An improved two-stage model predictive current control (MPCC) for three-phase three-level converters in the paper, which can simultaneously achieve common-mode voltage (CMV) reduction, effective dc-link capacitor voltage control, and decreased computational burden, is proposed. Compared to the other current control strategies, it has the capability of handling multiple control objectives and possesses a simple structure. Furthermore, it greatly reduces the CMV since the peak CMVs of all the candidate voltage vectors are constrained to be less than one sixth of the dc-link voltage. In addition, an optimal two-stage voltage vector selection mechanism is employed in the proposed method. It helps to significantly reduce the computational complexity. Simulation and experimental results are provided to verify the effectiveness of the proposed method. [ABSTRACT FROM AUTHOR]
Hartmann, Michael, Ertl, Hans, and Kolar, Johann W.
Subjects
*ELECTRIC power system control, *ELECTRIC current rectifiers, *ELECTRIC wire, *SWITCHING theory, *TRANSFER matrix, *METAL oxide semiconductor field-effect transistors, *ELECTRIC power factor
Abstract
Three-phase rectifier systems without connection of the neutral wire are characterized by the coupling of the phase input currents. Considering these couplings requires a transformation of the system equations into a static \alpha \bm \beta-frame or into the rotating dq-reference frame where instead of the three coupled phase currents two independent current components are controlled. In this paper, it is shown that, despite of the existing cross-couplings, three independent phase current controllers can be used to control the system. Thereto, the cross coupling elements of the system transfer matrix have to fulfill some requirements which are derived using the Gershgorin theorem. The three-phase \Delta-switch rectifier circuit is used for analysis and a detailed model of the rectifier system is derived where the cross couplings are visible. The model is subsequently used to evaluate the cross couplings and three independent current controllers are designed. Simulation and experimental results verify the control approach using three independent current controller for three-phase rectifier systems. [ABSTRACT FROM AUTHOR]
*PULSE width modulation, *ELECTRIC current rectifiers, *ELECTROMAGNETISM, *SWITCHING circuits, *NONLINEAR control theory, *SIGNAL processing, *ELECTRIC transformers, *HALL effect
Abstract
This paper presents a new current control method for three-phase pulse width modulation rectifiers with active power factor correction (PFC). Conventional three-phase PFC control requires sensing of at least two input phase currents. Since the input line must be isolated from the control circuitry, current transformers or Hall effects current sensors are required for sensing the phase currents, which are bulkier and more expensive than resistive current sensors. Such electromagnetic current sensors are also difficult to integrate with the rest of the control circuitry, representing a major barrier for low-cost integrated PFC control development. The proposed current control method solves these problems by using only the dc-rail current as the feedback signal. The dc-rail current can be easily sensed by a shunt resistor, and the sensed signal can be directly used by the control circuitry without isolation or level shifting. The control method is developed based on a nonlinear average current control principle and avoids the steady-state phase error of conventional linear PI control. [ABSTRACT FROM AUTHOR]