includes a synchro-nous machine capable of operating under AC excitationat a speed made variable through a frequency converter unit.
By way of example, there is disclosed in JP-A-Hl-231698 (Japanese Patent Application Laid-Open No.
231698/1989) an AC-excited rotary electric machine system of such a structure in which a function for regulating rapidly active (effective) and reactive powers i.e. the function characteristic of the AC excitation system, is implemented together with a self-excited operation capability as in the case of a DC-excited synchronous 1 machine, which capability or function is realized by suppressing an excitation frequency to a value lower than a preset one, when the rotary electric machine system is disconnected from the AC power line.
BRIEF DESCRIPTION OF THE DRAWINGS
In the course of the following description, reference is made to the accompanying drawings, in which:
Fig. 1 is a block diagram showing a structure of the AC-excited rotary electric machine system according to an exemplary embodiment of the present invention;
Fig. 2 is a block diagram showing another embodiment of the invention;
Fig. 3 is a block diagram showing a structure of an AC-excited rotary electric machine system known heretofore; and Figs. 4, 5, 6 and 7 show an equivalent circuit diagram and vector diagrams helpful for explaining the operation of the AC-excited rotary electric machine known heretofore.
Description of the Prior Art Fig. 3 shows a circuit structure of a pumping-up power plant to which an AC-excited rotary electric machine system known heretofore is applied. Referring to the figure, there is connected to an AC power line 1 through a system disconnecting breaker 2a is a main transformer 3 having a low-voltage side to which a primary winding 5a of an AC-excited synchronous machine 5 is connected through a synchronously closing breaker 2b, wherein the AC-excited synchronous machine 5 has a winding structure similarto that of a wound-rotor induction machine and is directly connected to a reversible pump turbine 4.
On the other hand, a frequency converter unit 6 includes a plurality of thyristor power converters 8 for converting an AC power supplied from the AC power line 1 and stepped down through an excitation transformer 7 to a low-frequency AC power, wherein the thyristor converters 8 are each provided for each phase of an exciting current winding 5b.
A slip phase detector 9 for deriving an AC
excitation frequency signal comprises a voltage transformer 10 for detecting a system voltage phase v~ a voltage phase arithmetric unit 11, a resolver unit 12 for detecting a rotation phase ~r of the AC-excited synchronous machine 5 given in terms of the electrical angle, and a slip phase arithmetric unit 13.
The voltage phase arithmetric unit 11 outputs two phase signals represented by cos v and sin ~v~ respectively.
The resolver unit 12 outputs two phase signals represented by cos r and sin r' respectively. The slip phase arithmetric unit 13 outputs two phase signals given by cos 05 and sin 05 respectively.
1 An excitation current command arithmetic unit 14 serves to regulate amplitudes and phases of three phase AC current rotating with the slip phase 6s with the aid of current commands I2 and Id of two axes which intersect orthogonally with each other.
Three phase current command values IUref, IVref and IWref are given by the following expressions:
uref Iq cos ~s + Id sin ~
vref q ( s 3 ) d sin (~s 3 ~) I f = Iq cos (~s + 3 ~) + d s 3 Current controllers 15 output thyristor firing angle signals to automatic pulse phase shifters 16 such that the secondary winding currents of the AC-excited synchronous machine 5 coincide with the current command values mentioned above, while the automatic pulse phase shifters 16 output firing pulse signals 17 for the respective thyristor power converters 8.
The current command signal regulated by the excitation current command arithmetic unit 14 can be obtained by methods disclosed, for example, in JP-B-53-7628 (Japanese Patent Publication No. 7628/1978) and JP-B-57-60645, respectively. More specifically, by regulating a current component Iq of a same phase as the slip phase ~s' the active for effective power output is controlled, 1 while the voltage is controlled by regulating a current component Id having a phase delayed by 90 relative to the slip phase ~s Signals representative of the effective power and voltage outputs to the AC power system 1 are extracted through an instrument current transformer 18 and an instrument voltage transformer 10, wherein the derived signals are converted to DC signals by a sensor unit (P/V sensor) 19 to be inputted to an automatic active power regulator (APR) 20 and an automatic voltage regulator (AVR) 21 for the control purpose.
