bluuebunny/crossref_metadata_2025 huggingface dataset:
Multiuser‐MIMO systems employing a broadcasting protocol under equally correlated generalised‐Rician fading for even degrees of freedom
Authors: Le Khoa N.
Published: October 2019

Using an opportunistic transmission protocol in which users contend for transmission to a base station under equal‐correlated generalised‐Rician fading, new single‐integral selection combiner output cumulative distribution functions (cdfs) of multivariate equal‐correlated generalised‐Rician fading for multiuser multiple‐input multiple‐output systems, and even degrees of freedom with multiple transmit and receive antennas per user are obtained in this study. Corresponding infinite‐summation cdfs of multivariate equal‐correlated generalised‐Rician fading are obtained. Cross‐verification is mathematically performed to validate the proposed findings. The new findings provide a useful mathematical framework to assess performance of wireless networks under equal‐correlated generalised‐Rician fading environments. The effectiveness of the new findings is exemplified by computing average bit error rates for the binary phase‐shift keying scheme under equal‐correlated generalised‐Rician fading, and plotted against (i) a common average branch normalised signal‐to‐noise ratio, (ii) line‐of‐sight power, (iii) an even number of independently and identically distributed underlying Gaussian random variables, (iv) a total number of transmit antennas, and (v) a total number of receive antennas. Simulation results are shown to exactly match numerical simulation. Detailed discussions are given.
Optimal multi‐controller placement strategy in SD‐WAN using modified density peak clustering
Authors: Sminesh Choorkunnu Narayanan , Kanaga Edward Grace Mary , Roy Aiswarya
Published: October 2019

In software‐defined wide area networks (SD‐WANs), finding an optimal number of controllers and their placement is termed as the controller placement problem. The existing solutions based on multi‐objective optimisation techniques incur high computation time. Heuristic algorithms based methods quickly converge to local optimum solutions and clustering‐based approaches demand that the number of controllers required to be predefined. In SD‐WANs, computationally simple solutions for controller placement can be developed using non‐parametric clustering algorithms. The proposed modified density peak (modified‐DP) clustering algorithm decides the multi‐controller placement for the selected networks from the Internet Topology Zoo. The computed performance metrics are compared with hierarchical k‐means, modified affinity propagation (modified‐AP), and basic DP (basic‐DP) clustering algorithms. The criteria importance through inter‐criteria correlation method calculates weights of each performance metric, and a normalised weighted additive utility function computes the utility value for the controller placement using each algorithm. The modified‐DP computes the minimum utility value and optimal placement of SDN controllers compared to hierarchical k‐means, modified‐AP, and basic‐DP. The Cbench tool calculates the maximum throughput for the controller placement in each network topology. The calculated fairness in the utilisation of the controllers justifies the optimal controller placement using modified‐DP.
High‐data‐rate PO‐CDSK: a high effective chaotic communication scheme
Authors: Duan Jun‐Yi , Yang Hua
Published: October 2019

To eliminate the intrasignal interference (ISI), phase‐orthogonality correlation‐delay‐shift‐keying (PO‐CDSK) alternately chooses quadrature sinusoidal wavelets to modulate the reference signals in different symbol durations and keeps the reference and information‐bearing signals orthogonal in one symbol duration. Unfortunately, in PO‐CDSK, one data‐modulated signal can carry only 1‐bit information, resulting in a relatively low data rate. In this brief, the authors design a high‐data‐rate PO‐CDSK system, in which 2‐bits information share one time slot but transmitted over the inphase and quadrature channels, respectively. Theoretical BER expression of the proposed system is studied analytically, and simulations are performed over additive white Gaussian noise and Rayleigh multipath fading channels for verification. Results show that, without ISI components, the authors' new system performs much better than differential‐chaos‐shift‐keying (DCSK), CDSK and high‐efficiency DCSK systems in BER performance. Besides, the proposed system also achieves doubled spectral and energy efficiencies in comparison with PO‐CDSK.
New upper bound for a rearrangeable non‐blocking WSW architecture
Authors: Lin Bey‐Chi
Published: October 2019

An optical network based on elastic optical switches allows requests using different spectrum widths to improve utilisation efficiency. This study considers one three‐stage WSW (waveband switching‐space switching‐waveband switching), optical node architecture for elastic optical networks. A sufficient condition for a rearrangeable non‐blocking WSW architecture with limited input/output links has been derived in an earlier work. In this study, the author improves the upper bound by adopting a new interstage link partition scheme associated with a tricky routing algorithm. Suppose a WSW architecture has r input/output links each of which has n frequency slot units (FSUs). Compared with earlier results, the results of the proposed scheme show that s − 1 (or 3s − 4) FSUs per interstage link can be reduced for even (or odd) min{r, n}, where s = min{⌈r/2⌉, ⌈n/2⌉}. The reduction gain is at least 3.5% (or 10%) for even (or odd) min{r, n} if r = n ≤ 26, even achieving 23.3% for limited odd r = n.
Sparse detection with orthogonal matching pursuit in multiuser uplink quadrature spatial modulation MIMO system
Authors: Adnan Saifullah , Fu Yuli , Junejo Naveed Ur Rehman , Chen Zhen , Esmaiel Hamada
Published: October 2019

