宽频锁相的一种实现方法

将PWM整流器用于小型风力发电机时,宽频率范围锁相技术是其关键环节。针对此需求,文中将基于二阶广义积分(SOGI)锁相环与过零测频功能结合,并根据频率变化和频率适应范围实时调整PI参数,使相位跟踪快速准确。仿真表明所提方法在输入信号频率、幅值和谐波等多扰动源工况下都能准确实现相位和频率跟踪。     

时间同步装置的高稳定性输出设计方法

为实现时间同步装置高稳定输出,针对多时源选择、守时算法、动态调整这3个关键环节提出了方法及实现步骤。在多时源选择方面,提出基于聚类算法的外部独立时源选择策略,对关联时源的品质输出进行了分析;在守时算法方面,提出了基于余数动态分摊的自适应精确守时算法,并分析了晶振参数对守时精度的影响;在动态调整方面,提出了基于硬件实现的频率与相位实时跟踪方法,当外部时源与本地时源相差较大时,本地时源频率与相位以小步长匀速逼近外部时源,并趋于稳定。试验证实,所提方法在守时精度与相位和频率动态调整方面取得了较好的效果,实现了时间的高稳定性输出。     

TEST PROCEDURE FOR VERY HIGH SPEED SPINDLE MOTORS

Abstract

In the last ten years, the new power electronic devices and the new control techniques have allowed to open new application fields for adjustable speed/torque electrical drives. Although the traditional dc drives keep still the market supremacy, the new ac drives have performance really attractive and some additional benefits due to the machine structure and to the maintenance costs. Usually, ac drives use induction or brushless motors and the power amplifiers are driven by variable voltage/frequency in order to obtain variable speed. The authors deal with induction motors fed by non conventional supplies at very high frequency. In order to evaluate the total motor losses and the single items, a test bench with a synchronous machine capable to work up to 2 kHz with sinusoidal output voltage has been set up. As a consequence, an induction motor equivalent circuit with parameters depending on the frequency has been proposed. Today, the empirical procedure is that to use for high frequency applications shelf motors derated of a factor 10 to 20 % in order to keep into account the extra harmonic losses. On the other hand, the authors propose to design ‘ad hoc’ the motors for six-steps continuous operation in order to get about the same efficiency of standard motors. The new proposed motor equivalent circuit together with the test procedure seem to be a practical tool in order to aid the new motor design.     

Slip-frequency detection for indirect field-oriented control drives

This paper presents a new technique to detect the slip angular frequency in induction motor drives with indirect field-oriented control (IFOC). Slip frequency is calculated by processing the effects exerted by an additional high-frequency signal on the zero-sequence stator voltage. By measuring such a zero-sequence voltage, it is possible to evaluate the air-gap flux and detect the slip frequency in order to implement an IFOC algorithm. According to the proposed approach, rotor time constant errors are not influent as in conventional field-oriented control schemes, thus, complex tuning or compensation techniques are not required. Simulations and experimental tests are performed to evaluate the consistency of the proposed approach.     

双馈感应发电机无锁相环直接功率控制

直接功率控制(DPC)策略由于实施结构简洁、响应速率快等优势,在新能源发电领域得到了广泛的应用,因此提出基于两相静止坐标系的双馈感应发电机(DFIG)无锁相环DPC策略。针对两相静止坐标系中DFIG有功、无功功率动态方程的参数时变特性,构建了DFIG的有功、无功励磁电压2个可控量,并将含有交流电压系数矩阵的DFIG有功、无功功率动态方程变换为常系数动态方程,简化了控制系统设计,并根据DFIG的转子位置角,DFIG转子励磁电压与有功、无功励磁电压间的转换。利用简单线性调节器,即可完成对DFIG有功、无功功率的解耦控制与无差跟踪。最后,通过试验验证了所提控制策略的有效性和频率适应性。     

基于陷波器和相关法的科氏流量计信号处理方法

科氏流量计信号处理的关键在于频率和相位差的准确估计,频率估计主要存在长时间持续跟踪精度不高的问题,相位差估计主要存在精度不够和实时性较差的问题。首先,通过引入负反馈控制,可有效解决自适应陷波器长时间持续跟踪问题,提高频率估计精度。然后,利用频率估计结果,对自适应陷波器滤波后的增强信号进行整周期数据处理。接着,对整周期数据处理后的信号进行希尔伯特变换。最后,对希尔伯特变换前后的信号进行相关运算,利用正弦公式即可求得相位差,进而求得质量流量。仿真结果表明,本文所提方法具有较高的频率和相位差估计精度,可用于科氏流量计的实时信号处理。     

Diagnosis of Broken-Bar Fault in Induction Machines Using Discrete Wavelet Transform Without Slip Estimation

The aim of this paper is to present a wavelet-based method for broken-bar detection in squirrel-cage induction machines. The frequency-domain methods, which are commonly used, need speed information or accurate slip estimation for frequency-component localization in any spectrum. Nevertheless, the fault frequency bandwidth can be well defined for any squirrel-cage induction machine due to numerous previous investigations. The proposed approach consists in the energy evaluation of a known bandwidth with time-scale analysis using the discrete wavelet transform. This new technique has been applied to the stator-current space-vector magnitude and the instantaneous magnitude of the stator-current signal for different broken-bar fault severities and load levels.     

