Modified vector controlled DFIG windenergy system based on barrier functionadaptive sliding mode control

Increased penetration of wind energy systems has serious concerns on power system stability. In spite of several advantages, doubly fed induction generator (DFIG) based wind energy systems are very sensitive to grid disturbances. DFIG system with conventional vector control is not robust to disturbances as it is based on PI controllers. The objective of this paper is to design a new vector control that is robust to external disturbances. To achieve this, inner current loop of the conventional vector control is replaced with sliding mode control. In order to avoid chattering effect and achieve finite time convergence, the control gains are selected based on positive semi-definite barrier function. The proposed barrier function adaptive sliding mode (BFASMC) is evaluated by testing it on a benchmark multi-machine power system model under various operating conditions. The simulated results show that the proposed method is robust to various disturbances.     

SELECTION OF SAMPLING PERIOD FOR AUTOMATIC GENERATION CONTROL

ABSTRACT

The paper presents the analysis of automatic generation control (AGC) of a two-equal area reheat thermal system in the presence of generation rate constraints considering a discrete-continuous time mathematical model. The effect of variation of sampling period on optimum integral gain setting and system dynamic performance has been analyzed considering supplementary controllers based on conventional area control errors (ACEs) and new area control errors (ACENs). Investigations reveal that the optimum integral gain setting and system dynamic performance are hardly affected over a wide range of sampling period T for controllers based on conventional ACEs. Studies also reveal that the permissible sampling period is further enhanced with integral controllers based on new area control errors (ACENs).     

保护测控装置嵌入式采样新平台的研制

在分析传统多CPU架构平台局限性的基础上,采用超级中断技术解决嵌入式平台的实时采样问题,提出了一种一体化的保护测控装置嵌入式采样新平台技术.介绍了该平台的软、硬件及网络架构,并重点阐述了统一平台的技术关键及嵌入式保护中断处理技术.提出的新平台已在工程实际中大量应用,取得了良好的效果.     

TMS320C32在励磁系统仿真测试中的应用

TMS320C32是TI公司的浮点系列高性能数字信号处理器(DSP),运算速度快,适合于电力系统的实时数据分析.在发电机不运行时而能得到励磁调节器的性能指标,具有很大的实用价值.本文提出一种基于TMS320C32的发电机励磁仿真测试系统,该系统能仿真同步发电机及电网等环节,并能实时分析采样数据,现场试验证明了该系统的可行性和实用性.     

单级光伏并网系统电流控制的仿真与实验研究

光伏并网发电系统需要一种快速准确的电流控制方法使其能最大限度地向电网输送高质量电能,在分析无差拍电流控制工作原理的基础上,对常规的无差拍控制算法进行了适当改进,并给出对控制效果影响较大的输出电流检测方法.基于PSIM对相关算法的控制效果进行了仿真,并最终应用到实际的单相单级式光伏并网系统的并网电流控制当中.良好的仿真和样机实验结果验证了该方法的可靠性和有效性.     

Fuzzy bang-bang control of static VAR compensators for damping system-wide low-frequency oscillations

Static VAR compensators (SVCs) have been widely used in power systems to keep terminal voltages within bounds. The other application is to improve power systems damping, especially for loosely connected power systems. In this paper, a scheme using fuzzy logic control (FLC) is connected in parallel with a conventional voltage regulation loop to form a supplementary damping loop for the SVC to increase the system's transmission capacity. The FLC is based on bang-bang control, and provides damping across each connected line to the SVC. Damping is of particular importance especially for weakly coupled power systems. Using rotor-angle signals that are estimated from voltage and power measurements at each connected line to the SVC, a fictitious generator at the remote end of each connected line is identified. The SVC receives control signals from all fictitious generators, which are competing and reacting differently at different phases of system oscillations. The final control for the SVC combines the control signals from all fictitious generators, which are scaled according to their individual contributions to damping. The proposed signal structure guarantees robustness and effectiveness of the final control with respect to different loading and fault conditions. The FLC design is based on Lyapunov function analysis, and is simulated on a three-generator power system for performance evaluation.     

Active power filters for harmonic cancellation in conventional and advanced aircraft electric power systems

Conventional and advanced civil aircraft electric power systems are simulated and controlled to be within standards regarding the voltage magnitude and frequency everywhere in the system at different loading scenarios. Harmonics in conventional and advanced aircraft power systems are calculated and reduced using a well-designed active power filter. The control circuit of the filter is based on the perfect harmonic cancellation method. The designed filter results in bringing the harmonics in both aircraft systems down to be within the standard limits of IEEE-519 and MIL-STD-704E.     

