H5™ inverter with constant-frequency asynchronous sigma-delta modulation

The objective of this paper is to propose a constant-frequency asynchronous sigma-delta modulation (CF-ASDM) control strategy for the transformerless H5™ inverter. By comparing to the conventional asynchronous sigma-delta modulation (ASDM) with variable switching frequency, the proposed CF-ASDM can simplify the filter design and reduce the computational burden of the digital signal processor while maintain the merit of quick dynamic response. The major contribution of this paper includes that developing the CF-ASDM control scheme thoroughly and applying it to the H5™ inverter successfully. In this paper, the mathematical expressions of the proposed CF-ASDM will be derived. Computer simulations and hardware experiments are shown to verify the performance of the H5™ inverter with proposed CF-ASDM.