Existence condition of state equations of linear active networks over F(z)

If the physical parameter of each branch of a linear active network is considered to be an independently variable parameter, then it is called a network over the field F(z) of all rational functions in its physical parameters. This paper discusses the existence condition of state equation over F(z) for the active network. The condition depends only on the network structure, and is applied to two examples, which shows that the method is straightforward. Copyright © 2006 John Wiley & Sons, Ltd.     

The generalized tree for state variables in linear active networks

A tree for the association of state variables in linear active networks is presented. This tree is selected in such a manner that the voltages across the capacitors contained in it and the currents through the inductors contained in its cotree may be chosen as state variables of a linear network. An algorithm for finding such a tree is given, and the association of state variables with this tree are demonstrated by examples.     

Some topologico-dynamical properties of linear passive reciprocal networks

The paper considers the complete solvability and the order of complexity of passive RLCT (T = multiwinding ideal transformer) networks. A topological approach based on the determinant polynomial of the matrix of hybrid equations, formed as a set of 1st-order differential and algebraic equations, reveals the structure of the formulation tree and the subnetworks accountable for degeneracies. Topological and algebraic degeneracies are defined. Necessary and sufficient conditions for complete solvability are derived, and two algorithms are given to determine the order of complexity topologically, i.e. without having an explicit state-space representation.     

Topological conditions for the solvability of linear active networks

The solvability problem of a linear active network is approached from a purely topological point of view using the two-graph method. It can be said that a topological condition for the solvability is the existence of a common tree of the voltage and current graphs. A few conditions for the existence of a common tree are derived. If there exists no common tree, subgraphs which cause the nonexistence can be distinguished, and a partition of two-graphs can be introduced. The partition has similar properties to the principal partition of a graph or the canonical form of a bipartite graph, and a structure of two-graphs represented by a partial ordering of sets of edges can be defined. An algorithm to find the partition and a common tree, if one exists, or if no common tree exists, a tree of one of the graphs which has as many common edges as possible with a tree of the other graph, is given. The decomposition of the coefficient matrix accompanying the structure is discussed, and algorithms to determine the decomposition is given.     

基于状态空间线性变换的主动配电网分布式电压控制

大规模分布式发电的接入使得主动配电网电压控制问题日益凸显。受限于配电网模型参数的精度,传统集中式的电压控制和基于模型的分布式电压控制策略效果受到显著影响。提出了一种基于状态空间线性升维变换的主动配电网分布式电压控制方法。通过矩阵分裂方法实现了海森矩阵的分布式求逆,将分布式控制收敛速提升至超线性收敛。基于Koopman数据驱动方法,利用配电网历史运行数据作为训练样本,构建高维线性精确潮流模型,从而推导得到电压-无功全局灵敏度,以此校正分布式牛顿控制中的迭代方向。算例结果证明,相比依赖于模型的分布式电压控制方法,所提方法具有更快的收敛速度和更优的控制收敛结果,且不受参数不精确问题影响,具有更强的工程适用性。     

Singular perturbations in the state space approach of linear electrical networks

Networks whose dynamic order is less than the number of energy storing elements they contain are considered. By adding parasitic elements, their dynamic order is restored. After selecting the state variables properly, singular perturbation theory is used to analyse the network behaviour with respect to the parasitic elements and to calculate the initial jumps in the network variables. Parasitic elements are seen to play a dominating role in dictating the stability of a network. The need for generalizing the presently available singular perturbation theory is pointed out by means of an example.     

Some new results on the controllability and observability of linear systems and networks

This paper introduces the concept of ‘hybrid-dual systems’ and presents some new results on the controllability and observability of these systems. Theorem 1 states that for hybrid-dual systems, which include dual systems as a special case, controllability of one implies observability of the other. Theorem 2 gives the topological conditions for RLC n-ports such that controllability and observability imply each other. Theorem 2 also shows that for any RLC n-port, observability implies controllability, but the converse is not true.     

On the existence of solutions to linear active networks: A state-space approach

In recent literature, several alternative conditions for the existence of solutions to active networks are given. In this paper, yet another condition is given which is both necessary and sufficient for the existence of a unique solution to the network. Based on this new condition a precise upper bound for the order of complexity of an active network is established which differs from published results. A Fortran coded program is also available.     