The upper and lower limit values of the output current Iq from the automatic active (effective) power regulator 20 are so constrained as to fall within a preset value range by a limiter 22. Similarly, the output current Id from the automatic voltage regulator 21 is limited in respect to the upper and lower limit values so as to lie within a preset range by means of a limiter 23. In this conjunction, it will be appreciated that the limiters 22 and 23 are so designed that the respective current command values do not exceed the current withstanding capability of the thyristor power converters 8.
The prior art AC-excited rotary electric machine system described above suffers from a problem that since the lower limit value of the vertical-axis current command has to be set to a value greater than zero (a positive finite value), the reactive power ~22~75 1 output range can not be widened for weak excitation because the rotary machine voltage is controlled continuously, even when the AC-excited rotary electric machine system is disconnected from the AC power system in the course of operation.
The above-mentioned problem will be discussed in more detail. Fig. 4(a) shows an equivalent circuit diagram of the AC-excited synchronous machine 5, and Fig. 4(b) is a vector diagram for the synchronous machine operating when the vertical-axis current (Id) command is set at a predetermined negative value. In the vector diagram shown in Fig. 4(b), the vertical-axis current Id is oriented in the negative direction with the secondary current I2 being of the positive direction.
Now assuming that the AC-excited rotary electric machine system is disconnected from the AC
power line in the state mentioned above, it becomes necessary to increase the secondary current since other-wise a terminal voltage Vl of the rotary machine drops to E. To this end, the current command value must be modified so that the value of the secondary current changes from the value I2 at this time point to a predetermined value I2', as shown in Fig. 5.
In this conjunction, it is noted that the automatic voltage regualtor (AVR) 21 causes the vertical-axis current command to change from the negative value to a positive value in the course of lowering of the 20~2375 1 terminal voltage. This process represents a positive - feedback operation or state.
Upon occurrence of the positive feedback state in this manner, the voltage makes disappearance, making impossible shifting to the self-excited operation.
For this reason, the lower limit value of the vertical-axis current Id is not allowed to be set at a negative value in the case of the prior art system.
Fig. 6 is a vector diagram illustrating opera-tion of the synchronous machine in the state in whichthe vertical-axis current command is of the positive direction. As will be seen in the figure, the secondary current I2 is oriented downwardly while the vertical-axis current Id assumes a predetermined positive value.
Assuming that the AC-excited rotary electric machine system is disconnected in the state mentioned above, the secondary current has to be decreased, since otherwise the terminal voltage of the rotary electric machine rises from Vl to E.
However, at that time, the horizontal-axis current (Iq) changes from a predetermined value Iq to a value Iql, being brought about by the disconnection from the AC power line, as shown in Fig. 7. The change of the horizontal-axis current Iq to the positive direction can be explained as follows.
When the horizontal-axis current Iq is gene-rated in response to the output command from a rotating 1 speed controllerr the rotating speed tends to increase upon disconnection of the rotary electric machine system from the AC power line to thereby cause the output of the rotary machine system to increase. As a result of this, a speed-reduction control operation is triggered, whereby the horizontal-axis current is caused to change to the positive direction.
On the other hand, when the horizontal-axis current Iq is generated in response to the output command from an active (effective) power control unit, the active (effective) power output becomes zero simul-taneously with disconnection of the rotary electric machine system from the AC power line. At this time, the rotating speed controller so operates as to hold the output of the rotary electric machine system at the command value. As a consequence, the horizontal-axis current changes to the positive direction.
As will be appreciated from the above discus-sion, the secondary current increases regardless of whether the horizontal-axis current originates in the output command from the rotating speed controller or the output command from the active (effective) current controller, as the result of which the terminal voltages becomes too high to shift to the self-excited operation, whereby the reactive power output range is narrowed.
SUMMARY OF THE INVENTION
It is an object of the present invention to 2~2237~
1 provide an AC-excited rotary electric machine in which the range of reactive power output is made available sufficiently widely for allowing the shift to the self-excited operation when the AC-excited rotary S electric machine system is disconnected from an AC
power line.
