【作者】 汪婷；

【导师】 李生虎；

【作者基本信息】 合肥工业大学 ， 电力系统及其自动化， 2019， 硕士

【摘要】 在电网多变运行场景下,统一潮流控制器(Unified Power Flow Controller,UPFC)根据控制目的确定其有功设定值,输电线路潮流方向可能发生变化,引起有功环流,影响电网安全经济运行,需量化有功设定值的可取范围以避免。同时随着UPFC在风电并网中应用愈来愈广泛,有功环流可能还会受到风电场出力影响,其出力不确定性将进一步影响UPFC有功设定值的可取范围。研究UPFC控制及参与电网安全经济的前提,是其精确的潮流建模。为改善潮流收敛性,需选取合理的UPFC变量初值和潮流控制目标范围。针对上述问题,基于含UPFC统一潮流模型,本文主要包括以下内容:(1)提出初值预估计的两阶段潮流算法,解决潮流收敛对UPFC变量初值敏感的问题。利用拓展雅克比矩阵,建立UPFC潮流控制目标对其串联控制变量的灵敏度模型,引入潮流约束确定潮流控制目标范围,避免因控制目标不合理引起潮流发散或串联变流器电压越限。(2)提出线路有功潮流与UPFC有功设定值的灵敏度模型,采用二阶求导确定两者间的单调性。基于牛顿法迭代修正灵敏度,可计算潮流方向对有功设定值敏感的关键线路有功为0对应的临界有功设定值,再根据受控潮流方向确定UPFC有功设定值可取范围。考虑到并联变流器和多个UPFC对有功环流的影响,提出串、并联变流器协调模型和多个UPFC有功设定值的协调模型。对Floyd-Warshall算法进行了改进,找到环流回路及关键线路,并与已有的Floyd-Warshall算法比较计算量。(3)提出有功环流统一潮流算法建立区间潮流模型,可计及风电场出力的不确定性对UPFC有功设定值可取范围的影响。扩展含UPFC的统一潮流方程和变量,采用区间数表示出力的波动范围,建立区间潮流模型。提出风电场有功出力与UPFC有功设定值之间的协调模型,从给定的出力波动范围中筛选出对有功设定值有影响的部分出力区间,再采用仿射Krawcyzk迭代法求解区间潮流。在中心点处线性化给出变量初始区间,迭代得到有功设定值极值区间。更多还原

【Abstract】 With its power setting decided by the power system conditions and basic purpose,the unifined power flow controller(UPFC)changes the direction of power flow of the transmission branches,possibly yielding or intensifying the active power loop flows,affecting the safe and economic operation of the system,thus it is necessary to quantify the controllable range of the active power setting of the UPFC to avoid the active power loop flows.At the same time,as the UPFC is more and more widely used in wind power integration,the active power loop flows may also be affected by the output of the wind farm,and its output uncertainty will further affect the controllable range of the active power setting of the UPFC.Accurate power flow model is the preconditition for(UPFC)to control and participate in the stability and economy of the power system.To improve the convergence of power flow,it is neccesarry to select propriate initial values of the UPFC variables and power settings.To solve above problems,based on the unified power flow model for UPFC,the main contents are as follows:(1)A two-stage power flow algorithm based on initial value estimation is newly proposed to avoid the vulnerability of power flow convergence to the intial values of the UPFC variables.The Jocabian matrix is extended to derive the sensitivity model between the series control variables of the UPFC to its power flow controllable range,and the power flow constraints is introduced to determine the range of power setting,thus avoid the divergence or the violation of the series voltage constraint of the UPFC due to its impropriate power setting.(2)The sensitivity between the active power setting of the UPFC and the active power flow of the line is newly proposed,whose monotonicity is validated with the 2~ndd order derivatives.The sensitivity is iteratively modified with Newton method to find the marginal power setting yielding zero active power flow of the critical line,whose power flow direction is sensitive to the active power setting of the UPFC.Based on the direction of controllable power flow,the controllable range of the active power setting is decided.Considering the impacts of the shunt converter and multiple UPFCs on the active power loop flows,the coordinated model between the series and shunt converters and the coordinated model of multiple active power settins of the UPFCs are proposed.The Floyd-Warshall algorithm is improved to find the active power loop flows and the critical lines,and its computational effort is compared with the exsiting algorithm.(3)An interval power flow model based on the unified power flow algorithm for the active power loop flows is proposed to consider the impact of the wind farm output fluctuations on the controllable range of the active power setting of the UPFC.The interval number is applied to describe the fluctuation range of output.A coordinated model between the active power output of the wind farm and the active power setting of the UPFC is proposed.The output intervals which affect the active power settings are selected from the given output range.Affine Krawcyzk method is used to solve the interval power flow,and the initial interval of the variable is linearized at the center point,so the limit interval of the active power setting is obtained by iterations.更多还原