Abstract
It is difficult to achieve accurate distribution of reactive power based on conventional droop control due to the line impedance mismatch in an islanded microgrid. An adaptive virtual impendence method based on consensus control of reactive current is proposed in this paper. A distributed control structure without the central controller has been established. In this structure, each distributed generation unit (DG) is an independent agent, one-way communication is used between the adjacent DGs, and the reactive power sharing is equivalent to a problem of reactive power current consensus. It has been proven that the system is asymptotically stable under the proposed control strategy. When the adjacent DG’s reactive power is not proportionally distributed, the current weight error term will generate a virtual impedance correction term through the proportional-integral controller based on the reactive current consensus control strategy, thus introducing adaptive virtual impedance to eliminate mismatches in output impedance between DGs. Reactive power auto-proportional distribution can be achieved without knowing the line impedance. At the same time, the power control loop is simplified and the virtual impedance compensation angle is employed to compensate the decreased reference voltage magnitude and varied phase angle due to the introduction of the virtual impedance, so the stability of the system can be improved. Finally, the correctness and effectiveness of the proposed strategy are verified by modeling analysis and microgrid simulations.
Highlights
The increasing demand for renewable energy-based power generation systems consisting of inverters necessitates the design of sophisticated inverter control systems [1,2,3]
∗ represents the static virtual, LV,i inductance and the reactive current error term ekni Iri is processed by the proportional integral controller (PI) to yield the virtual impedance correction term δIr,i
The microgrid system adopts a distributed control structure without a central controller, in which each distributed generation unit (DG) acts as an independent agent and adjacent DGs engage in one-way communication
Summary
The increasing demand for renewable energy-based power generation systems consisting of inverters necessitates the design of sophisticated inverter control systems [1,2,3]. To further improve the power sharing accuracy, reference [27,28,29] propose a virtual impedance method based on the line impedance estimation. References [33,34] apply multi-agent theory to the adjustment of virtual impedance This method only requires communication between adjacent micro-sources and is, characterized by higher system reliability. An adaptive virtual impedance control strategy based on reactive current consensus control is proposed to improve the accuracy of reactive power distribution. In this method, each DG unit is regarded as an independent agent.
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