For achieving the above object, there is proposed according to an aspect of the invention such arrangement in which when gap flux is supplied from an armature of an AC-excited synchronous machine, upper and lower limit values of a vertical-axis component of the secondary current are decreased by predetermined values, respectively, while when the gap flux is supplied from the field system the upper and lower limit values of the vertical-axis component are increased by predetermined values, respectively.
Further, according to the invention, it is taught that upper and lower limit values or a horizontal-axis current are forced to approach zero by predetermined values, respectively, when the AC-excited rotary electric machine system is disconnected from the AC power line.
In operation, a vertical-axis current limiter functions to widen an underexcitation operation range by setting the lower limit of the vertical-axis current at a negative value when the gap flux is generated from the armature. When the rotary electric machine system is disconnected from the AC power line, the lower limit value changes to a positive value from the negative 2~22375 1 as the vertical component Idl of the armature current changes from a positive value toward zero, as a result of which the lower limit of the vertical-axis current (Id) command assumes a positive value to thereby protect the automatic voltage regulator (AVR) from erroneous operation.
Upon occurrence of load shut-down, a horizontal-axis current limiter operates to set the upper and lower limit values of the horizontal-axis current close to zero, as the armature current approaches zero. In this manner, the control of the horizontal-axis current Iq is protected from erroneous operation.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
The present invention will now be described in detail in conjunction with a first preferred on exemplary embodiment thereof by reference to Fig. 1 in which same reference symbols as those used in Fig. 3 denote same or like parts shown in the latter. Accord-ingly, repeated description thereof will be unnecessary.
A primary current vector arithmetic unit 24 performs arithmetic operation on the primary current signals IUl, IVl and IWl supplied from a current trans-former 25 and the voltage phase signals cos ~v and sin ~v supplied from the voltage phase arithmetic unit 11 in accordance with the expression mentioned below to thereby output a d-axis current component Idl and a peak value Ilp of the primary current.
2~22~5 dl = - [IUl sin Gv + Ivl sin (~v 3 + Iwl sin (~v + 3 ~) , and lp J Idl + I 12 where I 1 = - [IUl cos av + IVl cos (~v 3 wl cos (~v 3 ~)]
1 When the primary current peak value Ilp from the primary current vector arithmetic unit 24 increases beyond a preset value Ilpo, the q-axis command limiter 26 outputs a limit value Iq2 of a range delimited by the upper and lower limits as follows:
qmaxl - q2 - qmaxl On the other hand, when the primary current peak value Ilp becomes smaller than the set value Ilpo, the q-axis command limiter 26 decides that the AC-excited rotary electric machine system is disconnected from the AC
power line and changes the range of the limit value Iq2 as follows:
qmax2 - q2 - qmax2 1 The relation between the maximum q-axis current I
and Iqmax2 is established as follows:
I 2 ~ I 1 Consequently, the limit value Iq2 is suppressed to a value close to zero when the primary current peak value Ilp becomes smaller than the set value Ilpo.
The d-axis command limiter 27 receives from the primary current vector arithmetic unit 24 a signal indicating the d-axis component Idl of the primary current and sets the limit value Id2 to be variable between the upper and lower limits, as follows.
dmin dl - d2 - dmax dl In other words, the limit value Id2 is variable within the range delimited by the upper and lower limits given by the above expression in which Idmin and IdmaX represent preset constants, respectively. The d-axis component Idl of the primary current increases more in the negative direction as the excitation of the AC-excited synchronous machine is strengthened. As a result of this, the upper and lower limits or range of the limit value Id2 is shifted in the positive direction as the excitation of the synchronous machine 5 is strengthened.
2~2~375 1 Thus, according to the first embodiment of the present invention, the primary current vector arithmetic unit 24 operates without exerting any influence to the secondary current control in the ordinary operation.
In general, the primary current vector arithmetic unit of the type mentioned above converts once the frequency signal of the AC power line to a DC
current. Thus, the primary current vector arithmetic unit is more susceptible or sensitive to noise and external dis-turbance than the excitation current command arithmetic unit which is designed to deal with the slip frequency.
