An input‐output linearization–based control strategy for wind energy conversion system to enhance stability

This paper proposes a novel control strategy for doubly fed induction generator (DFIG)‐based wind energy conversion system to investigate the potential of enhancing the stability of wind energy transmission system, a synchronous generator weakly integrated to a power system with a DFIG‐based wind farm. The proposed approach uses state feedback to exactly linearize the nonlinear wind energy transmission system from control actions (active power and reactive power control order of DFIG) to selected outputs (power angle and voltage behind transient resistance of synchronous generator) at first. Then, on account of the linearized subsystem, the stability enhancement controller is designed based on linear quadratic regulator algorithm to contribute adequate damping characteristics to oscillations of the synchronous generator system under various operation points. The proposed control strategy successfully deals with the nonlinear behaviors exist from the inputs to outputs and improve the robustness with respect to the variation of system operation points. Furthermore, not only the rotor angle stability but also the voltage stability is enhanced by using the proposed control strategy. The simulation results carried on the studied system verify the effectiveness of the proposed control strategy of wind energy conversion system for system stability enhancement and the robustness against various system operation points.     

Energy savings versus costs of implementation for demand side management strategies within an energy-efficient tropical residence

As renewable energy sources and net-zero energy homes become increasingly pervasive within the residential building industry, further reductions in consumption patterns will occur through demand side management (DSM). DSM can include measures such as energy-efficient system design, automated control and energy management systems, or policies and monitoring systems intended to alter user behavior. For an energy-efficient modern residence designed within a tropical context, several DSM strategies are considered for reductions in operational-phase energy consumption: a lightweight, thermally high-performing building envelope, installation of light dimmers to enhance user control of lighting, and comparison of a solar hot water system versus a point-of-use electric water heater to produce hot water for bathing demands. The energy-consumption savings associated with the three DSM strategies are simulated and normalized to an energy savings per cost of implementation basis in kWh per 1000 Thai Baht (THB) for comparison. The results show that financial investments in low-energy hot water heaters (i.e., solar water heating systems) result in relatively higher energy savings per unit financial investment than the other two strategies. Conversely, the installation of a lightweight, well-insulated envelope is highly expensive relative to its associated energy savings over a 25-year time frame. The savings associated with the insulated envelope, light dimmers, and hot water production strategies are evaluated at 80, 609 and 657 kWh/1000 THB investment, respectively.     

Promotion of grid-connected photovoltaic systems in Spain: Performance analysis of the period 1998–2008

This paper contributes a critical view of the development of grid-connected photovoltaic systems (GCPVS) in Spain during the period 1998–2008 by looking into the different actions that were intended to promote this technology. The Spanish photovoltaic (PV) sector has undergone bullish development in the recent years, but its underlying factors still lack systematic identification and analysis. Accordingly, this paper collects and presents detailed data for describing this evolution. It also makes a special case of the particular promotion of PV systems on roof and goes further to analyze how these actions have affected GCPVS evolution as well as the magnitude of their impact on its performance. The exponential growth of installed cumulative PV power at the end of this period, which largely exceeded the target set for 2008, is canvassed by building an analogy with feedback control systems. In this approach, market response or the PV power attained is considered as the system output, while the different regulation changes are regarded as control actions aimed at enabling GCPVS to hit the energy target. Such an analysis allows determining the most significant delays and control actions that explain the system's performance. Hence, this study suggests an alternative framework to support the formulation and assessment of energy policy as it puts the emphasis not only on the evolution of the system per se but rather on the performance of the system against the energy target. In this regard, it might contribute to enhance the promotion mechanisms of green technologies.     

