电力系统紧急状态下切负荷控制策略研究

发布时间：2018-04-16 04:27

本文选题：紧急状态 + 频率稳定　；参考：《华北电力大学》2014年博士论文

【摘要】：当前互联电网网架结构日趋复杂,使系统隐性故障和连锁故障发生的概率不断增多,解列事故频发；特别对于受端电网,解列事故会导致系统失去重要输电通道或联络线,出现大容量功率缺额,如果系统紧急控制措施有限,就很可能发生系统失稳。频率崩溃是造成系统大范围停电的重要原因之一,近些年发生的多起电网崩溃都有频率失稳的因素。本文结合国家自然科学基金(50837002)课题“集中决策与分布实现相协调的大电网后备保护系统研究”,深入系统地开展了“电力系统紧急状态下切负荷控制策略研究”的论文工作,主要创新性成果如下：分析系统运行状态的分类及对应采取的安全控制措施的基础上,深入研究了系统紧急状态的特征；以构建的单机带负荷系统为研究对象,建立了包括系统频率、电压和功角状态变量的代数微分方程组；借助Matlab编程求解系统稳定运行和紧急状态下的状态方程,仿真系统分别受到有功、无功功率扰动时,系统运行状态的变化情况。提出了预防控制与紧急控制作用相结合的系统稳定控制框架；电力系统受到大的有功扰动,预测和判断系统是否将进入紧急状态具有关键作用,进而及时地采取切负荷等有效控制措施,阻止系统中有功、无功功率平衡的破坏和维护系统的稳定。基于发电机有功功率扰动和频率变化之间的转子运动平衡方程,分析建立了单机系统的负荷频率控制原理框图,进而扩展到多机及多分区系统的频率响应建模研究；构建了考虑调速器、自动发电控制和联络线功率偏差控制的系统频率响应动态模型图,推导了系统受扰后频率轨迹变化的方程,用于研究系统的频率稳定变化。研究表明,扰动初期的频率变化率只与系统初始的不平衡功率有关,功率缺额越大,频率下降速度越快；系统的稳态频率偏差受到功率缺额和频率调节效应的共同影响；频率的动态过程不仅和有功缺额的大小有关,与扰动位置,电网结构都是密切相关的。建立了具有紧急控制作用模块的系统频率响应动态模型,包括系统参数,频率保护的门槛值,系统的受扰功率,紧急控制措施和互联线路的潮流变化对频率稳定的影响。利用建立的地区系统频率响应动态模型,从中长期的角度预测系统受扰后频率的轨迹变化和频率稳定控制的可行性。提出了一个新自适应UFLS控制策略,所建立的系统频率响应动态模型应用于系统紧急控制和保护策略的制定；新策略考虑和低频调速及系统备用容量的快速释放相协调,根据系统扰动自适应地确定减负荷的数量和动作级数,避免了负荷的过切或欠切；在考虑切负荷地点时,采取就地平衡扰动功率的原则,避免潮流转移引起级联事故的发生。在研究影响系统频率和频率变化率测量的因素基础上,推导了系统受扰后的有功功率缺额与频率变化率之间的准确函数关系式。进一步,在电压灵敏度分析的基础上,提出了利用电压灵敏度确定切负荷地点与相应切负荷量的自适应切负荷控制策略,目的在于考虑切负荷过程中,有效恢复系统有功平衡的同时,最大限度的实现无功的就地平衡；在系统的脆弱点,即电压和频率下降更多或无功需求更大的地点切负荷,可以提高系统的电压稳定边缘,降低了系统崩溃的风险。提出的切负荷策略有更强的自适应性,是切负荷量,切负荷地点和动作时间的函数关系,能够考虑系统网络拓扑的变化,更有利于系统稳定性的恢复,有应用的优势和价值。
[Abstract]:The network frame structure of the current interconnected power grid is more and more complex , so that the probability of the hidden trouble of the system and the occurrence of the chain fault is increased , and the accident frequency is solved ;
Especially for the power - receiving network , the breakdown accident will cause the system to lose important power transmission channel or contact line , the large - capacity power shortage occurs , and if the system emergency control measures are limited , the system instability can occur . The frequency collapse is one of the important causes of the large - scale power failure of the system .

Combined with the research on the centralized decision - making and distribution of the National Natural Science Foundation ( 50837002 ) , this paper systematically carries out the paper ' s work on the research on the control strategy of power system emergency , and the main innovative results are as follows :

Based on the classification of the running state of the system and the corresponding safety control measures , the characteristics of the emergency state of the system are further studied .
An algebraic differential equation group including system frequency , voltage and work angle state variables is established based on the constructed single - machine band - load system .
In this paper , the state equation of system steady operation and state of emergency is solved by Matlab programming , and the simulation system is affected by active and reactive power disturbance , and the change of system operating state is presented . A system stabilization control framework combining prevention control and emergency control is proposed .
Whether the power system is subjected to large active disturbance , predict and judge whether the system will enter the state of emergency has a key role , so as to take effective control measures such as cutting load in a timely manner , prevent the damage of active and reactive power balance in the system and maintain the stability of the system .

Based on the rotor motion balance equation between active power disturbance and frequency change of generator , the principle block diagram of load frequency control of single - machine system is analyzed , and the frequency response modeling of multi - machine and multi - partition system is extended .
The dynamic model diagram of the system frequency response considering governor , automatic power generation control and contact line power deviation control is constructed . The equation for the change of frequency locus of the system is derived , which is used to study the frequency stability change of the system . The research shows that the frequency change rate at the initial stage of disturbance is only related to the initial unbalanced power of the system , the larger the power shortage , the faster the frequency decreases .
The steady - state frequency deviation of the system is influenced by the power shortage and the frequency regulation effect .
The dynamic process of frequency is not only related to the magnitude of active default , but also closely related to disturbance position and grid structure .

The dynamic model of the frequency response of the system with the emergency control function module is established , including the system parameters , the threshold value of frequency protection , the disturbed power of the system , the emergency control measures and the trend change of the interconnection line on the frequency stability .
The new strategy is coordinated with the fast release of the low frequency speed regulation and the reserve capacity of the system . According to the system disturbance , the quantity of the load shedding and the number of action series are determined adaptively , so that the over - cutting or undercutting of the load is avoided ;
In consideration of the duty station , the principle of balanced disturbance power is adopted to avoid the occurrence of cascade accidents .

Based on the factors affecting system frequency and frequency change rate measurement , the exact function relation between active power shortage and frequency change rate is derived . Based on the analysis of voltage sensitivity , a self - adaptive load shedding control strategy is proposed to determine the load location and corresponding load load using voltage sensitivity .
It can improve the voltage stability margin of the system and reduce the risk of system crash . The proposed load strategy has stronger adaptability , it is a function relation of load load , load location and action time , which can take into account the change of the network topology of the system , which is more beneficial to the recovery of system stability , and has the advantage and value of application .

【学位授予单位】：华北电力大学
【学位级别】：博士
【学位授予年份】：2014
【分类号】：TM73

【参考文献】