However, according to the instant embodiment of the invention, the primary current vector arithmetic unit 24 can operate without exerting influence to the secondary current control in the normal operation, whereby there can be obtained an active (effective) power output and a reactive power output with less pulsation.
Fig. 2 shows a second embodiment of the invention. Referring to the figure, a current-to-voltage converter 28 converts a current signal of the AC power line detected by the current transformer 18 to a voltage which is rectified by a diode bridge circuit 29 to obtain a peak value IQp of the AC line current, the peak value being applied to a q-axis current limiter 30.
The q-axis current limiter 30 is implemented in a structure similar to that of the q-axis command limiter 26 described hereinbefore by reference to Fig. 1 1 and changes the upper and lower limits of the limit value to a predetermined range when the limit value to a predetermined range when the limit value becomes smaller than the set value IQpo, indicating disconnection of the rotary electric machine system from the AC power line.
Since the detection is performed after the current value of the AC power line becomes zero in suc-cession to the disconnection in the case of the second embodiment, the disconnection from the AC line can be detected with a higher reliability than the case where the detection is made on the basis of an armature current which still contains the residual self-excitation current component.
According to the teachings of the invention that the primary current of the AC-excited rotary electric machine system is detected for changing or altering the upper and lower limits of the secondary current value, the reactive power output range can be sufficiently widened, whereby the shifting or transition to the self-excitation operation can be achieved stably and reliably upon disconnection of the rotary electric machine system from the AC power line.
Field of the Invention The present invention relates generally to a speed-variable AC-excited rotary electric machine set or system which includes a synchronous machine operated by AC excitation. More particularly, the present invention is concerned with an AC-excited rotary electric machine system which is advantageously suited for a load regulator and a rotary phase modifier for enhancing the stability of an AC power system.
With progress in the technical field of semi-conductor power converters, there is employed increasingly and extensively in practical applications the AC-excited rotary electric machine system which includes a synchro-nous machine capable of operating under AC excitationat a speed made variable through a frequency converter unit.
By way of example, there is disclosed in JP-A-Hl-231698 (Japanese Patent Application Laid-Open No.
231698/1989) an AC-excited rotary electric machine system of such a structure in which a function for regulating rapidly active (effective) and reactive powers i.e. the function characteristic of the AC excitation system, is implemented together with a self-excited operation capability as in the case of a DC-excited synchronous 1 machine, which capability or function is realized by suppressing an excitation frequency to a value lower than a preset one, when the rotary electric machine system is disconnected from the AC power line.
BRIEF DESCRIPTION OF THE DRAWINGS
In the course of the following description, reference is made to the accompanying drawings, in which:
Fig. 1 is a block diagram showing a structure of the AC-excited rotary electric machine system according to an exemplary embodiment of the present invention;
Fig. 2 is a block diagram showing another embodiment of the invention;
Fig. 3 is a block diagram showing a structure of an AC-excited rotary electric machine system known heretofore; and Figs. 4, 5, 6 and 7 show an equivalent circuit diagram and vector diagrams helpful for explaining the operation of the AC-excited rotary electric machine known heretofore.
Description of the Prior Art Fig. 3 shows a circuit structure of a pumping-up power plant to which an AC-excited rotary electric machine system known heretofore is applied. Referring to the figure, there is connected to an AC power line 1 through a system disconnecting breaker 2a is a main transformer 3 having a low-voltage side to which a primary winding 5a of an AC-excited synchronous machine 5 is connected through a synchronously closing breaker 2b, wherein the AC-excited synchronous machine 5 has a winding structure similarto that of a wound-rotor induction machine and is directly connected to a reversible pump turbine 4.
On the other hand, a frequency converter unit 6 includes a plurality of thyristor power converters 8 for converting an AC power supplied from the AC power line 1 and stepped down through an excitation transformer 7 to a low-frequency AC power, wherein the thyristor converters 8 are each provided for each phase of an exciting current winding 5b.
A slip phase detector 9 for deriving an AC
excitation frequency signal comprises a voltage transformer 10 for detecting a system voltage phase v~ a voltage phase arithmetric unit 11, a resolver unit 12 for detecting a rotation phase ~r of the AC-excited synchronous machine 5 given in terms of the electrical angle, and a slip phase arithmetric unit 13.
