HVDC Floating current order system
First Claim
1. In an HVDC electric power delivery system including power converter means at each terminal of the system;
- each converter means comprising;
a plurality of controllable electric valves connected between alternating current and direct current electric power conductors, means for cyclically firing said valves in a predetermined sequence and at firing angles measured with respect to the alternating voltage that can be varied to control the flow of power between said alternating current and direct current power conductors, and regulator means for comparing a plurality of control signals which respectively represent different operating characteristics of the HVDC system during operation and for deriving an output error control signal for controlling the firing angle of said valves, the regulator means associated with one of said converter means receiving as one input a current order control signal for controlling the current transmitted by said system;
the improvement comprising;
(a) floating current order control means coupled to the regulator means of the power converter means not in control of current for the HVDC system for supplying to said latter regulator means as one of its input control signals a floating current order control signal for controlling the current ordered from said latter converter means,(b) said floating current order control signal being responsive to and dependent upon the magnitude of the direct current flowing through said direct current power conductor plus a current margin signal having a predetermined magnitude and a positive polarity with power flow in the system in one direction and a negative polarity with the power flow in the system in the opposite direction, and(c) said floating current order control means and the regulator means associated therewith being capable of acting to control the current ordered from said latter converter means without relying upon receipt of said current order control signal at said latter converter means.
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Accused Products
Abstract
An HVDC electric power delivery system having a floating current order current control subsystem is described. The system is comprised by power converters at each end of an HVDC power conductor link each of which includes a plurality of controllable electric valves connected between alternating current and the direct current electric power conductors together with means for cyclically firing the valves in a predetermined sequence and at firing angles measured with respect to the alternating voltage that can be varied to control the flow of power between the alternating current system and the direct current system. Each of the power converters further includes a regulator for comparing a plurality of input control signals which respectively represent different predetermined operating characteristics of the HVDC system during operation and for deriving an output error control signal that controls the firing angles of the valves. The present invention makes available a floating current order control subsystem which is coupled to the regulator of each power converter for supplying thereto as one of the input control signals a floating current order control signal representative of the magnitude of the direct current flowing in the direct current power conductors plus a predetermined current margin whose polarity is determined by the direction of power flow. The floating current order control subsystem further includes rate limiting means for limiting the rate of change of the floating current order control signal to some predetermined rate of change value either in an increasing or decreasing magnitude direction and maximum and minimum boundary setting limits for setting predetermined maximum and minimum magnitude value limits above and below which the floating current order control signal is not allowed to change the load current magnitude so that the load current magnitude is maintained within predetermined maximum and minimum load current values.
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Citations
34 Claims
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1. In an HVDC electric power delivery system including power converter means at each terminal of the system;
- each converter means comprising;
a plurality of controllable electric valves connected between alternating current and direct current electric power conductors, means for cyclically firing said valves in a predetermined sequence and at firing angles measured with respect to the alternating voltage that can be varied to control the flow of power between said alternating current and direct current power conductors, and regulator means for comparing a plurality of control signals which respectively represent different operating characteristics of the HVDC system during operation and for deriving an output error control signal for controlling the firing angle of said valves, the regulator means associated with one of said converter means receiving as one input a current order control signal for controlling the current transmitted by said system;
the improvement comprising;(a) floating current order control means coupled to the regulator means of the power converter means not in control of current for the HVDC system for supplying to said latter regulator means as one of its input control signals a floating current order control signal for controlling the current ordered from said latter converter means, (b) said floating current order control signal being responsive to and dependent upon the magnitude of the direct current flowing through said direct current power conductor plus a current margin signal having a predetermined magnitude and a positive polarity with power flow in the system in one direction and a negative polarity with the power flow in the system in the opposite direction, and (c) said floating current order control means and the regulator means associated therewith being capable of acting to control the current ordered from said latter converter means without relying upon receipt of said current order control signal at said latter converter means. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20)
- each converter means comprising;
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21. A floating current order control for use in:
- an HVDC electric power delivery system of the type employing at each terminal of the system power converter means connected between alternating current and direct current electric power conductors for controlling the flow of electric power between said alternating current and direct current electric power conductors, one converter means usually being in control of the direct current transmitted by said system at a given instant during system operation, said floating current order control comprising;
(a) direct current sensing means for sensing the magnitude of the direct current flowing in the direct current electric power conductors and deriving a feedback control signal representative of the actual measured value of direct current magnitude. (b) current margin signal generating means for deriving a current margin signal whose magnitude is representative of a desired value of current margin magnitude and whose polarity is either positive or negative dependent upon the desired direction of power flow through the power converter means, and (c) combining circuit means for combining said feedback control signal and said current margin signal and deriving a floating current order control signal for use in controlling the current ordered from the power converter means not then in control of system current, (d) said floating current order control means acting to control the current ordered from said latter converter means without relying upon receipt at said latter converter means of the current order control signal used for controlling said one converter means. - View Dependent Claims (22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33)
- an HVDC electric power delivery system of the type employing at each terminal of the system power converter means connected between alternating current and direct current electric power conductors for controlling the flow of electric power between said alternating current and direct current electric power conductors, one converter means usually being in control of the direct current transmitted by said system at a given instant during system operation, said floating current order control comprising;
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34. In an HVDC ekectric power delivery system including power converter means at each terminal of the system, each of said power converter means comprising a plurality of controllable electric valves connected between alternating current and direct current electric power conductors and means for cyclically firing said valves in a predetermined sequence and at firing angles measured with respect to the alternating voltage that can be varied to control the flow of power between said alternating current and direct current power conductors and having regulator means for each of said power converter means for comparing a plurality of control signals which respectively represent different operating characteristics of the HVDC system during operation and for deriving an output error control signal for controlling the firing angle of said valves;
- the improvement comprising;
(a) floating current order control means for each of said power converter means for supplying to the regulator means of the power converter means not then in control of current for the system a floating current order control signal, (b) said floating current order control signal being responsive to and dependent upon the magnitude of the direct current flowing through said direct current power conductors plus a current margin signal, (c) said floating current order control means for the respective power converter means at each terminal of the system including means for supplying a current margin signal of known magnitude and either positive or negative polarity dependent upon the direction of power flow through the respective power converter means whereby changes may be made in the level of the direct current transmitted by the system even in the absence of communications between the two terminals without risk of undesired reversal in the direction of power flow, and (d) said floating current order control means for each individual converter means and the regulator means associated therewith being capable of acting to control the current ordered from the associated converter means when not in control of system current without relying upon receipt at said latter converter means of the current order control signal used for controlling the particular converter means that is then in control of system current.
- the improvement comprising;
Specification