Nonlinear predictive control with dead-time compensator: Application to a solar power plant

This paper presents the application of a Nonlinear Model Predictive Controller (NMPC) extended with a dead-time compensator (DTC) to the control of a distributed solar collector field. This nonlinear controller uses the Nonlinear Extended Prediction Self-Adaptive Controller (NEPSAC) algorithm. A nonlinear grey-box model of the plant, based on first principles and tuned according to real measurements, is used in the simulation tests. The resulting controller is compared to other architectures based on DTC, showing very good performance for reference tracking and for disturbance rejection.     

GA-based fuzzy logic control of a solar power plant using distributed collector fields

A novel genetic algorithm (GA) based fuzzy logic control (FLC) system has been developed for the solar power plant, Plataforma Solar de Almería (PSA) at Tabernas, in Almería, Spain. The rule base encompasses an empirical set of 49 “if-then” rules. Chromosomes consisting of 49 genes of 5-bit data are created to link to the rule base. The 5-bit data of each gene represents the stength of the corresponding ‘If-Then’ rule. The GA performs the basic operations of reproduction, crossover and mutation on a pool of chromosomes to search for the best rule base which optimises the response time of the plant to input temperature or power demand by controlling the distributed collector field of the plant. The collect field is essentially an array of parabolic mirrors and oil pipes in which the transversal of solar energy takes place. Simulation results on the plant with an optimised rule-base using the 100th generation of the chromosome show that the proposed GA-FLC scheme gives a better and more robust performance of the plant than other schemes previously implemented.     

Autonomous micro hydro power plant with induction generator

Autonomous micro hydro power plants (MHPP) are a reliable solution for supplying small power consumers in areas located far from the distribution grid. When an induction generator (IG) is used in such a power plant, voltage and frequency need to be stabilized. This paper presents a single control structure that ensures both the voltage and frequency regulation of an isolated induction generator (IG). The control structure consists in a voltage source inverter (VSI) with a dump load (DL) circuit on its DC side. The VSI operates at constant frequency, thus stabilizing the IG frequency also. For voltage regulation two cascaded regulators are used, which have as reference the line voltage and the VSI DC voltage, respectively. Simulations and experiments are carried out in order to investigate the reliability of such configuration when supplying static and dynamic loads.     

Experimental investigation of a novel micro gas turbine with flexible switching function for distributed power system

Micro gas turbine (MGT) is widely used in small-scale distributed power systems because of its low emissions and fuel flexibility. However, the under-utilization of its exhaust heat and the low electric efficiency are the main bottlenecks that restrict its application. Additionally, the flexible switching between the power generated by the MGT and the power grid is also a key factor for keeping the secure operation of a distributed power station. Therefore, this paper conducted some experimental investigations of a 30 kW MGT to provide reference solutions for the above issues. This MGT is located at Shanghai Jiao Tong University (SJTU), which is designed by the Gas Turbine Research Institute of SJTU, and is manufactured by a turbo-machinery factory in Chongqing, China. The demonstration prototype is mainly composed of a single stage centrifugal compressor, a radial turbine, a combustor, a high-speed permanent magnet generator, and a control system. The results show that the MGT can achieve steady operation at a low rotational speed from 10000 r/min to 34000 r/min in the case of using oil lubricated bearings, which can greatly reduce the economic cost compared with the use of air bearings. At the same time, the ignition success rate of combustion chamber (CC) reaches 98% at a low rotational speed, and a wide range of stable combustion area can be obtained, because of the novel design method of combustor by referencing the way applied in an axial flow aero-engine. The MGT generating set can achieve functions, such as starting up, ignition, stable operation, loaded operation, grid-connection and stopping. This system also can realize flexibly switching from the start motor mode to the generator mode, and from grid-connected mode to off-grid mode, because the innovative multi-state switching control system is adopted. The above research work can make our state master independent intellectual property rights of micro gas turbine, rather than continue to be subject to the technological monopoly of the developed states, which can provide theoretical and experimental support for the industrialization of MGT in China.     

Application of a thermal model to a power plant reheater with irregular tube temperatures

A three-dimensional thermal model for the reheater of a utility boiler is applied to a 350 MWe power plant. The model permits the consideration of non-uniform steam flow inside the tubes, which can lead to excessive temperature and hence thermal stress in a part of these. Parametric calculations are performed to examine the influence of various empirical coefficients included in the model. Experimental on-line and off-line data will be obtained and will be introduced as boundary conditions or used to validate the model. The steam flow distribution inside the tubes will be considered uniform or non-uniform depending on the tube serpentine of the reheater. The results predicted by the model of the temperature of the tubes at the reheater outlet and the outlet steam temperature are satisfactorily compared with the experimental measurements. Moreover, the results predicted for the temperature of the gases in an intermediate section of the reheater are analysed and compared with the experimental results from off-line measurements.     

