What are the conditions for the parallel use of two generator sets? What device is used to complete the parallel operation?

The condition for parallel use is that the voltage, frequency and phase of the two machines are the same. Commonly known as "three simultaneous." Use a dedicated parallel device to complete the parallel operation. It is generally recommended to use fully automatic and cabinets. Try not to manually parallel. Because the success or failure of manual parallelism depends on human experience. The author has been vocal about more than 20 years of experience in electric power work. The reliable success rate of manual paralleling of diesel generators is equal to zero. It is never possible to apply a small power system with the concept of manual parallel power supply for the mains power system, because the protection levels of the two are completely different.