A multi-scale second-order autoregressive recursive filter approach for the sea ice concentration analysis

To effectively extract multi-scale information from observation data and improve computational efficiency,a multi-scale second-order autoregressive recursive filter(MSRF)method is designed.The second-order autoregressive filter used in this study has been attempted to replace the traditional first-order recursive filter used in spatial multi-scale recursive filter(SMRF)method.The experimental results indicate that the MSRF scheme successfully extracts various scale information resolved by observations.Moreover,compared with the SMRF scheme,the MSRF scheme improves computational accuracy and efficiency to some extent.The MSRF scheme can not only propagate to a longer distance without the attenuation of innovation,but also reduce the mean absolute deviation between the reconstructed sea ice concentration results and observations reduced by about 3.2%compared to the SMRF scheme.On the other hand,compared with traditional first-order recursive filters using in the SMRF scheme that multiple filters are executed,the MSRF scheme only needs to perform two filter processes in one iteration,greatly improving filtering efficiency.In the two-dimensional experiment of sea ice concentration,the calculation time of the MSRF scheme is only 1/7 of that of SMRF scheme.This means that the MSRF scheme can achieve better performance with less computational cost,which is of great significance for further application in real-time ocean or sea ice data assimilation systems in the future.

Second-order divided difference filter for vision-based relative navigation

A second-order divided difference filter (SDDF) is derived for integrating line of sight measurement from vision sensor with acceleration and angular rate measurements of the follower to estimate the precise relative position,velocity and attitude of two unmanned aerial vehicles (UAVs).The second-order divided difference filter which makes use of multidimensional interpolation formulations to approximate the nonlinear transformations could achieve more accurate estimation and faster convergence from inaccurate initial conditions than standard extended Kalman filter.The filter formulation is based on relative motion equations.The global attitude parameterization is given by quarternion,while a generalized three-dimensional attitude representation is used to define the local attitude error.Simulation results are shown to compare the performance of the second-order divided difference filter with a standard extended Kalman filter approach.

ENHANCEMENT OF DAMPING PERFORMANCE OF POLYMERS BY FUNCTIONAL SMALL MOLECULES

The addition effects of organic small molecular substances N,N'-dicyclohexyl-benzothiazyl-2-sulfenamide (DZ) and 3,9-bis{1,1-dimethyl-2[beta-(3-tert-butyl-4-hydroxy-5-methylphenyl)propionyloxy]ethyl}-2,4,8,10-tetraoxaspiro[5,5]-undecane (AO-80) on the dynamic mechanical properties of chlorinated polyethylene (CPE), chlorinated polypropylene (CPP), acrylate rubber (ACM) and their blends were investigated. In the case of compatible systems such as CPE/DZ and ACM/AO-80, the height of the loss tangent (tandelta) peak of a matrix polymer (CPE or ACM) increases, and its peak position shifts to a higher temperature with the addition of DZ or AO-80. By contrast, for incompatible CPE/AO-80, a novel transition appeared above the glass transition temperature of CPE. This additional transition was assigned to dissociation of the intermolecular hydrogen bond between the alpha-hydrogen of CPE and the hydroxyl groups of AO-80 within the AO-80-rich domain. This will provide a new concept for developing damping material. However, the minimum value between two tandelta peaks is lower. It was found that the temperature dependence of tandelta could be improved by adding chlorinated paraffin (CP) or ACM to CPE/AO-80. In addition, another ternary system of ACM/CPP with more AO-80 was found to be a very good self-adhesive damping material because of the appearance of a novel transition due to an interfacial layer of ACM/CPP.

A NOVEL SECOND-ORDER TRANSITION IN ORGANIC HYBRIDS CONSISTING OF POLYMERS AND SMALL MOLECULES

A novel transition appeared above thc glass transition temperature of chlorinated polyethylene (CPE) for binaryblends of CPE and additives such as organic small molecules or oligomers. This transition was assigned to the dissociation ofintermolecular hydrogen bonds between the polymer ard additive within the edditive rich phase. Of particular interest is thata novel pyramid crystal was observed in the annealed CPE/hindered phenol blends. Another intriguing observation is thatthese polymer/small molecule blends organized by intermolecular hydrogen bonding have several potential properties, suchas shape-memorization, self-restoration, self-adhesiveness and super damping.

