Apparatus for controlling reactive power in a HVDC system
AssigneeKabushiki Kaisha Toshiba
InventorTakami Sakai
Life of this patent
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Abstract
A power converter apparatus for a DC power transmission system or a frequency conversion system includes a control apparatus that functions such that during the operation of converters, when the output voltage of a constant reactive control circuit reaches the output voltage of a margin angle limited control circuit, a shunt reactor is interrupted or a shunt capacitor is closed, and when the output voltage of the constant reactive power control circuit reaches a control delay angle corresponding to the curve which has a difference .DELTA.Q compared with the curve P-Q at a minimum margin angle .gamma. min, the shunt reactor is closed or the shunt capacitor is interrupted.
Claims6
Apparatus for converting DC power to AC power comprising:
- means for converting DC power to AC power;
- first means for selectively rendering reactive power more leading;
- second means for selectively rendering reactive power more lagging;
- margin angle limiter control means for limiting a margin angle of said converting means;
- constant reactive control means for controlling said converting means to maintain constant a characteristics of said AC power influenced by all reactance connected to said AC power;
- means for generating a value corresponding to a control delay angle related to a characteristic of said AC power influenced by all resistance connected to said AC power;
- and
- a control structure including:
- (1) means for at least one of connecting said second means to said AC power and disconnecting said first means from said AC power when an output value of said constant reactive control means achieves a predetermined relationship with an output value of said margin angle limiter control means, and
- (2) means for at least one of disconnecting said second means from said AC power and connecting said first means to said AC power when an output value of said constant reactive control means achieves a predetermined relationship with said control delay angle value.
A power transmission system comprising:
- a first converter having an AC terminal and a DC terminal;
- a second converter having a DC terminal connected to said DC terminal of said first converter and an AC terminal;
- means for selecting one of said converters to pass power from said AC terminal to said DC terminal and the other of said converters to pass a power from said DC terminal to said AC terminal;
- first means for selectively rendering reactive power at said AC terminal of said other converter more leading;
- second means for selectively rendering reactive power at said AC terminal of said other converter more lagging;
- margin angle limiter control means for limiting a margin angle of said other converter;
- constant reactive control means for controlling said other converter to maintain constant a characteristic of AC power influenced by all reactance connected to said AC terminal of said other converter;
- means for generating a value corresponding to a control delay angle related to a characteristic of said AC power influenced by all resistance connected to said AC terminal of said other converter;
- and
- a control structure including:
- (1) means for at least one of connecting said second means to said AC terminal of said other converter and disconnecting said first means from said AC terminal of said other converter when an output value of said constant reactive control means achieves a predetermined relationship with an output value of said margin angle limiter control means, and
- (2) means for at least one of disconnecting said second means from said AC terminal of said other converter and connecting said first means to said AC terminal of said other converter when an output value of said constant reactive control means achieves a predetermined relationship with said control delay angle value.
Dependencies are inferred from the claim text.