Fast Power Control Research Articles

Resonant interaction of the electron beam with a synchronous wave in controlled magnetrons for high-current superconducting accelerators

A simplified analytical model of the resonant interaction of the beam of Larmor electrons drifting in the crossed constant fields of a magnetron with a synchronous wave providing a phase grouping of the drifting charge was developed to optimize the parameters of an rf resonant injected signal driving the magnetrons for management of phase and power of rf sources with a rate required for superconducting high-current accelerators. The model, which considers the impact of the rf resonant signal injected into the magnetron on the operation of the injection-locked tube, substantiates the recently developed method of fast power control of magnetrons in the range up to 10 dB at the highest generation efficiency, with low noise, precise stability of the carrier frequency, and the possibility of wideband phase control. Experiments with continuous wave 2.45 GHz, 1 kW microwave oven magnetrons have verified the correspondence of the behavior of these tubes to the analytical model. A proof of the principle of the novel method of power control in magnetrons, based on the developed model, was demonstrated in the experiments. The method is attractive for high-current superconducting rf accelerators. This paper also discusses vector methods of power control with the rates required for superconducting accelerators, the impact of the rf resonant signal injected into the magnetron on the rate of phase control of the injection-locked tubes, and a conceptual scheme of the magnetron transmitter with highest efficiency for high-current accelerators.

Fast Optimal Dispatch of Renewable Energy Sources in Distribution Networks

With the increasing penetration of distributed renewable energy sources such as photovoltaic and wind power generators in distribution networks, overvoltage problems occurred as a result of the reversed power flow. The randomness and intermittence of power outputs of the renewable energy sources make the operations of distribution systems complex at the same time. This paper proposes a simplified optimal dispatch algorithm for fast renewable energy sources power control to overcome voltage problems and permit better performance for distribution systems. Case study demonstrates the accuracy and efficiency of the optimal dispatch method proposed.

Improvement of Power System Transient Stability by PV Farm With Fuzzy Gain Scheduling of PID Controller

The extensive proliferation of large photovoltaic (PV) farms in power systems deteriorates both system inertia and synchronizing coupling. Under the occurrence of severe faults, the power system transient stability may be jeopardized. Nevertheless, the fast active power control ability of the PV inverter leads to the possibility of transient stability improvement. This paper focuses on the new application of large PV farms equipped with a fuzzy gain scheduling of proportional–integral–derivative (FGS-PID) controller for transient stabilization of a multimachine power system. The FGS-PID controller is used to control the PV inverter, so that the PV power output can be modulated to stabilize the transient power swing when the faults take place. To obtain the stabilizing performance, the scale factors, membership functions, and control rules of the FGS-PID controller are determined by a bee colony optimization. Simulation study in a two-area interconnected power system exhibits the superior stabilizing effect and robustness of the PV with FGS-PID controller over the PV with maximum power point tracking (MPPT) controller, optimal PID controller, and Ziegler–Nichols tuned PID controller, under various faults, line flows, and solar insolations. In addition, without losing the main function of power generation, the PV with FGS-PID control is able to supply energy to the system almost equal as the PV with MPPT, during stabilization.

Stably accessing octave-spanning microresonator frequency combs in the soliton regime.

Microresonator frequency combs can be an enabling technology for optical frequency synthesis and timekeeping in low size, weight, and power architectures. Such systems require comb operation in low-noise, phase-coherent states such as solitons, with broad spectral bandwidths (e.g., octave-spanning) for self-referencing to detect the carrier-envelope offset frequency. However, accessing such states is complicated by thermo-optic dispersion. For example, in the Si3N4 platform, precisely dispersion-engineered structures can support broadband operation, but microsecond thermal time constants often require fast pump power or frequency control to stabilize the solitons. In contrast, here we consider how broadband soliton states can be accessed with simple pump laser frequency tuning, at a rate much slower than the thermal dynamics. We demonstrate octave-spanning soliton frequency combs in Si3N4 microresonators, including the generation of a multi-soliton state with a pump power near 40 mW and a single-soliton state with a pump power near 120 mW. We also develop a simplified two-step analysis to explain how these states are accessed without fast control of the pump laser, and outline the required thermal properties for such operation. Our model agrees with experimental results as well as numerical simulations based on a Lugiato-Lefever equation that incorporates thermo-optic dispersion. Moreover, it also explains an experimental observation that a member of an adjacent mode family on the red-detuned side of the pump mode can mitigate the thermal requirements for accessing soliton states.