The voltage phase arithmetric unit 11 outputs two phase signals represented by cos v and sin ~v~ respectively.
The resolver unit 12 outputs two phase signals represented by cos r and sin r' respectively. The slip phase arithmetric unit 13 outputs two phase signals given by cos 05 and sin 05 respectively.
1 An excitation current command arithmetic unit 14 serves to regulate amplitudes and phases of three phase AC current rotating with the slip phase 6s with the aid of current commands I2 and Id of two axes which intersect orthogonally with each other.
Three phase current command values IUref, IVref and IWref are given by the following expressions:
uref Iq cos ~s + Id sin ~
vref q ( s 3 ) d sin (~s 3 ~) I f = Iq cos (~s + 3 ~) + d s 3 Current controllers 15 output thyristor firing angle signals to automatic pulse phase shifters 16 such that the secondary winding currents of the AC-excited synchronous machine 5 coincide with the current command values mentioned above, while the automatic pulse phase shifters 16 output firing pulse signals 17 for the respective thyristor power converters 8.
The current command signal regulated by the excitation current command arithmetic unit 14 can be obtained by methods disclosed, for example, in JP-B-53-7628 (Japanese Patent Publication No. 7628/1978) and JP-B-57-60645, respectively. More specifically, by regulating a current component Iq of a same phase as the slip phase ~s' the active for effective power output is controlled, 1 while the voltage is controlled by regulating a current component Id having a phase delayed by 90 relative to the slip phase ~s Signals representative of the effective power and voltage outputs to the AC power system 1 are extracted through an instrument current transformer 18 and an instrument voltage transformer 10, wherein the derived signals are converted to DC signals by a sensor unit (P/V sensor) 19 to be inputted to an automatic active power regulator (APR) 20 and an automatic voltage regulator (AVR) 21 for the control purpose.
The upper and lower limit values of the output current Iq from the automatic active (effective) power regulator 20 are so constrained as to fall within a preset value range by a limiter 22. Similarly, the output current Id from the automatic voltage regulator 21 is limited in respect to the upper and lower limit values so as to lie within a preset range by means of a limiter 23. In this conjunction, it will be appreciated that the limiters 22 and 23 are so designed that the respective current command values do not exceed the current withstanding capability of the thyristor power converters 8.
The prior art AC-excited rotary electric machine system described above suffers from a problem that since the lower limit value of the vertical-axis current command has to be set to a value greater than zero (a positive finite value), the reactive power ~22~75 1 output range can not be widened for weak excitation because the rotary machine voltage is controlled continuously, even when the AC-excited rotary electric machine system is disconnected from the AC power system in the course of operation.
The above-mentioned problem will be discussed in more detail. Fig. 4(a) shows an equivalent circuit diagram of the AC-excited synchronous machine 5, and Fig. 4(b) is a vector diagram for the synchronous machine operating when the vertical-axis current (Id) command is set at a predetermined negative value. In the vector diagram shown in Fig. 4(b), the vertical-axis current Id is oriented in the negative direction with the secondary current I2 being of the positive direction.
Now assuming that the AC-excited rotary electric machine system is disconnected from the AC
power line in the state mentioned above, it becomes necessary to increase the secondary current since other-wise a terminal voltage Vl of the rotary machine drops to E. To this end, the current command value must be modified so that the value of the secondary current changes from the value I2 at this time point to a predetermined value I2', as shown in Fig. 5.
In this conjunction, it is noted that the automatic voltage regualtor (AVR) 21 causes the vertical-axis current command to change from the negative value to a positive value in the course of lowering of the 20~2375 1 terminal voltage. This process represents a positive - feedback operation or state.
Upon occurrence of the positive feedback state in this manner, the voltage makes disappearance, making impossible shifting to the self-excited operation.
For this reason, the lower limit value of the vertical-axis current Id is not allowed to be set at a negative value in the case of the prior art system.
Fig. 6 is a vector diagram illustrating opera-tion of the synchronous machine in the state in whichthe vertical-axis current command is of the positive direction. As will be seen in the figure, the secondary current I2 is oriented downwardly while the vertical-axis current Id assumes a predetermined positive value.
