Showing papers in "IEEE Journal on Emerging and Selected Topics in Circuits and Systems in 2017"

A Circuits and Systems Perspective of Organic/Printed Electronics: Review, Challenges, and Contemporary and Emerging Design Approaches

Abstract: The often touted attractive attributes of printed/organic electronics are its mechanically flexible form-factor, low-cost, green, on-demand printing, scalability, low-power operation, and intelligence (signal processing) – ideally, the creation of intelligent lightweight electronics printed by simple ubiquitous printing processes, and integrated into new ways to exploit its mechanically flexible form-factor. Printed/Organic Electronics, now an industry on its own right and recognized as one of the key technological enablers for the Internet of Things, is largely complementary to silicon because the printed transistors are slow and the printed elements are large. The sanguine projected growth of the $29 B market today to $73 B by 2027 assumes that ‘intelligence’ (analog, mixed-signal and digital signal processing) would be realizable. Nevertheless, many of the said attributes of printed/organic electronics remain a challenge. In this paper, we exemplify this with a comprehensive and critical review and tabulation of the state-of-the art printed digital, analog, and mixed-signal circuits. We further review the application space of printed/organic electronics and the supply chain, including their classifications and delineate the associated challenges in each constituent chain. These challenges, largely unresolved, are indeed formidable, and are discussed with a critical circuits and systems perspective. Our review depicts that contemporary design philosophies and methodologies for silicon are largely inadequate for printed/organic electronics. To this end, we discuss esoteric analog and digital design philosophies and methodologies, with emphasis on co-design and co-optimization between the different constituent supply chains that may potentially circumvent the said formidable challenges, and discuss the associated penalties thereto.

Decentralized Baseband Processing for Massive MU-MIMO Systems

Abstract: Achieving high spectral efficiency in realistic massive multi-user (MU) multiple-input multiple-output (MIMO) wireless systems requires computationally complex algorithms for data detection in the uplink (users transmit to base-station) and beamforming in the downlink (base-station transmits to user). Most existing algorithms are designed to be executed on centralized computing hardware at the base-station (BS), which results in prohibitive complexity for systems with hundreds or thousands of antennas and generates raw baseband data rates that exceed the limits of current interconnect technology and chip I/O interfaces. This paper proposes a novel decentralized baseband processing architecture that alleviates these bottlenecks by partitioning the BS antenna array into clusters, each associated with independent radio-frequency chains, analog and digital modulation circuitry, and computing hardware. For this architecture, we develop novel decentralized data detection and beamforming algorithms that only access local channel-state information and require low communication bandwidth among the clusters. We study the associated tradeoffs between error-rate performance, computational complexity, and interconnect bandwidth, and we demonstrate the scalability of our solutions for massive MU-MIMO systems with thousands of BS antennas using reference implementations on a graphics processing unit (GPU) cluster.

Complex Networks Theory For Modern Smart Grid Applications: A Survey

Abstract: This paper provides a survey of studying complex network theory for modern smart grid applications. A brief overview of complex network theory will be explored first. Topological characteristics, statistic characteristics, such as self-organized criticality and critically slow down, and dynamical characteristics, including synchronizations, consensus control, and pinning control, will be briefly addressed. Then, we will illustrate how complex network theory can be applied to modern smart grids in structural vulnerability assessment, cascading blackouts, grid synchronization, network reconfigurations, distributed droop control, pinning control for micro-grid autonomous operations, and effective grid expansions. Some emerging topics and future perspectives are also addressed.

