An adaptive sliding mode observer based near-optimal OER tracking control approach for PEMFC under dynamic operation condition

Tracking control of oxygen excess ratio (OER) is crucial for dynamic performance and operating efficiency of the proton exchange membrane fuel cell (PEMFC). OER tracking errors and overshoots under dynamic load limit the PEMFC output power performance, and also could lead oxygen starvation which seriously affect the life of PEMFC. To solve this problem, an adaptive sliding mode observer based near-optimal OER tracking control approach is proposed in this paper. According to real time load demand, a dynamic OER optimization strategy is designed to obtain an optimal OER. A nonlinear system model based near-optimal controller is designed to minimize the OER tracking error under variable operation condition of PEMFC. An adaptive sliding mode observer is utilized to estimate the uncertain parameters of the PEMFC air supply system and update parameters in near-optimal controller. The proposed control approach is implemented in OER tracking experiments based on air supply system of a 5 kW PEMFC test platform. The experiment results are analyzed and demonstrate the efficacy of the proposed control approach under load changes, external disturbances and parameter uncertainties of PEFMC system.     

基于磁链观测器的定子频率算法研究

针对利用传统定子磁链观测器确定双馈风力发电系统定子侧频率的两大缺陷,提出了3种改进型定子频率算法:限制Uα算法、电压微分耦合算法、反余弦函数算法。通过理论分析和仿真研究,对3种改进型算法的性能进行了比较,结果表明,反余弦函数算法的性能最优。     

Measurements and simulations for peak electrical load reduction in cooling dominated climate

Peak electric demand due to cooling load in the Desert Southwest region of the US has been an issue for the electrical energy suppliers. To address this issue, a consortium has been formed between the University of Nevada Las Vegas, Pulte Homes (home builder) and NV Energy (local utility) in order to reduce the peak load by more than 65%. The implemented strategies that were used to accomplish that goal consist of energy efficiency in homes, onsite electricity generation through roof integrated PV, direct load control, and battery storage at the substation level. The simulation models developed using building energy analysis software were validated against measured data. The electrical energy demand for the upgraded home during peak period (1:00–7:00 PM) decreased by approximately 37% and 9% compared to a code standard home of the same size, due to energy efficiency and PV generation, respectively. The total decrease in electrical demand due to energy efficiency and PV generation during the peak period is 46%. Additionally, a 2.2 °C increase in thermostat temperature from 23.9 °C to 26.1 °C between 4:00 PM and 7:00 PM has further decreased the average demand during the peak period by 69% of demand from a standard home.     

基于干扰观测器的储能反步控制

当直流侧电压波动较大时,基于反步法设计的储能变流器无法依靠自身的鲁棒性平抑功率和直流电压波动.文章提出了一种基于干扰观测器的储能变流器反步控制算法,可提升控制器抗干扰的性能,有效抑制直流电压波动.首先建立双级式储能变流器数学模型并分析其工作原理;然后采用基于干扰观测器的反步法设计了储能变流器的控制器;最后,在Matla...     

Environmental climate instruments in Romania: A comparative approach using dynamic CGE modelling

This study simulates a CO₂ permit market in Romania using a dynamic general equilibrium model. The carbon constraint is set at 20.7% below the reference emissions level for sectors eligible according to the European Union Emission Trading Scheme (EU-ETS). Free permit distribution enhances growth despite a severe emissions cap, because environmental regulation stimulates structural changes [Porter, M., 1991. American's green strategy. Scientific American 264, 168]. That is, grandfathering allows sectors additional resources to invest in developing technologies, but it also raises the CO₂ abatement costs because of energy rebound effects from enhanced growth. Results under endogenous growth [Romer, P.M., 1990. Endogenous technological change. Journal of Political Economy 98 (5), 71–102] are very similar to those obtained under an exogenous growth scenario [Ramsey, Y.F., 1928. A mathematical theory of saving. Economic Journal 38, 543–559], as the substitution effects are responsible for the majority of variations; in addition, Romanian research activities are too modest to significantly impact this system. The abatement cost per unit of GDP is higher under endogenous growth, as spillover effects reduce incentives to invest. Technological diffusion continues to have a positive impact on economic growth, which counterbalances the free-riding attitude adopted by some energy-intensive sectors, such as glass and cement.     

Measurements of jet flows impinging into a channel containing a rod bundle using dynamic PIV

In this investigation, full-field velocity profiles of jet flows impinging into a rod bundle were measured using Particle Image Velocimetry (PIV) technique in a facility with Matched-Index of Refraction. The test section consisted of a 1 m long rectangular channel with a cross-sectional area of 76.2 × 76.2 mm². Water was pumped through either single or double jets located on the top wall of the channel. The Reynolds numbers of the inlet jets were varied from 4470 to 13,400. Inside the channel adjacent to the inlet jets, a rod bundle was configured with 29 staggered tubes of 10.67 mm outside diameter (O.D.). The time-resolved velocity fields were obtained for regions within the rod bundle from which the vorticity fields and the turbulent characteristics of those regions were calculated. The results are useful for developing new models to help predict the flow patterns in the lower plenum of Gas Cooled Reactors.     

