Ramp-rate control smoothing methods to control output power fluctuations from solar photovoltaic (PV) sources—A review

Abstract

Solar photovoltaic generator is an intermittent source and mitigating its output power ramp-rate is crucial as they threaten the stability of the utility grid. This paper is aimed at bringing out the latest comprehensive review on different ramp-rate control smoothing methods under three broad classifications: (i) moving average and exponential smoothing based methods, (ii) filter based methods, and (iii) ramp-rate based algorithms. Application of moving average and low pass filter from filter based methods is widely chosen by the researchers for solar photovoltaic ramp-rate control. Therefore, a detailed analysis on these methods supported by simulation results is carried out to analyze the capability of these methods to control the solar photovoltaic ramp-rate. On application of these methods, it was found that there will be an increase in the energy storage's degradation and size. In addition, reduction in energy storage's operating life can also be found. Later, a detailed comparison on different techniques are summarized in the discussion section, from which it was found that the ramp-rate based algorithms are advantageous than moving average and filter based method. The advantages of the ramp-rate based algorithms are discussed as well. In addition, the disadvantages of the existing ramp-rate based algorithms are also highlighted. Finally, the necessitate for, (i) improvement in ramp-rate based algorithms, (ii) application of dual energy storage for large solar photovoltaic plant, and (iii) regulation in control of solar photovoltaic ramp-rates is suggested in this paper. These suggestions will contribute to decrease in energy storage's capacity and degradation, and increase in its operation life. © 2018 Elsevier Ltd