Apparatus and method for transmission line control
View Patent ↗An apparatus includes a converter having an AC side and a DC side, a switch adapted to be connected to a transmission line on a first side and connected to a load on a second side connected to the AC side, an energy storage device, connected to the DC side. In a first operating mode, the switch is closed, such that an energy storage current flows to/from the energy storage device to charge/discharge the energy storage device, respectively. In a second operating mode, the switch is open, preventing current from flowing from the transmission line to the converter, and the energy storage device supplies a direct current which is converted to an alternating current by the converter. In the first operating mode, the apparatus is configured such that power transfer on the transmission line corresponds to a surge impedance loading of the transmission line, by affecting the energy storage current.
1. An apparatus comprising:
a converter having an AC side and a DC side,
a switch adapted to be connected to a transmission line on a first side and said switch being adapted to be connected to a load on a second side, said second side also being connected to said AC side of said converter,
an energy storage device, connected to said DC side of said converter, and
a controller,
wherein in a first operating mode, said switch is closed, such that an energy storage current flows to or from said energy storage device to charge or discharge said energy storage device, respectively, using said converter for any necessary conversion between AC and DC, and
in a second operating mode, said switch is open, preventing current from flowing from said transmission line to said converter, and said energy storage device supplies a direct current which is converted to an alternating current by said converter,
wherein, said controller is configured to control, in said first operating mode, power transfer on said transmission line to correspond to a surge impedance loading of the transmission line through affecting said energy storage current, wherein the transmission line neither absorbs nor produces reactive power at the surge impedance loading of the transmission line,
wherein said apparatus is configured such that said power transfer on said transmission line to correspond to said surge impedance loading of said transmission line only occurs in said first operating mode and does not occur in said second operating mode, and
wherein said converter comprises series connected high voltage circuits with embedded short circuit failure mode controlled with a pulse width modulation circuit.
2. The apparatus according to claim 1 , wherein, in said second operating mode, said controller is configured to control frequency and voltage of said alternating current provided to said load.
3. The apparatus according to claim 1 , further comprising a voltmeter and an ammeter, both meters adapted to provide measurements to said controller.
4. The apparatus according to claim 1 , wherein said switch is a transient free switch.
5. The apparatus according to claim 1 , wherein said apparatus is configured to switch from said first operating mode to said second operating mode when said energy storage device is determined to be full.
6. The apparatus according to claim 1 , wherein said apparatus is configured to switch from said second operating mode to said first operating mode when said energy storage device is determined to be below a threshold charge level.
7. The apparatus according to claim 1 , wherein said controller is configured to control switching of said apparatus between said first and second operating modes.
8. The apparatus according to claim 2 , further comprising a voltmeter and an ammeter, both meters adapted to provide measurements to said controller.
9. A method for operating an apparatus comprising:
a converter having an AC side and a DC side,
a switch adapted to be connected to a transmission line on a first side and said switch being adapted to be connected to a load on a second side, said second side also being connected to said AC side of said converter,
an energy storage device, connected to said DC side of said converter,
said method comprising the steps of:
closing said switch, such that an energy storage current flows to or from said energy storage device to charge or discharge said energy storage device, respectively, using said converter for any necessary conversion between AC and DC,
opening said switch, preventing current from flowing from said transmission line to said converter, and said energy storage device supplies a direct current which is converted to an alternating current by said converter, and
controlling, when said switch is closed, power transferred on said transmission line to correspond to a surge impedance loading of the transmission line through affecting said energy storage current, wherein the transmission line neither absorbs nor produces reactive power at the surge impedance loading of the transmission line,
wherein said controlling the power transfer on said transmission line to correspond to said surge impedance loading only occurs when said switch is closed and does not occur when said switch is open, and
wherein said converter comprises series connected high voltage circuits with embedded short circuit failure mode controlled with a pulse width modulation circuit.
10. The method according to claim 9 , wherein said closing and opening of said switch are repeated.
11. The method according to claim 9 , wherein said opening of said switch is performed when said energy storage device is determined to be full.
12. The method according to claim 9 , wherein said closing is performed when said energy storage device is determined to be below a threshold charge level.
13. The method according to claim 9 , further controlling frequency and voltage of said alternating current provided to said load when said switch is opened.