Quadrature spatial modulation (QSM) is one of the most prevalent transmission techniques for future wireless mobile network due to its high spectral efficiency (SE) and low complexity. However, it is restrictive to downlink of the cellular network deployments. Therefore, this paper proposes QSM for the multiuser uplink data transmission that increases the SE of the network by deploying multiple antennas at the mobile user with only two radio frequency (RF) chains. Maximum likelihood (ML) decoder is used to detect the received signal and attains the optimal detection performance but it is impractical because of its high computational complexity. Consequently, this paper proposes compressed sensing (CS) based orthogonal matching pursuit (OMP) detection as it has a suboptimal performance with a low computational complexity which can be a practical solution in the high‐density uplink multiuser network. However, conventional OMP algorithm has a low estimation performance due to multiuser interference which corrupt channel matrix. Thus, this work design an equalizer that mitigates the multiuser interference and improve the detection performance by orthonormalizing the columns of channel matrix. Simulation analysis confirm that the proposed QSM technique based on CS detector outperforms the conventional schemes in terms of SE and bit error rate (BER).
Online and robust resource allocation for D2D communications assisted by Green relays
Authors: Han Qiaoni , Yang Bo , Wang Xiaocheng
Published: October 2019

Device‐to‐device (D2D) communications in cellular networks allow proximity users to communicate directly without going through the base station. Concentrating on scenarios where the direct communication between potential D2D users may not be reliable due to poor proximity and link condition, and paying attention to energy harvesting wireless communications, this study focuses on the green relay‐assisted D2D communications, where long‐term evolution‐advanced layer‐3 relays powered by renewable energy are employed. To achieve the trade‐off between system capacity maximisation and user fairness, the authors formulate an offline resource block (RB) and power allocation problem under imperfect channel information with the objective of maximising the weighted sum‐rate of all users. Then, based on battery dynamics, the original problem is reformulated as an online one with energy outage avoidance. To obtain distributed solutions, the online problem is further transformed into a convex one, and the rate outage‐probability requirement is also converted for tractability. Finally, applying Lagrangian duality, the distributed RB and power allocation is derived, which is globally optimal to the reformulated online problem. Comparing with a baseline scheme where all users communicate directly without assistance of relays, numerical results show the superiority of the proposed approach in terms of the average achievable data rate.
Optimisation design of systematic fountain codes on fading channels
Authors: Dai Jingke , Chen Xiao , Zhang Fenggan , Kang Kai
Published: October 2019

The asymptotic performance and optimisation of systematic fountain codes are investigated on Rayleigh fading and Nakagami fading channels. Firstly, the closed‐form bit error rates (BER) of systematic LT (SLT) codes and systematic Raptor (SR) codes are derived based on Gaussian approximation method, the results of which are close to that obtained by discretised density evolution. Secondly, a novel optimisation model combining linear programming and theoretical error probability is proposed to design the degree distributions of SLT/SR codes on fading channels. The simulation results show that the optimised codes provide better BER performance than the codes originally designed for binary erasure channel and additive white Gaussian noise channel. Moreover, the proposed method is easily extended to Rician fading channel and unfading channel.
Orbit determination algorithm and performance analysis of high‐orbit spacecraft based on GNSS
Authors: Zou Deyue , Zhang Qi , Cui Yongen , Liu Yunfeng , Zhang Jing , Cheng Xinyi , Liu Jie
Published: October 2019

The study of using the Global Navigation Satellite System (GNSS) to locate Geostationary Earth Orbit (GEO) satellites is very valuable. In this thesis, a new RF strategy is proposed. The back‐lobe signal and the main‐lobe signal of GNSS satellites are used to provide positioning services for GEO satellites and the receiver antenna beam‐forming method is used to improve receiver sensitivity. Additionally, this thesis proposes a satellite selection algorithm that matches the proposed RF strategy. The simulation found that the receiver needs higher sensitivity to detect the back‐lobe signal of the GNSS satellite but that the number of visible satellites had doubled and the geometric distribution of the satellite had also been greatly improved. The simulation based on the measured data proves that using a 16*16 antenna array and beam‐forming by maximum signal‐to‐interference and noise ratio algorithm can make five beams of GNSS receivers in GEO orbit and that the side‐lobe suppression ratio is up to  dB, which greatly improves the signal receiving gain. After adopting the above technology, the GPS positioning accuracy of GEO spacecraft can be optimised from the order of kilometres to the metres.
Cooperative caching in fog radio access networks: a graph‐based approach
Authors: Jiang Yanxiang , Cui Xiaoting , Bennis Mehdi , Zheng Fu‐Chun , Fan Baotian , You Xiaohu
Published: October 2019

