Abstract
In literature, variations and distortions, and interruptions of voltages (or voltage waveforms) and currents (or current waveforms) have been considered in the framework of power quality (or voltage quality). With the massive penetration of renewable energy into power systems, variations including fluctuations and intermittences of output powers of these renewable sources are of great concerns. It is evidenced that with the high penetration of renewable energy, variations of renewable energy have increased the costs of UK’s balancing markets by 39% in this spring and summer (NGESO, 2020). Therefore, there are needs to introduce a technical framework, namely, ‘energy quality’ to (a) define the quality of power waveforms; (b) propose measures/indices to characterize the variations (fluctuations and intermittences) of powers and power flows; (c) present methods to improve energy quality. Finally, research directions of energy quality are highlighted to encourage more R&D as well as international collaborations in terms of standards and grid code developments.
Highlights
E LECTRICITY would progressively become the central energy carrier, growing from a 20% share of final consumption to an almost 50% share by 2050, and renewable power would be able to provide the bulk of global power demand (86%) economically [1]
Results show that the average power level is irrelevant with the sampling rate, but standard power deviation (SPD) and total power distortion (TPD) of a power flow would decrease as the sampling time becomes longer, because power variations with a bandwidth higher than the sampling rate would be removed by the sampling
The increasing penetration of renewable energy in power system brings stochastic power flows, uncertainties of energy market operations and power system planning and risks of wide frequency range oscillations and stability. These variations including fluctuations and intermittences of power waveforms are with natural contradictions to the needs of power system efficiency, security and stability
Summary
E LECTRICITY would progressively become the central energy carrier, growing from a 20% share of final consumption to an almost 50% share by 2050, and renewable power would be able to provide the bulk of global power demand (86%) economically [1]. Quite some research activities have been conducted to test the frequency response capability, ramping rate or limits to the rate of change of power levels of machines with different capacity in different time scales, power balancing of power systems with renewable energy sources [18], [19], [23]–[26] These works are in line with the scope of this paper, which are in echo with the development of a new framework of energy quality. Both of these have been recently upgraded in 2019 to meet new technical characteristics of the power system with increasing penetration of renewables These upgraded standards (e.g. limits to the rate of change of power levels of machines with different capacity in different time scales) are very relevant to the aspects of energy quality discussed in this article, but not yet fully extended and presented in the framework of energy quality. Conclusions are drawn and future research directions of energy quality are highlighted to encourage more R&D as well as international collaborations in terms of standards and grid code developments
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