US3701938A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Minimum valve voltage method and control apparatus for hvdc power converters
Assignee: CGEE ALSTHOM NORTH AMERICA Inc
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Filing: 1971-08-09
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Granted: 1972-10-31
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Expires: 1991-08-09
Abstract
Abstract A minimum valve voltage firing control method and circuit for HVDC thyristor power converter circuit operated in the rectifying mode. The valve of the commutating voltage across the respective thyristor valves is sampled and the minimum sampled value during each valve firing stored on a capacitor through the medium of suitable valve voltage sampling and gating circuits. The stored valve voltage samples are compared to a minimum valve voltage reference value and an error signal derived under conditions where an insufficient valve voltage is indicated. The error signal is employed to increase the minimum angle of delay of firing Alpha to a safe value adequate to assure a sufficient valve firing voltage.
Inventors
- 👤 Philip Chadwick
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-25 21:59
CPC Classifications
H; H02; H02M; H02M7/00; H02M7/66; H02M7/68; H02M7/72; H02M7/75; H02M7/757; H02M7/7575; Y; Y02; Y02E; Y02E60/00; Y02E60/60
Claims Analysis
Total Claims: 21
Claim 1
Independent Claim
206 words
A minimum valve voltage firing control circuit for thyristor converters operated in the rectifying mode comprising means for sampling the value of the commutating voltage associated with the respective thyristors of a converter at the time of firing thereof, valve voltage sample storing means, gating circuit means for supplying sampled values of the respective thyristor valve voltages to said valve voltage sample storing means, means for supplying gating signals to said gating circuit means synchronously with the firing pulses supplied to the respective thyristors whereby said gating circuit means supplies sampled values of the respective thyristor valve voltages successively to the valve voltage sample storing means, comparison circuit means coupled to the valve voltage sample storing means for comparing the stored value of a thyristor valve voltage sample to a preset minimum reference value and deriving an output error signal in the event that the valve voltage sample differs from the preset minimum reference value in a predetermined manner, and means for controlling the firing angles of the respective thyristors in response to the output error signal whereby subsequent firings of the thyristors occur under conditions where the minimum valve voltage existing across the respective thyristors exceeds a value established by the preset minimum reference value.
Claim 2
Dependent Claim
206 words
A minimum valve voltage firing control circuit for thyristor converters operated in the rectifying mode comprising means for sampling the value of the commutating voltage associated with the respective thyristors of a converter at the time of firing thereof, valve voltage sample storing means, gating circuit means for supplying sampled values of the respective thyristor valve voltages to said valve voltage sample storing means, means for supplying gating signals to said gating circuit means synchronously with the firing pulses supplied to the respective thyristors whereby said gating circuit means supplies sampled values of the respective thyristor valve voltages successively to the valve voltage sample storing means, comparison circuit means coupled to the valve voltage sample storing means for comparing the stored value of a thyristor valve voltage sample to a preset minimum reference value and deriving an output error signal in the event that the valve voltage sample differs from the preset minimum reference value in a predetermined manner, and means for controlling the firing angles of the respective thyristors in response to the output error signal whereby subsequent firings of the thyristors occur under conditions where the minimum valve voltage existing across the respective thyristors exceeds a value established by the preset minimum reference value.
Claim 3
Dependent Claim
28 words
A minimum valve voltage firing control circuit according to claim 1 wherein the output error signal controls the firing angles of all the thyristors of the converter simultaneously.
Claim 4
Dependent Claim
34 words
A minimum valve voltage firing control circuit according to claim 1 further including amplifying means for amplifying the output error signal severalfold to assure adequate control over the firing angles of the respective thyristors.