In this study, cooperative caching is investigated in fog radio access networks. To maximise the offloaded traffic, a cooperative caching optimisation problem is formulated. By analysing the relationship between clustering and cooperation and utilising the solutions of the knapsack problems, the above challenging optimisation problem is transformed into a clustering subproblem and a content placement subproblem. To further reduce complexity, the authors propose an effective graph‐based approach to solve the two subproblems. In the graph‐based clustering approach, a node graph and a weighted graph are constructed. By setting the weights of the vertices of the weighted graph to be the incremental offloaded traffics of their corresponding complete subgraphs, the objective cluster sets can be readily obtained by using an effective greedy algorithm to search for the max‐weight independent subset. In the graph‐based content placement approach, a redundancy graph is constructed by removing the edges in the complete subgraphs of the node graph corresponding to the obtained cluster sets. Furthermore, they enhance the caching decisions to ensure each duplicate file is cached only once. Compared with traditional approximate solutions, their proposed graph‐based approach has lower complexity. Simulation results show remarkable improvements in terms of offloaded traffic by using the proposed approach.
Stability analysis of systems with time‐varying delay: a quadratic‐partitioning method
Authors: Chen Jun , Park Ju H. , Xu Shengyuan
Published: October 2019

During the course of analysing the stability of systems with time‐varying delay, stability criteria are often shown in the form of the first‐ or second‐order polynomial functions with respect to the time‐varying delay. Therefore, the convex/concave property plays an important role in reducing the conservatism of stability criteria. In this note, the quadratic‐partitioning method is proposed to take full advantage of the convex/concave property of a quadratic function, which can further reduce the conservatism of some of existing results. Two well‐known numerical examples are given to illustrate the effectiveness of the proposed method.
Design of state‐dependent impulsive observer for non‐linear time‐delay systems
Authors: Kalamian Nasrin , Khaloozadeh Hamid , Ayati Moosa
Published: October 2019

In this study, a new state‐dependent impulsive observer (SDIO) is proposed for a class of non‐linear time‐delay systems. The proposed observer is based on the extended pseudo‐linearisation technique that parameterises the non‐linear time‐delay system to a pseudo‐linear structure with time delay and state‐dependent coefficients. Applying this technique, the presented observer is utilised for non‐linear systems with multiple, time‐varying and distributed delays. Furthermore, the extended pseudo‐linearisation technique simplifies the procedure of impulsive observer design for non‐linear time‐delay systems. The proposed SDIO is capable of continuously estimating system states using discrete samples of the system output that are available at discrete impulse times. The stability and convergence of the proposed observer are proven via a theorem utilising time‐varying and delay‐independent Lyapunov function and the comparison system theory of impulsive systems. It is guaranteed that the estimation error asymptotically converges to zero under well‐defined and less‐conservative sufficient conditions that are presented in terms of feasible linear matrix inequalities. In addition, the stability theorem specifies an upper bound on the time intervals between consecutive impulses. Results are simulated on Congo Ebola disease model which is an epidemic non‐linear time‐delay system. Simulation results confirm the effectiveness and performance of the proposed SDIO.
Path tracking control of a self‐driving wheel excavator via an enhanced data‐driven model‐free adaptive control approach
Authors: Liu Shida , Hou Zhongsheng , Tian Taotao , Deng Zhidong , Guo Lei
Published: October 2019

In this work, an enhanced model‐free adaptive control algorithm considering the time delay (EMFAC‐TD) is proposed for a class of multi‐input and multi‐output systems and is further applied to the path tracking control problem of a self‐driving wheel excavator. First, a preview‐deviation‐yaw‐based method is first proposed for the simplification of excavator dynamics. Then, based on the simplified dynamics, the EMFAC‐TD controller is designed via a novel dynamical linearisation technique with a time‐varying parameter termed pseudo Jacobian matrix, which contains the coupling information of the excavator driving dynamics. Moreover, for the time delay of the excavator, EMFAC‐TD method also handles it by introducing the Smith estimating method. The main feature of the proposed EMFAC‐TD is that the controller is designed only based on the input and output data of the excavator. Further, the stability of the proposed EMFAC‐TD is proved via rigorous mathematical analysis. The experimental results implemented on a real self‐driving excavator show that the maximum tracking error of the excavator controlled via EMFAC‐TD method can be limited as 0.3–0.7 m for different driving tasks, satisfying the practical requirement. The experimental results verify that EMFAC‐TD method can improve the tracking performance and complete the required task successfully.
Finite‐time control of switched affine non‐linear systems based on the Lie derivative and iteration technique
Authors: Gao Zairui , Wang Yan , Ji Zhicheng
Published: October 2019

In this study, the finite‐time control problem for a class of switched affine non‐linear systems is discussed in both continuous‐time and discrete‐time contexts. Firstly, the concepts of finite‐time boundedness are extended to switched non‐linear systems in both continuous‐time and discrete‐time cases, respectively. Secondly, based on the Lie derivative and iteration technique, some sufficient conditions, which can guarantee that switched affine non‐linear systems are finite‐time bounded with a prescribed performance, are derived by applying the mode‐dependent average dwell time and the multiple Lyapunov functions. It is worth pointing out that each subsystem satisfies finite‐time boundedness in the activation interval, and not in the whole time domain. Finally, two numerical examples are given to illustrate the feasibility and effectiveness of the obtained results.
Design scheme of discrete time variable structure controllers applied to multi‐input‐multi‐output linear systems with chattering elimination
Authors: Al‐Hadithi Basil Mohammed , Darío Luis‐Delgado José , Jiménez Agustín
Published: October 2019