Wind power applications of doubly-fed reluctance generators with parameter-free hysteresis control

The development and practical implementation aspects of a novel scheme for fast power control of the doubly-fed reluctance generator with a low-cost partially-rated converter, a promising brushless candidate for limited speed ranges of wind turbines, are presented in this paper. The proposed concept is derived from the fundamental dynamic analogies between the controllable and measurable properties of the machine: electro-magnetic torque and electrical power, and flux and reactive power. The algorithm is applied in a stationary reference frame without any knowledge of the machine parameters, including rotor angular position or velocity. It is then structurally simpler, easier to realize in real-time and more tolerant of the system operating uncertainties than model-based or proportional-integral control alternatives. Experimental results have demonstrated the excellent controller response for a variety of speed, load and/or power factor states of a custom-built generator prototype.

Burst‐mode analysis of XGPON Raman reach extender employing quantum‐dot lasers

Burst-mode operation of a Raman-based reach extender for the 10 Gbit passive optical networks upstream window is demonstrated using high-power semiconductor quantum-dot lasers as Raman pumps. Transmission over a 50 km optical trunk line is performed both in continuous and in burst-mode for a dynamic range up to 14 dB with a power budget capable of supporting a 64 split for the optical network units. The error distribution in packets reveals no position dependence within the bursts, thus excluding the presence of gain transients. This suggests that the amplifier is particularly suitable for application in burst-mode networks thanks to its fast dynamics, being a less complex alternative to concurrent technologies that require fast automatic power control schemes.

Virtual-Flux-Based Predictive Direct Power Control of Three-Phase PWM Rectifiers With Fast Dynamic Response

This paper proposes a power predictive control (PPC) method for three-phase pulse width modulated rectifiers without a proportional-integral controller. The proposed PPC method calculates the optimized voltage vector by analyzing the relationship between the virtual flux, active power, converter voltage, and filter parameters. Thus, an overshoot does not occur and the fast and accurate power control becomes possible. The predictive algorithm computes the power error that would be produced by applying each vector and selects the one that contributes the minimum error. The simulation and experimental results prove that the proposed method provides an excellent steady-state performance and quick dynamic response.

An Inductively Powered Wireless Solid-State Drive System With Merged Error Correction of High-Speed Wireless Data Links and NAND Flash Memories

A highly reliable wireless solid-state drive (SSD) system for future applications of large volume storage is presented. The wireless interface in the system consists of an inductively coupled power link with fast transmission power control and high-speed data links using transmission line couplers (TLCs). The wireless power link can deliver 1 W from the host to the SSD. The full duplex wireless data interface achieves raw data rate of 1.6 Gb/s. The reliability of the wireless interface is studied though simulation analysis and experiments. The error correction block for the NAND flash memory system can also correct errors in the wireless data links, allowing the requirements for the PHY layer to be relaxed. The error correction code is discussed, including optimization by analyzing the error bits on the wireless data links. The experimental results confirmed strong tolerance to the interference from the power link on the wireless data link, and the water proof property of both the data and power links.

