Generation expansion planning consists of finding the optimal long-term plan for the 5 construction of new generation capacity subject to various economic and technical constraints. It 6 usually involves solving a large-scale, non-linear discrete and dynamic optimisation problem in a 7 highly constrained and uncertain environment. Traditional approaches to capacity planning have 8 focused on achieving a least-cost plan. During the last two decades however, new paradigms for 9 expansion planning have emerged that are driven by environmental and political factors. This has 10 resulted in the formulation of multi-criteria approaches that enable power system planners to 11 simultaneously consider multiple and conflicting objectives in the decision-making process. 12 More recently, the increasing integration of intermittent renewable energy sources in the grid to 13 sustain power system decarbonisation and energy security has introduced new challenges. Such a 14 transition spawns new dynamics pertaining to the variability and uncertainty of these generation 15 resources in determining the best mix. In addition to ensuring adequacy of generation capacity, it 16 is essential to consider the operational characteristics of the generation sources in the planning 17 process. In this paper, we first review the evolution of generation expansion planning techniques 18 in the face of more stringent environmental policies and growing uncertainty. More importantly, 19 we highlight the emerging challenges presented by the intermittent nature of some renewable 20 energy sources. In particular, we discuss the power supply adequacy and operational flexibility 21 issues introduced by variable renewable sources as well as the attempts made to address them. 22 Finally, we identify important future research directions.

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We show that a systematic modern control technique such as linear–quadratic Gaussian (LQG) control can be applied to a problem in experimental quantum optics which has previously been addressed using traditional approaches to controller design. An LQG controller which includes integral action is synthesized to stabilize the frequency of the cavity to the laser frequency and to reject low frequency noise. The controller is successfully implemented in the laboratory using a dSpace digital signal processing board. One important advantage of the LQG technique is that it can be extended in a straightforward way to control systems with multiple measurements and multiple feedback loops. This work is expected to pave the way for extremely stable lasers with fluctuations approaching the quantum noise limit and which could be potentially used in a wide range of applications.