Performance Comparison of Three PWM Techniques for Three-Phase On-Line UPS with Switched Inductor Z-Source Inverter

Uninterruptible Power Supply (UPS) is provided between a primary power source and the input of the equipment to be protected, to eliminate the effects of a temporary power failure and power quality. To extend voltage adjustability, the proposed UPS with Switched Inductor Z-Source Inverter (SLZSI) employs a unique Switched Inductor(SL) impedance network to couple the inverter circuit and the power source. The proposed SLZSI fed UPS has the voltage boost capability through the shoot through zero state which is not available in traditional UPS system with step-up transformer, boost chopper. A very short shoot-through zero state is required to obtain high voltage boost, so the output voltage and current waveform distortions are reduced. The voltage stress of the proposed UPS with SLZSI is also minimized. The three Pulse Width Modulation (PWM) control techniques like Simple Boost (SB) PWM control, Maximum Boost (MB) PWM control and Third Harmonic Injected Maximum Constant Boost (THIMCB) PWM control are implemented and the results are compared for the performance analysis of three-phase UPS systems with SLZSI. Experimental setup has been developed for the proposed UPS with SLZSI by implementing THIMCB PWM control algorithm and measurements were taken to validate the theoretical and simulation results.