【作者】 竺炜；

【导师】 周有庆；

【作者基本信息】 湖南大学 ， 电气工程， 2010， 博士

【摘要】 论文介绍了电力系统稳定研究的发展历程和发电机稳定研究的背景及意义。针对发电机模型及参考系、功角稳定裕度的实用化分析、汽轮发电机组调速侧稳定控制及低频振荡的抑制等问题开展研究,取得了一些研究成果。论文选题具有理论意义和实际应用价值。目前,功角稳定控制中的发电机模型一般还是基于恒速旋转的x y坐标系,并近似以x轴为同步轴。在系统受到较大扰动并过渡到新的稳定状态后,即使系统频率变化不大,但发电机转子角(相对于x轴)会随时间积分而不断变化,使转子角偏差控制目标无法确定。此外,功率方程由于采用了转子相对角(相对其它转子),将负荷用恒阻抗元件代替,基于线性网络叠加而得,故较为复杂且与实际系统误差较大。考虑到扰动后转子的惯性,忽略电网(包括定子绕组)暂态,则机端电压矢量是与电网状态准同步的。仿真也表明,扰动后其变化远远快于转子角变化。故选择机端电压矢量作为转子准同步参考轴,建立了基于单机二系坐标的发电机模型。分析表明,在大、小扰动情况下该模型都适用,且保留功角作为稳定判据的特性,能方便地适用于现实的功角稳定控制。针对静态功角稳定分析及稳定裕度评估问题,分析发现传统的功角稳定性分析方法或者依赖于系统状态量的强制性解耦,或者依赖于系统的精确模型和参数,在非线性的电力系统状态变化后容易失效。借鉴运动力学空间中静态稳定的物理概念,将电力系统全映射到弹性力学空间,以便直观地理解多机系统的局部稳定与全系统稳定的关系。基于该映射,将发电机与系统解耦并进行了静态功角稳定性分析。利用广域测量系统对节点状态量的实时测量,可得到实用化的稳定判据和稳定裕度指标。数字电液调速系统投运后,一次调频的实际效果有时并不理想,主要问题是一次调频能力不足和出现振荡。通过对实际功频调节控制的理论分析发现,在电网侧发生突变扰动时,功率输出控制环节的动态调节过程表现为前馈开环控制特点,使一次调频初期出现“反调”,并引发过程振荡；而静态调节或以给定值主导调节时,则主要表现为闭环反馈控制特点,使一次调频静态调节能力下降,并使区域系统频率稳定性降低。仿真结果证明了定性分析和定量分析结果的正确性。振荡源和振荡起因问题是目前共振型低频振荡研究的主要问题。分析发现,当电网侧发生振荡功率扰动时,实际的汽轮发电机组功频控制方式会使机械功率阻尼降低。当扰动频率接近共振频率时,会引发机械功率共振。基于典型参数模型的仿真研究除证实了上述分析的正确性外,还表明若系统中某些机组共振频率相近,在小扰动下引起的振荡可能在机组间耦合放大；功率限幅环节,会使非等幅振荡变成等幅、变频的低频振荡模式。针对发电机稳定控制的阻尼方式,研究分析发现,现有控制阻尼是一种被动意义上的阻尼。它与转速偏差同相位,并不减小不平衡力矩,若扰动能量不耗尽,则不能消除振荡。因此,为抑制强迫性振荡,提出了一种减小不平衡力矩的主动阻尼方式,并比较了两种阻尼控制的效果。理论分析表明附加主动阻尼控制后的转速和转子角振幅都较小。基于这两种阻尼原理进行了调速侧电力系统稳定器的设计。仿真结果表明,基于主动阻尼的控制器对电网侧扰动引起的共振型低频振荡有更好的抑制效果。提出了一种新的用于电力系统低频振荡模式识别的改进Prony算法。将待求振荡幅值作为权值,基于神经网络训练,避免了实际计算中矩阵病态导致不可逆,或通过矩阵求逆计算幅值和相位时精度不高的问题；克服了传统Prony算法抗干扰较差的问题。仿真结果表明,该改进算法能有效地去除干扰,可靠、准确地识别主导模式,且计算量少。在振荡信号中含有噪声以及采样点数多的情况,该算法具有较大的优势。更多还原

