A new sinewave inverter with high frequency link and synchronous rectification using power MOSFETs

This research compared the performance of PWM (Pulse Width Modulation) inverter and multilevel inverter in terms of their output voltage and current total harmonic distortion (THD). The inverters were designed to have the output voltage of 220 V at 50 Hz. The input voltage for both inverters are 400 VDC. For PWM inverter, the PWM technique utilized was sinusoidal PWM (SPWM) and for multilevel converter, the number of voltage level is five with diode-clamped topology. The study included circuit implementation, analysis, and THD calculation, all of which were carried out through simulation using PSpice software. In controlling the SPWM inverter output, the adjusted parameters included amplitude modulation ratio, frequency modulation ratio, and filter components’ parameters. On the other hand, the firing angles of the switching components were designated as controlling parameters in multilevel inverter. From the study, it was found that the best THD values of the designed SPWM inverter are 4.2% (voltage) and 1.7% (current), while those of multilevel inverter are 27% and 11%, for voltage and current, respectively. Thus, it can be concluded that SPWM inverter is better than 5-level inverter for the application in solar panel due to its lower THD. In our study, 5-level inverter did not satisfy the THD requirement specified in IEEE 512-1992, i.e. 5%.

Nowadays power inverters are widely used in various applications which range from domestic to industrial facilities. The Pulse Width Modulation (PWM) techniques are extensively used for the controlling of inverter circuit in which dead time, duty cycle, and frequency are important performance parameters. In the case of controlling multiple inverters with a single controller, control signals with embedded dead-time for all the inverters may lead to poor performance for some inverters due to shoot through and controlling of multiple inverters with common duty cycle and frequency cannot fulfill the requirement. Moreover, the use of an individual controller for each inverter is not cost-effective. In this work, the PWM switching strategies are designed with Verilog Hardware Description Language (HDL) and implemented using Xilinx Spartan-6 Nexys3 FPGA with precise control of dead time, duty cycle and frequency. This FPGA based controller enables us to control any inverter designed for a specific purpose and the same inverter for different applications by configuring its frequency and duty cycle. For the present work, we have generated six PWM signals with three different dead times and duty cycles which can control three single-phase PWM inverters with specified dead time and found that FPGA implementation provide desired output with negligible distortion avoiding shoot through.

The authors present a type of PWM (pulse-width-modulated) inverter for a small-scale photovoltaic power system. It has five voltage levels, including the earth level, which is composed of charging two storage battery units in series or parallel combination. The waveform of the output voltage is more sinusoidal than that of the conventional PWM inverter. In the case of an inductive load, however, the waveform shows some deteriorations. The operation of this PWM inverter with an inductive load is analyzed. An advanced circuit is devised to eliminate these deteriorations. It is verified that the experimental results agree well with the theoretical results obtained using FFT (fast Fourier transform) analysis. A resonant-type five-level PWM inverter is also presented. >

The aim of this paper is to obtain the AC voltage from DC source with the help of Space vector based Inverter. In a space-vector PWM (Pulse Width Modulation) inverter, which is widely used, the voltage utilization factor can be increased to 0.906, normalized to that of the six step operation. Three phase voltage-source pulse width modulation inverters have been widely used for dc/ac power conversion since they can produce a variable voltage and variable frequency power. However, they require a dead time to avoid the arm-short and snubber circuits to suppress the switching spike. Apart from these ancillary aspects, the PWM inverters have an essential problem that they cannot produce voltages as large as the six-step inverters can. That is, the dc bus voltage cannot be utilized to the maximum. To increase the voltage utilization of the sinusoidal PWM inverter, a method of the addition of the third harmonics to the reference voltage was proposed by which the fundamental component can be increased by 15.5%. In a space-vector PWM inverter, which is widely used, the voltage utilization factor can be increased to 0.906, normalized to that of the sixstep operation. On the other hand, different discontinuous PWM strategies were analyzed, where the modulation waveform of a phase has at least one segment of 60 which is clamped to the positive and/or negative dc bus for, at most, a total of 120 in a fundamental period during which no switching in either inverter arm occurs. Recently, it is shown that discontinuous PWM schemes and the space-vector PWM can be obtained by properly adding a zero-sequence voltage to the original modulation waveform.

This paper presents a novel digital control scheme for the regulation of single-phase voltage source pulse width modulation (PWM) inverters used in AC power sources. The proposed scheme adopts two deadbeat controllers to regulate the inner current loop and the outer voltage loop of the PWM inverter. For the overhead of digital processing, the change of duty of PWM lags one carrier period behind the sampling signal, which is modeled as a first-order lag unit in a discrete domain. Based on this precise modeling, the deadbeat controllers make the inverter get a fast dynamic response, so that the inverter’s output voltage is obtained with a very low total harmonic distortion (THD), even when the load is fluctuating. The parameter sensitivity of the deadbeat control was analyzed, which shows that the proposed deadbeat control system can operate stably when the LC filter’s parameters vary within the range allowed. The experimental results of a 2kW inverter prototype show that the THD of the output voltage is less than 3% under resistive and rectifier loads, which verifies the feasibility of the proposed scheme. An additional advantage of the proposed scheme is that the parameter design of the controller can be fully programmed without the experience of a designer.

