A simple derivation of the spectral transformations for IIR filters

A simple method is given for deriving the spectral transformations for infinite-impulse response (IIR) filters, which can be used to transform a prototype low-pass (LP) digital filter to another LP, high-pass (HP), bandpass (BP), or band-stop (BS) digital filter with prescribed passband edge(s) and the same tolerances as those of the prototype. The method is based on a combination of bilinear transformation with the analog frequency transformation and is simpler-conceptually, as well as from the calculation point of view-than the conventional method based on all-pass transformation functions.     

旋转坐标变换谐波检测与带通滤波器的比较

基于旋转坐标变换的谐波检测方法应用非常广泛，分析其频域特性对认识控制性能和设计调节器具有重要意义。本文借用通信系统的幅度调制理论解释旋转坐标变换，借鉴幅度调制的频率搬移特性推导了d-q谐波检测方法的频域分析模型。为进一步简化模型，本文将相量的正负序对称分量法拓展为正负序坐标系。基于旋转变换的谐波检测方法在正负序坐标系下的频域分析模型非常简单，相当于将d-q旋转坐标系下低通滤波器的频谱搬移50Hz，从而获得一个带通滤波器，因此，d-q谐波检测是用低通滤波器实现了带通滤波器。之后，本文将d-q谐波检测算法与常规的带通滤波器进行比较。仿真和实验证实了以上分析。     

CASCADE SYNTHESIS OF MONOLITHIC CRYSTAL FILTFRS POSSESSING FINITE TRANSMISSION ZEROS

A simple method for the synthesis of bandpass or bandstop filters possessing finite transmission zeros as a cascade of shunted double-resonator monolithic crystal filter (MCF) sections is given. The lowpass or highpass prototype transfer function is synthesized as a cascade of MCF prototype sections for which explicit expressions for the element values are given. Application of the narrow-band lowpass to bandpass frequency transformation to the prototype network then yields a physically realizable filter with the desired bandpass or bandstop response. An example of the synthesis of a bandstop filter is given to illustrate the approach.     

A systematic class AB state space synthesis method based on MOSFET square law and translinear square‐root cells

A new state space Class AB synthesis method for the design of square‐root domain filter based on the MOSFET square law is proposed in this study. Those circuits designed by the proposed Class AB systematic synthesis method have the advantages of Class AB circuit structure and translinear circuits. Two alternative design procedures were suggested for designing new circuits. Proposed synthesis technique is applied for designing of a first order all‐pass filter and a third order low‐pass filter. Circuits are simulated in PSpice using 0.35 µm CMOS technology parameters. Time domain and frequency domain analysis of the proposed filters are performed, and simulation results of those are also presented. The simulation results show that the proposed synthesis technique is appropriate for the design of different types of filters and has the advantages of Class AB circuit structure. Copyright © 2015 John Wiley & Sons, Ltd.     

Reconfigurable narrowband microwave band‐pass filter

A method is proposed for the design of band‐pass filters with tunable centre frequency and bandwidth without the need for adjusting the inter‐resonator couplings. This is achieved by cascading a quasi low‐pass filter and a quasi high‐pass filter, while minimizing interaction between the filters without the need for an isolator between the filters. Simulated results are presented. Copyright © 2013 John Wiley & Sons, Ltd.     

Design of stable two-dimensional analogue and digital filters with applications in image processing

A method is proposed for the frequency domain design of linear two-dimensional analogue and digital filters with guaranteed stability. The technique used is based on the result that the numerator and the denominator of the input immittance of a two-variable network (which is passive and lossy) are strictly Hurwitz polynomials. One of these strictly Hurwitz polynomials is assigned to the denominator of a two-variable analogue transfer function and the network elements are then used as the variables of optimization thereby guaranteeing the stability of the analogue transfer function. The transfer function of the corresponding two-dimensional discrete (digital) filter is obtained from the analogue transfer function by the bilinear transformation. Examples illustrating the versatility of the technique in designing 2D digital filters of arbitrary order approximating a given magnitude and group delay response are presented. These filters are used to process a simple binary image. The results obtained demonstrate the importance of linear phase in image processing applications. The method presented here can be extended to the design of stable m-dimensional analogue and digital filters.     

