Fault Estimation for a Class of Markov Jump Piecewise-Affine Systems: Current Feedback Based Iterative Learning Approach

In this paper, the issues of stochastic stability analysis and fault estimation are investigated for a class of continuoustime Markov jump piecewise-affine(PWA) systems against actuator and sensor faults. Firstly, a novel mode-dependent PWA iterative learning observer with current feedback is designed to estimate the system states and faults, simultaneously, which contains both the previous iteration information and the current feedback mechanism. The auxiliary feedback channel optimizes the response speed of the observer, therefore the estimation error would converge to zero rapidly. Then, sufficient conditions for stochastic stability with guaranteed performance are demonstrated for the estimation error system, and the equivalence relations between the system information and the estimated information can be established via iterative accumulating representation.Finally, two illustrative examples containing a class of tunnel diode circuit systems are presented to fully demonstrate the effectiveness and superiority of the proposed iterative learning observer with current feedback.

WAVE CURRENT FORCE COEFFICIENTS ON INCLINED CYLINDER AND A NEW ESTIMATION METHOD

Based on the review of present force coefficients estimation methods, a new method in the frequency domain, revised cross-spectrum estimation method, is presented in this paper. Some experiments on the wave-current force on inclined cylinders are also described and the wave current force coefficients are estimated by the revised cross-spectrum estimation method. From the results, it is found that the wave and current directions have some regular effect on the coefficients. According to the results, some empirical formulas are obtained for converting the wave-current force coefficients on inclined cylinders into a unified coefficient. Comparisons show that the unified coefficients are in good agreement with other results.

Reference-input-based Imaginary Axis Current Estimation Method for DQ Control Strategy in Single-phase PWM Converters

For dq control strategies in single-phase pulse width modulation(PWM)converters,the-axis current must be created by imaginary axis current estimation(IACE)methods.The estimated error of the-axis current during the transient process causes d-q axis current loops to be incompletely decoupled,thereby affecting the dynamic performance of the current loop.The second-order generalized integrator(SOGI)method suffers from slow dynamic response.The fictive-axis emulation(FAE)method provides fast dynamic response but it is sensitive to circuit parameters.A reference-input(RI)-based IACE method is proposed to overcome the above shortcomings.According to the characteristic that the-axis current loop has no transient process,the-axis current is estimated by the d-q axis reference inputs.This is equivalent to introducing the-axis reference input as a feedforward term into the d-q axis current loop,so the parameter sensitivity problem is solved,and the parameter tuning is not needed.The proposed method can maintain good steadystate performance and significantly improve the dynamic performance of the current loop.Furthermore,it is straightforward and can be easily implemented in digital controllers.Comprehensive hardware-in-the-loop(HIL)experimental comparisons with the SOGI and FAE methods have been conducted to verify the correctness and effectiveness of the proposed RI-based IACE method.

State Estimation of Distribution Network Considering Data Compatibility

Considering that the measurement devices of the distribution network are becoming more and more abundant, on the basis of the traditional Supervisory Control And Data Acquisition (SCADA) measurement system, Phasor measurement unit (PMU) devices are also gradually applied to the distribution network. So when estimating the state of the distribution network, the above two devices need to be used. However, because the data of different measurement systems are different, it is necessary to balance this difference so that the data of different systems can be compatible to achieve the purpose of effective utilization of the estimated power distribution state. To this end, this paper starts with three aspects of data accuracy of the two measurement systems, data time section and data refresh frequency to eliminate the differences between system data, and then considers the actual situation of the three-phase asymmetry of the distribution network. The three-phase state estimation equations are constructed by the branch current method, and finally the state estimation results are solved by the weighted least square method.

Calculation of Eddy Current Loss and Short-circuit Force in SSZ11-50000/110 Power Transformer

The ?method is used in this paper to calculate the leakage magnetic field of SSZ11-50000/110 Power transformer, and by which the structures’ influences to the main leakage flux are analyzed. Through the combination of the product and TEAM Problem 21B, the surface impedance method shows its great advantage in the calculation of eddy current loss.

