A Remedial Control for Short-Circuit Fault in NPC/H-Bridge Inverters without Redundant Component

In this paper, a five-level neutral-point-clamped (NPC) inverter with short-circuit fault-tolerant capability is presented. Based on the proposed approach, in order to ensure service continuity subsequent to a short-circuit fault event in a switch, two steps are carried out. First of all, destructive consequences arising from short-circuit fault in a power switch is prevented. Afterwards, according to the defected component, remedial actions are taken. The proposed strategy does not require any redundant component. The service continuity is acquired by applying a remedial control and modifying switching commands applied to the power switches. Using the proposed approach helps to restore the rated voltage and rated current at the terminal, and there is no limit for modulation index during fault-tolerant operation under remedial control. Furthermore, compared to healthy operation, harmonic content of the terminal voltage and current is not deteriorated during fault-tolerant operation. Moreover, additional components, such as bidirectional switches and contactors, are not employed in this strategy. Only some fast fuses are placed in the converter circuit for protection purposes which do not impose a noticeable cost compared to the bidirectional switches and contactors.

An Eleven-Level Switched-Capacitor Inverter with Boosting Capability

An 11-level switched-capacitor multilevel inverter (SCMLI) with 2.5 times boosting feature is presented in this paper. It can produce an 11-level output voltage waveform by utilizing 14 switches, 3 capacitors, 2 diodes, and 1 DC source. Only nine driver circuits are needed as the topology has three pairs of complementary switches and two bidirectional switches. It has inherent capacitor self-balancing property as the capacitors are connected across the DC voltage source during several states within a fundamental cycle to charge the capacitors to the input voltage. A detailed comparison shows the effectiveness of the proposed topology in terms of the number of switches, number of capacitors, number of sources, total standing voltage (TSV), efficiency, and boosting ability with the state-of-art recently proposed circuits. Subsequently, the performance of the proposed SCMLI is validated experimentally utilizing the nearest level control (NLC), a fundamental frequency-based switching technique.

Trends and Challenges in Multi-Level Inverter with Reduced Switches

Multilevel inverter had been paid a lot of attention from the academia and research community in recent times due to its role in high and medium power applications. In this paper, a detailed survey is made on the recently designed multilevel inverter to find the suitability of the inverters for particular applications. Research is performed on various types of multilevel inverters such as: Symmetric, asymmetric, hybrid and modularized multilevel inverter in order to identify the issues in generating more levels at the output. A summary of various issues in multilevel inverter with reduced switch count is provided, so that a novel topology of multilevel inverter can be designed in future. Further, an 81-level switched ladder multilevel inverter using unidirectional and bidirectional switches is designed. Simulation work is carried out using Matlab/Simulink in order to validate the performance of the inverter with change in resistive load and impedance load. The output of the 81-level inverter is fed to a 110 V, 186.5 W single phase induction motor in order to study the characteristics, further speed control of motor is performed by varying the input voltage of the motor and the results are presented.

Control Techniques for a Single-Phase Matrix Converter

The single-phase matrix converter is an AC-AC power topology which consists of six bidirectional switches and it is considered the key unit in cascade or multilevel configurations. In this paper, a comparison between two control techniques is presented, one based on a proportional-integral-derivative control module with a pulse width modulator, and the other known as finite-state model predictive control. Simulation and experimental results are presented and discussed to demonstrate the feasibility and performance of both techniques.

A New Asymmetrical MLI with Reduced Switch Count for a Three Phase Induction Motor

This work explores a novel multilevel inverter (MLI) topology to minimize the number of power switches in the passage of current to accomplish each level of the output voltage. The unequal magnitudes of the dc voltage sources in attempt to realize higher levels of the output voltage bring in the asymmetrical nature of operation. It involves a series parallel switched configuration with bidirectional switches to avert the flow of circulating current in between the two H - bridges in each phase of the MLI. The effort incites to use the theory of a new Pulse Width Modulation (PWM) strategy for mitigating the higher frequency components of the voltage applied to the stator. It imbibes the Phase Disposition (PD) principles in the modulating strategy for arriving at the sinusoidal shape for the output voltage . Total Harmonic Distortion (THD) indexed by lower values for the output voltage over the traditional firing scheme serves to be the highlight for the MLI in acclaiming its place in the inverter world. The results obtained through MATLAB based simulation over a range of modulation indices. The performance measured in terms of the THD claims its suitability for use in Induction Motor (IM) drives.

A Compact Single-Phase Single stage AC-AC Impedance Source Converter

The paper presents a compact AC-AC single phase voltage regulator based on Impedance network. The proposed topology has ability to perform buck and boost operation in a single stage .The circuit is simple, highly efficient and more importantly reduced manufacturing cost due to its minimal number of active and passive components. The Impedance network has dual function of boosting and filtering. The proposed topology employs two bidirectional switches operating at high frequency PWM pulses. The high frequency switching reduces the size of the Impedance network. The gain of the system is controlled by controlling the duty cycle of the bidirectional switches. The operating mechanism of the proposed topology along with simulation and experimental results are presented.