US3648147A - Starting control scheme for rectifier-inverter systems - Google Patents

Starting control scheme for rectifier-inverter systems Download PDF

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Publication number
US3648147A
US3648147A US88668A US8866870A US3648147A US 3648147 A US3648147 A US 3648147A US 88668 A US88668 A US 88668A US 8866870 A US8866870 A US 8866870A US 3648147 A US3648147 A US 3648147A
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Prior art keywords
converter
starting
valves
control signals
pulses
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US88668A
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English (en)
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Bernard D Leete
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CGEE ALSTHOM NORTH AMERICA Inc
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General Electric Co
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Priority to US88668A priority Critical patent/US3648147A/en
Priority to CA123820A priority patent/CA938998A/en
Priority to DE19712155900 priority patent/DE2155900A1/de
Priority to GB5238871A priority patent/GB1377962A/en
Priority to GB5542473A priority patent/GB1377963A/en
Priority to JP9002271A priority patent/JPS4710574A/ja
Priority to FR7140642A priority patent/FR2114654A6/fr
Priority to IT31003/71A priority patent/IT968034B/it
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Publication of US3648147A publication Critical patent/US3648147A/en
Priority to JP13799378A priority patent/JPS54115729A/ja
Assigned to CGEE ALSTHOM NORTH AMERICA, INCORPORATED reassignment CGEE ALSTHOM NORTH AMERICA, INCORPORATED ASSIGNMENT OF ASSIGNORS INTEREST. Assignors: GENERAL ELECTRIC COMPANY
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    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M7/00—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output
    • H02M7/66—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output with possibility of reversal
    • H02M7/68—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output with possibility of reversal by static converters
    • H02M7/72—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output with possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
    • H02M7/75—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output with possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a thyratron or thyristor type requiring extinguishing means
    • H02M7/757—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output with possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a thyratron or thyristor type requiring extinguishing means using semiconductor devices only
    • H02M7/7575—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output with possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a thyratron or thyristor type requiring extinguishing means using semiconductor devices only for high voltage direct transmission link
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/60—Arrangements for transfer of electric power between AC networks or generators via a high voltage DC link [HVCD]

