Volume 19, Issue 2 -

The content of this paper addresses possible approaches that will eventually allow the development of microgrids for small and medium size industries on a massive scale. Therefore, it addresses in a comprehensive way, the most suitable communication technologies for microgrids in this type of enterprises. Several energy sources that can be implemented in industrial microgrids are also briefly addressed, including generation and storage units frequently adopted for power supply in small scale distribution grids. The overview of communication technologies and energy sources takes into account the financial limitations of small enterprises with the purpose of assisting the study of industrial microgrid architectures. In addition, a case study is presented in order to observe how a centralized and a decentralized deployment of energy sources affect the performance of a small or medium scale industrial microgrid. Since this sector is very important for the development of modern societies, it should make use of the most advanced infrastructures in order to be more sustainable, both environmentally and competitively. The practical limitations applied to industrial microgrids (e.g., lack of standards in the grid codes, some unfit technological performance and amiss system design) shows that the subject presented in this paper deserves much more research and developments. Thus, this work demonstrates the importance of the development of the microgrid for the small and medium-sized enterprises sector.

This paper proposes a distinct vehicle-to-grid (V2G) and grid-to-vehicle (G2V) coordination model to utilize the controllability of electric vehicle (EV) battery storage system during the charging and discharging phases for load levelling. The aspect of the vehicles of changeable locations is taken as the basis to obtain a defined mobility pattern, with home and work being selected as the operational places to perform G2V and V2G activities. The presented approach assisted in achieving peak shaving and valley filling (MW) of a typical two-peak daily load curve of a real system to a considerable extent, thereby levelling the load and reducing the complexities associated with the forecasting and dispatch of the oscillating load. The reduction in the ramp up and ramp down energy and reserve requirements (MW), as well as the cost savings associated with reduced generation ramping commitments, as seen from system operator’s perspective, is quantified with the proposed schemes. Results demonstrate that the proposed approach is capable of flattening a realistic amount of load. The associated cost savings with reduced ramping requirements from traditional sources can be allocated to participating vehicles for providing the grid services. The benefits derived can encourage their adoption which is contained due to its expensiveness in the current market scenario, apart from increasing the grid reliability.

In this paper, the concept of analog filter circuit is used for designing of wide area damping controller (WADC) in power system. The designed continuous mode filter based WADC is robust enough to deal with the problem of imperfect communication medium, which include process noise, measurement noise and signal latency in wide area remote signal. Residue method is used for the selection of wide area control signal and controller location. Modelling of imperfect communication network is done using Pade approximation and by inserting Gaussian random noise. The effectiveness of filter based WADC as a power system stability agent is assessed in the frequency domain using two typical test power systems and via appropriate time domain simulations based upon the non-linear model on MATLAB/Simulink software platform.

Abstract: The transfer of the power from the PV generator to the load is not always optimal. The operating point of the characteristic of the said generator is strongly linked to the temperature variations, the solar irradiation and the load. In order for the module to provide its maximum available power, it’s necessary to permanently adapt the load with the photovoltaic generator. This adaptation can be carried out by inserting a DC-DC converter (boost) controlled by a “Maximum Power Point Tracking” (MPPT). The work is a comparative study of the power maximization methods incremental conductance, Hill climbing and perturbation and observation. Matlab is used to implement modeling and simulation tasks and to compare the efficiency and accuracy of execution for the selected MPPT methods. The simulation results for operating characteristics I-V and P-V for various cell temperature and solar irradiation closely matched manufacturer data sheet of the solar panel. Also, the algorithms described in this work have a considerable higher precision and it can be concluded that the output power of the PV module for the Incremental Conductance method is comparatively greater than the P&O and Hill Climbing method in a different conditions.

Abstract: The autonomy of the Battery Electric Vehicle is a key point in the development and commercialization of this kind of vehicle. The requested autonomy is directly linked to the amount of the stored and remaining energy in the battery which is the State of Charge (SOC).This paper presents battery state of charge (SOC) estimation using coulomb counting method. So, the quantity of electric charge is calculated during the battery cycle of charge and discharge and compared to the estimated value based on the battery generic model. Also, experimental results are carried out in order to validate this study.

This paper presents a dynamic equivalent model for transmission network dynamic behavior analysis in MATLAB SIMULINK. The electromagnetic frequency response and electromechanical response are combined in the model. The dynamic behavior of distributed parameters line modeled by the EMTP equivalent model is compared with that corresponding to lumped parameter line represented by π model. The aim is to define the frequency band in which the lumped model can accurately represent the distributed parameters model on no load conditions but also when the network is loaded. The proposed equivalent model is explored to investigate the impact of topology on the network dynamics. Besides, the influence of load nature and compensation rate on the driving point frequency response are analyzed analytically and simulated via the proposed model.

