Alberto Berzoy

Direct Power Control of a Dual Converter Operating as a Synchronous Rectifier

This paper presents a dual converter employed as a rectifier with power factor regulation and bidirectional power flow. The active and reactive powers flowing into the converter is controlled using an optimized direct-power-control algorithm. The multilevel structure of the converter is exploited to control the voltage level in each subconverter by selecting the modulation method from one commonly found in the literature, with the option of clamping one of the subconverters. These modulation methods are used to control the power taken by each subconverter, providing limited dc-link voltage regulation. The system is first simulated in SIMULINK, and the results are experimentally validated using a digital-signal-processor-based test rig.

Switching Strategies for Fault Tolerant Operation of Single DC-link Dual Converters

This paper proposes a method that allows the operation with direct torque control under incipient faults of the power switching devices in single dc-link dual inverters. Once the fault onset of the switching device is detected, the troubled devices are put under trigger suppression to regain operation. The proposed control algorithm makes use of additional states, termed opportunistic states, to maintain control of the induction machine. Simulations and experimental results confirm the capabilities of the technique for up to six devices under trigger suppression.

Direct power control of a dual converter operating as synchronous rectifier

This work presents a dual converter employed as a rectifier with power factor regulation and bidirectional power flow. The active and reactive power flowing into the converter is controlled using an optimized direct power control algorithm. The multilevel structure of the converter is exploited to control the voltage level in each sub converter by selecting the modulation method from one commonly found in the literature, with the option of clamping one of the sub converters. These modulation methods are used to control the power taken by each sub converter, providing limited DC link voltage regulation. The system is first simulated in SIMULINK and the results were experimentally validated using a digital signal processor (DSP) based test rig.

Predictive DTC algorithm for induction machines using Sliding Horizon Prediction

This paper presents a predictive direct torque control PDTC algorithm for induction machine drives including a Sliding Horizon Prediction (SH-PDTC). The selected strategy for the SH-PDTC algorithm was to keep the motor torque and stator flux-linkage within predefined hysteresis bounds while reducing inverter switching losses. The proposed SH-PDTC algorithm shows better performance in torque and stator flux-linkage control in comparison with classical PDTC, without increasing power losses in the inverter. A sensitivity analysis allows to evaluate algorithm performance under parameter uncertainty, and the results show that SH-PDTC keeps torque ripple performance. The paper includes a simulation to verify the PDTC and SH-PDTC algorithms controlling an induction machine, with a standard two level inverter.

DC voltage estimation methods for multilevel converter operating with reduced number of sensors

Two methods for the estimation of the DC voltages in the capacitors associated to the DC buses in a cascaded multilevel converter topology are analyzed. To reduce the number of voltage sensors, available information from inductor currents and line voltage sensors is used as input to a discrete time model of the converter. Additionally, information from the switching state of each converters cell is used allowing an estimation of voltages in each capacitor. Both methods are developed, implemented and simulated for a 9 level three-phase cascaded multilevel converter when it is operated as a controlled rectifier at unity power factor. The analyzed methods have low computational cost allowing its implementation in real time.