The Influence Of Power Flow Controller And Its Configuration Scheme In The DC Grid

with a variety or distributed renewabie energy generation, distributed energy devices of acquisition and storage as well as plug and play devices connecting to network, the power transmission form of multiterminal DC transmission and DC power system has gradually become the new tendency. High quality operation of DC system depends on the effective control for the power flow distribution. Especially, in the DC grid who has meshes, all controllable branch could be gained not only by the control of converter stations on the bus voltages and their total power, but also through adding the DC power flow controllers (PFCs) to get reasonable power flow distribution and achieve the goal of high quality operation. Starting from the power flow calculation (PFCAL) of the multiterminal DC grid, this paper makes study on the DC PFCAL method with PFCs and the configuration scheme of PFCs.Firstly, according to current calculation method commonly used in AC power network, this paper derives the PFCAL methods suitable for DC grid by comparing AC system with DC system, including the real Newton-Raphson (NR) method, fast calculation method for fundamental PFCAL and simple optimal PFCAL. Secondly, through the classification of the existing DC PFCs, the equivalent external characteristics of different types of PFCs and their influence on the system are analyzed. Then based on the fast fundamental PFCAL, the function of controllers is added to the calculation by changing the line conductance parameters or power equations, which makes the realization of PFCAL with controllers in DC grid. Finally, aiming at a DC grid with determined topology and parameters, this paper discussed the configuration method of PFCs from three aspects of number, location and capacity. A systematic and practical configuration scheme of DC PFCs is proposed.The proposed algorithms are realized in MATLAB, and the results are validated with the existing power flow simulation tool PSAT. The developed program is more suitable for DC power flow calculation than PSAT, including the application in the DC grid with PFCs, which lays the foundation for the research of power flow optimization and the allocation of controllers. Using the proposed scheme, this paper gives an analysis for the configuration of PFCs for Zhoushan five-terminal DC grid and DCS3 of the CIGRE B4 DC grid test system, and the reasonable results are obtained. The configuration scheme gives a reference for the research of power flow control as well as planning and design of DC grids.