Lifetime commissioning as a tool to achieve energy‐efficient solutions

Quality control of the complete energy system is necessary if energy‐efficient solutions are to be met. To perform good building operation and quality control of a given system, it is necessary to have information about building systems and assessment tools. The paper presents Norwegian lifetime commissioning (LTC) procedures that are enabling follow‐up of the building performance during the building lifetime by establishing a generic framework on building performance data. Further, three developed assessment tools are presented: inspection algorithm for ventilation system, mass balance inspection algorithm for consumer substation, and advanced method for improved measurement of heat pump performance based on data fusion technique. The LTC procedures were tested on two case buildings. The results showed that 20% of all the defined building performance data can be monitored by BEMS. Using the mass balance inspection algorithm, it was found that fault in mass balance prevented implantation of desired temperature control for floor heating system. For heat pump performance, measurement of differential water temperature can be very erroneous. Hence, use of compressor electrical signal can give more precise data on heat pump performance. Comparative analysis showed that detailed monitoring system helps tracking energy use and fault detection in operation. Yearly and hourly profiles of energy consumption with separated use and energy carriers are given in the paper. Copyright © 2011 John Wiley & Sons, Ltd.     

A generic demand‐side management model for smart grid

The demand‐side management (DSM) is one of the most important aspects in future smart grids: towards electricity generation cost by minimizing the expensive thermal peak power plants. The DSM greatly affects the individual users' cost and per unit cost. The main objective of this research article is to develop a generic demand‐side management (G‐DSM) model for residential users to reduce peak‐to‐average ratio (PAR), total energy cost, and waiting time of appliances (WTA) along with fast execution of the proposed algorithm. We propose a system architecture and mathematical formulation for total energy cost minimization, PAR reduction, and WTA. The G‐DSM model is based on genetic algorithm (GA) for appliances scheduling and considers 20 users having a combination of appliances with different operational characteristics. Simulation results show the effectiveness of G‐DSM model for both single and multiple user scenarios. Copyright © 2015 John Wiley & Sons, Ltd.     

Application of terminal box optimization of single‐duct air‐handling units

Terminal boxes maintain room temperature by modulating supply air temperature and airflow in building heating, ventilation and air‐conditioning (HVAC) systems. Terminal boxes with conventional control sequences often supply inadequate airflow to a conditioned space, resulting in occupant discomfort, or provide excessive airflow that wastes significant reheat energy. In this study, the procedure for the optimal minimum airflow setpoint was developed to improve thermal comfort and reduce energy consumption. The determined minimum airflow setpoint was applied in an office building air‐conditioning system. Improvements in indoor thermal comfort and energy reduction were verified through measurement. The results show that the minimum airflow reset can stably maintain room temperature, satisfy comfort standards and reduce energy consumption compared with the conventional control. Copyright © 2009 John Wiley & Sons, Ltd.     

A grey‐box model of next‐day building thermal load prediction for energy‐efficient control

Accurate building thermal load prediction is essential to many building energy control strategies. To get reliable prediction of the hourly building load of the next day, air temperature/relative humidity and solar radiation prediction modules are integrated with a grey‐box model. The regressive solar radiation module predicts the solar radiation using the forecasted cloud amount, sky condition and extreme temperatures from on‐line weather stations, while the forecasted sky condition is used to correct the cloud amount forecast. The temperature/relative humidity prediction module uses a dynamic grey model (GM), which is specialized in the grey system with incomplete information. Both weather prediction modules are integrated into a building thermal load model for the on‐line prediction of the building thermal load in the next day. The validation of both weather prediction modules and the on‐line building thermal load prediction model are presented. Copyright © 2008 John Wiley & Sons, Ltd.     

A cost‐effective operating strategy to reduce energy consumption in a HVAC system

