Coordinated stable operation control method for island DC micro-grid

Abstract

The invention relates to a coordinated stable operation control method for an island DC micro-grid. By improving the double closed loop control of a conventional converter and using improved constant-voltage droop control, a current inner-loop control reference value is generated, and by introducing a SOC equalization factor into the current inner loop control, each energy storage unit dynamicallyadjusts the current inner-loop output current reference value according to its own capacity and a current SOC, and finally SOC equalization is achieved between the energy storage units connected in parallel. Compared with the prior art, the method eliminates the influence of the unmatched line impedance on the current load distribution accuracy, and does not produce a DC bus voltage drop similarto that caused by the conventional droop control.

Description

technical field [0001] The invention relates to the field of direct current microgrids, in particular to a method for controlling the coordinated and stable operation of isolated island direct current microgrids. Background technique [0002] Compared with the traditional AC microgrid, the DC microgrid does not need to consider voltage phase and frequency issues due to less energy conversion process, high efficiency, and low loss, so the controllability and reliability of the system operation are greatly improved; when the island is running, the microgrid It is necessary to rely on the coordinated control of distributed power sources in the self-network to maintain the stable operation of the microgrid. Compared with the grid-connected operation mode, the control is more complicated. Since the output of many renewable new energy sources such as photovoltaics and wind power is affected by external natural factors and presents intermittent, random and unstable characteristics,...

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Problems solved by technology

Some scholars have proposed an adaptive hierarchical coordination control method, which realizes the SOC balance between parallel multi-energy storage units through the coordinated control of the power distribution level and the power balance level, but this control method does not consider the influence of the mismatched line impedance; In addition, some scholars have proposed to dynamically change the droop coefficient to compensate for the influence of mismatched line impedance, but a large droop coefficient will inevitably cause a large drop in the DC bus voltage, resulting in the unstable operation of the microgrid; it can be achieved by adding a line impedance measurement device , it is convenient to correct the droop coefficient of each energy storage unit, but this control method requires additional hardware devices, which reduces the economy of the microgrid

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