Power System SmallSignal Oscillation Stability as Affected by Largescale PV Penetra
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Power System SmallSignal Oscillation Stability as Affected by Largescale PV Penetration W. Du, H. F. Wang, and R. Dunn Abstract — This paper investigates the impact of a large photovoltaic (PV) penetration on power system small signal oscillation stability. A comprehensive model of a singlemachine infinitebus power system integrated with a PV power generation power plant is established. Numerical computation of damping torque contribution from the PV power plant is carried out, which is confirmed by the results of calculation of system oscillation model and nonlinear simulation. Those results indicate that power system oscillation stability can be affected either positively or negatively. There exists an operational limit of the PV power plant as far as system oscillation stability is concerned. Beyond the operational limit, the PV generation supplies negative damping torque, thus damaging system oscillation stability. Hence for the safe penetration of PV generation into power systems, the operational limit of oscillation stability of the PV power plant must be considered. INTRODUCTION The fast development of photovoltaic (PV) technology in recent two decades strongly indicates that in medium to long term, PV generation will become one of most attractive renewable energy sources in largescale applications. Evidence of such indication is that the growth of demand on solar energy has consistently been by over 20% per annum due to the decreasing cost and price. The European Union is well on the track to fulfilling its own target of 3GW PV generation by 2010; While capacity of PV generation in the UK is forecasted to be 30GW by 2050 [1][2]. Grid connection is the operational practice of largescale PV generation for its best utilization. This has attracted the most R& D interests in the area [3]. So far, majority of work on the grid connection of PV generation has focused on the R&D issues of efficient and effective PV generation itself, such as generation control and design of interface power electronics [4][7]. Large scale gridconnected PV generation will significantly affect power transmission and generation systems. In this aspect, one of the most important issues is the impact of large penetration of PV generation on power system stability, which must be examined carefully [1]. Dynamic of PV generation is considerably different with that of conventional generation involving rotating machines. Hence a thorough study on the case of interaction of PV generation with conventional power generation and transmission systems is an urgent task to be pursued. [8] and [9] have reported the results of case studies about the effect of PV generation on power system dynamics, which have provided good foundation for further investigations. The objective of this paper is to examine the effect of operation of PV generation jointly with that of conventional generator and transmission system on power system small signal oscillation stability. The paper beings with the establishment of a comprehensive model of a singlemachine infinitebus power system integrated with a PV power generation plant. Then an example singlemachine infinitebus power system integrated with a PV power plant is presented. Results of numerical computation and nonlinear simulation at different operating conditions are given when the load conditions of conventional power generation and levels of mixture of conventional and FC generation change. Results from the example power system indicate that power system oscillation stability can be affected either positively or negatively. There exists an operational limit of the PV power plant as far as system oscillation stability is concerned. Beyond the operational limit, the PV generation supplies negative damping torque, thus damaging system oscillation stability. Hence for the safe penetration of PV generation into power systems, the operational limit of oscillation stability of the PV power plant must be considered. for more ::0> ieeexplore.ieeeiel5/5341887/5347868/05348073.pdf?arnumber=5348073 


