D-分割技术确定磁轴承的PID参数鲁棒稳定域

给出仅依靠频率响应确定磁轴承的PID控制参数鲁棒稳定域的方法。根据小增益定理得到闭环系统的鲁棒稳定性条件,由此推导出加性不确定性的内部稳定H∞指标,再由边界穿越定理和D-分割技术,推导了满足H∞指标的PID控制器的鲁棒参数稳定域边界的解析表达式。在稳定域中任选PID参数,可以使得系统稳定并满足鲁棒性能约束条件。该方法降低了PID控制器参数稳定域设计的难度,对磁轴承时滞系统PID参数调节具有良好的鲁棒性。仿真和实验证明了本文方法的有效性。     

Robust adaptive control using a combined approach

Direct control, indirect control and variable structure methods are combined with high-gain feedback in this paper for the robust adaptive control of first-, second- and third-order plants with increasing levels of uncertainty. The latter include external disturbance, unmodelled dynamics, time delay and sensor noise. A judicious combination of the methods is found to result in satisfactory response in most cases.     

采用Halbach磁场的新型被动磁轴承仿真

为了提高永磁磁轴承的轴向承载力和刚度,在对理想Halbach磁场进行分析的基础上,利用分段磁环构成的近似Halbach磁场设计了一个新型的轴向永磁磁轴承.通过有限元软件对这种磁轴承进行了建模仿真,计算了最大承载力以及刚度,并分析了磁环的厚度与高度比值对磁轴承刚度的影响.仿真结果表明,采用Halbach磁场的轴向磁轴承最大可以提供2×106N/m的刚度,高于相同永磁材料用量条件下传统轴向磁轴承的刚度.考虑到这种磁轴承的结构要比传统结构复杂,因此这种磁轴承更适合在对刚度要求高的场合应用.     

Control of magnetic bearing using the observer for unbalance

An unbalance on a rotor causes whirling motions of the rotor and alternating forces of the bearings in rotating machines. The authors have shown a magnetic bearing control system in which an unbalanced rotor can be suspended without whirling. The concept of designing the control system involved an observer estimating the effects of unbalance and then cancelling using the electromagnetic forces of the bearing. With the control method applied, the position of the rotor can be maintained at the desired position with high precision. However, it is suitable for some machines to minimize the variation of exciting currents or vibratory force transmitted to the base through the bearing. This paper presents control methods that can eliminate stationary alternating components from exciting currents or electromagnetic forces by using the output of the observer. Another control method is presented in which feedback of the estimated signals of the displacements of the principal axis occurs; such signals are obtained by compensating synchronous observatory disturbances by use of the output of the observer. It is shown that the proposed three control methods are equivalent when unbalance stiffness due to the bias magnetic flux is null.     

基于磁能恢复开关的单相串联补偿器的研究

作为一种新的无功补偿装置,不论负载阻抗如何变动,磁能恢复开关都能自动地校正功率因数,并且还具有结构简单、容易控制和损耗低等许多优点。基于磁能恢复开关的单相串联补偿器中,磁能恢复开关能够吸收并恢复负载电感中的磁场能量,实现无功功率的补偿。仿真分析获得了很高的功率因数,直流输出电压具有较小的纹波,并在实验中得到了验证。     

Power-system stabilizing control by SMES using fuzzy techniques and neural networks

It has been clarified that a superconducting magnetic energy storage (SMES) is very effective for power system stabilization. The control methods proposed for power system stabilization by SMES include the pole assignment, the optimum control, and so on, each of which, however, has its drawbacks. The application of fuzzy control is considered to overcome these drawbacks. This paper considers the power system stabilization by fuzzy control of the active and reactive power of SMES. First, the adequate fuzzy control rules of an SMES for the model power system is derived. Then, to alleviate the dependence of the fuzzy control on the operating condition and the fault, a method is proposed which adjusts the fuzzy parameter according to the operating condition and the fault using a neural network. The validity of the proposed method is examined by computer simulations.     

Wide area stabilization of a magnetic bearing using exact linearization

An active magnetic bearing (AMB) is a bearing used to suspend a rotor by magnetic forces without any contact. Feedback control is indispensable for a magnetic bearing, because it is essentially an unstable system. To design a feedback control system, a linear mathematical model of the plant is convenient; however, the force of the electromagnet is highly nonlinear. Thus, usually a linear approximation around the operating point is employed, but the obtained linearized model cannot express the exact behavior of the system at any other operating points. In this paper, we discuss the wide area stabilization of magnetic bearings using the exact linearization approach. First, we derive a nonlinear mathematical model for a magnetic bearing, then we show that this nonlinear system belongs to a class of exactly linearizable nonlinear systems. Next, by using the exact linearization method, we transfer the nonlinear model of a magnetic bearing to a linear time‐invariant state model in spite of change of the operating point and the rotational speed of the rotor. Then we construct the state feedback control system by the conventional LQ method. Finally, we evaluate the validity of our proposed method by experiments. © 1999 Scripta Technica, Electr Eng Jpn, 128(2): 53–62, 1999     

混合径向磁轴承非对称位移传感器容错控制

针对混合径向磁轴承用的位移传感器容易发生故障可靠性不高的问题,依据冗余位移传感器检测思路,采用坐标变换矩阵技术,提出一种位移传感器的故障识别与容错控制方法.通过将位移传感器非对称安装在混合径向磁轴承的外围,根据位移传感器的故障状态选取不同的坐标变换矩阵,实现转子在水平和竖直两个自由度上的位移检测.传感器位置的非对称安装...     

