ABSTRACT: The power extracted from renewable energy resources has some limitations that are occurred due to the weather changes and scarcity of sources. The power demand and scarcity can be minimized by improving the power extracting methods. Multilevel inverter requires several number of dc sources for synthesizing the ac output voltage waveform. Therefore a new method of multilevel inverter with reduced number of switches has been designed that uses hybrid modulation technique where it is the combination of Fundamental Frequency Pulse Width Modulation (FPWM) and Multi Sinusoidal Pulse Width Modulation MSPWM for each inverter cell operation that is processed by sequential switching pulse which reduces the power loss and conduction loss. This proposed designed with reduced number of switches, the conduction and switching losses gets decreased, which leads to increase the efficiency of the inverter. The size and power consumption in the driving circuits can also be minimized. This structure minimizes the Total Harmonic Distortion (THD) of the output voltage waveforms.
Recently, MultiLevel Inverter (MLI) topology is of paramount importance for high voltage and high power applications. Several topologies of MLI have been reported in the literature. But this paper presents an asymmetric cascaded multilevel inverter employing two unequal DC sources to generate seven-level output. The modulation control schemes for the multilevel inverter can be divided into two categories, fundamental switching frequency and high switching frequency Pulse Width Modulation (PWM). Further, the high frequency PWM is classified as multilevel carrier-based PWM, selective harmonic elimination and multilevel space vector PWM . The most popular and simple high frequency switching scheme for multilevel inverter is multi-carrier-PWM (MCPWM). It can be categorized into two groups: Carrier Disposition methods (CD) and phase shifted (PS) methods . Among the carrier disposition methods, Phase Disposition (PD) PWM technique is normally employed as the carriers need minimal amounts of alteration since they are all in phase with each other .This paper focuses on hybrid modulation strategy for MLI. The proposed technique combines the fundamental frequency switching scheme and variable frequency inverted sine pulse width modulation (VFISPWM) . The inverted sine PWM has a better spectral quality and a higher fundamental voltage compared to the triangular based PWM. But the main drawback is the marginal boost in the magnitude of lower order harmonics and unbalanced switch utilization. This is overcome by employing variable frequency inverted sine carrier signals which leads to reduced switching losses and low harmonic content.
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This section describes the determination of switching function for getting output of seventeen levels in the proposed inverter. The same procedure can be extended to drive the switching function for N level inverter. A hybrid PWM modulation technique was used to generate the PWM switching signals. Hybrid modulation switching strategy is a combination of fundamental frequency modulation (FPWM) and Multi- level Sinusoidal Pulse width modulation (MSPWM) for each inverter operation, so that the output inherits the features of switching-loss reduction from FPWM, and good harmonic performance from MSPWM. The power loss is the sum of switching and conduction losses. Hence, the proposed modulation technique yields the inverter to operate with reduced power loss across the switching devices. The well-known MSPWM scheme such as Single Carrier Sinusoidal Pulse Width Modulation (SCSPWM) is employed to generate the switching pulses. Compared to conventional MSPWM schemes, less number of commutations and considerable switching-loss reduction is obtained by using this modulation scheme.In this modulation technique, the upper bridge switches are commutated at FPWM, while the lower H-bridge switches are modulated at MSPWM, therefore the resultant switching patterns are the same as those obtained with MSPWM. A sequential switching scheme is embedded with this hybrid modulation in order to overcome unequal
This paper gives high-proficiency single-stage transformer less inverter with hybrid modulation method is proposed and assessed. Without input split capacitors, common-mode voltage and leakage current issues in a non-isolated framework with this design are disposed of, and the peculiarity of a three-level output voltage in the inverter bridge’s middle point helps inductors and power quality enhancement. The operation standards with hybrid modulation strategy combined with unipolar and bipolar pulse width modulation schemes are displayed.
