电力系统受迫振荡检测与自适应振荡抑制研究

电力系统受迫振荡的振荡频率与系统跨区域振荡模态接近,因而能够引发强烈振荡。文中首先提出了一种受迫振荡模态检测方法,其通过小信号分析方法得出系统在受迫扰动下对应受迫振荡模态的解析形式;同时提出一种不需要安装额外的功率振荡阻尼器的功率振荡阻尼控制策略用于抑制受迫振荡以及跨区域振荡。并通过改进的14机系统验证文中方法的鲁棒性和优越性。仿真算例证明本文所提方法对于外界扰动具有较强鲁棒性,且较传统方法具有明显优越性。     

Control schemes and transient characteristics of a high‐speed phase shifter for power flow control in power transmission systems

In recent years, attention has been paid to the concept of FACTS (Flexible AC Transmission Systems), along with significant progress in power electronic technology. A high‐speed phase shifter, which is one of the most promising devices in the FACTS concept, has the potential of power flow control and/or voltage stability in power transmission systems. In this paper, theory and experiment reveal that conventional high‐speed phase shifters may cause power swings in a transient state as a result of coupling between instantaneous active and reactive power control loops. Thus, two new control schemes for a high‐speed phase shifter are proposed to achieve both power flow control and power swing damping. The second proposed control scheme is based on the control scheme of an already proposed series active filter. Simulated and experimental results agree well with analytical results, not only in steady states but also in transient states. © 1999 Scripta Technica, Electr Eng Jpn, 128(2): 74–82, 1999     

双馈风电场阻尼系统次同步振荡的无功功率控制策略

引入无功-转速型传递函数,推导了双馈风电场无功功率对系统贡献的阻尼系数大小和性质的表达式,并基于分析获得的提供系统正阻尼条件,优化设计无功功率环附加阻尼控制策略抑制次同步振荡。以双馈风电场接入IEEE第一标准测试系统为例,基于Dig SILENT/Power Factory仿真平台对双馈风电场无功功率附加阻尼控制时的系统运行性能进行仿真比较。理论分析和时域仿真结果表明,推导的阻尼系数表达式以及得到的正阻尼范围条件可以有效分析双馈风电场无功功率对系统次同步振荡的作用,提出的风电场无功功率附加阻尼控制策略能在全次同步频段内提供最优正阻尼,且抑制效果优于有功功率附加PSS阻尼控制。     

七阶混沌振荡电力系统的自耦PD控制

为了抑制七阶电力系统中的混沌振荡,根据自耦PID控制理论提出了一种简单的混沌控制方法。该方法首先将七阶混沌系统控制问题分解为三个严格反馈子系统的控制问题,然后将每个子系统已知和未知动态分别定义为一个总扰动,进而将三个子系统等价映射为一个三阶线性扰动系统和两个二阶线性扰动系统。据此分别构建了在总扰动反相激励下的三个受控误差系统。根据自耦PID控制理论,分别设计了一个扩展自耦PD控制器和两个自耦PD控制器。最后分析了每个子系统的鲁棒稳定性和抗扰动鲁棒性。仿真结果验证了所提控制方法的有效性,每个状态变量均能由混沌振荡状态恢复到稳定运行状态,且控制信号光滑。因此该方法在电力混沌振荡控制系统领域具有良好的实际应用前景。     

基于自适应全局滑模的电力系统混沌振荡控制

对电力系统的二阶模型进行了混沌振荡的动力学行为分析,包括时域波形图、相图的分析。把全局滑模控制与自适应控制结合起来,设计了自适应全局滑模控制器来抑制该二阶电力系统的混沌振荡。设计的控制器克服了滑模控制需要知道系统扰动上界的缺点,同时保留了滑模控制具有良好的鲁棒性的优点。在控制器中,采用了两种不同的自适应率来对系统的扰动进行估计,并对这两种不同的自适应率在控制效果上进行了比较。仿真结果验证了控制器的有效性和良好的鲁棒性。     

An accurate power delivery system (PDS) design methodology for high‐speed digital systems

The trend in high‐speed digital circuits is to increase speed and density and to operate at lower voltage. This fast increase in the switching speed combined with the decrease of the operating voltage causes the allowable absolute voltage variations to decrease, which makes the PDS design a more challenging task than ever. Moreover, the complex 3D nature of the modern PDS causes it to be more sensitive to capacitors' placement as well as capacitance value. In this paper, we introduce an efficient complete solution for the design of high‐speed digital PDS. This solution (a) takes the effects of the decoupling capacitor placement into consideration through a 3D electromagnetic simulation of the PDS, (b) defines a more‐realistic PDS design target, and (c) presents a clear capacitor value selection methodology. Finally, we applied our methodology to an industrial test case, compared its results with that of industrial design, and showed its advantages. Copyright © 2010 John Wiley & Sons, Ltd.     

