Closing Thoughts for HRES in Grid

In summary, renewable energy is environmentally, socio-ethically, and economically sustainable compared with the dominant centralized and non-renewable energy generation systems. However, the techno-economic limitations for ever-growing renewables’ share of power generation in the majority of the countries are alike. The RES is not currently cost-competitive with base load coal-fired power and is geographically dispersed. However, it leads over a conventional generation in low emissions of air pollutants, free fuel, and a low gestation period.

Traditionally, the electric power system is not intended to handle RE generation and storage. But with the rapid growth in the alternate energy sector, the integration of the distributed energy and RES into an electric power grid can be done in many ways along with power quality solution. The power electronic technology plays a significant part in the integration of RES into the electrical grid. They offer exclusive competence over conventional interconnection technologies. They further provide additional power quality and voltage/reactive power support.

It has been discussed that utility RE investments are typically evaluated from regulatory, project finance, and engineering viewpoints. The regulatory evaluation focuses on ensuring utility conformance to RES and that expenses are kept judiciously limited. From a finance perspective, the return on the investment within disjunctive limits of the funding and cash flows for a particular project are evaluated. The technical evaluation determines the engineering and operational safety of the project and the specific technologies deployed. While these approaches are essential for investors, utilities, regulators, and ratepayers, they do not scope out the goodness that a RES can convey beyond the boundaries of a given project, such as the usefulness of transmission and storage and the organizational plus point of bringing an integrated grid.

Variability of RES occurs due to the nature of the climate. Therefore the uncertainty in the generation affecting up to 70% of daytime solar capacity due to passing clouds, and 100% of wind capacity on calm days, is much greater than the somewhat expected variations of a few percent in demand that system operators handle. It necessitates a more complicated voltage and frequency regulation. The larger the RE entrant, the more complicated (sometimes unattainable) is the management of this challenge. Spatial aggregation of RES greatly lessens forecast errors, just as it lessens variability. This may be due to the spatial smoothening effect. The forecast error rises further as the time range of the forecast is expanded. Forecasting techniques are improving constantly. But this requires a better weather model and better data collection and processing. In contrast to the convention fossil fuel power sources, selecting a site to exploit certain RES has few or no degrees of freedom. In other words, RE such as wind and PV, are site constrained. Transmission needs to be extended to these sources, not the other way around. Future distribution systems will contain MGs, and hence it is necessary to understand the steady-state and transient operating conditions of such systems to appraise their effects on the present grid.

Control system is the key element for flexible operation, high efficiency, and superior power quality in RE integration. In this regard, the control system fetches real-time states through local measures and via the communication, takes actions to attain the control objectives (for instance, maximum power extraction, output voltage and frequency regulation, reactive power compensation, etc.), and at last sends commands to the actuators, usually power electronic converters. Challenges in control design and realization, energy management strategies, communication layout and protocols, and topologies for power electronics-based distributed RES are all addressed in brief here. The energy storage by batteries in grid-level applications guides both transmission and generation services to the grid. It mitigates the unpredictability of generation. It has been emphasized to conduct a review of the technological potential for a range of battery chemistries. More detailed discussions on MG, off-grid hybrid RES and hybrid storage systems are given in Chapters 4 to 6. Lastly, it should be emphasized again that, because of some demerits and irrevocable externalities in conventional energy production, it has become essential to go for and uphold technologies and insist on RES. Power generation using RES should be enhanced in order to reduce the operational cost of power generation and protect environment.

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