Designing discrete time variable structure control with sliding mode (SM) schemes implies finding an asymptotically stable sliding surface with a control policy which assures the existence of a SM. Based on a recently innovative approach, where the authors developed a flexible design of sliding surfaces applied to discrete time linear multi‐input multi‐output (MIMO) systems, a novelty controller design strategy is proposed, where a switching surface parameter is used for the adjustment of the control signal limitations and for the improvement of the controlled system dynamics against model uncertainties. It is the first time that these drawbacks are solved modifying the switching surface values because it has been always resolved via control law adjustment. Moreover, a new chattering elimination method using adjustable sigmoid functions is also implemented in the controller. The main advantages of the proposed methodology are: firstly, it can be easily applied to high‐order linear MIMO systems; secondly, system dynamics coordinates representation transformations are not needed and thirdly, the non‐ideal SM dynamics is considered in the design procedure. Both the sliding surface and the control law specification are included in the proposed methodology. An illustrative example is included.
Event‐triggered robust adaptive control for discrete time uncertain systems with unmodelled dynamics and disturbances
Authors: Zhuang Wenxiu , Wen Changyun , Zhou Jing , Liu Zhitao , Su Hongye
Published: October 2019

In practice, modelling errors caused by high‐order unmodelled dynamics and external disturbances are unavoidable. How to ensure the robustness of an adaptive controller with respect to such modelling errors is always a critical concern. In this study, the authors consider the design of event‐triggered robust adaptive control for a class of discrete‐time uncertain systems which involve such modelling errors and also are allowed to be non‐minimum phase. Unlike some existing event‐triggered control schemes, the developed controllers do not require that the measurement errors meet the corresponding input‐to‐state stable condition. Global stability of the closed‐loop system which means that all the signals are bounded is established in the presence of unmodelled dynamics and disturbances. Besides, in contrast to existing robust adaptive schemes, the designed adaptive controller does not involve parameters related to unmodelled dynamics and disturbances which are difficult to be chosen for ensuring such stability. An example is given to verify the effectiveness of the proposed control strategy.
Spatial domain decomposition approach to dynamic compensator design for linear space‐varying parabolic MIMO PDEs
Authors: Wang Jun‐Wei
Published: October 2019

This study addresses the problem of dynamic compensator design for exponential stabilisation of linear space‐varying parabolic multiple‐input–multiple‐output (MIMO) partial differential equations (PDEs) subject to periodic boundary conditions. With the aid of the observer‐based feedback control technique, an observer‐based dynamic feedback compensator, whose implementation requires only a few actuators and sensors active over partial areas of the spatial domain, is constructed such that the resulting closed‐loop coupled PDEs is exponentially stable. The spatial domain is divided into multiple subdomains according to the minimum of the actuators' number and the sensors' one. By Lyapunov direct method and two general variants of Poincaré‐Wirtinger inequality at each subdomain, sufficient conditions for the existence of such feedback compensator are developed and presented in terms of algebraic linear matrix inequalities (LMIs) in space. Based on the extreme value theorem, LMI‐based sufficient and necessary conditions are presented for the feasibility of algebraic LMIs in space. Finally, numerical simulation results are presented to support the proposed design method.
Event‐triggered control of positive switched systems based on linear programming
Authors: Liu Laiyou , Zhang Junfeng , Shao Yu , Deng Xuanjin
Published: October 2019

This study focuses on the problem of event‐triggered control for positive switched systems without/with input saturation in both continuous‐time and discrete‐time contexts. First, a 1‐norm based event‐triggering mechanism is established for continuous‐time positive switched systems. By means of the matrix decomposition technique, an event‐triggered controller for the systems is designed by decomposing controller gain matrix into non‐positive and non‐negative components. Under the designed controller, the resulting closed‐loop systems are positive and stable. For the systems with input saturation, the saturation term is transformed into interval form under the event‐triggering condition. Then, an event‐triggered controller gain matrix and a cone domain of attraction gain matrix are designed for the corresponding interval systems in terms of linear programming, respectively. Furthermore, the presented approaches are extend to discrete‐time positive switched systems without/with input saturation. Compared with existing results on positive switched systems, the designed event‐triggered controller can reduce sampling frequency and save resources. Finally, two numerical examples are provided to verify the effectiveness of the obtained results.
Projective synchronisation of variable‐order systems via fractional sliding mode control approach
Authors: Meng Xin , Kao Yonggui , Gao Cunchen , Jiang Baoping
Published: October 2019

