Vector control of single-phase grid-connected inverters without virtual orthogonal quantities

PI regulators in rotating reference frame are widely used for current regulation of three-phase systems. Since traditional stationary-to-rotating reference-frame transformation requires two orthogonal signals, such transformation cannot be directly applied to single-phase systems as variables in single-phase system contain only one component. Common approach is to create virtual quantities orthogonal to existing physical ones by phase shifting the physical ones a quarter of fundamental period. However, current delaying usually deteriorates system dynamic response. This paper presents a new stationary-to-rotating reference-frame transformation strategy based on variable step-size least mean square (LMS) algorithm via analysis of relationship between AC and DC quantities. This strategy does not need virtual orthogonal quantities. Adding forecast link into the proposed strategy, system dynamic response speed is improved significantly. Simulation and experimental results verify its effectiveness. © 2015, Power System Technology Press. All right reserved.