| Mode switching strategy plays an important role in the microgrid controltechnology. However, for traditional master-slave control strategy, it is difficultto transfer the controllers' structure and hard to track the parameters. Meanwhile,droop control has poor dynamic characteristics and its operating point has a largedeviation. Due to the limitations, based on domestic and foreign status ofmicrogrid mode seamless switching, the traditional master-slave control strategyhas been improved in this paper. The improved master-slave configuration basedon multi-loop structure proposed by this paper overcomes all the shortcomingsmentioned above.This strategy solves three problems of the traditional master-slave controlconfiguration in mode transition. First, being difficult to automatically assign thepower can be solved by the outer voltage and frequency loop. Second, being hardto track the parameters can be solved by the parameters' tracking loop. Third,that the controller needs to switch the structures can also be avoided since thiscontrol strategy applies to the grid connected mode and the off-grid modesimultaneously. For the improved strategy, voltage loop tracks the steady-statevoltage with zero error while the current loop improves its dynamic performance.To verify the stability of the improved master-slave strategy, includingsteady-state stability and temporary stability, a micro-grid system and itsmathematical model is built. The steady-state stability is demonstrated by matrixof the state space equation through its eigenvalues because they all have negativereal parts. And the temporary stability is verified through the simulation resultsin numerous operation statuses. From these results, we are able to draw theconclusion that the transient time is less than the maximum fault clearing timeand thus prove the temporary stability.Finally, the proposed strategy is compared with the multi-loop droop controland the master-slave control to demonstrate its superiority once again. |
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