Y.H. Song

Two novel nonlinear companding schemes with iterative receiver to reduce PAPR in multi-carrier modulation systems

Companding transform is an efficient and simple method to reduce the Peak-to-Average Power Ratio (PAPR) for Multi-Carrier Modulation (MCM) systems. But if the MCM signal is only simply operated by inverse companding transform at the receiver, the resultant spectrum may exhibit severe in-band and out-of-band radiation of the distortion components, and considerable peak regrowth by excessive channel noises etc. In order to prevent these problems from occurring, in this paper, two novel nonlinear companding schemes with a iterative receiver are proposed to reduce the PAPR. By transforming the amplitude or power of the original MCM signals into uniform distributed signals, the novel schemes can effectively reduce PAPR for different modulation formats and sub-carrier sizes. Despite moderate complexity increasing at the receiver, but it is especially suitable to be combined with iterative channel estimation. Computer simulation results show that the proposed schemes can offer good system performances without any bandwidth expansion.

Modelling, simulation and performance analysis of a PV array in an embedded environment

Photovoltaic (PV) generation involves the direct conversion of sunlight into electrical energy. In recent years it has proved to be a cost-effective method for generating electricity with minimum environmental impact. Due to the environmental and economic benefits PV generation is now being deployed worldwide as an embedded renewable energy source and extensive research is being performed in order to study and assess the effectiveness of PV arrays in Distributed Generation (DG) systems either as a potential energy source or as energy reserve in combination with other types of distributed energy resources. This paper presents the modeling and MATLAB simulation of a stand-alone polycrystalline PV Array system and investigates load following performance efficiency under various loading and weather conditions as well as suitability with regard to enhancing power supply reliability to critical loads. The modeling of the PV array that has been performed in this research using MATLAB Simulink is based on the calculation of parameters for the Thevenins equivalent circuit of each cell of the array. The standard double exponential polycrystalline cell model has been adopted for this research with solar irradiance E and ambient temperature T as the input and Thevenins voltage Vthar and Thevenins resistance Rthar as the output.

Mathematical modelling and performance evaluation of a stand-alone polycrystalline PV plant with MPPT facility

Photovoltaic (PV) generation has now-a-days proved to be a cost-effective method for renewable power generation with minimum environmental impact. Due to environmental and economic benefits, PV is now being widely deployed as a distributed energy resources (DER) in distributed generation systems or microgrids. Extensive laboratory-based research and simulation studies are being performed for assessing its effectiveness as DER in microgrids. Simulation studies mostly involve development of mathematical models which can account for the variation of PV output with solar irradiance and ambient temperature as well as the simulation of MPPT feature that is built in the inverters usually interfaced with the PV arrays. Simulation studies of microgrids with interconnected DERs and elaborate control schemes often warrants the development of simple and robust mathematical models for PV arrays that would pose low mathematical burden on the system, have low data storage requirements and which can be represented by standard block sets of a modelling software. At the same time, the models should be able to simulate the weather dependent electrical behaviour of the PV modules. This paper reports on the development of a DC voltage source model of a polycrystalline PV Array in MATLAB Simulink and its performance analysis under various loading and weather conditions as well as the application of the model to develop a load shedding scheme for a stand-alone PV system.

Diversity Gain for DVB-H by Using Transmitter/Receiver Cyclic Delay Diversity

The objective of this paper is to investigate different diversity techniques for broadcast networks that will minimize the complexity and improve received SNR of broadcast systems. Resultant digital broadcast networks would require fewer transmitter sites and thus be more cost-effective and have less environmental impact. The techniques can be applied to DVB-T, DVB-H and DAB systems that use Orthogonal Frequency Division Multiplexing (OFDM). These are key radio broadcast network technologies, which are expected to complement emerging technologies such as WiMAX and future 4G networks for delivery of broadband content. Transmitter and receiver diversity technologies can increase the frequency and time selectivity of the resulting channel transfer function at the receiver. Diversity exploits the statistical nature of fading due to multipath and reduces the likelihood of deep fading by providing a diversity of transmission signals. Multiple signals are transmitted in such a way as to ensure that several signals reach the receiver each with uncorrelated fading. Transmit diversity is more practical than receive diversity due to the difficulty of locating two receive antennas far enough apart in a small mobile device. The schemes examined here comply with existing DVB standards and can be incorporated into existing systems without change. The diversity techniques introduced in this paper are applied to the DVB-H system. Bit error performance investigations were conducted by simulation for different DVB-H and diversity parameters

Performance analysis of time slicing in DVB-H

Digital Video Broadcasting for Handhelds (DVB-H) is the latest DVB standard from the DVB Group targeting handheld, battery powered devices such as mobile telephones, PDAs(Personal Digital Assistants). etc. DVB-H enables IP data services including low definition TV services to be received on battery powered handheld terminals. Time Division Multiplexing (TOM, is the technology that is usually used in computer and telecommunication systems for resoursce allocation. Time slicing is based on TDM and is one of the characteristics of DVB-H. This paper presents a basic model for predicting the power saving achieved by the time slicing algorithm used in DVB-H followed by analysis of the performance of the algorithm based on simulations using Matlab and Opnet; The simulations required the writing of Matlab and Opnet code to model the effect of time slicing. The model and simulations presented illustrate the significant power savings that can be achieved by time slicing.

