【作者】 刘道伟；

【导师】 韩学山；

【作者基本信息】 山东大学 ， 电力系统及其自动化， 2011， 博士

【摘要】 随着电网互联范围的不断扩大、电力工业市场化体制改革的不断深入,以及大规模风光等可再生资源并网发电迅猛增长的趋势,使电网运行环境日益复杂,电网安全运行面临严峻挑战。广域测量系统(Wide Area Measurement System, WAMS)技术的成熟以及智能化电网的发展,为电网在线稳定性能态势评估以及预防性控制奠定了基础。目前,基于实测信息的在线稳定性能态势评估主要聚焦于两个方面：一是基于戴维南等效方法的静态电压稳定评估；二是基于实测轨迹的暂态功角稳定预估。虽然,电网静态稳定问题的确涉及功角和电压两个侧面,但二者在一定条件下又是辨证的统一。因此,面临新的形势,在广域环境下开展电网在线静态稳定性能态势评估的研究,具有重要的理论意义和工程应用价值。由此,实现“在线评估、实时决策”的电网监控框架,把握电网输电规律和静态稳定机理是根本。本文研究思路：在广域环境下,以戴维南等效方法为手段,从静态稳定角度出发,将电磁有功功率作为联系电压和功角两个侧面辨证统一关系的纽带,进而丰富电网静态稳定评估理论,有助于电网在线稳定监控的实施。本文的主要工作和创新成果如下：(1)将戴维南等效参数辨识归结为优化问题,提出一种基于轨迹灵敏度的戴维南等效参数迭代优化辨识方法。该方法以节点电压计算值平方与电压实测值平方的差最小为目标,待辨识参数的物理限制作为约束,数学模型简捷、易于快速求解。结合戴维南等效参数对节点电压的轨迹灵敏度,对辨识参数初值进行自适应变步长修正,进而提高参数辨识的精度和速度。仿真算例表明,所提方法具有自适应性强、辨识结果有效等特点,具备在线应用前景。(2)继承传统静态的功角稳定和电压稳定假设条件和概念,在相角和功率因数角δ-Ф空间上构造一种线性化的静态稳定边界域,并以此为基础,提出一种以节点稳定裕度为目标的定量化切负荷快速计算方法。基于局部量测信息获得各节点戴维南等效参数,即可直观展示各节点所处的稳定模式及相对稳定裕度,当节点稳定裕度较低时快速获得近似切负荷量,供调度员参考。这一方法间接避免了潮流计算和具体临界值的求取,从而弥补了传统方法在线应用中存在的求解规模、网络参数依赖、收敛性和计算速度等困境。仿真结果表明,该方法物理概念清晰、计算快速,适于在线应用。(3)基于两节点系统模型,推导了一定有功输送条件下,有功损耗和静态稳定裕度与功率因数角间关系的解析表达式。以此为基础,在二维坐标系下构造出反映这种关系的实时运行域,并提出3个新指标,用以快速预估节点无功补偿情况、指导无功优化目标的选择。实时跟踪辨识戴维南等效参数,可清晰确定当前运行状态下各节点近似所需无功补偿量及无功优化方向,从而为广域环境下的电网局部化无功补偿、控制及均衡化规划等提供了一种新的思路。(4)针对静态的功角稳定和电压稳定在概念和机理上尚未统一,给稳定分析与控制带来不便的情形。在前述研究工作的基础上,从动力学角度出发,提出电网静态稳定实质是电磁有功功率牵引下,“源-网-荷”功率转化过程中的平衡性思想。电压只是这一过程的支撑,本质上属于非线性系统输出变量的有界性问题,而与稳定性没有必然关系。广域环境下基于全参量灵敏度给出广义同步力矩系数的概念,使静态稳定评估理论得到扩展。另外,给出电压支撑量化指标,衡量电网对电压的支撑水平。理论研究与多场景算例分析表明了新判据的有效性和合理性,广域环境下有望实现电网稳定性能态势在线评估和预警。(5)将本文研究方法嵌入到山东电网AVC系统中,实现电网静态稳定性能态势在线评估。将小扰动分析法和本文的稳定裕度指标相结合,分析了风电并网对烟台电网稳定性能的影响。另外,将连续潮流与戴维南等效方法结合,针对山东电网2010年冬季实际预测数据,对多种运行方式下的静态稳定性能和无功补偿进行详细分析,为山东电网运行和规划提供有益参考。最后,面向调度中心监控主站,介绍了“电网静态稳定监控与预警系统”的框架体系和设计理念,并完成相应功能模块的开发,可进一步扩展智能调度支持系统的稳定监控功能。综上所述,本文基于电网实测或仿真信息,就戴维南等效参数辨识、静态稳定域、定量化切负荷、局部化无功补偿、广义静态稳定统一判据等方面进行了比较全面的研究和探索。并提出了相应的模型和方法,经算例仿真和实际电网应用得到比较有效的验证。当然,在实际应用中还有若干细节问题需要深入研究,以便在理论和实践上得到进一步丰富、发展和完善。更多还原