基于Park变换的UPQC检测方法研究

介绍了一种综合型的电能质量补偿装置UPQC的功能和结构,分析了它的检测方法与单独的串、并联有源滤波器的不同之处。在此基础上,提出利用瞬时无功功率理论中的Park变换法,分别提取三相不对称及畸变电压系统中基波正序的幅值和相角,并让电源参考电流跟踪基波正序电压的检测方法。该方法与现有的UPQC检测方法相比,简单易行,实时性好,避免了大量的相量计算,且无须对三相不对称及畸变电压进行锁相和滤波。仿真结果验证了这种方法的正确性。     

基于多层带状线谐振子结构的带通滤波器设计

采用多层耦合带状线谐振子结构和高介电常数材料实现带通滤波器的微型化设计.谐振子的谐振频率采用Sonnet软件计算得出,谐振子的耦合系数采用Sonnet和HFSS仿真计算得到,最后采用HFSS进行结构调整以实现设计优化.该方法设计过程简便易行,得到的滤波器结构简单,易于制作.采用该设计方法设计并制作了一个L波段的5阶低温...     

一种用于电力线载波通信的椭圆滤波器设计

针对电力线通信中LC无源滤波器体积大、元件参数不易确定等问题,阐述了利用GIC设计椭圆低通和高通滤波器的方法。利用Filter Solutions软件设计归一化椭圆低通滤波器,用GIC代替D元件或电感,经过频率变换和阻抗变换,得到实际的低通或高通滤波器。经过仿真,滤波器达到设计指标。该设计方法在某电力线载波通信门禁系统得到应用,使112～114 kHz的载波信号被完整提取,保证了系统的完整性能。     

Approximation of fir digital filters by bilinear transformation

The approximation of the finite-impulse-response (FIR) digital filters using the bilinear transformation of a restricted class of the rational functions is considered. The reference rational functions are constructed for maximally flat selective and quadrature filters. The proposed method can be directly used for both even and odd degree filters, and yields simple explicit expressions for the filter coefficients.     

一种实用的谐波分频检测方法

针对基于瞬时功率理论的ip-iq算法无法单独提取各次谐波分量等情况,提出了一种改进的ip-iq谐波分频检测方法。利用改进的ip-iq法能直接对a-b-c三相坐标系下的单相电流进行分解,获得单相电流的有功电流和无功电流,通过低通滤波器后获得基波或者各次谐波的有功电流分量和无功电流分量,再直接转换为a-b-c三相坐标系下的基波电流和各次谐波电流,省去了三相至两相坐标变换及其逆变换,因此计算量更少。仿真分析结果表明该法能较好的实时检测三相电网基波和各次谐波分量。     

考虑群延迟和暂态时延的短窗低通滤波器设计

为采用基于采样值和正弦信号模型的快速保护算法,并防止重采样环节的频率混叠,智能变电站的数字化保护需要数字低通滤波器配合。提出一种基于Tukey窗函数,并且同时考虑滤波器幅频特性和群延迟、暂态时延的低通滤波器设计方法。该方法首先确定窗函数时域宽度Tc和截止频率fc,再根据采样频率fs和固定不变的fc,确定滤波器的长度N≤2fs/fc,最后根据N和fc得到完整的滤波器系数。通过理论分析、数字仿真和静态实验,研究了所设计滤波器的幅频特性、群延迟和暂态时延。对采用所设计滤波器的母线保护进行RTDS实验,通过对比表明,按所提方法设计的滤波器在群延迟和暂态时延性能上明显优于传统窗函数法设计的滤波器,降低了滤波器环节对保护速动性的影响。     

分次补偿方式的并联型混合电力滤波器研制

介绍了由有源电力滤波器和无源滤波器并联构成混合滤波系统的工作原理，分析了有源和无源滤波器并联补偿谐波时谐波电流分配的问题，提出采用分次补偿的控制策略，并对系统控制策略的软件方法和控制电路的硬件实现进行了阐述。在此基础上研制了一台250kVA／380V并联混合型电力滤波器装置。该装置已应用于治理中频炉负载的工业现场。仿真和现场应用结果表明，采用该控制方法，可以在保证良好的补偿特性的同时，有效减少有源滤波器部分的容量，从而降低了整个装置的成本，更加适用于治理中大容量谐波负载的场合。     

Design of fixed point state space digital filters with low round-off noise

A simple method is described for the design of fixed-point recursive digital filters with low round-off noise. the method is based on reducing to zero as many as possible of the coefficients of the filter state matrices. an optimization procedure is used to get the optimum value of linear transformation that minimizes the total output round-off noise power. Compared with the existing approaches, this method is characterized by its computational simplicity, very low output round-off noise (if not the lowest possible) and low coefficient sensitivity. the structure of the proposed technique is modular, which makes it suitable for VLSI implementation. the technique is then employed to obtain a reduced-order low-round-off-noise filter with characteristics equivalent to some desired FIR specifications. Illustrative examples are given to verify these advantages.     

