The Microprocessor-based Automatic Quasi-synchronizing Device

Quasi-synchronizing parallel is an important operation in the power system. Quasi -synchronization should parallel synchronous generator into the power system smoothly and rapidly. The voltage between the system and generator must be small enough to ensure minor current in the armature winding of generator, avoiding the impact to the coupling shaft. This means the difference of magnitude, frequency and phase of the voltages between the two sides of breaker must be small enough. Microprocessor-based automatic quasi-synchronizing device is the most representative kind of paralleling device.The microprocessor-based automatic quasi-synchronizing device designed in the paper measures the magnitude and frequency of the generated voltage of synchronous generator and of the power system directly and accurately. The measured quantities are compared and the result of the comparison determines the adjustment of the synchronous generator. The criteria of comparison can be set by the keyboard finely and flexibly. The differential frequency determines whether to increase or to decrease the rotate velocity of the synchronous generator and the differential voltage determines the adjustment of the generated voltage.The differential phase must be zero at the moment of closing breaker when the frequency and magnitude of the synchronous generator is satisfied. The device detects the differential phase accurately by a new circuit designed by author. The design of the hardware and software ensures the breaker closing at the just moment of zero- differential phase.Closing the breaker under the rigid condition of the magnitude, frequency and differential phase ensures paralleling the synchronous generator into the power system smoothly and rapidly without undesired large strike closing current.The device detects the phase order of both side of voltages before the beginning of the quasi-synchronizing process and detects the closing time interval of the closingcircuit on line. The closing time is stored into the EEROM of the device as the reference to adjust the ahead-time of the next paralleling operation adaptively.