A heuristic‐based design of robust SMES controller taking system uncertainties into consideration

In this paper, a heuristic‐based design of robust superconducting magnetic energy storage (SMES) controller is proposed taking system uncertainties into consideration. The SMES model with active and reactive power controllers is used. In addition, the effect of SMES coil current is also included in the model. The power system and the SMES unit with the designed controller are formulated as an optimization problem. The proposed objective function considers both the damping performance index and the robust stability index. In particular, the robust SMES controller is designed to enhance the system damping performance and robustness against system uncertainties such as various load and system parameter changes. The robust stability margin is guaranteed in terms of the multiplicative stability margin (MSM). In the proposed method, the robust SMES active and reactive power controllers are designed systematically by using hybrid tabu search and evolutionary programming, so that the desired damping performance and the best obtainable MSM are acquired. Finally, the designed SMES controller is examined under different situations to evaluate and confirm the effectiveness and robustness via eigenvalue analysis and nonlinear simulations. © 2006 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

A robust SMES controller design for stabilization of inter-area oscillations based on wide area synchronized phasor measurements

This paper proposes a robust power controller design of superconducting magnetic energy storage (SMES) based on wide area synchronized phasor measurement units (PMUs) for stabilization of inter-area oscillation. The structure of active and reactive power controllers of SMES is the first-order lead/lag compensator. Assuming multiple PMUs are located in an interconnected power system, the steady state phasor data are obtained by applying the small load perturbation. Using the phasor data, the simplified oscillation model (SOM) included with SMES power controllers can be identified and applied to estimate the dominant inter-area oscillation modes. In the robust control design, unstructured system uncertainties such as various operating conditions, system parameters variation, etc., are represented by the inverse additive perturbation and included in the SOM. To enhance the system robust stability margin, the optimization of SMES control parameters is solved by genetic algorithm in the SOM. Simulation studies in the West Japan 6-machine power system confirm that the robustness of the proposed SMES is much superior to the conventional SMES against various operating conditions and fault locations.     

超导磁储能系统的自适应单神经元控制

基于自适应单神经元的控制方法是将单个神经元与环境系统相连,利用结合了Hebbian学习和监督学习特点的迭代算法在线修改其连接权值以实现控制目标.将这种控制方法用于超导磁储能(SMES)控制器的设计无需进行系统建模,所得到的控制器结构简单,算法简便,适于工程应用.文章在MATLAB环境下建立了较精确的含SMES的电力系统非线性高阶模型,通过时域仿真考察了基于自适应单神经元的SMES控制器的性能,结果表明该控制器具有令人满意的控制效果和较好的鲁棒性.     

Coordinated stabilizing control for large-scale interconnected power systems,by superconducting magnetic energy storage unit and power system stabilizers

The purpose of large-scale power system interconnection is to achieve extremely economical and reliable power generation and transmission. It has established the present power systems of high quality. On the other hand, in the large power systems with complex configuration, an undamped power swing with low frequency caused by the synchronous power between interconnected systems tends to occur as well as an undamped power swing caused by the synchronous power of specific generators. Several coordinated stabilizing control schemes for the power systems by sets of power system stabilizers (PSSs) have been investigated so far. PSS is very effective for the stabilization of power swing among a few specific generators because the function of PSS is achieved by the voltage control using the generator field winding circuit. However, it seems that PSSs do not have sufficient ability to stabilize the power swings between interconnected systems. In this paper, the superconducting magnetic energy storage (SMES) which is significantly effective for the power swings between interconnected systems is introduced and a coordinated power system stabilizing control by SMES and PSSs is proposed. The advantages of the proposed control scheme are: 1) high efficiency of the controller by the distribution of functions; 2) independency of the control design for PSS and SMES; and 3) robustness of the controller, and so on.     

A fuzzy logic controlled superconducting magnetic energy storage,SMES frequency stabilizer

This paper presents application of fuzzy logic controlled superconducting magnetic energy storage device, SMES to damp the frequency oscillations of interconnected two-area power systems due to load excursions. The system frequency oscillations appear due to load disturbance. To stabilize the system frequency oscillations, the active power can be controlled via superconducting magnetic energy storage device, SMES. The error in the area control and its rate of change is used as controller input signals to the proposed fuzzy logic controller. In order to judge the effect of the proposed fuzzy logic controlled SMES, a comparative study is made between its effect and the effect of the conventional proportional plus integral (PI) controlled SMES. The studied system consists of two-area (thermal–thermal) power system each one equipped with SMES unit. The time simulation results indicate the superiority of the proposed fuzzy logic controlled SMES over the conventional PI SMES in damping the system oscillations and reach quickly to zero frequency deviation. The system is modeled and solved by using MATLAB software.     