The operation of the building heating, ventilating, and air conditioning (HVAC) system is a critical activity in terms of optimizing the building's energy consumption, ensuring the occupants' comfort, and preserving air quality. The performance of HVAC systems can be improved through optimized supervisory control strategies. Set points can be adjusted by the optimized supervisor to improve the operating efficiency. This paper presents a cost‐effective building operating strategy to reduce energy costs associated with the operation of the HVAC system. The strategy determines the set points of local‐loop controllers used in a multi‐zone HVAC system. The controller set points include the supply air temperature, the supply duct static pressure, and the chilled water supply temperature. The variation of zone air temperatures around the set point is also considered. The strategy provides proper set points to controllers for minimum energy use while maintaining the required thermal comfort. The proposed technology is computationally simple and suitable for online implementation; it requires access to some data that are already measured and therefore available in most existing building energy management and control systems. The strategy is evaluated for a case study in an existing variable air volume system. The results show that the proposed strategy may be an excellent means of reducing utility costs associated with maintaining or improving indoor environmental conditions. It may reduce energy consumption by about 11% when compared with the actual strategy applied on the investigated existing system. Copyright © 2007 John Wiley & Sons, Ltd.     

间接连接区域热水供暖系统特性及控制策略仿真

应用质量和能量守恒定律,创建间接连接热水区域供暖系统动态模型。通过仿真,分析系统补水率、散热器及换热器面积、室外温度、太阳辐射、室内得热、散热器循环流量和供水温度对系统和用户运行的影响。根据燃料控制器及温度控制器不同配置,仿真及分析了6种控制策略运行和能耗情况。控制仿真显示,基于用户侧的控制策略可实现系统节能及用户热舒适性双赢目标。     

Energy analysis of a low‐temperature heat pump heating system in a single‐family house

Energy costs and environmental concerns have made energy optimisation a viable option for buildings. Energy‐efficient heating systems together with an effective use of buildings thermal mass and tightness have a significant impact on the energy requirement and on the possibility for sizeable running cost savings. In this study we use the simulation tool TRNSYS‐EES to model and analyse the performance of a residential house and the low‐temperature heating system that serves its thermal needs. The building is a single‐family house with controlled ventilation and the chosen heating system is a hydronic floor heating system connected to an exhaust air heat pump. The aim of the simulation is to study the performance of the building, the heating system and the controls in an integrated manner. Overall, the results indicate that the energy efficiency issue implicates system design and system thinking concerns as well as techno‐economic difficulties. The controls and the choice of the operation mode are of a great importance. Copyright © 2004 John Wiley & Sons, Ltd.     

Using multi‐stack and variable‐speed‐drive systems to reduce laboratory exhaust fan energy

In buildings that contain laboratories, fume hoods are normally used to control contaminant concentrations. Exhaust stacks with a constant exit velocity are required to make sure that dangerous concentrations do not occur in occupied areas near the building or on the roof top. To achieve constant velocity when exhaust flow rates are less than design, makeup air is introduced to the system at the inlet of the exhaust fan. Since laboratory exhaust airflow is often significantly less than the design airflow, exhaust fans consume significantly more energy than is necessary. To reduce exhaust fan energy, techniques involving multiple exhaust stacks and a variable speed drive (VSD) can be applied to laboratory exhaust systems. The potential fan energy savings depend on optimal selection of the number of stacks, the sizes of the stacks, and the exhaust system ductwork design. This paper introduces application principles, describes the optimal methods of stack sizing, and presents an example to demonstrate these methods. Published in 2005 by John Wiley & Sons, Ltd.     

LOCAL OPERATING NETWORKS TECHNOLOGY AIMING TO IMPROVE BUILDING ENERGY MANAGEMENT SYSTEM PERFORMANCE SATISFYING THE USERS PREFERENCES

The available Building Energy Management Systems (BEMS), although they contribute to a significant reduction of energy consumption and improvement of the indoor environment, they can only be implemented in new buildings. Their installation in existing buildings is far from being cost effective due to the incompatibility of communication protocols between BEMS designed by various manufacturers and unavoidable modifications for data transmission. On the other hand, current research for energy efficient buildings has proved that although the design and the facilities including BEMS aim to satisfy the thermal and visual comfort plus the air quality demands while minimising the energy needs, they often do not reach their goals due to users interference. Latest trends in designing Intelligent Building Energy Management Systems (IBEMS) offer a Man Machine Interface that could store the users preferences and adapt the control strategy accordingly. The objectives of the present paper are to present the advantages of the use of a man machine interface based on a smart card terminal together with fuzzy control techniques in satisfying the users preferences plus to underline the capabilities that the LON network offers to the design. A fuzzy PID controller is developed to reach the first of the above objectives. The monitoring of the energy consumption along with satisfying the users preferences is achieved by the use of a suitable cost function for the whole system. All the above parameters as well as the cost function are kept between acceptable limits. The overall control system including the cost function is modeled and tested using MATLAB/SIMULINK. The implementation of the control system in an existing building requires interconnection of sensors and actuators installed across the building, is well served by the LonWorks technology due to its high standards and flexibility features.     