1-bit Massive MU-MIMO Precoding in VLSI

Abstract: Massive multi-user (MU) multiple-input multiple-output (MIMO) will be a core technology in fifth-generation (5G) wireless systems as it offers significant improvements in spectral efficiency compared to existing multi-antenna technologies. The presence of hundreds of antenna elements at the base station (BS), however, results in excessively high hardware costs and power consumption, and requires high interconnect throughput between the baseband-processing unit and the radio unit. Massive MU-MIMO that uses low-resolution analog-to-digital and digital-to-analog converters (DACs) has the potential to address all these issues. In this paper, we focus on downlink precoding for massive MU-MIMO systems with 1-bit DACs at the BS. The objective is to design precoders that simultaneously mitigate MU interference and quantization artifacts. We propose two nonlinear 1-bit precoding algorithms and corresponding very large-scale integration (VLSI) designs. Our algorithms rely on biconvex relaxation, which enables the design of efficient 1-bit precoding algorithms that achieve superior error-rate performance compared with that of linear precoding algorithms followed by quantization. To showcase the efficacy of our algorithms, we design VLSI architectures that enable efficient 1-bit precoding for massive MU-MIMO systems, in which hundreds of antennas serve tens of user equipments. We present corresponding field-programmable gate array (FPGA) reference implementations to demonstrate that 1-bit precoding enables reliable and high-rate downlink data transmission in practical systems.

Modeling the Dynamics of Cascading Failures in Power Systems

Abstract: In this paper, we use a circuit-based power flow model to study the cascading failure propagation process, and combine it with a stochastic model to describe the uncertain failure time instants, producing a model that gives a complete dynamic profile of the cascading failure propagation beginning from a dysfunctioned component and developing eventually to a large-scale blackout. The sequence of failures is determined by voltage and current stresses of individual elements, which are governed by deterministic circuit equations, while the time durations between failures are described by stochastic processes. The use of stochastic processes here addresses the uncertainties in individual components’ physical failure mechanisms, which may depend on manufacturing quality and environmental factors. The element failure rate is related to the extent of overloading. A network-based stochastic model is developed to study the failure propagation dynamics of the entire power network. Simulation results show that our model generates dynamic profiles of cascading failures that contain all salient features displayed in historical blackout data. The proposed model thus offers predictive information about occurrences of large-scale blackouts. We further plot cumulative distribution of the blackout size to assess the overall system’s robustness. We show that heavier loads increase the likelihood of large blackouts and that small-world network structure would make cascading failure propagate more widely and rapidly than a regular network structure.

Effects of Cyber Coupling on Cascading Failures in Power Systems

Abstract: In this paper, we propose a model to investigate the cascading failures in the coupled system (smart grid) that comprises a power grid and a coupling cyber network. In this model, we take into consideration the effects of power overloading, contagion, and interdependence between power grids and cyber networks on failure propagations in the coupled system, and then use a stochastic method to generate the time intervals between failures, thus producing the dynamic profile of the cascading failures caused by the attack of cyber malwares. We study several coupled systems generated by coupling the UIUC 150 Bus System with cyber networks of different structures and coupling patterns. Simulation results show that the dynamic profile of the cascading failures in a coupled system displays a “staircaselike” pattern which can be interpreted as a combined feature of the typical step propagation profile triggered repeatedly by cyber attacks due to network coupling. Results also show that cyber coupling can intensify both the extent and rapidity of power blackouts. Moreover, the cyber network structure and the coupling patterns affect the propagation of the cascading failures in smart grids. Scale-free cyber networks promote failure spreading, and the higher average cyber node degree also intensifies the spreading. Coupling power nodes with high-degree cyber nodes accelerates the failure propagation compared with random or low-degree couplings.

Microgrid Energy Management Combining Sensitivities, Interval and Probabilistic Uncertainties of Renewable Generation and Loads

Abstract: This paper proposes an optimal energy management approach combining sensitivities, interval, and probabilistic uncertainties of wind and solar power sources and loads in microgrid. Affine arithmetic (AA) is used to model the interval uncertainties and sensitivities in nodal power injections. However, all the elements in the interval solutions of AA-optimal power flow may not be significant in view of the probabilistic nature of statistical data. So, those elements which are significant with a desired confidence level are boxed using probability boxes obtained by deriving best fitting discrete state probability distribution functions (PDFs) for load and renewable power injections. Thus, the original hard bounded affine intervals are made soft bounded using the derived joint PDFs, forming new less conservative and more feasible intervals of cost and power flow variables. The minimization of the operational cost is taken care of by stochastic weight tradeoff particle swarm optimization. The method is tested in CIGRE LV benchmark microgrid with fuel cell, microturbine, diesel generator, wind, and solar power sources.

