CONTROL METHOD AND SYSTEM FOR PHOTOVOLTAIC INVERTERS WHOSE AC SIDES ARE CONNECTED IN PARALLEL

摘要

A control method and apparatus for photovoltaic inverters connected in parallel at an AC side are provided, the method is applied for an inverter system in which inverters are connected in parallel at an AC side and independent from each other at a DC side, where an input terminal of the first inverter is connected with a first PV array, an input terminal of the second inverter is connected with a second PV array, each of the first PV array and the second PV array has a parasitic capacitance to ground, and the first inverter and the second inverter form a common-mode loop by coupling with the parasitic capacitances, where the method includes the following steps: detecting a first direct voltage of the first inverter and a second direct voltage of the second inverter; obtaining a difference between the first direct voltage and the second direct voltage; and adjusting the direct voltages of the inverters to control the difference to be within a predetermined range and control a common-mode voltage in the common-mode loop to be within a predetermined common-mode voltage range. The smaller the difference between direct voltages of the inverters is, the smaller the common-mode voltage difference between the inverters is, and the smaller the common-mode current is, thereby restraining the common-mode circulation current between the inverters.