CA1149870A - Phase-shift detector - Google Patents
Phase-shift detectorInfo
- Publication number
- CA1149870A CA1149870A CA000356420A CA356420A CA1149870A CA 1149870 A CA1149870 A CA 1149870A CA 000356420 A CA000356420 A CA 000356420A CA 356420 A CA356420 A CA 356420A CA 1149870 A CA1149870 A CA 1149870A
- Authority
- CA
- Canada
- Prior art keywords
- phase
- mains
- voltage
- changes
- oscillating circuit
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Classifications
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R25/00—Arrangements for measuring phase angle between a voltage and a current or between voltages or currents
Landscapes
- Physics & Mathematics (AREA)
- General Physics & Mathematics (AREA)
- Inverter Devices (AREA)
- Control Of Ac Motors In General (AREA)
- Power Conversion In General (AREA)
- Stabilization Of Oscillater, Synchronisation, Frequency Synthesizers (AREA)
Abstract
ABSTRACT OF THE DISCLOSURE
For the purpose of detecting phase changes (sin .delta.) in an alternating-voltage mains, an apparatus is provided in which in each mains-phase a weakly attenuated oscillating circuit follows the mains-phase position after a considerable delay. Further, a multiplier is provided in each mains phase, to which are passed the output voltage from the relevant oscillating circuit and a voltage perpendicular to this voltage in the steady state. The phase-changes (sin .delta.) arising are taken off by passing the output voltages from the multipliers to an adding amplifier.
For the purpose of detecting phase changes (sin .delta.) in an alternating-voltage mains, an apparatus is provided in which in each mains-phase a weakly attenuated oscillating circuit follows the mains-phase position after a considerable delay. Further, a multiplier is provided in each mains phase, to which are passed the output voltage from the relevant oscillating circuit and a voltage perpendicular to this voltage in the steady state. The phase-changes (sin .delta.) arising are taken off by passing the output voltages from the multipliers to an adding amplifier.
Description
The invention relates to an apparatus for detecting phase-changes in an alternating-current mains by using multipliers.
It is kno~n from the pu~lication by Tietze/Schenk "Halbleiter-schaltungstechnik", Springer-Verlag, Berlin, 1978, pages 689 to 691, to use multipliers to determine the phase-diEference between two predetermined voltages.
In the case of high-voltage direct-current transmission installations CHVDC~, it may be important, especially for controlling the quenching angle of an inverter connecting the direct-current line to an alternating-voltage network, to detect phase-changes originating externally of the HVDC installation, for example overload-disconnects in a high-power consumer or part of a network. This is necessary to prevent the control from predetermining an incorrect firing angle for the inverter rectifiers in the event of phase changes, which might lead to commutation failure.
In order to avoid uncharacteristic harmonics, use is made in ~YDC installations, preferably, of control-units having self-excited, phase-controlled pulse-generators, the synchronous signal from which, in performing the said function, must have a delayed action, so that in 2Q the event of phase-shifts in the synchronizing network, e.g. for the reason indicated, the firing pulse, without additional information from the control-output, would return to its former angular setting only after ~-' a delay.
It is the purpose of the invention to provide a phase-shift detector which can deliver the necessary additional information for quenching-angle control in an inverter, to an alternating network, at low cost, without the need for an additional phase-standard.
-1- ~ :
,~. .
According to the invention, this purpose is achieved by providing an apparatus for detecting phase-changes in an alternating-current mains by using multipliers, characterized ln that: in each mains-phase a weakly attenu-ated oscillating circuit is provided, whlch follows a mains-phase position after a considerable delay; in each mains-phase a multiplier is provided, to which are fed an output voltage from the relevant oscillating circuit and a voltage per-pendicular to this voltage in steady state operation, and the output voltages from the multipliers are passed to an adding amplifier, so that any phase-changes (sin ~) arising can be taken off.
The apparatus according to the invention obtains a time standard from the alternating mains voltage itself, which has the advantage of providing a delay-free signal for the magnitude of the change in the mains phase. This is directly available for influencing the firing angle of inverter-rectifiers in an HVDC installation. In a quenching-angle control, this makes it possible to prevent the inverter from operating with an excessively small quenching angle as a result of incorrect firing-angle information, which may easily lead to flipping.
An example of embodiment of the invention is explained hereinafter in conjunction with the drawing attached hereto.
The drawing is a schematic circuit diagram of a phase-shift de-tector comprising an oscillating circuit consisting of three amplifier stages 1,2,3. Operative amplifiers 15,25,35 in amplifier stages 1,2,3, which are connected in series through ohmic resisiors 14,24,34, are each provided with an ohmic resistor 11,21,31 and a capacitor 12,22,32 connected in parallel in the feedback branch. Each amplifier stage 1,2,3 rotates its input voltage through 240 (electrical) at mains frequency, and has an amplification of about 0.95, for example.
It is kno~n from the pu~lication by Tietze/Schenk "Halbleiter-schaltungstechnik", Springer-Verlag, Berlin, 1978, pages 689 to 691, to use multipliers to determine the phase-diEference between two predetermined voltages.
