Reactive power compensating apparatus and method for reducing in switching loss in steady state operation thereof
First Claim
1. A self-commutated static vat compensator apparatus for stabilizing a power system, comprising:
- a self-commutated converter connected to said power system, for receiving/supplying a power from/to said power system, said self-commutated converter including a DC capacitor, a DC voltage detector for detecting a DC voltage charged in the DC capacitor, and a self-turnoff switching device having a DC terminal connected to the DC capacitor, an AC terminal connected to said power system, and a control terminal to which a control pulse is applied;
voltage detection means for detecting a voltage of said power system;
current detection means for detecting a current flowing between said power system and said self-commutated converter;
system voltage control means for outputting a first target value signal of a reactive current in accordance with a difference between a voltage value of the voltage detected by said voltage detection means and a reference voltage value in order to conform the voltage of said power system to a present reference voltage corresponding to the reference voltage value;
reactive current control means connected to said system voltage control means, for outputting a second target value signal of the reactive current to be output from said self-commutated converter, in accordance with a difference between the first target value signal of the reactive current and a current value of the current detected by said current detection means;
loss reduction means for stopping the control pulse corresponding to the second target value of the reactive current supplied to the control terminal of the self-turnoff switching device when a reactive power output from said self-commutated converter is close to zero;
DC voltage control means for outputting a first target value signal of an active current in accordance with a difference between a DC voltage value of a reference DC voltage set for maintaining a DC voltage of said DC capacitor and a DC voltage value of the DC voltage detected by said DC voltage detector;
active current control means for outputting a second target value signal of the active current to be output from said self-commutated converter, in accordance with a difference between the first target value of the active current and the current value of the current detected by said current detection means; and
converter control means for receiving the second target value signal of reactive current input from said reactive current control means and the second target value signal of active current input from said active current control means, and applying the control pulse to the control terminal of the self-turnoff switching device of the self-commutated converter in response to the second target value signal of the reactive current and the second target value of the active current respectively.
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Abstract
A self-commutated static var compensator and a method is used for stabilizing a power system by controlling an output of a self-commutated converter for receiving/supplying power from/to the power system. A constant system voltage maintaining controller calculates a first target value signal of the reactive current in accordance with a difference between a reference voltage and a voltage detected by a voltage detector, and a reactive current controller generates a second target value signal of the reactive current in accordance with a difference between the first target value signal of the reactive current and a detected current. A converter controller applies a gate driving pulse to the self-commutated converter in response to the second target value signal of the reactive current and second target value signal of the active current. A loss reduction circuit stops the gate driving pulse corresponding to the second target value of the reactive current from being supplied to the gate of the self-commutated converter when reactive power output from the self-commutated converter is close to zero.
27 Citations
9 Claims
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1. A self-commutated static vat compensator apparatus for stabilizing a power system, comprising:
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a self-commutated converter connected to said power system, for receiving/supplying a power from/to said power system, said self-commutated converter including a DC capacitor, a DC voltage detector for detecting a DC voltage charged in the DC capacitor, and a self-turnoff switching device having a DC terminal connected to the DC capacitor, an AC terminal connected to said power system, and a control terminal to which a control pulse is applied; voltage detection means for detecting a voltage of said power system; current detection means for detecting a current flowing between said power system and said self-commutated converter; system voltage control means for outputting a first target value signal of a reactive current in accordance with a difference between a voltage value of the voltage detected by said voltage detection means and a reference voltage value in order to conform the voltage of said power system to a present reference voltage corresponding to the reference voltage value; reactive current control means connected to said system voltage control means, for outputting a second target value signal of the reactive current to be output from said self-commutated converter, in accordance with a difference between the first target value signal of the reactive current and a current value of the current detected by said current detection means; loss reduction means for stopping the control pulse corresponding to the second target value of the reactive current supplied to the control terminal of the self-turnoff switching device when a reactive power output from said self-commutated converter is close to zero; DC voltage control means for outputting a first target value signal of an active current in accordance with a difference between a DC voltage value of a reference DC voltage set for maintaining a DC voltage of said DC capacitor and a DC voltage value of the DC voltage detected by said DC voltage detector; active current control means for outputting a second target value signal of the active current to be output from said self-commutated converter, in accordance with a difference between the first target value of the active current and the current value of the current detected by said current detection means; and converter control means for receiving the second target value signal of reactive current input from said reactive current control means and the second target value signal of active current input from said active current control means, and applying the control pulse to the control terminal of the self-turnoff switching device of the self-commutated converter in response to the second target value signal of the reactive current and the second target value of the active current respectively. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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9. A method for stabilizing a power system by controlling an output of a self-commutated converter for receiving/supplying a power from/to said power system, said self-commutated converter comprising a DC capacitor and a self-turnoff switching device having a DC terminal connected to the DC capacitor, an AC terminal connected to said power system, and a control terminal to which a control pulse is applied, said method comprising:
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a step of calculating a first target value signal of a reactive current in accordance with a difference between a voltage of said power system and a reference voltage; a step of calculating a second target value signal of the reactive current to be output from said self-commutated converter, in accordance with a difference between the first target value signal of the reactive current and a current value of a current flowing into said self-commutated converter; a step of calculating a first target value of an active current in accordance with a difference between a DC voltage of said DC capacitor and a reference DC voltage; a step of calculating a second target value of the active current to be output from said self-commutated converter, in accordance with a difference between the first target value signal of the active current and a current value of the current flowing into the self-commutated converter; a step of applying a control pulse to the control terminal of the self-turnoff switching device of said self-commutated converter in response to the second target value signal of the reactive current and the second target value of the active current respectively; and a step of stopping the control pulse corresponding to the second target value of the reactive current from being supplied to the control terminal of the self-turnoff switching device of said self-commutated converter, when a reactive power output from said self-commutated converter is close to zero.
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Specification