Cost-Effective Modular Design for Grid-Integrated Power Converters

Modular design is commonly used for industrial power electronics converters such as uninterrupted power supply (UPS), static var generator (SVG), active power filter (APF), etc. A single module is a fully functional power converter, and it usually consists of a controller, switching devices such as IGBTs, voltage and current transducers, DC-bus capacitors, and a passive output filter. The modular design standardizes the fabrication and maintenance of the converter product, and the power capacity can be scaled up simply by operating multiple modules in parallel. However, this design is not cost effective, as every module needs a controller and a full set of voltage and current transducers. This paper proposed a cost-effective modular design for grid-integrated converters. In the new design, multiple modules share one controller and a single set of voltage and current transducers. Carrier phase-shift pulse width modulation (CPS-PWM) is used to cancel the switching harmonic in the overall current injected to the grid. The commonly used LCL filter is replaced by an L filter, which further reduces the cost. The proposed design is analyzed and simulated with an SVG for a 3-phase 4-wire distribution system, and it can also be applied to other DC/AC converters with a few changes.