The industry of solar Photovoltaic (PV) energy and its exploitation are still booming to enhance the sustainability of the society. When PV systems are connected to the grid, challenging issues should be addressed. One of the challenges is related to interharmonics in PV systems, especially with a large-scale adoption of PV systems. However, the origins of interharmonics remain unclear, although the impact of interhamonics has been reported in literature. Thus, this paper explores the generation mechanisms of interharmonics in PV systems and its characteristics. The exploration reveals that the perturbation from the Maximum Power Point Tracking (MPPT) algorithm is one of the origins of interharmonics appearing in the grid current. Accordingly, the MPPT controller parameters such as the perturbation step-size and the sampling rate have an inevitable impact on the interharmonic characteristics. Furthermore, an approach to characterize the interharmonics in the grid current is proposed. With the proposed model, interharmonics can be predicted according to the designed controller parameters in terms of frequencies and amplitudes. Experimental tests are performed on a single-phase grid-connected PV system. The results are in a close agreement with the analysis, and thus validate the effectiveness of the proposed model.

Harmonic emissions have been changed in distribution networks, with respect to frequency range and magnitude, due to the penetration of modern power electronics systems. Two new frequency ranges 2-9 and 9-150 kHz have been identified as new disturbing frequency ranges affecting distribution networks. This paper presents the effects of grid-connected three-phase systems with different front-end topologies: conventional, small dc-link capacitor, and electronic inductor. A power converter with a small dc-link capacitor can create a resonant frequency with the line impedance below and above 1 kHz depending on the grid configurations. The resonant effects depend on many factors, such as load power levels, filter types, and the number of parallel drives. These issues can affect the grid current harmonics and power quality of the distribution networks. Analyses and simulations have been carried out for three different topologies and the results have been verified by experimental test at system level. Current harmonic emissions have been considered for 0-2, 2-9, and 9-150 kHz frequency ranges.

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.

Adjustable speed drives (ASDs) based on a three-phase front-end diode rectifier connected to a rearend inverter may generate interharmonic distortion in the grid. The interharmonic components can create power quality problems in the distribution networks such as interference with the ripple control signals, and consequently they can hamper the normal operation of the grid. This paper presents the effect of the symmetrical regularly sampled space vector modulation and discontinuous pulse width modulation-30° lag (DPWM2) techniques, as the most popular modulation methods in the ASD applications, on the drive's input current interharmonic magnitudes. Further investigations are also devoted to the cases where the random modulation technique is applied to the selected modulation strategies. The comparative results show how different modulation techniques can influence the ASD's input current interharmonics and consequently may not be a suitable choice of modulation from an interharmonics perspective. Finally, the theoretical analysis and simulation studies are validated with obtained experimental results on a 7.5-kW motor drive system.

This article analyzes the power transfer limit ( P_max ) of wind power plants (WPPs) under the weak grid condition. It is pointed out that the impact of different grid parameters and grid configurations on P_max cannot be fully reflected by the short-circuit ratio (SCR), but can be readily captured by voltage sensitivity (∂ Q /∂ V ). Hence, ∂ Q /∂ V turns out to be a more appropriate metric for the assessment of P_max compared with the SCR. Based on this insight, the voltage control of the WPP is suggested to be implemented at the bus with the highest ∂ Q /∂ V to maximize the power transfer capability. Moreover, a dynamic voltage control is further added at the turbine level to improve the disturbance rejection capability of the WPP as well as its dynamic robustness against grid strength variations. Finally, simulation and field test results are given to demonstrate the theoretical analysis and the effectiveness of the proposed control method.

Current and voltage source adjustable-speed drives (ASDs) exert the distortion current into the grid, which may produce some interharmonic components other than the characteristic harmonic components. This paper studies the effects of passive components on the input current interharmonics of ASDs with and/or without motor current imbalance. The investigation is done at different motor operating frequencies and load torque values. It shows that selecting the small filter components (ac choke, dc choke, and dc-link capacitor) results in different performances with respect to those interharmonics issued by motor current imbalance and other noncharacteristic interharmonics. The results are helpful for engineers investigating the effects of drive filters on the input current interharmonic components.