Algorithms for automatic measurement of SIS-type hysteretic underdamped Josephson junction’s parameters by current-voltage characteristics

Some electrical parameters of the SIS-type hysteretic underdamped Josephson junction(JJ)can be measured by its current-voltage characteristics(IVCs).Currents and voltages at JJ are commensurate with the intrinsic noise level of measuring instruments.This leads to the need for multiple measurements with subsequent statistical processing.In this paper,the digital algorithms are proposed for the automatic measurement of the JJ parameters by IVC.These algorithms make it possible to implement multiple measurements and check these JJ parameters in an automatic mode with the required accuracy.The complete sufficient statistics are used to minimize the root-mean-square error of parameter measurement.A sequence of current pulses with slow rising and falling edges is used to drive JJ,and synchronous current and voltage readings at JJ are used to realize measurement algorithms.The algorithm performance is estimated through computer simulations.The significant advantage of the proposed algorithms is the independence from current source noise and intrinsic noise of current and voltage meters,as well as the simple implementation in automatic digital measuring systems.The proposed algorithms can be used to control JJ parameters during mass production of superconducting integrated circuits,which will improve the production efficiency and product quality.

基于OCV模型优化的磷酸铁锂电池SOC估计

锂离子电池荷电状态(SOC)与开路电压(OCV)的关系曲线(OCV曲线)是影响其SOC估计精度的核心因素。针对小电流OCV(LO)测试耗时短但数据精度较低的问题,提出一种OCV模型及其优化方法。该方法基于LO测试的OCV数据,采用道格拉斯-普克算法和分段线性函数建立OCV模型。并将OCV曲线上的4个OCV点作为变量,建立了其他OCV点的随动模型,使曲线能够运用粒子群优化算法进行优化。基于优化后的OCV曲线,动态工况下的端电压估计绝对平均误差降低83.5%,采用自适应扩展卡尔曼滤波的SOC估计误差小于0.3%。该方法能够基于耗时短的LO测试获取准确OCV曲线,降低锂离子电池研究与应用的测试成本。

基于改进WOA-MP算法的多普勒海流计回波信号频率估计研究

受海洋环境复杂干扰影响,多普勒式海流计的超声波回波信号易受干扰影响,包含多种频率成分,这给海流流速信息的解算带来困难。为解决多普勒海流计回波信号频率估计精度较差的问题,提出一种基于信号匹配追踪(MP)的频率估计方法,并融合改进型鲸鱼优化算法(MWOA)提高估计过程的效率。该方法利用混沌映射提升初始种群多样性,并引入自适应权重和非线性收敛因子提高算法局部寻优能力、搜索速度和求解精度。而后,对改进算法与其他优化算法进行对比测试,结果显示所设计改进算法在收敛速度和寻优能力上具有有效性和优越性。此外,通过对多普勒回波信号进行特征重构,开展MWOA-MP算法在噪声环境下的频率估计精度性能测试。在回波信号信噪比为–10 dB条件下,MWOA-MP算法相对传统方法抗噪声能力提高30%。与其他智能方法融合MP后的频率估计算法相比,MWOA-MP算法的估计误差在10 Hz以内,可满足多普勒海流计频率测量精度要求。

永磁同步电机扩展卡尔曼滤波器电流观测方法

为提高前置电感电容LC滤波器永磁同步电机系统性能,提出一种基于扩展卡尔曼滤波器(extended Kalman filter,EKF)的电机电流观测控制方法。该方法采集逆变器侧电流,通过新型EKF观测器获得实际电机电流,并将估计的电机电流用于电流环反馈控制。论文给出了新型EKF电流观测器的结构和参数设计过程,并利用Lyapunov稳定性定理证明了该方法的稳定性。仿真结果表明,与传统Luenberger观测器相比,新型EKF观测方法的电流估计误差更小,电机电流跟踪性能更好,电磁转矩脉动及其谐波明显降低。

光学电流传感消抖卡尔曼本征信号高精度提取方法研究

本征信号是光学电流传感长期运行稳定性和高精度测量的重要性能参数。目前,传统方法如双光路法并不能消除本征信号的抖动,对光学电流传感高测量精度产生消极影响。为此,提出了光学电流传感消抖卡尔曼本征信号高精度提取方法来对本征信号进行消噪处理。首先对光学电流传感的噪声特性以及光路结构进行分析,建立了光学电流传感本征信号模型。引入消抖函数修正卡尔曼增益K,提出了消抖卡尔曼(Debouncing Kalman,DBK)算法,解决了标准卡尔曼增益K对初始状态依赖性强以及测量过程不确定性非常敏感带来的状态估计值严重抖动问题。并且引入了噪声方差递推估计,来保证在滤波过程中可以实时对噪声方差进行修正。在MATLAB进行了消抖卡尔曼滤波算法的验证并与标准卡尔曼算法进行了滤波效果的对比分析,验证了该算法的可行性,并结合李雅普诺夫稳定性分析法推导验证了该算法的稳定性。最后,搭建光学电流传感实验平台,将所提算法在LabVIEW FPGA硬件平台并行实现,验证了该算法的实时性,且能够满足实际工程需求。

