Contents I. Introduction
The single- and three-phase voltage source converter (VSC) have been widely used in the power grid. The fast and accurate control characteristic of the current control is important for the effect of the VSCs control and the stability of the power grid [1]–[2]. Many kinds of current control techniques have been researched. The classic proportion integral (PI) control is the most widely used. Hysteresis [3], deadbeat [4], predictive [5], repetitive [6], slide control [7] and proportional-resonant (PR) control [8] are also presented to achieve faster, more stable and more accurate current control. For the three phase application, the coordinate transformation method is used to change the three phase quantity into two phase DC components which can be controlled by the current controller [9]. For the single phase application, the direct sinusoidal current control and the coordinate transformation based control are the main control structure. The direct sinusoidal current control can not realize zero steady-state amplitude and phase errors through PI control. To make the synchronous reference frame can be adopted for the single phase application, the single phase reconstruction methods through phase shifting have been presented in many literatures [10]. The improvements of current control for single- and three-phase grid-connected VSCs can be get from the following points, (a) The different control strategies are inconvenience for the controller design and stability analysis; (b) The coordinate transformation needs large amount of calculation; (c) The unbalance and harmonic signals bring difficulty for the realization of zero steady-state error control.
