The Typical Problems And Solutions On Volt/Var Control Of Guangdong Power Grids

Since the further development of power systems interconnection, the application oflarge-capacity HVDC, the DG’s accessing to the networks, the rapid and uneven developmentof load and peak-valley difference of load is widening, significantly increases the reactivepower and voltage close-coupled complexity of Guangdong power grid, which has broughtgreat challenges and difficulty to volt/var control of large receiving-end provincial power grid.Based on the summary and analysis of volt/var regulation problems in main network anddistribution network, this thesis introduces several means of volt/var control, summarizes theresearch status of control modes and evaluation mechanism on volt/var control, and reviewsthe research survey and application of reactive power planning in distribution network inorder to conclude the research methods and solutions of volt/var control.Based on discussing the reasons for the formation of volt/var control problems in theGuangdong power grid, including the assessment index of volt/var control is less coordinated,the material basis of volt/var control is inadequate, the lower investment rates of VQC devices,AVC system operation experience is limited, significant changes in load characteristics, gridstructure appears new features and the impact of small hydropower access to the power grid,this thesis make a prilemenaly analysis of the countermeasures on volt/var control problemsin the Guangdong power grid.It is the key problem in automatic voltage control (AVC) of large-scale power grids toquantitatively assess the reactive power regulation capability of provincial power grid todetermine the control range of reactive power at the gateway of provincial power grid. Firstlythe definition of average coordination power factor limits (ACPF) is given to evaluate thelimit of provincial power grid to withstand the reactive power. Then based on the idea oflayered decoupling and considering the reactive power safe margin of provincial power grid,as well as the load characteristic difference and reactive power regulation capacity of aregional power grid, this thesis proposes the tuning method of coordinated power factor at thegateway between provincial and district power grids. Simulation results of a certain regionalpower grid in Guangdong power grid show that the proposed method effectively solves thelimitations to obtain the setting value of AVC system parameter depending on experts experience and global optimization calculation.For the present solutions to solve the high voltage problem of distribution lines causedby a large number of small hydropower access to distribution network are poor practical value,this paper proposes a centralized absorb inductive reactive power compensation method.According to the reactive power decoupling formula of voltage loss, the propose methoddetermine the optimized compensation point of parallel reactors and guide the reactive powercompensation switching by monitoring the node voltage of main wiring containing smallhydropower. Simulation results show that the proposed method greatly reduces the voltage ofdistribution lines containing small hydropower, combines security and ease of management,which is workable and has high practical value.The completion of this thesis work was funded by the National Natural ScienceFoundation of China (51377060) and Central Universities Fundamental Research Funds forthe Projects of South China University of Technology(2013ZM0013).