Proposal of an alternative transmission line model for symmetrical and asymmetrical configurations

This article shows a transmission line model for simulation of fast and slow transients, applied to symmetrical or asymmetrical configurations. A transmission line model is developed based on lumped elements representation and state-space techniques. The proposed methodology represents a practical procedure to model three-phase transmission lines directly in time domain, without the explicit or implicit use of inverse transforms. In three-phase representation, analysis modal techniques are applied to decouple the phases in their respective propagation modes, using a correction procedure to set a real and constant matrix for untransposed lines with or without vertical symmetry plane. The proposed methodology takes into account the frequency-dependent parameters of the line and in order to include this effect in the state matrices, a fitting procedure is applied. To verify the accuracy of the proposed state-space model in frequency domain, a simple methodology is described based on line distributed parameters and transfer function associated with input/output signals of the lumped parameters representation. In addition, this article proposes the use of a fast and robust integration procedure to solve the state equations, enabling transient and steady-state simulations. The results obtained by the proposed methodology are compared with several established transmission line models in EMTP, taking into account an asymmetrical three-phase transmission line. The principal contribution of the proposed methodology is to handle a steady fundamental signal mixed with fast and slow transients, including impulsive and oscillatory behavior, by a practical procedure applied directly in time domain for symmetrical or asymmetrical representations.     

开关磁阻电机固定频率预测电流控制策略

针对开关磁阻电机(SRM)传统电流斩波控制(CCC)开关频率不固定、电流跟踪效果差的问题,提出了一种固定频率的无差拍预测电流控制(DPCC)算法。基于对SRM静态电磁特性的精确解析拟合,建立SRM离散预测模型。为了减小转矩脉动,利用无差拍理论实时计算下一时刻所需电压,实现对电机参考电流的精确跟踪。为进一步提高效率,采用新型转矩分配函数代替传统线性转矩分配函数。基于试验样机测试数据,在MATLAB/Simulink中搭建仿真模型,对所提出的算法进行仿真分析。仿真结果表明,所提出的固定频率DPCC方法相比传统CCC方法,具有更小的电流跟踪误差,并且能够有效减小SRM的转矩脉动,提高系统效率。     

一种基于IMMPDA-UKF的机动目标跟踪算法

为了实现对在航捷点附近做机动运动目标的精确跟踪,提出采用不敏卡尔曼滤波（UKF）作为底层的滤波算法,解算出方位和俯仰的角度变化率,通过角度变化率解算出目标的切向速度,在过航捷时建立新的跟踪模型,将切向速度扩充到观测方程中,并结合交互多模型概率数据关联算法（IMMPDA）实现对过航捷机动目标的跟踪。仿真结果表明,该算法跟踪精度高,在航捷点附近无论是转弯机动还是加速运动,都可以保持对目标的持续跟踪,稳定性较高,可以直接应用于工程实践。     

一种软件频率跟踪方法

为了达到遥测0.5级精度,测控装置的交流采样必须设计有效的频率跟踪方法,使系统频率变化时采样频率能实时同步,也就是根据采样时的系统频率来确定采样间隔。文中分析了不进行频率跟踪时频率变化对遥测的影响,提出了一种易于实现的软件频率跟踪方法,并介绍了此方法应用于实际测控装置时的频率收敛时间和遥测精度。     

单相逆变器并网控制技术研究

设计了一种具有零稳态误差的并网逆变器系统，系统控制器由比例调节器P和谐振调节器R组成。与传统的PI控制器比较，该比例谐振控制器(PR)在基波频率处增益无穷大，因此可以完全消除稳态误差。通过理论分析，系统中采用了一种更易实现的准谐振控制器，并给出控制器参数具体的设计方法。此外，为了消除电网电压畸变或扰动对逆变器输出电流的影响，系统中引入了电网电压前馈解耦控制，改善了系统输出电流的质量。理论分析和实验结果验证了系统具有较好的稳态性能和抗扰性能。     

基于自适应观测器的双馈风力发电机控制

为了解决风力发电机系统中位置传感器故障率高的问题,提出了一种基于自适应观测器的速度辨识方案。应用Lyapunov稳定性理论,经过严格推导得出了速度辨识自适应律;利用极点配置得到观测器的增益。以速度估计自适应机构和矢量控制方案设计了无速度传感器双馈风力发电机矢量控制系统。仿真结果表明,自适应观测器无速度传感器控制能够准确获取双馈电机转速与角度信息,响应速度快,具有很好的稳态与动态性能,良好的鲁棒性,并基于此实现了最大功率跟踪控制。     

Susceptibility of Electrical Control Systems to Electromagnetic Disturbances

The susceptibility of electrical systems to electromagnetic disturbances is mostly specified in the frequency domain. Similarly, the efficiency of suppression techniques, such as filtering and shielding, is also presently specified in the frequency domain. As an appreciable part of the malfunctions (destructive and nondestructive) in control systems is caused by nonrepetitive transient type of electromagnetic disturbances, it is proposed that the susceptibility slhould additionally be specified in the time domain. This is particularly true for control systems containing semiconductor devices, because these devices operate on the principle of minimum clharge injection. Although a transient in the time domain can be mathematically converted into the frequency domain for the purpose of analysis, this procedure does not correspond to the physical situation and therefore does not give the true susceptibility of the system. Finally, several criteria are proposed for specifying the susceptibility of control systems to electromagnetic disturbances.     