In the case of high-voltage direct-current transmission installations CHVDC~, it may be important, especially for controlling the quenching angle of an inverter connecting the direct-current line to an alternating-voltage network, to detect phase-changes originating externally of the HVDC installation, for example overload-disconnects in a high-power consumer or part of a network. This is necessary to prevent the control from predetermining an incorrect firing angle for the inverter rectifiers in the event of phase changes, which might lead to commutation failure.
In order to avoid uncharacteristic harmonics, use is made in ~YDC installations, preferably, of control-units having self-excited, phase-controlled pulse-generators, the synchronous signal from which, in performing the said function, must have a delayed action, so that in 2Q the event of phase-shifts in the synchronizing network, e.g. for the reason indicated, the firing pulse, without additional information from the control-output, would return to its former angular setting only after ~-' a delay.
It is the purpose of the invention to provide a phase-shift detector which can deliver the necessary additional information for quenching-angle control in an inverter, to an alternating network, at low cost, without the need for an additional phase-standard.
-1- ~ :
,~. .
According to the invention, this purpose is achieved by providing an apparatus for detecting phase-changes in an alternating-current mains by using multipliers, characterized ln that: in each mains-phase a weakly attenu-ated oscillating circuit is provided, whlch follows a mains-phase position after a considerable delay; in each mains-phase a multiplier is provided, to which are fed an output voltage from the relevant oscillating circuit and a voltage per-pendicular to this voltage in steady state operation, and the output voltages from the multipliers are passed to an adding amplifier, so that any phase-changes (sin ~) arising can be taken off.
The apparatus according to the invention obtains a time standard from the alternating mains voltage itself, which has the advantage of providing a delay-free signal for the magnitude of the change in the mains phase. This is directly available for influencing the firing angle of inverter-rectifiers in an HVDC installation. In a quenching-angle control, this makes it possible to prevent the inverter from operating with an excessively small quenching angle as a result of incorrect firing-angle information, which may easily lead to flipping.
An example of embodiment of the invention is explained hereinafter in conjunction with the drawing attached hereto.
The drawing is a schematic circuit diagram of a phase-shift de-tector comprising an oscillating circuit consisting of three amplifier stages 1,2,3. Operative amplifiers 15,25,35 in amplifier stages 1,2,3, which are connected in series through ohmic resisiors 14,24,34, are each provided with an ohmic resistor 11,21,31 and a capacitor 12,22,32 connected in parallel in the feedback branch. Each amplifier stage 1,2,3 rotates its input voltage through 240 (electrical) at mains frequency, and has an amplification of about 0.95, for example.
-2-", .r, ~, , , . ~ .
~98'7~
By applying mains phase voltages UR, Us, UT, the phase changes of which are to ~e monitored, through ohmîc resistors 13,23,33, to the inputs to the operational amplifiers 15,25,35, the oscillating circuits are caused to oscillate at mains frequency and at a specific amplitude.
Since the oscillating circuits are only slightly attenuated, the quantity-accuracy is not particularly high; however, there is also no particular demand for this.
Each amplifier stage 1,2,3 delivers its output quantity to a multiplier 4,5,6 associated with it, where the said quantities are multi-plied by the mains quantities perpendicular thereto. The three products are added through ohmic resistors 41,51,61 and are passed to an ampliEier stage 7 comprising an operational amplifier 75. In the undisturbed state, the products consist only of alternating quantities at twice the mains frequency and they add up to zero. In the event of a phase-shift ~ in mains voltage UR, Us, UT, the output from the oscillating circuit follows the phase-change only after a delay; the products receive a decaying constant member of the size of the sine of the phase shift (sin ~), which can be taken from the output from amplifier-stage 7.
Operational amplifîer 75 is wired in parallel with an ohmic resistor 71, a rectifier bridge 76 and a delay-element 72,73,74 with regulated time-constant. The two other connections to rectifier bridge 76 are connected, through ohmic resistors 77,78, to a direct-voltage source.
This circuit shifts the amplifier curve away from the zero point. This is necessary in order to prevent harmonic-carrying voltages in the phase-shift detector from producing faulty indications, and to ensure that only actual phase changes lead to a sin ~ output signal.
, ~ -: , . : .
' :
.
987~) The delay-element with its regulated time-constant camprises a series circuit having a diode 73 and a capacitor 72, the ~unction between them being grounded through another diode 74. The delay-element is provided to enable the phase-shift detector to be used in a quenching-angle control in an inverter (e.g. in a H~DC installation). In this case, the said phase-shift detector is used to make a correction in the firing-angle reference input, in the event of phase-changes in the mains.
Actually, the delay-element with its regulated time-constant ensures that the sin ~ signal received is considered merely as positive, i.e.
as an additional predetermined value shifting the firing angle towards the safe operating side in controlling the quenching angle, so that the sin ~ sîgnal decays more slo~ly than with the angle control in the control-unit.
, . . . . . .
.. ~ . . . .
. - ' ' . . . . .
, . ' :
:- .
.
, - : - - .
