Yrjö Majanne - Academia.edu (original) (raw)

Papers by Yrjö Majanne

Elsevier eBooks, 2007

Industrial power plant is a large scale system. During every day operation the plant is exposed t... more Industrial power plant is a large scale system. During every day operation the plant is exposed to large load disturbances caused by trips and start ups of steam consuming processes. Pressure stability of the plant must be maintained also during the disturbances in order to ensure the trouble free and efficient operation of the production system. The required stability is achieved by using load leveling components for balancing the loads in the steam network. In large scale systems the dynamic simulation is the only possibility to analyze the responses caused by the disturbances and design the process and control system to meet the requirements set for the plant.

IEEE Control Systems Magazine, 1987

Large variations in moisture content and heat value of fuels (peat, bark, coal) can cause stabili... more Large variations in moisture content and heat value of fuels (peat, bark, coal) can cause stability problems in combustion. Some computer-based methods to improve the measurement and control of solid fuel boilers have been developed. A microprocessor-based four-beam infrared moisture measurement system has been developed, which has advantages compared with ordinary two-beam sensors. The paper also presents a digital measuring station for estimating the fuel power of the plant. Furthermore, flame monitors might give a false "flame-off" indication even if the fuel is still burning. The system developed herein estimates the changes of the combustion process by comparing the amount of flue gases generated in the process with the fuel and air feed. By adding this information to the signals obtained from the flame monitoring system, the existence of the flame can be verified. Finally, load level and combustion conditions in industrial power plants vary continuously, and when solid fuels are used, the optimal excess air in the flue gas does not stay constant. We have developed and tested a method for minimizing the losses of the boiler.

Proceedings of IEEE Systems Man and Cybernetics Conference - SMC

ABSTRACT It has proved to be difficult to apply model based diagnosis methods to process industry... more ABSTRACT It has proved to be difficult to apply model based diagnosis methods to process industry because of high development and maintenance efforts and real time requirements (Al applications). Hierarchical structure is one way to make model based systems easier to apply by decomposing the system into small and simple submodels. This paper presents the research work made about the hierarchical fault systems in the Control Engineering Laboratory of Tampere University of Technology (TUT)

Process control and technical diagnosis are typically processed as separate tasks. However, moder... more Process control and technical diagnosis are typically processed as separate tasks. However, modern process control methods and fault detection and identification methods utilize mathematical models which can be applied both to control and to diagnostic purposes to produce a fault tolerant control scheme. Model predictive control method has many properties like easy reconfigurability making it a promising platform for fault tolerant control applications. A model predictive fault tolerant control scheme utilizing Kalman filter based state estimation and parameter identification is discussed. Process parameter estimation with extended Kalman filtering is applied to diagnose the operation condition of the controlled process. In case of certain types of identified faults control algorithm can be modified automatically to meet the changed control goals of the faulty process.

6th IFAC Symposium on Power Plants and Power Systems Control (2009), 2009

Micro-size hydro power plants are commonly used at remote areas to supply islanded AC micro-grids... more Micro-size hydro power plants are commonly used at remote areas to supply islanded AC micro-grids. A typical way to control grid frequency is to manipulate active power dissipated in ballast loads by AC/AC converters. However, these asymmetrically switched thyristor controlled converters consume reactive power degrading the power factor at the generator output. In this paper the operation of a symmetric angle switched, bridged three-phase rectifier and three single-phase rectifiers connected in series with ballast load, are studied to improve the power factor of the system. As a consequence, the objective is to evaluated the use of the three and single-phase rectifiers switched with symmetrical angle to improve the power factor, by reactive power compensation, at the output terminal of the electric generator of µHPPs that use ballast load to regulate frequency.Postprint (published version

1986 American Control Conference, 1986

ABSTRACT Large variations in the moisture content and heat value of the fuels (peat, bark, coal, ... more ABSTRACT Large variations in the moisture content and heat value of the fuels (peat, bark, coal, etc.) can cause stability problems in the combustion. We have developed some computer based methods to improve the measurement and control of solid fuel boilers. A microprocessor based four-beam infrared moisture measurement system has been developed, which has advantages compared with ordinary two-beam sensors. The paper presents also a digital measuring station for estimating the fuel power of the plant. The flame monitors might give a "flame off" indication even if the fuel is still burning. The system we have developed estimates the changes of the combustion process by comparing the amount of flue gases generated in the process with the fuel and air feed. By adding this information to the signals obtained from the flame monitoring system the existence of the flame can be verified. The load level and combustion conditions in industrial power plants vary continuously, and when solid fuels are used, the optimal excess air in the flue gas does not stay constant. We have developed and tested a method for minimizing the losses of the boiler.

