Structure Analysis And Disturbance Rejection Design Of The Coordinated Control System For Power Generation Units

Coordinated control is the link between power generation units and power grid and its quality reflects the operation level of power plants. As a result, both researchers and engineers pay a lot of attention to the problem. This thesis studies the structure and disturbance rejection design of boiler-turbine units using partially decentralized control and linear active disturbance rejection control methods, with the motivation to improve the performance of the coordianted control system.In control structure analysis, partially decentralized control (PDC) via expansion procedure is studied for power generation units. PDC is preferred when decentralized controllers cannot achieve the desired performance and advanced multivariable controllers are difficult to implement due to their complexity for a strongly-coupled multivariable process.. First, the structure of partially decentralized controllers is analyzed, and then an independent design method is applied to design non-square decentralized controllers by the non-square internal model control (IMC) principle, which are transformed to partially decentralized ones. The stability of the closed-loop control system is guaranteed via the expandedμinteraction measure. The method is applied to a 500 MW unit and the results show that the partially decentralized controller can achieve comparable performance as the centralized one; however, it has a simpler structure and is easier to implement and tune.In disturbance rejection control, a novel scheme for the coordinated control of boiler-turbine units is presented using the linear active disturbance rejection control (LADRC) and a decoupling compensator. A decoupling compensator is first designed based on a simplified linear boiler-turbine model which captures the essential dynamics and interaction of a unit, then LADRCs for boiler and turbine are designed separately to further reduce the coupling by taking it as disturbance. Since LADRC estimates real-time disturbance via extended state observer (ESO), it can eliminate disturbance quickly via a disturbance compensation independent of the accuracy of the mathematical model of the plant. The method is applied to the same 500MW unit and the results show that it can provide good decoupling, strong robust ability and disturbance rejection; moreover, it is also easy to tune and implement.