交直流系统扰动后稳态频率预测与自动切负荷控制研究

发布时间：2018-12-28 21:21

【摘要】：受我国能源和负荷分布、地理特征等诸多原因影响,高压直流输电技术在能源大容量、远距离外送中发挥着至关重要的作用。随着能源战略的逐步实施,大型电源基地的逐渐涌现,特高压直流输电系统传输功率的逐步提高,交直流系统安全稳定运行变得日益复杂,交直流系统安全稳定性问题越来越受到人们的关注。交直流系统安全稳定性研究中,频率稳定是重要组成部分,利用特高压直流输电系统短时过载能力和功率快速可控的特点,可以达到提高系统频率稳定性的目的。本文针对计及紧急直流功率支援的交直流系统扰动后稳态频率预测及自动切负荷优化控制开展研究,主要研究内容如下:首先,介绍了电力系统频率特性的一些基本概念,包括电力系统的静态频率特性和动态频率特性。然后综述了几种电力系统动态频率分析方法,分别为:动态潮流法、频率稳定分析快速算法和基于广域量测的频率预测算法。其次,提出了一种计及紧急直流功率支援情况下,能同时考虑直流两侧电网频率响应的扰动后稳态频率预测算法。该算法首先建立扰动后瞬间和扰动后稳态发电机电磁功率增量方程、负荷功率增量方程、直流输电系统功率增量方程和系统网络方程,同时考虑紧急直流功率支援,推导了两区域交直流系统扰动后稳态频率预测方程,可以直接快速地计算出扰动后各区域的稳态频率。对一个典型的两区域交直流并联系统进行了仿真分析,仿真结果表明本算法具有较高的精度和较快的计算速度,证明了算法的适用性和有效性。该算法能够应用于电力系统频率安全稳定的在线评估。最后,针对两区域交直流互联系统,提出了一种计及紧急直流功率支援的频率稳定控制策略。当其中一个区域扰动后频率降低时,首先预测该区域扰动后系统的稳态频率,如果该频率低于整定值,则计算出系统频率恢复到整定值需要的直流功率支援量。如果该直流功率支援量大于另一个区域能提供的最大直流功率支援量,则利用线性优化的方法计算出系统在另一个区域能提供的最大直流功率支援量下还需切除的最少负荷,从而使系统的频率控制在整定值。通过算例分析,该策略能够快速、准确的计算出系统所需的直流功率支援量和切负荷量,满足系统频率稳定控制和经济性运行的要求。
[Abstract]:Under the influence of energy and load distribution, geographical characteristics and other reasons, HVDC technology plays an important role in large capacity and long distance transmission of energy. With the gradual implementation of the energy strategy, the emergence of large power supply bases and the gradual improvement of the transmission power of UHVDC transmission systems, the safe and stable operation of AC / DC systems becomes increasingly complex. People pay more and more attention to the safety and stability of AC / DC system. Frequency stability is an important part of the research on the safety and stability of AC / DC system. The frequency stability of UHVDC transmission system can be improved by utilizing the characteristics of fast and controllable capacity and power of UHVDC transmission system in short time. In this paper, the steady-state frequency prediction and automatic load shedding optimization control of AC / DC system after disturbance considering emergency DC power support are studied. The main research contents are as follows: firstly, some basic concepts of frequency characteristics of power system are introduced. It includes static frequency characteristic and dynamic frequency characteristic of power system. Then several dynamic frequency analysis methods of power system are summarized, which are dynamic power flow method, fast frequency stability analysis algorithm and frequency prediction algorithm based on wide area measurement. Secondly, a prediction algorithm for steady-state frequency is proposed, which can take into account the frequency response of both sides of the DC power system. In this algorithm, the electromagnetic power increment equations, load power increment equations, DC transmission system power increment equations and system network equations for transient and post-disturbance steady-state generators are established, and emergency DC power support is considered at the same time. The prediction equation of steady-state frequency after disturbance of two-region AC / DC system is derived. The steady state frequency of each region after disturbance can be calculated directly and quickly. A typical two-area AC / DC parallel system is simulated and analyzed. The simulation results show that the algorithm has higher accuracy and faster calculation speed, and proves the applicability and validity of the algorithm. This algorithm can be applied to the on-line evaluation of power system frequency security and stability. Finally, a frequency stability control strategy considering emergency DC power support is proposed for two area AC / DC interconnected systems. When the frequency of one region is reduced, the steady-state frequency of the system after the disturbance is first predicted. If the frequency is lower than the tuning value, the DC power support needed to recover the system frequency to the tuning value is calculated. If the DC power support is greater than the maximum DC power support provided by another region, the minimum load to be removed from the system under the maximum DC power support provided by the other region is calculated by linear optimization method. Thus, the frequency of the system is controlled at the set value. Through the example analysis, the strategy can quickly and accurately calculate the DC power support and load shedding of the system, and meet the requirements of frequency stability control and economic operation of the system.
【学位授予单位】：西南交通大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TM712

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