A novel quasi-oppositional harmony search algorithm and fuzzy logic controller for frequency stabilization of an isolated hybrid power system

The intermittent wind power in isolated hybrid distributed generation (IHDG) may cause serious problems associated with frequency (f) and power (P) fluctuation. Energy storage devices such as battery, super capacitor, and superconducting magnetic energy storage (SMES) may be used to reduce these fluctuations associated with f and P. This paper presents a study of IHDG power system for improving both f and P deviation profiles with the help of SMES. The studied IHDG power system is consisted of wind turbine generator and diesel engine generator. Both f and P control problems of the studied power system model are addressed in presence or absence of SMES. Fuzzy logic based proportional–integral–derivative (PID) controller with SMES is used for the purpose of minimization of f and P deviations. The different tunable parameters of the PID controller and those of the SMES are tuned by a novel quasi-oppositional harmony search algorithm. Performance study of the IHDG power system model is carried out under different perturbation conditions. The results demonstrate minimum f and P deviations may be achieved by using the proposed fuzzy logic based PID controller along with SMES.     

风力发电机组独立变桨鲁棒自适应桨距角跟踪控制

在全面考虑风力发电机组桨叶所受各种载荷的情况下,建立了含有时变不确定项、未知载荷干扰的桨叶动力学数学模型,该模型精确描述了桨叶系统的非线性动力学行为。模型存在很多不确定时变参数和未知干扰项,针对这一复杂多变的桨叶模型,采用鲁棒自适应控制方法,成功设计了独立桨距角跟踪控制器。利用李雅普诺夫(Lyapunov)稳定性理论,证明了系统的稳定性。采用Matlab/Simulink仿真软件,建立了风力机组桨叶动力学仿真模型。仿真结果表明,所设计的桨叶桨距角控制器,在系统参数和所受干扰完全未知、不确定且时变的情况下,能够快速跟踪期望的桨距角,表现出良好的鲁棒性。     

A robust centralized SMES controller design based on WAMS considering system and communication delay uncertainties

It is well known that the communication delay due to the phasor measurement in wide area monitoring system (WAMS) as well as various system operating conditions such as heavy line flows and unpredictable network structures, may deteriorate the wide-area stabilizing control effect. To overcome this problem, the inverse input and output multiplicative model is proposed to represent unstructured uncertainties due to system operations and communication delay in the robust centralized damping controller design of superconducting magnetic energy storage (SMES) based on WAMS. The structure of centralized controller for SMES is the practical 1st-order lead/lag compensator. To automatically tune the control parameters, the optimization problem based on the enhancement of damping performance and system robust stability margin is achieved by particle swarm optimization. Simulation studies in the West Japan six-area interconnected system confirm that the proposed robust SMES centralized controller is superior to the conventional SMES centralized controller in terms of damping performance and robustness against system and time delay uncertainties.     

基于超导储能的暂态稳定控制器设计

设计了用于提高电力系统的暂态稳定超导储能(SMES)装置的非线性鲁棒控制器,并从数字仿真和动模实验两方面进行了验证。为了简化动态性能分析和控制器设计,在实验样机的基础上,提出了新的基于电流型变流器的SMES的动态模型,并将其转化为标幺制模型。通过外部干扰的引入,得到了装设SMES的单机无穷大系统的动态模型,并采用精确线性化方法和线性H∞控制理论设计了SMES的非线性鲁棒控制器。为了验证该控制器的效果,对装设SMES单机无穷大系统进行了数字仿真和动模实验,并将其与常规PI控制器进行了比较。仿真和实验结果都证明了非线性鲁棒控制器具有良好性能。     

