To improve the match between the problem with generators and UPS equipments, try to use the excellent performance of the generator while attention should be primarily on improving the UPS input characteristics and improve the connection between the two on.
According to the UPS capacity, generally a traditional double conversion online UPS supporting the capacity of the generator set than 2 to 4 times. Fact, jaw tears general work in the range of 50% to 80% of rated capacity, and for generating set, its output power may be about 30 percent of the rated capacity. This will not only result in the capacity of the generator set can not take full advantage of the increased investment in equipment, resulting in the phenomenon of the "big horse cart", but they generator set is more prone to failure, maintenance, and reduce the reliability of the generator sets. The reason is that in accordance with the characteristics of the diesel generator, if the long-term work in the small load, the cylinder temperature is low, the normal access of lubricating oil within the cylinder is not completely burned, and the fuel is not fully burn, causing the piston ring at, injector mouth at serious coke, cylinder wear increased, thereby accelerating the production of these parts failure, then the performance of the diesel diesel generator system, exhaust black smoke.
The diesel engine is less than 30% of the rated load, the economy deteriorated. Typically, the generator set work load exceeds 60% of the rated load of the diesel engine is more favorable.
Method to solve this problem is to correct the generator load input characteristics. Below, the specific introduction of several commonly used methods.
(1) to improve the system power factor
There are many ways to improve system power factor, introduces the following.
The first method is to set the auto switch cabinet, then the other load of the generator is first access in the UPS. This method is only applicable to high-power diesel generator system-UPS power supply system. Such a system, in addition to the UPS outside there are other properties of the load. This automatic switch cabinet to implement certain difficulties, and manufacturers maintenance engineers need a separate UPS and generator commissioning.
The second method is to increase the inductive reactance of a permanent to compensate capacitive load, commonly used in parallel wirewound reactors connected in parallel to the generator output board, it is very easy to implement and low cost, but whether it is a heavy load or light load , the reactor is always in the absorption of current and to influence the load power factor. Moreover, regardless of the quantity of the UPS, the quantity of the reactor is always fixed.
The third method is able to compensate for the inductive reactance of the capacitive reactance of the UPS installation of each UPS just contactor (option) in the case of low load controlled reactor access. This method can be more accurately set the reactor, but the number is large and the high cost of installation and control.
The fourth method is installed in the filter capacitor before the contact device, at low load disconnect. As the contact time must be precise, the control more complex, and can only be installed in the factory.
The fifth hybrid active filter the DHM in front of the UPS system configuration, input power factor of the entire power supply system is maintained at above 0.95, the input current harmonic control in less than 10%.