改进惯性权重的粒子群目标跟踪算法

粒子群优化算法中惯性权重的设置极其重要,直接影响算法性能。提出了一种改进的粒子群优化算法,并应用到目标跟踪领域,提高算法运算效率。首先,设置粒子群优化算法中的参数;其次,结合粒子优化率的概念记录粒子的不同状态,进而调节惯性权重,更新粒子的速度和位置;最后,对目标相似性函数进行优化,实现目标的准确定位。实验结果表明,该方法可以有效应对目标出现部分遮挡的跟踪难题,同时提高目标跟踪效率,具有较好的实时性。     

电网电压骤降故障时双馈风机虚拟阻抗改进控制技术

针对电网电压骤降故障所导致的风电机组过电流问题,已有的基于虚拟电阻的过电流抑制技术无法兼顾过电流抑制效果和基频控制性能,同时未考虑系统的高频稳态性能,导致故障穿越期间的谐波抑制性能较差。为了兼顾故障穿越性能及故障穿越期间的谐波抑制性能,通过分析电网电压骤降时的双馈风机(DFIG)数学模型,研究了过电流及暂态磁链抑制机理,进一步基于虚拟阻抗技术,提出了电网电压骤降故障时DFIG改进控制技术。通过在机侧变流器转子电流控制环路中引入附加控制环,实现对暂态磁链振荡的抑制,从而提升DFIG低电压穿越性能。进一步地,对所提出的虚拟阻抗环节进行了参数设计分析,保证了该控制方法可以兼顾过电流抑制性能、高频性能及基频控制性能。最后,通过仿真结果验证了所提改进控制策略的有效性和可行性。     

行波型超声电机频率自动跟踪控制技术评述

在行波型超声电机结构分析和工作状态分析的基础上,对其频率跟踪技术的原理和实质进行了探讨。同时,根据行波型超声电机驱动器的设计原理,分析了频率跟踪技术可以采用的反馈信号。在此基础上,对超声电机频率跟踪技术进行了分类和总结,提出了五种频率跟踪方法,并对其进行了分析比较。最后,对行波型超声电机频率跟踪技术的应用和发展提出了见解。     

An Evaluation of Alternative Techniques for Monitoring Insulator Pollution

Electrical utility companies are constantly seeking predictive techniques that indicate the appropriate moment for maintenance intervention, while aiming toward a continuous increase in service indices. This paper proposes the use of pattern-recognition techniques to build classifiers that diagnose the operational state of the insulation structure in an online application. Important results were achieved during the study, mainly related to the types of sensors and features that need to be applied during the diagnosis process. Ultrasound and current leakage sensors, very-high frequency antenna, and thermovision instruments were employed to acquire signals and images in order to construct recognition systems. A number of specific features were applied to verify their importance during the classification process. Features were obtained in the time, frequency, and wavelet domains. Two groups of pattern-recognition techniques were applied: linear (Fisher and Karhunen-Loeve) and nonlinear (artificial neural network). The results indicated that pollution deposit can be evaluated by the proposed techniques, especially when a combination of sensors is employed.     

感应加热电源中频率跟踪控制电路的设计与分析

为使感应加热电源中的逆变器始终工作在功率因数接近或等于1的准谐振或谐振状态,设计出一种适合中频感应加热电源的频率跟踪控制电路。控制电路通过压控振荡器和逻辑电路实现了频率跟踪,经过示波器的测试,电路稳定性得到了提高,捕捉速度明显改善。     

基于改进型二阶广义积分器的同步信号检测

为了满足三相电压在不对称、直流分量及谐波畸变等情况下并网变换器的控制需求,需要准确地检测出电压信号的正序分量、幅值和基波频率。基于双二阶广义积分器锁频环的方法可实现电压在不对称和畸变下同步信号的提取。但当电压信号含有直流分量和多次谐波时,基本的SOGI结构滤波效果不理想,追踪的波形波动比较大,并降低了追踪速度。文中介绍一种改进的SOGI结构,该结构在SOGI的基础上增加求差节点和自适应滤波器,并保留SOGI-FLL的优势。电压的幅值和基波频率能准确快速被检测出来,很好的减小频率跳变后的波动、滤除谐波和消除直流分量。MATLAB仿真结果表明,其改进方法在电压信号不对称、直流分量及多次谐波存在条件下准确地检测出正序分量和基波频率。