BIDIRECTIONAL DIRECT CURRENT CIRCUIT BREAKER
The present invention relates to a bidirectional direct current (DC) circuit breaker for interrupting a fault current flowing through a DC line for power transmission or distribution in case a fault occurs at one side of the DC line. The bidirectional DC circuit breaker according to the present invention comprises: a main switch installed in a DC line, for interrupting the electric current of the DC line by being opened in case a fault occurs at one side or the other side of the DC line; an LC circuit, which is connected in parallel to the main switch ( 110 ) and comprises a capacitor and a reactor connected in series to each other; a switching element for charging, which is connected in series to the LC circuit and performs switching so as to supply a charging current for charging the capacitor; first and second switching elements for forming a first closed circuit between the LC circuit and the main switch and switching the flow of current in a first direction; and third and fourth switching elements for forming a second closed circuit between the LC circuit and the main switch and switching the flow of current in a second direction.
1 . A bidirectional DC circuit breaker for breaking current in a DC line, comprising:
a main switch ( 110 ), installed in the DC line, for breaking current of the DC line by being opened when a fault occurs on one side or the remaining side of the DC line;
an L/C circuit ( 130 ), which is connected in parallel with the main switch ( 110 ) and includes a capacitor ( 131 ) and a reactor ( 132 ), which are connected in series with each other;
a switching element for charging ( 140 ), which is connected in series with the L/C circuit ( 130 ) and is switched in order to supply a charging current for charging the capacitor ( 131 );
first and second switching elements ( 150 , 160 ) for forming a first closed circuit between the L/C circuit ( 130 ) and the main switch ( 110 ) and switching a flow of current in a first direction; and
third and fourth switching elements ( 170 , 180 ) for forming a second closed circuit between the L/C circuit ( 130 ) and the main switch ( 110 ) and switching a flow of current in a second direction,
wherein when the main switch ( 110 ) is opened, current is supplied to the main switch ( 110 ) in the first direction or the second direction by the voltage charged in the capacitor ( 131 ), whereby an arc generated in the main switch ( 110 ) is extinguished.
2 . The bidirectional DC circuit breaker of claim 1 , further comprising a charging resistor (Rc), installed between the L/C circuit ( 130 ) and a ground (GND), for charging the capacitor ( 131 ) using the charging current.
3 . The bidirectional DC circuit breaker of claim 1 , wherein each of the switching element for charging ( 140 ) and the first to fourth switching elements ( 150 to 180 ) includes a power semiconductor switch, turn-on/turn-off control of which is possible.
4 . The bidirectional DC circuit breaker of claim 3 , further comprising a diode ( 190 ), installed in the second closed circuit, for conducting current only in the second direction.
5 . The bidirectional DC circuit breaker of claim 4 , further comprising a nonlinear resistor ( 200 ) connected in series with the diode ( 190 ) in the second closed circuit.
6 . The bidirectional DC circuit breaker of claim 3 , wherein the first and second switching elements ( 150 , 160 ) are connected with two ends of the L/C circuit ( 130 ) and two ends of the main switch ( 110 ) in the first closed circuit so as to conduct current in the first direction.
7 . The bidirectional DC circuit breaker of claim 6 , wherein the third and fourth switching elements ( 170 , 180 ) are connected with the two ends of the L/C circuit ( 130 ) and the two ends of the main switch ( 110 ) in the second closed circuit so as to conduct current in the second direction.
8 . The bidirectional DC circuit breaker of claim 1 , wherein the switching element for charging ( 140 ) is configured to:
conduct the charging current to the capacitor ( 131 ) by being turned on in a state in which the main switch ( 110 ) is closed; and
break the charging current from being supplied to the capacitor ( 131 ) by being turned off when charging of the capacitor ( 131 ) is completed.
9 . The bidirectional DC circuit breaker of claim 8 , wherein if an arc is generated when the main switch ( 110 ) is opened, the first and second switching elements ( 150 , 160 ) are turned on, current is supplied to the main switch ( 110 ) in the first direction by the voltage (Vc) charged in the capacitor ( 131 ), and the supplied current causes a zero current at the main switch ( 110 ), whereby the arc generated in the main switch ( 110 ) is extinguished.
10 . The bidirectional DC circuit breaker of claim 9 , wherein the current supplied to the main switch ( 110 ) has a magnitude that is greater than that of a fault current and has a direction opposite to that of the fault current, which continuously flows through the arc in the main switch ( 110 ).
11 . The bidirectional DC circuit breaker of claim 8 , wherein if an arc is generated when the main switch ( 110 ) is opened, the third and fourth switching elements ( 170 , 180 ) are turned on, current is supplied to the main switch ( 110 ) in the second direction by the voltage (Vc) charged in the capacitor ( 131 ), and the supplied current causes a zero current at the main switch ( 110 ), whereby the arc generated in the main switch ( 110 ) is extinguished.
12 . The bidirectional DC circuit breaker of claim 11 , wherein the current supplied to the main switch ( 110 ) has a magnitude that is greater than that of a fault current and has a direction opposite to that of the fault current, which continuously flows through the arc in the main switch ( 110 ).
13 . The bidirectional DC circuit breaker of claim 9 , wherein when the arc is extinguished in the main switch ( 110 ), the switching element for charging ( 140 ) is turned on so as to charge the capacitor ( 131 ), and when charging of the capacitor ( 131 ) is completed, a closed circuit is formed by closing the main switch ( 110 ).
14 . The bidirectional DC circuit breaker of claim 2 , wherein each of the switching element for charging ( 140 ) and the first to fourth switching elements ( 150 to 180 ) includes a power semiconductor switch, turn-on/turn-off control of which is possible.
15 . The bidirectional DC circuit breaker of claim 11 , wherein when the arc is extinguished in the main switch ( 110 ), the switching element for charging ( 140 ) is turned on so as to charge the capacitor ( 131 ), and when charging of the capacitor ( 131 ) is completed, a closed circuit is formed by closing the main switch ( 110 ).