Coordinated design of under-excitation limiters and power systemstabilizers

The inherent dynamical relationship between the under-excitation limiter (UEL) and the power system stabilizer (PSS) control loops in synchronous generators is studied using the frequency response technique. While the stabilizers are effective in introducing electromechanical damping torque components into the generators, it is shown that the limiters should be designed to effect a much slower response characteristics as their main function is to prevent excessive stator end-core heating. The analysis also shows that a reduction in the values of the slope of the boundary curves, which prescribe the operating region of the limiters, is accompanied by a decrease in the damping level of the closed-loop excitation control systems. A method which decouples the design procedure of the UEL from that of the PSS is then proposed     

Impact of energy storage system on load frequency control for diverse sources of interconnected power system in deregulated power environment

This paper focuses Load Frequency Control (LFC) mechanism for multi-generating two areas interconnected power systems with energy storage system in a deregulated power environment. The two areas, demarcated as Area-I and Area-II, consist of thermal, hydro and gas power units. This paper also incorporates the economic load dispatch mechanism into the LFC for economical division of load during load deviation. Small signal stability analysis through participating factor has also been done to determine the oscillation state of the system, i.e., frequency deviation in both areas. Therefore, proper controller is required to reduce the oscillation of the system. The optimum value of the integral gain of the integral controller has to be selected to achieve the goal. Hence, Opposition-based Harmonic Search (OHS) technique is used for the optimization purpose. During major disturbance in the areas, primary and secondary controllers are not sufficient to reduce the frequency and tie-line power oscillation due to slow response of the governor mechanism. Therefore, energy storage system, i.e., Redox Flow Battery (RFB), is used for improvement of the dynamic response of the system which has very small time constant and quick response. The proposed control mechanism has been analyzed in a deregulated power environment with the help of different simulation case studies to find out improved dynamic performance over integral control strategies.     

Impact of the exciter voltage limit to small signal stability region of a three-bus power system

We investigate the influence of non-differential components to the power system small signal stability region in this paper. A method named unified expression function (UEF) is introduced to describe the piecewise, continuous and non-differential function in the small signal stability study. It converts non-differential points of the original function to poles of the UEF’s derivative function. Then the derivative at those poles can be approximated by UEF’s left-hand or right-hand derivative limits according to the requirement. Based on this method, impact of the exciter voltage limit to power system small signal stability region is then deeply discussed using a simple three-bus power system. We find that the exciter voltage limit can change elements of the system Jacobian matrix so as to cause jump of the system critical eigenvalue. As a result, two new Hopf bifurcation boundaries and a new instability hole emerge in the small signal stability region. When the exciter voltage limit varies, the new instability hole and the new Hopf bifurcation boundaries will change significantly. It makes the topological characteristics of the small signal stability region much more complicated. Since there are many non-differential components in power systems, they should be correctly considered in power system stability studies.     

Heirarchical power system control

The present status and future problems of hierarchical power system control are reviewed. Special emphasis is placed on the hierarchical structure of power system control. Power system control has been developed in close association with the progress of the power system itself. The hierarchical structure of the control system is closely connected, therefore, with that of the power system, and this structural relationship is reviewed. Motivations of using a hierarchical structure of power system control are reviewed in terms of power system control and planning. Required performances of computers installed at respective levels of hierarchical control system are discussed. Benefits resulting from the introduction of such control systems are summarized, and future problems associated with the further development of hierarchical power system control are considered.     

Impact of automatic switches on power distribution system reliability

In this paper quantitative impact of automatic switches on the reliability of power distribution systems is studied. Based on the characteristics of the studied system's topology, the reliability model is developed for the implementation of Monte Carlo simulation. Reliability indices on each load have been computed to obtain an overall reliability assessment of the system, and the sensitivity of the reliability indices to the location of automatic switches is also studied. Simulation results are used to illustrate the validity of the approach and are compared with the historical reliability records.     

