Island mircogrid parallel inter-inverter circulation suppression method

Abstract

The invention relates to an island mircogrid parallel inter-inverter circulation suppression method, being suitable for conditions that an inverter has a local load, the transmission line is large in impedance, and has difference. The control method includes measuring and indirectly calculate the equivalent line impedance of inverters through real-time power, improving the multi-loop control method through the sagging control without communication interconnection lines and equivalent lines, and weakening the influence of external inductance, local load, and line impedance difference between inverters to circulation. The control method includes equivalent line impedance calculation, equivalent line voltage drop compensation, improved droop control, and dynamic virtual complex impedance control. Compared with the prior art, the island mircogrid parallel inter-inverter circulation suppression method can effectively suppress the circulation between the parallel inverters and improve the power distribution precision.

Description

technical field [0001] The invention relates to a method for suppressing circulation between parallel inverters, in particular to a method for suppressing circulation between parallel inverters in an isolated island microgrid. Background technique [0002] The parallel connection of inverters is the main technical means to realize distributed power grid connection and system expansion. The difference in line impedance and output voltage of parallel inverters is an important reason for the circulation between inverters. When the microgrid operates in an isolated island, the circulation problem between parallel inverters cannot be ignored. The circulating current will overheat the power electronic equipment and reduce its safety performance. At the same time, the load will not be distributed proportionally and the transmission efficiency of the system will be reduced. [0003] The voltage regulation strategy based on droop control is the basic method of circulating current su...

AI Technical Summary

Problems solved by technology

However, due to the influence of line impedance, droop control will not only increase the circulating current but also cause power distribution errors when the line parameters do not match and the line voltage drop cannot be ignored.

In practice, considering the differences in the design parameters, connection impedance and closed-loop controller parameters of parallel inverters, the configuration of external inductors and virtual impedance control on the output side of the inverter can weaken the influence of line parameters on droop control, but too large external Inductance will increase investment cost and power loss, and the fixed proportional virtual impedance has limited control effect when the load fluctuates

[0004] The above scheme does not consider the virtual impedance and the voltage drop on the transmission line. When the load deviates from the rated value, the voltage at the common connection point will drop, the voltage deviation will increase, and the circulation will be aggravated.

Some scholars use the centralized secondary controller to restore the voltage amplitude through the hierarchical control of the micro-grid, which requires more complicated communication between the controllers, and cannot take advantage of droop control without communication interconnection lines.

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