996 research outputs found
THD Improvement for Variable Speed Drive Using Single Phase Multilevel Inverter
Low harmonic waveform is a very important requirement of the high power
applications. Nowadays many researchers are focusing on new voltage source. Such
voltage sources are formed by Cascade H-bridge Multilevel Inverter with low Total
Harmonic Distortion (THD). A multilevel inverter has wide applications especially for
High-Power Electrical Vehicle motor drive because they convert small DC voltage to
high AC voltage. This study investigates the performance and discusses the features of
transformer and transformer-less multilevel inverters. In order to generate sinusoidal
wave with minimum total harmonic distortion, one approach has been adapted to
calculate the conducting angles. Simple external circuit was employed to equalize the
magnetic flux via each transformer which makes it more efficient in order of the
manufacturability. All H-bridge will have the same specifications which enhance the
modularity of the system. THD values have been measured experimentally and from simulation results, the results show a good agreement with latest research. The
experimental result has been compared with the simulation values, considerable
difference have been notice because the effect of some factor such as the difference in
components quality and the precise of the microcontroller. The PIC microcontroller was
used to generate the gate signals and controlling the swapping circuit. The proposed
circuits were simulated using Orcad/Pspice and experimental prototype was build as a
drive for single phase induction motor based voltage 1 frequency method to show the
validity of this system. Simulation of the diode clamped and transformer-less cascade
multilevel inverter has been carried out to investigate their features
Direct usage of photovoltaic solar panels to supply a freezer motor with variable DC input voltage
In this paper, a single-phase photovoltaic (PV) inverter fed by a boost converter to supply a freezer motor with variable DC input is investigated. The proposed circuit has two stages. Firstly, the DC output of the PV panel that varies between 150 and 300 V will be applied to the boost converter. The boost converter will boost the input voltage to a fixed 300 V DC. Next, this voltage is supplied to the single-phase full-bridge inverter to obtain 230 V AC. In the end, The output of the inverter will feed a freezer motor. The PV panels can be stand-alone or grid-connected. The grid-connected PV is divided into two categories, such as with a transformer and without a transformer, a transformer type has galvanic isolation resulting in increasing the security and also provides no further DC current toward the grid, but it is expensive, heavy and bulky. The transformerless type holds high efficiency and it is cheaper, but it suffers from leakage current between PV and the grid. This paper proposes a stand-alone direct use of PV to supply a freezer; therefore, no grid connection will result in no leakage current between the PV and Grid. The proposed circuit has some features such as no filtering circuit at the output of the inverter, no battery in the system, DC-link instead of AC link that reduces no-loads, having a higher efficiency, and holding enough energy in the DC-link capacitor to get the motor started. The circuit uses no transformers, thus, it is cheaper and has a smaller size. In addition, the system does not require a complex pulse width modulation (PWM) technique, because the motor can operate with a pulsed waveform. The control strategy uses the PWM signal with the desired timing. With this type of square wave, the harmonics (5th and 7th) of the voltage are reduced. The experimental and simulation results are presented to verify the feasibility of the proposed strategy
FPGA based quasi z-source cascaded multilevel inverter using multicarrier PWM techniques
FPGA based Quasi Z-Source Cascaded Multilevel Inverter (Quasi Zs-CMLI) using multicarrier PluseWidth Modulation (PWM) techniques are presented in this paper. Multicarrier based PWM techniques have been proposed for seven level Quasi Zs-CMLI and implemented using Field Programmable Gate Array (FPGA). For generating gating pulses to the inverter switches, Phase Disposition (PD), Inverted Phase Disposition (IPD), Phase Opposition Disposition (POD) and Alternative Phase Opposition Disposition (APOD) techniques are programmed on FPGA. In the proposed system, three solar PV emulator modules are used. These are acting as input source to the inverter. Finally, THD comparison made between different carrier based modulation with shoot through and non-shoot through the states. The proposed quasi Zs-CMLI and PWM techniques are verified through MATLAB/Simulink. For confirmation of simulation results, A laboratory prototype model have been implemented using FPGA. The capture hardware results are matched with simulation results
Modelling, simulation and real time implementation of a three phase AC to AC matrix converter
