This paper discusses the power quality issues for distributed generation systems based on renewable energy sources, such as solar and wind energy. A thorough discussion about the power quality issues is conducted here. This paper starts with the power quality issues, followed by discussions of basic standards. A comprehensive study of power quality in power systems, including the systems with dc and renewable sources is done in this paper. Power quality monitoring techniques and possible solutions of the power quality issues for the power systems are elaborately studied. Then, we analyze the methods of mitigation of these problems using custom power devices, such as D-STATCOM, UPQC, UPS, TVSS, DVR, etc., for micro grid systems. For renewable energy systems, STATCOM can be a potential choice due to its several advantages, whereas spinning reserve can enhance the power quality in traditional systems. At Last, we study the power quality in dc systems. Simpler arrangement and higher reliability are two main advantages of the dc systems though it faces other power quality issues, such as instability and poor detection of faults.

A new three phase multilevel inverter with reduced number of components count is proposed in this paper. This inverter is designed using a single DC source per phase to generate multiple level output voltage which makes it suitable for low and medium voltage applications, including ac-coupled renewables or energy storages. A generalized circuit configuration is shown in this paper following which the number of output voltage level can be increased as per expectation. Although, each element endures the voltage stress equivalent to the input DC voltage, the value of total standing voltage (TSV) is reduced by the utilization of minimized number of components with respect to the number of series connected capacitors. Further, staircase modulation scheme is used to generate the switching signals. Hence, the proposed inverter can be operated at low switching frequency with optimal output current harmonic distortion which decreases switching losses and suppresses power factor falling. In order to validate the theoretical explanations and practical performances of the proposed inverter, the hypothesis is simulated for 9, 13 and 39 output voltage level inverters for three phase with a line voltage total harmonic distortion (THD) of 6.06%, 4.16% and 2.10% respectively in MATLAB/Simulink and a 5-level single phase laboratory prototype is implemented in the laboratory. INDEX TERMS Pulse width modulation inverters, multilevel inverters, total harmonic distortion, total standing voltage, photovoltaic systems, energy storage.

The main task of distribution systems is to provide acceptable reliability, economic and quality service of electrical power according to the demanded load value. To fulfill this task more accurately, the reliability performance of the distribution system can be performed and measured using a wide variety of indices, which are divided into energy indices and frequency/expectation indices. This study evaluates the reliability indices of a part of the distribution network selected as a model and deals with the selection of the most suitable feeder by connecting energy storage units to the busbars. Using IEEE Standard 1366 reliability indices, historical data from Prosperous Electricity Distribution Company (PEDC), which is used to evaluate reliability based on the 5-year past reliability assessment of the power system (RAPS), was selected. In addition, as an innovation in this application process, energy storage systems (ESS) have been evaluated according to four different network configurations (A-B-C-D) to increase RAPS and achieve more realistic results. Using DigSILENT, ESS-based configurations are designed, comparisons are made, and configuration B is the best result to increase system reliability and the 80E6 feeder is optimal. In addition, reliability changes achieved by network configuration have demonstrated the importance of optimal configuration planning to improve the uninterrupted and sustainable energy quality of the system based on storage technology. INDEX TERMS Energy storage, Monte Carlo methods, power distribution faults, power system control, power system reliability.

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