A novel strategy for a high-power utility interactive inverter with a series active filter

High-power utility interactive inverters used for large-capacity energy storage systems are composed of multiple connected inverters, in order to realize high efficiency and high performance of the harmonic elimination characteristic simultaneously. Some disadvantages of multiple connected inverters, such as harmonic current flowing from an inverter unit to the other one, and increase of the number of inverter units, cannot be overcome easily. This paper presents a novel strategy for a high-power utility interactive inverter, which is composed of a large power with low-switching-frequency PWM inverter (high-power PWM inverter), an LC passive filter, and a series active filter (series AF). Because harmonic components contained in the utility line current are absorbed by the series AF, the switching frequency of the PWM inverter can be selected to about 1 kHz. In addition because the power capacity and the output voltage of the series AF can be suppressed lower than 10% of the power capacity and the output voltage of PWM inverter, low-voltage and high-speed power devices can be applied to the series AF. Consequently, high power, high efficiency, and high harmonics elimination performance can be realized without increasing the number of inverter units.