【作者】 黄莹；

【导师】 徐政；

【作者基本信息】 浙江大学 ， 电力系统及其自动化， 2005， 博士

【摘要】 我国电网正处于高速发展时期,随着“全国联网、西电东送”战略的进一步实施,不远的将来将形成全国性的交直流混合电网。随之会出现一系列的重大技术问题,如低频振荡问题、多直流落点问题等。本文利用电力系统仿真软件PSS/E,结合我国“全国联网,西电东送”战略规划,重点研究了交直流系统的动态特性分析方法。主要内容包括: (1)研究了交直流电力系统机电暂态仿真中的直流输电系统模型,按照是否考虑直流系统高频控制和直流线路的动态特性,将直流系统模型分为响应特性模型和详细模型,并指出了PSS/E的直流模型的适用范围。通过对PSS/E中直流模型的分析和比较,表明响应特性模型CDC4简单明了,参数容易选定,能够满足实际大规模交直流系统仿真分析的要求。 (2)提出一种实用的大规模交直流电力系统低频振荡分析方法,该方法结合了QR特征值分析算法和Prony分析方法的优势,可以很容易在现有程序中实现。对多机系统的低频振荡分析计算表明,发电机采用经典模型与采用详细模型并计及励磁模型相比,系统各振荡模式的频率、振型和参与因子基本保持不变。因而大规模交直流电力系统的低频振荡分析可以分为两步:第一步发电机采用简化模型并利用QR算法计算出系统低频振荡的结构性特征,第二步发电机采用详细模型并考虑励磁控制等模型,再通过Prony方法求出低频振荡主导模式的阻尼。 (3)提出了一种基于同步相量测量单元(PMU)的直流附加控制器。该控制器以PMU得到的区域间电压相角差信号作为输入信号,能够直接有效地反映区域间低频振荡特性。小信号稳定分析结果表明,该控制器在系统较大的运行范围内能够较好地阻尼系统低频振荡,同时提高了交流系统传输能力,具有较好的鲁棒性。时域仿真验证了该控制器在系统大扰动下也能较好地发挥作用。 (4)提出了一种基于PMU的观测线性化最优直流附加控制器。该控制器利用由PMU测量得到的系统实际运行状态量,实现系统状态方程的观测线性化,再应用最优控制原理来实现直流附加控制器。该控制器设计不但避免了设计线性控制器时进行一点线性化的不精确性,而且也避免了设计非线性控制器时进行精确线性化模型的复杂性。小信号稳定分析和时域仿真分析结果表明该直流附加控更多还原

【Abstract】 China’s power grids are developing quickly. With the application of nation-wide power grid interconnection and China’s power transmission from the West to the East, a national hybrid AC/DC power grid will be formed in the future. However, that will bring some technical problems, such as low frequency oscillations, security problem in the system with several HVDC converters terminating in it. By using the power system simulation software PSS/E and combining the strategic planning of China’s national power grids, this dissertation focuses on the dynamic analysis of AC/DC power systems. The main works are organized as follows:The HVDC models for electromechanical transient simulations of AC/DC power systems are studied. According to whether considering the inductive transient processes in DC transmission line and the dynamic characteristics of the high frequency DC controller or not, the HVDC models can be classified into two kinds: HVDC response model and HVDC detail model. And the validity of these HVDC models is discussed. Through the analysis and comparison of the HVDC models in PSS/E, it is shown that the HVDC response model CDC4 is simple and suitable for the transient stability analysis of real large-scale AD/DC power systems.A practical analysis method of low frequency oscillations for large power systems is presented. This method combines the advantages of the QR eigenvalue algorithm and the Prony method. And it is easy to be realized in the existing power system software. The computation results of multi-machine power systems show that the frequency, mode shape and participation factors of each oscillation modes calculated with the classical generator models are basically identical to those with detailed generator models and exciter models. Thus, this proposed method has two steps: first, the basic inherent characteristics of the system oscillation modes are calculated using the QR eigenvalue algorithm with the classical generator models; second, the damping can be calculated using the Prony analysis method with detail generator models and exciter models.A novel HVDC supplementary controller based on Phasor Measurement Unit (PMU) is proposed. This controller’s input signal is the voltage phase angle difference between two areas obtained by PMU, which can effectively reflect the inter-area low frequency oscillation characteristics. The analysis results show that the proposed controller is capable of enhancing thesystem damping and the AC system’s transfer capability over a wide range of operation conditions. This controller can efficiently damp the system’s low frequency oscillation and works well under the condition of large disturbances. In addition, it is also robust.An observational linearization and optimal HVDC supplementary controller based on Phasor Measurement Unit (PMU) is presented. This controller utilizes the real-time state variables obtained by PMU to linearize the state equations of the system, and then the linear optimal control strategy is used to design HVDC supplementary controller. Compared with the controllers based on the models linearized in one operation point, the non-linearity of the system is considered in the presented controller, and its control rule varies with the real-time status of the system.Several important computations for the strategic planning of nation-wide power grid interconnection are accomplished, including the analysis of the low frequency oscillations and transient stability in the interconnection schemes of national power grids in the year of 2015, and the transient stability analysis in the pure DC interconnection scheme in the year of 2030. And the AC/DC interaction characteristics within the multi-infeed HVDC systems are also investigated.更多还原