A new state feedback

Boiler and turbine are main equipment of coal-fired power generation units, so the coordination control plays an important role in improving the performance of the generation system. The nonlinear control method which has been used in the coordinated control system can solve the optimizing operation problem over large range working point effectively. It becomes the hot topic in recent years. Backstepping method [

In this paper, firstly, the nonlinear coordinate system for boiler and steam turbine is transformed into a linear time-varying system with external disturbance. Then the

The model of boiler-turbine is the foundation of coordinate control. The Astrom model [

Considering the actual situation of the regulator and dynamic process itself, the opening position of the regulator and its changing rate are limited [

The opening degrees of the three regulators should satisfy the conditions below:

The output of the system is the drum pressure ^{2}), the output power

Set

At the selected working point

The coefficient matrix of model above will change with the states of working points selected, so that the whole system is transformed into a linear system with time-varying parameters. The opening degrees of the three regulators are restrained by the following conditions:

The actual system with external disturbance is considered, so the state feedback

The

For the system (

Combining (

The block diagram of the standard state feedback

The state feedback

The block diagram of the standard state feedback

In this paper, an improved particle swarm optimization algorithm is applied to seek the solution of Riccati equation, rewriting Riccati equation (

The fitness value of the objective function is

The particle swarm algorithm regards each individual as a particle with no weight and volume, which flights in the

The particle number of populations is

In this paper set the objective function of minimizing problem to be

Set the best position of all particles recorded as

The standard evolving equation of particle swarm algorithm can be described as follows:

For (

Traditional PSO algorithm has a potential property which would cause the algorithm entrapping into a local optimum. In addition, the parameters of traditional PSO algorithm have stronger dependence. In order to eliminate the stagnation and avoid premature convergence, the differential evolution (DE) algorithm is introduced, and an improved PSO algorithm guarantees the populations converging to the global optimal solution continuously.

DE algorithm has characteristics of remembering individual optimal solution and can share the information in populations [

In this paper a six-dimensional

Compare the target individual

The improved particle swarm optimizing algorithm by introducing differential evolution algorithm can eliminate stagnation and avoid premature convergence, and the procedure is as follows.

Initialize a population which contains

The dimension of the particle is six which is judged by the matrix

Compute the fitness value

Compare the fitness value of each current particle with the

The position and speed of each particle implement evolving according to (

Mutation and crossover operation are carried out for the position of particle according to (

If the maximum number of generations has not been reached, or a good enough fitness value has not been obtained, return to Step

The flow chart of improved particle swarm optimizing algorithm is shown in Figure

The flow chart of improved particle swarm optimizing algorithm.

Set

At ^{2}).

At

At ^{2}).

At

In all process the drum water level is stable in 0 (m), where

The response of the system outputs with two particle swarm optimizing algorithms is shown in Figures

Output response curve of drum pressure.

Output power response curve.

Output response curve of drum water level.

It can be seen from Figures

The simulation results show that the method can guarantee the closed-loop system asymptotical stability in a large range working point. The system has strong robustness for external disturbance.

In this paper, a new state feedback

The authors declare that there is no conflict of interests regarding the publication of this paper.