Simulating Feedback Linearization control of wind turbines using high‐order models

As wind turbines are becoming larger, wind turbine control must now encompass load control objectives as well as power and speed control to achieve a low cost of energy. Due to the inherent non‐linearities in a wind turbine system, the use of non‐linear model‐based controllers has the potential to increase control performance. A non‐linear feedback linearization controller with an Extended Kalman Filter is successfully used to control a FAST model of the controls advanced research turbine with active blade, tower and drive‐train dynamics in above rated wind conditions. The controller exhibits reductions in low speed shaft fatigue damage equivalent loads, power regulation and speed regulation when compared to a Gain Scheduled Proportional Integral controller, designed for speed regulation alone. The feedback linearization controller shows better rotor speed regulation than a Linear Quadratic Regulator (LQR) at close to rated wind speeds, but poorer rotor speed regulation at higher wind speeds. This is due to modeling inaccuracies and the addition of unmodeled dynamics during simulation. Similar performance between the feedback linearization controller and the LQR in reducing drive‐train fatigue damage and power regulation is observed. Improvements in control performance may be achieved through increasing the accuracy of the non‐linear model used for controller design. Copyright © 2009 John Wiley & Sons, Ltd.     

Evaluation of wind power forecasts—An up‐to‐date view

Wind power forecast evaluation is of key importance for forecast provider selection, forecast quality control, and model development. While forecasts are most often evaluated based on squared or absolute errors, these error measures do not always adequately reflect the loss functions and true expectations of the forecast user, neither do they provide enough information for the desired evaluation task. Over the last decade, research in forecast verification has intensified, and a number of verification frameworks and diagnostic tools have been proposed. However, the corresponding literature is generally very technical and most often dedicated to forecast model developers. This can make forecast users struggle to select the most appropriate verification tools for their application while not fully appraising subtleties related to their application and interpretation. This paper revisits the most common verification tools from a forecast user perspective and discusses their suitability for different application examples as well as evaluation setup design and significance of evaluation results.     

Multi‐agent‐based sharing power economy for a smart community

In this paper, a multi‐agent‐based locally administrated power distribution hub (PDH) for social welfare is proposed that optimizes energy consumption, allocation, and management of battery energy storage systems (ESSs) for a smart community. Initially, formulation regarding optimum selection of a power storage system for a home (in terms of storage capacity) is presented. Afterwards, the concept of sharing economy is inducted in the community by demonstrating PDH. PDH is composed of multiple small‐scale battery ESSs (each owned by community users), which are connected together to form a unified‐ESS. Proposed PDH offers a localized switching mechanism that takes decision of whether to buy electricity from utility or use unified‐ESS. This decision is based on the price of electricity at ‘time of use’ and ‘state of charge’ of unified‐ESS. In response to power use or share, electricity bills are created for individual smart homes by incrementing or decrementing respective submeters. There is no buying or selling of power from PDH; there is power sharing with the concept of ‘no profit, no loss’. The objective of the proposed PDH is to limit the purchase of electricity on ‘high priced’ hours from the utility. This not only benefits the utility at crucial hours but also provides effective use of power at the demand side. The proposed multi‐agent system depicts the concept of sharing power economy within a community. Finally, the proposed model is analyzed analytically, considering on‐peak, off‐peak, and mid‐level (mid‐peak) prices of a real‐time price signal during 24 h of a day. Results clearly show vital financial benefits of ‘sharing power economy’ for end users and efficient use of power within the smart community. Copyright © 2017 John Wiley & Sons, Ltd.     