Claim 5
Dependent Claim
172 words
A minimum valve voltage firing control circuit according to claim 1 further comprising firing time control variable frequency oscillator means for producing properly spaced, variable frequency output firing pulses for supply to the respective thyristors of the converter to control the firing thereof and Alpha MIN limit control circuit means coupled to the firing time control variable frequency oscillator means for establishing a minimum angle of delay Alpha with respect to the production of the firing pulses for firing the respective thyristors measured with respect to the phase of the supply alternating current waveform, and distributor means responsive to the output firing pulses from said firing time control variable frequency oscillator means for supplying firing pulses to the respective thyristors of the converter and to said gating circuit means, said output error signal being supplied to and controlling operation of said Alpha MIN limit control circuit means for rapidly increasing the minimum angle of delay to an increased delay angle in response to an output error signal indicative of insufficient valve voltage.
Claim 6
Dependent Claim
31 words
A minimum valve voltage firing control circuit according to claim 3 wherein the increase in the minimum angle of delay is in proportion to the magnitude of the output error signal.
Claim 7
Dependent Claim
45 words
A minimum valve voltage firing control circuit according to claim 5 further including circuit means for returning the output error signal towards zero value over a relatively long time constant period measured with respect to the period and repetition rate of the thyristor valve firings.
Claim 8
Dependent Claim
52 words
A minimum valve voltage firing control circuit according to claim 6 further including amplifying means for amplifying the output error signal severalfold in advance of supplying it to the Alpha MIN limit control circuit means to assure a rapid increase in the angle of delay Alpha in response to the error signal.
Claim 9
Dependent Claim
125 words
A minimum valve voltage firing control circuit according to claim 7 wherein said valve voltage sample storing means comprises a capacitor, said gating circuit means comprises low impedance transistor input circuit means coupled to said capacitor for coupling sampled values of the respective thyristor valve voltages to the capacitor, and transistor switching means intercoupled with the valve voltage sampling means, the distribution means and the low impedance transistor input circuit means for transferring to said capacitor charges representative of the successive thyristor valve voltages, and further including high impedance transistor output circuit means coupled to said capacitor and to said comparison circuit means for supplying to said comparison circuit means a signal representative of the successive thyristor valve voltage values without unduly loading the capacitor.
Claim 10
Dependent Claim
51 words
A minimum valve voltage firing control circuit according to claim 8 wherein the high impedance transistor output circuit means comprises the circuit means for returning the output error signal towards zero value over a relatively long time constant period by supplying a relatively long time constant charging current to said capacitor.
Claim 11
Dependent Claim
125 words
A minimum valve voltage firing control circuit according to claim 1 wherein said valve voltage sample storing means comprises a capacitor, said gating circuit means comprises low impedance transistor input circuit means coupled to said capacitor for coupling sampled values of the respective thyristor valve voltages to the capacitor, and transistor switching means intercoupled with the valve voltage sampling means, the distributor means and the low impedance transistor input circuit means for transferring to said capacitor charges representative of the successive thyristor valve voltages, and further including high impedance transistor output circuit means coupled to said capacitor and to said comparison circuit means for supplying to said comparison circuit means a signal representative of the successive thyristor valve voltage values without unduly loading the Capacitor.
Claim 12
Dependent Claim
85 words
A minimum valve voltage firing control circuit according to claim 10 wherein the output error signal controls the firing angles of all the thyristors of the converter simultaneously, and further including amplifying means for amplifying the output error signal severalfold to assure adequate control over the firing angles of the respective thyristors, and circuit means for returning the output error signal towards zero value over a relatively long time constant period measured with respect to the period and repetition rate of the thyristor valve firings.
Claim 13
Independent Claim
137 words
A method of assuring maintanence of minimum valve voltage across the thyristor valves of a power converter operated in the rectifying mode comprising sensing the value of the commutating voltage associated with each thyristor valve in the converter during a portion of its conduction interval, storing the sensed value of the respective thyristor valve voltages, comparing the stored thyristor valve voltage values to a preset minimum reference value and deriving an output error signal indicative of any difference, and applying output error signals indicative of insufficient valve voltages to control the firing angle of delay Alpha of the thyristor valves in the further operation of the power converter whereby the firing angle of delay Alpha of the thyristors is increased to assure sufficient valve firing voltage across the thyristor valves in the presence of AC system disturbances.