Selective digital filters with quadratic phase

A method for design of a new class of digital infinite impulse response filters realized as parallel connection of two all‐pass filters is presented in this paper. A new approach to approximation of quadratic phase of all‐pass filter at all frequencies is given. Chosen parallel structure offers opportunity for realization of filters with arbitrary shape phase. The presented algorithm is based on all‐pass filter phase approximation. Phases of both all‐pass filters approximate ideal quadratic phase in minimax sense at all frequencies. Such filters can be applied for chirp signal compression or expansion. Magnitude characteristic of described filters is very selective and elliptic‐like. Obtained filters are compared with elliptic filter and group delay corrector in cascade. For the same specifications, much better results are achieved by the proposed filters. Parallel connection of all‐pass filters introduces lower signal delay, and for a given maximal phase, approximation error demands less complex network. Examples to illustrate the proposed method are given. Copyright © 2016 John Wiley & Sons, Ltd.     

基于广义形态滤波的电力系统采样信号处理

数学形态学是以集合论和积分几何学为基础的一门对物体形态处理的学科,是一种非线性分析方法,在时域中对信号波形特征进行研究。针对电力系统采样信号,提出一种采用不同采样频率的广义形态滤波方法。该方法滤除白噪声和脉冲噪声时采用较高频率;滤除直流偏移时采用低频率。结构元素选取为与水平方向夹角为零度的直线型结构元素。由于滤除直流偏移时采用较低的采样频率,因此,结构元素较短、运算量较小、耗时少。仿真实验表明,该方法能有效地滤除白噪声、脉冲噪声和直流偏移量,信噪比显著增大,均方误差较小。     

相位噪声测量中环路滤波器研究与实现

环路滤波器是鉴相法测量相位噪声系统中决定相位噪声提取性能的重要部件,采用数字实现方法时,测量系统分析带宽和锁相环路工作要求决定了该滤波器为极窄带宽滤波器。针对高性能极窄带宽的设计要求,通过理论分析,提出了适用于相位噪声测量系统的分级多相抽取数字滤波器结构。该结构采用了多级抽取、多相结构、存储器优化、乘法器优化等改进方法。论文中对优化后的滤波器结构与现有滤波器实现结构分别在FPGA中进行实现。通过比较两者实验结果,给出的极窄带宽滤波器分级多相实现结构在达到系统指标要求的条件下,占用资源为传统结构的33．8％,计算量为传统结构的54．5％。     

On the design of 2D IIR digital filters using penalty optimization techniques

In this paper an efficient technique is developed for the design of two-dimensional recursive digital filters in the frequency domain. the formulation of the design problem is based upon a rational approximation method in parallel with a suitable interior penalty technique. the structure of the proposed approach permits one to include in the design optimization problem additional constraints related to the stability, linear phase and symmetries properties of the resultant filter. In contrast with previous design methods, the coefficients of the filters are determined directly and it is not required to apply any ‘inverse’ or stabilization technique. Analytical examples illustrate the features and effectiveness of the proposed approach.     

风电系统网侧LLCL型滤波器特性分析及仿真研究

风力发电系统通常采用L型和LCL型滤波器,这2种滤波器对变流器开关频率附近的高次谐波抑制能力相对有限。为此提出了LLCL型滤波器,即在LCL型滤波器电容支路中串联小电感达到开关频率处串联谐振,从而实现最大程度减小开关频率附近谐波对电网的影响。分析了L型、LCL型、LLCL型滤波器的结构及滤波特性,讨论了LLCL型滤波器参数的设计约束条件。仿真结果验证了LLCL型滤波器对开关频率附近的高次谐波抑制效果更显著,相对于LCL滤波器,在滤波器总电感相同的情况下,经过LLCL滤波器滤波后的电流纹波含量更少,开关频率附近的谐波含量更少,谐波畸变率更小。     

有源滤波器参考电流的无延时的生成方法

文章介绍了一种多级自适应滤波系统，用于无时延地生成有源滤波器(APF)参考电流。该滤波系统主要包括前置低通滤波器和自适应预测滤波器，可以从频率和幅值均变化的畸变波形中提取正弦有功电流，而不引起任何附加相移。通常APF只能对基波频率为恒值的电网进行谐波补偿，文章提出的APF结构也可用于输入信号基波频率变化的情况。