Definitions

  • ABSTRACT Appliumm Dim A high-voltage electric power converter comprises a plurality [63] continuatiomimpan of Sen 754,921, Aug 23 of electric valves interconnected in a bridge configuration. In ]968 operation the valves are cyclically fired in a predetermined normal sequence by a series of relatively short gate pulses [52 us.
  • a ..321/2 321/2 321/5 respectively aPll"ied sumflfu' "Ming, trols are arranged (1) to idle until the concurrence of a start- [5 l Int. Cl. ..l-l02m 5/40 ing command and a proper instant of time for firing any one of [5 of Search 4 5 S said valves, and, 13" t0 simultaneously a PUISC n to that one valve and a gate pulse to the immediately preceding valve in said normal sequence.
  • the controls are precondi- [56] References cued tioned so that the initial firing angle is within certain limits that UNITED STATES PATENTS ensure continuous conduction by the preceding valve at least from the starting instant to the time at which the succeeding Re2l,697 1/1941 Lord ..321/45 S valve is fi d 3,315,146 4/1967 Paige together ...321/45 S 3,399,337 8/1968 Stone ..32l/5 27 Claims, 9 Drawing Figures Mmm TEfiM/AAl.
  • This invention generally relates to electric power conver-- sion systems and more specifically it relates to control means for starting a static converter in such a system.
  • a converter comprises the combination of a polyphase power transformer and a plurality of interconnected electric current conducting valves.
  • Each valve can be a mercury arc tube, or a pluralityof semiconductor cells such as thyristors that are operated in unison.
  • the valves are arranged in a three-phase, double-way bridge configuration having three separate AC terminals and positive and negative DC terminals.
  • Each bridge contains six valves, and by sequentially applying turn-on (gate) pulses to the respective valves in the proper order and in timed relation to the alternating voltages of the three-phase electric power system to which theAC terminals of the bridge are connected, the flow of power between the AC and the DC terminals is controlled as desired.
  • the DC terminals oftwo such bridges are connected in series and the transformer windings associated with the AC terminals of the respective bridges are phase-displaced by an electrical angle of 38.
  • the time at which a valve is fired is known as the firing angle.
  • the firing angle As the firing angle is increased from zero, the averagemagnitude of the rectified voltage between the positive and negative DC terminals decreases from its maximum positive level. As the firing angle approaches 90, the average DC voltage reverses polarity and a converter will commence to operate as an inverter, whereby power can be transmitted from the DC to the AC terminals.
  • the six valves of a bridge are cyclically fired at intervals of 60 electrical degrees in a predetermined sequence. When fired, each will conduct continuously for approximately 120 3 at which time the current is transferred to asucceeding valve in the sequence. Thus, at least two valvesare always conducting, and current through-the bridge can be continuous.
  • a rectifier-inverter system there need be no particular steady-state phase.relationship or synchronism between the firing of the valves in one converter and in the other. At the instant of starting, however, no line current exists to be transferred from one valve to another, and it is necessary to fire two valves simultaneously.
  • the converter controls include first means for cyclically generating a family of six ,1 20 signals for effecting turn-on of the converter valves in a predetermined regular sequence.
  • the controls also include six valve-firing means respectively operative when activated to apply relatively short gate pulses to each of the valves in turn, and normally these means are respectively activated in response to the existence of corresponding control signals generatedby saidfirst means.
  • I provide blocking means for initially preventing activation of any of the valve-firing means until disabledby the coincidence of a starting or, recycling command and the leading edge of one of the control signals.
  • the aforesaid disabling action is additionally predicated on thecoincidence of the leading edge of any one of six similar control signals generated by the controls associated with the other converter.
  • I provide means for preconditioning the local controls to establish an initial firing angle within verter).
  • FIG. 1 is a schematiccircuit diagram of a portion of an HVDC electric power transmission system
  • FIG. 2 is aseries of timecharts showing the interrelationships between various voltages and control signals
  • FIG. 3 is a block diagram'ofa converter control scheme incorporating the starting controlcircuit of this invention.
  • FIG. 4 is a detailed circuit diagram of the terminal starting control ofFIG. 3;
  • FIG. 5 is a detailed circuit-diagram of the system starting control of FIG. 3;
  • FIG. 6, is .a detailed circuit diagram of an alternate embodiment of a system starting control
  • FIG. 7 is a detailed circuit diagram of a second alternative embodiment of asystem starting control
  • Each converter comprises N controlled valves arranged in at least one three-phase, double-way bridge configuration having three ACterminals A, B, C which are connected to polyphase conductors (not shown) by means of the set 11 of Y-transformer windings whose voltages alternate at f hertz in thephase rotation indicated.
  • f will be assumed equal to 60, and N is shown as 6.
  • the six valves, numbered 1 through 6, are fired (turned on) once each cycle in numerical sequence.
  • a converter By controlling the firing angle of the gating pulses applied to these valves, a converter can be made to operate as either a rectifier or as an inverter.
  • One converter in a system will be operated as a rectifier and one converter will be operated as an inverter, and the direction of power flow will be from the rectifier terminal (North) over the DC link to the inverter terminal (South).
  • valves 1 and 2 at each terminal are indicated by the arrows in FIG. 1. If the valves were gated with short pulses in a normal staggered or sequential manner, there would be no path for current when the first valve is fired, and it would revert to the blocking state when the gate pulse ceased. Then there would likewise be no path for current when the second valve is fired 60 later, and starting could not be accomplished. If the gate pulse for valve 1 persists for 60 or longer, starting can easily occur when valve 2 is subsequently fired.
  • the starting method to be described hereinafter can be used to start a static power conversion system when the duration of the gate pulses to the converter valves is shorter than 60
  • the gate pulse duration was selected to be 2 /2", and still shorter pulses are contemplated for future systems.
  • a requirement for successful start up is that the starting instant occur at a time when there are positive anode voltages on all valves simultaneously gated.
  • the three valves 1, 3, 5 with common cathode connection constitute a high-impedance balanced Y-load on the balanced Y-source 11. Similar conditions exist for the three valves 2, 4, 6 with common anode connection. Consequently, the voltage across each valve before starting is essentially the line-to-neutral voltage as is represented in graph A of FIG. 2 for valves 1 and 2.
  • the common-cathode connection (or plus side 7 of the DC link) is always connected to one of the three AC terminals through a conducting valve, and again similar conditions exist for the common anode connection.
  • a nonconducting valve under operating conditions is subjected to a line-to-line voltage which is higher in amplitude and 30 lagging in phase compared to the sine waves shown in FIG. 2A.
  • Another requirement for successful starting is that the current remain continuous from one valve firing to the next, which is 60. This may be no problem if the load is sufficiently inductive, but the firing angle should be limited to less than 60 for purely resistive loads. From graph A in FIG. 2 it can be observed that if starting were attempted by simultaneously firing valves 1 and 2 at the instant X corresponding to a steady-state delay angle exceeding 60 for valve 2 but 120 for valve 1, the valve 1 current (resistive load assumed) would fall to zero in less than 60 thereafter and would thus be extinguished before the firing of valve 3, thereby breaking continuity ofthe current path and making it impossible to start.
  • FIG. 3 is a block diagram of a converter control scheme which diagram shows converter starting controls for the North terminal of the FIG. 1 system and also shows controls which can be used for coordinated starting of the entire system. For clarity, means for controlling only one bridge is shown although it is to be understood that similar controls will ordinarily be provided for all of the bridges in each converter at each terminal of the electric power transmission system.
