Topic
Load rejection
About: Load rejection is a research topic. Over the lifetime, 591 publications have been published within this topic receiving 6161 citations.
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TL;DR: The simulation results verify that hybrid PV/WG systems feature lower system cost compared to the cases where either exclusively WG or exclusively PV sources are used, and also demonstrate the ability to attain the global optimum with relative computational simplicity.
723 citations
TL;DR: In this paper, a polynomial approximation with respect to time is applied to the waveform of the transients in estimating the inertia constant, and a simple model based on the idea of average system frequency is assumed to estimate the capacity of the generators.
Abstract: A procedure for estimating the inertia constant M(=2H) of a power system and total on-line capacity of spinning-reserve support generators, using transients of the frequency measured at an event such as a generator load rejection test, is presented. A polynomial approximation with respect to time is applied to the waveform of the transients in estimating the inertia constant, and a simple model based on the idea of average system frequency is assumed in estimating the capacity of the generators. Results of the estimation using the transients at 10 events show that the inertia constant of the 60 Hz power system of Japan is around 14 to 18 seconds in the system load base, and the capacity of the spinning-reserve support generators is 20 to 40% of the system load. The proposed procedure is expected to be tested by Kansai Electric Power Company with increased number of events. This effort will contribute to estimate and evaluate the dynamic behavior of the system frequency in loss of generation or load.
224 citations
TL;DR: Turbine start–stop cannot be avoided, but runner life may be improved by minimizing the unfavourable pressure loading on the blades during transients through strategic movement of guide vanes.
Abstract: The present electricity market and the injection of power generated using intermittent energy sources have brought instability in the operation of the power grid. This has resulted in frequent load variations, emergency shut-down and restart, total load rejections, and off-design operation of grid connected hydraulic turbines. The present paper reviews the available literature summarizing the effects of transients on Francis turbine investigated experimentally, numerically, and analytically. Transients create both steady and unsteady pressure loading on the runner blade, resulting in cyclic stresses and fatigue development in the runner. These effects shorten the runner life, increase cost of plant operation, and loss of power generation. The reviewed literature has shown that one start–stop cycle can shorten predefined refurbishment time up to 15 hours. Turbine start–stop cannot be avoided, but runner life may be improved by minimizing the unfavourable pressure loading on the blades during transients thr...
190 citations
TL;DR: In this paper, the simulation system of a typical hydroelectric power plant was developed in a MATLAB/Simulink-based software environment, which has a high water head and a long penstock with upstream and downstream surge tanks and is equipped with a Francis turbine.
Abstract: In this paper, the simulation system of a typical hydroelectric power plant was developed in a MATLAB/Simulink-based software environment, which has a high water head and a long penstock with upstream and downstream surge tanks and is equipped with a Francis turbine. With MATLAB/Simulink, the models of the proposed simulation system are all modularized and visualized, and can be reused easily. No complex codes have been programmed and the proposed simulation system adapts varieties of hydroelectric power plants. The nonlinear characteristics of hydraulic turbine and then inelastic water hammer effect were considered to calculate and simulate hydraulic transients. Moreover, the influences of different parameters, such as hydraulic turbine speed governor proportional-integral-derivative (PID) gains, pressure water supply system, as well as surge tanks, were analyzed for the dynamic performance of hydraulic turbine regulating system. The digital simulations of a sudden full load rejection for an actual hydroelectric power plant in China were performed, and the results indicate that the proposed MATLAB/Simulink-based hydroelectric power plant simulation system is accurate and effective enough to represent and simulate hydroelectric power plant's nonlinear dynamics as well as to design hydraulic turbine speed control system. The proposed simulation system has also been proved to be useful for preliminary designs or assessments of hydropower projects.
171 citations
TL;DR: In this article, a simple algorithm was developed to determine the required number of generating units of wind-turbine generator and photovoltaic array, and the associated storage capacity for stand-alone hybrid microgrid.
Abstract: In this paper, we develop a simple algorithm to determine the required number of generating units of wind-turbine generator and photovoltaic array, and the associated storage capacity for stand-alone hybrid microgrid. The algorithm is based on the observation that the state of charge of battery should be periodically invariant. The optimal sizing of hybrid microgrid is given in the sense that the life cycle cost of system is minimized while the given load power demand can be satisfied without load rejection. We also report a case study to show the efficacy of the developed algorithm.
147 citations