Abstract
For the operation of the supercritical once-through boiler generation units, the control of the temperature at intermediate point (IPT) is highly significant. IPT is the steam temperature at the outlet of the separator. Currently, PID control algorithms are widely adopted for the IPT control. However, PID cannot achieve the optimal performances as the units’ dynamic characteristic changes at different working points due to the severe nonlinearity. To address the problem, a new control algorithm using affine nonlinear system is adopted for a 600 MW unit in this paper. In order to establish the model of IPT via affine nonlinear system, the simplified mechanism equations on the evaporation zone and steam separator of the unit are established. Then, the feedback linearizing control law can be obtained. Full range simulations with the load varying from 100% to 30% are conducted. To verify the effectiveness of the proposed control algorithm, the performance of the new method is compared with the results of the PID control. The feed-water flow disturbances are considered in simulations of both of the two control methods. The comparison shows the new method has a better performance with a quicker response time and a smaller overshoot, which demonstrates the potential improvement for the supercritical once-through boiler generation unit control.
Highlights
Developing supercritical once-through boiler generation units [1] is of great importance due to the threats of global warming and severe air pollution
To compare it with t (s) the optimal control, the PID control is applied in this paper to control of intermediate point (IPT)
As the model via affine nonlinear system is state equation which cannot be simulated with PID controller directly, it is essential that the system transfer function should be calculated by point approximation linearization
Summary
Developing supercritical once-through boiler generation units [1] is of great importance due to the threats of global warming and severe air pollution. The supercritical units have the advantage of high power generation efficiency up to 45%. They are able to maintain relatively high efficiency even at low loads. High performance is required for the IPT control, as 1∘C variation of IPT could end up with fluctuations of main-steam temperature around 8∘C generally. The variation of main-steam temperature has profound effects on the stability, security, and efficiency of supercritical units. More and more distributed energy is integrated into the grid Renewable energy such as solar and wind power has bad capacity of peak regulation which leads to the increasing requirement of load regulation for the traditional units.
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