What is the inverter circuit of a UPS
The inverter is an important component of the double-conversion online UPS,
What is the inverter circuit of a UPS
The inverter is an important component of the double-conversion online UPS, which directly affects the reliability of the entire UPS and the quality of the output electrical indicators. The inverter of a UPS is divided into two types of circuits: PWM inverter and cyclic converter.
Sinusoidal PWM inverter
Sinusoidal PWM inverter circuit. The power switch tubes VT to VT form the four bridge arms of the full-bridge circuit, and the output inductance L and capacitor C form a high-frequency filter. The DC power supply of the full-bridge inverter comes from the front-end DC/DC high-frequency converter. When the power switch tubes VT: and VT are turned on under PWM drive, the output current Io supplies power to the load through the filter inductor L, forming the positive half cycle of alternating voltage and current, VT, and VT. When turned off, the energy storage of inductor L is transmitted through the load, D, power supply E and D. The continuous flow is released.
During the negative half-cycle, the power switch tube VT. When VT2 and VT are turned on in a PWM drive mode, the output current Io flows through the load in the opposite direction. When VT2 and VT are turned off, the energy storage of the inductor L is transmitted through D, E, and D. And load freewheeling release. Generate a negative half-cycle voltage and current on the load. Therefore, within one cycle, the load received AC power supply. In this type of circuit, the drive control mode of the power switch tube VT: ~VT generally adopts the PWM method generated by comparing the two-angled wave with the sine wave. The PWM control information generated by comparing the triangular wave with the sine wave
It can be seen that the width of the PWM drive signal generated after the sine wave and the triangular wave pass through the voltage comparator is directly proportional to the amplitude of the sine wave, as shown in Figure 9-8(b). When this PWM drive signal is used to control VT and VT in the inverter shown in Figure 9-7. When it is turned on or off, a series of square wave voltages with the same width as the drive pulse and an amplitude equal to the input DC voltage value of the inverter can be obtained at points A and b of the full-bridge circuit.
This pulse voltage Vab, after passing through the filter inductor L and capacitor C, is restored to a waveform V similar to the reference sine wave according to the modulation pulse width rule, as shown in Figure 9-8(d). When VT and VT operate in the same way under the same PWM drive, the difference is that a negative half-cycle voltage waveform of a sine wave is obtained at the AC output terminal.