Scenario Based Transmission Power Control (TPC) Analysis over Wireless Body Area Network (WBAN)

In the modern age, Wireless Body Area Network (WBAN) becomes very popular everywhere for monitoring healthcare services remotely. However, the WBAN system has lagged in efficient power consumption till now. As WBAN is formed with several portable devices, low power consumption will ensure battery lifetime. In this paper, an analysis of Transmission Power Control (TPC) over WBAN has been conducted. A ZigBee based WBAN model with different network topologies and data rates has been proposed in the experiment. WBAN data-management technique has been proposed due to reducing more data transmission. Less data transmission reduces overall power consumption. The whole work has been done using OPNET and OMNET++ network simulators. Six sensor nodes have been used with a ZigBee coordinator in the simulation scenario where throughput, load, delay, data traffic, amount of power consumption, packet delivery ratio, etc. have been used as simulation parameters. TPC analysis indicates the power consumptions in different topologies, with different data rates. Several simulation scenarios were run and the results were analyzed in this paper.

Steady-state voltage-control method considering large-scale wind-power transmission using half-wavelength transmission lines

Half-wavelength transmission can transmit large-scale renewable energy over very long distances.This paper proposes an improved steady-state voltage-control method for half-wavelength transmission systems considering largescale wind-power transmission.First,the unique voltage characteristics of half-wavelength lines are deduced based on the distributed parameter model.In the secondary voltage-control level,reactive power-transmission limits of half-wavelength lines are introduced as another control objective except for tracing the pilot bus voltage reference.Considering the uncertainty and fluctuation of wind power,the overvoltage risk-assessment method of half-wavelength lines is presented to determine specific voltage-control strategies.Simulation results demonstrate that the proposed voltage-control method delivers superior tracking performance according to a voltage reference value and prevents the overvoltage risk of halfwavelength lines effectively in different wind-power penetrations.

The Sixth International Conference on Fluid Power Transmission and Control(ICFP'2005)

Date: April 12-15, 2005 Venue: Zhejiang University, Hangzhou, P. R. China Organized by Institute of Mechatronic Control Engineering, Zhejiang University

An Adaptive Wireless Power Sharing Control for Multiterminal HVDC

Power sharing among multiterminal high voltage direct current terminals(MT-HVDC)is mainly developed based on a priority or sequential manners,which uses to prevent the problem of overloading due to a predefined controller coefficient.Furthermore,fixed power sharing control also suffers from an inability to identify power availability at a rectification station.There is a need for a controller that ensures an efficient power sharing among the MT-HVDC terminals,prevents the possibility of overloading,and utilizes the available power sharing.A new adaptive wireless control for active power sharing among multiterminal(MT-HVDC)systems,including power availability and power management policy,is proposed in this paper.The proposed control strategy solves these issues and,this proposed controller strategy is a generic method that can be applied for unlimited number of converter stations.The rational of this proposed controller is to increase the system reliability by avoiding the necessity of fast communication links.The test system in this paper consists of four converter stations based on three phase-two AC voltage levels.The proposed control strategy for a multiterminal HVDC system is conducted in the power systems computer aided design/electromagnetic transient design and control(PSCAD/EMTDC)simulation environment.The simulation results significantly show the flexibility and usefulness of the proposed power sharing control provided by the new adaptive wireless method.

Battery Charger for Electric Vehicles based on a Wireless Power Transmission

In this paper,the case of a battery charger for electric vehicles based on a wireless power transmission is addressed.The specificity of every stage of the overall system is presented.Based on calculated and measured results,relevant capacitive compensations of the transformer and models are suggested and discussed in order to best match the operating mode and aiming at simplifying as much as possible the control and the electronics of the charger.

Rate-aware optimal transmission power analysis in wireless ad hoc networks

The problem of transmission power control in a rate-aware way is investigated to improve the throughput of wireless ad hoc network. The behavior of basic IEEE 802.11 DCF is approximated by the p-persistent CSMA through a Markov chain model. The throughput model takes hidden terminals, muhi-hop flow and concurrent interference into account. Numerical results show that the optimal transmission power derived from this model could balance the tradeoff between spatial reuse and data rate and hence yield maximum throughput.