单元机组负荷非线性预测控制及其仿真研究

大型单元机组负荷控制系统存在着强耦合、非线性等特性,常规线性控制策略难取得满意的控制效果。为此,该文提出了一种新的基于模糊模型和免疫优化的非线性预测控制方法,将离线辨识到的全局模糊模型作为预测模型,然后利用实数编码的免疫优化算法在线实现非线性预测控制的滚动优化,给出每个采样时刻的最优控制量。该方法还可通过修正的遗传算子方便地解决控制量受限问题。通过对一个500MW单元机组负荷控制系统的仿真试验,验证了该非线性预测控制方法的有效性。     

状态空间设计在DC/DC变换器反馈控制中的应用

以Buck变换器为例将状态空间设计方法应用于DC/DC变换器的控制,设计了基于极点配置和二次型最优的DC/DC变换器反馈控制器.MATLAB软件的应用使得整个设计过程简捷、实用.利用Simulink和Power system工具箱对所设计的系统进行了仿真.研究结果表明,Buck变换器通过极点配置和二次型最优反馈控制策略,比使用传统的PI控制具有更好的动态响应调节和稳态误差调节特性,超调量、调节时间等都得到明显改善.     

Performance of an adaptive protection scheme for series compensated EHV transmission systems using neural networks

Since the complex variation of line impedance is accentuated as the capacitor's own protection equipment operates randomly under fault conditions in series compensated transmission systems, conventional distance protection schemes are limited to certain applications. This paper proposes an adaptive protection scheme based on neural networks with special emphasis on analysis of the first-zone performance. The paper describes in detail the feature extraction, sampling rate, data window and structures of the neural networks. The basic idea of the method is to design a protection scheme using a neural network approach by catching the feature signals in a certain frequency range under fault conditions. This is different from conventional schemes that are based on deriving implicit mathematical equations based on the information obtained by complex filtering techniques. System simulation and test results presented and analysed in the paper demonstrate the feasibility of the proposed scheme.     

Short-term reliability evaluation using control variable based dagger sampling method

Most of the reliability theory and applications are in the planning domain. When reliability concepts are applied in operations or operational planning, computational burden of the algorithms becomes a bottleneck as the speed of execution of algorithms becomes critical. This paper presents an efficient control variable based dagger sampling technique for reducing the computational effort in Monte-Carlo reliability evaluation for composite systems. The proposed variance reduction method is unique in combining the offline calculations with online computation. A large number of system states are simulated to calculate their consequences offline and stored. Short-term reliability sampling uses the information on offline computed consequences to construct a variance reduction function. In short-term reliability evaluation, the outage probability of each component is much smaller compared to long-term system reliability calculations. Dagger sampling is used to reduce the computation time under this condition. Test results on RTS show the improvement and effectiveness in convergence speed.     

应用于频率宽范围波动电网的自适应采样相位差校正法

指出了定速率采样下,非同步采样造成的频谱泄漏是相位差校正法测量误差的主要来源,尤其在对频率宽范围波动的电网信号进行连续测量时,采用相位差校正法可能造成测量失败。文中提出了一种基于自适应采样的改进方法。根据前次测得的基波频率与前次计算所得的频率变化率来预测电网的实时基波频率,并实时修正采样频率,使之跟踪变化的基波频率。分别在自适应采样与定速率采样下使用相位差校正法对频率动态变化的电网信号进行仿真对比。结果表明,该方法较定速率采样方法对同一变频电网信号的幅值测量精度提高一个数量级,相位测量精度提高3~14倍,采样窗长为IEC标准规定窗长的40%。该方法减小了因基波频率动态变化而产生的频谱泄漏,使相位差校正法在频率宽范围波动的电网中能够满足谐波连续测量的精度与实时性需要。     

基于复杂网络的电力系统鲁棒性分析

随着电力系统在现代社会发展中的地位不断提高,其面临的各种危险也越来越引起人们的高度关注.为探究电力系统鲁棒性,建立了考虑电力系统实际运行机理的网络化模型.基于复杂网络理论,按照方法论原则,提出了一种鲁棒性分析方法.分别从结构和功能上给出了电力系统的鲁棒性分析指标,并模拟了电力系统三种故障情形.运用IEEE30测试网络,...     

Comparative study of finite word length effects in digital filter design via the shift and delta transforms

This paper deals with the influence of the rounding of parameters represented in floating-point number systems in high-speed digital signal processing and control. It is shown that in high-performance applications, that may involve high sampling rates and/or shorter word lengths, the usual shift operator formulation is inferior to an alternative formulation based on the delta operator. The analysis is illustrated by an example.     