Matrix converters (MCs) are essentially forced commutated cycloconverters with inherent four quadrant operation consisting of a matrix of bidirectional switches such that there is a switch for each possible connection between the input and output lines. Matrix converter directly converts the AC input voltage at any given frequency to AC output voltage with arbitrary amplitude at any unrestricted frequency without the need for a dc link capacitor storage element at the input side.The introduction of bidirectional switches using power transistors and IGBTs made easy realization of the matrix converter. The real development of the matrix converter starts with the work of Venturini and Alesina who proposed a mathematical analysis and introduced the Low-Frequency Modulation Matrix concept to describe the low frequency behavior of the matrix converter [1-3]. In this, the output voltages are obtained by multiplication of the modulation matrix or transfer matrix with the input voltages. One of the essential requirements for switching three phase AC to three phase AC MC is that two or more bidirectional switches connected to any one output phase should NOT be closed simultaneously, as this will cause dangerously high short circuit current. Similarly any one bidirectional switch connected to each output phase should remain closed to provide a current path with inductive load.This thesis mainly provides an account of the three phase AC to three phase AC MC modelling concept with SIMULINK software using fundamental Venturini and Optimum Venturini modulation algorithm [1-8], advanced modulation algorithm such as that proposed by Sunter-Clare [11-12] and by Ned Mohan [13-14, 16-17], application of these algorithms for the Vector control of three phase Induction Motor (IM) drive [15], real time hardware in the loop simulation [51,54-55] for a three phase AC to single phase AC MC, three phase AC to three phase AC Multilevel MC (MMC) with three [18-19] and six flying capacitors per output phase using PSCAD software (as SIMULINK started shooting trouble), Indirect (ISVM) [25-30] and Direct (DASVM, DSSVM, CZASVM) [31-38] Space Vector Modulation, newly discovered dual programmable AC to DC rectifier concept using three phase AC to three phase AC MC [43-45], Delta-Sigma Modulated MC [46-49] and single phase AC to three phase AC MC [50].In addition a novel concept of a single phase / three phase AC to single phase / three phase AC converter using a DC link, complementary N and P MOSFETs and IGBTs is presented. A chapter on model verification is also presented where selected SIMULINK models from various chapters have been verified by using either PSCAD or PSIM software. An appendix on PIC microcontroller PIC16F84A application to saw-tooth carrier waveform generation and switching three phase AC to three phase AC converters using a DC link is added. Another appendix on speed control and brake by plugging of three phase induction motor fed by matrix converter is presented. List of publications from this thesis is presented on third appendix
Experimental investigation on the performances of a multilevel inverter using a field programmable gate array-based control system
The Field Programmable Gate Array (FPGA) represents a valid solution for the design of control systems for inverters adopted in many industry applications, because of both its high flexibility of use and its high-performance with respect to other types of digital controllers. In this context, this paper presents an experimental investigation on the harmonic content of the voltages produced by a three-phase, five level cascaded H-Bridge Multilevel inverter with an FPGA-based control board, aiming also to evaluate the performance of the FPGA through the implementation of the main common modulation techniques and the comparison between simulation and experimental results. The control algorithms are implemented by means of the VHDL programming language. The output voltage waveforms, which have been obtained by applying to the inverter the main PWM techniques, are compared in terms of THD%. Simulation and experimental results are analyzed, compared and finally discussed
Suppression of line voltage related distortion in current controlled grid connected inverters
The influence of selected control strategies on the level
of low-order current harmonic distortion generated by an inverter
connected to a distorted grid is investigated through a combination
of theoretical and experimental studies. A detailed theoretical
analysis, based on the concept of harmonic impedance, establishes
the suitability of inductor current feedback versus output
current feedback with respect to inverter power quality. Experimental
results, obtained from a purpose-built 500-W, three-level,
half-bridge inverter with an L-C-L output filter, verify the efficacy of inductor current as the feedback variable, yielding an
output current total harmonic distortion (THD) some 29% lower
than that achieved using output current feedback. A feed-forward
grid voltage disturbance rejection scheme is proposed as a means to
further reduce the level of low-order current harmonic distortion.
Results obtained from an inverter with inductor current feedback
and optimized feed-forward disturbance rejection show a THD of
just 3% at full-load, representing an improvement of some 53% on
the same inverter with output current feedback and no feed-forward
compensation. Significant improvements in THD were also
achieved across the entire load range. It is concluded that the use
of inductor current feedback and feed-forward voltage disturbance
rejection represent cost–effect mechanisms for achieving improved
output current quality
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