Carrier-Based Signal Injection Method for Harmonic Suppression in PWM Inverter Using Single DC-link Current Sensor

This paper proposes a method to reconstruct the three phase currents of voltage source PWM inverter using single current sensor. In this method a small voltage vectors are injected on reference voltage vectors to guarantee minimum duration of effective voltage vectors in SVPWM switching patterns. This causes undesirable harmonic terms in voltages and currents. In order to reduce the harmonic terms, the injected voltage vectors are selected to have minimum magnitude. The injected voltage vectors consist of two adjustment vectors. One is for guaranteeing measurement timing and the other is for compensating vector to sustain the average value of reference voltage vector. Two minimal injection voltage vectors are added to the reference voltage vector at the carrier frequency in first and later period of a PWM period. In this paper, it is shown that the sequence of them is closely related to the magnitude of the harmonic terms and that a scheme to determine a proper sequence is proposed with which the magnitudes of harmonic terms are kept small. The simulations and experimental results are given to show the effectiveness of the proposed method for reconstructing the phase currents and reducing the noises