Claim 14
Independent Claim
137 words
A method of assuring maintanence of minimum valve voltage across the thyristor valves of a power converter operated in the rectifying mode comprising sensing the value of the commutating voltage associated with each thyristor valve in the converter during a portion of its conduction interval, storing the sensed value of the respective thyristor valve voltages, comparing the stored thyristor valve voltage values to a preset minimum reference value and deriving an output error signal indicative of any difference, and applying output error signals indicative of insufficient valve voltages to control the firing angle of delay Alpha of the thyristor valves in the further operation of the power converter whereby the firing angle of delay Alpha of the thyristors is increased to assure sufficient valve firing voltage across the thyristor valves in the presence of AC system disturbances.
Claim 15
Dependent Claim
53 words
A method according to claim 12 further including automatically returning the firing angle of delay Alpha of the thyristor back to a normal setting determined by other control parameters of the converter over a relatively long time constant period measured with respect to the period and repetition rate of the thyristor valve firings.
Claim 16
Dependent Claim
25 words
A method according to claim 13 wherein the firing angle of delay Alpha of all the thyristor valves of the power converter are controlled simultaneously.
Claim 17
Dependent Claim
75 words
A method according to claim 14 wherein the output error signal is amplified severalfold in advance of applying it to increase the firing angle of delay Alpha of the thyristor valves of the converter whereby a sudden and rapid increase in the firing angle of delay Alpha is achieved in order to accommodate AC system transient disturbances that otherwise might result in an insufficient valve voltage across the thyristor valves at the time of firing.
Claim 18
Dependent Claim
131 words
A minimum valve voltage firing control circuit for thyristor converters operated in the rectifying mode comprising means for sampling the value of the commutating voltage associated with each respective thyristor of a converter at the time of firing thereof, means for comparing the value of the minimum thyristor valve voltage samples to a preset minimum reference value and deriving an output error signal in the event that a valve voltage sample differs from the preset minimum reference value in a predetermined manner, and means for increasing the firing angle of delay of the respective thyristors in response to the output error signal whereby subsequent firings of the thyristors occur under conditions where the minimum valve voltage existing across the respective thyristors exceeds a value established by the preset minimum reference value.
Claim 19
Dependent Claim
131 words
A minimum valve voltage firing control circuit for thyristor converters operated in the rectifying mode comprising means for sampling the value of the commutating voltage associated with each respective thyristor of a converter at the time of firing thereof, means for comparing the value of the minimum thyristor valve voltage samples to a preset minimum reference value and deriving an output error signal in the event that a valve voltage sample differs from the preset minimum reference value in a predetermined manner, and means for increasing the firing angle of delay of the respective thyristors in response to the output error signal whereby subsequent firings of the thyristors occur under conditions where the minimum valve voltage existing across the respective thyristors exceeds a value established by the preset minimum reference value.
Claim 20
Dependent Claim
64 words
A minimum valve voltage firing control circuit according to claim 16 wherein the output error signal controls the firing angles of all the thyristors of the converter simultaneously and the circuit further includes means for returning the output error signal toward zero value over a relatively long time constant period measured with respect to the period and repetition rate of the thyristor valve firings.
Claim 21
Dependent Claim
52 words
A minimum valve voltage firing control circuit according to claim 16 wherein the value of the commutating voltage associated with the respective thyristor is sampled continuously over a predetermined sampling interval of the order of 30* and the minimum valve voltage occurring during the interval compared to the prEset minimum reference value.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1975-10-31 | 1976-05-01 | 1976-10-31 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1979-10-31 | 1980-05-01 | 1980-10-31 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1983-10-31 | 1984-05-01 | 1984-10-31 | $7700.00 | Window Closed / Lapsed |