A fast channel assignment scheme based on power control in wireless ultraviolet networks

The Ultraviolet (UV) Non-line-of-sight (NOLS) communications are becoming a research hotspot in recent years. For wireless UV networks, there are some well-known existing issues such as network connectivity, power control and channel assignment. In this paper, a Fast Power Control and Channel Assignment scheme (FPCCA) is proposed to reduce interference and save energy. Firstly, the FPCCA is compared with the traditional channel assignment which without power control. It is proved that the approach of FPCCA can save energy more than 10%. Then, the FPCCA is both applied in the UV and Wireless Mesh Networks (WMN). The performance of FPCCA with different angles and network traffic loads is simulated and analyzed. When the traffic load is fixed, the performance metrics of FPCCA in UV are better than that in WMN. Meanwhile, the FPCCA not only ensures the quickness and accuracy of channel assignment, but also saves energy and improves the throughput.

Power headroom report-based uplink power control in 3GPP LTE-A HetNet

In a 3rd Generation Partnership Project Long Term Evolution-Advanced (3GPP LTE-A) uplink, user equipment (UE) has a maximum transmission power limit defined by the UE power class. Generally, the cell edge UE has a higher probability to be constrained by the maximum transmission power level owing to the compensation of the large pathloss. When the UE transmission power is constrained by the maximum level, allocating a higher number of physical resource blocks (PRBs) than the UE power capability can afford will reduce the transmission power to be allocated per PRB, resulting in inefficient use of power resources. To avoid this power inefficiency, the uplink transmission power can be controlled according to the number of PRBs allocated using the power headroom report-based power efficient resource allocation (PHR-PERA) scheme proposed in this paper. Furthermore, adaptive open-loop power control (OL-PC) based on the signal-to-interference-plus-noise ratio (SINR) and the uplink interference is used to improve the cell capacity. By the uplink power control employing the proposed PHR-PERA scheme, the macro and femto UE throughputs were increased by 49.9 and 5 %, respectively, compared to the case of conventional fractional power control (FPC). Additional gains of 21.9 and 4.8 % for macro and femto UE throughputs, respectively, were achieved by adaptive OL-PC. The performance of fast closed-loop power control (CL-PC) based on the received SINR is also evaluated in this paper. The simulation results demonstrate that CL-PC supports OL-PC by compensating the fading effect for the UE uplink SINR to meet the target SINR.

A Systematic Approach for Optimal Design of SVC Controller to Reduce the Disturbances in Electric Arc Furnace Using Generic Algorithm

Static Var Compensator (SVC) is one of FACTS devices which is used in power systems in order to have a better voltage quality. The fluctuations of voltage and current of the grid connected to electric arc furnace causes power quality problems in the network. SVC, as a fast reactive power control equipment, plays an important role in improving the voltage profile and the transient dynamics of the system arising from the nature of the arc. In this paper the effect of implementing SVC in Mobarakeh Steel Company, for mitigating the voltage transient of power system which is connected to an electric arc furnace, is studied. Then the coefficients of the SVC PI controller are optimized using genetic algorithm and the simulation results are presented.

Hierarchical Load Tracking Control of a Grid-Connected Solid Oxide Fuel Cell for Maximum Electrical Efficiency Operation

Based on the benchmark solid oxide fuel cell (SOFC) dynamic model for power system studies and the analysis of the SOFC operating conditions, the nonlinear programming (NLP) optimization method was used to determine the maximum electrical efficiency of the grid-connected SOFC subject to the constraints of fuel utilization factor, stack temperature and output active power. The optimal operating conditions of the grid-connected SOFC were obtained by solving the NLP problem considering the power consumed by the air compressor. With the optimal operating conditions of the SOFC for the maximum efficiency operation obtained at different active power output levels, a hierarchical load tracking control scheme for the grid-connected SOFC was proposed to realize the maximum electrical efficiency operation with the stack temperature bounded. The hierarchical control scheme consists of a fast active power control and a slower stack temperature control. The active power control was developed by using a decentralized control method. The efficiency of the proposed hierarchical control scheme was demonstrated by case studies using the benchmark SOFC dynamic model.

