Thyristor controlled series capacitor vernier control system

Claim 3

A method according to claim 1 further including the step of predicting an upcoming value of a parameter of interest for power flowing through the thyristor controlled series capacitor system.

Claim 4

A method according to claim 2 wherein the step of predicting an upcoming value of a parameter of interest comprises the step of predicting the upcoming value at a predetermined intra-cycle time during a thyristor current pulse.

Claim 5

A method according to claim 2 wherein the step of predicting an upcoming value of a parameter of interest comprises the step of predicting an upcoming initial capacitor offset voltage value.

Claim 6

A method according to claim 2 wherein the step of predicting an upcoming value of a parameter of interest comprises the step of predicting capacitor voltage.

Claim 7

A method according to claim 5 wherein the step of predicting the capacitor voltage comprises predicting the capacitor voltage at a predetermined intra-cycle time during a thyristor current pulse using the monitored line current.

Claim 8

A method according to claim 1 further including the step of modulating the switching of the commutating circuit to provide a resistive component behavior in the transmission line for the thyristor controlled series capacitor system.

Claim 9

A method according to claim 1 further including the steps of: monitoring a thyristor current pulse flowing through the commutating circuit; and responsive to the monitoring of the thyristor current pulse, correcting the predicted upcoming firing time.

Claim 10

A method according to claim 8 wherein the monitoring step comprises monitoring an ampsecond value of the thyristor current pulse flowing through the commutating circuit.

Claim 11

A method according to claim 1 further including the steps of: predicting an upcoming value of a parameter of interest for power flowing through the thyristor controlled series capacitor system; modulating the switching of the commutating circuit to provide a resistive component behavior in the transmission line for the thyristor controlled series capacitor system; monitoring the thyristor current pulse flowing through the commutating circuit; and responsive to the monitoring of the thyristor current pulse, correcting the predicted upcoming firing time.

Claim 12

A method according to claim 1 further including the steps of: predicting the capacitor voltage at a predetermined intra-cycle time during a thyristor current pulse using the monitored line current; modulating the switching of the commutating circuit to provide a resistive component behavior for the thyristor controlled series capacitor system with respect to the transmission line; monitoring an ampsecond value of the thyristor current pulse flowing through the commutating circuit; and responsive to the monitoring of the thyristor current pulse, correcting the predicted upcoming firing time using the monitored thyristor current pulse ampsecond value.

Claim 13

A method according to claim 1 further including the steps of: determining a predicted normal value of the capacitor voltage without any offset from the monitored line current; determining a measured line current offset component from the monitored line current; predicting an intra-cycle offset capacitor voltage by multiplying the measured line current offset component by a gain value; predicting an initial capacitor offset voltage at a predetermined intra-cycle time during a thyristor current pulse by subtracting the predicted normal value of the capacitor voltage without any offset from the sum of the monitored capacitor voltage and the intra-cycle offset capacitor voltage; and switching the commutating circuit in response to the predicted initial capacitor offset voltage.

Claim 14

A method according to claim 1 further including the steps of: predicting a normal value of the capacitor voltage without any offset from the monitored line current; predicting an initial capacitor offset voltage by subtracting the predicted normal value of the capacitor voltage without any offset from the monitored capacitor voltage; determining a measured line current offset component from the monitored line current; modulating a capacitor offset voltage command received from a higher-level controller to provide a resistive component behavior for the thyristor controlled series capacitor system with respect to the transmission line; limiting the initial capacitor offset voltage and the modulated capacitor offset voltage command to provide a limited final capacitor offset voltage and switching the commutating circuit in response to the predicted initial capacitor offset voltage and the limited final capacitor offset voltage.

Claim 15

A method according to claim 1 further including the steps of: predicting a normal value of the capacitor voltage without any offset from the monitored line current; predicting an initial capacitor offset voltage by subtracting the predicted normal value of the capacitor voltage without any offset from the monitored capacitor voltage; limiting the initial capacitor offset voltage and a capacitor offset voltage command received from a higher-level controller to provide a limited final capacitor offset voltage; predicting a firing angle command signal from the initial capacitor offset voltage and the limited final capacitor offset voltage; and switching the commutating circuit in response to the predicted firing angle command signal.

Claim 16

A method according to claim 14 further including the steps of: predicting the offset voltage change by subtracting the initial capacitor offset voltage from the limited final capacitor offset voltage; monitoring an ampsecond value of the thyristor current pulse flowing through the commutating circuit; and correcting the predicted upcoming firing time using the monitored thyristor current pulse ampsecond value and the predicted the offset voltage change.