Assuming that the AC-excited rotary electric machine system is disconnected in the state mentioned above, the secondary current has to be decreased, since otherwise the terminal voltage of the rotary electric machine rises from Vl to E.
However, at that time, the horizontal-axis current (Iq) changes from a predetermined value Iq to a value Iql, being brought about by the disconnection from the AC power line, as shown in Fig. 7. The change of the horizontal-axis current Iq to the positive direction can be explained as follows.
When the horizontal-axis current Iq is gene-rated in response to the output command from a rotating 1 speed controllerr the rotating speed tends to increase upon disconnection of the rotary electric machine system from the AC power line to thereby cause the output of the rotary machine system to increase. As a result of this, a speed-reduction control operation is triggered, whereby the horizontal-axis current is caused to change to the positive direction.
On the other hand, when the horizontal-axis current Iq is generated in response to the output command from an active (effective) power control unit, the active (effective) power output becomes zero simul-taneously with disconnection of the rotary electric machine system from the AC power line. At this time, the rotating speed controller so operates as to hold the output of the rotary electric machine system at the command value. As a consequence, the horizontal-axis current changes to the positive direction.
As will be appreciated from the above discus-sion, the secondary current increases regardless of whether the horizontal-axis current originates in the output command from the rotating speed controller or the output command from the active (effective) current controller, as the result of which the terminal voltages becomes too high to shift to the self-excited operation, whereby the reactive power output range is narrowed.
SUMMARY OF THE INVENTION
It is an object of the present invention to 2~2237~
1 provide an AC-excited rotary electric machine in which the range of reactive power output is made available sufficiently widely for allowing the shift to the self-excited operation when the AC-excited rotary S electric machine system is disconnected from an AC
power line.
For achieving the above object, there is proposed according to an aspect of the invention such arrangement in which when gap flux is supplied from an armature of an AC-excited synchronous machine, upper and lower limit values of a vertical-axis component of the secondary current are decreased by predetermined values, respectively, while when the gap flux is supplied from the field system the upper and lower limit values of the vertical-axis component are increased by predetermined values, respectively.
Further, according to the invention, it is taught that upper and lower limit values or a horizontal-axis current are forced to approach zero by predetermined values, respectively, when the AC-excited rotary electric machine system is disconnected from the AC power line.
In operation, a vertical-axis current limiter functions to widen an underexcitation operation range by setting the lower limit of the vertical-axis current at a negative value when the gap flux is generated from the armature. When the rotary electric machine system is disconnected from the AC power line, the lower limit value changes to a positive value from the negative 2~22375 1 as the vertical component Idl of the armature current changes from a positive value toward zero, as a result of which the lower limit of the vertical-axis current (Id) command assumes a positive value to thereby protect the automatic voltage regulator (AVR) from erroneous operation.
Upon occurrence of load shut-down, a horizontal-axis current limiter operates to set the upper and lower limit values of the horizontal-axis current close to zero, as the armature current approaches zero. In this manner, the control of the horizontal-axis current Iq is protected from erroneous operation.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
The present invention will now be described in detail in conjunction with a first preferred on exemplary embodiment thereof by reference to Fig. 1 in which same reference symbols as those used in Fig. 3 denote same or like parts shown in the latter. Accord-ingly, repeated description thereof will be unnecessary.
A primary current vector arithmetic unit 24 performs arithmetic operation on the primary current signals IUl, IVl and IWl supplied from a current trans-former 25 and the voltage phase signals cos ~v and sin ~v supplied from the voltage phase arithmetic unit 11 in accordance with the expression mentioned below to thereby output a d-axis current component Idl and a peak value Ilp of the primary current.