Improved GPS travelling wave fault locator for power cables by using wavelet analysis

The paper proposes an improved approach to cable-fault location, which is essentially based on synchronised sampling technique, wavelet analysis and travelling wave principle. After an outline of the new scheme and brief introduction to the three major techniques, wavelet analysis of faulty transient waveforms is conducted in details to determine the best wavelet levels for this particular application. Then a 400 kV underground cable system simulated by the Alternative Transient Program (ATP) under various system and fault conditions is used to fully evaluate the approach. Numerical results show that this scheme is reliable and accurate with errors of less than 2% of the length of the cable line.

Future transmitter/receiver diversity schemes in broadcast wireless networks

An open diversity architecture for a cooperating broadcast wireless network is presented that exploits the strengths of the existing digital broadcast standards. Different diversity techniques for broadcast networks that will minimize the complexity of broadcast systems and improve received SNR of broadcast signals are described. Resulting digital broadcast networks could require fewer transmitter sites and thus be more cost effective with less environmental impact. Transmit diversity is particularly investigated since it obviates the major disadvantage of receive diversity being the difficulty of locating two receive antennas far enough apart in a small mobile device. The schemes examined here are compatible with existing broadcast and cellular telecom standards, and can be incorporated into existing systems without change

A novel short-term generation scheduling technique of thermal units using ant colony search algorithms

This paper presents a novel co-operative agents approach, ant colony search algorithm (ACSA)-based scheme, for solving a short-term generation scheduling problem of thermal power systems. The main purpose of this paper is to investigate the applicability of an alternative intelligent search method in power system optimisation, particularly in short-term generation scheduling problems. The ACSA is derived from the theoretical biology of the topic of ant trail formation and foraging methods. A set of co-operating agents, ants, co-operate to find a good solution for the short-term generation scheduling problem of thermal units. In the ACSA, the state transition rule, global and local updating rules are also introduced to ensure the optimal solution. Once all the ants have completed their tours, a global pheromone-updating rule is then applied and the process is iterated until the stop condition is satisfied. The effectiveness of the proposed scheme has been demonstrated on the daily generation scheduling problem of model power systems.

Wavelet analysis and neural network based adaptive single-pole autoreclosure scheme for EHV transmission systems

This paper proposes a wavelet analysis and neural network based adaptive single-pole autoreclosure scheme for Extra High Voltage (EHV) transmission systems. First, the fault transients generated by the secondary arc and permanent faults are analysed using discrete wavelet transform with particular reference to the development of the adaptive autoreclosure scheme. Daubechies D4 wavelet transform is adopted and the numerical analyses reveal that certain wavelet components can be effectively used as the features to detect and identify the fault relevant characteristics in transmission systems. Several results of wavelet analysis are used as the feature vectors of artificial neural network which is designed to distinguish between transient and permanent faults, and to determine the secondary arc extinction point. The outcome of the study clearly indicates that the wavelet analysis combined with neural network approach can be used as an attractive and effective means of realising an adaptive autoreclosing scheme.

Key energy management issues of setting market clearing price (MCP) in micro-grid scenario

Micro grid is an epitome of a macro grid but works in low voltage comprising of various small-distributed energy resources (DERs), energy storage devices, and controllable loads being interfaced through fast acting power electronic devices. Combined heat and power (CHP) produced by DERs are utilized in the local market where Micro Grid operates either in island mode or in grid-connected mode. The CHP mode of operation makes the Micro Grid most efficient and economic. Like deregulation regime in Micro Grid market, multi agent generator providers may be considered to make the Micro Grid market competitive. The reason for competitive electricity market is to serve the consumers at a reduced price. The main purpose of this paper is to analyze and propose the pricing mechanism for Micro Grid energy in the competitive electricity market. Central controller of the Micro Grid (mucc) is the main brain behind all energy management system (EMS) activities, which includes participation in the bidding to settle market- clearing price (MCP). Two important market settlement techniques - Day-ahead and Real-time - have been discussed briefly in this paper. Uniform and Pay-as-bid pricing rules have been discussed separately for electricity pricing fixation in the context of Micro Grid. In this paper marketing strategies of some of the renewable DERs - mainly Photovoltaic (PV) and wind generator - have been considered. Wind power is now a potential candidate in non-conventional power generation family. Power available from wind and PV system cost high and is of intermittent in nature. Participation of these two renewable DERs along with Micro turbine, Diesel generator, fuel cells etc. in the bidding for market clearing price (MCP) make the market complex. This paper gives a brief guideline for marketing of PV and wind power. Consumers in the Micro Grid system are categorized as shed-able and non-shed-able according to their priority. How these loads affect demand curve have also been discussed. This paper presents a case study on price determination based on demand and supply side bidding strategies. The impacts of congestion management, market power, carbon taxation, price volatility, etc. on pricing have also been discussed in the context of Micro Grid.