Characteristics of Bi-2223 HTS Tapes Under Short-Circuit Current Impacts in Hybrid Energy Transmission Pipelines

A hybrid energy transmission pipeline is proposed with the aim of long-distance cooperative transmission of electricity and chemical fuels, which is composed of an inner high-temperature superconducting (HTS) power cable and outer liquefied natural gas (LNG) pipeline. The flowing LNG could maintain the operating temperature of the inner HTS power cable within the range of 85 K-90 K, thus the Bi-2223 superconductors in the HTS power cable produce little Joule loss with the transmission current below the critical current. Owing to the advantages of high power density, low transmission losses and economical manufacturing costs, the hybrid energy transmission pipeline is expected to be widely utilized in the near future. In order to ensure the safety of the HTS power cable and explosive LNG in case of short-circuit faults, this paper tests and analyzes the characteristics of Bi-2223 HTS tapes of the Type HT-CA, Type HT-SS and Type H models under short-circuit current impacts at the LNG cooling temperature (85 K-90 K). An experimental platform is designed and established for the ampacity tests of HTS tapes above LN2 cooling temperature (77 K). The AC over-current impact tests at 85 K-90 K are carried out on each sample of Bi-2223 tapes respectively, and the experimental results are analyzed and compared to evaluate their performances under different operating conditions. The results indicate that the Type HT-CA tape can withstand 50 Hz short-circuit current impact with the amplitude of 1108 A (10 times of critical current Ic ) for 100 ms at 90 K, and its resistance is the smallest of the three tested samples under similar current impacts. Therefore, the Type HT-CA Bi-2223 tape is the optimal superconductor of the HTS power cable in the hybrid energy transmission pipeline.

利用改进MUSIC方法进行洋流方位估计

洋流能够调节全球热量的分布,降低航运成本。以往的洋流方位估计方法未对洋流信号源之间的相关性进行完全消除,导致估计效果较差。因此,本文设计了基于改进MUSIC方法的洋流方位估计方法。首先,以采集到的洋流信号为基础,构建洋流阵列信号模型,并对洋流信号进行降噪处理,提高信号数据的质量。然后,为减少洋流信号源之间相关性对估计结果的影响,利用改进MUSIC方法及协方差矩阵,对洋流信号源相关性进行消除,通过计算信号源的相关参数,构建洋流方位估计模型。最后,通过对洋流信号源的转换,实现洋流方位的估计。在仿真试验中,以南海部分海域为试验对象,对不同谱点下估计方法的估计效果进行评价,与以往的洋流方位估计方法相比,设计的基于改进MUSIC方法的洋流方位估计方法精度高达97.2%,应用效果更好。

基于自适应神经模糊推理系统的避雷器有效运行寿命估计方法

估算金属氧化物避雷器的使用寿命一直是一项挑战,它决定着输电系统的安全稳定运行。基于此,文中提出了一种基于自适应神经模糊推理系统(adaptive neuro-fuzzy inference system,ANFIS)和支持向量机回归(support vector machine for regression,SVR)组成的组合时间序列预测模型,用于估算金属氧化物避雷器(metal oxide surge arrester,MOSA)的使用寿命。首先,文中进行了现场测量,考虑到该分量是避雷器监测中最常用的MOSAs劣化水平指标之一,以建立由泄漏电流三次谐波分量值组成的时间序列数据库;接着,利用ANFIS、SVR和仿真数据库,建立组合预测模型;随后,文中使用3种类型的误差:即MSE、MAE和MAPE评估预测模型的性能。最后,在对模型进行评估之后,利用所提模型对MOSA的使用寿命估算,研究结果表明,使用组合模型预测比基于ANFIS和SVR的模型提供的预测更准确,可提升估算MOSA使用寿命的精度18.9%。

利用健康因子的卫星电池容量估计方法

卫星在轨工作期间,准确估计电池容量对提高电源系统的安全性与可靠性有重要意义。为此,针对电池在工作过程中实际容量难以直接测量的问题,提出一种利用间接健康因子估计电池容量的方法。首先,从锂电池恒压充电模式下的电流数据中提取平均充电电流,将其作为反映电池容量变化的特征参数。在实现了锂电池健康状态表征的基础上,对比分析容量和平均充电电流随着充放电循环周期的变化曲线。然后,讨论了容量和平均充电电流之间的相关性,进而建立了容量估计模型。最后,通过从NASA锂电池数据集中提取容量和平均充电电流,划分训练集和测试集,验证了用该方法估计容量的有效性和准确性。