2~22~5 dl = - [IUl sin Gv + Ivl sin (~v 3 + Iwl sin (~v + 3 ~) , and lp J Idl + I 12 where I 1 = - [IUl cos av + IVl cos (~v 3 wl cos (~v 3 ~)]
1 When the primary current peak value Ilp from the primary current vector arithmetic unit 24 increases beyond a preset value Ilpo, the q-axis command limiter 26 outputs a limit value Iq2 of a range delimited by the upper and lower limits as follows:
qmaxl - q2 - qmaxl On the other hand, when the primary current peak value Ilp becomes smaller than the set value Ilpo, the q-axis command limiter 26 decides that the AC-excited rotary electric machine system is disconnected from the AC
power line and changes the range of the limit value Iq2 as follows:
qmax2 - q2 - qmax2 1 The relation between the maximum q-axis current I
and Iqmax2 is established as follows:
I 2 ~ I 1 Consequently, the limit value Iq2 is suppressed to a value close to zero when the primary current peak value Ilp becomes smaller than the set value Ilpo.
The d-axis command limiter 27 receives from the primary current vector arithmetic unit 24 a signal indicating the d-axis component Idl of the primary current and sets the limit value Id2 to be variable between the upper and lower limits, as follows.
dmin dl - d2 - dmax dl In other words, the limit value Id2 is variable within the range delimited by the upper and lower limits given by the above expression in which Idmin and IdmaX represent preset constants, respectively. The d-axis component Idl of the primary current increases more in the negative direction as the excitation of the AC-excited synchronous machine is strengthened. As a result of this, the upper and lower limits or range of the limit value Id2 is shifted in the positive direction as the excitation of the synchronous machine 5 is strengthened.
2~2~375 1 Thus, according to the first embodiment of the present invention, the primary current vector arithmetic unit 24 operates without exerting any influence to the secondary current control in the ordinary operation.
In general, the primary current vector arithmetic unit of the type mentioned above converts once the frequency signal of the AC power line to a DC
current. Thus, the primary current vector arithmetic unit is more susceptible or sensitive to noise and external dis-turbance than the excitation current command arithmetic unit which is designed to deal with the slip frequency.
However, according to the instant embodiment of the invention, the primary current vector arithmetic unit 24 can operate without exerting influence to the secondary current control in the normal operation, whereby there can be obtained an active (effective) power output and a reactive power output with less pulsation.
Fig. 2 shows a second embodiment of the invention. Referring to the figure, a current-to-voltage converter 28 converts a current signal of the AC power line detected by the current transformer 18 to a voltage which is rectified by a diode bridge circuit 29 to obtain a peak value IQp of the AC line current, the peak value being applied to a q-axis current limiter 30.
The q-axis current limiter 30 is implemented in a structure similar to that of the q-axis command limiter 26 described hereinbefore by reference to Fig. 1 1 and changes the upper and lower limits of the limit value to a predetermined range when the limit value to a predetermined range when the limit value becomes smaller than the set value IQpo, indicating disconnection of the rotary electric machine system from the AC power line.
Since the detection is performed after the current value of the AC power line becomes zero in suc-cession to the disconnection in the case of the second embodiment, the disconnection from the AC line can be detected with a higher reliability than the case where the detection is made on the basis of an armature current which still contains the residual self-excitation current component.
According to the teachings of the invention that the primary current of the AC-excited rotary electric machine system is detected for changing or altering the upper and lower limits of the secondary current value, the reactive power output range can be sufficiently widened, whereby the shifting or transition to the self-excitation operation can be achieved stably and reliably upon disconnection of the rotary electric machine system from the AC power line.
Claims (4)
1. An AC-excited rotary electric machine system, comprising:
an AC-excited rotary electric machine having a primary winding and a secondary winding in a winding structure, said primary winding being connected to an AC power line while said secondary winding is connected to said AC
power line through a frequency converter so that said AC-excited rotary electric machine can operate at a variable speed;
primary current detecting means for detecting a current flowing through the primary winding of said AC-excited rotary electric machine; and secondary current limit value control means for controlling a limit value for a secondary winding current command supplied to said frequency converter such that the limit value for said secondary winding current command is constrained to a predetermined value in accordance with the result of the detection by said primary current detecting means.
an AC-excited rotary electric machine having a primary winding and a secondary winding in a winding structure, said primary winding being connected to an AC power line while said secondary winding is connected to said AC
power line through a frequency converter so that said AC-excited rotary electric machine can operate at a variable speed;
primary current detecting means for detecting a current flowing through the primary winding of said AC-excited rotary electric machine; and secondary current limit value control means for controlling a limit value for a secondary winding current command supplied to said frequency converter such that the limit value for said secondary winding current command is constrained to a predetermined value in accordance with the result of the detection by said primary current detecting means.