The iron loss of an induction motor powered by the sinusoidal wave of a commercial power source has been remarkably decreased by improving the electrical steel sheet used in a motor. However, in recent years, the permanent magnet motor and induction motor used in electric vehicles are often powered by a Pulse Width Modulation (PWM) inverter which shows good controllability. Iron loss in a stator core is increased by the carrier wave used in the PWM inverter. The iron loss of a ring core specimen made of electrical steel sheets of three kinds of thicknesses was evaluated under PWM inverter excitation. The thicknesses of the prepared electrical steel sheets were 0.08 mm, 0.1 mm, and 0.35 mm, respectively. In addition, in this paper, a number of problems that present when iron loss is evaluated under PWM excitation were investigated. For instance, the influence of switching-noise and dead-time of the PWM inverter on the iron loss were examined. Moreover, relationships between the carrier frequency, the modulation index and the iron loss were investigated. As a result, it was found that the iron loss of the ultrathin electrical steel sheet does not increase much even under PWM excitation.

This paper presents a novel "Modular Multilevel Converter" (MMC) topology. The topology takes advantage of the MMC characteristics by offering multilevel output voltage with low Total Harmonic Distortion (THD), increased reliability, and design flexibility due to the modular nature of the converter [1] and [2]. This topology is composed of a "full-bridge converter" (FBC) connected to multiple "High Frequency Link" (HFL) modules via high frequency transformers. Each module produces its own isolated DC voltage that keeps the capacitor charged to a specific level, removing the need of a voltage-balancing algorithm. Furthermore the module voltage can be controlled by changing the FBC duty cycle in order to obtain lower output voltages without decreasing the number of levels. This topology fits well in large scale Photovoltaic (PV) power plants due to its capability to produce a high voltage output. This topology's feasibility is validated by simulation results (Matlab/Simulink).

A study is described of the system losses in a transistorized pulsewidth modulated (PWM) inverter and induction motor in a traction drive system and the development of a strategy for minimizing them. The losses include inverter losses, conventional fundamental frequency motor losses, and motor harmonic losses. The losses in both PWM and six-step square wave (SSSW) inverter operation are studied. The loss models are introduced into a motor performance analysis program allowing the computation of the drive system performance over the entire speedtorque range. The study shows that a strategy for minimizing drive system losses is a function of torque. The air gap flux density should be held at its maximum level until the torque requirement is reduced to a low value, and then the air gap flux level is reduced.

A 2D-3D hybrid finite element method (FEM) approach is proposed for fast analysis of eddy current loss in magnets of permanent magnetic synchronous motors (PMSM) driven by a pulse width modulation (PWM) inverter. A voltage-source PWM inverter circuit coupled 3D FEM model of a PMSM was built with the commercial FEM code JMAG and the eddy current loss in the magnets of the PMSM was calculated which was extremely time-consuming. As the eddy current loss in magnets is relatively small compared with the power capacity of the motor, a voltage-source PWM inverter circuit coupled 2D FEM model is built to calculate the current waveforms ignoring the division of permanent magnets along the axial direction. Applying the calculated current waveforms from the 2D calculation to a current-source circuit coupled 3D FEM model, the eddy current loss in the magnets can be obtained which needs much less computation time. The result is very close to that obtained directly from the voltage-source PWM inverter circuit coupled 3D FEM model.

The iron loss calculation is crucial issue in making hi-power density power converter. In this paper, the iron loss separation model for AC filter inductor on a pulse-width modulation (PWM) inverter is proposed. This paper features analyzing iron loss of inductor on PWM inverter excitation which contains rectangular voltage excitation and premagnetization condition. In order to verify the proposed model, the measurement results obtained using the real PWM inverter and the calculation results using the proposed model on both the single-phase and three-phase inverters are compared. The calculated iron losses agree with measured losses within 3%. Then, the iron loss is separated into hysteresis loss and a sum of eddy current loss and excess loss by proposed model. In the PWM inverter excitation, even a magnetic material which is made to suppress the eddy current loss, such as iron powder, eddy current loss and excess loss is seen in calculated iron loss. The sum of eddy current loss and excess loss value is approximately 30%.