模糊控制在直接转矩控制系统中的应用研究

通过实例介绍了模糊控制以及复合模糊控制在直接转矩控制系统中的应用,并以永磁同步电机的模糊控制为例进行了仿真验证,提出了有待进一步解决的问题和发展前景。     

Multivariable robust control of a power plant deaerator

The design of a robust controller for the deaerator of the Experimental Breeder Reactor-II (EBR-II) that uses the linear quadratic Gaussian with loop transfer recovery (LQG/LTR) procedure is described. At present, classical proportional-integral (PI) controllers are used to control the deaerator. When the operating condition changes, the system is disturbed, or a fault occurs, and the PI controllers may fail to maintain the desired performance. A robust controller that can accommodate system faults and obtain a reasonable behavior for a wide range of model uncertainty was designed. The controller provides the desired performance despite a considerable change in the operating condition, accommodates some of the failures that can occur, and provides the choice of penalizing one variable over another. The design is tested for robustness by varying the system operating conditions and simulating a steam valve failure. The set of nonlinear simulations using the modular modeling system and the advanced continuous simulation language is included     

模糊神经网络控制器用于电站主汽压控制的研究

锅炉的燃烧过程是一个多参数、非线性、时变以及变量强耦合的过程，很难建立被控对象的准确数学模型。根据主汽压被控对象的动态特性，设计了一个模糊神经网络自适应控制系统，引用模糊高斯基函数神经网络结构，并采用基于变尺度优化学习算法的改进型学习算法，其学习信号由神经网络辨识器(NNI)提供。利用神经网络的非线性映射能力，能很好的解决被制对象的动态特性具有非线性、时变性、参数可变等问题。仿真对比试验表明，主汽压控制系统引入模糊神经网络控制器(FNNC)后，系统的响应速度变快，调节精度提高。该控制器的适应性、鲁棒性也明显优于常规PID控制器。     

锅炉燃烧优化控制系统在火电厂的应用

针对某电厂330 MW机组锅炉上实施燃烧优化闭环控制系统项目,总结燃烧优化项目成功实施的几个重要步骤及实施中应该注意的问题,为此类项目在国内实施提供经验借鉴。     

燃煤电厂脱硫提效应用研究

在脱硫工程喷淋塔中,由于喷淋层周边与中心区域喷淋液分布密度存在明显偏差,使塔内烟气容易从吸收塔周边区域逃离,从而降低了吸收塔的脱硫效率.为解决这一问题,开发了一种吸收塔增效装置.该装置可以有效弥补脱硫吸收塔内喷淋层布置缺陷,改善塔内烟气分布和气液传质效果,从而提升吸收塔的烟气脱硫效率.针对某一脱硫增效改造工程应用,分析了增效装置在提高SO2脱除率、降低脱硫电耗方面的效果.结果表明,该吸收塔增效装置具有明显的节能减排作用,且安装方便、投资低、运行费用低,对不同大小的吸收塔的适应性强,适合于老机组的吸收塔增效改造.     

Adaptive control of a fuel cell-microturbine hybrid power plant

The composition of natural gas may vary significantly, and load power varies randomly. Traditional control design approaches consider a fixed operating point in the hope that the resulting controller is robust enough to stabilize the system for different operating conditions. On the other hand, adaptive control incorporates the time-varying dynamical properties of the model and considers the disturbances acting at the fuel cell-microturbine hybrid power plant. It may be possible to identify the parameters of the adaptive controller. This scheme is called direct adaptive control, because we are going to obtain directly the required controller parameters through their estimation in an appropriately redefined plant model. An adaptive minimum variance controller is developed in this paper.     

质子交换膜燃料电池的自适应模糊恒功率控制

质子交换膜燃料电池作为一种高效的绿色环保电源而受到越来越多关注。维持燃料电池的正确运行需要良好的控制系统。文章在建立质子交换膜燃料电池数学模型和仿真平台的基础上,针对恒功率燃料电池设计了自适应模糊控制器。仿真结果表明,该自适应模糊控制器可以控制质子交换膜燃料电池实现恒功率输     

Sustainability of a wind power plant: Application to different Moroccan sites

In this paper, three main steps allowing the definition of the sustainability of a wind power plant (WPP) are described in detail. The first step is to choose a site with a good wind potential. In this respect, two approaches have been introduced: traditional wind statistical estimations based on the identification of the Weibull probability density function on specific sites; and an innovative Kriging approach based on artificial neural networks to reconstruct the profile of the mean wind speed of the territory. In the second step, given technical details, the energetic sustainability of a WPP installation is assessed according to a model computing the wind energy production per year, as well as the details of its efficiency. Finally, as third step, a cost/benefit evaluation on the overall reduction in CO₂ emissions with respect to traditional fossil fuel energy plants is reported. From a wind speed characterisation viewpoint, the case study is referred to the overall Moroccan territory. From a WPP model viewpoint, the case study is referred to the installation of a specific WPP, which would allow the production of more than 2 GWh per year in the south Atlantic coast and of nearly 1 GWh per year in the Mediterranean coast in the neighbourhood of Tangier.     

