Study of two-cell immune feedback control for water level of boiler drum based on gray prediction
Due to the ‘false water level’ phenomenon in power station makes the traditional control strategy can't be a good solution to the problem, a two-cell immune feedback control strategy based on gray prediction for water level of boiler drum in power station is proposed, which using the function of gray prediction with strong self-adaptability and advanced control functions, and learning from bio-feedback mechanism of the immune system and regulating rule of response process. Through lots of simulation studies, it can achieve a more satisfied control quality with strong robustness and anti-jamming capability. Meanwhile, the structure and algorithm of the control strategy are simple and easy to engineering implementation.
Boiler Drum Level Control Using Internal Model Controller
The water level of boiler drum is one of the crucial control parameters for any process industry which reflects the control of mainly boiler load and feed water indirectly. If the level exceeds the limits, boiler water carryover into the superheater or the turbine may cause damage resulting in extensive maintenance costs. If the level is low, overheating of the water wall tubes may cause tube ruptures and serious accidents, resulting in expensive repairs, downtime, and injury or death to personnel.A rupture or crack most commonly occurs where the tubes connect to the drum. Damage may be a result of numerous or repeated low drum level conditions where the water level is below the tube entry into the drum. Boiler drum is one of the typical multi-input multi-output systems, and also shows high nonlinearities, time varying response and a transportation lag. Conventionally, such system has been controlled using PID (proportional, integral, derivative) controller. Due to presence of nonlinearity (dead time) boiler drum performance can be affected when it is controlled by PID controller.Moreover PID controller produces larger settling time. To have an effective tracking of set point, an internal model based control (IMC) methodology can be implemented.The transfer function for drum level is obtained using mathematical modeling and transfer function for steam flow rate is obtained using system identification tool box.single element control is implemented using PID and IMC controllers.Three element control is implemented using cascade structure in which PID is used in primary and secondary loops.From the performance criteria it has been analysed and found that the IMC controller has better settling time, rise time, peak time and peak overshoot compared to conventional PID controller.
Simulation and control of hybrid renewable energy system connected to the grid
This paper presents a control and simulation of hybrid renewable energy system connected to the grid. The studied system includes a photovoltaic panel, synchronous permanent magnet generator based wind turbine, and a battery for storage energy. The PV array and wind systems are connected to the common DC bus by a boost converter. The battery is connected by a bi-directional DC/DC converter, and then integrated into the AC utility grid via a common DC/AC inverter. In order to extract the maximum energy, a simulation study has been carried out according to the meteorological conditions (wind speed and variable solar irradiance) while maintaining power quality at a satisfactory level. In order to capture the maximum power, a MPPT algorithm is applied for both wind turbine and photovoltaic panel. The modeling and simulation of the whole system has been performed under Matlab/Simulink environment. The obtained results show that the current and the voltage of grid side are sinusoidal and alternative forms, and the power injected to the grid is around the power produced by the hybrid system.