Unbalanced power flow calculation of a power system containing a variable‐speed generator

There are some factors that render a power system network unbalanced: UHV transmission lines in which three‐phase transmission lines are not transposed, an unbalanced transformer, unbalanced load as well as sustained unbalanced faults. On the other hand, the number of variable‐speed generators used in pumping‐up power stations has recently been increasing in Japan. This paper presents a new means of calculating unbalanced power flow of a power system which contains variable‐speed pumping‐up generators. This new technique is based on the phase coordinate method, because a power system which has elements of unsymmetrical impedance can easily be analyzed by using it. In this paper, phase coordinate models of the variable‐speed generator and its secondary exciting circuit, composed of a GTO converter/inverter, are analyzed first. Procedures of power flow calculation of unbalanced power systems follow. © 2000 Scripta Technica, Electr Eng Jpn, 134(3): 34–43, 2001     

Virtual synchronous generator model control of PV for improving transient stability and damping in a large‐scale power system

Because of the significant changes in environmental policies and electric power deregulation in the last decade, a lot of photovoltaic generations (PV) have been and will be installed into the power system in Japan and the ratio of PVs to other synchronous generators will be increased. As a countermeasure against the decrease in the rotational inertia in the whole power system, a virtual synchronous generator (VSG) model control of the PV has so far been proposed. However, the system stabilization effect of the VSG in large‐scale power systems has been unclear. In this paper, a virtual step‐out blocking method of VSG for improving the transient stability is proposed. In addition, the necessity of governor control of VSG in a large‐scale power system is discussed. Finally, the rated kw and kwh capacities of the battery required for realizing the VSG‐model control are evaluated.     

Robust damping control of power oscillation incorporating parametric resonance

In this paper we consider a damping control of low‐frequency oscillations in an electric power system. On the basis of the hypothesis that an auto‐parametric resonance model can explain a power oscillation, we propose a new model for a robust damping control, by which the system maintains stability even if some auto‐parametric resonance happens. With this model, we can express a parametric variation of a principal oscillation mode and a class of uncertainties which cover neglected dynamics. Since the model has a certain structure of uncertain parameters, we design a robust controller via µ‐synthesis. The robust controller which can be obtained from the presented design strategy has the property that the control performances are more sophisticated in comparison to controllers designed with other existing methods based on the H_∞ control. © 2002 Wiley Periodicals, Inc. Electr Eng Jpn, 142(1): 42–49, 2003; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.10069     

光储联合发电系统的功率振荡特性分析与控制

高渗透光储并网发电系统功率振荡将因缺乏阻尼能力而威胁系统的动态稳定。首先分析通过调节光储系统的有功、无功增加系统阻尼的原理,并在光储联合系统并网功率控制的基础上,提出光储系统基于有功、无功控制的附加阻尼控制策略。该控制策略通过检测光伏侧直流电压变化,实现功率振荡过程中光伏并网逆变器和蓄电池储能系统的控制模式切换,使联合系统具备持续调节注入系统有功、无功功率的能力,并改善电网的阻尼特性。最后,基于渗透率约为30%的光储并网发电仿真系统,验证在系统出现振荡后,光储系统在所提控制策略下,具备通过快速功率调节抑制功率振荡的能力,从而实现多电源协调改善发电系统阻尼的控制目标。     

Examination of new vector control system of permanent magnet synchronous motor for high‐speed drives

