The traditional parallel mode relies on manual parallel, which is time-consuming and laborious, and the degree of automation is low, and the choice of parallel timing has a great relationship with the operation skills of the parallel operator. There are many human factors, and it is easy to appear large impulse current, which causes damage to the diesel generator set and shortens the life of the diesel generator set. Therefore, Cummins introduces the working principle and circuit design of the automatic synchronous parallel controller of diesel generator set. The synchronous parallel controller has simple structure, high reliability and high engineering application value.
The ideal condition for the synchronous parallel operation of the generator set and the power grid or the generator set is that the four state conditions of the power supply on both sides of the parallel circuit ，breaker are exactly the same, that is, the phase sequence of the power supply on both sides of the parallel side and the system side is the same, the voltage is equal, the frequency is equal, and the phase difference is zero.
The existence of voltage difference and frequency difference will lead to a certain exchange of reactive power and active power on both sides of the grid connection moment and connection point, and the grid or generator set will be affected to a certain extent. In contrast, the existence of phase difference will cause damage to the generator set, which will cause sub-synchronous resonance and damage the generator. Therefore, a good automatic synchronous parallel controller should ensure that the phase difference is “zero” to complete the grid connection, and in order to accelerate the grid connection process, allow a certain range of voltage differences and frequency differences.
The synchro module adopts the analog circuit control system, adopts the classical PI control theory, has the advantages of simple structure, mature circuit, good transient performance and so on. The working principle is: After receiving the synchronous input instruction, the automatic synchronizer detects the two AC voltage signals on the two units to be combined (or a grid and a unit), completes the phase comparison and generates a corrected analog DC signal. The signal is processed by PI arithmetic circuit and sent to the parallel end of the electronic speed control controller of the engine, so that the phase difference between one unit and another unit (or the power grid) disappears in a short time. At this time, after the synchronization detection circuit confirms the synchronization, the output closing signal completes the synchronization process.
Post time: Oct-24-2023