Research On Dynamic Optimal Power Flow Of AC/DC Hybrid Power Grid

The AC/DC hybrid power grid is usually a power grid that uses high-voltage DC transmission technology and contains both AC and DC.It is an important form of energy conversion across regions in my country currently.Its core component is a voltage source converter(VSC)with high controllability and flexible state transition.Optimal power flow(OPF)is an important method for optimal dispatching of power grids.On a certain static time section,based on the security of the power grid,OPF meets the economic requirements by adjusting the form of power flow distribution.Dynamic Optimal Power Flow(DOPF)studies the relevance of multiple time sections.It satisfies various safety constraints such as voltage quality and power flow carrying capacity.It realizes the overall optimal dispatch of the power grid,which is more in line with the actual situation.This paper summarizes the structural characteristics of HVDC and VSC components.This paper establishes a reactive power optimization model with the goal of minimizing network loss and studies the optimal dispatching strategy of the AC/DC hybrid power grid.The work of this paper is as follows:(1)This paper analyzes the research status of VSC-HVDC,reactive power optimization and optimization algorithm.We summarizes the stable operation characteristics of VSC-HVDC.This paper establishes a mathematical model that can meet the requirements of power flow calculation through equivalent simplification of the component model.(2)We analyze the DC variables and power balance conditions in the AC/DC hybrid power grid containing VSC-HVDC components,establish a power grid calculation model,and study the calculation methods and solving steps based on the unified iterative method.The results of the calculation examples show that the power flow calculations can converge correctly.In the power flow calculation,this paper verifies the flexibility and stability of VSC-HVDC by adjusting the parameters and control modes of VSC components,and explores the influence of DC parameters on the power flow distribution of the power grid.Because the power flow calculation lacks security constraints,unreasonable parameter adjustments will bring hidden dangers to the operation of the power grid.(3)This paper takes the minimum power loss as the objective function,and takes power balance,voltage constraints,transmission power,and generator output as constraints,and finally establishes a multi-time section DOPF calculation model.We study the solution steps and calculation formulas of the primal-dual interior point method,which has the advantages of good convergence effect and fast calculation speed,and explore the simplified solution steps at the generalized level.The test results of the actual power grid examples show that the DOPF calculation can not only greatly reduce the power grid loss,but also the voltage amplitude,phase angle,and line active and reactive power parameters are constrained within the specified interval,while meeting the power grid economy and safety requirements.(4)This paper verifies that DOPF can eliminate the influence of VSC DC parameters on the stability of the power grid by adjusting the control mode and control parameters of the VSC components.In the expansive test,this article only adjusts the DC side parameters,and obtains the power flow control interval and optimal control parameters of the VSC components.The results of multi-node calculation examples show that the model and algorithm in this paper are also practical and stable in large power grids.