Multi-Layer Interaction Graph for Analysis and Mitigation of Cascading Outages

Abstract: This paper proposes a multi-layer interaction graph on cascading outages of power systems as an extension of a single-layer interaction network proposed previously This multi-layer interaction graph provides a practical framework for the prediction of outage propagation and decision making on mitigation actions It has multiple layers to, respectively, identify key intra-layer links and components within each layer and key inter-layer links and components between layers, which contribute the most to outage propagation Each layer focuses on one of several aspects that are critical for system operators’ decision support, such as the number of line outages, the amount of load shedding, and the electrical distance of outage propagation Besides, the proposed integrated mitigation strategies can limit the propagation of cascading outages by weakening key intra-layer links All layers are constructed offline from a database of simulated cascades and then used online A three-layer interaction graph is presented in detail and demonstrated on the Northeastern Power Coordinating Council 48-machine 140-bus system The key intra- and inter-layer links and key components revealed by the multi-layer interaction graph provide useful insights on the mechanism and mitigation of cascading outages, which cannot be obtained from any single-layer

Memory-Efficient Polar Decoders

Abstract: Polar codes have gained a great amount of attention in the past few years, since they can provably achieve the capacity of a symmetric channel with a low-complexity encoding and decoding algorithm. As a result, polar codes have been selected as a coding scheme in the 5th generation wireless communication standard. Among different decoding schemes, successive-cancellation (SC) and SC list decoding yield good trade-off between error-correction performance and hardware implementation cost. However, both families of algorithms have large memory requirements. In this paper, we propose a set of novel techniques that aim at reducing the high-memory cost of SC-based decoders. These techniques are orthogonal to the specific decoder architecture considered, and can be applied on top of existing memory reduction techniques. We have designed and implemented different polar decoders on FPGA and also synthesized them in 65 nm TSMC CMOS technology to verify the effectiveness of the proposed memory reduction techniques. The benchmark decoders yield comparable or lower area occupation than the state of the art: the results show that the proposed methods can save up to 46% memory area occupation and 42% total area occupation compared with benchmark SC-based decoders.

Analogue Frontend Amplifiers for Bio-Potential Measurements Manufactured With a-IGZO TFTs on Flexible Substrate

Abstract: Three novel differential amplifier topologies using double gate a-IGZO TFTs on flexible substrate are presented in this paper. The designs exploit positive feedback and a load with self-biased top gate to achieve the highest static gain in single stage a-IGZO amplifiers reported to date. After fabrication, the three amplifiers exhibit respectively a static gain of 14 dB, 21.5 dB and 30 dB, with a bandwidth of 2 kHz, 400 Hz, and 150 Hz. Also, for each circuit the input referred noise has been measured to be $420~\mu \text {V}_{\mathrm {\mathbf {rms}}}$ , $195~\mu \text {V}_{\mathrm {\mathbf {rms}}}$ and $146~\mu \text {V}_{\mathrm {\mathbf {rms}}}$ , respectively. Based on these results, the a-IGZO amplifier providing the highest gain is suitable as front-end for heart rate measurements and, with some further optimization verified in simulation, can also be used for other bio-potential applications, like electro hysterogram and electro cardiogram.

