Boiler-turbine-grid Coordinated Control Applied To Unit Plant

In the configuration of the power system, generator sets running and grid’s power and frequency regulation are two relatively independent control objectives. Each has a standard for its optimization. Generator sets take boiler-turbine regulation characteristics as the basis, set the unit itself safely and stably operating as the control target, without considering the high demand of grid for steam turbine power adjustment. Grid regulation takes steam turbine power conditioning and AGC power scheduler as the basis, set meeting region grid load demand and control performance standard(CPS) for the control target, without considering the expense of the boiler when meeting steam turbine’s energy requirements. This is the main contradiction for the coordination of existing control systems.In order to consider the coordinated control of boiler-turbine-grid on the unit plant, using small deviation linearization to linearize the unit plant model including infinite power grid, the turbine, and the drum boiler. Then we analyze frequency characteristics of the linear system. The results showed that the bands of the grid frequency and the main steam pressure in response to the valve opening instruction are completely different. Taking the valve opening instruction as the single input can optimize the grid frequency and the main steam pressure at the same time.For the coordinated control, the ideal coordinated running states between turbine and boiler is like this, when the boiler is in high energy state and the turbine needs to produce more power, then open the valve at the convenience, to strengthen the energy supply of the boiler, thus bringing down the main steam pressure. The turbine can take the initiative to adjust the way increasing or decreasing power output according to CPS standard when participate in the grid adjusting the power demand, no longer passively waiting for the AGC system’s power scheduling instruction. This as guidance, designed two kinds of boiler-turbine-grid coordination controller including the switch controller based on boiler energy state and the linear quadratic optimal controller guided by the CPS standard, taking into account the state of the main steam pressure. Simulation results show that the two controllers have good performance on unit model.Since all power plant units are run in parallel, there is no coupling among the units, suppose that if we can achieve optimal control on each unit, each part gets optimized, then the overall grid optimization can be achieved. On the region multi-units system including parallel operation units, inter-regional power tie-line, and this region’s AGC control system, the coordination controller is applied to each unit, the results show that the assumption is correct. Simulation results show that, although the switch controller adaptability in multi-units system is not as the optimal controller, but the main steam pressure have been well suppressed for all the units, and the evaluation to the performance of the power grid gets good improvement, achieve a win-win grid-source control target.