This study concerns with the projective synchronisation problem of fractional variable‐order master–slave systems via the fractional sliding mode control. Firstly, an applicative index law is designed for the considered fractional variable‐order system based on the Grünwald–Letnikov definition. Secondly, two different fractional variable‐order sliding surface functions are proposed to study this projective synchronisation problem. Meanwhile, sufficient conditions are obtained to ensure the projective synchronising error is asymptotically stable. Finally, numerical examples show the validity and feasibility of the proposed approach.
Static and dynamic output feedback stabilisation of descriptor fractional order systems
Authors: Zhang Xuefeng , Zhao Zeli , Wang Qingguo
Published: October 2019

In this study, output feedback control is utilised to stabilise descriptor fractional order systems (FOS) with the fractional order belonging to and , respectively. Firstly, by the restricted equivalent transformations, a new necessary and sufficient condition of admissibility for descriptor FOS with is presented. Then, based on the methods of singular value decomposition, static and dynamic output feedback stabilisers of descriptor FOS with and are obtained, respectively. Finally, four numerical examples are provided to verify the effectiveness of the proposed approaches.
Electromagnetic performance analysis and thermal research of an outer‐rotor I‐shaped flux‐switching permanent‐magnet motor with considering driving cycles
Authors: Liu Lu , Ding Shichuan , Liu Chang , Zhang Dexiang , Wang Qunjing
Published: October 2019

In the operation of electric vehicles (EVs), the driving conditions of frequent acceleration and deceleration, sudden start–stop, heavy load, and hill‐climbing are usually required to meet the requirements of the increasing complexity of the modern transportation. Hence, the electromagnetic performance of traction motors in EVs should be investigated considering driving cycles. This study analyses the electromagnetic performance of an outer‐rotor I‐shaped flux‐switching permanent‐magnet (I‐FSPM) motor with considering driving cycles. Firstly, the electromagnetic performance including the basic no‐load characteristics, magnetic field distribution, and torque performances are analysed and compared under three different driving conditions. To analyse the proposed motor considering driving cycles comprehensively, the temperature rise is also calculated. Generally, the temperature rise is related to the loss characteristics. Thus, a loss prediction method considering the driving cycle for an I‐FSPM motor is presented, where the New European Driving Cycle is chosen as the sample driving cycle. Also a lumped parameter thermal model is built. The predicted results of the I‐FSPM motor are verified by the finite element calculations. Finally, experimental validation is carried out.
Improved vector selection based model predictive torque control for IPMSM
Authors: Gu Xin , Shen Pan , Li Xinmin , Zhang Guozheng , Wang Zhiqiang , Shi Tingna
Published: October 2019

The model predictive torque control (MPTC) is an effective strategy for high performance motor systems. The strategy obtains the optimal voltage vector more quickly and accurately compared with the traditional direct torque control. However, some problems of the strategy are needed to be solved, such as few active vectors, difficult cost function design, and hard duty cycle regulation and so on. An improved MPTC is put forward for these problems in this study. The number of the vector is increased by constructing virtual vectors in the improved method. The finite control set under the rotating coordinate system based on the stator flux orientation is established to select the vector and reduce the computation load. The evaluation mechanism of the selected vector is set by combined with the duty cycle method, so the weight factor of cost function in the traditional method is eliminated. And the duty cycle can play a full role in the adjustment. The prototype experiment system is built for verifying the proposed method. The results demonstrate that the proposed method has better torque and flux control performances and effectively improve the above problems in the traditional method.
Improvements in the permanent magnet synchronous motor torque model using incremental inductance
Authors: Wang Xinjian , Yi Peng , Zhou Zishen , Sun Zechang , Ruan Wenjin
Published: October 2019

This study proposes a method to improve the permanent magnet synchronous motor (PMSM) dq0 model for torque using incremental inductance. The torque model is essentially a partial differential equation considering flux linkage and magnetic energy. In practice, non‐ideal factors, such as saturation non‐linearity, the cogging structure, and the distortion current, increase the difficulty of solving this equation. In this study, two parameters related to flux linkage and magnetic energy are derived using incremental inductance. In the differential range, they are independent of the currents. Therefore, the partial derivatives of flux linkage and magnetic energy can be expressed in the form of derivatives under the saturation non‐linearity conditions. Thereby a dq0 model that describes the torque ripple of a PMSM is established. This model can be used to calculate and analyse the transient characteristics of torque regardless of steady or unsteady current excitation. The main parameters of the model are obtained from finite‐element analysis (FEA). To reduce the dependency on FEA in the application, a derived version of this model is obtained by extending the range of the linearisation assumption. Finally, the rationality and effectiveness of the models are proven by comparison with the FEA and experiments, respectively.
Robust predictive current control for IPMSM without rotor flux information based on a discrete‐time disturbance observer
Authors: Kang Shin‐Won , Soh Jae‐Hwan , Kim Rae‐Young , Lee Kui‐Jun , Kim Sang‐Il
Published: October 2019