Using of diffractive optical elements (DOE) in the Schupmann system offer a new way for the construction of ultra-large aperture telescope. The Fresnel Corrector, one of the DOEs, is the key device in the Schupmann system, which is used to correct the chromatic aberration introduced by the diffrac- tive primary lens called Magnifying Glass. Generally, in a large aperture tele- scope (>20 m), the Fresnel Corrector is a diffractive lens with a large aperture and a small f-number, which is difficult to process. In this article, an im- proved device with a small F number but a large rim feature size, called am- plitude and phase hybrid modulation Fresnel diffractive optical element (APHMFDOE), is used here as the Fresnel corrector. First, APHMFDOE with appropriate parameters is designed to match the dispersion of the Magnifying Glass so that the system meets the achromatic condition. Second, the optical characteristics of this improved system are simulated and compared with those of the general system based on the conventional Fresnel corrector. Our approach introduces a new dispersion correction device, which not only can eliminate the chromatic aberration caused by Magnifying Glass, but also can reduce the processing difficulty of Fresnel Corrector.
Permanent magnet synchronous motor (PMSM) system and proposes control method which can generate maximum output power in overall speed range for integrated starter/alternator. This project analyzes the dual inverter driven open-end machine system consists of two inverters which are connected to the both ends of the machine winding. By disconnecting one inverter from the power source, the dc-link voltage of flying capacitor can be boosted through the machine. Because one inverter is connected to the only power source, output power of the machine is regulated by the source connected inverter. In this paper, modulation method for maximizing output power of inverter and motor with reduced harmonic and loss is proposed. It is a hybrid modulation combining seven-step and fast space vector pulse width modulations. With proposed method, efficiency and operation area are improved and cost of entire driving system is also decreased due to the removing of dc–dc converter. Analyses, strategies, control method, and simulation results are descripted. The experiments with PMSM are accomplished to verify the feasibility of proposed method.
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Multi Level Inverters (MLI) are classified into three types: the flying capacitor inverter, the diode clamped inverter and the modular H-bridge inverter. In this work, modular H-bridge inverter is used. Tolbert et al. (2003) have derived a procedure to find all sets of switching angles for which the fundamental is produced while the 5 th and 7 th are eliminated. Palanivel and Dash (2010) have developed various carrier based pulse width modulation techniques which can minimise the total harmonic distortion and enhance the output voltage for a five level inverter. Du et al. (2009) discussed about the control of seven-level Hybrid Cascaded Multi Level Inverter (HCMLI) with fundamental frequency switching control and explained how its modulation index (m a )
Suzi Seroja Sarnin et. al.  highlights in the paper ” Performance Study of BPSK and 8-PSK Using Cyclic Codes in CDMA Environment” the performance of BPSK and 8-PSK in Code Division Multiple Access (CDMA) environment by using Cyclic Codes as the Forward Error Correction (FEC). The model presented by them consists of transmission medium, transmitter and receiver. Cyclic codes is use to encode and decode the digital signal of the two channels before modulation and after demodulation process. The result shows that the 8-PSK is more powerful compared to BPSK. CDMA, which uses multiple accesses for BPSK and 8-PSK, is likely to overcome some issues regarding noise and interference in the channel by introducing the spread spectrum signal. From the results, it has been proven that the 8-PSK satisfy 100% of the better performance comparing BPSK. By using CDMA, more capacity and bandwidth can be achieved and it is very effective for applications in modern communication.