Power system stabilizing control by a superconducting magnetic energy storage with a high-speed phase shifter

Electric power demand has increased rapidly and this is expected to continue. Undamped power swings with low frequency tend to occur in large power systems with complex configuration. Therefore, several stabilizing control schemes, e.g., a power system stabilizer (PSS), have already been investigated. On the other hand, superconducting magnetic energy storage (SMES) is expected to be an effective apparatus in power systems since any SMES located in power systems is capable of leveling load demand, compensating for load changes, maintaining bus voltages and stabilizing power swings. The effectiveness of each function, however, depends upon the location of the SMES in the power system because output power from the SMES is distributed according to the impedance ratio of the transmission line at the SMES location. Therefore, it is difficult for SMES to serve two different purposes simultaneously. This paper proposes a combination of SMES with a high-speed phase shifter (HSPS). The HSPS, which consists of a phase shift transformer and a set of power converters, is capable of controlling the power flow of the transmission line by adjusting the phase angle of a phase shift transformer. Therefore, it is expected that the combination of SMES and HSPS can realize a highly effective controller independent of its location. Numerical examples demonstrate that the proposed apparatus located far from a generator in a long distance bulk power transmission system is capable of stabilizing the power swing as effectively as the SMES located at a generator terminal. In addition, the effectiveness of both load change compensation and power system stabilization is confirmed numerically.     

Power system stability improvement using dynamic output feedback compensators

A novel approach is presented for the design of physically realizable dynamic output feedback compensators for linear time-invariant single-input single-output systems. The simplicity and effectiveness of the proposed method is demonstrated by an example of feedback compensator design for a power system.     

Voltage control stability and dynamic interaction phenomena ofstatic VAr compensators

This paper describes the results of a comprehensive investigation on: (1) small-signal dynamic interactions of voltage control loops of multiple static VAR compensators (SVCs); (2) the phenomena of SVC-network interactions; and (3) torsional interactions with SVCs. This paper is concerned with small-signal dynamics in the high frequency (HF) range, i.e. above 4 Hz. The studies are conducted on various power system configurations, based on the use of a newly developed eigen analysis software tool. The eigen analysis tool provides a systematic approach to include the dynamic mathematical model of the transmission network in the overall system model, which is necessary for HF dynamic studies. The investigations identify undesirable small-signal oscillations associated with SVC-SVC and/or SVC-network interactions, and provide fundamental information for design/coordination of SVCs     

磁悬浮辅助轴承用双层滚珠轴承性能分析

磁悬浮轴承常应用于高速工况,传统滚珠轴承的极限转速较低,成为制约其作为辅助轴承可靠性的关键因素,而采用双层轴承将有效提高轴承的极限转速.以单层混合陶瓷球轴承为对象,分析磁悬浮轴承失电后高速转子跌落至辅助轴承后的动力学过程,得到轴承转速变化规律;进而研究双层轴承相较于单层轴承的转速分配情况,分析其转速提升情况.通过对双层...     

A decentralized control system for stabilizing a longitudinal powersystem using tieline power flow measurements

A decentralized control system for stabilizing a longitudinal power system is studied. The system is designed by a design methodology proposed earlier for decentralized control. In the process of the design, it is found that only the control information of phase angles from other areas is indispensable for maintaining the system stability. New measurements of the tieline power flow are substituted for the indispensable information. Simulation studies demonstrate that the resulting decentralized control system using tieline power flow measurements has as excellent performance in enhancing the stability of a longitudinal power system as a centralized control system     

Robust excitation control design using sliding-mode technique for multimachine power systems

An output feedback controller is proposed to enhance the transient stability of nonlinear multimachine power systems considered as a classical model with flux decay dynamics. Combining high-order sliding-mode techniques with a robust high-order sliding-mode differentiator, a robust decentralized controller is obtained. Numerical results are presented to illustrate the performance of the proposed control scheme and its robustness properties.     

A global dynamic error driven control scheme for static VAR compensators

The paper presents a novel static VAR compensator SVC control scheme. The new SVC control strategy is validated on a single machine infinite bus power system with a dynamic nonlinear load.     

Robust speed control method for dc servomotors using adaptive gain law

The speed control ability of dc servomotors is affected by parameter variations and disturbance torque. In this paper, a robust speed control method for dc servomotors with a disturbance torque observer and a feedback controller is proposed. The disturbance torque observer is used for the compensation of parameter variations and disturbance. The feedback gain is adjusted in the aspect of stability by an adaptive gain law based on Lyapunov's direct method and is used to restrain the influence of estimation error for the disturbance observer. A robust current control scheme for a voltage source PWM inverter with disturbance observer is also presented, since current control ability affects the control performance of dc servomotors. The validity of this control scheme is verified by numerical simulations and experiments. © 1999 Scripta Technica, Electr Eng Jpn, 126(3): 30–40, 1999