The authors discuss high-voltage power conversion. Conventional series connection and three-level voltage source inverter techniques are reviewed and compared. A novel versatile multilevel commutation cell is introduced: it is shown that this topology is safer and more simple to control, and delivers purer output waveforms. The authors show how this technique can be applied to either choppers or voltage-source inverters and generalized to any number of switches.<<ETX>>

Multi-level conversion : high voltage choppers and voltage-source inverters

Each diagonal of a bridge type converter comprises the serial interconnection of the two semi-conductor switches and a diode connected between a reference potential and the junction of the respective switches. By operating individuals or pairs of switches in various diagonals, outputs of zero, +E, +2E, -E, -2E across the load are achieved and by given sequence of these outputs stepwise synthesis of AC waveform is achieved. Protection of individual switches is gained by the claming action of the diodes preventing open circuit switch breakdown.

Bridge converter circuit

This paper proposes a novel fuzzy switched controller (FSC) integrated in direct current control (DCC) algorithm for single phase active power filter (SPAPF). The controller under study consists of conventional PI controller, fractional order PI controller (FO-PI) and fuzzy decision maker (FDM) that switches between them using reduced fuzzy logic control. The proposed controller offers short response time with low damping and deals efficiently with the external disturbances while preserving the robustness properties. To fulfill the requirements of power quality, unity power factor and harmonics limitations in active power filtering an experimental test bench has been built using dSPACE 1104 to demonstrate the feasibility and effectiveness of the proposed controller. The obtained results present high performance in steady and transient states.

Design and real time implementation of fuzzy switched controller for single phase active power filter.

The high-order harmonics caused by the modulation strategy can deteriorate power quality. The harmonic characteristics of the carrier-based pulsewidth modulation are relatively fixed and difficult to optimize, while space vector pulsewidth modulation (SVPWM) has more flexibility. The unified SVPWM design method for single-phase three-level neutral-point clamped (NPC) converters is fully presented in this article. Based on the proposed unified SVPWM method, two existing traditional vector sequences are designed first, and then several advanced multisegment SVPWM algorithms are proposed. According to the particularity of the three-level NPC topology, two hybrid SVPWM algorithms are proposed to optimize harmonic performance. Moreover, the high-order harmonic characteristics and the number of switching actions are analyzed in detail for all SVPWM algorithm modes. In addition, these SVPWM algorithms are associated and unified by introducing weight coefficients of the redundant vectors. Simulation and experimental results verify the feasibility and effectiveness of the proposed SVPWM algorithms, which show that the proposed methods can optimize high-order harmonic distribution and reduce the line current harmonics.

Unified SVPWM Algorithm and Optimization for Single-Phase Three-Level NPC Converters

Alternating current (ac) active electronic loads (AELs) based on pulsewidth modulation (PWM) converters, capable of emulating nonlinear loads, require effective current control techniques and power stages. These two aspects of an AEL are interdependent mainly due to the presence of electromagnetic compatibility filters to reduce electromagnetic emissions. However, the filter components affect the dynamics of the system. In this context, this paper proposes a digitally implemented control strategy comprising the state feedback, robust observer, phase-locked loop, and linear current controller to cope with ac AEL applications. The control-oriented modeling and the control system design are presented. Experimental results obtained from a 10-kW three-phase three-level PWM converter prototype illustrate and demonstrate the feasibility of the proposed AEL control strategy.

Control Strategy for Current Harmonic Programmed AC Active Electronic Power Loads

Ac electronic loads are of interest in applications such as loss measurements in distribution transformers and small generators, UPS testing and other. In order to achieve high control bandwidth to inject current harmonics, it is important that EMC filters use small value passive components. Based on this requirement, three-level regenerative rectifiers are able to achieve better performance than two-level ones. Two candidate topologies for the implementation of a high performance 3.5 kW regenerative rectifier operating as ac electronic load are compared with respect to achievable efficiency numbers. Both topologies present the same external characteristics. The operation of the topologies is briefly reviewed in order to compute current efforts across the power devices. Based on which the losses for the converters are estimated along with their efficiency.

Semiconductors current efforts and losses evaluation for single-phase three-level regenerative PWM rectifiers

This work presents a Linear Quadratic Gaussian (LQG) controller in cascade loop applied to a Two‐Switch Forward Converter (2SFC). This arrange is suitable for low power battery chargers an...

LQG controller in cascade loop tuned by PSO applied to a DC–DC converter

In this work we present a method for off-line identification of induction motors with PWM drives, i.e., the standstill estimation of all its electrical parameters. The method is achieved when we digitize the PWM driven induction motor model by considering the PWM signal from the inverter as a sequence of continuous impulses. The PWM inverter nonlinearity caused by the turn on/off time dependency of the current level in the switching transistors is modeled, allowing the method to be based only on reference voltages and measured currents. Simulation and experimental results illustrate the methodology.

Off-line identification of PWM driven induction motors using reference voltages

This paper shows a three-phase feeding system to rural areas that are supplied by a single-phase feeder. This proposed system allows the use of three-phase agricultural equipments. The system proposed is formed by two bidirectional three-phase PWM converters, easily found to acquire at local market. The energy processed by single-phase transformer is maximized due the use of the Power Factor Correction technique at the input converter. The output voltages are free of harmonics and allow non-balanced loads. The control strategy and design procedure are presents to both rectifier and inverter stages. Finally, will be present the experimental results of the proposed feeding system.

Joselito A. Heerdt

Papers

Control Strategy for Current Harmonic Programmed AC Active Electronic Power Loads

Semiconductors current efforts and losses evaluation for single-phase three-level regenerative PWM rectifiers

LQG controller in cascade loop tuned by PSO applied to a DC–DC converter

Off-line identification of PWM driven induction motors using reference voltages

Three-phase feeding system for rural electrification