【Abstract】 Developing history of power system stability study, background and significance in generator stability are introduced. It aims at the problems of generator model and reference frame, practical analysis of generator’s static angle stability, practical turbo-generator power system stability and low-frequency oscillation suppression, has obtained the research results. The selected topics bear academic significance and practical applied values.At present, the generator model in power angle stability control based on the constant speed revolving x y reference frame generally, and takes x as the synchronized axis approximately. When system transit the new steady state after large disturbance, the rotor angle (relative to the x axis) will change unceasingly with time integral, even if the change of system frequency is not big, so that the control objective of rotor angular deviation is not definite. In addition, the power equation, used the rotor opposite angle (relative other rotors), loads replaced with the permanent impedance parts, based on linear network superimposition, therefore more complex and big error with the reality system. Considering the rotor inertia and ignoring network (including the stator windings) transient, the generator terminal voltage vector is synchronous with network, and much faster than the rotor angle in change after disturbing shown by the simulation. Therefore generator terminal voltage vector is selected as quasi-synchronous reference axis relative to rotor, and the generator model in two reference frames is established. Analysis shows the model is applicable to large and small disturbances, reservation of the characteristic of the power angle as the stability criterion, and adaptation to the practical control in power angle stability.With respect to stability analysis of the static power angle and evaluation of the stability margin, the study reveals that the traditional analysis methods of power angle stability depend on mandatory decoupling of system state values, or rely on system accurate model and parameters, which are easily invalidated with the state changes in the non-linear power system. Profits from the physical concept of static stability in kinetics space, the whole power system is mapped to the elastic mechanics space, but understands the relations between partial stability and the entire system stability intuitively in multi-generator power system. Based on this mapping, the static angle stability has analysed depend upon generators and the system decoupling. The practical stability criterion and indicator of stability margin are provided by real-time node status messages using wide-area measurement System.After implementation of a digital electro-hydraulic (DEH) control system, the effect of primary frequency regulation (PFR) is not ideal in some times. The main problems are existence of oscillations and insufficient PFR capability. Through detailed studies of actual power-frequency regulation control, it is discovered that he dynamic PFR process at the power output control module demonstrates feed-forward open-loop characteristics when subjected to abrupt disturbances, causes "reverse regulation" appearing in the initial period of the PFR, and initiates the process vibration. On the other hand, when the system is at steady state or leading regulate state by pre-set value, it mainly illustrates the closed-loop feedback characteristics, debase PFR static regulation capability, and debase the regional power system frequency stability. The simulation results prove the correctness of qualitative analysis and quantitative analysis.The source and cause of oscillation are studied as the main problem for the resonance-type low-frequency oscillation at present. Through the analysis, it’s concluded that practical turbo-generators power-frequency control mode makes mechanical power damping decrease when network side oscillation power disturbance occurs. When disturbance frequency is close to resonance frequency, mechanical power resonance will be triggered. Simulation research based on the typical parameters model demonstrates the above analysis is correct, and oscillation of some machine initiated by small disturbance may be coupled and amplified between generating units if resonance frequencies of generating units are close to each other, amplitude limiter make unequal amplitude oscillation become equal amplitude and frequency changed low-frequency oscillation mode.By studying damping modes of generator stability control, it manifests that existing damping is a passive one, which has the same phase with rotation deviation, can not reduce the unbalanced torque. If disturbance energy not be consumed, oscillation will not be eliminated. Therefore, for the suppression of forced oscillations, an active damping mode aimed to reduce unbalanced torque is put forward, and the control effects of the two kinds of damping are compared. Academic analysis shows amplitudes both of the rotor speed and rotor angle are rather small by additional active damping control. Based on the two damping theories, governor power system stabilizers are devised. Simulation results show the controller based on active damping has better restraining effect to resonance-type low-frequency oscillation aroused by power network side disturbance. A new improved Prony algorithm was presented for identifying power system low frequency oscillation mode. The amplitudes were used as weights and trained in neural network, to avoid some problems, such as irreversibility of ill-conditioned matrix during practical calculation, or poor accuracy of amplitude and phase angle gained by matrix inversion. This improved algorithm overcame poor Anti-Jamming in Prony algorithm. The simulation result show that this improved algorithm can remove interference effectively, identify the dominant mode of low frequency oscillation reliably and accurately, and decrease calculation amount. Especially, it has great advantages when oscillation signal exists interference noise, or amount of sampling points is excessive.更多还原