2. An AC-excited rotary electric machine system according to claim 1, wherein said secondary winding current command value contains a vertical-axis current component and a horizontal-axis current component to be supplied to said frequency converter.
3. An AC-excited rotary electric machine system, comprising:
an AC-excited rotary electric machine having a primary winding connected to an AC power line and a secondary winding connected to a frequency converter;
primary current detecting means for detecting a current flowing through the primary winding of said AC-excited rotary electric machine; and secondary current control means responsive to a detection value detected by said primary current detecting means to thereby change the range of a command value for the current flowing through said secondary winding of said AC-excited rotary electric machine to a predetermined range.
an AC-excited rotary electric machine having a primary winding connected to an AC power line and a secondary winding connected to a frequency converter;
primary current detecting means for detecting a current flowing through the primary winding of said AC-excited rotary electric machine; and secondary current control means responsive to a detection value detected by said primary current detecting means to thereby change the range of a command value for the current flowing through said secondary winding of said AC-excited rotary electric machine to a predetermined range.
4. An AC-excited rotary electric machine system, comprising:
an AC-excited rotary electric machine having a primary winding supplied with an AC current from an AC power line and a secondary winding supplied with an AC excitation current;
a frequency converter for supplying said AC
excitation current to the secodnary winding of said AC-excited rotary electric machine;
excitation current command means for supplying to said frequency converter secondary current a command value indicating a value of said AC excitation current flowing through said secondary winding;
primary current detecting means for detecting a current flowing through the primary winding of said AC-excited rotary electric machine; and secondary current control means responsive to a detection signal of said primary current detecting means to change the range of said secondary current command value supplied to said frequency conveter from said excitation current command means to within a predetermined range.
an AC-excited rotary electric machine having a primary winding supplied with an AC current from an AC power line and a secondary winding supplied with an AC excitation current;
a frequency converter for supplying said AC
excitation current to the secodnary winding of said AC-excited rotary electric machine;
excitation current command means for supplying to said frequency converter secondary current a command value indicating a value of said AC excitation current flowing through said secondary winding;
primary current detecting means for detecting a current flowing through the primary winding of said AC-excited rotary electric machine; and secondary current control means responsive to a detection signal of said primary current detecting means to change the range of said secondary current command value supplied to said frequency conveter from said excitation current command means to within a predetermined range.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP01202291A JP3097745B2 (en) | 1989-08-05 | 1989-08-05 | AC excitation rotating electric machine control device |
| JP01-202291 | 1989-08-05 |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CA2022375A1 CA2022375A1 (en) | 1991-02-06 |
| CA2022375C true CA2022375C (en) | 1996-11-19 |
Family
ID=16455111
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA 2022375 Expired - Fee Related CA2022375C (en) | 1989-08-05 | 1990-07-31 | Ac-excited rotary electric machine system |
Country Status (2)
| Country | Link |
|---|---|
| JP (1) | JP3097745B2 (en) |
| CA (1) | CA2022375C (en) |
Families Citing this family (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| FI119898B (en) * | 2007-02-14 | 2009-04-30 | Konecranes Oyj | The generator assembly |
| EP2015443B1 (en) | 2007-07-10 | 2010-04-07 | Jtekt Corporation | Motor control device |
| JP6173773B2 (en) * | 2013-05-24 | 2017-08-02 | 株式会社東芝 | Variable speed control device and operation method |
-
1989
- 1989-08-05 JP JP01202291A patent/JP3097745B2/en not_active Expired - Fee Related
-
1990
- 1990-07-31 CA CA 2022375 patent/CA2022375C/en not_active Expired - Fee Related
Also Published As
| Publication number | Publication date |
|---|---|
| CA2022375A1 (en) | 1991-02-06 |
| JPH0370498A (en) | 1991-03-26 |
| JP3097745B2 (en) | 2000-10-10 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| EEER | Examination request | ||
| MKLA | Lapsed |