The Extended Non-Elementary Amplitude Functions as Solutions to the Damped Pendulum Equation, the Van der Pol Equation, the Damped Duffing Equation, the Lienard Equation and the Lorenz Equations

In this paper, we define some non-elementary amplitude functions that are giving solutions to some well-known second-order nonlinear ODEs and the Lorenz equations, but not the chaos case. We are giving the solutions a name, a symbol and putting them into a group of functions and into the context of other functions. These solutions are equal to the amplitude, or upper limit of integration in a non-elementary integral that can be arbitrary. In order to define solutions to some short second-order nonlinear ODEs, we will make an extension to the general amplitude function. The only disadvantage is that the first derivative to these solutions contains an integral that disappear at the second derivation. We will also do a second extension: the two-integral amplitude function. With this extension we have the solution to a system of ODEs having a very strange behavior. Using the extended amplitude functions, we can define solutions to many short second-order nonlinear ODEs.

基于双二阶滤波器的LCL型并网逆变器延时补偿方法

为了抑制LCL型滤波器的谐振尖峰,电容电流反馈有源阻尼被广泛应用于LCL型并网逆变器中。由于数字控制延时带来的不利影响,电容电流反馈有源阻尼的阻尼性能被严重削弱。负阻尼区域出现在f_(s)/6到f_(s)/2之间,减弱了并网逆变器的稳定性和对电网阻抗变化下的鲁棒性。在电容电流反馈通道上插入一个双二阶滤波器来补偿数字控制延时带来的相位滞后,正阻尼范围可以扩展到f_(s)/3,从而实现了对电网阻抗变化的高鲁棒性。选择了合适的离散化方法,分析了补偿后的系统稳定性。提出了一个详细的闭环参数设计流程,以获得良好的控制性能。最后,实验结果验证所提方法的有效性和参数设计流程的可行性。

基于主动式阻尼的混合式步进电机转速振荡抑制控制

混合式步进电机因其特殊的机械结构导致自身阻尼极小,在实际运行过程中会发生振荡过大,甚至失步的问题。为提高混合式步进电机的控制品质,提出一种基于主动式阻尼的步进电机转速振荡抑制方法。首先,将电机模型转化至同步旋转dq坐标系,将电流i_d控制恒为额定电流,利用位置误差和速度误差调节电流i_q生成瞬时转矩,抑制电机运行时存在的振荡现象。其次,为实现电机闭环反馈控制,提出一种将同步频率提取滤波器(SFF)与三阶锁相环(PLL~3rd)相结合的无传感器控制方法。SFF可以滤除反电动势信号中的高次谐波,PLL~3rd能消除转速变化过程中的稳态误差。实验证明,该方法有效抑制了步进电机运行过程中的振荡现象,提升了电机的运行品质。

弱电网下LCL逆变器的有源阻尼控制策略研究

在弱电网中,由于电网阻抗的存在,会导致新能源并网LCL滤波器固有谐振频率发生偏移,传统有源阻尼控制策略则无法保证系统的稳定性。而且随着新能源发电在电力系统中的占比不断提高,如何降低运营成本成为了研究热点。因此本文提出一种基于并网电流和公共耦合电压反馈的新型控制策略,该控制策略不仅提供了有源阻尼以抑制LCL谐振,而且减少了传感器的使用,还能对大范围变化的电网阻抗有较强的适应能力。通过仿真和实验表明,与传统的控制策略相比,在改进的策略下弱电网的实用范围增加,系统的稳定性得到提高,对谐波的抑制能力提升,并网电流质量有了良好的改善。

基于虚拟导纳的LCL型并联有源电力滤波器鲁棒电流控制

基于电网电流和逆变侧电流的双环电流控制策略因其固有的有源阻尼作用而成为LCL型并联有源电力滤波器的研究热点,但控制回路中不同有源阻尼共存将导致系统特性难以确定。对此,通过虚拟导纳模型准确评估了系统的阻尼特性,发现其有源阻尼区域会随电网阻抗波动而变化,最大接近1/3采样频率;考虑LCL初始谐振频率处于不同的频率范围情况,利用开环极点及鲁棒性分析得到适用于不同情况的统一稳定性约束条件,并对应提出了一套鲁棒控制参数设计方法,从而充分保证电网阻抗波动下并联有源电力滤波器的稳定运行。在一台380V、45A的实验样机上验证了所提理论及控制策略的有效性。