This study proposes a novel robust predictive current control that is based on a discrete‐time disturbance observer for an interior permanent magnet synchronous motor (IPMSM), does not require rotor flux information. To confirm the effects of the current control response on a parameter mismatch, the parameter sensitivity for the current prediction of a conventional deadbeat predictive current control (DPCC) is analysed. With the proposed method, disturbances owing to a parameter mismatch, rotor flux term, and unmodelled dynamics are estimated using a Luenberger observer in the discrete‐time domain. The estimated disturbances are compensated with the predicted reference voltage model considering a digital delay. The stability of the proposed disturbance observer owing to a parameter mismatch of the stator resistance and d–q inductance is also analysed. The proposed method is robust against the stator resistance and an inductance variation, and an accurate predicted current control can be obtained without an offline or online estimation of the rotor flux. Compared with the conventional DPCC, the proposed method can eliminate a steady‐state current and transient state error caused by disturbances of the system. Experimental results are presented to verify the proposed control scheme even with mismatched parameters of the IPMSM.
Use of a scaling power law to incorporate asymmetrical minor loops in the inverse Jiles–Atherton model
Authors: Mohan Unniachanparambil Greeshma , Kulkarni Shrikrishana V.
Published: October 2019

Magnetic material characterisation and modelling are important for investigating losses and analysing the transient behaviour of electrical systems. This study attempts to contribute in modelling of magnetic materials under conditions of arbitrary flux waveforms. A simple modification of the inverse Jiles–Atherton model for accurately estimating losses in magnetic materials under asymmetrical minor loops is described. The additional losses due to minor loops are mainly due to irreversible domain wall displacements. The modelling presented in this work is based on a scaling power law, which ensures the closure of minor loops and allows better representation of the hysteresis behaviour. The proposed algorithm is verified by modelling hysteresis loops with multiple harmonics associated with pulse width modulated waveforms.
Influence of a novel flux‐absorbing structure on the performance of a surface‐mounted permanent‐magnet motor with overhang
Authors: Kwon Hyuk‐Sung , Yeo Han‐Kyeol , Jung Hyun‐Kyo
Published: October 2019

The demand for surface‐mounted permanent‐magnet (SPM) motors with high torque and power densities has increased as these motors are becoming more widely used in applications requiring high performance in limited spaces, such as electric vehicles and robot arms. Some studies have increased the torque and power densities, such as hybrid flux permanent‐magnet motors utilising radial and axial magnetic fluxes, dual‐rotor and dual‐stator permanent‐magnet motors. Although these motors offer high performance, there are some problems such as low productivity and poor applicability to small motors have arisen due to their complicated structures. An overhang structure can be a simple and effective means of solving the aforementioned problems. However, the overhang effects do not increase linearly but tend to converge as the length of the overhang increases. Therefore, a novel flux‐absorbing structure (FAS) that effectively enhances the overhang effects of SPM motors even in cases with considerable overhang was proposed. The magnetic flux path from the overhang to the stator can be efficiently improved via the proposed FAS. Thereby, the performances of a SPM motor can be effectively enhanced when the FAS is adopted. The effectiveness of the proposed FAS was verified via a 3D finite‐element analysis and in experiments.
Performance modifications and design aspects of rotating flux switching permanent magnet machines: a review
Authors: Nobahari Amin , Aliahmadi Mehdi , Faiz Jawad
Published: October 2019

Permanent magnet flux switching machines (FSPMs) have attracted considerable attention in recent years, due to their outstanding characteristics to operate as brushless AC drives. Since they are relatively new, there are particular challenges not only for their design procedure but also for their operating principle comprehension. This study highlights several issues on FSPMs from the basic operation description to their key design points. After a comprehensive description of FSPMs working principles, a detailed discussion is presented on their armature winding design. In addition, this study reviews various methods for their performance modification, including torque profile, electromotive force, and loss characteristics. This study also surveys field regulation technologies, modelling and design optimisation methods applied to FSPMs along with their fabrication and cost issues.
Self‐governing single‐stage photovoltaic water pumping system with voltage balancing control for a four‐phase SRM drive
Authors: Mishra Anjanee Kumar , Singh Bhim
Published: October 2019

This work deals with an efficient and reliable solution of a standalone solar water pumping system using a 4‐phase SRM (Switched Reluctance Motor) drive. Only a mid‐point converter is used to drive the SRM as well as to achieve the MPPT (Maximum Power Point Tracking Algorithm) operation. The elimination of DC–DC converter offers a fast dynamic response with enhanced system efficiency. An online flux optimization with single pulse mode of SRM drive is developed and implemented. The developed control scheme eliminates the need of any phase current sensor, and the motor speed is fully governed by the available PV array power. The developed control technique removes the need for any phase current sensor and the speed of the motor is regulated through available solar power. A deviation free MPPT technique is also implemented in this system to overcome the drift problem present in the conventional P&O (Perturb and observe) technique. The appropriateness of the proposed system with developed control is demonstrated through its performance assessment utilizing simulation and test results obtained through an experimental prototype.
Influence of open‐circuit fault on electromagnetic field of high‐speed permanent magnet generator with Gramme ring windings
Authors: Qiu Hongbo , Zhao Xifang , Yang Cunxiang , Yi Ran , Wei Yanqi
Published: October 2019