A new vector control system for permanent magnet synchronous motor drives has been developed. To stabilize the current control loop in the high‐rotating‐speed region, a novel configuration of current controller is introduced. The unique characteristic of the proposed current controller is that the current regulator is connected to the conventional motor model in a series. By analyzing the transfer characteristics of the control, it became clear that the influence of the coupling component between the d–q axes can be deleted theoretically if the control parameters are set properly. The stability and torque response of the proposed vector control system were improved, and the effectiveness of the proposed controller was demonstrated by a time domain simulation and some experiments. In addition, the robustness of the controlling system was investigated experimentally. © 2011 Wiley Periodicals, Inc. Electr Eng Jpn, 176(4): 61–72, 2011; Published online in Wiley Online Library ( wileyonlinelibrary.com ). DOI 10.1002/eej.21123     

Damping enhancement of multimachine power system using adaptive generator control system with neural networks

The authors proposed a nonlinear adaptive generator control system with neutral networks for improving damping of power systems, and showed its effectiveness in a one-machine infinite bus test power system in a previous paper. The proposed neurocontrol system adaptively generates appropriate supplementary control signals to the conventional controllers such as the automatic voltage regulator and speed governor so as to enhance transient stability and damping of the power system. In this paper, the applicability of the proposed neurocontrol system to multimachine power systems is discussed. Digital time simulations are carried out for a 4-machine test power system, where one or several synchronous generators is equipped with the neurocontrol system. As a result, also in the multimachine power system, the proposed adaptive neurocontrol systems improve the system damping effectively and they work adaptively against the wide changes of the operating conditions and the network configuration.     

Stabilization of a large‐capacity,long‐distance transmission system by a combination of a system damping resistor and an adjustable speed flywheel generator

A system damping resistor (SDR), which is a type of stabilizing equipment, is especially effective in decelerating the first synchronous generators' acceleration. An adjustable speed flywheel generator (FWG) is effective not only in decelerating the first acceleration but also in improving the dynamic stability. We have studied the combined effect of the SDR and FWG for a model network with a large‐capacity long‐distance transmission system. It has two types of instability mode. One is immediate step‐out type by unbalanced fault such as same‐phase 1LG‐OC (1 Φ2LG‐OC). The other is dynamic unstable type by balanced fault such as 3LG‐O. We found that SDR–FWG combination using proper control method has the effect of decreasing total capacity, yielding economical advantages. © 2001 Scripta Technica, Electr Eng Jpn, 138(3): 52–62, 2002     

电力系统低频振荡实时控制

低频振荡实时控制方法将小干扰稳定在线控制策略或设定的离线策略应用于控制实际发生的低频振荡。通过小干扰稳定计算得到电网的弱阻尼模式,分别计算将各弱阻尼模式的阻尼提高到不同档位的控制措施。在电网发生低频振荡时进行在线分析,采用实测主导模式的频率筛选出候选的模式集,根据振荡中心的信息在小干扰稳定性分析中对设备进行分群,并根据设备分群信息确定与实测主导模式对应的模式,根据实测主导模式阻尼与临界安全阻尼门槛值的差值确定对应的小干扰稳定计算得到的控制措施。若没有与实测主导模式对应的模式,则从离线策略表获取辅助决策信息。最后通过自动发电控制(AGC)系统或调度员命令实施相应的控制策略。     

基于分散控制理论的多机系统低频振荡抑制

常规的电力系统低频振荡抑制措施是在发电机励磁系统中加装电力系统稳定器(PSS),然而它在多机电力系统中的应用并没有充分的理论研究.将大系统分散控制原理应用于多机电力系统低频振荡抑制问题,只要分散阻尼控制器(DDC)的阶数足够高,分散闭环控制系统的低频振荡模态总可以在复平面内任意配置.分析了PSS与DDC的关系,论证了PSS是DDC的一种特殊形式,因而从理论上说明了DDC比PSS优越.将DDC的优化配置表示为一个带不等式约束的非光滑优化问题并用遗传算法求解.以新英格兰测试系统和我国西北电网为算例的计算结果表明,在发电机励磁系统中加装DDC是一种有效的低频振荡抑制新措施.     

