Renewable energy resources (RES) play a vital role in modern power systems, motivated by their social, environmental, and techno-economic advantages. Nowadays, the energy generation mix has been upgraded in many countries such as Germany, Australia, and the United Kingdom to include more RES instead of the conventional fossil-fuel-based resources to solve various challenges such as future energy needs, remarkable oil price fluctuations, increasing risks of fossil-fuel pollution, and energy conservation strategies to minimize transmission and distribution networks’ losses. Consequently, the liberalization of electric energy markets has led to an augmented integration of RES, such as photovoltaics (PV) and wind turbines (WT), in today’s power systems.
However, unplanned and excessive penetration of DG may turn its advantages into disadvantages with possible operational hazards such as increased overvoltage risks, overloading of electrical equipment, reverse power flows with their negative impacts on the network’s protection schemes, and power quality (PQ) problems. Electrical systems are highly vulnerable to these risks when DG penetration exceeds the maximum allowable level that ensures safe and reliable operation, the so-called system hosting capacity (HC) limit. In the literature, different performance indices were considered as HC restrictive limits to avoid the adverse impacts of high DG penetration on electrical distribution networks, namely, overvoltage, overloading and power loss, power quality, and protection problems.
Consequently, enhancing the system’s HC is considered one of the important goals for DSOs around the world. HC enhancement techniques are categorized into six main categories namely reactive power control, automatic voltage control techniques such as on-load tap changers (OLTC) transformers, active power curtailment, energy storage technologies, network reconfiguration and reinforcement, and harmonic mitigation techniques.
The HC is a site-dependent concept, i.e. hosting of new DGs can be acknowledged in certain locations, but not in others. The thermal capacity of the distribution feeders and the voltage profile along the feeder play an important role in assessing the system’s HC. Therefore, the HC maps have been introduced as an explanatory and real-time application of the network’s HC. These maps can be implemented on the geographical cable routing layouts or network one-line diagrams. Many distribution system operators availed their real-time HC maps online through their online portals to shed the light on the congested network locations and the most valuable locations for renewables integration to drive further investment in renewables integration in a cost-effective way.
Based on the experience gained during this research, it has been found that the HC assessment is not a single value that can be calculated once. It should be frequently assessed for various performance indices such as voltage violations, thermal capacity of the feeders, power quality, and protection system problems. Then, the least value of the HC obtained considering relevant performance index should be determined at each node to estimate the overall system’s HC.
Finally, various HC enhancement techniques have been introduced in the literature and each of them has its merits and demerits. A thorough system study should be accomplished to decide whether a solution provides promising benefits or not. It will then be possible to ascertain the most appropriate techniques for coping with the acceptable limits of network operators in relation to sustainability, operability, and techno-economic features.
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