PolarBear: A 28-nm FD-SOI ASIC for Decoding of Polar Codes

Abstract: Polar codes are a recently proposed class of block codes that provably achieve the capacity of various communication channels. They received a lot of attention as they can do so with low-complexity encoding and decoding algorithms, and they have an explicit construction. Their recent inclusion in a 5G communication standard will only spur more research. However, only a couple of ASICs featuring decoders for polar codes were fabricated, and none of them implements a list-based decoding algorithm. In this paper, we present ASIC measurement results for a fabricated 28-nm CMOS chip that implements two different decoders: the first decoder is tailored toward error-correction performance and flexibility. It supports any code rate as well as three different decoding algorithms: successive cancellation (SC), SC flip, and SC list (SCL). The flexible decoder can also decode both non-systematic and systematic polar codes. The second decoder targets speed and energy efficiency. We present measurement results for the first silicon-proven SCL decoder, where its coded throughput is shown to be of 306.8 Mbps with a latency of 3.34 us and an energy per bit of 418.3 pJ/b at a clock frequency of 721 MHz for a supply of 1.3 V. The energy per bit drops down to 178.1 pJ/b with a more modest clock frequency of 308 MHz, lower throughput of 130.9 Mbps and a reduced supply voltage of 0.9 V. For the other two operating modes, the energy per bit is shown to be of approximately 95 pJ/b. The less flexible high-throughput unrolled decoder can achieve a coded throughput of 9.2 Gbps and a latency of 628 ns for a measured energy per bit of 1.15 pJ/b at 451 MHz.

Printed Organic and Inorganic Electronics: Devices To Systems

Abstract: Affordable and versatile printed electronics can play a critical role for large area applications, such as for displays, sensors, energy harvesting, and storage. Significant advances including commercialization in the general area of printed electronics have been based on organic molecular electronics. Still some fundamental challenges remain: thermal instability, modest charge transport characteristics, and limited lithographic resolution. In the last decade, one-dimensional nanotubes and nanowires, like carbon nanotubes and silicon nanowires, followed by two-dimensional materials, like graphene and transitional dichalcogenide materials, have shown interesting promise as next-generation printed electronic materials. Challenges, such as non-uniformity in growth, limited scalability, and integration issues, need to be resolved for the viable application of these materials to technology. Recently, the concept of printed high-performance complementary metal–oxide semiconductor electronics has also emerged and been proven successful for application to electronics. Here, we review progress in CMOS technology and applications, including challenges faced and opportunities revealed.

An Effective Method for Low-Frequency Oscillations Damping in MultiBus DC Microgrids

Abstract: This paper proposes a new active method for low frequency (LF) current/power oscillations damping in droop-controlled dc microgrids. Since, LF oscillations are mainly affected by droop controllers of voltage controlled (VC) DGs, detailed small-signal analysis of VC-DGs is provided. Analysis shows that each droop-controlled VC-DG creates a pair of LF complex conjugate zeros. In the proposed method, these zeros are damped by a negative feedforward of the disturbance variables (output currents) of VC-DGs. Stability analysis of the overall dc microgrid reveals that the LF zeros of VC-DGs can affect the LF modes of the system. Therefore, in the proposed method, the effective tuning of feedforward gain of each VC-DG can increase the damping factor of microgrid LF modes and consequenctly improve the dynamic response of the whole system. Moreovere, to gurantee the plug-and-play performance of DGs, a coordinanted tuning criterion for adjusting the proper feedforward gains is presented. It is shown that the proposed method is also robust against structural changes in dc microgrids. A complete set of simulation studies using MATLAB/Simulink is provided which further supports the effectiveness of the proposed active damping method.

Analysis of Dynamical Robustness to Noise in Power Grids

Abstract: Resilience of power grids is a problem of tremendous practical and theoretical relevance. In this work, we model a power grid as a complex network of coupled oscillators. We investigate the robustness of synchronization, associated with the normal operating regime of the network, to partial malfunctioning of the nodes. Differently from previous efforts on power grid resilience, node malfunctioning is not modeled by removing a node from the network. Instead, we insert a continuous perturbation into the node dynamical equation, which reduces the degree of synchronization of the network. This framework enables an analytical treatment of the problem, ultimately leading to a detailed quantification of the criticality of each network node. The approach is applied to the UCTE European transmission network 1st synchronous area and to the IEEE 118-bus test case. The identification of nodes which are more critical to synchronization yields non-trivial hints at a complex interplay between topology and dynamics in shaping dynamical robustness of power grids.

