Research On Multi-time Scale Model Of Distributed Power Flow Controller

In the new normal state of Chinese unstrained power supply-demand relations,FACTS technology has provided a better idea for economical and efficient power supply.Derived from the Unified Power Flow Controller(UPFC),Distributed Power Flow Controller(DPFC)owned its innovation which utilized third harmonic 150 Hz current rather than common DC capacitor to realize active power’s transmission between shunt and series devices.Meanwhile,based on the theory of Ditributed Satic Series Compensator(DSSC),DPFC series devices achieved the function of flexible controlling and distributed compensation.This paper is mainly to study the multi-time scale model for the DPFC--a new FACTS technology.The paper firstly summarized the recent research status of DPFC at home and abroad,as well as the three main research areas which included mathematical model,control strategy and reliability analysis.Then,it narrated the power-flow control abilities of transmission lines installed DPFC after introducing devices’ structure and working principle.Afterwards,based on detailed analyses of the DPFC topology and respective deduction of the parallel-series components’ mathematical model,this paper put forward a five dimensional dynamic model,in which dq current component and DC capacitance voltage was taken as state variables.In terms of those state variables rendering different multi-time scale features,a conclusion of the dq current component equation and voltage equation was respectively defined as DPFC system’s “fast dynamic” and “slow dynamic” had been drawn,after analyzing the DPFC dynamic model by singular perturbation theory.According to the different multi-time scale features which DPFC system’s state variables showed,a corresponding control strategy was designed merely from the current model which rendering “fast dynamic” characteristic.This control strategy in the paper effectively achieved the decoupling of active power and reactive power components through the nonlinear feedback Linearization principle,aimed to realize the separate control of the active power flow and the reactive power flow in transmission lines.Lastly,the simulation model of DPFC testing system was built in PSCAD / EMTDC simulation platform at the end of this paper,and verified the validity of DPFC multi-time scale model by computer simulation analyzing on the active power exchanges between series-parallel components,steady-state characteristics and transient characteristics of DPFC testing system.