Under normal operating conditions, a MicroGrid is interconnected with the medium voltage network; however, in order to deal with black start and islanded operation following a general blackout, an emergency operation mode must be envisaged. A sequence of actions and conditions to be checked during the restoration stage are identified and tested through numerical simulation. Voltage and frequency control approaches, inverter control modes, and the need of storage devices are addressed in this paper in order to ensure system stability, achieve robustness of operation, and not jeopardize power quality during service restoration in the low voltage area.

This paper proposes a new methodology for coordinated voltage support in distribution networks with large integration of distributed generation and microgrids. Given the characteristics of the LV networks, it is shown that traditional control strategies using only reactive power control may not be sufficient in order to perform efficient voltage control. Therefore, microgeneration shedding must also be employed, especially in scenarios with extreme microgeneration penetration. An optimisation tool based on a meta-heuristic approach was developed to address the voltage control problem. In addition, neural networks were employed in order to decrease computational time, thus enabling the use of the tool for online operation. The results obtained revealed good performance of this control approach. Several authors have developed interesting work concerning the impact of DG on voltage control in distribution grids [2-5]. In [6], the authors formulate an algorithm for voltage control in distribution grids with DG by solving an optimisation problem, where active power losses are minimised, subject to a set of technical constraints. The control variables to consider are DG reactive power generation, On-line tap changing (OLTC) transformer settings and capacitor bank settings. One issue that frequently results from high DG penetration is voltage rise problems, especially in weak distribution networks [3, 7]. To overcome this problem, it is necessary to control both active and reactive power of the DG units and/or reduce the voltage at the HV/MV substation [3]. This voltage rise effect is partly the result of DSO policies based on a 'fit and forget' approach, which also requires DG to operate at a fixed power factor, thus limiting the

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Oxygenation of α-pinene using photochemically generated singlet oxygen ( 1 O 2 ) was studied in detail in several continuous flow photochemical reactors. Ferrioxalate actinometry and reaction kinetic data were used to compare light sources and reactor geometries, such as the immersed-well, an annular recirculating and microfluidic reactors. It is shown that reactor miniaturization, control of intensity and of spectral composition of light, and elevated oxygen pressure are the crucial factors for safe and efficient photo-oxygenation reactions. Higher quantum yields were generally obtained with the microreactor-LED assemblies due to better energy utilization, compared to all other systems studied. For the single-phase microreactor-LED system, an optimization model has been developed that revealed a broad optimal design window.