Hybrid Controller for Wind Turbine Generators to Ensure Adequate Frequency Response in Power Networks

Abstract: Converter-interfaced power sources (CIPS) are hybrid control systems as they may switch between multiple operating modes. Due to increasing penetration, the hybrid behavior of CIPS, such as wind turbine generators (WTGs), may have significant impact on power system dynamics. In this paper, the frequency dynamics under inertia emulation and primary support from WTG is studied. A mode switching for WTG to ensure adequate frequency response is proposed. The switching instants are determined by our proposed concept of a region of safety (ROS), which is the initial set of safe trajectories. The barrier certificate methodology is employed to derive a new algorithm to obtain and enlarge the ROS for the given desired safe limits and the worst case disturbance scenarios. Then, critical switching instants and a safe recovery procedure are found. In addition, the emulated inertia and load-damping effect are derived in the time frame of inertia and primary frequency response, respectively. The theoretical results under critical cases are consistent with simulations and can be used as guidance for a practical control design.

Automated Generation Algorithm for Synthetic Medium Voltage Radial Distribution Systems

Abstract: To introduce more automation in the distribution level of the power system, increasingly more data are needed to serve as input to control algorithms. To examine the complex interaction between the various layers of the system and verify the effectiveness of automation, difficult to obtain, realistic test systems are necessary. An algorithm for automatically synthesizing realistic medium voltage distribution feeders, and thus circumvent the data access problem, is presented. The algorithm treats distribution system feeders as graphs with nodes and edges, each with various properties, and leverages this structure to search for emerging statistical patterns. Using a large data set from a DSO in The Netherlands, clear statistical distributions are identified linking properties, such as load, node degree, or cable length, to the feeder structure. Specifically, many properties are linked to a node’s or edge’s distance, in hops, from the primary substation. With consideration for standard engineering practices, the statistical trends are exploited in the synthesis process, to generate feeders, which display similar characteristics to the real samples. The KL-divergence is used in the evaluation of analysis and synthesis results. Beyond solving the data access problem, the use of automatically generated, synthetic, distribution systems will enable testing and validation techniques, such as Monte Carlo simulations, which are currently not possible in this field, where single test cases are the norm.

Coordinated Active Power Dispatch for a Microgrid via Distributed Lambda Iteration

Abstract: A novel distributed optimal dispatch algorithm is proposed for coordinating the operation of multiple micro units in a microgrid, which has incorporated the distributed consensus algorithm in multi-agent systems and the $\lambda$ -iteration optimization algorithm in the economic dispatch of power systems. Specifically, the proposed algorithm considers the global active power constraint by adding a virtual pinner and it can deal with the optimization problem with any initial states. That is, it can realize the global optimization and avoid the defect of the initial conditions’ sensitivity in the optimization problem. On the other hand, the proposed optimization algorithm can either be used for off-line calculation or be utilized for online operation and has the ability to survive single-point failures and shows good robustness in the iteration process. Numerical studies in a seven-bus microgrid demonstrate the effectiveness of the proposed algorithm.

Information-Energy Flow Computation and Cyber-Physical Sensitivity Analysis for Power Systems

Abstract: Power systems are the typical cyber-physical systems in which the closed-loop hierarchical control systems (HCSs) are widely used to ensure their stable and safe operation To describe the coupling operation mechanism of an HCS and power grid by expanding current steady-state power flow analysis theory, we propose an information-energy flow model and develop a matrix-based computational approach With the help of the methods, we can directly calculate the mutual influence of the cyber and physical parts Since the mechanism of power flow computation is mature, we focus on the cyber side, proposing an information-flow-oriented network model as well as a matrix-based computation method for its information flow In particular, we develop a minimum-cut-set-based partition and equivalence method to address a complex cyber network with non-linearity issues associated with data processing Subsequently, we discuss cyber-physical sensitivity and vulnerability issues In the case study, we calculate the information-energy flow of an IEEE 14-node system with real time-voltage stability monitoring and control application and compare the results with simulation results The similarity of the results between the two methods verifies the effectiveness of our approach

