Analysis of Stationary- and Synchronous-Reference Frames for Three-Phase Three-Wire Grid-Connected Converter AC Current Regulators

The current state of the art shows that unbalance and distortion on the voltage waveforms at the terminals of a grid-connected inverter disturb its output currents. This paper compares AC linear current regulators for three-phase three-wire voltage source converters with three different reference frames, namely: (1) natural (abc), (2) orthogonal stationary (alpha beta), and (3) orthogonal synchronous (dq). The quantitative comparison analysis is based on mathematical models of grid disturbances using the impedance-based analysis, the computational effort assessment, as well as the steady-state and transient performance evaluation based on experimental results. The control scheme devised in the dq-frame has the highest computational effort and inferior performance under negative-sequence voltage disturbances, whereas it shows superior performance under positive-sequence voltages among the reference frames evaluated. In contrast, the stationary natural frame abc has the lowest computational effort due to its straightforward implementation, with similar results in terms of steady-state and transient behavior. The alpha beta-frame is an intermediate solution in terms of computational cost.

Automated summary

This paper compares the effects of different reference frames on AC linear current regulators for three-phase three-wire voltage source converters, finding that the dq-frame has the highest computational effort and inferior performance under negative-sequence voltage disturbances, but superior performance under positive-sequence voltages. In contrast, the abc frame has the lowest computational effort due to its straightforward implementation, with similar results in terms of steady-state and transient behavior, while the alpha beta-frame is an intermediate solution in terms of computational cost.