关于电力系统稳定控制方式的探讨

电力系统安全性与经济性之间的矛盾随着电力系统的发展而不断加剧。系统互联从一定程度上缓和了这一矛盾,然而大电网中由于故障引起连锁反应,而导致大面积停电的可能性也大大增加了。实践表明采用紧急控制则是经济、灵活和有效的。文中介绍了稳定控制装置的控制原理、结构组成和可采取的控制模式,提出了一种“集中管理,分区控制”的现代稳定控制模式。     

Stabilizing control of power system using fuzzy control

This paper presents an application of fuzzy control to enhance power system stability. The proposed control consists of the controller for large disturbance (FU 1), the fuzzy controller for small disturbance (FU 2), and the fuzzy judgment mechanism (FU 3). FU 1 is determined based on the fuzzy controller [FU 1(F)] is determined according to the control rules and its input signals, i.e., speed deviation and acceleration at every sampling time of the machine. FU 2 consists of two controllers, namely, FU 2-ω and FU 2-P; FU 2-ω has the same mechanism as FU 1, while the output signal of FU 2-P is determined according to the rules together with the change of error of electrical power and terminal voltage. To obtain the optimal desired control signal during both the large and the small disturbances, the operations of FU 1 and FU 2 are judged by FU 3, where the magnitude of speed deviation is chosen as its input signal. The determined control signal is fed to AVR of the machine. The implementation of the proposed control is simple due to the small amount of calculations and required data. The effectiveness of the proposed control is demonstrated by the one-machine infinite-bus system model and very good system performance is obtained throughout all the simulations.     

直驱永磁风电机组虚拟惯量控制对系统小干扰稳定性影响分析

虚拟惯量控制方式下,直驱永磁风力发电机组(DDPMSG)能够为电力系统提供较好的频率支撑,但虚拟惯量控制使DDPMSG与系统之间产生了新的耦合关系,给系统的小干扰稳定带来新的影响。建立了包含DDPMSG的风电并网系统状态空间平均模型,并通过线性化得到其小信号模型。基于该小信号模型,利用特征分析法分析了虚拟惯量控制的比例系数和微分系数对风电并网系统的小干扰稳定性的影响,同时对比分析了虚拟惯量控制及最大功率跟踪控制对系统小干扰稳定的影响。结果表明虚拟惯量控制对系统阻尼特性的影响与DDPMSG接入系统的位置及容量有关,且主要影响其所接入区域的局部振荡模式和系统的区域振荡模式。     

浅谈电力系统中电压无功功率的控制

电力系统的负荷需要消耗大量的无功功率,而无功功率平衡要满足众多的结点电压,就需要分级分层就地平衡。地区电网的电压无功控制,主要是控制其管辖范围内的各级变电站,使电网的电压合格,并实现无功的就地平衡,降低网损。为此,通过分析变电站电压无功控制的主要设备：有载调压变压器、并联电容器以及并联电抗器,说明变电站电压无功控制的原则、要求、实现方式。     

发电机组参与电网一次调频的特性研究

一次调频是确保电力系统频率稳定的主要途径之一,但目前采用DEH(数字式电液)控制系统的发电机组,通过调节系统设置较大的调频死区,切除一次调频的控制作用,大大降低了一次调频在突发性事故中稳定电网频率的作用。为研究发电机组参与电网一次调频的特性,建立了3区域互联系统的数学模型,并通过仿真试验,分析研究了不同的调频死区参数设置条件下,电网稳定所需要的一次调频容量,确定电网负荷扰动大小与机组调频容量之间的关系,对于指导电网中发电机组调节系统的参数设置和调整以及电网一次调频容量的确定具有重要的指导意义。     

An improved voltage control on large-scale power system

To achieve a better voltage-VAr control in the electric power transmission system, different facilities are used. Generators are equipped with automatic voltage regulators to cope with sudden and random voltage changes caused by natural load fluctuations or failures. Other devices like capacitors, inductors, transformers with on load tap changers are installed on the network. Faced with the evolution of the network and operating conditions, electricity utilities are more and more interested in overall and coherent control systems, automatic or not. These systems are expected to co-ordinate the actions of local facilities for a better voltage control (more stable and faster reaction) inside different areas of the network in case of greater voltage and VAr variations. They afford a better use of existing reactive resources. Also, installation of new devices can be avoided allowing economy of investment. With this in mind, EDF has designed a system called Co-ordinated Secondary Voltage Control (CSVC). It is an automatic closed loop system with a dynamic of a few minutes. It takes into account the network conditions (topology, loads), the voltage limits and the generator operating constraints. This paper presents improvements which allow the CSVC to control the voltage profile and different kinds of reactive means on a large-scale power system, Furthermore, this paper presents a solution to spread out investment costs over several years, considering a deployment gradually extended     

