A CC/VC-based power tracking method for photovoltaic inverter operated in voltage control mode

Abstract

The active power control of photovoltaic (PV) inverters without energy storage can flatten the fluctuating power and support the voltage amplitude and frequency of the grid. When operated in grid-forming voltage-control mode, because the PV power can change rapidly and widely, the PV inverter needs to track the power commands quickly and precisely. Traditionally, this goal is achieved with the estimation of PV power curve or PI-based multiple-loop feedback control, where flexibility, availability and accuracy are not satisfactory. Therefore, a CC/VC-based power tracking (CVPT) method is proposed, which only uses single-loop in control. The proposed method does not need to tune multiple loops and can respond faster, which is important for grid-forming voltage control. Furthermore, the different operating modes due to the limitation of PV maximum power are analysed, and a mode switch method is proposed. Simulation and experimental results demonstrate that the PV inverter can cope with power disturbances from both the power and grid sides and maintain the quality of grid voltage.