Control of a DC-AC inverter with unbalanced loading

摘要

A three phase inverter consisting of three single phase legs using either switch mode or linear control is fed by a DC-DC converter to provide input output isolation. This requires that the DC-DC converter delivers equal positive and negative voltages to the single phase legs to allow each output to generate a high fidelity sine wave outputs to the load. By measuring the error voltages on the positive output, the negative output and the total output of the DC-DC converter it is possible to control a single duty cycle while maintaining all three output voltages within the limits required by the DC-AC phase legs. This significantly reduces the cost and complexity of the DC-DC converter and eliminates the need to use a fourth phase leg to generate the neutral connection for a three phase output.