基于变压器延边三角形接法的36脉波整流系统研究

在大功率整流领域,通常采用多脉波整流技术来降低整流系统谐波含量,提高功率因数。提出了一种基于移相变压器延边三角形接法的36脉波整流系统结构,分析了整流系统的工作原理、系统网侧输入电流特性及直流输出电压特性,给出了移相变压器绕组参数计算方法,并推导了平衡电抗器选择条件。利用MATLAB/Simulink建立了36脉波整流系统模型,对理论分析进行了仿真验证,观测了传统6脉波整流系统和36脉波整流系统的输出电压波形及网侧电流谐波含量。对比了不同程度电网不平衡情况下,36脉波整流系统与传统6脉波整流系统输出电压波形、网侧电压总谐波含量(THD)和电流谐波含量。实验结果表明,36脉波整流系统整流电压波形和网侧电流谐波含量与理论分析一致,能够有效降低网侧电流谐波含量和输出电压脉动,且具有较好的抵抗电网不平衡的能力,较6脉波整流系统有很大的优越性。     

基于电流行波的小电流接地选线装置的试验

为了验证电流行波接地选线装置选线原理和各个功能的正确性，利用暂态行波保护测试仪模拟了各种现场接地，对选线装置进行了实验室验证。验证内容包括；装置是否实现了可靠的高速通信和数据采集，电流互感器安装方式、中性点接地方式和过渡电阻选线结果是否准确，接地发生后是否报警。结果证明，装置原理正确，各项功能达到研制目标，可实际应用于电力系统。     

Simulation and transient analysis of conventional and advanced aircraft electric power systems with harmonics mitigation

This paper presents the simulation and transient analysis of conventional and advanced aircraft electric power systems with harmonics mitigation. Complete modeling of aircraft electric power systems is proposed. The conventional aircraft electrical power system is analyzed considering equivalent passive AC and DC loads under transient and steady-state operating conditions. The electric power source is simulated to ensure constant frequency and voltage which meet the aircraft electrical standards for all loading cases. To mitigate the harmonics generated by the converters, passive input filters are designed to keep THD values within the standard limits. Furthermore, the advanced aircraft electrical system is simulated and analyzed under the same electric power source and loads. The results are compared to those of the conventional aircraft electric power system.     

Achievement method of high‐speed response of error prediction tracking control for optical disk system

This paper proposes the new design method of error‐prediction control systems combining the ZPET control and the robust feedback control. The error‐prediction control system based on ZPET control can reduce the tracking error caused by periodic disturbances more efficiently than the conventional repetitive control technique. However, the proposed tracking servo system does not reduce the residual tracking error caused by the low‐pass filter of the feedforward compensation and by the long sampling time. In order to overcome this problem, this paper proposes the new structure of the feedforward tracking control system. The modified ZPET control tracking servo system for optical disk recording system does not include the low‐pass filter and its sampling time becomes faster. On the other hand, the sudden disturbance observer reduces the influence of nonperiodic disturbances. The experimental results point out that the proposed tracking servo system has a precise tracking response against both the periodic disturbances and the nonperiodic disturbances. © 2009 Wiley Periodicals, Inc. Electr Eng Jpn, 170(4): 51–59, 2010; Published online in Wiley InterScience ( www.interscience. wiley.com ). DOI 10.1002/eej.20800     

基于预测控制的异步电机直接转矩控制性能的改善

分析了传统直接转矩控制中造成转矩脉动的原因,提出了一种预测控制算法以改善直接转矩控制性能的方法.在每个采样时刻,根据采样值求出一个能正确补偿当前定子磁链偏差和转矩偏差的定子电压矢量,在下个控制周期内作用于定子绕组,使再下一个控制周期到来时偏差刚好被消除.该电压矢量采用SVPWM进行合成并转化成相应的PWM开关信号,并且使用了一种定子磁链混合模型的磁链观测器以改善低速性能.仿真结果验证了该算法的有效性,明显抑制了转矩和磁链的脉动.     

基于点对点通信的分布式实时控制技术

对智能电网、清洁能源系统中存在的多种分布式系统进行了共性需求分析,针对分布式系统的工程技术特点,提出了一种基于点对点通信的新型分布式实时控制技术,通过点对点报文通信的方式实现了模拟量及开关量采集模块、出口控制模块和主处理器模块等环节的实时控制,满足了分布式系统对分散单元协同控制的工程应用需求。文中基于两种成熟的工业通信协议,针对两类分布式控制装置采用现场可编程逻辑门阵列(FPGA)对此技术进行了实现,并对装置进行了详细的测试与分析。两类典型装置已经在工程现场得到了试运行与推广,取得了良好的工程应用效果。