Le Wei

Evaluation of energy saving and emission reduction effect in thermal power plants based on entropy weight and PROMETHEE method

In order to evaluate scientifically and reasonably the energy saving and emission reduction effect in thermal power plants, on the basis of the existing evaluation index system construction principle, and based on the entropy weight and the PROMETHEE method, a comprehensive evaluation system for energy saving and emission reduction in thermal power plants is established: The entropy weight method is used to determine the objective weight of each index, so that the interference of human subjective factors in the evaluation process can be effectively avoided; and the PROMETHEE method is employed to establish the assignment precedence relation based on criterion with linear preference, and then calculates the positive flow, negative flow and net flow of each thermal power plant, then sorts the effect of energy saving and emission reduction according to the value of net flow. In this paper, taking five thermal power plants in a certain region as an example and nine relevanted indexes of the operation were selected to construct the comprehensive evaluation system of energy saving and emission reduction.

Reliability evaluation of thermal power units based on AHP and ELECTRE-III

The security and stable operation of thermal power units plays a very important role in a power system, so the reliability evaluation of thermal power units has become a critical problem. By combining the advantages of the Analytic Hierarchy Process (AHP) and the Elimination et Choice Translating Reality (ELECTRE) III, a reliability evaluation method for thermal power units based on AHP and ELECTRE-III is put forward. A new method of proposed “net” procedure is presented to rank these scheme with valued outranking relation. The advantages and disadvantages of the scheme are expressed from the harmony index and the discordance index, which constitute valued outranking relation by ELECTRE III and weights of criteria are determined by AHP. This method is clear and easily to be accepted by the decision maker with the persons actual decision thinking of human being. And the results of the example analysis show that the method is feasible for the reliability evaluation of thermal power units.

Application of improved gravitational search algorithm in PID control for boiler drum water level

The boiler drum water level reflects the equilibrium relationship between the steam load and the water supply of the drum boiler, which is an important monitoring parameter in boiler operation. Its object has the characteristics of non-self-balancing and pure delay, and its control quality directly affects the safe operation of a boiler-turbine unit. Based on the improved gravitational search algorithm, the parameter optimization method of the main controller is put forward according to the wide-used cascade control structure of drum water level in power plant. The gravitational search algorithm has the advantages of simple process, little parameter setting, strong universality of the algorithm, but easy to fall into local optimum. Combining with the memory function of particle swarm optimization algorithm and the high precision of other improved algorithms, the formulas of position and velocity are improved, an improved gravitational search algorithm (IGSA) is obtained. By applying this method to the optimization control of the drum water level, and comparing with trial-and-error method (TEM), genetic algorithm (GA), and the standard algorithm (GSA), simulation tests are carried out to verify its effectiveness.

Identification of the superheated steam temperature system based on the variable step improved fruit fly optimization algorithm

In order to establish an accurate model of the superheated steam temperature, the experimental data of a certain power plant was obtained by the method of field experiment which was preprocessed, and the paper proposed variable step improved fruit fly optimization algorithm to identify the model of superheated steam temperature. The ability of global search and local optimization is enhanced through search step size of the algorithm based on the iterative error and adding relaxation factor to the algorithm, and so the identification accuracy of the algorithm is improved. Finally, identification results of the simulation was compared with the simulation results which do not improve fruit fly optimization algorithm that in different range of random initial position and step length, and compared the simulation results with the field experimental data at the same time. The results show that variable step improved fruit fly optimization algorithm have the advantages that the demand for random initial position and step length is not high, identification error is small and highly precision; the simulation result of variable step improved fruit fly optimization algorithm was consistent with actual characteristic of unit which verified the practical effectiveness of the algorithm.

Competitive ability evaluation for generation enterprises based on combinational weight and improved TOPSIS

In allusion to the problems of competitive ability evaluation for generation enterprises, the improved TOPSIS method, which is based on combinational weight, is proposed. The objectivity of the entropy method and the practical rationality of the AHP is combined, through the entropy method and analytic hierarchy process method combination weighting. The vertical distance, instead of Euclidean distance evaluation, is adopted in case of the shortcomings of TOPSIS method in comprehensive evaluation. The rationality and the reliability of the proposed method are proved by combining with the concrete examples.

Design of power control system for thermal power units based on two degree of freedom control

For the power control system of thermal power unit, a two degree of freedom control structure is designed and the parameters of the controller are determined. In the process of design, the problem that the mechanical power of turbine can not be measured is solved by changing the structure and other methods. Compared with other two kinds of control system, the classic feedforward-feedback control and the inner model control, the simulation results show that the two degree of freedom control system can meet the requirements of system well and the performance is better than the other two.

A novel IMC cascade control structure of super-heated steam temperature system for super-critical coal-fired boilers

Super-heated steam temperature control system is very important for the safe and economic operation of super-critical coal-fired boilers. Basing on internal model control (IMC) method, a novel super-heated steam temperature control structure is presented. In this structure, two internal model controllers are cascaded to guarantee the accuracy and disturbance rejection performance of whole system. The parameters tuning steps of the two controllers are also given. To verify the effectiveness, three simulation tests are taken. The simulation results show that the proposed structure has good tracking, anti-disturbance and load adaptability performances.

Backstepping-based nonlinear adaptive control for boiler-turbine units

Adaptive nonlinear backstepping controllers for a typical nonlinear boiler-turbine unit model with several uncertain parameters are presented in this paper. The first step consists in system model processing, which involves adding integral actions to the basic backstepping algorithm to obtain zero static errors. Then, to follow the premise of backstepping, the system is divided into two sub-systems and the controllers are designed separately. During the design process, some virtual variables are introduced to define Control Lyapunov Functions (CLF) based on adaptive backstepping, then the nonlinear control laws of the system and adaptive updating laws of these uncertain parameters are deduced. At last, three simulation tests on a 500 MW boiler- turbine units in different operating conditions are done to prove the dynamic performance, disturbance rejection, and robustness of this system.