Evaluation of optimal UPFC allocation for improving transmission capacity

A unified power flow controller(UPFC)combines the advantages of various flexible alternating current transmission system(FACTS)devices into a powerful format.Using a 500 kV power grid,this study evaluates the selection and use of a UPFC to improve transmission capacity.The"UPFC unit capacity control proportionality coefficient"is introduced to quantify the control effect of the UPFC,and an optimal calculation method for the UPFC capacity is presented.Following the proposal of a UPFC site selection process,the data of an existing power grid is used to conduct simulations.The simulation results show that the UPFC has a strong ability to improve transmission capacity,and its use is greatly advantageous.Additionally,by applying the proposed selection method,the control effect and economic benefits of the UPFC can be comprehensively considered during project site selection.These findings have a guiding significance for UPFC site selection in ultra-high voltage power grids.

DC Emergency Power Control Strategy for AC/DC Multi-Channel Interconnected System

Inter-regional transmission line fault often results in power flow transferring, tie-line overloading and system islanding. Traditional control methods such asgenerator tripping and load shedding are costly, and also have undesirable impacts on theloadside. In this paper, a new emergency power control strategy is proposed for multi-channel interconnected system by using the overload capacity of non-fault DC lines. First of all, the capacity of emergency power control can be acquired by critical transmission power of a certain tie-line for stability. Secondly, the shortest electric distance can be calculated by Dijkstra algorithm, and then the priority of emergency control of the DC lines can be obtained by the entropy weight method. When the inter-regional transmission power decreases and the effect of single DC line emergency control is poor, the multi-channel cooperative emergency control strategy is proposed to ensure the system stability. Simulation results verify the effectiveness of the method proposed.

Frequency Control of Power System with Renewable Power Sources by HVDC Interconnection Line and Battery Considering Energy Balancing

Recently, introduction of renewable energy sources like wind power generation and photovoltaic power generation has been increasing from the viewpoint of environmental problems. However, renewable energy power supplies have unstable output due to the influence of weather conditions such as wind speed variations, which may cause fluctuations of voltage and frequency in the power system. This paper proposes fuzzy PD based virtual inertia control system to decrease frequency fluctuations in power system caused by fluctuating output of renewable energy sources. The proposed new method is based on the coordinated control of HVDC interconnection line and battery, and energy balancing control is also incorporated in it. Finally, it is concluded that the proposed system is very effective for suppressing the frequency fluctuations of the power system due to the large-scale wind power generation and solar power generation and also for keeping the energy balancing in the HVDC transmission line.

A Data Driven Security Correction Method for Power Systems with UPFC

The access of unified power flow controllers(UPFC)has changed the structure and operation mode of power grids all across the world,and it has brought severe challenges to the traditional real-time calculation of security correction based on traditionalmodels.Considering the limitation of computational efficiency regarding complex,physical models,a data-driven power system security correction method with UPFC is,in this paper,proposed.Based on the complex mapping relationship between the operation state data and the security correction strategy,a two-stage deep neural network(DNN)learning framework is proposed,which divides the offline training task of security correction into two stages:in the first stage,the stacked auto-encoder(SAE)classification model is established,and the node correction state(0/1)output based on the fault information;in the second stage,the DNN learningmodel is established,and the correction amount of each action node is obtained based on the action nodes output in the previous stage.In this paper,the UPFC demonstration project of NanjingWest Ring Network is taken as a case study to validate the proposed method.The results show that the proposed method can fully meet the real-time security correction time requirements of power grids,and avoid the inherent defects of the traditional model method without an iterative solution and can also provide reasonable security correction strategies for N-1 and N-2 faults.

