Why Kehua UPS can Realize the High Efficiency? -Three-level Technology for UPS


Famous for its high efficiency and low THDV, Kehua UPS is always trusted by our customers with its excellent performance. When we talk about how to realize the high efficiency, the three-level inverter technology always plays an important role.

What is three-level technology? Why it can realize the high efficiency? Let’s start explaining its structure.


The three-level circuit is more complex in topology. Compared with the traditional two-level circuit which can only output high and low levels, three-level circuit can output high and low levels by turning on the upper and lower tubes, and output zero level through the clamping action of the diode, a total of three level states. It shows the advantages of current ripple reduction, low THDV, high efficiency, low electromagnetic interference, and high reliability.


 (1)Reducing the withstand voltage level of power devices, higher transfer efficiency.

When the power devices are working in the three-level circuit, the withstand voltage of power devices is only half of the DC bus voltage. The low-voltage power devices can reduce the switching loss and improve the conversion efficiency.


 (2)Lower switching frequency , higher efficiency.

The three-level circuit is able to output a waveform with better sinusoid at a lower switching frequency. The lower switching frequency can reduce the switching loss and improve the conversion efficiency.


 (3)Reducing the voltage and current conversion rate, higher efficiency, less electromagnetic interference.

when the multi-level inverter switches, the voltage change rate dv/dt and current change rate di/dt will decrease with small voltage change, which can reduce the electromagnetic interference generated by the power electronic device. Meanwhile, it can reduce the switching loss and improve the conversion efficiency.


 (4)Lower THDV

The three-level circuit outputs a multiple voltage level of step waveform which is much more similar to sine wave. It will bring fewer harmonics and reduce the THD of output voltage.


 (5)Higher reliability of IGBT:

Due to the low switching loss of IGBT, the safe working area of IGBT with the same current capacity is different. The safe working area of the three-level IGBT is obviously wider than that of the two-level IGBT. When there is an abnormally large current in an instant or a short circuit in circuit, the three-level IGBT can withstand longer time than the two-level which makes it more reliable.


In conclusion, the three-level inverter technology can provide higher efficiency, lower THDV and reliability for UPS. In UPS industry, this technology is mostly used in medium and high-power products, while Kehua has applied three-level inverter technology for its entire series UPS from 1kVA to 1200kVA. With 30+ years’ experience in power electronics technology, Kehua is devoted to providing the high-efficient and green power guarantee in all-scenario application.

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