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19. Integrated Waveform Design for MIMO Radar and Communication via Spatio-Spectral Modulation.

Author

Yu, Xianxiang, Yao, Xue, Yang, Jing, Zhang, Lidong, Kong, Lingjiang, and Cui, Guolong

Subjects
MIMO radar, MIMO systems, SPECTRAL energy distribution, RADAR antennas, RADAR
Abstract

This paper considers the integrated waveform design to simultaneously achieve a desired radar beampattern and multi-users communication for a dual-function Multiple-Input Multiple-Output (MIMO) system. To this end, a spatio-spectral modulation strategy via shaping the spatial waveform Energy Spectral Density (ESD) in directions of communication is proposed for the communication function, while beampattern Integrated Sidelobe Level (ISL) is minimized to enhance radar detectability. Meanwhile, Peak-to-Average Ratio (PAR) and power restrictions to comply with the current hardware technique and the mainlobe width constraint to cohere the beampattern main energy on the spatial region of interest are forced, respectively. Exploiting an equivalent reformulation of the original non-convex optimization problem, a Sequential Block Enhancement (SBE) framework that alternately updates each waveform in each emitting antenna is developed to monotonically decrease ISL. Each block involves the Dinkelbach’s procedure, sequential convex approximation and Alternating Direction Method of Multipliers (ADMM) to obtain single waveform, while the analytic proof with the converged block being a Karush-Kuhn-Tucker (KKT) point is provided. Finally, numerical results highlight the effectiveness of both the proposed dual function scheme and the waveform synthesis technique in comparison with some counterparts. [ABSTRACT FROM AUTHOR]

Published
2022
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26. Investigation of a suitable material for automotive grade 0 requirement mitigating lead delamination

Author

Allen M. Descartin, Zhang Lidong, and Li Jun

Subjects
Thermal shock, Materials science, 020208 electrical & electronic engineering, 02 engineering and technology, Surface finish, Epoxy, medicine.disease_cause, Automotive electronics, Material selection, Mold, visual_art, Compatibility (mechanics), 0202 electrical engineering, electronic engineering, information engineering, medicine, visual_art.visual_art_medium, Surface roughness, Composite material
Abstract

In order to achieve a good package reliability performance it is essential to properly consider how well is the packaging material selection is. The interaction and compatibility of each material is widely considered in the development phase mitigating the risk that may encounter during the course of qualification. One of the package key integrity attributes is the package delamination specifically near at the 2nd bond region. Presence of such delamination between leadframe and molding compound interface over the ball bond or stitch bond region which could lead to a joint fatigue failures. Delamination determined normally through CSAM (C-mode Scanning Acoustic Microscopy) check. This paper studies the different material combinations & designs mainly addressing to minimize and resolve the impact of delamination to the 2nd bond stitch formation. Two types of (epoxy molding compound) EMC (G and H) were studied along with the two different types and designs of leadframe, standard and roughened leadframe surface finish. Reliability stress assessment based on the air to air temperature cycling (AATC) at −65 to 150°C and liquid to liquid thermal shock (LLTS) at −55 to 150°C that includes pre-conditioning (PC) at moisture sensitivity level 3 (MSL3) with 3× reflow at 260°C (peak level temperature). From all the results and data gathered on each experiments, it was found out that the molding compound G showed the best overall performance with no mold related defects, no delamination and good stitch bonding integrity that satisfies the AEC (automotive electronics council) Grade 0 reliability tier. The roughened leadframe surface is better than the standard leadframe surface finish consistently passing the two separate experiment with either G or H molding compound.

Published
2016
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32. Robust Analytic Design of Power-Synchronization Control.

Author

Harnefors, Lennart, Hinkkanen, Marko, Riaz, Usama, Rahman, F. M. Mahafugur, and Zhang, Lidong

Subjects
SYNCHRONIZATION, FREQUENCY-domain analysis, DIRECT currents, ROBUST control, ELECTRIC insulators & insulation
Abstract

This paper addresses robust design of the active-power and dc-link control loops of power-synchronization control. Robustness is obtained by analytic gain selections, which give large enough stability margins. The proposed design allows robust stability irrespective of the grid strength and of the operating point, the latter with one exception. The proposed design is compared to design based on the principle virtual synchronous machine. Experiments show that the time-domain results correlate well with the frequency-domain results. [ABSTRACT FROM AUTHOR]

Published
2019
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33. A Subtransmission Metropolitan Power Grid: Using High-Voltage dc for Enhancement and Modernization.

