Steady-State Modeling of Hybrid Unified Power Flow Controller with Additional Nodes

The hybrid unified power flow controller (HUPFC) consists of a “Sen” transformer (ST) and a unified power flow controller (UPFC) in series. It not only has the same control function of line power flow as the UPFC but also has a lower cost and less loss. In order to evaluate the application value of HUPFC in practical engineering, it is necessary to realize the power flow calculation of the system containing HUPFC. However, the relevant model has not been developed yet. Regarding the issue above, this paper proposes a steady-state mathematical model of HUPFC with additional nodes, which can quickly build an interface with commercial software. First, according to the topology of HUPFC, the series side is equivalent to a voltage source and impedance, the parallel side is equivalent to a current source, and it introduces additional nodes to establish a simplified equivalent circuit of HUPFC. Second, the voltage source is converted into additional power to the node and establishes the HUPFC power injection model. Finally, calculate the HUPFC controllable voltage source voltage according to the control objective, then obtain the UPFC and ST control parameters. Simulation examples verify the accuracy and validity of the proposed model.