Using the superposition method to formulate the state variablematrix for linear networks

This paper proposes a systematic method for writing the state variable matrix for nondegenerate linear electrical networks by using the superposition principle and also extends the procedure to cover degenerate networks. To use the proposed method, all inductances and capacitances in a network are replaced by ideal independent sources; the state variable equations are then written, often by inspection with nondegenerate networks, utilizing the superposition principle in conjunction with the resulting simplified electrical network     

基于改进Att-LSTNet与无迹粒子滤波融合的主动配电网预测辅助状态估计

针对传统的无迹粒子滤波(unscented particle filter, UPF)存在不准确的新息向量及未知的量测噪声协方差矩阵导致估计精度低的问题,提出一种改进Att-LSTNet与UPF融合的主动配电网预测辅助状态估计(forecasting-aided state estimation, FASE)方法。首先,采用引力搜索算法(gravitational search algorithm, GSA)对支持向量回归(support vector regression, SVR)的关键参数进行优化处理,利用历史数据建立GSA-SVR模型,并将其引入至Att-LSTNet模型的输出层,构建一种增强预测模型。然后,利用UPF中的新息向量来训练该模型,并结合孤立森林算法和箱线图法对原始新息向量进行监控和修正。最后,针对量测噪声协方差矩阵未知的情况,结合修正后的新息向量和UPF计算出未知量测噪声协方差矩阵,并进行状态估计。基于IEEE33与IEEE118节点标准配电系统的算例结果表明,所提出的方法在估计精度、泛化能力和鲁棒性等方面具有优越性。     

直线电机的线性自抗扰控制

光刻机的工件台是高动态精密伺服运动平台,它要求在系统高速运动的同时,采用长行程直线电机宏动跟随音圈电机高精密微动的驱动方式,实现系统纳米级的精确定位及跟踪。为减小微动电机的运动范围和加速度,必须提高直线电机的跟踪精度。针对该系统的直线电机模型设计了一种线性自抗扰控制方法,该方法的控制器首先通过扩张状态观测器观测系统的动态变化,补偿系统中的各种扰动,再运用前馈对系统的跟踪误差进行补偿,减小系统的动态跟踪误差。在此复合控制方式下,控制器实现了自抗扰控制,前馈控制器很好的补偿了误差,从而提高了系统的抗干扰和跟踪性能。实验表明,该方法与传统的控制方法相比,改善了系统的动态性能和抗干扰能力。     

A note on high-Q active networks

Levi's and Zeheb's approach for approximating a high-Q second-order section by n sections with lower Q's is compared with the optimal solution of this problem proposed by Khazanov. Tables relating the maximum error in the approximation to the values of n and the achievable Q-reduction (QR) are also given. They should prove useful to the designer. Finally, some comments on sensitivities are added.     

对微机保护使用现状的几点思考

简要介绍了我国微机保护的发展,对未来的客户需求和新产品开发趋势提出了一些看法.     

对微机保护使用现状的几点思考

简要介绍了我国微机保护的发展,对未来的客户需求和新产品开发趋势提出了一些看法。     

Some considerations on the iterative harmonic analysis convergence

The convergence difficulties of the iterative harmonic analysis (IHA) methodologies are considered. Two techniques proposed to improve IHA convergence are described and their applicability limits are analyzed. To overcome the aforementioned limits, a third improvement technique is presented. A critical case study is solved by means of IHA and the three improvement techniques, and the results are analyzed and discussed     

基于降阶线性扩张状态观测器的风电并网逆变器线性自抗扰控制*

针对风电并网逆变器直流母线电压易受电网电压波动和负载扰动影响的问题,文中提出了一种电压外环改进型线性自抗扰控制(LADRC)。首先建立了风电并网逆变器在d-q旋转坐标系下的数学模型,在此基础上,设计了基于降阶线性扩张状态观测器的线性自抗扰控制,减小了观测器的相位滞后,提高了系统的扰动观测精度;然后在观测器总扰动通道上增加了一个超前滞后的校正环节以减弱观测器的噪声放大效应;最后对改进型LADRC控制策略进行了频域特性分析。仿真结果表明,相比于传统LADRC控制策略,文中所提的控制策略对并网逆变器直流母线电压具有更好的控制效果。     

Stable high q active networks

A new approach is suggested to approximate the amplitude frequency behaviour of a given high Q poles network function, by an explicit function having poles with a predetermined desired low Q, and with explicit knowledge and control of the error. The method is practical for reducing Q's by the ratio of up to 6. Any critical pole-pair is replaced by an approximating function possessing a complex conjugate n-th order pole-pair and a (n?1)-th order zero-pair. A general second order low Q building block is derived as an example. Measured results proving the practical usefulness of the method, are reported.     

Some new algebraic criteria for chaos synchronization of Chua's circuits by linear state error feedback control

The research on the sufficient criterion for chaos synchronization of the master–slave Chua's circuits by linear state error feedback control has received much attention and some synchronization criteria for special control matrix were proposed. In this paper, the above synchronization issue is investigated in the situation of general linear state error feedback controller with propagation delay of control signals from the master Chua's circuit. First of all, a master–slave synchronization scheme for Chua's circuits with propagation delay is given and the relevant error system is derived. Using a quadratic Lyapunov function and frequency domain method, three new algebraic synchronization criteria for the synchronization scheme with general control matrix are proven. They are applied to derive the synchronization criteria for simple control matrices. Some examples are given to show the sharpness of these new criteria compared with the known criteria. Copyright © 2006 John Wiley & Sons, Ltd.