Author

Pan, Jiuping, Callavik, Magnus, Lundberg, Peter, and Zhang, Lidong

Abstract

Power demand in large or mega cities is increasing as the world urbanizes. Metropolitan transmission networks are continuously upgrading to meet the growing demand for power and to replace old-style generation with local renewable generation and power supplies from cleaner external sources. The cost of land and its scarcity make it difficult to secure new rights-of-way for traditional-style transmission lines. As power transmission levels increase, the risk of exceeding the short circuit capability of existing switchgear equipment as well as other network components becomes a major constraint to the expansion of power networks. Strategies to enhance urban transmission networks must address all of these issues and prioritize solutions that may be easily located within urban boundaries and have short lead times from decision to commercial operation. Advanced transmission technologies can effectively increase the capacity, efficiency, and utilization of existing infrastructure and improve grid resiliency under extreme contingencies or catastrophic events. These technologies have been considered and implemented by electric utilities for urban grid enhancement and modernization. [ABSTRACT FROM AUTHOR]

Published
2019
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34. Power System Stability Analysis Using Feedback Control System Modeling Including HVDC Transmission Links

Author

Bidadfar, Ali, Nee, Hans-Peter, Zhang, Lidong, Harnefors, Lennart, Namayantavana, Sanaz, Abedi, Mehrdad, Karrari, Mehdi, Gharehpetian, Gevork B., Bidadfar, Ali, Nee, Hans-Peter, Zhang, Lidong, Harnefors, Lennart, Namayantavana, Sanaz, Abedi, Mehrdad, Karrari, Mehdi, and Gharehpetian, Gevork B.

Abstract

A general platform is introduced to study the dynamics of power systems with high voltage dc (HVDC) transmission links. Small-signal stability, voltage stability, and interaction phenomena of power systems with both line-commutated-converter HVDC (LCC-HVDC) and voltage-source-converter HVDC (VSC-HVDC) are addressed using the proposed platform. In this platform, the entire power system is modeled as a multivariable feedback control system (FCS) which consists of three interconnected blocks. The contents as well as the inputs and outputs of the blocks are selected such that the conventional analysis tools for power system stability are applicable, both in the time and frequency domains. In the FCS model, the relationships between different instabilities are clear, and participant agents of each instability can be determined. The model is developed in a modular and hybrid style, to make it feasible for a large power system. The proposed model is validated against an electromagnetic transient simulation program (PSCAD) using time responses., QC 20160128

Published
2016
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40. Design of wide-angle scanning parabolic torus reflector antenna realized by rotation of sub-reflector

Author

Yuan-Yun Liu, Dai Zuoxing, Yuan-Bo Shang, Xiaobo Xuan, Zhang Lidong, and Fengwei Yao

Subjects
Beam waveguide antenna, Physics, Fan-beam antenna, Cassegrain antenna, business.industry, Offset dish antenna, Antenna measurement, Astrophysics::Instrumentation and Methods for Astrophysics, Physics::Optics, Reflector (antenna), Parabolic torus reflector antenna, Periscope antenna, Optics, business, Computer Science::Information Theory
Abstract

In order to meet wide angle scanning requirements of the satellite antenna, a side-fed parabolic torus reflector antenna is designed in this paper. The ellipsoid is adopted as sub-reflector with the purpose of reduction the mechanical equipments. The sub-reflector is rotated in azimuth to scan the antenna beam in the direction (±20°) for wide swath coverage. The calculated results guiding the antenna optimization are based on physical optics (PO) analysis and agree well with our design goals.

Published
2013
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41. A 400-V/50-kVA Digital?Physical Hybrid Real-Time Simulation Platform for Power Systems.

Author

Mao, Chengxiong, Leng, Feng, Li, Junlin, Zhang, Shuoting, Zhang, Lidong, Mo, Ran, Wang, Dan, Zeng, Jie, Chen, Xun, An, Ranran, and Zhao, Yanjun

Subjects
INTERFACE circuits, ELECTRIC power distribution grids, POWER system simulation, ELECTRIC power systems, INDUSTRIAL electronics
Abstract

Power system simulation is an important means to study the dynamic behavior, to ensure the safety and stability, and to optimize the operation of a power grid. Pure physical simulation and digital simulation have their own advantages and disadvantages. A three-phase four-wire hybrid simulation platform integrating the advantages of both the digital simulation and physical simulation is developed by combining the physical simulation system and real-time digital simulator. The platform is rated at 400 V and 50 kVA with the short-circuit capacity of 500 kVA and can supply ten times the rated current to support the simulation of various short-circuit faults. An improved interface algorithm based on an ideal transformer model is proposed to extend the stability region of a hybrid simulation. Hybrid simulation experiments are conducted under two cases, and the comparison with the digital simulation demonstrates the performance of this platform and the potential applied to a modern power system. This platform has been equipped in a key laboratory of smart power grid technology. [ABSTRACT FROM PUBLISHER]

Published
2018
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42. Impact on Interarea Modes of Fast HVDC Primary Frequency Control.