Claim 17

A method according to claim 1 further including the steps of: predicting a normal value of the capacitor voltage without any offset from the monitored line current; determining a measured line current offset component from the monitored line current; predicting an intra-cycle offset capacitor voltage by multiplying the measured line current offset component by a gain value; predicting an initial capacitor offset voltage at a predetermined intra-cycle time during the thyristor current pulse by subtracting the predicted normal value of the capacitor voltage without any offset from the sum of the monitored capacitor voltage and the intra-cycle offset capacitor voltage; modulating a capacitor offset voltage command received from a higher-level controller to provide a resistive component behavior for the thyristor controlled series capacitor system with respect to the transmission line; limiting the initial capacitor offset voltage and the modulated capacitor offset voltage command to provide a limited final capacitor offset voltage; predicting a firing angle command from the initial capacitor offset voltage and the limited final capacitor offset voltage; predicting the offset voltage change by subtracting the initial capacitor offset voltage from the limited final capacitor offset voltage; monitoring an ampsecond value of the thyristor current pulse flowing through the commutating circuit; correcting the predicted firing angle command using the monitored thyristor current pulse ampsecond value and the predicted the offset voltage change to provide a final firing angle command; determining a predetermined firing timing for the thyristors of the commutating circuit from the monitored line current; and switching the commutating circuit in response to the predetermined firing timing and the final firing angle command.

Claim 20

A method according to claim 17 further including the step of predicting an upcoming value of a parameter of interest for power flowing through the thyristor controlled series capacitor system.

Claim 21

A method according to claim 18 wherein the step of predicting an upcoming value of a parameter of interest comprises the step of predicting the upcoming value at a predetermined intra-cycle time during a thyristor current pulse.

Claim 22

A method according to claim 17 further including the step of predicting the capacitor voltage at a predetermined intra-cycle time during the thyristor current pulse using the monitored line current.

Claim 23

A method according to claim 17 further including the step of modulating the switching of the commutating circuit to provide a resistive component behavior in the transmission line for the thyristor controlled series capacitor system.

Claim 24

A method according to claim 17 further including the steps of: monitoring a thyristor current pulse flowing through the commutating circuit; and responsive to the monitoring of the thyristor current pulse, correcting the predicted upcoming firing time.

Claim 25

A method according to claim 17 further including the steps of: monitoring an ampsecond value of the thyristor current pulse flowing through the commutating circuit; and responsive to the monitoring of the thyristor current pulse, correcting the predicted upcoming firing time using the monitored thyristor current pulse ampsecond value.

Claim 26

A vernier controller for controlling a thyristor controlled series capacitor system having a capacitor with a capacitive reactance in series with a substantially inductive transmission line, a thyristor switched inductive commutating circuit in parallel with the capacitor, a voltage sensor monitoring the capacitor voltage across the capacitor, and a current sensor monitoring the line current through the transmission line, the controller comprising: a capacitor voltage predictor for predicting an initial capacitor offset voltage from the monitored line current received from the current sensor and the monitored capacitor voltage received from the voltage sensor; a limiter for limiting the initial capacitor offset voltage and a capacitor offset voltage command received from a higher-level controller to provide a limited final capacitor offset voltage; a storage device for determining a predicted firing angle from the limited final capacitor offset voltage and the predicted initial capacitor offset voltage; a synchronizer for generating a first timing signal in response to the monitored line current received from the current sensor; and a firing time computer for switching the commutating circuit to conduct a thyristor current pulse therethrough in response to the first timing signal and the predicted firing angle.

Claim 27

A vernier controller for controlling a thyristor controlled series capacitor system having a capacitor with a capacitive reactance in series with a substantially inductive transmission line, a thyristor switched inductive commutating circuit in parallel with the capacitor, a voltage sensor monitoring the capacitor voltage across the capacitor, and a current sensor monitoring the line current through the transmission line, the controller comprising: a capacitor voltage predictor for predicting an initial capacitor offset voltage from the monitored line current received from the current sensor and the monitored capacitor voltage received from the voltage sensor; a limiter for limiting the initial capacitor offset voltage and a capacitor offset voltage command received from a higher-level controller to provide a limited final capacitor offset voltage; a storage device for determining a predicted firing angle from the limited final capacitor offset voltage and the predicted initial capacitor offset voltage; a synchronizer for generating a first timing signal in response to the monitored line current received from the current sensor; and a firing time computer for switching the commutating circuit to conduct a thyristor current pulse therethrough in response to the first timing signal and the predicted firing angle.

Claim 28

A vernier controller according to claim 24 wherein the a capacitor voltage predictor comprises: normal capacitor voltage determining device for determining a normal capacitor voltage without any offset component from the monitored line current received from the current sensor; and voltage offset comparator for subtracting the normal capacitor voltage from the monitored capacitor voltage received from the voltage sensor to provide the initial capacitor offset voltage.

Claim 29

A vernier controller according to claim 25 wherein the capacitor voltage predictor further includes: a phase locked loop device for determining a second timing signal and a sinusoidal function corresponding to the first timing signal from the monitored line current received from the current sensor, with the phase locked loop device also serving as the synchronizer for determining the first timing signal; a capacitive reactance factoring device for multiplying the sinusoidal function by the capacitive reactance of the capacitor to provide a factored sinusoidal function; and a transduction device for determining a normal line current magnitude from the monitored line current and the second timing signal; wherein the normal capacitor voltage determining device determines the normal capacitor voltage without any offset component from the factored sinusoidal function and the normal line current magnitude.

