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Coordination control system of Ultra-supercritical unit is the core of thermal
power unit control system [3]. However, it needs to solve the following diculty:
(1) Coupling between boiler and turbine. (2) Strong nonlinearity. (3) Large delay.
Due to the above control diculty, the parameters of the coordination control
system based on PID controller suffer from a large fluctuation in the process
with changing load. For Model predictive control can effectively deal with the
coupling and time-delay problems, it has been applied successfully in chemical
industry and many other fields. It also began to be applied to the power plant
control. J. A. Rovnak and R. Corlis [4] discussed the DMC method in the con-
trol of generating units in both theoretical and practical. U. C. Moon and K.
Y. Lee [5] presented an adaptive DMC method for traditional unit and used
a three order model as a simplified model. For superheater outlet temperature
and reheater outlet temperature control problem, U. Moon and W. Kim [6] built
a 44 input output model, and presented the simulation results. For the system
with strong nonlinearity, Model predictive control based on a single model can't
guarantee a good performance. Multiple model method has the characteristics of
intelligent control and can combine the classical modeling, control method with
advanced control ideas. Goodwin and Narendra developed the stable multiple
model adaptive control. M.Y.Fu developed direct multiple model adaptive con-
trol method [7]. Z. Binder constructed multiple model controller based on the
probability weighted form. Narendra developed adaptive control of discrete-time
systems using multiple models, which belonged to indirect multiple model con-
trol [8]. However, there aren't many researches about controller based on MCPC
for the coordination control of Ultra-supercritical unit.
The multiple model predictive control method is explored to solve the non-
linear control problems for the control of process with changing load in this
paper. The paper is organized as following. A kind of Ultra-supercritical unit
coordination control system with three inputs and three outputs is analyzed in
section 2. In section 3, the multiple models MCPC with double-layer structure
is introduced and several groups of step response models at different load point
are established. Section 4 presented the simulation results. Conclusions are given
in section 5.
2 Ultra-supercritical Unit Coordination Control System
Analysis
This paper simplifies the coordination control system to a multivariable control
system with three inputs and three outputs. The three input variables were the
fuel flow (Kg/s), the governor valve opening (%) and the water flow (Kg/s).
And the three output variables were the steam pressure (MPa), load (MW),
and steam temperature (
). Their interaction relations were shown in Figure 1
[9]. Coordinated control system of Ultra-supercritical unit is a typical nonlinear
system. Once Load differs by 10%, the model will have a large deviation. Step
disturbance can be applied at different load work point to establish several groups
of step response models of the system. The input output relationship of the
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