As the core of the distributed generation system, the health status of high‐speed permanent magnet generator (HSPMG) has attracted much attention. HSPMG is often used in military, rescue and other fields. When the open‐circuit fault of HSPMG stator winding occurs, it will seriously affect the operation stability and power supply reliability. In this study, a 117 kW, 60,000 rpm HSPMG is taken as an example, and a 2D finite element model is established. The accuracy of the model is verified by comparing the calculated results with the experimental data. By the field‐circuit coupling method, the magnetic field changes pre‐and post‐fault is analysed, and the mechanism of magnetic field spatial distribution changes post‐fault is revealed. In addition, the changes in eddy current loss pre‐and post‐fault are analysed. The influence of the harmonic magnetic field and the rotating magnetic field produced by negative sequence current on eddy current loss is studied, and the dominant factors effecting eddy current loss post‐fault are investigated. The study provides some useful conclusions for HSPMG fault analysis.
Interdependent electric and water infrastructure modelling, optimisation and control
Authors: Zuloaga Scott , Khatavkar Puneet , Vittal Vijay , Mays Larry W.
Published: October 2019

The phrase water‐energy nexus is commonly used to describe the inherent and critical interdependencies between the electric power system (EPS) and the water distribution system (WDS). In this study, the analytical framework capturing the interactions between these two critical infrastructures is examined and a mathematical model to describe the associated dynamics is developed. Based on the time scale of these associated dynamics, the EPS simulation is conducted using time‐series power flows following unit commitment and optimal power flow solutions. The WDS control optimisation–simulation model formulated here is solved using a genetic algorithm solution technique interfaced with EPANET. An integrated simulation engine of the interdependent infrastructure systems was created to conduct long‐term simulations. The simulation engine was applied using representative WDS and EPS networks. The implemented control optimisation benefits both systems by reducing the effect of severe contingencies. The results of the simulations conducted prove the applicability of the proposed methodology for long‐term, water‐energy nexus contingency simulations having both power outages and droughts.
Locating and sizing of partition flexible interconnection converter station in large urban power grids
Authors: Jiang Xun , Xiao Jun , She Buxin , Zu Guoqiang
Published: October 2019

Partition flexible interconnection (PFI) is a new way to change the partitioned operation situation of urban power grids so as to promote their security, stability and flexibility. Locating and sizing of the PFI converter station (PFICS) is a key question. In this study, the concept of PFI and the operation mode of the converters are presented at first. An integral locating and sizing method of PFICS is proposed, which is divided into three stages – preliminary selection, location optimisation and capacity design. The preliminary selection can avoid many unnecessary simulations. In the second stage, the optimal location is determined by comprehensively comparing five indices (static security, transient voltage stability, power supply reliability, load balancing and total supply capacity) based on the analytic hierarchy process. In capacity design stage, the maximum VAR capacity curve is obtained via deduction, then the capacity of the PFICS is determined according to power demands of the two interconnected partitions. Finally, the proposed method is verified by the real PFI project in power grid of Beijing (China).
Enhanced self‐adaptive differential evolution multi‐Objective algorithm for coordination of directional overcurrent relays contemplating maximum and minimum fault points
Authors: Shih Meng Yen , Conde Arturo , Ángeles‐Camacho Cesar
Published: October 2019

In this study, a parameter tune free enhanced self‐adaptive differential evolution multi‐objective (ESA‐DEMO) approach has been proposed for coordination of directional overcurrent relays. The advantages of the proposed method are: avoid the use of conventional single‐objective function, which requires tuning of weighting parameters; avoid tuning of algorithm parameters; minimisation of primary, backup and coordination time interval; zero violation of coordination constraints in large interconnected network; and low computational resource consumption leading to fast algorithm execution time. The proposed method has been implemented on the highly interconnected 6‐bus, IEEE 14‐ and 30‐bus systems, where results have shown robustness and consistency of the algorithm. Moreover, two‐fault point coordination criterion considering close‐ and far‐end (maximum and minimum) faults has been performed. ESA‐DEMO has been compared with popular genetic algorithms and state‐of‐the‐art multi‐objective algorithm for protection coordination study.
Decentralised optimal dispatch of multi‐area power systems based on non‐linear value‐function approximation
Authors: Zhu Jianquan , Zhu Tao , Liu Mingbo , Lu Wentian
Published: October 2019

In recent years, the use of interconnected multi‐area systems has increased significantly. To operate these systems efficiently, a proper coordination approach among different areas is required. With this context, a novel decentralised optimal dispatch algorithm is proposed in this study. The centralised economic dispatch model is decoupled into a series of sub‐problems for different areas, allowing the independent decision of each area without a central operator. The detailed information of each area is not required for information exchange. To better estimate the impact of each area's decision on other areas, the approximate value functions of the tie‐line powers are added into the local objective function of the sub‐problem. This technique makes the decentralised solution of the proposed algorithm more explicit and rational compared with most existing distributed algorithms. Besides, the proposed technique does not require parameter tuning and has good convergence performance. Numerical simulations on several test systems and a real power system demonstrate that the proposed algorithm is favourable in terms of accuracy, adaptability, and computational efficiency.
Application of linearised load flow method for droop‐controlled DCMGs
Authors: Maulik Avirup , Das Debapriya
Published: October 2019