On distributed power control in full duplex wireless networks

In this paper, we first consider the problem of distributed power control in a Full Duplex （FD） wireless network consisting of multiple pairs of nodes, within which each node needs to communicate with its corresponding node. We aim to find the optimal transmition power for the FD transmitters such that the network-wide capacity is maximized. Based on the high Signal-to-Interference-Plus-Noise Ratio （SINR） approximation and a more general approximation method for logarithm functions, we develop effective distributed power control algorithms with the dual decomposition approach. We also extend the work to the general FD network scenario, which can be decomposed into subproblems of isolated nodes, paths, and cycles. The corresponding power control problem is then be solved with the distributed algorithm. The proposed algorithms are validated with simulation studies.

Study on Hydraulic Transmission of Offshore Low-speed Wind Energy Generator

For offshore hydraulic drive wind turbines,the problems of unsatisfactory speed control and low efficiency at low wind speeds are targeted.A low-speed high-torque radial piston pump is designed to replace the traditional fixed pump with a particular focus on its low-speed performance.The pump is characterized by small internal leakage at low wind speeds and high volumetric efficiency,which is beneficial to improve the power generation efficiency of the system.A new linear control method based on the PID algorithm and feedforward compensation was proposed to obtain the constant speed output control of variable motor at low wind speed.With the model for wind turbine and fixed pump-variable motor main drive system,the system was simulated and experimentally proved to verify the feasibility and anti-interference performance of the system control method at low wind speeds.A promising outcome was obtained on the response characteristics of system power and efficiency at low wind speeds.This can be a powerful technical support for the normal ustility of hydraulic drive wind turbines.

基于多电平变流器模块的直流输电系统控制

为了保证直流输电系统在发生三相短路故障时输电电压的稳定性,有效控制输电系统的运行,该文提出了基于多电平变流器模块(modular multilevel converter,MMC)的直流输电系统运行控制方法。利用反并联二极管与并联电容来设计多电平变流器模块,获得交流等效电感,保证换流站交直流量与有功功率相同,明确换流站内功率情况;将该模块与前馈解耦补偿项相结合,运用PI获得电流内环运行控制器的输入值,实现电流解耦,增强直流电压的稳定控制,提高输电系统抗扰动性能;通过修正与控制环节获得对应参考值,以及最佳运行控制结果。通过实验表明:设计的模块既能保证输电系统在正常工作状态下平稳运行,也能在发生故障时将影响控制在安全范围内,保证电力系统输电稳定。

大型光伏电站全直流送出关键问题研究

研究浙江舟山地区小洋山薄刀咀118 MW光伏电站全直流送出方案。介绍全直流送出系统的构建原理,重点阐述拓扑结构选择、接地方式、直流电压控制等关键技术问题。明确多级直流升压系统的构建原理。在PSCAD/EMTDC平台上搭建相应仿真系统,通过时域仿真验证所提小洋山薄刀咀118 MW光伏电站全直流送出方案的可行性。

大规模光伏经柔直送出系统的近工频耦合振荡机理与特性分析

针对近工频耦合振荡这类新型振荡稳定性问题,研究了其发生机理和稳定特性。建立大规模光伏经柔直送出系统的全电磁暂态模型,仿真展示了近工频耦合振荡的发生条件。通过分析设备在振荡频率下的复功率分布,阐明系统振荡源头与传播特性。基于在线阻抗分析研究振荡发生的电路机理,分析影响振荡稳定性的关键因素。结果表明,在次/超同步近工频段,光伏电站表现为电阻为负的容性元件,与柔直送端换流站、输电线路共同构成负阻尼的串联谐振电路,从而引发不稳定的近工频耦合振荡;光伏网侧换流器、柔直换流器控制参数和输电线路电抗等因素会影响系统的稳定性。

基于ARM架构柔性直流控制保护系统的低链路延时优化设计

基于进阶精简指令集机器(ARM)架构多核处理器芯片设计了柔性直流控制保护系统新一代平台,提出适用于柔性直流输电的4层控制系统通用架构,给出新平台控制保护主机配置方案及功能配置原则。建立换流器高频阻抗简化模型,推导得到负阻尼频率与控制链路延时的数学关系。分析柔性直流控制系统的链路延时构成,提出一种链路复用的在线延时测试方法;基于多核架构与高速接口,研究控制系统的低延时优化方案。最后,在基于实际工程参数的实时仿真系统中,对ARM架构新平台开展了功能和性能测试,并验证了低延时优化方案的有效性。

