Voltage or impedance-injection method using transformers with multiple secondary windings for dynamic power flow control
This patent discloses an active impedance-injection module for dynamic line balancing of a high-voltage (HV) transmission line. The impedance-injection module comprises a plurality of transformers each having a primary winding in series with a HV transmission line. Each transformer also has secondary windings, each connected to an individual electronic converter. The plurality of secondary windings are electrically isolated from the associated primary winding and extract power from the HV transmission line for operation of the converters and other circuits connected to the secondary windings. The active impedance-injection module is enabled to generate a controlled impedance, inductive or capacitive, to be impressed on the HV transmission line. A plurality of active impedance-injection modules spatially distributed on a HV transmission line are enabled to inject a controlled cumulative impedance on a HV transmission line while limiting the capacity of individual converters to that achievable with practical electronic components.
1. A system for dynamic line balancing in a high voltage electric power grid comprising:
a plurality of impedance-injection modules distributed along a transmission line of the high voltage electric power grid;
each impedance-injection module having;
a transformer having a transformer core with a plurality of secondary windings thereon;
a plurality of power-electronic circuits for generation and injection of the inductive and capacitive impedances, each power-electronic circuit being coupled to a respective secondary winding;
the transformer and the plurality of power-electronic circuits being enclosed in a single housing and with the high-voltage transmission line passing through the transformer core, thereby forming a transformer with a single-turn primary and the plurality of secondary windings.
2. The system of claim 1 wherein the transformer core is a split core, whereby the split core is assembled around the high-voltage transmission line.
3. The system of claim 2 wherein the transformer core, once positioned with the high voltage transmission line in place, may be assembled with or without a gap at a split of the split core.
4. The system of claim 1 , wherein each power-electronic circuit comprises a converter, a bypass circuit, and a controller coupled to a respective secondary winding.
5. The system of claim 4 wherein each controller is coupled to control a respective converter independently of its control of any other converter, whereby each controller may operate one or more converters at any one time.
6. The system of claim 5 wherein each impedance-injection module further comprises a master controller for controlling each controller controlling a respective converter in the respective impedance-injection module.
7. The system of claim 5 wherein each impedance-injection module includes a transceiver coupled to the master controller for remotely configuring the respective impedance-injection module and for remote control of the respective impedance-injection module.
8. The system of claim 7 wherein each impedance-injection module includes at least one sensor for sensing and reporting of transmission line conditions by the transceiver.
9. The system of claim 1 wherein at least one impedance-injection module is suspended directly on a transmission line.
10. The system of claim 1 wherein at least one impedance-injection module is suspended on at least one insulator from a transmission line tower.
11. The system of claim 1 wherein at least one impedance-injection module is suspended on at least one insulator by an additional support structure.
12. The module of claim 1 wherein the power-electronic circuits use mass-produced reliable semiconductors and other power-electronics components.
13. The system of claim 1 wherein a number (N) of secondary windings are selected to achieve a coupling capability to and from the high-voltage transmission line equal to a transformer having an N-turn primary.
14. The system of claim 13 , wherein each electronic circuit coupled to a secondary winding generates (1/N) of the active impedance to be injected by the module on to the transmission line.
15. The system of claim 14 wherein each power electronic circuit is a repeat of the same components and functionality as each other power electronic circuit in the respective impedance-injection module.
16. The system of claim 1 wherein each of the plurality of secondary windings has the same number of turns.
17. A method of providing dynamic and distributed line balancing of a high-voltage transmission line by active impedance-injection modules, the method comprising:
providing active impedance-injection modules for dynamic line balancing of a high-voltage transmission line, each active impedance-injection module having;
at least one transformer having a split transformer core, enabled for distributed installations over the high voltage transmission line, each transformer core having a plurality of secondary windings thereon, whereby the split core can be assembled around a high-voltage transmission line in place and the active impedance-injection module is at the potential of the high voltage transmission line to which it is coupled;
a plurality of power-electronic circuits, each of the power electronic circuits coupled to each secondary winding;
the transformer and the power-electronic circuits being packaged in a single housing as an active impedance-injection module for use with a high-voltage transmission line passing through the transformer core, thereby forming a transformer with a single-turn primary and the plurality of secondary windings; and
supporting each of the distributed active impedance-injection modules by the transmission line, by insulators on a respective high-voltage transmission line support tower, or by insulators on one or more special support structures.
18. The method of claim 17 wherein each single housing is opened and the respective split core is disassembled for passage of the high-voltage transmission line there through, and then the respective split core is reassembled and the respective single housing is closed.
19. The method of claim 18 wherein the split core is reassembled without a gap at each split of the split core.
20. The method of claim 17 wherein the module further comprises a plurality of bypass circuits, each bypass circuit being coupled to a respective secondary winding to bypass the power-electronic circuits.