Radial-Chordal Decomposition Control Method for Series-Type Electric Springs
Kwan-Tat Mok, Siew-Chong Tan, Shu-Yuen Ron Hui
The University of Hong Kong
A power electronic device known as the electric spring (ES), which is used in series connection with a non-critical load (such as thermal heaters) for active and reactive power compensation, has been invented by our research group. The basic functionality of the ES is to control the electrical parameters of a power network such as the grid-voltage amplitude, utility frequency, and/or the power factor of the ES-associated smart load. This project is related to a method of precisely controlling the electrical parameters of a power network independently and flexibly, using the ES. Specifically, the method involves the decomposition of the power-amplitude and power-angle, such that these parameters can be independently controlled without mutual effect on one another. This is of prime importance to the widespread application of ES. Moreover, the invented control scheme is also applicable to existing static synchronous series compensators (SSSC) used in medium or high voltage flexible AC transmission systems or any related DC/AC power electronic converters that require optimal and precise control of their line supply voltage or loads.
This is an important step towards the practical application of ES in power networks for power stabilization. Existing control schemes are imprecise and may sometime leads to system instability. The introduction of this decomposition control scheme completely resolves the issue.
The breakthroughs of this project include the following:
- A 2-kW laboratory-scale experiment has verified that a single ES operated under the proposed RCD control method can perform both the grid-voltage regulation and the power-factor correction functions independently and simultaneously without mutual effect on one another.
- The proposed RCD algorithm has been successfully implemented using a commercial low-cost digital-signal-processing (DSP) controller, TI TMS320F28069. This is the significant evidence that the theoretical analysis and derivation of the RCD approach can be practically realized which helps for its commercialization.
- The proposed RCD controller and control method has been filed an international patent application under the Patent Cooperation Treaty (PCT).