LCL并网逆变器滤波参数近似计算方法

在高频谐波衰减系数相同的条件下,LCL型滤波器的体积和感量要明显小于L型,但是其约束条件有所增加,参数计算也变得更加复杂,不仅要考虑并网电流的质量,还需要关注逆变器侧电感电流纹波和无功功率等限制条件。为简化计算流程,基于有源阻尼提出一种LCL型并网逆变器滤波参数近似计算法。首先,分析拓扑再利用仿真软件分析逆变器输出电压的谐波含量;其次,对滤波器设计相关约束条件的优先级进行重新排序,以谐振比为关键参数推导出计算公式,以谐振频率为关键参数快速计算出总电感值,再综合各个参数的极限值,给出设计流程图,并进行误差分析;最后,通过流程图输出一组参数进行仿真和实验分析,证明所提出的LCL滤波参数计算方法的合理性和有效性。

基于广义积分器二自由度PID控制的LCL逆变器

传统有源阻尼控制可抑制LCL逆变器谐振,但需要增加额外的电压或电流传感器。为此,提出了一种无需额外传感器的基于广义积分器的LCL并网逆变器单电流反馈二自由度PID控制(GI-2DoF-PID),GI-2DoF-PID比例积分环节实现并网电流无静差跟踪,而基于广义积分器的微分环节则增强LCL逆变器的阻尼特性。推导了控制系统的传递函数,分析了其稳定裕度与动态特性,提出跟踪和抗扰动优化的参数设计原则并选取了合适的控制参数。最后,构建了基于PLECS系统仿真模型,仿真结果表明:基于GI-2DoF-PID控制的LCL并网逆变器可以有效抑制谐振;电网电压严重畸变时,其满载并网电流畸变率仅为3%,远低于国家标准的要求;当系统从半载跳变到满载时,系统超调量低,响应速度快。

变频器输出侧的双LC型滤波器研究

在直流网组电动船舶上,电机驱动与日常用电都需要用到变频器。针对变频器输出侧电网谐波的问题,采用无源滤波器方法对其进行抑制。为解决常见的LCL型滤波器存在的动态性能差,滤波效果不理想,且容易在输出端产生较大振荡和电磁干扰问题。本文提出一种高阶的双LC型滤波器。基于对双LC型滤波器优化设计,并将无源阻尼法控制策略应用在此滤波器上,以减小系统在谐振频率处的谐振尖峰并降低高频段的谐波含量,进一步完善所采用滤波器在滤波效果和系统抗干扰上的性能。最后,通过仿真验证基于双LC型滤波器所提出控制策略的有效性。因此,采用双LC型滤波器替代传统LCL型滤波器可以更好地增加系统的效率与稳定性,确保设备的稳定运行。

基于复合谐波补偿和谐振阻尼的SAPF控制策略

针对独立小供电系统中发生的并联的校正电容器和电网阻抗之间的谐振现象,此处首先分析了在谐振状况时并联型有源电力滤波器(SAPF)在传统控制策略下检测负载电流的两种方式,分析表明,当检测点设立在非线性负载出口处时方案最优。接着分析了最优检测点下SAPF的谐波补偿和谐振阻尼效果,虽然在该方案下SAPF对非线性负载的谐波具有补偿效果,对谐振引起的谐波放大也有抑制效果,但该种传统控制策略下的阻尼效果并不能使谐波成分满足电能质量标注的要求。因此,这里提出了一种新型复合谐波补偿和谐振阻尼策略,在补偿谐波的同时能阻尼谐振,可以满足电能质量标注的要求。最后给出了实验结果。

基于风电网侧变流器虚拟阻尼控制策略的研究

由于风电变流器LCL滤波电路存在谐振问题,为提高风电变流器系统稳定性,目前无源阻尼技术和有源阻尼技术是实现滤波器谐振峰值抑制的有效方法,其中有源阻尼方案是近年来研究的热点。本文通过对LCL型风电并网变流器的入网电流闭环特性进行分析,提出一种基于LCL滤波器的电容电压反馈改进有源阻尼控制方法,在控制环节中构建滤波器增加闭环控制系统的阻尼抑制谐振的发生,提高系统稳定性,不增加额外硬件成本和系统损耗。通过搭建基于双馈感应发电机组网侧变流器仿真模型,对文中提出改进的控制策略进行验证,理论分析和仿真结果证明提出的虚拟阻尼控制策略具有有效性和可行性。