区域新能源并网暂态功角稳定分析与紧急控制策略优化

随着新型电力系统发展和新能源机组不断投产,南方区域将形成多区域新能源与邻近常规电源联合集中接入系统的场景。新能源集中接入常与常规电源共用输电通道,将影响区域系统暂态稳定特性及输送通道的传输能力,使南方区域系统的安全稳定运行和风险防控面临了前所未有的挑战。为深入研究区域新能源送出的稳定特性建立了区域新能源交流集中送出的等值系统模型,分析了新能源并入对区域系统对暂态稳定特性影响的主要机理。基于等面积法则对区域送出系统暂态过程的加、减速面积进行了定量分析,提出了紧急控制切机策略的协调优化方法,实现区域送出传统机组与新能源机组紧急控制切机量及控制代价的最小化的切机策略配置。最终,基于广东区域海风火电打捆送出系统为例,对分析结果的正确性进行了验证。

模块化多电平矩阵换流器接入下的工频故障特性分析

基于模块化多电平矩阵换流器(M3C)的柔性低频输电系统在中远海风电外送、异步电网互联等方面优势突出。然而,有别于模块化多电平换流器(MMC)等其他电力电子换流设备,M3C的控制策略将导致系统故障特性发生显著变化。现有将电力电子设备负序部分等效为开路的故障等值与响应特性计算方法无法适用。文中计及M3C正序定电容电压总平均值控制、负序电流注入控制以及环流控制分层构成的桥臂电容电压均衡策略,推导了工频侧线路故障以后,M3C输入输出功率均衡、桥臂功率均衡(电容电压均衡的必要条件)与正负序电压电流间的映射关系,由此构建了工频侧线路故障(不对称、对称)后的M3C输出电压电流响应特性的等效模型。在此基础上,提出了M3C接入下工频侧线路故障后电压电流响应特性的精确计算方法。最后,基于PSCAD/EMTDC仿真平台,搭建了海上风电柔性低频送出系统仿真模型,通过大量仿真算例充分验证了所提故障特性分析方法的正确性和精确性。

基于序列二次规划算法的双有源桥变换器优化控制策略

针对双有源桥变换器在充电领域电路损耗大、传输效率低的问题,提出一种结合序列二次规划算法与双重移相控制实现回流功率优化的控制策略。首先,建立双有源桥变换器在双重移相控制时以回流功率最小值为目标函数的二次规划问题数学模型;然后,提出一种采用序列二次规划算法求解上述多约束、非线性的数学模型,在算法中输入目标、约束函数的雅可比矩阵和变换器的相关参数,通过迭代求解出满足双有源桥电路在双重移相控制下最优工况的目标参数;最后,通过仿真验证所提控制策略的有效性。

基于二极管分散整流的风电机组中压直流汇集直接送出系统

基于二极管分散整流的风电机组中压直流汇集直接送出系统可以省去海上升压站及海上换流站,对于中远距离、中等规模海上风电具有突出经济优势。针对其特有的输电电流纹波问题,建立了多机动态移相参考坐标系(DPSRF)并提出按DPSRF坐标系d轴定向的电压矢量控制,实现多台机组的分散式二极管整流器整流电流矢量和输出电流纹波的交错分布,有效降低直流输电电流和电压纹波。计及纹波交错算法中动态移相角影响,建立风电机组网侧变换器小信号状态空间模型,基于特征根分析辨识系统弱阻尼环节,并针对性地提出镇定控制策略。发挥该系统有望免除直流断路器的优势,制定了基于扰动注入的故障定位策略,配合继电保护逻辑和机组动作时序实现无通信依赖的直流内网多故障位置故障定位与隔离。最后,PSCAD仿真和基于RT-LAB的硬件在环实验验证了所提控制保护策略的有效性。