Author

Harnefors, Lennart, Johansson, Nicklas, and Zhang, Lidong

Subjects
HIGH-voltage direct current transmission, INTEGRATED circuit interconnections, DAMPING (Mechanics), ELECTRON tube grids, ELECTRIC oscillators
Abstract

Primary frequency control is often added to the control system of a high-voltage DC (HVDC) transmission that interconnects two nonsynchronous ac grids. As the active-power actuation lag is typically in the range of hundreds of milliseconds, the HVDC primary frequency control can be made fast enough to permit inertia sharing among the interconnected ac grids. This reduces the maximum frequency fall after a loss-of-generation contingency (the nadir). A fast HVDC primary frequency control may affect the interarea modes of the interconnected grids. To this end, it is shown that, at least for the cases studied, the modal damping never decreases through the introduction of the mentioned control. [ABSTRACT FROM AUTHOR]

Published
2017
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46. HVDC SuperGrids with modular multilevel converters - The power transmission backbone of the future

Author

Ahmed, Noman, Norrga, Staffan, Nee, Hans-Peter, Haider, Arif, Van Hertem, Dirk, Zhang, Lidong, Harnefors, Lennart, Ahmed, Noman, Norrga, Staffan, Nee, Hans-Peter, Haider, Arif, Van Hertem, Dirk, Zhang, Lidong, and Harnefors, Lennart

Abstract

In order to transmit massive amounts of power generated by remotely located power plants, especially offshore wind farms, and to balance the intermittent nature of renewable energy sources, the need for a stronger high voltage transmission grid is anticipated. Due to limitations in ac power transmission the most likable choice for such a grid is a high-voltage dc (HVDC) grid. However, the concept of the HVDC grid is still under active development as different technical challenges exist, and it is not yet possible to construct such a dc grid. This paper deals with prospects and technical challenges for future HVDC SuperGrids. Different topologies for a SuperGrid and the possibility to use modular multilevel converters (M2Cs) are presented. A comprehensive overview of different submodule implementations of M2C is given as well as a discussion on the choice between cables or overhead lines, the protection system for the dc grid and dc-side resonance issues., QC 20150708

Published
2012
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47. Modelling and control of VSC-HVDC connected to island systems

Author

Zhang, Lidong, Harnefors, Lennart, Nee, Hans-Peter, Zhang, Lidong, Harnefors, Lennart, and Nee, Hans-Peter

Abstract

The recently proposed power-synchronization control for grid-connected voltage-source converters (VSCs) has been shown to be a feasible solution for high-voltage dc (HVDC) transmission connected to high-impedance weak ac systems. In this paper, power-synchronization control is investigated for VSC-HVDC connected to another type of weak ac system, i.e., low-inertia or island systems. As an example, a linear model of a typical island system feeding by a VSC-HVDC link, including a synchronous generator, an induction motor and some passive loads, is developed for tuning the control parameters of the VSCHVDC. Time simulations in PSCAD/EMTDC demonstrate that VSC-HVDC using power-synchronization control is flexible for various network conditions, such as large-ac-system connection, island systems, or passive networks. The time simulations also show that power-synchronization control can seamlessly handle transitions between the operation modes, as well as ride through ac-system faults in all network conditions., QC 20111109

Published
2010
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48. Multivariable feedback design of VSC-HVDC connected to weak ac systems

Author

Zhang, Lidong, Nee, Hans-Peter, Zhang, Lidong, and Nee, Hans-Peter

Abstract

Power-synchronization control is particularly applicable to voltage-source converters based high-voltage direct-current (HVDC) transmission connected to weak ac systems. In this paper, the multivariable feedback design aspect of the power-synchronization control is investigated by two design approaches: internal model control (IMC) and Hinfin control. The paper shows that both of the methods can meet the design requirements and show good robustness with different model uncertainties and load disturbances. The advantage of the IMC approach is that it provides a transparent framework for control-system design and tuning. The algorithm used for the IMC design in this paper is simple, yet it achieves similar or even better performance and robustness compared to the more advanced optimization-based Hinfin controller., QC 20111005

Published
2009
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