Research On Optimal Power Flow Of AC/DC Systems With VSC-HVDC

Liaoning power grid is the load center of Northeast power grid,concentrated load,the power supply is insufficient and distribution is not balanced.Along with the enlargement of the scale of high voltage power grid,there are two difficult problems which the Liaoning has to confront,i.e.,the bottleneck of power transmission and out-of-limit short circuit capability.Voltage source converter based high voltage direct current(VSC-HVDC)can effectively improve the economic benefit of long-distance,large-capacity power transmission.It has the characteristics of tide fast controllable,and there is no angle stability problem.Flexible looped network controller(FLNC)based on VSC-HVDC technology can realize grid district soft-dividing,fault current limitation,power flow optimization,and reactive power support.FLNC can ensure the ability of power supply,power supply reliability and power grid scheduling flexibility,simultaneously.It is of great significance to figure out how to determine VSC operation and system parameters,under different operation conditions.This paper studies the optimal power flow calculation of AC/DC systems with VSC-HVDC targeting above problems.Firstly,this paper analyzes the mechanism of VSC-HVDC steady-state,and determines its tidal current equivalent model,so that deduces VSC-HVDC and FLNC model.Secondly,this paper builds the model of total transfer capability of AC/DC systems considering the static voltage stability,security and economy.In order to determine the TTC effectively,this paper proposes a hybrid optimization approach based on continuous power flow.Then the paper takes modified IEEE30-bus system and Liaoning power grid as examples to verify the accuracy and the efficiency of the proposed model and algorithm.Finally,this paper proposes multi-objective power flow optimization model of AC/DC system with VSC-HVDC.In view of the defects of the proposed method,this paper improves alternating method and presents the primal dual interior point method and chaos SPEA,using fuzzy set theory to deal with multi objectives.Tests on IEEE benchmark systems illustrate the effectiveness and efficiency of the proposed approach.