  • signals representative of the actual converter response and the desired converter response or power order are fed into summing point 13.
  • the output of the summing point is the error between the desired converter response and the actual measured response and is fed into regulator amplifier 14.
  • the DC output signal of amplifier 14 is passed through starting bias circuit 15 to a firing time computer 19 which is also governed by other limits as desired.
  • the computer 19 additionally receives signals indicative of the AC system voltages. It responds to these various inputs by generating, at a frequency that is a multiple off, a train of discrete pulses which are converted by an appropriate distributor 20 into a family of six control signals at the respective points 21 through 26 shown in FIG. 3. These control signals are respectively adapted to effect cyclic firing of the six valves 1 through 6 of the local converter in numerical sequence. As is clearly shown in FIG. 2B, the control signals commence at intervals of approximately 60, and each subsists for one-third of a cycle (i.e., which is appreciably longer than lNf second.
  • the delay angle (a) relating the leading edge of each control signal to the positivegoing zero crossing of the anode voltage of the corresponding valve is normally determined by the magnitude of the error signal that is fed to the firing-time computer 19.
  • the control-signal points 21-26 are shown connected to firing-signal logic means 27 comprising a gate 28 and appropriate logic circuits which enable additional supervision to be exercised over the timing and the order of thefiring signals by other permissive and inhibit signals such as those applied to inputs 29 and 30, respectively, as desired.
  • the outputs of the logic circuits are fed to the valve-firing system which includes N (six) blocks 31 through 36 representing means respectively operative when activated to transmit relatively short turn-on or gate pulses to each of the corresponding valves 1-6 in turn.
  • the gate pulses may be in any suitable form, such as electric current or radiant energy (e.g., light). Activation of each of the blocks 31-36 is achieved in response to the existence of the corresponding control signal when permitted by the gate 28 and associated logic. 7
  • the gate 28 has been shown symbolically as an initially open multipole switch, persons skilled in the art will recognize that its function can be accomplished in many different ways, such as providing a normally deenergized input bus to AND-logic circuits, or a normally energized clamp that blocks or suppresses activation of a bank of transistors.
  • the gate 28 is initially operative to prevent activation of the valve-firing system and is subsequently disabled only under conditions ensuring that the unblocking action will occur at a particular instant relative to the valve voltages and that the firing angle at this instant is of the proper value.
  • the gates Until unblocked, the controls idle in which state the timing of the control signals at 21-26 is determinable but no gate pulses are actually applied to the valves.
  • the gate preferably comprises a normally conducting solid-state switch 28 which inhibits the activation of any of the means 31-36 in a manner more fully described below. This switch is turned off, thereby disabling the gate and permitting the valve-firing system to start the converter, at the first appropriate instant after a start switch 40 is actuated in response to receipt at 41 of a starting or recycling command.
  • Graph D of FIG. 2 illustrates the starting signal produced by the switch 40 when operated shortly after the control signal for valve 1 commenced, but the unblocking action is not allowed to occur before the leading edge of the next control signal appears.
  • pulse-mixing means 42 is provided for the deriving short pulses or spikes from the leading edge of the respective control signals which are supplied to it from the distributor through points 21-26.
  • the train of mixed pulses thus produced has been illustrated in graph C1 of FIG. 2.
  • Each of the Cl pulses indicates that a gate pulse is then due for one of the local valves 16. It may be desirable in some systems to stretch the mixed pulses into rectangular signals of particular width as shown in graph C2 of FIG. 2, and the mixer 42 is additionally designed to serve this purpose.
  • the formed pulses appear at the output terminal 43 of the mixer 42, and they are fed into a coincidence detector 44 along with a similar train of pulses (shown in graph C3 of FIG.
  • the coincidence detector 44 is designed to provide an output only during the time when pulses from both terminals 43 and 121 are in simultaneous existence. See graph C4 of FIG. 2. Where it is acceptable to start the local converter independently of the remote converter, the detector 44 can be omitted or the terminals 43 and 121 Y can be effectively interconnected, and selected pulses in the train generated by the firing-time computer 19 can be used to energize terminal 43 ifdesired thereby eliminating the pulse mixer 42.
  • the output from the coincidence detector 44 is connected to a switch driver 45 which drives via terminal 174 the blocking switch 28'.
  • Switch driver 45 can also beused to simultaneously actuate a similar blocking switch, via terminal 173, in the starting controls for one or more additional converters, thereby starting the other converters.
  • operation of the switch driver 45, and hence disabling of the gate28 requires the coincidence of a starting command 41 (start switch 40 operated) and an output of the coincidence detector 44, if used (signalling the beginning ofa control signal at one of the points 21-26).
  • start switch was operated after the first control signal commenced but before the leading edge of the second control signal, and unblocking occurred in response to the latter event.
  • the logic means 27 will pass energizing pulses to two consecutively numbered'components (e.g.,'31 and 32) of the valve-firing system which are immediately activated thereby to transmit short turn-on pulses simultaneously to two valves (e.g., l and 2) that are normally fired in succession (see FIG. 2F).
  • the DC power level is initially zero,and assuming the power order is suitably programmed the regulator amplifier 14 will call for the converter output to increase as rapidly as permitted by built-in limits.
  • I employ bias means 15 for preconditioning the firing angle computer 19 so as to override other inputs and to establish an initial firing angle that meets the previously explained criteria of ensuring positive anode voltage on each of the two valves first fired and of avoiding premature extinction of either of these valves before current is commutated to the valve that is next fired in the normal operating sequence.
  • the starting bias circuit 15 comprises means for temporarily superimposing a DC voltage level on the output of the regulator amplifier 14.
  • a bias voltage is taken from a variable resistor 16 paralleling a suitable DC source 17 and is applied through a solid-state switch 46 across a resistor 18 which is connected between the amplifier l4 and the firingtime computer 19.
  • the variable resistor 16 controls the magnitude of bias voltage, and appropriate .means including the switch driver 45 is provided to controltheconduction of solidstate switch 46.
  • a switch-opening signal is sent by the switch driver 45 to the solid-state switch 46 so that the starting bias is removed.
  • the prospective firing angle of one of the control signals can be measured by means of a firing-angle monitor 47 supplied from point 21 and from the AC voltage monitors.
  • the firing angle monitor 47 may be merely an oscilloscope or other suitable display. Then with the starting bias circuit 15 in operation and the controls idling, the variable resistor 16 can be adjusted until a firing angle within desired limits is obtained at the local terminal before operating the start switch 40.
  • FIGS. 2 and 3 show schematically controls that are useful to I start a converter at one terminal (North) of an HVDC transmission system in cooperation with concurrent starting of a remote converter at another terminal (South).
  • the two pulse trains C2 and C3 respectively applied to the input terminals 43 and 121 of the coincidence detector 44 have been shown in FIG. 2 after appropriate-phase shifts to accommodate for any predictable time delays in the communication channel that interconnects the converters whichzmay be separated by long distances.
  • the required coincidence between a pulse in train C2 and'a pulse in train C3 will always be obtained if the frequencies of oscillation of the firing time computers associated with the respective converters are not precisely the same.
  • FIG. 4 is a detailed circuit diagram of the pulse mixing and forming means 42 shown in block form in FIG. 3.