空间电源系统控制技术研究

小型智能飞行机器人系统是我国第一颗机器人卫星.针对小型智能飞行机器人卫星的电源系统,阐述了当今空间电源系统控制器的新型拓扑结构及功率调节技术等新技术特点和空间电源的发展方向.在对当代空间电源系统控制技术总结分析的基础上,结合航天器电源系统未来的发展趋势,对电源系统控制器中锂离子电池组的充电管理电路和S4R功率系统调节技术的原理及工作方式进行了详细的叙述.     

基于以太网的风力发电控制系统的研究

风能的能量密度低、波动性大、不能直接储存等特点,使得风力发电的控制系统成为保证其在恶劣环境下也能安全可靠运行的关键。在分析风力发电控制系统基本工作原理的基础上,设计了以PLC控制逻辑系统为主体的,以以太网为通信系统的风力发电控制系统,并进行了初步的可行性验证。结果证明,该系统运行稳定、可靠性强。     

电压下降时同步电动机的动态稳定极限

利用同步电机的状态方程,研究了同步电动机在电压下降时的动态过程。经过多次迭代,分别得到了当电压下降为不同值时,同步电动机保持动态稳定的极限时间;以及不同的机组惯性常数和电机的励磁状态对动态稳定极限时间的影响;最后得出了一些有用的结论。     

基于IPC模糊控制的互联电网联络线潮流控制研究

为了提高互联电网问联络线负荷的稳定性,提出了一种联络线传输功率和频率协调模糊控制方案。通过调节联络线两端发电机组对两侧电网频率差进行调整,调节相间功率控制器(IPC)元件参数调整联络线传输功率,对调节参数采用模糊逻辑控制。模拟通过IPC互联的东北-华北电网,对不同控制区域进行控制仿真。结果表明,在一侧发生小扰动时,另一侧电网和联络线功率几乎不受影响,在大扰动时,两侧系统能可靠实现同步运行。     

风光互补逆变器串联发电系统功率平衡控制

介绍了风光互补逆变器串联发电系统的拓扑结构,采用载波移相正弦波脉宽调制(CPS-SPWM)技术控制各个发电单元逆变器的通断,该调制方式下系统输出电压为多电平,且电压、电流的谐波含量大大降低。在功率预测和功率分配的基础上对发电系统进行能量管理,根据负载功率需求分别通过调节发电单元DC/DC变换器和蓄电池双向DC/DC变换器,控制各个发电单元以及蓄电池的输出功率,达到系统功率平衡控制的目的。仿真结果表明,该功率平衡控制策略能够保证系统功率平衡,满足系统在独立运行时负载功率跟踪控制的要求。     

Hierarchical optimization for power system control

This paper presents a practical feedback control strategy for the transient stability problem. The control configuration is hierarchical and is proposed to be installed in addition to existing machine excitation and turbine governor controls. The design proceeds in two steps. First, the local controllers associated with the subsystems are independently designed by fixing the interconnections. Then a higher hierarchical level is designed from the interconnection variables and nonlinear terms. The resulting parameter optimization problem is solved by a decentralized computational structure. The scheme is based on multilevel optimization techniques with multiple objectives given by relevant system disturbances, aggregated by means of a weighted sum. The usefulness of the proposed technique is demonstrated by its application to a power system optimization problem with practical soft constraints on the control variables.     

基于耗散系统实现电力系统励磁鲁棒非线性控制

对单机无穷大系统，通过适当的坐标变换，基于耗散系统的概念，提出了一种新的通过干扰抑制实现的励磁鲁棒非线性控制策略，在实现过程中不需要任何线性化方法．该控制策略可提高系统对动态不确定性的鲁棒性，可抑制干扰对系统的影响．仿真结果表明，提出的励磁控制策略可提高电力系统暂态稳定性．