A Fault-Tolerant T-Type Multilevel Inverter Topology with Soft-Switching Capability Based on Si and SiC Hybrid Phase Legs

The performance of a novel three-phase four-leg fault-tolerant T-Type inverter topology is presented in this paper, which significantly improves the inverter\u27s fault-tolerant capability regarding device switch faults. In this new modular inverter topology, only the redundant leg is composed of Silicon Carbide (SiC) power devices and all other phase legs are constituted by Silicon (Si) devices. The addition of the redundant leg, not only provides fault-tolerant solution to switch faults that could occur in the T-Type inverter, but also can share load current with other phase legs. Moreover, quasi zero-voltage switching (ZVS) and zero-current switching (ZCS) in the Si Insulated-Gate Bipolar Transistors (IGBTs) of the main phase legs can be achieved with the assistance of SiC Metal-Oxide Semiconductor Field-Effect Transistors (MOSFETs) in the redundant leg. Simulation and experimental results are given to verify the efficacy and merits of this high-performance fault-tolerant inverter topology

Single DC Source Fed Cascaded Multilevel Inverter along with AC L-C-L Resonant Converter for High Current and Low Voltage Applications

In the beginning, the power supplies employed in very low voltage and high current application such as arc welding, electroplating process. But in this power supplies use in line frequency step-down transformers and rectifier based control circuits, which has the demerits of large size, inefficient, high output ripple and more operational costs. So there is need to improve the power supplies for high current and low voltage applications. Recently, an efficient and switched-mode power supply (SMPS) suited for low voltage and very high current applications. In this uses a multi-level inverter (MLI) to convert line frequency input waveforms to high frequency for reduce the loss and cost. In the present work, we investigate different types of MLI, they are diode clamped MLI, flying capacitor MLI and cascaded H-bridge MLI, and finally proposed a new topology is single DC source fed CML by using single-phase transformers. The output of MLI feeds an AC L-C-L resonant converter and it behave as constant current source and it can reduce the peak-to-peak output ripple, total harmonic distortion (THD). The output stage of AC L-C-L resonant converters consisting of a number of easily constructed planar transformers with center tapped secondary side and rectifier circuit. The planar transformer gives significant advantage leakage inductance, skin effect and winding capacitance can be minimized and also provide isolation at the output side. The proposed structure is modeled and the simulated results are presented to verify its performance

Precise modelling of switching and conduction losses in cascaded h-bridge multilevel inverters

Nowadays, voltage source multilevel inverters are being used extensively in industry due to its many advantages, compared to conventional two level inverters, such as higher output voltage at low switching frequency, low voltage stress(dv/dt), lower total harmonic distortion (THD), less electro-magnetic interference (EMI), smaller output filter and higher fundamental output. However, the evaluation of multilevel inverter losses is much more complicated compared to two level inverters. This paper proposes an on-line model for precise calculation of conduction and switching losses for cascaded h-bridge multilevel inverter. The model is simple and efficient and gives clear process of loss calculation. A singlephase 7-level cascaded h-bridge with IGBT's as switching devices has been used as a case study of the proposed model. The inverter has been controlled using selective harmonic elimination in which the switching angles were determined using the Genetic Algorithm (GA). MATLAB-SIMULINK is used for the modelling and simulation

Variable var compensator circuits

A family of two reactive-power compensator circuit is presented. A general model of some basic linear elements and switching function blocks is developed first. Then the two proposed compensator circuits are derived from the generalised model. The proposed circuits are capable of supplying leading as well as lagging reactive currents in stepless variation without using an inverter configuration. The switching frequency is in the range of 2.5 kHz and the largest capacitor utilised does not exceed 60 muF. The generated reactive current, in either the leading or lagging modes, contains less than 2% total harmonic distortio

A Current-Dependent Switching Strategy for Si/SiC Hybrid Switch-Based Power Converters

Abstract: Hybrid switches configured by paralleling Silicon (Si) Insulated Gate Bipolar Transistors (IGBT) and Silicon Carbide (SiC) Metal-Oxide Semiconductor Field-Effect Transistors (MOSFET) have been verified to be a high-efficiency cost-effective device concept. In this paper, a current-dependent switching strategy is introduced and implemented to further improve the performance of Si/SiC hybrid switches. This proposed switching strategy is based on a comprehensive consideration of reducing device losses, reliable operation, and overload capability. Based on the utilization of such Si/SiC hybrid switches and the proposed switching strategy, a 15-kW single-phase H-bridge inverter prototype was implemented and tested in the laboratory. Simulation and experimental results are given to verify the performance of the hybrid switches and the new switching strategy

Supercapacitor assisted LDO (SCALDO) techniquean extra low frequency design approach to high efficiency DC-DC converters and how it compares with the classical switched capacitor converters

