Enhanced dq current control for single-phase voltage-source inverters

Designing the dq-frame current regulator for single-phase voltage-source inverters is a very challenging task. Since only one real current signal exists in the circuit, an orthogonal signal generation (OSG) block is required to generate the virtual orthogonal signal. Thus, ac variables can be turned into equivalent dc quantities through an /dq transformation. However, the OSG block makes the control system complex and introduces an extra transient disturbance. Consequently, the dynamic performance is deteriorated. In this study, the reference-current-based OSG method is analysed thoroughly. Based on this structure, the dq-axes decoupling control, which is widely discussed for three-phase systems and usually neglected for single-phase systems, is studied. Two decoupling techniques, i.e. the reference-current feed-forward control and the quasi-complex vector proportional-integrator control, are implemented and analysed. The proposed theories and control schemes are evaluated by experimental results.