A novel method for photovoltaic inverter applying vector resonant controller

PR controller in stationary frame which is equivalent to PI controller in synchronous frame has been widely used in the application of PV inverters. While little attention has been devoted to VR(vector-resonant) controller in the application of PV inverters. VR controller in stationary frame is equivalent to VPI(vector PI) controller in synchronous frame, which takes decoupling into consideration and has better performance than PI controller. This paper proves the theory of controller transformation between stationary frame and synchronous frame based on vector modeling, and analyses the feasibility of VR controller applied in PV inverters. In comparison with PR controller, the advantages and disadvantages of VR controller are figured. VR controller can control AC signals of positive sequence and negative sequence simultaneously with good accuracy, and can filter harmonic components in current instructions. Based on these characteristics, a new method of generating current instructions of PV inverters was proposed for VR controller, which doesn't need phase lock loop but may contain harmonics in the instructions when the grid voltage has harmonics. The drawback of VR controller is its low transient response. As a result, if VR controller is used in PV inverters, the computation burden of current loop can decrease a lot keeping good performance, but the period of voltage loop control should be set larger. Simulation results based on PSIM validate the theoretical analysis.