Sizing and Siting of Large-Scale Batteries in Transmission Grids to Optimize the Use of Renewables

Abstract: Power systems are a recent field of application of complex network research, which allows performing large-scale studies and evaluations. Based on this theory, a power grid is modeled as a weighted graph with several kinds of nodes and edges, and further analysis can help in investigating the behavior of the grid under critical conditions. Among the crucial aspects of a power network, those concerning flow limits and power flow distribution are gaining relevance due to the increasing introduction of large-scale renewable energy generation facilities. Storage systems are a key element in having a more sustainable but still reliable grid. This paper focuses on a new research challenge regarding the siting of the storage on the transmission grid and its appropriate sizing. The problem is tackled by considering realistic configurations based on the IEEE-RTS-96 bus and data coming from the Italian transmission operator, and evaluating novel economic and complex network-based metrics on these configurations. Power flows are modeled in a linear way, and the representative optimization problem is expressed as a linear programming problem. The results show the potential benefits of storage in transmission lines and indicate that the siting has a minor role in the optimal operation of the system.

Agent-Based Distributed Control Schemes for Distributed Energy Storage Systems Under Cyber Attacks

Abstract: In this paper, the ratios of the required power exchange by the distributed energy storage systems (DESSs) to their power capacity/maximum allowed power for charging or discharging operations are used as information to be exchanged among different battery agents associated with respective to DESSs First, a fuzzy logic-based information deviation detection scheme is proposed for detection of the effects of cyber-attacks on the information Two distributed control schemes, based on leader-follower distributed control schemes, are proposed to decide the power exchange by DESS under cyber-attack scenarios A consensus-based leader-follower distributed control scheme under cyber-attacks, with an arbitrary topology, is proposed while incorporating information deviation detection scheme Furthermore, a novel agent-based secure distributed optimal control scheme is proposed for charging and discharging of distributed energy storage systems Linear quadratic regulator-based distributed optimal control scheme is incorporated in this scheme In both proposed control schemes, the information deviation of agents is monitored and, based on their information deviations, the control actions are taken to ensure agents’ information convergence The electricity consumption data of a practical medium-voltage distribution system is used to validate the effectiveness of the proposed control schemes Both control schemes are demonstrated to ensure peak shaving operations in the power distribution system, which may consist of an unreliable communication network, by DESSs

Sticker-Type Hybrid Photoplethysmogram Monitoring System Integrating CMOS IC With Organic Optical Sensors

Abstract: A sticker-type system with hybrid integration of CMOS IC and organic optical sensors is proposed to monitor photoplethysmogram (PPG) signals. To solve problems with the previous solely organic sensor-based works, CMOS IC is implemented in 180 nm technology under 5 V/1.5 V dual power supply. The silver-wire printed planar-fashionable circuit board (P-FCB) is used to connect the CMOS IC with organic sensors. The proposed hybrid system has the five following key features: 1) Power-efficient structure of organic sensor; 2) Integrated analog front-end and digital processor; 3) Degradation compensation scheme; 4) Large parasitic elements optimized design; and 5) Motion artifact rejection scheme. The sticker-type PPG monitoring system has mass of only 2g, including the batteries, and consumes only $233~\mu \text{W}$ to operate. The PPG signal could be acquired from various body parts (finger, wrist, and neck). The peripheral oxygen saturation level (SpO2 extraction results are verified by comparison with a commercial sensor device.