高阶有源滤波电路的分析与设计

在模拟采样电路中,为避免杂波对采样信号造成干扰,采样信号需经滤波器处理后再送入DSP,这样往往能降低对模拟采样通道的硬件要求。相比无源滤波器,有源滤波器的放大倍数和频率特性基本不会随着负载的变化而变化,因此在小信号处理电路中,有源滤波器的使用更为广泛。但在实际设计高阶有源滤波器时,经常出现理论计算值与仿真值不一致的情况,导致所生成的电路参数往往不能满足器件选型要求。为此,文章从2阶有源滤波器出发,首先对传递函数进行分析,发现是系统阻尼系数的变化导致了这一情况的发生;接着提出了两种解决方案,一种是通过改变系统增益进而影响系统阻尼系数,另一种是通过调节滤波电路中的两个电容的比值来调节系统阻尼系数;之后通过分析计算,给出了使用这两种方案组成高阶滤波器时各级2阶滤波电路需具备的系统阻尼。对采用所述方法设计的截止频率为100 kHz的4阶和8阶滤波器进行PSPICE仿真分析,结果显示,其截止频率仿真值分别为98.828 kHz和96.200 kHz,与理论计算值基本一致,验证了所提高阶滤波器设计方法的有效性。

三相并网逆变器有源阻尼控制策略研究

LCL滤波器因其成本低、高次谐波衰减能力强,适用于大功率的三相并网逆变器,在各类新能源发电场合中应用广泛。LCL滤波器存在谐振问题,导致系统稳定性降低。通过建立LCL滤波器的传递函数分析LCL滤波器对系统的影响,并提出了通过电容电流前馈模拟虚拟阻抗的方法增加系统的阻尼,抑制LCL滤波器的谐振峰值,提高系统的稳定性。最后通过在Matlab/simulink中搭建仿真模型,验证算法的可行性。仿真结果表明:通过增加电容电流前馈环节的有源阻尼法可增加系统的稳定性,且不额外增加系统的损耗,三相并网逆变器的输出并网电流谐波含量低。

Single Current Feedback Control Strategy for Grid-connected Inverters With LCL Filters

LCL滤波器广泛应用于并网逆变器系统中,其对高次谐波具有良好的衰减作用;但LCL滤波器为低阻尼三阶系统,容易发生谐振。传统的有源阻尼方法,通过对电容电流进行采样并反馈,能够抑制系统振荡,但增加了传感器数量。提出一种单电流反馈控制策略,其采用入网电流两次微分的反馈方法,增加了系统阻尼,从而有效地抑制LCL滤波器的谐振尖峰,保证系统的稳定性;同时其对系统参数不敏感,并且不增加额外的传感器,是一种低成本高可靠性的控制策略。文中推导该控制策略下的系统传递函数,并分析系统的稳定性。最后,通过仿真和实验,验证提出的控制策略的可行性与有效性。

A Novel Control Strategy of PWM Rectifier with LCL Filter Under Unbalanced Grid Condition

The paper presents a successful design and good result of grid voltage feed-forward control strategy with no damping regulator of LCL filter applied in Three-phase Pulse Width Modulation( PWM) rectifier under unbalance grid condition for renewable energy processing. It is demonstrated that the closed-loop current control is decoupled with the grid voltage feed-forward control,and good waveform of grid current with low order harmonics is obtained under unbalance grid condition. This novel strategy is simple and reliable,applied with PI regulator but no resonant controller in α,β two-phase stationary frame. Moreover,the results of experiment and simulation are also illustrated to validate the novel strategy well applied in the closed-loop current control system under unbalanced grid condition.

Dual-loop Control Strategy for Grid-connected Inverter with LCL Filter

As to the concrete topology of three-phase LCL type grid-connected inverter with damping resistance, mathematical model was deduced in detail, using method of equivalent transformation to the structure diagram, damping resistance was virtualized, mathematical model under the DQ frame that can realize decoupling control was established, a dual-loop control strategy for grid-connected inverter with LCL filter was proposed, the system stability was analyzed and the design method of controller was given. The proposed method overcame the flaws of loss increase, efficiency reduce and cost increase which were caused by damping resistance in LCL type grid-connected inverter, the system efficiency and power supply quality of the output were improved. Feasibility and effectiveness of the new method were validated by simulation and experimental results.

基于改进无源性控制的三相LCL并网逆变器输出导纳重塑方法

基于能量函数的无源性控制(PBC)被广泛研究并用于并网变换器以获得更好的控制性能.然而,传统的PBC方法依赖并网变换器的精确数学模型,且已有研究较少考虑数字控制的延迟效应以及电容性电网或复杂弱电网下电网阻抗的不确定性对系统稳定控制的影响.鉴于此,针对三相LCL并网逆变器提出一种改进PBC方法以实现导纳重塑,通过增加电容电流前馈将系统无源区域扩展到奈奎斯特频率,在电网阻抗宽范围变化下实现LCL谐振频率的有源阻尼控制,并提出改进PBC控制参数设计方法.在3 kW并网逆变器样机平台上开展仿真和实验研究,验证了理论分析的正确性.