Spectral and energy efficiency analysis of uplink heterogeneous networks with small-cells on edge

This paper presents a tractable mathematical framework to analyze the spectral and energy efficiency of an operator initiated deployment of the small-cells (e.g., femtocells) where the small-cell base stations are deliberately positioned around the edge of the macrocell. The considered deployment facilitates the cell-edge mobile users in terms of their coverage, spectral, and energy efficiency and is referred to as cell-on-edge (COE) configuration. The reduction in energy consumption is achieved by considering fast power control where the mobile users transmit with adaptive power to compensate the path loss, shadowing and fading. In particular, we develop a moment generating function (MGF) based approach to derive analytical bounds on the area spectral efficiency and exact expressions for the energy efficiency of the mobile users in the considered COE configuration over generalized-K fading channels. Besides the COE configuration, the derived bounds are also shown to be useful in evaluating the performance of random small-cell deployments, e.g., uniformly distributed small-cells. Simulation results are presented to demonstrate the improvements in spectral and energy efficiency of the COE configuration with respect to macro-only networks and other unplanned deployment strategies.

Distance Protection of AC Grid With HVDC-Connected Offshore Wind Generators

When a transmission line close to points of common coupling (PCCs) experiences a short-circuit (SC) fault, the fast reactive power control of voltage-source converter-HVDC (VSC-HVDC) is likely to affect the protective relay operation of transmission lines. To study the performance of distance relays on an ac grid with an offshore wind HVDC network, this paper presents an apparent impedance calculation method, which utilizes the bus impedance matrix (Zbus) to calculate the impedances viewed by distance relays during a three-phase SC fault. The proposed method is used to identify the potential miscoordinated Zone 2 relays in the proposed combined ac/dc system. The analysis is verified by software simulation results. It is shown that the proposed method results in accurate impedances viewed by distance relays. It also identifies the protective device settings on the ac grid that need to be adjusted due to HVDC control of offshore wind generators.

A Statistical Model of Uplink Inter-Cell Interference with Slow and Fast Power Control Mechanisms

Uplink power control is in essence an interference mitigation technique that aims at minimizing the inter-cell interference (ICI) in cellular networks by reducing the transmit power levels of the mobile users while maintaining their target received signal quality levels at base stations. Power control mechanisms directly impact the interference dynamics and, thus, affect the overall achievable capacity and consumed power in cellular networks. Due to the stochastic nature of wireless channels and mobile users' locations, it is important to derive theoretical models for ICI that can capture the impact of design alternatives related to power control mechanisms. To this end, we derive and verify a novel statistical model for uplink ICI in Generalized-K composite fading environments as a function of various slow and fast power control mechanisms. The derived expressions are then utilized to quantify numerically key network performance metrics that include average resource fairness, average reduction in power consumption, and ergodic capacity. The accuracy of the derived expressions is validated via Monte-Carlo simulations. Results are generated for multiple network scenarios, and insights are extracted to assess various power control mechanisms as a function of system parameters.

A New Variable-Frequency Optimal Direct Power Control Algorithm

This paper presents a new formulation for direct power control (DPC) with several improvements over previous DPC formulations such as an exact discrete-time expression for the predicted power variations yielded by a given inverter switching state and the inclusion of the computing delay time in the model. Based on this formulation, a variable-frequency optimal DPC algorithm is presented that selects the inverter switching state that minimizes the power error. This algorithm shows an excellent precision in estimating power variations, therefore reducing power ripple and unwanted current harmonics, while retaining the fast dynamics inherent to variable-frequency DPC. This makes this algorithm suitable for interfacing distributed generation to microgrids, where a fast and accurate power control is desirable in order to perform voltage and frequency regulation. Additionally, studies are carried out regarding the average switching frequency and the influence of the model parameters on the algorithm robustness.