~98'7~
By applying mains phase voltages UR, Us, UT, the phase changes of which are to ~e monitored, through ohmîc resistors 13,23,33, to the inputs to the operational amplifiers 15,25,35, the oscillating circuits are caused to oscillate at mains frequency and at a specific amplitude.
Since the oscillating circuits are only slightly attenuated, the quantity-accuracy is not particularly high; however, there is also no particular demand for this.
Each amplifier stage 1,2,3 delivers its output quantity to a multiplier 4,5,6 associated with it, where the said quantities are multi-plied by the mains quantities perpendicular thereto. The three products are added through ohmic resistors 41,51,61 and are passed to an ampliEier stage 7 comprising an operational amplifier 75. In the undisturbed state, the products consist only of alternating quantities at twice the mains frequency and they add up to zero. In the event of a phase-shift ~ in mains voltage UR, Us, UT, the output from the oscillating circuit follows the phase-change only after a delay; the products receive a decaying constant member of the size of the sine of the phase shift (sin ~), which can be taken from the output from amplifier-stage 7.
Operational amplifîer 75 is wired in parallel with an ohmic resistor 71, a rectifier bridge 76 and a delay-element 72,73,74 with regulated time-constant. The two other connections to rectifier bridge 76 are connected, through ohmic resistors 77,78, to a direct-voltage source.
This circuit shifts the amplifier curve away from the zero point. This is necessary in order to prevent harmonic-carrying voltages in the phase-shift detector from producing faulty indications, and to ensure that only actual phase changes lead to a sin ~ output signal.
, ~ -: , . : .
' :
.
987~) The delay-element with its regulated time-constant camprises a series circuit having a diode 73 and a capacitor 72, the ~unction between them being grounded through another diode 74. The delay-element is provided to enable the phase-shift detector to be used in a quenching-angle control in an inverter (e.g. in a H~DC installation). In this case, the said phase-shift detector is used to make a correction in the firing-angle reference input, in the event of phase-changes in the mains.
Actually, the delay-element with its regulated time-constant ensures that the sin ~ signal received is considered merely as positive, i.e.
as an additional predetermined value shifting the firing angle towards the safe operating side in controlling the quenching angle, so that the sin ~ sîgnal decays more slo~ly than with the angle control in the control-unit.
, . . . . . .
.. ~ . . . .
. - ' ' . . . . .
, . ' :
:- .
.
, - : - - .
Claims (3)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. An apparatus for detecting phase-changes in an alternating-current mains by using multipliers, characterized in that: in each mains-phase a weakly attenuated oscillating circuit is provided, which follows a mains-phase position after a considerable delay; in each mains-phase a multiplier is provided, to which are fed an output voltage from the relevant oscillating circuit and a voltage perpendicular to this voltage in steady state operation, and the output voltages from the multipliers are passed to an adding amplifier, so that any phase-changes (sin .delta.) arising can be taken off.
2. An apparatus according to claim 1, characterized by the use there-of as an accessory in controlling the quenching angle of inverters in a high-voltage direct-current transmission installation, in such a manner that the output from the adding amplifier is also connected to an input of a control-unit.
3. An apparatus according to claim 2, characterized in that the add-ing amplifier contains a delay-element having a regulated time-constant which permits a shift of firing angle only in a safe direction, said element having a decay-time longer than the control time of the control unit.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| DE2929262A DE2929262C2 (en) | 1979-07-17 | 1979-07-17 | Device for detecting a jump in the phase position of a three-phase voltage |
| DEP2929262.4 | 1979-07-17 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1149870A true CA1149870A (en) | 1983-07-12 |
Family
ID=6076181
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000356420A Expired CA1149870A (en) | 1979-07-17 | 1980-07-17 | Phase-shift detector |
Country Status (5)
| Country | Link |
|---|---|
| CA (1) | CA1149870A (en) |
| CH (1) | CH652507A5 (en) |
| DE (1) | DE2929262C2 (en) |
| SE (1) | SE439381B (en) |
| ZA (1) | ZA804237B (en) |
Family Cites Families (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE2702011C2 (en) * | 1977-01-14 | 1983-06-16 | Licentia Patent-Verwaltungs-Gmbh, 6000 Frankfurt | Circuit arrangement for displaying and / or signaling the degree of asymmetry in three-phase networks |
-
1979
- 1979-07-17 DE DE2929262A patent/DE2929262C2/en not_active Expired
-
1980
- 1980-07-09 SE SE8005058A patent/SE439381B/en not_active IP Right Cessation
- 1980-07-14 ZA ZA00804237A patent/ZA804237B/en unknown
- 1980-07-16 CH CH5465/80A patent/CH652507A5/en not_active IP Right Cessation
- 1980-07-17 CA CA000356420A patent/CA1149870A/en not_active Expired
Also Published As
| Publication number | Publication date |
|---|---|
| DE2929262C2 (en) | 1985-12-05 |
| DE2929262A1 (en) | 1981-02-05 |
| CH652507A5 (en) | 1985-11-15 |
| SE439381B (en) | 1985-06-10 |
| SE8005058L (en) | 1981-01-18 |
| ZA804237B (en) | 1981-07-29 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKEX | Expiry |