Research Of UPFC Controller Based On Genetic Algorithm

As the realization of electricity from the western to the eastern regions and the changing of electricity demand and power supply with each passing day in our country,power systems will face the serious problems which are expropriation of transmission line passage way and stability of power grid.Meanwhile,the more capacity of power grid,the higher demand of power quality.How to ensure the stability and to enhance the reliability of the power systems is the main challenging problem.As the most complex element in the FACTS,UPFC can be used to adjust real and reactive power of the transmission line,maintain voltage of the bus where UPFC is connected,improve transient stability and damp out low frequency oscillate of power systems.This thesis devotes itself to the in-depth studies of UPFC, including the conventional proportion-integral(PI) control strategy,the Fuzzy-PI control strategy,the Fuzzy-PI control strategy based on genetic algorithm and the simulation model of UPFC.Firstly,introduce the process of birth,growth and the current situation of UPFC. This thesis elaborates on the UPFC shunt-series performance characteristic on the basis of analyzing the structure and work principle of UPFC.The shunt side of the UPFC is mainly used to maintain both the voltage of the AC system where the UPFC is connected as well as the voltage of the DC capacitor,and the series side of the UPFC is used to control the power flow of the transmission line.UPFC can make voltage regulate,series compensation,phase angle regulate and multifunction power control through superposing an amplitude and phase voltage which can be adjusted to the system.UPFC can improve the transmission capacity and steady operation of power systems,through further analysis on influence of UPFC on power performance of transmission system.Secondly,introduce the three-level control system of UPFC.Design the UPFC shunt-series controllers on the basis of the conventional PI control.Based on PI control strategy of fuzzy control theory,design Fuzzy-PI controller in series side,give the detailed design process and derivative process of fuzzy control rules.Make optimized design of UPFC series side Fuzzy-PI controller through making full use of robustness and applicability of genetic algorithm.Though optimizing quantification factor and proportionality factor of Fuzzy-PI controller,optimizing the membership function,then make the system response has good dynamic and steady performance.Finally,the simulation model of UPFC is set up in detail using PSCAD/EMTDC, the simulation model of the series side controller is set up in detail using MATLAB. Make simulation analysis under the circumstances of steady state of power transmission system and transient state of three phase short circuit.Simulation results show that the dynamic characteristic of UPFC with the proposed control is much better than that with the conventional PI control and Fuzzy-PI control.The power flow adjustment speed is greatly increased,and the stability of the system against the fault is also considerably improved.