基于现今值观测器的混合微网直流母线电压控制研究

文章针对混合微电网直流母线电压控制技术开展了研究。首先,建立了用于控制直流母线电压的双向DC/AC数学模型,并以稳定直流母线电压为目标,进行了带有电流前馈的控制系统设计。为了解决系统中直流母线负载电流测量难度较大的问题,基于现今观测器提出了一种负载电流的估计方法。最后,通过仿真验证了所提方法的有效性。     

An original observer design for reduced sensor control of Packed U Cells based renewable energy system

This paper presents an original Switched Observer (SO) for reduced-sensor control of a grid-connected Packed U Cells (PUC) multilevel inverter. The proposed SO performance is evaluated using a single-phase 7-level PUC inverter connected to the grid through filtering inductor. Based on the actual grid current, the proposed SO estimates accurately the PUC capacitor voltage, which is fed to the Model Predictive Control (MPC) algorithm while making use of a hybrid model considering both discrete and continuous variables. For real-time application, necessary conditions are given to guarantee the practical stability of the proposed SO under system parameters and input voltage variations according to the selected switching pattern. Theoretical analysis and simulation investigations are conducted to prove that the proposed SO-MPC scheme is stable in closed-loop for all system configurations and has good performances even during various disturbances (load change, parameters mismatch, and input voltage variation).     

基于Intranet的电厂信息动态发布

现代电力企业的发展，在向大电网，大容量，高电压，高自动化发展的同时，正逐步走向商业化运营，传统的网络结构已不再适应电力企业市场化要求，同时，随着Internet技术的发展，基于Internet技术的Intranet的开发已经使得很多企业深受其益，电力企业Internet的开发正处于应用初期，很有发展前途，同时Intranet的开发将会给电力企业的发展带来巨大的生机和活力，文中论述了Intranet上动态信息发布系统的实现，将企业管理信息动态发布到Intranet平台上，供企业内部查询。     

Robust fault diagnosis and fault tolerant control for PEMFC system based on an augmented LPV observer

In order to improve the safety and reliability of proton exchange membrane fuel cell system, this paper proposes a novel robust fault observer for the fault diagnosis and reconstruction of the PEMFC air management system. First, considering the complexity and large computation of the nonlinear PEMFC system, a linear parameter-varying (LPV) model is introduced to describe the system behavior and reduce the computation cost. Then, an augmented state observer based on the LPV model is proposed for simultaneously estimating the internal states and component faults. The robustness is guaranteed by taking the system disturbances and measurement noises into consideration when designing the observer gain. The observer design is transformed into a process of solving a set of linear inequality matrices. According to the results, the augmented robust observer can accurately estimate the system states and faults under different conditions. Moreover, to realize the fault tolerant control of the air supply, the oxygen stoichiometry estimator is designed taking consideration of system fault information and a corresponding controller is employed for air compressor voltage following the net power maximization strategy.     

Robust SVM-direct torque control of induction motor based on sliding mode controller and sliding mode observer

This paper proposes a design of control and estimation strategy for induction motor based on the variable structure approach. It describes a coupling of sliding mode direct torque control (DTC) with sliding mode flux and speed observer. This algorithm uses direct torque control basics and the sliding mode approach. A robust electromagnetic torque and flux controllers are designed to overcome the conventional SVM-DTC drawbacks and to ensure fast response and full reference tracking with desired dynamic behavior and low ripple level. The sliding mode controller is used to generate reference voltages in stationary frame and give them to the controlled motor after modulation by a space vector modulation (SVM) inverter. The second aim of this paper is to design a sliding mode speed/flux observer which can improve the control performances by using a sensorless algorithm to get an accurate estimation, and consequently, increase the reliability of the system and decrease the cost of using sensors. The effectiveness of the whole composed control algorithm is investigated in different robustness tests with simulation using Matlab/Simulink and verified by real time experimental implementation based on dS pace 1104 board.     

Assessment of a fuzzy logic based MRAS observer used in a photovoltaic array supplied AC drive

In this paper a fuzzy logic (FL) based model reference adaptive system (MRAS) speed observer for high performance AC drives is proposed. The error vector computation is made based on the rotor-flux derived from the reference and the adaptive model of the induction motor. The error signal is processed in the proposed fuzzy logic controller (FLC) for speed adaptation. The drive employs an indirect vector control scheme for achieving a good closed loop speed control. For powering the drive system, a standalone photovoltaic (PV) energy source is used. To extract the maximum power from the PV source, a constant voltage controller (CVC) is also proposed. The complete drive system is modeled in MATLAB/Simulink and the performance is analyzed for different operating conditions.     

