A Self-Balanced Modulation and Magnetic Rebalancing Method for Parallel Multi-level Inverters
A power inverter which can provide sinusoidal voltage or current is the key apparatus in the field of electrical machine drive and utility interface, such as in renewable energy generation systems and energy storage power conditioning systems. In order to achieve a higher power rating, each phase of the inverter may be constructed of paralleled phase legs. If two paralleled legs are connected to an output terminal by a magnetic coupling device, such as an "inter-phase transformer", or a "multi-winding autotransformer", or an "inter phase inductor", the output terminal of each phase will have a multilevel staircase waveform, which is closer to the desired sinusoidal waveform. Therefore, the inverter will require smaller magnetic components while still providing the benefit of higher dynamic response.
The technology developed provides a finite state machine (FSM) based modulation method for parallel multi-level inverters. Within this invention, a modulation waveform is fed into a comparator to compare with carrier waveforms. Then, a digitized ideal waveform is generated, and the digitized ideal waveform is fed into a finite state machine (FSM) module to generate a switching pattern for each switch of the parallel multi-level inverter.