MULTILEVEL inverters enable the synthesis of a sinusoidal output voltage from several steps of voltages. For this reason, multilevel inverters have low dv/dt characteristics and generally have low harmonics in the output voltage and current. In addition, the switching of very high voltages can be achieved by stacking multilevel inverter modules. Due to these advantages, multilevel inverters have been applied in various application fields. Among various topologies for multilevel inverters, the multilevel cascaded inverter (MLCI) structure is one of the prominent topologies because of its simple structure for modularization and fault- tolerant capability. Therefore, MLCIs are used for many applications, such as dynamic voltage restorer, static synchronous compensator (STATCOM), high-voltage energy storage device, photovoltaic inverters, medium-voltage drives, electric vehicle (EV) traction drives, and so on. In MLCI applications, a modulation strategy to generate gating signals is very crucial to achieve high-performance control. Regarding this issue, many studies have been conducted, and they are roughly categorized into multilevel selective harmonic elimination pulse width modulation
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Former two types of SM systems all have assumed that accurate channel state information is available at the receiver. Nevertheless, sometimes, it is costly and difficultly to obtain accurate channel state information especially in high-mobility situations. Therefore, differential signaling has been taken into SM systems and thus develop a Differential Spatial Modulation (DSM) scheme. Similar to STBC-SM, DSM collect the modulation signal vectors over several adjacent time intervals to transmit complex information symbols drawn from a ܯ -QAM constellation. Each interval only one transmit antenna was activated, however, the modulation signal matrix X satisfies the condition that each transmit antenna is activated only once. Take N T =2 for example, the
Fig. 2 shows the results obtained when the hybrid multilevel converter with four chain links per limb is operated at different load power factors. The system parameters are 4mF chain link capacitor, 2mH dc link inductor, and the converter transformer is rated at 100KVA 600/440V. The hybrid multilevel converter with only four chain link capacitors per limb generates nine-voltage levels per phase and nineteen voltage levels in the line voltage (Figs. 2a and 2b). This may result in significant improvement in output waveform quality, reduced dv/dt, and small converter footprint. Fig. 2c shows the load current is sinusoidal. Fig. 2d shows a step approximation of the rectified sinusoidal voltage across the upper limb. The switching of one voltage level at each instant is maintained at the chain links. This ensures low switching loss and dv/dt will be experienced by converter transformer. Fig. 2e shows that voltage balancing of the chain link capacitors is maintained when the converter delivers large reactive power, without the need for triplen harmonic injection as claimed in reference . Spectrums of line and phase voltages shown in Figs. 2e and 2f. Figs. 2e and 2f show that hybrid multilevel converter generates output voltages with extremely low harmonic content with a fewer number of chain links.
that the grid does not contribute common mode voltage in the system . The converter topology and modulation method have significant contribution in leakage current generation. Therefore, the transformer less cascaded mu ltilevel inverter shown in Fig. 1 is connected to a simp le resistive load for Evaluation of the proposed modulation technique. The leakage current is generated in the parasitic capacitance formed between the PV module and the ground, where common mode voltage is also induced at the same point as shown in Fig. 1. The common mode voltage of any electrical circu it is the mean value of voltage between the outputs and a common reference point.
In this chapter, we demonstrate a silicon-waveguide-based platform for efficiently cou- pling light into and out of guided plasmonic modes supported at the surface of a metal film. The potential of plasmonic devices for on-chip telecommunication applications and signal processing has generated increasing interest in recent years [125, 126]. Since they can be excited at optical frequencies, propagating surface plasmon po- laritons are capable of supporting higher bandwidths than electrical signals carried by conventional metal wires. Furthermore, in contrast to dielectric waveguides, plas- monic devices confine light to a surface, which can enhance interactions with matter for sensing  and light emission applications [128, 129] and allows for device dimen- sions below the diffraction limit [37, 130]. Finally, the ability to transmit light and electricity in the same component simultaneously opens up interesting possibilities for hybrid electrical-optical integration , and might also allow for optical devices with new functionalities. For example, an in-line optical power monitor has been re- cently demonstrated that measures changes in the temperature-dependent electrical resistivity of a metallic element, which can be correlated with the amount of power propagating in a plasmonic mode at the element’s surface .
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In this paper we have analysed 5 different modulation formats such as NRZ, RZ, CSRZ, Duo Binary, and the Modified Duo- binary signal with an objective to identify the most suitable modulation format for Hybrid PON. The eye diagrams obtained by simulating the different modulation formats are shown in Figure-7. The Bit Error is analysed for different lengths for each of the modulation formats and is shown in Figure-8. The BER of less than 10 -9 is used for evaluating the performance of the network. Figure-9 shows the Qfactor achieved by the different modulation formats.