Robust control and analysis of a wind-diesel hybrid power plant

The aim of this paper is twofold: first to present multivariable frequency domain techniques as a tool for controller design and dynamic analysis of an autonomous wind-diesel power system; and secondly to study how robust model based controllers can be designed for such systems. Dynamic system analyses using multivariable frequency domain techniques are verified against detailed nonlinear simulation studies. The results are encouraging in the sense that the main conclusions in terms of robust stability and performance agree very well with the simulation results. It is also shown that improved performance of the system can be achieved using simple model based controllers     

模糊控制算法在燃气轮机控制中的应用研究

利用模糊控制的快速动态响应和PID控制的稳态性能,设计了模糊自适应PID控制算法,实现了对燃气轮机转速的快速跟踪及稳态控制。仿真试验和工程应用均表明该控制算法的响应时间和稳态精度比常规控制算法有明显改善。     

Adaptive fuzzy control for wind-diesel weak power systems

This work is concerned with the development of an adaptive fuzzy logic controller for a wind-diesel system composed of a stall regulated wind turbine with an induction generator connected to an AC busbar in parallel with a diesel generator set having a synchronous generator. In this work we propose to use an adaptive network based inference system (ANFIS) in order to generate fuzzy membership functions and control rules for the controller. A feedback linearized proportional integral controller is used to provide the required expert knowledge. A controller design process is identified; it consists of generating input-output data pairs to identify the control variables range and initial fuzzy memberships, and then to tune or adapt them using an ANFIS network structure. The controller inputs are the frequency error and its integral for the governor part of the controller, and the voltage and frequency errors for the automatic voltage regulator. These are readily measurable quantities leading to a simple controller which can be easily implemented     

Wide range operation of a power unit via feedforward fuzzy control[thermal power plants]

A two-level hierarchical control scheme for wide-range operation of fossil fuel power units is presented. At the supervisory level, a fuzzy reference governor generates, according to a variable pressure operating policy, the set-point trajectories to command the unit along any load demand pattern. At the control level, a feedforward-feedback control strategy is implemented. The feedforward control path contains a set of multi-input single-output fuzzy inference systems, designed from steady-state input-output plant data. The feedback control path consists of PID controllers in a multi-loop configuration, as currently available at power units. With this strategy, the feedforward path provides most of the control signal for wide-range operation, diminishing the control effort on the PID controllers. The feedback path supplies the complementary control signal component for regulation and disturbance rejection in small neighborhoods about the commanded trajectories. Simulation results demonstrate the feasibility of the control scheme to attain cyclic load-following operation     

Startup optimization of a combined cycle power plant based oncooperative fuzzy reasoning and a neural network

A startup optimization control system for a gas and steam turbine combined cycle power plant is developed. The system can minimize startup time of the plant through cooperative fuzzy reasoning and a neural network autonomously adapting to varying process dynamics due to varying operational conditions, i.e. the ambient temperature and humidity. The operational conditions are taken into consideration by the neural network with a learning mechanism to optimize the schedule. The system is applied to a simulation for a plant with a three pressure staged reheat type 235.7 MW rated capacity, and the following points are seen. (1) The system can harmonize machines operations making good use of the operational margins, i.e. machine thermal stress and NO_x emission. (2) Startup time and energy loss are reduced by 35.6% and 26.3%, respectively, compared with the conventional off-line startup scheduling method     

Dynamic modelling of a low-concentration solar power plant: A control strategy to improve flexibility

This paper deals with a dynamic analysis on a low concentration solar power plants coupled with Organic Rankine Cycles (ORC), which can be an alternative to PV systems because of their capability of providing a smoother electricity production due to their thermal inertia. At least within certain restraints, moreover they are able to exploit diffused solar radiation.The dynamic model of a plant with static Compound Parabolic Collectors and an ORC system, using a rotary volumetric expander, was developed using the simulation tool AMESim. All the main components of the plant are modelled: solar collectors field, heat transfer fluid circuit, heat exchangers and the ORC system. The plant response to the radiation of different days was analyzed to quantify the daily production and the trend of various plant parameters. Real ambient conditions were employed for the simulations by using data obtained by historical series.The results showed that the employment of a volumetric expansion device with variable rotating speed allows the plant to operate at different radiations and ambient temperatures without the need of any storage system or external heat sources. Results can be extended to other applications, such as low temperature waste heat recovery or geothermal systems.