A grid-connection control scheme of PV system with fluctuant reactive load

The fluctuations of reactive load in micro-grid will have a great impact on the supply voltage. In this paper, a novel grid-connection control is proposed in view of this problem, based on a model of a PV system with load paralleled in large system. It can not only make full use of photovoltaic power, but also maintain a stable voltage with a fluctuant reactive load. It adopted double-loop principle in inverter control. The grid-connected current of the PV system and the current of large system are both decoupled into active and reactive component by abc/dq0 transformation to achieve the independent control of active and reactive power. On the one hand, the active component of the PV grid-connected current is adjusted to the reference value given by the Maximum Power Point Tracking (MPPT) in order to maintain maximum active power output of PV, the reactive component of the large system current is adjusted in order to maintain a constant reactive power output. Thus a stable supply voltage can be maintained with a fluctuant reactive load, as the supply voltage of the grid-connected PV system is mainly sustained by the large system. On the other hand;the main circuit topology of three-phase reactive power compensation device and three-phase grid-connected inverter is exactly the same. Thus, in support of a reasonable control strategy it can be integrated together with both function of grid connection and reactive power compensation control. These can ensure a stable voltage in the PV system with a fluctuant reactive load paralleled in large system by the regulation of power. Its advantages compared with the simple and traditional unity-power-factor inverter control scheme are validated by simulation with Matlab/Simulink.