Improvement of power system stability by high-speed power control of adjustable speed machines

Large-capacity adjustable speed machines (ASMs) at pumped storage power stations have been put into full operation and their operating characteristics have been highly evaluated from the viewpoint of power system operation. The output power (input power) of ASMs can be controlled very quickly by applying a vector control scheme to the excitation control. This quick responsive feature of ASMs can make it possible to improve the stability of the neighbor subpower system. For improvement of transient stability, the output power of ASMs is reduced very quickly in order to control the acceleration of neighbor generators during and after transmission line faults. For improvement of dynamic stability, the output power of ASMs is modulated in accordance with the stabilizing signals detected from the swing of generator rotor or the power flow fluctuation on the transmission line. This paper describes the design concepts and method of control system for improving the transient and dynamic stability and proposes a power system stabilizing control system. The effects of the proposed stabilizing control system have been verified by a power system simulator. © 1997 Scripta Technica, Inc. Electr Eng Jpn, 121(2): 27–36, 1997     

Autonomous decentralized system for torque control of high‐power permanent magnet synchronous motor

An autonomous decentralized system (ADS) for the control of a high‐power permanent magnet synchronous motor (PMSM) presented in this paper. The system decentralizes a centralized control system into several autonomous subsystems. Thus the power supply and power electronic devices of the control system can be replaced by smaller ones, thereby obtaining better fault tolerance of the system. The subsystems are connected only through the data field, which, in this paper consists of feedback elements and communication modules. This structure enables the autonomous controllability and autonomous coordinability of the system. The mathematical model of the PMSM with decentralized stator coils is proposed. This model takes into account the self‐ and mutual inductance of the coil, as well as the effect of the stator slot‐pitch angle. In addition, an autonomous algorithm for the torque control of the PMSM with decentralized stator coils is proposed, and the fault‐tolerance design is developed. Experimental results of the torque control and fault‐tolerance control confirm the validity of the proposed system. © 2012 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

A high‐speed reclosing method to improve the stability in a power system

This paper proposes a high‐speed reclosing operating method to improve the stability in a power system. The proposed method calculates the reclosing time, taking a standard case in which the reclosing is not done using the generator phase angle δ, and the angular velocity ω, and the field system voltage ed′. Also, the execution of reclosing time is calculated, while taking into consideration the acceleration/deceleration energy of the generator during a fault. It can be expected that δ is suppressed by this optimum reclosing operation. Therefore, the system stability can be expected to improve by carrying out high‐speed reclosing when a fault occurs. At present, it has been set at a value which seems to be optimal considering various problems in the reclosing time. However, in those methods, the system stability improvement effect cannot be expected. It was demonstrated that the high‐speed reclosing method serves to depress δ in the computer simulation. © 2004 Wiley Periodicals, Inc. Electr Eng Jpn, 147(2): 13–21, 2004; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.10317     

Dual high‐gain‐based adaptive output‐feedback control for a class of nonlinear systems

We propose an adaptive output‐feedback controller for a general class of nonlinear triangular (strict‐feedback‐like) systems. The design is based on our recent results on a new high‐gain control design approach utilizing a dual high‐gain observer and controller architecture with a dynamic scaling. The technique provides strong robustness properties and allows the system class to contain unknown functions dependent on all states and involving unknown parameters (with no magnitude bounds required). Unlike our earlier result on this problem where a time‐varying design of the high‐gain scaling parameter was utilized, the technique proposed here achieves an autonomous dynamic controller by introducing a novel design of the observer, the scaling parameter, and the adaptation parameter. This provides a time‐invariant dynamic output‐feedback globally asymptotically stabilizing solution for the benchmark open problem proposed in our earlier work with no magnitude bounds or sign information on the unknown parameter being necessary. Copyright © 2007 John Wiley & Sons, Ltd.     

Stabilization of a large‐capacity,long‐distance transmission system by an adjustable‐speed flywheel generator

An adjustable‐speed flywheel generator (FWG) can control both active power and reactive power rapidly. We have studied the effect of FWG installation on a large‐ capacity, long‐distance transmission system, especially when the system includes loops. In this paper, we describe the selection of FWG location, the selection of stabilizing control input signal, and the required quantities of FWG. FWG location is selected by a PQ‐sensitivity method, calculation of which is simple and permits easy understanding of the effect of both FWG's active and reactive power. As a stabilizing control input signal, we use bus voltage frequency instead of power flow because the flow changes stepwise by opening three‐phase single‐circuit. Additionally, we clarify the FWG quantities that must be designed, such as FWG's active power and reactive power. We considered FWG's slip to determine the quantity because the capacity of the exciter depends on slip. © 1999 Scripta Technica, Electr Eng Jpn, 127(2): 32–41, 1999