In this study, the authors present a linear power flow method for droop‐controlled DC microgrids (MGs). Traditional power flow techniques do not apply to droop‐controlled DCMGs owing to the power and voltage flexibility capability of the droop‐controlled dispatchable generation units. Therefore, new power flow techniques embodying the droop‐control operation philosophy were developed by the researchers. The existing methods are time‐consuming since they involve iterative solutions of a set of non‐linear equations. The proposed linear power flow method is accurate, simple, and gives faster results in comparison to the existing methods. The power flow model applies to all load types (constant power, constant current, and constant resistance) and works for both radial and non‐radial system configurations. The linear power flow can be applied for convex optimisation, optimal power flow, and network reconfiguration problems. The proposed method is validated on five test systems. A comparison with a modified Newton–Raphson power flow demonstrates that the proposed linear power flow technique provides accurate results. The maximum error in voltage calculation is not more than 0.0812%. The performance of the proposed method is also acceptable for heavy loads and high line resistances. The computational time reduces significantly with the proposed method.
Evaluation of supraharmonic emission levels of multiple grid‐connected VSCs
Authors: Wang Ying , Luo Daijun , Xiao Xianyong
Published: October 2019

Supraharmonic is an inevitable power quality issue, with the rapid development of power electronic technologies, receiving more and more attention. Firstly, this study analyses the supraharmonic emission mechanism of voltage source converter (VSC) based on sinusoidal pulse‐width modulation. The mathematical analysis shows that the supraharmonics emitted by grid‐connected VSC mainly distribute near the integer multiple of its switching frequency, and grid‐connected VSCs are essentially supraharmonic voltage sources. Then, this study proposes the supraharmonic equivalent circuit model of multiple VSCs grid‐connected system, by modelling grid‐connected VSCs as supraharmonic voltage sources and connecting them in parallel with the LCL filters. Based on the proposed model, considering the primary and secondary emissions, a method is proposed to evaluate the supraharmonic current emission of one VSC and the total supraharmonic current emission flowing into the grid. Finally, simulation and field measurements show that the proposed method can effectively evaluate the supraharmonic emission levels of multiple VSCs grid‐connected systems.
Frequency control of islanded wind‐powered microgrid based on coordinated robust dynamic droop power sharing
Authors: Roozbehani Sam , Hagh Mehrdad Tarafdar , Zadeh Saeid Ghassem
Published: October 2019

This study proposes a new frequency control of islanded and storage independent wind‐powered microgrid based on coordinated robust dynamic droop power sharing. The islanded microgrid includes wind turbine as undispatchable distributed generation (DG) and fuel cell as dispatchable DG. In the first layer of control, the reverse and direct droop controls are considered for wind turbine and fuel cell, respectively. Accordingly, the outputs of reverse droop control are active and reactive powers, which are used for wind turbine. Simultaneously, the outputs of direct droop control are frequency and voltage, which are used for the fuel cell. Since the generated power of wind turbine is not constant, so the coordinated dynamic droop coefficients for both DGs are modified as a function of available wind power. Then in the second layer, robust sliding mode control is designed for setpoints tracking of both DGs to control the frequency and voltage of islanded microgrid. The effectiveness evaluation of the proposed control scheme is performed by simulation studies on the islanded microgrid in different conditions such as single‐phase fault, load step change and variety of wind speeds in MATLAB/Simulink environment. Finally, results are validated experimentally through the implementation of real‐time hardware‐in‐the‐loop system.
Method for finding the important nodes of an electrical power system based on weighted‐SALSA algorithm
Authors: Geng Junqi , Piao Xuefeng , Qu Yanbin , Song Huihui , Zheng Kangxing
Published: October 2019

It is crucial to rank power system nodes in terms of importance. Once the ranking results are known, by imposing extra protection or changing the topology, strong robustness and low risks of the power system will be obtained. Inspired by the stochastic approach for link structure analysis (SALSA) algorithm, an algorithm for ranking web pages, the authors propose a weighted‐SALSA algorithm to evaluate the node importance for electrical power system. Since power features are different from web page relationships, a weighted and directed graph is adopted instead of an unweighted and directed graph abstracted from web pages. Moreover, considerations for the topology structure and the power flow are also embodied in the proposed algorithm. The results of comparative simulations with electrical betweenness algorithm and model based on cocitation hypertext induced topic search algorithm based on the IEEE 118‐bus system and the IEEE 300‐bus system are proved the effectiveness of the weighted‐SALSA algorithm for ranking nodes of the electrical power system. Moreover, the weighted‐SALSA algorithm has a lower computation complexity, which is an advantage for real‐time calculation.