Special issue on broadband mobile communications at very high speeds

Future mobile communication systems aim at providing very high-speed data transmission, even under very high mobility scenarios such as high speed wheel-track trains (up to 574.8 km/h test speed or 380 km/h commercial speed), maglev trains (up to 581 km/h test speed or 431 km/h commercial speed), airplanes (about 4001000 km/h commercial speed), guided missiles (about 980–20,000 km/h) or spacecraft (at least 28,440 km/h to remain on an earth orbit, at least 40,320 km/h to leave earth). A related and particularly important commercial application is the strong worldwide increasing demand for broadband wireless communications in high speed railways to provide information and onboard entertainment services to passengers, train control, train dispatch, train sensor status transmission, video surveillance, etc. Consequently, increasing demand on data rates to support broadband high speed communication systems in the presence of frequency selective fading channels with very high mobilities has resulted in research on designing computationally efficient yet faster new algorithms for channel estimation, equalization and detection, as well as fast handover, location update, modeling of rapidly time-varying channels, fast power control and dedicated network architectures, etc. Orthogonal frequency-division multiplexing (OFDM) is becoming a backbone structure of such systems, being standardized as the IEEE's 802.16 family better known as Mobile Worldwide Interoperability Microwave Systems for Next-Generation Wireless Communication Systems (WiMAX) and by the Third-Generation Partnership Project (3GPP) in the form of its Long-Term Evolution (LTE) project. Both systems employ orthogonal frequency division multiplexing/multiple access (OFDMA) as well as a new single-carrier frequency-division multiple access (SC-FDMA) format. To promote the IEEE 802.16 standards, recently, a high mobility feature has been introduced (IEEE 802.16 m) to enable mobile broadband

Design and experimental verification of a dead beat power control strategy for low cost three phase PWM converters

As a cost-effective and reliable alternative to standard three phase PWM converters, the low cost converters have attracted great attentions today. While the research trends mainly focused on using these converters for AC motor drives, some successful efforts in grid connected applications are also reported. These works use the voltage oriented technique to regulate the active and reactive power exchanges with the electric grid. This paper presents a dead beat direct power control strategy for grid integration of low cost three phase PWM converters. While keeping the advantages of fast and accurate power control associated to the VOC technique, the proposed strategy offers a considerably simpler algorithm. Extensive simulation and experimental results are provided which confirm the validity of the proposed technique.

Modeling and Control System Design of a Grid Connected VSC Considering the Effect of the Interface Transformer Type

In this paper, modeling and control system design of a three-phase VSC system are investigated. The linear model and the control design are developed in the stationary-frame. The model shows a highly coupled system along and coordinates when using a -Y transformer vs. two completely decoupled subsystems in the case of Y-Y transformer. This issue was often overlooked in literature. The developed model includes the phase shift caused by the -Y transformer to address its effect on the steady-state and the dynamic behaviors under balanced and unbalanced distorted three phase conditions. Linear state-space model of the closed-loop system is developed to study the dynamics and stability of the two configurations. Modal analysis shows that the phase shift introduced by the -Y configuration can reduce the ultimate gain of the open loop system by 62% as compared to the system interfaced using Y-Y configuration. The developed linear model has been simulated in MATLAB/SIMULINK and validated using a detailed switching model in PSCAD/EMTDC under balanced and unbalanced three-phase conditions. The proposed control method can provide fast active and reactive power control with a minimum harmonics distortion in the line current.

Enhancing the high speed downlink packet access operation of 3G WCDMA systems

ABSTRACTIn high‐speed downlink packet access (HSDPA), the combination of adaptive modulation and coding, hybrid automatic repeat request, and an extended multicode operation has replaced two fundamental aspects of wideband code division multiple access systems, namely, variable spreading factor and fast power control. Despite its enhanced characteristics, the HSDPA operation can be problematic when the majority of incoming traffic load consists of low data rate delay‐sensitive services such as mobile voice‐over‐Internet Protocol. To tackle this case, we propose an enhanced HSDPA operation that exploits multiple layers of the channelization code tree through a specifically designed packet scheduling and code allocation process. Enhanced HSDPA, when compared with the conventional HSDPA, provides a more flexible sharing of the available capacity and is able to increase the number of users that can be served with the required quality of service in terms of packet delay. The efficiency of the proposed scheme is confirmed by simulation results. Copyright © 2011 John Wiley & Sons, Ltd.