A DC link voltage control method piconet PV

The present invention is directed to a photovoltaic DC bus voltage piconet stability problem, DC bus voltage, a control method of a layered coordination: a first step according to the output power and load power balance principle photovoltaic array to the system DC link voltage value of the reference threshold value , the DC bus voltage into three layers. The second step, the hierarchical coordination control: a first layer, when the U dc1 system is in the range 239.8-242.6V islanding operation mode, using the controlled bus voltage droop control method; a second layer, when U dc2 is 249.6V-252.4V range, and the system will switch to the network operation, network side interface in the inverter state, id adjusted by directly adjusting the grid d-axis component of the inverter output current UDC2; third layer when U dc3 the range 259.6-262.2V, into the islanding operation control system, a micro network and the separation grid is still used method to maintain the bus voltage droop stable, but the need to add a virtual loop output impedance to achieve load sharing power.