This paper proposes a distributed fixed-time multiagentcontrol strategy for the frequency restoration, voltage regulation, state of charge balancing, and proportional reactive power sharing between photovoltaic batte...
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This paper proposes a distributed fixed-time multiagentcontrol strategy for the frequency restoration, voltage regulation, state of charge balancing, and proportional reactive power sharing between photovoltaic battery systems distributed in a microgrid with communication time delays. First, the feedback linearization method is applied to find the direct relationships between explicit states and control inputs. Then, based on the model, the distributed fixed-time cooperative control system restores the frequency, regulates the average voltage to the nominal value, and achieves accurate power sharing. For the state of charge balancing, a fixed-time observer is proposed to estimate the average state of charge of a battery using only information from neighbors. Based on the estimated value, a local fixed-time sliding mode control is applied to achieve the balanced state of charge. Due to robustness of the fixed-time control strategy, the balanced state of charge can be maintained despite intermittent photovoltaic generation and variable loads. The Artstein's transformation is applied to ensure the stability of the time delayed system. The dynamic performance is verified with an RTDS Technologies real-time digital simulator, using switching converter models, nonlinear lead-acid battery models, photovoltaic generation, and communication delays in a European benchmark microgrid.
The combined AC/DC grids have, due to their technological features of high voltage and large capacity as well as operating flexibility and reliability, become one of the most potential solutions to connect large-scale...
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The combined AC/DC grids have, due to their technological features of high voltage and large capacity as well as operating flexibility and reliability, become one of the most potential solutions to connect large-scale wind farms to power systems. The traditional centralised control lacks flexibility and robustness. In contrast, the distributedcontrol is unable to simultaneously consider global optimum and response speed. A scheme of intelligent distributedcontrol for combined AC/DC grids is proposed to constitute a multi-agent system by equipping each terminal with an agent. While adopting the proposed control method, the optimisation of the upper layer is similar to the traditional grid dispatch and the lower layer system achieves the group compromise through the interaction and coordination among the agents and between the agents and the system. Based on the state information such as the voltage and the frequency of the neighbouring converter stations, the combined AC/DC grids can allocate the active power reasonably through the consistency control and provide the frequency support of the AC grid. Finally, four operating scenarios, including wind speed jump, wind power plant cluster disconnection, converter station failure and load demand response, are verified in a typical model of combined AC/DC grids by using the PSCAD/EMTDC software.
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