Current Feedback with Decoupling Scheme for Single-Phase UPS Using a Single Current Sensor

This paper proposes an inductor current feedback plus load current decoupling scheme for single-phase uninterruptible power supply (UPS) applications using a single current sensor. At first, the inductor current feedback with and without load current decoupling are compared in the view point of the output voltage control performance. The output impedance of the entire control system is analytically compared by using the derived model. From this analysis, it is shown that using the load current decoupling is better than not using the load current decoupling in voltage regulation performance. In addition to this analysis, a current sensing technique is proposed to measure the inductor and load current with a single current sensor. The proposed sensing method is shown that a load current and a branch current are simultaneously sampled by using a single current sensor at both the peak and valley point of the pulse-width modulation (PWM) carriers regularly, and then the inductor current and load current are reconstructed with the proposed algorithm in a single PWM cycle. Accordingly, the number of sensor and potential current sensing error can be reduced.