A method is proposed to identify the generators participating in an inter-area mode and the coherent generators by analyzing the discrete signals from phasor measurement units (PMU). In the present work, Zolotarev polynomial based filter bank (ZPBFB) is adopted to decompose the measured signals into monocomponents for modal frequency and damping. ZPBFB is preferred due to the narrow bandwidth of 0.1 Hz and hence closely spaced modes can be distinguished. All the generator speed signals are analysed with ZPBFB to identify the generators participating in an inter-area mode. Principal component analysis (PCA) is widely used for clustering sampled data. It is proposed in the present work to apply PCA on the decomposed signals, obtained from ZPBFB, of those generators participating in an inter-area mode for generator coherency. The efficacy of the proposed method is demonstrated on IEEE two-area test system, 16-machine, 68-bus system and on real time signals recorded by wide area frequency measurement system (WAFMS) in India on November 30, 2011. The detailed simulation results are presented. The performance of the proposed method is compared with small signal stability analysis and wavelet phase difference (WPD) approach.

This paper proposes two techniques for the identification of critical buses in a power system. The technique of Network Structural Theory Participation Factor (NSTPF) depends on the network structural interconnection of buses as captured by the admittance matrix of the system and is formulated based on the fundamental circuit theory law using eigenvalue decomposition method. Another power flow based technique which depends on the system maximum loadability, the system step size among other factors is also proposed. Traditional power flow based techniques are used as benchmarks to determine the significance of the proposed methods. To ensure voltage stability enhancement, STATCOM FACTS device is installed at the selected weak load buses of the practical Nigerian 24 bus and IEEE 30 bus test systems. The results of the simulation obtained show that, the suggested approach of NSTPF is more suitable in the identification of weak buses that are liable to voltage instability in power systems as it requires less computational burden and also saves time compared to techniques based on power flow solutions.

The ever-growing demand for energy sources of low environmental impact has given a greater importance to wind farms in many countries. However, due to operational characteristics of these complexes, which are reflected into a variability of the energy produced and in the use of power electronic converters, the interaction between wind power plants and electrical networks shows itself to be an area of high investigative interest. In fact, among the various phenomena that exist, steady state voltage variations constitute a theme that is under the constant attention of electrical system operators. In this context, the present article is directed toward the analysis of a voltage regulation strategy aimed at wind power generation systems composed by synchronous machines and full converters. Once established the methodology that lead to an ancillary operation of the wind farm, the authors present results of computational simulations on ATP/EMTP platform that attest to the efficiency of the strategy.

With the advancement of smart grid technology, the consumers get the opportunity to participate in various demand response (DR) programs. They can reduce their electricity bill by participating in DR programs. Along with the consumers, the power utility companies also get benefits due to the reduction in high energy peaks on the demand curve. In this paper, we propose an energy scheduling model for the scheduling of smart appliances at home. For the scheduling of appliances, two different dynamic pricing schemes are selected, i) time of use scheme, ii) real time pricing scheme. Along with this, a small renewable energy source in form of rooftop photovoltaic panels is also included to analyse its effect on energy scheduling solution. Finally, the scheduling problem is solved by mixed integer linear programming (MILP) technique. The CPLEX solver of GAMS software is used to apply MILP technique. A case study by considering different cases is done to analyse the effectiveness of formulated model and selected solution approach for the scheduling of the appliances. The simulation results by considering both the pricing schemes have been achieved and compared to get the better idea of the pricing schemes on the energy scheduling results.

Aimed at the miniaturization of the power-supply system for electromagnetic launch (EML) system, this paper deals with the problem of high rate pulse discharge of lithium batteries in the EML system. In order to reduce the number of batteries on series-parallel to increase the energy density, the factors such as safety, exotherm and life cycle must be taken into consideration, and there is need for optimization in terms of selection and design as well as discharge control of the battery. According to the power requirements of the EML system, the battery safety and discharge ability are important indexes in the aspect of selection and design, which refer to the design principle for selected batteries and the design scheme for raising their discharge ability under the precondition of discharge, and in the aspect of discharge control, the balancing-discharge control strategy is adopted to reduce the duration of high-rate discharge and the heat generation and extend the service life of batteries according to the EML operating conditions. Finally a test platform is established for verification.

The conduction angles variation in operating a static var compensator can be used to meet the balanced and varying cyclic load of reactive power demand. However, this operation creates harmonics current into the system. An optimum combination of balanced reactive power from SVC and reactive power from the generator based on telephone influence factor (TIF), the total harmonic current factor (IT), and the distribution factor D is proposed. This approach is simulated to a typical distribution network. However, this operation creates harmonics currents into the AC system. This strategy is implemented to a conventional distribution network for various loading conditions is presented.