Study On Grouping Control Strategy Of AGC Units

In power system, automatic generation control is a universally applied technical means. It is one of the most important control functions in energy management system. The modern power system becomes larger and larger, more and more complicated, so that only automatic generation control can guarantee the quality of system frequency and operation safety. The effect of automatic generation control directly influences the quality of the system frequency and system operation safety. Therefore automatic generation control strategy is a very im-portant issue of dispatching automation. Since the birth of the automatic generation control in1950s, new automatic generation control strategies have been proposed constantly.Since the great difference of AGC performance among units in power system, if all units take the same control strategy, there would be some problems. The fast response units will approach their adjustive upper (or lower) limitation when load climbs upward (or downward) for a long time, and then power system will lose its rapid adjustable capability. Under normal circumstance, the power system frequency changes in the vicinity of rated frequency and the direction of frequency deviation changes frequently. The unit with good performance can re-spond regulation instructions quickly and track load variation. Meanwhile unit with bad per-formance maybe still execute former load instruction when direction of regulation instruction changes because of its long AGC period. This fact leads to reverse between unit power regu-lation and system regulation demand.To solve the above problems, this paper states the basic principle of automatic generation control at first, and introduces the primary and secondary frequency regulation of power system, mode and control process of automatic generation control. Then this paper analyses deeply the AGC performance of generator units and the variation law of daily load in power system. This paper points out some problems of traditional control strategy, that is exhaustion of rapid adjustable capability in power system and profitless reverse adjustment of units, by comparing AGC performance of different units (such as hydro power unit and thermal power unit, thermal power unit and thermal power unit) and analysing variation law of daily load in different period. And then this paper propose a new idea of AGC units grouping and time-sharing control, that is in load emergency period adjustive capability of all units in system should be fully used for tracking load and in the load steady period the power of fast units is replaced by slow units’so that power system can keep certain quick adjustable capability and reduce the units profitless reverse adjustment to system regulation demand. At the end of this paper, it is proved to be feasible and effective via simulation study. The result shows that with this control strategy, in load emergency period rapid adjustable capability in system can be fully used, and frequency deviation of system can be controlled in allowable range, and in the load steady period the system can keep certain rapid capability and reduce the units profitless reverse adjustment to system regulation demand effectively.