西安某小区供热系统气候补偿节能改造

以西安市某小区为例,对其进行气候补偿节能改造。通过调研提出其存在的其他问题,针对问题进行节能技术改造。主要采用了3种技术措施气候补偿、分时分区、加装自力式流量控制阀,达到节约能源的效果,并提高用户的舒适度。     

Measurements get together

EEveryday life relies heavily on the reliable operation and intelligent management of critical infrastructures, such as electric power systems, telecommunication networks, and water distribution networks. Designing, monitoring and controlling such systems is becoming increasingly more challenging as a consequence of the steady growth of their size, complexity, level of uncertainty, unpredictable behavior, and interactions. These critical infrastructures are susceptible to natural disasters, frequent failures, and malicious attacks. At the epicenter of the well-being and prosperity of society lie the electric power systems. The secure and reliable operation of modern power systems is an increasingly challenging task due to the ever-increasing demand for electricity, the growing number of interconnections, penetration of variable renewable energy sources, and deregulated energy market conditions. Power companies in different parts of the world are therefore feeling the need for a real-time wide area monitoring, protection, and control (WAMPAC) system. Synchronized measurement technology (SMT) has the potential of becoming the backbone of this system. The major advantages of using SMT are that 1) the measurements from widely dispersed locations can be synchronized with respect to a global positioning system (GPS) clock, 2) voltage phase angles can be measured directly, which was so far technically infeasible, and 3) the accuracy and speed of energy management system (EMS) applications (e.g., state estimation) increases manifold.     

Model‐based unscented Kalman filter observer design for lithium‐ion battery state of charge estimation

Accurate battery state‐of‐charge is essential for both driver notification and battery management units reliability in electric vehicle/hybrid electric vehicle. It is necessary to develop a robust state of charge (SOC) estimation approach to cope with nonlinear dynamic battery systems. This paper proposed an estimation method to identify the SOC online based on equivalent circuit battery model and unscented Kalman filter technique. Firstly, the parameters of dynamic battery model are identified offline and validated through typical electric vehicle road operation to guarantee its precision. Then the performance with respect to converge time, observer accuracy, robustness against system modeling errors, and mismatched initial SOC guess values is investigated. The accuracy of proposed estimation algorithm is validated under improved hybrid power pulse characterization test and New European Driving Cycle. Experiment and numerical simulation results clearly demonstrate that the proposed method is highly reliable with good robustness to different operating conditions and battery aging.     

Efficient climate policies under technology and climate uncertainty

This article explores efficient climate policies in terms of investment streams into fossil and renewable energy technologies. The investment decisions maximise social welfare while observing a probabilistic guardrail for global mean temperature rise under uncertain technology and climate parameters. Such a guardrail constitutes a chance constraint, and the resulting optimisation problem is an instance of chance constrained programming, not stochastic programming as often employed. Our analysis of a model of economic growth and endogenous technological change, MIND, suggests that stringent mitigation strategies cannot guarantee a very high probability of limiting warming to 2 °C since preindustrial time under current uncertainty about climate sensitivity and climate response time scale. Achieving the 2 °C temperature target with a probability P? of 75% requires drastic carbon dioxide emission cuts. This holds true even though we have assumed an aggressive mitigation policy on other greenhouse gases from, e.g., the agricultural sector. The emission cuts are deeper than estimated from a deterministic calculation with climate sensitivity fixed at the P? quantile of its marginal probability distribution (3.6 °C). We show that earlier and cumulatively larger investments into the renewable sector are triggered by including uncertainty in the technology and climate response time scale parameters. This comes at an additional GWP loss of 0.3%, resulting in a total loss of 0.8% GWP for observing the chance constraint. We obtained those results with a new numerical scheme to implement constrained welfare optimisation under uncertainty as a chance constrained programming problem in standard optimisation software such as GAMS. The scheme is able to incorporate multivariate non-factorial probability measures such as given by the joint distribution of climate sensitivity and response time. We demonstrate the scheme for the case of a four-dimensional parameter space capturing uncertainty about climate and technology.     

Wind climate from the regional climate model REMO

Selected outputs from simulations with the regional climate model REMO from the Max Planck Institute, Hamburg, Germany were studied in connection with wind energy resource assessment. It was found that the mean wind characteristics based on observations from six mid‐latitude stations are well described by the standard winds derived from the REMO pressure data. The mean wind parameters include the directional wind distribution, directional and omni‐directional mean values and Weibull fitting parameters, spectral analysis and interannual variability of the standard winds. It was also found that, on average, the wind characteristics from REMO are in better agreement with observations than those derived from the National Centers for Environmental Prediction/National Center for Atmospheric Research (NCEP/NCAR) re‐analysis pressure data. The spatial correlation of REMO surface winds in Europe is consistent with that of the NCEP/NCAR surface winds, as well as published observations over Europe at synoptic scales. Therefore, REMO outputs are well suited for wind energy assessment application in Northern Europe. Copyright © 2009 John Wiley & Sons, Ltd.     

基于动态负荷特性的家用光伏发电系统经济性评价

以家用光伏发电系统为研究对象,基于用户侧动态负荷特性与供给侧光伏发电出力特性的耦合解析,根据分布式光伏系统"自用为主、余电上网"的应用原则,构建家用分布式光伏发电系统经济性评价模型。应用该模型,以上海某家用光伏发电系统为例,分析其运行特性、经济性能及其影响因素。研究结果表明,现行政策下家用光伏发电系统的动态投资回收年限为12.4 a;在中国,促进光伏产业发展最实际、最有效的政策是提高上网电价。