大型风电机组的模糊增益调度PI控制器设计

当风速超出额定风速时,大型风电机组通常采用变桨距的控制方式,通过调整叶片桨距角,改变气流对叶片的攻角,从而改变风电机组获得的空气动力转矩,实现对额定功率的稳定追踪。结合模糊控制与PI（比例-积分）控制,分别设计了模糊PI与模糊增益调度PI 2种变桨距控制器,并在Simulink软件环境下,利用Fast软件提供的5 MW陆基风力发电机模型进行仿真实验。仿真表明,新的控制器能有效缩短调节时间,减小系统超调量,具有较好的控制效果。     

基于线性自抗扰技术的SMES储能变流器控制策略

储能系统作为微电网中不可或缺的重要组成部分,对保证微电网的稳定运行和提高微电网电能质量具有重要作用。提出一种基于线性自抗扰控制(linear active disturbance rejection control,LADRC)的超导磁储能系统(superconducting magnetic storage system,SMES)储能变流器控制策略,利用LADRC能够估计并补偿系统扰动,可有效改善储能系统输出电能质量和提高系统鲁棒性。通过对LADRC和比例积分(proportional integral,PI)控制系统进行频率响应特性分析可知,一阶LADRC的反馈补偿器可以等效为一个PI控制器串联一个一阶低通滤波器,能有效抑制系统高频噪声;同时使用根轨迹法分析了LADRC控制系统的稳定性和鲁棒性。MATLAB仿真结果表明,基于LADRC的SMES储能变流器控制策略具有响应速度快、控制精度高、抗扰能力强等优点,其控制效果和鲁棒性均优于传统PI控制器。     

Superconducting energy storage technology-based synthetic inertia system control to enhance frequency dynamic performance in microgrids with high renewable penetration

With high penetration of renewable energy sources (RESs) in modern power systems, system frequency becomes more prone to fluctuation as RESs do not naturally have inertial properties. A conventional energy storage system (ESS) based on a battery has been used to tackle the shortage in system inertia but has low and short-term power support during the disturbance. To address the issues, this paper proposes a new synthetic inertia control (SIC) design with a superconducting magnetic energy storage (SMES) system to mimic the necessary inertia power and damping properties in a short time and thereby regulate the microgrid (µG) frequency during disturbances. In addition, system frequency deviation is reduced by employing the proportional-integral (PI) controller with the proposed SIC system. The efficacy of the proposed SIC system is validated by comparison with the conventional ESS and SMES systems without using the PI controller, under various load/renewable perturbations, nonlinearities, and uncertainties. The simulation results highlight that the proposed system with SMES can efficiently manage several disturbances and high system uncertainty compared to the conventional ESS and SMES systems, without using the PI controller.     

Improvement of Wind-Generator Stability by Fuzzy-Logic-Controlled SMES

This paper proposes a fuzzy-logic-controlled superconducting magnetic energy storage (SMES) scheme for the stabilization of grid-connected wind-generator systems. The control scheme of SMES is based on a sinusoidal pulsewidth-modulation voltage-source converter and a two-quadrant dc–dc chopper using an insulated-gate bipolar transistor. A comparative study is carried out between the proposed fuzzy-logic-controlled SMES and the fuzzy-logic-based pitch controller to improve the wind-generator stability. Simulation results demonstrate that the performance of the proposed fuzzy-logic-controlled SMES is better than that of the fuzzy-logic-based pitch controller in order to stabilize the wind generator.      

Augmentation of transient stability using a superconducting coiland adaptive nonlinear control

The very nonlinear nature of the generator and system behaviour following a severe disturbance precludes the use of classical linear control techniques. In this paper, a nonlinear adaptive excitation and a thyristor-controlled superconducting magnetic energy storage (SMES) unit is proposed to enhance the transient stability of a power system with unknown or varying parameters like equivalent reactances of the transmission lines. The SMES unit is located near the generator bus terminal in a power system. A nonlinear feedback control law is found which linearizes and decouples the power system. An adaptive control law is used to design the controller for the generator excitation and SMES system. Simulation results demonstrate that the proposed controller can ensure transient stability of a single-machine-infinite-bus system under a large sudden fault which may occur near the generator bus terminal     

Decentralized model predictive‐based load‐frequency control in an interconnected power system concerning wind turbines

