Musse Mohamud Ahmed

Smart Zigbee/IEEE 802.15.4 MAC for wireless sensor multi-hop mesh networks

The future of Smart Grid is based on grid-integrated real-time communications between the grid elements of generation, transmission, distribution and loads. Due to Zigbee/IEEE 802.15.4 standards features such as low cost, low power, low data rate, short range, simplicity and free licensed spectrum which makes Zigbee-based wireless sensor networks (WSNs) the wireless technology of choice for smart grid applications. This paper focuses on the electricity distribution layer, ranging from Advanced Metering Infrastructure (AMI) gateways at the house-hold to the distribution point where a multi-hop mesh network is built for large coverage data exchanges. Although beacon-based mode of operation is adopted in IEEE802.15.4 standard, it does not, however, specify any mechanism to enable beacon mode in mesh networks. Therefore, in this paper, the Zigbee/IEEE 802.15.4 MAC protocol is modified to suit the beacon-based wireless sensor multi-hop mesh networks application. Such network configuration is expected to proliferate in is smart grid auto-metering scenarios. A simulation model was built and validated using the network simulator (NS-2) and the preliminary results showed considerable enhancements as expected for the ZigBee/IEEE 802.15.4 MAC protocol.

Identification of linearized regions of non-linear transducers responses

Transducers have found wide applications in industries, though, they possess nonlinear responses. The nonlinearity feature does not prevail over the entire range; rather there are sections (or regions) on the response curves that are easily regarded as linear. This work focuses on analyzing transducer characteristics by finding regions exhibiting larger level of linearity. The point of inflection is a joint between two consecutive linear segments, and it is where changes in the output signal in response to external parameter variations remain at minimum compared to its immediate neighboring points. It is shown through simulations on how, assuming that a given system does not operate over the entire range of the response curve, a linear response is assured. This is done by translating the circuit operating over the linear section by employing additional external circuit elements. This paper attempts at analyzing a transducer characteristics by showing regions around the points of inflections where variations remain most linear.

New costs optimization concepts for unit commitment and economic load dispatch in large scale power systems

Costs optimization in unit commitment (UC) and economic load dispatch (ELD) lead to remarkable saving in the power system operational cost. For this reason, UC and ELD main problems are to minimize the total fuel cost to obtain the maximum total profit and finding fast computation simulation time for the scheduling program. Lagrangian relaxation (LR) has become one of the best solution methods in solving the UC and ELD problems. This approach has been proved more efficient and easier than other methods in solving large-scale problems. When applying LR, the dual function needed to be updated at the higher level. Lately, bundling method (BM) is one of the best solution methods to Lagrangian dual problem. This paper presents combination of LR technique, BM and interior point method for solving the UC and ELD problems. It will also explore the best possible way of updating Lagrangian multipliers with minimum computation time using fast programming techniques.

New concepts of optimizing unit commitment and economic load dispatch costs in large scale power systems

Using suitable solution techniques to the unit commitment (UC) and economic load dispatch (ELD) problems play major role on finding an optimal power scheduling in electrical power system. The UC and ELD problems are to decide when and which generating units to commit and decommit, in order to minimize the total fuel cost over specified period subject to a large number of difficult constraints. Lagrangian relaxation (LR) has been widely used to solve UC and ELD. Recently bundling method (BM) has appeared to be one of the best multipliers updated techniques for LR. This method has promising and the fastest convergence characteristics for UC and ELD problems. For that reason, this paper is to solve the UC and ELD problems via LR, BM and interior point method. This paper explores also the best possible way of updating Lagrangian multipliers with minimum computation time using fast programming techniques.

A novel spiral back-off mechanism for wireless sensor networks MAC protocol in smart grid system

Wireless sensor networks are considered as the enabling technology for multiple smart grid applications such as remote metering, direct load control, renewable energy integration, substation monitoring etc. The IEEE 802.15.4 standard provides a basic foundation by defining the physical and MAC layer of the low power wireless sensor network. Carrier Sense Multiple Access-Collision Avoidance (CSMA-CA) with binary exponential backoff (BEB) algorithm is used as a technique to share the common wireless medium and avoids collision among the contending sensor nodes. However, this binary exponential algorithm does not account the application of traffic characteristics that essentially negatively affects the smart grid network performances in terms of packet delivery ratio and the time delay. In this paper, a novel spiral backoff mechanism is proposed that has considered the applications of traffic type to improve the network performances. Simulation results show that proposed spiral backoff algorithm reduces the end-to-end delay and increases packet delivery ratio (PDR) for the smart grid wireless sensor networks.

