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This paper presents a hexagonal-cascaded multilevel converter for two-motor asynchronous drive application. By adding an ac input to the hexagonal configuration, this multilevel converter becomes a tri-port system with one input port and two output ports, which can drive two motors with asynchronous operation by sending different control commands. The detailed analysis of power distribution is presented, and it is found that the six branches are equivalent to two groups of three-phase voltage sources, which can share the power of two motors. The regenerative energy from one generating motor can be directly supplied to the other one in motoring mode. Consequently, the dc-link voltage overshoot can be suppressed, and the energy storage requirement of capacitors can be reduced as well. A two-motor drive system has been tested in MATLAB/Simulink and a downscaled laboratory prototype. Simulation and experimental results are provided to demonstrate the effectiveness of the proposed motor drive system and control strategies.

Bad data must be detected in the microgrid because they mislead the decision making of energy management systems (EMSs). The authors propose a robust detection approach that combines an imp...

When a bus fault occurs in a low-voltage DC microgrid, solid-state circuit breakers (SSCB) on either end of the DC bus assume the responsibility of the isolation of the faulted section, while the freewheeling path attached between SSCB and the bus takes on the task of fault energy absorption and fault current damping. However, during fault interruption, the snubber attached in parallel with SSCB for overvoltage suppression will influence the fault energy absorption performance of freewheeling path, while the resistance of the freewheeling path will also influence the overvoltage suppression capability of the SSCB snubber. Hence, this paper analyzed the interaction between the two and proposed a combined design so as to optimize the fault interruption performance for minimum SSCB overvoltage, and shortest fault clearing time, with less cost and size. Preliminary experiments are conducted on a ±200V/DC prototype, and the experimental results demonstrated the effectiveness of the design.