Key Laboratory of Power System Intelligent Dispatch and Control of Ministry of Education,Shandong University
Compared with the conventional single-layer connection mode of ultra-high voltage direct current (UHVDC) system, the hierarchical connection mode improves the ability of AC system in acceptance and providing voltage support for multi-infeed UHVDC systems from the aspect of grid structure, and it makes power flow distribution and control more flexible and reasonable. In order to make full use of the fast power adjustment capability of UHVDC systems in the hierarchical connection mode, and avoid or reduce the economic loss caused by the load shedding during the medium-term and long-term voltage instability process, this paper proposes a coordinated control method for AC/DC power systems with hierarchical connection of UHVDC systems. Firstly, based on the quasi-steady model of UHVDC system in the hierarchical connection mode, this paper deduces the analytical expressions of sensitivities of the converter bus voltages with different control mode of UHVDC systems to the inverter transmission powers of UHVDC systems in hierarchical connection mode. Secondly, the voltage trajectory prediction model of AC/DC system is established based on the derived sensitivities. Finally, considering modulations of the DC current and the extinguishing angle of high and low ends of the inverter, a receding horizon optimization model of coordinated voltage control is constructed based on the predicted trajectory. The hierarchical DC injection powers and the voltage control means of AC system are coordinately controlled. The simulation analysis of the planning system of Shandong power grid shows that the proposed method can effectively coordinate the distribution of DC transmission power in AC grid, which enhances the system voltage stability and reduces the load shedding loss.
XIE Jiping,ZHANG Wen,YANG Hao.Coordinated Control for Medium-term and Long-term Voltage Stability of AC/DC Power Systems with Hierarchical Connection Mode of UHVDC System[J/OL].Automation of Electric Power Systems,http://doi.org/10.7500/AEPS20190403005.