计及用户响应成本的电采暖负荷群参与风电备用研究

分布式电采暖具有调度灵活、反应迅速的优点,可用于时序变化的可再生能源辅助服务中,但其响应成本和用户使用价格较高。文章通过负荷聚合商聚合用户群调节能力,并激励用户参与风电场备用,提高用户-负荷聚合商-电网综合收益。首先,负荷聚合商将用户群按建筑参数、初始状态和用户响应成本分组,应用二阶等效热力学模型模拟建筑物的储热过程;其次,提出含温差补贴的价格激励方法,负荷聚合商通过该方法激励用户参与响应以满足风电场的备用需求;最后,通过算例证明该方法降低了电采暖负荷参与风电备用的成本,提高了风电备用。     

Master‐slave game optimization method of smart energy systems considering the uncertainty of renewable energy

As the uncertainty of renewable energy output brings more and more risks to the day‐ahead dispatch of the power grid, an optimization scheduling strategy of a smart energy system based on improved master‐slave game model is proposed. Risk factors related to the uncertainties of renewable energy are introduced into the master‐slave game model. Taking the smart energy system as the leader and the end users as the follower, an optimized operation model of the smart energy system based on the improved master‐slave game model is established, which is transformed into a single‐layer linear programming model according to the Karush‐Kuhn‐Tucher conditions and the duality theorem. The benefits of the system and electric vehicle users in four application scenarios are obtained by the YALMIP algorithm and the sensitivity affecting the economics of the smart energy system is analyzed. The validity of the model is verified by a simulation analysis of actual operation data from the smart energy system in China. The simulation results show that the method proposed in this paper can increase the revenue of the smart energy system by 7%, reduce the risk cost and charging cost of electric vehicle users by 63.92% and 48.34%.     

End-user interfaces for energy-efficient semantically enabled smart homes

The need for energy efficient technological solutions is becoming ever more prevalent in today’s world. However, current advances are failing to offer end-consumers with a flexible solution that can be widely implemented in domestic or business environments. This is particularly relevant at the user interface level where energy consumers should be allowed to easily engage in effective energy saving technology. With the help of semantically linked data, we aim to actively assist end-consumers in making well-informed decisions in order to successfully control their energy consumption. By integrating smart metering and home automation functionality, our SESAME system offers end-consumers energy-efficient and cost-cutting options for their homes or businesses. The developed SESAME system conceptualizes, demonstrates and evaluates a variety of innovative end-consumer services, here focusing specifically on their user interface paradigms. In this paper, we present three types of interactive participatory user interfaces, all of which enable users to interact with the house automation settings modelled as semantic rules, as well their evaluation in user studies based on the demonstrator system. We show that the proposed interfaces have the potential for broad acceptance, and provide a detailed analysis of the effectiveness of their varying design principles and features.     

Advanced control systems engineering for energy and comfort management in a building environment—A review

Given restrictions that comfort conditions in the interior of a building are satisfied, it becomes obvious that the problem of energy conservation is a multidimensional one. Scientists from a variety of fields have been working on this problem for a few decades now; however, essentially it remains an open issue. In the beginning of this article, we define the whole problem in which the topics are: energy, comfort and control. Next, we briefly present the conventional control systems in buildings and their advantages and disadvantage. We will also see how the development of intelligent control systems has improved the efficiency of control systems for the management of indoor environment including user preferences. This paper presents a survey exploring state of the art control systems in buildings. Attention will be focused on the design of agent-based intelligent control systems in building environments. In particular, this paper presents a multi-agent control system (MACS). This advanced control system is simulated using TRNSYS/MATLAB. The simulation results show that the MACS successfully manage the user’s preferences for thermal and illuminance comfort, indoor air quality and energy conservation.