Application Research Of Phase Shifting Transformer In Power System

With the increasing complexity of the AC power grid,power flow distribution could be unreasonable in the operation of power system.As a kind of flexible power flow control device,Phase shifting transformer(PST)can effectively regulate power flow without changing power network,which has good application prospect.There is no engineering application about PST in China nowadays.Therefore,it is of great importance to study the steady-state mathematical model,optimal location and application analysis of PST.With the elaboration of the engineering applications of PST all over the world,improving transfer capability of power system and eliminating transmission line overload are the main application purposes of PST.In this paper,these two application purposes were determined as the two most important functions of PST in controlling power flow.A steady-state mathematical model of two-core symmetrical mechanical PST considering equivalent impedance was established in this paper.And a power flow calculation method was proposed for the power system containing PST.The effect of power flow control of PST was taken as an additional injection model in the installation line,which makes conventional method of power flow calculation still applicable.Then,this paper gave the detailed derivation of the additional injection power and power flow in the installation branch.Based on the actual equipment parameters provided by related manufacturer,power flow control characteristics of PST in different circumstances was simulated and analyzed.The simulation results illustrated that position of PST and difference of mathematical model have great influence on the effect of power flow control.Two mathematical models of PST optimal location were established in this paper,which were used to improve transfer capability of power system and eliminating transmission line overload.These two types of models took stall of PST as control variable.And the two sides of same line were determined as different locations of PST.To solve models mentioned above,quantum particle swarm algorithm was adopted in IEEE14-bus system.The simulation results verified the validity of the proposed model,and pointed out that the usage of PST ideal model in PST optimal location could cause errors because of its characteristics of ignoring impedance and shifting phase angle continuously.In contrast,the optimal location model and treatment method proposed in this paper can improve the reliability of results and meet practical engineering.Finally,a general simulation analysis method for the application of PST was given,which was based on the three key application problems,mathematical model and optimal location.These three key application problems include the application scene source of PST in the target power grid,the parameter determination of PST and the comprehensive evaluation of scheme.The actual power system simulation verified the effectiveness of proposed simulation analysis method.