  • a DC power supply (not shown) is connected between terminals 56. and 57, and an intermediate terminal 58 is held at zero volts by being connected to ground.
  • the control signals supplied to the mixer 42 from the respective points 21-26 are negative-going potentials which abruptly commence when, as is illustrated in particular for point 21, a normally conducting transistor (59) associated with that point in the distributor 20 is turned off.
  • Each of the six control signals are coupled into the pulse mixer through a separate capacitor 102 and an isolating diode 103 to the base 104 of a common transistor 105.
  • Two transistors 105 and 106 comprise a monostable multivibrator for which resistors 109,
  • Transistor 105 is normally conducting. However, when the leading edge of any one of the negative control signals arrives at its base 104 it ceases to conduct and turns off," and a positive pulse appears at its collector 114. Transistor 105 remains off for only a certain length of time determined by an RC time constant and then reverts to the conducting state.
  • the RC time constant which is determined by the values of a rheostat 113 and a capacitor 115, is
  • Capacitor 115 is charged by conduction of transistor 106 which is turned on when transistor 105 turns off. Current from transistor 106 charges capacitor 115 to a voltage sufficient to turn on transistor 105 once again, which turns off transistor 106 again.
  • a similar monostable multivibrator circuit located at a remote terminal of the HVDC transmission system provides a second train of pulses C3 at terminal 121 which is coupled through conductor 120 to the coincidence detector 44.
  • conductors 118 and 120 are shielded and the shields are connected through capacitors 119 to ground 58.
  • coincidence detector 44 provides an output C4 only during the time when pulses at its respective input terminals 43 and,121 are in simultaneous existence.
  • the output from the coincidence detector 44 is connected to the switch driver 45 which drives the blocking switch 28 when the first coincidence pulse C4 appears after the start switch 40 is operated. This will always happen within 10 following the leading edge of one of the control signals at points 21-26.
  • a conductor 122 is normally at ground potential. This conductor leads to the output terminal 174 which is externally connected through a resistor 125 to thebase 126 ofa normally conducting transistor 127 comprising the blockingswitch 28'.
  • a resistor 128 serves to furnish biasing for transistor 127 so as to cause it to be normally turned on in which state it maintains the blocking bus 28 at the potential of the positive power supply terminal 56.
  • the firing signal logic means 27 is arranged to prevent the valve-firing system 31-36 from being activated in response to the existence of any of the control signals at points 21-26 so long as the blocking bus 28 is clamped to terminal 56. However, this clamp is disabled and the logic means 27 is unblocked in response to the transistor 127 being driven off by the application to its base of a positive-going output signal from the switch driver 45.
  • Switch driver 45 also provides another output signal for starting a second converter if desired. This leads to the output terminal 173 which in turn can be connected to blocking switches (not shown) associated with the starting controls of other converters. To prevent disturbances and noise interference, the conductors 122 and 123 are shielded and the shields are connected through capacitors 129 to ground 58.
  • the output terminal 174 of the switch driver 45 is also coupled through a capacitor to a pulse transformer 51.
  • a secondary winding of the pulse transformer 51 is connected via a shielded conductor 52 to the starting bias circuit, and a signal induced in this winding serves to release the starting bias by initiating opening of the solid-state switch 46 shown symbolically in FIG. 3.
  • conductor 52 has its shielding connected through capacitor 53 to ground.
  • FIG. 5 shows details of the coincidence detector 44 used in one particular embodiment of the invention.
  • the coincidence detector 44 comprises a circuit arrangement for perfonning a NAND logic function.
  • the base of a transistor 131 is clamped to ground through diodes 132 and 133 so that the output potential at collector 134 of this normally off transistor is essentially the same as that of the positive power supply bus 56'.
  • Resistors 135, 136, 137, and 138, and capacitor 139 and diode 140 constitute a biasing arrangement for transistor 131.
  • An input signal at only one of the terminals 43 or121 does not change this situation since the base 130 remains grounded through a parallel path.
  • both input diodes 132 and 133 are back biased and the transistor 131 is forward biased into conduction.
  • a negative-going output pulse is created at collector 134 of transistor 131 for the duration of coincidence of the two inputs.
  • the negative coincidence output pulses atthe collector 134 of transistor 131 are coupled through a capacitor 141 and a diode 142 to a transistor 143 in the switch driver 45 which as is clearly shown in FIG. 5, preferably comprises a flip-flop circuit.
  • Transistor 143 is immediately turned off in response to such a pulse. Ordinarily, turning off of one side of a flip-flop (transistor) 143 would by reason of the collector 144 of transistor 143 being coupled throughresistor 145 and capacitor 146 to the base 147 of a companion transistor 148, cause the transistor which is the opposite side of the flip-flop to turn on.
  • this flip-flop is unconventional in that transistor 148 is normally prevented from turning on by supplying forward current through a base-to-emitter diode 149 connected so as to negatively bias the base.
  • the magnitude of this bias current is set so that the transient current from the positive DC supply bus 56 through resistor 153 at the input side of transistor 148 will not exceed the bias current, and therefore transistor 148 remains off despite the positive pulses received at its base 147 as a consequence of the turning off of transistor 143.
  • Transistor 143 returns to the conducting state in between successive pulses from transistor 131.
  • a start switch shown symbolically at 40 is connected through resistor 154 across capacitors 156 and 156.
  • the negative potential at the junction of resistors 150, 151 is reduced to nearly ground level, thereby removing the negative bias on base 147 of transistor 148. Removal of this bias does not itself cause transistor 148 to turn on if transistor 143 is then conducting, since a positive signal is required at base 147 to turn transistor 148 on.
  • transistor 148 is turned on at the next instance of transistor 143 turning off due to a negative input pulse from the coincidence detector 44.
  • Capacitors 155 and 156 provide some degree of filtering across switch 40 in order to prevent premature operation due topositive noise picked up if switch 40 is remotely located.
  • Resistors 150 and 158 provide biasing for transistor 148.
  • Resistor 159 and parallel capacitor 160 are connected between the collector 161 of the transistor 148 and the base 162 of the transistor 143 so that when transistor 148 does turn on a negative bias is imposed on the base 162 of transistor 143 to prevent its return to a conducting state, thus scaling in the flip-flop until subsequently reset by opening the switch 40 to terminate the starting signal. 7
  • transistor 148 Before starting, transistor 148 is off so that the potential at its collector 161 is high. Then current is provided through resistor 163 to a DC current amplifier comprising normally conducting transistors 164 and 165 and also through resistor 166 to a duplicate DC current amplifier comprising normally conducting transistors 167 and 168. Resistors 169, 170, 171, and
  • 172 furnish biasing for the. two amplifiers. These .amplifiers produce positivergoing outputs at the respective terminals 173 and 174 when the transistors 168 and 165 are turned off. In operation, transistors 164, 165, 167, and 168 are all turned off when the transistor 148 turns on.
  • the output terminals 173 and. 174 are coupled to.-external circuitsas shown in FIG. .4 and previouslydescribed.
  • FIG. 6 shows arsimplified alternative embodiment of a portion of the system and converter starting controls in which the blocking switch driver and the starting flip-flop .have .been omitted.
  • the pulse-forming and coincidencedetector circuits are substantially the sameasin FIGS.-4 and.5,-and circuitelements identified in FIG. 6 by primed reference numerals correspond to their unprimed counterpartsin FIGS. 4