Supercapacitor assisted low dropout regulators (SCALDO) were proposed as an alternative design approach to DC-DC converters, where the supercapacitor circulation frequency (switching frequency) is in the order of few Hz to few 10s of Hz, with an output stage based on a low dropout regulator stage. For converters such as 12–5V, 5–3.3V and 5–1.5V, the technique provides efficiency improvement factors of 2, 1.33 and 3 respectively, in compared to linear converters with same input-output combinations. In a 5–1.5V SCALDO regulator, using thin profile supercapacitors in the range of fractional farads to few farads, this translates to an approximate end to end efficiency of near 90%. However, there were concerns that this patented technique is merely a variation of well-known switched capacitor (charge pump) converters. This paper is aimed at providing a broad overview of the capability of SCALDO technique with generalized theory, indicating its capabilities and limitations, and comparing the practical performance with a typical switched capacitor converter of similar current capability

Linearized large signal modeling, analysis, and control design of phase-controlled series-parallel resonant converters using state feedback

This paper proposes a linearized large signal state-space model for the fixed-frequency phase-controlled series-parallel resonant converter. The proposed model utilizes state feedback of the output filter inductor current to perform linearization. The model combines multiple-frequency and average state-space modeling techniques to generate an aggregate model with dc state variables that are relatively easier to control and slower than the fast resonant tank dynamics. The main objective of the linearized model is to provide a linear representation of the converter behavior under large signal variation which is suitable for faster simulation and large signal estimation/calculation of the converter state variables. The model also provides insight into converter dynamics as well as a simplified reduced order transfer function for PI closed-loop design. Experimental and simulation results from a detailed switched converter model are compared with the proposed state-space model output to verify its accuracy and robustness

To develop an efficient variable speed compressor motor system

This research presents a proposed new method of improving the energy efficiency of a Variable Speed Drive (VSD) for induction motors. The principles of VSD are reviewed with emphasis on the efficiency and power losses associated with the operation of the variable speed compressor motor drive, particularly at low speed operation.The efficiency of induction motor when operated at rated speed and load torque is high. However at low load operation, application of the induction motor at rated flux will cause the iron losses to increase excessively, hence its efficiency will reduce dramatically. To improve this efficiency, it is essential to obtain the flux level that minimizes the total motor losses. This technique is known as an efficiency or energy optimization control method. In practice, typical of the compressor load does not require high dynamic response, therefore improvement of the efficiency optimization control that is proposed in this research is based on scalar control model.In this research, development of a new neural network controller for efficiency optimization control is proposed. The controller is designed to generate both voltage and frequency reference signals imultaneously. To achieve a robust controller from variation of motor parameters, a real-time or on-line learning algorithm based on a second order optimization Levenberg-Marquardt is employed. The simulation of the proposed controller for variable speed compressor is presented. The results obtained clearly show that the efficiency at low speed is significant increased. Besides that the speed of the motor can be maintained. Furthermore, the controller is also robust to the motor parameters variation. The simulation results are also verified by experiment

Penghasilan modul pembelajaran kendiri bahan dan binaan berasaskan web

Perkembangan teknologi maklumat dalam dunia pendidikan tidak Iagi boleh dinafikan pada masa kini. Keperluan yang meningkat dalam sistem pembelajaran dan pengajaran memerlukan mereka yang terlibat memberi sepenuh tumpuan terhadap mata pelajaran bagi mencapai matlamat, untuk tujuan ini modul pembelajaran kendiri di hasilkan bagi membantu memudahkan pelajar dan pensyarah dalam mata pelajaran Bahan dan Binaan agar dapat mengikuti pelajaran tersebut secara berkesan tanpa membuang masa. Seramai 35 orang pelajar diploma kejuruteraan Awam Politeknik Sultan Abdul Halim Muadzam Shah , Jitra Kedah terlibat sebagai responden. Statistik deskriptif digunakan dalam mengumpul dan menganalisis data. Secara keseluruhannya dari hasil kajian, menunjukkan para pelajar memberikan maklum balas yang positif terhadap modul pembelajaran kendiri Bahan dan Binaan berasaskan web ini. Dari hasil kajian ini juga didapati bahawa kebanyakan pelajar lebih berminat terhadap menggunakan media yang pelbagai seperti teks, audio dan visual. Walau bagaimana pun masih terdapat beberapa aspek yang perlu diperbaiki untuk memantapkan modul pembelajaran kendiri ini. Bagi menyokong perkembangan dan penggunaan teknologi maklumat dalam pendidikan keijasama daripada pelbagai pihak seperti Kementerian dan Politeknik sendiri diperlukan terutama dari segi kemudahan komputer, kursus penggunaan perisian dan sebagainya.ini adalah penting bagi melahirkan graduan yang berkualiti dan mempunyai pengetahuan yang meluas dalam bidang teknologi pada masa akan datang