Influence of UPS input power factor on power grid and load

Influence of UPS input power factor on power grid and load

UPS as an important part of the power supply system, it is also the load of the power grid, so like other loads, its power factor is also an important indicator of electrical performance to measure whether it is polluting the power grid.When the power factor is low, it means that it absorbs active power from the grid at the same time, but also absorb reactive power, the result is to increase the configuration capacity of the system, affect the power supply quality of the system, reduce the efficiency of UPS, increase the operation cost of UPS.If a UPS with a power factor of 0.8 and input power of 100kVA is configured, the UPS will absorb 80kW of active power and 60kVar of reactive power from the grid when the UPS output is full load, then it is necessary to equip the system with a power capacity of 150kVA.If diesel generators are used for power supply, two to four times the capacity of oil generators will be needed, and of course the capacity and cost of distribution equipment (switches, transformers and transmissions, etc.) will also increase significantly.

The power factor of backup UPS and online interactive UPS is equal to the power factor of the UPS output load. When the power supply is normal, their voltage regulation link does not have the power factor control function, but it does not increase the power factor distortion of the grid itself.The traditional double-transform UPS input AC/DC converter is a controllable rectifier filter circuit, due to the influence of high order harmonics, its power factor and low, only about 0.8, and has nothing to do with the nature of the UPS output load.In the input using the traditional double transform UPS, high frequency rectification and the high frequency series-parallel compensation circuit composed of UPS (Delta transformation technology, it is a series of transformation ideal sine wave current source, is actually equivalent to a typical power factor correcting circuit), the power factor is very high, over a wide range of input voltage and load can be reached 0.99, and has nothing to do with the nature of the UPS output load.

The power factor of the electrical equipment is required by the power sector, especially the high-power electrical equipment, whose power factor should be above 0.95. When it does not meet the requirements, it must be configured with passive or active power factor compensation link and equipment.If UPS AC/DC converter is made up of six pulse rectifier instead of 12 pulse rectifier, and configure corresponding lc filter, the power factor of this kind of UPS can be raised to 0.95 above, but the machine cost will increase by about 20%, and when the input voltage waveform distortion is too large, may cause the oscillation of the input filter, crisis UPS host and the safety of the load.