Claim 30

A vernier controller according to claim 25 further including: a phase locked loop device for determining a second timing signal from the monitored line current received from the current sensor, with the phase locked loop device also serving as the synchronizer for determining the first timing signal; a transduction device for determining a line current offset component from the monitored line current and the second timing signal; and a voltage prediction enhancer responsive to the line current offset component for enhancing the prediction of the initial capacitor offset voltage by the capacitor voltage predictor to predict the initial capacitor offset voltage during the thyristor current pulse.

Claim 31

A vernier controller according to claim 25 further including: a phase locked loop device for determining a second timing signal from the monitored line current received from the current sensor, with the phase locked loop device also serving as the synchronizer for determining the first timing signal; a transduction device for determining a line current offset component from the monitored line current and the second timing signal; and a resistive effect modulator for modulating the capacitor offset voltage command upon receipt from the higher-level controller to provide a resistive component behavior for the thyristor controlled series capacitor system with respect to the transmission line.

Claim 32

A vernier controller according to claim 24 further including: a thyristor ampsecond monitor for monitoring an ampsecond value of the thyristor current pulse flowing through the commutating circuit; and a thyristor ampseconds corrector for correcting the predicted firing angle in response to the monitored thyristor current pulse ampsecond value to provide a final firing angle; wherein the firing time computer is responsive to the final firing angle.

Claim 33

A vernier controller according to claim 24 wherein the capacitor voltage predictor comprises: a phase locked loop device for determining a second timing signal from the monitored line current received from the current sensor, with the phase locked loop device also serving as the synchronizer for determining the first timing signal; a transduction device for determining a line current offset component from the monitored line current and the second timing signal; a voltage prediction enhancer responsive to the line current offset component for enhancing the prediction of the initial capacitor offset voltage by the capacitor voltage predictor to predict the initial capacitor offset voltage during the thyristor current pulse; a resistive effect modulator for modulating the capacitor offset voltage command upon receipt from the higher-level controller to provide a resistive component behavior for the thyristor controlled series capacitor system with respect to the transmission line; a thyristor ampsecond monitor for monitoring an ampsecond value of the thyristor current pulse flowing through the commutating circuit; and a thyristor ampseconds corrector for correcting the predicted firing angle in response to the monitored thyristor current pulse ampsecond value to provide a final firing angle; wherein the firing time computer is responsive to the final firing angle.

Claim 34

A thyristor controlled series capacitor system for compensating a substantially inductive transmission line, comprising: a capacitor in series with the transmission line; a thyristor switched inductive commutating circuit in parallel with the capacitor, the commutating circuit having a thyristor valve responsive to a firing command to conduct a thyristor current pulse therethrough; a voltage sensor monitoring a capacitor voltage across the capacitor; a current sensor monitoring a line current flowing through the transmission line; and a controller responsive to the voltage and current sensors, and to a capacitor offset voltage command received from a higher-level controller, to provide the firing command to the thyristor valve, and responsive to the current sensor to synchronize the timing of the firing command.

Claim 35

A thyristor controlled series capacitor system for compensating a substantially inductive transmission line, comprising: a capacitor in series with the transmission line; a thyristor switched inductive commutating circuit in parallel with the capacitor, the commutating circuit having a thyristor valve responsive to a firing command to conduct a thyristor current pulse therethrough; a voltage sensor monitoring a capacitor voltage across the capacitor; a current sensor monitoring a line current flowing through the transmission line; and a controller responsive to the voltage and current sensors, and to a capacitor offset voltage command received from a higher-level controller, to provide the firing command to the thyristor valve, and responsive to the current sensor to synchronize the timing of the firing command.

Claim 36

A thyristor controlled series capacitor system according to claim 31 wherein the controller includes a resistive modeling modulator for modulating the firing of the thyristor valve to provide a resistive component behavior for the thyristor controlled series capacitor system with respect to the transmission line.

Claim 37

A thyristor controlled series capacitor system according to claim 31 wherein the controller includes a firing predictor for predicting an upcoming firing time from the monitored capacitor voltage and line current.

Claim 38

A thyristor controlled series capacitor system according to claim 33 wherein the controller further includes a voltage prediction enhancer using the monitored line current to enhance the prediction of the firing predictor to predict an upcoming firing time at a predetermined intra-cycle time during a thyristor current pulse.

Claim 39

A thyristor controlled series capacitor system according to claim 33 wherein the controller further includes: a thyristor ampsecond monitor for monitoring an ampsecond value of the thyristor current pulse flowing through the commutating circuit; and an ampsecond corrector for correcting the predicted upcoming firing time using the monitored thyristor current pulse ampsecond value.