Abstract
An intelligent control strategy based on a membership cloud model in a high reliable off-grid microgrid with a reconfigurable inverter is proposed in this paper. The operating principle of the off-grid microgrid with the reconfigurable inverter is provided, which contains four operating modes. An open-circuit fault diagnosis for the inverter is presented first. The polarities of the midpoint voltages defined in the paper are used to recognize the faulty power switch. The reconfigurable inverter allows the power switches of different bridges to be reconfigured, when there are power switches faulty, to let the inverter operate in faulty state. The working principle of the reconfigurable inverter is given. The membership cloud model with two output channels is built to obtain the virtual impedance to suppress the circulating currents between inverters when the reconfigurable inverter is in faulty state. A pulse resetting method is presented. The general intelligent control strategy for the reconfigurable inverter is formed as the droop-virtual impedance-voltage-current-pulses resetting control. The validity of the intelligent control strategy of the system is verified by simulation.
Highlights
Power electronic inverters play more and more important roles in many research fields like motor-driven machines, microgrids, photovoltaics (PVs) and so on [1,2,3,4,5]
When inverter 1 is diagnosed without fault and it runs in normal state, inverter 1 only uses the control strategy connecting droop-voltage-current three-loop with virtual impedance based on the membership cloud model, which is adopted in inverter 2
An intelligent control strategy for a highly reliable microgrid in off-grid mode with a twice reconfigurable inverter and its fault diagnosis is proposed in this paper
Summary
Power electronic inverters play more and more important roles in many research fields like motor-driven machines, microgrids, photovoltaics (PVs) and so on [1,2,3,4,5]. In [29,30], a fault tolerant inverter with the TPFS structure in a microgrid is proposed, which keeps the system operating after cutting the fault power switch devices from the inverter. Reference [31] proposes a finite states model predictive direct power control method for TPFS bidirectional alternating current (AC)/DC converters under unbalanced grid voltage conditions, which can realize the fault tolerant continuous operation of bidirectional. An intelligent control strategy based on the membership cloud model is proposed and applied in an off-grid microgrid with a reconfigurable inverter in this paper. The circulating currents between inverters which are suppressed by the virtual impedance based on the membership cloud model are analyzed when the reconfigurable inverter is faulty.
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