  • the start switch 181 is symbolically illustrated'as a two-pole normally closed switch.-.Before starting and with .the contactsof switch 181 closed, a thyristor blocking switch182 is maintained in a blocked condition (conducting) due to positive current at itsgate 183 regardless of whether or not the parallel'commutating transistor 184 is turned on as a result of coincidence output pulses received from thecollector 134 of transistor 131'. -W hen the start switch 181 is operated (opened) on command,.the thyristor control circuit, including resistors 185 and 186 and capacitor 187, is .deenergizedand the gate drive. for the thyristor blocking switch 182 is removed, but latchingaction keeps this switch conducting.
  • the transistor 184 On the expiration of the coincidence output pulse the transistor 184 immediately reverts to its nonconducting state and the potential of blocking bus'z28 is lowered, thereby disabling its blocking function and enabling the firing signallogic means 27.to energize the valve firing system 31-36 in response to the existence of corresponding control signals-at points.21-26.
  • a start switch 193 is normally closed so that silicon-controlled switch 191 isnormally biased on by means of resistors 194, 195, and 196 and capacitor 197. Since silicon-controlled switch 191is on, current is conductedthrough its anode gate 192 so that transistor 127 is also conducting.
  • transistor 207 When the silicon-controlled switch 198 is on, conduction occurs through its anode gate 199 sothat transistor 206 is turned onanamount determinedby the adjustment of resistor201. When transistor .206 is on,.a cascaded transistor 207 is also conducting. Transistor 207 conducts current from a DC powersupply 17p,,17n through-a diode 209, a-bias polarity .switch..2.1-0,.and the resistor 18. The resulting voltage drop .across resistor 18 is thestarting'bias voltage.
  • silicon controlled switch 198 is not turned-onand itstanode gate 199 is not conducting.
  • appropriate means shown symbolically as.a-normally open switch 211 is momentarily-actuated to connectabiasing network comprising resistors'213 andf2l4 and capacitor'215 across the DC supply terminals 17p and 17n.
  • a forward-bias is-normallyapplied across the silicon-controlled switch 198 by means of resistor 216, diode 217 and resistor 218.
  • an actuating signal is received from the 'startingbiasrelease' transformer 131 (shown in FIG. 4) over shielded conductor 132, which conductor is coupled .through a capacitor;219 tothe resistor218, a negative pulse is impressedacrossthe resistor 218 to direct anode current from thesilicon-controlledswitch 198 so as to commutate it off.
  • current ceasesin the. anode gate 199,- and the transistors 206and.207 tend to beturned off;
  • transistors 206 andz207 were conducting a capacitor 220 connected between.
  • .Bias polarity switch 210 provides for reversingthe polarity of the bias voltage appearing across resistor 18.
  • Rheostat 221 provides for adjusting the rate of decay of the starting bias voltage when silicon-controlled switch 198 is opened (turned off).
  • An indicatinglamp 222 is connected between the anode gate 199 of silicon-controlled.switch 198 and the positive supply voltage terminal 17p via a resistor 224.
  • Zener diode 223 is connected across the indicator lamp 222 to limit the voltage'thereacross.
  • the indicator lamp serves to give a visual indication of when silicon-controlled switch 198 is on and, hence, when the firing-time computer is preconditioned for starting.
  • the invention described above can readily be adapted to control the starting of a l2-pulse converter comprising two six-pulse bridges whose DC terminals are connected in series to the DC link and whose AC terminals are respectively connected to a three-phase AC power system by means of two sets of polyphase transformer windings which are phase displaced 30 electrical degrees with respect to each other.
  • the control components 27, 28, and 31-36 shown in FIG. 3 for one six-pulse bridge would be duplicated for the additional bridge.
  • a predetermined amount e.g. 60
  • successful starting can be obtained by having a common switch driver 45 actuate the blocking switches 28 of both bridges simultaneously.
  • my invention can be used to simultaneously start three bridges in an 18- pulse converter (with a maximum initial firing angle of 50) or four bridges in a 24-pulse converter (with a maximum initial firing angle of 45).
  • the respective bridges of a 12 or more pulse converter can be started seriatim, each in the 6- pulse mode hereinbefore described.
  • operation of the switch driver 45 can supply, via the output terminal 173, the starting command for another converter, and the blocking switch 28, 28 at the other converter can be arranged to immediately respond to this command. If such a scheme is used in a situation where the distal converter is not coordinated with the local converter by the coincidence detecting function previously described (i.e., coincidence detector input 121 omitted), and where the alternating voltage of the system to which the AC terminals of the distal converter are connected is not synchronized with that of the local AC system, the initial gate pulses for the valves of the distal converter will have a random firing angle which might be unpropitious.
  • Improper firing can nevertheless be avoided by initially preconditioning the firing time computer associated with the distal converter for generating gate pulses characterized by a firing angle which is no greater than the maximum permissible initial firing angle minus 360/N degrees, where N is the number of sequentially fired valves forming the converter.
  • the firing angle could be preset at 20 which equals the maximum angle 60 minus 360/12 degrees less a safety margin of
  • the blocking switch of the control means for the l2-pulse converter discussed in the preceding paragraph will immediately disable the idle-causing blocking means, whereupon simultaneous gate pulses are generated for and applied to the four valves which, in the normal firing sequence, in turn precede the one valve that is due to be fired by the gate pulse next generated, and successful starting of the converter is obtained.
  • This can be illustrated, by way of example, by assuming that the incidence of a starting command is 15 electrical degrees before the time when the control signal for valve 3 in the leading bridge is due to commence.
  • the foregoing random mode of operation of my invention is similar in result to the scanning mode previously described.
  • suitable means isprovided initially to precondition the firing time computer for generating control signals whose delay angle varies with time between predetermined maximum and minimum values. If the maximum value were set, for example, at 50 and the minimum at 20 in a l2-pulse converter, the moment of coincidence of the starting signal and the leading edge of one of the control signals, and hence the initial firing angle, could actually be anywhere in between. Since the initial firing angle is uncertain but within a proper range in either case, it may be preferable to use the random" mode of operation at the distal converter of the system, thereby eliminating the need for detecting pulse coincidence at opposite ends of the DC link.
  • the components and circuits of the modified starting bias means are intended to be the same as shown in FIG. 8 except for those changes and additions specifically indicated in FIG. 8A.
  • the modified version will operate in the manner previously described, in so far as its initial preconditioning effect on the firing time computer is concerned. However, in H6. 8A operation of the switch driver 45 is used to initiate an augmented preconditioning effect instead of immediately disabling the bias means.
  • the initially established value e.g. 20
  • a higher preset limit e.g.,'80
  • the above-described firing angle increase occurs over an operating interval of the order of a few milliseconds, for example, which interval is determined by the time constant of the charging circuit for the capacitor 220.
  • this time constant is selected so that the rate at which the firing angle increases to its higher limit will approximate the rate of rise of current in the DC link.
  • the starting bias means is disabled. Since the increase in firing angle was accompanied by a reduction in the DC voltage generated by the converters, the DC link current is now changing much less rapidly and is closer to the ordered value when the regulator assumes control of the firing angle. This results in a more orderly starting process than would be obtained if the regulator were allowed to take over control of the firing angle at a time when a large error exists between the ordered current and the actual current.
  • the modified starting bias means depicted in FIG. 8A is disabled in delayed response to the converter being started.
  • the disabling action is the same as that described in connection with FIG. 8 except that it is initiated by a timer 234 which is coupled through the capacitor 219 to the resistor 218.
  • the timer itself is activated when the converter starts, either by a current-sensing circuit 235 which responds to a threshold magnitude of current in the line 7 of the DC link, or alternatively by a signal conveyed over broken line 236 from the output terminal 173 of the switch driver.