A key issue for power electronic converters is the ability to tackle periodic signals in electrical power processing to precisely and flexibly convert and regulate electrical power. This book provides complete analysis and synthesis methods for periodic control systems. It covers the control, compensation, and filtering of periodic signals in power electronic power processing and proposes a unified framework for housing periodic control schemes for power converters, providing a general proportional-integral-derivative control solution to periodic signal compensation in extensive engineering applications - a perfect periodic control solution for power electronic conversion. It provides number of demonstrative practical examples of the application of periodic control to: standalone constant-voltage-constant-frequency (CVCF) singlephase Pulse Width Modulation (PWM) inverters; standalone CVCF singlephase High Frequency Link (HFL) inverters; standalone CVCF three-phase PWM inverters; grid-connected single-phase inverters; grid-connected singlephase Cycloconverter type HFL rectifiers; grid-connected three-phase PWM inverters; programmable AC power sources; shunt active power filters; and UPS systems. Periodic Control of Power Electronic Converters is of key importance for researchers and engineers in the field of power electronic converter systems and their applications, for control specialists exploring new applications of control theory in power electronics, and for advanced university students in these fields.

Pulse width modulation (PWM) switching technique is commonly used in full bridge converters to overcome the bulky filter requirements and efficient voltage control, at the cost of higher switching losses. However, all PWM techniques not only cause circuit complexity but also need high frequency switches such as MOSFETs with high conduction drop causing lower efficiency. This paper presents a novel sine wave inverter circuit which uses a full bridge topology with a PWM DC link. The PWM DC link is generated by using a buck switch in series with the DC source which is switched with unipolar sine PWM signal continuously. The bridge inverter switches are supplied with line frequency gate signals which are synchronized with the original modulating sine wave signal. The proposed inverter uses five switches out of which only one switch is switched at high frequency, while other switches operate at low (line) frequency which not only make the overall efficiency high but also make the voltage control simple as only one switch is supplied with controllable PWM signal. The proposed topology with switching technique was simulated and a prototype model was developed in the laboratory to prove its feasibility.

Recently, great attention has been addressed for multilevel inverters, as they exhibit low total harmonic distortion (THD) in the output voltage and low electromagnetic interference (EMI). This paper proposes a single-phase five-level pulse width modulation (PWM) inverter for grid connection. The proposed PWM technique has some switches operated at fundamental line frequency and the others operate at inverter switching frequency. The proposed inverter has advantages of less number of components and low THD compared with the conventional multilevel inverter. The inverter operational principles and the switching functions are analyzed in this paper. Moreover, a proportional integral (PI) current control algorithm is designed and implemented in DSPACE DS1103 to keep the current injected into the grid sinusoidal and in-phase with the grid voltage for unity power factor. Simulation and experimental results prove the powerful merits of the proposed multi-level inverter and the capabilities of the proposed PWM technique.

In this paper, comparisons are made on various parameters of electromagnetic fields like air gap flux density (radial), flux distribution, phase currents, speed and torque of a healthy and stator inter-turn fault induction motor (IM). Using FEM (Finite Element Method), the inter-turn short circuit fault analysis of PWM (Pulse Width Modulated) inverter fed 3 phase IM is analyzed. The inter-turn fault is the initial stage of a short circuit in the stator winding and it progresses to a phase to phase fault or phase to ground fault if left undetected. When the IM is directly fed from the mains, the inter-turn fault can be identified using a popular technique known as MCSA (Motor Current Signature Analysis). But this method fails when the IM is fed from a PWM inverter due to rich noise content observed in the current spectrum due to high frequency inverter switching making it difficult to detect the fault. The electromagnetic field analysis of PWM inverter fed 3 phase IM with 12.5% and 25% stator winding inter-turn fault is carried out on a 7.5kW IM using ANSYS Maxwell FEA (Finite Element Analysis) tool. The spatial FFT spectrum of air gap flux density (radial) indicates the presence of stator winding inter-turn fault with rich noise content compared to healthy motor.

This paper presents simulation and analysis of intelligent control-based boost converter interfaced with three-level-diode clamped inverter (TL-DCI) for renewable energy and AC motor drive applications. The main objective of a DC–DC boost converter is to maintain a constant output voltage with an optimum duty cycle despite variations in input voltage or load current using an intelligent control, i.e., fuzzy logic control (FLC) approach. Further, better conversion efficiency with reduced ripple can be obtained by keeping optimum range of output voltage. To achieve the desired results from a DC–DC converter, an intelligent controller is required. The open loop and conventional proportional integral (PI) controllers have certain limitations to improve dynamic performance due to variation of parasitic into components. The FLC uses voltage output as feedback for significantly improving the dynamic performance of boost DC–DC converter. In addition, an intelligent control-based boost converter interfaced with TL-DCI using sine pulse width modulation (PWM) to apply for AC motor drive applications. This paper shows an improved dynamic performance of boost converter using FLC compared to open loop and conventional PI controllers using MATLAB or Simulink. The performance of TL-DCI using sine PWM integrated with FLC-based boost converter has been analyzed in terms power quality with respect to voltage and current waveforms.KeywordsBoost converterPI controlIntelligent controlTL-DCISine PWM