A method for suppressing circulating current between parallel inverters in islanded microgrids
A circulating current suppression and inverter technology, applied in the direction of single-grid parallel feeding arrangement, etc., can solve the problems of voltage drop at the common connection point, unable to exert the advantage of droop control without communication interconnection, aggravating circulating current, etc., to improve power The effect of unreasonable allocation, good dynamic tracking ability and circulation suppression ability
Active Publication Date: 2020-02-14
TONGJI UNIV
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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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[0048] The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative work shall fall within the protection scope of the present invention.
[0049] The method for suppressing the circulating current between parallel inverters of the island microgrid in the present invention is based on the calculation of equivalent line impedance and proposes improved droop control and dynamic virtual complex impedance control.
[0050] Utilizing the characteristics of droop control that no communication interconnection line is required, measuring local voltage and current to calculate equivalent lin...
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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 circulating current between parallel inverters, in particular to a method for suppressing circulating current between parallel inverters of an island micro-grid. Background technique [0002] Inverter parallel connection 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 circulating current between inverters. When the microgrid is operating on islands, the circulation problem between parallel inverters cannot be ignored. Circulating current will overheat power electronic equipment and reduce its safety performance. At the same time, the load will not be distributed proportionally, which will reduce system transmission efficiency. [0003] The voltage regulation strategy based on droop control is the basic method of circulating current suppression. However, affected ...
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IPC IPC(8): H02J3/38
CPCH02J3/38
Inventor张明锐宋柏慧
OwnerTONGJI UNIV