供配電系統(tǒng)外文翻譯(2)-其他專業(yè)-全文預(yù)覽
【正文】 nerating units and their loadings,the connected loads, parallel paths for power to flow on other lines, and their relative impedances. For satisfactory operation of a power system, the frequency should remain nearly constant. Relatiyely close control of frequency ensures constancy of speed of induction and synchronous of speed of motor drives is particularly important for satisfactory performance of all the auxiliary drives associated with the fuel, the feedwater and the bustion air supply system. In a work, considerable drop in frequency could result in high magizing currents in induction motors and transformers. The extensive use of electric clocks and the use of frequency for other timing purpose require accurate maintenance of synchronous time which is proportional to integral. A change in active power demand at one point is reflected throughout the system by a change in frequency. Because there are many generators supplying power into system, some means must be provided to allocate change in demand to the generators. A speed governor on each generating unit provides the primmy speed control function, while supplementary control origination at a central control center allocates generation. In an interconnected system with two or more independently controlled areas, in addition to control of frequency, the generation within each area has to be controlled so as to maintain scheduled power interchange. The control of generation and frequency is monly referred to as loadfrequency control (LFC). The control measures of power and frequency include: (1) Regulation of the generator speed governor (2) Underfrequency load shedding (3) Automatic generation control (AGC) AGC is an effective means for power frequency control in largescale power systems. In an Interconnected power system, the primary objectives of AGC are to regulate frequency to the specified nominal value and to maintain the interchange power between control area at the scheduled values by adjust the output of the selected generators. This function is monly referred to as loadfrequency control. A secondary objective is to distribute the required change in generation omong units to minimize operating costs. For efficient and reliable operation of power system, the control of volta
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