【Abstract】 With the continuous expansion of power system interconnected range, the continuous development of power industry market reformation, and the rapid growth trend in large-scale renewable resources of power generation including wind energy, optical energy, etc, the power system running environment faces increasingly complex situation and the operation safety faces serious challenges. The maturity of wide-area measurement system (WAMS) technology and the development of smart power grid lay a foundation for on-line stability situation assessment and preventive control in power system. Currently, the on-line stability situation assessment, which bases on measured information, focuses mainly on two aspects:first, the static voltage stability situation assessment based on Thevenin equivalent method; second, the transient angle stability assessment based on measured power angle trajectory. Although the static stability of power system indeed involves two sides, voltage and power angle, the two are a dialectical unity under certain conditions. Consequently, facing the new situation, carrying out the study of on-line static stability situation assessment for power system under the wide-area environment, has important theoretical significance and engineering application value.Thus, the power transmission rules and the static stability mechanism is the fundamental to realize the "on-line assessment and real-time decision-making" power system monitoring framework. Under the wide-area environment, this thesis used Thevenin equivalent method as the means, and from the static stability point of view, the electromagnetic active power as a link to contact voltage and angle as a dialectical unity. Thus, the power system stability analysis theory is enriched, which contributes to the on-line stability monitoring implementation. The main research work and innovation of this thesis are shown as follows:(1) Formulating the identification of Thevenin equivalent parameters as an optimization problem, an iterative optimized identification method of Thevenin equivalent parameters based on trajectory sensitivity is proposed. Its objective is to minimize the difference between the square of calculated voltage and the one of the measured voltage, and its constraint is the physical limitations of identified parameters, which is simple and reliable to compute. The initial value of the identification parameter is adaptively step-changing adjusted based on the trajectory sensitivity of the equivalent parameters to the node voltage, which improves the identification precision. The simulation demonstrates the effectiveness and practicality of the proposed method, which has the prospect of application in real-time power system.(2) Inheriting the traditional static angle stability and voltage stability assumptions and concepts, a static stability region is constructed in the space of phase angle and power-factor angle (δ-φ). Based on this, a fast calculation method for quantitative load shedding is proposed, in which the node stability index is taken as an object. Based on local measurement information, the Thevenin equivalent parameters of each node can be acquired, so the stability patterns and the relative stability margin can be directly demonstrated. When the stability margin is at low degree, the approximate load-shedding can be quickly calculated for dispatcher to refer to. The method can indirectly avoid the calculation of power flow and specific critical value, and compensate for the defects of traditional method in the aspects of system scale, network parameters dependence, convergence and speed of calculation. Simulation results show the validity of this method, which has explicit physical meaning, requires less computation work and has the prospect of application in real-time stability assessment and preventive control of power system operating condition.(3) Based on Thevenin equivalent parameters, the analytical expression formulas of active power loss and static voltage stability related to power-factor angle under certain active power model are derived in this paper. According to these formulas, a real-time region reflecting the relationship between active power loss and static voltage stability margin is constructed in a two-dimensional coordinate system. Three new reference indexes are proposed, based on which node reactive power compensation can be quickly estimated and the objective of optimal reactive power flow can be chosen. Real-time tracking the Thevenin equivalence parameters, the reactive power compensation and optimizing direction of node can be confirmed clearly. The method provides a new idea for localized reactive power compensation, control and equalization planning under the wide-area environment.(4) The concepts of static angle stability and static voltage stability are inconsistent, which brings inconvenience to stability analysis and control. From the dynamics views, this thesis argues that the essence of the power system static stability is the balance during the source-network-load power transformation process, while voltage is just a physical quantity which supports the conversion process. And the value of voltage has not necessary internal relationship with system static stability, and it is just boundedness as a non-linear power system output variable. Therefore, this thesis deduces the maximum system active power transmission capability, and its semi-circular boundary in R-X coordinate system. Based on comprehensive physical parameter sensitivities, stability criterion of generalized synchronous torque coefficient, which expanded the static stability theory, is also presented in this paper. In addition, the voltage support level index is also given to measure system voltage support capability. Theory analysis and various simulation examples show the validity and rationality of the newly developed criterion, and it is expected to realize on-line stability monitoring in power system based on wide-area measurement system.(5) This thesis method has been embedded in Power Grid AVC system to realize on-line static stability situation evaluation. Combined the small single analysis and the stability index to analyze the stability performance of wind power to Yantai Power Grid. In addition, with continuation power flow and with the Thevenin equivalent, the static voltage stability and reactive power compensation analysis and research of variety Shandong Power Grid operation ways in the year of 2010 winter actual projections data is presented, the research results can give useful reference for Shandong Power Grid operation and planning. Finally, facing the dispatch center monitoring, It has introduced the frame and design concept of the "static stability of power system monitoring and early warning system", and has completed the corresponding function module development that will further expand the monitoring function of the intelligent scheduling support system.In summary, based on the power system measured or simulation information, this thesis has completed comprehensive research and exploration in the Thevenin equivalent parameters identification, the static stability margin, the quantitative load-shedding, the localized reactive power compensation, generalized static stability criterion and so on. And put forward the corresponding models and methods, the availability is effective verified by numerical simulation and practical power system applications. Of course, there are several details that need further research in practical applications, so that the theory and practice can be further enriched, developed and improved.更多还原