Consequently, robust spread spectrum modulation techniques are required, which result in low data rates. As an example, the IEEE 802.11-1997 standard for WLANs physical (PHY) layer specifies that either the direct-sequence spread spectrum (DSSS) or the frequency-hopping spread spectrum (FHSS) be used (and or PPM for IR wireless system, this will be discussed later in section 2.3.3) [WWW2, IEEE97]. The data rate of the PHY layer is standardised to operate at either 1 Mbps or 2 Mbps at maximum. This was then improved upon in 1999 with the ratification of the IEEE 802.11b standard, which adds two higher data rates of 5.5 Mbps and 11Mbps to the DSSS standard [IEEE99]. Many of the products currently on the market today are either based on this standard, or the HomeRF standard, which also operates in the ISM band, and achieves a maximum data rate of 10 Mbps using FHSS. The next generation RF WLAN products operate in the so-called 5 GHz band that was allocated solely for use by WLAN products. This allows systems to be optimised in terms of data rate and efficiency, free from the constraints associated when coexisting with other products. There are currently two competing standards in this band, these being IEEE 802.11a and HiperLAN2, both of which provide maximum data rates of 54 Mbps. Another standard worth mentioning is Bluetooth, which is a short range point-to-multipoint standard for voice and data transfer, also operating in the ISM band. The data rate is a mere 723.2 kbps and can operate up to a range of 10 metres. Though these are a few disadvantages of Bluetooth technology, the rationale behind it is low cost, thus allowing it to be integrated into a variety of portable electronics devices, which may then communicate with each other via ad hoc wireless networks termed piconets [Hayes02]. An experiment has been carried out to compare the performance between the DSSS and Bluetooth systems and the results showed that the DSSS system performs better in the presence of interference [PunnooseOl].
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A.A. Khadir, B. F. Dhahir have demonstrated the use of Optisystem software for modeling different design technologies of optical networks.P. Jain, K. Vashist , N. Gupta have investigated about the performance of DWDM system for enhancing the capacity of the communication system through Hybrid Optical Amplifier. H. Ziqiang , L. Hongzuo , Z. Ting  have introduced about Erbium laser amplifier. This paper is related to transient effects of EDFA that are caused by the signal and pump power. The conclusions show that when the pump power is fixed, saturation time decreases, and input signal gain recovery time increases.
Data broadcasted by source is received by destination by direct transmission and/or via one or more relay. By combining the copies of data received directly and/or via independent relays, destination node exploits the benefits of spatial diversity which improves the performance of wireless transmission. In wireless communication, quality of service (QoS) at physical layer is measured in term of bit error rate (BER) or throughput, which can be improved with cooperation among users. In conventional data transmission, all bits in a symbol are treated in similar manner, having same bit error rate (BER) performance. In order to provide differential service at physical layer, the bits in a symbol can be divided into layers using scalable modulation [2-3]. Potential benefits of cooperative communication include performance enhancement at physical layer such as improved channel reliability, improved system throughput, seamless service provision, and operational cost reduction .
The multicarrier modulation technique is used to transmit simultaneously data among several carriers and it follows flat fading per subcarrier, but a single carrier modulation is used to transmit the data over only single carrier and follows selective fading. For example, we assume a big truck and a bunch of smaller ones involved in an accident then that time big truck can not have any option to deliver the entire goods, but if one of the smaller truck lost goods, then it have one of the options like all others three trucks deliver the remaining goods .
In this proposed system the isolated boost resonant converter purposeis for more efficient and distributed PV conversion. The system is a hybrid between a traditional CCM boost converter and a series-resonant half-bridge. The design process was then defined, with a focus on the unique combined resonant and PWM behavior. In this, system consist of only two active switches. The results were a simple process, requiring only consideration of the resonant period length in selecting a valid converter duty cycle range. The principle advantages are low circulating energy and reduced switching loss with resonant energy transfer and output diode ZCS and converter efficiency is high, minimum number of active devices and a small overall component count, Galvanic isolation allows for the use of high efficiency inverter stages without additional concern over ground leakage current, Reduced control complexity provides lower auxiliary power loss and simpler controller IC configurations and The efficiency improvements are also possible.
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across the real and imaginary axes in the complex plane contains the constellation points. These metric locations were used to position the four QPSK complex signals using the driving bit (b5) located in each of the two sub groups(G1,G2) . For the first branch, the two output complex symbols from the four point modulation (QPSK modulation) was multiplied by the distance metrics (d1,d2) so as to be transformed into PSK complex symbols ready to be distributed across the eight point maps. The first complex symbol was assigned to the first PSK constellation, while the second symbol representing the third and fourth bits within G1 was a located to the second constellation (Figure 4). The binary value of the fifth bit represents the most significant bit of the PSK symbol (three bits symbol), and was used as a reference to identify the particular signal point on the map in which these symbols represents. In a similar manner, these steps were applied across the second branch in parallel to achieve the spectral efficiency of the system. The original four quadrature symbols represented as follows
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