Nikhil Pathak

Study the effect of system parameters on controller gains for discrete AGC of hydro-thermal system

This paper investigates the effect of system parameters on optimum controller gains for discrete data automatic generation control of an interconnected power system. The optimum gains of the system have been analyzed for different values of sampling periods in discrete mode of operation. The effect of different loading conditions on the optimum gains is also investigated. As we know that load varies widely throughout the day. The optimum gains calculated for the nominal loading may not be optimum at other loading condition. Therefore the system has been analyzed for different loading conditions. The load variation of 30-100% has been considered for the investigation. This paper also deals with the proper selection of speed regulation parameter R for the design of speed governor. The hydro-thermal system has been taken for investigation. The dynamic responses are obtained for 1% load perturbation in thermal area system. The Matlab/simulink software is used for the simulation work.

Discrete Data AGC of Hydro-Thermal Systems under Varying Turbine Time Constants along with the Power System loading Conditions

The paper deals with the discrete data automatic generation control (AGC) of two area hydrothermal power system operating at different loading conditions. The power system load varies considerably throughout the day and accordingly, thermal and hydropower systems are scheduled to operate at different loading conditions. It is found that steam as well as hydro turbine time constants vary as the power system loading varies. In earlier AGC studies, these parameters are considered to be constant, irrespective of power system loadings. This paper studies the dynamic performance of hydrothermal power system considering the variation of these turbine time constants along with the nominal loading of power system. The studies have been conducted for linear as well as nonlinear models of speed governor and hydroturbine models recommended by the IEEE committee. It is also discovered that conventional empirical formula-based hydraulic governor settings recommended by the IEEE working group are completely unacceptable for hydrothermal power system. A maiden attempt is made to optimize the hydraulic governor settings simultaneously along with the controller gains using metaheuristic algorithm. The comparison of system dynamic responses reveal that optimization-based hydrogovernor settings give the better dynamic performance in case of linear as well as nonlinear models of hydro system, and therefore are strongly recommended over the conventional settings. The paper also deals with the optimum selection of sampling periods for discrete data AGC operation of hydrothermal systems.

Real-time automatic generation control considering communication delays using linear matrix inequalities

This paper investigates the effect of communication delays on dynamic performance of automatic generation control (AGC) of thermal power system. Field data of power system i.e. frequency and tie-line power deviations are transmitted over the dedicated data links to control centres of the plant. Sometimes these data links introduce communication delays in between and degrade the dynamic performance of the AGC system. These communication delays have not been considered in the existing models of AGC system. This paper, considers the effect of these communication delays and presents a realistic model for AGC system. The global controller has been designed for the centralized control scheme using linear matrix inequalities (LMIs) technique. The system has been studied in real-time environment, using three personal computers (PCs) connected in series named as real-time three PC system (RTTPS).

Mitigation/suppression techniques of very fast transient over voltages of a gas insulated substation

There are different switching operations takes place in the gas insulated substations (GIS). These switching operations generate the very fast transient overvoltages (VFTOs) which are dangerous to the substation equipments. Sometimes these transient overvoltages may cross the basic insulation level of gas insulated substation. Hence it is very important to mitigate these transient overvoltages. In this paper, the mitigation techniques of transient overvoltages have been discussed. These mitigation techniques have been compared to determine the effectiveness of these techniques. The simulation results shows that the VFTOs can be reduced upto 1 p.u. with the reduced level of oscillation frequency. The simulation work has been done using the PSCAD/EMTDC software.

New optimization criterion for load frequency control of power system

The new optimization criterion has been proposed for the tuning of controller gains of load frequency control (LFC) of interconnected hydro-thermal power system. Dynamic performance of LFC system relies upon the optimization criteria used to find the values of optimum controller gain settings. This paper presents new optimization criterion for controller gains and its dynamic performance has been compared to the existing optimization criterion. The generation rate constraints (GRCs) of 3% per minute for thermal power system and 360% per minute to increase and 270% per minute to lower down the generation level of hydro power system have been considered. The dynamic responses have been obtained for 1% load disturbance in thermal area system. As linear model of LFC system is considered therefore such a small disturbance will be sufficient to draw the inferences.