This paper presents a centralized control system that coordinates parallel operations of different distributed generation (DG) inverters within a microgrid. The control design for the DG inverters employs a new Model Predictive Control algorithm that allows faster computational time for large power systems by optimizing the steady-state and the transient control problems separately. An overall energy management system is also implemented for the microgrid to coordinate load sharing among different DG units during both grid-connected and islanded operations. The design concept of the proposed control system is evaluated through simulation studies under different test scenarios. The impact of the increased penetration of DG units on the distribution grid is also investigated using the proposed microgrid. The simulation results show that the operations of the DG units within the microgrid can be coordinated effectively under the proposed control system to ensure stable operation of the overall microgrid.Index Terms-Centralized control, distributed generation, energy management, microgrids, parallel inverter operation.
This paper presents a novel approach to model the transfer function of electrical power lines for broadband power line communication. In this approach, the power line is approximated as a transmission line and the two intrinsic parameters, the characteristic impedance and the propagation constants, are derived based on the lumped-element circuit model. Using these intrinsic parameters, the transfer characteristics for a N-branch power distribution network are derived based on the scattering matrix method. Detail derivation of this line model is given in this paper. The model has been verified with practical measurements conducted on actual power networks. It is demonstrated that the model accurately determine the line characteristics under different network configuration and when different household appliances are connected. Index Terms-Channel modeling, communication channel, power line communications.
The impulsive noise and multipath effects are the main reasons to cause bit errors in power line communications. In this paper, the bit error rate (BER) performance of the orthogonal frequency division multiplexing (OFDM) system under the impulsive noise and multipath effects are theoretically analyzed in terms of closed form formulas. Through the analysis, it is shown that OFDM can mitigate the adverse effect of the impulsive noise and only the heavily disturbed impulsive noise will interfere the BER performance of the OFDM system. It is also shown that the adverse effect of multipath is more serious than that of impulsive noise. In this paper, the guard interval is used to improve the BER performance of the OFDM system. As the longer guard interval is inefficient in using the signal power, the optimum guard interval that can achieve the best BER performance is studied.Index Terms-Bit error rate (BER), impulsive noise, multipath effect, OFDM, power line communications.
In this paper, distributed energy storage systems (ESSs) are proposed to solve the voltage rise/drop issues in lowvoltage (LV) distribution networks with high penetration of rooftop photovoltaics (PVs). During peak PV generation period, the voltages are mitigated by charging the ESSs, and the stored energy is discharged for voltage support during peak load period. The impact of storage device integrated with PV source on feeder voltages is investigated in detail. A coordinated control method which includes both distributed and localized controls is proposed for distributed ESSs. The distributed control using consensus algorithm regulates the feeder voltages within the required limits, while the localized control regulates the state of charge (SoC) of each ESS within desired SoC range. The entire control structure ensures voltage regulation while effectively utilizes storage capacity under various operation conditions. The proposed control method is evaluated in LV distribution networks and the simulation results validate the effectiveness of this method.
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