Research On Nonlinear Control Of The Distributed Power Flow Controller

In order to respond to the actual needs of China's power grid and solve the power system dispatching and power quality problems caused by the increasing proportion of new energy sources and the rapid development of electric vehicles,flexible AC transmission(FACTS)technology emerges as the times require.The distributed power flow controller(DPFC),as a new FACTS technology,can fully meet the needs of modern power grid development.The further study of control strategy for the DPFC is an important cornerstone for its gradual improvement and maturity.Firstly,the research status of DPFC at home and abroad is summarized.Aiming at the defect of state information missing due to approximate linearization of linear control,the optimization strategies of linear controllers proposed by various scholars and the application of non-linear control theory in related FACTS devices are summarized.Subsequently,based on the analysis of DPFC's working principle,power exchange and power flow regulation characteristics,a linear controller of DPFC is constructed.In PSCAD/EMTDC simulation software,the power flow regulation characteristics of the test system including DPFC are simulated,and the simulations of single-phase short-circuit fault and three-phase short-circuit fault before and after installing DPFC are compared,which confirm the power flow adjustment and fault compensation of DPFC to the controlled system..Then,based on the mathematical model of the linear controller,the multi-objective coordinated optimization control equation of DPFC with relevant constraints is deduced.The optimal control parameters of DPFC linear controller are obtained by solving the equation with genetic algorithm.The correctness and effectiveness of the optimal control parameters are verified by comparing the simulations before the optimization of the control parameters,so as to obtain the optimal linear control of DPFC to make the subsequent comparative simulation more convincing.According to the theory of non-linear control,the 5-order nonlinear deterministic mathematical model of DPFC both in shunt side and series side is deduced.After proving that it satisfies the exact linearization condition,the nonlinear optimal controller of DPFC is designed.The contrast simulations proves the superiority of DPFC nonlinear optimal controller over linear controller with optimized control parameters when the operating point exceeds the fixed range of initial steady state.Based on the derived nonlinear deterministic mathematical models of DPFC both in shunt side and series side,the robust control mathematical models of DPFC both in shunt side and series side are derived by adding uncertain disturbance vectors in consideration of external disturbances.Based on the feedback linearization H_?method,the corresponding nonlinear robust controllers both in shunt side and series side are designed.Steady-state simulation and fault simulation show that DPFC nonlinear robust controller has better control effect than its nonlinear optimal controller.