Wireless communication techniques, the right path to Smart Grid distribution Systems: A review

The quality and reliability of electric power supply are the key indicators for the comfort of a society. Hence, to serve customers with high quality electricity, the Supervisory Control and Data Acquisition (SCADA) system is being used in the distribution system (DS) for power monitoring and control. The SCADA is feed with operation data like current and voltage via Feeder_Remote Terminal_Units (FRTUs). The FRTUs are capable of triggering actions to detach the portion of DS experiencing an unusual condition. Nevertheless, the existing grids do not operate at their optimal capacity due to the usage of one way data communication installations. Thus, to optimize the operation of the legacy power distribution grids, the innovation of the state-of-the-art communication techniques play a vital role-leading to the creation of smart grid Systems. This paper reviews the development of wireless communication technologies envisioned as full-duplex information exchange medium in the on-going development of Smart Grid Systems.

Stepped Waveform Generation for Multilevel Inverter Topology Applications

This paper presents a review of the various inverter topologies, showing their utility in generating stepped waveform. The role of the PWM is highlighted in the operation of inverter for generating stepped-wave forms. The results show how similarly generated PWM used by different topologies can result into a stepped-waveform output capable of producing and AC closer to single fundamental component of 50Hz. The total harmonic Distortion (THD) is given for each set of simulation result with a relatively marked, though marginal utility, of the PWM used.

Traffic Aware Wireless Sensor Networks MAC Protocol for Smart Grid Applications Using Spiral Backoff Mechanism

IEEE 802.15.4 standard provides a low cost, low power wireless sensor network solution for smart grid communication networks. This standard uses slotted Carrier Sense Multiple Access-Collision Avoidance (CSMA-CA) with binary exponential back off algorithm (BEB) to avoid collision between the sensor nodes. However, BEB does not consider the traffic characteristics which degrade the smart grid network performance. In this paper, a traffic aware spiral back off mechanism is proposed to improve the network performance. Simulation results show that proposed spiral back off algorithm reduces the end-to-end delay and increase packet delivery ratio (PDR) for real time data.

Optimal throughput and self-adaptability of robust real-time IEEE 802.15.4 MAC for AMI Mesh network

A smart grid refers to a modernization of the electricity system that brings intelligence, reliability, efficiency and optimality to the power grid. To provide an automated and widely distributed energy delivery, the smart grid will be branded by a two-way flow of electricity and information system between energy suppliers and their customers. Thus, the smart grid is a power grid that integrates data communication networks which provide the collected and analysed data at all levels in real time. Therefore, the performance of communication systems is so vital for the success of smart grid. Merit to the ZigBee/IEEE802.15.4std low cost, low power, low data rate, short range, simplicity and free licensed spectrum that makes wireless sensor networks (WSNs) the most suitable wireless technology for smart grid applications. Unfortunately, almost all ZigBee channels overlap with wireless local area network (WLAN) channels, resulting in severe performance degradation due to interference. In order to improve the performance of communication systems, this paper proposes an optimal throughput and self-adaptability of ZigBee/IEEE802.15.4std for smart grid.

New Supervisory Control and Data Acquisition (SCADA) based fault isolation system for low voltage distribution systems

This paper proposes a new supervisory control and data acquisition (SCADA) based fault isolation system on the low voltage (415/240 V) distribution system. It presents a customized distribution automation system (DAS) for automatic operation and secure fault isolation tested in the Malaysian utility distribution system; Tenaga Nasional Berhad (TNB) distribution system. It presents the first research work on customer side automation for operating and controlling between the consumer and the substation in an automated manner. The paper focuses on the development of very secure automated fault isolation work tested to TNB distribution operating principles as the fault is detected, identified, isolated and cleared in few seconds by just clicking the mouse of laptop or desktop connected to the system. Supervisory Control and Data Acquisition (SCADA) technique has been developed and utilized to build Human Machine Interface (HMI) that provides a Graphical User Interface (GUI) functions for the engineers and technicians to monitor and control the system. Microprocessor based Remote Monitoring Devices have been used for customized software integrated to the hardware. Power Line Carrier (PLC) has been used as communication media between the consumer and the substation. As a result, complete DAS and fault isolation system has been developed for remote automated operation, cost reduction, maintenance time saving and less human intervention during faults conditions.