Advanced Baseband Processing Algorithms, Circuits, and Implementations for 5G Communication

Abstract: The rapid emergence of 5G communications technology and standardization has seen an accelerated transfer of theoretical concepts to advanced development and implementation. Not only are 5G baseband signal processing algorithms becoming more important, but also the co-design and implementation of corresponding circuits, architectures, and platforms are becoming necessary due to rapid standardization of 5G communications. This timely overview paper introduces circuits and systems (CAS) for key enabling technologies for the new 5G era: massive MIMO, mmWave baseband systems, NOMA schemes, advanced channel coding, and so on. The state-of-the-art research progress in these areas is summarized for interested readers to initiate discussion on limitations of existing solutions and open research problems that are looking for innovative solutions, especially in the CAS area. We hope this paper can bridge the gap between the theoretical investigation and application implementation for 5G communications.

Flexible Hybrid Electronic Circuits and Systems

Abstract: Printed organic electronics are being explored for a wide range of possible applications, with much of the current focus on smart labels, wearables, health monitoring, sensors and displays. These applications typically integrate various types of sensors and often include silicon integrated circuits (IC) for computation and wireless communications. Organic thin film transistors (TFT), particularly when printed, have performance and yield limitations that must be accommodated by the circuit design. The circuit design also needs to select sensor technology, ICs and other circuit elements to integrate with the TFTs and match the functional and performance requirements of the application. This paper describes organic TFT properties and strategies for circuit and sensor design, with examples from various sensor systems.

A Comparison of Malicious Interdiction Strategies Against Electrical Networks

Abstract: How well can a typical electrical power system withstand a sophisticated malicious attack undertaken against its exposed branches? This paper seeks to articulate a comprehensive answer to this fundamental question of wide societal importance New and established techniques that an attacker might use to select promising attack targets are considered, spanning complex network analysis, metaheuristics, and classical optimization By simulating this wide gamut of attack strategies on several test power systems, each modeled under many representative operating states, this paper comprehensively articulates the expected robustness of electrical power grids against coordinated branch interdictions

A Modified Hybrid RF Predistorter Linearizer for Ultra Wideband 5G Systems

Abstract: The wide-bandwidth signal transmission is one of the requirements in upcoming 5G communication systems in its quest for high data rates. In this paper, a wideband hybrid RF/digital predistortion (HRF-DPD) linearization technique is reported to compensate for the nonlinearity of ultra-wideband power amplifier (PA) for 5G systems driven by carrier aggregated and wideband modulated signals. The proposed methodology is suitable for 5G PA design, since its power overhead and system bandwidth does not increase with an increase in signal bandwidth. Taking advantage of recent available digital signal processing solutions, the proposed method reduces hardware requirements of the conventional analog predistorter by alleviating the need of vector multiplier, branch line coupler, and delay lines. Such linear operations are controlled digitally, which provides flexibility in terms of digitally compensation of delay, gain and phase control of the signal. For establishing a proof of concept, HRF-DPD is implemented with ZX60V-82+ class AB PA and tested using a 100- and 50-MHz long term evolution-carrier aggregated (LTE-CA) signal at 2 GHz. Experimental results show that the wideband PA along with the proposed predistorter delivers an adjacent channel leakage ratio (ACLR) of −54 dBc with a cancellation of 30.6 dB for 100-MHz LTE-CA signal. With the proposed method PA, nonlinear distortion outside the 100-MHz band can be linearized leading to filter less architecture which provides 45-dBc ACLR performance.

A Framework for Dynamic Stability Analysis of Power Systems With Volatile Wind Power

Abstract: We propose a framework employing stochastic differential equations to facilitate the long-term stability analysis of power grids with intermittent wind power generations. This framework takes into account the discrete dynamics, which play a critical role in the long-term stability analysis, incorporates the model of wind speed with different probability distributions, and also develops an approximation methodology [by a deterministic hybrid model (DHM)] for the stochastic hybrid model (SHM) to reduce the computational burden brought about by the uncertainty of wind power. The theoretical and numerical studies show that a DHM can provide an accurate trajectory approximation and stability assessments for the SHM under mild conditions. In addition, we discuss the critical cases that the DHM fails and discover that these cases are caused by a violation of the proposed sufficient conditions. Such discussion complements the proposed framework and methodology and also reaffirms the importance of the SHM when the system operates close to its stability limit.

