To meet the fast-growing energy demand and, at the same time, tackle environmental concerns resulting from conventional energy sources, renewable energy sources are getting integrated in power networks to ensure reliable and affordable energy for the public and industrial sectors. However, the integration of renewable energy in the ageing electrical grids can result in new risks/challenges, such as security of supply, base load energy capacity, seasonal effects, and so on. Recent research and development in microgrids have proved that microgrids, which are fueled by renewable energy sources and managed by smart grids (use of smart sensors and smart energy management system), can offer higher reliability and more efficient energy systems in a cost-effective manner. Further improvement in the reliability and efficiency of electrical grids can be achieved by utilizing dc distribution in microgrid systems. DC microgrid is an attractive technology in the modern electrical grid system because of its natural interface with renewable energy sources, electric loads, and energy storage systems. In the recent past, an increase in research work has been observed in the area of dc microgrid, which brings this technology closer to practical implementation. This paper presents the state-of-the-art dc microgrid technology that covers ac interfaces, architectures, possible grounding schemes, power quality issues, and communication systems. The advantages of dc grids can be harvested in many applications to improve their reliability and efficiency. This paper also discusses benefits and challenges of using dc grid systems in several applications. This paper highlights the urgent need of standardizations for dc microgrid technology and presents recent updates in this area.

Electrolytic capacitor with a DC-side inductor is a typical DC-link filtering configuration in grid-connected diode rectified Adjustable Speed Drives. The criteria to size the DC-link filter are mainly from the aspects of stability and power quality. Nevertheless, the reliability of the DC-link filter is also an essential performance factor to be considered, which depends on both the component inherent capability and the operational conditions in the field operation. Nowadays, unbalanced voltage brings more electrical-thermal stress to the component, affecting the reliability of the capacitors. In order to study the reliability performance of the LC filter in an ASD system quantitatively, this paper proposes a mission profile based reliability evaluation method for capacitors, considering the nonlinear process of ESR growth and capacitance reduction during the degradation. Based on the proposed lifetime estimation procedure, four case studies are investigated: 1) Lifetime benchmarking of capacitors in LC filtering and slim capacitor filtering configurations; 2) Scalability analysis for the lifetime of capacitors in terms of system power rating and grid-unbalanced levels; 3) Lifetime estimation of capacitors in DC-link filter with long-term mission profile, and 4) The impact of the capacitor sizing on the lifetime of DC-link capacitor under grid-balanced and grid unbalanced conditions.

The recent trends to design more efficient and versatile maritime (both marine and offshore) vessels have attracted significant attention towards high penetration of power electronics systems in Electric Ship systems, which trigged variety of power system architectures in civilian and naval ships. The availability of advanced power electronics converters further supported to improve maneuverability, efficiency and compactness at reduced greenhouse gas emission in marine vessels. The fast-growing penetration of these power electronics converters add a number of advantages to the ship power system. However, risk factors associated with quality and reliability of the whole system should be considered. Power quality issues in marine networks have been reported from recent field accidents, therefore, the marine regulatory bodies need to revise and/or develop new power quality standards to ensure the reliability and scrutinize the safety of the whole ship system and crews. This paper presents a) a classification of marine vessels and their power system architectures, b) power electronics converters topologies and their non-linear characteristics, c) control and protection architecture, d) energy efficiency indicators, e) a comprehensive case study to elaborate power quality in marine system and f) extensive discussion about power quality standards and highlights the urgency to update existing power quality standards.

Modern industrial and commercial devices that are fed by power electronics circuits and behave non-linearly tend to produce power quality issues in power systems including harmonics and interharmonics, swell, flicker, spikes, notches, and transient instabilities. Among them, harmonic emission is the most significant challenge to be overcome by the distribution networks. Unwanted current, overheating motors and transformers, equipment failure, and circuit breaker misoperation are some of the harmonic consequences. While it is important to employ the best methods to mitigate or suppress the harmonic distortions in power systems, it is even more essential to estimate these harmonics at the outset by developing smart, efficient, and accurate techniques. Due to their capability for learning, predicting, and identifying, researchers have turned to Artificial Intelligence technologies for harmonic estimation in distribution networks. Although the power system parameters (impedance/admittance model) and many harmonic monitors are prerequisites for traditional harmonic estimation methods, by utilizing Artificial Intelligence, these requirements are minimized. In this paper, a comprehensive review of traditional and modern (smart) harmonic estimation techniques are discussed.

Mining is an important industry in many countries including Australia and plays a vital role in their economy. The industry heavily depends on electricity as it employs different types of electrical loads. Consequently, a stable and reliable supply of electricity is vital for running the production smoothly. In this review paper, electrical characteristics of mining power systems are described and common power quality and energy efficiency concerns in these systems are stated and classified. Different types of common power electronics topologies used in the industry are also studied and main requirements for reliable and robust operation of the system are categorized. A comprehensive case study to elaborate power quality challenges in mining distribution network is performed.

Due to the significant advances in fast switching semiconductor devices, harmonic emissions caused by the adjustable speed drives (ASDs) have been changed in terms of frequency range and magnitude. The frequency range of 2–150 kHz has been distinguished as a new interfering frequency range, disturbing the distribution networks. This article proposes a behavioral model of an ac motor to predict the common-mode (CM) current in ASDs. An approach is presented to calculate the parameters of the model, through which the dominant impact of each element at a specific frequency is considered. Moreover, along with the proposed motor model, a system modeling strategy is presented for filter design considerations at an emerging frequency range of 2–150 kHz. To verify the effectiveness of the proposed model, real-time experiments are conducted. The results prove that the introduced model can accurately predict the resonances of the CM loop created by the motor. Consequently, the proposed model is suitable for electromagnetic interference (EMI) filter design covering the 2–150-kHz standard.