Method and device for injecting reactive current during a mains supply voltage dip
View Patent ↗The invention relates to a method and device for injecting current during a mains supply voltage dip. The inventive method consists in permanently monitoring the magnitude and phase of the mains supply voltage and, upon detection of a voltage dip, injecting reactive current in the affected main supply phase(s) in a manner that can vary over the duration of the voltage dip, at very short intervals, proportionally to the magnitude of the dip, thereby absorbing the necessary active current. The device comprises a voltage measurement switch, a transformer (low voltage/medium voltage), a DC/AC inverter, a capacitor, a voltage dip detection circuit, and a control circuit.
1. A device for injecting reactive current onto an MV network ( 14 ) to which one or various electrical power generation machines are connected when a voltage dip occurs on said network ( 14 ) due to a mono-phase, two-phase, or three-phase fault, comprising:
a) a medium voltage switch ( 1 ) on the connection of an output from a wind farm 16 to the network ( 14 );
b) an LV/MV transformer ( 2 ) on each phase;
c) a dc/ac inverter ( 3 ) on each phase with IGBT or IGCT semiconductors;
d) a dc capacitor ( 4 ) on each phase; and
e) a control circuit ( 20 ) on each phase, connected to the controls ( 10 , 12 , 13 ) associated with each of the aforementioned units and which includes voltage and current sensors, a voltage dip detection circuit ( 10 ) with DSP, devices for calculating the instantaneous voltage on the network ( 14 ), and voltage comparison circuits, so that when the circuit ( 10 ) detects a voltage dip, reactive current from the output of the wind farm ( 16 ) is injected onto the MV network ( 14 ) in a variable manner at each time interval or cycle, based on the measurements provided by the sensors and circuits, taking the necessary active current from the network ( 14 ) to the capacitor ( 4 ).
2. A device for injecting reactive current into a MV network ( 14 ) to which one or various electrical power generation machines are connected when a voltage dip occurs on said network ( 14 ) due to a three-phase fault, comprising:
a) a medium voltage switch ( 1 ) on the connection of an output from a wind farm 16 to the network ( 14 );
b) an LV/MV three-phase transformer ( 2 );
c) a dc/ac three-phase inverter ( 3 ) with IGBT or IGCT semiconductors;
d) a dc capacitor ( 4 ); and
e) a control circuit ( 20 ) for the aforementioned units, connected to the controls ( 10 , 12 , 13 ) associated with each of the units and which includes voltage and current sensors, a voltage dip detection circuit ( 10 ) with DSP, devices for calculating the instantaneous voltage on the network ( 14 ), and voltage comparison circuits, so that when the circuit ( 10 ) detects a voltage dip, reactive current from the output of the wind farm ( 16 ) is injected onto the MV network ( 14 ) in a variable manner at each time interval or cycle, based on the measurements provided by the sensors and circuits, taking the necessary active current from the network ( 14 ) to the capacitor ( 4 ).
3. The device for injecting reactive current onto an MV network ( 14 ) to which one or various electrical power generation machines are connected when a voltage dip occurs on said network ( 14 ) due to a mono-phase, two-phase, or three-phase fault, according to claim 1 , wherein the voltage dip detection circuit ( 10 ) detects a voltage dip due to mono-phase, two-phase, or three-phase faults in a time frame equal to or less than 1 millisecond.
4. The device for injecting reactive current onto an MV network ( 14 ) to which one or various electrical power generation machines are connected when a voltage dip occurs on said network ( 14 ) due to a mono-phase, two-phase, or three-phase fault, according to claim 1 , wherein the control circuit ( 20 ) varies the magnitude of the reactive current injected in time intervals of less than or equal to 20 milliseconds.
5. The device for injecting reactive current onto an MV network ( 14 ) to which one or various electrical power generation machines are connected when a voltage dip occurs on said network ( 14 ) due to a mono-phase, two-phase, or three-phase fault, according to claim 1 , wherein the device takes its power from the MV network ( 14 ).
6. The device for injecting reactive current onto an MV network ( 14 ) to which one or various electrical power generation machines are connected when a voltage dip occurs on said network ( 14 ) due to a mono-phase, two-phase, or three-phase fault, in accordance with claim 1 , wherein said device is built in modules so that in the event of one of the modules failing, the remaining modules can continue to operate.
7. The device for injecting reactive current onto an MV network ( 14 ) to which one or various electrical power generation machines are connected when a voltage dip occurs on said network ( 14 ) due to a mono-phase, two-phase, or three-phase fault, according to claim 1 , wherein said machines are wind turbines.
8. A procedure for injecting reactive current with a device according to claim 1 onto a network to which one or various electrical power generation machines are connected when a voltage dip occurs on said network due to a mono-phase, two-phase, or three-phase fault, comprising:
a) permanent monitoring of the magnitude and phase of the network voltage; and
b) on detecting a mono-phase, two-phase, or three-phase voltage dip, injecting reactive current from the output of the wind farm ( 16 ) on the affected phase or phases of the network in proportion to the magnitude of the voltage dip, in a variable manner for the duration of the voltage dip, absorbing from the network ( 14 ) the active current necessary.
9. The procedure for injecting reactive current with a device according to claim 8 onto an MV network to which one or various electrical power generation machines are connected when a voltage dip occurs on said network due to a mono-phase, two-phase, or three-phase fault, wherein said monitoring performed by the detection circuit ( 10 ) allows a voltage dip to be detected in a time of less than or equal to 1 millisecond.
10. The procedure for injecting reactive current with a device according to claim 8 onto an MV network to which one or various electrical power generation machines are connected when a voltage dip occurs on said network due to a mono-phase, two-phase, or three-phase fault, wherein the variation of the injected reactive current performed by the control circuit ( 20 ) takes place in time intervals of a less than or equal to 20 milliseconds.
11. The procedure for injecting reactive current with a device according to claim 8 onto a network to which one or various electrical power generation machines are connected when a voltage dip occurs on said network due to a mono-phase, two-phase, or three-phase fault, wherein said machines are wind turbines.