基于相电流查表法的工业机器人用PMSM逆变器非线性补偿策略

针对传统方法无法完全考虑所有逆变器非线性因素的问题,提出一种基于相电流预估值查表法的误差电压精确计算方法。在综合考虑逆变器关断/开通延时、死区时间、寄生电容等多种非线性因素的影响的基础上,采用滤波后的电流指令进行误差电压查表,有效避免反馈电流引入谐波、电流钳位等干扰因素对查表法逆变器非线性补偿策略的影响。通过搭建伺服电机对托平台,验证了所提方法在工业机器人控制中的有效性。实验结果表明:与传统逆变器非线性补偿策略相比,所提算法具有更优秀的电流谐波抑制能力,可实现更优异的补偿效果,补偿后相电流THD小于1.5%。

基于变直流母线电压的磁耦合式励磁系统控制策略研究

磁耦合式无线励磁系统是电励磁同步电机无刷化研究的热点之一。该励磁系统包括原边能量发射装置和副边接收装置,其中副边固定在电机转子上,并与之同步转动。为实现副边无通讯并减轻转子质量,在电励磁同步电机无线励磁系统中提出一种变直流母线电压的原边控制策略。考虑到原边补偿电感电流受逆变器高次谐波电压影响,导致励磁电流估算存在误差,采用卡尔曼滤波,滤除高次谐波,提高系统励磁电流估算精度;利用发射线圈电流和滤波后的原边补偿电感电流,得到磁耦合式无线励磁电机的励磁电流估算值;基于该励磁电流估算模型调节原边侧DC-DC变换器的母线电压,实现原边侧对副边侧励磁电流的无通讯调节。仿真结果表明,所提方法在励磁绕组阻抗变化及励磁电流突变工况下,能有效提高励磁电流估算精度及控制精度。

IPOP型双有源桥变换器均流控制方法研究

为提高双有源全桥变换器的功率容量,各种模块化组合方式被相继提出。基于输入并联输出并联的模块化组合方式,首先建立了变换器的降阶小信号模型,然后分析了变换器相与相间的均流原理并给出了变换器的相固有参数估算方法和并联均流控制策略,最后基于仿真模型对所提出的控制方法的合理性和正确性进行了验证。

Placement optimization of Multi-Type fault current limiters based on genetic algorithm

The fault current limiter(FCL)is an effective measure for improving system stability and suppressing short-circuit fault current.Because of space and economic costs,the optimum placement of FCLs is vital in industrial applications.In this study,two objectives with the same dimensional measurement unit,namely,the total capital investment cost of FCLs and circuit breaker loss related to short-circuit currents,are considered.The circuit breaker loss model is developed based on the attenuation rule of the circuit breaker service life.The circuit breaker loss is used to quantify the current-limiting effect to avoid the problem of weight selection in a multi-objective problem.The IEEE 10-generator 39-bus system in New England is used to evaluate the performance of the proposed genetic algorithm(GA)method.Comparative and sensitivity analyses are performed.The results of the optimized plan are validated through simulations,indicating the significant potential of the GA for such optimization.

MIXED FINITE ELEMENT METHODS FOR THE SHALLOW WATER EQUATIONS INCLUDING CURRENT AND SILT SEDIMENTATION (Ⅱ)——THE DISCRETE-TIME CASE ALONG CHARACTERISTICS

The mixed finite element(MFE) methods for a shallow water equation system consisting of water dynamics equations,silt transport equation,and the equation of bottom topography change were derived.A fully discrete MFE scheme for the discrete_time along characteristics is presented and error estimates are established.The existence and convergence of MFE solution of the discrete current velocity,elevation of the bottom topography,thickness of fluid column,and mass rate of sediment is demonstrated.

MIXED FINITE ELEMENT METHODS FOR THE SHALLOW WATER EQUATIONS INCLUDING CURRENT AND SILT SEDIMENTA-TION (Ⅰ)-THE CONTINUOUS-TIME CASE

An initial-boundary value problem for shallow equation system consisting of water dynamics equations,silt transport equation, the equation of bottom topography change,and of some boundary and initial conditions is studied, the existence of its generalized solution and semidiscrete mixed finite element(MFE) solution was discussed, and the error estimates of the semidiscrete MFE solution was derived.The error estimates are optimal.