Overview of PI-based solutions for the control of the dc-buses of a single-phase H-bridge multilevel active rectifier
ABSTRACT The H-bridge based multilevel active rectifier is an attractive topology that allows feeding of multiple dc loads. However the balancing of the dc buses often causes instability problems. The main control problem is to manage n+1 state variables (one current plus n dc voltages) with only n switching functions. In this paper several PI-based solutions are reviewed through simulations and experimental tests.
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ABSTRACT: In this paper, a new strategy for voltage balancing of distinct dc buses in cascaded H-bridge rectifiers is presented. This method ensures that the dc bus capacitor voltages converge to the reference value, even when the loads attached to them are extracting different amounts of power. The proposed method can be used for an arbitrary number of series H-bridges, different voltage levels, and different power levels in unidirectional or bidirectional rectifiers. To reduce the current harmonics and distortion, the input current is programmed to be sinusoidal and in phase with the input voltage; however, it is possible to adjust the input power factor to control both the active and reactive powers. In the proposed approach, both the low frequency (stepped modulation) and high frequency [pulse-width modulation (PWM)] switching methods are utilized to improve the performance of the rectifier. Using theoretical analysis, the acceptable load power limits for a rectifier with N-H-bridge cells are derived. The validity of the proposed method is verified by simulation and experimental results.IEEE Transactions on Power Electronics 10/2008; · 4.65 Impact Factor