Indirect Modulation for Current Source PWM Converter

Compared with carrier based sinusoidal pulse width modulation (SPWM), space vector pulse width modulation (SVPWM) is widely used because of its higher current (voltage) utilization factor. In current source converter (CSC), SVPWM technique is harder to achieve than voltage source converter (VSC). To make the implementation of CSC SVPWM technique easier, this paper presents an indirect PWM method, which states that the modulation strategy of three phase CSC can be got from those used in three phase VSC by transforming bi-logic signals to tri-logic signals. In contrast to existing methods, a seven-segment modulation method is proposed. The presented method is validated by simulations, which show that the indirect PWM method has many advantages of easy implementation, low harmonic of AC side current, and low ripples of DC side current, etc.