Mixed Integer Second Order Cone Relaxation With Dynamic Simulation for Proper Power System Islanding Operations

Abstract: Power system islanding operation acts as an important attractive corrective measure that is widely studied. However, a proper splitting strategy for the islanding operation should satisfy both steady-state and transient stability constraints. As a result, an ac power flow-based optimization model with dynamic simulation is proposed to obtain a proper splitting strategy. Specifically, the method includes two steps: 1) optimization of a splitting strategy satisfying the steady-state constraints and 2) transient stability evaluation of the strategy by dynamic simulation. Furthermore, the optimization and evaluation steps are iterated until finding a splitting strategy that satisfies both the steady-state constraints and the transient stability constraints. Finally, the effectiveness of the proposed method is verified on the WSCC 9-bus and the IEEE RTS 24-bus test systems.

A Decentralized Approach for Frequency Control and Economic Dispatch in Smart Grids

Abstract: This paper proposes a decentralized approach for frequency control and economic dispatch in smart grids with distributed energy resources and responsive demands. The approach is implemented based on a distributed multi-agent system, in which each agent works in a collaborative manner via local computation and peer to peer communication. The approach is comprised of two strategies. A consensus-based strategy is implemented at the supply side to regulate system frequency economically. Self-adaptive updating rules are proposed for the key parameters to improve the accuracy and robustness of the consensus-based strategy. A threshold-based strategy is implemented at the demand side to provide ancillary services for frequency regulation. Simulation results are presented to demonstrate the effectiveness and robustness of the approach.

Which Generation Unit Should be Selected as Control Leader in Secondary Frequency Control of Microgrids

Abstract: In this paper, we propose a novel metric to choose control leaders in secondary frequency control of microgrids. The microgrid, as the building block of distributed generation systems, is assumed to be composed of both synchronous and inverter-connected generation units, e.g., renewable sources. Here, we formulate the stability analysis of secondary cooperative control in microgrids. To control the frequency of the microgrid, the secondary control should set one (or more) of generation units as master and the others as follower. A novel metric is proposed to measure the impact of different generation sources on the rate of frequency recovery of the distributed generation power system. The proposed metric is based on the eigenvalue perturbation analysis of the state matrix of the microgrid, which includes information on the topology of both physical power and data communication networks. Using this metric, one can rank all generation units and choose the one with the largest influence as the master node. The metric is simple to compute and can be easily used in microgrids with large number of small size generation units. Numerical simulations show the effectiveness of the proposed metric over heuristic methods such as choosing the master nodes based on their degrees, betweenness centrality, or closeness centrality values in the data communication network.

Development of a Simple Manufacturing Process for All-Inkjet Printed Organic Thin Film Transistors and Circuits

Abstract: In the last years there has been a growing interest in the realization of low-cost, flexible and large area electronic systems such as item-level RFID tags, flexible displays or smart labels, among others. Specifically, inkjet printing technology has been increasingly applied as advanced deposition technology in the field of printed electronics due to the high flexibility in terms of patterns (mask-less) and materials, and its low cost approach as only a small amount of materials is required in comparison to other solution-based deposition techniques. Our work focuses on the development of Organic Thin Film Transistors (OTFTs) by using organic, inorganic inks and low-cost all-inkjet purely printing process, thus centring the effort in the design, manufacturing and characterization point of view in order to fabricate all-inkjet printed organic integrated circuits. Electrical and morphological characterizations were performed in order to obtain device statistics to investigate the origins of the failures responsible for the low yields. Most of research works are based on laboratory inkjet equipment for manufacturing using single nozzle systems to fabricate small numbers of devices. The variability and mismatch of the printed devices are underrepresented in literature and are key factors towards commercialization of printed electronics.