The work described in this paper is conducted as a part of Measurement, Monitoring and Environmen... more The work described in this paper is conducted as a part of Measurement, Monitoring and Environmental Assessment (MMEA) program, which is one of the research programs managed by the CLEEN Ltd. The applications were developed in co-operation with Helen and IndMeas and applied in Salmisaari coal fired power plant. The overall goal of the study is to improve usability and economic efficiency of the desulphurization process by providing the operators assistance and to provide the plant operators early information of arising process problems. The goals are to be met through development of new monitoring applications that assist the plant personnel in day-to-day optimization of the process and help avoiding unexpected shutdowns. This paper introduces an indirect method to monitor calcium slurry spraying in a flue gas desulphurization process. The proposed method to monitor functioning of spraying is based on energy balance, and estimates that are only based on physical calculus were utiliz...

IFAC-PapersOnLine, 2020

In this work, the operating cost of the CHP production is reduced by creating optimization model ... more In this work, the operating cost of the CHP production is reduced by creating optimization model to schedule the operation of the heat storage. The objective function of the model targets to minimize heat production costs and maximize profits of electricity production. To implement the optimization model in practice and automate the operation, the heat storage operation in every normal production situation of the CHP production with its real-life process constraints is modelled. To model the time-variant and non-linear system detailed enough, a MILP (Mixed Integer Linear Programming) model was selected and used to create a piecewise linear model of the system. A sliding time window method was used in the optimization to enable the most optimal heat storage operation in practice. The output of the optimization model is the operation plan of a heat storage for the next day, which provides the smallest operating cost for CHP production. The model can be also applied for heat storage investment planning.

Energy Procedia, 2017

District heating networks are commonly addressed in the literature as one of the most effective s... more District heating networks are commonly addressed in the literature as one of the most effective solutions for decreasing the greenhouse gas emissions from the building sector. These systems require high investments which are returned through the heat sales. Due to the changed climate conditions and building renovation policies, heat demand in the future could decrease, prolonging the investment return period. The main scope of this paper is to assess the feasibility of using the heat demand-outdoor temperature function for heat demand forecast. The district of Alvalade, located in Lisbon (Portugal), was used as a case study. The district is consisted of 665 buildings that vary in both construction period and typology. Three weather scenarios (low, medium, high) and three district renovation scenarios were developed (shallow, intermediate, deep). To estimate the error, obtained heat demand values were compared with results from a dynamic heat demand model, previously developed and validated by the authors. The results showed that when only weather change is considered, the margin of error could be acceptable for some applications (the error in annual demand was lower than 20% for all weather scenarios considered). However, after introducing renovation scenarios, the error value increased up to 59.5% (depending on the weather and renovation scenarios combination considered). The value of slope coefficient increased on average within the range of 3.8% up to 8% per decade, that corresponds to the decrease in the number of heating hours of 22-139h during the heating season (depending on the combination of weather and renovation scenarios considered). On the other hand, function intercept increased for 7.8-12.7% per decade (depending on the coupled scenarios). The values suggested could be used to modify the function parameters for the scenarios considered, and improve the accuracy of heat demand estimations.

IFAC Proceedings Volumes, 1993

A schenll' fl)[ a Jiagn()st ic .JulollnmOllS control strategy of a power plant feed water process... more A schenll' fl)[ a Jiagn()st ic .JulollnmOllS control strategy of a power plant feed water process is discussed. lne control system is based on Model L>redictivc Control strategy. M PC' , applying diagnostic information to oplimisc the control result and the availability oftht• process. In this papt'r cOlldition monitoring and diagnostics are carried oul by diagnostic algorithms based on models describing the general propertiL'.\ and characlt"ristics of monitored components as a function of operating poi Ills and I imc. However, information from any kind of Jiagl}(ISis system C~Ul he applicd. The diagnostic information is used to update the constraints and control increment weights in the cost function unuc:r which the MPt• system calculates optimal control signals. The proposed system is able to change the dynam.ics and the structure of control system automatically during the operation of the pr ocess, if any malfunctions have been detected.

Control Engineering Practice, 2017

New emission regulations will increase the need for inexpensive NOx emission monitoring solutions... more New emission regulations will increase the need for inexpensive NOx emission monitoring solutions also in smaller power plants. The objective in this study is to find easily maintainable and transparent but still valid models to predict NOx emissions in natural gas fired hot water boilers utilizing existing process instrumentation. With a focus on long-term applicability in practical installations, the performance of linear regression is compared in two municipal 43 MW boilers with three widely used nonlinear methods: multilayer perceptron, support vector regression, and fuzzy inference system. The linear models were the most applicable providing the best estimation results (relative error of <3 % in all cases), generalizability and simplicity. Therefore, the approach fulfils the requirements of the Industrial Emission Directive and is valid to be applied as a soft sensor in PEMS 1 applications in practise. However, each boiler model should be identified individually.