  • the timer 234 can be arranged to delay disabling of the modified bias means for approximately 8 milliseconds, for example.
  • means other than the modified starting bias circuit that is particularly described above can be used to incrementally adjust the timing of the gate pulses during the early stages of the startingprocess.
  • this function can altematively be incorporated in the companion circuitry that is provided to impose limits on the firingtime computer 19.
  • the. same. basic starting scheme is applicable to either analog or digital forms of converter controls.
  • the .distributor20 can bedesigned to provide control signals'of 180 duration instead of l20?, in which event an additional but harmless gate pulse will be applied to a third valve. of the bridge at-the instant of starting; Ithas already been pointed out that the invention is useful for startinga convertereither independently or in cooperation with at'least'one otherconverter at the same'or a remoteterminal of the HVDC power transmission system.
  • control means for cyclically generating a succession of relatively short gate pulsesfor the respectivevalves of the converter and for applying said pulses to corresponding valves-so as'to firethe valves in saidnormalsequence;
  • controltmeans including meansinitially operative to cause said control means to idle, in which statethe timing of said gate pulses is determinablebut'no gate. pulses are actually applied .to said valves;
  • disabling means connected to said'control means and operative to disable said; initially operative means in response to the. coincidence of said starting signal being produced and one of said gate pulses being-due;
  • control means being arranged upon operation of said disabling means to apply-said one gate pulse tothecorrespondingvalve and simultaneously to applyagate pulse to the preceding'valve in said normal sequence, thereby starting the converter.
  • control means for cyclically generating a succession of relativelyshort gatepulses for the respective valvesofthe converter and for'applying said pulses tocorresponding valves so as to fire the valves in said normal sequence;
  • control means including meansinitiallyoperative to cause said control means to idle, i'n which .state the timing of said gate pulses is determinable but no gate pulses are actually applied'to said valves;
  • disabling means connected to said control means and operative in response to said starting-signal to disable the initially operative. means which is identified in the above paragraph (b) when one of said gate pulses is due;
  • said'control means beingsarran'ged upon operation-of said disabling means to apply said one gate pulse to the corresponding valve and simultaneously to apply a gate pulse to the.preceding-valve invsaid normal sequence, thereby startingthe converter;
  • a. .control means'for' cyclically generating a succession of relatively short: gate..pulses' for. the respective valves of saidfirst converterand for -applying said pulses to corresponding'valves so astofire the valves in said normal sequence;
  • said.control meansineluding means initially operative to cause. said control means to idle, in which state the timing of saidgate pulses is determinable but no gate pulses are actually applied torsaidvalves; meansforproducing astarting signal; and disabling meansnconnected to said control means and to said startingzsignalproducing means and also adapted to be. connected ito similar control means associated with said other-converter, saiddisablingmeans being operative to disableasaid:initiallypperativemeans in response to the coincidenceof i. saidstartingsignal,
  • control -means -forrsaid firstrconverter being arranged upon operation of said'ldisablingmeans to apply said one gate pulseto thecorresponding valve and simultaneously to 'applya-igateipulse to the:preceding valve in said normal sequence, thereby startingsaidfirst converter.
  • first meansassociated withthe converter for cyclically generatinga family'of N'control signals for effecting turn onof*the.respective-valves-of'thatconverter in a predeterminedsequence, each" of saidscontrol'signals subsisting appreciablyJonger-than llNf;
  • b.- avalve-firing system comprising N second means respectively operative when activated to transmit relatively shortturn-on pulses to each'valvein'tum;
  • an electric power converter comprising 6 electric valves connected in a double-way bridge configuration between a set of polyphase AC conductors and a pair of DC terminals, the combination of:
  • starting bias means for preconditioning said first means so that the initial firing angle of said control signals can not exceed 60 electrical degrees
  • valve-firing system comprising six means respectively operative when activated to apply relatively short gate pulses to each valve in turn; means interconnecting said first means and said valve-firing system for respectively activating each of, said six means in response to the existence of a corresponding control signal;
  • said interconnecting means including blocking means for initially preventing activation of any one of said six means;
  • g. means responsive to the converter starting for disabling said starting bias means.
  • an improved control circuit comprising:
  • first means associated with each of said converters for cyclically generating a series of control signals for effecting turn on of the respective valves of that converter in a predetermined sequence, the control signals generated by the first means at said first converter subsisting for appreciably longer than lNf and the control signals generated by the first means at said second converter subsisting appreciably longer than l/Nf';
  • second means connected to each of said first means and operative in response to the existence of the control signals respectively generated thereby for sequentially transmitting relatively short turn-on pulses to the respective valves of the associated converter; and
  • third means at each converter for initially blocking operation of the second means until disabled, said third means including means for disabling the same in response to the coincidence of;
  • an improved control circuit comprising:
  • means 42 for deriving a series of short pulses from the control signals of each first set
  • a cold starting process fora multivalve, double-way electric power converting bridge including the steps of a. cyclically generating a family of staggered, relatively long control signals adapted to activate a valve-firing system for turning on the respective valves of the bridge in a predetermined normal sequence in timed relation to the voltages across the AC terminals of the bridge;
  • control means for cyclically generating a succession of relatively short gate pulses for the respective valves of the converter and for applying said pulses to corresponding valves so as to fire the valves in said normal sequence;
  • control means including means initially operative to cause said con,rol means to idle, in which state the timing of said gate pulses is determinable but no gate pulses are actually applied to said valves;
  • disabling means connected to said control means and operative in immediate response to receipt of a starting command to disable the initially operative means which is identified in the above paragraph (b);
  • control means being arranged upon operation of said disabling means to generate and apply simultaneous gate.
  • an improved control circuit comprising:
  • first means associated with the converter for cyclically generating a family of N control signals for effecting turn on of the respective valves of that converter in a predetermined sequence in timed relation to the alternating voltage, each of said control signals subsisting appreciably longer than l/Nf;
  • starting bias means connected to said first means for establishing an initial firing angle of said control signals no greater than a predetermined maximum permissible initial firing angle minus 360/N degrees;
  • blocking means connected to said third means for initially preventing activation of any second means until disabled in response to said command.
  • an improved control circuit comprising:
  • c. means associated with said first converter and responsive to the coexistence of a starting command and one of said short pulses for deriving from the control signals at said first converter a set of gate pulses for the valves of that converter, thereby starting said first converter;
  • an improved control circuit comprising:
  • a valve-firing system comprising N second means respectively operative when activated to transmit relatively short turn-on pulses to each valve in turn;
  • said third means including blocking means for initially preventing activation of any second means until disabled;
  • bias means connected to said first means for temporarily effecting a progressively increasing firing angle in response to starting the converter.

