Control features of the HVDC Gezhouba-Shanghai transmission scheme

The HVDC transmission scheme, the first in China, transmits 1200 MW at ±500 kV from the Gezhouba hydro plant, in Central China to Nan-Qiao near Shanghai over a distance of 1045 km. The authors discuss the operating environment of the interconnected AC systems of Central and East China in terms of frequency and voltage variations. This leads to the establishment of the power regulation and the reactive power requirements of the HVDC transmission terminals. The authors then focus on the control strategies adopted by the HVDC scheme to match these requirements. Reactive power and AC voltage controls using the HVDC converter terminals represent the first application of such techniques in long transmission systems. Step-power modulation functions activated by the HVDC control system are also exercised. The features and functions of such a microprocessor based control scheme are presented in detail. A sample of commissioning field tests demonstrating these control features are also presented