Dual updating SVPWM-based circulating current control method for parallel three-phase inverters

Parallel three-phase inverters structure has become a popular way to increase capacity. However, circulating current will be produced. In practical application, inverters are controlled by digital system. Consequently, it is inevitable to consume time due to sampling and computing. As a result, the performance of zero-axis current loop would be directly affected. This paper presents a dual updating SVPWM-based method to control the circulating current exhibited in parallel three phase PWM inverters. With the employment of PI controller, better circulating current suppression performance can be achieved by means of the proposed method because of the realized dual sampling and dual PWM duty ratios updating (DSDU) in a carrier period, which results in dual updating of the circulating current control variable in a PWM period with switching frequency unchanged nor extra hardware added. By comparing the performance with the traditional SSSU method, the effectiveness of the proposed method is validated with implementation using TMS3202812 digital signal processor.