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  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Inverter Devices (AREA)
  • Ignition Installations For Internal Combustion Engines (AREA)
  • Rectifiers (AREA)
US88668A 1970-11-12 1970-11-12 Starting control scheme for rectifier-inverter systems Expired - Lifetime US3648147A (en)

Priority Applications (9)

Application Number Priority Date Filing Date Title
US88668A US3648147A (en) 1970-11-12 1970-11-12 Starting control scheme for rectifier-inverter systems
CA123820A CA938998A (en) 1970-11-12 1971-09-28 Starting control scheme for rectifier-inverter systems
DE19712155900 DE2155900A1 (de) 1970-11-12 1971-11-10 Anlaufsteuerung für Gleichrichter-Umformersysteme
GB5542473A GB1377963A (en) 1970-11-12 1971-11-11 Starting control scheme for redtifier-inverter systems
GB5238871A GB1377962A (en) 1970-11-12 1971-11-11 Starting control scheme for rectifier-inverter systems
JP9002271A JPS4710574A (fr) 1970-11-12 1971-11-12
FR7140642A FR2114654A6 (fr) 1970-11-12 1971-11-12
IT31003/71A IT968034B (it) 1970-11-12 1971-11-12 Controllo di avviamento per siste mi comprendenti raddrizzatori e invertituri
JP13799378A JPS54115729A (en) 1970-11-12 1978-11-10 Starttup control apparatus for power converter