This paper presents a load‐frequency control (LFC) design using the model predictive control (MPC) technique in a multi‐area power system in the presence of wind turbines (WTs). In the studied system, the controller of each local area is designed independently such that the stability of the overall closed‐loop system is guaranteed. A frequency response model of the multi‐area power system including WTs is introduced, and physical constraints of the governors and turbines are considered. The model was employed in the MPC structures. Digital simulations for a two‐area power system are provided to validate the effectiveness of the proposed scheme. The results show that with the proposed MPC technique the overall closed‐loop system performance shows robustness in the face of uncertainties due to governor and turbine parameter variation and load disturbances. A performance comparison between the proposed controller with WTs and MPC without WTs and a classical integral control scheme is carried out, confirming the superiority of the proposed MPC technique with WTs. © 2012 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

Superconducting magnetic energy storage controller design and stability analysis for a power system with various load characteristics

A simultaneous active power and reactive power (P–Q) control scheme of superconducting magnetic energy storage (SMES) unit is proposed to enhance the damping of a power system. In order to control the P–Q modulation to the power system, a proportional-integral (PI) controller is used to provide a supplementary damping signal. The parameters of the PI controller are determined by a systematic pole assignment method based on modal control theory. Both static load and dynamic load are included to improve the system model fidelity. Eigenvalue analysis and time-domain nonlinear simulation, using a power system incorporating a composite load, are illustrated to validate the effectiveness of the proposed PI SMES controller for the damping of the studied system over a wide range of operating conditions. The control scheme also shows that the stability margin of the power system is expanded.     

风力发电机独立变桨控制技术系统级优化研究

针对目前独立变桨距风力发电机存在桨叶受力载荷过大、输出功率和电压不稳定的问题,采用模型参考自适应控制方法进行控制器优化,研究了风力发电机独立变桨优化控制问题。讨论了模型参考自适应控制方法下参考模型选取的过程,根据Lyapunov稳定性理论对模型参考自适应控制器进行了设计,并将这一控制器应用在风力发电机的独立变桨距上。仿真结果表明,该控制方法不仅提高了变桨控制器的响应速度和跟踪精度,而且能够稳定输出功率和电压,同时也能够减少各桨叶的拍打震动。模型参考自适应控制器能够应用在风力发电机独立变桨距控制中,控制效果良好。     

应用超导储能装置阻尼次同步谐振的研究

提出了一种新的应用超导储能(SMES)装置阻尼电力系统次同步谐振(SSR)的方法。与以往的类似研究相比,由于本方法基于复转矩系数法, 因而不仅可以适应多机复杂电力系统, 还可以得到电气阻尼系数随扰动频率的变化曲线。在引入SMES控制装置后的IEEE第一基准模型中, 根据复转矩系数法的基本原理, 得出了发电机机械复转矩系数和考虑SMES装置时的电气复转矩系数的表达式, 给出了二者之间的定量关系式, 以此为基础研究了应用超导储能装置阻尼次同步谐振的控制策略, 设计了相应的比例积分(PI)控制器,给出了控制框图, 并在IEEE第一基准模型的系统结构和参数条件下得到了控制器参数。在PSCAD /EMTDC环境中将控制策略和超导磁储能装置应用于IEEE第一基准模型进行了动态仿真, 仿真结果验证了该控制方案的有效性和正确性。     

超导磁储能系统抑制风力发电功率波动的研究

建立含超导磁储能装置(SMES)的单机无穷大系统的Phillips-Heffron模型,导出含SMES电力系统总的电磁转矩表达式,从理论上分析SMES对增强系统阻尼的作用.并设计了SMES非线性比例积分微分控制器,数字仿真结果验证了SMES阻尼系统功率振荡的特性,同时表明该控制器具有较好的鲁棒性.     

柔性直流附加鲁棒阻尼控制器设计

针对包含柔性直流(VSC-HVDC)的交直流互联系统区间低频振荡现象,提出把基于线性矩阵不等式的多目标控制方法应用到柔性直流附加控制中。具体包括运用最小二乘旋转不变方法(TLS-ESPRIT)辨识出系统降阶模型,综合考虑控制器的鲁棒性和控制代价,设定多目标函数,设计出H₂/H_∞多目标鲁棒附加阻尼控制器,并设计传统极点配置控制器进行比较。在PSCAD/EMTDC中搭建包含柔性直流的四机两域电磁暂态模型,特征值分析和时域仿真结果表明:在系统内部参数发生较大变化情况下,多目标鲁棒阻尼控制器具有更好的阻尼特性,并兼顾了控制器的控制代价。