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JP (2) JPS4710574A (fr)
CA (1) CA938998A (fr)
DE (1) DE2155900A1 (fr)
FR (1) FR2114654A6 (fr)
GB (2) GB1377962A (fr)
IT (1) IT968034B (fr)

Cited By (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3848175A (en) * 1973-10-24 1974-11-12 Gen Electric Starting inhibit scheme for an hvdc converter
US3992659A (en) * 1974-07-19 1976-11-16 Allmanna Svenska Elektriska Aktiebolaget High voltage direct current transmission
US4023086A (en) * 1974-07-10 1977-05-10 Asea Aktiebolag Control system for rectifier equipment
US4638415A (en) * 1984-03-01 1987-01-20 Siemens Aktiengesellschaft Method and apparatus for resumption of normal operation of a high-voltage D. C. transmission line
US4638416A (en) * 1984-03-01 1987-01-20 Siemens Aktiengesellschaft Method and apparatus for high-voltage D.C. transmission with a bypass circuit for malfunctions
US4648018A (en) * 1984-03-01 1987-03-03 Siemens Aktiengesellschaft Method and apparatus to operate a high-voltage DC transmission system (HVDC) with automatic control of the converters
US5740023A (en) * 1996-05-24 1998-04-14 Lucent Technologies Inc. Control system for a modular power supply and method of operation thereof
US20040085046A1 (en) * 2002-11-01 2004-05-06 General Electric Company Power conditioning system for turbine motor/generator
EP2823557B1 (fr) 2012-03-09 2016-08-10 ABB Technology AG Unité électrique pour centrale de pompage

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS5349235A (en) * 1976-10-15 1978-05-04 Central Res Inst Of Electric Power Ind Starting system of multi-terminals direct current power transmission

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US21697A (en) * 1858-10-05 Dubois d
US3315146A (en) * 1962-11-09 1967-04-18 Rotax Ltd Inverters operated by controlled rectifiers
US3399337A (en) * 1966-11-10 1968-08-27 Harnischfeger Corp Electrical control circuit for converting alternating current to adjustable magnitude direct current
US3401327A (en) * 1966-03-11 1968-09-10 North Electric Co Inverter circuit having increased frequency starting
US3423664A (en) * 1967-05-24 1969-01-21 Gen Electric Means for suppressing commutation transients in a controlled rectifier converter for high-voltage electric power applications
US3470442A (en) * 1966-07-05 1969-09-30 English Electric Co Ltd Control systems for h.v.d.c. transmission links

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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US21697A (en) * 1858-10-05 Dubois d
US3315146A (en) * 1962-11-09 1967-04-18 Rotax Ltd Inverters operated by controlled rectifiers
US3401327A (en) * 1966-03-11 1968-09-10 North Electric Co Inverter circuit having increased frequency starting
US3470442A (en) * 1966-07-05 1969-09-30 English Electric Co Ltd Control systems for h.v.d.c. transmission links
US3399337A (en) * 1966-11-10 1968-08-27 Harnischfeger Corp Electrical control circuit for converting alternating current to adjustable magnitude direct current
US3423664A (en) * 1967-05-24 1969-01-21 Gen Electric Means for suppressing commutation transients in a controlled rectifier converter for high-voltage electric power applications

Cited By (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3848175A (en) * 1973-10-24 1974-11-12 Gen Electric Starting inhibit scheme for an hvdc converter
US4023086A (en) * 1974-07-10 1977-05-10 Asea Aktiebolag Control system for rectifier equipment
US3992659A (en) * 1974-07-19 1976-11-16 Allmanna Svenska Elektriska Aktiebolaget High voltage direct current transmission
US4638415A (en) * 1984-03-01 1987-01-20 Siemens Aktiengesellschaft Method and apparatus for resumption of normal operation of a high-voltage D. C. transmission line
US4638416A (en) * 1984-03-01 1987-01-20 Siemens Aktiengesellschaft Method and apparatus for high-voltage D.C. transmission with a bypass circuit for malfunctions
US4648018A (en) * 1984-03-01 1987-03-03 Siemens Aktiengesellschaft Method and apparatus to operate a high-voltage DC transmission system (HVDC) with automatic control of the converters
US5740023A (en) * 1996-05-24 1998-04-14 Lucent Technologies Inc. Control system for a modular power supply and method of operation thereof
US20040085046A1 (en) * 2002-11-01 2004-05-06 General Electric Company Power conditioning system for turbine motor/generator
EP2823557B1 (fr) 2012-03-09 2016-08-10 ABB Technology AG Unité électrique pour centrale de pompage

Also Published As

Publication number Publication date
CA938998A (en) 1973-12-25
JPS54115729A (en) 1979-09-08
FR2114654A6 (fr) 1972-06-30
DE2155900A1 (de) 1972-05-25
IT968034B (it) 1974-03-20
GB1377963A (en) 1974-12-18
GB1377962A (en) 1974-12-18
JPS4710574A (fr) 1972-05-27

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